Authors: Tan X. Jerilyn, BHlthSc, MPodPrac(Hons) Hylton B. Menz, PhD George S. Murley, PhD Shannon E. Munteanu, PhD
Foot Pain
Affiliations: From the Discipline of Podiatry, School of Allied Health (TXJ, HBM, GSM, SEM), and Lower Extremity and Gait Studies Program, School of Allied Health (HBM, GSM, SEM), La Trobe University, Bundoora, Victoria, Australia; and Department of Podiatry, Singapore General Hospital, Singapore (TXJ).
Correspondence: All correspondence and requests for reprints should be addressed to: Shannon E. Munteanu, PhD, Discipline of Podiatry, School of Allied Health, La Trobe University, Bundoora, Victoria 3086, Australia.
Disclosures: This study was funded by La Trobe University School of Allied Health. Prof Hylton Menz is currently a National Health and Medical Research Council Senior Research Fellow (ID: 1020925). The study sponsors had no involvement in the study design, collection, analysis, and interpretation of data; in the writing of the manuscript; and in the decision to submit the manuscript for publication. Financial disclosure statements have been obtained, and no conflicts of interest have been reported by the authors or by any individuals in control of the content of this article.
0894-9115/16/9502-0103 American Journal of Physical Medicine & Rehabilitation Copyright * 2015 Wolters Kluwer Health, Inc. All rights reserved. DOI: 10.1097/PHM.0000000000000350
ORIGINAL RESEARCH ARTICLE
Effectiveness of Shoe Stiffening Inserts for First Metatarsophalangeal Joint Osteoarthritis A Proof-of-Concept Study ABSTRACT Jerilyn TX, Menz HB, Murley GS, Munteanu SE: Effectiveness of shoe stiffening inserts for first metatarsophalangeal joint osteoarthritis: a proof-of-concept study. Am J Phys Med Rehabil 2016;95:103Y111.
Objective: The objective of this study was to determine the feasibility of shoe stiffening inserts to reduce pain in first metatarsophalangeal joint osteoarthritis.
Design: Thirty-one participants with first metatarsophalangeal joint osteoarthritis were prescribed shoe stiffening inserts and were evaluated at baseline and at 1 and 3 mos. The primary outcome measure was foot pain, assessed using the foot pain domain of the Foot Health Status Questionnaire (possible score ranges from 0 to 100). Secondary outcome measures included foot-related disability (foot function domain of the Foot Health Status Questionnaire), self-reported treatment effectiveness, use of rescue medication and other co-interventions, and adverse events.
Results: At 1 and 3 mos, statistically significant improvements in foot pain and foot-related disability were observed (mean difference at 3 mos: foot pain = 18.8, 95% confidence interval, 13.3Y24.3; foot function = 11.8, 95% confidence interval, 4.3Y17.3). Treatment was reported to be effective by 78% of participants. Few participants (4%) reported using pain-relieving medication. Minor adverse events were reported by 30% of participants.
Conclusions: Full-length shoe stiffening inserts may be an effective intervention in first metatarsophalangeal joint osteoarthritis. However, further controlled studies are required. Key Words:
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Osteoarthritis, Metatarsophalangeal Joint, Hallux Rigidus, Foot Orthoses
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F
irst metatarsophalangeal joint (MTPJ) osteoarthritis (OA) is a common degenerative disorder of the foot.1,2 The population prevalence of symptomatic radiographic first MTPJ OA has recently been estimated at 7.8%, with a higher prevalence observed in females, older people, and those from lower socioeconomic backgrounds.3 First MTPJ OA is characterized by localized pain, stiffness, and reduced joint range of motion.4 These symptoms have been speculated to be caused by dorsal compression at the joint between the first metatarsal head and proximal phalanx of the hallux that occurs during the propulsive phase of gait.2 In addition, the restricted joint dorsiflexion that occurs in first MTPJ OA leads to overloading of the hallux during propulsion, which may further aggravate pain.5,6 Other reported changes include altered gait patterns5,7 and a significant reduction in both foot-specific and general health-related quality-of-life.8 Seventy-one percent of people with first MTPJ OA report the condition to be disabling.3 The treatment goals for first MTPJ OA are to reduce pain and stiffness and to prevent further degeneration of the joint.9,10 At present, there are no evidence-based guidelines for the management of this condition. However, nonsurgical management is recognized as the first-line therapy.11 Numerous nonsurgical interventions have been proposed including pharmaceutic interventions, physical therapy, and mechanical interventions (such as accommodative and customized orthoses or insoles, strapping, splinting, and footwear modifications).12 Despite the broad range of treatment options for this disorder, very few have undergone rigorous scientific evaluation.12 Full-length shoe stiffening inserts are commonly recommended as an intervention for first MTPJ OA.12 Shoe stiffening inserts are made from a thin, rigid material that is placed inside the shoe with the aim of reducing the rate and magnitude of dorsiflexion at the MTPJs during the propulsive phase of gait. This effect is thought to reduce the symptoms of first MTPJ OA by decreasing the amount of motion and the resultant dorsal compression at the first MTPJ that occurs during propulsion.13 There is some evidence to suggest that shoe stiffening inserts can reduce dorsiflexion of the first MTPJ during gait. A study using participants with midfoot OA showed that shoe stiffening inserts significantly decreased first MTPJ dorsiflexion range of motion and first metatarsal range of motion.14 Supporting this, a recent biomechanical study using asymptomatic individuals showed that
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the addition of shoe stiffening inserts into shoes significantly reduced maximum dorsiflexion occurring at the first MTPJ during propulsion.15 Although these biomechanical effects on the first MTPJ would suggest that shoe stiffening inserts may favorably influence symptoms of first MTPJ OA, no study has investigated their effectiveness in reducing these symptoms. Therefore, the purpose of this study was to determine the feasibility (including effects on foot pain and foot-related disability, and rate of adverse effects) of using shoe stiffening inserts as a treatment for symptomatic first MTPJ OA.
METHODS This study used a prospective case-series design that involved an initial assessment, followed by a baseline assessment, with 1 and 3-mo follow-ups. All assessments were undertaken at the La Trobe University Health Sciences Clinic, Bundoora (Victoria, Australia). Ethical approval was granted from the La Trobe University Faculty of Health Sciences Human Ethics Committee (number FHEC12/188). Informed consent was obtained from all participants. The study was registered with the Australian New Zealand Clinical Trials Registry (ACTRN363501).
Participants Participants were recruited between February and April 2013. The study was advertised through local newspapers and posters displayed on public notice boards of universities and social clubs in Melbourne. Inclusion criteria were as follows: aged at least 18 yrs, symptoms of first MTPJ pain for at least 3 mos in one foot or in both feet, pain severity of at least 20 mm on a 100-mm visual analog pain scale at one or both first MTPJ(s),16 radiographic evidence of first MTPJ OA (score of Q2 for either osteophytes or joint space narrowing using the La Trobe University radiographic classification atlas17), and a willingness to discontinue consuming all pain-relieving medications (except paracetamol) for first MTPJ pain for 2 wks before the baseline assessment and then during the study. Participants who consumed paracetamol were required to discontinue its use at least 24 hrs before the baseline assessment and follow-up assessments.18 Participants were also required to refrain from receiving concurrent treatment of the pain at their first MTPJ during the study period, wear shoes that can accommodate the shoe stiffening inserts, and be able to ambulate without the need for assistive devices such as a cane.
