Static and Dynamic Plantar Pressures in Children With and Without Sever Disease: A Case-Control Study Ricardo Becerro-de-Bengoa-Vallejo, Marta E. Losa-Iglesias and David Rodriguez-Sanz PHYS THER. 2014; 94:818-826. Originally published online January 30, 2014 doi: 10.2522/ptj.20120164
The online version of this article, along with updated information and services, can be found online at: http://ptjournal.apta.org/content/94/6/818 Online-Only Material Collections
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Research Report
Static and Dynamic Plantar Pressures in Children With and Without Sever Disease: A Case-Control Study Ricardo Becerro-de-Bengoa-Vallejo, Marta E. Losa-Iglesias, David Rodriguez-Sanz R. Becerro-de-Bengoa-Vallejo, PhD, Escuela Universitaria de Enfermerı´a, Fisioterapia y Podologı´a, Universidad Complutense de Madrid, Madrid, Spain.
Background. Calcaneal apophysitis (Sever disease) has been reported to be the most common cause of heel pain in athletic children.
M.E. Losa-Iglesias, PhD, Facultad Ciencias de la Salud, Universidad Rey Juan Carlos, Avenida Atenas s/n 28922, Alcorco´n, Spain. Address all correspondence to Dr Losa-Iglesias at: [email protected].
tact area, distribution of body weight across the lower extremities, and prevalence of gastrocnemius ankle equinus and gastrocnemius-soleus ankle equinus (which can cause decreases in ankle dorsiflexion range of motion) in children with and without Sever disease.
Objective. The study aim was to compare plantar pressure, plantar surface con-
D. Rodriguez-Sanz, PhD, Centro Ortopedico y Quirurgico del Pie, Madrid, Spain.
Design. This was a case-control study.
[Becerro-de-Bengoa-Vallejo R, Losa-Iglesias ME, Rodriguez-Sanz D. Static and dynamic plantar pressures in children with and without Sever disease: a casecontrol study. Phys Ther. 2014;94:818 – 826.]
Twenty-eight participants had Sever disease (Sever disease group), and 28 participants were healthy (control group). Dynamic and static peak plantar pressures, plantar surface contact area, and body weight distribution were assessed with pedobarography. A goniometer was used to assess gastrocnemius and gastrocnemiussoleus ankle dorsiflexion range of motion.
© 2014 American Physical Therapy Association Published Ahead of Print: January 30, 2014 Accepted: January 22, 2014 Submitted: April 7, 2012
Methods. Participants were 56 male students enrolled in a soccer academy.
Results. Both maximum and average peak pressures and percentages of body weight supported by each heel were significantly higher in the symptomatic feet of participants in the Sever disease group than in the control group. Twenty-six participants with Sever disease but only 8 participants in the control group exhibited bilateral gastrocnemius ankle equinus.
Limitations. A limitation of the study is that measurements were obtained from participants who were symptomatic. Conclusions. Higher heel plantar pressures under dynamic and static conditions appear to be associated with Sever disease. It is unclear, however, whether these higher pressures are a predisposing factor contributing to the disease or a result of the condition. Gastrocnemius ankle equinus also may be a predisposing factor for Sever disease. Further research is needed to identify other biomechanical factors associated with the disease to enhance prevention and treatment strategies.
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Plantar Pressures in Children With and Without Sever Disease
T
he calcaneal apophysis is a cartilaginous growth center into which the Achilles tendon inserts.1,2 Apophysitis, or inflammation of an apophysis, is caused by microavulsions at the bone-cartilage junction.3 It is commonly the result of repetitive motion and overuse during periods of rapid growth. Calcaneal apophysitis was first described in 1912 by Sever4 and was later given the name Sever disease. Kvist and Heinonen5 and Kim et al6 refined the definition of Sever disease to indicate traction epiphysitis. On the basis of this definition, it is a disease most commonly associated with prepubescent children who are active in sports that involve running and jumping.7–9 The commonality of sports participation was documented by McKenzie et al,10 who conducted a retrospective study of 20 children diagnosed with Sever disease. McKenzie et al10 reported that all of the children participated in sports, with the majority participating in track and field or soccer. Sever disease has been reported to be the most common cause of heel pain in athletic children.8,11 Orava and Puranen12 and Orava and Virtanen13 found that Sever disease comprises 16.3% and 22.7% of exertion injuries in children, respectively. The heel pain limits physical activity and may interfere with activities of daily living in young athletes. The condition is self-limiting because the calcaneal cartilage disappears at 14 to 16 years of age to permit complete calcaneal ossification.5 The etiology of Sever disease is controversial.14 Potential contributing factors include participation in high-impact sports, improper footwear, running on hard surfaces, and excessive plantar heel pressures.15 The condition also is associated with radiographic changes, including variations in the normal ossification pattern.8 Currently, the cessation of June 2014
high-impact activities, thus reducing mechanical overload at the affected heel, is a standard component of treatment.16 –18 Further advancement in the treatment of Sever disease is predicated on a greater understanding of factors contributing to the pathology. Although controlling mechanical loading is a treatment strategy, we are unaware of previous work evaluating dynamic plantar pressure in children diagnosed with Sever disease. Therefore, we sought to investigate the relationship between mechanical loading and calcaneal apophysitis by measuring dynamic and static plantar pressures in young athletes with and without Sever disease. We also evaluated the distribution of body weight and plantar surface contact area between the lower extremities to determine whether asymmetrical loading is associated with the disease. Ankle dorsiflexion range of motion in children, measured with the knee in full extension, should be at least 10 degrees.19,20 Decreased ankle dorsiflexion range of motion, also called ankle equinus, differentiates the decreased ankle range of motion that is due to gastrocnemius ankle equinus from that due to gastrocnemiussoleus ankle equinus.21 The association of gastrocnemius ankle equinus, gastrocnemius-soleus ankle equinus, and Sever disease was evaluated on the basis of previous reports of a relationship between ankle equinus deformity and Achilles tendon thickening.22
Method Participants Participants in this study were male students who were enrolled in a soccer school and underwent an end-ofseason health screening. A total of 131 students between 8 and 15 years of age were evaluated for study eligibility. Exclusion criteria included
a recent history of ankle injury, such as sprain, tendinitis, or any pathology other than Sever disease, and the presence of a neurologic condition affecting either lower extremity. All children in this study were from the same school (a soccer-focused program). Thus, all were exposed to the same amount of training hours per week. We studied children who never had heel pain under these training conditions and children who experienced heel pain under the same training conditions. Of the 56 participants included in the study, 28 had symptomatic Sever disease. The left heel was symptomatic in 15 participants, the right heel was symptomatic in 5 participants, and 8 participants had bilateral heel symptoms, resulting in a total of 36 affected heels. Evaluation for the presence of Sever disease was performed by a podiatrist (R.B.B.V.). For diagnostic purposes, Sever disease was defined as pain with compression of the mediolateral calcaneus in the growth plate region.23 The pain had to be of at least 2 months’ duration, had to coincide with physical activity, and had to be severe enough to sufficiently interfere with normal physical activity, such as walking.11 Eight children were receiving treatment when they came to the school and were not allowed to play soccer because of their level of pain. Six children were receiving treatment and were still allowed to play, and 14 children reported pain at the end of the training sessions and during our evaluation. Twenty-eight of the 56 participants were healthy and comprised a conAvailable With This Article at ptjournal.apta.org • eTable: Technical Specifications of the Pressure Platform
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Plantar Pressures in Children With and Without Sever Disease trol group. These participants were selected from the total pool of eligible children by use of a random number generator program (Epidat 3.1, Pan American Health Organization, Washington, DC). There was no difference within or between groups for time spent in sports participation, including after-school or weekend training, or in competition. Procedure Before the initiation of data collection, written parental consent for study participation was obtained for each participant. The Silfverskio ¨ ld test was performed to assess the ankle range of motion and differentiate gastrocnemius ankle equinus (in which the gastrocnemius muscle limits ankle dorsiflexion range of motion) from gastrocnemius-soleus ankle equinus (in which the soleus muscle limits ankle dorsiflexion range of motion).19,24 Ankle joint dorsiflexion range of motion was determined for all participants by a clinician
with extensive experience in foot and ankle physical examinations. Ankle joint dorsiflexion range of motion was assessed by measurement with a standard clinical goniometer with the knee extended and with the knee flexed. The participant lay on his or her back with the knee flexed 90 degrees. Normal ankle dorsiflexion is approximately 10 degrees with the knee extended and 20 degrees with the knee flexed.19,25,26 Thus, the definition of gastrocnemius ankle equinus was the inability of the ankle to achieve dorsiflexion of 10 degrees with the knee extended and with the knee flexed. Gastrocnemius-soleus ankle equinus was defined as the inability of the ankle to achieve dorsiflexion beyond a neutral position with the knee extended (it remained ⬍0°) or with the knee flexed (it remained ⬍0°).21,27,28 The reported reliability of goniometric measurement of sagittal plane ankle motion in chil-
The Bottom Line What do we already know about this topic? Sever disease, one of the most common causes of heel pain in athletic children, is often associated with gastrocnemius ankle equinus.
