Evaluating Pyrocarbon Shoulder Hemiarthroplasty: Benefits and Drawbacks

Referenced article: Park et al… “Pyrocarbon hemiarthroplasty of the shoulder: a systematic review and meta-analysis of clinical results”¹

Introduction

Pyrocarbon shoulder hemiarthroplasty has been used in Europe since 2013, and it recently gained increased attention in the U.S. after the FDA approved the first pyrocarbon hemiarthroplasty implant in late 2022.

Historical Context and Challenges

Shoulder arthroplasty in the U.S. became prominent in the 1950s when Dr. Charles Neer developed his hemiarthroplasty prosthesis for treating proximal humerus fractures. Over time, the procedure expanded to include polyethylene glenoid components, which addressed glenoid-sided disease and helped prevent medial glenoid erosion. Studies have shown that anatomic total shoulder arthroplasty (aTSA) generally provides better pain relief and function compared to traditional hemiarthroplasty². However, polyethylene glenoid components are considered a weak point of aTSA, with relatively high rates of loosening that often require revision surgery, particular in studies looking at younger patients.³

Pyrocarbon Hemiarthroplasty: Findings and Comparisons

To address the issues of glenoid loosening, some surgeons have turned back to hemiarthroplasty using pyrocarbon, a material that may reduce bone wear compared to metal¹. Several pyrocarbon implants have been developed and studied since 2013.  The highlighted article is a meta-analysis that reviewed 12 studies involving 536 patients who had a minimum 2-year follow-up¹. The study found that the average postoperative Constant score was 70.9, with an average improvement of 36.2 points. However, radiographic analyses revealed that 22.8% of patients showed some glenoid erosion, and the overall revision rate was 7.7%, with 51.2% of those revisions being to reverse total shoulder arthroplasty.

The improvements in Constant score with pyrocarbon hemiarthroplasty in this meta-analysis are similar to those reported with aTSA, which is promising⁴. However, since Constant scores tend to decrease with age and pyrocarbon hemiarthroplasty is often used in younger patients, this comparison might be biased. A recent study by Gao et al. (2023) found that aTSA provided slightly better outcomes compared to both pyrocarbon and conventional metal hemiarthroplasty⁵, consistent with earlier studies comparing aTSA to traditional hemiarthroplasty. Additionally, glenoid erosion was one of the main issues that led to the development of glenoid components in the first place, and this meta-analysis reported a 22.8% erosion rate with pyrocarbon hemiarthroplasty at short- to mid-term follow-up (<10 years). While a recent study by McBride et al. (2022) showed that overall revision rates with pyrocarbon hemiarthroplasty are lower than with traditional metal hemiarthroplasty at mid-term follow-up⁶, symptomatic glenoid erosion is still an area of concern.

Future Considerations

Looking Ahead: Pyrocarbon hemiarthroplasty offers some potential improvements over traditional metal hemiarthroplasty, particularly in reducing revision rates. However, it still has similar drawbacks compared to aTSA, such as functional outcomes that are slightly worse and the persistent problem of glenoid erosion. Whether the benefits of avoiding glenoid component loosening outweigh these drawbacks compared to aTSA remains to be seen, particularly when considering other competing aTSA technologies aiming to decrease glenoid component loosening such as hybrid and inlay/inset glenoid components. At this point, the jury is still out on the best approach to treat shoulder arthritis in young patients, and long-term results will be needed to more conclusively determine the best approach.