The suture threads raw unit is a yarn. This yarn either natural or synthetic.

I. Natural threads :

1. Catgut (Absorbable) :
   It is produced from purified animal intestines (beef or sheep).
2. Silk (Non-Absorbable) :
   It is obtained from organic protein called fibroin which is derived from the domesticated species bombyx mori.

II. Synthetic threads :

1. Polyglycolic acid (PGA) (absorbable) :
   It is originating from polymerization of polyglycolic acid (100% PGA).
2. Polyglycolide-co-lactide (absorbable) :
   It is originating from polymerization of glycolic acid(glycolide) and lactic acid (lactide). This polymerization present in the market in different ratios 90% glycolic acid (glycolide) 10%lactic acide (lactide) e.g. Polygalactin 910, 95% PGA & 5% lactic acid. Every manufacturer has it's own ratio.
3. Polyglycolide-co-caprolactone(absorbable) :
   It is originating from polymerization of glycolic acid (glycolide) & caprolactone in ratio of 75% to 25% respectively.
4. Polydioxanone (absorbable) :
   It is originating from polymerization of poly dioxanone (100%).
5. Polypropylene (non-absorbable) :
   It is composed of an isotactic crystalline stereoisomer of polypropylene, a synthetic linear polyolefin.
6. Polyester ( non- absorbable) :
   It is originated by drawing polyethylene terephthalate.
7. Polyamid (non- absorbable) :
   It is originated from nylon.

Mono & multifilament and coating of threads :

The above thread types either multifilament ( braided or twisted ) or monofilament. The multifilament threads are usually coated by another material to minimize the Capillarity and the pores between the braided or twisted filaments, so it prevent barterial growth and provides a smooth passage of thread through the tissue.

Monofilament	Multifelament	Cross section of multifilament thread

Physical qualitative points for suture threads :

1. Diameter :
   The united state pharmacopeia (USP) has its scale to determine the thread diameter from USP 5( thicker) to USP 10/0 (thinner), although the pharmacopeia allows some overlap between the USP size range. The average diameter of the strands being measure is within the tolerances for the respective size. None of the observed measurements is less than midpoints of the range for the next smaller size or more than the midpoint of range for the next larger size (USP 26 page 1750). The European pharmacopeia (EP) also has its own scale to determine from metric 7(thicker) to metric 0.2 (thinner), and also this pharmacopeia allows some overlap between the metric sizes. The average of the measurements carried out on the suture diameter have to be within the standard range (column A table 0667-1) and non of the measurements is outside of the exceptional range (column B table 0667-1). EP4 page 2364.
   

   USP	METRIC	Sutures Diamater in mm
   3	6	0.600-0.699
   2	5	0.500-0.599
   1	4	0.400-0.499
   0	3.5	0.350-0.399
   2/0	3	0.300-0.349
   3/0	2	0.200-0.249
   4/0	1.5	0.150-0.199
   5/0	1	0.100-0.149
   6/0	0.7	0.070-0.099
   7/0	0.5	0.050-0.069
   8/0	0.4	0.040-0.049
   9/0	0.3	0.030-0.039
   10/0	0.2	0.020-0.029

   
    
2. Knot pull tensile strength :
   It is the breaking tensile strength of surgical knot of the suture (as higher as better).
   
   
    
3. Percent of breaking strength retention (BSR) :
   Every absorbable suture pass through several stages to be absorbed completely. The absorbable suture start to loss its tensile strength gradually up to total loss of mass. The tensile strength which retained in the suture 2 weeks post implantation is called breaking strength retention. The period of absorption is variable depending upon the type of each suture.
    
4. Knot configuration and security :
   The good knot configuration leading to a high knot security. The knot configuration and security depending on the suture type, monofilament or multifilament and type of coating in the case of multifilament
    

   Hight knot security	Low knot security

   
    
5. Water content :
   Based on the fact that the absorbable suture is absorbed due to exposure to body fluid (moisture), so the water content of the absorbable suture not allowed by USP and EP to be higher than 500ppm (as lower as better).
    
6. Thread memory :
   It is the ability of thread to restore its original straightening after its release from 8 shape winding (as lower as better).
   

   Low memory	Hight memory