Physeal injuries account for about one-fourth of all childhood fractures. They are most common in boys, in the upper limb, and in childhood. Physeal injury may also occur from infection, tumors, or ischemia. Physeal fractures are of great importance, as these injuries can affect subsequent growth and remodeling potential.
The physeal anatomy is varied but the pattern is similar.
Physes can be classified into three main categories:
- Long bones The femur is one of the long bones.
- Ring epiphyses occur in round bones (cuboid) and around secondary ossification centers.
- Apophyses occur at the site of muscle or tendon insertions (e.g., greater trochanteric apophysis).
Growth disturbances of long bone physes are most likely to be damaged and create the greatest deformity.
Long-bone physes often show an undulating pattern with mamallary processes. This provides greater sheer strength but may lead to an increased risk of physeal damage from high-impact injuries. An example is the greater likelihood of growth arrest from simple physeal fractures of the femoral physis.
The physis usually fractures through the zone of calcification, sparing the germinal cells so growth is unaffected. Less common injuries that damage the germinal zone or create a tethering bridge across the physis may slow or arrest growth.
Physeal susceptibility to arrest varies. The most sensitive long-bone physis is the anterior portion of the tibial epiphysis. Recurvatum deformity may occur from trivial injury.
Stress injuries to the physis are most commonly observed in athletes and children with myelodysplasia. The gymnast may develop a stress fracture of the radial physis. Such physeal injuries often cause growth arrest.
Physeal arrest is most common in injuries that allow the bone to bridge the growth plate. The location and percentage of the cross-sectional area occupied by the bony bridge determines the extent of the secondary deformity.
Several classification systems for physeal injuries exist. The most simple and widely used is that originated by Salter and Harris (SH). Fractures are divided into five categories. SH-5 injuries are very rare. More comprehensive classifications include those devised by Peterson and by Ogden. For complex injuries, use a more comprehensive classification.
Classification of injury type is usually done by radiography. Imaging by CT scans may clarify complex fracture patterns such as those in triplane fractures of the ankle. MRI studies often show considerably more physeal damage than was suspected from radiographs, and may change the SH category. Because experience is based on radiographic imaging, prognosis and management based on the more sensitive MRI may lead to overtreatment.
Most acute physeal injuries heal rapidly; any deformity remodels completely, and growth proceeds normally. About 1% of physeal injuries cause physeal bridging and altered growth. Small bridges (<10%) may lyse spontaneously. Central bridges are more likely to lyse and less likely to cause deformity than peripheral ones. Central bridges may cause a fishtail deformity, which only slows rather than arrests growth.
Physeal Bridge Management
Physeal bridge formation usually follows SH-3, SH-4, or SH-5 injuries. The mechanism is either a crush injury to the germinal layer or a displaced fracture that allows bone to form across the physis. The prognostic significance of the type is not always consistent. For example, physeal arrest also occurs in about half of SH-1 and SH-2 injuries of the distal femur in the older child or adolescent. Physeal injury may also follow fracture of the diaphysis. The mechanism is unclear.
Avoid physeal injury when placing fixation devices in children. Reaming of the upper femur for fixation of femoral shaft fractures is a common cause of physeal damage. Use alternative ways of fixation before the end of growth.
Prevention of physeal bridge formation is best achieved by an anatomic reduction of SH-3 and SH-4 fractures. Open reduction and fixation that does not traverse the physis is best. If fixation is necessary across the growth plate, use small, smooth K wires.
Monitor growth for detection of physeal bridge. If a bridge is found, make a radiograph of the involved bone and the contralateral side on the same film every 4–6 months. Note changes in relative overall length or angulation of the adjacent joint surface.
Imaging physeal bars may be done by CT scans or MRI studies. Order frontal and sagittal computer reconstruction of 1-mm CT scans. MRIs tend to show more soft tissue information but may be more difficult to interpret.
Physeal Bar Resection
Resect bars that occupy less than 50% of the physis and have two years of growth remaining. Once resected, bone growth may be accelerated, normal, retarded, or absent. Outcomes are related to the location of the bar, its size, and the health of the adjacent growth plate. Following successful resection, some correction of angulatory deformity may occur. This correction seldom exceeds 10°. For unacceptable deformity exceeding about 10°, consider a concurrent osteotomy. The osteotomy may not only correct the acquired deformity but may also facilitate excision of the bar.
Assess the deformity clinically and image the bar. Clinical assessment includes determining the length inequality and angular deformity in all three planes. Document shortening by an orthodiagram. Determine the child’s bone age. Document deformity with radiographs. Comparative bilateral study on the same x-ray is useful. Assess the bar by CT or MR reconstructions. On the MRI, the physis (white arrow) is abnormal on the lateral side (red arrow). A portion of the physis (yellow arrow) has been replaced by a bony bar. Estimate size and location of the the bar using frontal and sagittal reconstructions or use templates to make these determinations more accurately. Some computer software may make this calculation by generating a transverse plane image of the physis that provides this image. Make certain the exact location of the bar are known before resection. Based on the location of the bar, plan the operative approach. Make available an air drill, abundant saline irritation, good lighting, fluoroscopy, and a dental mirror.
Drape the limb to allow free mobility and allow exposure to the site of bar resection and fat harvest. Mark the site of the physis with the image intensifier. Perform an osteotomy if indicated. Approach the bar through the osteotomy or a metaphyseal window. Using the air drill, under image guidance, create a window about 1 cm, and extend the window toward the bridge. Locate the normal physis adjacent to the bar. Use the suction tip with irrigation to clear away cancellous bone from the physis. Identify the bar by seeing normal cartilage on both sides of the lesion. Resect the bar. When normal physeal cartilage is seen all the way around the operative window, resection is complete. Harvest subcutaneous fat for interposition. This may be possible from the operative site, behind the knee, or in the buttocks folds. Bone-wax cavity surfaces to reduce ooze. Place fat graft to fill cavity completely to provide hemostasis and ensure complete interposition. Replace cortical graft. Close soft tissue over the replaced cortical window. Close the wound and apply a cast. Immobilize for 2–8 weeks, depending upon extent of resection. Restrict activity until bone strength recovers. Following bar resection, a neophysis develops spanning the site of the previous bar, and growth resumes. Follow with AP comparative radiographs. Note the physeal bar.