Pyrolytic carbon head shoulder arthroplasty: CT scan glenoid bone modeling assessment and clinical results at 3-year follow-up

BACKGROUND: The aim of this study is to report the radiological glenoid modifications and clinical outcomes at 3 years mean follow-up of hemi shoulder arthroplasty (HA) with pyrocarbon (PYC) humeral head. Our hypothesis was that the PYC implants would provide good outcomes without major glenoid erosion. Additionally, we hypothesized that HA-PYC allowed for remodeling of the bone. METHODS: Patients underwent HA with PyC humeral head for treatment of primary or secondary osteoarthritis, excluding post-traumatic cases. All patients had a Constant Score assessed preoperatively and at the last follow-up. Preoperative and postoperative computed tomography scans at the last follow-up were performed to achieve 3-dimensional reconstructions of the scapulae. Deformities of the glenoid surface were analyzed as a distance differential between postoperative and preoperative to investigate potential bone remodeling vs. glenoid erosion. The subluxation index (SLI) was measured. RESULTS: We included 41 patients implanted with a HA-PYC. Average age at the time of implant was 63.8 (40 to 79 years). All patients were followed for ≥2 years with an average follow-up of 36.3 months (24 to 60 months). Constant Scores increased from 34 at baseline to 80 at the last follow-up points on average (P < .01). Return to work rate was 100% and 96% had resumed their physical activity. Ten (77%) of the 13 patients with posterior head subluxation had normalized their SLI. Furthermore, no significant differences were detected between the individuals having corrected their posterior subluxation and the others (preoperative SLI between 0.45 and 0.55). Glenoid wear is less than 0.6 mm at 3 years mean follow-up, ie, 5 times less than metallic implants. A tendency to recenter the head in the anteroposterior plane was found in type B glenoid, without increased erosion of the glenoid, with very good clinical results. We did not find any difference according to age or glenoid type for clinical and radiological results. CONCLUSION: HA-PYCs give, in the short term, excellent clinical results in terms of pain and function. The development of a precise and objective measurement method has made it possible to demonstrate that the glenoid surface is the site of modifications that may be part of bone remodeling or progression of the osteoarthritis disease.