Total hip replacement (THR) is widely regarded as one of the most successful orthopaedic procedures [18]. Implant positioning plays a critical role in determining postoperative stability and function.

The concept of acetabular safe zones was first described by Lewinnek et al. [1]; however, dislocations continue to occur even within these zones [9]. This has led to increasing interest in combined anteversion (CA), which incorporates both acetabular and femoral components [2,3,5].

Studies have demonstrated that CA is a better predictor of impingement and dislocation than isolated cup positioning [7,13]. Furthermore, spinopelvic mobility has been shown to influence functional orientation of the acetabulum [8,10,11,15].

In the Indian population, cultural activities such as squatting and cross-legged sitting place additional biomechanical demands on the hip joint, which are not considered in traditional Western models.

AIM

To determine the optimal combined anteversion range in Indian patients undergoing THR and correlate it with functional outcomes.

MATERIALS AND METHODS

1. Study Design

Prospective observational study.

2. Sample Size

82 patients undergoing primary THR.

3. Inclusion Criteria

• Age >18 years
• Primary THR (AVN, OA, fracture neck femur)

4. Exclusion Criteria

• Revision THR
• Neuromuscular disorders
• Severe deformities

5. Surgical Technique

All surgeries were performed using standard posterior approach. Component positioning followed conventional guidelines with intraoperative estimation of anteversion [12].

6. Measurement of Anteversion

Acetabular anteversion measured radiographically using standardized methods [4,6,21]. Femoral anteversion assessed intraoperatively and radiologically.

Combined Anteversion (CA) = cup + stem anteversion

Grouping

Group A: CA <25°

Group B: CA 25–50°

Group C: CA >50°

Outcome Measures

Functional Scores

Harris Hip Score (HHS)

WOMAC score

Lifestyle Assessment

Squatting

Cross-legged sitting

Complications

Dislocation

Impingement

Limp

Statistical Analysis

ANOVA for continuous variables

Chi-square test for categorical variables

p < 0.05 considered significant

RESULTS

Demographics

Mean age: 54.2 ± 12.1 years

AVN most common indication (52%)

Table 1: Functional Outcomes by Combined Anteversion

Patients in Group B (25–50°) showed significantly higher HHS compared to other groups (p < 0.001). [table 1, figure 1 & 2]

Figure 1: HHS vs Combined Anteversion

Figure 2: WOMAC vs Combined Anteversion

Lifestyle Outcomes [Figure 3]

Squatting ability highest in Group B

Cross-leg sitting significantly better in Group B

Figure 3: Lifestyle Outcomes

Complications

Dislocation occurred predominantly in Group A and Group C, consistent with previous literature highlighting the importance of optimal component positioning [14,16,17,20].

DISCUSSION

This study demonstrates that combined anteversion significantly influences functional outcomes following THR. Patients within the 25–50° range showed superior outcomes, consistent with previously described combined anteversion concepts [3,5].

However, our findings suggest that the optimal range for Indian patients may extend slightly beyond traditional values, supporting the concept of a functional safe zone rather than a fixed radiological target [19].

The role of spinopelvic dynamics further complicates the concept of a universal safe zone, as pelvic tilt can alter functional anteversion during daily activities [10,11,15].

Additionally, the persistence of dislocations within traditional safe zones highlights the limitations of relying solely on static measurements [9,14,16].

Our study uniquely incorporates lifestyle-based functional outcomes, demonstrating that slightly higher anteversion may facilitate activities such as squatting without compromising stability.

Limitations

Short follow-up duration

Moderate sample size

Radiographic measurement variability

Conclusion

Optimal combined anteversion for Indian patients undergoing THR appears to lie between 30°–55°, offering improved functional outcomes and reduced complications.

This study supports a shift toward patient-specific and function-oriented implant positioning rather than reliance on traditional universal safe zones.

REFERENCES

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