Arthroscopically Assisted Treatment of Complex Ankle Fractures: Intra-articular Findings and 1-Year Follow-Up

The Journal of Foot & Ankle Surgery 59 (2020) 9−15

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Arthroscopically Assisted Treatment of Complex Ankle Fractures: Intra-articular Findings and 1-Year Follow-Up Mareen Braunstein, MD1, Sebastian F. Baumbach, MD2, Marcel Urresti-Gundlach, MD1, € cker, MD4, Hans Polzer, MD2 Lars Borgmann, PhD3, Wolfgang Bo 1

Associate Registrar, Department of General, Trauma and Reconstructive Surgery, Munich University Hospital, Munich, Germany Surgeon, Associate Professor, Department of General, Trauma and Reconstructive Surgery, Munich University Hospital, Munich, Germany 3 Data Scientist, Center for Higher Education, TU Dortmund University, Dortmund, Germany 4 Surgeon, Professor, Department of General, Trauma and Reconstructive Surgery, Munich University Hospital, Munich, Germany 2

A R T I C L E

I N F O

Level of Clinical Evidence: 4 Keywords: ankle ankle fracture arthroscopy chondral lesion foot and ankle surgery microfracturing

A B S T R A C T

Especially after complex ankle fractures, patients regularly suffer from residual symptoms, presumably due to occult intra-articular injuries. The aim of this study was to evaluate the intra-articular lesions, identify fractures specifically at risk for these, and assess the results after arthroscopically assisted open reduction and internal fixation of complex ankle fractures after 1 year. The primary outcome was the American Orthopedic Foot and Ankle Society (AOFAS) hindfoot score. Secondary outcome parameters were the Olerud and Molander Ankle Score (OMAS), Tegner activity scale, arthroscopic findings, functional assessment, and complications. Thirty-two patients (56% female) were enrolled. Chondral lesions were detected in 91%. Full-thickness lesions treated by microfracturing were observed in 0% of unimalleolar, 43% of bimalleolar, and 40% of trimalleolar fractures. After 1 year, the median (interquartile range) AOFAS was 94 (9) and OMAS was 90 (10) for all patients. When analyzing factors possibly influencing the outcome, age, sex, smoking, grading for surgical procedures according to the American Society of Anesthesiologists, fracture type (uni-, bi-, or trimalleolar), severity of chondral lesions graded according to the International Cartilage Repair Society (grade <4 versus grade 4), and syndesmotic instability had no significant influence on the outcome. The only variable significantly influencing the AOFAS (p = .004) and OMAS (p < .001) was body mass index (BMI; rs = −0.522 and −0.606, respectively), with a higher BMI resulting in inferior outcome scores. Complications were observed in 3 patients, 2 with superficial skin necrosis at the posterolateral incision and 1 nonunion of the medial malleolus. Taken together, these data show that intra-articular injuries were common in ankle fractures. Bi- and trimalleolar fractures were particularly at risk for full-thickness lesions. A higher BMI tended to result in inferior outcome scores. Arthroscopically assisted open reduction and internal fixation led to good to excellent results in all but 1 patient. © 2019 by the American College of Foot and Ankle Surgeons. All rights reserved.

Ankle fractures are common injuries that regularly require operative treatment. Open reduction and internal fixation (ORIF) is the standard of care for dislocated or unstable fractures. Although the treatment of ankle fractures is part of our daily routine, the optimal management is still challenging. This is reflected by numerous patients with persistent unsatisfactory subjective and functional outcomes. According to several studies, they suffer from residual symptoms including chronic pain,

Financial Disclosure: None reported. Conflict of Interest: Hans Polzer is an advisor of Arthrex GmbH. This did not influence the study in any way. Implants from several companies have been used in this study. Arthrex GmbH was not involved in the planning, perception, or analysis of the study or preparation of the manuscript. All other authors have nothing to declare. Address correspondence to: Hans Polzer, MD, Department of General, Trauma and Reconstructive Surgery, Munich University Hospital, Ludwig-Maximilians-Universitat Munchen, Nussbaumstrasse 20, 80336 Munich, Germany. E-mail address: [email protected] (H. Polzer).

