Pure Ankle Dislocation Without Associated Fracture: A Series of Cases and Our Clinical Experience

Abstract

Purpose

Pure ankle dislocation without associated fracture is extremely rare. The current study reports eight cases of this type of injury, aiming to add some new material to the published data and present our clinical experience.

Methods

Six open and two closed posteromedial tibiotalar dislocations without associated fractures treated in our department from 2015 to 2019 were retrospectively analyzed. Emergent reduction was performed for all patients followed by an average of 6 weeks of immobilization with external fixators in open cases and a short leg cast in closed cases. No patients underwent ligament or capsule repair except one case. The clinical data were recorded and analyzed.

Results

At a mean follow-up of 33 months (range 13–61), the average AOFAS score was 91 (range 78–100) with five ankles rated as excellent and three rated as good. All of the eight patients returned to their prior daily life and the two closed patients with sports injuries resumed pre-injury activity level. The average range of motion (ROM) loss of the ankles was 9 degrees for plantarflexion and 3 degrees for dorsiflexion. Complications included superficial infection, moderate ankle stiffness, ankle degenerative change and residual numbness. None of the eight patients showed obvious ankle instability.

Conclusion

Pure ankle dislocation without associated fracture is a rare injury. Emergent reduction, appropriate wound care in open injuries and proper joint stabilisation with a cast or external fixator provide good clinical results and could be the mainstay of treatment.

Introduction

Ankle dislocation without associated fracture (pure ankle dislocation) is a rare injury accounting for only 0.065% of all ankle injuries and 0.46% of all ankle dislocations [1]. D'Anca [2] attributed the rarity to the mechanical efficiency of the mortise and the resistance of the ankle ligaments being greater than that of bone, thus causing ankle dislocation usually accompanied by lateral, medial or posterior malleolar fracture. Due to its rarity, pure ankle dislocation is not well understood with only a limited number of cases being described in the literature which was almost restricted to isolated reports and small case series [2–12].

Fahey and Murphy [13] classified this injury into five types based on the dislocation direction of the talar in relation to the tibia: anterior, posterior, medial, lateral, superior or any combination of these. Posteromedial dislocation is much more common than any other types because of the tendency to land with plantarflexion and inversion of the ankle in a fall from a height [4]. The high traumatic energy and the complicated mechanism of the lesion usually result in a complete tear of the lateral/medial collateral ligaments and even tibiofibular syndesmosis [2, 4, 5, 7]. Open dislocations account for half of the cases [1, 6] and the laceration of soft tissues is usually on the opposite side of the dislocation [4, 5].

Due to the rarity of this type of injury, the standardized treatment protocol is controversial and the studies of mechanism and outcome of the injury are still deficient [6]. To some extent, pure ankle dislocation is essentially a higher-grade ligamentous injury after successful reduction despite the possible injury of syndesmosis or cartilage. However, applying the principle of ankle sprain to pure ankle dislocation seems unpractical since the treatment methods for acute ruptures of the ankle ligaments are also controversial [14, 15]. External fixator is applied infrequently for primary immobilization [1] and the outcome report is relatively insufficient. In this study, we report a series of eight cases of pure tibiotalar dislocations managed with emergent reduction and other heterogenic procedures, aiming to add some new material to the published data and present our clinical experience.

Materials and Methods

Patients and Data Collection

Hospital medical records were searched for ankle dislocations with the ICD-10 code S93.0 between the dates 01/01/2015 and 31/12/2019 in our department. All medical records and radiographic images of the individual patient were studied to confirm the diagnosis of pure ankle dislocations without associated fractures. Eight patients between 2015 and 2019 were enrolled in this study with both pre-reduction and post-reduction radiographs available. Informed consent was obtained from all participants and the study was carried out in accordance with the Declaration of Helsinki.

In this series, there were two females and six males with an average age of 38 years (range, 18–54). All eight patients had posteromedial dislocations and six of them were open. The trauma mechanism was sports (basketball) injury in the two closed dislocations (case 1 and 4), traffic accident in four patients, falling from a height in one patient, and involving in a rotary cultivator in one patient (case 5). The patient (case 5) also suffered anterior tibial artery rupture, superficial peroneal nerve injury, fractures of high fibula and femoral shaft, rupture of extensor digitorum longus tendon and chondral lesion of tibiotalar facet. There was one patient (case 7) also suffered tendon rupture and another patient (case 2) had a chondral lesion. One patient (case 8) underwent closed reduction and Steinman pin fixation before transferring to our hospital. Details of the patients were listed in Table 1.

