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Peroneal strength as an indicator in selecting route of tibialis posterior transfer for foot drop correction in leprosy.

Introduction

Foot drop, caused by invasion of M. leprae into the lateral popliteal nerve, is a debilitating complication of leprosy, resulting in an abnormal high-stepping gait, associated with significant secondary impairments such as ulceration, absorption, deformity and disability, if left untreated. (1-3) Reconstructive surgeons have battled with this problem and developed procedures to correct it and enable affected patients to walk normally with or without additional orthoses. The tibialis posterior tendon (TPT) transfer using the circum-tibial (CT) or inter-osseous (IO) route for foot drop has remained the standard procedure for foot drop correction, (4-6) and over time, many improvements have evolved for better outcomes. (7-9) The TPT procedure aims to correct the resting position of the foot and active dorsiflexion at the ankle, restore normal gait and minimise the potential for further injury and deformity. The tendon transfer has evolved into a two slip technique with the aim to reduce inversion/ eversion of the foot. (10) For several years there has been a debate over the functional outcomes and risk of inversion deformity of one procedure or the other. (11-13) The need therefore arose to develop criteria to select a particular route for each patient. The relative merits of these two procedures and the reasons for the superiority of one over the other needs to be examined over a long period of follow-up based on sufficiently large samples. Therefore, in this paper we present such findings based on 381 cases of foot drop surgery done in a leprosy referral hospital in U.P. India, during 1999 to 2010. The findings are discussed and recommendations made.

Subjects and Methods

The Leprosy Mission Community Hospital at Naini, Allahabad district in Uttar Pradesh, India treats a large number of active untreated leprosy patients as well as those with serious complications. It has an excellent medical records system, and each patient has a unique registration number, facilitating the recording of every detail at baseline and during follow-up. All medical records were computerised in 2007.

All the patients who were admitted for foot drop correction from 1999 to 2010 are included in this study. Apart from basic demographic and socio-economic details, historical and clinical data on leprosy, the foot drop was assessed in terms of position at rest of the ankle, effective dorsiflexion (above 90 degrees, towards dorsiflexion), active & passive range of dorsiflexion & plantar flexion of the ankle joint during both knee flexion and extension, inversion at rest and on dorsiflexion and navicular height. These measurements were made using standard procedures with goniometer except navicular height measured using a centimetre scale. Gait was assessed by observation of the patient while walking, using heel to toe pattern as a normal gait. These assessments are available pre-operatively, post operatively after completion of post-op physiotherapy, as well as at later follow-up after surgery. Associated problems and post-operative complications are also recorded. All the assessments were done by a Physiotherapist or physio-technician and were recorded on a surgical audit form. All surgical procedures were done by the same surgeon. The pre- and post- operative physiotherapy programs were the same for all patients.

SURGICAL PROCEDURE

Patients who had peronei muscle Grade 4 or more underwent the Circum-tibial (CT) route procedure, and those with lower grades underwent the Inter-osseus (IO) route procedure for correction of foot drop. The surgery is done under spinal anaesthesia. All patients had a closed Z lengthening of the Tendo-achilles. The Tibialis posterior was split to the muscular level and tunnelled deep to the extensor retinaculum. This was done to improve cosmesis by avoiding bow-stringing of the Tendon under the sub-cutaneous tissue as it crosses the ankle. We insert one slip into the Extensor Hallucis Longus and the second into the Extensor Digitorum Longus including the peroneus tertius at maximal tension, using Linen and Nylon. At least two sutures are through the underlying periosteum to avoid late tendon stretch or migration and claw toes. The tenodesis is done at least 5-7 cm distal to the ankle mortice, to improve the mechanical advantage of the transferred tendon. Skin closure is with SSW. (6,10)

PRE AND POST-OPERATIVE PHYSIOTHERAPY MANAGEMENT

Pre-operative physiotherapy focuses on teaching the patient to learn isolated contraction of the tibialis posterior muscle. This is achieved by exercise with resistance to foot inversion in a crossed leg sitting position for three to four sessions in a day. (6) The patient is taught self-stretching exercises of the tendo- achilles to release the contracture as much as possible.

