Lateral ankle instability – repair/ reconstruct what’s new

Abstract

Lateral ankle instability is a common condition which responds well to non-surgical management. However, the chronic symptomatic instability may require surgical intervention. The acceptable and practiced procedure is the Brostom Gould modification and it has a high patient satisfaction score. However, the current understanding and newer techniques for stabilising the lateral ligament complex has resulted in arthroscopic repairs, augmentation and tendon graft reconstructions. The literature does not provide an answer to the efficacy of these new techniques but there is some preliminary information favouring some of the latest procedures. It is now accepted practise to include ankle arthroscopy as a pre repair step. Augmentation of anatomical repair is also favoured in a select group of patients. This article provides an up to date account of the newer techniques for lateral ankle stabilisation.

Introduction

Lateral ligament sprains (Incidence 30,000/per day in United States) ¹ and progression to chronic lateral ankle instability (CLAI) in 10–30% ² is a common injury occurring amongst the young and active population. Lateral ligament complex is involved in 80% of sprains with the anterior talofibular ligament (ATFL) component in 80% and the calcaneofibular ligament (CFL) in 40%. ³ Most are managed successfully with non-surgical intervention with minimum long term complications.

The surgical management of CLAI continues to evolve. Brostom’s anatomical repair of the lateral ligament in the primary setting is currently the ‘gold standard’. However the failed surgical repair, poor quality native tissue, patients with hyper laxity conditions, mal alignment of hind foot and elite athletes continue to be a difficult problem group to address.

There has been, recently, a better understanding of the pathology, improvement in radiological investigations, increased use of arthroscopy to detect associated pathologies and newer surgical techniques to augment the repair/reconstruction, accelerate rehabilitation and minimise tissue trauma. This article will focus on these current developments only as the topic of ankle instability has been comprehensively discussed in this supplement.

Newer concepts

Microinstability

A recent concept based on the evidence that a partial tear of ATFL involving its upper fibres, which are intra articular, has poor healing potential. With recurrent ankle inversion injuries this tear progresses distally to involve all of the ATFL and subsequently the CFL. The instability experienced is functional initially and eventually is an established mechanical condition.^4,5 Cadaveric study has shown that the superior fascicle of the ATFL is anatomically and functionally distinct from the inferior one. Vega et al showed that four types of lesions of the superior fascicle of the ATFL exist on arthroscopy. Type 1 was loss of tension, Type 2/3 were partial and total tears respectively and Type 4 was ligament remnant resorption. ⁶

The concept of anterolateral ankle impingement, in the past, was attributed to the synovitis, fibrosis and hypertrophy of the ATFL. This tissue was responsible for the pain and impingement experienced in the anterolateral aspect of the ankle by the patient.

Molloy Sign is a clinical provocative test which was attributed to synovial impingement on the anterolateral ankle aspect. The symptom was elicited with pressure over the lateral ankle joint line as it was passively moved from a plantar to dorsiflexion position. ⁷

In 2008 Takao ⁸ and in 2016 Vega ⁹ confirmed fibrosis and avulsion of the ATFL arthroscopically as the commonest finding in patients with functional instability and not synovitis as previously believed.

Microinstability should be considered in patients presenting with anterolateral ankle discomfort and functional instability with unelicitable or demonstrable signs of an unstable ankle on performing stress clinical examination.

MRI is a useful investigation, in patients with functional instability, to diagnose avulsion of the ATFL from its proximal attachment. ¹⁰ Arthroscopy remains a more definite means of confirming ATFL involvement and it is essential that the ligament is visualised in its entirety.

Rotational ankle instability

This condition involves injury to both the lateral ligament along with the medial or Deltoid ligament. It is estimated that 10–40% of all patients with CLAI will have a partial deltoid injury. ¹¹ Deltoid ligament is an external rotation restrainer of the talus. ¹² The anterior fibres of the deltoid are involved and usually injured either at the initial traumatic incident or due to recurrent inversion episodes and continued impaction of the talus with medial malleolus. Vega first described the insufficient deltoid ligament with the anterior fibres of the superficial deltoid avulsed off the medial malleolus. ⁷ This combination of CLAI and incompetence of the deltoid has been termed as Multidirectional ankle instability (MAI). ¹³

Patients with MAI not only have pain and discomfort on the lateral aspect but also on the medial side. Clinical examination involves performing the anteromedial Drawer and Valgus stress test. Arthroscopy of the ankle may show an “open book” lesion of the deltoid (detachment of the anterior fibres of deltoid from the medial malleolus) and passage of a 5 mm probe through the medial Tibiotalar space with ease. ¹⁴

Repair of the medial ligament concurrently with the lateral ligament complex either open or arthroscopically with suture anchors have shown good results.