Table 1.

Details of patients with pure ankle dislocation

Patient	Age/ Sex	Laterality/Type (posteromedial)	Cause of injury	Associated injuries	Main Treatment	Follow-up months/AOFAS-AHS/Results	Loss of ROM (degrees)	Instability/Stiffness /Pain/Posttraumatic arthritis/Function
1	19/M	Right/Closed	Basketball	A small compound contusion wounds at lateral aspect of the ankle	i. CR-SLC for 6 weeks ii. Secondary ligament repair at day 7	36 mo/98/Excellent	Slightly limited	Returned to pre-injury sports activity level
2	41/M	Right/Open	Motor vehicle accident	i. Skin and soft tissue defect at lateral aspect of the ankle ii. Chondral lesion of tibiotalar facet confirmed by intraoperative exploration	i. External fixation for 6 weeks ii. Repeatedly debridement & VAC for the developed superficial infection iii. Delayed closure & skin graft	61 mo/82/Good	PF: 15° DF: 5°	i. Superficial infection ii. Mild pain & moderate stiffness iii. X-rays showed degenerative change & osteophyte formation
3	52/F	Left/Open	Motorcycle accident	A compound laceration wound at the anterolateral side of the ankle	i. External fixation for 45 days	17 mo/95/Excellent	PF: 10° DF: Nil°	Slightly instable, functional irrelevant
4	18/M	Right/Closed	Basketball	Nil	CR-SLC for 6 weeks	13 mo/100/Excellent	Nil	Resume sport activity
5	39/M	Left/Open	Machine / rotary cultivator	i. A 10 cm compound laceration wound ii. Anterior tibial artery rupture iii. Extensor digitorum longus tendon defect iv. Injury of superficial peroneal nerve v. Fracture of high fibula & femoral shaft; inferior tibiofibular syndesmosis intact vi. Chondral lesion of tibiotalar facet	i. External fixation for 50 days ii. Delayed closure & VAC to avoid infection iii. ORIF of compound fractures iv. Repair of the artery, tendons v. Rebound air walker assisted rehabilitation	48 mo/78/Good	PF: 20° DF: 10°	i. Mild plantarflexion function limitation & moderate stiffness ii. Persistent mild pain with slightly abnormal gait iii. X-rays indicated posttraumatic arthritis changes iv. Persistent numbness
6	54/F	Left/Open	Motorcycle accident	i. Compound laceration wound ii. Craniocerebral injury	i. External fixation for 35 days	45 mo/97/Excellent	PF: 5° DF: Nil	No significant discomfort
7	47/M	Left/Open	Fall from a height	i. A 6 cm compound laceration wound ii. Injury of extensor digitorum longus tendon and extensor retinaculum	i. External fixation for 40 days ii. Tendons & retinaculum repair iii. Rebound air walker assisted rehabilitation	28 mo/95/Excellent	PF: 5° DF: 5°	Slight restriction when walking on uneven road
8	34/M	Left/Open	Motor vehicle accident	An 8 cm compound wound at the lateral side of the ankle	i. Closed reduction and Steinman pin fixation before transferring to our hospital ii. Combined external fixation for 6 weeks	16 mo/82/Good	PF: 15° DF: 5°	i. Mild pain ii. X-rays showed mild degenerative change
Mean	38 ± 14	2 Closed 6 Open	_	_	Average 6 weeks of immobilization	33 ± 17 mo 91 ± 9 points	PF: 9 ± 7° DF: 3 ± 4°	_

CR-SLC closed reduction and short leg cast immobilization, VAC vacuum-assisted closure therapy, ORIF open reduction internal fixation, AOFAS-AHS the American orthopedic foot and ankle society ankle hindfoot scale, PF plantarflexion, DF dorsiflexion, ROM range of motion

At the final follow-up, the active range of dorsiflexion and plantarflexion were measured with a goniometer to estimate the range of motion loss compared with the contralateral ankles. The patients were carefully examined for any sign of ankle instability by performing an anterior drawer test and inversion stress test. The discomforts of the involved ankles puzzling the patients were gathered, such as stiffness, pain, and paresthesia. Radiological examination was conducted to evaluate the condition of the injured ankle joints. The American Orthopaedic Foot & Ankle Society (AOFAS) Ankle-Hindfoot Scale was administered to assess the functional status. Depending on the score, results were rated as excellent (90 to 100), good (75 to 89), fair (50 to 74), or poor (less than 50).

