Chronic Lateral Ankle Instability
DEFINITION
Lateral ligament injuries of the ankle are treated conservatively with good results in most cases. However, several factors may lead to chronic ankle instability with recurring ankle sprains:
Inadequate primary treatment Incomplete healing of the ligaments
Repetitive trauma with deteriorated tissue quality
Patients with chronic ankle instability can be divided into two groups: Patients with sufficient tissue quality to perform a local repair Patients with inadequate tissue quality for a local repair
A Brostrom procedure for lateral ankle reconstruction is possible as long as there is sufficient tissue.
In patients with insufficient local tissue, an augmentation is needed to rebuild or reinforce the lateral ligaments. There are different options of tendon grafts, each with certain advantages and disadvantages:
Tenodesis
Semitendinosus tendon or gracilis tendon Plantaris longus tendon
Another surgical option is the augmentation of the ligaments with fibular periosteal flap.2
ANATOMY
Laterally, the ankle is stabilized by the anterior talofibular ligament (ATFL), posterior talofibular ligament (PTFL), and the calcaneofibular ligament (CFL) (FIG 1).6
Additional stability is provided by the bony structures. Especially in dorsal extension, the talus is locked between the medial and lateral malleolus.
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FIG 1 • Anatomy of the lateral ankle showing the three ligaments: ATFL, PTFL, and the CFL.
PATHOGENESIS
Torn lateral ligaments are the result of an ankle sprain. Depending on the severity of the sprain, one to three of the lateral ligaments are injured. A rupture of the ATFL is involved in most cases.
Anatomic classification
Grade I: ATFL sprain
Grade II: ATFL and CFL sprain
Grade III: ATFL, CFL, and PTFL sprain
American Medical Association (AMA) standard nomenclature system by severity
Grade I: ligament stretched Grade II: ligament partially torn Grade III: ligament completely torn
Grading by clinical presentation symptoms
Mild sprain: minimal functional loss, no limp, minimal or no swelling, point tenderness, pain with reproduction of mechanism of injury
Moderate sprain: moderate functional loss, unable to toe rise or hop on injured ankle, limp when walking, localized swelling, point tenderness
Severe sprain: diffuse tenderness and swelling, crutches preferred by patient for ambulation With each ankle sprain, proprioception of the ankle joint is compromised.
The risk for another ankle sprain increases after each injury. In an uninjured person, an ankle sprain will occur in 1:1,000,000 steps. This risk increases to 1:1000 steps after a severe ankle sprain.13
Chronic ankle instability is the combination of insufficient active and ligament stabilization mechanisms.
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FIG 2 • Synovial fluid between the two ends of torn ligaments can prevent the injury from healing.
There is some evidence that special anatomic variations increase the risk of developing chronic ankle instability after an injury.15
The healing of the ligaments can be compromised by synovial fluid between ligament and bone (FIG 2).
NATURAL HISTORY
Chronic instability is a risk factor for degenerative arthritis of the ankle joint. Valderrabano et al22 have shown an increased prevalence of arthritis in patients with chronic ankle instability.
Recurrent ankle sprains are likely in the future, but this is strongly dependent on lifestyle and sports activities.23
PATIENT HISTORY AND PHYSICAL FINDINGS
The patient history includes sustained injuries, frequency of ankle sprains, and causes of pain as well as restrictions in daily living and sports.
The degree of disability experienced by the patient depends on the degree of instability and the physical demands.
Many tests for ankle instability are strongly dependent on patient cooperation. If positive, however, they can be highly specific.
The examiner should check the range of motion of the ankle joint with a stretched and a bent knee to rule
out a shortening of the gastrocnemius or soleus muscle (or both). Restricted dorsiflexion with a stretched knee joint that is not found with a flexed knee is specific for a shortening of the gastrocnemius muscle (Silfverskiöld test).
The inversion test is used to assess for a ruptured CFL.
Medial ankle stability is checked in a plantarflexed position of the ankle to avoid a locking of the talus in the joint, which can mimic ligamentous stability. If positive, it is highly specific for a ruptured deltoid ligament.
Insufficiency of the fibulocalcaneus ligament often affects the stability of the subtalar joint. The stability is checked in dorsiflexion of the ankle to lock the talus in the upper ankle joint. If positive, it is highly specific
for a ruptured CFL in combination with subtalar instability.16
Effusion can be palpated ventrally, but smaller amounts of fluid are difficult to detect. The ankle drawer test strains the ATFL and is highly specific for rupture of this ligament.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Plain radiographs should be obtained to evaluate potential bony pathology.
