Introduction

Despite the development of ankle arthroplasty, ankle arthrodesis remains the gold standard in the treatment of end-stage degeneration in this joint. Immobilization of the ankle joint performed with appropriate indications, observing the principles of correct foot alignment and stable fixation gives a very high percentage of good and very good results [1-10]. Fear of the so-called “stiff foot” is unjustified provided that the transverse tarsal joint and talocalcaneal joint are in good condition. Especially the first one, if undamaged, allows for significant movement compensation in the immobilized ankle joint. It is worth mentioning that in a healthy foot, about 20% of the movement in the sagittal plane, i.e. dorsiflexion and plantar flexion, takes place in the transverse tarsal joint.
Due to surgical approach, ankle arthrodesis can be divided into:
• open (currently, it is most often lateral approach with complete or partial resection of the fibula),
• semi-open, through the recesses of the joint using arthroscopy,
• closed, with exclusive use of arthroscope.
Due to the stabilization technique, it can be divided into:
• stabilization with screws only,
• stabilization with plate and screws,
• stabilization with an external stabilizer, e.g. Ilizarov fixator,
• stabilization with intramedullary nail (in combination with arthrodesis of talo-calcaneal joint).
Due to the absence or presence of deformity, arthrodesis may be in situ in nature or it may be used to correct foot deformity at the ankle joint.
Qualification for surgery is based on the assessment of the patient’s clinical condition and imaging diagnostics. The set of qualifying X-rays should contain:
• anterior-posterior (AP) view of the ankle joint while standing up,
• lateral view of the whole foot while standing up,
• dorsal-plantar (AP) view of the foot, also while standing up.
In justified cases, computed tomography is helpful.

Technique

Placing the patient on the operating table
• During the surgery a patient is in supine position with support under the knee (flexion about 15 degrees) and buttock on the side of operated foot, which allowed to keep the lower extremity in minor hip and knee flexion as well as in internal rotation.
• Above knee the Esmarch tourniquet is applied.
• Surgical draping applied in such a way that the patella is visible, which allows for the assessment of foot position in relation to the knee joint.
• Placing a soft support (rolled sheet) under the distal tibia just above the foot), which will allow, after opening and releasing the joint, to move the resected articular surfaces in order to reduce them correctly.

Access to the ankle joint
• L-shaped skin incision starts from the lateral side of the talar head, through the sinus tarsi, above lateral malleollus along the anterior edge of the fibula, approximately 7-8 cm above the lateral malleolus (Fig. 1).
• After dissecting the subcutaneous tissue, in the distal approach, the proximal attachment of the extensor digitorum brevis muscle is cut off to visualize the sinus tarsi and the neck of the talus. This is the place where stabilizing screws are inserted.
• The distal fibula is then visualized and its periosteum is incised longitudinally from the front, starting from the top of the lateral malleolus and ending 7-8 cm above. Periosteum is complete denuded around end of incision over a length of 1 cm in planned osteotomy site. Lateral periosteum of the fibula is preserved.
• The fibula is cut diagonally, in the coronal plane, approximately 7-8 cm above the lateral malleolus. The intersection direction is proximal lateral and distal medial. The fibula should be shortened by a few millimetres at the site of osteotomy so as not to cause a conflict between lateral malleolus and calcaneus (Fig. 2A).
• The next step involves vertical osteotomy of the distal fibula performed with an oscillating saw and completed with an osteotome. The distal fibula, thus halved, adheres to the periosteum and soft tissues from the lateral side. The medial 1/2 – 1/3 part together with the tibiofibular syndesmosis is resected and removed (Fig. 2B). The obtained bone fragment can be used as a graft in place of arthrodesis in order to correct the deformity in any plane and/or to equalize the length of the limb. Removing this fragment and placing a Hohmann retractor under the tibia from the lateral and medial side reveals the ankle joint from the lateral and anterior side (Fig. 3).
Preparation of articular surfaces for arthrodesis
• Before opening the ankle joint, a chisel or oscillating saw is use to remove the articular cartilage from the lateral surface of the trochlea tali. In the last phase of the procedure, the halved distal fibula will adhere to it.
• The joint, the anterior part of which is obliterated by degenerative changes, is best opened by removing bone and connective tissue layers. Osteophytes and cartilage are best removed with a chisel by modelling the surface of the trochlea tali and the articular surface of the tibia, respectively, if we wish to correct valgus/varus, equinus/calcaneal and rotational deformity.
• At this stage, it is worth drilling the bone surface after cartilage removal. It is not necessary to remove the articular surface from the medial malleolus. If someone decides to do so, he must remember about the risk of the medial malleolus fracture.
• If the correction of equine position is incomplete, it is essential to lengthen the Achilles tendon at this stage, and not to resect the bone elements any further.

