Medial vs. Lateral Pinning

Pin configuration and the potential complications related to instability and iatrogenic ulnar nerve injury are recognized concerns in this population. Therefore the work group deemed it important to examine the technique of pin stabilization. 

Critical outcomes investigated were iatrogenic ulnar nerve injury, loss of reduction, malunion, and reoperation rate. This recommendation is based on data on 65 outcomes from 15 studies comparing pinning technique using lateral only pin entry to lateral and medial crossed pin technique.

Two of the six studies that were sufficiently powered for loss of reduction were statistically significant in favor of medial pins. The remaining four studies reported no statistically significant difference between lateral and medial pins. 

One randomized, prospective study by Kocher, et al., examined loss of reduction and found a loss of reduction rate of 21% (6/28) in lateral only pins. Medial and lateral pins had a statistically significant lower loss of reduction rate of 4% (1/24). This loss of reduction was not clinically significant enough to warrant re-operation in either group. Meta-analysis of low and moderate quality studies found no statistically significant difference between lateral and medial pin configurations with respect to Baumann’s angle, Baumann’s angle change, Flynn’s Criteria and infection.

The ulnar nerve was injured in 3 of 557 (0.53%) cases with laterally introduced pins. Medially introduced pins resulted in 49 of 808 (6%) cases of ulnar nerve injury. Iatrogenic ulnar nerve injury was noted to be statistically significant in favor of lateral pinning in 6 of 11 studies. A meta-analysis of these studies and three additional underpowered studies (1 moderate quality and 13 low quality) also demonstrated a statistically significant effect in favor of lateral pinning (Number Needed to Harm = 22, Odds ratio = 0.27).  This suggests a 1 in 22 chance of harm resulting from the medial pinning techniques used in these studies. Based on limited evidence, the practitioner might use two or three laterally introduced pins to stabilize the reduction of displaced pediatric supracondylar fractures of the humerus. The risk of potential harm from a medial pin must be weighed against the potential advantages.