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Fusion of the syndesmosis for isolated distal tibio-fibular arthritis

    Overview

    Learn the Fusion of the syndesmosis for isolated distal tibio-fibular arthritis surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Fusion of the syndesmosis for isolated distal tibio-fibular arthritis surgical procedure.
    The distal tibiofibular syndesmosis is a unique syndesmotic joint powerfully bound by a variety of ligaments to maintain the integrity of the ankle mortise. The distal anatomy of the two bones are created in such a way that the medial surface of the distal fibula fits into a groove on the lateral surface of the distal tibia called the incisura fibularis which offers the bony stability to this joint. The anterior part of this joint is stabilised by the Anterior Inferior Distal tibiofibular ligament (AITFL), the posterior aspect by the Posterior Inferior Distal Tibiofibular ligament (PITFL) and the transverse tibiofibular ligament. Directly between the contiguous surfaces of the tibia and fibula is the interosseous ligament which extends throughout the leg offering origins and beds for a number of muscular and neurovascular structures. The PITFL is by far the strongest ligament in this complex and is the least likely to be ruptured. Once ruptured however the PITFL is most likely to be associated with severe rotational or dislocating injuries of the ankle and associated ankle instability.
    The anterior part of the distal tibio-fibular joint is covered by cartilage for a small part behind which lies the syndesmotic recess and a fat pad. There is a small amount of movement afforded by this joint which includes about 2-3 degrees of external rotation of the fibula relative to the tibia. This occurs with widening of the syndesmosis by about 1 mm in maximal dorsiflexion of the ankle to allow the broadest part of the talar dome excursion through the mortise. This is possible due to the a small amount of isometric stretching of the ligaments and is essential for normal ankle movement. The function of the mortise is mainly to stabilise the ankle, keeping the talus congruous with its articulating osseous partners in all normal “physiological” positions by resisting rotational, translational and angular forces.
    Thus the syndesmosis is a pivotal structure in maintaining the anatomy and physiological function of the ankle. The syndesmotic ligaments are injured in rotational and translational injuries of the ankle. Approximately 10% of ankle sprains are associated with syndesmotic injury and symptoms from this so called ‘high ankle sprain’ can persist for several months after injury. Sadly this can often be missed and has significant consequences for the future of the ankle.
    The syndesmosis is disrupted often in conjunction with the medial deltoid ligament in over 50% of supination external rotation and almost all pronation external rotation/abduction injuries. Such disruption allows more than the required physiological shift of the talus within the ankle. 1 mm of talar shift decreases tibiotalar contact area by about 40 % and significantly increases the contact pressures at the articular surfaces which can lead to early onset arthrosis.
    Occasionally osseous trauma to the bones of the syndesmosis can render the syndesmosis incongruous and eventual arthritic and can present as syndesmotic pain which is often as disabling as more extensive ankle arthritis.
    In this particular case a middle aged female patient suffered a fracture of the tibia at the junction of the middle and lower thirds with an intact fibula. This was a short spiral fracture and was treated by closed intramedullary nailing with dynamic proximal and static distal locking with 2 locking screws from medial to lateral. It was noted that these screws were long and broached the cortex of the syndesmotic surface of the medial aspect of the lateral malleolus. This chronic abutting on the syndesmotic fibular surface appears to have caused injury to the surface with ongoing painful symptoms long after the tibial fracture was deemed to be healed and the distal screws removed. A CT SPECT confirmed the site of activity as within the distal syndesmosis and selective injection into the syndesmosis gave excellent but temporary relief of pain. It was then decided to undertake an in situ fusion of the syndesmosis after confirming that the incisura and the fibula were congruous and there was no significant loss of bone. Bone graft was used along with 2 partially threaded cancellous screws to fuse the joint. The patient felt immediate relief of pain even whilst in plaster and after removal was asymptomatic

