gender-specific pattern differences of the ossification centers in the pediatric elbow
TRANSCRIPT
ORIGINAL ARTICLE
Gender-specific pattern differences of the ossificationcenters in the pediatric elbow
Bijal Patel & Martin Reed & Shamir Patel
Received: 15 October 2008 /Revised: 2 November 2008 /Accepted: 14 November 2008 / Published online: 6 January 2009# Springer-Verlag 2008
AbstractBackground Only a limited number of studies haveinvestigated the age ranges in which the secondary centersof the elbow appear and ossify. Knowledge of sequence,gender differences and age ranges can aid in accurateassessment of radiographs, especially in cases of injury.Objective To determine the sequence and general ageranges in which each ossification center both appears andfuses, and also to identify differences between genders.Materials and methods This study included 412 sets ofradiographs of children’s elbows that were analyzedprospectively by a single experienced pediatric radiologist.The presence as well as state of fusion of each ossificationcenter was noted. The ages of the children ranged from2 months to 17 years.Results In girls, the radial head and medial epicondyleappeared at the same age. In boys, there was a trendtowards the radial head appearing earlier than the medialepicondyle. There was no statistically significant differencebetween the age at which the trochlea and olecranon
appeared. Our results demonstrate a statistically significantdifference between genders in both appearance and fusion.All centers both appeared and fused earlier in girls, with theexception of the appearance of the capitellum. Thesequence of appearance and fusion was similar betweengenders.Conclusion Ossification centers at the elbow both appearand fuse earlier in females but the normal range in age forthe times of appearance and fusion of these centers is quitewide for both sexes.
Keywords Elbow . Ossification centers . Children
Introduction
Six ossification centers appear progressively around theelbow joint in children. The most widely referenced patternfor the general order of appearance of these ossificationcenters is from Girdany and Golden [1] and Garn et al. [2].Only a few other studies have determined the age ranges inwhich the secondary centers appear and ossify, and mosthave not differentiated the appearance of these ossificationcenters between genders [3–7]. Furthermore, among thesestudies not all centers have been accounted for, or they haverestricted the population of subjects examined. The aim ofthis study was to determine the sequence and general ageranges in which each ossification center both appears andfuses and also to identify differences between genders.
Materials and methods
Institutional Review Board approval was not required forthis type of study at our institution. A series of radiographs
Pediatr Radiol (2009) 39:226–231DOI 10.1007/s00247-008-1078-4
B. PatelDepartment of Radiology, University of Manitoba,Winnipeg, Canada
M. ReedDepartment of Pediatric Radiology, University of Manitoba,Winnipeg, Canada
S. PatelDepartment of Radiology, University of Calgary,Calgary, Canada
B. Patel (*)1108 15 St. SW Apt. 403,Calgary, Canada T3C 1E8e-mail: [email protected]
of children’s elbows were collected and analyzed prospec-tively by a single experienced pediatric radiologist (M.R.).Most radiographs were obtained because of injury. Childrenwith previous fractures of the limb or chronic diseases wereexcluded. The elbow radiographs were taken with astandardized technique in the anteroposterior and lateralplanes. Films of poor technical quality were excluded. Thepresence as well as the state of fusion of the capitellum,radial head, medial epicondyle, trochlea, olecranon andlateral epicondyle ossification centers of each child werenoted. Fusion was defined as complete obliteration of thegrowth plate.
A total of 412 sets of radiographs met the inclusioncriteria. The ages of the children ranged from 2 months to17 years and 7 months, with 212 boys and 200 girls. Thedistribution of subjects within each age group is shown inFig. 1. Winnipeg is a multiethnic community [8] and ourpatient population included children from many ethnicgroups, including Canadian aboriginals, and therefore, itwas not possible to classify patients by ethnic origin.
The data were analyzed using analysis of covariance(ANCOVA, comparison of regression lines). Graphs werecreated plotting the percentage of children with absence ofappearance and fusion of each ossification center by age
and gender (Appendix 1). The means and standarddeviations for the age of appearance and fusion for eachof the ossification centers and for each sex were calculatedand compared by gender. The two-tailed P value was 0.05.
