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BackStop is intended for use in the ureter to prevent migration of renal calculi during intracorporeal lithotripsy procedures.

BackStop™ is a self-forming polymeric plug with reverse thermosensitive properties. At room temperature it is viscous but injectable. When the temperature of the plug increases , its viscosity increases and it forms a plug that is intended for use in the ureter to prevent migration of renal calculi during intracorporeal lithotripsy procedures. The material is water soluble and is removed by irrigating the plug with saline.

The provided text describes the 510(k) summary for the BackStop™ device, which is an ureteral stone dislodger. The information provided focuses on demonstrating substantial equivalence to predicate devices and the results of a clinical study.

Here's an analysis of the acceptance criteria and the study, structured as requested:

Acceptance Criteria and Device Performance

The document does not explicitly state pre-defined acceptance criteria in terms of numerical thresholds for device performance. Instead, the "acceptance criteria" are implicitly met by demonstrating safety, effectiveness, and non-inferiority/superiority compared to the standard of care in a clinical study for the primary endpoint.

Study Details

1. Sample Size Used for the Test Set and Data Provenance:

   • Test Set Sample Size: 68 subjects.
     • Experimental Group (BackStop™): n=34
     • Control Group (Standard of care, no anti-retropulsion device): n=34
   • Data Provenance: Prospective, randomized, single-blind, controlled multi-site clinical study. The country of origin for the data is not specified in the provided text.

2. Number of Experts Used to Establish the Ground Truth for the Test Set and Qualifications of those Experts:

   • The study is a clinical trial with patients, not an image-based study requiring "experts" to establish a ground truth for a test set of data. The "ground truth" here is the clinical outcome observed in actual patients.
   • "Experts" involved: The study was conducted by "investigators," who are medical professionals (likely urologists or surgeons experienced in lithotripsy). The number and specific qualifications (e.g., years of experience) of these investigators are not specified in this summary. They would have been responsible for patient selection, procedure execution, and outcome assessment.

3. Adjudication method for the Test Set:

   • The document describes a "single-blind" design, meaning patients were likely unaware of whether they received the BackStop™ device or were in the control group. However, the clinicians performing the procedure and assessing outcomes might have been aware.
   • The specific adjudication method for outcomes (e.g., how "retropulsion" was definitively determined if there was ambiguity) is not explicitly detailed. It can be inferred that the "investigators" assessed these clinical endpoints.

4. If a Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study was done:

   • No, an MRMC study was not done. This was a randomized controlled clinical trial comparing a medical device against the standard of care in actual patients. MRMC studies are typically performed for diagnostic devices (e.g., AI for image interpretation) to compare the performance of multiple human readers with and without AI assistance on a set of cases.

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

   • Not applicable. The BackStop™ device is a physical medical device (an implantable ureteral plug), not an algorithm or AI software. Therefore, there's no "standalone" algorithm performance to evaluate.

6. The Type of Ground Truth Used:

   • Clinical Outcomes/Observed Events in Patients: The ground truth was established by direct observation and measurement of clinical endpoints in patients during and after the medical procedure. These include:
     • Presence or absence of retropulsion (observed during lithotripsy).
     • Need for subsequent procedures (clinical follow-up).
     • Stone-free rate at follow-up (clinical follow-up, likely imaging-confirmed).
     • Occurrence of adverse events (clinical observation and reporting).
     • Ability to dissolve the device (observed during the procedure).

7. The Sample Size for the Training Set:

   • Not applicable. This device is a physical medical device, not an AI/ML algorithm that requires a "training set" of data.

8. How the Ground Truth for the Training Set was Established:

   • Not applicable. As above, no training set was involved for this type of device.

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