Acute Deltoid Injury in Ankle Fractures: A Biomechanical Analysis of Different Repair Constructs

BACKGROUND

The importance of the deltoid ligament in the congruency and coupling of the tibiotalar joint is well known. The current trend is to repair it in cases of acute injuries in the context of ankle fractures; however, there is limited information on how it should be reconstructed. The objective of this study was to compare different deltoid ligament repair types in an ankle fracture cadaveric model.

METHODS

Sixteen cadaveric foot-ankle-distal tibia specimens were used. All samples were prepared as a supination external rotation ankle fracture model. Axial load and cyclic axial rotations were applied on every specimen using a specifically designed frame. This test was performed without deltoid injury, with deltoid injury, and after repair. The reconstruction was performed in 4 different ways (anterior, posterior, middle, and combined). Medial clear space (MCS) was measured for each condition on simulated weightbearing (WB) and gravity stress (GS) radiographs. Reflective markers were used in tibia and talus, registering the kinematics through a motion analysis system to record the tibiotalar uncoupling.

RESULTS

After deltoid damage, in all cases the MCS increased significantly on GS radiographs, but there was no increase in the MCS on WB radiographs. After repair, in all cases, the MCS was normalized. Kinematically, after deltoid damage, the tibiotalar uncoupling increased significantly. All isolated repairs achieved a similar tibiotalar uncoupling value as its baseline condition. The combined repair resulted in a significant decrease in tibiotalar uncoupling.

CONCLUSION

Our results show that deltoid repair recovers the tibiotalar coupling mechanism in an ankle fracture model. Isolated deltoid repairs recovered baseline MCS and tibiotalar uncoupling values. Combined repairs may lead to overconstraint, which could lead to postoperative stiffness. Clinical studies are needed to prove these results and show clinically improved outcomes.

CLINICAL RELEVANCE

This study helps in finding the optimum deltoid repair to use in an acute trauma setting.

Deltoid ligament injury and repair

The deltoid ligament is the primary stabilizer of the medial side of the ankle joint. It is a complex structure with an origin at the medial malleolus from where it spreads fan shaped distally with an insertion into the medial side of the talus, calcaneus and navicular bone. This chapter gives an overview of the anatomy, function, and pathology of the deltoid ligament.The deltoid ligament can become insufficient as a result of an ankle injury or prolonged strain. In the acute setting, deltoid insufficiency often coincides with multi ligament injury the ankle joint; syndesmosis injury, or ankle fractures. Management in the acute phase remains a subject of debate. Some orthopedic surgeons have a tendency towards repair, whereas most trauma surgeons often treat the deltoid nonoperatively. In the chronic setting the ligament complex is often elongated as a result of prolonged strain. It often coexists with a hindfoot valgus, as is the case in planovalgus feet. In such a case a realignment procedure should be combined with the deltoid repair.

Instability of the distal tibiofibular syndesmosis

The distal tibiofibular syndesmosis (DTFS) is more frequently injured than previously thought. Early diagnosis and appropriate treatment is essential to avoid long term complications like chronic instability, early osteoarthritis and residual pain. Management of these injuries require a complete understanding of the anatomy of DTFS, and the role played by the ligaments stabilizing the DTFS and ankle. High index of suspicion, appreciating the areas of focal tenderness and utilizing the provocative maneuvers help in early diagnosis. In pure ligamentous injuries radiographs with stress of weight bearing help to detect subtle instability. If these images are inconclusive, then further imaging with MRI, CT scan, stress examination under anesthesia, and arthroscopic examination facilitate diagnosis. An injury to syndesmosis frequently accompanies rotational fractures and all ankle fractures need to be stressed intra-operatively under fluoroscopy after fixation of the osseous components to detect syndesmotic instability. Non-operative treatment is appropriate for stable injuries. Unstable injuries should be treated operatively. Anatomic reduction of the syndesmosis is critical, and currently both trans-syndesmotic screws and suture button fixation are commonly used for syndesmotic stabilization. Chronic syndesmotic instability (CSI) requires debridement of syndesmosis, restoration of ankle mortise with or without syndesmotic stabilization. Arthrodesis of ankle is used a last resort in the presence of significant ankle arthritis. This article reviews anatomy and biomechanics of the syndesmosis, the mechanism of pure ligamentous injury and injury associated with ankle fractures, clinical, radiological and arthroscopic diagnosis and surgical treatment.

Biomechanical Effect on Joint Stability of Including Deltoid Ligament Repair in an Ankle Fracture Soft Tissue Injury Model With Deltoid and Syndesmotic Disruption

BACKGROUND

The current operative standard of treatment for bimalleolar equivalent ankle fracture is open reduction and internal fixation (ORIF) of the lateral malleolus followed by syndesmotic stabilization if indicated. There is controversy surrounding the indication and need for deltoid ligament repair in this setting. The purpose of this study was to quantify the biomechanical effect of deltoid ligament repair in an ankle fracture soft tissue injury model.

METHODS

Nine fresh-frozen cadaveric specimens were included in this study. Each leg was tested under 5 conditions: intact, syndesmosis and deltoid ligament sectioned, syndesmosis fixed, deltoid repaired, and both the syndesmosis and deltoid ligament repaired. Anterior, posterior, lateral, and medial drawer and rotational stresses were applied to the foot, and the resulting talus displacement was documented.

RESULTS

Isolated deltoid repair significantly reduced anterior displacement to normal levels. Displacement with lateral drawer testing was not significantly corrected until both structures were repaired. Deltoid repair and syndesmosis fixation each reduced internal rotation significantly with further reduction to normal levels when both were repaired. External rotation remained elevated relative to the intact condition regardless of which structures were repaired.

CONCLUSION

There is existing controversy regarding the importance of deltoid ligament repair in the setting of ankle fractures. The findings of this biomechanical study indicate that deltoid ligament repair enhances ankle stability in ankle fractures with both syndesmotic and deltoid disruption.

CLINICAL RELEVANCE

Concomitant deltoid ligament repair in addition to stabilization of fracture and syndesmosis may improve long-term functioning of the ankle joint and clinical outcomes.

Technique for Arthroscopic Deltoid Ligament Repair With Description of Safe Zones

Level V, expert opinion.