59 PAEDIATRIC ORTHOPAEDIC SURGERY

# 60 PAEDIATRIC ORTHOPAEDIC SURGERY

Children are not small adults. Their bones contain growth plates, their cortex is plastic, their joints remodel, and their differential diagnosis is dominated by a handful of high-yield conditions clustered by age. MRCS Part A loves this topic precisely because pattern-recognition by age, sex, body habitus and symptom location will get you the mark almost every time.

Master table — limping child by age

Age	Most likely diagnosis	Classic exam clue
Birth – 6 months	Developmental dysplasia of the hip (DDH)	Breech delivery, female, positive Barlow/Ortolani
1 – 3 years	Septic arthritis / transient synovitis	Toddler refusing to weight-bear
3 – 10 years	Transient synovitis / Perthes	Boy, post-viral, painless limp
4 – 8 years	Perthes disease	M>F, painless limp, ↓ internal rotation
10 – 15 years	SUFE	Obese adolescent boy, knee or groin pain
Any age	Septic arthritis / osteomyelitis / fracture / NAI	Fever, refusal to weight-bear, point tenderness

👩‍⚕️ Knee pain in a child is hip pain until proven otherwise. The obturator nerve supplies both joints, so SUFE and Perthes frequently present with referred knee pain and a completely normal knee exam.

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Developmental dysplasia of the hip (DDH)

A spectrum from acetabular dysplasia (shallow socket) through subluxation to frank dislocation. The acetabulum and femoral head co-develop: if the head is not seated, the socket fails to deepen, and the dysplasia worsens. Early diagnosis is therefore everything.

Risk factors — "the 6 Fs"

- Female (6:1)

- First-born

- Family history

- Frank breech presentation

- Fluid (oligohydramnios)

- Foot — talipes / other packaging deformities

➡ Left hip is involved more often than right — the usual intrauterine position places the left hip against the maternal sacrum.

Examination

- Barlow — adduct + push posteriorly: dislocates an unstable hip ("can I pop it out?")

- Ortolani — abduct + lift anteriorly: relocates a dislocated hip ("can I put it back?")

- Other signs: asymmetric thigh skin creases, limb-length discrepancy (Galeazzi sign), restricted abduction, late-walking child with painless limp / waddling gait if bilateral.

Investigation

- <6 months ➡ ultrasound (Graf classification). The femoral head is still cartilaginous and invisible on X-ray.

- >6 months ➡ AP pelvis X-ray once the ossific nucleus appears.

Management

- <6 months ➡ Pavlik harness (holds hips flexed and abducted). ~95% success if started early.

- 6–18 months ➡ closed reduction + spica cast under GA.

- >18 months ➡ open reduction ± femoral or pelvic osteotomy (Salter, Pemberton).

👩‍⚕️ Untreated DDH leads to early secondary osteoarthritis — by the fourth decade in many cases. This is why every UK neonate is screened.

Perthes disease (Legg-Calvé-Perthes)

Idiopathic avascular necrosis of the femoral head in a 4–8 year old (range 3–12). M:F ≈ 4:1. Often a short, thin, hyperactive boy.

The lateral epiphyseal vessels (branches of the medial circumflex femoral) supply the femoral head in this age group, and they are vulnerable. Repeated micro-interruption leads to ischaemic necrosis, collapse, then revascularisation and remodelling over 18–24 months.

Presentation

- Insidious painless limp, sometimes vague hip/groin/thigh/knee pain.

- Reduced internal rotation and abduction (the first movements to go).

- Often bilateral in ~15%, but rarely simultaneous — bilateral simultaneous Perthes should prompt thoughts of skeletal dysplasia or hypothyroidism.

Imaging

X-ray pelvis (AP + frog-leg) shows the classic four stages:

1. Sclerosis and a smaller epiphysis

2. Fragmentation

3. Re-ossification

4. Remodelling (healed)

Management

- Younger children (<6) and limited involvement ➡ observation, physiotherapy, analgesia.

- Older children or significant collapse ➡ containment (femoral or pelvic osteotomy) to keep the femoral head spherical within the acetabulum during remodelling.

Slipped upper femoral epiphysis (SUFE / SCFE)

The femoral epiphysis slips posteriorly and medially off the metaphysis through the physis (a Salter-Harris I in evolution). Typical patient: obese boy aged 10–15 during the pubertal growth spurt, or a child with hypothyroidism / hypogonadism / renal osteodystrophy.

Presentation

- Groin, thigh or knee pain (referred via obturator nerve).

- Externally rotated leg; on passive hip flexion the leg obligatorily externally rotates (Drehmann sign).

- Antalgic or Trendelenburg limp; apparent leg shortening.

- Bilateral in ~20–40% — always image the other hip and warn the family.

