Xrays of a hip before and after replacement surgery
Total Hip Replacement
Hip arthritis is a common condition that affects several hundred thousand people every year in the United States. The hip joint is a ball and socket joint that can wear out over time leading to pain, shortening of the leg and limp. Most patients develop the condition in their 50's and 60's but it can develop much earlier. The most common cause of arthritis is men is a condition called impingement in which there is a slight discrepancy in the shape of the ball and socket (egg shaped ball in a round socket) that eventually leads to degeneration in the cartilage in the hip joint. In women, the most common cause is dysplasia or a mishapen and most commonly shallow hip socket that causes damage to the cartilage. Previous trauma and/or fractures are the most common cause in younger patients. Any fracture that involves the joint surface (intra-articular fracture) causes some damage to the cartilage. In cases where the joint surface is incongruous (not perfectly aligned) this places excessive stress and shear on the gliding surface of the joint and accelerate joint degeneration. This type of arthritis is referred to as secondary osteo-arthritis or post-traumatic arthritis. Finally, the blood supply to the femoral head (the ball of the hip joint) is easily damaged from fracture or dislocation. Injury to the blood supply leads to a condition called osteo-necrosis or avascular necrosis in which the bone softens and often collapses leading to hip arthritis.
Unlike many other joints in the body, the hip joint is fairly deep and covered by a thick layer of tissue and muscle. Because of this injections such as cortisone, which I routinely use for joint pain in many other joints, require the use of live x-ray to make sure the needle is in the correct position. I don't perform these types of the injections in the office. Pain in the hip can mimic other conditions such as sciatica or pinched nerves in the lower back. Although many patients have MRI scans performed to assess the condition of the joint, I still largely rely on high quality x-rays to make the diagnosis of arthritis.
The surgical options for hip arthritis are limited to hip replacement and resurfacing and each procedure has pluses and minuses. In general, the number of patients who are candidates for hip resurfacing surgery are limited. The best long term data from European and Australian national joint registries (we don't have a nation joint registry in the U.S.) keep track of the outcomes of every joint replacement done in these countries. This data demonstrates about equal functional outcome between joint replacement and joint resurfacing but a significantly higher revision (need for another surgery) at 10 years in patients who undergo resurfacing. As a consequence, I usually recommend total joint replacement unless there is a compelling reason to perform resurfacing.
Primary total hip replacement is probably the most successful surgery (for both the patient and the surgeon) in Orthopaedic surgery. The indications (reasons for doing the surgery) are severe osteo-arthritis (wear and tear arthritis), hip dysplasia (shallow hip socket) with arthritis and avascular necrosis (AVN) of the femoral head with collapse. Even though these entities have differing causes, the end clinical picture is the same: loss of cartilage in the joint causing pain, limitation of motion and impairment of activity. Most patients with severe arthritis have progressively incapacitating groin and thigh pain, limping and restricted range of motion.
There are several different implants available on the market and many manufacturers have started using direct to consumer (DTC) advertising. The basic choices for implants depend on the bearing surface of the implant (outlined below). Hip resurfacing surgery (also outlined below) is an option for younger patients but represents a much larger surgical procedure.
Diagram showing an arthritic hip
SURGICAL APPROACH
There are several surgical approaches to perform a total hip replacement outlined below. Each one has benefits and drawbacks. The anterior approach allows excellent access to the socket and the posterior approach is favored for revision surgery or in heavier patients. Although many patients focus on the length of the incision, this is probably the least important aspect of the operation. I try to keep the surgical dissection to the least amount possible but I focus on implanting the components in the best possible position. This has been shown to be the most important factor influencing the longevity of the implants. So if you have a hip done through a 3 inch incision you'll probably recover faster than if you have a 6 inch incision, but if the components aren't placed properly because the incision was too small and you have to have them revised in 3 years, this is a much worse outcome than if the hip were to last 20-25 years.
Posterior Approach
When I use this approach I perform the hip replacement through a minimally invasive (PATH) technique using a limited posterior approach. The surgery takes approximately one hour and can usually be done through a 3-4” incision in the back of the hip. The length of the incision depends on several factors including weight of the patient, history of previous surgeries and type of replacement surgery. Patient with several surgeries in the past require larger incisions to compensate for scar tissue and to protect the nerves and arteries in the area. After surgery all patients are started on a medication called low molecular weight heparin to prevent blood clots in the veins of the pelvis and leg, which is the single most common complication after surgery. I have patients stand the night of surgery and then physical therapy starts more aggressively on the first day after surgery. Most patients are comfortable and go home with a walker on the 3rd day after surgery. I allow my patients to shower after the 5th day and encourage them to walk as much as possible after the return home. Most patients are able to walk comfortably with a cane after about 2 weeks and without a cane after 6 weeks.
