Non-union of Foot and Ankle


Arthrodesis surgery is the mainstay of surgical management of many arthritic and painful deformity of foot and ankle conditions. Some surgeries such as ankle or 1st MTPJ fusion have success rates up to 90-95% with very high satisfaction.  Despite best efforts, non-union will be faced and dealt with in surgical practice.

Non-union is defined as the ‘absence of sufficient bony bridging across a surgical fusion site such as to relieve symptoms including pain or instability when other possible causes of such have been excluded.’

The acceptance of non-union is not easily defined by a set time with infected non-union having a different timescale from fibrous, as an example. Accepting non-union reflects so many elements (later discussed) that it is when a patient and surgeon agree that sufficient time and interruption to their lives has been spent recovering in the light of evidence available. 


Non-union without Infection

A work-up must include the factors below, and whilst the evidence for each may be variable, revision fusion surgery is of such nature that all should be optimised before commencing treatment.

  • Smoking
    • Enforce and even request proof of smoking abstinence in the weeks or months leading up to revision surgery
    • Saliva and blood tests are available and should be considered
    • Smoking has a proven negative impact on outcomes of foot & ankle surgery and arthrodesis
  • Alcohol
    • Abstinence from all alcohol should be considered in the perioperative period as part of a nutritional work-up
    • Chronic alcoholism is associated with:
      • Poor Vit D & calcium
      • Poor compliance with instructions
    • Direct alcohol osteoblast toxicity
  • Illicit Drugs
    • Illicit drugs should be avoided as they can be associated with:
      • Poor nutrition
      • Poor compliance
      • Possible similar effects to smoking
  • NSAIDs
    • If the patient had taken NSAIDS throughout their primary surgery recovery, consider avoiding it this time pragmatically; weak literature evidence to suggest chronic NSAID use can affect bone healing
  • Vascular Supply
    • Check pulses are intact
    • Check planned incision skin cap refill
    • Consider formal ABPI or even angiogram if any concern
    • Look for evidence of avascular bone necrosis on x-rays or MRI
  • Diabetes
    • Check HbA1c to ensure compliance; involve diabetologists
  • Peripheral neuropathy should be assessed and documented
  • Consider prolonged immobilisation post-operatively
  • Steroids & DMARDS
    • Liaise with rheumatology
    • Stop steroids if possible
    • Methotrexate and anti-TNF drugs should be refined in liaison with colleagues
  • Nutrition
    • Diet affects immunity, bone health and mental health, all of which are worth optimising if considering revision surgery
  • BMI
    • Avoid diet-controlled weight loss programs during peri-op period
  • Vitamin D & calcium
    • UK population sampling shows generally poor Vitamin D status
    • Consider supplements 1000-4000 IU/day
    • Liaise with rheumatology
    • Sunshine exposure
    • Consider summer surgery
    • Consider super-dosing in high risk patients
  • Vitamin C
    • Blood normal 0.6-2mg/dl
    • Key in collagen formation
    • Positive effect on trabecular bone formation
    • Low in alcoholism, smokers and poor diet
    • Consider supplements
  • Vitamin K
    • Works with Vit D & calcium
    • Blood normal 0.15-155mg/l
    • Dietary / supplement intake 100mg/day
    • Found in green leafy vegetables
  • Post-op compliance
    • Education
    • Support from family / specialist nurse or physio
    • Safer walking aids – knee scooter / Zimmer frame


Surgical planning

Following patient optimisation, it is important to plan the surgical procedure. Mostly, it will be more difficult and more unpredictable than the index surgery. Consent must emphasise that this is higher risk surgery which is performed less frequently than primary surgeries, and buy-in from the patient is vital. Risks must be outlined that potentially include:

  • Loss of limb
  • Bleeding
  • Infection
  • Nerve damage
  • Fracture
  • Further delayed or non-union
  • Metalwork problems
  • 2nd stage surgery to re-stimulate fusion
  • Thrombosis
  • Pain reaction
  • Altered gait
  • Leg length discrepancy
  • Alignment dissatisfaction
  • Bone donor site morbidity

Potentional problems encountered during surgery include:

  • Bone loss
  • Avascular bone
  • Metalwork issues
  • Malalignment
  • Neighbouring joint problems
  • Fractures

Preparatory options in work up for the operation:

  • Radiological
    • Establish bone stock and assess metalwork integrity
    • Weight-bearing x-rays & CT scan
      • Long leg alignment views
      • 3D reconstructions to plan 3D re-alignment
    • MRI scan
      • Establish extent of any avascular bone
    • Establish atrophic versus hypertrophic mode of non-union
    • 3D printed models to plan complex deformity correction

Establish,and prepare to correct, any apparent mechanical mode of non-union (often a combination).

