Classic Metaphyseal Lesions among Victims of Abuse

OBJECTIVE

To use legal statements by perpetrators to gain new insights into the causative mechanism of classic metaphyseal lesion (CML). The CML, so called "corner fracture," is considered a highly specific marker for abuse in infants. However, the precise correlation between CMLs and abusive head trauma is still unknown.

STUDY DESIGN

In this retrospective observational study, we selected 67 cases with at least 1 CML from a 15-year cohort of legally prosecuted child abuse cases. Their clinical, radiologic, and forensic records were analyzed. In 27 cases, the perpetrator confessed to abusing the child and described the events. Potential associations with subdural hematoma and with confession were evaluated using 2 separate binary logistic regression models.

RESULTS

All 67 infants showed other signs of abuse. Median age was 3.4 months. Over 65% had multiple CMLs. Knees and ankles were predominantly involved (64%). Only CMLs of the shoulder were significantly associated with subdural hematoma (P = .03). Different-age fractures were more common in the nonsubdural hematoma group (P = .01). In the group with confessions, perpetrators admitted inflicting violent indirect skeletal forces (torsion, traction, compression, and forced movements). The most common circumstance was diapering (44%), reported by male perpetrators only (P = .03) followed by dressing/undressing (30%). The violence was habitual in 67% of cases.

CONCLUSIONS

This unique forensic case series shows that CMLs are caused by violent acts inflicted most during physical care of infants. The frequency of habitual violence responsible for CMLs deserves greater attention.

The distal tibial classic metaphyseal lesion: medial versus lateral cortical injury

BACKGROUND

The distal tibia is a common location for the classic metaphyseal lesion (CML). Prior radiologic-pathologic studies have suggested a tendency for medial, as opposed to lateral, cortical injury with the CML, but there has been no formal study of the geographic distribution of this strong indicator of abuse.

OBJECTIVE

This study compares medial versus lateral cortical involvement of distal tibial CMLs in a clinical cohort of infants with suspected abuse.

MATERIALS AND METHODS

Reports of 1,020 skeletal surveys performed for suspected abuse (July 2005-June 2016) were reviewed. Twenty-six distal tibial CMLs (14 unilateral, 6 bilateral) with anteroposterior (AP) and lateral projections on the initial skeletal survey and at least an AP view on the follow-up survey were identified in 20 infants. Two blinded pediatric radiologists determined if the medial and/or lateral margins of the distal tibial metaphysis were involved by the CML.

RESULTS

Average interreader absolute agreement and kappa scores were 0.69-0.90 and 0.45-0.72, respectively. Average intrareader absolute agreement and kappa scores were 0.65-0.88 and 0.44-0.57, respectively. Analyses showed that the distal tibial CML almost always involved the medial cortical margin (reader 1=89%, reader 2=88%, pooled=89%) and the fracture infrequently involved the lateral cortical margin (reader 1=12%, reader 2=38%, pooled=26%). The percentage point difference between fracture involvement in medial and lateral margins was statistically significant from zero (P<0.001).

CONCLUSION

The distal tibial CML is most often encountered medially; lateral involvement is uncommon. This observation should help guide the radiologic diagnosis and could have implications for understanding the biomechanics of this distinctive injury.

Biomechanics of the classic metaphyseal lesion: finite element analysis

BACKGROUND

The classic metaphyseal lesion (CML) is strongly associated with infant abuse, but the biomechanics responsible for this injury have not been rigorously studied. Radiologic and CT-pathological correlates show that the distal tibial CML always involves the cortex near the subperiosteal bone collar, with variable extension of the fracture into the medullary cavity. Therefore, it is reasonable to assume that the primary site of bone failure is cortical, rather than intramedullary.

OBJECTIVE

This study focuses on the strain patterns generated from finite element modeling to identify loading scenarios and regions of the cortex that are susceptible to bone failure.

MATERIALS AND METHODS

A geometric model was constructed from a normal 3-month-old infant's distal tibia and fibula. The model's boundary conditions were set to mimic forceful manipulation of the ankle with eight load modalities (tension, compression, internal rotation, external rotation, dorsiflexion, plantar flexion, valgus bending and varus bending).

RESULTS

For all modalities except internal and external rotation, simulations showed increased cortical strains near the subperiosteal bone collar. Tension generated the largest magnitude of cortical strain (24%) that was uniformly distributed near the subperiosteal bone collar. Compression generated the same distribution of strain but to a lesser magnitude overall (15%). Dorsiflexion and plantar flexion generated high (22%) and moderate (14%) localized cortical strains, respectively, near the subperiosteal bone collar. Lower cortical strains resulted from valgus bending, varus bending, internal rotation and external rotation (8-10%). The highest valgus and varus bending cortical strains occurred medially.

