Introduction

Syndesmosis injuries account for 11% of all ankle injuries, and can lead to chronic pain and instability (1,2). Chronic conditions can be challenging for clinicians to diagnose, debilitating for the patient, and lead to instabilities of structures surrounding the joint (3,4,5). These conditions can lead to articular surface changes, heterotopic ossification, scaring, chronic pain, and instability (3,5,6,7). Patient’s rehabilitation protocols typically will extend for longer periods of time, which can result in time loss due to the extent of the injury (3,4,6,7,8).

The purpose of this literature review is to emphasize the research about the anatomy, pathomechanics, recognition, management, and rehabilitation protocols for conservative and non-conservative syndesmosis conditions. Further encompassing areas pertaining clinical tests, imaging techniques, surgical procedures, secondary injuries, and the need for future research studies to help recognize this condition.

Syndesmosis Anatomy

The distal syndesmosis joint consist of the tibia, fibula, anterior inferior tibio-fibular ligament (AIFL), posterior inferior tibio-fibula ligament (PIFL), inferior transverse tibio-fibula ligament (ITFL), inferior interosseous ligament (IL) and the interosseous membrane (IM) (3). These structures act to stabilize the distal syndesmosis joint, allowing optimal positioning of the talus within the medial and lateral malleolous and preventing tibio-fibula separation (10). The AIFL originates on the anterior-lateral aspect of the tibia and runs obliquely to the anterior- lateral malleolus of the fibula (3). With assistance from the anterior deltoid ligament, the AIFL prevents excessive eversion of the talus, and excessive external rotation of the fibula (11). The AIFL along with the PIFL provides most of the ligamentous stability for the distal syndesmosis joint (4,12,13).

The PIFL is the strongest syndesmosis ligament and runs obliquely from the posterior malleolus of the tibia to the posterior lateral malleolus of the fibula (4,10). The PIFL contains a superficial and deep component, which is known as the ITFL (3,10,11). The ITFL lies inferior and horizontal to the PIFL and is thought to be a continuation of the PIFL (3,10,11). The PIFL and ITFL help stabilize the posterior aspect of the syndesmosis joint and are the last ligaments to be injured (10).

The interosseous membrane is composed of fibrous tissue that arises from the superior lateral tibia, and extends to the distal medial fibula and prevents tibio-fibular separation (3). Researchers categorized the interosseous ligament as a continuation or thickening of the interosseous membrane at the distal end syndesmosis joint, and its function is to transmit up to 15% of axial loads from the tibia to the fibula during weight-bearing (3,4,14,15). The interosseous ligament can also assist with separation of the tibia and fibula during dorsiflexion, which allows the talus to properly fit within the joint space (3).

Pathomechanics

Syndesmosis injuries can occur in many sports including football, soccer, wrestling, skiing, or other types of instances where the foot comes with either a player or playing surfaces (8,10,16). Excessive external rotation motions can cause the talus to displace laterally against the fibula, which can cause the fibular to externally rotate and separate from the tibia (3,15,19,20). Research studies conducted on elite skiers concluded that there is an increase amount of stress placed upon the joint during a dorsiflexed position (4,17). As a result, the talus wedges itself between the tibia and fibula, increasing the joint space width between the tibia and fibula (4,17). Research suggests tibiotalar articulation decreases up to 42% when the talus is displaced laterally more than 1mm (3,15,21). Typically, the AIFL is the structure most likely to be injured during external rotation, eversion, dorsiflexion, or combined motions (3,4,10,22). The AIFL, PIFL, IL, and anterior deltoid ligament help’s prevent rotation, excessive eversion, and movement of the fibula in respect to the tibia (4,11,20). An injury to the AIFL can cause subsequent injury to the interosseous ligament (4,23). Research on cadavers concluded that disruption to the interosseous ligament does not cause disruption to the ankle mortise during injury loads (4,23).

Assisted by the anterior deltoid ligament during dorsiflexion, the AIFL, and IL are aligned in a horizontal plane during dorsiflexion (3,7,19,20). As a result, the talus wedges within the joint space allowing for optimal ankle mobility (3,7,19,20). During plantarflexion, motion occurs in the opposite direction causing the AIFL, and IL to move vertically (7). The fibula internally rotates and moves distally, placing tension on the AIFL during injury (7).

Clinical Examination Findings

Patients report a history of pain with activity, distal anterior-lateral leg pain, tenderness between tibia and fibula, weakness, instability, and reduced range of motion (3,4,8,9,20,24). It is critical for the examiner to note the location of tenderness from the distal end to proximal end of the tibia and fibula (4,8,10,20,24,25). Researchers indicate that tenderness length is directly correlated to time loss and severity of injury (4,8,20,24,25). Test frequently administered include a positive squeeze test, kleigers test, cotton test, and positive one-legged hop test (10,6,4,2,28).

