onlay humeral components in reverse total shoulder arthroplasty: a biorobotic shoulder simulator study

BACKGROUND

Both inlay and onlay humeral implants are available for reverse total shoulder arthroplasty (rTSA), but biomechanical data comparing these components remain limited. This study investigated the effects of inlay and onlay rTSA humeral components on shoulder biomechanics using a biorobotic shoulder simulator.

METHODS

Twenty fresh-frozen cadaveric shoulders were tested before and after rTSA with either an inlay or onlay humeral implant. Comparisons were performed between the most commonly implanted configurations for each implant (baseline) and with a modification to provide equivalent neck-shaft angles (NSAs) for the inlay and onlay configurations. Specimens underwent passive range-of-motion (ROM) assessment with the scapula held static, and scapular-plane abduction was performed, driven by previously collected human-subject scapulothoracic and glenohumeral kinematics. Passive ROM glenohumeral joint angles were compared using t tests, whereas muscle force and excursion data during scapular-plane elevation were evaluated with statistical parametric mapping and t tests.

RESULTS

Maximum passive elevation was reduced for the inlay vs. onlay humeral components, although both implants caused reduced passive elevation vs. the native joint. Inlay rTSA also demonstrated reduced passive internal rotation at rest and increased external rotation at 90° of humerothoracic elevation vs. the native joint. All preoperative planning estimates of ROM differed from experiments. Rotator cuff forces were elevated with an onlay vs. inlay humeral implant, but simulated muscle excursions did not differ between systems. Compared with the native joint, rotator cuff forces were increased for both inlay and onlay implants and deltoid forces were reduced for inlay implants. Muscle excursions were dramatically altered by rTSA vs. the native joint. Comparisons of inlay and onlay humeral implants with equivalent NSAs were consistent with the baseline comparisons.

CONCLUSIONS

Rotator cuff forces required to perform scapular-plane abduction increase following rTSA using both inlay and onlay implants. Rotator cuff forces are lower with inlay implants compared with onlay implants, although inlay implants also result in reduced passive-elevation ROM. Deltoid forces are lower with inlay implants in comparison to the native joint but not with onlay implants. The differences between inlay and onlay components are largely unaffected by NSA, indicating that these differences are inherent to the inlay and onlay designs. In those patients with an intact rotator cuff, decreased rotator cuff forces to perform abduction with an inlay humeral implant compared with an onlay implant may promote improved long-term outcomes owing to reduced deltoid muscle fatigue when using an inlay implant.

Influence of lateralized versus medialized reverse shoulder arthroplasty design on external and internal rotation: a systematic review and meta-analysis

BACKGROUND

Restoration of external (ER) and internal rotation (IR) after Grammont-style reverse shoulder arthroplasty (RSA) is often unreliable. The purpose of this systematic review was to evaluate the influence of RSA medio-lateral offset and subscapularis repair on axial rotation after RSA.

METHODS

We conducted a systematic review of studies evaluating axial rotation (ER, IR, or both) after RSA with a defined implant design. Medio-lateral implant classification was adopted from Werthel et al. Meta-analysis was conducted using a random-effects model.

RESULTS

Thirty-two studies reporting 2,233 RSAs were included (mean patient age, 72.5 years; follow-up, 43 months; 64% female). The subscapularis was repaired in 91% (n=2,032) of shoulders and did not differ based on global implant lateralization (91% for both, P=0.602). On meta-analysis, globally lateralized implants achieved greater postoperative ER (40° [36°-44°] vs. 27° [22°-32°], P<0.001) and postoperative improvement in ER (20° [15°-26°] vs. 10° [5°-15°], P<0.001). Lateralized implants with subscapularis repair or medialized implants without subscapularis repair had significantly greater postoperative ER and postoperative improvement in ER compared to globally medialized implants with subscapularis repair (P<0.001 for both). Mean postoperative IR was reported in 56% (n=18) of studies and achieved the minimum necessary IR in 51% of lateralized (n=325, 5 cohorts) versus 36% (n=177, 5 cohorts) of medialized implants.

CONCLUSIONS

Lateralized RSA produces superior axial rotation compared to medialized RSA. Lateralized RSA with subscapularis repair and medialized RSA without subscapularis repair provide greater axial rotation compared to medialized RSA with subscapularis repair. Level of evidence: 2A.

