Superior migration of the humeral head does not significantly affect outcomes at an average of 11 years after total shoulder arthroplasty

BACKGROUND

Superior migration of the humeral head has been linked with rotator cuff dysfunction and glenoid loosening after total shoulder arthroplasty (TSA). We aimed to determine if superior migration was associated with poor shoulder function following anatomic TSA at long-term follow-up.

METHODS

In this retrospective cohort study, we reviewed patients undergoing TSA by a single surgeon at an urban, academic institution. To study the effect of superior migration on TSA outcomes, we stratified the cohort by ≥ and <7 mm of acromiohumeral interval (AHI) and compared range of motion and patient reported outcomes (PROs). Clinical variables included preoperative and postoperative forward elevation (FE), internal rotation, external rotation, visual analog scale, American Shoulder and Elbow Surgeons shoulder score, and Simple Shoulder Text score. Radiographic variables included immediate postoperative and long-term follow-up AHI, lateral humeral offset, and glenoid loosening scores.

RESULTS

After applying exclusion criteria, 121 TSAs were included. The mean age was 63.9 ± 9.5 years, and 66 surgeries (55%) were in male patients. The mean follow-up for our cohort was 11.2 years (range, 5-26 years). Nine shoulders underwent revision surgery. All range of motion and PROs improved significantly from preoperative to the most recent postoperative follow-up. The mean AHI immediately following surgery was 10.9 ± 4.1 mm, while the mean AHI at most recent follow-up was 8.4 ± 3.5 mm. Glenoid loosening was observed in 29 (23.8%) shoulders at the most recent follow-up appointment. Although AHI correlated weakly with FE (r = 0.252; P = .006), we did not observe a clear threshold of migration which led to degraded function. Importantly, glenoid loosening was not related to AHI at long-term follow-up (P = .631). None of FE, internal rotation, external rotation, visual analog scale, American Shoulder and Elbow Surgeons shoulder score, Simple Shoulder Text, or revisions were significantly different between patients with ≥ and <7 mm of AHI.

CONCLUSION

Our results suggest that anatomic TSA provides durable improvements to pain, function, and PROs despite changes to the AHI.

Association Between Rotator Cuff Tears and Superior Migration of the Humeral Head: An MRI-Based Anatomic Study

Background:

Superior humeral migration has been established as a component of rotator cuff disease, as it disrupts normal glenohumeral kinematics. Decreased acromiohumeral interval (AHI) as measured on radiographs has been used to indicate rotator cuff tendinopathy. Currently, the data are mixed regarding the specific rotator cuff pathology that contributes the most to humeral head migration.

Purpose:

To determine the relationship between severity of rotator cuff tears (RCTs) and AHI via a large sample of magnetic resonance imaging (MRI) shoulder examinations.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

A search was performed for 3-T shoulder MRI performed in adults for any indication between January 2010 and June 2019 at a single institution. Three orthopaedic surgeons and 1 musculoskeletal radiologist measured AHI on 2 separate occasions for patients who met the inclusion criteria. Rotator cuff pathologies were recorded from imaging reports made by fellowship-trained musculoskeletal radiologists.

Results:

A total of 257 patients (mean age, 52 years) met the inclusion criteria. Of these, 199 (77%) had at least 1 RCT, involving the supraspinatus in 174 (67.7%), infraspinatus in 119 (46.3%), subscapularis in 80 (31.1%), and teres minor in 3 (0.1%). Full-thickness tears of the supraspinatus, infraspinatus, or subscapularis tendon were associated with significantly decreased AHI (7.1, 5.3, and 6.8 mm, respectively) compared with other tear severities (P < .001). Having a larger number of RCTs was also associated with decreased AHI (ρ = –0.157; P = .012). Isolated infraspinatus tears had the lowest AHI (7.7 mm), which was significantly lower than isolated supraspinatus tears (8.9 mm; P = .047).

Conclusion:

Although various types of RCTs have been associated with superior humeral head migration, this study demonstrated a significant correlation between a complete RCT and superior humeral migration. Tears of the infraspinatus tendon seemed to have the greatest effect on maintaining the native position of the humeral head. Further studies are needed to determine whether early repair of these tears can slow the progression of rotator cuff disease.

Three-dimensional kinematic features in large and massive rotator cuff tears with pseudoparesis

BACKGROUND

Although massive rotator cuff tears occasionally lead to severe impairment of shoulder function, the criteria for losing the ability to elevate the arm are unclear. This study aimed to analyze the features of both tear size and 3-dimensional (3D) shoulder kinematics that correspond to the loss of the ability to elevate the arm in patients with large and massive rotator cuff tears.

METHODS

We prospectively enrolled patients with rotator cuff tears, including the supraspinatus and more than half of the subscapularis or more than two-thirds of the infraspinatus, without severe pain. A total of 13 patients (15 shoulders) were divided into 2 groups: 9 shoulders in the pseudoparesis (P) group and 6 shoulders in the non-pseudoparesis (NP) group. Fluoroscopic images were collected during active scapular-plane elevation, and 3D shoulder kinematics was analyzed using 2-dimensional-3D registration techniques. The radiographic findings and 3D kinematic results were compared between the groups. The correlation between tear size and 3D kinematics was also investigated.

RESULTS

The most superior position of the humeral head center was significantly higher in the P group (6.7 ± 3.0 mm in P group vs. 3.6 ± 1.3 mm in NP group, P = .0321). Superior migration, which was defined as the most superior position > 5 mm, was significantly more frequent in the P group (7 shoulders and 1 shoulder in the P and NP groups, respectively; P = .0201). Thoracohumeral external rotation was significantly smaller in the P group (16° ± 31° in P group vs. 91° ± 21° in NP group, P < .0001). The total tear size and the tear sizes of the anterior and posterior rotator cuffs were significantly correlated with the superior (r = 0.68, P = .0056), anterior (r = 0.68, P = .0058), and posterior (r = -0.80, P = .0004) positions of the humeral head center. The tear size of the posterior rotator cuff also tended to be correlated with glenohumeral external rotation (r = -0.48, P = .0719).

CONCLUSION

Anterior and posterior rotator cuff tears cause significant superior and anteroposterior translations of the humeral head, and posterior cuff tears may lead to loss of glenohumeral external rotation. With these abnormal kinematics, superior migration and loss of thoracohumeral external rotation were identified as features of pseudoparesis.