The anatomical relationships of the gastrocnemius and peroneus longus muscles, determining the practicality of a novel tendon transfer

P.R. Patterson, B. Siddiqui, M.S. Siddique, C.S. Kumar, Q.A. Fogg

Introduction: Peroneal muscle weakness is a common pathology in foot and ankle surgery. Polio, charcot marie tooth disease and spina bifida are associated with varying degrees of peroneal muscle paralysis. Tibialis Posterior, an antagonist of the peroneal muscles, becomes pathologically dominant, causing foot adduction and contributes to cavus foot posture. Refunctioning the peroneus muscles would enhance stability in toe off and resist the deforming force of tibialis posterior. This study determines the feasibility of a novel tendon transfer between peroneus longus and gastrocnemius, thus enabling gastrocnemius to power a paralysed peroneus tendon.

Method: 12 human disarticulated lower limbs were dissected to determine the safety and practicality of a tendon transfer between peroneus longus and gastrocnemius at the junction of the middle and distal thirds of the fibula. The following measurements were made and anatomical relationships quantified at the proposed site of the tendon transfer: The distance of the sural nerve to the palpable posterior border of the fibula; the angular relationship of the peroneus longus tendon to gastrocnemius and the achilles tendon; the surgical field for the proposed tendon transfer was explored to determine the presence of hazards which would prevent the tendon transfer.

Results: The mean angle between the tendons of peroneus longus and gastrocnemius/achilles tendon was 3. The sural nerve lies on average 30 mm posterior to the palpable posterior border of the fibula. There were no significant intervening structures to prevent the proposed tendon transfer.

Conclusion: The line of action of peroneus longus and gastrocnemius are as near parallel as to be functionally collinear. The action of gastrocnemius may be harnessed to effectively power a paralysed peroneus longus tendon, without significant loss of force owing to revectoring of forces. The surgical approach to effect such a tendon transfer is both safe and practical.