(379 days)
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No
The summary describes a sensor that measures strain and uses RFID for data transmission. There is no mention of algorithms, learning, or data processing that would indicate AI/ML. The performance studies focus on the accuracy and usability of the strain measurement and RFID system.
No.
The device is an intraoperative surgical tool designed to measure rod microstrain. It is explicitly stated as an "adjunct to surgeon tactile feedback and is not intended to replace a surgeon's clinical judgment." This indicates its role as a measurement and information-providing tool, rather than directly treating or mitigating a disease or condition.
Yes
The device measures "unidirectional rod microstrain on posterior rods in the sagittal plane" and provides "objective readings of the change of mechanical unidirectional strain on a pedicle screw rod." While it "is not intended to replace a surgeon's clinical judgment," it provides data that can inform surgical decisions during spinal surgery, which is a form of diagnosis in the context of assessing the state and changes in the surgical correction.
No
The device description explicitly states it includes hardware components such as a titanium/zirconia ceramic strain sensing device, a passive transponder, an inserter, and a hand-held reader (scanner). While it uses RFID technology to access data, it is not solely software.
Based on the provided information, this device is not an IVD (In Vitro Diagnostic).
Here's why:
- Intended Use: The intended use is to measure rod microstrain on posterior rods during spine surgery. This is a mechanical measurement related to the surgical procedure itself, not a test performed on a biological sample (like blood, urine, or tissue) to diagnose a disease or condition.
- Device Description: The device measures mechanical strain using a sensor and RFID technology. It does not involve the analysis of biological samples.
- Performance Studies: The performance studies focus on the mechanical properties of the rod with the sensor, the accuracy and repeatability of the strain measurement, and the usability of the device in a surgical setting. There are no studies related to the analysis of biological samples or diagnostic performance metrics (like sensitivity, specificity, etc.).
IVD devices are specifically designed to perform tests on biological samples to provide information for the diagnosis, monitoring, or treatment of diseases or conditions. The LOADPRO™ Intraoperative Rod Strain Sensor does not fit this description.
N/A
Intended Use / Indications for Use
The LOADPRO™ Intraoperative Rod Strain Sensor is an intraoperative surgical tool that allows surgeons to measure unidirectional rod microstrain on posterior rods in the sagittal plane when performing spine surgery. This device is an adjunct to surgeon tactile feedback and is not intended to replace a surgeon's clinical judgment.
The LOADPRO™ Intraoperative Rod Strain Sensor is a single use, disposable tool to be used in conjunction with X-Spine Systems Fortex Pedicle Screw System for 5.5mm diameter titanium (ASTM F136) or cobalt chrome (ASTM F1537) rod configurations.
Product codes (comma separated list FDA assigned to the subject device)
QFP, OFP
Device Description
The LOADPRO™ Intraoperative Rod Strain Sensor includes a titanium/zirconia ceramic, single use strain sensing device, which includes radio-frequency identification (RFID) technology (13.56MHz), intended to enable access to strain measurement values, incorporating a passive transponder, inserter, and scanner (Figure 1 and 2). The transponder attaches to X-Spine Systems Fortex Pedicle Screw System using 5.5mm titanium alloy or cobalt chrome rods in corrective spinal surgeries (Figure 3). The transponder is used only to acquire rod microstrain values and a unique device identification code, which is read by the scanner, during the surgical correction.
The LOADPRO™ Intraoperative Rod Strain Sensor is a titanium/zirconia ceramic, ethylene oxide (EtO) sterilized, single use device designed to provide objective readings of the change of mechanical unidirectional strain on a pedicle screw rod. The LOADPRO™ Intraoperative Rod Strain Sensor consists of the following primary components, described in the proceeding sections:
- LOADPROTM Intraoperative Rod Strain Sensor ●
- . Hand Held Reader (scanner)
- . Manual Orthopaedic Surgical Instrumentation
Mentions image processing
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Mentions AI, DNN, or ML
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Input Imaging Modality
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Anatomical Site
posterior rods in the sagittal plane when performing spine surgery (spine)
Indicated Patient Age Range
Not Found
Intended User / Care Setting
surgeons, intraoperative setting
Description of the training set, sample size, data source, and annotation protocol
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Description of the test set, sample size, data source, and annotation protocol
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Summary of Performance Studies (study type, sample size, AUC, MRMC, standalone performance, key results)
Rod Durability:
Bench testing was performed to assess the effects that repetitive installations of a sensor might have on the mechanical performance and the fatigue endurance of pedicle screw system components and constructs.
