William C. McGarvey and Thomas O. Clanton
DEFINITION
Lateral ankle sprains are the most common injury in sports, accounting for 15% to 20% of all athletic injuries in some parts of the world. These injuries result in compromise or complete disruption of the lateral ankle, and, often subtalar, ligamentous complexes.12,15
Ankle sprains range in severity from mild stretching to complete disruption of the ligamentous structures. Often, the injuries of moderate or medium severity are the most difficult to accurately diagnose and, therefore, manage properly.
Most acute ankle sprains respond well to a course of nonoperative therapy, including standard rest-ice-compressionelevation (RICE) methods, functional bracing, and even immobilization followed by physical therapy.
From 30% to 40% of patients will have persistent problems related to pain and swelling for up to 6 months after the injury, and 10% to 20% will have difficulties with recurrent sprains, leading to chronic ankle instability.10
Chronic ankle instability usually manifests itself in one of two ways: (1) recurring symptoms after an acute episode of ankle sprain, or (2) a pervasive feeling of looseness or “giving way” without warning.
ANATOMY
The lateral ankle ligamentous complex is made up of three distinct ligaments: the anterior talofibular, the calcaneofibular, and the posterior talofibular ligaments. Other structures contributing to overall lateral ankle stability are the inferior extensor retinaculum and subtalar ligamentous complex.
The anterior talofibular ligament (ATFL), which blends with the anterolateral joint capsule, is 15 to 20 mm long, 6 to 8 mm wide, and 2 mm thick.
The ATFL originates from the anterior and distal fibula to insert on the lateral body of the talus, forming an angle of about 75 degrees to the floor.
The calcaneofibular ligament (CFL) is 20 to 30 mm long, 4 to 8 mm wide, and 3 to 5 mm thick. It originates from the posteromedial portion of the inferior fibula to travel within the peroneal tendon sheath, under the tendons, and attaches to the lateral wall of the calcaneus. The orientation is 10 to 45 degrees posterior to the longitudinal axis of the fibula. The angle formed between the ATFL and CFL is 100 to 105 degrees.
The posterior talofibular ligament (PTFL) is the largest of the lateral ankle ligaments, at 30 mm in length, 5 mm in width, and 5 to 8 mm in thickness. It has a broad insertion on nearly the entire posterior lip of the talus.
The ATFL has the lowest load to failure of the three ligaments. Conversely, it has a much higher capacity to withstand strain than the CFL or PTFL, thereby allowing the greatest deformation before failure of all three structures.16
The ATFL is taut with the ankle in plantarflexion, whereas the CFL is relatively loose. The reverse is true for the dorsiflexed ankle. The strength of the CFL and the stability afforded by the bony mortise at the malleoli in a neutral or dorsiflexed ankle make maximal plantarflexion the position of vulnerability for lateral ankle ligament injuries.1,2
The subtalar ligamentous structures include the lateral talocalcaneal ligament, cervical ligament, interosseous talocalcaneal ligament—thought to provide the greatest contribution to stability of the subtalar joint, and the calcaneofibular ligament. These provide some measure of stability to the lateral ankle.
PATHOGENESIS
Ankle instability is thought to be either acquired, as a result of repetitive trauma, or inherited due to ligamentous laxity, biomechanical abnormality (eg, heel varus, cavus foot position), or a combination of both.
The ATFL is most commonly injured, accounting for about 75% of injuries to the ligaments of the ankle, followed by the CFL, which accounts for about 20% to 25% of these injuries. Injury to the ligaments occurs when they are either stretched or completely torn, either by avulsion from bone, or, more commonly, from midsubstance tearing.
Neuromuscular deficits also result from these inversion injuries, leading to slower firing of the peroneal muscles in response to inversion stress, decreased responsiveness in the peronal nerve branches, weakness, and restricted dorsiflexion range of motion due to inadequate muscle forces.
Repetitive injury can result in accumulated scarring leading to anterolateral mechanical impingement or even sinus tarsi involvement.6,14
Subtalar ligaments also may be injured, although usually to a lesser extent.
