The three-dimensional glenoid vault model can estimate normal glenoid version in osteoarthritis

A scapular statistical shape model can reliably predict premorbid glenoid morphology in conditions of severe glenoid bone loss

BACKGROUND

Knowledge of premorbid glenoid parameters at the time of shoulder arthroplasty, such as inclination, version, joint line position, height, and width, can assist with implant selection, implant positioning, metal augment sizing, and/or bone graft dimensions. The objective of this study was to validate a scapular statistical shape model (SSM) in predicting patient-specific glenoid morphology in scapulae with clinically relevant glenoid erosion patterns.

METHODS

Computed tomography scans of 30 healthy scapulae were obtained and used as the control group. Each scapula was then virtually eroded to create 7 erosion patterns (Walch A1, A2, B2, B3, D, Favard E2, and E3). This resulted in 210 uniquely eroded glenoid models, forming the eroded glenoid group. A scapular SSM, created from a different database of 85 healthy scapulae, was then applied to each eroded scapula to predict the premorbid glenoid morphology. The premorbid glenoid inclination, version, height, width, radius of best-fit sphere, and glenoid joint line position were automatically calculated for each of the 210 eroded glenoids. The mean values for all outcome variables were compared across all erosion types between the healthy, eroded, and SSM-predicted groups using a 2-way repeated measures analysis of variance.

RESULTS

The SSM was able to predict the mean premorbid glenoid parameters of the eroded glenoids with a mean absolute difference of 3° ± 2° for inclination, 3° ± 2° for version, 2 ± 1 mm for glenoid height, 2 ± 1 mm for glenoid width, 5 ± 4 mm for radius of best-fit sphere, and 1 ± 1 mm for glenoid joint line. The mean SSM-predicted values for inclination, version, height, width, and radius were not significantly different than the control group (P > .05).

DISCUSSION

An SSM has been developed that can reliably predict premorbid glenoid morphology and glenoid indices in patients with common glenoid erosion patterns. This technology can serve as a useful template to visually represent the premorbid healthy glenoid in patients with severe glenoid bony erosions. Knowledge of the premorbid glenoid preoperatively can assist with implant selection, positioning, and sizing.

Glenoid-based reference system to differentiate shoulder pathologies on plain radiographs

BACKGROUND

Shoulder radiographs are used for evaluation and the planning of treatment of various pathologies. Making a diagnosis of these pathologies on plain radiographs occurs by recognizing the relationship of the humeral head on the registry of the glenoid. Quantification of these changes in registry does not currently exist. We hypothesize that a geometric relationship of the humeral head and the glenoid exists that is defined on an anteroposterior Grashey view radiograph by the relationship of the best-fit circle of the humeral head relative to the best-fit circle of the glenoid such that relative measurements will define the normal shoulder and the pathologic shoulder.

METHODS

One hundred fifty-six shoulders were included: 53 normal shoulders, 51 with primary glenohumeral osteoarthritis (GHOA), and 52 with cuff tear arthropathy (CTA). Humeral head best-fit circle was used to define the circle of the humeral head (cHH). A glenoid best-fit circle (cG) was defined by the following rules: (1) best fit of the glenoid articular surface and (2) was limited by the acromion such that either (a) it reaches maximal interaction with the inferior surface of the acromion or (b) the perimeter of the circle is at the lateralmost point of the acromion. The relationship between cHH and cG is defined by measurement of cHH in horizontal and vertical planes relative to the glenoid circle reference. The horizontal displacement angle (HDA) measures the horizontal position of cHH relative to cG, representing the degree of medialization toward the glenoid. The vertical displacement angle (VDA) measures the vertical position of cHH relative to cG, representing the degree of superiorization toward the acromion. Angles were compared by diagnosis and sex.

RESULTS

The mean HDA was 61.0° (95% confidence interval [CI] 60.3°-61.7°) in normal shoulders, 79.9° (95% CI 76.9°-82.9°) in GHOA, and 63.4° (95% CI 61.7°-65.1°) in CTA (P < .001). The mean VDA was 43.1° (95% CI 42.2°-44.0°) in normal shoulders, 40.9° (95% CI 39.9°-42.0°) in GHOA, and 59.7° (95% CI 57.6°-61.7°) in CTA (P < .001). Interobserver reliability was 0.991 (95% CI 0.94-1.0) and intraobserver reliability was 0.998 (95% CI 0.99-1.0). The geometric relationship of cHH to the glenoid circle reference was plotted for each group.

CONCLUSION

A geometric relationship exists of the humeral head in reference to the glenoid circle. Together, the HDA and the VDA distinguish between a normal shoulder and those with GHOA or CTA. This suggests that this novel methodology may provide a preoperative planning tool that is easily accessible.

Premorbid glenoid anatomy reconstruction from contralateral shoulder 3-dimensional measurements: a computed tomography scan analysis of 260 shoulders

BACKGROUND

Total shoulder arthroplasty (TSA) aims to reconstruct the premorbid anatomy of a pathologic shoulder. A healthy contralateral shoulder could be useful as a template in planning TSA. The symmetry between the left and right shoulders in healthy patients remains to be proved. The purpose of this study was to compare the 3-dimensional anatomy of the glenoid between sides in a healthy population.

METHODS

A multinational computed tomography scan database was retrospectively reviewed for all healthy bilateral shoulders in patients aged between 18 and 50 years. One hundred thirty pairs of healthy shoulder computed tomography scans were analyzed, and glenoid version, inclination, width, and height, as well as glenoid lateral offset and scapula lateral offset, were measured. All anatomic measures were computed with Blueprint, validated 3-dimensional planning software. The intraclass correlation coefficient was determined for each measure between left and right shoulders. The minimal detectable change (MDC) was calculated using the following formula: MDC=2×1.96×Standarderrorofmeasurement.

RESULTS

The comparison between 130 pairs of healthy scapulae showed statistically significant differences in absolute values between right and left glenoid version (-5.3° vs. -4.6°, P < .01), inclination (8.4° vs. 9.3°, P < .01), and width (25.6 mm vs. 25.4 mm, P < .01), as well as scapula offset (105.8 mm vs. 106.2 mm, P < .01). Glenoid height was comparable between right and left shoulders (33.3 mm vs. 33.3 mm, P = .9). The differences between the means were always inferior to the MDC regarding glenoid version, inclination, height, and width, as well as scapula offset. Very strong intraclass correlation coefficients between the left and right shoulders were found for all evaluated paired measures.

CONCLUSION

Healthy contralateral scapulae are highly reliable to predict inclination, height, width, and scapula offset and are reliable to predict version of a given scapula. Paired right and left scapulae were not statistically symmetrical regarding mean glenoid version, inclination, and width, as well as scapula offset. Nevertheless, the reported differences were not higher than the MDC for this cohort, confirming that healthy contralateral shoulders can be a useful template in TSA preoperative planning.

