Tibial stress changes in new combat recruits for special forces: patterns and timing at MR imaging

Significance of tibial MRI findings of special forces recruits at the onset of their training

INTRODUCTION

MRI is commonly used to evaluate medial tibial stress syndrome (MTSS), based on grading assessments developed in civilian populations. When MTSS represents stress fracture, rest is required to allow for bone remodelling to occur. False positive evaluations can lead to unnecessary recruit attrition.

METHODS

Thirty randomly selected new recruits to a special forces training unit underwent MRI of their tibias using the T2-Dixon sequence at the onset of training. Evaluation was according to the Fredericson MTSS grading system. Prior to undergoing MRI, anthropomorphic measurements, a survey of sports history and an orthopaedic examination of subject tibias were performed. Orthopaedic follow-up was through 11 weeks of training.

RESULTS

Medial periosteal oedema without the presence of bone marrow oedema, corresponding to a grade 1 stress reaction, was present on MRI in 10 recruits (17 tibias). In only one case did the periosteal oedema include the posterior aspect of the medial cortex where medial tibial stress fractures usually occur. Tibial tenderness was present in seven tibias on examination done just prior to the MRI studies, but none were symptomatic and only one had periosteal oedema present on MRI, but without anatomical correlation between the site of the tenderness and the periosteal oedema. During subsequent training, five tibias in four recruits developed pain and tenderness. Two had periosteal oedema in their prior MRIs, but the location did not coincide anatomically with that of the tibial tenderness. The time from stopping sports before induction and the presence of periosteal oedema was not significant.

CONCLUSION

Periosteal oedema, one of the hallmarks used in MRI grading systems to evaluate MTSS, was found to have a 37.7% false positive rate for anatomically corresponding tibial tenderness at the time of the examination and during subsequent training, indicating the grading systems' low utility for the military.

Asymptomatic Bone Marrow Edema in Weight-bearing Bones in Athletes and Military Trainees: A Systematic Literature Review

Asymptomatic bone marrow edema (aBME) is a non-specific radiographic finding often found in athletes. Although aBME may represent the body's physiological response to training load, the etiology, MRI characteristics, and natural history of aBME remain unknown. To better characterize aBME in the lower extremities of military trainees and athletes. A systematic literature review in accordance with PRISMA guidelines was performed to identify primary research articles reporting on aBME in the lower extremities of athletes and military trainees. We identified 347 unique articles and after applying inclusion and exclusion criteria, 10 articles were included for qualitative synthesis. There were a total of 444 patients with an average age of 28.4±9.6 included. The most commonly used MRI sequences were proton-density with fat-saturation and T1-weighted imaging. The pattern of BME was inconsistently described, with various classification schemas used. The changes in aBME during longitudinal follow-up were dynamic and demonstrated both radiographic progression and regression. aBME is a highly prevalent and radiographically dynamic entity observed in high-level athletes and military trainees. Although follow-up was limited in the included studies, aBME may represent a natural, non-pathologic, reaction in response to specific biomechanical stressors.

Retrospective Review of Radiographic Imaging of Tibial Bony Stress Injuries in Adolescent Athletes With Positive MRI Findings: A Comparative Study

BACKGROUND

It is difficult to diagnose and grade bony stress injury (BSI) in the athletic adolescent population without advanced imaging. Radiographs are recommended as a first imaging modality, but have limited sensitivity and, even when findings are present, advanced imaging is often recommended.

HYPOTHESIS

It was hypothesized that the significance of radiographs is underestimated for BSI in the adolescent with positive clinical examination and history findings.

STUDY DESIGN

Case series.

LEVEL OF EVIDENCE

Level 4.

METHODS

A total of 80 adolescent athletes with a history of shin pain underwent clinical examination by an orthopaedic surgeon. On the day of clinical examination, full-length bilateral tibial radiographs and magnetic resonance imaging (MRI) scans were obtained. MRI scans were reviewed using Fredericson grading for BSI. At the completion of the study, radiographic images were re-evaluated by 2 musculoskeletal (MSK) radiologists, blinded to MRI and clinical examination results, who reviewed the radiographs for evidence of BSI. Radiographic results were compared with clinical examination and MRI findings. Sensitivity, specificity, negative predictive value, and positive predictive value were calculated based on comparison with MRI.

