The primary focus of this study was to assess the postoperative midterm outcomes for patients with DIACF treated with a 2-point distractor method.

The current treatment of choice for displaced intra-articular fractures of the calcaneus is controversial. Although ORIF has the possibility of anatomical reduction, its main disadvantages remain as wound complications and infections are reported in up to 30% of patients [8]. To reduce these complications, many techniques for minimally invasive reduction and fixation of DIACF have been developed. In recent years, percutaneous fixation, external fixation, arthroscopically assisted fixation and minimal incision techniques have been described in the literature [9]. Percutaneous reduction and fixation with cannulated screws has therefore gained more popularity in the treatment of calcaneal fractures. Due to the advantages of minimally invasive surgery, they offer less morbidity, earlier recovery, a potentially decreased rehabilitation period and less tissue traumatization [10].

Most cases of calcaneal fractures are associated with severe swelling after injury, and an early operative intervention of intra-articular calcaneal fractures is extremely crucial [11]. To achieve the best results, timing is an important factor and surgery should be done within 5 days, especially percutaneous or minimally invasive surgery [12]. Percutaneous fixation techniques can be done within a short time after injury. Rodemund et al. [6]described a time to surgery of 2.7 days, which is even faster than our results of 4.5 days.

The AOFAS score provides a widely used tool for evaluating functional outcomes in patients with foot injuries. The reported AOFAS hindfoot scores for minimally invasive procedures are around 76–83 [13]. A probable explanation for the general heterogeneity in the literature is the different types of fractures and the different times of follow-up [14].

We reported a mean score for AOFAS of 81 and for MFS of 78 for follow-up, which were almost equal if compared to studies with comparable surgical techniques. Tomesen et al. achieved mean values of the AOFAS and MFS scores 84.1 and 86.4 points, respectively, with a mean follow-up of 66 months [15]. Schepers et al. used the technique described by Forgon in 61 calcaneal fractures. In that study, the mean values of the AOFAS and MFS scores were 83 and 79 points, respectively [16].

Evaluation of the outcome of DIACF can be challenging because of the many different available methods. A relatively common approach is using radiological measurements, such as the Böhler angle and the Gissane angle. These two parameters allow a relatively fast and easy evaluation of the anatomical position of the calcaneus [17].

The postoperative Böhler angle for patients treated with ORIF is described as around 26° [18, 19]. We achieved mean results between 27° and 30°, which is in line with other minimally invasive procedures, which were between 26° and 28° [12, 14]. At the follow-up time, a reduction of around 4–6° seems to be common [19, 20]. Our results are slightly lower with around 2°. The reason might be due to an increase of axial loading as once the patient starts with weight bearing the Achilles tendon and the foot flexors pull the calcaneus towards the talus [19]. A similar outcome can be observed for the Gissane angle [21].

Infections after calcaneal fractures are a problem. A significant advantage of a minimally invasive technique is the comparably lesser risk of postoperative infections and soft tissue damage. The main purpose of fixation with an external device is to provide sufficient reduction while avoiding the exposure of soft tissue [22]. The ORIF procedures within the first week post-injury lead to an increased incidence of wound healing problems [23]. Backes et al. reported an infection rate for ORIF of 2–25% of patients treated with the ORIF approach, with a 21% chance for further surgical revision [24]. The prospective randomized multicenter study of Buckley et al. in 2002 with over 300 DIACFs showed a superficial infection and wound complication rate of 17% for ORIF [25].

Infections with the minimally invasive approach are described to be between 3% and 18% [13, 26]. Our collective showed an infection rate of 5%, which is comparable to other minimally invasive techniques. It should be noted that these were superficial wound infections.

In our study 5 patients (8%) required secondary subtalar arthrodesis, which is slightly higher than the reported rate of the literature with 2.1–7.3% [11, 19] and less than in non-surgically treated patients. Buckley et al. reported about 4% arthrodesis for the ORIF group versus 20% in the conservative group [25]. A reason for our results could again be the higher number of patients with severe fractures as 16 patients (27%) were classified as Sanders type IV and a secondary subtalar arthrodesis was necessary only with these patients.

Many authors agree that treating Sanders types III and IV calcaneal fractures can be challenging and that the calcaneal joint surface is often extensively damaged [27]. Therefore, almost 70% of Sanders type IV comminuted calcaneal fractures can lead to posttraumatic arthritis, while 73% lead to secondary subtalar arthrodesis according to Sanders et al. [13]. Many studies assumed that severe cases with major changes of the Böhler’s angle are at high risk of developing posttraumatic arthrosis and lead to subtalar arthrodesis even with operative fixation and anatomical joint reduction techniques [28].

Lesions and displacement of the peroneal tendon accompanies an intra-articular calcaneal fracture and an anatomical fixation does not guarantee a stable tendon reposition [29].

According to Touissant et al. tendon dislocation often stay undetected. They showed a prevalence of 28% and a significant correlation with Sanders type IV fractures. They suggest furthermore that while ORIF and restoration of the normal anatomy can allow the tendons to be restored to their anatomical position, with the minimally invasive technique, these lesions have a high risk to stay untreated. Nonetheless, is has to be noted that this topic is rarely dealt with in the literature [30].