Fractures & Dislocations
Fracture management looks like a catalogue: hundreds of eponyms, dozens of classifications, and an implant for every bone.
It is not a catalogue. Two principles generate almost all of it, and both are mechanical.
The first is that a fracture is a soft-tissue injury that happens to include a broken bone. The bone is the part visible on a radiograph, but the periosteum, the muscle envelope, the vessels and the nerves determine whether the bone will heal and whether the limb will work afterwards.
The second is that the way a fracture heals is decided by how much movement is allowed at the fracture line. Hold it perfectly still and bone crosses directly with no callus. Hold it loosely and callus forms. Hold it badly and nothing forms at all.
Every implant decision, every "why did this not unite", and a large share of NEET PG's orthopaedics questions follow from those two sentences.
1. Describe Before You Diagnose
Most marks lost in fracture questions are lost before any decision is made, because the fracture was described sloppily.
A complete description answers six things in order: which bone, which part of it, whether the skin is intact, the fracture pattern, the displacement, and whether a joint is involved.
Site is proximal, shaft or distal third, and for articular injuries the specific segment. Pattern is transverse, oblique, spiral, comminuted or segmental. Displacement is described as the position of the distal fragment relative to the proximal one, in four terms: translation, angulation, rotation and shortening.
Why the pattern matters
The pattern is a record of the force that caused it. A transverse fracture means a bending or direct force. A spiral fracture means a twisting force. Comminution means high energy, and high energy means the soft tissues absorbed a great deal of it too.
This is why a comminuted tibial fracture in a road traffic collision is a more dangerous injury than a spiral one at the same level, even when the radiograph looks similar in length of bone involved.
2. Two Ways Bone Heals
Bone is one of the few tissues that repairs itself with the original tissue rather than a scar. Which repair pathway it uses depends on the mechanical environment.
Secondary (indirect) healing happens when there is controlled micromotion. Haematoma organises, inflammation recruits cells, soft callus of cartilage and fibrous tissue bridges the gap, it mineralises into hard callus, and remodelling restores the shape. Callus is visible on radiographs. This is the normal path for a cast, a nail or a bridging plate.
Primary (direct) healing happens only when the fragments are compressed together with no measurable motion. Osteoclasts at the cut ends bore cutting cones straight across the fracture line, and osteoblasts follow laying down new osteon. There is no callus at all.
The clinical consequence is one that catches candidates out.
Absent callus after a compression plate is normal and expected. Absent callus after an intramedullary nail at three months is a warning sign. The same radiograph means opposite things depending on the implant.
Perren's strain theory
Strain is the change in gap length divided by the original gap length. Granulation tissue tolerates strain above 100 per cent, cartilage about 10 per cent, and lamellar bone under 2 per cent.
A tissue cannot form in an environment whose strain exceeds its tolerance. This single rule explains the paradox of the small gap.
A 1 mm gap that moves 1 mm has 100 per cent strain and cannot make bone. A 10 mm gap that moves the same 1 mm has 10 per cent strain and will make cartilage, then callus, then bone. This is why a rigid plate spanning a tiny residual gap in a comminuted fracture fails, while the same fracture nailed with a bigger visible gap unites.
Comminution helps here rather than hurting: many small gaps share the total motion, so each individual gap sees low strain.
3. What Each Implant Actually Does
Implants are not ranked by strength. They are chosen by which healing environment the fracture needs.
| Construct | Stability | Healing | Typical use |
|---|---|---|---|
| Cast or brace | Relative | Callus | Undisplaced or stable patterns, most paediatric shafts |
| Lag screw plus neutralisation plate | Absolute | Direct, no callus | Simple oblique or spiral fractures |
| Compression plate | Absolute | Direct, no callus | Simple transverse fractures, forearm |
| Bridging plate over comminution | Relative | Callus | Comminuted metaphyseal fractures |
| Intramedullary nail | Relative | Callus | Femoral and tibial shafts |
| External fixator | Relative, adjustable | Callus | Open fractures, damage control, infection |
Articular fractures are the exception that proves the rule. A joint surface must be reduced anatomically and held with absolute stability, because cartilage cannot remodel a step and a step of more than about 2 mm produces post-traumatic arthritis.
The shaft, meanwhile, tolerates imperfection: it only needs correct length, alignment and rotation.
4. Salter-Harris: The Physis Fails Before the Ligament
In a child the growth plate is the mechanical weak link. The same force that sprains an adult ankle fractures a child's physis, which is why the phrase "children do not sprain, they fracture" is a useful working rule.
