5.2 Suture terminology

The flexor tendon repair is a composite of the core and peripheral sutures [55]. The core suture is the suture placed within the substance of the tendon proper and consists of at least two of three components—longitudinal, transverse and link. All core suture techniques have a longitudinal and link component.


Pennington [56] first described the relationship of the transverse and longitudinal components when he outlined his locking-loop technique. Locking suture configurations tighten around bundles of tendon fibres with tension [56]; it can only do this when the transverse component crosses just superficial to the longitudinal part of the suture. The result is a loop of suture locking around a small bundle of tendon fibres so that when more tension is applied to the repair site, the tighter the grip of the suture loop on these fibre bundles [56]. Grasping loops on the other hand have the transverse component passing deep to the longitudinal constituent so that the suture does not pass around or lock a bundle of tendon fibres [57]. Locking loops improve the ultimate force and gap resistance compared to grasping loops in flexor tendon repair [45]. Several studies have demonstrated that locking loops improve the ultimate force and gap resistance compared to grasping loops in flexor tendon repair [45, 58]. However, the biomechanical advantage of the locking loops is obtained only with 3–0 or larger suture [45]. This is because with 4–0 suture, the material strength is inferior to the holding capacity of the suture grips of the tendon

### Physiology of Flexor Tendon Healing and Rationale for Treatment Protocols DOI: http://dx.doi.org/10.5772/intechopen.86064

leading to failure by suture rupture before the true biomechanical properties of the locking loops are obtained [45]. Additionally, the size of the locking loop influences the biomechanical properties of the repair technique [59–61]. In the modified Pennington technique, increasing the cross-sectional area of each loop from 5 to 15% improved the ultimate force, whilst further increase did not improve strength, and the tendency for gap formation increased [60]. In the four-strand cruciate repair, the locking loops of 25% reached the highest gap force, ultimate force and stiffness [59].

Variations in the construction of the link component—arc, loop or knot—result in a sliding or an anchored suture on each half of the divided tendon [55].


### 5.3 Suture principles

tendon junction, therefore decreasing initial repair strength [49]. The initial strength of the repair depends on the material properties and knot security of the sutures as well as on the holding capacity of the suture grips of the tendon [45]. Immobilisation significantly decreases the strength of repair within the first 3 weeks of healing [50], whereas early passive and early active motion have been shown to prevent the initial weakening, leading to progressively increased repair strength, starting from the time of repair [50–52]. The initial strength of the repair depends on the material of the suture itself, knot security of the suture and the holding capacity of the suture grips on the tendon [45]. Therefore, the biomechanical

• Increasing the number of strands crossing the repair site [53]

The flexor tendon repair is a composite of the core and peripheral sutures [55]. The core suture is the suture placed within the substance of the tendon proper and consists of at least two of three components—longitudinal, transverse and link. All

• The link component is that part of the suture at the junction between longitudinal and the transverse components or between two longitudinal

• The longitudinal and transverse components are usually placed within the

• The transverse and/or link components convert the longitudinal pull of the suture to a transverse compressive force and prevent the longitudinal

• The longitudinal component in turn allows placement of the transverse and/or

Pennington [56] first described the relationship of the transverse and longitudinal components when he outlined his locking-loop technique. Locking suture configurations tighten around bundles of tendon fibres with tension [56]; it can only do this when the transverse component crosses just superficial to the longitudinal part of the suture. The result is a loop of suture locking around a small bundle of tendon fibres so that when more tension is applied to the repair site, the tighter the grip of the suture loop on these fibre bundles [56]. Grasping loops on the other hand have the transverse component passing deep to the longitudinal constituent so that the suture does not pass around or lock a bundle of tendon fibres [57]. Locking loops improve the ultimate force and gap resistance compared to grasping loops in flexor tendon repair [45]. Several studies have demonstrated that locking loops improve the ultimate force and gap resistance compared to grasping loops in flexor tendon repair [45, 58]. However, the biomechanical advantage of the locking loops is obtained only with 3–0 or larger suture [45]. This is because with 4–0 suture, the material strength is inferior to the holding capacity of the suture grips of the tendon

• The number, size and configuration of the grips [45, 53]

core suture techniques have a longitudinal and link component.

components. The link component lies outside the tendon.

link components away from the divided end of the tendon.

tendon substance, i.e. they are intratendinous.

component from pulling out.

110

properties of the suture can be improved by:

• Increasing the suture calibre [54]

5.2 Suture terminology

Tendons

The length of the core suture purchase in the tendon logically determines how much of the segment of the tendon is incorporated into the repair. The optimal range of core suture purchase has been determined as 1.0 cm with increased gap force, ultimate force and stiffness [62, 63]. The purchase of 0.4 cm results in very weak repairs, whilst any increase over 1 cm does not improve the biomechanical properties [63].

