Pairs Of Humeri Research Articles

Bilateral Asymmetry of Humeral Torsion and Length in African Apes and Humans

Few studies have directly compared human and African ape upper limb skeletal asymmetries despite the potential such comparisons have for understanding the origins of functional lateralization in humans and non-human primates. Here, we report the magnitude and direction of asymmetries in humeral torsion and humeral length in paired humeri of 40 Gorilla gorilla, 40 Pan troglodytes and 40 Homo sapiens. We test whether absolute and directional asymmetries differ between measurements, species and sexes. Our results show that humans are unique in being lateralized to the right for both measurements, consistent with human population-level handedness patterns, while apes show no significant directionality at the species level in either measurement. However, absolute torsion asymmetries in apes occur in the same magnitude as in humans, suggesting the existence of functional lateralization at the individual level.

Biomechanical in vitro assessment of screw augmentation in locked plating of proximal humerus fractures

IntroductionProximal humerus fracture fixation can be difficult because of osteoporosis making it difficult to achieve stable implant anchorage in the weak bone stock even when using locking plates. This may cause implant failure requiring revision surgery. Cement augmentation has, in principle, been shown to improve stability. The aim of this study was to investigate whether augmentation of particular screws of a locking plate aimed at a region of low bone quality is effective in improving stability in a proximal humerus fracture model. Materials and methodsTwelve paired human humerus specimens were included. Quantitative computed tomography was performed to determine bone mineral density (BMD). Local bone quality in the direction of the six proximal screws of a standard locking plate (PHILOS, Synthes) was assessed using mechanical means (DensiProbe™). A three-part fracture model with a metaphyseal defect was simulated and fixed with the plate. Within each pair of humeri the two screws aimed at the region of the lowest bone quality according to the DensiProbe™ were augmented in a randomised manner. For augmentation, 0.5ml of bone cement was injected in a screw with multiple outlets at its tip under fluoroscopic control. A cyclic varus-bending test with increasing upper load magnitude was performed until failure of the screw–bone fixation. ResultsThe augmented group withstood significantly more load cycles. The correlation of BMD with load cycles until failure and BMD with paired difference in load cycles to failure showed that augmentation could compensate for a low BMD. Discussion and conclusionThe results demonstrate that augmentation of screws in locked plating in a proximal humerus fracture model is effective in improving primary stability in a cyclic varus-bending test. The augmentation of two particular screws aimed at a region of low bone quality within the humeral head was almost as effective as four screws with twice the amount of bone cement. Screw augmentation combined with a knowledge of the local bone quality could be more effective in enhancing the primary stability of a proximal humerus locking plate because the effect of augmentation can be exploited more effectively limiting it to the degree required.

Could BMD Reflect the Real Change in Human Bone Mineral?

Background: Bone mineral density (BMD) is an important index in diagnosing osteoporosis and other metabolic bone diseases, predicting fractures, and monitoring treatment. Dual-energy X-ray absorptiometry (DXA) is most widely used technique for assessments of BMD and considered as the gold standard for the minumum exposure to radiation, low cost, high reproducibility, and ease of use. Author performed an experimental study to determine the relationship between the change in BMD measured by DXA and real change in mineral of human long bone. Materials and Methods: A pair of humeri and femora from one male cadaver was cut into specimen about half in length. Three specimens from a pair of humerus and 4 specimens from a pair of femur were immersed into 1N HCl from 10 minutes to maximum 70 minutes with 10 minutes’ interval for different level of demineralization. All 7 specimens were checked with BMD using by DXA (GE-Lunar Prodigy) and analysed respectively. The amount of calcium and phosphorus both from demineralized and normal area were measured and expressed in percentage of demineralizatioin. Results: As demineralization was going on with time of immersion into HCl, there was statistically significant correlation between the change of BMD and real change of calcium amount (?50.65) in humerus, and also in femur (?50.63). There was statistically significant correlation only in femur between BMD and phosphorus (?50.77), and not in humerus (?50.42). In summary, there was a high linear regression between BMD and real bone mineral with minimum of 89% and maximum of 97% as coefficient of determination (R-Square; R2) (p! 0.05). Through correlation analysis, correlation coefficient (?) between BMD measured by DXA and mineral of human long bone showed a high correlation as maximum of 0.84 (p!0.05). Conclusions: Our study showed a statistically significant high relationship between BMD measured by DXA and mineral of human long bone. Therefore, the measurement of DXA is considered to reflect the real change of mineral in human long bone as well as that of BMD. The limitation of this study was that it was based on artificially induced demineralization only one pair of cadaveric humerus and femur so that vertebrae were excluded.

