A symptom that is benign in adolescents and sinister in young children — the differential inverts with age
- Back pain in a child younger than 5 years is pathological until proven otherwise; in an adolescent athlete it is usually mechanical.
- Persistent pain beyond 4 weeks, night pain waking from sleep, systemic symptoms, neurological signs, scoliosis with a left thoracic curve or painful curve, and gait change are the red flags.
- Plain radiographs are normal in early discitis, early spondylolysis and in most osteoid osteomas of the posterior elements — a normal film never excludes disease.
- MRI with STIR is the single most informative test; it detects marrow oedema in pars stress reaction, discitis, tumour and sacroiliitis.
- Osteoid osteoma classically presents as a painful rigid scoliosis, convex away from the lesion, with the nidus in the pedicle or lamina on the concavity.
- Scheuermann kyphosis needs three consecutive vertebrae wedged 5 degrees or more with endplate irregularity and Schmorl nodes.
- Discitis in a toddler presents as refusal to walk or sit, irritability and low-grade fever — the child may never localise pain to the back.
- “"Left thoracic curve" and "painful scoliosis" are the two phrases that mandate MRI in a scoliosis viva.
- “Night pain relieved by NSAIDs is osteoid osteoma; night pain unrelieved by NSAIDs is tumour or infection.
- “The lateral radiograph is the highest-yield single view: it shows pars defect, kyphosis, disc space loss and vertebra plana.
- “Vertebra plana with preserved disc spaces in a child aged 5 to 10 is Langerhans cell histiocytosis until proven otherwise.
- “SPECT or MRI, not oblique 'Scottie dog' views, is the modern investigation for suspected pars stress injury — obliques double the gonadal dose for little gain.
Early discitis takes 2 to 3 weeks to show disc space narrowing; a pars stress reaction shows nothing until a frank lysis develops. If the story is red-flag positive, the next sentence must be "I would arrange an MRI", not "I would reassure and review".
It is common, but the same age group gets osteoid osteoma, osteoblastoma, aneurysmal bone cyst and Ewing sarcoma. Duration greater than 4 weeks, night waking or any neurology re-opens the differential.
Idiopathic adolescent scoliosis is painless, right-sided in the thorax, and neurologically normal. A painful curve, a left thoracic curve, rapid progression, or absent abdominal reflexes points to syrinx, tethered cord, tumour or osteoid osteoma.
A pars defect is present in about one in twenty of the asymptomatic population. Only a defect with marrow oedema on STIR or uptake on SPECT is an active, painful, healable lesion. Chronic sclerotic non-union may be an incidental finding.
Recognising the Pattern
The presentation. A child or adolescent presenting with pain localised to the thoracic, lumbar or lumbosacral spine, with or without radiation, deformity, gait change or systemic features. Unlike adult back pain, paediatric back pain has historically been taught as "always pathological"; the modern position is more nuanced — it is common in adolescents (particularly athletes and heavy schoolbag carriers), and rare and sinister in the pre-school child.
Confirming the pattern is genuine. Before generating a differential, establish that the pain is truly spinal:
- A toddler who "refuses to walk" may have a septic hip, a toddler's fracture, or discitis. Examine the hips and the whole lower limb, and observe the child picking an object off the floor — a child with discitis flexes the hips and knees and keeps the spine rigid.
- Referred pain from renal tract, pancreas, pneumonia or ovarian pathology can present as back pain; check for costovertebral angle tenderness, urinalysis and abdominal signs.
- Hamstring tightness with a flat-back gait and a palpable step-off suggests high-grade spondylolisthesis rather than a soft-tissue strain.
Words to use in the viva. "This is a plain lateral radiograph of the lumbar spine of a skeletally immature patient. There is a lucency through the pars interarticularis of L5 without translation of the vertebral body. The disc spaces and vertebral body heights are preserved and there is no paravertebral soft tissue mass. My differential is a spondylolytic defect; I would want to know whether this is an active lesion, and I would confirm with MRI including STIR sequences to look for pars marrow oedema."
Mimics and false positives.
- Nutrient vessel grooves and the Mach effect from overlapping transverse processes mimic a pars lucency on obliques.
- Physiological vertebral body wedging in the mid-thoracic spine of a young child; step-like anterior endplate irregularity is a normal growth variant and must not be called Scheuermann without three vertebrae wedged 5 degrees or more.
