Preoperative Planning for Primary Total Knee Arthroplasty

Nathanael Heckmann, MD

Kevin Bigart, MD

Aaron G. Rosenberg, MD

INTRODUCTION

Modern total knee arthroplasty has revolutionized the treatment of degenerative diseases about the knee. Today, total knee arthroplasty offers both surgeons and patients a reliable treatment for these conditions. When total knee arthroplasty is compared to other medical and surgical interventions for common diseases, the cost of quality-adjusted life years associated with this procedure is unparalleled.¹,²,³

The durability of modern total knee arthroplasty designs and component materials has led surgeons to broaden the indications for this procedure. Long-term follow-up of first-generation total condylar knee arthroplasty implants has shown survivorship of 77% to 91% at greater than 20-year follow-up.⁴,⁵ With further improvements in operative techniques, instrumentation, and prosthetic design combined with a better understanding of the mechanisms of failure, long-term survivorship of total knee arthroplasty has improved. Newer knee designs have shown 20-year survivorship of 87% to 97% in some series.⁶,⁷,⁸ Given the success of this procedure, surgeons have expanded the surgical indications, and a surgery once reserved for the elderly and low-demand patient is now being performed in younger, higher demand patients with increased frequency.⁹

Appropriate surgical indications are paramount to achieving successful outcomes. As the population continues to age, the number of patients with degenerative conditions of the knee will continue to increase. Furthermore, the recent increase in total knee arthroplasty procedures performed in patients 45 to 64 years old continues to change the overall population of patients undergoing this surgery. These demographic changes and broadened indications make an understanding of the limitations of total knee arthroplasty imperative for orthopedic surgeons, patients, and primary care physicians.

PATIENT SELECTION

With recent demographic changes and expanding indications, total knee arthroplasty has become one of the most common surgical procedures performed.¹⁰ However, the increased utilization of total knee arthroplasty should be approached with appropriate caution as younger patients have been shown to have two- to fivefold greater revision rate with decreased long-term implant survival compared to older patients.¹¹,¹²,¹³ Despite these concerns, long-term improvements in pain and function can be achieved in young patients who undergo total knee arthroplasty.¹⁴,¹⁵,¹⁶ However, any medical decision requires consideration of the risks and benefits of a given intervention, particularly surgical ones with rare but potentially catastrophic complications. Risk considerations should be weighed in light of the prospective benefits and limitations that a patient can experience following a total knee arthroplasty.

For total knee arthroplasty, any discussion about the appropriate indications for surgery mandates that the patient benefit from the intervention to warrant the specific risks involved. As with any surgery, determining whether or not a total knee arthroplasty is indicated or contraindicated involves the careful evaluation of the patient’s complaints, pathology, and overall health status, as well as the weighing of multiple risk factors for adverse outcomes and prognostic factors associated with a successful surgery. Finally, these considerations should result in a judgment as to whether the final balance of risks and benefits is appropriate for the individual patient under consideration. This judgment should involve the patient, as an accurate assessment of the surgical benefit relies on realistic patient expectations and a thorough understanding of the limitations of total knee arthroplasty.

An important consideration in the performance of any elective surgical procedure is the relative risk of perioperative events that carry with them significant morbidity or mortality. Total knee arthroplasty as practiced before the risk of thromboembolic disease was well understood, carried with it a mortality risk from pulmonary embolism. Although the incidence of fatal pulmonary embolism has decreased, as have the rates of infection and other serious postsurgical morbidities, one must compare the potential long-term benefits of pain reduction and improved function with the short-term risks of death and other complications.

Risk and benefit analyses regarding total knee arthroplasty are dependent on several factors in addition to the underlying pathology, including patient age, activity level, and comorbid disease burden. These patient factors must be weighed in light of several assumptions before a surgeon can determine if a total knee arthroplasty is
indicated for an individual patient. These assumptions include the finite durability of a total knee arthroplasty implant, the failure of nonsurgical treatment to alleviate pain, and the limitations to activity that are caused by a patient’s degenerative knee disease. These three assumptions ought to inform any risk-benefit analysis when determining if total knee arthroplasty surgery is indicated.

