# Does the restoration of the hindfoot alignment correlate with good clinical and functional outcomes in displaced intra-articular calcaneal fractures treated with Calcanail®?

Adrien Rossetti, Julien Maximen, Robin Delacroix, Christophe Szymanski, Mickael Ropars, Louis Rony

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Adrien Rossetti, Julien Maximen, Robin Delacroix, Christophe Szymanski, Mickael Ropars, et al. Does the restoration of the hindfoot alignment correlate with good clinical and functional outcomes in displaced intra-articular calcaneal fractures treated with Calcanail®?. Orthopaedics & Traumatology: Surgery & Research, 2025, pp.104329. 10.1016/j.otsr.2025.104329. hal-05239776

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Original article

# Does the restoration of the hindfoot alignment correlate with good clinical and functional outcomes in displaced intra-articular calcaneal fractures treated with Calcanail®?

Adrien Rossetti<sup>a,*</sup> <sup> ID </sup>, Julien Maximen<sup>a</sup>, Robin Delacroix<sup>a</sup>, Christophe Szymanski<sup>a</sup>, Mickael Ropars<sup>a</sup>, Louis Rony<sup>b ID</sup>

ARTICLE INFO

Keywords:

Percutaneous intramedullary nailing

Fracture

Long axial view

AOFAS

ABSTRACT

**Introduction:** Calcaneal fractures are quite common and can lead to serious functional consequences. Minimally invasive percutaneous techniques have reduced the incidence of wound and sepsis complications associated with open reduction and internal fixation. The use of intraosseous internal fixation, such as percutaneous intramedullary nailing, has decreased these complications and yielded good functional outcomes. The aim of this study was to assess the correlation between functional outcomes and the restoration of hindfoot alignment according to the long axial view in calcaneal joint fractures treated with percutaneous intramedullary nailing.

**Hypothesis:** Internal fixation using percutaneous intramedullary nailing restores hindfoot alignment associated with good functional outcomes.

**Materials and methods:** This was a retrospective single-center, multi-surgeon study involving 20 cases of displaced intra-articular calcaneal fractures treated with a percutaneous nail device (Calcanail®) between 2018 and 2022, with a minimum follow-up of one year. Among these, 11 were classified as Sanders-II and nine as Sanders-III fractures. The primary endpoint was clinical evaluation using the AOFAS scale (/100) and the investigation of a correlation with the radiographic hindfoot alignment according to the long axial view. NRS pain scores, EFAS functional scores (/24), SF-12 scores, and all complications were recorded. Clinical and radiographic follow-up data were analyzed in comparison to the healthy contralateral side at the final follow-up.

**Results:** The mean follow-up time was 40.1 months ± 14.0 (13–62). A correlation was found between hindfoot alignment and the AOFAS score ($r_s$ = -0.494, p = 0.026). The NRS at the last follow-up was 1.3 ± 1.9 (0.0–6.0). The mean AOFAS score was 81.8 ± 9.6 (57.0–92.0), and the EFAS score was 17.3 ± 3.7 (4.0–21.0).

**Discussion:** In our study, the use of internal fixation with percutaneous intramedullary nailing achieved acceptable functional and clinical outcomes, along with the restoration of hindfoot alignment, which correlated with the AOFAS functional score.

**Level of evidence:** IV; retrospective study

1. Introduction

Calcaneal fractures account for 1–2% of all fractures, with 75% involving the subtalar joint [1–4]. These fractures pose a significant clinical challenge with considerable functional and social repercussions [5–7].

If not managed properly, these fractures can lead to intra- and extra-articular impingement and may develop into post-traumatic subtalar

arthritis in the medium to long term [2,7–10]. The goal of surgical treatment is to prevent sequelae and avoid wound and septic complications by restoring the anatomic configuration of the entire calcaneus and the articular congruence of the posterior facet [8,11–16].

There is still no consensus on how to best manage these fractures: functional, orthopedic, or surgical [2,5,17,18]. Surgical techniques use or combine open reduction and internal fixation, cementoplasty [19, 20], external fixators [21,22], nails [13,23,24], and screws [25–27].