Clinical and functional outcomes of reverse total shoulder arthroplasty supplemented with latissimus dorsi transfer: a systematic review and meta-analysis

Background

To optimize patients' functional external rotation outcomes, reverse total shoulder arthroplasties (rTSAs) including a latissimus dorsi tendon transfer were undertaken with promising early results and no significant increase in complications in comparison to traditional rTSAs. This was especially utilized for patients with a pronounced combined loss of elevation and external rotation. The purpose of this study is to evaluate and synthesize the findings of all relevant publications assessing the outcomes of rTSAs with associated latissimus dorsi transfer.

Methods

We thoroughly searched the literature within the PubMed database using a standardized methodology. For our inclusion criteria, we included any study regarding rTSAs that contained functional outcome scores for postoperative range of motion (such as elevation, external rotation, etc.) or postoperative outcomes such as complications (reoperation, infection, etc.) and patient satisfaction. For the extraction of data, we used pilot-tested Google Forms to record extracted data. These data were then converted to spreadsheets (Microsoft Excel [Microsoft, Redmond, WA, USA]). This was done on 2 separate scenarios by 2 authors to ensure accuracy. We used the modified Coleman Methodology Score to assess the methodological quality of the studies in our samples. Meta-analysis mathematics and statistical analysis were performed using Stata software 17 (StataCorp, College Station, TX, USA).

Results

Our search returned a total of 12 studies containing data of 213 shoulders receiving RTSAs with a latissimus dorsi transfer. Functional outcomes were available for 160 shoulders. The mean preoperative elevation of the affected shoulder was 73.57 degrees, and the mean postoperative elevation was 141.80 degrees. For external rotation, the mean preoperative average was -6.71 degrees, and the mean postoperative average was 22.73 degrees. The absolute Constant score average was 31.56 preoperatively, while the postoperative value was 68.93. In our sample, 25 patients (11.73%) required a revision of the RTSA implant due to complications.

Discussion

Combined loss of elevation and external rotation can be a severely debilitating condition for those with a glenohumeral pathology. Latissimus dorsi transfer for this condition has been proven to be an effective modality. The reoperation and complication rate appears to be sizable, and as such surgeons should consider this when considering this modality for their patients.

Clinical and radiographic outcomes after reverse total shoulder arthroplasty in patients 80 years of age and older

BACKGROUND

Previous studies have found less favorable outcomes for patients aged 80 years and older after primary reverse total shoulder arthroplasty (rTSA). However, they are based on small sample sizes with no control group for comparison. The purpose of this study is to compare the clinical, functional, and radiographic outcomes after primary rTSA in patients aged 80 years and older with a younger cohort of patients aged 60-79 years.

METHODS

Patients undergoing primary rTSA between 2004 and 2018 were identified within a multi-institutional database with a minimum of 2 years of follow-up. All patients received the same platform prosthesis. Patients were divided into 2 groups based on age: 80 years and older (n = 369) and 60-79 years (n = 1764). Statistical analyses were performed to compare the 2 age cohorts based on pre- and postoperative function and range of motion (ROM) scores, adverse event rates, pain scores, and patient satisfaction.

RESULTS

Patients aged 80 years and older had lower preoperative functional and ROM scores relative to patients aged 60-79 years. The differences observed in active abduction, active forward elevation, and Constant scores exceed the minimal clinically important difference (MCID). The evaluation of function and ROM at latest follow-up showed that patients in both age cohorts had significant improvements that exceeded both the MCID and substantial clinical benefit, but older patients still scored lower relative to younger patients, with the differences in active abduction and Constant scores exceeding the MCID. Despite the lower scores observed in older patients, both groups report similar satisfaction (93% in older patients vs. 92% in younger patients, P = .379). There were no differences between the 2 age cohorts with regard to humeral radiolucent lines (9.2% vs. 8.7%, P = .765), scapular notching (11.0% vs. 10.3%, P = .727), adverse events (3.5% vs. 3.3%, P = .863), and revisions (0.8% vs. 1.8%, P = .188).

