Radiographic characterization of the B2 glenoid: the effect of computed tomographic axis orientation

Posterior Shoulder Instability in Tennis Players: Aetiology, Classification, Assessment and Management

Background

Micro-traumatic posterior shoulder instability (PSI) is an often missed and misdiagnosed pathology presenting in tennis players. The aetiology of micro-traumatic PSI in tennis players is multifactorial, including congenital factors, loss of strength and motor control, and sport-specific repetitive microtrauma. Repetitive forces placed on the dominant shoulder, particularly combinations of flexion, horizontal adduction, and internal rotation contribute to the microtrauma. These positions are characteristic for kick serves, backhand volleys, and the follow-through phase of forehands and serves. The aim of this clinical commentary is to present an overview of the aetiology, classification, clinical presentation, and treatment of micro-traumatic PSI, with a particular focus on tennis players.

Level of Evidence

5.

Can We Completely Trust in Automated Software for Preoperative Planning of Shoulder Arthroplasty? Software Update May Modify Glenoid Version, Glenoid Inclination and Humeral Head Subluxation Values

Background: The purpose of this study was to evaluate the impact of software updating on measurements of the glenoid inclination and version, along with humeral head subluxation performed by an automated 3D planning program. The hypothesis was that the software update could significantly modify the values of the glenoid inclination and version, as well as of the humeral head subluxation. Methods: A comprehensive pool of 76 shoulder computed tomography (CT) scans of patients who underwent total shoulder arthroplasty (TSA) or reverse total shoulder arthroplasty (RTSA) were analyzed with the automated program Blueprint in 2018 and again in 2020 after a software update. Results: A statistically significant difference of 8.1 ± 8.2 and 5.4 ± 7.8 (mean difference of −2.8 ± 5.0, p < 0.001) was indeed reached when comparing the mean glenoid inclination achieved with Blueprint 2018 and Blueprint 2020, respectively. The glenoid version, as well as the humeral head subluxation evaluations, were not significantly different between the two software versions, with mean values being −9.4 ± 8.9 and −9.0 ± 7.4 and 60.1 ± 12.6 and 61.8 ± 12.0, respectively (p = 0.708 and p = 0.115, respectively). In 22% of CT scans, the software update determined a variation of the glenoid inclination of more than 5° or 10°. Conclusion: The present study shows the software update of an automated preoperative planning program may significantly modify the values of glenoid inclination. Even though without a significant difference, variations were also found for the glenoid version and humeral head subluxation. Accordingly, these results should further advise surgeons to carefully and critically evaluate data acquired with automated software.

Three-Dimensional Scapular Border Method for Glenoid Version Measurements

Variations among methods to measure glenoid version have created uncertainty regarding which method provides the most consistent measurements of morphology. Greater deformity may also make accurate depiction of the native morphology more challenging. This study examined 4 current methods (Friedman, corrected Friedman, Ganapathi-Iannotti, and Matsumura) and an experimental scapular border-derived coordinate system method, to compare measurement inconsistencies between methods and reference systems and assess the impact of glenoid deformity on measured glenoid version.

Methods

Three-dimensional scapulae were created from computed tomography (CT) scans of 74 shoulders that had undergone arthroplasty (28 A2, 22 B2, 10 B3, and 14 C glenoids) and 34 shoulders that had not undergone arthroplasty. Glenoid version measurements were made in Mimics using the 4 methods. For the experimental method, scapulae were reconstructed, and 3 orthogonal global coordinate planes (GCPs) were derived from the medial and lateral borders. Version was measured as the angle between the sagittal reference plane and an anterior-posterior glenoid vector. The intraclass correlation coefficient (ICC) was calculated for the Friedman and corrected Friedman methods. Inconsistencies were assessed for all methods using the interquartile range, mean and standard deviation, and repeated-measures analysis of variance. Concordance correlation coefficients (CCCs) were calculated to assess agreement among the methods.

Results

Scapular plane-based methods (experimental, Friedman, and corrected Friedman) yielded an average version between -10° and -12°, with average measurement differences among these methods of <2°. Vault methods (Ganapathi-Iannotti and Matsumura) overestimated or underestimated version by an average of 5° to 7° compared with scapular plane-based methods, and showed significant differences of >12° when compared with each other. Scapular plane-based methods maintained consistency with increasing deformity.

Conclusions

The other methods of version measurement using the scapular planes as the reference were highly comparable with the corrected Friedman method. However, when the reference plane was the glenoid vault, version measurements were inconsistent with scapular plane-based methods, which is attributed to differences in the reference systems. In surgical planning, the coordinate system utilized will impact version measurements, which can result in variations in the planned surgical solutions. Additionally, as glenoid deformity increases, this variation resulting from the utilization of different coordinate systems is magnified.

Preoperative Planning for Anatomic Total Shoulder Arthroplasty

The success of total shoulder arthroplasty is dependent on both proper patient selection and restoration of the native anatomy. After proper patient selection, preoperative planning is essential to select implants that will allow the surgeon to properly restore soft-tissue tension and correct for deformity. Although it is possible to template implants with plain radiographs, these do not allow accurate measurements of the complex three-dimensional anatomy of the glenohumeral joint. CT can be used to further examine version of the glenoid and humerus, as well as humeral head subluxation. Three-dimensional reconstructions also allow for virtual implantation, resulting in a more reliable prediction of implant appearance. Commercial software is available that calculates parameters such as version; however, these have been shown to have variability when compared with measurements obtained by surgeons. Patient-specific instrumentation can also be obtained based on preoperative measurements; however, although it allowed for improved measurements when compared with two-dimensional imaging, there has been no difference in version error, inclination error, or positional offset of the glenoid implant when comparing patient-specific instrumentation with standard instrumentation. Intraoperative navigation can also be used to give real-time feedback on implant positioning; however, additional studies are needed to fully evaluate its benefit.

The addition of preoperative three-dimensional analysis alters implant choice in shoulder arthroplasty

BACKGROUND

The primary objective of the present study was to investigate how preoperative imaging modalities including 3D computed tomography (CT) scans with preoperative planning software affect implant choice for shoulder arthroplasty.

METHODS

X-ray, uncorrected 2D CT scans, and 3D CT scans from 21 patients undergoing primary arthroplasty were reviewed by five shoulder surgeons. Each surgeon measured glenoid version, inclination and humeral head subluxation, and then selected an anatomic or reverse shoulder arthroplasty implant based only on these imaging parameters. Each surgeon virtually positioned the implant. Agreement between surgeons and changes in plan for individual surgeons between imaging modalities were assessed.

