Contributions of bone density and geometry to the strength of the human second metatarsal

Cross-sectional size, shape, and estimated strength of the tibia, fibula and second metatarsal in female collegiate-level cross-country runners and soccer players

Bone stress injuries (BSIs) frequently occur in the leg and foot long bones of female distance runners. A potential means of preventing BSIs is to participate in multidirectional sports when younger to build a more robust skeleton. The current cross-sectional study compared differences in tibia, fibula, and second metatarsal diaphysis size, shape, and strength between female collegiate-level athletes specialized in cross-country running (RUN, n = 16) and soccer (SOC, n = 16). Assessments were performed using high-resolution peripheral quantitative computed tomography and outcomes corrected for measures at the radius diaphysis to control for selection bias and systemic differences between groups. The tibia in SOC had a 7.5 % larger total area than RUN, with a 29.4 % greater minimum second moment of area (IMIN) and 8.2 % greater estimated failure load (all p ≤ 0.02). Tibial values in SOC exceeded reference data indicating positive adaptation. In contrast, values in RUN were similar to reference data suggesting running induced limited tibial adaptation. RUN did have a larger ratio between their maximum second moment of area (IMAX) and IMIN than both SOC and reference values. This suggests the unidirectional loading associated with running altered tibial shape with material distributed more in the anteroposterior (IMAX) direction as opposed to the mediolateral (IMIN) direction. Comparatively, SOC had a similar IMAX/IMIN ratio to reference data suggesting the larger tibia in SOC resulted from multiplane adaptation. In addition to enhanced size and strength of their tibia, SOC had enhanced structure and strength of their fibula and second metatarsal. At both sites, polar moment of inertia was approximately 25 % larger in SOC compared to RUN (all p = 0.03). These data support calls for young female athletes to delay specialization in running and participate in multidirectional sports, like soccer, to build a more robust skeleton that is potentially more protected against BSIs.

Enhanced Bone Size, Microarchitecture, and Strength in Female Runners with a History of Playing Multidirectional Sports

PURPOSE

Female runners have high rates of bone stress injuries (BSIs), including stress reactions and fractures. The current study explored multidirectional sports (MDS) played when younger as a potential means of building stronger bones to reduce BSI risk in these athletes.

METHODS

Female collegiate-level cross-country runners were recruited into groups: 1) RUN, history of training and/or competing in cross-country, recreational running/jogging, swimming, and/or cycling only, and 2) RUN + MDS, additional history of training and/or competing in soccer or basketball. High-resolution peripheral quantitative computed tomography was used to assess the distal tibia, common BSI sites (diaphysis of the tibia, fibula, and second metatarsal), and high-risk BSI sites (base of the second metatarsal, navicular, and proximal diaphysis of the fifth metatarsal). Scans of the radius were used as control sites.

RESULTS

At the distal tibia, RUN + MDS ( n = 18) had enhanced cortical area (+17.1%) and thickness (+15.8%), and greater trabecular bone volume fraction (+14.6%) and thickness (+8.3%) compared with RUN ( n = 14; all P < 0.005). Failure load was 19.5% higher in RUN + MDS ( P < 0.001). The fibula diaphysis in RUN + MDS had an 11.6% greater total area and a 11.1% greater failure load (all P ≤ 0.03). At the second metatarsal diaphysis, total area in RUN + MDS was 10.4% larger with greater cortical area and thickness and 18.6% greater failure load (all P < 0.05). RUN + MDS had greater trabecular thickness at the base of the second metatarsal and navicular and greater cortical area and thickness at the proximal diaphysis of the fifth metatarsal (all P ≤ 0.02). No differences were observed at the tibial diaphysis or radius.

CONCLUSIONS

These findings support recommendations that athletes delay specialization in running and play MDS when younger to build a more robust skeleton and potentially prevent BSIs.

