HIP REPLACEMENT (arthroplasty)

History

The earliest recorded attempts at hip replacement (Gluck T, 1891), which were carried out in Germany, used ivory to replace the femoral head (the ball on the femur). In 1960 a Burmese orthopaedic surgeon, Dr. San Baw (29 June 1922 – 7 December 1984), pioneered the use of ivory hip prostheses to replace ununited fractures of the neck of femur ('hip bones'), when he first used an ivory prosthesis to replace the fractured hip bone of an 83 year old Burmese Buddhist nun, Daw Punya. This was done while Dr. San Baw was the chief of orthopeadic surgery at Mandalay General Hospital in Manadalay, Burma. Dr. San Baw used over 300 ivory hip replacements from the 1960s to 1980s. He presented a paper entitled 'Ivory hip replacements for ununited fractures of the neck of femur' at the conference of the British Orthopeadic Association held in London in September 1969. An 88% success rate was discerned in that Dr. San Baw's patients ranging from the ages of 24 to 87 were able to walk, squat, ride the bicycle and play football a few weeks after their fractured hip bones were replaced with ivory prostheses. Dr. San Baw's use of ivory was, at least in Burma during the 1960s, 1970s and 1980s (before the illicit ivory trade became rampant, starting around the early 1990s) cheaper than metal. Moreover, due to the physical, mechanical, chemical, and biological qualities of ivory, it was found that there was a better 'biological bonding' of ivory with the human tissues nearby the ivory prostheses. An extract from Dr San Baw's paper, which he presented at the British Orthopeadic Association's Conference in 1969, is published in Journal of Bone and Joint Surgery (British edition), February 1970.

Common procedure

Joint replacement is a common surgical procedure with a high success rate. In an arthritic hip, the damaged ball (the upper end of the femur) is replaced by a metal or ceramic ball attached to a metal stem fitted into the femur (with or without cement), and a plastic or ceramic socket (fitted into a metal socket) that is implanted into the pelvis, replacing the damaged socket.

Using a combination of metal and plastic, the joint implant surgeon creates a new ball and socket joint which will glide smoothly and painlessly. During the past two decades, multiple advances in hip arthroplasty have been accomplished and many types of prostheses are available and currently used. The metals used are chrome cobalt alloy and/or titanium alloy. These are super metals initially developed for the aerospace industry and now adapted for the orthopedic industry. The plastic is a high-density plastic polymer called polyethylene. In younger patients a ceramic ball is used with a polyethylene or ceramic socket.
 

Which type of hip prosthesis?

The joint implant surgeon decides for each patient individually which type of prosthesis he will implant. The decision depends on several factors, among them:

Age, bone quality, shape or deformation of the bone (upper part of femur) and  deformation of the bone of the pelvis

Based on those factors and radiographs, the most suited prosthesis can be selected.

At present there is a wide range of prostheses with different new types of articulations such as metal-on metal and ceramic-on-ceramic in stead of metal-on-polyethylene, based on new scientific research and availability of improved metal alloys which may reduce the wear. The use of exchangeable neck/ball (modular prosthesis) in primary as well as revision surgery has enhanced the surgeons amatory to create a stable prosthesis in most conditions and facilitates future revision surgery. On rare occasions of extreme deformation of the joint or femur, the surgeon may need to use an individually designed prosthesis based on radiographs and CT-scan of the patients’ hip.

Ceramic Implants and Metal-Against-Metal Implants.

The ceramic head implants
Cracking is the downside to using ceramics.

Metal against metal, they have recently found that toxic levels of metal-breakdown products show up in the joint and in the patients' urine. These toxic levels may be high enough to be cancer causing. How long does the toxicity stay? Does it get diluted with time and go away?

