Impact of Prior Anterior Instability on Shoulder Arthroplasty Outcomes: A Systematic Review

Moment arms of the coracobrachialis and short head of biceps following a Latarjet procedure: a modeling study

BACKGROUND

The Latarjet procedure transfers the coracoid process to the anterior glenoid. This prevents recurrent anterior humeral dislocation but alters the origins of the coracobrachialis (CBR) and short head of the biceps (SHB). The impact of this alteration on the moment arms of these muscles has not been examined.

METHODS

The Newcastle Shoulder Model was updated with 15 healthy cadaveric bone models to create customized shoulder models. The CBR and SHB muscles were attached to the anterior glenoid via an elliptical wrapping object. Muscle moment arms were calculated for abduction, forward flexion, scapular plane elevation, and internal rotation with 20° and 90° of abduction. Statistical comparison of moment arms between native and Latarjet shoulders was performed using spm1D.

RESULTS

By transferring the origins of the CBR and SHB to the anterior glenoid, both muscles had extension moment arms during glenohumeral elevation in the coronal, sagittal, and scapular planes. Their average moment arms during abduction (-30.4 ± 3.2 mm for CBR and -29.8 ± 3.0 mm for SHB) and forward flexion (-26.0 ± 3.1 mm for CBR and -26.2 ± 3.2 mm for SHB) suggested that their role after the Latarjet procedure changed compared with their role in the native shoulder (P < .001). At higher abduction levels, both the muscles had higher internal rotation moment arms compared with the native shoulder.

CONCLUSION

The Latarjet procedure affected the moment arms of the CBR and SHB. Both muscles had increased extension and internal rotation moment arms at higher degrees of elevation compared with the native shoulders. This finding suggests that these muscles act as dynamic stabilizers after the Latarjet procedure.

Shoulder arthroplasty in the setting of previous stabilization surgery: a systematic review of matched case control studies at minimum 2 years follow-up

Background

Anterior shoulder instability causes considerable patient morbidity and the volume of shoulder stabilization surgery being performed annually is rising. Despite stabilization surgery, instability arthropathy in the long-term may arise requiring consideration of shoulder arthroplasty. This study evaluated the outcomes of shoulder arthroplasty following previous stabilization surgery with their associated changes in bony anatomy or soft tissue structure.

Methods

A systematic review was performed as per Preferred Reporting Items for Systematic Review and Meta-Analysis guidelines to identify all studies reporting outcomes of shoulder arthroplasty in the setting of previous stabilization surgery. Studies of >10 patients with a minimum of 24 months follow-up were included.

Results

Overall, 377 shoulder arthroplasties composed of 247 anatomical total shoulder arthroplasties (aTSAs), 102 reverse total shoulder arthroplasties (RTSAs), and 28 hemiarthroplasties (HAs) were reported across 14 included studies at mean age 55.4 years, with 203 compared to 451 control shoulders in 7 matched case-control studies. The mean interval from arthroplasty to stabilization procedure was 19.7 years, with 27.2% of patients having undergone multiple procedures and 39.5% bone transfer procedures. Improvements in patient outcomes were observed both for patients who had underwent aTSA or RTSA, with the American Shoulder and Elbow Surgeons score the most commonly used scoring system. Across matched studies comparing to control, large improvements in American Shoulder and Elbow Surgeons were seen for both aTSA and RTSA implants, 38.1-80.5 and 34.9-82.3, which compared to control groups 38.0-85.5 and 35.5-82.3, respectively. There were differences observed in complication profiles between aTSA and RTSA procedures, with lower revision rates in the short-term to medium-term for RTSA implants in present literature. A significantly higher rate of aTSA revision was observed compared to matched control patients undergoing aTSA for primary osteoarthritis without previous stabilization surgery, 9.4% (13/139) vs. 4.1% (11/269) (P = .044). Aseptic loosening posed a particular challenge in the aTSA group, with significantly higher rates of 5.0% (7/139 f = 54.6 months) compared to control 0.74% (2/269 f = 49.1 months, P = .0088). No significant difference in infection rate was observed between matched study and control groups, 1.5% vs. 2.2% (P = .76).

Conclusion

Shoulder arthroplasty may improve functional outcomes for patients experiencing instability arthropathy with a history of stabilization surgery. Careful consideration of potential complications is warranted both in surgical planning and patient counselling given the altered anatomy and biomechanics, with significantly higher revision and loosening rates observed following aTSA compared to control.