Abstract
Objectives. The aim of this study was to access the postoperative functional results of posterior tibial tendon transfer for foot drop as a consequence of nerve palsy in leprosy. Material and Methods. Thirteen patients (9 males and 4 females) with ages ranging from 9 to 69 years were submitted to posterior tibial tendon transfer by the circumtibial route to correct foot drop in leprosy. The length of postoperative follow-up ranged from 1 to 5 years. The Stanmore system was used as a method for evaluating the functional results of postoperative posterior tibial tendon transfer. This system is made up of 7 different categories and the total score is 100. Results. According to the Stanmore system, the results were poor in 1 patient (7.6%), moderate in 2 feet (15.3%), good in 5 feet (38.4%), and excellent in 5 feet (38.4%). All the patients were satisfied with the final outcome. Conclusion. The posterior tibial tendon transfer for foot drop in leprosy was efficient in restoring normal function of the foot and gait without changing foot posture. In the absence of a standardized method for assessing the results of posterior tibial tendon transfer, the Stanmore system seems to be a good tool for an objective evaluation.
Neuropathy is the hallmark of leprosy, with Mycobacterium leprae affecting primarily skin and peripheral nerves.1,2 Leprosy stands out for its morbidity, notwithstanding its low mortality rates, leading to physical disability, deformity, psychological disturbances, economical dependence, and social exclusion. 3 Nerve lesion in leprosy leads to changes in muscle function, resulting in deformities of soft tissues and joints.2,4-7 In the lower limbs, tibial and the peroneal nerves are frequently involved and may result in permanent loss of the protective sensibility of the sole as well as equinovarus deformity. In this case swing phase and the toe-contact phase are problematic because of the malfunctioning of the dorsiflexors of the ankle; if it is not corrected, repeated plantar ulceration may lead to amputation.6,7
Leprosy stands out for its morbidity, notwithstanding its low mortality rates, leading to physical disability, deformity, psychological disturbances, economical dependence, and social exclusion.”
The surgical procedure proposed by Srinivasan et al 8 to correct foot drop is based on tibial posterior tendon transfer by a circumtibial route with the longitudinal tendon split into 2 tails. There is no consensus in the literature to evaluate the postoperative results of the transfer. Some authors used different criteria based on muscle strength, range of motion, and gait.8,9
The aim of this study was to compare the preoperative and postoperative functional outcome of tibial posterior tendon transfer for foot drop secondary to nerve palsy in leprosy patients using the Stanmore system.10,11
Materials and Methods
Ethical Considerations
Ethical approval for the study was given by the Research Ethics Committee of the Hospital Clementino Fraga Filho of the Federal University of Rio de Janeiro. Informed, written consent was obtained from the study participants before inclusion in the study using a standard consent form. No financial incentives were given to the participants.
At our department, 15 patients underwent transfer of the tibial posterior tendon. In all the cases the tendon was transferred through the circumtibial route. To create a homogenous cohort sample, patients were eligible if they were unable to actively dorsiflex the foot as a consequence of paralysis due to leprosy neuropathy for more than 1 year, had no plantar ulcer, had a minimum of 20° passive range of motion in terms of dorsiflexion, had tibial posterior muscle strength preserved (4/5 or 5/5), and had completed multidrug therapy (MDT) treatment.
All patients were examined by the surgeon (IGK) in the preoperative phase, immediately postoperatively, and at the follow-up visits. A physiotherapist (FJJR) was responsible during the preoperative and postoperative phases for the functional evaluation with the Stanmore system. The Stanmore system is made up of 7 sections: pain; the use of orthosis, braces, and special shoes; activities of daily living; active and passive articular mobility of the ankle; and the axis of the hindfoot. In addition, a physiotherapist was responsible for instructing patients about a specific physical therapy program or home-based exercises for tibial posterior muscle strength, gastrocnemius muscle stretch, and ankle range of motion exercises. 10
The assessment of functional outcome was made by the same physiotherapist in all the patients submitted to tibial posterior tendon transfer due to leprosy neuropathy. The examiner did not previously know the subjects and was not involved in the surgery.
