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Scintigraphy in Legg-Calvé-Perthes Disease
The Long-Term Prognostic Value of Bone
Scintigraphy in Legg-Calvé-Perthes Disease
Marcus Vinicius Moreira1,2,3, Luciano S Dias4* and Luiz R A de Angeli3,5
1Pediatric Orthopedic Division, Association for the Care of Disabled Children, Sao Paulo, Brazil
2Department of Orthopedics and Traumatology, Federal University of Sao Paulo (UNIFESP), Brazil
3Hospital Israelita Albert Einstein, Sao Paulo, Brazil
4Division of Orthopaedic Surgery, Ann & Robert H. Lurie Children’s Hospital of Chicago, Chicago, USA
5Department of Orthopedics and Traumatology, University of Sao Paulo, Sao Paulo, Brazil
Submission:March 18, 2021; Published: March 29, 2021
*Corresponding author: Luciano S Dias, Division of Orthopaedic Surgery, Ann & Robert H. Lurie Children’s Hospital of Chicago, Chicago, USA
How to cite this article: Moreira M V, Dias L S, de Angeli L R A. The Long-Term Prognostic Value of Bone Scintigraphy in Legg-Calvé-Perthes Disease.
Ortho & Rheum Open Access J. 2021; 17(5): 555973. DOI: 10.19080/OROAJ.2021.17.555973
Purpose: Predicting the prognosis of Legg-Calvé-Perthes disease (LCPD) in its earlier stages is still a challenge. The purpose of this study is to evaluate the reliability of Conway’s scintigraphic classification in a long-term follow-up cohort of patients with LCPD.
Methods: We reviewed the records of 44 consecutive patients diagnosed with LCPD at the Waldenström initial stage of the disease, who underwent serial bone scans and were treated conservatively. Patients were classified as Pathway A, B, or C, according to Conway’s classification. The age at onset of symptoms and the Stulberg classification at skeletal maturity were analyzed
Results: Of the 44 patients involved in this study, 31 were males and 13 were females. The average age at onset of symptoms was 5 years and 11 months, and the average follow-up time was 13.6 years (range, 9.2 to 20.7). Two patients had both hips affected. Thus, for a total of 46 hips, 33 were classified in Pathway A and 13 were classified in Pathway B. Group A had 81.8% good results (Stulberg I and II), and 18.2% had poor results (Stulberg III and IV). Group B had 23.1% good results and 76.9% had poor results. These results were statistically significant (P < 0.001). No Stulberg 5 hip was seen. The age of onset of symptoms did not correlate with the final outcome (P = 0,09).
Conclusion: Bone scintigraphy is a reliable and valuable tool in predicting long-term outcomes at the early stage of LCPD in patients below the age of 8 years.
Predicting the prognosis of Legg-Calvé-Perthes disease (LCPD) in its earlier stages is still a challenge. The long-term outcome can be a normal joint or arthritis secondary to the epiphyseal deformity and hip incongruity . It is known that the chances of retaining a spherical femoral head increase if the treatment is implemented in the early stages of the disease . However, the most reliable radiographic prognostic classifications systems can only be correctly applied in the late fragmentation phase [3–7]. Thus, there has been an increasing interest in other imaging methods to try to predict prognosis before the radiographic changes become advanced . Currently, Magnetic Resonance Imaging (MRI) is the most used method for this purpose. The vascularity assessment of the proximal femoral epiphysis in the early stages of LCPD is better done with advanced MRI techniques, such as the dynamic gadolinium-enhanced subtraction (DGS) MRI,
also known as perfusion MRI, and the diffusion-weighted imaging (DWI) MRI [8-13]. Both have demonstrated a good prognostic value in the short term follow-up [11,14–17]. However, despite the progress that has been made in this area, there are still no prognostic classifications or treatment recommendations derived from these investigations .
The first attempts to visualize bone revascularization patterns and to predict prognosis in the early stages of the disease were done using bone scintigraphy in the early 1980s, by Conway and Bensahel et al. [18–20]. In 1993, Conway described a four-stage classification based on the revascularization pattern of the femoral head . This classification divided the revascularization patterns into three groups: Pathway A (Figure 1), Pathway B (Figure 2) and Regression group, also known as Pathway C [21,22]. Basically, Pathway A correlates with early revascularization and the appearance of a lateral column in stage IIA, which indicates
a better prognosis. Pathway B, though, correlates with delayed
revascularization and a base-filling pattern in stage IIB, which
indicates a worse prognosis. Last, the Regression pattern refers
to a change in the revascularization from Pathway A to B, also
indicating a worse prognosis. In 1997, Tsao et al. demonstrated
that Conway’s classification had an important prognostic value
. Studies using advanced MRI techniques have shown
revascularization patterns that are similar to the ones described
by Conway [10,23].
