Painful Total Knee Arthroplasty Workup





Introduction


Total knee arthroplasty (TKA) has seen vast improvement over the past several decades with respect to implant design, improved polyethylene wear properties and advances in surgical technique, all of which have led to excellent survivorship. Despite these improvements, patient satisfaction following TKA continues to be a concern, with approximately 19% of patients not satisfied with their TKA. Patient satisfaction following TKA is based on several factors, including alleviating pain, achieving appropriate limb alignment, providing flexion and extension gap soft-tissue balance for stability, restoring knee motion for functional activities, and meeting patient expectations while minimizing complications. An understanding of the most common failure mechanisms following primary TKA is essential for the evaluation and treatment of the painful TKA. The etiology of the painful TKA can be divided into two primary categories: intrinsic and extrinsic. Intrinsic causes include periprosthetic joint infection (PJI), aseptic loosening, instability, malalignment, osteolysis, extensor mechanism disruption, contracture, and fracture. Extrinsic causes that can refer pain to the knee include spine or hip pathology; vascular etiology, such as claudication; local soft-tissue inflammatory processes, such as popliteal tendinitis and knee bursitis; and neurogenic pain from a neuroma or genicular nerve trauma. This chapter will provide an overview of the most recent literature on evaluation and subsequent workup for the etiology of the painful TKA.


History, Physical Examination, and Imaging


The differential diagnosis of a painful TKA begins with a thorough history of the patient’s index TKA followed by a physical examination. The thought process to identify the etiology of the painful TKA has to take into account multiple factors, including the length of time from the index procedure to the onset of the painful TKA along with the nature or characteristics of the pain, such as localized versus diffuse, severity, any radicular component, or any startup pain with activities or pain that persists even at rest. The nature of the pain is helpful since pain with initiation of weight bearing, such as startup pain, may suggest implant loosening, whereas a more constant pain may imply other etiologies, such as an infectious or inflammatory process. Persistent wound drainage greater than 5 to 7 days or delayed wound healing at the time of the index procedure also supports a chronic infectious etiology. An associated recent illness, dental procedure, or other recent surgical procedures prior to the onset of symptoms may also indicate hematogenous infection. A history of recurrent knee effusions along with difficulty with inclines or stairs may suggest instability despite normal-appearing radiographs. It is also important to identify the specific implant and manufacturer used for the index TKA. Following the initial history, physical exam, and initial radiographs (to include weight-bearing anteroposterior [AP], lateral, Merchant and long-leg imaging studies), a well-thought-out differential diagnosis should be developed.


The physical examination should note the prior surgical incision and integrity of the soft-tissue envelope, including signs of instability or malalignment in the coronal, sagittal, and axial planes, along with the presence of an effusion. Examination should include evaluation for tenderness along the periarticular soft tissues to help localize the pain. The hip joint should also be examined since hip pathology can refer pain to the knee. A neurovascular exam is important to assess for potential neurogenic pain emanating from the spine or local surrounding genicular nerves due to the surgical trauma. Knee pain can also be due to vascular etiology presenting as claudication. Knee range of motion (ROM)—along with quadriceps strength, extensor mechanism integrity, stiffness, and patella component tracking—should be assessed. For activities of daily living, it is ideal to have 105 degrees of knee flexion or greater. It is also important to evaluate the patient’s gait for any limp, dynamic instability, neurogenic conditions, and hip and spine pathology.


Adequate radiographs are essential during the workup for a painful TKA. Images should include weight-bearing AP and lateral radiographs along with a Merchant view to assess patellofemoral alignment in addition to wear, loosening, osteolysis, malposition, fracture, and patella alta or baja. Long-leg radiographs to include the hip, knee, and ankle are helpful to identify any malalignment and offer a limited radiographic evaluation for hip pathology ( Fig. 15.1 ). Radiographic images of the knee prior to the index TKA should also be reviewed in order to evaluate the extent of the preoperative arthritic disease and/or deformity and extent of the degenerative disease prior to the primary TKA. Advanced imaging in evaluation of painful TKA includes fluoroscopic views to assess for radiolucent lines along with computed tomography (CT) scans and nuclear medicine studies. CT scans allow for assessment of component rotation in the axial, sagittal, and coronal planes. Nuclear medicine imaging can also be used to evaluate for component loosening in the painful TKA. However, this should be reserved for delayed pain greater than 2 years postoperatively given the high false-positive rate if obtained prior to that time.




