Disease diagnosis and arthroplasty type are strongly associated with short-term postoperative patient-reported outcomes in patients undergoing primary total shoulder arthroplasty.

BACKGROUND: Prognostic factors for total shoulder arthroplasty (TSA) clinical outcomes are incompletely understood. This study investigates the associations of preoperative patient, disease-specific, and surgical factors with 1-year postoperative PENN Shoulder Score (PSS) in patients undergoing primary TSA. METHODS: Cleveland Clinic patients undergoing primary anatomic TSA (aTSA) or reverse TSA (rTSA) for glenohumeral osteoarthritis (GHOA) or rotator cuff tear arthropathy (CTA) between February 2015 and August 2019, and having complete preoperative and 1-year postoperative patient-reported outcome measures (PROMs), were included. Twenty preselected preoperative patient, disease-specific, and surgical factors were used to fit multivariable models for 1-year PSS and its subscores. RESULTS: Of 1427 eligible primary TSAs, 1174 had 1-year follow-up by PROMs (82%), with 1042 analyzed after additional exclusions, including 30% rTSAs for CTA (n = 308), 26% rTSAs for GHOA (n = 275), and 44% aTSAs for GHOA (n = 459). All PROMs showed statistically significant improvements postoperatively, with 89% of patients reaching an acceptable symptom state. Lower 1-year PSS was associated with younger age, female sex, current smoking, chronic pain diagnosis, history of prior surgery, worker's compensation claim, lower preoperative mental health, lower baseline PSS, absence of glenoid bone loss, and diagnosis-arthroplasty type (CTA-rTSA < GHOA-rTSA < GHOA-aTSA). The most important prognostic factors associated with 1-year PSS were diagnosis-arthroplasty type, baseline mental health status, and insurance status. CONCLUSIONS: Disease diagnosis, arthroplasty type, and several other baseline factors are strongly and individually associated with PROMs following primary TSA, with patients undergoing aTSA for GHOA demonstrating the highest PROM scores at 1-year follow-up. Patient, disease-specific, and surgical factors can be used to guide postoperative prognosis following primary TSA for improved preoperative patient counseling regarding expected outcomes of these procedures.

Three-dimensional computed tomography analysis of pathologic correction in total shoulder arthroplasty based on severity of preoperative pathology.

BACKGROUND: The purpose of this study was to quantify correction of glenoid deformity and humeral head alignment in anatomic total shoulder arthroplasty as a function of preoperative pathology (modified Walch classification) and glenoid implant type in a clinical cohort using 3-dimensional computed tomography (CT) analysis. METHODS: Patients undergoing anatomic total shoulder arthroplasty with a standard glenoid (SG) (n = 110) or posteriorly stepped augmented glenoid (AG) (n = 62) component were evaluated with a preoperative CT scan and a postoperative CT scan within 3 months of surgery. Glenoid version, inclination, and medial-lateral (ML) joint line position, as well as humeral head alignment, were assessed on both CT scans, with preoperative-to-postoperative changes analyzed relative to pathology and premorbid anatomy based on the modified Walch classification and glenoid implant type. RESULTS: On average, correction to the premorbid ML joint line position was significantly less in type A2 glenoids than in type A1 glenoids (-2.3 ± 2.1 mm vs. 1.1 ± 0.9 mm, P < .001). Correction to premorbid version was not different between type B2 glenoids with AG components and type A1 glenoids with SG components (-1.7° ± 6.6° vs. -1.0° ± 4.0°, P = .57), and the premorbid ML joint line position was restored on average in both groups (0.3 ± 1.6 mm vs. 1.1 ± 0.9 mm, P = .006). Correction to premorbid version was not different between type B3 glenoids with AG components and type A1 glenoids with SG components (-0.6° ± 5.1° vs. -1.0° ± 4.0°, P = .72), but correction relative to the premorbid ML joint line position was significantly less in type B3 glenoids with AG components than in type A1 glenoids with SG components (-2.2 ± 2.1 mm vs. 1.1 ± 0.9 mm, P < .001). Postoperative humeral glenoid alignment was not different in any group comparisons. DISCUSSION: In cases with posterior glenoid bone loss and retroversion (type B2 or B3 glenoids), an AG component can better correct retroversion and the glenoid ML joint line position compared with an SG component, with correction to premorbid version comparable to a type A1 glenoid with an SG component. However, restoration of the premorbid ML joint line position may not always be possible with SG or AG components in cases with more advanced central glenoid bone loss (type A2 or B3 glenoids). Further follow-up is needed to determine the clinical consequences of these findings.

Reliability of the modified Walch classification for advanced glenohumeral osteoarthritis using 3-dimensional computed tomography analysis: a study of the ASES B2 Glenoid Multicenter Research Group.

