Abstract
Implantation of metatarso-phalangeal prostheses or spacers has been widely indicated for the replacement of the articular surfaces in severe hallux rigidus. Giannini proposed a reabsorbable device in poly(D-L-lactic acid) (PDLLA) which is dome-shaped with a stem for implantation into the first metatarsal, avoiding any resection of the base of the proximal phalanx.
The rationale for the reabsorbable spacer is to maintain the distance between the articular surfaces for a predictable time and to provide a sliding surface suitable for articulation with the proximal phalanx. It is then reabsorbed by fragmentation and replaced by fibrous tissue, which maintains the articular space, allows motion and relieves pain.
Twenty-three reabsorbable spacers have been inserted for severe hallux rigidus in 20 patients aged from 26 to 76 years (average 58). Patients were reviewed with a follow-up ranging between 24 and 50 months (average 36). The results were assessed using the American Orthopaedic Foot and Ankle Society (A.O.F.A.S), hallux-metata-tarsophalangeal-interphalangeal scale. Anteroposterior and lateral weight-bearing X-rays were made preoperatively and at follow-up, evaluating the dimensions of the articular space and the length of the first metatarsal. The chronology of device reabsorption was studied in 10 patients with M.R.I., assessing complete reabsorption within 4 months of the operation.
Excellent and good results were obtained in 91% of patients. The A.O.F.A.S. score was 43.7±20.6 pre-operatively and 82±10.3 post-operatively. The reabsorbable spacer confirmed the expectations of its supporters. This procedure would appear to be an alternative to arthrodesis of the first metatarso-phalangeal joint or traditional permanent implants and represents an intermediate technique between an implant and resection arthroplasty.
