Hip Arthritis

Hip Replacement Surgery

Hip replacement surgery, also known as total hip replacement (THR) or total hip arthroplasty (THA), is most commonly used to treat a hip that is painful because of damage to the cartilage. The hip joint is a ball (femur) and socket (acetabulum) joint that normally has a cartilage layer lubricated by joint fluid to allow for smooth and painless motion. As people age, this cartilage may become damaged by mechanical wear and chronic inflammation, causing coarse motion in the joint. The damaged joint can subsequently become narrow, develop bone spurs and be very painful. There are other reasons that the hip joint may become damaged - including rheumatoid arthritis, previous fractures in the hip or avascular necrosis (bone death) of the hip. Unfortunately, the arthritis resulting from all of these conditions is irreversible. Although significant research advances in cartilage repair are being made, our understanding of cartilage repair has not been able to address the issue of end stage joint disease in the hip.

Image: http://www.eorthopod.com/images/ContentImages/hip/hip_anatomy/hip_anatomy_intro01.jpg

Image: http://www.eorthopod.com/images/ContentImages/hip/hip_arthroplasty/hip_arthroplasty_anat02.jpg

Image: http://www.eorthopod.com/images/ContentImages/hip/hip_osteoarthritis/hip_oa_intro01.jpg

Image: http://www.eorthopod.com/images/ContentImages/hip/hip_avn/hip_avn_intro01.jpg

Hip replacement involves removal of the arthritic femoral head and acetabular cartilage and implantation of a femoral and acetabular prosthesis (an artificial replacement). The femoral component is a stemmed prosthesis that fits into the femoral canal after the surgeon removes the femoral neck. A femoral head prosthesis is then attached to the top of the femoral prosthesis to mimic the "ball" part of the hip joint. The acetabular component is a cup that is placed into the location of the existing acetabular socket after it is prepared by reaming the existing damaged cartilage and underlying bone. A plastic polyethylene, ceramic, or metal liner is then inserted into the cup to enable smooth motion between the ball and socket.

Image: http://www.eorthopod.com/images/ContentImages/hip/hip_arthroplasty/hip_arthroplasty_intro01.jpg

Animation of total hip replacement
http://ww2.arthritis.org/conditions/surgerycenter/surgerycenterflash/totalhip.html

Video of live THR
http://www.slp3d2.com/sfi%5F1013/broadcast_post.cfm

Indications for surgery

Although very elderly patients (over 75) can also undergo THR, a detailed health examination is required to ensure that the patient is safe for surgery.

Ultimately, a patient must be evaluated by a physician to be determined if he or she is an appropriate candidate for hip replacement surgery.

Contraindications for surgery

Should I have a replacement?

THR is an elective surgery that is usually only done after more conservative treatments have been attempted and have failed. Conservative treatments include:

1. Weight loss - Reducing weight reduces the load through the hip joint which can reduce pain and the rate at which the hip joint degenerates. For patients above 300lb, weight loss is recommended prior to hip replacement because even if this measure does not achieve pain relief, many surgeons believe that the risks of surgery, including infection, implant failure, and dislocation of the prosthesis, are too high in obese patients.

2. Physical therapy - Strengthening of the musculature not only around the hip joint, but also around the trunk, lower back, knees, and ankles, improves gait mechanics. It is useful for patients to have experience with physical therapy before a THR because they will be undergoing an aggressive therapy regimen postoperatively.

3. Anti-inflammatory medications - Common agents used for pain control include nonsteroidal anti inflammatory agents (ibuprofen, naproxen). Other medications used include tramadol (Ultram), meloxicam (Mobic), nabumetone (Relafen), diclofenac (Voltaren), etodolac (Lodine), indomethacin (Indocin).

4. Activity modification -Patients with arthritis of the hip can often modify their daily activities and exercises regimen to reduce the pain in their hip. High impact activities such as running, jogging, and jumping should be minimized and avoided. Low impact activities such as swimming, walking, and bicycling are recommended alternatives. In addition, some patients are able to reduce the pain in their hip and increase their activities by using a cane in the opposite hand.

Are there alternative surgeries besides THR?

