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The iTotal CR Knee Replacement System (KRS) is intended for use as a total knee replacement in patients with knee joint pain and disability whose conditions cannot be solely addressed by the use of a prosthetic device that treats only one or two of the three knee compartments, such as a unicondylar, patellofemoral or bicompartmental prosthesis: The Indications for Use include:

• · Painful joint disease due to osteoarthritis, traumatoid arthritis, rheumatoid arthritis or osteonecrosis of the knee
• · Post traumatic loss of joint function.
• · Moderate varus, valgus or flexion deformity in which the ligamentous structurs can be returned to adequate function and stability.
• · Failed osteotomies, hemiarthroplasties, and unicondylar, patellofemoral or bicompartmental implants.
• · Revision procedures provided that anatomic landmarks necessary for alignment and positioning of the implant are identifiable on patient imaging scans.

This implant is intended for cemented use only.

The iTotal® CR Knee Replacement System (hereafter referred to as the "iTotal CR KRS") is a patient specific tricompartmental faceted posterior cruciate ligament (PCL) retaining knee replacement system. The iTotal® CR KRS is a semi-constrained, cemented knee implant which consists of a femoral, tibial, and patellar component.

Using patient imaging and a combination of proprietary and off the shelf software a patient specific implant is designed, that best meets the geometric and anatomic requirements of the specific patient. The femoral component is manufactured from cobalt chromium molybdenum ("CoCrMo") alloy. The tibial component includes a metal tray manufactured from CoCrMo alloy and either one or two polyethylene inserts. The polyethylene inserts may be manufactured from either UHMWPE or a highly cross-linked Vitamin E infused polyethylene (iPoly XE™) The patellar component is also manufactured from either UHMWPE or from a highly cross-linked Vitamin E infused polyethylene (iPoly XE™).

For user convenience, and similar to the predicate iTotal CR KRS, patient specific accessory orthopedic manual surgical instruments designed for use with the modified iTotal CR KRS are provided to assist in the positioning of the total knee replacement components intraoperatively and in guiding the cutting of bone. In addition, reusable orthopedic manual surgical instruments are provided separately.

The function and general design features of the patient specific implants and ancillary instruments remain similar to those described in the predicate 510(k)s K142161 and K152704.

The provided text describes a 510(k) premarket notification for a medical device called the ConforMIS iTotal Cruciate Retaining (CR) Knee Replacement System (KRS). The core of this submission is to demonstrate substantial equivalence to previously cleared predicate devices.

Here's an analysis of the acceptance criteria and the "study" that proves the device meets them, based on the provided document:

1. Table of Acceptance Criteria and Reported Device Performance

It's important to note that this document does not present acceptance criteria in the traditional sense of numerical thresholds for a new device's performance against a gold standard. Instead, the "acceptance criteria" are implied by the demonstration of substantial equivalence to predicate devices, focusing on the functionality and safety of the modifications made.

The primary "performance" being evaluated is the proper functioning of the updated CAD software used in the manufacturing process.

2. Sample Size Used for the Test Set and Data Provenance

• Test Set Sample Size: Not explicitly stated in terms of a number of patient cases or specific outputs. The testing was focused on software verification and validation testing of proprietary software iFit iTotalTib CR, and not on clinical patient data.
• Data Provenance: Not applicable in the context of patient data. The "data" being tested would be internal software outputs and comparisons, rather than external patient cases. The software itself is proprietary to ConforMIS.

3. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of Those Experts

• Number of Experts: Not specified.
• Qualifications of Experts: Not specified. Given that this is software verification and validation, the ground truth would typically be established based on engineering specifications, mathematical models, and perhaps manual expert review of CAD outputs to confirm their correctness against design requirements.

4. Adjudication Method for the Test Set

• Adjudication Method: Not specified. For software verification and validation, adjudication would involve comparing software outputs with expected results (ground truth defined by specifications or manual calculations/reviews).

5. Multi Reader Multi Case (MRMC) Comparative Effectiveness Study

• Was an MRMC study done? No, an MRMC comparative effectiveness study was not done. The submission explicitly states: "Clinical data is not necessary to demonstrate substantial equivalence." This is a software and device modification submission, not a new clinical efficacy claim requiring human-in-the-loop performance evaluation.
• Effect size of human readers improve with AI vs without AI assistance: Not applicable, as no MRMC study was performed and AI assistance for human readers is not the subject of this submission. The "AI" here refers to automated CAD processes, not decision support for human readers.

6. Standalone (Algorithm Only Without Human-in-the-Loop Performance) Study

• Was a standalone study done? Yes, in essence. The "software verification and validation testing of proprietary software iFit iTotalTib CR" constitutes a standalone evaluation of the algorithm's performance in generating the customized implant designs. Although not framed as a "study" in a clinical sense, this testing evaluates the algorithm's functional correctness without human intervention in the design generation phase itself (though humans define parameters and review outputs).

7. Type of Ground Truth Used

• Type of Ground Truth: The ground truth for the software verification and validation would be based on engineering specifications, design requirements, and potentially known correct outputs from previous versions of the software or manual calculations. It's likely a combination of:
  • Specification-based: Does the software produce outputs that meet predefined engineering specifications for implant geometry and fit?
  • Comparison-based: Are the outputs from the new automated CAD processes consistent with those generated by the predicate device's CAD processes or manual processes for similar inputs?

8. Sample Size for the Training Set

• Training Set Sample Size: Not applicable. This document describes a submission for a medical device (knee replacement system) with updated manufacturing software, not an AI/ML model that requires a training set of data in the common sense. The "training" for the software would be its initial development and programming based on engineering principles and design rules, not data-driven machine learning.

9. How the Ground Truth for the Training Set Was Established

• How Ground Truth for Training Set Was Established: Not applicable. As noted above, this is about software verification and validation for a manufacturing process, not an AI/ML model for which a "training set" with established ground truth is required. The software's "knowledge" is encoded during its development from established biomechanical, anatomical, and engineering principles used in knee replacement design.

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