Femoral Neck Stress Injuries: Analysis of 156 Cases in a U.S. Military Population and Proposal of a New MRI Classification System.

OBJECTIVE: The objective of this study is to formulate a new MRI classification system for fatigue-type femoral neck stress injuries (FNSIs) that is based on patient management and return-to-duty (RTD) time. MATERIALS AND METHODS: A retrospective review of 156 consecutive FNSIs in 127 U.S. Army soldiers over a 24-month period was performed. The width of marrow edema for low-grade FNSIs and the measurement of macroscopic fracture as a percentage of femoral neck width for high-grade FNSIs were recorded. RTD time was available for 90 soldiers. Nonparametric testing, univariate linear regression, and survival analysis on RTD time were used in conjunction with patient management criteria to develop a new FNSI MRI classification system. RESULTS: The FNSI incidence was 0.09%, and all FNSIs were compressive-sided injuries. RTD time was significantly longer for high-grade FNSIs versus low-grade FNSIs (p < 0.001). Our FNSI MRI classification system showed a significant difference in RTD time between grades 1 and 2 (p = 0.001-0.029), 1 and 3 (p < 0.001), and 1 and 4 (p = 0.001-0.01). There was no significant RTD time difference between the remaining grades. The rates of completing basic training (BT) and requiring medical discharge were significantly associated with the FNSI MRI grades (p = 0.038 and p = 0.001, respectively). CONCLUSION: The proposed FNSI MRI classification system provides a robust framework for patient management optimization by permitting differentiation between operative and nonoperative candidates, by allowing accurate prediction of RTD time, and by estimating the risk of not completing BT and requiring medical discharge from the military.

Hip arthroscopy enables classification and treatment of precollapse subchondral insufficiency fracture of the femoral head associated intra-articular pathology.

PURPOSE: The purposes of this study were to investigate (1) the clinical, radiographic and arthroscopic presentation of patients with subchondral insufficiency fracture of the femoral head (SIFFH) and (2) the outcomes following arthroscopic treatment with internal fixation using hydroxyapatite poly-lactate acid (HA/PLLA) threaded pins and concomitant arthroscopic treatment of associated findings. METHODS: Nine patients (median age 49.0 years, range 43-65, five female and four male patients) with SIFFH who underwent arthroscopic treatment with labral repair, capsular closure and internal fixation of SIFFH using HA/PLLA pins were retrospectively reviewed. Inclusion criteria were adult patients with precollapse SIFFH with minimum 1-year follow-up (median follow-up 30.0 months, range 12-56). RESULTS: Acetabular labral tears were observed in all patients. The median BMI was 24.3 kg/m2 (range 20.1-31.8). Clinical presentations and radiographic measurements demonstrated mixed type FAI in six patients, borderline developmental dysplasia in two patients and pincer type FAI in one patient. The median MHHS significantly improved from preoperatively (67.1, range 36.3-78.0) to post-operatively (96.8, range 82.5-100; p = 0.001). The median NAHS significantly improved from preoperatively (34.0, range 17-63) to post-operatively (78.0 range 61-80; p = 0.001). CONCLUSION: SIFFH is associated with bony deformities and labral tears. Precollapse SIFFH can be treated with bioabsorbable pin stabilization of unstable lesions and treatment of associated intra-capsular pathology in those with stable lesions as determined by a new arthroscopic classification system with promising early outcomes. LEVEL OF EVIDENCE: IV.

Prognostic classification of fifth metatarsal stress fracture using plantar gap.

