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Flexor tendon- Zone 2 repair

    Overview

    Learn the Flexor tendon: Zone 2 repair surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Flexor tendon: Zone 2 repair surgical procedure.
    Primary repair of a lacerated flexor tendon is a technically demanding procedure that requires careful exposure of the tendon ends with minimal disruption to adjacent structures, meticulous tissue handling and accurate coaptation with a robust suture repair.
    A sound repair should therefore allow institution of an early active rehabilitation protocol allowing early tendon gliding, intrinsic healing with minimal scarring and restoration of normal finger motion. Most flexor tendon repairs are today performed by specialist hand surgeons working closely with hand therapists.
    Each of Verdans flexor tendon zones has a unique set of anatomical considerations which the surgeon must be aware of.
    The following technique demonstrates repair of a zone II laceration of flexor digitorum profundus (FDP).
    This zone extends from the proximal margin of the A1 pulley to the insertion point of flexor digitorum superficialis (FDS). The zone is characterised by a tight fibro-osseous tunnel with closely related pulleys and a complex interweaving of tendons.
    Sterling Bunnel called this area ‘no mans land’ alluding to the difficulty of primary repair here and historical results of attempted repair were all too often compromised by infection, dense scarring and loss of motion. Early surgeons therefore favoured acute wound closure and secondary tendon grafting of FDP. In the late 1960s however Kleinerts group published 87% good to excellent results of flexor tendon repair and this lead to a resurgence of primary repair.
    The use of prophylactic antibiotics no doubt contributed to improved early results. However over recent decades, further refinements including the routine use of magnification, meticulous tissue handling, robust suture techniques and improved rehabilitation protocols, have all contributed to improved results of repair for these potentially devastating injuries.
    Today multiple techniques of flexor tendon repair are in use according to individual surgeon preference. Each technique aims to appose the tendon ends with minimal gapping and a smooth repair site with preservation of tendon vascularity, and adequate strength to withstand rehabilitation protocols.
    Readers will also find the following techniques on OrthOracle of interest:
    First stage flexor tendon reconstruction
    Flexor tendon reconstruction: Second stage.
    Reattachment of Flexor digitorum profundus tendon

    Indications

    INDICATIONS
    The indications for flexor tendon repair are any acute laceration of a flexor tendon.
    SYMPTOMS & EXAMINATION
    A complete history and examination are important and the mechanism of injury needs to be carefully established. This includes the position of the digit when the laceration was sustained as well as any associated sensory loss.
    All skin lacerations must be examined and may require exploration.
    Composite injuries are common in hand surgery and require a low threshold of suspicion for fractures or ligamentous injury.
    The resting cascade of the digits as well as a passive tenodesis test are often indicative of tendon injury. A loss of active flexion is then assessed and each of the tendons to each digit as described below can be examined systematically.
    The FDS can be isolated by holding adjacent digits in full extension and looking for active proximal interphalangeal joint (PIPJ) flexion. A partial injury may demonstrate preserved flexion, but this may be painful.
    The FDP is examined by stabilising the PIPJ in extension and checking the presence of distal interphalangeal joint (DIPJ) flexion in the same digit.
    Light touch within each digital nerve territory should be examined. Partial loss of sensation should be assed on a visual analogue scale. Partial or complete loss of sensation in the presence of an acute laceration represents digital nerve injury and should be explored at the same time as the flexor tendon.

