radiological outcome in ankylosing spondylitis - Rheumatology

British Journal of Rheumatology 1996;35:373-376
RADIOLOGICAL OUTCOME IN ANKYLOSING SPONDYLITIS: USE OF
THE STOKE ANKYLOSING SPONDYLITIS SPINE SCORE (SASSS)
H. L. AVERNS, J. OXTOBY,* H. G. TAYLOR,t P. W. JONES,J K. DZDEDZIC and P. T. DA WES
Staffordshire Rheumatology Centre, The Haywood, Stoke on Trent, 'Department of Radiology, North Staffs Royal
Infirmary, tRheumatology Department, Wanganui Hospital, New Zealand and \Department of Mathematics,
Keele University
SUMMARY
We investigated the role of the Stoke Ankylosing Spondylitis Spine Score (SASSS) in a longitudinal cohort study of 53 patients
with AS, assessed 9 yr apart, and its relation to clinical, functional and laboratory measures of disease activity and outcome.
We also examined the long-term predictive value of quantitative sacroiliac scintigraphy (QSS). SASSS correlated closely with
clinical measures, including occiput-wall distance (OWD) (P < 0.001) and modified Schober (P < 0.0001). QSS was significantly
correlated with final X-ray score (P < 0.05). SASSS changed significantly (P < 0.001) over the study period; two patterns of
change in spine score were discernible, one with little change in radiological score and the other showing marked progression.
The SASSS is a useful, valid score, which correlates with clinical outcome measures and which has identified specific patterns
of radiographic progression in AS.
KHY WORDS: Ankylosing spondylitis, Radiology, Scintigraphy.
OUTCOME in ankylosing spondylitis (AS) can be
assessed in terms of daily function, pain scores, clinical
measurements and radiological change. There are no
internationally agreed criteria for the assessment of
disease activity, and in the individual patient it is
difficult to predict who will have favourable or
unfavourable outcomes [1, 2]. Thus, identifying useful
predictors of long-term outcome is essential,
particularly if disease modification in AS becomes a
possibility.
ESR and CRP are not considered useful measures of
activity [3,4], except in those with a peripheral
arthritis, but their role in predicting long-term outcome
is unclear, unlike in rheumatoid arthritis.
Russell et al. [5] showed that quantitative radioisotope
sacroiliac scintigraphy (QSS) is sensitive in the
diagnosis of sacroiliitis, but other workers felt there
was a large overlap between control and diseased
patients, limiting the role of QSS in the routine
investigation and management of AS [6]. Assuming
that there is no increased uptake of radionuclide by the
sacrum may be misguided; Paquin. et al. [7] used
lumbar to soft tissue and sacrum to soft tissue ratios,
refining the technique of QSS. No studies have assessed
the long-term predictive value of QSS in AS.
In previous work at the Staffordshire Rheumatology
Centre, we analysed predictors of radiological change
over 12 months [8]. We have reviewed the patients
involved in this original study to identify prognostic
factors in radiological outcome over 9 yr and to
investigate the value of the lumbar spine X-ray score.
This study aimed to address the following. (1) Does
the Stoke AS Spine Score (SASSS) correlate with
Submitted 1 August 1995; revised version accepted 30 November
1995.
Correspondence to: H. L. Averns, Stoke Mandeville Hospital,
Mandeville Road, Aylesbury.
373
clinical measures of axial function and outcome in AS?
(2) Does QSS have a role in predicting long-term
outcome in AS? (3) Are there any laboratory,
radiological or clinical measurements which predict
radiological progression in AS?
METHODS
Sixty-one patients with definite AS (New York
Criteria) who were involved in the original studies of
the SASSS [8] were followed up for further clinical,
laboratory and radiological assessment. All patients
were assessed by the same examiner (HLA) in the early
afternoon. The examination included the modified
Schober test, total spine movement from neutral
between the seventh cervical vertebra and the fifth
lumbar vertebra, finger-floor distance on sagittal
flexion, occiput-wall distance, chest expansion and
Stoke Enthesitis Index [9]. To measure the Enthesitis
Index, various entheses which include the plantar
fascia, Achilles tendon insertion, greater trochanter,
adductor origin, iliac crest, ischial tuberosity,
sternoclavicular joint, sternocostal joints and the
vertebral processes at four levels are palpated with
enough force to make the thumb blanche. Each
enthesis scores from 0 (no pain) to 3 (withdrawal), the
sum of the scores making up the final enthesitis score.
