Trauma 101: Orthopedics Study Tool

A rotational injury to the loaded ankle — typically a twist while the foot is planted, going over on uneven ground, on stairs, or in sport. The foot's position at the moment of injury (supinated or pronated) and the direction of the rotational force determine the sequence in which the lateral structures, medial structures and syndesmosis fail, which is exactly what the mechanism-based classification encodes. Direct axial loading from a height produces a pilon-type injury instead, which is a different problem.

Forced hyperdorsiflexion of the foot drives the talar neck against the anterior tibial margin — historically the aviator's astragalus, now most often a road traffic collision or a fall from height. The talus has no muscular attachments and much of its surface is articular, so its blood supply enters over a limited area and displacement progressively strips it, which is why the osteonecrosis risk rises with the Hawkins grade.

A direct blow or a fall onto the arm produces transverse and comminuted patterns; a twisting force, including throwing or an arm-wrestling injury, produces spiral fractures. Pathological fracture through a metastatic deposit must always be considered in the older patient with a low-energy history.

Either a direct blow onto the point of the elbow, which tends to comminute, or a fall with a sudden violent triceps contraction against a flexed elbow, which produces a transverse avulsion-type separation. High-energy patterns extend to fracture-dislocations of the elbow.

A fall on the outstretched hand driving the radial head against the capitellum, often with a valgus and axial component. The same force pattern can rupture the medial collateral ligament or the interosseous membrane, so the injury is frequently part of a wider instability picture rather than an isolated bony event.

Almost always a fall onto the outstretched hand with the elbow hyperextended in a child, levering the distal fragment posteriorly — the extension type. A fall directly onto the flexed elbow produces the far less common flexion type.

Axial loading from a fall from height or a motor vehicle footwell injury drives the talus into the calcaneus, splitting the posterior facet and widening and shortening the heel. Because the mechanism is axial, always examine the spine and the contralateral limb — associated vertebral and lower limb injuries are common.

A fall onto the outstretched hand with a rotational component, a direct blow, or high-energy trauma. The forearm functions as a joint of rotation, so the injury is not simply two long bone fractures — restoring the radial bow, the relative lengths of the two bones and the interosseous space determines whether pronation and supination return.

A fall onto the outstretched hand with forced pronation, or a direct blow to the posterior forearm as in a defensive injury, fractures the ulna and forces the radial head out of its relationship with the capitellum. The essential concept is that an ulnar shaft fracture with any angulation must displace the radial head, because the two bones are tethered by the interosseous membrane and the annular ligament.

In elderly patients a simple fall from standing height with a torsional or direct lateral impact on the greater trochanter is enough, because of reduced bone mineral density. In young adults it takes high energy — a road traffic collision or a fall from height — with axial loading through an abducted or externally rotated limb, and is frequently part of a polytrauma picture. Stress fractures occur in runners and military recruits from repetitive loading without an acute event.

A simple fall from standing height with a direct impact on the greater trochanter in an osteoporotic elderly patient accounts for the overwhelming majority. High-energy trauma in the young produces the same fracture with more comminution and subtrochanteric extension. It is an extracapsular fracture, so the blood supply to the head is preserved and union is the rule.

A dashboard injury with the hip flexed and adducted drives the head posteriorly; an abducted externally rotated hip at impact drives it anteriorly. It takes considerable force in a normal hip, so associated acetabular, femoral head and knee injuries are common — the knee that struck the dashboard must always be examined.

Bimodal. High-energy axial loading with a varus, valgus or rotational component in the young, often a dashboard injury with the knee flexed. Low-energy twisting falls in the osteoporotic elderly, frequently around an existing knee replacement where the bone above the implant is stress-shielded.

A direct blow to the front of the knee, as in a fall onto the flexed knee or a dashboard impact, tends to comminute the patella. An indirect violent eccentric quadriceps contraction against a flexing knee produces a transverse fracture with separation. Assessment always centres on whether the extensor mechanism is intact.

Axial loading combined with a varus or valgus force drives the femoral condyle into the plateau. A pedestrian struck by a vehicle bumper classically produces a lateral plateau depression; a fall from height produces bicondylar comminution. Low-energy valgus injury in osteoporotic bone gives a depressed lateral plateau with little comminution.

A twisting injury in sport produces a spiral pattern; a direct blow or bumper injury produces transverse or comminuted patterns with a soft tissue crush. The tibia is subcutaneous over its anteromedial surface, so open injury is common and the soft tissue envelope dominates decision-making. Compartment syndrome is the complication to anticipate in every case.

The femoral head is driven into the acetabulum, and the position of the hip at impact determines the pattern — a flexed adducted hip in a dashboard injury tends to fracture the posterior wall with or without dislocation, while a laterally directed force through the greater trochanter produces transverse and both-column patterns. Low-energy falls in the osteoporotic elderly produce anterior column patterns with medial displacement and marked comminution.

High-energy trauma: a lateral impact from a vehicle, an anteroposterior crush such as a motorcyclist or a pedestrian, or a vertical shear from a fall from height. In the elderly, a simple fall can produce a fragility fracture of the pelvis with an intact-looking ring but genuine posterior insufficiency. The clinical priority is haemorrhage — the posterior venous plexus and branches of the internal iliac artery bleed into a pelvis that has lost its containment.

Usually a fall onto the point of the shoulder or a direct blow, transmitting force along the clavicle; less often a fall on the outstretched hand. Sporting collisions and bicycle falls dominate in young adults, simple domestic falls in the elderly.

A low-energy fall onto the outstretched hand or directly onto the shoulder in an osteoporotic patient is the classic route; high-energy trauma or a seizure or electric shock producing violent muscle contraction accounts for the young and the fracture-dislocation patterns.

Axial compression, usually a fall from height or a motor vehicle collision, fails the vertebral body in compression and retropulses fragments — often the posterosuperior corner — into the canal. The thoracolumbar junction is the transition from a rigid kyphotic thoracic spine to a mobile lordotic lumbar spine, which concentrates stress and explains why most of these injuries occur there.

High-energy trauma — road traffic collisions, falls from height, gunshot injury. Considerable force is needed in a normal adult femur, so a low-energy femoral shaft fracture should prompt a search for a pathological lesion or an atypical stress fracture in a patient on long-term antiresorptive therapy. Substantial blood loss into the thigh is expected.

Most commonly a fall on the outstretched hand with the wrist extended, driving an axial and dorsally directed load through the carpus into the metaphysis. Low-energy falls dominate in osteoporotic elderly patients; high-energy road traffic or sporting injuries in young adults produce more comminution, articular splitting and associated carpal or soft-tissue injury. A fall onto a flexed wrist produces the volar-displacement pattern instead.

A fall onto the outstretched hand with the wrist hyperextended and radially deviated, loading the scaphoid against the dorsal rim of the radius. Sporting and motorcycling injuries in young men predominate. The retrograde blood supply entering distally means the more proximal the fracture, the poorer the blood supply to the proximal fragment.