Abstract
During the last half century, total knee arthroplasty has evolved to become a common treatment for different knee maladies. During this time, advancements in preoperative and perioperative care, along with refinements in surgical technique, implant design, and postoperative rehabilitation, have been non-stop. With an appreciation for evidence-based outcomes, clinical practice guidelines for care and accompanying appropriate use criteria have been published. This chapter describes the current best evidence-based care and consensus-based treatment available at this time.
Keywords
knee reconstruction, knee replacement surgery, total knee arthroplasty, total knee replacement
| Synonyms | |
| |
| ICD-10 Codes | |
| M17.10 | Unilateral primary osteoarthritis, unspecified knee |
| M17.11 | Unilateral primary osteoarthritis, right knee |
| M17.12 | Unilateral primary osteoarthritis, left knee |
| M17.5 | Other unilateral secondary osteoarthritis of knee |
Definition
Arthroplasty involves the reconstruction of a diseased, damaged, or an ankylosed joint. This can be accomplished by modification of naturally occurring elements, by artificial replacement, or by a combination. Total knee arthroplasty (TKA) consists of resection of abnormal articular surfaces of the knee with resurfacing predominantly using metal and polyethylene components.
There are three basic types of TKA: totally constrained, semi-constrained, and unconstrained. The amount of constraint built into an artificial joint reflects the amount of stability that the hardware provides. A constrained joint has the femoral portion physically attached to the tibial component and requires no ligamentous or soft tissue support. The semi-constrained TKA has two separate components that glide upon each other, but the physical characteristics of the tibial component prevent excessive femoral glide. The unconstrained device relies completely on the body’s ligaments and soft tissues to maintain the stability of the joint. The semi-constrained and unconstrained knee implants are most often used. In general, the unconstrained implants have been found to afford the most normal range of motion and gait.
A subset within knee arthroplasty is referred to as unicompartmental knee arthroplasty (UKA). It differs from a traditional TKA in that the joint surfaces on only one side of the knee (usually the medial compartment) are replaced. UKA reportedly provides better pain relief than does high tibial osteotomy, and in skilled hands can achieve greater functional outcomes than TKA in younger patients as well as female patients. One limitation of UKA is that both the anterior and posterior cruciate ligaments are spared during the process and therefore must be intact and functioning in order to stabilize the knee. Notably, UKA is contraindicated for rheumatoid arthritis due to a tendency for bone and cartilaginous lesions to spread to involve the entire knee.
Approximately 700,000 TKAs are performed annually in the United States. The most common age group for total knee replacements remains from 65 to 84 years. With the aging of the US population, the number of annually performed TKAs is projected to increase to more than 3 million by the year 2030.
Absolute contraindications to knee replacement include purulent arthritis, tuberculosis, or other active infection. A non-functioning extensor mechanism, recurvatum deformity due to muscle weakness, poor circulation, or the presence of a well-functioning knee arthrodesis are also contraindications. Relative contraindications may include neuropathic joint, morbid obesity, a past history of osteomyelitis, and skin conditions such as psoriasis within the field of surgery.
Symptoms
Preoperatively, refractory knee pain is the most common symptom among patients who undergo TKA. Stiffness, deformity, and instability are also commonly noted. During the perioperative period, acute surgical pain is most intense during the initial 2 weeks postoperatively. Disruption and inflammation of the periarticular soft tissues are manifested as soft tissue stiffness. This stiffness differs in severity with regard to limitation of range of motion from the preoperative stiffness of advanced arthrosis. Surgical disruption of muscle and joint can impair proprioception immediately postoperatively and may give a sense of knee instability. Balance and proprioception can be impaired for patients perioperatively, but seem to improve during convalescence. Occasionally postoperatively, patients may experience a noise or sensation such as popping or grinding, and there have been cases reported of postoperative debris (biologic or wear particles) that may explain this.
Physical Exam
Physical examination of the patient begins with an overall inspection of the limbs. The skin over both legs should be assessed for signs of vascular disease or infection. The exam should progress to palpation of the knee to evaluate for effusion as well as joint line collateral ligament tenderness. The patient’s gait pattern should be documented with attention to the possible presence of knee thrust (abnormal medial or lateral movement of the knee), which may indicate ligamentous instability as well as valgus or varus deformity. Preoperative knee range of motion should be recorded to assess the extensor mechanism. Findings of either contracture or congenital hyper-ligamentous laxity should be noted, as these will need to be addressed at the time of operation. Due to the importance of preserving both medial and lateral collateral ligaments during a TKA surgery, preoperative assessment of the stability of these ligaments is a must. The lower back and hip should routinely be examined to rule out the possibility of referred symptoms to the knee.