    Indications

    INDICATIONS
    These include symptomatic arthrosis of the syndesmosis, post fracture deformity and arthritis of the joint, failed syndesmotic reconstruction with recurrent instability, as part of ankle fusion when syndesmotic pain and arthrosis form a significant component of pain and rarely as part of an ankle replacement procedure.
    SYMPTOMS & EXAMINATION
    The commonest complaint is of pain and is usually very specific to the syndesmotic region. Ballotment of the fibula against the tibia in an anteroposterior direction gives rise to pain as does dorsiflexion and external rotation to push apart the syndesmotic bones. Occasionally patients describe a functional instability pattern with twisting of the ankle in external rotation causing the ankle to give way due to sudden pain and reflex inhibition of musculature. Careful clinical examination is important to dichotomise the pain originating from the ankle joint proper, in particular anterolateral impingement pain which can mimic distal syndesmotic pain. Selective injection under fluoroscopy into the syndesmotic joint is almost diagnostic if it results in abolishing pain from the region.
    IMAGING
    The use of plain radiography is essential in identifying pathology especially if osseous and associated with arthrosis. Articular surface irregularity, sclerosis and cyst formation is pathognomonic in severe cases of arthritis and post traumatic deformation of the contours of the syndesmosis. Residual diastasis and the presence of fracture fragments in the syndesmosis is well defined using a standing ankle mortis anteroposterior view. Lateral standing views of the ankle will show up malunions of associated distal fibular fractures and will outline the position of fracture fragments in the vicinity.
    If there is no metalwork present then an MRI will clearly demonstrate the presence of syndesmotic pathology such as arthritis as well as the integrity of ligaments. This is important to delineate pathology of the ligaments from pathology of the joints themselves as the treatment is radically different for the two.
    In the presence of metalwork a CT scan will demonstrate the presence of incongruence, arthritis and malpositioning of the fibula into the incisura. In cases where the diagnosis is still in doubt an isotope bone scan or CT SPECT will accurately pinpoint the pathology to the syndesmosis and offer pathognomonic features.
    Ankle arthrography is very rarely used but can show irregularities in the syndesmosis when die leaks into the syndesmotic recess and shows up contour anomalies in the syndesmosis.
    ALTERNATIVE OPERATIVE TREATMENT
    Sometimes stabilisation of the syndesmosis can offer pain relief in early arthritis of the joint secondary to chronic instability. Arthroscopic debridement of the syndesmosis can also be very useful in controlling symptoms and can be used also to fuse the joint if the syndesmosis is easily accessible to the scope and instrumentation . This can be done particularly if the distal part of the syndesmosis is arthritic and there is concomitant instability allowing easy passage of shaving and cutting instruments.
    NON-OPERATIVE MANAGEMENT
    Symptomatic therapy such as analgesia foot wear modification physiotherapy etc are rarely sufficient to control pain due to mechanical functioning of the ankle with syndesmotic arthritis. Occasionally taping of the ankle in the syndesmotic level can decrease movement of the fibula on the tibia thereby decreasing pain. This can be used as a diagnostic test to prove the syndesmosis as a pain generator. Injections into the syndesmosis can offer long term relief in some patients and form an essential role as diagnostic tools to pinpoint the origin of pain.
    CONTRAINDICATIONS
    The presence of arthritis throughout the joint, severe chronic diastasis or shortened fibular malunion should not be treated with fusion unless the background pathology is treated with stabilisation and or fibular osteotomy etc. severe global arthritis in the syndesmosis is best treated with a interposition tricortical graft positioned higher in the syndesmosis to avoid the unfortunate complication of narrowing the ankle mortise thereby causing significant painful problems with stiffness and pain. This occurs as the maximum width of the talar dome is unable to excursion freely in the mortise. Other contraindications include peripheral vascular disease acute or chronic sepsis concomitant pathology in the ankle joint proper until after treatment of associated problems.

    Setup

    The patient is counselled on the nature of the operation and advised of the complications of the procedure including a high rate of non union and residual pain. Informed consent is then obtained for the fusion as well for the harvest of bone graft usually from the os calcis unless tricortical graft is required when it should be taken from the iliac crest.
    The operation is done either with a general anaesthetic, a spinal or regional block. This patient opted for GA. Antibiotics are given at induction. An above knee tourniquet is used rather than an above ankle so that inadvertent compression or distortion of the syndesmosis does not occur due to the pressure and the fibula can sit comfortably and congruously in the incisura. It will also allow harvest of graft from the proximal tibia if required. the leg is prepped with Iodine and or Chlorhexidine. A sand bag to rotate the leg into 20 deg of internal rotation is necessary to gain access to the syndesmosis and also the lateral calcaneus for bone graft.

