What is the recommended treatment for a 16-year-old female with grade one anterolisthesis of L5 on S1 and a potential L5 pars defect?

Treatment for Grade 1 Anterolisthesis L5-S1 with Potential L5 Pars Defect in a 16-Year-Old Female

Conservative management for at least 6 months is the first-line treatment, with surgical intervention reserved only for those who fail comprehensive non-operative therapy. 1

Initial Conservative Management (Minimum 6 Months)

Begin with a structured conservative approach that must include all of the following components:

• Formal physical therapy with flexion-based exercises for at least 6 weeks, focusing on core strengthening and avoiding hyperextension activities that stress the pars interarticularis 1
• Activity modification with temporary cessation of high-impact sports and activities involving repetitive hyperextension (gymnastics, football, weightlifting) 2, 3
• Neuroleptic medications (gabapentin or pregabalin) initiated early if radicular symptoms are present 1
• Anti-inflammatory therapy as part of comprehensive pain management 1
• Epidural steroid injections may provide short-term relief if radiculopathy develops, though evidence is limited for isolated back pain 1

The patient should be reassessed at 6 weeks to evaluate response, and again at 3 months to determine if surgical consultation is warranted. 1

Advanced Imaging to Confirm Diagnosis

Since the x-ray shows only a "potential" pars defect, further imaging is essential before finalizing treatment:

• SPECT bone scan is the reference standard for detecting radiographically occult active spondylolysis in young patients and can differentiate acute from chronic pars injuries 4
• MRI complete spine without contrast is appropriate if radiographs are negative or concerning clinical findings exist, as it provides superior soft tissue resolution and can identify vertebral marrow edema indicating acute stress injury 4
• CT spine without contrast has increased sensitivity for detecting non-displaced fractures and established spondylolysis, and is complementary to SPECT/MRI for higher specificity 4

Flexion-extension radiographs are essential to identify segmental motion and document instability, which is critical for surgical decision-making if conservative management fails 1

Surgical Indications (Only After Failed Conservative Management)

Surgery should be considered only if ALL of the following criteria are met:

• Failure of comprehensive conservative management for at least 6 months including formal physical therapy, medications, and activity modification 1, 5
• Persistent disabling symptoms that significantly interfere with daily activities and quality of life 1
• Documented instability on flexion-extension radiographs or progression of spondylolisthesis 1
• Confirmed pars defect on advanced imaging (SPECT, CT, or MRI) 4

Surgical Options When Conservative Management Fails

For a 16-year-old with L5 pars defect and grade 1 spondylolisthesis, two surgical approaches exist:

Option 1: Direct Pars Repair (Preferred for Young Athletes)

Direct pars repair is the preferred option for adolescents with isolated pars defects who desire return to high-level athletic activity:

• Percutaneous direct pars repair achieves 95% fusion rates with minimal soft tissue dissection, reduced blood loss, and early mobilization 3
• Pedicle screw-rod-laminar hook fixation provides durable fixation with 100% osseous union rates in published series 6
• This technique preserves motion segments and avoids fusion, which is particularly important in young patients 6, 7
• Best results occur when the defect is acute or subacute (demonstrated by bone marrow edema on MRI or increased uptake on SPECT) 2, 3
• Patients must have temporary relief with lidocaine infiltration of the pars defect to predict successful outcome 6

Option 2: In Situ Posterolateral L5-S1 Fusion

Fusion is indicated when:

• Pars repair is not feasible due to chronic defect without healing potential 5
• Significant disc degeneration is present at L5-S1 (not a criterion for exclusion from pars repair, but influences decision) 6
• Grade 1 spondylolisthesis with documented instability persists despite conservative management 5

In situ posterolateral L5-S1 fusion is the best option for low-grade slips secondary to L5 pars defects, providing excellent pain relief and neurologic symptom resolution 5

Critical Pitfalls to Avoid

• Do not proceed to surgery without completing at least 6 months of comprehensive conservative management including formal physical therapy 1
• Do not perform fusion as first-line surgery in a 16-year-old without considering direct pars repair, which preserves motion and has excellent outcomes in this age group 3, 6, 7
• Do not rely solely on plain radiographs to confirm or exclude pars defects, as they have low sensitivity; obtain SPECT or MRI for definitive diagnosis 4
• Do not ignore flexion-extension radiographs before surgical planning, as they are essential for identifying instability 1
• Avoid operating on chronic, asymptomatic pars defects discovered incidentally, as surgery is indicated only for symptomatic defects that fail conservative management 5, 6

Expected Outcomes

With appropriate conservative management:

• Complete bony union of acute pars fractures can occur with 1 year of conservative treatment, particularly in younger adolescents 2
• Symptomatic pain relief and return to full sporting activity is achievable without surgery in many cases 2

With direct pars repair (when surgery is needed):

• Visual analog scale pain scores decrease from 7.6 preoperatively to 0.3 postoperatively 3
• 95% fusion rate with return to high-level athletic activity 3
• 100% osseous union with relief of symptoms in properly selected patients 6

With L5-S1 fusion (when indicated):

• Effective for alleviating back pain and neurologic symptoms in patients with low-grade spondylolisthesis 5
• Safe and effective long-term outcomes when performed for appropriate indications 5