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Scaphoid fracture- Vascularised graft based on the volar carpal artery for non-union

    Overview

    Learn the Scaphoid fracture: Vascularised graft based on the volar carpal artery for non-union surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Scaphoid fracture: Vascularised graft based on the volar carpal artery for non-union surgical procedure.
    Approximately 10% of scaphoid fractures will proceed to a non-union. The incidence is higher for fractures involving the proximal pole (up to 90%) and also is increased if there is a delay to diagnosis, inadequate immobilisation or significant displacement of the fracture.
    There are two anatomical factors in particular that predispose the scaphoid to non-union. The first is that it is almost entirely intra-articular with limited soft tissue attachment for vascular inflow. With respect to the proximal pole it is served by an intra-medullary vessel that enters the dorsal distal waist which makes proximal pole fractures particularly prone to non-union due disruption of this vessel. The second that the scaphoid has no periosteum and so requires primary bone healing. Furthermore the scaphoids shape and articulations makes it difficult to immobilise. Fractures across its waist having a tendency to displace into a flexed position.
    Scaphoid non-union represents a difficult surgical problem. Although some authors report satisfactory union rates following standard bone grafting techniques, others report failure rates as high as 65%.
    A variety of techniques have been described to treat scaphoid non-union but the use of a vascularised rather than a non-vascularised graft has been shown to improve overall union rates especially where there is doubt about the vascularity of the proximal pole. One RCT directly comparing union rates in proximal pole non-union demonstrated an 89% union rate using vascularised bone graft compared to 72% with non-vascularised graft.
    Various vascularised bone graft techniques are described in the literature. These include a dorsal distal radius bone graft raised upon the 1/2 inter-compartmental supraretinacular artery found between the 1st and second dorsal extensor compartments first described by Zaidemburg in 1988.
    Another technique described is the use of a free vascularised bone graft taken from the medial femoral condyle. A summary of the techniques available is listed in the references at the end.
    In this case a vascularised graft from the volar aspect of the distal radius is was used to fix a scaphoid non-union using a volar approach.
    The mini Acutrak headless screw system is used in this case. It offers a tapered, fully threaded designed with a variable pitch and thus offers compression and sits beneath the bone surface.
    The history, presentation, imaging and surgical decision making are described in the next section.
    Readers will also find of use the following OrthOracle techniques:
    Scaphoid non-union: Zaidemberg (1-2 Intercompartmental Supraretinacular) Vascularised Bone Graft with Acumed Screw Fixation.
    Arthroscopic assisted Scaphoid non-union grafting and fixation using Acutrak screw

    Indications

    INDICATIONS
    A vascularised bone graft fixation of a scaphoid non-union aims to achieve union across the fracture site restoring length and alignment, restoring stability across the wrist joint.
    SYMPTOMS & EXAMINATION
    A scaphoid non-union is conventionally defined as one that has failed to unite by 6 months. It may present as an incidental finding but often present with a variable period of wrist pain following an injury that may or may not be recalled by the patient. A axial load in hyperextension and radial deviation is the common mechanism of initial injury.
    Examination reveals pain on wrist motion and loading and tenderness over the scaphoid tubercle and within the anatomical snuffbox.
    Often an asymptomatic scaphoid non-union may be detected incidentally following another injury. Conversely an adequately treated scaphoid fracture can progress to a non-union.
    IMAGING
    Plain radiographs will usually reveal the non-union. There may be cystic change at the fracture or sclerosis present.
    A CT is a useful adjunct, to further define fracture anatomy and exclude, for example a humpback deformity. In this case a humpback deformity was seen with a large proximal pole fragment. CT may also be useful to demonstrate the potential for union in a delayed union scenario. The presence of bridging trabeculae provide evidence of healing and likely progression to union.
    An MRI demonstrates the vascularity of the fragments. MRI in the acute setting is useful to diagnose a scaphoid fracture. Gadolinium enhancement is useful to demonstrate avascularity of the proximal pole.
    All of these modalities may demonstrate secondary degenerative joint change.
    ALTERNATIVE OPERATIVE TREATMENT
    Some surgeons would opt for a non-vascularised cortico-cancellous bone graft from the iliac crest or distal radius with a compression screw. Alternatively a vascularised graft could be taken from either the dorsum of the wrist, such as the Zaidemburg graft raised on the 1,2 intercompartmental supraretinacular artery. This would necessitate a dorsal approach to the scaphoid, and is often preferred when access to the proximal pole is critical such as for a proximal pole non union.
    In this case the presence of a relatively large proximal pole fragment with humpback deformity was deemed more easily correctable using a volar approach and therefore a volar distal radius graft raised on the transverse carpal artery was used.
    NON-OPERATIVE MANAGEMENT
    Untreated, a scaphoid fracture will cause the wrist joint to progress through a sequence of degeneration eventually involving the entire wrist joint known as scaphoid non-union advanced collapse (SNAC). A patient presenting with evidence of degenerative joint disease will require an alternative treatment approach.
    CONTRAINDICATIONS
    The general contraindications for any hand surgical procedure apply. In addition the presence of degenerative changes indicative of a SNAC wrist demand a different approach to treatment and these are described elsewhere. It is worth mentioning that scaphoid non-union surgery in general has poorer outcomes in smokers and this must be discussed with the patient.

