High and low performers in internal rotation after reverse total shoulder arthroplasty: a biplane fluoroscopic study

Reverse shoulder arthroplasty implant design and configuration has a significant effect on conjoint tendon impingement

BACKGROUND

Anterior shoulder pain after reverse shoulder arthroplasty (RSA) is not uncommon and may be due to humeral impingement against the conjoint tendon during internal rotation (IR). It is unknown what effect different implant designs and configurations have on conjoint tendon impingement. The purpose of this study was to investigate the influence of several RSA implant design parameters on conjoint tendon impingement during IR.

METHODS

Twelve upper extremity cadavers were dissected to visualize and digitize the path of the coracobrachialis using a tracking system. This data were transformed onto the corresponding computer tomography derived bone models, while previous literature was used to approximate the muscle attachment locations for the conjoint tendon origin and short head of the biceps insertion. Each model then underwent three-dimensional virtual RSA implantation using a generic implant design. A baseline configuration was first implanted which utilized a 25 mm glenoid baseplate placed in 0° inclination and version and positioned flush to the inferior glenoid rim with a 36 mm glenosphere. The humeral baseline configuration consisted of an implant placed in 20° retroversion at a neck shaft angle (NSA) of 135°, centered on the humeral cut plane with a zero-thickness polyethylene cup. Additional implant designs were then configured by independently changing various design parameters including glenoid lateralization, glenosphere diameter, glenoid baseplate position, humeral polyethylene thickness, humeral component position, humeral NSA, and humeral version. Each implant configuration was then examined using a custom motion software which modeled the muscle path of both the coracobrachialis and short head of the biceps. IR was performed until conjoint tendon impingement was detected. All implant configurations were compared using a repeated measures analysis of variance (P < .05).

RESULTS

Glenosphere size, glenoid baseplate anterior-posterior and superior-inferior position, humeral polyethylene insert thickness, humeral anterior-posterior and medial-lateral position, and humeral version significantly influenced conjoint tendon impingement (P < .001). Glenoid lateralization and humeral NSA did not have a significant effect on conjoint tendon impingement (P > .293). Overall, earlier conjoint tendon impingement occurred with larger glenosphere sizes, anteriorly and superiorly positioned glenoid baseplates, greater polyethylene thickness, medially and posteriorly positioned humeral implants, and greater humeral retroversion.

CONCLUSION

RSA implant parameters and positions have been identified that can significantly increase the risk of conjoint tendon impingement, such as larger glenospheres, anterosuperior baseplate and glenosphere positioning, humeral implants or trays positioned medial and posterior, and increased humeral component retroversion. These results may be considered by surgeons preoperatively to limit conjoint tendon impingement, or intra-operatively when conjoint tendon impingement is identified.

Isolated humeral distalization in reverse total shoulder arthroplasty: a biorobotic shoulder simulator study

BACKGROUND

Humeral distalization is inherent to reverse total shoulder arthroplasty (rTSA) and is often produced with concomitant humeral lateralization via the level of the humeral head cut, implant positioning, implant neck shaft angle, and polymer insert thickness. Biomechanical data on the isolated effects of humeral distalization remain limited but could be important to consider when optimizing postoperative rTSA shoulder function. This study investigated the effects of isolated humeral distalization on shoulder biomechanics using a biorobotic shoulder simulator.

METHODS

Eight fresh-frozen cadaveric shoulders were tested using custom polymer inserts that translated the bearing surface 0, +5, +10, and +15 mm along the humeral stem axis, producing isolated distalization without lateralization. Specimens underwent passive elevation in the scapular plane with a static scapula to assess glenohumeral range of motion. Scapular plane abduction motion trajectories were then performed, driven by previously collected scapulothoracic and glenohumeral kinematics from rTSA patients. The effect of isolated distalization on passive elevation was tested using mixed-effects linear regression and the effect on muscle force, joint reaction force, and muscle excursion during active scapular-plane abduction was tested using statistical parametric mapping random effects analysis.

RESULTS

Maximum passive scapular plane elevation increased with humeral distalization (4° per 5 mm distalization). During active elevation, deltoid and rotator cuff muscle forces, and joint reaction forces, increased up to 37% per 5 mm of distalization. Simulated deltoid muscle excursion was altered with increasing distalization but amounted to no more than 0.8 mm change from baseline per 5 mm of distalization. Rotator cuff muscles were consistently lengthened throughout abduction, up to 1.6 mm per 5 mm of distalization. These trends were observed across various patient motions.