Micro-CT analysis of the Lisfranc complex reveals higher bone mineral density in dorsal compared to plantar regions

Injuries to the Lisfranc complex may require surgical fixation, the stability of which may be correlated with bone mineral density (BMD). However, there is limited research on regional BMD variations in the Lisfranc complex. This study used quantitative micro-CT to characterize regional BMD in the four bones (medial cuneiform, intermediate cuneiform, first metatarsal, and second metatarsal) of this complex. Twenty-four cadaveric specimens were imaged with a calibration phantom using micro-CT. Each bone was segmented and divided into eight regions based on an anatomical coordinate system. BMD for each octant was calculated using scan-specific calibration equations and average image intensity. Differences between regions were analyzed using ANOVA with post hoc analysis and differences between groups of four octants in each plane were analyzed with t-tests with significance level α = 0.05. The highest density region in the medial cuneiform was the distal-dorsal-lateral and dorsal regions showed significantly higher BMD than plantar regions. The intermediate cuneiform had the highest density in the distal-dorsal-medial region and the dorsal and medial regions had higher BMD than the plantar and lateral regions, respectively. The densest region of the first metatarsal was the distal-dorsal-lateral and distal regions had significantly higher BMD than proximal regions. In the second metatarsal, the distal-dorsal-medial region had the highest density, and the distal, dorsal, and medial regions had significantly higher BMD than the proximal, plantar, and lateral regions, respectively. The predominant finding was a pattern of increased density in the dorsal bone regions, which may be relevant in the surgical management of Lisfranc injuries.

A Narrative Review of Metatarsal Bone Stress Injury in Athletic Populations: Etiology, Biomechanics, and Management

Metatarsal bone stress injuries (BSIs) are common in athletic populations. BSIs are overuse injuries that result from an accumulation of microdamage that exceeds bone remodeling. Risk for metatarsal BSI is multifactorial and includes factors related to anatomy, biology, and biomechanics. In this article, anatomic factors including foot type, metatarsal length, bone density, bone geometry, and intrinsic muscle strength, which each influence how the foot responds to load, are discussed. Biologic factors such as low energy availability and impaired bone metabolism influence the quality of the bone. Finally, the influence of biomechanical loads to bone such as peak forces, load rates, and loading cycles are reviewed. General management of metatarsal BSI is discussed, including acute care, rehabilitation, treatment of refractory metatarsal BSI, and evaluation of healing/return to sport. Finally, we identify future research priorities and emerging treatments for metatarsal BSI.

Bone density of the calcaneus correlates with radiologic and clinical outcomes after calcaneal fracture fixation

BACKGROUND

This study aimed to determine whether bone density correlates with radiologic and clinical outcomes after screw fixation of displaced intra-articular calcaneal fractures (DIACF) with the sinus tarsi approach.

MATERIALS AND METHODS

We retrospectively evaluated 43 consecutive cases of unilateral DIACF between March 2015 and December 2017. Radiologic evaluations were performed using preoperative, postoperative, and last follow-up calcaneal lateral and axial radiographs. In all patients, preoperative CT scanning of both injured and uninjured calcaneus were performed at one scanning and dual x-ray absorptiometry (DXA) scans were obtained. Hounsfield unit (HU) measurement values were determined by placing an elliptical region of interest confined to the cancellous region of the uninjured calcaneus. Clinical outcomes were assessed at a minimum of 12 months postoperatively using Foot and Ankle Outcome Scores (FAOS).

RESULTS

Mean HU values of the uninjured calcaneus significantly correlated with bone mineral density scores obtained from DXA scans of the lumbar and femur (Spearman ρ = 0.656 - 0.748; p < 0.001 for both). Decreased HU values of the uninjured calcaneus significantly correlated with decreased Böhler's angle and widening of calcaneal width from postoperative to last follow-up. (Pearson r = 0.348, p = 0.022; Pearson r = -0.582, p < 0.001, respectively). Increased HU values of the uninjured calcaneus significantly correlated with improved clinical outcomes in three of five FAOS domains, including activities of daily living, sports, and quality of life (beta = 0.283 - 0.322; p < 0.05 for all).

