Resection of the distal femur to properly fit the prosthetic component is a crucial step for prosthesis alignment during TKA. In this study, we development a new integrative(Five-In-One, FIO) femur resection method, which performs distal femoral resection in one procedure instead of the standard five cutting steps. The accuracy and operating time are comparable to the conventional cutting methods using foam bone model experimentation and in 9 patients.

In vitro comparison: Uniformly-sized foam bone femur models were used in this study. New five-in-one cutting devices and conventional cutting devices of the same prosthetic size of #44 were installed and resection of the distal femur by five experienced orthopaedic surgeons. Each surgeon performed five cases with each device. Then a femoral prosthesis (#44) was installed on each cut femur mode and anterior-posterior and lateral X-ray radiographs were taken. The angles facet length and distance between anterior and posterior oblique facets were then measured with goniometer and vernier calliper. The corresponding angles from a standard femoral prosthesis (#44) were also measured. The angular difference between the resection femur and prosthesis was calculated and named Angular Deviation. The valgus angle and anteversion angle were measured on anteriorposterior and lateral X-ray radiographs respectively. The mean value from the five measurements obtained from each surgeon using the same cutting method was used for the comparison of the modified and standard resection model. The operating time of each cutting procedure was recorded. students’t-tests were used for the statistical analysis.

In vivo following up: 9 patients with use of the five-in-one cutting instrument and the Deluxe prosthesis have been evaluated during operating, and followed up for at least one year. Operating time were recorded and HSS clinical and functional scoring systems before the surgery, three months and one year after surgery.

The angular deviation of the new FIO Cutting Device was significantly less than the conventional device in all four anatomic measurements (p < 0.05). The distance deviation in the FIO group was also significantly less in the FIO group compared to the conventional procedure (p < 0.05). The average valgus angle and anteversion angle of the five-in-one cutting device which were measured on anterior-posterior and lateral X-ray radiographs respectively were 6.86° and 3.02° respectively. They were not significantly different when compared with the data of the conventional cutting device, which were 6.56o and 3.06o respectively. The mean of the cutting time of the five-in-one device was 9.70 minutes, which was significantly less than the conventional cutting device which was 21.84 minutes averaged (p < 0.05).

Our data demonstrated that the angular accuracy of the distal femoral resection with the newly Five-in-one technique was greatly improved compared to the conventional cutting method. With the use of the new technique, operative time was also shortened over two folds compared to the conventional method. We conclude that the new five-in-one cutting device is more accurate and shorten operating time compared with the conventional device in the vitro study.

The mean HSS score before surgery was 48.69, 84.7 three months after surgery, and 85.6 at one year after surgery. The survivorship was 100% of patients.