RESULTS

Average measurements of native version, inclination, and subluxation were similar across all imaging modalities with very good interobserver reliability. Overall, there was a high rate of variability in choice of implant depending on imaging modality. Agreement on implant selection between surgeons improved from 68.6% using x-ray to 80.0% with 3D CT. Introducing age added significant variability, reducing agreement on implant choice to 61.0% with 3D CT.

CONCLUSIONS

The use of preoperative 3D planning changes implant choice in nearly one-third of cases compared to plain radiographs and improves surgeon agreement on implant choice compared to x-ray and 2D CT.Level of evidence: III.

Identifying areas of screw fixation in glenoids with severe bone loss in shoulder arthroplasty

BACKGROUND

Severe glenoid bone loss (SGBL) poses significant technical challenges. Adequate fixation of glenoid implants may require the use of alternative screw placement. Although bone volumes for the spine and lateral pillars have previously been defined, insufficient evidence exists regarding the distribution of screw placement for fixation in such regions for cases with SGBL. The purpose of this study is to evaluate the variability of screw placement. We hypothesize that determining this variability and establishing common patterns of glenoid bone loss will allow for recommendations for preoperative planning, and implant design and selection.

METHODS

An internal registry of 2 high-volume shoulder and elbow surgeons was queried, and 65 three-dimensional scapulae models exhibiting SGBL were identified. A fellowship-trained shoulder and elbow surgeon simulated the placement of two 3.5 mm × 30 mm screws, one in the scapular spine (CS) bone volume and one in the inferior column (IS) bone volume. Three orthogonal reference planes were created using anatomic reference points: the scapula trigonum, estimated glenoid center, and inferior pole. Screw positions were mapped, and deviations from the reference planes were calculated. Mutual positions of the IS to CS were also computed. Intraobserver reliability was assessed using 10 randomly selected samples. Median and 25th and 75th percentiles were reported for screw orientation distributions. Means and standard deviations were reported for screw head positions.

RESULTS

We demonstrated excellent intraobserver reliability (intraclass correlation coefficients, 0.90-0.98). Fifty percent of CS were oriented 10° ± 5° of retroversion from the scapula plane, with 5° ± 5° of inclination. For IS, 50% were positioned 0° ± 4° from the scapula plane, with -33° ± 7° of inclination. The relationship of the IS with the CS was medial and posterior in 49% of cases, lateral and posterior in 45%, and lateral and anterior in 6% of cases. On average, the distance between the CS and IS heads was 25 mm ± 4 mm.

DISCUSSION

For SGBL, adequate fixation of glenoid implants can be achieved by placing screws in the spine and lateral columns, with excellent reproducibility. Future implant designs should accommodate CS positioned -16° to -5° from the scapula plane, with 0° to 12° of inclination, and IS positioned -6° to 4° from the scapula plane, with -40° to -25° of inclination. Moreover, mutual screw positions suggested bone loss distributions anteriorly and inferiorly. Future implant designs should consider the potential benefits of augmentation to accommodate interscrew distances of 21-29 mm and anatomic locations of the IS relative to the CS.

Walch B2 glenoids. 2D vs 3D comparison of humeral head subluxation and glenoid retroversion

Background

The posterior subluxation and glenoid version in Walch B2 glenoids are routinely assessed by 2-dimensional (2D) computed tomography (CT). Different methods of calculation are used to analyze these parameters. Alternatively, the rising use of 3-dimensional (3D) planification tools in arthroplasty requires the clarification if the 3D measurements are equivalent to 2D. The aim of this study was to compare B2 glenoids characteristics between 2D CT assessment method and 3D automated software method.

Methods

CT scans from patients who underwent a shoulder arthroplasty were identified. In the 2D method, measurement of glenoid version was determined. Measurement of the humeral head subluxation (HHS) (scapula axis method) was determined by the percentage of the humeral head posterior to the Friedman line (scapula axis). Three-dimensional analysis allowed an automated segmentation of the humerus and scapula, definition of scapular planes, and determination of glenoid version and HHS.

Results

Fifty-one CT scans met inclusion criteria. The intraobserver and interobserver reliability of the 2D retroversion (RV) and 2D HHS intraclass correlation coefficient was excellent (intraclass correlation coefficient>0.9).The median RV was 16° [12-20] in 2D and 19° [16-23] in 3D (P < .0001). The median subluxation was 71% [66-75] in 2D and 81% [78-86] in 3D (P < .0001). Linear regression analysis demonstrated low positive correlation between RV and subluxation in 2D and 3D (R² = 0.31 and R² = 0.23, respectively).

Discussion/Conclusion

The assessment of version and HHS in Walch B2 glenoids between 2D CT and a 3D planification were significantly different. Low correlation between RV and HHS was observed (2D and 3D assessment).

Biconcave glenoids show 3 differently oriented posterior erosion patterns

BACKGROUND

Posterior glenoid wear remains a challenge in anatomic and reverse total shoulder arthroplasty (rTSA) because of an asymmetric erosion with altered retroversion. The purpose of this study was to assess glenoid morphology and evaluate the influence of acromial orientation in posterior glenoid erosion patterns by using 3-dimensional (3D) models.

MATERIAL AND METHODS

Computed tomographic (CT) shoulder scans from 3 study centers of patients awaiting rTSA between 2017 and 2018 were converted into 3D models and analyzed by 2 observers. Morphology, orientation and greatest depth of erosion, inclination, current retroversion and premorbid retroversion, surface areas of the glenoid, and external acromial orientation and posterior acromial slope were assessed. Measurements were compared between wear patterns, glenoid erosion entities, and genders.

