The management of displaced intra-articular calcaneal fractures (DIACFs) remains challenging and controversial [1]. Open reduction and internal fixation (ORIF) through an extensile lateral approach has been widely accepted and established as a standard treatment for DIACFs [2, 3]. However, a fairly high wound-related complication rate has been reported with this approach, including wound edge necrosis, dehiscence, hematoma, infection and injury to the sural nerve [4–7].

In an attempt to lower the complication rate, various minimally invasive techniques have recently been introduced, including external fixation, percutaneous fixation, arthroscopically assisted fixation, and minimal incision techniques via medial, modified lateral (such as the sinus tarsi approach), longitudinal, or combined approaches [8–14]. These techniques have been reported as effective in minimizing soft tissue trauma, thereby reducing the incidence of wound-related complications.

As one of the most popular and effective minimally invasive techniques, the sinus tarsi approach not only can fully expose the posterior facet and the anterolateral fragment, but it also significantly reduces the incidence of postoperative wound complications [11, 12, 15]. In order to further shorten the operative time and decrease the wound complication rate, we introduced, in 2006, percutaneous reduction, cannulated screw fixation and calcium sulfate cement (CSC) grafting. A preliminary clinical study carried out by our team found that compared with the traditional L-shaped extensile lateral approach, this new technique allowed earlier weight-bearing, reduced subtalar joint stiffness and a reduced wound complication rate, while improving the patients’ satisfaction [16]. The purpose of the present study was to compare the functional and radiological outcomes and complications of our percutaneous reduction, cannulated screw fixation and CSC grafting with those of the minimally invasive sinus tarsi approach and plate fixation for treatment of DIACFs.

A total of 146 adult patients were assessed in our study (Fig. 3). Thirty-two patients did not meet the inclusion criteria and were excluded. Eighteen patients were excluded due to severe medical ailments (4 patients) and non-adherence to the treatment plan (14 patients). Therefore, 96 patients with an average age of 40.3 years old (range, 18 to 66 years) including 80 men and 16 women participated in the study. 16 patients were lost during the follow-up. A remaining of 80 patients (66 men and 14 women) were followed-up for 24 months averagely (range, 20 to 29 months).

The mean time from surgery to partial weight-bearing was comparable between the PR+CSC group and the MISTA group (6.2 weeks vs 6.0 weeks; p < 0.05). At the last follow-up, posttraumatic subtalar arthritis was observed in two patients in the PR+CSC group and one patient in the MISTA group as shown by radiographs.

The optimal management of displaced intra-articular calcaneal fractures remains controversial [1]. An increasing number of studies have shown a trend toward better functional outcomes in the operatively managed groups than those treated non-operatively [18, 19]. However, the high concern about wound-related complications with the extensile lateral L-shaped approach has troubled many orthopedic surgeons [7]. The complication rate after surgical treatment has been reported to range from 11 to 25 % [4–7, 20, 21]. As one of the most widely applied minimally invasive techniques, the sinus tarsi approach has the advantage of direct visualization of the posterior articular facet and fewer wound-related complications [11, 12, 15]. In order to minimize the wound-related complications and explore the optimal treatment for DIACFs, in 2006, we introduced percutaneous reduction, cannulated screw fixation and CSC grafting for treatment of DIACFs. We reported the first clinical data using this technique to treat 90 patients with 90 DIACFs in an article published in 2011 [16]. We found that, compared with ORIF, this minimally invasive technique allowed earlier weight bearing, reduced subtalar joint stiffness, and improved patient satisfaction. To further optimize the minimally invasive percutaneous technique in the treatment of DIACFs, in this study, we aimed to compare the functional outcomes, radiographic results and the postoperative wound-related complications between the minimally invasive percutaneous fixation and the minimally invasive sinus tarsi approach.