CONCLUSION

These simulations suggest that the likelihood of the initial cortical bone failure of the CML is higher along the margin of the subperiosteal bone collar when the ankle is under tension, compression, valgus bending, varus bending, dorsiflexion and plantar flexion, but not under internal and external rotation. Focal cortical strains along the medial margins of the subperiosteal bone collar with varus and valgus bending may explain the known tendency for focal distal tibial CMLs to occur medially. Further research is needed to determine the threshold of applied forces required to produce this strong indicator of infant abuse.

Biomechanical investigation of the classic metaphyseal lesion using an immature porcine model

OBJECTIVE

The classic metaphyseal lesion is highly associated with abuse in infants. Classic metaphyseal lesions, also referred to as corner or bucket-handle fractures, are fractures through the metaphyseal region of the long bones near the growth plate. Knowledge of the biomechanics and mechanisms necessary to produce a classic metaphyseal lesion may provide insight into the injury causation associated with this unique fracture type. Thus, the purpose of this study was to investigate loading conditions necessary to create a classic metaphyseal lesion using an immature porcine model.

MATERIALS AND METHODS

Twenty-four pelvic limb specimens from 7-day-old and 3-day-old piglets were tested in lateral bending (varus and valgus) using an electromechanical testing machine. All specimens were loaded dynamically in four-point bending at a rate of 100 inches/min. Microcomputed tomography was performed on specimens before and after testing. Pre- and posttest CT images were compared to assess whether fracture had occurred.

RESULTS

Fractures resembling classic metaphyseal lesions were identified in 12 of the 24 specimens. Microcomputed tomography images revealed trabecular disruptions visually similar to classic metaphyseal lesions in children.

CONCLUSION

Metaphyseal fractures, consistent with clinical classic metaphyseal lesions, resulted from a single loading event delivering varus or valgus bending to the stifle (knee). A classic metaphyseal lesion is a unique type of fracture with specific morphologic characteristics. Therefore, we suggest using the term "classic metaphyseal fracture" in lieu of classic metaphyseal lesion to improve precision of terminology.

Optimization of image quality and patient dose in radiographs of paediatric extremities using direct digital radiography

OBJECTIVE

The purpose of this study was to evaluate the effect of beam quality on the image quality (IQ) of ankle radiographs of paediatric patients in the age range of 0-1 year whilst maintaining constant effective dose (ED).

METHODS

Lateral ankle radiographs of an infant foot phantom were taken at a range of tube potentials (40.0-64.5 kVp) with and without 0.1-mm copper (Cu) filtration using a Trixell Pixium 4600 detector (Trixell, Morains, France). ED to the patient was computed for the default exposure parameters using PCXMC v. 2.0 and was fixed for other beam qualities by modulating the tube current-time product. The contrast-to-noise ratio (CNR) was measured between the tibia and adjacent soft tissue. The IQ of the phantom images was assessed by three radiologists and a reporting radiographer. Four IQ criteria were defined each with a scale of 1-3, giving a maximum score of 12. Finally, a service audit of clinical images at the default and optimum beam qualities was undertaken.

RESULTS

The measured CNR for the 40 kVp/no Cu image was 12.0 compared with 7.6 for the default mode (55  0.1 mm Cu). An improvement in the clinical IQ scores was also apparent at this lower beam quality.

CONCLUSION

Lowering tube potential and removing filtration improved the clinical IQ of paediatric ankle radiographs in this age range.

ADVANCES IN KNOWLEDGE

There are currently no UK guidelines on exposure protocols for paediatric imaging using direct digital radiography. A lower beam quality will produce better IQ with no additional dose penalty for infant extremity imaging.

Digital imaging is not superior to film-screen imaging for the detection of periprosthetic osteolysis around total knee arthroplasties

Our aim was to compare the assessment of periprosthetic osteolysis around total knee arthroplasties using digital images against film-screen images. Simulated osteolytic lesions were created around 3 cadaveric total knee arthroplasties images acquired using fluoroscopic-assisted radiography and Computed Tomography. Three surgeons reviewed the film-screen images (AP/Lateral, Oblique, and Computed Tomography (CAT)) and the same images digitally. Combinations of 2 or more images that included the AP/Lateral views had superior performance in both film-screen and digital imaging to AP/Lateral views alone, except for the digital AP/Lateral/OBL combination. Lesion detection and volume appreciation were superior for film versus digital assessment for most angles. The addition of obliques to assessment using digital imaging improved performance, but film-screen remained superior to digital imaging for assessment of periprosthetic osteolysis.

Yield of radiographic skeletal surveys for detection of hand, foot, and spine fractures in suspected child abuse

OBJECTIVE

Previous studies have found that fractures involving the spine, hands, and feet are rare on skeletal surveys in cases of suspected child abuse, leading some authors to suggest eliminating these regions from the initial skeletal survey protocol. We assessed this recommendation by performing a historical review of these injuries in a pediatric population undergoing film screen-based radiographic skeletal surveys for suspected child abuse.