RESULTS

In the complete cohort of 68 patients (63.8 ± 10.0 years; 19 female, 49 male), a mean of 85.9° (±22.2°) was observed for the glenoid erosion orientation. Additionally, a further distinct classification of the glenoid erosion as posterior-central (PC, n = 39), posterior-inferior (PI, n = 12), and posterior-superior (PS, n = 17) wear patterns was possible. These wear patterns significantly (P < .001) distinguished by erosion orientation (PC = 86.9° ± 12.0°, PI = 116.3° ± 10.3°, PS = 62.3° ± 18.9°). The greatest depth of erosion found was 7.3 ± 2.7 mm in PC wear patterns (PC vs. PI: P = .03; PC vs. PS: n.s.; PI vs. PS: n.s.). Overall, the observed erosion divided the glenoid surface into a paleoglenoid proportion of 48% (±11%) and a neoglenoid proportion of 52% (±12%). For the complete cohort, glenoid inclination was 85.4° (±6.6°), premorbid glenoid retroversion was 80.7° (±8.1°), and current glenoid retroversion was 73.4° (±7.4°), with an estimated increase of 6.9° (±6.0°). The mean external acromial orientation was 118.2° (±8.9°), and the mean posterior acromial slope was 107.2° (±9.6°). There were no further significant differences if parameters were compared by wear patterns, entities, and gender.

CONCLUSION

Three significantly differently oriented wear patterns (posterior-superior, posterior-central, and posterior-inferior) were distinguished in shoulders demonstrating posterior wear on axillary imaging. No significant differences between the observed erosion patterns or any relevant correlations were found regarding the orientation of the acromion.

Preoperative three-dimensional computer planning for reverse total shoulder arthroplasty and bone grafting for severe glenoid deformity

BACKGROUND

Computer assisted planning without patient specific instrumentation may be utilized to guide reverse total shoulder arthroplasty baseplate placement. The purpose of this study was to determine the difference between planned and achieved inclination and retroversion correction with three-dimensional preoperative computer assisted planning in reverse total shoulder arthroplasty without patient specific instrumentation with bone grafting for severe glenoid erosion.

METHODS

Preoperative three-dimensional computer assisted planning without patient specific instrumentation was performed on 15 patients undergoing primary reverse total shoulder arthroplasty with glenoid bone grafting for severe glenoid erosion. On preoperative and immediate postoperative computed tomography slices, two-dimensional retroversion and inclination were measured. Preoperative three-dimensional baseline retroversion and inclination and planned postoperative three-dimensional retroversion and inclination were measured. Planned and achieved version and inclination changes were compared.

RESULTS

The planned and achieved retroversion corrections were 18° and 12°, respectively (p < 0.001). The planned and achieved inclination corrections were 11° and 11°, respectively (p = 0.803).

CONCLUSIONS

Three-dimensional computer assisted planning without patient specific instrumentation in the setting of reverse total shoulder arthroplasty with severe glenoid erosion requiring bone grafting can accurately guide baseplate placement. All cases in which failure to correct retroversion or inclination within 10° of planning occurred in patients with severe erosion (B3 or E3 glenoids), therefore patient specific guides may be warranted in these cases to improve accuracy of implantation.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Computer-Assisted Preoperative Planning and Patient-Specific Instrumentation for Glenoid Implants in Shoulder Arthroplasty

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Glenoid component positioning affects implant survival after total shoulder arthroplasty, and accurate glenoid-component positioning is an important technical aspect.

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The use of virtual planning and patient-specific instrumentation has been shown to produce reliable implant placement in the laboratory and in some clinical studies.

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Currently available preoperative planning software programs employ different techniques to generate 3-dimensional models and produce anatomic measurements potentially affecting clinical decisions.

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There are no published data, to our knowledge, on the effect of preoperative computer planning and patient-specific instrumentation on long-term clinical outcomes.

Subluxation in the Arthritic Shoulder

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The term "subluxation" means partial separation of the joint surfaces. In the arthritic shoulder, "arthritic glenohumeral subluxation" refers to displacement of the humeral head on the surface of the glenoid.

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The degree of arthritic glenohumeral subluxation can be measured using radiography with standardized axillary views or computed tomography (CT).

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Shoulders with a type-B1 or B2 glenoid may show more posterior subluxation on an axillary radiograph that is made with the arm in an elevated position than on a CT scan that is made with the arm at the side.

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The degree of arthritic glenohumeral subluxation is not closely related to glenoid retroversion.

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The position of the humeral head with respect to the plane of the scapula is related to glenoid retroversion and is not a measure of glenohumeral subluxation.

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Studies measuring glenohumeral subluxation before and after arthroplasty should clarify its importance to the clinical outcomes of shoulder reconstruction.

Determination of predisposing scapular anatomy with a statistical shape model-Part II: shoulder osteoarthritis

HYPOTHESIS AND BACKGROUND

Shoulder osteoarthritis can be divided into different glenoid types (A, B, C, and D) and subtypes. The aim of this study was to investigate if there is an association between the prearthropathy scapular anatomy, shoulder osteoarthritis, and different glenoid types and subtypes.

METHODS

Using principal components analysis, a statistical shape model (SSM) of the scapula was constructed from a data set of 110 computed tomographic (CT) scans. These subjects formed the control group. Next, CT scan images of 117 patients with osteoarthritis were classified according to the modified Walch classification. A complete 3-dimensional (3D) scapular bone model was created for every patient, and using the SSM, a reconstruction of their prearthropathy scapular anatomy was performed. Automated 3D measurements were performed in both the patient and control group to obtain glenoid version and inclination, critical shoulder angle (CSA), posterior acromial slope (PAS), lateral acromion angle, scapular offset, and the rotational alignment of the coracoacromial complex. These parameters were compared between controls, patients with osteoarthritis, and glenoid types and subtypes.

RESULTS

Mean version and inclination for the control group was 6° retroversion and 8° superior inclination (both SD 4°). The mean CSA, PAS, coracoid-posterior acromion angle, posterior acromion-scapular plane angle, and fulcrum axis ratio were 30° (SD 4°), 64° (SD 8°), 116° (SD 9°), 55° (SD 7°), and 46% (SD 4%), respectively. Patients with osteoarthritis had a significant lower CSA, posterior acromion-scapular plane angle, coracoid-posterior acromion angle, and fulcrum axis ratio (27°, 50°, 111°, and 44%, all P < .001). We found a significant difference between the control group and the respective glenoid types for the following parameters: mean CSA and coracoid-posterior acromion angle for A glenoids (27°, P = .001, and 111°, P = .007); mean version, CSA, PAS, coracoid-posterior acromion angle, posterior acromion-scapular plane angle, and fulcrum axis ratio for B glenoids (11°, 27°, 71°, 111°, 49°, and 43%, all P < .001); and mean version, CSA, and posterior acromion-scapular plane angle for D glenoids (2°, P = .002, 26°, P = .003, and 48°, P = .007).

