Comparison of the direct and indirect reduction techniques during the surgical management of posterior malleolar fractures
© The Author(s). 2017
Received: 18 June 2016
Accepted: 6 March 2017
Published: 14 March 2017
The optimal method for the reduction and fixation of posterior malleolar fracture (PMF) remains inconclusive. Currently, both of the indirect and direct reduction techniques are widely used. We aimed to compare the reduction quality and clinical outcome of posterior malleolar fracture managed with the direct reduction technique through posterolateral approach or the indirect reduction technique using ligamentotaxis.
Patients with a PMF involving over 25% of the articular surface were recruited and assigned to the direct reduction (DR) group or the indirect reduction (IR) group. Following reduction and fixation of the fracture, the quality of fracture reduction was evaluated in post-operative CT images. Clinical and radiological follow-ups were performed at 6 weeks, 3 months, 6 months, 12 months, and then at 6 month-intervals postoperatively. Functional outcome (AOFAS score), ankle range of motion, and Visual Analog Scale (VAS) were evaluated at the last follow-up. Statistical differences were compared between the DR and IR groups considering the patient demographics, quality of fracture reduction, AOFAS score, and VAS.
Totally 116 patients were included, wherein 64 cases were assigned to the DR group and 52 cases were assigned to the IR group. The quality of fracture reduction was significant higher in the DR group (P = 0.038). In the patients who completed a minimum of 12 months’ follow-up, a median AOFAS score of 87 was recorded in the DR group, which was significantly higher than that recorded in the IR group (a median score of 80). The ankle range of motion was slightly better in the DR group, with the mean dorsiflexion restriction recorded to be 5.2° and 6.1° in the DR and IR group respectively (P = 0.331). Similar VAS score was observed in the two groups (P = 0.419).
The direct reduction technique through a posterolateral approach provide better quality of fracture reduction and functional outcome in the management of PMF over 25% of articular surface, as compared with the indirect reduction technique using ligamentotaxis.
NCT02801474 (retrospectively registered, June 2016, ClinicalTrails.gov).
KeywordsPosterior malleolar fracture Posterolateral approach Buttress plate Ligamentotaxis
The incidence of the posterior malleolar fracture (PMF) was reported to be 7 to 44% of all ankle fractures . Despite of the evidence provided by anatomical and biomechanical studies that the posterior malleolus serves as an important contributor to the stability of ankle mortise and syndesmosis, the indication of surgical reduction and fixation of PMF remains controversial [2–4]. Fragment size is frequently used as a reference for surgical intervention, and the posterior malleolar fracture involves more than 25% of articular surface is generally recommended to be reduced and fixed to prevent instability and reduce the risk of post-traumatic degenerative changes .
The optimal method for the reduction and fixation of PMF remains inconclusive. Often, the posterior fragment, also known as Volkmann’s fragment, reduces simultaneously via ligamentotaxis of the posteroinferior tibiofibular ligament (PITL) following an anatomical reduction of the lateral malleolus . Following this indirect reduction procedure, percutaneous screw fixation can be achieved through a stab incision. Alternatively, the posterior malleolus fragment can be direct visualized and reduced through a posterolateral approach with the patient in a prone position . Buttress plate or lag screws can then be placed to stabilize the fragment.
Currently, both of the indirect and direct reduction techniques are widely used among orthopaedic surgeons during the operative treatment of PMF, while conflicting data has been published regarding the subsequent clinical outcomes [7–10]. Few studies could be found comparing the quality of fracture reduction, as well as the functional and clinical outcomes between the indirect and direct reduction techniques. In this study, we aimed to compare the reduction quality and clinical outcome of PMF managed with the direct reduction technique through a posterolateral approach or the indirect reduction technique using ligamentotaxis.
This study was approved by the ethics committee of the authors’ institution (Ref. No. 115690). Between January 2012 and December 2014, patients with a posterior malleolus fracture were recruited as candidates for this prospective study. Following screening by two of the senior surgeons (HFS and XSQ), the patients were finally included meeting the inclusion criteria of (1) age between18 to 70 years, (2) unstable and displaced (more than 2 mm) posterior malleolar fractures requiring surgical management, (3) posterior malleolar fragment involving over 25% of the articular surface measured in preoperative lateral view radiographs and sagittal reconstruction of CT images. Patients with open fractures, pathological fractures, delayed fractures, or additional ipsilateral lower extremity fractures were excluded. Informed-consent documents were obtained from all the eligible patients that stated the aim and protocol of this study. Preoperative anteroposterior (AP), lateral, and mortise view radiographs as well as computed tomography (CT) scans were routinely obtained to evaluate the characteristic of the fracture according to the Lauge-Hansen classification and AO/OTA classification. The injury mechanism was recorded as low-energy injury (a small-level fall or a sprain) or high-energy injury (a motor-vehicle accident or a fall from a height > 1 meter). Patients were then assigned to the direct reduction (DR) group or the indirect reduction (IR) group by monthly turns.