CONCLUSIONS

Patients aged 80 years and older can expect significant improvements in function and ROM after primary rTSA, with satisfaction similar to that of patients aged 60-79 years. Patients in both age cohorts have similar rates of adverse events and revisions, and the rates observed in patients 80 years and older are much lower than what has previously been reported in the literature. rTSA in patients age 80 years and older is a beneficial surgery with outcomes similar to those found in younger patients, and age should not be a limiting factor when considering rTSA.

Augmented reality for base plate component placement in reverse total shoulder arthroplasty: a feasibility study

BACKGROUND

Accurate glenoid positioning in reverse total shoulder arthroplasty (RSA) is important to achieve satisfying functional outcome and prosthesis longevity. Optimal component placement can be challenging, especially in severe glenoid deformities. The use of patient-specific instruments (PSI) and 3D computer-assisted optical tracking navigation (NAV) are already established methods to improve surgical precision. Augmented reality technology (AR) promises similar results at low cost and ease of use. With AR, the planned component placement can be superimposed to the surgical situs and shown directly in the operating field using a head mounted display. We introduce a new navigation technique using AR via head mounted display for surgical navigation in this feasibility study, aiming to improve and enhance the surgical planning.

METHODS

3D surface models of ten human scapulae were printed from computed tomography (CT) data of cadaver scapulae. Guidewire positioning of the central back of the glenoid baseplate was planned with a dedicated computer software. A hologram of the planned guidewire with dynamic navigation was then projected onto the 3D-created models of the cadaver shoulders. The registration of the plan to the anatomy was realized by digitizing the glenoid surface and the base of the coracoid with optical tracking using a fiducial marker. After navigated placement of the central guidewires, another CT imaging was recorded, and the 3D model was superimposed with the preoperative planning to analyze the deviation from the planned and executed central guides trajectory and entry point.

RESULTS

The mean deviation of the ten placed guidewires from the planned trajectory was 2.7° ± 1.3° (95% CI 1.9°; 3.6°). The mean deviation to the planned entry point of the ten placed guidewires measured 2.3 mm ± 1.1 mm (95% CI 1.5 mm; 3.1 mm).

CONCLUSION

AR may be a promising new technology for highly precise surgical execution of 3D preoperative planning in RSA.

Assessment of surgeon variability in preoperative planning of reverse total shoulder arthroplasty: a quantitative comparison of 49 cases planned by 9 surgeons

BACKGROUND

Preoperative planning software is gaining utility in reverse total shoulder arthroplasty (RTSA), particularly when addressing pathologic glenoid wear. The purpose of this study was to quantify inter- and intrasurgeon variability in preoperative planning a series of RTSA cases to identify differences in how surgeons consider optimal implant placement. This may help identify opportunities to establish consensus when correlating plan differences with clinical data.

METHODS

A total of 49 computed tomography scans from actual RTSA cases were planned for RTSA by 9 fellowship-trained shoulder surgeons using the same platform (Exactech GPS, Exactech Inc., Gainesville, FL, USA). Each case was planned a second time 6-12 weeks later. Variability within and between surgeons was measured for implant selection, version correction, inclination correction, and implant face position. Interclass correlation coefficients, and Pearson and Light's kappa coefficient were used for statistical analysis.

RESULTS

There was considerable variation in the frequency of augmented baseplate selection between surgeons and between rounds for the same surgeon. Thresholds for augment use also varied between surgeons. Interclass correlation coefficients for intersurgeon variability ranged from 0.43 for version, 0.42 for inclination, and 0.25 for baseplate type. Pearson coefficients for intrasurgeon variability were 0.34 for version and 0.30 for inclination. Light's kappa coefficient for baseplate type was 0.61.

CONCLUSIONS

This study demonstrates substantial variability both between surgeons and between rounds for individual surgeons when planning RTSA. Although average differences between plans were relatively small, there were large differences in specific cases suggesting little consensus on optimal planning parameters and opportunities to establish guidelines based on glenoid pathoanatomy. The correlation of preoperative planning with clinical outcomes will help to establish such guidelines.

Preoperative external rotation deficit does not predict poor outcomes or lack of improvement after reverse total shoulder arthroplasty

INTRODUCTION

The purpose was to compare postoperative outcomes and functional improvement between patients with preoperative aER deficits vs. preserved aER function.

