Hip Resurfacing and Conventional THR Comparison of Acetabular Bone Stock Removal, Leg Length, and Offset Medical Study 2013
http://www.healio.com/orthopedics/journals/ORTHO/%7BACDF855C-1EA2-4525-9017-3B3127D94918%7D/Hip-Resurfacing-and-Conventional-THA-Comparison-of-Acetabular-Bone-Stock-Removal-Leg-Length-and-Offset
Nicholas M. Brown, MD; Jared R. H. Foran, MD; Craig J. Della Valle, MD
May 2013
The purpose of this study was to compare total hip arthroplasty (THA) and hip
resurfacing arthroplasty (HRA) with regard to the amount of acetabular bone
stock removed and the ability to restore leg length and offset. Anteroposterior
pelvis radiographs of 153 consecutive THAs and 84 consecutive HRAs were
compared. Excluded patients were those with prior hip surgery, those in which a
best-fit circle could not be adequately matched to the femoral head, and those
with preoperative radiographic findings that precluded consideration for HRA (ie,
disease severity, deformity, leg-length discrepancy).
A significant difference was found between THA and HRA with regards to age and
sex but not primary diagnosis. Relative differences in acetabular bone removal
were compared using a ratio of acetabular implant diameter to preoperative
ipsilateral femoral head diameter measured with a best-fit circle. The ratio of
acetabular cup diameter to preoperative ipsilateral femoral head diameter was
significantly greater following THA than following HRA, indicating relatively
more acetabular bone removal in THA procedures. Mean leg-length discrepancy was
significantly greater following THA than following HRA. Offset was increased to
a greater extent following THA than following HRA. Overall, HRA was associated
with relatively less acetabular bone stock removal and less alteration in leg
length and offset than was THA…
…The current results suggest that in this surgeon’s practice, HRA was associated
with significantly less acetabular bone stock removal. Although this difference
was statistically significant, the difference was small and likely not
clinically significant. The finding of more acetabular bone removal in the THA
group may be related to the surgeon’s desire to maximize femoral head size when
performing conventional THA and, in cases where it was safe to do so, a larger
acetabular component size may have been inserted in an attempt to accommodate a
larger femoral head size. Furthermore, the surgeon routinely started preparing
the femoral head for HRA prior to acetabular component placement, and greater
certainty regarding the femoral head size may have allowed for the placement of
smaller acetabular components. Nonetheless, the current study suggests that HRA
is not necessarily associated with more acetabular bone stock removal, as was
suggested by the first studies on this topic.