Human Factors Analysis-(Ver. 5)April 21, 2008
Team Members: Mitch Barnett, Adrienne Belasco, Urvi Patel, Daniel Wilkinson Advisors: Richard Debski, PhD, Jan Grudziak, MD, PhD, Prerana Patel, MD
Human Factors Analysis
Bone Screw System for Slipped Capital Femoral Epiphysis Applications
Device Users
Pediatric orthopaedic surgeons, SCFE patients, intermediate handlers
Typical and Atypical Device Use
The typical use is in the treatment of SCFE. Atypical use is when the bone screw and/or removal device is used in a surgical application other than that for SCFE. These scenarios may include procedures used to treat spinal compression fractures, femoral or hip fractures, and/or tibial epiphyseal fractures.
Device Characteristics
The screw should be removed (if recommended by the surgeon) from the patient by inserting the hexagonal male part of the removal device into the hexagonal female part of the screw. The first hexagonal depression of the screw descends 3mm from the head down the length of the screw, and the second hexagonal depression descends 9mm from the end of the first. The second hexagonal depression is proposed to reduce the risk of stripping during removal,to minimize the stress raiser experienced at the connection between the screw head and shaft by increasing contact area between the removal device and the screw interface, and to act as a guide pin to favorably align the removal device and sockets.
The surgeon will apply the necessary torque to the removal device to dislodge the screw, resulting in its removal from the bone. Any device use deviating from this protocol results in a deviation from the purpose of the device. Some possible errors that may arise from improper human use of the device are screw breakage, bone fracture, bone degradation due to improper screw application, or removal device breakage.
Environments in Which the Device Will be Used
There are three environments for this system that must be considered: pre-operative storage, a surgical setting, and the patient’s body.
Before the screws and removal devices will be used, they will not require specialized storage. However prior to being used, they must be sterilized with a steam autoclave. During this time period, if the devices are tampered with or not sterilized properly, use in surgery and in patient healing may be compromised.
During the surgical procedure, the devices will be used by surgeons and handled by other surgical technicians and nurses. The realistic human errors which may occur during this environmentare discussed in the Device Characteristics section.
While the screw is inside the patient’s body, it will experience natural forces, both cyclic and continuous. Should the patient exert themselves in a way that is contrary to their recovery plan, the bone screw may loosen, break, or cause trauma to surrounding tissue. The patient may also take pharmaceuticals which weaken bone recovery. This may increase the risk of the screw coming loose and being ineffective or detrimental in patient recovery. Furthermore, the patient may refuse to take pharmaceuticals necessary for proper recovery such as anti-inflammatoryagents, antibiotics, or other necessary supplements. These cases also may lead to unnecessary infection, inflammation, or an overall decrease in patient recovery.