Cation disorder in Ga1212.

Substitution of calcium for strontium in LnSr2-xCaxCu2GaO7 (Ln = La, Pr, Nd, Gd, Ho, Er, Tm, and Yb) materials at ambient pressure and 975 degrees C results in complete substitution of calcium for strontium in the lanthanum and praseodymium systems and partial substitution in the other lanthanide systems. The calcium saturation level depends on the size of the Ln cation, and in all cases, a decrease in the lattice parameters with calcium concentration was observed until a common, lower bound, average A-cation size is reached. Site occupancies from X-ray and neutron diffraction experiments for LnSr2-xCaxCu2GaO7 (x = 0 and x = 2) confirm that the A-cations distribute between the two blocking-layer sites and the active-layer site based on size. A quantitative link between cation distribution and relative site-specific cation enthalpy for calcium, strontium, and lanthanum within the gallate structure is derived. The cation distribution in other similar materials can potentially be modeled.

Massive fibrolipoma of a toe.

Soft-tissue tumors of the toes are not particularly common; more tumors of the toes arise from the skin. The deeper tumors can be either benign or malignant and must be treated with caution until a histologic diagnosis has been made. However, malignant soft-tissue tumors of the toes are fairly rare. An unusual case of a massive benign lipoma was treated by an excisional biopsy (disarticulation).

Multiple loose bodies: formation, revascularization, and resorption. A 29-year followup study.

A 45-year-old patient sustained a traumatic dislocation of 1 hip. During a 29-year period, 10 to 13 multiple calcified loose bodies developed slowly in the hip. These first grew in size and became very radiodense, but later showed progressively less radiodensity. Progressive osteoarthritis of the hip was the indication for hip arthrotomy. The loose bodies had become reattached to the synovial surface of the hip joint and were revascularized, having converted from calcified cartilage to bone. This case dramatically shows the body's mechanism for attempting to remove loose bodies from joints.

Osteomyelitis in the foot and ankle associated with diabetes mellitus.

Osteomyelitis in a foot or ankle is a common complication in patients with diabetes mellitus. Although acute osteomyelitis can be a surgical emergency, this presentation is uncommon. Chronic bone infection in most patients is associated with either vascular impairment or neuropathic skin breakdown or both. Neuropathic joints and stress fractures have to be differentiated from radiographic abnormalities caused by infection.

Unusual arthroscopic knee lesions: case report of an intra-articular lipoma.

Intra-articular lipoma is a rare benign tumor that should be considered in the differential diagnosis of a smooth lobular synovial mass. This article reports a patient who presented with right knee pain, locking, and swelling. At surgery, an intra-articular lipoma was found.

Resection arthroplasty for septic arthritis of the hip in ambulatory and nonambulatory adult patients.

Twenty-three patients who required resection arthroplasty because of pyogenic infection of a hip joint were reviewed. Nine of the patients were ambulatory, and the others were either paraplegic or bed-ridden because of chronic neurologic disease. The average duration of symptoms was more than two months. The only consistently abnormal laboratory test was the erythrocyte sedimentation rate (ESR). Joint-space narrowing and bone erosion due to osteomyelitis were the most common roentgenographic findings. Different microorganisms were isolated from the different cases, but Staphylococcus aureus was documented in eight hips. Femoral head dislocation of subluxation was documented in 11 of 24 hips. Osteoarthrosis or osteonecrosis was a preexisting condition in only four hips, all in ambulatory patients. Pathologic findings included loss of articular cartilage by surface erosion and by subchondral bone resorption, resulting in the separation of the cartilage from the underlying bone, bone erosion, osteomyelitis, and segmental osteonecrosis.

Nonunion and pseudarthrosis of fracture healing. A histopathologic study of 95 human specimens.

Forty-one human tissue specimens from fracture nonunions in extraarticular locations demonstrated a spectrum of clefts at the site of nonunion ranging from tiny microscopic spaces within the soft tissue of the nonunion to dominant clefts that completely separated the ends of the fracture. These latter specimens were examples of frank pseudarthrosis. The soft tissues lining the large clefts were often considerably eroded. Pseudarthrosis of fracture healing may be a late manifestation of more mobile nonunions that progressively tear apart. Fifty-four additional nonunion or pseudarthrosis specimens from former intraarticular fractures demonstrated the same sequence of changes occurring in 24 of the cases. However, 30 of the intraarticular fractures demonstrated no tissues of a fibrous nonunion, which could indicate that in such locations pseudarthrosis may exist from the date of the original fracture.