Foot alignment
After resection of the articular surfaces and lengthening of shortened tendons, the foot acquires the possibility of movement in any planes relative to the tibia. Choosing the correct position for arthrodesis is facilitated by the support placed under the further part of the shin. Thanks to this, you can manoeuvre your foot in any plane.

Stabilization
• The foot must be stabilized in proper position: at right angles of the whole foot to the tibia in sagittal plane, valgus position of hindfoot about 5 degrees in coronal plane and external rotation 10-15 degrees to patella in horizontal plane. It is up to the surgeon to use the graft taken from the fibula to reconstruct the axis and length of the limb.
• It is best to immediately stabilize the foot in the correct position with a Kirschner wire with or without bone graft along which the first cannulated screw with a diameter of 6.5-7 mm can be inserted. You can use screws with different threads. A guidewire should be inserted from the side of the sinus tarsi into the talus body, slightly anteriorly and above the anterior surface of the talocalcaneal joint. Next, the wire should be directed through the surfaces of the ankle joint and inserted from the medial side through the cortex of the tibia above the flexors and the neurovascular bundle. Leading out the wire in this way and holding the mosquito Kocher forceps facilitates controlled insertion and removal of the drill bit. The screw is inserted in such a way that ends in cortical layer of the tibia, and the head into the talar neck and body. After inserting the first screw, a guidewire should be left in its hole, which will indicate the direction of insertion of the second parallel screw. The second screw should be inserted approximately 5-10 mm proximally and slightly higher than the first. Spongy screws can be replaced with cortical screws, however, one must remember about the high probability of periosteal thickening on the anteromedial surface of the tibia. The end of the screw should not protrude beyond the cortical layer of the tibia (Fig. 5).
• The next step is to fix the halved fibula to the talus and tibia with two cortical screws. Sometimes one screw is enough for such stabilization. If there is a free space between the stabilized part of the fibula and the tibia, it can be filled with bone chips from resected fibula. The length of the fixed fibula fragment should be adjusted depending on the height of the talus to prevent the formation of a conflict between the lateral malleolus and calcaneus (Fig. 6).

Closing the wound
• Please note to suture the proximal part of the detached short extensor digitorum brevis muscle to the place of attachment.
• Haemostasis, suction drainage and layered wound suture complete the surgery.

Immobilization
• Immediately after surgery, the foot is stabilized with a below knee plaster cast splint cut above the foot and tibia.

Additional procedures
• During surgery it is possible to combine ankle arthrodesis with correction of the big toe, toes and the raised or lowered first metatarsal bone. However, additional procedures should be performed after arthrodesis and intraoperative assessment of foot alignment.

Postoperative management
• On the second day after surgery, the drain is removed, the plaster splint is opened again and the dressing is changed. The splint is closed with an elastic bandage for 2 weeks without changing the dressings.
• Hospitalization time is 1-2 days.
• After 2 weeks and after changing the dressings, a full below knee plaster cast is put on, most often mixed (classic plaster cast with a layer of fiberglass soft cast). The patient still cannot weight-bearing operated foot.
• After another 4 weeks (6 weeks after surgery), a final plaster cast is put on, also mixed, but with fiberglass stiff plastic as the top layer. Patients were allowed to begin weightbearing in plaster cast gradually.
• After another 4 weeks (10 weeks after surgery), the plaster cast is cut into below knee splint, in which the patient can walk for some time until the footwear is adjusted to the operated foot. The splint can be replaced with an orthosis.
Radiological follow-up does not need to be performed during surgery but it is obligatory to take X-rays immediately after it. Subsequent X-rays are taken during 10 weeks follow-up. The final X-rays are taken 6 months after surgery, all in standing. It should be remembered that arthrodesis union takes 4 to 6 months.
In the authors’ experience, the described technique is relatively simple and economical, because it does not require the use of a large number of implants. Due to the lateral approach it does not disturb the vascularity. An additional argument in favour of this technique is the fact that the screws are inserted from the talus to the tibia, i.e. the smaller element is attached to the larger one, which gives a sense of greater stability. During surgery, bone grafts are obtained that can be used to correct deformity and length of the limb [8].

References

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8. Napiontek M, Jaszczak T: Ankle arthrodesis from lateral transfibular approach: analysis of treatment results of 23 feet treated by the modified Mann’s technique. Eur J Orthop Surg Traumatol. 2015 Oct;25(7):1195-9. doi: 10.1007/s00590-015-1663-9. Epub 2015 Jul 7.
9. Boszczyk A: Artrodeza skokowo-goleniowa i podskokowa (Ankle and subtalar arthrodesis). In: Napiontek M. ed. Stopa i staw skokowo-goleniowy w praktyce ortopedycznej (Foot and ankle in orthopaedic practice), 2nd edition, MediPage, Warszawa 2022: 569-579.
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