Emerging Technologies in Shoulder Arthroplasty: Navigation, Mixed Reality, and Preoperative Planning

Shoulder arthroplasty is a rapidly improving and utilized management for end-stage arthritis that is associated with improved functional outcomes, pain relief, and long-term implant survival. Accurate placement of the glenoid and humeral components is critical for improved outcomes. Traditionally, preoperative planning was limited to radiographs and 2-dimensional computed tomography (CT); however, 3-dimensional CT is becoming more commonly utilized and necessary to understand complex glenoid and humeral deformities. To further increase accurate component placement, intraoperative assistive devices-patient-specific instrumentation, navigation, and mixed reality-minimize malpositioning, increase surgeon accuracy, and maximize fixation. These intraoperative technologies likely represent the future of shoulder arthroplasty.

Does fluoroscopy improve baseplate position compared to conventional technique in reverse shoulder arthroplasty? A preliminary study

Background

Accurate placement of glenoid component in reverse shoulder arthroplasty remains a challenge for surgeons of all levels of expertise; however, no studies have evaluated the utility of fluoroscopy as a surgical assistance method.

Methods

Prospective comparative study of 33 patients undergoing primary reverse shoulder arthroplasty during a 12-month period. Fifteen patients had a baseplate placed using the conventional "free hand" technique (control group), and 18 patients using intraoperative fluoroscopy assistance group, in a case-control design. Postoperative glenoid position was evaluated on postoperative Computed Tomography (CT) scan.

Results

The mean deviation of version and inclination for fluoroscopy assistance vs. control group was 1.75° (0.675-3.125) vs. 4.2° (1.975-10.45) (p = .015), and 3.85° (0-7.225) vs. 10.35° (4.35-18.75) (p = .009). The distance from the central peg midpoint to the inferior glenoid rim (fluoroscopy assistance 14.61 mm/control 4.75 mm, p = .581) and the surgical time (fluoroscopy assistance 1.93 ± 0.57/control 2.18 ± 0.44 h, p = .400) showed no differences, with an average radiation dose of 0.45 mGy and fluoroscopy time of 14 s.

Conclusions

Accurate axial and coronal scapular plane positioning of glenoid component is improved with intraoperative fluoroscopy at the cost of a greater radiation dose and without differences in surgical time. Comparative studies are needed to determine whether their use in relation to more expensive surgical assistance systems result in similar effectiveness.L evel of evidence : Level III, therapeutic study.

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.

Description and Validation of the Anterior Glenoid Angle: A Novel MRI-Based Measure of Glenoid Morphologic Features and Version

The goal of this study was to establish a normal value for, and evaluate the reliability of, a new measurement of glenoid morphologic features using magnetic resonance imaging: the anterior glenoid angle. A total of 90 magnetic resonance imaging scans of patients without shoulder arthritis were reviewed. The anterior glenoid angle of each glenoid was measured by 4 blinded physicians. The images were randomized and measured again. Finally, the Friedman angle was measured on the same images for reference. Descriptive statistics and inter- and intraclass correlation coefficients were calculated. The mean anterior glenoid angle was 60.4°±3.6°. Of the measured values, 77% were between 56° and 64°. Intraobserver reliability was very good to excellent in single measure (range, 0.763-0.901) and mean measure (range, 0.865-0.948) comparisons. Interobserver reliability was very good to excellent in both single measure (0.769) and mean measure (0.964) comparisons. The mean Friedman angle was 10.2°. Correlation between the anterior glenoid angle and Friedman angle ranged from a moderate negative (-0.496) to a strong negative correlation (-0.711) among the observers. The mean anterior glenoid angle measured via magnetic resonance imaging scan was 60.4° in normal shoulders, and more than 75% of the values were within 4° of the mean. The anterior glenoid angle has excellent inter- and intrarater reliability without using computed tomography scan or including the entire scapula in the field of view. The anterior glenoid angle has a good to very good negative correlation with the Friedman angle because decreasing anterior glenoid angles indicate increasing retroversion. [Orthopedics. 2022;45(6):361-366.].

Concordance of Preoperative 3D Templating in Stemless Anatomic Total Shoulder Arthroplasty

INTRODUCTION

Recent advances in preoperative 3D templating software allow surgeons to plan implant size and position for stemless total shoulder arthroplasty (TSA). Whether these preoperative plans accurately reflect intraoperative decisions is yet unknown, and the purpose of this study was to evaluate concordance between planned and actual implant sizes in a series of patients undergoing stemless TSA.

METHODS

A retrospective cohort of consecutive, anatomic, stemless TSA cases performed by two surgeons between September 2019 and February 2021 was examined. Preoperative templated plans were collected using 3D planning software, and the sizes of planned glenoid, humeral head, and nucleus "stem" implants and other procedural data were recorded, along with sociodemographic information. These predicted parameters were compared with the implant sizes, and the concordance of these templated plans was quantified by direct comparison and bootstrapped simulations.

RESULTS

Fifty cases met inclusion criteria, among which perfect concordance across all three implants was observed in 11 cases (22%). The glenoid implant had the highest concordance (80%) relative to the humeral head and nucleus implants (38% and 60%, respectively), which was statistically significant ( P < 0.001). Planned humeral head implants were more often oversized relative to their actual implanted size. However, 84% of the planned humeral heads were within 1 diameter size; in addition, 98% of the planned glenoid implants were within one size and all were within 10 mm of the implanted glenoid backside radius. All nucleus implants were within one size.

DISCUSSION

Final implant sizes demonstrated variable concordance relative to preoperative plans, with glenoid implants having the highest accuracy and humeral heads having the highest variability. Multiple factors contributed to the varying concordances for the different implants, suggesting possible areas of improvement in this technology. These results may have implications for logistics, intraoperative efficiency, and overall cost and underscore the potential value of this technology.

LEVEL OF EVIDENCE

Level III.

[3D printing in the field of shoulder surgery]

The 3D printing technology is a relatively new procedure with a high potential, especially in the field of shoulder surgery. The 3D printing procedures are increasingly being developed and also gaining new users. Principally, 3D printing procedures can be applied preoperatively in planning the surgical procedure, patient clarification and in teaching; however, the technology is increasing being used intraoperatively. In addition to intraoperative visualization of the models, 3D printing permits the use of individual and specific instruments and implants. This allows the precise transfer of the preoperative planning to the surgical procedure. Inaccuracies are mainly caused by soft tissues. The 3D printing can be beneficial in the fields of arthroplasty, shoulder instability as well as orthopedic trauma. The literature shows promising results in relation to duration of surgery, blood loss and clinical results of the procedure. On the other hand, it is still unclear which indications warrant the use of 3D printing. Other aspects that raise questions are the time of planning, the production time and the additional cost that the use of 3D printing entails. Nonetheless, 3D printing represents a meaningful enhancement of the portfolio of surgeons, which becomes highly beneficial and useful in complex situations. Furthermore, this procedure enables a certain amount of flexibility when reacting to certain circumstances.

When should reverse total shoulder arthroplasty be considered in glenohumeral joint arthritis?

