Radiographic classification for fractures of the fifth metatarsal base

Running Title:

Fracture types of the fifth metatarsal base

Alexander T. Mehlhorn MD, Jörn Zwingmann MD, Anja Hirschmüller MD, Norbert P. Südkamp MD, PhD, Hagen Schmal MD, PhD

Department of Orthopaedic Surgery, University of Freiburg Medical Center, 79106 Freiburg, Germany

Corresponding address:

Hagen Schmal, M.D.

University of Freiburg Medical Center

Department of Orthopaedic Surgery

Hugstetter Str. 55

D-79106 Freiburg i.Br.

e-mail: hagen.schmal@freenet.de

Phone: +49 761 270 90160

Fax: +49 761 270 28000

Key Words:

radiomorphometry – fracture – fifth metatarsal base - classification

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ABSTRACT

Objective

Avulsion fractures of the fifth metatarsal base (MTB5) are common fore foot injuries. Based on a

radiomorphometric analysis reflecting the risk for a secondary displacement a new classification was

developed.

Materials and Methods

A cohort of 95 healthy, sportive and young patients (age ≤ 50 yrs) with avulsion fractures of the

MTB5 was included in the study and divided in groups with non-displaced, primary-displaced and

secondary-displaced fractures. Radiomorphometric data obtained using standard oblique and dorso-

plantar views were analyzed in association with secondary displacement. Based on this, a

classification was developed and checked for reproducibility.

Results

Fractures with a longer distance between the lateral edge of the styloid process and the lateral

fracture step-off and fractures with a more medial joint entry of the fracture line at the MTB5 are at

higher risk to displace secondarily. Based on these findings, all fractures were divided in three types:

type I with a fracture entry in the lateral third, type II in the middle third and type III in the medial

third of the MTB5. Additionally, the three types were subdivided in an A-type with a fracture

displacement <2mm and a B-type with a fracture displacement ≥ 2mm. A substantial level of

interoberserver agreement was found in the assignment of all 95 fractures to the 6 fracture types

(κ=0.72). The secondary displacement of fractures was confirmed by all examiners in 100%.

Conclusions

Radiomorphometric data may identify fractures at risk for secondary displacement of the MTB5.

Based on this, a reliable classification was developed.

Introduction

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Avulsion fractures of the base of the fifth metatarsal are a common foot injury that causes dorso-

lateral forefoot pain [1-3]. These injuries have to be clearly distinguished from the “true” Jones

fractures, which is located at the junction between the proximal diaphysis and the metaphysis of the

fifth metatarsal involving the 4-5th intermetatarsal articulation [4] and from the proximal diaphyseal

fracture, which is located distally to the 4-5th intermetatarsal articulation [5].

Avulsion fractures of the fifth metatarsal base occur by indirect force when the foot is plantar-

flexed and inverted. The exact pathomechanism is controversially discussed, but recently some

cadaver studies revealed that the causing force is traction of the lateral cord of plantar aponeurosis

and the short peroneal muscle tendon [6, 7].

Therapy recommendation of non-displaced fractures of the fifth metatarsal base includes

conservative treatment with protected weight bearing in a walking cast, hard-sole-shoe or a

compression wrap [4, 8, 9]. Extended non-weight bearing was identified as a predictor of a poor

functional outcome [10]. The therapy of displaced fractures is controversially discussed, both

conservative and operative treatment with open reduction, screw fixation or tension band wiring

[11-13] is possible [14]. Decision for treatment depends on the patients’ age, activity level and co-

morbidities; for healthy and young patients with athletic ambitions operative treatment is more

favourable.

In the present paper, the hypothesis was tested whether radiomorphometric parameters of

fractures of the fifth metatarsal base allow the reliable prediction of a possible secondary

displacement. Along with this, a classification was developed considering these observations.

Materials and Methods

Patients

From 2001 through 2009 a cohort of 95 patients treated for avulsion fractures of fifth metatarsal

base was included in the study. Only healthy (patients graded 1 or 2 according to the ASA

classification [15]), young (age ≤ 50 yrs) and sportive patients (at least one sportive activity was

performed at time of injury) were included in the present study. All patients considered their sports

activities as an essential component for their quality of life. In the same time period a total of 183

patients were operatively treated for metatarsal fractures. Multiple injured patients were excluded,

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4 patients had additional fractures of the foot skeleton. Considering the overall rate of operative

treatment following presentation in the emergency department with 70%, the inclusion rate was

40% of all patients with fractures of the fifth metatarsal base treated in the examined time period (95

of 238 patients).

