Three-dimensional kinematics of shoulder laxity examination and the relationship to clinical interpretation

Justin L Staker,Amy E Lelwica,Paula M Ludewig,Jonathan P Braman

doi:10.1080/23335432.2017.1372217

Justin L Staker, Amy E Lelwica + Show 2 more

Open Access

https://doi.org/10.1080/23335432.2017.1372217

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Abstract

Understanding clinical test kinematics improves utility of exam techniques. The purposes of this study were as follows: (1) determine inter-examiner repeatability of translation magnitude for the Anterior/Posterior Drawer and Sulcus shoulder laxity tests; (2) describe the relationships between glenohumeral joint translations and subjective grades for each laxity test; and (3) describe the relationship of overall glenohumeral joint laxity to a composite subjective score from the three laxity tests. Eleven subjects with shoulder symptomology were examined with three laxity tests. Motion was tracked with electromagnetic sensors affixed to the humerus and scapula via transcortical pins. ICCs were calculated to determine repeatability of translation magnitudes between two examiners for each test. Descriptive statistics and regression analyses were performed for comparisons of single laxity test grades with translation magnitudes and for composite subjective laxity scores and overall translation across all three tests. Inter-examiner ICCs regarding kinematic repeatability were 0.87 for Anterior Drawer, 0.84 for the Sulcus test, and not calculable for the Posterior Drawer. No linear relationships between subjective grades of individual tests and translation magnitudes were found. The relationship of overall translation with the composite subjective score from all laxity tests was r2 = 0.75 (r = 0.86). Clinicians from different disciplines are capable of imparting similar translations during laxity tests. Single-test subjective laxity grades demonstrate large ranges of translation between subjects for the same grade. By combining results of three laxity tests, clinicians are capable of identifying the level of overall shoulder joint laxity in patients.

Highlights

Shoulder pain is the second most prevalent musculoskeletal complaint with a 21% point prevalence (Picavet and Schouten 2003)
The translation magnitude for each subject, test, and examiner has been provided as supplementary material (Supplementary Table 1)
Paired t-tests demonstrated significantly less mean translation by EX1 for the Anterior Drawer test compared to EX2 (Anterior Drawer 0.9 mm, p < 0.05) and significantly more translation by EX1 for the Posterior Drawer test (2.2 mm, p < 0.05)

Summary

Introduction

Shoulder pain is the second most prevalent musculoskeletal complaint with a 21% point prevalence (Picavet and Schouten 2003). Most clinical shoulder tests are designed to elicit a sign or symptom as a result of tissue being placed under stress by the test position. Unlike the majority of clinical tests, Anterior/ Posterior Drawer, and Sulcus tests are developed to quantify the magnitude of glenohumeral translations, or joint laxity, through subjective grading (Neer and Foster 1980; Gerber and Ganz 1984; Hawkins and Mohtadi 1991). Increased joint laxity is thought to lead to excessive and deleterious glenohumeral translations during functional movements (Neer and Foster 1980; Matsen et al 2006; Longo et al 2015). Construct validation of these laxity tests should assess any relationship of subjective grades to the amount of humeral head translation during testing

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