Metal against plastic hip implants, 90% of them are still functioning twenty years later. Metal against plastic, there's no metal breakdown or toxicity, because the plastic wears out first. At least you know that is going to happen. There's no cracking or toxic. Due to past problems with polyethylene-wear new polyethylenes are produced. They are called highly cross linked poly. These should be stronger and more wear resistant. When the plastic wears out, say in twenty years revision surgery is to snap the plastic out and snap a new piece of plastic in. Compared to the initial hip replacement the revision surgery is only about 10% of the trauma, healing, and pain.
Ceramic Implants and Metal-Against-Metal Implants.

                                                    Fitting the Prosthesis             

There are currently several methods used for attaching the prosthesis to the bone and providing stable fixation to prevent movement between prosthesis and bone.
Bone cement (=polymethylmetacrylate or PMMA) provides mechanical attachment of the prosthesis to the bone.
Press fit: depends on a very tight fit of the device into the bone. This is achieved by placing a somewhat bigger device into a somewhat smaller shaft or socket under pressure.
Biological in growth: uses a metal prosthesis fabricated with a special surface (ex. porous coating, rough surface), which enhances bone growth into and onto the surface. Extra surface coatings, such as hydroxyapatite, are also being used to hasten and enhance bone fixation.

Surgery

There are several different incisions or approaches used to access the hip joint including the posterior (Kocher), anterolateral (Hardinge or Liverpool), and anterior (Smith-Peterson).

The posterior (Kocher) approach accesses the joint through the back, taking Piriformis and Quadratus internis off the lesser trochanter. This approach gives excellent access to the acetabulum and preserves the hip abductors however is supposed to have a higher dislocation rate.

The anterolateral approach is the most commonly used approach as it is also the usual approach for trauma replacements (hemiarthroplasties). The approach requires division of the hip abductors (Gluteus Medius and Minimus) in order to access the joint. The abductors may be lifted up by cutting of the greater trochanter and reapplying it afterwards using cables (as per Charnley), or may be divided at there tendinous portion and repaired using sutures.

In contrast to the posterior approach and lateral approach, the anterior approach uses a natural interval between soft tissue to gain access to the hip joint. The interval is found between the sartorius and tensor fascia latae. The main disadvantages to the anterior approach are that it risks damage to the lateral femoral cutaneous nerve, and it is not widely available to the public because fewer surgeons have been trained in this technique.
Prior to surgery allow for necessary preoperative examinations such as blood sampling, X-ray of the chest and ECG. You may consider consultation with anesthetist, heart and lung specialist.

In most cases surgery is performed under general anesthesia

Before the operation the surgeon determines the size of the prosthesis with templates on the X-rays of the hip.

After the operation, patient will be transferred to the recovery room for observation for a couple of hours. A check X-ray of the new hip will be taken and shown to the surgeon before patient returns to the hospital ward. There will be a drain in the hip wound draining blood from the operation site. Onset of rehabilitation depends on the type of prosthesis or surgery: the next day in case of a resurfacing procedure, and in case of a classical total hip replacement after 2-5 days in case of revision surgery.

Discharge out of the hospital depends on type of prosthesis, surgery and physical condition of the patient :
Typically resurfacing procedure : after 3-4 days
Total hip prosthesis in the young active patient : after 5-7 days
Total hip prosthesis in the elderly : after 7–14 days
for revision surgery depending on extensiveness of the surgery and age of patient : after 7–21 days

Complications

There are certain risks or complications associated with total hip replacement. The optimum environment for your surgery and recovery is important so make the right choice to begin with.

The most encountered complications are:

Deep Vein Thrombosis (DVT) and Pulmonary Embolus (PE); Post-operative DVT is one of the most common complications following hip and knee surgery, and is caused by immobilization in combination with damage of the veins because of the manipulation during operation.

