ORTHOPEDIC SURGERY – BCSE Study Guide

Overview and Clinical Importance

Orthopedic surgery represents a critical component of veterinary practice, addressing fractures, joint diseases, and ligamentous injuries across all species. This study guide covers the essential orthopedic topics tested on the BCSE, including fracture classification and healing, fixation methods, joint diseases, cruciate ligament disease, and patellar luxation.

Section 1: Fracture Classification

Basic Fracture Terminology

Accurate fracture classification is essential for communication between veterinarians and for treatment planning. Fractures are systematically described by location, configuration, stability, and soft tissue involvement.

Anatomic Location

Diaphyseal: Fractures of the shaft (middle portion) of long bones. Metaphyseal: Fractures near the flared ends of long bones. Epiphyseal: Fractures involving the bone ends and articular surfaces. Physeal: Fractures involving the growth plate in immature animals. Articular: Fractures extending into the joint surface.

MEMORY AID - Anatomic Bone Regions: Think 'DIME-PA' - Diaphysis (shaft), Metaphysis (flare), Epiphysis (end), Physis (growth plate), Articular (joint surface). Moving from center to ends: D-M-P-E-A.

Fracture Configuration

[Include Image: Figure 1. Fracture configuration types showing transverse, oblique, spiral, and comminuted patterns]

Open vs. Closed Fractures

Closed (Simple): Skin intact; no communication between fracture and external environment. Open (Compound): Skin breached; fracture communicates with external environment, creating infection risk.

Gustilo-Anderson Classification for Open Fractures:

Type I: Wound less than 1 cm; minimal soft tissue damage; low-energy mechanism

Type II: Wound 1-10 cm; moderate soft tissue damage; no extensive soft tissue loss

Type III: Wound greater than 10 cm; extensive soft tissue damage; high-energy mechanism. Subdivided into IIIA (adequate soft tissue coverage), IIIB (requires soft tissue reconstruction), and IIIC (vascular injury requiring repair)

MEMORY AID - Gustilo Classification: Remember '1-10-EXTREME': Type I = less than 1cm wound, Type II = 1-10cm wound, Type III = EXTREME damage (greater than 10cm with subdivisions A, B, C).

Salter-Harris Physeal Fracture Classification

The Salter-Harris classification system categorizes growth plate (physeal) fractures in immature animals. This system is crucial for predicting prognosis and planning treatment, as physeal injuries can result in premature growth plate closure and angular limb deformities.

MEMORY AID - Salter-Harris Types: Use the mnemonic 'SALTR' - Type I: Slipped (Straight across physis), Type II: Above (fracture extends into metaphysis), Type III: Lower (fracture extends into epiphysis), Type IV: Through (crosses physis into both metaphysis AND epiphysis), Type V: Rammed/cRushed (compression injury).

[Include Image: Figure 2. Salter-Harris Classification Types I-V diagram showing fracture patterns relative to the growth plate]

MEMORY AID - Physeal Fracture Prognosis: As Salter-Harris type NUMBER increases, PROGNOSIS generally worsens. Type I/II = Good, Type III = Fair, Type IV/V = Poor. Also remember: The YOUNGER the animal, the GREATER the potential for growth disturbance if premature closure occurs.

Section 2: Fracture Healing

Types of Bone Healing

Bone is unique among tissues in its ability to regenerate completely without scar formation. Understanding the two pathways of bone healing is essential for selecting appropriate fixation methods.

Primary (Direct) Bone Healing

Requirements: Absolute stability with anatomic reduction, direct bone contact (gap less than 0.01 mm for contact healing, less than 1 mm for gap healing), interfragmentary strain less than 2%.

Mechanism: Haversian remodeling - cutting cones of osteoclasts cross the fracture line followed by osteoblasts laying down new bone. No external callus formation.

Clinical application: Achieved with compression plating and lag screw fixation. Required for articular fractures to restore joint congruity.

