Acceptable Range of Femoral Stem Anteversion in Total Hip Replacement
The acceptable range of femoral stem anteversion in total hip replacement is 10° to 20°, though achieving this target consistently is challenging and clinical outcomes remain acceptable within a broader range of 0° to 25°.
Target Anteversion Range
The generally accepted target for femoral stem anteversion is 10° to 20° 1. However, clinical reality demonstrates significant variability in achieving this range:
- In a prospective study of 109 consecutive cementless THAs, only 45% of stems were positioned within the intended 10-20° range 1
- 39% were positioned between 0-9° of anteversion
- 7% exceeded 20° of anteversion
- 8% were in retroversion 1
Despite this variability, most patients achieved satisfactory clinical outcomes, suggesting the acceptable range may be broader than traditionally taught.
Broader Acceptable Range
A practical acceptable range extends from 0° to 25° of anteversion 2. This broader range accommodates:
- Normal anatomical variation in native femoral anteversion
- Technical limitations of intraoperative assessment
- Gender differences (women typically require higher anteversion angles) 3
Critical Considerations for Extreme Cases
When dealing with abnormal femoral anatomy:
- Stem anteversion from 0° to 75° can be accommodated using modular neck systems with configurations ranging from 15° anteverted to 30° retroverted necks, combined with 40° cup inclination 2
- Below 0° or above 25° increases risk of impingement and instability
- For patients requiring high range of motion (floor sitting, deep flexion), target anteversion should be adjusted upward—15° at 40° cup inclination for standard activities, 25° for 40° internal rotation at 90° flexion, and 35° for 50° internal rotation at 90° flexion 4
Accuracy of Intraoperative Assessment
Surgeon visual estimation of stem anteversion has poor precision 1:
- Correlation between surgeon estimate and CT measurement was only 0.688
- 92% of stems had abnormal anteversion when strict 10-15° criteria were applied 3
- CT-based navigation systems reduce absolute discrepancy to 2.9° ± 3.1° compared to 7.6° ± 5.2° with mechanical alignment guides 5
Clinical Implications
Minimizing deviation from native femoral anteversion is more important than achieving an arbitrary target number 6. Patients with stems aligned closer to their native anatomy demonstrated significantly higher satisfaction scores and better functional outcomes.
Key Pitfalls to Avoid:
- Retroversion (negative anteversion) significantly increases dislocation risk
- Excessive anteversion >30° increases anterior impingement and instability
- Ignoring combined anteversion concept—the relationship between cup and stem anteversion must be considered together, though this concept breaks down at extreme anteversion values 2
- Gender-specific differences—women average 8.0° stem anteversion versus 1.5° in men 3
Practical Algorithm
- Target 10-20° anteversion as the primary goal
- Accept 0-25° range as clinically acceptable if combined anteversion is optimized
- For high-demand patients (requiring deep flexion/floor sitting), increase target to 25-35° based on lifestyle requirements 4
- Use CT-based navigation when available to improve accuracy 5
- Consider modular necks for cases with extreme native femoral version outside 0-25° range 2
- Prioritize minimizing change from native anteversion over achieving arbitrary targets 6
The evidence demonstrates that while 10-20° remains the ideal target, the acceptable functional range is broader, and optimizing combined anteversion with the acetabular component is equally critical for preventing complications.