Mechanical considerations in impaction bone grafting

In impaction grafting of contained bone defects after revision joint arthroplasty the graft behaves as a friable aggregate and its resistance to complex forces depends on grading, normal load and compaction. Bone mills in current use produce a distribution of particle sizes more uniform than is desirable for maximising resistance to shear stresses. We have performed experiments in vitro using morsellised allograft bone from the femoral head which have shown that its mechanical properties improve with increasing normal load and with increasing shear strains (strain hardening). The mechanical strength also increases with increasing compaction energy, and with the addition of bioglass particles to make good the deficiency in small and very small fragments. Donor femoral heads may be milled while frozen without affecting the profile of the particle size. Osteoporotic femoral heads provide a similar grading of sizes, although fewer particles are obtained from each specimen. Our findings have implications for current practice and for the future development of materials and techniques.     

Environmental covariates: effects on the power of sib-pair linkage methods

The effect of inclusion of environmental risk factors on the power of sib-pair linkage methods was tested for a qualitative trait. It was found that inclusion of an environmental variable did not increase the power of the Haseman-Elston (H-E) sib-pair nonparametric linkage analysis test. However, a significant increase in power was observed for both the H-E and affected-sib-pair tests, even in small samples, when persons unexposed to the environmental risk factor were coded as unknown.     

Sham radiation in clinical trials assessing radiotherapy for exudative age-related macular degeneration

BACKGROUND: To evaluate the effectiveness of sham radiation treatments in masking patients to their randomization group in the Radiation of Age-Related Macular Degeneration (ROARMD) Study. METHODS: Patients with choroidal neovascularization complicating age-related macular degeneration were randomized to a treatment (RAD) group that received external beam irradiation (seven treatment sessions) or to a control (SHAM) group that received sham radiation (one sham treatment session). During a telephone survey, 62 of 73 randomized patients responded to the following questions: Do you think you received radiation? Why do you feel that way? Did the vision in your study eye worsen after enrollment? RESULTS: Eighty-one percent of the RAD group and 59% of the SHAM group thought that they had received radiation. In patients who thought that their vision had stabilized or improved, 82% thought that they had received radiation. In patients who thought that their vision was worse, only 39% thought that they had received radiation. In 54% of patients, subjective perception of vision influenced their guess as to whether they received radiation. CONCLUSIONS: Subjective patient perception of visual outcome was the most influential variable for masking. Variation between radiation treatment and sham session techniques, such as equipment used and duration of treatments, played a lesser role in the masking of patients. Seven treatment days correlated with a higher number of patients who thought that they had received radiation. Although our procedures do not strictly mask the two groups, one sham radiation session was effective in keeping patients guessing their randomization group.     

Thallium-201 myocardial perfusion scintigrams in the evaluation of aorto-coronary saphenous bypass surgery.

The effect of aorto-coronary bypass graft surgery (CBG) upon regional myocardial perfusion (RMP) was studied in 23 patients using thallium-201 myocardial perfusing imaging after exercise. We compared the changes in RMP with the clinical status and ECG's during graded treadmill exercise (GTX) before and after CBG. After CBG, the New York Heart Association's "functional class" improved from 3.2 +/- 0.1 (mean +/- SE) to 1.2 +/- 0.2, p less than 0.005. The GTX performance of the patients was also significantly improved postoperatively as judged by the total exercise time (11.7 +/- 0.6 min postop, compared with 7.2 +/- 0.5 min preop; p less than 0.005). Postoperative improved Tl-201 scintigrams were observed in 19 patients, but in only nine patients did the perfusion distribution return to normal. Thus, Tl-201 exercise scintigrams following CBG demonstrate improved RMP in most patients. Failure of regional myocardial perfusion to improve postoperatively, however, does not preclude marked alleviation of angina and improved exercise tolerance.     

Can knee replacements be assessed by post?

The audit of knee replacement surgery requires long-term follow-up. The aim of this Bristol study was to examine whether an accurate assessment of knee replacement surgery could be undertaken by post, thus obviating the need for patients to visit hospital. A patient's questionnaire was designed to complement the clinic therapist's assessment form currently in use, and this was completed by 73 patients without supervision prior to the therapist's assessment. A comparison of the two assessments shows a significant discrepancy between their results, particularly in the assessment of pain, walking distance, and range of movement. The authors conclude that postal follow-up of knee replacements should be viewed with caution.     

