Metaphyseal corner fracture caused in utero by external cephalic version – a rare presentation

Introduction

The radiological sign of a classic metaphyseal lesion (CML), also known as “metaphyseal corner fracture” in infants is highly suspicious and specific for inflicted injury in infants [1]. The distal femur and proximal tibia are most commonly involved, occurring due to a sudden torsional and shearing force [2]. The classic “metaphyseal corner fracture” was first described by Caffey in 1957. On the basis of the radiological findings. Caffey proposed that stripping of the periosteum was key to the production of metaphyseal lesions, and was closely associated with abused infants. It was hypothesised that a “small chunk” of bone pulled from the margin of the metaphysis projects as a discrete metaphyseal fragment. This pattern was referred to as the “corner fracture” [1]. Computed tomography (CT) imaging and histopathological analysis have refined our understanding of the underlying fracture pattern, which involves the subperiosteal bone collar and zone of provisional calcification, and nowadays “corner fracture” or “bucket-handle” fracture on skeletal survey are considered almost pathognomonic of infant abuse [3].

Upon diagnosis of metaphyseal corner fractures (MCFs) in an infant, further investigation and multi-disciplinary involvement by child protection services are vital until abuse can be excluded as the cause of injury. This report is of a classic distal femur MCF in a neonate, caused not by physical abuse but by external cephalic version (ECV). It is critical that clinicians and child protection services understand that this is a possible mechanism for a MCF.

Case report

A healthy 36-year-old primipara women was admitted to the obstetric unit for an elective ECV of a singleton foetus at 37 weeks’ gestation. The lie of the foetus was breech, with the hips flexed and knees extended. The pregnancy was healthy, with no issues of hypertension, diabetes or infection. After an ultrasound scan, an ECV was performed by an experienced consultant obstetrician without anaesthesia and no significant pain was reported during the procedure. The foetal pelvis was disengaged from the maternal pelvis and the foetus was successfully manoeuvred into a cephalic presentation. In doing so, the infant did a forward roll with a twist. The successful version required 25 min of manipulation. The baby was confirmed to be in a vertex position for subsequent vaginal delivery. There was no foetal compromise. However, due to a blood-stained discharge from the cervix, an urgent and successful caesarean section was performed. The foetal heart rate and the cardiotocography (CTG) was monitored throughout. The neonate was healthy, but was noted to have a swollen right thigh and less movement was observed compared to the left. This is illustrated in the photographs taken by the parents on the day of delivery, whilst still in hospital (Figure 1A and B). Despite this, no abnormality was detected on the newborn and infant physical examination (NIPE) and mother and child were discharged home. The parents alerted the health visitor due to persistent decreased right lower limb movements. Radiographs then performed at 1 week of age demonstrated a classic MCF of the distal femur (Figure 2A and B). Periosteal new bone formation is already visible, consistent with the fracture occurring 1 week prior. The mechanism of turning in utero would have locked the knees into further extension, and a simultaneous twisting could explain the mechanism. As the infant was already moving his leg and appeared comfortable, no splintage was necessary at this point. A Pavlik harness would have been the splintage of choice for the first week. A follow-up radiograph at 4 weeks of age demonstrated complete radiological union (Figure 3A and B). A note was made of the extensive callus formation from the periosteal stripping along much of the length of the femur. A routine hip ultrasound scan for breech presentation risk factor showed no hip dysplasia.

Figure 1:

(A and B) Photographs illustrating the swelling in the right lower limb and reduced mobility.

Figure 2:

(A and B) Radiographs at 1 week post birth, demonstrating the classic MCF with associated early periosteal new bone formation.

Figure 3:

(A and B) Radiographs at 4 weeks of age. The extensive callus along the length of the femur is indication of the extent of periosteal stripping.

Discussion

MCF occur close to the growth plate, unlike accidental metaphyseal fractures which occur at the junction of the diaphysis and the metaphysis. They require a significant indirect shearing force applied to the metaphysis when the limb is wrenched or when the infant is shaken. These fractures are virtually impossible for normal infants to sustain with daily activities or falls. A study has identified MCFs in 11% of abused infants, in the femur, tibia and rarely in the humerus and radius [4]. Consequently, these fractures have become virtually synonymous with child abuse.

It has been suggested that these forces produce a plane of injury through the primary spongiosa that may extend partially or entirely across the metaphysis. The result is separation of a complete or partial disc of bone that maintains its relationship to the contiguous physeal plate [1]. The histological and radiological study by Tsai et al. [5] confirms that these metaphyseal fractures occur through the most immature part of the chondro-osseous junction, involving the thicker peripheral subperiosteal bone collar and the thinner central zone of provisional calcification. Depending on the radiographic projection the resultant fracture fragment, comprising epiphysis, physis and a thin layer of metaphyseal bone may appear as a “bucket handle” or “corner fracture”. It is important to recognise that these fractures are trans-metaphyseal and not just avulsions of the periphery of the metaphysis. The associated subperiosteal haematoma from the fracture may extend along the diaphysis, creating a much more extensive periosteal reaction than an accidental metaphyseal torus or greenstick fracture. In later diagnoses, the resulting periosteal reaction can be mistaken for metabolic bone disease, lesions, infection or dysplasia [1], [5], [6].

Femoral fractures can rarely occur from birth injuries, with an incidence of 0.13 per 1000 live births. Fourteen percent of birth-related fractures occur in the femur, with the clavicle being by far the commonest site of bony obstetric injury [7]. There is also a single report of CML caused by ECV [8]. The authors describe a case of a metaphyseal fracture in the proximal tibia following ECV for frank breech presentation. This delivery also required urgent caesarean section. Post-partum radiographs of the infant showed “classic metaphyseal lesion” in the proximal tibia, due to significant torsional forces involved during delivery or ECV. The limb was briefly splinted and follow-up was unremarkable with good healing and normal function. The clinical course of this case, described in Australia in 2003, is practically identical to the case described in this paper. It is crucial that this unusual mechanism of injury is reported in the literature to promote its recognition as an accidental cause of the CML. An incorrect diagnosis of inflicted (non-accidental) injury in a child has terrible implications on the parents and the caregivers.

Conclusion

Awareness of this causative mechanism for MCF is critical for child protection services and in cases where there are legal proceedings. To erroneously dismiss in law a MCF as not able to be caused by ECV could have disastrous consequences.