Introduction

Calcaneal fractures account for only 2% of all fractures, but they represent 60–75% of all tarsal fractures. About 10% are bilateral calcaneal fractures. For the patient, this injury represents a life-changing event with questionable return to work [1,2,3].

Calcaneal fractures are usually accompanied by varus malalignment, plantar widening and, above all, a reduction or even negation of the Böhler angle. The last-mentioned factor represents an essential success control and is one of the measured outcome parameters.

Owing to its complexity, surgical treatment still remains a challenge in calcaneal fractures; the extensile lateral approach is still one of the most frequently used methods for treatment [4,5,6,7,8,9].

However, given the high complication rates reported, this approach has become increasingly less popular. The demand for minimally invasive approaches as well as the comparative results with conservative therapy has regained popularity [10, 11].

Despite critical examination of the choice of approach and constant improvement of surgical instruments and osteosynthesis material, it is not always possible to achieve a satisfactory outcome. The possible causes include material failure, implant loosening, early and late infections, malunion, nonunion, and posttraumatic arthrosis [12]. On the patient side, nicotine abuse, being overweight, diseases such as diabetes mellitus, and lack of compliance are contributing factors [13,14,15].

In this study, we evaluated the role of the surgeon in the treatment of displaced intra-articular calcaneal fractures.

Patients and methods

Population

In this retrospective study, all calcaneal fractures treated in the study center between 2014 and 2017 were recorded. A total of 192 fractures were identified from the clinic's internal database. Taking into account the inclusion and exclusion criteria (Fig. 1), 120 patients were considered eligible, of which 86 patients with 94 fractures (74 male, 78.7%; 20 female, 21.3%) were finally included in the study. The remaining patients refused to participate in the study or could not be contacted. The mean age at surgery was 51 (range: 22–76) years (Table 1, Fig. 1). The patients included in the study were invited, in writing, to a follow-up examination. The mean follow-up time was 3.2 (range: 2.6–3.9) years.

Fig. 1
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Flow chart

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Table 1 Patient characteristics and type of fracture (n = 94)
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Inclusion and exclusion criteria

The inclusion criteria were: only displaced intra-articular calcaneal fractures (AO C1-3 classification) in patients who underwent surgery exclusively at our study center; treatment using locking compression plate via the extensile lateral approach (ELA); and a minimum age of 18 years and a written declaration of consent to participate in the study. The exclusion criteria were patients with concomitant or previous injuries and those with non-displaced or extraarticular calcaneal fractures.

Assessments methods

In this study, fractures were classified according to Sanders and the modified AO classification [16, 17]. Demographic data, body mass index (BMI), and nicotine abuse were recorded.

The AOFAS-Score (American Orthopedic Foot and Ankle Society), the Kiel score for calcaneus fractures, and the VAS FA (Visual-Analogue-Scale Foot and Ankle) were used to assess quality of life and performance. Furthermore, the duration of surgery and time of incapacity to work were recorded.

In addition, the documentation of possible complications such as infections, revision procedures, material removal, and subtalar arthrodesis was carried out during the course of the procedure. In addition, an assessment of the preoperative and current Böhler angle was performed in the radiographic control.

All results were classified into treatment by particularly experienced surgeons (ES, n = 2) and less experienced surgeons (LES, n = 2). The term “experienced surgeon” was derived based on the number of calcaneus fracture treatments that were performed independently. Regardless of the study, the average number was 30 per year. In the LES group, less than 10 per year calcaneus fracture treatments were performed by the surgeon. In the present study, 60 and 34 fractures were treated by particularly experienced and less experienced surgeons, respectively. Furthermore, the scores of all surgeons were compared over time (“treatment in early half of the study” and “late half of the study”).

All procedures performed in this study were in accordance with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. The ethics committee of the institutional review board approved this study (FF 92/2016). Informed consent was obtained from all patients. None of the authors have any conflict of interest to declare.

Surgical procedure

The treatment of complex intra-articular calcaneal fractures (AO C1-3) was performed routinely by means of locking compression plate via the ELA with closed femoral blood vessels. Intra-operative fluoroscopic 3D-imaging for reduction control was used routinely [18]. All operations were performed according to a standardized procedure at the specialist level (Figs. 2, 3a, b) [19]. In two cases, 2–3° open fractures were initially treated with an external fixator [20]. The definitive treatment of all fractures took place on average after 7 days.

Fig. 2
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a Calcaneal fracture intraoperatively before reduction. b Calcaneal fracture intraoperatively after reduction

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Fig. 3
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a Preoperative computer tomography. b Intraoperative C-arm 3D-imaging

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The goal of any treatment is always preservation of the subtalar joint. To avoid overloading the neighboring joints with resulting arthrosis of the upper ankle and Chopart' joints, the authors felt the need to preserve the lower ankle joint [21]. An arthrodesis was considered the ultima ratio.

