M. Mentzel

Correlation of bone mineral density with strength and microstructural parameters of cortical bone in vitro

The aim of this study was to evaluate the influence of microstructural parameters, such as porosity and osteon dimensions, on strength. Therefore, the predictive value of bone mineral density (BMD) measured by quantitative computed tomography (QCT) for intracortical porosity and other microstructural parameters, as well as for strength of cortical bone biopsies, was investigated. Femoral cortical bone specimens from the middiaphysis of 23 patients were harvested during total hip replacement while drilling a hole (dia. 4.5 mm) for the relief of the intramedullary pressure. In vitro structural parameters assessed in histological sections as well as BMD determined by quantitative computed tomography were correlated with yield stress, and elastic modulus assessed by a compression test of the same specimens. Significant correlations were found between BMD and all mechanical parameters (elastic modulus: r = 0.69, p < 0.005; yield stress: r = 0.64, p < 0.005). Significant correlations between most structural parameters assessed by histology and yield stress were discovered. Structural parameters related to pore dimensions revealed higher correlation coefficients with yield stress (r = -0.69 for average pore diameter and r = -0.62 for fraction of porous structures, p < 0.005) than parameters related to osteons (r = 0.60 for osteon density and average osteonal area, p < 0.005), whereas elastic modulus was predicted equally well by both types of parameters. Significant correlations were found between BMD and parameters related to porous structures (r = 0.85 for porosity, 0.80 for average pore area, and r = 0.79 for average pore diameter in polynomial regression, p < 0.005). Histologically assessed porosity correlated significantly with parameters describing porous structures and haversian canal dimensions. Our results indicate a relevance of osteon density and fraction of osteonal structures for the mechanical parameters of cortical bone. We consider the measurement of BMD by quantitative computed tomography to be helpful for the estimation of bone strength as well as for the prediction of intracortical porosity and parameters related to porous structures of cortical bone.

Prediction of cortical bone porosity In Vitro by microcomputed tomography

The high importance of intracortical porosity for mechanical strength of cortical bone has been established. The contribution of other parameters of microstructure such as osteon dimensions for strength is in discussion. The aim of this study was to evaluate the predictive value of microcomputed tomography (µCT) for porosity and other microstructural parameters of cortical bone in cortical bone biopsies. Femoral cortical bone specimens from the middiaphysis of 24 patients were harvested during the procedure of total hip replacement at the location where normally one hole (Ø 4.5 mm) for the relief of the intramedullary pressure is placed.In vitro intracortical porosity and bone mineral density (BMD) measurements by µCT were compared with structural parameters assessed in histological sections of the same specimens. A strong correlation was found between intracortical porosity measured by µCT and histological porosity (r=0.95,P<0.0001). Porosity measured by µCT was also a strong predictor for other parameters describing dimensions of porous structures. BMD−1 was associated with osteonal area (r=−0.76,P<0.0001). We consider the measurement of porosity by µCT as a very potent procedure for assessing intracortical porosity and parameters related to porous structures of cortical bone nondestructivelyin vitro.

Predictive value of bone mineral density and morphology determined by peripheral quantitative computed tomography for cancellous bone strength of the proximal femur.

Peripheral quantitative computed tomography (pQCT) is an established diagnostic method for assessment of bone mineral density in the diagnosis of osteoporosis. However, the capacity of structural parameters of cancellous bone measured by high-resolution computed tomography remains to be explored. In 33 patients, bone mineral density (BMD) of the proximal femur was measured in vitro by pQCT using cylindrical biopsies from the intertrochanteric region harvested before the implantation of an artificial hip joint. By digital image analysis of CT scans, parameters derived from histomorphometry describing the microarchitecture of cancellous bone were measured. The biopsies were also loaded to failure by an uniaxial compression test to determine the biomechanical parameters, Youngs modulus, strength, and maximum energy absorption (E(max)). Strong correlations were found for BMD vs. mechanical parameters (r = 0.73 for Youngs modulus, r = 0.82 for strength, and r = 0.79 for E(max); p < 0.001, n = 29). The morphological parameters, bone volume per trabecular volume (BV/TV), apparent trabecular thickness (app.Tb.Th), apparent trabecular separation (app.Tb.Sp), and trabecular number (Tb.N), correlated significantly with all mechanical parameters. The combination of morphological parameters with BMD in a multivariate regression model led to an overall, but only moderate, increase in R(2) in all cases. Our data confirm the high predictive value of BMD for the mechanical competence of cancellous bone of the intertrochanteric region. However, quantification of cancellous bone structure by image analysis of CT scans may provide additional qualitative information for the analysis of bone strength.

