The Effect Of Abnormal Tibial Slope And Mechanical Axis Deviation On Medial Meniscus Tear

Objective:The aim of this study was to evaluate the value of tibial slope and mechanical axis in patients with medial meniscal tears and to analyze abnormal anatomic factors that could affect medial meniscus tears.Methods:The patients(111 knees,116 patients)that underwent arthroscopic surgery were classified into two groups.Group I with definite medial meniscus tear,Group II without medial meniscus tear and accepted other operation.All medial meniscus tears could be classified according to the location and type on arthroscopy.The posterior tibial slope(PTS)was measured on magnetic resonance images(MRI),mechanical axis angle(hip—knee—ankle angle)(HKA)and the medial proximal tibial angle(MPTA)was evaluated on the anteroposterior weight-bearing full-length radiographs.T test and Chi-square test of two independent samples were used to determine the statistical significance.The independent risk factors of medial meniscal tear were determined by Binary logistic regression analysis,and the OR value was calculated.A p-value <0.05 was considered statistically significant.Results: There were 60 knees in group ?,and 51 knees in group ?.With regard to age,gender,and BMI,there was no statistically significant difference between the groups(p>0.05).The main tear site of medial meniscus were posterior horn tears(65.0%)and body tears(16.7%),the main tear type of tears were complex tears(41.7%)and horizontal tears(23.3%).The mean varus HKA in group I(3.8o)was significantly greater than in group II(0.1o)(p<0.05).The mean MPTA in group I(86.1o)was smaller than in group II(87.7o)(p<0.05).The mean PTS was significantly greater in group I(6.4o)than in group II(2.7 o)(p<0.05).PTS and HKA have statistical significance in Binary logistic regression analysis,MPTA was not statistically significant(p > 0.05),so we think that,the increase of PTS(OR 1.97,95% CI,1.50-2.58)and the increase of HKA(OR 1.41,95% CI,1.14-1.74)were independent risk factors for medial meniscus injury.Conclusions: This study showed that MM had significant high varus HKA,and high PTS.Knee varus and tibial plateau slope was identified to be specific anatomic risk factor of MM,particularly for those with complex tears in posterior horn.