Post-operatively, below-the-knee POP is applied, incorporating a posterior slab with the foot in 65 to 70 degrees of dorsiflexion. On the 4th or 5th day a Bohler-iron is applied to assist ambulation and the patient is discharged. The plaster is cut on the first day of the 6th week; the patient practices contraction of the tibialis posterior action with gravity elimination. The posterior slab is retained and continued for night use till the patient progresses to full weight bearing. At the 7th week the same is followed but against gravity. At the 8th week, partial weight bearing is commenced after fitting an appropriate orthosis in the footwear. A tarsal cradle or anti-pronatory orthosis is used, depending on the position of the ankle and mid-tarsal joints. (14) At the 9th week, the patient is allowed full weight bearing and taught to walk in a heel to toe pattern between the parallel bars. Once the patient is walking confidently, he is allowed to continue outside the parallel bars and discharged from therapy.

Results

Demographic data of patients is shown in Table 1.

In total, 381 feet were operated for foot-drop during the period of 1999-2010, of which 32 were in female patients. The mean (SD) age of the study population was 36-2 (12-7) years. The mean (SD) duration of deformity was 3-5 (3-7) years. Of the 381 feet, 211 surgeries were on the right foot and 170 on the left foot. Six patients had bilateral foot drop. The CT route was used in 162 feet and IO route was used in 219 feet. After completion of post- operative physiotherapy 270 (71 %) feet had one or more follow-up. The mean (SD) duration of followup in CT group was 22-9 (25-8) months, ranging from 2-3 months to 10 years 7 months. The mean (SD) duration of follow-up in IO group was 24 (23-1) months ranging from 2-6 months to 7 years 5 months.

The resting position of ankle and active dorsiflexion are shown in Table 2.

The resting position was effectively corrected for almost all the patients post-operatively. A large majority of the patients, 98%, had active dorsiflexion above 90 degrees, correcting drop foot and suggesting normal gait of heel to toe pattern.

Effective dorsiflexion (range above 90 degree) and total active range of motion of the ankle are shown in Table 3.

The range showed steady improvement after post-operative physiotherapy before final follow-up.

The extent of inversion deformity is indicated in Table 4.

On average there was no inversion deformity during dorsiflexion. A total of 3-7 % or 14 feet among the two groups (nine in IO & five in CT) developed inversion deformity of more than five degrees.

Table 5 shows the analysis done to assess arch stability or collapse after removal of the tibialis posterior tendon.

The medial arch of the foot was maintained in both the groups during the post-op period. Table 6 shows whether duration of foot drop had any impact on the final outcome of surgery, in terms of Effective Range of Motion.

Although the difference was statistically significant for the combined and IO group, the variation of only 1-2 degrees between them and has no clinical implications.

Table 7 shows whether the results of surgery were impacted by the duration of follow up. There was a difference of only 1-3 degrees between the groups and this was not statistically significant.

The aim of surgery in foot-drop deformity is to restore active dorsiflexion thereby restoring normal gait and to prevent secondary impairments due to foot-drop. (4,10) Both techniques, using the CT and IO routes for Tibialis Posterior Tendon transfer (TPT), are established procedures for correction of foot drop. (9,13,15) Though the dorsiflexion is restored, the inversion deformity has been an associated complication in the CT technique after TPT. (11-13,16) Due to the risk of vascular injury and adhesion, (4,17) as well as dependence on adequate inter-osseous space for the transferred tendon with the IO route, several surgeons prefer the CT route for transfer. Several publications have reported the outcome of a single route (7, 8, 10, 18) but there is scant literature available comparing the two routes, (11,13) particularly when done by the same team, in the same time period. There are no convincing guidelines on when to select which route. In this case series, we have allocated the type of route based on the muscle power of evertors (peronei) and studied their outcome prospectively in terms of restoring active/ effective dorsiflexion and preventing inversion deformity.