After clinical examination, the diagnosis was confirmed by X-rays of the affected foot in a dorso-

plantar and an oblique plane. All included observed fractures were proximal to the 4-5th

intermetatarsal articulation in both radiographic planes and were related to an indirect forefoot

trauma. The study was approved by the Ethical board.

The patients were distributed into three groups: group 1 included patients with non-displaced

fractures (step-off < 2mm), who were treated conservatively for 6 weeks. Patients with fractures

showing a step-off exceeding 2mm in at least one radiographic plane in initial X-rays were considered

primarily displaced and were treated operatively (group 2). Group 3 included patients with initially

non-displaced fractures, who were treated conservatively and secondarily displaced (fracture step-

off > 2mm). Following this, they were referred to operative treatment. Conservative treatment

consisted of 15kg partial weight bearing for 6 weeks in a lower leg cast (VACOpedes, OPED,

Germany). Operative treatment was performed with open reduction and internal fixation using a

bicortical screw or tension band wiring followed by 15kg partial weight bearing for 6 weeks in a lower

leg cast. Secondary displacement was defined when the initial step-off increased from less to higher

than 2mm. During conservative treatment control radiographs were performed 0.5, 1, 2, 4 and 6

weeks after trauma.

Radiographic assessment

All radiographs were performed in two standard planes including an oblique and a dorso-plantar

view by one investigator (A.T.M., 7 years of experience as a dedicated foot and ankle surgeon).

Radiographic measurements were performed in the dorso-plantar view using a radiomorphometric

analysis tool (Tiani J-Vision, Version 3.3.16, Tiani Medgraph AG, 1150 Wien, Austria/Europe).

The lateral fracture step off at the lateral border of the fifth metatarsal base, the tip of the

styloid process, the medial fracture step at the metatarso-cuboid joint and the tip of the medial edge

of the fifth metatarsal base were defined as the anatomical landmarks. In order to standardize for

bone size and to exclude radiographic magnification errors the following proportions and angles

were calculated:

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joint fracture angle (JFA) α (Fig. 1, left)

joint ratio (JR) C/A (Fig. 1, right)

lateral edge length (LEL) B (Fig. 1, right)

the lateral edge ratio (LER) B/A (Fig. 1, right)

The joint-fracture angle (JFA) α was measured between the proximal articular surface of the fifth

metatarsal base and the line connecting the lateral and the proximal fracture step off (Fig. 1, left).

The Joint Ratio (JR = C/A) was calculated dividing the line tangential to the metatarso-cuboid joint

reaching from the tip of the styloid process to the fracture step-off (C) through the total length of the

fifth metatarsal base (A) (Fig. 1, right). The lateral edge length (LEL) was calculated measuring the

distance from the tip of the styloid process to the lateral fracture step-off of the lateral surface of the

fifth metatarsal (B) (Fig. 1, right). The lateral edge ratio (LER = B/A) was calculated dividing the LEL (B)

through the total length of the fifth metatarsal base (A) (Fig. 1, right). Regarding functional anatomy,

the LEL and C correspond with the insertion area of the peroneus brevis tendon and the lateral

aspect of the plantar aponeurosis [16].

Interobserver reliability and clinical practicability of classification system

Based on the results of the radiomorphometric evaluation a classification system was developed,

which considers parameters of an increased fracture displacement risk. All X-rays were collected and

numerated; patient identification data was rendered anonymously. Then, the X-rays were evaluated

by two different observers. Observer 1 was an experienced orthopaedic surgeon with special interest

in foot surgery. Observer 2 was a fellow for orthopaedic surgery also with special interest in foot

surgery. None of the observers had any experience with the classification before study onset to

exclude the influence of training on reliability. At the beginning of the study, the classification was

provided to the observers in a written form. In addition, the first author gave a 15minute

introductory explanation of the classification. The evaluation of the X-rays by the two observers took

place independently.

Statistical assessment

Numerical data were analysed by computer software package for statistical analysis (SPSS

statistical program, version 11.5, SPSS Inc. Chicago, USA). All values are reported as mean ± standard

deviation. Statistical significance was determined using the Mann-Whitney U-Test and the Kruskal-

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Wallis H-Test for comparing the medians of two and multiple populations, respectively. Categorial

data are presented as absolute frequency and percent distribution. Data (incidences) were arranged

in R by C tables, and statistical significance of differences calculated using a 2 –test. A significance

level of 0.05 was used throughout the study.