What new information does this study offer? The study defined dynamic and static plantar pressure maps of the heel and forefoot for physically active children with and without symptomatic Sever disease and demonstrated a significant pressure increase for patients with the disease.
If you’re a patient, what might these findings mean for you? The unequal distribution of body weight across the limbs of patients with Sever disease suggests that reducing weight bearing in the affected limb can reduce plantar pressures and associated symptoms. A diagnosis of gastrocnemius ankle equinus may predispose these patients to increased plantar pressure in the heel, providing a potential screening tool to determine the need for further assessments, such as plantar pressure mapping.
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dren29 suggests that ankle dorsiflexion measures are highly variable among examiners. Measurement of gastrocnemius ankle motion is more reliable than that of soleus ankle motion, and measurement of ankle dorsiflexion with the knee extended is more reliable than that with the knee flexed.29 During measurement of ankle dorsiflexion range of motion, care was taken to maintain the subtalar joint in a neutral position to ensure that talocrural motion, not midfoot dorsiflexion (rocker bottom), was evaluated.19 Dynamic plantar pressure was measured by an independent clinician using a digital portable pressure sensor platform (Medicapteurs, Balma, France) embedded in a 5-m walkway. The technical specifications of the pressure platform are shown in the eTable (available at ptjournal. apta.org). Pressure sensor measurements from the platform were accurate to the nearest 0.001 kg/cm2. Before each use, autocalibration was performed in accordance with manufacturer specifications. During practice and testing, participants were barefoot and walked at a steady, self-selected speed. Practice trials were performed to establish a preferred walking speed for each participant and to facilitate platform striking with the entire foot. After familiarization with testing procedures was complete, data collection was initiated. A trial was considered valid when a heel-strike–toe-off pattern was observed and the walking speed was consistent.30,31 Trials that did not meet each of these criteria were not used for subsequent analysis. A 2-step method in which plantar pressure data were obtained on the second step of each foot was used for each walking trial, and data for 6 steps with each foot were collected per session from each participant.20 The mean of 6 trials per foot was used for statistical testing. Plantar
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Plantar Pressures in Children With and Without Sever Disease Table 1. Participant Characteristics XⴞSD (Range) for the Following Group: Characteristic
Sever Disease
Age (y)
10.78⫾1.46 (8–15)
Pa
10.65⫾1.75 (8–15)
1.01 (0.93–1.09)
.931
0.98 (0.94–1.01)
.142
38.9⫾7.6
39.7⫾7.9
0.98 (0.88–1.08)
.112
17.1⫾1.87
17.3⫾1.94
0.99 (0.93–1.05)
.223
0.39 (0.36–0.42)
.001
143.47⫾9.8
Weight (kg) Body mass index (kg/m2) Dorsiflexion range of motion (°)
Ratio of Means (95% Confidence Interval)
146.88⫾10.1
Height (cm)
b
Control
6.88⫾1.03 (4–8)
17.71⫾1.95 (14–20)
a
Determined with independent Student t tests. P values of less than .05 were considered statistically significant. b Total dorsiflexion range of motion measured from knee in extension to knee in flexion.
pressure data collected with the 2-step method were comparable to those collected with the midgait method; therefore, the former method may be preferred for examining children because of its ease and speed of data collection.28 Static plantar pressure measurements were collected with the same pressure sensor platform as that used during dynamic conditions. During testing, participants stood on the pressure sensor platform in a natural manner while barefoot. Participants were instructed to look straight ahead and keep their arms relaxed at the side. Plantar foot pressure measurements were collected simultaneously for both feet for 30 seconds. If the participant moved during testing, then the data were discarded and the trial was repeated. Testing continued until data were collected from 6 trials during which the participant remained stationary. The participant did not know when a trial was actually being recorded. The mean of 6 valid trials per foot was used for subsequent analysis. Data Management Data recording was performed with a personal computer linked to the pressure sensor platform. The commercially available software program S-plate (interactive rehabilitation software) for Windows (Medicapteurs) was used for all data collection June 2014
and management. Software output included pressure maps, which provided the plantar pressure magnitude (kilopascals), contact area (square centimeters), and percent body weight (%BW) distribution through each limb. The dynamic plantar pressure outline for each participant was divided into 4 distinct regions (heel, midfoot, forefoot, and toes). The heel, midfoot, and forefoot regions were defined as equal thirds of the plantar pressure outline (omitting the toes).31,32 Variables of interest for dynamic plantar pressure included the surface contact area of the forefoot and heel and the maximum and average peak pressures of the forefoot and heel. Variables of interest for static plantar pressure included the total surface contact area, surface contact area of the forefoot and heel, maximum and average peak pressures of the forefoot and heel, %BW supported by each limb, and %BW supported in the forefoot and heel. Data Analysis Demographic characteristics, including participant height, weight, age, and body mass index, and each of the plantar measurements were summarized as mean⫾standard deviation; these data were compared in children with Sever disease and children who were healthy. The ratio of means was calculated to describe
the change in 2 means. Independent Student t tests were performed to determine whether differences were statistically significant. The Kolmogorov-Smirnov test was used to confirm a normal distribution for each of the plantar measurements. Measurements that were not normally distributed were tested with a nonparametric method, the Wilcoxon test. The F test was used to confirm variance equality. If equal variance could not be confirmed, then Satterthwaite approximation was used in the t tests. To make an overall comparison, we combined the heel with more severe symptoms for the 8 participants who had bilateral heel symptoms (6 right and 2 left feet) with the feet of the 20 participants who had unilateral heel symptoms, yielding a total of 28 symptomatic feet assessed (17 left and 11 right feet). We then randomly selected 28 feet of participants without Sever disease (control feet) and matched the numbers of left and right control feet to the symptomatic feet. Thus, the comparison involved 28 symptomatic feet and 28 control feet matched by side. The association between gastrocnemius ankle equinus or gastrocnemius-soleus ankle equinus and Sever disease was evaluated with a chi-square test. In all of the analyses, statistical significance was established by a P value of less than .05. All of the analyses
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Plantar Pressures in Children With and Without Sever Disease Table 2. Dynamic Plantar Pressures Values for the Following Groupa:
Ratio of Means (95% Confidence Interval)
Pb
55.86⫾6.03
1.00 (0.94–1.06)
.890c
134.23⫾35.25
103.6⫾10.52
1.30 (1.14–1.45)
.003d
Average peak pressure (kPa)
98.55⫾25.97
74.16⫾7.73
1.33 (1.17–1.48)
⬍.001d
Surface area (cm2)
33.61⫾2.62
33.89⫾2.39
0.99 (0.95–1.03)
.688c
Maximum peak pressure (kPa)
876.16⫾90.35
91.21⫾11.14
9.61 (9.00–10.21)
⬍.001c
Average peak pressure (kPa)
648.02⫾98.47
71.56⫾7.37
9.06 (8.38–9.73)
⬍.001c
Foot Left
Variable No. of feet
Forefoot
2
Surface area (cm ) Maximum peak pressure (kPa)
Heel
Right
No. of feet
Forefoot
Forefoot
28
56.09⫾5.66
28 58.86⫾4.44
1.05 (1.01–1.10)
.035c
Maximum peak pressure (kPa)
149.16⫾32.45
106.49⫾19.82
1.40 (1.20–1.60)
.001d
Average peak pressure (kPa)
112.51⫾32.01
77.41⫾18.25
1.45 (1.19–1.72)
.003d
34.62⫾2.69
32.89⫾3.82
1.05 (0.99–1.12)
.152c
Maximum peak pressure (kPa)
839.82⫾68.65
88.18⫾10.29
9.52 (8.91–10.13)
⬍.001c
Average peak pressure (kPa)
654.37⫾61.88
70.58⫾10.5
9.27 (8.55–9.99)
⬍.001c
28
28
57.64⫾6.03
56.79⫾5.66
1.01 (0.96–1.07)
.5402c
Maximum peak pressure (kPa)
134.56⫾36.38
104.60⫾10.92
1.29 (1.15–1.43)
.0001c
Average peak pressure (kPa)
103.11⫾29.75
74.74⫾12.80
1.38 (1.20–1.55)
⬍.0001c
34.00⫾2.88
33.79⫾2.60
1.01 (0.96–1.05)
.7716c
Maximum peak pressure (kPa)
880.31⫾77.74
87.52⫾11.71
10.06 (9.45–10.67)
⬍.0001c
Average peak pressure (kPa)
664.09⫾83.52
71.48⫾7.32
9.29 (8.72–9.86)
⬍.0001c
No. of feet 2
Surface area (cm )
Surface area (cm2)
Heel
23
13
Surface area (cm )
Both left and right
Control
62.00⫾3.87
Surface area (cm2)
2
Heel
Sever Disease
a
Values are reported as mean⫾standard deviation unless otherwise indicated. P values of less than .05 were considered statistically significant. Determined with the independent Student t test. d Determined with the Wilcoxon test. b c
were performed with commercially available software (SPSS 19.0, SPSS Inc, Chicago, Illinois).
