Maria Apreleva

The cortical thickness of the proximal humeral diaphysis predicts bone mineral density of the proximal humerus

The operative treatment of fractures of the proximal humerus can be complicated by poor bone quality. Our aim was to evaluate a new method which allows prediction of the bone quality of the proximal humerus from radiographs. Anteroposterior radiographs were taken of 19 human cadaver humeri. The cortical thickness was measured at two levels of the proximal humeral diaphysis. The bone mineral density (BMD) was determined for the humeral head (HH), the surgical neck (SN), the greater tuberosity (GT) and lesser tuberosity (LT) using dual-energy x-ray absorptiometry. The mean cortical thickness was 4.4 +/- 1.0 mm. Specimens aged 70 years or less had a significantly higher cortical thickness than those aged over 70 years. A significant positive correlation was found between cortical thickness and the BMD for each region of interest. The cortical thickness of the proximal diaphysis is a reliable predictor of the bone quality of the proximal humerus.

Anchor Design and Bone Mineral Density Affect the Pull-out Strength of Suture Anchors in Rotator Cuff Repair Which Anchors Are Best to Use in Patients With Low Bone Quality?

Background Different metal and biodegradable suture anchors are available for rotator cuff repair. Poor bone quality may result in anchor loosening and tendon rerupture. Hypotheses Higher bone mineral density is associated with higher pull-out strength of suture anchors. Depending on anchor placement, pull-out strengths of anchors are different within the greater tuberosity. Study Design Cadaveric biomechanical study. Methods Trabecular and cortical bone mineral densities were determined for different regions within the greater tuberosity. Metal screw-type and biodegradable hook-type anchors were cyclically loaded. Results Mean failure load of metal and biodegradable anchors was 273 N and 162 N, respectively, for the proximal part (P < .01) and 184 N and 112 N, respectively, for the distal part (P < .01). Both types of anchors showed higher failure loads in the proximal-anterior and -middle parts of the greater tuberosity than in the distal part (P < .01). A significant positive correlation was found between cortical bone mineral density and failure load of metal anchors (P < .01). Conclusion Bone quality, anchor type, and anchor placement have a significant impact on anchor failure loads. Clinical Relevance Suture anchors should be placed in the proximal-anterior and -middle parts of the greater tuberosity. In the distal parts, biodegradable hook-like anchors should be used with caution.

Pullout Strength of Suture Anchors Used in Rotator Cuff Repair

BACKGROUND Surgical treatment of rotator cuff tears may be complicated by osteoporosis of the proximal part of the humerus. The purpose of this study was to determine whether pullout strength of suture anchors is affected by the location of the anchor placement and by bone mineral density. We hypothesized that higher bone mineral density is associated with higher pullout strength of suture anchors. METHODS Peripheral quantitative computed tomography was used to measure total, trabecular, and cortical bone mineral density in different regions of the lesser and greater tuberosities in seventeen cadaveric humeri. Suture anchors were inserted into individual regions and subjected to cyclic loading. Repeated-measures analysis of variance was used to assess differences in bone mineral density and load to failure between regions of interest. Pearson correlation was used to determine the association between bone mineral density and pullout strength of suture anchors. RESULTS Total, trabecular, and cortical bone mineral densities were an average of 50%, 50%, and 10% higher, respectively, in the proximal part of the tuberosities compared with the distal part (p < 0.01). Within the proximal part of the greater tuberosity, trabecular bone mineral density of the posterior region and cortical bone mineral density of the middle region were, on the average, 25% and 16% higher, respectively, than the densities in the other regions (p < 0.01). Load to failure in the proximal part of the tuberosities was an average of 53% higher than that in the distal part (p < 0.01). The lesser tuberosity showed, on the average, a 32% higher load to failure than did the greater tuberosity (p < 0.01). Within the proximal part of the greater tuberosity, loads to failure in the anterior and middle regions were, on the average, 62% higher than the load to failure in the posterior region (p < 0.01). Overall positive correlations were found between bone mineral density and load to failure (0.65 </= r </= 0.74, p < 0.01). CONCLUSIONS We found that pullout strength of suture anchors correlates well with bone mineral density of the tuberosities. Higher loads to failure were found in regions in the proximal part of the tuberosities. Placement of anchors in these regions may prevent anchor loosening, formation of a tendon-bone gap, and failure of the rotator cuff repair.

