![]() ![]() The uncemented prosthetic designs were advanced to overcome the complication faced with cemented fixations. Comparison of cemented and uncemented fixation The uncemented type of fixation is the preferred type of fixation in elderly patients with a good bone stock, young patients, and in the setting of a revision hip replacement surgery. The fixation is usually aided with the screws that help secure the acetabulum shell in place until the bone ingrowth occurs. The acetabular component is mostly uncemented unless the patient has poor bone stock or has a history of irradiation. X-ray showing an uncemented total hip replacement. The insertion of a slightly larger implant ensures a press-fit prosthesis that is snuggly fit. The operating surgeon prepares the bony femoral canal by broaching and inserting the implant slightly bigger than the final broach. Uncemented fixation is the most common method of total hip replacement in the United states. The natural bone grows on and in the porous surface creating a gridlock that binds the implant to the bone. The porous sprayed surface has microscopic contoured troughs and ridges. The femoral component is usually covered with a porous surface on the upper end. Uncemented hip replacement uses specially designed prosthetic components for the bone to implant fixation. The cement mantle ensures adequate fixation in patients with a wide femur (Dorr C). ![]() Patients with abnormally wide femoral canal are ill-suited for an uncemented hip replacement.The irradiated bone has poor potential for bone on-growth or bone in-growth. Patients with a history of bone irradiation as a result of any malignancy who may need a hip replacement are best managed with a cemented hip replacement.A cemented implant has a better fixation as a result of cement penetration of the porous bone. The porous bones may not support the uncemented implant due to poor bone ingrowth. Osteopenic or osteoporotic patients have thin and porous bones.The cemented hip replacements are indicated only in limited cases: Beads may be used at the cement implant prosthesis to ensure an even cement distribution and to prevent bottoming out of the cement. The acetabulum cementing is rarely done but is similarly done to ensure adequate fixation.A proximal seal is made to ensure adequate pressure during the polymerization of the cement. The femoral stem is inserted to pressurize the cement and the tapered stem design ensures the cement pressure is maintained during the insertion.The gun ensures the cement is not eviscerated by the bleeding in the canal. The cement is filled in the canal using a cement gun that pressurizes the cement injection in the canal.A cement restrictor is placed at an appropriate distance to prevent the cement from traveling down the canal.Preparation of the femoral canal using serial broaching and using a pulsatile lavage to wash the canal and remove debris.The modern technique of cementing involves: The bone cement hardens in about 10 minutes in the OR temperature. The modern mixing in the operating room involves the use of a vacuum mixer. The mixing and cementing techniques have evolved in the past decades to achieve maximum fixation. The bone cement is made by mixing powder and liquid components. The bone cement creates a grout and fixes the implant by acting as an interlocking surface between the implant and the bone rather than simply gluing the implant to the bone. Cemented Hip ReplacementĪ cemented hip replacement uses a polymethylmethacrylate (PMMA) bone cement to fix the implant surface to the bone. Uncemented hip replacements rely on bone on-growth over specially designed implants. A cemented hip arthroplasty relies on bone cement to fix the implants to the bone interface. X-ray of the hip in lateral view showing a partial cemented hip replacement.Ĭemented and uncemented hip arthroplasties differ in how the prosthetic implant is fixed to the natural bone.
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