Malignant transformation in bone lipomas.

This report presents four cases of presumed malignant transformation within intraosseous lipomas, one occurring in a stage I lesion and three in stage III lesions, according to my classification. These lesions demonstrated radiologic and histologic features of benign lipomas together with histologic fields of either malignant fibrous histiocytoma or liposarcoma. In two of the three patients who were followed up, the tumors were fatal despite amputation. Malignant transformation of a lipoma should be suspected when rapid bone destruction is seen in a stage I radiolucent lipoma. Malignant transformation of stage III lipomas could be mistaken for malignant transformation within bone infarcts.

Synovial osteochondromatosis in the subacromial bursa.

Synovial osteochondromatosis may occur within an otherwise normal synovial joint (primary disease), within a diseased joint (secondary disease), within tendon sheaths, and within extraarticular bursal cavities. Each of these four types of disease can present in one of three progressive morphologic stages in which the intrasynovial proliferations of cartilage and bone break free to form loose bodies. A 61-year-old man presented with loose bodies about his right shoulder. This case report demonstrates that the disease was a true example of bursal osteochondromatosis of the subacromial bursa, Stage III, rather than synovial osteochondromatosis of the shoulder joint. Well-documented cases of bursal osteochondromatosis are rare.

Intraosseous lipomas. A clinicopathologic study of 66 cases.

Sixty-one cases of histologically confirmed solitary intraosseous lipomas were analyzed with respect to clinical, roentgenographic, gross, and histologic features. Two additional cases with multiple intraosseous sites and three additional cases not treated with surgery are also described. Intraosseous lipomas may be subdivided into three groups depending on the degree of involution: I, solid tumors of viable lipocytes; II, transitional cases with partial fat necrosis and focal calcification but also regions of viable lipocytes; and III, late cases in which the fat cells have died with variable degree of cyst formation, calcification, and reactive new bone formation of a characteristic morphology. The tumor is a well-defined entity that may present with varying features due to its stage of evolution. Thus, lipomas have been confused with other benign tumors, cysts, and cases of bone infarction. Intraosseous lipoma is not as rare as the literature suggests, but has been rarely diagnosed. The lesion appears to undergo spontaneous involution, so that surgical excision may not be necessary in some cases.

Intraosseous lipomas: radiologic and pathologic manifestations.

Sixty-one cases of surgically treated solitary intraosseous lipoma were staged into three categories depending on the degree of involution present histologically: stage 1, tumors of viable fat cells; stage 2, transitional cases composed partly of viable fat cells but also demonstrating fat necrosis and calcification; and stage 3, lesions demonstrating necrotic fat, calcification of necrotic fat, variable degrees of cyst formation, and reactive woven bone formation. Each of these stages had radiologic features that could be correlated with the histopathologic findings in the excised tissue. Examples of stage 3 lesions have frequently been misdiagnosed as unusual bone infarcts or other lesions. Intraosseous lipoma may be a less rare lesion than has previously been suggested.

Synovial osteochondromatosis in the foot.

Two cases of synovial osteochondromatosis of the first toe are reported. A third case of a loose body associated with joint destruction is presented for comparison.

Injury to articular cartilage joint surfaces: II. Displaced fractures of underlying bone. A histopathologic study of human tissue specimens.

Thirty-two pathologic specimens from patients who previously had sustained intraarticular fractures, usually of either the radial head or the patella, and subsequently had excision of the affected bone, were analyzed with respect to the healing mechanisms of articular fractures in humans. The cases were divided into five groups based on the duration of the time interval between fracture and joint-surface resection. The fracture clefts were sometimes perpendicular to the joint surface but often were more complex, and microscopically showed far more comminution than was appreciated from the gross examination. In all cases the articular chondrocytes demonstrated minimal reactive or reparative response to the injuries, even those cells that were situated directly adjacent to a fracture cleft. All significant repair was derived from the fracture-exposed bone marrow. At early stages, this consisted of granulation tissue. Later specimens showed fibrous tissue bridging the cartilage fracture gaps. Chondrous metaplasia within the surface layers of this fibrous callus could be observed occasionally, particularly in specimens with older fractures. However, it was often absent. In the cancellous bone, the healing of the fractures was by osseous, not chondroosseous, callus. In comminuted fractures areas of osteonecrosis were demonstrated in a number of cases.

