Fixation of posterior malleolus fractures through posterior access in the ankle : case series Fixação de fraturas do maléolo posterior por acesso posterior no tornozelo : série de casos

Objective: The aim of this study is to present the preliminary results of posterior malleolus fixation in a case series by evaluating clinical and radiographic outcomes as well as possible complications related to this approach. Methods: This study involved a case series of 7 patients with posterior malleolus fractures, either isolated or associated with other tibiotarsal injuries, who were surgically treated and evaluated from January 2014 to December 2016 in one of the hospitals of our service. The patients were evaluated for consolidation, pain (Visual Analog Scale (VAS) score), function (American Foot and Ankle Society (AOFAS) score), surgical wound complications and joint degeneration in the postoperative period. Results: The mean follow-up was 66 weeks. All patients presented clinical and radiographic consolidation of the fractures by the sixth week of the follow-up. The mean pain score according to the VAS was 1.5 and the mean AOFAS score was 92.5. At the end of follow-up, no clinical or radiographic evidence of joint degeneration was observed. Conclusion: Posterior access is a viable alternative that provides good results with few complications for the treatment of posterior malleolus fractures. Level of Evidence IV; Therapeutic Studies; Case Series.


INTRODUCTION
Trimalleolar fractures are a complex injury of the ankle joint as they affect the tibial loading area and compromise tibiotarsal and distal tibiofibular stability. Deviation of the posterior malleolus in this type of fracture, which is called the Volkmann fragment, complicates treatment and contributes to an increased risk of unfavorable results (1,2) .
Fractures of the posterior malleolus are associated with scientific controversies ranging from diagnosis, treatment indications, and long-term local joint repercussions. Their identification can vary from easy visualization on profile radiographs for large fragments to the need for complementary tomographic evaluation for small fragments or subtle deviations (2)(3)(4) . The presence of posterior malleolus fracture leads to questions regarding whether the injury should be fixed, with little consensus in the current literature. Fixation of the medial and lateral malleoli is routinely performed for posterior fractures compromising more than 25% of the anteroposterior diameter of the tibia (4)(5)(6) .
Normally, reduction of the posterior malleolus after lateral malleolus fixation is expected due to its respective attachment to the posterior tibial-fibular ligament. The posterior malleolus is also frequently fixed with screws inserted in the anterior to posterior direction. This indirect form of fixation represents an early local approach since it becomes unfeasible in the absence of reduction (7) . In addition, situations in which correct noun may not occur are unusual.
Positioning in the supine position, which is typical for ankle fixation, facilitates access to the medial and lateral malleoli, but adequate evaluation and treatment of posterior malleolus fractures are more difficult. Alternatives in this situation include reduction and fixation using arthroscopic (8) or transmalleolar (9) techniques.

This study was approved by the Research Ethics
Committee with registration in the Brazil Platform under CAAE number: 88071118.8.0000.5505.
A case series of 7 patients with posterior malleolus fractures, either isolated or associated with other tibiotarsal injuries (lateral malleolus fracture, posteromedial malleolus fracture, medial malleolus fracture, deltoid injury, and syndesmosis injury), was analyzed in this study.
We included patients who were surgically treated and evaluated from January 2014 to December 2016 in one of the hospitals of our service. Patients whose records were incomplete and did not allow data analysis were excluded from the study.
The patients were diagnosed with ankle fractures with involvement of the posterior malleolus and corresponding injuries on radiographs and exhibited deviation greater than 2 mm affecting the articular surface with possible impairment of tibiotarsal and distal tibiofibular stability. The patients were evaluated for consolidation, pain (Visual Analog Scale (VAS) score), function (American Foot and Ankle Society (AOFAS) score), surgical wound complications and joint degeneration in the postoperative period. The mean age of the patients was 53.85 years (26 years to 76 years).
Data from the patients' charts from January 2014 to December 2017 were collected at the hospital of our service. This information is confidential according to the researcher commitment form.

