6 - Delayed Union, Nonunion, Malunion Flashcards
Anatomy of long bones - Epiphyseal complex
o Secondary ossification center
o Adjacent to metaphysis
o Separated from metaphysis by growth plate (physis)
Anatomy of long bones - Metaphysis
o Interposed between epiphyseal complex and diaphysis
o Trabeculae remodeling
Anatomy of long bones - diaphysis
o Long central aspect of bone
o Contains primary growth center
Anatomy of long bones - physis
o AKA epiphyseal plate
o Cartilaginous disk separating epiphysis and metaphysis
o Pediatric and adolescent trauma
o Allows for uniform linear growth
Osseous blood supply: Adult long bone has 3 main afferent blood supplies
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Principal nutrient artery
o Penetrates cortex through a foramen direct to medullary canal
o Location of foramen dependent on specific bone
o Forms ascending and descending arteries providing main blood supply to diaphysis
Metaphyseal-epiphyseal arteries
o Penetrate cortex at both metaphyses
o Anastomose with the medullary arteries
o Can compensate for damaged nutrient artery
Periosteal arteries
o Supply the outer 1/4 to 1/3 of bone
Fracture healing
- Occurs secondary to cascade of cellular events
- Dependent on environmental forces surrounding the fracture
Bone heals via o Secondary (indirect or callus) healing o Primary (direct) healing
Secondary bone healing
- Inflammatory phase
- Reparative (proliferative phase)
- Remodeling phase
Inflammatory phase of secondary bone healing
o Begins immediately after the injury
o Hematoma forms at the injury site
o Mast cells, PMNs, macrophages, lysosomal enzymes present
o Pain and swelling occurs to splint the area and to immobilize the fracture site
o Typically lasts 3 to 4 days
Reparative (proliferative) phase of secondary bone healing
o Fibrin scaffold provided during inflammatory phase is replaced with mesenchymal cells which produce granulation tissue
o Callus formation begins as islands of cartilage, osteoid cells form in granulation tissue
o At 7-10 days, chondrocytes produce matrix that spans fracture site allowing stabilization
o The cartilage is gradually replaced by bone during enchondral ossification
o Summary – “Splinting phase” to stabilize the fracture and begin to form new bone
Remodeling phase of secondary bone healing
o Begins after fracture site has been successfully bridged
o Osteoclastic resorption of woven bone and replaced with lamellar bone
- Lines of stress
- Medullary Canal reconstruction
- Pre-injury bone morphology
- Depending on severity of fracture and patient factors, stage may last for years
o How long does a fracture take to heal? Healthy individual = 6-8 weeks, but can take up to a year or 18 months to be at 100% (completely healed)
Primary bone healing
In 1958, AO formulated four basic principles, which have become the guidelines for internal fixation: (this is the “gold standard” principle for internal fixation)
o Anatomic Reduction (restore good anatomic alignment, interface of fracture lines up)
o Rigid/Stable Fixation
o Preservation of blood supply
o Early mobilization (depends on patient, if otherwise healthy, NWB for 6 weeks post-op the walking boot for an additional 2 weeks before progressing out of boot) – as early as possible based on the patient
What does primary bone healing “skip”?
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PRIMARY BONE HEALING Bypasses the fibrocartilaginous callus phase***
Mechanism of priarmy boen healing
Heals through Haversian remodeling
o Reduced/stable fracture fragments –> capillary budding from haversian canals –> bridging of fracture interface through cutting cones
o Cutting cones
- Leading tip of osteoclasts that phagocytose osteoid at end of Haversian canals
- Cutting cones cross fracture site followed by capillary budding and osteoblasts to lay down new bone
Factors that determine rate of bone healing
- Specific bone involved and location of fracture on the bone
- Severity of fracture and method utilized to treat fracture
- Weightbearing status, soft tissue damage
- Vascularity surrounding fracture
- Age of patient, patient compliance, tobacco usage, comorbid conditions
Complications of bone healing
- Malunion
- Delayed union
- Nonunion
Malunion
- Non-anatomical alignment at fracture site*** (You can get angulation, shortening, rotation, translation)
- Is a malunion always a bad thing? Not always. You need to consider who your patient is and what their long-term goal is. Sometimes you just need to keep a limb and be able to transfer, not full function.
Treatment for malunion
o Malunion may be tolerated well and no further treatment necessary
o Bracing, orthotics, lifts
o Surgical intervention may be necessary to realign fracture site
Delayed union
Any fracture that has not healed in a reasonable period of time (Not a true number of days on a delayed union, need to use clinical judgement)
Evaluation of patient with suspected delayed union:
o Serial Radiographs – continue taking radiographs if you are not seeing healing
- Presence of unchanged irritation callus (every 2-3 weeks)
- Persistent fracture cleft
o Persistent edema and pain (still in the inflammatory phase)
o Metabolic state/co-morbidities
- Diabetes (HbA1c, blood glucose, diet, exercise)
- Nutritional status (albumin, metabolics)
- Vitamin D (supplement patients with vitamin D while treating for fracture)
- Bone density (doesn’t get this for everyone, but does always supplement vit. D)
Treatment of malunion
o Continued non-weight bearing and immobilization
o Initiate Electrical Bone Growth Stimulation (EBGS) – can be very helpful - For private insurance, need to be able to demonstrate 90 days of treatment
Nonunion
- Failure to achieve stable fracture healing after 8-9 months of treatment
- Evaluation of patients with suspected nonunion:
o Follow same serial radiographs as would with delayed union - Reasons for nonunion
o Distraction
o Poor reduction
o Soft tissue interposition
o Infection
o Vascular compromise
o Excessive motion at fracture site
Viable nonunion
HYPERTROPHIC
3 types (based on callus appearance) o Hypertrophic (Exuberant callus, “Elephant Foot”) o Slightly Hypertrophic (Less exuberant callus, “Horses hoof") o Oligotrophic (No callus formation, usually due to lack of reduction and distraction, Can be difficult to differentiate from non-viable non-union, Bone scans (absent of “cold cleft”) and serial radiographs reveal viable, vascular bone ends)
Viable nonunions have OSTEOGENIC capability
Treatment of viable non-union
o Prolonged immobilization
o Electrical Bone Stimulation
o Surgical
Contraindications to electrical bone stimulation
- Gap greater than 1/2 the diameter of the bone involved
- Pseudoarthritis
Surgical treatment options
- Remove interposed tissue
- Revise unstable hardware
- Bone grafting (possibly needed)
Non-viable nonunion
ATROPHIC
4 types
- Dystrophic - Intermediate fragment has healed to
only one side of fracture – only viable
vascular supply on one side of fragment “Torsional Wedge”
- Necrotic - Comminuted fracture
- Defect - Gap present due to bone loss
- Atrophic - End result of one of the other three non-viable non-unions, Pseudoarthrosis with osteogenic reabsorption
Characteristics of non-viable nonunion
- Considered avascular
- Lacks stability and osteogenic capability