Anatomical total shoulder arthroplasty (TSA) has been used widely in treatment of glenohumeral osteoarthritis and provides excellent pain relief and functional results. Reverse total shoulder arthroplasty (RSA) was created to treat the complex problem of rotator cuff tear arthropathy. RSA also has been performed for glenohumeral osteoarthritis even in cases where the rotator cuff is preserved and has shown good results comparable with TSA. The indications for RSA are expanding to include tumors of the proximal humerus, revision of hemiarthroplasty to RSA, and revision of failed TSA to RSA. The purposes of this article were to describe comprehensively the conditions under which RSA should be considered in glenohumeral osteoarthritis, to explain its theoretical background, and to review the literature.

A lower critical coracoid process angle is associated with type-B osteoarthritis: a radiological study of normal and diseased shoulders

Background

Degenerative rotator cuff tears and osteoarthritis (OA) are associated with differences in coronal plane scapular morphology, with particular focus on the effect of the critical shoulder angle (CSA) on shoulder biomechanics. The effect, if any, of axial plane scapular morphology is less well established. We have noticed wide disparity of axial coracoid tip position in relation to the face of the glenoid and sought to investigate the significance of this through measurement of the critical coracoid process angle (CCPA), which incorporates coracoid tip position and glenoid version.

Methods

CCPA, CSA, and glenoid retroversion were measured by three independent reviewers from the cross-sectional two-dimensional computed tomography (CT) and magnetic resonance imaging of 160 patients in four equal and matched case-control groups: (1) a control group of patients with a radiologically normal shoulder and no history of shoulder symptoms who had a CT thorax for another reason, (2) patients with primary OA with Walch type-A glenoid wear pattern on CT scan, (3) patients with type-B glenoid primary OA, and (4) patients with magnetic resonance imaging–proven atraumatic tears of the posterosuperior rotator cuff.

Results

Interobserver agreement was excellent for all measured parameters. The median CCPA was significantly lower in the type-B OA group (9.3˚) than that in controls (18.7˚), but not significantly different in the other study groups. There was a trend toward greater glenoid retroversion in the type-B OA group, but receiver operating characteristic curve analysis demonstrated the CCPA to be by far the most powerful discriminator for type-B OA. The optimal cutoff value was calculated for the CCPA at 14.3˚ with a sensitivity of 93% and specificity of 90% for type-B OA. Compared with controls, the CSA was significantly higher in the rotator cuff tear group and lower in both OA groups, but did not differentiate between type-A and type-B OA.

Conclusion

Combined with a lower CSA, a lower CCPA (<14.3˚) is strongly predictive of type-B glenoid OA. The authors propose a simple model of pectoralis major biomechanics to explain the effect of this axial plane anatomical variation, which requires further investigation.

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.

The in vivo impact of computer navigation on screw number and length in reverse total shoulder arthroplasty

BACKGROUND

Little information exists regarding the benefit of computer navigation in shoulder arthroplasty in the clinical setting. This study aimed to quantify how computer navigation affects the number and length of screws used during in vivo reverse total shoulder arthroplasty (RSA) placement.

METHODS

We performed a retrospective review of a research database to identify patients who underwent primary RSA before and after the use of computer navigation between January 1, 2015, and December 31, 2019. One hundred consecutive RSAs were selected from the computer navigation implantation date; then, 100 consecutive sex-matched RSAs were chosen prior to navigation implantation in reverse chronologic order. Baseplate augmentations were chosen based on surgeon discretion, with the goal of restoring version to within 10° of neutral and inclination to neutral or slightly inferior with removal of the smallest amount of subchondral bone possible. Screws were placed with the goal of ≥3 screws with good purchase and were added as needed, with up to 5 screws used. We compared demographic factors, comorbidities, preoperative diagnosis, number of screws, screw length, number of wasted screws, and number of cases with bone graft used behind the baseplate between the 2 groups. We used the χ² test for bivariate analysis and the Student t test for continuous variables.

RESULTS

A total of 200 RSAs were included, with 100 primary RSAs (mean age, 69.3 years) performed prior to computer navigation compared with 100 primary RSAs (mean age, 69.7 years) performed using computer navigation. The total number of screws used in RSAs without computer navigation was 414; the total used in the computer navigation cases was 344. RSAs placed with computer navigation used significantly fewer screws per case (3.4 screws vs. 4.1 screws, P < .001) and had a significantly greater average screw length (35.0 mm vs. 32.6 mm, P < .001). Three screws were implanted in 61% of computer navigation cases vs. 1% of cases without computer navigation (P < .001). Screws ≥ 30 mm in length were more commonly used in patients undergoing RSA using computer navigation (84.6% vs. 73.7%, P < .001).

CONCLUSION

This study shows that computer navigation in RSA leads to longer and fewer glenoid baseplate screws being implanted. Computer navigation appears to assist with better screw placement, which may have similar clinical benefits of better glenoid fixation. Additionally, using fewer screws can save glenoid bone stock, avoid added glenoid stress risers, and decrease operative time.

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.

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.

The Glenoid Vault Outer Cortex a new more accurate radiological reference for shoulder arthroplasty

Introduction: Correct positioning of the glenoid component is an important determinant of outcome in shoulder arthroplasty. We describe and assess a new radiological plane of reference for improving the accuracy of glenoid preparation prior to component implantation – the Glenoid Vault Outer Cortex (GvOC) plane. Methods: One hundred and five CT scans of normal scapulae were obtained. Forty six females and 59 males aged between 22 and 30 years. The accuracy of the GvOC plane was then compared against the current “gold standard” – the scapular border (SB). Measurements of glenoid inclination, version, rotation, and offset were obtained using both the GvOC and SB planes. These were then compared to actual values. Results: The mean difference between version obtained using the GvOC plane and the actual value was 1.8° (−2 to 5, SD 1.6) as compared to 6.7° (−2 to 17, SD 4.3) when the SB plane was used, (p < 0.001). The mean difference between estimates of inclination obtained using the GvOC plane and the actual were 1.9° (−4 to 6, SD 1.6) as compared to 11.2° (−4 to 25, SD 6.1) when the SB plane was used, (p < 0.001). Conclusions: The GvOC plane produced estimates of glenoid version and inclination closer to actual values with lower variance than when the SB plane was used. The GvOC may be a more accurate and reproducible radiological method for surgeons to use when defining glenoid anatomy prior to arthroplasty surgery.

Decreased Glenoid Retroversion Is a Risk Factor for Failure of Primary Arthroscopic Bankart Repair in Individuals With Subcritical Bone Loss Versus No Bone Loss

PURPOSE

To determine whether glenoid retroversion is an independent risk factor for failure after arthroscopic Bankart repair.

