## Introduction
Dislocation is the most common reason for early revision in Total Hip Replacement (THR). The most significant advancement in preventing this complication is the move toward **Large Diameter Femoral Heads**.
## The Biomechanics of Stability
Historically, 22mm or 28mm heads were the standard. Today, **32mm and 36mm** heads are the preferred choice.
### 1. Increased “Jump Distance”
The “jump distance” is the amount the femoral head must travel before it physically pops out of the cup.
* **A larger head** has a significantly greater jump distance, meaning it can tolerate much more movement before dislocating.
### 2. Improved Head-to-Neck Ratio
A larger head relative to the thickness of the neck prevents “Impingement.”
* **Impingement** occurs when the metal neck hits the edge of the cup, acting as a lever that pries the head out. A 36mm head allows for a wider range of motion before this contact happens.
## Material Science Makes it Possible
In the past, large heads were avoided because they caused high wear on traditional polyethylene. The introduction of **Highly Cross-linked Polyethylene (HXLPE)** and **Ceramic-on-Ceramic** bearings has eliminated the wear problem, allowing surgeons to use 36mm+ heads with total confidence.
## Clinical Outcomes
Studies show that increasing head size from 28mm to 36mm can reduce the risk of dislocation by up to **80%**, particularly in high-risk patients like the elderly or those with neuromuscular disorders.
## Conclusion
Size matters for stability. Ortholyx provides a full range of large-diameter ceramic and cobalt-chrome heads, giving surgeons the biomechanical tools needed to build a “dislocation-proof” hip.