Secondary (Indirect) Bone Healing

Requirements: Relative stability allowing some micromotion; does not require anatomic reduction.

Mechanism: External callus formation through endochondral and intramembranous ossification. This is the MOST COMMON form of fracture healing.

Phases of Secondary Bone Healing

MEMORY AID - Healing Phases Timeline: Think 'I See Hard Rocks': Inflammation (days 0-5), Soft callus (days 5-21), Hard callus (weeks 3-12), Remodeling (months-years). Or use the numbers: 5-21-84 (days for inflammation end, soft callus end, hard callus approximately 12 weeks).

[Include Image: Figure 3. Secondary bone healing phases showing hematoma, soft callus, hard callus, and remodeling stages]

Factors Affecting Fracture Healing

MEMORY AID - Nonunion Types: Hypertrophic = 'Elephant foot' appearance with abundant callus but no bridging - problem is MECHANICAL (needs stability). Atrophic = 'Horse hoof' appearance with tapered bone ends and no callus - problem is BIOLOGICAL (needs bone graft and blood supply).

Section 3: Fracture Fixation Methods

External Coaptation

Definition: Non-invasive stabilization using casts, splints, or bandages applied externally.

Indications: Incomplete (greenstick) fractures, minimally displaced closed fractures of distal limb, temporary stabilization, young animals with high healing capacity, fractures where joints above and below can be immobilized.

Contraindications: Fractures of humerus or femur (cannot immobilize shoulder or hip), open fractures, highly unstable fractures, patients unable to tolerate bandage management.

Complications: Cast sores, vascular compromise, slippage, soiling, muscle atrophy, joint stiffness, delayed union from excessive motion.

MEMORY AID - External Coaptation Rule: The '50-50 Rule': External coaptation is most suitable for fractures in the distal 50% of the limb in patients with greater than 50% intact cortical contact. Also remember: Must immobilize joints ABOVE and BELOW the fracture.

Internal Fixation Methods

Intramedullary (IM) Pins

Mechanism: Pins placed within the medullary canal to provide axial alignment.

Advantages: Simple, economical, good for transverse diaphyseal fractures, can be combined with other fixation methods.

Disadvantages: Poor rotational stability (unless stacked or combined with cerclage), cannot resist bending forces alone, pin migration possible.

Pin size: Should fill 60-70% of medullary canal at narrowest point for adequate three-point fixation.

Bone Plates and Screws

Types of plates:

Dynamic Compression Plate (DCP): Eccentric screw placement creates compression across fracture for primary bone healing. Standard plating technique.

Locking Plate: Screws lock into plate creating fixed-angle construct. Acts as internal fixator - does not require plate-bone contact. Superior for osteoporotic bone and biological osteosynthesis.

Reconstruction Plate: Can be contoured in multiple planes. Used for irregular bone surfaces (pelvis, mandible).

Buttress Plate: Provides support against axial loading in periarticular fractures.

Plate function principles:

Compression: Plate used to compress fracture ends together (anatomic reduction, primary healing).

Neutralization: Plate protects other fixation (lag screws) from bending/rotational forces.

Bridging: Plate spans comminuted fracture zone; relies on biological osteosynthesis.

Lag Screw Technique

Principle: Screw threads engage only the far fragment, creating interfragmentary compression as the screw is tightened. The near cortex (glide hole) is overdrilled to allow the screw shaft to slide.

Applications: Long oblique fractures, spiral fractures, articular fractures, butterfly fragments. Fracture line length should be at least 2x bone diameter for adequate screw purchase.

[Include Image: Figure 4. Comparison of internal fixation methods: IM pin, bone plate with compression, and lag screw technique]

External Skeletal Fixation (ESF)

Mechanism: Pins placed percutaneously through bone above and below fracture, connected to external frame/bar.

Types:

Type I (Unilateral): Pins enter from one side only; simplest configuration.

Type II (Bilateral): Pins pass through bone with connections on both sides; increased rigidity.

