TEW Cranial/Spinal Retractor™ is made from titanium and the blades, micro-retractors and flexarm assemblies are made from stainless steel. It has two movable arms, which operate independently by rotating a worm on a worm gear thus allowing an acme threaded shaft to translate through the worm gear (Patent pending). The mechanism of the TEW Retractor is self locking due to the worm/worm gear design. A hex wrench is used to drive the system. TEW Retractor blades can be pre-attached to the arms outside of the wound and a formed locking edge on the blades prevent them from falling off. The blades can also be pre-positioned and once retraction has been initiated, blades will remain in a fixed position. TEW Retractor micro-retraction is accomplished by unrestricted placement of the flexarm assemblies along the entire length of the retractor arms. There is no limit to the number of flexarms that can be used.

AI/ML Overview

The provided document is a 510(k) premarket notification for a medical device, the "TEW Cranial/Spinal Retractor™". As such, it does not describe a clinical study in the traditional sense with acceptance criteria and device performance metrics against a ground truth, as would be expected for an AI/ML medical device or a diagnostic device.

The purpose of a 510(k) submission is to demonstrate substantial equivalence to a legally marketed predicate device, not to prove clinical efficacy through a detailed study. Therefore, most of the requested information (sample size, experts, adjudication, MRMC, standalone performance, training data, etc.) is not applicable to this type of submission.

Here's an analysis of the provided text based on the nature of a 510(k) submission:

1. Table of Acceptance Criteria and Reported Device Performance

Acceptance Criteria:
For a 510(k) submission, the primary "acceptance criterion" is demonstrating substantial equivalence to a predicate device in terms of indications for use, design, materials, manufacturing processes, and specifications, such that no new questions of safety or effectiveness are raised. There are no specific quantitative performance metrics provided that would typically populate such a table for a diagnostic or AI device.

Reported Device Performance:
The document describes the device's features and how they compare to the predicates, highlighting similarities and some design improvements, but does not present quantitative performance data from a study.

Acceptance Criteria (510(k) Context)	Reported Device Performance (Summary of Equivalence)
Indications for Use are equivalent	The TEW Cranial/Spinal Retractor™ is designed for posterior fossa or intraspinal microsurgery where retraction is required, similar to predicate devices.
Design is substantially equivalent or improved without raising new safety/effectiveness concerns	- TEW has two independently movable arms with a worm/worm gear self-locking design (vs. Karlin's one movable arm with pinion gear and latch lock). - TEW blades can be pre-attached and have a formed locking edge (vs. Karlin blades which lack this). - TEW allows unrestricted placement and number of flexarm assemblies (vs. Karlin's single slide holder for two retractors; Apfelbaum's fixed posts for two flexarms).
Materials are substantially equivalent	TEW Retractor: Titanium frame, stainless steel blades and flexarm assemblies (vs. Karlin: all stainless steel; Apfelbaum: all stainless steel). The difference in frame material (titanium vs. stainless steel) is presented as not raising new safety/effectiveness issues.
Manufacturing processes are equivalent	The manufacturing processes (milling, wire cutting and forming) are the same as those used in the predicate devices.
Specifications are equivalent	The specifications of the TEW Cranial Retractor™ are the same as those of the predicate devices.
No new issues relating to safety and effectiveness are raised	Conclusion: "The indications, design, materials, manufacturing and specifications of the TEW Cranial/Spinal Retractor™ do not raise any new issues relating to safety and effectiveness."

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

Not Applicable. This is a 510(k) submission for a mechanical surgical retractor. It does not involve a "test set" of data in the sense of a diagnostic or AI device. The submission relies on design comparisons, material compatibility, and manufacturing process equivalence to established predicate devices.

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

Not Applicable. There is no "ground truth" to establish for this type of device in the context of a 510(k) as there is no diagnostic outcome being evaluated. The safety and effectiveness are inferred from equivalence to existing devices.

4. Adjudication Method for the Test Set

Not Applicable. No test set or human interpretation requiring adjudication.

5. 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 device is a surgical instrument (retractor), not an AI-powered diagnostic or assistive tool. MRMC studies are irrelevant here.

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

Not Applicable. This is a mechanical device, not an algorithm.

7. The Type of Ground Truth Used (expert consensus, pathology, outcomes data, etc.)

Not Applicable. For a 510(k) of this nature, the "ground truth" for safety and effectiveness is primarily established through the long-standing safe use and regulatory clearance of the predicate devices. The submission asserts that the new device shares sufficient characteristics with these predicates.

8. The Sample Size for the Training Set

Not Applicable. There is no "training set" as this is not an AI/ML device.

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

Not Applicable. No training set exists.

In summary: The provided document is a regulatory submission for a medical device (a surgical retractor) seeking market clearance through the 510(k) pathway. This pathway focuses on demonstrating substantial equivalence to existing, legally marketed devices rather than conducting clinical trials or performance studies with "acceptance criteria" and "ground truth" as would be done for novel diagnostic tools or AI/ML-powered devices. Therefore, most of the detailed questions about study methodology are not relevant to this type of documentation.

Summary

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K960807

II SUMMARY AND CERTIFICATION

Summary of Safety and Effectiveness TEW Cranial/Spinal Retractor™

Pursuant to Section 513(I) of the Federal Food, Drug and Cosmetics Act.

