History and Diagnostic Testing

Introduction

Since its popularization by Sir John Charnley in 1962 and subsequent globalization, total hip arthroplasty (THA) has become recognized as one of the most successful surgical procedures in all of medicine, providing lasting pain relief and functional restoration. Of the several complications associated with joint arthroplasty operations, none is more challenging than periprosthetic joint infection (PJI).

PJI is by no means a new obstacle for joint replacement surgeons. Deep postoperative wound infections have complicated total joint replacement operations since the birth of the procedure. In the late 1960s and early 1970s, the incidence of infection after primary THA was as high as 7% to 10%. After institution of routine prophylactic antibiotics for surgery in the mid-1970s, the infection rate diminished drastically and remained relatively stable at 1.0% to 2.5% ( Fig.74.1 ). Implementation of modern surgical concepts, such as unidirectional laminar flow, ultraviolet lights, body exhaust suits, patient barrier draping, decreased operating room traffic, and fewer persons involved in each case, led to infection rates of 0.5% to 1.0% for THA and 1.0% to 2.0% for total knee arthroplasty (TKA).

Management of infected joint arthroplasty is a challenge for the orthopedic surgeon, infectious disease physician, microbiologist, anesthesiologist, and patient ( Fig. 74.2 ). A major difficulty when dealing with an infected arthroplasty is making a rapid and accurate diagnosis. This may ultimately dictate the success of ensuing treatment strategies. Historically, physicians have used erratic diagnostic criteria when deciding on whether a failed arthroplasty is septic or aseptic. Most physicians use some combination of clinical examination, joint aspirate white blood cell (WBC) count and differential, cultures, laboratory markers such as the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) level, and radiographic evidence to make this diagnosis. Due to the high numbers of false-positive and false-negative results, none of these tests can be relied on alone for the diagnosis of PJI, leading to an ongoing debate about which combination of criteria is ideal.

In this chapter, we discuss the history and physical examination of patients with suspected PJI, review the diagnostic tests available, propose a standardized definition for PJI, and consider future endeavors in diagnostic testing.

Examination and Imaging

Similar to the diagnostic algorithms in all other medical specialties, when evaluating a patient for possible PJI, the first step is obtaining a thorough history followed by a complete physical examination. The history should encompass the preoperative, intraoperative, and postoperative periods.

Preoperative comorbidities are well-known risk factors for PJI. One group examining more than 80,000 Medicare patients concluded that (in decreasing order of significance) congestive heart failure, chronic pulmonary disease, preoperative anemia, and diabetes were the most common independent risk factors for PJI, with obesity and renal disease providing additional risk factors.

In addition to comorbidities, physicians often ask patients about recent dental procedures. The presumption is that invasive dental work may be a considerable risk factor for PJI. However, several orthopedic surgeons, infectious disease specialists, and dentists now think that dental procedures are not a significant cause of PJI and that routine antibiotic prophylaxis may not be warranted in all procedures. Nonetheless, the American Academy of Orthopaedic Surgeons (AAOS) recommends that in patients with previous joint replacement (especially those who are immunocompromised), antibiotic prophylaxis should be considered before undergoing invasive procedures such as dental work.

Several studies, including one by Pulido and colleagues, have shown that intraoperative blood loss with allogenic transfusion, bilateral arthroplasty, increased operative times, and evidence of previous operations on an extremity are important variables in predicting the risk of PJI. Patients should be asked about a history of trauma, injury, falls, drainage, hematoma formation, or wound dehiscence, because these events may point to the need for a thorough infection workup.

An acute onset of continuous pain may be the only hallmark symptom offered by a patient during the examination. Aside from obvious purulent drainage emitting from the wound or a sinus tract, local signs include joint inflammation, erythema, swelling or effusion, and warmth and tenderness to palpation. Systemic signs, including fevers, chills, and night sweats, may or may not be identified. These systemic signs may not be reliable in the immediate postoperative period; for example, one study showed that development of pyrexia was a very poor indicator of PJI. As is the case with most diagnoses, the history and physical examination can provide valuable information and therapeutic guidance, but further diagnostic testing is usually required.