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Pos ope a i e Sagi al Balance has Only a Limi ed Role in he De elopmen o Adjacen
Segmen Disease a e Lumba Spine Fusion o Degene a i e Lumba Spine Diso de s :
A Subanalysis o he 10-yea Follow-up S udy
© 2022 The Au ho (s). Published by Wol e s Kluwe Heal h, Inc.
Published e sion
Toi onen, Lee i A.; Män ymäki, Heikki; Häkkinen, A ja; Kau iainen, Hannu; Ne a,
Ma ko H.
Toi onen, L. A., Män ymäki, H., Häkkinen, A., Kau iainen, H., & Ne a, M. H. (2022).
Pos ope a i e Sagi al Balance has Only a Limi ed Role in he De elopmen o Adjacen Segmen
Disease a e Lumba Spine Fusion o Degene a i e Lumba Spine Diso de s : A Subanalysis o
he 10-yea Follow-up S udy. Spine, 47(19), 1357-1361.
h ps://doi.o g/10.1097/BRS.0000000000004400
2022
SURGERY
Pos ope a i e Sagi al Balance Has Only a Limi ed
Role in he De elopmen o Adjacen Segmen
Disease A e Lumba Spine Fusion o
Degene a i e Lumba Spine Diso de s:
A Subanalysis o he 10-yea Follow-up S udy
Lee i A. Toi onen, MD,
a
Heikki Män ymäki, MD, PhD,
a
A ja Häkkinen, PhD,
b
Hannu Kau iainen, PhD,
c
and Ma ko H. Ne a, MD, PhD
a
S udy Design. Re ospec i e addi ional analysis o a p ospec i e
ollow-up s udy.
Objec i es. We aimed o find ou whe he poo pos ope a i e
sagi al alignmen inc eases e isions o adjacen segmen disease
(ASD) a e lumba spine usion (LSF) pe o med o degene a i e
lumba spine disease.
Summa y o Backg ound Da a. Re isions o ASD accumula e
o e ime a e LSF o degene a i e lumba spine disease. The
e iology o ASD is conside ed mul i ac o ial. Ye , he ole o pos -
ope a i e sagi al balance in his p ocess emains con o e sial.
Ma e ials and Me hods. A o al o 215 consecu i e pa ien s
who had unde gone an elec i e LSF su ge y o spinal s enosis wi h
(80%) o wi hou (20%) spondylolis hesis we e analyzed. Spinal
eope a ions we e collec ed om he hospi al eco ds. P eope a i e
and pos ope a i e sagi al alignmen we e e alua ed om s anding
adiog aphs. The isk o e isions o ASD was e alua ed by Cox
p opo ional haza ds eg ession models.
Resul s. We did no find he poo pos ope a i e balance [pel ic
incidence−lumba lo dosis (LL) >9°] o significan ly inc ease he
isk o e isions o ASD. c ude haza d a io (HR) =1.5 [95%
confidence in e al (CI): 0.8–2.7], adjus ed (by age, sex, pel ic
incidence, usion leng h, and he le el o he caudal end o usion):
HR =1.7 (95% CI: 0.9–3.3). We ound highe LL ou side he usion
segmen (LL−segmen al lo dosis) o dec ease he isk o e isions
o ASD: HR =0.9 (95% CI: 0.9–1.0).
Conclusion. Poo sagi al balance has only a limi ed ole as a isk
ac o o he e isions o ASD among pa ien s wi h degene a i e
spinal disease. Howe e , he isk o ASD migh be he g ea es
among pa ien s wi h educed spinal mobili y.