METHODS

This was a retrospective review of patients with a minimum 2-year follow-up. In part 1 of the study, individuals with no glenoid bone loss on magnetic resonance imaging (MRI) and who failed arthroscopic Bankart repair (cases) were compared with individuals who did not fail Bankart repair (controls). In part 2 of the study, cases with subcritical (<20%) glenoid bone loss as measured on sagittal T1 MRI sequences who failed arthroscopic Bankart repair were compared with controls who did not. For each part of the study, glenoid version was measured using axial T2 MRI sequences. Positive angular measurements were designated to represent glenoid anteversion, whereas negative measurements were designated to represent glenoid retroversion. Independent t tests were conducted to determine the association between glenoid version and failure after arthroscopic Bankart repair.

RESULTS

There were 20 cases and 40 controls in part 1 of the study. In part 2, there were 19 cases and 21 controls. There was no difference in baseline characteristics between cases and controls. Among individuals with no glenoid bone loss, there was no difference in glenoid version between cases and controls (cases: 6.0° ± 8.1° vs controls: 5.1° ± 7.8°, P = .22). Among individuals with subcritical bone loss, cases (3.8° ± 4.4°) were associated with significantly less mean retroversion compared with controls (7.1° ± 2.8°, P = .0085). Decreased retroversion (odds ratio 1.34; 95% confidence interval 1.05-1.72, P = 20) was a significant independent predictor of failure using univariable logistic regression.

CONCLUSIONS

While glenoid retroversion is not associated with failure after arthroscopic Bankart repair in individuals with no glenoid bone loss, decreased retroversion is associated with failure in individuals with subcritical bone loss.

LEVEL OF EVIDENCE

Level 3: Retrospective review.

Ricchetti ET, Khazzam MS, Denard PJ, Dines DM, Bradley Edwards T, Entezari V, Friedman RJ, Garrigues GE, Gillespie RJ, Grawe BM, Green A, Hatzidakis AM, Gabriel Horneff J, Hsu JE, Jawa A, Jin Y, Johnston PS, Jun BJ, Keener JD, Kelly JD, Kwon YW, Miniaci A, Morris BJ, Namdari S, Spencer EE, Strnad G, Williams GR, Iannotti JP. 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.

Analysis of revision shoulder arthroplasty in the German nationwide registry from 2014 to 2018

Background

The purpose of this study is to identify and analyze primary revision arthroplasties of the shoulder in the Germany Shoulder Arthroplasty Registry. The objective is to provide demographic and clinical data of the included cases and information about the revision surgery itself and to compare the findings to other registry studies and clinical studies.

Methods

All documented cases of primary revision arthroplasties of the Germany Shoulder Arthroplasty Registry in the time period 2014-2018 (n = 975) were included in the initial data analysis. Exclusion criteria were multiple revisions and data sets with a missing link of the revision arthroplasty to the data set of the primary implantation leaving n = 433 cases that were included. SPSS software (IBM SPSS Statistics for Windows, version 24.0; IBM Corp., Armonk, NY, USA) was used for statistical analyses.

Results

The age of patients with revised anatomic implants (66.3 years) was significantly lower than that of patients with reverse implants (77.1 years) (P = .001). Female patients with anatomic and fracture implants were significantly older than their male counterparts (70.1 vs. 60.5 years, P = .001; 74.3 vs. 62 years, P = .019) and showed a significantly higher rate of revision than their male counterparts (P = .001). The reason for revision was significantly different for anatomic and reverse implant systems (P = .001). Aseptic loosening of either the humeral or glenoid component was the most common reason for revision for anatomic implants, whereas unspecified reasons, dislocation, and loosening of the glenosphere were the most common reasons for reverse implants. The most common type of revision procedure for anatomic implants was conversion to a reverse system in about one third of the cases. Most of the revisions of reverse implants were not specified and almost equally distributed for revision at the humeral or the glenoid side. Anatomic implants showed significantly better Constant-Murley scores (26.1 points) than reverse implants (19.6 points) (P = .001) and significantly better function before revision for passive flexion (P = .002), passive abduction (P = .015), active external rotation (P = .002), and passive external rotation (P = .002).

Conclusion

This study provides a well-documented basis to compare revision arthroplasties of the shoulder performed in Germany over the last decade as documented in the nationwide registry with other nationwide registries and with clinical studies. Especially, the detailed analysis of intraoperative and postoperative complications and the shoulder function at the time of revision offers new information in addition to the results of other registries.

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.

Exploring Alternative Sites for Glenoid Component Fixation Through Three-Dimensional Digitization of the Glenoid Vault: An Anatomic Analysis

Glenoid component loosening has remained one of the most common complications for total shoulder arthroplasty. Three-dimensional modeling of the glenoid may reveal novel information regarding glenoid vault morphology, providing a foundation for implant designs that possess the potential to extend the survivorship of the prosthesis.

CT-Based 3D Printing of the Glenoid Prior to Shoulder Arthroplasty: Bony Morphology and Model Evaluation

To demonstrate the 3D printed appearance of glenoid morphologies relevant to shoulder replacement surgery and to evaluate the benefits of printed models of the glenoid with regard to surgical planning. A retrospective review of patients referred for shoulder CT was performed, leading to a cohort of nine patients without arthroplasty hardware and exhibiting glenoid changes relevant to shoulder arthroplasty planning. Thin slice CT images were used to create both humerus-subtracted volume renderings of the glenoid, as well as 3D surface models of the glenoid, and 11 printed models were created. Volume renderings, surface models, and printed models were reviewed by a musculoskeletal radiologist for accuracy. Four fellowship-trained orthopaedic surgeons specializing in shoulder surgery reviewed each case individually as follows: First, the source CT images were reviewed, and a score for the clarity of the bony morphologies relevant to shoulder arthroplasty surgery was given. The volume rendering was reviewed, and the clarity was again scored. Finally, the printed model was reviewed, and the clarity again scored. Each printed model was also scored for morphologic complexity, expected usefulness of the printed model, and physical properties of the model. Mann-Whitney-Wilcoxon signed rank tests of the clarity scores were calculated, and the Spearman's ρ correlation coefficient between complexity and usefulness scores was computed. Printed models demonstrated a range of glenoid bony changes including osteophytes, glenoid bone loss, retroversion, and biconcavity. Surgeons rated the glenoid morphology as more clear after review of humerus-subtracted volume rendering, compared with review of the source CT images (p = 0.00903). Clarity was also better with 3D printed models compared to CT (p = 0.00903) and better with 3D printed models compared to humerus-subtracted volume rendering (p = 0. 00879). The expected usefulness of printed models demonstrated a positive correlation with morphologic complexity, with Spearman's ρ 0.73 (p = 0.0108). 3D printing of the glenoid based on pre-operative CT provides a physical representation of patient anatomy. Printed models enabled shoulder surgeons to appreciate glenoid bony morphology more clearly compared to review of CT images or humerus-subtracted volume renderings. These models were more useful as glenoid complexity increased.