stiffness, recurrent swelling, and ankle instability. Winters (1) reported moderate to poor results after 1 year of follow-up in >20% of isolated, simple fractures to the distal fibula. Hong et al (2) reported that >50% of their patients with bi- or trimalleolar fractures suffered from stiffness and pain, and 18% did not return to sports after 2 years. In a long-term study with a follow-up of 10 years, 48% of patients showed moderate to poor results after bimalleolar fractures (3). Anatomic reduction has been identified as a prerequisite for satisfactory postoperative results (4); nevertheless, it does not automatically lead to a favorable clinical outcome. Growing evidence suggests that a poor result might be related to occult intra-articular injuries involving cartilage and soft tissues. Consequently, an increasing number of authors emphasize the value of ankle arthroscopy in acute fracture treatment. Arthroscopically assisted open reduction and internal fixation (AORIF) allows verification of the anatomic reduction, examination of all intra-articular structures, and if

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M. Braunstein et al. / The Journal of Foot & Ankle Surgery 59 (2020) 9−15

necessary, the immediate treatment of traumatic intra-articular pathologies. To date, there has been no proof that supplementary arthroscopy increases complication rates in acute fracture treatment (5,6); however, a positive effect has not been verified either, because of the paucity of studies correlating intra-articular lesions and their treatment to subjective and functional outcomes (5,7−11). Although the concept of intraarticular injuries as a crucial determinant affecting the postoperative result is intuitively comprehensible, arthroscopy is still rarely performed in ankle fracture management. A database review (12) analyzed 32,307 patients treated operatively for an ankle fracture in the United States; in <1%, additional ankle arthroscopy was performed. This is remarkable, especially considering that chondral lesions (CLs) are detected in up to 89% of ankle fractures (5). The few studies reporting on the outcome after performing AORIF included patients with simple ankle fractures only. As an example, the 2 existing randomized controlled trails exclusively enrolled patients €r with isolated fractures to the distal fibula (Arbeitsgemeinschaft fu Osteosynthesefragen [AO] type 44 B1), representing the simplest fracture, which is regularly treated operatively (6,13). The only comparative retrospective cohort study also included only isolated fibula fractures (14). This is regrettable, as the number and severity of CLs is known to increase with the complexity of the fracture (4,8,9). Consequently, it can be hypothesized that the effect of AORIF might be more pronounced in complex fractures (15). Only a few studies have reported on the results of AORIF in patients with bi- and trimalleolar fractures (16,17). In contrast to all other studies, Aktas et al (16) observed the highest number of CLs and the most inferior AOFAS score for unimalleolar fractures compared to bi- and trimalleolar fractures. Unfortunately, the authors stated neither the severity of the CLs nor the arthroscopic treatment performed, making interpretation of the outcome difficult. Only a few arthroscopic studies have reported on intra-articular lesions in ankle fractures. Even fewer have described complex fractures, reported on arthroscopic procedures, or assessed clinical results after AORIF. It is of great interest to identify fracture types with an increased risk of suffering a severe CL, which would potentially benefit most from AORIF. Therefore, the aim of this prospective study was to report all aspects in complex ankle fractures: intra-articular pathologies, arthroscopic treatment, and complications, as well as subjective and functional outcomes 1 year after arthroscopically assisted ankle fracture treatment. Patients and Methods

Study Design After approval from our institutional review board (AZ 117-15), we performed a prospective study from May 2013 to December 2014. Patients with complex ankle fractures, >17 years old, who sustained the injury <14 days before surgery and gave informed consent were consecutively enrolled. A complex fracture was defined as either an isolated malleolar fracture in combination with ligamentous instability or a bi- or trimalleolar fracture. An unstable ligamentous injury was defined as either a disruption of the deltoid ligament leading to increased medial talar tilt or an unstable syndesmotic injury assessed by the external rotation test, both after osteosynthesis of all fractures. Exclusion criteria were isolated unimalleolar fractures, pilon fractures, open fractures, multiple injuries, mental illness, noncompliance, or pregnancy. The inclusion and exclusion criteria are depicted in Table 1. Fractures were evaluated and classified according to the AO classification system based on preoperative computed tomography (CT) scan in all patients by 2 surgeons (S.F.B. and M.B.) independently. Disagreement was resolved by discussion. All fractures were initially reduced, followed by immobilization in a plaster cast. If sufficient reduction could not be achieved, an external fixator was applied. Osteosynthesis was performed when skin wrinkling was observed. Data obtained prospectively included the patient’s age, sex, medical history (comorbidities and medication), diabetes mellitus status, smoking habits, date of injury/surgery, AO classification, intra-articular findings, and arthroscopic procedures. All patients were followed for 6 weeks and 12 months after surgery. The clinical and radiographic analysis was performed by 2 members of the foot and ankle team (S.F.B. and M.B., not the surgeon). The primary outcome was the American Orthopedic Foot and Ankle Society (AOFAS) hindfoot score. The secondary outcomes were the Olerud and Molander Ankle Score (OMAS), the Tegner activity scale (TAS), arthroscopic findings and procedures, functional assessments, and complications.

