12.1.2025 - SAS

Introduction to Case Discussions

• Initiation of complex clinical cases for comprehensive discussion and collaborative learning among students.

• Emphasis on encouraging active student participation and input, acknowledging that initial thoughts, even if not fully accurate, are crucial for stimulating critical thinking and facilitating a deeper understanding of the subject matter within the group.

Goals of Case Discussions

• To develop diagnostic and therapeutic reasoning skills.

• To foster a collaborative learning environment.

• To critically evaluate various treatment modalities.

Case 1: Two-Year-Old Great Dane

• Description of Case:

  • A large, 110-pound (approximately 50 kg) Great Dane presented three hours post-trauma (hit by a car).

  • Initial assessment would include stabilization for shock, pain management, and assessment of other potential injuries given the high-impact trauma.

• Fracture Classification:

  • Fracture described as a short, oblique diaphyseal fracture of the humerus.

  • Type: Short and oblique, indicating the fracture line runs obliquely across the bone shaft, typically at an angle less than 45-60 degrees to the long axis. This configuration offers some inherent stability but also allows for potential shear forces.

  • Location: Primarily located in the mid to slightly distal diaphysis (the main shaft) of the humerus, distinguishing it from fractures of the metaphysis or epiphysis.

  • Characteristics: Classified as a simple fracture (two main fragments) and most likely reducible, meaning the bone fragments can be accurately realigned with minimal difficulty during surgery. This implies a good prognosis for direct bone healing with proper fixation.

• Fracture Assessment Score:

  • The overall fracture assessment score for this case fell in the mid-range, approximately between 5 to 7 out of a possible 10 (higher scores generally indicate better prognosis or easier fixation).

  • Rationale for Score:

    • The relatively simple nature of the fracture (simple, reducible, short oblique) contributes positively.

    • The young age of the patient (two years old) is a significant positive factor, as younger animals typically have a robust healing capacity, excellent blood supply, and faster revascularization.

    • The fracture is not severely comminuted (more than two fragments) nor is it an open fracture (no communication with the external environment), both of which would significantly lower the score due to increased complexity and risk of infection.

Key Considerations in Fracture Assessment

• Larger breed dogs, such as Great Danes, often yield lower fracture assessment scores compared to smaller breeds for similar fracture types.

  • This is primarily due to the greater biomechanical stress placed on implants in larger, heavier animals, requiring more robust and stable fixation methods to successfully withstand forces during weight-bearing and activity. Bone healing also tends to be slower.

  • Any identified negative factors (e.g., patient size, concurrent injuries, poor bone quality, highly comminuted fractures) will necessitate a more aggressive, competent, and often multi-modal management approach to ensure successful outcomes.

Suggested Repair Methods for Case 1

• Bone Plates:

  • The use of a cranial or craniomedial bone plate is a strong indication given the mid-diaphyseal location of the humeral fracture. Plating allows for rigid internal fixation, promoting primary bone healing if interfragmentary compression is achieved.

  • In larger patients like a Great Dane, a combination of a plate and an intramedullary (IM) rod (e.g., an IMEX Intramedullary Interlocking Nail system or a locking plate with an IM pin) may be considered for additional stabilization. The IM rod acts as a load-sharing device, reducing bending and torsional stresses on the plate, while the plate provides rotational stability and compression.

  • A debate exists on the absolute necessity of a plate-rod combination, with the decision often dependent on individual patient factors (e.g., activity level, bone quality), fracture configuration, and surgeon's preference.

• Alternative Methods of Fixation:

  • Mentioned use of a scorpion technique (pinning technique where pins cross at the fracture site to achieve stabilization) for short oblique fractures. However, it was noted that this technique is often not definitive on its own for a substantial bone like the humerus in a large dog and typically requires additional support like a bone plate or an external fixator to prevent rotation and maintain rigid fixation.

  • Type 1 External Skeletal Fixator (ESF): Noted as having stability issues for a humeral fracture specifically. The extensive muscle mass surrounding the humerus can make pin placement challenging, and a Type 1 (unilateral, uniplanar) ESF may not provide sufficient torsional or bending rigidity, especially in a large dog, leading to implant failure or non-union. More rigid ESF constructs (e.g., Type II or hybrid) might be considered but are still less common for humeral diaphyseal fractures.

  • Interlocking Nails (ILN):

    • Advantages include achieving excellent fracture apposition and crucial load sharing with the bone, which is highly beneficial in large breeds. ILNs are placed within the medullary canal and locked to the bone proximally and distally, providing good bending and torsional stability with minimal soft tissue disruption.

