Approach to Nonunion

Courtesy: Dr Dheendhayalan, Ganga Hospital, Coimbatore, India

 

NON-UNION

• FDA definition of Non union: “Established when a minimum of 9 months have elapsed since fracture with no visible progressive signs of healing for 3 months”
• Dr. Mark Brinker: A fracture, in the opinion of the treating doctor, has no possibility of healing without any further intervention.
• Delayed Union : a fracture that has failed to achieve full bony union by 6 months after the injury
• Every fracture has its own time to heal..!

Perkin’s Rule : Dr. George Perkins
o Rough guide : Time taken for a Fracture to unite in adults (in weeks)
o Child – Time can be halved

INTERFRAGMENTARY STRAIN THEORY- STEPHAN PERREN (1975)

• The type & extent of tissue repair within a fracture gap depend on the amount of interfragmentary strain, or relative motion between the fracture fragments
• A tissue cannot survive in an environment that exceeds its strain tolerance
• Strain tolerance : Granulation tissue – 100%, Cartilage -10%, Bone – 2%
• Each tissue prepares the local environment biologically & mechanically for the next tissue
• Bone is a very aerobic tissue and requires an intact capillary network to survive ? Capillaries needs low strain
• To Obtain Union : Implant & callus together must control motion at the fracture gap such that capillaries can begin to cross.

ETIOLOGY

• Biologic Etiologies Mechanical Etiologies
• Local : excessive soft tissue stripping, bone loss, vascular injury, radiation, infection Malreduction : malposition, malalignment, distraction
• Systemic : age, chronic diseases, DM, chronic anemia, metabolic and endocrine abnormalities ((vit D deficiency), malnutrition, medications (steroid, NSAIDs, antiepileptics), smoking Inappropriate stabilization : too little or insufficient fixation, too much or too rigid fixation, inappropriate implant choice, inappropriate implant position, technical errors
• Location : Scaphoid, Neck Of femur, Talus, distal tibia, base of the 5th metatarsal are at higher risk
• Pattern : Segmental fractures & those with butterfly fragments

CLASSIFICATION
Based on
• Location : Epiphyseal, Metaphyseal or diaphyseal
• Extra articular or intra articular
• Septic or Aseptic
• Hypertrophic, oligotrophic or Atrophic

• Pseudoarthrosis : Fibrous capsule around a cavity filled with viscous fluid, creating a false joint.
o Bone scan : “Cold Cleft” between areas of increased activity.
o Sealed medullary canal.

WEBER-CECH CLASSIFICATION FOR HYPERVASCULAR NON-UNION

1. ELEPHANT’S FOOT NON-UNION
Hypertrophic, Rich in callus
Good vascular supply with good healing potential
Cause – Inadequate Stability, insecure fixation, inadequate immobilization, premature weight bearing

2. HORSE HOOF NON-UNION
Mildly hypertrophic
Some callus present
Cause : moderately unstable fixation, early mobilization

3. OLIGOTROPHIC NON-UNION
Vascular but not hypertrophic
No callus
Cause : inadequate reduction with major displacement/ distraction

WEBER-CECH CLASSIFICATION FOR AVASCULAR NON-UNION

1. TORSION WEDGE NONUNION (DYSTROPHIC)
– Intermediate fragment with decreased or absent blood supply
– Intermediate fragment heals with one main fragment but not with the other

2. COMMINUTED NONUNION (NECROTIC)
– One or more intermediate fragment is necrotic
– no callus present

3. DEFECT/GAP NONUNION
– Loss of a fragment of bone
– After open fracture, sequestrectomy, resection of tumor etc

4. ATROPHIC NONUNION (RAT’S TAIL)
– Loss of intermediate fragments
– Scar tissue with no osteogenic potential connects fragments
– absence of callus, bone ends are tapered

CLASSIFICATION (PALEY ET AL)
• TYPE A 1 cm between fracture ends

ULTRASOUND STIMULATION

• Low intensity pulsed ultrasound is of low energy – stimulate ossification
• Frequency of 1.5 MHz a signal burst width of 200 micro sec a repetation
• 1 MHz an intensity of 300 mW/cm

EXTRACORPORAL SHOCK WAVE THERAPY

• Requires regional anaesthesia
• Principle : To stimulate the Osteogenic cells & growth factors to form new bone & thus, to achieve union by callous formation.
• Contraindications : Pseudoarthrosis, Gap >1cm between fragments

GENE THERAPY
• Aspirated iliac crest stem cells
• Enhance the activity of osteoconductive grafts.
• Recombinant BMP – Commercially available

OPERATIVE MANAGEMENT GOALS

1. Thorough Debridement of the infected tissues
2. Provision of healthy soft tissue envelope
3. Restoration of the correct alignment & length
4. Provision of a stable construct promoting the healing of the infection & the non-union
5. Augmentation of the bony defect if it is of critical size with Bone Grafts

