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Straight proximal humeral nails are surrounded by more bone stock in comparison to bent nails in an experimental cadaveric study.

Günther CM, Müller PE, Mutschler W, Sprecher CM, Milz S, Braunstein V - Patient Saf Surg (2014)

Bottom Line: For both straight and bent volumes of interest a considerably declining bone mineral density was found in craniocaudal direction.Mean densities of bent volumes were significantly lower in comparison to their corresponding straight counterparts (p < 0.01) Intra-individual comparison yielded high bivariate correlations of the corresponding Volumes of Interest of the right and the left side (p < 0.01).The high correlation between the Volumes of Interest of the corresponding right and left sides could aid in preoperative planning when considering an intra- or extramedullary approach.

View Article: PubMed Central - HTML - PubMed

Affiliation: University Hospital of Munich, Department of Orthopaedic Surgery, Physical Medicine and Rehabilitation - Campus Großhadern, Ludwig-Maximilians-University, Marchioninistr. 15, 81377 Munich, Germany.

ABSTRACT

Background: In the management of proximal humeral fractures intramedullary implants with bent and straight shape of the proximal part of nail are available. Based on data from previous studies on bone distribution in the humeral head, we hypothesized, that higher densities might exist in the bone stock surrounding straight nails in comparison to their angulated counterparts. With a known positive correlation between bone density and mechanical stability, this could indicate potentially higher rigidity of osteosyntheses done with straight implants.

Methods: We performed high resolution peripheral quantitative computed tomographies of the potential straight and bent implant bearing regions of 27 cadaveric proximal humeri. The acquired data were analyzed for differences between straight and bent Volumes of Interest as well as intra- and interindividual bone stock distribution.

Results: For both straight and bent volumes of interest a considerably declining bone mineral density was found in craniocaudal direction. Mean densities of bent volumes were significantly lower in comparison to their corresponding straight counterparts (p < 0.01) Intra-individual comparison yielded high bivariate correlations of the corresponding Volumes of Interest of the right and the left side (p < 0.01).

Conclusions: Based on the volumetric data a statistically relevant biomechanical superiority of straight shaped implants can be assumed. Since we found a rapid decrease of bone density in cranio-caudal direction, intramedullary implants should be anchored as proximally in the subcortical area as possible to minimize the risk of displacement or cutout. The high correlation between the Volumes of Interest of the corresponding right and left sides could aid in preoperative planning when considering an intra- or extramedullary approach.

No MeSH data available.


Related in: MedlinePlus

Schematic view of the bent and straight regions of interest (with sub-regions representing tubular quarters of the entire volume) in a frontal plane.
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Figure 2: Schematic view of the bent and straight regions of interest (with sub-regions representing tubular quarters of the entire volume) in a frontal plane.

Mentions: The boundaries of the Volumes of Interest (VOI) was selected on the basis of two of the most commonly used intramedullary proximal humeral nailing systems, the Expert Humeral Nail (Synthes® Inc.) and its bent precursor, the Proximal Humerus Nail, PHN (Synthes® Inc.). The inner diameter of the tubular shaped VOI was set at 9 mm, surrounding the area that has not to be analyzed, since in reality it is filled by the implant, The outer diameter was set at 12 mm, forming a compromise between the area mechanically affected and the discriminatory power between bent and straight volumes. A horizontal line at the most distal point of the glenohumeral cartilage defined the lower border of the humeral head and thus the lower border of the specimen’s VOI to account for different head sizes. Straight VOIs were aligned along to the extended longitudinal humeral shaft axis and oriented transversally at the zenith of the humeral head. Bent VOIs were angulated 5° and positioned according to the implantation specification of the Expert PHN System, which postulates a lateral view positioning in projection of the extended central humeral shaft axis and in anterior-posterior-projection of the bone-cartilage-border (Figures 1 and 2). Since a variable, non-linear distribution of bone mineral density was expected, we further segmented the tubular VOIs into isovolumetric quarters to improve characterization and comparability of the quarters (Figure 2). Those were numbered from proximal to distal with 1 to 4. For binary segmentation, a uniform threshold of 11% of the maximal gray scale value was selected for all samples. This value in the gray value distribution histogram represents the peak characteristic of bone tissue. The segmented VOIs contained only cancellous bone. Separation of cortical from subcortical areas was done manually on inspection using axial views. Bone volume (BV) was calculated using a tetrahedron meshing technique generated with the marching cubes method. The total volume (TV) was defined as the complete volume of the respective VOIs. From BV and TV, the mean bone volume to total volume (BV/TV) value was calculated.


