We included 32 comparative studies overall.w1-w32 We included 26 cross sectional studies in the meta-analyses; six additional studies provided useful comparative data but were not eligible for meta-analysis. Seventy eight per cent of studies were done in the United States; 78% had a ranking of 1-3 (table 1) for abuse, and 80% had a ranking of 1 or 2 for the non-abused group (web extra tables 2-6). All were retrospective studies and based in the hospital setting. However, studies variously included children attending or admitted to hospital. Data sources included reviews of a combination of medical records, social records, and radiographs. A small proportion implemented independent review of records or radiographs by several investigators who were blinded to case allocation. Web extra tables 2-6 summarise citations, results, and critical appraisals, according to the relevant fracture site.
Fracture patterns in physical abuse and non-abuse
Seven studies compared the distribution of fractures in cases of abuse and non-abuse. Fractures resulting from abuse predominantly occurred in infant and toddler age groups. Worlock and colleagues studied children under 12 years old and showed that 80% of all fractures from abuse were seen in children under 18 months.w1
In contrast, 85% of fractures not caused by abuse occurred in children over 5 years. Figures from the study gave an estimated population annual incidence of fracture due to abuse of 4 per 10
000 children under 18 months. The authors estimated that in children under 18 months, one in nine fractures were due to confirmed abuse compared with one in 205 for those aged between 19 and 60 months and none in children over 5 years. Six further studies estimated that between 25% and 56% of fractures in children under 1 year of age arose from child abuse; prevalence figures varied between studies according to the definition of abuse and the inclusion criteria used.w2-w7
Studies showed that in children under 3 years old, skull fractures were by far the most common fracture type in both abused and non-abused children (web table 2).w3 w4
Worlock found a highly significant association between multiple fractures and abuse—for example, 74% (26/35) of abused children had two or more fractures compared with 16% (19/116) of non-abused children.w1 This was supported by Leventhal and colleagues in their study of fractures from traumatic causes but not by McClelland and Heiple’s study, in which half of the children in the non-abused group had factors predisposing to bone fragility (web table 2).w4 w5
Fractures of lower limbs
Thirteen studies of femoral fractures met the criteria for meta-analysis.w3 w6 w8-w18 These included 1100 children under the age of 15, of whom 222 were classified as confirmed abuse, 120 were classified as suspected abuse, 223 had been involved in motor vehicle crashes or violent trauma, 29 had pathological fractures, and 506 were from other non-abusive incidents. Four of these studies looked specifically at fractures of the femoral shaft.w10 w14-w16
For the studies that included the combined categories of suspected and confirmed abuse, the overall estimated probability of abuse given a femoral fracture was 0.43 (95% confidence interval 0.32 to 0.54) (top panel, fig 2), excluding children who were involved in a motor vehicle crash or violent trauma. When we excluded cases of suspected abuse, the probability that a femoral fracture was due to confirmed abuse was 0.28 (0.15 to 0.44) (bottom panel, fig 2).
Fig 2Probability of abuse given femoral fracture after exclusion of children involved in motor vehicle crash or violent trauma, using threshold of suspected and confirmed abuse (top) and threshold of confirmed abuse (bottom)
Five studies provided sufficient data to enable a comparison between the mean ages of children who had a femoral fracture from abuse and those who had femoral fractures from other causes.w8-w10 w15 w16 However, in some cases we had to estimate standard deviations; we deliberately overestimated these, to give conservative results. In these five studies, the mean age in the abused cases was significantly less than in the non-abused ones. Schwend and colleagues looked at motor milestones and found that fractures from abuse were significantly more common in children who were not walking (web table 3).w16
The most common location of femoral fracture in both abused and non-abused children was the mid-shaft of the femur.w9 w10 Overall, we found no difference in the distribution of transverse, spiral, or oblique fractures between the groups.w6 w8 w10 w12 w15 w17 Only one study analysed spiral fractures by age; it found that a spiral fracture was the most common abusive femoral fracture in children under 15 months, and no significant difference existed between the distribution of spiral fractures in abuse and non-abuse in children older than 15 months.w12 Metaphyseal fractures were reported in a greater proportion of abused than non-abused children (web table 3),w8 w9 but insufficient data were available for further meaningful analysis.
Only two studies described tibial or fibular fractures.w3 w11 In children under 3 years old, Kowal-Vern and colleagues reported one fracture from abuse out of a total of eight fractures. For children under 18 months, Coffey and colleagues stated that 96% (23/24) of all tibial or fibular fractures resulted from abuse.
Fractures of upper limbs
Six cross sectional studies looked at abusive humeral fractures: two studies examined specific fracture types,w19 w20 and four studies were suitable for meta-analysis.w3 w6 w17 w21 These studies included a total of 154 children who sustained a fracture of the humerus, of whom 30 were classified as abused, 23 had suspected abuse, 100 had fractures resulting from non-abusive injury, and one was involved in a motor vehicle crash. All children were under 3 years old.
The overall estimate of the probability of suspected abuse, given a humeral fracture, in a child under 3 was 0.54 (0.20 to 0.88) (top panel, fig 3). When we excluded cases of suspected abuse, the probability that a humeral fracture was due to abuse was 0.48 (0.06 to 0.94) (bottom panel, fig 3).