Increasing the suture calibre has been shown to increase the ultimate force in static testing and fatigue strength in dynamic testing; however, it has not been shown to improve the yield force or gap resistance of the repairs [45]. The strength of the 4–0 suture has been reported to be less than the holding capacity of several locking and grasping repair techniques with failure occurring mostly by suture rupture [54, 64]. A 3–0 suture failure due to suture rupture and pullout has been reported [54, 64]. Therefore, the use of 3–0 suture is generally recommended to offer safety over the 4–0 suture by increasing the material strength [45, 54, 64].

The ideal suture material for flexor tendon repair should be strong enough; prevent gapping; be easy to use and knot; be absorbable but maintain its tensile properties until tendon repair has achieved adequate strength; and have minimal tissue response [65]. Non-absorbable, synthetic sutures, (especially coated braided polyester), monofilament nylon and monofilament polypropylene are used in flexor tendon repair [45]. Coated braided polyester suture is the most common core suture material, though nylon is also used, especially in repairs performed with looped suture. Monofilament polypropylene is mainly used in the peripheral sutures. Coated braided polyester suture demonstrates significantly higher tensile strength and stiffness than monofilament nylon and polypropylene sutures and maintains its tensile properties in the body temperature, whilst the stiffness of both polypropylene and nylon suture has been shown to decrease significantly [66, 67]. A braided polyblend polyethylene suture (Fiberwire®) has been introduced for flexor tendon repair. It has significantly higher ultimate force and stiffness than coated braided polyester, monofilament nylon and polypropylene sutures and a similar ultimate force but higher stiffness than braided stainless steel [66]. Bioabsorbable suture

materials are not widely used in flexor tendon repair due to the lack of sufficient tensile strength half-life and potential increased tissue reaction and adhesion formation [45].

discontinued at 6 weeks. From here, differential FDS and FDP gliding exercises are

• To isolate FDP gliding, both the MP and PIP joints are held in extension, and the patient flexes the distal interphalangeal (DIP) joint. This prevents FDS

• The FDS tendon glide exercise is achieved by isolating all fingers in extension, whilst the patient actively flexes the PIP joint of the affected finger. Holding the fingers in extension ensures that the common muscle belly of the FDP is

• At postoperative week 8, sustained grip activities are added to the programme with resistance increasing over the next 4 weeks. Heavy resistive exercises are

The inhibition of adhesion formation, promotion of intrinsic healing and production of a stronger repair can be encouraged with early passive mobilisation [77–79, 82–84]. The best known early passive mobilisation protocols are the Duran

• A postoperative dorsal blocking splint holds the MP joints at 50° of flexion and the wrist at 20° of flexion. The following regimen is followed twice daily to ensure that 3–5 mm of tendon excursion occurs to prevent firm tendon

• The patient uses the opposite hand to bring the PIP and the DIP joints from full flexion to full extension. This is done for eight repetitions for each joint.

• Then, the patient performs eight repetitions of composite MP, PIP and DIP flexion. The protocol continues through the fourth postoperative week.

• At 5 weeks, the patients begin active extension exercises with the use of a wristband. A rubber band is attached from the tip of the finger to the wristband, providing passive flexion and active extension. During this time,

• The late stage begins 8 weeks postoperatively. Progressive strength building is

• A dorsal plaster splint is applied immediately at surgery. This splint blocks the wrist and MP joint in flexion. The wrist is placed at approximately 45° of flexion, the MP joints rest at approximately 20° of flexion and the IP joints are

• One week following surgery, the plaster is replaced with a thermoplastic splint

the patient also performs blocking and FDS gliding exercises.

that maintains the same flexion angles as above.

held to its full length, preventing it from assisting in flexion.

Physiology of Flexor Tendon Healing and Rationale for Treatment Protocols

avoided before 12 weeks due to the risk of tendon rupture.

performed every hour for 10 repetitions [74]:

DOI: http://dx.doi.org/10.5772/intechopen.86064

glide.

6.2 Early passive mobilisation

adhesions [73].

encouraged.

in neutral.

113

In the Kleinert protocol:

and Houser and Kleinert regimens [73, 74]. In the Duran and Houser protocol:

The original peripheral or epitendinous suture was thought of a "tidying up" suture to improve tendon gliding within the flexor sheath [68]. It has now been shown that the peripheral suture improves the gap resistance and strength of repair [45, 58]. The simple running peripheral suture is the most investigated and used technique in flexor tendon repair because of its simplicity [45]. The strength and stiffness of the running peripheral suture can be increased by:


The location and number of knots influence the strength of the tendon repair [72]. Ex vivo studies show that decreasing the number of knots and placing them outside the repair on the tendon surface increase the strength of the repair compared to knots placed between the tendon ends [45]. However, in in vivo studies, the knots placed inside the repair sites were stronger than those outsiders after 6 weeks [72].