Functional Limitations
Advanced arthrosis can affect a person’s ability to perform functional tasks such as arising from a chair, walking, or utilizing stairs. Table 80.1 depicts the required knee range of motion for specific functional mobility tasks. In an otherwise healthy patient population, knee arthritis may impede participation in recreational or sporting activities, or even in more basic activities of daily living.
| Activity of Daily Living | Extension-Flexion |
|---|---|
| Walking in stance phase | 15–40° |
| Walking in swing phase | 15–70° |
| Stair climbing step over step | 0–83° |
| Standing up from a chair | 0–93° |
| Standing up from a toilet | 0–105° |
| Stooping to lift an object | 0–117° |
| Tying a shoelace | 0–106° |
These functional limitations play a role in selecting patients for whom TKA seems to be most beneficial. The profile of a patient with the highest chance of postoperative locomotor recovery is a male with relatively low body mass index, few comorbidities, relatively greater knee range of motion, preserved lower extremity strength and relatively better preoperative locomotion as measured by the 6-minute walk test. The converse is also true, as the profile of a patient at risk for poor postoperative locomotor recovery is a woman with a high body mass index, many comorbidities, high intensity of knee pain, restriction in flexion amplitude, deficits in knee strength, as well as poor preoperative locomotion.
Multiple studies have further identified and corroborated factors associated with a suboptimal postoperative functional outcome. These factors include marked functional limitation, severe pain, low mental health score, and other comorbid conditions prior to TKA. These are associated with worse outcomes at 1 year and 2 years postoperatively. A recurring finding among studies is that patients who had lower preoperative functional status related to knee arthritis functioned at a lower level postoperatively than did patients with a higher preoperative functional status.
Several studies have focused on quadriceps strength as a significant contributing factor to postoperative functional recovery. They have found that functional measures declined early after TKA, but postoperative recovery was more rapid than anticipated and long-term outcomes were better in patients with higher baseline quadriceps strength. The high correlation between quadriceps strength and functional performance suggests that an emphasis on postoperative quadriceps strengthening is vital to enhance the potential benefits of TKA. Preoperative quadriceps strength training has not been proven to enhance long-term functional outcome after TKA.
Diagnostic Studies
Plain radiographs of the knee remain the mainstay of diagnosis and preoperative planning. Three basic views are often used. These include standing anteroposterior view to assess the medial and lateral joint spaces while the joint is under load, the lateral view to assess all joint compartments including the patellofemoral joint and position of the patella, and finally, the merchant view taken tangential to the flexed knee to assess the patellofemoral joint space. A fourth view, the Notch or Rosenberg view, is integral in assessing the posterior aspect of the femoral condyles and earlier arthritic changes within the notch itself. Magnetic resonance imaging is more sensitive than plain radiography in assessing cartilage, meniscus, and ligament integrity, but may overestimate meniscal and ligament damage in the older population and underestimate the amount of degenerative damage of the articular surfaces.
Consideration should also be given to radiographic evaluation of the cervical spine in patients with rheumatoid arthritis. These patients are at increased risk for atlantodental instability and therefore may be at increased risk for spinal cord impingement secondary to perioperative positioning, movement, and manipulation. Patients with rheumatoid arthritis are thought to be at 2.6-fold greater risk of infections than patients with osteoarthritis. Therefore, rheumatoid arthritis patients should be screened for potential sources of infections, including urinary tract infections, skin infections, and dental infections, before TKA.
In all situations where knee infection is suspected, it must be fully assessed and remedied prior to considering TKA. Aspiration of the knee for aerobic and anaerobic cultures and sensitivities is the most reliable method for diagnosis of infection. Strict sterile technique must be used throughout the aspiration procedure.
Treatment
Initial
During the first 48 to 72 hours, patients can receive controlled analgesia therapy administered via intravenous or epidural route. Patients often receive oral opioids. Controlled-release and short-acting opioids may be used, depending on the clinician’s and patient’s preferences, and can be given on a fixed schedule as a rescue medication, or both. Opioids should be titrated to achieve balance of analgesia while minimizing side effects. Several studies have found that nonsteroidal anti-inflammatory drugs (NSAIDs) may adversely affect bone healing via their effect on prostaglandins.
Care for the incision postoperatively involves dry, sterile gauze dressings to be re-applied as long as drainage is present. Bleeding can continue at incision site and through the surgical drain, which blood can be collected and used for reinfusion, thus decreasing the need for donor blood. Bleeding tends to be greater for cementless than for cemented prostheses. Staples and sutures can safely be removed 10 to 14 days after surgery.
Knee immobilizers may be used postoperatively to maintain knee extension and to avoid flexion contracture. Range of motion exercises supervised by a physical therapist should be initiated as soon as possible. Properly fitting, thigh-high elastic compression stockings and local cryotherapy can be used to manage swelling.