NATURAL HISTORY
Even though most ankle sprains and instability receive some form of treatment, there is little consistency in treatment regimens. The natural history is sketchy as to what would happen in the truly untreated situation.
In one long-term study, one third of patients treated functionally for ankle sprains had continued complaints of pain, swelling, or instability in the form of recurrent sprains.10
Nearly three fourths had some level of impairment on return to sporting activity, with almost 20% incurring repeated sprains and 4% with pain at rest or severe disability.
Dysfunction after an acute sprain will persist for 6 months in 40% of injured athletes.5
While it has been suggested that long-term lateral ankle instability and repeated traumatic events to the ankle can lead to advanced stages of degenerative disease, there is no actual proof of this theory.
Nevertheless, it is presumed that continued ankle injuries as a result of lateral ankle instability can, and often will, lead to osteochondral injuries, abnormal joint mechanics, and neuromuscular dysfunction, predisposing the individual to risk of more severe injury to the extremity or disabling degenerative arthritis of the ankle and, possibly, the subtalar joints.
PATIENT HISTORY AND PHYSICAL FINDINGS
Patients experiencing acute ankle sprains often describe a painful tearing or pop after sustaining an inversion type injury. Longer-standing instabilities will cause complaints of lack of confidence in the joint under high demands or frequent giving way; pain and swelling often are less severe and are of secondary concern to the patient.
Findings on examination in the acute situation are reliably present and include anterolateral ankle pain, swelling, and pain on passive plantarflexion or inversion. In the patient with a chronically unstable ankle, the examination focuses more on the anterior drawer and talar tilt tests and the “suction sign.”
Assessment for structural abnormalities also is important. Heel position should be examined in every patient, by looking at the patient from behind while he or she is standing, to determine the possible presence of varus malalignment.
Neuromuscular function is another important part of the examination. Peroneal muscle group function, specifically, is critical. Strength and stability of the peroneals should be assessed by resistive muscle grading against plantarflexion and eversion. Provocative maneuvers such as the plantarflexion eversion stress test also should be performed to ensure that the peroneal tendons do not subluxate from the retrofibular groove.
Sensory nerves should always be inspected to ensure no neurapraxia has taken place as a result of the traction from the injury.
Syndesmotic integrity should be tested with palpation, the “squeeze” test, and dorsiflexion–external rotation provocative manipulations.
IMAGING AND OTHER DIAGNOSTIC STUDIES
According to the Ottawa Ankle Rules,11 nearly 100% sensitivity is approached if the following criteria are used in the acute setting:
Tenderness at the posteroanterior edge or tip of the medial or lateral malleolus
Inability to bear weight (4 steps) right after the injury or in the emergency room
Pain at the base of the fifth metatarsal
If radiographs are required, anteroposterior, lateral, and mortise views, preferably weight bearing, should be performed, looking for avulsion fractures of the tip of either malleolus, or, less frequently, the lateral calcaneus. One also should inspect for osteochondral fractures, joint malposition, and other fractures that may mimic lateral ankle sprains (see Differential Diagnosis).
Stress views can be obtained in either the AP (talar tilt) or lateral (anterior drawer) position. Performing the study while stressing the ankle (as described in the section on examination of the patient) can give meaningful information regarding the stability of the joint. Significant controversy exists on what constitutes an abnormal study, but on the basis of the cumulative review of literature on this topic, more than 15 degrees of varus tilt and 5 mm of anterior translation are reasonably considered abnormal.
MRI is valuable for determining whether the ligamentous structures have been injured and in what time frame. Attenuation, wavy fibers, or disruption in the face of fluid accumulation suggests recent injury, whereas thickening or intrasubstance signal change gives rise to suspicion for a more remote injury. Infrequently, an absence of ligament tissue is noted, reflecting repeated injuries leading to degeneration of the complex.
