Relationship between plain radiographic patterns and three- dimensional trabecular architecture in the human calcaneus.

The purpose of this study was to determine the relationship between three-dimensional (3D) trabecular structure and two-dimensional plain radiographic patterns. An in vitro cylinder of human calcaneal trabecular bone was three-dimensionally imaged by micro-CT using synchrotron radiation, at 33.4 micrometer resolution. The original 3D image was processed using 14 distinct sequences of morphologic operations, i.e., of dilations and erosions, to obtain a total of 15 3D models or images of calcaneal trabecular bone. These 15 models had distinct densities (volume fractions) and architectures. The 3D structure of each calcaneal model was assessed using mean intercept length (fabric), by averaging individual fabric measurements associated with each medial-lateral image slice, and determining the relative anisotropy, R(3D), of the structure. A summated pattern or plain radiograph was also computed from the 3D image data for each calcaneal model. Each summated pattern was then locally thresholded, and the resulting two-dimensional (2D) binary image analyzed using the same fabric analysis as used for the 3D data. The anisotropy of the 2D summated pattern was denoted by R(x-ray). The volume fractions of the 15 models ranged from 0.08 to 0.19 with a mean of 0. 14. The medial-lateral anisotropies, R(3D), ranged from 1.38 to 2.54 with a mean of 1.88. The anisotropy of the 2D summated patterns, R(x-ray), ranged from 1.35 to 2.18 with a mean of 1.71. The linear correlation of the 3D trabecular architecture, R(3D), with the radiographic trabecular architecture, R(x-ray), was 0.99 (p<0.0001). This study shows that the plain radiograph contains architectural information directly related to the underlying 3D structure. A well-controlled sequential reproducible plain radiograph may prove useful for monitoring changes in trabecular architecture in vivo and in identifying those individuals at increased risk of osteoporotic fracture.

Computational methods for ultrasonic bone assessment.

Ultrasound has been proposed as a means to noninvasively assess bone and, particularly, bone strength and fracture risk. Although there has been some success in this application, there is still much that is unknown regarding the propagation of ultrasound through bone. Because strength and fracture risk are a function of both bone mineral density and architectural structure, this study was carried out to examine how architecture and density interact in ultrasound propagation. Due to the difficulties inherent in obtaining fresh bone specimens and associated architectural and density features, simulation methods were used to explore the interactions of ultrasound with bone. A sample of calcaneal trabecular bone was scanned with micro-CT and subjected to morphological image processing (erosions and dilations) operations to obtain a total of 15 three-dimensional (3-D) data sets. Fifteen two-dimensional (2-D) slices obtained from the 3-D data sets were then analyzed to evaluate their respective architectures and densities. The architecture was characterized through the fabric feature, and the density was represented in terms of the bone volume fraction. Computer simulations of ultrasonic propagation through each of the 15 2-D bone slices were carried out, and the ultrasonic velocity and mean frequency of the received waveforms were evaluated. Results demonstrate that ultrasound propagation is affected by both density and architecture, although there was not a simple linear correlation between the relative degree of structural anisotropy with the ultrasound measurements. This study elucidates further aspects of propagation of ultrasound through bone, and demonstrates as well as the power of computational methods for ultrasound research in general and tissue and bone characterization in particular.

Acoustic assessment of fracture healing. Capabilities and limitations of "a lost art".

The ability of bone to conduct sound was applied clinically over 50 years ago to identify the presence of fresh fractures, although the technique has become a relatively "a lost art" as more sophisticated X-ray and other imaging techniques have been developed. The objective of this report is to challenge clinical orthopaedic surgeons unfamiliar with the technique to explore this simple beside method in the clinical management of fractures. A portable computer-based vibrational analysis device was employed and experiments conducted to objectively evaluate the capabilities of auscultatory percussion techniques. Auscultatory percussion can, with certain limitations, detect the presence of fractures, assess qualitatively the progress of healing, detect delayed or nonunions, and indicate when sufficiently firm continuity has occurred to permit early mobilization or loadbearing. Vibrational assessment is, however, subject to systematic and random errors, and thus cannot always discriminate between the stages of healing in a fractured bone; in addition, various artifacts can lead to significant uncertainty in the diagnosis. Nevertheless, auscultatory percussion is a useful tool in clinical fracture management, and particularly where roentgenographic facilities are inadequate or not available. Computerized vibrational analysis can be used in place of classical percussion/stethoscope methods by those with poor tonal capabilities,or when more objective record keeping is desired.

