Saturday February 24, 1996

Surgical technique may help prevent glenohumeral instability

A new study stresses the importance of surgical technique to prevent glenohumeral instability following shoulder replacement arthroplasty. The study was detailed in scientific paper 207 presented on Friday.

A retrospective review of the medical records of 400 patients who had undergone shoulder replacement arthroplasty was conducted by orthopaedic surgeons at the University of Texas Health Science Center at San Antonio. In their review, the orthopaedic surgeons identified 58 patients who were referred to their institution for revision surgery following previous arthroplasty surgery.

"Of the revision cases, we noticed a similarity between 18 patients," reported study co-author Michael A. Wirth, MD, assistant professor, University of Texas Health Science Center at San Antonio, department of orthopaedic surgery, shoulder and elbow service. "Each patient had encountered glenohumeral instability problems following previous arthroplasty surgery."

An average of two revision procedures was performed on ten of the shoulders prior to referral, Dr. Wirth said. "The instability found in each of the shoulders was diagnosed upon referral to our institution," he said.

"Very little research is available about this type of complication, making it easy to go undetected. It is our hope that the study helps inform orthopaedic surgeons by providing information about the types of surgical approaches that can be used to prevent glenohumeral instability problems."

Dr. Wirth and his colleagues noticed that the patients suffering from glenohumeral instability following their initial arthroplasty displayed three different directions of instability-posterior in 11 patients; anterior in six patients; and inferior in one patient.

Surgical findings in the 11 patients suffering from posterior instability included increased retroversion of the humeral component (greater than 80 degrees) in six patients; posterior glenoid erosion in four patients; and a nonunion of the greater tuberosity in one patient.

The orthopaedic surgeons corrected the posterior instability problems by restoring normal retrotorsion of the humeral component by sculpting or reaming the glenoid to reestablish proper glenoid version and posterior capsulorraphy.

In the six patients suffering from anterior instability problems, surgical findings revealed decreased retroversion of the humeral component (less than 20 degrees) in all of the shoulders. "In addition to this problem, some patients also suffered from disruption or scarring of the subscapularis muscle-tendon unit and erosion of the anterior glenoid," said Dr. Wirth.

According to Dr. Wirth, revision of the shoulders with anterior instability problems involved a variety of surgical techniques, including restoration of normal humeral component retrotorsion, coracoacromial ligament reconstruction, and pectoralis major tendon transfer.

The patient suffering from inferior instability had a humeral component that was grossly loose, and a posteroinferior glenoid that was severely eroded.

The orthopaedic surgeons corrected the problem by a bone graft augmentation of the deficient glenoid, restoring the humeral length, and performing a cemented total shoulder arthroplasty.

"After using our surgical methods to repair the existing glenohumeral instability problems, we found that all of the patients noted a marked improvement in pain relief, motion, and daily activities," said Dr. Wirth.

Co-author of the study with Dr. Wirth is Charles A. Rockwood Jr., MD, chairman emeritus, department of orthopaedic surgery, University of Texas Health Science Center, department of orthopaedics, San Antonio, Texas.

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