Human Cadaveric Femora Research Articles

Quantitative Effect of Metal Artefact Reduction on CT-based attenuation correction in FDG PET/CT in patients with hip prosthesis

BackgroundMetal artefact reduction (MAR) techniques still are in limited use in positron emission tomography/computed tomography (PET/CT). This study aimed to investigate the effect of Smart MAR on quantitative PET analysis in the vicinity of hip prostheses.Materials and methodsActivities were measured on PET/CT images in 6 sources with tenfold activity concentration contrast to background, attached to the head, neck and the major trochanter of a human cadaveric femur, and in the same sources in similar locations after a hip prosthesis (titanium cup, ceramic head, chrome-cobalt stem) had been inserted into the femur. Measurements were compared between PET attenuation corrected using either conventional or MAR CT. In 38 patients harbouring 49 hip prostheses, standardized uptake values (SUV) in 6 periprosthetic regions and the bladder were compared between PET attenuation corrected with either conventional or MAR CT.ResultsUsing conventional CT, measured activity decreased with 2 to 13% when the prosthesis was inserted. Use of MAR CT increased measured activity by up to 11% compared with conventional CT and reduced the relative difference with the reference values to under 5% in all sources. In all regions, to the exception of the prosthesis shaft, SUVmean increased significantly (p < 0.001) by use of MAR CT. Median (interquartile range) percentual increases of SUVmean were 1.4 (0.0–4.2), 4.0 (1.8–7.8), 7.8 (4.1–12.4), 1.5 (0.0–3.2), 1.4 (0.8–2.8) in acetabulum, lateral neck, medial neck, lateral diaphysis and medial diaphysis, respectively. Except for the shaft, the coefficient of variation did not increase significantly. Except for the erratic changes in the prosthesis shaft, decreases in SUVmean were rare and small. Bladder SUVmean increased by 0.9% in patients with unilateral prosthesis and by 4.1% in patients with bilateral prosthesis.ConclusionsIn a realistic hip prosthesis phantom, Smart MAR restores quantitative accuracy by recovering counts in underestimated sources. In patient studies, Smart MAR increases SUV in all areas surrounding the prosthesis, most markedly in the femoral neck region. This proves that underestimation of activity in the PET image is the most prevalent effect due to metal artefacts in the CT image in patients with hip prostheses. Smart MAR increases SUV in the urinary bladder, indicating effects at a distance from the prosthesis.

Normalized vertebral-level specific range of motion corridors for female spines in rear impact

Objective It is well known that the biomechanical responses of female and male spines are different in rear impacts. Female-specific finite element models are being developed as improvements over generic models. Such advancements need female-specific segmental responses for validation. The objectives of the study were to develop vertebral level-specific range of motion corridors from female human cadaver head-neck complexes exposed to rear impact loading. Methods Previously conducted experiments from five human cadaver head-neck complexes were used in this analysis-based study. Briefly, the female head-neck complexes were isolated at the second thoracic vertebral level from the whole body such that the skin and the surrounding tissues of the osteoligamentous complex were intact. The distal end was fixed to the platform of a min-sled testing device. The anterior angulation of T1 was at 25 degrees with respect to the horizontal axis to simulate the normal driver posture. The occipital condyles were directly superior to the T1 body, and the Frankfort plane was horizontal. Rear impact loading were applied at a velocity of 2.6 m/s. The range of motion was defined as the inter-segmental angle at each level of the subaxial spinal column, and it was obtained by tracking the motion of the retroreflective targets that were secured on vertebral bodies and lateral masses of C2 through C7 vertebrae. Data were normalized with respect to the fifth percentile female total body mass, and corridors were developed using the equal stress equal velocity approach and expressed as mean ± 1 standard deviation corridors for each segment. Results The segmental motions of the subaxial cervical spinal column were such that the upper regions responded with flexion while the lower regions responded with extension during the initial accelerative loading phase of the impact, resulting in a non-physiological curvature. During the later phase, all segments were in extension. individual corridors are presented as temporal responses in the body of the manuscript. A comparison of the mean temporal responses at each segment are presented to depict the angulation motion differences within the spinal column. Conclusions The present corridors are unique to the female spines. Because female spines have significantly (p < 0.05) different biomechanical responses when compared to male spines, local anatomical differences exist between male and female spines, and field data and clinical studies show female bias to whiplash associated disorders under the rear impact of loading, the present set of corridors serve as a fundamental dataset for the validation of female-specific finite element models. Current computational models can also use these corridors for improved validation to add confidence in their outputs.

