G Model
JINJ-6230; No. of Pages 5 Injury, Int. J. Care Injured xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Injury journal homepage: www.elsevier.com/locate/injury
Nail–medullary canal ratio affects mechanical axis deviation during femoral lengthening with an intramedullary distractor Nael Hawi a,*, Mohamed Kenawey b, Martin Panzica a, Timo Stuebig a, Mohamed Omar a, Christian Krettek a, Emmanouil Liodakis a a b
Trauma Department, Hannover Medical School, Germany Orthopaedic Surgery Department, Sohag University, Egypt
A R T I C L E I N F O
A B S T R A C T
Article history: Accepted 14 May 2015
Introduction: Callus distraction of the femur using an intramedullary distractor has several advantages over the use of external fixators. However, difficulty in controlling the mechanical axis during lengthening may cause deformities and knee osteoarthritis. Purpose of the study is to answer the following questions: (1) is lengthening with an intramedullary device associated with a medial or lateral shift of the mechanical axis? (2) Which factors are associated with varisation/valgisation of the mechanical axis during lengthening? Materials and methods: We analysed pre-treatment and post-treatment radiographs from 20 patients who underwent unilateral femoral-lengthening procedures using intramedullary distractors. Patients with acute correction of pre-existing deformities or combined ipsilateral femoral and tibial lengthening were excluded. Mechanical axis deviations, osteotomy level, and nail–medullary canal ratio were recorded. Results: Compared to the preoperative axis, the mechanical axis shifted medially in 7 patients (varisation group) and laterally in 13 patients (valgisation group). The groups did not significantly differ regarding preoperative leg length discrepancy (LLD), mechanical axis alignment, LLD-cause and implants used. The nail–medullary canal ratio significantly differed between groups (p < 0.001), being 85% in the valgisation group. The distance between the lesser trochanter and the osteotomy site was significantly longer in the valgisation group (58.9 16.3 mm, middle third of the femur) compared to the varisation group (40.6 11.4 mm, proximal third of the femur; p = 0.02). Conclusion: The nail–medullary canal ratio should be considered during preoperative planning. To avoid a varisation effect—for example, in cases with pre-existing varus alignment—it would be advisable to perform an osteotomy at the middle third of the femur with implantation of a nail that fully covers the medullary canal at the osteotomy site. Level of evidence: Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence. ß 2015 Elsevier Ltd. All rights reserved.
Keywords: Telescopic nails Femoral lengthening Mechanical axis changes Level of osteotomy
Introduction
* Corresponding author at: Trauma Department, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany. Tel.: +49 17615326964; fax: +49 5115325877. E-mail addresses: [email protected] (N. Hawi), [email protected] (M. Kenawey), [email protected] (M. Panzica), [email protected] (T. Stuebig), [email protected] (M. Omar), [email protected] (C. Krettek), [email protected] (E. Liodakis).
The last 20 years have seen much progress towards the development and establishment of totally implantable intramedullary lengthening nails in clinical practice [1–5]. This technique carries the main advantage of avoiding complications associated with external fixators, such as pin tract infections, neurovascular injuries, transfixation of soft tissues, and refractures [2,4,6–9]. Additional advantages include earlier rehabilitation, reduced pain, reduced risk of infection, earlier normal joint motion and activity level, and improved patient comfort [2–6,10,11].
