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Updated: Jun 10, 2026
Individualized Stem-positioning in Calcar-guided Short-stem Total Hip Arthroplasty
Published on: February 27, 2018
The John Charnley Award: risk factors for cup malpositioning: quality improvement through a joint registry at a
Mark C Callanan1, Bryan Jarrett, Charles R Bragdon
1Harris Orthopaedic Laboratory, Massachusetts General Hospital, 55 Fruit Street, GRJ 1206, Boston, MA 02114, USA.
Insights
Optimally positioned acetabular cups in total hip arthroplasty are influenced by surgical approach, surgeon volume, and patient obesity. Minimally invasive surgery, lower surgeon volume, and obesity increase the risk of malpositioned acetabular components.
Area of Science:
- Orthopedic surgery
- Biomedical engineering
- Radiology
Background:
- Acetabular cup positioning is critical in total hip arthroplasty (THA) to prevent complications like dislocation and excessive wear.
- Limited research exists on the specific factors influencing acetabular cup placement accuracy.
Purpose of the Study:
- To quantify the percentage of optimally positioned acetabular cups following THA.
- To identify patient and surgical variables associated with suboptimal acetabular component positioning.
Main Methods:
- Postoperative radiographs (AP pelvis and cross-table lateral) from 2061 THA or hip resurfacing patients were analyzed.
- Cup inclination and version angles were measured using specialized software (Hip Analysis Suite™).
- Optimal ranges were defined as 30°-45° for abduction and 5°-25° for version.
Main Results:
- Of 1823 hips with measurable angles, 50% had both optimal abduction and version.
- Malpositioned acetabular cups were independently predicted by surgical approach, surgeon volume, and obesity (BMI > 30).
- Minimally invasive surgery, low surgeon volume, and obesity were associated with a significantly increased risk of malpositioning.
Conclusions:
- Surgical approach, surgeon experience, and patient body mass index are significant factors affecting acetabular cup positioning in THA.
- Minimally invasive approaches, lower surgeon volume, and obesity are linked to a higher likelihood of malpositioned acetabular components.
- Further research comparing outcomes at lower-volume centers is warranted to validate these findings.
Background:
Few studies have examined factors that affect acetabular cup positioning. Since cup positioning has been linked to dislocation and increased bearing surface wear, these factors affecting cup position are important considerations.
Question/Purposes:
We determined the percent of optimally positioned acetabular cups and whether patient and surgical factors affected acetabular component position.
Methods:
We obtained postoperative AP pelvis and cross-table lateral radiographs on 2061 consecutive patients who received a THA or hip resurfacing from 2004 to 2008. One thousand nine hundred and fifty-two hips had AP pelvic radiographs with correct position of the hip center, and 1823 had both version and abduction angles measured. The AP radiograph was measured using Hip Analysis Suite™ to calculate the cup inclination and version angles, using the lateral film to determine version direction. Acceptable ranges were defined for abduction (30°-45°) and version (5°-25°).
Results:
From the 1823 hips, 1144 (63%) acetabular cups were within the abduction range, 1441 (79%) were within the version range, and 917 (50%) were within the range for both. Surgical approach, surgeon volume, and obesity (body mass index > 30) independently predicted malpositioned cups. Comparison of low versus high volume surgeons, minimally invasive surgical versus posterolateral approach, and obesity versus all other body mass index groups showed a twofold (1.5-2.8), sixfold (3.5-10.7), and 1.3-fold (1.1-1.7) increased risk for malpositioned cups, respectively.
Conclusions:
Factors correlated to malpositioned cups included surgical approach, surgeon volume, and body mass index with increased risk of malpositioning for minimally invasive surgical approach, low volume surgeons, and obese patients. Further analyses on patient and surgical factors' influence on cup position at a lower volume medical center would provide a valuable comparison.
Level Of Evidence:
Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.
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