Total Hip Replacement: Operation of the Century

If anyone asks me today --What is the best operation in orthopedic surgery? My answer without hesitation would be: Total hip replacement. Since the 1960’s hip replacement surgery has completely revolutionized how we care for those that are limited by severe arthritis of the hips. Today hip replacement surgery is performed routinely in multiple centers. In 2017 more than 370,000 hip replacements were performed in the USA and those numbers continue to increase.

To most patients, once fully healed the new hip feels “normal” and will have full range of motion and strength. The hip joint has the quickest recovery, and with the advent of new bearing materials it is one of the most durable. Developments in total hip replacement have been aimed at reducing the rate of failure while accommodating the high-activity profile and increased longevity of the modern patient.

The most significant advances have been related to our improved understanding of bearing materials, bone fixation, joint stability and implant design. Modern hip replacement implants should be expected to last at least 25 years in active patients with rates of joint dislocation and complications well below 1%. What follows is a brief overview of hip replacement surgery and the current state of this great procedure.

WHY IS HIP ARTHRITIS SO CRIPPLING?

To help answer this question, just think about what your hips allow you to do every day:

• The hip joints are centrally located in your body and allow most of the forward flexion, rotation and side movement of your lower extremities.
• Healthy hips are essential for comfortable walking, sitting, sleeping, stooping, squatting, climbing, twisting, turning, dancing, etc. That is a lot of what we do moment to moment.
• With arthritis, the cartilage layer in the joint wears down causing bone to rub against bone. This causes inflammation, stiffness and pain. Severe hip arthritis makes the activities above difficult and sometimes impossible.

WHEN WAS HIP REPLACEMENT INVENTED?

Two centuries ago, there was no cure for arthritis, people with it had to stop walking and moving, leading to limited and painful end of life. In the late 19th century and early 20th century, initial attempts at surgical management of severe hip degeneration were not that successful. However, in the 1950’s Sir John Charnley, a British orthopedic surgeon, made three major contribution to hip replacement surgery:

1. The concept of low-torque, low-friction hip arthroplasty
2. The use of acrylic cement to fix implants to living bone
3. Introduction of high-density polyethylene as a bearing material.

These contributions revolutionized the outcomes of hip replacement. All modern implants today constitute an evolution of those basic concepts. In the 1970’s the introduction of cementless hip implants led the second wave of meaningful innovation by allowing the biologic fixation of hip implants to bone. Along the way innovations in implant materials, shape and fixation modes have made hip replacement the most durable of all mobile joint replacements. In fact, some of the most durable designs today are expected to last at least 30 years in active patients.

HIP REPLACEMENT INCISION: WHAT REALLY MATTERS

As surgeons became comfortable with hip replacement surgery, they began looking at other ways to make this successful operation less painful, recovery time faster and the hospital stay shorter. Obviously, any changes made to improve short term outcomes (pain, healing time, etc.) should not take place to the detriment of long term durability.

INCISION SIZE:

One of the changes that came, was the utilization of smaller incisions. Intuitively it makes sense, smaller incisions must mean less pain, faster healing and more rapid recovery.

However, it is not that simple. A small incision brings other concerns and problems:

- Decreased visualization. Small incisions will limit what the surgeon can see and feel, which may result in poor implant positioning. Malposition of an implant may decrease its longevity by making it unstable or increasing the rate of wear. Surgeons have compensated for the lack of visibility by utilizing x-ray and computer navigation. These technologies help but cannot fully prevent soft-tissue interposition or entrapment. X-ray is only a two-dimensional projection of a complex three-dimensional structure and the surgeon needs to be certain that he/she is interpreting this image correctly. Computer navigation is only as good as the information fed to the computer, which could be faulty. As they say in computer science: garbage in-garbage out. Also, robotic surgery cannot fully account for soft tissue changes associated with arthritis.

- Increase the potential of soft tissue injury. Excessive soft tissue injury during surgery through a small incision due to vigorous retraction will increase pain, impair healing and increase the likelihood of wound infection.

Today, most hip surgeons will use an incision that allows sufficient visualization of the joint for proper placement of the implants, prevent soft tissue interposition, allow soft tissue correction, and minimize soft tissue surgical trauma.

INCISION LOCATION:

Historically, the hip joint can be safely accessed by three different surgical exposures, posterior, lateral and anterior. There are some variations of each and each incision carries its own set of risks and benefits. If properly done by experienced surgeons all incisions will provide a good outcome once the healing process is complete.

Recently, the surgical approach is being hailed as the primary factor determining the success of this intervention. The direct anterior approach is being widely marketed to patients with claims of less muscle damage, improved stability, less pain, faster recovery, and greater overall superiority when compared to all other surgical approaches. These claims of superiority are not founded in what the peer-reviewed literature has shown. Unfortunately, the public’s perception of this approach has been biased by this intense marketing effort and today patients come to surgeons’ offices with the preconceived notion that anything different from the anterior approach would be a serious compromise in the quality of their surgery and outcomes.

Despite these claims, ther

e are no studies that establish long-term clinical benefits for the anterior approach. Several studies that have positively viewed the anterior approach are biased and/or scientifically flawed. Both approaches have benefits and carry certain risks. In fact, in expert and experienced hands there is little difference, if any, between the anterior and the mini-posterior hip approaches with regards to short and medium-term results. Predictably, marketing for the anterior approach exaggerate its purported benefits and most omit to mention its associated risks.

The most unfortunate consequence of all this marketing is that it is unfairly shifting the focus away from the real goal of any joint replacement procedure which is TO PROVIDE YOU WITH A STABLE, PAIN-FREE AND DURABLE JOINT. To achieve this goal reliably, your surgeon will carefully choose the surgical technique and the implants used based on safety, experience, quality and an excellent track record of implant durability. The choices you make regarding this surgery must focus primarily on safety and excellent LONG-TERM outcomes.

Most of the hype regarding the anterior hip approach stems from surgeons, hospitals and manufacturing companies that advertise and market their skills in a constant effort to gain market share. The ethical implications of this exercise are unclear. What is clear is that there is no solid and convincing scientific evidence that one surgical approach is superior to the other. Hospital stay, postoperative narcotic requirements, speed of rehab, time spent on a walker or cane, time back to sports and work, and other parameters of judging a successful result are similar when the operation is performed by an experienced hip surgeon. Your preoperative medical fitness and pain control techniques used postoperatively will determine how quickly you will be returning home, not the incision.

While a modest, early functional benefit of the direct anterior approach may be real, recent scientific papers point to an increase in fractures, femoral implant loosening, early need for revision surgery, bleeding and wound healing problems with the anterior approach. Furthermore, we do not have long-term data regarding the success of the anterior hip approach and the novel implants created to facilitate it.

Therefore, you need to choose your surgeon based on otherfactors, such as experience, trust and complication rates. Let your chosen surgeon decide on the technology and surgical technique based on his professional experience. That will guarantee you, the patient, a quick and successful recovery and a durable pain-free hip replacement.