The dorsiflexion range above 90 degrees (from neutral position of the ankle) after surgery, is considered to restore normal gait (heel to toe) pattern. Therefore, instead of just considering the total active range from active plantar flexion to active dorsiflexion, it is important to look at how much a patient can take his or her foot above 90 degrees, towards dorsiflexion. This range we refer to as the effective range of motion (EROM). In this case series the mean (SD) effective range was 11[degrees] (four) and 12[degrees] (four) in CT and IO routes, respectively, at discharge from post-operative physiotherapy and 12[degrees] (six), 12[degrees] (five) at final follow-up. The range compares favourably with earlier publications. (7,8,13,15) The drop in active dorsiflexion range is less compared with another study. (13) There is no evidence from this study, of the reduction in ROM anticipated due to adhesions in the IO route (4,17,18) and contrary to this, the IO group in this study had a higher range as compared to the CT group. A similar result was also reported in another publication. (13) Increased range in IO could be because of the biomechanical advantage of this route. (19) Thus, there is no evidence from this study that IO route reduces the range of motion of the transferred tendon. This study shows that the two techniques produce comparable results in terms of rest position, active dorsiflexion and effective range of motion. All patients had a post-operative heel to toe gait except for one of the 381 operated.

There has been a negative impression concerning the CT route that it causes iatrogenic inversion deformity and lateral border ulceration. (13) This may have influenced surgeons to choose only the IO route. However, success has been achieved in preventing inversion deformity through pre-selection based on evertor strength. The modifications at the point of insertion of Tibialis Posterior (first slip passed through the extensor hallucis longus and second slip through extensor digitorum longus with the peroneus tertius tendon (10) and sutured to it and the underlying periosteum) may have also contributed. In this series without further changes in surgery only 3-7% (14) feet developed some iatrogenic inversion. The results of this study strongly suggest that the inversion deformity can be prevented if CT is done for those with strong evertors (Grade 4 and 5) and IO for those with weak evertors (Grade 3 and less) without compromising on active dorsiflexion. This finding is in contradiction to Soares (13) who reported that 3/6 patients (50%) with normal evertors in CT group developed inversion deformity against 0/10 in IO group.

The occurrence of a medial arch collapse was a major concern in tibialis posterior removal. (14) Only three of the 381 feet had a reduction of navicular height of more than 2 cm, the medial arch being maintained in the others. This was possible by using appropriate orthoses depending on the foot position after the patient starts weight bearing. Medial arch support, tarsal cradle and anti-pronatory orthoses (14) were common orthoses used in footwear.

There was no impact of duration of deformity on the results of surgery and this is described in Table 6.

There was a reduction in the number of patients who returned for follow-up after discharge from post-operative physiotherapy. Most of the patients who were operated on at TLM Naini come from hundreds of kilometres away and poverty, loss of wages with travel expenses prevent some of them from returning for late follow-up. There was a large variation in the follow up duration ranging from 2 months to 10 years; hence patients were grouped into three time periods of less than 1 year, 1-5 years and > 5 years. The difference in the EROM between these groups was 1-3 degrees and did not show any statistical significance.

Conclusion

TPT (Tibialis Posterior Transfer) is a standard procedure to correct foot drop deformity in leprosy. Pre-selection for route of transfer, circum-tibial or inter-osseous, based on peronei strength avoids the complication of inversion. The technique of insertion and routine tendoachilles lengthening provides a good range of movement. The deep tunnelling has not compromised on results while giving excellent cosmetic appearance.

Acknowledgements

We thank the staff in the physiotherapy department, medical records department and operation theatre as well as the ward staff for their co-operation and compassionate services. Thank you to the patients for their co-operation during the procedure and physiotherapy as well as travelling long distances for follow-up.

References

(1) Van Brakel WH, Khawas IB. Nerve damage in leprosy: an epidemiological and clinical study of 396 patients in west Nepal--Part 1: Definitions, methods and frequencies. Lepr Rev, 1994; 65: 204-221.

(2) Schipper A, Lubbers WJ, Hogeweg M, de Soldenhoff R. Disabilities of hands, feet and eyes in newly diagnosed leprosy patients in eastern Nepal. Lepr Rev, 1994; 65: 239-247.

