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Optimal acetabular cup positioning is attained in less than 50% of
cases, study reports
http://www.orthosupersite.com/view.aspx?rid=61685
NEW ORLEANS - High-volume surgeons are more likely than low-volume
surgeons to attain optimal cup positioning for total hip arthroplasty,
but both groups still attain optimal cup positioning less than half of
the time, according to a study presented here.
The findings were presented by Bryan Jarrett, BS, at the 56th Annual
Meeting of the Orthopaedic Research Society.
Jarrett said the purpose of the study was to attempt to correlate the
influence of various patient factors - body mass index (BMI), age,
gender and primary diagnosis for the total hip arthroplasty (THA) - with
the positioning of the acetabular cup.
"Cup positioning and implant positioning are extremely important to
attain long-term success," he noted.
Methods and measurements
The researchers compiled data from 2,063 patients who underwent a
primary THA, revision THA or Birmingham hip resurfacing from 2004
through 2008. Postoperative anteroposterior (AP) pelvis and cross table
lateral digital radiographs were obtained for each patient, and the AP
radiographs were measured to calculate cup inclination and version
angles. Version direction was determined through the lateral
radiographs.
Acceptable angle ranges were defined as 30° to 45° for abduction and 5°
to 25° for version.
Study results
There were 1,954 qualifying patients, with 1,218 (62%) acetabular
cups falling within the optimal abduction range and 1,576 (87%) in the
optimal version range. There were 921 (47%) patients with both
inclination and version angles within the optimal ranges.
In the combined analysis, low-volume surgeons showed a 2-fold increase
in risk for cup malpositioning compared with high-volume surgeons.
Minimally-invasive surgery, as an approach, showed a 6-fold increase in
risk for cup malpositioning when compared to the posterolateral
approach. Obesity, defined as a BMI greater than 30, showed a 1.3-fold
increase in risk.
Less than half
With patient influences taken into account, the high-volume surgeons
outperformed their low-volume counterparts, but both still attained
optimal ranges in less than 50% of patients.
"When we just looked at high-volume surgeons, 38% of the patients fell
within the optimal ranges," Jarrett said. "When we just looked at
low-volume surgeons, we saw that 26% of the patients were within the
optimal ranges."
•Reference:
Callanan M, Bragdon CR, Zurakowski D, Rubash H. An analysis of cup
positioning in total hip arthroplasty: quality improvement by use of a
local joint registry. Paper 362. Presented at the 56th Annual Meeting of
the Orthopaedic Research Society. March 6-9, 2010. New Orleans.
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