What’s new in radiological investigations

A thorough history and meticulous clinical examination still remains an accurate means of diagnosing mechanical and symptomatic CLAI. The accuracy of clinical assessment has been shown to be 100% in Grade 3 lateral ligament tears but falls to only 25% in Grade 2 tears. ⁷ The commonly radiological tools utilised to confirm clinical suspicion are X-rays (including stress views), Ultrasound and MRI. Both Ultrasound (91%) and MRI (97%) have high accuracy but Ultrasound is operator dependent and 1.5 T MRI have difficulty in interpreting the degree of damage to ATFL and specially CFL. ¹⁵

MRI

The 3T MRI now in use provides superior images. Intact ligaments have a low signal intensity surrounded by high signal intensity fat. Axial views with fat suppression and local gradient provides more information about the state of ATFL and PTFL. Coronal sections show CFL and posterior Syndesmotic ligaments in greater clarity. The Deltoid ligament as well as the spring ligament can be visualised with greater accuracy. Three dimensional reconstructions are possible and other associated intra articular pathologies can also be diagnosed.

The diagnostic sensitivity of MRI without contrast for ATFL is 100% sensitive but only 50% without contrast. The accuracy can be increased to 100% with MRI arthrography.

Recent study conducted by Wenning et al where a comparison between manual stress, Ultrasound stress test and 3D MRI stress imaging was made. They concluded that both US and 3D MRI were more reliable as objective and quantitative measures in chronic ankle instability. ¹⁶

Another study compared the relative diagnostic value of anterior Drawer, stress radiographs, stress US and MRI using arthroscopy as a reference standard. Results showed 79.6% sensitivity of anterior Drawer, 86% of stress radiographs and 100% of both stress US and MRI. ¹⁷

Role of ankle arthroscopy

Ankle arthroscopy has become the standard initial step before repair/reconstruction is performed of the lateral ligament and has demonstrated its usefulness in diagnosing and delineating associated pathologies. The most commonly present pathologies in association with lateral ligament injuries are Osteochondral lesions, deltoid ligament injuries, loose bodies, anterior impingement and peroneal tendon problems. Hintermann in his study ¹¹ found that 66% of patients had cartilage injury and in 98% of cases with medial instability on scoping the ankle at the time of stabilisation. Vega ¹⁴ found in 24 patients 100% intra articular pathology with ankle instability.

It is also becoming popular in repair or reconstruction of the lateral ligament. Over the years it has progressed from being an arthroscopic assisted technique to an all arthroscopic repair/reconstruction and now an all inside technique.

Arthroscopic repair/reconstruction requires training and is a demanding technique.

What’s new in surgical procedure

More than 50 surgical procedures have been described to repair/reconstruct the lateral ligament complex.

These can be broadly grouped into anatomical repair or reconstruction, non-anatomical reconstruction and anatomical augmented repair or reconstruction.

The current accepted approach to the symptomatic and failed conservative management CLAI is to perform Brostrom repair with either Gould or Karlsson modification. Gould modification involves the use of Inferior extensor retinaculum to re-enforce the anatomical repair. Karlsson modification involves ligament imbrication and attachment to the fibula with suture anchors. The rationale behind imbrication is that the ligament complex tissue is usually stretched and scarred. Other modifications of the Brostrom technique have also been reported in literature – Lasso technique by Tay et al. ¹⁸ triple breasting with suture anchors by Molloy et al. ¹⁹ and Brostrom-Evans. ²⁰ Gould modification has a success rate of 87-95% and 90% patient satisfaction. ²¹ However, this success is not reproduced in certain groups of patients – hyper laxity, obese, Hind foot varus mal alignment, poor native tissue for repair and the elite athlete. The failure and recurrent instability rate varies from 2-18% ²² after primary anatomical repair but in the above group it can be as high as 45.2%. ²³

More recently a Level 1 randomised trial conducted by Ko et al. ³⁰ concluded that repair of the ATFL only achieved the same results as when both ATFL and CFL were repaired. This follows similar findings from previous studies by Lei et al. ²⁶ and Maffulli et al. ³¹ in 2011 and 2013.

