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Scaphoid fracture- Percutaneous retrograde headless screw fixation using the Acumed Acutrak screw system

    Overview

    Learn the Scaphoid fracture: Percutaneous retrograde headless screw fixation using the Acumed Acutrak screw system 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: Percutaneous retrograde headless screw fixation using the Acumed Acutrak screw system surgical procedure.
    Scaphoid fractures are commonly seen in the young adult male following a sporting injury or a fall on the outstretched hand. More than half of scaphoid fractures occur in the middle third of the bone, as the trabeculae here are the thinnest and most sparsely distributed. The fractures heal by intramembranous ossification with minimal callus to provide initial stability. Premature wrist loading results in varying degrees of shearing, bending and translational forces and will predictably angulate as volar bone is reabsorbed, yielding a “humpback” of flexion deformity of the scaphoid. An untreated or poorly treated scaphoid fracture is highly likely to progress to malunion or non-union. As the scaphoid is a pivotal bone joining the proximal and distal rows, this can result in significant alteration in the wrist biomechanics and degenerative arthritis. Therefore, timely management of the scaphoid fracture is crucial.
    Scaphoid fractures are the second most common injuries in the wrist after distal radius fractures and treatments of the undisplaced and minimally displaced fractures of the scaphoid waist have been a source of debate for a long time. The advantages of conservative management in plaster versus surgical internal fixation have been extensively studied, with no clear consensus (Bond et al 2001, Buijze et al 2010, Dias et al SWIFFT Trial 2020) other than an agreement that a surgically fixed scaphoid fracture is likely to return to activity earlier.
    The implants for surgical fixation of scaphoid have evolved significantly over the last 3 decades. Development of cannulated screws, which can be threaded over guide wires and inserted under fluoroscopic control, has minimized the soft tissue exposure and injury following an open fixation.
    The Acumed Acutrak Headless Compression screw is a conical cannulated screw with the following features:
    1. Minimal soft tissue irritation through Headless Fixation
    2. Enhanced fracture fixation and improved pull-out strength through a Fully Threaded Construct using a Cancellous Based Thread Design
    3. Enhanced window of compression through a Continuously Variable Screw Pitch
    This is a Titanium implant with diameters ranging from 2.5mm-7.0mm; making it a versatile tool for a variety of surgical fixations. The Micro(2.5mm), Mini(3.5mm) and Standard(4.0mm) sizes are most suitable for a scaphoid fracture.

    Bond CD, Shin AY, McBride MT, Dao KD. Percutaneous screw fixation or cast immobilization for nondisplaced scaphoid fractures. JBJS. 2001 Apr 1;83(4):483.
    Buijze GA, Doornberg JN, Ham JS, Ring D, Bhandari M, Poolman RW. Surgical compared with conservative treatment for acute nondisplaced or minimally displaced scaphoid fractures: a systematic review and meta-analysis of randomized controlled trials. JBJS. 2010 Jun 1;92(6):1534-44.
    Dias JJ, Brealey SD, Fairhurst C, Amirfeyz R, Bhowal B, Blewitt N, Brewster M, Brown D, Choudhary S, Coapes C, Cook L. Surgery versus cast immobilisation for adults with a bicortical fracture of the scaphoid waist (SWIFFT): a pragmatic, multicentre, open-label, randomised superiority trial. The Lancet. 2020 Aug 8;396(10248):390-401.

