[Interpositional arthrodesis of the first metatarsophalangeal joint]

Interpositional arthrodesis of the first metatarsophalangeal joint is a rare procedure which is indicated for reconstruction of an insufficient, short first ray due to loosening of an endoprosthesis, osteomyelitis or after a Keller procedure.

In a retrospective study we evaluated the outcome of 15 patients with a mean age of 62 years, who underwent an interpositional arthrodesis of the first MTP joint. Correction of the deformity was achieved by osteotomy of the tricortical bone graft. Osteosynthesis was performed by use of screw fixation alone or by combined screw, plate and K-wire fixation. Postoperatively patients were mobilised for 10 weeks in a forefoot off loading shoe. Clinical and radiological examination was performed 10 weeks postoperatively. Radiological parameters such as hallux valgus angle, MTP dorsiflexion angle and the graft size were measured. In all patients pre- and postoperatively, the intensity of pain (VAS), the overall satisfaction with the procedure and the American orthopaedic foot and ankle score (AOFAS score) were evaluated.

The mean follow-up was 26 months (range 4-48 months). The mean pain intensity measured with the VAS was reduced from 7.5 preoperatively to 0.5 postoperatively. In 14 patients fusion of the arthrodesis was achieved at a mean of 12 weeks. One patient developed a pseudarthrosis which was effectively treated by extracorporeal shockwaves. Postoperatively radiological measurements demonstrated a mean hallux valgus angle of 16° (range 6-28°), a mean MTP dorsiflexion angle of 17° (range 12-27°) and a mean graft size of 16 mm (range 10-30 mm). The mean AOFAS score improved from 26 preoperatively to 81 postoperatively. All but 1 patient were satisfied with the final outcome and achieved free mobility.

Interpositional arthrodesis of the first MTP joint achieves good clinical and radiological results with a high level of patient satisfaction in patients with an insufficient and short first ray of the foot.