Hip Replacement Implant Options — What's Actually Inside Your New Hip

When patients consent to hip replacement surgery, they often sign paperwork that mentions "metal and plastic implants" without much further detail. The variability in implant design and materials — and the genuine differences in who they're suited for and how long they last — almost never gets explained.

It should. The implant choice is one of the most consequential decisions made in the pre-operative planning of hip replacement. Getting it right for the specific patient's age, activity level, and bone quality significantly influences how long the implant lasts and whether revision surgery becomes necessary.

The Four Components of a Hip Replacement

A total hip replacement has four main parts

1. Femoral stem: A metal shaft inserted into the hollow canal of the femur (thigh bone)
2. Femoral head: A ball sitting atop the stem, which articulates against the cup
3. Acetabular cup: Fixed into the acetabulum (the socket in the pelvis)
4. Liner: The bearing surface inside the cup, which the femoral head articulates against

The femoral stem and acetabular cup are fixed to bone (either with cement or by bone ingrowth). The femoral head and liner are the articulating components — the bearing surface — and wear is what most implant longevity discussion focuses on.

Fixation: Cemented vs Cementless

Cemented Fixation

Polymethylmethacrylate bone cement is used to bond the implant to the surrounding bone. The cement fills microscopic gaps between implant and bone, creating an immediate, strong mechanical bond.

Advantages: Immediate stability from Day 1. Well-suited for osteoporotic bone where bone ingrowth may be unreliable. Decades of clinical data.

Best for: Older patients (typically over 70), osteoporotic bone, patients where early weight-bearing is critical.

Cementless (Press-Fit / Porous-Coated) Fixation

No cement is used. The implant is designed with a porous or roughened surface. Initial stability comes from a tight press-fit into the bone. Over 6–12 weeks, the patient's own bone grows into the porous surface (osseointegration), creating a durable biological bond.

Advantages: No cement debris. Better bone preservation for future revision. Potentially better long-term bond in young patients with good bone quality.

Best for: Younger patients (under 65–70), good bone quality, higher activity levels where very long-term implant survival is a priority.

Many surgeons use hybrid fixation — cemented femoral stem (for reliable proximal fixation even in varied bone quality) combined with cementless acetabular cup (where cementless porous ingrowth is highly reliable).

Bearing Surface Options: Where the Real Wear Discussion Happens

The bearing surface is the pairing of femoral head material against liner material. This interface is where wear occurs.

Metal on Polyethylene (MoP) — Most Common

Standard: Cobalt-chromium femoral head articulates against a high-density polyethylene liner.

Modern upgrade: Highly cross-linked polyethylene (HXLPE) has replaced conventional polyethylene in most current hip replacement systems. Cross-linking dramatically reduces wear rates — by 50–80% compared to conventional polyethylene in laboratory and clinical studies.

HXLPE with a cobalt-chrome head is the most commonly used bearing surface worldwide for total hip replacement. It has an outstanding clinical track record, very low wear rates, and is appropriate for most patients.

Best for: Most patients. Cost-effective, reliable, excellent long-term data.

Ceramic on Polyethylene (CoP)

What it is: Ceramic femoral head (alumina or zirconia-toughened alumina composite such as Biolox Delta) articulating against a HXLPE liner.

Advantage over MoP: Ceramic heads are harder and smoother than metal, producing less abrasive wear on the polyethylene liner. They also don't produce metal ions. In patients with metal hypersensitivity, ceramic heads are preferable.

Very small risk of ceramic fracture: Modern third and fourth generation ceramics have extremely low fracture rates (under 1 in 10,000 with current Biolox Delta). If fracture occurs, it requires revision surgery and ceramic debris is difficult to manage — but the risk is genuinely very low with modern materials.

Best for: Younger active patients, patients with documented metal hypersensitivity, patients who want minimal bearing wear debris.

Ceramic on Ceramic (CoC)

What it is: Both femoral head and liner are made of ceramic. The ceramic-on-ceramic bearing has the lowest wear rate of any hip replacement bearing surface — wear is almost negligible.

Advantage: In terms of wear, this is the most durable option. For very young and active patients who may stress the bearing surface for decades, the wear advantage is clinically meaningful.

Issues:

• Squeaking: CoC bearings occasionally produce an audible squeak, estimated at 1–2% of cases. Usually intermittent and doesn't indicate failure, but can be socially uncomfortable and occasionally persistent enough to require revision.
• Fracture risk: Low but higher than metal or HXLPE.
• Cost: Higher than other options.

Best for: Young patients (under 55), very active patients, patients where very long implant longevity without revision is a high priority.

Metal on Metal (MoM) — Largely Abandoned

Metal-on-metal bearings (large metal heads articulating against metal acetabular components) were promoted in the 2000s as ideal for young active patients. Studies subsequently showed that metal ion release caused adverse local tissue reactions (pseudotumours, tissue necrosis) in a significant proportion of patients, requiring revision.

MoM total hip replacement is no longer routinely performed. Hip resurfacing using a smaller metal-on-metal bearing (a different design) continues in specific centres for young patients, but with careful monitoring.

Femoral Stem Materials

Cobalt-chromium (CoCr): Strong, stiff, widely used. Used in both cemented and cementless designs.

Titanium alloy: Lighter, more elastic (closer to bone modulus), excellent biocompatibility and osseointegration. Preferred material for cementless stems. Used in most modern porous-coated stems.

Stainless steel: Used in older designs. Less common in modern hip replacement.

Femoral Head Sizes

The femoral head size matters for dislocation risk and range of motion.

Smaller heads (28mm) were standard for decades. Larger heads (36–40mm or more in hip resurfacing) provide greater jump distance — the femoral head must travel further before dislocating. Large heads significantly reduce dislocation risk.

Modern hip replacement typically uses 36mm or 40mm heads with ceramic-on-HXLPE or CoCr-on-HXLPE. The larger head is one of the reasons dislocation rates have fallen substantially compared to older-generation hip replacements.

What Determines Implant Selection for You?

Your surgeon selects implants based on

• Age: Younger patients favour cementless fixation and ceramic or CoC bearings. Older patients benefit from cemented fixation.
• Bone quality: Osteoporotic bone favours cemented fixation.
• Activity level: More active patients benefit from bearing surfaces with the lowest wear rates.
• Body weight: Heavier patients produce more wear per step.
• Medical history: Metal hypersensitivity guides away from metal-on-metal or metal head options.
• Cause of hip disease: AVN, dysplasia, and fracture may require specific stem lengths or head sizes.
• Surgeon experience: Surgeons tend to use implants they know well and have reliable long-term results with.

It is entirely reasonable to ask your surgeon: "What bearing surface and fixation are you using for me, and why?" A confident, experienced surgeon will explain this clearly.

Hip Replacement at Prakash Hospital, Noida

Dr. Mayank Chauhan at Prakash Hospital, Sector 33, Noida, selects hip replacement implants based on each patient's specific clinical profile — age, bone quality, activity level, and disease cause. He uses internationally registered implants from established manufacturers with long-term survivorship data.

To book a consultation, call the number listed on the website.