Volume-Outcome Benchmarks in Lumbar Spine Surgery

Outstanding Paper: Value in Spine Care awarded at the North American Spine Society 2017 Annual Meeting.

Using data from over 180,000 spine surgeries, Andrew J. Schoenfeld, MD, MSc, and colleagues established volume-based benchmarks for common lumbar spine surgeries, including decompression, discectomy, and fusion-based procedures. The study won The Spine Journal award for Outstanding Paper: Value in Spine Care at the North American Spine Society (NASS) 32nd Annual Meeting October 25-28, 2017 in Orlando, Florida.

The following volume-outcome cut points were defined using data from the Florida Statewide Inpatient Dataset (2011-2014):

  • Discectomy = 25 annually
  • Lumbar interbody fusion = 40 annually
  • Posterolateral fusion = 35 annually
  • Interbody fusion = 43 annually

Lumbar Spine RadiographResearchers sought to establish objective volume-based benchmarks for common lumbar spine surgical procedures. Photo Source:123RF.com.

“In terms of benchmarking, we have identified regular achievable goals for individual surgeons, which include between three and four fusions and discectomy procedures per month, and at least one decompression surgery every other week,” explained Dr. Schoenfeld, who is Assistant Professor in the Department of Orthopaedic Surgery at Brigham and Women’s Hospital, Harvard Medical School, Boston, MA. “These obviously could be performed sequentially or together, where decompression and a fusion-based procedure of any kind would obviously count toward both interventions.”

Importance of Volume-Outcome Benchmarks in Spine Surgery

“The volume-outcome relationship has been recognized for a number of disciplines within the field of medicine, including joint arthroplasty (knees and hips), sports medicine, shoulder surgery, and hip fracture care,” Dr. Schoenfeld said.

“The concept of volume-outcome theory is quite intuitive,” Dr. Schoenfeld told attendees. “The more facile and experienced a provider is with a particular surgical procedure, the more proficient they may be in its execution. In addition, sufficient annual volume allows the providers to maintain skills developed earlier in their career, for which skill degradation might occur during procedural hiatus.”
“At the current nexus in healthcare where we find ourselves, it is especially important for us to establish meaningful benchmarks as more scrutiny is given by third-party payer boards, insurers, and networks,” Dr. Schoenfeld explained. “The benchmarks may define how much the individual surgeon gets paid or what percent bonus they might get paid.”

Study Design

Within this context, the researchers sought to establish objective volume-based benchmarks for common lumbar spine surgical procedures that influence short-term quality measures, including complications or hospital readmissions within 90-days of surgery for the following four common lumbar spine surgeries: discectomy, decompression, lumbar interbody fusion, and lumbar posterolateral fusion.

The retrospective review is based on findings in the Florida Statewide Inpatient Dataset (2011-2014), which includes data from all non-Federal facilities in the state and follows patients up to 90 days from hospital discharge. This database has anonymized specific identifiers for surgeons and hospitals who perform the indexed procedure, Dr. Schoenfeld explained.

“We then used the volume of surgical procedures limited to each individual procedure, and to specific surgeons cataloged within the calendar year. For each procedure, the individual surgeon’s volume was separately plotted against the number of complications and readmissions, and then merged in a spline analysis that adjusted for all covariates.
“Spline cut points were created and used as a categorical variable for procedure volume for each individual procedure,” Dr. Schoenfeld said. Next, multivariate logistic regression analysis was performed using the categorical volume-outcome metric for each procedure and for the outcomes of 90-day complications and readmissions.

The researchers identified 187,185 spine surgical procedures performed by 5,514 different surgeons at 178 different hospitals in the state of Florida. These procedures included:

  • 69,598 (37%) discectomies
  • 43,572 (23%) interbody fusions
  • 38,632 (21%) decompressions
  • 35,383 (19%) posterolateral fusions


During 90-day follow-up, 3,829 (2%) patients died, 30,046 (16%) were readmitted, and 17,588 (9.4%) had one or more post-operative complication.  These outcomes are in-line with the current literature regarding these types of lumbar spine surgical interventions, and speaks to the potential for a generalization of this data, Dr. Schoenfeld said. 

The procedure volume benchmarks ranged from 25 to 43 annually. Surgeons who failed to meet these benchmarks were at significantly increased risk for complications and hospital readmission (by 15% to 63% and 11% to 45%, respectively, depending on procedure). The findings were unchanged after accounting for the use of bone morphogenetic proteins.

The following benchmark goals were established for individual surgeons:

  • 4 discectomy and lumbar interbody fusion procedures per month
  • 3 posterolateral lumbar fusions per month
  • At least 1 decompression surgery every other week

Clinical Implications for Spine Surgeons

“Currently, we only recommend [use of these benchmarks] among individual providers to look at their own complication and readmission rates and see how they might reflect based on their performance,” Dr. Schoenfeld concluded.

“In terms of the additional applications, these findings could be used for maintenance of privileges or defining insurance tiers,” Dr. Schoenfeld said. However, he cautioned that the benchmarking measures need to be independently validated before such approaches can be supported.

“I think most people, especially doctors, accept the notion that the more experience someone has with a given procedure or disease, the more effectively and efficiently they will be able to manage it,” commented Eeric Truumees, MD, who moderated the NASS session. “That said, many of us are concerned about the unintended consequences of payer or federally mandated volume requirements. There are too many perverse incentives to ‘keep the numbers up.’ We also do not have reliable ways to ensure fair treatment of newly trained doctors or those practicing in less densely populated areas.”

“Of course, that is not what Schoenfeld and his co-authors are doing here,” said Dr. Truumees who is an orthopaedic spine surgeon and Chief Executive Officer of Seton Brain and Spine Institute in Austin Texas as well as Professor of Surgery and Perioperative Care at the University of Texas at Austin, Dell Medical School. “They are looking at the data in a medically meaningful way to more clearly establish the relationship between surgical volumes and complications.”

“I congratulate them on this excellent study,” Dr. Truumees told SpineUniverse. “I look forward to the day when registries or other tools can be used to look beyond the 90 days to describe surgical outcomes. Those data may address the issue of volumes versus surgical indications.”

“For now, the key issue is: how do we use these data?,” Dr. Truumees said. “We know that, as spine surgeons, our performance is being measured, and those measures are increasingly published online or elsewhere. At the very least, we should make sure that what is published is meaningful and accurate.”

Limitations of the study include the inability to assess type of instrumentation and use of minimally invasive approach, Dr. Schoenfeld said. Surgeon training and prior experience outside of the period of the study were not known. In addition, the findings are based on inpatient procedures only and do not take into account outpatient spine surgical procedures. Lastly, the findings are informed by the procedural practice within the state of Florida; however, Dr. Schoenfeld noted that this practice largely reflects on practice across the United States.

Dr. Schoenfeld has received grants (National Institutes of Health, United states Department of Defense, Orthopaedic Research and Education Foundation, Centers for Medicare & Medicaid Services); royalties (Springer, Wolters Kluwer); consultant (Arbormetrix LLC); editorial board (The Journal of Bone & Joint Surgery).

Dr. Truumees disclosed no consulting, royalty, or other industry relationships. He is on the NASS Board of Directors and is Editor in Chief of AAOS Now.

Updated on: 03/19/19
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Volume Benchmarks for Common Lumbar Spine Surgeries Defined in Recent Study

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