Prediction of strength of cortical bone in vitro by microcomputed tomography

OBJECTIVE The aim of this study was to evaluate the predictive value of bone mineral density and intracortical porosity measured by microcomputed tomography for the strength of cortical bone biopsies. DESIGN Experimental study comparing the predictive value of bone mineral density and of intracortical porosity determined in vitro by microcomputed tomography for the mechanical properties of cortical bone cylinders. BACKGROUND The assessment of cortical bone strength might be relevant for the prediction of fracture risk or the choice of suitable therapy strategies in orthopaedic surgery. The predictive value of cortical density for the mechanical properties is discussed controversially. The relevance of intracortical porosity measured by histomorphometry has been established, but the predictive value of porosity determined by microcomputed tomography remains to be explored. METHODS Femoral cortical bone specimens from the mid diaphysis of 24 patients were harvested during total hip replacement procedure at the location, where a diaphyseal hole (diameter 4.5 mm) was drilled in order to reduce the intramedullary pressure. In vitro intracortical porosity and bone mineral density measurements by microcomputed tomography were compared with strength and elastic modulus assessed by a compression test transverse to the Haversian systems of the same specimens. RESULTS Significant negative correlations were found between porosity measured by microcomputed tomography scans and yield stress, stiffness and elastic modulus (P<0.001), however, the positive correlations between bone mineral density and mechanical parameters were stronger (P<0.0001). The mechanical parameter best predicted by mineral density as well as by porosity was yield stress (r=0.72,P<0.0001;r=-0.64,P<0.001). CONCLUSIONS Bone mineral density determined by microcomputed tomography imaging in vitro may be a potent method to predict mechanical properties of cortical bone non-destructively. The application in vivo remains to be explored.

The Effectiveness of ADCON-T/N, a New Anti-Adhesion Barrier Gel, in Fresh Divisions of the Flexor Tendons in Zone II

In a prospective randomized clinical trial, ADCON-T/N was investigated with regard to its effectiveness in fresh traumatic injuries of the flexor tendons in Zone II of the hand. Thirty patients participated in the trial. Following a standardized technique of tendon repair, the total active motion (TAM) and total extension lag (TEL) were determined after 12 weeks and evaluated according to the Buck-Gramcko score. Excellent results were achieved in 15 out of 16 patients in the ADCON-T/N group and 12 out of 14 in the control group. However, no statistically significant difference was found between the mean TAM and TEL in the two groups.

Predictive value of Singh index and bone mineral density measured by quantitative computed tomography in determining the local cancellous bone quality of the proximal femur