Dynamic ASTM F1717-13 compression bend runout testing was performed on non-sensored rods and on sensored rods after fifteen (15) LOADPRO™ Intraoperative Rod Strain Sensor installations / removals were performed at the same location. The results indicate there was no change between the sensor and non-sensor groups.
The static cantilever bend tests for the non-sensored and repetitive sensor implantation rods were run for 3 samples per group per ASTM F2193-2. There was no meaningful difference in strength and stiffness per the static cantilever bend tests, and the dynamic compression bend run-out loads were equivalent between groups.
System Characterization Testing:
- Test 1: Kyphotic Rod Function Testing (See ACCURACY AND REPEATABILTY TESTING Section below).
- Test 2: Sensor Limit Testing: Performed to show that the disposable sensor can withstand high levels of strain on the rod to which they are attached. Acceptance criterion requires the rod strain value be greater than the yield strain for each material.
- Test 3: Sensor Variability Testing: Evaluated Sensor-to-Sensor variations. An ASTM F1717 construct was used with the LOADPRO™ Intraoperative Rod Strain Sensors mounted on one rod and a strain gage on the other. Loads of 50N, 100N, 150N, 200N, -50N, -100N, -150N, and -200N were applied. Results show that the LOADPROTM Intraoperative Rod Strain Sensors measure strain linearly and are not load dependent.
- Test 4: Sensor Longevity Test: Assessed the accuracy of the sensor when seated on the rod construct for 8 hours with strain readings recorded every hour.
- Test 5: Sensor Temperature Variability Test: Assured that the sensors will not dramatically change in strain value as the environmental temperature fluctuates within the limits of an operating room environment (65°F. 70°F, 75°F).
- Test 6: Reader Duration Test: Evaluated the Reader in scanning mode for 5 minute intervals up to 120 minutes of total scanning time to ensure the Reader can function without battery change for the entire duration of a typical surgery.
Accuracy and Repeatability Testing:
Test 1 verified that the system can accurately and repeatably measure the load placed on a cantilevered rod. Two cantilevered rods, one with a strain gage and one with the LOADPRO™ Intraoperative Rod Strain Sensor, were used. The same load was applied to both rods so that the mounted strain gage recorded 1400 u-strain. Strain data was then collected from the LOADPROTM Intraoperative Rod Strain Sensor (Ti Rods and CoCr Rods). All tested Sensors passed the success criteria.
Additional performance testing (cantilever bend testing with rods having coronal curvature, off axis loading, wetted rods, and varying ambient temperature) demonstrated that individual and combined effects resulted in microstrain reading errors of less than 10%.
USABILITY TESTING:
- Table Top Usability Study: Performed on a table top spine model with currently practicing orthopedic spine surgeons and fellows (15 users). Each user reviewed technique and instrument, sensor installation and removal, and reader. Graded on a scale of 1 to 5 (strongly disagree to strongly agree) and converted to an overall score (0-100). An adjusted total score of 70 or greater was acceptable. Average scores: Instruments 89.5 ± 12.8, Sensor 84.5 ± 12.3, Reader 85.7 ± 13.2. All average scores were above the acceptance criteria.
- Intraoperative Usability Testing: Conducted on five patients undergoing posterior spinal surgeries using 13 sensors in six surgeries at two clinical sites. Four participating surgeons were blinded to the values obtained by the sensors. The device demonstrated the ability to obtain measurements in an intraoperative setting. Surgeon feedback indicated that the LOADPRO™ Intraoperative Rod Strain sensor does not appear to significantly prolong operative times or greatly increase attributed blood loss.
Key Metrics (Sensitivity, Specificity, PPV, NPV, etc.)
Variability in resistance for Sensor to Sensor Variability Test (Test 3):
-50N: 9.9%
-100N: 6.2%
-150N: 5.8%
-200N: 5.2%
Microstrain reading errors for additional performance testing: less than 10%.