    Operation – 1

    The original fracture pattern is short spiral fracture of the lower tibia with an intact fibula. Radiographs must include the proximal fibula so as to not miss a proximal fracture which may indicate a concomitant ankle injury with extensive tearing of the interosseous membrane and other syndesmotic ligaments.
    In this patient no distal symptoms were noted at presentation and immediately post operatively. No fractures of the fibula were identified. Examination of the syndesmosis was unremarkable.

    Post op radiographs after fixation with the intramedullary nail. Note the excessive length of the distal screw and is broaching the fibular surface within the syndesmosis in its distal part.

    The distal screws have been removed and the deformity and sclerosis at the distal syndesmosis is now visible. Note that there is some medial malleolar periosteal calcification suggesting the possibility of occult deltoid injury although this was asymptomatic. Also note that the ankle did not show any evidence of arthrosis. The distal locking screws have been removed with some relief of symptoms initially but subsequently symptoms continued to worsen.

    A CT scan confirms significant sclerosis and incongruence in the distal syndesmosis with evidence of osteoarthritic change.

    A CT SPECT accurately maps out the location of activity as being in the syndesmosis.

    The leg is positioned with a sandbag under the ipsilateral buttock so that access to the lateral aspect of the foot and ankle is possible.

    A image intensifier picture helps identify the syndesmosis if location is difficult or confusing. The temptation is to use an incision that is too high or too low. Screening with fluoroscopy helps to accurately position the incision over the syndesmosis thereby minimising surgical exposure.

    The skin incision is marked directly over the syndesmosis, for which an image intensifier can sometimes be useful in identifying.It is to be noted that the superficial peroneal nerve lies well anterior to this incision although aberrant posterior branches can occasionally be encountered and care must be taken to preserve these branches whenever possible.

    The skin and the subcutaneous tissue are then divided, taking care in the fat layer to avoid cutaneous nerves.

    A self retaining retractor can now be positioned to improve the exposure to deeper dissection.

    At six months further and convincing bony union has occurred.

    A deeply placed self-retaining retractor assists with identification of the AITFL.The syndesmosis is fairly superficial although it may be covered in scar-tissue over its anterior aspect. The overlying scar tissue is excised and the AITFL is now identified.

    The AITFL is divided to expose the syndesmosis.Sharp subperiosteal dissection and elevation of the 2 halves of the AITFL medially and laterally from the tibia and fibula respectively is needed to visualize the syndesmosis in its entirety from proximal to distal

    An osteotome is used to initially plumb the depth of the syndesmosis, taking great care not to pass deep to the posterior aspect of the Fibula.This serves to divide any scars or adhesions that are present in the syndesmosis. In this case a sharp 8mm flexible osteotome was used.

    The proximal limit of the syndesmosis is mapped out, which is usually the superior border of the AITFL but may extend a few mm beyond it.Identifying the fibres of the interosseous ligament would confirm the superior boundary of the syndesmosis



    The scar tissue in the anterior aspect of the syndesmosis is excised with nibblers. The osteophytes that are often found at the bones anterior margins are also excised.

    A Hintermann self retaining retractor is now positioned optimally over the syndesmosis.

    A 2 mm Kirschner Wire is inserted into the distal tibia taking care to ensure that it is directed slightly superiorly to avoid broaching the ankle joint.

    A second Kirschner Wire is introduced through the Hintermann retractor into the distal fibula. This is directed posteriorly as the fibula at this level lies somewhat posterior to the tibia.

    K Wires are inserted through the Hintermann retractor into both tibia and Fibula, and distraction then applied.The retractor is then cranked open to separate the bones which exposes the articular surfaces of the syndesmosis.
    It is particularly difficult to access the posterior part of the syndesmosis and occasionally it may be necessary to partially divide the PITFL through the joint to better expose the surfaces.

