Maria H. Niva

Bone Stress Injuries in Asymptomatic Elite Recruits A Clinical and Magnetic Resonance Imaging Study

Background The occurrence and clinical significance of asymptomatic bone stress injuries is unknown. Hypothesis To evaluate by clinical and magnetic resonance imaging follow-up the occurrence of asymptomatic bone stress injuries, their clinical significance, and whether they all progress to stress fractures in subjects undergoing intensive physical training. Study Design Cohort study (prognosis); Level of evidence, 1. Methods Twenty-one male elite-unit military recruits voluntarily underwent clinical examination and magnetic resonance imaging before their intensive training period, 6 weeks into it, and on completion of the 5-month training program. Results Based on magnetic resonance imaging, a total of 75 bone stress injuries were detected. Only 40% (30/75) of the bone stress injuries had been symptomatic. Symptoms depended on location and magnetic resonance imaging grade of injury, with higher grades usually more symptomatic. Repeated clinical and magnetic resonance imaging assessment indicated that asymptomatic grade I bone stress injuries healed (21/25, 84%) or remained grade I and asymptomatic (3/25, 12%). The numbers of bone stress injuries, symptomatic cases, and recruits with bone stress injury increased toward the end of the intensive training period. Conclusions Asymptomatic grade I bone stress injuries seem common in subjects undergoing intensive physical training. Such bone stress injuries heal or remain asymptomatic grade I bone stress injuries even if intensive physical activity continues. They are therefore of no clinical significance. Only subjects who exhibit symptoms need undergo imaging studies. Subjects with an asymptomatic grade I bone stress injury may continue training but should be clinically monitored for symptoms.

Bone Stress Injuries of the Ankle and Foot An 86-Month Magnetic Resonance Imaging–based Study of Physically Active Young Adults

Background No comprehensive studies of bone stress injuries in the ankle and foot based on magnetic resonance imaging findings have been published. Purpose Using magnetic resonance imaging findings to assess incidence, location, and type of bone stress injuries of the ankle and foot in military conscripts with ankle and/or foot pain. Study Design Case series; Level of evidence, 4. Methods All patients with ankle or foot pain, negative findings on plain radiography, and magnetic resonance images obtained of the ankle or foot were included in this 86-month study. Magnetic resonance images with bone stress injury findings were re-evaluated regarding location and injury type. Based on the number of conscripts within the hospital catchment area, the person-based incidence of bone stress injuries was calculated. Results One hundred thirty-one conscripts displayed 378 bone stress injuries in 142 ankles and feet imaged, the incidence being 126 per 100 000 person-years. This incidence represents the stress injuries not diagnosable with radiographs and requiring magnetic resonance images. Of injuries, 57.7% occurred in the tarsal and 35.7% in the metatarsal bones. Multiple bone stress injuries in 1 foot were found in 63% of the cases. The calcaneus and fifth metatarsal bone were usually affected alone. Injuries to the other bones of the foot were usually associated with at least 1 other stress injury. The talus and calcaneus were the most commonly affected single bones. High-grade bone stress injury (grade IV-V) with a fracture line on magnetic resonance images occurred in 12% (talus, calcaneus), and low-grade injury (grade I-III) presented only as edema in 88% of the cases. Conclusion Multiple, various-stage bone stress injuries of the ankle and foot may occur simultaneously in physically active young adults. When considering injuries that were missed by plain radiographs but detected by magnetic resonance imaging, the bones most often affected were the tarsal bones, of which the talus and calcaneus were the most prominent single bones and most common locations for higher grade (IV-V) bone stress injuries. With use of magnetic resonance imaging, early detection and grading of bone stress injuries are available, which enable early and appropriate injury management.

Stress injuries of the calcaneus detected with magnetic resonance imaging in military recruits.