Fig. 15.1


A, B, Anteroposterior and lateral radiographs of a 65-year-old patient with a painful total knee arthroplasty. C, Full-length lower extremity radiographs demonstrating valgus malalignment. D, Postoperative radiographs following revision demonstrating correction of the valgus deformity.


Intrinsic Etiologies for Knee Pain Following Total Knee Arthroplasty


As the projected volume of TKA is expected to increase to over 3 million procedures per year in the United States, it is important that the common reasons for TKA failure are understood. The success rate of primary TKA is approximately between 80% to 85% with respect to patient satisfaction. However, there are 15% to 20% of patients who continue to have ongoing pain. Pain following TKA can result from several etiologies, some of which can be readily apparent—such as a culture-positive PJI or instability presenting with an effusion and gross laxity ( Boxes 15.1 and 15.2 ). The etiology of a painful TKA can also be elusive; in that case, it requires a thorough, algorithmic workup with a process of elimination to narrow the differential diagnosis ( Table 15.1 ). The most common etiologies for failed TKA requiring revision surgery include aseptic loosening, PJI, instability, periprosthetic fracture, and arthrofibrosis. , The incidence of polyethylene wear leading to failed TKA requiring revision has declined due to improvements in polyethylene wear characteristics. This chapter will explore the evaluation of a painful TKA and discuss some of the more common etiologies, such as PJI, loosening, malalignment, arthrofibrosis, instability, polyethylene wear, and osteolysis. Other more obvious etiologies for pain after a TKA include extensor mechanism disruption and periprosthetic fractures, which are covered in detail in Chapter 11, Chapter 14 , respectively.



BOX 15.1

Intrinsic Causes Leading to a Painful Total Knee Arthroplasty


Common



  • 1.

    Infection


  • 2.

    Instability



    • a.

      Coronal plane


    • b.

      Sagittal plane



      • i.

        Flexion instability


      • ii.

        Mid-flexion


      • iii.

        Extension



    • c.

      Global



  • 3.

    Loosening



    • a.

      Aseptic


    • b.

      Septic



  • 4.

    Periprosthetic fracture



    • a.

      Femur


    • b.

      Patella


    • c.

      Tibia



  • 5.

    Arthrofibrosis



    • a.

      Flexion contracture


    • b.

      Extension contracture


    • c.

      Global arthrofibrosis



  • 6.

    Patella



    • a.

      Unresurfaced patella


    • b.

      Lateral facet overhang


    • c.

      Patellar maltracking and instability



  • 7.

    Polyethylene wear


  • 8.

    Osteolysis


  • 9.

    Component malalignment



    • a.

      Coronal plane


    • b.

      Sagittal plane


    • c.

      Axial/rotational



  • 10.

    Extensor mechanism disruption



    • a.

      Patellar tendon rupture


    • b.

      Quadriceps tendon rupture




Uncommon



  • 1.

    Heterotopic ossification


  • 2.

    Soft tissue pathology



    • a.

      Snapping popliteus


    • b.

      Patellar clunk



  • 3.

    Metal sensitivity


  • 4.

    Recurrent hemarthrosis




BOX 15.2

Extrinsic Causes Leading to a Painful Total Knee Arthroplasty




  • 1.

    Hip pathology



    • a.

      Osteoarthritis


    • b.

      Avascular necrosis


    • c.

      Fracture



  • 2.

    Spine pathology



    • a.

      Spinal stenosis


    • b.

      Disk herniation


    • c.

      Lumbar radiculopathy



  • 3.

    Vascular



    • a.

      Claudication


    • b.

      Peripheral neuropathy


    • c.

      Deep vein thrombosis



  • 4.

    Local soft-tissue pathology



    • a.

      Pes anserine bursitis


    • b.

      Iliotibial band syndrome


    • c.

      Patellofemoral maltracking



  • 5.

    Neuropathic



    • a.

      Complex regional pain syndrome


    • b.

      Peripheral neuropathy


    • c.

      Fibromyalgia


    • d.

      Neuroma



  • 6.

    Psychiatric


  • 7.

    Lack of preoperative degenerative change




Prosthetic Joint Infection


PJI should always be included in the differential diagnosis when evaluating a painful TKA, especially in the first few months following the index procedure. PJI is the most common mode of failure within 2 years of the primary TKA, with an incidence between 1% and 2%. PJI is associated with high economic burden and significantly decreased patient satisfaction scores. A 2012 study by Kurtz et al. highlighted the financial impacts of infected hip and knee arthroplasty surgeries, expected to exceed $1.62 billion dollars by the year 2020. The workup of PJI begins with a thorough history and physical examination. PJI can present as an acute postoperative infection, chronic infection, or acute hematogenous infection in an otherwise well-functioning prior TKA. Persistent wound drainage at the time of index arthroplasty, presence of a sinus tract, erythema, painful effusion, and restricted ROM at evaluation can point to an infectious etiology. , However, sometimes the diagnosis of a PJI may not be obvious and requires further diagnostic workup and confirmation.


