Pyrocarbon interposition shoulder arthroplasty in advanced collapse of the humeral head

Pyrocarbon (PyC) interposition shoulder arthroplasty can be used to treat advanced collapse of the humeral head after avascular necrosis.

We examined outcomes for this bone-preserving implant which has a PyC coating and a novel biomechanical concept.

For a minimum of 2 years, we followed 10 patients (4 men, 6 women, 55.6 ± 12.9 years) treated with a free interposition PyC arthroplasty ("snookerball") due to advanced humeral head collapse but with an intact glenoid and rotator cuff. Anteroposterior radiographs, the Constant score (CS), adjusted CS, DASH score, and the EuroQol 5D-5L score from the preoperative and the latest follow-up presentation were compared.

At a mean of 3.6 years (±15 months), the mean absolute CS was 70.6 (±13.6; adjusted CS 81.4 ± 16.4), the DASH score was 25.6 (±16.1), the mean EQ subjective VAS score was 72.6 (±15.9), and the EQ index score was 0.9 (±0.11). Scores improved: CS: +63.2 ± 12.9; adjusted CS: +72.9 ± 15.5; DASH: +47.2 ± 14.7; EQ VAS: +42.6 ± 16.8; EQ index score +0.52 ± 0.23. Mean glenoid erosion was 1.4 mm (±1.3 mm), thinning of the tuberosities was -0.8 mm (±3.3 mm), and superior migration of the implant was 2.0 mm (±2.2). A thin radiolucent zone around the implant with bone densification on the metaphyseal side was observed in all cases (mean 1.8 ± 0.6 mm).

Excellent improvement of function and quality of life which are comparable to total shoulder arthroplasty data were observed. Significant bone remodeling occurs in the metaphysis around the implant. Further studies are needed to evaluate longevity and applicability of the implant. These results indicate that advanced collapse of the humeral head with an intact glenoid and rotator cuff are an optimal indication for this implant.