The non-anatomical reconstruction procedures (Evans, Chrisman Snook and Watson Jones) have largely fallen out of favour due to altered ankle and sub-talar joint mechanics and potential degenerate arthritic changes in the ankle. Osteoarthritis of the ankle after non-anatomical reconstruction has been reported to occur in 10% of patients and recurrent instability in up to 67% at long term follow up. ³² In 2013 a consensus in CLAI recommended that non-anatomical reconstructions procedures should be avoided. ³³

Comparison of non-anatomical (Watson Jones, Evans and Castaing) with anatomical repair (Brostom, Duquennoy) with minimum 10 year follow up in a systematic review by Noailles et al. ³⁴ concluded that anatomical repair had better functional outcome with loss of range of motion and secondary arthritis occurring in the non-anatomical group. ¹¹

Foot and ankle literature has, recently, displayed an increasing number of studies related to the advantages of arthroscopic repair/reconstruction of the lateral ligament and the use of augmentation with anatomical repairs.

Augmentation with anatomical repair

Anatomical primary repair of lateral ligament complex has a high success rate at long term follow up. Augmentation can be considered in the group of patients with higher failure rate – generalised ligament laxity (Beighton score of 7 or more), obese, poor native tissue, elite athletes and abnormal collagen structure disorders (Marfans, Ehlers-Danlos). Recent studies report on the outcomes of augmentation with suture tape, LARS, autograft or allograft. The benefit of augmentation is to strengthen the Brostrom Gould ligament repair and protect it during earlier rehabilitation.

The strength of the anatomical repairs (Modified Brostrom) has been a concern. Schuh and colleagues compared three repairs on cadavers – Brostrom without suture anchors, with suture anchors and with internal brace. Statistically significant difference in failure rate was found between the two repairs without the internal brace and with it. ³⁵

Comparison between native ATFL and internal brace group in cadavers conducted by Willegger showed higher stability in the internal brace group.

Lewis et al. (2021) conducted a systematic review of Modified Brostrom repair and suture tape augmentation in 10 studies including 333 patients with a mean follow up of 24.8 months and concluded that augmentation may result in an earlier return to sporting activities with potentially reduced rates of recurrent instability when compared to modified Brostrom repair alone. ²⁴ He, however, cautioned about the limited quality of the evidence.

Cho et al in 2019 performed a randomised comparison between suture tape augmentation and modified Brostrom repair in young females with CLAI. He concluded that the outcome was not significantly different though the cost was higher with use of suture tape. ²⁵

Lei et al (2021) performed a meta-analysis of RCT(4 studies with 209 patients) between LARS augmentation and Brostrom Gould modification repair and concluded no clinical superiority of LARS over the anatomical repair. No comparison in outcomes between high risk patients and non-high risk was done in this study. ²⁶

Tang et al (2021) conducted a systematic review to answer the question whether generalised ligament laxity was a contraindication for modified Brostrom repair in CLAI.

A total of 447 patients from cohort studies and case series were analysed. Comparison was done between the patients with and without generalised ligament laxity pre- and post-operatively and concluded that modified Brostrom repair is not a contraindication for treating CLAI in generalised ligament laxity but some form of augmentation should be included in patients with Beighton score of >7. It should also be considered in patient with abnormal Talar tilt angle and Anterior talar translation in the contra lateral ankle. ²⁷

Cho reported on the use of suture tape augmentation in patients with failed initial Brostrom repair. He carried out a revision Brostrom repair with suture tape augmentation in 24 patients with improvement in functional score and stress radiographs at a mean follow up of 38.5 months. ³⁶

The current literature recommends a prospective randomised control trial to attempt to answer the question of routine augmentation in selected high risk group of patients.

Anatomical reconstruction – autograft or allograft

The use of tendon auto or allograft for anatomical reconstruction is indicated in certain patient groups where anatomical repair is either not possible due to poor capsular and ligamentous tissue or presence of certain risk factors that may predispose to earlier failure. Obesity, Generalised ligament laxity, high level sports participation or patients involved in heavy manual labour are groups that may benefit from this procedure.