The assessment of functional outcomes in our study revealed an overall good to excellent rate of 81.0 % in the PR+CSC group compared with 89.5 % in the MISTA group. The mean AOFAS score was 84.6 in the PR+CSC group, which was higher than that 82.5 in the MISTA group. However, both differences were not statistically significant. There was also no significant difference between the two groups in terms of the good to excellent rate for Sanders Type-II fractures. Wang YM et al. reported percutaneous reduction and Steinman pin fixation minimized complications and achieved functional outcomes comparable to those of the open techniques in patients with Sanders Type-II calcaneal fractures [22]. For Sanders Type-III fractures, however, the MISTA group could achieve better functional outcomes than the PR+CSC group. For this reason, we believed that the minimally invasive sinus tarsi approach was superior to the percutaneous cannulated screw fixation in acquiring a better articular surface reduction, especially for Sanders Type-III fractures. Thus different functional outcomes may be attributed to different qualities of articular reduction. Consistently, Mulcahy et al. also suggessted that a minor residual step-off of the posterior facet could cause a significant load shift within the subtalar joint [23], which might have an adverse effect on functional outcome [24, 25]. Therefore, using the percutaneous reduction and cannulated screw fixation to treat comminuted calcaneal fractures may carry a risk of inadequate reduction of the articular surface.

The results analysis from the partial variables of the AOFAS scoring system suggested that patients in the PR+CSC group suffered from less pain, less activity limitations, less gait abnormality, and less demand on walking surfaces. Meanwhile, they obtained better sagittal motion and hindfoot motion than patients in the MISTA group. However, the difference was only statistically significant for two variables; sagittal motion and hindfoot motion, which suggests, compared with the minimally invasive sinus tarsi approach, that percutaneous reduction and cannulated screw fixation may be more minimally invasive and favor earlier and painless functional exercise.

The radiographic results revealed the significant differences between the two groups in terms of the calcaneal width immediately postoperatively and at the final follow-up. Therefore, the role of the percutaneous reduction and cannulated screw fixation restoring the calcaneal width was weaker than the minimally invasive sinus tarsi approach. Although it is known that the widened calcaneus is the main reason for patients suffering from lateral impingement syndrome [26–28], the difference in the overall functional outcomes between the two groups was not statistically significant. Our data suggested that the reduction of the posterior articular surface might be the most important factor associated with the functional outcome of calcaneal fractures [3, 24, 25].

The wound-healing complication rate was significantly lower in the PR+CSC group than that in the MISTA group (2.4 vs 18.4 %). The minimized disturbance to the blood supply and the soft tissue of the lateral aspect of the calcaneal [29], coupled with the significantly shorter operative time, may have contributed to the lower rate of wound-healing complications in the PR+CSC group. Furthermore, the PR+CSC group had a lower risk of sural nerve injury and musculus peroneus brevis injury compared with the MISTA group, however, the difference was not statistically significant. Although the overall complication rate was found to be quite high in the MISTA group, most of the complications appeared in the early days. The complication rate decreased significantly as our experience improved and the waiting time to operation extended.

There are a few limitations in this study. First, we had a relatively small number of patients and short average follow-up time. Therefore, further investigation with a larger sample size and longer follow-up time is needed to obtain more overall clinical data. In addition, the differences in surgeons’ performances might have decreased the generalization power of this study. Assigning all the patients to only one surgeon would be much beneficial to reduce the variability caused by the surgeon’s performance, but this would be practically impossible in our hospital. Furthermore, the quality of joint surface reduction was not specifically analyzed or compared between the two groups. It needs to be studied further.

The percutaneous reduction, cannulated screw fixation and CSC grafting for treatment of Sanders Type-II DIACFs can achieve almost equivalent functional outcomes compared with the minimally invasive sinus tarsi approach and plate fixation. The two techniques have their own advantages. The PR+CSC grafting is superior to the MISTA procedure in terms of the average time between initial injury and operation, operation time, wound-related complications and subtalar joint activity. However, the MISTA procedure has its own advantages in improving the calcaneal width, providing clear visualization and more accurate reduction of the articular surface, especially for Sanders Type-III DIACFs. The functional outcomes of Sanders Type-III DIACFs treated by MISTA excelled the PR+CSC grafting.

AOFAS, American Orthopaedic Foot and Ankle Society; CONSORT, Consolidated Standards of Reporting Trials; CSC, calcium sulfate cement; CT, computed tomography; DIACFs, displaced intra-articular calcaneal fractures; MISTA, minimally invasive sinus tarsi approach; ORIF, open reduction and internal fixation; PR, percutaneous reduction