Preparation of Papers in Two-Column Format



Victoria Hicks

Laura Riley

Rena Tchen

Caressa Watson

University of Pittsburgh

Department of Bioengineering

Benedum Engineering Hall B62

Pittsburgh, PA 15213

vagspec@

22 April 2008

Dear Mr. Gartner,

Our senior design team is redesigning the vaginal speculum for optimal patient comfort and physician functionality. By reducing pain and discomfort during pelvic exams, it is our hope to increase the number of women receiving exams annually. To verify the best design for this purpose, we considered patient and physician feedback throughout the redesigning process.

With the help of generous funding from Dr. Hal Wrigley, Dr. Linda Baker and the Department of Bioengineering; and with the mentorship of Dr. Harold Wiesenfeld of Magee Women’s Hospital, we achieved two functional prototypes along the following timeline:

|Task |Date Completed |

|Reception of Pre-design Surveys (Laura, Victoria, Caressa) |January 1st |

|Device Design Plan (All) |January 7th |

|SolidWorks Design, (Caressa, Rena, Laura) |February 8th |

|Acquiring Materials / Physical Prototyping (Caressa, Rena) |February 11th |

|Initial Patient and Physician Feedback (Laura, Victoria) |February 5th |

|Re-design (Caressa, Rena, Laura) |March 24th |

|Acquiring Materials / Final Physical Prototype (Rena, Caressa) |March 26th |

|Mechanical Testing (Laura, Victoria, Caressa) |March 31st |

|Clinical Testing (All) |April 22nd |

|Design History File Documentation (Victoria, Rena) |April 22nd |

|Project Overview Journal Article (All) |April 22nd |

Attached is our full proposal for your review. Thank you for your time.

Sincerely,

Victoria Hicks, Laura Riley, Rena Tchen, Caressa Watson

REDESIGNING THE VAGINAL SPECULUM

Victoria Hicks[1] , Laura Riley[2], Rena Tchen[3], and Caressa Watson[4]

Undergraduate Department of Bioengineering, University of Pittsburgh

Abstract - Current vaginal specula adequately allow physicians to perform pelvic exams, but pain or discomfort experienced during this procedure discourage women from reporting annually to receive this exam. Clinicians also report less-than-optimal visualization of and access to the cervix due to prolapsed vaginal walls, an issue commonly associated with multiparous and obese patients. To improve the exam experience for both clinicians and patients, a novel redesign of the speculum is proposed here. The discomfort and pain can be partially attributed to the pressure the speculum places on the bladder. The new design will be similar to current bi-valve specula, but with the lower valve opening posteriorly toward the rectum. This will allow physicians to easily adapt to the new speculum while improving patient comfort. Finite element analysis of the stress distribution showed that the improved speculum design encounters the greatest stress at the hinges and the handle that controls the valve expansion. Further analysis demonstrated that all components are above a factor of safety of four. Visual access and pressure distribution with the improved vaginal speculum was analyzed using a pelvic exam trainer and validated with a series of clinician surveys conducted at Magee Women’s Hospital in Pittsburgh, PA. Unfortunately, inconclusive results were obtained due to device failure. Future directions include designing a more intuitive trigger mechanism to open and expand the valves as well as an additional compatibility for a lateral wall retraction device.

Key Words: vaginal speculum, Pap smear, gynecologic examination, gynecology

Introduction

Necessity of Vaginal Speculum Design Modification

The vaginal speculum is the primary instrument used by clinicians when performing gynecological exams. During an exam, the speculum is used to expand the vaginal canal for visual inspection of the cervix and cervical cell sampling. These cells are tested for infection, abnormalities (such as those found in pre-cancerous cells), and cancer. An annual pelvic exam is suggested for females who are sexually active or over the age of 21, but physicians have suggested that often failure to adhere to these recommendations is due to the discomfort that patients experience during gynecological exams. In a pelvic exam, the patient lies on her back with her legs in stirrups. The clinician first inserts the speculum and then opens the top valve upward until the cervix comes into view. A swab of the cervix is taken and tested for infection or cancer. Lastly, during the bimanual portion of the exam, the clinician places one hand into the vagina and the other over the abdomen and palpates the reproductive organs.