CONCLUSION

Decreased preoperative bone density significantly correlated with decreased Böhler's angle, widening of calcaneal width, and inferior short-term clinical outcomes after screw fixation of DIACF. By quantifying bone density using HU value in area where DXA cannot be performed, such foot bones, determining whether different fixation methods or systemic treatments can be tailored to bone density could help in optimizing clinical outcomes.

LEVEL OF EVIDENCE

Level III, Retrospective case series.

Sex differences in the patterning of age-related bone loss in the human hallucal metatarsal in rural and urban populations

OBJECTIVES

Age-degenerative features of the metatarsals are poorly known despite the importance of metatarsal bone properties for investigating mobility patterns. We assessed the role of habitual activity in shaping the patterning and magnitude of sexual dimorphism in age-related bone loss in the hallucal metatarsal.

MATERIALS AND METHODS

Cross-sections were extracted at midshaft from micro-computed tomography scan models of individuals from medieval rural (Abingdon Vineyard) and early industrial urban (Spitalfields) settings (n = 71). A suite of cross-sectional geometry dimensions and biomechanical properties were compared between populations.

RESULTS

The rural group display generally stronger and larger metatarsals that show a greater capacity to resist torsion and that have comparatively greater bending strength along the medio-lateral plane. Men in both groups show greater values of cortical area than women, but only in the urban group do men show lower magnitudes of age-related decline compared to females. Women in rural and urban populations show different patterns of age-related decline in bone mass, particularly old women in the urban group show a marked decline in cortical area that is absent for women in the rural group.

DISCUSSION

Lifetime exposure to hard, physical activity in an agricultural setting has contributed to the attainment of greater bone mass and stronger bones in young adults. Furthermore, over the life-course, less of this greater amount of bone is lost, such that sustained activity levels may have acted to buffer against age-related decline, and this is most pronounced for women, who are expected to experience greater bone loss later in life than men.

A multiscale model to predict current absolute risk of femoral fracture in a postmenopausal population

Osteoporotic hip fractures are a major healthcare problem. Fall severity and bone strength are important risk factors of hip fracture. This study aims to obtain a mechanistic explanation for fracture risk in dependence of these risk factors. A novel modelling approach is developed that combines models at different scales to overcome the challenge of a large space-time domain of interest and considers the variability of impact forces between potential falls in a subject. The multiscale model and its component models are verified with respect to numerical approximations made therein, the propagation of measurement uncertainties of model inputs is quantified, and model predictions are validated against experimental and clinical data. The main results are model predicted absolute risk of current fracture (ARF0) that ranged from 1.93 to 81.6% (median 36.1%) for subjects in a retrospective cohort of 98 postmenopausal British women (49 fracture cases and 49 controls); ARF0 was computed up to a precision of 1.92 percentage points (pp) due to numerical approximations made in the model; ARF0 possessed an uncertainty of 4.00 pp due to uncertainties in measuring model inputs; ARF0 classified observed fracture status in the above cohort with AUC = 0.852 (95% CI 0.753-0.918), 77.6% specificity (95% CI 63.4-86.5%) and 81.6% sensitivity (95% CI 68.3-91.1%). These results demonstrate that ARF0 can be computed using the model with sufficient precision to distinguish between subjects and that the novel mechanism of fracture risk determination based on fall dynamics, hip impact and bone strength can be considered validated.

Computed tomography derived bone density measurement in the diabetic foot

Background

The accurate and reliable measurement of foot bone density is challenging and there is currently no gold standard technique. Such measurement is particularly valuable in populations at risk of foot bone pathology such as in those with long term diabetes. With research and development, computed tomography may prove to be a useful tool for this assessment. The aim of this study was to establish the reliability of a novel method of foot bone density measurement in people with diabetes using computed tomography.

Methods

Ten feet in people with diabetes were scanned with computed tomography twice with repositioning. Bone density (in Hounsfield units) was assessed in the trabecular and cortical bone in all tarsals and metatarsals. Reliability was assessed with intra-class correlation coefficients (95% confidence intervals), limits of agreement and standard error of measurement.