Results
The first ossification center to appear was that for the capitellum,virtually always by 1 year of age (Tables 1 and 2). In girls, theradial head and medial epicondyle appeared at the same age. Inboys, however, there was a trend of the radial head appearingearlier than the medial epicondyle at 5.9 and 6.8 years,respectively.
No significant difference between the age at which thetrochlea and olecranon appeared was identified. Thetrochlea and olecranon appeared at 8.4 and 8.3 years,respectively, in girls, and at 9.7 and 9.9 years, respectively,in boys. There was a statistically significant differencebetween males and females in both the appearance andfusion of all ossification centers. All centers both appearedand fused earlier in girls, with the exception of theappearance of the capitellum. The sequence of appearanceand fusion, however, was similar between genders.
Age Distribution
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Fig. 1 Distribution of ages
Table 1 Ages (years) of boys and girls at the 5th, 50th and 95th percentiles for the appearance of ossification centers.
Ossification center Boys Girls
5th percentile 50th percentile 95th percentile 5th percentile 50th percentile 95th percentile
Capitelluma – – – – – –Radial head 3.3 5.9 8.5 1.6 4.2 6.8Medial epicondyle 3.9 6.8 9.7 1.3 4.2 7.1Trochlea 7.0 9.7 12.5 5.7 8.4 11.1Olecranon 7.6 9.9 12.2 6.0 8.3 10.6Lateral epicondyle 8.0 11.2 14.4 7.3 9.4 11.6
a Inadequate number of subjects in this category.
Pediatr Radiol (2009) 39:226–231 227
Discussion
A number of previous studies have investigated theappearance and fusion of the ossification centers at theelbow. These studies, however, based their conclusions onvery small numbers of subjects and provided inadequateinformation about the sources of their data [2–4, 9–11, 13,17], or their results were reported in a summary thatcannot be easily compared with ours [12, 15]. Bajaj et al.[13] reported, although very briefly, a study in an Indianpopulation and provided detailed information about thesources of their data. Their results can be compared withour data (Table 3). Garn et al. [2] and Girdany and Golden[1], whose article reproduces a chart originally publishedby Camp and Cilley [17], are frequently quoted asauthorities on skeletal development, and their dataconcerning the elbow are also included in Table 3. Anearly article by Khanna and Kiran [14] provides good datafrom an Indian population, but focused only on the ages offusion of the ossification centers (Table 4). The onlyrecent comparable article to ours is that by Cheng et al.[7], who studied elbow development in a Chinesepopulation, although they only provide data on the timesof appearance of the ossification centers and not on thetimes of fusion.
Our results are similar to those of Cheng et al. (Table 3).In boys, with the exception of the capitellum, an average
delay of 2 years was found in the appearance of each of theossification centers as compared to girls. It has been shown,however, that girls are ahead of boys in the speed withwhich they move toward skeletal maturity and growth [18].Therefore these gender differences in the elbow are notunique. In our study, however, the ages at which theossification centers appeared in both genders were consis-tently lower than those reported by Cheng et al. In ourstudy and other studies, with the exception of the study byBajaj et al. [13], the trochlea, capitellum and lateralepicondyle all appeared to fuse first at similar ages in bothgenders (Table 4). In the distal humerus, generally thetrochlea, capitellum and lateral epicondyle all tend to fusetogether and then fuse as a block to the humeral shaft(conjoint epiphysis) [3].
There is considerable evidence that patterns of ossificationare significantly affected by genetic, racial and environmen-tal factors, and by pathologic conditions that can affectgrowth and skeletal maturation [7, 16]. A comparison of theages in an Indian population [13] and in a Chinesepopulation [7] (Table 3) would support this racial difference,and probably also explain the differences between thefindings of our study and those of some other studies.
Because of the large number of secondary ossificationcenters at the elbow, data on their times of appearance andtimes of fusion are important for the radiologist. In cases ofinjury, for example, a small metaphyseal fragment associ-
Table 3 Data from selected literature on the approximate ages (years) in boys and girls at which the ossification centers appear.
