Lepr Rev (2015) 86, 213 219 Changes in plantar load distribution and gait pattern following foot drop correction in leprosy affected patients MRINMOY KARMAKAR*, JERRY JOSHUA* & NIDHU MAHATO* *Premananda Memorial Leprosy Hospital, 259/A, Acharya Prafulla Chandra Road, Manicktala, Kolkata, West Bengal, 700006, India Accepted for publication 12 August 2015 Summary This study was done to compare the changes in plantar load (weight distribution) and gait patterns before and after tibialis posterior transfer surgery in people affected by leprosy. Changes in gait patterns were observed and proportionate changes in plantar load were quantified using data captured by a baropodometer. All the eight patients who underwent tibialis posterior transfer surgery in 2013 in our hospital were included in the study. In addition to the regular erative and erative assessments, the patients also underwent baropodometric evaluation. There was a significant change in plantar load at the heel, lateral border and forefoot. Using the foot pressure scan, it was noted that the progression of the centre of mass (displayed graphically as the gait line ) was also affected by the altered pattern of weight distribution. This study reiterates the importance of tibialis posterior transfer because: it restores the normal gait pattern of 1, 2, 3 (where 1 is heel strike, 2 is mid foot contact and 3 is forefoot contact) and provides a more uniform distribution of planter load. Introduction It is generally understood that neuropathy is a characteristic feature of leprosy which affects primarily the skin and peripheral nerves. 1,2 In the lower limbs the posterior tibial and common peroneal nerves are most frequently involved. This can result in permanent loss of the protective sensibility of the sole and, through loss of motor function, to equinovarus impairment. When these two effects are combined, the main impact is that force, effected by walking, is concentrated on the anaesthetic forefoot. The resultant pressure causes ulceration which can lead to neurological bone disorganisation of the foot. 3 Correspondence to: Mrinmoy Karmakar, Senior Occupational Therapist, Premananda Memorial Leprosy Hospital, 259/A, Acharya Prafulla Chandra Road, Manicktala, Kolkata, West Bengal, 700006, India (e-mail: mrinmoykarmakar1805@gmail.com) 0305-7518/15/064053+07 $1.00 q Lepra 213
214 M. Karmakar et al. Tibialis posterior tendon (TPT) transfer using either the circumtibial (CT) or interosseous (IO) route is the standard procedure for foot drop correction. 4 The TPT procedure aims to correct the resting position of the foot, restore active dorsiflexion at the ankle and to restore normal gait pattern (heel strike, mid-stance and then propulsion) and thus it reduces the risk of further injury to, and deformity of the forefoot. 5 TPT aims to redistribute load to avoid foci of excessive pressure on the forefoot. 6 The present study was done to quantify and compare the proportionate changes of load bearing and the changes in gait line before and after Tibialis posterior transfer. Subjects and Methods The study was carried out at the Premananda Memorial Leprosy Hospital, Kolkata, in West Bengal. The hospital is recognised by the Government of India as a tertiary referral hospital for ulcer care, reaction and neuritis care and reconstructive surgery for people affected by leprosy. All the eight patients who presented with foot drop and were operated on in 2013 were included in the study. Regular pre- and erative assessments were done at which the following parameters were assessed: position of the ankle at rest, effective dorsiflexion (above 90 degrees), active and passive range of dorsiflexion and plantar flexion of the ankle joint during both knee flexion and extension, inversion at rest and on dorsiflexion. These measurements were made using standard goniometric procedures. The erative assessments were done 3 to 4 days before surgery and the erative assessments were done after the 4 weeks of erative physiotherapy. In addition to clinical assessments, both static and dynamic measurements of bodyweight distribution and changes in gait line were recorded. To accomplish this we used a registering device that has 4096 sensors and a scan rate of 300 frames per second. Subjects practiced walking barefoot until they were comfortable with the requirement to step on the plate without altering stride. Readings were only recorded when subjects stepped on the plate without altering stride. The baropodometer yielded both static and dynamic readings. Static readings showed the distribution of load when the person was standing on the plate, whereas dynamic readings showed the percentage of load on the different areas of the foot when the person was walking normally. PRE- AND POST-OPERATIVE PHYSIOTHERAPY