What causes acetabular erosion?

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Acetabular Erosion: Causes and Mechanisms

Acetabular erosion is primarily caused by mechanical wear from repetitive loading and friction between the femoral head (prosthetic or native) and acetabular cartilage, with the severity and rate of progression determined by patient activity level, prosthetic positioning, and underlying bone quality.

Primary Mechanical Causes

In Hip Hemiarthroplasty (Most Common Context)

  • Prosthetic head position is the most critical factor: High positioning of the prosthetic head relative to the greater trochanter apex accelerates erosion, with early revision required at an average of 22 months, compared to 68 months for neutral or low positioning 1

  • Physical activity level directly correlates with erosion severity: Erosion through acetabular cartilage into bone develops in 89% (34/38) of active patients versus 0% (0/34) of inactive patients, making activity the strongest predictor of erosion 2

  • Femoral neck resection level determines head position: The surgical resection level of the femoral neck establishes prosthetic head positioning, which then dictates the direction and rate of acetabular erosion 1

Direction of Prosthetic Migration

The prosthetic head migrates in predictable patterns based on three biomechanical factors 1:

  • Proximomedial migration: Occurs with specific combinations of head position, center-edge (CE) angle, and stem positioning in the medullary canal
  • Purely proximal migration: Results from different biomechanical alignment
  • Proximolateral migration: Third pattern dependent on the same anatomical variables

Inflammatory and Biological Causes

Erosive Osteoarthritis

  • Central erosions with inflammatory features: Erosive osteoarthritis targets interphalangeal joints and shows characteristic subchondral erosion that may progress to marked bone and cartilage attrition, instability, and bony ankylosis 3

  • Inflammatory component: Typically presents with abrupt onset, marked pain, inflammatory symptoms (stiffness, soft tissue swelling, erythema), and mildly elevated CRP levels 3

Inflammatory Arthritides

  • Rheumatoid arthritis: Causes marginal erosions at synovial joints through inflammatory synovitis and pannus formation 3

  • Spondyloarthropathies: Produce erosions at joint margins and entheses through chronic inflammation 3

  • Gout: Creates periarticular erosions through crystal deposition and inflammatory response 3

Infectious Causes

Rapid acetabular erosion occurring within weeks of hemiarthroplasty should raise immediate suspicion for infection 4:

  • Accelerated timeline: Erosion developing in weeks rather than months/years indicates possible infectious etiology
  • Clinical presentation: May lead to acetabular fracture and requires urgent infection workup including joint aspiration, cell count, Gram stain, and cultures 4

Prosthetic-Related Factors

Wear Mechanisms

  • Polyethylene wear: Progressive thinning of acetabular liner contour from repetitive loading 3

  • Metal-on-metal articulation: Can cause metallosis and osteolysis leading to erosion through acetabular components 5

  • Femoral head erosion through components: Rare but documented cases of prosthetic femoral heads eroding through polyethylene liner, acetabular shell, and into the ilium 5

Patient-Specific Risk Factors

Predictive Factors for Erosion

  • Age and residence status: Patients under 80 years from private homes remain active and develop erosion; those over 80 or from nursing facilities typically remain inactive with good long-term results 2

  • Duration of follow-up: Erosion severity increases with time, but only in active patients 2

  • Bone quality: Osteoporosis and aging (average age 65 years) increase erosion risk in vertebral contexts 3

Clinical Implications

Common Pitfall to Avoid

Do not assume all acetabular erosion follows a slow, predictable course. Rapid erosion within weeks to months mandates infection workup before attributing symptoms solely to mechanical wear 4. The presence of pain and functional impairment during walking correlates with erosion severity and should prompt imaging evaluation 2.

Differential Diagnosis Considerations

When evaluating acetabular erosion, exclude 3:

  • Psoriatic arthritis (may target specific joints)
  • Rheumatoid arthritis (mainly MCPJs, PIPJs, wrists)
  • Gout (may superimpose on pre-existing osteoarthritis)
  • Hemochromatosis (mainly MCPJs, wrists)
  • Infection (requires joint aspiration for definitive diagnosis)

References

1
Research

[Acetabular erosion after hip hemiarthroplasty. Clinical and biomechanical study].

Rozhledy v chirurgii : mesicnik Ceskoslovenske chirurgicke spolecnosti, 2009

2
Research

Thompson hemiarthroplasty and acetabular erosion.

The Journal of bone and joint surgery. American volume, 1989

3
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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