Is anterior and posterior ankle impingement under-diagnosed? A review

Introduction

Anterior ankle impingement has been variously described as “athlete’s” ankle and “footballers” ankle in early descriptions before investigation into the etiopathogenesis of the condition and the terminology has since been replaced with anterior ankle impingement syndrome.^[1] Restricted ankle dorsiflexion with ankle pain has been the hallmark of this condition and causes of the condition include not just bony but also soft tissues impingement.

Posterior ankle impingement syndrome (PAIS) is a clinical disorder characterized by pain in posterior ankle on performing activities involving forced plantar flexion.^[2] PAIS is also referred to as “Os trigonum syndrome” and “posterior tibiotalar compression syndrome.”^[3] The condition does not only necessarily arise from bone but also arises from soft-tissue component also. It arises from compression of soft tissues between posterior process of calcaneus and posterior tibia on plantar flexion of ankle which includes the posterior talofibular, intermalleolar, tibiofibular ligaments, and the posterior capsule. Unlike anterior ankle impingement that is common in sportsmen, posterior impingement is commonly seen in dancers.^[4] The specific dance position associated with posterior impingement is sustained and frequent high degree plantar flexion (en point or demi-pointe).^[5] Other professions involving regular use of such ankle movements include footballers, gymnasts, cricketers, horizontal jumpers, and they commonly experience features of PAIS.^[6-8]

Non-operative treatment has been suggested as the initial management for this condition which includes rest, bracing, and physical therapy. In most cases, this is not successful and surgical intervention is warranted.^[9-11] Classically, open ankle arthrotomy has been used but has been associated with various complications including excessive scarring, delayed wound healing, and iatrogenic damage to tendons and cutaneous nerves.^[12,13] Over time arthroscopic debridement has taken over traditional open approaches with equivalent to better outcomes and lower complication rate.^[9,10,14]

The purpose of this study was to appraise the available literature and describe current knowledge regarding ankle impingement, describe the author’s technique for surgical management of various impingement syndromes and simultaneously provide an evidence based review of various treatment options available for managing this under diagnosed and ignored entity.

Etiopathogenesis

Ankle impingement can either be bony or soft-tissue impingement. In addition, impingement can be either anteromedial or anterolateral. Classically, anteromedial impingement is described in sportsmen.^[15] It was earlier thought that forceful plantar flexion in athletes to be the most important etiological factor leading to anterior capsular traction and later capsular hypertrophy.^[1,9] This was deemed implausible as the capsule is attached more proximal to origin of spurs.^[16] This lead to more a recent and plausible explanations including recurrent microtrauma leading to bony impingement of talar neck to distal tibia.^[17,18] Moreover, chronic ankle instability is associated with osteophyte formation in medial ankle compartment which originates at the non-weight bearing cartilage rim which occurs most in supination trauma.^[19-21]

Anterolateral impingements are mostly post-traumatic. The etiology for anterolateral impingement is more diverse and has been thought to be a result of chronic ankle instability, recurrent micro-trauma, traction, and a myriad of other mechanical factors.^[18] Soft-tissue impingement occurs due to hypertrophy of synovium, capsule, and adjoining capsular ligaments which are believed to get entrapped, torn, and inflamed in the lateral gutter of ankle joint. This occurs due to incomplete healing leading to persistent inflammation with subsequent scarring and synovitis.^[22] Another explanation for anterolateral impingement is reactive synovitis in the lateral gutter following intra-articular hematoma.^[23]

Clinical features

Patients are typically young athletes with persistent ankle swelling, pain, and limited ankle dorsiflexion who often have a preceding history of recurrent ankle sprains.^[12,24] The pain is classically exaggerated with kicking, stair climbing, and running. Hyperdorsiflexion causes pain with a false negative test has been frequently reported making it a non-specific finding. Establishing a diagnosis is, thus, dependent a combination of clinical and radiological findings. Location of anteromedial (medial to tibialis anterior tendon) and anterolateral tenderness differentiates the two impingement types clinically.^[12] Common differential diagnosis include stress fractures (Tibiotalar), osteochondral lesions (OCD), loose bodies, ankle arthritis, and painful instability. Pain in OCD is deeper and not movement specific unlike impingement pain which is often localized to a superficial plane.

