To investigate the clinical outcomes of total knee arthroplasty(TKA)for severe knee flexion contracture of rheumatoid arthritis(RA) and severe osteoporosis and explore the technique of TKA and rehabilitation after TKA.

From January 2010 to December 2015, 21 patients including 27 knees with rheumatoid arthritis and severe osteoporosis with severe flexion contracture underwent primary bilateral TKA with soft tissue balancing. Thirteen cases of 17 knees(the posterior stabilized group) were treated with posterior stabilized prosthesis(LPS prothesis), and eight cases with 10 knees(restrictive group) were treated with limited prosthesis. Inclusion criteria: rheumatoid arthritis with severe varus of knee joint; T-score<-2.8 of the patients with rheumatoid arthritis with knee joint; no serious cardiopulmonary disease. Exclusive criteria: joint primary or secondary active infection; combined deformity of external joint can not be corrected by simple osteotomy. Statistical analysis was carried out with SPSS 16 software. The average values of preoperation, postoperatively flexion contracture degree, joint activity and tibial angle were compared by paired sample t test.

The duration of follow-up was (3.8±1.1) years on average. The preoperative knee flexion contracture decreased from (55.5±12.5)°(65.0°-85.0°) to the last follow-up(5.5±3.5)°(0°-10.0°)(t =28.868, P<0.01), joint activity improved from (32.5±6.5)°(0°-40.0°) to the final follow-up (105.5±10.5)° (85.0°-130.0°)(t =94.83, P<0.01) in the posterior stabilized prosthesis group(LPS prosthesis); the tibial angle was corrected from preoperative (31.0±3.5)°(23.0°-45.0°) to the last follow-up(8.5±2.5)°(0°-12.0°)(t =116.913, P<0.01) .In the restrictive group, the preoperative knee flexion contracture decreased from (56.5±15.5)° (65.5°-80.0°) to the last follow-up (5.0±5.0)°(5.0°-15.0°)(t =25.486, P<0.01) , joint activity improved from (32.0±8.0)°(0°-40.0°) to the final follow-up (100.0±5.5)° (80.0°-120.0°)(t=141.335, P<0.01) in the posterior stabilized group; the tibial angle was corrected from preoperative (31.5±5.5)°(22.0°-45.0°)to the last follow-up(8.0±4.5)°(0°-12.0°)(t=122.11, P<0.01). All the differences were statistically significant. The indexes were compared between the two groups before and at the follow-up. The range of motion of restriction group was significantly lower than that of the posterior stabilization group (t=5.716, P<0.01), and the difference was statistically significant.

In the advanced RA patients with severe varus flexion deformity of knee joint and severe osteoporosis, the posterior stabilized prosthesis can provide much better activities, but shows no advantage in correction of varus flexion deformity and femor-tibial angle.