12.2 Musculoskeletal Trauma: Open Fractures, Luxations, Splints & Compartment Syndrome

Musculoskeletal Trauma: Open Fractures, Luxations, Splints & Compartment Syndrome

VTS Critical Concept: In emergency musculoskeletal trauma, the primary rule of triage is absolute: Orthopedic injuries are NEVER immediate surgical emergencies ahead of Airway, Breathing, Cardiovascular stability, or active cavitary hemorrhage. A dog will not die in the first 30 minutes from a fractured femur, but it will succumb rapidly to a tension pneumothorax, hemoperitoneum, or hypovolemic shock. Once stabilized, open fractures, neurovascular compromise, and acute compartment syndrome demand rapid, meticulous intervention to prevent limb amputation or death.

1. Trauma Triage Hierarchy & Distal Neurovascular Assessment

The Triage Hierarchy in Polytrauma

1. A (Airway & Cervical Spine): Ensure patency, suction blood/vomitus, intubate if comatose or severe upper airway trauma.
2. B (Breathing & Ventilation): Address tension pneumothorax, flail chest, diaphragmatic hernia, or pulmonary contusions.
3. C (Circulation & Hemostasis): Control active external arterial hemorrhage via direct pressure; resuscitate hypovolemic shock with balanced crystalloids and blood products; rule out hemoperitoneum and hemothorax.
4. D (Disability & Neurological): Modified Glasgow Coma Scale (MGCS) evaluation for traumatic brain injury; spinal cord evaluation.
5. E (Examination / Extremities): Orthopedic assessment, open wounds, temporary coaptation, and fracture stabilization.

[ Distal Neurovascular Examination Protocol ]
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[ Vascular Perfusion Assessment ]      [ Neurological Integrity Assessment ]
• Peripheral Arterial Pulse             • Superficial vs. Deep Pain Sensation
  (Dorsal pedal / Femoral pulse)          (Conscious cortical response vs reflex)
• Extremity Temperature                 • Motor Function & Weight-Bearing
  (Compare bilateral paws / pads)       • Specific Peripheral Nerve Deficits:
• Capillary Refill Time (CRT)             - Radial Nerve (extensor tone / knuckling)
  (Pad / nailbed blanching < 2 sec)       - Sciatic Nerve (tibial / peroneal loss)
• Bleeding on Nailbed Quick Clip          - Femoral Nerve (stifle extension loss)

Systematic Distal Neurovascular Assessment

Every musculoskeletal injury must undergo a thorough distal neurovascular examination prior to and immediately following the application of any splint or bandage:

1. Peripheral Pulse Quality: Palpate the dorsal pedal artery (cranial branch of the saphenous artery on the dorsal tarsus/metatarsus) for hindlimb injuries and the radial/brachial artery for forelimb injuries. A weak or absent pulse indicates arterial laceration, thrombosis, or compression by displaced fracture fragments.
2. Extremity Temperature & Perfusion: Compare the temperature of the injured paw pads directly with the contralateral uninjured limb. Cold, clammy extremities with delayed pad blanching or purple/cyanotic nailbeds indicate vascular compromise.
3. Sensory & Deep Pain Sensation:
   • Superficial Sensation: Lightly pinch the webbing between digits.
   • Deep Pain Perception: Apply forceful mechanical pressure to the periosteum of the distal phalanges using a pair of heavy hemostats. Critical Distinction: The technician must observe a conscious cerebral response (vocalizing, turning head, attempting to bite, dilated pupils) rather than a simple spinal withdrawal reflex (which is a local spinal reflex arc that can persist even with complete transection of the spinal cord or proximal peripheral nerves).
4. Peripheral Nerve Mapping:
   • Radial Nerve (C6-T2): Innervates all extensor muscles of the elbow, carpus, and digits. Injury causes inability to bear weight, loss of carpal/digital extension (knuckling), and loss of sensation over the dorsal aspect of the paw.
   • Sciatic Nerve (L6-S1): Transverses caudal to the femoral shaft; highly susceptible to injury during ilial, acetabular, or proximal femoral fractures. Injury causes loss of stifle flexion, loss of digital flexion/extension, dropped hock, and absent sensation over the lateral/plantar paw.
   • Femoral Nerve (L4-L6): Controls the quadriceps femoris muscle. Injury prevents active stifle extension, rendering the animal incapable of bearing weight on the limb.