    • Suggested as a highly stable and biological method for humeral fractures in larger breeds, particularly for diaphyseal fractures, offering a relatively minimally invasive approach.

Surgical Anatomy Considerations

• Radial Nerve Protection:

  • Paramount importance of meticulous identification and protection of the radial nerve during surgical approaches to the humerus, especially when placing bone plates via a craniolateral or lateral approach. The radial nerve courses spirally around the mid-diaphysis of the humerus, making it highly susceptible to iatrogenic damage (laceration, compression) if not carefully retracted, which can lead to severe neurological deficits (e.g., dropped elbow, inability to extend carpus/digits).

• External Fixator Anatomy Consideration:

  • In cases where an external fixator might be considered (less common for humerus), meticulous and precise dissection is recommended for proper identification of surrounding musculature, neurovascular structures, and bone anatomy prior to surgical placement of transfixation pins. This minimizes the risk of damage to vital structures and ensures optimal pin purchase and construct stability.

Case 2: Four-Year-Old Spayed Female Dalmatian

• Description of Case:

  • A 26 kg (approximately 57 lbs) spayed female Dalmatian involved in an accident, presenting with an ipsilateral tibial tarsal luxation.

  • Concurrent injuries are common in trauma cases and require a holistic approach.

• Fracture Classification:

  • An olecranon fracture was observed in addition to the tibial tarsal luxation. The olecranon is the proximal projection of the ulna, forming the point of the elbow, and serves as the insertion point for the triceps brachii muscle group, making it prone to avulsion fractures due to powerful muscular forces.

• Fracture Assessment Score:

  • A high score might initially be assigned (possibly around 8) for the olecranon fracture alone, indicative of its relatively straightforward nature for repair. However, this score is decreased significantly due to the presence of the concurrent ipsilateral tibial tarsal luxation.

Factors Affecting Healing and Assessment

• Analysis indicates that concurrent injuries primarily impact healing under weight-bearing conditions by altering load distribution, increasing overall systemic stress, and potentially lengthening the recovery period. For instance, a luxation in the same limb will delay full weight-bearing on that limb, affecting the timeline for rehabilitation and the ultimate functional outcome of the primary fracture repair.

• Importance of understanding compensating mechanisms in the overall assessment and healing potential of primary injuries. The animal may shift weight to other limbs, leading to compensatory lameness, muscle atrophy, and increased stress on uninjured joints, which must be managed during the rehabilitation phase.

Repair Methods for Case 2

• Tension Band Fixation:

  • Mentioned as the primary repair choice for olecranon fractures, particularly for avulsion types, due to the biomechanical nature of the injury and the strong distractive forces exerted by the triceps muscle.

  • Principle: Tension band fixation converts distractive (pulling apart) forces acting on the fracture site into compressive forces, promoting tight apposition and stable healing.

  • Technique: Typically involves placing two K-wires (Kirschner wires) longitudinally across the fracture site and then placing a figure-of-eight tension band wire around the K-wires and through a transverse bone tunnel or around the triceps tendon via a circumosseous loop. The wire is then tightened, compressing the fragments.

• Alternative Option:

  • Possible use of a lag screw with proper surgical technique for drilling and positioning. A lag screw provides interfragmentary compression by ‘lagging’ one fragment to another and can be used alone for stable, simple fractures or, more commonly, in conjunction with a tension band for enhanced stability, especially in larger breeds or active patients.

Tension Band Mechanics

• The fundamental mechanics of tension band fixation include counteracting the powerful distractive forces exerted by muscular tension (e.g., triceps pull on the olecranon). By placing the fixation on the tension side of the bone, it converts these forces into compression across the fracture site, which is crucial for achieving stable interfragmentary compression and facilitating primary bone healing. The Z effect of the wire and pins provides the necessary counter-force.

Notable Fractures Requiring Attention

• Listing of other specific fractures discussed as requiring particular attention and fixation due to their anatomical location and biomechanical challenges:

  • Glenoid tubercle fractures: Occur at the attachment point of the biceps brachii tendon. Often avulsion fractures, requiring tension band or lag screw fixation.

  • Acromion fractures: Part of the scapula. Depending on displacement, may require plating or lag screw fixation.

  • Shoulder malleolus fractures (medial/lateral epicondylar fractures of the humerus): These are common in young animals due to anatomical weakness at the growth plates and involve the articular surface, often requiring precise anatomical reduction and lag screw fixation.

