Short-term outcomes following 159 stemmed pyrolytic carbon shoulder hemiarthroplasties and how they compare with conventional hemiarthroplasties and total shoulder arthroplasties in patients younger than 60 years with osteoarthritis: results from the New Zealand National Joint Registry

Abstract

Background: Despite the increasing use of pyrolytic carbon (pyrocarbon) hemiarthroplasty (PyCHA), clinical data reporting on its outcomes remain scarce. To date, no studies have compared the outcomes of stemmed PyCHA vs. conventional hemiarthroplasty (HA) and anatomic total shoulder arthroplasty (aTSA) in young patients. The primary aim of this study was to report on the outcomes of the first 159 stemmed PyCHAs performed in New Zealand. The secondary aim was to compare the outcomes of stemmed PyCHA vs. HA and aTSA in patients aged <60 years with osteoarthritis. We hypothesized that stemmed PyCHA would be associated with a low revision rate. We further hypothesized that in young patients, PyCHA would be associated with a lower revision rate and superior functional outcomes compared with HA and aTSA.

Methods: Data from the New Zealand National Joint Registry were used to identify patients who underwent PyCHA, HA, and aTSA between January 2000 and July 2022. The total number of revisions in the PyCHA group was determined, and the indications for surgery, reasons for revision, and types of revision were recorded. In patients aged <60 years, a matched-cohort analysis was performed comparing functional outcomes using the Oxford Shoulder Score (OSS). The revision rate of PyCHA was compared with that of HA and aTSA, calculated as revisions per 100 component-years.

Results: In total, 159 cases of stemmed PyCHA were performed and 5 cases underwent revision, resulting in an implant retention rate of 97%. Among patients aged <60 years with shoulder osteoarthritis, 48 underwent PyCHA compared with 150 who underwent HA and 550 who underwent aTSA. Patients treated with aTSA had a superior OSS compared with PyCHA and HA patients. The difference in the OSS between the aTSA and PyCHA groups exceeded the minimal clinically important difference of 4.3. There was no difference in revision rates between the groups.

Conclusions: This study represents the largest cohort of patients treated with PyCHA and is the first to compare stemmed PyCHA with HA and aTSA in young patients. In the short term, PyCHA appear to be a promising implant with an excellent implant retention rate. In patients aged <60 years, the revision rate is comparable between PyCHA and aTSA. However, aTSA remains the implant of choice to optimize early postoperative function. Further studies are required to elucidate the long-term outcomes of PyCHA, particularly how they compare with those of HA and aTSA in young patients.

Keywords: Pyrocarbon; anatomic shoulder arthroplasty; hemiarthroplasty; osteoarthritis; pyrolytic carbon; total shoulder arthroplasty.