<footnote><sup>a</sup> Service de Chirurgie Orthopédique et Traumatologique, CHU de Rennes, 35000, Rennes, France</footnote>

<footnote><sup>b</sup> Département de Chirurgie Osseuse, CHU d'Angers, 49033, Angers, France</footnote>

<footnote>* Corresponding author.</footnote>

<footnote>E-mail address: adrien.rossetti@chu-rennes.fr (A. Rossetti).</footnote>
<figure><img src="image_3.png" /><figcaption>Fig. 1. Study flow chart.</figcaption></figure>

Some teams also carry out arthroscopic-assisted joint reduction [28,29].

No single technique has proven superior regarding functional outcomes. However, minimally invasive approaches reportedly have fewer complications, particularly wound healing, compared to extensile lateral approaches [30–35]. Internal fixation with percutaneous intramedullary nailing appears to yield favorable clinical and biomechanical outcomes [24,36–40]. Restoring hindfoot alignment remains a crucial consideration in these surgeries and may be more complicated with percutaneous methods.

The primary purpose of this study was to assess the correlation between functional outcomes and the restoration of hindfoot alignment in displaced intra-articular calcaneal fractures treated with percutaneous intramedullary nailing. The secondary objectives were to evaluate radiographic parameters in comparison to the healthy contralateral side and to document any complications that may arise. Our hypothesis was that internal fixation using percutaneous intramedullary nailing would restore hindfoot alignment, correlating with favorable functional outcomes.

## 2. Patients and methods

### 2.1. Patients

This retrospective, single-center, multi-surgeon study examined displaced intra-articular calcaneal fractures treated with percutaneous intramedullary nailing from January 2018 to July 2022, with a minimum follow-up of one year. The local ethics committee approved this study.

### 2.2. Inclusion criteria

Autonomous adult patients who were able to provide informed consent and were followed for over one year were included in this study. The exclusion criteria were refusal to participate, bilateral calcaneal fractures, and incomplete radiographic and clinical records.

Seventeen out of 37 patients were excluded during the study period (Fig. 1).

### 2.3. Methods

#### 2.3.1. Surgical procedure

Internal fixation was conducted using percutaneous intramedullary nailing (Calcanail®, FH Orthopedics, Heimsbrunn, France) through an incision in the talar capsule. Patients were positioned in either the lateral decubitus or prone position, depending on available options and the surgeon's preference. Distraction of the divergent pins in the talus and calcaneus allowed for automatic correction of the varus deformity of the tuberosity. The working channel facilitated the reduction of the subtalar joint surface under fluoroscopic guidance. No open reduction was carried out. The implant was measured and placed with a cancellous bone autograft. The nail was then locked with two lateral and medial cannulated screws using the ancillary device [23].