Surgical Technique
For this study, all surgical procedures were made by an expert orthopedic surgeon of our group (IGK), a professor in the Department of Traumatology and Orthopedical Surgery in University of Rio de Janeiro Medicine School. The technique used was proposed by Srinivasan et al 8 and consists of using the tibial posterior tendon as a dorsiflexor.
The operation was done under spinal anesthesia and in a bloodless field. All patients were positioned supine under tourniquet, with a pad under the feet. The tibial posterior tendon was identified through a 2-cm incision in the navicular bone. The tendon was detached from its insertion. A longitudinal incision was made close to the medial border of the tibia starting at 3 cm and extending to 7 cm above the medial malleus and was freed by taking care not to damage the artery vein in the tendomuscular complex (Figure 1). Subsequently, through the incision on the medial border of the tibia, the tendon of the tibial posterior muscle was identified, pulled out, and an incision made splitting the tendon into 2 tails (Figure 2).
Identifying the tibial posterior muscle tendon.
Splitting the tendon into 2 tails.
Comparison between preoperative and postoperative functional results of each patient.
Two transverse incisions were made on the back of the foot over the extensor hallucis longus (EHL) tendon, thereby revealing the extensor hallucis (EHL), extensor digitorum (EDL), and peroneus tertius (PT) tendons. A subcutaneous tunnel extending across the tibia medial fascia was made with the aid of Andersen-Brand’s tunneller, and the tibial posterior tendon was transferred to the back of the foot.
The tendon was brought to the back of the foot using Andersen-Brand’s tunneller used to pass the tendon subcutaneously. The lateral slip was attached in tendons of EHL and the medial slip in the EDL and PT tendons using a No. 2/0 nonabsorbable suture material. Tenodesis was the loop type, transfixing the paralyzed tendon and loops back to be sutured side-to-side.
The tendon transfers should be attached as low as possible to allow the tendons to pull in a straight line. Tendon suture should be performed with maximum dorsiflexion of the foot and extension of the toes. In the meanwhile, the ankle was positioned at 10° dorsiflexion and at maximum possible eversion. When necessary, lengthening of the calcaneal tendon should be performed prior to tendon suture.
The tourniquet was then released to check for hemorrhage and a below-knee cast was applied with the ankle in a maximum dorsiflexion for 6 weeks, in order to release any tension on the tendon sutures during healing.
Statistical Analysis
After data collection all results were stored in an electronic database (SPSS 13.0.0; SPSS Inc, Chicago, IL). Descriptive statistical analysis was made showing mean, standard deviation, and variance of the preoperative and postoperative scores in the Stanmore system. Differences among preoperative and postoperative periods were analyzed by using a paired-sample t test for continuous variables to verify if the difference was statistically significant.
The relationship of the total score with age, period of palsy, and postoperative length was analyzed using Spearman’s rank correlation test. A significance level of P < .05 was considered in both tests.
Results
Fifteen subjects participated in the current study. Two patients were excluded, one with plantar ulcer and the other with Charcot arthropathy before surgery. Thus, the sample consisted of 13 patients, 9 males and 4 females. The ages of the patients ranged from 9 to 69 years (mean = 39.5 ± 14.7 years). All the patients had had a foot drop from 1 to 7 years (mean = 4.08 ± 1.8 years), and the length of postoperative follow-up ranged from 1 to 5 years (mean = 2.3 ± 1.44 years). None presented bilateral injury; 7 patients had the sequelae in the right foot and 6 in the left.
Before tendon transfer all patients were unable to actively dorsiflex the foot (muscle power 0/1), and 2 needed orthosis. After surgery no patient had any complication; however, in these 2 cases the orthosis was kept by the subjects. The results of the tibial posterior tendon transfer assessed using the Stanmore system were the following: 5 of 13 (38.4%) patients had excellent results, 5 (38.4%) had good results, 2 (15.3%) had fair results, and 1 (7.6%) had a poor result (Table 1). The average score was 78.6 ± 19.2 (36-100) and the median 76 points.