    The wires are then bent to prevent riding up of the retractor and to keep it in place close to the bones.

    The anterior surface of the joint is then smoothened by excising the osteophytes and decorticating it to increase the area of fusion.

    Residual scar tissue and articular cartilage especially in the inferior part of the joint nearest to the ankle joint is excised with nibblers. Drilling with a K wire is also undertaken for the sclerotic bone on both sides of the joint.The articular cartilage is mainly in the anterior half or less of the joint and it is important to clear the scar tissue to be able to visualise this cartilage as it is essential that this is removed thoroughly. to expose subchondral bone.

    A Kirschner wire is then used to drill multiple holes in the tibial surface.
    This is often the toughest and most sclerotic part of the bone and should be irrigated during this process to avoid thermal injury to the bone.

    The fibular surface is similarly drilled with the Kirschner wire and multiple drill holes are made to expose subchondral bone.

    Operation – 2

    The peroneal tendons are then mapped out to ensure these are not damaged in the next part of the procedure to harvest bone graft.
    The sural nerve lies posteriorly and should be borne in mind as it is easy to damage the nerve or its branches during this process.

    A 1 cm incision is then made about 1.5-2.0 cm posterior to the tendons over the lateral wall of the os calcis.The incision should only be made through the skin to avoid damage to the sural nerve or its branches.

    A haemostat is then introduced into this incision and this is used to spread the tissue. This is important to avoid sharp damage to the sural nerve.

    The incision is stretched to allow the smallest of the graft harvest cutting drills to enter.

    I use the Acumed Bone Graft Harvesting system to harvest graft from the Os Calcis. This system allows the surgeon to harvest graft from any bone utilising a small incision.
    The system uses a hollow cutting drill to take cores of morcellized graft from bone. The cutting drills come in a variety of diameters and require a Hudson fitting adapter to be mounted on to. I generally use the 6 or 8 mm drills if harvesting from the Os calcis. The smaller drills have a window in their proximal part that allows graft to be visualised to assess its quality and texture and also make retrieval from the drill easier.
    A trocar is first introduced to broach the lateral wall of the Os Calcis. This serves as a starting point for the drill.

    The Acumed Bone Graft Harvesting system is used to harvest bone graft from the calcaneus using trocar cutting drills and a paddle to push graft out from drills.Through the same opening the cutting drill is introduced, usually to a depth of between 2 and 3 cm. One must be very careful not to broach the medial wall for fear of damaging the neurovascular structures on the medial side. The drill must also be directed slightly inferiorly to avoid broaching the subtalar joint or the sinus tarsi.

    Insertion of the drill then extracts a core of morselised cancellous bone graft which can be inspected for quality and density through the window on the drill .
    If bone quality or quantity is poor it may then be necessary to use the proximal tibia as a donor site for additional graft.

    A bone graft removal paddle is inserted in a retrograde direction through the drill to extract the graft from it.
    The paddle is eccentrically placed with a thin handle. This is introduced through the cutting end of the drill by slightly tilting it to allow the rim of the disc to enter the drill and then by pushing it to push the graft out through the window at the proximal end.

    The bone graft removal paddle.

    Multiple passes can be made varying the entry angle through the same portal made in the lateral wall of the body of the Os Calcis to extract cylinders of morselised bone graft. This is carefully saved in a Gallipot on a wet piece of smooth gauze to prevent it from drying.

    Bone graft is packed carefully into the joint.

    Often a significant amount of graft is required, some of which has also come from the bone surfaces previously decorticated. Care must be taken not to stuff too much graft between the tibia and fibula as this may impede reduction of the fibula into the incisura leaving a fusion that is that is not apposed satisfactorily because of the bone graft.

    The final appearance of the grafted site.

    The tension of the retractor is released after grafting. This allows the fusion site to be assessed for “overstuffing” with graft.
    One should ensure that it is possible to compress the fusion surfaces together. This can also be assessed by screening particularly to ensure that graft has not overdistracted the posterior part of the joint, with residual loss of fusion surface contact.