#### 2.3.2. Postoperative care

An immobilization boot covering the foot and lower leg was worn for six weeks without any weight-bearing. Rehabilitation for subtalar stiffness began once the soft tissue wound had healed.
<table><caption>**Table 1**
Study clinical and demographic characteristics.</caption><thead><tr><th>Variable</th><th>Overall population (n = 20)</th></tr></thead><tbody><tr><td>Age at surgery</td><td>42.1 ± 15.9 (18.0-69.0)</td></tr><tr><td>Sex</td><td></td></tr><tr><td>Female</td><td>5 (25%)</td></tr><tr><td>Male</td><td>15 (75%)</td></tr><tr><td>ASA (American Society of Anesthesiologists)</td><td></td></tr><tr><td>1</td><td>13 (65%)</td></tr><tr><td>2</td><td>7 (35%)</td></tr><tr><td>BMI (Body Mass Index)</td><td>23.8 ± 5.9 (19.2-37.0)</td></tr><tr><td>Time to last follow-up (months)</td><td>40.1 ± 14.0 (13.0-62.0)</td></tr><tr><td>Tobacco use</td><td></td></tr><tr><td>No</td><td>16 (80%)</td></tr><tr><td>Yes</td><td>4 (20%)</td></tr><tr><td>Alcohol use</td><td></td></tr><tr><td>No</td><td>18 (90%)</td></tr><tr><td>Yes</td><td>2 (10%)</td></tr><tr><td>Psychiatric history</td><td></td></tr><tr><td>No</td><td>17 (85%)</td></tr><tr><td>Yes</td><td>3 (15%)</td></tr><tr><td>Type of trauma</td><td></td></tr><tr><td>RTA</td><td>1 (5%)</td></tr><tr><td>Fall &lt;1.5 m</td><td>2 (10%)</td></tr><tr><td>Fall &gt;1.5 m</td><td>17 (85%)</td></tr><tr><td>Work accident</td><td></td></tr><tr><td>No</td><td>16 (80%)</td></tr><tr><td>Yes</td><td>4 (20%)</td></tr><tr><td>Affected side</td><td></td></tr><tr><td>Right</td><td>10 (50%)</td></tr><tr><td>Left</td><td>10 (50%)</td></tr><tr><td>Fracture type (Sanders)</td><td></td></tr><tr><td>IIA</td><td>5 (25%)</td></tr><tr><td>IIB</td><td>6 (30%)</td></tr><tr><td>IIC</td><td>0 (0%)</td></tr><tr><td>IIIAB</td><td>4 (20%)</td></tr><tr><td>IIIAC</td><td>4 (20%)</td></tr><tr><td>IIIBC</td><td>1 (5%)</td></tr><tr><td>IV</td><td>0 (0%)</td></tr><tr><td>Mean time to surgery (days)</td><td>6.5 ± 3.9 (1.0-14.0)</td></tr><tr><td>Tourniquet</td><td></td></tr><tr><td>No</td><td>17 (85%)</td></tr><tr><td>Yes</td><td>3 (15%)</td></tr><tr><td>Duration of procedure (min)</td><td>59.5 ± 18.1 (35.0-105.0)</td></tr><tr><td>Positioning</td><td></td></tr><tr><td>Lateral decubitus</td><td>16 (80%)</td></tr><tr><td>Prone</td><td>4 (20%)</td></tr><tr><td>Surgical experience (Tang)</td><td></td></tr><tr><td>Level II</td><td>6 (30%)</td></tr><tr><td>Level III</td><td>14 (70%)</td></tr><tr><td>Length of hospital stay (days)</td><td>9.7 ± 9.4 (1.0-35.0)</td></tr><tr><td>Time to return to work and sports (months)</td><td>7.9 ± 4.6 (3.0-18.0)</td></tr></tbody></table>

## 2.4. Assessment methods

### 2.4.1. Data collection and assessment

A radiographic and clinical follow-up was conducted for all patients by their surgeon and then, at the final follow-up, by an independent assessor.

The collected demographic data included age, sex, follow-up, BMI (kg/m²), American Society of Anesthesiologists (ASA) score, history (psychiatric, addictions), pre- and postoperative occupation, mechanism of injury, side operated on, and Sanders CT classification (Table 1).

The recorded surgical information included the time to surgery, procedure duration, surgical position, and the surgeon's level of expertise based on the Tang et al. classification system (I: nonspecialist, II: less experienced, III: experienced, IV: highly experienced, V: expert) [41].

### 2.4.2. Clinical assessment

The subtalar range of motion was assessed compared to the healthy contralateral side using the three American Orthopedic Foot Ankle Society (AOFAS) categories: severe restriction <25%, moderate restriction

<figure><img src="image_4.png" /><figcaption>**Fig. 2.** Radiographic findings for assessing hindfoot alignment in comparison to the healthy contralateral side.</figcaption></figure>

A: Long axial view: leg axis (blue line); calcaneus axis (red line); angular hindfoot deviation (yellow angle).

B: Meary's view and the Djian method: the vertical axis runs through the center of the ankle (blue line); the hindfoot axis lies between the center of the mortise and the center of the heel support (red line); angular hindfoot deviation (yellow angle).

25-75%, and normal >75% [42,43]. Patients self-reported residual pain and subjective visual aesthetics of the foot against the healthy contralateral side using the Numerical Rating Scale (NRS) (/10). AOFAS (/100) and European Foot Ankle Society (EFAS) (/24) [44] scores were utilized to evaluate foot and ankle function. Additionally, the 12-item Short Form (SF-12) survey was conducted to assess health-related quality of life [45]. Recovery time and types of activities were also evaluated.