Although bone scintigraphy and advanced MRI techniques
have shown a good prognostic value, to date, there are still no
studies about their long-term assessment in LCPD. Thus, the
purpose of this study is to evaluate the reliability of Conway’s
scintigraphic classification [21,22] in a long-term follow-up cohort
of patients with LCPD, who underwent conservative treatment.
This protocol was approved by the Institutional Review Board
and was in compliance with the Helsinki declaration. From 1993
to 2004, we reviewed the records of 44 consecutive patients
diagnosed with LCPD at the initial stage (or necrosis stage)
according to the Waldenström classification [24,25] who were
submitted to serial bone scintigraphic studies and were treated
conservatively. Patients who had surgery were excluded from
this study. All patients were followed until skeletal maturity by
the senior author. The age at onset of symptoms and the Stulberg
classification  in the last follow-up radiographs were analyzed.
All patients underwent conservative treatment, which
included: medication for pain control, rest, avoiding running and
jumping sports, and partial weight-bearing during the stages
when the patient has shown a decreased range of motion and
pain. Serial bone scans with pinhole magnification and pelvis
plain radiographs were done at 3 to 4-month intervals. The first
scintigraphic study was done at the initial presentation, and the
subsequent ones were obtained until the definition of one Pathway
pattern (Figures 1 & 2). Usually, 4 bone scans were sufficient to
achieve this objective. The acquisition technique and safety of the
procedure were previously reported .
The last radiographic study was then classified using the
Stulberg classification . Three types of congruency were then
defined: (1) spherical congruency, types I and II; (2) aspherical
congruency, types III and IV; and (3) aspherical incongruency,
For the purpose of statistical analysis, a comparative study
among the Stulberg classified groups was made by using the
Fisher test. The analysis of the age of onset of symptoms, in
comparison with Conway’s scintigraphic classification and
Stulberg classification, was done using the Kruskal-Wallis test.
The significance level was 5%.
Of the 44 patients involved in this study, 31 were males and
13 were females. Two patients had both hips affected. Thus, for
a total of 46 hips, we analyzed 28 left hips and 18 right hips. The
average age at onset of symptoms was 5 years and 11 months,
ranging between 2 years and 8 months to 10 years and 2 months.
The average follow-up time was 13.6 years (range, 9.2 to 20.7). All
patients included were at the initial stage [24,25]. – or necrosis
stage – of the disease when the first bone scintigraphy was done.
According to the visualized bone scan pattern, patients were
divided in 2 groups: Pathway A or Pathway B. In this study, none
of the subjects were classified as Pathway C. The average age at
onset of symptoms for Pathway A was 5 years and 11 months,
and for Pathway B was 5 years and 10 months. Both groups were
similar regarding the age at onset of symptoms (P = 0.866) (Table
Of the 46 hips involved in the final analysis, 33 were classified
in Pathway A and 13 were classified in Pathway B. The final
Stulberg classification for Pathways A and B is demonstrated in
Table 2. Group A had 81.8% good results (Stulberg I and II), and
18.2% had poor results (Stulberg III and IV). Group B had 23.1%
good results and 76.9% had poor results. These results were
statistically significant (P < 0.001). No Stulberg 5 hip was seen.
The age at onset of symptoms did not correlate with the final
outcome (P = 0,09) (Table 3).
The poor results in Pathway A included 6 patients with an
average age at onset of symptoms of 6 years and 11 months. The
single Stulberg 4 in this group was 8 years and 9 months old at the
onset of symptoms. Furthermore, there were only 3 patients with
good results in Pathway B, which presented with an average age at
onset of symptoms of 4 years (Table 2).
The vascular origin for LCPD has been reported by several
authors [18–20,22]. Avascularity patterns of the femoral head
with subsequent necrosis and bone resorption are present during
the initial stages of the disease and are followed by reparative
steps including revascularization and reconstitution of the bony
structure [19,20,22]. In this healing phase, the balance between the
new bone formation and the mechanical forces on the hip defines
whether the patient will develop a structural deformity. A rapid
rate of healing should prevent the occurrence of microfractures,
collapse, and subluxation, which will lead to the ultimate femoral
head bone deformity.