2. Open Fractures: Gustilo-Anderson Classification & Emergency Wound Care

An open fracture exists whenever a traumatic disruption of the skin and underlying soft tissues establishes direct communication between the external environment and the fracture hematoma/bone fragments. All open fractures are contaminated and carry a profound risk of osteomyelitis, non-union, and sepsis.

Gustilo-Anderson Classification Scheme

Emergency Wound Care Protocol: 'The Golden Rules'

[ Emergency Open Fracture Wound Care Protocol ]
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1. INTRAVENOUS ANTIMICROBIALS WITHIN 60 MINUTES
   • First-generation Cephalosporin: Cefazolin 22 mg/kg IV q90-120 min
   • Grade III add: Enrofloxacin 10-15 mg/kg IV q24h (or Marbofloxacin/Aminoglycoside)
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2. WOUND PACKING & MARGIN PREPARATION
   • Pack open wound cavity with STERILE WATER-SOLUBLE KY JELLY
   • Clip wide hair margins around wound (KY jelly catches loose hair clippings)
   • Scrub intact peripheral skin with Chlorhexidine (keep soap OUT of wound)
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3. COPIOUS LOW-PRESSURE LAVAGE
   • Lavage with 1-3 Liters of STERILE 0.9% SALINE or LRS (Warm 37-38°C)
   • Ideal pressure: 7-8 psi (1-L bag in pressure infuser at 300 mmHg with 18G needle)
   • AVOID cytotoxic antiseptics (NO undiluted chlorhexidine or hydrogen peroxide in open bone!)
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4. STERILE COVERAGE & RIGID TEMPORARY COAPTATION
   • Apply sterile non-adherent primary dressing (Telfa / hydrogel / wet-to-dry)
   • Apply Robert Jones / Modified Robert Jones bandage with rigid lateral splint
   • Transfer to OR for definitive debridement and stabilization

3. Coaptation, Bandaging & Splinting Principles

The Cardinal Rules of Coaptation

• The Rule of Two Joints: To achieve mechanical stability and neutralize bending, rotational, and shear forces, any splint or cast must rigidly immobilize the joint immediately proximal (above) and the joint immediately distal (below) the fracture line.
• Example: A radial/ulnar diaphyseal fracture requires rigid coaptation immobilizing both the elbow joint and the carpal joint.
• Proximal Fractures (Humerus & Femur): Standard splints (lateral splints, spoon splints) CANNOT stabilize fractures of the humerus or femur because the proximal joint (shoulder or hip) cannot be captured. Applying a standard distal splint to a humeral or femoral fracture creates a dangerous mechanical fulcrum at the fracture site, drastically increasing bone displacement, soft tissue laceration, and neurovascular transection. Proximal fractures require a Spica Splint or strict cage confinement pending surgery.

Bandage & Splint Types

4. Acute Joint Luxations: Diagnosis & Reduction

Coxofemoral (Hip) Luxation

Coxofemoral luxations account for $>90%$ of all traumatic joint luxations in small animals, resulting from severe blunt trauma (vehicular accidents) that ruptures the round ligament of the femoral head (ligamentum teres) and the joint capsule:

• Craniodorsal Luxation (~75% of cases): The femoral head displaces craniodorsally into the gluteal musculature. Clinically, the affected limb appears shortened, adducted, and externally rotated (the stifle points outward). The distance between the greater trochanter and the tuber ischiadicum is markedly increased.
  • Management: Closed reduction under general anesthesia with profound muscle relaxation (fentanyl + midazolam/propofol). Post-reduction: Apply an Ehmer sling for $7-10\text{ days}$.
• Caudoventral Luxation (~25% of cases): The femoral head displaces into the obturator foramen. Clinically, the affected limb appears lengthened and abducted.
  • Management: Closed reduction via lateral traction; post-reduction: Apply Hobbles (connecting the pelvic limbs at the hocks to prevent abduction) or a 90-90 flexion sling. Ehmer slings are strictly contraindicated in caudoventral luxations as they promote reluxation.

Elbow Luxation

Traumatic elbow luxation involves displacement of the radial head and the anconeal process of the ulna relative to the humeral condyle. Over $90%$ are lateral luxations due to the large medial humeral condylar ridge preventing medial displacement.

