Split tibials posterior tendon transfer in the management of spastic talipes varus

Abstracts

Foram avaliados dez pacientes (12 pés) com paralisia cerebral espástica submetidos à hemitransposição do tendão do tibial posterior para correção da deformidade em varo do pé. Quatro pacientes eram do sexo feminino e 6 do sexo masculino. A idade média dos pacientes foi de 8 anos e 9 meses. Seis pacientes apresentavam paralisia cerebral espástica hemiplégica; 2,diplégica e 2 pacientes, paralisia cerebral tipo misto. O tempo médio de seguimento foi de 26 meses. Cirurgias associadas foram realizadas em 11 pés (92%). Oito pés apresentaram bom resultado (67%), três pés (25%), resultado regular e um pé (8%), mau resultado. Nenhum dos pés desenvolveu deformidade em calcâneo-valgo. Os resultados regulares e mau estiveram associados principalmente à insuficiência do músculo tibial anterior que levou à necessidade de manutenção do uso de órtese no pós-operatório, à influência de outras forças deformantes no pé além do músculo tibial posterior e à presença de deformidade óssea estruturada. Os autores concluem que a técnica de hemitransposição do tendão do tibial posterior, associada a outras cirurgias quando necessário, tem bom resultado na correção da deformidade em varo do pé na paralisia cerebral; desde que sejam determinadas corretamente as características dinâmicas da deformidade e eventuais deformidades associadas sejam tratadas de forma apropriada, concomitantemente.

Paralisia cerebral; Pé varo; Espasticidade muscular

ORIGINAL ARTICLE

Split tibials posterior tendon transfer in the management of spastic talipes varus

Ana Paula T. Gabrieli^I; Helena Elisa Stein^II; Lauro Machado Neto^III

^IMaster in Orthopedics and Traumatology, Professor of Orthopedics and Traumatology at the University of Caxias do Sul

^IIDoctorate Student at the Univesity of Caxias do Sul

^IIIOrthopedist and Traumatologist

^{Correspondence}

SUMMARY

Ten patients with cerebral palsy and varus spastic deformity (12 feet) were evaluated after hemitransposition of posterior tibial tendon. There were 4 female and 6 male patients. Mean age at surgery was 8 years and 9 months. Regarding motor involvement, 6 patients were hemiplegic, 2, diplegic and 2 patients had mixed type cerebral palsy. Mean follow-up was 26 months. Associated surgeries were performed in 92% of the cases (11 feet). Good results were achieved in 67% of the cases and regular results in 25% . There was one bad result (8%). None of the feet developed a calcaneovalgus deformity. Regular and bad results were mainly associated to anterior tibial insufficiency, leading to the maintenance of the orthosis; the influence of other deforming forces on the foot besides the posterior tibial and to the presence of structural bony deformities. The technique of hemitransposition of tibial posterior tendon, associated to other procedures as indicated, leads to good results in correcting spastic varus deformity of the foot in cerebral palsy. Dynamic components of the deformity need to be determined pre-operatively and structural bony deformities must be corrected concomitantly.

Keywords: Cerebral palsy; Varus foot; Muscle Spasticity.

Equinus, valgus, and varus talipes are frequently found in patients with cerebral palsy (CP). Varus talipes is much rarer than valgus talipes and more frequent in hemiplegic patients. Imbalance in the dynamics between the tibialis posterior and toe flexor muscles (spastic) and peroneus muscles leads to varus talipes, often associated with equinus talipes ^{[5, 7]}. Varus talipes adversely affects support and gait by modifying the mechanisms of support and cycle balance phases not only of the foot and ankle, but also of the knee joint and hip ^[4]. In addition, the use of shoes and orthoses is difficult, pain and callosities develop in areas under pressure ^{[13, 14]}.

The tibialis posterior muscle is the main muscle involved in dynamic varus abnormality during gait ^[5]. Careful physical examination, including muscular tests, can distinguish the participation of the tibialis posterior muscle from that of the tibialis anterior muscle in the causation of deformity. Associated structured bone abnormalities must also be investigated since varus deformity can be dynamic and evidenced during walking only, appearing during the support and/or the balance phase. Physical examination can reveal correction of adduction and talipes equinus at rest and during walking. Initial treatment for this deformity is based upon lengthening exercises and use of orthosis while focal treatment for spasticity of tibialis posterior muscle with type A botulinum toxin has also been used. Surgical therapy is indicated when conservative therapy fails ^{[9, 14]}.

Several techniques are used in the management of spastic talipes varus. Tenectomy of the tibialis posterior muscle at its insertion on the navicular bone is frequently associated with talonavicular joint collapse, resulting in hindfoot valgus ^[1]. Intramural or tibialis posterior muscle lengthening leads to muscular weakening but do not enhance redirection of anomalous forces acting upon the foot, theoretically favoring deformity recurrence. Techniques of anterior redirection of the tibialis posterior tendon on the medial malleolus and total or partial transposition of the tibialis posterior tendon through interosseous membrane to the back of the foot have been associated with inconsistent results ^{[1, 2, 8, 10, 11]}.