1. General Information:

Classification Name:	Self-retaining retractor for neurosurgery
Common/Usual Name:	Self-retaining Retractor
Proprietary Name:	TEW Cranial/Spinal Retractor™
Applicant's Name and Address:	F. William Sweet, Regulatory Affairs ManagerOhio Medical Instrument Company, Inc. (OMI)3924 Virginia Avenue.Cincinnati, Ohio 45227

2. Name of predicate device(s):

Karlin Crank Frame Spinal Retractor Set Apfelbaum Cerebellar Retractor Budde® Halo Retractor - for blades, micro-retractors and flex arms

3. Classification:

Self-retaining retractor for neurosurgery are Class II (21CFR 882.4800).

4. Performance Standards:

No applicable performance standards have been established by FDA under section 514 of the Food, Drug and Cosmetic Act.

5. Intended Use and Device Description:

Intended Use: The TEW Cranial Spinal Retractor (A-1090) is designed for posterior fossa or intraspinal microsurgery where retraction is required.

The TEW Cranial/Spinal Retractor is a combination of a frame retractor body for skin or muscle retraction and flexible micro-retractor arms for delicate neural tissue retraction.

Device Description: TEW Cranial/Spinal Retractor™ is made from titanium and the blades, micro-retractors and flexarm assemblies are made from stainless steel. It has two movable arms, which operate independently by rotating a worm on a worm gear thus allowing an acme threaded shaft to translate through the worm gear (Patent pending). The

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II SUMMARY AND CERTIFICATION - Continued

5. Intended Use and Device Description: - Continued

mechanism of the TEW Retractor is self locking due to the worm/worm gear design. A hex wrench is used to drive the system.

TEW Retractor blades can be pre-attached to the arms outside of the wound and a formed locking edge on the blades prevent them from falling off. The blades can also be prepositioned and once retraction has been initiated, blades will remain in a fixed position ..

TEW Retractor micro-retraction is accomplished by unrestricted placement of the flexarm assemblies along the entire length of the retractor arms. There is no limit to the number of flexarms that can be used.

Options:

A-1055	Tew Micro-Retractors
A-1057	Curved Blades
A-1071	Serrated TEW Micro Retractors
A-1074	Tapered Retractor Blade Set
A-1076	Hooked TEW Micro Retractors
4-38-A-1011	9" Flex Arm
4-38-A-1012	12" Flex Arm
4-38-A-1140	Halo Mini Vise Assembly

6. Summary of Substantial Equivalence:

Indications: The TEW Cranial/Spinal Retractor (A-1090) is designed for posterior forsa or intraspinal microsurgery where retraction is required.

Design: KARLIN Retractor crank frame has one movable arm, operated by rotating a pinion gear on a gear rack with a latch lock on the rack teeth. A square drive wrench is used to drive the system.
TEW Retractor has two movable arms, operating independently by rotating a worm on a worm gear allowing an acme threaded shaft to translate through the worm gear. The mechanism of the TEW Retractor is self locking due to the worm/worm gear design. A hex wrench is used to drive the system.

KARLIN Retractor blades are pre-positioned in the wound. The blades have no locking device to keep them from falling off the arms if blade attachment is performed outside of the wound.

TEW Retractor blades can be pre-attached to the arms outside of the wound and a formed locking edge on the blades prevent them from falling off. The blades can also be pre-positioned and once force is applied to them they will snap into place.

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II SUMMARY AND CERTIFICATION - Continued

6. Summary of Substantial Equivalence - Continued

Blade configuration between the KARLIN and TEW is the same for the only blade that KARLIN offers with differences of width and height. TEW also has blades with points for anchoring to bone and another for soft tissue use. TEW Retractor micro-retraction is accomplished by unrestricted placement of the flexarm assemblies along the entire length of the retractor arms. There is no limit to the number of flexarms that can be used. KARLIN Retractor has a selfretaining attachment to either retractor arm from which a single slide holder can be positioned along the arm length. Suction retractors are mounted in the slide holder and placed accordingly. The KARLIN attachment allows for two such retractors.

APFELBAUM Retractor, self-retaining retractor with 4x4 prongs. It has a pawl and gear rack lock system, similar to a rack and pinion gear lock, and two hexagonal posts fixed to each arm for flexarm attachment. Two flexarms can be used with the unit.

APFELBAUM Retractor uses the 4x4 prong for retaining tissue instead of separate blades capable of moving on a retractor arm system such as KARLIN or TEW. Three blades are available with the APFELBAUM unit for microretraction, one set being a left and right hand.

Materials: KARLIN Retractor, blades and self-retaining attachment is made from stainless steel.
TEW Retractor is titanium and the blades are stainless steel. TEW self-retaining flexarm assemblies are made from stainless steel

APFELBAUM Retractor and blades are made from stainless steel and blades are malleable for soft tissue use.

Manufacturing: The manufacturing processes (milling, wire cutting and forming) used in the TEW Cranial/Spinal Retractor™ are the same as those used in the predicate devices ( Karlin Crank Frame Spinal Retractor and Apfelbaum Cerebellar Retractor).
Specifications: The specifications of the TEW Cranial Retractor™ are the same as those of the predicate devices.
Conclusion: The indications, design, materials, manufacturing and specifications of the TEW Cranial/Spinal Retractor™ do not raise any new issues relating to safety and effectiveness.

OMI thus considers the TEW Cranial Spinal Retractor TV to be equivalent to the predicate devices.

Regulation Number and Section

§ 882.4800 Self-retaining retractor for neurosurgery.

(a)
Identification. A self-retaining retractor for neurosurgery is a self-locking device used to hold the edges of a wound open during neurosurgery.(b)
Classification. Class II (performance standards).