Rehabilitation protocol

The post-treatment recovery provided for wearing an orthotic boot for 12 weeks on forearm crutches for 6 weeks, 24 h/day with sole contact. Removal of the boot for personal hygiene and physiotherapy was permitted. Six weeks postoperatively, radiography was followed by subsequent load build-up over the next 6 weeks. During the load build-up, the boot could be removed at night. At 12 weeks postoperatively, computed tomographic (CT) imaging was carried out before granting permission to wear normal street shoes.

An exception to this scheme was made for the nine bilateral fractures. After the 6-week relief, the weight was alternately applied in the wheelchair and on the anti-gravity treadmill (AlterG®). In addition to gait training, the accompanying physiotherapy included lymphatic drainage, toe mobilization, and active-assistive exercise of the upper ankle joint.

Statistical analysis

It is a monocentric comparative case study with data collection averaging 3.2 (2.6–3.9) years postoperatively. Case number calculation was omitted in the sense of the retrospective design. The statistical analysis was conducted using IBM SPSS Statistics version 23 (IBM Dtl. GmbH, Ehningen, Germany) and JASP 0.12.1 (2013–2020 University of Amsterdam, Netherlands). Mean values from the ES and LES groups were compared using the Student's t-test for independent samples. The significance level was set at p < 0.05.

Results

As shown in Table 1, there was an equal distribution of demographic data; risk profile (age, nicotine abuse, BMI); and fracture type in both groups.

The fractures were always displaced intra-articular calcaneal fractures of Sanders type 3 and 4 (Sanders 3: 57.4%, Sanders 4: 42.6%) or AO C1-3 (Table 1, Fig. 4a–c). All patients were treated by locking compression plate via the extensile lateral approach.

Fig. 4
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a–c Outcome scores (LES less experienced surgeon, ES experienced surgeon)

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Scores

The mean AOFAS, VAS FA, and Kiel scores of all patients was 73.6 (range: 27–100), 65.8 (range: 20–100), and 60.7 (range: 12–99), respectively. The comparison of the results from the LES and ES groups showed significantly better results for the experienced surgeon in all presented scores (p < 0.05) (Table 2).

Table 2 Outcome
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Times

The mean duration of surgery was significantly longer in the LES group (128.4 min) than in the ES group (114.6 min, p = 0.047). The overall mean time of incapacity of all patients was 28.5 weeks (31.3 (SD: 27.4) vs. 26.8 (SD: 27.4) weeks, in the LES and ES groups, respectively (p > 0.05) (Table 2).

Radiological results

The radiographically determined Böhler angle improved from preoperative 11.5° to postoperative 32.8° in the Les group and from preoperative 8.1° to postoperative 31.8° in the ES group. Thus, the LES and ES groups achieved a mean improvement of 20.8° and 23.8°, respectively. The difference between LES and ES was not significant (p > 0.05).

Implant removal and complications

In 38 cases (40.4%), metal removal was carried out in the meantime because of local irritation. The frequency was quite similar in the two groups (23 [38.3%] vs. 15 [44.1%] in the ES and LES groups, respectively).

Regardless of group affiliation, 32 (84%) patients reported a subjective relief of symptoms after metal removal.

Five relevant complications with wound conditions required revision. Two cases could be treated by irrigation, superficial debridement. In the remaining three cases, a deep wound infection was detected, and the implant was removed prematurely. In two cases, a 3° open fracture was the cause.

Overall, one and four complications occurred in the ES and LES groups, respectively. The results of patients with bilateral fractures did not differ significantly from those with unilateral fractures in the 3-year study with regard to the parameters mentioned above and were therefore not listed separately.

In cases of advanced arthrosis of the subtalar joint, six subtalar arthrodesis (LES: 2, ES: 4) were performed in the further course of the procedure. Their results too did not differ significantly from the rest of the patients and are also not listed separately owing to the small number of cases.

Discussion

The results of our study confirm that surgeon’s experience is a particularly relevant influencing variable. We were able to show significant differences between the LES and ES groups.

As early as 1993, Sanders et al. published a paper on the outcome of osteosynthetically treated calcaneal fractures and observed the learning curve in the treatment. In the years 1987–1990, an improvement in the radiographic reduction result of type II and III fractures n. Sanders, but surprisingly not for type IV fractures.

However, the study at that time also included non-displaced type II fractures. And even a conservative treatment was part of the study.

In addition, the study was conducted before the advent of today's common use of locking compression plates [22]. The question regarding the role of the surgeon remained of unrestricted importance [23].

Recent studies have emphasized the need for exact anatomical reduction using locking plates [24]. Significant surgical expertise is required to achieve such a result. As reported by Persson et al., the Böhler angle was also used in the present study to assess the success of the procedure [25]. In the present study, the reconstruction of the Böhler angle, an important radiological feature, tended to be better for experienced surgeons, but this was not statistically significant. Irrespective of the frequent mentions, the actual significance of the Böhler angle must therefore be questioned. Furthermore, no positive correlation could be found between Böhler angles and the clinical scores discussed below.

