Tibialis Anterior Tendon Rupture

Introduction

Tibialis anterior tendon (TAT) rupture is a rare injury, although it is the third most common tendon rupture in the lower limb, after the Achilles and patella tendons. 

 

Classification 

  • Complete or partial 
  • Acute or chronic (cut off at 4/52 for most authors) 
  • Traumatic, atraumatic or iatrogenic 

 

Aetiology 

  • Traumatic (younger patients) - open injuries, blunt trauma, forced plantar flexion and eversion of a dorsiflexed ankle.
  • Atraumatic (older patients, mostly men > 60y) - overuse and degeneration. Risk factors include diabetes, RA, psoriasis, gout, hypothyroidism, prostate Ca, HTN, steroids. Not documented to be associated with fluoroquinolone use.
  • Iatrogenic - Lapidus or midfoot fusion surgery, debridement of distal TAT for tendinopathy, following local steroid injection.

 

Anatomy and biomechanics 

Origin: anterolateral proximal tibia and interosseous membrane.

Insertion: medial cuneiform and first metatarsal base.

Function: primarily as ankle dorsiflexor, and secondarily as subtalar joint inverter. Eccentric contraction occurs during heel strike and early in stance phase, and concentric contraction occurs during in swing phase.

Avascular zone is located on the anterior half of the tendon, beneath the superior and inferior extensor retinacula, 5-30mm proximal to its insertion.

 

Clinical presentation 

TAT rupture results in slapping of the foot during heel strike and a high-stepping gait, due to difficulty clearing the foot during swing phase.  It is easily missed in atraumatic / degenerative cases, as recruitment of EHL and EDL may mask the functional deficit, especially in relatively low demand patients. 

Typical triad:  

  • pseudotumor at anterior ankle (corresponds to ruptured tendon end) 
  • loss of the normal contour of the tendon 
  • weak dorsiflexion of the ankle accompanied by hyperextension of all toes 

In the long term, compensation by EHL/EDL may result in claw toes and hallux cock-up deformity, and Achilles tendon shortening may also be identified. 

 

Imaging  

Radiographs may reveal avulsion fractures or bony prominences which caused the rupture (e.g. anterior ankle or midfoot osteophytes) . Ultrasound allows dynamic testing, and estimation of the gap during various degrees of ankle motion. MRI may assess the quality of the tibialis anterior muscle in cases of chronic ruptures; fatty infiltration may suggest an EHL transfer might be more appropriate than grafting a weak muscle.

 

Management 

Dependent upon:

  • Patient factors (previous mobility, functional demands, surgical contraindications) 
  • Chronicity of the rupture (may lead to proximal stump retraction and scarring) 
  • Gap (large gaps may need an interposition graft) 
  • Location (distal ruptures may need additional fixation at insertion) 
  • Cause of rupture (atraumatic rupture are more likely degenerate and therefore less appropriate for primary repair) 
  • Tibialis anterior muscle status (if weak secondary to inactivity, addtional EHL tendon transfer to aid in dorsiflexion may be needed) 
  • Achilles release contracture (more likely in chronic cases)  

Non-operative  

Can be offered to very low demand patients or those with significant contraindications to surgery. Low demand patients may respond relatively well to treatment with orthoses, activity modification and physiotherapy. 

Operative options 

  1. Direct end to end repair indicated for acute traumatic cases if gap <2.5cm.
  2. Atraumatic rupture suggests a degenerate tendon; one should consider reinforcement and must be prepared to perform extensive debridement intra-operatively.
  3. Fixation to medial cuneiform or navicular with suture anchors, bone tunnel, interference screw, suture button 
  4. Lengthening and rotationplasty / turn-down flap procedures for gap <5cm and absence of significant tendon degeneration 
  5. Tendon transfer for gap >5cm, for tibialis anterior muscle fatty infiltration / weakness. EHL tendon most commonly used (nearest tendon to TAT, agonist action). Alternatively use EDL, peroneus tertius or tibialis posterior tendons.
  6. Free allograft or autograft interposition for gap >5cm when tibialis anterior muscle belly is intact and functional.
  • Autograft: semitendinosus, gracilis, Achilles, peroneus brevis, plantaris, EDL. 
  • Allograft: tibialis anterior, Achilles, peroneus longus, gracilis, semitendinosus.
  • Allografts: practical, reliable, no donor site morbidity, not sacrificing a local tendon, decreased operative time, infection risk.

In all cases, check for equinus contracture and consider gastrocnemius recession or TA percutaneous release.

Post-operative management 

  1. 6 weeks in below knee cast, non-weight bearing.    
  2. 6 weeks in walking boot, start passive ankle mobilisation and progress from partial to full weight-bearing.
  3. Active strengthening tp start at 12 weeks post-operatively.

 

Summary 

TAT rupture is a rare injury, easily missed when atraumatic.

Typical triad is anterior ankle pseudotumour, loss of tendon contour, weakness in ankle dorsiflexion; high-stepping gait.

Non-operative treatment should be reserved only for very low demand patients, or those with significant contra-indications to surgery.

Usually, only acute traumatic cases can undergo direct repair; spontaneous ruptures are associated with tendon degeneration; chronic ruptures may have significant gaps.

Operative options are direct repair (gap <2.5cm), lengthening or turn-down procedures (gap <5cm), tendon transfers (mostly EHL) and autografts (mostly semitendinosous) or allografts (mostly semitendinosous or tibialis anterior) (gap >5cm). 

 

References 

  • Vosoughi AR, Heyes G, Molloy AP, Mason LW, Hoveidaei AH. Management of tibialis anterior tendon rupture: Recommendations based on the literature review. Foot Ankle Surg. 2020;26(5):487-493. doi:10.1016/j.fas.2019.06.003 
  • Tickner A, Thorng S, Martin M, Marmolejo V. Management of Isolated Anterior Tibial Tendon Rupture: A Systematic Review and Meta-Analysis. J Foot Ankle Surg. 2019;58(2):213-220. doi:10.1053/j.jfas.2018.08.001 
  • Christman-Skieller C, Merz MK, Tansey JP. A systematic review of tibialis anterior tendon rupture treatments and outcomes. Am J Orthop (Belle Mead NJ). 2015;44(4):E94-E99