Biomechanics of a calcar loading and a shortened tapered femoral stem: Comparative in-vitro testing of primary stability and strain distribution

PurposeThe most common femoral short stems available on the market can, in principle, be divided with regard to their anchoring concepts into a calcar loading and a shortened tapered design. The purpose of this study was to compare the primary stability and stress-shielding of two short stems, which correspond to these two different anchoring concepts.MethodsUsing seven paired fresh frozen human cadaver femurs, primary axial and rotational stabilities under dynamic load (100–1600 N) were evaluated by miniature displacement transducers after 100,000 load cycles. Changes in cortical strains were measured before and after implantation of both stem types to detect implant-specific load transmission and possible stress-shielding effects.ResultsReversible and irreversible micromotions under dynamic load displayed no significant differences between the two implants. Implantation of either stem types resulted in a reduction of cortical strains in the proximal femur, which was less pronounced for the calcar loading implant.ConclusionsBoth short stems displayed comparable micromotions far below the critical threshold above which osseointegration may disturbed. Neither short stem could avoid proximal stress-shielding. This effect was less pronounced for the calcar loading short stem, which corresponds to a more physiological load transmission.

3D geometry of femoral reaming for bone graft harvesting

The reamer-irrigator-aspirator (RIA) technique allows to collect large bone graft amounts without the drawbacks of iliac crest harvesting. Nevertheless, clinical cases with occurrence of femur fractures have been reported. Therefore, this study aimed to systematically investigate the three-dimensional geometry of the reamed bone as a function of the reaming diameter and its influence on the associated potential fracture pattern. Forty-five intact fresh-frozen human cadaveric femora underwent computed tomography (CT). They were randomized to three groups (n = 15) for reaming at a diameter of either 1.5 mm (Group 1), 2.5 mm (Group 2) or 4.0 mm (Group 3) larger than their isthmus using RIA. Reaming was followed by a second CT scan, biomechanical testing until failure and a third CT scan. All CT scans of each femur were aligned via rigid registration, and fracture lines were visualized. Subsequently, a decrease in wall thickness, cross-sectional area, and harvested bone volume have been evaluated. The total volume of the bone graft was significantly higher for Group 3 (7.8 ± 2.9 ml) compared to Group 1 (2.9 ± 1.1 ml) and Group 2 (3.0 ± 1.1 ml). The maximal relative decrease of the wall thickness was located medially (72.7%) in the third (61.4%), fourth (18.2%) and second (9.1%) eighth for all groups. As the diameter of the reaming increased, an overlap of the fracture line with the maximal relative decrease in wall thickness and a maximal average relative decrease of the cross-sectional area became more frequent. This suggests that a reaming-associated fracture is most likely to occur in this region.

Extended Trochanteric Osteotomy Closure Performed Before or After Canal Preparation and Stem Impaction Does Not Affect Axial Stability

BackgroundAn extended trochanteric osteotomy (ETO) safely addresses femoral component removal during challenging revision total hip arthroplasty. However, no prior study has evaluated whether a difference in axial stability exists between ETO closure performed before (reconstitution) or after (scaffolding) canal preparation and stem impaction. We hypothesized that given the absence of clinical reports of outcome differences despite the wide use of both practices, no significant difference in the initial axial stability would exist between the 2 fixation techniques. MethodsETOs were performed and repaired using the reconstitution technique for the 6 right-sided femora and the scaffolding technique for the six left-sided femora. The 195-mm long, 3.5°-tapered splined titanium monobloc stems were impacted into 6 matched pairs of human fresh cadaveric femora. Three beaded cables were placed in a standardized fashion on each specimen, 1 for prophylaxis against osteotomy propagation during reaming/impaction and 2 to close the ETO. Stepwise axial loading was performed to 2600 N or until failure, which was defined as subsidence >5 mm or femoral/cable fracture. ResultsAll specimens successfully resisted axial testing, with no stem in either ETO repair group subsiding >2 mm. The mean subsidence for the reconstitution group was 0.9 ± 0.4 mm, compared to 1.2 ± 0.5 mm for the scaffolding group (P = .2). ConclusionIn this cadaveric model with satisfactory proximal bone stock, no difference existed between the reconstitution and scaffolding ETO repair techniques, and both provide sufficient immediate axial stability in a simulated revision total hip arthroplasty setting under physiologic loads.