BACKGROUND: There have been diverse results even in same Torg type of fifth metatarsal stress fractures. METHODS: Eighty-six cases with a fifth metatarsal stress fracture that were treated with modified tension band wiring from January 2003 to May 2009 were evaluated retrospectively. Each case was classified according to Torg's classification and a new classification. Using the new proposed classification, cases were subdivided into complete fracture and incomplete fracture. The cases of incomplete fracture were subdivided based on presence or absence of plantar gap more than 1 mm. After surgery, bone union was determined by CT. Statistical analysis of the Torg classification and time for bone union as well as the proposed new classification and time for bone union was performed. RESULTS: There was a significant difference in the time for bone union among the three Torg types (P = 0.004). The mean time for bone union in group A (complete fracture, n = 32) was 67.5 ± 28.8, and it was 103.2 ± 47.7 for group B (incomplete fracture, n = 54). There was a significant difference in time for bone union between them (P < 0.001). The mean time for bone union in group B1 (incomplete fracture, plantar gap less than 1 mm, n = 16) was 73.9 ± 26.7, and it was 115.5 ± 45.4 for group B2 (incomplete fracture, plantar gap 1 mm or more, n = 38). There was a significant difference in time for bone union between them (P < 0.001). CONCLUSION: The results of this study suggest that the classification incorporating the plantar gap might be used for classification of fifth metatarsal stress fractures. LEVEL OF EVIDENCE: Level III, retrospective comparative series.

Discrepancies in clinical definitions of stress fractures: implications for the United States Army.

ABSTRACT In the United States Army initial entry training (IET) environment, stress fractures are common musculoskeletal injuries. Due to the repetitive physical demands placed on soldiers, stress fractures are particularly common in individuals matriculating through basic combat training (BCT) and advanced individual training (AIT). Within the Army medical department, the clinical definitions of stress fractures vary widely among providers who are directly responsible for diagnosing these injuries. The use of diversified definitions of stress fractures in patient evaluations, treatment, communication measures, and injury data collection negatively affect patient dispositions and soldier training outcomes. This report identifies discrepancies in clinical definitions of stress fractures and the implications for the Army regarding the lack of a standardized definition for stress fractures.

The classification systems of stress fractures: a systematic review.

BACKGROUND: Stress fractures of the upper and lower extremity are troublesome overuse injuries in athletes and nonathletes alike. These injuries have a broad spectrum of severity and prognosis. We performed a systematic search of the literature, which revealed multiple classification systems; however, we did not uncover a general system that offered both validated radiographic and clinical parameters. METHODS: A literature search was conducted using Ovid/Medline, Embase, and the Cochrane Library, with publication dates ranging from 1960 to December 2009. Inclusion criteria included all studies and review articles regarding stress or fatigue fractures and their classification. RESULTS: Forty-three studies and/or articles were identified for this review. Of these articles, 27 classification systems were referenced. Sixteen of the systems were applicable to any injury location, and 1 applied to specific bones (femoral neck, tibia, tarsal navicular, pars interarticularis, and fifth metatarsal). Four classification systems were referenced more often than others. Of the classification systems, 11 were based on radiographs alone, while the other 16 used a variety of radiographic modalities, including radiographs, bone scans, computed tomography, ultrasound, and magnetic resonance imaging. CONCLUSION: There are many different stress fracture classification systems in the literature. These systems employ various imaging modalities, but few include clinical parameters. Many are site specific. Of those that are widely applicable, no general classification system has been shown to be reproducible, easily accessible, safe, inexpensive, and clinically relevant. A gold standard classification system for describing stress fractures has yet to be determined.

Total knee arthroplasty for arthritic knees with tibiofibular stress fractures: classification and treatment guidelines.

Forty-two tibial and 5 fibular stress fractures in 34 patients with knee arthritis were radiologically classified into intraarticular malunited and ununited fractures, and extraarticular impending, acute, united, malunited, and ununited fractures. Depending on fracture type, total knee arthroplasty was performed using long-stem tibial component, metal augments, corrective osteotomy, or in routine fashion. At a mean follow-up of 36 months, the mean Knee Society knee score improved from 36.7 points preoperatively to 90.3 points; function score improved from 24 to 86.2 points. All fractures had united at the last follow-up with no complications of infection, joint instability, and patellar problems. Total knee arthroplasty for knee arthritis in the presence of tibiofibular stress fractures restores limb alignment and facilitates fracture healing with excellent functional outcome.