RESULTS

All radiographs were originally read as normal. Of the tibia studied, 80% (127 of 160) showed evidence of BSI on MRI. None of the original radiographs demonstrated a fracture line on initial review by the orthopaedic surgeons. Retrospective review by 2 MSK radiologists identified 27% of radiographs (34 of 127) with evidence of abnormality, which correlated with clinical examination and significant findings on MRI. Review of radiographs found evidence of new bone on 0 of 28 Fredericson grade 0, 0 of 19 Fredericson grade I, 11 of 80 (13.7%) Fredericson grade II, 18 of 28 (64%) Fredericson grade III, and 5 of 5 (100%) Fredericson grade IV. Sensitivity of radiographs showed evidence of new bone on 27% (34 of 127) of initial radiographs, with presence more common with greater degree of BSI, as 23 of 33 (70%) were higher-grade injuries (III of IV) of BSI. Specificity and positive predictive value were 100%, while negative predictive value was 17%.

CONCLUSION

These findings highlight the importance of initial radiographs in identifying high-grade BSI. As radiographs are readily available in most office settings of sports medicine physicians, this information can influence the management of adolescent athletic BSI without the need to delay treatment to obtain an MRI.

CLINICAL RELEVANCE

Adolescent athletes with radiographic evidence of BSI should be treated in a timely and more conservative manner, given the likelihood of higher-grade BSI. In addition, clinicians knowledgeable of the radiographic findings of high-grade BSI should feel more confident that a negative initial radiograph is not likely to be a high-grade BSI and can modify their treatment plans accordingly.

Metatarsal Bone Marrow Edema on Magnetic Resonance Imaging and Its Correlation to Bone Stress Injuries in Male Collegiate Basketball Players

Background:

The presence of bone marrow edema (BME) on magnetic resonance imaging (MRI) has been used to evaluate for bone stress injuries in athletes.

Purpose:

To examine the prevalence of MRI findings, including BME, in a single male collegiate basketball team before and after a single season and to assess its association with clinically symptomatic metatarsal bone stress injuries.

Study Design:

Cohort Study; Level of evidence, 3.

Methods:

A total of 16 men on a single collegiate basketball team (mean age, 20.0 ± 1.8 years) underwent 1.5-T MRI focused on both midfeet during the preseason, and 13 underwent repeat MRI during the postseason. MRI findings included the presence of BME and the radiographic classification of the bone stress injury (grades 1-4). Injury surveillance performed by athletic trainers was used to identify metatarsal bone stress injuries over the course of the season.

Results:

Preseason MRI demonstrated metatarsal BME in 5 of the 16 participants, and postseason MRI demonstrated metatarsal BME in 4 of the 13 participants. All 4 of the participants with postseason BME had MRI findings of BME in the same metatarsals. Compared to those without BME, participants with metatarsal BME had a shorter history of basketball exposure (preseason: 10.4 ± 4.1 vs 14.2 ± 1.9 years, respectively [ P = .023]; postseason: 9.6 ± 4.1 vs 14.0 ± 2.1 years, respectively [ P = .024]), and those with postseason BME had started playing at an older age (9.8 ± 4.3 vs 6.2 ± 1.6 years, respectively; P = .050). The preseason MRI classification for metatarsals included grade 1 (n = 3), followed by grades 2 and 3 (n = 2 each). In the 4 participants with postseason MRI findings, the grade increased from 1 to 4 in 1 participant and was stable in the other 3. No participants were diagnosed clinically with a metatarsal bone stress injury during the season. BME of the sesamoids was identified in 6 participants, who trended toward being older (21.0 ± 2.2 vs 19.4 ± 1.3 years, respectively; P < .10), with the abnormalities persisting on postseason MRI in all players.

Conclusion:

Collegiate male basketball players may have a high prevalence of BME, often without associated symptoms. The absence of foot pain or a corresponding diagnosis of a metatarsal bone stress injury in this study suggests that MRI findings of BME in asymptomatic athletes should be interpreted with caution.

Tibial bone stress injury: diagnostic performance and inter-reader agreement of an abbreviated 5-min magnetic resonance protocol

OBJECTIVE

To compare the diagnostic performance and inter-reader agreement of an abbreviated (5 min) MR protocol compared to a complete (25 min) protocol, for evaluation of suspected tibial bone stress injury.

MATERIALS AND METHODS

This IRB-approved retrospective study consisted of 95 consecutive MR examinations in 88 patients with suspected tibial bone stress injury. Three musculoskeletal radiologists independently classified all examinations utilizing both an abbreviated protocol consisting only of axial T2-weighted images with fat suppression, and after a washout period again classified the complete examinations. Accuracy was calculated as proportion of cases classified exactly, within 1 grade, within 2 grades, and also utilizing a simplified "clinically relevant" classification combining grades 2, 3, and 4A into a single group. Significance testing was performed with the chi-test, and a post-hoc power analysis was performed. Inter-reader agreement was calculated with Kendall's coefficient of concordance, with significance testing performed utilizing the z-test after bootstrapping to obtain the standard error.