Functional anatomy of the gastroesophageal junction

The study of the functional anatomy of the gastroesophageal junction allows for the demonstration of a double mechanism that combats the conflict of pressures that tends to lead to gastroesophageal reflux. On one hand, the LES, an intrinsic structure, is directly related to the muscle fibers of the organ and responds to a neurohormonal physiologic command. On the other hand is an anatomic entity, centered by the crura of the diaphragm, closely related to the movements of respiration. These structures constitute a second, extrinsic sphincter that gives rise to the zone of high pressure in the terminal esophagus. This role is difficult to assess, and its importance is underestimated. The proper functioning of these two mechanisms implies that the gastroesophageal junction remains in place within the diaphragmatic channel of the esophagus. Also important are the postural phenomena associated with the sloping position of the fundus. In patients with gastroesophageal reflux, the decrease of the pressure measured in the terminal esophagus accounts for the occurrence of reflux. Investigators concede that, under the influence of abdominal straining, the gastroesophageal junction tends to ascend into the diaphragmatic channel. The results are twofold: (1) the muscle fibers of the lower esophagus relax, explaining the incompetence of the intrinsic sphincter, and (2) the sphincteric zone is withdrawn from its muscular diaphragmatic environment. Physicians should consider these structures as a whole in approaching the surgical treatment of reflux. The construction of a periesophageal valve has no anatomophysiologic basis. A gastropexy procedure must be added to replace the gastroesophageal junction in its anatomic setting and keep it there. This procedure also allows retightening of the muscle fibers of the esophageal wall, which is essential in long-term surgical correction.     

PRIMARY INTRACRANIAL GERM CELL TUMORS: Clinicopathologic Review of 32 Cases

Primary intracranial germ cell neoplasms are rare tumors and constitute a heterogeneous group. We have reviewed 32 cases, over a 21-year period, from the University of Florida. The cases include 22 germinomas, 6 mixed germ cell tumors, and 4 teratomas. The clinical presentations in these cases were more closely related to the location of the tumor, that is, pineal or suprasellar, rather than the histologic subtype. Neuroimaging evaluation was useful in distinguishing between germinomas, teratomas, and other mixed germ cell tumors (MGCTs), primarily by evaluation of cystic versus solid lesions (teratoma versus germinoma), contents of cysts (teratoma versus MGCT), and infiltrative nature of the tumors (MGCT), although cytologic-histopathologic confirmation remains necessary. Germinomas responded favorably to radiation therapy with survival periods of over 16 years; MGCTs were treated with combination chemotherapy and radiation, with a markedly poorer prognosis. This study underlines the critical significance of histopathologic evaluation of the tumor in determining therapeutic interventions as well as prognosis.     

A New Technique for Hypoglossal-Facial Nerve Repair

Hypoglossal reinnervation of the facial nerve may be required after a proximal facial nerve injury. The classic hypoglossal-facial graft procedure involves transection of the donor hypoglossal nerve, resulting in hemiglottic paralysis that, in association with paralysis of other cranial nerves, may cause speech and swallowing difficulties. Multiple lower cranial nerve palsies in conjunction with facial paralysis, as may occur after procedures such as skull base surgery, contraindicate the use of such techniques. The successful use of XII-VII “interposition jump grafts” without hemiglossal weakness has been described However, a prolonged recovery period and weaker facial reanimation have been seen. In order to attain maximum facial reinnervation while preserving hypoglossal function, we have developed a new technique of XII-VII repair. This method involves mobilization of the intratemporal portion of the facial nerve remnant, achieving a single anastomosis with the hypoglossal nerve, which has been partially incised. This technique has been used in three patients to date, with 6 to 11 months follow-up. In all cases facial tone and symmetry have been restored and voluntary facial expression accomplished. The authors conclude that by employing the techniques described highly satisfactory cosmetic and functional results may be expected, without compromising hypoglossal nerve function.