Shoulder
Relationship of individual scapular anatomy and degenerative rotator cuff tears

https://doi.org/10.1016/j.jse.2013.11.008Get rights and content

Background

The etiology of rotator cuff disease is age related, as documented by prevalence data. Despite conflicting results, growing evidence suggests that distinct scapular morphologies may accelerate the underlying degenerative process. The purpose of the present study was to evaluate the predictive power of 5 commonly used radiologic parameters of scapular morphology to discriminate between patients with intact rotator cuff tendons and those with torn rotator cuff tendons.

Methods

A pre hoc power analysis was performed to determine the sample size. Two independent readers measured the acromion index, lateral acromion angle, and critical shoulder angle on standardized anteroposterior radiographs. In addition, the acromial morphology according to Bigliani and the acromial slope were determined on true outlet views. Measurements were performed in 51 consecutive patients with documented degenerative rotator cuff tears and in an age- and sex-matched control group of 51 patients with intact rotator cuff tendons. Receiver operating characteristic analyses were performed to determine cutoff values and to assess the sensitivity and specificity of each parameter.

Results

Patients with degenerative rotator cuff tears demonstrated significantly higher acromion indices, smaller lateral acromion angles, and larger critical shoulder angles than patients with intact rotator cuffs. However, no difference was found between the acromial morphology according to Bigliani and the acromial slope. With an area under the receiver operating characteristic curve of 0.855 and an odds ratio of 10.8, the critical shoulder angle represented the strongest predictor for the presence of a rotator cuff tear.

Conclusion

The acromion index, lateral acromion angle, and critical shoulder angle accurately predict the presence of degenerative rotator cuff tears.

Section snippets

Patient selection

On the basis of data from previously published series, pre hoc power analysis was performed for each of the outcome measures.1, 2, 3, 9, 11, 12, 18, 23 This analysis determined that for a significance level (type I error) of 5%, a sample size of 51 patients in each group was sufficient to provide a desired power of 95%.

The RCT group consisted of 51 consecutive patients who underwent arthroscopic rotator cuff surgery between January 2012 and October 2012 for a degenerative full-thickness tear

Results

The data for all parameters (median and interquartile range) are summarized in Table I.

ICCs were good to excellent for all parameters studied, with an ICCAI and ICCCSA of 0.98, ICCLAA of 0.94, ICCBigliani of 0.79, and ICCAS of 0.95.

The mean AI of the control and RCT groups was 0.66 (SD, 0.06; range, 0.53-0.79) and 0.75 (SD, 0.06; range, 0.63-0.87), respectively (P < .001). The mean LAA was 86° (SD, 7.7; range, 72°-103°) in the control group and 80° (SD, 6.3; range, 66°-93°) in the RCT group.

Discussion

The influence of individual scapular morphology on the pathogenesis of RCTs remains controversial. Although some authors place great importance on anatomic variants, particularly those of the acromion, other authors have suggested that these changes are the result of rather than the cause of degenerative rotator cuff disease.17, 19, 21, 24

Since the introduction of the AI by Nyffeler in 2006, his concept was strengthened by the contribution of several authors.2, 9, 11, 13, 18, 23, 25 In 2007,

Conclusion

This study confirms the previously reported association of the AI, LAA, and CSA with the occurrence of degenerative RCTs. Of all the assessed parameters, the CSA allowed the most accurate prediction of a patient's individual risk of experiencing a RCT.

In contrast to these findings, neither the relationship between rotator cuff disease and different types of the acromion morphology according to Bigliani and Morrison nor the association of RCTs with flattened acromial slopes could be confirmed.

Disclaimer

The authors, their immediate families, and any research foundation with which they are affiliated did not receive any financial payments or other benefits from any commercial entity related to the subject of this article.

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    Funding: This was an internally financed study. There were no external funding sources.

    IRB: This study was conducted at the Balgrist University Hospital, Zürich, according to medical-ethical guidelines after informed consent was obtained from all of the individuals studied for retrospective data analysis.

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