Fig 3Probability of abuse given humeral fracture, using threshold of suspected and confirmed abuse (top) and threshold of confirmed abuse (bottom)
Strait and colleagues gave the lowest probability for abuse.w21 This study adopted very high diagnostic criteria for abuse and excluded cases of abuse that were diagnosed before the discovery of the humeral fracture (web table 4). The authors analysed the data by age and found that the prevalence of abuse was significantly greater in children under 15 months with a humeral fracture than in those between 15 months and 3 years of age. Shaw and colleagues confirmed this finding in their analysis of fractures of the humeral shaft.w20
Supracondylar fractures were more likely to be associated with non-abusive injury.w17 w21 This was confirmed in a large cross sectional study that looked specifically at displaced supracondylar fractures in 388 children of all ages.w19 Seventy nine per cent of these fractures occurred after a fall, and only 0.5% were the result of abuse. However Strait and colleagues reported supracondylar fractures from abuse in three of 10 abused children under 3, and the authors cautioned that a supracondylar fracture should not be assumed to have non-abusive causes without careful consideration.w21 The most common type of humeral fracture from abuse in children under 15 months of age was a spiral/oblique fracture (web table 4).w1 w20 w21
The study of Kowal-Vern and colleagues was the only one to comment on the proportion of radial and ulnar fractures that were caused by abuse.w3 They identified an overall abuse rate of 25% (4/12). Worlock and colleagues described the location of fractures in 10 children with radial/ulnar fractures from abuse, of which two were greenstick, one was transverse, one was periosteal, and three were metaphyseal chip fractures; in comparison, 37/40 fractures from other causes were greenstick fractures.w1
Seven cross sectional studies including rib fractures were suitable for meta-analysis.w22-w28 They included details of a total of 233 children: 128 were abused, 24 had diagnosed bone dysplasia, 17 were preterm babies with perinatal complications, 43 had fractures due to motor vehicle crashes or violent trauma, seven had postsurgical fractures, three had birth injuries, and 11 had fractures from unknown or other non-abusive traumatic causes. After exclusion of children who were involved in a motor vehicle crash, documented violent trauma cases, and postsurgical cases, the pooled estimate of the probability of abuse given a rib fracture was 0.71 (0.42 to 0.91) (fig 4). The data presented did not allow us to estimate a probability for confirmed cases. Five studies included conditions that predispose to bone fragility as a possible cause and showed that osteopenia of prematurity or bone dysplasia were common causes of rib fractures in the infant/toddler population.w22-w24 w27 w28
Fig 4Probability of abuse given rib fracture after exclusion of children involved in motor vehicle crash or violent trauma, using threshold of confirmed abuse
The radiological investigations varied between studies and may explain the variation in prevalence figures. One study included oblique views of the chest in the investigation of children with suspected abuse,w22 and one study included additional scintigraphy in half of the abused group.w24 Both of these investigations increase the sensitivity for detection of rib fractures. The details of chest radiograph technique were not reported in the remaining studies. Two studies included an independent radiology review,w22 w23 whereas the remainder relied on a review of case and radiograph records.
All but one study showed that children who had rib fractures from abuse had more rib fractures than those who had not been abused (web table 5).w23 Rib fractures from abuse were reported at any location on the ribw23-w25 w28; they could be unilateral or bilateral. Two studies confirmed that anterior fractures were significantly more common in abuse and that lateral fractures were more common in non-abused children.w22 w24 Findings on posterior fractures were variable. Barsness and colleagues found that posterior rib fractures were significantly more common in abuse than in non-abuse,w22 whereas neither Cadzow and Armstrong nor Bulloch and colleagues supported this finding.w23 w24
Seven studies of children with skull fractures met our criteria for meta-analysis.w3 w5 w6 w29-w32 These involved a total of 520 children under the age of 6.5 years; 124 were classified as abused, 18 had fractures caused by motor vehicle crashes or violent trauma, and 378 were non-abused. All but one study covered an infant/toddler age group.w32
Skull fractures are more commonly reported after non-abusive trauma than after abusive head injury; the point estimate of the probability of abuse given a skull fracture was 0.30 (0.19 to 0.46) (fig 5). We could not give an estimate for confirmed cases of abuse alone or exclude motor vehicle crashes.
Fig 5Probability of abuse given skull fracture, using threshold of suspected and confirmed abuse
The most common fracture site in both the abuse and non-abuse groups was parietal,w30 and the most common fracture type was linear.w31 This finding was supported in two further comparative studies that were not eligible for the meta-analysis.w1 w4
The significance of complex fractures varied between studies (web table 6). Meservy and colleagues found no significant differences between the two groups with respect to depressed, diastatic, or complex fractures but found that multiple or bilateral fractures or those that crossed suture lines were significantly more common in abused children.w30 Billmire and Myers found that depressed skull fractures were equally common in abuse and non-abuse; complex multiple fractures were associated with intracranial injury in 4/30 abused infants but in none of the 54 non-abused cases.w29 Stewart and colleagues studied children under 3 months of age and stated that diastatic and multiple fractures were more common in abuse than in non-abuse.w32 However, neither Reece and Sege nor Leventhal and colleagues found any significant difference between the prevalence of complicated fractures in the two groups.w4 w31