Distal Fibula
There is a dearth of articles concerning isolated distal fibular physeal fractures. Nearly all patient series re- ports are in conjunction with distal tibial fractures [1, 4, 9, 11–13, 15, 23, 24].
Anatomy and Growth
The distal fibular physis is transverse at birth. With growth it becomes convoluted and contains periph- eral lappet formations [19]. These convolutions reduce the likelihood of separation and displacement. The distal fibular secondary center of ossification (SCO) may be present at one year of life and is usually pres- ent by the third year.
The distal fibular epiphysis may have an accessory SCO, referred to as the os subfibulae (Fig. 11C.12a).
When present it may become roentgenographically apparent by age 6 or 7 years and might easily be confused with a fracture of the tip of the lateral mal- leolus [3, 8, 16, 18, 19]. If this accessory ossification
Contents
Anatomy and Growth .. . . ..389 Classification ... .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .390 Epidemiology .. . . .390 Literature.Review.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .390 Olmsted.County.Study. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .391 Evaluation . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .392 Management ... .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ...396 Complications . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .396 Author’s Perspective. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .397 References . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .397
center is considered a satellite epiphysis, then its avul- sion would be a type 3 apophyseal fracture separa- tion.
At birth the fibula has 20% of its final length. The distal fibular physis provides more growth than the proximal fibular physis until the fibula has reached 30% of its length. Then the proximal fibular physis becomes the dominant growth center [14]. By age 7 years the proximal fibular physis has become the more dominant growth center (Fig. 12.1), so that by maturity the distal physis has contributed only 40% of the length of the fibula (Fig. 12.2). When caring for a child with arrest of any tibial or fibular physis, knowl- edge of the amount of growth remaining in the distal fibula is valuable (Fig. 12.3).
The level of the fibular physis relative to the distal tibia also changes with growth. In the neonate it is located at the level of the mid tibial epiphysis. By age three (and thereafter) it is level with the tibiotalar joint [2, 10, 11]. This knowledge is valuable when as- sessing any ankle fracture. The distal fibular epiphy- sis fuses with the metaphysis by age 15–17 years in boys, earlier in girls.
The distal fibula metaphysis lies in a groove on the lateral side of the tibia, between the anterior and pos- terior tibial tubercles. It is held in position by strong anterior and posterior tibiofibular ligaments [1]. The distal fibular epiphysis lies distal to these ligaments and is subjected to the forces of ankle motion through the lateral ankle ligaments, making the physis a vul- nerable site for fracture separation.
Relative shortening of the fibula from any cause
leads to progressive ankle valgus during growth
(Fig. 11B.9e, f). Analysis of several factors showed that
soleus strength and anatomical continuity of the fib-
ula are important factors in normal fibular growth
[5]. Thus, in addition to distal fibular premature phy-
seal closure from any cause, neurologic conditions
such as meningomyelocele or absence of any portion
of the diaphysis such as partial fibulectomy for bone
graft use, will lead to relative fibula shortening and
progressive ankle valgus.
Classification
Several classification systems of ankle fractures have been devised based on mechanism of injury, i.e., supi- nation, pronation, varus, valgus, rotation stress, etc.
Since children can rarely supply this information, the fracture type is usually assessed by attempting to re- construct the information from the roentgenograph.
Communication among physicians is more reliable using the anatomic classification (Fig. 3.6).
Epidemiology Literature Review
Most fractures of the distal fibular physis occur con- comitantly with fractures of the distal tibia. The fibu- lar physeal fracture is usually of less significance and receives less treatment (Figs. 3E.5a, 11A.6a). Thus, it often is unreported for statistical analysis. Even when it is reported, it is often difficult to separate distal fibular information from that of the distal tibia.
Fig. 12.1
The. percentage. of. growth. of.
the. fibula. contributed. by. the.
proximal.physis.is.shown.above.
the.solid line,.and.by.the.distal.
physis.below.the.line .The.verti- cal axis. shows. the. relative. ac- tivity. of. the. growth. plates . (Adapted. from. Pritchett. [22],.
with.permission)
É Fig. 12.2
The.percentage.of.growth.of.the.proximal.and.distal.
fibular.physis.at.birth,.mid-childhood,.and.at.maturity .
(Adapted.from.Pritchett.[22],.with.permission)
Landin and Danielsson [15], evaluating 8,682 childhood (age 0–16 years) fractures, found 373 (4%) that involved the ankle. Of fractures of the distal fibu- lar epiphysis, avulsion of the tip of the lateral malleo- lus (an epiphyseal, but not a physeal fracture) was the most frequent, followed by fracture of the distal fibu- lar physis. Distal fibular physeal fractures account for 4–10% of all physeal fractures (Tables 4.5, 4.6) and for 95% of all fibular physeal fractures (Table 4.7). Males predominate 2:1 [17]. The Salter-Harris (S-H) type 1 is by far the most common physeal fracture (Ta- ble 12.1). It may, however, be significantly over-diag- nosed (see Evaluation).
