Oblique or short incisions reduce the risk of saphenous nerve damage during hamstrings harvesting. A model for mapping nerve pathways at the harvest site.

Introduction: Hamstring autografts are frequently used for ligament reconstruction surgery. Twelve to 84% of patients describe hypo or dysaesthesia secondary to injury of the saphenous nerve or one of its branches after hamstring harvesting. Type of incision (orientation and length) is subject of much debate to limit the risk of nerve damage. A cadaveric study was performed to determine which type of incision limits the risk of injury to the saphenous nerve or one of its branches, based on an anatomic model for mapping nerve pathways at the harvest site.

Methods: An anatomical study was performed on 20 knees from 12 embalmed bodies. Distance between saphenous nerve branches and 4 points of interest along the tibial crest was measured. Based on these measurements, a digital model of the saphenous nerve and its branches was created. A model of three common types of incision (vertical, horizontal and oblique) was overlaid. Each incision was modelled for three lengths (2, 3 and 4cm). Percentage of collision between nerve course model and incision model was then calculated to determine the risk of nerve damage for each type of incision. Based on the nerve course model, a "low collision risk" safe zone was identified.

Results: Nerve damage risk after an oblique incision was significantly lower than for a horizontal or vertical incision, for incision lengths of 3 and 4cm (p<0.05). For a specific incision orientation, the length of the incision did not affect the risk of nerve damage. A trapezoidal space close to the tibial crest and distal to the anterior tibial tuberosity appears to reduce risk of nerve damage.

Conclusion: This cadaveric study suggests that during hamstring harvesting, incisions shorter than 2cm reduce the risk of saphenous nerve's branches injuries. For incisions longer than 2cm, using an oblique incision may reduce the risk compared to vertical or horizontal incisions.

Level of evidence: Level of evidence not applicable: Laboratory experiments.