DISCUSSION

There seems to be an association between prearthropathy scapular anatomy and shoulder osteoarthritis. A small lateral extension and less posterior rotation of the acromion is associated with shoulder osteoarthritis and is present in almost all types and subtypes of glenoid morphology. Furthermore, B and D glenoids are associated with, respectively, a more and less pronounced prearthropathy glenoid retroversion.

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 in total shoulder arthroplasty planning software compared to a control CT-derived 3D printed scapula

BACKGROUND

Two techniques exist from which all 3D preoperative planning software for total shoulder arthroplasty are based. One technique is based on measurements constructed on the mid-glenoid and scapular landmarks (Landmark). The second is an automated system using a best-fit sphere technique (Automated). The purpose was to compare glenoid measurements from the two techniques against a control computed tomography-derived 3D printed scapula.

METHODS

Computed tomography scans of osteoarthritic shoulders of 20 patients undergoing primary total shoulder arthroplasty were analyzed with both 3D planning software techniques. Measurements from a 3D printed scapula (Scapula) from the true 3D computed tomography scan served as controls. Glenoid version and inclination measurements from each group were blinded and reviewed.

RESULTS

In 65% (Automated) and 45% (Landmark) of cases, either inclination or version varied by 5° or more versus 3D printed scapula. Significant variability in version differences compared to the scapula group existed (p = 0.007). Glenoid version from the Scapula = 13.0° ± 10.6°, Automated = 15.0° ± 13.9°, and Landmark = 12.2° ± 7.8°. Inclination from Scapula = 5.4° ± 7.9°, Automated = 6.1° ± 12.6°, and Landmark = 6.2° ± 9.1°.

DISCUSSION

A high percentage of cases showed discrepancies in glenoid inclination and version values from both techniques. Surgeons should be aware that regardless of software technique, there is variability compared to measurements from a control 3D computed tomography printed scapula.

Glenoid bony morphology of osteoarthritis prior to shoulder arthroplasty: what the surgeon wants to know and why

Shoulder arthroplasty is performed with increasing frequency, and osteoarthritis is the most common indication for this procedure. However, the glenoid side of the joint is widely recognized as a limiting factor in the long-term durability of shoulder replacement, and osteoarthritis leads to characteristic bony changes at the glenoid which can exacerbate this challenge by reducing the already limited glenoid bone stock, by altering biomechanics, and by interfering with operative exposure. This article reviews the Walch classification system for glenoid morphology. Several typical findings of osteoarthritis at the glenoid are discussed including central bone loss, posterior bone loss, retroversion, biconcavity, inclination, osteophyte formation, subchondral bone quality, and bone density. The three primary types of shoulder arthroplasty are reviewed, along with several techniques for addressing glenoid deformity, including eccentric reaming, bone grafting, and the use of augmented glenoid components. Ultimately, a primary objective at shoulder arthroplasty is to correct glenoid deformity while preserving bone stock, which depends critically on characterizing the glenoid at pre-operative imaging. Understanding the surgical techniques and the implications of glenoid morphology on surgical decision-making enables the radiologist to provide the morphologic information needed by the surgeon.

Does commercially available shoulder arthroplasty preoperative planning software agree with surgeon measurements of version, inclination, and subluxation?

BACKGROUND

Preoperative planning with commercially available imaging software in shoulder arthroplasty may allow for improved decision-making and more accurate placement of the glenoid component.

METHODS

A total of 81 consecutive shoulder computed tomography scans obtained for preoperative planning purposes for shoulder arthroplasty were analyzed by commercially available software from 4 companies (Blueprint: Wright Medical, Memphis, TN, USA; GPS: Exactech, Gainesville, FL, USA; Materialise: DJO, Vista, CA, USA; and VIP: Arthrex, Naples, FL, USA) and by 5 fellowship-trained sports medicine/shoulder surgeons. Inclination, version, and subluxation of the humerus were measured in a blinded fashion on axial and coronal sequences at the mid-glenoid. Surgeon measurements were analyzed for agreement and were compared with the 4 commercial programs.

RESULTS

Surgeon reliability was acceptable for version (intraclass correlation coefficient [ICC]: 0.876), inclination (ICC: 0.84), and subluxation (ICC: 0.523). Significant differences were found between surgeon and commercial software measurements in version (P = .03), inclination (P = .023), and subluxation (P < .001). Software measurements tended to be more superiorly inclined (average -2° to 2° greater), more retroverted (average 2°-5° greater), and more posteriorly subluxed (average 7°-10° greater) than surgeon measurements. In comparing imaging software measurements, only Blueprint was found to produce significantly different version measurements than surgeon measurements (P = .02).

CONCLUSION

Preoperative planning software for shoulder arthroplasty has limited agreement in measures of version, inclination, and subluxation measurements, whereas surgeons have high inter-reliability. Surgeons should be cautious when using commercial software planning systems and when comparing publications that use different planning systems to determine preoperative glenoid deformity measurements.

Intersurgeon and intrasurgeon variability in preoperative planning of anatomic total shoulder arthroplasty: a quantitative comparison of 49 cases planned by 9 surgeons

BACKGROUND

Preoperative planning software is widely available for most anatomic total shoulder arthroplasty (ATSA) systems. It can be most useful in determining implant selection and placement with advanced glenoid wear. The purpose of this study was to quantify inter- and intrasurgeon variability in preoperative planning of a series of ATSA cases.

METHODS

Forty-nine computed tomography scans were planned for ATSA by 9 fellowship-trained shoulder surgeons using the ExactechGPS platform (Exactech Inc., Gainesville, FL, USA). Each case was planned a second time between 4 and 12 weeks later. Variability within and between surgeons was measured for implant type, size, version and inclination correction, and implant face position. Interclass correlation coefficients, Pearson, and Light's kappa coefficients were used for statistical analysis.

RESULTS

There was considerable variation in the frequency of augment use between surgeons and between rounds for the same surgeon. Thresholds for augment use also varied between surgeons. Interclass correlation coefficients for intersurgeon variability were 0.37 for version, 0.80 for inclination, 0.36 for implant type, and 0.36 for implant size. Pearson coefficients for intrasurgeon variability were 0.17 for version and 0.53 for inclination. Light's kappa coefficient for implant type was 0.64.

