2.1

This study was approved by our hospital’s Institutional Review Board, and the requirement for informed consent was waived due to its retrospective design. The authors confirmed calcaneal-side CFL rupture by MRI in a case with diffuse swelling and echymosis on the lateral side of the ankle and heel with prominent tenderness to the calcaneal attachment of CFL. Forty-six patients diagnosed with acute ankle sprain accompanied by complete ruptures of ATFL and calcaneal-side CFL were consecutively treated by a single surgeon between January 2016 and December 2019. After applying the inclusion and exclusion criteria, 36 patients remained eligible for the study ( Table 1 ).

All patients were followed up for a minimum of 24 months after treatment. Two patients with generalized ligamentous laxity, six with deltoid or syndesmotic ligament injuries, and two with acute osteochondral fractures were excluded. Consequently, 36 patients were included in this study. Among them, the initial 14 patients received conservative treatment (group C), whereas the subsequent 22 patients underwent surgical treatment (group S). Age, gender, injured side, injury mechanism, sports level, and follow-up duration were similar between groups C and S. The demographic characteristics of the two groups are listed in Table 2 .

2.2

Clinical outcomes were assessed using the Cumberland Ankle Instability Tool (CAIT) at the last follow-up. The CAIT consists of nine items designed to assess different aspects of CAI. These items measure the difficulty in performing various physical activities owing to the CAI of the affected ankle. The total score of the nine items ranges from 0 (indicating severe instability) to 30 (reflecting normal stability). Typically, if the CAIT score ≤ 24 points, the likelihood ratio is 32 %, indicating a high probability of experiencing recurrent sprains owing to persistent CAI.

The timing of return to sports (RTS) after treatment was compared between groups. The timing of RTS was evaluated regarding when the patients could resume running and when they could participate in sports competitions.

At the last follow-up, patients’ satisfaction with the treatments was assessed based on their responses, including “very satisfied,” “satisfied,” “fair,” or “dissatisfied.” In cases where a patient reported being “dissatisfied,” the reasons for the dissatisfaction were assessed.

To compensate for the absence of a preoperative radiographic stress test, a manual anterior drawer test (ADT) was used. In Group C, the test was performed in the outpatient clinic after aspiration of intra-articular hemarthrosis, while in Group S, it was conducted in the operating room under sciatic nerve block. A skilled ankle specialist administered manual ADT preoperatively and at the last follow-up. Instability was graded as normal (grade 0), mild (grade I, slight anterior translation compared with the contralateral ankle), moderate (grade II, significant anterior translation exceeding that of the contralateral ankle with a firm endpoint), or severe (grade III, significant anterior translation without an endpoint), with grades II and III indicating an unstable ankle . Ankle stability was compared between the groups before and after treatment.

2.3

MRI examinations were conducted using 3.0-T scanners (Achieva 3.0 T, Philips Medical System), consisting of fat-suppressed T2 coronal, sagittal, ATFL axial transverse, and 45º oblique coronal images. All MRIs were conducted in the supine position with the foot in a plantigrade position. Images were reviewed by a ankle specialist and a musculoskeletal radiologist. Any disagreements were resolved through discussion and, if necessary, a third musculoskeletal radiologist was consulted. ATFL ruptures were assessed using MRI; if present, the rupture sites were categorized as a fibular attachment, talar attachment, and midsubstance. The difference in the ATFL rupture sites between groups C and S was compared. To evaluate the proximal migration of the distal end of the ruptured CFL, the proximal migration distance (PMD) was measured. PMD was defined as the distance from the rupture site on the calcaneus to the distal end of the ruptured CFL in a 45º oblique coronal plane ( Fig. 2 ) . When the CFL severely migrated proximally and slipped to the outside of the peroneal tendons, it was defined as a Stener’s-like lesion ( Fig. 3 ). PMD and incidence of Stener’s-like lesions were compared between groups C and S. In addition, the relationship between PMD and the incidence of Stener’s-like lesions was evaluated in both groups.

(A) The proximal migration distance (PMD) was evaluated in a 45º oblique coronal plane of magnetic resonance imaging. (B) The PMD (dotted line) was defined as the distance from the rupture site on the calcaneus (arrowhead) to the distal end of the ruptured calcaneofibular ligament (arrow).