Current vaginal specula are the metal Graves speculum and the Patton speculum; the latter of the two is less widely used (Figure 1). The Graves speculum is a bi-valve speculum that opens anteriorly, toward the bladder.1 The Patton speculum is used for multiparous or obese patients when the bi-valve Graves speculum is insufficient for the clinician to examine the cervix.2 These specula are approximately $20.00 USD and can be reusable or disposable.1 While the current vaginal specula are usually sufficient, modifications to the current designs may lead to enhanced visualization and cervical access for clinicians while minimizing the discomfort for the patients. [pic] [pic]

Figure 1: Graves metal speculum (left)1 and Patton speculum (right)2.

Current models of vaginal specula include valves that open and expand anteriorly, placing pressure on the bladder. This pressure placed on the bladder is hypothesized to contribute to the discomfort that patients experience. The proposed redesign of the vaginal speculum attempts to alleviate the discomfort associated with current bi-valve specula. The device design would be classified as a Class II device by the Food and Drug Administration (FDA) and would follow a 510(k) guidance (CFR Title 21; Obstetric-gynecologic general manual instrument standards) for approval.3

The objectives of redesigning the vaginal speculum were: 1.) to be operable with one hand, 2.) maintain a minimal insertion size, but be able to scale up for clinical needs, 3.) retain vaginal walls in all directions to allow for optimal visualization of the cervix., 4.) be able to be temporarily locked into an open position, and 5.) improve comfort for all women. Enhancing the patient experience of Pap exams by decreasing or eliminating any discomfort will encourage more women to report annually for this important test. Furthermore, increasing cervical visualization and access for clinicians will ensure improved accuracy in testing. Taken together, our improved vaginal speculum design may increase the rates of early detection while decreasing the incidents of death due to cervical cancer.

Materials & Methods

Pre-Design Surveys

The redesign of the vaginal speculum is an attempt to improve the experience of both patient and practitioner during the routine pelvic examination and certain other gynecological procedures. The beneficiaries of this project include two separate populations—the patient and the practitioner. Thus, it is an important component of this project to fully understand the needs of both. The initial proposed design modification was to alter the opening mechanism of the device to have it open in the posterior direction toward the rectum, in order to relieve pressure placed on the bladder during anterior opening of the device during gynecologic examination, which was hypothesized to cause patient discomfort during examinations. Several rounds of surveys were conducted to quantify the need for this design modification. Preliminary surveys, consisting of seven multiple choice questions and an area for additional comments, were sent to a population of clinicians, with 71 clinicians participating in the survey. The survey was administered using the online survey administration software provided by . Emails were sent to clinicians requesting participation, and the clinicians could access the survey through a provided internet link. The multiple choice questions in the survey assessed: clinician experience in gynecologic field, clinician profession, clinician preference for vaginal speculum material, clinician preference for speculum opening mechanism, clinician preferred light source during gynecologic examinations, clinician opinion of relevance of proposed design modifications, and whether or not the clinician performs exams requiring cervical access. Respondents were randomly selected, geographically diverse clinicians who regularly use vaginal specula in practice at Magee Women’s Hospital in Pittsburgh, PA. Responses from this survey were important to the initial design plans and to the development of a second, more specific survey. A second validation survey, with nine questions and one section for comments, was completed by three clinicians at Magee Women’s Hospital in Pittsburgh, PA. Results from this second survey dictated the design modifications that would be incorporated into the design of a second prototype.

