S51 COMPARISON OF RADIOGRAPHIC OSTEOLYTIC CHANGES AFTER SWANSON AND SUTTER METACARPOHALANGEAL ARTHROPLASTY BASED ON NEW GRADING OF OSTEOLYSIS

Abstract

Since the 1970s Swanson implant arthroplasty has become a treatment of choice in metacarpohalangeal (MCP) joint arthroplasty in destructed MCP joints of rheumatoid patients. Sutter (Avanta) implant is also composed of silicone but the centre of rotation is more anatomical, and volar to improve extension moment. Clinical results about these implants have been similar but fracture rates of Sutter implant have been reported to be high. Reason for osteolysis is inflammation reaction to silicone particles released from prostheses due to movement of prosthesis in bone or implant fractures. Reports about osteolysis around Swanson implants present variable result.

There is not grading of osteolysis in the literature before and we created a new radiographic grading for osteolysis around silicone MCP implants. Grading is based on involvement of cortical bone: Grade I: Osteolysis varying from a single clear line adjacent to the stem of the prosthesis to a larger, clear area which did not involve the bone cortex; Grade II: Osteolysis affecting the bone cortex to a maximum of one half of the thickness of the cortex; Grade III: Osteolysis affecting the cortex to more than one half of its thickness but not perforating the cortex; Grade IV: Osteolysis perforating the cortex.

In this study we compare the incidence of radiographic osteolysis following insertion of 89 Swanson and 126 Sutter MCP implants in rheumatoid arthritis patients. Before surgery hands were randomised one by one to Swanson and Sutter implant groups. The mean follow-up time in the two groups of patients was 57 (40–80) and 55 (36–79) months, respectively.

A total of 45 (60%) metacarpal and 40 (53%) proximal phalangeal bones showed no osteolytic changes in the Swanson group. In the Sutter group numbers were 20 (21%) and 26 (27%). In the Swanson group, there was less cortical osteolysis and there were 4 (5%) perforations of a metacarpal and no perforations of a proximal phalanx. In the Sutter group, there were 9 (9%) perforations in a metacarpal and 5 (5%) in a proximal phalanx. (p< 0.001). To create a single independent observation of osteolysis for a hand, the worst osteolysis of a metacarpal or proximal phalanx was recorded. There was only one (5%) perforation in the Swanson group, while there were 8 (30%) perforations in the Sutter group (p=0.011). In all grades of our classification, osteolysis was more frequent in the Sutter than in the Swanson group.