Glenoid Retroversion Associates With Asymmetric Rotator Cuff Muscle Atrophy in Those With Walch B-type 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.

Are glenoid retroversion, humeral subluxation, and Walch classification associated with a muscle imbalance?

BACKGROUND

The etiology of humeral posterior subluxation remains unknown, and it has been hypothesized that horizontal muscle imbalance could cause this condition. The objective of this study was to compare the ratio of anterior-to-posterior rotator cuff and deltoid muscle volume as a function of humeral subluxation and glenoid morphology when analyzed as a continuous variable in arthritic shoulders.

METHODS

In total, 333 computed tomography scans of shoulders (273 arthritic shoulders and 60 healthy controls) were included in this study and were segmented automatically. For each muscle, the volume of muscle fibers without intramuscular fat was measured. The ratio between the volume of the subscapularis and the volume of the infraspinatus plus teres minor (AP ratio) and the ratio between the anterior and posterior deltoids (APdeltoid) were calculated. Statistical analyses were performed to determine whether a correlation could be found between these ratios and glenoid version, humeral subluxation, and/or glenoid type per the Walch classification.

RESULTS

Within the arthritic cohort, no statistically significant difference in the AP ratio was found between type A glenoids (1.09 ± 0.22) and type B glenoids (1.03 ± 0.16, P = .09), type D glenoids (1.12 ± 0.27, P = .77), or type C glenoids (1.10 ± 0.19, P > .999). No correlation was found between the AP ratio and glenoid version (ρ = -0.0360, P = .55) or humeral subluxation (ρ = 0.076, P = .21). The APdeltoid ratio of type A glenoids (0.48 ± 0.15) was significantly greater than that of type B glenoids (0.35 ± 0.16, P < .01) and type C glenoids (0.21 ± 0.10, P < .01) but was not significantly different from that of type D glenoids (0.64 ± 0.34, P > .999). When evaluating both healthy control and arthritic shoulders, moderate correlations were found between the APdeltoid ratio and both glenoid version (ρ = 0.55, P < .01) and humeral subluxation (ρ = -0.61, P < .01).

CONCLUSION

This in vitro study supports the use of software for fully automated 3-dimensional reconstruction of the 4 rotator cuff muscles and the deltoid. Compared with previous 2-dimensional computed tomography scan studies, our study did not find any correlation between the anteroposterior muscle volume ratio and glenoid parameters in arthritic shoulders. However, once deformity occurred, the observed APdeltoid ratio was lower with type B and C glenoids. These findings suggest that rotator cuff muscle imbalance may not be the precipitating etiology for the posterior humeral subluxation and secondary posterior glenoid erosion characteristic of Walch type B glenoids.

Non-operative management of shoulder osteoarthritis: Current concepts

Glenohumeral osteoarthritis (OA) is one of the most common causes of shoulder pain. Conservative treatment options include physical therapy, pharmacological therapy, and biological therapy. Patients with glenohumeral OA present shoulder pain and decreased shoulder range of motion (ROM). Abnormal scapular motion is also seen in patients as adaptation to the restricted glenohumeral motion. Physical therapy is performed to (1) decrease pain, (2) increase shoulder ROM, and (3) protect the glenohumeral joint. To decrease pain, it should be assessed whether the pain appears at rest or during shoulder motion. Physical therapy may be effective for motion pain rather than rest pain. To increase shoulder ROM, the soft tissues responsible for the ROM loss need to be identified and targeted for intervention. To protect the glenohumeral joint, rotator cuff strengthening exercises are recommended. Administration of pharmacological agents is the major part next to physical therapy in the conservative treatment. The main aim of pharmacological treatment is the reduction of pain and diminution of inflammation in the joint. To achieve this aim, non-steroidal anti-inflammatory drugs are recommended as first-line therapy. Additionally, the supplementation of oral vitamin C and vitamin D can help to slow down cartilage degeneration. Depending on the individual comorbidities and contraindications, sufficient medication with good pain reduction is thus possible for each patient. This interrupts the chronic inflammatory state in the joint and, in turn, enables pain-free physical therapy. Biologics such as platelet-rich plasma, bone marrow aspirate concentrate, and mesenchymal stem cells have gathered increased attention. Good clinical outcomes have been reported, but we need to be aware that these options are helpful in decreasing shoulder pain but neither stopping the progression nor improving OA. Further evidence of biologics needs to be obtained to determine their effectiveness. In athletes, a combined approach of activity modification and physical therapy can be effective. Oral medications can provide patients with transient pain relief. Intra-articular corticosteroid injection, which provides longer-term effects, must be used cautiously in athletes. There is mixed evidence for the efficacy of hyaluronic acid injections. There is still limited evidence regarding the use of biologics.

