Abstract
Limb length discrepancy (LLD) is a complication of total hip arthroplasty (THR). We reviewed the x-rays of patients who underwent THR in our unit to establish the incidence and magnitude of LLD, and try to identify reasons why a length discrepancy arose. Patients with abnormalities of the opposite hip (previous THR, significant osteoarthritis) were excluded, to allow comparison with a normal contralateral side.
100 consecutive patients who fulfilled these criteria were included. There were 38 male and 62 female patients. The implants used were Charnley (89 cases), Elite (4 cases), and Exeter (7 cases). The following measurements were made on pre-and post-operative films on the hospital PACS system: centre of lesser trochanter to ischial tuberosity; tip of greater trochanter to centre of femoral head; centre of head to base of teardrop. The distance from the osteotomy in the femoral neck to the centre of the lesser trochanter was also measured. The interval from the greater trochanter to the closest margin of the pelvis, and the interval from the lesser trochanter to the base of the teardrop (compared to the normal side) were recorded as indices on adduction. Surgery was performed via a direct lateral (Hardinge) approach (95 cases) or through transtrochanteric approach (5 cases).
There was a radiographic difference between limbs of > 1cm in 43 cases; in 9 of these, the operated limb was longer, and in 34 cases it was shortened. In those cases where the operated side was lengthened, the cause was on the acetabular side in 2 patients, and on the femoral side in 25 cases, and on the femoral side in 9 cases. The shortened limb was noted to be adducted relative to the opposite side in 29 patients. There was difference noted in the incidence of discrepancy between different implants. The transtrochanteric approach was associated with significantly (p< 0.01) less length discrepancy.
Our findings suggest that shortening is much more common than lengthening following THR, and that incorrect positioning of the acetabulum is the more likely cause. Persistence of an adduction contracture may also contribute to an apparent shortening postoperatively. The transtrochanteric approach appeared to make LLD less likely. Surgeons should be aware of these findings when performing THR. The clinical effect of differing degrees of LLD is till debatable.
The abstracts were prepared by Raymond Moran. Correspondence should be addressed to him at the Irish Orthopaedic Assocation, c/o Cappagh National Orthopaedic Hospital, Finglas, Dublin 11, Ireland.