The classification runs through the physis and asks where else the line goes.
| Type | Line runs | Frequency | Growth risk |
|---|---|---|---|
| I | Through physis only | About 5 per cent | Low |
| II | Physis plus metaphyseal fragment (Thurston Holland) | About 75 per cent, commonest | Low |
| III | Physis plus epiphysis, into joint | 6 to 8 per cent | Higher, articular |
| IV | Metaphysis through physis into epiphysis | Uncommon | High, articular |
| V | Crush of the physis | Rare | Highest |
Types I and II usually reduce closed and heal in a cast. Types III and IV cross the joint surface as well as the physis, so they need anatomical reduction and internal fixation, generally with screws placed parallel to and not across the physis.
Type V is almost always a retrospective diagnosis. The initial radiograph looks normal or nearly so, and the injury declares itself months later as a growth arrest. This is worth stating explicitly to parents at the first visit for any physeal injury.
The bar and the deformity
Growth arrest happens when a bony bar tethers part of the plate. A central bar shortens the bone symmetrically. A peripheral bar tethers one side while the rest keeps growing, producing progressive angular deformity.
The younger the child, the more growth remains and the worse the eventual deformity, which inverts the usual reassurance that children heal better.
5. Upper Limb Fractures That Are Always Asked
Supracondylar humerus
The commonest elbow fracture in children, typically from a fall on an outstretched hand producing an extension-type injury. Gartland grades it: I undisplaced, II angulated with intact posterior cortex, III completely displaced, IV unstable in both flexion and extension.
Gartland III carries the vascular and neurological risk. The anterior interosseous nerve is the classic injury in extension type; test it by asking the child to make an "OK" sign, which requires flexor pollicis longus and the index flexor digitorum profundus.
The pink pulseless hand is the decision that gets examined. A hand that is warm and well perfused with normal capillary refill but no palpable radial pulse is perfused through collaterals around the elbow. The primary treatment is urgent reduction and percutaneous pinning, after which the pulse commonly returns.
A hand that is pale, cold and poorly perfused is a true ischaemic emergency and needs vascular exploration. Series of Gartland III fractures report acute ischaemia or a pink pulseless hand in roughly one in six, so this is not a rare scenario.
Do not confuse either with the late catastrophe: Volkmann ischaemic contracture follows unrecognised forearm compartment syndrome, and pain on passive extension of the fingers is its earliest sign.
Scaphoid
The scaphoid is supplied retrograde by the dorsal carpal branch of the radial artery, entering distally. A waist or proximal pole fracture therefore devascularises the proximal fragment, and the more proximal the fracture, the higher the risk of avascular necrosis and nonunion.
A patient with anatomical snuffbox tenderness and a normal radiograph has a clinical scaphoid fracture until proven otherwise. Immobilise and image again. MRI is the reference standard for occult fracture, with sensitivity of about 95 to 100 per cent and specificity near 100 per cent, and early MRI within one to three days is now the recommended pathway where available.
Untreated, the sequence is nonunion, then carpal collapse, then scaphoid nonunion advanced collapse arthritis in a young hand.
Distal radius
Colles is dorsal displacement of the distal radius, classically in an older person after a fall on an outstretched hand, giving the dinner fork deformity. Smith is the volar equivalent. Barton is an intra-articular shear with subluxation of the carpus.
The complication to know is median nerve compression, either immediate from displacement or late from callus. Extensor pollicis longus rupture is the delayed tendon complication, characteristically after an undisplaced fracture rather than a displaced one, because the intact retinacular sheath compromises the tendon's blood supply.
The two forearm eponyms
Monteggia is a proximal ulnar fracture with radial head dislocation. Galeazzi is a distal radial fracture with distal radioulnar joint disruption.
The rule behind both is that the radius and ulna form a ring with the two joints. A ring cannot break in only one place, so a single-bone forearm fracture with any shortening or angulation obliges you to radiograph both the elbow and the wrist.
6. The Hip Fracture Is a Medical Emergency
Femoral neck fractures are intracapsular. The blood supply to the head runs retrograde through the retinacular vessels of the medial femoral circumflex artery, so a displaced neck fracture may destroy it. Intertrochanteric fractures are extracapsular, heal reliably, and are fixed rather than replaced.