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Exclusion criteria were as follows: previous surgery on the symptomatic first MTPJ; intraarticular injection at the first MTPJ in the last 3 mos; significant deformity of the first MTPJ including hallux valgus (grade 3 or 4 using the Manchester Scale19); presence of confounding conditions that may influence pain and functional assessments at the first MPTJ, such as metatarsalgia, symptomatic degenerative joint disease of the foot (other than the first MTPJ), and painful callus; and the presence of systemic inflammatory conditions or diabetes. During the baseline assessment, the following participant characteristics were determined by the same investigator (TXJ): age (in years); sex; height (in centimeters); weight (in kilograms); waist-hip ratio; duration of symptoms (in months); side(s) affected; severity of pain when walking during previous week using a 100-mm visual analog pain scale20; previous treatment of first MTPJ pain; highest level of education21; passive, nonYweightbearing dorsiflexion range of motion of the first MTPJ20; foot posture using the Foot Posture Index-622; and the style of footwear most usually worn using the Footwear Assessment Tool.23
Radiographic Assessment Participants were required to undergo radiographic imaging of their symptomatic foot (or most symptomatic foot) to determine the presence and severity of first MTPJ OA. Dorso-plantar and lateral radiographic projections were obtained with the participant weight bearing in a relaxed bipedal stance position, as described previously.17 The severity of the osteophytes and the joint space narrowing at the first MTPJ were determined using the La Trobe University radiographic atlas for first
MTPJ OA.17 All measures were conducted by one experienced rater (SEM) who was involved in the development of the atlas. Participants were diagnosed as having radiographic first MTPJ OA if a score of 2 or more was graded for either osteophytes or joint space narrowing in either the dorso-plantar or lateral radiographic projections.17 The atlas has excellent reliability.17
Full-Length Shoe Stiffening Inserts Participants were prescribed a single (or a pair, if symptoms were bilateral) full-length shoe stiffening insert at the baseline assessment. The shoe stiffening inserts are low mass (22 g for 28 cm length insert of Bsoft[ stiffness) with minimal thickness (approximately 1.1 mm) to allow easy fitting into different types of footwear. The shoe stiffening inserts are commercially available and are fabricated from semirigid carbon graphite (Otto Bock Springlite Carbon Foot Plates, Otto Bock Pty Ltd, Baulkham Hills, Australia) with the following design characteristics: (1) full length that extends from the heel to the tip of the toes and (2) no arch buildup or contour at the heel (Fig. 1). The shoe stiffening inserts are available at varying stiffness dependent on the individual_s body weight. As there are no empirical guidelines to suggest the most appropriate stiffness for use, participants were prescribed an insert of either Bsoft[ or Bmedium[ stiffness, where a soft stiffness insert was more flexible than a medium stiffness insert. Selection of insert type was dependent on the participant_s preference based on the comfort of the inserts that was evaluated at baseline. The shoe stiffening insert was placed beneath the liner of the participants_ footwear. If the footwear did not have a liner, the insert was placed inside the shoes and participants
FIGURE 1 Full-length shoe stiffening insert of 1-mm semirigid carbon graphite (Otto Bock Springlite Carbon Foot Plates). www.ajpmr.com
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were provided with the option of having the insert covered with 2.0 mm of Lunasoft EVA foam.
Outcome Measures Outcome measures were performed on three occasions: at baseline and then at 1 and 3 mos after intervention. Postal survey was used to collect data at 1 and 3 mos. One month was considered the earliest time of maximum effect; however, 3 mos was considered a clinically feasible time point when maximum treatment effect would have been expected and was therefore set as the primary end point.16
Primary Outcome Measure The primary outcome measure was the foot pain domain of the Foot Health Status Questionnaire (FHSQ).24 The FHSQ consists of 13 questions that assess foot health in four domains: Bfoot pain,[ Bfoot function,[ Bfootwear,[ and Bgeneral foot health.[ There are a total of four questions under the foot pain domain. Questions are scored using a Likert response format and the participants_ responses are transformed into a score ranging from 0 to 100 for each domain (0, worst foot health; 100, optimal foot health).24 The FHSQ has been subjected to an extensive validation process, with each domain being shown to demonstrate high internal consistency (Cronbach > Q 0.851), good reproducibility (intraclass correlation coefficients Q 0.740), and good discriminative capabilities.24 Further, the FHSQ is rated as one of the highest-quality foot health status measures currently available25,26 and has been used previously in clinical trials of interventions for first MTPJ OA.16
Secondary Outcome Measures The following were the secondary outcome measures: (i) Foot-related disability (using the foot function domain of the FHSQ).24 (ii) Self-reported magnitude of symptom change (using a 15-point Likert scale). This variable was then dichotomized into the categories of Beffective[ (Ba very great deal better,[ Ba great deal better,[ Ba good deal better,[ Bmoderately better,[ and Bsomewhat better[) and Bineffective[ (Ba little better,[ Babout the same, hardly any better at all,[ Bno change,[ Babout the same, hardly any worse at all,[ Ba little worse,[ Bsomewhat worse,[ Bmoderately worse,[ Ba good deal worse,[ Ba great deal worse,[ and Ba very great deal worse[).27 (iii) Level of physical activity (using the Stanford 7day Physical Activity Recall Questionnaire).28
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(iv) Comfort of the shoe insert(s) (using a fivepoint Likert scale response [Bvery comfortable,[ Bsomewhat comfortable,[ Bneither comfortable nor uncomfortable,[ Bsomewhat uncomfortable,[ or Bvery uncomfortable[]). This variable was then dichotomized into categories of Bcomfortable[ (Bvery comfortable,[ Bsomewhat comfortable,[ and Bneither comfortable nor uncomfortable[) and Buncomfortable[ (Bsomewhat uncomfortable[ or Bvery uncomfortable[). (v) Adherence to the use of the shoe stiffening insert(s) by asking participants the number of days (and number of hours each day) the insert(s) was worn on average in the past week. Total hours per week was determined by multiplying number of days and number of hours each day. (vi) Use of paracetamol rescue medication (used as a backup in case of insufficient efficacy of the shoe stiffening inserts and recorded through the use of a medication diary that participants self-completed) and other co-interventions.29 (vii) Tolerability of the shoe stiffening insert(s) (determined by the frequency, types, and severity of adverse events).30
Sample Size The sample size was determined a priori based on the FHSQ pain domain as the primary outcome measure. Using a power of 80%, a minimal important difference of 14 points in the foot pain domain of the FHSQ,16 an SD of 18.9,16 assuming a 10% dropout rate, and a significance level set at > less than 0.05, the authors estimated that a total of 31 participants were required.
Statistical Analysis Symptoms were described without specific reference to an individual foot (i.e., bilateral pain was evaluated as one independent sample), and assessment findings were taken from the more symptomatic foot. Statistical analysis was performed using SPSS version 21.0 (IBM Corporation, USA). All data were explored for assumptions of statistical analyses including normality (by visual inspection of histograms and Q-Q plots, determination of skewness and kurtosis [values G |2|], and Shapiro-Wilk tests). The authors used completer analysis only (the authors did not replace missing data at 1 and 3 mos, as this was a proof-of-concept study). Differences in scores for the outcome measures (i.e., foot pain, foot-related disability, and level
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of physical activity) at 1 and 3 mos were compared using a repeated-measures one-way analysis of variance. P less than 0.05 was considered statistically significant. Post hoc comparisons (vs. baseline) were performed using Bonferroni-adjusted paired t tests (P G 0.025), with 3 mos being the primary end point.
RESULTS Thirty-one participants were assessed and received the intervention between February and May 2013. A total of 74 individuals expressed interest in the study. Among the 43 individuals who were excluded from the study, 32 declined to participate and 11 did not meet the inclusion criteria (Fig. 2). Data were obtained from 30 participants at 1 mo and 27 participants at 3 mos (Fig. 2). Table 1 displays the participants_ characteristics at baseline. Of the 31 participants, 22 (71.0%) chose to use a shoe stiffening insert of a medium flexibility.
difference = 18.8; 95% CI, 13.3Y24.3; P G 0.001) (Table 2).
