Lecture 10 - Suture Materials and Patterns LA

Major factors determining suture selection

Tissue type, wound environment, healing time, forces on tissue, suture material properties, contamination, inflammatory response

Effect of suture size on inflammation

Larger size increases knot volume → increases inflammation → weakens closure

Why monofilament is preferred in contaminated wounds

Decreases bacterial wicking and transport into deeper tissues

Why elasticity is ideal for skin closure

Accommodates edema and reduces tension on skin edges

Why stiffness is ideal for abdominal closure

Resists deformation and maintains closure strength under load

Why oversized suture weakens closure

Increases tissue reaction and inflammation

Preferred method for wounds under tension

Increase number of sutures or use tension‑relieving patterns, not suture size

Healing time of internal organs and subQ

Few days to seal; full strength in a couple weeks

Healing time of fascia

Initial strength in weeks; full strength in months

Healing time of equine linea alba

Baseline strength at 8 weeks

Skin healing timeline

Seals in 1 day; heals in 10-14 days; full strength <30 days

Effect of apposition on skin healing

Better apposition decreases healing time

Absorbable suture categories

Short‑term, medium‑term, long‑term

Common long‑term absorbable sutures

PDS, Maxon, Biosyn

Common medium‑term absorbable sutures

Vicryl, Dexon

Common short‑term absorbable sutures

Vicryl Rapide, Caprosyn

Common nonabsorbable monofilament sutures

Prolene, Ethilon, Dermalon

Common nonabsorbable braided sutures

Ethibond, Supramid, Braunamid

Farm animal cost‑saving sutures

Catgut, Supramid, Braunamid

Most common needle shapes in LA surgery

3/8 and 1/2 circle

Use of 5/8 circle needle

Deep or confined locations

Use of 1/4 circle needle

Ophthalmologic surgery

Tissues requiring taper‑point needle

Delicate tissues; does not enlarge hole

Tissues requiring reverse‑cutting needle

Skin and fibrous tissue; stronger and less cut‑out

Purpose of S‑needle

Closing thick cow skin without needle drivers

Purpose of Buhner needle

Purse‑string closure of vaginal prolapse in cattle

Weakest point in a suture pattern

The knot

Throws needed for 2‑0 PDS or nylon

Four throws

Throws needed for #2-#3 suture

Five throws

Minimum suture tag length

At least 3 mm

When to use a surgeon's throw

When a square throw slips; increases friction

Knots that are NOT secure

Granny knot and half‑hitch

Why tension impedes healing

Reduces blood supply, prevents apposition, increases shear stress

Definition of Langer's lines

Relaxed skin tension lines guiding incision orientation

Incision orientation with least tension

Parallel to Langer's lines

Incision orientation with most tension

Perpendicular to Langer's lines

Preferred tension‑management strategies

Immobilization, more sutures, tension‑relieving patterns, release incisions, walking sutures, stents

Why not increase suture size for tension

Increases inflammation; does not reduce tension

Vertical mattress characteristics

Good apposition, some eversion, less vascular compromise

Horizontal mattress characteristics

Strong tension relief, most eversion, impedes blood supply, often needs stents

Near‑far‑far‑near characteristics

Excellent tension relief and apposition; interrupted only

Ford interlocking characteristics

Mild tension relief, continuous, good apposition; common in cow flank

Purpose of release incisions

Allow primary closure; release incisions heal by second intention

Purpose of walking sutures

Pull skin over defect, distribute tension, obliterate dead space

Purpose of stents

Distribute tension and prevent pull‑through

Preferred suture type for equine skin

Nonabsorbable monofilament (nylon or polypropylene)

Typical size for equine skin with no tension

2‑0 simple interrupted

Distance of skin bites from edge

~5 mm; further if collagenase risk

Patterns for equine skin under tension

Vertical mattress, horizontal mattress (with stents), near‑far‑far‑near

Most common tissue requiring strong closure

Linea alba

Distance of fascia bites from edge in LA

15 mm

Suture types for fascia

Vicryl or PDS; #2-#3 most common

Common cow fascia suture

Catgut (cheap)

Suture types for delicate tissues

PDS, Vicryl, Monocryl (typically 2‑0)

GI suture patterns

Inverting patterns: Lembert, Cushing, Utrecht

Why inverting patterns are used in GI

Create a seal and prevent leakage

Suture type required for contaminated wounds

Monofilament only

Why all equine wounds are contaminated

Environmental exposure and equine skin flora

Skin suture removal timeline

10-14 days; staged removal for tension

PDS absorption and strength loss

Absorbs in 180 days; 50% strength loss at 42 days

Vicryl absorption and strength loss

Absorbs in 56-70 days; 50% strength loss at 21 days

Monocryl absorption and strength loss

Absorbs in 90-180 days; 50% strength loss at 7 days