The Reliability and Variation of Acetabular Component Anteversion Measurements From Cross-Table Lateral Radiographs

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Abstract

Although cross-table lateral (CL) radiographs are frequently used to assess acetabular component anteversion, the reliability of this method has not been established. We compared serial CL radiographs with computed tomography (CT) scans for 98 total hip arthroplasty patients (119 hips) undergoing surveillance of primary or revision total hip arthroplasty. Acetabular anteversion averaged 26.1° (range, −2° to 48.3°) on CL imaging and 28.8° (range, −7° to 54°) on CT scan. There was a strong correlation between anteversion determined from CT scans and serial CL images. However, variation on serial CL studies exceeded 10° for 20% of patients. Although CL imaging provides acceptable assessment of general component position, it has limited use for precise analysis in research, outcome reporting, or determination of cause of implant failure.

Section snippets

Clinical Data

Ninety-eight patients (119 hips) who underwent a primary THA (86 hips) or a femoral head and acetabular liner exchange with retention of a stable acetabular component (33 hips) between August 1996 and January 2003 were assessed with CT scan as a part of 2 institutional review board–approved studies at our institution. The patients also had a minimum of 3 postoperative CL radiographs (range, 3-6) taken as a part of their clinical follow-up. There were 49 men (61 hips) and 49 women (58 hips) with

Results

Anteversion values from CL x-rays had a mean of 26.1° ± 9.5° (range, −2° to 48.3°). Computed tomographic scan anteversion averaged 28.8° ± 11.8° (range, −7° to 54°). There was a significant, positive correlation between acetabular-version values on CL x-rays and on CT (P = .82, P < .001). The variation of anteversion values in serial CL x-rays of each patient averaged 6.1° ± 3.8° (range, 0°-18.3°). Neither sex (P = .68) nor BMI (P = .78) had a statistically significant influence on anteversion

Discussion

Obtaining optimal acetabular component position has been shown to be crucial for limiting dislocation, decreasing wear and rim-loading, and increasing impingement-free range of motion 1, 2, 3, 4, 5, 24, 25, 26. Although a safe zone of component placement was initially advocated to minimize prosthetic dislocation, additional concerns have been noted with the use of hard-on-hard articulations. Langton et al [27] noted an increased early failure rate of metal-on-metal articulations associated with

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      This difference in reliability was significant in our analysis and authors are not aware of any previous report attempting to compare the reliability of measuring anteversion in two types of cups. Some authors have preferred the cross-table lateral radiographs as these are easier to read for measuring anteversion25,26 but this method can be cumbersome and lead to errors due to movements of the pelvis during flexion of the opposite limb.27,28 Moreover, the direction of the central beam has to be ideally modified according to the angle of inclination, and the vertical plumb line might not always represent the true anteroposterior axis.29

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    No benefits or funds were received in support of the study.

    This study was performed at Washington University School of Medicine and Barnes-Jewish Hospital, St. Louis, MO.

    The Conflict of Interest statement associated with this article can be found at doi:10.1016/j.arth.2011.03.039.

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