Results

The reliability of the trabecular density of most bones was excellent with intra-class correlation coefficients ranging from 0.68 to 0.91. Additionally, cortical bone density showed fair to good reliability at the talus (0.52), calcaneus (0.59), navicular (0.70), cuboid (0.69), intermediate cuneiform (0.46) and first metatarsal (0.61).

Conclusions

The study established the reliability of a practical method of assessing the trabecular and cortical foot bone density using computed tomography scanning. This methodology may be useful in the investigation of foot bone disease occurring in diabetes and its early diagnosis, intervention and assessment of treatment efficacy. Further development of this method is warranted.

Electronic supplementary material

The online version of this article (doi:10.1186/s13047-017-0192-7) contains supplementary material, which is available to authorized users.

A THREE-DIMENSIONAL MORPOLOGICAL MEASUREMENT AND IN VITRO BIOMECHANICAL STUDY OF METATARSALS

Stress fracture of the metatarsal (MT) is often reported clinically. This study was aimed to measure and compare the three-dimensional (3D) morphological structure of five MTs, and investigate the in vitro biomechanics of five MTs under simulated stance phase. A total of seven foot-ankle samples of human cadavers were collected for this experiment. All samples were CT-scanned and 3D re-constructed for digital measurements. To simulate the stance phase, each sample was vertically loaded with 700-N through a material testing machine. The 3D-reconstruction-based measurement showed significant differences of the shaft length, vertical height, and inclination angle between the second MT and four others. Experimental strain measurements at dorsal MTs along the principal axis are all compressive. The values are respectively [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] micro-strain from the first to fifth MTs. This study proposed a new load condition of plantar-flexed simply supported beam to describe the MT loading mechanism. The second and third MTs have higher risk of stress fracture due to combined effects of inhomogeneous load distribution, unfavorable geometry and structure, and limited joint motion. This finding would be helpful for design of protective equipment.

Reproducibility of a peripheral quantitative computed tomography scan protocol to measure the material properties of the second metatarsal

Background

Peripheral quantitative computed tomography (pQCT) is an established technology that allows for the measurement of the material properties of bone. Alterations to bone architecture are associated with an increased risk of fracture. Further pQCT research is necessary to identify regions of interest that are prone to fracture risk in people with chronic diseases. The second metatarsal is a common site for the development of insufficiency fractures, and as such the aim of this study was to assess the reproducibility of a novel scanning protocol of the second metatarsal using pQCT.

Methods

Eleven embalmed cadaveric leg specimens were scanned six times; three times with and without repositioning. Each foot was positioned on a custom-designed acrylic foot plate to permit unimpeded scans of the region of interest. Sixty-six scans were obtained at 15% (distal) and 50% (mid shaft) of the second metatarsal. Voxel size and scan speed were reduced to 0.40 mm and 25 mm.sec^-1. The reference line was positioned at the most distal portion of the 2^nd metatarsal. Repeated measurements of six key variables related to bone properties were subject to reproducibility testing. Data were log transformed and reproducibility of scans were assessed using intraclass correlation coefficients (ICC) and coefficients of variation (CV%).

Results

Reproducibility of the measurements without repositioning were estimated as: trabecular area (ICC 0.95; CV% 2.4), trabecular density (ICC 0.98; CV% 3.0), Strength Strain Index (SSI) - distal (ICC 0.99; CV% 5.6), cortical area (ICC 1.0; CV% 1.5), cortical density (ICC 0.99; CV% 0.1), SSI – mid shaft (ICC 1.0; CV% 2.4). Reproducibility of the measurements after repositioning were estimated as: trabecular area (ICC 0.96; CV% 2.4), trabecular density (ICC 0.98; CV% 2.8), SSI - distal (ICC 1.0; CV% 3.5), cortical area (ICC 0.99; CV%2.4), cortical density (ICC 0.98; CV% 0.8), SSI – mid shaft (ICC 0.99; CV% 3.2).