A uniform recommendation for the radiological evaluation of the reduction result is missing in the literature so far [26]. The work of Keizer et al. in 2017, who initiated a uniform scoring protocol for radiological assessment, seems promising [27].

Ahn et al. 2019 proposed a trend-setting assessment of the surgeon’s learning curve. In all, 45 cases were CT-morphologically examined for the reduction result and Böhler and Gissane angles were compared. They concluded that a minimum of 20 fracture treatments of the calcaneus lead to significantly better results. This is consistent with the mean value between the ES and LES groups in the present study. Moreover, the mean surgery time was almost identical, at 117 min. However, the heterogeneous fracture classification (Sanders type 2–4) should be noted [23].

To reduce approach morbidity and the associated wound complications, the demand for less invasive approaches have been made in recent years. Stabilization of the calcaneus fracture is achieved either by minimally invasive plate osteosynthesis (MIPO) or treated by an intramedullary nail. The present study lacks a direct comparison of the bony reconstruction of the calcaneus using a locking compression plate versus the intramedullary nail. However, based on the clinical scores and complication rates, the locking compression plate shows comparably good results in a previously published study [28]. The present study with a large number of cases thus confirms that ELA remains a safe approach in the surgical treatment of complex intra-articular calcaneal fractures [4, 6, 29]. The alarming revision rates of over 25% due to wound infections and wound margin necrosis in the literature can, in the authors' view, be significantly reduced by careful soft tissue management [30,31,32,33].

The clinical results presented in the present manuscript are consistent with studies in the literature [34, 35]. The complication rate was remarkably lower than with the sinus-tarsi approach or a minimally invasive procedure [37]. The results of the present study confirm the surgeon himself as an important influencing factor [38]. In the authors' view, the low complication rate and comparably good results mean that the need for newer implants and minimally invasive approaches is secondary.

We agree with Rammelt et al. that an optimal result in surgical restoration can only be achieved with anatomically correct reduction. This ability is because of experience and the growing expertise of the surgeon.

If the reduction is insufficient, the disadvantages of surgical and non-operative treatment are combined [24]. Even though four of the five relevant complications occurred in the LES group, the overall acceptably low infection rate of 5.3% must be emphasized, especially with regard to the exclusively displaced fractures type AO C1-3.

It is noteworthy that nicotine abuse did not have a significant influence on the clinical scores in the present study. However, the aforementioned five complications all occurred in smokers, which likely confirms the known negative influence of nicotine abuse on soft tissue and bone healing [39,40,41,42].

In both groups, implant removal was performed with the same frequency in about 40% of patients, mainly owing to local irritation. The question of the benefit of a planned implant removal from the calcaneus after bony consolidation is still debatable [43], with a prospective comparison missing in published literature. In the present study, the majority of patients reported a significant reduction in symptoms after implant removal, but there was no objectifiable assessment of the symptoms prior to removal. The 10% wound infections reported by Backes et al. [44] after removal of material from the lower leg were not observed in our study.

The significantly shorter duration of operations in the ES group and the tendency towards a shorter period of incapacity to work after treatment by an experienced surgeon leads to expectations of cost efficiency from an economic perspective. For further proof of this assumption, subsequent studies would require an additional cost breakdown of reintegration measures and outpatient and inpatient rehabilitation.

Our study has some limitations. First is the retrospective design and the difference in group size between the ES and LES groups. Second is the lack of a uniform protocol for the evaluation of postoperative CT. The results of the present study show that the much-cited Böhler angle correlates only insufficiently with the clinical outcome. Therefore, the evaluation of the calcaneal height, arch collapse, and varus or valgus deformity of the calcaneus would be interesting in further studies.

The term “experienced surgeon” was derived from an observation of the annual fracture treatments performed on the calcaneus. The number of interventions after which this effect becomes significant should be compared in a prospective study based on the available results.

The use of the AOFAS score should be viewed critically, as it has not been validated for the German-speaking countries, and the quality of pain is of comparatively high importance. Nonetheless, the AOFAS score was used in this study because it is one of the best-known scores in literature, is used internationally, and is easily understood by patients. The Kiel Score is less common in international literature, but it has been validated for German-speaking countries and is highly specific for the injury pattern and, in the authors' view, is clearly underrepresented.

The strengths of the study are the high number of cases and the homogeneous injury pattern (AO C1-3) that were exclusively treated by means of locking compression plate via the extensile lateral approach.

Conclusion

We were able to show significant differences between the LES and ES groups especially in the clinical results. The high value of the Böhler angle as the most important radiological parameter could not be proven.

The significantly better clinical scores in ES with shorter duration of surgery, shorter time of incapacity, and lower complication rate prove the necessity to have displaced intra-articular calcaneal fractures operated upon by an experienced surgeon.

The overall low complication rate and comparably good results emphasize the need for surgical expertise and obscure the demand for minimally invasive approaches.