Surgery Websites
Advanced Open Surgical Skills »  ATOSS Tasks »  Task 1: Tying without needles

Task 1: Suture Tying Without Needle

Instructional Video


Task Details


Summary: This task requires using 1-handed technique to tie 10 knots with single armed suture.

Equipment: One fine needle holder, one fine forceps, one 75cm 6-0 Prolene single armed suture on a C1 needle.

Task set-up: Position fabric at the base of the model (lowest platform level) as follows: 


Task steps:

  1. Load needle into fine needle holder.
  2. Throw a single suture through the fabric on either side of the slit.
  3. Set needle holder and forceps aside.
  4. Hold the suture ends in each hand (uncrossed) with equal tails (suture with needle in post hand).
  5. Tie 2 slip knots then 8 square knots. For each throw, use as many gathering maneuvers as needed for forefinger to lay down the knot securely.
  6. The task is completed when the last (10th) knot is secured.

Tips & tricks:

  • Throw each knot above the level of the model cavity to maximize working space.
  • Three ways to avoid shortening on the 1st knot:
    1. “See-saw” the 2 ends of the suture once the 1st knot is down to correct any length discrepancies prior to placing the 2nd knot; or
    2. Keep your post elbow fixed against your chest wall to reduce lengthening the post hand; or
    3. Overcompensate by starting with a tail end of the suture that is long anticipating some degree of shortening.
  • For slip knots, keep the post at 90 degrees with limited movement of the hand holding the post. For square knots, equal and opposite tension should be placed on the suture in opposite direction for each throw in order for each knot to lay down flat.

Cutoff time: Maximum time for task completion is 90 seconds. During formal assessment, the timing will start after the suture is in place and hand movement is initiated. If the task is not completed within the allotted time, you will be asked to stop.

Scoring: A score will be assigned for 6 micro-skills. Score assignments are based on the following:








Unable to complete task

Completed task w/ major errors

Completed task w/ minor errors

Proficient, no errors, some awkward moves

Expert, no errors, smooth and efficient


Score (1-5)

1. Throwing knot


2. Suture gathering


3. Suture sliding


4. Atraumatic technique


5. Maintenance of post


6. Overall rating


Total (Sum of Scores for All Micro-Skills) [Max = 30]


Scoring Formula: see Task & Scoring Overview or score calculator (access via Google doc or download excel file)

Expert Score: 50

Example Video


Site Directory