    The Kirschner wires tare then carefully unbent. The wires are then removed by hand with wire holders if still slightly bent to prevent fatigue fracturing of the wire or with a driver if straight.

    A final inspection is carefully made without dislodging graft to ensure that the fibula fits accurately into the incisura.

    A Mantis reduction clamp with a ball tip is used to compress the syndesmosis.The positioning of the clamp is very important to ensure concentric reduction and compression of the joint. The fibular tine of the clamp sits posteriorly as shown here and and the tibial tine is relatively anterior.
    A small incision medially is necessary to position the clamp’s tibial tine to sit on the bone without damage to the saphenous nerve or vein . The tibial tine sits anterior to the coronal plane of the joint so that the posterior fibula is reduced and compressed into the incisura fibularis.
    The ankle must be positioned in neutral or 5 degrees plantar flexed to allow satisfactory compression of the construct. Dorsiflexion will not allow compression as the syndesmosis is distracted by the widest part of the talar dome. Conversely compression of the syndesmosis with plantar flexion of more than 5 degrees will decrease the range of movement of the ankle joint in the sagittal plane as it will not allow the talar dome excursion to its widest part.
    It is thus vitally important at this stage to assess the range of movement of the ankle to ensure it does move in its full physiological range and if needed by comparing it with the opposite side. If the joint is restricted in dorsiflexion the ankle needs to be re-positioned in optimal dorsiflexion and clamp reapplied.

    The position of the compressed construct is screened to ensure that it is satisfactorily positioned.Note the slightly anterior position of the tibial tine and the posterior position of the fibular tine in the preceding photograph.

    Two guidewires are then passed through the construct at least 2 cm apart, their direction being perpendicular to the vertical axis of the fusion site.The guidewires must pass through the centre of the fibula, lying posteriorly, to end slightly anteriorly on the tibial side.
    The guide wire must end flush with the tibial side so that screws, which are measured from the wires length, will not protrude medially over a part of the tibia that is subcutaneous. The wires have a laser mark which is used to read off the length of the screw when measured with a depth gauge.

    The skin around the wires are released to allow the screw heads to pass through comfortably.

    These incisions are made on the skin and then spread with a haemostat to have a clearance around the wires for the screws to pass without crushing skin and soft tissues.

    A depth gauge is used to measure the length of the screws.


    A depth gauge is used to accurately measure the length of the screws taking note to decrease screw length by 2 mm to allow for countersinking causing loss of length. The measurements can be repeated after use of the countersink to ensure accuracy of length. It is essential that the screws do not protrude outside the cortex by more than 1 mm as it can prove to be a source of pain and prominence on the anteromedial tibia. It can also irritate the saphenous nerve branches which may lie close to the screw tip.

    A countersink is used to seat the headed screw.Care must be taken if using this on power and slow speed with irrigation must be used to avoid both thermal necrosis of bone as also over penetration of the countersink. Fluoroscopy may be used to ensure that the counter sink does not enter too far into bone with loss of compression. It must be confined to cortical bone.

    Both the screw sites are countersunk. The cannulated countersinks are especially useful in dense sclerotic bone. If it is anticipated that the fibular bone is very soft then I do not use the countersink but allow the screw head to deform the cortex thereby maximising compression.
    If I anticipate that the bone is very sclerotic, then I use a dedicated drill to drill through the sclerotic parts of the bone to make screw placement easier.

    Operation – 3

    It is best to re-measure screw length after countersinking so that the accuracy of screw length is assured.

    The 4mm ACE cannulated screws are threaded over the guide-wires and tightened by hand, whilst carefully maintaining the ankle position in the sagittal plane.

    The position and especially the trajectory of the screws are checked with fluoroscopy. Note the postero-anterior trajectory of the screws on this lateral view.

    The wound is irrigated with aqueous iodine solution and saline. Interrupted subcutaneous sutures with 2-0 Vicryl is used to close this layer.

    I use subcuticular undyed vicryl for skin closure.

    Local anaesthesia with 0.5 % Chirocaine is infiltrated into all the wounds.