Design Process and Implementation

Results from the preliminary survey allowed for the conception of two different bi-valve speculum designs. Each design was modeled using SolidWorks, a three-dimensional computer-aided design (CAD) software program. A first, bi-valve design prototype was produced, incorporating the desired design modifications. The valve length was approximately 15.0 ± 0.1 cm, the circumference of the valves was about 1.5 ± 0.1 cm and the length of the handle was approximately 12.0 ± 0.5 cm. The maximum diameter of the opened valves was about 30.0 ± 2.0 cm to allow for adequate visual access to the cervix during the pelvic exam. Device dimensions of the Welch-Allyn bi-valve speculum were maintained in both prototype designs. Because each design consisted of several parts (i.e. the top and bottom valves, the handle, and an adjustable screw locking mechanism), each component was modeled individually and designed to hinge together. Using SolidWorks, assembly-structure editing was used, along with collision detection to ensure proper fitting, assembly, and function. Once each part was modeled, the parts were assembled into one complete, movable vaginal speculum. Once assembly in SolidWorks was finalized, stereolithography (SLA) rapid-prototyping was used to fabricate the device components. The resulting device components, made using a photopolymer material, were then physically assembled. Hardware from a stainless steel Graves speculum was used to secure the devices and facilitate the locking mechanisms. Responses to the second validation survey were used to guide modifications for the design of a second prototype. To make the prototype more mechanically robust, the second prototype was made with a thickness of 4.0 ± 0.2 mm using SLA. As well, both the top and bottom valves were rounded to prevent tissue pinching. In addition, a vertical track was added which allowed for further expansion of the two valves if the physician needed more retraction of the vaginal walls. The same hardware was implemented in the second design which allowed for a smooth, continuous expansion of the valves.

Testing: Mechanical and In Vitro

The second prototype was subjected to both mechanical and in vitro testing. Using COSMOSWorks, finite element analysis (FEA) of stresses on the device and the device factor of saftey (FoS) was performed on the 3D SolidWorks design of the second prototype. During this analysis, a 5N normal force was applied to both valves (top and bottom), a 7N normal force was applied to the handle and the device was restrained in space in order to simulate the pressures applied when the device is used in gynecologic applications.

In vitro testing was performed on the device using a female pelvic trainer. The pelvic trainer was designed to simulate pelvic anatomy and appropriate landmarks of a human female. The final vaginal speculum prototype was subjected to physician opinion of device efficacy. Using the pelvic trainer, Dr. Harold Wiesenfeld, M.D. of Magee Women’s Hospital in Pittsburgh, PA performed a pelvic exam using the second design prototype and compared the prototype to two current plastic models. Our prototype most closely resembled the metal Graves speculum, however using metal specula in the pelvic trainer was prohibited due to increased risk of tearing the trainer. During the examinations, the resulting visualization in the pelvic trainer was recorded. The performance of the prototype and the two plastic models were assessed by the physician using a physician survey. The physician completed the survey, ranking functional elements of the devices using a 1-5 scale with 1 being unacceptable, 3 being neutral, and 5 being excellent. Specifically, the physician was asked to rank the following elements regarding the visibility provided by the devices: sufficient opening of the vaginal canal for visualization, sufficient external light reaching the cervix, and obstruction of the cervix. The physician also ranked the following elements of device “feel”: smoothness of opening and sturdiness of hinging mechanism. Further, the physician ranked the overall ease of use of the devices by analyzing if the speculum handle was in the way and if the sizing of the device was appropriate.

Pressurex (Madison, NJ) tactile pressure sensor films were also employed in the in vitro testing to evaluate the pressure distributions produced by the device designs when used in the pelvic trainer. These pressure sensor films capture a still image of pressure sensor distribution and magnitude. Pressure readings were performed by the group members using the sensors. The pressure sensors were secured to both the top and bottom blades of the prototype and the two plastic specula. The devices were then independently inserted in the pelvic trainer and opened as would occur during a pelvic examination procedure (until the cervix came into view). The resulting pressure readings were recorded and evaluated.

To obtain further visualization data, testing was performed by inserting the prototype and the two plastic specula into 4 layered condoms each. This condom layering was to simulate physiologic pressure applied to the specula during gynecologic examinations. Once inserted, the visualization achieved by the three devices was recorded. Pressurex pressure sensor films were again applied to the valves of the specula to determine the pressure distributions and magnitudes caused by each device when encountering the simulated resistance.

