Chronic Neglected Achilles Ruptures: FHL Tendon Transfer Rehabilitation

A neglected or chronic Achilles tendon rupture is clinically defined as an untreated or missed rupture presenting more than four to six weeks following the initial injury. In these delayed presentations, direct end-to-end surgical repair is virtually impossible. The proximal gastrocnemius-soleus muscle belly undergoes severe retraction and irreversible fatty degeneration, while the interposed rupture gap fills with weak, fibrous scar tissue, leaving a structural defect frequently exceeding five to eight centimeters. To restore plantarflexion continuity and push-off power, orthopaedic surgeons perform a Flexor Hallucis Longus (FHL) tendon transfer. Harvested through a medial midfoot or retromalleolar approach, the long, powerful tendon of the big toe flexor is mobilized, routed through a drill hole in the calcaneus, and secured with an interference screw, effectively serving as an active biological motor to replace the absent Achilles.

Diagnostic Delays in Indian Rural and Suburban Areas, Bone-Setter Pitfalls

In India, chronic neglected Achilles ruptures are unfortunately common, particularly across rural and suburban areas. When an individual suffers an acute rupture, they frequently consult traditional unverified bone-setters or local practitioners who misdiagnose the injury as a minor ankle sprain. Patients are often subjected to tight, unpadded bamboo splinting or aggressive massage with warm herbal oils, while continuing to walk in a limping, flat-footed manner for months. By the time the patient consults an orthopaedic specialist due to persistent inability to climb stairs or push off, the tendon ends have retracted by several inches. Educating families on recognizing neglected tears and navigating prolonged FHL post-surgical rehabilitation is critical to restoring walking autonomy.

FHL Donor Biomechanics, In-Phase Electromyography, and Great Toe Stability

The anatomical selection of the FHL tendon as the primary transfer graft is based on unique biomechanical synergies. First, the FHL is the second strongest plantarflexor of the ankle after the triceps surae, possessing an axis of pull almost identical to the native Achilles tendon. Second, dynamic electromyography proves that the FHL is already an in-phase muscle during the normal gait cycle: it naturally fires during late stance to stabilize the first metatarsophalangeal joint and assist push-off, requiring minimal central nervous system motor re-education. Third, the FHL muscle belly extends deep into the lower leg, providing a rich vascular bed that enhances biological graft survival. While the tendon is harvested, the distal stump is often sutured to the adjacent flexor digitorum longus (FDL) to preserve interphalangeal stability and prevent great toe clawing.

The 6-Phase Postoperative FHL Transfer Roadmap

Rehabilitation following an FHL transfer requires a more prolonged, cautious timeline than acute repairs, reflecting the time needed for tendon-to-bone integration inside the calcaneal tunnel. Weeks zero to two involve non-weight-bearing in a rigid equinus splint. Weeks two to six advance to progressive partial weight-bearing in an adjustable orthotic boot with heel wedges, while introducing gentle active great toe flexion to prevent donor site adhesions. Weeks six to ten involve gradual wedge removal to neutral, progressing to full weight-bearing in the boot. Weeks ten to fourteen transition the patient into structured shoes with a heel lift. Dedicated eccentric calf retraining begins at month four, with running and functional sports drills delayed until months seven to nine.

Frequently Asked Questions