Relative skeletal maturity status affects injury burden in U14 elite academy football players

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Scand J Med Sci Spo s. 2022;32:1400–1409.wileyonlinelib a y.com/jou nal/sms
Recei ed: 31 July 2021
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Re ised: 7 Decembe 2021
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Accep ed: 11 June 2022
DOI: 10.1111/sms.14204
ORIGINAL ARTICLE
Rela i e skele al ma u i y s a us a ec s inju y bu den in
U14 eli e academy oo ball playe s
Xabie Monas e io1,2
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I aiaBidau azaga- Le ona1
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JonLa uskain2
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Jose A.Lekue1,2
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Gon zalDiaz- Bei ia1,2
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Juan M.San is eban1,2
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ImanolMa in- Ga e xana1,2
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Susana M.Gil1
1Depa men o Physiology, Facul y
o Medicine and Nu sing, Uni e si y
o he Basque Coun y (UPV/EHU),
Leioa, Spain
2Medical Se ices, A hle ic Club,
Lezama, Spain
Co espondence
Xabie Monas e io, Depa men o
Physiology, Facul y o Medicine and
Nu sing, Uni e si y o he Basque
Coun y (UPV/EHU), Ba io Sa iena
s/n, 48940 Leioa, Spain.
Email: xabie [email p o ec ed]
Funding in o ma ion
Euskal He iko Unibe si a ea; Eusko
Jau la i za
Ma u a ion p og esses a di e en imes and a di e en a es be ween indi-
iduals. Thus, di e ences in ma u i y s a us exis among playe s in he same
ch onological age- based ca ego y, especially in U14 playe s. The pu pose o his
p ospec i e s udy was o desc ibe inju y bu den acco ding o he ela i e skele al
ma u i y s a us in U14 eli e academy oo ball playe s. F om 2011 o 2020, inju ies
and indi idual exposu e ( aining and ma ch) we e p ospec i ely eco ded in 183
male U14 playe s. Skele al age (SA) was assessed using he Tanne - Whi ehouse
2 me hod. Rela i e skele al ma u i y s a us [SA minus ch onological age (CA)]
was classi ied as ollows: ea ly (SA– CA > 0.5), on- ime (SA– CA ± 0.5), and la e
(SA– CA < −0.5). O e all and speci ic inju y bu den (days los /1000 h) and a e
a ios o compa isons be ween g oups we e calcula ed. O e all inju y bu den
was 2.8 imes highe (3.6 imes in aining) in ea ly ma u e s compa ed wi h la e
ma u e s. G ow h- ela ed inju ies we e he mos bu densome inju ies in all h ee
g oups, bu signi ican di e ences we e no ound be ween g oups. Muscle inju-
ies we e 4 imes mo e bu densome in ea ly ma u e s compa ed wi h on- ime and
la e ma u e s. Besides, join /ligamen inju ies we e 7 and 12 imes less bu den-
some in la e ma u e s han in on- ime and la e ma u e s, espec i ely. Signi ican
di e ences be ween g oups in o e all and speci ic inju y bu den we e no ound
in ma ches. Ou esul s showed di e en inju y pa e ns in U14 ea ly, on- ime,
and la e ma u e s. Hence, moni o ing ma u i y seems c ucial o de ec po en ial
inju ies ha cause he g ea es dis up ion, and acili a e design o a ge ed inju y
p e en ion p og ams.
KEYWORDS
adolescence, bu den, epidemiology, oo ball, g ow h and de elopmen , inju y, ma u a ion,
you h
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© 2022 The Au ho s. Scandina ian Jou nal o Medicine & Science In Spo s published by John Wiley & Sons L d.
16000838, 2022, 9, Downloaded om h ps://onlinelib a y.wiley.com/doi/10.1111/sms.14204 by Xabie Monas e io - Spanish Coch ane Na ional P o ision (Minis e io de Sanidad) , Wiley Online Lib a y on [13/10/2022]. See he Te ms and Condi ions (h ps://onlinelib a y.wiley.com/ e ms-and-condi ions) on Wiley Online Lib a y o ules o use; OA a icles a e go e ned by he applicable C ea i e Commons License
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1
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INTRODUCTION
P o essional oo ball clubs in es many esou ces in
hei you h academies o de elop young oo ball playe s,
wi h he aim o p o iding new playe s o he Fi s eam.
Remaining ee o inju y is a key ac o o p og essing,1
no only ha , inju ies lead o inc eased suscep ibili y o
u u e inju ies and long- e m heal h isks in adul hood.2
Thus, p e en ing inju ies is a p io i y in oo ball.
Inju y incidence (inju y equency) and bu den ( he
p oduc o inju y equency and se e i y) peaks since
ea ly- (Unde U12– U14) and mid- adolescence (Unde
U15– 17),3 when ma ked soma ic g ow h and signi ican
musculoskele al and physiological de elopmen occu .
