Jason C. Ho, MS, et al.
Glenoid Component Retroversion is Associated with Osteolysis. In The Journal of Bone and Joint Surgery. June 19, 2013. Vol. 95A. No. 12. Pp. e82(1)-e82(8).
Total shoulder replacement for severe joint osteoarthritis has come a long way since its first use. Even so, 10-15% of patients receiving this implant later develop loosening of the glenoid component.
The reason for glenoid component loosening is the focus of this study. The type of implant used was a polyethylene press-fit design. A peg in the centre of the socket implant helps hold it in place until bone in-fill takes place.
Loosening is observed on x-rays as osteolysis. What causes this? Is it more likely to develop the more time goes by after shoulder replacement? Is it linked with the shape of the glenoid side of the shoulder before surgery?
To find out, 66 patients who received the DePuy Anchor Peg Glenoid Component were followed up. All surgeries to implant the shoulder replacement were done by one surgeon. When there was too much retroversion, the surgeon did his best to correct the problem. He did this by shaving or cutting away excess bone along the front of the glenoid. The goal was to create a socket that was perpendicular to the scapula.
In some cases, the surgeon was unable to obtain a perfect fit with complete correction. To get complete correction of glenoid retroversion would require taking off too much bone. It was better to remove as much bone as possible to re-align the glenoid but without taking so much that it was no longer possible to insert the glenoid component.
To measure results, patients completed a health survey and answered questions about satisfaction after surgery. X-rays were taken before and after surgery and compared. About half of the patients had CT scans ordered when x-rays were not enough to fully see the glenoid. These imaging studies were repeated postoperatively and made it possible for the surgeon to evaluate the bone, assess alignment and look for any signs of implant loosening around the central peg.
It turned out that pre- and postoperative glenoid retroversion was the main factor in osteolysis and peg loosening. More than 15 degrees of tilt still remaining after surgery contributed to early loosening. It is believed (but not proven) that the retroversion causes increased load on the humeral head.
The surgeon concluded by suggesting that whenever possible, glenoid retroversion should be corrected to within 15 degrees before placing the implant into the shoulder. This also means that many things must be taken into account when preparing for shoulder replacement.