Tibialis Posterior Tendon Transfer Corrects the Foot Drop Component

Home , Achilles tendon, Foot, Peroneus brevis, Tibialis anterior muscle

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Tibialis Posterior Tendon Transfer Corrects the Foot DropComponentofCavovarusFootDeformity in Charcot-Marie-Tooth Disease

T. Dreher, MD, S.I. Wolf, PhD, D. Heitzmann, MSc, C. Fremd, M.C. Klotz, MD, and W. Wenz, MD

Investigation performed at the Division for Paediatric Orthopaedics and Foot Surgery, Department for Orthopaedic and Trauma Surgery, Heidelberg University Clinics, Heidelberg, Germany

Background: The foot drop component of cavovarus foot deformity in patients with Charcot-Marie-Tooth disease is commonly treated by tendon transfer to provide substitute foot dorsiflexion or by tenodesis to prevent the foot from dropping. Our goals were to use three-dimensional foot analysis to evaluate the outcome of tibialis posterior tendon transfer to the dorsum of the foot and to investigate whether the transfer works as an active substitution or as a tenodesis. Methods: We prospectively studied fourteen patients with Charcot-Marie-Tooth disease and cavovarus foot deformity in whom twenty-three feet were treated with tibialis posterior tendon transfer to correct the foot drop component as part of a foot deformity correction procedure. Five patients underwent unilateral treatment and nine underwent bilateral treatment; only one foot was analyzed in each of the latter patients. Standardized clinical examinations and three-dimensional gait analysis with a special foot model (Heidelberg Foot Measurement Method) were performed before and at a mean of 28.8 months after surgery. Results: The three-dimensional gait analysis revealed significant increases in tibiotalar and foot-tibia dorsiflexion during the swing phase after surgery. These increases were accompanied by a significant reduction in maximum plantar flexion at the stance-swing transition but without a reduction in active range of motion. Passive ankle dorsiflexion measured in knee flexion and extension increased significantly without any relevant decrease in passive plantar flexion. The AOFAS (American Orthopaedic Foot & Ankle Society) score improved significantly. Conclusions: Tibialis posterior tendon transfer was effective at correcting the foot drop component of cavovarus foot deformity in patients with Charcot-Marie-Tooth disease, with the transfer apparently working as an active substitution. Although passive plantar flexion was not limited after surgery, active plantar flexion at push-off was significantly reduced and it is unknown whether this reduction was the result of a tenodesis effect or calf muscle weakness. Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Peer Review: This article was reviewed by the Editor-in-Chief and one Deputy Editor, and it underwent blinded review by two or more outside experts. It was also reviewed by an expert in methodology and statistics. The Deputy Editor reviewed each revision of the article, and it underwent a ﬁnal review by the Editor-in-Chief prior to publication. Final corrections and clariﬁcations occurred during one or more exchanges between the author(s) and copyeditors.

Disclosure: None of the authors received payments or services, either A commentary by Michael S. Aronow, MD, directly or indirectly (i.e., via his or her institution), from a third party in is linked to the online version of this article support of any aspect of this work. None of the authors, or their in- at jbjs.org. stitution(s), have had any financial relationship, in the thirty-six months prior to submission of this work, with any entity in the bio- medical arena that could be perceived to influence or have the potential to influence what is written in this work. Also, no author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Con- flicts of Interest submitted by authors are always provided with the online version of the article.

J Bone Joint Surg Am. 2014;96:456-62 d http://dx.doi.org/10.2106/JBJS.L.01749

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T HE J OURNAL OF B ONE &JOINT SURGERY d JBJS. ORG TIBIALIS P OSTERIOR T ENDON T RANSFER CORRECTS THE F OOT VOLUME 96-A d NUMBER 6 d M ARCH 19, 2014 DROP COMPONENT OF CAVOVARUS F OOT DEFORMITY