Surgical technique
The patient is placed in the prone position with a cushion placed under the affected leg ( Figure 1). A longi-tudinal incision is made in the distal posterolateral region of the leg in the center of the space between the Achilles tendon and the fibula (6,10,11) . Identification and protection of the sural nerve and the small saphenous vein should be prioritized since this nerve runs from the central to the lateral side of the Achilles tendon at approximately 10mm from the insertion of this tendon in the calcaneus (12) . The surgeon should be aware that the anatomy of the sural nerve is variable and exercise appropriate caution, with meticulous blunt soft tissue dissection to avoid injury and the formation of local neuromas (13) .
The posterior fascia of the leg is opened, and the flexor hallucis longus tendon and muscle are identified. These structures are elevated from the posterior aspect of the tibia, allowing access to the posterior malleolus (10) . Preservation of the posterior tibiofibular ligament and its capsular insertions and insertions in the bone fragment is critical. The fragment should be opened in book form for direct inspection of the joint. Local fixation can be performed with a posterior plate, which provides an anti-shear stop (preferred in our service), or screws placed in the posterior to anterior direction according to the need for stabiliza-tion and the size of the fragment (Figures 2, 3 and 4) (6,7,10,11) . Posterior malleolus fracture must be treated before other lesions for better articular manipulation and visualization and for fluoroscopic verification of reduction without interference from other implants.
The proximal fascia of the fibular tendons is opened longitudinally following the incision (the distal retinaculum is kept intact), and these tendons can be removed medially or laterally, allowing identification and evaluation of fibular fractures (6) . Such fractures are usually fixed with   a plate and cortical screws from posterior to anterior, with the plate placed under the anti-shear principle ( Figure 2). However, this construction may vary according to the fracture pattern and comminution observed (14) .
For fractures of the posteromedial component of the posterior malleolus, a new posteromedial access approach can be used. Despite slightly more difficulty, this approach also allows access to simple fractures of the medial malleolus or injuries of the deltoid complex. The procedure is concluded by suturing in layers, focusing on closure of the fibular muscle fascia. Dressing is followed by postoperative immobilization with a long-leg orthosis. The patient is instructed to avoid weight-bearing but to engage in early mobilization until the third week. Then, progressive partial weight-bearing with a boot is initiated. Physical therapy is performed from the first week to the fifth month after surgery.

RESULTS
According to Table 1, five female and two male patients were included in the case series. Four patients had fractures on the left side and three had fractures on the right side. The mean VAS pain score was 1.5 (1.6-3) and the mean AOFAS score was 92.5 (80-100). The mean follow-up time was 15.4 months (6-36 months). All patients presented clinical and radiographic consolidation of the fractures at the sixth week (4 to 8 weeks) of the follow-up.
At the end of the follow-up, no evidence of joint degeneration was noted, and clinical symptoms of arthrosis were correlated with radiographic findings. Although only early results were available for the cases with a shorter follow-up, the cases with a longer follow-up presented similar results.
Only one minor complication, superficial wound dehiscence, was reported, which was treated with dressings and closed on the seventh week without compromising the final functional and clinical result.

DISCUSSION
Few studies have directly addressed the results of using posterolateral access to treat ankle fractures. In 1974, Miller (15) reported 5 cases of internal fixation of the posterior malleolus through posterolateral access, with few details regarding the technique and the outcomes of his patients.   Subsequently, Heim (16) reported a larger case series of 60 patients treated for trimalleolar fractures; only 16 patients were surgically treated using posterior access, and this technique was noted to be potentially useful for small fragments, but no details regarding the results of the patients were provided. In a more recent report, Carmont and Davies (10) describe the similarity of this technique used in the ankle to the use of volar access to the wrist, but no cases or results were reported. The results of the present study are similar to those obtained by Abdelgwad et al. (11) with regard to scarring and the occurrence of few local complications. In their study, Abdelgawad et al. (11) evaluated 10 patients with a minimum follow-up of 2 months, and no local dehiscence or signs of infection were observed. Additionally, complete consolidation was noted in all patients by the fourth postoperative month.
Anatomical reduction of joint surfaces is a basic principle in the surgical treatment of fractures considering that joint irregularities affect the biomechanics of the joint and can lead to joint degeneration. Accordingly, fractures of the posterior malleolus should be treated pursuant to the same principle since they affect the distal articular surface of the tibia. Thus, anatomical reduction should be performed whenever possible, regardless of the technique used. For fractures of the posterior malleolus, complete reduction using the standard indirect technique with screws placed from anterior to posterior has been reported to be performed in only 27% of cases, with a reduction rate of 83% by direct visualization (17) . The posterior approach allows objective visualization of the posterior malleolus, enabling removal of interposed callus or periosteum and management of talar chondral damage or injuries due to impaction of the tibial plafond, which are important when surgical treatment is delayed and early consolidation prevents mobilization of the fragment to the appropriate position (6,7) .
The posterior approach also allows placement of additional fixation to the posterior malleolus, such as a plate to counteract the shear forces occurring at this site during weight discharge (Figure 4). Fixation of small fragments of the posterior malleolus can create a more stable construction and assist in syndesmosis stabilization, thus facilitating patient rehabilitation (7) .
Despite the favorable results associated with this technique, caution should be exercised during its execution, especially in dissection and protection of the sural nerve (6,10) . Positioning of a posterior plate in the fibula can cause friction symptoms in the fibular tendons, necessitating subsequent removal of the fixation. One of the disadvantages of this technique is greater difficulty in treating medial injuries and in approaching possible associated lesions of the hindfoot and midfoot (6,7) .

CONCLUSION
Posterior access is a viable alternative that provides favorable results for the treatment of posterior malleolus fractures and can be considered a feasible technique with few complications for ankle fixation.