Abstract： Background This work was carried out to evaluate the clinical efficacy and the complications of S-ROM modular hip arthroplasty combined with transverse subtrochanteric shortening for Crowe type IV congenital dislocation of the hip (CDH).Methods A totoal of 28 consecutive patients with Crowe type IV CDH received treatment using this surgical technique from June 2003 to June 2010.The follow-up was conducted at 3 days,1,6,and 12 months after the operation and later annually at the outpatient of our hospital.Sequential pelvic plain film and normotopia film of the affected hip joint were taken.The limp and the Trendelenburg sign were also assessed,the ischiadic nerve injury was also evaluated by electromyogram,and Harris hip scores were recorded.Results After operation,both the alignment and the position of the transverse osteotomies were good.None of the patients had presented complications of joint infection,prosthesis loosening,joint dislocation,or nerve injury.Conclusions S-ROM modular hip arthroplasty combined with transverse subtrochanteric shortening was a satisfactory and safe technique for the Crowe type IV congenital hip dislocation within a mean follow up of 53 months.Transverse subtrochanteric shortening could effectively prevent the distraction injury of sciatic nerve.