Impact on periosteal vasculature after dual plating of the distal femur: a cadaveric study.

Objectives:Although dual plating of distal femur fractures has been described for injuries at risk of varus displacement, the vascular insult to the medial distal femur utilizing this technique is unknown. The aim of this study was to evaluate the perfusion of the medial distal femoral periosteal arteries after supplemental medial plating of the distal femur.Methods:Fifteen human fresh-frozen cadaveric femora were thawed and randomized to lateral locked plating alone or with supplemental medial plate fixation. Conventional submuscular medial plating was performed using a 12-hole small fragment plate and multiple cortical screws. The superficial femoral artery was injected with latex dye. Specimens were dissected. The patency of the medial distal femoral periosteal vessels was evaluated.Results:Four vessels were consistently observed traversing the distal medial femur: the transverse and descending (d-MMPA) branches of the medial metaphyseal periosteal artery, and the transverse and longitudinal branches of the descending geniculate artery. The anterior longitudinal arch (ALA) was present in 13 of 15 specimens and was fed by the d-MMPA. The median number of periosteal arteries occluded by the medial plate was 2 (6 out of 8 specimens). The d-MMPA was occluded in 6 of 8 medially plated femurs, resulting in a complete lack of perfusion of the ALA.Conclusions:Submuscular medial plating of the distal femur compressed the d-MMPA in the majority of specimens. This vessel gives rise to the ALA, which lacked perfusion in these specimens. This vascular insult could affect the healing of metaphyseal distal femur fractures treated with dual plating.

Volumetric Morphology of Segmental Trachea Sections

Introduction & Objective The trachea is the airway between the larynx and primary bronchi, extending from the inferior aspect of the cricoid cartilage to its bifurcation at the carina. Its anterior and lateral walls are comprised of 16-22 C-shaped cartilaginous rings held together by annular ligaments, while its posterior wall consists primarily of trachealis muscle. Studies of trachea length, coronal and sagittal diameters, and dynamics are well represented in the literature with significant differences reported between genders. However, studies regarding volumetric morphology of the trachea are limited. Several structures (e.g., thyroid gland, brachiocephalic trunk, left brachiocephalic vein, etc.) are in contact with different regions of the trachea and could potentially affect lumen volumes. The objective of this study was to investigate tracheal volumetric morphology through segmental area analysis of cadaveric male and female tracheas and compare those results to a known case of distal trachea constriction. Materials & Methods Tracheas of seven male and seven female human cadavers were dissected, eviscerated, and photographed (iPad Pro, Apple Inc.). Trachea lengths were recorded to the nearest millimeter via gross measurement. Tracheas were covered at the proximal end and filled with water. Water volumes were subsequently measured in triplicate. Tracheas were then sectioned into ten equal segments and photographed (iPad Pro, Apple Inc.). Lumen areas of each segment were measured in triplicate (ImageJ, 1.52q), and mean segmental areas were multiplied by trachea length to determine segmentally derived trachea volumes. T-tests were used to compare segmentally derived volumes to actual volumes measured by water displacement. Male and female data were compared separately, and comparable data from a separate clinical case of distal tracheal constriction in a female cadaver was compared to the female data collected in this study. Results Male tracheas were longer (11.9 ± 0.7 cm vs. 10.3 ± 0.7 cm, p < 0.05) and of greater volume (28.7 ± 5.0 mL vs. 16.5 ± 0.8 mL, p < 0.05) compared to female tracheas. While sequential comparison of segmentally derived volumes in both genders suggest similar regions of natural trachea constriction (middle third) and dilation (distal third), both regions were statistically indifferent from actual trachea volume. The segmentally derived volumes from the distal half of the clinically constricted trachea were considerably less than the female volumetric data (distal half) quantified in this study (8.82 ± 1.36 mL vs. 14.86 ± 0.90 mL, p < 0.05). Conclusions & Significance While variations in lumen area of sequential trachea segments are apparent, they have little to no significant effect on total trachea volume unless substantially impacted by a clinical condition. Certain segments of the trachea may be more accurate for estimating its total volume. The noted mid-section constriction is believed to be caused by the brachiocephalic artery and left brachiocephalic vein crossing obliquely over the anterior aspect of trachea but merits more study. This study and future data expansion via additional tracheal measurements will help define “normal” tracheal volumetric morphology. This information may be valuable to physicians performing surgical procedures and diagnosing abnormalities of the trachea.