Alternatives to THR depend on the age of the patient, the source of the hip degeneration, and the quality of the bone in the patient. Surgical alternatives include:

1. Hip arthroscopy - Hip arthroscopy involves using an arthroscopic camera and instruments to inspect and repair the hip joint. The procedure involves first creating small portals into the hip joint through which the camera and instruments can be introduced. Results of hip arthroscopy are heavily dependent on the specific condition being treated. Hip arthroscopy can be a useful tool to remove loose bodies from the joint which may be causing mechanical symptoms (e.g., catching and clicking) in the hip, repair and/or resect tears of the acetabular labrum (a fibrocartilage that surrounds the hip socket), remove bone spurs caused by femoroacetabular impingement (FAI), and repair limited areas of cartilage damage on the femoral head. Although in certain cases hip arthroscopy to remove loose bodies or to reshape the femoral neck (for a condition called femoroacetabular impingement) may slow the progression of osteoarthritis, in general, it is NOT recommended for patients who have diffuse arthritic changes in their hip. Complications with hip arthroscopy can occur in 1-6% of cases and include damage to nerves (from stretching or direct trauma) and direct trauma to the joint when using arthroscopic instruments. Nerve injury caused by stretching during positioning is usually temporary.

Image: http://www.eorthopod.com/images/ContentImages/hip/hip_osteoarthritis/hip_oa_surgery01.jpg

2. Femoral or periacetabular osteotomy - Osteotomies, which involve cutting and re-orienting the bones around the hip joint, are used occasionally in young patients who may benefit from a total hip arthroplasty but have more than 30 years of life expectancy. Osteotomies are ways to surgically cut and realign the bones around the hip joint to redistribute the joint forces in a way that makes it easier for the patient to move the hip and to slow the degeneration of the hip. There are many different types of osteotomies, each tailored to specific hip mechanical pathologies. The outcomes for osteotomies are mixed. For some patients, an osteotomy may buy the patient additional time before eventually undergoing a THR. Osteotomies are becoming rarer as improvements in prosthestic design and surgical technique have increased durability of a primary THR.

3. Core decompression and vascularized fibular grafting - This is a treatment for relatively early stage avascular necrosis (bone death) of the femoral head. Avascular necrosis results from decreased blood flow (ischemia) to the femoral head, and can be associated with steroid use, alcoholism, and other systemic diseases, including HIV disease. Decreased blood flow causes the femoral head to collapse over time, ultimately leading to hip arthritis. The surgery involves drilling a hole through the femoral neck into the femoral head to decrease pressure within the bone. In the case of vascularized fibular grafting, the fibula bone is harvested with its blood vessel from the leg and placed into the drill hole, and the blood vessel connected to a vessel near the hip. This is thought to increase blood flow to the hip. Again, this treatment is typically reserved for younger patients and results are mixed.
Image: http://www.eorthopod.com/images/ContentImages/hip/hip_avn/hip_avn_treatment01.jpg

4. Hip resurfacing - Hip resurfacing is a technique that can be used to treat Hip Arthritis and avascular necrosis of the femoral head in younger patients with good bone quality. It involves "capping" the femoral head with a metal prosthesis and allowing this capped femoral head to articulate with the patient's own acetabulum or an acetabulum prosthesis. In previous decades, hip resurfacing had fallen out of favor due to poor outcomes because of the materials used in the past. Recent modifications with metal components and improvements in surgical techniques have brought resurfacing back to the attention of surgeons and patients. Patients who have collapse of the femoral head, poor bone quality, or large bone cysts are considered poor candidates for hip resurfacing. In addition, resurfacing is typically reserved for patients younger than 65 with a body mass index (BMI) less than 35 and good bone quality.

Image: http://www.smith-nephew.com/pics/picture-library/products/BHR_component.jpg

The main advantage of hip resurfacing is the preservation of bone stock in the femur in comparison to a THR. Because the femur is being capped, very little bone is being removed. If revision surgery is ever required, there is more of the patient's own bone remaining, which can make revision surgery easier in hip resurfacing patients than in patients who have previously undergone THR. For this reason, hip resurfacing has a theoretical benefit for younger patients who may need revision surgery in the future because conversion to a THR is still possible. However, once someone has a THR, hip resurfacing is no longer an option. Another advantage of hip resurfacing is that a larger diameter femoral head diameter prosthesis is used, which could theoretically reduce the rate of postoperative dislocation rates.

