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Posterior Ankle decompression-Arthroscopic technique

    Overview

    Learn the Posterior Ankle decompression-Arthroscopic technique surgical technique with step by step instructions on OrthOracle. Our e-learning platform contains high resolution images and a certified CME of the Posterior Ankle decompression-Arthroscopic technique surgical procedure.
    Posterior ankle impingement may occur as a result of an acute injury such as an ankle sprain, or as a result of repetitive trauma. The anatomy of the posterior ankle plays an important role in the syndrome. The most common predispositions tend to be osseous, such as an Os Trigonum, a Steida process, a prominent posterior tibial plafond or a posterior tibial osteophyte, or. Less frequently the impingement is soft tissue, related to a thickened posterior capsule, scar tissue or calcific bodies. The common feature of all these pathologies is that they predispose to compression during plantar flexion.
    The most common cause of posterior impingement is the Os Trigonum, The ossific Os appears between 7 and 13 yrs of age and fuses to the body of the talus within 1-2 years, forming a trigonal (steida) process of varying size. In 10% of patients, it remains a distinct ossicle. The Os Trigonum can become symptomatic due to abutment between calcaneum and tibia, or due to disruption of the fibro-cartilagenous synchondrosis.
    Repetitive impingement can lead to thickening of the posterior capsule, the intermalleolar ligament or the posterior talo-fibular ligament.
    Various pathologies are related to the posterior ankle and subtalar joint. Arthroscopic access to the anatomical region is a useful tool in the surgeons armoury. The arthroscopic approach to the posterior ankle is advantageous, as it provides excellent visualisation to all of the posterior ankle and subtalar joint and FHL tendon, whilst the smaller surgical insult, when compared to open surgery, leans itself towards accelerated rehabilitation.
    the structures at risk during the surgery, include the achilles tendon, the flexor hallucis longus tendon, the sural nerve and the tibial nerve, and a comprehensive understanding of the anatomy of the posterior ankle is important when plotting ones approach.
    The posterior portals provide good access to the posterior ankle and subtalar joint. The posterior facet of the subtalar joint is not traversed by ligamentous structures, and normally can be clearly identified, however when there is a large steida process or Os Trigonum, the view will be obscured. Access to the posterior ankle joint however is obscured by the posterior Talofibular, tibiofibular ligament and the posterior inter malleolar ligaments, and access must be gained between these ligaments.
    Parisien first described the technique to assess the posterior subtalar joint in 1985, this was popularised by Van Dijk in 2000 when he reported successful posterior arthroscopic treatment of a Ballerina presenting with an Os Trigonum and FHL tendinosis.
    Author : Mr Nick Cullen FRCS (Tr & Orth)
    Institution :The Royal National Orthopaedic Hospital ,Stanmore ,UK.
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    Indications

    INDICATIONS
    Posterior ankle arthroscopy is a useful technique in treating the common causes of symptomatic pathology of the posterior ankle and subtalar joint and flexor hallucis longus(FHL) tendons, include posterior ankle impingement (caused by Os Trigonum, Steida process, synovitis), articular pathology in the posterior ankle and subtalar joint, including osteochondral lesions and loose bodies. Access to the FHL allows treatment of tenosynovitis, stenosis of the FHL sheath/fibro-osseous tunnel. Posterior arthroscopy can be useful in harvesting the FHL tendon as part of a tendon transfer technique for example in augmented chronic achilles repair. A posterior arthroscopic approach can be used for a arthroscopic subtalar arthrodesis.

    SYMPTOMS & EXAMINATION:
    The most frequent indication for the technique is posterior ankle impingement. Posterior impingement is characterised by a deep posterior ankle pain provoked by loaded plantar flexion, or push-off forces. The classical description of this is in ballerinas who have pain when performing en pointe, or releve. The condition is common across sports that involve repetitive plantar flexion or explosive push-off, such as basketball and in line out jumpers in rugby union, impingement pain is reproduced in soccer players when they strike the ball with their shoelaces. Posterior impingement pain can often be provoked by wearing high heels.
    Patients will usually locate the pain to the posterior ankle, it is not unusual that they will relate their symptoms to the achilles tendon, however closer questioning usually pinpoints the pain deeper in the ankle.
    Focal tenderness may be experienced with deep palpation of the posterolateral ankle between the peroneal tendons and the achilles tendon.
    A posterior impingement test is performed with rapid plantar flexion of the ankle, which replicates the deep posterior ankle pain, (occasionally patients will report anterior pain which is not a positive test). The test may be more sensitive when axial load is combined with plantar-flexion; this is best achieved with the patient lying prone, the knee flexed to 90 degrees and axial force applied with one hand through the heel pad whilst the other plantar-flexes the ankle. A proportion of patients will experience posterior pain with dorsiflexion, which is usually caused by traction from the posterior talofibular ligament and posterior ankle capsule which both attach to the posterolateral process.
    The posterior impingement test will be abolished following flouroscopic or ultrasound directed injection of local anaesthetic into the posterior capsule of the ankle and subtalar joint, which can be a useful diagnostic adjunct.