CONCLUSIONS

Isolated humeral distalization caused dramatic increases in the muscle forces required to perform scapular-plane abduction. Joint reaction forces increased correspondingly. These results suggest that implant and surgical strategies to generate deltoid muscle tension without humeral distalization may promote better active range of motion and more durable long-term outcomes over approaches that rely on distalization.

Functional internal rotation is associated with subscapularis tendon healing and increased scapular tilt after Grammont style bony increased offset reverse shoulder arthroplasty with 155° humeral implant

BACKGROUND

While forward flexion consistently improves after reverse shoulder arthroplasty (RSA), restoration of internal rotation behind the back (IR1) is much less predictable. This study aims to evaluate the role of the subscapularis tendon in restoration of IR and identify other factors that may influence IR such as anterior scapular tilt and postoperative passive internal rotation at 90° of abduction (IR2). The hypothesis was that IR1 is positively associated with both subscapularis healing, postoperative passive IR2, and anterior scapular tilt.

METHODS

A retrospective review was performed on a consecutive series of Grammont style bony increased offset RSAs performed by a single surgeon between January 2014 and December 2015. Inclusion criteria were: (1) primary RSA for rotator cuff arthropathy, massive irreparable rotator cuff tear, or primary osteoarthritis with B2 glenoid morphology, (2) minimum of two years clinical follow-up, and (3) complete intraoperative repair of a repairable subscapularis tendon. The primary outcomes were postoperative return of IR1 compared to postoperative IR2, healing rate of subscapularis tendon, and scapular tilt.

RESULTS

The cohort included 77 patients, aged 72.6 ± 7.0 years at index surgery and comprising 32 men (42%) and 45 women (58%). At a mean follow-up of 3.3 ± 1.0 years, ultrasound evaluation revealed a successful repair of the subscapularis in 41 patients (53%). Healed subscapularis repair was significantly associated with greater IR1 (85% vs. 53%, P = .031). A multivariate logistic regression revealed functional postoperative IR1 was independently associated with subscapularis healing (odds ratio [OR], 4.3; 95% confidence interval [CI] [1.1-20.2]; P = .046) as well as greater anterior tilt (OR, 1.2; 95% CI [1.1-1.5]; P = .008) and postoperative IR2 (OR, 1.09; 95% CI [1.05-1.14]; P < .001) but lower postoperative passive abduction (OR, 0.96; 95% CI [0.92-1.00], P = .045). The area under receiver operating characteristic curve obtained with the Youden index was 0.88 with a sensitivity of 81.8% and specificity of 90.6%.

CONCLUSIONS

This study revealed that in a Grammont-type RSA, postoperative IR1 recovery is first associated with subscapularis tendon healing, followed by IR2 and finally the ability to tilt the scapula anteriorly. Better understanding of these factors preoperatively may provide greater insight on expected return of functional internal after RSA.

Preoperative planning and inferior glenosphere overhang increases the odds of achieving high internal rotation after Univers reverse total shoulder arthroplasty

BACKGROUND

Despite advances in surgical technique and implant design, internal rotation (IR) after reverse total shoulder arthroplasty (rTSA) continues to be relatively unpredictable. The purpose of this study was to compare patient characteristics, use of 3-dimensional computed tomography (3D CT)-based preoperative planning, and postoperative implant position between patients with high or low IR after rTSA.

METHODS

A retrospective review was performed of a multicenter prospectively collected database on patients who underwent primary rTSA (Univers Revers; Arthrex, Inc.) from 2016-2021 with a minimum 2-year follow-up. Patients were selected for a comparative analysis who either achieved high IR (T12 or better) or low IR (below the hip) postoperatively. Baseline demographics and postoperative radiographs were evaluated for association with IR. Implant position was assessed on radiographs for lateralization shoulder angle (LSA), distalization shoulder angle (DSA), inferior glenosphere overhang, and coracoid-to-glenosphere distance. Regression analyses were performed on component and clinical variables to assess for factors predictive of high vs. low IR.