X-ray

Radiographs typically are used to rule out avulsion fractures, fibula displacement and any heterotopic ossification within the joint (4,5,8,9,10,20,21,27). Research suggests that an anterior-posterior, lateral, and mortise view should be taken to confirm the integrity of the tibiofibular clear space, tibiofibular overlap and mortise (4,5,8,9,10,20,27). An anterior-posterior can determine the tibiofibular clear space, which is normally less than 6mm (4,5,8,9,10,20,27). The amount of tibiofibular overlap with anterior-posterior views is typically greater than 42% of the fibula width (4,8,9,10,19,20,27,28).

Studies suggest lateral views could be taken with patients in non-weight bearing, and external rotation to determine the extent of fibula displacement (4,19,29,30). Researchers indicate normal medial clearance space to be between 2-4 mm (10,27,31). Radiographs can exclude anterior deltoid ligament injuries exceeding in 1-2mm width between the medial malleolus and the medial talus (10,27,31).

MRI & CT Scan

MRI and CT scans are 3 dimensional images that are usually taken in a front, axial, and saggital view to determine the extent of injury (9,10,27,31). MRI can be used as a tool to confirm the severity of disruption to ligaments, articular surfaces, and provide information about the integrity of the distal tibiofibular joint (4,9,10,27,31,32). In addition, MRI’s can detect any secondary conditions associated with the injury (4,9,10,21,27,31,32). Research suggest CT scans can be more effective than radiographs by showing less than 3mm of disruptions within joint (9,10,33,34).

Arthroscopy

Arthroscopy is considered to be the most reliable and precise tool when predicting syndesmosis disruptions (5,36). Arthroscopic finding indicate that injuries can occur to the AIFL, articular surfaces, and tibiofibular clear space (5,36). Researchers used the Outerbridge Classification Scale to grade the extent of articular surface damage found during arthroscopy (5,36). Researchers distinguish articular surface damage into five different classifications: Grade 0 indicates normal cartilage (5,36). Grade 1 indicates softening and swelling to the surfaces (5,36). Grade 2 indicates fissures and flaking of the subchondral bone (5,36). Grade 3 indicates increase erosion and damage to the subchrondral bone (5,36). Grade 4 indicates exposure to the subchrondral bone (5,36).

Classification of Injury

Researchers used the West Point Ankle Instability Scale to classify injuries into three categories including mild, moderate to severe (9,20,37,38,39). Grade 1 syndesmosis is considered to be a mild disruption of the AIFL, and the IL without instability (9,20,37,38,39). Grade 2 and Grade 3 syndesmosis injuries are considered to be unstable injuries, which require surgical intervention (9,20,37,38,39). Grade 2 injuries can cause disruption of the AIFL, IL, and anterior deltoid ligament causing possible joint instability (9,20,37,38,39). Grade 3 injuries are associated with disruption of the AIFL, IL, anterior deltoid ligament, which could be associated with several fractures (9,20,37,38,39). Research suggests acute injuries are less than four weeks while chronic injuries persist more than three months (9).

Treatment

Treatment of syndesmosis injures can vary and are based on the length of symptoms and severity of the injury (4,7,8,9,10,20,33). Protocols can consist of conservative treatment or operative treatment depending on the patient’s goals, and recommendations of medical personnel. Grade 1 injuries, non-fractures, and possibly Grade 2 injuries can be treated with conservative treatment (4,7,8,9,10,20,33). Grade III injuries typically require operative treatment to restore mobility (4,8,7,9,10, 20,33).

Conservative Rehabilitation Protocols

Rehabilitation results can vary from patient to patient, but usually range from 2-4 weeks for Grade 1 sprains, and 6-8 weeks for Grade 2 sprains (4,7,8,9,10). The goals of phase I are to reduce pain, reduce inflammation, reduce scaring, protect the injury, increase range of motion and maintain cardiovascular fitness (4,7,8,9,10,20,33).

Phase I of the rehabilitation typically begins 0-5 days for Grade 1 sprains and 5-10 days for Grade 2 sprains (1,4,7,8,9,10). Immobilization can range from 0-5 days for Grade 1 sprains and 6-8 weeks for Grade 2 sprains (1,4,7,8,9,10,20). Immobilization techniques include splinting, casting, cam-walkers, and crutches (1,4,7,8,9,10,20). Researchers recommend non-thermal ultrasound, cryotherapy, and electric-stimulation to manage pain and swelling (1,4,7,8,9,10,20). Manual exercises consisting of 30*degrees of plantar flexion, light passive stretches, dorsiflexion towel stretches, ankle pumps and toe curls are recommended to increase range of motion, and reduce inflammation (4,8).

Phase II of the rehabilitation could range from 6-10 days for Grade 1 sprains and up to 2-8 weeks for Grade 2 sprains (1,433,40,41). The goals of phase II are progression to a full range of motion, injury protection, pain reduction, increase proprioception, increase strength, functional activity, progression to pre-injury levels, and maintaining cardiovascular fitness (1,4,7,8,10,20,33). For example, balance pads, toe raises, single leg raises, baps boards, resistance bands, manual resistance, joint mobilization, cycle ergometer, and light sports specific exercises are recommend during this stage of the rehabilitation (1,4,7,8,10,20,33). Bracing, ultrasound, cryotherapy, stretching and other modalities are recommended during this stage of the rehabilitation (7,8).