Standardized artificially created stable pertrochanteric femur fractures present more homogenous results compared to osteotomies for orthopaedic implant testing

BackgroundWith regard to biomechanical testing of orthopaedic implants, there is no consensus on whether artificial creation of standardized bone fractures or their simulation by means of osteotomies result in more realistic outcomes. Therefore, the aim of this study was to artificially create and analyze in an appropriate setting the biomechanical behavior of standardized stable pertrochanteric fractures versus their simulation via osteotomizing.MethodsEight pairs of fresh-frozen human cadaveric femora aged 72.7 ± 14.9 years (range 48–89 years) were assigned in paired fashion to two study groups. In Group 1, stable pertrochanteric fractures AO/OTA 31-A1 were artificially created via constant force application on the anterior cortex of the femur through a blunt guillotine blade. The same fracture type was simulated in Group 2 by means of osteotomies. All femora were implanted with a dynamic hip screw and biomechanically tested in 20° adduction under progressively increasing physiologic cyclic axial loading at 2 Hz, starting at 500 N and increasing at a rate of 0.1 N/cycle. Femoral head fragment movements with respect to the shaft were monitored by means of optical motion tracking.ResultsCycles/failure load at 15° varus deformation, 10 mm leg shortening and 15° femoral head rotation around neck axis were 11324 ± 848/1632.4 ± 584.8 N, 11052 ± 1573/1605.2 ± 657.3 N and 11849 ± 1120/1684.9 ± 612.0 N in Group 1, and 10971 ± 2019/1597.1 ± 701.9 N, 10681 ± 1868/1568.1 ± 686.8 N and 10017 ± 4081/1501.7 ± 908.1 N in Group 2, respectively, with no significant differences between the two groups, p ≥ 0.233.ConclusionFrom a biomechanical perspective, by resulting in more consistent outcomes under dynamic loading, standardized artificial stable pertrochanteric femur fracture creation may be more suitable for orthopaedic implant testing compared to osteotomizing the bone.

Biomechanics of a cemented short stem: a comparative in vitro study regarding primary stability and maximum fracture load

PurposeIn total hip arthroplasty, uncemented short stems have been used more and more frequently in recent years. Especially for short and curved femoral implants, bone-preserving and soft tissue-sparing properties are postulated. However, indication is limited to sufficient bone quality. At present, there are no curved short stems available which are based on cemented fixation.MethodsIn this in vitro study, primary stability and maximum fracture load of a newly developed cemented short-stem implant was evaluated in comparison to an already well-established cemented conventional straight stem using six pairs of human cadaver femurs with minor bone quality. Primary stability, including reversible micromotion and irreversible migration, was assessed in a dynamic material-testing machine. Furthermore, a subsequent load-to-failure test revealed the periprosthetic fracture characteristics.ResultsReversible and irreversible micromotions showed no statistical difference between the two investigated stems. All short stems fractured under maximum load according to Vancouver type B3, whereas 4 out of 6 conventional stems suffered a periprosthetic fracture according to Vancouver type C. Mean fracture load of the short stems was 3062 N versus 3160 N for the conventional stems (p = 0.84).ConclusionPrimary stability of the cemented short stem was not negatively influenced compared to the cemented conventional stem and no significant difference in fracture load was observed. However, a clear difference in the fracture pattern has been identified.