Image: http://www.eorthopod.com/images/ContentImages/hip/hip_arthroplasty_resurface/hip_arthroplasty_resurface_rationale02.jpg

One of the major drawbacks of hip resurfacing is the risk of femoral neck fracture, which would require conversion to THR. The rate of fracture has been reported to be 0-4%. Other disadvantages include the uncertainty of long term outcomes, potential for loosening of the prosthesis, and the fact that few surgeons have extensive experience with doing this surgery. Results from the Australian hip registry suggest that the survival rate of hip resurfacing implants is lower than the survival rate for hip replacement implants during the first five years following surgery (Buergi MR, 2007). Hip resurfacing is not appropriate for many patients who require hip surgery, and patients who are interested in hip resurfacing should seek consultation with an orthopaedic surgeon.

Source: Mont MA et al., "Hip Resurfacing Arthroplasty", Journal of AmericanAcademy of Orthopaedic Surgeons, August 2006; 14: 454 - 463

Video of hip resurfacing

http://www.or-live.com/shawneeMission/1663/event/webcast.cfm

5. Arthrodesis (Fusion) and Girdlestone (resection arthroplasty) - These alternatives are considered last resort surgical options. Often these surgeries are considered in patients who have had multiple failed THA procedures or who have had chronic joint infections which make THA impossible.

What will the surgeon do to determine whether I need a hip replacement?

1. Clinical History

During evaluation for a THA, the surgeon will ask many questions about a patient's pain and activity.
Pain from the hip may manifest itself over the outside of the hip, in the groin area, over the thigh, or in the lower back and buttock area. Similarly pain from other joints including the low back and knee may manifest itself as hip pain. Hip arthritis pain is typically worse with activity and improved with rest and anti-inflammatory medications. In some patients, hip arthritis pain progresses to the point that it can occur at rest and can wake the patient at night. The surgeon will typically ask if the other hip hurts as well, as many patients with Hip Arthritis have bilateral disease (diseases in both hips).

Questions about activity level will include: How far can the patient walk? Does the patient need assistance with a cane or walker? What types of the activities can the patient do? What types of activities does the patient like to do?

A complete history will involve questions about the patient's past medical, surgical history, medications. It is important for the surgeon to know whether the patient has had previous hip surgery, has had any infections, or has ever injured or dislocated the hip previously.

2. Physical Exam

The physical exam will involve examining how the patient walks, the active and passive range of motion of the hip, whether there is pain with moving the hip, whether there is any signs of skin changes or infections on the patients hip and leg, whether the nerves and blood vessels in the operated leg are functioning normally, and whether the leg lengths are the same in both legs. It is very important for the surgeon to differentiate between low back and hip pain. Additional tests may be ordered in order to differentiate back problems from hip problems.

3. Diagnostic tests

X-rays are the standard technique to tell whether a patient has arthritis of the hip. Signs of osteoarthritis on xray include joint space narrowing, osteophytes (bone spurs) near the joint, cysts in the bone, and sclerosis of the bone near the joint. Avascular necrosis of the hip manifests itself as sclerosis and collapse of the femoral head. An MRI of the hip may be obtained if avascular necrosis is suspected. Rheumatoid arthritis has relatively similar features to osteoarthritis, although the arthritis has a more destructive appearance on x-ray.

If there is a question about a history of infection in the hip, the surgeon may order a bone scan or white blood cell scan.

Image: http://www.utdol.com

Image: http://orthoinfo.aaos.org/topic.cfm?topic=A00213

Typically patients will need to see a general medicine (internal medicine, family practice) physician or cardiologist prior to surgery. These physicians will evaluate the patient and optimize their overall medical health prior to surgery. They may order blood tests, chest x-rays, electrocardiogram (EKG), and echocardiogram for the evaluation.

What does the operation entail?

1. Types of anesthesia

General anesthesia involves putting the patient to sleep with a combination of inhaled and intravenous anesthetic agents and placing a breathing tube into the trachea (windpipe). This type of anesthesia affects the whole body and affects blood pressure and respiratory function. It also causes dilation of the veins causing greater blood loss. General anesthesia is reserved for patients with relatively normal heart and lung function.

Regional anesthesia involves administering pharmacologic agents (such as local anesthetics (e.g., lidocaine) and narcotic pain medicines (e.g., morphine)) near the spinal cord to provide anesthesia to the legs without affecting the heart or lungs. In a spinal block, the anesthesiologist injects the drug around the spinal cord through the back immediately before surgery. This provides a one time dosing of anesthesia that lasts the duration of surgery and for a few hours after surgery. An epidural block involves the placement of a catheter just outside the spinal cord from the back. The anesthestic agent can then be administered through the catheter during surgery and during the postoperative period. The catheter is removed after surgery, either the night of surgery or the next day. Regional anesthesia is safer for those with heart or lung problems, but can cause urinary retention and/or headaches. In addition, regional anesthesia is associated with a lower rate of postoperative deep venous thrombosis a blood clot in a vein deep inside the body) development than in general anesthesia.