That anatomical difference produces the treatment split.
| Fracture | Patient | Treatment |
|---|---|---|
| Undisplaced neck | Any | Internal fixation with screws or sliding hip screw |
| Displaced neck | Older, lower demand | Hemiarthroplasty |
| Displaced neck | Older, active, independent | Total hip arthroplasty |
| Displaced neck | Young | Urgent anatomical reduction and fixation, salvage the head |
| Intertrochanteric | Any | Sliding hip screw or cephalomedullary nail |
The evidence supports the split. In displaced fractures, reoperation rates after internal fixation run far higher than after arthroplasty, and in the FAITH trial 18 per cent of fixed patients converted to arthroplasty within 24 months.
Timing is the modifiable variable that changes mortality. Meta-analysis of over 190,000 patients found surgery within 48 hours associated with roughly 20 per cent lower one-year mortality. The fracture itself is survivable; the immobility, delirium, pneumonia and pressure injury that accumulate while waiting are what kill.
This is why hip fracture is now managed as a time-critical pathway with orthogeriatric co-care rather than as an elective list item.
7. Dislocations: Reduce Early, Then Ask Why
A dislocation compresses vessels, stretches nerves and starves cartilage of nutrition. The urgency is not the pain, it is the tissue clock.
Anterior shoulder dislocation is the commonest major joint dislocation. The axillary nerve is at risk, tested by sensation over the deltoid badge area before and after reduction. The structural lesions are the Bankart lesion of the anteroinferior labrum and the Hill-Sachs impaction on the posterolateral humeral head.
Age drives prognosis. Young patients, particularly athletes in contact sport, have recurrence rates reported between about two-thirds and over 90 per cent after a first dislocation, which is why arthroscopic stabilisation is discussed early rather than after the fifth episode.
Posterior shoulder dislocation is the one that is missed, classically after a seizure or electric shock. The arm is held internally rotated, the anteroposterior film shows the light bulb sign, and the axillary or scapular Y view makes the diagnosis. Any shoulder radiograph without a second orthogonal view is an incomplete examination.
Posterior hip dislocation accounts for the large majority of hip dislocations and typically follows a dashboard injury with the hip flexed and adducted. The limb lies shortened, flexed, adducted and internally rotated. The sciatic nerve, especially its peroneal division, is at risk.
Reduction should be achieved within about six hours, because the rate of avascular necrosis of the femoral head rises steeply with delay. A post-reduction CT is standard to look for the acetabular wall fracture and any incarcerated fragment.
8. When Healing Fails
Delayed union is a fracture taking longer than expected for its site. Nonunion is a fracture that has stopped trying, defined clinically and radiologically rather than purely by a date.
Nonunions divide by their biology, and the division dictates treatment.
Hypertrophic nonunion shows abundant callus with a persistent line, often described as an elephant foot. The biology is good and the mechanics are bad: it is moving too much. Stabilise it and it unites.
Atrophic nonunion shows no callus and tapered bone ends. The mechanics may be adequate but the biology has failed, from stripped periosteum, infection, poor blood supply, smoking or diabetes. It needs debridement, bone graft and correction of the underlying cause, not simply a stronger implant.
The reliable framework is the diamond concept: union requires mechanical stability, osteogenic cells, an osteoconductive scaffold and osteoinductive signals. Ask which of the four is missing before choosing the revision.
Malunion and other outcomes
Malunion is union in an unacceptable position. Rotational malunion of the femur is the classic example, because rotation is the deformity that does not remodel at any age and is easy to miss intraoperatively.
Complex regional pain syndrome deserves separate mention: pain disproportionate to the injury with vasomotor, sudomotor and trophic changes, most often after distal radius fracture. Early mobilisation and analgesia matter more than any single drug.
Fat embolism syndrome appears 24 to 72 hours after long bone or pelvic fracture with the triad of hypoxia, neurological change and a petechial rash in the axilla, conjunctiva and upper chest. Early fracture fixation reduces the risk; treatment is supportive.
9. High-Yield Associations
| Fracture or dislocation | Complication to expect |
|---|---|
| Femoral neck, displaced | AVN of femoral head |
| Scaphoid waist or proximal pole | AVN of proximal pole, nonunion |
| Talar neck | AVN of talar body |
| Humeral shaft, distal third | Radial nerve palsy, wrist drop |
| Supracondylar humerus, extension | Anterior interosseous nerve, brachial artery |
| Medial epicondyle | Ulnar nerve |
| Surgical neck of humerus, anterior shoulder dislocation | Axillary nerve |
| Posterior hip dislocation | Sciatic nerve, AVN of femoral head |
| Knee dislocation | Popliteal artery, common peroneal nerve |
| Distal radius | Median nerve, late EPL rupture |
Knee dislocation deserves emphasis. It may reduce spontaneously before arrival, so a knee that is grossly unstable in multiple planes after trauma should be treated as a dislocation even if it looks normal on the film. Popliteal artery injury is the limb-threatening complication and mandates vascular assessment, with ankle-brachial index and CT angiography as indicated.
