Fracture Repair Notes
Introduction to Fracture Repair
Course reference: VMS 5689
Focus: Small Animal Surgery. This specialized field focuses on restoring mobility and quality of life in companion animals suffering from orthopedic injuries.
Definition of Fracture
A fracture is defined as a break in the continuity of a bone.
Goal of Fracture Repair
To restore the structural integrity and function of the fractured bone, aiming to return the limb to its pre-injury physiological state. This involves not only re-establishing the normal anatomy (correct alignment and length) but also restoring biomechanics, ensuring the bone can bear weight and withstand normal physiological stresses.
To ensure proper healing by re-establishing the normal anatomy and biomechanics.
Methods of Classification
Fractures can be classified based on several criteria:
Direction of the fracture lines
Location of the fracture on the bone
Reducibility: whether the fracture fragments can be realigned manually or surgically to their anatomical position
Displacement: whether bone segments have shifted from their normal positions, indicating the severity of the traumatic force and influencing repair strategy
Open or closed fracture: open fractures communicate with the external environment. This distinction is crucial for prognosis due to the significant difference in infection risk and soft tissue damage.
Specific types of fractures: defined below
Direction of Fracture Lines
Transverse: Horizontal line; fractures that run straight across the bone. Often caused by a direct blow or bending force, leading to a break perpendicular to the long axis of the bone.
Oblique: Slanted line; fractures that are not horizontal nor vertical. Resulting from a combination of forces (e.g., compression and bending), creating a slanted break across the bone.
Spiral: Twisted fracture; caused by rotational forces. Typically caused by severe rotational (torsional) forces, leading to an S-shaped or corkscrew fracture line.
Comminuted: Multiple fracture lines; indicates bone is broken into several pieces. Indicates high-energy trauma where the bone is shattered into three or more pieces. Management is often complex due to multiple fragments.
Reducible: Can realign with manipulation. Fragments can be accurately re-positioned and maintained with appropriate fixation.
Non-reducible: Cannot be realigned without surgery. Surgical intervention is required, often involving more complex reconstruction or bridge plating techniques.
Anatomical Location
Fractures can occur in various parts of the bone:
Diaphyseal: In the long shaft of the bone. Occurring in the long, central shaft of the bone, which is primarily cortical bone.
Metaphyseal: Above the diaphysis, near the end of the bone. Located in the wider part of the bone near the ends, containing cancellous bone and often high metabolic activity.
Physeal: In the growth plate region (critical in young animals). Fractures involving the epiphyseal growth plate, unique to skeletally immature animals, with potential for growth disturbances if not properly managed.
Articular/Epiphyseal: At the joint surface. Fractures extending into the joint surface, critical for joint function and requiring precise anatomical reduction to prevent osteoarthritis.
Sub-capital: Below the head of the bone. Fractures just below the head of the bone, commonly seen in the femur.
Capital: Involving the joint head. Involving the joint head itself, often intra-articular and challenging to repair.
Sub-trochanteric: Below the trochanter. Below the trochanters (bony prominences) of the femur.
Condylar: Involving the joint condyles. Fractures involving the condyles, the rounded prominences at the ends of some bones (e.g., humerus or femur) that articulate with other bones in a joint.
Medullary Cavity: The central cavity of the bone where marrow is found.
Periosteum: The outer fibrous layer of bone.
Articular Cartilage: Smooth tissue that covers the ends of bones in a joint.
Salter-Harris Classification of Physeal Fractures
This classification system is vital for predicting growth disturbance, as damage to the germinal cells within the physis can impair bone longitudinal growth.
Type I: Fracture through the growth plate only.
Type II: Fracture through growth plate and metaphysis.
Type III: Fracture through growth plate and epiphysis.
Type IV: Fracture through all three: metaphysis, growth plate, and epiphysis.
Type V: Compression fracture of the growth plate.
Classification of Fractures
Non-displaced: Fracture parts remain in alignment.
Displaced: Fracture parts misaligned.
Reducible: Can be aligned without surgery.
Non-reducible: Requires surgical intervention to realign.
Specific Fracture Types
Incomplete (Greenstick): Bone bends and partially cracks, common in young animals. Partial fracture where one side of the bone breaks and the other side bends; common in young, flexible bones due to incomplete ossification.
Avulsion: A fragment of bone is pulled away by a tendon or ligament. A fragment of bone is pulled away by the strong pull of a tendon or ligament insertion, often indicating significant soft tissue component.
Pathological Fracture: Occurs in bones weakened by diseases, like tumors. Occurs in bones weakened by underlying disease processes, such as primary or metastatic tumors, metabolic bone disease, or osteomyelitis, often with minimal trauma.
Compression Fracture: Resulting from squeezing or crushing. Resulting from axial loading or squeezing forces, typically affecting cancellous bone (e.g., vertebrae), leading to a reduction in bone height.
Chip, Butterfly, or Slab: Terms that describe the shape of the fractured bone piece. These terms describe specific fragment shapes:
Chip: A small fragment broken off the edge of a bone, often intra-articular.
Butterfly: A triangular fragment broken off typically from the shaft, common in comminuted fractures.
