Management of a Normally Growing Child with Sacral Dimple and Mild Scoliosis
For a normally growing child with a benign midline sacral dimple and mild scoliosis, the sacral dimple requires no imaging if it meets simple criteria (midline, <5mm diameter, <2.5cm from anus, no associated skin stigmata), while the mild scoliosis should be monitored with PA and lateral spine radiographs every 6-12 months depending on skeletal maturity. 1, 2
Sacral Dimple Assessment
Clinical Evaluation Criteria
The key distinction is between simple (benign) and atypical (high-risk) sacral dimples 2:
Simple sacral dimples that do NOT require imaging have all of the following features 2, 3:
- Solitary midline depression
- Diameter <5mm
- Located within 2.5cm of the anus
- No associated cutaneous stigmata (hair tufts, hemangiomas, skin tags, subcutaneous masses)
Atypical dimples requiring imaging include 2, 3:
- Large (>5mm) or deep dimples
- Off-midline location
- Distance >2.5cm from anus
- Associated with skin markers (faun tail nevi, large skin tags, subcutaneous lipomas, vascular marks)
Imaging Recommendations for Sacral Dimples
If the dimple is simple and the child is asymptomatic with normal growth, no imaging is indicated 2, 4. The risk of significant spinal malformations in healthy infants with isolated simple sacral dimples is exceedingly low (0.13%) 4.
If atypical features are present, obtain **spinal ultrasound in neonates <4 months** or **MRI of the lumbosacral spine without contrast in older infants** 5, 2, 3. Pediatric neurosurgeons demonstrate >90% consensus that deep/atypical dimples warrant imaging 3.
Mild Scoliosis Management
Initial Imaging
Obtain upright PA and lateral spine radiographs as the primary imaging modality to diagnose, classify severity, and assess progression risk 1. PA technique (rather than AP) reduces breast radiation dose 1.
The radiographs serve to 1:
- Exclude congenital vertebral anomalies
- Measure Cobb angle for severity assessment
- Evaluate Risser index for skeletal maturity
- Differentiate idiopathic from congenital scoliosis
Follow-up Imaging Schedule
Limit radiographic follow-up to no more than once every 6 months for actively growing children 1. More specifically 1:
- Every 12 months for patients at Risser stages 0-3 (skeletally immature)
- Every 18 months for patients at Risser stages 4-5 (approaching skeletal maturity)
- More frequent imaging only if objective clinical changes occur
MRI Considerations for Scoliosis
MRI is NOT routinely indicated for mild idiopathic scoliosis in a normally growing child with normal neurologic examination 1. However, MRI of the complete spine should be obtained if any of the following risk factors are present 1:
- Left thoracic curve pattern
- Rapid curve progression (>1° per month)
- Functionally disruptive pain
- Focal neurologic findings
- Absence of apical segment lordosis (hyperkyphosis)
- Male sex with scoliosis
- Pes cavus deformity
- Short segment curve (4-6 levels)
The rationale is that 2-4% of adolescent idiopathic scoliosis patients have neural axis abnormalities (Chiari I malformation, syrinx, tethered cord, intrinsic tumor) 1. However, two studies showed that in presurgical patients with completely normal neurologic examinations, these findings resulted in either low rates or no change in management 1.
Clinical Pitfalls to Avoid
Do not obtain spinal ultrasound or MRI for simple sacral dimples in asymptomatic children—this leads to unnecessary investigations with extremely low diagnostic yield (0.13% surgical intervention rate) 4, 6.
Do not perform MRI for mild scoliosis without specific risk factors—the clinical relevance of incidental neural axis findings in asymptomatic patients with normal examinations is unclear and rarely changes management 1.
Do not use CT as initial imaging for scoliosis evaluation—it provides no intraspinal information and exposes children to unnecessary radiation 1. CT is reserved for presurgical planning when surgery is indicated 1.
Avoid excessive radiographic follow-up—adhere to the 6-12 month intervals to minimize cumulative radiation exposure while maintaining adequate surveillance 1.
Conservative Management
For mild scoliosis in a growing child, conservative management with observation is appropriate until curves reach treatment thresholds 7, 8. Skeletally immature patients with Cobb angles >20° have >70% likelihood of progression and may require bracing 1. General physical activity and sport participation should be encouraged 7.