What is the initial approach to managing a pars defect at L5?

Initial Management of L5 Pars Defect

For an L5 pars defect, begin with plain radiographs including oblique views, followed by CT scan to determine fracture stage (acute vs chronic), and initiate conservative management with activity restriction, bracing, and physical therapy for 3-6 months before considering surgical intervention. 1, 2, 3

Diagnostic Imaging Algorithm

Initial imaging should prioritize CT over plain radiographs for definitive diagnosis, as CT has superior sensitivity for detecting non-displaced pars fractures that radiographs frequently miss. 1, 2

• Start with anteroposterior and lateral radiographs with oblique views to visualize the pars interarticularis, though these have low sensitivity (miss up to 15% of defects). 1, 3
• Obtain CT spine without contrast of the area of interest as the next step, which provides increased sensitivity for detecting non-displaced fractures and established spondylolysis compared to radiography. 1, 2
• Add MRI without contrast if CT shows no lysis but clinical suspicion remains high, as MRI detects stress injuries with bone marrow edema indicating acute injury without complete fracture. 1, 2
• Consider bone scan if plain films are normal but history and examination strongly suggest pars defect, particularly in young athletes with extension-based back pain. 3, 4

The CT determines fracture stage, which directly dictates treatment approach—acute stress reactions have higher healing potential with conservative management than established chronic defects. 1, 2

Conservative Management Protocol (First-Line Treatment)

All patients should undergo 3-6 months of structured conservative therapy before surgical consideration, as 84% achieve excellent results with this approach. 3

Activity Modification

• Immediately restrict all activities involving repetitive hyperextension and extension-rotation of the lumbar spine (gymnastics, football, diving, weightlifting), as 98% of symptomatic patients report pain with these movements. 3
• Complete cessation of sports participation for minimum 3 months during initial healing phase. 3, 4

Bracing

• Apply rigid thoracolumbosacral orthosis (TLSO) for 23 hours daily for 3-6 months to limit lumbar extension and promote healing. 3
• Bracing is particularly effective for acute stress reactions detected on MRI or bone scan before complete lysis occurs. 4

Physical Therapy

• Initiate formal structured physical therapy focusing on core stabilization, hamstring flexibility, and avoidance of extension-based exercises. 3
• Therapy should continue throughout the bracing period and for 2-3 months after brace discontinuation. 3

Expected Outcomes

• 85% of patients with spondylolysis achieve excellent or good results with conservative management alone. 3
• Complete bony union occurs in acute fractures (positive bone scan, MRI edema) within 12 months of conservative treatment. 4
• Chronic established defects may remain radiographically unchanged but become asymptomatic with conservative care. 3

Surgical Indications (After Failed Conservative Management)

Surgery is reserved for patients who fail 3-6 months of comprehensive conservative therapy or develop progressive spondylolisthesis. 2, 5, 3

Absolute Indications

• Persistent disabling pain after minimum 6 months of appropriate conservative management including bracing, activity restriction, and physical therapy. 2, 5
• Progressive spondylolisthesis >5mm or Grade II or higher documented on serial radiographs. 5, 6
• Neurological deficits including radiculopathy or cauda equina syndrome (rare with isolated pars defect). 6

Surgical Options

• Direct pars repair (modified Bucks procedure) for young patients with isolated pars defect without spondylolisthesis, using compression screws across the defect with or without patient-specific drill guides. 7
• L5-S1 fusion with instrumentation for patients with established spondylolisthesis or failed pars repair, using transforaminal lumbar interbody fusion (TLIF) or posterolateral fusion. 5, 6

Critical Pitfalls to Avoid

• Do not rely solely on plain radiographs—they miss 15% of pars defects, particularly unilateral defects and acute stress reactions. 1, 3
• Do not skip oblique radiographs when obtaining plain films, as they provide better visualization of the pars interarticularis than AP/lateral views alone. 1
• Do not proceed to surgery without documented failure of comprehensive conservative management for at least 3-6 months, as 84% respond to non-operative treatment. 3
• Do not assume bilateral involvement—40% of pars defects are unilateral, requiring careful imaging review. 3
• Do not overlook nonconsecutive multilevel defects (L3 and L5), which occur rarely but require multiplanar CT reconstruction for complete assessment. 4

Special Considerations for Athletes

• 90% of pars defects occur at the most caudad mobile vertebra (L5 in 85% of cases, L4 in 15%). 3
• Young athletes with extension-based sports (gymnastics, football, diving, wrestling) have highest risk and should undergo bone scan if radiographs are negative but clinical suspicion is high. 3, 4
• Return to sport requires minimum 3 months of conservative treatment, pain-free status, and gradual return-to-play protocol with continued core strengthening. 3, 4
• Complete bony union on follow-up CT at 5-6 months predicts successful return to full sporting activity. 4