Important to Know

When working with neurosurgical clamps, it’s important to take anatomy into consideration for the design process. The pins of the Mayfield Clamp are connected to the external table of the skull as shown in Image 1. As Thijs and Menovsky et al (2021) suggested, “These pins must never penetrate the weakened or the thin region.” The anatomy section aims to show a representation of the brain sections, their purpose, and location to understand the approach required to avoid damaging any sections with M.O.C.C.A.’s product.

Frontal Sinus

The frontal sinus is paranasal1 sinus within the frontal bone. Although the size and shape can vary by person, the two asymmetrical chambers on each side of the septum extend from the medial end of the eyebrow to the orbital portion of the frontal bone. The purpose of the frontal sinus is to produce mucus to keep the nose from drying out. When planning the design specifications for children, it’s important to consider the development begins from ages 1-12 years old. As previously mentioned, variant anatomy can be present in patients such as the frontal sinus may be absent (aplasia), underdeveloped (hypoplasia), or may be large.

Temporalis Muscle

The temporalis muscle is a broad, radiating muscle located in the temporal fossa of the skull from the zygomatic arch to the coronoid process of mandible (Gatterman & McDowell, 2012). A main function of the temporalis muscle is to produce the movement of the mandible at the temporomandibular join to produce the act closing the mouth through the upper and anterior fibers and retracting mandible through the posterior fibers (Grujicic, 2022) (Gaillard, 2022).

Mastoid Bone

The mastoid bone is a section of the temporal bone also known as the mastoid process. It’s located right behind the ear and serves as an attachment to head muscles. The mastoid is composed of air-filled spaces that extend from the antrum called mastoid air cells (Shahid, 2022). The air cells protect the delicate structure of the ear, regulate the ear pressure, and protect the temporal bone from trauma (Marks, 2021). The mastoid bone joins with the superior, posterior and anterior bones. The mastoid bone is absent at birth, however, at infancy to puberty, the mastoid develops from the squamous and petrous part of the temporal bone. By the age of 4, mastoid air cells are created in 80% of people

Temporal Squamous

The squamous temporal lobe is the convex shaped area of the skull that attaches to the temporalis muscles and creates a boundary known as the temporal fossa. The squamous temporal lobe forms the zygomatic process which is the bone structures that protect the eye and provide movement for the mandible which is part of the masseter muscle and is crucial in the formation of the masseter muscle (Deng, 2021). It’s important to note that the temporal squama protects the temporal section of the cranium which tends to be softer and more prone to injuries from blunt force traumas such as the 60–80-pound force applied by the Mayfield clamp.

Skull Fractures

A depressed skull fracture occurs when part of the skull presses inwards which happens when areas such as the middle cranial fossa are impacted. Overall areas of the skull that should be avoided are the middle cranial fossa, cribriform plate, the anterior cranial fossa, and the area in between the Dural sinuses and the mastoid region (Martinez-Lage, 2010). In the figure below a depressed skull fracture is evident in the patient's skull which is caused by using the pin type head holder otherwise known as the Mayfield clamp.

FDA Approval

510(k) Procedure/Testing. A 510(k) or Premarket Notification (PMN) is the sections of the Food, Drug and Cosmetic Act, which manufacturers have to notify the FDA of a intention to request a new medical device 90 days before being released on the market. The 510(k) procedure for a skull clamp to specific a Mayfield Skull Clamp under the Integra LifeScience Corporation consist of several test show below:

Test	Result
Skull Clamp Gauge Characteristics – Establishes the characteristics of the integral force gauge on the skull clamp	Pass – The skull clamp was capable of indicating impingement force in increments of 20 lbs. up to 80 lbs., and was accurate to within the ± 4 lb. limit at each force graduation.
Skull Clamp Range – Determines the physical limits of the skull clamp adjustment	Pass – The clamp provided a range of positions form 4 inches through 9 inches.
Skull Clamp Static Load – Verifies the ability of the skull clamp to sustain an 80 lb. load to a 2x factor of safety	Pass – The clamp supported 160 lb. for no less than 24 hours without mechanical failure.
Skull Clamp Load Loss – Verifies the ability of the skull clamp to maintain a user defined load in use	Pass – The clamp provided a static clamping for of 80 lbs. for 24 hours without a loss of loading greater than 5%.
Skull Clamp Transient Torque – Verifies the ability of the skull clamp to resist transient torque while in use	Pass – The swivel locking mechanism was capable of withstanding a dynamic torque of 20lb/ft. for 30 seconds without mechanical failure.
Skull Clamp Vertical Shear – Verifies the ability of the skull clamp to support an applied vertical load	Pass – The loading mechanism was capable of withstanding a vertical shear loading of at least 100 lbs. at 80 lbs. pin loading.
Skull Pin Compatibility – Verifies compatibility of the skull clamp with MAYFIELD Skull Pins and Base Units.	Pass – The skull clamp demonstrated compatibility with MAYFIELD Skull Pins and the A3100 series of MAYFIELD Base Units.
Manual Cleaning Validation – Validates the effectiveness of the manual cleaning process on the skull clamp.	Pass – The skull clamp demonstrated a protein level < 6.4 pg/cm^2 and hemoglobin < 2.2 pg/cm^2 following the manual cleaning process.
Low Level Disinfection Validation – Validates the effectiveness of the low-level disinfection process on the skull clamp	Pass – The skull clamp demonstrated a 6 log ₁₀ reduction or better for S. aureus, E. coli. K. pneumoniae and P. aeruginosa following the thermal disinfection process.
Thermal Disinfection Validation – Validates the effectiveness of the thermal disinfection process of the skull clamp	Pass – The skull clamp demonstrated a 6 log ₁₀ reduction or better for S. aureus, E. coli. K. pneumoniae and P. aeruginosa following the thermal disinfection process.
WHO Performance Test – Verifies the ability of the skull clamp to withstand repeated cycles of the WHO (World Health Organization) recommended guidelines for decontamination without mechanical failure	Pass – The skull clamp was capable of withstanding 15 cycles of the WHO decontamination process without mechanical failure.
Autoclave Preconditioning Test – Verifies the ability of the skull clamp to withstand repeated autoclave cycles without mechanical failure	Pass – The skull clamp was capable of withstanding 15 autoclave cycles of 134℃ for 60 minutes and passed all mechanical testing following autoclave preconditioning.
Shipping Verification Test – Verifies that the packaging for the skull clamp is capable of protecting the device during transit to ISTA Procedure 2A standards	Pass – The packaging for the skull clamp was not breached during the ship test. The skull clamp remained undamaged and passed all function checks during inspection.
Biocompatibility	Pass – No component contacts the patient; therefore, no biocompatibility studies are required