Key wo ds: lumba spine usion, degene a i e spinal disease,
sagi al balance, e isions, adjacen segmen disease, adjacen
segmen pa hology
Le el o E idence: 3
Spine 2022;47:1357–1361
Lumba spine usion (LSF) su ge y is a common
p ocedu e in he ea men o se e al spinal pa holo-
gies. Degene a i e lumba spine diso de s (DLSDs) a e
he mos common eason o LSF, while is hmic spondylo-
lis hesis (IS) co e s up o 20% o he cases.1,2 LSF su ge ies
occasionally become complica ed by he need o epea
su ge ies.3,4 Adjacen segmen disease (ASD) is a majo
eason o la e eope a ions a e LSF.5By defini ion, ASD is
a degene a i e condi ion ha pos ope a i ely de elops o
he disk le el nex o he usion segmen and causes
symp oms ia ins abili y o neu al comp ession.6ASD is he
mos equen among he pa ien s wi h DLSD whe e eop-
e a ions accumula e by ime, on con as o he pa ien s
wi h IS, who in equen ly acqui e his complica ion.4,7,8
DOI: 10.1097/BRS.0000000000004400
F om he
a
Depa men o O hopaedics and T auma, Facul y o Medicine
and Li e Sciences and Tampe e Uni e si y Hospi al, Uni e si y o Tampe e,
Tampe e, Finland;
b
Facul y o Spo and Heal h Sciences, Uni e si y o
Jy äskylä, Jy äskylä, Finland; and
c
P ima y Heal h Ca e Uni , Kuopio
Uni e si y Hospi al, Kuopio, Finland; Folkhälsan Resea ch Cen e ,
Helsinki, Finland.
Acknowledgmen da e: Decembe 8, 2021. Fi s e ision da e: Ma ch 1,
2022. Accep ance da e: Ma ch 14, 2022.
Suppo ed by he Compe i i e S a e Financing o he Expe Responsibili y
A ea o Tampe e Uni e si y Hospi al.
The au ho s epo no conflic s o in e es .
This is an open access a icle dis ibu ed unde he e ms o he C ea i e
Commons A ibu ion-Non Comme cial-No De i a i es License 4.0 (CCBY-
NC-ND), whe e i is pe missible o download and sha e he wo k p o ided
i is p ope ly ci ed. The wo k canno be changed in any way o used
comme cially wi hou pe mission om he jou nal.
Add ess co espondence and ep in eques s o Lee i A. Toi onen, MD,
Depa men o O hopaedics and T auma, Tampe e Uni e si y Hospi al,
Elämänaukio 2, Tampe e 33520, Finland; E-mail: lee i. oi onen@pshp.fi
SPINE Volume 47, Numbe 19, pp 1357–1361
© 2022 The Au ho (s). Published by Wol e s Kluwe Heal h, Inc.
Spine www.spinejou nal.com 1357
E iology o ASD is hough o be mul i ac o ial. Ye , he
de ailed pa hogenesis emains no ho oughly cla ified. On
he one hand, LSF su ge y may con ibu e o he pa ho-
genesis by al e ing he adjacen le el biomechanics. On he
o he hand, he ongoing degene a i e p ocess ou side he
usion i sel seems o ha e a significan ole, as well.9
Se e al po en ial isk ac o s a e linked o he p og ession o
ASD, bu hei significance a ies in he li e a u e.5,10 Sag-
i al alignmen a e LSF is gene ally conside ed ele an
he e, so ha ailu e o es o e no mal lo dosis o loss o
lo dosis in LSF inc eases he isk o ASD.5,11 I he pos -
ope a i e balance can be linked o he occu ence o
ASD, his would also suppo he ole o su ge y in he
pa hogenesis o ASD.
In a 10-yea p ospec i e ollow-up s udy o elec i e LSF
su ge ies pe o med in a single uni e si y cen e , we ound
e isions o ASD o accumula e o e ime among pa ien s
wi h DLSD while hey we e spo adic wi h IS. He e, we pe -
o med addi ional analysis among he DLSD pa ien s o find
ou whe he poo pos ope a i e sagi al alignmen inc eases
he e isions o ASD in a 10-yea ollow-up a e LSF.
MATERIALS AND METHODS
Pa ien s
Be ween 2008 and 2012, all elec i e LSF pa ien s in Tampe e
Uni e si y Hospi al we e ec ui ed in o a p ospec i e ollow-
up s udy. In Finland, a single public uni pe o ms LSF
su ge ies and eope a ions o a ce ain popula ion. Hence,
he s udy popula ion ep esen s a ce ain geog aphical
ca chmen a ea. A he baseline, su geons and s udy pe -
sonnel filled in he demog aphic and su gical da a, and he
pa ien s answe ed he ollowing ques ionnai es: Oswes y
Disabili y Index, Dep ession Scale, and a Visual Analog Scale
o back and leg pain. All pa ien s signed w i en consen ,
and he Tampe e Uni e si y Hospi al E hics Commi ee ap-
p o ed he s udy (R07108).
