Frequency and Characteristics of Metacarpal Pseudoepiphyses in Healthy Children Aged 5-15 Years

Abstract

Objective:

Pseudoepiphyses are notches and clefts located at the non-epiphyseal ends of the metacarpal bones. There are very few studies regarding the frequency of pseudoepiphysis.

Material and Methods:

Subjects between the ages of 5 and 15, whose hand radiographs were obtained between 2015 and 2021 in our Radiology Department, were included in this study. A total of 1071 patients were included in the study. A single radiologist evaluated these radiographs in 3 different time periods. Pseudoepiphyses that involve one cortex of the metacarpal bone are considered as partial pseudoepiphyses, whereas those that involve both cortices are considered as complete pseudoepiphyses.

Results:

Of the 1071 patients included in the study, 65.9% (n = 706) were girls. The mean age was 9.5 ± 2.6 years. Pseudoepiphysis was detected in 222 (20.7%) cases. Pseudoepiphysis was more common in boys (27.4%) than girls (17.3%) (P < .001). The frequency of partial pseudoepiphysis was found to be significantly higher than that of complete pseudoepiphysis [n = 212 (19.8%) and n = 20 (1.9%), respectively, P < .001]. Partial pseudoepiphysis was most frequently detected in the second metacarpal bone, and complete pseudoepiphysis was most frequently detected in the first metacarpal bone. Of 222 cases with pseudoepiphysis, 76.6% (n = 170) had in 1 location, while 21.2% (n = 47) had in 2 locations, 1.8% (n = 4) in 3 locations, and 0.5% (n = 1) in 4 locations.

Conclusion:

Pseudoepiphysis is a normal variant of metacarpal ossification; it does not adversely affect the development of the bone and is frequently seen in healthy children.

What is already known on this topic?

• Pseudoepiphyses are notches and clefts located at the non-epiphyseal ends of the metacarpal bones. It is frequently seen in healthy children. It does not affect the normal development of the bone and can be confused with bone fracture in children with incomplete skeletal maturation.

What this study adds on this topic?

• Although it is reported to be common, it is not known whether it shows ethnic variation. There are few frequency studies in the literature about pseudoepiphysis. This study provides frequency data for the literature.

Introduction

There are 48 separate ossification centers in a growing hand, of which 29 of them are primary ossification centers and the remaining 19 are secondary ossification centers.¹ Primary ossification centers are the first ossification areas that appear in the early fetal period and after birth in the diaphyseal regions of the metacarpal bones.² Secondary ossification centers are the areas that occur sequentially between the primary ossification centers in the epiphyseal areas (base of the first, head of the second and fifth) of the metacarpal (MC) bones. Therefore, both primary and secondary ossification centers can be observed together in plain radiographs.^1,2 The fusion of these centers shows a wide variation according to age and gender.³

Pseudoepiphyses (PEs), on the other hand, are notches and clefts located at the non-epiphyseal ends of the MC bones (head of the first MC, base of the second and fifth MC).¹ Pseudoepiphysis, which was first described in the 18th century, can occur during the normal development of the bone and is therefore accepted as a normal variant of physeal ossification.^4,5 However, it can also be seen in many diseases such as Down syndrome, hypothyroidism, and achondroplasia.^6,7

In the literature, there are more case series rather than prevalence studies, regarding the frequency of PE.^3,6,8,9 There are 2 studies conducted in 2 different populations in the latest literature. The first of these was done over English children in 2011 and the frequency was between 25% and 30%; the second one was reported as 13.1% in Korean children.^10,11 There is no study that investigates the frequency of PE in healthy Turkish children.

Pseudoepiphysis can be mistaken for fracture lines and, therefore, become clinically important when evaluating patients after trauma, with congenital anomalies or metabolic bone disease.¹² In this study, the frequency of PE was investigated by examining the plain radiographs of healthy Turkish children 5-15 years of age.