U14 age g oup gene ally coincides wi h he peak heigh
eloci y (PHV) in males, which is he pe iod o maximal
g ow h du ing adolescence.4 Howe e , due o indi idual
a iance in pube al iming, no all boys will expe ience
he g ow h spu a he same age.4 Consequen ly, in e -
indi idual di e ences in ma u i y s a us can be ound
among playe s o he same age- based ca ego y, especially
in U14s.5,6 The la ge a ia ions in ma u i y s a us wi hin
ch onological age g oups ha e been p oposed as ac o s
ha may in luence inju y isk in young oo balle s. On he
one hand, i is assumed ha ea ly ma u e s, whose ma u-
a ion occu s in ad ance o he mean and a e likely o be
bigge , hea ie , and s onge ,4 may be a highe isk due o
g ea e engagemen and in ol emen in compe i i e play.
Besides, inapp op ia e aining load in g oups o playe s
wi h mixed ma u i y and de elopmen al s a us is ano he
ela ed wo y.7 Howe e , a ailable da a on g ow h, ma u-
a ion, and inju y isk in oo ball p o ide con lic ing e i-
dence due o me hodological di e ences and limi a ions.
Skele al ma u a ion is conside ed he single bes ma-
u i y indica o , as he s a (skele on o ca ilage) and
endpoin s (skele on o ma u e bone) a e known and can
be ollowed h oughou he ma u a ion p ocess wi h p e-
cise and eliable es ima es.4 Ne e heless, o da e, mos o
he s udies ha e used non- in asi e me hods wi h limi ed
accu acy and only 3 s udies ha e conside ed he e ec o
skele al ma u i y on inju ies in eli e you h oo ball play-
e s.8– 10 A ailable esea ch assessing skele al age sugges s
ha ea ly ma u e s, who ha e ad anced skele al age com-
pa ed o hei ch onological age ( ela i e ma u i y s a us),
ha e a highe inju y incidence compa ed wi h on- ime
and la e ma u e s.8– 10 Rega ding speci ic inju y isk, ea ly
ma u e s seem o be mo e p one o muscle and endon in-
ju ies, while on- ime and la e ma u e s ha e highe inci-
dence o g ow h- ela ed inju ies.8,9
A ailable esea ch which measu ed skele al age also
has inhe en limi a ions. Fi s ly, hey measu ed inju y
incidence, which does no accoun o inju y se e i y.
Iden i ying inju ies wi h he highes inju y bu den is i al
o de ec po en ial inju ies ha cause he g ea es dis up-
ion, and acili a e design o a ge ed inju y p e en ion
p og ams.11 Secondly, hey did no accoun o indi idual
exposu e da a. Recen esea ch sugges s ha ad anced
ma u i y s a us in U11, U13, and U14 g oups is associ-
a ed wi h highe g ades in coaches' e alua ions o ma ch
pe o mance.12 This may ansla e o mo e playing oppo -
uni ies, and he e o e, esea ch which includes indi id-
ual aining and ma ch exposu e is needed o allow o
di ec compa isons and mo e nuanced in e p e a ion.13
This s udy aimed o build on hese limi a ions by using
9- season inju y, exposu e ( aining and ma ch), and skel-
e al ma u a ion da a o desc ibe o e all and speci ic in-
ju y bu den in U14 ea ly, on- ime, and la e ma u ing eli e
academy oo ball playe s.
2
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MATERIALS AND METHODS
2.1
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S udy design and s udy popula ion
A p ospec i e obse a ional s udy o 183 male U14 playe s
o an eli e Spanish oo ball academy was ca ied ou be-
ween he 2011– 2012 and 2019– 2020 playing seasons. The
male p o essional eam plays in he Spanish LaLiga, and
he de elopmen o academy playe s is key o he club's
success because only playe s de eloped in he academy o
bo n in he Basque Coun y can play in his club. Playe s
we e single spo s a hle es, ained 4 imes pe week, and
played a game e e y weekend. This s udy was app o ed
by he E hics Commi ee o he Uni e si y o he Basque
Coun y (UPV/EHU). W i en in o med consen o use
egula ly collec ed da a o esea ch pu poses was ob-
ained om he playe s gua dians.
2.2
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Reco ding o inju ies and exposu e
Playe s' aining/ma ch exposu e in minu es (daily) and
inju ies we e eco ded. The club's medical s a diagnosed,
ea ed, and eco ded all ime- loss inju ies ollowing he
consensus on de ini ions and da a collec ion p ocedu es
ou lined by he In e na ional Fede a ion o Associa ion
Foo ball (FIFA).14 Inju ies we e eco ded when a playe
was unable o pa icipa e in a u u e aining session o
ma ch due o a physical complain . A playe was consid-
e ed inju ed un il he medical s a clea ed he playe o
ull pa icipa ion.
G ow h- ela ed inju ies we e no explici ly conside ed
by he 2006 consensus s a emen on inju y de ini ions.14
Thus, we included an addi ional ca ego y o “g ow h-
ela ed inju ies,” de ined as unique inju ies no seen in
adul s bu common in skele ally imma u e a hle es (e.g.,
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MONASTERIO e al.
g ow h pla e ac u es, apophysi is, apophyseal a ulsion
ac u es, and g eens ick ac u es).15 Inju ies we e clas-
si ied in o h ee g oups based p e ious esea ch3,5,16,17
and p ac i ione expe ience: (1) g ow h- ela ed inju ies
(Se e 's disease, Osgood Schla e disease, apophyseal in-
ju ies [os eochond osis o a ulsion] o he an e io in e-
io iliac spine, ischial ube osi y, o an e io supe io iliac
spine and spondylolysis), (2) muscle inju ies (quad iceps,
hams ing, and adduc o ), and (3) join /ligamen inju ies
(knee and ankle). The same doc o eco ded inju ies since
he s a o he s udy, he eby educing he chance o bias,
di e ences in inju y in e p e a ion, and changes in obse -
a ion me hods be ween doc o s.
