Reconstruction of tibiofibular syndesmosis using autologous semitendinosus graft and lengthening derotational osteotomy of the distal fibula

Introduction

Distal tibiofibular syndesmosis is a complex anatomical structure that is essential for the stability and function of the ankle. Ankle fractures are a common source of chronic syndesmosis instability with associated functional impairments and early development of osteoarthritis. Case presentation: we described a case of a 28-year-old patient who presented with symptomatic ankle subluxation and chronic syndesmosis instability. Eight months earlier, the patient sustained a minimally displaced ankle fracture that had been treated conservatively elsewhere. The surgical approach included the anatomical realignment of the distal fibula with a lengthening derotational osteotomy and tibiofibular syndesmosis reconstruction using an autologous semitendinosus tendon graft. One year after surgery, the ankle function was restored, and the patient was asymptomatic. Conclusion: The instability of ankle fractures should be carefully evaluated during the treatment decision-making. Surgical treatment of syndesmosis instability should be performed even in chronic cases to restore function. The reconstruction of syndesmosis with semitendinous tendon graft associated with fibular length and realignment improves the ankle stability and function.

1. Introduction

Distal tibiofibular syndesmosis is a complex anatomical structure that is essential for ankle stability and function. The syndesmosis is composed of four ligaments, anteroinferior tibiofibular (AITF), interosseous (IO), posteroinferior tibiofibular, and inferior-transverse tibiofibular.¹ The most common mechanism of syndesmosis injury is protonation with external rotation of the ankle, occurring in up to 18% of sprains and approximately 23% of all ankle fractures.² The diagnosis of the syndesmosis injury is made by physical examination (pain on direct palpation of tibiofibular syndesmosis and positive external rotation test) combined with imaging exams such as radiographs (Anteroposterior [AP] view with and without load, lateral and Mortise view of the ankle), computed tomography, and magnetic resonance imaging.^1,2 Intraoperatively, squeezing test and the lateral (bone hook) stress test or Cotton test may increase the rate of detection of syndesmotic instability.³ The gold standard for the diagnosis of syndesmosis instability is the arthroscopic measurement of the tibiofibular distance of ≥2 mm.⁴ However, there is still no definite preoperative evaluation algorithm.^5,6

Chronic syndesmosis instability (CSI) is defined by the presence of pain that is aggravated by a combination of dorsiflexion and external rotation forces, persistent swelling at the anterolateral region of the syndesmosis, perceptions of the ankle giving way, and restricted dorsiflexion of the ankle joint six months following a post-traumatic ligament injury.^{5, 6, 7} A neglected or undertreated syndesmosis injury following an ankle fracture, lack or insufficient stabilization during surgical treatment or early screw removal could be associated with CSI.⁶ The diagnosis is controversial because physical exam and different imaging methods are not able to reliably predict the instability at the initial presentation.² Surgical treatment options include simple arthroscopic debridement with or without screw or suture button device, anatomical syndesmosis repair, tendon graft ligament reconstruction, associated or not with fibular osteotomy, and arthrodesis.^{2, 3, 4, 5, 6, 7}

Several techniques have been described for the treatment of CSI, although, no consensus on the optimal method has been established.^2,3,5,6 Here, we describe a case of a 28-year-old male who presented CSI symptoms eight months following conservative treatment of an ankle fracture. The radiographic study revealed chronic instability of syndesmosis with ankle joint subluxation. Syndesmosis reconstruction with autologous semitendinosus tendon graft and fibular lengthening derotational osteotomy was performed with a good outcome within a one-year follow-up.

1.1. Case presentation

A 28-year-old male presented to our outpatient clinic eight months following a right ankle sprain. At the injury date, he was seen at the Emergency Department of an outside facility, and plain radiographs of his ankle were obtained (Fig. 1) with the initial impression of a stable ankle fracture. The patient reported that no stress radiograph views were obtained. The treatment involved a below-knee non-weight bearing plaster cast for eight weeks, followed by physical therapy rehabilitation. There was no history of prior musculoskeletal lesions on the affected ankle.

Fig. 1.

Initial radiographs in Anteroposterior and Lateral view showing lateral malleolus fracture after acute ankle sprain.

After the rehabilitation program, the right ankle evolved with persisting pain, swelling, and inability to perform physical activities. Eight months after the trauma, the patient searched for a specialized evaluation at our Institution. The physical examination revealed ankle swelling, anterolateral tenderness, limitation in the range of movement (ROM), and pain on palpation of the medial side of the ankle and tibiofibular syndesmosis. No skin lesion or neurovascular deficits were noted. Right ankle mortise, lateral, and weight-bearing comparative anteroposterior views were obtained. Radiographs revealed right lateral malleolus fracture viciously consolidated with shortening of the fibula, ankle subluxation with opening of the distal tibiofibular space, and clear widening of the medial tibiotalar space (talocrural angle difference between ankles of 8°) (Fig. 2). Because of the joint incongruence and chronic syndesmosis instability, we proposed the surgical treatment, with a shared decision with the patient. The surgical planning included debridement of the medial space with deltoid ligament imbrication, lengthening derotational osteotomy of the fibula, and reconstruction of the tibiofibular syndesmosis.