Results

Of the 70 responses to the pre-design surveys, 82.6% preferred a stainless steel speculum over plastic, 58.0% favored using a speculum with an external light source, and 95.6% would choose a gradual, continuous expansion/locking mechanism versus a step-wise, discontinuous one. An interim validation survey on the first prototype was given to nurse practitioners for feedback and to guide redesigns of the second prototype. Three clinicians were asked:

| |Survey Questions |General Consensus |

| |Would opening the speculum |Maybe |

| |downwards toward the rectum | |

| |decrease patient discomfort? | |

| |Do you believe that this new design|Yes |

| |would be useful in clinical | |

| |practice? | |

| |If you were in charge of modifying |Round the edges, intuitive trigger|

| |our design – what changes would you|mechanism, make valves longer, |

| |make? |smoother handle |

| |Would you add this device to your |Yes |

| |repertoire? | |

Finite element analysis of the top piece, seen in Figure 2, showed that the highest stresses occurred at the 90° corners between the valve and handle. The maximum von Mises stress reported in this area were approximately 24.220 kPa. Analysis of the bottom piece, also seen in Figure 2, revealed that it experienced higher stresses centered within the lever used for opening the device, sometimes referred to as the thumb-piece. This area experienced stress reaching up to about 4388 kPa.

Figure 2: FEA stress analysis of top (top) and bottom (bottom) pieces is shown above.

Factor of safety (FoS) analysis, shown in Figure 3, revealed that both top and bottom pieces exceeded the necessary expectations for a vaginal speculum. The top piece maintained a factor of safety around 100. Most of the bottom piece also showed a factor of safety near 100, however the thumb-piece showed a minimum factor of safety of 4.274. Both pieces met and exceeded the requirements for critical components for medical devices (FoS > 4).

[pic]

[pic]

Figure 3: Factor of safety (FoS) analysis for top (top) and bottom (bottom) pieces is shown above.

In vitro comparison testing for visibility, relative pressure, and overall ease of use, returned inconclusive results. After both plastic models (seen in Figure 4) had been tested and rated for visibility and overall ease of use, the second prototype was inserted for testing. Device failure occurred during the opening of the prototype in the pelvic model, as seen in Figure 5. Due to the device failure, no data could be obtained to compare its visibility with either plastic model, nor could relative pressure testing take place. However, some feedback was received from the testing physician prior to failure and this was recorded, along with the comparison between plastic specula, in Table 1. The physician rated the prototype as having a smoother opening mechanism than either of the two plastic models and all three specula were determine to be of appropriate size for both physician handling and patient comfort.

Other comments noted include praise for the device design and an “excellent opening mechanism”. The physician also reported that the rigidity of the pelvic trainer was very unrealistic and that the prototype would have worked in an environment that more closely resembled actual physiological conditions of the vagina. Damage to both the prototype and one of the plastic specula was incurred due to the rigidity of the pelvic trainer’s exterior and vaginal canal (see Figure 6).

[pic]

[pic]

Figure 4: Plastic specula used for in-vitro testing with the pelvic trainer. (Top) Plastic speculum #1. (Bottom) Plastic speculum #2.

Table 1: Results from in vitro testing with the pelvic trainer model.

[pic]

Figure 5: Second SLA prototype broke during in-vitro testing due to excessively rigid external genitalia of the pelvic trainer.

[pic]

Figure 6: Picture of shredded teeth in Plastic speculum #1.

While the trainer’s rigidity compromised the integrity of two specula, testing for relative pressure experienced by the valves of a speculum was completed for only one of the plastic models. As shown in Figure 7, greater pressure is exerted by the top valve compared to the bottom valve when inserted into the pelvic trainer.

[pic]

Figure 7: Pressure test results for Plastic speculum #1 when inserted into the pelvic trainer.

Further pressure testing using layered condoms was performed after the prototype was mended with special epoxy. This testing yielded more inconclusive data regarding the relative pressure exerted by the valves of each speculum. However, it showed that the prototype did in fact provide adequate visibility, similar to current plastic specula. (See Figure 8 below for visualization testing results.)

[pic]

Figure 8: Visualization of our second prototype was similar to the metal and plastic specula when constrained by layered condoms during the second round of in vitro tests.

Discussion

The most pressing question when reviewing the results is why, despite the positive FEA and FoS analyses, did the prototype break during in vitro testing? Evaluating the FEA stress analysis showed that the improved speculum would sustain high stress in all areas except for the sharp corners of the top valve and the midsubstance of the thumb-piece which corresponded to areas where the prototype suffered damage during testing. When assessing the areas of relatively high stress with respect to the prototype factor of safety, the stresses found were minimal in comparison to the prototype yield stress. A critical component, one whose failure results in serious injury, death or financial loss, is generally engineered to maintain a factor of safety of four or greater. A non-critical component is engineered to a factor of safety of two or greater. By these standards, our non-critical prototype with a minimum factor of safety of 4.274 for both top and bottom valves was predicted to have been more than sufficient to withstand loading during in vitro testing with the pelvic trainer.