Type III (Combined): Unilateral and bilateral frames combined for maximum stability.

Advantages: Minimally invasive, preserves blood supply, adjustable during healing, can be staged or combined with IM pins (tie-in configuration).

Disadvantages: Pin tract infections (most common complication), patient compliance required, pin loosening, bulky apparatus.

MEMORY AID - Fixation Selection: Think 'CAST the RIGHT fix': Compression for articular fractures, Alignment (bridging) for Severely comminuted fractures, Three-point fixation for Transverse fractures. RIGHT: Reducible = anatomic reconstruction, Irreducible = biological bridging, Gap = bone graft, High energy = staged approach, Tiny patient = external coaptation may work.

Section 4: Cranial Cruciate Ligament Disease

Anatomy and Function

The cranial cruciate ligament (CCL) is analogous to the anterior cruciate ligament (ACL) in humans. It originates from the caudomedial aspect of the lateral femoral condyle and inserts on the cranial intercondylar area of the tibia. The CCL and caudal cruciate ligament (CaCL) cross within the stifle joint.

CCL Functions:

1. Prevents cranial translation of the tibia relative to the femur

2. Limits internal rotation of the tibia

3. Prevents hyperextension of the stifle

4. Provides proprioceptive feedback to the joint

Pathophysiology

CCL disease is the MOST COMMON cause of pelvic limb lameness in dogs. Unlike acute ACL tears in humans (usually traumatic), canine CCL disease is typically a degenerative process with progressive fiber failure over time.

Risk factors: Obesity, steep tibial plateau angle, straight pelvic limb conformation, immune-mediated synovitis, genetic predisposition (Labrador Retrievers, Rottweilers, Newfoundlands, Staffordshire Bull Terriers).

Tibial thrust: When the CCL is deficient, ground reaction forces during weight-bearing cause the tibia to thrust cranially relative to the femur due to the caudally-sloped tibial plateau. This is the biomechanical basis for osteotomy-based surgical treatments.

Clinical Signs and Diagnosis

Acute complete rupture: Non-weight-bearing lameness progressing to weight-bearing lameness, stifle effusion, pain on manipulation.

Chronic/partial rupture: Gradual onset of hindlimb lameness, muscle atrophy, stifle thickening (periarticular fibrosis - 'medial buttress'), difficulty rising.

Diagnostic Tests:

Cranial drawer test: With stifle in slight flexion, stabilize femur and attempt to translate tibia cranially. Positive test indicates CCL rupture. May require sedation in tense patients.

Tibial thrust test (Tibial Compression Test): With stifle extended, flex the hock - if CCL is ruptured, tibia thrusts cranially as gastrocnemius muscle tension is transferred through intact CaCL.

Sit test: Dogs with CCL disease often sit with affected limb extended rather than fully flexed.

MEMORY AID - Stifle Examination: Remember 'DRAW the THRUST while they SIT': Drawer test (direct manipulation), Thrust test (tibial compression), Sit test (postural observation). All three should be assessed. A positive drawer is definitive; tibial thrust is more sensitive in large dogs.

[Include Image: Figure 5. Cranial drawer test technique demonstrating positive drawer sign indicating CCL rupture]

Surgical Treatment Options

[Include Image: Figure 6. TPLO procedure diagram showing the radial osteotomy and plate fixation to reduce tibial plateau angle]

MEMORY AID - CCL Surgery Selection: Think 'Size Matters': SMALL dogs (less than 15 kg) = Lateral Suture often sufficient. MEDIUM-LARGE dogs = Osteotomy (TPLO preferred). Remember the goal: Change the BIOMECHANICS so the ruptured CCL is no longer needed for stability.

Meniscal Injury

The medial meniscus is commonly injured secondary to CCL rupture because it is firmly attached to the tibia and cannot escape abnormal motion. The lateral meniscus is more mobile and less frequently damaged.