The supratrochlear foramen of the humerus in a south african dry bone sample

The supratrochlear foramen (STF) of the humerus is the aperture that forms when the septum separating the coronoid and olecranon fossa is perforated. There are no known studies in the literature on the STF among various South African ethnic groups. The presence and shapes of the STF were established by visual observation from a sample of 538 skeletonized individuals with paired humeri (1,076) and of equal numbers between the sexes. Measurements of the transverse (TD) and vertical (VD) distance of the STF were obtained using extended jaw calipers. An osteometric board was used to measure the epicondylar breadth (EB). Sliding calipers were used to measure the distance of the medial epicondyle to medial aspect of the STF (MB) and that of the lateral epicondyle to lateral border of the STF (LB). The prevalence of STF in the South African population was 32.5% and predominantly on the left with the highest incidence among the Sotho population (41%) and the lowest incidence in Whites (16%). Females (19.5%) had a higher frequency of the STF compared with males (13%). The STF occurred in oval (136), round (77), triangular (9), and irregular (34) shapes. The average EB in this study was 56.1 mm, whereas the average MB and LB were 25.4 mm and 26.3 mm, respectively. The average TD was 6.3 mm and average VD was 4.3 mm. These findings may be of clinical significance to surgeons and osteologists and may have anthropological or forensic importance.

Biomechanical analysis of a novel locking plate with smooth pegs versus a conventional locking plate with threaded screws for proximal humerus fractures

Repair of proximal humeral fractures with locking plates has greatly improved outcomes. However, an alarming rate of complications including screw cutout and impingement under the acromion has recently been reported. A novel locking plate with smooth pegs was developed to reduce these risks. The purpose of this study was to compare these 2 fixation methods with a cadaveric biomechanical study. Fourteen pairs of cadaveric proximal humeri (mean age, 77 years) were harvested, and bone density was measured. Osteosynthesis was performed on each pair using either a locking plate with threaded screws (TS group) or smooth pegs (SP group) on the contralateral side. Seven pairs of humeri were tested for cyclic bending, and 7 pairs for cyclic torsional evaluation: TS bending, SP bending, TS torsion, and SP torsion. The bending protocol consisted of cyclically loading to a maximum of 7.5 Nm bending moment for 10,000 cycles. The torsion protocol consisted of ±2 Nm of axial torque for 10,000cycles. Surgical neck fractures were simulated by excising a 10-mm wedge of bone. No implant failure or screw cutout was observed in any of the groups tested. Under bending loads, mean displacement of the distal fragment was significantly less for the SP group than that for the TS group over 5,000 cycles. In torsion tests, no significant differences were observed between the 2 fixation methods. The SP group demonstrated superior biomechanical characteristics to the TS group in regards to cyclic bending.

The Challenge of Managing Change

Multi-fragmented fractures of the proximal humerus are difficult to treat, especially in the case of osteoporotic bone. Intra-operative risks include cartilage damage when inserting multiple screws. A common post-operative complication is distal-varus collapse of the head. The aim of this study was to investigate if an Innovative technique (reduced number of screws and injection of a beta-TCP additivated partially resorbable cement) provides the same or better stability of the reconstructed head compared to the Standard technique (using more screws). A four-fragment fracture was simulated in six pairs of humeri, with partial removal of the cancellous bone to simulate osteoporotic “eggshell” defect. One humerus of each pair was repaired with a Standard (locking plate, 2 cortical and 6 locking screws), and the other with the Innovative technique (same plate, 2 cortical and only 3 locking screws, plus cement injection). The reconstructed specimens were subjected to a biomechanical test where a cyclic force of increasing amplitude was applied axially until failure. The Innovative reconstructions withstood a force 3.49 times larger than the contralateral Standard reconstructions before failure started. The maximum force before final collapse for the Innovative reconstructions was 4.24 times larger than the contralateral Standard reconstructions. These differences were statistically significant. The Innovative reconstructions, based on fewer screws and beta-TCP additivated acrylic cement, showed positive results, demonstrating better biomechanical properties compared to the Standard reconstructions. These laboratory findings, along with the advantages of a reduced number of screws, may help perform a surgically safer, and more effective procedure in osteoporotic patients.