cavovarus foot deformity may limit quality of life, re- foot deformity12,13. Some authors recommend transfer of the ducing the ability to perform daily activities, and it may tibialis posterior tendon to the dorsum of the foot and report be associated with a high level of disability1,2.Charcot- satisfactory results12-16. However, previous studies have lacked an A 3 Marie-Tooth disease represents one of the most common neu- objective evaluation of ankle function after this transfer. Tendons rogenic causes of bilateral cavovarus foot4. This progressive disease are transferred to create an active substitution for a weak muscle is caused by malfunction of the myelin sheath leading to muscle or a tenodesis effect to dynamically fix a joint in a favorable atrophy and muscle imbalance5-9. position. An active substitution should be preferred for patients An abnormal gait, painful callus formation, and ankle in- who are potentially able to relearn active function, such as pa- stability may develop as part of the characteristic cavovarus foot tients with Charcot-Marie-Tooth disease. The tibialis posterior deformity5-9. One important etiologic factor is weakness of the normally generates an internal plantar flexing moment and is tibialis anterior muscle, which presents clinically as foot drop. In coactivated with other plantar flexors (calf muscles and long toe combination with an abnormally strong pull by the peroneus flexors)17; however, it is not known whether it can adapt to a longus to compensate for peroneus brevis weakness, tibialis an- different activation pattern and act as an active dorsiflexor after terior weakness is a major underlying cause of cavovarus foot10,11. being transferred to the dorsum of the foot in patients with As a result of foot drop, gait impairment can occur during the Charcot-Marie-Tooth disease. These effects have not yet been swing and stance phases of the gait cycle. Ferrarin et al. defined investigated and compared with each other. three gait patterns in young patients with Charcot-Marie-Tooth A major limitation of the use of conventional gait analysis disease according to the results of a clustering analysis: pseudo- models18 in evaluating foot deformities is their representation normal, foot drop only, and foot drop with a push-off deficit11. of the foot as a single rigid lever. The cavovarus foot also in- Various procedures have been described to correct the foot volves forefoot equinus (cavus), and changes in the arch as a drop component during a surgical intervention to correct the result of cavus correction have a major impact on sagittal ankle

TABLE I Outcomes for the Fourteen Involved Feet

Parameter Baseline* Follow-up* P Value† Normal*

Clinical examination AOFAS hindfoot score 55 ± 11 76 ± 10‡ <0.001 100 Passive ankle dorsiflexion at 90° knee flexion (deg) 0 ± 11 15 ± 6‡ <0.001 15-25 Passive ankle dorsiflexion in knee extension (deg) 24 ± 11 9 ± 5‡ <0.001 10-15 Passive ankle plantar flexion (deg) 45 ± 536± 8‡ 0.031 30-50 Range of passive ankle dorsiflexion and plantar flexion 41 ± 12 45 ± 9‡ 0.340 40-65 in knee extension (deg) HFMM three-dimensional gait and foot analysis (deg) Swing phase Max. tibiotalar dorsiflexion 0.0 ± 5.5 6.3 ± 2.1‡ <0.001 7.4 ± 2.2 Max. tibiotalar plantar flexion 23.9 ± 4.5 2.8 ± 2.5‡ <0.001 212.8 ± 5.6 Range of tibiotalar dorsiflexion and plantar flexion 3.8 ± 2.3 3.6 ± 2.0 0.726 19.3 ± 5.1 Max. foot-tibia dorsiflexion 215.9 ± 11.7 21.8 ± 4.9‡ <0.001 23.0 ± 2.9 Max. foot-tibia plantar flexion 220.5 ± 10.4 25.4 ± 5.3‡ <0.001 229.0 ± 6.6 Range of foot-tibia dorsiflexion and plantar flexion 4.6 ± 2.8 3.6 ± 2.0 0.305 25.9 ± 6.2 Stance phase Max. tibiotalar dorsiflexion 9.6 ± 5.6 12.4 ± 2.3‡ 0.093 10.1 ± 2.8 Max. tibiotalar plantar flexion 211.8 ± 5.8 25.5 ± 3.5‡ 0.002 210.4 ± 4.8 Range of tibiotalar dorsiflexion and plantar flexion 21.3 ± 7.4 17.8 ± 2.7 0.109 20.4 ± 4.7 Max. foot-tibia dorsiflexion 25.1 ± 12.0 7.7 ± 3.0‡ <0.001 4.6 ± 3.5 Max. foot-tibia plantar flexion 230.0 ± 9.6 214.0 ± 5.6‡ <0.001 227.7 ± 6.2 Range of foot-tibia dorsiflexion and plantar flexion 24.9 ± 11.0 21.6 ± 3.1 0.291 32.3 ± 6.0 Mean medial arch 107.2 ± 11.1 118.9 ± 5.6‡ 0.002 123.7 ± 5.9 Lateral standing radiograph (deg) Calcaneal pitch 25.1 ± 8.4 15.4 ± 6.3‡ 0.009 10-20 Talometatarsal angle 20.9 ± 7.1 0.7 ± 12.8‡ <0.001 0

*The values are given as the mean and the standard deviation, or as the mean or the range. †Unpaired t test. ‡Signiﬁcantly different, at the p < 0.01 level, from the preoperative value.

