Fractures - The biological healing process, new fractures, non unions and fracture pain

At 50, I had managed to avoid fracturing anything, and then at the end of a week in France, I slipped down ONE ceramic tiled step and broke my tibia and fibula. The nearest hospital were amazing and after a temporary overnight cast they did an Open Reduction & Internal Fixation (ORIF) to fix the complicated spiral fracture of my tibia with a plate and 10 pins. Unfortunately after 4 months at home in Worcestershire, I was diagnosed with a non-union fracture BUT my lovely Orthopaedic consultant in Cheltenham suggested we try Exogen Ⓡ Ultrasound Bone Healing treatment. I’m very happy to say it was successful. After 3 months of daily ultrasound treatment ‘cotton wool like growth’ was visible in the (quite large) gap on x-ray, and after a further 3 months of treatment I was completely healed. I was so relieved to avoid further surgery which would have involved a bone graft from my hip.

Ultrasound bone healing machines are particularly well known for assisting non-union fracture healing, as well as speeding up healing in new / recent breaks. In the comfort of your own home you can use an Ultrasound bone healing machine for just 20 minutes a day. We offer machines to rent in UK and many EU countries.

Now for the scientific bit about fractures

The Biology of Bone Fracture Healing

Bone fracture healing is a complex, continuous biological process that occurs in five distinct but overlapping stages: hematoma formation, inflammation, soft callus formation, hard callus formation, and bone remodeling.
1. Hematoma Formation (Days 1–5): When a bone breaks, blood vessels rupture, causing blood to pool and clot at the fracture site. This clot (hematoma) forms a structural framework that stops further bleeding and provides a base for new tissue to grow. Key cells: Platelets and phagocytes (which clean up dead tissue and debris).
2. Inflammation (Days 5–11): The body mounts an intense localised immune response. The area becomes swollen, red, and painful as blood flow increases to deliver essential nutrients, oxygen, and specialsed cells to begin the repair process. Key cells: Macrophages, white blood cells, and mesenchymal stem cells.
3. Soft Callus Formation (Weeks 2–3): The inflammatory cells are replaced by granulation tissue. Blood vessels begin to regrow, and the body creates a "soft callus" made of fibrous tissue and cartilage to act as a temporary splint bridging the broken bone ends together. Key cells: Fibroblasts and chondroblasts.
4. Hard Callus Formation (Weeks 3–12): The soft, cartilaginous callus is gradually replaced by woven, immature bone through a process called endochondral ossification. This hard callus acts as a rigid, bony bridge that secures the fracture. Key cells: Osteoblasts (bone-forming cells).
5. Bone Remodeling (Months to Years): The final and longest stage. The rigid woven bone is continuously broken down and reorganized into stronger, dense, mature lamellar bone, matching the original shape and structural strength. Key cells: Osteoclasts (bone-resorbing cells) and osteoblasts.

Fracture Pain

Post-fracture pain is the body's natural response to broken bones and damaged surrounding tissues (like muscles, nerves, and ligaments). Pain serves as your body's alarm system to protect the injured area. Discomfort naturally fluctuates from sharp, sudden aches right after the break to a dull, lingering soreness and stiffness during immobilisation. Fracture pain generally progresses through clinical phases: Acute 1-7 days (intense, immediate pain right after the break); and Sub-acute 2-6 weeks (dull, aching pain during the healing weeks).

Pain that persists beyond normal healing time (typically >3 months) is known as Chronic Pain (when the healing is complete). It is frequently triggered by over activity, weather changes, and scar tissue stiffness, rather than direct bone movement and it’s often a dull, aching, or neuropathic pain that can occur at rest.

In contrast, after the expected time frame for healing has passed, sudden spikes of pain, returning, or worsening of pain, can signal a complication referred to as Nonunion. This may be characterised by localised tenderness, aching, and sharp mechanical pain that worsens when weight is applied or when the limb is moved. More about the treatment available for Nonunion fractures below.

Non-union Fractures 

A non-union fracture occurs when a broken bone fails to heal naturally or within the expected time frame. Instead of fusing together, the fracture site remains unstable, leading to persistent, dull, or sharp pain that worsens when weight is applied or the limb is moved. Biologically, a non-union fracture is defined by a persistent failure of the bone to bridge with new bone after 9 months, or if there has been no progressive healing for 3 consecutive months. The biology of a non-union is driven by a breakdown in three physiological requirements for bone regeneration: adequate blood supply, sufficient mechanical stability, and a robust cellular response.