  • Greater trochanter fractures: Avulsion fractures due to pull of gluteal muscles. Often repaired with tension band fixation or lag screws.

• It is crucial to understand the dynamic forces (muscle pull, weight-bearing, joint movement) affecting these specific anatomical areas during repair and the profound implications these forces have on healing dynamics and the choice of fixation method.

Case 3: Five-Month-Old Saluki

• Interpretation of Trauma:

  • Significant focus on the interpretation of fracture lines and the critical differentiation between true pathological fractures and normal growth plate (physis) injuries, particularly in immature animals like a five-month-old Saluki. Growth plates are softer than mature bone and are common sites of injury in young, growing animals.

• Fracture Identification and Risk Analysis:

  • Acknowledgment of the inherent susceptibility of youthful skeletal systems (with active physes) to misinterpretation of normal growth patterns on radiographs versus actual pathological fractures. Care must be taken to distinguish physeal lines from fracture lines.

  • The necessity of using tension band fixation and associated techniques (e.g., K-wires) that specifically focus on growth plate preservation is paramount in young animals. Techniques should avoid damaging the physis to prevent growth deformities (e.g., limb shortening or angulation) as the animal matures. These methods allow for some controlled motion that is beneficial for physeal healing while providing sufficient stability.

Case 4: Young Canine with Distal Femur Fracture

• Classification of Fracture:

  • Typically recognized as a Salter Harris Type II fracture if it involves the distal femur (the most common physeal fracture type).

  • A Salter-Harris Type II fracture extends through the physis and then exits through the metaphysis, leaving the epiphysis intact. This type generally has a good prognosis with proper fixation and minimal physeal damage.

• Fracture Assessment Score and Stability:

  • Often noted for inherently high stability because of rapid healing potential in young patients and the presence of intact periosteum that acts as a hinge, especially on the metaphyseal side of a Salter-Harris Type II fracture.

  • Adjustable parameters for the careful application of stabilizing pins (e.g., cross-pinning with small diameter K-wires) are emphasized in young, rapidly healing patients to provide sufficient stability without overly rigid fixation that might impair growth, and to allow for early implant removal to minimize complications.

Healing Considerations and Quadriceps Contracture Risks

• Extensive discussion around managing the healing process and the potential dreaded complication of quadriceps contracture (fixed extension of the stifle and inability to flex the hip) in distal femoral fractures of young animals. This complication can arise from prolonged immobilization, excessive inflammation, or scar tissue formation around the quadriceps muscle group.

• Prevention and management strategies include early detection, appropriate surgical stabilization to allow early mobilization, physical therapy, and careful attention to postoperative rehabilitation protocols, ensuring the encouragement of early limb use and range of motion post-fracture management to prevent fibrotic changes and maintain joint function.

Fracture Management Approach and Techniques Overview

• Detailed techniques for specific fracture types were heavily emphasized:

  • Cross-pinning: Commonly used for Salter-Harris physeal fractures, especially in the distal femur or humerus. Involves placing two or more K-wires in a crossed configuration through the metaphysis into the epiphysis, avoiding damage to the growth plate.

  • Rush pin fixation: A type of intramedullary pinning where pins are inserted from the metaphyseal region into the medullary canal, providing elastic intramedullary fixation.

  • Interdigitated stabilization methods: Involve engaging irregular fracture surfaces or using specific implant designs that interlock the fragments, enhancing rotational stability.

• All methodologies have detailed descriptions emphasizing patient-specific considerations, including age, weight, activity level, fracture configuration, bone quality, and concurrent injuries.

Understanding Fracture Healing Dynamics

• Detailed information on clinical observations surrounding expected healing timelines for different fracture types and locations (e.g., 4-6 weeks for small animal long bones, longer for large breeds or complex fractures).

• Processes for post-surgical radiological evaluations (e.g., 2-, 4-, 6-week radiographs) to assess callus formation, bone bridging, remodeling, and proper implant position.

• Physical evaluation metrics (e.g., lameness score, range of motion, pain assessment, muscle atrophy) to assess successful healing, functional recovery, and guide rehabilitation protocols.

Conclusion

• Overall emphasis on developing a robust understanding of diverse fracture types, comprehensive assessment metrics (including patient, fracture, and surgeon factors), their anatomical and physiological implications, and the selection of appropriate surgical intervention techniques for optimal patient outcomes in veterinary orthopedics. This includes appreciating the interplay of biomechanics, biological factors, and patient-specific needs for successful fracture management.