A device for partial acetabular replacement includes a patient-specific acetabular guide. The acetabular guide has a first surface configured to nestingly mate in only one position to the patient's acetabulum. The acetabular guide includes a patient-specific guiding formation configured to guide a cutting tool to remove damaged tissue from a defect of the patient's acetabulum and prepare a patient-specific implantation slot corresponding to the defect after removal of the damaged tissue. A patient-specific partial acetabular implant can be configured to nestingly mate with the patient-specific implantation slot.