Functional Results of Preoperative/Postoperative Period Using the Stanmore System a
100-85 points = very good; 84-70 points = good; 69-55 points = fair; 55 points = poor.
Comparison of the Stanmore system data obtained from preoperative and postoperative phases was carried out with the use of the paired-sample t test, |tcalc| = 8.76 > t(0.05, 12) = 1.78.Spearman’s rank correlation was used to verify the association between Stanmore system score with age, palsy, and postoperative time with P < .05. A negative low correlation was observed for age (rs = −.27) and palsy time (rs = −.25). However, a positive moderate correlation was present in postoperative time (rs = .48).
Discussion
Peripheral neuropathy is a cardinal manifestation in leprosy affecting sensory, motor, and autonomic fibers and resulting in physical impairment.1,2,12-15 In lower limbs nerves commonly involved include the tibial and common peroneal nerve, resulting in sensory loss of plantar region and foot drop.16-25
Tibial posterior tendon transfer through the circumtibial route in cases lacking or poor functionality of the extensors is a surgical procedure often reported in literature. The procedure is indicated in neurological damage caused by cerebral palsy, spastic paraparesis with an equinovarus position of the foot, leprosy, and peripheral damages of the sciatic truncus and the common peroneal nerve that cause a deficit in the extensors of the toes, in the extensors of the hallux, and the tibialis anterior, with a normal function of the flexors and good functionality of the tibial posterior.26-31
In our study, posterior tibial tendon transfer by the circumtibial route was employed on 13 patients with drop foot deformity who have difficulties in conducting daily activities. Released from its attachment place at the navicular bone in the foot medial, the posterior tibial tendon was subcutaneously transferred through the tibia medial fascia and the dorsal fascia of the foot onto the EHL, EDC, and PT.
The transfer through the interosseous membrane provides a stronger foot dorsiflexion compared with the circumtibial. However, the risk of vascular injuries and adhesions in the interosseous membrane are key problems. 22 While the subcutaneous transfer of the tibial posterior tendon to the dorsum of the foot by taking it around the tibia medial fascia is technically easier and is a less risky method, it provides a lesser degree of range of motion in the joint. Many surgeons fix the tendons splits transferred into an osseous tunnel in the tarsal or metatarsal bone, but in leprosy patients it must be performed in the tendons of EHL, EDC, and PT to avoid neuropathic arthropathy of the tarsal joints. 20
Considering that although many distinct surgical procedures have been described, there is no agreement in the literature about the most important criteria to assess the functional outcome in postoperative period. There are a large number of studies that consider active dorsiflexion, foot posture, necessity of orthosis, and gait pattern as criteria for postoperative evaluation. The absence of a consensus makes the comparison of the postoperative results between previous studies difficult. The Stanmore system has been shown to be a useful tool for assessing functional outcome in the preoperative and postoperative periods of tibial posterior tendon transfer.16,18,22-25,32-36
In the current study of 13 patients, the functional results using the Stanmore system were the following: 5 (38.4%) patients had excellent results, 5 (38.4%) had good results, 2 (15.3%) had fair results, and 1 (7.6%) had a poor result. Similar results were observed by Andersen, 19 in a study with 108 patients: 72 had excellent or good results (66%), 30 had fair results, and 6 had poor results. Srinivasan et al 8 performed 39 tibial posterior tendon transfers in 33 patients and reported excellent results in 34 cases (87%) and poor results in 3 cases. The results found in the original study of Yeap et al, 10 using the Stanmore System, showed that 11 of 18 (61%) patients had excellent or good results, and the average score was 67.2.
Unsatisfactory results were observed in 3 cases, 2 fair (Nos. 4 and 5) and 1 poor (No. 2). In case 4, there were complaints of pain and limited recreation activity. Pain was related as a burning sensation in the foot. It was confirmed as neuropathic pain due to leprosy and treated with corticosteroid by 4 weeks. In one case (No. 5), the subject kept the orthosis and had limited daily activity and recreation. Besides the correction of foot drop this patient preferred to maintain the orthosis because of feeling more secure. This case was oriented with a specific physiotherapy program for muscle strength and gait.