Meniscal pathology: Caudal pole tears are most common. May be present at time of CCL surgery (concurrent injury) or develop later (subsequent meniscal tear - 3-20% incidence post-surgery).

Treatment: Partial meniscectomy (removal of damaged portion). Meniscal release (cutting caudal meniscotibial ligament) is sometimes performed prophylactically but is controversial.

Section 5: Patellar Luxation

Overview and Classification

Patellar luxation is one of the most common orthopedic conditions in dogs, particularly toy and small breeds. The patella (kneecap) displaces from the trochlear groove of the femur, most commonly in a MEDIAL direction (medial patellar luxation, MPL).

Medial Patellar Luxation (MPL): Accounts for approximately 75-80% of cases. Common in small/toy breeds (Chihuahua, Pomeranian, Yorkshire Terrier, Toy Poodle, Boston Terrier).

Lateral Patellar Luxation (LPL): More common in large/giant breeds. Associated with genu valgum (knock-kneed) conformation. Often more severe.

Grading System

The most commonly used grading system in veterinary medicine was adapted from Singleton (1969) and Putnam (1968). Grade determines treatment recommendations.

MEMORY AID - Patellar Luxation Grades: Think 'Can it be PUT back?': Grade I = Pops back on its own. Grade II = Put it back, it stays (until flexion). Grade III = Put it back, it pops out again. Grade IV = Can't Put it back at all. As grade increases, severity and need for surgery increases.

Underlying Skeletal Abnormalities

Congenital patellar luxation results from multiple developmental abnormalities of the extensor mechanism and supporting structures:

Femoral deformities: Femoral varus (bowing), internal femoral torsion, hypoplastic medial trochlear ridge, shallow trochlear groove (trochlear hypoplasia).

Tibial deformities: Medial deviation of tibial tuberosity, external tibial torsion, proximal tibial varus.

Soft tissue abnormalities: Medial soft tissue contracture (retinaculum, joint capsule), lateral soft tissue laxity, malalignment of quadriceps mechanism.

Surgical Treatment

Surgical correction addresses the specific abnormalities present in each patient. Multiple procedures are typically combined.

Soft Tissue Procedures

Lateral imbrication (for MPL): Tightening of the lateral joint capsule/retinaculum to pull patella laterally.

Medial release (for MPL): Incision of contracted medial retinaculum/joint capsule to allow lateral repositioning.

Osseous Procedures

Tibial tuberosity transposition (TTT): Osteotomy and lateral repositioning of the tibial tuberosity to realign the quadriceps mechanism. MOST COMMONLY PERFORMED osseous procedure for MPL.

Trochleoplasty: Deepening of the trochlear groove to provide better patellar retention. Techniques include:

- Trochlear wedge recession: Remove wedge, deepen groove, replace wedge (preserves cartilage)

- Trochlear block recession: Remove rectangular block, deepen, replace

- Trochlear chondroplasty/sulcoplasty: Abrade hyaline cartilage and deepen (for young animals with soft cartilage)

Corrective osteotomies: For severe skeletal deformities (Grade III-IV), femoral and/or tibial corrective osteotomies may be required to address varus/valgus and rotational deformities.

[Include Image: Figure 7. Surgical techniques for patellar luxation: tibial tuberosity transposition and trochlear wedge recession]

MEMORY AID - MPL Surgery Components: Remember 'TTS': Tibial Tuberosity Transposition, Trochlear deepening (sulcoplasty), Soft tissue reconstruction. Most MPL surgeries need all THREE components. Think of 'Tuning, Tracking, and Tightening' the extensor mechanism.

Complications and Prognosis

Complications: Reluxation (most common - 8-15%), implant failure/migration, tibial tuberosity fracture, wound complications, arthritis progression.

Prognosis: Grade I-II with appropriate surgery: Excellent (greater than 90% good-excellent outcomes). Grade III: Good (85-90%). Grade IV: Fair to good, depending on severity of deformity and whether corrective osteotomies are performed.