RESULTS

A total of 344 rTSAs were eligible, of which 98 patients met criteria for the high-IR group and 50 met criteria for the low-IR group. Decreased body mass index (BMI) (odds ratio [OR] 1.14, 95% confidence interval [CI] 1.01-1.30, P = .044), high preoperative IR (OR 1.30, 95% CI 1.02-1.66, P = .034), and surgery on the dominant arm (OR 5.38, 95% CI 1.31-22.1, P = .019) correlated with an increased odds of high IR. The use of 3D CT-based preoperative planning was associated with having high IR (OR 9.69, 95% CI 1.83-51.3, P = .008). Radiographically, increased DSA (OR 1.09, 95% CI 1.02-1.16, P = .012) and increased inferior glenoid overhang (OR 1.39, 95% CI 1.07-1.80, P = .013) were associated with a greater chance of being in the high-IR group.

CONCLUSION

Although specific baseline patient characteristics influence the ability to obtain high IR after rTSA including increased preoperative IR, decreased BMI, and surgery on the dominant arm, there are several factors within the surgeon's control. The use of 3D CT-based preoperative planning greatly increases the odds of obtaining increased postoperative IR. More precisely, mindful implant positioning including inferior glenosphere overhang and slight distalization increased postoperative IR. Therefore, the use of 3D CT-based preoperative planning may be considered in order to carefully and consciously position the glenosphere to slightly increase distalization and inferior overhang in order to optimize IR. However, further evaluation with regard to 3D planned position and postoperative outcomes are required.

Surgical Parameters During Reverse Shoulder Arthroplasty Predict Post-Surgical Kinematics During the Hand-to-Head Motion

PURPOSE

This study aimed to identify surgical parameters during reverse shoulder arthroplasty (RSA) that predict post-surgical kinematics during the hand-to-head motion (H2H) and to identify associations between kinematics and outcomes. We hypothesized that greater humeral retroversion and lateralization predict kinematics, and that more scapular upward rotation is associated with better PROs and more range of motion (ROM).

METHODS

Thirty-five post-RSA patients consented to participate. All surgical parameters were recorded while operating or measured on CT. Participants performed H2H while synchronized biplane radiographs were collected at 50 images/second. Digitally reconstructed radiographs were matched to biplane radiographs to determine glenohumeral and scapular kinematics. For all rotations, the contribution, end position, peak angles, and ROM were calculated. Contact path between the glenosphere and polyethylene insert was calculated. Patient-reported outcomes (PROs), clinical ROM, and strength were measured. Multiple linear regression identified surgical parameters that predicted kinematics, and Pearson correlation identified associations between kinematics and outcomes.

RESULTS

Less humeral retroversion predicted greater peak abduction (p = 0.035). Humeral neck-shaft angle, retroversion, and glenoid tilt predicted the peak posterior contact path (p = 0.012). Better PROs were associated with more superior contact path (p < 0.001), more abduction (p < 0.001), and greater peak scapular upward rotation (p = 0.017). Greater strength was correlated with more peak external rotation (p = 0.035). Greater external rotation at 90º was associated with more abduction (p = 0.008) and upward scapula rotation ROM (p = 0.015) during H2H.

CONCLUSION

Less humeral retroversion predicted kinematics during H2H that were associated with more favorable PROs and clinical outcomes.

Predictors of Internal Rotation-Dependent Activities of Daily Living Performance and Favorable Satisfaction Despite Loss of Objective Internal Rotation After Reverse Shoulder Arthroplasty

INTRODUCTION

Previous research has determined that objective and subjective internal rotation (IR) may be discordant. The purpose of this study was to identify predictors of patient-reported ability to perform IR-dependent activities of daily living (IRADLs) and favorable patient satisfaction after reverse shoulder arthroplasty (RSA) despite the loss of objective IR.

METHODS

A single, institutional, shoulder arthroplasty database was queried for patients undergoing primary RSA with a minimum 2-year follow-up. Patients who were wheelchair bound or had a preoperative diagnosis of infection, fracture, or tumor were excluded. We first identified patients in the overall cohort that lost objective IR from pre- to postoperative assessment, defined as a one-point reduction in the eight-point Flurin scale. In this cohort, we identified patient characteristics that were predictive of patient-reported ability to perform IRADLs and overall patient satisfaction and thresholds in postoperative objective IR.