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Fig. 1 The T-SPOTT tibialis posterior tendon transfer technique. The complete tibialis posterior tendon is released at its insertion on the navicular bone through a medial approach (ﬁrst panel). The tendon is pulled out and split in half, and the two halves are tagged with number-1 Vicryl sutures (second panel). Both tendon halves are transferred through the interosseous membrane behind the tibia to the extensor compartment (third panel). After exposing the tibialis anterior tendon, forceps are driven proximally through the tendon sheath beneath the retinaculum extensorum to the anterior approach and one half of the tibialis posterior tendon is grasped and transferred distally (fourth panel). Another approach is used at the lateral aspect of the foot to expose the peroneal tendons and the long toe extensors; the tendon sheath of the long toe extensors is then incised and the forceps are driven proximally within the sheath to the anterior approach at the distal aspect of the leg, where the second half of the tibialis posterior tendon is grasped and then transferred distally (ﬁfth panel). After the transfer, one of the halves of the tibialis posterior tendon is sutured to the tibialis anterior tendon at the medial border of the foot, and the other half is sutured to the peroneus brevis or tertius tendon at the lateral aspect of the foot for balancing (sixth panel). (Reproduced, with permission, from: Wiesel SW. Operative techniques in orthopaedic surgery. Philadelphia: Lippincott Williams & Wilkins; 2012. http://lww.com.)

kinematics in conventional gait analysis. More recently, kine- indicated. Inclusion criteria were the ability to walk independently without any matic foot models have been introduced19-21 that permit eval- assistive device, an age of seventeen to fifty years, and a diagnosis of foot drop. uation of changes in foot and ankle function after corrective Patients with prior surgery involving the lower extremities, foot ulcerations, or gait disturbances due to concomitant hip dysplasia were excluded. All patients surgery in more detail. Only a few studies of the outcomes of provided written informed consent, and the study was approved by the local foot deformity correction have included such a foot model ethical committee. Demographic details are summarized in the Appendix. A analysis, and to our knowledge such an analysis has not pre- total of twenty-three involved feet were treated with tibialis posterior tendon viously been applied to cavovarus foot deformity. The major transfer to the dorsum of the foot as a part of foot deformity correction. Five advantage of use of such a kinematic foot model is that forefoot patients underwent unilateral treatment and nine underwent bilateral treat- equinus (cavus) does not influence the hindfoot results because ment; only one foot was analyzed in each of the latter patients. hindfoot and forefoot motion can be evaluated separately. The purpose of the present prospective study was to Surgery use three-dimensional foot analysis to evaluate the outcome In all patients, the tibialis posterior tendon transfer was performed according to a standardized surgical technique (total split posterior tibial tendon transfer, of standardized tibialis posterior transfer to the dorsum of T-SPOTT)10 as part of a surgical intervention in which all components of the foot the foot as a part of cavovarus correction in patients with deformity were corrected. The concomitant soft-tissue and osseous procedures Charcot-Marie-Tooth disease. The study was intended to are summarized in the Appendix. In our surgical routine, tendon transfers are evaluate whether the transfer works as an active transfer or as prepared first, then hindfoot and midfoot deformities (cavovarus) are corrected a tenodesis. by Chopart arthrodesis and/or osteotomies, followed by correction of the first ray (Jones procedure and/or extension osteotomy). After the foot is corrected and stabilized with Kirschner wires, the ankle is assessed for the presence of Materials and Methods hindfoot equinus and, if necessary, aponeurotic calf muscle lengthening or Subjects Achilles tendon lengthening is performed to correct the equinus. Finally, the ourteen patients with Charcot-Marie-Tooth disease and unilateral or bi- tendon transfers are anchored under tension and sutured with number-1 Vicryl Flateral cavovarus foot deformity with a foot drop component were enrolled (Ethicon). Other than Kirschner wires, the only other type of internal fixation prospectively as a sample of convenience. The patients were recruited at the used was locking plates for the supramalleolar tibial derotation osteotomies special foot deformity outpatient clinic in our hospital if surgical correction was performed in two patients (see Appendix).