Peripheral nerve blockade (e.g., lumbosacral plexus block) involves administering pharmacologic agents in a more directed fashion to the nerves in the lower extremity of the operative leg. Peripheral nerve blocks can be given as a single injection, or through a catheter which is left in place after the surgery to help with post-operative pain control. This form of adjunctive anesthesia has only recently been used in hip replacement surgery, and can have a significant benefit in terms of reducing the need for post-operative narcotic pain medicines.

American Academy of Orthopaedic Surgeons (AAOS) patient information on anesthesia

http://orthoinfo.aaos.org/topic.cfm?topic=A00372&return_link=0

2. Surgical approach

Posterior approach - For this technique, the patient is placed on their side with the unaffected hip side down. A curved incision is made and dissection is carried down through the gluteus maximus muscle. Next the external rotating muscles of the hip are cut, the hip capsule opened, and the hip dislocated. At this point, the femoral head is cut and removed. The femoral and acetabulum are prepared by reaming and placing trial components. The femoral and acetabular prostheses are then relocated into the hip and the hip taken through a range of motion to check for stability. At this point, the hip is dislocated again and the trial components removed. The final components are then either press fit or cemented in place, depending on surgeon technique. The external rotators of the hip are repaired. The primary advantages of the posterior approach are that it is familiar to most hip replacement surgeons and it does not violate the abductor muscles (the muscles that allow you to pull your leg away from the midline of your body). A disadvantage of the posterior approach is that it has been associated with a higher rate of postoperative dislocation of the hip. Newer surgical techniques (including repair of the posteriorz capsule) and implant designs (e.g., larger diameter femoral heads) may reduce the incidence of hip dislocation associated with the posterior approach.

Direct lateral approach - The direct lateral approach is also performed with the patient on their side. Dissection is carried down through the lateral musculature of the hip, including the gluteus maximum, gluteus medius, and gluteus minimus, and the anterior aspect (front) of the hip joint is exposed. The primary advantage of the lateral approach is that it spares the posterior musculature and capsule of the hip, and therefore can be particularly beneficial for patients in whom posterior dislocation of the hip is a concern (e.g., elderly patients with dementia or neurologic disease). Some surgeons have found a lower dislocation rate with the direct lateral approach, but there is also an associated risk of persistent limp due to damage to the abductor muscles and/or nerves, and a higher rate of heterotopic bone formation in the muscle surrounding the hip.

Anterior approach - The anterior approach to the hip has gained popularity among some hip surgeons over the past 10 years. The proposed advantage of the anterior approach is that most of the muscles around the hip are left intact. Some surgeons prefer this approach because of a theoretical reduction in postoperative hip dislocation, and faster rehabilitation. The anterior approach involves placing the patient on their back on a special operating room table. The dissection is carried out carefully between the muscles in front of the hip without detaching them. At this point, the preparation of the femur and acetabulum are done in a similar fashion to the posterior approach. Little data is available regarding the outcomes of patients undergoing hip replacement with the anterior approach. Disadvantages of the anterior approach include the need for specialized equipment, including a specialized operating table, additional surgeon training, and potentially a higher complication rate, including risk of injury to the lateral cutaneous nerve of the thigh, femoral nerve, and femoral artery. There are few surgeons with extensive experience with the anterior approach and it is still unclear as to its clinical benefit.

Animation of anterior approach

http://www.or-live.com/DePuy/2051/animation.cfm?

Video of anterior approach by Dr. Joel Matta

http://www.or-live.com/DePuy/2051/event/rnh.cfm?

What is the postoperative course after surgery?

Physical therapy starts on the first day after surgery; most patients are allowed to walk that first day. In addition patients will begin taking some form of prophylaxis to prevent deep vein thrombosis (blood clots) in the form of low molecular weight heparin (Lovenox), warfarin (Coumadin), aspirin, or newer agents available on the market. Patients typically stay in the hospital for three to ten days after surgery. Some patients go to a rehabilitation or skilled nursing facility after discharge for additional physical therapy. The full rehabilitation course can take from two to six months depending on the preoperative condition of the patient. Patients should not return to driving for at least six weeks after surgery. Patients may need to take antibiotics prior to dental procedures to prevent seeding of bacteria into the artificial joint.

