After stratification on follow-up time and age , the revision rates were not substantially different , aside for younger patients in short term from studies with short-term follow-up .
Conclusion No essential differences between the two design s were observed .
MB and FB UKA design s have comparable revision rates .
Purpose Two design concepts are currently used for unicondylar knee arthroplasty ( UKA ) prostheses :  fixed bearing ( FB ) and mobile bearing ( MB ) .
While MB prostheses have theoretical advantages over their FB counterparts , it is not clear whether they are associated with better outcomes .
Flexion and extension laxity after medial, mobile-bearing unicompartmental knee arthroplasty: a comparison between a spacer- and a tension-guided technique
Purpose In a mobile-bearing unicompartmental knee arthroplasty ( UKA ) , stability is of utmost importance to promote knee function and to prevent dislocation of the insert . Gap balancing can be guided by the use of spacers or a tensioner . The goal of this study is to compare laxity of a tension-guided implantation technique versus a spacer-guided technique for medial UKA with a mobile bearing . Also clinical function was compared between the groups . Methods The tension-guided UKA system ( BalanSys ™ , Mathys Ltd , Bettlach , Switzerl and ) was compared with a retrospective group with a  spacer-guided system  ( Oxford , Biomet Ltd , Bridgend , UK ) . A total of 30 tension-guided medial UKAs were implanted and compared with 35 spacer-guided medial prostheses .  In both groups , valgus laxity was measured at least 4 months postoperatively in extension and 70 ° flexion using stress radiographs . Knee Society Scores ( KSS ) were obtained at the 6-month follow-up . Results Valgus laxity in flexion was significantly higher in the tension-guided group compared with the spacer-guided group : 3.9 ° ( SD 1.8 ° ) versus 2.4 ° ( SD 1.2 ° ) , respectively , P < 0.001 ) . In extension , valgus laxity was significantly different : 1.8 ° ( SD 1.0 ° ) in the tension-guided group compared with 2.7 ° ( SD 0.9 ° ) in the spacer-guided group ( P < 0.001 ) . There was no significant difference between the KSS for the two groups ( n.s . ) . Conclusions The tensor-guided system result ed in significantly more valgus laxity in flexion compared with the spacer-guided system . However , in extension , the situation was reversed : the tension-guided system result ed in less valgus laxity than the spacer-guided system . Clinical ly , there were no differences between the groups . The valgus laxity found with the spacer-guided system better approximates the valgus laxity values of the healthy elderly . Level of evidence Lower quality prospect i ve cohort study ( < 80 % follow-up , patients enrolled at different time points in disease ) , Level II
After stratification on follow-up time and age , the revision rates were not substantially different , aside for younger patients in short term from studies with short-term follow-up .
Conclusion No essential differences between the two design s were observed .
MB and FB UKA design s have comparable revision rates .
Purpose Two design concepts are currently used for unicondylar knee arthroplasty ( UKA ) prostheses :  fixed bearing ( FB ) and mobile bearing ( MB ) .
While MB prostheses have theoretical advantages over their FB counterparts , it is not clear whether they are associated with better outcomes .