2.3
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An h opome ic measu emen s
S anding heigh (±0.1cm; Añó Sayol, Ba celona, Spain)
and weigh (±0.1kg; (Seca) we e measu ed by doc o s be-
o e a e noon ainings. The same wo doc o s measu ed
playe s du ing he en i e s udy pe iod, he eby educing
chance o bias.
2.4
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Skele al ma u i y s a us
Skele al ma u a ion was assessed a he beginning o he
season, using X- ay images o he a hle e's le hand and
w is complex. Skele al age was de e mined using he
Tanne – Whi ehouse adius- ulna- sho bone p o ocol
(TW2 RUS) using sample da a o he Basque Coun y.18
This allowed us o make be e compa isons wi h e e -
ence o sample da a as ou academy only admi s playe s
bo n o de eloped in he Basque Coun y. TW2 RUS has
been shown o be he me hod o choice o hose using
he Tanne – Whi ehouse p o ocol wi h you h oo ball
playe s.19
The images we e in e p e ed by wo expe ienced doc-
o s who we e based a he academy o o e 20 yea s
and we e in place h oughou he 9- season pe iod o
he p esen s udy. Doc o s we e ained in he use o
his me hod and ha e a decade expe ience ca ying ou
skele al age assessmen s using TW2 RUS. To es he e-
p oducibili y o he assessmen s o he bone age, he in-
es iga o s e- e alua ed andomly selec ed hand– w is
adiog aphs om 10 subjec s in 2021. The coe icien s
o in a- obse e and in e - obse e eliabili y we e 0.99
(0.98– 1) and 0.95 (0.84– 0.99) wi h an e o o 0.10 and
0.25 yea s, espec i ely.
Playe s we e assigned in o h ee ca ego ies acco d-
ing o hei ela i e skele al ma u i y s a us: ea ly, on-
ime, o la e. On- ime ma u e s e e o playe s whose
SA is wi hin 0.5 yea s o he CA, ea ly ma u e s e e
o playe s whose SA is olde han CA by mo e han
0.5 yea s and la e ma u e s e e o playe s whose SA is
younge han CA by mo e han 0.5 yea s. Ma u e playe s
(SA > 18 yea s) wi h hand and w is ully ossi ied we e
no ound.
Adul heigh was es ima ed using bone age a es ac-
co ding o TW2- RUS me hod,18 and pe cen age o p e-
dic ed adul heigh was calcula ed using playe s s anding
heigh .
2.5
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Da a analysis
Di e ences in exposu e ime we e compa ed using
K uskal– Wallis es . Inju y bu den was calcula ed o
accoun o bo h equency (incidence) and se e i y
(mean absence) o inju ies11 and was p esen ed as he
numbe o days los / 1000 playe hou s.13 Inju y bu den
o ea ly e sus on- ime e sus la e ma u e s we e com-
pa ed by calcula ing a e a ios (RRs). Ra e a ios o 1.2,
1.9, and 3.0 can be aken as small, medium, and la ge,
TABLE 1 Numbe o playe s, ch onological age, skele al age, and a e age exposu e (hou s pe season) acco ding o ela i e skele al
ma u i y s a us
Ea ly On- ime La e All
Numbe o playe s 74 (40.6%) 80 (44%) 28 (15.4%) 182
Heigh 169.79 ± 6.45 162.57 ± 6.42 158.92 ± 6.58 164.62 ± 7.68
Weigh 55.84 ± 7.1 47.68 ± 6.45 43.36 ± 6.05 50.29 ± 8.18
P edic ed adul heigh 181.2 ± 5.57 179.95 ± 4.92 181.46 ± 5.81 180.69 ± 5.33
Pe cen age o p edic ed adul heigh 93.72 ± 2.82 90.33 ± 1.98 87.64 ± 2.80 91.30 ± 3.30
Ch onological age 13.5 ± 0.5 13.5 ± 0.4 13.7 ± 0.4 13.5 ± 0.5
Skele al age 14.8 ± 0.8 13.7 ± 0.6 12.6 ± 0.9 14 ± 1
A e age o al exposu e 204.7 ± 64.8 201.3 ± 59.4 226.5 ± 45 206.6 ± 59.9
A e age aining exposu e 175.7 ± 53.9 175.3 ± 50 196.2 ± 36.3 178.7 ± 50
A e age ma ch exposu e 29.4 ± 12.9 26.7 ± 11.4 30.3 ± 10.6 27.9 ± 12.4
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MONASTERIO e al.
espec i ely.20 Ze o- in la ed nega i e binomial models
we e i ed o accoun o he excess o ze os and o e d-
ispe sion in he da a21 using he glmmTMB package in
R ( e sion 3.6.2).
