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Biomedical subjects

J D Michelson

Publications and source records attributed to J D Michelson.

At least 37 records · Page 2Linked to original sources
PubMed1996

Clinical safety and efficacy of calf tourniquets.

A clinical study was undertaken to ascertain the utility and complication rate of proximal calf tourniquet use for foot and ankle surgery. The surgical and clinical records of 446 patients undergoing foot and ankle surgery between March 1992 and December 1994 were examined for details pertaining to intraoperative tourniquet use and postoperative evidence of neurologic or vascular complications. All patients who had surgery performed under tourniquet control were included in the study. A total of 454 limbs were operated on: 8 patients underwent bilateral surgical procedures. The patients comprised 172 men and 274 women. The average age was 48.9 (+/-16.0 SD) years. Surgery was completed in one tourniquet period in 435 cases (95.8%) and in two periods of tourniquet inflation in 19 cases (4.2%). The average duration of tourniquet ischemia was 49.2 minutes (+/-30.7 SD) for one tourniquet period and 131.1 minutes (+/-46.0 SD) for two tourniquet periods. No postoperative compromise to either neurologic or vascular function was detected. Specifically, no alteration in peroneal nerve function was seen. We conclude that a calf tourniquet placed proximally with adequate cast padding is a safe and effective method to achieve a bloodless surgical field for foot and ankle surgery.

Adult↗
PubMed1995

Economic analysis of roentgenogram use in the closed treatment of stable ankle fractures.

Fractures of the ankle are one of the most commonly treated injuries by orthopedic surgeons. The adequacy of closed treatment of stable lateral malleolar ankle fractures is frequently assessed by repeated roentgenograms. There are no standards, nor studies, however, that provide guidelines as to the necessity of such roentgenograms. This study was designed to determine the average frequency of follow-up roentgenograms in ankle fractures treated by casting, as well as the clinical impact of these roentgenograms. The clinical radiographic data base of a university hospital was reviewed to identify all ankle fractures treated between January 1, 1992 and June 30, 1993. A total of 82 patients satisfied the study criteria of having sustained a stable ankle fracture that was treated by closed means, with sufficient clinical and radiographic follow-up to assess healing of the fracture. All patients healed their fractures at an average of 8.4 weeks (+/- 3.0 weeks), with weight-bearing initiated at 4.0 weeks (+/- 2.7 weeks). No patients developed radiographic evidence of a talar shift during treatment, and none required surgery for a failure of closed treatment. At no time did any ankle exhibit a significant change in fibular alignment relative to the initial injury films. Each patient had an average of 4.5 (+/- 2.0) radiographic studies performed throughout their treatment. This study indicates that secondary displacement of either the talus or fibula in a stable ankle fracture is very unusual. In conjunction with the generally excellent outcome for such fractures, this suggests that frequent roentgenograms are not justified on clinical grounds.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Kinematics of the axially loaded ankle.

An apparatus that allowed the application of a 900 N axial load and the simultaneous measurement of rotation in the sagittal, coronal, and axial planes was used to study the normal kinematics of the ankle in 13 below-knee amputation specimens. Two testing routines were done on all specimens. In the first sequence, specimens were moved through a dorsiflexion (DF) and plantarflexion (PF) arc of 60 degrees (25 degrees DF and 35 degrees PF). DF was associated with an average of 2.5 degrees of external rotation, and PF was associated with an average of < 1 degree of internal rotation. In the coronal plane, PF and DF were both associated with < 1 degree of varus. In the second part of the testing, the ankle position in the sagittal plane (DF/PF) was fixed and the axial load was increased from 50 N to 750 N in 100-N intervals. Increasing the axial load caused an increase in external rotation and valgus of 1 degree to 2 degrees. For axial rotation, external rotation was more pronounced in PF than DF. The effect of load on the increase on valgus was not affected by sagittal ankle position. The effect of increasing axial load on sagittal rotation was to increase DF or PF < 2 degrees over the entire range of loads and sagittal positions. The understanding of ankle biomechanics is essential to the formulation of rational guidelines for the treatment of ankle pathology and the prediction of the long-term consequences of ankle injuries.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1995

Epidemiology of hip fractures among the elderly. Risk factors for fracture type.