Exercises after THR

http://orthoinfo.aaos.org/topic.cfm?topic=A00303&return_link=0

Postoperative activities after THR (including list of activity limitations)

http://orthoinfo.aaos.org/topic.cfm?topic=A00356

Recommendation for antibiotics and dental procedures after THR http://orthoinfo.aaos.org/topic.cfm?topic=A00226

What are the potential complications from hip replacement surgery?

Although the results of THR are quite successful, THR is a major surgery. Patients may require a blood transfusion after surgery. The mortality rate is less than 0.5-1% in the first 30 days after surgery and is mainly associated with the stress of the surgery on the heart, and the development of lung problems such as pneumonia or a pulmonary embolus. This is why it is critical for many patients to obtain a medical clearance prior to surgery.

Deep venous thrombosis (DVT) and pulmonary embolism (PE)

During surgery, blood venous stasis (slowing or stoping of the blood) and the release of inflammatory chemicals into the blood can result in the development of DVT. These clots can break free and travel to the lungs, blocking the oxygenation of the blood in the circulatory system. This development is called a pulmonary embolism; it is a very serious complication that can lead to death. Orthopaedic surgeons have recognized this problem associated with THR and routinely give their patients prophylactic medications to prevent DVT and PE. Prior to the use of routine DVT prophylaxis, the rate of PE after THR was 8%, with 1% being fatal. Patients are now often given coumadin, heparin, low molecular weight heparin, aspirin, or direct thrombin inhibitors after surgery for one to four weeks. The rates of fatal PE are now 0-0.2%. Studies directly comparing the different DVT prophylaxis agents have been inconclusive.

Dislocation

Dislocation is a complication that can lead to a poor result, patient dissatisfaction, and the need for revision surgery. A review of 60, 000 THA and 13, 000 revision THA procedures showed a dislocation rate of 3.9% in the first six months for primary THA and 14.4% for revision THR (Phillips, C.B., 2003). Approximately 2/3 of dislocations occur in the first month after surgery. Patients are given very specific activity restrictions following surgery to prevent dislocation. These include no flexing at the hip past 90 degrees, no crossing legs, and no excessive internal rotations. Certain patient populations are more prone to dislocation including female gender, and those with neuromuscular disease, dementia, alcohol abuse, previous hip surgery, and higher level of activity. Surgeons attempt to reduce dislocation rates by proper component positioning, sizing, and surgical approach. As described earlier, the posterior approach has traditionally been associated with a higher rate of dislocation, although this may be changing with newer surgical techniques and implant designs.

Those patients who do experience recurrent dislocation may need to undergo revision THR during which the components may be realigned and/or more constrained prostheses implanted.

Nerve palsy

The sciatic nerve is at risk of being stretched and/or compressed during THR. The nerve can be stretched if the limb is lengthened more than four centimeters or during the dislocation of the hip. Compression of the nerve can be due to retractor placement or a collection of blood forming around the nerve. Unfortunately, the exact cause of sciatic nerve injury can rarely be identified. The common presentation of sciatic nerve injury is inability to raise the foot towards the head, also known as foot drop. This may also be associated with numbness in the foot. The rate of injury is 0.67-3.7%. The rate of nerve palsy is higher in patients undergoing THR for developmental dysplasia of the hip or revision THR. Patients who have a sciatic nerve palsy are placed in an ankle foot orthosis (AFO) which prevents the foot from developing a contracture (tightness of the tendons and ligaments around the joint limiting normal motion). Signs of sciatic nerve recovery can occur anywhere between 0-1 year from injury.

Limb length discrepancy

A discrepancy in limb length can occur after THR. It is important for patients to realize that although their surgeon will make every attempt to equalize leg lengths after surgery, the primary goal is to achieve a stable hip construct, and other factors outside the control of the surgeon, including spinal curvature and other bony abnormalities, may contribute to a limb length inequality following hip replacement surgery. A discrepancy of two centimeters or less can be managed with the use of a shoe lift. A larger discrepancy can be managed by revising the prosthesis to make appropriate adjustments. Some postoperative limb length discrepancies may be due to abductor weakness and/or contractures that have been present due to long standing hip pain and improper gait.