Rotator cuff muscle imbalance associates with shoulder instability direction

BACKGROUND

Although muscle weakness and/or imbalance of the rotator cuff are thought to contribute to the development of shoulder instability, the association between muscular dysfunction and shoulder instability is not completely understood. The purpose of this study was to evaluate rotator cuff and deltoid muscle cross-sectional areas in different types of shoulder instability (anterior, posterior, and multidirectional instability [MDI]) and to determine the associations between muscular imbalance and shoulder instability direction.

METHODS

Preoperative magnetic resonance images of patients with shoulder instability who subsequently underwent arthroscopic glenohumeral labral repair or capsular plication were evaluated. Shoulder instability was classified into 3 categories by direction: (1) anterior, (2) posterior, and (3) MDI. The rotator cuff (supraspinatus, subscapularis, and infraspinatus + teres minor) and deltoid (anterior and posterior portions, and total) muscle areas were measured on T1 sagittal and axial slices, respectively. The ratios of the subscapularis to infraspinatus + teres minor area and the anterior deltoid to posterior deltoid area were calculated to quantify the transverse force couple imbalance.

RESULTS

A total of 189 patients were included, where each group consisted of 63 patients. The infraspinatus + teres minor muscle area was smaller than the subscapularis muscle area in the anterior instability group (P = .007). The subscapularis muscle area was smaller than the infraspinatus + teres minor muscle area in the posterior instability and MDI groups (P ≤ .003). The anterior deltoid muscle area was smaller than the posterior deltoid muscle area in all groups (P ≤ .001). The subscapularis-to-infraspinatus + teres minor area ratio in the anterior instability group (1.18 ± 0.40) was higher than that in the posterior instability and MDI groups (0.79 ± 0.31 and 0.93 ± 0.33, respectively; P < .001). There was no difference in the anterior deltoid-to-posterior deltoid area ratio among the 3 groups.

CONCLUSION

Patients with anterior instability have smaller muscle area of the posterior rotator cuff as compared with the anterior rotator cuff. In contrast, patients with posterior instability and MDI have smaller muscle area of the anterior rotator cuff as compared with the posterior rotator cuff. Thus, the direction of shoulder instability is associated with rotator cuff muscle area.

The Influence of Age at Pediatric-Onset Spinal Cord Injury and Years of Wheelchair Use on Shoulder Complex Joint Dynamics During Manual Wheelchair Propulsion

Objective

To assess the association of age at pediatric-onset spinal cord injury (SCI) and years of manual wheelchair use with shoulder dynamics.

Design

Upper extremity kinematics and hand-rim kinetics were obtained during manual wheelchair propulsion. An inverse dynamics model computed three-dimensional acromioclavicular, sternoclavicular, and glenohumeral joint dynamics. Linear mixed effects models evaluated the association of age at injury onset and years of wheelchair use with shoulder dynamics.

Setting

Motion laboratory within a children's hospital.

Participants

Seventeen manual wheelchair users (N=17; 6 female, 11 male; mean age: 17.2 years, mean age at SCI onset: 11.5 years) with pediatric-onset SCI (levels: C4-T11) and International Standards for Neurological Classification of SCI grades: A (11), B (3), C (2), and N/A (2).

Interventions

Not applicable.

Main Outcome Measures

Acromioclavicular, sternoclavicular, and glenohumeral angles and ranges of motion, and glenohumeral forces and moments.

Results

We observed a decrease in maximum acromioclavicular upward rotation (ß [95% confidence interval {CI}]=3.02 [0.15,5.89], P=.039) and an increase in acromioclavicular downward/upward rotation range of motion (ß [95% CI]=0.44 [0.08,0.80], P=.016) with increasing age at SCI onset. We found interactions between age at onset and years of use for maximum glenohumeral abduction (ß [95% CI]=0.16 [0.03,0.29], P=.017), acromioclavicular downward/upward rotation range of motion (ß [95% CI]=-0.05 [-0.09,-0.01], P=.008), minimum acromioclavicular upward rotation (ß [95% CI]=-0.34 [-0.64,-0.04], P=.026). A decrease in glenohumeral internal rotation moment (ß [95% CI]=-0.09 [-0.17,-0.009], P=.029) with increasing years of use was found.

