Correlation of MRI grading of bone stress injuries with clinical risk factors and return to play: a 5-year prospective study in collegiate track and field athletes

Abstract

Background: Bone stress injuries are common in track and field athletes. Knowledge of risk factors and correlation of these to magnetic resonance imaging (MRI) grading could be helpful in determining recovery time.

Purpose: To examine the relationships between MRI grading of bone stress injuries with clinical risk factors and time to return to sport in collegiate track and field athletes.

Study design: Cohort study (prognosis); Level of evidence, 2.

Methods: A total of 211 male and female collegiate track and field and cross-country athletes were followed prospectively through their competitive seasons. All athletes had preparticipation history, physical examination, and anthropometric measurements obtained annually. An additional questionnaire was completed regarding nutritional behaviors, menstrual patterns, and prior injuries, as well as a 3-day diet record. Dual-energy X-ray absorptiometry was performed at baseline and each year of participation in the study. Athletes with clinical evidence of bone stress injuries had plain radiographs. If radiograph findings were negative, MRI was performed. Bone stress injuries were evaluated by 2 independent radiologists utilizing an MRI grading system. The MRI grading and risk factors were evaluated to identify predictors of time to return to sport.

Results: Thirty-four of the athletes (12 men, 22 women) sustained 61 bone stress injuries during the 5-year study period. The mean prospective assessment for participants was 2.7 years. In the multiple regression model, MRI grade and total-body bone mineral density (BMD) emerged as significant and independent predictors of time to return to sport. Specifically, the higher the MRI grade (P = .004) and lower the BMD (P = .030), the longer the recovery time. Location of the bone injury at predominantly trabecular sites of the femoral neck, pubic bone, and sacrum was also associated with a prolonged time to return to sport. Female athletes with oligomenorrhea and amenorrhea had bone stress injuries of higher MRI grades compared with eumenorrheic athletes (P = .009).

Conclusion: Higher MRI grade, lower BMD, and skeletal sites of predominant trabecular bone structures were associated with a delayed recovery of bone stress injuries in track and field athletes. Knowledge of these risk factors, as well as nutritional and menstrual factors, can be clinically useful in determining injury severity and time to return to sport.

Keywords: MRI grading; bone stress injury; female athlete triad; stress fracture.

Figure 1

Number of bone stress injuries incurred, diagnostic imaging utilized- and the magnetic resonance imaging (MRI) grade results. ^§Three MRI images were not graded due to incomplete time to return to sport data.

Figure 2

MRI grade 1 bone stress injury of tibia. Arrow points to mild periosteal edema depicted in this axial image of the posteromedial tibia. MRI grade 1 includes mild marrow or periosteal edema on T2-weighted images (but not T1).

Figure 3

MRI grade 2 bone stress injury of tibia. Arrow points to moderate marrow edema on T2-weighted image. MRI grade 2 includes moderate marrow or periosteal edema on T2-weighted image (but not T1).

Figure 4

A and B MRI grade 3 bone stress injury of tibia. Arrow in 4A points to severe marrow edema on T2-weighted image, and arrow on 4B illustrates corresponding marrow edema on the T1-weighted image. MRI grade 3 bone stress injury includes severe marrow edema or periosteal edema on T2 and T1-weighted images.

Figure 5

A and B MRI grade 4 bone stress injury of femoral neck Arrow in 5A points to severe marrow edema on T2-weighted image plus a fracture line. Arrow in 5B points to severe marrow edema on corresponding T1-weighted image. MRI grade 4 bone stress injury includes severe marrow or periosteal edema on T2 and T1-weighted images plus a fracture line.

Figure 6

Time to full return to sport (weeks) for injuries evaluated using MRI (N= 43), comparison between grades 1 & 2 (N= 25) vs. grades 3 & 4 (N= 18). ^aGrades 3 & 4 significantly longer than grade 1 & 2, (23.6 ± 2.4 vs. 13.1 ± 2.0 weeks, respectively, p= 0.002, Independent t-tests).

Figure 7

Time to full return to sport (weeks) for injuries evaluated using MRI (N=43), comparison between grades 1 & 2 (N=25) vs. grades 3 & 4 (N=18) for injuries occurring at the cortical (N= 36) and trabecular (N= 7) bone sites. ^aGrades 3 & 4 trabecular bone stress injuries significantly longer than grades 3 & 4 cortical bone stress injuries (38.1 ± 6.4 vs. 18.8 ± 2.1 weeks. p= 0.005). No differences observed between grades 1 & 2 trabecular bone stress injuries vs. grades 1 & 2 cortical bone stress injuries, p=0.75. Independent t-tests).