Porous metal wedge augments to address glenoid retroversion in anatomic shoulder arthroplasty: midterm update

BACKGROUND

Wedge-shaped porous metal augments were used to address bone deficiency in shoulder arthroplasty as part of a hybrid combination of high-density polyethylene, polymethyl methacrylate bone cement, and porous metal implant. This article presents an ongoing review of the use of the generically designed augments in the shoulder to address glenoid retroversion as part of anatomic total shoulder arthroplasty (aTSA).

MATERIALS

Seventy-five shoulders in 66 patients (23 women and 43 men, aged 42-85 years) with Walch grade B2 or C glenoids underwent porous metal glenoid augment (PMGA) insertion as part of aTSA. Patients underwent preoperative 3-dimensional (3D) templating; based on that planning, patients received either a 15° or 30° PMGA wedge (secured by screws to the native glenoid) to correct excessive glenoid retroversion before a standard glenoid component was implanted using bone cement. Neither patient-specific guides nor navigation were used. Intraoperative glenoid alignment was assessed using a reusable guide that referenced the anterior scapular neck. Patients were prospectively assessed using shoulder functional assessments (Oxford Shoulder Score [OSS], American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form [ASES], visual analog scale [VAS] pain scores, and forward elevation [FE]) preoperatively; at 3, 6, and 12 months postoperation; and yearly thereafter, with similar radiologic surveillance.

RESULTS

Of the total consecutive series, 49 shoulders had a follow-up of greater than 24 months, with a median follow-up of 48 months (range: 24-87 months). For this cohort, median outcome scores improved for OSS (21 to 44), ASES (24 to 92), VAS (7 to 0), and FE (90° to 140°) from preoperative outcomes to the most recent review, respectively. Four patients died, but no others were lost to follow-up. Apart from 1 infection at 18 months postoperatively and 1 minor peg perforation, there were no complications, hardware failures, implant displacements, significant lucency, or posterior resubluxations. Radiographs showed good incorporation of the wedge augment, with correction of glenoid retroversion from median 22° (13° to 46°) to 4° (17° to anteversion 16°). All but 4 glenoids were corrected to within the target range (less than 10° retroversion), and only 2 glenoid components were implanted outside 15° of neutral glenoid version.

CONCLUSIONS

The porous metal wedge-shaped augments effectively addressed posterior glenoid deficiency as part of aTSA for rotator cuff intact osteoarthritis, producing satisfactory clinical outcomes with no signs of impending future failure.

Preoperative glenoid considerations for shoulder arthroplasty: a review

Preoperative assessment of the glenoid in the setting of shoulder arthroplasty is critical to account for variations in glenoid morphology, wear, version, inclination, and glenohumeral subluxation.

Three-dimensional computed tomography (3D CT) scan assessment of the morphology of glenoid erosion allows for a more accurate surgical decision-making process to correct deformity and restore the joint line.

Newer technology has brought forth computer-assisted software for glenoid planning in shoulder arthroplasty and patient-specific instrumentation.

There have been promising early findings, although further evaluation is needed to determine how this technology impacts implant survivorship, function, and patient-reported outcomes.

Cite this article: EFORT Open Rev 2020;5:126-137. DOI: 10.1302/2058-5241.5.190011

Shoulder MR Imaging and MR Arthrography Techniques: New Advances

MR imaging is the standard diagnostic modality that provides a comprehensive and accurate assessment for both osseous and soft-tissue pathologic conditions of the shoulder. This article discusses standard MR imaging and arthrography protocols used routinely in clinical practice, as well as more innovative sequences and reconstruction techniques, facilitated by the increasing availability of high-field-strength magnets and multichannel phased array surface coils and incorporation of artificial intelligence. These exciting innovations allow for a more detailed and diagnostic imaging assessment, improvements in image quality, and more rapid image acquisition.

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.

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.

Outcomes of Anatomic Total Shoulder Arthroplasty with B2 Glenoids: A Systematic Review

BACKGROUND

Total shoulder arthroplasty remains an effective procedure for shoulder pain relief. Despite the negative effect of abnormal glenoid morphology and specifically retroverted and posteriorly subluxated glenoids, there is no consensus for management of B2 glenoids in total shoulder arthroplasty. The purpose of this study was to compare the outcomes and complication rates for B2 glenoid techniques so as to provide a baseline understanding of the current state of treatment of this pathology.

METHODS

A systematic review evaluating outcomes of total shoulder arthroplasty with biconcave glenoids using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) methodology included searches up to December 31, 2015, of PubMed, Embase, MEDLINE, Cochrane Reviews, and Google Scholar. Nine articles met inclusion and exclusion criteria.

RESULTS

In this study, 239 total shoulder arthroplasties with B2 glenoids with a mean follow-up of 55.5 months (range, 24 to 91 months) were included. The mean patient age was 63.3 years (range, 55.8 to 68.7 years). Asymmetric reaming was performed in 127 glenoids, posterior bone-grafting was included in 53 glenoids, and 34 received an augmented glenoid component to correct glenoid retroversion and bone loss. Overall, the mean Constant and Neer scores improved from preoperative measures. Fifty-eight percent of patients had no loosening, and 42% had some loosening, although not all of these patients were symptomatic. Despite variation in outcome measures hindering treatment approach comparison, the posteriorly augmented glenoid was generally reported to provide better outcomes with few complications. Although posterior glenoid bone-grafting results in acceptable outcomes, it also represents the highest rate of complications. The revision rate was 15.6% for asymmetric reaming, 9.5% for posterior glenoid bone-grafting, and 0% for posteriorly augmented glenoids.

CONCLUSIONS

Surgical treatment of the B2 glenoid remains a challenge to the shoulder surgeon, with worse outcomes and higher complication rates. Longer follow-up, consistent outcome measures, and result stratification based on glenoid type may allow for direct comparison in the future.

LEVEL OF EVIDENCE

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

A novel radiopaque tissue marker for soft tissue localization and in vivo length and area measurements

PURPOSE

The purpose of the study was to describe the characteristics and demonstrate proof-of-concept and clinical use of a barium sulfate infused polypropylene radiopaque tissue marker for soft tissue localization and in vivo measurement of lengths and areas.

METHODS

Marker mechanical properties were evaluated by tensile tests. Biocompatibility was evaluated following 8-12 weeks' implantation in a pig model. Proof-of-concept of marker application was performed in a human cadaveric shoulder model, and methods for CT imaging and measurement of dimensions were established. Lastly, the method of clinical use of the markers was described in one patient undergoing arthroscopic rotator cuff repair (RCR).

RESULTS

The radiopaque markers had a tensile strength of 28 ±4.7 N and were associated with minimal to mild inflammatory tissue reaction similar to polypropylene control. CT-based measurements showed relatively high precisions for lengths (0.66 mm), areas (6.97 mm2), and humeral orientation angles (2.1°) in the cadaveric model, and demonstrated 19 ±3 mm medio-lateral tendon retraction and 227 ±3 mm2 increase in tendon area in the patient during 26 weeks following RCR. No radiographic leaching, calcification or local adverse events were observed.