(3) Srinivasan H. Prevention of disabilities in patients with leprosy. A practical guide: Preventing damage to insensitive feet. WHO, Geneva, 1993; pp. 50-74.

(4) Anderson JG. Foot drop in leprosy and its surgical correction. Act Orthop Scand, 1963; 33: 151-171.

(5) Anderson JG. Footdrop in leprosy. Lepr Rev, 1964; 35: 41.

(6) Srinivasan H, Palande. Essential surgery in leprosy techniques for district hospitals: Surgery for correction of foot drop. WHO, Geneva, 1997; pp. 68-78.

(7) Ozkan T, Tuncer S, Ozturk K et al. Tibialis posterior tendon transfer for persistent drop foot after peroneal nerve repair. J Reconstr Microsurg, 2009; 25: 157-164.

(8) Kilic A, Parmaksizoglu AS, Kabukculoglu Y et al. Extramembranous transfer of the Tibialis posterior tendon for the correction of drop foot deformity. Acta Orthop Traumatol Turc, 2008; 42(5): 310-315.

(9) Shah RK. Tibialis posterior transfer by interosseous route for correction of foot drop in leprosy. Int Orthop, 2009; 33(6): 1637-1640.

(10) Srinivasan H, Mukherjee SM, Subramaniam RA. Two-tailed transfer of tibialis posterior for correction of dropfoot in leprosy. J Bone Joint Surg [Br], 1968; 50B: 623-628.

(11) Fritchi EP, Brand PW. The place of reconstructive surgery in prevention of foot ulceration in leprosy. Int J Lepr, 1957; 25: 1-8.

(12) Hall G. A review of drop-foot corrective surgery. Lepr Rev, 1977; 48: 185-192.

(13) Soares D. Tibialis posterior transfer in the correction of footdrop due to leprosy. Lepr Rev, 1995; 66: 229 -234.

(14) Cross H. Foot orthotic therapy. In: Schwarz R, Brandsma W (eds). Surgical reconstruction & rehabilitation in leprosy and other neuropathies. Ekta books, Kathmandu, Nepal, 2004; pp. 237-248.

(15) Soares D. Tibialis posterior transfer for the correction of foot drop in leprosy. Long-term outcome. J Bone Joint Surg [Br], 1996; 78: 61-62.

(16) Thangaraj RH. Drop foot in leprosy and its treatment. Lepr India, 1969; 314-316.

(17) Hove LM, Nilsen PT. Posterior tibial tendon transfer for drop-foot. 20 cases followed for 1 -5 years. Acta Orthop Scand, 1998; 69: 608-610.

(18) Richard BM. Interosseious transfer of tibialis posterior for common peroneal nerve palsy. Bone Joint Surg [Br], 1989; 71B: 834-837.

(19) Goh JC, Lee PY, Lee EH, Bose K. Biomechanical study on tibialis posterior tendon transfers. Clin Orthop Relat Res, 1995; Oct (319): 297-302.

PREMAL DAS *, JULIUS KUMAR *, G KARTHIKEYAN * & PSS SUNDAR RAO **

* TLM Community Hospital Naini, Allahabad, Uttar Pradesh, India

** TLM RRC, Noida, Uttar Pradesh, India

Accepted for publication 2 July 2013

Correspondence to: Premal Das, Surgeon & Superintendent, The Leprosy Mission Hospital, Naini, Allahabad--211 008, Uttar Pradesh, India. (e-mail: tlmnaini@tlmindia.org & premal.das@tlmindia.org)
Table 1. Demographic data of patients

                                 CT             IO           Total

Number of feet              162            219            381
  operated
Mean age in                  37.4 (13.3)    35.3 (12.2)    36.2 (12.7)
  years (SD)
Side                Right    89            122            211
                    Left     73             97            170
Duration of foot              3.4 (3.6)      3.6 (3.7)      3.5 (3.7)
  drop in years
  (Mean & SD)
Duration of                  22.9 (25.8)    24 (23.1)      23.6 (24.2)
  final
  follow-up in
  months (Mean &
  SD)