Foot-Related Disability, Perception of Treatment Effectiveness, and Physical Activity There was a significant difference in FHSQ foot function scores between the three time points (F2 = 8.390; P = 0.001). Post hoc comparisons revealed statistically significant improvements in foot function at 1 mo (mean difference = 10.8; 95% CI, 4.4Y17.2; P = 0.002) and 3 mos (mean difference = 11.8; 95% CI, 4.3Y17.3; P = 0.002) (Table 2). For the outcome Bself-reported magnitude of symptom change,[ 70.0% (21 of 30) and 77.8% (21 of 27, 77.7%) of participants reported that the treatment was effective at 1 and 3 mos, respectively. There was no significant change in physical activity during the study (F2 = 0.059; P = 0.943).
Comfort and Adherence Primary Outcome Measure: Foot Pain There was a significant difference in FHSQ foot pain scores between the three time points (F2 = 37.406; P G 0.001). Post hoc comparisons revealed statistically significant improvements in foot pain at 1 mo (mean difference = 15.2; 95% confidence interval [CI], 9.1Y21.2; P G 0.001) and 3 mos (mean
For the outcome Bcomfort of the shoe insert(s),[ 30 (of 31, 96.8%), 25 (of 30, 86.7%), and 26 (of 27, 96.3%) participants reported that the shoe stiffening inserts were comfortable at baseline and at 1 and 3 mos, respectively. Participants wore the shoe stiffening inserts for a mean (SD) of 36.9 (27.3) hrs/wk at 1 mo and 41.7 (28.8) hrs/wk at 3 mos.
FIGURE 2 Participant flow diagram. *One participant had both gout and diabetes. www.ajpmr.com
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TABLE 1 Participant characteristics (N = 31) Characteristic
Value
Age, yrs Male sex, n (%) Height, cm Weight, kg BMI, kg/m2 Waist-hip ratio Duration of symptoms, mos Side affected (left/right/bilateral), n Target side (left), n (%) Severity of OA (median, IQR) [range]a Dorsal osteophytes Dorsal joint space narrowing Lateral osteophytes Lateral joint space narrowing Total score Highest level of education, (median, IQR) [range]b Passive, nonYweight-bearing dorsiflexion range of motion of the first MTPJ, degrees Foot posturec Walking pain (VAPS) Previous treatment, n (%) Style of footwear most regularly worn, n (%)d Walking shoe Boot Slipper Sandal Athletic shoe Oxford shoe High heel shoe Court shoe Other
55.5 (11.8) 12 (38.7) 168.3 (8.9) 71.8 (20.0) 25.0 (4.9) 0.86 (0.1) 50.8 (46.1) 4/15/12 10 (32.3) 2 (1) [1Y3] 1 (1) [0Y3] 2 (1) [0Y3] 1 (1) [0Y3] 7.2 (2.5) 6 (3) [4Y7] 47.7 (14.8) 2.7 (3.5) 53.5 (19.0) 27 (87.1) 9 3 3 2 4 2 2 1 5
(29.0) (9.7) (9.7) (6.5) (12.9) (6.5) (6.5) (3.2) (16.1)
Data are expressed as mean (SD) unless shown otherwise. a Severity of OA graded using the radiographic atlas of Menz et al.17 where the presence of osteophytes was graded as absent (score = 0), small (score = 1), moderate (score = 2), and severe (score = 3), and the presence of joint space narrowing was graded as none (score = 0), reduced (score = 1), severe (score = 2), and joint fusionVat least one point (score = 3). b Education was recorded as no formal schooling (score = 1), less than primary school (score = 2), primary school completed (score = 3), high school (or equivalent) completed (score = 4), technical and further education completed (score = 5), college/ university completed (score = 6), and postgraduate degree completed (score =7). c Foot posture was assessed using the Foot Posture Index-6.22 d Style of footwear most regularly worn was assessed using the Footwear Assessment Tool.23 BMI, body mass index; IQR, interquartile range; VAPS, visual analog pain scale.
Use of Co-Interventions At 1 mo, 9 participants (of 31 calendars received, 29.0%) reported using medication (8 paracetamol, 1 nonsteroidal anti-inflammatory drug). At 2 mos, 3 participants (of 27 calendars received, 11.1%) reported using a nonsteroidal antiinflammatory drug, and at 3 mos, 1 participant (of 25 calendars received, 4.0%) reported using a nonsteroidal anti-inflammatory drug. Changes to footwear were reported by 12 (of 30, 40.0%) and 7 (of 27, 25.9%) participants at 1 and 3 mos. One participant reported using massage at the first MTPJ during the study.
Adverse Events Nine (of 30, 30.0%) and 4 (of 27, 14.8%) participants reported at least one adverse event at 1 and
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3 mos, respectively. During the study, the most common adverse events were foot pain (excluding pain at the first MTPJ) (n = 4) and knee pain (n = 3). Two participants withdrew from the study after 1 mo because of adverse events (knee pain [n = 1]; heel pain [n = 1]).
DISCUSSION This proof-of concept study showed that the provision of shoe stiffening inserts was associated with statistically significant improvements in foot pain and foot-related disability in people with first MTPJ OA that occurred as early as 1 mo and were maintained for the study duration of 3 mos. Furthermore, the shoe stiffening inserts were well tolerated; they were worn for an average of 41.7 hrs/wk at 3 mos.
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TABLE 2 Continuous-scaled outcome measures at baseline and at 1 and 3 mos Outcome Measure Foot painb Baseline 1 mo 3 mosc,d Foot-related disabilityb Baseline 1 mo 3 mosd Physical activity, kcal/day Baseline 1 mo 3 mosd
Baseline
Mean Difference (95% CI)
Pa
55.4 (17.9) 70.0 (14.3) 73.8 (11.9)
V 15.2 (9.1 to 21.2) 18.8 (13.3 to 24.3)
V G0.001 G0.001
71.0 (24.9) 81.7 (16.7) 84.4 (14.6)
V 10.8 (4.4 to 17.2) 11.8 (4.3 to 17.3)
0.002 0.002
2963 (831) 2930 (836) 2921 (982)
V j17 (j249 to 216) j27 (j251 to 196)
0.884 0.802
a
Compared with baseline using paired t tests. Higher scores indicate better foot health. c Bold entry denotes the primary outcome measure and the primary end point. d n = 26 because 1 participant (of the 27 participants who returned questionnaires) did not respond to these questionnaire items. b
The primary outcome measure was foot pain assessed using the FHSQ foot pain domain. The magnitude of improvement in foot pain at 1 mo (15.2 points; 95% CI, 9.1Y21.2) and 3 mos (18.8 points; 95% CI, 13.3Y24.3) was greater than the reported minimal important difference of 14 points.16 This suggests that the improvement in foot pain associated with the use of shoe stiffening inserts may be clinically important. In addition, other outcomes suggested an improvement in symptoms and function in participants during this study. Foot-related disability (FHSQ foot function domain) improved 10.8 points (95% CI, 4.4Y17.2) at 1 mo and 11.8 points (95% CI, 4.3Y17.3) at 3 mos. This is also greater than the reported minimal important difference of 7 for foot-specific problems,27 which highlights the clinical importance of this finding. These improvements are consistent with the observation that 78% of study participants reported their treatment to be effective at 3 mos (using the cutoff for defining treatment effectiveness for the variable self-reported magnitude of symptom change). Pain associated with first MTPJ OA has been attributed to dorsal compression at the joint during the propulsive phase of gait. Previous literature has shown that shoe stiffening inserts reduce first MTPJ dorsiflexion range of motion14 and the magnitude of dorsiflexion at the first MTPJ.15 This suggests that the shoe stiffening inserts may have reduced symptoms in the participants by reducing first MTPJ dorsiflexion, thereby reducing the dorsal compression that occurs during propulsion. Further research is required to test this hypothesis as the authors did not directly measure the effects of www.ajpmr.com