CONCLUSIONS

The radiopaque tissue marker was biocompatible and had adequate strength for handling and affixation to soft tissues using standard suturing techniques. The marker could be used with low-dose, sequential CT imaging to quantitatively measure rotator cuff tendon retractions with clinically acceptable accuracy. We envision the radiopaque tissue marker to be useful for soft tissue localization and in vivo measurement of tissue and organ dimensions following surgery.

Outcomes of anatomic total shoulder arthroplasty in patients with excessive glenoid retroversion: a case-control study

BACKGROUND

Ideal management of severe glenoid retroversion during anatomic total shoulder arthroplasty (TSA) remains controversial, as previous reports have suggested that severe retroversion may negatively impact clinical outcomes. The purpose of this study was to evaluate the impact of severe glenoid retroversion on clinical and radiographic TSA outcomes using a standard glenoid component, as well as to compare outcomes among patients with less severe retroversion.

METHODS

A case-control study was performed comparing 40 patients treated with TSA with more than 20° of glenoid retroversion preoperatively (average follow-up, 53 months) vs. a matched cohort of 80 patients with less than 20° of retroversion (average follow-up, 49 months). In all patients, the surgical technique, implant design, and postoperative rehabilitation protocol were identical. Patients were matched based on sex, age, indication, and prosthetic size. Comparisons were made regarding patient-reported outcome measures (PROMs), motion, postoperative radiographic loosening, and the presence of medial calcar resorption.

RESULTS

Preoperatively, both groups demonstrated similar PROMs and measured motion, except for preoperative Single Assessment Numeric Evaluation scores and American Shoulder and Elbow Surgeons total scores, which were higher for the severe retroversion group (44.4 vs. 31.3 [P = .012] and 34.9 vs. 29.4 [P = .048], respectively). Postoperative PROMs and motion were also similar between the 2 cohorts. No significant differences were observed for postoperative radiographic findings. Medial calcar resorption was identified in 74 patients (61.7%). Calcar resorption and individual resorption grades were not found to differ significantly.

CONCLUSION

At midterm follow-up, preoperative severe glenoid retroversion does not appear to influence clinical or radiographic outcomes of TSA using a standard glenoid component.

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.

Multilevel glenoid morphology and retroversion assessment in Walch B2 and B3 types

OBJECTIVE

A major factor that impacts the long-term outcome and complication rates of total shoulder arthroplasty is the preoperative posterior glenoid bone loss quantified by glenoid retroversion. The purpose of this study was to assess if glenoid retroversion varies significantly at different glenoid heights in Walch B2 and B3 glenoids.

MATERIALS AND METHODS

Patients with B2 and B3 glenoid types were included following retrospective review of 386 consecutive CT shoulder studies performed for arthroplasty preoperative planning. True axial CT reconstructions were created using a validated technique. Two readers independently measured the glenoid retroversion angles according to the Friedman method using the "intermediate" glenoid at three glenoid heights: 75% (upper), 50% (equator), and 25% (lower). The variances between the three levels for a given patient were calculated.

RESULTS

Twenty-nine B2 and 8 B3 glenoid types were included. There was no significant difference in variance of glenoid version among the three levels in B2 or B3 groups. The mean variance in retroversion degree between equator-lower, upper-equator, and upper-lower glenoid was - 0.4, 0.3, and - 0.2 for B2; and - 0.2, 1.9, and 1.9 for B3 glenoid, respectively. The level of inter-reader agreement was fair to good for variance at equator-lower, and good to excellent for upper-equator and upper-lower glenoid.

CONCLUSIONS

Glenoid version can be accurately measured at any level between 25 and 75% of glenoid height for Walch B2 and B3. We recommend that the glenoid equator be used as the reference to assure consistent and reliable version measurements in this group of patients.

A new geometric model to quantify the area of glenoid bone defect and medialisation of the native joint line in glenohumeral arthritis

PURPOSE

To propose a geometric model to quantify the bone defect and the glenoid medialisation (in millimetres) compared to the native joint line. We also evaluated the reliability of this geometric model.

METHODS

Using two-dimensional CT imaging, we built a hypothetical triangle on the axial scan consisting of the following: side A, length (millimetres) of the glenoid bone; side B, average length (millimetres) of the glenoid in a healthy population; side C, the missing side; and angle α, the retroversion angle calculated using the Friedman method. The resulting triangle represents the bone defect, and its height represents the medialisation of the native joint line. To estimate inter-operator reliability, two physicians (operator 1 and operator 2) took the following measurements: angle α, side A, side C, semi-perimeter, area defect and height.

RESULTS

Forty participants (mean age ± SD 45 ± 10 years, range 26-43 years)-22 women and 18 men-participated in the study. We applied the cosine theorem (Carnot theorem) to calculate side C. After obtaining the three sides, the area of the triangle can be determined. Once the area is known, it is possible to extrapolate the height of the triangle, which corresponds to the loss of vault depth due to the bone defect. With respect to inter-operator reliability, the ICCs for all measurements were > 0.99, exhibiting a very high correlation.

CONCLUSIONS

The proposed geometric model can be used to quantify the glenoid bone deficit and the glenoid medialisation compared to the native joint line, which can be used to improve surgical treatment.

Accuracy of 3-Dimensional Planning, Implant Templating, and Patient-Specific Instrumentation in Anatomic Total Shoulder Arthroplasty

BACKGROUND

Use of 3-dimensional (3D) computed tomography (CT) preoperative planning and patient-specific instrumentation has been demonstrated to improve the accuracy of glenoid implant placement in total shoulder arthroplasty (TSA). The purpose of this study was to compare the accuracy of glenoid implant placement in primary TSA among different types of instrumentation used with the 3D CT preoperative planning.

METHODS

One hundred and seventy-three patients with end-stage glenohumeral arthritis were enrolled in 3 prospective studies evaluating patient-specific instrumentation and 3D preoperative planning. All patients underwent preoperative 3D CT planning to determine optimal glenoid component and guide pin position based on surgeon preference. Patients were placed into 1 of 5 instrument groups used for intraoperative guide pin placement: (1) standard instrumentation, (2) standard instrumentation combined with use of a 3D glenoid bone model containing the guide pin, (3) use of the 3D glenoid bone model combined with single-use patient-specific instrumentation, (4) use of the 3D glenoid bone model combined with reusable patient-specific instrumentation, and (5) use of reusable patient-specific instrumentation with an adjustable, reusable base. Postoperatively, all patients underwent 3D CT to compare actual versus planned glenoid component position. Deviation from the plan (in terms of orientation and location) was compared across groups on the basis of absolute differences and outlier analysis. Univariable and multivariable comparisons were performed. As the initial analyses showed no significant differences in preoperative factors or in deviation from the plan between Groups 1 and 2 or between Groups 4 and 5 across studies, the final analysis was across 3 major treatment groups: standard instrumentation (Groups 1 and 2), single-use patient-specific instrumentation (Group 3), and reusable patient-specific instrumentation (Groups 4 and 5).