Table 1 Inclusion and exclusion criteria Inclusion

Exclusion

Unimalleolar fracture and ligamentous injury Bi- or trimalleolar fracture § ligamentous injury ≥18 years old Date of injury ≤14 days

Isolated unimalleolar fracture

Written informed consent

Pilon fracture Open fracture Mental illness, noncompliance, pregnancy Multiple injuries

Radiographic Analysis Radiographic assessment comprised routine x-rays (non-weightbearing, anteroposterior, lateral, and mortise view) and CT scans before surgery and postoperatively. Six weeks after the operation, non-weightbearing films were taken. In all cases, position of implants, reduction, and fracture healing were evaluated. Operative Technique Standardized AORIF was performed by 1 surgeon (H.P.). The operative technique was described in detail previously (18). Arthroscopy Ankle arthroscopy was performed first, without a distraction device, with standard anteromedial and anterolateral portals using a 2.7-mm 30° arthroscope. A systematic examination was performed to inspect all intra-articular structures (19). Loose bodies and loose aspects of cartilage were removed. Lesions of the articular cartilage were graded according to depth by inspection and probing (superficial, partial-thickness, or full-thickness cartilage defect). Grading was carried out as recommended by the International Cartilage Repair Society (ICRS), and the localization was documented (20). Debridement and chondroplasty were performed for CLs grades 2 and 3 according to the ICRS, whereas grade 4 lesions (full-thickness lesions) were treated by chondroplasty and microfracturing. Osteosynthesis In the first step, ORIF of posterior malleolus (PM) fracture was performed using a posterolateral approach whenever the fragment size allowed for it. The rationale was that the fracture to the PM is considered a bony avulsion of the posterior tibiofibular ligament with the ligament intact (21). By anatomical reduction of the PM fragment, the bony anatomy and length of the intact posterior tibiofibular ligament are restored. Thereby, the fibula is reduced anatomically into the tibial groove (21,22). Consequently, an increasing number of studies argue for ORIF of the PM fragment independent of its size (22−28). Thereafter, the lateral malleolus was fixed, either using the same posterolateral approach in case of PM fracture or using a standard lateral approach according to AO standards. € nchen, Either a tubular plate (Synthes, Umkirch, Germany) or a locking plate (Arthrex, Mu Germany) was used for multifragmentary fractures, small distal fragments, or osteoporotic bone. Medial malleolus fractures were fixed using 2 cannulated lag screws if the size of the fragment allowed for it. If the fragment was too small for 2 cannulated screws, a locking hook plate was used (Arthrex). In comminuted fractures, tension band wiring was applied. Syndesmotic Instability After fracture fixation, syndesmotic stability was tested with the external rotation test under fluoroscopy (29). Widening of the tibiofibular clear space was considered to be tibiofibular joint instability. When in doubt, the uninjured side was assessed with the external rotation test under fluoroscopy (without removing the covering). In case of instability, the distal tibiofibular joint was reduced using a reduction clamp in neutral axis (30), and an intraoperative assessment of the reduction was performed using € rnberg, Germany). After correct 3-dimensional visualization (Iso-C-3D, Ziehm Imaging, Nu reduction was confirmed, either a TightRope (Arthrex) or positioning screw was applied based on the decision of the surgeon. Ligamentous Injury In case of medial instability, the deltoid ligament was repaired using sutures. Medial instability was defined as increased medial talar tilt or increased medial clear space after osteosynthesis of all fractures and stabilization of the syndesmosis if necessary. Final Ankle Arthroscopy and Radiographic Assessment A final examination of anatomic reduction and intra-articular structures was performed by ankle arthroscopy in all cases. Displacement was graded into 3 groups (no dislocation, dislocation ≤2 mm, and dislocation >2 mm). In case of malreduction (≥2 mm), fixation would be removed and reduction would be performed again.