Straight proximal humeral nails are surrounded by more bone stock in comparison to bent nails in an experimental cadaveric study.

Günther CM, Müller PE, Mutschler W, Sprecher CM, Milz S, Braunstein V - Patient Saf Surg (2014)

Schematic view of the bent and straight regions of interest (with sub-regions representing tubular quarters of the entire volume) in a frontal plane.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4016779&req=5

Figure 2: Schematic view of the bent and straight regions of interest (with sub-regions representing tubular quarters of the entire volume) in a frontal plane.
Mentions: The boundaries of the Volumes of Interest (VOI) was selected on the basis of two of the most commonly used intramedullary proximal humeral nailing systems, the Expert Humeral Nail (Synthes® Inc.) and its bent precursor, the Proximal Humerus Nail, PHN (Synthes® Inc.). The inner diameter of the tubular shaped VOI was set at 9 mm, surrounding the area that has not to be analyzed, since in reality it is filled by the implant, The outer diameter was set at 12 mm, forming a compromise between the area mechanically affected and the discriminatory power between bent and straight volumes. A horizontal line at the most distal point of the glenohumeral cartilage defined the lower border of the humeral head and thus the lower border of the specimen’s VOI to account for different head sizes. Straight VOIs were aligned along to the extended longitudinal humeral shaft axis and oriented transversally at the zenith of the humeral head. Bent VOIs were angulated 5° and positioned according to the implantation specification of the Expert PHN System, which postulates a lateral view positioning in projection of the extended central humeral shaft axis and in anterior-posterior-projection of the bone-cartilage-border (Figures 1 and 2). Since a variable, non-linear distribution of bone mineral density was expected, we further segmented the tubular VOIs into isovolumetric quarters to improve characterization and comparability of the quarters (Figure 2). Those were numbered from proximal to distal with 1 to 4. For binary segmentation, a uniform threshold of 11% of the maximal gray scale value was selected for all samples. This value in the gray value distribution histogram represents the peak characteristic of bone tissue. The segmented VOIs contained only cancellous bone. Separation of cortical from subcortical areas was done manually on inspection using axial views. Bone volume (BV) was calculated using a tetrahedron meshing technique generated with the marching cubes method. The total volume (TV) was defined as the complete volume of the respective VOIs. From BV and TV, the mean bone volume to total volume (BV/TV) value was calculated.

Bottom Line: For both straight and bent volumes of interest a considerably declining bone mineral density was found in craniocaudal direction.Mean densities of bent volumes were significantly lower in comparison to their corresponding straight counterparts (p < 0.01) Intra-individual comparison yielded high bivariate correlations of the corresponding Volumes of Interest of the right and the left side (p < 0.01).The high correlation between the Volumes of Interest of the corresponding right and left sides could aid in preoperative planning when considering an intra- or extramedullary approach.

View Article: PubMed Central - HTML - PubMed

Affiliation: University Hospital of Munich, Department of Orthopaedic Surgery, Physical Medicine and Rehabilitation - Campus Großhadern, Ludwig-Maximilians-University, Marchioninistr. 15, 81377 Munich, Germany.

ABSTRACT

Background: In the management of proximal humeral fractures intramedullary implants with bent and straight shape of the proximal part of nail are available. Based on data from previous studies on bone distribution in the humeral head, we hypothesized, that higher densities might exist in the bone stock surrounding straight nails in comparison to their angulated counterparts. With a known positive correlation between bone density and mechanical stability, this could indicate potentially higher rigidity of osteosyntheses done with straight implants.

Methods: We performed high resolution peripheral quantitative computed tomographies of the potential straight and bent implant bearing regions of 27 cadaveric proximal humeri. The acquired data were analyzed for differences between straight and bent Volumes of Interest as well as intra- and interindividual bone stock distribution.

Results: For both straight and bent volumes of interest a considerably declining bone mineral density was found in craniocaudal direction. Mean densities of bent volumes were significantly lower in comparison to their corresponding straight counterparts (p < 0.01) Intra-individual comparison yielded high bivariate correlations of the corresponding Volumes of Interest of the right and the left side (p < 0.01).

Conclusions: Based on the volumetric data a statistically relevant biomechanical superiority of straight shaped implants can be assumed. Since we found a rapid decrease of bone density in cranio-caudal direction, intramedullary implants should be anchored as proximally in the subcortical area as possible to minimize the risk of displacement or cutout. The high correlation between the Volumes of Interest of the corresponding right and left sides could aid in preoperative planning when considering an intra- or extramedullary approach.

No MeSH data available.


Related in: MedlinePlus