Infection

Infection is a complication that can occur both the in the early and late postoperative periods. It presents as a chronically draining wound, redness around the incision site, fevers, chills, or as chronic pain in the hip. Superficial infections can be treated with a short course of oral or intravenous antibiotics. If the infection tracks deep to the prosthesis, the results can be catastrophic to the hip. Early deep infections can be treated by taking the patient back to surgery, removing infected tissue, washing the recently implanted metal prostheses, and exchanging the modular parts of the prosthesis (e.g., the femoral head and acetabular liner). Late, deep infections are treated by removing the entire prostheses, and placement of an antibiotic impregnated cement spacer. After six weeks of intravenous antibiotics and blood tests that are negative for signs of infection, the patient may in some cases be taken back for implantation of a new prosthesis.

Wear/osteolysis

The implanted hip prosthesis can be subject to both mechanical and biologic sources of wear. Mechanical wear of the prosthesis, particularly the polyethylene liner, can occur from third body particles (eg. metal or cement) that have found their way into the joint, misalignment of components, or simply repetitive loads experienced across the hip (particularly in younger, more active patients). Over time, the polyethylene liner may be thinned due to these processes, altering hip mechanics, and subsequently cause a painful hip. The polyethylene wear particles may cause an inflammatory reaction resulting in resorption (dissolving) of the bone around the prosthesis (known as "osetolysis"), and in some cases, loosening of the prosthesis. Advances in prosthetic design and materials research have also been directed and reducing both the production of wear particles and the ability of wear particles to access the bone-implant interface.

Recent Developments

• Minimally invasive surgery

Minimally invasive surgery (MIS) techniques for THR have been developed with the aim of reduceing incision length, blood loss, recovery time, soft tissue damage and post-operative pain, and lengths of hospital stay. These techniques are quite varied in terms of incision length (range 2-20 cm), number of incisions (one versus two), and approach (posterior, lateral, anterior). There is not one standard MIS approach. There is significant controversy among the surgeon community as to whether these techniques are beneficial. Proponents of MIS claim that the surgery does achieve some of the aims listed above. Critics of MIS argue that there is no evidence that this techniques achieves those goals. Many of the critics argue that with smaller incisions there is higher chance for component misalignment and increased soft tissue damage because the surgical retractors are pulled more to gain visualization to the surgical field. In a recent review of available literature by Vail and Callaghan, there were no definitive benefits to MIS techniques.

Courtesy: Vail TP et al, "Minimal Incision Total Hip Arthroplasty" Journal of American Association of Orthopaedic Surgeons. December 2007; 15:707-15

Courtesy: Vail TP et al, "Minimal Incision Total Hip Arthroplasty" Journal of American Association of Orthopaedic Surgeons. December 2007; 15:707-15

Statement by American Association of Hip and Knee Surgeons on MIS techniques

http://www.aahks.org/pdf/MIS_Patients.pdf

Patient education on MIS by American Academy of Orthopaedic Surgeons

http://orthoinfo.aaos.org/topic.cfm?topic=A00404

Video of MIS THR http://www.or-live.com/Zimmer/1604/event/webcast.cfm

Video of MIS THR http://www.or-live.com/Path/event/webcast.cfm

Video of MIS - 2 incision THR http://www.or-live.com/zimmer/1606/event/webcast.cfm

Video of MIS THR http://www.or-live.com/vanderbilt/1329/

Alternative bearing surfaces

Given the problem of wear and osteolysis with standard polyethylene and metal bearing surfaces, developments in implant materials have been made with the goal to have longer lasting hip implants. The hope is that these new materials will allow younger patients to undergo THR instead of living with pain until they reach the age at which THR is indicated.

1. Cross-linking of ultra high molecular weight polyethylene (UHMWPE) has been developed to reduce wear rates of the polyethylene liner. Below is a graph showing the decreased wear rate of highly cross-linked UHMWPE, and a chart that shows clinical studies that have demonstrated decreased wear with implanted highly cross-linked UHMWPE acetabular liner.

Courtesy: Gordon AC, "Highly Cross-linked Polyethylene in Total Hip Arthroplasty" Journal of American Association of Orthopaedic Surgeons. September 2006. 14:511-23.

Courtesy: Gordon AC, "Highly Cross-linked Polyethylene in Total Hip Arthroplasty" Journal of American Association of Orthopaedic Surgeons. September 2006. 14:511-23.

