Design and development of a new biomedical/open sur-gical instrument

doi:10.4236/jbise.2009.26063

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Vol.2, No.6, 435-438 (2009)

doi:10.4236/jbise.2009.26063

JBiSE

Design and development of a new biomedical/open

surgical instrument

Zheng Li

University of Bridgeport, Bridgeport, USA

Email: [email protected]

Received 19 May 2009; revised 30 May 2009; accepted 1 June 2009.

ABSTRACT

This article introduces a new biomedical / open

surgical instrument to assist surgeon in apply-

ing surgical clips to patient’s body tissue and

blood vessel during surgical processes. The

new clip delivery system is designed to better

the clip’s distal advance through internal clip

channel, jaw guiding track, and all other transi-

tion areas to keep surgical clip from accidental

shooting out during clip’s distal move into jaws.

Currently the clip distal move in normal surgical

instrument is usually driven by compression

springs and some complains of clip accidental

drop-off were recorded in surgical procedures.

Because higher request of dimensional toler-

ance and better component surface quality are

needed in case the compression springs are

used as driven force, a little dimensional devia-

tion or less qualified part surface produced from

manufacturing processes will potentially cause

surgical clip device malfunction or misfiring of

the clips. It is clearly known that the jaws can

seriously sever or damage patient’s blood ves-

sel or body tissue if there is no clip inside the

jaws due to accidental clip drop-off, when sur-

geons close instrument handles. The improved

internal system design in this new open surgical

instrument can prevent clip from accidental

drop-off because of well guided and controlled

clip distal move through internal clip channel

and track. Besides the operational force to fully

form clip is lower than existing surgical clip de-

vices due to better mechanical advantage in this

new instrument design. In addition to the above,

manufacturing and product cost can be de-

creased since lower requirement of dimensional

tolerance and surface quality of instrumental

parts is allowed in this new surgical instrument

design. This new instrumental prototype is build

upon the analysis of computer aided modeling

and simulation to prove its good mechanical

advantage, feasible function, reliable perform-

ance. The preliminary results of instrument fir-

ing force from both computer aided modeling

and prototype testing are very close to each

other, and preliminary prototype testing shows

no accidental clip drop-off in this new biomedi-

cal / surgical clip instrument.

Keywords: Blood Vessel; Body Tissue; Ligation;

Computational Modeling; Mechanical Advantage

1. INTRODUCTION

It is critical for surgeons to apply surgical clip instru-

ment to the severed organs, blood vessels and body tis-

sues to stop bleeding in surgical procedure [1,2,3]. The

surgical clip instrument jaws should be put around patent

blood vessel or body tissue and clips can be closed to

secure the vessel and tissue to prevent them from bleed-

ing when surgeon bring instrument handles together.

Next surgical clip will be automatically driven into in-

strument jaws through internal clip channel when sur-

geons release instrument handles.

The surgical devices to apply clips onto blood vessel

and body tissue have been developed for many years [4,

5,6]. It includes single clip and multiple clip applications

[7,8,9]. Next clip can be loaded into instrument after

firing each clip in single clip applications and multiple

clips can be sequentially applied to the vessel or tissue in

multiple clip applications. The surgical clip devices usu-

ally have two handles, a master body, a clip loading and

crimping assembly, clip driving mechanism and some

other functioning components such as clip pusher and

jaws. The improvement for better clip advancement and

lower cost instrument is continued to develop more reli-

able, better functional and cost-effective clip instruments

to support surgeons in their surgical processes.

Some complains were previously recorded from clinic

fields showing several incidents of accidental clip

shooting out from jaws while clip was driven into jaws

Z. Li / J. Biomedical Science and Engineering 2 (2009) 435-438

436

Openly accessible at

in clip instruments using compression springs as driving

force. These incidents showed that the closed jaws will

potentially sever or damage blood vessel or body tissue

if there is no clip in jaws. The accidental clip drop-off is

mainly caused by improper control of dimensional tol-

erance when manufacture the instrumental components.

