Despite its complexity, hip replacement surgery is a procedure with a high success rate. Although any surgical procedure carries the risk of complications, they are quite rare. It is important for patients to understand these risks prior to consenting to surgery. You should discuss the possible complications with your surgeon and learn about ways to lessen your risks. But keep in mind these risks are only that – a risk and not a certainty. The vast majority of hip replacements are successful and patients go on to enjoy their life with a new hip.
Developing a blood clot or deep vein thrombosis (DVT) in the leg veins is one risk of hip replacement surgery that is usually on every patient’s mind. If a clot forms. it could dislodge and travel through the heart to the lungs (pulmonary embolism). Although it’s not very common, a pulmonary embolism is potentially very serious and should be dealt with immediately as an emergency. Blood thinners, compressive calf cuffs, and exercise are all prescribed for a period of time immediately following surgery and during the early weeks of recovery. These are very effective to help avoid clotting. One of the newest technologies available for the prevention of DVTs is the geko™ a unique neuromuscular elctrostimulation (NMES) device that increases blood circulation and reduces swelling in addition to reducing the risk of developing blood clots.
Problems with the implant selection or alignment
The goal of hip replacement surgery it to improve joint mobility and restore the ability to safely perform activities of daily living. To meet this goal, the mechanics of the hip joint are a critical consideration for your surgeon. Misalignment or selecting improper implant components can lead to loosening, impingement, undue wear, pain, and post-op hip dislocation. Patients can minimize this risk by making sure their chosen surgeon has both considerable experience with hip replacements and a high rate of successful surgeries.
The acetabular cup placement has a direct influence on the location of the center of rotation of the hip. Alignment of the femoral components and acetabular cup influences the mechanics of the joint, including the functional range of motion of hip articulation as well as the joint positions in which impingement can and cannot occur.
Practice makes perfect and the more hip replacements a surgeon does, the lower his error rate should be. During surgery, a good surgeon will spend considerable time analyzing the natural mechanics of a patient’s hip and test-manipulating it with the implant to ensure components are the correct size and they function properly for full range of motion.
There have been significant advances in the technology available to surgeon during the past decade. Cementless hip implants are now the standard of care as they produce a longer-lasting, more durable bond between the implant and the patient’s bone. Some surgeons can use fluoroscopic image guidance that can offers greater quality control to properly align the implant to a patient’s unique anatomy. Better control over the accuracy of implant placement means it is more likely that the patient can forgo some of the typical restrictions such as not crossing your legs or the 90-degree bending rule to prevent dislocation in the early weeks following surgery that were so frequently imposed in years past.
Dislocation is a complication that many hip replacement patients fear. There is some evidence that this risk is lower with the anterior approach in hip replacement surgery or by using an implant with a large femoral head, but neither offers a guarantee. The most common reason for a dislocation is misalignment of the implants. Ensuring you have an experienced surgeon is important to reduce the risk of dislocation after surgery.
Dislocations in a well-placed hip implant primarily occur in people who have weak muscle tone around the hip joint or who tend to take risks with certain movements in the early weeks after surgery. During the first six weeks after you receive your new hip joint, the ball is only held in the socket by muscle tension. As part of the healing process, scar tissue forms around the ball and with exercise and movement, muscle strength will return making dislocation less likely as time goes by. A physical therapist can help teach appropriate movements and exercises for the post-op recovery period to help strengthen muscles without increasing the risk of dislocation.
Should a patient have repeated dislocations, a brace may be worn for several months to prevent further problems until the hip regains tone. But ultimately, corrective surgery may be needed to better align the implant and resolve the problem.
Leg length differential (LLD)
In some cases, surgeons will note post-op patients experiencing actual leg differential or apparent leg differential.
Actual leg length differential is when the measurement from one bony point to another shows a discrepancy. Where there is an actual bony discrepancy before surgery, some leg length difference may be unavoidable even though surgeons make every effort to achieve accurate leg length by measuring during surgery and adjusting cuts to the bone. There also can be issues with the vertical elevation of the femoral component that might result in some degree of leg length change.
Apparent leg length differential is when the measurement between the bony points are the same but the patient still feels a discrepancy because the pelvis is tilted. This occurs because the patient has been accommodating body balance to cope with pain. Apparent leg length discrepancy can be resolved with careful therapy and exercises.
Some patients complain in the first few weeks following surgery that their leg feels too long. This is very normal until the body has adjusted from the pre-operative adaptation to the arthritic joint.
Infections are rare with joint replacement surgery but can involve a primary infection, late onset infection, or a superficial infection.
Hip replacement surgery is conducted in a filtered operating room with sterile instruments. Antibiotics are given to the patient before, during and after the operation to lower the risk for infection.
Even with these precautions, infections can still occur. The risk for infection is increased in patients with rheumatoid arthritis or diabetes, patients who have been taking cortisone for prolonged periods, patients whose joint previously was infected, and patients who had infection in another part of their body before going in for surgery.
Implant loosening from the bone is one of the most concerning potential problems in the long-term. Loosening can be the result of infection, but usually it is or the result of faulty techniques during surgery, poor bones that are damaged and softened by osteoporosis or rheumatoid arthritis, obesity, or unnecessary force (as in accidents).
By far the most common problem is that the implant just works loose from the bone. The more experienced the surgeon, the lower his or her error rate should be. Be sure to find a surgeon with considerable experience in hip replacements to lower the risk of post-op implant loosening.
Fractures can occur around or at the end of the prosthetic stem, generally due to inaccurate positioning of the implant. Occasionally the prosthesis stem itself can break, but this is usually the result of extreme trauma or (in very rare cases) product failure.
The femur (thighbone) can be split or cracked during hip replacement surgery due to poor use of instruments during bone preparation or unexpectedly soft bone. There are a variety of straps and wires used to fix such fractures. Often the recovery is not overly impacted by a bone fracture unless it is severe and requires a period of non-weight bearing.
Allergic or other reactions
In some cases, the articulating surfaces of an implant may produce microscopic particles from the two surfaces rubbing against one another. This can occur when the cup is not properly positioned or from an inherent allergy in the patient such as a nickel allergy. However, reports of proven allergies to metal implants are relatively rare. Allergy to plastic implant components has never been reported. This problem is more frequently seen in hips that are “metal on metal” (a metal ball is placed in a metal cup). Patients with metal on metal hips should be monitored regularly to ensure there is no increase in metal ions in their blood (metalosis) in the years following surgery.
Squeaky Hip or Noisy Hip
It is possible for any hip implant to make a variety of noises that have been described as squeaking, clicking, popping, clunking, grinding, or snapping. In 2008, as ceramic hip implants were becoming more common, patients began to increasingly report a disruption to their quality of life when their implants began making audible squeaking noises. Ceramic components were supposed to be more durable than other materials, and doctors worried that these noises might signal a deterioration of the implants. This did not prove to be the case and ceramic hip implants are still used today. Improvements in the implant manufacturing process and surgical techniques have significantly reduced the incidence of hip squeaking and it should not be a concern. Oftentimes any noise associated with a hip replacement comes down to the way pressure is exerted on the new joint with movement and it’s not a reason for surgical intervention.
Remember these are risks and not certainties…
Although these are the most common complications of hip replacement surgery, they do not happen often. 98% of all hip replacements occur without any significant problems. There may be other risks involved with hip replacement surgery that could impact you, and you should be sure to ask your surgeon to explain all potential risks before consenting to surgery.
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