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Fig. 2 Figs. 2-A through 2-D Description of the Heidelberg Foot Measurement Method (HFMM) according to Simon et al.19. Fig. 2-A Placement of markers in the lateral and medial epicondyles (LEP and MEP [not shown]), tibial tuberosity (TTU), two points on the medial side of the shin (SH1 and SH2), lateral and medial malleoli (LML and MML [not shown]), lateral, dorsal, and medial aspects of the calcaneus (LCL, CCL, and MCL), navicular (NAV), proximal and distal ends of the first metatarsal (P1MT and D1MT), hallux (HLX), distal end of the second metatarsal (D2MT), and distal and proximal ends of the fifth metatarsal (D5MT and P5MT). (Reproduced, with permission of Elsevier, from: Simon J, Doederlein L, McIntosh AS, Metaxiotis D, Bock HG, Wolf SI. The Heidelberg Foot Measurement Method: development, description and assessment. Gait Posture. 2006 Jun;23[4]:411-24. Epub 2005 Sep 12. Copyright [2006]. http://www.sciencedirect.com/science/journal/09666362.) Fig. 2-B The tibiotalar flexion parameter (flexion between the tibia and the talus, represented by the motion of the calcaneus and navicular) is calculated as the rotation around the malleolar line. Positive values indicate dorsiflexion and negative values indicate plantar flexion. This parameter was chosen to evaluate ankle function independently of the midfoot and forefoot. Fig. 2-C The foot-tibia flexion parameter (flexion between the tibia and the medial longitudinal foot axis) is determined by the line between the calcaneus and the distal end of the first metatarsal (D1MT in Fig. 2-A). Positive values indicate dorsiflexion and negative values indicate plantar flexion. This parameter describes the sagittal motion between the whole foot and the tibia, and it is influenced by the severity of the cavus deformity. Fig. 2-D The medial arch is measured as the absolute angle between the first metatarsal (MT1) and a line from the marker in the medial calcaneus to the navicular. A smaller angle indicates a higher arch. This parameter provides information regarding the severity of the cavus deformity.

T-SPOTT Surgical Technique (Fig. 1) lyzed with use of custom MATLAB (MathWorks, Natick, Massachusetts) soft- The complete tibialis posterior tendon is released, split in half, and transferred ware (MoMo, written by Jan Simon, University of Heidelberg). anteriorly through the interosseous membrane to the dorsum of the foot. One Passive ankle range of motion was assessed in knee extension and at 90° tendon half is transferred to the tibialis anterior tendon, and the other half is of knee flexion during the clinical examination. The AOFAS (American Or- 22 transferred to the peroneus brevis or tertius tendon. thopaedic Foot & Ankle Society) ankle-hindfoot score was assessed in all subjects before and after the surgery; however, it should be noted that the Postoperative Care AOFAS scale is not a validated instrument. All examinations were performed by a physiotherapist and a study nurse who have specialized in gait and foot Non-weight-bearing plaster casts were used postoperatively for a period of five to analysis techniques for more than ten years. six weeks because of the concomitant osseous procedures. After the Kirschner wires were removed, a weight-bearing cast was used for an additional six weeks, followed by use of an ankle-foot orthosis for an additional three months. Data Analysis Physiotherapy (two to three times a week) was begun at nine weeks postopera- Three parameters from the three-dimensional foot analysis were chosen to tively and consisted of passive and active mobilization of the ankle and concentric study the effects of tendon transfer surgery on ankle dorsiflexion. Tibiotalar and eccentric strength training to strengthen dorsiflexion and plantar flexion. All dorsiflexion or plantar flexion describes the motion of the hindfoot in relation patients received at least six months of regular physiotherapy. to the tibia in the sagittal plane. This parameter was chosen to evaluate ankle function independently of the midfoot and forefoot. Foot-tibia dorsiflexion or Evaluation plantar flexion describes the sagittal motion of the whole foot in relation to the All patients were examined preoperatively and postoperatively according to a tibia. This parameter is influenced by the extent of the cavus deformity. The standardized protocol. The mean duration (and standard deviation) of follow- medial arch angle indicates the severity of the cavus deformity (Fig. 2). These up after the intervention was 28.8 ± 12.8 months. Clinical examination and three parameters were evaluated during the stance and swing phases of the gait instrumented three-dimensional gait analysis (Vicon, Oxford, United King- cycle. Within each gait phase, the mean, maximum, minimum, and range were dom) with use of a validated foot model19 (Heidelberg Foot Measurement calculated for each parameter. Method, HFMM) were performed in all patients. Seventeen reflective markers One side of each of the patients with bilateral involvement was ran- were placed at well-defined osseous landmarks of the leg and the foot (Fig. 2). A domly selected for analysis, resulting in a total of fourteen analyzed feet in the heel alignment device was used to standardize the placement of the calcaneal study. Descriptive statistics were used to summarize each parameter of interest. markers. The patient was asked to walk barefoot along a 7-m walkway. At least Unpaired Student t tests were used to evaluate changes over time. A p value of ten valid strides were collected, and the trajectories of the markers were ana- <0.01 was considered significant.

