Growth Plate (Physeal) Fractures

Updated: Jul 13, 2017
  • Author: Steven I Rabin, MD; Chief Editor: Jeffrey D Thomson, MD  more...
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Overview

Background

Growth plate (physeal) fractures may be defined as disruptions in the cartilaginous physis of long bones that may or may not involve epiphyseal or metaphyseal bone. [1]

Injuries to the physes are more likely to occur in an active pediatric population than sprains or ligament injuries are, in part because the ligaments and joint capsules have greater structural strength and integrity than the growth plates do. These ligamentous structures are two to five times stronger than the growth plates at either end of a long bone and therefore are less often injured in children sustaining excessive external loads to the joints.

This article discusses some of the important orthopedic history relative to the physes, the relevant anatomy, the most commonly used classification system, and some details of physeal fractures in specific areas of the body. It is essential to keep in mind that with growth plate fractures, as with real estate, the most important datum is location, and timing is the key to treatment.

Furthermore, it must be clearly understood that children are not merely smaller versions of adults. There are specific considerations in treating childhood fractures that differ from those appropriate in treating adult fractures, often including different surgical approaches and technical concerns, different alignment goals, different fixation devices, and different follow-up intervals. What is unacceptable in an adult might be acceptable in a child.

The treating provider needs to know which fractures are likely to remodel (usually those with angulation in the plane of joint motion) and which are unlikely to remodel (eg, fractures with rotational deformity, joint incongruity, or physeal stepoff, as well as those occurring in patients near skeletal maturity). Surgical approaches may also be different in children as compared with adults; percutaneous Kirschner wire (K-wire) fixation may be stable enough, and prevention of iatrogenic injury to the physis is of significant importance. 

When growth deformity is possible, the treating provider must predict the degree of expected remodeling, and this requires an understanding of the specific fracture. Assessment of bone age using the Greulich-Pyle atlas and charts can give an estimate of remaining growth. Fractures in the metaphysis, closer to the growth plate, remodel more reliably than those in the diaphysis do. If inadequate remodeling is predicted, then corrective surgery is usually required. 

If surgery is required, it is best to initiate treatment promptly, before healing begins and fracture surfaces smooth off or Z-deformities develop with partial continued growth. If a chronic deformity has developed, correction with epiphyseodesis is commonly preferred to the more invasive osteotomy.

In general, the limited access and small bones encountered in pediatric procedures make surgical treatment more technically challenging in children than similar operations in adults would be.

See Common Pediatric Sports and Recreational Injuries, a Critical Images slideshow, to help recognize some of the more common injuries and conditions associated with pediatric recreational activities.

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Anatomy

Technically, two growth plates may be considered to exist in immature long bones: the horizontal growth plate (physis) and the spherical growth plate (enables epiphyseal growth). For the purposes of this article, the horizontal growth plate is addressed.

The horizontal growth plate is easily seen on radiographs of most growing long bones as a horizontal radiolucent region near the end of the bone. It may also be referred to as the cartilaginous growth plate, physis, or epiphyseal plate. The epiphysis is not the cartilaginous growth plate—epiphysis and growth plate are not synonyms—but, rather, the bone of the secondary ossification center.

Zones of physis

The physis is an organized system of tissue located at the ends of long bones, consisting of an arrangement of chondrocytes surrounded by a matrix consisting of proteoglycan aggregates. The chondrocytes of the physis are divided into a system of zones based on different stages of maturation in the endochondral sequence of ossification and their function, as follows.

Reserve/resting zone

The reserve/resting zone is immediately adjacent to the epiphysis and consists of irregularly scattered chondrocytes with low rates of proliferation. This layer supplies developing cartilage cells and stores necessary materials (eg, lipids, glycogen, and proteoglycan aggregates) for later growth, and injury to this layer results in cessation of growth.

Proliferative zone

In this zone, chondrocytes are flattened and stacked upon each other in well-defined columns. These cells produce necessary matrix and are responsible for longitudinal growth of the bone via active cell division.

Hypertrophic zone

In the hypertrophic zone, adjacent to the metaphysis (which is further subdivided into maturation, degeneration, and provisional calcification zones), cells increase in size, accumulate calcium within their mitochondria, and deteriorate. The ultimate result is cell death, which releases calcium from matrix vesicles, impregnating the matrix with calcium salt (a process necessary for invasion of metaphyseal blood vessels, ingrowth of chondroclasts and osteblasts, destruction of cartilage cells, and bone formation along the walls of the calcified cartilage matrix).

No active growth occurs in this layer. Columns of cells extending toward the metaphysis are at various stages of maturation. This is the weakest portion of the physis and is commonly a site of fracture or alteration (eg, widening, as in rickets)

Metaphysis

The metaphysis, adjacent to the physis, is composed of primary and secondary spongiosa layers. Primary spongiosa is mineralized to form woven bone and is subsequently remodeled to form secondary spongiosa. Branches of the metaphyseal and nutrient arteries enter the secondary spongiosa and form closed capillary loops in the primary spongiosa.

