Clinical Effect Of Total Hip Arthroplasty In The Treatment Of DDH Using An Elevated Hip Rotation Center

Objective:To evaluate the early effect on the joint stablityjoint function,abductor muscle strength,leg length when an elevated hip rotation center (<20mm) was used in the total hip arthroplasty of DDH.Methods:17 patients with DDH were treated with THA in our hospital from December 2011 to December 2014.According to the classification of Crowe,1 cases were type?,3 cases were type?,8 cases were typeIII,5 cases were type?. according to the hip center of postoperative pelvis radiographs,all cases were divided into 2 groups. GroupA,the elevated hip center type of 3 male patients with 3 hips and 6 female patients with 6 hips,aged from 40 to 76 years(mean 55.8 years); GroupB,the ture hip center type of 2 male patients with 2 hips and 6 female patients with 6 hips,aged from 21 to 61 years(mean 47.1 years). The elevating distance of hip rotation center, offset and the diameter of the acetabular cup were measured on the postoperative radiographs of the pelvis.The preoperative and postoperative Trendelenburg sign,Harris score, LLD, the surgery blood loss, the operation time, the elevating distance of hip center, offset were recored. Complications such as dislocation,loosening rates, vascular and nerve injuries were record.The effect of using an elevated hip center were comprehensive analysised.Results:GroupA was followed up for an average 17.6 months and GroupB was followed up for an average 17.2 months..No complications were found with dislocation,infection,prosthesis adjacent fracture,loosening , vascular and nerve injuries except that one patient had incomplete sciatic nerve injury recovered after one year in groupB. The hip center was elevated at an average 13.3mm distance in group A and the difference of femoral offset between the two sides was less than 4mm.In groupB, difference of femoral offset between the two sides among all cases was less than 4mm except 1 case with 5mm. the diameter of the acetabular cup was 48 to 52mm in group A while group B was 46 to 50mm.There was significant difference in the operation time,the bleeding volume of the two groups (P<0.05).Positive Trendelenburg sign in all cases became negative at one year after operation.The postoperative Harris scores of the two groups improved greatly compared to the preoperative, There was significant difference between the postoperative and preoperative Harris scores (P< 0.05). There was no significant difference in the Harris score,leg lengthened distance and the function of abductor muscle between the two groups (P>0.05).Conclusion:There were no differences on the joint stablityjoint function,abductor muscle strength,leg length between the elevated hip center group(<20mm) and the ture hip center group in the treatment of DDH.Using an elevated hip rotation center to reconstruct acetabulum at a place of better bone conditions between the true and false acetabulum is feasible in THA of DDH,avoiding subtrochanteric shortening osteotomy and acetabular structural bone graft,reducing bleeding and operation time.While the long term follow-up is necessary.