CONCLUSIONS

This study demonstrates substantial inter- and intrasurgeon variability in preoperative planning of ATSA. Although the magnitude of differences in correction was small, surgeons differed significantly in the use of augments to achieve the resultant plan. Surgeons differed from each other on thresholds for augment use and maximum allowable residual retroversion. This suggests that there may a range of acceptable corrections for each shoulder rather than a single optimal plan.

Acromial morphology is not associated with rotator cuff tearing or repair healing

BACKGROUND

The purposes of this study were to determine whether acromial morphology (1) could be measured accurately on magnetic resonance images (MRIs) as compared to computed tomographs (CTs) as a gold standard, (2) could be measured reliably on MRIs, (3) differed between patients with rotator cuff tears (RCTs) and those without evidence of RCTs or glenohumeral osteoarthritis, and (4) differed between patients with rotator cuff repairs (RCRs) that healed and those that did not.

METHODS

This is a retrospective comparative study. We measured coronal, axial, and sagittal acromial tilt; acromial width, acromial anterior and posterior coverage, and glenoid version and inclination on MRI corrected into the plane of the glenoid. We determined accuracy by comparison with CT via intraclass correlation coefficients (ICCs). To determine reliability, these same measurements were made on MRI by 2 observers and ICCs calculated. We compared these measurements between patients with a full-thickness RCT and patients aged >50 years without evidence of an RCT or glenohumeral osteoarthritis. We then compared these measurements between those patients with healed RCRs and those with a retorn rotator cuff on MRI. In this portion, we only included patients with both a preoperative MRI and a postoperative MRI at least 1 year from RCR. Only those patients without tendon defects on postoperative MRIs were considered to be healed. In these patients, we also radiographically measured the critical shoulder angle.

RESULTS

In a validation cohort of 30 patients with MRI and CT, all ICCs were greater than 0.86. In these patients, the inter-rater ICCs of the MRI measurements were >0.53. In our RCT group of 110 patients, there was greater acromial width [mean difference (95% confidence interval) = 0.1 (0, 0.2) mm, P = .012] and significantly less sagittal acromial tilt [9° (5°-12°), P < .001] than in our comparison group of 107 patients. A total of 110 RCRs were included. Postoperative MRI scans were obtained at a mean follow-up of 24.2 ± 15.8 months, showing 84 patients (76%) had healed RCRs. Aside from acromial width, which was 0.2 mm different and thus did not have clinical significance, there was no association between healing and any of the measured morphologic characteristics. Patients with healed repairs had significantly smaller tears in terms of both width (P < .001) and retraction (P < .001).

CONCLUSION

Although the acromion is wider in RCTs, the difference of 0.1 mm likely has no clinical significance. The acromion is more steeply sloped from posteroinferior to anterosuperior in those with RCTs. These findings call into question subacromial impingement due to native acromial morphology as a cause of rotator cuff tearing. Acromial morphology, critical shoulder angle, and glenoid inclination were not associated with healing after RCR. This study does not support lateral acromioplasty.

Vault perforation after eccentric glenoid reaming for deformity correction in anatomic total shoulder arthroplasty

BACKGROUND

The management of glenoid deformity during anatomic total shoulder arthroplasty remains controversial. In this study, we evaluate variable correction of glenoid deformity by eccentric reaming. We hypothesize that partial correction of modified Walch B/C-type glenoid deformities can achieve 75% bone-implant contact area (BICA) with a reduced vault perforation risk compared with complete correction.

METHODS

Fifty shoulder computed tomographic scans with glenohumeral osteoarthritis were retrospectively evaluated. The Tornier BluePrint v2.1.5 software simulated 3 eccentric reaming scenarios including no, partial, and complete deformity correction. Each scenario was evaluated at 4 BICAs and using 3 implant fixation types. Three-dimensional surface representations were used to evaluate medialization and vault perforation.

RESULTS

The patients had mean glenoid retroversion and inclination of 18.5° and 8.8°, respectively, and mean posterior humeral head subluxation of 76%. With 75% BICA, the 3 fixation types had glenoid vault perforation in 6%-26% and 26%-54% of cases for partial and complete glenoid deformity correction, respectively. The central and posterior-inferior implant components were most likely to perforate across all scenarios.

DISCUSSION

Eccentric reaming for glenoid deformity correction increases the risk of vault perforation. Severe glenoid deformity required increased medialization to achieve 75% BICA. Pegged implants have increased chances of perforation compared with a keeled design; the central and posterior-inferior components were most likely to perforate during deformity correction.

CONCLUSION

Partial deformity correction of modified Walch B/C-type glenoid deformities can achieve 75% BICA while reducing the risk of vault perforation compared with complete correction at the time of anatomic total shoulder arthroplasty.

The Ellipse modification of the Friedman method for measuring glenoid version

AIMS

Accurate measurement of the glenoid version is important in performing total shoulder arthroplasty (TSA). Our aim was to evaluate the Ellipse method, which involves formally defining the vertical mid-point of the glenoid prior to measuring the glenoid version and comparing it with the 'classic' Friedman method.

METHODS

This was a retrospective study which evaluated 100 CT scans for patients who underwent a primary TSA. The glenoid version was measured using the Friedman and Ellipse methods by two senior observers. Statistical analyses were performed using the paired t-test for significance and the Bland-Altman plot for agreement.

RESULTS

The mean glenoid version was -3.11° (-23.8° to 17.9°) using the Friedman method and -1.95° (-29.8° to 24.6°) using the Ellipse method (p = 0.002). In 16 patients the difference between methods was greater than 5°, which we considered to be clinically significant. There was poor agreement between methods with relatively large 95% limits of agreement. There was excellent inter-rater agreement between the observers for the Ellipse method and similarly, the intrarater agreement was excellent with a repeatability coefficient of 0.94.

CONCLUSION

We recommend the use of the Ellipse modification to define the mid glenoid point prior to measuring the glenoid version in patients undergoing TSA. Cite this article: Bone Joint J 2020;102-B(2):232-238.

Automated three-dimensional measurements of version, inclination, and subluxation

BACKGROUND

Preoperative planning software has been developed to measure glenoid version, glenoid inclination, and humeral head subluxation on computed tomography (CT) for shoulder arthroplasty. However, most studies analyzing the effect of glenoid positioning on outcome were done prior to the introduction of planning software. Thus, measurements obtained from the software can only be extrapolated to predict failure provided they are similar to classic measurements. The purpose of this study was to compare measurements obtained using classic manual measuring techniques and measurements generated from automated image analysis software.