Results
Figure 1. Dynamic plantar pressure map of the heel and forefoot. Red indicates areas with the highest plantar pressures. (A) Increase in heel pressure in a participant with Sever disease and gastrocnemius ankle equinus. (B) Normal distribution in a participant from the control group with no gastrocnemius ankle equinus.
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There was no difference between the groups in participant age, height, or body mass index (Tab. 1). There was a statistically significant difference between the groups in the prevalence of gastrocnemius ankle equinus, with 26 of 28 participants in the Sever disease group but only 8 of 28 participants in the control group exhibiting bilateral gastrocnemius ankle equinus (P⫽.019). There was no difference between the groups in the prevalence of gastrocnemius-soleus ankle equinus, with 3 of 28 participants in both
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Plantar Pressures in Children With and Without Sever Disease Table 3. Static Plantar Pressures Values for the Following Groupa:
Ratio of Means (95% Confidence Interval)
Pb
69.46⫾2.56
1.00 (0.98–1.02)
.999c
39.00⫾1.04
38.57⫾1.71
1.01 (0.99–1.03)
.277c
Heel
30.52⫾1.34
30.89⫾1.71
0.99 (0.96–1.02)
.400c
Forefoot, maximum peak pressure
95.76⫾3.69
91.11⫾5.4
1.05 (1.02–1.08)
.005d
Forefoot, average peak pressure
74.28⫾4.03
70.32⫾3.41
1.06 (1.03–1.09)
⬍.001c
Heel, maximum peak pressure
347.88⫾24.69
83.06⫾1.92
4.19 (4.06–4.32)
⬍.001c
Heel, average peak pressure
258.59⫾27.7
71.38⫾1.80
3.62 (3.46–3.79)
⬍.001c
13
28
Total
69.62⫾2.18
69.46⫾2.56
1.00 (0.98–1.02)
.851c
Forefoot
39.00⫾1.96
38.57⫾1.71
1.01 (0.98–1.04)
.479c
Heel
30.62⫾1.33
30.89⫾1.71
0.99 (0.96–1.02)
.609c
Forefoot, maximum peak pressure
95.01⫾3.13
92.35⫾5.5
1.03 (1.00–1.06)
.110c
Forefoot, average peak pressure
72.62⫾3.76
1.04 (1.01–1.07)
.035d
Foot and Measure Left
Variable
Sever Disease
Control
23
28
Total
69.52⫾1.75
Forefoot
No. of feet 2
Surface area (cm )
Plantar pressure (kPa)
Right
No. of feet 2
Surface area (cm )
Plantar pressure (kPa)
Both left and right
Heel, maximum peak pressure
325.90⫾23.91
82.84⫾2.3
3.93 (3.77–4.10)
⬍.001c
Heel, average peak pressure
247.73⫾34.9
70.87⫾1.04
3.50 (3.22–3.77)
⬍.001c
28
28
Total
69.21⫾1.57
69.46⫾2.56
1.00 (0.98–1.01)
.6634c
Forefoot
38.89⫾1.31
38.57⫾1.71
1.01 (0.99–1.03)
.4369c
Heel
30.32⫾1.33
30.89⫾1.71
0.98 (0.96–1.01)
.1723c
Forefoot, maximum peak pressure
95.78⫾3.52
92.35⫾5.64
1.04 (1.01–1.07)
.0091c
Forefoot, average peak pressure
74.07⫾4.06
70.45⫾3.24
1.05 (1.02–1.08)
.0003c
Heel, maximum peak pressure
339.40⫾26.96
83.02⫾2.10
4.09 (3.96–4.22)
⬍.0001c
Heel, average peak pressure
254.56⫾29.75
71.33⫾1.27
3.57 (3.41–3.73)
⬍.0001c
No. of feet 2
Surface area (cm )
Plantar pressure (kPa)
69.8⫾2.95
a
Values are reported as mean⫾standard deviation unless otherwise indicated. P values of less than .05 were considered statistically significant. Determined with the independent Student t test. d Determined with the Wilcoxon test. b c
groups exhibiting bilateral gastrocnemius-soleus ankle equinus (P⫽1.000). When we assessed dynamic plantar pressure measurements, we found that maximum and average peak pressures were significantly higher in the affected heel of participants in the Sever disease group than in the control group (Tab. 2, Fig. 1). Maximum and average forefoot pressures were also significantly higher on the side of the affected heel of partici-
June 2014
pants in the Sever disease group than in the control group (Tab. 2, Fig. 1). There was no difference between groups in surface contact area (Tab. 2). The ratios of means were consistent with the P values. The lower bound of a confidence interval for a ratio of means was greater than 1 when the mean for the Sever disease group was significantly higher than that for the control group (P⬍.05). When we assessed static plantar pressures, we found that maximum
and average peak pressures were higher in both the heel and the forefoot on the involved side of participants in the Sever disease group than in the control group (Tab. 3, Fig. 2). There was no difference between groups in total, heel, or forefoot surface contact area (Tab. 3). The %BW supported by the forefoot of each foot was significantly lower in participants in the Sever disease group than in the control group for both feet (Tab. 4). The %BW supported by the heel was significantly higher in participants in the Sever disease
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Plantar Pressures in Children With and Without Sever Disease
Figure 2. Static plantar pressure map of the heel and forefoot. Red indicates areas with the highest plantar pressures. (A) Increase in pressure in both heels in a participant with Sever disease and gastrocnemius ankle equinus. (B) Normal distribution in a participant from the control group with no gastrocnemius ankle equinus.
group than in the control group for both feet (P⬍.001) (Tab. 4), indicating a significant load for both heels of participants in the Sever disease group.
Discussion Many authors4,5,10,12,18,33–38 have noted that children with Sever disease are regular participants in sports activities. In the present investigation, we compared the dynamic and static plantar pressures in physically active children with symptomatic Sever disease. Our comparison involved children who spent the
same amounts of time in physical activity. The higher plantar pressures found in participants with a symptomatic foot and Sever disease in the present study are consistent with the findings of a previous investigation.39 Higher maximum and average peak pressures and higher %BW supported by the symptomatic heel could translate to a secondary injury to the immature calcaneal cartilage. Overload in tissues may be associated with an inability to adequately attenuate forces during gait. Lower loading rates are widely regarded as less damaging than higher loading
Table 4. Body Weight Distribution Values for the Following Groupa Pb
Foot
Variable
Sever Disease
Control
Left
No. of feet
23
28
Total
48.11⫾0.99
51.68⫾1.68
.001
Forefoot
17.57⫾0.88
31.29⫾0.90
.001
Heel
30.54⫾1.07
20.39⫾1.42
.001
13
28
Total
51.89⫾0.99
48.32⫾1.68
.001
Forefoot
18.79⫾0.79
27.39⫾2.08
.001
Heel
33.11⫾1.20
20.93⫾1.02
.001
Right
No. of feet
a
Values are reported as mean⫾standard deviation percent body weight unless otherwise indicated. b Determined with independent Student t tests. P values of less than .05 were considered statistically significant.
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rates. Jahss et al40 postulated that if force or repetition of force is not attenuated to below a critical level, then tissue destruction can result; healing responses can lead to further structural changes and alterations in tissue mechanics, which can increase forces on the heel during gait and lead to repetitive microtrauma to the subcalcaneal tissues.41 This scenario supports the pathophysiologic concept most often presented in the literature of Sever disease as an overuse syndrome caused by repetitive microtrauma from increased traction on the apophysis.8,42– 44 Our investigation identified an unequal distribution of body weight across the limbs in participants with Sever disease. The %BW in the symptomatic heel and in the forefoot of the involved foot of participants with Sever disease was significantly higher than that in the control group. In the absence of differences in surface contact area, these findings suggest that weight-bearing strategies may be a significant factor contributing to elevated plantar pressure in the involved foot of children with Sever disease. Similarly, in a previous case-control study in which static plantar pressures and distribution of body weight across the 2 lower extremities were evaluated in children with and without calcaneal apophysitis,39 participants in the control group (who had no history of heel pain) had a more equal distribution of body weight, with each foot supporting approximately half the load. Collectively, these findings suggest that balancing weight distribution between the sides, thus reducing weight bearing by the affected limb, can serve as an effective strategy for reducing plantar pressures and the symptoms associated with Sever disease. Studies that specifically test this clinical intervention strategy are needed to validate this hypothesis.