Removal of cement-augmented screws in distal femoral fractures and the effect of retained screws and cement on total knee arthroplasty: a biomechanical investigation

BackgroundGiven the increasing number of osteoporotic fractures of the distal femur, screw augmentation with bone cement is an option to enhance implant anchorage. However, in implant removal or revision surgeries, the cement cannot be removed from the distal femur without an extended surgical procedure. Therefore, the aims of this study were to investigate (1) whether cement augmentation has any influence on screw removal and removal torque, and (2) whether the implantation of a femoral component of a knee arthroplasty and its initial interface stability are affected by the remaining screws/cement.Material and methodsEight pairs of fresh-frozen human female cadaveric distal femurs (mean age, 86 years) with a simulated AO/OTA 33 A3 fracture were randomized in paired fashion to two groups and fixed with a distal femoral locking plate using cannulated perforated locking screws. Screw augmentation with bone cement was performed in one of the groups, while the other group received no screw augmentation. Following biomechanical testing until failure (results published separately), the screws were removed and the removal torque was measured. A femoral component of a knee arthroplasty was then implanted, and pull-out tests were performed after cement curing. Interference from broken screws/cement was assessed, and the maximum pull-out force was measured.ResultsThe mean screw removal torque was not significantly different between the augmented (4.9 Nm, SD 0.9) and nonaugmented (4.6 Nm, SD 1.3, p = 0.65) screw groups. However, there were significantly more broken screws in in the augmented screw group (17 versus 9; p < 0.001). There was no significant difference in the pull-out force of the femoral component between the augmented (2625 N, SD 603) and nonaugmented (2653 N, SD 542, p = 0.94) screw groups.ConclusionThe screw removal torque during implant removal surgery does not significantly differ between augmented and nonaugmented screws. In the augmented screw group, significantly more screws failed. To overcome this, the use of solid screws in holes B, C, and G can be considered. Additionally, it is possible to implant a femoral component for knee arthroplasty that retains the initial anchorage and does not suffer from interference with broken screws and/or residual cement.Level of Evidence 5

The Prevalence of Cam Morphology: A Cross-Sectional Evaluation of 3,558 Cadaveric Femora.

Purpose: We sought to determine (1) the prevalence of cam deformity in the population and that of bilateral cam deformity, (2) the typical location of a cam lesion, and (3) the typical size of a cam lesion by direct visualization in cadaveric femora.Methods: Two observers inspected 3,558 human cadaveric femora from the Hamann–Todd Osteological Collection from the Cleveland Museum of Natural History. Any asphericity >2 mm from the anterior femoral neck line was classified as a cam lesion. Once lesions had been inspected, the prevalence in the population, prevalence by gender, and prevalence of bilateral deformity were determined. Additionally, each lesion was measured and localized to a specific quadrant on the femoral neck based upon location of maximal deformity.Results: Cam lesions were noted in 33% of males and 20% of females. Eighty percent of patients with a cam lesion had bilateral lesions. When stratified by location of maximal deformity, 90.9% of lesions were in the anterosuperior quadrant and 9.1% were in the anteroinferior quadrants. The average lesion measured 17 mm long × 24 mm wide × 6 mm thick in men and 14 mm × 22 mm × 4 mm in women (p < 0.05).Conclusions: The population prevalence of cam deformity determined by direct visualization in cadavers may be higher than has been suggested in studies utilizing imaging modalities.Level of Evidence : Level II, diagnostic study.

Post-operative fracture risk assessment following tumor curettage in the distal femur: a hybrid in vitro and in silico biomechanical approach

The distal femur is the predominant site for benign bone tumours and a common site for fracture following tumour removal or cementation. However, the lack of conclusive assessment criterion for post-operative fracture risk and appropriate devices for cement augmentation are serious concerns. Hence, a validated biomechanical tool was developed to assess bone strength, depending on the size and location of artificially created tumorous defects in the distal femora. The mechanics of the bone–cement interface was investigated to determine the main causes of reconstruction failure. Based on quantitative-CT images, non-linear and heterogeneous finite element (FE) models of human cadaveric distal femora with simulated tumourous defects were created and validated using in vitro mechanical tests from 14 cadaveric samples. Statistical analyses demonstrated a strong linear relationship (R2 = 0.95, slope = 1.12) with no significant difference between bone strengths predicted by in silico analyses and in vitro tests (P = 0.174). FE analyses showed little reduction in bone strength until the defect was 35% or more of epiphyseal volume, and reduction in bone strength was less pronounced for laterally located defects than medial side defects. Moreover, the proximal end of the cortical window and the most interior wall of the bone–cement interface were the most vulnerable sites for reconstruction failure.

