Flexor hallucis longus tendon transfer in treatment of Achilles tendinosis.

BACKGROUND: 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.
METHODS: 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.
RESULTS: 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).
CONCLUSIONS: 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.