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Plantar Pressures in Children With and Without Sever Disease With the 2-step method used in the present investigation, 93% (26/28) of symptomatic participants exhibited bilateral gastrocnemius ankle equinus, whereas only 10% (3/28) exhibited bilateral gastrocnemius-soleus ankle equinus. The presence of a potential equinus deformity has been reported in patients with foot and ankle complaints.21 Furthermore, gastrocnemius ankle equinus and gastrocnemius-soleus ankle equinus are not uncommon among people who are asymptomatic.21 The exact mechanism by which ankle equinus may influence Sever disease is unknown.19 The presence of gastrocnemius ankle equinus may contribute to mechanical overloading in the symptomatic heel as a consequence of soft tissue tightness. This theory is supported by an investigation performed by Szames et al,22 who evaluated 79 cases of calcaneal apophysitis in 53 patients. They found that 82.3% of the cases had ankle equinus due to muscular retraction.22 They did not, however, distinguish between gastrocnemius ankle equinus contractures and gastrocnemius-soleus ankle equinus contractures. The pathogenesis of Sever disease has been suggested to occur through repetitive microtrauma at the apophysis as a consequence of increased musculotendinous traction. The calcaneal growth plate and the apophysis are situated in an area subject to high stress from the plantar fascia and Achilles tendon.45 The theory that a tight triceps surae muscle causes excessive tension through the Achilles tendon and increases traction on the apophysis has been commonly cited as a mechanical factor contributing to Sever disease.3,7,8,17,18,22,46 –54 The same musculotendinous tightness contributes to ankle equinus deformity. The strong relationship between calcaneal apophysitis and gastrocnemius ankle equinus may explain why June 2014
treatments that include a heel lift to reduce Achilles tendon tension and limitation of strenuous activity are effective in relieving symptoms in patients with Sever disease. An important limitation of the present study is that measures were obtained from participants who were symptomatic. We could not determine whether the elevated plantar pressures and unequal body weight distributions were causative factors in disease development or consequences of the disease. Furthermore, gastrocnemius-soleus ankle equinus tightness (limited ankle dorsiflexion with knee extended and with knee flexed) typically accompanies gastrocnemius ankle equinus tightness (limited ankle dorsiflexion with knee extended but not flexed), but there is no assessment for making a distinction. When ankle dorsiflexion is limited with the knee extended and with the knee flexed, one can be certain that the soleus muscle is tight. Alternatively, the soleus muscle is not tight when dorsiflexion occurs with the knee flexed. Unfortunately, there is no optimal assessment for clarifying whether the gastrocnemius muscle is tight when the soleus muscle is also tight. Prospective, longitudinal studies are needed to determine the exact etiology of Sever disease. Furthermore, in the present investigation we evaluated a limited number of physical and biomechanical variables that we believe may be related to Sever disease. Additional work is needed to identify other factors that may be associated with the disease. In conclusion, children with Sever disease had higher maximum and average heel plantar pressures in the involved feet than children who were healthy. These findings indicate that high heel plantar pressures may be associated with symptoms that characterize this disease. Gastrocnemius ankle equinus may be a
predisposing factor for the increased plantar pressure in the heel in patients with Sever disease. This clinical indication may serve as a screening tool for determining whether further assessments, including plantar pressure measurements, are warranted. All authors provided concept/idea/research design, data collection and analysis, and study participants. Dr Losa-Iglesias and Dr Becerro-de-Bengoa-Vallejo provided writing, project management, and facilities/equipment. Dr Becerro-de-Bengoa-Vallejo provided consultation (including review of manuscript before submission). All study procedures conformed to the guidelines set forth in the Declaration of Helsinki, with the Research Committee of the Complutense University of Madrid, Madrid, Spain, approving the study methods. DOI: 10.2522/ptj.20120164
References 1 Ogden JA, Ganey TM, Hill JD, Jaakkola JI. Sever’s injury: a stress fracture of the immature calcaneal metaphysis. J Pediatr Orthop. 2004;24:488 – 492. 2 Peck DM. Apophyseal injuries in the young athlete. Am Fam Physician. 1995; 51:1891–1895, 1897–1898. 3 Saperstein AL, Nicholas SJ. Pediatric and adolescent sports medicine. Pediatr Clin North Am. 1996;43:1013–1033. 4 Sever JW. Apophysitis of the os calcis. N Y Med J. 1912;95:1025. 5 Kvist MH, Heinonen OJ. Calcaneal apophysitis (Sever’s disease): a common cause of heel pain in young athletes. Scand J Med Sci Sports. 1991;1:235. 6 Kim CW, Shea K, Chambers HG. Heel pain in children: diagnosis and treatment. J Am Podiatr Med Assoc. 1999;89:67–74. 7 Madden CC, Mellion MB. Sever’s disease and other causes of heel pain in adolescents. Am Fam Physician. 1996;54:1995– 2000. 8 Micheli LJ, Ireland ML. Prevention and management of calcaneal apophysitis in children: an overuse syndrome. J Pediatr Orthop. 1987;7:34 –38. 9 Wirtz PD, Vito GR, Long DH. Calcaneal apophysitis (Sever’s disease) associated with Tae Kwon Do injuries. J Am Podiatr Med Assoc. 1988;78:474 – 475. 10 McKenzie DC, Taunton JE, Clement DB, et al. Calcaneal epiphysitis in adolescent athletes. Can J Appl Sport Sci. 1981;6:123. 11 Ishikawa SN. Conditions of the calcaneus in skeletally immature patients. Foot Ankle Clin. 2005;10:503–513, vi.
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Plantar Pressures in Children With and Without Sever Disease 12 Orava S, Puranen J. Exertion injuries in adolescent athletes. Br J Sports Med. 1978; 12:4 –10. 13 Orava S, Virtanen K. Osteochondroses in athletes. Br J Sports Med. 1982;16:161. 14 Hendrix CL. Calcaneal apophysitis (Sever’s disease). Clin Podiatr Med Surg. 2005;22: 55– 62, vi. 15 Rome K. Anthropometric and biomechanical risk factors in the development of plantar heel pain: a review of the literature. Phys Ther Rev. 1997;3:123. 16 Adirim TA, Cheng TL. Overview of injuries in the young athlete. Sports Med. 2003;33: 75– 81. 17 Clain MR, Hershman EB. Overuse injuries in children and adolescents. Phys Sports Med. 1989;17:111. 18 Micheli LJ, Fehlandt AF Jr. Overuse injuries to tendons and apophyses in children and adolescents. Clin Sports Med. 1992; 11:713–726. 19 Lamm BM, Paley D, Herzenberg JE. Gastrocnemius soleus recession: a simpler, more limited approach. J Am Podiatr Med Assoc. 2005;95:18 –25. 20 White RL. Ketoprofen gel as an adjunct to physical therapist management of a child with Sever disease. Phys Ther. 2006;86: 424 – 433. 21 Digiovanni CW, Kuo R, Tejwani N, et al. Isolated gastrocnemius tightness. J Bone Joint Surg Am. 2002;84:962–970. 22 Szames SE, Forman WM, Oster J, et al. Sever’s disease and its relationship to equinus: a statistical analysis. Clin Podiatr Med Surg. 1990;7:377–384. 23 Walling AK, Grogan DP, Carty CT, et al. Fractures of the calcaneal apophysis. J Orthop Trauma. 1990;4:349 –355. 24 Silfverskio ¨ LDN. Reduction of the uncrossed two-joint muscles of the leg to one-joint muscles in spastic conditions. Acta Chir Scand. 1924;56:315. 25 Downey MS. Ankle equinus. In: McGlamry ED, Banks AS, Downey MS, eds. Comprehensive Textbook of Foot Surgery. Vol 1. 2nd ed. Baltimore, MD: Williams & Wilkins; 1992:687–730.
