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Four Corner carpal Fusion using Medartis plate and scaphoid excision

    Overview

    Learn the Four Corner carpal Fusion using Medartis plate and scaphoid excision surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Four Corner carpal Fusion using Medartis plate and scaphoid excision surgical procedure.
    This is a detailed step by step instruction through a Four Corner fusion and scaphoid excision using a dorsal low profile titanium plate from MedartisTM.
    This is a salvage operation usually undertaken when the scaphoid fossa is damaged and arthritic most commonly from a Scaphoid non-union advanced collapse (SNAC ) stage 2 and above or Scapholunate advanced collapse (SLAC) stage 2 and above. Rarely it can also be undertaken in the acute setting with complex carpal injuries and dislocations.
    Following a period of 6-8 weeks in plaster cast and the rehabilitation it is expected the patient will achieve 30-50% of their normal range of movement. The operation has a non-union rate of around 10%


    Indications

    Indications
    Articular damage to the mid-carpal or radio-scaphoid joint or mid-carpal instability causing pain with preservation of the Radio-lunate articulation.
    Failure of non-operative treatment.
    Causes would include : post traumatic arthritis, Scaphoid non-union advanced collapse (SNAC) grade 2-3, Scapho-lunate advanced collapse (SLAC) grade 2-3, failed scaphoid non-union surgery, failed partial wrist fusion (e.g. Capitolunate fusion), post traumatic mid carpal instability failing non-operative treatment especially in the hyperlaxity patients.
    Symptoms
    The symptoms experienced will depend on the underlying pathology however in the main the operation is undertaken for pain or dysfunction due to instability.
    Patients with degenerative change in the scaphoid fossa or mid-carpal joint will complain of pain on movement and loading and occasionally pain at rest in more severe cases. Patients with instability often complain of a painful clunk or a reluctance to use the hand for loading tasks due to its unreliability or pain when they experience the clunking.
    The patient’s job and hobbies often play a major role in their symptoms and therefore discussing these details and realistic expectations of the post-operative outcomes are essential in treatment selection.
    Examination
    For the arthritic patient (SLAC, SNAC etc.) the patients often already have a reduced range of movement and complain of pain during active and passive movement especially at the end of range and into radial deviation. Palpation over the affected joint can be painful due to synovitis.
    A Kirk-Waston test is often painful as this will shear the scaphoid in its fossa and irritate both the Radio-scaphoid joint and Scapho-trapezium-trapezoid (STT) joint.
    It is useful during the examination to try to elicit which joint (radiocarpal or midcarpal or both) the patient’s movement is coming from as often pre-operatively there has already been a loss of movement at the arthritic joint and therefore the post-operative range of movement is likely to be 30-50% of the normal movement not the pre-operative range.
    For instability cases a Kirk-Watson test may be positive if SLAC is the pathology although it is often just painful with no clunking. There may be a positive mid-carpal clunk (Lichtman test) in the hyperlaxity patient or those with Luno-triquetral or volar extrinsic ligament injuries. A positive Reagan test or Kleinman Shuck test may also be positive with underlying Luno-triquetral injuries.
    It may be difficult to elicit a positive result in some of these tests if pain is a major issue and the patient’s wrist is not relaxed during the examination.
    Investigations
    Investigations include plain PA and lateral radiographs which can reveal which joints are arthritic and also the type of lunate (type 1 or 2) which is useful to know during the surgery.
    A CT scan can be useful and on occasion in SLAC wrists the scaphoid fossa appears falsely normal on plain radiograph and on a CT the scaphoid can be seen sitting on the dorsal lip of the radius confirming the diagnosis. An MRI may be useful to review the intercarpal ligaments if considering other surgical options however they are often unreliable in assessing luno-triquetral and volar extrinsic ligament chronic injuries.
    For the mid-carpal instability, hyperlaxity patients with no arthritis, a diagnostic arthroscopy may be the only way to determine if there are any other ligament injuries which could be managed without a major fusion operations.
    Non-operative Management
    Non-operative management for arthritis includes, analgesia, activity modification, wrist splinting, physiotherapy with wrist strengthening and occasionally steroid injections for temporary pain relief.
    For instability patients with no ligament injury the key is to strengthen the wrist not only as a potential curative therapy but it is essential to optimise the wrist strength before any surgery for best outcomes.
    For these instability patients a wrist splint which applies Pisiform pressure to support the ulnar carpus can also be useful.
    Alternative operative Management
    For this operation numerous fixation methods can be used including plates, memory staples, headless screws or simple wires. This operation uses the MedartisTM APTUS Four Corner Fusion plate.
    The alternative operation to a four corner fusion will depend upon the underlying pathology.
    Scaphoid fossa arthritis – e.g. Trauma, SLAC stage 2 (where proximal capitate preserved) – Wrist Denervation, Proximal Row carpectomy, limited wrist fusion (capito-lunate with scaphoid excision, radio-scapholunate with distal scaphoid exicision), arthroplasty.
    Mid-carpal arthritis – e.g. Trauma, SLAC stage 3 and SNAC grade 2 + 3 – Wrist Denervation, limited wrist fusion (capito-lunate with scaphoid excision), arthroplasty. (SNAC stage 2 can also undergo a PRC where proximal capitate is preserved).
    Midcarpal instability with no arthritis – ligament stabilisations (e.g. ECRB transfer through capitate and triquetrum) other partial wrist fusions (capito-lunate).
    Contraindications
    Lunate fossa arthritis is the main contraindication. If other surgical options such as PRC are possible then smoking or major skin conditions such as poorly controlled eczema or psoriasis over the incision site would be relative contraindications in four corner fusion surgery.