Influence of marrow on ultrasonic velocity and attenuation in bovine trabecular bone.

Measurements of ultrasonic velocity and specific differential attenuation (SDA) were obtained on 24 bovine trabecular bone specimens from the femoral condyles. The measurements were obtained using two pairs of ultrasonic transducers, one with a low nominal center frequency (500 kHz) and the other pair with a high nominal center frequency (1 MHz). The ultrasonic velocity and specific differential attenuation associated with the bone samples were determined both with and without marrow, i.e., replacing the marrow with water in the pores of the trabecular bone. Significant increases (2.1% and 2.9%) in the velocity of ultrasound were observed after removal of the marrow, for the low and high frequency transducer pairs, respectively. In contrast, significant decreases (-6.5% and -8.8%) in SDA were observed after removal of the marrow, for the low and high frequency transducer pairs, respectively. The bone densities (BD) of the samples were also determined using single photon absorptiometry (SPA). Correlations between ultrasonic parameters and bone densities for samples both with and without marrow were found to be similar. For example, for the 1 MHz transducer pair, the correlation between BD and velocity was r = 0. 86 with marrow, and r = 0.89 without marrow. This study also compared the results obtained using a contact (no water bath) technique and an insertion (with a water bath) technique of ultrasonic measurements. For the high frequency transducer pair, the correlation coefficients between the two methods were r = 0.99 and r = 0.93, for the velocity and specific differential attenuation, respectively. Similar results were found for the low frequency transducer pair as well. In addition, approximately equal correlations between BD and ultrasonic velocity and SDA were also found, indicating that contact and insertion measurements provide essentially equivalent information.

Ultrasonic assessment of human and bovine trabecular bone: a comparison study.

A comparison study is reported on the ultrasonic assessment of human trabecular and bovine trabecular bone samples. Both ultrasonic velocity and ultrasonic attenuation were evaluated through a transmission insertion technique and correlated with bone mineral density as determined with single photon absorptiometry. For a 1-MHz ultrasonic transducer pair and the human cancellous bone samples the correlations were 0.91 and 0.89 between density and velocity and attenuation, respectively. For a 500-kHz ultrasonic transducer pair the correlations were 0.89 and 0.81 between density and velocity and attenuation, respectively. For the bovine bone samples, the correlations were 0.90 and -0.31 for the velocity and attenuation, respectively, for the 1 MHz transducer pair. For the 500-kHz transducers, the correlations were 0.85 and -0.17 for the velocity and attenuation, respectively. By combining both velocity and attenuation in a multivariate regression, an improvement was achieved in the estimation of bone density in the human samples for both the 500-kHz and 1-MHz transducer pairs. No significant improvement was achieved in the multivariate regressions for the bovine bone samples. In conclusion, the results indicate that ultrasonic measurements are in general highly correlated with bone mineral density in trabecular bone samples. This correlation is more consistent and strong in relatively low density human samples compared with the higher density bovine samples.

Dynamic relationships of trabecular bone density, architecture, and strength in a computational model of osteopenia.

A computational model was developed to study the effects of short- and long-term periods of disuse osteopenia and repair to elucidate the interrelationships between bone mass, architecture, and strength. The model is one in which the sequence of structural change events is followed in time. This temporal feature contrasts with studies of real trabecular tissue which are necessarily cross-sectional in nature and do not lend themselves to insights into the dynamic nature of the structural changes with time. In the model it was assumed that the stimulus for bone adaptation to mechanical load is the local mechanical strain rate, according to which the trabecular surfaces are differentially formed and resorbed. The effects of mechanical loading and unloading (disuse) on the cancelous bone properties were studied. The bone mass, architecture, and elastic stiffness were shown to be strongly dependent upon the period of the unloading phase, as well as the period of the reloading phase. Mechanical stiffness is demonstrated computationally to be a multivalued function of bone mass, if architecture is not accounted for. The model shows how the same value of trabecular bone mass can be associated with two or more distinct values of biomechanical stiffness. This result is the first explicit demonstration of how bone mass, architecture, and strength are related under dynamical load-bearing conditions. The results explain the empirical observation that bone mass can account for about 65% of the observed variation in bone strength, but that by incorporating measures of bony architecture into the analysis, the predictability is increased to 94%. The computational model may be used to explore the effects of different loading regimes on mass, architecture, and strength, and potentially for assistance in designing both animal and clinical bone loss studies.

