The mechanical properties of cancellous bone in the proximal tibia of ovariectomized rats.

The "mature rat model" is an effective and often-used surrogate for studying mechanisms and characteristics of estrogen-deficient osteopenia. The purpose of this study was to extend our understanding of this animal model to include the mechanical properties of cancellous bone in the proximal tibia. Female Sprague-Dawley rats were divided into two groups (n=13 each) at 14 weeks of age: an ovariectomized group (OVX) and a sham-operated control group (sham). The study terminated after a duration of 5 weeks. Specimens 2 mm long were cut from the proximal tibial metaphysis just below the growth plate and tested using two methods: (1) "whole-slice" compression, in which the entire specimen is loaded between two larger flat platens and (2) "reduced-platen" compression (RPC), which uses platens sized and aligned to load only the cancellous bone in the center of the sample. Three-point bending tests also were conducted on the femur. The short duration of estrogen deficiency yielded only minimal differences (< 10%) in femoral cortical bone but dramatic reductions (approximately 60%) in cancellous bone properties as determined by the RPC method. Ultimate stress was 7.23 MPa +/- 1.97 MPa for OVX versus 18.1 MPa +/- 5.21 MPa for sham; and elastic modulus was 252 MPa +/- 104 MPa for OVX versus 603 MPa +/- 180 MPa for sham. These changes in mechanical properties are similar in many respects to the dramatic effects reported in histomorphometric studies. For the whole-slice method, differences in mechanical properties between the two groups were not as large because the test directly loads both cancellous and cortical bone, and the latter is not affected as severely by estrogen deficiency. In this case, ultimate stress and elastic modulus were only 30% (or less) lower for the OVX group.     

Dependence of trabecular damage on mechanical strain

Trabecular damage may play a role in hip fracture, bone remodeling, and prosthesis loosening. We hypothesized that when trabecular bone is loaded beyond its elastic range, both the type and the amount of damage depend on the applied strains. Thirty specimens of trabecular bone from the bovine tibia underwent compression tests to one of three levels of strain (0.4,1.0, and 2.5%) (n = 10 per group). The 0.4% level was a mechanically nondestructive control group that accounted for any systematic errors. Optical microscopy at magnifications as high as × 200 was then used to quantify the trabecular damage for each group. The amount of damage in the yield group (1.0% strain) did not differ from that in the control group (p = 0.66), whereas damage in the post-ultimate strain group (2.5% strain) increased more than 3-fold (p < 0.0008). Four types of damage were observed: transverse cracks, shear bands, parallel cracks, and complete fractures, of which the first two were dominant. These findings therefore indicate that damage occurs within trabeculae at yield. By comparison with our previous work, it can also be concluded that substantial modulus reductions in trabecular bone (as much as 60%) are caused by damage primarily within trabeculae. The ability to detect such damage clinically may improve in vivo estimates of whole-bone strength by identifying regions of densito metrically normal but mechanically compromised trabecular bone.     

Quantitative computed tomography estimates of the mechanical properties of human vertebral trabecular bone.

The objective of this study was to report our quantitative computed tomography (QCT) density-mechanical property regressions for trabecular bone for use in biomechanical modelling of the human spine. Cylindrical specimens of human vertebral trabecular bone (from T10 to L4) were cored from 32 cadavers (mean +/- SD age = 70.1 +/- 16.8; 13 females, 19 males) and scanned using QCT. Mechanical tests were conducted using a protocol that minimized end-artifacts over the apparent density range tested (0.09-0.38 g/cm3). To account for the presence of multiple specimens per donor in this data set, donor was treated as a random effect in the regression model. Mean modulus (319 +/- 189 MPa) was higher and mean yield strain (0.78 +/- 0.06%) was lower than typical values reported previously due to minimization of the end-artifact errors. QCT density showed a strong positive correlation with modulus (n = 76) and yield stress (r2 = 0.90-0.95, n = 53, p < 0.001). There was a weak positive linear correlation with yield strain (r2 = 0.58, n = 53, p = 0.07). Prediction errors, incurred when estimating modulus or strength for specimens from a new donor, were 30-36% of the mean values of these properties. Direct QCT density-mechanical property regressions gave more precise predictions of mechanical properties than if physically measured wet apparent density was used as an intermediate variable to predict mechanical properties from QCT density. Use of these QCT density-mechanical property regressions should improve the fidelity of QCT-based biomechanical models of the human spine for whole bone and bone-implant analyses.     