Usability Results (15 Users):
Instruments: 89.5 ± 12.8 (Average Score)
Sensor: 84.5 ± 12.3 (Average Score)
Reader: 85.7 ± 13.2 (Average Score)
Predicate Device(s): If the device was cleared using the 510(k) pathway, identify the Predicate Device(s) K/DEN number used to claim substantial equivalence and list them here in a comma separated list exactly as they appear in the text. List the primary predicate first in the list.
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Reference Device(s): Identify the Reference Device(s) K/DEN number and list them here in a comma separated list exactly as they appear in the text.
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Predetermined Change Control Plan (PCCP) - All Relevant Information for the subject device only (e.g. presence / absence, what scope was granted / cleared under the PCCP, any restrictions, etc).
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§ 888.3090 Intraoperative orthopedic strain sensor.
(a)
Identification. A strain sensor device is an adjunct tool intended to measure strain on an orthopedic implant in the intraoperative setting only. The device is not intended to provide diagnostic information or influence clinical decision making.(b)
Classification. Class II (special controls). The special controls for this device are:(1) Non-clinical performance testing must demonstrate that the device performs as intended under anticipated conditions of use. The following performance testing must be conducted:
(i) Mechanical testing to evaluate the effect of the device on the mechanical performance of the implant and to characterize the mechanical limits of the components used with the implant; and
(ii) Accuracy and repeatability testing of strain measurements.
(2) Usability testing must evaluate the effect of the device on the performance of the surgical procedure.
(3) The patient-contacting components of the device must be demonstrated to be biocompatible.
(4) Performance testing must support the sterility and shelf life of the patient-contacting components of the device.
(5) Software verification, validation, and hazard analysis must be performed.
(6) Performance data must validate the reprocessing instructions for reusable components of the device.
(7) Performance data must be provided to demonstrate the electromagnetic compatibility (EMC) and electrical safety of the device.
(8) Labeling must include the following:
(i) A shelf life;
(ii) Instructions for use;
(iii) Reprocessing instructions for any reusable components; and
(iv) A statement that the device is not intended to provide diagnostic information or influence clinical decision making.
0
DE NOVO CLASSIFICATION REQUEST FOR LOADPRO™ INTRAOPERATIVE ROD STRAIN SENSOR
REGULATORY INFORMATION
FDA identifies this type of device as:
Intraoperative orthopedic strain sensor. A strain sensor device is an adjunct tool to measure strain on an orthopedic implant in the intraoperative setting only. The device is not intended to provide diagnostic information or influence clinical decision making.
NEW REGULATION NUMBER: 21 CFR 888.3090
CLASSIFICATION: Class II
PRODUCT CODE: QFP
BACKGROUND
DEVICE NAME: LOADPRO™ Intraoperative Rod Strain Sensor
SUBMISSION NUMBER: DEN180012
DATE OF DE NOVO: July 19, 2018
Intellirod Spine, Inc. CONTACT: 554F White Pond Drive Akron, OH 44320
INDICATIONS FOR USE
The LOADPRO™ Intraoperative Rod Strain Sensor is an intraoperative surgical tool that allows surgeons to measure unidirectional rod microstrain on posterior rods in the sagittal plane when performing spine surgery. This device is an adjunct to surgeon tactile feedback and is not intended to replace a surgeon's clinical judgment.
The LOADPRO™ Intraoperative Rod Strain Sensor is a single use, disposable tool to be used in conjunction with X-Spine Systems Fortex Pedicle Screw System for 5.5mm diameter titanium (ASTM F136) or cobalt chrome (ASTM F1537) rod configurations.
LIMITATIONS
PLEASE REFER TO THE LABELING FOR A COMPLETE LIST OF WARNINGS, PRECAUTIONS AND CONTRAINDICATIONS.
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DEVICE DESCRIPTION
The LOADPRO™ Intraoperative Rod Strain Sensor includes a titanium/zirconia ceramic, single use strain sensing device, which includes radio-frequency identification (RFID) technology (13.56MHz), intended to enable access to strain measurement values, incorporating a passive transponder, inserter, and scanner (Figure 1 and 2). The transponder attaches to X-Spine Systems Fortex Pedicle Screw System using 5.5mm titanium alloy or cobalt chrome rods in corrective spinal surgeries (Figure 3). The transponder is used only to acquire rod microstrain values and a unique device identification code, which is read by the scanner, during the surgical correction.