In the IR group, the lateral and/or medial malleolar fractures received open reduction and internal fixation (ORIF) using standard AO (Arbeitsgemeinschaft für Osteosynthesefragen) osteosynthesis technique with the patients in supine position. Anatomical reduction of the lateral and/or medial malleolus was confirmed under fluoroscopy. The posterior malleolus was then reduced through ligamentotaxis with the ankle in dorsiflexion. If necessary, percutaneously applied pointed reduction forceps, bone hook, K-wire, or periosteal elevator was used to reduce the posterior malleolar fragment anatomically [13, 14]. Intraoperative lateral view radiographs were taken using C-arm to verify the reduction. One or two 4.0 mm cannulated screws were then used to fix the posterior malleolar in anterior-to-posterior direction.
In both groups, intraoperative external rotation stress test and Cotton test were performed to evaluate the stability of syndesmosis following reduction and fixation of the fractures. Syndesmotic screws were placed when positive results were observed in the external rotation stress test (increased medial clear space at the ankle mortise) or in the Cotton test (>2 mm of lateral migration of the lateral malleolus) [15, 16].
Postoperatively, all the fractures were stabilized with a short leg splint for 2 weeks, followed by 4 weeks of non-weight-bearing rehabilitation focusing on the range of motion. Regular clinical and radiological assessments were performed at 6 weeks, 3 months, 6 months, 12 months, and then at 6 month-intervals according to our routine follow-up regime. Progressive weight bearing and strengthening was initiated since 6 weeks postoperatively, with reference to the healing status checked in follow-up radiographs. The syndesmotic screws were removed, if any, at 3 months postoperatively.
Postoperative radiographs and CT scan were obtained routinely to evaluate the quality of fracture reduction. The maximum residual displacement of the posterior malleolus, the gap in the joint surface, and/or the articular step-off were measured in sagittal cuts of the CT scan. The quality of fracture reduction was graded as excellent (less than 1 mm), good (1 to 2 mm), or poor (more than 2 mm) as described in literature .
Functional outcome was evaluated according to the American Orthopaedic Foot and Ankle Society ankle-hindfoot score (AOFAS) at the last follow-up . The ankle range of motion (ROM) was measured, and the difference of the dorsiflexion between the injured and uninjured side was calculated and presented as dorsiflexion restriction [19, 20]. Visual Analog Scale (VAS) was used to evaluate local pain.
All the evaluations were performed by two of the senior surgeons (JFW and YHW) independently. The interobserver quantitative data were averaged for further statistical analysis. IBM SPSS version 19.0 software (SPSS Inc., Chicago, IL) was used with the statistical significance set at a P value of less than 0.05. The assumption of normal distribution of the parametric data was testified using Q-Q plots. Demographics of the two groups were compared using independent t test or Chi-Square test. The quality of fracture reduction were compared using Chi-Square test. The AOFAS score and VAS were analyzed using Mann-Whitney U test to compare the difference between groups.
Patient demographics and results
Direct reduction group
Indirect reduction group
No. of patients
49.0 ± 12.4
48.1 ± 15.2
Time before surgery (days)
4.3 ± 2.0
4.5 ± 2.8
Quality of reduction
Follow-up duration (months)
19.9 ± 5.2
20.0 ± 5.8
87 (58 to 95)
80 (59 to 95)
Dorsiflexion restriction (°)
5.2 ± 4.5
6.1 ± 4.3
2 (0 to 7)
2 (0 to 7)
As measured in the postoperative radiographs and CT scan, 34 (53.1%) and 16 (30.8%) patients achieved excellent fracture reduction in the DR and IR group respectively (Table 1). The percentage of excellent fracture reduction was 22.3% higher in the DR group than in the IR group. A good fracture reduction was observed in 25 (39.1%) patients in the DR group and in 27 (51.9%) patients in the IR group. The percentage of excellent or good reduction was 9.5% higher in the DR group than in the IR group. More than 2 mm residual fracture displacement and/or articular step-off were found in 5 (7.8%) patients in the DR group and in 9 (17.3%) patients in the IR group. The quality of fracture reduction was significant higher in the DR group compared with that in the IR group (P = 0.038).
No major intraoperative complications was observed. Two patient in the DR group developed superficial infection postoperatively. Both of them were managed successfully with local dressing changes and oral antibiotics. Calf muscle vein thrombosis was diagnosed in one patient in the DR group and two patients in the IR group during follow-up. Therapeutic dosages of low-molecular-weight heparins (LMWH) was prescribed till thrombolysis confirmed using color duplex Doppler ultrasound. Fracture nonunion, implant loosening or failure was not observed in each of the groups.
Surgical management of ankle fractures aims to achieve articular congruity, ankle alignment and stability with maximal functional recovery. Unlike the studies on the management of lateral and medial malleolar fractures, the surgical indication and optimal technique for the management of PMF remains inconclusive. In the study, we compared the radiological and functional outcome of PMF managed with the direct or indirect reduction technique. Higher quality of fracture reduction and better functional outcome were achieved when the PMF was treated with direct reduction technique through a posterolateral approach, while similar ankle range of motion and VAS score were observed when compared with the patients managed with the indirect reduction technique using ligamentotaxis.
