Supracondylar fracture of the humerus is the most common type of elbow injury in children. The incidence of nerve injury remains controversial. The majority of supracondylar fractures are extension type with the proximal piece moving forward. This jeopardizes the integrity of the median and radial nerves. In contrast, flexion supracondylar fractures tend to injure the ulnar nerve as the fragment displaces in the opposite direction. The purpose of this study was to perform a large meta-analysis to assess the risk of traumatic nerve injuries associated with supracondylar fractures. The authors also perform the subgroup analysis of iatrogenic nerve injuries to determine whether medial or lateral pinning was associated with increased incidence of nerve injury.
The authors performed an exhaustive review of a variety of databases in search of supracondylar fractures. Any study with less than 10 patients or any study that included open procedures was excluded. The data was carefully extracted and pooled. The statistical analysis was performed to assess the incidence of nerve injuries. The iatrogenic nerve injures were pooled separately to make distinction regarding iatrogenic nerve injuries.
Analysis of the data indicates that traumatic neurapraxia occurred at weighted event of 11%. In the extension type of fracture, anterior interosseous nerve predominated over radial nerve. The majority of the injuries were considered to be neurapraxia. The authors further discuss that many anterior interosseous nerve injuries go unrecognized and the incidence may be higher. In flexion type fractures, ulnar nerve palsies predominated. In fact, the ulnar nerve was the only nerve injured in all but 2 of the 146 patients studied. Anterior displacement of the distal humerus fragment tends to induce stretching and angulation of the ulnar nerve as the proximal humerus projects in a posterior direction. The nerve is often trapped between the fractured fragments as seen at the time of surgery.
With regards to lateral versus medial pinning, the authors did find that the insertion of a medial pin increases the incidence of ulnar neurapraxia. However, previous work indicated that in most cases the ulnar nerve is trapped by the pin without direct injury by the pin. The authors make no recommendations regarding treatment. However, other studies have indicated that the majority of nerve injuries associated with supracondylar fractures resolve over time. On some occasions, the child will present with lack of movement and increase pain indicative of nerve regeneration. Desensitization techniques have been useful in these cases with slow improvement over time.