Superior Gluteal Nerve — Nerve Lesions of the Lower Limb

00:01 and leg flexion. Now let’s turn to the superior gluteal nerve. The superior gluteal nerve passes out superior to the piriformis muscle, which we can see here. So it passes out above piriformis, and it’s going to pass out and supply importantly, gluteus medius and gluteus minimus. And that’s what we can see here, the nerve supply to these muscles from the superior gluteal nerve. So if we were to have damage to the superior gluteal nerve, then the superior gluteal nerve supplying gluteus medius and supplying gluteus minimus, these muscles are involved in keeping the pelvis level when the contralateral limb is elevated.

00:44 So that if the superior gluteal nerve, we can see it here, is damaged, these two muscles are going to be paralyzed. And when the patient stands on one leg, when the patient stands on one leg, the leg that is standing, these gluteal muscles contract, and that stabilizes the pelvis. So when you’re standing on one leg, that leg is fixed. Gluteus medius and gluteus minimus will contract, and that will pull the pelvis level. If gluteus medius and gluteus minimus are paralyzed, then that muscle cannot hold the pelvis level. So it all drops to the opposite side. The pelvis would drop to the opposite side that gluteus medius is damaged. And this is known, when you’re asked to stand on one leg, as a positive Trendelenburg test. You ask the patient to walk, and if you have drooping of the pelvis, it indicates that the superior gluteal nerve may be damaged, and gluteus medius and minimus may be paralyzed.

01:53 When the patient is asked to walk, they may compensate with a gluteal limp or waddling appearance as they try to compensate movement of the body to the affected side.

02:04 So they may have this waddling appearance as they’re trying to walk. Here, we can see how the gluteus medius and gluteus minimus muscles will contract. We can see them here. So that with this leg being fixed, contraction of this muscle is going to shorten this distance here and here, and that’s going to have the effect of tilting the pelvis upwards. So the pelvis then stays leveled. Remember now, this leg is fixed because it’s on the floor. It’s not elevated like this leg. So when the gluteus medius and minimus contracts, it’s going to pull the iliac crest downwards, which is going to maintain the level of the pelvis. With this muscle in this diagram being paralyzed, then you’re not going to pull the iliac crest downwards.

02:57 It’s going to be allowed to fall as this leg is no longer supported because it’s been elevated, and the pelvis will now fall down to the unaffected side, the side opposite paralysis of the gluteus medius muscle. And we can see that you’ll have this waddling appearance, so you’ll try and move your body across to the supported leg as you try and walk. Now let’s turn to the common fibular nerve, and we know the common fibular nerve