A study was undertaken in September 1988 of 169 patients who were > 50 years of age receiving care for hip fractures at 4 university-affiliated hospitals during a 2-year period. Demographics, medical history, cognitive function, mobility, and environmental factors surrounding the hip fractures were ascertained by patient or proxy interview and review of medical records. These were then related to the type and severity of hip fracture. Eighty-three (49%) patients had intertrochanteric fractures, 23 (14%) had subtrochanteric fractures, and 63 (37%) had intracapsular fractures. Walking versus standing, sitting, or getting up at the time of fracture (relative odds = 3.2, p = .041), and no mobility difficulty versus some mobility difficulty (relative odds = 5.2, p = .047) were associated with increased comminution in intertrochanteric or subtrochanteric fractures. The location of the fracture occurrence (indoor versus outdoors) was associated with greater displacement in intracapsular fractures (relative odds = 6.7, p = 0.021). Only 2 of 169 patients had spontaneous hip fractures, defined as hip pain that preceded the fall. Because spontaneous fractures are rare, efforts directed toward preventing falls would be expected to decrease the incidence of hip fractures. Future possibilities include the development of protective garments that can reduce impact loading to the hip during a fall.

Accidental Falls↗
PubMed1995

Mechanoreceptors in human ankle ligaments.

Chronic ankle instability after ligamentous injuries has been attributed to loss of proprioception, but there has been no previous study of the mechanoreceptors in human ligaments at this joint. We have examined the ligaments from five cadaver ankles for mechanoreceptors and classified them into the four types described by Wyke and Freeman in their study of feline ligaments. Type-II receptors, thought to provide the sensation of the beginning of joint motion, and type-III receptors, thought to be activated at the extremes of movement, were the most common. Our findings provide some neuroanatomical data to validate further research into the use of proprioceptive training after ligamentous injuries about the ankle.

Ankle Joint↗
PubMed1993

Bone morphology after bone marrow transplantation for Hodgkin's and non-Hodgkin's lymphoma.

The osteogenic consequences of bone marrow ablation followed by bone marrow transplantation for Hodgkin's and non-Hodgkin's lymphoma were examined. Pre- and post-transplantation iliac crest bone biopsies were reviewed for all patients undergoing transplantation at the Johns Hopkins Oncology Center between January 1981 and December 1989. Histomorphometric measurements included percentage of filled trabecular lacunae to estimate osteocyte viability, marrow cellularity and marrow fibrosis. A total of 37 non-Hodgkin's and 32 Hodgkin's patients had adequate biopsies for study inclusion. Twenty-seven received chemotherapy alone, while the remaining 42 had lethal total body irradiation plus chemotherapy. Twelve transplants were allogeneic. Estimated osteocyte viability was decreased for over 4 weeks after bone marrow transplantation. Continuing osteocyte dropout in the central regions of trabeculae was seen in conjunction with active new osteocyte formation along the periphery. Marrow fibrosis was significantly increased and marrow cellularity decreased. There were no major distinctions based on lymphoma type, pretransplant treatment regimen or type of bone marrow transplant. The results indicate that disruption of marrow hematopoiesis causes a diminution in osteocyte viability. Although there is an early appearance of new osteogenesis, the source of progenitor cells cannot be determined from this study.

Adolescent↗
PubMed1992

Examination of the pathologic anatomy of ankle fractures.

A prospective study of the translational and rotational displacement of the lateral malleolus in ankle fractures was carried out utilizing roentgenographic techniques. Twenty-six ankle fractures in 25 patients were studied using both routine plain films and CT scanning with two- and three-dimensional multiplanar reconstruction. Eighty-one percent were Lauge-Hansen supination-external rotation type injuries. Overall, 21 fractures did not involve the medial malleolus. Initial talar shift was less than or equal to 2 mm in 15 fractures. Although all patients exhibited external rotation deformities of the lateral malleolus on plain films, only one fracture was found to possess any degree of external rotation relative to the talus. The proximal fibula was seen on CT scans to have increased internal rotation with respect to the tibia in 19 cases. One patient had a slightly externally rotated proximal fibula; the remainder appeared normally aligned. The displacements measured by the CT scans at the talofibular articulation were compared with the standard plain film measurements. The displacements at the distal lateral malleolus were consistently overestimated by the plain roentgenograms, presumably because the capsular and ligamentous attachments to the distal fibula limit malleolar displacement. The talocrural angle, determined on both plain films and CT scans, was also not found to be a sensitive measure of fibular shortening nor of the severity of the fracture. The results of this study suggest that, in an isolated lateral malleolar ankle fracture, the apparent external rotation of the fracture fragment is relative only to the proximal fibula and is not associated with derangement of the talofibular articulation. Based on these mechanical considerations, surgical intervention for such fractures may not be necessary. This hypothesis is consistent with previous long-term clinical studies.

