Background: Total Hip Arthroplasty remains the standard treatment protocol for patients with neglected traumatic dislocations of the hip with arthritis. A total hip arthroplasty needs to be frequently combined with a subtrochanteric shortening femoral osteotomy to aid in the reduction of the hip joint in such cases. Still long-term stable implant fixation, rigid construct, and favorable functional outcome remain a challenge. In respect to subtrochanteric shortening osteotomy, various techniques have been described in the literature, including the step-cut, double chevron, transverse, and oblique osteotomies. Out of these types, a subtrochanteric step-cut osteotomy provides a better rotational stability and a larger surface of contact to aid in union. As there is a paucity in the literature regarding the step-cut osteotomy for traumatic dislocations of the hip, we designed this study to evaluate the outcomes of this procedure. Methods: We prospectively evaluated 24 patients with neglected traumatic dislocations of the hip, who underwent total hip arthroplasty with a step-cut subtrochanteric shortening osteotomy using a long modular stem within a span of 4 years. The indications were severe pain and difficulty in walking and performing activities of daily living. Patients fulfilling the inclusion criteria were evaluated in terms of Harris Hip Score, leg length discrepancy, neurological status, union of the osteotomy, and implant stability. Results: The mean Harris Hip Score significantly improved from 33.4 preoperatively to 89.2 postoperatively at the latest follow-up. At the final follow-up, all patients showed union at the osteotomy site and there were no cases of implant loosening or instability. No neurological complications were reported. Conclusions Total hip arthroplasty combined with a step-cut subtrochanteric femoral shortening osteotomy in patients with neglected dislocations of the hip was associated with good functional outcome and higher success rates in terms of stable implant fixation and union at the site of osteotomy.