Investigations

Baseline investigations needed in patient suspected of having impingement symptoms is a weight bearing anteroposterior (AP) and lateral X-ray of the ankle that shows findings when there is obvious bone impingement, osteophytes, and reduction in tibiotalar joint space if present.^[25] An oblique AMI X-ray has also been described where the beam is tilted in a 45° craniocaudal direction and the leg is rotated 30° in external rotation with foot plantar-flexed. This view has been reported to detect osteophytes in cases with anteromedial impingement when the same cannot be picked up by lateral X-rays.^[26]

Magnetic resonance imaging (MRI) shows thickened synovium, anterolateral gutter scarring, and soft-tissue impingement. It is also important to cover differential diagnosis with inversion ankle injuries which include stress fractures (Tibiotalar), OCD, loose bodies, ankle arthritis, and painful instability. Axial T1-weighted images are useful to detect anterolateral gutter scarring while a coronal images can identify injury to anterior band of deltoid ligament which is apparent as thickening and edematous. Variable sensitivities and specificities are described in literature but the authors of present review believe MRI to be the most efficient investigation in cases of suspected anterior ankle impingement [Figure 1].^[27-29]

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Figure 1:: (a) Lateral ankle radiograph with associated osteophytes from the anterior tibial plafond (solid arrow) and anterior talar neck (outlined arrow), (b and c) axial and sagittal magnetic resonance imaging cuts showing anterior impingement lesion, and (d) arthroscopic view of anterior impingement lesion before debridement (outlined arrow).

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CT scan has been described but it does not add much to existing diagnostic modalities. It, however, helps in clear delineation of bony pathologies such as osteophytes, ossicles, and loose bodies.^[30] Ultrasound has been investigated by McCarthy et al. and has a high correlation to operative findings to detect soft-tissue hypertrophy and impingement.^[31] Pre-operative planning using all feasible investigation should be carried out to distinguish between soft-tissue and bony impingement.

Setup for ankle arthroscopy

Ankle arthroscopy for impingement is carried out under spinal or general anesthesia with the patient placed supine on the operating table. The authors prefer foot at the edge of bed without use of traction for ankle arthroscopy for impingement lesion [Figure 2]. A pouch placed at the edge of the table helps catch the fluid overflow and gravity flow saline is used conventionally. The surgeon stands at the end of the bed looking toward the head with the screen in the line of vision. The authors prefer to use a 4 mm shaver and 4 mm arthroscope which is adequate for most procedures. Some surgeons use smaller arthroscopes which is more of personal preference and as per ones comfort. A long curved and thin (4 mm) beveled osteotome is used which is longer with a broad handle. The osteotome has angled tip which helps get out bone from different positions around the ankle which the authors feel is quite a useful device. A 4 mm round or oval burr which is occasionally used along with occasional use of an arthrowand for soft-tissue debridement.

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Figure 2:: (a-c) Arthroscopy portals for anterior ankle arthroscopy used in managing anterior ankle impingement.

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Procedure

The anteromedial and anterolateral portals allow for proper visualization during anterior ankle arthroscopy. The first portal is the anteromedial portal which is entered first. One can inject saline depending on one’e comfort which helps in locating the anterolateral portal. The arthroscope is inserted in the medial portal that helps visualize the lateral side well and helps visualize neuro-vascular structures before making the lateral portal. Additional use of the posterolateral portal has been described by some authors.^[14] As determined by thorough pre-operative evaluation of radiology, first soft-tissue impingement is removed, followed by removal of bony impingement The gutters are cleared and the osteophytes are shaved with use of osteotome. After major bone is removed, the edges are shaved off with use of a burr. The anteromedial tibia, talus, and medial malleolus are cleared in cases with anteromedial impingement. Similar clearance is carried out anterolaterally. Arthrofibrosis is cleared using a arthrowand as this tissue is fairly strong and its rather hard to remove using a shaver. Occasionally, an 11 number blade can be used to break it up taking care not to damage the articular surface.

Post-operative protocol

Weight bearing is avoided for a couple of days following the procedure with use of crutches to ambulate. Weight bearing is gradually begun with gait training started at 2 weeks and full weight bearing resumed at 4 weeks. Closed lunge maneuvers are avoided for the initial 4 weeks as this is expected to cause inflammation along anterior part of ankle and can promote fibrosis. Open chain exercises, calf relaxation, massage, and range of motion (ROM) exercises are promoted for next 6–8 weeks.

Post-operative failure/complications

Poorly done arthroscopy seldom works and a major cause for second opinions are insufficient clearance and this is along the medial gutter. The surgeon must look along the antermedial gutter when looking at the anterior ankle. Another major cause is post-operative arthrofibrosis and this is commonly due to aggressive physiotherapy, early return to sport or rarely genetic predisposition to arthrofibrosis.

