Fractures — Types, Healing and Complications

• Patterns: transverse (direct blow), oblique, spiral (rotational force — in a non-ambulatory infant this raises concern for non-accidental injury), comminuted (high energy), greenstick and torus/buckle (incomplete, paediatric, because immature bone is plastic), avulsion, and pathological through abnormal bone.
• Open (compound) fracture communicates with the environment and is a surgical emergency: antibiotics, tetanus prophylaxis and urgent debridement.
• Stress fracture from repetitive loading — often normal initial radiographs, so MRI is the sensitive test.
• Salter–Harris classification describes physeal injury in children: SALTR — Slipped, Above, Lower, Through, Rammed (types I–V). Higher types carry greater growth-arrest risk.
• Healing proceeds through haematoma → inflammation → soft (fibrocartilaginous) callus → hard (bony) callus → remodelling.
• Complications: compartment syndrome, neurovascular injury, fat embolism (long bones, 24–72 h, hypoxia, petechiae, confusion), avascular necrosis (femoral neck, scaphoid, talus), nonunion and malunion, infection, and venous thromboembolism.
• Classic pairings: humeral shaft → radial nerve; surgical neck of humerus → axillary nerve; scaphoid → snuffbox tenderness with normal early films.

Mechanism-based causes

• High-energy direct trauma: motor vehicle collision, fall from height, crush. Produces transverse or comminuted patterns, soft-tissue stripping and open wounds; suspect multisystem injury and evaluate by ATLS principles.
• Indirect/rotational force: twisting on a fixed foot gives spiral patterns; sudden muscle contraction gives avulsion (tibial tubercle, base of 5th metatarsal).
• Low-energy fragility mechanism: fall from standing height in bone weakened by osteoporosis — hip, distal radius (Colles), vertebral compression, proximal humerus. Any fracture from a fall at or below standing height in an adult over 50 is a fragility fracture until proven otherwise.
• Repetitive submaximal loading: stress fracture in runners, dancers and military recruits, when osteoclastic resorption outpaces osteoblastic repair.
• Pathological: fracture through abnormal bone — metastasis (breast, lung, thyroid, kidney, prostate), multiple myeloma, primary bone tumour, Paget disease, osteogenesis imperfecta, renal osteodystrophy, bone cyst in children.
• Non-accidental trauma: posterior rib, metaphyseal corner (bucket-handle), or long-bone fracture in a non-ambulatory infant; the AAP advises a skeletal survey in suspected abuse under age 2.

Non-modifiable risk factors

• Age and female sex: cortical thinning and post-menopausal oestrogen loss accelerate trabecular resorption; USPSTF recommends DXA screening in women 65 and older, and in younger post-menopausal women at increased risk.
• Prior fragility fracture and parental hip fracture: the strongest clinical predictors, both captured in the FRAX tool.
• White or Asian ancestry, low peak bone mass, connective tissue disease (type I collagen defects in osteogenesis imperfecta).

Modifiable risk factors

• Glucocorticoid therapy: suppresses osteoblasts and calcium absorption — the classic drug-induced cause.
• Smoking and heavy alcohol use: impair osteoblast function and healing, and alcohol adds fall risk.
• Low body weight, calcium and vitamin D deficiency, immobility, hypogonadism, hyperthyroidism/over-replacement.
• Fall-promoting factors: sedatives, antihypertensives with orthostasis, polypharmacy, visual impairment, home hazards, peripheral neuropathy. Also anticonvulsants and chronic proton pump inhibitor use.