Periphery of physis

The periphery of the physis consists of the following two elements:

  • Groove of Ranvier
  • Perichondrial ring (of Lacroix)

The groove of Ranvier is a wedge-shaped zone of cells contiguous with the epiphysis at the periphery. It supplies chondrocytes to the periphery of the physis, enabling lateral growth or increased width of the physis. Langenskiold proposed that cells from the reserve zone migrate into the region of the groove of Ranvier. [2]  The perichondrial ring is a dense fibrous ring that surrounds the physis and is critical to the overall stability of the growth plate. The perichondrial ring's stabilizing effect may be lost in pathologic conditions such as slipped capital femoral epiphysis (SCFE).

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Pathophysiology

Growth plate (physeal) fractures are typically believed to occur through the zone of provisional calcification but may traverse several zones, depending on the type of external load application. For instance, with application of compression-type loads, the histologic zone of failure is typically the provisional calcification portion of the hypertrophic zone. Shear forces may also cause failure in the hypertrophic zone. Tension forces lead to failure of the proliferative zone.

Growth plate injury can also be iatrogrenic.  A common concern is repair of the anterior cruciate ligament (ACL) in the skeletally immature. Wall et al reported an "all-epiphyseal" anterior cruciate reconstruction to avoid transfixation or drilling across active open growth plates. [3] Although there were no growth arrests, three patients had knee overgrowth, with two requiring further surgery. The ACL reconstructions had excellent functional outcomes despite high rates of complications (48%) and secondary procedures (37%). The incidence of graft failure was similar to that seen with other ACL techniques.

Classification

Growth plate injuries were first classified by Poland in 1898; his four-part classification system progressed from a simple epiphyseal separation to an epiphyseal separation in which it is split in two. Many other classification systems followed, including a system suggested by Petersen in 1994. This system was constructed on the basis of a population-based epidemiologic study and arranged from the physis least involved progressing to the injury that posed the greatest threat to the physis.

Of the various classification systems used throughout the world, the Salter-Harris (SH) classification, initially proposed in 1963 by Robert Salter and W Robert Harris of Toronto, [4]  is generally preferred and is the accepted standard in North America to facilitate communication among healthcare professionals. [5, 6]  The SH system categorized the various fracture patterns into five types (subsequently expanded to six) as follows.

Salter-Harris type I

An SH I fracture typically traverses through the hypertrophic zone of the cartilaginous physis, splitting it and separating the epiphysis from the metaphysis. When these fractures are nondisplaced, they may not be readily evident on radiographs because of the lack of bony involvement. In many instances, only mild-to-moderate soft-tissue swelling is noted radiographically.

Clinical findings may be more impressive than imaging (see the first image below); however, subsequent radiographs may demonstrate physeal widening or new bone growth along physeal margins, indicating the presence of a healing fracture (see the second image below). In general, the prognosis for this type of fracture is excellent. Usually, only closed reduction is necessary for displaced fractures; however, open reduction and internal fixation (ORIF) may be necessary if a stable satisfactory reduction cannot be maintained.

Growth plate (physeal) fractures. Clinical appeara Growth plate (physeal) fractures. Clinical appearance of knee of patient with minimally displaced Salter-Harris I fracture of distal femur. Impressive swelling was noted adjacent to joint, but no evidence of intra-articular swelling was present. Patient was markedly tender to palpation about distal femoral physis.
Growth plate (physeal) fractures. Anteroposterior Growth plate (physeal) fractures. Anteroposterior radiograph of knee of patient in previous image. Note subtle physeal widening, confirming diagnosis of Salter-Harris I fracture of distal femur.

Salter-Harris type II

An SH II fracture splits partially through the physis and includes a variably sized triangular bone fragment of metaphysis (see the image below). This fragment is often referred to as the Thurstan Holland fragment in honor of the British radiologist, Charles Thurstan Holland, who drew attention to its existence in 1929.

Growth plate (physeal) fractures. Anteroposterior Growth plate (physeal) fractures. Anteroposterior ankle radiograph demonstrates impressively displaced Salter-Harris II fracture of distal tibial epiphysis (along with comminuted fracture of distal fibular diaphysis).

Periosteum on the side of the Thurstan Holland fragment often remains intact, thus facilitating reduction. This particular fracture pattern occurs in an estimated 75% of all physeal fractures, and it is the most common physeal fracture. The image below illustrates an SH II fracture of the distal femur.

Growth plate (physeal) fractures. Displaced Salter Growth plate (physeal) fractures. Displaced Salter-Harris II fracture of distal femur. Large Thurstan Holland (metaphyseal) fragment may serve as important fixation point for either Steinmann pin or lag screw.

Salter-Harris type III

A SH III fracture pattern combines physeal injury with an articular discontinuity. This fracture partially involves the physis and then extends through the epiphysis into the joint. It has the potential to disrupt the joint surface. This injury is less common and often requires ORIF to ensure proper anatomic realignment of both the physis and the joint surface. .

The image below depicts a common SH III fracture of the distal tibia, a Tillaux fracture, on computed tomography (CT).

