Surgical Treatment of Growth Arrest

Lauren E. LaMont

Emily R. Dodwell

OVERVIEW

Growth arrest typically occurs due to some traumatic insult to the physis. Multiple etiologies may cause this insult that leads to injury to germinal cells and, ultimately, some degree of bony bridge formation. The cartilaginous component of the physis consists of resting, germinal, and proliferating cells (Fig. 39.1). Physeal separations due to trauma typically occur in the weakest layer of the physis, the hypertrophying layer.¹ In some injuries, they can also occur within the germinal layer or at the junction between cartilage and bone.² The majority of growth arrests occur at the periphery of the physis.

Most growth arrests are seen in the adolescent population; they most commonly occur after trauma. Mizuta et al.³ collected over 2,000 bony injuries in children with open physes and found 18% of fractures had physeal involvement. In this series, growth arrest occurred just over 1% of the time and the proximal tibia was the most common site.³ The occurrence of growth arrest in adolescence does not necessarily correlate with time of injury. Bony bridges may form within 1 to 2 months after injury. However, it may take months to years before deformity or shortening due to growth arrest manifest clinically. Although there is risk stratification based on type and degree of physeal injury, it is not possible to predict which children will go on to have growth arrest. For this reason, children with a confirmed or suspected growth plate injury require surveillance for growth arrest. Early identification of a bony bridge may allow more directed and less extensive treatment. Growth arrest tends to occur more commonly in boys than in girls.⁴ Growth arrests are seen more commonly in the distal femur, proximal tibia, distal tibia, and distal radius.

Etiology

All five types of Salter-Harris fractures (Fig. 39.2) have been associated with growth arrest and development of physeal bar. Bony physeal bridges typically occur when injury to the physis results in contact between epiphyseal and metaphyseal bone. This bony contact can occur as result of displacement of fracture (Fig. 39.3) or destruction of physis from injury. Growth arrest is seen more commonly in the lower than upper extremity, although this is thought to relate to mechanism and energy of injury. Growth arrest is most common in distal femoral physeal fractures and may cause significant deformity due to the large contribution of distal femoral growth to overall limb length. High rates of shortening and angular deformity have been seen with both Salter-Harris types II and IV distal femur fractures.⁵ If Salter-Harris type IV fractures are not properly reduced, then the child is at particularly high risk for physeal arrest due to the risk of metaphyseal-epiphyseal contact. Epidemiologic studies have found that Salter-Harris type III fractures tend to occur near the end of growth so they do not often produce clinically significant deformity or shortening.⁶

Trauma alone is not the sole cause of growth arrest in a physis nor does it have to be acute. Repetitive loading and stress-related injuries have been suggested to be causes of growth arrest.⁷ Bony bridges may also be caused by infections, tumors, disuse, irradiation (Fig. 39.4), thermal injuries, laser beam, metabolic disorders, vascular insufficiency, or hematologic disorders.⁸,⁹ A growth arrest may also be caused iatrogenically by violating the physis with either pins or screws. Smooth pins are thought to have minimal impact on the physis, although in an animal model, they have been associated with a small percentage of growth arrests.¹⁰ Growth arrest has been documented following anterior cruciate ligament (ACL) reconstruction in children and adolescents with transphyseal tunnel placement.¹¹ Any type of threaded wire or screw can cause disruption of the physis and higher risk of growth arrest. Screws across the physis are sufficiently effective at growth arrest that they are commonly used when epiphysiodesis (growth plate closure) is clinically warranted.

Pathoanatomy

The various etiologies of growth arrest result in varying patterns which help guide the surgical approach to correction. Both the size as well as the location of a growth arrest influence the deformity that develops. In patients who have a complete growth arrest, the affected limb will be shortened but is less likely to develop angular deformity. Partial growth arrests will commonly lead to angular deformity of the limb, the degree of which is determined by remaining growth of the physis.

Classification

Growth arrest is classified into three separate patterns. A type I arrest is a peripheral growth arrest and a resulting peripheral bony bar. In patients with type II arrest, there is central physeal tethering due to a central arrest. In these patients, the peripheral physis continues to develop normally and the perichondrial ring is intact. Type III growth arrest is a combination of the first two; these patients demonstrate a linear bar involving the peripheral
and central portions of the physeal plate (Fig. 39.5). Linear bar formation is more commonly seen after a Salter-Harris type III or IV fracture.¹² These were similarly described by Peterson⁸ as peripheral bridge, elongated bridge, and central bridge formation.

Figure 39.1. Layers of the physis. From Flynn J, Skaggs D, Waters P. Rockwood and Wilkins Fractures in Children. 8th ed. Philadelphia, PA: Wolters Kluwer; 2014, with permission.

