Estimation of femoral version based on broach geometry after femoral-neck osteotomy / 北京大学学报(医学版)

ABSTRACT

Objective:To find out whether it is accurate to estimate femoral version based on femoral broach after femoral neck osteotomy using computed tomography scans.Methods:In 32 total hip arthro-plasty (THA),we performed CT scans before and after operation.Four possible levels (lesser trochan-ter,5 mm above,10 mm above and 15 mm above the lesser trochanter)of broach version were calculated based on the pre-operative CT scan.Stem versions were measured on the post-operative CT scan.We de-termined the difference between the preoperative broach version and the postoperative stem version using the Student’s t-test for paired samples assuming equal variance.Results:For the operated hips,pre-operative hip version differed according to the level of measurement.Our findings showed that the average femoral version was 37.0°±11.0°at the level of the lesser trochanter (section 1),34.3°±10.6°at 5 mm above the lesser trochanter (section 2),28.1°±10.9°at 10 mm above the lesser trochanter (sec-tion 3),and 22.4°±13.7°at 15 mm above the lesser trochanter (section 4),and that the average ver-sion for the femoral neck (FNV)was 12.9°±13.8°.The postoperative hip version was the stem version (FSV),which we found to be an average of 26.1°±11.0°.The mean femoral version for section 1 and 2 was larger than the mean postoperative stem version (P0.05).The mean femoral neck version was less than the mean postoperative stem version (P<0.01);the difference was 13.2°±11.1°of the in-creased anteversion on average for the FSV compared with FNV.Conclusion:The accuracy of estimated femoral version after arthroplasty depends on broach level.When it is 10 mm above the lesser trochanter, stem version estimation is accurate,but below that level,there is a tendency to overestimate.