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82
hips), and patient dissatisfaction resulting in litigation. The
incidence of LLD varies from 16-96%. A long leg is more
common, more perceived by the patient, and statistically
correlated with reduced hip function scores. Patient perception
of a leg length inequality often correlates poorly with true
radiographic leg length measurements. Patients at risk for
a symptomatic leg length discrepancy include those with
short stature, coxa vara, acetabulae protrusio, preoperative
pelvic obliquity, and preoperative flexion contracture.
Preoperative LLD can occur due to distorted hip anatomy or
false discrepancy due to pelvic obliquity associated with hip
soft tissue contractures or lumbar scoliosis. Post-operative
LLD is most commonly due to intraoperative technical errors
including errors in neck resection, failure to duplicate the
anatomic hip center, accurate choice of prosthetic neck length,
or failure to duplicate femoral offset requiring increased vertical
length to gain hip stability.
Prevention of LLD requires preoperative planning and accurate
intraoperative execution of the preoperative plan. Preoperatively,
true leg length discrepancies can be determined by
tape measurement (anterior-superior iliac spine to medial
malleolus), floor blocks, and assessment of the level of the
iliac crests. Various radiographic measurements are available
typically using a combination of landmarks including the
trans-ischial line, inter-teardrop line, femoral head center,
and the greater and lesser trochanters. Additional, more
precise radiographic leg length assessment options include
orthoroentgenograms and CT scanning. Templating of preoperative
radiographs is critical to determine intraoperative
decisions, such as the level of the femoral neck resection,
choice of prosthetic neck length and offset, and positioning
of the acetabular component. Multiple intraoperative techniques
are available to assist in accurate leg length determination.
Many utilize measurements from fixed landmarks proximal
and distal to the hip joint. These measurements are initially
obtained before the hip is dislocated and repeated after trial
components are inserted to determine intraoperative leg
length changes. An intraoperative radiograph can be obtained
to assure that precise execution of the preoperative plan has
obtained.
Treatment of LLD is based on etiology and patient disability.
Many discrepancies are not perceived by the patient and can
be ignored. Others can be managed with utilization of heel
lifts. Operative treatment options include manipulation of modular
femoral and acetabular components, component revision
in cases of major component malposition, and greater trochanteric
advancement in cases requiring substantial component
shortening.
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