Adolescent↗
PubMed1992

Investigations into the fat pads of the sole of the foot: heel pressure studies.

The fat pads of the heel have a structure that is optimized for load bearing. In various diseases and aging, the load-carrying ability of the heel pad is clinically impaired. The loading pattern was examined in subjects having normal heel pads and those with atrophic heel pads, both with and without clinical symptoms. Normal heel pads showed a broad region of high pressure, which accounted for a high percentage of the total load transmission. In contrast, the atrophic heels showed a high but narrow peak pressure. However, most of the load was transmitted over a large area of low pressure. There was no difference between symptomatic and asymptomatic heels. The mechanical behavior of the fat pad is discussed with particular reference to the anatomic structure of the pads. Pad thickness and septal integrity are both important to the mechanical characteristics of the fat pad. The load-bearing patterns observed are discussed in terms of the mechanical components influencing fat pad resilience. These results have direct relevance to understanding the pathophysiology of heel pain secondary to degeneration of the fat pad.

Adipose Tissue↗
PubMed1992

Investigations into the fat pads of the sole of the foot: anatomy and histology.

Anatomical, histological, and histochemical studies were performed on normal and abnormal fat pads of the sole of cadaver feet. The fat pads were found to contain a significant nerve and blood supply separate from that to the surrounding musculature and skin. Pacinian corpuscles and free nerve endings within the fat were identified. Histological analysis indicated a meshwork of fibroelastic septae arranged in a closed-cell configuration. The mechanical consequences of this organization are discussed in the context of the weightbearing role of the fat pads of the feet. Alterations seen in dysvascular or senescent feet are consistent with the hypothesis that the septal anatomy of the fat pads is central to their cushioning function.

Adipose Tissue↗
PubMed1992

Tibiotalar contact and fibular malunion in ankle fractures. A cadaver study.

Six cadaveric ankles were dissected, preserving medial and lateral ligaments; an axial load of 455N was applied to the tibia supported by the foot and ankle. The unconstrained tibia was moved through 20 degrees of flexion and extension to simulate walking. The tibiotalar contact area was defined using carbon black suspension, recorded photographically, and measured using computerized area analysis. Osteotomy of the distal fibula was performed and fixed with a specially modified plate; a selection of plates provided fixation with 0 degrees or 30 degrees of external rotation in combination with 0 or 2 mm of shortening. The contact area was measured for each of the plates and after division of the deltoid ligament. There were greater than 30 percent decreases in tibiotalar contact with both fibular shortening and external rotation, doubled with a divided deltoid ligament. Anatomic restoration of both fibular length and rotation is essential for normal ankle mechanics. The deltoid ligament has crucial effects on the stability of the ankle mortise.

Ankle Joint↗
PubMed1991

Hip fractures among the elderly: factors associated with in-hospital mortality.

Factors associated with mortality were examined for 27,370 hip fracture patients aged 65 years or older in Maryland hospitals, using discharge data for 1979-1988. Variables of interest included sociodemography, principal medical and injury diagnoses, E-code, year, disposition, and hospital. For both white males and white females, the hip fracture rate doubled with each 5-year increment in age. The overall proportion who died during hospitalization was 4.9% (n = 1,339). After multivariate adjustment, there remained a substantially increased risk of death for males. The relative odds (RO) of dying for males versus females were 1.6. Other factors associated with high relative odds of dying during hospitalization included the diagnosis of septicemia (RO = 12.3), pneumonia/influenza (RO = 4.9), and digestive system disorder (RO = 3.6). The RO of dying doubled in the presence of cardiac, neoplastic, or cerebrovascular disease. Patients with diagnoses of nervous system or mental disorder, hypertension, anemia, musculoskeletal system disease, or urinary tract infection were at decreased risk of dying. Results of the study suggest that the prevention or early diagnosis and treatment of serious infections in the elderly patient with a hip fracture remain an important challenge to clinicians.