The first assumption that a knee arthroplasty is a time-limited operation relies on an understanding of fixation longevity, material wear, and implant failure. While several previously referenced series demonstrate improved component survival in young and highly active patients, it is unreasonable to assume that young adults with a normal life span will reliably outlive a total knee implant in all instances. Thus, age becomes an important factor in the decision to proceed with total knee arthroplasty, particularly at extremely young ages, when the assumption that a total knee arthroplasty has a finite life span is thoughtfully considered. For this reason, ceteris paribus, older patients continue to be better candidates for total knee arthroplasty, as the likelihood that an implant will outlive the patient increases with age, obviating the need for revision surgery or potentially multiple subsequent surgical interventions. However, with improved surgical techniques, modern implant designs, and improved material properties, considerations about the time-limited nature of implants have led many surgeons to pursue knee arthroplasty in younger patients that were previously thought to be “out of bounds” based on age-related implant concerns. However, the pediatric and young adult patient clearly deserve an attempt at alternative treatments, such as osteotomy or cartilage restoration procedures, if such treatment will relieve symptoms sufficiently to postpone arthroplasty and not make subsequent treatment exceedingly complex.

Another assumption is that nonoperative treatment should be attempted before proceeding with arthroplasty. This may include the use of assistive devices for ambulation, weight loss, systemic or local medications, physiotherapy, bracing, and activity modification. A concerted effort at nonsurgical therapy may be more reasonable in the younger patient than in the elderly, in whom prolonged attempts are time consuming and rarely effective in relieving symptoms and improving function. These modalities should be attempted more aggressively in the younger patient than in the elderly. In some settings, the symptoms, physical findings, and radiographic changes are severe enough to warrant consideration of total knee arthroplasty even if the patient has had no prior nonoperative treatment. For example, in an elderly patient with progressively worsening localized knee pain and severe radiographic osteoarthritis (i.e., joint space obliteration, abundant marginal osteophytes, subchondral sclerosis or cystic changes, etc.), surgery may be indicated, given the futile likelihood that nonsurgical treatments will provide lasting relief. In most cases, however, particularly in the younger individual, it may be wiser to demonstrate to the patient that conservative or nonsurgical treatment will not relieve symptoms or improve function before recommending more aggressive surgical treatment that has more substantial risk of complications.

The level of patient activity and symptom severity are other important factors to consider when determining whether arthroplasty is indicated. Although pain is the most common complaint before surgical intervention, in many cases, symptoms are activity related. If the patient’s symptoms are clearly amenable to activity modification and if total knee arthroplasty is not an ideal option due to age, comorbidities, expectation mismatch, or other factors, the surgeon should opt for activity modification over operative intervention. If the individual has little or no symptoms with activity modification, then activity limitation may be a reasonable course of action. However, marked limitation in functional capacity may be an indication for joint arthroplasty in the elderly. Understanding the patient’s requirements for performing activities of daily living is essential in this determination. A patient’s ability to perform a job, do household tasks, and maintain personal hygiene can be used as measures of the effect of knee function on the patient’s quality of life. Walking tolerance, defined as the length of time or distance one can walk without rest, can be an important benchmark in assessing the severity of disease and limitation of function. In general, if an elderly patient cannot perform activities of daily living despite nonoperative treatment, knee function has decreased to the point at which intervention is indicated. However, in a younger patient, surgery may be indicated following more moderate limitations in activity, provided the patient and surgeon have realistic expectations in terms of postoperative function, implant longevity, and postoperative complications.

In summary, total knee arthroplasty is often indicated in patients who have painful arthritic changes in the knee that limit or alter physical activity in a way that negatively affects their quality of life. However, the surgeon should bear in mind that the final determination of whether a knee arthroplasty is indicated for an individual should follow a risk-benefit analysis that takes into account a patient’s age, comorbidities, functional limitation, and postsurgical expectations. This analysis should be followed by a shared patient-surgeon decision in which the surgeon bears the responsibility of ensuring that the patient has reasonable expectations following surgery, understands the limitation of a total knee arthroplasty, and is aware of the risks and benefits associated with the procedure and possible future procedures.