Root cause analysis of internal hernia and Roux limb compression after laparoscopic Roux-en-Y gastric bypass using observational clinical human reliability assessment

BackgroundInternal hernia (IH) and Roux limb compression (RC) are recognized complications after retrocolic laparoscopic Roux-en-Y gastric bypass for obesity. The aim of the present study was to systematically identify the surgical technical errors leading to these complications.MethodsAn observational clinical human reliability assessment approach was used to analyze the operating videos of 3 groups: an IH group (n = 12), a Roux compression group (n = 13), and a control group (no complications, n = 21). Two investigators, unaware of the outcomes, reviewed all videos, using special rating software. All errors were categorized using the external error mode system and further described if a direct consequential error (e.g., bleeding) was found.ResultsAn analysis of data showed that, on average, more errors occurred in the complication groups than in the control group (IH 5.85, Roux compression 3.54, control .90, P < .001). The strongest differences were found for missing intermesenteric stitches on both sides of the Roux limb. Logistic regression analysis showed that a missed stitch between the mesentery of the Roux limb and the transverse mesocolon was an independent predictor for IH (B = 1.727, P = .025). No technical or consequential errors could be identified as responsible for RC.ConclusionThe observational clinical human reliability analysis is a useful method to identify operative failure. For retrocolic, retrogastric laparoscopic Roux-en-Y gastric bypass, a systematic approach for the closure of the transverse mesenteric window might prevent IH complications.     

Why should diagnostic benign breast biopsies weight less than twenty grams?

To reduce the cosmetic deformity resulting from diagnostic biopsies, current breast screening guidelines recommend that 80% of biopsy specimens that subsequently prove to be benign should weigh less than 20 g. The relationship between specimen weight and cosmesis is unknown and evidence to support a 20 g upper limit is lacking. Patient satisfaction following all benign biopsies weighing more than 20 g (n = 49) and a random sample of 30 of those weighing less than 20 g (n = 103) performed by one screening unit, over a 6 year period, was assessed by a postal questionnaire. Overall, 32% of patients were unhappy with the cosmetic outcome of their surgery. Patient dissatisfaction appeared to increase with specimen weight (6/23 [26%] < 20 g versus 13/36 [36%] > 20 g) but no statistically significant relationship between weight and cosmesis was apparent (P = 0.57). Reducing benign breast biopsy specimen weights to a minimum is a desirable objective. However, the current quality standard is not evidence-based, is too stringent and should be revised. Strategies need to be introduced to improve patient satisfaction following breast wire-localisation biopsies. In particular, patients should be counselled pre-operatively regarding possible adverse cosmetic outcome.     

Surgical specimen identification errors: a new measure of quality in surgical care

BACKGROUND: Communication errors are the primary factor contributing to all types of sentinel events including those involving surgical patients. One type of communication error is mislabeled specimens. The extent to which these errors occur is poorly quantified. We designed a study to measure the incidence and type of specimen identification errors in the surgical patient population. METHODS: We performed a prospective cohort study that included all patients who underwent surgery in an outpatient clinic or hospital operating room and for whom a pathology specimen was sent to the laboratory. The study took place during a 6-month period (October 2004 to April 2005) at an urban, academic medical center. The study's main end-points were the incidence and type of specimen labeling errors in the hospital operating room and the outpatient clinic. The specimen was the unit of analysis. All specimens were screened for "identification errors," which, for the purposes of this study, were defined as any discrepancy between information on the specimen requisition form and the accompanying labeled specimen received in the laboratory. Errors were stratified by the type of identification error, source, location, and type of procedure. RESULTS: A total of 21,351 surgical specimens were included in the analysis. There were 91 (4.3/1000) surgical specimen identification errors (18, specimen not labeled; 16, empty container; 16, laterality incorrect; 14, incorrect tissue site; 11, incorrect patient; 9, no patient name; and 7, no tissue site). Identification errors occurred in 0.512% of specimens originating from an outpatient clinic (53/10,354 specimens) and 0.346% of specimens originating from an operating room (38/10,997 specimens). Procedures involving the breast were the most common type to involve an identification error (breast = 11, skin = 10, colon = 8); in addition, 59.3% (54/91) of errors were associated with a biopsy procedure. Follow-up was complete in all cases found to have an identification error. CONCLUSIONS: Surgical specimen identification errors are common and pose important risks to all patients. In our study, these events occurred in 4.3 per 1000 surgical specimens or an annualized rate of occurrence of 182 mislabeled specimens per year. Given the frequency with which these errors occur and their potential effect on patients, the rate of surgical specimen identification errors may be an important measure of patient safety. Strategies to reduce the rate of these errors should be a research priority.     