- Limbus vertebra — a triangular ossicle at the anterosuperior corner from a herniated disc through the ring apophysis — is a corticated, chronic finding, not an acute fracture.
- Normal ring apophyses are unfused until the late teens and simulate avulsion.
- Mild scoliosis on a rotated film: confirm with a true standing PA before diagnosing deformity.
- Growing pains are bilateral, in the legs, nocturnal but resolve with rubbing, and never localise to the spine — spinal night pain is never "growing pains".
Next Investigation
- What it means
- Discitis
- Immediate action
- Admit, blood cultures, MRI with contrast, empirical anti-staphylococcal antibiotics
- What it means
- Langerhans cell histiocytosis until proven otherwise
- Immediate action
- Skeletal survey or whole-body MRI; refer to paediatric oncology; most heal without surgery
- What it means
- Ewing sarcoma, osteosarcoma or aggressive infection
- Immediate action
- Urgent referral to a bone tumour unit; biopsy only at the treating centre
- What it means
- Active spondylolysis with healing potential
- Immediate action
- Activity cessation, bracing or rest for 3 months, repeat imaging
- What it means
- Chronic established non-union, possibly incidental
- Immediate action
- Treat symptoms; do not chase healing; look for another cause if pain is atypical
- What it means
- Nothing excluded
- Immediate action
- MRI whole spine with STIR — do not reassure on a normal plain film
RED FLAGSRed flags in paediatric back pain
The Differential
- Typical age / setting
- 1 to 5 years; also any age with immunosuppression
- Discriminating feature
- Refusal to walk or sit, rigid lumbar spine, low-grade fever; disc space narrowing with endplate erosion — the disc is involved, unlike tumour
- What confirms it
- MRI with contrast (disc and adjacent endplate oedema, paravertebral collection); raised CRP; blood culture, Staph aureus commonest
- Typical age / setting
- Any age; endemic exposure, contact history, migrant background
- Discriminating feature
- Insidious months of pain, thoracolumbar junction, anterior body destruction with relative disc preservation and a large cold paravertebral abscess; gibbus deformity
- What confirms it
- MRI showing multilevel skip lesions and subligamentous spread; CT-guided biopsy with AFB culture and GeneXpert
- Typical age / setting
- 10 to 20 years; sacrum and posterior elements
- Discriminating feature
- Progressive unremitting night pain, permeative destruction with a soft tissue mass out of proportion to bone loss, may have fever and raised inflammatory markers mimicking infection
- What confirms it
- MRI whole spine, staging CT chest, biopsy through a planned resection tract at the treating tumour unit
- Typical age / setting
- 2 to 10 years; systemically unwell child
- Discriminating feature
- Diffuse bone pain in more than one site, pallor, bruising, hepatosplenomegaly; diffuse osteopenia with vertebral compression fractures rather than a focal lesion
- What confirms it
- Full blood count with film, blood pressure and urinary catecholamines, bone marrow aspirate, MRI whole spine
- Typical age / setting
- 5 to 10 years; thoracic spine commonest
- Discriminating feature
- Vertebra plana — symmetrical collapse to a wafer with completely preserved adjacent disc spaces and no kyphosis; often surprisingly little pain
- What confirms it
- Radiograph is often diagnostic; skeletal survey or MRI for other lesions; biopsy if atypical. Most heal with height restoration
- Typical age / setting
- Any age; painful or left thoracic scoliosis
- Discriminating feature
- Neurological signs: absent abdominal reflexes, asymmetric foot deformity, cavus, bladder change; interpedicular widening or posterior vertebral scalloping on plain film
- What confirms it
- MRI whole neuraxis — mandatory in juvenile scoliosis, left thoracic curves and any painful curve
- Typical age / setting
- 10 to 18 years; gymnast, cricket fast bowler, footballer; extension-loading sport
- Discriminating feature
- Pain reproduced by single-leg hyperextension (stork test), relieved by rest; unilateral or bilateral L5 pars defect with no vertebral collapse
- What confirms it
- MRI with STIR shows pars marrow oedema in an active lesion; thin-slice CT grades the defect and healing potential
- Typical age / setting
- Adolescent growth spurt; L5-S1
- Discriminating feature
- Palpable step-off, hamstring tightness, flat buttocks, crouched gait; anterior translation on standing lateral with the Scottie dog collar
- What confirms it
- Standing lateral radiograph with Meyerding grade and slip angle; flexion-extension views for instability; MRI if radicular symptoms