• Mechanical failure: bone fractures when applied load exceeds its strength. Cortical bone resists compression well but fails under tension and torsion, which is why bending produces a transverse fracture on the tensile side and twisting produces a spiral one. In osteoporosis, loss of trabecular connectivity lowers the failure threshold, so a trivial load suffices.
• Immediate tissue injury: the fracture tears periosteum (densely innervated — hence severe, localised pain), ruptures medullary and periosteal vessels, and disrupts the endosteal blood supply. Bleeding into the surrounding soft tissue produces the swelling and ecchymosis; a femoral shaft fracture can sequester enough blood to cause hypovolaemia, and pelvic fractures more.
• Secondary (indirect) healing occurs whenever fixation is not rigid — casts, intramedullary nails, non-operative care:
• Haematoma and inflammation: clot releases IL-1, IL-6, TNF-α and bone morphogenetic proteins, recruiting mesenchymal stem cells and neovascularisation over the first days.
• Soft callus: fibrocartilage rich in type II collagen bridges the gap over weeks — clinically the point at which the fracture becomes "sticky" but is not yet radiographically dense.
• Hard callus: endochondral ossification converts cartilage to woven bone, visible on radiographs as fusiform callus.
• Remodelling: osteoclast–osteoblast coupling replaces woven with lamellar bone along lines of stress (Wolff's law), a process taking months to years and far more complete in children.
• Primary (direct/Haversian) healing occurs only with anatomic reduction and absolute compression, as after plate-and-screw ORIF: cutting cones cross the fracture line and no visible callus forms — so absent callus after rigid fixation is expected, not failure.
• Downstream systemic effects: marrow fat and tissue thromboplastin enter torn venous sinusoids, causing fat embolism and a hypercoagulable, immobilised state that drives VTE. Bleeding and oedema within a closed fascial compartment raise interstitial pressure above capillary perfusion pressure, producing ischaemia that worsens oedema in a self-amplifying loop.
• Paediatric difference: the physeal cartilage is weaker than surrounding ligament, so the same force that sprains an adult fractures a child's growth plate.

Cardinal local findings

• Pain and point tenderness over the fracture line, worse with axial loading — from periosteal nociceptors.
• Swelling and ecchymosis from fracture haematoma; ecchymosis may track distally with gravity hours to days later.
• Deformity, shortening or rotation when displaced, from unopposed muscle pull.
• Loss of function, crepitus and abnormal motion at a non-joint segment (pathognomonic but should not be deliberately elicited).
• Open fracture: any wound over a fracture, or fat droplets/bone visible in the wound — a surgical emergency.

Presentations examiners favour

• Elderly woman after a mechanical fall with a shortened, externally rotated leg and pain on log-roll — femoral neck fracture.
• Fall on outstretched hand with dinner-fork deformity (dorsally displaced distal radius, Colles), or with anatomic snuffbox tenderness and normal initial films — scaphoid fracture.
• Runner or military recruit with insidious activity-related shin or metatarsal pain relieved by rest, focal tenderness, normal early radiographs — stress fracture; ask about amenorrhoea and low energy availability (*female athlete triad*/RED-S).
• Non-ambulatory infant with a spiral femur fracture or posterior rib fractures — non-accidental injury.
• Adolescent with knee/ankle injury and physeal tenderness — Salter–Harris injury even with subtle films.

Findings that signal a complication (assess at presentation and serially)

• Pain out of proportion, pain on passive stretch of the compartment, tense compartment, paraesthesia — compartment syndrome; pulselessness and pallor are late and their presence does not exclude it.
• Cool, pulseless limb after supracondylar humerus fracture or knee dislocation — arterial injury.
• Nerve deficits by site: humeral shaft → wrist drop (radial nerve); surgical neck → deltoid weakness and lateral shoulder numbness (axillary nerve); hip dislocation/acetabular fracture → sciatic nerve; fibular neck → foot drop (common peroneal).
• 24–72 hours after long-bone fracture: dyspnoea and hypoxaemia, confusion, and a transient axillary/subconjunctival petechial rash — fat embolism syndrome.

Step 1 — plain radiographs

• Two orthogonal views at minimum, including the joints above and below, per ACR Appropriateness Criteria. A single view misses non-displaced and angulated fractures.
• Decision rules limit unnecessary films: the Ottawa ankle and foot rules (malleolar/midfoot tenderness at specified bony points, or inability to bear weight four steps) and the Ottawa knee rule have high sensitivity for clinically significant fractures.
• Describe systematically: open vs closed, location, pattern, displacement, angulation, rotation, shortening, intra-articular extension.