BACKGROUNDnCalcaneal stress injuries are fairly common overuse injuries in military recruits and athletes. We assessed the anatomic distribution, nature, and healing of calcaneal stress injuries in a group of military recruits.nnnMETHODSnMilitary recruits who underwent magnetic resonance imaging for the evaluation of exercise-induced ankle and/or heel pain were identified from the medical archives. The magnetic resonance images, plain radiographs, and medical records of these patients were evaluated with regard to fracture type and the natural history of the injury.nnnRESULTSnOver ninety-six months, magnetic resonance imaging revealed calcaneal stress injuries in thirty recruits in a population with a total exposure time of 117,149 person-years, yielding an incidence of 2.6 (95% confidence interval, 1.6 to 3.4) per 10,000 person-years. Four patients exhibited a bilateral injury. Of the thirty-four injuries, nineteen occurred in the posterior part of the calcaneus, six occurred in the middle part of the calcaneus, and nine occurred in the anterior part of the calcaneus, with 79% occurring in the upper region and 21% occurring in the lower region. The calcaneus alone was affected in twelve cases. In twenty-two cases, stress injury was also present in one or several other tarsal bones. A distinct association emerged between injuries of the different parts of the calcaneus and stress injuries in the surrounding bones. In only 15% of the patients was the stress injury visible on plain radiographs. With the numbers available, there were no significant differences between the patients with calcaneal stress injuries and unaffected recruits with regard to age, height, weight, body mass index, or physical fitness.nnnCONCLUSIONSnThe majority of stress injuries of the calcaneus occur in the posterior part of the bone, but a considerable proportion can also be found in the middle and anterior parts. To obtain a diagnosis, magnetic resonance imaging is warranted if plain radiography does not show abnormalities in a physically active patient with exercise-induced pain in the ankle or heel.

Bone Stress Injuries Are Common in Female Military Trainees: A Preliminary Study

Although bone stress injuries are common in male military trainees, it is not known how common they are in female trainees. It also is unclear whether asymptomatic bone stress injuries heal if intensive training is continued. We prospectively followed 10 female trainees of a military Reserve Officer Course. The subjects underwent clinical and MRI examinations of the pelvis, thighs, and lower legs at the beginning, once during, and at the end of their 3-month course. We identified two to five injuries in every female trainee, all of whom already had the injuries at the beginning of the officer course. None of these injuries increased their severity despite vigorous training. Two-thirds were asymptomatic and low grade. Femoral and tibial shafts were the most common locations. Higher-grade injuries were more likely symptomatic, but regardless of the MRI findings, female trainees expressed only mild to moderate symptoms. Asymptomatic, low-grade bone stress injuries of the femoral and tibial shaft are common in female recruits undergoing heavy physical training. Because these injuries seem to remain constant or even disappear despite continued heavy physical activity, we do not recommend routine screening of asymptomatic trainees. As some bone stress fractures may have severe consequences (eg, in the femoral neck), symptomatic bone stress injuries should be examined and treated.

Outcomes of Stress Fractures of the Talus

Background Stress fractures of the talus are rare, and only a few small studies have been published. In the absence of follow-up studies, the outcomes of these injuries are unknown. Hypothesis Traumatic fractures of the talus frequently heal poorly, and stress fracture healing might remain inadequate. The purpose of this study was to determine the outcome of stress fractures of the talus treated in the authors’ institution with reduced exercise and nonweightbearing. Study Design Case series (prognosis); Level of evidence, 4. Methods Patients with a diagnosed stress fracture in the talus by magnetic resonance imaging between April 1997 and March 2005 were recalled for a follow-up inspection by an orthopaedic surgeon, magnetic resonance imaging, and plain radiographs to determine the outcome of the injury. Results One of the 9 patients in our sample declined the invitation, leaving 8 patients with 9 stress fractures in the talus who participated in the follow-up examination. Five patients displayed subchondral degeneration and edema near the original injury area in the follow-up magnetic resonance imaging. In 2 patients, the degeneration was also visible on the plain radiographs. Three patients had mild and 2 moderate symptoms after the mean follow-up time of 45 months (range, 12-74 months). No serious complications in the healing process were seen. Conclusion Stress fractures of the talus do not seem to seriously damage the foot. In a middle-term follow-up, however, minor to moderate symptoms and radiological degeneration of the injured area prevailed in roughly half of the patients.

