Arthritis is the most common cause of disability in people over the age of 65, and the hip is one of the most commonly affected sites of injury. When conservative treatment options fail to alleviate pain and dysfunction, hip replacement surgery or total hip arthroplasty (THA) can cure these symptoms. There is an abundance of information regarding THA: surgical approach, implant type, expected recovery, and goals of surgery. What should a patient know when they are considering this surgery?
THA became available to the general population in the late 1960’s largely through the pioneering work of Dr. John Charnley, a British orthopaedic surgeon who developed the technique and engineered the components required for long-term clinical success. Over the past 40 years THA has become commonplace worldwide in the treatment of severe hip arthritis due to the vastly improved quality of life provided by this intervention.
THA is indicated for patients with severe radiographic arthritis who have failed conservative treatment and are, in general, over age 50. Meeting these three criteria is a key qualifier to long-term success. The hip joint is a ball and socket-type joint composed of the femoral head (ball on top of the thigh bone) and acetabulum (socket of the pelvis). These surfaces are normally covered with articular cartilage (like the white on the end of a chicken bone), the smooth substance which allows the joint to move with little friction, great flexibility, and no pain. When the articular cartilage wears out – due to trauma, disease, or age – pain, stiffness, and dysfunction result. Walking becomes difficult and quality of life is impaired. Conservative measures including anti-inflammatory medication, physical therapy, walking assistive devices such as a cane, and cortisone injections in the hip may alleviate symptoms. However, when these interventions fail to improve the pain, THA may be considered.
THA surgery involves making an incision over the hip joint, exposing the joint through various surgical approaches, removing the native joint with surgical instruments, and replacing it with an artificial hip composed of a metal stem implanted in the femur, a metal or ceramic ball attached to the stem, and a socket composed of metal with a plastic (polyethylene) liner or ceramic socket implanted in the pelvis. This new ball articulates with the new socket allowing pain-free mobility with improved flexibility. Total recovery takes several months but most patients experience pain relief within the first few weeks after surgery. In general, standard THA technique and implants used in patients who meet appropriate surgical criteria lead to successful results in 95% of patients in terms of decreased pain and significantly improved function. Published medical data indicate that 90% of appropriately-performed THA’s should last at least 15 to 20 years, with many functioning well up to 30 years after implantation.
So what should a patient be aware of when considering THA? First and foremost, the qualifying criteria need to be met prior to surgery. Hip arthritis should be radiographically-severe prior to surgery in most cases. This means complete loss of joint space on xrays, or bone-on-bone, indicating complete loss of articular cartilage. The purpose of a THA is to resurface a completely worn-out joint, and if there is remaining cartilage you are probably not ready yet. Exceptions to this rule may include hip replacement for entities such as tumor, fracture, or avascular necrosis. A patient should in general be over the age of 50 and have appropriate post-operative expectations. Hip replacements are mechanical devices which will eventually wear out. The goal of the surgery is to place an implant in the appropriate position in a qualified patient such that the implant will function well for 20 to 30 years. When used in patients who are too young or too active, risk of premature failure is significantly increased. The problem with this situation is that revision hip replacement, after failure of the original THA, has poor results in terms of long term performance of the implant, and increased risks of complications such as infection, dislocation, and fracture compared to primary THA. Thus, the goal is to place an implant that will hopefully at most only need to be revised once in a person’s lifetime. Finally, a patient should have pain that significantly impacts their life and fails to respond to non-surgical interventions. Just because your xray shows arthritis does not mean you need a THA. There are many people who function well with conservative care. Only when these measures fail should a THA be considered.
In terms of surgical technique, the most important point to remember is that your goals are long-term success with a stable, pain-free hip that lasts 20-30 years. This is the standard that has been set by traditional THA, and any alterations in technique should have good, unbiased data justifying improvement in these goals. There are numerous examples of technical changes that have been attempted by orthopaedic surgeons in the past 30 years to try to improve outcomes. Some, such as improvements in wear properties of the bearing surfaces – the ball, socket, and plastic liner – have been helpful. Outcomes data helping us to decrease risk of complications such as infection, blood loss/transfusion requirements, and deep vein thrombosis (blood clots) have improved results. However, there are numerous examples of technical changes that have had the opposite effect, resulting in premature failure of the prosthesis or increased complication rates. Examples of these include the metal-on-metal THA explosion about ten years ago, catastrophic failure of some ceramic implants, and the high complication rates seen with “minimally invasive” 2-incision THA.
The most widely-publicized recent technical change has been the use of the Smith-Peterson or anterior approach for THA. Traditional THA utilizes a posterior or anterolateral approach for placement of the prosthesis. These approaches have proven over decades of use to allow accurate placement of the prosthesis in a position that allows long-term survival with low complication rates. The newer anterior approach utilizes a muscle-splitting incision under xray guidance, and has been marketed to the public as allowing more rapid recovery with lower complication rates in terms of dislocation than traditional THA. Unfortunately, there is insufficient long-term data available from unbiased sources to justify these claims at this point. In fact, four studies presented at the American Academy of Orthopaedic Surgeons’ Annual Meeting in 2016 compared anterior approach to posterior and found no improvement in rates of dislocation or post-operative care requirements, and questioned whether this approach actually led to increased early failure rates of the prosthesis. In the January 2017 issue of the Journal of Bone and Joint Surgery, the preeminent orthopaedic journal world-wide, the lead study comparing complications in THA’s performed at 3 major academic institutions (Rothman Institute Philadelphia, Indiana University, OrthoCarolina Joint Center Charlotte) found that early failure of the femoral stem – less than 5 years after THA – occurred almost 4 times more often with an anterior approach compared to a posterior approach. In addition, the rate of dislocation was similar in these groups. The authors of this paper were critical of the marketing claims of this approach.
The bottom line here is that a patient should use discernment and appropriate cynicism when evaluating claims of amazing results with new or altered techniques for this procedure. The bar has been set very high for what are considered acceptable results for THA, and most components should last 20 years in practice. If long-term (15-20 year) data is not available for such techniques, patients should be guarded in their choices. The goal is not a smaller incision at 4 weeks, but fewer incisions at 20 years, because first procedure lasted a long time and worked well. I hope this information is helpful to you.