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Study Design: Cross-sectional observational study (consecutive case series). Objectives: The aim of this study was to define a criterion for achieving successful decompression of lumbar spinal stenosis (LSS) using intraoperative ultrasonography (IOUS) and to investigate the pathogenesis of redundant nerve roots (RNRs) based on the ultrasonographic findings. Methods: A total of 100 LSS patients (71 males, 29 females, mean age, 71 ± 8 years) with RNRs were enrolled as subjects in this study. IOUS was performed to evaluate pulsatile motion of the cauda equina (PMCE) just before and after decompressive laminectomy. To determine the decompression status of the cauda equina, the ultrasonographic findings were classified into 3 types on the basis of the presence or absence of PMCE: type 1, predecompression PMCE (−) to postdecompression PMCE (+); type 2, pre- and postdecompression PMCE (+); and type 3, pre- and postdecompression PMCE (−). The pathogenesis of RNRs was also investigated based on the ultrasonographic findings. Results: Around the stenosis, PMCE was almost always absent before decompression and appeared after decompression (type 1 in 94 patients, type 2 in 6, type 3 in 0). IOUS showed that, before decompression, the cauda equina was held at the stenosis and could not pulsate beyond the stenotic site, and after decompression, PMCE recovered in the craniocaudal direction, leading to the resolution of RNRs. Conclusions: The emergence of PMCE can be a sign of successful decompression for LSS. Ultrasonographic findings support the notion that disturbance of PMCE around the stenosis is a basic component of the pathogenesis of RNRs.

Objective In contrast to acrometastasis, defined as bone metastasis to the hand or foot, the frequency and prognosis of bone metastasis of other limb segments remain unclear. To compare prognosis according to sites of bone metastasis, we defined two new terms in this study: ‘mesometastasis’ and ‘rhizometastasis’ as bone metastasis of ‘forearm or lower leg’ and ‘arm or thigh’, respectively. Methods A total of 539 patients who were registered to the bone metastasis database of The University of Tokyo Hospital from April 2012 to May 2016 were retrospectively surveyed. All patients who were diagnosed to have bone metastases in our hospital are registered to the database. Patients were categorized into four groups according to the most distal site of bone metastases: ‘acrometastasis’, ‘mesometastasis’, ‘rhizometastasis’ and ‘body trunk metastasis’. Results The frequency of rhizometastasis (22.5%) or body trunk metastasis (73.1%) was significantly higher than that of acrometastasis (2.0%) or mesometastasis (2.4%). The median survival time after diagnosis of bone metastases for each group was as follows: 6.5 months in acrometastasis, 4.0 months in mesometastasis, 16 months in rhizometastasis, 17 months in body trunk metastasis and 16 months overall. In survival curve, there was a statistically significant difference between mesometastasis and body trunk metastasis. Conclusions Our findings suggest that ‘mesometastasis’ could be another poor prognostic factor in cancer patients and that patients with mesometastasis should receive appropriate treatments according to their expected prognosis., We coined a new word mesometastasis: bone metastasis in the forearm or lower leg. Like acrometastasis, mesometastasis could be a poor prognostic factor in cancer patients.