    IMAGING
    Plain X-rays are useful to rule out associated fracture, or if a retained foreign body such as glass is suspected.
    Imaging of the tendon itself using ultrasound is not routinely required unless there is doubt about the diagnosis or if patient factors dictate.
    ALTERNATIVE OPERATIVE TREATMENT
    An acute flexor tendon injury in the absence of any contraindications to surgery necessitates exploration and surgical repair.
    Emergency surgical treatment is warranted if the vascularity to the digit is also compromised. Otherwise tendon repair can be performed within days of the injury. The upper limit for delayed primary repair is not clearly known. Most surgeons would attempt a primary repair up to two weeks but there are many reports of successsful repair beyond this period. Delay can make a good repair more difficult to achieve, and retracted ends may be impossible to bring into apposition.
    Patients do often present with a long or unknown delay since injury. In these cases consideration should be given to flexor tendon reconstruction rather than delayed primary repair. This is covered on OrthOracle as a two stage procedure, First stage flexor tendon reconstruction and Flexor tendon reconstruction: Second stage.
    NON-OPERATIVE MANAGEMENT
    There is no role for non-operative management in an acutely lacerated flexor tendon. In one landmark study partial tendon injuries in zone 2 even involving more than 50% of the tendon width were been treated without repair but all were explored and any free tendon edge or pulley causing triggering were trimmed and patients were mobilised in a dorsal blocking splint for 4 weeks.
    CONTRAINDICATIONS
    These include local or systemic contraindications to any surgery.
    Contraindications include certain mutilating hand injuries and those with skin loss of the tendon injury as well as injuries in the presence of a grossly contaminated wound.
    Anaesthetic considerations are important. However flexor tendon repair can be carried out under regional block or local nerve block, including with adrenaline to allow surgery without tourniquet.

    Setup

    The surgery may be performed under general or regional anaesthesia. More recently a local field blockade with local anaesthetic infiltration with adrenaline. This so called wide-awake technique avoids the use of a tourniquet and preserves active muscle activation permitting active testing of gliding prior to closure.
    In this case a brachial plexus block and high arm tourniquet are used.
    The patient is supine with the arm placed on an arm table.
    Intravenenous antibiotics are used prior to tourniquet inflation.

    Operation

    The hand is placed on an arm table with an upper arm tourniquet applied.
    During positioning, the hand may be examined under anaesthetic. The loss of flexor tendon integrity is obvious here with loss of the normal resting cascade at the index finger which is resting in an extended position.
    There is a suggestion that the FDS is at least partly intact given that there is a degree of proximal interphalangeal joint (PIPJ) flexion.
    This will be exposed as part of the procedure.

    Skin preparation is applied to the hand and forearm skinThe elbow is included.
    Routine precautions regarding skin preparation are used, ensuring full coverage without pooling

    The hand is positioned in a lead handThis holds the fingers apart and extended.
    The volar laceration is examined and skin incisions are planned and marked.
    When planning incisions typically, the laceration is included and Brunners or half Brunners incisions are made. One can also make use of a midlateral incision or a transverse incision within the skin crease.
    Incisions are planned to maximise exposure without causing scar contracture.
    The history of injury and, in particular, the position of the finger at the time of laceration is an important consideration when planning the approach and deciding upon the extent of exposure required.
    A deeply flexed finger at the time of laceration results in a much more distal tendon laceration than the skin incision would indicate, whereas a laceration sustained in extension typically results in a tendon laceration at the same level as the skin laceration.
    The tourniquet is inflated prior to making the first incision.

    The skin incisions are madeFull thickness flaps are raised.
    Traversing vessels are coagulated with a bipolar diathermy.
    Digital nerve injury commonly presents alongside a flexor tendon injury. In any case the nerves must be exposed and protected as part of the approach.
    The digital nerves lie alongside the flexor sheath in a layer of fat and are closely related to the digital artery and vein.

    Stay sutures are applied to each skin flap.A 4/0 nylon suture is used here. The sutures can be secured to the dorsal skin or left long and clipped, as here.
    This reduces the need for retraction and frees up the assistant for other tasks.

    The distal flexor sheath is exposedGentle blunt dissection with a pair of tenotomy scissors allows the volar fat to spread apart exposing the flexor sheath.

    The following slides assume a working knowledge of the flexor sheath and arrangement of pulleys, as demonstrated in this diagram.

