Background In rheumatoid arthritis (RA), the arthritis in metacarpophalangeal (MCP) joints often cause dislocation of the MCP joints and ulnar deviation of the fingers. Arthroplasty with silicone implant for MCP joint is one of the most frequently performed procedure to improve hand function, appearance, and relief of chronic joint pain. However, there are limited reports for detailed analysis of postoperative radiological changes of ulnar deviation angle with different implants.

Objectives The purpose of this study was to investigate the factors influenced in radiological changes of ulnar deviation in RA patients who underwent MCP joint arthroplasty using silicone implants. We also investigated postoperative range of motion (ROM), ulnar deviation, and patient-reported satisfaction in a randomized trial of two different MCP joint implants.

Methods A total of 24 RA patients who underwent MCP arthroplasty of all 4 fingers: 11 cases received Swanson implants, and 13 cases received Avanta implants. Ulnar deviation angle, correction of ulnar deviation angle, and loss of correction angle at 6 months after surgery were analyzed. Additionally, all data was divided into two groups, radial fingers group and ulnar fingers group, and then statistically analyzed. Postoperative patient-reported satisfaction was assessed using visual analogue scale (VAS) and the Quick Disability of the Arm, Shoulder, and Hand (Quick DASH) Questionnaire.

Results Mean ulnar deviation angle was corrected significantly from 43.1°preoperatively to 9.5° immediate postoperatively; however, ulnar deviation angle was progressed to 13.7° at 6 months after surgery. Mean correction angle of immediate postoperatively was 33.6°, and loss of correction angle at 6 months after surgery was 4.2°. There was no correlation between preoperative ulnar deviation angle and loss of correction angle, correction angle and loss of correction angle. For preoperative ulnar deviation angle and loss of correction angle at 6 months after surgery, there was no statistical difference between radial fingers and ulnar fingers. However, at 6 months after surgery, mean ulnar deviation angle in radial fingers was 18.3°, which was significantly higher than that of in ulnar fingers (9.2°, p<0.01). At final follow-up, Avanta group achieved significantly greater active MCP joint flexion than in Swanson group (64.3° and 45.5° respectively, p<0.01). On the other hand, active MCP joint extension was greater in Swanson group (p<0.01). Although there was no significant difference in postoperative VAS and the Quick DASH between two groups, the Avanta group showed greater mean VAS (83 points for Avanta and 70 points for Swanson group).

Conclusions The Avanta group demonstrated superior MCP flexion, whereas the Swanson group had better angle in MCP extension. In clinical and patient-reported satisfaction, both implants groups showed good results after surgery. From current study, slight progression of postoperative ulnar deviation in radial fingers was observed regardless of the implants. This ulnar deviation in radial fingers will be due to postoperative improved pinch movement after surgery. Therefore, tight and enough soft tissue reconstruction for radial fingers was thought to be very important.

Disclosure of Interest None Declared