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Keys To Deltoid Ligament Repair After Ankle Fracture

Combining a review of the literature with their own clinical experience, these authors describe the pertinent anatomy of the deltoid ligament, share diagnostic pearls and discuss treatment options for acute deltoid injuries.

Acute deltoid rupture is a relatively uncommon injury in isolation.1 Deltoid ligament ruptures are associated with ankle fractures with up to 40 percent of ankle fractures having an associated deltoid ligament injury apparent on arthroscopic examination.2

The preferred method of treatment for acute and chronic ankle sprains remains conservative therapy with aggressive physical therapy for proprioceptive training and strengthening of the lower extremity musculature.1,3 However, oftentimes pain and instability will persist despite these modalities, and surgical intervention is warranted.

Injury to the deltoid ligament can be a source of persistent pain or develop into a longstanding pronation deformity. Complete deltoid rupture is sometimes present in association with bimalleolar fractures and lateral malleolar fractures.2 Hintermann and coworkers reported that 26 percent of bimalleolar fractures they observed had radiographic evidence of deltoid ligament incompetence after medial malleolar fixation.2 The supination-external rotation injury pattern accounts for up to 85 percent of all injury patterns. Schuberth and colleagues report that during their arthroscopic examination of isolated fibular fractures, one-third of ankles showed evidence of deep deltoid tears.3

In a retrospective study, the most common rupture site of the superficial and deep deltoid ligament was the medial malleolar attachment.4 Except for two midsubstance ruptures, all of the superficial deltoid ligament ruptures occurred in the medial malleolar attachment, including three avulsion fractures. Rupture of the distal site occurred in 10 patients and all were deep deltoid ligament ruptures, including two small avulsion fractures of the talar attachment. There was no mid-substance rupture of the deep deltoid ligament. There were four partial ruptures of the superficial deltoid ligament, which accompanied complete rupture of the deep deltoid ligament.

Based on prior studies, the treatment of ankle fractures with a deltoid ligament injury consists of fibular fixation with the addition of syndesmotic screws, which indirectly addresses the deltoid ligament.5,6 However, there is no consensus on the optimal treatment or preferred operative technique for acute deltoid ligament injuries.3,7-11 Long-term sequelae of mistreated tears may include chronic subluxation of the talus, pes planovalgus, osteochondral injury and early tibiotalar osteoarthritis.

A Guide To The Anatomy Of The Deltoid Ligament

The first anatomical division in the deltoid ligament is between the superficial and deep layers of the ligament.12 The superficial fibers are fan-shaped and originate on the anterior colliculus and cross the tibiotalar and subtalar joints.13

According to a cadaveric study by Clanton and coworkers, the deltoid ligament has four superficial bands: tibionavicular, tibiospring, tibiocalcaneal and superficial posterior tibiotalar ligaments.14 The tibionavicular ligament was the most anterior and attached 7.6 ± 1.9 mm superior and anterior to the inferior tip of the medial malleolus. The tibiospring ligament attached 12.1 ± 2.2 mm superior and anterior to the inferior tip of the medial malleolus, and attached to the spring ligament, which coursed from its origin 12.3 ± 1.6 mm anterior and slightly inferior to the posterior point of the sustentaculum tali to its insertion on the navicular tuberosity. The tibiocalcaneal ligament and superficial posterior tibiotalar ligament were located posteriorly in the majority of specimens.

The deep deltoid ligament spans only the tibiotalar joint and is visible on ankle arthroscopy medially. Researchers describe the deep deltoid ligament as having two constituents.14 The deep posterior tibiotalar ligament is larger and courses from the tibia, 8.1 ± 2.2 mm posterior and superior to the inferior tip of the medial malleolus to its attachment on the talus, and 15.5 ± 2.4 mm superior and anterior to the posterior inferior point of the talus.14 The presence of the deep anterior tibiotalar ligament is variable.14,15 We have just begun to fully grasp the anatomy of the deltoid ligament, which provides us inherent knowledge about the injury pattern and operative management.

Key Insights On The Biomechanics Of The Deltoid Ligament

The deltoid ligament complex plays an important role in ankle joint stability. It is the primary restraint of posterior translation of the talus, particularly in plantarflexion. The deltoid ligament complex also functions to restrict lateral shifting and anterior displacement of the talus.16 It controls external and internal rotation of the talus in conjunction with the anterior talofibular ligament.4

Biomechanical studies involving a physiologically loaded ankle model demonstrate that an uninjured medial complex of the ankle centers the talus beneath the tibial plafond, regardless of the presence of a displaced lateral malleolar fracture.3,17,18 Disruption of the medial deltoid ligament complex allows the talus to migrate laterally or tilt within the mortise. Such malalignment will result in altered joint mechanics.

