Pyrocarbon Interposition Arthroplasty of the Trapeziometacarpal Joint With the PyroDisk

Abstract

Introduction: Pyrocarbon is a high-strength, low-friction carbon material. It is isoelastic to bone and therefore considered ideal for a hemiarthroplasty. Pyrocarbon interposition arthroplasty is an alternative to the traditional tendon interposition arthroplasty in the trapeziometacarpal joint, but follow-up series are rare. Objectives: We aimed to evaluate the short-term results and safety of pyrocarbon prosthesis in a younger population. Methods: Between February 2006 and April 2009, 25 patients (29 arthroplasties) were operated with a PyroDisk interposition arthroplasty (Ascension Orthopedics/Integra, Austin, Texas). The mean age was 61 years (range, 52-71 years). Four patients were males and 21 females. The mean follow-up time was 28 months (range, 10-44 months). The patients were evaluated subjectively using the Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH) score as well as a visual analogue scale (VAS 0-10 cm) regarding pain at rest and at activity, and the cosmetic. Grip strength was recorded with a JAMAR dynamometer and the pinch grip strength as well as volar and radial thumb abduction noted. Results: Six prostheses were revised: 4 due to prostheses dislocation, 1 due to scapho-trapezium-trapezoid (STT) arthritis and persistent, and 1 due to persistent pain without any cause. All 6 patients were converted into abductor pollicis longus (APL) tendon interposition arthroplasty. The average pinch grip strength was 5.0 kg force (range, 1.2-9.5 kg) in the operated hands. In patients with unilateral surgery (n = 21), the pinch grip strength was 86 % of the untreated hands. The mean VAS pain at rest was 1.1 cm (SD = 2.0 cm), and 17 of 25 patients were pain free at rest. Six patients reported mild pain (VAS 1-3), and 2 patients reported VAS 7 at rest. VAS pain at activity was 4.2 cm (SD = 2.5 cm). The average DASH score was 32 (range, 0-93). Conclusion: The use of PyroDisk arthroplasty gives good range of motion and pain relief at rest, and the pinch grip after mean 28 months was close to the nonaffected side but not completely normalized. However, a large number (6/29) of the prostheses were revised, which is a major concern.