REIDER PART 209

Chaptf.r 5_Pelvis, Hip, and Thigh 169

Figurę 5-7. Distal posterior thigh with resisted knee flejdon. A, Semitendinosus. B, Biceps femoris.

to stand facing away from the examiner. The patient should be barefoot, with the knees fułly extended and the feet together. The examiner then places a finger or two of each hand on each of the patients iliac crests and imagines a linę drawn between the two crests (Fig. 5-10). Pelvic obliquity is present when this imaginary linę is not parallel to the floor. The many possible causes of obliquity can be divided into two large groups: factors resulting in a true leg length discrepancy and factors resulting in a functional, or appar-ent, leg length discrepancy.

True Versus Functional Leg Length Discrepancy. In a truć leg length discrepancy, the actual length of the patients two lower limbs, when ineasured from the femoral heads to the plantar surfaces of the feet, is differ-ent. In a functional leg length discrepancy, or apparent leg length discrepancy, the patients two lower limbs, as measured from the femoral heads to the plantar surfaces of the feet, are identical in length; however, other factors, such as joint or muscle contracturcs, cause one of the lower limbs to function as if it were shorter or longer than the other.

The true leg length discrepancy is causcd by abnor-malities that result in one of the bones of the lower limb

actually being shorter or longer than its countcrpart on the other side, such as varus or valgus deformities of the femoral neck, congenital anomalies of the femur or tibia, or growth disturbances of the femur or tibia. Possible causes of a functional leg length discrepancy include contracturcs at the lumbosacral junction due to scoliosis or other causes, posttraumatic deformities of the pelvis, and abduction or adduction contractures of the hip or flexion contracture of the knee.

In evaluating a casc of pelvic obliquity, the examiner should have three goals: (1) to determine whethcr a true leg length discrepancy or an apparent limb length discrepancy is present, (2) to determine the source of the discrepancy, and (3) to determine the magnitude of the discrepancy.

Direct Measurement. To distinguish between a true and a functional leg length discrepancy, the patient is asked to lie supine on the examination table with the body as straight as possible. To check for a true leg length discrepancy, the examiner then identifies the patients right ASIS and places the free end of a tape measure on it. The patient is asked to hołd the end in place so that the examiner can unwind the tape measure in a straight linę