• Clinical Signs: Non-weight-bearing lameness; the elbow is held in slight flexion with the antebrachium abducted and pronated.
• Management: Closed reduction under deep general anesthesia: Flex elbow to $100-110^\circ$, apply medial pressure to radial head while rotating the anconeus into the olecranon fossa. Maintain in an extended Modified Robert Jones or Spica splint for $10-14\text{ days}$.

5. Acute Compartment Syndrome (ACS)

Acute Compartment Syndrome (ACS) is a catastrophic orthopedic emergency characterized by increased tissue pressure within a closed osteofascial compartment that compromises microvascular capillary perfusion, culminating in rapid neuromuscular ischemia, irreversible myonecrosis, and permanent limb paralysis.

[ Pathophysiology of Acute Compartment Syndrome ]
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Trauma / High-Energy Fracture / Crush Injury / Constrictive Bandage
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Bleeding & Edema within Rigid, Inelastic Osteofascial Compartment
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Elevation of Intracompartmental Pressure (> 30 mmHg)
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Intracompartmental Pressure Exceeds Capillary Perfusion Pressure
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Capillary Bed Collapse ──► Severe Tissue Hypoxia & Lactic Acidosis
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Endothelial Necrosis & Massive Permeability Leak (Vicious Cycle)
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       ┌────────────────┴────────────────────────┐
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[ Irreversible Myonecrosis (4-8 hr) ]     [ Irreversible Nerve Ischemia (12 hr) ]
• Volkmann's Ischemic Contracture         • Permanent motor paralysis
• Massive Rhabdomyolysis & AKI            • Complete loss of sensory perception

Anatomy & Predisposing Sites

Osteofascial compartments consist of muscles, nerves, and blood vessels enveloped by thick, unyielding fibrous fascia anchored to bone. The most common veterinary anatomical sites include:

• Craniolateral compartment of the crus (tibia): Encloses the cranial tibial and long digital extensor muscles.
• Caudal deep compartment of the crus: Encloses the deep digital flexor.
• Volar/flexor compartments of the antebrachium (radius/ulna).

The Clinical '5 Ps' of Compartment Syndrome

1. Pain Out of Proportion to Injury: The earliest and most reliable clinical indicator. Characterized by excruciating, escalating pain refractory to pure $\mu$-opioids, and severe agony upon passive stretching of the muscles traversing the affected compartment (e.g., severe pain on passive extension of digits in craniolateral crus syndrome).
2. Pressure: Palpation reveals an extremely tense, rock-hard, non-compliant, 'wooden' compartment.
3. Paresthesia / Hypoesthesia: Loss of cutaneous sensory perception in the distribution of nerves traversing the compartment (e.g., deep peroneal nerve deficits on dorsal paw).
4. Pallor & Poikilothermia: The distal extremity becomes cold and pale due to advanced microvascular shutdown.
5. Paralysis: Late, terminal sign indicating complete motor nerve and myocyte death.

Objective Diagnostic Criteria & Emergency Interventions

• Intracompartmental Pressure Measurement: Measured directly using a Stryker intra-compartmental pressure monitor or needle manometer.
  • Normal Resting Pressure: $0-8\text{ mmHg}$.
  • Diagnostic Threshold for ACS: Absolute pressure $>30\text{ mmHg}$, or a perfusion pressure difference (delta pressure $\Delta P$) of $<30\text{ mmHg}$ relative to diastolic arterial blood pressure ($\Delta P = DBP - \text{Compartment Pressure}$). A $\Delta P < 30\text{ mmHg}$ indicates critical capillary bed collapse.
• IMMEDIATE EMERGENCY ACTIONS:
  1. Immediately bivalve and completely remove all casts, splints, and circumferential bandages. Bandage removal alone reduces intracompartmental pressure by up to $50-70%$.
  2. Emergency Decompressive Fasciotomy: If compartment pressure remains elevated ($>30\text{ mmHg}$) or clinical signs of severe pain and swelling persist, immediate longitudinal surgical incisional release of the overlying skin and tense fascia is mandatory. The wound must be left wide open under sterile non-adherent dressings or vacuum-assisted closure (VAC) until swelling subsides.