Definition

Total hip arthroplasty (THA), commonly called hip replacement surgery, involves the reconstruction of a diseased, damaged, or ankylosed hip joint. The most common causes of adult hip disease are osteoarthritis, inflammatory arthritides, avascular necrosis, post-traumatic degenerative joint disease, congenital hip disease, oncologic bone disease, and infection involving the hip joint. The surgical treatment of hip arthritides has evolved from the first excisional arthroplasty by Anthony White in 1821 into the modern THA. The modern era of hip joint replacement began in the late 1960s when Sir John Charnley combined a stainless steel femoral component with a polyethylene socket fixed to the adjacent acetabulum with polymethyl methacrylate (cement). Since that time, arthroplasty of the hip joint has become an accepted and standard treatment of common adult hip joint disease. Modern hip arthroplasty surgery has resulted in the restoration of pain-free motion and improved quality of life for millions of people and is the most commonly performed adult reconstructive hip procedure. Over 310,000 inpatient hip replacements were performed in 2010; 58% of the patients receiving new hips are women, according to the American Joint Replacement Registry. The majority of hip replacements are done for osteoarthritis (70%), with femoral neck fractures accounting for 10% and avascular necrosis and rheumatoid arthritis, combined, leading to 3% of the procedures. It is estimated that in 2010 2.5 million individuals (1.4 million women and 1.1 million men) were living in the United States with a total hip replacement.

Hip joint arthroplasty can be divided into either THA, which provides a prosthetic replacement of the proximal femur and acetabulum, or hemiarthroplasty, which replaces the proximal femur while leaving the native acetabulum intact. Hip hemiarthroplasty is reserved for patients with a healthy articular surface in the acetabulum and is most commonly seen after proximal femur fractures. The focus of this chapter is on THA, which is the preferred surgical option for patients with degenerative changes affecting both the femur and acetabulum. Further categorization for hip arthroplasty can be made by prosthetic hardware components, surgical approach, or fixation method of the prosthesis (cement vs. biologic or “press-fit” integration). Surgical decision-making for hardware type, approach, and prosthetic fixation is beyond the scope of this chapter, but it is important to note that there are no published consensus guidelines on best prostheses, approach, or fixation method among surgeons performing total hip arthroplasties.

Symptoms

The primary symptom of hip disease is groin pain, but patients may also have associated back or knee pain. Patients may describe a decline in mobility, self-care, and activities of daily living. They may present with an abnormal gait or may describe difficulty in walking long distances and need for an assistive device. Donning their shoes or socks or taking them off, and getting in and out of the seated position may be difficult daily activities. Inability to participate in recreational activities or light sports may be a presenting complaint.

Physical Examination

Patients with hip disease are likely to have physical examination findings that will require continued attention postoperatively. The examiner should examine both hips, knees, and back for range of motion. Decreased range of motion of the affected hip will be found and may be the first physical examination finding in cases of mild disease. Groin pain with passive range of motion will become evident as the disease progresses. A thorough neurovascular examination of all extremities should be performed. One of the most commonly observed examination findings is an antalgic (painful) gait pattern representing a combination of pain that inhibits motion, structural loss of joint motion, avoidance behavior, and weakness. Hip pain or weakness of the hip abductors can result in contralateral pelvic tilt or drop (Trendelenburg sign) with ipsilateral weight bearing ( Fig. 61.1 ). During ambulation, the patient may shift their trunk over the affected hip to lessen the load on the joint. This is a compensated Trendelenburg gait. Muscle weakness is typically not true neurologic weakness, but rather represents a disuse weakness associated with pain and avoidance. A hip flexion contracture may be observed with the Thomas test ( Fig. 61.2 ). Accentuated lumbar lordosis may be seen in those with a hip flexion contracture or ankylosis or severe restriction of extension of the hip joint, which may result in secondary mechanical low back pain due to alteration of normal spine mechanics. A limb length discrepancy may be observed, with the affected hip being the shorter limb.

Trendelenburg sign.

From Goldstein B, Chavez F. Applied anatomy of the lower extremities. Phys Med Rehabil State Art Rev. 1996;10:601–630 .

Thomas test to assess a hip flexion contracture. The patient lies supine while a hip is flexed, bringing the knee to the chest and flattening the lumbar spine. The patient holds the flexed knee and hip against the chest. If there is a flexion contracture of the hip, the patient’s other leg will rise off the table.