As ASD is mainly ela ed o degene a i e spinal dis-
o de s, we excluded pa ien s wi h IS he e. Ou p e ious
ollow-up showed de o mi y pa ien s o esemble DSLS
pa ien s demog aphically and in e ms o e isions o
ASD.4Howe e , gi en hei condi ion which po en ially
equi es mo e ex ensi e su ge y and indi idual judgemen ,
we excluded pa ien s wi h de o mi y he e o acili a e an-
swe ing o he p esen ques ion. Hence, ou exclusion
c i e ia we e: (1) usion eaching he ho acic spine, (2)
o me spine su ge y, (3) IS, (4) de o mi y, (5) ac u e, o
(6) umo . Ou whole s udy popula ion su e ed om
degene a i e lumba spine pa hology wi h ela ed neu al
comp ession, ha is, spinal s enosis wi h (80%) o wi h-
ou (20%) spondylolis hesis. Fusion was implemen ed o
add ess he spondylolis hesis o o acili a e o aminal
decomp ession. All su ge ies we e ins umen ed pos e o-
la e al usions om midline incision wi h o wi hou
in e body usion ( ans o aminal lumba in e body
usion/pos e io lumba in e body usion) combined wi h
necessa y decomp ession.
We in es iga ed all spinal eope a ions om he pa ien
eco ds. Dea h o eope a ion o ASD ended he ollow-up
o a single pa ien —o he wise, he ollow-up con inued o
June o 2020.
Spinopel ic Pa ame e s
Lumba lo dosis (LL), pel ic incidence (PI), sac al slope,
pel ic il , and segmen al lo dosis (SL) o he usion segmen
we e de e mined om sagi al s anding lumba spine a-
diog aphs be o e and 3 mon hs a e su ge y. The p e-
ope a i e s anding adiog aph was missing om 7 pa ien s
— hey we e excluded om he analysis. Figu e 1 shows he
defini ions o hese pa ame e s. PI is ega ded a cons an
alue de e mined by indi idual pel ic ana omy. We
de e mined LL as an angle be ween he uppe endpla es o
L1 and S1 e eb ae. Schwab e al12 pos ula ed a o mula
LL =PI ±9° in he no mal popula ion. Acco ding o ha ,
he pa ien can be conside ed hypolo do ic in spine su ge y
se ings wi h PI−LL >9°. The op imal a ge lo dosis in
LSF, howe e , dec eases wi h he pa ien ’s age.13,14 A single
h eshold was chosen o s a is ical analysis. Fu he ,
analyses we e pe o med sepa a ely o he pa ien s unde
and o e 65 yea s o a oid he po en ial e ec o he
di e ence be ween he age-app op ia e h eshold and he
fixed cu o o 9°. Sac al slope desc ibes he pel ic
alignmen , and pel ic il indica es he amoun o pel ic
e o e sion which is needed o main ain a s anding
pos u e. A e LSF, LL−SL ep esen s he mobile segmen
o he lumba spine.
LL
SS
PI
PT
SL
Figu e 1. Lumba spinopel ic pa ame e s: lumba lo dosis (LL), pel ic
incidence (PI), sac al slope (SS), pel ic il (PT), and segmen al lo dosis
(SL) o he usion segmen . Values a e p esen ed in deg ees.
