In a prospective randomised clinical study acetabular components were implanted either freehand (n = 30) or using CT-based (n = 30) or imageless navigation (n = 30). The position of the component was determined post-operatively on CT scans of the pelvis. Following conventional freehand placement of the acetabular component, only 14 of the 30 were within the safe zone as defined by Lewinnek et al (40 degrees inclination sd 10 degrees ; 15 degrees anteversion sd 10 degrees ). After computer-assisted navigation 25 of 30 acetabular components (CT-based) and 28 of 30 components (imageless) were positioned within this limit (overall p < 0.001). No significant differences were observed between CT-based and imageless navigation (p = 0.23); both showed a significant reduction in variation of the position of the acetabular component compared with conventional freehand arthroplasty (p < 0.001). The duration of the operation was increased by eight minutes with imageless and by 17 minutes with CT-based navigation. Imageless navigation proved as reliable as that using CT in positioning the acetabular component.

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There is growing evidence that cytokines such as tumor necrosis factor (TNF) alpha, interleukin (IL) 1beta, IL-6, bone morphogenetic proteins (BMP), and nitric oxide (NO) play an important role in the pathogenesis of bone tunnel enlargement following anterior cruciate ligament (ACL) reconstruction. Furthermore, the release of these mediators has been considered a possible reason for the higher incidence of bone tunnel enlargement following hamstring tendon (HST) than following patellar tendon (PT) ACL reconstruction observed in several studies. In this investigation synovial fluid samples from 13 patients were collected immediately before (24+/-7 days after ACL rupture) and 7 days after ACL surgery and values of TNF-alpha, IL-1beta, IL-6, NO, and BMP-2 were analyzed. Furthermore, the incidence of bone tunnel enlargement was assessed using radiographs 38+/-7 weeks after surgery. Six patients underwent autologous HST ACL reconstruction, and in seven patients an PT autograft was used. In the overall patient population there were significantly higher synovial fluid concentrations of IL-6 and BMP-2 postoperatively than preoperatively; TNF-alpha showed a trend towards lower postoperative levels while IL-1beta and NO remained unchanged. The concentrations of NO, TNF-alpha, and IL-6 found in the present study were clearly higher than normal values given in the literature. Assessment of bone tunnel enlargement revealed an average increase in tibial tunnel width of 28.4+/-3.1% with comparable values for HST and PT ACL reconstructions. There was no significant correlation between bone tunnel enlargement and postoperative synovial fluid concentrations of TNF-alpha, IL-1beta, IL-6, NO, and BMP-2. However, all patients with bone tunnel enlargement had higher postoperative concentrations of TNF-alpha, IL-6, and NO in the synovial fluid. There were no significant differences in concentrations between HST and PT groups. In conclusion, we observed an association between tibial bone tunnel enlargement and elevated synovial fluid concentrations of IL-6, TNF-alpha, and NO 7 days after ACL surgery indicating the potential involvement of these biological mediators in the pathogenesis of bone tunnel enlargement. However, there was no difference between HST and PT ACL reconstructions regarding synovial fluid contents of IL-6, TNF-alpha, IL-1beta, NO, and BMP-2, suggesting a comparable biological response between these autografts following their use in ACL reconstruction.

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).