Introduction: The theory that usingmobile bearing (MB) design for total kneereplacementsurgeries can reduce the riskof tibial component loosening compared tofixed-bearing (FB) designs is still unclear.Arthroplastic surgeries developed rapidlywithin recent 10 years, but there is no similarstudy performed yet. This randomized studyinvestigated the impact of prosthesis design toloosening of components at 2 years for totalknee replacement surgeries.Materials and Methods: 479 patientswho underwent total knee arthroplastyin FirstCentral Hospital of Mongolia were allocated toeither FB or MB tibialarticulation.We comparedour results to similar studies which performedabroad due to there is no such a studyperformed before in Mongolia.Results: There is no significant differenceby age, sex, weight, height, body mass index,operation side (right or left) in both groups.Pre- and postoperative range of motionwasalmostsame for MB and FB groups.Butloosening complication was higher for the FBgroup (1.16%) than MB group (0%).Conclusion: Using MB design for total kneearthroplasty has less loosening complicationthan using FB design in Mongolians. Bonemineral density (dual energy absorptiometry)and radiostereometric analysis are necessaryfor widening studies in field of total kneereplacement surgeries in the future.

joints with severe defects of the medialtibia usually progress as varus or valgusdeformities, with daily functional handicapssuch as, limping, aches and instability. Duringthe last seven years, in total 1200 knees ofpatients were treated by both bilateral andunilateral total knee arthroplasty in the Jointcenter of National First Central Hospital. Thisresearch shed a light on patients that weretreated by unilateral total knee arthroplastyto correct large defects of tibia.Materials and Methods: The objectiveof this paper is to compare patients whowere treated with auto bone graft withpatients who were treated without auto bonegraft, in order to assess the effectiveness ofthe auto bone graft technique through theretrospective method.Results: The unilateral total kneearthroplasty was operated on 553 patients,30 (5,42%) of whom were treated withautobone graft and 523(94,58%) of whomwere treated without the auto bone graft.Postoperative complication was observed in3 cases (9,9%) among the first group ofpatients, and in 25 cases (4,5%) amongthe second group of patients. As patients,diagnosed with osteoarthrotic knees withsevere tibial bone defects, were treatedthrough the auto bone graft, it could beconcluded that more complications wereobserved on patients with large tibialbone losses. However, no complicationwas observed in other 27 cases that weretreated with the bone graft during the postoperativefollow-up period ranged fromtwelve to eighty four months.Conclusion: In conclusion, total kneearthroplasty using auto bone graft forpatients with severe tibial bone defects iseconomically as well as clinically effectivetechnique for our country.