Can bone tissue appear green in a living patient, and what pathological conditions cause this?

Green Bone: A Real but Benign Phenomenon

Yes, bone tissue can appear green in living patients, and this is most commonly caused by prior tetracycline antibiotic use, particularly minocycline, which incorporates into bone during periods of active mineralization and remodeling. 1, 2

Primary Etiology: Tetracycline Antibiotics

• Minocycline (used chronically for acne treatment) is the most common cause of green bone discoloration, staining bone dark green through incorporation into areas of active bone formation and mineralization. 1, 2
• Tetracycline itself produces yellow-green fluorescent bone rather than the darker green seen with minocycline. 1
• The discoloration occurs during childhood bone growth or during adult bone remodeling associated with fractures, tumors, or surgical sites—explaining why it appears unexpectedly during orbital, foot, and ankle surgeries. 1, 2

Clinical Presentation and Recognition

• Green bone is typically discovered intraoperatively as a surprising finding during routine orthopedic, orbital tumor excision, or fracture repair procedures. 1, 2
• The pigmentation may be visible through delicate, thin tissue as a dark blue-gray color before bone exposure. 2
• Patients often have healthy white dentition because tetracycline exposure after ages 8-10 years (after permanent tooth mineralization) does not affect teeth, leaving no external clues to the bone discoloration. 1
• The only consistent historical finding is prior tetracycline or minocycline use during adolescence for conditions like acne. 1, 2

Diagnostic Confirmation

• Ultraviolet light exposure (365 nm) causes the bone to fluoresce with bright yellow-green color, with fluorescence concentrated near haversian canals. 1
• Spectrophotometry reveals absorption at four wavelengths specific to tetracycline: 230,275,380, and 440 nm. 1
• Histologic examination demonstrates the fluorescence pattern and, critically, confirms absence of neoplasia or bone disease—this is a completely benign finding. 1, 2

Critical Clinical Algorithm

1. Obtain detailed medication history focusing on tetracycline-class antibiotics (tetracycline, minocycline, doxycycline) used during adolescence or young adulthood. 1, 2

2. If green bone is encountered intraoperatively without prior knowledge:

   • Send specimen for histologic examination to exclude malignancy. 1, 2
   • Request fluorescent microscopy and ultraviolet photography. 1
   • Perform spectrophotometry if diagnosis remains uncertain. 1

3. Document the finding but proceed with planned surgery—green bone has normal structural integrity and requires no special surgical technique modifications. 1, 2

Key Pitfalls to Avoid

• Do not assume malignancy based on unusual bone color alone—green bone from tetracycline is histologically benign and shows no evidence of bone disease. 1, 2
• Do not overlook the diagnosis in patients with white teeth—dental staining only occurs with tetracycline exposure before age 8-10 years, while bone can be affected by exposure during adolescence or even adulthood during remodeling. 1
• Always obtain tissue for histology when green bone is encountered without definitive clinical correlation (prior tetracycline use)—in the absence of clear history, biopsy is warranted to exclude other pathology. 2
• Recognize that green bone is rarely reported in foot and ankle literature compared to oral and orbital surgery, potentially leading to misdiagnosis or unnecessary concern. 2

Mechanism and Permanence

• Tetracycline antibiotics incorporate into bone similarly to bisphosphonates, binding to calcium in areas of active mineralization. 2
• Once mineralized, the discoloration is permanent—the drug remains incorporated in the bone matrix indefinitely. 1
• Fixation occurs predominantly during new bone growth (childhood) and bone remodeling (fracture healing, tumor-associated remodeling, surgical sites). 1