http://dx.doi.org/10.1016/j.injury.2015.05.040 0020–1383/ß 2015 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Hawi N, et al. Nail–medullary canal ratio affects mechanical axis deviation during femoral lengthening with an intramedullary distractor. Injury (2015), http://dx.doi.org/10.1016/j.injury.2015.05.040
G Model
JINJ-6230; No. of Pages 5 N. Hawi et al. / Injury, Int. J. Care Injured xxx (2015) xxx–xxx
2
Despite these advantages, intramedullary lengthening is also associated with problems and complications. Implant availability and cost can pose problems. Additionally, mechanically activated lengthening nails—such as the Albizzia nail and the intramedullary skeletal kinetic distractor (ISKD)—have fallen out of favour due to difficulties with the ratchet mechanism and the inability to control the distraction rate [10,12,13]. Moreover, intramedullary lengthening occurs along the anatomical axis of the femur, which carries the theoretical risk of medially displacing the knee joint and therefore causing genu valgum deformity—a secondary effect that would become more evident with increasing lengthening magnitude [8,14]. There are currently no consistent recommendations concerning the level of femoral osteotomy. It can generally be assumed that the proximal third of the femur, as a metaphyseal area, should have better bony regeneration and healing characteristics [11]. On the other hand, the femur diameter is wider in the proximal part compared to in the middle third or isthmus [15]. The authors believe that mechanical axis changes during limb lengthening with an intramedullary device can be better controlled by an osteotomy at the most narrow area of the bone (isthmus) than by an osteotomy at the subtrochanteric area (proximal third). Purpose of the study is to answer the following questions: (1) is lengthening with an intramedullary device associated with a medial or lateral shift of the mechanical axis? (2) Which factors are associated with varisation/valgisation of the mechanical axis during lengthening? Materials and methods The present study was approved by the Institutional Review Board (2164–2014). We retrospectively reviewed the charts of all patients who underwent intramedullary femoral lengthening procedures at our institution (Hannover Medical School, Hannover, Germany) between July 2002 and August 2014. The study included all patients who had long-standing radiographs taken before and after femoral lengthening with an intramedullary distractor. Patients with acute correction of preexisting deformities or who underwent combined ipsilateral femoral and tibial lengthening were excluded. Patients were also excluded if they did not have weight-bearing radiographs taken before and after lengthening. To maintain the control of the femoral rotation and to eliminate the effect of a possible malrotation on the mechanical axis, as described by Gungenheim et al. [16], an external fixator with 2 parallel 5 mm Schanz screws in the proximal and distal part of the femur was used. The fixator was placed before the femoral osteotomy and was removed after proximal and distal locking of the nail. A total of 20 patients (11 males and 9 females) underwent isolated femoral lengthening and met our inclusion criteria. The mean age at the time of the lengthening procedure was 29 11 years. Causes of leg length discrepancy included congenital shortening (n = 8) and post-traumatic shortening (n = 12). The mean amount of lengthening achieved was 4.1 1.9 cm, with a mean distraction rate of 1.3 0.5 mm/day. Preoperatively, 12 patients had a varus alignment and 8 had a valgus alignment. An ISKD nail (Orthofix, Valley, Germany) was used in 18 patients, while a Precice nail (Ellipse Technologies, Irvine, USA) was used in 2 patients. The implant diameter was either 10.7 mm or 12.5 mm. A trochanteric entry point was used in 17 cases and a piriformis entry in 3 cases. The mean osteotomy level was 52.4 17 mm (range, 34–75 mm) distal to the lesser trochanter. The preoperative and post-healing long-standing lower extremity X-rays were used to verify the lower limb alignment changes using the system described by Paley et al. [17]. In each
Table 1 Patient demographics and perioperative characteristics. Age (years) Female-gender Leg length discrepancy (LLD) Cause of LLD – post-traumatic Preoperative axis-varus Osteotomy side (proximal third) Percentage of medullary canal occupied by nail Transport index (mm/day) ISKD nail Piriformis entry point
29 11 9 (45%) 4.1 1.9 12 (60%) 12 (60%) 8 (40%) 86 14 (%) 1.3 0.5 18 (90%) 3 (15%)
radiograph, we measured the mechanical femoro-tibial angle (mFTA) and the mechanical axis deviation (MAD). The direct postoperative X-rays were used to measure the percentage of the femoral medullar canal that was occupied by the nail at the osteotomy level. All measurements were performed digitally on a computer with the use of FDA-approved medical planning software (MediCAD version 2.0, Hectec, Altfraunhofen, Germany) [18]. Continuous variables were checked for normal distribution using the Shapiro–Wilk test, and presented as mean standard deviation (SD). Categorical variables were described as frequencies with percentages. Between-group differences were evaluated with the Mann–Whitney U test for non-parametric continuous data, while Pearson’s chi-square test was used for categorical values. A two-tailed p-value of 0.05 was considered to be statistically significant. The SPSS 22.0 program (SPSS Inc., Chicago, IL) was used for statistical analyses. Table 1 shows the preoperative characteristics of the patients. Results Table 2 summarises the postoperative data. The mechanical axis shifted medially in 7 patients (varisation group) and laterally in 13 patients (valgisation group). The overall absolute change of the mechanical femoro-tibial angle was 1.68 1.28 (range: 0.18– 4.28, 25th–75th percentile: 0.68–2.18). This change was 1.48 1.48 (range: 0.18–4.28, 25th–75th percentile: 0.58–2.48) for the varisation group, and 1.88 1.18 (range: 0.38–3.98, 25th–75th percentile: 0.68– 2.48) for the valgisation group (p = 0.588). Table 2 Postoperative data.
