The role of greater tuberosity healing in reverse shoulder arthroplasty: a finite element analysis

BACKGROUND

The lack of greater tuberosity (GT) healing in proximal humerus fractures has been negatively correlated with outcomes for hemiarthroplasty; however, there is still debate regarding the effects of GT healing in reverse shoulder arthroplasty (RSA). Our goal was to examine the effects of GT healing using a kinematic finite element analysis (FEA) model.

MATERIAL AND METHODS

Computer-aided design models of a medialized glenoid with a lateralized humerus (MGLH) RSA design were uploaded into an FEA shoulder model in 2 different configurations: healed greater tuberosity (HGT) and nonunion greater tuberosity (NGT). Deltoid muscle forces and joint reaction forces (JRFs) on the shoulder were calculated during abduction (ABD), forward flexion (FF), and external rotation (ER).

RESULTS

Force magnitude of the anterior, middle, and posterior deltoid muscle as well as JRFs modeled in both GT scenarios were similar for ABD (muscle forces P = .91, P = .75, P = .71, respectively; and JRF P = .93) and for FF (muscle forces P = .89, P = .83, P = .99, respectively; and JRF P = .90). For ER, the force magnitude between 2 GT settings showed statistically significant differences (HGT: 9.51 N vs. NGT: 6.13 N) (P < .001). Likewise, during ER, JRFs were different, and the NGT group showed a steep drop in JRF after 10° of ER (HGT: 28.4 N vs. NGT: 18.38 N) (P < .001).

CONCLUSION

GT healing does not seem to impact RSA biomechanics during abduction or forward flexion; however, it does affect biomechanics during external rotation. Overall orthopedic surgeons can expect good results for patients after RSA even with poor GT healing.

How the greater tuberosity affects clinical outcomes after reverse shoulder arthroplasty for proximal humeral fractures

BACKGROUND

Our purpose was to evaluate the clinical and radiologic outcomes of reverse shoulder arthroplasty for proximal humeral fractures in a large cohort of elderly patients and compare the results in the case of tuberosity excision, failed fixation, or anatomic healing.

METHODS

In this retrospective multicenter study, 420 patients underwent review and radiography with a minimum follow-up period of 12 months. The patients were divided into 3 groups according to the status of the greater tuberosity (GT) on the last anteroposterior radiographs: anatomic GT healing (group A, n = 169); GT resorption, malunion, or nonunion (group B, n = 131); and GT excision (group C, n = 120). Complications were recorded; shoulder function, active mobility, and subjective results were assessed.

RESULTS

At a mean follow-up of 28 months, the mean Simple Shoulder Value in group A (75%) outperformed the results found in groups B (69%, P < .001) and C (56%, P < .001). Overall, the mean adjusted Constant-Murley score was significantly higher in group A (93% ± 22%) than in group B (82% ± 22%) and group C (80% ± 24%) (P < .001), but there was no difference between groups B and C (P = .88). Anterior active elevation and external rotation were significantly better in group A than in groups B and C (P < .001). The instability rate was significantly higher in group C (n = 15 [12.5%], P < .001) than in group A (n = 2) or group B (n = 3).

CONCLUSION

In elderly patients who have undergone a reverse shoulder arthroplasty for acute proximal humeral fractures, anatomic tuberosity healing improves objective and subjective outcomes. GT excision is associated with the worst functional results and increases the risk of postoperative shoulder instability.

Reverse total shoulder arthroplasty for acute head-splitting, 3- and 4-part fractures of the proximal humerus in the elderly

BACKGROUND

Anatomic reduction and stable internal fixation of complex proximal humeral fractures in the elderly is challenging. Secondary displacement, screw perforation, and humeral head necrosis are common complications. The outcome of hemiarthroplasty is unpredictable and strongly dependent on the uncertain healing of the greater tuberosity. This multicenter study retrospectively analyzes the midterm results of primary reverse total shoulder arthroplasty for the treatment of acute, complex fractures of the humerus in an elderly population.

METHODS

Fifty-two shoulders in 51 patients with a mean age of 77 years treated with reverse total shoulder arthroplasty for an acute, complex fracture of the proximal humerus were clinically and radiographically analyzed after a mean follow-up period of 35 months (range, 12-90 months).

RESULTS

There were no intraoperative complications. Revision surgery was performed in 4 shoulders. At final follow-up, the absolute and relative Constant scores averaged 62 points (range, 21-83 points) and 86% (range, 30%-100%), respectively, with a mean Subjective Shoulder Value of 83% (range, 30%-100%). Of the patients, 92% rated the treatment outcome as excellent or good. Patients with a resected or secondarily displaced greater tuberosity had an inferior clinical outcome to those with a healed greater tuberosity.

CONCLUSION

The midterm clinical results are predictably good, with low complication rates and a rapid postoperative recovery of painfree everyday function. If secondary displacement of the greater tuberosity occurs, revision surgery may warrant consideration in view of potential improvement of ultimate outcome.