- Typical age / setting
- 13 to 17 years; boys more than girls
- Discriminating feature
- Rigid thoracic kyphosis that does not correct on prone extension; three or more consecutive vertebrae wedged 5 degrees or more with irregular endplates and Schmorl nodes
- What confirms it
- Standing lateral radiograph plus hyperextension over a bolster to assess flexibility
- Typical age / setting
- 12 to 18 years; deconditioning, heavy bags, sudden training increase
- Discriminating feature
- Pain is activity-related, absent at night, diffuse and paraspinal, with a completely normal neurological examination and normal radiograph
- What confirms it
- Diagnosis of exclusion after 4 to 6 weeks with red flags absent; responds to physiotherapy and core conditioning
- Typical age / setting
- 14 to 18 years; weightlifting, axial loading injury
- Discriminating feature
- Sciatica with marked hamstring tightness and a sciatic list; a bony fragment displaced into the canal from the posterior ring apophysis
- What confirms it
- MRI shows the herniation; CT best demonstrates the bony apophyseal fragment, which will not resolve with conservative care
- Typical age / setting
- 10 to 20 years; posterior elements, pedicle and lamina
- Discriminating feature
- Night pain dramatically relieved by NSAIDs; painful rigid scoliosis with the lesion at the apex on the concave side. Osteoblastoma is larger than 1.5 cm and more expansile
- What confirms it
- CT is the test of choice — a lucent nidus with central mineralisation and reactive sclerosis; bone scan shows intense focal uptake
- Typical age / setting
- 5 to 20 years; posterior elements, expansile
- Discriminating feature
- Expansile lucent lesion with fluid-fluid levels and a thin eggshell rim; can cause pathological collapse and neurological compromise
- What confirms it
- MRI showing fluid-fluid levels with septations; biopsy to exclude telangiectatic osteosarcoma before treating
- Typical age / setting
- Male adolescent; HLA-B27, family history, uveitis, enthesitis
- Discriminating feature
- Inflammatory pattern: morning stiffness greater than 30 minutes, pain improves with activity and wakes in the second half of the night, alternating buttock pain
- What confirms it
- MRI sacroiliac joints with STIR showing subchondral bone marrow oedema; HLA-B27, raised CRP; plain films are normal early
- Typical age / setting
- 7 to 14 years; girls more than boys
- Discriminating feature
- Multifocal sterile lesions, often clavicle and metaphyses as well as spine; relapsing-remitting course, cultures negative, no response to antibiotics; may cause vertebra plana
- What confirms it
- Whole-body MRI showing multiple asymptomatic lesions; diagnosis of exclusion after biopsy of an atypical lesion
Narrowing It Down
- 1Step 1 — How old is the child?
Establish the age before considering any other feature, and treat 'under 5' as a red flag in its own right.
Under 5 years: discitis, tumour (leukaemia, neuroblastoma), Langerhans cell histiocytosis, and non-accidental injury. Mechanical pain essentially does not occur. Aged 10 to 18 in a sporting adolescent: spondylolysis, Scheuermann, disc herniation and mechanical pain dominate - but tumour remains on the list. Age alone reorders the entire differential.
- 2Step 2 — Are there red flags?
Ask specifically for duration beyond 4 weeks, night pain waking the child, fever or weight loss, any neurological deficit, bladder or bowel change, painful or atypical scoliosis, and age under 5.
Any ONE of these converts the pathway from 'physiotherapy and review' to 'MRI and bloods now'. Absence of all of them, in an adolescent with activity-related pain, permits a trial of conservative management - which is the common situation, since roughly one adolescent in six reports back pain in the general population (ALSPAC).
- 3Step 3 — Is the pain mechanical, inflammatory or neoplastic?
Ask what the pain does at night and what it does to activity - the two questions that separate the three families.
Mechanical: worse with activity, better with rest, absent at night. Inflammatory: morning stiffness beyond 30 minutes, better with movement, wakes in the second half of the night, alternating buttock pain, enthesitis and uveitis. Neoplastic or infective: constant, progressive, night pain unrelieved by rest. Osteoid osteoma is the exception - night pain that resolves within 20 to 30 minutes of an NSAID.
- 4Step 4 — Solitary or multiple lesions?
Once a lesion is found, image the rest of the skeleton or neuraxis before committing to a single-lesion diagnosis.