Black or African American↗
PubMed1991

Tibio-talar stability in bimalleolar ankle fractures: a dynamic in vitro contact area study.

A dynamic weight-bearing model has been developed in a cadaveric ankle model to assess the contact areas of the talus in varying degrees of bimalleolar ankle fractures. A surgically created transverse fibula osteotomy with up to 6 mm of displacement did not cause a significant change in the contact area. Sectioning of the deltoid ligament, regardless of fibular displacement, created a 15% to 20% decrease in the contact area (P less than .001). This model represents a clinically relevant situation, as it examines motion of an unconstrained, axillary loaded ankle. Additional medial side disruption increases ankle instability by allowing anterior and lateral translation of the talus out of the mortise. Isolated lateral malleolar displacement does not appear to cause ankle instability.

Adult↗
PubMed1990

The effect of loading on tibiotalar alignment in cadaver ankles.

The tibiotalar movements which occur with axial loading, without applied moment forces were studied in cadaver ankles using a minimally constrained testing apparatus. Lateral translation of the talus measured up to 2 mm, which was associated with increased tibiotalar valgus angulation. Neither displacing the distal fibula laterally, nor sectioning the deltoid ligament, significantly influenced the talar shift. The tibiotalar motion which was observed after simple axial loading in a stable configuration (e.g., fibula and deltoid ligament intact) is of the same magnitude that is usually regarded as signifying an unstable ankle fracture. Consequently, this study suggests that the criteria for an unstable ankle fracture may need closer scrutiny.

Adult↗
PubMed1990

Adult ankle fractures: comparison of plain films and interactive two- and three-dimensional CT scans.

Thirteen patients with 15 ankle fractures potentially requiring surgical reduction according to plain film criteria were studied with transaxial CT, from which static and animated interactive two-dimensional (2-D) images and animated volumetric three-dimensional (3-D) images were generated. CT criteria believed to parallel well-accepted plain film criteria for triage of ankle fractures were developed and applied. The tibiofibular, talofibular, and tibiotalar articulations were characterized and, where possible (nine cases), compared with the (presumably normal) contralateral ankle. Talocrural angle measurements were made on interactive coronal measurements and compared with standard plain film measurements. Fracture fragment displacement, rotation, and impaction were noted. Posterior tibial lip disruption was quantified. Information derived from the 2-D/3-D CT study led to cancellation of proposed surgery in three of the distal fibular fractures and in two distal tibial fractures. There was far less variation than anticipated between the talocrural angles of the injured and normal ankles, and both injured and normal ankles deviated significantly from the accepted standard of 84 degrees. Displacement at the level of the fibular fracture was a poor predictor of more distal disruption. Two-dimensional CT was found to provide anatomic detail and information superior to either plain film or 3-D CT; 3-D CT was preferred by the surgeons for final surgical planning and for integration of the 2-D data. CT altered management in five of the 13 patients studied, supporting our belief that 2-D/3-D CT can be of significant value in assessing ankle fractures.

Adolescent↗
PubMed1989

The effects of demineralized bone matrix and direct current on an "in vivo" culture of bone marrow cells.

Bone marrow cells (BMCs) from rabbit femora and tibiae were grown in diffusion chambers implanted in rabbit muscle. At 42 days 80% of the BMC chambers exhibited cartilage formation within them. Demineralized bone matrix added to the marrow cell suspension in the chamber accelerated the appearance and increased the number of chambers with cartilage. Mineralization of the cartilage also occurred earlier in the chambers with bone matrix. In a second experiment, a 5-microA direct current cathode in the bone marrow chamber increased the number of chambers containing cartilage from 50 to 80% at day 25. Mineralization also occurred earlier in the chambers with direct current.

Animals↗