Image /page/1/Picture/2 description: The image shows a close-up of a mechanical device, possibly a component of a larger machine. The device is primarily composed of metal and plastic parts, with a gray metal frame forming the main structure. A beige plastic box is attached to the top of the frame, and there are cylindrical metal elements extending from the frame. The device appears to be designed for precision and durability, suggesting it may be used in an industrial or engineering application.
Figure 1: Profile view of the LOADPRO™ Intraoperative Rod Strain Sensor
Image /page/1/Picture/4 description: This image shows an exploded view of a mechanical assembly. The assembly consists of a screw, a ceramic enclosure, a bridge with strain gauges, foil cover, and feedthru, a clamp with a platform, a simple clamp, and a pin. The components are arranged in a way that shows how they fit together.
Figure 2: Profile exploded view of the LOADPRO™ Intraoperative Rod Strain Sensor
Image /page/1/Picture/6 description: The image shows a diagram of spinal fusion surgery. The first image shows a spine with scoliosis. The second image shows a rod being inserted into the spine to correct the curvature. The third and fourth images show the spine after the surgery, with the rod in place. The fifth image shows a spine with screws and rods in place.
Figure 3: Image of the LOADPRO™ Intraoperative Rod Strain Sensor attached to a pedicle screw system using 5.5mm titanium alloy rods
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The LOADPRO™ Intraoperative Rod Strain Sensor is a titanium/zirconia ceramic, ethylene oxide (EtO) sterilized, single use device designed to provide objective readings of the change of mechanical unidirectional strain on a pedicle screw rod. The LOADPRO™ Intraoperative Rod Strain Sensor consists of the following primary components, described in the proceeding sections:
- LOADPROTM Intraoperative Rod Strain Sensor ●
- . Hand Held Reader (scanner)
- . Manual Orthopaedic Surgical Instrumentation
LOADPRO™M Intraoperative Rod Strain Sensor
The LOADPRO™ Intraoperative Rod Strain Sensor consists of a titanium clamp and housing unit: a sealed zirconia ceramic and titanium enclosure containing a batterv-less, wireless sensor. designed to provide objective readings of the change of mechanical strain in one plane on the pedicle screw and rod system during a surgical procedure. The sensing element is capable of measuring static and dynamic strain and converting it to an electrical signal. The electronic data acquisition circuitry is connected via a built-in antenna. The reading results are communicated telemetrically to a hand-held Reader unit. The LOADPRO™ Intraoperative Rod Strain Sensor, provided in a single size, is comprised of multiple sub-components (Figure 4).
Image /page/2/Picture/6 description: The image shows an exploded view of a device with several components labeled. The components include a ceramic enclosure, a coil and frame, a PC board, and a clamp-bridge assembly. The ceramic enclosure is at the top, followed by the coil and frame, then the PC board, and finally the clamp-bridge assembly at the bottom. The image provides a clear visual representation of the device's construction and the relationship between its parts.
Image /page/2/Figure/7 description: The image is a figure that shows a profile exploded view of the LOADPROT™ Intraoperative Rod Strain Sensor electronic acquisition circuitry. The figure is labeled as "Figure 4". The text describes the figure as a profile exploded view. The figure is likely a diagram or illustration showing the different components of the sensor and how they fit together.
The LOADPRO™ Intraoperative Rod Strain Sensors are attached directly to 5.5mm rods in the space between upper and lower pedicle screw sets. Attachment is accomplished by a straightforward non-abrasive clamp mechanism in which the clamp body surrounds the rod and a screw compresses the open side of the clamp. The LOADPRO™ Intraoperative Rod Strain Sensor monitors the rod microstrain in one plane, providing objective readings of the mechanical strain during rod manipulation to provide the surgeon with a real-time measurement of strain on the rod. The clinical significance of knowing and/or modifying unidirectional, sagittal plane rod microstrain values is unknown.