    Setup

    A standard operating arm table is used. The patient is positioned supine and a general anaesthetic or regional block (as here) may be used.
    A dose of prophylactic antibiotics is administered.
    Local thromboprophylactic protocols are followed.
    An upper arm tourniquet is inflated after exanguination of the limb.
    Bipolar diathermy, fluoroscopy and loupe magnification are required.

    Operation – 1

    This plain X-ray demonstrates the fracture non-union with a reasonably large proximal pole fragment as well as some cystic changes.
    It is important to note that there are no secondary degenerative changes within the wrist joint.

    A CT is useful to further define fracture anatomy and in this case demonstrates a flexed distal fragment as well as some cystic changes in both fragments
    CT may also be useful demonstrate the potential for union with the presence of bridging trabeculae indicating evidence of healing.

    Proximal pole necrosis is a poor prognostic factor in scaphoid nonunion.
    A proximal pole showing low T1 signal and bright STIR signal denotes the presence of avascular necrosis.
    In this case the MRI scan demonstrated a degree of oedema in the proximal pole. This is associated with poor vascularity but is not clear evidence of avascular necrosis.

    The scaphoid tubercle (marked A) is palpated and the location of the FCR tendon is also confirmed when planning the volar approach.

    The incisions are marked out.
    A curvilinear incision crossing the wrist joint is centred upon the easily palpable scaphoid tubercle distally. The proximal extension is marked radial to the FCR tendon.

    The hand and wrist are held in position using a lead hand. Adequate exposure of the scaphoid will require the wrist to be placed into a degree of extension and ulnar deviation.
    The skin incision is made.

    Any large veins crossing the field at the wrist crease are coagulated.

    Dissection proceeds just radial to the flexor carpi radialis tendon, avoiding any exposure of the radial artery, the most radial structure visible, at this stage.
    The anterior capsule containing the radioscaphocapitate (RSC) ligament is reflected to expose the distal volar margin of the radius and the scaphoid.
    A – Tubercle
    B – Capsule and RSC ligament

    The scaphoid is now visualised. Some further reflection of the capsule may be needed to obtain a good exposure.
    At this stage the non-union may well be obvious but occasionally there is a bridge of fibrous tissue and it may not be apparent until further attempts are made to locate and define it.
    Here a Watson-Cheyne elevator is gently introduced into the non union site.

    There is a significant humpack deformity and the nonunion site cannot be entered until the distal scaphoid is distracted to open up the gap.
    Various techniques are described to achieve this.
    Here a 1.25mm K-wire is passed into the the distal scaphoid. This can be used as a joystick to extend the scaphoid and open up the volar non-union site.
    Traction on the thumb may also help to distract the distal scaphoid.
    An alternative means of opening the volar surface of the scaphoid and improve access to the fracture surfaces is to use a small laminar spreader placed within the non-union site.

