Interposition arthroplasty in the treatment of hallux rigidus.

Objectives: We evaluated the outcomes of interposition arthroplasty performed for the treatment of hallux rigidus.

Methods: The study included 19 feet (4 left, 15 right) of 17 patients (14 females, 3 males; mean age 61+/-5 years; range 55 to 71 years) who were treated with interposition arthroplasty for hallux rigidus. According to the grading system of Coughlin and Shurnas, 18 feet were grade 3, one foot was grade 4. One-third of the base of the proximal phalanx was resected at surgery. Preoperative and postoperative radiographic assessments included the measurements of the joint space width of the first metatarsophalangeal (MTP) joint, hallux valgus angle, and intermetatarsal angle. Clinical evaluations were made using the AOFAS (American Orthopaedic Foot and Ankle Society) hallux metatarsophalangeal-interphalangeal scale. Postoperative satisfaction levels of the patients were questioned. The mean follow-up period was 21 months (range 9 to 32 months).

Results: According to the AOFAS scale, the results were excellent in seven feet (36.8%), good in nine feet (47.4%), and fair in three feet (15.8%), with excellent and good results accounting for 84.2%. The mean total AOFAS score increased by 24.6 points postoperatively (p<0.05). The mean range of motion of the first MTP joint improved significantly from preoperative 24.2+/-5.4 degrees (range 10 degrees to 30 degrees) to postoperative 54.3+/-9.4 degrees (p<0.05). The mean joint space width of the first MTP joint was 1.0+/-0.3 mm (range 1 to 2 mm) preoperatively, it increased to 3.0+/-1.1 mm (range 1 to 5 mm) on final radiographs (p<0.05). The mean hallux valgus angle decreased from preoperative 13.8 degrees (range 9 degrees to 17 degrees) to postoperative 10.2 degrees (range 4 degrees to 13 degrees), and the mean intermetatarsal angle increased from preoperative 10.5 degrees (range 8 degrees to 14 degrees) to postoperative 11.2 degrees (range 8 degrees to 15 degrees). Patient satisfaction levels were very good in nine feet (47.4%), good in seven feet (36.8%), moderate in one foot (5.3%), and poor in two feet (10.5%). Complications included metatarsalgia aggravated by long walks (n=11, 57.9%), hypoesthesia of the big toe (n=3, 15.8%), and loss of ground contact of the big toe (n=15, 79%). The push-off power of the big toes was measured as 3/5 in five cases, 4/5 in 11 cases, and 5/5 in three cases. None of the patients developed infection or osteonecrosis postoperatively.

Conclusion: Interposition arthroplasty is an appropriate surgical treatment method for hallux rigidus for elderly patients with low functional capacity.