Discovery Elbow System: clinical and radiological results after 2- to 10-year follow-up.

BACKGROUND

Discovery Elbow System (DES) is a semi-constrained prosthesis, mainly used for patients with rheumatoid arthritis (RA).

METHODS

Records from 79 patients with RA (90 DES arthroplasties) were reviewed; 47 patients with 55 DES elbows were re-examined. Range of motion (ROM) of both elbows, upper limb function, and quality of life (Disabilities of the Arm, Shoulder, and Hand [DASH] score, Mayo Elbow Performance Score [MEPS], and the RAND 36-Item Health Survey [RAND-36]) were assessed. Cementing quality was assessed, and radiolucent lines measured from plain radiographs. Mean follow-up was 64 (range 24-123) months.

RESULTS

Pre-operatively to post-operatively, mean elbow flexion improved from 120° to 146° (p < 0.001) and mean extension lag improved from 29° to 24° (p = 0.02), respectively. At follow-up, mean supination was 66°, mean pronation was 69°, and mean grip strength was 14 kg. Grip strength and ROM (except supination) were similar between the DES elbow and contralateral un-operated elbow. Mean post-operative MEPS was 93 points (excellent, n = 38; good, n = 14; fair, n = 2; and poor, n = 1). Mean DASH score was 43 points. The RAND-36 showed that physical functioning, physical role functioning, bodily pain, and general health were lower than the Finnish reference values. Primary cementing was challenging, and radiolucent lines appeared during follow-up. Four prostheses were revised because of aseptic loosening (n = 3) and periprosthetic fracture (n = 1).

CONCLUSION

DES provides significant improvement in patient's flexion-extension arc. Cementing of the elbow prosthesis was challenging; radiolucent lines appeared during the 5-year follow-up, but their clinical relevance remains unclear. First-generation locking screws may loosen over time.

LEVEL OF EVIDENCE: Level IV.