properties.
• Oligotrophic: no obvious (or only a small amount) callus changes at the fracture site from bone resorption.
• Atrophic: minimal/no callus and bone edges typically become sclerotic-must address biology (see ▶Fig. 7.2 for clinical example).
d. Common fracture healing scores—RUST score:
i. “Radiographic union scale in tibial” fractures.
ii. Callus is evaluated at each of the four cortices on standard anteroposterior and lateral radiographs.
Fig. 7.1 Weber–Cech classification of nonunions.
Fig. 7.2 (a, b) Anteroposterior and lateral humerus views of a 77-year-old female with an atrophic nonunion 8 months following the closed treatment with a fracture brace. Note that the bone edges appear thinned with no callus seen. The metabolic workup was negative. (c, d) Seven months after nonunion repair with rigid fixation and autogenous bone grafting demonstrating healing.
iii Each of the four cortices is scored between 1 and 3 and then added together for a total score of 4 to 12.
• 1 point = no callus.
• 2 points = visible fracture line with callus.
• 3 points = no fracture line with bridging callus.
iv. A score of 9 or higher is considered a radiographically healed fracture (must match with clinical findings).
• Food and Drug Administration definition of nonunion: failure of fracture union by 9 months post injury. Clinicians will commonly use a time frame of 6 months assuming the fracture is reasonably well aligned and stable with no gaps > 1 cm. Absence of progressive signs of healing on successive radiographs can also be an indicator for nonunion.
2. Other imaging modalities:
a. Computed tomography:
i. One study demonstrated a significant false positive rate for nonunion.
ii. Helpful to evaluate three-dimensional anatomy and look at the location and volume of callus, if present.
iii. Gives an estimate of bone density and helps locate areas for future fixation if revision surgery is planned.
iv. The image is somewhat affected by local hardware but this can be minimized with mono-energy techniques.
b. Ultrasound:
i. Has been shown to have very good sensitivity and specificity for tibia fracture healing.
ii. User dependent.
iii. Advantage of being able to adjust the beam to work around hardware but requires an experienced technician and radiologist to interpret the images.
iv. Advantage of being a dynamic exam and so could potentially visualize motion at a nonunion site.
c. Fluoroscopy:
i. Beneficial when evaluating for pathologic motion.
ii. Ability to adjust the limb in real time to obtain oblique or special images more accurately.
iii. Images are not as crisp as standard X-rays.
d. Bone scan:
i. Aids in determining vascularity and ability of a fracture to heal.
ii. Tagged white blood cell (or indium) scans are of limited value and may not be cost effective in evaluating for infection as a source of nonunion.
e. Magnetic resonance imaging:
i. Can be particularly helpful in cases of infection.
ii. More susceptible to artifact from previous hardware (especially stainless steel).
D. Laboratory testing
1. Concern for infection:
a. Infection is high on the list of differential diagnoses when searching for the etiology of a nonunion.
b. Important to rule out infection prior to choosing a treatment plan.
c. Lab testing can be helpful when determining whether an infection is present.
d. Preoperatively, common laboratory values to evaluate are:
i. Complete blood count (CBC)—often normal but may be elevated in acute osteomyelitis.
ii. Erythrocyte sedimentation rate (ESR)—tends to rise and fall more slowly.
• Elevation within days of insult (injury, inflammation, or infection).
• Normalization may take up to several weeks after the insult is removed.
iii C-reactive protein (CRP)—tends to rise and fall quickly.
• Elevation can be observed within 4 to 6 hours of the insult.
• Reaches maximum value within 24 to 48 hours.
• Resolution within days after the insult is removed.
iv. Both ESR and CRP may be normal or only mildly elevated in the setting of chronic osteomyelitis.
v. ESR and CRP should be significantly elevated if acute osteomyelitis is present. The absolute values may be less important than the trend toward normal as treatment progresses appropriately.
e. If there is a pseudoarthrosis or fluid collection adjacent to the fracture site, it is possible to aspirate the area and send it for cell count, differential, and culture with gram stain.
f. Intraoperative tissue samples should also be sent for pathology and culture if infection is considered in the differential. If possible, have the patient discontinue any current antibiotics approximately 5 days prior to the surgery and wait on preoperative antibiotics until after cultures are obtained. This should increase the positive intraoperative culture yield.
2. Nutritional, metabolic, and endocrine:
a. If there is clinical concern for nutritional deficiency, metabolic derangement, or endocrine abnormality which may be contributory, lab testing can often aid the diagnosis.
b. Consultation and referral to general medicine or endocrinology is reasonable if clinical concern exists.
c. Typical labs include infection (CBC, ESR, CRP), Vitamin D (most common associated endocrine abnormality), and nutrition (albumin,