MATERIALS AND METHODS

This cross-sectional retrospective study reviewed reports of initial skeletal surveys of all children younger than 2 years with suspected abuse imaged between April 1988 and December 2001. Radiographic skeletal survey imaging was performed according to American College of Radiology standards. Sixty-two percent (225/365) of all skeletal surveys had positive findings, and 44% (98/225) showed more than one fracture. Surveys with fractures involving the spine, hands, or feet were identified, and the data were tabulated and analyzed.

RESULTS

Twenty of 365 studies (5.5%) yielded fractures involving the spine, hands, or feet. Of all positive skeletal surveys, 8.9% (20/225) had fractures involving the spine, hands, or feet. Of all patients with more than one fracture on skeletal survey, 20.4% (20/98) had fractures involving these regions.

CONCLUSION

These data, acquired during the film-screen era, suggest that fractures of the spine, hands, and feet may not be rare in infants and toddlers in cases of suspected child abuse. The benefits of eliminating views of these regions from the initial skeletal survey should be carefully weighed against the cost of missing these potentially important injuries in at-risk pediatric populations.

Evaluation of ultra-low dose CT in the diagnosis of pediatric-like fractures using an experimental animal study

Objective

The aim of this prospective study was to evaluate the performance of ultra-low dose CT for the diagnosis of pediatric-like fractures and ascertain the lowest dose level sufficient for diagnostics.

Materials and Methods

Fifty-one bones of young pig cadavers were artificially fractured and subsequently examined by using a 64 multi-detector CT with 36 various dose levels down to a dose comparable with that of X-rays. Two pediatric radiologists analysed the CT scans according to the presence or absence of a fracture, determination of the fracture type and the displacement as well as the diagnostic certainty. For each dose protocol, a success rate for the correct determination of the above-mentioned CT analyses was calculated. A success rate of at least 95% was considered sufficient for diagnostics.

Results

All but the lowest dose levels were sufficient to identify the fracture. Only the two lowest dose levels were insufficient to detect the fracture type. All dose levels were adequate for the identification of the displacement. The lowest dose level sufficient for diagnostics was 120 kVp, 11 mAs, and pitch 1.5, with a CTDIvol of 10% of a standard dose and an effective dose three times as large as that of X-rays.

Conclusion

Ultra-low dose CT provides the feasibility of a significant dose reduction, still allowing sufficient diagnostics of pediatric-like fractures.

Prevalence of the classic metaphyseal lesion in infants at low versus high risk for abuse

OBJECTIVE

The purpose of this article is to determine the relative likelihood of encountering a classic metaphyseal lesion in infants at low and high risk for abuse.

MATERIALS AND METHODS

This 10-year retrospective study compared the prevalence of the classic metaphyseal lesion on high-detail American College of Radiology-standardized skeletal surveys in infants at low and high risk for abuse. Low-risk infants met all of the following criteria: skull fracture without significant intracranial injury on CT, history of a fall, and no other social risk factors for abuse. High-risk infants met all of the following criteria: significant intracranial injury, retinal hemorrhages, and skeletal injuries (excluding classic metaphyseal lesions and skull fractures). Differences between the two groups were calculated using the Fisher exact test.

RESULTS

There were 42 low-risk infants (age range, 0.4-12 months; mean age, 4.4 months) and 18 high-risk infants (age range, 0.8-10.3 months; mean age, 4.6 months). At least one classic metaphyseal lesion was identified in nine infants (50%) in the high-risk category. No classic metaphyseal lesions were identified in the low-risk group. The relative prevalence of classic metaphyseal lesions in the low-risk group (0/42) versus that in the high-risk group (9/18) was statistically significant (p < 0.0001; 95% CI, 0-8% to 29-76%).

CONCLUSION

Classic metaphyseal lesions are commonly encountered in infants at high risk for abuse and are rare in infants with skull fractures associated with falls, but no other risk factors. The findings support the view that the classic metaphyseal lesion is a high-specificity indicator of infant abuse.

Skeletal imaging of child abuse (non-accidental injury)

In recent years there has been a worldwide increased awareness that children are physically abused by their carers. Radiologists play a vital role in the detection of inflicted injuries. This article reviews the skeletal imaging findings seen in child abuse.

The challenge of establishing preclinical models for segmental bone defect research

A considerable number of international research groups as well as commercial entities work on the development of new bone grafting materials, carriers, growth factors and specifically tissue-engineered constructs for bone regeneration. They are strongly interested in evaluating their concepts in highly reproducible large segmental defects in preclinical and large animal models. To allow comparison between different studies and their outcomes, it is essential that animal models, fixation devices, surgical procedures and methods of taking measurements are well standardized to produce reliable data pools and act as a base for further directions to orthopaedic and tissue engineering developments, specifically translation into the clinic. In this leading opinion paper, we aim to review and critically discuss the different large animal bone defect models reported in the literature. We conclude that most publications provide only rudimentary information on how to establish relevant preclinical segmental bone defects in large animals. Hence, we express our opinion on methodologies to establish preclinical critically sized, segmental bone defect models used in past research with reference to surgical techniques, fixation methods and postoperative management focusing on tibial fracture and segmental defect models.