Methods

Thirty-four patients who underwent divergent peg TSA had data collected prospectively. The data from these patients was retrospectively reviewed, primarily for radiographic evidence of glenoid component loosening. The endpoint was defined as the need for revision secondary to glenoid loosening. Secondary outcome measures such as SPADI (shoulder pain and disability index), active forward elevation, abduction, internal rotation, and external rotation were also collected. Data was obtained preoperatively and at the following postoperative intervals: 3 months, 6 months, and yearly. The last available postoperative radiographs were also reviewed and graded on a modified Franklin glenoid lucency scale described by Lazarus et al.

Materials/Methods:

A retrospective review was performed identifying all patients that underwent reverse total shoulder arthroplasty (RTSA) between May 2007 and December 2010. Medical records and a prospective research database were reviewed for demographic, operative, and clinical information. Inclusion criteria were a primary reverse total shoulder arthroplasty from one manufacturer with a grit-blasted humeral metaphyseal stem and minimum follow-up of 2 years. Exclusion criteria included shoulder arthroplasty for fractures, fracture sequelae, or inflammatory arthropathy. Antibiotics were not routinely added to the cement. The radiographic and functional outcomes were compared between the uncemented and cemented groups. Statistical analysis was performed using the Fisher Exact test to compare the dichotomous variables between the groups. The functional outcome data between the groups was calculated using the two-tailed Wilcoxon Rank Sum test.

Materials and Methods

The instrumented shoulder prosthesis measures the contact force vector between the glenosphere and humeral tray. This force sensor is a custom instrumented trial implant that can be used with an existing RTSA system (EQUINOXE, Exactech Inc, Gainesville, FL) just as a standard trial implant is used. Four uniaxial foil strain gauges (QFLG-02-11-3LJB, Tokyo Sokki Kenkyujo Co., Ltd., JP) are instrumented inside the sensor. Using a calibration matrix, the three force components were calculated from four strain gauge outputs (3).

Sixteen patients who underwent RTSA took part in this IRB approved study. All patients were greater than 50 years of age and willing to review and sign the study informed consent form. After obtaining informed consent for surgery, a standard deltopectoral approach to the shoulder was performed. The instrumented trial prostheses were assembled on the glenoid baseplate instead of a standard glenosphere. After the joint was reduced, joint forces were recorded during cyclic rotation, flexion, scapular plane movement (scaption), and adduction of the shoulder. Strain gauge outputs were recorded during these movements as well as the neutral position just before movements. Mean values of forces with each motion were compared by one-way analysis of variance (ANOVA). A multiple comparisons test was subsequently performed to examine differences between motions.