A solitary lesion favours osteoid osteoma, aneurysmal bone cyst, single-level discitis or a primary sarcoma. Multiple lesions favour Langerhans cell histiocytosis, CRMO, leukaemia or metastatic neuroblastoma. This question mandates whole-body imaging: whole-spine MRI, skeletal survey or whole-body MRI depending on the suspected diagnosis.
- 5Step 5 — Where within the spinal segment is the abnormality?
Localise the lesion to posterior elements, vertebral body, disc space or sacroiliac joint - the compartment narrows the list further than the appearance does.
Posterior elements (pedicle, lamina, facet): osteoid osteoma, osteoblastoma, aneurysmal bone cyst, spondylolysis. Vertebral body: Langerhans cell histiocytosis, infection, metastasis, Ewing. Disc space plus two endplates: pyogenic discitis. Anterior body with preserved disc and skip lesions: tuberculosis. Sacroiliac joints: enthesitis-related arthritis or sacral insufficiency.
- 6Step 6 — How aggressive is the lesion?
Grade the margin and the periosteal reaction, then ask whether the appearance and the bloods actually separate the two diagnoses you are choosing between.
Geographic with a sclerotic rim and no periosteal reaction: benign and slow (osteoid osteoma, fibrous lesions). Permeative or moth-eaten with a soft tissue mass, cortical breach and lamellated periosteal reaction: aggressive - Ewing, osteosarcoma or infection. An aggressive appearance with fever and raised CRP still does NOT distinguish Ewing from osteomyelitis; biopsy and culture both.
- 7Step 7 — Are there systemic or neurological features?
Examine for fever, weight loss, night sweats and lymphadenopathy, then perform a full neurological examination including abdominal reflexes and the feet.
Systemic features point to infection or malignancy - and per Altaf, associated systemic illness is the stated trigger for actively excluding malignancy and infection. Abnormal neurology, absent abdominal reflexes, cavus feet, asymmetric lower limb signs or bladder dysfunction demand urgent whole-neuraxis MRI to exclude cord tumour, syrinx, tethered cord or epidural abscess, IRRESPECTIVE of the plain film.
MCQ Practice Points
Q: A 7-year-old presents with mild thoracic back pain. The lateral radiograph shows a single vertebral body collapsed to a thin wafer with normal adjacent disc heights. What is the most likely diagnosis?
A: Langerhans cell histiocytosis (eosinophilic granuloma) producing vertebra plana. Preserved disc spaces exclude infection; the absence of a soft tissue mass and the relatively mild symptoms argue against Ewing sarcoma. Most cases regain substantial vertebral height with observation alone.
Q: Which single MRI sequence is most useful for detecting an active pars stress injury, and why does it matter more than finding the defect?
A: STIR (or fat-suppressed T2). It demonstrates pars and pedicle marrow oedema, indicating a lesion with healing potential; a defect with normal marrow signal is a chronic non-union that will not heal with rest. The reason this is the whole question is that the defect itself is common and usually silent: Fredrickson found spondylolysis in 4.4 per cent of six-year-olds rising to 6 per cent in adulthood, and in that cohort the slip was never symptomatic. Advanced imaging is not for finding the pars defect — a plain film usually does that — it is for deciding whether this defect is active and whether it is the source of this child's pain.
Q: What are the radiological criteria for Scheuermann kyphosis?
A: Three or more consecutive thoracic vertebrae wedged 5 degrees or more, with endplate irregularity, Schmorl nodes, disc space narrowing and a rigid kyphosis that does not correct on hyperextension. Postural kyphosis is flexible and lacks the vertebral changes.
Q: A 13-year-old boy has night back pain completely relieved within 30 minutes of ibuprofen and a new rigid scoliosis. Radiographs appear normal. What imaging do you request?
A: Thin-slice CT of the concave apex of the curve, looking for a lucent nidus with central mineralisation in the pedicle or lamina — osteoid osteoma. Bone scan or SPECT-CT can localise the lesion first if the level is uncertain. MRI alone can mislead, because extensive reactive oedema obscures the small nidus — one of the few situations on this page where MRI is not the answer.
Q: Which historical feature best distinguishes enthesitis-related arthritis from mechanical adolescent back pain?
A: Morning stiffness lasting more than 30 minutes, with pain that IMPROVES with activity and wakes the patient in the second half of the night, often with alternating buttock pain, enthesitis and a family history of HLA-B27 disease. Mechanical pain is the mirror image — worse with activity and absent at night.