Conclusions

The scanning protocol generated excellent reproducibility for key bone properties measured at the distal and mid-shaft regions of the 2^nd metatarsal. This protocol extends the capabilities of pQCT to evaluate bone quality in people who may be at an increased risk of metatarsal insufficiency fractures.

Pedal bone density, strength, orientation, and plantar loads preceding incipient metatarsal fracture after charcot neuroarthropathy: 2 case reports

STUDY DESIGN

Case report.

BACKGROUND

Charcot neuroarthropathy is a progressive, noninfective, inflammatory destruction of bones and joints leading to foot deformities and plantar ulceration. Though individuals with Charcot neuroarthropathy typically have low areal bone mineral density, little is known regarding changes in volumetric bone mineral density (vBMD), bone geometry, joint malalignment, and biomechanical loads preceding fracture.

CASE DESCRIPTION

Two women, aged 45 and 54 years at the onset of an acute, nonfracture Charcot neuroarthropathy event, received regular physical therapy with wound care and total-contact casting. Both enrolled in a larger research study that included plantar pressure assessment and quantitative computed tomography at enrollment and 3, 6, and 12 months later. The women sustained mid-diaphyseal fifth metatarsal fracture 10 to 11 months after enrollment. Quantitative computed tomography image-analysis techniques were used to measure vBMD; bone geometric indices reflecting strength in compression, bending, and cortical buckling; and 3-D bone-to-bone orientation angles reflecting foot deformity.

OUTCOMES

Fifth metatarsal mid-diaphyseal vBMD decreased during offloading treatment from 0 to 3 months, then increased to above baseline levels by 6 months. All geometric strength indices improved from baseline through 6 months. Plantar loading in the lateral midfoot increased preceding fracture, concomitant with alterations in bone orientation angles, which suggest progressive development of metatarsus adductus and equinovarus foot deformity.

DISCUSSION

Fractures may occur when bone strength decreases or when biomechanical loading increases. Incipient fracture was preceded by increased loading in the lateral midfoot but not by reductions in vBMD or geometric strength indices, suggesting that loading played a greater role in fracture. Moreover, the progression of foot deformities may be causally linked to the increased plantar loading.

LEVEL OF EVIDENCE

Prognosis, level 4.

Impact of Charcot neuroarthropathy on metatarsal bone mineral density and geometric strength indices

Charcot neuroarthropathy (CN), an inflammatory condition characterized by rapid and progressive destruction of pedal bones and joints, often leads to deformity and ulceration in individuals with diabetes mellitus (DM) and peripheral neuropathy (PN). Repetitive, unperceived joint trauma may trigger initial CN damage, causing a proinflammatory cascade that can result in osteolysis and contribute to subsequent neuropathic fracture. We aimed to characterize osteolytic changes related to development and progression of CN by measuring bone mineral density (BMD) and geometric strength indices using volumetric quantitative computed tomography. Twenty individuals with DM+PN were compared to twenty age-, sex-, and race-matched individuals with DM+PN and acute CN. We hypothesized that individuals with acute CN would have decreased BMD and decreased total area, cortical area, minimum section modulus, and cortical thickness in the diaphysis of the second and fifth metatarsals. Results showed BMD was lower in both involved and uninvolved feet of CN participants compared to DM+PN participants, with greater reductions in involved CN feet compared to uninvolved CN feet. There was a non-significant increase in total area and cortical area in the CN metatarsals, which helps explain the finding of similar minimum section modulus in DM+PN and CN subjects despite the CN group's significantly lower BMD. Larger cortical area and section modulus are typically considered signs of greater bone strength due to higher resistance to compressive and bending loads, respectively. In CN metatarsals, however, these findings may reflect periosteal woven bone apposition, i.e., a hypertrophic response to injury rather than increased fracture resistance. Future research using these techniques will aid further understanding of the inflammation-mediated bony changes associated with development and progression of CN and other diseases.

Dual-energy X-ray absorptiometry of human metatarsals: precision, least significant change and association to ex vivo fracture force

BACKGROUND

Fractures are common in foot bones, but clinicians lack adequate indices of bone strength.

