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The purpose of this study was to determine whether bone mineral density of the host bone, measured using conventional dual photon absorptiometry techniques, and insertion torque can predict part of the ultimate failure strength of interference screw fixation of quadrupled hamstring tendon grafts. The semitendinosus and gracilis tendons were harvested from 10 human cadaveric knees, mean age 66.5 years (range, 53 to 81). The bone tunnel was sized within 0.5 mm of the graft. The graft was fixed with a biodegradable screw (7 x 25 mm for the femur, and 9 x 25 mm for the tibia) directly against the tendon and at the joint surfaces. Tibial fixation and femoral fixation were tested to failure using a materials testing system. Bone mineral density was measured in the metaphyseal region of the tibia and femur. The results of multiple regression analyses showed that both insertion torque and bone mineral density were related to the maximum load the graft withstood. These two variables explained 77.1% of the maximum load observed. We concluded that bone mineral density measurements of the host bone site are an important determinant of postoperative graft strength and thus have an important, but previously unrecognized, clinical role in establishing individual postsurgery rehabilitation protocols. Insertion torque in this study was a useful predictor of graft fixation strength.

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Fractionated external beam radiotherapy is an important component of standard treatment for high grade glioma. Due to resource constraints, patients may experience delays in receiving treatment. The purpose of this study was to evaluate the effect of radiotherapy waiting time on survival in patients with high grade glioma. A retrospective analysis was performed of 172 patients with a histological diagnosis of WHO Grade 3 or 4 Astrocytoma who had undergone surgery at Wellington Hospital between 1993 and 2003, and who subsequently underwent radiotherapy. Time to radiotherapy after surgery varied from 7 days to over 16 weeks. Multiple Cox regression analysis showed that age, performance status, tumour grade, extent of surgical resection, radiotherapy dose, and time to radiotherapy from day of surgery were all independently related to survival. Every additional week of delay until the start of radiotherapy increases the risk of death (hazard ratio) by 8.9% (95%CI 2.0%-16.1%). A 6 week delay in starting radiotherapy (from 2 weeks post-op to 8 weeks) reduces median survival by 11 weeks for a typical patient. Delay in radiotherapy results in a clinically significant reduction in survival. These findings have implications for resource allocation and for the design of clinical trials.

To determine the indications for postoperative radiotherapy after surgical resection of a nonfunctioning pituitary macroadenoma. A retrospective chart review of 72 patients with histologically proven chromophobe adenoma who presented for pituitary surgery between January 1985 and June 1998, with a minimum follow-up period of 12 months. The study endpoint was tumour recurrence or progression detected either by routine follow-up imaging or by clinical progression with subsequent confirmation by imaging. A proportional hazards model was used to determine independent prognostic factors. Mean follow-up was 64 months. In the radiotherapy group 13 of 50 recurred (or progressed) (26%), while in the nonradiotherapy group 10 of 22 recurred (46%), logrank test, P = 0.025. In patients assessed as having complete excision of tumour (n = 20) only two recurred (10%), both in patients without radiotherapy. No further treatment has been required in either case to date. In patients with residual tumour (n = 52), 41 had radiotherapy with 13 recurrences (32%), while 11 patients had no radiotherapy with eight subsequent recurrences (73%); logrank test, P = 0.007. Further treatment has been required in the majority of these cases. Cox's proportional hazards model analysis showed that only complete tumour removal and postoperative radiotherapy were independent favourable prognostic factors. The goal of surgery should be complete surgical excision where possible. The risk of recurrence in patients with no residual tumour on postoperative imaging is low enough to justify withholding routine postoperative radiotherapy in this group. In patients with residual tumour, conventional external beam radiotherapy administered within 12 months of surgery is effective at reducing recurrence or progression.