METHODS

Ninety-five two-dimensional computed tomography scans of shoulders with primary glenohumeral osteoarthritis were measured for version according to Friedman method, inclination according to Maurer method, and subluxation according to Walch method. DICOM files were loaded into an image analysis software (Blueprint, Wright Medical) and the output was compared with values obtained manually using a paired sample t-test.

RESULTS

Average manual measurements included 13.8° version, 13.2° inclination, and 56.2% subluxation. Average image analysis software values included 17.4° version (3.5° difference, p < 0.0001), 9.2° inclination (3.9° difference, p < 0.001), and 74.2% for subluxation (18% difference, p < 0.0001).

CONCLUSIONS

Glenoid version and inclination values from the software and manual measurement on two-dimensional computed tomography were relatively similar, within approximately 4°. However, subluxation measurements differed by approximately 20%.

Normal and Pathoanatomy of the Arthritic Shoulder: Considerations for Shoulder Arthroplasty

The glenohumeral joint is a highly mobile, complex articulation that relies not only on the bony support between the humeral head and glenoid but also on appropriate balance and tension of the surrounding soft-tissue structures. Recreating the normal anatomic relationships is a basic premise in joint arthroplasty, which can be challenging in shoulder arthroplasty, as the normal glenohumeral anatomy has considerable variation from patient to patient. Also, as the anatomy of the glenohumeral joint becomes distorted with advanced shoulder pathology, it becomes a challenge to return the shoulder to its premorbid anatomic state. Failure to restore normal anatomic parameters after shoulder arthroplasty has been shown to have deleterious effects on postoperative function and implant survival. As the recognition of this has grown, shoulder prostheses have evolved to allow for considerable more variation in an attempt to recreate patient-specific anatomy. However, understanding the progression of shoulder pathology to better predict the patient's premorbid anatomy remains limited. A thorough understanding of the premorbid and pathologic anatomy of the glenohumeral joint will aid in preoperative planning and intraoperative execution and lead to a more predictable reconstruction of the shoulder, which is critical for a successful outcome after shoulder arthroplasty.

Association Between Rotator Cuff Muscle Size and Glenoid Deformity in Primary Glenohumeral Osteoarthritis

BACKGROUND

Although glenoid morphology has been associated with fatty infiltration of the rotator cuff in arthritic shoulders, the association of rotator cuff muscle area with specific patterns of glenoid wear has not been studied. The purpose of our study was to assess the associations of glenoid deformity in primary glenohumeral osteoarthritis and rotator cuff muscle area.

METHODS

A retrospective study of 370 computed tomographic (CT) scans of osteoarthritic shoulders was performed. Glenoid deformity according to the modified Walch classification was determined, and retroversion, inclination, and humeral-head subluxation were calculated using automated 3-dimensional software. Rotator cuff muscle area was measured on sagittal CT scan reconstructions. A ratio of the area of the posterior rotator cuff muscles to the subscapularis was calculated to approximate axial plane potential force imbalance. Univariate and multivariate analyses to determine associations with glenoid bone deformity and rotator cuff measurements were performed.

RESULTS

Patient age and sex were significantly related to cuff muscle area across glenoid types. Multivariate analysis did not find significant differences in individual rotator cuff cross-sectional areas across glenoid types, with the exception of a larger supraspinatus area in Type-B2 glenoids compared with Type-A glenoids (odds ratio [OR], 1.5; p = 0.04). An increased ratio of the posterior cuff area to the subscapularis area was associated with increased odds of a Type-B2 deformity (OR, 1.3; p = 0.002). Similarly, an increase in this ratio was significantly associated with increased glenoid retroversion (beta = 0.92; p = 0.01) and humeral-head subluxation (beta = 1.48; p = 0.001). Within the Type-B glenoids, only posterior humeral subluxation was related to the ratio of the posterior cuff to the subscapularis (beta = 1.15; p = 0.001).

CONCLUSIONS

Age and sex are significantly associated with cuff muscle area in arthritic shoulders. Asymmetric glenoid wear and humeral-head subluxation in osteoarthritis are associated with asymmetric atrophy within the rotator cuff transverse plane. Increased posterior rotator cuff muscle area compared with anterior rotator cuff muscle area is associated with greater posterior glenoid wear and subluxation. It is unclear if the results are causative or associative; further research is required to clarify the relationship.

LEVEL OF EVIDENCE

Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

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.

Influence of Radiographic Viewing Perspective on Glenoid Inclination Measurement

Introduction

The purposes of this study were to determine (1) whether glenoid inclination (GI) could be accurately measured on plain radiographs as compared to a gold-standard 3-dimensional (3D) measure and (2) whether GI could be reliably measured on plain radiographs.

Materials and Methods

Digitally reconstructed radiographs (DRRs) were made from 3D computed tomography reconstructions of 68 normal cadaver scapulae. DRRs were made in a variety of viewing angles. Inclination was measured on these DRRs. These measurements were also made using a gold-standard 3D method. Measurements were made by 2 orthopedic surgeons and 1 surgeon twice, to calculate interrater and intrarater intraclass correlation coefficients (ICCs).

Results

The gold-standard 3D β was 83 ± 5° (72°–98°). On neutral plain radiographs, the mean ± standard deviation 2D β angle was 80 ± 6° (range, 66°–99°). With regard to accuracy, the 2D β angle was significantly different from the 3D β angle, with the 2D β underestimating the 3D β by 5° (95% confidence intervals −1 to 12). With regard to reliability, interrater ICCs for 2D β with a neutral viewing angle was 0.79. Two-dimensional β varied widely with viewing angle from 0.24 to 0.88. Interrater ICCs for the 3D method was 0.83 (0.60–0.92). Intrarater ICCs for all 3 techniques were high (>0.91).

Conclusions

Two-dimensional radiographic GI measurement is not accurate, as it underestimates the 3D value by an average of 5° when compared to the gold-standard 3D measurement. GI 2D measurement reliability varies with viewing angle on plain radiographs and thus to accurately and reliably measure inclination 3D imaging is necessary.

A computed tomography analysis of three-dimensional glenoid orientation modified by glenoid torsion

Background

The longitudinal axis of the glenoid is not always parallel to the scapular body, and glenoid torsion could affect the values of glenoid orientation. The purpose of this study was to evaluate 3-dimensional glenoid version and inclination modified by glenoid torsion and to clarify the differences between the values of conventional and of modified glenoid orientations.