M. Braunstein et al. / The Journal of Foot & Ankle Surgery 59 (2020) 9−15

Table 2 Demographics and risk factors according to fracture type

Table 4 Treatment of bony and ligamentous injuries according to fracture type

Fracture Type (n)

Age

ASA

BMI

Smoking

Diabetes

All (32) Unimalleolar (5) Bimalleolar (7) Trimalleolar (20) p Value

46 (27) 32 (26) 36 (29) 54 (26) .038

2 (1) 1 (1) 1 (1) 2 (0) .036

26 (8) 25 (6) 23 (6) 29 (9) .205

11 2 2 7 NA

1 0 1 0 NA

Abbreviations: ASA, American Society of Anesthesiologists; BMI, body mass index; NA, not applicable. Values are presented as n or median (interquartile range).

Postoperative Treatment All patients followed the same postoperative protocol, with partial weightbearing (20 kg) for 6 weeks followed by full weightbearing. Range of motion exercises were performed immediately after operative treatment.

Injury

Lag Screw

Unimalleolar fracture (5) Lateral (4) Medial (1) Syndesmosis (5) Bimalleolar fracture (7) Lateral (5) Medial (3) Posterior (6) Syndesmosis (3) Trimalleolar fracture (20) Lateral (20) Medial (20) Posterior (20) Syndesmosis (2)

Tubular Plate

2

Locking Plate

Tight Rope

Positioning Screw

2

3

2

1

1

1

2

1

4 3 2

4

4 17 5

1

16 3

14

The number of lag screws only refers to isolated lag screws. Lag screws that were used in case of tubular or locking plates are not listed.

Statistical Methods The Shapiro-Wilk test revealed nonnormal distribution for either primary outcome parameter (AOFAS, p = .009, and OMAS, p = .030). Therefore, nonparametric tests were chosen for further analysis. Next to standard descriptive statistics, group comparisons were conducted using the chi-squared, Mann-Whitney U test, Spearman’s correlation, and Kruskal-Wallis analysis of variance. If not stated differently, values are given as median (interquartile range). Because of multiple testing, a Bonferroni alpha level correction was performed, setting the level of significance at p ≤ 0.007.

Results Between May 2013 and December 2014, 89 patients presented with an acute ankle fracture. Thirty-two patients were eligible for inclusion. The exact inclusion and exclusion criteria are depicted in Table 1. Twenty patients were female (56%), and 12 patients were male (44%). The median age was 46 (27) years. Table 2 displays the demographics and risk factors subdivided according to fracture type. Overall, no significant differences could be found between the 3 groups. Of all patients, 16% suffered an unimalleolar fracture combined with syndesmotic instability (n = 5) or deltoid ligament rupture (n = 1), 22% a bimalleolar fracture, and 64% a trimalleolar fracture. All fractures were further classified according to the AO classification system (Table 3). Intraoperatively, no malreduction was observed in the final ankle arthroscopy or the final radiographic assessment. Consequently, no fixation had to be removed intraoperatively. Furthermore, anatomic reduction was verified in all cases by postoperative CT scans in all patients. A detailed overview of the operative treatment is depicted in Table 4. Intraarticular Findings Of the 32 patients included, 5 suffered a unimalleor, 7 a bimalleolar, and 20 a trimalleolar fracture. In 1 patient with a bimalleolar fracture

Table 3 Distribution of the different fracture types according to the AO classification system AO Classification

n (%)

All 44 A 3.3 44 B1.2 44 B1.3 44 B2.3 44 B 3.1 44 B 3.2 44 B 3.3 44 C 2.2 44 C 2.3 44 C 3.2

32 (100) 3 (9) 1 (3) 2 (7) 3 (9) 3 (9) 1 (3) 12 (41) 1 (3) 5 (13) 1 (3)

