Ten aspects of failed internal fixation for femoral shaft fractures: detailed causes and prevention

Today, let'sdelve deeper into the causes and preventative measures for internal fixationfailure in femoral shaft fractures:

1. Patient Factors:

• Detailed Causes:

• Metabolic Disorders (Diabetes):
  Compromised blood sugar      control hinders osteoblast function, reduces bone formation, and      increases infection risk, weakening fixation.
       

• Immunosuppression: Predisposes      to infection and delays bone healing. Medications like corticosteroids      directly inhibit osteoblast activity and bone remodeling.
       

• Smoking: Nicotine      constricts blood vessels, reducing blood flow to the fracture site. This      impairs oxygen and nutrient delivery crucial for healing, increasing      non-union risk.
       

• Osteoporosis: Characterized      by low bone density, osteoporosis weakens bone stock, making it less able      to withstand mechanical stress, increasing implant loosening and failure      risk.
       

• Higher BMI and Activity Level:
  Increased      body weight and dynamic loading place higher stress on the implant,      potentially exceeding its fatigue limit and leading to breakage.
     

• Prevention Strategies:

• Optimize Comorbidities: Pre-operative management of diabetes, smoking cessation      programs, and addressing nutritional deficiencies are crucial.
       

• Bone Health Assessment: Screen for osteoporosis and consider pre-operative      treatment (bisphosphonates) to improve bone density before surgery.
     

• Patient Education: Thoroughly      explain weight-bearing restrictions and activity modifications based on      individual healing progress and risk factors.
       

2. Cerclage Wire Use:2.

• Detailed Causes:

• Disrupting Callus Formation:
  Placing wires at the fracture      line disrupts the natural process of callus formation, a critical step in      bone healing. Wires act as a barrier, preventing bridging of the fracture      gap.
       

• Compromising Blood Supply:
        Multiple closely spaced wires      constrict blood vessels surrounding the fracture. This reduces oxygen and      nutrient supply essential for bone healing, leading to delayed union or      non-union.
       

• Prevention Strategies:

• Strategic Placement: Avoid      placing cerclage wires directly at the fracture site, especially in      simple fractures where alternative fixation methods suffice.
       

• Minimizing Wire Number: Use the minimum number of wires necessary to achieve      stability. Explore other fixation options (intramedullary nails, plates)      in complex fractures.
       

3. Cerclage Wire Placement:

• Detailed Causes:

• Arterial Injury: Inadvertent      placement around the circumflex femoral artery can lead to acute      occlusion, compromising blood supply to the femoral head and neck,      potentially resulting in avascular necrosis.
  
  

• Nerve Damage: Incorrect      wire positioning can injure nearby nerves (e.g., sciatic nerve, lateral      femoral cutaneous nerve), leading to pain, numbness, weakness, or      paralysis.
  
  

• Prevention Strategies:

• Anatomical Knowledge:Precise      understanding of regional anatomy is essential. Surgeons must carefully      identify and protect critical neurovascular structures during surgery.     

• Image Guidance:Intraoperative      fluoroscopy is crucial for visualizing wire placement in relation to      surrounding anatomy, minimizing the risk of injury.
  
  

4. Screw Placement in IntramedullaryNailing (IMF):

• Detailed Causes:

• Lag Screw Vulnerability:The proximal screw hole, often used for lag screw      fixation, represents a stress concentrator in the nail. Incorrectly      placed screws at this point significantly increase the risk of nail      breakage.
  
  

• Off-Axis Drilling: If      the screw hole is drilled at an angle or off-center, it weakens the nail      and creates stress points, making it more susceptible to fatigue failure      under load.
  
  

• Prevention Strategies:

• Precise Drilling: Meticulous      surgical technique and image guidance (fluoroscopy) are vital for      ensuring accurate screw hole placement and avoiding nail weakening.
       

• Choosing Appropriate Screws:
        Screw length and diameter must      be carefully selected based on patient anatomy and bone quality.      Oversized screws further weaken the nail.
  
  

5. Screw Placement in PlateOsteosynthesis (PO):

• Detailed Causes:

• Stress Risers: Each      screw hole acts as a stress riser in the plate, concentrating forces at      these points. Filling every hole significantly weakens the plate and      increases the likelihood of breakage, especially near the fracture site.
  
  

• Interference with Callus:
       Placing screws directly within      the fracture line disrupts callus formation by inhibiting bone-to-bone      contact and bridging of the fracture gap.
       

• Prevention Strategies:

• Strategic Screw Placement:
        Utilize a limited number of      screws to provide adequate stability. Space them strategically along the      plate, avoiding over-crowding near the fracture site.
       

