Injury of the Infrapatellar Branch of Saphenous Nerve Between Vertical and Oblique Skin Incision in Medial Opening Wedge High Tibial Osteotomy.

Introduction: The infrapatellar branch of saphenous nerve (IPBSN) has anatomic variations and prone to injury during surgery around the medial side of the knee. High tibial osteotomy is one of the procedures that may be risky to the IPBSN. This research was aimed to establish which skin incision (vertical vs oblique) is less likely to damage to the IPBSN and also to study the anatomy of the IPBSN, with the institutional review board reference (No. LH611054, date 10/1/2020). The primary outcomes are aimed to establish which skin incision (vertical vs oblique) is less damaging to the IPBSN. The secondary outcome is to study about the anatomy of the IPBSN.

Materials and methods: Twenty-two fresh cadavers (forty-four knees) were dissected by randomisation under the block of four technique, and two different incisions were performed for each knee. Exploration was performed from the skin incision to the IPBSN around the incision zone. If the discontinuity of the nerve was found, it was classified as IPBSN injury. The anatomic measurement was performed. The IPBSN injury between two groups were analysed with the chi-square test.

Results: The risk of IPBSN injury in the oblique group was 2 from 22 knees (9.1%), and 12 knees from 22 knees (54.5%) in the vertical group (P=0.001). Most common number of branch(es) found, is one branch, the horizontal distance ranged from 2.6cm to 8.5cm (average 5.7±1.6), the vertical distance ranged from 4.4cm to 12.6cm (average 7.6±1.9) and the declination angle ranged from 6° to 87° (average 34.7±24.3).

Conclusion: The risk of the IPBSN injury in oblique skin incision may be less than the vertical incision in the medial opening wedge HTO.