Materials and Methods

Subjects between the ages of 5 and 15, whose left-hand wrist radiographs were obtained between 2015 and 2021 in Aydın Adnan Menderes University, Department of Radiology, were included in this study. The medical data of the patients were retrospectively reviewed from the hospital archive, and 2,190 patients were identified in this age range. The clinical data of these patients were reviewed individually, and the following patients were excluded from the study: (a) patients with a history of trauma and fracture, (b) patients with a severe short stature, (c) patients with growth hormone (GH) – Insulin Like Growth Factor 1 (IGF1), (d) patients with congenital anomalies, (e) patients with skeletal dysplasias, (f) patients with hypothyroidism, (g) patients with genetic syndromes (Down syndrome, etc.), and (h) patients whose image quality was not sufficient for evaluation. Patients with left hand-wrist radiographs for bone age determination, who did not meet any exclusion criteria, such as premature adrenarche and pubertal evaluation, constitutional delay of growth and puberty, and familial short stature, were included in this study. A total of 1,119 patients (51.1%) were excluded from the study, and 1,071 patients were included in the study (Figure 1).

Figure 1.

Flowchart of the patients included in the study.

A total of 1,071 plain radiographs were evaluated in 3 different time periods by a single radiologist experienced in the field of musculoskeletal radiology. Three evaluations were made with a 1-week interval. Partial PE was considered if the PE only involved 1 cortex of the bone, and complete PE was considered if it involved both cortices.

IBM Statistical Package for Social Sciences program was used for statistical analysis of the data (IBM Corp. Released 2012. IBM SPSS Statistics for Windows, Version 21.0. Armonk, NY, USA). The descriptive statistics of the study are presented as percentage, frequency, and median (Q1:Q3). The chi-square test was used for categorical data in statistical analysis. Type I error level was determined as 0.05, and P < .05 was considered statistically significant.

This study was approved by the Aydın Adnan Menderes University, Education Research Ethics Committee (no.: 2022/40).

Results

Of the 1,071 patients included in the study, 65.9% (n = 706) were girls. The mean age was 9.5 ± 2.6 [9.0 (5.0-15.0)] years. Three evaluations were consistent, and intraobserver reliability was evaluated with intraclass correlation, which was good (0.865). In this study group, PE was detected in 222 (20.7%) patients. Pseudoepiphysis was more common in boys (27.4%) than girls (17.3%) (P < .001). Considering the distribution by age, it was found that PE was most common at the age of 12 in boys and at the age of 8 in girls, and it was evaluated by post hoc analyses that it was low for the 13-15 age group (Table 1). For both boys and girls, the frequency of PE according to age groups is given in Table 1 and Figure 2.

Table 1.

Distribution of Pseudoepiphysis by Age and Gender and Detailed Frequencies of Complete and Partial Pseudoepiphyses According to Genders and Ages

Pseudoepiphysis				Partial Pseudoepiphysis			Complete Pseudoepiphysis
	Present	P		Total	Boys	Girls	Total	Boys	Girls
Gender
Boys	100 (27.12)	<.001
Girls	122 (17.28)
Age group			Age
			5	9 (14.52)	5 (17.24)	4 (12.12)	2 (3.23)	1 (3.45)	1 (3.03)
			6	13 (18.84)	3 (11.11)	10 (23.81)	1 (1.45)	1 (3.70)	0 (0)
5-8	96 (23.82)		7	24 (23.08)	9 (28.13)	15 (20.83)	3 (2.88)	2 (6.25)	1 (1.39)
			8	45 (26.79)	6 (18.18)	39 (28.89)	2 (1.19)	1 (3.03)	1 (0.74)
9-12	113 (22.18)	<.001	9	36 (21.69)	16 (35.56)	20 (16.53)	1 (0.60)	0 (0)	1 (0.83)
			10	24 (14.04)	10 (26.32)	14 (10.53)	5 (2.92)	2 (5.26)	3 (2.26)
13-15	13 (7.98)		11	27 (27.84)	18 (39.13)	9 (17.65)	4 (4.12)	4 (8.70)	0 (0)
			12	21 (29.58)	16 (55.17)	5 (11.90)	2 (2.82)	2 (6.90)	0 (0)
			13	8 (10.81)	7 (21.88)	1 (2.38)	0 (0)	0 (0)	0 (0)
			14	3 (7.69)	3 (11.11)	0 (0)	0 (0)	0 (0)	0 (0)
			15	2 (4.00)	2 (7.41)	0 (0)	0 (0)	0 (0)	0 (0)
Total				212 (19.79)	95 (26.03)	117 (16.57)	20 (1.88)	13 (3.56)	7 (0.99)

Figure 2.

Age and gender distribution of the frequency of pseudoepiphysis (%).