Step 2 — advanced imaging when radiographs are negative or insufficient

• MRI is the most sensitive test for occult hip fracture, stress fracture (marrow oedema before any cortical change), and occult scaphoid fracture; it is the preferred confirmatory study in an elderly patient who cannot bear weight despite normal films.
• CT defines intra-articular, pelvic, acetabular, calcaneal and complex comminuted fractures and guides operative planning.
• Bone scintigraphy is an alternative when MRI is contraindicated but is less specific.
• Suspected scaphoid fracture with normal films: immobilise in a thumb spica and re-image or obtain MRI — never discharge as a "sprain".

Named classifications examiners use

• Salter–Harris I–V for physeal injuries; Gustilo–Anderson I–III for open fractures (grade drives antibiotic choice); Garden for femoral neck; Weber for ankle.

Adjunctive testing

• Trauma labs: CBC, type and screen; creatine kinase and potassium if crush injury.
• Compartment syndrome is a clinical diagnosis; when the patient is obtunded, manometry with a delta pressure (diastolic BP minus compartment pressure) under 30 mmHg supports fasciotomy. Do not delay surgery to measure.
• Fat embolism syndrome is clinical, supported by the Gurd criteria; imaging and labs are non-specific.
• Fragility fracture workup: DXA plus serum calcium, phosphate, 25-OH vitamin D, PTH, creatinine, TSH; a hip or vertebral fragility fracture establishes osteoporosis regardless of T-score. Skeletal survey per AAP if abuse is suspected.

Immediate stabilisation

• ATLS sequence first: airway, breathing, circulation. Control external haemorrhage, apply a pelvic binder for suspected unstable pelvic ring injury, and resuscitate before addressing the limb.
• Splint in the position found (traction splint for femoral shaft), elevate, and document neurovascular status before and after every reduction or splint application.
• Analgesia: multimodal per AAOS — regional block (fascia iliaca or femoral nerve block for hip fracture) plus scheduled acetaminophen, with opioids limited and short-course, consistent with the CDC opioid prescribing guideline. NSAIDs are effective but are often limited around fresh fracture healing.

Open fractures (surgical emergency)

• IV antibiotics as soon as possible, per EAST guidelines: a first-generation cephalosporin (cefazolin) for Gustilo type I–II; add gram-negative coverage for type III; add penicillin coverage when there is farmyard or faecal contamination (clostridial risk).
• Tetanus prophylaxis per CDC/ACIP based on immunisation history.
• Urgent irrigation and debridement in the operating theatre, then stabilisation; the wound is not closed primarily in the field.

Definitive fracture care

• Non-operative: closed reduction and cast/functional bracing for stable, minimally displaced, extra-articular fractures; avoid a tight circumferential cast over an acutely swelling limb — bivalve it.
• Operative for displaced, unstable, intra-articular, open, or pathological fractures and for most fractures in the elderly: ORIF (plate/screw, giving primary healing), intramedullary nailing for femoral and tibial shafts, percutaneous pinning for many paediatric supracondylar fractures, and arthroplasty (hemiarthroplasty or total hip) for displaced femoral neck fractures. AAOS supports surgical fixation of hip fracture within roughly 24–48 hours of admission when medically feasible.
• VTE prophylaxis after hip fracture and major lower-limb surgery — low-molecular-weight heparin or aspirin regimens per ACCP/CHEST.
• Secondary fracture prevention after a fragility fracture: calcium and vitamin D plus an antiresorptive (bisphosphonate such as alendronate or zoledronic acid) or, for very high risk, an anabolic agent (teriparatide, romosozumab), per the Endocrine Society and Bone Health and Osteoporosis Foundation.