RESULTS

Out of 599 RSAs initially identified, 107 RSAs lost objective IR (45% female, mean age 70 years). On average, patients lost 1.7 IR score points pre- to postoperatively. Greater preoperative IR and lesser loss of objective IR pre- to postoperatively were associated with greater patient-reported ability to perform all 4 IRADLs (odds ratio 1.54 to 2.5), whereas female sex was associated with worse patient-reported ability to perform 3 IRADLs (odds ratio 0.26 to 0.36). We identified that patients with postoperative IR below the sacrum were unlikely to be able to perform IRADLs and those with postoperative IR at or above L4-L5 were likely to be satisfied.

CONCLUSION

Despite losing objectively assessed IR after RSA, many patients are still able to perform IRADLs and report favorable satisfaction as long as objective IR reaches L4/5. Female sex and postoperative IR below the sacrum were associated with the inability to perform IRADLs, whereas postoperative IR to or above L4-L5 was associated with subjective ratings of satisfaction.

Defining the tipping point for revision reverse shoulder arthroplasty

Background

This study sought to characterize the tipping point values (the functional scores that patients deem dysfunctional enough to warrant surgery) for patients undergoing first revision reverse total shoulder arthroplasty (rTSA).

Methods

This study was a retrospective review of a prospectively collected single-institution database of patients undergoing first revision rTSA between August 2015 and December 2019. Tipping point evaluation utilized preoperative scores including the American Shoulder and Elbow Surgeons (ASES), raw and normalized Constant, Shoulder Pain and Disability Index (SPADI), Simple Shoulder Test (SST), and University of California-Los Angeles (UCLA) scores, and active range of motion including abduction, forward elevation (FE), external rotation (ER), and internal rotation score (IR) prior to elective revision rTSA.

Results

We included 125 revision rTSAs. Tipping points were 37.6 ASES score, 30.5 raw Constant score, 35.5 normalized Constant score, 68.1 SPADI, 3.7 SST, 13.2 UCLA score, 64° abduction, 69° FE, 23° ER, and 3.1 IR. Higher SST was found for older patients and patients with a lower body mass index. Lower abduction and FE tipping points were reported in patients undergoing revision rTSA for rotator cuff failure, unexplained pain, and implant wear.

Discussion

These tipping points can help surgeons counsel patients regarding when to undergo revision rTSA.

Level of evidence

Level III; retrospective cohort study; treatment study.

The impact of scapular posture and sagittal spine alignment on motion and functional outcomes following reverse total shoulder arthroplasty: a scoping review

Background

Reverse total shoulder arthroplasty (RTSA) has evolved beyond its initial indication for elderly patients with rotator cuff arthropathy and is now performed in younger patients for various shoulder pathologies. This surgical procedure has recently gained popularity and has been shown to result in similar functional improvements and complication rates compared to anatomical total shoulder arthroplasty. Scapular posture and sagittal spine alignment (SSPA) have recently emerged as factors potentially influencing RTSA outcomes. This scoping review aimed to assess the existing body of evidence on this topic.

Methods

A systematic search was conducted on MEDLINE, Embase, and CENTRAL databases to evaluate the impact of scapular posture and SSPA on RTSA outcomes.

Results

A total of 6 studies (616 shoulders) were included in this review. Scapular posture was found to influence RTSA outcomes, with studies reporting correlations between scapular posture with postoperative range of motion and functional scores. Suboptimal scapular posture, particularly type C (kyphotic posture with protracted scapulae), appeared to be associated with reduced external rotation. However, findings among the included studies regarding SSPA were varied. Some studies suggested that SSPA, notably thoracic kyphosis, might impact RTSA outcomes by influencing scapular posture, while others did not find a clear relationship.

Conclusion

Scapular posture was implicated as a potential factor affecting RTSA outcomes; however, the role of SSPA remains inconclusive. There is currently a lack of high-quality evidence in the literature to draw definitive conclusions regarding the impact of scapular posture and SSPA on RTSA outcomes. More research is warranted to investigate these relationships more comprehensively.

