Читать книгу Synopsis of Orthopaedic Trauma Management - Brian H. Mullis - Страница 55

Factors leading to nonunion can generally be grouped into two categories: biologic and mechanical. The assessment is a gathering of data on known factors which may have contributed to a failure of the biologic and mechanical success of the fracture healing.

A. History

1. Common presenting symptoms:

a. Pain at the fracture site (increased with weightbearing).

b. Subjective feelings of instability in the affected bone.

c. Symptoms (or history of symptoms) associated with infection: erythema, swelling, drainage, fevers, chills.

2. The data of patient-specific risk factors is obtained after completing a thorough history with each individual patient.

a. Demographic/patient directed risk factors:

i. Smoking has negative effects on many pathways necessary for bone healing.

ii. Nicotine diminishes arterial blood flow.

iii. Nonsteroidal anti-inflammatory drugs negatively affect the pathways responsible for bone healing.

iv. In some studies, female patients and older patients had an increased rate of nonunion.

v. Poor nutrition is associated with nonunion.

b. Associated comorbidities:

i. Metabolic and endocrine dysfunction can impair fracture healing.

ii. Diseases that negatively affect vascularity, such as diabetes mellitus and other vascular disorders, can impair fracture healing.

3. Fracture-dependent risk factors are independent of the patient; each practitioner must have an adequate baseline knowledge of previous reported literature on fracture healing.

a. Certain bone-specific anatomy is associated with nonunion, often due to poor vascularity in these areas. Examples include:

i. Open tibia fractures.

ii. Intracapsular hip fractures.

iii. Talar neck fractures.

iv. Proximal metadiaphyseal fifth metatarsal fractures.

b. Open fractures and bone loss are associated with increased nonunion rates. The higher the open fracture type, the greater is the risk of nonunion (and infection).

4. Risk factors from previous care:

These can be investigated using previous operative reports and medical documentation from the original perioperative period.

a. Soft tissue destruction impairs the vascularity at the fracture site.

i. Traumatic or surgical disruption—this can be due to vascular damage or due to excessive soft tissue stripping either from the injury or from a surgical procedure which was not biologically friendly.

b. Interposed soft tissue at the fracture site if the fracture was not opened and debrided.

c. History of infection at the fracture site:

i. Previously undiagnosed infection.

ii. Important to determine if the patient had cellulitis, wound drainage, or other concerning symptoms after the original treatment.

d. Improper fixation—too much or too little strain at the fracture site (refer to Chapter 4, Biomechanics of Internal Fracture Fixation, for additional details).

i. Doctor needs to critically assess the method of fixation and correlate it to the desired mode of healing at the fracture site.

ii. Too rigid fixation in a zone of comminution will lead to a lack of callus formation.

iii. Too flexible or inadequate fixation may cause excess soft callus to form without eventual maturation to rigid callus.

e. Improper fixation—residual fracture gap, especially if > 1 cm.

B. Physical exam

1. Inspection:

a. Deformity at the fracture site—look for alterations in length, alignment, and rotation. Note if deformity occurs with passive motion or only with active motion or weight bearing.

b. Current soft tissue envelope is very important in developing a treatment plan.

i. Ulceration.

ii. Open wounds.

iii. Exposed hardware.

iv. Damaged tissue.

c. Evidence of decreased vascularity to the region:

i. Previous scars.

ii. Thin or damaged skin.

iii. Atrophic or damaged muscle.

d. Evidence of vascular disease:

i. Varicosities.

ii. Cool limbs.

iii. Poor hair/nail growth.

iv. Chronic erythema of skin.

2. Palpation:

a. Tenderness at the fracture site.

b. Pathologic motion at the fracture site (should not have any detectable motion).

c. Palpable distal pulses indicate reliable overall vascularity.

d. Decreased sensation distal to the fracture site is a marker for neuropathy or nerve injury.

e. Evaluate motion at the joints above and below the nonunion site and test them both actively and passively.

3. Gait evaluation:

a. Observe for signs of muscle weakness:

i. Antalgic gait.

ii. Trendelenburg gait.

C. Imaging

1. Radiographs:

These are the mainstay of the assessment; it is important to obtain historical imaging if the patient has been treated at other facilities. Obtain full-length anteroposterior and lateral X-rays of the involved bone. Additional oblique or specialty views may be necessary depending on the location.

a. Expected results:

It is important to understand what to expect on an X-ray based on the previous method of fixation (refer to Chapter 1, Physiology of Fracture Healing, for additional information).

i. Primary bone healing—no callus.

ii. Secondary bone healing—callus formation.

b. General signs of nonunion:

i. Absence of bone bridging at the fracture site/persistent fracture line. Particularly the lack of progression on serial radiographs.

ii. Sclerotic edges at the fracture site.

iii. Implant loosening or breakage can be indicative of pathologic motion from a nonunion.

iv. Change in fracture alignment.

v. Typically painful for the patient.

c. General classification of nonunions:

It is important to have a good working knowledge of bone healing and the biomechanics of fracture repair.

i. Primarily mechanical issues.

ii. Primarily biologic issues.

iii. Combination of mechanical and biologic factors.

iv. Several classification schemes have been developed, however understanding the principles at play is the critical aspect as the treatment will be based on addressing the mechanical and biologic factors.

v. Weber–Cech System (▶Fig. 7.1a–c) uses the most common general descriptive breakdown based on radiographs.

• Hypertrophic: abundant callus often indicates reasonable fracture biology but improper mechanical 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, prealbumin, and total protein). Other labs to consider as more rare causes include the following: basic chemistry including calcium, magnesium, phosphorous, alkaline phosphatase, thyroid function tests, parathyroid hormone, iron studies, growth hormone, cortisol, and testosterone.

E. When to intervene operatively?

1. This is a difficult question to answer with a large subjective component; however, it is the most important decision on which all others are based.

2. Nonoperative treatment is always an option.

3. Ultimately, each case is unique and must be examined independently.

4. Several factors can help determine when to intervene:

a. How much does the malunion/nonunion impact the patient’s daily life?

b. How much patient function can you improve with surgery?

c. Is there a surgical option which can increase that function without exposing the patient to extreme risk?

d. Does the surgeon have the skills and equipment necessary to complete the operation and deal with any potential intraoperative complications, or should it be referred to a specialist?

e. Investigation of patient support system and motivation.