Source: Wolters Kluwer Health: Lippincott Williams & Wilkins

Released: Thu 13-Nov-2008, 15:20 ET  Embargo expired: Mon 17-Nov-2008, 00:00 ET  Printer-friendly Version

'Invasiveness Index' Helps in Assessing Risks of Spinal Surgery

Newswise — A new "invasiveness index" is closely related to key measures of the magnitude of spinal surgery, reports a study in the November 15 issue of Spine. The journal is published by Lippincott Williams & Wilkins, a part of Wolters Kluwer Health, a leading provider of information and business intelligence for students, professionals, and institutions in medicine, nursing, allied health, pharmacy and the pharmaceutical industry.

Because invasiveness affects the risk of complications, the new score may be helpful for doctors and patients weighing their options for surgical treatment of spinal problems. The study was led by Dr. Sohail K. Mirza of University of Washington, Seattle.

Score Adds Up the Extent of Spinal Surgery
Dr. Mirza and colleagues created the invasiveness index by combining six possible components of spinal surgery, including the number of vertebrae undergoing decompression (surgery to relieve pressure on the spinal cord or spinal nerves), fusion (surgery to join two or more vertebrae together), or instrumentation (placing hardware to straighten or stabilize the spine).

Each component was further classified as to whether it was done at the front (anterior) or back (posterior) of the vertebrae. Based on the six components, the researchers were able to add up a total invasiveness score for any patient undergoing spinal surgery. Possible scores ranged from 0 (least invasive) to 48 (most invasive).

The researchers calculated the invasiveness index for 1,723 patients undergoing spinal surgery, then compared the scores with two indicators reflecting the extent of any type of surgery: blood loss and duration of surgery. Both factors are related to the risk of surgical complications.

After adjustment for other key factors, the invasiveness index was significantly related to both indicators. For each one-point increase in invasiveness score, blood loss increased by 11.5 percent and duration of surgery increased by about 13 minutes.

Overall, the invasiveness index explained 44 percent of the variation in blood loss between patients, and 52 percent of the variation in duration of surgery. The component of surgery with the greatest impact on invasiveness was anterior instrumentation—for each vertebra undergoing anterior instrumentation, blood loss increased by 19.4 percent and duration of surgery by 34 minutes.

Index May Aid in Discussing Risks with Patients
The extent or invasiveness of surgery is an important consideration when patients and surgeons are weighing surgical options. Invasiveness may have important effects on the risk of complications, recovery and healing time, and long-term outcomes. This is especially important when considering spinal surgery, for which patients may be offered several surgical options. If effectiveness is similar—or unknown, as is often the case for spinal surgery—then the comparative risk of complications "becomes paramount for informed choice," according to the researchers.

The new invasiveness index provides a useful measure for comparing the magnitude of spinal operations, Dr. Mirza and colleagues believe. For surgeons and patients discussing surgical procedures, adding up the invasiveness score on a scale of 0 to 48 can provide a quick estimate of the extent and risks of the various options. Especially when combined with other patient characteristics, "[A]n invasiveness index could help surgeons and patients make informed surgical choices based on the individualized increase in risk associated with more invasive spinal procedures," the researchers write.

About Spine
Recognized internationally as the leading journal in its field, Spine is an international, peer-reviewed, bi-weekly periodical that considers for publication original articles in the field of spine. It is the leading subspecialty journal for the treatment of spinal disorders. Only original papers are considered for publication with the understanding that they are contributed solely to Spine. According to the latest ISI Science Citation Impact Factor, Spine ranks highest among general orthopaedic journals and subspecialty titles. Visit the journal website at http://www.spinejournal.com

About Lippincott Williams & Wilkins
Lippincott Williams & Wilkins (www.LWW.com) is a leading international publisher for healthcare professionals and students with nearly 300 periodicals and 1,500 books in more than 100 disciplines publishing under the LWW brand, as well as content-based sites and online corporate and customer services. LWW is part of Wolters Kluwer Health, a leading provider of information and business intelligence for students, professionals and institutions in medicine, nursing, allied health, pharmacy and the pharmaceutical industry.

Wolters Kluwer Health is a division of Wolters Kluwer, a leading global information services and publishing company with annual revenues (2007) of €3.4 billion ($4.8 billion), maintains operations in over 33 countries across Europe, North America, and Asia Pacific and employs approximately 19,500 people worldwide. Visit www.wolterskluwer.com for information about our market positions, customers, brands, and organization.