Abstract
Purpose:
We compared patients, (group A) who had severe varus deformity with posterolateral varus thrust, with patients,(group B) who didn't have varus thrust for results of total knee arthroplasty.
Materials and Methods:
The average follow-up period was 33 months in group A (25 cases out of 23 patients) and 67 months in group B (50 cases out of 50 patients). We evaluated which kind of implant the patient had, the thickness of the polyethylene and changes of joint levels. Also we measured preoperative and postoperative mechanical axis deviation, tibio-femoral angle, and implant positions. Clinical results included preoperative and postoperative HSS, KSS, range of motion, and remained posterolateral instability on final follow-ups (Fig 1, Fig 2).
Results:
The used implants in group A were 11 cases of Lospa®(Corentec), 10 cases of Scorpio NRG®(Stryker), 2 cases of LPS Flex®(CCK, Zimmer). The used implants in group B were 15 cases of Lospa®(Corentec). 20 cases of Scorpio NRG®(Stryker), 15 cases of LPS Flex®(Zimmer). Linked constrained prosthesis of RHK (Zimmer) was not used in any cases. The changes of mechanical axis deviations in groups A and B were respectively from preoperative average varus 66.5 mm, 32.6 mm to average varus 1.09 mm (p = 0.01), 1.8 mm (p = 0.021) in final follow-ups. Group A and Group B were corrected with statistical significance, but didn't show statistical significance between groups (p = 0.058). The changes of tibio-femoral angles were respectively from preoperative average varus 14.9°, 5.4° to average valgus 6.8°(p = 0.01), 7.6°(p = 0.013) in last follow-ups, but didn't show statistical significance between groups (p = 0.058). Preoperative stress varus angles were corrected respectively from average 18.0°, 6.2° to average 3.1°(p = 0.012), 2.3°(p = 0.064) and preoperative stress valgus angles were corrected respectively from average 9.2°, 3.0° to average 3.0°(p = 0.043), 1.9°(p = 0.068), but didn't show statistical significance in change of varus angle (p = 0.071) and in change of valgus angle (p = 0.063). Any remained posterolateral instability was not demonstrated in final follow-ups. Joint level changes in A and B were respectively from mean 13.6 mm, 12.8 mm to 18.5 mm, 17.2 mm, but didn't show statistical significance between groups (p = 0.059)(Fig 3). Postoperative implant position (α,β,γ,δ angles) was 94.6/90.3/89.7/3.86 in group A and 94.0/91.0/89.0/4.1 in group B, but didn't show statistical significance between groups (p = 0.058 in α, p = 0.061 in β, p = 0.064 in γ, p = 0.068 in γ). HSS (Hospital for Special Surgery) score improved from 47 point to 85 point (p = 0.021) in group A and from 51 point to 89 point (p = 0.032) in group B, but didn't show statistical significance between group (p = 0.061). KSS (Knee Society Scale) score was improved from 45.7 pointê3¼ to 86.2 point (p = 0.011) in group A and form 52.3 point to 88.4 point (p = 0.013), but didn't show statistical significance between group (p = 0.056).
Conclusion:
Advanced osteoarthritis induced severe varus deformity with varus thrust could be effectively treated through total knee arthroplasty. But we should make a careful observation for attenuation of the lateral ligament structures in ahead.
Key words: lateral ligament structures, osteoarthritis, posterolateral instability, total knee arthroplasty
