Converting 1st metatarsophalangeal joint fusion to interposition arthroplasty. Mid-term results of a case series

Fusion of the first metatarsophalangeal (MTP) joint has been considered as the gold standard for treatment of advanced hallux rigidus. The main disadvantage is the restriction of movement which may not be as favorable as anticipated by several patients. The purpose of this study was to report clinical and functional outcomes on patients who were treated with interposition arthroplasty after a 1st MTP joint fusion which had not fulfilled their expectations.

Between 2009 and 2014, 11 patients who were not satisfied by 1st MTP joint fusion for hallux rigidus, underwent a conversion to interposition arthroplasty. After removal of hardware, the fusion was taken down by removal of a bone block from the fused joint. A fascia lata graft was interposed. Intraoperative and postoperative complications, range of motion of the first MTP joint, length of first ray, and patients' satisfaction were recorded as the primary outcomes.

Mean age was 34 years (range, 24-42 y). The mean ± SD AOFAS/H/MTP/IP score was 61 ± 5.5 preoperatively, 90.5 ± 4.5 at one year and 92 ± 4 at five years postoperatively (p < 0.001). The mean ± SD VAS-FA score was 91 ± 3.5 preoperatively, 94.5 ± 2.5 at one year and 95 ± 2.5 at five years postoperatively (p > 0.05). Mean ROM at the final follow-up was 58° ± 5° of dorsiflexion and 27° ± 4° of plantarflexion. No inter- or postoperative complications were encountered. The length of the hallux was decreased by a mean of 1.5 mm (range, 1-2.5 mm). All patients were satisfied with the overall outcome, walking ability and shoe-wear convenience and graded their condition as excellent (9 cases) or good (2 cases).

Converting a 1st MTP joint fusion to interposition arthroplasty with a fascia lata allograft could be a safe alternative with promising results in selected cases especially in relatively young and athletic population.

Level IV retrospective case series.