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FIG 3 • Stress radiographs of a patient with a chronic high-grade instability of the ankle joint.
Stress radiographs: The anteroposterior (AP) view shows the lateral opening of the joint. An anterior talar shift can be seen on the lateral stress view (FIG 3).
Magnetic resonance imaging (MRI) gives valuable information on the lateral ligaments and other pathology. In chronic instability scarring, effusion and synovitis war often found. However, it is impossible to judge functional stability in an MRI. Frequent additional pathologies visible on MRI are tears of the peroneal tendons, osteochondral lesions, and bone edema.
DIFFERENTIAL DIAGNOSIS
Articular injury (chondral or osteochondral fractures) Nerve injuries (sural, superficial peroneal, posterior tibial)
Tendon injury (peroneal tendon tear or dislocation, tibialis posterior)
Other ligamentous injuries (syndesmosis, subtalar, bifurcate, calcaneocuboid) Impingement (anterior osteophyte, anteroinferior tibiofibular ligament, scars)
Unrelated pathology, masked by routine sprain (undetected rheumatoid condition, diabetic neuroarthropathy, tumor)
Lateral ankle instability with hindfoot varus deformity21
NONOPERATIVE MANAGEMENT
The goals of nonoperative treatment are improving proprioception and strength. This can be achieved by physiotherapy and exercises.
Shoe modifications include a lateral wedge or a flare.
Means of external fixation are orthoses, braces, or taping. However, those methods are limited.
Tape loses 30% of its stability after 200 steps. Skin problems are reported in up to 28%. Within the group of orthoses, semirigid, warped types provide the highest degree of stability.3
For many patients with symptomatic instability or pain, nonsurgical measures are not acceptable as a long-
term solution. Usually, these patients require a lateral ligament repair.
SURGICAL MANAGEMENT
In patients with no previous surgery and good tissue quality, the Brostrom procedure is a good option, reinserting the original ligaments in place.5 Especially with modern anchor techniques, this procedure has
regained a great deal of popularity. Broström4 showed in his work that even after a longer period of chronic instability, a reconstruction of the original ligaments is possible, providing sufficient stability and function of the ankle joint.
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Due to improvements in suture anchor techniques, the possibilities of local, anatomic repair either open or arthroscopically have broadened over the last years.8
However, some patients with a history of recurrent inversion trauma do not have adequate tissue quality to perform a Brostrom procedure.7,12,19
Insufficient local tissue can be augmented or replaced by a tendon graft or a periosteal flap. There are different options of tendon grafts, each with certain advantages and disadvantages.
Tenodesis: The major disadvantage of tenodesis procedures (eg, Evans or Watson-Jones) is that they often end up in persistent pain17,18 in combination with an increasing lack of stability over time.14,20
Autologous or homologous semitendinosus tendon or gracilis tendon can be used as graft. Although, in
general, tolerated well, there is some risk of donor site morbidity after harvesting those tendons.1 If a homologous graft is used, there is a small risk of infection.
A local tendon that can easily be harvested with a minimum of donor site morbidity is the plantaris longus tendon.9
Preoperative Planning
In about 3% of the patients, no plantaris longus tendon can be found or it is not long enough for transplantation. A strategy has to be discussed with the patient as to how to proceed in this case. An option is to change to a technique using another transplant (eg, the gracilis or semitendinosus tendon) or to use a periosteal flap.
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FIG 4 • The patient is positioned supine with a sand sack under the injured side.
Examinations performed under anesthesia include range of motion of the ankle joint and the ankle stress tests to confirm the previous results, without an active stabilization of the ankle joint by the patient.
Additional intra-articular pathology is a common finding. In most cases, it is advisable to do an arthroscopy of the ankle joint before the final reconstruction.10
Positioning
The patient is positioned supine with a sand sack under the injured side. The procedure is performed with a tourniquet (FIG 4).
Approach
The plantaris longus tendon is harvested using a medial cut between the soleus and gastrocnemius muscle
(FIG 5A).
The procedure is performed with a standard lateral approach, straight, from the fibula directed to the base of the fifth metatarsal (FIG 5B).