Exam Viva Scenarios
Practise clinical reasoning and management decisions out loud
“You are shown this lateral lumbar radiograph of a 3-year-old girl brought in by her mother because she has stopped walking over the past ten days and cries when lifted. Temperature 37.8 degrees. The radiograph shows narrowing of the L3-L4 disc space with irregularity of the adjacent endplates.”
“You are shown this standing lateral lumbar radiograph of a 15-year-old cricket fast bowler with six months of low back pain, worse on bowling and on extension, absent at night. There is a lucency through the pars interarticularis of L5 with no anterior translation.”
“You are shown this standing PA radiograph of an 11-year-old girl with a 30-degree left thoracic curve. She reports back pain and her mother has noticed she trips frequently. Abdominal reflexes are absent on the left.”
Age drives the differential
- Under 5 years: discitis, leukaemia, neuroblastoma metastasis, Langerhans cell histiocytosis, non-accidental injury
- 5 to 10 years: Langerhans cell histiocytosis, CRMO, discitis, tumour
- 10 to 18 years: spondylolysis, spondylolisthesis, Scheuermann, disc herniation, mechanical pain, osteoid osteoma, Ewing
Red flags demanding MRI
- Age under 5; duration greater than 4 weeks; progressive symptoms
- Night pain waking from sleep; fever, weight loss, night sweats
- Any neurological sign, bladder or bowel change, gait change or refusal to walk
- Painful, left thoracic, juvenile-onset or rapidly progressive scoliosis
Discriminators to say out loud
- Disc involved equals infection; disc spared with body destruction equals tumour or tuberculosis
- Night pain relieved by NSAIDs equals osteoid osteoma; unrelieved equals tumour or infection
- Vertebra plana with normal discs equals Langerhans cell histiocytosis
- Posterior element lesion equals osteoid osteoma, osteoblastoma, aneurysmal bone cyst or spondylolysis
- Multifocal sterile lesions with a relapsing course equals CRMO
Imaging strategy
- Standing PA and lateral first; skip routine obliques
- MRI whole spine with STIR for any red flag; add gadolinium for infection or tumour
- CT for the osteoid osteoma nidus, apophyseal ring fracture and pars grading
- Bloods: FBC with film, CRP, ESR; blood cultures before antibiotics
- No imaging beyond plain films for a well adolescent with less than 4 weeks of activity-related pain
Management anchors
- Discitis: intravenous anti-staphylococcal antibiotics, 4 to 6 weeks total, surgery only for abscess or neurology
- Active spondylolysis: 3 months activity cessation with or without bracing; repair or fusion only after failed conservative care
- Scheuermann: bracing while growing for curves that are progressive; fusion for severe rigid deformity with pain
- Suspected primary bone sarcoma: no local biopsy — refer to the tumour unit first
Evidence Base
The Impact of Small Spinal Curves in Adolescents Who Have Not Presented to Secondary Care (ALSPAC)
- A prospective population-based birth cohort - the Avon Longitudinal Study of Parents and Children - with spinal curvature measured in 5299 fifteen-year-olds and a structured pain questionnaire in 4083 eighteen-year-olds
- THE BASE RATE THIS PAGE NEEDS: at 18, 46.3 per cent reported aches or pains lasting a day or longer in the previous month, and 16.3 PER CENT REPORTED BACK PAIN
- Spinal curve of 6 degrees or more in 6.3 per cent, and 10 degrees or more in 3.9 per cent (median 11 degrees)
- Those with a curve were 42 per cent more likely to report back pain (odds ratio 1.42, 95% CI 1.00 to 2.02, p = 0.047) and had more days off school
- The authors' conclusion: small curves 'may be less benign than previously thought'
The Natural History of Spondylolysis and Spondylolisthesis
- A prospective radiographic study of 500 UNSELECTED first-grade children from 1955 to 1957, with the families of affected children followed in the same way
- Incidence of spondylolysis was 4.4 PER CENT at age six, rising to 6 PER CENT in adulthood - this is the source of the 'about one in twenty' figure
- Slip progression was UNUSUAL, and unlikely after adolescence; the greatest slip was 28 per cent
- THE SENTENCE THAT MATTERS MOST: 'the slip was NEVER SYMPTOMATIC in the population that we studied'
- Hereditary predisposition, and a strong association with spina bifida occulta; the authors favour a defect in the cartilaginous anlage rather than pure repetitive stress