Automated femoral landmark extraction for optimal prosthesis placement in total hip arthroplasty.

The automated extraction of anatomical reference landmarks in the femoral volume may improve speed, precision, and accuracy of surgical procedures, such as total hip arthroplasty. These landmarks are often hard to achieve, even via surgical incision. In addition, it provides a presurgical guidance for prosthesis sizing and placement. This study presents an automated workflow for femoral orientation and landmark extraction from a 3D surface mesh. The extraction of parameters such as the femoral neck axis, the femoral middle diaphysis axis, both trochanters and the center of the femoral head will allow the surgeon to establish the correct position of bony cuts to restore leg length and femoral offset. The definition of the medullary canal endosteal wall is used to position the prosthesis' stem. Furthermore, prosthesis alignment and sizing methods were implemented to provide the surgeon with presurgical information about performance of each of the patient-specific femur-implant couplings. The workflow considers different commercially available hip stems and has the potential to help the preoperative planning of a total hip arthroplasty in an accurate, repeatable, and reliable way. The positional and orientation errors are significantly reduced, and therefore, the risk of implant failure and subsequent revision surgery are also reduced.

Sensory nerve conduction of the plantar nerve compared with other nerve conduction tests in rats.

OBJECTIVE: In rats the available techniques for evaluation of sensory nerve conduction are limited. We report a new method of sensory nerve conduction of the plantar nerve using needle electrodes as the recording electrodes behind the medial malleolus and ring electrodes as the stimulating electrodes around the three middle toes. METHODS: We performed this sensory nerve conduction test in 25 rats during their growth over a 6 weeks' period and compared this method with the motor nerve conduction and H-reflex sensory nerve conduction of the tibial nerve in 10 rats, and with the motor and mixed nerve conductions of the tail nerve in 15 rats. RESULTS: There was a highly or moderately significant correlation between the body weight and sensory nerve conduction velocity (NCV) of the plantar nerve, mixed NCV and motor NCV of the tail nerve, indicating a growth-related increase in the NCV. The growth-related increase in the NCV was not observed in the motor and H-reflex sensory nerve conductions of the tibial nerves. CONCLUSIONS: This test is simple and reliable and can be used for the sensory nerve conduction test in rats.