BACKGROUND: Variations in glenoid morphology affect surgical treatment and outcome of advanced glenohumeral osteoarthritis (OA). The purpose of this study was to assess the inter- and intraobserver reliability of the modified Walch classification using 3-dimensional (3D) computed tomography (CT) imaging in a multicenter research group. METHODS: Deidentified preoperative CTs of patients with primary glenohumeral OA undergoing anatomic or reverse total shoulder arthroplasty (TSA) were reviewed with 3D imaging software by 23 experienced shoulder surgeons across 19 institutions. CTs were separated into 2 groups for review: group 1 (96 cases involving all modified Walch classification categories evaluated by 12 readers) and group 2 (98 cases involving posterior glenoid deformity categories [B2, B3, C1, C2] evaluated by 11 readers other than the first 12). Each case group was reviewed by the same set of readers 4 different times (with and without the glenoid vault model present), blindly and in random order. Inter- and intraobserver reliabilities were calculated to assess agreement (slight, fair, moderate, substantial, almost perfect) within groups and by modified Walch classification categories. RESULTS: Interobserver reliability showed fair to moderate agreement for both groups. Group 1 had a kappa of 0.43 (95% confidence interval [CI]: 0.38, 0.48) with the glenoid vault model absent and 0.41 (95% CI: 0.37, 0.46) with it present. Group 2 had a kappa of 0.38 (95% CI: 0.33, 0.43) with the glenoid vault model absent and 0.37 (95% CI: 0.32, 0.43) with it present. Intraobserver reliability showed substantial agreement for group 1 with (0.63, range 0.47-0.71) and without (0.61, range 0.52-0.69) the glenoid vault model present. For group 2, intraobserver reliability showed moderate agreement with the glenoid vault model absent (0.51, range 0.30-0.72), which improved to substantial agreement with the glenoid vault model present (0.61, range 0.34-0.87). DISCUSSION: Inter- and intraobserver reliability of the modified Walch classification were fair to moderate and moderate to substantial, respectively, using standardized 3D CT imaging analysis in a large multicenter study. The findings potentially suggest that cases with a spectrum of posterior glenoid bone loss and/or dysplasia can be harder to distinguish by modified Walch type because of a lack of defined thresholds, and the glenoid vault model may be beneficial in determining Walch type in certain scenarios. The ability to reproducibly separate patients into groups based on preoperative pathology, including Walch type, is important for future studies to accurately evaluate postoperative outcomes in TSA patient cohorts.

Estimation of anterior glenoid bone loss area using the ratio of bone defect length to the distance from posterior glenoid rim to the centre of the glenoid.

PURPOSE: Estimation of anterior glenoid bone loss is important for surgical decision-making. The purpose of this study was to describe a method for estimating anterior glenoid bone loss. METHODS: Thirty-nine cadaveric glenoids were digitized to obtain glenoid geometry. Glenoid bare spot centre, arthroscopic centre, and centre of the inferior glenoid circle relative to the geometric centre were measured. To simulate anterior glenoid bone loss, imaginary sequential osteotomies were created 0°, 22.5°, and 45° to the superior-inferior line in a 3D digitizing programme. Per cent of anterior glenoid bone loss area was calculated as the percentage of defect area relative to the entire area of the glenoid. The relationship between area loss and ratio of bone defect length to the distance from posterior glenoid to various centres was determined. RESULTS: As the ratio of bone defect length to the distance from posterior glenoid to all three centres increased, the per cent area of bone loss increased exponentially. The ratio using the inferior circle centre and arthroscopic centre was highly correlated to the actual glenoid bone loss in all osteotomies (R 2 > 0.90). The ratio using the centre of bare area had the lowest correlation. The ratio of defect length to distance from posterior glenoid to arthroscopic centre greater than 2.4 for 0° and 2.0 for 45° osteotomies results in bone loss area greater than 25 %. The bare area centre had the largest variation. Average bone loss was overestimated when the centre of bare spot was used compared to other centre locations. CONCLUSION: Per cent of anterior glenoid bone loss can be estimated using the ratio of bone defect length to the distance from posterior glenoid rim to the centre of inferior glenoid circle or arthroscopic centre either preoperatively using 3D CT or arthroscopically which can be useful for determining surgical treatment.

Sequential 3-dimensional computed tomography analysis of implant position following total shoulder arthroplasty.

