Primary total hip arthroplasties have reported success rates of greater than 95% in many series with a longer than 10-year follow-up. Revision total hip arthroplasty due to such factors as increased high-activity levels, younger patients undergoing the procedure and increasing life expectancy has become more prevalent. An understanding of the mechanisms and timing of total hip arthroplasty failure can direct efforts aimed at reducing revision rates. This study was conducted to evaluate the indications for revision hip arthroplasty and relate these to the time after the index primary hip arthroplasty. A review of all revision hip arthroplasties at two centres over a 6-year time period identified 225 patients who underwent 237 revisions. The overall mean time to revision was 83 months (range: 0-360 months). The cause of failure was aseptic loosening in 123 hips (51.9%), instability in 40 hips (16.9%) and infection in 37 hips (5.5%). When stratified into two groups (less than 5 years, more than 5 years after the index primary hip arthroplasty), 118 of 237 (50%) revisions occurred in less than 5 years, with 33% due to instability and 24% resulting from infection. The majority of the causes of failure within 5 years in these early revisions were instability and deep infection. The success of hip arthroplasty is likely to be compromized if technical aspects of the surgery for appropriate component positioning and critical protocols to minimise complications such as infection are not given the proper attention.

The surgical management of sacral tumors requires partial or total sacrectomy and spinopelvic reconstruction. These lesions present a great surgical challenge, because most spine surgeons are unfamiliar with the techniques required for these procedures. The authors describe a step-by-step operative technique and provide several illustrations. Total sacrectomy is performed by sequential anterior and posterior approaches that involve a rectus abdominis pull-through pedicle flap reconstruction. The anterior procedure is an intraperitoneal approach used to expose the anterior aspect of the tumor, to ligate the main tumor vessels, and to conduct an anterior partial sacrectomy. After this, the rectus abdominis myocutaneous flap, based on the inferior epigastric vessel, is prepared, and a posterior sacrectomy is performed, dividing all sacral nerve roots in the thecal sac. After complete en bloc extirpation of the sacrum with tumor, spinopelvic reconstruction and closure with a myocutaneous flap are performed. Spinopelvic reconstruction is undertaken using a modified Galveston technique or double iliac screw fixation combined with posterior lumbar segmental fixation. These provide a long lever arm within the ilium to counteract the forces exerted by the lumbar spine. Understanding the nature of the disease as well as the biomechanics of the lumbosacral pelvic area and spinopelvic fixation will help surgeons select the appropriate treatment for sacral tumors.

Early attempts at spinal arthroplasty in the 1950s yielded limited success. A revival of this procedure occurred in the 1980s and became a realistic treatment option in the 1990s. Both lumbar and cervical arthroplasties have been introduced in the US since 2000 for randomized, prospective studies in accordance with the Food and Drug Administration (FDA) investigational device exemption provisions. In June 2004 the first lumbar arthroplasty device was approved by the FDA for use in the US. It is likely that cervical arthroplasty will soon follow and may be available for widespread use as early as 2006. In this paper the authors review the historical development of cervical arthroplasty.

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The concept of minimally invasive spinal surgery embodies the goal of achieving clinical outcomes comparable to those of conventional open surgery, while minimizing the risk of iatrogenic injury that may be incurred during the exposure process. The development of microscopy, laser technology, endoscopy, and video and image guidance systems provided the foundation on which minimally invasive spinal surgery is based. Minimally invasive treatments have been undertaken in all areas of the spinal axis since the 20th century. Lumbar disc disease has been treated using chemonucleolysis, percutaneous discectomy, laser discectomy, intradiscal thermoablation, and minimally invasive microdiscectomy techniques. The initial use of thoracoscopy for thoracic discs and tumor biopsies has expanded to include deformity correction, sympathectomy, vertebrectomy with reconstruction and instrumentation, and resection of paraspinal neurogenic tumors. Laparoscopic techniques, such as those used for appendectomy or cholecystectomy by general surgeons, have evolved into procedures performed by spinal surgeons for anterior lumbar discectomy and fusion. Image-guided systems have been adapted to facilitate pedicle screw placement with increased accuracy. Over the past decade, minimally invasive treatment of cervical spinal disorders has become feasible by applying technologies similar to those developed for the thoracic and lumbar spine. Endoscope-assisted transoral surgery, cervical lam-inectomy, discectomy, and foraminotomy all represent the continual evolution of minimally invasive spinal surgery. Further improvement in optics and imaging resources, development of biological agents, and introduction of instrumentation systems designed for minimally invasive procedures will inevitably lead to further applications in minimally invasive spine surgery.