    Setup

    Pre-operative preparations and Equipment
    The operation can be performed under general or regional anaesthetic. As the duration of surgery is around 2 hours, a sterile Esmarch is used once the skin marking are completed to reduce tourniquet time and access to a sterile forearm tourniquet may useful if the patient under regional anaesthetic starts to struggle with tourniquet pain. Tourniquet is set to 250mmHg
    Distal radius bone graft is used for this procedure which is ample in volume and has low additional morbidity and possible under a regional/axillary block due to its location.
    Equipment – Fine bone nibblers, a sharp curved periosteal elevator, Medartis TM APTUS 4 corner fusion plate and set (k-wires on the set), image intensifier, plaster cast. NOTE: You may also need additional equipment to remove previous metalwork i.e. scaphoid screws.
    A single dose of antibiotics are given pre-operatively.

    Operation – 1

    The distal radius and ulna, level of the CMCJs , Lister’s tubercle and the dorsal midline incision are marked.
    The incision is sited over the 4th extensor compartment (EC) extending from just proximal to the 3rd CMCJ to 2cm proximal to the level of Lister’s tubercle (to access the distal radius bone graft).
    A -Lister’s Tubercle
    B- Bone graft site
    C- Level of CMCJs

    Soft tissues are dissected to expose the transverse fibres of the Extensor Retinaculum (ER).As the incision is in the midline there are rarely any large cutaneous nerve branches seen although a number of small vessels perforate the ER which are best coagulated. The fat, veins and superficial nerves are elevated as one.
    Cut directly onto the bony prominence of Lister’s tubercle to open the radial side of the 3rd EC.
    A – Forceps pointing at Lister’s tubercle beneath ER.

    The 3rd EC is opened.Use tenotomy scissors with the blades very slightly open either side of the retinaculum. Open along the 3rd EC by pushing distally and proximally as shown on the image (don’t close the scissors and cut, just push firmly).

    Use the same technique to open the 4th EC.This is accessed at its proximal radial border where the tendons of EDC are clearly visible through the thin film of synovium.

    Excise the Posterior Interosseous Nerve and Artery from bed of 4th EC using diathermy to coagulate the vessel.Place a small self retainer at the level of radio-carpal joint on tendons of 2nd and 4th extensor compartments.
    A- Forceps pointing to PIN and PIA

    Open the joint using the Berger, ligament preserving approach.Identify Dorsoradiocarpal ligament -DRC (fibres from dorsal radius in line with Lister’s tubercle to triquetrum) and Dorsointercarpal ligament -DIC (fibres from Triquetrum to Scapho-trapezial-trapezoid region).
    A- Forceps pointing at Dorsal Capsule

    Pierce the DRC ligament in line with the fibres and open the scissors.This will split along the ligaments fibres without risk to deeper structures (i.e. Scapho-lunate interosseos ligaments- SLIL essential to protect in others surgical techniques) or the EDM tendon which in the 5th EC is at risk of laceration behind the reflected ER.