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26 Root ML, Orien WP, Weed JH. Normal and Abnormal Function of the Foot [Spanish edition]. Los Angeles, CA: Clinical Biomechanics Corp; 1977. 27 Downey MS, Banks AS. Gastrocnemius recession in the treatment of nonspastic ankle equinus: a retrospective study. J Am Podiatr Med Assoc. 1989;79:159 –174. 28 Oladeji O, Stackhouse C, Gracely E, Orlin M. Comparison of the two-step and midgait methods of plantar pressure measurement in children. J Am Podiatr Med Assoc. 2008;98:268 –277. 29 Evans AM, Scutter SD. Sagittal plane range of motion of the pediatric ankle joint: a reliability study. J Am Podiatr Med Assoc. 2006;96:418 – 422. 30 Wearing SC, Urry S, Smeathers JE, Battistutta D. A comparison of gait initiation and termination methods for obtaining plantar foot pressures. Gait Posture. 1999; 10:255–263. 31 Decock A, Willems T, Witvrouw E, et al. A functional foot type classification with cluster analysis based on plantar pressure distribution during jogging. Gait Posture. 2006;23:339 –347. 32 Cavanagh PR, Rodgers MM. The arch index: a useful measure from footprints. J Biomech. 1987;20:547. 33 Meyerding HW, Stuck WG. Painful heels among children [apophysitis]. JAMA. 1934; 102:1658. 34 Crawford AH, Gabriel KR. Foot and ankle problems. Orthop Clin North Am. 1987; 18:649 – 666. 35 Omey ML, Micheli LJ. Foot and ankle problems in the young athlete. Med Sci Sports Exerc. 1999;31(7 suppl):S470 –S486. 36 Hetherington BH. Sever’s disease: traction apophysitis of calcaneum. N Z J Sports Med. 1985;13:58. 37 Santopietro FJ. Foot and foot-related injuries in the young athlete. Clin Sports Med. 1988;7:563–589. 38 Bartold S. Heel pain in young athletes. Aust Podiatrist. 1993;27:103. 39 Becerro-de-Bengoa-Vallejo R, Losa-Iglesias ME, Rodriguez-Sanz D, et al. Plantar pressures in children with and without Sever’s disease. J Am Podiatr Med Assoc. 2011; 101:17–24.
40 Jahss MH, Kummer F, Michelson JD. Investigations into the fat pads of the sole of the foot: heel pressure studies. Foot Ankle. 1992;13:227–232. 41 Perry J. Anatomy and biomechanics of the hindfoot. Clin Orthop. 1983;177:9 –15. 42 McGlamry ED, Kitting RW. Aquinus foot: an analysis of the etiology, pathology and treatment techniques. J Am Podiatry Assoc. 1973;63:165–184. 43 Knutzen KM, Price A. Lower extremity static and dynamic relationships with rearfoot motion in gait. J Am Podiatr Med Assoc. 1994;84:171–180. 44 Nuber GW. Biomechanics of the foot and ankle during gait. Clin Sports Med. 1988; 7:1–15. 45 Liberson A, Lieberson S, Mendes DG, et al. Remodeling of the calcaneus apophysis in the growing child. J Pediatr Orthop B. 1995;4:74 –79. 46 Krantz MK. Calcaneal apophysitis: a clinical and roentgenologic study. J Am Podiatry Assoc. 1965;55:801– 807. 47 McCrea JD. Pediatric Orthopedics of the Lower Extremity. Mount Kisco, NY: Futura; 1985. 48 Hauser EDW. Diseases of the Foot. Philadelphia, PA: WB Saunders Co; 1939. 49 Dalgleish M. Calcaneal apophysitis [Sever’s disease] clinically based treatment. Sportsmed News. June 1990:15. 50 Subotnik SJ, ed. Sports Medicine of the Lower Extremity. New York, NY: Churchill Livingstone Inc; 1989. 51 Gregg JR, Das M. Foot and ankle problems in the preadolescent and adolescent athlete. Clin Sports Med. 1982;1:131–147. 52 Stess RM. Persistent calcaneal apophysitis. J Am Podiatry Assoc. 1973;63:147–149. 53 Garbett L. Calcaneal apophysitis: Sever’s disease. Sportsmed News. December 1991:9. 54 Bruns W, Maffulli N. Lower limb injuries in children in sports. Clin Sports Med. 2000; 19:637– 662.
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Static and Dynamic Plantar Pressures in Children With and Without Sever Disease: A Case-Control Study Ricardo Becerro-de-Bengoa-Vallejo, Marta E. Losa-Iglesias and David Rodriguez-Sanz PHYS THER. 2014; 94:818-826. Originally published online January 30, 2014 doi: 10.2522/ptj.20120164
References
This article cites 48 articles, 4 of which you can access for free at: http://ptjournal.apta.org/content/94/6/818#BIBL
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http://ptjournal.apta.org/content/suppl/2014/05/28/ptj.201 20164.DC1.html This article, along with others on similar topics, appears in the following collection(s): Injuries and Conditions: Ankle Injuries and Conditions: Foot Kinesiology/Biomechanics Pediatrics: Other Sports Physical Therapy
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Research Report
Static and Dynamic Plantar Pressures in Children With and Without Sever Disease: A Case-Control Study Ricardo Becerro-de-Bengoa-Vallejo, Marta E. Losa-Iglesias, David Rodriguez-Sanz R. Becerro-de-Bengoa-Vallejo, PhD, Escuela Universitaria de Enfermerı´a, Fisioterapia y Podologı´a, Universidad Complutense de Madrid, Madrid, Spain.
Background. Calcaneal apophysitis (Sever disease) has been reported to be the most common cause of heel pain in athletic children.
M.E. Losa-Iglesias, PhD, Facultad Ciencias de la Salud, Universidad Rey Juan Carlos, Avenida Atenas s/n 28922, Alcorco´n, Spain. Address all correspondence to Dr Losa-Iglesias at: [email protected].
tact area, distribution of body weight across the lower extremities, and prevalence of gastrocnemius ankle equinus and gastrocnemius-soleus ankle equinus (which can cause decreases in ankle dorsiflexion range of motion) in children with and without Sever disease.
Objective. The study aim was to compare plantar pressure, plantar surface con-
D. Rodriguez-Sanz, PhD, Centro Ortopedico y Quirurgico del Pie, Madrid, Spain.
Design. This was a case-control study.
[Becerro-de-Bengoa-Vallejo R, Losa-Iglesias ME, Rodriguez-Sanz D. Static and dynamic plantar pressures in children with and without Sever disease: a casecontrol study. Phys Ther. 2014;94:818 – 826.]
Twenty-eight participants had Sever disease (Sever disease group), and 28 participants were healthy (control group). Dynamic and static peak plantar pressures, plantar surface contact area, and body weight distribution were assessed with pedobarography. A goniometer was used to assess gastrocnemius and gastrocnemiussoleus ankle dorsiflexion range of motion.
© 2014 American Physical Therapy Association Published Ahead of Print: January 30, 2014 Accepted: January 22, 2014 Submitted: April 7, 2012
Methods. Participants were 56 male students enrolled in a soccer academy.
Results. Both maximum and average peak pressures and percentages of body weight supported by each heel were significantly higher in the symptomatic feet of participants in the Sever disease group than in the control group. Twenty-six participants with Sever disease but only 8 participants in the control group exhibited bilateral gastrocnemius ankle equinus.
Limitations. A limitation of the study is that measurements were obtained from participants who were symptomatic. Conclusions. Higher heel plantar pressures under dynamic and static conditions appear to be associated with Sever disease. It is unclear, however, whether these higher pressures are a predisposing factor contributing to the disease or a result of the condition. Gastrocnemius ankle equinus also may be a predisposing factor for Sever disease. Further research is needed to identify other biomechanical factors associated with the disease to enhance prevention and treatment strategies.
