Biological resurfacing of the knee: a review of surgical management

Lesions of the articular surfaces of the knee have been managed by various techniques over the last 50 years. Surgical management has involved: excising the damaged area, refashioning the underlying bone to produce a fibrous response, and introducing allograft, autograft and synthetic materials to encourage a repair matrix. The techniques and their pitfalls are reviewed and discussed, and suggestions made as to the direction of future studies for the repair of osteochondral lesions in the painful knee.     

Differential distribution of spinal cord field potentials

Summary Electrical stimulation of the sural, superficial peroneal and plantar nerves in anesthetized cats produces a sequence of potentials in the spinal cord lumbosacral enlargement. The distributions of the spinal cord dorsum negative intermediary potential (N1 wave) and of the associated field potential recorded in depth from the spinal gray matter were mapped. The N1 wave produced by the sural nerve was largest at the junction of the S1 and L7 segments, whereas that evoked by the other two nerves was maximum in L6 and L7. The field potentials recorded in depth also showed a differential distribution. The maximum negativity during phase 2, corresponding to the N1 cord dorsum potential, was found to lie laterally in the dorsal horn when the sural nerve was stimulated, but medially when the plantar nerve was activated. The superficial peroneal nerve produced its largest negative field potential in the central region of the dorsal horn. The negative field potentials from the sural and superficial peroneal nerves were not as well separated spatially from each other as they were from the potential evoked by the plantar nerve.     

Immunological factors in endometriosis-associated reproductive failure: studies in fertile and infertile women with and without endometriosis

Immunopathophysiological mechanisms in endometriosis-associated reproductive failure were studied in appropriate populations: infertile and fertile women with and without endometriosis. The incidence of sera positive for any of the autoantibodies tested among infertile women with endometriosis (n = 25) was similar to that observed in the three control groups [unexplained infertility patients (n = 25) and fertile women with (n = 10) and without (n = 25) endometriosis]. The mean volume of peritoneal fluid was significantly elevated in women with endometriosis (both fertile and infertile) as compared with patients without endometriosis (fertile or infertile). The concentration of peritoneal fluid leukocytes and the percentage of cells positive for macrophage markers were significantly increased and the percentage of T lymphocytes significantly decreased in infertile women with endometriosis but not in patients with unexplained infertility and fertile women with endometriosis, as compared with fertile controls without endometriosis. Macrophages from infertile patients with endometriosis had higher sperm phagocytosis than did those from infertile women without endometriosis or fertile subjects with or without endometriosis. Incidences of serum and peritoneal fluid samples embryotoxic to the in-vitro development of 2-cell mouse embryos were significantly higher in infertile patients with endometriosis than in unexplained infertility patients and fertile women with or without endometriosis. It is concluded that immunological mechanisms of endometriosis-associated infertility exist but that these peritoneal immunological factors in infertile women with endometriosis are related to their subfertility rather than to the presence of ectopic endometrial implants. This is supported by the lack of immunological abnormalities observed among fertile women with endometriosis. These immunological abnormalities are lacking in patients with unexplained infertility.      

The ileoanal J pouch: radiographic evaluation

Endorectal ileoanal pull-through offers an attractive alternative to proctocolectomy and ileostomy for patients with ulcerative colitis, Gardner syndrome, and familial polyposis. To our knowledge, a careful radiographic analysis of the ileum, ileal pouch, and ileoanal anastomosis after ileoanal pull-through has not been reported. Thirty-two patients with ulcerative colitis, Gardner syndrome, and familial polyposis underwent colectomy, mucosal proctectomy, and endorectal ileoanal pull-through of a 15-cm ileal "J" pouch and loop ileostomy. Twenty-five (78%) of 32 of all the pouches radiographically demonstrated spiral folds extending from the middle of the pouch to the pectinate line. Other radiographic features included a mesenteric mass effect, pseudopolyps, and a central lucency that indicated intrapouch sutures. Radiographs provide useful information in the postoperative management of the ileal pull-through.     

Variations in the density of bone cement after centrifugation

Barium sulfate added to bone cement to provide radiopacity has a density about four times greater than that of polymerized radiolucent bone cement. Because centrifugation might make a clinically significant change in the distribution of barium sulfate, this process was studied. Radiolucent and radiopaque Simplex-P bone cement (Howmedica, Inc., Rutherford, New Jersey) were mixed with and without cooling and centrifuged for two or four minutes at 2,000 g or 1,000 g (gravity acceleration). The density of sections of the hardened bone cement was measured using the Archimedes principle. Erythromycin and colistin were added to cement batches to test whether or not centrifugation affected the distribution of antibiotics. Direct and radiographic observation and density measurements (cooled specimens, 2,000 g, p less than 0.01) verified that barium sulfate does accumulate at the bottom of the centrifugation tubes. Thin sections of the bone cement revealed that only larger particles (20-100 micron) of barium sulfate were deposited at the bottom. No evidence of redistribution of antibiotics after centrifugation was seen. It is recommended that Simplex-P bone cement be reformulated to eliminate concern about inhomogeneities that arise from centrifugation. Further, it is recommended that cooled, centrifuged antibiotic cement be used for long-stem revision hip surgery, where longer setting times are necessary, and room temperature cement for "fresh" hip surgery. A total centrifuge time of two minutes with a 2,000 g maximum force is recommended.     

An immunocytochemical study of malignant melanoma and its differential diagnosis from other malignant tumours.

A series of 41 fresh and 36 routinely processed malignant melanomas were immunostained with a panel of 12 monoclonal antibodies reactive against a range of epithelial, lymphoid, and melanoma associated antigens. The aim of the study was to determine whether this panel of antibodies would be useful in diagnostically difficult cases for differentiating melanomas from other tumours, particularly carcinomas and lymphomas. The results confirmed that most unequivocal malignant melanomas can be identified by positivity for S100 protein and for the antigen recognised by antibody NK1/C3, and by negativity for epithelial and lymphoid antigens. The incidence of melanomas expressing cytokeratin antigens was higher, however, particularly in cryostat sections than has previously been reported. It is therefore suggested that a panel of antibodies with more than one marker in each category should be used for identifying melanomas in clinical practice.     

Preventing alcohol problems: survey of Canadian medical schools.

In preparation for a national conference on medical education in the prevention of alcohol problems, a survey of conference participants was conducted. Participants were undergraduate and postgraduate representatives from each Canadian medical school and representatives from 11 provincial and territorial alcohol and other drug agencies. There was agreement that physicians and medical schools have important roles in prevention and treatment of alcohol problems, with "traditional" medical roles seen as the most important. Current training is variable and was seen as inadequate, with more time devoted to treatment than prevention. To correct this situation, renewed priorities and faculty leadership are needed. Respondents felt that there should be uniform standards for assessing undergraduate students' skills in dealing with alcohol problems. Provincial alcohol and other drug agencies are underused in medical education in the prevention and treatment of alcohol problems.     

What do stochastic frontier cost functions tell us about inefficiency?

Recent studies using the stochastic frontier approach have suggested high levels of inefficiency in nursing home and hospital facilities. This paper makes two observations. First, one could falsely estimate high levels of inefficiency if a statistical assumption--zero skewness of the random component of the cost residual--is violated. Second, an inefficient industry may be difficult to distinguish either statistically or visually from an industry free of inefficiency. If available, panel data yields more robust estimates of cost differences among nursing homes or hospitals.