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FIG 5 • A. Medial approach to harvest the plantaris longus tendon. B. Lateral approach with a 6- to 8-cm cut from the fibula toward the base of the fifth metatarsal.
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TECHNIQUES
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Harvesting of Plantaris Longus
Make a 3-cm cut at the medial aspect of the calf where the muscle has its highest volume (TECH FIG 1). When the muscular fascia is split, the soleus and the gastrocnemius can be bluntly separated.
The tendon structure found medially between the two muscles is the plantaris longus tendon, which can easily be harvested with a tendon stripper. The plantaris longus tendon often is much easier to identify at this location than at the medial aspect of the calcaneus.
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TECH FIG 1 • Harvesting of the plantaris longus tendon. A. Medial incision between the soleus and gastrocnemius muscle. The fascia is directly under the fatty tissue. B. After a longitudinal incision of the fascia, the plantaris longus tendon is found right between the soleus and gastrocnemius muscle. C. The tendon is mobilized with a tendon stripper. D. The end of the plantaris longus is reinforced with a 0 nonabsorbable suture and stored in a moist compress.
If it is not possible to mobilize the plantaris longus tendon distally with the tendon stripper, the tendon can be cut through a small longitudinal incision (about 1 cm).
Free the tendon from any muscular or fatty tissue.
Reinforce one end of the tendon with a 0 nonabsorbable suture. Store the tendon in a moist compress.
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Anatomic Reconstruction of the Lateral Ligaments with the Plantaris Longus Tendon
Expose the lateral ligaments and the distal fibula via a lateral approach.
The tissue of the sinus tarsi can be reamed, especially if there is any evidence of inflammation. Inspect the quality of ligaments and local tissue.
Drill two holes at the ventral aspect of the fibula with a diameter of 3.2 mm and a distance of 7 and 13 mm from the tip of the fibula (TECH FIG 2).
Drill a third hole on the lateral side.
With a small Weber forceps, connect the ventral holes and flatten the sharp edges surrounding them.
Drill another two holes at the lateral aspect of the neck of the talus with a diameter of 3.2 mm and a distance of about 8 mm. The holes are located just at the border of the cartilage. In quite a few cases, remnants of the original ligaments can be found at this location.
Again, create a canal with the Weber forceps.
Retract the peroneal tendons and have the assistant position the hindfoot in maximum pronation. Drill two holes and connect them, 13 mm from the joint line of the subtalar joint, similar to the technique mentioned before.
The plantaris longus transplant (which is armed with 0 nonabsorbable sutures) can be pulled through the holes with a sharp needle.
When bringing the transplant under tension, the foot should be in a neutral position. Connect both ends of the transplant with 0 nonabsorbable sutures.
If there are parts of the transplant left, they can be used to augment the reconstructed ligaments and held in place with sideto-side sutures.
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TECH FIG 2 • Anatomic reconstruction with the plantaris longus tendon. A. Drilling a hole at the anatomic insertion of the ATFL. B. Creating a canal between the drill holes with a Weber forceps. C. Routing the tendon through the drill holes. D. Any spare tissue of the tendon can be used for a further reinforcement. E-
O. Routing the tendon through the drill holes. (continued)
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TECH FIG 2 • (continued)
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PEARLS AND PITFALLS |
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Indications ▪ A complete history and physical examination should be performed.
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POSTOPERATIVE CARE
All patients are kept in a walking boot or walking cast for 2 weeks, and weight bearing is limited to 10 kg. After 2 weeks, they get an ankle brace for another 4 weeks with full weight bearing in normal shoes. The ankle brace should be used day and night. In addition, physiotherapy with active stabilization is started in the third week. Cycling is normally possible after 4 to 6 weeks and running after 8 to 10 weeks. The patient should avoid contact sports, including soccer, for 3 to 5 months.
OUTCOMES
Hintermann and Renggli11 published a series on this technique and found 78% excellent, 18% good, and 4% satisfying results in the American Orthopaedic Foot and Ankle Society (AOFAS) hindfoot score.
Those good results match our experience.
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Especially athletic patients benefit from anatomic repair of the ligaments, which seems to produce more reliable and much better results than tenodesis.
COMPLICATIONS
Intraoperative graft mishandling Graft failure or rupture
Fracture of the fibula Deep venous thrombosis Infection
Loss of motion
REFERENCES
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