Greater accuracy in positioning of the acetabular cup by using an image-free navigation system

Abstract

In a prospective and randomised clinical study, acetabular cups were implanted free-hand (control group n=22) or with computer assistance using an image-free navigation system (study group n=23). The cup position was determined postoperatively on pelvic CT. An average inclination of 42.3°(range: 30°-53°; SD±7.0°) and an average anteversion of 24.0°(range: −3°to 51°; SD±15.0°) were found in the control group, and an average inclination of 45.0°(ranage: 40°-50°; SD±2.8°) and an average anteversion of 14.4°(range: 5°-25°; SS±5.0°) in the computer-assisted study group. The deviations from the desired cup position (45°inclination, 15°anteversion) were significantly lower in the computer-assisted study group (p<0.001 each). While only 11/22 of the cups in the control group were within the Lewinnek safe zone, 21/23 of the cups in the study group were placed in this target region (p=0.003).Résumé Dans un étude clinique prospective et randomisé, les cupules acétabulaires ont été implantées de façon habituelle (n=22; groupe témoin) ou avec assistance d'un ordinateur qui utilise un système de navigation imagelibre (n=23; groupe d'étude). La place de la cupule a été déterminée après l'opération sur un scanner pelvien. Une inclinaison moyenne de 42,3°(30°à 53°; ±7.0°) et une antéversion moyenne de 24,0°(−3°à 51°; ±15.0°) ont été trouvées dans le groupe témoin et une inclinaison moyenne de 45,0°(40°à 50°; ±2.8°) et une antéversion moyenne de 14,4°(5°à 25°; ±5.0°) dans le groupe de l'étude assistée par ordinateur. Les déviations par rapport à la position désirée de la cupule (45°d'inclinaison, 15°d'antéversion) étaient notablement inférieures dans le groupe de l'étude assistée par ordinateur (p<0.001 chacun). Alors que seulement 11 des 22 cupules du groupe témoin étaient dans la zone sûre de Lewinnek, 21 des 23 cupules du groupe d'étude ont été placées dans cette région cible (p=0.003).

Intraoperative Radiographs for Placing Acetabular Components in Hip Resurfacing Arthroplasty

“…A ''safe'' zone of acetabular component position was suggested for small-bearing metal-on-polyethylene THA in a retrospective study [20]. Although this study had some weaknesses, the safe range of 30°to 50°suggested in that study has been generally accepted as a gold standard by surgeons [14,16,25], which was also targeted in our study. An AP pelvis radiograph remains a universal tool for assessing acetabular inclination angles after hip arthroplasties in the United States.…”

“…Numerous studies have documented surgical navigation holds the promise for providing most accurate intraoperative guidance for acetabular component position [10,16,29,34]. However, the equipment is not available to most surgeons.…”

“…Many methods, including visual inspection [32], use of specialized jigs [23], intraoperative fluoroscopic guidance [21], image-free navigation [16,24], and CT-based computer navigation [10,17,27], reportedly assist surgeons in achieving the safe target during the placement of acetabular components. However, all of these techniques have disadvantages, such as a lack of accuracy, high cost, a requirement for special training, and extra preparation and operating room (OR) time.…”

Computer-assisted versus Manual Alignment in THA: A Probabilistic Approach to Range of Motion

“…Within the level of variability considered here, CAS alignment produced resultant ROM that was always within acceptable limits. While CAS techniques decrease variability in implant alignment [13][14][15]24], this study provides quantitative support for the ability of CAS methods to decrease the probability of hip dislocation compared to conventional techniques.…”

“…There is also natural variability in how precisely a surgical plan can be executed [20]. Computer-assisted surgical (CAS) techniques reduce but do not eliminate this variability [13][14][15]. However, the effect of reduced variability on a clinical outcome such as ROM has not been fully determined.…”