Fig. 2.

Radiographs on the (a) comparatively Mortise view with load, and (b) Anteroposterior and Lateral views showing right lateral malleolus fracture viciously consolidated with shortening of the fibula, ankle subluxation with opening of the distal tibiofibular space, and clear widening of the medial tibiotalar space (talocrural angle difference between ankles of 8°).

The surgery was performed with the patient in a supine position, under spinal anesthesia. A cushion was placed under the right hip, and a pneumatic tourniquet at the proximal thigh was inflated to 300 mmHg after Esmarch bandage exsanguination. Through a direct anteromedial approach at the proximal tibia, the semitendinosus tendon was harvest using a stripper, and cortico-cancellous bone graft was collected from the proximal metaphysis of the ipsilateral tibia. At the ankle, we initially performed an anteromedial approach to debride the scar and fibrosis of the medial gutter. The deltoid ligament was imbricated through simple suture with absorbable stitches. Then, through a direct lateral approach to the ankle, the syndesmosis was debrided and an osteotomy of the fibula was performed. The autologous bone graft from the proximal tibia of approximately 10 mm in height was placed into the osteotomy site, with correction of the rotation and length of the lateral malleolus, and fixated with a one-third tubular 3.5 mm plate. Intraoperatively, we assessed the talocrural angle to guide the decision for fibular lengthening. Finally, the non-anatomical ligament reconstruction of syndesmosis was performed according to technique previously described (Fig. 3).⁸ Based on the thickness of the tendon graft, tunnels of 4.5 mm were drilled at the footprint of the AITF ligament. Firstly at the distal fibula from anterior to posterior, the second transversally at the anterolateral region of the distal tibia, and the third at the fibula from lateral to medial, intersecting the previous tunnels, about 1.0–1.5 cm above the tibiotalar joint. The semitendinous tendon was passed through the tunnels and fixed using a metal anchor inserted into the lateral malleolus. Two cortical screws were finally introduced to stabilize and protect the syndesmosis reconstruction (Fig. 4). After wound closure, a simple dressing and a below-knee cast were applied. The total procedure lasted approximately 110 minutes.

Fig. 3.

Non-anatomical AITF ligament reconstruction illustrated from axial and coronal planes, including the harvested semitendinous tendon.

Fig. 4.

(a) Through a direct anteromedial approach at the proximal tibia, the semitendinosus tendon was harvest using a stripper, and cortico-cancellous bone graft was collected from the proximal metaphysis of the ipsilateral tibia; (b) Anteromedial ankle approach for debridement of the scar and fibrosis of the medial gutter, and deltoid ligament imbrication; (c) Direct lateral approach to the ankle; (d) Fibula derotation and lengthening osteotomy fixed with a third tubular plate and reconstruction of the syndesmosis with semitendinous tendon graft; (e) Postoperative radiographs with restoration of fibular length and ankle joint congruence.

The patient was discharged after 24 hours. Rehabilitation involved casting without weight-bearing up to six weeks following the surgery. Then, the cast was removed, a removable walking boot was prescribed, and partial load discharge with crutches was recommended for the next six weeks. Physical therapy was initiated to recover the range of motion. Full weight-bearing was allowed after 12 weeks, when signs of partial consolidation of the fibula osteotomy were observed on radiographs, without graft absorption or collapse, or fibular shortening. Radiographs at eight months postoperatively showed complete graft integration and fibular consolidation and joint congruence. After 12 months the patient returned for reevaluation. At this moment, AP and lateral weight-bearing views showed joint congruence, however with reduction of the tibiotalar joint space and ossification at the distal tibiofibular space. The patient presented with a wide range of motion (50° plantar flexion, 10° dorsiflexion), no significant complaint of pain, good ankle function (AOFAS Ankle-Hindfoot scale 91 points) and had resumed sports activities (recreational soccer) (Fig. 5).

Fig. 5.

Clinical and radiographic aspect of the ankle 12 months postoperatively. The patient presented with a wide range of motion, no significant complaint of pain, and good ankle function. X-ray revealed joint congruence, bone graft integration, and fibular osteotomy consolidation.

2. Discussion

Chronic syndesmosis instability is usually secondary to unstable ankle fractures with further vicious consolidation of the fibula and changes in the talus position into the malleolar mortise. CSI can lead to a clinically debilitating status, abnormal joint surface overload, and a secondary degenerative process.^5,7,9 Several surgical techniques have been described for the treatment of CSI, however, there is no consensus of the ideal method of treatment.^{2, 3, 4, 5, 6, 7} The syndesmosis reconstruction with autologous semitendinosus tendon graft and fibular lengthening derotational osteotomy technique described herein performed eight months after the initial injury resulted in a good outcome.

