Results of Computer Assisted Mini-Incision Subvastus Approach for Total Knee Arthroplasty
Thana Turajane MD*, Viroj Larbpaiboonpong MD*, Jatupon Kongtharvonskul MD*, Samart Maungsiri MD*
Affiliation : * Department of Orthopedic Surgery, Police General Hospital, Bangkok, Thailand
Background : Mini-incision subvastus approach is soft tissue preservation of the knee. Advantages of the
mini-incision subvastus approach included reduced blood loss, reduced pain, self rehabilitation and faster
recovery. However, the improved visualization, component alignment, and more blood preservation have been
debatable to achieve the better outcome and preventing early failure of the Total Knee Arthroplasty (TKA).
The computer navigation has been introduced to improve alignment and blood loss. The purpose of this study
was to evaluate the short term outcomes of the combination of computer assisted mini-incision subvastus
approach for Total Knee Arthroplasty (CMS-TKA)
Material and Method: A prospective case series of the initial 80 patients who underwent computer assisted
mini-incision subvastus approach for CMS-TKA from January 2007 to October 2008 was carried out. The
patients’ conditions were classified into 2 groups, the simple OA knee (varus deformity was less than 15
degree, BMI was less than 20%, no associated deformities) and the complex deformity (varus deformity was
more than 15 degrees, BMI more was than 20% , associated with flexion contractor). There were 59 patients
in group 1 and 21 patients in group 2. Of the 80 knees, 38 were on the left and 42 on the right.
Results : The results of CMS-TKA [the mean (range)] in group 1: group 2 were respectively shown as the
incision length [10.88 (8-13): 11.92 (10-14], the operation time [118 (111.88-125.12): 131 (119.29-143.71)
minutes, lateral releases (0 in both groups), postoperative range of motion in flexion [94.5 (90-100): 95.25
(90-105) degree] and extension [1.75 (0-5): 1.5 (0-5) degree] Blood loss in 24 hours [489.09 (414.7-563.48):
520 (503.46-636.54) ml] and blood transfusion [1 (0-1) unit? in both groups], Tibiofemoral angle preoperative
[Varus = 4 (varus 0-10): Varus = 17.14 (varus 15.7-18.5) degree, Tibiofemoral angle postoperative [Valgus =
1.38 (Valgus 0-4): Valgus = 2.85 (valgus 2.1-3.5) degree], Tibiofemoral angle outlier (85% both groups), and
Knee society score preoperative and postoperative [64.6 (59.8-69.4) and 93.7 (90.8-96.65)]: 69 (63.6-74.39)
92.36 (88.22-96.5)]. The complications found in both groups were similar. No deep vein thrombosis, no
fracture at both femur and tibia, no vascular injury, and no pin tract pain or infection was found in both
groups.
Conclusion : The computer assisted CMS-TKA) is one of the appropriate procedures for all varus deformity, no
limitation with the associated bone loss, flexion contractor, BMI, except the fixed valgus deformity. To ensure
the clinical outcomes, multiple key steps were considered as the appropriate techniques for this approach
which included the accurate registration, precision bone cut and ligament balances, and the good cement
techniques.
Keywords : Total knee arthroplasty (TKA), Navigator, Subvastus approach
