chronic ankle instability and syndesmotic injuries

Chronic Ankle Instability and Syndesmotic InjuriesKent Heady, M.D.

OverviewThe vast majority of ankle sprains heal without long term sequelae.Ankle instability is a debilitating condition incorporating recurrent sprains, persistent pain and repeated instances of giving way.

OverviewMultifactorialStatic alignment, muscle weakness, poor proprioception, and ligamentous injury.Decreases level of function and quality of life.Potentially to lead to arthritis and chronic pain.

AnatomyLateral ankle ligaments and bone congruency are main static stabilizers.Peroneal tendons provide dynamic stability.

Anterior Talofibular LigamentATFL primarily resists translational laxity of the talus in the sagittal plane. ATFL has the lowest threshold for failure and thus is the most commonly injured ligament.

Calcaneofibular Ligament

CFL resists excessive supination at both the mortise and the subtalar joint.

Posterior Talofibular LigamentPTFL is a robust ligament with a broad surface conferring a high tensile strength. Provides resistance to inversion and internal rotation. Injury to the PTFL is the least likely to occur.

PathogenesisUsually the sequelae of an acute sprain that fails to heal properly.Ligaments may remain torn.Most commonly, heal but in an elongated fashion.Can result from loss of proprioception, muscle weakness, nerve injury, or tendon damage.

Functional InstabilityCan result from alteration in proprioception, neuromuscular control, postural control and the resultant strength deficits after sustaining an ankle sprain. The end result is a propensity for recurrent ankle sprains, persistent pain, and muscular weakness.

Clinical PresentationPersistent painRecurrent sprainsFeeling of giving way

Physical Exam96% sensitive and 84% specific in the diagnosis of chronic instabilityAssessment of overall weightbearing alignment. BEWARE THE SUBTLE CAVOVARUS FOOT!Neuromuscular exam

Physical ExamLateral sided ankle tenderness Range of motion Provocative tests including anterior drawer (sulcus sign) and the talar tilt test

Physical ExamAssessment for hindfoot alignment, equinus contracture and generalized signs of hypermobility Romberg test for proprioception

Imaging StudiesPlain standing films--Alignment and bone injury (nonunited avulsion fractures)Stress radiographs comparing the affected side to the unaffected sign are the gold standard for mechanical stability.

Stress ViewsA difference of >3mm in anterior drawer and >3 degrees on talar tilt is significant for instability>15 degrees of talar tilt or >1 cm anterior translation also usually considered abnormal.Look for motion of avulsion fragments!Normal stress films are not absolute contraindication to surgery.

MRIUseful adjunct in assessing the soft tissue structures as well as chondral injury. Not a dynamic study--limited usefulness.

TreatmentNon-operative treatment is the first line of therapy. Strength training and proprioception instruction are used, focusing on taking the ankle through a full range of normal motion.Bracing may help protect from reinjury but does not correct underlying pathology. Poor surgical candidates?

Surgical TreatmentIndicated if instability symptoms persist after rehab attempts.Two main types: anatomic repair or tenodesis stabilizationAnatomic repair restores normal anatomy and biomechanics while maintaining ankle motionTenodesis stabilization restricts laxity and pathologic motion but ignores the underlying ligamentous pathology. Stabilization is achieved at the expense of altering normal ankle and hindfoot biomechanics.

Tenodesis ProceduresLargely abandoned and obsolete.Sacrifices peroneal tendon function unnecessarily.Increased incidence of sural nerve injury and “too tight” ankle.

Tenodesis Procedures8th Edition of Mann’s Surgery of the Foot and Ankle: “We do not advocate any of these procedures...Due to the well-documented inherent problems of nonanatomic tenodesis procedures, we consider these procedures primarily of historical value.”

Modified Brostrum RepairMost commonly utilized anatomic repair. Imbrication of the ATFL and CFL are followed by fortification with a mobilized portion of the inferior extensor retinaculum (Gould modification).

Tendon Graft AugmentationTendon autograft (hamstring, plantaris, third toe extensor) or allograft reconstruction also and option.Usually reserved for patients with generalized ligamentous laxity, unreconstructable ligament damage, or salvage of prior failed repair.

Syndesmosis InjuriesAKA “High ankle sprains”Injury to the ligamentous complex stabilizing the interconnection between the distal fibula and tibia forming the lateral ankle joint.Occurs in 0.5% of all ankle sprains without fracture15% of all ankle fractures involve syndesmosis injuries.

Mechanism of InjuryMost commonly associated with external rotation injuries.External rotation forces the talus to rotate laterally and push the fibula away from tibia.May lead to increased compressive stresses seen by the tibia, lateral subluxation of the distal fibula, and incongruence of the ankle joint.

Associated InjuriesOsteochondral defects (15% to 25%)

Peroneal tendon injuries (up to 25%)

All Weber C and some Weber B fractures.

5th metatarsal base, anterior process of calcaneus, and lateral or posterior process of talus fractures.

Associated InjuriesDeltoid ligament injury

Loose bodies

PrognosisMissed injuries may result in end-stage ankle arthritis

Excellent functional outcomes if syndesmosis is anatomically reduced and stabilized

AnatomyAnterior Inferior Talofibular Ligament (AITFL)originates from anterolateral tubercle of tibia

(Chaput's)inserts on anterior tubercle of fibula (Wagstaffe's)

AnatomyPosterior-inferior tibiofibular ligament (PITFL)originates from posterior tubercle of tibia

(Volkmann's)inserts on posterior part of lateral malleolusstrongest component of syndesmosis

AnatomyInterosseous membrane

Interosseous ligament (IOL)distal continuation of the interosseous membranemain restraint to proximal migration of the talus

Inferior transverse ligament (ITL)

Syndesmosis BiomechanicsMaintains integrity between tibia and fibula

Resists axial, rotational, and translational forces

Syndesmosis widens 1mm during normal gait

Deltoid ligament indirectly stabilizes medial mortise

PresentationAnterolateral ankle pain proximal to AITFL

May have medial sided ankle tenderness/swelling

Often difficulty bearing weight (in contrast to most lateral ankle sprains).

