Published online Apr 18, 2017. doi: 10.5312/wjo.v8.i4.310
Peer-review started: April 6, 2016
First decision: May 17, 2016
Revised: February 7, 2017
Accepted: February 28, 2017
Article in press: March 2, 2017
Published online: April 18, 2017
Processing time: 379 Days and 15.1 Hours
To provide a “patient-normalized” parameter in the proximal forearm.
Sixty-three cadaveric upper extremities from thirty-five cadavers were studied. A muscle splitting approach was utilized to locate the posterior interosseous nerve (PIN) at the point where it emerges from beneath the supinator. The supinator was carefully incised to expose the midpoint length of the nerve as it passes into the forearm while preserving the associated fascial connections, thereby preserving the relationship of the nerve with the muscle. We measured the transepicondylar distance (TED), PIN distance in the forearm’s neutral rotation position, pronation position, supination position, and the nerve width. Two individuals performed measurements using a digital caliper with inter-observer and intra-observer blinding. The results were analyzed with the Wilcoxon-Mann-Whitney test for paired samples.
In pronation, the PIN was within two confidence intervals of 1.0 TED in 95% of cases (range 0.7-1.3 TED); in neutral, within two confidence intervals of 0.84 TED in 95% of cases (range 0.5-1.1 TED); in supination, within two confidence intervals of 0.72 TED in 95% of cases (range 0.5-0.9 TED). The mean PIN distance from the lateral epicondyle was 100% of TED in a pronated forearm, 84% in neutral, and 72% in supination. Predictive accuracy was highest in supination; in all cases the majority of specimens (90.47%-95.23%) are within 2 cm of the forearm position-specific percentage of TED. When comparing right to left sides for TEDs with the signed Wilcoxon-Mann-Whitney test for paired samples as well as a significance test (with normal distribution), the P-value was 0.0357 (significance - 0.05) indicating a significant difference between the two sides.
This “patient normalized” parameter localizes the PIN crossing a line drawn between the lateral epicondyle and the radial styloid. Accurate PIN localization will aid in diagnosis, injections, and surgical approaches.
Core tip: We present a “patient normalized” parameter that localizes posterior interosseous nerve (PIN) crossing point with a line interconnecting the lateral epicondyle and the radial styloid, with the “70-85-100” rule. The mean PIN distance from the lateral epicondyle was 100% of transepicondylar distance (TED) in a pronated forearm, 85% in neutral, and 70% in supination. Predictive accuracy was highest in supination; in all cases the majority of specimens (90.47%-95.23%) are within 2 cm of the forearm position-specific percentage of TED. Non-invasive accurate PIN localization will aid in diagnosis, injections, surgical approaches, and understanding neurological symptoms in the forearm.