Pulmonary embolism (blood clot traveling to the lung) can be fatal and can occur suddenly. Several measures are used to prevent the formation of blood clots in the legs : TED stockings day and night during hospital stay, bed exercises and blood thinning drugs (Low Molecular Weight Heparin) subcutaneous once a day during 3 weeks

Dislocation; Dislocation occurs when the ball of the hip joint pops out of the socket. There is dislocation rate of 1% is reported as usual following total hip replacement, reaching 10%-15% after revision surgery. Prevention depends largely on patient education and care in the postoperative period. Hip dislocation can occur at any time after surgery. However, it is most likely to occur within the first six weeks post-operatively. The muscles and soft tissue (capsula) around the hip socket are healing during this time. They are not strong enough to hold the ball in the socket when the hip joint is under certain kinds of stress. Movements and positions that produce these stresses should be avoided in the post-operative period. Dislocation is confirmed by X-ray. If the hip is dislocated, it is usually reduced (put back in position) under general anesthetic. This procedure is called a closed reduction; a surgical incision is not required but on the rare occasion may be.

Nerve injury; Incision can result in damage to the sensory nerves in the area of the incision. Significant nerve damage, which may cause loss of muscle function, can occur after hip replacement. This type of injury is rare and is most common when the leg is lengthened more than one inch (such as in surgery for congenital hip deformity or revision total hip replacement). Nerve injuries of this type can lead to a ‘foot drop’ or the inability to raise the ankle or toe, in case of damage to the Ischial Nerve.
In case of palsy of the Femoral Nerve, there will be inability to keep the leg extended during gait. Most palsies recover spontaneously.
In case of an sciatic nerve problem, recovery is less common. It can take 2 years to be able to see any recovery.
Fracture of the shaft (femur); When inserting the femoral stem (prosthesis), it might happen that the shaft of the femur fractures due to severe osteoporosis or bone loss in case of revision surgery due to osteolysis.        

Infection; Overall incidence of infection is approximate 1%. Infection may occur early, within 6 weeks or late, even years after surgery. Early infection is treated with antibiotics and possible re-operation to clean out the hip and try to save the prosthesis from removal. Late infection generally requires re-operation with removal of the prosthesis and possibly a second stage operation to re-implant a new hip when it is safe (after 6 weeks of intravenous antibiotics). A 2-stage revision can be done with use of an antibiotic impregnated spacer.
Blood loss and transfusion; Joint replacement surgery involves significant blood loss usually requiring blood transfusion. Banked ‘homologous’ blood is not guaranteed and may cause a blood reaction.
In primary hip procedures and resurfacing the risk of bloodtransfusion is becoming low. In bilateral hipprosthesis a bloodtransfusion is more often used. In these cases a cellsaver can be used.

Leg length discrepancy; Most total hip replacements are unconstrained. This means that the ball is not locked into the socket, and the hip can theoretically dislocate with extreme movement. Stability is produced, in part , by soft tissue tension in the muscles and ligaments around the hip. Sometimes it is necessary to lengthen the leg, which tightens the soft tissues, to improve the stability of the hip. Leg length difference is usually less than 5 mm in the vast majority of cases, but can be up to 2.5 cm in unusual circumstances, requiring a shoe raise the other side. Some patients feel longer after hip replacement without true lengthening. This is called “functional leg length discrepancy” and is due to tightening of the muscles around the new hip. This feeling of lengthening of the leg can take 6 weeks to 3 months to improve and requires stretching exercises of the hip and pelvis.

Heterotopic ossification – HO; This is an abnormal calcification/ossification of the muscles around the hip joint, creating a stiff hip joint! Prevention consists of daily admission of indomethacin (or another NSAID), a strong anti-inflammatory drug, during 3 weeks after surgery. In case of contraindications for admission of the drug (e.g. Stomach ulcer) or when patient is severe at risk for HO (e.g. spondylitis ankylosans – Bechterew disease), a single dose of radiation (700 rad) is given the day before or after the operation to prevent HO. When the hip becomes completely stiff, surgical resection of the ossification is mandatory  

Osteolysis the bond between the femeral component and the femur weakens, and this may require more surgery. Due to longer living patients and hip replacements being more common, longer term problems have been noticed in the use of polyethylene acetabular cups. The wear debris from these components can cause osteolysis

Will a hip implant last a lifetime?