Physical ExamPalpation for syndesmosis tenderness (single best predictor for return to play)Provocative testing.

Physical ExamSqueeze test (Hopkin's): compression of tibia and fibula at midcalf level causes pain at syndesmosisExternal rotation stress test: pain over syndesmosis is elicited with external rotation/dorsiflexion of the foot with knee and hip flexed to 90 degrees

Physical ExamCotton: widening of the syndesmosis with lateral pull on the fibulaFibular translation: anterior and posterior drawer force to the fibula with the tibia stabilized causes increased translation of the fibula and pain

ImagingAP, lateral, mortise view (whole leg if Maisonneuve’s fracture suspected.External rotation stress radiographGravity stress view (helps determine competence of deltoid ligament)Contralateral views may help clarify syndesmosis widening versus anatomic variant

Imaging StudiesDecreased tibiofibular overlapNormal >10 mm on AP view, >1 mm on mortise view

Imaging StudiesIncreased medial clear spaceNormal 4 mm or less

Imaging StudiesIncreased tibiofibular clear space. Normal <6 mm on both AP and mortise views

CT ScanMay be useful if clinical suspicion of syndesmotic injury with normal radiographs.Useful post-operatively to assess reduction of syndesmosis.More sensitive than radiographs for detecting minor injuries.

MRIAlso for clinical suspicion of syndesmotic injury with normal radiographs. Highly sensitive and specific for detecting syndesmotic injury.

Can show tears of ligaments without displacement.

Nonoperative TreatmentNWB CAM boot or cast for 2 to 3 weeks for syndesmotic sprain without diastasis or ankle instability.Delayed weight-bearing until pain freePhysical therapy program using a brace that limits external rotation

Nonoperative TreatmentTypically display a notoriously prolonged and highly variable recovery period Recovery may extend to twice that of standard ankle sprain

Operative treatment: Syndesmotic ScrewIndicationssyndesmotic sprain (without fracture) with instability

on stress radiographssyndesmotic sprain refractory to conservative

treatmentsyndesmotic injury with associated fracture that

remains unstable after fixation of fracture

Operative treatment: Syndesmotic ScrewExcellent functional outcomes if syndesmosis is accurately reduced.Requires removal (controversial).Bone Joint J. 2014 Dec;96-B(12):1699-705. “Removal of the syndesmotic screw after the surgical treatment of a fracture of the ankle in adult patients does not affect one-year outcomes: a randomised controlled trial.”Boyle MJ1, Gao R1, Frampton CM2, Coleman B1.“We conclude that removal of a syndesmotic screw produces no significant functional, clinical or radiological benefit in adult patients who are treated surgically for a fracture of the ankle.”

Operative Treatment: Suture Button (Tightrope)Indications same as for screw fixation.

Fiberwire suture with two buttons tensioned around the syndesmosis

May be performed in addition to a screw or after screw removal.

Operative Treatment: Suture Button (Tightrope)Early results promising with some showing earlier return to activity when compared to screw fixation.Does not (usually) require removal.Fraying of fiberwire with foreign body granuloma formation can occur longer term.

Surgical Technique: Screw FixationTwo 3.5 or 4.5 mm syndesmotic screws through 3 or 4 cortices placed 2-5 cm above the plafond.May use SS, titanium, or bioresorbable screw.No difference between 3 or 4 cortices.

Two screws vs. one.

Surgical Technique: Screw FixationRecent study challenges the need to hold the ankle in maximal dorsiflexion to avoid overtightening.J Bone Joint Surg Am. 2001 Apr;83-A(4):489-92. “Overtightening of the ankle syndesmosis: is it really possible?” Tornetta P, Spoo JE, Reynolds FA, Lee C.“Maximal dorsiflexion of the ankle during syndesmotic fixation is not required in order to avoid loss of dorsiflexion. It is likely that the most important aspect of syndesmotic fixation is anatomic reduction of the syndesmosis and that the degree of ankle dorsiflexion during fixation is not important.”

Surgical Technique: Screw FixationMy preference:

One 4.5 mm screw if through plate--easier to remove, no breakage.

Two 3.5 mm solid or 4.0 mm cannulated screws if no plate.

Four cortices--allows removal from medial side if they break.

Routinely remove after 12 weeks--much easier to remove before they break, can become painful.

Postoperative CareTypically non-weight-bearing for 6-12 weeks (longer time if screw breakage is a concern)

ComplicationsPosttraumatic tibiofibular synostosis: ~10% after Weber C ankle fracturesSurgical excision reserved for persistent pain that fails to respond to nonsurgical management.Ossification must be "cold" on bone scintigraphy prior to removal

ReferencesAOFAS Physician Resource Center, “Ankle Instability,” written by Sourendra Raut, MD, reviewed by John Early, MD.

“High Ankle Sprain & Syndesmosis Injury”, Mark Karadsheh. http://www.orthobullets.com/foot-and-ankle/7029/high-ankle-sprain-and-syndesmosis-injury

Surgery of the Foot and Ankle, 8th Ed., M. Coughlin, R. Mann, C. Salzman, pp. 1464-1473.

Master Techniques in Ortho. Surgery: The Foot and Ankle, 2nd Ed., H. Kitaoka, pp. 487-496.

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