Multi-Axial Knee Laxity Measurement for Reliable 3-Plane Testing
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Solution Overview
Problem
Existing joint laxity measurement devices are expensive, time-consuming, require substantial training, and lack reliability and agreement among testers, with no device available for comprehensive assessment of frontal plane knee laxity, which is a strong predictor of ACL injury risk.
Innovation Solution
A multi-axial joint laxity testing apparatus comprising a thigh cradle, shank cradle, and heel cradle assembly, capable of measuring knee laxity in three planes of motion (anterior-posterior, varus-valgus, and internal-external rotations) with automated sensors and motors to ensure accurate and reproducible measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If prior joint laxity measurement devices are used, then measurement capability is provided, but the devices are expensive, time-consuming, require substantial training, and lack reliability
Solution Approach 1:
The device segments the knee joint assessment into three independent measurement planes (anterior-posterior, varus-valgus, internal-external rotation), each with dedicated fixtures and sensors. This segmentation allows each subsystem to be optimized for its specific function while maintaining overall system reliability without excessive complexity.
Solution Approach 2:
The apparatus integrates multiple measurement functions into a single unified device that can assess all three planes of knee joint motion. The common base structure and standardized measurement protocol enable the device to perform diverse laxity assessments reliably without requiring multiple separate instruments.
2Measurement precision
If comprehensive multi-axial measurement capability is added, then diagnostic accuracy improves, but device complexity and cost increase
Solution Approach 1:
The device transitions from traditional single-plane measurement to three-dimensional multi-axial assessment by adding varus-valgus and internal-external rotation measurement capabilities to the standard anterior-posterior assessment. Each dimension has its own dedicated fixture and sensor arrangement, enabling comprehensive spatial characterization of knee laxity.
3Reliability
If automated sensors and motors are implemented, then measurement consistency improves, but device complexity increases
Solution Approach 1:
The apparatus incorporates sensors that provide real-time feedback on joint position and applied force, enabling automated control systems to maintain precise measurement conditions. This feedback mechanism ensures consistent measurement protocols across different users and sessions, improving reliability through automated monitoring and adjustment.
4Ease of operation
If the device is designed for mass screening, then accessibility improves, but measurement comprehensiveness may be reduced
Solution Approach 1:
The device incorporates preliminary positioning fixtures and alignment guides that automatically prepare the knee joint for measurement before the actual laxity assessment. This preliminary action ensures proper setup and alignment even for users with minimal training, making the device accessible for mass screening while maintaining measurement precision through standardized initial positioning.
Data Source
AI summary
Knee joint laxity testing apparatus includes a thigh cradle assembly, a shank cradle assembly, and a heel cradle assembly. The apparatus is configured to measure knee laxity in three planes of motion: anterior-posterior translations; varus-valgus rotations; and internal-external rotations. The thigh cradle assembly, shank cradle assembly, and heel cradle assembly are mounted on a common base. A thigh fixation system is attached to the thigh cradle assembly both at the proximal and distal ends to firmly stabilize the thigh in the thigh cradle. The patella pad and distal thigh fixation system are mounted on a U-bar assembly. The distal thigh fixation system includes two condyle pad adjustment arms upon which a respective condyle pad is mounted, and a patella pad mounted to a linear track on an underside of the U-bar assembly.