Current solutions include the following:

Head support and stabilization system (F. Sklar, C. E. Dinkler, & K. R. Easton | Integra Lifesciences Corp).

The patent product created by Intergra Lifesciences Corp serves the purpose of solving the issue of flexibility caused by the 3-pin Skull Clamp structure that is commonly used. The product provides high flexibility to use in a wide range of surgical procedures. The system provides sperate and independent support and stabilization devices and is located close to the end of the patient support table to provide complete support to pediatric patients. Although the project doesn’t solve the original problem, it should be taken into consideration due to its ability to be used in a range of surgical procedures.

Why is this problem important?

Our main motivation to work on this project is to address complications that are caused by the Mayfield Skull Clamp’s unnecessary and accidental penetration of the human skull due to the improper use of the pins resulted in Internal bleeding, accidental insertion of air or gas into veins or the cranial region, and damage to major arteries. Medical cases in which the previously mentioned complications have occurred are included below:

Discussion 1: Epidural Hematoma caused by the Mayfield Skull Clamp

The first discussion is based on the pin mechanism as this is the most crucial factor that must be considered during any future attempt at redesigning this device. This reasoning being that EDH (Epidural Hematoma) is one of the most common complications that occurs with the use of the Mayfield Skull Clamp.

The first recording of a patient acquiring Epidural Hematoma due to the Mayfield Skull Clamp occurred in 1984, this was on a 10-year-old female patient who was referred because of strong headaches, vomiting, and was experiencing hemiparesis (bodily weakness) on the left hemisphere of her body. After a CT (computed tomography) scan had detected a large lesion within her right frontal-temporal region. A craniotomy was performed as soon as possible to remove the lesion. However, ten days after the procedure the female patient pointed out a reemergence of headaches and vomiting. A CT scan showed that there was EDH at the right parieto-occipital skull region, where the child pin was inserted. This eventually caused an additional craniotomy to remove the hematoma near the skull lesion. After this, the patient experienced a full recovery in 4 weeks.

Based on the interpretation of the doctors that performed the surgery, the impression fracture caused by the Mayfield Skull Clamp was due to the long-standing intercranial pressure or hydrocephalus. Hydrocephalus is a condition in which cerebrospinal fluid (CSF) builds up within the brain's ventricles. CSF surrounds the brain and the spinal cord, which if blocked up (through the pin in the clamp), the ventricles enlarge which increases the pressure inside the head of a patient.

Discussion 2: Venous Air Embolism caused by the Mayfield Skull Clamp

The second part of this discussion concerns the second most common complication that occurs due to the improper usage of the Mayfield Skull Clamp. This being the Venous Air Embolism, this condition is when the outside air enters a vein and creates a bubble or a clot. This eventually results in a patient experiencing a heart attack, stroke, or even a respiratory failure as the clot can move throughout the system.

The underlying mechanism behind this deadly condition is that bubbles caused by external gases like air move through the body. If it reaches the heart, the pulmonary artery pressure rises rapidly, this results in a rapid blood pressure decrease in the systemic blood pressure. As a result, it generates a respiratory arrest as the peripheral pulmonary pressure drops due to the rapid pressure drop, which usually results in a heart attack or stroke.

From Discussions 1 and 2, we can prevent a patient’s chance of acquiring Epidural Hematoma and Venous Air Embolism through two means. First by preventing full penetration of the skull or having strict guidelines to how much force surgical pins (for children and adults) provide to a patient's skull. Ideally, this can be modeled by finding the relation between the thickness of the skull to the geometric constraints of the pins being inserted into the skull.

