Fractures & Dislocations — Practice

Question 1

Which Salter-Harris type is the most common physeal fracture?

Accepted Answer

B

Question 2

A patient with a mid-to-distal humeral shaft fracture is unable to extend the wrist. Which nerve is injured?

Accepted Answer

C

Question 3

A simple transverse femoral fracture is treated with a compression plate. At 12 weeks the radiograph shows no callus and the patient is comfortable and weight bearing. What does this indicate?

Accepted Answer

B

Question 4

A 6-year-old has a Gartland III supracondylar fracture. The hand is warm and pink with capillary refill under 2 seconds, but no radial pulse is palpable. What is the immediate management?

Accepted Answer

B

Question 5

A man is brought in after a generalised seizure with a painful shoulder held in internal rotation, unable to externally rotate. The anteroposterior radiograph shows a rounded humeral head. What is the diagnosis and the next step?

Accepted Answer

Posterior shoulder dislocation, the classic post-seizure and post-electrocution injury. The rounded appearance is the light bulb sign, produced by the internally rotated head.

The next step is a second orthogonal projection, an axillary or scapular Y view, which confirms the posterior displacement. This dislocation is the one most often missed precisely because the anteroposterior film can look almost normal, and a shoulder series without an orthogonal view is incomplete.

Question 6

A spiral tibial fracture is plated rigidly with a 1 mm residual gap. At six months there is no union and no callus. Explain the mechanical error using strain theory.

Accepted Answer

Strain equals change in gap length divided by original gap length, so a very small gap converts even minimal residual micromotion into very high strain. Lamellar bone requires strain under about 2 per cent and cartilage about 10 per cent, so neither tissue could form in that environment.

The gap was too small for the motion the construct still permitted. The two valid solutions are opposite in direction: achieve true interfragmentary compression so that motion approaches zero and direct healing can occur, or increase the working length so that strain falls into the range that permits callus.

Question 7

A 78-year-old woman who lives independently and walks to the market daily sustains a displaced intracapsular femoral neck fracture. The operating list is full for two days. State the two key management decisions and justify each.

Accepted Answer

First, prioritise surgery within 48 hours rather than deferring her. Meta-analysis of over 190,000 patients found surgery within that window associated with roughly 20 per cent lower one-year mortality, and the excess deaths arise from immobility, delirium, pneumonia and pressure injury accumulated while waiting.

Second, choose total hip arthroplasty. She is active and independent with a displaced intracapsular fracture, a group in which total hip arthroplasty gives better patient-reported function than hemiarthroplasty and far lower reoperation than internal fixation, which in trial data converted to arthroplasty in a substantial minority within two years.

Question 8

A 12-year-old is treated in a cast for an ankle injury with distal tibial physeal tenderness and normal radiographs. Eighteen months later the ankle is progressively deforming into varus. Explain the mechanism.

Accepted Answer

A Salter-Harris type V crush injury, diagnosed only in retrospect. The physis was compressed at the moment of injury without producing a visible fracture line, which is why the initial films were normal.

A bony bar then formed at the medial periphery of the plate. Because the bar was peripheral rather than central, it tethered the medial side while the lateral physis continued to grow, and the asymmetry produced progressive varus rather than simple shortening. The younger the child at injury, the more remaining growth and therefore the greater the eventual deformity, which is why physeal injuries need explicit counselling and planned follow-up rather than discharge at cast removal.

Question 9

Two tibial nonunions present at nine months. The first shows abundant flared callus with a persistent lucent line. The second shows no callus and tapered, sclerotic bone ends. How does management differ, and why?

Accepted Answer

The first is a hypertrophic nonunion. Abundant callus proves the biology is intact and that the bone has been trying to unite, so the failure is mechanical: the construct permits too much motion. Improving stability alone, typically by exchange nailing or plating, usually achieves union without any need for graft.

The second is an atrophic nonunion. The absence of callus indicates that the biological response has failed, from stripped periosteum, occult infection, poor vascularity, smoking or diabetes. Stabilisation alone will not work, and treatment requires debridement back to bleeding bone, bone grafting, and correction of the underlying cause including exclusion of infection. The diamond concept frames it: identify which of stability, cells, scaffold and signals is missing before revising.

Practice — Fractures & Dislocations

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