    The flexor sheath is openedThe sheath is opened over the laceration and can be lifted to one side as a flap (A), using a sharp blade.
    The A3 pulley is included in this particular approach but the image shows the intact distal A2 pulley just proximal to the cut tendon end (B).
    It has long been regarded as important to preserve the A2 and A4 pulleys to prevent bowstringing.
    Venting of these pulleys in part, where snagging of the tendon ends or repair may inhibit free gliding, is now regarded as accepted practice and is described later.
    More recently, opinion has shifted to suggest that where required for tendon gliding without impediment, opening up the entire A2 or entire A4 pulleys to improve exposure and prevent catching or tethering should be prioritised over preserving these pulleys at all costs.
    Relevant studies regarding the changing priorities in pulley management are included in the results section at the end.

    The extent of damage to the tendons is assessedThere is a high chance that the distal A2 will need opening up in this procedure given the location of the repair.
    Therefore the distal half is opened at the outset to improve access.
    Once this is done, the proximal FDP stump can be identified.
    The A4 pulley has been preserved as exposure is adequate, but may require venting after the repair is complete.
    This injury is consistent with a laceration sustained with the digit in an extended position.
    The FDP is completely divided and there is a partial laceration of FDS at its insertion.
    The wound is irrigated with normal saline.
    The distal tendon end may be brought into view by passively flexing the DIPJ.
    This step may be complicated by a retracted proximal tendon. A number of techniques for retrieving a retracted tendon stump are described. Initially, milking the sheath by massaging the finger in a proximal to distal direction. If this proves difficult, extending the incision proximally may be tried. Alternatively a separate incision in the distal palm can be utilised to expose it proximal to the injury. One may then use forceps to ‘walk’ the tendon up into the distal sheath.
    Sourmelis and McGrouther describe a method for tendon retrieval using a paediatric feeding tube passed into the sheath into the palm, proximal to the A1 pulley. The tube is sutured to the tendons proximally and pulled through distally.

    The proximal tendon end is secured to prevent retraction into the sheath, using a blue hypodermic needle.This helps to minimise handling of the tendon which is a rather mobile structure with a tendency to retract.
    A skin hook may enable traction to be applied from a single point of contact without grasping the tendon.
    It is important to note that handling of the tendon with instruments, however gently, causes surface trauma to the tendon and may predispose to adhesion formation.
    A blue hypodermic needle is used to secure the tendon once the tendon end is correctly aligned and apposed to the distal stump.

    This image shows (at A) the long vinculum to the FDP containing the vincular artery that supplies the tendon. Core sutures are passed in the volar aspect of the tendon to prevent disruption to this dorsal network of vessels.

    The FDP is partially lacerated but largely intact.
    Any loose flaps of tendon may be trimmed away, or sutured down to ensure that there is no loose flap to interfere with tendon gliding within the sheath.

    The radial slip of the FDS is repairedA 6/0 prolene suture is used to place a running stitch along the FDP radial slip laceration where the lacerated flap is mobile.

    A backwall first technique is employed for the FDP repairThe standard flexor tendon repair utilises a multi-strand core suture with a peripheral epitendinous suture.
    The back wall epitendinous suture is placed first, as a continuous running suture using 6/0 double ended Prolene.
    This “backwall first” technique is particularly useful where access to the back wall will be limited after the core sutures have been placed.
    It also helps achieve correct alignment and orientation of the tendon ends prior to core suture placement.

    The backwall sutures also help orientate the tendon ends prior to placement of the core sutures.
    One the backwall is complete the two suture ends are clipped and preserved for the front wall epitendinous sutures to be plaed after placement of the core sutures.

    There are numerous core suture configurations described.
    Here a 4 strand cruciate technique, also known as the Adelaide technique, is described.
    Increasing the number of strands from 2 to 4 or 6 core strands has been shown in laboratory testing to increase load to failure( a good thing). However meta-analyses of clinical data show no difference in rupture rate and number of core strands. In addition the placement of extra strands possibly increases tendon handling and may increase the bulk of the repair, compromising gliding within the confines of the fibro-osseous sheath.
    In this technique the knot will be situated in the centre of the repair site.
    The technique utilises a cross locked arrangement with four externally visible crossed suture lines, one on each side of each tendon end.

