[Comparison of measurement methods of lower limb length in hip arthroplasty for femoral neck fracture].

Objective: To compare the accuracy of three methods for measuring the length of both lower limbs in hip arthroplasty for femoral neck fracture in the elderly, and to introduce a "shoulder to shoulder" anatomical location marking method for femur.
Methods: From January 2017 to January 2019, 90 elderly patients with femoral neck fracture were treated with hip replacement, including 39 males and 51 females, aged 65 to 96(78.0±7.4) years, 56 cases of total hip and 34 cases of hemi hip. According to garden classification, there were 7 cases of typeⅡ, 63 cases of type Ⅲ and 20 cases of type Ⅳ. The patients were divided into three groups according to different measurement methods:contralateral contrast method (group A) of 19 cases, shuck test method (group B) of 28 cases, and "shoulder to shoulder" anatomical marker localization method (Group C) of 43 cases. The accuracy of the three methods was compared by measuring the length difference of lower limbs in vitro and imaging.
Results: All patients completed the operation successfully. After total hip arthroplasty, the length of lower limbs in group A was(12.9±8.6) mm, and that in group B was(10.3±4.4) mm. After hemiarthroplasty, the length of lower limbs in group A was (13.2±7.2) mm, group B was (8.7±3.5) mm, and group C was (6.3±2.8) mm; the measurement results of unequal length of lower limbs after total hip arthroplasty were(12.9±8.1) mm in group A, (9.6±4.0) mm in group B and (6.6±2.6) mm in group C. The results of factorial analysis of variance showed that the differences among the three groups were statistically significant ( F =9.763, P <0.01). The difference between two groups showed that the length of lower limbs in group A and group B was higher than that in group C( P <0.05). There was no significant differencebetween total hip arthroplasty and hemiarthroplasty ( F =0.270, P =0.605). Three different intraoperative measurement methods for postoperative lower limb length difference were group CConclusion: The "shoulder to shoulder" anatomic localization marking method can reduce the length of lower limbs simply, effectively and accurately in the elderly patients with femoral neck fracture hip replacement.