Age (years) mFTA (8) Limb length discrepancy (mm) Transport index (mm/day) Distance distal to Lesser Trochanter (mm) Medullary canal -nail ratio (%)
Varisation group
Valgisation group
p-Value
24.7 10.7 1.4 1.4 49.0 24.4 1.3 1.2 40.6 11.4
31.5 11.8 1.8 1.1 36.3 14.9 2.2 1.2 58.9 16.3
0.26 0.59 0.26 0.18 0.02
69.7 6.6
95.0 6.9
Cause of LLD Post-traumatic Congenital
4 (20%) 3 (15%)
8 (40%) 5 (25%)
1.0
Entry point Piriformis Trochanteric
2 (10%) 11 (55%)
1 (5%) 6 (30%)
1.0
Type of nail ISKD Precice
5 (25%) 0 (0%)
13 (75%) 2 (10%)
0.11
Preoperative alignment Varus Valgus
4 (20%) 3 (15%)
9 (45%) 4 (20%)
0.65
JINJ-6230; No. of Pages 5 Injury, Int. J. Care Injured xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Injury journal homepage: www.elsevier.com/locate/injury
Nail–medullary canal ratio affects mechanical axis deviation during femoral lengthening with an intramedullary distractor Nael Hawi a,*, Mohamed Kenawey b, Martin Panzica a, Timo Stuebig a, Mohamed Omar a, Christian Krettek a, Emmanouil Liodakis a a b
Trauma Department, Hannover Medical School, Germany Orthopaedic Surgery Department, Sohag University, Egypt
A R T I C L E I N F O
A B S T R A C T
Article history: Accepted 14 May 2015
Introduction: Callus distraction of the femur using an intramedullary distractor has several advantages over the use of external fixators. However, difficulty in controlling the mechanical axis during lengthening may cause deformities and knee osteoarthritis. Purpose of the study is to answer the following questions: (1) is lengthening with an intramedullary device associated with a medial or lateral shift of the mechanical axis? (2) Which factors are associated with varisation/valgisation of the mechanical axis during lengthening? Materials and methods: We analysed pre-treatment and post-treatment radiographs from 20 patients who underwent unilateral femoral-lengthening procedures using intramedullary distractors. Patients with acute correction of pre-existing deformities or combined ipsilateral femoral and tibial lengthening were excluded. Mechanical axis deviations, osteotomy level, and nail–medullary canal ratio were recorded. Results: Compared to the preoperative axis, the mechanical axis shifted medially in 7 patients (varisation group) and laterally in 13 patients (valgisation group). The groups did not significantly differ regarding preoperative leg length discrepancy (LLD), mechanical axis alignment, LLD-cause and implants used. The nail–medullary canal ratio significantly differed between groups (p < 0.001), being 85% in the valgisation group. The distance between the lesser trochanter and the osteotomy site was significantly longer in the valgisation group (58.9 16.3 mm, middle third of the femur) compared to the varisation group (40.6 11.4 mm, proximal third of the femur; p = 0.02). Conclusion: The nail–medullary canal ratio should be considered during preoperative planning. To avoid a varisation effect—for example, in cases with pre-existing varus alignment—it would be advisable to perform an osteotomy at the middle third of the femur with implantation of a nail that fully covers the medullary canal at the osteotomy site. Level of evidence: Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence. ß 2015 Elsevier Ltd. All rights reserved.