Another reason why arthroscopy does not work is a different diagnosis which includes arthritis, osteochondral defect, ongoing missed instability, and rarely navicular osteophyte or low grade stress fracture of the navicular. This re-emphasizes the need for a proper and detailed pre-operative workup. Recurrent arthrofibrosis can be managed by systemic use of steroids, nonsteroidal anti-inflammatory drugs, gentle mobilization, and steroid injection into the joint that may have to be repeated at 4–6 weeks. Other complications such as complex regional pain syndrome and superficial peroneal nerve neuropraxia have been reported.^[22] Complication rate is rather low and has been reported to be under 5%.^[32]

Operative outcomes

The results and reported surgical outcomes of arthroscopic resection of anterolateral impingement are good to excellent over mid to long term.^[33-38] There is, however, paucity of data for anteromedial impingement resection.^[22] van Dijk et al. have compared results of anteromedial to anterolateral impingement resection and have found superior outcomes with anteromedial impingement lesions following surgery.^[39]

Etiopathogenesis

As with anterior impingement syndromes, posterior impingement can be both soft tissue and bony. Major cause of impingement posteriorly is bony and arises due to two very related pathologies which are the “Os trigonum” and stieda process.^[40] A secondary ossification center forms at the posterolateral aspect of talus and usually fuses with the posterior talus in adolescence, if this fusion creates a large posterolateral talar process, it is called the stieda process.^[41] However, if the same fails to fuse, an os trigonum is formed, which articulates with the talus through a synchondrosis (7–14% cases).^[42] The specific dance position associated with posterior impingement is sustained and frequent high degree plantar flexion (en point or demi-pointe). Repetitive plantarflexion trauma is postulated to prevent proper closure of os trigonum ossification center.^[43]

Investigations

Conventional radiography including weight bearing AP and lateral views of the ankle is carried out. The lateral view is more helpful in confirming presence of stieda process/os trigonum. This also tells about the size of the pathological lesion. Lateral radiograph in 25° of external rotation gives more detailed information about the size. This is because axis of the talus is not 90°. Size may be under-estimated in neutral rotation. Additional X-ray views are carried out in ankle plantar-flexion.^[40]

MRI helps confirm diagnosis and excludes any other pathology in posterior ankle like a cyst or a low lying FHL muscle belly. T2-weighted image shows bone edema, synchondrosis, and soft-tissue signal changes [Figure 3].^[43,45]

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Figure 3:: (a) Lateral ankle radiograph with associated osteophytes from the posterior tibial plafond (solid arrow), (b) Sagittal magnetic resonance imaging showing posterior impingement lesion (outlined arrow), and (c) arthroscopic view of posterior impingement lesion before debridement (outlined arrow).

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Treatment options start with physical therapy, activity modification, and ultrasound-guided injections.^[46] Athletes looking for fast solutions is candidates for early arthroscopic resection of soft tissue and joint washout. Good symptomatic and functional results have been shown in resistant cases with arthroscopic debridement.^[47]

Arthroscopic setup for posterior ankle arthroscopy

The authors of the present study opt for the endoscopic excision of the os trigonum because of reported advantages of minimal scar and good soft-tissue healing, ability to assess, and address any associated intra-articular pathology and the advantage of early return to sports.^[48] In prone position under general anesthesia with tourniquet control, surface marking demarcating the Achilles tendon, both malleoli, and the desired portal sites is done [Figure 4].

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Figure 4:: Setup for posterior ankle arthroscopy used in managing posterior ankle impingement.

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A horizontal line is made from lateral to medial across the Achilles Tendon, starting at the tip of lateral malleolus. Standard poster medial and poster lateral portals were made 5 mm anterior to tendon-Achilles just above the horizontal line. A 4 mm arthroscope and normal saline through a pressure pump set at 40 mmHg pressure are used as the irrigating fluid. Diagnostic endoscopy is first performed.

Surgical technique

The portals are made lateral and medial to the Achilles Tendon. Once the lateral portal is made, nick and spread technique is used. Posteromedial portal is made rather carefully to avoid neurovascular structures.

Post-operative protocol

Initial post-operative management is same as anterior ankle arthroscopy with icing and compression. Gait training with crutches, gentle ROM and core exercises are begun in the first 2 weeks. Patients remain non-weight bearing for the first 2 days with gradual return to full weight bearing by 4 weeks. Once swelling subsides by the 3^rd week joint mobilization, gait reeducation and compression manual therapy is initiated. Patients reach full strength by 6–8 weeks; however, return to full training and sports specific drill should begin by 12–14 weeks.^[48]

Complications

Complication rates range from 2.3% to 8.5% which include sural nerve injury, injury to medial neurovascular structures, and difficult identification and impalement of FHL.^[32,49]