Distal tibiofibular syndesmosis reconstruction has an important role in CSI’s surgical treatment.^{2,9, 10, 11} Ligament reconstruction is assumed to be a more anatomic procedure, in theory restoring ankle joint biomechanics and motion, which would be especially considered for younger patients and athletes.^2,5 Therefore, in our case we opted to perform the syndesmosis ligament reconstruction with a semitendinous tendon graft. In agreement, a systematic review showed the highest rates of success for treatment of CSI the anatomical reconstruction of the syndesmotic ligaments with screw fixation in eight of 11 studies.⁶ Previous studies^10,11 suggested the gracilis tendon graft to reconstruct the syndesmosis and restore the normal anatomy of the ankle, showing significant increase in AOFAS. Another study⁹ described the reconstruction of the syndesmosis with hamstring graft after the arthroscopic debridement in eight patients, with an average follow-up of 13 months, observing final AOFAS score of 85 points. Syndesmosis reconstruction can be performed with a single or double band tendon graft. A concern on ligament reconstruction with multiples tunnels and drilling of the fibula and tibia is for possible fibular fracture, synostosis, or even arthrodesis of the syndesmosis, with potential stiffness of the distal tibiofibular joint. Moravek et al.¹² performed the double allograft reconstruction in six patients with CSI, after an average 14 months following the initial trauma. After a mean follow-up of 12 months, the authors reported restriction of ankle ROM, and one fibular fracture requiring a new surgery. We chose to perform the AITF ligament reconstruction with semitendinous tendon graft and cortical screw fixation once it is the weakest component of the syndesmosis, consequently most often affected.^1,3 Also, potentially, the function of the IO ligament was sustained by the syndesmotic screws.

Other techniques have been described for the CSI treatment. The lengthening and derotational osteotomy of the fibula associated to the syndesmosis reconstruction has been suggested when fibular malunion prevents an adequate reduction of the distal tibiofibular syndesmosis and ankle joint.^10,11 Sarkisian and Cody¹³ described in 1976 the talocrural angle to determine the fibular length, considering the most significant radiographic marker as a predictor for post-traumatic ankle arthropathy. Comparing to the healthy side of our case, we observed in the weight-bearing mortise view, reduction in the talocrural angle, widening of the medial clear space, and fibular shortening. Therefore, associated to the syndesmosis reconstruction, we corrected the fibular length and rotation simultaneously through a suprasyndesmal osteotomy using an autologous tibial graft. The choice of the donor site of the bone graft was to minimize the morbidity of the procedure since the hamstring tendon was obtained through the same incision. A previous study suggested that the proximal tibia is a source of adequate autogenous cancellous bone graft, adding low morbidity to the surgery.¹⁴ The approach to the medial aspect of the ankle joint has been focus of studies, and the role of the deltoid ligament repair or reconstruction in the setting of a CSI still needs to be determined.¹⁵ Also, the arthrodesis of the syndesmosis may be an option as a salvage procedure, in cases of advanced CSI.¹⁶

In our report, the CSI occurred after a misdiagnosis of an unstable ankle fracture that has been conservatively treated. The unfavorable evolution showed that there was an associated ligament injury (syndesmosis and deltoid ligaments), making the ankle unstable. Therefore, immediately after the injury, a proper assessment of the fracture instability, including stressed ankle radiographs, should have been performed to define the correct treatment of the injury. In accordance, Egol et al.¹⁷ highlighted the need for differentiation of ankle fracture patterns and showed the importance of clinical signs of ligament injury and ankle stress radiography. The authors warned about the risk of ankle joint subluxation if conservative treatment of fractures is elected for unstable lesions. At 12 months FU, the patient had a wide ROM of the ankle, no significant pain, and an AOFAS score of 91 points. Final radiographic showed partial ossification around the syndesmosis and reduction in the tibiotalar space. Even with partial or total synostosis of the syndesmosis, physical activity is still possible after ankle instability treatment.¹⁸ Although, no other signs of advanced osteoarthritis such as osteophytes, subchondral cysts, or obliteration of the chondral space were observed, which could explain the good functional result observed. An important limitation that should be mentioned is the lack of an ankle CT scan before surgical treatment. Since the patient had had syndesmosis instability for eight months, CT scan could depict the articular degeneration, fibular malleolus congruence, length and rotation, ossification at the syndesmosis, or medial articular space that could interfere with surgical reduction of the joint, presence of osteochondral lesions, and loose bodies. However, we could not obtain a preoperative CT scan in this case due to temporary unavailability at the Institution during the surgical planning period.

Our patient had a good outcome, returning to work and recreational sports activities, however, early diagnosis of syndesmosis injuries, isolated or associated with ankle fractures, is essential. We believe that late repair of chronic syndesmosis instability has satisfactory but less favorable functional results compared to acute injuries. Nevertheless, the influence to prevent or at least delay the process of ankle osteoarthrosis needs to be determined.

3. Conclusion

The instability of ankle fractures should be carefully evaluated before conservative treatment is indicated. We believe that surgical treatment of syndesmosis instability should be performed even in chronic cases.

Authors’ contributions

HM: analyzed and interpreted the patient data regarding the postoperative outcome, collect data and was a major contributor in writing the manuscript. SDS was a major contributor in writing the manuscript. DAM: was a major contributor in writing and major revision of the manuscript. All authors read and approved the final manuscript.

Declaration of competing interest

None.