Discussion 3: Additional Complications caused by the Mayfield Skull Clamp

The third part of this discussion involves the other miscellaneous recorded complications that occurred due to the Mayfield Skull Clamp usage in neurosurgery.

The first is Traumatic superficial temporal artery aneurysms, a condition in which an aneurysm is caused by trauma at the superficial temporal artery. This classifies them as pseudoaneurysm instead of a true aneurysm in which true aneurysms are induced by blockages of arteries which creates ballooning in the artery and ruptures the artery. In this recorded case, this traumatic superficial temporal artery aneurysm occurred after an intracranial aneurysm surgery was performed. Three weeks later, the patient returned after a growing mass was in the left of the temporal region, where a pin had punctured during the procedure. This mass was tied up and removed.

The second is Tension Pneumocephalus, a condition in which air accumulation in the intracranial cavity in the epidural, intracerebral, intraventricular, or subarachnoid region. The first documented case of Tension pneumocephalus was in April 1982, after headache and vomiting, the patient entered a coma. An emergency ventriculus-peritoneal (VP) shunting was performed successfully. A computerized tomographic (CT) scan showed that there was a large, yet partially calcified tumor. A craniotomy was performed successfully to remove the calcified tumor. However, after an hour, the patient developed a seizure and comatose at the right frontal area where the pin for the head holder was placed. Air had entered the subdural space through the stab wound. After 14 days (about 2 weeks) an infarction in her right occipital lobe had caused the patient to be in a vegetative state until her death after 3 years.

Competitive Products:

Dr. Nawaz Hack is a neurosurgeon in McAllen Hospital who uses the Mayfield Clamp in his everyday work life. His main issue with the skull clamp is that it causes post operative complications due to lack of safety valves such as pressure monitors. In addition, he specified that he would like for the clamp to be more mobile since the clamp tends to be fixed and does not allow for a large range of motion. Dr. Hack highly emphasized that by including a pressure monitor on the device many of the issues previously mentioned could be eliminated since the over-tightening of the bolts is one of the main faults of the Mayfield clamp.

Dr. Jacob Freeman is a neurosurgeon in Florida, and he too handles the Mayfield clamp at work. Dr. Freeman’s main issue with the clamp is the way that the Mayfield clamp is adjusted since it has a release mechanism that makes it harder for the clamp to be adjusted quickly. In addition, he specified that some aesthetic issues such as blood and fluid building up towards the bottom of the clamp’s base.

Our proposed solution

“We propose this design to liberate the amount of pressure in the skull and have a safer way by preventing slippery before and after surgery. The prototype will be more efficient and minimums work need for setup as well to release when emergencies happened during surgery.

Eliminated concept designs:

The Audrino is utilizing 2 Load Cells connected to 2 HX711 amplifiers and transmitted wirelessly via a HC-05 Bluetooth Sensor.

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Final Product

The final product created will focus on both main points which are pressure/load reading electronically as for the single screw will have the distribution of load using the spring-bearing system. Having this point cover will make the changes that will be an improvement to the Skull Clamp. This will facilitate the operation process as well as data analysis for future surgeries for each patient. This will also help out for future research on the cranial area of human development and foster a new field of research to explore for many scientists. Our Skull Clamp , proven to be an innovative prototype that engineers and medical professionals will acknowledge the improvement that the skull clamp will bring to the medical field.

Future Work

Summer 2023 (May - August)	Fall 2023 (August - December)
May – Ensure materials arrive and confer description details.	August: – Setup Clamp with electrical mechanism together
June – Code/Assemble Load Cells with Pins and manufacture Design Attachment for Pin & Clamp	September – Further optimize final design
June - July – Improve Simulation of Clamp and begin Hallow Clamp Machining	October – All data base collected and final improvement
August – Continue Machining "Begin Trails"	November – Final Working prototype
	December – Start treating patients

In Conclusion

According to the results of the study it can be concluded that the integration of the spring-bearing like design is effective in decreasing the maximum contact pressure at the singular site. The contact pressure decreased in comparison to the current clamp. In addition, a peak load of 90lb-130lb before the skull cracked was reached using the spring-bearing like design which further proves the efficiency and improvement that the new design provides. Overall, further medical testing needs to be done on cadavers to fully substantiate the previous claims. However, with the data gathered it is a promising approach that can improve patients' safety and postsurgical outcomes.

References

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Acknowledgements

We would like to extend our gratitude to the following for their integral roles in our school engineering project:

Course Instructors: Dr. Noe Vargas Hernandez and Mr. Greg Potter for exceptional guidance.

Advisors: Dr. Nawaz Hack, Dr. Arturo Fuentes, and Dr. Javier Ortega for invaluable mentorship.

Institutional Support: UTRGV for a conducive environment.

Peers: Fellow students for collaboration and shared passion.

Our team members for dedication and diverse skills.
This project's success is a result of collective efforts and expertise.
Thank you all, From: Team M.O.C.C.A @UTRGV