Imaging

- AP pelvis + frog-leg lateral (the lateral is the most sensitive view).

- Trethowan's sign — a line drawn along the superior femoral neck (Klein's line) fails to intersect the epiphysis.

Management

- Surgical emergency to prevent further slip and avascular necrosis.

- In-situ percutaneous screw fixation of the slipped epiphysis. Do not reduce a chronic slip (risk of AVN).

- Prophylactic pinning of the contralateral hip is often offered.

Feature	Perthes	SUFE
Age	4–8	10–15
Sex	M >> F	M > F
Body habitus	Thin, active	Overweight
Pathology	AVN of femoral head	Physeal slip
Pain	Painless or mild	Groin/thigh/knee
Management	Observe / containment osteotomy	Urgent in-situ pinning

Septic arthritis

Joint destruction can occur within 8 hours — this is an orthopaedic emergency. Commonest organism: Staphylococcus aureus (in neonates also Group B Strep and Gram-negatives; in unvaccinated children Haemophilus influenzae b; in sexually active adolescents Neisseria gonorrhoeae).

Kocher criteria (predicting septic arthritis of the hip vs transient synovitis)

- Non–weight-bearing

- Temperature >38.5°C

- ESR >40 mm/hr

- WCC >12 × 10⁹/L

Criteria met	Probability of septic arthritis
1	~3%
2	~40%
3	~93%
4	~99%

Management

- Urgent joint aspiration ➡ Gram stain, culture, WCC (>50,000/mm³ suggestive).

- Surgical washout under GA (open or arthroscopic).

- Empirical IV antibiotics after cultures — typically flucloxacillin ± gentamicin per local protocol.

Transient synovitis ("irritable hip")

Self-limiting post-viral inflammation of the hip in a 3–8 year old. Diagnosis of exclusion — you must rule out septic arthritis using Kocher and clinical judgement.

➡ Child is systemically well, apyrexial or low-grade fever, can usually weight-bear with some pain, NSAIDs settle symptoms within 1–2 weeks.

Osteomyelitis

In children, infection is almost always haematogenous and seeds the metaphysis of long bones (distal femur, proximal tibia, proximal humerus) — the sluggish loops of the metaphyseal capillaries trap bacteria. Organism: Staphylococcus aureus (sickle-cell patients: think Salmonella).

Presentation and investigation

- Localised bone pain, refusal to use the limb, fever.

- X-ray is normal for 10–14 days ➡ do not rely on it.

- MRI is the investigation of choice (early marrow oedema).

- Blood cultures positive in ~50%; bone biopsy/aspirate confirms organism.

Management

- Prolonged IV antibiotics (typically 4–6 weeks total, oral switch when settled).

- Surgical debridement if abscess, sequestrum, or failure to respond.

Osteochondritis dissecans

A subchondral bone fragment loses its blood supply, may separate, and can become a loose body. Adolescents, classically the lateral aspect of the medial femoral condyle of the knee. Presents with vague activity-related pain, swelling, mechanical symptoms (locking, catching) if a fragment detaches. MRI grades stability. Stable lesions in skeletally immature patients often heal with rest; unstable or detached fragments need arthroscopic fixation or removal.

Osgood-Schlatter disease

Traction apophysitis of the tibial tuberosity in adolescent athletes (typically 10–15, jumping/running sports). Repetitive quadriceps pull on the immature apophysis ➡ pain, swelling and a tender bony prominence below the patella. Self-limiting; treated with relative rest, ice and NSAIDs. Resolves at skeletal maturity, often leaving a permanent bony lump.

👩‍⚕️ Sinding-Larsen-Johansson is the same disease one bone proximally — apophysitis of the inferior pole of the patella.

Scoliosis

Lateral curvature of the spine >10° with rotational deformity. Subtypes:

- Idiopathic adolescent — by far the commonest (~80%), girls > boys, age 10–16.

- Congenital — vertebral malformations (hemivertebrae, failure of segmentation).

- Neuromuscular — cerebral palsy, muscular dystrophy, spina bifida. Long C-shaped curves.

- Syndromic — Marfan, neurofibromatosis.

Assessment

- Adam's forward bend test ➡ rib hump on the convex side.

- Cobb angle on a standing PA radiograph — measure from the most tilted vertebrae above and below the curve.

Management by Cobb angle

Cobb angle	Management
<25°	Observation, serial imaging
25–40° (skeletally immature)	Bracing (e.g. Boston brace)
>40–50° or progressive	Surgical correction with posterior spinal fusion

Talipes equinovarus (clubfoot)

Congenital deformity with four components — CAVE:

- Cavus (high arch)

- Adductus (forefoot)

- Varus (heel)

- Equinus (ankle plantarflexion)

1 in 1000 live births; M:F = 2:1; bilateral in ~50%. Most are idiopathic but check for associations (spina bifida, arthrogryposis, DDH).