    Readers will also find the following OrthOracle operative techniques of interest:
    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
    Scaphoid non-union: Vascularised graft based on the volar carpal artery
    Four Corner carpal Fusion using Medartis plate and scaphoid excision
    Radioscapholunate fusion using Medartis plate with distal Scaphoid excision


    Indications

    Scaphoid fractures are commonly seen in the young adult male following a sporting injury or a fall on the outstretched hand. More than half of scaphoid fractures occur in the middle third of the bone, as the trabeculae here are the thinnest and most sparsely distributed. The fractures heal by intramembranous ossification with minimal callus to provide initial stability. Premature wrist loading results in varying degrees of shearing, bending and translational forces and will predictably angulate as volar bone is reabsorbed, yielding a “humpback” of flexion deformity of the scaphoid. An untreated or poorly treated scaphoid fracture is highly likely to progress to malunion or non-union. As the scaphoid is a pivotal bone joining the proximal and distal rows, this can result in significant alteration in the wrist biomechanics and degenerative arthritis. Therefore, timely management of the scaphoid fracture is crucial.
    Various classification systems have been proposed for the scaphoid fracture (Bohler-1954, Russe-1960, Cooney-1980, Herbert-1984). Cooney’s modification, identifying unstable fractures, is very useful in planning management. These unstable fractures have greater than 1 mm of displacement, a lateral intrascaphoid angle greater than 35 degrees, bone loss or comminution, perilunate fracture-dislocation, DISI alignment, and proximal pole fractures. He advocated open surgical fixation for all unstable injuries.
    Screw fixation of scaphoid has evolved over the years with improving knowledge of biomechanics and advancements in metallurgy. McLaughlin (1954) originally described fixation with solid lag screws. The first significant innovation was by Herbert and Fisher (1984) with the introduction of a headless screw that could be buried under the articular surface. In addition, the screw had two heads of different thread pitch, a concept that allowed the surgeon to achieve some compression at the fracture site during screw insertion. However, the technique of screw insertion was very demanding. Although Huene subsequently devised a drill guide to simplify the placement of the Herbert screw, it was Whipple who introduced the cannulated screw. This could be threaded over a guide wire inserted under fluoroscopic guidance, which made the technique far less challenging and more reproducible. The Acumed Acutrak Headless Compression screw is a conical cannulated screw, with a continuous variable pitch of the screw threads, and provides better and reliable compression across the fracture site.
    INDICATIONS
    This technique is best suited for the following types of acute scaphoid fractures.
    Undisplaced or minimally displaced fracture of the middle third of scaphoid
    Displaced fracture which can be anatomically reduced with manipulation
    SYMPTOMS & EXAMINATION
    The patient often presents with a history of a fall on the outstretched hand or a sporting injury. Cadaveric studies have shown that axial loading on a hyperextended and radially deviated wrist produces tensile force on the scaphoid bone, resulting in its fracture. High-energy forces, as in a Road Traffic Accident, can result in a more severe pattern, with concomitant carpal and ligamentous injuries.
    The clinical signs are bruising and swelling along the radial and dorso-radial aspect of the wrist. Tenderness can be elicited in the anatomical snuff box and over the scaphoid tubercle. Axial loading of the scaphoid is likely to be painful.
    It is important to remember that none of these signs are specific for a scaphoid fracture and can be deemed positive in a variety of conditions such as DeQuervain’s tenosynovitis, degenerative changes in the radio-scaphoid, scaphotrapezial and trapezo-matacarpal joints, ligamentous injuries along the dorso-radial wrist, and fractures of the radial styloid, trapezium and thumb metacarpus. A high index of suspicion and correlation with radiographic assessments is vital in identifying a scaphoid fracture.
    Finally, it is important to rule out any concomitant injuries, especially in a high-energy mechanism.
    IMAGING
    Xrays – These is the mainstay of investigations. It is recommended that the patients undergo 5 specific radiographic views. These are:
    Postero-anterior view (PA view) – preferably with a clenched fist so as to rule out any associated scapholunate ligament injury
    Lateral view – to identify any carpal malalignment
    Semipronated oblique view
    Semisupinated oblique
    PA view with wrist in ulnar deviation – which will show the entire length of the scaphoid bone in profile.
    Plain X-rays do not always identify an acute fracture of scaphoid – especially if it is incomplete or undisplaced. Historically, repeat radiographs were recommended at 2 weeks to look for the “Hawkin’s line” – an area of radiolucency around the fracture due to resorption of bone. This has now been superseded with other investigations that prevent delay in management.
    Bone scans – These are highly sensitive investigations showing increased uptake in the injured area (Tiel-van Buul et al 1993). They are most effective when done at 2 weeks after the injury. Unfortunately, bone scans are not specific for scaphoid fractures and have been superseded by other investigations.
    CT scans – These are ideal to delineate the fracture anatomy. They are highly specific for a scaphoid fracture but are less sensitive when compared to MRI scans. However, they remain the investigation of choice to identify fracture healing; being far superior to plain radiographs in sensitivity and specificity (Dias et al 1988 and Farracho et al 2020).