2. Metal on metal THR imlants have been devised to reduce wear as well. Original metal on metal THR designs were associated with poor results two to three decades ago because of poor surface finishing techniques that actually caused increased metal wear. Now with new finishing techniques, some believe that there is new hope for metal on metal THR. The theoretical advantages of metal on metal are decreased wear and the ability to use a larger head implant which is associated with a decreased dislocation rate. This would provide more stable implants for younger patients. Laboratory wear studies have showed that metal on metal implants today have 100 fold decreased wear rates. There is, however, a thre to five fold increase in the concentration of metal ions in the blood of patients who have metal on metal THR. The clinical significance of this finding is unknown, but some are wary of the long term effects. Also, some patients may have an allergic reaction to metal wear debris, causing pain, and in some cases, the need for revision surgery. Patients with renal (kidney) insufficiency and women of childbearin age should not undergo metal on metal THR.

Video of metal on metal THR

http://www.or-live.com/sinai/1250/

3. Ceramic on ceramic technology is another development aimed at allowing younger, more active patients to get a THR. Ceramics are thought to decrease wear rates, decrease friction, and reduce the rates of fracture of the acetabular liner. However, ceramics are brittle, and fractures of ceramic femoral heads and acetabular liners have been reported, particularly with zirconia ceramics. Like metal on metal technologies, little is known about the longer term clinical outcomes of ceramic on ceramic bearing surfaces. In laboratory studies, there is decreased wear of ceramic on ceramic compared to metal on metal.

Image: http://www.zimmer.co.uk/web/images/uk_english/Hips/TriloAB2.jpg

Courtesy: Williams, Sophie et al. "Ceramic-on-Metal Hip Arthroplasties: A Comparative In Vitro and In Vivo Study" Clinical Orthopaedics and Related Research" December 2007. 465:23-32

• Computer assisted surgery All surgeons agree that there is no replacement for sound clinical experience and judgment in choosing component alignment, but computer assisted surgery has been developed to theoretically help the surgeon place the components in the proper alignment. In this technique the alignment of bone cuts and implant positioning are detected by a camera in the operating room and compared to the desired preoperative plan. Although computer navigation may improve component alignment in certain cases, there is controversy in the literature as to whether there is a long-term clinical benefit from computer navigation.
  

  Image: http://www.devicelink.com/mddi/archive/05/11/mddi0511p80e.jpg

  Video of computer assisted THA

  http://www.or-live.com/distributors/NLM/rnh.cfm?id=208

  Useful websites

  • American Academy of Orthopaedic Surgeons (AAOS)
    

  http://orthoinfo.aaos.org/
  http://orthoinfo.aaos.org/menus/hip.cfm

  AAOS Compendium of Evidence Based Resources for Osteoarthritis of the Hip

  http://www.aaos.org/Research/documents/oainfo_hip.asp
  

  AAOS Video: "Total Hip Replacement: Improving Quality of Life Patient Education Video"

  http://www4.aaos.org/product/productpage.cfm?code=20141
  

  
  

  • American Association of Hip and Knee Surgeons (AAHKS)
    

  http://www.aahks.org

  • Medline: Hip Replacement

  http://www.nlm.nih.gov/medlineplus/hipreplacement.html

  Images

  • eOrthopod
    
  http://www.eorthopod.com

  
  

  Videos:

  • OR-Live
  http://www.or-live.com

• References

  
  

  Buergi MR et al, "Hip Resurfacing Arthroplasty: The Australian Experience, Journal of Arthroplasty, September 2007 22:61-5

  Gordon AC, "Highly Cross-linked Polyethylene in Total Hip Arthroplasty" Journal of American Association of Orthopaedic Surgeons. September 2006. 14:511-23

  Mont MA et al., "Hip Resurfacing Arthroplasty", Journal of American Academy of Orthopaedic Surgeons, August 2006; 14: 454 - 463

  Phillips, C.B., et al., Incidence rates of dislocation, pulmonary embolism, and deep infection during the first six months after elective total hip replacement. Journal of Bone and Joint Surgery Am, 2003. 85-A(1): p. 20-6

  Vail TP et al, "Minimal Incision Total Hip Arthroplasty" Journal of American Association of Orthopaedic Surgeons. December 2007; 15:707-15

  Williams, Sophie et al. "Ceramic-on-Metal Hip Arthroplasties: A Comparative In Vitro and In Vivo Study" Clinical Orthopaedics and Related Research" December 2007. 465:23-32