Density-Matched Orthopedic Implants for Stress Shielding
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Solution Overview
Problem
Current orthopedic implants do not account for varying bone mineral density (BMD) at the site of intervention, leading to suboptimal performance and increased failure rates, particularly in osteoporotic bones, as they do not match the mechanical properties of the surrounding bone, resulting in stress shielding and implant failure.
Innovation Solution
A kit of orthopedic implants with varying densities, manufactured from materials like metal, plastic, or titanium, designed to match the patient's bone density through DEXA scan T-scores, ensuring the implant's modulus of elasticity closely approximates that of the native bone, thereby reducing the risk of implant failure and improving surgical outcomes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard orthopedic implant is used regardless of bone density, then the implantation process is simple and quick, but the implant fails to match the mechanical properties of surrounding bone, leading to stress shielding and implant failure
Solution Approach 1:
The patent applies parameter changes by varying the density of the implant material to match the bone mineral density (BMD) of the patient's surrounding bone. Implants are manufactured with different density parameters based on preoperative DEXA scan results, allowing the implant's mechanical properties to align with the patient's bone characteristics, thereby reducing stress shielding and improving long-term success rates
Solution Approach 2:
The patent implements preliminary action by performing DEXA scans and determining BMD values before implantation. This preoperative assessment allows the surgical team to select the appropriate implant density in advance, matching the implant properties to the patient's bone characteristics before the actual implantation procedure begins
2Strength
If an implant with higher density is used to strengthen fixation, then pullout strength improves, but the implant creates stress shielding in osteoporotic bone, leading to bone resorption and eventual implant failure
Solution Approach 1:
The patent applies local quality by matching the implant's density locally to the surrounding bone's density characteristics. Rather than using a uniformly high-density implant for all patients, the implant density is tailored to match each patient's specific bone quality, providing adequate fixation strength without creating excessive stiffness that would cause stress shielding in osteoporotic bone
Solution Approach 2:
The patent changes the density parameter of the implant material to match the patient's bone mineral density. By adjusting this physical parameter based on preoperative DEXA scan results, the implant provides appropriate mechanical support without creating the stiffness mismatch that leads to stress shielding and bone resorption
3Manufacturing precision
If bone density scanning is performed preoperatively, then implant matching accuracy improves, but the treatment process time and complexity increase
Solution Approach 1:
The patent replaces complex mechanical matching processes with a simplified density-based selection system. By using DEXA scan T-scores to directly guide implant density selection, the system eliminates the need for complex intraoperative adjustments or trial fittings, streamlining the process despite the added preoperative scanning step
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides customized implants that better match the mechanical properties of the surrounding bone, reducing the incidence of implant failure, improving fusion stability, and extending the lifespan of orthopedic implants by selecting the appropriate density based on preoperative DEXA scan results.
Implementation Method 1
A DEXA scan is a means of measuring bone density by directing two x-ray beams with different energy levels at the patient's bone at the diseased or injured site or the site of diagnosis for age-related routine scans to determine BMD. When soft tissue absorption is subtracted out, the BMD can be determined from the absorption of each beam by the bone.
Data Source
AI summary
A method of treating a patient who requires surgical implantation of an orthopedic implant is described. The method includes the steps of: determining the DEXA scan T-score of the patient's native bone at a site of surgical implantation where the implant will be in contact with the patient's native bone; retrieve from among three or more implants of the same type an implant that has a density that is closest to the density of the patient's native bone at the site of surgical implantation based on the DEXA scan T-score of the patient's native bone; and implanting the retrieved implant in the patient to the exclusion of the other two or more implants.