    MRI scans – These are currently established as the investigation of choice for suspected scaphoid fractures that are not clearly identified on plain radiographs. They can be done soon after the injury and have been reported to be nearly 100% sensitive and specific. The MRI scans also have an added advantage in identifying any concurrent ligament injury in the wrist. The argument about their relatively high expense is mitigated by the reduction in lost working days due to early management of the injury (Patel et al 2013).
    At my Unit plain radiographs are the initial investigation of choice to identify a scaphoid fracture. In suspected fractures with a high index of suspicion, an MRI scan is the next investigative modality of choice. I only use a CT scan if I need to delineate the architecture of the fracture to guide in its management.
    NON-OPERATIVE MANAGEMENT
    Undisplaced and minimally displaced fractures can be treated non-operatively with plaster immobilization. There is no agreement in the literature as to the optimum position of immobilization or type of cast, with all showing nearly equivalent results. Recently, Buijze et al (CAST Trial 2014) suggested that the plaster cast can be of a short arm variety (below the elbow) and does not necessarily need to include the thumb. Long-term outcomes with conservative treatment have been reported to be similar to those treated with surgical fixation.
    However, immobilization may be required for up to 12 weeks with repeated radiographs to exclude fracture displacement. This may lead to muscle atrophy, possible joint contracture, disuse osteopenia, and potential financial hardship; that requires targeted rehabilitation before return to activity. Therefore, conservative treatment is best reserved for paediatric patients or those with sedentary and low-demand activities. At our Unit, all patients with undisplaced and minimally displaced fractures of the scaphoid waist are offered the option of conservative management with an explanation of its risks and benefits.
    ALTERNATIVE OPERATIVE TREATMENT
    1.Percutaneous screw fixation through dorsal approach
    I find the volar approach easier in identifying the entry point of the screw, as well as for maintaining reduction during screw insertion with forced dorsiflexion of the wrist. There are no significant advantages with the dorsal approach, unless the fracture lies in the proximal third of the bone. In these injuries, the retrograde insertion of the screw is less likely to engage the small proximal fragment. Therefore, a dorsally inserted antegrade screw is the approach of choice in this small cohort.
    2.K wire fixation
    This is a very useful tool in the armamentarium of a surgeon. They are easy to insert and can be left flush with the bone as a permanent implant, or left protruding outside the skin for later removal. However, the stability afforded with K wires is unsatisfactory when compared to other rigid implants. In addition, they do not provide any compression at the fracture site.
    3.Open reduction and internal fixation
    Open reduction through a volar or dorsal approach allows the surgeon to reduce and stabilise the fracture under direct vision and has remained the “gold standard” of care. The fixation can be achieved with screws, K-wires, staples or plates. The disadvantage of this approach is the potential for significant tissue damage and interruption of the precarious blood supply to the bone. Hence, it is best reserved for fractures that cannot be reduced with manipulation. This technique is also suitable for established malunions and nonunions that may require bone graft supplementation.
    4.Arthroscopic aided fixation
    This allows the surgeon to visualize the articular surface to confirm anatomical reduction of the fracture. It also allows identification of any protruding screw threads. However, arthroscopy is a specialized skill set with a long learning curve. It can be superior to an open approach in established nonunions or in patients with concomitant ligamentous injuries requiring repair.
    CONTRAINDICATIONS (to percutaneous screw fixation)
    Displaced fracture which cannot be anatomically reduced with manipulation
    Fractures with comminution
    Fractures of the proximal pole (ideally treated with a dorsal approach)
    Malunited fractures (require osteotomy)
    Established nonunion of scaphoid (requires supplementation with bone graft).
    Buijze GA, Goslings JC, Rhemrev SJ, Weening AA, Van Dijkman B, Doornberg JN, Ring D, CAST Trial Collaboration. Cast immobilization with and without immobilization of the thumb for nondisplaced and minimally displaced scaphoid waist fractures: a multicenter, randomized, controlled trial. The Journal of hand surgery. 2014 Apr 1;39(4):621-7.
    Cooney WP, Dobyns JH, Linscheid RL. Fractures of the scaphoid: a rational approach to management. Clinical Orthopaedics and Related Research (1976-2007). 1980 Jun 1;149:90-7.
    Dias JJ, Taylor M, Thompson J, Brenkel IJ, Gregg PJ. Radiographic signs of union of scaphoid fractures. An analysis of inter-observer agreement and reproducibility. The Journal of bone and joint surgery. British volume. 1988 Mar;70(2):299-301.
    Farracho LC, Moutinot B, Neroladaki A, Hamard M, Gorican K, Poletti PA, Beaulieu JY, Bouvet C, Boudabbous S. Determining diagnosis of scaphoid healing: Comparison of cone beam CT and X-ray after six weeks of immobilization. European Journal of Radiology Open. 2020 Jan 1;7:100251.
    Herbert TJ, Fisher WE. Management of the fractured scaphoid using a new bone screw. The Journal of bone and joint surgery. British volume. 1984 Jan;66(1):114-23.
    Patel NK, Davies N, Mirza Z, Watson M. Cost and clinical effectiveness of MRI in occult scaphoid fractures: a randomised controlled trial. Emergency Medicine Journal. 2013 Mar 1;30(3):202-7.
    Tiel-van Buul MM, van Beek EJ, Borm JJ, Gubler FM, Broekhuizen AH, van Royen EA. The value of radiographs and bone scintigraphy in suspected scaphoid fracture: a statistical analysis. Journal of Hand Surgery. 1993 Jun;18(3):403-6.