Percentage agreement and interobserver reliability were assessed with the JMP-statistical

package (Version 6, SAS Campus Drive, Building S, Cary, NC, 27513, USA). For intraobserver and

interobserver reliability, the kappa statistic function of the JMP-statistical package was used

measuring kappa values (ĸ) to describe the agreement between observers [17]. Kappa values were

interpreted using the guidelines proposed by Landis and Koch [18].

Results

Epidemiological data

The mean age of all patients was 39±18 years (41 females and 54 males). 56 fractures,

representing group 2, were treated with open reduction and internal fixation (ORIF) with a bicortical

screw (n=43) or a tension band wiring (n=13). The remaining fractures (n=39) were initially treated

non-operatively. A total of 10 patients, representing group 3, were treated by ORIF following initial

non-operative therapy because of secondary displacement. The remaining patients with initial

conservative treatment (n=29) represent group 1. All patients were immobilized in a cast as

described and performed partial weight bearing for 6 weeks. Secondary displacement was diagnosed

within the first 2 weeks of conservative treatment, all fractures consolidated after 3 months.

Radiographic assessment

The Spearman Rank Correlation revealed a significant correlation between the Joint Ratio (JR)

and the Lateral Edge Length (LEL) (ρ=0.63), and the JR and the Lateral Edge Ratio (LER) (ρ=0.65) for all

fractures (p<0.0001).

The joint-fracture angle (JFA) α was 51±18° in group 1, 55±16° in group 2, and 57±15° in group 3

(Fig. 2A). There was no significant difference between any group.

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In group 1 the JR was 0.48±0.25, in group 2, 0.63±0.26 and in group 3 0.84±0.16 (Fig. 2B). There

was a significant difference between group 1 and 3 (p=0.033) as well as group 2 and 3 (p=0.0004).

There was also a significant difference between group 1 and 2 (p=0.018).

The LEL was 9.8±4.2 mm in group 1, 12.5±4.2 mm in group 2, and 15.6±2.7 mm in group 3 (Fig.

2C). There was a significant difference between group 1 and 3 (p=0.012) as well as group 2 and 3

(p=0.0006). There was also a significant difference between group 1 and 2 (p=0.009).

In group 1 the LER was 0.44±0.18, in group 2 0.56±0.20, and in group 3 0.66±0.11 (Fig. 2D). There

was a significant difference between group 1 and group 3 (p=0.014) and group 2 and group 3

(p=0.0007). There was also a significant difference between group 1 and 2 (p=0.030).

Development of classification system

As shown above, a secondary displacement was associated with a higher JR. An association of

secondary displacement with the LER could also be demonstrated, but both parameters highly

statistically significantly correlated. Therefore, we decided to build up the classification system only

on the JR, because the additional parameter LER would not add further information, but complicate

the arrangement. The AO classification is based on a 3 class system for all anatomical regions and has

been shown to be able to predict outcome [19]. By following this strategy, the total length of the

joint surface of the fifth metatarsal base was divided into three equal parts and assigned to three

fracture types as follows: type I fractures included fractures of the lateral third, type II fractures of

the middle third and type III fractures of the medial third. Type I fractures correlate with a JR≤0.33,

type II fractures with a JR>0.33 and ≤ 0.66, and type III fractures with a JR >0.66. Fractures with a

step-off exceeding 2mm were generally considered to influence the clinical outcome [11-13] and

defined as displaced. Therefore, we introduced an A-Type (I-IIIA) without a relevant displacement

and a B-type (I-IIIB) with a fracture-step-off ≥2mm (Fig. 3).

Validation and interoberserver reliability of the classification system

In our study we classified 26% of fractures as Type I (n=24) with a JR of 0.33 or less. Of Type I

fractures 50% (n =12) were non-displaced (IA) and 50% (n=12) were displaced (IB). We classified 37%

of the fractures as Type II (n=35) with a JR of 0.34 to 0.66. 40% (n=14) were non-displaced fractures

of Type IIA and 60% (n=21) were displaced Type IIB fractures. We classified 37% (n=35) of fractures

Type III with a JR of greater than 0.66. Type IIIA 25% (n=9) were non-displaced and Type IIIB 75%

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(n=26) were displaced. This classification was a consensus decision of three surgeons including the

author.