Ossification center Bajaj et al. [13] Girdany and Golden [1] Garn et al. [2] Cheng et al. [7] Reed [5]
Boys Girls Boys Girls Boys Girls Boys Girls Boys Girls
Capitellum 0.5 0.5 0.08–0.67 0.33 0.26 1 1 – –Radial head 6.2 3.5 2.9–5.5 5.21 3.87 7 5 5.9 4.2Medial epicondyle 7.4 5.0 4.75-7 2.25–5.1 6.25 3.40 7 5 6.8 4.2Trochlea 7.9 7.7 7–9 – – 11 9 9.7 8.4Olecranon 10.4 8.6 8–11 9.67 8.01 11 9 9.9 8.3Lateral epicondyle 10.2 7.5 11–14 11.24 9.24 12 10 11.2 9.4
Table 2 Ages (years) of boys and girls at the 5th, 50th and 95th percentiles for the fusion of ossification centers.
Ossification center Boys Girls
5th percentile 50th percentile 95th percentile 5th percentile 50th percentile 95th percentile
Capitellum 12.0 13.7 15.3 9.4 11.0 12.6Radial head 12.4 14.8 17.1 10.2 12.5 14.8Medial epicondyle 13.0 14.9 16.8 11.5 13.4 15.3Trochlea 11.6 13.4 15.2 9.2 11.0 12.7Olecranon 12.4 14.5 16.5 10.8 12.8 14.8Lateral epicondyle 12.1 14.0 15.9 9.5 11.4 13.3
228 Pediatr Radiol (2009) 39:226–231
ated with a fracture of the lateral condyle in a young childshould not be mistaken for an ossification center for thelateral epicondyle, which appears later. Conversely, in anolder child an ossification center for the lateral epicondyleshould not be mistaken for an avulsion fracture.
Conclusion
In general, ossification centers at the elbow both appear andfuse earlier in girls, but the normal range in age for thetimes of appearances and fusion of these centers is quitewide for both sexes. However, the sequence of appearanceand fusion of these ossification centers is predictable.
Appendix
Ossification center appearance
Radial Head
male
female
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Age (yrs.)
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Graph 2 Percentage of children with the radial head present atvarious ages. In girls the radial head appeared earlier than in boys. Atany given age a greater percentage of girls demonstrated a radial head(% P<0.05, slope P=0.20)
Capitellum
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Graph 1 Percentage of children with the capitellum present atvarious ages. There was no significant difference between gendersfor the percentage of subjects at a given age (P=0.81). However, thenumber of children in this category was inadequate
Table 4 Data from selected literature on the approximate ages (years) in boys and girls at which the ossification centers fuse.
Ossificationcenter
Reed [5] Khanna and Kiran [14] Bajaj et al. [13] Girdany and Golden [1]a
Boys Girls Boys Girls Boys Girls
Capitellum 13.7 11.0 14 13 17.5 16.5 15Radial head 14.8 12.5 16 14 16.2 14.5 15Medial epicondyle 14.9 13.4 16 14 16.3 14.3 20Trochlea 13.4 11.0 14 13 14.0 13.0 14Olecranon 14.5 12.8 15 13 16.4 14.1 14Lateral epicondyle 14.0 11.4 – – – – 20
a No distinction was made between genders.