BACKGROUND: Detection of postoperative component position and implant shift following total shoulder arthroplasty (TSA) can be challenging using routine imaging. The purpose of this study was to evaluate glenoid component position over time using 3-dimensional computed tomography (CT) analysis with minimum 2-year follow-up. METHODS: Twenty patients underwent primary TSA with sequential CT scanning of the shoulder: a preoperative study, an immediate postoperative study within 2 weeks of surgery, and a postoperative study performed at minimum 2-year follow-up (CT3). Postoperative glenoid component position and central peg osteolysis were assessed across the immediate postoperative CT scan and CT3. Glenoids with evidence of component shift and/or grade 1 central peg osteolysis on CT3 were considered at risk of loosening. RESULTS: Of the patients, 7 (35%) showed evidence of glenoid components at risk of loosening on CT3, 6 with component shift (3 with increased inclination alone, 1 with increased retroversion alone, and 2 with both increased inclination and retroversion). Significantly more patients with glenoid component shift had grade 1 central peg osteolysis on CT3 compared with those without shift (83% vs 7%, P = .002). One clinical failure occurred, with the patient undergoing revision to reverse TSA for rotator cuff deficiency. CONCLUSIONS: Three-dimensional CT imaging analysis following TSA identified changes in glenoid component position over time, with inclination being the most common direction of shift and grade 1 central peg osteolysis commonly associated with shift. These findings raise concern for glenoids at risk of loosening, but further follow-up is needed to determine the long-term clinical impact of these findings.

Bridging suture makes consistent and secure fixation in double-row rotator cuff repair.

BACKGROUND: Inconsistent tension distribution may decrease the biomechanical properties of the rotator cuff tendon after double-row repair, resulting in repair failure. The purpose of this study was to compare the tension distribution along the repaired rotator cuff tendon among three double-row repair techniques. METHODS: In each of 42 fresh-frozen porcine shoulders, a simulated infraspinatus tendon tear was repaired by using 1 of 3 double-row techniques: (1) conventional double-row repair (no bridging suture); (2) transosseous-equivalent repair (bridging suture alone); and (3) compression double-row repair (which combined conventional double-row and bridging sutures). Each specimen underwent cyclic testing at a simulated shoulder abduction angle of 0° or 40° on a material-testing machine. Gap formation and tendon strain were measured during the 1st and 30th cycles. To evaluate tension distribution after cuff repair, difference in gap and tendon strain between the superior and inferior fixations was compared among three double-row techniques. RESULTS: At an abduction angle of 0°, gap formation after either transosseous-equivalent or compression double-row repair was significantly less than that after conventional double-row repair (p < 0.01). During the 30th cycle, both transosseous-equivalent repair (p = 0.02) and compression double-row repair (p = 0.01) at 0° abduction had significantly less difference in gap formation between the superior and inferior fixations than did conventional double-row repair. After the 30th cycle, the difference in longitudinal strain between the superior and inferior fixations at 0° abduction was significantly less with compression double-row repair (2.7% ± 2.4%) than with conventional double-row repair (8.6% ± 5.5%, p = 0.03). CONCLUSIONS: Bridging sutures facilitate consistent and secure fixation in double-row rotator cuff repairs, suggesting that bridging sutures may be beneficial for distributing tension equally among all sutures during double-row repair of rotator cuff tears.

The effects of prosthetic humeral head shape on glenohumeral joint kinematics during humeral axial rotation in total shoulder arthroplasty.

BACKGROUND: A non-spherical humeral head has been shown to influence kinematics and stability of the glenohumeral joint; yet, most prosthetic humeral head components are designed to be a perfect sphere. The effect of humeral head shape on prosthetic joint kinematics after total shoulder arthroplasty is not well understood. We hypothesized that prosthetic joint kinematics during humeral axial rotation is dependent on humeral head shape, regardless of joint conformity. METHODS: Four prosthetic configurations were investigated using a spherical and a non-spherical prosthetic humeral head articulated with a conforming and a non-conforming glenoid component. Testing was performed in the coronal, scapular, and forward flexion plane at 0°, 30°, and 60° of abduction. Prosthetic joint kinematics was measured in 10° intervals during a 100° arc of humeral axial rotation. Glenohumeral translation patterns, net glenohumeral translation, and averaged glenohumeral translation were compared for each of 4 configurations. RESULTS: Non-spherical head configurations increased the net glenohumeral translation during humeral axial rotation in multiple test positions compared with spherical head configurations (P < .05). Spherical head configurations resulted in a relatively small amount of glenohumeral translation, less than 2 mm. The radius of curvature of the glenoid component alone did not affect the net glenohumeral translation within each of the 2 head groups (P > .05). CONCLUSION: During humeral axial rotation, the non-spherical humeral head shape contributes to increased glenohumeral translation during humeral axial rotation. However, the spherical head shape does not show significant glenohumeral translation during humeral axial rotation, regardless of glenoid conformity.