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Plantar Pressures in Children With and Without Sever Disease
T
he calcaneal apophysis is a cartilaginous growth center into which the Achilles tendon inserts.1,2 Apophysitis, or inflammation of an apophysis, is caused by microavulsions at the bone-cartilage junction.3 It is commonly the result of repetitive motion and overuse during periods of rapid growth. Calcaneal apophysitis was first described in 1912 by Sever4 and was later given the name Sever disease. Kvist and Heinonen5 and Kim et al6 refined the definition of Sever disease to indicate traction epiphysitis. On the basis of this definition, it is a disease most commonly associated with prepubescent children who are active in sports that involve running and jumping.7–9 The commonality of sports participation was documented by McKenzie et al,10 who conducted a retrospective study of 20 children diagnosed with Sever disease. McKenzie et al10 reported that all of the children participated in sports, with the majority participating in track and field or soccer. Sever disease has been reported to be the most common cause of heel pain in athletic children.8,11 Orava and Puranen12 and Orava and Virtanen13 found that Sever disease comprises 16.3% and 22.7% of exertion injuries in children, respectively. The heel pain limits physical activity and may interfere with activities of daily living in young athletes. The condition is self-limiting because the calcaneal cartilage disappears at 14 to 16 years of age to permit complete calcaneal ossification.5 The etiology of Sever disease is controversial.14 Potential contributing factors include participation in high-impact sports, improper footwear, running on hard surfaces, and excessive plantar heel pressures.15 The condition also is associated with radiographic changes, including variations in the normal ossification pattern.8 Currently, the cessation of June 2014
high-impact activities, thus reducing mechanical overload at the affected heel, is a standard component of treatment.16 –18 Further advancement in the treatment of Sever disease is predicated on a greater understanding of factors contributing to the pathology. Although controlling mechanical loading is a treatment strategy, we are unaware of previous work evaluating dynamic plantar pressure in children diagnosed with Sever disease. Therefore, we sought to investigate the relationship between mechanical loading and calcaneal apophysitis by measuring dynamic and static plantar pressures in young athletes with and without Sever disease. We also evaluated the distribution of body weight and plantar surface contact area between the lower extremities to determine whether asymmetrical loading is associated with the disease. Ankle dorsiflexion range of motion in children, measured with the knee in full extension, should be at least 10 degrees.19,20 Decreased ankle dorsiflexion range of motion, also called ankle equinus, differentiates the decreased ankle range of motion that is due to gastrocnemius ankle equinus from that due to gastrocnemiussoleus ankle equinus.21 The association of gastrocnemius ankle equinus, gastrocnemius-soleus ankle equinus, and Sever disease was evaluated on the basis of previous reports of a relationship between ankle equinus deformity and Achilles tendon thickening.22
Method Participants Participants in this study were male students who were enrolled in a soccer school and underwent an end-ofseason health screening. A total of 131 students between 8 and 15 years of age were evaluated for study eligibility. Exclusion criteria included
a recent history of ankle injury, such as sprain, tendinitis, or any pathology other than Sever disease, and the presence of a neurologic condition affecting either lower extremity. All children in this study were from the same school (a soccer-focused program). Thus, all were exposed to the same amount of training hours per week. We studied children who never had heel pain under these training conditions and children who experienced heel pain under the same training conditions. Of the 56 participants included in the study, 28 had symptomatic Sever disease. The left heel was symptomatic in 15 participants, the right heel was symptomatic in 5 participants, and 8 participants had bilateral heel symptoms, resulting in a total of 36 affected heels. Evaluation for the presence of Sever disease was performed by a podiatrist (R.B.B.V.). For diagnostic purposes, Sever disease was defined as pain with compression of the mediolateral calcaneus in the growth plate region.23 The pain had to be of at least 2 months’ duration, had to coincide with physical activity, and had to be severe enough to sufficiently interfere with normal physical activity, such as walking.11 Eight children were receiving treatment when they came to the school and were not allowed to play soccer because of their level of pain. Six children were receiving treatment and were still allowed to play, and 14 children reported pain at the end of the training sessions and during our evaluation. Twenty-eight of the 56 participants were healthy and comprised a conAvailable With This Article at ptjournal.apta.org • eTable: Technical Specifications of the Pressure Platform
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Plantar Pressures in Children With and Without Sever Disease trol group. These participants were selected from the total pool of eligible children by use of a random number generator program (Epidat 3.1, Pan American Health Organization, Washington, DC). There was no difference within or between groups for time spent in sports participation, including after-school or weekend training, or in competition. Procedure Before the initiation of data collection, written parental consent for study participation was obtained for each participant. The Silfverskio ¨ ld test was performed to assess the ankle range of motion and differentiate gastrocnemius ankle equinus (in which the gastrocnemius muscle limits ankle dorsiflexion range of motion) from gastrocnemius-soleus ankle equinus (in which the soleus muscle limits ankle dorsiflexion range of motion).19,24 Ankle joint dorsiflexion range of motion was determined for all participants by a clinician
with extensive experience in foot and ankle physical examinations. Ankle joint dorsiflexion range of motion was assessed by measurement with a standard clinical goniometer with the knee extended and with the knee flexed. The participant lay on his or her back with the knee flexed 90 degrees. Normal ankle dorsiflexion is approximately 10 degrees with the knee extended and 20 degrees with the knee flexed.19,25,26 Thus, the definition of gastrocnemius ankle equinus was the inability of the ankle to achieve dorsiflexion of 10 degrees with the knee extended and with the knee flexed. Gastrocnemius-soleus ankle equinus was defined as the inability of the ankle to achieve dorsiflexion beyond a neutral position with the knee extended (it remained ⬍0°) or with the knee flexed (it remained ⬍0°).21,27,28 The reported reliability of goniometric measurement of sagittal plane ankle motion in chil-
The Bottom Line What do we already know about this topic? Sever disease, one of the most common causes of heel pain in athletic children, is often associated with gastrocnemius ankle equinus.
What new information does this study offer? The study defined dynamic and static plantar pressure maps of the heel and forefoot for physically active children with and without symptomatic Sever disease and demonstrated a significant pressure increase for patients with the disease.
If you’re a patient, what might these findings mean for you? The unequal distribution of body weight across the limbs of patients with Sever disease suggests that reducing weight bearing in the affected limb can reduce plantar pressures and associated symptoms. A diagnosis of gastrocnemius ankle equinus may predispose these patients to increased plantar pressure in the heel, providing a potential screening tool to determine the need for further assessments, such as plantar pressure mapping.
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dren29 suggests that ankle dorsiflexion measures are highly variable among examiners. Measurement of gastrocnemius ankle motion is more reliable than that of soleus ankle motion, and measurement of ankle dorsiflexion with the knee extended is more reliable than that with the knee flexed.29 During measurement of ankle dorsiflexion range of motion, care was taken to maintain the subtalar joint in a neutral position to ensure that talocrural motion, not midfoot dorsiflexion (rocker bottom), was evaluated.19 Dynamic plantar pressure was measured by an independent clinician using a digital portable pressure sensor platform (Medicapteurs, Balma, France) embedded in a 5-m walkway. The technical specifications of the pressure platform are shown in the eTable (available at ptjournal. apta.org). Pressure sensor measurements from the platform were accurate to the nearest 0.001 kg/cm2. Before each use, autocalibration was performed in accordance with manufacturer specifications. During practice and testing, participants were barefoot and walked at a steady, self-selected speed. Practice trials were performed to establish a preferred walking speed for each participant and to facilitate platform striking with the entire foot. After familiarization with testing procedures was complete, data collection was initiated. A trial was considered valid when a heel-strike–toe-off pattern was observed and the walking speed was consistent.30,31 Trials that did not meet each of these criteria were not used for subsequent analysis. A 2-step method in which plantar pressure data were obtained on the second step of each foot was used for each walking trial, and data for 6 steps with each foot were collected per session from each participant.20 The mean of 6 trials per foot was used for statistical testing. Plantar
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Plantar Pressures in Children With and Without Sever Disease Table 1. Participant Characteristics XⴞSD (Range) for the Following Group: Characteristic
Sever Disease
Age (y)
10.78⫾1.46 (8–15)
Pa
10.65⫾1.75 (8–15)
1.01 (0.93–1.09)
.931
0.98 (0.94–1.01)
.142
38.9⫾7.6
39.7⫾7.9
0.98 (0.88–1.08)
.112
17.1⫾1.87
17.3⫾1.94
0.99 (0.93–1.05)
.223
0.39 (0.36–0.42)
.001
143.47⫾9.8
Weight (kg) Body mass index (kg/m2) Dorsiflexion range of motion (°)
Ratio of Means (95% Confidence Interval)
146.88⫾10.1
Height (cm)
b
Control
6.88⫾1.03 (4–8)
17.71⫾1.95 (14–20)
a
Determined with independent Student t tests. P values of less than .05 were considered statistically significant. b Total dorsiflexion range of motion measured from knee in extension to knee in flexion.