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Titanium Fixation Clamps
The LOADPRO™ Intraoperative Rod Strain Sensor attaches directly to 5.5mm rods in the vertical space between the heads of adjacent level pedicle screws, on one side of the construct. Attachment is accomplished by a straightforward non-abrasive clamp mechanism in which the clamp body surrounds the rod and a screw compresses the open side of the clamp.
The LOADPRO™ Intraoperative Rod Strain Sensor allows for independent movement of the two clamps to allow clamping on straight as well as curved rods. The clamps transmit rod microstrain from the sagittal plane to the sensing element. Bench testing confirms that this attachment mechanism does not impact the mechanical integrity of the rod or rod/screw construct fatigue life.
Electronic Elements
The electronics in the LOADPRO™ Intraoperative Rod Strain Sensor consist of:
- . A Strain Sensor
- Sensor Telemetry Circuit Board .
- . Reader Inductive Link and Display
The electronic components into the Inductive Link and Data Convertor Electronics subassembly include: antenna, resistors, capacitors, transistor (MOSFET), and integrated circuits (microchips). This is sealed in zirconia ceramic and titanium to protect the electronics.
Strain Sensor
The LOADPRO™ Intraoperative Rod Strain Sensor consists of a series of semiconductor strain gages that measure strain in a loaded element, in this case the 5.5mm rods used during rod manipulation in spine surgery. The semiconductor strain gage is commercially available and has history of use in aeronautical, military, and medical device applications.
Sensor Telemetry Circuit
A radio frequency telemetry circuit is used to transmit data to a hand-held Reader. The telemetry circuit and sensor are powered by inductive coupling from the Reader, thus no power source is needed in the Sensor.
The strain measurement electronics are powered wirelessly using inductive coupling. Power is provided by a 13.56 MHz electro-magnetic field sourced by a reader coil that is placed near the sensor. This same inductive link is used to transfer data from the Sensor to the Reader. If the Reader antenna is not close enough to the Sensor's antenna to fully operate the device, any partial / corrupt data will be rejected by the Reader. This technology is derived from RFID shortrange systems used worldwide and is robust and dependable. The Sensor's circuit rectifies the power signal for operation of a field-programmable gate array (FPGA) integrated circuit and strain sensor. An oscillator (resistance to frequency converter) is used to measure the resistance of the strain sensor. The signal is then conditioned and used to modulate a load placed across the
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Sensor's coil. The Reader detects the Sensor's signal as a varying load. The nominal data frequency is 33 kHz (a 66-bit data packet transmitted in 2 msec bursts).
Hand Held Reader
The LOADPRO™ Reader is a handheld electronic device that is used to read the LOADPRO™ Intraoperative Rod Strain Sensor. It consists of an integrated antenna, display screen, and "Scan" and "Clear" buttons. When a reading is required, the Reader is powered on and the Scan button pressed. The Reader (inside a sterile sheath) is then placed near the patient in proximity of the Sensor to begin data collection. The Reader receives the data from the Sensor, performs validity checks and then displays the value for that reading in units of microinches/inch). If two Sensors are within the inductive link field, data from both Sensors are displayed (one on each line with their corresponding serial numbers).
Handheld LOADPRO™ Reader
The LOADPRO™ Reader utilizes a Microchip PIC microcontroller (Figure 5). The primary functions of the reader include:
- Transmit signal to power the sensor ●
- . Read data from the sensor
- . Determine if data reading is valid
- . Display valid readings
The reader software is designed to be streamlined and simple. The user interface requires the user to power the reader on (slide switch), press a button (Scan) to initiate reads, press a different button (Clear) to clear the screen and turn off the inductive link.
When a data is obtained from the Sensor(s), the Reader software confirms it is an acceptable reading through a series of validity checks such as checksum verification and data range parameters. If the reading does not pass all validity checks, the data is discarded and the next reading is collected.
The Sensor continuously collects and sends data to the Reader as long as the inductive link provides power.
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Image /page/5/Figure/0 description: The image shows an exploded view of a handheld metal detector. The metal detector is black and has a loop at the top and bottom. The top loop is labeled as the antenna, and the bottom loop is labeled as the RF board. The handle of the metal detector contains the scan button, clear button, PC board, and LCD display.