MANAGEMENT An aim of erative physiotherapy was to teach patients to learn isolated contraction and strengthening of the tibialis posterior muscle. Patients were also taught exercises to stretch the Tendo Achilles to maximal effect. Post-operatively, below-knee Plaster-of-Paris casts, incorporating a posterior slab with the foot in 70 to 80 degrees of dorsiflexion were applied. On the 4 th or 5 th day, Bohler irons were applied to assist ambulation. The plaster was cut on the first day of the 5 th week; patients then practiced contraction of the tibialis posterior with gravity eliminated. The posterior slabs were retained and continued for night use until the patients progressed to full weight bearing. At the 6 th week the same exercises were followed but against gravity. At the 7 th week, partial weight bearing was commenced after fitting medial arch supports in the footwear. Isometric exercises of the tendo Achilles were also started. At the 8 th week, patients were allowed to
Changes following foot drop correction in leprosy 215 Table 1. Demographic Data Sl. No Age (years) Gender Right/Left Duration of impairment (years) 1 65 M Left 5 2 50 M Right 2 3 31 M Left 3 4 44 M Left 6 5 59 M Left 3 6 32 M Right 2 7 28 M Right 2 8 18 M Right 3 walk and climb stairs with full weight bearing. By the end of 8 th week patients were discharged. 4 Results There were eight patients who underwent foot drop correction in our hospital in 2013. They were all included as subjects in our study. The demographic data of study subjects are shown in Table 1. The average age of the subjects was 40 88 years (Standard Deviation/SD16 340 years) and the mean duration of the impairment was 3 25 years (SD1 49 years). All the eight subjects were male. The following parameters were measured for the study: 1. Start time for heel strike, 2. Load applied to the heel, 3. Load applied to the mid-foot, 4. Load applied across the metatarsal heads (MTH) and 5. Percentage of time of through which the heel, the mid-foot or the MTH were on the pressure sensing plate. STATIC SCAN RESULTS FOR AFFECTED FEET Applying the Chi Squared test it was found that the erative static load changes on the forefoot and hind foot were not statistically significant when compared to erative values. Table 4 shows the proportion of stance phase over which load was applied on the heel, mid-foot and MTH area at erative and erative assessments of dynamic weight bearing. DYNAMIC SCAN RESULTS FOR AFFECTED FEET The mean percentage (%) of load on the heel in the erative assessment was 72 5 (Standard Deviation/SD 12 53) which increased to 89 38 (SD 7 76) in the evaluation.
216 M. Karmakar et al. Table 2a. Static proportion of load applied on forefeet and hind feet Patient Fore foot Fore foot Hind foot Hind foot Right Foot affected 2 17 20 15 50 37 30 28 50 4 26 60 25 90 33 70 24 70 5 25 40 25 60 24 20 23 60 6 21 70 20 90 21 10 26 70 Left Foot Affected 7 29 20 30 70 24 80 18 20 8 23 80 20 10 25 40 27 30 1 27 40 36 10 26 30 24 20 3 28 80 17 40 25 50 25 30 Table 2b. Changes in static load (applying Chi Squared Test for significance) Sig. level Right Forefoot Pre op Right Forefoot Post op 0 484 Left Forefoot Pre op Left Forefoot Post op 0 575 Right Hind foot Pre op Right Hind foot Post op 0 779 Left Hind foot Pre op-left Hind foot Post op 0 674 The average % of load on the mid-foot in the assessment was 65 63 (SD37 363) which decreased to 41 88 (SD32 50) in the evaluation. The average % of load on the Metatarsal heads in the assessment was 40 (SD13 89) which decreased to 19 13 (SD10 64) in the evaluation. The mean time of commencement of heel strike in the assessment was at 5 75% of the total stance phase (SD 2 71) which decreased to 0 00 % of the total stance phase during the erative assessment (i.e. heel strike was not delayed). The mean percentage of time the heel was in contact with the baropedometer plate in the erative assessment was 63 075% of the total stance phase (SD10 82) which increased to 83% of the total stance phase (SD 4 46) during the erative assessment. The mean percentage of time the mid-foot was in contact with the baropedometer plate in the erative assessment was 66 65% of the total stance phase (SD 9 39) which decreased to 57 07% of the total stance phase (SD 17) during the erative assessment. The mean percentage of time the MTH was in contact with the baropedometer plate in the erative assessment was 91 48% of the total stance phase (SD3 96) which decreased to 74 81% of the total stance phase (SD 9 75) during the erative assessment. The analysis of data suggested that there was a statistically significant increase in duration of load at the heel and decreases in the duration of load at the mid-foot and MTH area when comparing erative findings with erative findings (P, 0 05).