Anterior Approach
This surgical approach has been popularized in the last 5-7 years with the introduction of specialized operating room tables which assist in the exposure of the joint during the procedure. I routinely use this approach currently for hip replacements. The surgery takes approximately 1 and a half hours and is done through a 3-5” incision in the side of the hip. I don’t offer this approach in heavier patients with a BMI (body mass index) over 30 because of an increased risk of complications. After surgery all patients are started on a medication called low molecular weight heparin to prevent blood clots in the veins of the pelvis and leg, which is the single most common complication after surgery. I have patients stand the night of surgery and then physical therapy starts more aggressively on the first day after surgery. Most patients are comfortable and go home with a walker on the 3rd day after surgery. I allow my patients to shower after the 5th day and encourage them to walk as much as possible after the return home. Most patients are able to walk comfortably with a cane after about 2 weeks and without a cane after 6 weeks.
Diagram showing the components of a hip replacement
Types of Implants
Metal on Plastic - this is the most common type of bearing surface and re-approximates the characteristics of normal bone and cartilage fairly well. The cup component contains a plastic liner made of high molecular weight polyethylene while the ball component is constructed of metal alloy such as cobalt chrome. This bearing surface is both durable and flexible and allows the surgeon a wide variety of combinations of head size, neck length and cup size and shape to allow me to re-create normal hip mechanics in most people. I use this type of construct primarily in patients over age 60.
Metal on Metal - This is the main bearing surface on resurfacing implants. There has been a large amount of negative press recently with several designs and reports of catastrophic failure. The mechanism for this is still largely unknown. Currently, there is a moratorium on the use of metal on metal components in the UK. I do not currently implant this bearing surface. Metal on metal prostheses have larger femoral head diameters; clinically this translates into a lower risk of dislocation. The bearing surface is very durable; however, it is unclear whether these prosthesis design offers an advantage over the newer plastic designs. Other issues include the elevated concentration of metal ions in the blood samples from patients with metal prostheses, but it is unclear whether this leads to any long term problems. Although I believe this is a good implant bearing surface the press and plaintiff attorneys have severely damaged the reputation of this prosthesis. This type of prosthesis should be avoided in any patient with a metal allergy.
Ceramic on Ceramic - This type of prosthesis was introduced about 15 years ago, there are two manufacturers in the USA. This type of bearing surface has the lowest wear rate of any bearing surface by a factor of 10. The ceramic, not unlike a ceramic tile, is extremely hard and durable; however, they are also brittle and have been reported to crack or fracture with hard falls. Other problems reported with this prosthesis are “squeaking” in which the bearing surface makes a noise when the hip is flexed. Although painless, this problem can be troublesome. I believe that ceramic prostheses are reasonable options in younger patients (under 45 years of age) with degenerative arthritis of hip.
I currently use two manufacturer (Zimmer/ Stryker) of prosthesis for primary total hip replacement depending on the age of the patient and the anatomy of the proximal femur (which can be quite variable) listed below. Both implants use a cobalt chrome head on a highly cross-linked poly-ethylene liner. In patients under the age of 45, I will consider the use of a ceramic on ceramic implant to reduce wear.
Zimmer ML taper Stem
Zimmer TM cup
Stryker Accolade
Stryker Ceramic
Stryker Trident Cup
After Surgery
The surgery is done as an inpatient meaning you are admitted to the hospital and stay for 2-3 days. I do the surgery with a combination of epidural and general anesthesia. The epidural is very effective in controlling post-operative pain and allows lower use of narcotics in the first few days after surgery. Depending on the surgical approach, your therapist will go over anterior or posterior hip precautions (positions to avoid for the first 6 weeks after surgery). The three most common complications after surgery are infection (0.5-1.0%), dislocation (0.1-0.4%) and deep venous thrombosis (blood clots in the leg 2.0-5.0%). All patients receive intravenous antibiotics for the first 24 hours to minimize the risk of infection. I have all patients started on low-molecular weight heparin (lovenox) to reduce the risk of blood clots after surgery. You will continue on this medication for 10-14 days after leaving the hospital and the nurse will show you or a family member how to administer this medication.
Lovenox
By the time you leave the hospital you should be able to get out of bed on your own, stand a walk with a walker to help you balance and get on and off the toilet without assistance. Most people will get a shower chair and elevated toilet seat to take home or have delivered. You will start physical therapy in the hospital and continue at home. Your first post-surgery office visit is generally 10-14 days to have the stitches or staples removed and to go-over your therapy and progress. Most patients transition to a cane at 2-4 weeks and can walk without a cane at 4-6 weeks. My hip replacement instruction are listed below
Hip replacement instructions