Intraoperative considerations:

  • Gaps between exposed surfaces must be filled and compressed
  • Bone surfaces preparation must be meticulous to expose healthy cancellous bone
  • Malalignment must be planed achieving correction through the arthrodesis site +/- other joints or osteotomies
  • Stability must be appropriate 
  • Prepare to remove broken metalwork
    • Look at screw / locking screw configuration
    • Consider alternative stabilising metalwork or include adjacent joint(s)
  • Consider mode of subsequent revision metalwork working
    • Excessive stiffness in neighbouring joint(s)?

Plan rehab carefully with longer immobilisation. Consider alternatives, perhaps revise to arthroplasty (excision or implant).

Deal with the problem recognised and adapt revision approach and metalwork accordingly.

Alternatives to revision fusion surgery that must be discussed with your patient prior to revision surgery:

  • Continued non-operative care 
  • Shoe wear, braces, walking aids, wheelchair
  • External bone stimulators
  • Remove metalwork and trial of fibrous non-union
  • Revision to joint replacement where applicable
  • Amputation


Surgical Technique

A basic revision fusion surgical plan will include:

  • Optimal incision
    • Extended old scars +/- new
  • Remove old metalwork
  • Remove dead bone and non-union fibrous tissue
  • Send more samples for microbiology & histology
  • Correct malalignment
  • Aim for direct bone-on-bone contact
  • Balance against further deformity – shortening, varus/valgus etc.
  • Fill all voids
    • Small gap options
      • Cancellous bone graft
      • Bone substitutes
      • Orthobiologics
    • Large gap options
      • Structural bone graft
      • Metal cages packed with cancellous bone
      • Solid metal implants
  • Obtain rigid and stable fixation
  • Fixation may be either internal or using ring external fixators
    • May need to bridge and include neighbouring joint e.g. convert non-union of the ankle to TTC fusion


Post-operative recovery

  • Continue optimised patient health
  • Ensure compliance with weight bearing
  • Monitor wounds closely for infection
  • Consider external bone stimulators
  • Consider second surgery need to re-stimulate part of the fusion site
  • Use radiography to confirm state of fusion before pushing rehabilitation


Non-union with Infection

Clinical suspicion remains the mainstay of deciding whether or not to proceed with infection-related techniques. A multidisciplinary approach is vital, in liaison with radiologists, microbiologists and often specialist surgeons and centres.

Supporting evidence that can help identify if infection is present:

  • Haematological
    • Full Blood Count
    • WCC with differential
    • Chronic anaemia
    • ESR & CRP
  • Radiological
    • Plain x-rays
      • Periosteal / cortical reaction, bone demineralisation
    • MRI - incl. Gadolinium
      • (collections, monitoring extent of oedema)
    • Radio-labelled white cell scan / PET scan
  • Biopsies
    • Send for culture & histology
    • Open biopsy of non-union, metalwork and neighbouring bones
    • 2 weeks off antibiotics if possible
    • At least 5 samples for microbiology
    • Clean instruments for each sample
    • Couriered straight to laboratory
    • Prepare lab for:
      • Broth enrichment culture
      • Extended sensitivities
      • PCR for fastidious organisms (e.g. kingellakingae)
    • Once organism established then plan surgical MDT episode


Surgical principles

One-stage and Two-stage surgery remain debated but is guided often by the virulence, purulence and extent of the organism and its infection.

One-stage surgery concept:

  • Radical debridement of non-union site and neighbouring bone with good margin (red & amber zones)
  • Perform or repeat diagnostic biopsies
  • Antibiotic-impregnated / eluting bone substitutes
  • Reconstruct void with auto/allograft, metalwork and stabilise
  • Optimal stability of revision fusion with internal or external fixation
  • Prolonged course of antibiotics guided by:
    • MDT & microbiology
    • Inflammatory markers
  • Local preferences and evolving experience

Two-stage surgery concept:

1st Stage

  • Debridement of non-union site and local bone with good margin (red & amber zones)
  • Perform or repeat diagnostic biopsies
  • Insert antibiotic-impregnated / eluting spacer for 6 weeks and/or until inflammatory markers normalise

2nd stage

  • Re-biopsy with extended broths etc.
  • Reconstruct void with auto/allograft, metalwork and stabilise with internal or external fixation
  • Consider antibiotic-eluting bone substitutes
  • Keep on antibiotics until microbiology results known

Occasionally, an uninfected fibrous union after first stage is of such acceptable comfort and stability that the 2nd stage is not performed, e.g. diabetic neuropathy cases.



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