Knee Arthroplasty Planning Using JLO and HKA Alignment

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Solution Overview

Problem

Traditional alignment techniques in total knee arthroplasty (TKA) fail to account for individual anatomical differences, leading to suboptimal knee function and patient satisfaction due to variations in bone morphology, joint alignment, and soft tissue properties.

Innovation Solution

A method utilizing a joint line obliquity (JLO) classification system for patient-specific surgical planning, which involves determining anatomical parameters like JLO and hip-knee-ankle (HKA) angles, comparing them to reference values, and adjusting these parameters to generate a surgical plan for optimal alignment, including bone resections and soft tissue releases, using statistical methods and intraoperative assessments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If traditional mechanical alignment techniques are used, then the surgical procedure is simple and standardized, but the individual anatomical differences are not accounted for, leading to suboptimal knee function

Engineering Contradiction:
Improveadaptability to individual anatomical differencesVSAvoidcomplexity of surgical planning system
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The system performs preliminary classification of patient knee phenotypes based on joint line obliquity and HKA angle measurements before surgery. This pre-operative classification enables tailoring of surgical plans to individual anatomical characteristics, improving adaptability while maintaining procedural simplicity during the actual surgery.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The system uses specific anatomical parameters (joint line obliquity and HKA angle) to classify patients into different phenotypes. By changing from generic alignment targets to parameter-based classification, the system adapts to individual anatomy while providing clear, measurable guidance for surgical planning.

Inventive Principle:
Principle #35Parameter changes

2Reliability

If kinematic alignment techniques are used to restore pre-disease alignment, then patient-specific biomechanics are improved, but the complexity of determining proper surgical corrections increases

Engineering Contradiction:
Improveaccuracy of restoring natural knee biomechanicsVSAvoidcomplexity of determining surgical corrections
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The system segments the complex problem of kinematic alignment into distinct phenotypes based on joint line obliquity and HKA angle. By dividing patients into categories (e.g., neutral, varus, valgus phenotypes), the system simplifies the determination of surgical corrections while maintaining accuracy in restoring natural biomechanics for each group.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The system provides feedback by comparing measured anatomical parameters against reference values and phenotype classifications. This feedback mechanism guides surgeons in determining appropriate surgical corrections, reducing the complexity of decision-making while ensuring accurate restoration of knee biomechanics.

Inventive Principle:
Principle #23Feedback

3Ease of operation

If generic alignment targets are used, then the surgical planning is straightforward, but the soft tissue balance and implant positioning are suboptimal

Engineering Contradiction:
Improveease of surgical planningVSAvoidprecision of implant positioning and bone resections
Core Design Contradiction:
Ease of operationVSManufacturing precision

Solution Approach 1:

The system applies local quality by providing different alignment targets and surgical recommendations tailored to each patient's specific phenotype. Instead of a single generic target, the system offers localized guidance based on individual joint line obliquity and HKA angle measurements, improving implant positioning precision while maintaining ease of operation through standardized phenotype-based protocols.

Inventive Principle:
Principle #3Local quality

Data Source

PatentEP4702946A1Knee planning
Publication Date: 2026.03.04 MAKO SURGICAL CORP
  • EP4702946A1 patent drawingFigure 1
  • EP4702946A1 patent drawingFigure 2
  • EP4702946A1 patent drawingFigure 3

AI summary

Disclosed herein is a method for surgical planning of a knee joint. The method can include determining a joint line obliquity of a knee j oint and a hip-knee-ankle angle of the knee joint. The method can include comparing the joint line obliquity and the hip-knee-ankle angle to a predetermined value, and generating a surgical plan including recommended adjustments of the joint line obliquity and hip-knee-ankle angle of the knee joint if the joint line obliquity and the hip-knee-ankle angle are different from the predetermined value. The joint line obliquity can be any of an extension line joint line obliquity and flexion joint line obliquity.