Stress fractures: classification and management.

Stress fractures occur as a result of microdamage secondary to repetitive strains. A mechanism for the development of stress fractures involves the accumulation of microdamage, which occurs with multiple subultimate failure loads applied to the bone. Stress fractures may be classified as high or low risk, depending on the grade of the injury. The most common site of injury is the lower extremity. In this article, we review the pathophysiology, etiology, diagnosis, and management of stress fractures, and present treatment guidelines for return to play.

Classification of stress fractures of the first rib in adolescent athletes.

Stress fractures of the first rib occur infrequently in adolescent athletes; therefore, there have been few case reports. Initial radiographs do not always lead to the diagnosis of first rib stress fractures. This study proposed a classification system and a possible mechanism for stress fractures of the first rib using three-dimensional computed tomography (3D-CT). The data of 10 stress fractures of the first rib in adolescent athletes obtained using 3D-CT between 2007 and 2018 were reviewed. Fractures of the first rib were classified according to the location and type of the fracture line. Stress fractures of the first rib were classified into three types: type 1, center-transverse fracture; type 2, center to posterior-oblique fracture; and type 3, posterior-transverse fracture. There were three type 1 fractures, five type 2 fractures, and two type 3 fractures. The fracture lines of types 1 and 2 were on the deep groove of the subclavian artery between the anterior and middle scalene muscle attachments, which is the thinnest and weakest portion of the first rib. However, the fracture line of type 3 was across the posterior part of the first rib and located slightly away from the deep groove of the subclavian artery. A 3D-CT classification of stress fractures of the first rib in adolescent athletes was proposed. Our results suggested that there are three types of the fracture and different mechanisms that cause this type of injury. This classification system helped to implement adequate conservative therapeutic plans based on the proposed mechanism.

[Bone fracture and the healing mechanisms. Fragility fracture and bone quality].

Fracture occurs in bone having less than normal elastic resistance without any violence. Numerous terms have been used to classify various types of fractures from low trauma events; "fragility fracture", "stress fracture", "insufficiency fracture", "fatigue fracture", "pathologic fracture", etc. The definitions of these terms and clinical characteristics of these fractures are discussed. Also state-of-the-art bone quality assessments; Finite element analysis of clinical CT scans, assessments of the Microdamage, and the Cross-links of Collagen are introduced in this review.

Comparison of planar scintigraphy alone and with SPECT for the initial evaluation of femoral neck stress fracture.

OBJECTIVE: The objective of our study was to compare the accuracy of planar scintigraphy alone versus planar scintigraphy with SPECT for the initial evaluation of femoral neck stress fractures in a young military population. MATERIALS AND METHODS: We retrospectively identified 38 patients who had undergone planar scintigraphy and 33 patients who had undergone planar scintigraphy and SPECT before MRI of the hips over a 6-month period for evaluation of suspected femoral neck fracture. Data were analyzed regarding the sensitivity and specificity of bone scanning alone and with SPECT for detecting femoral neck stress fracture and grading fractures as low grade (grades I and II) or high grade (grades III and IV). RESULTS: Twelve fractures were identified in the group who underwent planar scintigraphy alone and 13 in the group who underwent planar scintigraphy with SPECT. The sensitivities of planar scintigraphy alone and with SPECT were 50% and 92.3%, respectively (p = 0.03). The accuracy of each technique for the detection of high-grade fractures was 12.5% and 70%, respectively (p = 0.025). CONCLUSION: Planar scintigraphy with SPECT had a higher sensitivity and accuracy in assessing the grade of femoral neck stress fractures than planar scintigraphy alone. The results of this study suggest that SPECT should be performed with planar bone scintigraphy for the evaluation of patients with suspected femoral neck stress fractures.

Intravital microlesions in the human otic capsule. Detection, classification and pathogenetic significance revisited.

