The impact of joint line alteration on patients underwent primary medial pivot total knee arthroplast / 中华骨科杂志

ABSTRACT

Objective:To investigate the influence of joint line alteration on the mid-term clinical effects of primary medial pivot total knee arthroplasty (MP-TKA).Methods:Data of a total 189 patients (233 knees) with 30 males (30 knees) and 159 females (203 knees) with age 66.42±6.12, diagnosed as knee osteoarthritis and underwent primary MP-TKA from January to December 2015, were retrospectively analyzed. All cases were followed up for at least 4 years. The patients were divided into four groups according to the extent of alteration, namely <-4 mm, -4- mm, 0- mm and >4 mm. Range of motion (ROM), Knee Society's Knee Scoring System (KSS), the Western Ontario and McMaster University (WOMAC) osteoarthritis index score were compared preoperatively and at 4 years postoperatively.Results:The postoperative follow-up duration was 52.20± 2.94 months (48-59 months). A total of 133 knee (57%) had joint line raised and 100 cases (43%) joint line distal shifted. The overall height of joint line before surgery was 16.56±3.54 mm (7.33-25.32 mm) and 17.34±2.92 mm (7.25-25.43 mm) postoperatively. The average alteration was 0.78±3.17 mm (-6.00-9.91 mm) with statistically significant difference ( t=-2.596, P=0.010). There was no statistical difference among the four groups in terms of gender, body mass index, pre-operative tibia slope and post condylar offset. The overall preoperative ROM of the all groups was 90.45°±20.44°, which increased from baseline to 108.95°±12.55° at 4 years postoperatively ( t=-22.381, P<0.001). There was statistical difference in term of ROM among each group ( F=7.101, P<0.001). The ROM in group 0- mm and >4 mm was significantly higher than that in group <-4 mm and -4- mm ( P<0.05). The KSS function score and clinic score at 4 years postoperatively were significantly higher that those before surgery, the WOMAC score was statistically lower at 4 years postoperatively ( F=0.723, P<0.001; F=1.138, P<0.001; F=2.502, P<0.001). There was no significant difference among the four groups in terms of KSS score and WOMAC ( P>0.05). One case in >4 mm group had gasket prolapse at 6 month after surgery and 3 cases with immediate anterior knee pain occurred in <-4 mm group. Conclusion:MP-TKA can lead to significant joint line alteration. The overall ROM after surgery is positively correlated with the quantity of joint line alteration. However, there was no correlation between quantity of joint line alteration and the joint function scores. Thus, MP-TKA can achieve good mid-term clinical effects.