Improved accuracy of component alignment with the implementation of image-free navigation in total knee arthroplasty

Abstract

Accuracy of implant positioning and reconstruction of the mechanical leg axis are major requirements for achieving good long-term results in total knee arthroplasty (TKA). The purpose of the present study was to determine whether image-free computer navigation technology has the potential to improve the accuracy of component alignment in TKA cohorts of experienced surgeons immediately and constantly. One hundred patients with primary arthritis of the knee underwent the unilateral total knee arthroplasty. The cohort of 50 TKAs implanted with conventional instrumentation was directly followed by the cohort of the very first 50 computer-assisted TKAs. All surgeries were performed by two senior surgeons. All patients received the Zimmer NexGen total knee prosthesis (Zimmer Inc., Warsaw, IN, USA). There was no variability regarding surgeons or surgical technique, except for the use of the navigation system (StealthStation) Treon plus Medtronic Inc., Minnesota, MI, USA). Accuracy of implant positioning was measured on postoperative long-leg standing radiographs and standard lateral X-rays with regard to the valgus angle and the coronal and sagittal component angles. In addition, preoperative deformities of the mechanical leg axis, tourniquet time, age, and gender were correlated. Statistical analyses were performed using the SPSS 15.0 (SPSS Inc., Chicago, IL, USA) software package. Independent t-tests were used, with significance set at P < 0.05 (two-tailed) to compare differences in mean angular values and frontal mechanical alignment between the two cohorts. To compute the rate of optimally implanted prostheses between the two groups we used the chi(2) test. The average postoperative radiological frontal mechanical alignment was 1.88 degrees of varus (range 6.1 degrees of valgus-10.1 degrees of varus; SD 3.68 degrees ) in the conventional cohort and 0.28 degrees of varus (range 3.7 degrees -6.0 degrees of varus; SD 1.97 degrees ) in the navigated cohort. Including all criteria for optimal implant alignment, 16 cases (32%) in the conventional cohort and 31 cases (62%) in the navigated cohort have been implanted optimally. The average difference in tourniquet time was modest with additional 12.9 min in the navigated cohort compared to the conventional cohort. Our findings suggest that the experienced knee surgeons can improve immediately and constantly the accuracy of component orientation using an image-free computer-assisted navigation system in TKA. The computer-assisted technology has shown to be easy to use, safe, and efficient in routine knee replacement surgery. We believe that navigation is a key technology for various current and future surgical alignment topics and minimal-invasive lower limb surgery.

Femoral Lateral Bowing and Varus Condylar Orientation Are Prevalent and Affect Axial Alignment of TKA in Koreans

“…This finding is also intuitive because surgeons would be able to place the cutting block independently of the anatomy whether a standard extramedullary guiding system or a navigation system is used. Numerous studies have documented the use of navigation improves alignment [12,22,24,28,34,37], but relatively few previous studies have addressed the issue of navigation in the context of the alignment of knees with severe deformity [12,22,24,28,34,37]. Our findings are generally in accord with two previous studies, which found that the use of navigation reduces outliers in knees with severe deformity [12,22,24,28,34,37].…”

“…Numerous studies have documented the use of navigation improves alignment [12,22,24,28,34,37], but relatively few previous studies have addressed the issue of navigation in the context of the alignment of knees with severe deformity [12,22,24,28,34,37]. Our findings are generally in accord with two previous studies, which found that the use of navigation reduces outliers in knees with severe deformity [12,22,24,28,34,37]. Furthermore, in the present study, the navigation group also had no outliers in femoral or tibial component alignment.…”

Alignment in total knee arthroplasty, still more questions than answers…

“…Similar results have also been reported in a meta-analysis of level-I studies [6]. Unfortunately, the total time spent in the operating room and the lack of clinical amelioration has tempered its uniform acceptance by the surgical community [3,14].Patient-specific instruments (PSI), recently introduced as a new technology, could demonstrate the same advantage of navigation in increasing accuracy, but without the practical inconveniences such as, the need to perform anatomical mapping or to position trackers during the procedure [10].The virtual planning of the TKA procedure is outsourced to engineers who identify the anatomical landmarks needed for alignment on CT/MRI based 3D models, after which the information is transferred to patient-specific instruments that can be used during surgery. These instruments, created by laser sintering, can be produced in the most complex forms and are thus patient specific [1,5].…”

Differences between Sagittal Femoral Mechanical and Distal Reference Axes Should Be Considered in Navigated TKA

“…Numerous studies report use of a computer-assisted navigation system limits the prevalence of outlier values of limb and/or implant alignment measurements in the coronal plane [2,5,8,9,12,14,21,30,32,37]. Whether the same benefits are realized in the sagittal plane when a surgical navigation system is used is unclear [2, 6-8, 12, 18, 32].…”