Management

After the neurovascular state and the risks were carefully evaluated, prompt reduction was performed in the emergency room under intravenous sedation for all patients. The reduction maneuver was pulling the foot longitudinally with the knee flexed first, and then pronating and dorsiflexing the foot. No significant deformity recurred and spontaneous dislocation of the ankles happened after reduction. There was no neurovascular compromise before and after reduction except one (case 5) presented unpalpable dorsalis pedis artery and paresthesia of the lateral dorsum of the foot. The post-reduction X-rays showed congruent ankle mortise in all patients.

The two closed patients underwent short leg cast immobilization for 6 weeks. One of them adopted non-surgical treatment (Fig. 1) while the other got secondary medial and lateral ligaments to repair 7 days after injury because of the patient’s strong will to repair the torn ligaments (Fig. 2). Emergent debridement was performed in the open cases under general anesthesia in the operating room. Prophylactic intra-venous antibiotics were administrated. All the six open cases were stabilized with triangular external fixators considering the severe trauma and to make the wound care easily. None of the patients got the capsules or ligaments repaired though massive ligaments rupture was expected and observed under direct vision, especially in the lateral ligament complex. The ruptured arteries, nerves, and tendons were repaired whenever possible, just as patient #5 (Fig. 3) underwent. Primary closure was performed in four open cases considering the relatively clean laceration wound, and vacuum-assisted closure therapy (VAC) helped a lot in the two delayed closure cases (case 2 and 5). The patient with soft tissue defect and superficial infection (case 2) were managed with debridement, dressing change, and skin grafting. No pin site infection occurred.

Fig. 1.

Radiographs of patient #4. a The preoperative X-rays confirmed posteromedial dislocation of the right ankle without associated fracture. b The final follow-up radiographs 13 months later showed a great state of the involved ankle

Fig. 2.

Photographs and radiographs of patient #1. a The image demonstrated the inversion and internal rotation deformity of the right ankle without laceration of the skin. b The preoperative X-rays confirmed no associated fracture. c Anteroposterior and lateral views of the ankle after immediate reduction and short leg cast immobilization. d The medial and lateral ligaments were repaired with suture anchors on day 7 after reduction and the final follow-up radiographs 2 years later showed a well state of the injured ankle joint

Fig. 3.

The X-rays and three-dimensional CT of patient #5. The involved left ankle was lacerated at the anterolateral aspect with the tibiotalar joint exposed and there were compound fractures of the proximal fibular and femoral shaft. The syndesmosis was confirmed intact by coronal section CT. a The images demonstrated the posteromedial dislocation of the left ankle without associated fracture (malleolar fracture). b A triangular external fixator was applied for immobilization with three transfixion pins used for tibia, calcaneus, and the forefoot separately. The post-reduction X-rays showed congruent ankle mortise. c The final follow-up radiographs presented posttraumatic arthritis of the involved ankle

Partially weight-bearing walking assisted with crutches was allowed 14 days after surgery in the external fixation group while after removal of immobilization in the cast group. All the cast and the external fixators were removed around 6 weeks later. Gradually weight-bearing and functional rehabilitation training then started up in the following 3 weeks. Rebound air walker was applied to assist weight-bearing walking on the basis of freewill purchase in two patients.