### 2.4.3. Radiographic assessment

A preoperative workup that included X-rays and CT scans was conducted to assess subtalar joint impairment and plan the surgical approach. The postoperative follow-up X-rays of the ankle and foot
<figure><img src="image_5.png" /><figcaption>**Fig. 3.** Long axial view measurement method (Neri et al. [46]).
A: The subject stands on the cassette with the beam angled at 45° toward the floor.
B: Hindfoot alignment is determined by measuring the distance between the anatomical axis of the tibia (green line) and the calcaneus axis (red line).</figcaption></figure>

<table><caption>**Table 2**
Comparison of AOFAS scores and angular differences between healthy feet and operated feet based on surgeon experience.</caption><thead><tr><th rowspan="2">Variable</th><th rowspan="2">Population<br>(n = 20)</th><th colspan="2">Surgeon experience</th><th rowspan="2">p</th></tr><tr><th>Level 2 (n = 6)</th><th>Level 3<br>(n = 14)</th></tr></thead><tbody><tr><td>AOFAS</td><td>81.8 ± 9.6<br>(57.0-92.0)</td><td>78.3 ± 12.8<br>(57.0-92.0)</td><td>83.2 ± 8.0<br>(57.0-90.0)</td><td>p = 0.45<br>(W)</td></tr><tr><td>Bohler<br>difference</td><td>11.9 ± 12.0<br>(2.0-52.0)</td><td>19.3 ± 18.2<br>(2.0-52.0)</td><td>8.6 ± 6.7<br>(2.0-25.0)</td><td>p = 0.16<br>(W)</td></tr><tr><td>Gissane<br>difference</td><td>5.4 ± 5.5<br>(0.0-24.0)</td><td>8.5 ± 8.5<br>(2.0-24.0)</td><td>4.1 ± 3.3<br>(0.0-12.0)</td><td>p = 0.36<br>(W)</td></tr><tr><td>Meary-<br>Tomeno<br>difference</td><td>3.4 ± 6.3<br>(0.0-24.0)</td><td>8.0 ± 10.6<br>(0.0-24.0)</td><td>1.4 ± 0.9<br>(0.0-3.0)</td><td>p = 0.29<br>(W)</td></tr><tr><td>Djian-<br>Annonier<br>difference</td><td>3.6 ± 3.0<br>(0.0-11.0)</td><td>5.7 ± 4.3<br>(0.0-11.0)</td><td>2.7 ± 1.8<br>(0.0-60)</td><td>p = 0.18<br>(W)</td></tr><tr><td>Long axial<br>view<br>difference</td><td>3.0 ± 3.8<br>(0.2-15.0)</td><td>3.9 ± 4.2<br>(0.7-11.3)</td><td>2.6 ± 3.7<br>(0.2-15.0)</td><td>p = 0.62<br>(W)</td></tr><tr><td>Meary<br>difference</td><td>3.4 ± 3.5<br>(0.5-9.0)</td><td>3.2 ± 2.4<br>(0.5-5.2)</td><td>3.5 ± 2.6<br>(0.6-9.0)</td><td>p = 0.16<br>(W)</td></tr></tbody></table>

Mann-Whitney U test (W).

included bilateral weight-bearing anteroposterior and lateral views, the Meary view with cerclage of the hindfoot, the Djian method, and the long axial view (Fig. 2) [46-48]. The long axial view was obtained in a standing position with weight evenly distributed on both legs, with the X-ray beam angled at 45° (Fig. 3). This allowed us to measure and compare the Bohler angle, the angle of Gissane, the Djian-Annonier angle, the Meary-Tomeno angle, hindfoot alignment, and varus/valgus against the contralateral healthy foot [13,49]. The differences between hindfoot alignment angles were measured and compared between healthy and operated feet. These measurements were performed using PACS software (Telemis SA, Leuven, Belgium).

Patients were assessed for complications at each consultation.