Con idence in e als we e calcula ed a he 95% con i-
dence le el o a es and RRs using a pa ame ic boo s ap
p ocedu e. p- alues we e adjus ed o mul iple compa -
ison wi h he Benjamini and Hochbe g me hod using R
unc ion p.adjus on he package s a s. The signi icance
le el was se a <0.05.
3
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RESULTS
A o al numbe o 277 inju ies (157 du ing aining and
120 in ma ches) we e eco ded which caused 7301 days
los (4405 in aining and 2896 in ma ches). Desc ip i e
da a a e shown in Table1. Signi ican di e ences be ween
g oups we e no ound o a e age o al, aining and
ma ch exposu e.
O e all inju y bu den was 2.8 imes highe in ea ly
ma u e s compa ed wi h la e ma u e s (Table2). This
di e ence was mo e p onounced du ing aining ses-
sions, as inju y bu den was 3.6 imes highe in ea ly ma-
u e s compa ed o la e ma u e s (Table3). Signi ican
di e ences be ween g oups we e no ound in he
ma ches (Table4).
G ow h- ela ed inju ies we e he mos bu densome
inju ies in all ma u i y s a us g oups. Despi e no inding
signi ican di e ences among ma u i y g oups, Se e 's
disease and AIIS apophyseal inju ies we e mo e bu den-
some in la e ma u e s while ASIS apophyseal inju ies and
spondylolysis we e mo e bu densome in ea ly ma u e s
(Tables2, 3 and 4).
Muscle inju ies in ea ly ma u e s we e 4 imes mo e
bu densome compa ed wi h on- ime and la e ma u e s
(Table2). Di e ences in inju y bu den we e mo e p o-
nounced du ing ainings [RR o ea ly e sus on- ime:
7.30 (1.78– 89.98)] (Table3). This end emained simi-
la o hams ing inju ies, in which ea ly ma u e s had
6 imes highe (12 imes in ainings) bu den han on-
ime ma u e s (Tables2 and 3). Signi ican di e ences
be ween ma u i y g oups we e no ound in ma ches
(Table4).
Join /ligamen inju ies in la e ma u e s we e 7 and 12
imes less bu densome han in on- ime and ea ly ma u -
e s, espec i ely (Table2). In aining sessions, signi ican
di e ences we e only ound in ea ly e sus la e ma u -
e s; wi h ea ly ma u e s showing 6 imes highe bu den
(Table3). Conce ning speci ic inju ies, signi ican di e -
ences o ankle join/ligamen inju ies we e also ound,
being inju ies in ea ly ma u e s 16 imes mo e bu den-
some han in la e ma u e s (Table2).
4
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DISCUSSION
This s udy aimed o desc ibe and compa e o e all and
speci ic inju y bu den in ea ly, on- ime, and la e ma u -
ing U14 academy oo ball playe s. Inju ies o ea ly ma u -
e s we e mo e bu densome han hose o la e de elope s.
Conce ning speci ic inju ies, muscle inju ies we e mo e
bu densome in ea ly e sus on- ime/la e ma u e s while
join /ligamen inju ies we e mo e bu densome in ea ly/
on- ime e sus la e ma u e s.
In line wi h p e ious da a in eli e oo ball academies,
ou esea ch showed a clea unde ep esen a ion o U14
la e ma u e s (15%). I mus be highligh ed ha he less
conse a i e band o ±0.5 yea s applied in ou s udy and
in p e ious esea ch12,22– 24 iden i ied a g ea e p opo ion
o ea ly ma u e s han hose s udies using a mo e con-
se a i e ±1 band.22,25 Signi ican di e ences be ween
ea ly, on- ime, and la e ma u e s we e no ound o o al,
aining and ma ch exposu e. This is in acco dance wi h
p e ious esea ch which only ound longe pi ch ime in
U9 and U10 ea ly ma u e s.26 Ne e heless, ecen s udies
sugges ed ha ad anced ma u i y s a us in U14s is asso-
cia ed wi h highe g ades in ma ch- unning me ics6 and
coaches' e alua ions o ma ch pe o mance12; which migh
lead he coaches o ely mo e on ea ly ma u e s and hus,
o highe ma ch exposu e. Howe e , apa om coaches'
pe cep ions, o he ac o s such as a ailabili y migh also
ha e an impac in playe 's a e age exposu e. Al hough we
did no s udy playe 's a ailabili y, ou esul s showed 2.8
imes highe inju y bu den (3.6 imes in ainings) in ea ly
e sus la e ma u e s, and as a consequence, ea ly ma u -
e s migh ha e been less a ailable due o longe pe iods o
absence caused by inju ies.11
The highe inju y bu den (p oduc o incidence and
se e i y) ound in ea ly ma u e s is in line wi h esul s in
p e ious esea ch which ound a highe incidence in his
g oup.8– 10,27 Conce ning he se e i y o inju ies, con a y
o ou esul s, Le Gall e al.8 ound longe a e age layo
ime pe inju y and longe pe iods o absence in U14 on-
ime and la e ma u e s. None heless, compa isons wi h
p e ious s udies mus be made cau iously as hey applied
di e en me hods o skele al age es ima ion, used di e -
en cu o alues o classi ying playe s and we e ca ied
ou in di e en popula ions. Mos impo an ly, hey did
no accoun o indi idual exposu e da a.