MRI-derived porosity index is associated with whole-bone stiffness and mineral density in human cadaveric femora.

Ultrashort echo time (UTE) magnetic resonance imaging (MRI) measures proton signals in cortical bone from two distinct water pools, bound water, or water that is tightly bound to bone matrix, and pore water, or water that is freely moving in the pore spaces in bone. By isolating the signal contribution from the pore water pool, UTE biomarkers can directly quantify cortical bone porosity in vivo. The Porosity Index (PI) is one non-invasive, clinically viable UTE-derived technique that has shown strong associations in the tibia with μCT porosity and other UTE measures of bone water. However, the efficacy of the PI biomarker has never been examined in the proximal femur, which is the site of the most catastrophic osteoporotic fractures. Additionally, the loads experienced during a sideways fall are complex and the femoral neck is difficult to image with UTE, so the usefulness of the PI in the femur was unknown. Therefore, the aim of this study was to examine the relationships between the PI measure in the proximal cortical shaft of human cadaveric femora specimens compared to (1) QCT-derived bone mineral density (BMD) and (2) whole bone stiffness obtained from mechanical testing mimicking a sideways fall. Fifteen fresh, frozen whole cadaveric femora specimens (age 72.1±15.0years old, 10 male, 5 female) were scanned on a clinical 3-T MRI using a dual-echo UTE sequence. Specimens were then scanned on a clinical CT scanner to measure volumetric BMD (vBMD) and then non-destructively mechanically tested in a sideways fall configuration. The PI in the cortical shaft demonstrated strong correlations with bone stiffness (r=-0.82, P=0.0014), CT-derived vBMD (r=-0.64, P=0.0149), and with average cortical thickness (r=-0.60, P=0.0180). Furthermore, a hierarchical regression showed that PI was a strong predictor of bone stiffness which was independent of the other parameters. The findings from this study validate the MRI-derived porosity index as a useful measure of whole-bone mechanical integrity and stiffness.

Cemented short-stem total hip arthroplasty: Characteristics of line-to-line versus undersized cementing techniques using a validated CT-based finite element analysis.

Short stems are becoming increasingly popular in total hip arthroplasty as they preserve the bone stock and simplify the implantation process. Short stems are advised mainly for patients with good bone stock. The clinical use of short stems could be enlarged to patients with poor bone stock if a cemented alternative would be available. Therefore, this study aimed to quantify the mechanical performance of a cemented short stem and to compare the "undersized" cementing strategy (stem one size smaller than the rasp) with the "line-to-line" technique (stem and rasp with identical size). A prototype cemented short stem was implanted in eight pairs of human cadaveric femora using the two cementing strategies. Four pairs were experimentally tested in a single-legged stance condition; stiffness, strength, and bone surface displacements were measured. Subject-specific nonlinear finite element models of all the implanted femora were developed, validated against the experimental data, and used to evaluate the behavior of cemented short stems under physiological loading conditions resembling level walking. The two cementing techniques resulted in nonsignificant differences in stiffness and strength. Strength and stiffness as calculated from finite element were 8.7 ± 16% and 9.9 ± 15.0% higher than experimentally measured. Displacements as calculated from finite element analyses corresponded strongly (R 2 ≥ .97) with those measured by digital image correlation. Stresses during level walking were far below the fatigue limit for bone and bone cement. The present study suggests that cemented short stems are a promising solution in osteoporotic bone, and that the line-to-line and undersized cementing techniques provide similar outcomes.

