What are the causes and treatments for sacral pressure causing femur pain?

Sacral Pressure Causing Femur Pain: Causes and Treatment

Sacral stress fractures are the most likely cause of sacral pressure causing femur pain and require MRI for definitive diagnosis when radiographs are negative.

Causes of Sacral Pressure Causing Femur Pain

Stress Fractures

• Sacral stress fractures are a common cause of pain that radiates to the femur 1
  • Can be either fatigue fractures (normal bone with abnormal stress) or insufficiency fractures (abnormal bone with normal stress)
  • Often present with intractable lower back or pelvic pain that worsens with weight bearing 1
  • Pain can radiate to the hip and femur, mimicking femoral pathology 1

Other Potential Causes

• Cauda equina compression - can cause radiating pain to lower extremities 1

  • May present with back pain with or without radicular symptoms
  • Can cause weakness, sensory changes, or numbness in lower limbs
  • Most commonly caused by lumbar disc herniation at L4-L5 and L5-S1 levels

• Lumbar radiculopathy - nerve root compression can cause referred pain 1

  • Disc herniation is present in 65% of patients with radiculopathy
  • Can cause radiating pain along nerve distribution

Diagnostic Approach

Initial Imaging

1. Plain radiographs should be the first imaging test 1, 2

   • AP pelvis and lateral hip views
   • However, radiographs have low sensitivity for sacral fractures due to:
     • Overlying bowel gas
     • Fecal material
     • Vascular calcifications
     • Sacral curvature
     • Copious soft tissue 1

2. When radiographs are negative but clinical suspicion remains high:

   • MRI without contrast is the preferred next imaging study 1, 2
   • MRI is extremely sensitive and can detect stress abnormalities early 1
   • MRI has higher specificity than bone scintigraphy 1
   • MRI can predict time to return to normal activities 1

3. CT imaging may be useful when MRI is contraindicated 1

   • Less sensitive than MRI but can show periosteal reaction, sclerosis, or fracture lines if symptoms have been present for several weeks

Red Flags Requiring Urgent Evaluation

• Fever (possible infection)
• Severe pain unresponsive to conservative measures
• Inability to bear weight
• Bladder or bowel dysfunction (possible cauda equina syndrome)
• Night pain or unexplained weight loss (possible malignancy) 2

Treatment Approach

For Sacral Stress Fractures

1. Conservative management for stable fractures 1

   • Rest and activity modification
   • Non-weight bearing or limited weight bearing as tolerated
   • Pain management with acetaminophen or NSAIDs 1, 3
   • Heat therapy can be effective 3
   • Physical therapy once acute pain improves 3

2. Surgical intervention may be necessary for:

   • Unstable fractures
   • Fractures that fail to heal with conservative management
   • High-risk fractures with displacement 1

For Femoral Neck Stress Fractures (if present)

• Medial "compression-type" femoral neck stress fractures are low risk and can be treated with a non-weight bearing regimen 1
• Lateral "tension-type" femoral neck stress fractures are high-risk and often require percutaneous screw fixation 1

For Cauda Equina Syndrome

• Urgent surgical decompression if diagnosed 1

Monitoring and Follow-up

• Regular clinical reassessment to monitor symptom improvement
• Follow-up imaging may be necessary to assess healing
• MRI can be used to predict time to return to normal activities 1
• Return to full activities should be guided by clinical improvement and evidence of healing on imaging

Common Pitfalls to Avoid

• Relying solely on negative radiographs when clinical suspicion remains high 2
• Confusing sacral insufficiency fractures with metastatic disease on MRI 1
• Failing to include the sacrum in imaging studies when evaluating hip pain, as sacral stress fractures can be the source of radiated hip/groin pain 1
• Delaying diagnosis, which can increase complications, hospital stays, and mortality rates 2