Ceramics in Hip Arthroplasty

Overview

Types of Ceramic Materials

• Miller's Review of Orthopaedics 9th Ed., Table 5.5

Bearing Friction

• Miller's Review of Orthopaedics 9th Ed., Table 5.6

Generations of Ceramic Bearings

First-Generation Alumina

• Head fracture rate up to 13.4%
• Reasons: thick neck/skirt design leading to adverse head-neck ratio; coarse microstructure; low ceramic density; poor manufacturing technique; neck impingement was the dominant failure mode.

Third-Generation (Current Standard)

• Hot isostatic pressing (HIP) technique
• High ceramic density + fine microstructure
• Elimination of the skirt → improved head-neck ratio
• Fracture rates dramatically reduced

Modern Alumina Matrix Composite (AMC)

• Zirconia-reinforced alumina composites (e.g., BIOLOX delta)
• Very low reported fracture rates
• Used in both femoral heads and acetabular liners

Advantages of Ceramic Bearings

1. Lowest wear rate - less linear and volumetric wear than metal-on-metal (MoM)
2. Fewer particles generated compared to MoM
3. Bioinert debris - no ionization of particles; no cancer risk; no dysplasia or metaplastic effects on local soft tissues
4. No metal ion release - avoids the pseudotumors, solid-organ metal deposits, and hypersensitivity reactions seen with MoM
5. Osteolysis reduction - biocompatible particles are less osteolytic than polyethylene or metal debris

• Miller's Review of Orthopaedics 9th Ed., Section: Ceramic-on-Ceramic Bearing
• Schwartz's Principles of Surgery 11th Ed., p. 1935

Disadvantages and Complications

1. Hip Squeaking

• Implant malpositioning
• Lever-range wear
• Stripe line formation (arcuate roughened area on head/cup from repetitive subclinical subluxation - see diagram below)
• Implant resonance - vibratory resonance from lever range over the rough stripe amplified by the prosthetic construct to an audible frequency

2. Fracture

• Due to low fracture toughness (brittleness despite hardness)
• Treatment: Replace with another CoC bearing. Important: microscopic ceramic shards remain after fracture and are severely abrasive; if polyethylene is used instead after ceramic fracture, highly cross-linked polyethylene (HCLPE) is preferred over conventional PE to resist abrasive wear by residual ceramic debris.
• Modern AMC ceramics have very low fracture rates.

3. Head Size Limitation

• The ceramic liner must maintain minimum thickness within the metal shell, limiting achievable femoral head diameter
• Smaller heads = less stability and less optimal fluid film lubrication compared to large-diameter MoM bearings

4. Head Length Limitation

• No skirts allowed on modern ceramic heads (to maintain head-neck ratio)
• This can restrict hip offset options, potentially contributing to hip impingement or instability

5. Head Change on a Used Femoral Neck

• Any ceramic head placed on a previously used (roughened) femoral neck requires an internal titanium adapter sleeve
• A used neck is roughened by wear and corrosion; high-point contact from the roughened surface can cause burst fracture of a new ceramic head with repetitive loading
• Miller's Review of Orthopaedics 9th Ed., Section: Ceramic-on-Ceramic Bearing, pp. 446-447

Ceramic-on-Ceramic vs. Ceramic-on-Polyethylene

• No significant difference in dislocation, DVT, infection, wear debris/osteolysis, or revision rates between CoC and CoP
• Postoperative Harris Hip Score was higher in the CoC group, though evidence quality is moderate
• CoC is more commonly chosen for younger, healthier, more active patients
• Large multicentre trials with >15 years follow-up are still needed

Clinical Decision-Making Summary

• Schwartz's Principles of Surgery 11th Ed., p. 1935
• Campbell's Operative Orthopaedics 15th Ed. 2026, Bearings section