The Presence of Hip Joint Effusion on MRI Is Predictive of a Grade 4 Femoral Neck Stress Injury

INTRODUCTION

One of the most debilitating types of bone stress injuries is those occurring at the femoral neck. This problem occurs in the military population with much higher incidence than in the normal population and is of great concern to military medical providers. Early detection and accurate diagnosis are key in protecting soldiers and recruits from sustaining a potentially career-ending fracture. In a case study, a 16-year-old elite male distance runner presented with hip pain. MRI found hip joint effusion but was unremarkable for marrow edema and a low-signal fracture line. The initial diagnosis was acute arthritis; however, a follow-up radiograph 1 month later, after the patient had been refraining from running, confirmed a significant non-displaced compression-side Grade 4 femoral neck stress injury (FNSI). In light of the case study and our similar clinical experience, we tested the hypothesis that an MRI study positive for an FNSI, combined with the evidence of a hip joint effusion, is indicative of a Grade 4 FNSI, even without visualization of a low-signal intensity fracture line on T1 or short tau inversion recovery images.

MATERIALS AND METHODS

Recruits in Army Basic Combat Training were included in the investigation if 1) diagnosed with a unilateral FNSI, 2) had an initial positive MRI for an FNSI, 3) had a positive bone scan for uptake in the femoral neck area (to validate the diagnosis), 4) had no other hip/pelvis injuries, and 5) had a follow-up MRI within 60 days. Hip joint effusion was defined as 1) ≥2-mm measurable difference in the thickness of fluid along the length of the involved femoral neck when compared to the contralateral uninvolved femoral neck on the initial MRI; 2) visibly assessed as a prominent collection of fluid distending the posterior hip joint capsule on the initial MRI coronal short tau inversion recovery sequence (called the "flash sign").

RESULTS

A total of 162 recruits met the study inclusion criteria. For the detection of a Grade 4 FNSI on the first MRI, the sensitivity, specificity, and positive predictive value of the measured joint effusion criteria were 0.52, 0.94, and 0.89, respectively. or the non-measured flash sign, these values were 0.70, 0.83, and 0.80, respectively.

CONCLUSIONS

Both the measured hip joint effusion criteria and the non-measured flash sign were predictive of a Grade 4 FNSI and may be useful in clinical evaluation.

[Femoral neck stress fractures and femoroacetabular impingement : A retrospective case study and literature review]

BACKGROUND

Femoroacetabular impingement (FAI) can lead to morphologic damage of both the acetabulum and the femoral neck. Recent reports have found an association between impingement deformities and the development of femoral neck stress fractures. The aim of this study was to report a series of patients with these findings and to update the current evidence on the topic.

MATERIAL AND METHODS

5 patients (6 cases) with atraumatic femoral neck fractures and FAI were identified in the Dresden hip registry from 2015 to 2018. Demographic data, comorbidities, radiographic results and bone metabolism results were described. A literature search was conducted using keywords related to femoral neck stress fractures and FAI syndrome.

RESULTS

The average age of the series was 39 (range: 22-52), 2 patients were female and 3 male. A total of 12 surgical procedures were performed. 4 of the 5 patients showed radiographic features of pincer and/or cam-FAI, whereas 3 patients had a decreased femoral antetorsion (-7° to +7° antetorsion). In 3 patients, magnetic resonance imaging revealed additional signs of avascular necrosis ARCO I. There was a lack of FAI-specific treatment recommendations in the available literature.

DISCUSSION

Radiographic results of the patients evaluated suggested that impingement-associated deformities of the hip may cause femoral neck stress fractures, which is in line with the available literature. This potential coincidence should be integrated in diagnostic algorithms and therapeutic approaches.

The Prevalence and Body Site Distribution of Stress Fractures among Female Combat Soldiers in the Israeli Defense Forces: A Cross-Sectional Study

One of the most troublesome overuse injuries is stress fractures, for which female gender is a major risk factor. In 2015, the Israeli government opened identical combat duties for both genders. The purpose of this study is to provide a detailed report regarding the prevalence and characteristics of stress fractures in females that will serve as an evidence-based platform for future policy planning and implementation regarding female integration in combat units. This is a report of a cross-sectional study of 2223 female soldiers recruited to combat units between 2010 and 2013. Data were collected from the Israeli Defense Force's (IDF's) computerized medical consultation records package. Descriptive and analytic statistics were performed to obtain and analyze results. The overall stress fractures rate was 11.6% (258 soldiers). The most frequent site for stress fracture was the distal tibia (215 cases, 83%). The average lost training days due to a stress fracture were 26.6 days. The risk for developing a stress fracture was 2.15 (215%) times higher in the noninfantry group than in the infantry group, ( p = 0.0232, 95% confidence interval 1.346, 4.536). The rate of stress fractures and the consequent lost training days in the IDF are high and necessitate the planning and implementation of a comprehensive intervention policy to reduce overuse injuries and stress fracture rates among female warriors.

