Minimally invasive surgery (MIS)

1. Main forms of MIS

2. How laparoscopy works

1. The patient is given anesthesia, usually general anesthesia.
2. A small incision is made, commonly near the umbilicus.
3. The abdomen is inflated with carbon dioxide (CO₂) to create a working space called a pneumoperitoneum.
4. A camera-bearing laparoscope is inserted through a port.
5. Additional ports allow insertion of graspers, scissors, energy devices, staplers, suction, and suturing instruments.
6. The surgeon operates while watching a magnified video image.
7. The specimen may be removed through a port that is enlarged slightly, or through a small extraction incision.
8. CO₂ is released and the port wounds are closed.

3. Why CO₂ is used

• Increased intra-abdominal pressure
• Reduced venous return in some settings
• Raised diaphragm with reduced lung compliance
• Increased CO₂ absorption, potentially causing hypercapnia
• Higher airway pressures during ventilation
• Position-related effects, especially Trendelenburg position

4. Instruments used

• Laparoscope: telescope with light source and camera
• Trocars/ports: sleeve-like access devices placed through the abdominal wall
• Graspers and dissectors: hold and separate tissue
• Scissors: divide tissue
• Energy devices: control bleeding and divide vessels or tissue, such as monopolar/bipolar cautery, ultrasonic and advanced bipolar devices
• Suction-irrigation device: clears blood, bile, pus, or smoke
• Clip appliers and staplers: seal ducts, vessels, or bowel
• Needle holders: intracorporeal suturing
• Retrieval bag: removes specimens while limiting contamination or tumor spillage

5. Advantages compared with open surgery

• Smaller incisions and less tissue trauma
• Less postoperative pain and lower analgesic requirement
• Lower wound complication and surgical-site infection rates in many operations
• Less blood loss in selected procedures
• Earlier mobilization
• Faster return of bowel function after many abdominal procedures
• Shorter hospital stay
• Earlier return to work and ordinary activity
• Better cosmetic result
• Reduced surgical stress response

6. Limitations and disadvantages

• Reduced tactile feedback compared with open surgery
• Two-dimensional vision in standard laparoscopy, though 3D systems are available
• Long instruments amplify tremor and can create an awkward fulcrum effect at the abdominal wall
• Complex suturing and knot tying require training
• Equipment failure or limited availability
• Some procedures take longer, particularly early in a surgeon’s learning curve
• May require conversion to open surgery
• Robotic systems can add substantial capital, maintenance, and disposable-instrument costs

7. Complications

A. Access-related complications

• Injury to bowel, bladder, uterus, or solid organs
• Major vascular injury, though uncommon but potentially life-threatening
• Abdominal wall bleeding, including inferior epigastric vessel injury
• Port-site hematoma
• Port-site hernia
• Subcutaneous emphysema
• Failed access or extraperitoneal insufflation

B. CO₂ pneumoperitoneum-related complications

• Hypercapnia and respiratory acidosis
• Reduced venous return and hemodynamic instability
• Cardiac arrhythmia
• Pneumothorax or pneumomediastinum
• Rare CO₂ gas embolism
• Shoulder-tip pain after surgery, often from diaphragmatic irritation by residual gas

C. Procedure-specific complications

• Bleeding
• Infection
• Leak after bowel, biliary, urinary, or vascular repair
• Injury to adjacent structures
• Deep venous thrombosis or pulmonary embolism
• Anastomotic leak
• Persistent disease, recurrence, or need for reintervention

D. Conversion to open surgery

• Uncontrolled bleeding
• Dense adhesions
• Severe inflammation
• Difficult tumor invasion
• Unclear anatomy
• Organ injury
• Equipment problems
• Inability to safely complete the intended repair

8. Robotic-assisted surgery

• High-definition magnified, often three-dimensional vision
• Wristed instruments with more degrees of freedom than straight laparoscopic instruments
• Motion scaling
• Tremor filtration
• Improved surgeon ergonomics
• Potential benefit for fine dissection and suturing in confined spaces, such as the pelvis

9. Common operations done minimally invasively

• Laparoscopic cholecystectomy
• Laparoscopic appendicectomy
• Laparoscopic inguinal and ventral hernia repair
• Anti-reflux surgery, such as fundoplication
• Bariatric surgery
• Colectomy and rectal cancer surgery
• Hysterectomy and gynecologic cancer surgery
• Prostatectomy and partial nephrectomy
• Adrenalectomy
• Thoracoscopic lung and pleural procedures
• Arthroscopic knee and shoulder procedures
• Endoscopic sinus, skull-base, gastrointestinal, and urologic surgery
• Catheter-based cardiovascular interventions