the shoe stiffening inserts on the kinematics of the first MTPJ. Although the use of shoe stiffening inserts was associated with an improvement in symptoms of first MTPJ OA, several participants (30% at 1 mo) reported at least one adverse event. The most common adverse events observed in this study were foot pain (excluding first MTPJ pain) (n = 4) and knee pain (n = 3). Two participants withdrew after 1 mo because of the development of severe heel and knee pain. The mechanism for the development of these more severe adverse events is unclear. It is possible that the shoe stiffening inserts may increase the risk of plantar foot pain by increasing plantar pressures at specific regions of the foot such as the heel.31,32 The shoe stiffening inserts may also cause changes to lower limb kinematics and kinetics through the restriction of first MTPJ dorsiflexion,33 which may increase the risk of proximal pathologies in predisposed individuals. There is evidence that rigid-soled shoes lead to higher knee moments during locomotion.34 The decrease in shoe flexibility restricts normal foot motion and in turn leads to an increase in the external knee adduction moment.34,35 Considering the association between increased external knee adduction moment and the onset of knee pain,36,37 it is plausible that the shoe stiffening inserts used in the current study may have led to an increase in knee pain through the increase of external knee adduction moment. Further study is required to confirm this hypothesis. This study has several strengths. First, participants were representative of those who develop first MTPJ OA in terms of age,38 body mass index,16 foot Shoe Stiffening Inserts for First MTPJ OA
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posture,39 and clinical signs of first MTPJ OA40; therefore, the study findings are broadly generalizable. Second, the shoe stiffening inserts are commercially available and low cost (AUS $60/US $56). Third, because of their low bulk, the inserts can fit in a range of footwear styles that may encourage greater adherence. The findings of this study need to be interpreted with the consideration of the study limitations. Firstly, because of the absence of a control group and a randomization protocol, the authors cannot delineate intervention effects (improvement in symptoms and adverse events) from any nonintervention effects such as placebo response, use of co-interventions such as alternative styles of footwear, or Rosenthal effects. To overcome this limitation, future rigorous randomized controlled trials using longer follow-up are required. Second, we did not determine the effects of shoe stiffening inserts on lower limb biomechanics. Future studies should consider analyzing lower limb kinetics and kinematics to provide a better indication of the effects shoe stiffening inserts have on foot and lower limb mechanics.
CONCLUSION In summary, this proof-of-concept study showed that the use of full-length shoe stiffening inserts was associated with statistically and clinically significant improvements in foot pain and foot-related disability in individuals with symptomatic first MTPJ OA. Shoe stiffening inserts were generally well tolerated although there was some risk of participants developing adverse events. These findings provide preliminary evidence to support full-length shoe stiffening inserts as an intervention for symptomatic first MTPJ OA. Further study using rigorous randomized controlled trial methods is required to confirm these preliminary findings. ACKNOWLEDGMENTS
The authors thank Mr Daniel Bonanno and the staff of Southern Cross Medical Imaging for their assistance. REFERENCES 1. Keen HI, Redmond A, Wakefield RJ, et al: An ultrasonographic study of metatarsophalangeal joint pain: Synovitis, structural pathology and their relationship to symptoms and function. Ann Rheum Dis 2011; 70:2140Y3 2. Camasta CA: Hallux limitus and hallux rigidus. Clinical examination, radiographic findings, and natural history. Clin Podiatr Med Surg 1996;13:423Y48
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3. Roddy E, Thomas MJ, Marshall M, et al: The population prevalence of symptomatic radiographic foot osteoarthritis in community-dwelling older adults: Cross-sectional findings from the Clinical Assessment Study of the Foot. Ann Rheum Dis 2015; 74:156Y63 4. Vanore JV, Christensen JC, Kravitz SR, et al: Diagnosis and treatment of first metatarsophalangeal joint disorders. Section 2: Hallux rigidus. J Foot Ankle Surg 2003;42:124Y36 5. Zammit GV, Menz HB, Munteanu SE, et al: Plantar pressure distribution in older people with osteoarthritis of the first metatarsophalangeal joint (hallux limitus/rigidus). J Orthop Res 2008;26:1665Y9 6. Van Gheluwe B, Dananberg HJ, Hagman F, et al: Effects of hallux limitus on plantar foot pressure and foot kinematics during walking. J Am Podiatr Med Assoc 2006;96:428Y36 7. Canseco K, Long J, Marks R, et al: Quantitative characterization of gait kinematics in patients with hallux rigidus using the Milwaukee foot model. J Orthop Res 2008;26:419Y27 8. Bergin SM, Munteanu SE, Zammit GV, et al: Impact of first metatarsophalangeal joint osteoarthritis on health-related quality of life. Arthritis Care Res (Hoboken) 2012;64:1691Y8 9. Schurman DJ, Smith RL: Osteoarthritis: Current treatment and future prospects for surgical, medical, and biologic intervention. Clin Orthop Relat Res 2004;(427 suppl):S183Y9 10. Zhang W, Moskowitz RW, Nuki G, et al: OARSI recommendations for the management of hip and knee osteoarthritis, part II: OARSI evidence-based, expert consensus guidelines. Osteoarthritis Cartilage 2008; 16:137Y62 11. McAllister JL, Thordarson DB: Complications of foot and ankle surgery. Clin Sports Med 1999;18: 927Y39 12. Zammit GV, Menz HB, Munteanu SE, et al: Interventions for treating osteoarthritis of the big toe joint. Cochrane Database Syst Rev 2010:CD007809 13. Medical edge: Shoe inserts, surgery ease arthritis in big toe. Journal - Gazette. Ft. Wayne, Ind., United States, Ft. Wayne, Ind. 2007:0Y4D 14. Rao S, Baumhauer JF, Tome J, et al: Orthoses alter in vivo segmental foot kinematics during walking in patients with midfoot arthritis. Arch Phys Med Rehabil 2010;91:608Y14 15. Lin SC, Chen CP, Tang SF, et al: Changes in windlass effect in response to different shoe and insole designs during walking. Gait Posture 2013;37:235Y41 16. Munteanu SE, Zammit GV, Menz HB, et al: Effectiveness of intra-articular hyaluronan (Synvisc, hylan G-F 20) for the treatment of first metatarsophalangeal joint osteoarthritis: A randomised placebo-controlled trial. Ann Rheum Dis 2011;70:1838Y41 17. Menz HB, Munteanu SE, Landorf KB, et al: Radiographic classification of osteoarthritis in commonly