The e a e mul iple easons ha migh explain he
highe o e all inju y bu den in ea ly ma u e s compa ed
wi h U14 on- ime and la e ma u e s. In line wi h ou e-
sul s, p e ious esea ch has al eady shown ha playe s
who a e close o hei biological ma u i y ha e mo e bu -
densome inju ies17,24,28 and ea ly ma u e s migh be mo e
ma u e han hei on- ime and la e pee s. Fu he mo e,
co e ing g ea e dis ances a highe speeds,6,29 a mo e
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MONASTERIO e al.
TABLE 2 Numbe o days los /1000 h (95% CI) acco ding o ela i e skele al ma u i y s a us in U14 oo ball playe s, and a e a ios (95% CI) o compa isons be ween g oups
Numbe o days los /1000 h Ra e- Ra ios
Ea ly On- ime La e Ea ly e sus On- ime Ea ly e sus La e
On- ime e sus
La e
O e all bu den 392.1 (253.7– 559.4) L265.2 (172.8– 377.4) 140 (60.4– 256) E1.48 (0.88– 2.57) 2.80 (1.32– 6.81)* 1.89 (0.89– 4.62)
G ow h- ela ed inju ies 205.5 (104.1– 327.6) 184.2 (106.6– 280.8) 100 (35.3– 190.9) 1.12 (0.51– 2.31) 2.06 (0.81– 6.32) 1.84 (0.76– 5.71)
Se e 's disease 2.2 (0.2– 5.2) 5.8 (0.6– 13.5) 9.1 (0.9– 20.2) 0.37 (0.03– 4.45) 0.24 (0.02– 2.68) 0.64 (0.05– 6.89)
Osgood- Schla e 's disease 6.4 (0.6– 15.4) 12.5 (3.1– 26.5) 0.52 (0.04– 3.24)
Ischial ube osi ies inju ies 11.5 (0.1– 30.5) 17.6 (5– 36.3) 18.9 (0.1– 51) 0.66 (0.01– 3.02) 0.61 (0.01– 9.16·107)0.93 (0.21– 1.25·108)
AIIS inju ies 19.9 (1.9– 47.6) 49.7 (19.6– 83.7) 64.1 (13.2– 132.8) 0.40 (0.03– 1.40) 0.31 (0.03– 1.80) 0.78 (0.25– 4.14)
ASIS inju ies 63.5 (0.1– 252.5)
Spondylolysis 67.6 (14.1– 144.5) 73.3 (9.6– 168.7) 0.92 (0.16– 12.06)
Muscle inju ies 76.2 (3– 144.5) O,L 17.7 (5.3– 35) E18.8 (2.9– 44.9) E4.30 (1.34– 16.48)* 4.06 (1.23– 31.02)* 0.94 (0.21– 6.62)
Hams ing 35 (7.4– 73.5) O5.6 (0.7– 14.1) E7.1 (0.1– 22.4) 6.23 (1.07– 53.03)* 4.95 (0.78– 2.71·108)0.79 (0.10– 5.49·107)
Quad iceps 35.9 (3.1– 89.4) 4.5 (0.1– 14) 3.4 (0.1– 16.7) 7.99 (0.68– 1.67·109)10.59 (0.74– 4.20·109)1.32 (0.01– 2.77·108)
Join /Ligamen inju ies 35.5 (12.6– 62.9) L19.11 (6.6– 35.3) L2.84 (0.2– 7.5) E,O 1.86 (0.59– 6.06) 12.51 (3.35– 175.09)** 6.73 (1.69– 93)*
Knee 0.4 (0.11– 1.5) 8.2 (0.6– 19.6) 0.9 (0.1– 3.9) 0.05 (0.01– 830) 0.43 (0.01– 1.58·109)9.55 (0.66– 3.14·1014)
Ankle 31.3 (10.3– 58.4) L8.9 (1.2– 20.1) 1.98 (0.1– 5.7) E3.52 (0.87– 25.14) 15.76 (3.37– 1.85·108)** 4.47 (0.52– 6.17·107)
No e: Signi ican di e ences (*p < 0.05, **p < 0.01) be ween ma u i y s a us g oups: E(ea ly), O(on- ime), o L(la e).
Abb e ia ions: AIIS, an e io in e io iliac spine; ASIS: an e io in e io iliac spine.
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MONASTERIO e al.