    IMAGING
    MRI scan: There MRI findings associated with posterior ankle impingement includie bone marrow oedema in the posterior talus, the posterolateral talar process or the os trigonum. Fluid signal around the Os Trigonum or in the synchondrosis. Synovitis maybe seen in the posterior ankle recess and sometimes oedema in the posterior talofibular ligament. Fluid maybe seen in the FHL tendon sheath indicating tenosynovitis, and the FHL tendon may show features of tendinosis, with intrasubstance signal change.
    Functional xrays, with the ankle plantar flexed may demonstrate bony impingement between the posterior tibial plafond, the calcaneum and posterior talus.

    ALTERNATIVE OPERATIVE TREATMENT
    Open posterior ankle debridement can be performed using an extensile medial or lateral approach, with good reported outcomes. The open postero-medial approach is detailed elsewhere in OrthOracle. The approaches provide good exposure to the posterior ankle, the sural nerve is at risk laterally, the tibial nerve medially. The potential advantages of an arthroscopic approach are a reduced incidence of wound complications and an accelerated recovery time.
    NON-OPERATIVE MANAGEMENT
    physiotherapy
    activity modification
    flouroscopic steroid/la
    CONTRAINDICATIONS:
    Contra-indications include sepsis, or local infection, severe peripheral vascular disease, CRPS.

    Setup

    The procedure is performed under a general anaesthetic with a thigh tourniquet.
    The authors favour a 4mm arthroscope. which provides a wide visual field, along with a saline irrigation system using a pump or gravity to produce adequate pressure.
    A 3.5-4.5mm burr and shaver along with arthroscopic rongeurs and currettes are needed to debride the posterior bone and soft tissues.

    Operation – 1

    The patient is positioned in a lateral position, operated leg down. A bolster is used anteriorly and posteriorly to gently support the pelvis, the trunk is rolled forward to rest on a pillow, and the lower leg rested on a leg support attached to the side of the table.

    The shin is rested on a leg support, which is draped with a gel pad, care should be taken to ensure that there is no pressure over the peroneal nerve and fibular neck (1).

    The ankle is left free of support, the foot orientated perpendicular to the floor.

    The arthroscopy stack should be positioned on the opposite side of the table in the direct field of view of the operating surgeon.

    Posterior portals are made in line with the tips of the malleoli, which correspond to the posterior ankle and subtalar joint..

    The medial incision is made adjacent to the border of the Achilles tendon, at the level of the medial malleolus.

    The lateral portal is made in line with the tip of the lateral malleolus.

    The lateral portal is marked adjacent to the achilles tendon (1). Ensuring that this is posterior to the sural nerve (2).

    Plan the projection of the medial portal. The “safe” vector is towards the 2nd toe, working lateral to the arthroscope will then allow a working field lateral to the FHL tendon.

    The posterior ankle is insufflated with 10ml of saline with the needle directed towards the second toe.

    The medial portal is made medial to the achilles tendon, with an incision through the skin only, so as not to injure the achilles tendon or deeper neurovascular structures.

    blunt dissection in the line of the 2nd toe down to the posterior ankle. There is a loss of resistance as the forceps pass through the subcutaneous tissue, and firm resistance as the posterior ankle capsule is reached.

    A vertical incision, lateral to the achilles tendon (1), The tip of the scalpel is not passed deeply, only the skin is incised, the sural nerve (2) is at risk of injury, it passes lateral to the incision, approximately half-way between the achilles and the lateral malleolus, .

    The arthroscopic sleeve with blunt obturator is passed through the medial portal, again aiming at the second toe (2), to ensure that it passes laterally to the FHL tendon.

    The arthroscope is introduced, a 4mm arthroscope provides a wide field of view, the scope is used to define the most medial aspect of the ‘safe’ working field. The scope is introduced until it reaches resistance at the posterior aspect of the ankle and withdrawn slightly.

    A soft tissue shaver (4.5mm) is passed into the lateral portal, it is advanced towards the back of the ankle and medially until it makes contact with the arthroscopic sleeve. The shaver is withdrawn slightly, the tip should be visualised before the power is engaged.

    The table height should be adjusted so that the surgeons shoulders are relaxed, and the screen positioned for optimal visibility.