Obesity is associated with improvement in functional outcome but lower internal rotation after reverse shoulder arthroplasty

Background

The role of obesity as an independent risk factor for increased complications following reverse shoulder arthroplasty (RSA) continues to generate debate. While no standardized body mass index (BMI) cutoff values for shoulder arthroplasty exist, many surgeons are concerned about the potential for poor outcomes and decreased range of motion (ROM) in patients with a high BMI. The purpose of this study was to compare functional outcomes in obese and nonobese patients preoperatively and at short-term follow-up after RSA.

Methods

A retrospective review was performed of a prospectively maintained, multicenter database of primary RSAs performed by 14 surgeons between 2015 and 2019 with minimum 2-year follow-up. A total of 245 patients met the study criteria, including 111 obese (BMI >30) and 134 nonobese (BMI <30) patients. Patient-reported outcomes (PROs) as well as ROM measurements were compared between the 2 groups.

Results

At baseline, obese patients had significantly lower American Shoulder and Elbow Surgeons (36.6 vs. 42.0, P = .014), Western Ontario Osteoarthritis of the Shoulder scores (33.1 vs. 37.8, P = .043), external rotation at 90° (19° vs. 28°, P = .007), internal rotation (IR) spinal level (L5 vs. L4, P = .002), and belly press strength (P = .003) compared to the nonobese cohort. There were no statistical differences in 2-year outcomes (PROs, ROM, and strength) other than a worse IR (spinal level) in the low BMI group (L4 vs. L3, P = .002). In linear regression analyses controlling for confounding variables, increasing BMI was negatively correlated with preoperative external rotation (B = -0.591, P = .034) and preoperative IR spinal level (B = 0.089, P = .002). Increasing BMI was not correlated with postoperative external rotation at 90° (B = 0.189, P = .490) but was associated with worse postoperative IR by spinal level (B = 0.066, P = .043).

Conclusions

Obese patients have greater restrictions in external and internal rotation as well as American Shoulder and Elbow Surgeons and Western Ontario Osteoarthritis of the Shoulder scores at baseline prior to RSA. However, there are no major differences in postoperative PROs or ROM measurements between obese and nonobese patients apart from a worse active IR by spinal level in the obese group (L4 vs. L3, P = .002). This study suggests that an RSA procedure does not need to be restricted solely based on BMI.

Practical considerations for determination of scapular internal rotation and its relevance in reverse total shoulder arthroplasty planning

BACKGROUND

Scapulothoracic orientation, especially scapular internal rotation (SIR) may influence range of motion in reverse total shoulder arthroplasty (RTSA) and is subjected to body posture. Clinical measurements of SIR rely on apical bony landmarks, which depend on changes in scapulothoracic orientation, while radiographic measurements are often limited by the restricted field of view (FOV) in CT scans. Therefore, the goal of this study was (1) to determine whether the use of CT scans with a limited FOV to measure SIR is reliable and (2) if a clinical measurement could be a valuable alternative.

METHODS

This anatomical study analyzed the whole-body CT scans of 100 shoulders in 50 patients (32 male and 18 female) with a mean age of 61.2 ± 20.1 years (range 18; 91). (1) CT scans were rendered into 3D models and SIR was determined as previously described. Results were compared to measurements taken in 2D CT scans with a limited FOV. (2) Three apical bony landmarks were defined: (the angulus acromii (AA), the midpoint between the AA and the coracoid process tip (C) and the acromioclavicular (AC) joint. The scapular axis was determined connecting the trigonum scapulae with these landmarks and referenced to the glenoid center. The measurements were repeated with 0°, 10°, 20°, 30° and 40° anterior scapular tilt.

RESULTS

Mean SIR was 44.8° ± 5.9° and 45.6° ± 6.6° in the 3D and 2D model, respectively (p < 0.371). Mean difference between the measurements was 0.8° ± 2.5° with a maximum of 10.5°. Midpoint AA/C showed no significant difference to the scapular axis at 0° (p = 0.203) as did the AC-joint at 10° anterior scapular tilt (p = 0.949). All other points showed a significant difference from the scapular axis at all degrees of tilt.

CONCLUSION

2D CT scans are reliable to determine SIR, even if the spine is not depicted. Clinical measurements using apical superficial scapula landmarks are a possible alternative; however, anterior tilt influenced by posture alters measured SIR.