Subscapularis tendon tear classification based on 3-dimensional anatomic footprint: a cadaveric and prospective clinical observational study.

PURPOSE: The purpose of this study was to define the subscapularis tendon footprint anatomy in 3-dimensional (3D) perspective, report the incidence of tears, and classify the tear patterns prospectively during shoulder arthroscopic surgery. METHODS: The cadaveric study consisted of a pilot study that revealed 4 different bony facets by simple observation at the subscapularis attachment. The 3D footprint anatomy was digitally evaluated in 39 cadavers. The clinical study was conducted from 2011 to 2013 and was based on 3D footprint anatomy. All consecutive arthroscopic shoulder operations were prospectively evaluated for subscapularis tendon integrity. A new classification system was developed with 5 categories: (1) type I-fraying or longitudinal split of the subscapularis tendon leading edge; (2) type IIA-less than 50% subscapularis tendon detachment of the first facet; (3) type IIB-greater than 50% detachment without complete disruption of the lateral hood, which is approximately a one-quarter to one-third tear of the entire subscapularis tendon's superior-inferior length; (5) type III-entire first facet with complete-thickness tear (lateral hood tear), (5) type IV-first and second facets are exposed with much medial retraction of the tendon (approximately a two-thirds tear of the entire footprint; entire tendinous portion), and (6) type V-complete subscapularis tendon involving the muscular portion (rare). RESULTS: The medial-lateral and superior-inferior dimensions of the first facet dimensions were 13.8 × 13.5 mm, respectively; its surface area was 34% of the entire footprint. From superior to inferior, the facet's medial-lateral dimensions and surface area decreased. The fourth facet was 77 mm(2) from medial to lateral and encompassed 15% of the footprint. Clinically, among 821 shoulder arthroscopies performed over a 29-month-period, the incidence of subscapularis tears was 415 (50.5%). The most common tear was type IIB (29.4%) or a one-quarter to one-third tear of the entire subscapularis footprint length. However, the incidence between types I, IIA, and IIB did not show a statistically significant difference, indicating an equal distribution. The mean ages of the torn group versus the intact subscapularis group showed a difference. CONCLUSIONS: The first facet of the subscapularis tendon footprint consists of approximately one third of the entire footprint, and the first 2 facets consist of 60% of the entire footprint. The probability of finding any extension of the subscapularis tendon tear occurs in approximately 50% of the patients who undergo shoulder arthroscopy for all forms of shoulder disease. Among those subscapularis tendon tears, less than or equal to 80% are first facet tears. LEVEL OF EVIDENCE: Level II, diagnostic study.

The influence of partial subscapularis tendon tears combined with supraspinatus tendon tears.

BACKGROUND: With the advent of arthroscopy, more partial subscapularis tears are being recognized. The biomechanical effects of partial subscapularis tears are unknown, and there is no consensus as to their treatment. Therefore, the objective of this study was to evaluate and to quantify the changes in range of motion and glenohumeral kinematics for isolated subscapularis partial tears, combined subscapularis and supraspinatus tears, supraspinatus repair, and combined supraspinatus and subscapularis repair. METHODS: Six cadaveric shoulders were tested in the scapular plane with 0°, 30°, and 60° shoulder abduction under 6 conditions: intact; » subscapularis tear; ½ subscapularis tear; ½ subscapularis and complete supraspinatus tear; supraspinatus repair; and supraspinatus and subscapularis repair. Maximum internal and external rotation and glenohumeral kinematics were measured under physiologic muscle loading condition. A repeated measures analysis of variance with a Tukey post hoc test was used for statistical analysis. RESULTS: Maximum external rotation was significantly increased after » subscapularis tear at 30° abduction and in all abduction angles with ½ subscapularis tear (P < .05). The 2 repair conditions did not restore external rotation to the intact level. At maximum internal and external rotation, there was a significant superior shift in the humeral head apex position with » subscapularis tear at 30° abduction and with ½ subscapularis tear at 60° abduction (P < .05). Repair of the supraspinatus tendon partially corrected abnormal kinematics; however, neither repair restored abnormal kinematics to intact. CONCLUSION: Additional repair of the partial subscapularis tear with supraspinatus tear did not affect external rotation or glenohumeral kinematics. Further studies are needed to evaluate different subscapularis repair techniques. LEVEL OF EVIDENCE: Basic science study, biomechanics.

Anterior capsulolabral lesions combined with supraspinatus tendon tears: biomechanical effects of the pathologic condition and repair in human cadaveric shoulders.

