Subinternship Surgery · Year 4 · from Subinternship Surgery
Case 2: Suturing and Knot Tying
Clinical Image
Source: Wikimedia Commons - Surgical Suturing - CC BY-SA 3.0
Case Presentation
A surgery sub-intern is asked to close the skin after an open appendectomy. The attending provides Vicryl 3-0 for subcutaneous closure and nylon 4-0 for skin. The sub-intern demonstrates proper technique for subcutaneous closure: using the needle driver to grasp the needle at the junction of the middle and back third, she places buried interrupted sutures to approximate the dermis without tension. For each suture, she performs an instrument tie: wrapping the suture around the needle driver, grasping the short end, and pulling through. She alternates wrap direction with each throw to create a square knot (first throw, then opposite direction, then same as first). She cuts the suture, leaving appropriate tail length (short for braided Vicryl). For skin closure, she places simple interrupted nylon sutures, entering perpendicular to the skin, curving through the dermis, and exiting perpendicular on the opposite side. She everts the skin edges slightly to optimize healing. The attending notes her sutures are evenly spaced but the bites are slightly unequal. She provides feedback: "Try to enter and exit at equal distances from the wound edge and equal depth on each side." The sub-intern incorporates this feedback on the remaining sutures. Post-operatively, the wound heals well with minimal scarring.
Key Learning Points
- Suture selection depends on tissue: absorbable (Vicryl, PDS) for deep tissue, non-absorbable (nylon, prolene) for skin; size matches tissue strength (larger for fascia, finer for skin)
- Square knots require alternating throw direction; same direction creates a slip knot that will not hold
- Instrument ties use the needle driver to wrap and pull suture; two-hand ties are used for deep ties or when more control is needed
- Suture cutting: braided sutures (Vicryl, silk) can be cut short (2-3 mm); monofilament (nylon, prolene) requires longer tails (5+ mm) as they are more prone to untying