10. Worked Examples
Example 1. A 7-year-old falls on an outstretched hand. The elbow is swollen, radiographs show a completely displaced supracondylar fracture, and the hand is warm and pink with brisk capillary refill but no radial pulse. What is the immediate management?
Urgent closed reduction and percutaneous pinning under anaesthesia. The hand is perfused through collaterals, and the pulse usually returns once the fracture is reduced and the brachial artery is no longer tented. Vascular exploration is reserved for a hand that is pale, cold or shows deteriorating perfusion after reduction. Document anterior interosseous nerve function before and after.
Example 2. A comminuted distal femoral fracture is treated with a bridging plate. At 12 weeks there is abundant callus but the patient still has pain on weight bearing. A second patient with a simple transverse femoral fracture treated by compression plating shows no callus at all at 12 weeks and is comfortable. Which one is failing?
Neither is failing on the callus finding. The bridging plate provides relative stability, so callus is the expected and correct appearance. The compression plate provides absolute stability, so direct healing with no callus is expected. Callus after a compression plate would suggest the construct is loose. Judge each construct against the healing pathway it was designed to produce.
Example 3. A 22-year-old sustains a spiral tibial fracture. It is fixed with a rigid plate leaving a 1 mm residual gap. At six months there is no union and no callus. Explain the mechanical error.
Perren's strain theory. A tiny gap subjected to any residual micromotion generates very high strain, because strain is motion divided by gap length. Above roughly 2 per cent, lamellar bone cannot form, and above about 10 per cent even cartilage cannot. The gap was too small to tolerate the motion that the construct still permitted. Either true compression with no motion, or a larger working length allowing callus, would have united it.
Example 4. A 78-year-old woman with a displaced femoral neck fracture is admitted on Friday evening. She lives independently and walks to the market daily. The list is full until Monday. What are the two key decisions?
First, operate within 48 hours: delay beyond that is associated with roughly 20 per cent higher one-year mortality, so she should be prioritised rather than deferred. Second, because she is active and independent with a displaced intracapsular fracture, total hip arthroplasty gives better function and lower reoperation than internal fixation or hemiarthroplasty in this group.
Example 5. A 12-year-old has an ankle injury with tenderness over the distal tibial physis and normal radiographs. He is treated in a cast and recovers. Eighteen months later the ankle is progressively angulating into varus. What happened?
A Salter-Harris type V crush injury, diagnosed retrospectively. The physis was compressed at the time of injury without a visible fracture line, a bony bar formed peripherally on the medial side, and the tethered medial physis stopped growing while the lateral side continued, producing progressive varus. This is why every physeal injury warrants a warning about growth and follow-up rather than discharge at cast removal.
Summary
A fracture is a soft-tissue injury that includes a broken bone, and the soft tissues decide the outcome.
Describe before diagnosing: bone, site, skin, pattern, displacement, joint involvement.
Bone heals two ways. Absolute stability gives direct healing with no callus; relative stability gives callus. The implant chosen determines which appearance is normal.
Perren's strain theory explains failures: strain is motion divided by gap length, so small gaps are dangerous, and lamellar bone needs strain under 2 per cent.
Joint surfaces need anatomical reduction and absolute stability; shafts need only length, alignment and rotation.
In children the physis fails before the ligament. Salter-Harris II is commonest; III and IV cross the joint and need fixation; V is diagnosed retrospectively as growth arrest.
Supracondylar Gartland III: reduce and pin urgently, and distinguish the pink pulseless hand from true ischaemia.
Retrograde blood supply explains the AVN triad: femoral head, scaphoid proximal pole, talar body.
Displaced femoral neck fractures in older active patients do better with total hip arthroplasty, and surgery within 48 hours lowers one-year mortality by about a fifth.
Reduce dislocations early: six hours for the hip before AVN risk climbs, and never accept a single view of a shoulder.
Hypertrophic nonunion is a mechanical problem, atrophic nonunion a biological one. Fix the one that is actually missing.