    Applying gentle thumb pressure upon the K-wire, one is able to extend the distal scaphoid, opening up the non-union whilst a curette is used to remove any loose debris and expose the proximal and distal bone surfaces.

    The fracture surfaces are hard with some sclerotic bone. These are gently scraped and roughened with a curette.
    The most dorsal layer of fibrotic tissue at the very base of this opening is left intact in order to contain the bone graft and prevent extrusion into the dorsal soft tissues.

    Additionally a fine burr may be used to remove some of this sclerotic bone. At this stage it is important to plan ahead and decide upon the size and shape of graft that will be placed here.
    The cortical component of the graft will need to be seated into the volar aspect of the non-union to hold it open and correct the humpback deformity.
    The burr therefore aids in removing a few mm of bone to create an even shaped gap within which a trapezoidal graft will be seated.


    The proximal pole here is harder and paler in colour.
    Releasing the tourniquet will allow examination of the proximal pole for punctate bleeding indicating some preserved vascularity.

    The proximal part of the incision is now made to obtain the graft.
    The interval between the radial artery and FCR is entered.

    Tenotomy scissors are used here to divide the fascia.

    This image is taken from the opposite side of the table with the right side now distal.
    The FCR tendon (B) is retracted in an ulnar direction. The muscle fibres of pronator quadratus can be seen in the depths of the wound. (A)
    The fascia over the distal 5mm of this muscle is incised with an underlying strip of muscle and this should be included in the pedicle when it is mobilised in the next step.
    The wire indicates the position of the distal scaphoid. (C)

    Tenotomy scissors are used for blunt dissection in the fatty layer just radial to the FCR tendon. This reveals the radial artery and its venae commitantes.
    Great care is required to avoid damage to the artery and to its volar carpal branch which will be running in an ulnar direction within the fat at this level.

    The volar carpal artery can now be seen running along the distal margin of the pronator quadratus muscle. It can be seen running within the fat laterally at its origin from the radial artery.
    Dissecting such a small vessel may lead to inadvertent damage and a cuff of adjacent tissue should therefore be preserved.
    As the vessel passes along the distal margin of the pronator quadratus muscle it is adherent to the periosteum and must be raised with a cuff of periosteum as well as the fascia and muscle of the distal 5mm of pronator quadratus.

    The volar carpal artery (A) can be seen here branching away from the radial artery (B), running from radial to ulnar and passing into the subperiosteal plane just distal to pronator quadratus.
    The Mcdonalds elevator indicates the location of the distal edge of pronator quadratus.
    Because only the wide cuff that is left around the pedicle is handled directly, micro instruments are not used.

    This slide returns to the original viewing angle with the distal scaphoid seen on the left and the radial artery at the top of the image.
    A cuff of periosteum is preserved around the pedicle and over the graft itself. This is lifted using a combination of 5mm osteotomes and a sharp blade.

    The periosteum is lifted and traced back towards the main artery, there will be some bleeding from the bone. Suction is used to ensure the field is kept clear.
    In this way the entire pedicle is isolated and mobilised off the bone prior to harvest of the bone graft.
    This slide demonstrates:
    A – The radial artery
    B – The cuff of fat surrounding the lateral part of the pedicle
    C- The periosteal sleeve in which the medial part of the pedicle lies. This is being elevated.
    D – The bone graft site (not yet elevated)
    E – The distal edge of pronator quadratus

    The graft dimensions are marked onto the volar surface of the radius.
    A 10mm osteotome is used to harvest the graft. The periosteum on the volar surface of the graft contains the pedicle (A) and is protected.
    This slide shows a block of cancellous bone is included in the graft.
    To prevent delamination of the cortical bone from this layer a 5mm osteotome is angled to raise a trapezoidal block of cancellous bone.
    In this step it is possible to breach either the distal radius articular surface or the DRUJ joint by misjudging the position of the donor site. If there is any doubt, a hypodermic needle can be inserted into the joint and left as a reference point.
    Furthermore some authors suggest placing a temporary wire into the ulnar corner of the distal radius to mark the limit of bone graft harvest and prevent a breach of the distal radio-ulnar joint.