Result

The average postoperative follow-up period was 33 months (range, 13–61). Based on the AOFAS scores, all patients had a satisfactory result at the final follow-up (five rated as excellent and three rated as good) with a mean score of 91 ± 9 (range 78–100). All the patients but patient #5 who suffered severe compound injury returned to their daily life within 10 weeks and the two closed patients who got injured in basketball games returned to their pre-injury sports levels finally. There were three patients complaining of persistent mild pain and the follow-up radiographic examination presented evidence of ankle degeneration change. Among them, two patients also complained of moderate stiffness. The average range of motion (ROM) loss of the involved ankles was 9 degrees for plantarflexion and 3 degrees for dorsiflexion. Particularly, patient #5 demonstrated 30 degrees restriction in sagittal plane movement of the ankle and the patient also developed numbness at the lateral dorsum of the foot due to the injury of the superficial peroneal nerve. No other neurovascular deficit was noted at the final follow-up. Osteophyte formation was apparent in one patient (case 2) after 5 years. The detailed outcome was as listed in Table 1.

Discussion

In this study, we reported eight cases of pure ankle dislocation, which is extremely rare and the relevant literature remains limited. The current study reported one of the largest series and the largest series managed with an external fixator in literature. After emergent reduction, thorough debridement, short period of immobilization, and functional rehabilitation, all cases of ours presented a satisfactory outcome despite some complications that did not disturb daily life significantly. External fixator for open cases and no primary ligament repair yielded good clinical results.

According to Wight [1], neurovascular compromise prior to reduction occurred in 19% pure ankle dislocations. Immediate reduction as soon as possible to reduce the risk of neurovascular complications is in agreement with researchers [1, 6, 16]. Anesthesia or sedation before reduction is recommended to permit complete relaxation of the muscles and the knee should be flexed to relax the pull of the sural triceps on the calcaneus [4, 16]. Longitudinal traction is the first step, and the following manipulative reduction direction is just on the contrary to the dislocation mechanism [4]. Open injuries usually have a propensity for neurovascular deficits and infections, therefore appropriate treatment should never be postponed [6, 17]. Prompt intra-venous antibiotics prophylaxis is recommended and thorough debridement is principal [3].

The literature recommends an average six-week immobilization without bearing weight and a short leg cast was applied most often [1, 2, 12, 13]. After that, a gradual increase of load and remobilization therapy can be started. Time to full weight-bearing averaged 6.2 weeks in the literature and some authors advocated early weight-bearing [3, 7, 18]. External fixator was seldom applied in contrast to cast [9, 17, 19–21]. In our study, we applied an external fixator in all the six open cases and gained as good an outcome as those with a cast. We hypothesized that it could be suitable for the primary stabilisation of the affected joint, especially in open cases with severe compound wound, for it could provide firmer stability and facilitate wound care. Sayit et al. [21] stated that rigid fixation of the ankle for 6 weeks with an external fixator shortened the disability period and assisted in a faster recovery. In our cases, we allowed early weight-bearing walking 14 days after surgery and hold the view that it could facilitate the following rehabilitation exercise. Though there were two out of six patients immobilized with external fixators complaining of stiffness, the average loss of ROM in these cases was no worse than the data reported in the literature [4, 8, 12, 22, 23]. According to the systematic review by Wight [1], 3/7 patients immobilized with external fixators developed stiffness while 17.2% patients immobilized with cast did. However, the difference was not statistically significant, and the choice of immobilization device did not affect ankle stiffness or instability [1]. We reported a good outcome of open dislocations immobilized with an external fixator in our series and recommended it could be an alternative to cast.

Inversion injury usually results in the tear of the lateral collateral ligament complex, while eversion injury commonly leads to rupture of the deltoid ligament [2, 4, 5, 7, 24]. Whether the torn ligaments in this lesion should be repaired is still in controversy [1, 8]. As for closed cases, most authors recommended nonoperative treatment [18]. Closed reduction followed by immobilization in a cast for six to eight weeks yields a good long-term prognosis [5, 8, 10] and instability is rare despite massive ligamentous disruption [6]. As for open dislocations, more controversies exist. While many authors recommended repairing the torn ligaments primarily [5–7, 10, 25], many authors had reported good function without ligament repair [3, 12, 18, 26]. Toohey and Worsing [8] treated their six open dislocations with ligament repair in two and found that ligament repair did not alter the outcome. Ucar et al. [22] reported favorable long-term results without ligament or capsule repair in open pure ankle dislocations. When considering the specific ligaments that involved, most researchers believed it was not necessary to repair the medial collateral ligaments [3, 5–7, 27]. The intact fibula in this injury could be in favor of the non-necessity to repair the torn deltoid ligament [28–30]. In the rare cases of superior and lateral pure ankle dislocations, the syndesmosis rupture accompanying deltoid ligament torn is expected [31, 32]. Ankle syndesmosis reduction and fixation are indicated in this condition [32, 33]. As for torn lateral ligament complex, some authors [6, 7, 10] recommended repairing them in open cases but many authors held the opposite view [3, 12, 21, 25]. Kelly [12] suggested that lateral ligaments repair is unnecessary and difficult since they were usually shredded, contused and unrecognizable. Though controversy remains and high-quality evidence deficits [14], for complete lateral ankle ligament ruptures, a short period of immobilization followed by a range of motion exercises has been proved to provide patients with similar outcomes to ligament repair [14, 34, 35].