Retrograde nailing versus locking plate osteosynthesis of proximal humeral fractures: a biomechanical study

In locking plate osteosynthesis of proximal humeral fractures, secondary varus malalignment is a specific complication. Retron nails (Tantum AG, Neumunster, Germany), among others, have been designed to improve medial support of the calcar humeri. The aim of our biomechanical study was to examine whether Retron nails provide increased stiffness for axial loads and adequate stiffness for torsional loads when compared with Philos plates (Synthes AG, Umkirch, Germany). Twenty-two fresh-frozen paired humeri were collected. After potting the specimens, intact bones were exposed to sinusoidal axial (10-120 N) and torsional (±2.5 Nm) loading for 8 cycles to calculate the initial stiffness and exclude pairs with differences. Afterward, an unstable proximal humeral fracture (AO 11-A3) was created by means of an oscillating saw, and the respective osteosynthesis devices were implanted. After another 4 cycles, initial changes in stiffness were measured. Subsequently, all specimens were tested for 1,000 cycles of loading before final stiffness was assessed. We found no statistically significant differences between Retron and Philos specimens after 4 or 1,000 cycles of loading. Our study suggests that retrograde nailing provides sufficient stability for axial and torsional loading in 2-part fractures of proximal humeri.

Biomechanical Evaluation of 3-Part Proximal Humerus Fractures: A Cadaveric Study

Proximal humerus fractures occur frequently, and treatment remains controversial. This study compares stiffness in axial loading for 3 methods of fixation (locking compression plate, standard (nonlocking) proximal humerus plate, and blade plate) in a 3-part proximal humerus fracture model. Twelve paired proximal humeri were obtained from embalmed human cadavers and separated into 3 groups. Osteotomies of the surgical neck and greater tuberosity were created to simulate a 3-part proximal humerus fracture. After fixation, constructs were axially loaded in 20 degrees of abduction for 200 cycles in an Instron materials testing machine (Norwood, Massachusetts). The blade plate (mean, 146.87+/-28.9 N/mm) demonstrated 29% more mean stiffness than the standard plate (mean, 113.0+/-22.3 N/mm; P=.19). The locking compression plate (mean, 130.71+/-39.2 N/mm) exhibited 15% greater stiffness compared to the standard plate in our 3-part model (P=.58). The blade plate demonstrated 12% greater stiffness than the locking compression plate (P=.64). There was no significant difference in mean stiffness between the fixed-angle devices and the standard plate. Future in vitro and clinical studies of plate devices for proximal humerus fractures would be worthwhile to determine the benefits and limitations of various implants for specific types of fractures, including clinical performance and cost of care.

A biomechanical comparison of 3.5 locking compression plate fixation to 3.5 limited contact dynamic compression plate fixation in a canine cadaveric distal humeral metaphyseal gap model

3.5 locking compression plate (LCP) fixation was compared to 3.5 limited contact dynamic compression plate (LC-DCP) fixation in a canine cadaveric, distal humeral metaphyseal gap model. Thirty paired humeri from adult, large breed dogs were separated into equal groups based on testing: static compression, cyclic compression, and cyclic torsion. Humeral constructs stabilised with LCP were significantly stiffer than those plated with LC-DCP when loaded in static axial compression (P = 0.0004). When cyclically loaded in axial compression, the LCP constructs were significantly less stiff than the LC-DCP constructs (P = 0.0029). Constructs plated with LCP were significantly less resistant to torsion over 500 cycles than those plated with LC-DCP (P<0.0001). The increased stiffness of LCP constructs in monotonic loading compared to constructs stabilised with non-locking plates may be attributed to the stability afforded by the plate-screw interface of locking plates. The LCP constructs demonstrated less stiffness in dynamic testing in this model, likely due to plate-bone offset secondary to non-anatomic contouring and occasional incomplete seating of the locking screws when using the torque-limiting screw driver. Resolution of these aspects of LCP application may help improve the stiffness of fixation in fractures modeled by the experimental set-up of this investigation.

