The Day After Tomorrow Complication Rates in Posterior Lumbar Fusion

Could PearlDiver be the Nostradamus of orthopedics? Spine fusion is most commonly performed on the lumbar region of the spine. Studies have revealed that spinal instrumentation, as an adjunct to fusion, has been associated with increased fusion rates and improved spinal stability following fusion. We used the PearlDiver Patient Records Database to examine complications associated with instrumented posterior lumbar fusion. Are you ready for some orthopedic quatrains about what happens next?

Instrumented Posterior Lumbar Fusion: Methodology

We used the PearlDiver database to zero in on patients who underwent instrumented posterior lumbar fusion, using CPT codes that represent non-segmental and segmental instrumentation together with ICD-9 procedure codes. ICD-9 procedure code 81.08 (posterior lumbar fusion) represents the most common approach to lumbar fusion. This approach was employed in over 70% of lumbar fusions in the database. We included only those patients who were coded with 81.08 as a primary procedure and whose records in the database extended for at least 12 months following the qualifying event—a requirement for our complications analysis.

We then searched for patients who had 81.08 and were coded with CPT 22840 (posterior non-segmental instrumentation) or 22842 (posterior segmental instrumentation representing 3 – 6 vertebral levels) in order to analyze patients who had instrumented posterior lumbar fusion. We then sorted these records by gender and year in order to analyze trends and outcomes. We also analyzed trends in instrumented levels as defined by the CPT codes and postoperative complications associated with this type of instrumentation.

Orthopedic Quatrain 1: Posterior Instrumentation Usage in Lumbar Fusion

Is segmental or non-segmental instrumentation used more often in posterior lumbar fusion surgery? Overall, we found that in inpatient surgeries where posterior lumbar fusion was the primary procedure, the use of posterior instrumentation rose from 83% in 2004 to 86% during the first half of 2007.

Patients who had posterior instrumentation were then separated by non-segmental and segmental instrumentation usage. According to the PearlDiver database, the use of non-segmental instrumentation in posterior lumbar fusions increased from 43.4% in 2004 to 48% through the first two quarters of 2007. Use of segmental instrumentation (defined as instrumentation implanted that spans 3 – 6 vertebral levels) declined from 54.7% to 50.6% during the same period of time.

We also performed the same analysis with respect to all lumbar fusions in the database, regardless of surgical approach. In this analysis the following ICD-9 procedure codes were used:

• Anterior lumbar fusion  – 81.06
• Lateral lumbar fusion – 81.07
• Posterior lumbar fusion – 81.08

Patients who had posterior instrumentation were then separated by non-segmental and segmental instrumentation usage, as was done in the prior analysis which focused only on the posterior approach (ICD 81.08). As can be seen in Chart 1 below, non-segmental posterior instrumentation was implanted in 46.3% of instrumented lumbar cases. Segmental instrumentation (3 – 6 vertebral levels) was implanted in 52% of instrumented cases.

As mentioned earlier, by the first half of 2007, 86% of patients undergoing posterior lumbar fusion had instrumentation implanted. But in comparison, when the lateral and anterior approaches were included in the analysis, the percentage receiving instrumentation fell to 80%. We believe part of this drop can be explained by the fact that anterior lumbar fusion is being increasingly performed on a stand-alone basis. This trend is being augmented by increasing success with stand-alone intervertebral body spacers, such as Synthes’ SynFix-LR device, that are used in the anterior approach.

Chart 1: Usage of Instrumentation in Lumbar Fusion*

Source: PearlDiver Patient Records Database (January 2004 - June 2007)
*Defined by ICD-9 procedure codes (81.06-81.08)

Orthopedic Quatrain 2: Posterior Instrumentation and Levels Fused

The use of segmental or non-segmental instrumentation depends on trends in the levels being fused. According to Orthopedic Network News (Vol. 18, October 2007), “Of lumbar vertebrae fused in 2007, 83% were for single-level fusions L5-S1 and L4-L5, or two-level fusions L4-S1 and L3-L5.” The remaining 17% comprised fusion of other vertebral levels.

According to PearlDiver data, single-level lumbar fusions have been on the rise from 2004 to June 2007. In 2004, 53.1% of posterior lumbar fusions were coded as being single level, but through the first two quarters of 2007 this had risen to over 57%. Multilevel fusions comprised 43% of posterior lumbar fusions through June 2007, falling from 47% in 2004.

Orthopedic Quatrain 3: Complications Following Instrumented Posterior Lumbar Fusion

Instrumented fusion has been associated with increased fusion rates and spinal stability following fusion and has been the “backbone” of billions in revenues for the spine industry. What are the potential complications associated with instrumented spine fusion? We discuss below the outcomes associated with tposterior lumbar fusions when instrumentation is used.

In developing our study, we analyzed patients who had instrumented posterior lumbar fusion as their primary procedure and sorted this group by gender and year. We included patients who had the procedure from January 2004 through June 2007. Patients were separated based on whether they had been implanted with non-segmental or segmental instrumentation, and complications were analyzed.