Table 2. Mean (SD) position of ankle at rest and at active
dorsiflexion (in degrees) when knee is in 90 degrees of flexion

                      Ankle at rest in degrees

                        CT                IO

                   N    Mean (SD)    N    Mean (SD)

Pre op            162    113 (7)    219    112 (6)
Post op           162     83 (6)    219     83 (5)
Final follow-up   114     87 (7)    156     88 (6)

                   Active dorsiflexion in degrees

                        CT                IO

                   N    Mean (SD)    N    Mean (SD)

Pre op            162    111 (8)    219    110 (9)
Post op           162     72 (6)    219     71 (6)
Final follow-up   114     73 (7)    156     74 (7)

Table 3. Mean (SD) effective dorsiflexion and total active range of
motion (in degrees) of ankle with knee at 90 degrees of flexion

                      Effective dorsiflexion *

                        CT                IO

                   N    Mean (SD)    N    Mean (SD)

Pre op            162     0         219     0
Post op           162    11 (4)     219    12 (4)
Final follow-up   114    12 (6)     156    12 (5)

                   Total active range of motion **

                        CT                IO

                   N    Mean (SD)    N    Mean (SD)

Pre op            162    13 (7)     219    10 (7)
Post op           162    15 (5)     219    16 (6)
Final follow-up   114    20 (7)     156    19 (7)

* Dorsiflexion range above 90 degrees at ankle.

** Total ankle motion from active plantar flexion to active
dorsiflexion.

Table 4. Mean (SD) inversion at rest and at dorsiflexion (in degrees)
with knee in full extension

                            Inversion at rest

                          CT                 IO

                   N     Mean (SD)      N    Mean (SD)

Pre op            162      6.8 (6.7)   219   15.7 (7.2)
Post op           162   -0.8 * (4)     219    1.1 (4.2)
Final follow-up   114   -0.5 * (4)     156      1 (4)

                         Inversion at dorsiflexion

                          CT                   IO

                   N      Mean (SD)      N     Mean (SD)

Pre op            162     12.2 (11.1)   219   20.4 (11.4)
Post op           162   -1.5 * (5.3)    219    0.5 (5.3)
Final follow-up   114     -2 * (5)      156      1 (4)

* Negative symbol indicates that the foot is in eversion.

Table 5. Mean (SD) navicular height during standing position
(in centimetres)

                           CT                IO

Navicular height *    N    Mean (SD)    N    Mean (SD)

Pre op               162   3.3 (0.8)   219   3.3 (0.8)
Post op              162   3.2 (0.8)   219   3.2 (0.8)
Final follow-up      114     3 (0.8)   156     3 (0.8)

* The distance between floor and tuberosity of navicular.

Table 6. Analysis of duration of foot drop on Effective Range of
Motion (EROM in degrees)

                          Duration of foot drop

               < 2 years        2-5 years        > 5 years

                    Mean             Mean             Mean        P
             N    EROM (SD)   N    EROM (SD)   N    EROM (SD)   Value

CT and IO   154    13 (5)     71    11 (4)     45    12 (4)     .030
CT           70    13 (5)     28    11 (4)     16    12 (5)     .375
IO           84    14 (5)     43    12 (5)     29    12 (4)     .039

Table 7. Impact of duration of follow-up on EROM (in degrees)

                           Length of follow-up

               < 1 year          1-5 years        > 5 years

                    Mean              Mean             Mean        P
             N    EROM (SD)    N    EROM (SD)   N    EROM (SD)   Value

CT and IO   123    13 (4)     122    12 (5)     25    12 (4)     .786
CT           53    12 (4)      51    12 (6)     10    14 (3)     .363
IO           70    14 (5)      71    12 (5)     15    11 (4)     .105
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Author:Das, Premal; Kumar, Julius; Karthikeyan, G.; Rao, P.S.S. Sundar
Publication:Leprosy Review
Date:Sep 1, 2013
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