TABLE 3 Numbe o days los /1000 h (95% CI) in ainings acco ding o ela i e skele al ma u i y s a us in U14 oo ball playe s, and a e a ios (95% CI) o compa isons be ween g oups
Numbe o days los /1000 h Ra e- Ra ios
Ea ly On- ime La e Ea ly e sus On- ime Ea ly e sus La e
On- ime e sus
La e
O e all bu den 292.4 (170.6– 434)L188.9 (101– 315) 81.6 (23.9– 174.3) E1.55 (0.75– 3.28) 3.58 (1.42– 12.75)* 2.31 (0.88– 8.92)
G ow h- ela ed inju ies 165 (77.7– 283) 127.5 (53.3– 227) 59.5 (7.2– 153.7) 1.29 (0.52– 3.76) 2.77 (0.85– 23.21) 2.14 (0.63– 18.25)
Se e 's disease 2.54 (0.15– 6.07) 4.6 (0.1– 13.6) 10.2 (1– 22.6) 0.56 (0.03– 6.28·109)0.25 (0.02– 2.60) 0.45 (0.01– 6.43)
Osgood- Schla e 's disease 6.4 (0.3– 14.7) 7.8 (1.4– 16.2) 0.83 (0.07– 4.98)
Ischial apophyseal inju ies 9.9 (0.1– 24.3) 10.4 (0.1– 28.9) 0.95 (0.01– 4.73*108)
AIIS apophyseal inju ies 10 (0.1– 33.6) 25.3 (0.1– 58.5) 49 (0.1– 159.6) 0.40 (0.01– 3.21) 0.20 (0.01– 8.65·107)0.52 (0.07– 2.49·108)
ASIS apophyseal inju ies 38.3 (0.1– 117.2)
Spondylolysis 64.9 (9.9– 145.5) 56.8 (0.1– 160) 1.14 (0.09– 1.29·109)
Muscle inju ies 79 (26.3– 150.3) O,L 10.8 (0.9– 28.1) E19 (2.6– 47) E7.30 (1.78– 89.98)* 4.16 (1.04– 29.77)* 0.57 (0.04– 5.62)
Hams ing 37.2 (6.7– 88.9) O0.3 (0.1– 1.5) E7.9 (0.1– 23.6) 12.17 (1.24– 6.15·1010)* 4.73 (0.70– 1.44·109)0.04 (0.01– 1.41·107)
Quad iceps 37.2 (5.2– 80.9) 4.9 (0.1– 17.1) 3.8 (0.1– 18.9) 7.60 (0.94– 1.01·1010)9.71 (0.96– 2.69·109)1.28 (0.01– 1.99·108)
Join /Ligamen inju ies 19.1 (3.9– 40) L17.4 (3.3– 36.7) 3.3 (0.2– 8.3) E1.09 (0.22– 6.45) 5.84 (1.11– 116.49)* 5.34 (0.89– 77.94)
Knee 0.4 (0.1– 1.9) 9.4 (0.2– 24.9) 1 (0.1– 4.5) 0.05 (0.01– 1.87) 0.43 (0.01– 7.74·108)9.40 (0.26– 2.57·1010)
Ankle 13.9 (1.1– 35) 7.1 (0.1– 20.1) 2.3 (0.1– 6.6) 1.97 (0.2– 6.20·109)6.13 (0.60– 1.57·108)3.12 (0.01– 8.92·107)
No e: Signi ican di e ences (*p < 0.05) be ween ma u i y s a us g oups: E(ea ly), O(on- ime), o L(la e).
Abb e ia ions: AIIS, an e io in e io iliac spine; ASIS, an e io in e io iliac spine.
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MONASTERIO e al.
TABLE 4 Numbe o days los /1000 h (95% CI) in ma ches acco ding o ela i e skele al ma u i y s a us in U14 oo ball playe s, and a e a ios (95% CI) o compa isons be ween g oups
Numbe o days los /1000 h Ra e- Ra ios
Ea ly On- ime La e Ea ly e sus On- ime Ea ly e sus La e
On- ime e sus
La e
O e all bu den 773.7 (417.8– 1192) 450.5 (232.1– 723) 736.8 (213.9– 1491.1) 1.72 (0.77– 3.66) 1.05 (0.43– 3.85) 0.61 (0.24– 2.33)
G ow h- ela ed inju ies 496 (207.8– 886.8) 265 (110.3– 453.1) 463.4 (0.1– 1304.6) 1.87 (0.66– 5.47) 1.07 (0.26– 5.60·108)0.57 (0.14– 2.96·108)
Se e 's disease 5.4 (0.1– 14.5) 4.3 (0.1– 14.9) 1.23 (0.01– 8.84·1037)
Osgood- Schla e 's disease 44.6 (0.1– 167.3) 3.9 (0.1– 18.3) 11.39 (0.01– 1.31·1012)
Ischial apophyseal inju ies 104.5 (10.6– 238.4) 20 (0.1– 50) 64.7 (0.1– 228.5) 5.23 (0.41– 2.37·108)1.62 (0.09– 8.77·108)0.31 (0.26– 1.85·108)
AIIS apophyseal inju ies 46.9 (5.6– 103.6) 122.2 (45.3– 212.9) 320.3 (0.1– 703.4) 0.38 (0.05– 1.25) 0.15 (0.02– 1.28·108)0.38 (0.11– 3.61·108)
ASIS apophyseal inju ies 196.3 (0.1– 603.9)
Spondylolysis 119.1 (0.1– 341.1)
Muscle inju ies 19.7 (0.5– 51.6) 39.5 (9.2– 83.9) 52.3 (2.3– 143.9) 0.44 (0.01– 1.17·109)0.25 (0.01– 9.64·107)0.56 (0.01– 1.17·108)
Hams ing 10.3 (0.1– 32.4) 23.1 (0.1– 63.1) 41.2 (0.1– 114.5) 0.44 (0.01– 1.17·109)0.25 (0.01– 9.64·107)0.56 (0.01– 2.38·108)
Quad iceps 1 (0.1– 4)
Join /Ligamen inju ies 35.2 (0.1– 99.5) 92.2 (8– 213.4) 48.3 (4.6– 118.8) 0.38 (0.01– 4.22) 0.73 (0.01– 8.46) 1.91 (0.17– 27.30)
Knee
Ankle 35.2 (0.1– 89.4) 84.2 (5.5– 212.5) 48.3 (2.4– 115.5) 0.42 (0.01– 6.22) 0.73 (0.01– 12.14) 1.74 (0.12– 38.08)
Abb e ia ions: AIIS: an e io in e io iliac spine; ASIS: an e io in e io iliac spine.
