eMedicine Specialties > Orthopedic Surgery > Knee

Total Knee Arthroplasty: Treatment

Author: Simon H Palmer, MD, Consultant Surgeon, Department of Orthopedics and Trauma, Worthing and Southlands NHS trust, Sussex
Coauthor(s): Mervyn J Cross, MBBS, FRACS, Director of the Australian Institute of Musculoskeletal Research, Department of Orthopedic Surgery, North Sydney Orthopedic/Sports Medicine Center, Crows Nest, Australia
Contributor Information and Disclosures

Updated: Apr 14, 2009

Treatment

Medical Therapy

Initial management of most patients with osteoarthritis should be nonoperative and may include nonsteroidal anti-inflammatory medications, intra-articular viscosupplementation (eg, hylan GF 20[Synvisc], sodium hyaluronate [Hyalgan]), analgesics, bracing, orthoses, shoe modifications, weight loss, and ambulatory aids (eg, walking stick held in the opposite hand). Activity modification may also be necessary. Home health care–assistive devices for daily living (eg, toilet extenders, safety rails, bath seats) may help the patient cope with disability and should be prescribed after consultation with an occupational therapist. Knee rehabilitation under the supervision of a physiotherapist may include strengthening and range-of-motion exercises, gait training, and patient education.

Joint aspiration and intra-articular steroid injection may be used to improve synovitis. Osteoarthritis in the knee usually progresses slowly, thus affording opportunities for nonoperative treatment. Responses to nonoperative treatment, however, are varied and unpredictable because none of the treatments are specific for the disease. Because of the progressive nature of the disease, many patients with osteoarthritis of the knee eventually require operative treatment.

Surgical Therapy

A number of operative procedures should be considered in patients with degenerative disease of the knee. Arthroscopic debridement is sometimes indicated in mild degenerative joint disease with mechanical symptoms and recurrent persistent effusions. Proximal tibial valgus osteotomy should be reserved for patients with medial tibiofemoral compartment disease, stable collateral ligaments, and a correctable varus deformity of the knee joint (see Image 8).

These procedures restore the mechanical axis of the lower limb and off-load the diseased compartment. Proximal tibial valgus osteotomy and distal femoral varus osteotomy are generally reserved for young high-demand patients because of concerns about the durability of total knee replacement in this patient group. Unicompartmental knee replacement or hemiarthroplasty can be used in low-demand younger patients with unicompartmental disease or in elderly patients with unicompartmental disease of the knee joint who are not obese (see Image 10).

A prospective, randomized, controlled trial in England compared unicompartmental with total knee replacement over 8, 10, 12, and 15 years follow-up. At 5 years, the number of failures were equal in the 2 groups. At 15 years follow-up, the survivorship rate for unicompartmental knee replacement was 89.8% and was 78.7% for total knee replacement. Four of the unicompartmental knees failed, and 6 of the total replacement knees failed. Newman et al determined from their findings that the results of their study justify increased use of unicompartmental replacement.¹⁰

Arthrodesis or fusion of the knee is rarely performed but should be considered in patients with chronic sepsis, younger patients with tricompartmental disease (eg, following trauma) who require stability and durability, and patients with deficient extensor mechanisms. TKA is performed in patients with symptomatic advanced degenerative changes in one or more compartments of the knee joint.

The aim of total knee replacement is to resurface the deficient and damaged tibiofemoral joint surfaces with metal components and provide a low-friction articulation with a polyethylene bearing. If significant patellofemoral disease is present, this joint can also be resurfaced, although the need for this is rather variable. The mechanical alignment and soft-tissue balance around the knee should be anatomically restored for optimum function and longevity of the knee replacement.

Preoperative Details

A thorough preoperative medical evaluation of patients undergoing total knee arthroplasty is important to prevent potential complications in the perioperative period. Complete the evaluation in an elective preadmission clinic well before the date for surgery. This allows for a careful and unhurried assessment with adequate time for investigations, specialist anesthetic and medical opinion, and consent. It also allows operating schedules to be reorganized if patients are deferred from surgery.

Most patients who undergo TKA are elderly with comorbid diseases. Patients must have good cardiopulmonary function to withstand anesthesia and to withstand a blood loss of 1000-1500 mL over the perioperative period. Routine preoperative electrocardiography should be performed on elderly patients. Patients with ischemic heart disease, congestive heart failure, and chronic obstructive airway disease should be seen by a medical specialist or anesthetist. Patients with significant peripheral vascular disease should be seen by a vascular surgeon.