    The suture material used in this case is a 4/0 Prolene. The monofilament suture handles well, is non absorbable and therefore maintains its strength throughout the rehabilitation period and causes minimal soft tissue reaction. It slides well through the tendon substance and therefore is amenable to final adjustments in tension when the knot is being placed.
    A round bodied needle is preferred by most hand surgeons as this is assumed to cause less damage by pushing collagen fibres apart rather than dividing them. Perhaps more importantly a cutting needle may cut or damage previous suture material in a multi strand repair.
    As the core sutures are placed. each bite should emerge at 1 cm from the tendon end.
    The strands should be passed within the volar half of the tendon substance to protect the dorsal blood supply, described above.

    Here the final component of the first crossed suture is being placed.
    Note the entry point of the needle in relation to the previous part of the cross and the relatively volar position of the needle within the tendon.
    Handling of the tendon itself is minimised, and most sutures can be placed without the need to handle the tendon at all.
    If tendon handling with forceps is required, a fine set of Adsons may be used to grasp the tendon at the endo-tenon and avoid microinjury to the epitendinous tissue

    The corresponding suture in the distal tendon has been placed.
    The needle is now directed to emerge in the centre point of the gap in order to cross the midpoint and enter the radial half of the proximal tendon.
    As the suture is puled through the proximal suture is guided down into position.
    This must be done without grasping the prolene suture at any point as any kinking or crushing of the tendon significantly increases the risk of suture failure.

    With all four strands placed, one can see the external locked suture crosses in each half of each tendon end.
    The non-braided prolene suture will continue to glide through the tendon and final tension should be adjusted to a point where all suture material is seated securely without gapping at the repair site, as demonstrated here.

    The knot is placed carefully, maintaining the tension achieved.
    The knots are seated squarely and 4 to 6 knots are placed.
    The suture ends are divided, ensuring that the suture ends are buried in the repair.
    Some studies have shown single knotted arrangements to be superior to those with double knots and these are detailed in the references section.

    The wound is irrigated with normal saline.

    The front wall suture is completedThe 6/0 double ended Prolene suture is now unclipped and used to complete the front wall.
    Here a Silverskold suture technique is demonstrated.
    One can vary the length of each bite to capture any prominent ends of tendon at the repair site.
    The epitendinous suture adds strength to the repair as well as making the repair as neat as possible.
    This Silverskold technique is stronger than a simple running suture but does leave more tendon material exposed on the gliding surface.

    The final repair is demonstrated here.
    The finger is moved passively to check the integrity of the repair as well as any impediments to free gliding of the tendon within the sheath.
    The edge of the remaining A2 or A4 pulleys may require venting

    Pulley venting is performed if necessary prior to closure.The distal edge of A2 is being vented a few millimeteres. Gliding will be rechecked.
    The method of venting these pulleys is to simply divide the pulley along its volar midline to the length required for adequate tendon gliding.
    Some authors recommend that the A4 pulley can be entirely vented and the A2 to 2/3 of its length without undue concern about bowstringing.
    More recently, opinion has shifted to suggest that where required for tendon gliding without impediment, opening up the entire A2 or entire A4 pulleys to improve exposure and prevent catching or tethering should be prioritised over preserving these pulleys at all costs, as true bowstringing is rare and seldom as much of a concern as impaired gliding.

    Tendon gliding is checked prior to wound closure.Pressure over the flexor compartment of the forearm mimics active flexion and demonstrates tendon gliding.
    It does not mimic deep flexion effectively however and this is better assessed using the wide awake technique described earlier.

    Wound closure is performedAfter irrigation of the wound and flexor sheath, the wound is closed with simple interrupted skin sutures.
    An absorbable suture in the form of 5/0 Vicryl rapide is used here but a non-absorbable suture could also be used.