Accuracy and repeatability of a pressure measurement system in the patellofemoral joint.

The objective of this study was to assess how accurately and repeatably the Iscan system measures force and pressure in the natural patellofemoral joint. These measurements must be made to test widely held assumptions about the relationships between mechanics, pain and cartilage degeneration. We assessed the systems accuracy by using test rigs in a materials testing machine to apply known forces and force distributions across the sensor. The root mean squared error in measuring resultant force (for five trials at each of seven load levels) was 6.5 +/- 4.4% (mean +/- standard deviation over all trials at all load levels), while the absolute error was -5.5 +/- 5.6%. For force distribution, the root mean squared error (for five trials at each of five force distributions) was 0.86 +/- 0.58%, while the absolute error was -0.22 +/- 1.03%. We assessed the repeatability of the systems measurements of patellofemoral contact force, pressure and force distribution in four cadaver specimens loaded in continuous and static flexion. Variability in measurement (standard deviation expressed as a percentage of the mean) was 9.1% for resultant force measurements and 3.0% for force distribution measurements for static loads, and 7.3% for resultant force and 2.2% for force distribution measurements for continuous flexion. Cementing the sensor to the cartilage lowered readings of resultant force by 31 +/- 32% (mean +/- standard deviation), area by 24 +/- 13% and mean pressure by 9 +/- 34% (relative to the uncemented sensor). Maximum pressure measurement, however, was 24 +/- 43% higher in the cemented sensor than in the uncemented sensor. The results suggest that the sensor measures force distribution more accurately and repeatably than absolute force. A limitation of our work, however, is that the sensor must be cemented to the patellar articular surface to make the force distribution measurements, and our results suggest that this process reduces the accuracy of force, pressure and area measurements. Our results suggest that the Iscan systems pressure measurement accuracy and repeatability are comparable to that of Fuji Prescale film, but its advantages are that it is thinner than most Fuji Prescale film, it measures contact area more accurately and that it makes continuous measurements of force, pressure and area.

Magnetic resonance imaging in quantitative analysis of rotator cuff muscle volume.

Tears of the rotator cuff are accompanied by muscle atrophy, which has direct implications on patient outcome after rotator cuff surgery. However, no reliable method exists to determine muscle volumes in situ. The current authors evaluated the reliability of magnetic resonance imaging in assessing rotator cuff muscle volumes. Muscle volumes were determined in 10 shoulders from cadavers using two methods: (1) oblique sagittal shoulder scans were obtained, the contours of the supraspinatus, infraspinatus and teres minor, and subscapularis muscles were traced, and muscle volumes were calculated using image analysis software; and (2) rotator cuff muscles were dissected and muscle volumes were measured by water displacement. The average magnetic resonance imaging volume of the supraspinatus, infraspinatus and teres minor, and subscapularis muscles were 36 ± 12, 96 ± 41, and 99 ± 33 mL, respectively. There was a significant correlation between magnetic resonance imaging and water displacement measurements. The intraobserver and interobserver variabilities were less than 4%. The results indicate the magnetic resonance imaging is a reliable method to determine rotator cuff muscle volumes with good intraobserver and interobserver variability. This method may prove valuable preoperative assessment of rotator cuff muscles and prediction of outcome after rotator cuff repair.

The Effects of Medialization and Anteromedialization of the Tibial Tubercle on Patellofemoral Mechanics and Kinematics

Background Medialization and anteromedialization of the tibial tubercle are used to correct patellar subluxation in adults. Purpose To compare the effects of the 2 osteotomies on patellofemoral joint contact pressures and kinematics. Study Design Controlled laboratory study. Methods Tibial tubercle osteotomies were performed on 10 cadaveric human knees. The knees were tested between 0° and 90° of flexion while dynamic patellofemoral joint contact pressure and kinematic data were simultaneously obtained. Four conditions were tested: normal knee alignment, simulated increased Q angle, postmedialization of the tibial tubercle, and postanteromedialization of the tubercle. Results An increased Q angle laterally translated the patella, shifted force to the lateral facet, and increased patella contact pressures. Both medialization and anteromedialization partially corrected the abnormal contact pressures. Medialization partially corrected the shift of force to the lateral facet induced by an increased Q angle, whereas the anteromedialization could not. Both medialization and anteromedialization corrected the patella maltracking. Conclusion Medialization and anteromedialization are equivalent in their ability to correct abnormal patellar mechanics and kinematics.

