Dislocation, i.e., the displacement of a hip prosthesis (hip replacement), is one of the most feared complications after hip replacement surgery. Modern implant technologies, such as short-stem prostheses, have significantly contributed to reducing the risk of dislocation. This article highlights the reasons for the reduced risk of dislocation with short-stem prostheses and explains why they have established themselves as an optimal solution for patients in many cases.

Why dislocations can occur with hip prostheses (hip replacement)

Dislocation of a hip prosthesis can have various causes:

1. Suboptimal reconstruction of the hip anatomy: If the original anatomy of the hip is not precisely restored, the risk of instability increases.
2. Soft tissue tension: Incorrect tension in the surrounding muscles and ligaments can promote dislocation.
3. Movement patterns: Risk movements such as strong flexions or rotations can displace the prosthesis from its position.

The type of prosthesis and the surgical technique play a central role in minimizing these risks.

The advantage of short-stem prosthesis in reconstructing the anatomy

The short-stem prosthesis differs significantly from longer, traditional straight-stem prostheses. Its design allows for a true-to-life reconstruction of the individual hip anatomy, particularly through consideration of the so-called anterior tilt.

(see also: "Short-stem prosthesis: advantages, challenges, and success factors")

What is the anterior tilt?

The anterior tilt describes the natural, forward-facing inclination of the femoral neck in the region of the hip joint. This inclination ensures biomechanically optimal load distribution and stability in the joint.

With a long stem anchored in the diaphysis of the femur, the possibility of precisely reconstructing this anatomical angle is limited. The diaphysis, i.e. the central tubular portion of the femur, forces an alignment along its natural axis, which often does not correspond to the individual inclination of the femoral neck.

Why short stem prostheses support the anterior tilt

The short-stem prosthesis is primarily anchored in the upper part of the femur, the so-called metaphysis. This starting point allows for a more precise adaptation to the natural inclination of the femoral neck. A short stem does not threaten to break through the bone wall, the so-called cortex, due to its shorter stem length despite this inclination. This results in:

1. A biomechanically optimal reconstruction of the anatomy is ensured.
2. A higher stability of the hip joint is made possible because the natural axis of movement is maintained.
3. Minimizes the risk of dislocation, as the femoral head is in the correct position relative to the acetabulum.

Straight stem vs. short stem: Why the difference is crucial

Longer, straight stems require anchoring in the diaphysis. This has several disadvantages:

1. Biomechanical conflict: The rigid alignment of the shaft often contradicts the natural oblique position of the femoral neck.
2. Increased risk of dislocation: Non-anatomical alignment results in instability in the joint.
3. More soft tissue damage: When implanting a long shaft, more bone substance and soft tissue often need to be removed, which complicates healing.

In contrast, short-stem prostheses preserve the individual geometry and ensure a functional reconstruction of the hip.

Short-stem prostheses: less invasive, more safety

The shorter length of the short-stem prosthesis enables not only a better anatomical adaptation but also a less invasive surgical technique. This results in:

• The surrounding tissue and muscles are spared, which accelerates postoperative mobility.
• The bone structure is preserved: This facilitates later revisions, if necessary.

(see also: "Only 90-degree flexion after hip replacement: Is it really necessary?"

Minimizing dislocations in hip prostheses – Conclusion

The short-stem prosthesis has proven to be particularly safe and effective in hip surgery, especially when it comes to reducing the risk of dislocation. Due to its ability to take into account the anterior tilt and precisely reconstruct the hip anatomy, it sets new standards in endoprosthetics. Patients benefit from greater stability, fewer complications, and faster recovery. In specialized centers that use modern surgical techniques such as AMIS or ALMIS, this type of prosthesis can be optimally implanted.

The use of short-stem prostheses brings a significant gain in quality of life for many patients – with maximum safety and new freedom of movement without pain.