PURPOSE: Our purpose was to investigate the effect of supraspinatus tendon tear combined with anterior capsulolabral injury on glenohumeral joint biomechanics and to identify which structures should be repaired when both pathologic conditions are present. METHODS: Eight cadaveric shoulders were tested on a custom system. Five conditions were tested: intact supraspinatus full-thickness tear, supraspinatus tear combined with Bankart lesion, supraspinatus repair, and supraspinatus repair combined with Bankart repair. Rotational range of motion, glenohumeral kinematics, and the force required for anteroinferior dislocation were measured at 30° and 60° of glenohumeral abduction. Repeated-measures analysis of variance with Tukey post hoc test was used for statistical analysis. RESULTS: Bankart lesions combined with supraspinatus tears significantly increased total rotational range of motion (7.6° ± 6.3° at 30° of glenohumeral abduction and 14.1° ± 10.3° at 60° of glenohumeral abduction; P < .05). Bankart lesions combined with supraspinatus tears also significantly decreased the force required for dislocation normalized to range of motion (26.6% ± 21.0% at 60° of abduction) compared with intact shoulders (P = .04). Bankart repair combined with supraspinatus repair restored range of motion and the force required for dislocation; however, Bankart repair combined with supraspinatus repair shifted the humeral head posteriorly at the midrange of rotation in 30° and 60° of abduction (P < .05). CONCLUSIONS: Supraspinatus tendon tears combined with Bankart lesions increased humeral rotational range of motion and decreased the force required for dislocation. Repair of both pathologic conditions successfully restored range of motion and increased the force required for dislocation. CLINICAL RELEVANCE: Both supraspinatus tendon and anterior labral repair are suggested for patients with combined Bankart lesions and supraspinatus tears to restore shoulder function and possibly prevent recurrent dislocation. However, when repairing both pathologic conditions, care should be taken not to overtighten the joint, which may lead to stiffness or osteoarthritis.

The effects of prosthetic humeral head shape on glenohumeral joint kinematics: a comparison of non-spherical and spherical prosthetic heads to the native humeral head.

BACKGROUND: The purpose of this study was to quantitatively evaluate the effect of the prosthetic humeral head shape on rotational range of motion and glenohumeral joint kinematics. METHODS: Six fresh-frozen cadaveric shoulders were tested in multiple positions under anatomic muscle loading. Specimens were tested for the native head, and then the spherical and non-spherical prosthetic heads were randomly implanted in the same stem to preserve the center of rotation. Rotational range of motion was measured with 3.3 Nm of torque. Glenohumeral joint kinematics was quantified by the position vectors of the humeral head apex (HHA) and geometric center of the humeral head (GCHH) to calculate translation of HHA and GCHH per degree of humeral rotation. RESULTS: The non-spherical prosthetic head replicated the native head shape more accurately than the spherical prosthetic head. Between the non-spherical and native heads, there was no statistical difference in rotational range of motion (P > .05), but a statistical difference in HHA and GCHH translation was found at 60° of scapular plane abduction in the interval from 30° of internal rotation to neutral rotation and at 30° of forward flexion plane abduction in the interval from 30° of external rotation to maximum external rotation, respectively (P < .05). The spherical head significantly decreased rotational range of motion (P < .05), increased HHA translation per degree (P < .05), and decreased GCHH translation per degree (P < .05) in multiple positions compared with the native humeral head. CONCLUSION: The custom, non-spherical prosthetic head more accurately replicated the head shape, rotational range of motion, and glenohumeral joint kinematics than the commercially available, spherical prosthetic head compared with the native humeral head.

Margin convergence anchorage to bone for reconstruction of the anterior attachment of the rotator cable.

PURPOSE: The purpose of this study was to compare the biomechanical characteristics of a massive L-shaped retracted rotator cuff tear repaired with either soft-tissue side-to-side sutures or margin convergence anchorage to bone. METHODS: Eight matched pairs of cadaveric shoulders were used. The supraspinatus and infraspinatus were secured in a clamp at 30° of glenohumeral abduction. The subscapularis was secured in a separate clamp, and a constant load was applied. A massive L-shaped rotator cuff tear of the supraspinatus and infraspinatus tendon was created. In all specimens the posterior aspect of the tear was repaired by a transosseous-equivalent technique. In 1 group we placed 2 margin convergence sutures between the supraspinatus and the rotator interval. In the comparison group, a suture anchor was inserted at the anterior attachment of the rotator cable. Margin convergence anchorage to bone was then performed between the supraspinatus and the rotator interval. Each specimen was tested with an Instron machine (Instron, Canton, MA) and a video digitizing system. A paired t test was used for statistical analysis. RESULTS: Margin convergence anchorage to bone decreased gap formation at cycle 1, cycle 30, and yield load across the entire footprint (P < .05). In both constructs the anterior gap was greater than the posterior gap at cycle 1, cycle 30, and yield load (P < .05). Margin convergence anchorage to bone decreased hysteresis and increased stiffness during the first cycle and increased yield load (P < .05). CONCLUSIONS: Using margin convergence anchorage to bone to restore the anterior attachment of the rotator cable decreased gap formation across the entire footprint and improved biomechanical properties for cycle 1 and yield load compared with soft-tissue margin convergence for massive rotator cuff repairs. CLINICAL RELEVANCE: Repairing the anterior rotator cuff with margin convergence anchorage to bone may improve clinical outcomes of an L-shaped massive tear repair.

