The influence of gravity on the unstable elbow

Abstract

Safely permitting early range of motion after a destabilizing injury to the elbow is believed to optimize return of function. However, the range-of-motion exercises must be balanced against the risk of re-dislocation or subluxation. The goal of this study was to describe the position of the upper limb that permitted the greatest motion while minimizing the risk of re-dislocation or subluxation. Seven cadaveric elbows were affixed with a 3-dimensional motion capture system. Ulnohumeral distraction was recorded at flexion angles from 10° to 90° for intact, approach only (sham procedure), and LCL-sectioned. Ulnohumeral separation was recorded in 3 distinct positions of the upper limb that are frequently used in a clinical setting: 1) trunk seated upright with arm at the side; 2) trunk seated upright with elbow in hinged-brace; and 3) trunk supine with shoulder flexed and internally rotated - "gravity-assisted overhead motion" protocol. A significant ulnohumeral distraction difference was found between the supine and the upright protocols. Upon direct comparison, 104% more displacement occurred across the ulnohumeral joint in the upright LCL-sectioned condition compared to the supine LCL-sectioned condition (P = .001). The greatest ulnohumeral distraction occurred in the seated upright range of motion with a hinged elbow brace (range, 2.5-5.6 mm). The overhead motion protocol is a safe protocol for unstable elbows. The supine position results in the least amount of ulnohumeral distraction across flexion angles from 10° to 90°. The upright protocols, especially with the hinged elbow brace, exhibited ulnohumeral distraction that may result in dislocation.