OBJECTIVE The purpose of this study was to assess the predictive value of the Singh index as well as quantitative computed tomography for the in vitro local mechanical competence of the cancellous bone of the proximal femur. DESIGN An experimental study examining the relation between mechanical properties and bone mineral density of the femoral neck determined in vitro and the clinical estimated Singh index on X-rays. BACKGROUND Evaluation of the predictive value of the Singh index, an inexpensive and simple technique for the mechanical properties of the cancellous bone of the proximal femur. METHODS The bone quality of the proximal femur of 34 patients undergoing total hip replacement was estimated by roentgenography using the Singh index. Bone mineral density was quantified by quantitative computed tomography using cylindrical cancellous bone biopsies harvested during the total hip replacement procedure by a new biopsy method. The mechanical properties of the bone specimens (Youngs modulus, strength and maximum energy absorption E(max)) were measured by mechanical testing of the bone biopsies. RESULTS A strong correlation of the Singh index versus material properties of cancellous bone was noted (r=0.66 for Youngs modulus, r=0.73 for strength and r=0.69 for E(max), P<0.0001). The correlations of bone mineral density measured by quantitative computed tomography versus Youngs modulus, strength and energy absorption E(max) were significant. Strength was predicted best (r=0.82; P<0.0001), followed by E(max) (r=0.79; P<0.0001) and Youngs Modulus (r=0.73; P<0.0001). CONCLUSIONS We conclude, that assessment of bone mineral density by quantitative computed tomography is a reliable and precise method for the estimation of cancellous bone material properties. The Singh index provides a rough estimate for the mechanical competence of the proximal femur. It is inexpensive, simply to assess and can in some cases replace the measurement of bone mineral density, notably in cases of marked decrease in bone density.

Problematik der in Fehlstellung ausgeheilten distalen Radiusfraktur

ZusammenfassungDie wesentliche Problematik der distalen Radiusfraktur liegt in der Qualität ihrer Reposition und Retention. 35 Patienten mit distalen Radiusfrakturen und Abrissfrakturen des Processus styloideus ulnae wurden hinsichtlich ihrer funktionellen und radiologischen Ergebnisses sowie ihrer subjektiven Beschwerden nachuntersucht.Dabei zeigten sich signifikant schlechtere funktionelle Ergebnisse bei Patienten mit intraartikulären gegenüber solchen mit extraartikulären Frakturen. 29 von 35 Patienten entwickelten eine Pseudarthrose des Processus styloideus ulnae im Sinne einer Erfordernisfehlstellung bei signifikant nach dorsal abgekippter Radiusgelenkfläche. Auch ihr funktionelles Ergebnis war signifikant schlechter als das der übrigen 6 Patienten. Signifikant schlechtere funktionelle Ergebnisse und eine im Mittel um 5° nach dorsal abgekippte Gelenkfläche wiesen ebenfalls die Patienten mit einer Radiusverkürzung von mehr als 2 mm auf. Bei einer Neigung der Radiusgelenkfläche von mehr als 5° nach dorsal war ein signifikanter Anstieg des skapholunären Winkels mit durchschnittlich 62° festzustellen.Aus diesen Zahlen folgern wir, dass bei der Reposition der distalen Radiusfraktur eine Verkürzung von nicht mehr als 2 mm und eine Neigung der Radiusgelenkfläche im seitlichen Strahlengang von nicht mehr als 5° nach dorsal toleriert werden sollte, um Funktionseinschränkungen des Handgelenks zu minimieren.AbstractThe essential problematic of the distal fracture of the radius lies in the quality of its reduction and retention. 35 patients with distal fractures of the radius and strain fractures of the styloid process of the ulna were followed up with regard to their functional and radiological results and their subjective symptoms.Patients with intra-articular fractures were found to have significantly poorer functional results compared to those with extra-articular fractures. 29 out of 35 patients developed a nonunion of the styloid process of the ulna in the form of a compensatory false position with a significant dorsal tilt of the articular surface of the radius. Their functional results were also significantly poorer than those of the other 6 patients. The patients whose radii were shortened by more than 2 mm also had significantly poorer functional results and a median dorsal tilt of 5 degrees of the articular surface. Where the dorsal inclination of the articular surface of the radius exceeded 5 degrees, a significant increase in the scapholunar angle, which averaged 62 degrees, was found.On the basis of these figures, we conclude that in the reduction of the distal fracture of the radius, shortening by not more than 2 mm and a dorsal inclination of the articular surface of the radius, taken laterally, of not more than 5 degrees should be tolerated in order to minimise functional impairments of the wrist.