    The bone graft is lifted out.
    A – Radial artery
    B – Cortical bone
    C – Cancellous bone
    D – Pedicle
    At this point the tourniquet is released to confirm bleeding of the bone graft.

    A sharp blade is used to lift the final few mm of periosteum containing the pedicle. This is at the radial edge of the graft site.
    The remaining pedicle between this and the radial artery itself has already been mobilised earlier.

    Operation – 2

    Further cancellous bone graft is harvested from the graft site using a curette.
    The curette is aimed in a radial and proximal direction, away from the subchondral bone. This avoids the risk of breaching either articular surface (radiocarpal joint or distal radioulnar joint) and is also the location of softer metaphyseal bone.

    With the humpback deformity held in a corrected position. The Acutrak guide wire is passed into the distal scaphoid and across the nonunion into the proximal pole.
    A degree of overcorrection of the deformity is necessary as some correction will be lost as the graft is placed and the compression screw is placed.

    Here the guidewire has been placed and the gap in the volar surface is apparent.
    A – Guidewire
    B – Distal scaphoid
    C – Proximal scaphoid

    Morsellised cancellous bone is initially placed into the gap, packing the dorsal and central aspects of the defect.

    The pedicled bone graft is now brought into the non-union and should sit into the volar aspect of the scaphoid, upon the cancellous graft packed undeneath.
    The cortical component and pedicle will face volar and the cancellous component should face the inside of the non-union in a dorsal direction.
    Ideally the cortical component should lodge into the edge of the non union just beneath the volar surface.
    The integrity of the vessel within the pedicle should be confirmed and there should be some ongoing bleeding from the graft.
    The pedicle should not be under any tension.
    This is a difficult stage and some adjustment is usually required to get the graft to sit correctly.
    This may include:
    1. Adjusting the wire position to widen or narrow the volar gap.
    2. Trimming the edge of the graft with fine nibblers.
    3. The pedicle should not be under tension and it may therefore be necessary to free any tight fascial connections in the cuff of soft tissue surrounding the proximal aspect of pedicle. This is preferable to placing any tension on the pedicle
    4. If there is still difficulty in getting the graft to reach the non-unon site, the radial artery proximal to the pedicle take off may be mobilised along its length.
    4. Further cancellous bone graft is usually needed to pack around the graft once seated.

    With the pedicle held in the volar aspect of the gap, the guidewire is advanced to secure it.
    The guide wire is not passed through the vascularised graft, and care is taken to avoid injury to the pedicle.

    Images are next taken using a mini c-arm. These should confirm:
    1. Adequate position of the guide wire and the subsequent screw.
    2. Adequate correction of the humpback deformity.
    3. Adequate positioning of the bone graft within the non-union.
    The measuring tool gives an idea of the screw length. The Mini-Acutrak manufacturer recommends subtracting 2-4mm from the measured length to allow for compression and to ensure the screw remains buried beneath the articular surface.
    Two drill bits are used in succession to drill first the entire length of the guide wire, followed by the short drill to widen the near cortex only.

    The Mini Accutrak screws are packed individually. Once opened, the screw length is checked and it is mounted onto the screwdriver.
    The screw length is typically no longer than 26mm for adult males and 22mm for females.

    The screw is carefully passed from distal to proximal. Here a digit is placed over the graft. This allows one to assess the effect of compression upon the graft.

    The final compression is applied with a great deal of care ensuring that the graft remains in position without fracture or extrusion.
    There is a degree of fine judgement required here. Ideally as the screw reaches the proximal pole it will offer more resistance as it engages and compresses the construct. An attempt to gain extra compression beyond this risks losing the compression and position already achieved.
    Repeated images can be taken to judge the screw position and deformity correction. Due to the scaphoids unique shape, a number of projections are required to confirm that the position is correct. Any screw prominence proximally or distally can be visualised directly in this open technique.

