Lumbar surgery in adults can be divided into three general levels of complexity and associated morbidity. The first, an operation to treat herniated lumbar nucleus pulposus, is relatively straightforward from a medical management perspective. The second, an operation for multilevel lumbar stenosis, is usually more involved and tends to be performed for older patients with more comorbidities. The most complicated surgeries are fusion surgeries, which may be carried out with a posterior or anterior approach, or with both approaches.

Patients with a lumbar disc herniation present with radiculopathy in a dermatomal pattern, and may exhibit motor weakness or reflex changes which correspond to the anatomic level of neural compression. The patient is typically a young adult in good health. Axial back pain is not a predominant symptom of this condition and is generally unimproved with a discectomy. If the symptoms produced by lumbar disc herniation fail to respond to appropriate non-operative therapy, laminotomy and discectomy are indicated. Patients are placed either prone or in the knee–chest position on a specially designed operating table; the latter position affords decompression of the abdominal cavity and the epidural veins. The procedure is performed with either loupe magnification or use of the surgical microscope through a posterior midline incision measuring 2.5–5 cm. The operative level is confirmed radiographically to prevent harm to an otherwise normal intervertebral disc. Blood loss is minimal and the total anesthetic time is usually 1–2 hours. A subset of these patients will present with acutely worsening neurologic dysfunction with or without cauda equina syndrome. In these cases, the herniated nuclear fragment is so large that it causes ischemia of the nerve roots. Although unusual, this situation is a true surgical emergency and requires prompt clinical diagnosis to give the patient the best chance of neurologic recovery.

Cervical spine disorders that require surgical intervention can include degenerative disorders causing radiculopathy or myelopathy, trauma, tumors, and infections. Radiculopathy can present as parasthesias or weakness in a specific root level(s). Myelopathy is a condition caused by spinal cord compression; once manifest clinically, the only treatment for this process is surgery to prevent further neurologic decline. Tumors or infections can present in the cervical spine as radiculopathy, myelopathy, or pain due to instability or pathologic fracture.

The cervical spine can be accessed via anterior or posterior approaches; a combined anterior–posterior approach (360° approach) may be utilized when necessary. The choice of approach is largely dependent upon location of the pathology, history of previous surgery, body habitus, and patient comorbidities. The anterior approach allows exposure of the spine by mobilization of the trachea and esophagus to exploit the interval between these structures and the carotid sheath. The anterior approach allows performance of anterior cervical discectomy and fusion (ACDF) as well as vertebral corpectomy.

Anterior cervical discectomy and fusion involves removing the pathologic disc material and then replacing this void with a spacer fashioned from autograft bone, allograft bone, or synthetic devices. This procedure is employed primarily in treating radiculopathy and multilevel (< 3 levels) cervical spondylitic myelopathy. Anterior cervical discectomy and fusion can also be used in the treatment of certain fractures (e.g., unstable facet fractures or floating lateral mass fractures) and for infections.

What can more than two thousand years of human thought and several hundred years of hard science tell us finally about the true nature of space and time? This is the question that the philosopher Jeremy Butterfield and I posed to a unique panel of top mathematicians, physicists and theologians in a public discussion that took place at Emmanuel College, Cambridge in September 2006, and this is the book that grew out of that event. All four other panellists, myself and the astronomer Andy Taylor who spoke at a related workshop, now present our personal but passionately held insights in rather more depth.

The first thing that can be said is we do not honestly know the true nature of space and time. Therefore this book is not about selling a particular theory but rather it provides six refreshingly diverse points of view from which the reader can see that the topic is very much as alive today as it was at the time of St Augustine or of Newton or of Einstein. Our goal is not only to expose to the modern public revolutionary ideas at the cutting edge of theoretical physics, mathematics and astronomy but to expose that there is a debate to be had in the first place and at all levels, including a wider human context. Moreover, the reader will find here essays from leading figures unconstrained by peer pressure, fashion or dogma.