Arthroscopic localization of the ulnar nerve behind the medial capsule is unreliable

Abstract

Purpose: Ulnar nerve injury is the most common neurologic complication of elbow arthroscopy. The purpose of this cadaveric study was to quantify the ability of surgeons to locate the ulnar nerve behind the posteromedial capsule during elbow arthroscopy using sole arthroscopic vision.

Methods: Twenty-one surgeons were asked to pin the ulnar nerve at the medial gutter and the posteromedial compartment using arthroscopic visualization of the medial capsule only. Pinning of the ulnar nerve was performed from extra-articular. Then, the cadaveric specimens were dissected and the shortest distances between the pins and ulnar nerve measured.

Results: Median pin-to-nerve distances at the medial gutter and posteromedial compartment were 0 mm (interquartile range [IQR], 0-3 mm) and 2 mm (IQR, 0-6 mm), respectively. The ulnar nerve was pinned by 11/21 surgeons (52%) at the medial gutter, and 7/21 surgeons (33%) at the posteromedial compartment. Three of 21 surgeons (14%) pinned the ulnar nerve at both the medial gutter and the posteromedial compartment. Surgeon's experience and operation volume did not affect these outcomes (P > .05).

Conclusions: Surgeons' ability to locate the ulnar nerve behind the posteromedial capsule using sole arthroscopic visualization, without external palpation, is poor. We recommend to proceed carefully when performing arthroscopic procedures in the posteromedial elbow, and identify and mobilize the ulnar nerve prior to any posteromedial capsular procedures.

Keywords: Elbow; arthroscopy; complication; nerve injury; prevention; ulnar nerve.

Figure 1

Schematic representation of the elbow, the ulnar nerve and elbow capsule with the elbow positioned in approximately 90° flexion as is common during elbow arthroscopy from both a posterior and medial view. The green- and red-circumscribed areas mark the elbow capsule at the medial gutter and posteromedial compartment, respectively. A needle is shown hitting the ulnar nerve in both areas. The direct posterior portal (A) and proximal posterolateral portal (B) are provided as reference.

Figure 2

Arthroscopic view of the medial compartment via a direct posterior portal in a right-sided elbow after an attempt to pin the ulnar nerve at the medial gutter (A) and the posteromedial compartment (B) using a needle from the outside-in. The asterisk (∗) marks the tip of the olecranon

Figure 3

The upper 2 circle diagrams represent the proportions of surgeons who transfixed the ulnar nerve at the medial gutter and posteromedial compartment, respectively. The lower circle diagram shows the proportion of surgeons who transfixed the ulnar nerve at both locations.

Figure 4

This image shows a left-sided flexed elbow after identification and mobilization of the ulnar nerve via an open medial approach.