Proper femoral stem and acetabular implant orientation is critical to the initial and long-term success of THA. Post-operative determination of cup and stem anteversion is important in cases of hip instability and planning isolated component revisions. At ISTA 2010 Dubai, we introduced a novel, simple stem modification that can be added to any stem design to help assess stem, and possibly cup anteversion with plain post-operative radiographs throughout the lifespan of the implant. [Figure 1] As the stem is rotated, the visible hole pattern changes. [Figure 2] This study was performed to further validate the accuracy and potential usefulness of this design. We prospectively reviewed 100 consecutive THA cases using the stem reference hole modification on rectangular tapered Zweymuller-type stems implanted from September 2010 to May 2012. Post-operative hip/femur CT scans were obtained to determine the true cup and stem orientation to validate and quanitify the precision of the reference holes. Intra-operative estimates of stem anteversion and combined anteversion (Ranawat Sign) were recorded. Post-operative radiograph measurement of stem anteversion (AP hip x-ray with leg in neutral rotation) was obtained and compared to the CT scan measurement referencing stem rotation relative to the knee epicondylar axis. [Figure 3] In addition, we compared the modified reference hole anteversion assessment to a control group of original unmodified stems assessed using the same methods.Introduction
Methods
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. 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).Introduction
Methods
