Sato A, et al. - Charts of 373 individuals (461 hips) who were undergoing THA (mean age 58 years) were evaluated and 31 individuals (412 hips) followed up for ≥ 5 years were involved for radiographic analysis in order to present mean 6.8-year outcomes of cementless primary THA using S-ROM-A (modified modular stem for Asian patients) femoral prosthesis in anatomically complex cases. No postoperative dislocation or deep infection transpired. The mean modified Merle d’Aubigné-Postel score notably enhanced. Cumulative 5- and 10-year stem survival rates, respectively, were 100% and 84%. Every stem was labeled as bone ingrown fixation. Osteolysis transpired in metal-on-metal (42.8%) and metal-on-polyethylene (15.8%) groups. With no important variation among the three groups, the mean time to osteolysis was ∼3 years. In logistic regression, the lower cup inclination angle was significantly related to osteolysis. In conclusion, S-ROM-A femoral prosthesis attained superior mid-term fixation, and in primary THA with severe deformity, the modular system was beneficial. Furthermore, bearing couples are possibly related to adverse reactions to metal debris. Thus, for anatomically complex THA, S-ROM-A with ceramic-on-polyethylene bearing couples could be an alternative.