PURPOSE OF THE STUDY: To verify microcracks in human temporal bones by a method which distinguishes intravital lesions from artifacts, to revisit previous information derived from decalcified materials on their morphology and classification and to discuss the possible clinical significance. PROCEDURES: Histological analysis of 210 undecalcified adult human temporal bones bulk-stained by basic fuchsin in ethanol prior to embedding in methyl methacrylate and processing by the cutting and grinding method. RESULTS: Intravital crack lesions appeared in all specimens and could be distinguished from artifacts regardless of crack morphology and size. Particularly, large microfissures were found around the labyrinthine windows, while smaller microfissures originating at the perilymphatic space were found throughout perilabyrinthine bone. Small noncommunicating fatigue microdamage was identified for the first time. All lesions were reorganized according to morphology, topography and possible clinical significance. CONCLUSION: Microfissures accumulate in the adult otic capsule as expected when bone remodeling is low. Any capsular microlesion may introduce a possible barrier in the recently discovered antiresorptive signaling pathway from inner ear structures via the lacunocanalicular osteocytic network to perilabyrinthine bone. For this reason intravital microfissures may interfere with in vivo inhibition of temporal bone remodeling and consequently offer another pathogenetic factor in otosclerosis.

Bone stress injuries in the Army cadets of Pakistan Military Academy.

BACKGROUND: Bone stress injuries are common among army cadets during training period and these injuries give rise to morbidity and loss of training hours. Some cadets with stress fractures re-join their duties while some are kept out of services resulting in attrition and economic loss. A retrospective analysis of bone stress injuries of one hundred and twenty cadets between June 2006 and Dec 2007 was conducted from the case documents available at Institute of Nuclear Medicine, Oncology & Radiotherapy (INOR) Abbottabad. RESULTS: The occurrence of stress fractures among cadets at Pakistan Military Academy, presenting with exercise induced pain was 68.3% amongst these cadets. Seventy fours percent of the fractures were labelled grade-I. High grade fractures were confined to tibia. Tibia was the commonest site of stress fractures in both sexes, accounting for about 73% of all stress fractures. Fifty percent of these patients were labelled as having shin splints and 3% as thigh splints. CONCLUSIONS: Most of the stress injuries were confined to the tibia. The referral was considered early as most of the stress injuries were of low grade.

Expected Time to Return to Athletic Participation After Stress Fracture in Division I Collegiate Athletes.

BACKGROUND: Few studies have documented expected time to return to athletic participation after stress fractures in elite athletes. HYPOTHESIS: Time to return to athletic participation after stress fractures would vary by site and severity of stress fracture. STUDY DESIGN: Retrospective cohort study. LEVEL OF EVIDENCE: Level 3. METHODS: All stress fractures diagnosed in a single Division I collegiate men's and women's track and field/cross-country team were recorded over a 3-year period. Site and severity of injury were graded based on Kaeding-Miller classification system for stress fractures. Time to return to full unrestricted athletic participation was recorded for each athlete and correlated with patient sex and site and severity grade of injury. RESULTS: Fifty-seven stress fractures were diagnosed in 38 athletes (mean age, 20.48 years; range, 18-23 years). Ten athletes sustained recurrent or multiple stress fractures. Thirty-seven injuries occurred in women and 20 in men. Thirty-three stress fractures occurred in the tibia, 10 occurred in the second through fourth metatarsals, 3 occurred in the fifth metatarsal, 6 in the tarsal bones (2 navicular), 2 in the femur, and 5 in the pelvis. There were 31 grade II stress fractures, 11 grade III stress fractures, and 2 grade V stress fractures (in the same patient). Mean time to return to unrestricted sport participation was 12.9 ± 5.2 weeks (range, 6-27 weeks). No significant differences in time to return were noted based on injury location or whether stress fracture was grade II or III. CONCLUSION: The expected time to return to full unrestricted athletic participation after diagnosis of a stress fracture is 12 to 13 weeks for all injury sites. CLINICAL RELEVANCE: Athletes with grade V (nonunion) stress fractures may require more time to return to sport.