The effect of the number of cross-stitches on the biomechanical properties of the modified becker extensor tendon repair.

PURPOSE: The optimum number of cross-stitches in modified Becker repair for extensor tendon injury is not known. The purpose of this study was to compare the biomechanical characteristics of 1, 2, and 3 cross-stitches in modified Becker extensor repairs. METHODS: We used 8 fresh-frozen cadaveric hands (24 fingers). We exposed extensor tendons of the index, middle, and ring fingers over the proximal phalanx, cut them transversely at the mid-portion of zone IV (proximal phalanx), and repaired them in situ with a modified Becker technique with 1, 2, or 3 cross-stitches using 4-0 braided suture. We randomized the tendons within each hand for the number of cross-stitches. Stiffness, yield load, ultimate load, energy absorbed, and gap formation were measured. After a 5 N preload, each repair was cyclically loaded from 5 to 25 N for 30 cycles and from 5 to 35 N for 30 cycles at a rate of 20 mm/min to simulate loads during postoperative rehabilitation. After cyclic loading, the specimens were loaded to failure. RESULTS: The repair with 1 cross-stitch showed superior gap resistance and stiffness during cyclic loading compared with 2 and 3 cross-stitches. One cross-stitch also resulted in higher stiffness and yield strength in load to failure testing. However, 3 cross-stitch configurations displayed higher ultimate strength. All repairs failed by knot slippage. CONCLUSIONS: A modified Becker extensor tendon repair with 1 cross-stitch provides superior mechanical properties for loads seen with postoperative rehabilitation compared with 2 and 3 cross-stitches for similar loads. CLINICAL RELEVANCE: These findings may lead to reduced operative time and decreased tendon damage with superior results.

Validation of a 3D CT imaging method for quantifying implant migration following anatomic total shoulder arthroplasty.

Glenoid component loosening remains a common complication following anatomic total shoulder arthroplasty (TSA); however, plain radiographs are unable to accurately detect early implant migration. The purpose of this study was to validate the accuracy of a method of postoperative, three-dimensional (3D) computed tomography (CT) imaging with metal artifact reduction (MAR) to detect glenoid component migration following anatomic TSA. Tantalum bead markers were inserted into polyethylene glenoid components for implant detection on 3D CT. In-vitro validation was performed using a glenoid component placed into a scapula sawbone and incrementally translated and rotated, with MAR 3D CT acquired at each test position. Accuracy was evaluated by root mean square error (RMSE). In-vivo validation was performed on six patients who underwent anatomic TSA, with two postoperative CT scans acquired in each patient and marker-based radiostereometric analysis (RSA) performed on the same days. Glenoid component migration was calculated relative to a scapular coordinate system for both MAR 3D CT and RSA. Accuracy was evaluated by RMSE and paired Student's t-tests. The largest RMSE on in-vitro testing was 0.24 mm in translation and 0.11° in rotation, and on in-vivo testing was 0.47 mm in translation and 1.04° in rotation. There were no significant differences between MAR 3D CT and RSA measurement methods. MAR 3D CT imaging is capable of quantifying glenoid component migration with a high level of accuracy. MAR 3D CT imaging is advantageous over RSA because it is readily available clinically and can also be used to evaluate the implant-bone interface.

Biomechanical evaluation of parallel versus orthogonal plate fixation of intra-articular distal humerus fractures.

BACKGROUND: Orthogonal and parallel plate constructs are used for fixation of intra-articular distal humerus fractures but optimal plate configuration remains controversial. The purpose of this study was to compare the biomechanical properties of orthogonal versus parallel plate constructs in a cadaver distal humerus fracture model. MATERIAL AND METHODS: An intra-articular distal humerus fracture with a metaphyseal defect was created in 14 matched pairs of cadaver elbows. Paired specimens were fixed with either orthogonal or parallel plates from a single elbow plating system using nonlocking screws. Using a novel testing protocol, loading was applied to the forearm and was transmitted to the distal humerus through intact collateral ligaments, olecranon, and radial head. Seven matched pairs were tested under varus loading and seven under axial/sagittal loading. Each specimen underwent cyclic loading first, followed by loading to failure. RESULTS: Parallel plate constructs had significantly higher stiffness than orthogonal ones during cyclic varus loading (P = .002). Screw loosening occurred in all posterior plates of orthogonal constructs but in no plates of parallel constructs (P = .001). Parallel constructs had significantly higher ultimate torque in varus loading to failure (20.7 vs 15.9 Nm, P = .008), and higher ultimate load in axial/sagittal loading to failure (1287.8 vs 800.0 N, P = .03). DISCUSSION: Parallel plating of intra-articular distal humerus fractures with a metaphyseal defect demonstrates superior biomechanical properties compared to orthogonal plating, and may be preferable for fixation of these fractures.