SURGERY Sagi al Balance and ASD •Toi onen e al
1358 www.spinejou nal.com Oc obe 2022
S a is ics
The desc ip i e s a is ics a e p esen ed as means wi h SD, as
medians wi h in e qua ile ange o as coun s wi h pe cen-
ages. Cox p opo ional haza ds eg ession models we e
used o es ima e he adjus ed haza d a ios (HRs) and hei
95% confidence in e als (CIs). Age, sex, usion leng h, and
he le el o he caudal end o usion we e used as co a ia es
in hese models. The possible nonlinea ela ionship be-
ween LL and SL and he isk o e ision o ASD was
modeled using es ic ed cubic splines wi h 4 kno s a he
fi h, 35 h, 65 h, and 95 h pe cen iles. Spline unc ions
we e es ima ed using mul i a iable Cox p opo ional haz-
a d eg ession models, including age, sex, usion leng h, and
he le el o he caudal end o usion as a co a ia e. All
analyses we e pe o med using STATA so wa e, e sion
16.1 (S a aCo p LP, College S a ion, TX).
RESULTS
A o al o 215 pa ien s (mean age: 66 y , SD: 10 y ) me he
inclusion c i e ia. Mos o hem we e women (76%) who
mos commonly unde wen wo-segmen usion in he lowe
lumba spine (Table 1).
Du ing he ollow-up wi h a median o 9.2 yea s,
43 (20%) pa ien s unde wen a e ision o ASD.
The spinopel ic pa ame e s o he pa ien s we e equal
p eope a i ely and pos ope a i ely (Table 2). By mean, he
di e ence PI−LL anged in no mal lo dosis be o e and a e
su ge y. Howe e , 83 (39%) pa ien s we e hypolo do ic
a e su ge y acco ding o he misma ch o PI−LL >9°.
The pos ope a i e imbalance (PI−LL >9°) did no esul
in a significan ly inc eased isk o e ision o ASD ac-
co ding o he Cox mul i a ia e model. The c ude HR o
1.5 (95% CI: 0.8–2.7) and adjus ed (by age, sex, PI, usion
leng h, and he le el o he caudal end o usion) HR o 1.7
(95% CI: 0.9–3.3) emained s a is ically insignifican . HR
was he same, insignifican , i pa ien s unde and o e
65 yea s we e analyzed sepa a ely.
Pos ope a i e segmen al hypolo dosis migh lead o hy-
pe lo dosis ou side he usion segmen (LL−SL) as a com-
pensa o y mechanism. Ne e heless, we ound highe LL
−SL o esul in less e isions o ASD: HR =0.9 (95% CI:
0.9–1.0). The e ec o con inuous di e ence LL−SL on e-
isions o ASD is shown in Figu e 2 ein o ced his finding.
DISCUSSION
Among pa ien s who unde wen LSF su ge y o DLSD, we
did no find pos ope a i e hypolo dosis (by PI−LL >9°) o
esul in a significan inc ease o he isk o e ision o
ASD du ing a 10-yea ollow-up. Howe e , misma ch o 9°
does no always ep esen a clinical h eshold o sa -
is ac o y and poo alignmen . Olde age g oups epo edly
ole a e lowe lo dosis and g ea e misma ch han younge
pa ien s.13,14 Ne e heless, one fixed cu o was used o
di e en ia e good and poo alignmen in s a is ical analysis.
As p e iously indica ed, e isions o ASD a e in equen
a e LSF o IS.4Con a y o ha , hey accumula e almos
linea ly o e ime among pa ien s ha ha e unde gone LSF o
TABLE 1. The Baseline Demog aphic Da a, Sel -
epo ed (*) Symp oms and
Como bidi ies, and he Type o
P ima y Su ge y
N=215
Women [n (%)] 164 (76)
Age [mean (SD)] 66 (10)
BMI [mean (SD)] 28.6 (4.4)
Smoking* [n (%)] 12 (6)
Educa ion yea s [mean (SD)] 11.1 (3.9)
Physical ac i i y* [mean (SD)] (h/wk) 4 (2, 9)
Du a ion o he spinal p oblem* [median (IQR)] (y) 9 (4, 20)
Back pain* VAS [mean (SD)] 61 (26)
Leg pain* VAS [mean (SD)] 68 (23)
ODI* [mean (SD)] 45 (15)
DEPS* [mean (SD)] 10.5 (6.1)
Como bidi ie* [n (%)]
Ca dio ascula 118 (60)
Diabe es 24 (12)
Psychia ic diso de 5 (3)
Pulmona y 11 (6)
Neu ological 5 (3)
Rheuma oid 14 (7)
Indica ion o su ge y
Spinal s enosis wi h spondylolis hesis [n (%)] 172 (80)
Spinal s enosis wi hou spondylolis hesis [n (%)] 43 (20)
Fusion
Le el o he lowe end [n (%)]
L3 o L4 9 (4)
L5 o L6 114 (53)
S1 92 (43)
Leng h, le els [n (%)]
1 59 (27)
2 84 (39)
3 54 (25)
4 17 (8)
5 1 (0)
In e body cage (TLIF/PLIF) [n (%)] 23 (11)
BMI indica es body mass index; DEPS, Dep ession Scale; IQR, in e qua ile
ange; ODI, Oswes y Disabili y Index; PLIF, pos e io lumba in e body u-
sion; TLIF, ans o aminal lumba in e body usion; VAS, Visual Analog Scale.