    The dorsal capsule is raised off the radial styloid.Once the DRC is split with the scissors, sharply dissect the capsule distally for around 0.5cm on the radial border of the reflected extensor retinaculum to cut half way across the DIC ligament then sharply incise in line with the DIC fibres full thickness to bone over to the STT joint.

    The capsular flap is then retracted distally to reveal the proximal carpal row.The flap has been extended by sharply dissecting along the dorsal distal radius from Listers tubercle to the styloid protecting ECRL/B thus giving clear access to the scaphoid.

    The scaphoid is excised in pieces with an osteotome and nibblers.At this point it is essential to identify whether there is a type 1 or type 2 lunate and therefore how the capitate articulates with the lunate (central or slightly radially) to replicate this in the fusion process.
    The scaphoid is removed while taking care to protect the volar ligaments (Radioscaphocapitate – RSC). If the scaphoid bone is of good quality (no Avascular necrosis, sclerosis ) it may be decorticated and used as bone graft.

    The Capitolunate, Hamotriquetral, Capitohamate and Lunotriquetral joints are now decorticated.A curved sharp periosteal elevator is excellent for this job on curved surfaces i.e. proximal capitate and distal lunate and a fine bone nibble (see image) and osteotome can be used to decorticate the other surfaces
    A burr may be required if the bone surface is very sclerotic as there needs to be bleeding bone visible at each joint surface to allow adequate bone healing.

    When decorticating the joints the volar most cartilage and cortical bone is preserved to contain the bone graft and maintain normal spacing between the bones (this is not possible on the curved surface of the Capitolunate joint therefore the joint space will need to be filled with bone graft.
    A cross of cancellous bone should be revealed by the end of this process as shown in the image.

    A retrograde k-wire is used to fix the capitate to the lunate with the lunate in a neutral position.Remembering the pattern which the capitate articulated with the lunate, a 1.2mm k-wire from the fusion set is passed retrograde from the radial aspect of the 3rd metacarpal base around 20 degrees elevated off the skin to then pass through the volar half of the Capitolunate joint. This position allows reaming of the bones without having to remove the wire.

    The location of the tip of the wire exiting the Capitate can be seen in the image.
    Once the wire is across the joint the range of extension is then assessed. The wrist extension seen should be that achieved at the end of the operation however flexion is not easily assessed due to the lack of dorsal capsule intact.

    The position of the wire and orientation of the bones are checked on x-ray.Although classically it is described to correct the DISI deformity or Capitolunate angle, the important post-operative outcome is to gain the correct range of movement and therefore if an extension of 45-50 degrees is seen with the wire in situ and the wire on intra-operative imaging is in an acceptable position then reaming can start.
    If the range of movement is not correct the wire can simply be withdrawn into the capitate, the angle readjusted and then the movement and imaging reassessed.
    NOTE: Due to some dorsal distal lunate lip debridement during decortication the lunate may appear more extended on a lateral radiograph and therefore appear poorly corrected.

    PA of K-wire in situ

    On the Medartis fusion set there are 3 plates and 3 reamers. An STT fusion plate and 2 sizes of 4 Corner Fusion plate with corresponding labelled reamers.
    Hold the 4 Corner fusion reamers with the central spike in cruciate point between the 4 bones and identify which is the appropriate size (often the size is determined by the coverage over the lunate which needs to be sunken enough into the lunate to avoid dorsal impingement on wrist extension.
    Due to the intact volar ligament no wire is usually required to stabilise the hamate or triquetrum during reaming

    The carpal bones are reamed to allow the plate to be seated flush and avoid impingement.The reamer is placed with neutral radial to ulnar angulation and 20 degree proximal to distal angulation aiming the reamer face more distally to ensure a deeper ream of the lunate and triquetrum to avoid dorsal metalwork impingement on wrist extension
    Ream to a depth to allow the plate to be comfortably seated with no prominence over the dorsal lip of the lunate.
    Don’t press to hard when reaming as the reamers are sharp and can ream too deeply quite easily.

    Place the plate in the reamed site and decide on its orientation for maximal bony purchase.The most critical joint to ensure fusion is the Capitolunate joint and therefore it is essential to get at least 2 screws (one locking and one non-locking) into each of these 2 bones.
    Once the perfect position is decided this should be memorised or marked as it becomes more difficult to identify the ideal rotation of the plate once all the gaps are filled with bone graft.

