Anatomic Study of the Distal Arcade of Superficial Layer of Supinator Muscle

Introduction: Compression of the Posterior Interosseous Nerve (PIN) can cause pain on the lateral aspect of the proximal forearm and weak extension of the wrist and fingers. The distal arcade of the superficial layer of the supinator muscle can entrap the PIN, as it passes beneath it. Knowing the exact location of the distal arcade in relation to adjacent anatomical landmarks can help in decompression of the PIN. Aim: The aim of the study was to describe the morphology of the distal arcade of the supinator muscle and its relation with the PIN. Materials and Methods: An anatomic dissection of 40 upper extremities was conducted and the distances of the distal arcade and the PIN from adjacent landmarks were determined from Jan 2016 to Jun 2017. The mean, standard deviation and range were calculated for each of the measurements. The comparison of the parameters between sides was done using paired t-test. Data obtained was tabulated and analysed in Statistical Package For Social Sciences (SPSS) Software version 16.0. Results: A muscular distal arcade was the most common type seen in 17 (42.5%) upper limb. Distances between the distal arcade and the humero-radial and trans-epicondylar lines were 90.27 mm and 105.62 mm, respectively. The distance from the lateral epicondyle and the entrance and exit of the PIN from supinator was 61.47 mm and 85.60 mm, respectively. The distance between the proximal and distal arcades showed statistically significant difference (p-value=0.041). Conclusion: Knowledge of the anatomic findings of the distal arcade of the superficial layer of the supinator and the localisation of the PIN are important in the surgical management of PIN entrapment.