Stepped Augmented Glenoid Component in Anatomic Total Shoulder Arthroplasty for B2 and B3 Glenoid Pathology: A Study of Early Outcomes.

BACKGROUND: Posterior glenoid bone loss is commonly associated with primary glenohumeral osteoarthritis. Surgical management of bone loss in anatomic total shoulder arthroplasty (aTSA) remains controversial. We studied the use of a stepped augmented glenoid component for management of Walch B2 and B3 glenoids and compared the radiographic and clinical outcomes at short-term follow-up with those achieved with a non-augmented component of the same design in Walch A1 glenoids. METHODS: Ninety-two patients (42 A1, 29 B2, and 21 B3 glenoids) were prospectively followed after aTSA. Sequential 3-dimensional (3D) computed tomography (CT) imaging was performed preoperatively, within 3 months postoperatively with metal artifact reduction (MAR) to define implant position, and at a minimum of 2 years postoperatively with MAR. Scapular 3D registration with implant registration allowed 3D measurement of glenoid implant position, implant shift, and central peg osteolysis (CPO). RESULTS: CPO with or without implant shift occurred in a higher percentage of B3 glenoids treated with the augmented glenoid component (29%) than A1 glenoids treated with a standard component (5%) (p = 0.028). There was no significant difference in the frequency of CPO between B2 glenoids with the augmented component (10%) and A1 glenoids with the standard component. There was no difference in postoperative glenoid component version and inclination between groups. B3 glenoids were associated with more component medialization relative to the premorbid joint line compared with A1 and B2 glenoids (p < 0.001). CONCLUSIONS: A stepped augmented glenoid component can restore premorbid glenoid anatomy in patients with asymmetric biconcave glenoid bone loss (Walch B2), with short-term clinical and radiographic results equivalent to those for patients without glenoid bone loss (Walch A1) treated with a non-augmented component. There is a greater risk of CPO in patients with moderate-to-severe B3 glenoid pathology with this stepped augmented glenoid component. Longer follow-up will help define the clinical implications of CPO over time. LEVEL OF EVIDENCE: Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

Relationship Between Glenoid Component Shift and Osteolysis After Anatomic Total Shoulder Arthroplasty: Three-Dimensional Computed Tomography Analysis.

BACKGROUND: The purpose of this study was to evaluate glenoid component position and radiolucency following anatomic total shoulder arthroplasty (TSA) using sequential 3-dimensional computed tomography (3D CT) analysis. METHODS: In a series of 152 patients (42 Walch A1, 16 A2, 7 B1, 49 B2, 29 B3, 3 C1, 3 C2, and 3 D glenoids) undergoing anatomic TSA with a polyethylene glenoid component, sequential 3D CT analysis was performed preoperatively (CT1), early postoperatively (CT2), and at a minimum 2-year follow-up (CT3). Glenoid component shift was defined as a change in component version or inclination of ≥3° from CT2 to CT3. Glenoid component central anchor peg osteolysis (CPO) was assessed at CT3. Factors associated with glenoid component shift and CPO were evaluated. RESULTS: Glenoid component shift occurred from CT2 to CT3 in 78 (51%) of the 152 patients. CPO was seen at CT3 in 19 (13%) of the 152 patients, including 15 (19%) of the 78 with component shift. Walch B2 glenoids with a standard component and glenoids with higher preoperative retroversion were associated with a higher rate of shift, but not of CPO. B3 glenoids with an augmented component and glenoids with greater preoperative joint-line medialization were associated with CPO, but not with shift. More glenoid component joint-line medialization from CT2 to CT3 was associated with higher rates of shift and CPO. A greater absolute change in glenoid component inclination from CT2 to CT3 and a combined absolute glenoid component version and inclination change from CT2 to CT3 were associated with CPO. Neither glenoid component shift nor CPO was associated with worse clinical outcomes. CONCLUSIONS: Postoperative 3D CT analysis demonstrated that glenoid component shift commonly occurs following anatomic TSA, with increased inclination the most common direction. Most (81%) of the patients with glenoid component shift did not develop CPO. Longer follow-up is needed to determine the relationships of glenoid component shift and CPO with loosening over time. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Variability of glenohumeral positioning and bone-to-tendon marker length measurements in repaired rotator cuffs from longitudinal computed tomographic imaging.