RESULTS

In nearly all comparisons, there were no significant differences in the deviation from the plan (absolute differences or outlier frequency) for glenoid implant orientation or location across the 3 major treatment groups.

CONCLUSIONS

This study did not demonstrate that any type of patient-specific instrumentation resulted in consistent differences in accuracy of glenoid implant placement in primary TSA with 3D CT preoperative planning. Surgeons have multiple patient-specific instrumentation options available for improving accuracy of glenoid implant placement when compared with 2D imaging without patient-specific instrumentation.

LEVEL OF EVIDENCE

Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

Different acromial roof morphology in concentric and eccentric osteoarthritis of the shoulder: a multiplane reconstruction analysis of 105 shoulder computed tomography scans

BACKGROUND

The pathomechanisms of eccentric osteoarthritis of the shoulder remain unclear. Although there is increasing evidence of bony differences between shoulders with rotator cuff tears and osteoarthritis, analogous differences have not been identified for primary concentric and eccentric osteoarthritis. This study examined the shape and orientation of the acromial roof as a potential risk factor for the development of posterior glenoid wear.

METHODS

We analyzed computed tomography images of 105 shoulders with primary osteoarthritis. Based on the classification of Walch, 45 shoulders had concentric osteoarthritis (Walch A) and 60 shoulders were affected by eccentric osteoarthritis (Walch B; EOA). A comparison of acromial morphology was performed in a multiplanar reconstruction analysis of computed tomography scans.

RESULTS

Acromial shape: Acromial length, width, and area were not significantly different. Acromial roof orientation: The acromial roof in EOA was an average of 5° flatter (sagittal tilt; P < .01) and 5° more downward tilted (coronal tilt; P < .01). There was no difference in axial rotation (axial tilt; P = .47). Anteroposterior glenoid coverage: The glenoid in EOA was covered an average of 4° less posteriorly (P = .01) and 4° more anteriorly (P = .04). No differences were shown for overall glenoid coverage.

CONCLUSIONS

The acromial roof could play a role in the pathogenesis of EOA. Less posterior support due to a flatter acromion with less posterior glenoid coverage could contribute to static posterior subluxation of the humeral head and posterior glenoid wear. Further biomechanical investigations are needed to confirm these findings.

A statistical shape model to predict the premorbid glenoid cavity

BACKGROUND

This study proposes a method for inferring the premorbid glenoid shape and orientation of scapulae affected by glenohumeral osteoarthritis (OA) to inform restorative surgery.

METHODS

A statistical shape model (SSM) built from 64 healthy scapulae was used to reconstruct the premorbid glenoid shape based on anatomic features that are considered unaffected by OA. First, the method was validated on healthy scapulae by quantifying the accuracy of the predicted shape in terms of surface distance, glenoid version, and inclination. The SSM-based reconstruction was then applied to 30 OA scapulae. Glenoid version and inclination were measured fully automatically and compared between the original OA glenoids, SSM-based glenoid reconstructions, and healthy scapulae.

RESULTS

Validation on healthy scapulae showed a root-mean-square surface distance between original and predicted glenoids of 1.0 ± 0.2 mm. The prediction error was 2.3° ± 1.8° for glenoid version and 2.1° ± 2.0° for inclination. When applied to an OA dataset, SSM-based reconstruction restored average glenoid version and inclination to values similar to the healthy situation. No differences were observed between average orientation values measured on SSM-based reconstructed and healthy scapulae (P ≥ .10). However, the average orientation of the reconstructed premorbid glenoid differed from the average orientation of OA glenoids for Walch classes A1 (version) and B2 (version, inclination, and medialization).

CONCLUSION

The proposed SSM can predict the premorbid glenoid cavity of healthy scapulae with millimeter accuracy. This technique has the potential to reconstruct the premorbid glenoid cavity shape, as it was prior to OA, and thus to guide the positioning of glenoid implants in total shoulder arthroplasty.

Relationship of Intraoperative Anatomical Landmarks, the Scapular Plane and the Perpendicular Plane with Glenoid for Central Guide Insertion during Shoulder Arthroplasty

Background

This study was undertaken to evaluate the positional relationship between planes of the glenoid component (the scapular plane and the perpendicular plane to the glenoid) and its surrounding structures.

Methods

Computed tomography (CT) images of both shoulders of 100 patients were evaluated using the 3-dimensional CT reconstruction program (Aquarius^®; TeraRecon). We determined the most lateral scapular bony structure of the scapular plane and measured the shortest distance between the anterolateral corner of the acromion and the scapular plane. The distance between the scapular plane and the midpoint of the line connecting the posterolateral corner of acromion and the anterior tip of the coracoid process (fulcrum axis) was also evaluated. The perpendicular plane was then adjusted to the glenoid and the same values were re-assessed.

Results

The acromion was the most lateral scapular structure of scapular plane and perpendicular plane to the glenoid. The average distance from the anterolateral corner of the acromion to the scapular plane was 10.44 ± 5.11 mm, and to the plane perpendicular to the glenoid was 9.55 ± 5.13 mm. The midpoint of fulcrum axis was positioned towards the acromion and was measured at 3.90 ± 3.21 mm from the scapular plane and at 3.84 ± 3.17 mm from the perpendicular plane to the glenoid.

Conclusions

Our data indicates that the relationship between the perpendicular plane to the glenoid plane and its surrounding structures is reliable and can be used as guidelines during glenoid component insertion (level of evidence: Level IV, case series, treatment study).

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.

The Association Between Rotator Cuff Muscle Fatty Infiltration and Glenoid Morphology in Glenohumeral Osteoarthritis

BACKGROUND

Glenoid morphology and rotator cuff muscle quality are important anatomic factors that can impact longevity of the glenoid component following total shoulder arthroplasty (TSA). We hypothesized that rotator cuff muscle fatty infiltration is associated with increased pathologic glenoid bone loss in glenohumeral osteoarthritis (OA).

METHODS

We retrospectively reviewed 190 preoperative computed tomography (CT) scans of 175 patients (mean age, 66 years; range, 44 to 90 years) who underwent TSA for the treatment of primary glenohumeral OA. Two-dimensional orthogonal CT images were reformatted in the plane of the scapula from 3-dimensional images. Pathologic joint-line medialization was defined with use of the glenoid vault model. Pathologic glenoid version was measured directly. Glenoid morphology was graded according to a modified Walch classification (subtypes A1, A2, B1, B2, B3, C1, and C2). Rotator cuff muscle fatty infiltration was assessed and assigned a Goutallier score on the sagittal CT slice just medial to the spinoglenoid notch for each muscle.

