Degenerative Joint Disease (DJD)

Macroscopic & Microscopic Appearance of Normal vs. Damaged Articular Hyaline Cartilage by DJD

Hip Osteoarthritis (OA) aka Osteoarthrosis

• Symptomatic and potentially disabling DJD
• Progressive damage and loss of the articular cartilage causing denudation and eburnation of articular bone
• Cystic changes, osteophytes and gradual joint destruction
• Develops d/t repeated joint loading and microtrama
• Obesity, metabolic/genetic factors
• Secondary Causes: trauma, FAI syndrome, osteonecrosis, pyrophosphate crystal depostion, previous inflammatory arthritis, Slipped Capital Femoral Epiphysis, Leg-Calves-Perthes disease in children etc.
• Hip OA, 2nd m/c after knee OA. Women>men
• 88-100 symptomatic cases per 100000

Radiography is the Modality of Choice for the Dx and Grading of DJD

• Special imaging is not required unless other complicating factors exist
• Acetabular-femoral joint is divided into superior, axial and medial compartments/spaces
• Normal joint space at the superior compartment should be 3-4-mm on the AP hip/pelvis view
• Understanding the pattern of hip joint narrowing/migration helps with the DDx of DJD vs. Inflammatory arthritis
• In DJD, m/c hip narrowing is superior-lateral (non-uniform) vs. inflammatory axial (uniform)

AP Hip Radiograph Demonstrates DJD

• With non-uniform loss of joint space (superior migration), large subcortical cysts and subchondral sclerosis
• Radiographic features:
• Like with any DJD changes: radiography will reveal L.O.S.S.
• L: loss of joint space (non-uniform or asymmetrical)
• O: osteophytes aka bony proliferation/spurs
• S: Subchondral sclerosis/thickening
• S: Subcortical aka subchondral cysts “geodes”
• Hip migration is m/c superior resulting in a “tilt deformity”

Radiographic Presentation of Hip OA May Vary Depending On Severity

• Mild OA: mild reduction of joint space often w/o marked osteophytes and cystic changes
• During further changes, collar osteophytes may affect femoral head-neck junction with more significant jint space loss and subchondral bone sclerosis (eburnation)
• Cyst formation will often occur along the acetabular and femoral head subarticular/subchondral bone “geodes” and usually filled with joint fluid and some intra-articular gas
• Subchondral cysts may be occasionally very large and DDx from neoplasms or infection or other pahtology

Coronal Reconstructed CT Slices in Bone Window

• Note moderate joint narrowing that appears non-uniform
• Sub-chondral cysts formation (geodes) are noted along the acetabular and femoral head subchondral bone
• Other features include collar osteophytes along head-neck junction
• Dx: DJD of moderate intensity
• Referral to the Orthopedic surgeon will be helpful for this patient

AP Pelvis (below first image), AP Hip Spot (below second image) CT Coronal Slice

• Note multiple subchondral cysts, sever non-uniform joint narrowing (superior-lateral) and subchondral sclerosis with osteophytes
• Advanced hip arthrosis

Severe DJD, Left Hip

• When reading radiological reports pay particular attention to grading of hip OA
• Most severe (advanced) OA cases require total hip arthroplasty (THA)
• Refer your patients to the Orthopedic surgeon for a consultation
• Most mild cases are good candidate for conservative care

Hip Arthroplasty aka Hip Replacement

• Can be total or hemiarthroplasty
• THA can be metal on metal, metal on polythelen and ceramic on ceramic
• Hybrid acetabular component with polyethelen and metal backing is also used (above right image)
• THA can be cemented (above right image) and non-cemented (above left image)
• Non-cemented arthroplasty is used on younger patients utilizing porous metallic parts allowing good fusion and bone ingrowth into the prosthesis

Failed THA May Develop

• Most develop within first year and require revision
• Femoral stem may fracture (above left)
• Postsurgical infection (above right)
• Fracture adjacent to prosthesis (stress riser)
• Particle disease

Femoroacetabular Impingement Syndrome

• (FAI): abnormality of normal morphology of the hip leading to eventual  cartilage damage and premature DJD
• Clinically: hip/groin pain aggravated by sitting (e.g. hip flexed & externally rotated). Activity related pain on axial loading esp. with hip flexion (e.g. walking uphill)
• Pincer type acetabulum: > in middle age women potentially  many causes
• CAM-type deformity: > in men in 20-50 m/c 30s
• Mixed type (pincer-CAM) is most frequent
• Up until the 90s FAI was not well-recongnised

FAI Syndrome

• CAM-type FAI syndrome
• Radiography can be a reliable Dx tool
• X-radiography findings: osseous bump on the lateral aspect of femoral head-neck junction. Pistol-grip deformity. Loss of normal head sphericity. Associated features: os acetabule, synovial herniation pit (Pit’s pit). Evidence of DJD in advanced cases
• MRI and MR arthrography (most accurate Dx of labral tear) can aid the diagnosis of labral tear and other changes of FAI
• Referral to the Orthopedic surgeon is necessary to prevent DJD progression and repair labral abnormalities. Late Dx may lead to irreversible changes of DJD

AP Pelvis: B/L CAM-type FAI syndrome

Pincer-Type FAI with Acetabula Over-Coverage

• Key radiographic signs: “Cross-over sign” and abnormal center-edge and Alfa-angle evaluation methods

Dx of FAI

• Center-edge angle (above the first image) and Alfa-angle (above the second image)
• B/L CAM-type FAI with os acetabule (above right image)

MR Arthrography

• Labral tear and CAM-type FAI syndrome on axial (above left) and coronal T2 W (above right) MR arthrography
• Note acetabula labral tear. Referral to orthopedic surgeon is required. For more information: 
• https://radiopaedia.org/articles/femoroacetabular-impingment-1

Hip Pelvis Arthritis & Neoplasms