Olmsted County Study
The distal fibular physis is the fourth most frequently injured physis accounting for 7% of all physeal frac- tures (Table 4.12) [20]. Of 69 fibular physeal fractures, 68 (99%) were in the distal fibula and only one in the proximal tibia (Table 4.13). Forty-eight of the 68 cases were boys and 20 were girls (3.4 to 1). This contrasts with distal tibial physeal fractures which are more prevalent in girls than boys (Chapter 11). There were 28.7 fractures per 100,000 boys/year and 11.7 frac- tures per 100,000 girls. The age of maximal incidence was 13–14 years for boys and 12–13 years for girls (Table 12.2). The age spread for boys was age 1 through 18 years, and for girls age 3 through 14 years.
Fig. 12.3
The.amount.of.growth.remain- ing.in.the.distal.fibula.from.age.
7.years.to.maturity .The.central line.represents.the.average,.the.
dotted lines. are. one. standard.
deviation. to. each. side. of. the.
average .(Adapted.from.Pritch- ett.[22],.with.permission)
Table 12.1. Distal.fibular.physeal.fractures.by.type.(Salter-Harris.classification)
Year Author
a1 2 3 4 5 Unclassified Total
1982 Karrholm.[12] 69 27 14 0 0 5 115
1990 Mann.[17] 68 26 2 1 0 – . 97
T
oTal137 53 16 1 0 5 212
Percent . 64 6 . 25 0 . . 7 5 0 5 0 2 4 100 0
a
.Both.articles.have.more.than.one.author;.see.References
Table 12.2. Distal.fibular.physeal.fractures.by.age.(years).and.gender.in.the.Olmsted.County.study.[20]
Age 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Total Percent
Male 1 – – – – – – 3 – 1 4 5 3 9 9 7 4 1 1 – – – 48 . 70 6
Female – – – 2 – 2 1 1 – 1 2 1 4 4 2 – – – – – – – 20 . 29 4
T
oTal1 0 0 2 0 2 1 4 0 2 6 6 7 13 11 7 4 1 1 0 0 0 68 100 0
The most common distal fibular physeal fracture was type 3, barely exceeding type 2 (Table 12.3). The distal fibula was also the most common site (25%) of all type 3 fractures at all sites (Table 3C.2), whereas the distal fibula accounted for only 6% of all type 2 fractures at all sites (Table 3B.2). The peak age for both type 2 and 3 fractures was similar at 13 and 14 years (Table 12.4). Type 1 fractures accounted for 4% of distal fibular physeal fractures, and 2% of type 1 fractures at all sites (Table 3A.2). These low percent- ages may be explained by the unlikelihood of direct longitudinal compression on the distal fibula. As mentioned in previous chapters, type 1 was not rec- ognized prior to the review and is therefore antici- pated to be more common in future studies. Type 6 fracture of the distal fibula was common among re- ferral patients, but did not occur in the Olmsted County study.
Evaluation
Most isolated distal fibular physeal fractures occur from twisting falls or falls with the foot impinged, for
example in a fence, or caught in a bicycle wheel [15].
Swelling and tenderness of the lateral ankle and the inability to bear weight are frequent after any twisting ankle injury. Both an inversion sprain of the ankle and a distal fibular physeal fracture can result in lat- eral ankle swelling. Sometimes, however, the swelling and tenderness of a physeal fracture are well localized over the lateral malleolus at the level of the physis, well above the lateral ankle ligaments. This swelling over the distal fibula following minor inversion or twisting ankle injury is frequently diagnosed as a type 3 fracture despite negative roentgenographs (Fig. 12.4). These cases are common and inflate the rate of distal tibial fractures. Ultrasound evaluation [6, 7] or MRI might confirm cartilaginous or soft tis- sue etiology for the swelling, but cost more in time and money than a cast which treats the symptoms as well as a possible undisplaced physeal fracture.
Prior to skeletal maturity, conventional teaching is that the ligaments about the ankle in children are bio- mechanically stronger than the tibial or fibular phy- ses. Thus, fibular physeal fractures are thought to be common and ligamentous ankle injuries rare. Farley and associates [6] have challenged this hypothesis.
Table 12.3. Distal.fibular.physeal.fractures.by.type.in.the.Olmsted.County.study.[20].(Peterson.classification)
Year Author
a1 2 3 4 5 6 Total
1994 Peterson 3 30 32 2 1 0 68
Percent 4 4 44 1 47 1 2 9 1 5 0 100 0
a