The frequency of partial PE involving a single cortex was found to be significantly higher than that of complete PE involving both cortices [n = 212 (19.8%) and n = 20 (1.9%), respectively] (Tables 1 and 2). Partial PE was most frequently detected in the second MC bone, with decreasing frequency in the fifth, first, and third MCs (Figure 3, Table 3). No PE was detected in the fourth MC. Complete PE was most frequently detected in the first and second MCs and was not detected in the third, fourth, and fifth MCs (Tables 2 and 3). The rates of partial PE and complete PE according to age and gender are given in Table 1.

Table 2.

Summary of the Frequencies of Complete and Partial Pseudoepiphyses by Metacarpal Bone Location

	Complete PE, n (%)	Partial PE, n (%)
First MC bone	11 (1.03)	27 (2.52)
Second MC bone	10 (0.93)	153 (14.29)
Third MC bone	-	3 (0.28)
Fourth MC bone	-	-
Fifth MC bone	-	76 (7.10)
Total	20 (1.87)	212 (19.79)

PE, pseudoepiphysis; MC, metacarpal.

Figure 3.

A 14-year-old boy with partial pseudoepiphysis involving a single cortex in the first metacarpal bone (arrow).

Table 3.

Frequencies and Number of Cases in First, Second, and Fifth Metacarpal Bones According to the Age and Gender Distribution of the Patients

	First MC Bone						Second MC Bone						Fifth MC Bone
Partial PE			Complete PE			Partial PE			Complete PE			Partial PE
Age	Total, n (%)	Boys, n (%)	Girls, n (%)	Total, n (%)	Boys, n (%)	Girls, n (%)	Total, n (%)	Boys, n (%)	Girls, n (%)	Total, n (%)	Boys, n (%)	Girls, n (%)	Total, n (%)	Boys, n (%)	Girls, n (%)
5	-	-	-	1 (1.61)	-	1 (3.03)	9 (14.52)	5 (17.24)	4 (12.12)	1 (1.61)	1 (3.45)	-	2 (3.23)	1 (3.45)	1 (3.03)
6	1 (1.45)	-	1 (2.38)	-	-	-	11 (15.94)	2 (7.41)	9 (21.43)	1 (1.45)	1 (3.70)	-	2 (2.90)	2 (7.41)	-
7	3 (2.88)	1 (3.13)	2 (2.78)	1 (0.96)	1 (3.13)	-	18 (17.31)	7 (21.88)	11 (15.28)	2 (1.92)	1 (3.13)	1 (1.39)	10 (9.62)	5 (15.63)	5 (6.94)
8	4 (2.38)	1 (3.03)	3 (2.22)	1 (0.60)	1 (3.03)	-	38 (22.62)	6 (18.18)	32 (23.70)	1 (0.60)	-	1 (0.74)	14 (8.33)	4 (12.12)	10 (7.41)
9	7 (4.22)	6 (13.33)	1 (0.83)	1 (0.60)	-	1 (0.83)	22 (13.25)	8 (17.78)	14 (11.57)	-	-	-	17 (10.24)	8 (17.78)	9 (7.44)
10	2 (1.17)	2 (5.26)	-	4 (2.34)	1 (2.63)	3 (2.26)	15 (8.77)	3 (7.89)	12 (9.02)	1 (0.58)	1 (2.63)	-	12 (7.02)	6 (15.79)	6 (4.51)
11	1 (1.03)	-	1 (1.96)	3 (3.09)	3 (6.52)	-	16 (16.19)	10 (21.74)	6 (11.76)	2 (2.06)	2 (4.35)	-	12 (12.37)	10 (21.74)	2 (3.92)
12	6 (8.45)	4 (13.79)	2 (4.76)	-	-	-	14 (19.72)	11 (37.93)	3 (7.14)	2 (2.82)	2 (6.90)	-	4 (5.63)	4 (13.79)	–
13	1 (1.35)	-	1 (2.38)	-	-	-	7 (9.46)	7 (21.88)	-	-	-	-	2 (2.70)	2 (6.25)	-
14	1 (2.56)	1 (3.70)	-	-	-	-	2 (5.13)	2 (7.41)	-	-	-	-	-	-	-
15	1 (2.00)	1 (3.70)	-	-	-	-	1 (2.00)	1 (3.70)	-	-	-	-	1 (2.00)	1 (3.70)	-
Total	27 (2.52)	16 (4.38)	11 (1.56)	11 (1.03)	6 (1.64)	5 (0.71)	153 (14.29)	62 (16.99)	91 (12.89)	10 (0.93)	8 (2.19)	2 (0.28)	76 (7.10)	43 (11.78)	33 (4.67)

MC, metacarpal; PE, pseudoepiphysis.

