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The iNSitu Total Hip System is indicated for use in skeletally mature individuals undergoing surgery for total hip replacement due to:

· A severely painful and or disabled joint from osteoarthritis, theumator arthritis, avascular necrosis, or congenital hip dysplasia;

· Acute traumatic fracture of the femoral head or neck;

· Failed previous hip surgery including joint reconstruction, arthrodesis, hemiarthroplasty, surface replacement arthroplasty or total hip replacement

The iNSitu Total Hip System femoral stem is intended for cementless fixation. The iNSitu Total Hip System acetabular cup is intended for cementless fixation. The porous structured surfaces provide biological fixation in a cementless application.

The NextStep Arthropedix Total Hip Replacement System includes a family of femoral stems, femoral head components, acetabular UHMWPE liners, acetabular cups (including solid, 3-holed, and the subject multiholed), acetabular hole covers, optional acetabular screws, instruments, and sterilization cases (K161184/K172501). The implants are packaged in single use, sterile packages with a 5-year shelf life and the re-usable instruments are contained in sterilization cases for steam sterilization.

Here's an analysis of the provided text regarding the acceptance criteria and supporting study for the iNSitu Total Hip System:

The provided text is a 510(k) summary for a medical device (iNSitu Total Hip System) that is seeking clearance as substantially equivalent to existing devices. In this context, "acceptance criteria" and "study" are interpreted in terms of demonstrating substantial equivalence, rather than directly measuring performance against predefined clinical metrics like sensitivity or specificity for a diagnostic algorithm.

Specifically, this submission is to add a multi-holed acetabular cup to an already cleared total hip system. Therefore, the "acceptance criteria" revolve around showing that the new component does not raise new questions of safety or effectiveness and performs comparably to the previously cleared predicate device.

Acceptance Criteria and Reported Device Performance

| Acceptance Criteria Category | Specific Criteria (Implied) | Reported Device Performance |
| Intended Use Equivalence | The new multi-holed acetabular cup must have the same indications for use as the predicate device. | "The iNSitu Total Hip System multi-holed acetabular cup has the indications for use as the iNSitu Total Hip System acetabular cup predicate device." This explicitly states that the intended use is the same. |
| Technological Characteristics Equivalence | The materials, manufacturing processes, and design features of the new multi-holed component must be comparable to the predicate, with consideration given to the impact of the added holes. Changes should not introduce new safety concerns. | "The multi-holed acetabular cups are manufactured from the same materials and processes as the family of acetabular cups in the original iNSitu Total Hip System (K161184/K172501). All iNSitu Total Hip System components...are cleaned, packaged and sterilized using the same processes as previously described..." "The subject multi-holed acetabular cup is equivalent to the original acetabular cup based on comparisons of intended use, design features, and technological characteristics." |
| Performance (Mechanical) Equivalence | The mechanical performance of the multi-holed acetabular cup, particularly regarding fatigue strength, must be demonstrated to be equivalent or superior to the predicate, especially considering the new holes for fixation. | "2-point fatigue testing was performed on the multi-holed acetabular cup to show substantial equivalence to the predicate device." (It explicitly states the test was performed to show substantial equivalence). |
| Sterilization Equivalence | The sterilization process must effectively sterilize the new component, and the introduction of the multi-holed design should not create a new worst-case scenario that invalidates the existing sterilization validation for the system. | "Risk based EO sterilization was performed to document that the newly introduced iNSitu Multi-Holed Acetabular Cup did not present a new worst-case scenario, and therefore included into the documentation for the existing sterilization process for the predicate device (K161184/K172501)." |
| Overall Substantial Equivalence (Conclusion) | The cumulative evidence from intended use, technological characteristics, and performance testing must demonstrate that the device is substantially equivalent to legally marketed predicate devices and does not raise new questions of safety or effectiveness. | "A comparison of technological characteristics and performance testing demonstrates that the NextStep Arthropedix iNSitu Total Hip System multi-holed acetabular cup is substantially equivalent to the predicate system (K161184/K172501)." |

Study Details (for demonstrating Substantial Equivalence of a Physical Device)

It's crucial to understand that the "study" described here is for a physical orthopedic implant, not an AI/Software as a Medical Device (SaMD). Therefore, many of the typical questions for AI/SaMD (like "number of experts," "adjudication," "MRMC," "ground truth type," "training set size") are not applicable in this context. The "study" involves engineering and biocompatibility testing of the material and design.

Here's an analysis based on the provided text, recognizing the nature of the device:

1. Sample size used for the test set and the data provenance:

   • Test Set Sample Size: The document does not specify a numerical sample size for the "2-point fatigue testing" or "Risk based EO sterilization." For physical device testing, sample sizes are typically determined by relevant ISO or ASTM standards (e.g., a certain number of units or specimens). The text implies sufficient samples were tested to demonstrate substantial equivalence, but the exact number isn't stated.
   • Data Provenance: Not explicitly stated, but typically these tests would be performed in a controlled laboratory environment by the manufacturer or a third-party testing facility. The data is prospective in the sense that the tests were specifically conducted for this submission.

2. Number of experts used to establish the ground truth for the test set and the qualifications of those experts:

   • Not Applicable. For a physical implant, "ground truth" is established through engineering and material science standards (e.g., ISO, ASTM) and physical measurements. There isn't a "ground truth expert" in the same way there would be for image interpretation. The "ground truth" is the established mechanical properties required for the device or established sterility assurance levels.

3. Adjudication method (e.g. 2+1, 3+1, none) for the test set:

   • None. Adjudication methods are relevant for subjective interpretations (like medical image reading). For physical device testing, results are typically quantitative measurements against predefined pass/fail criteria from engineering standards.

4. If a multi reader multi case (MRMC) comparative effectiveness study was done, If so, what was the effect size of how much human readers improve with AI vs without AI assistance:

   • Not Applicable. This is a physical orthopedic implant, not an AI-assisted diagnostic or therapeutic device. No human-in-the-loop performance or reader studies were conducted or are relevant for this type of device.

5. If a standalone (i.e. algorithm only without human-in-the-loop performance) was done:

   • Not Applicable. This is a physical orthopedic implant. There is no algorithm.

6. The type of ground truth used (expert consensus, pathology, outcomes data, etc.):

   • Engineering Standards and Measurements. The "ground truth" for the performance tests (fatigue, sterilization) would be derived from:
     • Mechanical Properties: Compliance with established ISO/ASTM standards for orthopedic implants (e.g., fatigue limits for hip components).
     • Sterilization: Achievement of a specified Sterility Assurance Level (SAL) (e.g., 10^-6) as per ISO 11135 for EO sterilization.
     • Biocompatibility: Adherence to ISO 10993 for material safety. (Though not explicitly detailed as a test in this summary, it would have been part of the initial K161184/K172501 clearance).

7. The sample size for the training set:

   • Not Applicable. This is a physical device, not a machine learning model. There is no "training set."

8. How the ground truth for the training set was established:

   • Not Applicable. As there is no training set, this question is not relevant.

In summary: K191936 is a 510(k) submission for a change to an existing physical medical device. The "acceptance criteria" discussed are largely met by demonstrating (through materials characterization, design comparison, and specific engineering tests like fatigue and sterilization validation) that the new component is as safe and effective as the previously cleared predicate device. The framework for evaluating AI/SaMD does not directly apply here.

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