Variations in the Anatomic Morphology of the Scapular Spine and Implications on Fracture After Reverse Shoulder Arthroplasty.

INTRODUCTION: This study evaluates the role of anatomic scapular morphology in acromion and scapular spine fracture (SSAF) risk after reverse shoulder arthroplasty (RSA). METHODS: Twelve scapular measurements were captured based on pilot study data, including scapular width measurements at the acromion (Z1), middle of the scapular spine (Z2), and medial to the first major angulation (Z3). Measurements were applied to 3D-CT scans from patients who sustained SSAF after RSA (SSAF group) and compared with those who did not (control group). Measurements were done by four investigators, and the intraclass correlation coefficient was calculated. Regression analysis determined trends in fracture incidence. RESULTS: One hundred forty-nine patients from two separate surgeons (J.L., A.M.) were matched by age and surgical indication of whom 51 sustained SSAF after reverse shoulder arthroplasty. Average ages for the SSAF and control cohorts were 78.6 and 72.1 years, respectively. Among the SSAF group, 15 were Levy type I, 26 Levy type II, and 10 Levy type 3 fractures. The intraclass correlation coefficient of Z1, Z2, and Z3 measurements was excellent (0.92, 0.92, and 0.94, respectively). Zone 1 and 3 measurements for the control group were 18.6 ± 3.7 mm and 3.2 ± 1.0 mm, respectively, compared with 22.5 ± 5.9 mm and 2.0 ± 0.70 mm in the SSAF group, respectively. The fracture group trended toward larger Z1 and smaller Z3 measurements. The average scapular spine proportion (SSP), Z1/Z3, was significantly greater in the control 6.20 ± 1.80 versus (12.60 ± 6.30; P < 0.05). Regression analysis showed a scapular spine proportion of ≤5 was associated with a fracture risk <5%, whereas an SSP of 9.2 correlated with a 50% fracture risk. DISCUSSION: Patients with a thicker acromions (Z1) and thinner medial scapular spines (Z3) have increased fracture risk. Understanding anatomic scapular morphology may allow for better identification of high-risk patients preoperatively.

Contact Mechanics of Elliptical and Spherical Head Implants during Axial Rotation in Anatomic Total Shoulder Arthroplasty: A Biomechanical Comparison.

BACKGROUND: Elliptical humeral head implants have been proposed to result in more anatomic kinematics following total shoulder arthroplasty (aTSA). The purpose of this study was to compare glenohumeral contact mechanics during axial rotation using spherical and elliptical humeral head implants in the setting of aTSA. METHODS: Seven fresh-frozen cadaveric shoulders were utilized for biomechanical testing in neutral (NR), internal (IR), and external (ER) rotation at various levels of abduction (0°, 15°, 30°, 45°, 60°) with lines of pull along each of the rotator cuff muscles. Each specimen underwent the following three conditions: (1) native, and TSA using (2) an elliptical and (3) spherical humeral head implant. Glenohumeral contact mechanics, including contact pressure (CP; kPa), peak contact pressure (PCP; kPa), and contact area (CA; mm2), were measured in neutral rotation as well as external and internal rotation using a pressure mapping sensor. RESULTS: Elliptical head implants showed a significantly lower PCP in ER compared to spherical implants at 0° (Δ-712.0 kPa; p = 0.034), 15° (Δ-894.9 kPa; p = 0.004), 30° (Δ-897.7 kPa; p = 0.004), and 45° (Δ-796.9 kPa; p = 0.010) of abduction, while no significant difference was observed in ER at 60° of abduction or at all angles in NR and IR. Both implant designs had similar CA in NR, ER, and IR at all tested angles of abduction (p > 0.05, respectively). CONCLUSIONS: In the setting of aTSA, elliptical heads showed significantly lower PCP during ER at 0° to 45° of abduction, when compared to spherical head implants. However, in NR and IR, PCP was similar between implant designs. Both designs showed similar CA during NR, ER, and IR at all abduction angles. LEVEL OF EVIDENCE: basic science; controlled laboratory study.

Anterior cruciate ligament (ACL) repair using cortical or anchor fixation with suture tape augmentation vs ACL reconstruction: A comparative biomechanical analysis.