Radiographic classifications have been developed in an
attempt to document changes during the disease evolution
and their relationship with the outcomes [5–7,26,27]. These
classifications can only be correctly used in the late fragmentation
stage, which takes about 11 months to be visualized after the
onset of symptoms . Unfortunately, at this point, the femoral
head collapse is too advanced to allow proper treatment [2,3,8].
Kelly et al.  demonstrated that the Catterall classification
could not be accurately applied for an average of 8.1 months after
the onset of the disease. Lappin et al.  demonstrated that 75%
of Herring grade A cases and 30% of Herring grade B required
upgrading, only being confirmed with an average of 7 months
after the onset of the symptoms. Bone scintigraphy has high
accuracy in detecting vascular changes during the early stages of
LCPD, and its prognostic value was well demonstrated by Tsao et
This particular study  was the first one to evaluate the
prognosis of LCPD using an imaging method during the initial
stages . With an average follow-up time of 4.4 years, Conway’s
classification was correlated with the Catterall classification,
the presence of head-at-risk signs, and the Mose score [4,30].
The results showed that patients included in Pathway A had
significantly better results according to the Mose score and the
hip range-of-motion. No head-at-risk signs were seen in this
group, which was also correlated with a better overall Catterall
classification. Furthermore, Tsao et al.  demonstrated that the
average time to identify children who progressed to Pathway A
was 4.6 months after the onset of symptoms. According to Joseph
et al. , the late fragmentation stage can only be identified
approximately 11 months after the onset of symptoms, so that the
radiographic classifications can be correctly applied. Consequently,
Conway’s classification might be able to predict the prognosis of
the LCPD up to 6 months earlier than conventional radiographs,
allowing faster decision-making regarding management.
In our study, the average follow-up time was 13.6 years.
Patients included in pathway A (33 patients) had 81.8% good
results (Stulberg I and II). Those who presented poor results
(Stulberg III and IV) showed an average age at onset higher than
the entire cohort. Patients included in pathway B (13 patients)
presented 76,9% of poor results and only 3 patients had good
outcomes, and their average age at onset was lower than that of
the entire cohort (Table 2). These findings suggest that the age
at onset might play an independent role in the disease outcome,
regardless of the avascularity index or the revascularization
pattern. Even though we did not find a statistically significant
correlation of the age at onset with the final Stulberg classification
(Table 3), further investigation with larger cohorts and advanced
imaging methods applied in the initial stages of the disease may
confirm this hypothesis in the future.
Our study has several strengths. To the best of our knowledge,
this is the first study to show the long-term follow-up prognostic
value of an advanced imaging method classification system applied
in the initial stage of LCPD. Previous bone scan investigations
showed the short-term correlation of the revascularization
patterns with several radiographic classifications and outcome
measures, but no long-term follow up study was further published
[22,31–34]. Advanced MRI techniques still lack long-term followup
studies. Previous reports showed a good correlation in the use
of DGS and DWI images with the Herring classification and head
deformity at a 2-year follow-up [11,14,15,17]. However, there’s
still no classification system derived from these MRI imaging
methods ready to be applied in clinical practice. Another strength
of this report is the homogeneity of our cohort, formed only by
children diagnosed in the early stages of the disease and treated
conservatively by the senior author, which decreases the possible
bias generated by different treatment modalities in the outcomes.
Lastly, our results are based in the Stulberg classification, which is,
to date, the most reliable radiographic outcome measure in LCPD
There are, still, some weaknesses in this study. First, its
retrospective nature accounts for some limitations in data
acquisition. Second, it lacks clinical data, which is important to
completely understand the outcomes. We believe that if the hip
range-of-motion, quality of life questionnaires, and gait analysis
data could be gathered together, our study would be even
more powerful. Third, it has a small sample size, which might
underpower some of the statistical analysis done.
In conclusion, this study shows that serial bone scintigraphy
is a reliable tool in predicting the long-term outcomes in young
patients - below the age of 8 years - with LCPD. This approach
provides more information during the early stages of the disease,
allowing the pediatric orthopedic surgeon to make more effective
interventions to alter the natural course of the disease, whenever
Ethical approval: All procedures performed in studies
involving human partic-ipants were in accordance with the ethical
standards of the institutional and/or national research committee
and with the 1964 Helsinki declaration and its later amendments
or comparable ethical standards.