What is the appropriate management for an adolescent or young adult with bilateral L5 pars defects (bilateral spondylolysis) presenting with low‑back pain that worsens with extension?

Management of Bilateral L5 Pars Defects

Begin with standing AP and lateral lumbar spine radiographs, add oblique views to visualize the pars interarticularis defect, then proceed with conservative management consisting of activity restriction, bracing, and physical therapy for at least 6 months before considering surgical intervention. 1, 2

Initial Diagnostic Imaging Algorithm

Start with plain radiographs as the foundation:

• Obtain standing anteroposterior and lateral lumbar spine radiographs as your first-line study; these remain standard of care despite limited sensitivity for detecting spondylolysis without spondylolisthesis 1, 2
• Add oblique lumbar radiographic views specifically to visualize the pars interarticularis ("Scotty-dog" collar sign), which markedly improves detection of defects in patients with extension-based pain 1, 2
• Do not rely solely on standard AP/lateral views when clinical suspicion is high, as their sensitivity for isolated spondylolysis is limited 2

If radiographs are negative but clinical suspicion remains high (young athlete with extension-based pain):

• SPECT bone scan with or without CT is the reference standard for identifying radiographically occult, active pars stress injuries in young patients 1, 2
• SPECT shows increased radiotracer uptake in areas of active bone turnover and is highly sensitive for detecting stress reactions 1, 2
• MRI without contrast detects bone marrow edema within the pars or adjacent pedicle, indicating an active stress injury, and provides superior soft-tissue detail for assessing coexisting disc pathology 1, 2
• CT without contrast has increased sensitivity for detecting non-displaced fractures and established spondylolysis compared to radiographs, and serves as a complementary tool when combined with SPECT or MRI 1, 2

Conservative Management Protocol (First-Line Treatment)

Conservative treatment is successful in 84% of patients with spondylolysis and should be attempted for at least 6 months before considering surgery:

• Restrict activities involving repetitive hyperextension and extension-rotation of the lumbar spine (the movements that provoke pain in 98% of patients) 3
• Apply bracing to limit lumbar motion during the healing phase 3, 4
• Implement physical therapy focusing on core stabilization and flexibility 3
• Monitor for resolution of bone marrow edema on MRI if obtained, as this indicates response to therapy and potential prevention of progression to complete fracture 2
• Conservative management with bracing and decreased activity is most effective with early diagnosis and treatment 4
• In multilevel pars fractures, conservative management can achieve complete bony union of acute fractures within 1 year 5

Surgical Indications and Approach

Surgery is indicated only after failure of at least 6 months of conservative management to provide sustained pain relief for activities of daily living:

• Percutaneous direct pars repair using a pedicle screw-based approach is preferred over spinal fusion in young athletes who desire return to high-level physical activity 6, 7, 4
• This technique achieves fusion in 95% of patients and reduces visual analog scale pain scores from 7.62 preoperatively to 0.28 postoperatively 6
• Advantages include minimized muscle and soft tissue dissection, reduced blood loss, and early mobilization and recovery 6
• The pedicle screw-hook technique and pedicle screw-rod technique show low rates of hardware failure, increased maintenance of mobility, and lack of postoperative bracing requirement 4

Critical Pitfalls to Avoid

Imaging errors:

• Do not limit evaluation to standard AP/lateral radiographs when clinical suspicion is high; low sensitivity may miss isolated pars defects 2
• Do not order oblique lumbar radiographs for generic low-back pain; reserve them specifically for suspected pars visualization 2
• Avoid whole-spine imaging when stress injuries are typically confined to a single lumbar level (L5 in 85% of cases); targeted imaging reduces unnecessary radiation and cost 1, 2, 3

Management errors:

• Do not proceed to surgery without attempting at least 6 months of conservative management, as 84% of spondylolysis patients achieve excellent or good results with non-operative treatment 3, 4
• Promptly obtain advanced imaging (SPECT or MRI) when radiographs are negative but presentation is classic for pars stress injury to avoid diagnostic delay 2
• In patients with spondylolisthesis (subluxation), surgical rates are higher (60% require surgery), so monitor more closely for progression 3