Keywords: Telescopic nails Femoral lengthening Mechanical axis changes Level of osteotomy
Introduction
* Corresponding author at: Trauma Department, Hannover Medical School, Carl-Neuberg-Str. 1, 30625 Hannover, Germany. Tel.: +49 17615326964; fax: +49 5115325877. E-mail addresses: [email protected] (N. Hawi), [email protected] (M. Kenawey), [email protected] (M. Panzica), [email protected] (T. Stuebig), [email protected] (M. Omar), [email protected] (C. Krettek), [email protected] (E. Liodakis).
The last 20 years have seen much progress towards the development and establishment of totally implantable intramedullary lengthening nails in clinical practice [1–5]. This technique carries the main advantage of avoiding complications associated with external fixators, such as pin tract infections, neurovascular injuries, transfixation of soft tissues, and refractures [2,4,6–9]. Additional advantages include earlier rehabilitation, reduced pain, reduced risk of infection, earlier normal joint motion and activity level, and improved patient comfort [2–6,10,11].
http://dx.doi.org/10.1016/j.injury.2015.05.040 0020–1383/ß 2015 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Hawi N, et al. Nail–medullary canal ratio affects mechanical axis deviation during femoral lengthening with an intramedullary distractor. Injury (2015), http://dx.doi.org/10.1016/j.injury.2015.05.040
G Model
JINJ-6230; No. of Pages 5 N. Hawi et al. / Injury, Int. J. Care Injured xxx (2015) xxx–xxx
2
Despite these advantages, intramedullary lengthening is also associated with problems and complications. Implant availability and cost can pose problems. Additionally, mechanically activated lengthening nails—such as the Albizzia nail and the intramedullary skeletal kinetic distractor (ISKD)—have fallen out of favour due to difficulties with the ratchet mechanism and the inability to control the distraction rate [10,12,13]. Moreover, intramedullary lengthening occurs along the anatomical axis of the femur, which carries the theoretical risk of medially displacing the knee joint and therefore causing genu valgum deformity—a secondary effect that would become more evident with increasing lengthening magnitude [8,14]. There are currently no consistent recommendations concerning the level of femoral osteotomy. It can generally be assumed that the proximal third of the femur, as a metaphyseal area, should have better bony regeneration and healing characteristics [11]. On the other hand, the femur diameter is wider in the proximal part compared to in the middle third or isthmus [15]. The authors believe that mechanical axis changes during limb lengthening with an intramedullary device can be better controlled by an osteotomy at the most narrow area of the bone (isthmus) than by an osteotomy at the subtrochanteric area (proximal third). Purpose of the study is to answer the following questions: (1) is lengthening with an intramedullary device associated with a medial or lateral shift of the mechanical axis? (2) Which factors are associated with varisation/valgisation of the mechanical axis during lengthening? Materials and methods The present study was approved by the Institutional Review Board (2164–2014). We retrospectively reviewed the charts of all patients who underwent intramedullary femoral lengthening procedures at our institution (Hannover Medical School, Hannover, Germany) between July 2002 and August 2014. The study included all patients who had long-standing radiographs taken before and after femoral lengthening with an intramedullary distractor. Patients with acute correction of preexisting deformities or who underwent combined ipsilateral femoral and tibial lengthening were excluded. Patients were also excluded if they did not have weight-bearing radiographs taken before and after lengthening. To maintain the control of the femoral rotation and to eliminate the effect of a possible