Of 222 cases with PE, 76.6% (n = 170) had PE in 1 location, 21.2% (n = 47) had PE in 2 locations, 1.8% (n = 4) in 3 locations, and 0.5% (n = 1) in 4 locations. In the case of 4 locations, partial PE was observed in the third and fifth MCs, and complete PE was observed in the first and second MCs. In the 4 cases of 3 locations, partial PE was observed in the first, second, and fifth MCs in 2 cases and partial PE in the second and fifth MCs with complete PE in the first MC in 2 other cases. For the 47 cases with 2 locations, 33 had partial PE in the second and fifth MCs, 4 had partial PE in the first and second MCs, 3 had partial PE in the fifth MC with complete PE in the first MC, 2 had partial PE in the fifth MC with complete PE in the second MC, 2 had partial PE in the first and fifth MCs, 2 had partial PE in the second MC with complete PE in the first MC, and finally 1 had partial PE in the second and third MCs. Ten subjects (4.5%) had both partial and complete PE (1 case in 4 location groups, 2 cases in 3 location groups, and 7 cases in 2 location groups).

Discussion

Pseudoepiphysis occurs at the non-epiphyseal ends of the bones and is most frequently observed at the head of the first MC and the bases of the second and fifth MCs.¹³ For those frequent sites for PE, our study had the same findings. Partial PE involving a single cortex are more common and are observed in the second MC, fifth MC, first MC, and third MC, respectively. In the study conducted by Limb et al¹⁰ in 2012 in 610 British children, the frequency order of partial PE was reported as second MC, third MC, and fifth MC. In Lee et al’s¹¹ study, the frequency order was listed as first MC, second MC, and fifth MC. Complete PE involving both cortices were less common than partial PE in all studies, and our study also supported this finding. In our study, the locations and frequency of the complete PE were as follows: 1.0% in the first MC and 0.9% in the second MC; these findings are consistent with the literature.¹⁰

Limb et al.¹⁰ who reviewed serial radiographs of healthy English children aged between 5 and 13 years, could not comment about the timing of PE formation. This is because they did not have the data for the age group before 5, as in our study group. However, it has previously been suggested that they can be identified on plain radiographs from between the ages 1 and 5 and remain potentially identifiable until completion of fusion within the hand.^1,5 In our study, we did not have longitudinal data for our patient group, so we could not comment about when PE fuses. However, Limb et al.¹⁰ who reviewed 5-year longitudinal data, suggested that there is a wide variation in the age at which both complete and partial PE appeared to fuse and noted that they were often fused before the normal epiphyseal plates within the hand.

The mechanism of PE formation is not fully understood, and its histological definition varies. However, it is considered as a normal variant of physeal development and eventually shows completely normal bone formation. The results of this study and other studies in the literature support that the prevalence of partial PE is high; however, these structures are temporary, do not cause any symptoms, and do not affect normal MC bone development.^2,6,10,11 It should also be noted that PE can be seen in some congenital anomalies or diseases that cause growth retardation (Down syndrome, hypothyroidism, achondroplasia, cleidocranial dysostosis, and Laurence–Moon–Biedl–Bardet syndrome).^6,7,14 It is thought that PEs are detected more frequently in these diseases because of a general slowdown in bone maturation and growth.^6,7,14

Our study is the first study conducted in healthy Turkish children with a sufficient sample size for a frequency study. The study is strengthened by the reduction of the potential risk of bias through repeating the evaluation of the cases at 3 different intervals.

The limitations of this study include that it is a retrospective study, the study group is not representative of the whole population, it is a single-center study, the evaluation of the cases were conducted by a single radiologist, intraobserver reliability could not be estimated, and finally, we did not have longitudinal data of the children with PE.

In conclusion, PE is a normal variant of MC ossification; it does not adversely affect the development of the bone and is frequently seen in healthy children.

Figure 4.

Total pseudoepiphysis in a 10-year-old boy involving both cortices in the second metacarpal bone (arrow).