Split tibialis posterior tendon transfer to the peroneus brevis tendon was first described by Green ^[5] for correction of talipes varus in patients with CP. This author recommends the use of this technique when the tibialis posterior muscle is spastic, the tibialis anterior muscle is weak, and peroneus muscles are weak or lacking. Surgical treatment aims to produce and maintain a platigrade foot, prevent skeletal deformities, and make walking possible or improve it. With surgery hindfoot is balanced without the excessive weakening of the tibialis posterior muscle. Other authors have obtained good results with the technique ^{[3, 6, 7, 8, 11, 14]}.

The present study describes and evaluates the results obtained in 10 patients (12 feet) in whom spastic talipes varus was treated with split tibialis posterior tendon transfer according to the technique described by Green.

MATERIALS AND METHODS

Medical records of patients operated from July 1996 to June 2001 were reviewed. Six male and 4 female community ambulatory patients with spastic cerebral palsy and talipes varus (10 patients with a total of 12 feet) were submitted to split tibialis posterior tendon transfer. Patients were aged 4 years and 2 months to 16 years (mean age: 8 years and 9 months). Unilateral deformity was present in 8 (80%) patients and bilateral deformity was found in 2 (20%) patients.

As for the type of CP, 6 (60%) were of the spastic hemiplegic type; 2 (20%) were of the spastic diplegic type; and 2 (20%) were of the mixed diplegic type (athetotic or dystonic component). Talipes varus and equinus were associated in nine feet. Dynamic varus deformity was present in 8 feet and structured varus deformity was found in 4 feet. Talipes cavus was also present in four feet with a positive Coleman test.

Postoperative follow-up ranged from 12 to 67 months with a mean of 26.6 months.

Conservative treatment was used by all patients before surgery, including physical therapy, use of orthoses, type-A botulinum toxin. Surgery was later indicated because previous treatments had been unsuccessful. Surgical indication was based upon physical examination; varus deformity was present throughout the walking cycle and callosities were found on the lateral side of the foot, as well as shoe changes. Electromyography or walking analysis were not carried out.

Two different surgeons performed the operation according to the technique described by Green ^[5].

Associated surgeries were carried out as needed according to associated deformities present in individual cases.

Informed consent was not required since the present study was retrospective and based upon review of medical records.

RESULTS

Results were evaluated through clinical criteria of deformity correction and need for orthoses following surgery. The following definitions were adopted: good result: corrected deformity and no need for orthosis; modest result: corrected deformity and need for orthosis (polypropylene splint) so as to make walking possible; poor result: residual deformity and need for posterior surgical correction. Good results were obtained in 67% of cases (8 feet - 7 patients). Three feet (2 patients obtained modest results (25%) and a poor result was obtained in 1 foot (8%). No patient developed surgical complications (Table 1).

In the case with poor result deforming forces acting upon the lower limb other than the tibialis posterior muscle were present and accounted for walking abnormality together with structured talipes varus. Following medial ischiotibial lengthening, Dwyer-type osteotomy, and split tibialis anterior tendon transfer the foot became plantigrade with improved walking pattern and no need for orthosis (a good final result). In cases with modest results the need for orthosis was due to residual deformity, not talipes equinovarus but adduction of the front foot or faulty release of the foot in the balance phase due to insufficiency of the tibialis anterior muscle. In both cases, walking pattern was improved with the use of orthosis and posterior surgical repairs were not required.

Concomitant surgeries were carried out to correct associated deformities of 10 feet, including lengthening of gastrocnemius muscle according the Strayer , Vulpius, or Baker technique (9 feet), plantar fasciotomy (3 feet), calcaneus osteotomy by Dwyer technique (3 feet). Split tibialis posterior tendon transfer was the sole surgery in one foot only (Table 1).

DISCUSSION

Hyperactivity of the tibialis posterior muscle is often responsible for talipes varus in patients with CP. According to studies carried out by Green ^[5] using dynamic electromyography and video analysis of walking pattern, the tibialis posterior muscle is continuously stimulated during walking cycles in children with this deformity. Laboratory analysis of walking reveals changes in sagittal kinematics in patients with CP and talipes varus. Foot and ankle motion range is descreased during the support phase and predominantly appears with plantar flexion when foot prepositioning angle is in the varus position ^[11]. Dynamic changes in walking, more easily demonstrated and quantified by laboratory analysis, should be carefully investigated and recorded before therapy is considered. One must clinically establish whether deformity results from the tibialis posterior or anterior muscle action. When the tibialis posterior muscle is involved, it is usually tense and produces varus shift of the hindfoot, often in association with talipes equinus. In contrast, when the tibialis anterior muscle is involved, deformity occurs with dynamic adduction and supination of the foot. However, in many situations, concomitant spasticity of the tibialis anterior muscle cannot be ruled out ^{[8, 11]}. In the present study, laboratory analysis of walking was not carried out before surgery, as most published studies evaluating this technique. Knowledge of deformity physiopathology in spastic cerebral palsy and a careful and thorough physical examination together with videos of patients seem to suffice for indication of surgery, an idea shared by other authors ^{[3, 14]}. Laboratory analysis of walking, however, is an important tool in the evaluation of patients with cerebral palsy. Patients with mixed cerebral palsy (in whom good results were not obtained with preliminary treatment) perhaps could be best evaluated and treated based upon data obtained by laboratory analysis of walking since clinical evaluation can be difficult in these cases.

