TOTAL HIP ARTHROPLASTY
Most patients undergoing total hip replacement suffer from osteoarthritis (degenerative joint dis-ease), autoimmune conditions such as rheumatoid arthritis (RA), or avascular necrosis. Osteoarthritis is a degenerative disease affecting the articular sur-face of one or more joints (most commonly the hips and knees). The etiology of osteoarthritis appears to involve repetitive joint trauma. Because osteoarthri-tis may also involve the spine, neck manipulation during tracheal intubation should be minimized to avoid nerve root compression or disc protrusion.
RA is characterized by immune-mediated joint destruction with chronic and progressive inflam-mation of synovial membranes, as opposed to the articular wear and tear of osteoarthritis. RA is a systemic disease affecting multiple organ systems (Table 38–1). RA often affects the small joints of the hands, wrists, and feet causing severe deformity; when this occurs, intravenous and radial artery can-nulation can be challenging.
Extreme cases of RA involve almost all synovial membranes, including those in the cervical spine and temporomandibular joint. Atlantoaxial subluxation, which can be diagnosed radiologically, may lead to protrusion of the odontoid process into the foramen magnum during intubation, compromising vertebral blood flow and compressing the spinal cord or brainstem (Figure 38–3). Flexion and extension lat-eral radiographs of the cervical spine should beobtained preoperatively in patients with RA severe enough to require steroids, immune therapy, or methotrexate. If atlantoaxial instability is present, tracheal intubation should be performed with inline stabilization utilizing video or fiberoptic laryngos-copy. Involvement of the temporomandibular joint can limit jaw mobility and range of motion to such a degree that conventional orotracheal intubation may be impossible. Hoarseness or inspiratory stridor may signal a narrowing of the glottic opening caused by cricoarytenoid arthritis. This condition may lead to postextubation airway obstruction even when a smaller diameter tracheal tube has been used.
Patients with RA or osteoarthritis commonly receive nonsteroidal antiinflammatory drugs (NSAIDs) for pain management. These drugs can have serious side effects such as gastrointestinal bleeding, renal toxicity, and platelet dysfunction.
Total hip replacement (THR) involves several surgi-cal steps, including positioning of the patient (usu-ally in the lateral decubitus position), dislocation and removal of the femoral head, reaming of the acetabulum and insertion of a prosthetic acetabular cup (with or without cement), and reaming of the femur and insertion of a femoral component (femo-ral head and stem) into the femoral shaft (with or without cement). THR is also associated with three potentially life-threatening complications: bone cement implantation syndrome, intra- and postop-erative hemorrhage, and venous thromboembolism. Thus, invasive arterial monitoring may be justified for select patients undergoing these procedures. Neuraxial administration of opioids such as mor-phine in the perioperative period extends the dura-tion of postoperative analgesia.
The increasing number of younger patients presenting for hip arthroplasty and of other patients who require revision of standard (metal-on-polyethylene) total hip arthroplasty implants has led to redevelopment of hip resurfacing arthroplasty techniques. Compared with traditional hip arthroplasty implants, hip resur-facing maintains patients’ native bone to a greater degree. Metal-on-metal hybrid implants are usually employed. Surgical approaches can be anterolateral or posterior, with the posterior approach theoreti-cally providing greater preservation of the blood sup-ply to the femoral head. With the posterior approach, patients are placed in the lateral decubitus position similar to traditional hip arthroplasty.
Outcomes data related to hip resurfacing versus traditional total hip arthroplasty are controversial. Prospective studies have not shown a difference in gait or postural balance at 3 months postoperatively. A recent meta-analysis favored resurfacing in terms of functional outcome and blood loss despite com-parable results for postoperative pain scores and patient satisfaction. Of particular concern is the finding that patients who undergo resurfacing are nearly twice as likely to require revision surgery as those receiving traditional hip arthroplasty. There is a higher incidence of aseptic component loosening (possibly from metal hypersensitivity) and femo-ral neck fracture, particularly in women. Finally, the presence of metal debris in the joint space (from metal-on-metal contact) has led to a marked narrowing of indications for the prostheses and the procedure.
Bilateral hip arthroplasty can be safely performed in fit patients as a combined procedure, assuming the absence of significant pulmonary embolization after insertion of the first femoral component. Monitoringmay include echocardiography. Effective com-munication between the anesthesia provider and surgeon is essential. If major hemodynamic instability occurs during the first hip replacement procedure, the second arthroplasty should be postponed.
Revision of a prior hip arthroplasty may be associated with much greater blood loss than in the initial pro-cedure. Blood loss depends on many factors, includ-ing the experience and skill of the surgeon. Some studies suggest that blood loss may be decreased during hip surgery if a regional anesthesia technique is used (eg, spinal or epidural anesthesia) compared with general anesthesia even at similar mean arte-rial blood pressures. The mechanism is unclear. Because the likelihood of perioperative blood trans-fusion is high, preoperative autologous blood dona-tion and intraoperative blood salvage should be considered. Preoperative administration of vitamins (B12 and K) and iron can treat mild forms of chronic anemia. Alternatively (and more expensively), recombinant human erythropoietin (600 IU/kg subcutaneously weekly beginning 21 days before surgery and ending on the day of surgery) may also decrease the need for perioperative allogeneic blood transfusion. Erythropoietin increases red blood cell production by stimulating the division and differen-tiation of erythroid progenitors in the bone marrow. Maintaining normal body temperature during hip replacement surgery reduces blood loss.
Computer-assisted surgery (CAS) may improve surgical outcomes and promote early rehabilitation through minimally invasive techniques employ-ing cementless implants. Computer software can accurately reconstruct three-dimensional images of bone and soft tissue based on radiographs, fluo-roscopy, computed tomography, or magnetic reso-nance imaging. The computer matches preoperative images or planning information to the position of the patient on the operating room table. Tracking devices are attached to target bones (Figure 38–4) and instruments used during surgery, and the navi-gation system utilizes optical cameras and infrared light-emitting diodes to sense their positions. CAS thus allows accurate placement of implants through
small incisions, and the resulting reduction in tissue and muscle damage could lead to less pain and early rehabilitation. The lateral approach utilizes a single 3-in. incision with the patient in the lateral decubitus position (Figure 38–4); an anterior approach utilizes two separate 2-in. incisions (one for the acetabular component and another for the femoral compo-nent) with the patient supine. Minimally invasive techniques can reduce hospitalization to 24 h or less. Anesthetic techniques should promote rapid recov-ery and can include neuraxial regional anesthesia or total intravenous general anesthesia.
In recent years, hip arthroscopy has increased in popularity as a minimally invasive alternative to open arthrotomy for a variety of surgical indications such as femoroacetabular impingement (FAI), ace-tabular labral tears, loose bodies, and osteoarthritis. At present, there is fair evidence in the published lit-erature (small, randomized controlled trials) to sup-port hip arthroscopy for FAI, but evidence is lacking for other indications.
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