Aim: The study was conducted to evaluate differences between simultaneous and sequential cementing of the tibial and femoral components in total knee joint replacement in relation to final component alignment. Our hypothesis was that cementing the components sequentially increases accuracy of the final position.

Method: This was a prospective and randomised study, performed using a computer navigation system as the evaluation technique to determine the accuracy of implant positioning. All knee replacements (Scorpio, Stryker) were implanted with the assistance of computer navigation. The patients were divided into two groups of 20 patients each. The first group had implants cemented simultaneously where the tibial and femoral components were implanted with a single mix of cement and then pressurized by extending the leg. The second group of patients had the tibial component inserted with the first mix of cement and then impacted. Then the femoral component was inserted using a second mix of cement. Computer navigation was used to measure varus/ valgus cut of the femur, varus/ valgus cut of the tibia, and sagital slope of the tibia. Measurements were made with the components in place, both before cementing and then after cement cure.

Results: Our results show a statistically significant improvement in accuracy of femoral varus/ valgus alignment using the sequential cementing technique.

Introduction: We present our early results using the Stryker navigated knee system, since March 2003. There have been several papers showing an improvement in alignment of prostheses using navigation but few series have mentioned the problems of introducing this new technology.

Method: 214 consecutive operations were audited retrospectively from operation notes, discharge summaries and clinic notes.

Results: 11 surgeons performed 214 operations on 196 patients. 205 operations were primary knee joint replacements and 9 revisions. Average operation time was 149 minutes. 96% had an excellent outcome (pain free with a good range of motion), 2.6% had a moderate outcome and 1.4% had a poor outcome. 17 patients had superficial wound infections; 4 patients required an MUA for stiffness (with a good outcome); 3 DVTs (all below knee); 1 acute and 3 delayed haemarthroses; 1 temporarily unstable knee; 5 suffered prolonged pain, 1 peri-prosthetic fracture due to anterior notching of the femur requiring revision and there was 1 quads tendon rupture. There were 4 procedures abandoned, 2 because the femoral pin was unstable in osteoporotic bone and because of 2 software errors. Average range of motion was 0–110°. There was one deep infection following pyelonephritis. Average follow up has so far been 20.6 (2–104) weeks.

Conclusion: We have found that our results compare favourably with conventional techniques. We found it particularly useful for revision surgery and those patients who had intramedullary devices for previous fractures of the femur where conventional jigs could not be used.

The study was conducted to investigate differences between simultaneous and sequential cementing of the tibial and femoral components in total knee joint replacements. Our hypothesis was that cementing the components sequentially increases accuracy of the final position.

This was a prospective and randomized study, performed using a computer navigation system as the evaluation technique to determine the accuracy of implant positioning. All knee replacements (Scorpio, Stryker) were implanted using navigation technique.

The patients were divided in two groups. The first group had implants cemented simultaneously where the tibial and femoral components were implanted with a single mix of cement and then pressurized by extending the leg.

The second group of patients had the tibial component inserted with the first mix of cement and then impacted. The cement was allowed to set before proceeding with insertion of the femoral component using a second mix of cement.

The computer navigation system was utilized for bone cuts. It was then used to measure 3 sets of angles. The first set was varus/valgus cut of the femur, varus/valgus cut of the tibia and posterior slope of the tibia. The second set of measurements were the same angles, this time of the position of the prosthetic components before cementing, and the third set after cementing.

Our interim results show just a small difference between the two techniques.

It does not appear there is substantial difference in positioning of the implants between these two different techniques.