SURGERY Sagi al Balance and ASD •Toi onen e al
Spine www.spinejou nal.com 1359
DLSD. This phenomenon highligh s he ole o he ongoing
degene a i e p ocess in he spine in he de elopmen o ASD.
Gene ally, he e ec o pos ope a i e sagi al alignmen
on clinical ou come is es ablished, bu i s ole in he
p e en ion o ASD is mo e unclea .15,16 In he li e a u e, he
case-con ol s udy o Dju aso ic and colleagues is o en
e e ed o as a p oo o an associa ion be ween pos -
ope a i e hypolo dosis and he inc eased e isions o
ASD.5,11,17 In ha s udy, he mean in e al be ween he
ini ial su ge y and he e ision was 58 mon hs, while he
mean ollow-up pe iod o con ols was only 55 mon hs,
which we conside ela i ely sho . As e isions accumula e
o e ime, and secondly, pa ien s may die du ing he ollow-
up, we conside he Kaplan-Meie me hod an app op ia e
way o assess his phenomenon.
Kim e al18 e ospec i ely analyzed 69 pa ien s who
unde wen L4–L5 usion o IS o degene a i e spondylo-
lis hesis. They concluded ha main aining a segmen al lo -
dosis o 20° o mo e was impo an in he p e en ion o
ASD. Bae e al,19 in hei e ospec i e analysis, sugges ed
ha es o a ion o segmen al lo dosis is impo an in he
p e en ion o ASD. Ne e heless, hey ound only a s a is-
ically insignifican di e ence o 3° be ween ASD and non-
ASD g oups. In a p ospec i e 5-yea ollow-up a e LSF,
Anandjiwala e al20 ound p eexis ing adjacen segmen
degene a ion, no pos ope a i e balance, o be a isk ac o
o adiological ASD. Fu he mo e, hey ound no co ela-
ion be ween he clinical ou come and adiological ASD. In
a e ospec i e 10-yea ollow-up o pos e io lumba in-
e body usion su ge ies, Nakashima e al21 ound high PI,
no LL, a significan isk ac o o ea ly-onse ASD. In a
e ospec i e analysis o Alen ado e al,10 SL and LL we e
no significan isk ac o s o ASD.
Despi e a ela i ely la ge s udy popula ion and a long
ollow-up, we did no find a s a is ically significan e ec o
poo pos ope a i e balance on he a e o e isions o ASD.
Hence, we pos ula e ha alignmen plays a less significan
ole in he mul i ac o ial pa hogenesis o ASD han com-
monly p oposed. We conside he ongoing degene a i e
spinal disease he mos impo an single ac o in his en i y.
Poo segmen al alignmen equi es compensa o y mech-
anisms om he pa ien o main ain global balance. Hy-
pe lo dosis in he mobile segmen o he lumba spine,
usually abo e he used segmen , is one o he compensa o y
mechanisms a e LSF.22 Thus, we expec ed highe LL−SL
o ela e o inc eased e isions o ASD caused by he in-
c eased s ess a he adjacen segmen s. Howe e , he con-
nec ion was he opposi e. This may indica e ha he
pa ien s wi h mobile spine p esen mo e capaci y o com-
pensa e and hus less s ess o he adjacen segmen s.