Conclusions

Age at injury and the years of wheelchair use are associated with shoulder complex biomechanics during wheelchair propulsion. These results are noteworthy, as both age at SCI onset and years of wheelchair use are considered important factors in the incidence of shoulder pain. These results suggest that investigations of biomechanical changes over the lifespan are critical.

Rotator cuff fatty infiltration and muscle atrophy: relation to glenoid deformity in primary glenohumeral osteoarthritis

BACKGROUND

Muscle atrophy (MA) and fatty infiltration (FI) are degenerative processes of the rotator cuff musculature that have incompletely understood relationships with the development of eccentric glenoid wear in the setting of primary glenohumeral osteoarthritis (GHOA).

METHODS

All patients with GHOA and an intact rotator cuff who underwent both magnetic resonance imaging and computed tomography scans of the affected shoulder prior to total shoulder arthroplasty between 2015 and 2020 were identified from a prospectively maintained registry. Rotator cuff MA was measured quantitatively on sequential sagittal magnetic resonance images, whereas FI was assessed on sagittal magnetic resonance imaging slices using the Goutallier classification. Preoperative computed tomography scans were reconstructed using automated 3-dimensional software to determine glenoid retroversion, glenoid inclination, and humeral head subluxation. Glenoid deformity was classified according to the Walch classification. Univariate and multivariable regression analyses were performed to characterize associations between age, sex, muscle area, FI, and glenoid morphology.

RESULTS

Among the 127 included patients, significant associations were found between male sex and larger overall rotator cuff musculature (P < .01), increased ratio of the posterior rotator cuff (PRC) to the subscapularis area (P = .01), and glenoid retroversion (19° vs. 14°, P < .01). Larger supraspinatus and PRC muscle size was correlated with increased retroversion (r = 0.23 [P = .006] for supraspinatus and r = 0.25 [P = .004] for PRC) and humeral head subluxation (r = 0.25 [P = .004] for supraspinatus and r = 0.28 [P = .001] for PRC). The ratio of PRC muscle size to anterior rotator cuff muscle size was not associated with evidence of eccentric glenoid wear (P > .05). After we controlled for confounding factors, increasing glenoid retroversion was associated with high-grade infraspinatus FI (β, 6.8; 95% confidence interval, 2.9-10.7; P < .01) whereas larger PRC musculature was predictive of a Walch type B (vs. type A) glenoid (odds ratio, 1.3; 95% confidence interval, 1.0-1.5; P = .04).

CONCLUSION

Patients with eccentric glenoid wear in the setting of primary GHOA and an intact rotator cuff appear to have both larger PRC musculature and higher rates of infraspinatus FI. Although the temporal and causal relationships of these associations remain ambiguous, MA and FI should be considered 2 discrete processes in the natural history of GHOA.

Rotator cuff fatty infiltration and muscle atrophy do not impact clinical outcomes after reverse total shoulder arthroplasty for glenohumeral osteoarthritis with intact rotator cuff

BACKGROUND

The clinical significance of rotator cuff muscle quality following reverse total shoulder arthroplasty (RTSA) remains uncertain. The purpose of this study was to evaluate the influence of rotator cuff fatty infiltration (FI) and muscle atrophy (MA) on clinical outcomes following RTSA for glenohumeral osteoarthritis (GHOA).

METHODS

One hundred eight shoulders with primary GHOA that underwent RTSA with a lateralized glenosphere for GHOA with a minimum of 2-year follow-up were identified from a prospectively maintained registry. Each rotator cuff muscle was assessed on preoperative magnetic resonance imaging for FI and quantitative amount of MA. Pre- and postoperative outcomes included American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form score, Single Assessment Numerical Evaluation (SANE) score, visual analog scale pain score, and range of motion (ROM) measurements.

RESULTS

Eighty-one patients with a mean age of 70.7 ± 5.4 years (range: 57-85) were included who underwent RTSA with a mean follow-up of 2.1 years (range: 2-3.9 years). There was a significant improvement in all outcome measures postoperatively (P < .01). Twenty-two patients (27.1%) had moderate to severe combined infraspinatus and teres minor FI. There was no significant difference in the postoperative external rotation or clinical outcomes compared with those patients with only mild FI (P > .05). Forty-three patients (53.1%) had moderate to severe global rotator cuff FI. There was no significant difference in postoperative outcomes compared with those patients with only mild FI (P < .01). Univariate analysis did not reveal any significant association between the degree of FI or MA of any individual rotator cuff muscle and postoperative clinical outcomes or ROM. The size ratio of the posterior rotator cuff to the subscapularis muscle was positively correlated with preoperative SANE scores but negatively correlated with absolute postoperative and change in preoperative to postoperative SANE scores. However, there were no significant correlations between this size ratio and the other outcome measures.

