Devices, Energy & Technology

Definition

Energy devices in surgery are instruments that utilise various forms of energy — electrical, mechanical, ultrasonic, or thermal — to cut, coagulate, seal, or ablate tissue, thereby reducing blood loss and operative time.

Classification

Key Devices — Principles

1. Harmonic Scalpel (Ultrasonic)

• Converts electrical → mechanical energy at 55,000 Hz vibration
• Causes protein denaturation and vessel sealing without current passing through tissue
• Temperature: 80–100°C (much lower than electrocautery)
• Advantages: Minimal smoke, less thermal damage, effective vessel sealing ≤5 mm

2. Advanced Bipolar Devices (LigaSure, Enseal)

• Use pressure + controlled bipolar energy
• Denature collagen and elastin forming a permanent tissue seal
• Impedance feedback mechanism stops energy delivery when seal is complete
• Seals vessels up to 7 mm

3. Laser Surgery

• CO&sub2; laser: superficial vaporisation (laryngeal, skin, ENT)
• Nd:YAG: deep penetration (GI endoscopy, tumour ablation)
• KTP: photocoagulation (prostate, ENT)
• Hazards: eye injury, smoke plume, fire risk

4. Argon Plasma Coagulation (APC)

• Non-contact modality — ionised argon gas conducts current without touching tissue
• Uniform superficial coagulation, especially in endoscopic and hepatic surgery
• Limitation: poor depth control → risk of perforation

5. Radiofrequency Ablation (RFA)

• Used for: hepatic, renal, thyroid, and pulmonary tumours
• Generates ionic agitation and localised heat → coagulative necrosis

Comparison Table

Device Selection Algorithm

Safety & Precautions

• Proper placement of return electrode pad (monopolar)
• Avoid flammable agents near monopolar (oxygen, alcohol-based prep)
• Smoke evacuation — surgical plume contains toxins and aerosolised viral/bacterial particles
• Beware insulation failure and capacitive coupling in laparoscopy
• Periodic calibration and staff training essential

Recent Advances

• Thunderbeat: Combines ultrasonic + bipolar energy in a single instrument for rapid dissection with reliable sealing
• CoolSeal: Reduced thermal spread sealing device
• Smart impedance feedback: AI-integrated real-time energy modulation; stops delivery at optimal seal endpoint
• Caiman long-jaw design: More uniform energy delivery, improved burst pressure, reduced thermal spread
• Plasma/tissue-plasma cutting devices: Increasing use in robotic settings for controlled vaporisation

Principle

Diathermy uses high-frequency alternating current (300 kHz – 3 MHz) to generate heat at the electrode–tissue interface. At these frequencies, current does not stimulate nerve or muscle (no electrocution), but generates enough thermal energy to cut or coagulate.

Types

Monopolar Diathermy

• Current flows from active electrode → through patient's body → return (dispersive) pad
• Modes: Cut (continuous waveform, rapid heating → vaporises cells) and Coagulate (interrupted waveform, slower heating → protein denaturation)
• Blend mode: mixture of cut and coag waveforms
• Contraindications: pacemakers, implanted metallic devices, crossing vital structures

Bipolar Diathermy

• Current confined between two tips of forceps — no return pad needed
• Suitable for precise coagulation of small vessels, neurosurgery, and ophthalmic work
• Disadvantage: cannot cut, slower than monopolar, limited to small tissue volumes

Complications of Diathermy

Definition

A surgical stapler is a mechanical device that applies metallic or absorbable staples to close or join tissues, offering a faster and more consistent alternative to manual suturing.

