Hip replacement surgery is a proven method for relieving pain and regaining mobility. Nevertheless, complications occasionally arise that complicate recovery. One frequently discussed consequence is leg length discrepancy. This blog explores the causes of such discrepancies and provides an overview of preventative measures and treatment options. It also explains the unstable hip prosthesis – a contrasting problem – and its connection to leg length discrepancy in more detail.

What is a leg length discrepancy after a hip replacement?

Leg length discrepancies occur when one leg appears visually or functionally longer or shorter than the other due to hip replacement surgery. Even a difference of just a few millimeters can be noticeable and cause discomfort. These discrepancies arise from biomechanical factors, surgical decisions, or faulty implantation.

Causes of leg length discrepancies

1. Surgical reasons:

A leg length discrepancy can arise from the intention to stabilize an unstable hip joint. In such cases, doctors often choose a longer prosthesis to increase the tension in the soft tissues. This improves stability but can inevitably lead to a leg length discrepancy.

2. Errors in preoperative planning:

Inaccurate or inadequate X-ray images can lead to incorrect hip axis correction. However, digital preoperative planning methods have significantly improved this aspect.

3. Soft tissue tension:

After surgery, the natural soft tissues, muscles, and tendons must be correctly positioned. A joint that is too tight or too loose impairs the body's stability and can create a feeling of unevenness.

4. Bony causes:

Pre-existing differences in bone alignment – ​​such as those caused by osteoarthritis or deformities – increase the risk of a difference.

Instability and leg length discrepancy: Opposing challenges

An unstable prosthesis and a leg length discrepancy are two extremes that compete with each other.

Instability:

Instability can occur if the hip prosthesis is too loose. This increases the risk of dislocations (hip slippage) and creates instability when walking. To avoid this, surgeons often choose a compromise by lengthening the prosthesis slightly.

Leg length difference:

Excessive lengthening, on the other hand, leads to a discrepancy. Maintaining a balance between stable positioning and equal leg length presents the greatest surgical challenge.

Prevention of leg length discrepancies: Preoperative digital planning

Scaled X-ray:

Digital preoperative planning uses scaled X-rays to analyze hip anatomy with millimeter precision. This allows surgeons to determine exact stem positions and the required implant size.

3D models:

In addition, 3D models allow for a virtual simulation of the implantation. They help to identify potential differences in advance and to compensate for them in a targeted manner.

Simulation:

Simulations are now standard practice in modern clinics. These simulations analyze the expected hip mechanics during movement. This allows for better prevention of unwanted anatomical changes.

Treatment approaches for leg length discrepancy after hip replacement

1. Physiotherapy and gait analysis:

Minor differences can be corrected through targeted physiotherapy. Gait analysis identifies imbalances that can then be individually adjusted.

2. Shoe modifications:

Orthopedic insoles or shoe modifications compensate for differences and provide stability in everyday life.

3. Secondary operations:

Significant discrepancies can be surgically corrected. Replacing or adjusting the prosthesis often achieves the desired alignment.

4. Muscle building:

By specifically building up the muscles, the tension around the prosthesis can be optimized and thus differences can be compensated for.

Effects of leg length discrepancy on everyday life

Those affected often report symptoms such as back and leg pain or unsteadiness when walking. Uneven weight distribution can also cause long-term damage to the joints and spine. This highlights the importance of timely diagnosis and treatment.

Conclusion: Why careful planning is crucial

Leg length discrepancies after hip replacement surgery can often be avoided through modern surgical techniques, digital planning, and experienced surgeons. Should a discrepancy nevertheless occur, effective treatment options are available. Specialized centers, in particular, offer the best conditions for achieving optimal results. An artificial hip joint not only improves quality of life but also restores mobility – provided the implantation is carefully planned and performed.