Radiographic analysis in a suspected septic prosthetic joint can be subtle and nonspecific. Plain film findings may demonstrate periprosthetic radiolucent lines suggestive of loosening. These may be present in both cemented or cementless components but do not definitively indicate infection in the absence of other clinical signs. CT, magnetic resonance imaging (MRI), and nuclear medicine imaging are not routinely used for the diagnosis of a PJI. The diagnosis and management of PJI will be covered, in depth, in another chapter. Here, we will discuss current workup practices for prosthetic joint infection briefly, as it is a major cause of ongoing pain in TKA.


The diagnosis for a PJI is based on clinical and diagnostic criteria established by the Musculoskeletal Infection Society in 2011, which was modified in 2013 at the International Consensus Meeting on Surgical Site and Periprosthetic Joint Infection. , These criteria have been further updated by Parvizi et al. to include the use of newer advanced diagnostic tests for the identification of PJI. When evaluating for a PJI, the initial laboratory workup should consist of serum erythrocyte sedimentation rate and C-reactive protein along with an aspiration of the knee for synovial fluid analysis. More recent tests have been introduced, such as the alpha-defensin test and next-generation DNA sequencing techniques, to provide additional data for the diagnosis of PJI. Chapter 26 will cover prosthetic joint infection and its diagnosis and management in greater detail.


Instability


In one study, instability accounted for approximately 20% of failed primary TKA cases progressing to revision surgery. Revisions for instability are done more frequently in younger patients and females; therefore; they should be included in the differential diagnosis in this demographic group. There are several causes of instability following primary TKA leading to pain and dissatisfaction, including alteration of the native joint line, an incompetent posterior cruciate ligament (PCL) in a cruciate-retaining TKA, mismatch in the flexion and extension gaps, malalignment, loss of integrity of the medial and/or lateral soft-tissue structures, and extensor mechanism dysfunction. Patients with instability can present with various symptoms of discomfort and pain that may not be well localized. Often, they have recurrent effusions, difficulty with getting out of a seated position, and/or difficulty with stair climbing. Patients can present with pain during both activities and at rest. Pain with weight bearing typically implies loosening, malalignment, or instability. Pain at rest can also be due to tight flexion or extension gaps, impingement of soft tissues, component malposition leading to increased strain on the soft-tissue sleeve, or infection. Patients with instability often complain of the knee “not feeling right” despite normal-appearing radiographic findings. If the diagnosis of instability is suspected based on the history, then a physical exam along with radiographic evaluation to determine implant type, level of constraint, fixation mode, and implant alignment in all planes can help confirm the diagnosis.


The pathomechanics leading to instability is often multifactorial and can involve implant malposition in coronal, axial, and/or sagittal planes; ligamentous insufficiency or rupture; extensor mechanism deficiency; or a mismatch of the flexion and extension gaps. Instability can also present late in patients with well-functioning total knees for months or years postoperatively due to polyethylene wear or laxity associated with attrition of collateral or posterior cruciate ligaments.


During the physical exam, ligamentous structures along with the soft-tissue sleeve in the coronal, axial, and sagittal planes need to be evaluated. Range of motion, along with the patient’s gait and ability to get out of a chair, also needs to be examined. The patient should be evaluated for overall limb alignment and observation of any gait abnormalities, such as varus or valgus instability or a recurvatum deformity. Soft tissues should also be palpated to identify any effusion and exact area of pain generation that can help identify irritation in the synovium, soft-tissue impingement due to implant overhang, or pes bursitis. Diffuse soft-tissue pain can also be a symptom of instability in a well-aligned TKA.


Flexion instability occurs when the flexion gap is greater than the extension gap. This phenomenon is thought to be due to design of the femoral component in the sagittal plane, anterior medial collateral ligament attenuation, and the geometry of the tibiofemoral joint. Flexion instability can occur in knees that are well aligned with well-fixed implants. The knee can be stable in extension, but patients often sense an uneasy feeling of instability with activities of daily living. Additionally, patients may complain of pain and tenderness in the surrounding soft tissues about the knee, along with recurrent effusions ( Fig. 15.2 ). Stability of the knee in the sagittal and coronal plane should be checked in extension followed by subsequent increasing increments of flexion ( ). Flexion instability can be tested with the anterior and posterior drawer test. Flexion instability in a cruciate-retaining knee may demonstrate posterior translation of the tibia “posterior sag sign” indicating the presence of an attenuated or incompetent PCL.




