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Minimally invasive total hip arthroplasty

AORN Journal, June, 2004 by Sharon E. Hohler

Total hip arthroplasty (THA) surgery eases pain and enhances the quality of life for many people. This is accomplished by retreading or resurfacing the acetabulum (ie, socket) and the femoral head. Arthritic hip pain is markedly improved for patients after these two worn, arthritic surfaces are replaced.

THE BACKGROUND OF THA

Since the initial total hip replacement surgeries were performed in the 1960s, emphasis has been placed on relieving arthritic pain and developing replacement parts that will last. Sir John Charnley, MD, a British orthopedist, is credited with developing the modern total hip implant. He combined a metal stem and ball with a plastic shell and held them in the place with methyl methacrylate cement.

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During the past 40 years, improvements have resulted in better implant materials and improved mechanisms for holding implants in place. Lifespan for cemented and cementless THA prostheses is 80% at 20 years. (1) Development and improvement of porous acetabular and femoral stem prostheses eliminated the need for gluing the prostheses into place (Figure 1). These irregular metal components encourage bony ingrowth, allowing a patient's bone cells to intertwine with the irregular metal finish, which holds the implants securely in place. After analyzing data from second-generation cementless THA procedures, surgeons reported a 10-year implant survival rate of 96.4%. (2) Efforts continue to focus on making prostheses that will last a patient's lifetime, thus eliminating the need for revision surgery.

[FIGURE 1 OMITTED]

Minimally invasive surgery has been defined as a "procedure being performed through an incision less than 10-cm long." (3) Surgeons report that they even can perform cemented THA through a minimally invasive incision. (3) Minimally invasive procedures are creating exciting changes in the orthopedic world similar to the way laparoscopic procedures have affected general surgery.

The major disadvantage of a minimally invasive approach is the potential for poor visualization, which could lead to fractures or malpositioning of implant components. Initially, surgeons reported that the procedure was technically challenging and required longer surgical time, although a surgeon's experience minimizes these challenges. Additionally, limited scientific data exist and long-term results are unknown because the minimally invasive procedure is relatively new. (3)

Recent innovations have allowed orthopedic surgeons to decrease the incision size and to preserve all possible muscle and ligament strength. In a recent study, the posterior approach to performing minimally invasive total hip arthroplasty (MITHA) decreased blood loss during surgery and caused less soft tissue trauma. Patients returned home sooner, and some patients returned home as early as the evening after surgery. Additionally, patients experienced improved ambulation at six weeks and had faster rehabilitation. At two years, however, there was no difference between patients who underwent the minimally invasive approach compared to those who had a standard incision. (4) Surgeons also report that patients who undergo MITHA procedures prefer the smaller incisions and subsequent smaller scars.

ANATOMY OF THE HIP

Three pelvic bones (ie, ilium, ischium, pubis) form the innominate bone. The innominate bone (ie, os coxae) forms a stable circular base, called the pelvis, which supports the trunk and serves as an attachment for the legs. The socket portion of the innominate bone (ie, acetabulum) forms a deep, round cavity in which the femoral head rests and articulates, forming a ball and socket joint. The proximal end of the femur consists of the femoral head auld neck, upper end of the femoral shaft, and greater and lesser trochanters. The trochanters are insertion points for muscles. The capsule, muscles, and ligaments provide stability for the hip joint. (5) A total hip replacement implant consists of the

* ball that replaces the spherical head of the femur;

* stem that fits into the femur and provides stability; and

* cup, presently consisting of a porous metal shell and plastic liner that replaces the worn-out acetabulum.

PATHOPHYSIOLOGY

Arthritis is a disease of the joints. Although most patients who undergo THA suffer from osteoarthritis, patients with both rheumatoid arthritis and osteonecrosis (ie, avascular necrosis) also may need to undergo THA. Signs that a patient's condition requires total joint replacement include that

* a series of different pain medications no longer relieve the pain;

* activity is restricted to the point that the patient has trouble getting out of a chair, going up stairs, getting off the toilet, or getting up from the floor;

* the patient cannot sleep at night because of pain; and

* the patient's pain prevents him of her from participating in activities of normal living (ie, shopping, taking a vacation). (6)

OSTEOARTHRITIS. So Osteoarthritis, which is considered "wear and tear" arthritis, affects 30 million Americans, (7) making it the most common form of arthritis. Osteoarthritis develops when the smooth articular cartilage covering the ends of bones wears thin. As the cartilage wears away completely, bones rub against each other and cause pain. Nonsurgical treatment for osteoarthritis includes rest, gentle exercise, and use of nonsteroidal anti-inflammatory drugs (NSAIDs).

Health Care Industry

Minimally invasive total hip arthroplasty

AORN Journal, June, 2004 by Sharon E. Hohler

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