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MONASTERIO e al.
agg essi e way o playing oo ball and assuming mo e
leade ship oles30 migh lead o mo e bu densome inju-
ies in ea ly ma u e s. Besides, di e en inju y pa e ns in
ea ly, on- ime, and la e ma u e s migh also ha e con ib-
u ed o di e ences in o al inju y bu den.
G ow h- ela ed inju ies we e he mos bu densome in-
ju ies in all ma u i y s a us g oups, which is in line wi h
p e ious esea ch which ound ha g ow h- ela ed inju-
ies we e he mos common ime- loss inju ies in U14 play-
e s.3 Signi ican di e ences be ween ea ly, on- ime, and
la e ma u e s we e no ound o absolu e g ow h- ela ed
inju y bu den. Howe e , di e en speci ic g ow h- ela ed
inju y bu dens we e ound in ea ly, on- ime, and la e ma-
u e s, which migh be explained by he dis al o p oximal
sequence o he physeal endochond al ossi ica ion om
ca ilage o comple e bony usion.31 Ou esul s showed
ha dis al g ow h- ela ed inju ies (e.g., Se e 's disease)
we e mo e bu densome in U14 la e ma u e s while in-
ju ies in he hip/ unk (ASIS apophyseal inju ies and
spondylolysis) peaked in ea ly ma u e s. Ne e heless, we
canno o ge ha ossi ica ion cen e s in he same bone
can ollow di e en ossi ica ion pa e ns. Fo ins ance,
he appea ance and closu e o he AIIS ossi ica ion cen e
occu ea lie han o he cen e s in he pel is (e.g., AIIS
and ischial ube osi y)32 and may explain why AIIS apoph-
yseal inju ies peaked in la e ma u e s despi e being a p ox-
imal segmen inju y.
On he con a y, he bu den o muscle inju ies was
highe in ea ly ma u e s compa ed wi h U14 on- ime and
la e ma u e s and he e a e mul iple ac o s which migh
ha e con ibu ed o i . Fi s ly, in playe s wi h ad anced
skele al ma u i y, which a e mo e likely o ha e ossi ica-
ion cen e s closed in di e en egions o he body, mus-
cle migh be he s uc u al poin o o inju ies.17 Besides,
ea ly ma u e s, who a e physically supe io o hei on-
ime and la e pee s, migh de elop a mo e physical way
o playing oo ball33 ha may p edispose hem o u he
muscle inju ies. Mo eo e , ecen e idence has sugges ed
ha in U14 ca ego y ea ly ma u e s we e quicke , made
mo e accele a ions and co e g ea e dis ances a high
speed.29 Taking in o accoun ha high- in ensi y unning
has been associa ed wi h hams ing inju ies,34 he mo e
physical way o playing o ea ly ma u e s migh ha e con-
ibu ed o he highe bu den o hams ing inju ies ob-
se ed in he esul s.
Besides, he bu den o join /ligamen inju ies was
lowe in la e ma u e s compa ed o on- ime and la e ma-
u e. Fu he mo e, 16 imes lowe bu den o ankle join/
ligamen inju ies was ound in la e e sus ea ly ma u e s.
U14 la e ma u e s migh be p e- o ci ca- PHV, pe iods a
which join/ligamen inju y bu den has been shown o be
lowe .17 Mo eo e , ankle sp ains in playe s wi h less de-
layed ma u a ion and dec eased bone densi y migh lead
o ankle epiphyseal inju ies35; which we e classi ied as
g ow h- ela ed inju ies in ou s udy. Rega ding la e ma-
u e s way o playing, i is possible ha smalle and ligh e
la e ma u e s a oid con ac and isk- aking si ua ions ha
could lead hem o acu e join/ligamen inju ies.36
4.1
|
Me hodological conside a ions
The p esen s udy p o ides a obus inju y eco ding
me hodology by ha ing medical s a om he same club
diagnose, ea , and eco d inju ies, a oiding po en ially
un eliable da a ha migh come om medical s a s a di -
e en clubs.37 Besides, some o he weaknesses iden i ied
o ea lie esea ch on g ow h, ma u a ion, and inju ies
ha e been add essed; using gold- s anda d skele al age in-
s ead o less accu a e non- in asi e me hods, accoun ing
o indi idual exposu e, eco ding speci ic inju y da a and
calcula ing inju y bu den o de ec inju ies ha cause he
g ea es dis up ion.