Estimates of Tibial Shock Magnitude in Men and Women at the Start and End of a Military Drill Training Program.

INTRODUCTION: Foot drill is a key component of military training and is characterized by frequent heel stamping, likely resulting in high tibial shock magnitudes. Higher tibial shock during running has previously been associated with risk of lower limb stress fractures, which are prevalent among military populations. Quantification of tibial shock during drill training is, therefore, warranted. This study aimed to provide estimates of tibial shock during military drill in British Army Basic training. The study also aimed to compare values between men and women, and to identify any differences between the first and final sessions of training. MATERIALS AND METHODS: Tibial accelerometers were secured on the right medial, distal shank of 10 British Army recruits (n = 5 men; n = 5 women) throughout a scheduled drill training session in week 1 and week 12 of basic military training. Peak positive accelerations, the average magnitude above given thresholds, and the rate at which each threshold was exceeded were quantified. RESULTS: Mean (SD) peak positive acceleration was 20.8 (2.2) g across all sessions, which is considerably higher than values typically observed during high impact physical activity. Magnitudes of tibial shock were higher in men than women, and higher in week 12 compared with week 1 of training. CONCLUSIONS: This study provides the first estimates of tibial shock magnitude during military drill training in the field. The high values suggest that military drill is a demanding activity and this should be considered when developing and evaluating military training programs. Further exploration is required to understand the response of the lower limb to military drill training and the etiology of these responses in the development of lower limb stress fractures.

Navicular stress fractures: a prospective study on athletes.

BACKGROUND: Navicular stress fractures of the foot often are difficult to diagnose and treat. METHODS: Nineteen athletic patients seen from 1999 to 2003, were compared to a previously treated group of 22 athletes with similar injuries treated from 1994 to 1998. Based on the frontal plane CT images, a previously described classification system was used to assess the injury: type I dorsal cortical break; type II fracture extending into the navicular body; and type III fracture breaches two cortices. Nonoperative treatment was recommended for patients with type I injuries and open reduction and internal fixation (ORIF) were recommended for those with type II and III injuries. The time to return to activity and ability to return to competition were assessed, along with differences between fracture type and gender. RESULTS: Return to activity (RTA) was 4.0 months for the entire group. RTA for type I (four injuries), type II (eight injuries), and type III (seven injuries) was 3.8, 3.7, and 4.2 months, respectively. Fifteen of 16 competitive athletes returned to full competition, including all who had ORIF. CONCLUSIONS: Navicular stress fractures can take 4 months to heal with nonoperative or operative treatment. Surgery should be considered for more severe injuries, which can be assessed by CT scan.

Risk factors for clinical stress fractures in male military recruits: a prospective cohort study.

This prospective study was aimed at evaluating risk factors for symptomatic stress fractures among 179 Finnish male military recruits, aged 18 to 20 years. The subjects were studied in the very beginning of the military service of 6 to 12 months in summer. Bone mineral content (BMC) and density (BMD) were measured by dual energy X-ray absorptiometry (DXA) at the lumbar spine and at the hip and heel ultrasound investigation was performed. Blood was sampled for determination of serum total and free testosterone, total and free estradiol, sex hormone-binding globulin (SHBG), procollagen type I N propeptide, total and carboxylated osteocalcin, tartrate-resistant acid phosphatase 5b, 25-hydroxyvitamin D (25-OHD), and intact parathyroid hormone (iPTH), as well as for studying the XbaI and PvuII polymorphisms of the estrogen receptor gene and the CAG repeat polymorphism of the androgen receptor gene. Urine was collected for the determination of N-terminal cross-linking telopeptide of type I collagen. Muscle strength was measured and Cooper's test was performed. Current exercise, smoking, calcium intake, and alcohol consumption were recorded using a questionnaire. During military service, 15 men experienced a stress fracture, diagnosed with X-ray in 14 and with nuclear magnetic resonance in one man. Those who experienced a fracture were taller than those who did not (P = 0.047). The result of Cooper's test was worse in the fracture group than in the non-fracture group (P = 0.026). Femoral neck and total hip BMC and BMD, adjusted for age, weight, height, exercise, smoking, and alcohol and calcium intake were lower (P = 0.021-0.041) for the fracture group. Stress fractures associated with higher iPTH levels (P = 0.022) but not with lower 25-OHD levels. Bone turnover markers as well as sex hormone and SHBG levels were similar for men with and without stress fracture. There was no difference in the genetic analyses between the groups. In conclusion, tall height, poor physical conditioning, low hip BMC and BMD, as well as high serum PTH level are risk factors for stress fractures in male Finnish military recruits. Given the poor vitamin D status of young Finnish men, intervention studies of vitamin D supplementation to lower serum PTH levels and to possibly reduce the incidence of stress fractures are warranted.

