Donald A. Nagel

The function of the primary ligaments of the knee in varus-valgus and axial rotation

Abstract Four in vitro human knee specimens have been loaded, two with varus-valgus femoral rotations and two with internal and external axial tibial rotations. Each specimen has been tested in full extension and in 30° of flexion. All orthogonal components of applied force and moment required to cause the rotations were measured as were all resultant orthogonal components of load on the femur. Curves fit to the data were studied to establish the portions of the applied load transmitted by each ligament.

The function of the primary ligaments of the knee in anterior-posterior and medial-lateral motions

Abstract The functions of the primary ligaments of the human knee have been investigated during anterior, posterior, medial and lateral tibial displacements. The ligaments of in vitro knee specimens have been loaded to large load levels and all three resultant orthogonal components of force and of moment acting on the femur as a result of the applied tibial displacements have been measured. Least squares cubic spline curves fit to the data have been analyzed to determine what percentage of a given applied load is transmitted by each ligament. These curves can also provide data for a computer model of the human leg.

Benign metastasizing giant-cell tumor of bone. Report of three cases and review of the literature.

Three cases of benign giant-cell tumor (GCT) of bone with pulmonary metastasis are reported. In addition, 28 cases from the literature are reviewed. The patients were followed for a mean of 7.8 years (range from two to 29 years). The interval to metastasis ranged from zero to ten years with a mean of 3.2 years. Metastasis was not related to the number of previous operations. The local recurrence rate in the tumors that metastasized was 63%, suggesting that GCTs that metastasize may be an aggressive form of the tumor. The overall mortality rate was 16%. Persistent pulmonary disease does not carry a poor prognosis; surgical resection of accessible pulmonary nodules is recommended to provide histologic confirmation of the diagnosis, and prevent future complications secondary to local growth of the implants, as well as provide a potential cure. Chemotherapy has not improved survival and is associated with significant morbidity and is thus not recommended. Adjuvant radiation is recommended only for control of surgically unresectable lesions because of its potential association with sarcomatous degeneration in GCT.

Natural frequency analysis of a human tibia

Abstract A beam type finite element computer model is used to predict the natural frequency response of a human tibia with varying geometries, mass formulations and boundary conditions. Results are compared to analytic solutions and to published computer and experimental results. Variations between lumped and consistent mass formulations were found to be small, but significant. The effects of tibial twist and curvature were generally of the same order as the mass effects, with notable exceptions depending on boundary conditions. In fact, the major changes in predicted frequencies occurred with changes in boundary conditions. Variable springs at the boundaries were introduced to show a more continuous variation between free and fixed boundary conditions. Accuracy and repeatability of experimental and analytic results are examined in light of possible clinical applications.

An extended structural analysis of long bones—Application to the human tibia

Abstract A computer model is used to investigate the importance of several assumptions associated with whole bone modeling. The importance of shearing deformations relative to bending deformations, and the coupling between transverse loading and torsion are shown to be negligible. A more rigorous solution for torsion in hollow, irregular solids, the three dimensional twisted geometry of the tibia and the values chosen for Youngs modulus and Poissons ratio are all shown to be significant factors. The material properties are assumed to be linear, elastic and isotropic. The analysis is concerned primarily with modeling the response of the whole bone to loads transmitted through the epiphyses, and with detailed stress distributions in the diaphysis. An outline of the computer model and the experimental data are presented.

Measurement of the nonlinear, coupled stiffness characteristics of the human knee.

Abstract The structural characteristics of the human knee have been determined using the stiffness influence coefficient method. The nonlinear load-displacement data is approximated by a least squares polynomial and differentiated to determine the stiffness coefficient as a function of displacement. Cross axes coupling produces a full matrix and individual stiffness curves are seen to be a function of the initial displacement state of the joint. The resulting data provides a complex, but accurate description of joint stiffness in a format consistent with matrix structural analysis. The methods are described in detail; the data is taken from a single fresh human knee.

GEOMETRIC PROPERTIES OF HUMAN LEG BONES

Abstract In analytical models of human lower extremities, the geometric properties of the bones are needed along with the material properties of compact and cancellous bone. This paper presents the geometric data for the right and left femurs, tibias and fibulas from a single donor, along with the results of two additional tibias. Data includes the areas, polar moments of inertia, torsional rigidities, angles from anatomical axes to principal axes, and the position of the centers of mass along the lengths of the bones. The results from a single speciment provide data for entire limb models.

The dashboard knee injury.

An in-depth study of 74 motor vehicle accidents involving 222 people revealed that 57 of the 153 people injured sustained 69 knee injuries from contact with the instrument panel. There were 51 mild, 10 moderate, and 8 severe knee injuries. Low force contact caused bruising, and more serious injuries occurred when a greater magnitude of force was applied. Injury was most severe when this force was concentrated in a small area and caused lacerations, fractured patella, and open wounds of the joint. Legs trapped under the dashboard with simultaneous rotational, varus, valgus, or frontal forces by the inertial motion of the body produced serious injuries similar to those recieved in sports. Degenerative arthritis was more likely to occur in the seriously injured knees, but generally was not predictable. Long-term disability might be mitigated by early diagnosis and treatment of the specific injury.

Allescheria boydii osteomyelitis following multiple steroid injections and surgery.

This is a report of a 46-year-old male who developed an Allescheria boydii infection secondary to excision of an interdigital neuroma. Previously reported cases of infection occurred in an immunosuppressed patient and in patients on systemic corticosteroid therapy, but not associated with a surgical wound. This patient received multiple local corticosteroid injections which may have produced local as well as systemic immunosuppression. Fungal cultures were not taken for many months and thus the true etiology of the infection was not discovered until late. The importance of obtaining fungal cultures particularly in patients receiving corticosteroid therapy, either local infiltration or systemic, cannot be overemphasized.

Compartment syndromes of the forearm: early recognition using tissue pressure measurements.

A compartment syndrome of the forearm can be a devastating injury if not relieved promptly by early fasciotomy. Of five patients who developed compartment syndromes, compartment pressures were measured in four and found to average 69 mm Hg. Tissue pressure measurements provided early objective evidence of the presence of the compartment syndrome and contributed significantly to the ultimate functional recovery. We would advise repeating the measurement for pressures in excess of 30 mm Hg in the upper extremity, and fasciotomy for pressures in excess of 40 mm Hg when accompanied by any neurovascular compromise.