Ultrasound assessment of the posterolateral elbow ulnohumeral gap in normal subjects with and without posterolateral drawer testing.

BACKGROUND

Posterolateral rotator instability (PLRI) is the most common pattern of recurrent elbow instability, and current imaging to aid PLRI diagnosis is limited. Thus, we sought to define use of ultrasound (US) to determine normal lateral ulnohumeral joint measurements, with and without posterolateral drawer testing to provide an insight into how US may aid diagnosis.

METHODS

Sixty elbows were evaluated in thirty healthy volunteers. The lateral ulnohumeral gap (LUHG) was measured with US in the resting position while the posterolateral drawer stress test maneuver was applied. Joint laxity was calculated as the difference between maximum stress and average rest measurements. Two independent readers assessed each elbow with comparison performed between stress and rest positions.

RESULTS

Differences in the LUHG were evident between stress and rest conditions (reader 1:  < .0001 and reader 2:  = .0002). At rest, median LUHG values were 2.31 mm and 2.05 mm for readers 1 and 2 respectively, while at stress 2.88 mm and 2.9 mm for readers 1 and 2. Median joint laxity was 0.8 mm for reader 1 and 1.1 mm for reader 2. Pearson correlation was r = 0.457 (absolute intraclass correlation coefficient [ICC] = 0.608) while under stress and r = 0.308 (absolute intraclass correlation coefficient [ICC] = 0.417) at rest. Median joint laxity demonstrated a Pearson correlation of r = 0.161 and absolute intraclass correlation coefficient [ICC] = 0.252.

CONCLUSIONS

This study demonstrates a dynamic US assessment for PLRI, which aimed to assess the usefulness and feasibility of a laxity measurement after the application of a posterolateral drawer stress maneuver in a healthy population. Although establishing concordance between readers in measuring an LUHG under stress, the utility of a laxity measurement alone is not clear as correlation of measurements is not excellent; hence, an upper limit of normal for the ulnohumeral gap under stress may be more useful. Further evaluation of this technique is required in patients with PLRI.