Medial Epicondyle
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Graph 3 Percentage of children with the medial epicondyle presentat various ages. In girls the medial epicondyle appeared earlier than inboys. At any given age a greater percentage of girls demonstrated amedial epicondyle (% P<0.05, slope P=0.67)
Pediatr Radiol (2009) 39:226–231 229
Ossification center fusion
Lateral Epicondyle
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Graph 6 Percentage of children with the lateral epicondyle present atvarious ages. In girls the lateral epicondyle appeared earlier than in boys. Atany given age a greater percentage of girls demonstrated a lateral epicondyle(% P<0.05). The rate of change of the percentage of children at any givenage was significantly different between genders (slope P<0.05)
Olecranon
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Graph 5 Percentage of childrenwith the olecranon present at various ages.In girls the olecranon appeared earlier than in boys. At any given age agreater percentage of girls demonstrated an olecranon (% P<0.05, slopeP=0.47)
Trochlea
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Graph 4 Percentage of children with the trochlea present at various ages.In girls the trochlea appeared earlier than in boys. At any given age a greaterpercentage of girls demonstrated a trochlea (% P<0.05, slope P=0.88)
Capitellum
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Graph 7 Percentage of children with a fused capitellum at various ages.In girls the capitellum fused earlier than in boys. At any given age agreater percentage of girls demonstrated fusion (% P<0.05, slope P=0.07)
Radial Head
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Graph 8 Percentage of children with a fused radial head at various ages.In girls the radial head fused earlier than in boys. At any given age agreater percentage of girls demonstrated fusion (% P<0.05, slope P=0.41)
Medial Epicondyle
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Graph 9 Percentage of children with a fused medial epicondyle atvarious ages. In girls the medial epicondyle fused earlier than in boys. Atany given age a greater percentage of girls demonstrated fusion(% P<0.05, slope P=0.10)
230 Pediatr Radiol (2009) 39:226–231
References
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2. Garn SM, Rohmann CG, Silverman FN (1967) Radiographicstandards for postnatal ossification and tooth calcification. MedRadiogr Photogr 43:45–66
3. McCarthy SM, Ogden JA (1982) Radiology of postnatal skeletaldevelopment: VI. Elbow joint, proximal radius, and ulna. SkeletalRadiol 9:17–26
4. McCarthy SM, Ogden JA (1982) Radiology of postnatal skeletaldevelopment: V. Distal humerus. Skeletal Radiol 9:239–249
5. Reed MH (1992) Pediatric skeletal radiology: appendicularskeleton. Williams & Wilkins, Baltimore, MD, pp 352–357Section 3
6. Poznanski AK (1976) Radiologic evaluation of maturation.Practical approaches to pediatric radiology. Year Book, Chicago,IL, pp 293–309
7. Cheng JC, Wing-Man K, Shen WY et al (1998) A new look at thesequential development of elbow-ossification centers in children. JPediatr Orthop 18:161–167
8. Census data, the City of Winnipeg. Available via http://winnipeg.ca/Census/2001/City%20of%20Winnipeg/City%20of%20Winnipeg/City%20of%20Winnipeg.pdf Accessed Sep 2007
9. Davies DA, Parsons FG (1927) The age order of the appearanceand union of the normal epiphyses as seen by x-rays. J Anat62:59–71
10. Galstaun G (1937) A study of ossification as observed in Indiansubjects. Indian J Med Res 25:267–291
11. Patterson RS (1929) A radiological investigation of the epiphysesof the long bones. J Anat 64:29–46
12. Flecker H (1942) Time of appearance and fusion of ossificationcenters as observed by roentgenographic methods. AJR 47:97–120
13. Bajaj ID, Bhardwaj OP, Bhardwaj S (1967) Appearance andfusion of important ossification centers: a study in Delphipopulation. Indian J Med Res 55:1064–1067
14. Khanna KK, Kiran S (1979) Radiological study at wrist andelbow-epiphysial fusion with diaphysis. Indian J Med Sci 33:121–125
15. Sempe M (1976) Skeletal growth and maturation of the elbow.Kinetic study. Ann Radiol (Paris) 19:733–742
16. Eveleth PB, Tanner JM (1990) Worldwide variation in humangrowth, 2nd edn. Cambridge University Press, Cambridge, MA
17. Camp JD, Cilley EI (1931) Diagrammatic chart showing time ofappearance of various centers of ossification and period of union.AJR 26:905
18. Flory CD (1935) Sex differences in skeletal development. ChildDev 6:205–212
Trochlea
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Graph 10 Percentage of children with a fused trochlea at various ages.In girls the trochlea fused earlier than in boys. At any given age a greaterpercentage of girls demonstrated fusion (% P<0.05, slope P=0.75)
Olecranon
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Graph 11 Percentage of subjects with a fused olecranon at various ages.In girls the olecranon fused earlier than in boys. At any given age a greaterpercentage of girls demonstrated fusion (% P<0.05, slope P=0.21)
Lateral Epicondyle
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Graph 12 Percentage of children with a fused lateral epicondyle atvarious ages. In girls the lateral epicondyle fused earlier than in boys.At any given age a greater percentage of girls demonstrated fusion(% P<0.05, slope P=0.70)
Pediatr Radiol (2009) 39:226–231 231