Patients should have completed an informed consent for surgery and fully understand the risks and possible complications of the procedure. They should have had all medical conditions optimized before surgery and be free of intercurrent infections. Two units of blood should be available for perioperative transfusion, either from the blood bank or preferably as predonated blood. Full medical and surgical backup must be available in case unforeseen complications occur.

Use of anesthesia

Selection of regional or general anesthesia is made following preoperative discussion between the anesthetist and the patient, with some input from the surgical team. This decision is affected partly by the medical condition of the patient, although cardiovascular outcomes, cognitive function, and mortality rates of regional and general anesthesia have not been proved to be significantly different.

Patients who have epidural anesthesia have been shown to develop fewer perioperative deep vein thromboses. Whether this has any overall positive benefit to the patient is not known. Another benefit of epidural anesthesia is the presence of an indwelling catheter for 48-72 hours postoperatively for pain control, thus avoiding the need for excessive amounts of centrally acting analgesics. Adverse effects of continuous postoperative epidural analgesia include pruritus, urinary retention, nausea, vomiting, and formation of an epidural hematoma (on rare occasions).^11,12

In a study by Shum et al, continuous femoral nerve block for analgesia, versus no femoral nerve block, resulted in less pain, higher satisfaction, and lower morphine use in patients immediately after total knee arthroplasty. At 2-year follow-up, no significant differences in functional outcome were identified¹²

Use of antibiotics and antithromboembolic devices

Antibiotics and antithrombotic prophylaxis are administered approximately 30 minutes before the incision is made, and mechanical antithromboembolic devices (eg, stockings, foot pumps) are used intraoperatively.

Intraoperative Details

A thigh tourniquet is generally used to aid surgical exposure, although it should be avoided in patients with a history of previous deep vein thrombosis or significant vascular disease. The operation should be performed in a laminar flow operating theatre with meticulous attention to detail to prevent contamination of the operation site.

The knee joint is usually approached anteriorly through a medial parapatellar approach, although some surgeons use a lateral or subvastus approach. Osteophytes and intra-articular soft tissues are then cleared. Bone cuts in the distal femur are made perpendicular to the mechanical axis, usually using an intramedullary alignment system, which is then checked against the center of the hip. The proximal tibia is cut perpendicular to the mechanical axis of the tibia using either intramedullary or extramedullary alignment rods. Restoration of mechanical alignment is important to allow optimum load sharing and prevent eccentric loading through the prosthesis. Sufficient bone is removed so that the prosthesis re-creates the level of the joint line. This allows the ligaments around the knee to be balanced accurately and prevents alteration in patella height, which can have a deleterious effect on patellofemoral mechanics.

Because of preoperative deformity, some ligaments around the knee are contracted. These are carefully released in a step-wise fashion to balance the soft tissues around the knee and allow optimum knee kinematics (see Image 12).

Once the definitive components have been selected, they are cemented into place with polymethyl methacrylate cement. If an uncemented system is being used (see Image 13), press-fit and bony ingrowth provides the short-term and long-term fixation of the component (see Image 14). The tourniquet should be deflated prior to closure to allow accurate hemostasis, and the knee joint is usually drained and dressed in extension. Foot pulses are checked at the end of the procedure.

Postoperative Details

The patient is recovered and usually observed for a 24-hour period in a high-dependency ward. Adequate hydration and analgesia are essential in this time of high physical stress. Analgesia is provided through continuation of the intraoperative epidural, patient-controlled intravenous analgesia, or oral analgesia. At this early stage, the patient begins knee movement sometimes using a continuous passive motion (CPM) machine and exercises. These are continued under the supervision of a physiotherapist until discharge.^13,14

Follow-up

Follow-up depends on the surgeon, the patient, and the health care system. A typical example would be a surgical follow-up appointment at 6 weeks, 3 months, 6 months, 1 year, 2 years, 5 years, 10 years, and thereafter as appropriate. This is modified for each patient according to age, degree of activity, and presence of complications.

For excellent patient education resources, visit eMedicine's Foot, Ankle, Knee, and Hip Center, Bone Health Center, and Arthritis Center. Also, see eMedicine's patient education articles Knee Joint Replacement and Knee Pain.

