Kinematically Aligned TKA Instruments for Natural Joint Restoration
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Solution Overview
Problem
Conventional total knee arthroplasty (TKA) procedures often fail to restore the patient's natural joint alignment and soft tissue laxity, leading to suboptimal patient satisfaction and mobility, as they typically aim for neutral mechanical alignment regardless of the individual's pre-arthritic state.
Innovation Solution
The use of kinematically aligned TKA systems and surgical instruments, including reference blocks and shims, to accurately position the femoral and tibial components based on the patient's pre-arthritic alignment, accounting for cartilage wear on the distal femoral condyles, and employing spacers for precise bone resections to restore the natural joint line and soft tissue envelope.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional total knee arthroplasty aims for neutral mechanical alignment regardless of pre-arthritic state, then surgical procedure is simplified, but patient satisfaction and mobility are suboptimal due to failure to restore natural joint alignment
Solution Approach 1:
The patent applies preliminary action by using reference blocks and shims pre-configured with specific thicknesses to compensate for cartilage wear before the actual bone resection. The reference block is attached to the femur and shims are positioned against the condyles to establish the correct resection depth that accounts for pre-arthritic alignment, thereby restoring natural joint alignment while maintaining surgical efficiency
Solution Approach 2:
The patent uses reference blocks and shims as intermediary tools between the surgeon and the bone resection process. These intermediaries carry pre-calculated compensation values for cartilage wear and automatically transfer the correct resection depth to the bone, eliminating the need for complex intraoperative measurements while restoring natural alignment
2Manufacturing precision
If shims are used to compensate for cartilage wear on distal femoral condyles, then accurate positioning of prosthetic components is achieved, but device complexity increases
Solution Approach 1:
The patent merges the reference block and shims into an integrated assembly where the reference block contains attachment features for the shims. This combination reduces the number of separate components the surgeon must handle while maintaining the precision of cartilage wear compensation. The merged assembly is attached to the femur as a single unit, simplifying the surgical procedure
Solution Approach 2:
The reference block serves multiple functions: it provides a stable attachment base for shims, establishes the correct resection depth, ensures proper alignment during bone cutting, and facilitates accurate positioning of the prosthetic component. This multi-functionality reduces the need for multiple specialized tools while maintaining high positioning accuracy
Data Source
AI summary
Methods and instruments for performing a kinematically-aligned total knee arthroplasty (TKA) are disclosed. Goals of the kinematically-aligned TKA can include restoration of (1) the femoral and tibial joint lines to the patient's natural joint line, (2) the patient's Hip-Knee-Ankle alignment to their constitutional alignment prior to developing osteoarthritis and (3) restoration of the patient's natural soft tissue laxity and envelope. A shim block assembly can be used in resecting the distal medial and lateral condyles to account for cartilage wear on the distal condyles from osteoarthritis. The shim block assembly can include a plurality of shims, and each shim can be attachable to or integral with a reference block. At least one of the plurality of shims can have a medial portion with a thickness different from a thickness of a lateral portion of the shim. The shims need not be joined together as a single medial/lateral component but may be independent of one another. A particular shim can be selected for use based on matching the medial and lateral thicknesses with a determined wear of cartilage on the distal medial and lateral condyles.