    Bone graft is harvested from the dorsal distal radius.A trap-door of cortex is opened about 1cm proxminal to Lister’s tubercle leaving a periosteal hinge (if possible).
    Bone graft is harvested with an narrow osteotome to slice into the cancellous bone and sweep sheets of it into the hole from each direction. This is then retrieved carefully with non-toothed forceps.
    This technique gives much better graft maintaining its cancellous structure than using a curette which often crushes the cancellous matrix.

    The trapdoor of cortex is closed over the graft donor site.The graft is placed into a dry pot (not a wet swab which delays retrieving it and risks loss of graft as it get tangles in the fibres).
    If this cortical flap collapses, bone wax can be used to seal the defect and reduce bleeding.

    Cancellous bone graft is then packed into the 4 decorticated joints.The C-L joint may need to be distracted by spinning the wire and applying traction and recompressing after graft insertion.
    It is easy to put too much graft centrally in the bone mass which will obstruct the plate positioning.
    To avoid this, the reamer can be used slowly on reverse to compress the graft before plate placement.

    At this point around 90 mins of tourniquet time the patient was starting to feel pain from the upper arm tourniquet.
    A sterile forearm tourniquet was therefore sited and inflated then the upper arm tourniquet released.

    The fusion plate contains a ring of deep non-locking and a ring of superficial locking screws. The locking screws have an ability to be angled with an arc of 30 degrees (15 degrees in any direction) to allow better placement in good quality bone.
    The angulation is set by the drill guide which can lean 15 degree off central and still remain in the plate. It is however very easy to lean the guide too far and exceed the 15 degrees in a single direction as the guide clicks out of the low profile plate. If this happens the screw will not lock.
    For this reason it can be useful to place locking screws 1 mm too short and if they do not lock and the tract in the bone is threaded then a longer non locking screw can be used instead.
    With this plate it is also crucial to understand the locking mechanism of the screw which on tightening clicks once as the head engages in the plate and then locks with an interference fit with a further half turn of the screw driver.
    It is useful if you are new to the plating system to try one screw in the plate to get the feel of the locking mechanism before the plate is in the patient.
    The 4 deep non-locking (GOLD) screws are designed to be sited one in each bone allowing compressing between the 4 bones and the plate to be pulled onto the carpus to avoid dorsal prominence.
    The locking (BLUE) screws then hold the bones in place with angular stability.



    Resite the plate in the memorised orientation to maximise screw purchase and insert screws.With the plate firmly pressed into place drill the deep lunate non-locking hole first.
    All carpal bones are drilled unicortically to avoid nerve injury or long screws irritating the palmar structures.
    When the lunate screw is tightened fully it often lifts the distal end of the plate, it is therefore easier to leave the lunate screw slightly loose when drilling the capitate deep non locking hole making sure the plate is fully seated.
    Once the capitate and lunate screws are fully tightened and ensuring the plate is not prominent over the dorsal lunate risking impingement, the deep triquetral and hamate screws can be sited
    At this point a X-ray is taken to check screw positioning and also where the empty screw holes lie and therefore the optimal orientation of the locking screws to be placed.
    The k-wire is removed and remaining locking holes drilled unicortically, measured and screws inserted.
    Usually at least 1 screw hole will align with a joint and therefore not be filled.

    Operation – 2

    A PA and lateral radiograph is taken to check screw placement.Once all screws are sited a PA X-ray is taken taking care to identify any remaining large scaphoid fragments and the plate and screw positions.

    A lateral X-ray is taken with focus on the length of the screws. Particular issues can occur with the Capitate and Hamate screws crossing the CMCJ and with the Triquetral screw irritating the Pisiform. Slightly oblique views may help identify any of these potential issues

    Extension is assessed and imaged to detect any dorsal plate impingement.Finally a lateral view in full wrist extension is taken to assess extension and any dorsal metal work prominence or impingement.

    The Berger capsular flap is closed.Closure is with a continuous 3/0 vicryl suture taking care at its ulna tip not to suture the EDM tendon.

    The extensor tendons are relocated and the ER is closed with 2 interrupted stitches of 3/0 vicryl.This is performed at the level of Lister’s tubercle where the fibres are thickest. This creates a combined EC 3 and 4.

