Is proximal tibia the major problem in varus gonarthrosis? Evaluation of femur and ankle.

OBJECTIVES: In this study, we aimed to evaluate the components of knee varus in the adjacent joints and to investigate the possible correlations between them.

PATIENTS AND METHODS: Between January 2005 and December 2010, 315 lower limbs of 164 patients who underwent high tibial osteotomy (HTO) due to varus gonarthrosis were analyzed. Alignment and orientation angles of these limbs using preoperative orthoroentgenography were measured. The results were compared with normal values and evaluated statistically for possible correlations.

RESULTS: Statistical analysis of the data showed that the mean value of mechanical lateral distal femoral angle (mLDFA) increases in varus knees and thus distal femoral joint orientation showed less valgus. The effect of mLDFA on mechanical tibiofemoral angle (mTFA) was almost the same as medial proximal tibial angle (MPTA). Both together; they explain 52.2% of variance in mTFA. mLDFA has a negative and MPTA has a positive and significant influence on mTFA (b= -0.765, p<0.001) and (b= 0.798, p<0.001) respectively. A moderate correlation was found between the mTFA and lateral distal tibial angle (LDTA) in the lower limbs grounding at the same angle (r=0.634, R=0.40, p<0.001). A slight, but significant correlation between mTFA and medial neck shaft angle (MNSA) was found (r=0.15, R=0.02, p<0.01).

CONCLUSION: Distal femoral joint showing less valgus significantly contributes to the deformity in varus gonarthrosis, also a very important contributor to the deformity. Abnormal forces applied to ankle may cause collapse in distal lateral tibial metaphysis and decrease LDTA in varus knees. Medial neck shaft angle may decrease due to possible abnormal loading angles to the femoral neck in some individuals with varus gonarthrosis.