Influence of the Reamer-Irrigator-Aspirator diameter on femoral bone strength and amount of harvested bone graft – a biomechanical cadaveric study

BackgroundTreatment of large bone defects is still related to unsolved problems in orthopaedic trauma surgery. Minimally invasive intramedullary reaming with the use of the Reamer-Irrigator-Aspirator (RIA) device allows autograft harvesting of large bone graft amounts from the medullary canal of the femur. The aim of this study was to investigate the influence of RIA diameter on femoral bone strength and amount of harvested bone graft in a human cadaveric model. MethodsForty-five pairs human cadaveric femora were randomized to 3 paired groups with 15 pairs each. One femur of each pair was reamed with RIA at a diameter of either 1.5 mm (group 1), 2.5 mm (group 2) or 4.0 mm (group 3) larger than its isthmus, whereas its contralateral femur was left intact without reaming. The amount of harvested bone graft was determined for each specimen and all femora were destructively tested in internal rotation under 750 N axial compression to calculate their torsional stiffness and torque at failure. ResultsSignificant reduction in torsional stiffness was detected after reaming in group 3 (p = 0.03) in contrast to groups 1 and 2 where no such significant reduction was observed (p ≥ 0.34). Torque at failure was significantly reduced after reaming in all 3 groups (p ≤ 0.04). Collected bone graft amount in group 3 was significantly bigger compared to groups 1 and 2 (p ≤ 0.04). ConclusionsReaming with RIA diameter of 4.0 mm larger than the isthmus of the femur seems to influence considerably its torsional stiffness, however, it allows harvesting of a significantly bigger bone graft amount.

Differences in Trochlear Morphology from Native Using a Femoral Component Interfaced with an Anatomical Patellar Prosthesis in Kinematic Alignment and Mechanical Alignment.

Patellofemoral complications following total knee arthroplasty can be traced in part to alignment of the femoral component. Kinematic alignment (KA) and mechanical alignment (MA) use the same femoral component but align the component differently. Our objective was to determine differences in trochlear morphology from native for a femoral component interfaced with an anatomical patellar prosthesis in KA and MA. Ten three-dimensional femur-cartilage models were created by combining computed tomography and laser scans of native human cadaveric femurs free of skeletal abnormalities. The femoral component was positioned using KA and MA. Measurements of the prosthetic and native trochlea were made along the arc length of the native trochlear groove and differences from native were computed for the medial-lateral and radial locations of the groove and sulcus angle. Mean medial-lateral locations of the prosthetic groove were within 1.5 and 3.5 mm of native for KA and MA, respectively. Mean radial locations of the prosthetic groove were as large as 5 mm less than native for KA and differences were greater for MA. Sulcus angles of the prosthetic trochlea were 10 degrees steeper proximally, and 10 degrees flatter distally than native for both KA and MA. Largest differences from native occurred for radial locations and sulcus angles for both KA and MA. The consistency of these results with those of other fundamentally different designs which use a modified dome (i.e., sombrero hat) patellar prosthesis highlights the need to reassess the design of the prosthetic trochlea on the part of multiple manufacturers worldwide.

Femoral interference screw insertion significantly increases graft tension in medial patellofemoral ligament reconstruction.

This study aimed to quantify the effect of interference screw insertion on MPFL graft tension when securing the femoral attachment after patellar fixation. It was hypothesized that interference screw insertion significantly increases graft tension. Ten fresh frozen human cadaveric femurs were utilized to compare graft tension at three different preloading conditions (2N, 5N, 10N) using a tensile testing machine (Admet Inc., Norwood, MA). Each preloading condition was analyzed with varying graft sizes (5-8mm), tunnel diameters (7-9mm), and interference screw sizes (7-9mm). Non-parametric statistical analysis was utilized to compare testing conditions among each other. Graft tension significantly increased after interference screw insertion by 100% to 552%, with 2N preload showing the greatest increase (p < 0.001). Grafts with a larger diameter (7-8mm) had a significantly greater increase in tension than smaller grafts (5-6mm), regardless of preloading conditions (p < 0.001). Interference screw size had no influence on graft tension (n.s.). A graft-tunnel interference (tunnel diameter-graft diameter) fit of 0mm and 1mm significantly increased graft tension for each preloading condition when compared to a slightly looser fit of ≥ 2mm (p < 0.05). Femoral interference screw insertion significantly increases graft tension in MPFL reconstruction even in low preloading conditions, with graft size and graft-tunnel interference fit having a considerably effect on graft tension. Surgeons should be aware of the inadvertent increases in graft tension even in low preloading conditions to mitigate the risk of graft overtensioning.