An anthropometric study of the bilateral anatomy of the humerus

The purpose of this study was to describe the extramedullary humeral morphology in paired humeri to determine whether geometric differences exist from side to side in the same individual. The anatomic characteristics of 28 paired, dry cadaveric humeri were measured by use of an electromagnetic tracking system. Of the characteristics examined, only the humeral head height was significantly different between right and left humeri in the same individual (P < .005). Most of the characteristics had excellent intra-specimen repeatability. In conclusion, there are few significant differences between contralateral humeral anatomic characteristics. Therefore, the uninjured contralateral humerus can provide a reasonable approximation to the native geometry of the fractured humerus and should be a reliable model for measuring parameters related to implant geometry and optimal positioning during hemiarthroplasty for the treatment of proximal humeral fractures.

Locked vs. unlocked plate osteosynthesis of the proximal humerus – A biomechanical study

Locked plates (internal fixators) have been found to be an optimal method for the fixation in proximal humeral fractures. In a biomechanical cadaver study the difference between locked and non-locked osteosyntheses was investigated. Paired humeri were harvested, bone density measured. Locked internal fixators were mounted on one specimen; identical plate-screw-systems without locking mechanism applied to the contralateral specimen for comparison. After that, a transverse subcapital osteotomy was performed. With 7 pairs of humeri static tests with increasing axial loads and with 5 pairs dynamic tests with 10 N preload and 80 N maximal axial load for up to 1 million cycles were performed. In the static experiments the elastic stiffness of the construct was 74% higher in the locked group (median 80 N/mm, quartile range 77-86 N/mm) compared with the non-locked group (46 N/mm, 35.5-56.5 N/mm). The difference was statistically significant (Wilcoxon test for paired samples, P<0.05). Similarly, the linear range until failure was definitely extended in the locked group by 64% (92 N, 89-98 N vs. 56 N, 36.5-73.5 N, P<0.05). Under dynamic loading the non-locked group showed fixation failures between 97,000 and 500,000 cycles. In the locked group no failure was observed until the end of the experiment at 1 million cycles (P<0.0.5). The final deformation was found to be 1 mm (median, quartil range 1.0-1.2 mm) in the non-locked group and 0.3 mm (0.2-0.3 mm) in the locked group (P<0.05). The differences were found equally in lower as well as in higher bone density specimen. Because of the optimal load transfer between implant and cancellous bone, a locked screw plate interface will reduce fixation failure in proximal humeral fractures.

Bilateral asymmetry in the limb bones of the chimpanzee (Pan troglodytes)

There is much debate in behavioral primatology on the existence of population-level handedness in chimpanzees. The presence or absence of functional laterality in great apes may shed light on the origins of human handedness and on the evolution of cerebral asymmetry. The plasticity of long bone diaphyses in response to mechanical loading allows the functional interpretation of differences in cross-sectional geometric. While left-right asymmetry in upper limb diaphyseal morphology is a known property in human populations, it remains relatively unexplored in apes. We studied bilateral asymmetry in 64 skeletons of wild-caught chimpanzee using the humerus, second metacarpal, and femur. The total subperiosteal area (TA) of the diaphyses was measured at 40% of maximum humeral length and at the midshaft of the metacarpals and femora using external silicone molds. Overall, the TA values of the left humeri were significantly greater than the right, indicating directional asymmetry. This effect was even greater when the magnitude of difference in TA between each pair of humeri was compared. The right second metacarpals showed a tendency toward greater area than did the left, but this did not reach statistical significance. The lack of asymmetry in the femur serves as a lower limb control, and suggests that the upper limb results are not a product of fluctuating asymmetry. These findings imply behavioral laterality in upper limb function in chimpanzees, and suggest a complementary relationship between precision and power.