DIFFERENTIAL DIAGNOSIS
Acute
Lateral malleolar fracture
Fifth metatarsal fracture
Lateral talar process or “snowboarder’s” fracture
Peroneal tendon dislocation
Osteochondral defect
Superficial peroneal neurapraxia
Chronic
Peroneal instability
Peroneal split tears
Subtalar instability
Osteochondral defect
Tibiotalar or subtalar arthritis
NONOPERATIVE MANAGEMENT
Nonoperative management is the mainstay of treatment for both acute and chronic instabilities. Most patients will respond to conservative management; consequently, it is essential that appropriate conservative treatment be tried for all patients before surgery is suggested.
Acute swelling and pain, whether from a new injury or recent repeat injury, is best managed with RICE. Immobilization in a walking cast or boot should be considered for anyone demonstrating a positive drawer or talar tilt after an acute episode or recurrence.
Once the acute symptoms have subsided, functional strapping, taping, or bracing should be instituted along with an exercise regimen emphasizing peroneal strengthening, proprioceptive training, and Achilles tendon stretching.
In the patient with a chronically unstable ankle, shoe wear modifications can be added as the individual returns to sports or activities. Orthoses with lateral heel and sole wedges or flare on the lateral sole of the shoe can promote a valgus moment and help avoid injury in the vulnerable patient. Reducing heel height and stiffening the sole of the shoe also can be helpful.
Prophylactic brace wear or taping has been shown to have some benefit in prevention of injury. It also has a positive effect on reduction in severity of sprains if reinjury occurs while these measures are in effect.
SURGICAL MANAGEMENT
Surgery rarely is indicated for an initial acute injury.
Acute injuries failing appropriate conservative care, in our opinion, are best treated with an anatomic repair and reinforcement using a modified Brostrom procedure.
Chronic instability failing appropriate conservative measures is more complex.
In a previously unoperated patient with MRI evidence of tissue remnants, an anatomic repair (modified Brostrom procedure) is very effective.
FIG 1 • Plain radiograph of an unstressed, non–weight-bearing ankle after injury and before anatomic repair.
In patients who have repeated injuries and are left without evidence of ATFL or CFL remnant by MRI, or in patients who have previously undergone an attempt at surgical correction, reconstruction with free tendon graft is our preferred method.3,4,7,13,17
Preoperative Planning
All imaging studies, including MRI, are reviewed, and any adjunctive pathology that may need to be addressed at the time of surgery, such as fragments of bone, OCLs, or peroneal tendon pathology, is noted.
The joint (and the contralateral joint) is examined under anesthesia to detemine the true nature of instability and also to gauge the effect of the repair (FIGS 1 AND 2).
Graft choice also is an important preoperative consideration. An autogenous hamstring graft can be chosen and harvested in similar fashion to that of ACL graft harvests.3,4,7,13,17 Alternatively, should the patient be averse to violating his or her own knee, an allograft gracilis tendon has been shown to be a very suitable alternative, with the advantages of reduced pain, no donor site morbidity, and risk and effectiveness virtually the same as using the patient’s own tissue.
FIG 2 • Preoperative stress radiograph of the same ankle demonstrating talar tilt.
The presence of a varus heel may necessitate the addition of a laterally based closing wedge calcaneal osteotomy.
Positioning
The patient is placed in the supine position, typically with an ipsilateral hip roll to allow access to the posterolateral corner of the ankle.
Arthroscopic examination is performed to identify any unseen intra-articular pathology.9 A thigh holder and soft tissue ankle joint distractor often are necessary for the initial portion of the procedure.
Approach
One of two approaches may be chosen, depending on the degree of pathology that is to be addressed.
For ankle ligament reconstruction alone, an anterior curvilinear incision bordering the distal inferior tip of the fibula is preferred.
If it is necessary to address peroneal pathology or anterior osteophytes, a more extensile lateral malleolar incision, curving distally after the tip of the fibula, is useful (FIG 3).
An oblique incision over the calcaneus usually can be added to either approach without great concern for increased wound morbidity.
FIG 3 • Surgical approach parallelling the posterior border of the fibula is marked on the skin.
TECHNIQUES
TALAR TUNNEL PLACEMENT
The lateral ankle is exposed by one of two incisions, as previously described.
