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
KNOW THIS
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”?
KNWO THIS
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
Treatment of non-viable nonuion
SRUGICAL - these patienst NEED surgery o Remove non-viable bone ends o Revise unstable hardware o Bone grafting o Autogenous preferred o Electrical Bone Stimulation o Internal or external fixation
Notes on bone graft
- When you go in surgically, you need to clean it out completely. At that point you may have bone loss and need bone grafting to restore shape or length of bone
- Autogenous preferred
External fixation
- Distraction
- Correction of limb deformity
- Maintaining reduction during staged procedure
- Compression
- In lieu of internal fixation
o Not everyone has the anatomy and bone quality to put plates and screws
o Infection (osteomyelitis) is a contraindication to internal fixation
Indivations for bone grafting
o Delayed unions o Non-unions o Pseudoarthroses o Osseous defects left after trauma, infection, tumors o Arthrodesis of joints o Congenital defects
Dr. Drown opinion - uses an allograft after all fusions
- Physiologic properties of bone grafts
Osteogenesis
o Formation of new bone by living cells
o Occurs in autografts
Osteoconduction (the “garden”)
o Ability to provide structural framework for ingrowth of vessels, osteoblasts and osteoprogenitor cells
Osteoinduction (what you put in the “garden” to make it grow)
o Ability to transform pluripotent stem cells in recipient bed into osteoblasts
o Bone morphogenic protein (BMPs)
o Platelet-derived growth factor (PDGF)
o Insulin-like growth factor I and II
o Fibroblast growth factors
o Epidermal growth factor
3 structural types of bone grafts
Cortical
o Dense, compact bone containing few viable cells
o Provides stability
o Can accept fixation hardware/devices
Cancellous
o Spongy bone
o Contains viable cells to stimulate osteogenesis –> rapid incorporation
o Does not provide any structural strength
Corticocancellous = BEST ONE TO USE
o **Hybrid between cortical and cancellous bone **
o Cortical bone provides stability
o Cancellous portion provides osteogenic, and osteoinductive abilities
o Found in body of calcaneus and iliac crest
o If you had a choice, you would ALWAYS chose corticocancellous
3 types of bone grafts
- Autograft (yourself)
- Allograft (donor)
- Xenograft (another species, not generally used)
Autograft
Originates in the recipient host, isograft – originates in an identical twin
Advantages: o Immunocompatibility o Osteoconductive o Osteoinductive o Osteogenic
Disadvantages:
o Potential for stress risers/fracture at donor site
o Creation of a second surgical wound
Allograft
- Also known as a homograft, originates in donor of same species
- Suitable for filling voids, useful if donor autograft is limited
Electrical bone growth stimulation
Based on electronegativity displayed during bone growth/healing: (we won’t get into physics)
o Due to stress-generated (piezoelectric) polarity
o Bone forming growth factors are upregulated in presence of electronegativity
o Exogenous application of electroneg. current may stimulate osteogenesis (form bone)
Indications for electrical bone growth stimulation
o Non-union and delayed union o Augment bone grafting o Failed Arthrodesis o Charcot Arthropathy o Avascular Necrosis o Acute Fractures (i.e. Jones Fracture)
Contraindications for electrical bone grwoth stimulation
o Isolated malunion
o Pseudoarthrosis
o Non-union site deficit larger than ½ the diameter of the bone
o Isolated usage in pathological fractures due to tumor or infection
Types of stimulators
Invasive Devices – Implantable
o Need to be removed
o No issues with patient compliance
Semi-Invasive – Percutaneous
Noninvasive
o Does not require additional surgery to remove
o Difficulties with patient compliance
Inductive coupling
o Known as “Pulse electromagnetic fields (PEMF)
o Coil is applied over fracture site
Combined magnetic field
o Coil is applied over fracture site
Capacitive coupling
o Two electrode discs applied on opposite sides of fracture site
Using a bone stimulator
Amount of time to wear stimulator depends on manufacturer - 20 minutes to over 10 hours a day
Multiple Bone Stimulator systems available o Exogen o OrthoPak o OrthoLogic o OsteoGen o Orthofix
Case study
- 76 year old male with extensive medial history including diabetes, renal disease, atrial fibrillation, hypertension, hyperlipidemia, ischemic cardiomyopathy, coronary artery disease with 11% ejection fraction.
- Had a talar fracture with bone deterioration. Not a surgical candidate.
What do you do?
o Build a custom brace to stabilize the joint and reduce pain give a bone stimulator to possibly help bone growth
SUMMARY OF IMPORTANT CONCEPTS
- Be familiar with the three types of bone healing complications
- Be familiar with the types of grafts covered in this lecture
- Know the properties associated with the types of grafts covered in this lecture
o Osteoconductive, osteoinductive, etc.