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Fig. 3 Results of the three-dimensional foot analysis (tibiotalar ﬂexion, foot-tibia ﬂexion, and medial arch angle) are shown during the stance and swing phases of the gait cycle as averaged curves of the fourteen feet preoperatively (blue lines) and postoperatively (red lines). Each solid line represents the mean, and the dotted lines represent one standard deviation above or below the mean. The range for twenty-six age-matched normal feet is represented by the gray shading.

Source of Funding Discussion No external source of funding was used for this investigation. endon transfer surgery is commonly used to correct neu- Trogenic foot deformities12-16.Whetherthetendonofa Results muscle transferred to another site can provide an active substi- Clinical Examination tution has always been a matter of concern, especially when the assive ankle dorsiflexion, measured at 90° of knee flexion muscle is normally an antagonist to the one requiring support. Pand in knee extension, had increased significantly (p < In a patient population such as individuals with Charcot-Marie- 0.001) at the time of the follow-up examination, at a mean of Tooth disease who potentially are able to relearn function, an twenty-nine months postoperatively (Table I). Passive plantar active substitution is superior to a simple tenodesis since teno- flexion had decreased slightly (p = 0.031) but remained at a desis would reduce function, especially during activities that mean of 36° (Table I). The AOFAS score improved significantly require a large range of motion and a fast switch from extension from 55 to 76 (p < 0.001), indicating an overall improvement to flexion of the involved joint. Foot drop poses a particular after foot deformity correction. problem as the number of muscles providing foot and ankle dorsiflexion is smaller than the number providing plantar flex- Three-Dimensional Gait and Foot Analysis (HFMM) ion. In patients with Charcot-Marie-Tooth disease, the tibialis Significant increases in tibiotalar dorsiflexion and foot-tibia anterior muscle is often degenerated and the long toe extensors dorsiflexion during the swing phase (p < 0.001) occurred be- are often concomitantly involved7,9. Thus, none of the dorsi- tween the baseline and postoperative time points (Fig. 3 and flexors that are active during the swing phase of gait are available Table I). The postoperative mean values were within the normal as substitutes17, and other muscles need to be considered. In ranges of an age-matched reference group. These changes were these patients, the tibialis posterior tendon is commonly trans- accompanied by significant reductions in maximum plantar ferred to the dorsum of the foot10,12,13. However, the question flexion (minimum dorsiflexion) at the stance-swing transition of whether the transfer can function as an active substitution (p < 0.001) (Fig. 3), but the total ranges of dorsiflexion-plantar during gait has not yet been adequately answered. flexion during the stance and swing phases did not change sig- In the present study, significant increases in tibiotalar and nificantly. The entire flexion curves in Figure 3 were thus shifted foot-tibia dorsiflexion during swing phase were found at a mean of toward dorsiflexion, with an improvement during swing phase two years after the transfer surgery. The objective, computerized but at the cost of plantar flexion at push-off. The mean medial data presented demonstrate that tibialis posterior tendon transfer arch angle increased significantly from 107.2° to 118.9° (p = was an effective procedure to correct the foot drop component 0.002), indicating that the cavus deformity had been corrected. of the cavovarus foot deformity in patients with Charcot-Marie- Tooth disease. However, the increase in dorsiflexion was accom- Radiographic Results panied by a significant reduction in peak plantar flexion at the The calcaneal pitch angle and talometatarsal angle decreased stance-swing transition without any clinically relevant loss of active significantly after surgery (p = 0.009 and p < 0.001, respec- range of motion compared with the normal range, indicating that tively) (Table I). the entire motion curve was shifted toward dorsiflexion, which

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Fig. 4 Figs. 4-A and 4-B The inﬂuence of calcaneal pitch on the tension of the gastrocnemius-soleus complex. Fig. 4-A Preoperative radiograph of a foot with severe cavovarus. The calcaneal pitch is increased, the vertical distance H between the insertion point of the Achilles tendon and the center of the ankle joint is relatively large, and the tension of the gastrocnemius-soleus complex is therefore relatively high. Fig. 4-B Postoperative radiograph showing that foot correction has resulted in correction of the calcaneal pitch and a decrease in the height H. This has decreased the tension of the gastrocnemius-soleus complex, reducing the muscle strength.

