What are the symptoms and management options for a patient with bilateral iliac crest aneurysmal bone cysts?

Bilateral Iliac Crest Aneurysmal Bone Cysts: Symptoms and Management

Clinical Presentation

Patients with bilateral iliac crest aneurysmal bone cysts typically present with pain and/or swelling, with symptoms usually present for less than 6 months. 1

Key Symptoms to Assess:

• Pain: The primary presenting complaint in most patients with pelvic aneurysmal bone cysts 1, 2
• Swelling or palpable mass: Common in accessible locations 1
• Pathological fracture: Occurs in destructive acetabular lesions and should be evaluated with weight-bearing radiographs 2
• Neurological symptoms: Particularly if the lesion extends to the sacrum or involves neural foramina 2
• Hip joint involvement: Assess for medial migration of the femoral head, subluxation, or dislocation 2
• Duration of symptoms: Typically less than 6 months, which helps distinguish from other chronic processes 1

Patient Demographics:

• Age: Approximately 80% of patients are less than 20 years old 1
• Location: The pelvis accounts for about half of all flat bone aneurysmal bone cysts 1

Diagnostic Imaging Algorithm

Initial Evaluation:

Plain radiographs should be obtained first, showing an eccentric, lytic lesion with an expanded, remodeled "blown-out" or "ballooned" bony contour with a delicate trabeculated appearance. 1

Advanced Imaging:

• CT scanning: Essential for pelvic lesions where bony anatomy is complex and not adequately evaluated by plain films; defines the extent of bone destruction 1, 2
• MRI without and with IV contrast: Provides definitive characterization, identifies fluid-fluid levels (highly characteristic), and distinguishes primary from secondary aneurysmal bone cysts 3, 1
• Fluid-fluid levels: Common finding on both CT and MRI that supports the diagnosis 1

Critical Diagnostic Considerations:

• Identify preexisting lesions: In approximately one-third of cases, a preexisting lesion can be identified (giant cell tumor accounts for 19-39% of these cases) 1
• Rule out malignancy: Osteosarcoma with superimposed secondary aneurysmal bone cyst change must be excluded, as treatment differs fundamentally 1

Management Strategy

Primary Treatment Approach:

For bilateral iliac crest aneurysmal bone cysts, percutaneous sclerotherapy with polidocanol should be considered as first-line treatment, showing healing or stable disease in 96% of cases with a median of 4 injections. 4

Sclerotherapy Protocol:

• Technique: Under general anesthesia and fluoroscopic guidance, perform repeated percutaneous injections of 4mg polidocanol/kg body weight 4
• Expected outcomes: Complete clinical and radiographic healing in 70% of cases, partial healing with pain resolution in 26% 4
• Number of treatments: Median of 4 injections (range 1-8) 4
• Follow-up: Median radiographic follow-up of 19.5 months to assess healing 4

Advantages of Sclerotherapy:

• Minimally invasive: Avoids extensive surgical morbidity in the pelvis 4
• Safe profile: Only one case of transient hypotension in a large pelvic lesion, quickly reversed 4
• Effective for recurrent disease: Works in both primary and previously treated cases 4

Surgical Treatment (When Sclerotherapy Fails or Is Not Feasible):

If sclerotherapy fails or the lesion is not amenable to percutaneous treatment, surgical excision-curettage with bone grafting should be performed, preceded by preoperative selective arterial embolization. 2

Surgical Protocol:

• Preoperative embolization: Mandatory for pelvic lesions due to high vascularity 2
• Surgical technique: Excision-curettage (preferred over intralesional excision based on lower recurrence rates) 2
• Bone grafting: Use allograft chips or polymethylmethacrylate; some cases may use autografts 5, 2
• Expected recurrence: 14-20% local recurrence rate, typically occurring within 18 months postoperatively 5, 2

Special Considerations for Bilateral Pelvic Lesions:

Bilateral iliac crest lesions require staged treatment, addressing the more symptomatic or structurally compromised side first. 2

• Iliosacral involvement: Seventeen of forty pelvic cases in one series were iliosacral, requiring careful neurological monitoring 2
• Acetabular involvement: High risk of pathological fracture and hip joint compromise; requires urgent intervention if weight-bearing structures are threatened 2
• Sacral extension: All sacral lesions extending to more than one segment were associated with neurological signs and require decompression 2

Treatment Algorithm by Clinical Scenario:

For Stable, Non-Fracture Cases:

1. First-line: Percutaneous sclerotherapy with polidocanol 4
2. Monitor: Clinical and radiographic assessment every 3-4 months during treatment phase 4
3. If no response after 6-8 injections: Proceed to surgical excision-curettage 4, 2

For Pathological Fracture or Joint Involvement:

1. Immediate: Preoperative selective arterial embolization 2
2. Definitive: Surgical excision-curettage with bone grafting 2
3. Protected weight-bearing: Until radiographic healing confirmed 2

For Recurrent Disease After Previous Surgery:

1. Preferred: Percutaneous sclerotherapy (effective in 96% of recurrent cases) 4
2. Alternative: Repeat surgical excision with more aggressive curettage and adjuvant treatment 2

Critical Pitfalls to Avoid:

• Do not proceed with surgery without preoperative embolization in pelvic lesions, as these are highly vascular and can result in massive intraoperative hemorrhage 2
• Do not mistake for malignancy: Flocculent densities within the lesion may mimic chondroid matrix but are benign 1
• Do not assume single lesion: Although synchronous primary aneurysmal bone cysts are exceedingly rare, bilateral involvement requires complete skeletal survey 6
• Do not delay treatment: Pelvic aneurysmal bone cysts are usually aggressive with substantial bone destruction; early intervention prevents pathological fractures 2
• Do not use radiation therapy as primary treatment: Only two patients in a large series received adjuvant radiation, and this is not standard of care due to risk of malignant transformation 2

Long-Term Outcomes:

• Disease-free survival: 100% at mean 13-year follow-up (range 3-53 years) 2
• Symptomatic relief: 70% of patients asymptomatic at latest follow-up 2
• Recurrence timing: All recurrences noted within 18 months of initial treatment 2
• Complications: Deep infection rate of 5% with surgical treatment 2