The surgical instruments in which surgical clips were

driven by compression spring require higher dimensional

tolerance control and better surface quality during com-

ponent manufacturing and this will lead a low volume

and high cost instrumental production, otherwise the

clips will drop-off or shooting out if dimensional toler-

ance are too loose or clips will jam or not move by

spring force if dimensions are too tight.

This new instrument design has different clip delivery

system compared with current clip instruments. The dis-

tal movement of clip pusher driven by instrument han-

dles gradually advances clip from clip magazine,

through clip channel and transition area between clip

channel and jaws, and finally form clip after clip being

driven into guide track in jaws. The clip pusher returns

proximally to its original start position when surgeons

release instrument handles and then readily picks up next

clip. Since the internal clip delivery can be easily and

well controlled through simple lever-linkage driving

system in this new design, the accurate dimensional tol-

erance control and higher surface quality are not re-

quired during production and manufacturing processes

of instrumental components. This can lead cost-effective

machining process, increase production volume, and

reduce production cost. The preliminary prototype test-

ing also indicates that there is no accidental clip shooting

out in this new instrument design and operational force

to fully form clip is lower than current surgical clip in-

struments.

This new instrumental prototype testing has been

conducted on dogs including vascular occlusion, ligating

for tubular ducts, and applying surgical clip to animal

tissue. In vitro and in vivo studies were conducted to

investigate the clip holding force, degradation rate, and

tissue reactivity for clips of titanium material. The clips

were applied across excised canine cystic ducts by this

new instrument and both axial and transverse pull-off

forces have been recorded and measured. In the next

phase, the titanium clips were implanted subcutaneously

into the animals and the remaining strength within the

clips has been measured after 1, 3, 5, 7, 9, 11, 13, or 21

days. The preliminary results show that the clips applied

by this new surgical instrument function properly.

The preliminary testing results also indicated that

there is no clip shooting out in this surgical instrument

design and the operating force to fully form the clip is

between 3.16 lbf and 3.30 lbf which are lower than 4 lbf

in existing surgical instrument.

2. ANALYSIS OF NEW SURGICAL CLIP

INSTRUMENT

The prototype, instrument front and rear portion views

of this new surgical instrument are indicated in Figure

1-3. First the instrument will be put around patient blood

vessel or body tissue. When surgeons start and gradually

close instrument handles, clip driven by clip pusher ad-

vances distally from clip magazine through internal track

and channel into jaws and finally secured blood vessel or

body tissue. The instrument jaws can be open as sur-

geons release instrument handles, and clip pusher and

driving bar return to its original start positions. Com-

pared with current instrument that clip delivery is driven

by compression spring, the clip being loaded into jaws is

well guided and controlled in this new instrument design.

The driving bar linked to instrument handles at pivot

point moves distally to drive clip pusher that advances

clip steadily into jaws as surgeons gradually close surgi-

cal instrument handles. Such a stable clip linear motion

in this new design can be easily and well controlled by

surgeons to prevent clip from accidentally shooting out

from instrument. The preliminary prototype testing of

Figure 1. Prototype of new surgical instrument.

Figure 2. Front portion view of new surgical instrument.

Z. Li / J. Biomedical Science and Engineering 2 (2009) 435-438

437

Openly accessible at

Figure 3. Rear portion view of new surgical instrument.

Figure 4. Force analysis diagram in instrument.

this new design indicated its proper and reliable per-

formances with no clip shooting out and lower opera-

tional force than usual to form surgical clips.

3. COMPUTATIONAL MODELING AND

ANALYSIS

Referring Figure 4, the energy balance and force equa-

tions in this new surgical instrument design can be de-

rived as follows.

Fload * Vlinear = T * ω (1)

Because torque T = Fpivot * R,

T * ω = Fpivot * R * ω = Fpivot * Vangular (2)

Then

Fload * Vlinear = Fpivot * Vangular (3)

Fload = (Vangular / Vlinear ) * Fpivot = (VR) * F

pivot (4)

Referring the force diagram of this instrument handle

in Figure 4:

Ffinger * L = Fpivot * R (5)

The different Ffinger can be determined with different

combination of L and R. The computational simulation

can find the optimized values of L and R to reduce the

operational force to fully form clip. The computer aided

solution suggested L = 4.85 inch and R = 2.20 inch for

best instrument performance.

