[Peroneal Nerve Palsy Management by Tibialis Posterior Muscle Transposition - Anatomical and Clinical Study]

PURPOSE OF THE STUDY Transposition of tibialis posterior muscle ranks among the methods of dorsiflexion restoration in patients with peroneal nerve palsy. Even though this method is commonly used, anatomical variations are still encountered which make us modify the established procedures. The purpose of this study is to evaluate the functional outcomes of operated patients and based on the clinical experience to define by cadaver preparation the anatomical causes preventing the use of the standard transposition technique. MATERIAL AND METHODS The clinical group includes 21 patients (15 men, 6 women) with the mean age of 34.2 years and with common peroneal nerve palsy confirmed by EMG. In 20 patients, transposition of the tendon of the tibialis posterior muscle (MTP) through the interosseous membrane of the leg was performed. In one patient the tendon was transposed ventrally to the distal end of the tibia and fixed in the lateral cuneiform bone due to an extremely narrow space of the interosseous membrane of the leg distally between the lower limb bones. In 18 patients the tendon was fixed by osteosuture to the base of 3rd metatarsal bone, in three patients to the lateral cuneiform bone. The outcomes were evaluated at 6 months after the surgery, when active ankle dorsiflexion (DF) range of motion greater than 5° was considered an excellent outcome, active position at 90° up to DF less than 5° a satisfactory outcome, and any plantigrade position as a poor outcome. The anatomical study included 20 extremities fixed by formalin (10 cadavers, 5 men and 5 women with the mean age of 71.3 years). The length of the individual parts of tibialis posterior muscle was measured and the variations of the muscle attachment were evaluated. The measurement was concluded by a simulation of surgical procedure. RESULTS When evaluating the clinical group, an excellent outcome was reported in 12 patients (57%), a satisfactory outcome in 8 patients (38%) and a poor outcome in one patient (5%). When evaluating the anatomical group, a division of the attaching part of the tendon into three main strips was observed. The thickest middle strip attached to the tuberosity of navicular bone and medial cuneiform bone was reported in all the specimens. The thinner lateral strip (originating from the tendon in 90% of specimens) was attached to the intermediate and lateral cuneiform bone, the cuboid bone, metatarsal bones II-V, and moreover it grows into the origin of the flexor hallucis brevis muscle. The third strip of the tendon attached to the sustentaculum tali, plantar calcaneonavicular ligament and fibrocartilago navicularis was missing in one specimen (5%). When the passing the tendon through the interosseous space between the lower limb bones was simulated in order for the tendon to go in the direction of the planned traction, in two specimens (10%) the pulling through was impossible due to the tendon being thicker than the interosseous space. In two specimens (10%) it was not the tendon, but already the muscular belly which passed through the given space. DISCUSSION In our group, 95% of the functional outcomes were excellent or satisfactory. A poor result was reported in one patient, in whom the EMG examination was not performed as a standard procedure and in whom the muscular strength was insufficient to achieve full dorsiflexion of the ankle. The anatomical study indicates that the narrow space between the lower limb bones can prevent the pulling through of the tendon, which can be addressed intraoperatively by the transposition of the tendon ventrally to tibia. The study reveals that the tendon necessary for transposition can be elongated by the strips of the tendon attached to the sole of the foot. CONCLUSIONS The knowledge of the anatomical conditions may help us better manage potential complications intraoperatively. Key words: tibialis posterior muscle, peroneal nerve palsy, transposition of tibialis posterior muscle, anatomy of tibialis posterior muscle, common fibular nerve palsy.