The Correlation Between The Restoration Of Femoral Offset And Leg Length Discrepancy After Total Hip Arthroplasty

Background and PurposeTotal hip arthroplasty (total hip arthroplasty, THA) is a common hip arthroplasty,THA solve the hip pain caused by hip disease priority, while also improving thefunction of the affected hip joint. THA patients improve their quality of life in hipdisease but also brought some postoperative complications, such as leg lengthdiscrepancy (LLD), which make patients and doctors distressed. Leg length extend ismore common than reduction and more difficult to patients who receive THA. Limblengthening can caused by the insufficient osteotomy of the femoral neck, or thefemoral neck is too long, or move down of the rotation center. If the extension is morethan2.5cm, the sciatic nerve can cause paralysis and limp. LLD is often caused by thefollowing reasons:1)Older patients, Soft tissue tension decreased, THA surgery underanesthesia on a further decline intension, need more soft tissue relaxation during thesurgery.2)Preoperative use of templates improperly failed to select the appropriateprosthesis.3) insufficient osteotomy of the femoral neck.4) correct the limb flexionadduction deformity. LLD is a common complication after hip replacement, it canlead to limp, back pain, and even finally need to wear insoles or receive revision.Femoral offset (FO) is defined as: distance between the femoral head center andthe axis perpendicular to the femoral anatomy. Researches show that there is a strongcorrelations between postoperative abductor strength and the femoral offset,eccentricity rebuild better postoperative hip abductor reconstruction is insufficientcompared to the eccentricity excellent, and both showed a correlation. The patientswho have a restoration of femoral offset will have a better abductor tension or softbalance. The abductor muscle tension is closely related to a series of complications,such as: closely related to dislocation, lameness, etc. Thus the reconstruction of femoral offset and double lower extremities isometricis the decisive factor in the decision THA surgery effects, both domestic andinternational research to verify this. Currently studies about Femoral offsetreconstruction studies are mostly focus on about the relationship with the hipabductor or prosthesis wear rate and prosthesis loosening. Study about the correlationbetween reconstruction femoral offset and postoperative leg length difference are lessinvolved.The study was part of a retrospective study. The purpose of the study is toexplore the correlation between the restoration of femoral offset and leg lengthdifferences and the isometric rate. Determine whether to rebuild. FO can reduce theincidence of LLD or reduce the lower limbs length difference.Method1.Patient data: Select the patient of study from July2009to July2013to acceptunilateral total hip arthroplasty115hips in115patients, including61males and54females, including60cases of left hip and55right hips. Age22to80years, mean51.78years, of which67cases of aseptic necrosis of the femoral head, congenital hipdysplasia in13cases,35cases of femoral neck fracture, with an averagefollow-uptime of23.2months (3months to4years).2.Radiographic: the study of patients with preoperative and follow-up allreceived a standard pelvic AP film: Patients sit on the bed, feet parallel and thefemoral rotation20°, so we can make the neck into the coronal position. X-raytransmitter vertical projection distance is1m, unity magnification of1.15:1. Eachpicture includes the proximal femur. X ray equipment was GE Difinium6000DR.3.Methods of data’s measurement:1) determine the center of the femoral head ofthe operative side and normal side.2)Then determine the axis of the femoral, definedthe distance from the center of the femoral head to the axis of the femur as FO.3)Draw a line cross tears on both sides on X-ray film and marked the apex of bilaterallesser trochanter.4)The difference between the distance from the line on both sides ofthe lesser trochanter presents the difference of the lower extremities. The absolute value of D at the time of5mm or less can be considered leg length equal. When theabsolute value of the femoral offset difference is4mm or less can be consideredipsilateral femoral offset has been rebuilt.4.The group of patients with unilateral total hip arthroplasty (THA) performedby the same group of surgeons. Posterolateral approach was adopted. After incision ofthe gluteus maximus fibers then cut gluteal muscle and joint capsule，exposure the thehip joint. Keep appropriate length of calcar femorale. After installing trail satisfactionto15°anteversion of the acetabular component installation. After inserting the femoralstem and the appropriate size of the femoral head after hip reset.5.Statistical: Statistical analysis using SPSS17.0statistical analysis software. Werepresented the measurement data as the way of mean±standard deviation. Pairedtwo-sample t test was used for the measurement data. The patients were divided into treconstruction group and unreconstruction group based on the standard of femoraloffset’s rebuilt, then compare the proportion of the equal leg length between the twogroups, P <0.05difference has significance statistics. Divide all the patients into6different groups based on the differences of femoral offset postoperative, X2test wasperformed on the proportion of the equal leg length between each two groups, therewas significant different when P <0.05.Result1. Significant correlation between postoperative femoral offset difference andleg length difference. There was a positive correlation between femoral offsetdifference and leg length difference（r=0.632,P＜0.05）.2. In reconstruction group,71in the92cases were lower limb equal length while5in the23cases were lower limb equal length in the femoral offset unreconstructiongroup, across chi-square test, the result was2=25.229, P＜0.05. Femoral offsetreconstruction can construct the lower limb length after THA.3.In the the femoral offset reconstruction group, the most of the groups, lessfemoral offset differences lead to a higher proportion of equal leg length. ConclusionsIn the purpose of making the legs to equal length and obtain a higher livingquality postoperative, we should try our best to rebuilt the femoral offset duringTHA.