Uma nova e simplificada técnica ultra-sônica clínica para a caracterizaçäo de tecido ósseo / A new and simplified clinical ultrasound technical for bone tissue caracterization

A atenuação (BUA), medida pela técnica ultra-sônica de caracterização de tecido ósseo, pode ser substituída pela frequência instantânea média (MIF), que é um parâmetro mais simples de ser medido e sem perda de informação, utilizando-se a técnica de inserção por contato no calcanhar do paciente. Uma nova forma de classificação da osteoporose poderá ser criada baseada neste novo parâmetro.

An easy to measure ultrasonic feature namely mean instantanaeous frequency (MJF) has been demonstrated to provide about the sarne information as attenuation (BUA) in a new contact clinical ultrasonic system. A new classification of osteoporosis may be achieved using this new parameter.

Non-invasive low-intensity pulsed ultrasound accelerates bone healing in the rabbit.

The effect of ultrasound (US) on the rate of fibula osteotomy healing in 139 mature New Zealand white rabbits was assessed in this study. Bilateral midshaft fibular osteotomies were made using a 1-mm Gigli saw. US was noninvasively applied to one limb for 20 minutes daily, while the contralateral limb served as a control. A 2.5-cm PZT transducer was applied to both limbs, with the treated limb receiving a 200-microseconds burst of 1.5-MHz sine waves repeated at 1.0 kHz. The incident intensity was approximately 30 mW/cm2. Animals were killed at intervals between 14 and 28 days. Maximum strength increases (significant to p less than or equal to 0.01) ranged from 40 to 85% from postoperative day 14 to 23. On day 28, no significant difference in ultimate strength was noted. From day 17 through day 28, all US-treated fractures were as strong as intact bones (p less than or equal to 0.005). On the other hand, the ultimate strength of the control osteotomies attained intact values only by day 28. These results indicate that biomechanical healing is accelerated by a factor of nearly 1.7. This occurs with an overall acceleration of the healing curve in this fresh fracture model. If noninvasive low-intensity pulsed sine wave ultrasound can significantly accelerate bone repair in clinical application with an in-home treatment of 20 minutes daily, then US may be a useful adjunct for fracture care with a concomitant impact on patient morbidity.

Deterioration of trapeziometacarpal arthritis due to trigger thumb: a biomechanical evaluation.

Patients with trigger thumb and trapeziometacarpal joint arthritis accompanied by swan-neck deformity of their first rays find that their arthritic pain becomes worse whenever their thumbs "catch." Six hands with adduction contracture and arthritis of the trapeziometacarpal joint are studied biomechanically and demonstrate significantly excessive shear forces (p less than 0.01) around their trapeziometacarpal joint relative to six normal hands. Increased pain with deformity suggests aggressive treatment of trigger thumb in cases such as these.

A neural network approach for bone fracture healing assessment.

An approach based on auscultatory percussion, a technique used by some orthopedists both for bone fracture detection and bone fracture healing assessment, is described. Low-frequency, low-intensity mechanical power, very much like the finger tap of orthopedists, is used to evaluate the vibrational response of the bone. The novel element is the data processing, which incorporates specialized preprocessing and a neural network for estimating fractured bone strength. In addition, a new mathematical model for the vibrational response of a fractured limb, which provides data to design and test the neural network processing scheme, is presented. An experimental procedure is described for acquiring real data from animal and human fractures in a form necessary for neural network input.

Fractional brownian motion: a maximum likelihood estimator and its application to image texture.

Fractals have been shown to be useful in characterizing texture in a variety of contexts. Use of this methodology normally involves measurement of a parameter H, which is directly related to fractal dimension. In this work the basic theory of fractional Brownian motion is extended to the discrete case. It is shown that the power spectral density of such a discrete process is only approximately proportional to |f|a instead of in direct proportion as in the continuous case. An asymptotic Cramer-Rao bound is derived for the variance of an estimate of H. Subsequently, a maximum likelihood estimator (MLE) is developed to estimate H. It is shown that the variance of this estimator nearly achieves the minimum bound. A generation algorithm for discrete fractional motion is presented and used to demonstrate the capabilities of the MLE when the discrete fractional Brownian process is contaminated with additive Gaussian noise. The results show that even at signal-to-noise ratios of 30 dB, significant errors in estimation of H can result when noise is present. The MLE is then applied to X-ray images of the human calcaneus to demonstrate how the line-to-line formulation can be applied to the two-dimensional case. These results indicate that it has strong potential for quantifying texture.

