Measurement of Acetabular Component Position in Total Hip Arthroplasty in Dogs: Comparison of a Radio-Opaque Cup Position Assessment Device Using Fluoroscopy with CT Assessment and Direct Measurement

Abstract

Objectives The aim of this study was to compare measurements of angle of lateral opening (ALO) and version determined using a radioopaque cup position assessment device imaged with fluoroscopy to measurements obtained by CT and direct measurement in a cadaveric model. Our null hypothesis was that there would not be any difference in the angles measured by the techniques. Methods Six cadavers were implanted with BFX acetabular components. The CPAD was placed and images were obtained with fluoroscopy. Measurements were obtained from the radiopaque marker bars on the CPAD device, and version and ALO were calculated. The ALO and version were determined by CT and DM. Comparisons were made using a two-way analysis of variance and a generalized linear model procedure analysis. Results There were no significant differences between the measurements for ALO (p = 0.275) or version (p = 0.226). Correlation between methods was 0.948 and 0.951 for ALO and version, respectively. The mean difference (standard deviation [SD], and 95% confidence interval [CI]) for ALO were: CT versus CPAD 1.85 degrees (± 2.32 degrees [-2.99–3.31]), CT versus DM 1.96 degrees (± 1.99 degrees [−2.2–4.27]), CPAD versus DM1.74 degrees (±2.21 degrees [−1.13 and 5.24]). The mean difference (SD [CI]) for version was CT versus CPAD 2.86 degrees (±1.56 degrees [ −2.63–1.69]), CT versus DM 1.10 degrees (±1.42 degrees [−1.57–2.09]), CPAD versus DM 1.07 degrees (±0.76 degrees [0.13–2.09]). Clinical Relevance The results demonstrate that intraoperative imaging in cadaveric specimens with the CPAD is an accurate method to determine ALO and version of the acetabular component.

Fluoroscopic Categorization of Cementless Acetabular Component Positioning

“…1 2 3 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 Postoperative luxation is the most widely reported complication of THA, occurring in 1 to 20% of cases. 2 6 13 15 19 21 24 25 26 27…”

“…28 29 30 31 32 33 34 35 One prior study by Dalbeth and colleagues described a method for assessment of acetabular component positioning using fluoroscopy and a cup positioning assessment device that could potentially be used intraoperatively to estimate ALO. 26…”

“…Previous studies have identified and defined ideal acetabular component positioning based on these parameters (inclination declined 20-25 degrees below the ilio-ischial axis, retroversion of 10-15 degrees, ALO of 45 degrees) to reduce the risk of postoperative luxation. 26,[28][29][30] Proper orientation of the acetabular component relies on precise preoperative patient positioning in a true lateral position, maintenance of true lateral positioning throughout the surgical procedure and visual estimation of acetabular component orientation parameters intraoperatively based on local landmarks and the horizontal plane, as proper positioning and implantation of the acetabular component are made on the premise that the pelvis is positioned in true lateral recumbency. 26,[28][29][30][31] Correct orientation of the acetabular component requires the patient to be positioned in true lateral recumbency.…”

“…[1][2][3][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] Postoperative luxation is the most widely reported complication of THA, occurring in 1 to 20% of cases. 2,6,13,15,19,21,[24][25][26][27] Improper orientation of the acetabular component has been identified as an important contributing factor for postoperative luxation in THA in the dog. 1,2,6,13,15,19 The orientation of the acetabular component is defined by three parameters: angle of inclination, version angle and angle of lateral opening (ALO).…”

“…26,[28][29][30] Proper orientation of the acetabular component relies on precise preoperative patient positioning in a true lateral position, maintenance of true lateral positioning throughout the surgical procedure and visual estimation of acetabular component orientation parameters intraoperatively based on local landmarks and the horizontal plane, as proper positioning and implantation of the acetabular component are made on the premise that the pelvis is positioned in true lateral recumbency. 26,[28][29][30][31] Correct orientation of the acetabular component requires the patient to be positioned in true lateral recumbency. To facilitate proper patient positioning for THA, devices such as positioning bags and positioning boards are used to try to maintain the patient in true lateral recumbency on the operating table.…”