Background
& Purpose:
Clinical tests used to diagnose SLAP lesions have debatable diagnostic accuracy. One of the factors that can significantly influence the test accuracy is the deltoid muscle activity during the tests. The author developed a testing protocol that involves positioning the arm in a novel way to minimize the activity of deltoid while recreating the load on the biceps anchor. Diagnostic study was undertaken to establish the diagnostic accuracy of this novel test (RK Test).
Study design:
A prospective study was undertaken on subsequent patients presenting with suspected SLAP injury to the outpatient sports medicine clinic of a tertiary care teaching hospital.
Methodology
A total of 38 individuals with suspected SLAP injury were subjected to RK test by the author. There were 15 patients who tested positive for RK test and 23 who tested negative for the test. Patients with a positive RK test were subjected to an MRI evaluation of the shoulder, while patients in the negative group were given the option of opting out of the MRI. All patients who tested positive at initial visit were subjected to repeat assessment with RK test performed with surface EMG to document deltoid muscle activity during the test.
Result:
12 of the 15 patients who had a positive RK test showed MRI evidence of a SLAP lesion, with 10 of them underwent arthroscopic SLAP repair. 2 patients had partial cuff tear. Only 14 of the 23 RK Test negative patients received a shoulder MRI, and 3 of patients had MRI evidence of slap and underwent surgical SLAP repair. All patients had minimal or no activity of deltoid when test position was achieved as described in the protocol. Diagnostic accuracy of the test was analysed using standardized statistical measures of sensitivity, specificity, Positive Predictive value, Negative Predictive value, and Positive and Negative likelihood ratios. Statistical analysis demonstrated that RK test had a sensitivity of 76.92 %, a specificity of 84.61 %, a PPV of 83.33 %, a NPV of 78.57 %, a positive likelihood ratio of 4.94, and a negative likelihood ratio of 0.27.
Conclusion
The results of the study indicate that, compared to the existing clinical tests for SLAP injuries, the RK test showed better diagnostic accuracy. We conclude that this is due to the elimination of the deltoid activity during the testing that was achieved by the novel positioning of the arm during the application of biceps load during the testing.