€ r Osteosynthesefragen. Abbreviation: AO, Arbeitsgemeinschaft fu

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and 2 patients with a trimalleolar fracture, no CL was observed. In all of the remaining 29 patients, ≥1 CLs were present. The severity of all CLs observed ranged from ICRS grade 2 to 4. Taken together, 45 CLs were documented in 32 patients. We observed 27 multifocal lesions in 11 patients, 18 unifocal CLs in 18 patients, and no CLs in 3 patients. Of these 45 CLs, 37 were located talar and 8 tibial. When looking at the 27 multifocal lesions only, 17 were located talar (63%), 2 tibial (7%), and 8 both talar and tibial (30%). The median (interquartile range) ICRS grade of the multifocal lesions was 2 (0). Of the 18 unifocal lesions, 17 were located talar (94%) and 1 was located tibial (6%). The ICRS grade of these unifocal lesions was 3 (2). Table 5 depicts the severity of the CL per fracture type and occurrence (uni- and multifocal). In unimalleolar fractures, most CLs (40%) were observed at the lateral third of the talus; in bimalleolar fractures, most CLs (68%) were located at the medial third of the talus; and in trimalleolar fractures most CLs (38%) were observed at the medial third of the talus. The exact localization of all chondral injuries is illustrated in the Figure. Arthroscopic Procedures A detailed overview regarding the incidence and severity of all CLs, as well as the arthroscopic treatment according to the type of fracture, is depicted in Table 6. Partial synovectomy was performed in all patients. In 29 of 32 patients (91%), a chondroplasty was performed, and in 11 of 32 patients (34%), microfracturing was performed. Loose bodies were removed in 27 of 32 patients (84%), again with no significant differences among the fracture types (Table 6). No malreduction was observed during the final ankle arthroscopy or the final radiographic assessment.

Table 5 Severity of chondral lesions according to the ICRS criteria in regard to fracture type Fracture Type (n)

Chondral Lesions

Unimalleolar (5)

Unifocal Multifocal Unifocal Multifocal Unifocal Multifocal

Bimalleolar (7) Trimalleolar (20)

Grade 0

Grade 1

Grade 2

Grade 3

Grade 4

1

3

2 1

6 1

1 4 2 5 3

If multiple chondral lesions were present, only the most severe chondral lesion per patient is depicted.

M. Braunstein et al. / The Journal of Foot & Ankle Surgery 59 (2020) 9−15

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Fig. Distribution of all chondral injuries according to fracture type.

Table 6 Incidence and severity of chondral lesions, arthroscopic treatment, and outcome according to type of fracture Fracture Type (n)

Chondral Lesion

Grade (ICRS)*

Microfracturing

Loose Bodies Removed

AOFAS

OMAS

TAS

TAS at 1 yr

All (32) Unimalleolar (5) Bimalleolar (7) Trimalleolar (20) p Value

29 (91) 5 (100 ) 6 (86) 18 (90) .654

2.5 (2) 2.0 (2) 3.5 (2) 3.0 (2) .063

11 (34) 0 (0) 3 (43) 8 (40) .210

27 (84) 3 (60) 6 (86) 18 (90) .102

94 (9) 98 (2) 97 (10) 90 (10) .048

90 (10) 95 (4) 95 (10) 85 (15) .024

5 6 5 5 .382

4 6 5 4 .095

Abbreviations: AOFAS, American Orthopedic Foot and Ankle Society hindfoot score; ICRS, International Cartilage Repair Society; OMAS, Olerud and Molander Ankle Score; TAS, Tegner activity scale. If multiple chondral lesions were present only the most severe chondral lesion per patient was used. Values are presented as n (%) or median (interquartile range). *Patients with chondral lesions only.

Complications Complications were documented in 3 patients (9%). Two patients (patients 1 and 2) had prolonged wound healing with superficial skin necrosis at the posterolateral skin incision and were treated with antibiotics and a single superficial surgical debridement. There were no signs of deep infection, and the wounds healed without further interventions or complications. One patient (patient 3) developed nonunion of the medial malleolus that was revised surgically (conversion from cannulated screws to locking hook plate). All patients suffering from postoperative complications had at least 1 risk factor in their medical history: patient 1 (female, 64 years old): smoking; patient 2 (female, 58 years old): obesity; and patient 3 (male, 54 years old): smoking, obesity, and diabetes mellitus type 2. Outcomes A detailed overview regarding the incidence and severity of all CLs, arthroscopic treatment, and outcome according to the type of fracture is depicted in Table 6. Three patients (9%) were lost to follow-up after 1 year. The AOFAS was 94 (9) for all patients, and the OMAS was 90 (10). The TAS score was 5 before injury and 4 a year after surgery. Patients suffering from unimalleolar fractures had AOFAS scores of 98 (2) and OMAS of 95 (4). The TAS was 6 initially and the same after 1 year. After a bimalleolar fracture, AOFAS was 97 (10) and OMAS was 95 (0). The TAS score was 5 before the ankle fracture and 5 after 1 year of followup. One year after a trimalleolar fracture, the AOFAS was 90 (10), and OMAS was 85 (15). The TAS score was 5 initially and 4 after 1 year of