Mechanical Performance of a Screw‐Type Veterinary Suture Anchor Subjected to Single Load to Failure and Cyclic Loads

To characterize the mechanical performance of a veterinary bone anchor under static and cyclic loads. Mechanical testing study. Cadaveric canine humeri. Humeri (6 pairs) were collected from skeletally mature dogs (mean [+/-SD] age, 17.2+/-2.1 months; weight, 20.8+/-1.5 kg). Bone anchors were inserted in the proximal metaphysis using nylon, and were longitudinally extracted. For the opposite humerus, anchors were subjected to longitudinal cyclic load (50% of the load at failure of their pair) for 1200 cycles then longitudinally loaded to failure. Anchors were then installed in a similar and adjacent area of these 2(nd) humeri with nylon and cyclically tested perpendicular to the axis of anchor insertion (100% of the longitudinal holding power of their pair) for 1200 cycles, then perpendicularly loaded to failure. Paired t-tests were used to compare holding power before and after longitudinal cyclic testing. Longitudinal holding power of the screw-type anchor in the proximal humerus was 385+/-30 N. Anchor pullout was the only mode of failure. Anchors in the paired humeri did not fail after 1200 cycles of 50% longitudinal loading, and post-cycle holding strength was not different (335+/-87 N; P=.32). Perpendicularly loaded anchors did not fail after 1200 cycles of 100% of opposite longitudinal holding strength, and had post-cycle perpendicular holding strengths of 514+/-72 N. Suture breakage was the mode of failure. Bone anchor holding strength is dependent on orientation of suture load. Screw-type bone anchor holding strength was not affected by longitudinal cyclic loading, and holding strengths of approximately 385 N can be expected in metaphyseal bone of large-breed mature dogs. Perpendicularly loaded anchors have higher failure loads, and holding strength of approximately 514 N can be expected in metaphyseal bone of the proximal humerus.

Fixed-angle plate fixation in simulated fractures of the proximal humerus: a biomechanical study of a new device

This study was performed to evaluate the biomechanical properties of a new device for displaced fractures of the proximal humerus. The device is a low-profile, fixed-angle plate specially designed for percutaneous application. With the use of embalmed cadaveric humeri, we simulated both noncomminuted and comminuted 2-part surgical neck fractures of the proximal humerus. Each humerus of a pair was then randomly fixed with either the new experimental device or the Association for the Study of Internal Fixation (ASIF) T-plate and mechanically tested to failure in an axial shear-loading model. The two fixation devices were evaluated in paired humeri with regard to mode of failure, stiffness, displacement at physiologic loads, and displacement, load, and energy at the point of ultimate load before failure. In the noncomminuted fracture trials the experimental device exhibited significantly greater stiffness ( P < .001; P = .002 for normalized values) and ultimate load before failure ( P = .015) and significantly less displacement at higher physiologic loads ( P = .031). In the comminuted fracture trials the experimental device exhibited significantly greater stiffness ( P = .048), ultimate load ( P < .001) and energy absorbed ( P = .048) before failure, and significantly less displacement at higher ( P = .004) and lower physiologic loads ( P = .011). The study demonstrates improved biomechanical properties for the new experimental device over the T-plate in simulated fractures of the proximal humerus. We extrapolate that these improved biomechanical properties may prove advantageous in future clinical investigation.

Cross- sectional geometric properties along the diaphysis of femur and humerus in chimpanzees and humans

The cross-sectional geometric parameters were determined serially along the diaphysis of 3 paired humeri and femora of chimpanzees by using the computed X-ray tomographic scans, and compared with those of humans. In magnitude, the femoral parameters were greater and humeral parameters were less, respectively, in humans than in chimpanzees. While the changing pattern among the parameters along the diaphysis was very similar both in the femur and humerus of chimpanzees, the pattern in the humans was reversed between the cross-sectional area and area moments of inertia. In chimpanzees, the femoral parameters increased toward the most proximal diaphysis, whereas humeral parameters yielded a moderate peak in a portion slightly proximal to mid-shaft. Potential mechanisms responsible for these findings were discussed.

Biomechanical beam analysis of long bones from a late 18th century slave cemetery in Cape Town, South Africa.

