Extremity Injuries

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Chapter 54 Extremity Injuries

John M. Loiselle, MD

Development

1 How do the pediatric musculoskeletal system and its response to stress differ from those in the adult?

The pediatric skeleton is less densely calcified than the adult version. It is composed of a higher percentage of cartilage. Pediatric bones are lighter and more porous than adult bones, with haversian canals making up a greater percentage.

The pediatric musculoskeletal system is an actively growing structure. Long bones contain growth plates or physes that are the primary site of this growth. The ends of the bone contain a chondro-osseous segment termed the epiphysis or secondary site of ossification.

The bones in a child are surrounded by a thick and very active periosteum. This structure provides additional support as well as a high capacity for remodeling injured bone.

The relative strengths of the different musculoskeletal components differ from child to adult. In the child, the ligaments and periosteum are stronger than the bone itself and less likely to give way under stress. The physis is the weak link. As a result, fractures tend to be relatively more common than sprains or ligamentous injuries in children than in adults.

The degree of ossification, the thickness of the periosteum, and the width of the growth plate vary with age. Therefore, the age of the child and the corresponding anatomy dictate the response of the musculoskeletal system to trauma.

KEY POINTS: UNIQUE CHARACTERISTICS OF THE PEDIATRIC MUSCULOSKELETAL SYSTEM

1 Less densely calcified

2 Thick periosteum

3 Presence of the growth plate

4 Relatively strong ligaments

2 What unique categories of fractures are commonly seen in pediatrics as a result of these differences?

Physeal or Salter-Harris fractures

Plastic deformation fractures

Avulsion fractures

Bachman D, Santora S: Orthopedic trauma. In Fleisher G, Ludwig S, Henretig FM (eds): Textbook of Pediatric Emergency Medicine, 5th ed. Philadelphia, Lippincott Williams & Wilkins 2006, pp 1525–1569.

3 Describe the Salter-Harris classification of fractures.

Salter I: A fracture within the growth plate. The fracture line itself is not visible on radiographs, but a widening of the physis or displacement of the epiphysis may be suggestive of such a fracture.

Salter II: A fracture that extends through the growth plate and metaphysis

Salter III: An intra-articular fracture that extends through the growth plate and the epiphysis

Salter IV: An intra-articular fracture that involves the metaphysis, growth plate, and epiphysis

Salter V: A compression fracture of the growth plate. This injury is also unlikely to be detected initially by radiographs and often becomes evident only as the result of eventual growth arrest in the affected limb.

Salter RB, Harris WR: Injuries involving the epiphyseal growth plate. J Bone Joint Surg 45A:587–622, 1963.

4 Why is the Salter-Harris classification important?

The Salter-Harris classification of fractures categorizes fractures that involve the growth plate. The classification has implications for both prognosis and treatment. Fractures categorized within the higher numbers of the classification are more likely to affect joint congruity and disrupt blood supply to the growth centers of the bone, leading to greater potential for future growth disturbance.

5 What is the Thurston-Holland sign?

This is the triangular fracture segment of the metaphysis found in Salter-Harris type II fractures.

6 What are the four zones in the physis? Through which zone do fractures commonly occur?

There are four zones in the physis, which are found in the following order from the epiphysis to the metaphysis:

1 The zone of resting cells

2 The zone of proliferating cells

3 The zone of hypertrophic/maturing cells

4 The zone of provisional calcification

Fractures typically occur through the zone of hypertrophic/maturing cells. The blood supply enters the bone through the epiphysis and is most crucial to the resting and proliferating cell layers.

7 At what age are physeal injuries most likely to occur?

Eighty percent occur between 10 and 16 years of age, with a median age of 13 years. Hypertrophy of the physis during the growth spurt and increased participation in physical activity and sports at this age are responsible for the increased incidence.

Peterson CA, Peterson HA: Analysis of the incidence of injuries to the epiphyseal growth plate. J Trauma 12:275–281, 1972.

8 How does a mallet finger deformity differ in children and adults?

The adult mallet finger is the result of disruption of the extensor tendon. In young children, the underlying injury involves a fracture through the growth plate—a Salter I fracture with displacement of the epiphysis. In older children or teenagers, the injury is an avulsion or Salter III fracture through the epiphysis. Such injuries may cause difficulty in reducing the finger and may require open reduction.

10 What are plastic fractures?

Plastic fractures result from the pliability of the bones in childhood. Pediatric bones respond to compressive and transverse forces through plastic deformation. With a small amount of force, the bone is capable of bending slightly and then returning to its natural state. If excessive force is applied, the bone eventually exceeds its capacity for full elastic recoil and deforms. Depending on the degree of force and how it is applied, one of the three plastic fractures of childhood may result.

11 Name the three types of plastic fractures of childhood.

1 Buckle or torus fracture

2 Greenstick fracture

3 Bowing or bending fracture

12 Why is it important to reduce a forearm bowing fracture?

These fractures do not include injury to the periosteum and therefore do not undergo as vigorous stimulation to remodel. This may result in permanent angulation of the bone, which can have deleterious effects on the normal range of motion and function of the involved forearm.

Vorlat P, De Boeck H: Bowing fractures of the forearm in children. Clin Orthop Relat Res 413:233–237, 2003.

KEY POINTS: PEDIATRIC FRACTURES

1 Any fracture can be the result of abuse, although certain extremity fractures are specific for abuse.

2 Because of its increased pliability, the pediatric bone can go through several stages of deformity prior to fracture.

3 Salter-Harris fractures are those involving the growth plate.

Diagnosis

13 In what situations are comparison films most useful?

Suspicion of a bowing fracture

Suspicion of a nondisplaced Salter I fracture

Discriminating a secondary or accessory site of ossification from a fracture

Discriminating a possible anatomic variant from a fracture

14 How do you evaluate distal nerve function in an uncooperative or preverbal child following extremity or digit injury?

Placing the fingers in a bowl of warm water for several minutes results in wrinkling of the skin on the finger pads if distal nerve function is intact.

Eberlein R: Hand and finger injuries. In King C, Henretig FM (eds): Textbook of Pediatric Emergency Procedures. Baltimore, Williams & Wilkins, 2007.

15 What is a FOOSH? What is its significance to pediatric extremity injuries?

A FOOSH is a fall on an outstretched h

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