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Stem - PSA Type is included in U2 Total Knee System-PSA type. U2 Total Knee System-PSA type is indicated for use in skeletally mature patients with severe knee pain and disability undergoing surgery for knee arthroplasty due to rheumatoid arthritis, osteoarthritis, primary and secondary traumatic arthritis, polyarthritis, collagen disorders, avascular necrosis of the femoral condyle or pseudogout, posttraumatic loss of joint configuration, particularly when there is patellofemoral erosion, dysfunction or prior patellectomy, moderate valgus, varus, or flexion contraction. This device is intended for use in patients who require augmentation and/or stem extensions due to inadequate bone stock and/or require constrained stabilization for tibiofemoral joint due to soft tissue imbalance. U2 Total Knee System-PSA type is designed for cemented use only.

"UNITED Stem-PSA Type is an additional size extension of stem to the existing, previously cleared "UNITED" U2 Total Knee system product line (K082424). The materials, design, safety and effectiveness of this subject are identical to the previously cleared U2 Total Knee system. The only difference from the existing products is the length of stem. This subject stem made of Ti-6A1-4V alloy and will be offered in two types which include straight stem and curved stem. The length of extended straight stem distribute to 150, 200 and 240mm, while the curved stem has 240mm only. Each size of stem has fifteen options in diameter which ranging from 10mm to 24mm. Canal filling stems with spline and flute design provide immediate rigid fixation and resistance to torsional movements. Distal taper is designed to address the problems associated with proximal stress shielding, resulting from distal fixation.

The provided text describes a 510(k) premarket notification for a medical device called "Stem, PSA Type" (K100981). This document primarily focuses on establishing substantial equivalence to existing devices rather than presenting a performance study with detailed acceptance criteria and testing methodology as one might find for a novel diagnostic or AI-driven device.

Therefore, many of the requested elements (sample size of test set, data provenance, number of experts, adjudication method, MRMC study, standalone performance, training set details, etc.) are not applicable or not provided in this type of submission.

Here's an analysis based on the information available:

1. Table of Acceptance Criteria and Reported Device Performance

• Indications for use
• Materials
• Design
• Manufacturing process
• Sterilization
• Comparable locking strength of Morse Taper | The subject device ("Stem, PSA Type") is stated to be identical to the previously cleared "UNITED" U2 Total Knee system in terms of materials, design, safety, and effectiveness, except for the length of the stem.
  The subject device's larger stem lengths (straight stem: 150, 200, 240 mm; curved stem: 240 mm) are substantially equivalent to:
• "UNITED" U2 Total Knee system - PSA Type (straight stem: 30, 75, 100 mm; curved stem: 150, 200 mm)
• "DEPUY" Anatomic Modular Knee (AMK) System (K864671) for the straight stem.
• "SMITH & NEPHEW" LEGION Revision Knee System (K043440) for the curved stem.
  Locking strength test of Morse Taper demonstrated the device is safe and effective and substantially equivalent to the predicate device. |

2. Sample Size for the Test Set and Data Provenance

• Sample Size: Not applicable/not provided. This submission is for a new size extension of an existing mechanical implant, relying on substantial equivalence to predicates, not a clinical trial or performance study requiring a test set of patient data.
• Data Provenance: Not applicable/not provided. There are no patient data used for "testing" in the traditional sense. The data relates to mechanical property testing.

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

• Not applicable/not provided. Ground truth, in the context of patient data, is not established for this type of submission. The evaluation is based on engineering principles and comparison to predicate devices.

4. Adjudication Method for the Test Set

• Not applicable/not provided.

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

• Not applicable. This device is a mechanical implant, not an AI-assisted diagnostic tool or an imaging reader.

6. Standalone (Algorithm Only) Performance Study

• Not applicable. This device is a mechanical implant, not an algorithm.

7. Type of Ground Truth Used

• Not applicable in the conventional sense. The "ground truth" here is the established safety and effectiveness of the predicate devices based on their prior clearances and the engineering standards applied to their design, materials, and manufacturing. For the specific performance data mentioned (locking strength), the ground truth would be established mechanical engineering standards for such components.

8. Sample Size for the Training Set

• Not applicable/not provided. 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/not provided.

Summary of the Study (Performance Data):

The "study" referenced in the 510(k) is a locking strength test of the Morse Taper. This mechanical test was performed as part of the design assurance process. The purpose was to demonstrate that the expanded stem sizes maintain similar safety and effectiveness characteristics to the predicate devices. The document states that this test demonstrated the device is safe and effective and is substantially equivalent to the predicate device in this regard. No specific acceptance values or detailed test results are provided in this summary, but the conclusion of substantial equivalence is drawn based on these tests.

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