Mo eo e , Figu e 2 indica ed a s ong e ec om he
change in LL−SL on he e isions o ASD. Ou da a
p o ide no defini i e answe whe he his, in ac , mo e
eflec s he indi idual alignmen o mobili y in he mobile
segmen . I is also possible ha some o he pa ien s had an
un ulfilled need o compensa ion be o e and a e su ge y
due o a s i spine. Ea lie , di use idiopa hic skele al
hype os osis, a condi ion esul ing in se e ely es ic ed
spinal mobili y, is epo ed as a significan isk ac o o
ASD a e sho segmen LSF.23 We assume ha he benefi
o easonable segmen al lo dosis in he p e en ion o ASD
migh be he mos impo an wi h educed spinal mobili y.
Du ing he da a collec ing pe iod, use o in e body cage
was less common han nowadays. The main indica ion o
in e body cage hen was o aminal decomp ession o
s eng hening he usion o p e en ins umen a ion ailu es.
TABLE 2. The Spinopel ic Pa ame e s (°) Be o e
and A e Lumba Spine Fusion
Su ge y
Mean (SD)
P eope a i e Pos ope a i e
LL 50 (13) 49 (12)
PI 56 (10) —
PI−LL 6.7 (11.1) 6.7 (11.1)
PT 20 (8) 21 (7)
SS 37 (9) 36 (8)
SL 29 (14) 27 (12)
LL−SL 21 (14) 22 (13)
LL indica es lumba lo dosis; PI, pel ic incidence; PT, pel ic il ; SL,
segmen al lo dosis; SS, sac al slope.
LL-SL pos
-100 10203040506070
F equency, %
0
1
2
3
4
5
6
7
8
Adjus ed Haza d Ra io (95% CI)
0,02
0,05
0,2
0,5
1
2
5
10
Figu e 2. Highe lo dosis in he mobile segmen o he lumba spine
(LL−SL) a e lumba spine usion was linked o dec eased e isions o
adjacen segmen disease. Re e ence le el (haza d a io =1) o LL−SL
was he e se o 21°. CI indica es con idence in e al; LL, lumba
lo dosis; SL, segmen al lo dosis.
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The use o ans o aminal lumba in e body usion in he
co ec ion o sagi al alignmen has inc eased he ea e .
The e o e, we did no assess he ole o he in e body cage
in he p e en ion o ASD he e.
Al hough he connec ion be ween pos ope a i e sagi al
alignmen and he occu ence o ASD seems less s aigh -
o wa d as occasionally p oposed, he pu sui o no mal
alignmen is impo an , especially o he clinical ou come.
In his s udy, we ha e no in es iga ed how pos ope a i e
sagi al balance a ec s he unc ionali y o he heal h-
ela ed quali y o li e. Mo eo e , ending up in kyphosis
du ing LSF su ge y usually hampe s u u e e ision
su ge ies, whe e es o ing no mal balance may equi e
conside ably hea ie su ge y. All his migh ha e he
g ea es impac wi h limi ed spinal mobili y.
This s udy does no p o e ha sagi al alignmen has no
e ec on he de elopmen o ASD. Howe e , ou esul s
ein o ce he pe cep ion om he li e a u e ha sagi al
alignmen has only a limi ed e ec on he p og ession
o ASD.
CONCLUSION
Poo sagi al alignmen (misma ch PI−LL >9°) did no
significan ly inc ease e isions o ASD in a 10-yea ollow-
up o he pa ien s who unde wen LSF o DLSD. Achie ing
app op ia e segmen al lo dosis in LSF migh be he mos
impo an in pa ien s wi h educed spinal mobili y.
➢Key Poin s
❑We pe o med a e ospec i e addi ional analysis
o e alua e he effec o sagi al alignmen on he
isk o e isions o adjacen segmen disease
a e LSFs.
❑The s udy popula ion had been p ospec i ely
ollowed up o 10 yea s a e ha ing unde gone
LSF o a degene a i e spinal diso de (s enosis
wi h o wi hou spondylolis hesis).
❑We did no find poo pos ope a i e balance o
significan ly inc ease he isk o e isions o ASD.
Re e ences
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