All prosthetic hips may need to be revised (replaced) at some point.

How much does a hip implant cost?

The cost of a total hip implant varies, depending on the type of implant used. Typically, a total hip procedure includes four major implant components and the total implant price ranges from $4000 to $6000 (USD).

Minimally invasive hip replacement surgery

Doctors are still doing major surgery through these small incisions, surgery that replaces your own natural cartilage with artificial implants. No matter how long the incision, implant materials can wear out, loosen, or even dislocate.

Done through a few small portals, instead of the 12- to 18-inch incision used in traditional hip replacement surgery, the procedure dramatically reduces time in the hospital, pain and expenses. Surgeons access the hip, cut the bone and insert the artificial hip through two portals—each less than two inches long—instead of one large incision but it depends on the size of the patient and the difficulty of the procedure. The incision is usually placed over the outside of the hip. The muscles and tendons are split or detached, but to a lesser extent than in the traditional hip replacement operation. They are routinely repaired after the surgeon places the implants. This helps healing. It helps prevent dislocation of the hip. This minimally invasive approach uses a non-cement implant that grows into the bone. The artificial implants used for the minimally invasive hip replacement procedures are the same as those used for traditional hip replacement.

Two-incision hip replacement involves making a 2-inch to 3-inch incision over the groin for placement of the socket and a 1-inch to 2-inch incision over the buttock for placement of the stem. To perform the two-incision procedure, the surgeon needs guidance from X-rays. It may take up to two or three times as long to perform this surgery, as it takes to perform traditional hip replacement surgery.
Reported benefits of less invasive hip replacement include: Less pain, less incision scaring, Less muscle damage, there is less soft-tissue dissection than with longer incisions. Rehabilitation is faster, Hospital stays are shorter the hospital stay may be as short as one or two days. Some patients can go home the day of surgery.

Studies suggest that minimally invasive hip replacement surgery streamlines the recovery process.

Hip Arthroscopy

Hip arthroscopy, actually helps break the vicious cycle caused by hip arthritis and may postpone some of the damage. Hip arthroscopy offers patients with hip pain a viable alternative to hip replacement.

An Outpatient Procedure
In less then an hour hip arthroscopy is done on an outpatient basis and performed under a regional or general anesthesia with a set of tools specifically designed for hip arthroscopy.

Hip arthroscopy small holes are made in the patient's hip area. Through these openings a camera lens is inserted and the image is displayed on a video screen
With specialized instruments the frayed lining and inflammation is cleaned out providing pain relief which may prevent further deterioration of the joint.

Microfracture

Microfracture is a surgical procedure in which a surgeon clears damaged tissue from a knee. The surgeon then creates tiny holes (microfractures) in the bone areas where cartilage is defective. Bone marrow containing stem cells seeps through the holes. The stem cells can then form new cartilage between the bone surfaces of the knee. Post-surgery rehabilitation involving aggressive physical therapy is key to this procedure’s success.

Synvisk Injections

Synvisk and other lubricating agents were originally designed in Canada as an outgrowth of that country's socialized medicine. Synvisk has is a means for postponing surgeries and buying patients time before they can schedule hip implant surgery. Ultimately surgery may not be avoided but it can buy you some time to shop around.

Resurfacing of the Femoral Head

A procedure that resurfaces only the femoral head, the ball side of the ball and socket joint of hip. It doesn't require the removal of the head of the femur, nor does it need an implant placed inside the femur (thigh bone).
Resurfacing the femoral requires less cutting and removal of bone on the ball side of the joint but the larger head that's created requires that you remove more bone on the socket side to accommodate it. This means less bone and less room for future revisions of the surgery which is inevitable. Removing too much bone from the socket side of the joint, from the pelvis, the surgeon is causing problems for the next surgery fifteen or twenty years from now. You want to remove as little bone as possible from the socket side of the joint, even if that means having to remove the femoral head and having to place an anchor down the femur, which is exactly what the implant is.