Abstract
Introduction
Proper total knee arthroplasty balancing relies on accurate component positioning and alignment as well as soft tissue tensioning. Technology for cutting guide alignment has evolved from the “free hand” technique in the 1970's, to traditional intra/extra medullary rods in the 1980's and 1990's, to computer navigated surgery in the 2000's, and finally to patient specific custom cutting blocks in the 2010's. The latest technique is a modification to conventional computer navigation assisted surgery using Brainlab's Dash™ TKA/THA software platform that runs as an application on an Apple IPod held by the surgeon in a sterile pouch in the operative field. The handheld IPod touch screen allows the surgeon to control all aspects of the navigation interface without needing the assistance of an observer to manually run the software. In addition, the surgeon is able to always focus on the operative field while ‘navigating’ without looking up at a remote image monitor. This study represents a prospective analysis of the first 30 U.S. TKA cases performed using the newly commercially released Dash™ software using an IPod during surgery.
Methods
Thirty consecutive primary total knee arthroplasty procedures were performed using the Dash™ software (Brainlab) and an IPod touch (Apple). A cemented Genesis II (Smith Nephew) posterior stabilized implant was used in all cases. Femoral and tibial sensor arrays were placed in meta-diaphyseal regions for bone registration. We recorded the time spent to set up the arrays, time for bony registration, time to navigate the cutting guides, and the tourniquet time. After all bone cuts were completed, the tibial cut was manually measured with an intramedullary angle check instrument to assess the planned zero degree posterior slope and neutral varus/valgus coronal alignment. Final femoral and tibial component alignment and orientation was measured on standing long axis AP and lateral radiographs. Measurements from the Dash™ alignment group were compared to 30 consecutive surgeries using the author's traditional technique of intramedullary cutting block alignment (control group).
Results
In the initial 6 surgeries conducted, total navigation time exceeded 20 minutes reflecting the learning curve. In the remaining computer navigation group cases, average time for array set up was 3 minutes, average time for bony registration was 3 minutes, average time for navigating the cutting guides was 12 minutes, and average tourniquet time was 53 minutes. In the control group, the average tourniquet time was 44 minutes. There was no statistically significant difference in component alignment between the two groups when measuring distal femoral valgus angle, posterior condylar offset, femoral flexion/extension angle, tibial slope angle, or tibial varus/valgus angle.
Conclusions
Total knee arthroplasty using computer navigation and an IPod interface with Dash™ software is as accurate when compared to a traditional intramedullary TKA alignment technique. Only an additional average time of 9 minutes (after initial learning curve) using Dash™ navigation was needed. Further studies will compare these alignment techniques to extramedullary alignment and custom patient specific cutting block procedures.