CONCLUSION

Rotator cuff muscle quality as assessed by MA and FI does not impact clinical outcomes following RTSA with a lateralized glenosphere in patients with GHOA and an intact rotator cuff.

CT-based volumetric assessment of rotator cuff muscle in shoulder arthroplasty preoperative planning

Aims

The aim of this study was to describe a quantitative 3D CT method to measure rotator cuff muscle volume, atrophy, and balance in healthy controls and in three pathological shoulder cohorts.

Methods

In all, 102 CT scans were included in the analysis: 46 healthy, 21 cuff tear arthropathy (CTA), 18 irreparable rotator cuff tear (IRCT), and 17 primary osteoarthritis (OA). The four rotator cuff muscles were manually segmented and their volume, including intramuscular fat, was calculated. The normalized volume (NV) of each muscle was calculated by dividing muscle volume to the patient’s scapular bone volume. Muscle volume and percentage of muscle atrophy were compared between muscles and between cohorts.

Results

Rotator cuff muscle volume was significantly decreased in patients with OA, CTA, and IRCT compared to healthy patients (p < 0.0001). Atrophy was comparable for all muscles between CTA, IRCT, and OA patients, except for the supraspinatus, which was significantly more atrophied in CTA and IRCT (p = 0.002). In healthy shoulders, the anterior cuff represented 45% of the entire cuff, while the posterior cuff represented 40%. A similar partition between anterior and posterior cuff was also found in both CTA and IRCT patients. However, in OA patients, the relative volume of the anterior (42%) and posterior cuff (45%) were similar.

Conclusion

This study shows that rotator cuff muscle volume is significantly decreased in patients with OA, CTA, or IRCT compared to healthy patients, but that only minimal differences can be observed between the different pathological groups. This suggests that the influence of rotator cuff muscle volume and atrophy (including intramuscular fat) as an independent factor of outcome may be overestimated.

Cite this article: Bone Jt Open 2021;2(7):552–561.

Similar scapular morphology in patients with dynamic and static posterior shoulder instability

Background

There is evidence that specific variants of scapular morphology are associated with dynamic and static posterior shoulder instability. To this date, observations regarding glenoid and/or acromial variants were analyzed independently, with two-dimensional imaging or without comparison with a healthy control group. Therefore, the purpose of this study was to analyze and describe the three-dimensional (3D) shape of the scapula in healthy and in shoulders with static or dynamic posterior instability using 3D surface models and 3D measurement methods.

Methods

In this study, 30 patients with unidirectional posterior instability and 20 patients with static posterior humeral head subluxation (static posterior instability, Walch B1) were analyzed. Both cohorts were compared with a control group of 40 patients with stable, centered shoulders and without any clinical symptoms. 3D surface models were obtained through segmentation of computed tomography images and 3D measurements were performed for glenoid (version and inclination) and acromion (tilt, coverage, height).

Results

Overall, the scapulae of patients with dynamic and static instability differed only marginally among themselves. Compared with the control group, the glenoid was 2.5° (P = .032), respectively, 5.7° (P = .001) more retroverted and 2.9° (P = .025), respectively, 3.7° (P = .014) more downward tilted in dynamic, respectively, static instability. The acromial roof of dynamic instability was significantly higher and on average 6.2° (P = .007) less posterior covering with an increased posterior acromial height of +4.8mm (P = .001). The acromial roof of static instability was on average 4.8° (P = .041) more externally rotated (axial tilt), 7.3° (P = .004) flatter (sagittal tilt), 8.3° (P = .001) less posterior covered with an increased posterior acromial height of +5.8 mm (0.001).

Conclusion

The scapula of shoulders with dynamic and static posterior instability is characterized by an increased glenoid retroversion and an acromion that is shorter posterolaterally, higher, and more horizontal in the sagittal plane. All these deviations from the normal scapula values were more pronounced in static posterior instability.

Glenoid retroversion associates with deltoid muscle asymmetry in Walch B-type glenohumeral osteoarthritis

Background

The etiologies of glenohumeral osteoarthritis (GHOA) and eccentric glenoid wear within GHOA are unknown, but muscular imbalance may play a role. The purpose of the present study was to determine the relationship between deltoid muscle area, GHOA, and eccentric glenoid wear. We hypothesized that patients with GHOA would have overall deltoid atrophy as compared with controls and that increasing posterior deltoid areas would associate with glenoid retroversion in the Walch B-type (eccentric) GHOA group.

