Total hip replacement is most commonly used to treat joint failure caused by osteoarthritis. Other indications include rheumatoid arthritis, avascular necrosis, traumatic arthritis,protrusio acetabuli, certain hip fractures, benign and malignant bone tumors, arthritis associated with Paget's disease, ankylosing spondylitis and juvenile rheumatoid arthritis. The aims of the procedure are pain relief and improvement in hip function. Hip replacement is usually considered only after other therapies, such as physical therapy and pain medications, have failed.

---

Top of page

_{Dislocated artificial hip}

_{Hip prosthesis displaying aseptic loosening (arrows)}

Risks and complications in hip replacement are similar to those associated with all joint replacements. They can include dislocation, loosening, impingement, infection, osteolysis, metal sensitivity, nerve palsy, pain and death.

Vein thrombosis

Venous thrombosis such as deep vein thrombosis and pulmonary embolism are relatively common following hip replacement surgery. Standard treatment with anticoagulants is for 7–10 days; however treatment for more than 21 days may be superior.

Some physicians and patients may consider having lower limbs venous ultrasonography to screen for deep vein thrombosis after hip replacement. However, this kind of screening should only be done when indicated because to perform it routinely would be unnecessary health care.

Dislocation

Dislocation is the most common complication of hip replacement surgery. At surgery the femoral head is taken out of the socket, hip implants are placed and the hip put back into proper position. It takes eight to twelve weeks for the soft tissues injured or cut during surgery to heal. During this period, the hip ball can come out of the socket. The chance of this is diminished if less tissue is cut, if the tissue cut is repaired and if large diameter head balls are used. Surgeons who perform more of the operations each year tend to have fewer patients dislocate. Doing the surgery from an anterior approach seems to lower dislocation rates when small diameter heads are used, but the benefit has not been shown when compared to modern posterior incisions with the use of larger diameter heads. Patients can decrease the risk further by keeping the leg out of certain positions during the first few months after surgery. Use of alcohol by patients during this early period is also associated with an increased rate of dislocation.

Fracture

Bones with internal fixation devices in situ are at risk of periprosthetic fractures at the end of the implant, an area of relative mechanical stress. Post-operative femoral fractures are graded by the Vancouver classification.

Osteolysis

Many long-term problems with hip replacements are the result of osteolysis. This is the loss of bone caused by the body's reaction to polyethylene wear debris, fine bits of plastic that come off the cup liner over time. An inflammatory process causes bone resorption that may lead to subsequent loosening of the hip implants and even fractures in the bone around the implants.

Metal toxicity

Most hip replacements consist of cobalt and chromium alloys, or titanium. Stainless steel is no longer used. All implants release their constituent ions into the blood. Typically these are excreted in the urine, but in certain individuals the ions can accumulate in the body. In implants which involve metal-on-metal contact, microscopic fragments of cobaltand chromium can be absorbed into the patient's bloodstream. There are reports of cobalt toxicity with hip replacement patients.

Nerve palsy

Post operative sciatic nerve palsy is another possible complication. The incidence of this complication is low. Femoral nerve palsy is another but much more rare complication. Both of these will typically resolve over time, but the healing process is slow. Patients with pre-existing nerve injury are at greater risk of experiencing this complication and are also slower to recover.

Chronic pain

A few patients who have had a hip replacement suffer chronic pain after the surgery. Groin pain can develop if the muscle that raises the hip (iliopsoas) rubs against the edge of the acetabular cup. Bursitis can develop at the trochanter where a surgical scar crosses the bone, or if the femoral component used pushes the leg out to the side too far. Also some patients can experience pain in cold or damp weather. Incision made in the front of the hip (anterior approach) can cut a nerve running down the thigh leading to numbness in the thigh and occasionally chronic pain at the point where the nerve was cut (a neuroma).

Leg length inequality

The leg can be lengthened or shortened during surgery. Unequal legs are the most common complaint by patients after surgery with over lengthening the most common problem. Sometimes the leg seems long immediately after surgery when in fact both are equal length. An arthritic hip can develop contractures that make the leg behave as if it is short. When these are relieved with replacement surgery and normal motion and function are restored, the body feels that the limb is now longer than it was. If the legs are truly equal, the sense of inequality resolves within a month or two of surgery. If the leg is unequal, it will not. A shoe lift for the short leg, or in extreme cases, a corrective operation may be needed.

True leg length inequality may sometimes be caused by improper implant selection. The femoral component may be too large and stick out of the femur further than needed. The head ball selected may sit too proud on the stem. Stiffness in the lower back from arthritis or previous fusion surgery seems to magnify the perception of leg length inequality.

