EFFECT OF BODY-MASS INDEX ON LOWER-LIMB ALIGNMENT OF THE FEMORAL–TIBIAL ANGLE IN PATIENTS WITH VARUS KNEE OSTEOARTHRITIS UNDERGOING HIGH TIBIAL OSTEOTOMY

Dapeng Zhao, Ning Pu, Huihui Zhou, Honghai Wang, Xi Li, Linhai Gong^*

One Ward Department of Orthopedics, Benxi Iron and Steel General Hospital, China Resources Liaojian Group, Benxi 117000, Liaoning Province, China

Objective: To analyse the effect of body-mass index (BMI) on lower-limb alignment in patients with varus knee osteoarthritis (KOA) during high tibial osteotomy (HTO).

Methods: Sixty-nine patients with varus KOA who attended our hospital between March 2019 and April 2020 were selected and divided into normal, overweight and obese groups based on the adult BMI classification standard formulated by China. The joint symptoms of the KOA patients were measured using the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index. The patients were followed up on one month after the HTO surgery and then during a final visit. Both times, the entire lengths of the lower limbs were X-rayed. The distributions of the femoral–tibial angle, hip–knee–ankle angle and lower-limb mechanical-force line in the tibial plateau were observed and analysed. 

Results: There were no significant differences in the gender, age or Kellgren–Lawrence osteoarthritis classification among the three groups (P>0.05). Compared with the normal group, the incidence rates of pain and duration of pain in the overweight and obese groups were significantly higher (P<0.05). There were no statistically significant differences between the overweight and obese groups (P>0.05). Compared with the normal group, the WOMAC Osteoarthritis Index scores for the overweight and obese groups for pain, stiffness and daily activities were significantly higher (P<0.05), but there were no significant differences between the overweight and obese groups (P>0.05). Compared with the normal group, the total WOMAC Osteoarthritis Index scores for the overweight and obese groups were significantly higher (P<0.05), with the obese group score being significantly higher than that of the overweight group (P<0.05). Prior to the operation, there were no significant differences in the femoral–tibial angle, hip–knee–ankle angle or lower-limb mechanical-force line between the two groups (P>0.05). At one month after the operation and then on the final visit, the femoral–tibial angle, hip–knee–ankle angle and lower-limb mechanical-force line of the two groups were significantly higher than before the operation (P<0.05), although there were no significant differences between the two groups after one month and on the last visit (P>0.05). On the last visit, the femoral–tibial angle, hip–knee–ankle angle and lower-limb mechanical-force line of the two groups were significantly higher than before the operation (P<0.05). There were no significant differences between the two groups one month after the operation and on the last visit (P>0.05). The lower-limb mechanical-force line of the obese group was significantly lower than that of the normal group at the same time point (P>0.05). 

Conclusion: In HTO, the BMI can affect the effective positioning of the lower-limb alignment when the femoral-tibial angle is 93°.