Functional Limitations

Functional limitations from severe hip disease include difficulty in walking and with all mobility, even rising from a seated position, because of pain and weakness. This may affect a patient’s ability to dress, to bathe, to perform household chores, to participate in recreational activities, and to work outside the home. In advanced cases, patients will have difficulty sleeping. The goal of THA is to improve pain and consequently to improve function with activities of daily living.

Diagnostic Studies

Plain radiography remains the primary imaging tool for evaluation of hip disease and for postoperative assessment of THA. On radiographic examination, significant loss of joint cartilage as demonstrated by joint space narrowing, joint incongruity, osteophyte formation, subchondral cysts, and sclerosis are seen in individuals being considered for THA ( Fig. 61.3 ). Many postoperative complications after THA can be evaluated by plain radiography. In patients thought to have a dislocation after THA, radiographs should be obtained urgently because a true dislocation must be relocated expediently ( Fig. 61.4 ). Plain radiographs are also obtained in patients thought to have prosthetic loosening or periprosthetic fracture ( Fig. 61.5 ). If plain radiographs do not show pathologic changes in a patient with enigmatic hip pain after THA, magnetic resonance imaging can be done with minimal artifact and can demonstrate disease in the periprosthetic soft tissues, including synovitis, periprosthetic inflammation, osteolysis, and iliopsoas tendinitis. As groin pain may come from hip joint pathology, tendon or muscle pathology, or adjacent hernia, ultrasound evaluation may be a valuable tool to narrow the differential. Nuclear imaging such as tagged white cells, F-18 fluorodeoxyglucose-positron emission tomography (FDG-PET) imaging, or gallium imaging may be of benefit, but limited information supports their routine use.

Anteroposterior pelvis radiograph showing moderate to severe degenerative changes of the hips. Notice the sclerotic changes at the acetabular and femoral heads. Note the loss of joint space, especially inferiorly, and osteophytes.

Total hip replacement—dislocation. The femur has dislocated superiorly and laterally relative to the acetabulum. This dislocation is due to abnormal (vertical) position of the acetabular cup that occurred from loosening (see widened cement-bone interface).

From Katz DS, Math KR, Groskin SA. Radiology Secrets. Philadelphia: Hanley & Belfus; 1998.

Total hip replacement—loose femoral component. There is a wide area of lucency between the opaque cement (C) and the adjacent bone at the medial aspect of the proximal femur in addition to the area of lucency at the metal-bone interface surrounding the acetabular prosthesis. These were new findings indicative of loosening of both components.

From Katz DS, Math KR, Groskin SA. Radiology Secrets. Philadelphia: Hanley & Belfus; 1998.

Treatment

Treatment protocols after THA can be broadly divided into an initial (acute postoperative) phase and a rehabilitation phase. All patients will have weight-bearing and activity restrictions for approximately 6 weeks postoperatively. These restrictions are not universally accepted, are influenced by surgical technique (cemented versus uncemented fixation of the prosthesis), and can vary by surgeon preference. Ultimately, postoperative restrictions should be clarified by communication with the surgeon.

Initial

The initial phase (acute postoperative) usually includes up to 4 days after surgery and may be performed on an inpatient basis. Therapy typically begins on postoperative day 1 and focuses on getting the patient out of bed; education is provided on safe transfers, and static exercises are performed for gluteal muscles, quadriceps, and ankle pumps. Early use of closed kinetic chain exercises (e.g., mini-squats, step-ups) has been shown to shorten length of stay in some acute facilities. Pain control strategies frequently begin with intravenous narcotics (patient-controlled analgesic pumps), cryotherapy, and appropriate education to reduce anxiety. Rehabilitation strategies on postoperative day 2 through the day of discharge should stress education on hip precautions, compliance with weight-bearing restrictions, early mobilization with use of an assistive device, instruction on the use of adaptive equipment for functional independence (bathing, grooming), and continued pain control. Hip precautions ( Table 61.1 ) vary by surgical approach and the surgeon’s preference. Duration of hip precautions may coincide with healing (e.g., 6 to 12 weeks) or may be permanent. Again, this is up to the surgeon.

Table 61.1

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