pressure data collected with the 2-step method were comparable to those collected with the midgait method; therefore, the former method may be preferred for examining children because of its ease and speed of data collection.28 Static plantar pressure measurements were collected with the same pressure sensor platform as that used during dynamic conditions. During testing, participants stood on the pressure sensor platform in a natural manner while barefoot. Participants were instructed to look straight ahead and keep their arms relaxed at the side. Plantar foot pressure measurements were collected simultaneously for both feet for 30 seconds. If the participant moved during testing, then the data were discarded and the trial was repeated. Testing continued until data were collected from 6 trials during which the participant remained stationary. The participant did not know when a trial was actually being recorded. The mean of 6 valid trials per foot was used for subsequent analysis. Data Management Data recording was performed with a personal computer linked to the pressure sensor platform. The commercially available software program S-plate (interactive rehabilitation software) for Windows (Medicapteurs) was used for all data collection June 2014
and management. Software output included pressure maps, which provided the plantar pressure magnitude (kilopascals), contact area (square centimeters), and percent body weight (%BW) distribution through each limb. The dynamic plantar pressure outline for each participant was divided into 4 distinct regions (heel, midfoot, forefoot, and toes). The heel, midfoot, and forefoot regions were defined as equal thirds of the plantar pressure outline (omitting the toes).31,32 Variables of interest for dynamic plantar pressure included the surface contact area of the forefoot and heel and the maximum and average peak pressures of the forefoot and heel. Variables of interest for static plantar pressure included the total surface contact area, surface contact area of the forefoot and heel, maximum and average peak pressures of the forefoot and heel, %BW supported by each limb, and %BW supported in the forefoot and heel. Data Analysis Demographic characteristics, including participant height, weight, age, and body mass index, and each of the plantar measurements were summarized as mean⫾standard deviation; these data were compared in children with Sever disease and children who were healthy. The ratio of means was calculated to describe
the change in 2 means. Independent Student t tests were performed to determine whether differences were statistically significant. The Kolmogorov-Smirnov test was used to confirm a normal distribution for each of the plantar measurements. Measurements that were not normally distributed were tested with a nonparametric method, the Wilcoxon test. The F test was used to confirm variance equality. If equal variance could not be confirmed, then Satterthwaite approximation was used in the t tests. To make an overall comparison, we combined the heel with more severe symptoms for the 8 participants who had bilateral heel symptoms (6 right and 2 left feet) with the feet of the 20 participants who had unilateral heel symptoms, yielding a total of 28 symptomatic feet assessed (17 left and 11 right feet). We then randomly selected 28 feet of participants without Sever disease (control feet) and matched the numbers of left and right control feet to the symptomatic feet. Thus, the comparison involved 28 symptomatic feet and 28 control feet matched by side. The association between gastrocnemius ankle equinus or gastrocnemius-soleus ankle equinus and Sever disease was evaluated with a chi-square test. In all of the analyses, statistical significance was established by a P value of less than .05. All of the analyses
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Plantar Pressures in Children With and Without Sever Disease Table 2. Dynamic Plantar Pressures Values for the Following Groupa:
Ratio of Means (95% Confidence Interval)
Pb
55.86⫾6.03
1.00 (0.94–1.06)
.890c
134.23⫾35.25
103.6⫾10.52
1.30 (1.14–1.45)
.003d
Average peak pressure (kPa)
98.55⫾25.97
74.16⫾7.73
1.33 (1.17–1.48)
⬍.001d
Surface area (cm2)
33.61⫾2.62
33.89⫾2.39
0.99 (0.95–1.03)
.688c
Maximum peak pressure (kPa)
876.16⫾90.35
91.21⫾11.14
9.61 (9.00–10.21)
⬍.001c
Average peak pressure (kPa)
648.02⫾98.47
71.56⫾7.37
9.06 (8.38–9.73)
⬍.001c
Foot Left
Variable No. of feet
Forefoot
2
Surface area (cm ) Maximum peak pressure (kPa)
Heel
Right
No. of feet
Forefoot
Forefoot
28
56.09⫾5.66
28 58.86⫾4.44
1.05 (1.01–1.10)
.035c
Maximum peak pressure (kPa)
149.16⫾32.45
106.49⫾19.82
1.40 (1.20–1.60)
.001d
Average peak pressure (kPa)
112.51⫾32.01
77.41⫾18.25
1.45 (1.19–1.72)
.003d
34.62⫾2.69
32.89⫾3.82
1.05 (0.99–1.12)
.152c
Maximum peak pressure (kPa)
839.82⫾68.65
88.18⫾10.29
9.52 (8.91–10.13)
⬍.001c
Average peak pressure (kPa)
654.37⫾61.88
70.58⫾10.5
9.27 (8.55–9.99)
⬍.001c
28
28
57.64⫾6.03
56.79⫾5.66
1.01 (0.96–1.07)
.5402c
Maximum peak pressure (kPa)
134.56⫾36.38
104.60⫾10.92
1.29 (1.15–1.43)
.0001c
Average peak pressure (kPa)
103.11⫾29.75
74.74⫾12.80
1.38 (1.20–1.55)
⬍.0001c
34.00⫾2.88
33.79⫾2.60
1.01 (0.96–1.05)
.7716c
Maximum peak pressure (kPa)
880.31⫾77.74
87.52⫾11.71
10.06 (9.45–10.67)
⬍.0001c
Average peak pressure (kPa)
664.09⫾83.52
71.48⫾7.32
9.29 (8.72–9.86)
⬍.0001c
No. of feet 2
Surface area (cm )
Surface area (cm2)
Heel
23
13
Surface area (cm )
Both left and right
Control
62.00⫾3.87
Surface area (cm2)
2
Heel
Sever Disease
a
Values are reported as mean⫾standard deviation unless otherwise indicated. P values of less than .05 were considered statistically significant. Determined with the independent Student t test. d Determined with the Wilcoxon test. b c
were performed with commercially available software (SPSS 19.0, SPSS Inc, Chicago, Illinois).
Results
Figure 1. Dynamic plantar pressure map of the heel and forefoot. Red indicates areas with the highest plantar pressures. (A) Increase in heel pressure in a participant with Sever disease and gastrocnemius ankle equinus. (B) Normal distribution in a participant from the control group with no gastrocnemius ankle equinus.
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There was no difference between the groups in participant age, height, or body mass index (Tab. 1). There was a statistically significant difference between the groups in the prevalence of gastrocnemius ankle equinus, with 26 of 28 participants in the Sever disease group but only 8 of 28 participants in the control group exhibiting bilateral gastrocnemius ankle equinus (P⫽.019). There was no difference between the groups in the prevalence of gastrocnemius-soleus ankle equinus, with 3 of 28 participants in both
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Plantar Pressures in Children With and Without Sever Disease Table 3. Static Plantar Pressures Values for the Following Groupa:
Ratio of Means (95% Confidence Interval)
Pb
69.46⫾2.56
1.00 (0.98–1.02)
.999c
39.00⫾1.04
38.57⫾1.71
1.01 (0.99–1.03)
.277c
Heel
30.52⫾1.34
30.89⫾1.71
0.99 (0.96–1.02)
.400c
Forefoot, maximum peak pressure
95.76⫾3.69
91.11⫾5.4
1.05 (1.02–1.08)
.005d
Forefoot, average peak pressure
74.28⫾4.03
70.32⫾3.41
1.06 (1.03–1.09)
⬍.001c
Heel, maximum peak pressure
347.88⫾24.69
83.06⫾1.92
4.19 (4.06–4.32)
⬍.001c
Heel, average peak pressure
258.59⫾27.7
71.38⫾1.80
3.62 (3.46–3.79)
⬍.001c
13
28
Total
69.62⫾2.18
69.46⫾2.56
1.00 (0.98–1.02)
.851c
Forefoot
39.00⫾1.96
38.57⫾1.71
1.01 (0.98–1.04)
.479c
Heel
30.62⫾1.33
30.89⫾1.71
0.99 (0.96–1.02)
.609c
Forefoot, maximum peak pressure
95.01⫾3.13
92.35⫾5.5
1.03 (1.00–1.06)
.110c
Forefoot, average peak pressure
72.62⫾3.76
1.04 (1.01–1.07)
.035d
Foot and Measure Left
Variable
Sever Disease
Control
23
28
Total
69.52⫾1.75
Forefoot
No. of feet 2
Surface area (cm )
Plantar pressure (kPa)
Right
No. of feet 2
Surface area (cm )
Plantar pressure (kPa)
Both left and right
Heel, maximum peak pressure
325.90⫾23.91
82.84⫾2.3
3.93 (3.77–4.10)
⬍.001c
Heel, average peak pressure
247.73⫾34.9
70.87⫾1.04
3.50 (3.22–3.77)
⬍.001c
28
28
Total
69.21⫾1.57
69.46⫾2.56
1.00 (0.98–1.01)
.6634c
Forefoot
38.89⫾1.31
38.57⫾1.71
1.01 (0.99–1.03)
.4369c
Heel
30.32⫾1.33
30.89⫾1.71
0.98 (0.96–1.01)
.1723c
Forefoot, maximum peak pressure
95.78⫾3.52
92.35⫾5.64
1.04 (1.01–1.07)
.0091c
Forefoot, average peak pressure
74.07⫾4.06
70.45⫾3.24
1.05 (1.02–1.08)
.0003c
Heel, maximum peak pressure
339.40⫾26.96
83.02⫾2.10
4.09 (3.96–4.22)
⬍.0001c
Heel, average peak pressure
254.56⫾29.75
71.33⫾1.27
3.57 (3.41–3.73)
⬍.0001c
No. of feet 2
Surface area (cm )
Plantar pressure (kPa)
69.8⫾2.95
a
Values are reported as mean⫾standard deviation unless otherwise indicated. P values of less than .05 were considered statistically significant. Determined with the independent Student t test. d Determined with the Wilcoxon test. b c
groups exhibiting bilateral gastrocnemius-soleus ankle equinus (P⫽1.000). When we assessed dynamic plantar pressure measurements, we found that maximum and average peak pressures were significantly higher in the affected heel of participants in the Sever disease group than in the control group (Tab. 2, Fig. 1). Maximum and average forefoot pressures were also significantly higher on the side of the affected heel of partici-
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pants in the Sever disease group than in the control group (Tab. 2, Fig. 1). There was no difference between groups in surface contact area (Tab. 2). The ratios of means were consistent with the P values. The lower bound of a confidence interval for a ratio of means was greater than 1 when the mean for the Sever disease group was significantly higher than that for the control group (P⬍.05). When we assessed static plantar pressures, we found that maximum
and average peak pressures were higher in both the heel and the forefoot on the involved side of participants in the Sever disease group than in the control group (Tab. 3, Fig. 2). There was no difference between groups in total, heel, or forefoot surface contact area (Tab. 3). The %BW supported by the forefoot of each foot was significantly lower in participants in the Sever disease group than in the control group for both feet (Tab. 4). The %BW supported by the heel was significantly higher in participants in the Sever disease
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Plantar Pressures in Children With and Without Sever Disease
Figure 2. Static plantar pressure map of the heel and forefoot. Red indicates areas with the highest plantar pressures. (A) Increase in pressure in both heels in a participant with Sever disease and gastrocnemius ankle equinus. (B) Normal distribution in a participant from the control group with no gastrocnemius ankle equinus.
