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

Research output: Contribution to journalArticlepeer-review

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.

Original languageEnglish
JournalOrthopaedic Journal of Sports Medicine
Volume9
Issue number11
DOIs
StatePublished - 2021

Keywords

  • biomechanics
  • diagnostic ultrasound
  • elbow
  • lateral collateral ligament
  • varus laxity

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