Slab: A long, thin fragment detached from the main bone, often seen in condylar fractures.
Fissure Fracture: A narrow crack in the bone without complete separation. A narrow crack in the bone without complete separation of the segments, often stable but can progress to a complete fracture.
Folded Fracture: Characterized by bending or folding of the bone rather than breaking outright. Characterized by bending or folding of the bone rather than a clear break, often seen in long bones with high elasticity.
Classification of Fractures Continued
Closed Fracture: Does not break through the skin.
Open Fracture: Breaks through the skin, increasing risk of infection.
Open Fracture Classification
This classification, often called the Gustilo-Anderson classification adapted for animals, is crucial for determining prognosis and management strategy, with increasing severity types indicating higher infection risk and poorer outcomes.
Type 1: Bone through the skin; laceration < 1 \text{ cm} with clean edges. Bone penetrates skin from inside-out, creating a small, clean wound. Minimal soft tissue damage.
Type 2: External object penetrates tissue; laceration > 1 \text{ cm} with mild soft tissue injury. External force causes the wound, with moderate soft tissue injury and a laceration greater than . Contamination is a concern.
Type 3a: Extensive soft tissue laceration but with tissue available for closure. Extensive soft tissue laceration and degloving, but adequate soft tissue remains to cover the bone after debridement. High-energy trauma.
Type 3b: Extensive injury with exposure of bone and loss of periosteum. Severe soft tissue injury with significant periosteal stripping, bone exposure, and substantial contamination, requiring reconstructive soft tissue procedures (e.g., skin grafts or flaps).
Type 3c: Involves arterial injury requiring repair for salvage. The most severe type, involving major arterial injury that necessitates vascular repair for limb viability, in addition to extensive soft tissue and bone damage.
Forces That Cause Fracture Lines
Fractures result from various forces:
Bending: Can create a transverse fracture. A force applied perpendicular to the long axis of the bone, causing tension on one side and compression on the other, often resulting in transverse or short oblique fractures.
Axial Compression: Also causes changes in fracture patterns. Force applied along the longitudinal axis, causing bone segments to be crushed together, leading to comminuted or compression fractures, especially in cancellous bone.
Torsional Forces: Contributes to spiral fractures. Twisting forces around the long axis of the bone, commonly resulting in spiral fractures.
Definitions in Fracture Repair
Closed Reduction: Manipulation method that conserves blood supply, has lower infection risk, is quicker but more challenging. Manipulation of fracture fragments externally without surgical incision, preserving the periosteal blood supply. Benefits include lower infection risk, faster procedure, but it is technically more challenging and may not achieve perfect anatomical alignment for all fractures.
Open Reduction: Surgical realignment; can damage blood supply, has increased infection risk, takes longer but easier to perform. Surgical exposure of the fracture site to directly visualize and realign bone fragments. While offering precise anatomical reduction and easier fixation, it can compromise local blood supply, carries a higher infection risk, and is more invasive.
Fixation: Stabilization of bone fragments during healing. The process of stabilizing bone fragments using internal or external implants to maintain proper alignment during healing, counteracting forces that could cause displacement.
Cis/Trans Cortex: Refers to the cortices of the bone during fixation procedures. Refers to the cortices (outer layers) of the bone. 'Cis' (near) cortex is the cortex closer to the surgeon or plate, 'trans' (far) cortex is the opposite cortex. Important for screw placement and plate application.
Bone Purchase: Describes the anchorage strength achieved by fixation methods. Describes the strength of the anchorage established by a screw or pin within the bone. Good purchase is critical for stable fixation and involves engaging sufficient cortical bone.
External Coaptation
Method of closed reduction and fixation.
Indications: Primarily suited for fractures where minimal instability is present or can be readily controlled, enhancing comfort and promoting healing without invasive surgery.
For closed fractures distal to stifle or elbow, as these areas often have less muscle mass to stabilize, and soft tissue coverage is more challenging proximally.
Fractures anticipated to heal quickly, such as simple, non-displaced fractures in young animals with good healing potential.
Recommended for certain small/long dog breeds where minimal forces are expected on the fracture site or internal fixation may be overly invasive.
Effective for Greenstick and intact periosteal sleeve fractures due to the intact periosteal sleeve providing inherent stability, and for intact periosteal sleeve fractures which have a biological splint.
Indications for Open Reduction
Ideal for situations where precise anatomical reduction and rigid stabilization are paramount, or when closed methods are insufficient:
Unstable fractures: where fragments cannot be maintained in alignment by closed methods due to muscle pull or fragment configuration.
Open fractures requiring urgent care: allowing thorough debridement, lavage, and direct stabilization while managing contamination.
Articular fractures that influence joint surfaces: demanding anatomical reduction and rigid fixation to ensure smooth joint movement and prevent degenerative joint disease.
Complicated fractures, including comminuted fractures: where multiple fragments necessitate direct visualization for reduction and complex reconstruction.
Most fractures in medium or larger breeds: due to higher loads and activity levels requiring stronger and more stable fixation than external coaptation can provide.
Reducing a Transverse Fracture
Steps to correctly realign a transverse fracture, focusing on restoring bone length and axial alignment:
Apply traction: Longitudinal pull applied to the distal bone segment to overcome muscle contraction and realign bone ends along the long axis.
