It is an expectation that all patients receive care/services from a licensed clinician. All appropriate supporting documentation, including recent pertinent office visit notes, laboratory data, and results of any special testing must be provided. If applicable: All prior relevant imaging results and the reason that alternative imaging cannot be performed must be included in the documentation submitted.

Where a specific clinical indication is not directly addressed in this guideline, medical necessity determination will be made based on widely accepted standard of care criteria. These criteria are supported by evidence-based or peer-reviewed sources such as medical literature, societal guidelines and state/national recommendations.
 

Policy
INDICATIONS FOR LOWER EXTREMITY CT (FOOT, ANKLE, KNEE, LEG, OR HIP)
Pre-condition
Plain radiographs must precede CT evaluation.
 

Joint or Muscle Pain (1,2,3)
Negative Findings on Orthopedic Exam and after X-Ray Completed
NOTE: Does not apply to young children (up to age 12). If MRI contraindicated or cannot be performed or requested as a CT arthrogram.

• Persistent joint or musculotendinous pain unresponsive to conservative treatment*, within the last 6 months which includes active medical therapy (physical therapy, chiropractic treatments, and/or physician supervised exercise**) of at least four (4) weeks
• With progression or worsening of symptoms during the course of conservative treatment

Joint Specific Provocative Exam Tests and Suspected Injuries (4)
Approvable Orthopedic Test:
With a positive orthopedic sign, an initial x-ray is always preferred; however, it is not required to approve advanced imaging UNLESS otherwise specified in bold below. Any test that suggests joint instability requires further imaging (the below list is not all inclusive)
NOTE: If MRI contraindicated or cannot be performed or requested as a CT arthrogram

Ankle (5,6)
If MRI contraindicated or cannot be performed;

• Thompson test or palpable partial or complete Achilles tendon defect on physical examination

Knee (11,12)
If MRI contraindicated or cannot be performed;

• Posterior drawer
• Posterior tibial sag (Godfrey or step-off test)
• Medial collateral ligament tear
  • Positive valgus stress testing/laxity
• Lateral Collateral ligament tear
  • Positive Varus stress testing/laxity

Hip
If MRI contraindicated or cannot be performed;

• Femoroacetabular impingement (FAI) / Labral tear^(18,19,20)
  • Anterior Impingement sign (aka FADIR test) (Hip or groin pain with hip flexion, adduction, and internal rotation
  • Posterior Impingement sign (Pain with hip extension and external rotation on exam)
  • Persistent hip mechanical symptoms (after initial radiographs completed) including clicking, locking, catching, giving way or hip instability with a clinical suspicion of labral tear and/or radiographic findings suggestive of FAI (i.e., cross over sign, pistol grip deformity, alpha angle over 50 degrees) and suspected labral tear
  • Determine candidacy for hip preservation surgery for known FAI

NOTE: For evaluation of both hips when the patient meets hip MRI guidelines (x-ray + persistent pain unresponsive to conservative treatment) for both the right and left hip, Pelvis MRI (Evolent_CG_037) is the preferred study.

• Labral tear is suspected and fulfills above criteria, then bilateral hip MRIs are the preferred studies (not Pelvis MRI)
• Bilateral hip arthrograms are requested and otherwise meet guidelines, bilateral hip MRIs are the preferred studies (not Pelvis MRI)

Tendon Rupture (21,22)
After X-Ray and not Listed Above
High clinical suspicion of specific tendon rupture based on mechanism of injury and physical findings (i.e., palpable defect in quadriceps or patellar tendon rupture)
 

Trauma
Bone Fracture

• Hip and Femur⁽²³⁾
  • Suspected occult, stress or insufficiency fracture with a negative or non- diagnostic initial x-ray
    • Approve an immediate CT if contraindication to MRI or MRI cannot be performed (no follow up radiographs required)
  • Suspicion of a hip fracture in a pregnant patient does not require an initial x-ray
• Non-hip extremities: suspected occult, stress, or insufficiency fracture⁽²⁴⁾
  • If x-rays, taken 10-14 days after the injury or clinical assessment, are negative or non-diagnostic
  • If at high risk for a complete fracture with conservative therapy (e.g., navicular bone), then immediate CT is warranted
• Pathologic or concern for impending fracture on x-ray or CT⁽²⁴⁾ – approve immediate CT
• Suspected ligamentous/tendon injury with known fractures on x-ray/CT that may require surgery

Osteochondral Lesions (12,25,26)
Defects, Fractures, Osteochondritis Dissecans
Clinical suspicion based on mechanism of injury and physical findings
NOTE: X-ray completed

Joint Prosthesis/Replacement (27)

• Suspected Metallosis with painful metal on metal hip replacement⁽²⁸⁾ after initial x- rays
  • After initial x-rays
  • Cobalt and chromium levels > 7ppb(29)
  • Abnormal joint aspiration

Extremity Mass (30)

• Mass or lesion after non-diagnostic x-ray or ultrasound. CT is better than MRI to evaluate mass calcification or bone involvement and may complement or replace MRI (MRI is preferred)
  • Baker’s cyst should be initially evaluated with ultrasound
  • Superficial mass, then ultrasound is the initial study
  • Deep mass, then x-ray is the initial study
• Vascular malformations⁽³¹⁾
  • After initial evaluation with ultrasound and results will change management or preoperative planning
    • CTA is also approvable for initial evaluation
  • Follow up after treatment/embolization

Known Primary Cancer of the Extremity (32,33,34,35)

• Initial staging primary extremity tumor
• Follow-up of known primary cancer of patient undergoing active treatment within the past year or as per surveillance imaging guidance for that cancer
• Signs or symptoms or imaging findings suspicious for recurrence
• Suspected metastatic disease with signs/symptoms and after initial imaging with radiographs

Further Evaluation of Indeterminate Findings on Prior Imaging
Unless follow-up is otherwise specified within the guideline

• For initial evaluation of an inconclusive finding on a prior imaging report that requires further clarification
• One follow-up exam of a prior indeterminate MR/CT finding to ensure no suspicious interval change has occurred. (No further surveillance unless specified as highly suspicious or change was found on last follow-up exam.)