PATIENT EXPECTATIONS

The surgeon often encounters patients with unrealistic expectations for surgical intervention. These expectations must be tempered by the surgeon’s experience and a
thorough understanding of outcomes that can be obtained following total knee arthroplasty. A patient must understand that the goal of knee arthroplasty is to alleviate pain and improve function, not to restore the patient’s knee to a prearthritic state. The patient must also understand that functional limitations may still exist after knee arthroplasty. Normal range of motion may not be restored after years of reduced motion and extensive flexion contracture. In some patients, range of motion may be less after surgery than before. These concepts should be discussed extensively with the patient prior to any surgical intervention as unmet expectations are associated with poor outcomes following total knee arthroplasty.¹⁷

Finally, it is important to discuss the responsibility patients must assume for their prosthetic knees. Patients must understand that this implant is a walking device designed to relieve pain and thus patients must be willing to modify their activity to prevent early mechanical failure. Although certain activities such as walking, swimming, and golf are compatible with a long-term successful outcome, higher impact sports such as long distance running may not be compatible with optimal implant longevity. By assuming responsibility for their actions, patients must realize that certain activities may result in diminished longevity of the knee and subsequent need for revision surgery. Along these same lines, before embarking on surgical intervention, the surgeon must be confident that a given patient is willing and able to comply with the necessary postoperative rehabilitation protocols compatible with a successful outcome.

PATIENT ASSESSMENT

Not unlike most orthopedic procedures, determining whether total knee arthroplasty is indicated for a given patient consists of obtaining a history that includes pain and disability, combined with corroborative physical examination and radiographic findings. These three facets of the patient evaluation should all confirm the presence of end-stage arthritis of the knee before the surgeon recommends a total knee arthroplasty. If any one of these evaluations fails to support this diagnosis, the surgeon should be alerted to the possibility of a mistaken diagnosis or the possibility that the patient’s complaints will not be adequately addressed by this procedure.

History

The primary indication for total knee arthroplasty is recalcitrant pain in the knee caused by degenerative joint disease. Pain is the most reliably addressed symptom of knee arthritis after total knee arthroplasty is performed. The character and degree of pain is important to document, as is the presence of pain at night or at rest. If no other diagnosis is present, night or rest pain often heralds the final stage of knee osteoarthritis that may not respond to nonoperative treatment. Inflammatory arthritis can also be associated with significant discomfort both at rest and at night. If the knee pain is associated with groin or anterior thigh pain, the clinician must be careful to evaluate the hip, as hip pathology may cause pain that is referred to the knee. Pain from knee osteoarthritis frequently extends below the knee, but pain down into the foot must be distinguished from radicular pain.

Pain associated with arthritis of the knee is typically related to activity, and the physician should establish the functional disability this has created. Specifically, the physician should determine how the patients’ pain has affected their ability to perform their activities of daily living such as shopping, cleaning, and personal hygiene. These facets of the history are important to delineate, as pain is an individual experience that may hamper patients’ ability to care for him- or herself and impact their lifestyle in uniquely individual ways. Patients who exhibit both severe pain and functional disability will derive the most benefit from total knee arthroplasty. It is also important to identify those patients with unrealistic expectations from total knee arthroplasty, such as those who only experience pain and disability in the context of intense physical exertion, in whom activity modification, rather than surgery, may be more appropriate.

The patient history should also include an assessment of prior nonoperative and operative treatments. A thorough trial of nonoperative treatment is appropriate for the majority of patients as previously discussed. Nonoperative treatment including activity modification, nonsteroidal anti-inflammatory medications, hyaluronate or corticosteroid injections, and the use of an assist device should all be considered and discussed with patients as potential forms of nonoperative management of knee arthritis. Failure of these modalities should be considered a good indication for surgery in the presence of corroborative physical examination and radiographic findings.