(A) The ruptured calcaneofibular ligament (CFL) migrated severely proximal and slipped to the outside of the peroneal tendons (arrowheads) on preoperative magnetic resonance imaging MRI). (B) The torn CFL was repaired with a knotless anchor at the calcaneal attachment site (arrows) on postoperative MRI.

All radiographs were obtained at the same facility using the same technique. Talar tilt angle (TTA) and anterior talar displacement (ATD) were measured from stress radiographs using a Telos SE 2000 stress device (ARD Medizin Produkte GmbH, Germany) with 150 N force. In cases of acute ankle sprains, assessing the exact degree of instability using stress radiographs can be challenging because of pain. In addition, in cases of calcaneal-side CFL rupture, stress radiographs, particularly the varus stress test, can potentially exacerbate proximal migration or cause a Stener-like lesion in the torn calcaneal-side CFL stump. Therefore, preoperative stress radiographs were not obtained.

The TTA and ATD were measured using stress radiographs at the last follow-up, and the results were compared between the two groups. TTA was defined as the angle between the articular surfaces of the tibia and talus in the varus stress view. ATD was defined as the shortest distance between the posterior lip of the tibia and the talar dome in the anterior drawer stress view. Each radiographic measurement was performed twice independently by an observer who was not a part of the surgical team, and the average values were calculated for analysis to minimize potential bias.

2.4

Conservative treatment consisted of protection, optimal loading, ice, compression, and elevation (POLICE) therapy. A short leg cast was applied at a 90º angle for 2 weeks, and weight bearing was allowed. After 2 weeks, the cast was replaced with a removable ankle brace. The patients were instructed to continue wearing the braces at night. In addition, a combination of physical therapy, manual therapy for edema control, and passive exercise therapy was used to increase the ankle’s range of motion. After 4 weeks, the patients resumed exercise to improve muscle strength and body balance. After 8 weeks, the patients were allowed to run within their tolerable pain range.

In all surgical cases, the patients underwent a sciatic nerve block and were placed in the semi-decubitus position. A 4–5 cm incision was made along the anterior surface of the fibula to access and identify the torn ligaments. A torn CFL displaced outside the peroneal tendon was termed a Stener’s-like lesion ( Fig. 4 A) (Video). Typically, the peroneal sheath was dissected, and the peroneal tendons were gently lifted with a retractor to confirm the extent of the torn CFL ( Fig. 4 B). The torn CFL was then sutured with a non-absorbable suture (FiberWire #2 with a needle; Arthrex, Naples, USA) using the modified Bunnel technique. The suture was secured to the calcaneal attachment site using a knotless anchor (PushLock, Arthrex, Naples, USA) ( Fig. 4 C). The method for suturing the ATFL varied depending on the location and type of tear. All suture anchors (TruShot, ConMed, USA) were used if a tear occurred at the fibular or talar bony attachment sites. An absorbable suture (Vicryl #2, Ethicon, USA) was used to treat midsubstance tears. The postoperative protocol was the same as that used for group C.

(A) The Stener’s-like lesion in which the calcaneofibular ligament (CFL) (arrowheads) slipped out of its original attachment was observed intraoperatively. (B) The torn CFL was pulled out to reveal the full length of the CFL. (C) The torn CFL was sutured with a non-absorbable suture using the modified Bunnel technique and secured to the calcaneal attachment site with a knotless anchor.

2.5

All dependent variables were tested for normality of distribution and equality of variances and were analyzed using nonparametric tests as they had non-normal distributions. The Mann-Whitney U and chi-squared tests were used to compare demographic data between the groups. The Mann-Whitney U test was used to compare the CAIT score and timing of RTS, PMD, TTA, and ATD between the groups. The Fisher’s exact test was used to compare the ATFL rupture sites, the occurrence of Stener’s-like lesions, and manual ADT between the groups. Regression analysis was used to evaluate the correlation between PMD and the occurrence of Stener’s-like lesions. Statistical significance was set at P < 0.05. Statistical analyses were performed using SPSS (version 18.0; SPSS Inc., Chicago, IL, USA).