Ye , some impo an me hodological limi a ions mus
be acknowledged. Conce ning he skele al age assess-
men , TW2- RUS me hod o e looks he ime lag be ween
onse and comple ion o union in he c i e ion o he
inal s age o he dis al adial epiphysis. Ne e heless,
U14 playe s a e a ely a his inal s age (3% o ou play-
e s), and his limi a ion migh no ha e impac ed ou e-
sul s. Fu he mo e, he less conse a i e ±0.5- yea band
o classi ying playe s acco ding o hei ela i e skele al
ma u i y s a us di e s wi h p e ious esea ch s udying
skele al ma u i y s a us and inju y isk.8– 10 Howe e , his
band has al eady been applied in o he s udies o SA–
CA23 and ela i e soma ic ma u a ion.12,22,24 C i e ion ha
is oo conse a i e (SA– CA ± 1.0 yea s) may ha e ailed o
di e en ia e be ween on- ime ma u e s ha a e ma kedly
di e en in e ms o ma u i y s a us, inc easing he likeli-
hood o ype wo e o s. Howe e , i should be no ed ha
he less conse a i e c i e ion o de e mining ma u i y
s a us (SA– CA ± 0.5 yea s) also inc eases he likelihood
o he esea che making a ype one e o (i.e., de ec -
ing a bias when no such bias exis s). The ±0.5yea ange
used o he cu en s udy is well ou side he ange o he
e o o bone age assessmen (~0.18 yea s) so i migh be
ele an o he sample in his s udy. Besides, he skele al
age de e mina ion was based on he ma u i y o he hand
and w is , which does no necessa ily e lec he ma u a-
ion o o he bones, issues, and o gan sys ems. No only
ha , he w is X- ays we e only a ailable in p eseason. As
ma u a ion p og esses a di e en a es ( empo),4 playe s'
ma u i y s a us migh change du ing he season. Besides,
only U14 playe s we e included in he s udy, and u u e
esea ch should conside s udying o he age g oups.
Finally, o al ma ch exposu e was smalle han exposu e
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1408
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MONASTERIO e al.
in aining, and i migh ha e con ibu ed o no inding
signi ican di e ences be ween g oups in ma ches.
5
|
PERSPECTIVE
Ou esul s showed highe o e all inju y bu den in U14
ea ly ma u ing academy oo ball playe s and di e en in-
ju y pa e ns in ea ly, on- ime, and la e ma u e s. Hence,
moni o ing ma u i y s a us seems c ucial o de ec playe s a
highe isk o being dis up ed by inju ies and po en ial inju-
ies ha cause he g ea es dis up ion. This would acili a e
design o a ge ed inju y p e en ion p og ams o educe he
impac o bu densome inju ies which migh nega i ely a -
ec indi idual de elopmen and long- e m pe o mance.38
G ow h and ma u a ion a e non- modi iable isk ac-
o s, and he e is li le ha can be done o in luence hese
p ocesses. Howe e , educa ing key s akeholde s (playe s,
coaches, di ec o s, pa en s) abou he e ec o ma u a ion
seems i al. Fi s ly, coaches should be awa e ha he en-
dency o ely mo e on ea ly ma u e s in U14 ca ego y12 can
lead hem o highe exposu e, mo e leade ship oles and
highe inju y bu den. In his con ex , load managemen
s a egies such as modi ying aining sessions (e.g., selec -
ing playe s as “ loa e s” du ing possession d ills) o u i-
lizing ma u i y- ca ego ized s a egies (bio- banding)7,30,33
would enable be e managemen o he equency and
olume o exposu e. Besides, p esc ibing ac i i ies o
acili a e de elopmen (e.g., wo king on echnical p o-
iciency o mo emen , co e s eng h o mobili y) while
p e en ing unwan ed mechanical s ess would enable be -
e managemen o he equency and olume o exposu e
o s ess ul ac i i ies.7 Conside ing inju ies ha cause he
g ea es dis up ion acco ding o each playe s ma u a ion
p o ile would be c ucial when p esc ibing hose ac i i ies.
None heless, inju ies a e mul i ac o ial, and we canno
o ge o he isk ac o s ( aining load, neu omuscula
and biomechanical ac o s, physio he apy, coaching, com-
munica ion, psychosocial ac o s, e c.) when designing in-
ju y p e en ion p og ams.39
ACKNOWLEDGEMENTS
This wo k was pa ially suppo ed by he Uni e si y o
he Basque Coun y (UPV/EHU) (GIU20/006). The co -
esponding au ho was suppo ed by a PhD s uden ship
om he Basque Go e nmen (PRE_2020_2_0145). These
o ganiza ions ha e no oles in he collec ion o da a, anal-
ysis, in e p e a ion, and publica ion o he pape .
DATA AVAILABILITY STATEMENT
The da a ha suppo he indings o his s udy a e a ail-
able om he co esponding au ho , [XM], upon eason-
able eques .
ORCID
Xabie Monas e io h ps://o cid.
o g/0000-0001-9409-0059
Susana M. Gil h ps://o cid.o g/0000-0003-0596-7627
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