Effects of the liver volume and donor steatosis on errors in the estimated standard liver volume

An accurate assessment of donor and recipient liver volumes is essential in living donor liver transplantation. Many liver donors are affected by mild to moderate steatosis, and steatotic livers are known to have larger volumes. This study analyzes errors in liver volume estimation by commonly used formulas and the effects of donor steatosis on these errors. Three hundred twenty-five Asian donors who underwent right lobe donor hepatectomy were the subjects of this study. The percentage differences between the liver volumes from computed tomography (CT) and the liver volumes estimated with each formula (ie, the error percentages) were calculated. Five popular formulas were tested. The degrees of steatosis were categorized as follows: no steatosis [n = 178 (54.8%)], ≤ 10% steatosis [n = 128 (39.4%)], and >10% to 20% steatosis [n = 19 (5.8%)]. The median errors ranged from 0.6% (7 mL) to 24.6% (360 mL). The lowest was seen with the locally derived formula. All the formulas showed a significant association between the error percentage and the CT liver volume (P < 0.001). Overestimation was seen with smaller liver volumes, whereas underestimation was seen with larger volumes. The locally derived formula was most accurate when the liver volume was 1001 to 1250 mL. A multivariate analysis showed that the estimation error was dependent on the liver volume (P = 0.001) and the anthropometric measurement that was used in the calculation (P < 0.001) rather than steatosis (P ≥ 0.07). In conclusion, all the formulas have a similar pattern of error that is possibly related to the anthropometric measurement. Clinicians should be aware of this pattern of error and the liver volume with which their formula is most accurate.     

Experimental method for the measurement of the elastic modulus of trabecular bone tissue

A procedure has been developed to measure the elastic modulus of small, irregularly shaped specimens without significantly disturbing the specimen's internal or surface structure. This procedure was developed to measure the average elastic modulus of isolated trabeculae from human cancellous bone tissue. The procedure combines direct testing of a cantilever beam-type specimen, along with finite element modeling of the specimen and the testing conditions. Initial estimates for the bone tissue material properties are input into the finite element model; differences between the calculated finite element displacement and the experimentally observed displacement allows the actual material modulus to be determined. Machined aluminum and cortical bone specimens were used to test the accuracy and repeatability of the procedure. Manipulations of the finite element models were performed to examine the effect that mesh construction errors might have on the accuracy of the results. None of the parameters examined resulted in changes in the measured finite element displacements of greater than 8%. In tests on six trabecular bone specimens, an average elastic modulus of 7.8 GPa was calculated. Even taking into account the possible sources of error, this value remains significantly less than the accepted value for cortical bone.     

Bilateral measurement of femoral bone mineral density.

Both femora were measured on 61 normal adults using dual X-ray absorptiometry (DXA). In a subset of 31 subjects, each femur was scanned once using the conventional leg-positioning device supplied with the densitometer, and once using a new positioning device and software that allowed both legs to be measured simultaneously. In another subgroup (n = 30), subjects were measured three times using the new dual-femur approach to better assess precision error. The data were analyzed for differences owing to the different positioning devices and for differences between right and left sides. The correlation between results with the old and new positioners was high (r > 0.99, standard error of the estimate [SEE] = 0.01-0.02 g/cm(2)). There was no significant difference in the average bone mineral density (BMD) values between the old and new positioner. The precision errors for each femur alone with the dual-femur approach were similar to those reported for the single-femur scans (1 to 2%), but the precision errors for the combined femora were reduced by 30% as expected. The correlation between right and left sides was high (r = 0.94-0.96), and the SEE in predicting one side from the other was moderate for total, trochanteric, and femoral neck BMD (0.05, 0. 05, and 0.06 g/cm(2), respectively). These SEE equate to about 0.5 standard deviation in terms of T-score. Differences in many individual cases between the right and left sides were significantly greater than the precision error. The new dual-femur software and leg positioner allows rapid measurement and analysis of both femora, thereby eliminating the uncertainty between sides.     

