Evaluation of radiological methods of assessing cup anteversion in total hip replacement.

STUDY

DESIGN

Prospective clinical study.

BACK GROUND: In total hip replacement, the placement of the cup is critical as inaccurate placement can cause impingement, accelerated wear and dislocations. The position of the cup is assessed by abduction and anteversion. There are many radiological methods available for this purpose, while the reliability and validity of the methods have not been adequately done. Calculation by CT method is a gold standard. The aim of study was to evaluate the reliability and validity of all the methods.

METHODS

In 30 hips of 25 consecutive patients, 13 females and 12 males who underwent primary total hip replacement in our institution, the component version in all the five radiological methods was calculated and compared with CT evaluation of angles. The intra- and interobserver reliabilities were assessed.

RESULTS

Average CT measurement was 23.28 for anteversion. Lewinnek, Liaw, Hassan, Widmer and Ritun methods had average deviation of 4.330, 4.390, 4.880, 6.840 and 6.220, respectively. All the radiographic and CT methods had excellent intra- and interobserver reliabilities (C.I. 0.894-0.960 and 0.861-0.953). All the methods except Widmer had a significant validity against CT.

CONCLUSION

Plain X-rays (AP) are reliable for measuring cup anteversion. Lewinnek, Liaw, Riten and Hassans methods for calculation of cup anteversion are closer to CT in accuracy (p value >0.05). Widmer method varies significantly (p value <0.05) from CT.