This study aims to quantify the physical demands of a sample of late 18th century skeletons from an unmarked burial site on Cobern Street, Cape Town, South Africa. Historical studies suggest that these individuals were either slaves or "free black" people of low socioeconomic standing. Cortical cross-sectional areas of paired humeri and tibiae from the Cobern Street collection (N = 29), a modern cadaver collection (N = 31), and a hunter-gatherer collection (N = 30) were compared by means of biomechanical beam analysis on computerized tomography scans. Results showed that the Cobern Street sample, both males and females, were closer to the modern group in total tibial cortical area and in the second moments and polar moments of cortical area, than to the hunter-gatherer group. It is assumed that these results can be explained by differences in lower limb activity. Tibial strength properties showed the hunter-gatherer peoples to be highly mobile and active walkers in comparison to the Cobern Street and modern samples. The males from the Cobern Street sample showed significantly higher values for humeral strength properties than either the hunter-gatherer or modern individuals, attesting to their status as manual laborers. The humeral cross-sectional strength properties for females were very similar between the Cobern Street and modern groups but again significantly different from the hunter-gatherer sample. The domestic chores performed by females of the recent cadaver sample may be very similar to those performed by the Cobern Street sample.

Biomechanical beam analysis of long bones from a late 18th century slave cemetery in Cape Town, South Africa

This study aims to quantify the physical demands of a sample of late 18th century skeletons from an unmarked burial site on Cobern Street, Cape Town, South Africa. Historical studies suggest that these individuals were either slaves or “free black” people of low socioeconomic standing. Cortical cross-sectional areas of paired humeri and tibiae from the Cobern Street collection (N = 29), a modern cadaver collection (N = 31), and a hunter-gatherer collection (N = 30) were compared by means of biomechanical beam analysis on computerized tomography scans. Results showed that the Cobern Street sample, both males and females, were closer to the modern group in total tibial cortical area and in the second moments and polar moments of cortical area, than to the hunter-gatherer group. It is assumed that these results can be explained by differences in lower limb activity. Tibial strength properties showed the hunter-gatherer peoples to be highly mobile and active walkers in comparison to the Cobern Street and modern samples. The males from the Cobern Street sample showed significantly higher values for humeral strength properties than either the hunter-gatherer or modern individuals, attesting to their status as manual laborers. The humeral cross-sectional strength properties for females were very similar between the Cobern Street and modern groups but again significantly different from the hunter-gatherer sample. The domestic chores performed by females of the recent cadaver sample may be very similar to those performed by the Cobern Street sample. Am J Phys Anthropol 112:207–216, 2000. © 2000 Wiley-Liss, Inc.

Asymmetry and activity‐related change in the male humerus

AbstractSome previous studies of activity‐related change in the human skeleton have been of doubtful validity because specific changes have been related to particular tasks. Claims to establish such relationships have often concentrated on the development of entheses. Such work is marred by the incorrect assumption that muscles work in isolation in the performance of a single activity. In addition, normal skeletal asymmetry is often ignored, as is age and sex.In the present work, paired humeri of males from two medieval British sites, Norwich and Henry VIII's flagship, the Mary Rose, were compared using a series of measurements. Comparison of left and right sides demonstrated that humeral asymmetry decreases with age. Comparison of the sites showed that the Norwich males were more asymmetric than those from the Mary Rose. All asymmetries exhibited a right‐sided dominance. The majority of the species is right‐handed: the Norwich males followed this trend. The general lack of asymmetry in the Mary Rose males suggests that they were using their arms more equally. When left and right sides were compared directly, a new measurement of the greater tubercle (where three muscles insert) and measurement of the diameter of the head demonstrated that the Mary Rose males had significantly larger dimensions of the left shoulder than the Norwich males. These results extend earlier work, which had suggested a correlation between the use of heavy medieval longbows and os acromiale. Statistical comparison of the sites demonstrated that such work can indicate patterns of activity but not individual occupations.

Biomechanical Comparison of Methods of Fixation of a Midshaft Osteotomy of the Humerus

Using paired humeri with a midshaft osteotomy, the biomechanical stiffness of four intramedullary internal fixation devices were compared with each other, a dynamic compression plate, and with the intact bone. In posterior and lateral bending and in torsion, flexible intramedullary pin fixed humeri (Enders and Hackethal) performed similarly and were less stiff than intact specimens were. Interlocking intermedullary nail constructs (Russell-Taylor and Seidel) also tested similarly to each other, and were stiffer than the flexible pins in all bending tests. Compared with the intact humerus, interlocking nails were stiffer in torsion, but in bending they more closely simulated the stiffness of the bone.