RESULTS

There were 115 patients in the <0° aER group and 314 in the ≥30° aER group. Preoperative patients in the <0° group were worse for all measures except subjective pain while post-operatively, they had significantly greater improvement for all measures of motion. Postoperatively, both groups achieved comparable scores for forward elevation, pain, SST and ASES.

CONCLUSION

This study demonstrates that patients with a complete aER deficit can recover substantial and comparable function after RTSA.

Clinical measurements versus patient-reported outcomes: analysis of the American Shoulder and Elbow Surgeons physician assessment in patients undergoing reverse total shoulder arthroplasty

Background

The American Shoulder and Elbow Surgeons (ASES) score is composed of a patient-reported portion and a physician assessment. Although the patient-reported score is frequently used to assess postoperative outcomes after shoulder arthroplasty, no previous studies have used the physician-assessment component. This study evaluated the relationship of the ASES physician-assessment measurements with patient-reported shoulder and general health outcomes.

Methods

A retrospective review of a prospectively collected multicenter database was used to analyze patients who underwent primary reverse total shoulder arthroplasty (RTSA) from 2012 to 2015 with a minimum 2-year follow-up. ASES physician-assessment and patient-reported components and 12-Item Short Form Health Survey (SF-12) general health questionnaires were obtained preoperatively and 2 years postoperatively. The relationship between ASES physician measurements with ASES patient-reported outcome (PRO) scores and SF-12 Physical and Mental domain scores was assessed with Pearson correlation coefficients.

Results

Included were 74 patients (32 men; mean age, 69.2 years; body mass index, 29.4 kg/m²). Preoperative physician measurements and PRO scores were not significantly correlated. Postoperatively, only the ASES physician-measured active (R = 0.54, P < .01) and passive forward flexion (R = 0.53, P < .01) demonstrated moderate correlation with ASES patient scores. The remaining clinical measurements had no significant correlations with ASES patient or SF-12 scores. During the 2-year period, only improvements in active forward flexion correlated with improvements in ASES patient scores (R = 0.36, P < .01).

Conclusions

Little correlation exists between clinical measurements from the ASES physician component and PROs, including the ASES patient-reported and SF-12 general health surveys, in RTSA patients. Improvement in active forward flexion is the only clinical measurement correlated with PRO improvement at 2 years.

Scapula fracture incidence in reverse total shoulder arthroplasty using screws above or below metaglene central cage: clinical and biomechanical outcomes

BACKGROUND

Reverse total shoulder arthroplasty (RTSA) is a viable treatment option for rotator cuff tear arthropathy but carries a complication risk of scapular fracture. We hypothesized that using screws above the central glenoid axis for metaglene fixation creates a stress riser contributing to increased scapula fracture incidence. Clinical type III scapular fracture incidence was determined with screw placement correlation: superior screw vs. screws placed exclusively below the glenoid midpoint. Cadaveric RTSA biomechanical modeling was employed to analyze scapular fractures.

METHODS

We reviewed 318 single-surgeon single-implant RTSAs with screw correlation to identify type III scapular fractures. Seventeen cadaveric scapula specimens were matched for bone mineral density, metaglenes implanted, and fixation with 2 screw configurations: inferior screws alone (group 1_INF) vs. inferior screws with one additional superior screw (group 2_SUP). Biomechanical load to failure was analyzed.

RESULTS

Of 206 patients, 9 (4.4%) from the superior screw group experienced scapula fractures (type III); 0 fractures (0/112; 0%) were identified in the inferior screw group. Biomechanically, superior screw constructs (group 2_SUP) demonstrated significantly (P < .05) lower load to failure (1077 N vs. 1970 N) compared with constructs with no superior screws (group 1_INF). There was no significant age or bone mineral density discrepancy.

CONCLUSION

Clinical scapular fracture incidence significantly decreased (P < .05) for patients with no screws placed above the central cage compared with patients with superior metaglene screws. Biomechanical modeling demonstrates significant construct compromise when screws are used above the central cage, fracturing at nearly half the ultimate load of the inferior screw constructs. We recommend use of inferior screws, all positioned below the central glenoid axis, unless necessary to stabilize the metaglene construct.