Interfragmentary compression across a simulated scaphoid fracture--analysis of 3 screws

PURPOSE: To measure the interfragmentary compression generated across a simulated fracture in cadaveric scaphoids by 3 different headless compression screws. METHODS: A transverse osteotomy was made through the waist of each scaphoid and a load cell to measure compression was interposed between the fragments, which were then fixed internally retrograde with either an Acutrak Standard (n = 10), Acutrak Mini (n = 12), or Bold (n = 10) screw. The surgeon was blinded to the measured compression, which was recorded during screw insertion and for the following 5 minutes. As a measure of scaphoid bone quality the modulus of elasticity of the trabecular bone of each specimen was then calculated from uniaxial compression tests. RESULTS: The mean interfragmentary compression generated by the Acutrak Standard screw was significantly greater and more consistent than the Bold screw or the Acutrak Mini screw. The compression achieved by the Acutrak Standard screw was also more consistent than that obtained by either the Bold or the Acutrak Mini screws as reflected by the lower standard deviation. The mean modulus of elasticity of the scaphoid trabecular bone was similar for each screw group. CONCLUSIONS: The interfragmentary compression generated by the Acutrak Standard screw was significantly greater and more consistent than that generated by either the Bold or Acutrak Mini screws. The compression generated by the Acutrak Standard and Mini screws was significantly better sustained over time than that generated by the Bold screw; however, these differences were small and may not be clinically important. The optimal compression required to promote scaphoid fracture union remains unknown and clinical trials are needed to further evaluate the outcome from using these devices.     

Fit assessment of anatomic plates for the distal medial tibia

OBJECTIVES: With the development and popularization of minimally invasive surgical methods and implants for fracture fixation, it is increasingly important that the available implants are precontoured to the specific anatomic location for which they are designed. The objective of this study was to develop a noninvasive method and criteria for quantifying the fit of a distal periarticular medial tibia plate and to test the method on a small set of tibia models. METHODS: The undersurface of the plate was extracted from a digital model of the plate. The surface of the plate was fitted to 21 computer tomography (CT)-based 3-dimensional (3-D) models of human tibiae. Four criteria were defined that constitute an anatomic plate fit and subsequently were applied for the quantitative fit assessment. The fitting of the plate undersurface to the bone was entirely conducted in a virtual environment. RESULTS: An anatomic fit of the plate was achieved for 4 of the models (19%). The individual categories generated fits of 62% (n = 13) for the proximal end; 43% (n = 9) for the proximal angle; 57% (n = 12) for the middle distance; and 57% (n = 12) for a distal fit. CONCLUSIONS: Although for the 4 individual criteria plate fits of 43%-62% were achieved, a global/anatomic fit only occurred for 19% of the bone models. This outcome is likely a result of bone morphology variations, which exist in a random population sample combined with the effects of a nonoptimized plate shape. Recommendations for optimizing the fit of the plate are discussed.     