## 2.5. Statistical analysis

Quantitative variables were expressed as the mean and standard deviation for normal distributions, and as the mean (minimum-maximum) for non-normal distributions. Qualitative variables were reported as counts and percentages. Groups were compared using the

parametric *t* test for normally distributed data; otherwise, the Mann-Whitney U nonparametric test was utilized. Paired data were compared with either the paired *t* test or the nonparametric Wilcoxon signed-rank test. The correlation between two continuous variables was assessed using Spearman's rank correlation (rs) for non-normal distributions, where 0 indicates no relationship, and -1 or +1 indicates a perfect correlation. The significance threshold was set at *p* < 0.05. The statistical analyses were conducted by an independent biostatistician using SAS software (SAS Institute, Cary, USA, version 9.4).

## 3. Results

### 3.1. Population

A total of 20 patients were included, with a mean follow-up of 40.1 months (13.0-62.0). The mean age at surgery was 42.1 years ± 15.9 (18.0-69.0), and 75% were men. Seventeen of them were falls from a height of more than 1.5 m (Table 1).

### 3.2. Surgery

The surgeon's expertise did not seem to affect radiographic and functional outcomes (Table 2).

### 3.3. Clinical results

The mean AOFAS score was 81.8 ± 9.6 at the last follow-up. A moderate negative correlation was found between the AOFAS score and the difference in angular deviation for the long axial view (-0.494; *p* = 0.026).

Patients returned to work after 7.9 ± 4.6 months (3.0-18.0). Three patients returned to work at a higher level than their previous positions, ten patients continued at the same level, and seven patients were unable to return to work (work stoppage or reassignment). Patient characteristics are summarized in Table 3.

The results of the AOFAS, EFAS, SF-12, and NRS (pain and aesthetic) tests compared to the healthy foot are summarized in Table 4.

Nine of the 20 patients (45%) displayed normal hindfoot inversion and eversion range of motion, 10 out of 20 (50%) showed moderate stiffness, and 1 out of 20 (5%) experienced severe stiffness.

Two patients (10%) experienced symptomatic subtalar arthritis, exhibiting an NRS greater than 5/10, a reduced gait perimeter, and
<table><caption>**Table 3**
Comparison of patients' pre- and postoperative physical activities and recovery at a mean follow-up of 3.3 years.</caption><thead><tr><th rowspan="2">Patient</th><th colspan="2">Preoperative Activity</th><th colspan="2">Postoperative Activity</th><th rowspan="2">evolution</th></tr><tr><th>Professional</th><th>Sport</th><th>Professional</th><th>Sport</th></tr></thead><tbody><tr><td>1</td><td>Student</td><td>.</td><td>Special-education teacher</td><td>.</td><td>+</td></tr><tr><td>2</td><td>Real estate agent</td><td>.</td><td>Office worker</td><td>.</td><td>-</td></tr><tr><td>3</td><td>Marquee rigger</td><td>.</td><td>Marquee rigger</td><td>.</td><td>=</td></tr><tr><td>4</td><td>Active retiree</td><td>.</td><td>Active retiree</td><td>.</td><td>=</td></tr><tr><td>5</td><td>Student</td><td>Running</td><td>Student</td><td>Running</td><td>=</td></tr><tr><td>6</td><td>Bar manager</td><td>Cycling</td><td>Bar manager</td><td>Cycling</td><td>=</td></tr><tr><td>7</td><td>Mason</td><td>.</td><td>Mason</td><td>.</td><td>=</td></tr><tr><td>8</td><td>Warehouse operator</td><td>.</td><td>Sedentary retiree</td><td>.</td><td>-</td></tr><tr><td>9</td><td>Office worker</td><td>Hiking</td><td>Office worker</td><td>Hiking</td><td>=</td></tr><tr><td>10</td><td>Teacher</td><td>.</td><td>Seafarer</td><td>Cycling</td><td>+</td></tr><tr><td>11</td><td>Farmer</td><td>.</td><td>Occupationally Disabled</td><td>.</td><td>-</td></tr><tr><td>12</td><td>Salesperson</td><td>Walking</td><td>Salesperson</td><td>Walking</td><td>=</td></tr><tr><td>13</td><td>Craftsperson</td><td>.</td><td>Sedentary retiree</td><td>.</td><td>-</td></tr><tr><td>14</td><td>Mechanic</td><td>Volleyball</td><td>Mechanic + Bartender</td><td>Volleyball, Skiing, Rollerblading</td><td>+</td></tr><tr><td>15</td><td>Student</td><td>Bodybuilding</td><td>Student</td><td>Bodybuilding</td><td>=</td></tr><tr><td>16</td><td>Warehouse operator</td><td>.</td><td>Office worker</td><td>.</td><td>-</td></tr><tr><td>17</td><td>Service person</td><td>Running</td><td>Service person (para)</td><td>Running</td><td>=</td></tr><tr><td>18</td><td>Craftsperson</td><td>.</td><td>Work stoppage</td><td>.</td><td>-</td></tr><tr><td>19</td><td>Warehouse operator</td><td>.</td><td>Work stoppage</td><td>.</td><td>-</td></tr><tr><td>20</td><td>Active retiree</td><td>Jogging</td><td>Active retiree</td><td>Hiking + Cycling</td><td>=</td></tr></tbody></table>