    Setup

    Informed consent is an important part of the procedure and the risks and benefits should be clearly explained to the patient. It is of particular importance to discuss the significant risk of nonunion despite surgical fixation. Nonunions will require further surgical intervention. I always counsel patients regarding risk of screw protrusion and need for implant removal, persistent stiffness, secondary osteoarthritis and complex regional pain syndrome.
    I prefer regional anaesthesia with axillary block for this procedure. The patient is placed supine with the limb extended on an arm table. Upper arm tourniquet is applied and inflated after exsanguination. A prescrub is performed followed by a sterile prep with Chlorhexidine. A rolled towel is used to support the wrist in dorsiflexion. I routinely administer a single dose of antibiotics for this procedure.

    Operation – 1

    The proximal pole of the scaphoid is marked on the dorsum of the wrist.
    This is identified as a “dip” on palpation just distal to the Listers tubercle (Annotated L). The “dip” signifies the scapho-lunate joint in the wrist and is a landmark for the proximal pole of the scaphoid (Annotated P).

    The distal pole of the scaphoid (scaphoid tubercle) is marked on the volar aspect of the wrist.This is identified by palpating the first bony prominence (Marked ST on the hand) on the volar radial aspect just distal to the tendon of FCR (Flexor Carpi Radialis), in line with the thumb metacarpus. It lies at the level of the wrist crease.

