Flexor Hallucis Longus Tendon Transfer in Treatment of Achilles Tendinosis

Abstract

In patients with Achilles tendinosis, Achilles tendon debridement can be supplemented with flexor hallucis longus tendon transfer. Outcomes have not been studied prospectively in older, sedentary, and overweight patients. Fifty-eight consecutive limbs in fifty-six consecutive older, sedentary patients with insertional or midsubstance Achilles tendinosis were enrolled prospectively and underwent the procedure. Ten patients were lost to follow-up, leaving forty-eight limbs in forty-six patients available for evaluation after twenty-four months. The forty-six patients who were included in the study had an average age of 54 ± 10 years with an average body mass index of 33.8 ± 6.8 kg/m². Significant improvement was observed between baseline and twenty-four months in terms of the visual analog scale for overall pain intensity (6.7 ± 2.3 versus 0.8 ± 2.0; p < 0.001), the Short Form-36 physical score (34.3 ± 8.0 versus 49.0 ± 9.3; p < 0.001), the Ankle Osteoarthritis Scale pain (54.4 ± 19.2 versus 1.9 ± 2.7; p < 0.001) and dysfunction (62.6 ± 21.4 versus 11.0 ± 24.2; p < 0.001) subscale scores, and performance of a single-leg heel rise (1.9 ± 3.0 versus 7.3 ± 2.7 cm; p < 0.001). Significant improvement compared with baseline was observed at three or six months except in the single-leg heel rise. Improvements in terms of pain and function occurred over twenty-four months, with the most improvement occurring in the first twelve months. At twenty-four months, maximum gastrocnemius circumference was significantly less in the involved compared with the uninvolved leg (40.2 ± 5.1 versus 41.2 ± 4.8 cm; p < 0.001). The mean passive range of motion of the first metatarsophalangeal joint decreased from 85.1° ± 25.3° preoperatively to 68.1° ± 36.7° (a 20% change) at six months (p = 0.03). Most patients reported no hallux weakness (57%; twenty-six of forty-six patients) and no loss of balance due to hallux weakness (76%; thirty-five of forty-six patients). Postoperative peroneal tendinitis was observed in seven patients. Complications included deep-vein thrombosis (two patients), superficial infection or delayed wound-healing (six), scar pain (four), and early disruption of the reconstruction due to a fall (one). Surgical debridement of the Achilles tendon with flexor hallucis longus tendon transfer was associated with significant improvement in terms of Achilles tendon function, physical function, and pain intensity in a group of relatively inactive, older, overweight patients. When present, hallux weakness had minimal functional sequelae.