malrotation on the mechanical axis, as described by Gungenheim et al. [16], an external fixator with 2 parallel 5 mm Schanz screws in the proximal and distal part of the femur was used. The fixator was placed before the femoral osteotomy and was removed after proximal and distal locking of the nail. A total of 20 patients (11 males and 9 females) underwent isolated femoral lengthening and met our inclusion criteria. The mean age at the time of the lengthening procedure was 29 11 years. Causes of leg length discrepancy included congenital shortening (n = 8) and post-traumatic shortening (n = 12). The mean amount of lengthening achieved was 4.1 1.9 cm, with a mean distraction rate of 1.3 0.5 mm/day. Preoperatively, 12 patients had a varus alignment and 8 had a valgus alignment. An ISKD nail (Orthofix, Valley, Germany) was used in 18 patients, while a Precice nail (Ellipse Technologies, Irvine, USA) was used in 2 patients. The implant diameter was either 10.7 mm or 12.5 mm. A trochanteric entry point was used in 17 cases and a piriformis entry in 3 cases. The mean osteotomy level was 52.4 17 mm (range, 34–75 mm) distal to the lesser trochanter. The preoperative and post-healing long-standing lower extremity X-rays were used to verify the lower limb alignment changes using the system described by Paley et al. [17]. In each
Table 1 Patient demographics and perioperative characteristics. Age (years) Female-gender Leg length discrepancy (LLD) Cause of LLD – post-traumatic Preoperative axis-varus Osteotomy side (proximal third) Percentage of medullary canal occupied by nail Transport index (mm/day) ISKD nail Piriformis entry point
29 11 9 (45%) 4.1 1.9 12 (60%) 12 (60%) 8 (40%) 86 14 (%) 1.3 0.5 18 (90%) 3 (15%)
radiograph, we measured the mechanical femoro-tibial angle (mFTA) and the mechanical axis deviation (MAD). The direct postoperative X-rays were used to measure the percentage of the femoral medullar canal that was occupied by the nail at the osteotomy level. All measurements were performed digitally on a computer with the use of FDA-approved medical planning software (MediCAD version 2.0, Hectec, Altfraunhofen, Germany) [18]. Continuous variables were checked for normal distribution using the Shapiro–Wilk test, and presented as mean standard deviation (SD). Categorical variables were described as frequencies with percentages. Between-group differences were evaluated with the Mann–Whitney U test for non-parametric continuous data, while Pearson’s chi-square test was used for categorical values. A two-tailed p-value of 0.05 was considered to be statistically significant. The SPSS 22.0 program (SPSS Inc., Chicago, IL) was used for statistical analyses. Table 1 shows the preoperative characteristics of the patients. Results Table 2 summarises the postoperative data. The mechanical axis shifted medially in 7 patients (varisation group) and laterally in 13 patients (valgisation group). The overall absolute change of the mechanical femoro-tibial angle was 1.68 1.28 (range: 0.18– 4.28, 25th–75th percentile: 0.68–2.18). This change was 1.48 1.48 (range: 0.18–4.28, 25th–75th percentile: 0.58–2.48) for the varisation group, and 1.88 1.18 (range: 0.38–3.98, 25th–75th percentile: 0.68– 2.48) for the valgisation group (p = 0.588). Table 2 Postoperative data.
Age (years) mFTA (8) Limb length discrepancy (mm) Transport index (mm/day) Distance distal to Lesser Trochanter (mm) Medullary canal -nail ratio (%)
Varisation group
Valgisation group
p-Value
24.7 10.7 1.4 1.4 49.0 24.4 1.3 1.2 40.6 11.4
31.5 11.8 1.8 1.1 36.3 14.9 2.2 1.2 58.9 16.3
0.26 0.59 0.26 0.18 0.02
69.7 6.6
95.0 6.9
Cause of LLD Post-traumatic Congenital
4 (20%) 3 (15%)
8 (40%) 5 (25%)
1.0
Entry point Piriformis Trochanteric
2 (10%) 11 (55%)
1 (5%) 6 (30%)
1.0
Type of nail ISKD Precice
5 (25%) 0 (0%)
13 (75%) 2 (10%)
0.11
Preoperative alignment Varus Valgus
4 (20%) 3 (15%)
9 (45%) 4 (20%)
0.65