10. Patient selection

• Nature and severity of the disease
• Need for emergency surgery
• Previous operations and expected adhesions
• Size and location of a tumor
• Bleeding risk
• Obesity
• Heart and lung function
• Pregnancy
• Presence of severe infection, perforation, or instability
• Availability of equipment and an appropriately trained surgical team

11. Enhanced recovery connection

• Preoperative optimization and counseling
• Multimodal, opioid-sparing analgesia
• Prevention of nausea and vomiting
• Early oral intake when appropriate
• Early walking and physiotherapy
• Avoiding unnecessary tubes and drains
• Venous thromboembolism prevention

Key takeaway

MIS reduces the trauma of surgical access, not the seriousness of the operation itself.

Ergonomics of Minimal Access Surgery (MAS)

Why MAS is ergonomically difficult

1. Fulcrum effect
   The abdominal wall acts as a pivot. Moving the external handle left makes the instrument tip move right internally. This counterintuitive movement initially increases workload and fatigue.
2. Long instruments
   Long "straight-stick" instruments place the surgeon farther from the patient and may force reaching, shoulder abduction, and trunk extension.
3. Reduced degrees of freedom
   Open surgical hands have many movement possibilities, whereas straight laparoscopic instruments substantially restrict movement. This promotes fixed, non-neutral postures.
4. Loss of tactile feedback
   The surgeon relies more heavily on vision, increasing visual and mental demand.
5. Static posture
   Prolonged standing with the arms held elevated causes sustained contraction of neck, shoulder, back, forearm, and hand muscles.
6. Indirect visualization
   A poorly located monitor makes the surgeon rotate, flex, or extend the neck and trunk. This increases eye, neck, and shoulder strain.
7. Poorly designed handles and pedals
   Ring handles can cause wrist flexion and ulnar deviation. A badly positioned diathermy foot pedal can disturb balance and cause calf or lower-limb fatigue.

Consequences of poor ergonomics

• Neck pain and cervical muscle strain
• Shoulder pain, especially trapezius and deltoid fatigue
• Low-back pain from leaning or hyperextension
• Forearm fatigue
• Wrist pain, flexion, extension, or ulnar deviation strain
• Hand and finger numbness or paresthesia
• Reduced precision and tremor control
• Slower task performance
• Reduced concentration during long procedures
• Work-related musculoskeletal disorders and reduced career longevity

Principles of ideal MAS ergonomics

1. Surgeon posture

Ideal posture

• Head and neck in a neutral or slightly flexed position
• Relaxed shoulders, not elevated
• Upright trunk, avoiding leaning, twisting, and overextension
• Elbows near the side of the body
• Elbow flexion roughly 90° to 120°
• Forearms approximately parallel to the floor where feasible
• Wrists in a neutral position, without marked flexion, extension, radial deviation, or ulnar deviation
• Balanced stance, with feet shoulder-width apart
• Body weight distributed evenly across both feet
• Instruments handled close to the body rather than at full reach

Avoid

• Chin-up position to view a high monitor
• Constant neck rotation toward a side monitor
• Excessive shoulder abduction
• Bending forward to reach the patient
• Leaning backward to accommodate a high table
• Twisting the trunk while the feet remain fixed
• Prolonged single-leg stance when using a foot pedal

2. Operating-table height

Practical rule

Effects of wrong table height

3. Monitor position

Recommended setup

• Place the primary monitor directly in front of the surgeon, across the operating table.
• Ideally, the patient and operative field lie between surgeon and monitor.
• Place the top of the screen at about eye level or slightly lower.
• The monitor image is commonly recommended at up to 25° below the horizontal visual axis to reduce neck strain.
• Keep the monitor about an arm's length away. If it is too close or too far, visual fatigue increases.
• Use high-resolution, appropriately bright displays and reduce glare.
• Use two or more monitors for operations requiring changes in surgeon position or for assistants who otherwise have to twist their necks.