BACKGROUND: The purpose was to compare knee kinematics in a cadaveric model of anterior cruciate ligament (ACL) repair using an adjustable-loop femoral cortical suspensory (AL-CSF) or independent bundle suture anchor fixation (IB-SAF) with suture tape augmentation to a bone-patellar tendon-bone (BPTB) ACL reconstruction. METHODS: Twenty-seven cadaveric knees were randomly assigned to one of three surgical techniques: (1) ACL repair using the AL-CSF technique with suture tape augmentation, (2) ACL repair using the IB-SAF technique with suture tape augmentation, (3) ACL reconstruction using a BPTB autograft. Each specimen underwent three conditions according to the state of the ACL (native, proximal transection, repair/reconstruction) with each condition tested at four different angles of knee flexion (0°, 30°, 60°, 90°). Anterior tibial translation (ATT) and internal tibial rotation (ITR) were evaluated using 3-dimensional motion tracking software. RESULTS: ACL transection resulted in a significant increase in ATT and ITR when compared to the native state (P < 0.001, respectively). ACL repair with the AL-CSF or IB-SAF technique as well as BPTB reconstruction restored native ATT and ITR at all tested angles of knee flexion, while showing significantly less ATT at 0°, 30°, 60°, and 90° as well as significantly less ITR at 30°, 60°, and 90° of knee flexion when compared to the ACL-deficient state. There were no significant differences in ATT and ITR between the three techniques utilized. CONCLUSION: ACL repair using the AL-CSF or IB-SAF technique with suture tape augmentation as well as BPTB ACL reconstruction each restored native anteroposterior and rotational laxity, without significant differences in knee kinematics between the three techniques utilized. LEVEL OF EVIDENCE: Controlled Laboratory Study.

Clinical and Functional Outcomes After Operative and Nonoperative Treatment of Distal Biceps Brachii Tendon Ruptures in a Consecutive Case Series.

BACKGROUND: Patients with ruptures of the distal biceps brachii tendon (DBBT) have traditionally been treated via surgical repair, despite limited patient data on nonoperative management. PURPOSE/HYPOTHESIS: To determine the clinical and functional outcomes for patients with partial and complete DBBT injuries treated nonoperatively or surgically through an anatomic single-incision technique. We hypothesized that there would be no difference in outcomes in patients treated with nonoperative or operative management. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: A retrospective chart review identified all patients with a partial or complete DBBT injury sustained between 2003 and 2017. Surgically treated patients underwent DBBT repair using an anatomic single-incision technique. Nonoperative management consisted of formal physical therapy. The following clinical outcome measures were included for analysis: American Shoulder and Elbow Surgeons (ASES) score; the Disabilities of the Arm, Shoulder and Hand (DASH) upper extremity patient questionnaire; the Single Assessment Numeric Evaluation (SANE) score; and the 36-Item Short Form Health Survey. RESULTS: A total of 60 patients (mean ± SD age, 47.8 ± 11.5 years; range, 18-70 years) sustained DBBT ruptures (38 complete and 22 partial) during the study period. Of patients with complete DBBT, 34 were treated operatively and 4 nonoperatively; of those with partial DBBT, 11 were treated operatively and 11 nonoperatively. At a mean follow-up of 5.4 ± 4.0 years (range, 0.5-16.6 years), patients with complete DBBT ruptures achieved overall similar improvements with respect to mean ASES pain, ASES function, SANE, and DASH scores, regardless of whether they were treated operatively or nonoperatively. Subjective satisfaction and functional scores were comparable between the groups. Similarly, at a mean follow-up of 4.1 ± 3.8 years (range, 0.5-11.3 years), patients with partial DBBT injuries had improved mean ASES pain, ASES function, SANE, and DASH scores, regardless of operative or nonoperative treatment. Subjective satisfaction and functional scores were comparable between these groups. For those treated surgically, 5 patients (11.1%) sustained a surgical postoperative complication. CONCLUSION: In our case series, patients were able to achieve satisfactory outcomes regardless of whether they were treated nonoperatively or with an anatomic single-incision approach for complete or partial DBBT ruptures.