Osteonecrosis (36)

• Normal or Indeterminate X-rays, but symptomatic and high risk (such as glucocorticosteroid use, renal transplant, glycogen storage disease, alcohol abuse, sickle cell anemia)
• Known osteonecrosis to evaluate a contralateral joint after initial x-rays

e.g., Avascular Necrosis (AVN), Legg-Calve-Perthes Disease

Loose Bodies or Synovial Chondromatosis (37)
(After X-Ray or Ultrasound Completed)

• In the setting of joint pain or mechanical symptoms

Infection of Bone, Joint, or Soft Tissue Abscess (38)

• Abnormal x-ray or ultrasound
• Negative x-ray or ultrasound but with a clinical suspicion of infection based on either of the following:
  • Signs and symptoms of joint or bone infection such as:
    • Pain and swelling
    • Decreased range of motion
    • Fevers
  • Laboratory findings of infection include any of the following:
    • Elevated ESR or CRP
    • Elevated white blood cell count
    • Positive joint aspiration
• Ulcer (diabetic, pressure, ischemic, traumatic) with signs of infection (redness, warmth, swelling, pain, discharge which may range from white to serosanguineous) that is not improving despite treatment and bone, or deep infection is suspected⁽³⁹⁾
  • Increased suspicion if size or temperature increases, bone is exposed/positive probe-to-bone test, new areas of breakdown, new smell
• Neuropathic foot with friable or discolored granulation tissue, foul odor, non-purulent discharge, and delayed wound healing⁽³⁹⁾

NOTE: MRI and nuclear medicine studies are recommended for acute infection as they are more sensitive in detecting early changes of osteomyelitis. CT is better at demonstrating findings of chronic osteomyelitis (sequestra, involucrum, cloaca, sinus tracts) as well as detecting soft tissue gas and foreign bodies.

Pre-Operative/Procedural Evaluation
Pre-operative evaluation for a planned surgery or procedure

Evaluation of Tumor
When needed for clarification of vascular invasion from tumor after prior imaging.

Post-Operative/Procedural Evaluation

• When imaging, physical or laboratory findings indicate joint infection, delayed or non- healing or other surgical/procedural complications.
• Trendelenburg sign⁽⁴⁰⁾ or other indication of muscle or nerve damage after recent hip surgery

Evaluation of Known or Suspected Autoimmune Disease (41,42)

MRI is contraindicated or cannot be performed:

• Further evaluation of an abnormality or non-diagnostic findings on prior imaging
• Initial imaging of a single joint for diagnosis or response to therapy after plain films and appropriate lab tests (e.g., RF, ANA, CRP, ESR)
• To determine change in treatment or when diagnosis is uncertain prior to start of treatment
• Follow-up to determine treatment efficacy of the following:
  • Early rheumatoid arthritis
  • Advanced rheumatoid arthritis if x-ray and ultrasound are equivocal or noncontributory

e.g., Rheumatoid Arthritis

Known or Suspected Inflammatory Myopathies (43)

• For diagnosis
• For biopsy planning

NOTE: If MRI is contraindicated or cannot be performed. Includes polymyositis, dermatomyositis, immune-mediated necrotizing myopathy, inclusion body myositis.

Crystalline Arthropathy (44)

• Dual-energy CT can be used to characterize crystal deposition disease (i.e., gout) after:
  • Appropriate rheumatological work up and initial x-rays AND
  • After inconclusive joint aspiration or when joint aspiration cannot be performed

OR

• In the setting of extra-articular crystal deposits (i.e., tendons or bursa)

Peripheral Nerve Entrapment (45,46)
MRI is contraindicated or cannot be performed, including any of the following:

• Abnormal electromyogram or nerve conduction study
• Abnormal x-ray or ultrasound
• Clinical suspicion and failed 4 weeks conservative treatment including at least two of the following (active treatment with physical therapy is not required):
  • Activity modification
  • Rest, ice, or heat
  • Splinting or orthotics
  • Medication

e.g., Tarsal tunnel, Morton’s neuroma

Foreign Body (47)
Indeterminate x-ray and ultrasound

Painful Acquired or Congenital Flatfoot Deformity (48,49)
Adult

■    Activity modification
■    Rest, ice, or heat
■    Splinting or orthotics
■    Medication
 

Pediatrics (Up to Age 18)

• Osteoid Osteoma after and x-ray is done⁽⁵⁰⁾
• Painful flatfoot (pes planus) deformity with suspected tarsal coalition, not responsive to non-active conservative care (such as orthotics, rest etc.)⁽⁵¹⁾
  • When MRI cannot be performed
  • Extra articular coalition is suspected (bony bridges around the joints)
  • Surgical planning

Rationale
MRI
Plain radiographs are typically used as the first-line modality for assessment of lower extremity conditions. Computed tomography (CT) is used for evaluation of tumors, metastatic lesions, infection, fractures, and other problems. Magnetic resonance imaging (MRI) is the first-line choice for imaging of many conditions, but CT may be used in these cases if MRI is contraindicated or unable to be performed.

Special Note