Figure 5: Exploded view of the LOADPROTM Reader
Manual Orthopedic Surgical Instrumentation
Manual orthopedic surgical instruments are used for the connection of the LOADPRO™ Intraoperative Rod Strain Sensor.
SUMMARY OF NON-CLINICAL TESTING
BIOCOMPATIBILITY / MATERIALS
The LOADPRO™ Intraoperative Rod Strain Sensor is made from the following medicalgrade materials, some of which are sealed and not patient-contacting:
- Titanium alloy (Ti6AlV-ELI) per ASTM F136/ISO 5832-3 =
- Nusil Med-2000 (D) (4) (4) Silicone per ASTM D792, ASTM D2240, ASTM . D412 and ASTM D624
- Titanium Niobium per AMS 4982-B -
- -Zirconia ceramic per ASTM D2442
- (0) (4) .
- -(b) (4)
The LOADPROTM Instruments are made from (b) (4) stainless steel per (b) (4)
These components are patient contacting with limited exposure ((b) (4) strain, CoCr > (b) (4) strain).
Test 3: Sensor Variability Testing
Test 3 focuses on Sensor-to-Sensor variations and ensures that all incoming sensors can repeatability measure strain and function similarly. In this setup, an ASTM F1717 construct was used. The LOADPRO™ Intraoperative Rod Strain Sensors were mounted on one rod and a strain gage on the other rod. Using the test machine, the F1717 construct was loaded to specific loads of 50N, 100N, 150N, 200N, -50N, -100N, -150N, and -200N. The max load was limited to +/- 200N as this equates to (D) (4) strain. which is the elastic deformation limit for Cobalt/Chrome rods. Strain values were recorded as determined by the LOADPRO™ Intraoperative Rod Strain Sensors for comparison at
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each load. These test results (Figure 6 and Table 3) show that the LOADPROTM Intraoperative Rod Strain Sensors measure strain linearly and are not load dependent.
| Load (N) | Variability in resistance |
|---|---|
| -50 | 9.9% |
| -100 | 6.2% |
| -150 | 5.8% |
| -200 | 5.2% |
Table 3: Sensor to Sensor Resistance Variability
Image /page/10/Figure/3 description: The image is a graph titled "Sensor Sensitivity ASTM F1717 Testing Micro Strain Vs. Load". The x-axis is labeled "Load (N)" and ranges from -200 to 0. The y-axis is labeled "Rod Surface Strain (με)" and ranges from -2250 to 0. There are 6 different lines on the graph labeled SN 1, SN 2, SN 4, SN 5, sn 3, and SN 9, as well as a line labeled "Average Slope". The average sensitivity is y = 9.9569x and R^2 = 1.
Figure 6: Sensor to Sensor Variability Results
Test 4: Sensor Longevity Test
The sensor longevity testing was performed to assess the accuracy of the sensor when seated on the rod construct for 8 hours with strain readings recorded every hour. Eight hours was selected as a period of time that would exceed a normal surgery.
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Test 5: Sensor Temperature Variability Test
The sensor temperature variability testing was performed to assure that the sensors will not dramatically change in strain value as the environmental temperature fluctuates within the limits of an operating room environment (65°F. 70°F, 75°F).
Test 6: Reader Duration Test
The reader duration test evaluated the Reader in scanning mode for 5 minute intervals up to 120 minutes of total scanning time to ensure that the Reader can function without the need to change the batteries for the entire duration of a typical surgery.
Accuracy and Repeatability Testing
Test 1 described above verified that the system can accurately and repeatably measure the load placed on a cantilevered rod. Two (2) cantilevered rods, one with a strain gage mounted to the rod and the other with the LOADPRO™ Intraoperative Rod Strain Sensor. were used. The same load was applied to both rods so that the mounted strain gage recorded 1400 u-strain. Strain data was then collected from the LOADPROTM Intraoperative Rod Strain Sensor (Ti Rods: Figure 7 and Table 4; CoCr Rods: Figure 8 and Table 5). This test was performed with both Titanium Alloy (Ti) and Cobalt/Chrome (CoCr) rods, and all tested Sensors passed the success criteria.
Image /page/11/Figure/6 description: The image shows a figure or plot related to Ti Rods. The title of the plot is "Ti Rods". The plot is labeled as "(b) (4)" and the y-axis is labeled as "Rod Surface Strain (uE)".