Complications

Thromboembolism

Thromboembolism includes deep vein thrombosis (DVT) with subsequent life-threatening pulmonary embolism (PE). Predisposing factors for increased risk of DVT include age older than 40 years, female sex, obesity, varicose veins, smoking, past history of DVT, diabetes mellitus, and coronary artery disease. Overall incidence of DVT following total knee replacement without any prophylaxis has been reported at 40-88%. Most of these are calf thromboses. The risk of fatal PE, however, is the important figure and varies from 0.1-1%.

Many current methods of DVT prophylaxis are available and are used, including mechanical compression stockings or foot pumps and pharmaceutical agents, including low-dose warfarin, low-molecular-weight heparin, and aspirin. Many studies show evidence of reduction of rates of DVT, but how this affects overall death rates from PE is unclear at this time, with many of the current studies concluding after only 10 days. Using a multifactorial approach to prevent DVT, including intraoperative foot pumps, epidurals, pharmaceutical agents, antithromboembolic stockings, adequate hydration, early mobilization of the patient, and regular postoperative surveillance, is probably prudent.

Infection

Prevention of infection in total knee replacement begins in the preoperative examination to exclude intercurrent infection. In the operating room, personnel should be kept to the smallest number, and traffic in and out of the room should be kept to a minimum. Use of vertical laminar flow in operating theaters, prophylactic antibiotics, ultraviolet light, body exhaust systems to prevent bacterial shedding, and meticulous and expeditious surgery all help to reduce the occurrence of infections to less than 1% of operations performed.

Factors relating to a higher rate of infection following TKA include rheumatoid arthritis, skin breakdown, prolonged wound drainage (>6 d), previous knee surgery, use of a hinged knee prosthesis, obesity, concomitant urinary tract infection, steroid use, renal failure, diabetes mellitus, malignant disease, and psoriasis.

Treatment of the infected total knee replacement often is laborious and time consuming and a disaster for the patient. The risk is minimized by a theater team obsessed with detail supported by good nursing skills on the ward and vigilance by the surgeon in the postoperative period.

Patellofemoral complications

Patellofemoral complications include patellofemoral instability (see Image 16), patellar fracture, patellar component failure, patellar clunk syndrome, and extensor mechanism tendon rupture. All of these complications have been cited as the common reasons for reoperation. These can be avoided by attention to detail, meticulous technique, and avoidance of component malposition.

Neurovascular complications

Arterial thrombosis following total knee replacement is a rare (ie, 0.03-0.17%) but devastating complication, frequently resulting in amputation. Several authors have recommended performing TKA without the use of a tourniquet in patients with significant vascular disease. Such patients should undergo a vascular surgery consultation prior to knee replacement.

Peroneal nerve palsy is the commonly reported nerve palsy following total knee replacement. It usually occurs in the correction of combined fixed valgus and flexion deformities often observed in patients with rheumatoid arthritis. Fifty percent undergo spontaneous recovery, and 50% undergo partial recovery with conservative treatment. Some good results have been obtained with surgical decompression.

Periprosthetic fractures

Supracondylar fractures of the femur are not common following total knee replacement (ie, 0.2-1%). These fractures are observed if the anterior femoral cortex is notched and weakened during surgery and in patients with osteoporosis, rheumatoid arthritis, poor flexion, revision arthroplasty, and neurologic disorders. Treatment is with internal fixation or revision TKA. Tibial fractures are uncommonly observed.

Aseptic loosening

Loosening leads to the ultimate failure of the prosthesis and occurs at an approximate rate of 5-10% of patients at 10-15 years. It may be complicated by bone loss or osteolysis, which can lead to catastrophic deterioration and make revision surgery difficult. The etiology of this problem is not entirely understood but is related to polyethylene debris causing mechanisms at a cellular level to result in bone resorption. Once a component is loose, it becomes mechanically unstable with worsening osteolysis. Treatment is revision with bone grafting.

Arthrofibrosis

This is a condition of excessive scar tissue causing restriction of knee movement. Etiology is unknown. It is more common in young patients and in patients taking warfarin. It occurs in less than 1% of patients. Conservative management includes anti-inflammatory medication, physiotherapy, and reassurance. More aggressive treatment includes manipulation under anesthetic with CPM therapy and excision of scar tissue.

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