Emergencies

• Compartment syndrome (emergency): bleeding/oedema in a closed fascial space raises pressure above capillary perfusion, causing muscle and nerve ischaemia. Classic after tibial shaft and supracondylar humerus fractures. Signalled by pain out of proportion and pain on passive stretch; treatment is immediate fasciotomy. Untreated it produces Volkmann ischaemic contracture and myonecrosis with rhabdomyolysis, hyperkalaemia and AKI.
• Arterial injury (emergency): brachial artery with supracondylar humerus fracture, popliteal artery with knee dislocation or proximal tibia fracture — cool pulseless limb, requiring urgent reduction and vascular assessment.
• Haemorrhagic shock (emergency): pelvic ring and femoral shaft fractures can sequester large volumes.
• Fat embolism syndrome (emergency): marrow fat and inflammatory mediators reach the pulmonary and systemic circulation 24–72 hours after long-bone or pelvic fracture — hypoxaemia, neurologic change and petechiae; care is supportive, and early fracture fixation reduces risk.
• Venous thromboembolism (emergency if PE): immobility plus tissue-factor release.
• Infection/osteomyelitis (urgent): open fractures and hardware; fever, wound drainage, rising CRP, and eventual periosteal reaction or sequestrum.

Delayed and chronic complications

• Avascular necrosis: retrograde blood supply is disrupted — femoral head after displaced femoral neck fracture, proximal scaphoid pole, talar body, humeral head. Presents as persistent pain with late sclerosis and collapse on imaging.
• Nonunion: failure to progress radiographically across serial films; risk factors are smoking, infection, gap/motion, poor vascularity, NSAIDs and diabetes. Atrophic nonunion reflects poor biology, hypertrophic reflects excess motion with adequate blood supply.
• Malunion: healing in unacceptable alignment, causing deformity, limb-length discrepancy and post-traumatic arthritis.
• Growth arrest and angular deformity after Salter–Harris III–V physeal injury.
• Complex regional pain syndrome: burning pain, allodynia, vasomotor and trophic skin changes, classically after distal radius fracture.
• Heterotopic ossification/myositis ossificans, joint stiffness, refracture and hardware failure.
• Treatment-related: cast-induced pressure ulcers and compartment syndrome; anaesthetic and thromboembolic risk of surgery; and atypical femoral fracture — a transverse subtrochanteric fracture preceded by prodromal thigh pain — with long-term bisphosphonate therapy.

• Snuffbox tenderness with a normal radiograph is a scaphoid fracture until proven otherwise. Best next step: thumb spica immobilisation with repeat imaging or MRI — never "reassure and discharge". The complication tested is proximal-pole avascular necrosis, because the scaphoid's blood supply is retrograde.
• Pain out of proportion to injury plus pain on passive stretch = compartment syndrome; the next step is fasciotomy, not imaging or opioids. Pulselessness is a late sign — a palpable pulse does not exclude the diagnosis. Bivalve or remove any cast first.
• Long-bone fracture → 24–72 h later → hypoxia, confusion and petechiae = fat embolism syndrome. The distractor is pulmonary embolism; the petechial rash and the early time course point to fat embolism, and management is supportive.
• Nerve pairings are near-guaranteed points: humeral shaft → radial nerve (wrist drop); surgical neck of humerus → axillary nerve; supracondylar humerus → brachial artery and median/anterior interosseous nerve; fibular neck → common peroneal nerve (foot drop).
• **A spiral femur fracture in a non-ambulatory infant, posterior rib fractures, or metaphyseal corner (bucket-handle) fractures mandate evaluation for non-accidental trauma**, with a skeletal survey under age 2 per the AAP.
• Any open fracture gets IV antibiotics within the shortest feasible time, tetanus prophylaxis and operative debridement — cefazolin for Gustilo I–II, with added gram-negative coverage for type III (EAST guideline). Do not close the wound primarily.
• A hip or vertebral fracture from a fall from standing height diagnoses osteoporosis regardless of the DXA T-score, and warrants pharmacologic therapy plus calcium and vitamin D. Conversely, a transverse subtrochanteric fracture with prodromal thigh pain in a patient on years of bisphosphonate is an atypical femoral fracture.
• Absent callus after rigid plate fixation is normal (primary Haversian healing) — do not call it nonunion; nonunion is defined by lack of progression across serial radiographs, most often with smoking, infection or motion at the site.