may indicate a potential tenodesis effect. The passive ankle lengthening procedure were performed. The progression of dorsiflexion measured in knee flexion and extension, however, the Charcot-Marie-Tooth disease may have influenced increased significantly without any relevant loss of passive plantar plantar flexor muscle strength. Use of a cast over a period of flexion. Thus, ankle excursion during walking was reduced at the nearly three months should also be taken into consideration. end of the stance phase (push-off) despite the fact that the trans- Finally, since the position of the calcaneus in the sagittal ferred muscle allowed passive stretching of the ankle over nearly plane affects the triceps surae23,thereductionintensionof normal plantar flexion ranges after surgery. the gastrocnemius-soleus complex following correction of If the transferred tibialis posterior muscle were active calcaneal pitch (Fig. 4) may aggravate plantar flexor weak- during its former phase of the gait cycle (when it worked as a ness. Calcaneal pitch decreased significantly after surgery in plantar flexor at the same time that the calf muscles were acti- the present study because of Chopart arthrodesis and plantar vated to initiate push-off17), this activity would counteract the fascia release. push-off motion, resulting in reduced plantar flexion during late Postoperative physiotherapy should focus on coordinating stance phase. In this case, the transfer would be working as a the plantar flexors and the transferred muscle, on early mobili- tenodesis. Alternatively, if the transfer does not work actively, a zation (active and passive range of motion), and on early strength neutral ankle position would remain during the swing phase training to improve calf and dorsiflexor muscle strength. In our without a further increase in ankle dorsiflexion until terminal opinion, surgical lengthening of the calf muscles should be swing. Since dorsiflexion increased further during the swing avoided in some patients, especially those who present preoper- phase, this suggests that these postoperative measurements may atively with calf muscle weakness. Surgical calf muscle lengthening represent active dorsiflexion. This hypothesis is strengthened should be limited to the very rare cases of persistent hindfoot by the observation of improved function of the first rocker17 equinus after correction of the cavus deformity. In these patients, during the loading response at the beginning of the stance phase, three-dimensional gait analysis with use of a multisegmental foot when the tibialis anterior muscle is important for controlling model provides important information about the severity of the plantar flexion. If a tenodesis effect had been present, this plantar cavus deformity and the true degree of hindfoot equinus. flexion would have been counteracted; however, our results The variety of concomitant procedures performed in showed harmonious plantar flexion motion after the transfer addition to the tibialis posterior tendon transfer represents a (Fig. 3). On the basis of these observations, the activation pattern weakness of this study with respect to determining the isolated of the tibialis posterior muscle potentially changed after the effects of the tibialis posterior tendon transfer. In particular, the transfer, a finding that has not been reported previously to our modified Jones procedure (in which the extensor hallucis longus knowledge. However, the presence of an active transfer cannot tendon insertion is transferred proximally to the first metatarsal) ultimately be proven by the results of the present study, and fur- can have a potential influence on ankle dorsiflexion during the ther investigations to confirm these findings should therefore swing phase. focus on dynamic electromyography of the tibialis posterior mus- In conclusion, tibialis posterior tendon transfer was ef- cle and calf muscles during walking following transfer surgery. fective at correcting the foot drop component of cavovarus foot Another possible explanation for the decrease in active deformity in patients with Charcot-Marie-Tooth disease. The plantar flexion is weakness of plantar flexor muscles after the tendon transfer appeared to function as an active substitution. surgery, resulting in impaired push-off. Various conditions Although passive plantar flexion was not limited after surgery, may cause plantar flexor weakness. It may result from calf active plantar flexion at push-off was significantly reduced. muscle lengthening surgery, which is needed in rare cases Further studies should investigate whether this reduction is an of cavovarus foot. In the present study, however, only one effect of tenodesis or of calf muscle weakness, the cause of Achilles tendon lengthening and one aponeurotic calf muscle which may be multifactorial.

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Appendix M.C. Klotz, MD A table summarizing patient demographics and surgical Division for Paediatric Orthopaedics and Foot Surgery, procedures is available with the online version of this Department for Orthopaedic and Trauma Surgery, n Heidelberg University Clinics, article as a data supplement at jbjs.org. Schlierbacher Landstraße 200a, 69118 Heidelberg, Germany. Email addresses for T. Dreher: [email protected]; [email protected]

T. Dreher, MD W. Wenz, MD S.I. Wolf, PhD Foot Surgery and Paediatric Orthopaedics, D. Heitzmann, MSc ATOS Clinic, C. Fremd Heidelberg, Germany

References

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