Primary partial humeral head resurfacing: outcomes with the HemiCAP implant

Humeral head defects such as degenerative disease or avascular necrosis are often treated with stemmed hemiarthroplasty or total shoulder arthroplasty. Despite its historical and clinical significance, stemmed humeral head replacement poses inherent technical challenges to placing spherical implants at the anatomically correct head height, version, and neck-shaft angle.

The aim of this study was to assess humeral head inlay arthroplasty as a joint-preserving alternative that maintains the individual head-neck-shaft anatomy. Humeral head inlay arthroplasty also allows intraoperative surface mapping and placement of a contoured articular component that is matched to the patient's defect size, location, and individual surface geometry.

Case series; Level of evidence, 4.

This retrospective case series included 19 patients (20 shoulders), with an average age of 48.9 years (range, 32-58 years; 16 men, 3 women). Preoperative diagnoses were osteoarthritis in 16 shoulders and osteonecrosis in 4 shoulders. Pre- and postoperative evaluations included physical examination, radiographic assessment, the American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form, the Simple Shoulder Test, a pain visual analog scale, and patient satisfaction rating.

The mean follow-up period was 32.7 months (range, 17-66 months). The mean American Shoulder and Elbow Surgeons score improved from 24.1 to 78.8, mean Simple Shoulder Test score from 3.95 to 9.3, mean visual analog scale score from 8.2 to 2.1, mean forward flexion from 100° to 129°, and mean external rotation from 23° to 43° (P < .001 for all). Radiographic follow-up showed no evidence of periprosthetic fracture, component loosening, osteolysis, or device failure. Patient shoulder self-assessment was 90% poor before surgery and improved to 75% good to excellent at last follow-up; 20% of patients self-rated as somewhat good to somewhat poor, and 5% self-rated as poor. Ninety percent of patients were satisfied with the choice of the procedure. Three patients had postoperative complications unrelated to the implants, including a partial rotator cuff tear treated with physical therapy, preexisting glenoid wear treated with arthroscopic debridement and microfracture, and infection complicated by subscapularis rupture requiring several subsequent surgical procedures but with retention of the implant.

Humeral head inlay arthroplasty is effective in providing pain relief, functional improvement, and patient satisfaction. Rather than delaying shoulder arthroplasty to end-stage osteoarthritis, humeral head inlay arthroplasty is a promising new direction in primary shoulder arthroplasty for younger and active patients with earlier stage disease.