Lift ends from incision: Through surgical access (open reduction), one or both bone ends are carefully elevated to enable clear visualization and manipulation without further damaging soft tissues.
Place ends in contact: Ensure the fractured bone ends are brought into precise apposition (end-to-end contact) to facilitate primary bone healing.
Force application: Apply constant, controlled effort to normalize the position, often involving rotational or bending forces to 'seat' the fracture fragments correctly, ensuring no gapping or overriding.
Reducing an Oblique Fracture
Specific methods for re-aligning oblique fractures, which often involve addressing rotational instability:
Distract bone segments: Gently separate fragments longitudinally to unlock any overlapping segments and allow for easier manipulation.
Utilize pointed reduction forceps: These instruments are invaluable for grasping and manipulating bone fragments, holding them firmly in proper position during reduction and initial fixation (e.g., lag screw placement).
Position obliquely: Manipulate the angle of the main fragments to align the oblique fracture planes before attempting full reduction, ensuring maximum contact surface for stability.
Choosing a Method of Fixation
Considerations for selecting the optimal fixation method, balancing biomechanical stability with biological preservation:
Identify which bone is fractured (e.g., a weight-bearing long bone like the femur versus a non-weight-bearing bone like the fibula) as this dictates load requirements.
Locate the precise position of the fracture (e.g., epiphyseal/articular fractures require anatomical reduction and specific fixation, while diaphyseal fractures tolerate some callus formation).
Assess size and weight of the patient to determine appropriate device strength and size, ensuring the implants can withstand physiological loads.
Analyze specific fracture characteristics (e.g., direction of fracture lines, degree of comminution, loss of bone substance) to predict instability and required counter-forces.
Further Considerations on Forces Acting on Fractures
Important forces: Understanding these forces helps dictate the type and strength of fixation required:
Compression: Stabilizes some fractures in alignment. Axial force that pushes bone ends together, stabilizing some fractures (e.g., transverse) if applied correctly; can promote primary bone healing.
Bending: Causes instability, particularly in transverse fractures. Flexural forces cause instability, especially in transverse fractures, and require anti-bending fixation (e.g., bone plates).
Torsion: Leads to instability during rotation; particularly dangerous. Twisting forces that lead to instability during rotation; particularly dangerous for spiral fractures, requiring effective anti-rotational control.
Ideal for Load Sharing: Proper method reduces fixation stress optimally while allowing movement to enhance healing. A proper fixation method reduces excessive stress on the implant (fixation device) by allowing the bone fragments themselves to bear some of the load, which helps prevent implant failure and stimulates bone healing through controlled mechanical stimulation.
Summary of Forces Acting on Different Fractures
Transverse Fracture:
Stable in compression, unstable in bending and rotation.
Oblique Fracture:
Unstable in compression, but more stable in bending and rotation compared to transverse fractures.
Comminuted Fracture:
Unstable in all forces applied (compression, bending, torsion) with substantial risk of displacement and collapse.
Methods of Surgical Fracture Repair
Various techniques include: Each designed to address specific fracture configurations and biomechanical demands:
Intramedullary pin + cerclage wire: Composite method for stabilization. A composite method often used for diaphyseal fractures. The IM pin resists bending, while cerclage wires (full cerclage for long oblique/spiral, hemicerclage for short oblique) provide compression and anti-rotational stability. Not ideal for comminuted fractures or as a sole fixation.
External fixator +/− cerclage wire: Useful for open fractures. Consists of pins inserted through the bone and connected externally by bars. Highly versatile for open fractures (allowing wound access), comminuted fractures, and those with significant soft tissue injury. Can provide rigid or flexible fixation depending on frame configuration.
Tension band fixation: Best for tensile forces (like avulsion fractures). Specifically used for avulsion fractures where a powerful muscle or ligament pulls a bone fragment away. Converts tensile forces into compressive forces across the fracture site, promoting stable healing (e.g., olecranon, greater trochanter).
Bone plate and screws: Provides stable, direct fixation. Considered the 'gold standard' for many fractures, particularly those requiring strong, stable, and rigid fixation. Plates can apply compression, neutralization, or bridging principles, counteracting all forces (bending, torsion, compression-distraction) effectively.
Lag screw: Used for compressing fracture fragments together. A compression screw designed to create interfragmentary compression across a fracture line, often used for oblique or spiral fractures, or to secure large fragments in comminuted fractures. It is an effect, not a device.
Interlocking nail: Offers robust internal fixation with minimal exposure. A specialized intramedullary nail with screws locking it to the bone at both ends, providing robust internal fixation with excellent resistance to bending, torsion, and compression without extensive soft tissue dissection, suitable for diaphyseal fractures.
Each method of fixation aims to counteract specific forces acting on the fractured bone, providing a stable environment for osteogenesis. Optimal healing occurs when bones are appropriately stressed (controlled load sharing) and stabilized, although severely comminuted fractures present challenges to achieving load sharing effectively, often requiring biological fixation principles (e.g., bridge plating) to preserve blood supply rather than direct anatomical reduction.