The positive predictive value for a secondary displacement was 0 in Type I fractures (0 of 12

cases), 0.0625 in Type II fractures (1 case of 16), and 0.45 in Type III fractures (9 of 20 cases).

Correspondingly, the risk for secondary displacement of initially non displaced fractures is 0% in Type

I fractures, 6.25% in Type II fractures, and 45% in Type III fractures. The distribution of risk for

secondary displacement is statistically significantly different comparing all groups (p=0.019). This is

confirmed calculating the individual risk differences between Type I und III fractures (p=0.01) and

Type II and III fractures (p=0.006). If all Type III fractures would have undergone primary operative

treatment, 55% would have been stabilized unnecessarily.

The JFA was higher in Type I than Type II and III fractures (60±21° vs. 52.5±15° vs. 51.7±14° mm,

p=0.033, Fig. 4A). In order to confirm the classification, results for JR are also indicated, although this

was the basis for developing the classification types. The JR was significantly higher in Type III

fractures compared to Type II and Type I fractures (0.29±0.11 vs. 0.53±0.14mm vs. 0.90±0.09mm,

p<0.0001, Fig. 4B). The LEL was significantly higher in Type III fractures compared to Type II and Type

I fractures (15±4mm vs. 12±3mm vs. 8±3mm, p<0.0001, Fig. 4C). The Lateral Edge Ratio (LER) was

also compared between all three fracture types (Fig. 4D). It was significantly higher in Type III than in

Type II and Type I fractures (0.67±0.18 vs. 0.51±0.11 vs. 0.36±0.13, p<0.0001). P-values represent the

tests for multiple comparisons; p-values for individual comparisons may be seen in Figure 4.

The visually analysed fractures using the introduced classification system revealed in 74% an

identical result. A substantial level of agreement (κ=0.72) according to Landis and Koch [18] was

found in the evaluation of the different fracture types by observer 1 and 2. The secondary

displacement of fractures was confirmed by all examiners in 100%.

Discussion

Fractures of the fifth metatarsal base are common fore foot injury and are found following

indirect trauma. The fracture mechanism is considered to be a fore foot supination with plantar

flexion, which leads to an extended muscle force of the peroneus brevis tendon, the metatarso-

cuboid ligaments and the lateral cord of the plantar fascia at the fifth metatarsal base. Thus, the

fracture morphology is strongly dependant on the anatomic predisposition and the type of forces

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affecting the fifth metatarsal base. We analysed a total of 95 fractures of the fifth metatarsal base for

epidemiologic and radiomorphometric characteristics as well as for fracture stability during follow

up. Based on these findings we developed a new classification for fractures of the fifth metatarsal

base considering the risk for secondary displacement. All observations taken together, the largest

fragments had the highest risk for secondary displacement.

Fractures of the fifth metatarsal base are generally found at all ages and gender. In young

patients they have to be strongly separated from the apophysitis at fifth metatarsal base in the

growing skeleton [20]. Recent epidemiologic studies on osteoporotic women have shown a high

prevalence of fractures of the fifth metatarsal in women older than 65 years and a strong association

with a low bone mineral density [21, 22]. In contrast, the introduced analysis focuses more on a

population with a high degree of sports activities, which is reflected by the mean age of 39 years.

The treatment of fifth metatarsal base fractures ranges from non-operative treatment with a

lower leg cast and non-weight or partial bearing for 6 weeks to open reduction and internal fixation

with screws or tension band wiring [9, 23-25]. In general, a good healing potential of the fifth

metatarsal base is assumed due to its sufficient circulation. Therefore, some authors concluded that

metaphyseal fractures not extending beyond the distal end of the 4-5th intermetatarsal articulation

should be treated functionally, regardless of the number of fragments, displacement and

intraarticular involvement [26]. Based on the same metaanalysis it was further concluded that only

meta-diaphyseal fractures located at the distal end of the 4-5th intermetatarsal articulation or just

distally require early ORIF. This is mainly based on the results of the study by Mologne et al. [27]

showing shorter return to sport periods in the intervention group with screw fixation. The conclusion

for the proximal fractures of the fifth metatarsal base not extending beyond the distal end of the 4-