    The anatomical location of the scaphoid bone is marked from the scaphoid tubercle to its proximal pole.The scaphoid is a bean shaped bone that lies in an oblique plane (in both anteroposterior and lateral). The curious anatomy also includes a rotation of the bone along its long axis.
    One can see that the axis of the scaphoid is at 45 degrees from distal radial to proximal ulnar. Additionally, the axis is at an angle of 45 degrees from volar to dorsal.
    ST – Scaphoid tubercle (Distal pole)
    P – Proximal pole

    A 1-2 cm incision is marked and then made along the AP axis of the scaphoid bone at its distal poleThe incision should incorporate the tubercle in its proximal third.
    There should be more incision distal to the tubercle to allow for safe passage of the guide wire and the reamer, which would otherwise injure the distal skin when inserted.

    The skin incision is made with a No.15 blade
    Dorsiflexion of the wrist over a rolled towel makes the scaphoid tubercle more prominent and allows it to be palpated easily. In addition, dorsiflexion corrects the most common displacement of flexion at the fracture site. I keep the wrist dorsiflexed through the entire procedure.

    The skin and subcutaneous tissues are retracted, so the scaphoid tubercle, which lies in the proximal aspect of the incision, can be palpated with an instrument such as the forceps.The thenar muscles can be seen on the ulnar aspect of the incision.
    Sometimes, you need to do a bit of blunt dissection over the tubercle to allow for entry of the guide wire.
    The most prominent and palpated part of the scaphoid tubercle is volar. A guide wire entered from here will lie in an incorrect axis to the bone causing it to exit on the dorsal surface of the waist. The correct entry point lies more dorsal to this .
    My technique involves walking the tip of the guide wire from the prominent pole, which is easily palpable, along the distal surface until I reach the correct entry point.
    The entry point should be approximately 1/3 the way across the scaphoid from the tuberosity in the A/P plane and central in the lateral plane.

    Choose the screw implant system appropriate for the particular patient and fracture.
    Acumed® Acutrak 2® Headless Compression Screw System contains the following options for scaphoid fracture fixation:
    Micro – Colour coded Purple; Screw diameter of tip 2.5mm and head 2.8 mm; in lengths 8-28 mm; using 0.8 mm guide wire
    Mini – Colour coded Blue; Screw diameter of tip 3.5mm and head 3.6 mm; in lengths 16-28 mm; using 1.1 mm guide wire
    Standard – Colour coded Stainless steel grey; Screw diameter of tip 4.0mm and head 4.1 mm; in lengths 16-34 mm; using 1.4 mm guide wire

    The instrumentation for insertion of the screw is colour coded similarly.
    As can be seen in this picture, the instruments to be used for insertion of a Mini Screw (BLUE) are all coded with a blue band across them. This reduces the risk of choosing a wrong sized guide wire or drill.

    The entry point of the guide wire is identified on the distal pole, and wire inserted while simultaneously reducing the fracture by dorsiflexing the wrist.Note that the wrist is dorsiflexed over a rolled towel by the surgeon using his non-dominant hand. Ulnar deviation of the wrist can additionally aid in making the tubercle more accessible.
    The index finger of the surgeon’s non-dominant hand (Annotated F) lies over the proximal pole of scaphoid on the dorsum of the wrist. This allows the surgeon to visualize the axis of the bone while inserting the guide wire. It is important to remember the 45 degree obliqueness of the long axis of the bone in both anteroposterior and lateral planes.
    Traction by the assistant on the thumb metacarpus (Annotated T) allows the surgeon to walk the tip of the guide wire from the prominent volar tubercle to the correctly aligned dorsal surface.

    The axis of the guide wire is aligned to the long axis of the scaphoid bone.The tip of the guide wire is maintained on the previously identified distal entry point, while the surgeon aligns the wire to the long axis of the scaphoid bone.
    The index finger of the surgeon’s non-dominant hand on the proximal pole is a very useful guide to visualize this axis orientation. The reduction of the fracture with wrist dorsiflexion is continued. Traction of the thumb metacarpus away from the wire allows for easier insertion of the wire.
    An image intensifier radiographic view may be taken at this stage to confirm the alignment of the guide wire with the long axis of the bone.