    The wounds are dressed with a non-adherent dressig such as Jelonet.
    This is covered with a layer of blue gauze.
    A layer of extra padding with sterile wool is applied over the hand and forearm up to the elbow.

    A dorsal plaster of Paris slab is applied.
    The plaster must extend beyond the finger tips.
    The wrist and MCP joints should be placed in 20 to 30 degrees of flexion and the PIPJ and DIPJs are placed in 0-10 degrees of flexion.

    Post Operative

    The arm is placed in a Bradford sling.
    The patient may be discharged home at on the day of surgery if safe.
    The patient will return to hand therapy appointment at 2-5 days post-operatively and placed into a dorsal blocking splint with 70 degrees of MCPJ flexion. Within this splint the patient is then taught to place the fingers into a fist and perform a number of passive flexion and active extension exercises within the splint.
    This is followed by a tenodesis cycle that is repeated 10 times. This requires passive flexion of the fingers with the wrist in extension, out of the splint. A series of active finger flexion exercises are followed by holding the fingers passively flexed using the uninjured hand for 5 seconds. This is followed by wrist flexion and passive finger extension.
    At three weeks post operatively composite active range of motion exercises are commenced.
    The hand therapist assesses risk and patient progress throughout the programme and may accelerate or decelerate the programme according to the individual patient.
    The splint is usually discarded at 6 weeks. At this stage any PIPJ contractures may require stretching with static progressive splinting.

    Recommended Reading

    Most units report 70-90% good to excellent outcomes from flexor tendon repair, with a rupture rate of approximately 5% and a tenolysis rate of 5%.
    The following studies are important background reading with some guidance about current trends.
    Primary repair of lacerated flexor tendons in “No Man’s Land” Kleinert HE, Kutz JE, Ashbell TS, Martinez E. J Bone Joint Surg Am. 1967;49:577.
    An early paper described above, that heralded the current era of flexor tendon repair.
    Comparison of 1- and 2-knot, 4-strand, double-modified Kessler tendon repairs in a porcine model. Rees L, Matthews A, Masouros SD, Bull AM, Haywood R. J Hand Surg Am. 2009;34:705–9.
    A laboratory based study demonstrating the superiority of a 1 knot core suture configuration over two knot methods.
    Flexor tendon repair in the hand with the M-Tang technique (without peripheral sutures), pulley division, and early active motion. Giesen, T, Reissner, L, Besmens, I, Politikou, O, Calcagni, M. J Hand Surg Eur. 2018, 43: 474–9.
    This study is one of a few recent reports appearing to demonstrate no adverse effects from releasing the entire A2 pulley.
    This has lead some surgeons to advocate more extensive venting or release in those cases where it is required for full and unimpeded tendon gliding as it is felt that even minor bowstringing is preferable to a restricted tendon.
    A systematic review of 2-strand versus multistrand core suture techniques and functional outcome after digital flexor tendon repair. Hardwicke JT, Tan JJ, Foster MA, Titley OG. J Hand Surg Am. 2014 Apr;39(4):686-695.e2.
    AN important systematic review comparing 2 strand and multistrand core suture techniques. The evidence supporting multi-strand repairs over raditional 2 strand techniques appear to be largely based on laboratory testing
    The cellular effect of a single interrupted suture on tendon. Wong JK, Cerovac S, Ferguson MW, McGrouther DA
    J Hand Surg Br. 2006 Aug; 31(4):358-67.
    An important study demonstrating a zone of reduced cell populations around suture material.
    Recent evolutions in flexor tendon repairs and rehabilitation. Tang JB. J Hand Surg Eur Vol. 2018 Jun;43(5):469-473.
    An essential read. Tangs reviews much of the recent literature and identifies some important trends. Of particular note is the move towards a tolerance for bulkier repairs that may be less liable to gap during active motion. Also mentioned are the newer rehabilitation regimes such as those using the Manchester short arm splint.

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