    Initially the tip of the shaver is seen to be surrounded by the amorphous fatty tissue (1) of the posterior ankle and Kagers’ fat pad.
    The tip of the shaver should be in view and workshould be performed lateral to the arthroscope at all times, the fatty tissue is slowly debrided in order to expose the posterior subtalar joint and provide a clear working space.

    Once sufficient adipose tissue is excised, the posterior ankle and subtalar recess appears. The Os Naviculare is usually covered in fibrous tissue (1), the synchondrosis is usually not well visualised. The posterior ankle ligaments and capsule (2) obscure the posterior ankle joint.

    Whilst the posterior facet of the subtalar joint is usually visible, the Os Trigonum (OT) tends to be obscure it, the Os Trigonum often projects more posteriorly than expected and is covered in a layer of connective tissue (1) as seen here.

    The connective tissue is carefully shaved away in order to define the Os Trigonum (1), shaver placement should be over the lateral aspect of the os before proceeding systematically towards the medial side of the process, in order to reduce the risk of injury to the FHL which abuts the medial border.

    Once the FHL tendon is identified passing longitudinally (1), The medial border of the Os Trigonum can be debrided, keeping the tendon in direct vision and the blades of the shaver pointing laterally.

    Once the fibrous tissue is adequately cleared, an arthroscopic probe can then be used to define the synchondrosis (1) with an Os Trigonum (although this isn’t possible with a steida process).

    A rongeur is useful in carefully debriding soft tissue or bony lesions (1) from the margins of the posterolateral talar process or Os Trigonum.

    As the Os Trigonum is debrided with a combination of burrs and rongeurs, the posterior facet of the subtalar joint (1) becomes visible.

    Operation – 2

    The Os trigonum is debrided back to the synchondrosis using a combination of Burr and rongeurs. Often there is a medial projection of bone and soft tissue around the FHL tendon (1), this needs to be carefully removed with rongeurs and soft tissue shavers whilst protecting the tendon, the sleeve of the shaver can be used to gently retract the tendon whilst keeping the teeth of the shaver pointing laterally away from the FHL.

    Once the medial soft tissue and bone is adequately debrided, the FHL can seen to freely glide through the fibro-osseous tunnel.

    Dorsiflex the hallux and ankle to bring the FHL muscle belly (1) into view and assess for any muscle impingement within the fibro-osseous sheath.

    Once the Os Trigonum is excised, the posterior subtalar joint (1) should be inspected for pathology, such as chondral flaps, the joint can be seen to move with inversion and eversion.

    20 ml of long acting local anaesthetic is infiltrated around the wounds and posterior ankle after the procedure.

    Long acting local anaesthetic is infiltrated around the wounds and posterior ankle after the procedure.

    Adhesive waterproof dressings are applied to the wounds.

    a compression bandage stays in situ for 72 hours, before it is removed in order to encourage early range of movement.

    T1 weighted MRI Sagittal section showing Os Trigonum with surrounding synovitis in the posterior ankle recess.

    T2 weighted MRI scan Sagittal section showing high signal in the Os Trigonum, with surrounding synovitis and a posterior ankle effusion.

    Post Operative

    Waterproof adhesive dressings are applied to the wounds, along with an outer dry compressive dressing with blue gauze, wool and crepe. The outer dressing is removed at 72 hours, leaving the adhesive dressings.
    Swelling is managed with elevation of the leg and regular application of cold packs for 14 days.
    A graduated compression stocking is applied to the contralateral leg for 4 weeks until fully mobile.
    Full weight bearing is allowed immediately.
    Patients are encouraged to begin active and passive dorsiflexion and plantarflexion exercises immediately in order to maintain range of movement. Physiotherapy should begin to continue with range of movement exercises and to begin strengthening at 2 weeks post-operatively.
    Sutures removed at 14 days.
    Low impact exercise such as gentle cycling and swimming from 2 weeks. Plyometric work and light running from 6 weeks.
    Return to sport and dance from 8-12 weeks.

    Recommended Reading

    Ferretti and Morelli (journal of foot and ankle surgery 2017), report results in 12 professional dancers of arthroscopic treatment for Os Trigonum syndrome, return to dance at mean of 8.7 (8-10) weeks with excellent functional results and low morbidity.
    Heyer and Rose (Foot and Ankle International 2017), report a retrospective series of open excision of Os Trigonum in 40 dancers with good functional results, high return to dance, an a 10% incidence of wound complications.
    Carreira (Foot and Ankle international 2016), reported good results with low complication rates in 20 athletes, range of movement was significantly improved.
    Lopez valerio and Cugat (Foot and Ankle Int 2015) Retrospective study treatment of 20 footballers presenting with posterior ankle impingement. Mean return to pre-surgical level of sport was 46.9 days.

    Reference

    • orthoracle.com

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