A prior history of operative treatment is also important to document, as various other operative treatments may influence the operative techniques used and compromise the final outcome of total knee arthroplasty. If possible, previous operative reports should be reviewed to confirm the surgical findings and treatment rendered.

The patient history should also include an assessment of the patient’s general health including any medical problems. Appropriate preoperative medical consultation is imperative to identify medical comorbidities that can be optimized preoperatively or that may argue against elective surgery. A history of disease associated with an immunocompromised state (e.g., diabetes mellitus, renal failure, acquired immune deficiency syndrome, etc.) is also important to obtain, to more carefully counsel patients about the risks of periprosthetic joint infection. The history should also seek to identify other medical problems that may be associated with persistent bacteremia such as recurrent urinary tract infections in women, urinary
outlet obstruction in men, or dental problems that can be addressed before operative intervention.

A thorough history should also include drug allergies and metal sensitivities. A notably small proportion of candidates for total knee arthroplasty who report a penicillin allergy actually have a true IgE-mediated reaction to cephalosporins.¹⁸ However, given the potential severity of these types of reactions, the orthopedic surgeon should consider a preoperative skin testing with an allergist or a preoperative test dose, prior to the administration of a therapeutic dose of a preoperative first-generation cephalosporin. These considerations should be weighed with recent data suggesting patient who receive noncephalosporin antibiotics may be at increased risk of developing a postoperative periprosthetic joint infection.¹⁹ Lastly, if a patient reports a history of metal sensitivity or metal allergies, the surgeon should consider sending the patient to an allergist for metal patch testing or ordering a lymphocyte transformation testing. In these patients, alternative implants that do not contain cobalt or chromium may be considered. However, one should note the lack of data supporting the use of preoperative allergy testing and alternative implants as a means to decrease complications in patients with metal allergies.

Physical Examination

Physical examination should begin with an assessment of gait. An antalgic gait is commonly encountered in patient with moderate to severe arthritis; however, the presence of a Trendelenburg gait should alert the physician to a problem with the ipsilateral hip joint or neuromuscular disease. A patient’s gait is often illustrative of the amount of disability that they are encountering and helps the surgeon to determine if a given patient’s arthritis warrants total knee arthroplasty. The alignment of the lower extremity is also noted to assist with preoperative planning of anticipated ligament releases if total knee arthroplasty is in fact indicated.

Inspection of the soft-tissue envelope is performed next. The location and age of prior incisions should be noted, as they may impact the surgical approach used in subsequent knee arthroplasty. If there is a question as to the suitability of the soft-tissue envelope for surgical intervention, a preoperative consultation with a plastic surgeon is recommended. The presence of cutaneous lesions is also important to note, because they may indicate the cause of arthritis (i.e., psoriatic arthritis) or may influence the decision to proceed with surgery, as surgery will need to be delayed for patients with active skin lesions until the soft-tissue envelope is intact to prevent an unacceptably high rate of infection.

A neurovascular examination including the palpation of dorsalis pedis and posterior tibial pulses follows. If they are not palpable, a vascular consultation may be warranted, and the avoidance of a tourniquet intraoperatively may be considered. The neurologic examination may alert the physician to the presence of preoperative neurologic deficits and may also identify a radiculopathy as the cause of the patient’s pain. Other nonmusculoskeletal disease processes such as venous insufficiency, complex regional pain syndrome, and diabetic neuropathy can be identified with a thorough examination and should be noted as they may affect a patient’s outcome.

