Leg Length Discrepancy After Hip Replacement

Leg length discrepancy after hip replacement can occur due to the size of the implants used and the measures your surgeon needs to take to ensure they are securely in place. When one leg ends up longer than the other, it's most often the leg on the side that the hip was operated on.

This article discusses why hip replacement surgery sometimes causes a leg length discrepancy, the issues this can cause, and how it can either be prevented or corrected.

What Causes Leg Length Discrepancy?

When you undergo a hip replacement, it's important that the new ball and socket are stable, so they will not come out of position.

If the hip is felt to be too loose, making it unstable and prone to hip dislocation, your surgeon may elect to adjust the tension between the ball and socket by placing larger or longer implants in the joint.

The downside of placing these larger implants is the lengthening of the limb. Ideally, your surgeon wants the leg lengths to end up being symmetric, but that is not always the final result.

The size of the implants and exactly how they are placed will determine the length of the leg after surgery.

Preventing Leg Length Discrepancy

To prevent a postoperative leg length discrepancy, your surgeon will create templates using X-rays of your hip and overlays of the hip replacement prosthesis.

This can help your surgeon determine two things:

• The expected size of the implant needed at the time of surgery
• How much bone to remove during the procedure

There are some surgical techniques that may lower the chance of developing a significant leg length discrepancy. With some approaches, such as anterior hip replacement, surgeons may feel more comfortable restoring leg length without having to worry about dislocation risk.

In addition, some surgeons are now using computer-guided systems to help confirm the position and size of the hip replacement implants. Computer-guided surgery is the operating room equivalent to driving with the help of a GPS system. It shows your anatomy on a screen to help guide the positioning of the implants.

Consequences of a Leg Length Discrepancy

When leg lengths are unequal, patients may experience increased pain and muscle fatigue. When the leg length is increased by more than a few centimeters, the nerves of the leg may become stretched to the point that patients experience numbness or pain further down the limb.

Interestingly, many people with severe degenerative arthritis of their hip joint develop a leg length discrepancy over time. It is not uncommon for these people to have a leg length discrepancy prior to undergoing hip replacement as a result of cartilage and bone wearing away from the hip joint.

Your surgeon may correct this when a total hip replacement is performed. After surgery, you may still have the sensation of having legs of different lengths, though that's no longer the case. Most people gradually adapt to having symmetrical legs again, and the sensation usually goes away.

Correcting Leg Length Discrepancy

Your surgeon can help you understand why your leg lengths are different. In some cases, a leg length difference may have been anticipated, and in others, unexpected.

A small leg length discrepancy after hip replacement is usually corrected with a lift in the shoe of the shorter leg. If the discrepancy is more than about 2 centimeters, then a build-up of the sole of the shoe may be necessary.

In larger leg length discrepancies, surgery may be considered to re-size the implants or remove additional bone, but that is usually only undertaken in individuals severely affected by the difference in leg length.

It is important to note that differences in leg length have not been shown to affect how long the hip replacement will last.

Summary

After hip replacement surgery, some people will notice that the opposite leg seems shorter than the one that was operated on. This can happen when the surgeon needs to create stability in the new ball and socket, so it won't dislocate.

A leg length discrepancy can cause pain and muscle fatigue. It can often be corrected simply by wearing a lift in the shoe of the shorter leg. In more severe cases, surgery may be required to resize the implants and correct the discrepancy.