Fig. 15.2


A 66-year-old morbidly obese patient presenting with a painful total knee arthroplasty (TKA) 12 years following the index TKA with radiographs demonstrating loosening of the cemented tibial baseplate.


Video 15.1A 60-year-old male patient presenting with painful total knee arthroplasty (TKA) with flexion instability due to an incompetent posterior cruciate ligament in a cruciate-retaining TKA.


Mid-flexion instability is a phenomenon that can be seen on physical exam when a knee is balanced in full extension and at 90 degrees of flexion. However, the instability occurs between 40 and 70 degrees during the swing phase of gait. , Mid-flexion instability can occur when a large distal femoral resection is made to correct for preoperative flexion contracture. Following an excessive distal femoral resection, the knee can be stable in extension due to a tight posterior capsule. However, it becomes unstable in flexion due to the elevation in the joint line causing the collaterals to become lax in mid-flexion. This can be avoided by removal of the posterior osteophytes and posterior capsular release prior to additional resection of the distal femur in order to obtain full extension.


Extension instability will occur when the extension gap is larger than the flexion gap and may present with an obvious or subtle recurvatum deformity. Instability in extension can be symmetric or asymmetric. When symmetric, it is often caused by over-resection of bone from the distal femur and results in implants not adequately filling the extension space compared with the flexion gap. Using a thicker polyethylene to correct the extension gap due to excessive resection of the distal femur can result in making the flexion gap too tight. Asymmetric extension instability is much more common and can be caused by significant preoperative angular deformity of the knee with subsequent postoperative ligamentous asymmetry following TKA. This occurs with undercorrection of the varus or valgus knee, with medial ligamentous structures remaining tight in the varus knee and lateral ligaments remaining tight in the valgus knee.


Aseptic Loosening


Sharkey et al. found aseptic loosening to be the most common etiology of failure following primary TKA, leading to revision surgery comprising approximately 40% of all TKA revisions at their institution. Large registry studies from England and Sweden have also identified aseptic loosening to be one of the most common causes of failure leading to TKA revision. , There are few large-scale studies demonstrating links between patient factors and aseptic loosening of TKA. Patients with a body mass index (BMI) >50 showed no increase in revision rates for aseptic loosening when compared with their nonobese counterparts. However, multiple other studies have found higher rates of aseptic loosening in patients with a BMI >35. Patients under the age of 50 years at the time of the index TKA have also demonstrated higher failure rates due to aseptic loosening compared with individuals older than 65 years. In obese patients, it can sometimes be challenging to obtain the ideal cement mantle due to poor bony hemostasis, leading to inadequate canal preparation for cement pressurization with resultant radiolucent lines. Cement technique has been found to be optimum when 3 to 4 mm of cement interdigitation occurs into the trabecular bone.


Varus tibial component alignment of greater than 3 degrees has demonstrated increased rates of failure. An increase in radiolucent lines has also been shown in tibial components placed in >2 degrees of tibial varus. However, a recent study by Young et al. found no midterm functional or radiographic differences between TKAs with mechanical alignment or kinematic alignment. The initial presentation of a patient with aseptic loosening is usually pain described primarily as startup pain, which occurs at the onset of weight bearing. It is important to correlate the patient’s symptoms with radiographic findings to confirm the diagnosis of aseptic loosening. In most cases with aseptic loosening of a cemented TKA, radiographs may demonstrate progressive radiolucent lines, implant subsidence, large osteolytic defects, or catastrophic collapse (see Fig. 15.2 ). In some cases, it may be difficult to confirm the diagnosis of aseptic loosening, especially if the implant has debonded from the cement mantle but the cement bone interface is still intact ( Fig. 15.3 ). In these cases, the diagnosis can be difficult to confirm with radiographic studies and bone scans may be of some help. However, in large part, the surgeon has to rely on the history, physical exam, and process of elimination with a thorough diagnostic workup. With aseptic failure of cementless TKA, confirming the diagnosis can also be difficult when obvious radiographic findings such as progressive radiolucent lines, osteolysis, or implant subsidence are not visible. In cases in which the radiographic studies are not obvious for aseptic loosening, bone scans can also be helpful along with a thorough workup of the differential diagnosis.


Jun 18, 2022 | Posted by in ORTHOPEDIC | Comments Off on Painful Total Knee Arthroplasty Workup
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