Tuesday, September 20, 2016

Is a 'hip-style' prosthesis of use in cases of severe glenoid bone loss?

Primary shoulder arthroplasty using a custom-made hip-inspired implant for the treatment of advanced glenohumeral arthritis in the presence of severe glenoid bone loss

These authors present 37 patients with rotator cuff–deficient end-stage glenohumeral arthritis and severe glenoid bone loss (assessed as not amenable to treatment with standard anatomic or reverse total shoulder implants) who were treated  between 2006 and 2013 with a computer-aided design–computer-aided manufacturing (CAD-CAM) total shoulder replacement resembling a total hip prosthesis. 

An “acetabulum” for the uncemented titanium glenoid shell was created by concentric reaming of the lateral scapular angle to permit the shell to abut the anterior edge of the scapular spine while its inferior rim rests on the infraglenoid tubercle region and the anterior rim remains in line with the coracoid tip. The shell was then secured with 3 or 4 independently oriented nonlocking 3.5-mm titanium cortical screws to the scapular spine and the base of the coracoid and to the lateral column of the scapula and the remaining glenoid body.

Postoperatively, the pain level with activity decreased from 9.2 ± 1.7 to 2.4 ± 2.9 (P < .001). The Oxford Shoulder Score improved from 11 ± 8 points to 27 ± 11 points (P < .001), and the Subjective Shoulder Value (on a 0%-100% scale) improved from 23% ± 14% to 60% ± 24% (P < .001). Active forward elevation improved from 39° ± 23° to 63° ± 38° (P < .001), and external rotation improved from 6° ± 16° to 15° ± 17° (P = .001). Component revision was required in 6 of 37 patients (16%) (glenoid loosening in 1, humeral stem loosening in 3, periprosthetic fracture in 1, and prosthesis dislocation in 1).

The authors concluded that "the CAD-CAM TSR offers a reliable alternative for the treatment of end-stage glenohumeral arthritis with severe glenoid deficiency not amenable to standard anatomic or reverse total shoulder implants".

Comment: The one set of preoperative x-rays included 

suggest that the pathology may well have been treated with more conventional methods, such as a CTA prosthesis (see this link) or a standard reverse total shoulder (see this link). While the approach suggested by these authors may have a role, one must be concerned about the cost (which is not provided in the paper) and the risk of humeral and glenoid fixation (loosening), instability, and fracture. Although scapular spine fractures were not identified, it would appear that the spine may be weakened somewhat in this surgery.