    The final few turns of the screw are made. The Mini Accutrak screw is below the surface of the scaphoid
    A – Distal scaphoid + screw driver over screw head
    B – Vascularised bone graft sited at non-union site
    C – Pedicle
    D – FCR tendon

    Intra-operative images demonstrate the final screw position. It demonstrates the graft placed with the gap.
    This image also shows the donor site in the distal radius. It is worth noting its proximity to the articular surface of the wrist joint.

    The wound is thoroughly irrigated with normal saline.
    A final haemostatic check is made and the tourniquet may be released to aid this.
    A layered closure is performed. The radioscaphocapitate ligament and capsule are closed as a single layer with 3/0 vicryl.

    The superficial layers are closed with monocryl with a running subcuticular suture to close the skin.

    Steristrips are used to support the closure.

    A well padded below elbow volar plaster slab is applied with the wrist in 45 degrees of extension and the digits left free.
    The patient is placed into a Bradford sling for elevation and protection of the limb

    Post Operative

    The patient is allowed to return home the same day if postoperative pain is under control. Strict elevation in a Bradford sling is recommended for the first 72 hours.
    A wound check is performed at 1 week in the outpatient clinic. The backslab is replaced with a lightweight full below elbow cast with the thumb and digits left free.
    A repeat X-ray is taken at 6 weeks to look for evidence of union. A further 6 weeks of immobilisation with further radiographs to follow are required if there is no evidence of union.
    Immobilisation is continued until there is radiographic evidence of union. CT is helpful to confirm union where there is doubt.

    Recommended Reading

    Scaphoid Plate Fixation and Volar Carpal Artery Vascularized Bone Graft for Recalcitrant Scaphoid Nonunions.Dodds SD et al.J Hand Surg Am. 2016 Jul;41(7):e191-8.
    A recent series using a volar buttress plate with a volar carpal artery graft demonstrated vascularised union in 8/9 patients.
    Scaphoid Nonunion With Poor Prognostic Factors: The Role of the Free Medial Femoral Condyle Vascularized Bone Graft. Chaudhry T, Uppal L, Power D, Craigen M, Tan S. Hand (N Y). 2017 Mar;12(2):135-139.
    This is our series using an MFC free flap in non-unions with poor prognostic factors. Union rates are comparable to earlier series of this technique reported by other groups.

    The prevalence of established scaphoid fracture non-union found on incidental radiography. Sehat KR, Bannister GC. Injury. 2000 May;31(4):275-6.
    An interesting study demonstrating a 0.14% prevalence of scaphoid non union in the general population.

    Natural history of scaphoid non-union, with special reference to “asymptomatic” cases. Lindström G, Nyström A. J Hand Surg Br. 1992 Dec;17(6):697-700.
    A classic study. 33 patients with scaphoid non union were followed for a period of up to 37 years and revealed radiographic changes of OA in all.

    Treatment of scaphoid nonunion with vascularised and nonvascularised dorsal bone grafting from the distal radius.
    Ribak S, Medina CE, Mattar R Jr, Ulson HJ, Ulson HJ, Etchebehere M. Int Orthop. 2010 Jun;34(5):683-8. doi: 10.1007/s00264-009-0862-6.
    An RCT directly comparing vascularised with non vascularised bone grafting for proximal pole non-unions demonstrating higher union rates with vascularised grafts (89% vs 72%)

    The natural history of scaphoid non-union. A review of fifty-five cases. Ruby LK, Stinson J, Belsky MR. J Bone Joint Surg Am. 1985 Mar;67(3):428-32

    Treatment of scaphoid nonunions: quantitative meta-analysis of the literature. Merrell GA, Wolfe SW, Slade JF 3rd. J Hand Surg Am. 2002 Jul;27(4):685-91.
    Vascularized bone graft pedicled on the volar carpal artery for non-union of the scaphoid.
    Kuhlmann JN, Mimoun M, Boabighi A, Baux S. J Hand Surg Br. 1987 Jun;12(2):203-10.

    Reference

    • orthoracle.com

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