group than in the control group for both feet (P⬍.001) (Tab. 4), indicating a significant load for both heels of participants in the Sever disease group.
Discussion Many authors4,5,10,12,18,33–38 have noted that children with Sever disease are regular participants in sports activities. In the present investigation, we compared the dynamic and static plantar pressures in physically active children with symptomatic Sever disease. Our comparison involved children who spent the
same amounts of time in physical activity. The higher plantar pressures found in participants with a symptomatic foot and Sever disease in the present study are consistent with the findings of a previous investigation.39 Higher maximum and average peak pressures and higher %BW supported by the symptomatic heel could translate to a secondary injury to the immature calcaneal cartilage. Overload in tissues may be associated with an inability to adequately attenuate forces during gait. Lower loading rates are widely regarded as less damaging than higher loading
Table 4. Body Weight Distribution Values for the Following Groupa Pb
Foot
Variable
Sever Disease
Control
Left
No. of feet
23
28
Total
48.11⫾0.99
51.68⫾1.68
.001
Forefoot
17.57⫾0.88
31.29⫾0.90
.001
Heel
30.54⫾1.07
20.39⫾1.42
.001
13
28
Total
51.89⫾0.99
48.32⫾1.68
.001
Forefoot
18.79⫾0.79
27.39⫾2.08
.001
Heel
33.11⫾1.20
20.93⫾1.02
.001
Right
No. of feet
a
Values are reported as mean⫾standard deviation percent body weight unless otherwise indicated. b Determined with independent Student t tests. P values of less than .05 were considered statistically significant.
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rates. Jahss et al40 postulated that if force or repetition of force is not attenuated to below a critical level, then tissue destruction can result; healing responses can lead to further structural changes and alterations in tissue mechanics, which can increase forces on the heel during gait and lead to repetitive microtrauma to the subcalcaneal tissues.41 This scenario supports the pathophysiologic concept most often presented in the literature of Sever disease as an overuse syndrome caused by repetitive microtrauma from increased traction on the apophysis.8,42– 44 Our investigation identified an unequal distribution of body weight across the limbs in participants with Sever disease. The %BW in the symptomatic heel and in the forefoot of the involved foot of participants with Sever disease was significantly higher than that in the control group. In the absence of differences in surface contact area, these findings suggest that weight-bearing strategies may be a significant factor contributing to elevated plantar pressure in the involved foot of children with Sever disease. Similarly, in a previous case-control study in which static plantar pressures and distribution of body weight across the 2 lower extremities were evaluated in children with and without calcaneal apophysitis,39 participants in the control group (who had no history of heel pain) had a more equal distribution of body weight, with each foot supporting approximately half the load. Collectively, these findings suggest that balancing weight distribution between the sides, thus reducing weight bearing by the affected limb, can serve as an effective strategy for reducing plantar pressures and the symptoms associated with Sever disease. Studies that specifically test this clinical intervention strategy are needed to validate this hypothesis.
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Plantar Pressures in Children With and Without Sever Disease With the 2-step method used in the present investigation, 93% (26/28) of symptomatic participants exhibited bilateral gastrocnemius ankle equinus, whereas only 10% (3/28) exhibited bilateral gastrocnemius-soleus ankle equinus. The presence of a potential equinus deformity has been reported in patients with foot and ankle complaints.21 Furthermore, gastrocnemius ankle equinus and gastrocnemius-soleus ankle equinus are not uncommon among people who are asymptomatic.21 The exact mechanism by which ankle equinus may influence Sever disease is unknown.19 The presence of gastrocnemius ankle equinus may contribute to mechanical overloading in the symptomatic heel as a consequence of soft tissue tightness. This theory is supported by an investigation performed by Szames et al,22 who evaluated 79 cases of calcaneal apophysitis in 53 patients. They found that 82.3% of the cases had ankle equinus due to muscular retraction.22 They did not, however, distinguish between gastrocnemius ankle equinus contractures and gastrocnemius-soleus ankle equinus contractures. The pathogenesis of Sever disease has been suggested to occur through repetitive microtrauma at the apophysis as a consequence of increased musculotendinous traction. The calcaneal growth plate and the apophysis are situated in an area subject to high stress from the plantar fascia and Achilles tendon.45 The theory that a tight triceps surae muscle causes excessive tension through the Achilles tendon and increases traction on the apophysis has been commonly cited as a mechanical factor contributing to Sever disease.3,7,8,17,18,22,46 –54 The same musculotendinous tightness contributes to ankle equinus deformity. The strong relationship between calcaneal apophysitis and gastrocnemius ankle equinus may explain why June 2014
treatments that include a heel lift to reduce Achilles tendon tension and limitation of strenuous activity are effective in relieving symptoms in patients with Sever disease. An important limitation of the present study is that measures were obtained from participants who were symptomatic. We could not determine whether the elevated plantar pressures and unequal body weight distributions were causative factors in disease development or consequences of the disease. Furthermore, gastrocnemius-soleus ankle equinus tightness (limited ankle dorsiflexion with knee extended and with knee flexed) typically accompanies gastrocnemius ankle equinus tightness (limited ankle dorsiflexion with knee extended but not flexed), but there is no assessment for making a distinction. When ankle dorsiflexion is limited with the knee extended and with the knee flexed, one can be certain that the soleus muscle is tight. Alternatively, the soleus muscle is not tight when dorsiflexion occurs with the knee flexed. Unfortunately, there is no optimal assessment for clarifying whether the gastrocnemius muscle is tight when the soleus muscle is also tight. Prospective, longitudinal studies are needed to determine the exact etiology of Sever disease. Furthermore, in the present investigation we evaluated a limited number of physical and biomechanical variables that we believe may be related to Sever disease. Additional work is needed to identify other factors that may be associated with the disease. In conclusion, children with Sever disease had higher maximum and average heel plantar pressures in the involved feet than children who were healthy. These findings indicate that high heel plantar pressures may be associated with symptoms that characterize this disease. Gastrocnemius ankle equinus may be a
predisposing factor for the increased plantar pressure in the heel in patients with Sever disease. This clinical indication may serve as a screening tool for determining whether further assessments, including plantar pressure measurements, are warranted. All authors provided concept/idea/research design, data collection and analysis, and study participants. Dr Losa-Iglesias and Dr Becerro-de-Bengoa-Vallejo provided writing, project management, and facilities/equipment. Dr Becerro-de-Bengoa-Vallejo provided consultation (including review of manuscript before submission). All study procedures conformed to the guidelines set forth in the Declaration of Helsinki, with the Research Committee of the Complutense University of Madrid, Madrid, Spain, approving the study methods. DOI: 10.2522/ptj.20120164
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Static and Dynamic Plantar Pressures in Children With and Without Sever Disease: A Case-Control Study Ricardo Becerro-de-Bengoa-Vallejo, Marta E. Losa-Iglesias and David Rodriguez-Sanz PHYS THER. 2014; 94:818-826. Originally published online January 30, 2014 doi: 10.2522/ptj.20120164
References
This article cites 48 articles, 4 of which you can access for free at: http://ptjournal.apta.org/content/94/6/818#BIBL
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