Methods

The study was a retrospective review of computed tomography imaging studies. We included a control group of subjects without GHOA and a group of individuals with GHOA before undergoing total shoulder arthroplasty. We assigned Walch types via consensus. Cross-sectional area was measured for the anterior and posterior deltoid musculature demarcated via the scapular line, normalized to the total deltoid area. Absolute and normalized total, anterior, and posterior deltoid areas were compared between controls and the entire GHOA group. Normalized anterior and posterior deltoid areas were compared between Walch A-type and B-type GHOA patients within the GHOA group. Univariate linear regression was used to evaluate for an association between glenoid retroversion and normalized posterior deltoid areas in controls, Walch A-type, and Walch B-type patients. Multivariate linear regression analysis was used to evaluate the effects of normalized posterior deltoid area, age, sex, and height on glenoid retroversion within the Walch B-type subgroup.

Results

We included 99 patients with GHOA and 47 controls. The control and GHOA patients did not differ in absolute deltoid areas (21.8 ± 8.8cm² vs. 20.6 ± 7.9cm²; P = .488). Patients with GHOA had a statistically significant increase in normalized posterior deltoid area (0.50 ± 0.10 vs. 0.46 ± 0.10; P = .032) and a reciprocal decrease in normalized anterior deltoid area (0.50 ± 0.10 vs. 0.54 ± 0.10; P = .040) compared with controls. Walch A-type and B-type patients did not differ in normalized posterior deltoid areas (0.50 ± 0.11 vs. 0.50 ± 0.10; P = .780). Normalized posterior deltoid area positively associated with glenohumeral retroversion in Walch B-type GHOA (R² = 0.102; P = .020), a relationship maintained in multivariate linear regression, using gender, age, and height as covariates (standardized beta = 0.309, P = .027).

Conclusion

GHOA is not associated with deltoid atrophy, calling into question the suggestion that periarticular muscular atrophy in GHOA is secondary to disuse. Increasing normalized posterior deltoid area associates with increased glenoid retroversion in patients with Walch B-type glenoid morphology. Muscular imbalance may play a role in the etiology or progression of the glenoid deformity observed in eccentric GHOA.

The implications of the glenoid angles and rotator cuff status in patients with osteoarthritis undergoing shoulder arthroplasty

BACKGROUND

The success of shoulder arthroplasty, both reverse and anatomical, depends on correcting the underlying glenoid deformity especially in patients with an osteoarthritis. We hypothesized that the distribution of glenoid version and especially inclination are underestimated in the shoulder arthritis population, and also that superior glenoid inclination can be detected through 3-dimensional (3D) software program of computed tomography (CT) to a greater proportion in patients with rotator cuff insufficiency, but also in patients with osteoarthritis with an intact rotator cuff. Because of the influence of rotator cuff imbalance on secondary glenoid wear the values of the critical shoulder angle (CSA) and the fatty infiltration of the rotator cuff are further analyzed. The aim of our study is to determine; 1) the distribution of glenoid inclination and version; 2) the relationship between glenoid inclination, version, the critical shoulder angle (CSA) to the status of the rotator cuff; 3) the proportion of patients with both an intact rotator cuff and a superior inclination greater than 10°.

METHODS

A total of 231 shoulders were evaluated with X-ray images, 3-dimentional (3D) software program of computed tomography (CT), and magnetic resonance imaging. The cohort was divided into 3 groups according to their inclination angles and also grouped as intact-rotator cuff and torn-cuff group.

RESULTS

The median (min/max) values for the 231 shoulders were 8° (- 23°/56°) for the inclination angle, - 11°(- 55°/23°) for the version angle, and 31.5°(17.6°/61.6°) for the CSA. The majority of the glenoids were found to show posterior-superior erosion. Glenoid inclination angle and CSA were significantly higher in torn-cuff group when compared with intact-cuff group (P < 0.001, both). The rotator cuff tears were statistically significant in high inclination group than low inclination group and no inclination group (p < 0.001). In the high inclination group, 41 of 105 (39%) shoulders had an intact rotator cuff, in about 18% of all shoulders.

CONCLUSION

Our findings show that 3D evaluation of glenoid inclination is mandatory for preoperative planning of shoulder replacement in order to properly assess superior inclination and that reverse shoulder arthroplasty may be considered more frequently than as previously expected, even when the rotator cuff is intact.

LEVEL OF EVIDENCE

Level III.