Pyrocarbon in shoulder hemi arthroplasty

Pyrolytic carbon, or pyrocarbon (PyC), has biocompatibility, a low friction coefficient and good wear resistance, making it a material of great potential for use in orthopaedics. PyC shoulder implants have shown promising mid-term results, but there is a shortage of research that support expectations of reduced glenoid wear in shoulder hemi arthroplasty (HA), and a lack of randomised trials comparing PyC to other options of shoulder arthroplasty.

This thesis synthesizes findings from four studies focusing on shoulder arthroplasty outcomes and PyC, using data from the Swedish Shoulder Arthroplasty Registry (SSAR), and clinical trials. The studies investigate various implants and describe patient-reported outcome measures (PROMs), implant stability, and revision rates across different arthroplasty types.

For study 1 we utilized data on 1140 shoulders from the SSAR to compare the results after resurfacing hemi arthroplasty (HA) and stemmed HA. Younger patients were shown to have higher revision rate irrespective of implant type. Patient-reported outcome was better for patients with primary osteoarthritis (OA) when compared to patients with secondary OA.

In study 2 we evaluated the reliability, validity, and responsiveness of the Swedish translation of the Western Ontario Osteoarthritis of the Shoulder index (WOOS), affirming its suitability for assessing clinical outcomes in shoulder arthroplasty patients. We could also show that WOOS is a stable and consistent tool for longitudinal outcome measurement.

Study 3 compares the performance of pyrocarbon (PyC) versus CobaltChromium (CoCr) resurfacing implants in a randomised controlled trial (RCT). Findings suggest that PyC implants may offer advantages in terms of reduced glenoid erosion and lower risk of revision compared to CoCr implants, although larger studies are needed to confirm these results.

In study 4, extracting data from SSAR, we analysed results after stemmed PyC HA (n=101) and compared them to results after total shoulder arthroplasty (TSA) (n=142). We noted comparable hazard ratios (HR) for revision when adjusted for confounding factors. The results from PROMs for TSA were superior to PyC HA.

In conclusion, PyC HA appears to be a safe alternative in shoulder arthroplasty surgery. Our results show comparable or better outcomes than other options for HA. In comparison to TSA, PyC HA have lower outcome in PROMs but similar risk of revision. The patient demographics differ between the groups, clouding interpretation of outcomes.

List of scientific papers

I. Ödquist M, Hallberg K, Rahme H, Salomonsson B, Rosso A. Lower age increases the risk of revision for stemmed and resurfacing shoulder hemi arthroplasty. Acta Orthop. 2018 Feb;89(1):3-9.
https://doi.org/10.1080/17453674.2017.1411081

II. Hallberg K, Salomonsson B. Validity, reliability, and responsiveness of the Swedish version of Western Ontario Osteoarthritis of the Shoulder index. BMC Musculoskelet Disord. 2022 Apr 11;23(1):351.
https://doi.org/10.1186/s12891-022-05300-1

III. Hallberg K, Stark A, Ross M, Salomonsson B, Sköldenberg O. A comparison of migration patterns, glenoid erosion and clinical outcomes between a metal and a pyrocarbon resurfacing shoulder arthroplasty. A prospective single-blind randomized trial using radiostereometric analysis. [Manuscript]

IV. Hallberg K, Stark A, Salomonsson B, Sköldenberg O. Pyrocarbon Stemmed Hemi Arthroplasty compared to Anatomical Total Shoulder Arthroplasty. Short-to-Mid-term Outcomes from the Swedish Shoulder Arthroplasty Registry. [Manuscript]