Studies have shown that even small deviations from anatomic alignment will result in a greatly reduced joint contact area.19 Earll and colleagues reported that the tibiotalar joint contact area decreased 43 percent after sectioning the superficial deltoid ligament complex.20 Additionally, the peak pressures increased 30 percent. These changes in loading characteristics may predispose individuals to degenerative processes of the ankle. Clinical investigators have shown radiographic signs of osteoarthritis develop in ankles with a lateral shift greater than 2 mm.17

How To Diagnose An Acute Deltoid Injury

The primary mechanism of acute isolated deltoid ligament injury is eversion, abduction or external rotation of the talus on the tibia.1 Hintermann described how typical injuries occur when landing on an uneven surface or running downstairs with the key history point being an eversion injury.21 The patient may endorse a feeling of “giving way” medially when on uneven ground, downhill or downstairs.1

On physical examination, assess for malalignment, deformity, asymmetry, ecchymosis and edema of the affected foot. Patients may have asymmetrical pes planus and pronation deformity of the affected side. Perform an investigation of clinical stress. Patients should be sitting on an elevated table with their feet hanging off the edge. One hand should secure the tibia and the other should grasp the heel while applying a valgus stress to the heel. Compare this to the contralateral side.1 Additionally, perform an anterior drawer test to assess for laxity of the lateral collateral ligaments. Obtain weightbearing plain radiographs to assess radiographic parameters and the presence of osseous injuries.

Despite a thorough clinical examination, researchers have shown medial tenderness, swelling and ecchymosis to be poor indicators of deltoid ligament injury.22-25 These physical findings are no longer considered acceptable for evaluating the competency of the deltoid ligament.26

In an isolated fibular fracture, ascertaining the status of the deep deltoid ligament is important to help differentiate a stable ankle fracture versus an unstable ankle fracture.26 Stress radiography is important to determine the status of the deltoid ligament and is an objective measurement of stability in ankle fractures.26 Stress radiography consists of either gravity stress views or manual external rotation stress views. The gravity stress view consists of an anteroposterior radiograph taken with the leg horizontal and the medial side up without any ankle support.26 One can perform the external rotation stress test by having the leg in 10 degrees of internal rotation to obtain a mortise view, neutral dorsiflexion and an external rotation force placed on the ankle by the provider.22,26

Both stress views measure the medial clear space, which is the distance between the lateral border of the medial malleolus and the medial border of the talus at the level of the talar dome.27 A medial clear space of greater than 5 mm is predictive of a deep deltoid ligament injury and thus an unstable ankle fracture. Clement and coworkers found that a higher medial clear space (over 5 mm) on the gravity radiographs correlates with a lower American Orthopaedic Foot and Ankle Society (AOFAS) score in patients with an isolated lateral malleolar fracture. Therefore, large medial clear space values seem amenable to operative treatment.28 Multiple studies have shown gravity stress views to be as effective as manual external rotation stress views in detecting medial clear space widening in isolated fibular fractures.26,29

When Surgery Is Indicated For Acute Deltoid Injuries

Operative management of bimalleolar equivalent fractures is necessary when the medial clear space fails to reduce to anatomic limits as this will likely lead to mechanical instability.1 Additionally, a displaced lateral malleolus fracture with a concurrent deltoid ligament rupture is equivalent to a bimalleolar fracture. Therefore, surgical fixation is indicated.26

One study reported that over 60 percent of patients with a fibula fracture and deltoid ligament rupture had tenderness over the deltoid ligament with conservative treatment and 38 percent of patients had medial instability with conservative treatment of a deltoid ligament injury after ankle fracture fixation.30 Given the previous work reported by Earll and Hintermann and their colleagues, surgical stabilization of the deltoid ligament confers protection of the articular cartilage from degenerative processes and other late sequelae.15,20

A Step-By-Step Guide To The Surgical Technique

Various authors have described reconstruction techniques using posterior tibial tendon, flexor hallucis longus, peroneus longus, plantaris autograft or Achilles allografts.31-33 These techniques have been developed for the treatment of stage IV posterior tibial tendon dysfunction. For acute injury of the deltoid, repair techniques include direct end-to-end repair and ligament-to-bone repair using anchors or bone tunnels.31-34 Given the high incidence of osteochondral lesions following ankle trauma, we routinely perform arthroscopy prior to repair.

Once the patient has received general anesthesia, position the patient in the supine position. If one is performing arthroscopy or open reduction and internal fixation, complete this before addressing the deltoid ligament. Even after fixation of the syndesmosis, we recommend performing an intraoperative stress examination. If there is greater than 5 mm of medial clear space on the mortise view or evidence of residual talar eversion, we recommend direct repair of the deltoid ligament.

