Gluteal skyline (G.S.L.). A search for an objective sign in the diagnosis of disc lesions of the lower lumbar spine

In attempting to improve diagnostic accuracy in lumbar disc herniation, we have observed that there is another useful clinical sign, that being an atony or an atrophy of the gluteus maximus. This large muscle is innervated by the inferior gluteal nerve, whose origin is in the roots of L5-S1-S2(Gray, and the unwitting patient has no control of its activity and contour. When there is pressure onto the involved roots, there first appears an atony which is followed by an atrophy of the involved muscle. Clinically this can be evaluated by having the patient lie prone and relaxed, with his head straight and his arms beside his body. The observer stands at the foot of the examining table and by lowering his line of vision to the level of the buttocks can see the contours produced by the glutei. These contours, when seen against a background, form a 'gluteal skyline.'