• Respecting Fracture Biology:
        Avoid placing screws directly      within the fracture line to allow for unobstructed callus formation and      bridging.
       

6. Choice of Implant and Fixation:

• Detailed Causes:

• Underestimation of Load: Selecting an implant with insufficient strength (e.g.,      too thin a nail, inadequate plate size) for the patient's weight,      activity level, and fracture pattern will likely lead to failure under      physiological loads.
  
  

• Inappropriate Fixation:Using      a fixation method not suited to the fracture pattern can result in      inadequate stability and increased stress on the implant. For example, a      transverse fracture treated with a single lag screw without additional      fixation might experience excessive shearing forces, leading to failure.
  
  

• Prevention Strategies:

• Thorough Pre-operative Planning:
  Carefully assess fracture type,      location, complexity, patient factors, and functional demands. Consider      expected loads and choose implants that provide adequate strength and      stability.
  
  

• Following Established Guidelines:
  Adhering to AO principles and      established surgical guidelines for specific fracture patterns helps      ensure appropriate fixation techniques are employed.
  
  

7. Technical Errors During Surgery:

• Detailed Causes:

• Inadequate Reduction: Failure      to achieve anatomical reduction can lead to uneven force distribution      across the fracture site, placing excessive stress on the implant and      increasing the risk of loosening or breakage.
  
  

• Periosteal Damage:Excessive      stripping of the periosteum, which provides blood supply and contributes      to bone healing, can impair fracture healing and compromise implant      stability.
  

• Prevention Strategies:

• Gentle Tissue Handling: Minimize periosteal stripping during surgery. Employ      minimally invasive techniques when possible to preserve blood supply and      promote healing.
       

• Intraoperative Imaging: Utilize fluoroscopy to confirm accurate anatomical      reduction and guide implant placement, ensuring optimal stability and      load distribution.
  
  

8. Infection:

• Detailed Causes:

• Osteolysis and Implant Loosening:
  Infection triggers an      inflammatory response that leads to bone resorption (osteolysis) around      the implant. This weakens the bone-implant interface, increasing the risk      of loosening and failure.
  
  

• Impaired Bone Healing: Infection      disrupts the normal cascade of bone healing, reducing callus formation      and increasing the likelihood of non-union. This prolonged instability      further challenges implant integrity.
     

• Prevention Strategies:

• Strict Asepsis: Adhere      to stringent sterile techniques throughout the surgical procedure to      minimize the risk of contamination.
       

• Prophylactic Antibiotics:
  Administer pre-operative      antibiotics and consider continuing them post-operatively, especially in      open fractures or cases with higher infection risk.
       

9. Inadequate Fracture Stabilization:

• Detailed Causes:

• Implant Micromotion:Excessive      movement at the fracture site, even at a microscopic level, can prevent      the formation of a stable callus bridge. This continuous instability can      lead to implant fatigue and failure over time.
       

• Delayed Union or Non-Union:
        Prolonged healing times or      complete failure of the fracture to heal increases the duration and      magnitude of stress on the implant, increasing the likelihood of failure.
       

• Prevention Strategies:

• Achieving Absolute Stability (When Indicated):
        For specific fracture      patterns where absolute stability is crucial for healing, ensure adequate      compression and rigid fixation to minimize micromotion.
       

• Biological Augmentation: In complex cases or those with compromised healing      potential, consider adjunctive therapies like bone grafting, growth      factors, or bone marrow aspirate to stimulate bone formation and enhance      stability.
       

10. Mechanical Overload:

• Detailed Causes:

• Implant Fatigue: Repetitive      cyclic loading, especially beyond the implant's intended capacity, leads      to microscopic cracks in the metal. Over time, these cracks propagate and      eventually lead to fatigue failure.
       

• Sudden Impact: High-energy      impacts or falls can generate forces exceeding the implant's ultimate      tensile strength, causing immediate breakage or catastrophic failure.
       

• Prevention Strategies:

• Gradual Return to Activity:
  Implement a staged      rehabilitation program that gradually increases weight-bearing and      activity levels, allowing the bone and implant to adapt to progressively      higher loads.
  
  

• Fall Prevention: Educate      patients, particularly the elderly or those with balance issues, on fall      prevention strategies to minimize the risk of sudden impacts on the      healing fracture.
  
  

By meticulously addressing these tenaspects, surgeons can significantly reduce the occurrence of internal fixationfailure in femoral shaft fractures. A thorough understanding of the underlyingcauses, combined with careful surgical planning, precise technique, andcomprehensive patient management, is vital for achieving optimal outcomes andimproving patient lives.