Understanding hip replacement
There is more than one way to replace a hip.
You may hear about anterior approaches, head sizes, dual mobility, fixation, and robotics. You do not need to choose every technical detail yourself. You need a surgeon who can explain why each choice fits your body and goals. Here is what the published evidence actually says.
Three common paths to the hip
The approach changes which soft tissues are moved or opened.
All three approaches can be used to perform an excellent total hip replacement. The skin incision is only the surface difference. What matters is the deeper path, the tissues that must heal, and how experienced the surgeon and care team are with that approach.
From the front—between muscle groups
What is opened: The surgeon works through an interval between the tensor fasciae latae and sartorius, then between deeper muscle groups. Muscles are retracted rather than deliberately detached, although the joint capsule is opened.
- May provide slightly faster walking and functional recovery early after surgery.
- Preserves the major hip abductor muscles and posterior soft tissues.
- Supine positioning can make X-ray checks and leg comparison convenient.
- Numbness or burning from the lateral femoral cutaneous nerve can occur.
- Femoral exposure can be demanding, especially during the surgeon’s learning curve.
- Wound problems or femur fracture may be more relevant in selected patients.
From the back—behind the hip
What is opened: The gluteus maximus fibers are separated. The short external rotator tendons and posterior capsule are usually opened to reach the joint, then repaired at closure. The main hip abductor mechanism is preserved.
- Excellent view of the femur and socket through a familiar, extensile approach.
- Preserves the gluteus medius abductor mechanism.
- Can be adapted for complex anatomy and many revision operations.
- Historically associated with more dislocation than anterior or lateral paths.
- The posterior tendons and capsule need to heal after repair.
- Precautions and restrictions vary with the repair, implants, and surgeon.
From the side—through or beside the abductors
What is opened: “Lateral” includes more than one technique. A direct lateral approach splits and repairs part of the gluteus medius and minimus. Anterolateral variants use a more forward interval and may disturb less of the abductor mechanism.
- Good exposure of both the socket and femur.
- Large pooled studies have found a lower dislocation risk than posterior approaches.
- May be useful when stability is a particular concern.
- Direct lateral techniques can cause temporary abductor weakness or a limp.
- Outer-hip pain can occur while the abductor repair heals.
- “Lateral” and “anterolateral” are not identical operations—ask which is planned.
What surveyed U.S. hip surgeons reported
Anterior has become the most commonly reported primary approach.
At the 2022 AAHKS Annual Meeting, participating hip and knee replacement surgeons reported which approach they used for primary total hip replacement.
These figures describe responses from AAHKS meeting participants—not every U.S. surgeon and not the percentage of all U.S. hip operations. They measure reported practice preference, not which approach produces the best outcome.
What the literature says
No approach is best for every patient.
A 2023 network meta-analysis of 63 randomized trials and 4,859 patients found broadly similar safety among approaches and did not establish one universally superior path. Direct anterior surgery may offer modest early recovery advantages in some comparisons, while complication profiles differ by approach and study. A large complications review found lower pooled dislocation risk with anterior and lateral approaches than posterior, but rated the evidence low or very low and could not confidently name a superior approach. Surgeon experience and patient anatomy should drive the choice.
“Which exact approach will you use, how many hip replacements do you perform through it each year, what are your approach-specific complications, and why does this path fit my anatomy and risk?”
How the implant resists dislocation
A larger effective ball is harder to lever out—but size is not the whole operation.
A hip dislocates when the ball escapes the socket. A larger head generally travels farther before it can come out—called greater jump distance—and allows more motion before the neck contacts the liner. Stability also depends on component position, soft-tissue tension, surgical approach, anatomy, neuromuscular control, and how the spine and pelvis move.
Conventional fixed bearing
Head size usually rises with socket size.
The metal or ceramic head moves directly against a polyethylene liner. A larger head can improve stability, but the socket must still leave enough polyethylene around it. The largest head that physically fits is not automatically the best choice.
- More jump distance before the ball can escape the socket.
- More range of motion before implant-to-implant impingement.
- A randomized trial found first-year primary dislocation of 0.8% with 36 mm versus 4.4% with 28 mm.
- A larger head may require a thinner liner when the socket is small.
- Larger heads increase forces at the modular head-neck taper; corrosion risk is multifactorial.
- AJRR data found less revision for dislocation with 36 versus 32 mm, but no additional reduction at 40 mm or larger.
Dual mobility
Two moving surfaces create a much larger effective head.
A small metal or ceramic head is captured inside a larger polyethylene bearing. The small head can move inside the polyethylene, and the polyethylene can move inside the metal socket. That outer diameter acts like a very large head, increasing jump distance and motion before impingement.
Dual mobility has been used extensively in revision hip replacement—especially for recurrent instability—and is increasingly used for selected high-risk primary hips. Examples include prior spine fusion or abnormal spine-pelvis motion, neuromuscular or cognitive disorders, fracture, deficient hip muscles, or another reason the surgeon believes instability risk is elevated.
Many routine primary hip replacements are stable with a conventional 32- or 36-mm fixed bearing. Dual mobility should address a specific instability risk rather than function as an upgrade package or marketing feature.
- Very large effective head and increased jump distance.
- Lower dislocation risk in many comparative primary and revision studies.
- Particularly useful when revising an unstable hip or treating a patient at elevated instability risk.
- Provides added stability without locking the head into a constrained liner.
- Intraprosthetic dislocation: the small head can separate from the polyethylene bearing—a complication unique to dual mobility.
- If the hip dislocates, attempted closed reduction can cause or miss that separation and may require surgery.
- There is an additional polyethylene articulation, so long-term wear and durability remain important.
- Some modular designs add a metal liner-shell junction that can release metal ions or corrode.
- More components, cost, and design-specific considerations than a conventional bearing.
What the evidence can—and cannot—say
Dual mobility lowers instability in many studies, but patient selection matters.
A revision meta-analysis reported 2.2% dislocation and 0.3% intraprosthetic dislocation with modern dual-mobility cups, with lower odds of dislocation than fixed bearings. More recent reviews also favor dual mobility for instability, but long-term comparative evidence and randomized primary-hip evidence remain less mature. These results do not mean every patient needs dual mobility.
“What head size will fit my socket, what is my personal dislocation risk, would dual mobility meaningfully reduce that risk, and which added risks come with the exact dual-mobility design you use?”
Other choices your surgeon will explain
Fixation
A stem or socket may be press-fit, cemented, or combined.
Bone quality, age, anatomy, and surgeon judgment shape this choice. Ask why the fixation is appropriate for your bone—not merely which is newest.
Technology
Navigation or robotic assistance can help execute a plan.
Technology is a tool in the surgeon’s hands. Ask what it changes in your case and whether it improves an outcome you care about.
Surgery location
Hip replacement is performed both in ambulatory surgery centers and in hospitals. Compare the two settings — including safety findings, candidacy, and Medicare cost differences.
Keep reading
Wondering whether joint replacement fits your situation? Take the free TJV Fit Score — a cited, methodology-first assessment.