4. Port placement and triangulation

Principles

1. Optical port
   • Usually positioned centrally for the best view of the target.
   • The camera should provide a direct, stable view rather than forcing awkward instrument angles.
2. Working ports
   • Positioned on either side of the camera port to create a triangular configuration.
   • Permit two-handed work and reduce external clashing.
   • Should allow instrument manipulation without excessive elbow elevation or extreme wrist angles.
3. Target distance
   • A commonly taught arrangement places the target around 15 to 20 cm from the camera port.
   • Working ports are placed along the same arc, approximately 5 to 7 cm on either side of the optical port, adjusted for procedure and patient anatomy.
4. Instrument-target angle
   • An angle of approximately 60° to 90° between instruments at the target often permits efficient dissection and suturing.
   • Very narrow angles create crowding and "sword fighting."
   • Very wide angles increase shoulder abduction, hand fatigue, and loss of precision.
5. Retracting ports
   • Place more laterally when appropriate so retraction does not clash with the camera and working instruments.

Poor port placement causes

• Instrument collision outside and inside the body
• Excessive manipulation of the abdominal wall
• Poor view of target anatomy
• Reduced range of motion
• Need for awkward hand crossing
• Excessive arm abduction and shoulder fatigue
• Longer operation time and increased technical errors

5. Instrument design and handling

Handle ergonomics

• Finger flexion
• Wrist deviation
• High gripping force
• Compression of digital nerves
• Forearm muscle fatigue

• Pistol-grip or axial handles, depending on the task
• Reduced required grip force
• Spring mechanisms that do not require sustained compression
• Rotatable shafts
• Instrument length appropriate to patient habitus and depth of operation

Handling principles

• Hold instruments with a gentle but secure grip.
• Avoid prolonged maximum grip force.
• Keep the wrist neutral.
• Use both hands efficiently and alternate tasks if possible.
• Rest the arms intermittently during noncritical phases.
• Use an appropriate instrument length. Instruments that are too long increase torque and fatigue; those too short may force uncomfortable reaching.

6. Foot pedal ergonomics

Good pedal position

• Near the operating foot
• Clearly distinguishable from other pedals
• Positioned so it can be reached without stepping, leaning, or twisting
• Allowing the surgeon to retain a balanced stance
• Cables organized to avoid tripping

Problems with bad pedal placement

• Lower-limb cramps and fatigue
• Shift of center of gravity
• Loss of balance
• Increased back and core strain
• Unintended activation of energy devices

7. Camera-holder and assistant ergonomics

• Their own monitor, in front of them
• A clear line of sight
• Adequate space around the table
• A neutral neck and trunk position
• Camera position that avoids sustained shoulder elevation
• Clearly assigned roles and verbal communication with the operating surgeon

8. Operating-room design

Desirable features

• Ceiling-mounted or mobile monitors
• Mobile equipment towers
• Organized cables and tubing
• Adequate space for staff movement
• Easy access to insufflator, electrosurgical unit, suction, and imaging
• Multiple displays where needed
• Clear positioning of anesthetic equipment and patient monitors
• Adjustable operating table and monitor arms

Robotic surgery and ergonomics

• Seated operating position
• Adjustable console height and arm support
• Three-dimensional magnified vision
• Wristed instruments
• Motion scaling
• Tremor filtration
• Less need for extreme wrist positions and shoulder elevation

• The bedside assistant may still have laparoscopic strain.
• A poorly adjusted console can cause neck, shoulder, or eye strain.
• Long console work can still produce static posture fatigue.
• The console surgeon may become less aware of nonverbal communication and events at the patient bedside.

Ergonomic checklist before starting MAS

Surgeon checklist

• Is the operating table at elbow-level working height?
• Is the monitor directly ahead and slightly below eye level?
• Is the monitor at a comfortable viewing distance?
• Are shoulders relaxed and elbows close to the trunk?
• Can both wrists remain neutral?
• Are the ports positioned for triangulation and instrument mobility?
• Are instrument handles suitable for the surgeon's hand?
• Is the energy foot pedal close, identifiable, and stable?
• Is there a second monitor for the assistant or for anticipated changes in surgeon position?
• Are cables and tubing organized and out of the walking path?
• Is a short stretch or posture reset planned during a long operation?

Exam summary

1. Neutral surgeon posture
2. Correct operating-table height
3. Monitor directly ahead and slightly below eye level
4. Proper port placement with triangulation
5. Comfortable instrument handles and neutral wrist alignment
6. Correct placement of foot pedals
7. Adequate monitors and ergonomic positioning for assistants
8. Organized operating room with minimal cable clutter
9. Regular posture adjustment during long cases
10. Appropriate training in laparoscopic and robotic technique

Angles in ergonomics of minimal access surgery

1. Manipulation angle

 Working instrument \     / Working instrument
                    \   /
                     \ /
                  Target tissue
           
          Manipulation angle

Ideal range

• 45° to 75° is commonly regarded as ergonomically favorable.
• Around 60° is often considered an excellent practical target for two-handed tasks such as dissection and suturing.
• Some teaching sources allow 60° to 90°, depending on the operation, anatomy, and required maneuver.