Bone Stress Injuries Causing Exercise-Induced Knee Pain

Background No comprehensive studies of bone stress injuries in the knee based on magnetic resonance imaging findings have been published. Purpose Assess the incidence, location, nature, and patterns of bone stress injuries in the knee in military conscripts with exercise-induced knee pain. Study Design Case series; Level of evidence, 4. Methods During a period of 70 months, 1330 patients with exercise-induced knee pain underwent magnetic resonance imaging of the knee. A total of 1577 knees were imaged; the images with bone stress injury findings were retrospectively reevaluated with respect to location and type of injury. The person-based incidence of bone stress injuries in the knee was calculated, based on the number of conscripts within the hospitals catchment area. Results Of the 1330 patients, 88 (7%) met the inclusion criteria, and 141 bone stress injuries were found in the 110 knees imaged. The incidence of bone stress injuries was 103 per 100 000 person-years. Of the patients, 25% had bilateral bone stress injuries; 28% had 2 solitary bone stress injuries in the same knee simultaneously, all situated in the femoral condyle and tibial plateau. The most common anatomical location for a bone stress injury was the medial tibial plateau (31%), which was also the most typical location for a more advanced injury. After the commencement of military service, a bone stress injury in the medial tibial plateau caused knee pain earlier than did a bone stress injury elsewhere in the knee (P=. 014). Conclusion The incidence of bone stress injuries in the knee with exercise-induced knee pain is relatively high in conscripts. Multiple and bilateral injuries can occur. For accurate diagnosis and to ensure appropriate treatment, magnetic resonance imaging is recommended as a routine imaging method when a physical activity can be regularly associated with the onset of symptoms.

Magnetic Resonance Imaging in Acute Traumatic and Chronic Meniscal Tears of the Knee A Diagnostic Accuracy Study in Young Adults

Background No previous research has investigated the diagnostic validity of magnetic resonance imaging for acute versus chronic meniscal tears using comparable materials and methods. Hypothesis There is no difference in the diagnostic validity of magnetic resonance imaging for acute versus chronic meniscal tears in young adults. Study Design Cohort study (diagnosis); Level of evidence, 2. Methods A total of 628 young adult military personnel underwent magnetic resonance imaging and arthroscopy of the knee over a 6-year period. Inclusion criteria were met by 82 patients with acute knee trauma (magnetic resonance imaging within 30 days from trauma) and 40 patients with chronic knee symptoms (symptoms lasting over 6 months before magnetic resonance imaging). The original magnetic resonance imaging and arthroscopy records were reviewed twice by a musculoskeletally trained radiologist, blinded to previous magnetic resonance imaging and arthroscopy findings. Interobserver correlations and intraobserver reliability were calculated and reported. Arthroscopy served as the gold standard when calculating the diagnostic values of magnetic resonance imaging for acute and chronic meniscal tears. Results The median age of the patients was 20 years (range, 18-25). Magnetic resonance imaging detected acute meniscal tears with sensitivity of 67%, specificity of 93%, and diagnostic accuracy of 88% and chronic meniscal tears with 64%, 91%, and 86%, respectively. There was no statistically significant difference in magnetic resonance imaging results between the 2 groups. Conclusion The diagnostic validity of magnetic resonance imaging is similar for meniscal tears in acute knee trauma and in knee symptoms lasting over 6 months in young adults. The results also suggest that effusion or hemarthrosis do not weaken the diagnostic validity of magnetic resonance imaging. The magnetic resonance imaging sensitivity achieved in the present study was relatively poor, but the specificity was good for both acute and chronic meniscal tears. Despite negative magnetic resonance imaging findings at the acute stage of knee trauma, patient monitoring and readiness for arthroscopy should be considered if justified by the patients symptoms.