OPERATIVE MANAGEMENT

Hypervascular nonunions : Often has biologically viable ends

• Issue with fixation, not the biology
• requires only stable fixation of fragment; bone grafting is not essential

Oligotrophic nonunions :

• Often have biologically viable bone ends
• May require biological stimulation
• Requires internal fixation

Avascular nonunion :

• requires decortications and bone grafting in addition to internal fixation
• Atrophic nonunions : have dysvascular bone ends
•  Need to ensure biologically viable bony ends are apposed
• Fixation needs to be mechanically stable + Bone grafting

Establishment of healthy soft tissue flap/envelope

• Fibrous union with good alignment : stabilization + bridge grafting sufficient. Excise fibrous tissue from gap & sclerotic bone ends . Avoid extensive dissection helps to retain vascularity.
• Paley A : most can be treated with restoration of alignment and compression of fracture site
• Paley B : needs additional cortical osteotomy + internal bone transport or overall lengthening of bone

Infected nonunion

• Chance of fracture healing is low if infection isn’t eradicated
• Staged approach often important
• Need to remove all infected/devitalized soft tissue
• Use antibiotic beads, VAC dressings to manage the wound
• With significant bone loss, bone transport may be an option
• Muscle flaps can be critical in wound management with soft tissue loss

Pseudoarthrosis : May be found in association with infection

• Removal of atrophic, non-viable bone ends
• Internal fixation with mechanical stability
• Maintenance of viable soft tissue envelope

OPERATIVE MANAGEMENT OPTIONS

1. Timing of operative intervention
2. Plate and screw fixation
3. IM nailing
4. External fixation
5. Arthroplasty
6. Amputation
7. Arthrodesis
8. Fragment excision & resection arthroplasty
9. Osteotomy
10. Synostosis

TIMING OF OPERATIVE INTERVENTION

• Difficulty in establishing the optimal time to intervene surgically in treatment of non union parallels the difficulty in the diagnosis of non union
• Treat infection before operating
• Timing depends on Presence of infection, Location, Fracture morphology, Condition of soft tissues, Experience of the surgeon .

PLATE AND SCREW FIXATION

• Locking plates have improved stability and fixation strength
• Reduction obtained by bringing plate to the shaft
• Surgical technique – Aim for absolute stability
• Absolute stability with lag screw
  Other indications:
  o Absent medullary canal
  o Metaphyseal nonunions
  o When open reduction or removal of prior implants is required
  o Significant deformity

IM NAIL

• Three forms : Pre existing nail , Exchange nail , Dynamization
• Ideal case — Femur or tibia with an existing canal and no prior implants
• Exchange nailing is a good option for the tibia and femur
• Special reamers needed to traverse sclerotic canals

EXTERNAL FIXATION

• Temporary stabilization & Correction of stiff deformity and lengthening

Monofocal
o Compression
o Sequential distraction & compression
o Distraction
o Sequential compression & distraction

Bifocal
o Compression-distraction lengthening
o Distraction-compression transport (bone transport)

Trifocal
o Various combinations

ILIZAROV TECHNIQUE

• Principle of Tension stress
• New bone formation in response to gradual increase in tension
• Basis of technique
  o Iatrogenic fracture
  o Wait for callus
  o Distraction of callus

Accordion Manoeuver
o “Bloodless stimulation” of bone healing
o Alternate compression & distraction at fracture site
o Compression – brings fragments into contact & crushes the scar tissue between them
o Distraction creates columnar fibrovascular tissues & osteoblast synthesis

Ilizarov Method

• External fixator applied using transfixing wires or screws
• Iatrogenic fracture by corticotomy or periosteum incised, bone drilled with osteotome, periosteum repaired
• Initial wait of 5 to 10 days
• Distraction started at 1 mm/day , over 4 sittings each day
• First callus seen after 3-4 weeks, called regenerate
• Once desired length of bone reached, second period of waiting
• Weight bearing permitted to stimulate consolidation
• ‘Fibrous interzone’ disappears once ossification over
• Fixator removed once regenerate shows cortices of even thickness

LIMB RECONSTRUCTION SYSTEMS

• The Orthofix Limb Reconstruction System
• Consists of an assembly of clamps (usually 2 or 3) which can slide on a rigid rail and can be connected by compression-distraction units
• Used to achieve 15 cm or more of lengthening
• Used to obtain maximum stability
• Three main indications :
  Bone loss, with or without shortening
  Deformity, with or without shortening

Extreme shortening

JUDET’S DECORTICATION (1972)

• Osteo-Periosteal decortication
• Faster & firmer healing achieved by surrounding the fracture site in bone chips from the un-united bone itself, as long as the bone chips remained attached to their blood supply.
• Method :
  o Incision made over periosteum to reach the bone
  o Chisel to evelvate cortical bone chips (1-3mm) on either sides till 5-10 cm for 60-75% circumference, maintaining blood supply.
  o Underlying bone debrided or osteotomised
  o Bone graft over the fracture site
  o Osteoprogenitor cells are stimulated into increased osteogenesis & Union is achieved.