Several factors might contribute to the better quality of fracture reduction achieved via the direct reduction technique. First, it’s more convenient to use the typical metaphyseal-diaphyseal spike of the posterior malleolus as reference to reduce the posterior fragment when exposed through the posterolateral approach. Second, fixation of small posterior malleolar fragment to larger distal tibia might be biomechanically stronger than anterior-to-posterior screw fixation, which would help to achieve better interfragmentary compression and reduce gaps between the posterior fragment and distal tibia . Gravity would also help to reduce the talus and PMF in prone position. In case of the occurrence of articular impaction, the posterior lateral approach might provide adequate visualization of the posterior fragment compared with the indirect reduction technique. The impacted articular fragment could then be meticulously accessed and reduced through fracture line or via cortical window.
Despite of the advantages described above, the direct reduction technique did not prevail over the indirect reduction technique in clinical practice . It was reported that 83% of posterior malleolar fractures were fixed using anterior-to-posterior screws with indirect reduction technique.  Some authors believed that indirect reduction and percutaneous screw fixation were less traumatic, while posterolateral approach might increase the risk of posterior scarring, tendon impingement, and sural nerve injury [27, 28]. Provided that PITL was intact, the posterolateral fragment could be easily reduced using ligamentotaxis following anatomical reduction of the fibula . However, when the PMF was severely comminuted, impacted, or accompanied by medial extension (described as Haraguchi type-II fracture), direct reduction technique was preferred  (Fig. 1).
Functional outcome of ankle fractures was believed to be associated with fracture morphology, articular involvement, fracture fragment size, severity of comminution, and residual step-off or gaps. In our study, provided a better quality of fracture reduction, the DR group presented significantly higher AOFAS score than the IR group. The ankle range of motion, on the other hand, was only slightly better in the DR group, as reflected by the recorded dorsiflexion restriction. In literature, very different results were reported considering the functional outcome of PMF following surgical reduction and fixation. Choi reported a mean AOFAS score of 90.6 following ORIF of PMF through a modified posterolateral approach . Erdem achieved a mean AOFAS score of 94.1 of PMF following posterior-to-anterior lag screw fixation or buttress plate fixation through posterolateral approach . Compared with our study, the patients with a PMF smaller than 25% of articular surface were included in these studies, which might contribute to the higher AOFAS scores reported in these studies. Besides, the pilon-type PMFs, characterized by posteromedial fracture extension to the medial malleolus with varying articular impaction, were exclude from Erdem’s study . The pilon-type PMFs were generally believed to lead to inferior functional outcomes than regular ankle fractures [31–33]. Evers and Drijfhout van Hooff reported mean AOFAS scores of 70.9 and 81 in their studies respectively, wherein the PMFs greater than 25% of the joint surface were fixed [9, 20]. These results were similar with our study, while detailed techniques of fracture reduction and fixation, unfortunately, were not described in these two studies.
In this study, as one of the limitations, the radiographic osteoarthritis status was not graded or compared between groups due to limited time of follow-up . Theoretically, an anatomically reduced and fixed posterior malleolus would provide important buttress to contain the talus, stabilize syndesmosis, and reduce the risk of post-traumatic osteoarthritis . Future study with long-term follow-up results would provide further information considering the influence of different rate of anatomical reduction on the grade of post-traumatic arthrosis between the DR and the IR groups.
In conclusion, the direct reduction technique through a posterolateral approach provide better quality of fracture reduction and functional outcome in the management of PMF over 25% of articular surface, as compared with the indirect reduction technique using ligamentotaxis.
American Orthopaedic Foot and Ankle Society
Open reduction and internal fixation
Posteroinferior tibiofibular ligament
Posterior malleolar fracture
Range of motion
Visual Analog Scale
We would like to thank Li-ping Chen, Xiao-xia Zhong, and Bei Cheng for their assistance during patient recruitment and data collection.
This study was supported by the National Natural Science Foundation of China (81401793, 81572132, and 81271997) and the Six Talent Peeks Project in Jiangsu Province (2016-WSW-060).
Availability of data and material
Results from the dataset are presented in this paper. The full dataset is available from the first and corresponding authors upon request.
All authors read and agreed with the contents of the manuscript. HFS and JX participated in the study design. The patients included in this study were screened by HFS and XSQ, and then were operated on by JX and YXC. JFW and YHW performed the radiographic evaluations and functional assessments. HFS was in charge of interpreting the data analysis and drafting the manuscript. JH, XYG and SYW assisted in revising the manuscript.
There’s no competing interest. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.
Consent to publication
Written informed consent was obtained from each patient for publication, along with any accompanying images.
Ethics approval and consent to participate
This study was approved by the Medical Ethics Committee of Nanjing Drum Tower Hospital (Ref. No. 115690).
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