Center a curvilinear incision over the medial malleolus heading distally over the course of the posterior tibial tendon. One should perform deep dissection while electrocauterizing the tributaries of the saphenous vein. Then thoroughly inspect the superficial and deep deltoid branches. Typically, the deep deltoid will rupture off the medial aspect of the talus and the superficial deltoid will rupture off the anterior distal tibia. One may raise a periosteal flap off the medial malleolus 3 to 4 mm proximally if necessary. In select instances, the deltoid ligament may be ruptured.

Proceed to prepare the distal medial malleolus with a rongeur to promote osseoligamentous integration. Use suture anchors to secure the medial aspect of the talus into the anterior medial malleolus. Then pass the sutures through the ligament with the ankle in a neutral position. The fibers of the ligament complex are oriented parallel to the pull of the anchors and can easily tear through the tissue. Therefore, one may place a proximal locking stitch with one limb of the suture. Pass the other limb distal to the locking stitch so the pull of the sliding limb will advance and post the ligament to the bone. Proceed to tie the sutures down to secure the construct. Then one may use intraoperative fluoroscopy to ensure the joint is reduced and congruent. A stress examination confirms symmetric and appropriate medial clear space, and tibiofibular clear space and overlap.

What The Literature Reveals

Evidence of improved patient outcomes after acute deltoid repair is controversial. In a randomized study, Stromsoe and colleagues compared immediate repair of acute deltoid ruptures with Weber type B and C fractures to a deltoid repair group and a no repair group.6 The authors found no significant difference in their treatment group in comparison with the conservative deltoid management group with respect to working ability, sports activities, pain and swelling at a mean follow-up of 17 months.6 However, some patients had suboptimal outcomes, leaving questions regarding whether some would have benefited from direct anatomic repair. Persistent medial ankle pain after bimalleolar equivalent injuries may be related to the subtle or dynamic medial instability from nonoperative deltoid management.2,35

Johnson and Hill reported on lateral malleolar fractures with a deltoid ligament rupture in 29 patients treated with fracture fixation only.30 Ten patients had residual pain along the medial side of the ankle and 18 patients had medial ligament tenderness.The deltoid ligament had laxity on examination with abduction or external rotation tests in eight patients.More recent evidence suggests one should repair a deltoid ligament rupture in patients with an unstable medial ankle after fracture fixation, which can prevent late ankle instability.36 Repairing the deltoid complex at the time of the lateral malleolus fixation has subjective, functional and radiologic outcomes that are similar to a lateral malleolus fixation with syndesmotic fixation for bimalleolar equivalent ankle fractures.9

One may confer indirect stability to the deltoid ligament complex by lateral malleolus fixation followed by surrogate syndesmotic fixation whereas primary deltoid ligament repair provides direct stability. While surrogate syndesmotic fixation does provide indirect stability to the deltoid ligament, the deltoid ligament heals in a non-anatomic position. Various authors have shown non-anatomic healing of the deltoid ligament complex to negatively affect clinical and functional outcomes.9,22,34,37 Additionally, postoperative computed tomography (CT) would suggest that there is a significant rate of syndesmotic malreduction when performing transsyndesmotic fixation.38,39 Thus, repairing the deltoid ligament at the time of lateral malleolus fixation may prevent the need to fixate the syndesmosis and its associated complications.

Woo and coworkers reported on 78 consecutive cases of a ruptured deltoid ligament with an associated ankle fracture and a mean follow-up of 17 months.4 When the ruptured deltoid ligament was accompanied by a syndesmotic injury, the final follow-up medial clear space and the clinical outcomes were superior in the deltoid repair group. In the case of high-grade unstable fractures of the ankle with syndesmotic instability, a direct repair of the deltoid ligament was adequate for restoring medial stability. The authors concluded that direct repair of the deltoid ligament plays an important role in maintaining ankle stability in high-energy injuries, such as syndesmotic diastasis and deltoid ligament ruptures associated with ankle fractures.

In Conclusion

The deltoid ligament complex is an important stabilizer of the ankle joint. Recent literature suggests that direct repair of the deltoid ligament may facilitate superior clinical and radiographic outcomes. Despite equivocal clinical outcomes in the short term, improper treatment of acute deltoid injuries may lead to unwanted late sequelae. The clinician should have a high index of suspicion of acute deltoid injury with isolated fibular fractures. History and clinical examination, radiographic parameters, and stress evaluation are paramount in the diagnosis of acute deltoid injuries with ankle fractures.

Dr. McAlister is an attending at The CORE Institute in Phoenix. He is a board-certified, fellowship-trained foot and ankle surgeon. Dr. McAlister is a Fellow of the American College of Foot and Ankle Surgeons.

Dr. So is a Fellow at the CORE Institute.

References
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Features
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By Jeffrey E. McAlister, DPM, FACFAS, and Eric So, DPM, AACFAS
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