follow-up. According to the AOFAS score after 1 year, 55% of all patients achieved an excellent result, 41% good, 4% fair, and 0% poor.

Factors Possibly Influencing Outcomes We tried to identify factors possibly influencing the outcome of arthroscopically treated ankle fractures (AOFAS/OMAS score being the dependent variables). The following factors were analyzed: age, sex, smoking, body mass index (BMI), grading for surgical procedures according to the American Society of Anesthesiologists (ASA), fracture type (uni-, bi-, or trimalleolar), severity of CLs (ICRS grade <4 versus grade 4), application of an external fixateur, and syndesmotic instability (independent variables). Diabetes was not included, as only 1 patient had diabetes. First, the influence of each independent variable was calculated (Table 7). After the alpha-level adjustment, the only variable significantly influencing the AOFAS (p = .004) and OMAS (p < .001) was BMI (rs = −0.522 and −0.606, respectively), where a higher BMI tended to result in inferior outcome scores. Notably, no significant differences could be detected for the AOFAS (p = .363) or OMAS (p = .580) when comparing patients with full-thickness CLs (ICRS grade 4) to patients with less severe CLs (ICRS grade ≤3). Patients with a full-thickness lesion achieved an AOFAS of 97 (8) and an OMAS of 95 (10), whereas patients with a CL of ICRS grade ≤3 achieved an AOFAS of 92 (10) and an OMAS of 90 (11). Five patients were treated by application of an external fixateur. These 5 patients achieved an inferior result for both AOFAS (90 [13]), and OMAS (85 [15]), compared with patients who did not require an external fixateur (AOFAS 97 [9] and OMAS 95 [10]), but

M. Braunstein et al. / The Journal of Foot & Ankle Surgery 59 (2020) 9−15

Table 7 Factors possibly influencing the outcome of arthroscopically assisted treated complex ankle fractures AOFAS Factor Age Sex Female Male Smoking No Yes BMI ASA External fixateur No Yes Syndesmotic instability No Yes Chondral lesion ICRS <4 ICRS 4 Fracture type Unimalleolar Bimalleolar Trimalleolar

Median (IQR)

OMAS

rs

p

−0.322

.089 .679

90 (9) 97 (10)

Median (IQR)

rs

p

−0.465

.011 .444

85 (13) 95 (10) .740

92 (9) 97 (13)

.521 88 (11) 95 (10)

−0.522

−0.606

.004* .094 .142

97 (9) 90 (13)

95 (10) 85 (15) .615

94 (9) 98 (10)

.324 85 (13) 95 (9)

.363 92 (10) 97 (8)

.580 90 (11) 95 (10)

.048 98 (2) 97 (10) 90 (10)

.001* .036 .142

.024 95 (4) 95 (10) 85 (15)

Abbreviations: AOFAS, American Orthopedic Foot and Ankle Society hindfoot score; ASA, American Society of Anesthesiologists; BMI, body mass index; ICRS, International Cartilage Repair Society; IQR, interquartile range; OMAS, Olerud and Molander Ankle Score; rs, Spearman’s correlation coefficient.