Injury to articular cartilage joint surfaces. I. Chondral injury produced by patellar shaving: a histopathologic study of human tissue specimens.

Five patella specimens from patients who had previously undergone elective shaving procedures for chondromalacia five months to two years prior to patellectomy were examined. There was no significant repair arising from the articular chondrocytes. Fibrous pannus that originated from the subchondral osseous tissue filled the surgical defects. These cases of failed shaving procedures suggest that it is not advisable to assume that all articular defects that are shaved down to bone will be repaired by new cartilage tissue.

Reparative cartilaginous callus in subarticular osteonecrosis of bone. A histopathological study of the femoral head.

A histopathologic study of a series of 346 resected femoral heads with gross osteonecrosis secondary to trauma, steroid therapy, idiopathic or other disease processes demonstrated the production of significant cartilaginous callus tissue at fracture clefts in 19 specimens (5.5%). Although subarticular fracture clefts were commonly present in such specimens, the formation of cartilaginous callus occurred only when one of the two opposing surfaces at the fracture cleft consisted of viable bone. Usually this was osseous tissue that originally had composed a portion of the infarct but had undergone revascularization. In another group of five cases from the same series, fragmentation of all tissue superior to the layer of cartilaginous callus had occurred by the time of surgery. The previously formed cartilaginous callus layer then became the actual weightbearing surface. Pathologically, callus must be differentiated from the cartilaginous tuft phenomenon of exposed intra-articular bone.

The origins of osteochondromas and enchondromas. A histopathologic study.

Histopathologic sections of large pieces of tissue obtained from both surgical and postmortem specimens of osteochondromas and enchondromas were analyzed to elucidate the pathogenesis of these two lesions. The osteochondroma is derived from aberrant cartilaginous epiphyseal growth plate tissue, which proliferates autonomously and separates from the normal growth plate near its edge. As growth progresses, the aberrant tissue remains in a subperiosteal location, where it may either disappear through remodeling or proliferate as an early osteochondroma perpendicular to the orientation of the growth plate from which it was derived. The enchondroma also is derived from the actively proliferating cartilaginous tissue of growth plates. For unknown reasons certain groups of chondrocytes do not proceed to undergo hypertrophy and death. As a result, a column of uncalcified cartilage extends from the underside of the growth plate into the region in which all other cartilaginous tissue has been remodeled into primary bone. The bridge to the plate may either remain intact or become interrupted by normal bone. An isolated group of chondrocytes may (1) be walled off from normal tissue by lamellar bone; (2) undergo calcification and secondary osseous remodeling, either in part or in total; or (3) proliferate as an intraosseous chondroma (benign enchondroma). A similar but not identical process of enchondroma formation may occur in fibrous dysplasia of bone, systemic growth plate dysplasias similar to achondroplasia, and osteogenesis imperfecta.

Morphologic alterations of the subchondral bone in advanced degenerative arthritis.

A series of 535 femoral heads surgically excised at the time of total hip arthroplasty for degenerative arthritis were analyzed by gross photography, specimen roentgenograms, and whole-mount histologic sections. Limited regenerative capacity was apparent in the chondrous tufts in the exposed bone of the osteoarthritic joint surface. The mechanism for the formation of subchondral cysts was interpreted to be the proliferation of viable myxomatous cells within the bone marrow. Osseous remodeling adjacent to the cysts was secondary to expansion of the soft tissue contents of the early cysts and later vascularization with fibrosis in the older cysts. Stress fracturing was a focal feature secondary to the remodeling of live bone. Advanced degenerative arthritis demonstrated focal osteocytic necrosis in the exposed osseous surface. Bone necrosis was also observed when small segments of the surface were undermined by cysts. Finally, bone necrosis was occasionally observed as focal infarcts of the joint surface (2-6 mm). In all three instances, bone necrosis in degenerative arthritis appeared to be a secondary reaction, presumably related to local disruption of blood supply.