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affected joints of the foot. Osteoarthritis Cartilage 2007;15:1333Y8 18. Altman R, Brandt K, Hochberg M, et al: Design and conduct of clinical trials in patients with osteoarthritis: Recommendations from a task force of the Osteoarthritis Research Society. Results from a workshop. Osteoarthritis Cartilage 1996;4: 217Y43 19. Garrow AP, Papageorgiou A, Silman AJ, et al: The grading of hallux valgus. The Manchester Scale. J Am Podiatr Med Assoc 2001;91:74Y8 20. Munteanu SE, Zammit GV, Menz HB: Factors associated with foot pain severity and foot-related disability in individuals with first metatarsophalangeal joint OA. Rheumatology (Oxford) 2012;51:176Y83
28. Sallis JF, Haskell WL, Wood PD, et al: Physical activity assessment methodology in the Five-City Project. Am J Epidemiol 1985;121:91Y106 29. Munteanu SE, Menz HB, Zammit GV, et al: Efficacy of intra-articular hyaluronan (Synvisc(R)) for the treatment of osteoarthritis affecting the first metatarsophalangeal joint of the foot (Hallux limitus): Study protocol for a randomised placebo controlled trial. J Foot Ankle Res 2009;2:2 30. Munteanu SE, Landorf KB, Menz HB, et al: Efficacy of customised foot orthoses in the treatment of Achilles tendinopathy: Study protocol for a randomised trial. J Foot Ankle Res 2009;2:27 31. Queen RM, Verma R, Abbey AN, et al: Plantar loading during jumping while wearing a rigid carbon graphite footplate. Gait Posture 2014;39:707Y11
21. Pincus T, Santos R, Breen A, et al: A review and proposal for a core set of factors for prospective cohorts in low back pain: A consensus statement. Arthritis Rheum 2008;59:14Y24
32. Queen RM, Abbey AN, Verma R, et al: Plantar loading during cutting while wearing a rigid carbon fiber insert. J Athl Train 2014;49:297Y303
22. Redmond AC, Crosbie J, Ouvrier RA: Development and validation of a novel rating system for scoring standing foot posture: The Foot Posture Index. Clin Biomech (Bristol, Avon) 2006;21:89Y98
33. Hall C, Nester CJ: Sagittal plane compensations for artificially induced limitation of the first metatarsophalangeal joint: A preliminary study. J Am Podiatr Med Assoc 2004;94:269Y74
23. Barton CJ, Bonanno D, Menz HB: Development and evaluation of a tool for the assessment of footwear characteristics. J Foot Ankle Res 2009;2:10
34. Radzimski AO, Mu¨ndermann A, Sole G: Effect of footwear on the external knee adduction momentVA systematic review. Knee 2012;19:163Y75
24. Bennett PJ, Patterson C, Wearing S, et al: Development and validation of a questionnaire designed to measure foot-health status. J Am Podiatr Med Assoc 1998;88:419Y28
35. Shakoor N, Lidtke RH, Wimmer MA, et al: Improvement in knee loading after use of specialized footwear for knee osteoarthritis: Results of a six-month pilot investigation. Arthritis Rheum 2013;65:1282Y9
25. Martin RL, Irrgang JJ: A survey of self-reported outcome instruments for the foot and ankle. J Orthop Sports Phys Ther 2007;37:72Y84
36. Amin S, Luepongsak N, McGibbon CA, et al: Knee adduction moment and development of chronic knee pain in elders. Arthritis Rheum 2004;51:371Y6
26. Riskowski JL, Hagedorn TJ, Hannan MT: Measures of foot function, foot health, and foot pain: American Academy of Orthopedic Surgeons Lower Limb Outcomes Assessment: Foot and Ankle Module (AAOSFAM), Bristol Foot Score (BFS), Revised Foot Function Index (FFI-R), Foot Health Status Questionnaire (FHSQ), Manchester Foot Pain and Disability Index (MFPDI), Podiatric Health Questionnaire (PHQ), and Rowan Foot Pain Assessment (ROFPAQ). Arthritis Care Res (Hoboken) 2011;63:S229Y39
37. Thorp LE, Sumner DR, Wimmer MA, et al: Relationship between pain and medial knee joint loading in mild radiographic knee osteoarthritis. Arthritis Rheum 2007;57:1254Y60
39. Redmond AC, Crane YZ, Menz HB: Normative values for the Foot Posture Index. J Foot Ankle Res 2008;1:6
27. Landorf KB, Radford JA, Hudson S: Minimal Important Difference (MID) of two commonly used outcome measures for foot problems. J Foot Ankle Res 2010;3:7
40. Zammit GV, Munteanu SE, Menz HB: Development of a diagnostic rule for identifying radiographic osteoarthritis in people with first metatarsophalangeal joint pain. Osteoarthritis Cartilage 2011;19:939Y45
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38. Beeson P, Phillips C, Corr S, et al: Hallux rigidus: A cross-sectional study to evaluate clinical parameters. Foot (Edinb) 2009;19:80Y92
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Foot Pain
Affiliations: From the Discipline of Podiatry, School of Allied Health (TXJ, HBM, GSM, SEM), and Lower Extremity and Gait Studies Program, School of Allied Health (HBM, GSM, SEM), La Trobe University, Bundoora, Victoria, Australia; and Department of Podiatry, Singapore General Hospital, Singapore (TXJ).
Correspondence: All correspondence and requests for reprints should be addressed to: Shannon E. Munteanu, PhD, Discipline of Podiatry, School of Allied Health, La Trobe University, Bundoora, Victoria 3086, Australia.
Disclosures: This study was funded by La Trobe University School of Allied Health. Prof Hylton Menz is currently a National Health and Medical Research Council Senior Research Fellow (ID: 1020925). The study sponsors had no involvement in the study design, collection, analysis, and interpretation of data; in the writing of the manuscript; and in the decision to submit the manuscript for publication. Financial disclosure statements have been obtained, and no conflicts of interest have been reported by the authors or by any individuals in control of the content of this article.
0894-9115/16/9502-0103 American Journal of Physical Medicine & Rehabilitation Copyright * 2015 Wolters Kluwer Health, Inc. All rights reserved. DOI: 10.1097/PHM.0000000000000350
ORIGINAL RESEARCH ARTICLE
Effectiveness of Shoe Stiffening Inserts for First Metatarsophalangeal Joint Osteoarthritis A Proof-of-Concept Study ABSTRACT Jerilyn TX, Menz HB, Murley GS, Munteanu SE: Effectiveness of shoe stiffening inserts for first metatarsophalangeal joint osteoarthritis: a proof-of-concept study. Am J Phys Med Rehabil 2016;95:103Y111.
Objective: The objective of this study was to determine the feasibility of shoe stiffening inserts to reduce pain in first metatarsophalangeal joint osteoarthritis.
Design: Thirty-one participants with first metatarsophalangeal joint osteoarthritis were prescribed shoe stiffening inserts and were evaluated at baseline and at 1 and 3 mos. The primary outcome measure was foot pain, assessed using the foot pain domain of the Foot Health Status Questionnaire (possible score ranges from 0 to 100). Secondary outcome measures included foot-related disability (foot function domain of the Foot Health Status Questionnaire), self-reported treatment effectiveness, use of rescue medication and other co-interventions, and adverse events.
Results: At 1 and 3 mos, statistically significant improvements in foot pain and foot-related disability were observed (mean difference at 3 mos: foot pain = 18.8, 95% confidence interval, 13.3Y24.3; foot function = 11.8, 95% confidence interval, 4.3Y17.3). Treatment was reported to be effective by 78% of participants. Few participants (4%) reported using pain-relieving medication. Minor adverse events were reported by 30% of participants.