    The guide wire is inserted across the reduced fractureThe guide wire is inserted with a power drill. A tissue protector may be used for this step. Once the guide wire is deemed to have crossed the fracture line, the power drill is disengaged from the wire. The alignment of the wire is visually checked against the skin markings.

    Confirm the correct placement of the guide wire with image intensifier radiographs.This is a very crucial step in the procedure. The reduction of the fracture and correct placement of the guide wire is imperative before proceeding further. The alignment of the wire should be checked on multiple radiographic views (AP/lateral/oblique) to ensure that it lies in the middle of the bone. Eccentric placement of the wire will result in an unsatisfactory screw placement across the fracture.
    I have a fairly low threshold for reinsertion of the guide wire if I deem its position in the bone as unsatisfactory.

    I do not like to remove an unsatisfactory guide wire at this stage. I retain it so as to guide me with the insertion of a second wire. The second wire is loaded onto the power drill and the insertion point is identified again.
    In this particular case, I needed the entry point to be slightly more dorsal. The retained wire helps me to orient the tip of the second wire in the correct location on the distal surface of the scaphoid bone.

    The second guide wire is aligned in the correct axis using the previous wire as a guide.
    The power drill is used to insert the wire across the fracture site as before.

    Remove the unsatisfactory guide wire after insertion of the new wire.
    This will leave just one guide wire in the bone for further imaging. Presence of multiple wires in the bone can sometimes be confusing in the radiographs. In addition, there is very limited space remaining if the guide wire has to be inserted again. I suggest that the insertion of the guide wire should be undertaken as many times as required until a satisfactory position is achieved. Experience with the procedure can allow a surgeon to complete this in a maximum of 2-3 attempts.
    Do not proceed to the next step until you are satisfied with fracture reduction and the guide wire placement.

    Advance the tip of the wire into the proximal pole of scaphoid.Use the Image intensifier radiographic views to achieve this. The wire tip should reach (but not breach) the proximal pole. This step is important to ensure correct screw measurement.

    Measure the screw length required using a direct measuring depth gauge.The direct measuring depth gauge is included in the instrumentation set.
    This has markings for the three available screw dimensions (Standard, Mini and Micro). Make sure that you are using the correct markings for the chosen screw.
    The tip of the depth gauge must lie flush with the bone. A common mistake here is an inability to push the tip of the gauge onto the bone. This will result in an erroneous reading of the screw length.
    The chosen screw length should be 4mm shorter than the reading obtained. This is to allow for compression at the fracture site as well as to bury the screw head under the cortical surface of the bone.
    A longer screw will protrude into the radioscaphoid joint proximally or the scaphotrapezial joint distally – both resulting in intractable pain for the patient.
    Alternatively, the screw length can be measured by advancing a second guide wire of the same length up to the distal cortex of the scaphoid and measuring the difference between the two wire lengths.

    Advance the guide wire into the distal radius.I routinely perform this step.
    Advancement into the distal radius secures the guide wire, preventing its inadvertent removal during the following steps. It can be extremely frustrating to have to reinsert the guide wire into its correct position in the bone repeatedly.

    Choose the correct drill bit for drilling the path of the headless screw.The instrumentation set contains a long drill (Annotated A), a profile drill (Annotated B) and a screwdriver (Annotated C) each for the three available dimensions of the screw (Standard, Mini and Micro).
    All these instruments are colour coded and are cannulated to accommodate the guide wire.
    The surgeon must ensure that the correct instrument set is being used for the screw dimension chosen (A blue coded instrumentation is being chosen here for the blue Mini Acutrak Screw).
    A thicker drill path will prevent adequate screw hold within the bone, while a thinner drill path can result in an inability to advance the screw through the path.