Management — Ponseti method

Weekly serial manipulation and casting from the first weeks of life (5–8 casts), correcting each element in the CAVE order except equinus, which is corrected last with a percutaneous Achilles tenotomy in ~80% of cases. Foot abduction brace ("boots and bar") worn until ~age 4 to prevent relapse. Surgery is reserved for resistant or syndromic cases.

Paediatric fracture patterns

Children's bones are more porous, more vascular and have a thicker periosteum than adult bone. This produces incomplete fractures and rapid, vigorous healing — but the growth plate (physis) is a structural weak point.

Salter-Harris classification (physeal fractures)

Mnemonic SALTR:

Type	Pattern	Mnemonic
I	Slip through the physis	S
II	Above the physis (through metaphysis) — commonest	A
III	BeLow the physis (through epiphysis into joint)	L
IV	Through metaphysis, physis and epiphysis	T
V	CRush of the physis	R

➡ Higher Salter-Harris numbers = higher risk of growth arrest. Type V often missed acutely and presents later with limb deformity.

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Greenstick and buckle (torus) fractures

- Greenstick — incomplete fracture; one cortex breaks while the opposite cortex bends (like snapping a green twig). Typically diaphyseal forearm.

- Buckle (torus) — compressive failure causing a wrinkle of one cortex without a true break. Classic at the distal radial metaphysis after a fall on outstretched hand. Stable; treated with a removable splint for 3 weeks.

👩‍⚕️ Suspect non-accidental injury (NAI) when the fracture doesn't fit the story: multiple fractures of different ages, posterior rib fractures, metaphyseal corner ("bucket-handle") fractures, or any fracture in a non-mobile infant.

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Test yourself

A 4-week-old girl, born by breech delivery, is being screened for hip pathology. Which investigation is most appropriate?

• ((Ultrasound of both hips::☑️ Femoral head is cartilaginous before 6 months — USS is gold standard for DDH screening.))
• ((AP pelvis X-ray::Useless before 6 months; the ossific nucleus has not appeared.))
• ((MRI hips::Not first line; requires sedation and adds little over USS at this age.))
• ((CT pelvis::Avoided in neonates due to radiation; not used for DDH.))

👩‍⚕️ Switch from USS to X-ray at 6 months once the femoral head ossifies.

A 6-year-old boy presents with a 6-week painless limp. Examination shows reduced internal rotation and abduction of the right hip. He is afebrile. Most likely diagnosis?

• ((Perthes disease::☑️ Idiopathic AVN of femoral head in 4–8 year old boys; classic loss of IR and abduction.))
• ((Septic arthritis::Acutely unwell, febrile, refusing to weight-bear — not a chronic painless limp.))
• ((SUFE::Wrong age and habitus; SUFE is 10–15 year old obese adolescents.))
• ((Transient synovitis::Post-viral, resolves within 1–2 weeks, not 6.))

A 13-year-old obese boy presents with 3 weeks of left knee pain and a limp. Knee examination is normal. Which view is most sensitive for the likely diagnosis?

• ((AP pelvis alone::Subtle slips can be missed without a lateral view.))
• ((Frog-leg lateral of both hips::☑️ SUFE slips posteriorly — best seen on the lateral; image both hips as ~30% are bilateral.))
• ((MRI knee::Misses the actual pathology — the hip.))
• ((CT pelvis::Excessive radiation; not first line.))

👩‍⚕️ Knee pain in an adolescent is hip pain (SUFE) until imaged.

A 3-year-old refuses to weight-bear on the right leg. Temp 39°C, WCC 15, ESR 55, CRP raised. What is the next step?

• ((Oral antibiotics and review in 48h::Septic arthritis destroys cartilage within hours — never delay.))
• ((Ibuprofen and reassurance::Appropriate for transient synovitis, not this presentation.))
• ((MRI hip in 24h::Adds delay; aspiration confirms the diagnosis immediately.))
• ((Urgent joint aspiration and surgical washout::☑️ All 4 Kocher criteria met — ~99% probability of septic arthritis; emergency theatre.))

A 7-year-old with sickle cell disease has a 2-day history of right tibial pain, fever and refusal to walk. X-ray is normal. Most likely organism?

• ((Staphylococcus aureus::Commonest overall, but sickle cell patients are specifically at risk of Salmonella.))
• ((Salmonella::☑️ Classic association with sickle cell osteomyelitis.))
• ((Streptococcus pyogenes::Soft-tissue infections more typical.))
• ((Pseudomonas aeruginosa::Puncture wounds through trainers, not haematogenous spread.))

👩‍⚕️ Normal X-ray does not exclude osteomyelitis — bony changes take 10–14 days. MRI is the investigation of choice.