Conclusions: Full-length shoe stiffening inserts may be an effective intervention in first metatarsophalangeal joint osteoarthritis. However, further controlled studies are required. Key Words:
www.ajpmr.com
Osteoarthritis, Metatarsophalangeal Joint, Hallux Rigidus, Foot Orthoses
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F
irst metatarsophalangeal joint (MTPJ) osteoarthritis (OA) is a common degenerative disorder of the foot.1,2 The population prevalence of symptomatic radiographic first MTPJ OA has recently been estimated at 7.8%, with a higher prevalence observed in females, older people, and those from lower socioeconomic backgrounds.3 First MTPJ OA is characterized by localized pain, stiffness, and reduced joint range of motion.4 These symptoms have been speculated to be caused by dorsal compression at the joint between the first metatarsal head and proximal phalanx of the hallux that occurs during the propulsive phase of gait.2 In addition, the restricted joint dorsiflexion that occurs in first MTPJ OA leads to overloading of the hallux during propulsion, which may further aggravate pain.5,6 Other reported changes include altered gait patterns5,7 and a significant reduction in both foot-specific and general health-related quality-of-life.8 Seventy-one percent of people with first MTPJ OA report the condition to be disabling.3 The treatment goals for first MTPJ OA are to reduce pain and stiffness and to prevent further degeneration of the joint.9,10 At present, there are no evidence-based guidelines for the management of this condition. However, nonsurgical management is recognized as the first-line therapy.11 Numerous nonsurgical interventions have been proposed including pharmaceutic interventions, physical therapy, and mechanical interventions (such as accommodative and customized orthoses or insoles, strapping, splinting, and footwear modifications).12 Despite the broad range of treatment options for this disorder, very few have undergone rigorous scientific evaluation.12 Full-length shoe stiffening inserts are commonly recommended as an intervention for first MTPJ OA.12 Shoe stiffening inserts are made from a thin, rigid material that is placed inside the shoe with the aim of reducing the rate and magnitude of dorsiflexion at the MTPJs during the propulsive phase of gait. This effect is thought to reduce the symptoms of first MTPJ OA by decreasing the amount of motion and the resultant dorsal compression at the first MTPJ that occurs during propulsion.13 There is some evidence to suggest that shoe stiffening inserts can reduce dorsiflexion of the first MTPJ during gait. A study using participants with midfoot OA showed that shoe stiffening inserts significantly decreased first MTPJ dorsiflexion range of motion and first metatarsal range of motion.14 Supporting this, a recent biomechanical study using asymptomatic individuals showed that
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the addition of shoe stiffening inserts into shoes significantly reduced maximum dorsiflexion occurring at the first MTPJ during propulsion.15 Although these biomechanical effects on the first MTPJ would suggest that shoe stiffening inserts may favorably influence symptoms of first MTPJ OA, no study has investigated their effectiveness in reducing these symptoms. Therefore, the purpose of this study was to determine the feasibility (including effects on foot pain and foot-related disability, and rate of adverse effects) of using shoe stiffening inserts as a treatment for symptomatic first MTPJ OA.
METHODS This study used a prospective case-series design that involved an initial assessment, followed by a baseline assessment, with 1 and 3-mo follow-ups. All assessments were undertaken at the La Trobe University Health Sciences Clinic, Bundoora (Victoria, Australia). Ethical approval was granted from the La Trobe University Faculty of Health Sciences Human Ethics Committee (number FHEC12/188). Informed consent was obtained from all participants. The study was registered with the Australian New Zealand Clinical Trials Registry (ACTRN363501).
Participants Participants were recruited between February and April 2013. The study was advertised through local newspapers and posters displayed on public notice boards of universities and social clubs in Melbourne. Inclusion criteria were as follows: aged at least 18 yrs, symptoms of first MTPJ pain for at least 3 mos in one foot or in both feet, pain severity of at least 20 mm on a 100-mm visual analog pain scale at one or both first MTPJ(s),16 radiographic evidence of first MTPJ OA (score of Q2 for either osteophytes or joint space narrowing using the La Trobe University radiographic classification atlas17), and a willingness to discontinue consuming all pain-relieving medications (except paracetamol) for first MTPJ pain for 2 wks before the baseline assessment and then during the study. Participants who consumed paracetamol were required to discontinue its use at least 24 hrs before the baseline assessment and follow-up assessments.18 Participants were also required to refrain from receiving concurrent treatment of the pain at their first MTPJ during the study period, wear shoes that can accommodate the shoe stiffening inserts, and be able to ambulate without the need for assistive devices such as a cane.
Am. J. Phys. Med. Rehabil. & Vol. 95, No. 2, February 2016 Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.
Exclusion criteria were as follows: previous surgery on the symptomatic first MTPJ; intraarticular injection at the first MTPJ in the last 3 mos; significant deformity of the first MTPJ including hallux valgus (grade 3 or 4 using the Manchester Scale19); presence of confounding conditions that may influence pain and functional assessments at the first MPTJ, such as metatarsalgia, symptomatic degenerative joint disease of the foot (other than the first MTPJ), and painful callus; and the presence of systemic inflammatory conditions or diabetes. During the baseline assessment, the following participant characteristics were determined by the same investigator (TXJ): age (in years); sex; height (in centimeters); weight (in kilograms); waist-hip ratio; duration of symptoms (in months); side(s) affected; severity of pain when walking during previous week using a 100-mm visual analog pain scale20; previous treatment of first MTPJ pain; highest level of education21; passive, nonYweightbearing dorsiflexion range of motion of the first MTPJ20; foot posture using the Foot Posture Index-622; and the style of footwear most usually worn using the Footwear Assessment Tool.23
Radiographic Assessment Participants were required to undergo radiographic imaging of their symptomatic foot (or most symptomatic foot) to determine the presence and severity of first MTPJ OA. Dorso-plantar and lateral radiographic projections were obtained with the participant weight bearing in a relaxed bipedal stance position, as described previously.17 The severity of the osteophytes and the joint space narrowing at the first MTPJ were determined using the La Trobe University radiographic atlas for first
MTPJ OA.17 All measures were conducted by one experienced rater (SEM) who was involved in the development of the atlas. Participants were diagnosed as having radiographic first MTPJ OA if a score of 2 or more was graded for either osteophytes or joint space narrowing in either the dorso-plantar or lateral radiographic projections.17 The atlas has excellent reliability.17
Full-Length Shoe Stiffening Inserts Participants were prescribed a single (or a pair, if symptoms were bilateral) full-length shoe stiffening insert at the baseline assessment. The shoe stiffening inserts are low mass (22 g for 28 cm length insert of Bsoft[ stiffness) with minimal thickness (approximately 1.1 mm) to allow easy fitting into different types of footwear. The shoe stiffening inserts are commercially available and are fabricated from semirigid carbon graphite (Otto Bock Springlite Carbon Foot Plates, Otto Bock Pty Ltd, Baulkham Hills, Australia) with the following design characteristics: (1) full length that extends from the heel to the tip of the toes and (2) no arch buildup or contour at the heel (Fig. 1). The shoe stiffening inserts are available at varying stiffness dependent on the individual_s body weight. As there are no empirical guidelines to suggest the most appropriate stiffness for use, participants were prescribed an insert of either Bsoft[ or Bmedium[ stiffness, where a soft stiffness insert was more flexible than a medium stiffness insert. Selection of insert type was dependent on the participant_s preference based on the comfort of the inserts that was evaluated at baseline. The shoe stiffening insert was placed beneath the liner of the participants_ footwear. If the footwear did not have a liner, the insert was placed inside the shoes and participants
FIGURE 1 Full-length shoe stiffening insert of 1-mm semirigid carbon graphite (Otto Bock Springlite Carbon Foot Plates). www.ajpmr.com
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were provided with the option of having the insert covered with 2.0 mm of Lunasoft EVA foam.