Measuring Marrow Density and Area Using Peripheral Quantitative Computed Tomography at the Tibia: Precision in Young and Older Adults and Individuals With Spinal Cord Injury

The objective of this study was to compare the test-retest precision error for peripheral quantitative computed tomography (pQCT)-derived marrow density and marrow area segmentation at the tibia using 3 software packages. A secondary analysis of pQCT data in young adults (n?=?18, mean?±?standard deviation 25.4?±?3.2?yr), older adults (n?=?47, 71.8?±?8.2?yr), and individuals with spinal cord injury (C1–T12 American Spinal Injury Association Impairment Scale, classes A–C; n?=?19, 43.5?±?8.6?yr) was conducted. Repeat scans of the tibial shaft (66%) were performed using pQCT (Stratec XCT2000). Test-retest precision errors (root mean square standard deviation and root mean square coefficient of variation [RMSCV%]) for marrow density (mg/cm³) and marrow area (mm²) were reported for the watershed-guided manual segmentation method (SliceOmatic version 4.3 [Sliceo-WS]) and the 2 threshold-based edge detection methods (Stratec version 6.0 [Stratec-TB] and BoneJ version 1.3.14 [BoneJ-TB]). Bland-Altman plots and 95% limits of agreement were computed to evaluate test-retest discrepancies within and between methods of analysis and subgroups. RMSCV% for marrow density segmentation was >5% for all methods across subgroups (Stratec-TB: 12.2%–28.5%, BoneJ-TB: 14.5%–25.2%, and Sliceo-WS: 10.9%–23.0%). RMSCV% for marrow area segmentation was within 5% for all methods across subgroups (Stratec-TB: 1.9%–4.4%, BoneJ-TB: 2.6%–5.1%, and Sliceo-WS: 2.4%–4.5%), except using BoneJ-TB in older adults. Intermethod discrepancies in marrow density appeared to be present across the range of marrow density values and did not differ by subgroup. Intermethod discrepancies varied to a greater extent for marrow area and were found to be more frequently at mid- to higher-range values for those with spinal cord injury. Precision error for pQCT-derived marrow density segmentation exceeded 5% for all methods of analysis across a range of bone mineral densities and fat infiltration, whereas precision error for marrow area segmentation ranged from 2% to 5%. Further investigation is necessary to determine alternative acquisition and analysis methods for pQCT-derived marrow segmentation.     

Specimen diameter and “side artifacts” in cancellous bone evaluated using end-constrained elastic tension

In cancellous bone testing of cored samples, side artifacts are the underestimation of the true (i.e. in situ) mechanical properties due to the severing of the trabecular network during specimen preparation. Although other researchers have suggested correction factors derived from finite element method (FEM) models, it is proposed that side effects can be minimized by increasing the specimen diameter. Six different diameter specimens (3.1–10.6 mm), from two different anatomic sites (bovine femoral condyle and bovine lumbar vertebrae), were mechanically tested in elastic tension using an epoxy endcap protocol to eliminate end artifacts. Elastic modulus was found to be significantly affected by diameter in both sites. For example, the 5.1 mm samples underestimated the elastic modulus of the 10.6 mm samples by an average of roughly 20%. Yet no statistical difference was detected between the 8.3 and 10.6 mm samples in either anatomic site, suggesting that 8.3 mm diameter specimens were sufficiently large to avoid side artifacts. FEM models created from micro-CT images reveal that modulus approaches an asymptotic value with increasing diameter, and demonstrate an architecture-dependent drop in modulus at decreasing diameters. These results confirm, both experimentally and numerically, that side effects can be ignored given a suitably large specimen diameter and that this minimum diameter will be dependent on the cancellous architecture. An important implication of the latter result is that specimen diameters must be chosen appropriately when comparing test groups with different architectures (e.g. normal versus osteoporotic) to ensure that the magnitude of side artifacts does not confound the true differences between the groups.     

Mechanical behavior of human trabecular bone after overloading.