Patients were asked to record the severity of current
pain, night pain and stiffness on a visual analogue scale
(VAS), and completed a functional index as described
by Dougados et al. [10]. The functional index examines
various activities of daily living, such as ability to dress,
to get into a car and to get out of bed, the score being
proportional to the difficulty perceived by the patient.
Blood was taken for FBC, ESR, CRP, biochemical
profile, osteocalcin, immunoglobulins A, G and M, and
a-1-glycoprotein. Lateral X-rays of the lumbar spine
and pelvic X-rays were taken if there had been none
© 1996 British Society for Rheumatology
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374 BRITISH JOURNAL OF RHEUMATOLOGY VOL. 35 NO. 4
FIG. 1.—Radiographic scoring system (see the text for details).
performed in the previous 12 months. All corners of
each vertebra between the lower border of T12 and the
upper border of SI are examined and scored 1 for
erosion, squaring or sclerosis, 2 for syndesmophyte
formation, and 3 for total bony bridging, giving a
maximum possible score of 72 (see Fig. 1). In ~ 10%
of films, the upper sacrum is poorly shown on the
lateral lumbar spine view and a lateral sacral film is
needed in order not to compromise the analysis.
Following a period of training, the available X-rays
from the original study and all the latest X-rays were
scored independently by a rheumatologjst and a
radiologist, but for the purpose of this study we
subsequently examined each X-ray jointly to agree on
the final score. The effective radiation dose of a lateral
lumbar spine X-ray taken at 80 kVp is 0.205 mSv.
Forty-two patients had had quantitative sacroiliac
scintigraphy using 450 mBq Tc-99m-labelled methylose
diphosphonate (MDP) in a previous study to assess the
role of isotope scanning in the management of AS [11].
Ratios were calculated, including sacroiliac: soft tissue
(SIJ:ST) and sacrum:ST.
Statistical analyses were performed with the Number
Cruncher Statistical System 5.01. Spearman's cor-
relation was used to investigate the relationship of
SASSS with other variables.
RESULTS
We have defined initial results as time (t) = 0 and the
latest results as t = 1.
Five patients failed to attend the whole study and
three more were reclassified as diffuse idiopathic
skeletal hyperostosis, so 53 patients with definite AS
were fully assessed. The median age of patients at
follow-up was 47.5 yr (range 32-66) and the median
duration of history was 20 yr (range 9-48). The median
study follow-up time was 9 yr.
Thirty-two patients had definite syndesmophytes and
21 had no sign of syndesmophytes.
Change in SASSS over time
The median total spine score at / = 0 was 5.5 (range
0-52); 9 yr later the median score was 28.5 (range 0-72)
(P < 0.0001).
Figure 2 shows the interindividual variation in
change in spine score, and in particular shows that
while in some patients there is little change, others
show considerable progression of radiological changes
during the study period. By choosing an arbitrary value
of 12 to separate the patients into slow and fast
progressors, we were unable to demonstrate any
variable that could predict outcome.
Change in spine score was not significantly related to
clinic attendance, length of history, age of patient or
age at diagnosis.
Relationship between SASSS and clinical measurements
SASSS was significantly correlated with chest
expansion, occiput-wall distance, finger-floor distance,
72 -
TIME
FK}. 2.—Change in Stoke AS Spine Score in patients with AS
over 9 yr.
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TABLE I
Correlation (Spearman) between Stoke AS Spine Score and clinical
measures
Chest expansion
Occiput-wall distance
Finger-floor distance
Schober test
Total spinal movement
AVERNS ET AL:. USE OF STOKE AS SPINE SCORE 375
r
-0.396
0.503
0.351
-0.690
-0.717
P
< 0.01
< 0.001

376 BRITISH JOURNAL OF RHEUMATOLOGY VOL. 35 NO. 4
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