Subluxation in the Arthritic Shoulder

Minimum 10-year follow-up of anatomic total shoulder arthroplasty and ream-and-run arthroplasty for primary glenohumeral osteoarthritis

BACKGROUND

Reports on long term outcomes and failures of shoulder arthroplasty are uncommon. The purpose of this study is to present minimum 10-year outcomes in consecutive patients undergoing ream-and-run and anatomic total shoulder arthroplasty (TSA) for primary glenohumeral arthritis.

METHODS

This study analyzed consecutive patients who had undergone a ream-and-run or TSA with minimum 10-year follow-up. Pain scores and Simple Shoulder Test (SST) values were obtained preoperatively and at a minimum of 10 years postoperatively via e-mail or mail-in response. Percentage of maximum possible improvement (%MPI) was also calculated.

RESULTS

Of 127 eligible patients, 63 (50%) responded to a 10-year survey. This included 34 patients undergoing ream-and-run arthroplasty and 29 patients undergoing TSA. The ream-and-run patients were significantly younger than the TSA patients (60 ± 7 vs. 68 ± 8, P < .001), predominantly male (97% vs. 41%, P < .001), and had a lower American Society of Anesthesiologists classification (P = .018). In the ream-and-run group, the mean pain score improved from a preoperative value of 6.5 ± 1.9 to 0.9 ± 1.3 (P < .001), and the mean SST score improved from 5.4 ± 2.4 to 10.3 ± 2.1 at 10-year follow-up (P < .001). Twenty-eight (82%) achieved an SST improvement above the minimally clinically important difference (MCID) of 2.6. Four patients (12%) underwent single-stage exchange to another hemiarthroplasty, whereas 1 (3%) required manipulation under anesthesia. In the TSA group, the pain score improved from a preoperative value of 6.6 ± 2.2 to 1.2 ± 2.3 (P < .001), and the SST score improved from 3.8 ± 2.6 to 8.9 ± 2.6 at 10-year follow-up (P < .001). Of the 29 patients who underwent a TSA, 27 (93%) achieved an SST improvement above the MCID of 1.6. No patient in the TSA group required reoperation.

CONCLUSION

Although the characteristics of the patients differ between the 2 groups, excellent functional results can be obtained with the ream-and-run arthroplasty and TSA for glenohumeral osteoarthritis.

Three-dimensional evaluation of the transverse rotator cuff muscle's resultant force angle in relation to scapulohumeral subluxation and glenoid vault morphology in nonpathological shoulders

BACKGROUND

Static posterior subluxation of the humeral head (SPSH) results in glenohumeral osteoarthritis. Treatment strategies for SPSH with or without resulting osteoarthritis remain challenging. There is growing interest in evaluating the rotator cuff muscle volume, fatty infiltration, or forces in osteoarthritic shoulders with SPSH, mainly due to a possible transverse force imbalance. In nonpathological shoulders, the transverse angle of the rotator cuff muscle's resultant force may be associated with scapulohumeral alignment and glenoid vault morphology, despite an assumed transverse force balance. The purpose of this study was to assess the transverse rotator cuff muscle's resultant force angle (TRFA) and its relationship with the scapulohumeral subluxation index (SHSI) and selected glenoid vault parameters using computer modeling.

METHODS

Computed tomography scans of 55 trauma patients (age 31 ± 13 years, 36 males) with nonpathological shoulders were analyzed and all measurements performed in 3-dimension. We placed landmarks manually to determine the humeral head center and the rotator cuff tendon footprints. The contours of the rotator cuff muscle cross-sectional areas were automatically predicted in a plane perpendicular to the scapula. Each rotator cuff muscle was divided into virtual vector fibers with homogeneous density. The resultant force vector direction for each muscle, corresponding to the rotator cuff action line, was calculated by vectorially summing the normalized fiber vectors for each muscle, weighted by the muscle trophic ratio. The resultant force vector was projected on the axial plane, and its angle with the mediolateral scapular axis was used to determine TRFA. The SHSI according to Walch, glenoid version angle (GVA), glenoid anteroposterior offset angle (GOA), glenoid depth, glenoid width, and glenoid radius were also evaluated.

RESULTS

The mean values for TRFA, SHSI, GVA, GOA, glenoid depth, glenoid width, and glenoid radius were 7.4 ± 4.5°, 54.3 ± 4.8%, -4.1 ± 4.4°, 5.1 ± 10.8°, 3.3 ± 0.6 mm, 20 ± 2 mm, and 33.6 ± 4.6 mm, respectively. The TRFA correlated strongly with SHSI (R = 0.731, P < .001) and GVA (R = 0.716, P < .001) and moderately with GOA (R = 0.663, P < .001). The SHSI was strongly negatively correlated with GVA (R = -0.813, P < .001) and moderately with GOA (R = -0.552, P < .001). The GVA correlated strongly with GOA (R = 0.768, P < .001). In contrast, TRFA, SHSI, GVA, and GOA did not correlate with glenoid depth, width, or radius.

CONCLUSION

Despite an assumed balance in the transverse volume of the rotator cuff muscles in nonpathological shoulders, variations exist regarding the transverse resultant force depending on the SHSI, GVA, and GOA. In healthy/nonosteoarthritic shoulders, an increased glenoid retroversion is associated with a decreased anterior glenoid offset.