With the etiology of osteoporotic fractures as motivation, the goal of this study was to characterize the mechanical behavior of human trabecular bone after overloading. Specifically, we quantified the reductions in modulus and strength and the development of residual deformations and determined the dependence of these parameters on the applied strain and apparent density. Forty cylindrical specimens of human L1 vertebral trabecular bone were destructively loaded in compression at 0.5% strain per second to strains of up to 3.0% and then immediately unloaded to zero stress and reloaded. (An ancillary experiment on more readily available bovine bone had been performed previously to develop this testing protocol.) In general, the reloading stress-strain curve had a short initial nonlinear region with a tangent modulus similar to Young's modulus. This was followed by an approximately linear region spanning to 0.7% strain, with a reduced residual modulus. The reloading curve always approached the extrapolated envelope of the original loading curve. Percent modulus reduction (between Young's and residual), a quantitative measure of mechanical damage, ranged from 5.2 to 91.0% across the specimens. It increased with increasing plastic strain (r2 = 0.97) but was not related to modulus or apparent density. Percent strength reduction, in the range of 3.6-63.8%, increased with increasing plastic strain (r2 = 0.61) and decreasing apparent density (r2 = 0.23). The residual strains of up to 1.05% depended strongly on applied strain (r2 = 0.96). Statistical comparisons with previous data for bovine tibial bone lend substantial generality to these trends and provide an envelope of expected behavior for other sites. In addition to providing a basis for biomechanical analysis of the effects of damage in trabecular bone at the organ level, these findings support the concept that occasional overloads may increase the risk of fracture by substantially degrading the mechanical properties of the underlying trabecular bone.     

Correlation of mechanical properties of vertebral trabecular bone with equivalent mineral density as measured by computed tomography

We tried to determine whether mineral-equivalent measurements that were obtained using computed tomography could be used to predict the mechanical properties of vertebral trabecular bone. Vertebral bodies that had been obtained during routine autopsy were evaluated by computed tomography. The mechanical properties of the vertebral trabecular bone were determined by subjecting cylindrical specimens to simple compression until failure occurred. The ultimate strength and elastic modulus were determined from load time curves, using constant displacement rate loading. Atomic absorption spectrophotometry was used to determine the weight per cent calcium of each specimen, and quantitative light microscopy was used to determine area fraction bone. Significant positive correlations were found between the observed mechanical properties of the trabecular bone and the equivalent mineral density as measured by computed tomography. Compressive strength (r = 0.720), elastic modulus (r = 0.574), trabecular calcium density (r = 0.780), and area fraction bone (r = 0.579) were all correlated with the equivalent mineral density.     

Mast cell hyperplasia in chronic rejection after liver transplantation

The pathogenesis of chronic hepatic allograft rejection is poorly understood. Recent studies suggested that hepatic mast cells may be involved in the pathogenesis of chronic cholestatic liver disease. Because chronic rejection after liver transplantation is predominantly a cholestatic process, the aim of this study is to determine whether hepatic mast cells are involved in its pathogenesis. Biopsy specimens from (1) normal livers (n = 5), (2) transplanted livers with end-stage chronic rejection (n = 8), and (3) transplanted livers with acute cellular rejection (mild, n = 7; moderate, n = 5; severe, n = 7) were studied. Biopsy specimens were stained immunohistochemically for mast cells with human antitryptase antibody. Mast cell density was significantly increased in the chronic-rejection group (4.9 [plusmn] 0.6/mm²) compared with controls (2.9 [plusmn] 0.5/mm²; P [lt ] .05). The percentage of portal tracts containing mast cells was significantly greater in chronic-rejection (89% [plusmn] 8%) than control biopsy specimens (69% [plusmn] 5%; P [lt ] .05), as was the average number of mast cells per portal tract (5.4 [plusmn] 0.9 v 1.9 [plusmn] 0.4 cells; P [lt ] .01). In chronic rejection, tissue mast cells frequently were seen surrounding damaged bile ducts in inflamed portal tracts. Neither mast cell density nor distribution was significantly different from controls in posttransplantation biopsy specimens with acute cellular rejection of mild, moderate, or severe degree. The finding of mast cells infiltrating portal tracts and surrounding damaged bile ducts in chronic rejection suggests that hepatic mast cells may be important effector cells in the pathogenesis of chronic rejection. (Liver Transpl 2002;8:50-57.)     

