Hip Osteoarthritis - Recon

Introduction

Definition
- degenerative disease of synovial joints that causes progressive loss of articular cartilage
Epidemiology
- incidence
  - hip OA (symptomatic)
    - 88 per 100,000 per year
  - knee OA (symptomatic)
    - 240 per 100,000 per year
Risk factors
- modifiable
  - articular trauma
  - muscle weakness
  - heavy physical stress at work
  - high impact sporting activities
- non-modifiable
  - gender
    - females >males
  - increased age
  - genetics
  - developmental or acquired deformities
    - hip dysplasia
    - slipped capital femoral epiphysis
    - Legg-Calvé-Perthes disease
Pathophysiology
- pathoanatomy
  - articular cartilage
    - increased water content
    - alterations in proteoglycans
      - eventual decrease in amount of proteoglycans
    - collagen abnormalities
      - organization and orientation are lost
      - binding of proteoglycans to hyaluronic acid
  - synovium and capsule
    - early phase of OA
      - mild inflammatory changes in synovium
    - middle phase of OA
      - moderate inflammatory changes of synovium
      - synovium becomes hypervascular
    - late phases of OA
      - synovium becomes increasingly thick and vascular
      - bone
      - subchondral bone attempts to remodel
      - forming lytic lesion with sclerotic edges (different than bone cysts in RA)
      - bone cysts form in late stages
Cell biology
- proteolytic enzymes
  - matrix metalloproteases (MMPs)
    - responsible for cartilage matrix digestion
    - examples
      - stromelysin
      - plasmin
      - aggrecanase-1 (ADAMTS-4)
  - tissue inhibitors of MMPS (TIMPs)
    - control MMP activity preventing excessive degradation
    - imbalance between MMPs and TIMPs has been demonstrated in OA tissues
  - inflammatory cytokines
    - secreted by synoviocytes and increase MMP synthesis
      - examples
        
        IL-1
        
        IL-6
        
        TNF-alpha
Genetics
- inheritance
  - non-mendilian
- genes potentially linked to OA
  - vitamin D receptor
  - estrogen receptor 1
  - inflammatory cytokines
    - IL-1
      - leads to catabolic effect
    - IL-4
    - matrilin-3
    - BMP-2, BMP-5

Classification

Tonnis Classification
Grade 0	• normal radiographs
Grade 1	• sclerosis of femoral head and acetabulum • slight joint space narrowing • slight lipping at joint margins
Grade 2	• small cysts in femoral head/acetabulum • moderate joint space narrowing • moderate loss of head sphericity
Grade 3	• large cysts in femoral head/acetabulum • joint space obliteration/severe narrowing • severe femoral head deformity vs. AVN

Presentation

History
- identify age, functional activity, pattern of arthritic involvement, overall health and duration of symptoms
Symptoms
- function-limiting hip pain
  - effect on walking distances
- pain at night or rest
- hip stiffness
- mechanical
  - instability, locking, catching sensation
Physical exam
- inspection
  - body habitus
  - gait
  - leg length discrepancy
  - skin (e.g. scars)
- range of motion
  - lack of full extension (>5 degrees flexion contracture)
  - lack of full flexion (flexion < 90-100 degrees)
  - limited internal rotation
Neurovascular exam
- straight leg test negative

Imaging

Radiographs
- recommended views
  - standing AP pelvis
  - AP + lateral hip
- optional views
  - false profile view (e.g. hip dysplasia)
- findings
  - osteoarthritis
    - joint space narrowing
    - osteophytes
    - subchondral sclerosis
    - subchondral cysts
  - pelvic obliquity
    - may be secondary to spinal deformity
    - may cause leg-length issues
  - acetabular retroversion
    - makes appropriate positioning of acetabular component more difficult intraoperatively

Studies

Histology
- loss of superficial chondrocytes
- replication and breakdown of the tidemark
- fissuring
- cartilage destruction with eburnation of subchondral bone

Treatment

Nonoperative
- NSAIDs and/or tramadol
  - indications
    - first line treatment for all patients with symptomatic arthritis
  - technique
    - NSAID selection should be based on physician preference, patient acceptability and cost
- walking stick
  - decreases the joint reaction force on the affected hip when used in the contralateral upper extremity
- weight loss, activity modification and exercise program/physical therapy
  - indications
    - first line treatment for all patients with symptomatic arthritis
    - BMI > 25
  - technique
    - exercise aimed at increasing flexibility and aerobic capacity
- corticosteroid joint injections
  - indications
    - can be therapeutic and/or diagnostic of symptomatic hip osteoarthritis
    - use for short-term pain relief strongly supported in 2013 AAOS CPG
- controversial treatments
  - acupuncture
  - viscoelastic joint injections
  - glucosamine and chondroitin
Operative
- arthroscopic debridement
  - indications
    - controversial
    - degenerative labral tears
- periacetabular osteotomy +/- femoral osteotomy
  - indications
    - symptomatic dysplasia in an adolescent or young adult with concentrically reduced hip and mild-to-moderate arthritis
  - outcomes
    - mixed results
    - literature suggest this can delay need for arthroplasty
- femoral head resection
  - indications
    - pathological hip lesions
    - painful head subluxation
- hip resurfacing
  - indications
    - young active, male, patients with hip osteoarthritis
    - increasing concern for metal-on-metal adverse events, procedure therefore decreasing in use
- total hip arthroplasty (THA)
  - indications
    - end-stage, symptomatic or severe osteoarthritis arthritis
    - preferred treatment for older patients (>50) and those with advanced structural changes
    - recommendation is to wait at least 3 months after ipsilateral intaarticular hip injection to decrease risk of prosthetic joint infection