Excessive Femoral Version in Bipolar Hemiarthroplasty: Consequences
Exceeding normal femoral version values (>30° anteversion or any retroversion) in bipolar hemiarthroplasty significantly increases the risk of dislocation, reduces range of motion in certain planes, and can lead to prosthetic impingement.
Primary Consequences
Dislocation Risk
The most critical complication of abnormal femoral version is prosthetic instability and dislocation. While the AAOS guidelines 1, 2 recommend bipolar hemiarthroplasty for displaced femoral neck fractures with moderate evidence, they do not specifically address version parameters—however, dislocation remains a primary concern affecting both morbidity and quality of life.
Research demonstrates that version directly impacts hip stability 3. Specifically:
Excessive anteversion (>30°): While increased anteversion improves flexion and internal rotation range of motion, it dramatically reduces external rotation capacity 3. This creates a paradoxical instability pattern where the hip may be prone to posterior dislocation during activities requiring external rotation.
Retroversion (any degree): Retroversion severely restricts flexion and internal rotation, increasing anterior impingement and risk of anterior dislocation 3. This is particularly problematic as most daily activities require hip flexion.
Biomechanical Alterations
Abnormal version changes the mechanical loading patterns on the femoral stem, which has several downstream effects 4:
- Altered construct stiffness
- Increased or unpredictable subsidence patterns
- Changes in stress distribution to the proximal femur
- Potential for accelerated acetabular wear due to altered contact mechanics
The study by 4 found that stems placed at 15° from native version showed greater subsidence (1.045 mm vs 0.778 mm at 0° and 0.648 mm at 30°), though clinical significance remains uncertain.
Range of Motion Limitations
Version abnormalities create predictable impingement patterns 3:
- High anteversion: Limits external rotation, potentially causing posterior impingement
- Retroversion: Limits flexion and internal rotation, causing anterior impingement
- Both scenarios reduce functional capacity and increase fall risk in elderly patients
Clinical Pitfalls to Avoid
Stem size reduction: Increasing anteversion relative to native anatomy requires smaller stem sizes 4, potentially compromising initial fixation stability—critical in osteoporotic bone.
Compounding errors: Version errors are often accompanied by other technical issues. In one series 5, 2 of 4 dislocations occurred due to stem malalignment requiring revision.
Patient-specific factors: Younger patients and those with developmental dysplasia of the hip have higher native femoral anteversion 6. Failing to account for this increases the likelihood of exceeding safe version ranges.
Practical Implications
Intraoperative assessment of version is mandatory. While guidelines 1, 2 strongly recommend cemented stems and support either unipolar or bipolar designs, they assume proper component positioning. The surgeon must:
- Measure native femoral version preoperatively (ideally with CT)
- Target 10-20° anteversion in most cases
- Never accept retroversion
- Consider neck-adjustable stems when native version exceeds 30° 6
The functional consequences manifest as reduced Harris Hip Scores, increased pain, and higher revision rates—all directly impacting the quality of life outcomes that should guide surgical decision-making over technical ease of implantation.