+: improved; = similar to preoperative period; -: decreased.

<table><caption>**Table 4**
Functional results at a mean follow-up of 3.3 years.</caption><thead><tr><th>Variable</th><th>Overall population (n = 26)</th></tr></thead><tbody><tr><td>NRS-Pain (/10)</td><td>1.3 ± 1.9 (0.0–6.0)</td></tr><tr><td>AOFAS-H (/100)</td><td>81.8 ± 9.6 (57.0–92.0)</td></tr><tr><td>Pain (/40)</td><td>29.5 ± 4.9 (20.0–40.0)</td></tr><tr><td>Function (/50)</td><td>43.3 ± 5.1 (32.0–50.0)</td></tr><tr><td>Hindfoot alignment (/10)</td><td>8.2 ± 2.8 (0.0–10.0)</td></tr><tr><td>EFAS (/24)</td><td>17.3 ± 3.7 (4.0–21.0)</td></tr><tr><td>SF-12</td><td></td></tr><tr><td>PCS-12</td><td>50.6 ± 5.2 (39.1–58.6)</td></tr><tr><td>MCS-12</td><td>49.4 ± 7.4 (24.8–61.4)</td></tr><tr><td>NRS-Aesthetic (/10)</td><td>8.3 ± 1.5 (5.0–10.0)</td></tr></tbody></table>

AOFAS-H: American Orthopaedic Foot and Ankle Society – Hindfoot.

EFAS: European Foot and Ankle Society.

SF-12: Short Form 12.

PCS: Physical Component Summary.

MCS: Mental Component Summary.

radiographic signs of arthritis. Their scores were the lowest in the study (AOFAS 57 and 57; EFAS 13 and 4).

### 3.4. Radiographic findings

During the last follow-up, we measured and compared the pre- and postoperative radiographic findings of the operated foot to those of the healthy contralateral foot, which served as a unique reference for each patient (Fig. 4). The angular difference between the two feet, based on the long axial view, was 3.0° of valgus ± 3.8 (0.2–15.0) for the operated feet (p = 0.0328). According to the Djian method on Meary hindfoot views for fractured feet (p = 0.0421), this was 3.4° of valgus ± 2.5 (0.5–9.0) (Figs. 2 and 3; Table 5).

### 3.5. Complications

Five out of 20 patients (25%) underwent additional surgery for hardware removal, with subtalar arthrodesis performed concurrently. Three nails were removed due to impingement: heel discomfort, lateral discomfort, and occupational constraints (military). Hardware removal occurred on average 23.6 ± 11.5 months (15.0–46.0) after the primary surgery. No infections, nerve damage, delayed healing, skin necrosis, or complex regional pain syndrome were observed.

## 4. Discussion

Our study found that adequate hindfoot alignment following percutaneous intramedullary nailing in Sanders II and III displaced intra-articular calcaneus fractures was associated with satisfactory functional outcomes. Therefore, our hypothesis was confirmed.

The demographic characteristics of our population were comparable to those reported in other studies on calcaneal fractures regarding age, gender, severity, and etiology [5,6,40,50–54]. Our findings align with the literature, including the systematic review by Van Hoeve et al. on the outcomes of calcaneal fractures treated with percutaneous and minimally invasive techniques, which found a mean AOFAS of 83/100 across 46 studies involving 1,776 patients and 2,018 fractures [55]. Studies on the Calcanail® reported similar results, with mean AOFAS scores ranging from 79 to 92.6, depending on the series (60–100) [32,40, 50–53]. On average, resumption of activities and return to work occurred at 7.9 months (3.0–18.0) in our study, which is consistent with the findings of Fourgeaux et al., who reported a mean resumption at 6.5 months (3.0–24.0) [53].