"Beak" triple arthrodesis for severe cavus deformity.

Attention is called to the principles of a technique described more than 20 years ago that has proved clinically useful in the correction of severe cavus and cavovarus deformities when foot stabilization by triple arthrodesis is indicated. The method obtains correction of the cavus deformity by depressing the anterior aspect of the foot beneath a beak or ledge created in the talus, thereby preserving the vascularity to the talus and the integrity of the anterior ankle joint without shortening the foot.

Growth recovery zones.

Growth arrest lines and zones have been reinvestigated. Sequential studies after dietary deprivation reveal transformations of the physis with diminution in formation of the zone of cell columns, resorption of previously formed bone, and cessation of new bone formation. At 6 weeks post diet restriction, the physis is prominently narrowed with transversely oriented, thin bone plaque sealing it from the subjacent marrow. Initially, restoration of stock diet thickens the bony plaque, creating a growth arrest line. Later the zone of osteogenesis adds new bone as a dense metaphyseal band.

Complications of Ender-pin fixation in basicervical, intertrochanteric, and subtrochanteric fractures of the hip.

Two hundred patients with a basicervical, intertrochanteric, or subtrochanteric fracture were treated by Ender-pin fixation during a three-year period. Their median age was 73.5 years and there was a 10 per cent mortality rate. Early partial weight-bearing with some external support was allowed for most patients. Minimum shortening and one non-union occurred. However, there was a substantial incidence of complications. The fixation failed in all basicervical fractures. Distal pin migration of more than two centimeters occurred in 50 per cent of the unstable intertrochanteric fractures. Seventy-six per cent of the forty-two patients who were personally examined at follow-up had pain in the knee and 36 per cent had external malrotation. The incidence of pin migration increased in the more unstable fractures.

Surgical management of metastatic disease of bone at the hip.

Concordant advances in cancer chemotherapy, radiotherapy, and surgical technique have been of apparent benefit to many cancer patients suffering from skeletal involvement at the hip. Consideration of the effects of underlying disease and prior treatment must be evaluated prior to developing a surgical plan. Acetabular involvement can be treated by either conventional or augmented total hip arthroplasty using protrusio rings and acetabular meshes, depending upon minor or major degrees of tumor destruction. Girdlestone resection arthroplasty for massive degrees of acetabular involvement yields only modest results. Femoral neck fractures can be treated by endoprosthetic replacement. However, the association of acetabular disease should be considered, and if present, total hip arthroplasty should be performed. Intertrochanteric fractures can be stabilized with the use of a stout tubeplate nail device plus cement. Subtrochanteric fractures can be stabilized with a Zickel nail device plus cement. The goals of treatment are to relieve pain and restore function by using a device with an anticipated fatigue life which should exceed the patient's life expectancy.

Tissue antibiotic levels with tourniquet use in orthopedic surgery.

Ten adult mongrel dogs were given 500 mg of cefazolin intravenously, before and after tourniquet cuff inflation. Muscle tissue antibiotic levels were comparable to the control side when the antibiotic was administered prior to tourniquet inflation. Muscle tissue antibiotic levels were markedly diminished compared to the control limb when the antibiotic was given after the tourniquet was inflated. The low level of antibiotic appeared slowly and peaked at 60 minutes as a reflection of minimal limb blood flow. It was questionable whether the small antibiotic concentration in the latter situation served adequate protective cover.

Intraepiphyseal osteotomy for progressive tibia vara: case report and rationale of management.

Tibia vara (Blount's disease) is characterized by two components, the epiphyseal, which is concerned with articular relationships, and physeal/metaphyseal, which may produce angulation of a long bone. Although the initial etiology is not known, it appears that asymmetrical pressure applied to the angulated proximal tibia results in progressive deformity. In the initial stages, medial and posteromedial pressure causes growth retardation of the epiphysis (articular instability) and the physis (tibia vara). Nonsurgical or surgical treatment that relieves the pressure generally permits reconstitution of normal growth. Continued abnormal pressure and shear forces applied to the physis may result in disorderly enchondral ossification and produce a true osteochondrosis, which may lead to permanent physeal arrest. Osteotomy alone to relieve medial pressure may allow the tibia to grow straight, but residual medial epiphyseal compression and joint instability may persist. A case is reported of a 13 1/2 year follow-up of a patient in whom intraepiphyseal osteotomy restored articular congruity without interfering with longitudinal growth. The risks and experimental nature of this procedure are emphasized.