(50 days)
The Marker System is intended for establishing fixed reference points in patients requiring stereotactic surgery. Examples of situations necessitating stereotaxy could include patients in need of biopsy, resection, lesion generation, implantation of radioisotopes, and small field external beam radiotherapy. The Marker System can be used as an accessory with all currently marketed Howmedica Leibinger® stereotactic systems and can also be used with frameless navigation systems from other manufacturers.
The Marker System for Stereotaxic Navigation creates reference points fixed to the patient's skull. The system uses bone screws, adapted from craniofacial fracture fixation, to secure three to five markers into the calvarium. Each assembly consists of a screw, base component, and marker ball or optical marker. Screws are made from commercially pure titanium, have threaded lengths of 6 mm, and come in two overall lengths--9 mm and 18 mm--to accommodate different soft tissue thicknesses. A polysulfone base component screws onto the head of each screw and holds a transparent marker ball of the same material or an aluminum alloy optical marker. The marker ball, containing the medium visible during imaging, is 5 mm in diameter and has an internal cavity 2 mm in diameter. For angiography or CT imaging, these markers contain a gold ball for contrast. Markers intended for MRI and PET use are hollow. allowing injection of appropriate contrast media such as gadolinium, copper sulfate, or "F-labeled fluorodeoxyglucose solutions . This cavitv is accessed by a hole 0.6 mm in diameter descending from the top of the marker. Flat optical markers sit in the base component with the sa.ne profile as the marker balls. Fabricated from an aluminum alloy, they are anodized black and have a machined spot in the center where the true silver color of the alloy is visible; the position of this spot is identical to the center of the imaging marker ball.
Here's an analysis of the acceptance criteria and the studies performed for the Howmedica Leibinger, Inc. Marker System for Stereotaxic Navigation, based on the provided text:
1. Acceptance Criteria and Reported Device Performance
The acceptance criteria for this device seem to be implicitly tied to the performance of predicate devices and general "clinically accepted accuracy levels for stereotaxic procedures." The primary performance measure is "image registration accuracy."
| Acceptance Criteria / Performance Metric | Predicate Device Performance (ZD Stereotactic Frame) | Reported Device Performance (Marker System) |
|---|---|---|
| Stereotaxic Accuracy | 1 mm | 0.6 mm - 2.2 mm (Phantom Study) |
| 0.6 mm - 1.5 mm (Clinical Study) | ||
| Image Clarity Artifacts | Not explicitly stated, implied minimal | Not impaired |
| Bone Screw Placement / Tissue Condition | Not explicitly stated, implied problem-free | No problems encountered |
| Infection | Not explicitly stated, implied low | No infection |
2. Sample Size Used for the Test Set and Data Provenance
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Non-Clinical Study (Phantom Study):
- Sample Size: 35 markers placed on three platforms of a phantom assembly. 16 combinations of 4 markers and 16 combinations of 3 markers were tested for accuracy.
- Data Provenance: Retrospective (implicitly, as it's a controlled phantom study). The study was conducted at the University of Innsbruck, Innsbruck, Austria.
-
Clinical Study:
- Sample Size: 15 patients.
- Data Provenance: Prospective (implicitly, as it describes patients undergoing surgery). The study was conducted at the Neurosurgery Department, Hopitaux des Armees, Paris, France.
3. Number of Experts Used to Establish Ground Truth for the Test Set and Their Qualifications
- Non-Clinical Study: Not applicable. The ground truth for the phantom study was the known, precise positions of the holes on the phantom assembly.
- Clinical Study: Not explicitly stated how many neurosurgeons were involved in assessing the screw placement and clinical outcomes. However, the study was conducted by the "Neurosurgery Department, Hopitaux des Armees," implying involvement of qualified neurosurgical staff. The placement sites were "determined by the neurosurgeon."
4. Adjudication Method for the Test Set
- Non-Clinical Study: Not applicable for adjudication in the traditional sense. The accuracy was determined by manually placing a cursor in the center of each visible marker dot on the monitor and comparing it to the known positions. There's no mention of multiple readers or a consensus process.
- Clinical Study: Not explicitly stated. Clinical outcomes (screw placement, tissue condition, infection, image clarity) were assessed, but the method of adjudication (e.g., whether multiple surgeons independently assessed and then converged) is not detailed.
5. Multi-Reader Multi-Case (MRMC) Comparative Effectiveness Study
No. The provided text does not describe a multi-reader multi-case (MRMC) comparative effectiveness study, nor does it quantify the effect size of human readers improving with AI assistance. This device is a passive marker system, not an AI-assisted diagnostic tool.
6. Standalone (Algorithm Only Without Human-in-the-Loop Performance) Study
Yes, in a sense, the non-clinical phantom study represents a standalone evaluation of the marker system's inherent accuracy in imaging. The "image registration accuracy" was measured by comparing the detected marker positions to known physical positions. The text notes that this testing "did not involve the use of an automatic detection algorithm for determining image center," meaning the measurement of the marker's center was a manual, human-in-the-loop task during the evaluation, but the device itself (the marker system) was being evaluated for its ability to provide accurate reference points, independently of human interpretation of those points for surgical navigation.
The clinical study also evaluated the device's accuracy in a standalone manner, with optical referencing accuracies being reported (0.6 mm to 1.5 mm).
7. Type of Ground Truth Used
- Non-Clinical Study (Phantom Study): The ground truth was based on the known, precise physical positions of the holes on the phantom assembly. This is a highly controlled, objective form of ground truth.
- Clinical Study: The ground truth for evaluating clinical performance aspects like screw placement, tissue condition, infection, and image clarity appears to be clinical observation and assessment by neurosurgeons. For optical referencing accuracy, the ground truth would be the actual physical target position during navigation.
8. Sample Size for the Training Set
No training set is mentioned or applicable for this device. This is a physical marker system for stereotaxic navigation, not a machine learning or AI algorithm that requires a training phase.
9. How the Ground Truth for the Training Set Was Established
Not applicable, as there is no training set for this device.
§ 882.4560 Stereotaxic instrument.
(a)
Identification. A stereotaxic instrument is a device consisting of a rigid frame with a calibrated guide mechanism for precisely positioning probes or other devices within a patient's brain, spinal cord, or other part of the nervous system.(b)
Classification. Class II (performance standards).