Hip Replacement Surgery - Tips to a Quick Recovery

Cemented Total Hip In India

Cemented Hip Replacement Implants

The cemented hip replacement implant is designed to be implanted using bone cement (a grout that helps position the implant within the bone). Bone cement is injected into the prepared femoral canal. The surgeon then positions the implant within the canal and the grout helps to hold it in the desired position.

Cemented fixation relies on a stable interface between the prosthesis and the cement and a solid mechanical bond between the cement and the bone. Today's metal alloy stems rarely break, but they can occasionally loosen. Two processes, one mechanical and one biological, can contribute to loosening.

In the femoral component, cracks (fatigue fractures) in the cement that occur over time can cause the prosthetic stem to loosen and become unstable. This occurs more often with patients who are very active or very heavy. The action of the metal ball against the polyethylene cup of the acetabular component creates polyethylene wear debris. The cement or polyethylene debris particles generated can then trigger a biologic response that further contributes to loosening of the implant and sometime to loss of bone around the implant.

Bone cements

The microscopic debris particles are absorbed by cells around the joint and initiate an inflammatory response from the body, which tries to remove them. This inflammatory response can also cause cells to remove bits of bone around the implant, a condition called osteolysis. As the bone weakens, the instability increases. Bone loss can occur around both the acetabulum and the femur, progressing from the edges of the implant.

Despite these recognized failure mechanisms, the bond between cement and bone is generally very durable and reliable. Cemented total hip replacement is more commonly recommended for older patients, for patients with conditions such as rheumatoid arthritis, and for younger patients with compromised health or poor bone quality and density. These patients are less likely to put stresses on the cement that could lead to fatigue fractures.

Cemented Total Hip Replacement in India

Cement fixation has a 30-year history in total hip arthroplasty. Cement fixation is a durable and reproducible means of fixation in a variety of hips. A key determinant to a cement mantle's longevity is the technique of cementing. This article reviews what has been learned in the past and outlines the state of the art in cement technique today.

One of the relatively recent changes in cement and arthroplasty is that a multitude of cements are available on the market. Although the durability of well-made cement mantles around implants is fairly consistent among cements, the products differ in terms of viscosity, working time, and setting. A surgeon must know the details of the particular cement he or she intends to use, as it will influence the cement technique. Working time and setting time vary among the different cements.

Data have shown that different types of femoral stems should be inserted with different types of cements. For example, a rougher stem should be inserted in an earlier phase of cement polymerization, whereas a smoother stem should be inserted in a more doughy state. Therefore, a surgeon who uses a smooth stem should use cement with a longer doughy phase, whereas a surgeon who uses a rougher stem should use cement with a longer liquid phase. Failure to appreciate the working characteristics of the different cements can potentially lead to complications during the surgery.

The overall technique of cementing THR has evolved from first- to third-generation techniques (Table). Major improvements between these 'generations' have been stratified in terms of bone preparation, cement preparation, and cement delivery. Improvements in bone preparation include the use of a plug for compression of cement, pulsatile lavage to remove loose cancellous bone, and blood to improve interdigitation of cement to bone and proximal pressurization of the cement mantle. Cement delivery has also been improved with the use of a cement gun to provide consistent retrograde filling of the canal followed by pressurization of the mantle. The literature supports improved outcomes in cemented THR with these improvements in cement techniques.

Cementing Technique

Bone preparation is critical for long-term survivorship of both the cemented stem and the cup.4 The aim is to provide a clean, stable bony bed for cement interdigitation into the remaining cancellous bone and to maintain stable interfaces between the implant and cement, and the cement and the bone.

Most investigators would agree that a surgeon should remove all loose cancellous bone but leave the remaining dense bone nearest to the cortex to enhance interdigitation of the cement into the remaining bone. This increases the shear strength of the cement and gives the best contact of the cement mantle to the remaining bone stock. Reaming with cylindrical or tapered reamers in the femur is often performed to remove the loosest bone but should be done by hand to leave a remnant of cancellous bone. It is important not to ream away all cancellous bone, as this will leave a smooth inner cortex and diminish the ability for the cement to bond to the bone.

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