A 14-year-old footballer has anterior knee pain and a tender swelling over the tibial tuberosity. No effusion. Diagnosis?

• ((Osgood-Schlatter disease::☑️ Traction apophysitis of the tibial tuberosity in adolescent athletes.))
• ((Sinding-Larsen-Johansson::Apophysitis of the inferior pole of the patella — wrong site.))
• ((Patellar tendinopathy::Adults; pain at inferior patella, no bony lump.))
• ((Osteochondritis dissecans::Mechanical symptoms; tenderness over femoral condyle, not tibial tuberosity.))

A 13-year-old girl has a 35° thoracic scoliosis with 2 years of growth remaining. Best management?

• ((Observation only::Will progress through skeletal growth without intervention.))
• ((Bracing::☑️ 25–40° in a skeletally immature patient — bracing can halt progression.))
• ((Posterior spinal fusion::Reserved for curves >40–50° or those progressing despite bracing.))
• ((Physiotherapy alone::No evidence it alters curve progression.))

A newborn has bilateral clubfoot. What is the first-line treatment?

• ((Surgical posteromedial release at 6 months::Reserved for resistant or syndromic cases.))
• ((Ponseti serial casting started in the first weeks of life::☑️ Weekly manipulation and casting; correct cavus, adductus, varus then equinus.))
• ((Boots and bar alone::Used only after correction to prevent relapse, not as initial treatment.))
• ((Botulinum toxin to gastrocnemius::Not standard of care for idiopathic clubfoot.))

👩‍⚕️ ~80% of Ponseti-treated feet require a percutaneous Achilles tenotomy to correct the residual equinus.

A 9-year-old falls and sustains a distal tibial fracture extending through the metaphysis, physis and epiphysis. Which Salter-Harris type?

• ((Type I::Slip through the physis only.))
• ((Type II::Through metaphysis and physis — does not enter the epiphysis.))
• ((Type III::Through epiphysis and physis only, sparing metaphysis.))
• ((Type IV::☑️ Crosses metaphysis, physis and epiphysis — high risk of growth arrest.))
• ((Type V::Crush of the physis; usually a retrospective diagnosis.))

A 5-year-old falls onto an outstretched hand. X-ray shows a wrinkle in the distal radial cortex without a complete fracture line. Diagnosis?

• ((Greenstick fracture::Diaphyseal; one cortex breaks while the other bends.))
• ((Buckle (torus) fracture::☑️ Compressive failure of one cortex at the metaphysis — classic FOOSH injury in a young child.))
• ((Salter-Harris I::Involves the physis, not a cortical wrinkle.))
• ((Complete transverse fracture::Both cortices broken — not the description.))

A 4-year-old has a 3-day painful limp. Temp 37.4°C, WCC 9, ESR 18, can partially weight-bear. URTI 1 week ago. Most likely diagnosis?

• ((Septic arthritis::No Kocher criteria met; child is systemically well.))
• ((Perthes::Painless and chronic, not 3 days post-viral.))
• ((Transient synovitis::☑️ Post-viral, self-limiting, diagnosis of exclusion once Kocher is reassuring.))
• ((Juvenile idiopathic arthritis::Persistent >6 weeks with multiple joints.))

Revision summary

- Limp by age: <6m DDH; 1–3y septic arthritis/NAI; 4–8y Perthes; 10–15y SUFE.

- DDH: female, breech, FHx, oligohydramnios. Barlow dislocates, Ortolani relocates. USS <6m, X-ray >6m. Pavlik harness if <6m.

- Perthes: 4–8y boy, painless limp, ↓ IR and abduction. AVN of femoral head. Observe vs containment osteotomy.

- SUFE: obese 10–15y boy, knee/groin pain, externally rotated leg. Frog-leg lateral. Urgent in-situ pinning; 20–40% bilateral.

- Septic arthritis: emergency washout within hours. Kocher (NWB, T>38.5, ESR>40, WCC>12); 4/4 = ~99%. S. aureus.

- Osteomyelitis: haematogenous, metaphysis, S. aureus (Salmonella in sickle cell). MRI > X-ray early.

- Transient synovitis: post-viral, systemically well, diagnosis of exclusion.

- Osgood-Schlatter: tibial tuberosity apophysitis, adolescent athlete, rest.

- Scoliosis: idiopathic adolescent commonest. Cobb <25° observe, 25–40° brace, >40–50° fuse.

- Clubfoot (CAVE): Ponseti casts then Achilles tenotomy then boots-and-bar.

- Salter-Harris (SALTR): I Slip, II Above (commonest), III beLow, IV Through, V cRush (worst prognosis).

- Buckle/torus = cortical wrinkle of distal radial metaphysis; greenstick = one cortex breaks, other bends.

- Knee pain in a child = hip pain until proven otherwise.