Case 2 had a poor result 1 year after surgery. This could be explained by insufficient tension in tendon splits. This patient needed to be submitted to the same surgical procedure to retension the tibial posterior tendon tails and correct the failure. After the second surgical intervention the patient was able to dorsiflex the foot beyond the neutral position and gait was restored and considered normal. Results of this second procedure are not discussed is this article.
In this study, it was observed that only 1 patient related pain. Preoperative or postoperative pain was not common probably because of nerve damage in leprosy. In spite of the correction of the equinovarus deformity, 4 patients were unable to do active dorsiflexion of the foot more than 90°. In these cases, these results could be explained by different tensions in the tendon splits (No. 2) and the others patients (Nos. 6, 7, and 8) not completing the physical therapy program before surgery. Functional outcome could be restored with normal daily activity and recreation in 10 patients. In this series, impairment in recreation was related to activities with running skills, such as soccer. Similar results in functional activity were reported by Rodriguez, 21 Pinzur et al, 23 and Prahinski et al. 25
In 3 cases some deformities were present in the preoperative evaluation and still remained after surgery: 1 with claw toe, 1 with partial osteolysis of the V metatarsal bone, and 1 with metatarsal adduction. Despite these deformities, a plantigrade posture was acquired and there was no impairment in walking pattern.
Statistical analysis showed a significant result in the paired-sample t test, not expected by chance when comparing preoperative and postoperative patients expressing the efficiency of tibial tendon transfer in restoring function. Correlation between score, age, and palsy duration were not statistical significant, indicating that tibial posterior tendon transfer should be performed independent of age and palsy duration. On the other hand, the postoperative length can modify the functional results in categories such as pain, range of motion, and muscle power, which could be explained by the spontaneous progression after surgery or the physical therapy program.
The small population in this study may reflect that despite foot drop being a common deformity in leprosy, surgery is rarely performed. It might be explained because anterior tibial muscle paralysis is found in only 2% to 5% of newly diagnosed patients and sometimes foot drop is considered as definitive sequelae.6,7
In our study, 1 child (No. 11) was submitted to the tibial posterior tendon transfer with a good result in the postoperative evaluation. Leprosy among children is a public health problem reflecting the disease’s transmission in the community. Deformity seen in children with leprosy has not often been studied, and the disease itself is less common in children.
Monitoring childhood leprosy in terms of incidence and occurrence of deformities is crucial for better control and understanding the transmission of the disease. Horo et al 37 observed in a study with 151 children that 16% had already developed grade 2 disability (World Health Organization criteria). Multiple nerve involvement was seen in a quarter of children. Rao and Balachandran 38 reported the case of an 11-year-old female child with trophic ulceration of right foot and triple nerve paralysis (ie, total claw hand with wrist drop) of the left hand of 2 years duration. Rao 39 found 32 children among 280 diagnosed cases of leprosy, and reactional states and deformities were less common in their study. In Brazil, Imbiriba et al 40 studied 474 leprosy cases detected in children aged 15 years and younger, of whom 2.9% had physical disabilities.
Various factors may contribute significantly to the deformities in children such as delay in accessing health care, multiple skin lesions, multibacillary disease, smear positivity, multiple nerve involvement, and reaction at the time of presentation to the hospital. Logistic regression analysis showed that children with thickened nerve trunks had 6.1 times higher risk of developing deformities compared with those who did not have nerve enlargement. 41
In conclusion, the tibial posterior tendon transfer through the circumtibial route was shown to be efficient in the restoration of normal function of the foot and greatly improved gait, thus enhancing the life quality of the patient. The transfer of the tibial posterior tendon to EHL, EDC, and PT is an efficient and low-risk method that permits easy fixation in the recovery of the dorsiflexion. The Stanmore system was shown to be useful in the assessment of the preoperative and postoperative outcomes of tibial posterior tendon transfer in foot drop due to leprosy.