Baseball Diamond Concept for Port Position in Laparoscopy

Jibran MohsinResident, Surgical Unit I

SIMS/Services Hospital, Lahore

Where should I insert the port?

First query and common problem which the beginners encounter

Common cause of stressful surgery is wrong port position

If one port is at wrong place, surgeon will struggle throughout surgery due to bad ergonomics

May be sometime one of causes of complication and more rate of conversion

Answer lies in Baseball Field

Target of Dissection

Outer Arc

Inner Arc

Working/Secondary Port

Working/Secondary Port

Primary/Optical Port (Telescope)

First Principle of Baseball Diamond Concept

Half of the instrument should be in and half out.

1st Rationale for 1st Principle

Laparoscopic instruments works on Lever action.

Type I Lever……….Fulcrum in the center and load is equal and opposite to the force applied

Generally all laparoscopic instruments should behave like type 1 Lever

1st Rationale for 1st Principle

If fulcrum is very close to load arm:

i.e. maximum length of instrument outside (Port very near to target of dissection)

Force is magnified……………leading to tissue tear or avulsion of CBD movement will be rectified.

1st Rationale for 1st Principle

If fulcrum is very close to force arm:

i.e. maximum length of instrument is inside abdomen (Port very far from target of dissection)

Little movement outside leads to magnified distance moved inside again leading to collateral damage(diaphragm, bowel) i.e. overshooting

Force will be rectified inside.

2nd Rationale for 1st Principle

If port is very close to target of dissection………………elevation angle will be 90O ……surgery can’t be performed….as instrument will not lift the tissue e.g. fork at 90o can’t turn the omelette

If port is very far from target of dissection………….elevation angle will be less i.e. 10o……handle of instrument will touch the body of the patient

_________________________________________________________________________________________________________

Elevation Angle = angle between instrument and body of patient Ideally it should be 60o and equals the manipulation angle during cooking, stirring etc 60o elevation angle is used

3rd Rationale for 1st Principle

If port is very close to target of dissection………metallic cannula of port will touch the non insulated part of instrument….direct coupling occur….injury to nearby bowel or bladder

If port is very far away from target of dissection…………………entry and exit will not be witnessed by telescope as cannula will be behind the telescope and long pathway of entry/exit is blind and bowel damage may occur

If half is out and half is in………no chance of direct coupling and no blind long pathway

How to get 1st Principle?

Step I: Find out the target of dissection (defined as most critical part of dissection, requiring most attention and linked with max anxiety)

E.g. calot triangle , base of appendix, splenic artery/vein

Step II: Find the length of instrument Neonatal………..20 cm Pediatric……..28 cm Adult………….36 cm Morbid Obese………..45 cm

How to get 1st Principle?

Step III: Draw the line of optimum area Keeping target at center, draw 2 arcs 1st arc at 18 cm (half the length of instrument) 2nd arc at 24 cm (2/3rd of length of instrument)

All ports including telescope MUST ALWAYS be placed anywhere in between these 2 arcs.

Second Principle of Baseball Diamond Concept

Telescope should be in middle of working instruments i.e. Azimuth angle (defined as angle between telescope and working port/hand instrument) must be equal i.e. 30o (normal range 15o to 45o)

i.e. contralateral port position

Etymology: Azimuth Arabic al-sumūt, meaning "the directions"

Rationale for 2nd Principle

Contralateral Port Position Depth Perception

1. Linear Parallax

Rationale for 2nd Principle

2. Motion Parallax

Object near will appears to move more and vice versa

Rationale for 2nd Principle

3. Relative Size

Object far will appears to be small and vice versa

Rationale for 2nd Principle

4. Aerial gradient/persecption Object near will appear to have better contrast and better color

Rationale for 2nd Principle

5. Correct Shadow

Rationale for 2nd Principle

6. Texture Gradient

Near object appears to have more rough and detailed surface

Rationale for 2nd Principle

Versus ipsilateral port position DEMERIT: Less depth perception…….1 instrument too near to telescope and other

away from telescope. Acceptable only for simple procedures such as appendectomy, ventral

hernia but doesn’t works for advanced surgery such as fundoplication, inguinal

hernia repair, hiatus hernia + knotting/suturing. MERIT: Allows sectorisation i.e. surgeon can move freely as camera is away from

operative field no physical contact between surgeon and camera holder

Third Principle of Baseball Diamond Concept

Manipulation angle(defined as angle between two working hand instruments)should be 60o ± 15o

How to get 3rd Principle?

How to get 3rd Principle?

Put tip of index finger over target of dissection Put tip of thumb over site of telescope Position of anatomical snuff box will give you rough estimation of

secondary port position in adult on both sides Target of dissection

Optical port

ANATOMICAL SNUFF BOXWorking port position ~

18

cm~7.5 cm

How to get 3rd Principle?

LIMITATIONS:

Not applicable for pediatric patients Measurements are for average adult male surgeon………..in female

reference point is approximately radial styloid process

SUMMARY

1st Principle: Half (i.e. 18 cm in adult) of the instrument should be in and half out so that elevation angle is 60 degree.

2nd Principle: Contralateral port position with equal Azimuth angle is ergonomically better

3rd Principle: Manipulation angle should be 60 degree.

Available at surgicalpresentations