RESULTS AND CONCLUSIONS

There was no significant difference in accuracy of grading tibial bone stress injuries between complete and abbreviated examinations. For complete exams, pooled exact accuracy was 47.8%; accuracy within 1 grade was 82.8%; and accuracy within 2 grades was 96.1%. For the abbreviated protocol, corresponding accuracies were 50.2, 82.0, and 93.9%. With the "clinically relevant" simplified classification, accuracy was 58.6% for complete exams and 64.2% for abbreviated exams. There was no significant difference in inter-reader agreement, with substantial agreement demonstrated for both complete (Kendall coefficient of concordance 0.805) and abbreviated examinations (coefficient of 0.767).

Bone Marrow Oedema in the Knees of Asymptomatic High-Level Athletes: Prevalence and Associated Factors

BACKGROUND

Bone marrow oedema (BMO), seen on magnetic resonance imaging, can be associated with various injuries to the knee but may also occur in asymptomatic athletes. The prevalence and causal factors for these observations are not well understood. The aim of this study was to determine the prevalence of BMO in asymptomatic knees of athletes, competing at a high level, and to investigate the associated factors.

MATERIALS AND METHODS

Twenty-five asymptomatic university athletes, competing at regional to international level, were recruited. Bilateral knee magnetic resonance imaging was performed in each athlete (total 50 knee scans) at the end of their competitive season. Imaging studies were reported independently by two experienced consultant musculoskeletal radiologists.

RESULTS

There was almost perfect agreement between reporters for diagnosis of BMO (κ = 0.896). Seven participants (28%) were found to have BMO (six in one knee and one bilaterally). The amount of time spent training, during the season, was significantly associated with the appearance of BMO (p < 0.05).

CONCLUSION

The occurrence of BMO in asymptomatic knees of athletes is common (occurring in over one-quarter of knees) and may be associated with training intensity. This should be considered when treating athletes and deciding upon appropriate treatment plans.

Tibial stress injuries - location, severity, and classification in magnetic resonance imaging examination

Purpose

To describe and illustrate the spectrum of magnetic resonance imaging (MRI) findings of tibial stress injuries (TSI) and propose a simplified classification system.

Material and methods

Retrospective analysis of MRI exams of 44 patients with clinical suspicion of unilateral or bilateral TSI, using a modified classification system to evaluate the intensity and location of soft-tissue changes and bone changes.

Results

Most of the patients were young athletic men diagnosed in late stage of TSI. Changes were predominantly found in the middle and distal parts of tibias along medial and posterior borders.

Conclusions

TSI may be suspected in young, healthy patients with exertional lower leg pain. MRI is the only diagnostic method to visualise early oedematic signs of TSI. Knowledge of typical locations of TSI can be helpful in proper diagnosis before its evolution to stress fracture.

Effect of cardiovascular and muscular endurance is not associated with stress fracture incidence in female military recruits: a 12-month follow up study

BACKGROUND

Stress fracture (SF) is a common injury among military recruits, especially among women, during the army basic training (ABT). The purpose of this study was to evaluate the effects of health habits and physical activity before recruitment on the fitness level and the incidence of SF during the 4-month ABT.

METHODS

We screened 226 female recruit volunteers (weight: 60.5±10 kg; height: 163±6 cm) from an integrated combat unit and 124 aged-matched female controls (weight: 57.0±8.3 kg, height 162±7 cm) from a non-combat unit. A self-report questionnaire on their habits pertaining to smoking, physical activity, and orthopedic injuries prior to recruitment were analyzed in relation to the incidences of SF during ABT.

RESULTS

Aerobic fitness was similar between the two groups. The overall incidence of SFs was 10.2%. Physical training prior to recruitment had no significant effect on the incidence of SF during ABT (11.7% vs. 9.6% in those who trained and did not train before recruitment, respectively) (Odds ratio, OR)=1.24, p=0.236). Nearly 42% of the female recruits smoked regularly, and the incidence of SFs among smokers was 10.5% compared with 9.9% among the non-smokers (OR=1.07, p=0.188). The overall incidence of SFs 12 months after recruitment was 1.78%. The use of contraceptive medication did not affect the incidence of SF: 10.0% among prior-trained vs. 6.4% in non-prior trained (p>0.05) recruits. SFs were not correlated to these variables at the end of the ABT program and 16 months after recruitment.

CONCLUSIONS

In the present female cohort, physical activity prior to recruitment had no protective effect against SF during or after ABT. The incidence of SFs during the 12-month period after ABT was negligible.