According to the systematic review of Wight [1], 46% of patients had nonoperative treatment, and ligament repair was described in 48% of open dislocations and 5% of closed injuries, in which 66% repaired lateral ligaments, 24% medial ligaments and 58% anterior capsules. Ankle instability was rare (2.6%) and not influenced by acute ligament repair [1]. In our study, none of the eight patients showed obvious instability though only one patient underwent primary ligament repair. In our opinion, though open dislocation permits exploration and repair of the ligamentous injuries through the wound conveniently, the primary introduction of foreign materials does not seem to be advisable regarding the risks of infection. Regarding the satisfactory result we obtained with neither ligament nor capsule repaired and the data in the literature, we concur with the viewpoint that late secondary ligament repair is the optimum choice if there is chronic problematic instability failed conservative treatment [36].

The most common complication in the literature is stiffness [1]. It is affected by immobilization and decided by the severity of the trauma. Rehabilitation exercise is vital to reduce its occurrence. Limited ankle range of motion is a frequent long-term complication in literature [3, 4], but the restriction is usually functionally not significant [8, 27]. Our patients presented fairly well functional outcome with regard to instability and mobility of the affected ankles, especially the closed ones. The literature reported that 10% cases developed arthritis [1]. Narrowed joint space was found in five out of nine cases in Garbuio’s study [5] and four out of 16 cases in Elisé’ s study [10]. In our cases, patients developed more severe posttraumatic arthritis in whom the tibiotalar facet chondral lesions were observed intraoperatively. Lui [9] hold the view that the chondral lesion is the single most important contributing factor to the development of posttraumatic ankle degeneration. It is reported that osteochondral lesions of the talus occur in up to 50% of acute ankle fractures and sprains [37] and a more severe fracture pattern correlates with more severe chondral lesions [38]. We have reasons to believe that it is the same with ankle dislocations. However, the patients may have joint space narrowing but good outcomes [22]. Despite the varying degrees of complications, the result remains satisfactory in most cases over the long term, particularly in closed dislocations [1, 8, 10, 23]. The good clinical outcome of our cases supports this viewpoint.

The major weaknesses of the present report were the small number of cases, and the series were limited to posteromedial dislocations. Definite conclusions about the management cannot be made with the reported cases and the findings shall be interpreted cautiously. However, the current study including eight cases is one of the largest series in English and French-language literature and the largest series managed with an external fixator. We believe our case series provide additional material to help recognizing this type of injury.

Conclusion

Pure ankle dislocation is a rare injury with massive ligamentous disruption. Proper treatment of this type of injury could provide good clinical results despite the varying degrees of complications. Emergent reduction, appropriate wound care in open injuries and proper joint stabilisation with a cast or external fixator could be the mainstay of treatment. Primary ligament repair seems unnecessary since ankle instability is uncommon.

Funding

No funding was received for conducting this study.

Data availability

The data of the current study are available from the corresponding author on a reasonable request.

Declarations

Conflict of interest

All authors declare that they have no competing interests.

Ethical approval

This study was performed in accordance with the Helsinki declaration of 1964, and it was approved by the relevant Institutional Review Board at the West China Hospital of Sichuan University.

Informed consent

Informed consent was obtained from all individual participants included in the study.

Consent for publication

Informed consent was obtained.