The origin sites of both ATFL and CFL are identified (TECH FIG 1A).
TECH FIG 1 • A. The talar tunnel is placed just anterior to the neck–body junction, aiming slightly posterior and lateral. B. A rent in the capsule and previously repaired anterior talofibular ligament (ATFL) is evident. C. The area of deficient capsule and ATFL is identified by instrument. D. Location of the proposed talar tunnel. E. Reaming is performed slightly deeper than the chosen screw length.
Dissection proceeds to expose the insertion of the ATFL on the lateral talus just at the corner of the lateral process as it blends from the body to the neck (TECH FIG 1B,C).
A 15to 20-mm tunnel is drilled horizontally at this point with a 4.5to 6-mm drill to accept the first limb of the tendon graft (TECH FIG 1D,E).
FIBULAR TUNNEL PLACEMENT
The fibula is exposed and a 4.5to 6-mm tunnel is drilled from the insertion of the ATFL through the posterior fibular cortex (TECH FIG 2A–C).
A second tunnel is made more distally from the CFL insertion to a point about 3 to 4 mm distal to the previous exit point on the posterior fibular cortex. This allows for graft passage over a cortical bridge, and, in addition, the graft can be sutured to periosteum to prevent sliding (TECH FIGS 2D–F AND 3).
An alternative method uses a single tunnel from a point between the ATFL and CFL insertions, not violating the posterior cortex, that would accept a folded or doubled graft fixed with a single interference screw within this single tunnel.
TECH FIG 2 • A. The origin of the ATFL is used as the entry point for the first fibular tunnel. B. The guide pin is inserted aiming superior and posterior at 45 to 60 degrees to allow for another more inferior tunnel for the calcaneofibular ligament (CFL) limb of the graft. C. Reaming of the first tunnel is done with a size-matched reamer based on screw size and graft diameter. D. A second guide pin is inserted from the CFL origin, aiming superior and posterior, but 3 to 4 mm below the previously created tunnel. Care must be taken to avoid tunnel blowout. E. Reaming the second fibular tunnel. F. A bony bridge is preserved between fibular tunnels.
TECH FIG 3 • Postoperative non–weight-bearing radiograph after reconstruction of lateral ligaments with allograft.
CALCANEAL TUNNEL PLACEMENT
A tunnel of similar size is then drilled bicortically through the lateral calcaneal wall at the level of the CFL insertion (TECH FIG 4).
TECH FIG 4 • A. The guide pin for the calcaneal tunnel is placed with the peroneal muscle group swept posterior. The tunnel is placed just inferior to the insertion point of the CFL. B. Verification of tunnel position. C.Reaming the calcaneal tunnel. D. Note the relation between the calcaneal insertion of CFL and the reamed tunnel.
GRAFT PASSAGE
The sutured tendon is inserted first into the talar tunnel and fixed with an interference screw (TECH FIGS 5 AND 6).
It is then woven through the fibular tunnel from the ATFL insertion, through the more proximal posterior exit tunnel, back through the more inferior fibular hole and out the CFL origin. This gives the most anatomic origin and insertion points (TECH FIG 7 A–C).
Lastly, the graft is passed through the calcaneal tunnel.
The foot is held neutral to slightly everted, and a roll of towels is placed under the calf to allow a slight posterior drawer effect. The graft is held taut as it is brought through the skin on the medial side (TECH FIG 8).
A second interference screw is placed in the calcaneus (TECH FIG 9).
Range of motion and stability are assessed. If tension does not feel appropriate, the calcaneal screw can be removed, the graft retensioned, and the screw replaced.
The tendon can receive a few sutures at the fibular tunnels to maintain tension of the individual limbs representing ATFL and CFL (TECH FIGS 10A,B AND 11).
If the surgeon prefers the single fibular tunnel technique, the interference screw is placed in the fibula with one limb of the graft directed toward the talus (ATFL) and one to the calcaneus (CFL). These are then similarly tensioned and fixed with individual interference screw fixation. This method is more exacting, as the limbs of tendon must be cut to exact length and fit into the proper depths of their respective tunnels.