SEGMENTAL BONE LOSS
• They are due to high velocity injury or infected non union
Surgical options include
o Autogenous bone graft
o Free vascularized bone graft
o Bone transport
• A critical sized defect is generally regarded as the that requires surgery
• It depends on particular bone involved , location within the bone , surrounding tissue , host biological response.

BONE GRAFT
• Gold standard for biological and mechanical purposes.

Properties of Autograft
o Osteogenic – a source of vital bone cells
o Osteoinductive – recruitment of local mesenchymal cells
o Osteoconductive – scaffold for ingrowth of new bone
• Bone graft can also be allograft

BONE GRAFT SUBSTITUTES
• Often unnecessary in hypertrophic cases with sufficient inherent biologic activity
Options:

• Aspirated stem cells (with or without expansion)
• Demineralized Bone Matrix
• Autogenous Cancellous Graft
• Platelet rich plasma
• Growth Factors – Platelet derived & Recombinant BMPs

THE INFECTION PROBLEM

• How does it happen?
• Inadequate debridement of an open fracture
• Bacterial contamination at the time of surgery
• Failure of primary wound healing
• Exists on a time spectrum

1. Acute infection with hardware
2. Late infection with hardware
3. Chronic osteomyelitis

Consider every nonunion that was open or has had surgery as potentially infected

MANAGEMENT OF INFECTIVE NON UNION
o Plane radiographs
o CT scan – very useful after hardware out
o MRI – Medullary extent of infection
o Indium WBC scans – beware false negative
o Preop blood studies – WBC, CRP, ESR
o If all are negative, high likelihood not infected
o However – could still be infected with a quiescent organism (p. acnes, staph epi.)
o Always culture and include fungus and AFB
o Consider two stage management if obviously infected

Management
o Two important aspects : Infection & Non-Union
o Initial focus – Suppress/eradicate the Infection Focus.
o Single/Multiple Staged Procedures.
o 1st stage – Culture/Open Biopsy + Control of infection +/- temporary stabilization
o 2nd stage – Removal of Implant + Re-culture + Anti-microbial (Specific) management + Fixation + Bone Graft
o Local delivery of Antibiotics is key –
o PMMA is mixed with heat stable antimicrobials (Tobramycin, Gentamycin, Vancomycin)
o Left inside for 2-3 months
o Achieve 200 times the antibiotic concentration achieved with intravenous administration.

Antibiotic Resistance
o Biofilm layer dramatically reduces the metabolic rate of bacteria.
o MIC 50-100 times higher in biofilm colonies than swarmer cells
o After the biofilm is well established, the surface has to be debrided or removed to resolve the infection
o Surface Specific: Titanium < Stainless Steel < PMMA 1 year – send to pathology (squamous cell carcinoma)
o Do not elevate flaps (make a canyon)
o Use a burr with constant cooling

Based on the location of dead bone
o External – Burr / Curette
o Medullary Diaphysis – Ream / RIA
o Metaphyseal – Slot the cortex to gain access

Debridement of hardware
o Hardware / Tracts are contaminated
o Plates: Curette/burr under surface
o Screws: Overdrill – remove broken
o IM nail: Ream and flush canal antegrade and retrograde

Dead space management
o Temporary:
o Antibiotic beads (pouch)
o +/-VAC sponges

Systemic Antibiotics
o Generally 4-6 weeks IV
o Consider short IV (2 weeks) then oral
o Oral Rifampin in Gm+ if hardware retained – penetrates biofilm
o Don’t use: bacteriostatic antibiotic with bactericidal antibiotic
o Manage antibiotic levels, monitor toxicity, good medico-legal sense

MASQULET TECHNIQUE/INDUCED MEMBRANE TECHNIQUE (IMT)
o Principle: inducing pseudomembrane by the physiological foreign-body reactions surrounding the polymethyl methacrylate spacer. Then PMMA spacer is replaced by the bone grafts to stimulate the bone union

CONCLUSION

• Single stage strategies with non-union debridement and use of circular fixators led to
  Union rates of 70–100%
• Recurrence of the infection 0–55%
• Multiple stage strategy with initial debridement and subsequent internal fixation and bone grafting led to
• Union rates of 66–100%
• Recurrence of the infection 0– 60%
• Multiple stage strategy with initial debridement, delivery of local antibiotics, and subsequent internal fixation and bone grafting led to
• Union rates of 93–100%
• Recurrence of the infection 0–18%.