Assessment of inter- and intra-observer reliability in the determination of radiographic version and inclination of the cup in metal-on-metal hip resurfacing

Abstract

Purpose Determination of the cup orientation after metal-on-metal hip resurfacing may provide important information in the postoperative follow-up. We present a mathematical method based on a previously described approach to assess the version and inclination of the cup in the metal-on-metal bearing without a separate software computation from plain radiographs. The aim of the study was to assess the intra-and inter-observer reliability of this method. Methods Calculation of version and inclination were done twice for 20 hip resurfacings by four observers. Intraobserver reliability was estimated by mean error and correlation of the two sets of measurement for version and inclination. Bland-Altman plots, intra-class coefficient and mean error were used to assess the inter-observer reliability of the measurements. Results Intra-observer correlation for version measurement ranged from 0.74 to 0.94. Correlation for inclination varied between 0.94 and 0.97. Upper and lower limits of agreement in Bland-Altman plots for version measurements between observers ranged from 4.1 to 7.2 degrees and from −3.2 to −8.3 degrees, respectively. For inclination measurements the upper and lower limits ranged from 3.1 to 5.3 degrees and from −2.7 to −6.0 degrees.Conclusions Mean errors, correlation coefficients and 95% limits of agreement were on an acceptable level. We believe that this method is applicable for clinical use.

601 metal-on-metal total hip replacements with 36 mm heads a 5 minimum year follow up: Levels of ARMD remain low despite a comprehensive screening program

“…Blood was taken for cobalt and chromium levels and a plain radiograph taken. Inclination angle was assessed by the method described by Reito et al 34 Patients were allocated into either ''asymptomatic hip'' or ''symptomatic hip'' by the reviewing clinician. Symptomatic hips were defined as those with pain around the hip joint and/or mechanical hip symptoms (clicking/clunking or giving way).…”

Reply to comments on: assessment of inter- and intra-observer reliability in the determination of radiographic version and inclination of the cup in metal-on-metal hip resurfacing

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We read the comments of Bachhal et al with interest regarding our article entitled "Assessment of inter-and intraobserver reliability in the determination of radiographic version and inclination of the cup in metal-on-metal hip resurfacing" [1]. They state that our method to measure version in MMHR is not the easiest.

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Comments on Reito et al.: Assessment of inter- and intra-observer reliability in the determination of radiographic version and inclination of the cup in metal-on-metal hip resurfacing

“…We read the article by Reito et al [1] which discussed the radiographic method of determining version and inclination in metal-on-metal hip arthroplasty with interest. Although we agree with the validity of the method used by the authors [2], it is not the easiest for measuring anteversion for metalon-metal arthroplasty.…”

“…Using Table 1 ( in article by Reito et al [1]), with p/e0 0.14 and r/e01.06 (both rounded to 2 decimals), the angle calculated will be 23.5 while using the equation (ours or as given in this article) it is 24.62, and it is 24.83 when using Table 1 for ratio p/h. This clearly shows that our suggested method involves fewer measurements (p and h vs p, r and e), fewer calculations (one ratio vs two) and is more accurate if using a table as it involves approximation of one ratio as compared to two.…”

“…can be used. If one wishes to use ready tables, then it is easy to see that calculation of two fractions (p/e and r/e, Table used in article by Reito et al [1]) might give values between those provided in the table, thus requiring rounding off of two fractions while a similar table prepared for arcsine function would require rounding off of a single fraction resulting in more accurate calculation of anteversion. We have provided Table 1 for such purposes.…”