RESULTS

There was a significant difference in the Goutallier score for the supraspinatus, infraspinatus, and teres minor muscles between Walch subtypes (p ≤ 0.05). High-grade posterior rotator cuff muscle fatty infiltration was present in 55% (21) of 38 B3 glenoids compared with 8% (3) of 39 A1 glenoids. Increasing joint-line medialization was associated with increasing fatty infiltration of all rotator cuff muscles (p ≤ 0.05). Higher fatty infiltration of the infraspinatus, teres minor, and combined posterior rotator cuff muscles was associated with increasing glenoid retroversion (p ≤ 0.05). After controlling for joint-line medialization and retroversion, B3 glenoids were more likely to have fatty infiltration of the supraspinatus and infraspinatus muscles than B2 glenoids were.

CONCLUSIONS

High-grade rotator cuff muscle fatty infiltration is associated with B3 glenoids, increased pathologic glenoid retroversion, and increased joint-line medialization. Additional studies are needed to determine the causal relationship between these muscle changes and glenoid wear, whether these muscle changes independently affect clinical and radiographic outcomes in anatomic TSA, and whether fatty infiltration can improve postoperatively with correction of pathologic version and/or joint-line restoration.

CLINICAL RELEVANCE

This study investigates the association between different patterns of glenoid bone loss and rotator cuff muscle fatty infiltration. Both factors have been shown to affect clinical outcome following TSA.

The Normal 3D Gleno-humeral Relationship and Anatomy of the Glenoid Planes

Knowledge of the normal and pathological three-dimensional (3D) gleno-humeral relationship is imperative when planning and performing a total shoulder arthroplasty. Currently, two-dimensional (2D) parameters are used to describe this anatomy and despite the fact that these 2D measurements have a wide distribution in the normal population, they are commonly accepted. This broad distribution can be explained on one hand by anatomical factors and on the other hand, by positional errors. A 3D CT-scan reconstruction and evaluation can overcome this shortcoming and can be used to determine more accurately the surgical planes on the normal and pathological shoulder joint. There is, however, no consensus on which references should be used when studying this 3D relationship. This thesis describes the normal 3D gleno-humeral relationship and the best glenoid plane to use in surgery, based on 3D CT-scan. Furthermore, a glenoid aiming device that can be of surgical help in the reconstruction of the normal glenoid anatomy was developed based on these measurements.

Progression of Glenoid Morphology in Glenohumeral Osteoarthritis

BACKGROUND

Walch defined the pathologic characteristics of glenohumeral osteoarthritis on the basis of patterns of glenoid morphology and humeral head subluxation. However, it is unclear how pathologic changes evolve over time. The purpose of this study was to determine whether there are common patterns of pathologic progression based on the Walch classification in primary glenohumeral osteoarthritis and if glenoid bone-loss patterns correlate with rotator cuff fatty infiltration.

METHODS

A retrospective chart review identified 65 shoulders with glenohumeral osteoarthritis for which at least 2 computed tomography (CT) scans had been performed at least 24 months apart. The CT scans were classified using a modification of the Walch classification. The amount and location of glenoid bone loss were measured using a vault model, and rotator cuff fatty infiltration was calculated as a percentage of cross-sectional muscle area.

RESULTS

The initial CT scans showed 42 A-type glenoids and 23 B-type glenoids. CT scans made at an average (and standard deviation) of 74 ± 32 months after the initial scans showed that only 8 of the 42 A1 glenoids had evidence of pathologic progression (5 to A2 type and 3 to B type) whereas 17 of 19 B1 glenoids had progressed (15 to B2 and 2 to B3); this difference was significant on univariate and multivariate analysis (p < 0.001). The odds of joint line medialization occurring were 8.1 times higher (95% confidence interval [CI]: 2.1 to 31.4) for B-type glenoids than for A-type glenoids. Among the glenoids that underwent medialization, those classified as B-type showed more medialization over time (estimated change, 0.70 mm/year; p = 0.036), whereas no significant relationship between medialization and time was observed for A-type glenoids (estimated change, 0.013 mm/year; p = 0.95). The median percent fatty infiltration in the infraspinatus muscle was higher in association with B-type glenoids than in association with A-type glenoids on both the initial (14% versus 7%; p < 0.001) and the final follow-up (16% versus 10%; p = 0.003) CT scans.

CONCLUSIONS

Asymmetric bone loss rarely develops in A1 glenoids, whereas initial posterior translation of the humeral head (B1 glenoids) may be associated with subsequent development and progression of posterior glenoid bone loss over time. Differences in fatty infiltration of the posterior aspect of the rotator cuff were seen between A-type and B-type glenoids, but the clinical relevance of this finding is currently unknown.

LEVEL OF EVIDENCE

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

Automated Three-Dimensional Measurement of Glenoid Version and Inclination in Arthritic Shoulders

BACKGROUND

Preoperative computed tomography (CT) measurements of glenoid version and inclination are recommended for planning glenoid implantation in shoulder arthroplasty. However, current manual or semi-automated 2-dimensional (2D) and 3-dimensional (3D) methods are user-dependent and time-consuming. We assessed whether the use of a 3D automated method is accurate and reliable to measure glenoid version and inclination in osteoarthritic shoulders.

METHODS

CT scans of osteoarthritic shoulders of 60 patients scheduled for shoulder arthroplasty were obtained. Automated, surgeon-operated, image analysis software (Glenosys; Imascap) was developed to measure glenoid version and inclination. The anatomic scapular reference planes were defined as the mean of the peripheral points of the scapular body as well as the plane perpendicular to it, passing along the supraspinatus fossa line. Measurements were compared with those obtained using previously described manual or semi-automated methods, including the Friedman version angle on 2D CTs, Friedman method on 3D multiplanar reconstructions (corrected Friedman method), Ganapathi-Iannotti and Lewis-Armstrong methods on 3D volumetric reconstructions (for glenoid version), and Maurer method (for glenoid inclination).The mean differences (and standard deviation) and the concordance correlation coefficients (CCCs) were calculated. Two orthopaedic surgeons independently examined the images for the interobserver analysis, with one of them measuring them twice more for the intraobserver analysis; interobserver and intraobserver reliability was calculated using the intraclass correlation coefficients (ICCs).

RESULTS

The mean difference in the Glenosys glenoid version measurement was 2.0° ± 4.5° (CCC = 0.93) compared with the Friedman method, 2.5° ± 3.2° (CCC = 0.95) compared with the corrected Friedman method, 1.5° ± 4.5° (CCC = 0.94) compared with the Ganapathi-Iannotti method, and 1.8° ± 3.8° (CCC = 0.95) compared with the Lewis-Armstrong method. There was a mean difference of 0.2° ± 4.7° (CCC = 0.78) between the inclination measurements made with the Glenosys and Maurer methods. The difference between the overall average 2D and 3D measurements was not significant (p = 0.45).

CONCLUSIONS

Use of fully automated software for 3D measurement of glenoid version and inclination in arthritic shoulders is reliable and accurate, showing excellent correlation with previously described manual or semi-automated methods.

CLINICAL RELEVANCE

The use of automated surgeon-operated image analysis software to evaluate 3D glenoid anatomy eliminates interobserver and intraobserver discrepancies, improves the accuracy of preoperative planning for shoulder replacement, and offers a potential gain of time for the surgeon.