Abstract and Introduction
Background: We examined the relationship between the Kaeding-Miller (K-M) stress fracture classification system with time to return to running or practice in female track and field athletes diagnosed with tibial stress fracture.
Methods: All female athletes with tibial stress injuries who competed for a Division I university from 2011–2014 were identified. Their charts were reviewed retrospectively to collect demographic variables, medical history, training variables, injury history, and nutritional or dietary risk factors. The K-M classification system was used to grade all injuries and to compare the time to return to practice. Body mass index (BMI) was evaluated independently with time to recovery.
Results: Twenty-four tibial stress injuries were identified in 18 female track and field athletes on the same Division I collegiate team over a 3-year period. The average time to return to running was 13.7 wk (SD 5.02). Athletes with a K-M grade of V had an average time to return to running of 17 wk compared with 11.7 and 13.7 in Grade II and III, respectively. This difference did not reach significance (P=0.534), but there was a positive relationship between K-M grade and time to recovery (coefficient=0.785). There was no statistically significant relationship between BMI and time to return to sport (P=0.767), but there was an inverse relationship between BMI and time to clinical healing (coefficient=−0.191).
Conclusions: Data suggest that higher K-M grade injuries correlate with longer time to recovery, but larger studies are needed to determine if this relationship is significant.
Stress fractures are troublesome overuse injuries that commonly occur in athletes who participate in sports that expose bones to repetitive loading and mechanical stress.[1,2] Because of high-intensity and high-volume training, competitive track and field athletes are a high risk group for stress fractures, with reported incidences of up to 21%. The tibia is one of the most frequent sites of injury in this population.[2,3] These injuries have a broad spectrum of severity and prognosis and account for a significant amount of missed training and competition. Prevention and early intervention is the preferable treatment. Therefore, it is important to identify athletes at greatest risk of stress fracture and those at risk of having a prolonged or complicated treatment course resulting in longer expected time to return to play.
Previous studies have identified a variety of risk factors for stress fractures in female athletes, including low body mass index (BMI), menstrual irregularities, poor eating habits, low bone mineral density, and previous stress fracture.[4–6] However, these injuries are difficult to predict in track and field athletes because of variations in biomechanics, training methods, diet, muscle strength, and flexibility.
Stress fractures represent a continuum of structural damage, making each fracture unique in location, severity, and healing potential. There have been many classification systems proposed for stress fractures, but the Kaeding-Miller (K-M) system is the first to incorporate both clinical and radiographic findings, which can include radiographs, CT, MRI, or bone scans. In this newly developed classification system (Table 1), grade I indicates asymptomatic (often incidental) stress reaction on imaging; grade II indicates pain with no fracture line but bony edema or periosteal reaction is present (Figure 1); grade III indicates a nondisplaced fracture (Figure 2); grade IV indicates displaced fracture; and grade V indicates nonunion, including the chronic anterior cortex tibial stress fracture known as the "dreaded black line" (Figure 3). The K-M system has proven to be clinically relevant, easily applicable, generalizable, and has high interobserver and intraobserver reliability. However, no studies have been conducted to determine if K-M grade correlates with time to return to play in athletes with stress fractures.
T2 coronal MRI of a 19-year-old female distance runner demonstrating bilateral tibial stress reactions (Kaeding-Miller grade II).
T1 Coronal MRI of a 20-year-old female, multi-event, track and field athlete with medial proximal tibial stress fracture with fracture line (Kaeding-Miller grade III).
Lateral tibial radiograph of a 19-year-old female 400 meter runner with chronic anterior tibial cortex stress fracture nonunion (Kaeding- Miller grade V).
To prevent and optimize treatment of tibial stress fractures in collegiate track and field athletes, the identification of risk factors and the classification of the stress fractures into treatment groups are essential. It is also crucial to maximize healing potential and predict the expected time away from sport. A retrospective chart review of all track and field athletes competing for a Division I university from 2011 to 2014 was performed. The primary aim of this study was to evaluate tibial stress fractures in female track and field athletes and assess correlation of the K-M grade with time to return to competition. Secondarily, body mass index (BMI), t-score reported from dual-energy x-ray absorptiometry (DEXA) scans, and menstrual abnormalities were analyzed and correlated with time to return to competition. We hypothesized that time to return to running or practice would correlate with the K-M classification system grade and that BMI would not.
Curr Orthop Pract. 2017;28(4):393-397. © 2017