[Bone morphing system for ligament balancing in total knee arthroplasty].

OBJECTIVE: To investigate effectiveness of applying the Bone Morphing based image-free computer-assisted system for the ligament balancing management in the total knee arthroplasty (TKA).

METHODS: Between November 2002 and June 2003, twenty-one posterior stabilized total knee prostheses (Craver, France) were implanted in 21 patients using the Bone Morphing based image-free Ceravision system. This cohort included 5 men and 16 women with an average age of 72.4 years, two undergoing high tibial osteotomy and 1 undergoing distal femoral osteotomy before. The preoperative deviation was measured by the full-length AP X-rays. The knees were in varus deviation in 14 patients and in valgus deviation in 7 patients, with an average of 2.36 degrees (varus 13 degrees-valgus 13 degrees). The frontal X-rays of the knee were assessed, the mean value of the varus force-stress test was 8.47 degrees (varus 2 degrees-varus 20 degrees), and the mean value of the valgus force-stress test was 3. 63 degrees (varus 7 degrees-valgus 12 degrees).

RESULTS: With the Ceravision-recorded data, the intraoperative alignment was assessed, the mean lower limb axis was 3.33 degrees (varus 12 degrees-valgus 10 degrees), and compared with the preoperative data, the difference was significant (P < 0.05); the mean value of the varus force-stress test was 6. 47 degrees (varus 0 degree - varus 24 degrees), the mean value of the valgus force-stress test was 4.32 degrees (varus 8 degrees-valgus 15 degrees), and compared with the preoperative data, the difference was significant (P < 0.05). The post-prosthetic alignment on Ceravision with a deviation of 0.175 degrees (varus 2 degrees-valgus 3 degrees) was compared with the postoperative alignment by the full-length AP X-rays, with a deviation of 0.3 degrees (varus 3.5 degrees-valgus 1.5 degrees), the difference wasn't significant (P > 0.05). The clinical check-up performed 3 months after operation showed that the average range of movement (ROM) was 115 degrees (105-130 degrees), the mean frontal laxity was 0.27 mm (0.2-0.5 mm). The femoral and tibial components were implanted in the satisfactory 3 dimensional position without ligament imbalance in all the patients, and there were no instability or patella complications.

CONCLUSION: Utilization of the Bone Morphing based image-free computer-assisted system can achieve an accurate component 3 dimensional alignment, optimal bone resection, optimal control of surgical decision in releasing the soft tissues, rotating the femoral component to gain an extension/flexion rectangular gap, and managing the ligament balancing so as to achieve a satisfactory initial clinical outcome. This system can be routinely used in the TKA.