CT and PCT in Orthopedic Case Sheet Examination
CT (Computed Tomography) in Orthopedic Examination
CT is the gold standard imaging modality for detailed osseous evaluation in orthopedic cases, particularly for fracture characterization, surgical planning, and assessment of bone destruction. 1
Primary Indications for CT in Orthopedics
Fracture assessment: CT is the first-line study after radiographs to determine extent, displacement, comminution, intra-articular extension, and classification of complex fractures, especially in subtalar, calcaneal, and talar injuries. 1
Preoperative planning: CT provides superior osseous detail for surgical planning in high-impact polytrauma or complex comminuted injuries where multiplanar imaging is essential. 1
Bone tumor evaluation: CT excels at demonstrating cortical destruction, matrix mineralization patterns, and subtle osseous changes that may be missed on radiographs, particularly in osteosarcomas where it detects matrix mineralization in 85% of cases. 1
Hardware complications: CT with metal artifact reduction protocols evaluates hardware position, integrity, component alignment, periprosthetic lucency, osteolysis, and surrounding bone stock in post-arthroplasty patients. 1
When to Order CT
Order CT immediately after radiographs show fractures requiring surgical intervention, particularly in ankle, tibial plateau, and calcaneal fractures where it significantly impacts surgical approach selection. 1, 2
Use CT for indeterminate bone lesions on radiographs, especially when mineralized matrix is present or cortical involvement needs assessment. 1
CT is essential when radiographs demonstrate bone destruction, spinal deformity, or hardware-related complications. 1
CT Limitations
CT has limited soft tissue contrast resolution compared to MRI, making it suboptimal for evaluating rotator cuff tears, ligamentous injuries, or marrow edema without contrast enhancement. 1
Metal artifact can degrade image quality in patients with hardware, though modern metal artifact reduction techniques have significantly improved evaluation. 1, 3
PCT (Procalcitonin) in Orthopedic Examination
PCT is a host-response biomarker used to assess the likelihood of bacterial infection and guide antibiotic stewardship, but it should NOT be used as a standalone diagnostic marker in orthopedic infections. 4
Role of PCT in Orthopedic Infections
Infection screening: PCT helps differentiate bacterial from non-bacterial infections when combined with clinical assessment, particularly in suspected osteomyelitis or periprosthetic joint infections. 4
Antibiotic stewardship: Low PCT levels (<0.25 ng/mL) help rule out bacterial infection in patients with low pretest probability and low-risk general condition, potentially avoiding unnecessary antibiotics. 4
Treatment monitoring: Serial PCT measurements track infection resolution and guide decisions regarding early termination of antibiotic treatment when levels decline appropriately. 4
Critical Limitations in Orthopedics
Not a standalone test: PCT must be combined with inflammatory markers (ESR, CRP), complete blood count, clinical assessment, and imaging findings—never use PCT alone to diagnose orthopedic infections. 3, 4
False positives: PCT can be elevated in non-infectious conditions including trauma, surgery, and certain malignancies (particularly medullary thyroid cancer), making it unreliable in these contexts. 5
Timing matters: In high-risk patients or high pretest probability for infection, empiric antibiotic treatment is mandatory regardless of PCT levels—do not delay treatment waiting for PCT results. 4
Practical Algorithm for PCT Use
Check PCT alongside ESR, CRP, and CBC when bacterial infection is suspected but not clinically obvious. 3, 4
If PCT <0.25 ng/mL AND low clinical suspicion: consider withholding antibiotics and monitoring closely. 4
If PCT >0.5 ng/mL AND moderate-to-high clinical suspicion: initiate antibiotics and obtain tissue cultures. 4
In post-surgical orthopedic patients with hardware: PCT is less reliable; prioritize MRI with contrast, joint aspiration with culture, and surgical consultation over PCT levels. 3
Integration into Orthopedic Case Sheets
Document CT findings with specific attention to: fracture pattern and classification, cortical integrity, hardware position and lucency, soft tissue extension, and bone quality for surgical planning. 1
Document PCT values with context: include timing relative to surgery/trauma, concurrent inflammatory markers, clinical probability of infection, and whether antibiotics were started empirically before PCT resulted. 4, 5