Chart 2 below displays common complications seen in male patients who underwent instrumented posterior lumbar fusion in 2006. There were 427 patients who had non-segmental instrumentation implanted and 520 who had segmental. The data revealed that device complications were more common in patients who had segmental instrumentation. Hemorrhage/hematoma, postoperative infection, and urinary tract infection also appeared more often in these patients.

Chart 2: Complications in Segmental and Non-Segmental Instrumented Posterior Lumbar Fusion (Males)*

Source: PearlDiver Patient Records Database (2006)
*Defined by ICD-9 procedure code (81.08)

Chart 3 below displays complications in non-segmental instrumented posterior lumbar fusions by gender. The study comprised 427 males and 625 females who underwent instrumented posterior lumbar fusion in 2006. Device-related complications were relatively equivalent between genders in this dataset. However, females displayed a much higher incidence of postoperative infection, hematoma, and urinary tract infection.

Chart 3: Complications in Non-Segmental Instrumented Posterior Lumbar Fusion by Gender*

Source: PearlDiver Patient Records Database (2006)
*Defined by ICD-9 procedure code (81.08)

There will probably always be complications associated with spine surgery—it’s just a fact of life. However, PearlDiver data can—through an examination of recent patient records―assist surgeons and patients in understanding the likelihood of certain complications occurring. Based on our research, posterior lumbar fusion with non-segmental instrumentation yields lower overall complication rates than posterior lumbar fusion using segmental instrumentation. We would expect this as there are fewer vertebral levels being fused, shorter operating times, and presumably less blood loss. Also, there are differences in complication rates with respect to gender, as device-related complications occurred more often in males, while postoperative infections, hematomas and respiratory complications were reported more often in females.

Orthopedic Quatrain 4: Refusion Rates Following Instrumented Posterior Lumbar Fusion

In our quest for outcomes, we designed an analysis to track the percentage of patients who subsequently had posterior lumbar refusion (ICD-9 code 81.38) after instrumented posterior lumbar fusion. We also sorted this data by gender and pulled patients who had posterior lumbar fusion in 2004 and tracked them through the first two quarters of 2007.

Males and females who had segmental instrumentation underwent a subsequent refusion 4.1% and 4.2% of the time, respectively. With respect to patients who had non-segmental instrumentation, a subsequent refusion operation was seen in 2.2% of males and 3.1% of females. Diagnoses associated with refusions included pseudoarthrosis, device complications, graft or implant complications, and spinal stenosis.

Orthopedic Quatrain 5: AAOS 2008 Submissions on Instrumented Fusion

Research continues on instrumented and non-instrumented fusion. We are highlighting two significant papers on the subject. The first paper was presented at AAOS 2008 and is a study with respect to single-level instrumented lumbar fusion; the second study, presented at NASS 2007, reported good outcomes in uninstrumented PLF (posterolateral fusion), which is an important surgical technique for patients with osteoporosis or contraindications for instrumented fusion.

The second study was presented at NASS 2007 and provides additional evidence to confirm good outcomes in instrumented posterolateral lumbar fusions using single-level posterior instrumentation.

Paper Number 087: Two Year Outcomes in 224 Patients Treated With a Single-Level Posterolateral Fusion With ICBG (Presented at AAOS 2008)

This paper was written by Dr. John R. Dimar II, Dr. Steven Glassman, Dr. J. Kenneth Burkus, Dr. Philip Prior, Dr. James Hardacker, and Dr. Leah Carreon. According to the abstract, the study reports “two-year results of single-level instrumented posterolateral fusions evaluated with radiographs, fine-cut CT scans with reconstructions, and outcome measures.”

With respect to complications, the authors reported a 10.7% rate of perioperative infections, 8% incidental durotomies, 1.3% intraoperative factures, and 1.3% loosened implants. The authors stated “In a large series of patients who had primary single-level instrumented posterolateral fusion with ICBG [iliac crest bone graft], evidence of bridging bone on fine-cut CT scans improved with time to 83.8% at 24 months. Significant improvement from baseline was noted in all clinical outcomes measures at all time intervals.”

NASS 2007: Special Interest Poster Presentation 4: Fusion

#49 Two-Year Outcomes of Lumbar Decompression and Uninstrumented Fusion With Iliac Crest Bone Graft: A Multicenter Prospective Study With Independent Assessments

This paper was written by Dr. Tushar Patel, Dr. Alexander Vaccaro, Dr. Michael Fehlings, and Dr. Jeffrey Fischgrund.  The authors stated that the purpose of the study was “to present two-year efficacy and safety results from a cohort of patients undergoing uninstrumented posterolateral fusion (PLF) with autogenous iliac crest bone graft (ICBG).” The paper illustrated positive outcomes in select patients. In their conclusion, the authors stated that “These data suggest that uninstrumented PLF with ICBG is associated with significant improvements in clinical outcomes with acceptable rates of fusion success.” The authors also noted that patient selection is important as this technique exposes patients to higher risk of non-union and complications.

Orthopedic Quatrain 7: Concluding Thoughts