    Drill the scaphoid bone over the guide wire to create a path for the screwSome surgeons use the profile drill to enlarge the entry point before using the long drill. I prefer to first use the long drill to create the screw path across the entire long axis of the bone. I find that this prevents the long drill from wobbling within the larger dimension hole created by the profile drill.
    The long drill is marked with screw lengths across its surface to guide the surgeon. I use the previous reading from the depth gauge (before removing the 4mm for fracture compression) to inform me on the length of this initial drilling required. If in doubt, Image intensifier radiographs can be used to ensure that the bone has been drilled to the required length.

    Carefully remove the drill bit while retaining the guide wire within the scaphoid bone.The proximal extent of the drilling is checked regularly under the Image Intensifier to ensure that the proximal cortex in not breached. Once drilling is deemed adequate and complete, the drill bit is removed from the bone.
    I use the power drill, continuing to rotate in the clockwise fashion, while withdrawing it. A useful tip here is to stop withdrawing as soon as the tip of the drill bit is outside the bone. Grasp the guide wire at the tip of the drill bit with a pair of haemostat forceps. The assistant keeps a hold of this, while the surgeon withdraws the remaining drill bit. This ensures that the guide wire is not inadvertently removed from the bone. The advancement of the guide wire into the distal radius in the previous step, also ensures against its inadvertent removal.

    If the guide wire does fall out, it should be replaced immediately.
    The position of the wire in the bone must be checked on Image intensifier radiographs again before proceeding to the next step.

    Use a profile drill to over-ream the near cortexThis step ensures that the larger dimension of the screwhead is accommodated and buried under the cortex.
    The profile drill has a short cutting tip that flares onto the shaft, acting as a guard against overdrilling.

    Remove the profile drill ensuring that the guide wire is retained in the bone.I use the same technique with the haemostat forceps to ensure that the guide wire is not inadvertently removed.

    A screw of the appropriate length is chosen and loaded onto the screw driver.The screw dimension is decided preoperatively. A Mini Acutrak screw was decided for this patient. This is colour coded blue (Standard size screws are steel gery while the Micro size screws are purple in colour).
    The screw has a thread pitch that varies continuously from tip to tail. This ensures each screw rotation engages threads into new bone along the screw’s entire length. As each successive individual thread advances faster than the trailing thread counterpart, the conical shape becomes seated into bone. This radial expansion of the screw threads, combined with their axial advancement, creates the ability to reduce & compress bone fragments without a traditional screw head.
    The screw is loaded onto the cannulated screwdriver

    Operation – 2

    This image shows how the screw will lie within the scaphoid bone.

    The cannulated headless screw is threaded over the guide wire.It is important to maintain fracture reduction during screw insertion by continued dorsiflexion of the wrist. A bone clamp can be used to maintain reduction during an open approach to the fracture; but is not a suitable instrument for a percutaneous fixation.

    The screw is inserted into the scaphoid bone.It is important to protect the skin and soft tissues while tightening the screw. This can be achieved by extending the thumb away as shown in the picture. Alternatively, a soft tissue retractor can be used to protect the skin.
    The fracture reduction should be maintained while advancing the screw across the fracture site. Some surgeons insert a second derotation guide wire to prevent malrotation and displacement during this step. Regular imaging under Image Intensifier should be undertaken to confirm fracture reduction.
    Further advancement will cause compression at the fracture site due to the differential pitch of the screw threads. The larger head should be buried under the cortex of the bone to prevent joint irritation and the resulting pain.

    The screw placement should be checked on Image intensifier radiographs.Multiple radiographic views of the scaphoid should be taken to confirm fracture reduction and screw placement. The screw should be fully contained within the scaphoid bone in all radiographic views, with no protrusion proximally or distally.

    One must be careful that the guide wire does not bend during all the steps previously described. However, if it does happen (as seen in this image), the wire should be backed out before final screw placement to prevent its breakage.

