To investigate the method and clinical effect of primary total knee arthroplasty(TKA) for the patients with severe later unstable knee.

A respective analysis was carried out. From January 2010 to June 2017, 17 patients (20 knees) with severe lateral instability underwent primary TKA in the joint department of the Lanzhou General Hospital of PLA. Among them, eight knees were from six males and 12 knees were from 11 females. Inclusion criteria: late stage of osteoarthritis or rheumatoid arthritis with medial-lateral instability of knee who underwent primary TKA. Exclusion cariteria: varus or valgus deformity of knee, extension subluxation of knee. In this group, osteoarthritis were nine cases (11 knees) and rheumatoid arthritis were eight cases (11 knees). The preoperative medial-lateral instability in the coronal plane was (12.0± 2.3) mm on anterior-posterior views. The functions of knee joint before and after the operation were evaluated with the American Knee Society score (KSS) and the range of motion (ROM). SPSS 18.0 statistic software was used to analyze the data, comparing the preoperative and postoperative data by paired t test.

All the patients were followed up for (31.5±0.3) months on average. KSS clinical score improved from preoperative (33±12)to( 89±7), and the KSS functional score improved from preoperative (36±9) to (86±6) at the final follow-up. The range of motion of the knee was improved from (69±29)° to (103±13)°. There was no complication such as infection, deep vein thrombosis, knee inst-ability or component loosening.

TKA for the knees with lateral instability demands precise evaluation for the structure and function of the ligaments of knee; good balance of soft tissues and correct prothesis selection of is the key to operation.