Patient-Specific Hip Cup Alignment via Pelvic Tilt Simulation
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Solution Overview
Problem
Current hip surgery methods face challenges in accurately positioning the acetabular cup due to uncertainties in pelvic tilt and stem version, leading to potential impingement and excessive wear, which can result in dislocation and the need for revision surgery.
Innovation Solution
A surgical technique that uses digital x-ray imaging and motion data to determine the pelvic tilt and calculate a safe range of acetabular cup inclination and anteversion angles, avoiding impingement by virtually implanting the hip stem and cup and simulating daily activities to identify a 'safe zone' for optimal alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the acetabular cup is positioned using conventional alignment guides that reference the surgical table, then the cup can be implanted at standard angles (45° inclination, 20° anteversion), but the actual cup position in relation to the patient's pelvis may be incorrect due to unknown pelvic tilt, leading to impingement and dislocation
Solution Approach 1:
The surgeon performs preliminary actions by obtaining standing radiographs before surgery to measure the patient's natural pelvic tilt and femoral neck version. These measurements are used to pre-calculate the optimal cup inclination and anteversion angles that will avoid impingement during the patient's specific range of motion activities. This preliminary measurement and calculation phase allows the surgeon to account for individual anatomical variations before the actual implantation occurs.
Solution Approach 2:
The system incorporates feedback by using the measured pelvic tilt and femoral neck version to adjust the target cup positioning angles. The calculated safe zone provides feedback on the boundaries for acceptable cup positioning, allowing the surgeon to adjust the implantation angles accordingly. Post-implantation, the actual cup position can be verified against the predetermined safe zone to ensure it falls within the acceptable range.
2Ease of operation
If the surgeon relies on experience to position the cup, then the procedure can be performed without complex pre-operative measurements, but the cup may not be implanted in the intended orientation, especially for less experienced surgeons
Solution Approach 1:
The method performs preliminary measurements and calculations before surgery to establish patient-specific safe zone boundaries. By pre-determining the optimal cup positioning angles based on the patient's anatomy and activity requirements, the surgeon has clear numerical guidance to follow during implantation, reducing reliance on subjective experience and ensuring consistent, reliable results.
Solution Approach 2:
The system changes the approach from using fixed standard angles (45°/20°) to using calculated patient-specific angles based on pelvic tilt and femoral neck version measurements. This parameter transformation allows the safe zone to be adapted to each patient's unique anatomy, improving reliability while maintaining procedural simplicity through clear numerical targets.
3Reliability
If the cup is positioned to avoid impingement by using patient-specific measurements and simulations, then the risk of dislocation and wear is reduced, but the surgical planning and implantation process becomes more complex
Solution Approach 1:
The complexity is moved to the pre-operative planning phase where digital simulations and safe zone calculations are performed. Once the safe zone boundaries are established, the actual surgical implantation becomes straightforward by positioning the cup within these predetermined boundaries. This separates the complex planning work from the surgical execution, maintaining operational simplicity while achieving reliable impingement-free positioning.
Solution Approach 2:
The method creates a digital copy or virtual model of the patient's hip anatomy and implant configuration to perform simulations and determine the safe zone. This virtual modeling allows complex impingement analysis to be performed without physical complexity during surgery. The virtual safe zone boundaries are then used as practical guides during the actual implantation procedure.
4Ease of manufacture
If conventional alignment guides reference the surgical table assuming the pelvis is parallel to the table, then the cup can be implanted at standard angles, but the resultant inclination and anteversion in relation to the alignment guide often differ from expected
Solution Approach 1:
The method performs preliminary measurement of the patient's actual pelvic tilt angle from standing radiographs before surgery. This preliminary data allows the surgeon to calculate adjusted target angles that compensate for the pelvic tilt, ensuring that the cup is positioned at the correct orientation relative to the patient's anatomy rather than relying on assumptions about table-pelvis alignment.
Solution Approach 2:
The system transforms the fixed standard angles (45° inclination, 20° anteversion) into patient-specific adjusted angles by incorporating the measured pelvic tilt and femoral neck version. This parameter adjustment ensures that the cup positioning accounts for individual anatomical variations, improving angular precision while maintaining the simplicity of using numerical targets during implantation.
Data Source
AI summary
A method for avoiding impingement between an implanted prosthetic hip stem and acetabular cup uses at least one digital x-ray of a standing patient preferably including a lateral x-ray to determine a pelvic tilt angle of the patient. A hip stem is virtually implanted at an initial stem version angle into a virtual femur constructed from the digital x-ray. Data of at least one hip joint motion is obtained from at least one individual. A range of inclination and anteversion angles is calculated for a virtually implanted acetabular cup that avoids impingement with the virtually implanted hip stem. The calculated range of inclination or anteversion angles is based at least in part on the pelvic tilt angle of the patient, the initial hip stem version angle and the obtained joint motion data.