Failed primary repairs requiring revision procedures may also benefit from replacement with graft inserted in an anatomical fashion.

The issues arising from use of autograft – increased post-operative pain, donor site morbidity, increased surgical time have prompted the use of allografts although the literature has not provided evidence in favour of one or the other. ³⁷

Donor sites for autografts can be both local or distal from the foot and ankle. Examples of autograft used for anatomical reconstruction include gracilis, semitendinosus, plantaris tendon, split peronei, palmaris longus, fascia lata, patella bone tendon bone. The maximum failure load of the ATFL is 350N which is low compared to other tendons. The length for a graft need not be more than 12 cms.

Brambilla et al (2020) performed a systematic review comparing outcomes between auto and allograft use for anatomical lateral ligament reconstruction. 12 studies with 357 patients undergoing lateral ligament reconstruction were included. He concluded that poor methodology and low level evidence made it difficult to decide which alternative was safer or better. With qualitative analysis only they found no difference in graft survivorship, graft dependent variables, patient satisfaction, clinical and radiograph outcomes between allograft or autograft. Both gracilis and anterior half of peroneus longus were the most commonly used autografts. ²⁸

Xu et al. did a retrospective comparison between semitendinosus auto and allograft and found no difference except that the autograft showed faster healing time. ²⁹

Arthroscopic repair

The aim of lateral ligament repair/reconstruction is to provide a mobile and stable ankle joint. To achieve this goal various techniques have developed to perform the procedure expeditiously and with minimal morbidity and complications. A natural progression towards this goal was the introduction of ankle arthroscopy which has now shown to generate acceptable outcomes with high patient satisfaction. Arthroscopic repair of the ATFL was first introduced in the 90s by Hawkins. ³⁸

Arthroscopic repair is carried out as an arthroscopic assisted, all arthroscopic technique or an all inside repair. The difference between them lies upon the number of additional portals or incisions required to perform the repair.

Arthroscopic assisted procedure involves the use of at least 1 accessory portal. This helps to pass sutures or bone anchors through for repair. Kim et al. ³⁹ Corte-Real and Moreira. ⁴⁰ and other studies have shown acceptable results but with a wide range of complication rates (up to 29.6%). Most of the complications are related to the surrounding neural structures specially the Superficial Peroneal nerve.

Due to the entrapment of structures – tendon, nerve in the suture knot the All Arthroscopic technique was developed. This utilised the two portals for a standard ankle arthroscope but additionally a small incision was made to tie the sutures. Nery. ⁴¹ Acevedo and Mangone. ⁴² Pelligrini ⁴³ with a mean follow up of approximately 2 years showed a high patient satisfaction with minimal complications.

Vega and colleagues in 2018 introduced the knotless suture technique to repair the ligament. This All Inside arthroscopic technique only requires the two standard ankle scope portals and the knot is either tied arthroscopically or knotless suture anchors are used. ⁴⁴

Rigby et al. (2019) reviewed the outcomes of 62 patients comparing open to an all inside arthroscopic Brostom repair. They found no significant difference in any functional or patient outcome scores in the two groups. ⁴⁷

A systematic review of open (13 studies involving 505 patients) and arthroscopic lateral ligament repair (6 studies with 216 patients) carried out by Guelfi et al. concluded that both were procedures which provided high patient satisfaction. The arthroscopic group reported a higher complication rate of 15.2% as compared to open repairs which was 7.92%. ⁴⁵

The strength of the repair arthroscopically has been shown to equal the open procedure and Giza et al. ⁴⁶ found no difference in open and 2 bone anchors arthroscopic repair in cadavers.

In conclusion, arthroscopic assessment of the ankle and addressing the intra articular pathology prior to repairing or reconstructing the lateral ligament, open or arthroscopically, is now considered standard practice. Anatomical repairs are strongly recommended and in certain sub groups augmentation with artificial material or autograft should be considered.

If reconstruction is being considered it should be anatomical with graft according to surgeons preference. Gracilis is the most frequently used autograft.

It should be emphasised that the arthroscopic procedures are technically demanding and so it is imperative that the surgeon proceed with a procedure he is comfortable and experienced with.