Changes following foot drop correction in leprosy 217 Table 3a. Details of % load on the heel, midfoot and MTH of the affected foot (Dynamic) Sl. No. Heel load Heel load Midfoot load Midfoot load MTH load MTH load 1 60 85 100 60 65 38 2 65 80 80 75 45 20 3 70 90 0 0 20 5 4 65 90 45 20 30 15 5 80 90 100 80 40 30 6 90 100 70 20 50 15 7 60 100 30 10 30 10 8 90 80 100 70 40 20 Table 3b. Changes in load distribution during the stance phase of gait (applying Chi Squared Test for significance) Sig. level Heel load Heel load 0 024 Mid foot load Mid foot load 0 018 MTH load MTH load 0 012 Discussion Comparison of the erative and erative results showed that there was an increase in the mean percentage of load on the heel which was statistically significant. We attribute this to the restoration of heel strike in the erative condition (normal heel strike was absent during the condition). Pre-operatively, the heel did not contribute to weight bearing adequately and the load was borne mainly by the metatarsal heads and the lateral aspect of the mid-foot. After tibialis posterior transfer surgery, the load was shared by the heel, relieving the mid-foot and forefoot of excessive load. The percentage of time through the stance phase of gait when the MTH and the mid foot areas were on the pressure plate decreased significantly after the surgery. The mean percentage of time that the mid-foot was in contact with the baropedometer plate in the preoperative assessment was 66 65% of the total stance phase which decreased to 57 07% of the total stance phase at the erative assessment. The mean percentage of time the MTH was in contact with the gait scan plate in the erative assessment constituted 91 48% of the total stance phase; this had decreased to 74 81% of the total stance phase at the postoperative assessment. The mean percentage of time taken for the commencement of heel strike (i.e. % of time of the whole stance phase) had decreased from 5 75% to 0 0%. That is, normal timing of heel strike was restored after surgery. This is attributed to the dorsiflexion of the foot; a postoperative effect of tibialis posterior transfer. The clinical significance of these findings is that surgery may decrease the occurrence of ulcers in the fore-foot in people with foot drop and sole anaesthesia. Repetitive pressure has been implicated as a cause of ulceration. Pressure is the result of force x unit area over which
218 M. Karmakar et al. Table 4a. Proportion of time spent on sites of interest of affected feet during the stance phase (Dynamic) In % of stance phase Proportion (%) of the stance phase taken Heel strike start time Heel strike start time Heel Heel Mid foot Mid foot MTH MTH 4 7 0 48 2 81 1 49 8 17 93 6 60 2 10 0 70 7 81 8 72 71 1 92 98 80 42 8 3 0 65 89 7 61 5 56 1 91 76 62 3 2 0 48 3 82 9 64 57 8 87 06 80 84 3 8 0 79 83 7 83 69 4 95 34 83 74 7 0 65 3 83 2 68 4 63 93 88 85 46 3 3 0 58 7 87 1 67 3 61 6 93 4 69 26 6 8 0 69 4 74 5 67 2 60 6 83 76 76 28 Table 4b. Changes in the proportion of time spent on sites of interest of affected feet during the stance phase (applying Chi Squared Test for significance) Sig. level Heel strike start time Heel strike start time 0 012 Heel time Heel time 0 012 Mid foot time -Midfoot time 0 012 MTH time MTD time 0 012 that force is distributed. Redistributing load results in lower force and therefore less pressure. Reducing pressure will reduce the potential for ulceration. Conclusion This study demonstrates the importance of tibialis posterior transfer surgery in the following ways: a) It restores the normal gait pattern of 1, 2, 3 (where 1 is heel strike, 2 is mid-foot contact and 3 is fore foot contact). b) It provides a more uniform and near normal distribution of planter weight bearing by decreasing the load over the forefoot whilst concomitantly increasing the load on the heel. We suggest that tibialis posterior transfer surgery, therefore, will contribute to reducing ulceration and further foot impairment. Acknowledgements We acknowledge the help and support of Medical Superintendent, Dr. Helen Roberts and all the staff of the hospital who have helped in caring for the patients in the study.
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