OBJECTIVES

We used dual-energy X-ray absorptiometry (DXA) to measure bone mineral density (BMD) and content (BMC) of excised human metatarsals, determined intra- and inter-rater measurement precision, and assessed associations between BMD/BMC and ex vivo bone fracture strength.

METHODS

Two raters each made two measurements of whole-bone and sub-regional BMD and BMC in both second and third metatarsals from 10 cadavers. Variance components analysis was used to assess variability attributable to repeat measurements, raters, sub-regions, bones, sides, and cadavers. Root-mean-square standard deviation (RMS-SD) and least-significant change (LSC) were used to assess rater precision and ultimate forces during 3-point bending were tested for correlations with BMD and BMC.

RESULTS

Variation due to repeat measurements and rater was low (<1% combined) for BMD and BMC. RMS-SD for whole metatarsal BMD of both metatarsals ranged from 0.004 to 0.010 g/cm(2) and 0.062 to 0.086 g for BMC. Whole metatarsal and sub-region BMD and BMC were strongly correlated to ex vivo fracture force (r(2)=0.67-0.93).

CONCLUSIONS

DXA measurements of BMD and BMC have high intra- and inter-rater precision and are strongly correlated to ex vivo bone strength.

Predicting ex vivo failure loads in human metatarsals using bone strength indices derived from volumetric quantitative computed tomography

We investigated the capacity of bone quantity and bone geometric strength indices to predict ultimate force in the human second metatarsal (Met2) and third metatarsal (Met3). Intact lower extremity cadaver samples were measured using clinical, volumetric quantitative computed tomography (vQCT) with positioning and parameters applicable to in vivo scanning. During processing, raw voxel data (0.4mm isotropic voxels) were converted from Hounsfield units to apparent bone mineral density (BMD) using hydroxyapatite calibration phantoms to allow direct volumetric assessment of whole-bone and subregional metatarsal BMD. Voxel data were realigned to produce cross-sectional slices perpendicular to the longitudinal axes of the metatarsals. Average mid-diaphyseal BMD, bone thickness, and buckling ratio were measured using an optimized threshold to distinguish bone from non-bone material. Minimum and maximum moments of inertia and section moduli were measured in the mid-diaphysis region using both a binary threshold for areal, unit-density measures and a novel technique for density-weighted measures. BMD and geometric strength indices were strongly correlated to ultimate force measured by ex vivo 3-point bending. Geometric indices were more highly correlated to ultimate force than was BMD; bone thickness and density-weighted minimum section modulus had the highest individual correlations to ultimate force. Density-weighted geometric indices explained more variance than their binary analogs. Multiple regression analyses defined models that predicted 85-89% of variance in ultimate force in Met2 and Met3 using bone thickness and minimum section modulus in the mid-diaphysis. These results have implications for future in vivo imaging to non-invasively assess bone strength and metatarsal fracture risk.

MECHANICAL PROPERTIES OF THE HUMAN METATARSAL BONES

Despite the incidence of metatarsal fractures and the associated risk of significant disability, little is known about the biomechanical properties (strength and stiffness) of metatarsal bones. In most cases a single metatarsal bone (first, second and fifth) has been investigated. An extensive investigation of the biomechanical properties of the metatarsal bones is essential in the understanding and prevention of metatarsal injuries. Entire sets of metatarsal bones from four feet were tested. The first foot was used to fine-tune the testing set-ups. To measure the stiffness, each metatarsal bone was subjected to non-destructive four-point-bending in the sagittal and transverse planes, axial compression and torsion. Strain was measured at two locations. To measure the strength, each metatarsal bone was tested to failure in torsion. Significant differences (p < 0.0001) existed among the stiffness of the five metatarsal bones: (i) in torsion the first metatarsal bone was 2–3 times stiffer than the others; (ii) in four-point-bending and axial compression this difference was less pronounced than in torsion; (iii) differences were smaller among the other metatarsal bones; (iv) the second metatarsal bone was less stiff than the third and fourth in bending. The second, third and fourth metatarsal bones were stiffer in the sagittal than in the transverse plane (p < 0.0001). Conversely, there was no significant difference between the two planes of bending for the first and fifth bones. During destructive testing, all metatarsal bones exhibited a linear elastic behavior and brittle failure. The torsional strength at failure ranged between 1.9 Nm and 6.9 Nm. The first metatarsal bone was stronger than all the others. Stiffness in different loading conditions and failure were measured and compared for all metatarsal bones. These data corroborate previous biomechanical studies concerning the role and load sharing of the different metatarsal bones.