Negative magnetic resonance imaging in femoral neck stress fracture with joint effusion: a case report

Femoral neck stress fracture (FNSF) is well documented in the orthopedic literature and is generally associated with strenuous activities such as long-distance running and military training. The diagnostic yield of magnetic resonance imaging (MRI) for FNSF was reported to be 100 %, and early MRI is recommended when this fracture is suspected. We encountered a 16-year-old male long-distance runner with FNSF in whom the left femoral neck showed no signal changes on MRI although an effusion was detected in the left hip joint. One month later, roentgenograms revealed periosteal callus and oblique consolidation of the left femoral neck, confirming the diagnosis of compression FNSF. Because FNSF with a normal bone marrow signal on MRI is very rare, this patient is presented here.

A case report of missed femoral neck stress fracture

Femoral neck stress fracture (FNSF) is an uncommon but potentially serious orthopaedic problem. This is a case report on missed femoral neck stress fracture in a 62-year-old female who was initially treated as early-onset coxarthrosis. She later presented to us with a displaced intra-capsular neck of left femur fracture and underwent total hip replacement. This case illustrates that causes other than osteoarthritis should be taken into consideration in patients presenting with anterior hip pain where symptoms are disproportionate to clinical and radiological findings. More advanced investigations such as MRI scan or regular follow up with plain radiographs should be performed. A delay in diagnosis can lead to secondary displacement of the femoral neck stress fracture.

Incidence and Time to Return to Training for Stress Fractures during Military Basic Training

Currently, little is known about the length of time required to rehabilitate patients from stress fractures and their return to preinjury level of physical activity. Previous studies have looked at the return to sport in athletes, in a general population, where rehabilitation is not as controlled as within a captive military population. In this study, a longitudinal prospective epidemiological database was assessed to determine the incidence of stress fractures and the time taken to rehabilitate recruits to preinjury stage of training. Findings demonstrated a background prevalence of 5% stress fractures in Royal Marine training; femoral and tibial stress fractures take 21.1 weeks to return to training with metatarsal stress fractures being the most common injury taking 12.2 weeks. Rehabilitation from stress fractures accounts for 814 weeks of recruit rehabilitation time per annum. Stress fracture incidence is still common in military training; despite this stress fracture recovery times remain constant and represent a significant interruption in training. It takes on average 5 weeks after exercise specific training has restarted to reenter training at a preinjury level, regardless of which bone has a stress fracture. Further research into their prevention, treatment, and rehabilitation is required to help reduce these burdens.

Mechanical strain regulates osteoblast proliferation through integrin-mediated ERK activation

Mechanical strain plays a critical role in the proliferation, differentiation and maturation of bone cells. As mechanical receptor cells, osteoblasts perceive and respond to stress force, such as those associated with compression, strain and shear stress. However, the underlying molecular mechanisms of this process remain unclear. Using a four-point bending device, mouse MC3T3-E1 cells was exposed to mechanical tensile strain. Cell proliferation was determined to be most efficient when stimulated once a day by mechanical strain at a frequency of 0.5 Hz and intensities of 2500 µε with once a day, and a periodicity of 1 h/day for 3 days. The applied mechanical strain resulted in the altered expression of 1992 genes, 41 of which are involved in the mitogen-activated protein kinase (MAPK) signaling pathway. Activation of ERK by mechanical strain promoted cell proliferation and inactivation of ERK by PD98059 suppressed proliferation, confirming that ERK plays an important role in the response to mechanical strain. Furthermore, the membrane-associated receptors integrin β1 and integrin β5 were determined to regulate ERK activity and the proliferation of mechanical strain-treated MC3T3-E1 cells in opposite ways. The knockdown of integrin β1 led to the inhibition of ERK activity and cell proliferation, whereas the knockdown of integrin β5 led to the enhancement of both processes. This study proposes a novel mechanism by which mechanical strain regulates bone growth and remodeling.

Simultaneous bilateral femoral neck stress fractures in a young military cadet: a rare case report

Simultaneous bilateral femoral neck stress fracture in healthy young adult is one of the very rare clinical entities that an orthopedic surgeon may encounter once in lifetime. Bilateral femoral neck stress fractures have been very well documented in elderly and osteomalacia patients; however, its simultaneous occurrence in a healthy adult is challenging to diagnose and manage. This article describes a 34-year-old man a military personnel who sustained bilateral stress femoral neck fractures, during a routine training activity. The patient was come to our institution, and a full endocrine evaluation was performed and proved unremarkable. He underwent closed reduction and internal fixation of the fractures using cannulated screws on both the sides. At 1-year follow-up, the fractures went on to complete union. Despite strict non-weight-bearing instructions for initial 3-month period, patient bore weight on the limbs resulting in varus union on the left side. Our case emphasizes the significance of obtaining a complete and thorough medical history on physical examination and appropriately counseling patients regarding activity level even after successful fixation.