Growth plate (physeal) fractures. Multiple compute Growth plate (physeal) fractures. Multiple computed tomography (CT) scans depict displaced Salter-Harris III fracture of distal anterolateral tibial epiphysis (ie, Tillaux fracture).

Salter-Harris type IV

An SH IV fracture runs obliquely through the metaphysis, traverses the physis and epiphysis, and enters the joint. The Thurstan Holland sign (ie, a Thurstan Holland fragment) is also seen with this fracture pattern. The image below illustrates such a fracture of the proximal tibia.

Growth plate (physeal) fractures. Displaced Salter Growth plate (physeal) fractures. Displaced Salter-Harris IV fracture of proximal tibia. Lateral portion of epiphysis (with Thurstan Holland fragment) and medial portion of epiphysis are independently displaced (ie, each is free-floating fragment).

Salter-Harris type V

An SH V lesion involves compression or crush injuries to the physis and is often impossible to diagnose definitively at the time of injury. Knowledge of the injury mechanism simply makes one more or less suspicious of this injury. No fracture lines are evident on initial radiographs, but they may be associated with diaphyseal or metaphyseal fractures. (See the images below.)

Growth plate (physeal) fractures. Salter-Harris V Growth plate (physeal) fractures. Salter-Harris V fracture pattern must be strongly suspected whenever mechanism of injury includes significant compressive forces. This is initial injury radiograph of child's ankle that was subjected to significant compressive and inversion forces. It demonstrates minimally displaced fractures of tibia and fibula with apparent maintenance of distal tibial physeal architecture.
Growth plate (physeal) fractures. Follow-up radiog Growth plate (physeal) fractures. Follow-up radiograph of ankle of child in preceding image. This radiograph depicts growth arrest secondary to Salter-Harris V nature of the injury. Note markedly asymmetric Park-Harris growth recovery line, indicating that lateral portion of growth plate continues to function and medial portion does not.

SH V fractures are generally very rare; however, family members should be warned of the potential disturbance in growth and should be made aware that if growth disturbance occurs, treatment is still available (depending on the child's age and remaining growth potential).

Salter-Harris type VI

An additional classification of physeal fractures that was not considered in the original SH classification but is now occasionally included is SH VI, which describes an injury to the peripheral portion of the physis and may result in a peripheral bony bridge formation that may produce considerable angular deformity by tethering the intact physis. [7]  (See the images below.)

Growth plate (physeal) fractures. Mortise radiogra Growth plate (physeal) fractures. Mortise radiograph demonstrating somewhat subtle physeal injury to distal tibia. Salter-Harris VI pattern may be suspected on basis of history and physical examination. In this case, radiograph indicates that it is quite likely that small portion of peripheral medial physis (as well as small amount of adjacent epiphyseal and metaphyseal bone) has been avulsed.
Growth plate (physeal) fractures. Clinical photogr Growth plate (physeal) fractures. Clinical photograph of patient above with displaced Salter-Harris II fracture of distal femur. Mechanism of injury and physical examination findings are consistent with Salter-Harris VI physeal injury pattern. Some may also refer to this injury type as Kessel fracture.

This injury was suggested by Lipmann Kessel, who described it as follows: "A rare injury of growth plate results from damage to the periosteum or perichondral ring ... following burns or a blow to the surface of the limb, for example a run over injury." [8]

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Epidemiology

Mann and Rajmaira collected data on 2650 long bone fractures, 30% of which involved the physes. [9] Neer and Horowitz evaluated 2500 fractures to the physes (growth plate) and determined that the distal radius was the most frequent site of injury (44%), followed by the distal humerus (13%), distal fibula, distal tibia, distal ulna, proximal humerus, distal femur, proximal tibia, and proximal fibula. [10]

According to a 1972 retrospective analysis of 330 acute physeal (growth plate) injuries seen over the course of 20 years, males were affected more than twice as often as females. Females were most frequently affected at a younger age than males (11-12 years vs 12-14 years). These findings correspond with the growth spurts (when the physes are weakest) of the respective sexes and with males' increased willingness to engage in high-risk activities. Within this population, upper-extremity injuries were more frequent than lower-extremity injuries overall.

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Prognosis

Prognosis depends on the severity of physeal damage, the skeletal age of the patient, and the site of the fracture.

The severity of physeal damage is categorized according to the SH classification (see Pathophysiology). Type I injury (separation through the physis) has the best prognosis, whereas type V injury (a crush injury to the physis) and type VI injury have worse prognoses.

Pediatric patients who are still growing have the potential to remodel or restore angulation with continued growth, especially in the plane of joint motion. (Intra-articular stepoffs and rotational deformities do not remodel.) The closer the patient is to skeletal maturity, the less likely it is that full correction of the deformity will occur.

The site of the fracture also influences remodeling. The undulating nature of the distal femur physis makes any displacement of the epiphysis relative to the metaphysis more difficult to reduce anatomically and more prone to the development of bone bars crossing the physis and tethering growth, resulting in angulation and shortening. The proximal femur physis is intra-articular, with potential disruption of the vascular supply also increasing the risk of complications after physeal injury. The proximal tibia has a tendency to angulate with growth as well, even with an anatomic reduction.

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