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Loosening of Shoulder Replacements

Shoulder replacements are wonderful inventions. They help restore pain free shoulder and arm motion. Patients are almost always fully satisfied with the results. But from the surgeon's point-of-view, the results aren't always 100 per cent acceptable. Complications can occur such as joint infection, dislocation, or nerve injury. Problems with the implant including loosening and subsidence (sinking down into the bone) also occur more often than they would like.

In this study, an orthopedic surgeon from Germany followed 39 of his patients for 10 to 15 years and reported on the long-term results. He used the same third-generation cemented total shoulder replacement in each patient so that results could be compared directly. Pain, shoulder range-of-motion, and X-ray findings were the main measures of outcomes. Third generation refers to the number of times the implant has been redesigned, revised, and improved.

In all cases, pain, range-of-motion and function improved. And along with those results were consistent reports of patient satisfaction. Loosening of the glenoid component (socket side of the implant) occurred in 36 per cent of the group. The author provided a detailed description of the X-ray measurements to diagnose implant loosening. Despite the loosening, the implant remained intact and the patients still had good, pain free motion.

Reasons for the high rate of loosening were explored. Possible risk factors include: the design and shape of the glenoid component, surgical technique (removing too much of the arthritic bone before putting the implant in place), and cementing technique. It is also possible that there are some as yet unknown patient factors.

Younger patients tend to develop loosening more often than older adults, so maybe a higher activity level is part of the picture. And then there is always the possibility that some aspect of the postoperative protocol (either right after surgery or during rehab) that could be a contributing factor. These are all variables that must be evaluated more closely in future studies.

Two-thirds of the group experienced something called cranial migration of the humerus (upper arm). This refers to a gradual change in the position of the humerus upwards toward the top of the shoulder socket. Using X-rays, the condition was classified as mild, moderate, or severe based on how far up the humerus had moved. The problem develops as a result of rotator cuff failure that cannot be corrected surgically.

All in all, even with these reported problems the implant was still intact after 10 years for everyone. No one had to have revision surgery to remove, replace, or repair the loosening or migration. This study demonstrates the long-term satisfactory function patients can have with today's modern total shoulder replacements. The high rate of loosening still needs to be addressed and corrected in the next generation of implants.

References: Patric Raiss, MD, et al. Results of Cemented Total Shoulder Replacement with a Minimum Follow-Up of Ten Years. In The Journal of Bone and Joint Surgery. December 5, 2013. Vol. 94A. No. 23. Pp. e171(1)-e171(10).

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