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Outcomes of Pyrolytic Carbon Hemiarthroplasty for Thumb Basal Joint Arthritis: A Single Centre Experience
Imran Ratanshi, MD, MSc; Kenneth A. Murray, MD, FRCSC; Avinash Islur, MD, FRCSC
Department of Surgery/Section of Plastic Surgery, University of Manitoba, Winnipeg, MB, Canada

Purpose: The carpometacarpal (CMC) joint is a common site of degenerative osteoarthritis resulting in pain, swelling, and stiffness at the base of the thumb. When conservative measures fail, surface replacement is a surgical strategy to restore geometric articulation and range of motion. Pyrolytic carbon has been shown to be reliable biomaterial for joint surface replacement that is resistant to wear and inflammatory reaction, and it does not require additional bone cement for fixation. As a result, pyrocarbon implants have garnered interest for use in moderate stage (Eaton-Littler stage II-III) thumb basal joint arthritis. Given the paucity of clinical studies available, we present our center’s experience with this surgical modality.

Materials and Methods: A retrospective chart review was undertaken for patients undergoing elective thumb CMC joint replacement from 2007 to 2014. All patients presenting with Eaton-Littler stage II-III thumb CMC osteoarthritis undergoing joint surface replacement with Pyrohemisphere™ implant arthroplasty (Smith & Nephew | Ascension® Orthopedics Ltd., Austin, TX) were included in the study. Patients were followed-up until their final clinical visit when satisfaction with the outcome was reached. Patients were assessed for thumb range of motion, pain, sensory disturbances and overall hand function. In addition, patients were assessed for radiographic evidence of implant migration, subluxation, and failure.

Results: 45 patients (32F:13M) were included in the study. The mean age at the time of surgery was 60.6 ± 8.8 years (range 41 to 83 years). Average time to final follow-up was 5.2 ± 5.7 months. Mean post-operative thumb CMC radial and palmar abduction was 47.5 ± 5.2° and 40.0° ±7.7°, respectively. 29 patients (64%) achieved functional thumb opposition. 32 patients (70%) expressed general satisfaction with the procedure, and 10 patients (21.7%) had the procedure repeated on the contralateral thumb. There was no radiographic evidence of implant failure or fracture. Two (4.3%) occurrences of implant subluxation were observed of which one required removal. 24 patients (52.2%) had persistent low grade discomfort at final follow-up but deemed tolerable by each patient. 5 patients (11.1%) experienced parasthesias of the dorsal radial sensory branch requiring desensitization therapy or neurolysis. 3 patients (6.6%) experienced persistent numbness in the hand. 2 patients (4.3%) developed post-operative infection.

Conclusions: Pyrohemisphere implants can be a useful modality for joint surface replacement. They can reduce pain and restore thumb range of motion in patients with low-to-moderate stage basal joint arthritis. However, patients must be counseled carefully about post-operative expectations.


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