Examination of the knee itself includes an assessment of range of motion, which is typically decreased. In addition, it is important to recognize that preoperative range of motion is often predictive of postoperative range of motion.²⁰ Some patients may seek total knee arthroplasty primarily to increase their range of motion, and the ability to improve their range of motion must be carefully discussed with the patient before surgery. Preoperative flexion contractures are also important to identify so that they can be appropriately addressed at the time of surgery. The knee is next palpated to determine areas of maximal tenderness. If the patient has pain in areas that do not correspond to the radiographic location of arthritis, other diagnoses should be examined. Ligamentous stability should be tested next, with care taken to examine the medial and lateral collateral ligaments, as well as the anterior and posterior cruciate ligaments. Lower extremity alignment should be noted and compared to the contralateral extremity. If any valgus or varus deformity is present, the ability to correct all or part of the deformity should be noted as should the ability to overcorrect the deformity.

The physical examination should include a thorough assessment of the lower back and hip to ensure that the pain experienced by the patient is not referred from a distant anatomic location. Lastly, the foot should also be evaluated as a pes planus deformity can accentuate a valgus deformity preoperatively and lead to valgus instability postoperatively. In cases in which the cause of the patient’s pain is unclear, an intra-articular lidocaine injection can be used as a diagnostic test to confirm the pain is arising from the knee joint itself.

Radiographic Analysis

Radiographic confirmation of knee arthritis is important in the evaluation of the patient considered for total knee arthroplasty. Clinical symptoms, however, oftentimes do not correlate directly with the severity of radiographic findings. Specifically, the radiographic presence of severe arthritic changes in the absence of clinical symptoms or disability referable to the knee is clearly not an indication for total knee arthroplasty. Similarly, the absence of radiographic findings should alert the physician to an alternative diagnosis.

Radiographs obtained should include standing anteroposterior, lateral, and patellofemoral views. Standing radiographs are imperative to detect subtle joint space narrowing associated with loss of articular cartilage. A standing view with the knee flexed may further assist
in identifying subtle joint space narrowing, particularly along the posterior femoral condyles. It is not uncommon for patients with minimal radiographic changes to undergo an extensive course of nonoperative treatment only for severe cartilaginous destruction to be found at the time of surgery. Thus, radiographs must always be interpreted in the context of clinical symptoms. Patellofemoral views are equally important as anteroposterior and lateral views alone can underestimate the degree of patellofemoral arthritis present. Full-length lower extremity mechanical axis views may provide the surgeon with additional information regarding the patient’s coronal deformity. Lastly, if digital templating is performed, a calibrated radiographic marker should be used to increase accuracy.

CONTRAINDICATIONS AND ALTERNATIVES TO TOTAL KNEE ARTHROPLASTY

Contraindications

Although total knee arthroplasty is appropriate management for the majority of patients with a severely arthritic knee, the surgeon must be aware of alternate surgical therapies that may be more appropriate for certain patients. Alternative surgical options to total knee arthroplasty include osteotomy, unicompartmental arthroplasty, and arthrodesis. Osteotomy of the knee is reserved for patients with symptomatic unicompartmental arthritis who have a focal biomechanical derangement of the knee joint with an adjacent area of intact cartilage available for redirection into the weight-bearing portion of the joint. Osteotomy can be performed on either the tibial or femoral side of the joint. For these procedures, a congruous, stable knee with good range of motion is a prerequisite. These procedures are often used in younger patients with early degenerative arthritis that is limited to either the medial or lateral compartment. Unicompartmental arthroplasty is indicated for patients with unicompartmental tibiofemoral arthritis without significant deformity, concomitant patellofemoral disease, ligamentous instability, or inflammatory arthritis. Arthrodesis of the knee is infrequently indicated except for patients with a clear contraindication to total knee arthroplasty such as active sepsis.

Arthroscopy of the knee has a very limited role in the treatment of knee osteoarthritis and has been performed with decreasing frequency given its lack of efficacy.²¹ However, patients with degenerative arthritis and mechanical symptoms may benefit from operative arthroscopy, but the surgeon should be aware that symptoms may worsen after surgery. Arthroscopic synovectomy may have a role in the treatment of patients with inflammatory arthritis of the knee before severe cartilaginous destruction has occurred; however, the long-term benefits of such intervention are currently unproven.²²

Only gold members can continue reading. Log In or Register to continue