Outcome Measures Outcome measures were performed on three occasions: at baseline and then at 1 and 3 mos after intervention. Postal survey was used to collect data at 1 and 3 mos. One month was considered the earliest time of maximum effect; however, 3 mos was considered a clinically feasible time point when maximum treatment effect would have been expected and was therefore set as the primary end point.16
Primary Outcome Measure The primary outcome measure was the foot pain domain of the Foot Health Status Questionnaire (FHSQ).24 The FHSQ consists of 13 questions that assess foot health in four domains: Bfoot pain,[ Bfoot function,[ Bfootwear,[ and Bgeneral foot health.[ There are a total of four questions under the foot pain domain. Questions are scored using a Likert response format and the participants_ responses are transformed into a score ranging from 0 to 100 for each domain (0, worst foot health; 100, optimal foot health).24 The FHSQ has been subjected to an extensive validation process, with each domain being shown to demonstrate high internal consistency (Cronbach > Q 0.851), good reproducibility (intraclass correlation coefficients Q 0.740), and good discriminative capabilities.24 Further, the FHSQ is rated as one of the highest-quality foot health status measures currently available25,26 and has been used previously in clinical trials of interventions for first MTPJ OA.16
Secondary Outcome Measures The following were the secondary outcome measures: (i) Foot-related disability (using the foot function domain of the FHSQ).24 (ii) Self-reported magnitude of symptom change (using a 15-point Likert scale). This variable was then dichotomized into the categories of Beffective[ (Ba very great deal better,[ Ba great deal better,[ Ba good deal better,[ Bmoderately better,[ and Bsomewhat better[) and Bineffective[ (Ba little better,[ Babout the same, hardly any better at all,[ Bno change,[ Babout the same, hardly any worse at all,[ Ba little worse,[ Bsomewhat worse,[ Bmoderately worse,[ Ba good deal worse,[ Ba great deal worse,[ and Ba very great deal worse[).27 (iii) Level of physical activity (using the Stanford 7day Physical Activity Recall Questionnaire).28
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(iv) Comfort of the shoe insert(s) (using a fivepoint Likert scale response [Bvery comfortable,[ Bsomewhat comfortable,[ Bneither comfortable nor uncomfortable,[ Bsomewhat uncomfortable,[ or Bvery uncomfortable[]). This variable was then dichotomized into categories of Bcomfortable[ (Bvery comfortable,[ Bsomewhat comfortable,[ and Bneither comfortable nor uncomfortable[) and Buncomfortable[ (Bsomewhat uncomfortable[ or Bvery uncomfortable[). (v) Adherence to the use of the shoe stiffening insert(s) by asking participants the number of days (and number of hours each day) the insert(s) was worn on average in the past week. Total hours per week was determined by multiplying number of days and number of hours each day. (vi) Use of paracetamol rescue medication (used as a backup in case of insufficient efficacy of the shoe stiffening inserts and recorded through the use of a medication diary that participants self-completed) and other co-interventions.29 (vii) Tolerability of the shoe stiffening insert(s) (determined by the frequency, types, and severity of adverse events).30
Sample Size The sample size was determined a priori based on the FHSQ pain domain as the primary outcome measure. Using a power of 80%, a minimal important difference of 14 points in the foot pain domain of the FHSQ,16 an SD of 18.9,16 assuming a 10% dropout rate, and a significance level set at > less than 0.05, the authors estimated that a total of 31 participants were required.
Statistical Analysis Symptoms were described without specific reference to an individual foot (i.e., bilateral pain was evaluated as one independent sample), and assessment findings were taken from the more symptomatic foot. Statistical analysis was performed using SPSS version 21.0 (IBM Corporation, USA). All data were explored for assumptions of statistical analyses including normality (by visual inspection of histograms and Q-Q plots, determination of skewness and kurtosis [values G |2|], and Shapiro-Wilk tests). The authors used completer analysis only (the authors did not replace missing data at 1 and 3 mos, as this was a proof-of-concept study). Differences in scores for the outcome measures (i.e., foot pain, foot-related disability, and level
Am. J. Phys. Med. Rehabil. & Vol. 95, No. 2, February 2016 Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.
of physical activity) at 1 and 3 mos were compared using a repeated-measures one-way analysis of variance. P less than 0.05 was considered statistically significant. Post hoc comparisons (vs. baseline) were performed using Bonferroni-adjusted paired t tests (P G 0.025), with 3 mos being the primary end point.
RESULTS Thirty-one participants were assessed and received the intervention between February and May 2013. A total of 74 individuals expressed interest in the study. Among the 43 individuals who were excluded from the study, 32 declined to participate and 11 did not meet the inclusion criteria (Fig. 2). Data were obtained from 30 participants at 1 mo and 27 participants at 3 mos (Fig. 2). Table 1 displays the participants_ characteristics at baseline. Of the 31 participants, 22 (71.0%) chose to use a shoe stiffening insert of a medium flexibility.
difference = 18.8; 95% CI, 13.3Y24.3; P G 0.001) (Table 2).
Foot-Related Disability, Perception of Treatment Effectiveness, and Physical Activity There was a significant difference in FHSQ foot function scores between the three time points (F2 = 8.390; P = 0.001). Post hoc comparisons revealed statistically significant improvements in foot function at 1 mo (mean difference = 10.8; 95% CI, 4.4Y17.2; P = 0.002) and 3 mos (mean difference = 11.8; 95% CI, 4.3Y17.3; P = 0.002) (Table 2). For the outcome Bself-reported magnitude of symptom change,[ 70.0% (21 of 30) and 77.8% (21 of 27, 77.7%) of participants reported that the treatment was effective at 1 and 3 mos, respectively. There was no significant change in physical activity during the study (F2 = 0.059; P = 0.943).
Comfort and Adherence Primary Outcome Measure: Foot Pain There was a significant difference in FHSQ foot pain scores between the three time points (F2 = 37.406; P G 0.001). Post hoc comparisons revealed statistically significant improvements in foot pain at 1 mo (mean difference = 15.2; 95% confidence interval [CI], 9.1Y21.2; P G 0.001) and 3 mos (mean
For the outcome Bcomfort of the shoe insert(s),[ 30 (of 31, 96.8%), 25 (of 30, 86.7%), and 26 (of 27, 96.3%) participants reported that the shoe stiffening inserts were comfortable at baseline and at 1 and 3 mos, respectively. Participants wore the shoe stiffening inserts for a mean (SD) of 36.9 (27.3) hrs/wk at 1 mo and 41.7 (28.8) hrs/wk at 3 mos.
FIGURE 2 Participant flow diagram. *One participant had both gout and diabetes. www.ajpmr.com
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TABLE 1 Participant characteristics (N = 31) Characteristic
Value
Age, yrs Male sex, n (%) Height, cm Weight, kg BMI, kg/m2 Waist-hip ratio Duration of symptoms, mos Side affected (left/right/bilateral), n Target side (left), n (%) Severity of OA (median, IQR) [range]a Dorsal osteophytes Dorsal joint space narrowing Lateral osteophytes Lateral joint space narrowing Total score Highest level of education, (median, IQR) [range]b Passive, nonYweight-bearing dorsiflexion range of motion of the first MTPJ, degrees Foot posturec Walking pain (VAPS) Previous treatment, n (%) Style of footwear most regularly worn, n (%)d Walking shoe Boot Slipper Sandal Athletic shoe Oxford shoe High heel shoe Court shoe Other
55.5 (11.8) 12 (38.7) 168.3 (8.9) 71.8 (20.0) 25.0 (4.9) 0.86 (0.1) 50.8 (46.1) 4/15/12 10 (32.3) 2 (1) [1Y3] 1 (1) [0Y3] 2 (1) [0Y3] 1 (1) [0Y3] 7.2 (2.5) 6 (3) [4Y7] 47.7 (14.8) 2.7 (3.5) 53.5 (19.0) 27 (87.1) 9 3 3 2 4 2 2 1 5
(29.0) (9.7) (9.7) (6.5) (12.9) (6.5) (6.5) (3.2) (16.1)
Data are expressed as mean (SD) unless shown otherwise. a Severity of OA graded using the radiographic atlas of Menz et al.17 where the presence of osteophytes was graded as absent (score = 0), small (score = 1), moderate (score = 2), and severe (score = 3), and the presence of joint space narrowing was graded as none (score = 0), reduced (score = 1), severe (score = 2), and joint fusionVat least one point (score = 3). b Education was recorded as no formal schooling (score = 1), less than primary school (score = 2), primary school completed (score = 3), high school (or equivalent) completed (score = 4), technical and further education completed (score = 5), college/ university completed (score = 6), and postgraduate degree completed (score =7). c Foot posture was assessed using the Foot Posture Index-6.22 d Style of footwear most regularly worn was assessed using the Footwear Assessment Tool.23 BMI, body mass index; IQR, interquartile range; VAPS, visual analog pain scale.
