Computer assisted surgical anatomy mapping (CASAM) of the distal Posterior Interosseous Nerve (PIN) and its relation to the wrist arthroscopy portals: A cadaver study.

Introduction: The distal Posterior Interosseous Nerve (PIN) plays an important part in the sensory innervation of the wrist joint. Introduction of the arthroscopy portals during wrist arthroscopy might injure the PIN. The anatomic variation in the trajectory of the PIN and the proximity to the dorsal arthroscopy portals have not yet been fully explored. Materials and methods: Computer assisted surgical anatomy mapping (CASAM) is a technique to digitally compute and merge photographic images using anatomic landmarks and visualize variation in anatomy. A standard wrist arthroscopy procedure was carried out on eight cadaver forearms. CASAM was used to map the trajectory of the distal PIN and measure the distance to bony landmarks and the nearest wrist arthroscopy portals. Descriptive statistics were provided for anatomical measurements. Results: CASAM illustrated great variation in the PIN trajectories between the specimens. The mean distance from the PIN to Lister's tubercle was 9 ​mm (range 3-14, SD 3.9), the distance to the ulnar styloid was 27 ​mm (range 23-32, SD 3.3). None of the nerves showed signs of iatrogenic injury from placement of the arthroscopy portals. The 3-4 portal and the 6R portal were closest to the PIN with a respective mean distance of 9 ​mm (range 4-15, SD 3.8) and 19 ​mm (range 13-22, SD 3.2). Conclusion: CASAM demonstrated the importance of understanding nerve anatomy variations and offered insight into which arthroscopy portals are most likely to damage the distal PIN. However, we conclude that the overall risk of PIN injury from wrist arthroscopy is low due to the proximity to the portals.