Phase III of the rehabilitation can range from 18-25 days depending on the severity of the injury (1,33). The goals are to reduce pain, increase pain free activity, increase strength, proprioception, advance sport specific activities, and maintain cardiovascular fitness (1,4,7,8,10,33). Researchers recommend using a single leg hop test to determine if the patient is able to perform advance sports specific activities (8). Rehabilitation exercises can include shuttle runs, advanced single leg exercises, figure eight drills, cycle, advanced sports specific activities, and high intensity cardiovascular training using stirrup bracing for protection (1,4,8,9,10,18,20,33). Researchers indicate full return to play when patients can demonstrate full strength, full range of motion and can pass all functional testing (8,20,38).

Phase IV of the rehabilitation can range from 28-56 days depending on the severity of the grade II injury (10,33,40,41). Rehabilitation exercises can include dumbbell squats, lunges, figure eight drills, advanced sports specific activities, and Phase III exercises (4,33,40,41). Full return to play can range from 6-8 weeks depending on the patients ability to demonstrate full strength, full range of motion and pass all functional tests (10).

Operative Treatment

Arthroscopy can be used for patients with acute or chronic disruptions (4,7,8,9,10, 20,33). Operative treatment is indicated for Grade 2 and Grade 3 injuries, which can cause instability and leave the patient at risk for further injuries (4,7,8,9,10, 20,33). The goals for surgical intervention are to restore disrupted structures thru reduction, fixations, and autographs (1,4,9,10,33). Rehabilitation goals consist of protecting the surgical repair, reduce pain, reducing inflammation, restoring range of motion, proprioception, and strength to pre-injury levels (1,4,9,10,33).

Open Reduction and Internal Fixations

Open reduction and internal fixation techniques can be used to restore unstable fractures, tibiofibular clearance space, with emphasis placed on the integrity of structural ligaments (9,10). Researchers recommend four 4.5mm cortical screws if a fracture occurs to the fibula, medial malleolus, or displacement of the fibula and mortise. (9,10,42,43). Research indicates using a modified brostrum procedure to repair the deltoid ligament if disruption occurs (9,27). The semitendinosus, gracilis and plantaris could be used as autographs to restore the integrity of disrupted ligaments (9,27). Complications associated with the procedure include screw breakage, types of screws, wound infections, interosseous membrane calcification, and stiffness within the joint (9,10).

Post-Operative Rehabilitation Protocols

Post-operative rehabilitation results can vary from patient to patient, but usually range from 4-8 months for a full return to play (9,18). Research suggests that follow up radiographs be performed every two weeks to assess the integrity of the surgical repair (10). The goals of phase I are to reduce pain, reduce inflammation, protect the surgical repair, and increase range of motion (9).

Phase I of the rehabilitation begins with immobilization of the injury using splinting, cam-walkers, casting and crutches for 6-8 weeks (7,9,10). None weight bearing, crutches, home stretching programs, and cryotherapy are recommended during the first week of rehabilitation (9). Manual exercises performed during phase I of conservative treatment can be used during this stage of the rehabilitation (4,8,9).

Phase II of the rehabilitation can begin at three to six weeks. The patient can begin partial weight bearing using one crutch and a cam-walker at 3-6 weeks (9,18). The goals are to reduce pain, increase pain free activities, increase strength, proprioception, and maintain cardiovascular fitness (9). Rehabilitation exercises can include baps board, resistance bands, stationary bikes, gait training and manual exercises performed during phase I of the conservative rehabilitation protocol (9). Research indicates that patients should progress from stationary bike to the elliptical at six weeks (9).

Phase III is when patients are allowed full weight bearing using a cam-walker at eight to twelve weeks (4,9,18,44). Patients can progress to functional activities including running, and exercises used during phase II of the conservative rehabilitation (9). Screw fixations are typically removed at 3 months, and patients should continue a progression in full weight bearing activities (9,18).

Phase IV of the rehabilitation can begin at four to eight months, and typically return to full participation is at 6-8 months (9,18). Patients should perform exercises using phase III and phase IV of the conservative rehabilitation protocol and progress as tolerated using bracing up to the first year post injury (9,18,33,40,41,43). Patients should successfully perform strength, range of motion, and functional tests before full participation is granted. (8,20,37).

Conclusion

Syndesmosis injuries can be more challenging to recognize and manage when compared to lateral ankle sprains (1,3,4,6,7,8,9). It is important for clinicians to recognize the extent of injury and rule out associated injuries using clinical examinations, imaging techniques, and surgical intervention to successfully manage syndesmosis injuries. Further research is warranted in regards to imaging reliability, clinical tests reliability, predicting time loss, predicting the extent of injury and the effectiveness of surgical techniques to effectively manage syndesmosis injuries (4,8,9,10,18,20). Furthermore, research is warranted to effectively develop a standard rehabilitation protocol to properly manage this condition.