A Systematic Review Investigating the Effectiveness of Surgical Versus Conservative Management of Unstable Ankle Fractures in Adults

Nine percent of all fractures affect the ankle, with an annual incidence of 122/100,000 in Edinburgh, UK. While unstable fractures are usually treated surgically, there has been no recent systematic review of the evidence supporting this decision. In this systematic review, relevant electronic databases (such as MEDLINE and CINHAL) were searched from inception to February 2017. Five randomized controlled trials that examined surgical versus conservative interventions in 951 adults with closed ankle fractures, with follow-up for at least 6 months, were selected for further synthesis of evidence. The risk of selection bias in all selected trials was relatively low. However, most of the trials had a high risk of performance and detection bias. Three of the 5 selected trials used the validated functional Olerud Molander Ankle Score. One trial (n = 43), reported a statistically better score for the surgical group at 27-month follow-up, whereas a second (n = 81) and a third (n = 620) trial found no significant difference at 12 and 6 months, respectively. No significant differences between surgical and conservative treatments were reported in 2 trials (n = 111) and (n = 96) in nonvalidated functional outcome measures. Other outcomes were malunion (9/334 [2.6%] versus 48/301 [15.9%], p < .0001) and nonunion (3/408 [0.7%] versus 28/383 [7.3%], p < .0001) and were considerably higher in the conservatively treated group. Early treatment failure was significantly lower with surgery (7/435 [1.6%] versus 70/419 [16.7%], p < .0001). The risk of malunion, nonunion, and loss of reduction were greater in nonoperative care. However, the 2 treatment approaches provided equivalent functional outcomes.     

Depth-dependent compressive properties of normal aged human femoral head articular cartilage: relationship to fixed charge density

OBJECTIVES: Determine the depth-varying confined and osmotic compression moduli of normal human articular cartilage from the femoral head, and test whether these moduli are dependent on fixed charge density. METHODS AND RESULTS: Using an automated instrument to allow epifluorescence microscopy analysis during confined compression testing on cartilage samples, the equilibrium confined compression modulus (H(A 0)) was found to vary markedly with depth (z=0-1500 microm) from the articular surface. H(A 0) increased from 1.16+/-0.20 MPa in the superficial (0-125 microm) layer to 7.75+/-1.45 MPa in the deepest (1250-1500 microm) layer tested, and was fit by the expression, H(A 0)(z) [MPa]=1.44 exp(0.0012.z [microm]). Also, in successive slices of cartilage extending from the articular surface to the middle-deep regions, the bulk modulus (K(0)) and fixed charge density (FCD) increased, consistent with previous findings. While H(A 0), K(0), and FCD each varied with depth from the articular surface, the dependence of H(A 0) and K(0) on depth did not appear to be completely related to variations in FCD. CONCLUSIONS: The confined compression modulus of normal aged human femoral head articular cartilage increases markedly with depth from the articular surface, a trend similar to that observed for articular cartilage from other joints in animals but with an absolute amplitude that is several-fold higher. The compressive properties were not simply related to FCD at different depths from the articular surface, suggesting that other as yet undefined factors also contribute to compressive properties.     

Ankle fracture configuration following treatment with and without arthroscopic-assisted reduction and fixation

AIM: To report ankle fracture configurations and bone quality following arthroscopic-assisted reduction and internal-fixation(ARIF) or open reduction and internalfixation(ORIF). METHODS: The patients of ARIF(n = 16) or ORIF(n = 29) to treat unstable ankle fracture between 2006 and 2014 were reviewed retrospectively. Baseline data, including age, sex, type of injury, immediate postoperative fracture configuration(assessed on X-rays and graded by widest gap and largest step-off of any intraarticular site), bone quality [assessed with bone mineral density(BMD) testing] and arthritic changes on X-rays following surgical treatments were recorded for each group.RESULTS: Immediate-postoperative fracture configurations did not differ significantly between the ARIF and ORIF groups. There were anatomic alignments as 8(50%) and 8(27.6%) patients in ARIF and ORIF groups(P = 0.539) respectively. There were acceptable alignments as 12(75%) and 17(58.6%) patients in ARIF and ORIF groups(P = 0.341) respectively. The arthritic changes in follow-up period as at least 16 wk following the surgeries were shown as 6(75%) and 10(83.3%) patients in ARIF and ORIF groups(P = 0.300) respectively. Significantly more BMD tests were performed in patients aged 60 years(P 0.001), ARIF patients(P = 0.021), and female patients(P = 0.029). There was no significant difference in BMD test t scores between the two groups. CONCLUSION: Ankle fracture configurations following surgeries are similar between ARIF and ORIF groups, suggesting that ARIF is not superior to ORIF in treatment of unstable ankle fractures.