Based on Eq.5,

Ffinger * 4.85 = Fpivot * 2.20

Fpivot = 2.20 * Ffinger

Referring Eq.4,

Fload = (VR) * Fpivot = (VR) * 2.20 * Ffinger (6)

The velocity ratio of (Vangular / Vlinear) can be deter-

mined by computer aided simulation targeting optimized

instrument performance, and simulation results are

shown in Figure 5.

The mechanical advantage of this new instrument can

be found when surgical clip is fully formed:

Mechanical advantage = (VR) * 2.20 (7)

= (.04940 / .03548) * .20 = 3.063

This result shows that, if 20 lbf forces are required to

fully form the surgical clip, the operational force that

surgeon needed is 3.265 lbf that is lower than normal

spec of 4 lbf and this will benefit surgeons in their sur-

gical procedure. Also, both computational simulation

and prototype testing results are very close which verify

and prove the credibility of this new instrument design

and research methodology.

4. CONCLUSIONS

The prototype of this new surgical clip instrument has

been proved to have feasible function and better per-

formance based on instrumental functional study, com-

puter aided modeling and solution, and preliminary pro-

totype testing. This new instrument design has several

Figure 5. Linear and angular velocity vs. time phase in op-

erating the instrument.

Z. Li / J. Biomedical Science and Engineering 2 (2009) 435-438

438

[2] D. Chan, J. Bishoff, I. Ratner, L. Kavoussi, and T. Jarrett,

(2000) Endovascular gastrointestinal stapler device mal-

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major advantages compared with some current surgical

clip devices including: the clip’s distal move can be

properly guided and controlled to prevent patient’s blood

vessel and body tissue from damage that caused by ac-

cidental clip shooting out during surgical processes, op-

erational force to form clip is lower than usual surgical

clip instruments, instrument production and product cost

can be decreased since loose dimensional tolerance and

low surface quality of instrumental components are al-

lowed in this new design. The prototype testing has been

conducted in lab and the preliminary result has shown

the potential improvement over some current instru-

ments including reliable performance without accidental

clip drop-off, reduced operational force to form clip, and

lower product cost. While the prototype this new in-

strument is being sent to fields for more clinical trials

and evaluations, further analysis and improvement will

be conducted including adding support to enhance jaw

pair structure to prevent jaws from twisting when unex-

pected torque load exerted to the instrument due to im-

proper usage in surgical procedure, adding enhancing

structure to prevent jaws from accidental close when

unanticipated side load exerted to instrument jaws, sim-

plifying the instrument design to further reduce the

product cost.

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(2005) Clinical experience with a circumferential clip-

based vascular closure device in diagnostic catheteriza-

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reconstructive surgery using a commercial image-guid-

ance system, Journal of Neurosurgery, 104(1 Suppl),

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(2004) Endoscopic hemostasis for bleeding gastric

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tissue engineering for design and evaluation of lumbar-

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REFERENCES

[9] F. C. Chu and B. C. Chang, (2005) Automatic visual

tracking control system using embedded computers,

Proceeding of the 2005 IEEE International Conference

on Mechatronics, July 10–12, 2005.

[1] H. J. Lin, W. C. Lo, Y. C. Cheng, and C. L. Peng, (2007)

Endoscopic hemoclip versus triclip placement in patients

with high risk peptic ulcer bleeding, Journal of Gastro-

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Openly accessible at

APPENDIX

Nomenclature

Ffinger – lbf, load on surgeon’s finger

T – inch-lbf, torque on pivot point of handle

Vlinear – inch per second, linear distal moving velocity of

instrument drive bar

Fload – lbf, force required to close jaws to form clip

L – inch, distance between handle pivot point and sur-

geon’s finger position (VR) – velocity ratio

R – inch, distance between handle pivot and linkage

pivot

Fpivot – lbf, load on linkage pivot

ω – degree per second, angular speed of handle at pivot

point