Does the line-to-line cementing technique of the femoral stem create an adequate cement mantle?

Background:The line-to-line cementing technique is proposed to create a press-fit in the femoral canal, which is contrary to modern cementing techniques. The term ‘French paradox’ has been used to describe the acceptable results associated with this technique. It has been suggested that the quality of the mantle may not be satisfactory, predisposing to early failure and aseptic loosening.Methods:The line-to-line cementing technique, where the femoral stem was oversized by 1 size compared to the broach, was compared to the standard cementing technique using corresponding sized broaches and stems, in 6 pairs of human cadaver femora with taper-slip design C-stems. Cement pressure was measured, and cement mantle thickness was analysed. A mixed effects model with random intercepts was used to examine the relationship between thickness of mantle and cementing technique and between pressure and cementing technique.Results:Line-to-line cementing results in significantly higher pressurisation for longer periods of time leading to better interdigitation but a thinner mantle in some areas.Conclusions:The results of this study describe the in-vitro advantages and disadvantages of the line-to-line cementing technique.

Cement augmentation of metastatic lesions in the proximal femur can improve bone strength

Prophylactic treatment is advised for metastatic bone disease patients with a high risk for fracture. Femoroplasty provides a minimally invasive procedure to stabilize the femur by injecting bone cement into the lesion. However, uncertainty remains whether it provides sufficient mechanical strength to the weight-bearing femur. The goal of this study was to quantify the improvement in bone stiffness, failure load and energy to failure due to cement augmentation of metastatic lesions at varying locations in the proximal femur.Eight pairs of human cadaveric femurs were mechanically tested until failure in a single-leg stance configuration. In each pair, an identical defect was milled in the left and right femur using a programmable milling machine to simulate an osteolytic lesion. The location of the defects varied amongst the eight pairs. One femur of each pair was augmented with polymethylmethacrylate, while the contralateral femur was left untreated. Digital image correlation was applied to measure strains on the bone surface during mechanical testing.Only femurs with a critical lesion showed an improvement in failure load and energy to failure due to augmentation. In these femurs, bone strength improved with 28% (±17%) on average and energy to failure with 58% (±41%), while stiffness did not show a significant improvement. The strain measurements from digital image correlation showed that cement augmentation reinforced the lesion, resulting in reduced strain magnitudes in the bone tissue adjacent to the lesion. The results indicate that femoroplasty may be an effective treatment to prevent fractures in several metastatic bone disease patients. However, the large scatter in the data clarifies the need for developing strategies to identify those patients who will benefit the most from the procedure.

Three-dimensional rendering of trabecular bone microarchitecture using a probabilistic approach

In the past, researchers have attempted to model trabecular bone using computational techniques. However, only a few of these models are visually similar, but not representative of the microstructural characteristics of real trabecular bones. In this study, we hypothesized that probabilistic modeling approaches could be used to generate representative digital models that capture the microstructural features of real trabecular bones. To test this hypothesis, we proposed a novel mathematical framework to build the digital models and compared the digital models to real bone specimens. First, an initial three-dimensional cellular structure was generated using Voronoi tessellation, with the faces and edges of the Voronoi cells considered as a pool of potential trabecular plates and rods, respectively. Then, inverse Monte Carlo simulations were performed to select, delete, or reassign plates and rods until the underlying size, orientation, and spatial distributions of the plates and rods converged to the target distributions obtained from real trabecular bone microstructures. Next, digital graphics techniques were used to define the thickness of trabecular plates and the diameter of trabecular rods, followed by writing the model into a Standard Tessellation Language file and then smoothing the model surfaces for a more natural appearance. To verify the efficacy of the digital model in capturing the microstructural features of real trabecular bones, forty-six digital models with a large variation in microstructural features were generated based on the target distributions obtained from trabecular bone specimens of twelve human cadaveric femurs. Then, the histomorphological parameters of the digital models were compared with those of the real trabecular bone specimens. The results indicate that the digital models are capable of capturing major microstructural features of the trabecular bone samples, thus proving the hypothesis that the proposed probabilistic modeling approach could render real trabecular bone microstructures.