Two preventable causes contributed to prototype failure: approximated FEA analysis and unrealistic mechanical properties of the pelvic trainer. Due to software difficulty when performing the FEA, only the average yield stress of SLA (45 MPa) was input into COSMOSWorks for the stress and factor of safety analyses. All other mechanical properties of the material were defined as ABS plastic, which is much stronger than the resin used to produce the SLA device. Although the yield stress was very low, the overall material behaved differently than SLA. This user error may have contributed to premature prototype failure. With this in mind, the FEA showed areas that would undergo the greatest amount of stress, but did not accurately gauge the amount of stress that would lead to prototype failure. Secondly, the mechanical properties of the pelvic trainer were physiologically inaccurate; applying nearly 85 psi (586.05 kPa) to the pressure strips placed on the plastic speculum #1, far exceeding the in vivo loading conditions (up to approximately 485.44 Pa).4 The excessive pressure also compromised the teeth of the locking mechanism in plastic speculum #1, refer to Figure 6. Even in disregard of the information obtained from the stress analysis, the prototype still may have failed during expansion in the vagina of the pelvic trainer due to the excessively rigid vaginal walls of the pelvic trainer. Physician feedback during in vitro testing suggested the rigid walls of the pelvic trainer were to blame for prototype failure, rather than the prototype design itself.

Qualitative feedback from Dr. Wiesenfeld during in vitro testing showed that Plastic speculum #1 was inferior to Plastic speculum #2 in regard to visualization of the cervix due to obstruction of the view by the handle. While many of the fields of comparison of the plastic specula to our prototype were not applicable due to device failure, the physician did positively note that the prototype had smooth, incremental expansion compared to the plastic specula. In addition, the sizing of the prototype was appropriate. To avoid bias, further follow-up surveys by a number of physicians upon creation of a third and final prototype is required.

Despite the inconclusive results of in vitro testing, the pressure strip test performed using Plastic speculum #1 supported our proof of concept, indicating that more pressure is focused on the top valve compared to the bottom valve. It showed that at least with common plastic specula used today, there is greater force exerted on the top valve than on the bottom valve during speculum expansion. Because our prototype broke prior to pressure strip testing, we were unable to determine if our design would exert less pressure anteriorly on the top valve, and more pressure posteriorly on the bottom valve. Additional testing would be necessary to confirm our suspicions.

The second round of testing conducted with layered condoms demonstrated that our repaired prototype maintained adequate visibility, similar to current speculum designs. The pressure sensor results were also inconclusive because the device was inserted into condoms, which exerted similar pressure on both the top and bottom valves. Additionally, the condoms were not able to simulate anatomical downward slope of the vaginal canal.

Review of Progress

According to the project timeline created at the beginning of the spring semester, we were able to maintain project deadlines. The surveys of physician design feedback were completed by January 1st. The first prototype design plans were completed by January 7th; the SolidWorks design of the first prototype was completed by February 8th and produced using stereolithography by February 11th. The initial physician surveys were completed by February 5th and a SolidWorks design of the second prototype was completed by March 24th. The second prototype was rapid prototyped by March 26th and modified to fit hardware on March 28th. In vitro testing was performed on March 28th as well. Finite element analysis of stress and factor of safety analysis were completed on March 31st. A second round of in vitro testing with layered condoms occurred on April 2nd, completing the in vitro testing of the second prototype.

As the design and redesign process progressed, some original goals were dismissed and others emphasized. For the first two prototypes, expansion of the lateral walls was not considered as we focused on the visibility and functionality of the design. Both prototypes were made to dimensional specifications, operable with one hand, were expandable posteriorly, had smooth expansion control, and were able to be locked temporarily in an open position. The first prototype had an ergonomically designed handle that was removed due to potential difficulty in cleaning the device before sterilization. The design of the handle in the second prototype was adapted from the Graves metal speculum and a third piece was added to the assembly to allow for vertical expansion of the valves. The second prototype was also thickened for testing purposes to 4 mm ± 0.2 mm.