_{Hip replacement}

---

Top of page

There are several incisions, defined by their relation to the gluteus medius. The approaches are posterior (Moore), lateral (Hardinge or Liverpool), antero-lateral (Watson-Jones), anterior (Smith-Petersen) and greater trochanter osteotomy.

Posterior approach

The posterior (Moore or Southern) approach accesses the joint and capsule through the back, taking piriformis muscle and the short external rotators off the femur. This approach gives excellent access to the acetabulum and femur and preserves the hip abductors and thus minimises the risk of abductor dysfunction post operatively. It has the advantage of becoming a more extensile approach if needed.

Lateral approach

The lateral approach is also commonly used for hip replacement. The approach requires elevation of the hip abductors (gluteus medius and gluteus minimus) to access the joint. The abductors may be lifted up by osteotomy of the greater trochanter and reapplying it afterwards using wires (as per Charnley), or may be divided at their tendinous portion, or through the functional tendon (as per Hardinge) and repaired using sutures.

Antero-lateral approach

The anterolateral approach develops the interval between the tensor fasciae latae and the gluteus medius.

Anterior approach

The anterior approach uses an interval between the sartorius muscle and tensor fasciae latae.  The anterior approach results in a quicker and less painful recovery. Immediately following surgery patients are instructed to go about their normal hip function, including weight bearing activity and bending their hip freely.

Minimally invasive approach

The double incision surgery and minimally invasive surgery seeks to reduce soft tissue damage through reducing the size of the incision. However, component positioning accuracy and visualization of the bone structures is significantly impaired. This can result in unintended fractures and soft tissue injury. Surgeons using these approaches are advised to use intraoperative x-ray fluoroscopy or computer guidance systems.

Computer-assisted surgery techniques are also available to guide the surgeon to provide enhanced accuracy. Several commercial CAS systems are available for use worldwide.HipNav was the first system developed specifically for total hip replacement, and included navigation and preoperative planning based on a preoperative CT scan of the patient. Improved patient outcomes and reduced complications have not been demonstrated when these systems are used when compared to standard techniques.

---

Top of page

Cement-free implant sixteen days after surgery. Femoral component is cobalt chromium combined with titanium which induces bone growth into the implant. Ceramic head. Acetabular cup coated with bone growth-inducing material and held temporarily in place with a single screw.

The prosthetic implant used in hip replacement consists of three parts: the acetabular cup, the femoral component, and the articular interface. Options exist for different people and indications. The evidence for a number of newer devices is not very good, including: ceramic-on-ceramic bearings, modular femoral necks, and uncemented monoblock cups. Correct selection of the prosthesis is important.

Acetabular cup

The acetabular cup is the component which is placed into the acetabulum (hip socket). Cartilage and bone are removed from the acetabulum and the acetabular cup is attached using friction or cement.

Femoral component

The femoral component is the component that fits in the femur (thigh bone). Bone is removed and the femur is shaped to accept the femoral stem with attached prosthetic femoral head (ball). There are two types of fixation: cemented and uncemented. Cemented stems use acrylic bone cement to form a mantle between the stem and to the bone. Uncemented stems use friction, shape and surface coatings to stimulate bone to remodel and bond to the implant. Stems are made of multiple materials (titanium, cobalt chromium, stainless steel, and polymer composites) and they can be monolithic or modular. Modular components consist of different head dimensions and/or modular neck orientations; these attach via a taper similar to a Morse taper.

Articular interface

The articular interface is not part of either implant, rather it is the area between the acetabular cup and femoral component. The articular interface of the hip is a simple ball and socket joint. Size, material properties and machining tolerances at the articular interface can be selected based on patient demand to optimise implant function and longevity whilst mitigating associated risks. The interface size is measured by the outside diameter of the head or the inside diameter of the socket.

---

Top of page

Conservative management

The first line approach as an alternative to hip replacement is conservative management which involves a multimodal approach of medication, activity modification and physical therapy. Conservative management can prevent or delay the need for hip replacement.

Hemiarthroplasty

Hemiarthroplasty is a surgical procedure which replaces one half of the joint with an artificial surface and leaves the other part in its natural (pre-operative) state. This class of procedure is most commonly performed on the hip after a subcapital (just below the head) fracture of the neck of the femur (a hip fracture). The procedure is performed by removing the head of the femur and replacing it with a metal or composite prosthesis.

Hip resurfacing

Hip resurfacing is an alternative to hip replacement surgery. It has been used in Europe for over seventeen years and become a common procedure. Health-related quality of life measures are markedly improved and patient satisfaction is favorable after hip resurfacing arthroplasty.

The minimally invasive hip resurfacing procedure is a further refinement to hip resurfacing.

---

Back to Top

CONTACT OUR OFFICE TO SCHEDULE A CONSULTATION