Figure 7: Cantilever Bend Measurement Accuracy Results - Titanium Rods
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| Ti Rods, Strain(b) (4) | |||
|---|---|---|---|
| SN | Delta | ||
| Resistance | |||
| (KΩ) | Sensor | ||
| Strain (με) | %Erro |
Table 4: Measurement Accuracy Results - Titanium Rods
Image /page/12/Figure/2 description: The image shows the text "CoCr Rods" at the top. Below that, the text "(b) (4)" is visible in the upper left corner. The rest of the image is a solid gray color. The image appears to be a cropped portion of a larger figure or document.
Figure 8: Cantilever Bend Measurement Accuracy Results – Cobalt Chrome Rods
| CoCr Rods, Strain (b) (4) | |||
|---|---|---|---|
| SN | Delta | ||
| Resistance | |||
| (KΩ) | Sensor | ||
| Strain (με) | % | ||
| Error |
Table 5: Measurement Accuracy Results - Cobalt Chrome Rods
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Additional performance testing was conducted to demonstrate that the LOADPROTM Intraoperative Rod Strain Sensor provides repeatable and accurate readings despite potential sources of error. This included cantilever bend testing with rods having coronal curvature, cantilever bend testing with off axis loading, cantilever bend testing with wetted rods, and cantilever bend testing with varying ambient temperature. Tests demonstrated that individual and combined effects resulted in microstrain reading errors of less than 10%.
USABILITY TESTING
Table Top Usability Study
Usability testing was performed using a table top spine model to obtain feedback from end-user spine surgeons regarding the usability of the LOADPROTM System (instruments, sensor, and reader).
A modified usability scale12, was used to measure usability effectiveness and usability issues requiring attention with added terminology related to the LOADPRO™ product. Currently practicing orthopedic spine surgeons and fellows were selected as the targeted user population. Each user reviewed:
-
- Technique and instrument review
-
- Sensor installation and removal review
-
- Reader review
Each item was graded on a scale of 1 to 5 (strongly disagree to strongly agree) and converted to an overall score ranging from 0 to 100. An adjusted total score of 70 or greater was determined to be acceptable based on the scoring and grading system in Brooke and Duncan. A score less than 70 would require a review by the sponsor and adjustment based on the user's feedback. The results of the usability testing are summarized in Table 6. The average score for each application was above the acceptance criteria of 70.
| Application | Average Score |
|---|---|
| Instruments | $89.5 \pm 12.8$ |
| Sensor | $84.5 \pm 12.3$ |
| Reader | $85.7 \pm 13.2$ |
| Table 6: Usability Results (15 Users) |
|---|
Additional user feedback from the participating surgeons was incorporated into the design and instructions for use of the device. The usability testing did not reveal any enduser problems with device usage.
Brooke IB and Duncan KD. Effects of system display format on performance in a fault location task. Ergonomics (1981); 24:175-189.
Brooke J. A "quick and dirty" usebility" scale. In P. Jordan, B. Thomas, B.A. Weerdmester, and AL McClelland (Eds), Usability Svaluation in Industry. London: Taylor and Francis (1996).
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Intraoperative Usability Testing
The sponsor conducted an intraoperative usability test on five patients undergoing posterior spinal surgeries. The four participating surgeons were blinded to the values obtained by the sensors. A total of 13 sensors were used in six surgeries* at two clinical sites. Summary data for the surgical cases is shown in Table 7 below.
| Table 7: Summary of Intraoperative Usability Testing - Estimated Blood Loss and Operating | |
|---|---|
| Time |
| Patient
| Clinical
Site | M/F | Age | # of
sensors
used | Total
Blood
Loss
(cc) | Est. Blood
Loss during
LOADPRO
use (cc) | Total O.R.
Time (hrs:
mins) | LOADPRO O.R.
usage time
(min: sec) |
|--------------|------------------|-----|-----|-------------------------|--------------------------------|--------------------------------------------------|-----------------------------------|------------------------------------------|
| 1 | (b) (6) | | | 2 | 1,100 | 0 | 4hrs 41min | 16min 30sec |
| 2 | | | | 1 | 3,000 |