Several reports consider split tibialis posterior tendon transfer a safe and effective technique for correction of spastic talipes varus. With this technique, walking mechanisms are improved and, lateral border support is eliminated, thus allowing calcaneus to be the first to come in contact with the floor with no lateral column load and no need for orthoses. In a singular study using laboratory analysis of walking, O'Byrne ^[11] has objectively shown an improvement of hindfoot alignment in the sagittal plane following surgery with excellent results in 13 out of 16 patients. Using anatomical specimens Piazza et al. ^[12] have shown that split tibialis posterior and anterior tendon transfer substantially decreased inversions of the subtalar joint. As a result, these techniques are very susceptible to technical failures, specially those related to tension balance between the medial and lateral portions of tendons. This shows that good results are obtained only if the originally described technique is rigorously adopted.

This technique is also associated with a low complication rate, such as correction loss in the long run and overcorrections or undercorrections, resulting in talipes valgus or calcaneus. Fucs et al. ^[3] reported good results in 90.24%; Green ^[5] reported one unsatisfactory result in 16 patients; Kling ^[8] reported excellent results in 30 cases, good results in 4 and poor results in 3 out of 31 patients. The present study found good results in 67% of cases and no valgus overcorrection or other complications (Figure 1).

Modest results obtained in patients who still neeeded orthosis following surgery can be related to lack of active dorsiflexion of the foot, as seen in 2 feet; active dorsiflexion of the foot is required to make detachment easier, a fact also observed by Kling ^[8]. O'Byrne ^[11] have shown that some of his patients who did not present active dorsiflexion before surgery developed this movement following transfer. In the present study this fact was not seen. In another case a modest result was due to a foot deformity in dynamic adduction that could be managed by an orthosis, and to a mild residual deformity in varus position that should be treated through calcaneus osteotomy in advance. This individual patient had mixed cerebral palsy (athetoid component).

According to literature poor results associated with this technique include undercorrections with excessive varus hindfoot as well as overcorrection resulting in valgus foot. Synder ^[14] and Fucs et al. ^[3] among others reported a poor result in 3 cases in each study, all of them with residual varus foot. Structured bone deformities must be identified before surgery and can be adequately treated before or concomitantly with split tibialis posterior tendon since soft tissue surgery only is not able to correct such deformities. In the present study structured bone deformities of the hindfoot diagnosed before surgery were treated with calcaneus osteotomy during tendon transfer.

The poor result seen in the present study was probably due to an incorrect preoperative evaluation in one dystonic patient. In this case, due to peculiar characteristics of muscular tonus changes, the foot deformity was due to changes in the tibialis anterior and ischiotibial muscles and not to changes in tibialis posterior muscle. In addition, in this case the structured bone deformity of hindfoot was not adequately treated during first surgery. With lengthening of medial ischiotibial musculature, split tibialis anterior tendon transfer, and calcaneus osteotomy, the foot became plantigrade, orthosis being not required.

In cases where preoperative evaluation is difficult, a repeated physical examination, recording of walking, and ideally laboratory analysis of walking can be indicated. According to literature dystonic components or involuntary movements associated with spasticity do not contraindicate the use of this technique ^[7].

Several authors who described their results with the use of this technique have emphasized the need for simultaneous lengthening of Achilles tendon in the majority of patients.

This was needed in 11 out of 12 feet in our study. Lengthening of the plantar flexor musculature was not needed in one patient since he had 10-degree dorsiflexion with extended knee and plantigrade foot in the support phase.

Although Green ^[5] stated that the maintenance of half of the tibialis posterior tendon preserves the plantar flexor force, thus preventing calcaneus deformity, we decided to lengthen musculature and not tendons because a decreased loss of propulsive force of the ankle associated with the latter was desirable ^{[3, 4, 5, 8, 11, 14]}.

CONCLUSION

Split tibialis posterior tendon transfer in the management of the spastic talipes varus leads to good results as far as correction of this deformity is concerned. For concomitant correction of talipes equinus, lengthening of plantar flexor muscles is needed in the majority of cases. Structured bone deformities must be identified and adequately treated. Careful clinical evaluation before surgery is essential to define abnormal walking components.

REFERÊNCIAS BIBLIOGRÁFICAS

Trabalho recebido em 25/04/2003.

Aprovado em 12/08/2003

Work performed at the University of Caxias do Sul, Department of Surgical Clinics of Center of Biological Sciences and Health , Orthopedics and Traumatology.

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Publication Dates

• Publication in this collection
  01 Mar 2005
• Date of issue
  Dec 2004

History

• Accepted
  12 Aug 2003
• Received
  25 May 2003