To investigate the mid and long-term effects of selectively upward placement of acetabular implants on post-operative function and implant survival rate of cementless total hip arthroplasty (THA) in developmental dysplasia of the hip (DDH) patients.

Inclusion criteria: hip dysplasia followed by osteoarthritis, total hip replacement; the use of non-cemented hip prosthesis; all surgeries were performed by the same group of doctors.Exclusion criteria: missing visit or incomplete follow-up data; bilateral total hip arthroplasty was performed simultaneously; osteoarthritis secondary to hip dysplasia. Twenty-four cases were received the final follow-up in selective 26 cases of DDH received THA between January 2008 and December 2013, including five males and 19 females with an average age of (62±11) years.The left hip was involved in seven cases and the right hip in 17 cases, including 10 cases of Crowe type I, eight cases of Crowe type II, six cases of Crowe type III. The Harris score and Western Ontario and McMaster University scores(WOMAC) were analyzed at the last follow-up compared to pre-operation. The anteroposterior X-ray films of the pelvis, anteroposterior and lateral X-ray films of the femur were performed routinely before operation and follow-up. Age, follow-up time, score and surgical indicators were analyzed by t test or rank sum test, respectively.

The follow-up time was (80± 23) months.The Harris score improved to(91±13)from (43±13) (Z=-5.867, P<0.01), and WOMAC score reduced from(58±13)to (10±4) (Z=-5.957, P<0.01). The leg length discrepancy was decreased to (5±4)mm from (10±5)mm after surgery (Z=-4.525, P<0.01). No loosening or subsidence of the implant was observed by X-ray during the follow-up.The upward distance of acetabular implant was 3~15 mm, among which eight cases were moved up 0~5 mm, seven cases were moved up 6~10 mm, and nine cases were moved up 11~15 mm. At the last follow-up, Harris scores and WOMAC scores of the three groups were significantly improved compared with those before surgery, and the differences were statistically significant (Harris: Z ₁=-3.366, Z₂=-5.355, Z ₃=-3.524; WOMAC: Z ₁=-3.602, Z ₂= -3.144, Z₃=-3.373; P< 0.05). But there was no statistical difference among these three groups (P>0.05).

The placement of acetabular components in an anatomic position and less than 15mm superior to the approximate femoral head center could promote middle and long-term satisfaction after cementless THA in DDH patients.