5th intermetatarsal articulation is only based on trials comparing different conservative treatment

methods [28, 29], but not operative versus non-operative intervention. Especially in a population

with a high sports level, early return to physical activities may play a decisive role. Since continuous

traction of the peroneus brevis tendon may result in fracture instability with possible development of

a non-union, which certainly is a problem [27] in these fractures, the risk for secondary displacement

should be reflected by a fracture classification. The highest risk (45%) was found to be associated

with Type III fractures with the step-off in the medial part of the fifth metatarsal base. Regarding the

risk for development of a posttraumatic osteoarthritis (OA) of the metatarso-cuboid joint some

authors strongly recommend operation for displaced, intraarticular fractures [12, 13]. Hereby, a

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fracture step-off exceeding 2mm is widely recognized as a risk factor for OA [30] and has been

introduced in the presented classification system. Although classifications inaugurated for this

anatomical region by Stewart [31], Lawrence [4] or Holzach [32] sufficiently discriminate between

meta-diaphyseal Jones fractures and proximal fractures of the fifth metatarsal not extending beyond

the distal end of the 4-5th intermetatarsal articulation, they all do not reflect the risk for a secondary

displacement within the second fracture entity. Therefore, our radiomorphometric analysis of the 95

fractures distinguished between non-displaced, primary displaced and secondary displaced fractures

in order to deduce a risk adapted classification. It could be shown that secondary displaced fractures

had a longer distance between the lateral edge and the lateral fracture step-off (=LEL). Anatomical

studies have shown that the peroneus brevis tendon has a lateral insertion up to 15mm at the fifth

metatarsal base [6]. Since the muscle pull of the peroneus brevis tendon is considered as one of the

major causes for avulsion fracture mechanisms at the fifth metatarsal base, it is obvious that LELs

larger than 15mm increase the risk for displacement. In this case all muscle fibers are attached to the

small proximal fracture piece and pull it away more easily, a fact, which could be confirmed in the

presented analysis. However, it remains unclear why some fractures primarily displaced and other

after a few days. We assume that in secondary displaced fractures the initial fracture energy was

lower, but we were not able to clearly confirm this assumption by the histories of our patients.

Actually, there are only few studies exactly describing the acting forces as by Orendurff et al. [33]

describing the largest bending moments to the fifth metatarsal during acceleration manoeuvres

(20±13.1 N/cm2) followed by running straight (11.6±8 N/cm2). Unfortunately, such an exact

measurement will not be possible within the setup of a clinical trial. Further, it can be supposed that

for initially not displaced fractures a lower leg cast is not able to completely reduce the pulling force

of the peroneus brevis tendon allowing the secondary displacement despite cast treatment. Casting

the hind-foot in valgus position is maybe an option to reduce the tension of the peroneus brevis

tendon. Since avulsion fractures are caused by exceeding muscle force it can be suggested that non-

displaced fractures of the fifth metatarsal base can displace secondarily during conservative

treatment. Heineck and collegues [34] found that a reduced activity of the peroneus muscle is critical

for adequate treatment and can be achieved by partial weight bearing but not by immobilisation of

the talo-crural joint. This is in concordance with the fact that the risk of fracture displacement

depends on fracture morphology related to the anatomical onset of the lateral cord of plantar

aponeurosis and of the short peroneal muscle tendon.

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A second risk factor for a secondary displacement was a high joint ratio (JR); a high JR stands for

a medial fracture entry into the metatarso-cuboid joint. As recent studies revealed, another avulsion

force for fractures of the fifth metatarsal base is mediated by the lateral aspect of the plantar

aponeurosis and of the plantar metatarso-cuboidal ligaments [6, 7]. From this point of view it could

be assumed that a fracture portion with a more medial proximal entry within the metatarso-cuboid

joint is more unstable, because the fracture does not run through the middle of the plantar

ligamentous structures but medial of its main cord. We additionally could show that fractures with

more medial joint entry are associated with a longer Lateral Edge Length (LEL), which destabilizes the

distal fracture piece additionally as discussed above.

According to these findings we developed a classification system based on the JR and the

fractures step-off. The last criterion has already been considered as a general prognostic criterion for

fifth metatarsal fractures [30]. The lateral edge length (LEL) was not directly included in the

classification; however, since the LEL and the lateral edge ratio (LER) statistically significantly

correlated with the joint ratio (JR), both were indirectly taken into account. Further, it was shown

that LEL and LER were significantly higher in Type III than in Type II and I fractures.