Our radiographic findings showed an improvement in the Bohler angle and the angle of Gissane. While previous studies have reported a correlation between postoperative parameters and functional recovery [32,56], radiographic differences between the operated and healthy feet should be interpreted cautiously, taking into account the good outcomes and patient-reported satisfaction, with patients describing their operated foot as pain-free (NRS = 1.3) and aesthetically pleasing compared with the healthy foot (NRS = 8.3).

One innovative contribution of this study was the use of the long axial view with full weight-bearing in a double-leg stance, thereby showing the calcaneus axis in a functional position. Several studies have reported that this technique is reliable and reproducible, and it has been employed in elective surgery by some teams [46–48,57]. Using the long axial view for follow-up X-rays is advantageous because it permits visualization of the subtalar joint without the need for repeated CT scans, which involve radiation exposure.

Patients in our study were managed by Level II and III surgeons according to the 2016 classification system by Tang et al. This approach differed from previously published series. Bernasconi et al. reported in 2021 that, out of the six published studies on the Calcanail, five were published by either implant designers or FH Orthopedics consultants [3, 32,40,50,52,53]. The patients in these studies were also operated on by either Level IV or V surgeons. Nevertheless, our study reported
<figure><img src="image_6.png" /><figcaption>**Fig. 4.** X-rays of a 25-year-old patient after internal fixation of a Sanders IIB calcaneal fracture.</figcaption></figure>

A: Post-traumatic, preoperative

B: Immediate postoperative

C: At 6 months

D: Healthy contralateral foot at 57 months, with Bohler (red line), Gissane (blue line), Djian-Annonier (green line), and Meary-Tomeno (yellow line) angle measurements.

E: Operated foot during the last follow-up at 57 months

<caption>**Table 5**</caption>

Changes in radiographic findings of the operated foot before surgery and during the last consultation, compared to the healthy foot at the final follow-up for angles.

<table><thead><tr><th>Variable</th><th>Preop operated foot</th><th>Operated foot at last follow-up</th><th>Healthy foot</th><th>p</th></tr></thead><tbody><tr><td>Bohler</td><td>-6.7 ± 12.1 (-28-12)</td><td>18.6 ± 15.5 (-27-46)</td><td>30.2 ± 6.4 (15-42)</td><td></td></tr><tr><td></td><td></td><td>Δ</td><td>Δ</td><td>p = 0.0002 (SR)</td></tr><tr><td></td><td>#</td><td></td><td>#</td><td>p &lt; 0.0001 (paired T)</td></tr><tr><td>Gissane</td><td>116.6 ± 10.1 (100-135)</td><td>100.6 ± 7.5 (81-114)</td><td>104.3 ± 4.6 (98-115)</td><td></td></tr><tr><td></td><td></td><td>Δ</td><td>Δ</td><td>p = 0.0088 (SR)</td></tr><tr><td></td><td>#</td><td></td><td>#</td><td>p &lt; 0.0001 (paired T)</td></tr><tr><td>Meary-Tomeno</td><td>-</td><td>5.3 ± 7.7 (-7-24)</td><td>2.5 ± 4.5 (-9-13)</td><td></td></tr><tr><td></td><td></td><td>Δ</td><td>Δ</td><td>p = 0.0108 (SR)</td></tr><tr><td>Djian-Annonier</td><td>-</td><td>120.7 ± 5.8 (107-127)</td><td>117.8 ± 4.9 (107-127)</td><td></td></tr><tr><td></td><td></td><td>#</td><td>#</td><td>p = 0.0025 (paired T)</td></tr><tr><td>Long axial view</td><td>-</td><td>2.9 ± 5.7 (-3.7-10.8)</td><td>-0.1 ± 3.4 (-5.0-5.8)</td><td></td></tr><tr><td></td><td></td><td>Δ</td><td>Δ</td><td>p = 0.0328 (SR)</td></tr></tbody></table>

Mean ± standard deviation (min-max).