Methods

Computed tomography scans of 30 shoulders without shoulder pathology, 30 shoulders with primary osteoarthritis, and 30 shoulders with a massive rotator cuff tear or cuff tear arthropathy were retrospectively evaluated. After determining the glenoid axis and the scapular planes and calculating conventional glenoid version and inclination, modified glenoid version and inclination, and glenoid torsion, the values of conventional glenoid orientation and those of modified glenoid orientation were compared statistically.

Results

All shoulders showed anterior torsion of the glenoid with an average of 16° ± 5°. The values of modified glenoid retroversion were significantly smaller than those of conventional glenoid retroversion in all groups (P < .033), and the values of the modified glenoid inferior inclination were significantly larger than those of conventional glenoid inferior inclination in all groups (P < .001).

Conclusions

The present study showed that the glenoid twists with respect to the scapular body and that modification by glenoid torsion could affect the values of glenoid orientation. These results indicated that glenoid orientation with respect to the glenoid longitudinal axis will help surgeons determine proper placement of the glenoid component during shoulder arthroplasty.

Version and inclination obtained with 3-dimensional planning in total shoulder arthroplasty: do different programs produce the same results?

Background

Our purpose was to compare the output of glenoid measurements with 2 commercially available preoperative 3-dimensional (3D) total shoulder arthroplasty planning systems. The hypothesis was that there would be no difference in product-derived measurements between the systems.

Methods

Preoperative 3D computed tomography scans of 63 consecutive patients undergoing primary arthroplasty were analyzed using 2 product-derived techniques: Blueprint and VIP. Glenoid version and inclination measurements with each system were blinded and statistically compared, and the amount of variance was recorded.

Results

Glenoid version based on Blueprint was -10.9° ± 9.0° (range, -41° to 14°) compared with -9.3° ± 8.2° (range, -36° to 8°) for VIP (P = .04). Inclination was 9.0° ± 8.8° (range, -12° to 29°) with Blueprint compared with 9.7° ± 6.1° (range, -6° to 22°) for VIP (P = .463). For version, the difference between the 2 systems was less than 5° in 44 cases (69.8%), 5°-10° in 12 cases (19.0%), and greater than 10° in 7 cases (11.1%). For inclination, the difference was less than 5° in 34 cases (54.0%), 5°-10° in 17 cases (27.0%), and greater than 10° in 12 cases (19.0%). We found no differences in glenoid version or inclination based on glenoid morphology between the 2 systems (P = .908) and no differences between patients with the most severe arthritis and posterior wear (P = .202).

Conclusions

There is considerable variability between preoperative measurements obtained for 3D planning of shoulder arthroplasty with the use of Blueprint and VIP. Given that implant choice and desired component positioning are based on preoperative measurements, further study is needed to evaluate the differences between the measurements obtained with different techniques.

Superior glenoid inclination and rotator cuff tears

BACKGROUND

The objectives of this study were to determine whether glenoid inclination (1) could be measured accurately on magnetic resonance imaging (MRI) using computed tomography (CT) as a gold standard, (2) could be measured reliably on MRI, and (3) whether it differed between patients with rotator cuff tears and age-matched controls without evidence of rotator cuff tears or glenohumeral osteoarthritis.

METHODS

In this comparative retrospective radiographic study, we measured glenoid inclination on T1 coronal MRI corrected into the plane of the scapula. We determined accuracy by comparison with CT and inter-rater reliability. We compared glenoid inclination between patients with full-thickness rotator cuff tears and patients aged >50 years without evidence of a rotator cuff tear or glenohumeral arthritis. An a priori power analysis determined adequate power to detect a 2° difference in glenoid inclination.

RESULTS

(1) In a validation cohort of 37 patients with MRI and CT, the intraclass correlation coefficient was 0.877, with a mean difference of 0° (95% confidence interval, -1° to 1°). (2) For MRI inclination, the inter-rater intraclass correlation coefficient was 0.911. (3) Superior glenoid inclination was 2° higher (range, 1°-4°, P < .001) in the rotator cuff tear group of 192 patients than in the control cohort of 107 patients.

CONCLUSIONS

Glenoid inclination can be accurately and reliably measured on MRI. Although superior glenoid inclination is statistically greater in those with rotator cuff tears than in patients of similar age without rotator cuff tears or glenohumeral arthritis, the difference is likely below clinical significance.

Risk of Perforation Is High During Corrective Reaming of Retroverted Glenoids: A Computer Simulation Study

BACKGROUND

Corrective anterior reaming is an accepted method for addressing retroversion in a biconcave retroverted (Walch classification, type B2) glenoid in anatomic total shoulder arthroplasty. However, concern still exists regarding early glenoid component failure in the setting of severe retroversion, which may be related to loss of component containment and/or violation of subchondral bone resulting from reaming. The goal of this study was to determine what characteristics of B2 glenoids are less amenable to corrective reaming by virtually implanting anatomic glenoid components.

QUESTIONS/PURPOSES

(1) How much medial reaming is required to correct the version of a B2 glenoid to an acceptable position? (2) Are glenoids with more severe retroversion (> 25°) at higher risk of component perforation than less retroverted glenoids? (3) Is correcting to 10° of retroversion associated with greater risk as compared with reaming to 15°? (4) How does corrective reaming affect the underlying bone density on the glenoid face of B2 glenoids?

METHODS

A series of 71 patients with B2 glenoids (posterior subluxation of the humeral head with posterior bone loss) with CT scans who were indicated for shoulder arthroplasty were reviewed. Forty-four of 71 glenoids (62.5%) had < 25° of native retroversion. Anatomic glenoid implants were then virtually implanted using three-dimensional CT software that allows for preoperative shoulder arthroplasty planning to correct native retroversion to 15° or 10° of retroversion using both a central peg with an inverted triangle peg configuration or a keel. The amount of reaming of the anterior glenoid required to correct retroversion, perforation of peripheral pegs, or keel was compared. Additionally, assessment of the surface area of the glenoid that had poor bone density (defined as cancellous bone under the subchondral plate) was analyzed by the software after correction.

