Physiology Of Musculoskeletal System In Children

Physis Zone

FIG. 132-1. Relationship between anatomic regions of a typical long bone and and the physis. Detail: cellular zones of physis. (Reproduced with permission from Tolo and Wood, 1994.)

It has been demonstrated that compression forces applied to the physis can affect bone growth. This is particularly true when compression forces are applied to the epiphyseal side of the physis. The injury to bone growth caused by compression results from interruption of the epiphyseal circulation to the reproductive cells of the physis.

Although several authors have classified injuries to the physis, the Salter and Harris classification system offers a thorough and practical classification based on the mechanism of injury, the relationship of the fracture line to the germinal (reproductive zone) layer of the physis, and the prognosis for disturbance of bone growth ( Fig. 132-2).

Physis Layer

FIG. 132-2. Salter-Harris classification of physeal injuries. (Reproduced with permission from Tolo and Wood, 1994.)

TYPE I PHYSEAL FRACTURE In type I physeal fracture (representing 6 percent of physeal injuries), the epiphysis separates from the metaphysis. The cleavage is through the hypertrophic cell zone of the physis. The reproductive cells of the physis remain with the epiphysis. There are no associated fragments of bones, since the thick periosteal attachments surrounding the physis remain intact. However, the epiphysis may be somewhat displaced from the metaphysis. Bone growth is not usually disturbed (Fig 132-2).

Diagnosis is suspected clinically in a child with point tenderness over a physis. Radiographically, the only abnormality may be an associated joint effusion. Any epiphyseal displacement is usually apparent on one or more views. In the absence of epiphyseal displacement, the diagnosis is a clinical one, supported by the appearance of the typical joint effusion.

Treatment consists of immobilization of the suspected fracture using an appropriate splint, the application of cold compresses for 48 h, and elevation. Referral to an orthopedic surgeon is probably warranted in order to render aftercare and to ensure monitoring for bone growth disturbances. Analgesia may be necessary, despite immobilization, for 24 to 72 h, after which time the child usually remains quite comfortable in the immobilization device.

TYPE II PHYSEAL FRACTURE Type II physeal fractures are the most common, representing 75 percent of physeal injuries. The line of fracture extends a variable distance along the hypertrophic cell zone of the physis and then out through a piece of metaphyseal bone. The periosteum on the concave side (overlying the metaphyseal fragment) remains intact, whereas the periosteum on the convex (opposite) side of the fracture is torn away from the diaphysis while remaining adherent to the epiphysis (Fig 132-2). Growth is preserved, since the reproduction layers of the physis maintain their position with the epiphysis and the epiphyseal circulation.

Diagnosis is made radiographically by noting the triangular fragment of metaphysis (Holland sign) unassociated with discernible injury to the epiphysis.

Reduction of the fracture should be gentle and is usually easily achieved. Analgesia with or without sedation should be offered to the child prior to any reduction maneuvers. When using sedation and analgesics, precautions should be taken as to patient selection, premedication assessments, monitoring, and postmedication observation consistent with institutional guidelines. Overreduction of the type II fracture is usually prevented by the periosteal hinge remaining on the concave side of the fracture.

Immobilization, cold compresses, and elevation are principles of management, as in the case of type I fractures. Referral to an orthopedic surgeon for aftercare and observation is important, as is the provision of adequate analgesia in the initial days following the fracture.

TYPE III PHYSEAL FRACTURE The hallmark of this injury is an intraarticular fracture of the epiphysis extending to the hypertrophic cell zone of the physis, with the cleavage plane continuing along the physis to the periphery ( Fig 132.-2). The injury, usually involving the proximal or distal tibia epiphysis, is caused by severe intraarticular shearing forces. The prognosis for subsequent bone growth is related to the preservation of circulation to the epiphyseal bone fragment and is usually favorable. The type III physeal fracture represents less than 10 percent of physeal injuries.

Diagnosis is a radiographic one based on the appearance of an epiphyseal fragment unassociated with an apparent metaphyseal fracture. There may or may not be an associated periosteal injury.

Reduction of the unstable epiphyseal fragment with careful restoration of the alignment of the articular surface is critically important. Open surgical techniques are frequently necessary in order to ensure the necessary anatomic reduction of the articular surface, especially with severely displaced fractures. This fracture warrants consultation with an orthopedic surgeon in the emergency department.

Decisions regarding admission or operative open reduction are made in consultation with an orthopedic surgeon experienced in the management of physeal injuries. If closed reduction techniques are successfully employed by the orthopedic consultant, aftercare instructions are similar to those offered to patients suffering from type II physeal injuries.

TYPE IV PHYSEAL FRACTURE The fracture line originates at the articular surface and extends through the epiphysis, the entire thickness of the physis, and through the metaphysis (Fig, 13.2.-2). It is an injury pattern most often involving the distal humerus and represents about 10 percent of physeal injuries. Future bone growth is at risk. Perfect anatomic reduction of the articular surface and of the physis is required to minimize the potential for premature bone growth arrest.

The diagnosis is made upon identification of epiphyseal and metaphyseal fragments radiographically. The fragments may or may not be variably displaced. Radiographic interpretation of fractures involving the distal humerus and elbow can be challenging because of the dynamic nature of the ossification centers of the region.

Open surgical reduction should be performed early by an experienced orthopedic surgeon. Internal fixation of the fragments is accomplished using fine, smooth Kirschner wires traversing the physeal growth plate perpendicularly.

TYPE V PHYSEAL FRACTURE This fortunately rare injury pattern (1 percent of physeal injuries) usually involves the knee or ankle. It is the result of severe abduction or adduction to the joint, which transmits profound compressive forces to a local segment of the physis, crushing the reproductive chondrocytes of the reserve zone and proliferative zone. Minimal or no displacement of the epiphysis occurs ( Fig 132:2).

The diagnosis of type V physeal injuries may be very difficult initially. Often, the seriousness of the injury is underappreciated. An initial diagnosis of sprain or possible type I physeal fracture may prove incorrect in view of subsequent development of premature growth arrest. Radiographs may appear normal or may demonstrate focal narrowing of the physeal plate. An associated joint effusion is the norm, although its presence is nonspecific.

Treatment of type V physeal injuries consists of cast support of the knee or ankle, non-weight-bearing for at least 3 weeks and close orthopedic outpatient follow-up in anticipation of the nearly inevitable focal bone growth arrest.

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