Three-dimensional distribution of bone density in the proximal humerus

Bone quality of the proximal humerus is important for the surgical treatment of proximal humeral fractures and rotator cull tears. However, very few studies have evaluated the areal bone mineral density (BMD) of the proximal humerus. The aim of this study was to analyze the volumetric BMD (vBMD) using peripheral-quantitative-computed-tomography. Total, trabecular and cortical vBMD were determined separately for the proximal and distal half of the humeral head, the surgical neck and seven specific regions of interest. The greater tuberosity (GT) was divided into three regions, and the lesser tuberosity (LT) and articular surface (AS) were each divided into two regions. The proximal head showed a significantly higher trabecular (+46%) and cortical vBMD (+15%) than the distal one. The mean trabecular vBMD of AS was significantly higher (+80%), and the cortical vBMD was significantly lower (-11%) than that of the tuberosities. In the proximal half of GT, trabecular vBMD was higher in the posterior than in the middle and anterior regions. Cortical vBMD was higher in middle region than in the anterior and posterior ones. In the distal half of GT, trabecular vBMD was significantly higher in the posterior than in the middle region, and cortical vBMD was significantly higher in the anterior than in the middle region. In the proximal half of AS, trabecular vBMD was significantly higher in the posterior region than in the anterior one. These results point to bone sites that may provide stronger fixation for implants, reduce the risk of implant loosening, and therefore improve patient outcome.

Practical assessment of rotator cuff muscle volumes using shoulder MRI.

Reliable quantitative assessment of rotator cuff (RC) muscle volumes can be done by reconstructing multiple MRI images of the entire shoulder. However, an equally reliable, but less time-consuming, method is needed for clinical practice. We compared the only method reported for estimation of volume with a new simple MRI technique. Both methods were validated by multiple MRI image reconstruction. We performed MRI scans of 10 cadaver shoulders and determined the cross-sectional areas of RC muscles with two methods, using image analyzing software. In Method 1, the cross-sections were determined on a single image, previously described as a Y-shaped image. In Method 2, the cross-sections were calculated from two images: the Y-shaped and an image located medially, twice the distance from the glenoid articular surface compared to the Y-shaped image. We compared the results of these two methods with the volume of multiple MRI image reconstruction, which took into account all images consisting of RC cross-sections. Pearson correlations for Method 1 were 0.96, 0.94 and 0.75, and for Method 2, 0.96, 0.97 and 0.93 for the supraspinatus, infraspinatus/teres minor and subscapularis muscle volumes when compared with the volumes determined by the multiple image reconstruction method. The Bland-Altman method showed better agreement with multiple MRI image reconstruction, using Method 2, to determine supraspinatus, infraspinatus, and subscapularis muscle volumes (p<0.001 for each). The mean intra- and inter-observer variabilities of Method 1 was 3.9% and 2.9% and that of Method 2, 3.0% and 1.7%, respectively. Both methods can be used for quantitative assessment of RC muscle volumes. However, Method 2, using two easily reproducible MRI images is more accurate for the evaluation of the supraspinatus and infraspinatus/teres minor muscles and particularly for the subscapularis muscle.

Quantitative morphology of the scapula : Normal variation of the superomedial scapular angle, and superior and inferior pole thickness

This study examined the normal variation of the superomedial scapular angle and the thickness of the superior and inferior scapular borders. Scapulae of 53 cadaver shoulders were dissected free from all soft tissue. A line was drawn from the most superior to the most inferior point on each scapula, and the scapulae were cut along this line to obtain cross sections. The supero-medial scapular angle (alpha) was measured with a goniometer from the cross section as a ABC: through the inferior tip (A), base of the spine (B), and superior tip (C). Superior and inferior pole thickness was measured with a digital caliper from the thickest portions on the cross section of the poles. Average superomedial angle was 139 degrees +/- 6 degrees (range: 125 degrees - 156 degrees). Average thickness for the superior and inferior poles was 3.9 +/- 0.9 mm (range: 2.1 - 8.3 mm) and 7.5 +/- 1.5 mm (range: 4 - 11 mm), respectively. The thickness of both superior and inferior poles was significantly different between male and female specimens (P < .05), with male scapulae having the higher values.