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[Impingement Free Motion in Total Hip Arthroplasty - How Can We Implement It?]
1Universität Basel, Orthopädie und Traumatologie, Kantonsspital Schaffhausen, Schweiz.
Zeitschrift Fur Orthopadie Und Unfallchirurgie
|June 24, 2016
Summary
This study introduces the combined safe zone (cSafe-Zone) for total hip arthroplasty, optimizing component positioning to reduce dislocation risk. The cSafe-Zone provides dynamic guidelines for maximizing range of motion and improving surgical outcomes.
Area of Science:
- Orthopedic surgery
- Biomechanical engineering
- Medical device design
Background:
- Prosthetic impingement and insufficient soft tissue tension are key factors in early total hip arthroplasty dislocation.
- Optimal positioning and design of hip implants are crucial for reducing impingement.
- Restoring individual hip biomechanics is essential for implant success.
Purpose of the Study:
- To introduce the combined safe zone (cSafe-Zone) concept for optimal total hip prosthesis component positioning.
- To provide guidelines for positioning the femoral stem and acetabular cup to minimize impingement.
- To enhance the range of motion and reduce dislocation risk in total hip arthroplasty.
Main Methods:
- Utilized a CAD model of a total hip prosthesis to analyze design and positioning parameters.
- Investigated the impact of head-to-neck ratio, CCD angle, cup inclination/anteversion, and stem antetorsion on range of motion.
- Defined the combined safe zone by identifying positioning combinations that allow the intended range of movement (iROM).
Main Results:
- The combined safe zone is dynamic, varying with prosthesis system and specific parameters.
- Optimal positioning involves complementary cup anteversion and stem antetorsion; high antetorsion requires lower anteversion.
- Specific cup inclination ranges are recommended based on femoral head size (e.g., 40-45° for 28mm heads).
- Anatomical stems necessitate less cup anteversion compared to straight stems.
- CCD shaft angles >135° are not recommended as they reduce the cSafe-Zone size.
Conclusions:
- The combined safe zone concept offers clear guidelines for positioning total hip prosthesis components.
- This approach maximizes range of motion and minimizes the risk of prosthetic impingement.
- The cSafe-Zone is foundational to the stem-first surgical technique and can be implemented using computer-based navigation or mechanical instruments.