the differences (AOFAS, p = .142; OMAS, p = .142) did not reach the level of significance. Discussion Only very few studies have reported on arthroscopic findings in complex ankle fractures. Even fewer are available that not only assess the findings but also report on the arthroscopic procedures or assess clinical results after AORIF. Furthermore, fracture types with an increased risk of suffering a full-thickness CL have not yet been identified. In this study, CLs were present in 91% of all fractures, with the vast majority of CLs (82%) located talar. This is in line with most studies available (8,9,13); only 2 studies reported a remarkably lower incidence, with 20% and 28% of CLs, respectively (16,17). The reason for this discrepancy is the diverse definition of CL, as both studies reported only deep CLs (either 50% or full-thickness lesions). From our point of view, this is problematic, as it suggests that only deep lesions are of relevance. Therefore, this study reports all cartilage lesions according to the ICRS classification. Surprisingly, all patients in this study with a unimalleolar fracture suffered a CL. Furthermore, most of these were multifocal injuries. However, all lesions were superficial (ICRS grade 2). Patients suffering a bi- or trimalleolar fracture predominantly suffered a unifocal lesion, though these were more severe. Grade 3 or 4 lesions were observed in 57% of bimalleolar and 50% of trimalleolar fractures. Regarding the frequency of CL, Leontaritis et al (9) found that a type 4 supination/external rotation fracture was 8.1 times more likely to be associated with multifocal CLs compared with type 1 supination/external rotation or pronation/external rotation fracture, which is in contrast to our findings. However, they did not assess the depth of the CL but only the frequency. Similar to our findings, most authors showed that the extent of the CLs increased with the complexity of the fracture (4,8). Whether the number of CLs or the severity is decisive for the prognosis is still unclear. Only Stufkens et al (4) explicitly focused on this question and

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demonstrated that lesions of >50% depth at the anterolateral aspect of the talus or the medial malleolus are associated with an inferior result in unimalleolar fractures. In their study, the number of lesions did not affect the outcome (4). To identify fracture types specifically associated with deep CLs would be desirable, as these might gain most from AORIF. Therefore, Lambers et al (31) performed a study analyzing postoperative CT scans to identify fracture types regularly associated with osteochondral lesions. They identified an osteochondral lesion in 14% of rotational type ankle fractures with syndesmotic injury. We believe this falls short, as by using CT scans only, all isolated CLs, also grade 4 lesions, will be missed. In our study, 41% of the patients with a bi- or trimalleolar fracture suffered a full-thickness chondral injury treated by microfracturing. From our point of view, this is an important finding, as immediate treatment of such lesions by microfracturing seems to be beneficial (32). This suggests that bi- and trimalleolar fractures might particularly benefit from arthroscopically assisted fracture treatment. To evaluate the impact of AORIF, both intra-articular findings and procedures as well as outcomes have to be reported. In this series, 55% of all patients achieved an excellent result, 41% good, and 4% fair according to the AOFAS score after 1 year. This is remarkable, in particular when considering the high proportion of trimalleolar fractures included. As expected, patients with an unimalleolar fracture (AOFAS 98) had superior clinical results compared with patients with bimalleolar (AOFAS 97) or trimalleolar (AOFAS 90) fractures. When comparing the outcome of studies evaluating ORIF to the results obtained by AORIF in this study, AORIF led to excellent clinical results, with an OMAS of 90 (10) for all patients. Lash et al (33) followed 74 patients after surgery for an isolated malleolus fracture. The mean OMAS was 71 after 2 years. Ponzer et al (34) reported a mean OMAS of 84 § 23 for type B fractures, again with a follow-up of 2 years. By that time, only 36% of the patients reported a complete recovery, whereas 64% had sports- or work-related problems (34). The good results for complex ankle fractures in the study here might be attributed to the full-thickness CLs being not only identified but also treated. Consequently, neither the presence of a CL nor the fracture type had a significant influence on the outcome in this study. Only a few studies have reported outcomes after AORIF. Stufkens et al (4) observed clinical signs of osteoarthritis in 39% and radiological signs in 43% after 12.9 years, with a mean AOFAS of 88.9 (range 18 to 100). This result is especially notable, as only patients with isolated lateral malleolus fractures were enrolled. Da Cunha et al (35) observed statistically significantly worse clinical outcomes in patients with CLs than in patients without them (Foot and Ankle Outcome Score 81.2 versus 92.1). Turhan et al (36) included only patients with isolated medial malleolus fracture and retrospectively compared AORIF to ORIF. AORIF (OMAS 92) led to significantly better results compared with ORIF (OMAS 86). Fuchs et al (14) performed a retrospective cohort study comparing ORIF to AORIF, again including only isolated fibula fractures. They also observed better results for Patient-Reported Outcomes Measurement Information System (PROMIS) physical function score, visual analog scale, or OMAS score after 67 months when treated by additional arthroscopy, but none of the differences reached the level of significance; the complication rate was comparable. Two randomized controlled trials compared ORIF to AORIF, unfortunately enrolling only simple lateral malleolus fractures (type Weber B). Thordarson et al (13) found better, although not significant, results in favor of AORIF. Presumably, the study was underpowered, as only 19 patients (10 versus 9) were enrolled. Takao et al (37) found significantly better results for AORIF (AOFAS 91) compared with ORIF (AOFAS 88). The simple fracture type investigated in that study might be accountable for the slight differences observed. Remarkably, Aktas et al (16) observed, in contrast to all other studies, a lower incidence of CLs in trimalleolar fractures compared with unimalleolar fractures. Concurrently, the results for the AOFAS score were most superior for the most complex fracture type.