TECH FIG 5 • A. All tunnel holes are reamed in advance of graft passage. B. Allograft tendon is mounted for insertion into the tibia tunnel with the first interference screw. C. The graft is inserted into the talar tunnel and fixed by interference screw.
TECH FIG 6 • Schematic of interference fit tenodesis screw.
TECH FIG 7 • A. The graft is pulled through the first fibular tunnel by a previously placed pull-through suture weave. B. The graft is then pulled through the second fibular tunnel and tension maintained. A stay suture can be placed in the graft and the fibular periosteum to maintain the ATFL tension. C. Graft pulled through both tunnels.
TECH FIG 8 • A Beath pin is used to pull the suture through the medial side of the tunnel and then out through the skin for final tensioning.
TECH FIG 9 • After appropriate positioning of the ankle and tensioning of the graft, the calcaneal interference screw is inserted.
TECH FIG 10 • A. Graft position is supported by a fibular bone bridge. (Without a bony bridge, the graft could subside and thus loosen in the soft cancellous bone trough.) B. Finished anatomic ligament weave featuring ATFL and CFL reconstruction.
TECH FIG 11 • Postoperative stress radiograph. Note that there is no talar tilt.
WOUND CLOSURE
Layered closure is performed, usually with a subcutaneous layer of 2-0 Vicryl or monocryl followed by skin sutures with 3-0 nylon.
CALCANEAL OSTEOTOMY
If heel varus is present, a laterally based closing wedge calcaneal osteotomy may be performed.
An oblique incision is carried out directly over the area of the planned osteotomy (usually about 2 cm posterior to any other concurrent incision).
Periosteum is raised in each direction.
A 1to 1.5-cm width is marked on the lateral wall of the calcaneal tuberosity verifying that the osteotomy will not breach the bone tunnel.
Saw cuts are made convergently to meet just before violating medial cortex.
The wedge is removed and the osteotomy closed.
Fixation can be achieved through either a large axially directed screw or staples.
POSTOPERATIVE CARE
Bulky, padded splinting in neutral positions are maintained for 10 to 14 days postoperatively.
Once wounds are healed satisfactorily, the patient may begin protected weight bearing in a cast, as tolerated, for another 4 weeks.
Gradual transition from cast to boot and introduction of range of motion begin 5 to 6 weeks after surgery.
Rehabilitation is then instituted focusing on restoration of motion, Achilles stretching, proprioceptive training, and peroneal strengthening.
Athletic activity usually is withheld for 4 to 6 months.
OUTCOMES
Anatomic reconstruction for failed acute and chronic instability patterns continues to be our preferred method of lateral ankle ligament reconstruction. This has been shown in the literature to be extremely successful for return to function and reduction or elimination of symptoms in appropriately selected patients.
When a patient has lost reliable lateral soft tissue structures by virtue of repetitive injury or previous failed procedures, an anatomic free graft lateral ligament reconstruction provides a very good alternative.
Reconstruction using this method reconstitutes the ATFL and CFL, thus providing restoration of both ankle and subtalar stability.
Anatomic reconstruction coupled with the preservation of native peroneal tendon function provides an optimum environment for return to function.
Paterson et al13 showed 81% complete or substantial symptom resolution in 26 patients at 2-year follow-up by performing reconstruction of the ATFL alone. No significant differences were noted between operated and contralateral ankles with respect to range of motion or uniaxial balancing.
Coughlin et al3,4 reported on 2-year follow-up in 28 patients. All patients were rated to have good or excellent outcomes with objective improvement in talar tilt measurements (13 degrees prevs 3 degrees postoperatively) and anterior drawer testing (on average, 10 mm prevs 5 mm postoperatively).
Addition of tenodesis or interference screw fixation adds the advantage of being able to promote range of motion earlier with less concern for graft loosening.8,17
COMPLICATIONS
Nerve injury
Wound problems
Infection
Joint stiffness
Deep venous thrombosis
Subjective underor over-tightening
REFERENCES
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