Four cases of pathologic periacetabular insufficiency/fracture in patients with extensive neoplastic metastatic involvement of the hemipelvis were treated by pelvic reconstruction with hemipelvis pin reinforcement with total hip arthroplasty (THA). Reconstruction was reserved for patients with limited other bony or visceral metastases, and had extreme narcotic-dependent pain and debilitation, or failed prior management, but had reasonable life/activity expectancy. Tumor palliation and hemipelvis reconstruction was obtained by ilioinguinal (pelvic) and posterolateral (hip) incisions. Iliac crest exposure allowed iliacus elevation, debulking of any intrapelvic soft-tissue mass, and exposure of the medial acetabulum. Rows of threaded Steinman pins were selectively passed from iliac crest (ilioinguinal incision) to superior and medial acetabular deficiencies (hip incision) in guided antegrade fashion. A reinforced polymethylmethacrylate (PMMA) acetabular reconstruction was then created, with PMMA incorporating medial and superior pins, an anti-protrusio ring, and a standard cemented acetabular component. A long-stem cemented femoral component was placed for proximal femoral metastasis prophylaxis. Postoperative rehabilitation (mean hospitalization, 12.7 days) was as for cemented THA. Mean survival was 15 months with integrity of the hip construct maintained throughout. All four patients progressed to independent ambulation with walking aids and were gratified that they had elected surgical treatment with reconstruction.