Use of Co-Interventions At 1 mo, 9 participants (of 31 calendars received, 29.0%) reported using medication (8 paracetamol, 1 nonsteroidal anti-inflammatory drug). At 2 mos, 3 participants (of 27 calendars received, 11.1%) reported using a nonsteroidal antiinflammatory drug, and at 3 mos, 1 participant (of 25 calendars received, 4.0%) reported using a nonsteroidal anti-inflammatory drug. Changes to footwear were reported by 12 (of 30, 40.0%) and 7 (of 27, 25.9%) participants at 1 and 3 mos. One participant reported using massage at the first MTPJ during the study.
Adverse Events Nine (of 30, 30.0%) and 4 (of 27, 14.8%) participants reported at least one adverse event at 1 and
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3 mos, respectively. During the study, the most common adverse events were foot pain (excluding pain at the first MTPJ) (n = 4) and knee pain (n = 3). Two participants withdrew from the study after 1 mo because of adverse events (knee pain [n = 1]; heel pain [n = 1]).
DISCUSSION This proof-of concept study showed that the provision of shoe stiffening inserts was associated with statistically significant improvements in foot pain and foot-related disability in people with first MTPJ OA that occurred as early as 1 mo and were maintained for the study duration of 3 mos. Furthermore, the shoe stiffening inserts were well tolerated; they were worn for an average of 41.7 hrs/wk at 3 mos.
Am. J. Phys. Med. Rehabil. & Vol. 95, No. 2, February 2016 Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved.
TABLE 2 Continuous-scaled outcome measures at baseline and at 1 and 3 mos Outcome Measure Foot painb Baseline 1 mo 3 mosc,d Foot-related disabilityb Baseline 1 mo 3 mosd Physical activity, kcal/day Baseline 1 mo 3 mosd
Baseline
Mean Difference (95% CI)
Pa
55.4 (17.9) 70.0 (14.3) 73.8 (11.9)
V 15.2 (9.1 to 21.2) 18.8 (13.3 to 24.3)
V G0.001 G0.001
71.0 (24.9) 81.7 (16.7) 84.4 (14.6)
V 10.8 (4.4 to 17.2) 11.8 (4.3 to 17.3)
0.002 0.002
2963 (831) 2930 (836) 2921 (982)
V j17 (j249 to 216) j27 (j251 to 196)
0.884 0.802
a
Compared with baseline using paired t tests. Higher scores indicate better foot health. c Bold entry denotes the primary outcome measure and the primary end point. d n = 26 because 1 participant (of the 27 participants who returned questionnaires) did not respond to these questionnaire items. b
The primary outcome measure was foot pain assessed using the FHSQ foot pain domain. The magnitude of improvement in foot pain at 1 mo (15.2 points; 95% CI, 9.1Y21.2) and 3 mos (18.8 points; 95% CI, 13.3Y24.3) was greater than the reported minimal important difference of 14 points.16 This suggests that the improvement in foot pain associated with the use of shoe stiffening inserts may be clinically important. In addition, other outcomes suggested an improvement in symptoms and function in participants during this study. Foot-related disability (FHSQ foot function domain) improved 10.8 points (95% CI, 4.4Y17.2) at 1 mo and 11.8 points (95% CI, 4.3Y17.3) at 3 mos. This is also greater than the reported minimal important difference of 7 for foot-specific problems,27 which highlights the clinical importance of this finding. These improvements are consistent with the observation that 78% of study participants reported their treatment to be effective at 3 mos (using the cutoff for defining treatment effectiveness for the variable self-reported magnitude of symptom change). Pain associated with first MTPJ OA has been attributed to dorsal compression at the joint during the propulsive phase of gait. Previous literature has shown that shoe stiffening inserts reduce first MTPJ dorsiflexion range of motion14 and the magnitude of dorsiflexion at the first MTPJ.15 This suggests that the shoe stiffening inserts may have reduced symptoms in the participants by reducing first MTPJ dorsiflexion, thereby reducing the dorsal compression that occurs during propulsion. Further research is required to test this hypothesis as the authors did not directly measure the effects of www.ajpmr.com
the shoe stiffening inserts on the kinematics of the first MTPJ. Although the use of shoe stiffening inserts was associated with an improvement in symptoms of first MTPJ OA, several participants (30% at 1 mo) reported at least one adverse event. The most common adverse events observed in this study were foot pain (excluding first MTPJ pain) (n = 4) and knee pain (n = 3). Two participants withdrew after 1 mo because of the development of severe heel and knee pain. The mechanism for the development of these more severe adverse events is unclear. It is possible that the shoe stiffening inserts may increase the risk of plantar foot pain by increasing plantar pressures at specific regions of the foot such as the heel.31,32 The shoe stiffening inserts may also cause changes to lower limb kinematics and kinetics through the restriction of first MTPJ dorsiflexion,33 which may increase the risk of proximal pathologies in predisposed individuals. There is evidence that rigid-soled shoes lead to higher knee moments during locomotion.34 The decrease in shoe flexibility restricts normal foot motion and in turn leads to an increase in the external knee adduction moment.34,35 Considering the association between increased external knee adduction moment and the onset of knee pain,36,37 it is plausible that the shoe stiffening inserts used in the current study may have led to an increase in knee pain through the increase of external knee adduction moment. Further study is required to confirm this hypothesis. This study has several strengths. First, participants were representative of those who develop first MTPJ OA in terms of age,38 body mass index,16 foot Shoe Stiffening Inserts for First MTPJ OA
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posture,39 and clinical signs of first MTPJ OA40; therefore, the study findings are broadly generalizable. Second, the shoe stiffening inserts are commercially available and low cost (AUS $60/US $56). Third, because of their low bulk, the inserts can fit in a range of footwear styles that may encourage greater adherence. The findings of this study need to be interpreted with the consideration of the study limitations. Firstly, because of the absence of a control group and a randomization protocol, the authors cannot delineate intervention effects (improvement in symptoms and adverse events) from any nonintervention effects such as placebo response, use of co-interventions such as alternative styles of footwear, or Rosenthal effects. To overcome this limitation, future rigorous randomized controlled trials using longer follow-up are required. Second, we did not determine the effects of shoe stiffening inserts on lower limb biomechanics. Future studies should consider analyzing lower limb kinetics and kinematics to provide a better indication of the effects shoe stiffening inserts have on foot and lower limb mechanics.
CONCLUSION In summary, this proof-of-concept study showed that the use of full-length shoe stiffening inserts was associated with statistically and clinically significant improvements in foot pain and foot-related disability in individuals with symptomatic first MTPJ OA. Shoe stiffening inserts were generally well tolerated although there was some risk of participants developing adverse events. These findings provide preliminary evidence to support full-length shoe stiffening inserts as an intervention for symptomatic first MTPJ OA. Further study using rigorous randomized controlled trial methods is required to confirm these preliminary findings. ACKNOWLEDGMENTS
The authors thank Mr Daniel Bonanno and the staff of Southern Cross Medical Imaging for their assistance. REFERENCES 1. Keen HI, Redmond A, Wakefield RJ, et al: An ultrasonographic study of metatarsophalangeal joint pain: Synovitis, structural pathology and their relationship to symptoms and function. Ann Rheum Dis 2011; 70:2140Y3 2. Camasta CA: Hallux limitus and hallux rigidus. Clinical examination, radiographic findings, and natural history. Clin Podiatr Med Surg 1996;13:423Y48
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