Current concepts of shockwave therapy in stress fractures.

Stress fractures are common painful conditions in athletes, usually associated to biomechanical overloads. Low risk stress fractures usually respond well to conservative treatments, but up to one third of the athletes may not respond, and evolve into high-risk stress fractures. Surgical stabilization may be the final treatment, but it is a highly invasive procedure with known complications. Shockwave treatments (ESWT), based upon the stimulation of bone turnover, osteoblast stimulation and neovascularization by mechanotransduction, have been successfully used to treat delayed unions and avascular necrosis. Since 1999 it has also been proposed in the treatment of stress fractures with excellent results and no complications. We have used focused shockwave treatments in professional athletes and military personnel with a high rate of recovery, return to competition and pain control. We present the current concepts of shockwave treatments for stress fractures, and recommend it as the primary standard of care in low risk patients with poor response to conventional treatments.

Microcrack accumulation at different intervals during fatigue testing of compact bone.

Fatigue damage in bone occurs in the form of microcracks. This microdamage contributes to the formation of stress fractures and acts as a stimulus for bone remodelling. A technique has been developed, which allows microcrack growth to be monitored during the course of a fatigue test by the application of a series of fluorescent chelating agents. Specimens were taken from bovine tibiae and fatigue tested in cyclic compression at a stress range of 80MPa. The specimens were stained before testing with alizarin and up to three other chelating agents were applied during testing to label microcracks formed at different times. Microcracks initiated in interstitial bone in the early part of a specimen's life. Further accumulation of microcracks is then suppressed until the period late in the specimen's life. Microcracks were found to be longer in the longitudinal than in the transverse direction. Only a small proportion of cracks are actively propagating; these are longer than non-propagating cracks. These results support the concept of a microstructural barrier effect existing in bone, whereby cracks initiate easily but slow down or stop at barriers such as cement lines.

Do microcracks decrease or increase fatigue resistance in cortical bone?

Fatigue of cortical bone produces microcracks; it has been hypothesized that these cracks are analogous to those occurring in engineered composite materials and constitute a similar mechanism for fatigue resistance. However, the numbers of these linear microcracks increase substantially with age, suggesting that they contribute to increased fracture incidence among the elderly. To test these opposing hypotheses, we fatigued 20 beams of femoral cortical bone from elderly men and women in load-controlled four point bending having initial strain ranges of 3000 or 5000 microstrain. Loading was stopped at fracture or 10(6) cycles, whichever occurred first, and microcrack density and length were measured in the loaded region and in a control region that was not loaded. We studied the dependence of fatigue life and induced microdamage on initial microdamage, cortical region, subject gender and age, and several other variables. When the effect of modulus variability was controlled, longer fatigue life was associated with higher rather than lower initial crack density, particularly in the medial cortex. The increase in crack density following fatigue loading was greater in specimens from older individuals and those initially having longer microcracks. Crack density increased as much in specimens fatigued short of the failure point as in those that fractured, and microcracks were, on average, shorter in specimens with greater numbers of resorption spaces, a measure of remodeling rate.