Future Works

If additional resources were available, a third and final prototype would be designed using SolidWorks. The final design would primarily consist of adjustments to the second prototype to allow easier assembly, specifically the fitting of hardware. More importantly, the third design would include a small clip of both sides of the handle that would be compatible with a lateral wall retention device, the LEEP Redundant Wall Vaginal Retractor 7-3/4” (19.5cm) long, medium 22mm x 57mm blade.5 The wall retractor would improve visibility for physicians when examining prolapsed and obese women, while maintaining the versatility of removing the retractor to examine the vaginal walls. The LEEP Wall Retractor is pictured below in Figure 9. A more intuitive trigger mechanism for opening may also be considered. However, the trigger mechanism would require two levers and three hinges to work appropriately. While the design is possible, the intricacies of the design may interfere with cleaning and be less beneficial than anticipated.

[pic]

Figure 9: LEEP Redundant Wall Vaginal Retractor 7-3/4” (19.5cm) long, medium 22mm x 57mm blade would be made compatible with the final prototype for lateral wall retention.5

The third and final prototype would be stamped out of stainless steel. Type 316, 316L, and similar grades of stainless steel are known to be highly biocompatible for both implants and medical equipment.6 For redesigning the vaginal speculum, stainless steel will provide the necessary strength and smoothness for clean insertion without binding or pinching the vaginal tissue. Plastic is also commonly used for speculum strength and smoothness; however stainless steel can be conveniently sterilized for multiple uses. Therefore, the entire construct will be manufactured out of stainless steel. Two types of stainless steel are the most appropriate for this application: type 316 or versions of type 316 with improved machinability such as “Ugima”.7 Despite variations in production, stainless steel can withstand up to 170 MPa of pressure, exceeding the strength needed for this application. Type 316 is the second most common grade of surgical stainless steel used. It is also known as "marine grade" stainless steel due to its increased resistance to corrosion compared to other materials. The alternative versions of type 316 offer significantly improved machinability compared to standard 316 or 316L stainless steel, giving higher machining rates and lower tool wear in many operations without compromising the mechanical or material properties.7 “Ugima” in particular is available in round and hollow bar products, which may be ideal for machining the final speculum design.

In addition, the final prototype would be used in clinical trials to determine if posterior expansion is truly more comfortable for patients than the anterior expansion of current specula. Visibility and mechanical testing will need to be revisited as well to ensure the safety and efficacy of the device. Prior to clinical testing, IRB approval would be needed and an FDA 510(k) application for a Class II device submitted according to CFR Title 21; Volume 8; Sec. 884.4530 Obstetric-gynecologic general manual instrument.3

Acknowledgments

We would like to thank our mentor Dr. Harold Wiesenfeld of Magee Women’s Hospital, Joseph Samosky, PhD of the WISER Center and Andy Holmes for their guidance. We would like to additionally acknowledge our sources of funding from the generous gift of Drs. Hal Wrigley and Linda Baker and the University of Pittsburgh, Department of Bioengineering.

References

1] NexTag, Inc., Graves Speculum – Compare Prices, Reviews and Buy. 2008. Last Accessed 4/21/08.

2] Gynecological Speculum for Obese Women. Department of Mechanical, Industrial and Manufacturing engineering, College of Engineering, Northeastern University. 2002. iris.lib.neu.edu/getblob?blobid=2896777267340242

3] CFR Title 21Volume 8, Part 884 Obstetrical and Gynecological Devices. Food and Drug Administration. 2007. Last Accessed 4/21/08.

4] Baguley SDK et al. Vaginal algometer: development and application of a device to monitor vaginal wall pressure pain threshold. Physiol Meas. 2003 (24): 833-836.

5] Claflin Medical Equipment: Miltex Inc., 2006. Accessed 4/21/08.

6] Ratner, B.D. Biomaterials Science: An Introduction to Materials in Medicine. Elsevier, New York. Pg 539, 141-143. Second Edition, 2004.

7] “The A to Z of Materials.” 03 December 2007.

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[1] Victoria Hicks, Victoria.j.hicks@gmail.edu

[2] Laura Riley, laurariley@

[3] Rena Tchen. rena.tchen@

[4] Caressa Watson, cnw2@pitt.edu

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