Three-dimensional ankle kinematics and kinetics during running in women

Stress fractures are common in athletics and are more prevalent in women. The current literature has not identified a reason for this gender difference. We hypothesized that females with a history of a second/third metatarsal stress fracture will demonstrate differences in ankle kinematics, kinetics and ground reaction forces when compared with a group of age-matched females with no stress fracture history. A total of 15 control females and nine females with a history of a second/third metatarsal stress fracture were asked to run at 3.3m/s+/-5% along a 10-m runway. Kinematics and kinetics were obtained using an 8-camera motion analysis system (240Hz) and two force plates (1200Hz). Significant differences existed in height and weight between the groups. No other statistically significant differences existed between the fracture group and the control group. Kinematic measurements do not differ significantly between women with a history of second/third metatarsal stress fracture and female control subjects. The reported kinematic and kinetic measurements do not appear to be influenced in subjects with metatarsal stress fractures, which likely result from the complex relationships between the joints in the foot and ankle. The development of second/third metatarsal stress fractures could result more from over training or changes in plantar loading instead of changes in lower extremity joint kinematics while running.

Second metatarsal stress fracture in sport: comparative risk factors between proximal and non-proximal locations

BACKGROUND

Stress fractures of the second metatarsal are common injuries in athletes and military recruits. There are two distinct areas in the second metatarsal where stress fractures develop: one proximal (at the base) and the other non-proximal (distal). Diagnosis can be difficult, and there is a difference in prognosis and treatment of the two types of stress fracture. Therefore differentiation of fracture location is warranted. Differences in risk factors and clinical outcomes between proximal and non-proximal stress fractures have not been studied.

OBJECTIVE

To determine whether different risk factors and/or clinical outcomes associated with proximal and non-proximal stress fractures of the second metatarsal exist.

METHODS

Patients diagnosed with proximal stress fractures of the second metatarsal were included in the study. Retrospectively, an age-matched control group with a non-proximal stress fracture was selected for comparison. Statistical analysis involved bivariate comparisons of demographic variables and clinical measurement between the two groups.

RESULTS

Patients with proximal stress fractures were more likely to be chronically affected, usually exhibited an Achilles contracture, showed differences in length of first compared with second metatarsal, were more likely to experience multiple stress fractures, and exhibited low bone mass. In addition, a high degree of training slightly increased the risk of a non-proximal fracture, whereas low training volume was associated with a proximal stress fracture.

CONCLUSION

The signs, symptoms and clinical findings associated with proximal metatarsal stress fractures are different from those of non-proximal stress fractures.

Stress fractures of the second metatarsal base occur in nondancers

Stress fractures of the base of the second metatarsal are common in ballet dancers and essentially are unreported in nondancers. We presumed base of the second metatarsal stress fractures in nondancers occur in a wide variety of individuals regardless of demographics, are highly associated with athletic activities, and have specific examination findings and poor clinical outcomes. Using a retrospective chart review, we identified 12 stress fractures at the base of the second metatarsal (nine patients) in nondancers. Our review suggests second metatarsal base stress fractures occur in nondancers in a diverse population, and nonoperative treatment provides limited success. Advanced radiographic study, specifically MRI, is useful to assist the early diagnosis and prognostication. All of the stress fractures were treated nonoperatively; six fractures (50%) developed nonunion and five underwent subsequent surgery. The surgery for nonunion provided successful outcomes; however, risk factors such as low bone mass and comorbidities may have played important roles in the prognosis.