Visual Identification of Avascular Necrosis During Surgery
Avascular necrosis (AVN) can sometimes be identified during surgery through visual inspection, but this method is unreliable and should not be the primary diagnostic approach. Intraoperative findings such as absence of punctate bleeding from bone are used as indicators, but these visual assessments have significant limitations in distinguishing true irreversible bone death from reversible AVN 1.
Intraoperative Visual Findings
During surgery, surgeons typically assess for AVN by looking for:
- Absence of punctate bleeding from the bone surface when drilled or cut
- Color changes in the bone (pale, yellowish, or gray appearance versus healthy pink/red bone)
- Texture abnormalities (soft, crumbly, or abnormally hard bone)
However, the reliability of these visual findings is problematic. In a systematic review of scaphoid AVN, 308 out of 356 patients (86.5%) with no intraoperative punctate bleeding eventually healed, demonstrating that absence of bleeding does not reliably predict irreversible bone death 1. This means visual inspection alone has poor specificity and cannot definitively distinguish between reversible AVN and true irreversible bone death.
Critical Limitations of Visual Assessment
The fundamental problem is that all current diagnostic methods, including intraoperative visual inspection, conflate AVN with irreversible bone death despite their distinct pathologies and prognoses 1. Visual examination during surgery cannot:
- Determine the extent of necrotic volume (critical for prognosis, as >30% necrotic volume leads to collapse in 46-83% of cases) 2
- Assess early-stage AVN before structural changes occur
- Differentiate between temporary ischemia and permanent necrosis
- Predict which cases will progress to articular collapse
Proper Diagnostic Approach
MRI without IV contrast remains the gold standard for AVN diagnosis and should be obtained preoperatively when AVN is suspected 2. The ACR Appropriateness Criteria (2022) clearly establish that:
- Radiography is the initial imaging study for suspected osteonecrosis 2
- MRI without contrast is the definitive next step when radiographs are normal or suspicious 2
- CT without contrast is valuable for surgical planning to show location and extent of articular collapse 2
For preoperative planning before procedures like core decompression or arthroplasty, imaging is essential because visual inspection during surgery cannot provide the quantitative assessment needed. Studies show that 21% of cases staged as early AVN (ARCO stage I or II) on radiographs were actually stage III with articular collapse on preoperative CT 2.
Clinical Implications
Do not rely on intraoperative visual assessment alone to diagnose or stage AVN. If AVN is suspected based on patient risk factors (corticosteroid use, alcohol, trauma, HIV, chemotherapy, radiation) 2, obtain appropriate imaging preoperatively. The pathophysiology involves ischemia-driven osteocyte death that precedes visible structural changes 3, meaning early AVN is invisible to the naked eye during surgery.
When performing procedures on bones at risk for AVN, the absence of bleeding may indicate compromised vascularity but does not confirm irreversible necrosis—many such cases still heal 1. Conversely, the presence of some bleeding does not exclude AVN.