BACKGROUND: To address the need for more objective and quantitative measures of tendon healing in research studies, we intend to use computed tomography (CT) with implanted radiopaque markers on the repaired tendon to measure tendon retraction following rotator cuff repair. In our small prior study, retraction at 1-year follow-up averaged 16.1± 5.3 mm and exceeded 10.0 mm in 12 of 13 patients, and thus tendon retraction appears to be a common clinical phenomenon. This study's objectives were to assess, using 5 longitudinal CT scans obtained over 1 year following rotator cuff repair, the variability in glenohumeral positioning because of pragmatic variations in achieving perfect arm repositioning and to estimate the associated measurement variability in bone-to-tendon marker length measurements. METHODS: Forty-eight patients underwent rotator cuff repair with intraoperative placement of radiopaque tendon markers at the repair site. All patients had a CT scan with their arms at the side on the day of surgery and at 3, 12, 26, and 52 weeks postoperatively. Glenohumeral position (defined by the orientation and distance of the humerus with respect to the scapula) and bone-to-tendon marker lengths were measured from each scan. Within-patient variation in glenohumeral position measurements was described by their pooled within-patient standard deviations (SDs), and variation in bone-to-tendon marker lengths by their standard errors of measurement (SEMs) and 95% confidence level minimally detectable distances (MDD95) and changes (MDC95). RESULTS: The mean glenohumeral orientation from the 5 longitudinal CT scans averaged across the 48 patients was 12.6° abduction, 0.4° flexion, and -0.1° internal rotation. Within-patient SDs (95% confidence intervals) of glenohumeral orientation were 3.0° (2.7°-3.4°) in extension/flexion, 5.2° (4.6°-5.8°) in abduction/adduction, and 8.2° (7.3°-9.2°) in internal/external rotation. The SDs of glenohumeral distances were less than 1 mm in any direction. The estimated SEMs of bone-to-tendon lengths were consistent with a common value of 2.4 mm for any of the tendon markers placed across the repair, with MDD95 of 4.7 mm and MDC95 of 6.7 mm. CONCLUSION: Apparent tendon retraction of 5 mm or more, when measured as the distance from a tendon marker's day of surgery location to its new location on a volumetrically registered longitudinal CT scan, may be considered above the usual range of measurement variation. Tendon retraction measured using implanted radiopaque tendon markers offers an objective and sufficiently reliable means for quantifying the commonly expected changes in structural healing following rotator cuff repair.

Humeral Head Shape in Native and Prosthetic Joint Replacement.

BACKGROUND: Nonspherical prosthetic humeral head designs have become increasingly popular as they better approximate the native shoulder anatomy and biomechanical properties and is supported by the existing literature. It remains to be seen how this will impact postoperative outcomes for total shoulder arthroplasty providing a justification for this review. METHODS: A review and synthesis of the literature on the subject of joint replacement in the native and prosthetic humeral head was performed. RESULTS: Our review encompasses the anatomical, biomechanical, and finite element data present in the literature for native and prosthetic joint replacement. They describe the native humeral head as more elliptical (nonspherical) than circular (spherical) and that nonspherical prosthetics more closely approximate glenohumeral kinematic properties. CONCLUSION: A nonspherical prosthetic may influence long-term clinical outcomes in hemiarthroplasty and anatomic total shoulder arthroplasty though further research in this area is necessary.

Imaging of the B2 Glenoid: An Assessment of Glenoid Wear.

BACKGROUND: Glenohumeral osteoarthritis (OA) carries a spectrum of morphology and wear patterns of the glenoid surface exemplified by complex patterns such as glenoid biconcavity and acquired retroversion seen in the B2 glenoid. Multiple imaging methods are available for evaluation of the complex glenoid structure seen in B2 glenoids. The purpose of this article is to review imaging assessment of the type B2 glenoid. METHODS: The current literature on imaging of the B2 glenoid was reviewed to describe the unique anatomy of this OA variant and how to appropriately assess its characteristics. RESULTS: Plain radiographs, magnetic resonance imaging, and standard 2-dimensional computed tomography (CT) have all shown acceptable assessments of arthritic glenoids but lack the detailed and highly accurate evaluation of bone loss and retroversion seen with 3-dimensional CT. CONCLUSION: Accurate preoperative identification of complex B2 pathology on imaging remains essential in planning and achieving precise implant placement at the time of shoulder arthroplasty.