Risk of Superior Gluteal Nerve and Gluteus Medius Muscle Injury During Femoral Nail Insertion

Background: Abduction weakness and limping is a well-recognized complication of closed antegrade insertion of femoral nails. Iatrogenic injuries to the superior gluteal nerve and the gluteus medius muscle are the most likely contributing factors. The purpose of this study of cadavers was to assess the risk of nerve and muscle injury with various lower-limb positions used during nail insertion. Methods: We studied thirteen hips of ten formalin-fixed adult cadavers. With the cadaver in the full lateral position, a 9-mm reamer was introduced in a retrograde fashion from the intercondylar notch and passed through the gluteus medius muscle. The distance between the point of entry of the reamer into the undersurface of this muscle and the inferior main branch of the superior gluteal nerve (the nerve-reamer distance) and the distance between the entry and exit points of the reamer in the gluteus medius muscle (the intramuscle distance) were measured in three different hip positions: 15° of flexion and 15° of adduction (Position 1), 30° of flexion and 30° of adduction (Position 2), and 60° of flexion and 30° of adduction (Position 3). Results: In Position 1, the average nerve-reamer distance was 7 mm and the average intramuscle distance was 24 mm. In three hips the reamer injured the nerve directly, and in two other hips the distance was ≤5 mm. In Position 2, the average nerve-reamer distance was 21 mm and the average intramuscle distance was 18 mm. In Position 3, the average nerve-reamer distance was 33 mm and the average intramuscle distance was 11 mm. None of the reamers in this position came closer than 20 mm to the nerve. Conclusions: The risk of injury to the superior gluteal nerve and the gluteus medius muscle during closed antegrade insertion of a femoral nail is lessened by increasing the amount of hip flexion and adduction. Clinical Relevance: The risk of injury to both the superior gluteal nerve and the gluteus medius muscle is higher with limited degrees of hip flexion and adduction, such as are possible in the supine position on a fracture table, than it is with greater degrees of hip flexion and adduction, which are possible in the lateral position on a fracture table or in the so-called sloppy lateral position on an ordinary table. Therefore, insertion of a femoral nail with the hip in increased flexion and adduction might help to lower the risk of injuries to the superior gluteal nerve and the gluteus medius muscle.