The clinical practicability and interobserver reliability of the classification system were tested by

two surgeons with different experience level and no experience with the classification before study

onset. A substantial level of agreement was found in the assignment of all fractures to the different

fracture types of our classification system. Especially, a definitive distinction between fractures of

Type II and III seems to be crucial since later therapy decision might depend on this correct

classification. Therefore, we recommend an exact radiomorphometric analysis (digital or manual e.g.

using a ruler or an electronic measurement device) in case of doubt. Based on the average length of

the fifth metatarsal base of 22mm the measurement accuracy should be between 1mm and 2mm

considering a confidence interval less than 10%. Overall, the suggested classification was only

examined for reproducibility and needs to be further validated in a separate data set.

The limitations of this study are the small number of cases in group 3, which included the

secondarily displaced fractures. Despite, all cases were assessed by two independent observers as

secondary displacements and differences concerning the radiomorphometric data were statistically

significant. The informative value of the study is further restricted by the limited number of

observers.

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Summarizing the results of this study, at first radiomorphometric characteristics of fifth

metatarsal base fractures were evaluated identifying risk factors for a secondary displacement

following initial conservative treatment. Based on this, a new classification system dividing the

articular surface into thirds was introduced demonstrating good interoberver reliability. Considering

a fracture step-off larger than 2mm as a risk factor for a posttraumatic OA, open reduction and

internal fixation (ORIF) of all Type B-fractures may be recommended. However, a fracture treatment

remains individually decided and is dependent on general health conditions and functional demands.

Furthermore, all initially non-displaced fractures with a more medial joint fracture step-off (Type IIIA)

may - considering the same circumstances – be recommended for ORIF because of its risk for

secondary displacement. At least the risk of 45% should be part of the discussion with the patient

about treatment risk when deciding for conservative treatment. If non-operative treatment is

preferred, fractures at risk for secondary displacement should undergo frequent X-ray controls within

the first 2 weeks, in case a secondary displacement would trigger the decision for ORIF.

Legends

Figure 1

Overview about the evaluated radiographic parameters used for analysis. Radiographic

measurements of all fifth metatarsal base fractures were performed in the dorso-plantar view. The

joint-fracture angle (JFA) α, the Joint Ratio (JR = C/A), the lateral edge length (LEL=B), and the lateral

edge ratio (LER = B/A) were calculated based on these measurements.

Figure 2A-D

The patients were distributed into three groups: group 1 included patients with non-displaced

fractures (step-off < 2mm), who were treated conservatively. Patients with fractures showing a step-

off exceeding 2mm in at least one radiographic plane in initial X-rays were considered primarily

displaced and were treated operatively (group 2). Group 3 included patients with initially non-

displaced fractures, who were treated conservatively and secondarily displaced (fracture step-off >

12

2mm). The joint fracture angle α (shown in part A), the ratio of base length/basal fracture length (JR,

shown in part B), the lateral edge length (LEL, shown in part C), and the ratio of the lateral edge

length and base length (LER, shown in part D) were measured, calculated and compared between the

different groups. All values are reported as mean ± SD. Results for statistical comparisons are

indicated in the figures.

Figure 3

A classification system was developed based on an increased risk for secondary displacement of

fractures with a more medial joint entry of the fracture line at the fifth metatarsal base. Dependant

on the joint entry of the fracture line at the fifth metatarsal base (lateral one-third, middle one-third

and medial one-third) Type I, II or III were defined. Fractures without displacement were summarized

as A-Type (I-IIIA) and with a fracture-step-off >2mm as B-Type (I-IIIB).

Figure 4A-E

The radiomorphometric parameters joint-fracture angle α (JFA, shown in part A), ratio of base

length/basal fracture length (JR, only shown in part B to confirm accuracy of classification), lateral

edge length (LEL, shown in part C), and the lateral edge ratio (LER, shown in part D) were compared

between all three fracture types. All values are reported as mean ± SD. Results for statistical

comparisons are indicated in the figures. Part E demonstrates an example for secondary

displacement of a Type III fracture.

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Conflict of Interest Statement

Each author certifies that he has no commercial associations (e.g. consultancies, stock

ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest

in connection with the submitted article.

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Figure 1

Figure 2

Figure 3

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p<0.0001 p<0.0001

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p<0.0001 p<0.0001

p<0.0001

p<0.0001 p<0.0001

Figure 4

E