Abstract
Purpose
Computer navigation for hip resurfacing has been shown to reduce the incidence of technical error during femoral head preparation and provides increased accuracy compared to conventional instrumentation for insertion of the initial femoral guidewire. Limitations to the widespread use of navigation in hip resurfacing include access and cost. A novel, patient specific nylon jig has been developed as a cost effective alternative for placement of the initial guidewire. The purpose of this study was to compare the accuracy of femoral guidewire insertion between imageless navigation, conventional instrumentation and a new type of CT-based custom jig.
Method
Six pairs of cadaveric femora were used in the study. Each pair was divided randomly between a group utilizing firstly a conventional lateral pin jig (BHR, Smith & Nephew Inc.) followed by navigation (Vector Vision SR, BrainLAB) and a group utilizing a CT-based, patient specific custom jig (Visionaire, Smith & Nephew Inc.). A single surgeon inserted all guidewires. The planned guidewire position was approximately 10 degrees of relative valgus to the native neck-shaft angle in the coronal plane and neutral version in the sagittal plane. The same coronal alignment angle was used between paired femora. Femurs were positioned in a draped synthetic foam hip model prepared with a standard posterior approach. Guidewire insertion time and placement accuracy for each of the three alignment methods was assessed. Guidewire placement accuracy for coronal inclination and version was assessed by anteroposterior and lateral digital radiographs and was defined as the mean deviation from the planned alignment value.
Results
Imageless navigation was more accurate than both the custom and the conventional jigs in coronal guidewire inclination (mean 1.3 degrees, SD 1.2, p<0.047). The custom jig (mean 6.4 degrees, SD 2.9) provided a comparable level of accuracy to that of the conventional jig (mean 5.5 degrees, SD 3.6, p=0.851). Guidewire version using the custom jig (mean 1.0 degrees, SD 0.4) was comparable to imageless navigation (mean 3.9 degrees, SD 2.1, p=0.101) and was superior to the conventional jig (mean 5.6 degrees, SD 2.9, p=0.008). The time required for guidewire insertion using the custom alignment jig was significantly reduced compared to both the conventional jig and imageless computer navigation (p<0.001), with imageless navigation requiring more time than the conventional jig (p=0.038).
Conclusion
The CT-based custom alignment jig was superior to conventional instrumentation for guidewire version while providing a similar level of accuracy for coronal guidewire inclination. Imageless navigation provided the highest level of accuracy for coronal guidewire placement. A custom alignment jig may be a better alternative to conventional instrumentation for placement of the initial femoral guidewire in hip resurfacing.