Hypertrophic Non-Unions: These have abundant blood supply and biological activity but lack mechanical stability. The body attempts to heal by generating massive amounts of fibrous, cartilaginous "callus," which cannot bridge the gap because the bone segments are moving too much. Fixing the mechanical instability is typically the primary treatment.

Atrophic Non-Unions: These have poor blood supply and inadequate biological activity. The bone ends look "starved," lack callus formation, and the fracture gap is filled with inactive fibrous scar tissue. Treatment usually requires surgically stimulating the biology (e.g. bone grafting) and improving stability

Non-Union Pain

Pain is one of the primary symptoms of a non-union. It happens because: 

  • Instability: The broken bone segments never fully stabilised into a single unit. 

  • Micro-movement: Whenever the limb is used, the bone ends rub against each other or put stress on the surrounding hardware (such as surgical plates or rods). 

  • Pseudoarthrosis: If left untreated for months or years, the body may attempt to bridge the gap by creating a "false joint" with a capsule, cartilage, and joint fluid, causing chronic deep pain and joint dysfunction. 

Signs that a fracture has not united, aside from pain

  • Tenderness and swelling directly at the break site.

  • Feeling a "giving way" sensation or abnormal movement where the bone should be rigid.

  • Visible limb or joint deformity.

  • Difficulty bearing weight or inability to use the limb as expected. 

Common Causes of Non-inion

  • Poor blood supply: Bone ends require adequate blood and nutrients to rebuild tissue; without it, healing halts.

  • Infection: Bacteria at the fracture site can prevent proper bone regeneration.

  • Excessive movement: Moving the bone too early or the cast/implant failing to keep the fragments perfectly still.

  • Underlying health issues: Conditions like severe diabetes, anemia, or the use of certain medications (such as long-term anti-inflammatories) can suppress bone healing. 

Non-Union Treatment

Unfortunately non-unions rarely heal without intervention.

The Non-invasive Option:

Ultrasound Bone Healing Stimulators: - a small device is placed over the skin of the fracture site and uses Low Intensity Pulsed Ultrasound  (LIPUS) waves to kick start the bone-healing process. You might wish to Google ‘Low Intensity Pulsed Ultrasound (LIPUS)’, the word Exogen Ⓡ or the word Osteotron Ⓡ for more information on how ultrasound bone healing machines work. Take your Orthopaedic Consultant’s advice.
We offer machines for rent in UK and many EU countries.

The Surgical Options:

Surgery: Procedures like bone grafting (using bone from another part of the body or a donor) to stimulate growth and seal the fracture.

Hardware Revision: Adjusting, tightening, or replacing surgical plates and screws to provide better stability.

Disclaimer: This information is for educational purposes. If you are experiencing unexplained, persistent pain following a bone fracture, please contact your doctor or an orthopedic specialist for an evaluation and imaging.

NHS Guidelines for their funding of new Exogen® ultrasound machines for patients in the UK

As far as we are aware, the NHS sometimes provides the Exogen ® Ultrasound Bone Healing System under strict circumstances, when a patient’s long bone fracture has failed to heal after 9 months (non-union). Low Intensity pulsed ultrasound can be considered for treatment of long bone fractures (like the femur, tibia, or humerus) with non-union for appropriate skeletally mature patients when certain criteria are met.

The updated NICE MTG12 Guidance supports the use of the Exogen® ultrasound bone healing system for non-union long bone fractures (failure to heal after 9 months). Clinical evidence demonstrates high healing rates and potential cost savings by preventing further surgery. 

NHS commissioning bodies and local Integrated Care Boards (ICBs) routinely adopt this guidance, albeit with strict clinical criteria. When determining patient eligibility for Exogen® therapy, regional policies commonly enforce the following parameters:

  • Patient Profile: Patients must be aged 18 or older.

  • Fracture Type: Applies to stable, un-displaced long bone fractures (e.g., tibia, femur, radius, ulna, or humerus).

  • Timeline: Non-union must be confirmed (failure to heal after 9 months).

  • Gap Limitations: The fracture gap must be 1 cm or less.

  • Exclusions: It is not commissioned for use in cases of infection, fractures caused by bone cancer, skeletal immaturity (children/adolescents), or during pregnancy.

For more precise details regarding your local NHS trust's prescribing policies, please consult them.