If the patient was receiving oral anticoagulation therapy preoperatively, bridging therapy with a low-molecular-weight heparin compound may be considered. Even for those not previously anticoagulated, prophylactic anticoagulation significantly reduces the incidence of symptomatic venous thromboembolism (VTE) during hospitalization. In selecting a prophylactic agent, consideration should be given to patient-specific factors, such as bleeding risk, kidney function, and other comorbidities.
Intermittent pneumatic compression has also been used for prophylaxis. It works by increasing venous blood flow in the deep veins of the legs and by reducing plasminogen activator inhibitor. This mechanical prophylaxis has not been found to be as effective as warfarin and by corollary is not as effective as the other pharmacologic prophylaxis. It can still be considered when pharmacologic options are contraindicated or in conjunction with pharmacologic prophylaxis in patients at high risk for VTE.
Perioperative antibiotic use has been addressed in the literature and evidence supporting the preoperative and intraoperative administration of antibiotics has been well established. The International Consensus Meeting on Periprosthetic Joint Infection held in 2013 recommended pre-intraoperative antibiotic prophylaxis starting no less than 1 hour prior to knee arthroplasty. Despite the consensus for pre- and intraoperative antibiotics, the efficacy of postoperative prophylactic antibiotic administration has not been established and is typically limited to no more than 24 hours postoperatively. Vancomycin is often used for this purpose, but other antibiotics may also be used.
Rehabilitation
The focus of postoperative rehabilitation in the TKA patient should include joint range of motion, quadriceps strengthening, and training in gait and activities of daily living. Specific protocols may vary depending upon surgeon preference, incision type, type of implant, and patient bone stock, but in general, the rehabilitation program can be conceptualized as occurring in stages or phases.
Phase One
In the immediate postoperative period, the inhibited quadriceps and hamstrings may not adequately stabilize the knee. A knee immobilizer may be of help for transfers and walking. The patient may often require a two-handed assistive device (e.g., walker or axillary crutches) for initial gait training to help with balance and proprioception. Adaptive equipment for bathing and dressing (e.g., tub or shower seat, grab bars, dressing sticks, sock aid) is generally very helpful as well due to limitations in early range of motion. Some patients may not have sufficient range of motion during the first week postoperatively to negotiate stairs. The motor reactions typically normalize by the third week; therefore, patients may return to driving activities if they can perform car transfers independently and can tolerate sitting for prolonged periods (see Table 80.2 ).
| Postoperative Day | Exercise | Mobility | Ambulation | Activities of Daily Living |
|---|---|---|---|---|
| 0 | Deep breathing | Sits to chair transfer | ||
| Incentive spirometer | ||||
| Quadriceps and gluteal sets | Education on continuous passive motion machine | |||
| Straight-leg raise | ||||
| Hip abduction | ||||
| Ankle pumps | ||||
| 1 | Deep breathing | Bed mobility | Assess adaptive equipment: reachers, long-handled sponges, and shoehorns | |
| Lower extremity static resistance exercises | Bed to chair transfers with knee immobilizer | |||
| Ankle pumps and circles | ||||
| Continuous passive motion | ||||
| 2 | Continue previously described exercises | Continue bed mobility and transfers | Assisted ambulation in room, partial weight bearing or weight bearing as tolerated with knee immobilizer | Raised toilet seat |
| Short arc quads | Grooming and dressing well while seated | |||
| Straight-leg raise with knee immobilizer | Begin toilet transfers | |||
| Upper extremity strengthening | ||||
| 3 | Continue previously described exercises | Decreased assistance in basic transfers | Independent ambulation with walker or crutches in room, partial weight bearing or weight bearing as tolerated with knee immobilizer | Independent toileting and grooming |
| Sitting full arc motion flexion and extension in conjunction with supine passive flexion and extension | Trial of ambulation in corridor, possibly practice negotiating 2–4 stairs | Education on joint protection and energy conservation techniques | ||
| Depending on community resources and home safety and support availability, the patient may be ready for hospital discharge and post-acute care rehabilitation at this time. | ||||
| 4 | Continue previously described exercises with increased intensity | Independent in basic transfers | Gait training to improve pattern and endurance | Continue previously described activities of daily living |
| Discontinue knee immobilizer (if quadriceps strength is greater than 3/5) | ||||
| Initiate active assistive range of motion exercises and quadriceps and hamstrings self-stretch | ||||
| 5–6 | Continue previously described exercises | Independent ambulation with assistive device | Independent dressing with tapered use of adaptive equipment | |
| Transition from passive to active assistive range of motion exercises | Begin stairs with railing, cane as needed | |||
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