    The screwdriver and guide wire are removed.It is important to ensure satisfactory screw placement and advancement before removing the guide wire.
    Tip: If you need to tighten/loosen the screw after the wire removal, I suggest that you reinsert the guide wire with hand (and not on a power drill). The presence of the wire will help in reintroducing the screwdriver perfectly onto the screw head.

    Close the skin incision with interrupted nonabsorbable monofilament suture.The wound is washed with normal saline. The subcutaneous tissues are allowed to fall over the wound. The skin can now be closed. I prefer interrupted nonabsorbale monofilament nylon 5’0. However one can use continuous closure using an absorbable suture as per the surgeon’s preference.

    Post-op splintage with POP volar slabI use nonadherent dressings (Mepitel) over the wound. This is followed with a layer of wool and POP volar slab with the wrist in mild dorsiflexion. The purpose of the plaster splintage is to provide immediate post-operative rest and comfort. It is important to remind the patient regarding their first postoperative review within a week to commence early rehabilitation with mobilization exercises.
    Ensure that the tourniquet has been released and removed before transferring the patient from the theatre table.

    Post Operative

    The plaster splint and sutures are removed in the clinic in 10 days. Following this, active wrist range of movement is commenced. I provide my patients with a Futura splint for intermittent use during this period.
    Gentle routine activities of daily living can be started as soon as comfortable. Rigorous and heavy activity is avoided.
    Radiographs are repeated at 6 weeks and 12 weeks. If fracture healing cannot be confirmed, CT scans are performed at 3 months. The enhanced resolution of a CT scan gives more reliable information regarding bony trabeculae bridging the fracture site. I advise patients against heavy activities until the fracture is healed.

    Recommended Reading

    Herbert TJ, Fisher WE: Management of the fractured scaphoid using a new bone screw. J Bone Joint Surg [Br] 66:114-123, 1984. This is a landmark paper, which outlines Herbert’s classification system of scaphoid fractures and introduces the principles of the revolutionary screw that has remained the mainstay of surgical fixation of this injury. The screw has undergone many modifications over the years and has evolved into the Acutrak screw described here. However, the principles of the screw, as outlined in this paper, have remained largely unchanged.
    Gelberman RH, Menon J. The vascularity of the scaphoid bone. Journal of Hand Surgery. 1980 Sep 1;5(5):508-13. This paper is the cornerstone of our understanding of the blood supply of the scaphoid bone and explains the high risk of non-union and avascular necrosis seen after poorly managed fractures. This cadaveric study, using injection techniques, highlights the importance of the dorsal and interosseous blood supply to the proximal pole of scaphoid, and suggests the volar approach to be safer.
    Dias JJ, Brealey SD, Fairhurst C, Amirfeyz R, Bhowal B, Blewitt N, Brewster M, Brown D, Choudhary S, Coapes C, Cook L. Surgery versus cast immobilisation for adults with a bicortical fracture of the scaphoid waist (SWIFFT): a pragmatic, multicentre, open-label, randomised superiority trial. The Lancet. 2020 Aug 8; 396(10248): 390-401. This prospective randomised multicentric trial reported on the outcome of 408 patients in 31 hospitals across the UK that were included in the study. They reported no significant difference in the Patient Reported Wrist Evaluation (PRWE) scores between the surgically and conservatively treated at 52 weeks. They recommended that minimally displaced fractures should preferably be treated with cast immobilisation with surgery being reserved for those fractures that failed to unite.
    Barton NJ. Twenty questions about scaphoid fractures. Journal of hand surgery. 1992 Jun;17(3):289-310. This paper takes an innovative approach to the dilemma of scaphoid fractures and distils the available evidence at the time into 20 questions that all surgeons ask. It provokes thought and enables the surgeon to seek appropriate current evidence to the pertinent question. Although some of the answers suggested in the paper have evolved with newer evidence, the questions have remained unchanged.

    Reference

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