RESULTS

Correction to 15° of retroversion required 5 ± 3 mm of reaming, and correction to 10° of retroversion required 8 ± 3 mm of reaming to obtain at least 80% seating. Peripheral peg perforation with correction to 15° occurred in 15 of 27 (56%) glenoids with > 25° of retroversion compared with 10 of 44 (23%) of glenoids with < 25° of retroversion (relative risk [RR], 2.4; 95% confidence interval [CI], 1.3-4.6; p = 0.006). There was no difference in perforation with keeled components. Increased correction to 10° did not increase the risk of component perforation. When correction to 15°, glenoids with higher native version (> 25°) had a greater risk of poor bone quality support (10 of 27 [37%]) when compared with glenoids with less version (four of 44 [9%]; RR, 4.1; 95% CI, 1.5-12.8; p = 0.006). Increased correction resulted in 13 of 27 (48%) glenoids with version > 25° having poor bone density versus 10 of 44 (23%) with ≤ 25° of version (RR, 2.1; 95% CI, 1.1-4.1; p = 0.028).

CONCLUSIONS

There is a high risk of vault perforation after corrective reaming. Glenoid retroversions > 25° are at a higher risk of having poor bone quality supporting the component.

CLINICAL RELEVANCE

When contemplating options for patients with severe retroversion, surgeons should consider alternatives other than corrective reaming if achieving normal glenoid version is desired.

Interdepartmental imaging protocol for clinically based three-dimensional computed tomography can provide accurate measurement of glenoid version

BACKGROUND

Conventional computed tomography (CT) is not accurate for glenoid version measurement. This study sought to examine the feasibility of an interdepartmental protocol implemented between orthopedic surgery and radiology departments for acquisition of anatomic axial CT images and to validate the glenoid version measured through such a protocol.

MATERIALS AND METHODS

Data of 30 conventional CT scans of 10 normal and 20 osteoarthritic glenoids were transferred to clinical 3-dimensional imaging software by a radiology technician trained for the study. The technician independently reoriented the scapulae to generate anatomic CT images. A separate team of orthopedic researchers used laboratory-based 3-dimensional reconstruction software (Mimics; Materialise, Leuven, Belgium) to generate anatomic axial images. Three independent examiners measured glenoid version on the conventional CT, reoriented anatomic CT, and Mimics images at the superior, middle, and inferior levels. Data were analyzed using the Mimics data as the "gold standard."

RESULTS

Reoriented anatomic CT images generated by the technician resulted in almost identical version measurements to the Mimics images in both normal and arthritic glenoids. The conventional CT images had poor agreement with the Mimics images in normal glenoids but had good agreement in arthritic glenoids. Both normal and arthritic glenoids had increased retroversion superiorly (P < .05), and this phenomenon was significantly exaggerated on the conventional CT images (P < .05).

CONCLUSIONS

This study demonstrated that an interdepartmental protocol can produce reoriented anatomic axial CT images on which true glenoid version can be accurately measured. Such an institutional protocol would help surgeons accurately evaluate glenoid version preoperatively with reduced workload and expense.

Total shoulder arthroplasty in patients with a B2 glenoid addressed with corrective reaming

BACKGROUND

This study describes the short-term functional and radiographic outcomes after total shoulder arthroplasty (TSA) in shoulders with a B2 glenoid deformity addressed with corrective reaming.

METHODS

We conducted a retrospective series of consecutive patients who underwent TSA with a Walch B2 glenoid quantified by computed tomography scan. All glenoid deformities were addressed using partially corrective glenoid reaming. Radiographic and functional outcome measures, including scores on the visual analog scale for pain, American Shoulder and Elbow Standardized Shoulder Assessment, and Simple Shoulder Test were collected.

RESULTS

Functional outcome scores were available for 59 of 92 eligible subjects (64%) at a mean of 50 months. The mean preoperative retroversion measured 18° (range, -1° to 36°), superior inclination was 8° (range, -11° to 27°), and posterior subluxation was 67% (range, 39%-91%). Mean visual analog scale improved from 7.4 to 1.4, the American Shoulder and Elbow Shoulder Standardized Assessment improved from 35.4 to 84.3, and the SST improved from 4.5 to 9.1. Radiographs were evaluated at a mean of 31 months: 38 had no glenoid radiolucent lines, 13 glenoids had grade 1, 2 had grade 2, and 5 had grade 3 lucencies. There was no difference in the rate of progression of glenoid radiolucencies between shoulders with a preoperative glenoid version of ≤20° (27.8%) compared with glenoids with >20° of retroversion (22.7%, P = .670). No shoulders were revised due to glenoid loosening or instability.

CONCLUSION

TSA with partial corrective glenoid reaming in selected shoulders with a B2 glenoid deformity resulted in excellent functional and radiographic outcomes at short-term follow-up, with a low risk of revision surgery.

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.

Guidelines for humeral subluxation cutoff values: a comparative study between conventional, reoriented, and three-dimensional computed tomography scans of healthy shoulders

BACKGROUND

The humeral subluxation index (HSI) is frequently assessed on computed tomography (CT) scans in conditions of the shoulder characterized by humeral displacement. An arbitrarily set HSI cutoff value of 45% for anterior subluxation and 55% for posterior subluxation has been widely accepted. We studied whether mean values and thresholds of humeral subluxation, in relation to the glenoid and scapula, were influenced by different imaging modalities.

METHODS

The HSIs referenced to the scapula (SHSI) and glenoid (GHSI) were compared between conventional CT scans, CT scans reoriented into the corresponding reference plane (ie, scapular plane for the SHSI and glenoid center plane for the GHSI), and 3-dimensional (3D) CT reconstructions of 120 healthy shoulders. The 95% normal range determined the cutoff values of humeral subluxation.

RESULTS

The SHSI thresholds for conventional, reoriented, and 3D CT scans were 33%-61%, 44%-68%, and 49%-61%, respectively. A different mean SHSI was found for each imaging modality (conventional, 47%; reoriented, 56%; 3D, 55%; P ≤ .014), with the conventional SHSI showing an underestimation in 89% of the cases. GHSI thresholds for conventional, reoriented, and 3D CT scans were 40%-61%, 44%-56%, and 46%-54%, respectively. The mean GHSI did not differ between each imaging modality (conventional, 51%; reoriented, 50%; 3D, 50%; P = .146).

CONCLUSIONS

The SHSI and GHSI are susceptible to different imaging modalities with consequently different cutoff values. The redefined HSI cutoff values guide physicians in the evaluation of humeral subluxation in conditions characterized by humeral displacement, depending on the available image data.