    A 4/0 vicryl interrupted sutures are used to close the deep dermal layer and a 4/0 monocryl absorbable sub-cuticular continuous suture is used for skin.This sub-cuticular suture starts and ends outside the skin with bulky knots which can be trimmed or will fall of in 2-3 weeks.
    An adherent dressing is used over the main wound and the k-wire wound which if forgotten can bleed a lot.
    The tourniquet is then released and the hand rested on the table for 5 MINUTES. This allows the initial reperfusion and swelling to occur before the wool and plaster cast is applied.

    An adherent dressing is applied and wool applied and split to allow for swelling.The wool is split (see image) then covered with a layer of non circumferential wool to allow for swelling and reduce painful constriction of the dressings.

    A dorsal slab of plaster is then applied and held with a bandage and tape.

    Preoperative PA radiograph of failed Scaphoid ORIF and vascularised Khulmann graft from beneath Pronater Quadratus

    CT of Scaphoid ORIF non-union

    CT of scaphoid ORIF non-union with graft extruded volarly and screw penetrating proximal scaphoid

    PA post operative radiograph at 6 weeks

    Lateral post operative radiograph at 6 weeks

    Post Operative

    As this is a painful operation it is paramount to advise the patient that it is very painful, advise strict elevation in a sling provided and provide opiate analgesia.
    We provide paracetamol, codeine and oral morphine with an antiemetic (cyclizine) and laxative (senna). Anti-inflammatory medications are not used for the first 2 weeks.
    Patients are sent home the same day and return to clinic for a wound review and cast change within the week.
    At this point the wrist is still swollen and will need reviewing again in another week for conversion to a full cast and possible trimming of suture ends.
    If the fingers are stiff at this point a hand therapy review with the new cast in place is advised.
    The cast is then continued for another 4 weeks to make a total of 6 weeks in cast.
    If the patient is unreliable and very keen to go back to a manual labouring heavy job continue the cast for a further 2 weeks, making a total of 8 weeks.
    Once the cast is discontinued X-ray PA and lateral and if all is as expected then start hand therapy for wrist movement.
    If there are concerns over union then splinting and a CT scan is advised.
    It is expected that patients will regain 30 degrees extension and 30 degrees flexion. There is a 10% non-union rate and a number of patients complain of mild ulna sided wrist pain on ulna deviation.
    It will usually take patients 8-10 weeks to return to light work and 4-6 months to return to heavy work.

    Recommended Reading

    Four corner fusion using a multidirectional angular stable locking plate.
    World J Orthop. 2016 Aug 18;7(8):501-6. doi: 10.5312/wjo.v7.i8.501. eCollection 2016 Aug 18.
    Chaudhry T1, Spiteri M1, Power D1, Brewster M1.
    Abstract
    AIM:
    To review the results of our experience with the Medartis Aptus plating system for four corner arthrodesis of the wrist, which uses a combination of compression screws and variable angle locking screws.
    METHODS:
    We reviewed the results of 17 procedures in 16 patients that underwent scaphoid excision and four corner fusion using the Medartis Aptus system between May 2010 and June 2014. The primary outcome measure was radiographic and clinical union.
    RESULTS:
    The mean clinical follow up time was 20.6 mo. The mean union time was 6 mo. Two non-unions required revision procedures. The mean disabilities of the arm, shoulder and hand score taken after union was 36. The mean final grip strength was 27 kg. The mean final range of movement was 30° flexion and 31° of extension. All patients had a restored scapholunate angle on postoperative radiographs. There were no incidences of dorsal impingement.
    CONCLUSION:
    Overall our experience with the Aptus plating system shows comparable results to other methods of fixation for four corner fusion, in the short to medium term.
    Proximal row carpectomy vs four corner fusion for scapholunate (Slac) or scaphoid nonunion advanced collapse (Snac) wrists: a systematic review of outcomes.
    J Hand Surg Eur Vol. 2009 Apr;34(2):256-63. doi: 10.1177/1753193408100954.
    Mulford JS1, Ceulemans LJ, Nam D, Axelrod TS.
    In summary this review looked at 52 articles comparing 4CF and PRC for SNAC and SLAC.
    They found that bot procedures gave similar pain relief, grip strength and subjective outcomes.
    PRC may provide a better ROM and does not have complications such as non-union, metal work or dorsal impingement problems but does show a significantly higher frequency of arthritic changes in the remaining joints. This arthritis however is not necessarily symptomatic.

    Reference

    • orthoracle.com

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