Navigation systems that increase alignment accuracies of the lower limbs have been applied widely in total knee arthroplasty and are currently being adopted for minimally invasive UKA (MIS UKA) with good alignment results. There is little debate that when compared with total knee arthroplasty (TKA), UKA is less invasive, causes less morbidity, better reproduces kinematics, and therefore offers quicker recovery, better range of movement and more physiologic function. However, despite improved alignment accuracies, advantages of use of navigation system in UKA in clinical outcomes and survivals are still debatable. To the best of our knowledge, no reports are available on the long-term results after UKA performing using a navigation system. The purpose of this prospective study was to compare the radiological, clinical, and survival outcomes of UKA that performed using the navigation system and using the conventional technique at average 8 years follows up.

Between January 2003 and December 2005, Total of 98 UKAs were enrolled for this study, 56 UKAs in the navigation group and 42 UKAs in conventional group were included in this study after a average 8 years follow-up. At the final follow up, the radiological measurements with regard to the mechanical axis, the inclination of the femoral and tibial components, and radiolucent line or loosening were evaluated and compared between two groups. The clinical evaluations were performed using range of motion, Western Ontario and McMaster Arthritis index (WOMAC) scores and Knee Society (KS) score.

Of the 98 patients (98 UNI knees), 2 (2.0%) had died at a mean 5.8years after surgery because of cardiovascular disease, 3 (3.1%) underwent revision surgery that 1 cases of periprosthetic stress fractures in medial tibial plateaus in the navigation group and a case of tibial component loosening and polyethylene wear in conventional groups were observed. At a final follow up, the mean of mechanical axis was statistically different between two groups (2.7 vs. 3.9 of varus). And there were significant difference between 2 groups in terms of the mean values (p=0.042) for the tibial component coronal alignment, mean coronal alignments of tibial components were 89.1 ± 2.4° in the NA-MIS and 87.6 ± 1.8° in the MIS group, however outlier result were similar in the 2 group (5 and 5 knees, respectively, p=0.673). Sagittal alignments of femoral and tibial component were similar in the two groups (p>0.05) Significant differences were found in WOMAC or HSS knee scores, in which, stiffness did not show any difference between two groups, but pain and function showed difference at the last follow-up. The mean knee flexion has improved from 135.0 ± 14.8° and 135.0 ± 14.1° preoperatively to 137.1 ± 6.5° and 136.5 ± 7.2° in the NA-MIS and MIS groups on the latest follow-up, which was not significant different (p=0.883). The navigation system in UKA can provide improved alignment accuracy. And better clinical outcomes in pain and HSS score compared with conventional technique after a average of 8 year follow-up.

The radiologic and clinical results of High Tibial Osteotomies (HTO) strongly rely on the accuracy of correction, and inadequate intraoperative measurements of the leg axis can lead to over or under- correction. Over the past few years, navigation systems have been proven that navigation systems provide reliable real-time intro-operative information, may increase accuracy, and improves the precision of orthopaedic surgeries. We assessed the radiological and clinical results of navigation- assisted open wedge HTO versus conventional HTO at 24 months after surgery.

A total of sixty-five open wedge HTOs were performed using navigation system and compared with forty-six open HTOs that had been performed using the conventional cable technique in terms of intraoperative leg axis assess. The Orthopilot navigation system (HTO version 1.3, B. Braun Aesculap, Tuttligen, Germany) used throughout the procedure of navigated open wedge HTO. The aim of the correction was to achieve of 3°of valgus (2–4°) on both method. For the radiological evaluation, postoperative leg axes were examined using weight bearing full-leg radiography obtained at postoperative two years after surgery. To assess correction accuracies, we compared mechanical tibiofemoral angles and intersections of the mechanical axis of the tibial plateau (%) in both groups. Outliers were defined as under-corrections of < 2° of valgus and as over-corrections of > 5° of valgus. The posterior slope of the proximal tibia was measured using the proximal tibial anatomical axis (PTAA) method. HSS (Hospital for Special Surgery) scores and ROMs (ranges of motion) were evaluated and all complications were recorded and surgical and radiation times were measured.

Navigated HTOs corrected mechanical axes to 2.8° valgus (range −3.1∼5.3) with few outliers (9.5%), and maintained posterior slopes (8.5±2.3° preoperatively and 11.0±2.8° postoperatively) (P>0.05). In the conventional group, the mean valgus correction was satisfactory (2.2° valgus), but only 67.4% were within the required range (2∼5° valgus), and 26.1% of cases were under-corrected and 6.5% of cases were over-corrected. Posterior slope increased from 8.0° to 10.6° on average without significant change after surgery. Total fluoroscopic radiation time during navigated HTO was 8.1 seconds (5∼12s) as compared with 46.2 seconds (28∼64 s) during conventional HTO (p<0.05). The surgery time for navigated HTO was 11.2 minutes longer than for conventional HTO (55.5 minutes). No specific complications related to the navigation were encountered. At clinical follow up, mean HSS scores of the navigated HTO and conventional groups improved to 91.8 and 92.5 from preoperative values of 55.3 and 55.9, respectively (p>0.05), and all patients achieved full ROM.

Navigation for HTO significantly improved the accuracy of postoperative leg axis, and decreased the variability of correction with fewer outliers, and without any complications. Moreover, it allows multi-plane measurements to be made, in the sagittal and transverse planes as well as the frontal plane intra-operatively in real time, compensates to some extent for preoperative planning shortcomings based on radiography, and significantly reduces radiation time.