    The movement of the ankle should be checked before closure to ensure optimal compression of the construct and to avoid narrowing the trajectory of the excursioning talus from plantarflexion to dorsiflexion.If there has been a significant decrease in dorsiflexion not noted in prior examination it is necessary to reopen the wound and potentially reduce the amount of compression being excerted.

    The wound is dressed with iodine dressing, absorbent gauze and wool.

    A below knee plaster of Paris back and U-slab is then used to hold the foot in a plantigrade position.

    AP radiographs at 4 weeks done on this patient due to a fall whilst in plaster show the position of the construct at that time. There is evidence of fusion progressing well. Note the position of the screws which whilst appearing to be short in the tibia are actually are not.

    A separate case, showing significant widening on the axial CT of the medial joint space.
    This was a Weber C ankle fracture in whom the syndesmosis screw had been removed at 3 months, which was followed by a progressive talar shift.
    Presenting 18 months following the fracture the ankle joint was none the less still non-arthritic.

    Another axial of the same case demonstrates some minor degenerative change at the distal tibio-fibular articulation.

    The proximal location of the previous fibula fracture can be seen easily still.
    The same technique has been used to fuse the syndesmosis and these X-rays at 4 months demonstrate excellent progressing union, though with breakage of the internal fixation. At this relatively late stage with excellent bone formation this is of no consequence.
    The regained symmetry of the mortis is well demonstrated.

    Post Operative

    The limb is elevated on 2 pillows or a Braun’s frame. Ice packs are especially useful to reduce postoperative swelling and pain. Adequate analgesia and Dalteparin thromboprophylaxis is prescribed for as long as the limb is immobilised in plaster.
    The plaster is completed in 24 to 48 hours and maintained for 6-10 weeks. I am conservative and cautious in immobilising these fusions for longer than others as they do suffer from a higher rate of non unions as compared to other fusions around the ankle. The patient is reviewed at 1 week for wound assessment and a plaster change. It is important at this stage to ensure that the ankle is is plantigrade in plaster. The patient is advised to be strictly non weight bearing for 6 weeks and then pending satisfactory radiographs at that time can either go into a weightbearing plaster or a pneumatic compression boot and allowed to weight bear. Physiotherapy may started at this stages providing radiographs show good fusion. At 3 months if there is still doubt about the quality of fusion then I would perform a CT scan before discarding the boot and starting unprotected weightbearing. Dalteparin is stopped when the patient is allowed to walk without a plaster.

    Recommended Reading

    Very little evidence is available for the functional results following fusion of the distal tibiofibular syndesmosis. There are several short case series which appear to suggest that patients reported significant pain relief and the the procedure was predictable in rendering a painful or unstable syndesmosis symptom free.
    Pena and Coetzee (Foot and Ankle Clinics 2006 Mar;11(1):35-50, viii) have suggested arthrodoesis of the syndesmosis for chronic incongruence of the ankle due to disruption of the syndesmosis that have been present for at least 6 months. They have suggested that it was their perception that the final ankle functions was definitely not adequate to pursue an active athletic life. It has been suggested that such fusion may result in some restriction of dorsiflexion and may accelerate the process of ankle arthritis but there is no convincing evidence for the same.
    Katznelson et al (Injury. 1983;15:170-172) reported the results of syndesmotic fusion in 5 patients, 4 of whom were asymptomatic with full range of ankle movement a year after surgery.
    Tun Hing Lui (Arthrosc.Tech 2016 Apr; 5(2): e419–e424, J Foot Ankle Surg. 2015;54:953–957 ) described the technique of syndesmotic fusion using endoscopic technique but does not inform about the outcomes of such fusion. This has been deemed by the author of the publication as being technically demanding and suitable only for experienced arthroscopic foot and ankle surgeons!
    It is thus the case that whilst it may render the syndesmosis painless, there may be sequelae such as stiffness and perhaps an acceleration of arthritic changes in the tibiotalar joint possibly due to the alteration of biomechanics and increased constraint of the articulation due to loss of fibular external rotation and altered kinematics of the ankle joint. However no evidence exists currently to either confirm or quantify such risks.

    Reference

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