Basic Components

• Handle/Trigger — activates the stapling mechanism
• Cartridge — contains the staples (replaceable/reloadable)
• Anvil — shapes and bends the staples into a B-shape
• Knife blade (in cutting staplers) — divides tissue between staple rows simultaneously

Staple Materials

• Metallic: Titanium (commonest), stainless steel
• Absorbable: Polyglycolic acid (PGA), Polylactide (PLA) — useful where imaging interference is a concern

Types of Staplers

Advantages — Mnemonic “FAST”

• F — Fast: quicker than hand suturing
• A — Atraumatic: minimal tissue handling
• S — Secure: uniform, reproducible staple line
• T — Time-saving: reduces operative duration

Additional: better haemostasis, reduced anastomotic leak rates.

Disadvantages / Complications

• Expensive; requires experience and precision
• Not ideal for very thick or oedematous tissue
• Staple-line bleeding or anastomotic leak
• Device malfunction — incomplete firing or misfire
• Stricture formation at circular anastomosis sites

Recent Advances

• Powered staplers: Battery/electronic activation — uniform compression force regardless of tissue thickness
• Articulating staplers: Adjustable angles for deep pelvic or laparoscopic work
• Smart staplers: Pressure sensors that optimise staple height based on tissue thickness
• Bioabsorbable staples: Minimal imaging interference; under investigation

Definition

Composite meshes are dual-layer or multi-layer prosthetic materials designed for intraperitoneal hernia repair, consisting of a permanent structural layer (polypropylene) on the abdominal wall side and an anti-adhesion layer (absorbable or non-absorbable) on the visceral side to prevent bowel adhesion to the mesh.

Why Composite Meshes?

Plain polypropylene mesh in direct contact with bowel causes dense adhesions, erosion, and fistula formation. Composite meshes solve this by keeping reactive material away from the viscera.

Types / Layers

Common Composite Mesh Products

• Proceed (PP + ORC + PDS film) — absorbable visceral layer
• Parietex Composite (polyester + collagen film) — excellent tissue integration
• Ventralight (PP + hydroxyethyl cellulose) — lightweight
• DualMesh (ePTFE) — smooth visceral side, microporous parietal side
• Bard Davol / Sepramesh (PP + Seprafilm derivative)

Mesh Weight Classification

Indications for Composite Mesh

• Intraperitoneal onlay mesh (IPOM) repair of ventral/incisional hernia
• Any laparoscopic ventral hernia repair where mesh contacts bowel
• Re-do hernia repair after adhesiolysis

Definition

A scaffold in tissue engineering is a three-dimensional (3D) biocompatible structure that provides a temporary framework for cell attachment, proliferation, differentiation, and extracellular matrix (ECM) formation, ultimately guiding the regeneration of functional tissue.

Ideal Properties of a Scaffold

1. Biocompatibility — must not evoke immune or inflammatory reaction
2. Biodegradability — degrades at a controlled rate matching tissue formation
3. Mechanical strength — adequate to withstand physiological stress
4. Porosity & interconnectivity — allows nutrient diffusion, vascular ingrowth, and waste removal
5. Surface chemistry — promotes cell adhesion and growth
6. Sterilisability — must withstand sterilisation without altering properties
7. Processability — easy to fabricate into desired shape and size

Functions

• Acts as template for tissue regeneration
• Facilitates cell attachment and migration
• Allows vascular ingrowth and nutrient diffusion
• Provides mechanical support until native tissue regenerates
• Serves as delivery system for growth factors, drugs, or genes

Applications by Tissue Type

Fabrication Techniques

• Solvent casting & particulate leaching — creates porous structure
• Freeze-drying (lyophilisation) — highly porous, interconnected scaffolds
• Electrospinning — produces nanofibrous mats mimicking ECM architecture
• 3D bioprinting — precise architecture with defined cell distribution
• Gas foaming / phase separation — creates pores without organic solvents

Recent Advances

• Decellularised organ scaffolds — retain natural ECM composition and architecture; used for tracheal, oesophageal, and bladder reconstruction
• Smart scaffolds — responsive to pH, temperature, or bioactive signals; release growth factors on demand
• Nanocomposite scaffolds — improved mechanical and biofunctional properties
• 3D bioprinted scaffolds — patient-specific tissue constructs with incorporated cells