2-3 year outcomes of the Primus silastic joint replacement for degenerative disease of the 1st metatarsal phalangeal joint

S. Borland, G. deKiewiet, P. Bansal

Background: Arthritis of the 1st MTPJ is common. It may occur in isolation or associated with deformity such as hallux valgus. Silastic implants have been used with good patient satisfaction but reported complications include synovitis, lymphadenopathy and implant fracture. The Primus implant (Tournier) is composed of silicone elastomer and is designed specifically for the geometry of the first MTPJ. We report the 2-3 year outcomes of 27 cases performed in our unit.

Methods: We examined 27 arthroplasties of the 1st MTPJ using the Primus implant, performed between January 2012 and March 2013. 18 were performed for isolated hallux rigidus. 5 had associated hallux valgus. 4 had associated lesser toe deformities which were also corrected. All patients had degenerative change of the joint consistent with at least grade 3. The Manchester-Oxford foot and ankle questionnaire (MOXFQ) was obtained reflecting the preoperative period and at a minimum of 2 years post operatively.

Results: The mean pain score was 60.3 pre-operatively (range 10-80). Post operatively the mean pain score was 16.1 (Range 0- 60). The main walking /standing score preoperatively was 54.8 (range 0-84.3). Post operatively the mean score was 14.8 (range 0-50.1). The mean social score preoperatively was 40.9 (range 0- 68.8). Postoperatively this fell to a score of 25.1 (range 0-62.5). There were 2 superficial infections treated with antibiotics and dressings. There were no deep infections. There were no failures due to synovitis or cases of lymphadenopathy. One case failed due to recurrence of valgus deformity and implant failure.

Conclusion: Use of the Primus implant for arthroplasty of the 1st MTPJ can produce excellent results. Many patients reported complete resolution of symptoms. Some patients still had some pain and difficulty walking. This case series should be the basis for randomised controlled trials comparing this to other treatments.