Ultrasonographic Measurement of Elbow Varus Laxity With a Sequential Injury Model of the Lateral Collateral Ligament-Capsular Complex

Jae-Man Kwak; Dani Rotman; Jorge Rojas Lievano; James S Fitzsimmons; Shawn W O'Driscoll

doi:10.1177/23259671211048941

Ultrasonographic Measurement of Elbow Varus Laxity With a Sequential Injury Model of the Lateral Collateral Ligament-Capsular Complex

Orthop J Sports Med. 2021 Nov 10;9(11):23259671211048941. doi: 10.1177/23259671211048941. eCollection 2021 Nov.

Authors

Jae-Man Kwak^{1

2}, Dani Rotman^{1

3}, Jorge Rojas Lievano¹, James S Fitzsimmons¹, Shawn W O'Driscoll¹

Affiliations

¹ Department of Orthopedic Surgery, Mayo Clinic, Rochester, Minnesota, USA.
² Department of Orthopedic Surgery, Uijeongbu Eulji Medical Center, College of Medicine, Eulji University, Uijeongbu, Republic of Korea.
³ Division of Orthopaedic Surgery, Tel Aviv Sourasky Medical Center, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.

Abstract

Background: There is no consensus how to determine the varus laxity due to the LCL injury using the ultrasonography. There is a risk of lateral collateral ligament injury during or after arthroscopic extensor carpi radialis brevis release for tennis elbow. The equator of the radial head has been suggested as a landmark for the safe zone to not increase this risk; however, the safe zone from the intra-articular space has not been established.

Hypothesis: Increased elbow varus laxity due to lateral collateral ligament-capsular complex (LCL-cc) injury could be assessed reliably via ultrasound.

Study design: Descriptive laboratory study.

Methods: Eight cadaveric elbows were evaluated using a custom-made machine allowing passive elbow flexion under gravity varus stress. The radiocapitellar joint (RCJ) space was measured via ultrasound at 30° and 90° of flexion during 4 stages: intact elbow (stage 0), release of the anterior one-third of the LCL-cc (stage 1), release of the anterior two-thirds (stage 2), and release of the entire LCL-cc (stage 3). Two observers conducted the measurements separately, and the mean RCJ space in the 3 LCL-cc injury models (stages 1-3) at both flexion angles was compared with that of the intact elbow (stage 0). We also compared the measurements at 30° versus 90° of flexion.

Results: At 30° of elbow flexion, the RCJ space increased 2 mm between stages 0 and 2 (95% confidence interval [CI], 1-3 mm; P < .01) and 4 mm between stages 0 and 3 (95% CI, 2-5 mm; P < .01). At 90° of elbow flexion, the RCJ space increased 1 mm between stages 0 and 2 (95% CI, 1-2 mm; P < .01) and 2 mm between stages 0 and 3 (95% CI, 2-3 mm; P < .01).

Conclusion: Elbow varus laxity under gravity stress can be reliably assessed via ultrasound by measuring the RCJ space.

Clinical relevance: Because ultrasonographic measurement of the RCJ space can distinguish the increasing varus laxity seen with release of two-thirds or more of the LCL-cc, the anterior one-third of the LCL-cc, based on the diameter of the radial head, can be considered the safe zone in arthroscopic extensor carpi radialis brevis release for tennis elbow.

Keywords: biomechanics; diagnostic ultrasound; elbow; lateral collateral ligament; varus laxity.