Xrays of a hip before and after replacement surgery

Total Hip Replacement

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, hip dysplasia 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.

Posterior Approach
I perform most of my primary total hip arthroplasties 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. 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. The surgery takes approximately 1 and a half hours and is done through a 3-5” incision in the front 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

Bearing Surfaces
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 an increasingly popular bearing surface for hip replacement and the studies in the literature have reported and good clinical track record with mid-term follow-up. 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. As a precaution, I do not implant this type of hip prosthesis into any patient who is contemplating becoming pregnant in the future as the metal ion concentration has an unknown effect on the developing fetus. This type of prosthesis should be avoided in any patient with a metal allergy.

Ceramic on Ceramic - This type of prosthesis was introduced about 10 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.