Acetabulumfraktur beim alten Menschen

In the Department of Traumatology at the University of Ulm, 26 elderly patients with displaced acetabular fractures were treated with primary implantation of a hip joint endoprosthesis between 1986 and 1996. The principles of operative therapy are stabilization of the acetabular ring, grafting of acetabular defects with autogenous corticocancellous bone and cranial buttressing with a reinforcing ring. This concept permits immediate mobilization of elderly patients and full weight-bearing and thus results in favorable early postoperative results. Secondary complications typically caused by immobilization can therefore be avoided.ZusammenfassungIn der Unfallchirurgischen Abteilung der Universitäts-Klinik Ulm wurden von 1986–1996 26 alte Patienten, die eine dislozierte Acetabulumfraktur erlitten hatten, mit einer primären Hüftgelenkstotalendoprothese versorgt. Das operative Konzept ist die Stabilisation des acetabulären Rings, Auffüllung von Defekten des Pfannenbodens durch autogene kortikospongiöse Transplantate und Schaffung einer kranialen Verankerung durch einen Abstützring. Die Frühergebnisse bestätigten das eingeschlagene Therapiekonzept der sofortigen belastungsstabilen Frühmobilisation alter Patienten. Immobilisationsbedingte Sekundärkomplikationen wurden dadurch vermieden.SummaryIn the Department of Traumatology at the University of Ulm, 26 elderly patients with displaced acetabular fractures were treated with primary implantation of a hip joint endoprosthesis between 1986 and 1996. The principles of operative therapy are stabilization of the acetabular ring, grafting of acetabular defects with autogenous corticocancellous bone and cranial buttressing with a reinforcing ring. This concept permits immediate mobilization of elderly patients and full weight-bearing and thus results in favorable early postoperative results. Secondary complications typically caused by immobilization can therefore be avoided.

Konservatives Management artikulärer Grundgliedbasisfrakturen der dreigliedrigen Finger

ZusammenfassungBei Gelenkfrakturen der Grundphalanxbasis wurde nach der Frakturreposition eine funktionelle Behandlung durch aktives Bewegen der PIP- und DIP-Gelenke in einem Schienensystem durchgeführt. Die Therapie baut auf den periartikulären Weichteilen und deren funktioneller Anatomie auf. Der das Grundgelenk umgebende Zancolli-Haltekomplex führt zu einer Stabilisierung des Bewegungsablaufs mit Brace-ähnlichem Effekt. In einem Nachuntersuchungszeitraum von durchschnittlich 2 Jahren konnte durch dieses Behandlungsregime bei 31 Patienten mit Gelenkfrakturen der Grundphalanxbasis ein gutes funktionelles Ergebnis erzielt werden.AbstractWe present a splint system for a protected mobilization program after closed reduction of articular proximal phalangeal base fractures. This therapy consists of the periarticular soft tissue and functional anatomy. The soft-tissue around the base of the proximal phalanx leads to a circular stabilization effect. This so called Zancolli Complex (Metacarpophalangeal Retention Apparatus) can be used with the effect of a brace treatment. Treating 31 patients with articular fractures of the proximal phalanx way we found good functional results within a mean follow up period of 2 years after the accident.

Magnetresonanztomographie bei häufigen Verletzungen des Handgelenks

Falling on the outstretched hand is a common trauma mechanism. In contrast to fractures of the distal radius, which usually are diagnosed on plain film radiographs, identifying wrist injuries requires further diagnostic methods, e.g., MRI or CT. This article provides a review of the use of MRI in the most common traumatic wrist injuries, including scaphoid fractures, TFCC lesions, and tears of the scapholunate ligament. Early and selective use of MRI as a further diagnostic method in cases of adequate clinical suspicion helps to initiate the correct treatment and, thus, prevents long-term arthrotic injuries and reduces unnecessary absence due to illness. MRI shows a high reliability in the diagnosis of scaphoid fractures and the America College of Radiology recommends MRI as method of choice after X-ray images have been made. In the diagnosis of ligament and discoid lesions, MR arthrography (MRA) using intraarticular contrast agent has considerably higher accuracy than i.v.-enhanced and especially unenhanced MRI.