The Ellipse modification of the Friedman method for measuring glenoid version

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.

Glenoid Version Assessment When the CT Field of View Does Not Permit the Friedman Method: The Robertson Method

Background:

To improve spatial resolution, current clinical shoulder cross-sectional imaging studies reduce the field of view of the shoulder, excluding the medial scapula border and preventing glenoid version measurement according to the Friedman method.

Purpose:

To evaluate a method to accurately and reliably measure glenoid version on cross-sectional shoulder images when the medial scapula border is not included in the field of view, and to establish measurements equivalent to the Friedman method.

Study Design:

Controlled laboratory study.

Methods:

Sixty-five scapulae underwent computed tomography (CT) scanning with an optimal shoulder CT-positioning protocol. Glenoid version was measured on CT images of the full scapula using the Friedman method. We developed a measurement method (named the Robertson method) based on the glenoid vault version from partial scapula images, with a correction angle subtracted from the articular-surface-glenoid vault measurement. Comparison with the Friedman method defined the accuracy of the Robertson method. Three observers tested inter- and intraobserver reliability of the Robertson method. Accuracy was statistically evaluated with t tests and reliability with the intraclass correlation coefficient (ICC).

Results:

The statistical distribution of glenoid version was similar to published data,–0.5° ± 3° [mean ± SD]. The initial measurement using the Robertson method resulted in a more retroverted angle compared with the Friedman method, and a correction angle of 7° was then applied. After this adjustment, the difference between the 2 methods was nonsignificant (0.1° ± 4°; P > .65). Reliability of the Robertson method was excellent, as the interrater ICC was 0.77, the standard error of measurement (SEM) was 1.1° with P < .001. The intrarater ICC ranged between 0.84 and 0.92, the SEM ranged between 0.9° and 1.2° with P < .01.

Conclusion:

A validated glenoid version measurement method is now available for current clinical shoulder CT protocols that reliably create Friedman-equivalent values.

Clinical Relevance:

Friedman-equivalent values may be made from common clinical CTs of the shoulder and compared with prior and future Friedman measurements of the scapula.

Midterm clinical and radiologic survivorship of a stemless total shoulder arthroplasty

AIM

The aim of this study was to evaluate the clinical and radiologic outcomes of stemless total shoulder arthroplasty (TSA) in patients with glenohumeral arthritis.

PATIENTS AND METHODS

This is a retrospective case series of all patients who underwent a TSA with Affinis Short prosthesis during the period 2010-2017. Seventy-two TSAs were performed within our unit, in 62 patients (45 females and 17 males), with 10 patients having bilateral TSAs with this prosthesis. The mean follow-up was 3.9 years (2-8.7 years). Patients were evaluated clinically with the Oxford Shoulder Score, range of movement assessment, and a numerical patient satisfaction score. Follow-up radiographs were evaluated by 2 reviewers assessing for lucency and assigned a Lazarus grade.

RESULTS

Six patients were lost to follow-up prior to their 2-year review. At last follow-up, the mean forward elevation was 157° (80°-180°), abduction was 150° (60°-180°), and external rotation was 39° (20°-60°). The mode internal rotation was to the lumbar spine, with 95% of patients achieving internal rotation to L5 or higher. The mean Oxford Shoulder Score was 45 (18-48). The mean patient satisfaction score was 4.93/5. No humeral lucencies were observed. Sixty-four percent (n=47) of the glenoids were Lazarus grade 0, showing no evidence of radiolucency. The remaining patients were Lazarus grade 1-3, although none were progressive and all patients were asymptomatic. No patients were revised for aseptic loosening. Four patients underwent revision: 1 for infection, 1 for heterotrophic ossification and stiffness, and 2 for rotator cuff failure.

CONCLUSION

Midterm follow-up results indicate good clinical and radiologic survivorship for this stemless TSA. Our findings suggest good patient function and satisfaction, and no patients have required revision for aseptic loosening. Further follow-up is required to determine long-term survivorship.

A novel method for localization of the maximum glenoid bone defect during reverse shoulder arthroplasty

Background

Management of glenoid bone defects during reverse shoulder arthroplasty remains a challenge. The aim of our study was to preoperatively localize the maximal depth of glenoid bone defects in relation to glenoid reaming.

Methods

Thirty preoperative shoulder computed tomography scans were collected. Three assessors created standardized surgical plans, using 3-dimensional (3D) computed tomography–based Blueprint planning software in which the reaming axis was held constant at zero degrees of version and inclination. Each plan resulted in a 2-dimensional (2D) image of the reamer’s contact on the glenoid and a corresponding 3D representation of the glenoid bone defect. The position of the maximum glenoid defect was localized on both the 2D and 3D images. Descriptive statistics were calculated. The correlation between angles from 2D and 3D images was assessed, and intraclass correlation was used to assess inter-rater and intrarater reliability.

Results

Twenty-eight patients were included. The overall mean difference between 2D and 3D angles was 5.4° (standard deviation 5.2°). The correlation between 2D and 3D angles was almost perfect. Intraclass correlation results demonstrated near-perfect agreement. The maximal glenoid defect was within 5% of a circle (or +/- 9°) from perpendicular to the high-side ream line in 85.1% of comparisons and was within 10% of a circle in 97.6% of comparisons.

Conclusion

Using Blueprint planning software, we have demonstrated with almost perfect agreement among 3 assessors that when the reaming axis is held constant, the maximum glenoid bone defect is reliably located perpendicular to the glenoid ream line.