It is currently estimated that over 30 million youth between the ages of 6 and 18 participate in organized sports and millions more in recreational activities. Although youth sports remain an overall positive endeavor, changes in culture and training raise significant concerns on how this trend may affect the unique anatomy and physiology of young athletes compared to their adult counterparts. One of the biggest differences between young and adult athletes is the presence of growth plates, otherwise known as physes. Both acute and repetitive or chronic forces can affect the physes, however, with improved understanding of physeal injuries and their appropriate treatment we can reduce the impact they have on our youth participating in sports.

Anatomy of the Developing Bone

In order for the body to gain height and its mature shape, the bones of a child need to have the ability to grow. Growth plates are made up of different layers of developing, rubbery and flexible tissue called cartilage that allows the bone to grow and ultimately mature into the mineralized bone that makes up the adult skeleton. When a child’s bones have reached skeletal maturity, the growth plates ossify (harden) and fuse together forming one complete bone.

There are two types of physes. One is located at end of long bones (physis) and adds length as one gets older, while the other is at sites where some of the major muscle tendons attach to bone (apophysis) thereby contributing to adult shape but not growth.

Vulnerability to Injury

Physes are subject to constant change during the body’s growth phase and therefore, are susceptible to different injury patterns than those seen in a fully developed adult bone. Studies have shown that there is a decrease in the strength of the physes during times of rapid growth, with the most risk occurring during puberty. The increase in rate of growth in addition to the structural make-up of the cartilage results in a more fragile zone in the bone. It is also hypothesized that the bone mineralization in the physis may lag behind the longitudinal growth during growth spurts making this area less solidified and therefore at increased risk for injury. Multiple studies support this hypothesis with an increase in incidence of physeal injuries noted during pubescence.

In addition, unlike the end of adult bones that have a dense ossification, the growth plate creates a weakened structure that is easily affected by increased stress. With the physis considered the weak link, mechanisms that may result in muscle or ligamentous injury in an adult, are more likely to result in damage to the growth plate and bone of a child.

Because changes in physes occur over a large span of years, this area is subject to a variety of injuries that are classified as either acute (immediate onset) or chronic (repetitive insult). An injured growth plate might not do its job properly, which can lead to crooked or misshapen bones, limbs that are too short, or even arthritis.

Acute Physeal (Growth Plate) Injuries

Most acute injuries to the growth plates are the result of a fall. There is usually a greater force involved due to increased speed, like running or falling from an elevated position. Sports make up the largest proportion of acute injuries (33%) with hockey, football and baseball being the biggest culprits, while recreational activities such as biking, skiing and snowboarding come in second (22%).

Approximately 15% of all fractures in children involve the physis. The most widely used classification system for acute physeal injuries was developed by Salter and Harris and depicted five different types of growth plate fractures. Type I traverses through the growth plate, separating the epiphysis from the metaphysis. Type II, which is the most common type, is a fracture through the growth plate, but ultimately breaks out through a portion of the metaphysis. Type III fractures also traverse through the growth plate, and ultimately breaks out through the epiphysis. Type IV is a fracture that extends from the joint surface, through the growth plate and into the metaphysis. Type V is a compression fracture or crush injury of the growth plate.

Treatment for acute physeal injuries may involve immobilization (cast or splint), manipulation or even surgery depending on the type of fracture and its location. Prognosis for Type I and Type II fractures is fairly good since the fracture does not usually damage the growth plate itself, it just separates it from the metaphysis and blood circulation to the physis is usually unaffected. Type III fractures usually have good prognosis as well if the blood supply to the affected portion of the epiphysis is still intact and the fracture is not displaced. Type IV injuries usually require surgery to align the growth plate and joint surface. Type V injuries have a poor prognosis unless the growth plate is able to be completely realigned.

Chronic Physeal Injuries

It is believed that repetitive stress to the growth plate via overuse and inadequate recovery time can effect this portion of bone due to altered blood flow. Although these changes usually resolve with rest or modified activity, there have been cases where this repetitive stress has resulted in breakdown of the bone. Consequences can range from angular deformities to slowing down the rate of growth to even complete cessation of growth.

Chronic injuries can be seen in any sport that puts repetitive stress onto a single joint, but the most recognized of these injuries occurs in baseball. “Little League Shoulder” is a term used to describe chronic stress to the physis of the proximal humerus of pitchers. These athletes usually complain of persistent anterior shoulder pain in their throwing arm. It is believed that the repetitive twisting motion this part of the body goes through to while pitching sends a repeated stress through the weakest link in the shoulder joint system, which is the developing physis. Although given the term “Little League Shoulder” due to its common presentation in baseball pitchers, it can occur in any athlete that uses a repetitive overhead motion. Locations of other common chronic physeal injuries include the distal humerus and proximal radius of baseball players, the middle phalanx in climbers and the distal radius in gymnasts. The diagnosis of chronic physeal injuries is usually made by history and physical exam, however more advanced cases can be confirmed with widening of the growth plate visible on X-ray.

With proper diagnosis, the prognosis for these injuries are good. Most athletes see their symptoms resolve by relieving the chronic stress placed on the physis through activity modification, improved mechanics and correcting biomechanical imbalances with physical therapy.

Apophyseal Injuries

Although insult to longitudinal growth of the bone does not occur, injuries to these sites can result in significant pain and activity limitation. There are both acute and chronic versions of these injuries as well.

Overuse and subsequent repetitive traction of the inserting muscle-tendon complex puts stress on to the apophysis resulting in pain and a condition known as apophysitis. The apophysis is the weakest link and takes the brunt of the forces from the muscle-tendon that attaches to it. The most common sites for this injury include the tibial tubercle (the attachment of the patellar tendon) which is called Osgood-Schlatter disease, the calcaneal apophysis (the attachement of the Achilles tendon) which is called Sever’s disease, and the medial epicondylar apophysis (the attachment for the forearm flexing and pronating muscles) which is called Little League Elbow.

On the other hand, apophyseal avulsion fractures are usually acute, and the displaced fragment may be bony or cartilaginous. The mechanism of injury is from a violent muscle contraction that occurs across an open apophysis (kick, sprint, etc). Typical symptoms include sudden onset of pain, swelling, and weakness. X-rays will confirm the diagnosis.

Treatment of all of the apophyseal conditions is usually non-operative including rest, reduction of the repetitive stress and physical therapy to address underlying biomechanical issues.

Conclusion

With rising numbers of youth sport participants, more athletes playing year round sports and athletes specializing in one sport at a younger age, it is important to assess the risks this has on the developing body and try to protect these young athletes from the possible harms this may cause. Both acute and chronic physeal injuries can have a long-term impact on the growth and performance of young athletes. Proper recognition and response starts with understanding the common causes of these injuries and the basic anatomy that makes these athletes unique.

AMSSM Member Authors
Ryan Kelln, DO and Alex Diamond, DO, MPH