Performance limitations of flat-histogram methods.

We determine the optimal scaling of local-update flat-histogram methods with system size by using a perfect flat-histogram scheme based upon the exact density of states of 2D Ising models. The typical tunneling time needed to sample the entire bandwidth does not scale with the number of spins N as the minimal N2 of an unbiased random walk in energy space. While the scaling is power law for the ferromagnetic and fully frustrated Ising model, for the +/-J nearest-neighbor spin glass the distribution of tunneling times is governed by a fat-tailed Fréchet extremal value distribution that obeys exponential scaling. Furthermore, the shape parameters of these distributions indicate that statistical sample means become ill defined already for moderate system sizes within these complex energy landscapes.

Local progression after operative treatment of metastatic kidney cancer.

The cases of 78 patients with osseous metastases from kidney cancer were reviewed to determine the rate of local progression after operative resection as compared with more traditional intralesional procedures. Group I consisted of 41 (53%) patients who were treated with intralesional procedures involving internal fixation with or without curettage or polymethylmethacrylate. Of the 41 patients, additional operations were recommended for 17 (41%) of the patients who had local osseous progression. Fourteen additional procedures including nine wide resections with reconstruction, three amputations, and two mass excisions were done. Group II consisted of 37 (47%) patients who were treated with marginal or wide resection with or without reconstruction. In this group, only one patient required additional operative intervention for local osseous progression. Median survival of patients in Group I was 20 months compared with 35 months for patients in Group IL This study shows that despite shorter average survival, patients who undergo intralesional surgery are at high risk of reoperation for local progression. Resectional surgery should be considered in patients with skeletal metastases from kidney cancer to lessen the risk of reoperation for local progression.

Loss of external rotation following anterior capsulorrhaphy of the shoulder.

A retrospective study was performed on twenty shoulders in nineteen patients who had been managed for severe loss of external rotation of the glenohumeral joint after a previous anterior capsulorrhaphy for recurrent instability. All patients had noted a restricted range of motion, and seventeen shoulders had been painful. In seven shoulders, the humeral head had been subluxated or dislocated posteriorly, and sixteen shoulders had been affected by mild to severe glenohumeral osteoarthrosis. All twenty shoulders were treated with a reoperation, which consisted of a release of the anterior soft tissue. In addition, eight shoulders had a total arthroplasty and one had a hemiarthroplasty. At an average duration of follow-up of forty-eight months, all shoulders had an improvement in the ratings for pain and range of motion. The average increase in external rotation was 45 degrees (range, 25 to 65 degrees). Patients who have a major loss of external rotation following anterior capsulorrhaphy of the shoulder may be at risk for the development of posterior subluxation and glenohumeral osteoarthrosis. The performance of an anterior release should be considered for these patients.