Histopathology

Once insult has occurred to cells of physis, the resulting bony bridge consists of dense, sclerotic bone. Normal and abnormal physeal cartilage can be distinguished visually at time of surgery if physeal bar excision is indicated. The normal physis is opaque white with a bluish hue. In contrast, the injured physis has a more grayish, translucent color.¹³

Figure 39.2. Salter-Harris Categorization of growth plate fractures. (From Flynn J, Skaggs D, Waters P. Rockwood and Wilkins Fractures in Children. 8th ed. Philadelphia, PA: Wolters Kluwer; 2014, with permission.)

Imaging

Radiographs are first obtained in order to evaluate planes of deformity. In patients with growth arrest over time, a physeal bar will be visible. Additionally, Harris growth arrest lines may be noted on the diaphyseal side of the physis and may be the first sign of bony bridge formation.¹⁴ These lines indicate slowing growth of the physis that may be due to either a localized or a systemic process. When the insult is uniform, the arrest lines are parallel to the physis. When there is a partial growth arrest,
these lines will be oblique or asymmetrical in nature (Fig. 39.6). When adequate time has passed since injury, often, a distinct bridge of bone or blurred or narrowed physis will be evident. When a physeal bar from a growth arrest is noted, more advanced imaging is indicated to determine size and location in every plane (Fig. 39.7).

Figure 39.3. Malalignment of the growth plate fracture allows epiphyseal bone to contact metaphyseal bone. (From Flynn J, Skaggs D, Waters P. Rockwood and Wilkins Fractures in Children. 8th ed. Philadelphia, PA: Wolters Kluwer; 2014, with permission.)

Figure 39.4. Proximal tibial physeal growth disturbance with angular deformity after irradiation for Ewing sarcoma. (From Flynn J, Skaggs D, Waters P. Rockwood and Wilkins Fractures in Children. 8th ed. Philadelphia, PA: Wolters Kluwer; 2014, with permission.)

Bone age radiographs of the left hand may also be indicated to predict remaining growth. When attempting to correct limb length discrepancy, exact leg lengths should be determined. Computed tomography (CT) scanogram is an accurate method to determine differences in leg lengths, especially in the setting of joint contractures which may be inaccurate on standing radiographs.⁴ If an angular deformity is present, assessing length on both anteroposterior (AP) and lateral views of standing radiographs or low-dose biplanar radiograph (EOS) may be useful.

In order to determine the precise size and location of the bony bridge, multiplanar imaging is necessary. CT imaging can be used to determine the cross-sectional area involved by the physeal arrest. Carlson and Wenger¹⁵ described a technique on graph paper from axial images to generate a cross-sectional map from biplane polytomography. Although CT imaging is a short exam, it does involve radiation to the child, an issue of increasing concern to parents and the general population.

Figure 39.5. Anatomic classification of physeal arrests. Central arrests are surrounded by a perimeter of normal physis. Peripheral arrests are located at the perimeter of the physis. Linear arrests are “through-and-through” lesions with normal physis on either side of the arrest area. (From Flynn J, Skaggs D, Waters P. Rockwood and Wilkins Fractures in Children. 8th ed. Philadelphia, PA: Wolters Kluwer; 2014, with permission.)

Magnetic resonance imaging (MRI) provides another option for the evaluation of physeal bridges. Ecklund and Jaramillo¹⁶ described use of fat-suppressed three-dimensional (3-D) spoiled gradient recalled echo imaging to assess growth disturbance. MRI has the benefit of no radiation exposure to the child compared with CT. The drawback to MRI is the longer length of the scan, which younger children may not be able to tolerate. Sedation may be required to obtain quality images. Findings on MRI include bridge size and location, signal intensity, growth recovery lines, avascular necrosis, and metaphyseal cartilage tongues.

Surgical Interventions

Surgical treatment is based on location, size, type of growth arrest, remaining growth, and anticipated deformity.¹² Patient goals and activity level must also be factored into management. Treatment is necessary in patients who have or are developing significant deformity with remaining growth.¹⁷ Remaining growth for a child and ultimate limb length discrepancy can be measured in a number of ways. Commonly used techniques include the arithmetic method, the growth remaining method, the Moseley straight-line graph method, and the Paley multiplier method.¹⁸,¹⁹,²⁰,²¹ Surgical treatment for growth arrest can consist of one or a combination of corrective osteotomy, completion epiphysiodesis, contralateral epiphysiodesis, limb lengthening, deformity correction with frame, or excision of the physeal bridge.

Complete Growth Arrest

In a complete physeal arrest, the most common deformity to address is limb length inequality. Decision making for approach is largely based on remaining growth. If a patient is nearing end of growth, then a complete arrest in the lower extremity may be managed nonoperatively and followed clinically. Leg length discrepancies less than 2.5 cm have been shown to have little functional deficit, although it is unclear how those deficits affect patients into adulthood. Differences of this scale are generally treated with a shoe lift or not at all. If the estimated discrepancy is greater than 2.5 cm and less than 5 cm, then epiphysiodesis of the contralateral leg may be performed. This must be made with the understanding that this will decrease the overall height of the patient. When limb length discrepancy will be greater than 5 cm, then lengthening procedures are typically indicated.

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