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The reason for these unclear results in the studies available might be the differing fracture types included. This underlines the importance of identifying the fracture types benefiting from additional arthroscopy. Of the independent variables age, sex, smoking, BMI, ASA, fracture type (uni-, bi-, or trimalleolar), severity of CLs (ICRS grade <4 versus 4), application of an external fixateur, and syndesmotic instability, in this study the only variable significantly influencing the AOFAS (p = .004) and OMAS (p < .001) was the BMI (rs = −0.522 and −0.606, respectively). A higher BMI tended to result in inferior outcome scores. This is well in line with previous studies. Obese patients were observed to suffer more severe complications and inferior OMAS, Self-Reported Foot and Ankle Questionnaire, and Lower Extremity Functional Scale scores than patients with normal weight (38). It has been hypothesized that these patients suffer more complex fractures (39), but the exact reason for the finding is unknown. The complication rate in our patient sample was comparable to previous studies performing ORIF only (40,41). Although only complex fractures were included, which are more frequently associated with complications, the presented rate was not higher (42,43). The patient in our cohort who suffered a nonunion of the medial malleolus had various factors (diabetes, smoking, and obesity) that are known to increase the risk of nonunion (40). To date, no study has provided evidence that ankle arthroscopy in acute fracture treatment increases complication rates (6,13). The main limitation of this study is that we cannot provide a comparison group treated with ORIF. Consequently, the 2 operative strategies could not be compared. Further, only a short-term follow-up (12 months) is reported; a longer-term follow-up would be desirable. Although predominantly used to define chronic CLs, the area of the lesions was not assessed, but only the depth, as this was the determinant for surgical treatment. Additionally, we are missing bilateral CT scans for assessment of the congruence of reduction of the fibula in relation to the fibular notch of the distal tibia in case of syndesmotic stabilization to compare the injured to the uninjured ankle. Finally, the cohort of this series is relatively small, especially for uni- and bimalleolar fractures. Therefore, the results of the multiple logistic regression analysis must be interpreted with care, as they are of limited validity. Based on the sample size and the number of predictors, the current power of the study is 0.685. In conclusion, intra-articular injuries are commonly observed in complex ankle fractures, which regularly require arthroscopic treatment. The more complex the fracture, the more pronounced the cartilage lesion. Arthroscopically assisted fracture management leads to good to excellent results in complex ankle fractures, with a rate of complications comparable to that of ORIF. Based on our findings, AORIF seems to be reasonable for bi- and trimalleolar fractures, which are particularly at risk of suffering severe intra-articular lesions. Acknowledgments We thank Maren Hella Thun for the preparation of the figure. References 1. Winters K. Functional outcome of surgery for fractures of the ankle. N Z Med J 2009;122:57–62. 2. Hong CC, Roy SP, Nashi N, Tan KJ. Functional outcome and limitation of sporting activities after bimalleolar and trimalleolar ankle fractures. Foot Ankle Int 2013;34:805– 810. 3. Day GA, Swanson CE, Hulcombe BG. Operative treatment of ankle fractures: a minimum ten-year follow-up. Foot Ankle Int 2001;22:102–106. 4. Stufkens SA, Knupp M, Horisberger M, Lampert C, Hintermann B. Cartilage lesions and the development of osteoarthritis after internal fixation of ankle fractures: a prospective study. J Bone Joint Surg Am 2010;92:279–286. 5. Chen XZ, Chen Y, Liu CG, Yang H, Xu XD, Lin P. Arthroscopy-assisted surgery for acute ankle fractures: a systematic review. Arthroscopy 2015;31:2224–2231.

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