#: paired *t* test (paired T).

Δ: Wilcoxon signed-rank test (SR).

comparable functional and radiographic outcomes. Therefore, the lack of expertise seems to have a minor effect when treating these fractures with percutaneous intramedullary nailing. This may be due to the design of the implant itself, which aims to correct the varus deformity of the tuberosity. Indeed, placing divergent pins, as described in the leading articles on this surgical technique, enables varus correction through distraction and restores the parallel pin configuration. The working channel is then used to restore the height of the thalamic fragment and position the supporting nail under the main fragment. This ensures a stable reduction and correction of the overall calcaneal axis, resulting in a decrease in postoperative complications, primarily wound healing [23, 51-53].

Although our findings indicated a significant correlation between the restoration of hindfoot alignment and AOFAS scores, this relationship cannot be interpreted as causal due to the inherent limitations of correlational analyses. This study had several limitations. The retrospective and single-center design limited the generalizability of our findings. Additionally, our study excluded Sanders IV fractures, and,

likely, the outcomes of treating these types of fractures with percutaneous intramedullary nailing may be less successful.

Due to the study's limited statistical power, resulting from the small sample size and the loss of some patients to follow-up, we considered analyzing the results by subgroup (i.e., age and fracture severity). However, such analyses were likely to be statistically insignificant and susceptible to interpretation bias given our cohort's limited size. A future study with a larger sample size could examine these categories with sufficient statistical power. The lack of standardized surgical positioning (lateral decubitus or prone) introduced a bias that is difficult to control in trauma settings. The multi-surgeon aspect of our study is another limitation, but it reflects the real-world application of this implant in trauma situations by less experienced surgeons. The absence of a control group prevents us from drawing formal conclusions about the unique efficacy of this technique. Nevertheless, this must be approached with nuance, as using each patient's contralateral side for comparison purposes mitigates these biases [13].

The radiographic assessment was also subject to measurement bias,
which could be minimized through automated measurements of CT images, for example [27]. To our knowledge, our follow-up period was the longest reported in the literature for this type of implant. The study findings suggest that the long axial view could become a standard in the postoperative assessment of calcaneal fractures, facilitating the evaluation of alignment and predicting long-term functional outcomes.

It may be valuable to compare the efficacy of long axial views with other techniques, such as weight-bearing CT scans, and to investigate their role in the early detection of postoperative complications, including secondary displacement and calcaneal impaction. While our study focused on the internal fixation of calcaneal joint fractures using Calcanail®, other recent studies have examined different locations of calcaneal fractures, particularly the anterior process in Chopart's injuries [58]. Although these fractures differ from our research subject, they highlight the growing importance of radiographic assessment and minimally invasive management.

Prospective multicenter studies with control groups will be necessary to confirm these results and evaluate the impact of alignment on complications, such as subtalar arthritis and the need for arthrodesis.

## 5. Conclusion

This study demonstrated adequate functional and radiographic outcomes in patients who underwent internal fixation using percutaneous intramedullary nails after a displaced intra-articular calcaneal fracture. A correlation was found between the restoration of hindfoot alignment and improvement in the AOFAS score. Further research is necessary, particularly in the long term, to assess the incidence of post-traumatic arthritis following this technique.

### CRediT authorship contribution statement

AR: conception, design, enrollment, data collection, writing, correction, submission JM: methodology, correction, review RD: inclusion, data collection, review CS: review MR: design, methodology, review LR: design, methodology, review

### Declaration of Generative AI and AI-assisted technologies in the writing process

No use of any generative AI or AI-assisted technologies to write this manuscript.

### Funding

None.

### Declaration of competing interest

Robin Delacroix: Zimmer Biomet France SAS, Johnson & Johnson Medical SAS, Orthofix SA. Christophe Szymanski: Novastep, Stryker France SAS, AbbVie. Mickael Ropars: Sanofi Aventis France, Sanofi Winthrop Industrie, AbbVie. Associate editor of the OTSR and Sofcot teaching conferences Louis Rony: Newclip Technics, Novastep, Johnson & Johnson Medical SAS, Sanofi Aventis France, Stryker Trauma GmbH. Julien Maximen, Adrien Rossetti: none.

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