Why it matters

• Effective bimanual dissection
• Better depth perception and tissue traction-countertraction
• Less instrument clashing
• Less shoulder abduction and wrist deviation
• Improved precision and task speed

If the angle is too narrow: <45°

      \ /
       V
     Target

• Instruments collide externally and internally, called sword fighting
• Reduced freedom of movement
• Handles may cross
• Surgeon adopts awkward wrist and shoulder positions
• Suturing and knot tying become difficult
• Camera may obstruct instrument movement

If the angle is too wide: >75° to 90°

 \               /
  \             /
   \           /
      Target

• Excessive reaching and shoulder abduction
• Loss of fine control
• Increased torque at abdominal wall ports
• More muscle fatigue
• Difficulty maintaining a comfortable stance

The ideal manipulation angle in laparoscopy is approximately 45° to 75°, with about 60° giving efficient instrument handling in many tasks.

2. Elevation angle

          Instrument
              \
               \  Elevation angle
----------------\---------------- Abdominal wall plane
                 \
                 Target

Important relationship

Problems with a wrong elevation angle

• Too low or shallow: limited access, instrument collision, poor reach
• Too high or steep: excessive vertical force at the port, reduced working space, awkward arm and wrist posture
• Mismatch with manipulation angle: slower, less precise movement and more fatigue

3. Azimuth angle

              Camera port
                   |
                   |  Azimuth angle
                   |
Working port ------ Target ------ Working port

Ergonomic principle

• The two working ports should usually have approximately equal azimuth angles relative to the camera port.
• This creates symmetrical triangulation.
• Equal or near-equal azimuth angles improve visualization, bimanual access, and balance between right and left hands.

Practical meaning

• The near instrument may collide with the laparoscope
• The far instrument may force reaching
• The surgeon may twist the trunk or wrists
• Dissection becomes asymmetrical and less controlled

Equal azimuth angles around the camera port provide symmetrical triangulation and better ergonomic instrument movement.

4. Target distance from ports

Optical port to target

• Commonly 15 to 20 cm from the target organ or operative site.

Working ports

• Often placed on the same 15 to 20 cm arc around the target.
• Common teaching is about 5 to 7 cm to either side of the optical port, adjusted to patient size and the procedure.

Too close to target

• Poor overview
• Instrument crowding
• Excessive movement at handles
• Clashing at the abdominal wall

Too far from target

• Loss of force transmission and precision
• Long, tiring movements
• Excessive shoulder and arm movement
• Difficulty in suturing

5. Camera angle

Ergonomic rule

6. Monitor viewing angle

Preferred monitor angle

• Monitor should be at eye level or slightly below it
• The image is ideally up to about 25° below the horizontal eye line
• Avoid placing the monitor above eye level, which creates a “chin-up” posture

Eye line  ------------------------>
                    \
                     \  0° to 25° downward
                      \
                     Monitor

Why?

7. Elbow and shoulder angles

Elbow

• Keep elbows close to the trunk
• Aim for roughly 90° to 120° elbow flexion
• Instrument handles should be near elbow level or slightly below

Shoulder

• Keep shoulder abduction low, ideally less than 30°
• Avoid sustained shoulder elevation and reaching away from the body

Wrist

• Maintain a near-neutral wrist
• Avoid prolonged flexion, extension, radial deviation, and ulnar deviation

8. Ergonomic triangulation: putting the angles together

                  Camera port
                      |
                      |
              15-20 cm to target
                      |
                   Target
                  /      \
        Working port      Working port

Ideal practical configuration

• Central camera port
• Two working ports on either side
• Manipulation angle: 45° to 75°, preferably near 60°
• Elevation angle: approximately equal to manipulation angle
• Azimuth angles: approximately equal on both sides
• Target-to-camera distance: 15 to 20 cm
• Monitor angle: 0° to 25° below horizontal eye level
• Elbow flexion: about 90° to 120°
• Shoulder abduction: minimized, preferably <30°

9. Special situation: single-incision laparoscopic surgery

• Very narrow manipulation angle
• Instrument clashing
• External handle collision
• Crossed-hand technique
• Greater ergonomic difficulty
• Less intuitive movement

High-yield table

One-line memory aid

“60-60-20-25”: approximately 60° manipulation, 60° elevation, 20 cm camera-to-target distance, and monitor up to 25° below eye level.