Single-level Posterolateral Lumbar Fusion Research Articles

Does decompression adjacent to arthrodesis in the lumbar spine predispose patients to adjacent segment degeneration and disease: A retrospective analysis

BackgroundThe treatment for multi-level spinal stenosis in the setting of single-level instability is a common operative scenario for surgeons who treat degenerative lumbar spine pathology. However, there is conflicting evidence regarding the inclusion of adjacent “stable” levels in the arthrodesis construct because of the potential for iatrogenic instability placed on those segments with decompressive laminectomy alone. This study aims to determine whether decompression adjacent to arthrodesis in the lumbar spine is a risk factor for adjacent segment disease (AS Disease). MethodsA retrospective analysis identified consecutive patients over a three-year period who underwent single-level posterolateral lumbar fusion (PLF) in the setting of single or multi-level spinal stenosis. Patients were required to have a minimum of two-year follow-up. AS Disease was defined as the development of new radicular symptoms referable to a motion segment adjacent to the lumbar arthrodesis construct. The incidence of AS Disease and reoperation rates were compared between cohorts. Results133 patients met the inclusion criteria with an average follow-up of 54 months. Fifty-four patients had a PLF with adjacent segment decompression, and 79 underwent a single-segment decompression and PLF. 24.1% (13/54) of patients who had a PLF with adjacent level decompression developed AS Disease resulting in a 5.5% (3/54) reoperation rate. 15.2% (12/79) of patients who did not receive an adjacent level decompression developed AS Disease resulting in a reoperation rate of 7.5% (6/79). There was neither a significantly higher rate of AS Disease (p = 0.26) nor reoperation (p = 0.74) between the cohorts. ConclusionsDecompression adjacent to single-level PLF was not associated with an increased rate of AS Disease relative to single-level decompression and PLF.

Postoperative Opioid Use Following Single-Level Transforaminal Lumbar Interbody Fusion Compared with Posterolateral Lumbar Fusion

To compare postoperative opioid morphine milligram equivalents (MME) prescriptions for opioid-naïve patients undergoing single-level transforaminal lumbar interbody fusion (TLIF) versus posterolateral lumbar fusion (PLF) and total postoperative MME prescribed based on operative duration. Patients undergoing single-level TLIF or PLF from September 2017 to June 2020 were identified from a single institution. Patients were first grouped based on procedure type (TLIF or PLF) and subsequently regrouped based on median operative duration. Statistical tests compared patient demographics and opioid prescription data between groups. Multivariate regressions were performed to control for demographics, operative time, and procedure type. Of 345 patients undergoing single-level PLF or TLIF, 174 (50.4%) were opioid-naïve; 101 opioid-naïve patients (58.0%) underwent PLF and 73 (42.0%) underwent TLIF. Patients undergoing TLIF received more opioid prescriptions (1.99 vs. 1.26, P < 0.001) and total MME (91.2 vs. 66.8, P= 0.002). After regrouping patients based on operative duration, independent of procedure type, there were no differences in postoperative opioid prescriptions, and Spearman rank correlation coefficient between total MME and operative duration was r= 0.014. Multivariate analysis identified TLIF as an independent predictor of increased postoperative opioid prescriptions (β= 0.64, P < 0.001), prescribers (β= 0.49, P= 0.003), and MME (β= 24.4, P= 0.030). Opioid-naïve patients undergoing single-level TLIF receive a greater number of postoperative opioids than patients undergoing single-level PLF, and TLIF was an independent predictor of increased postoperative opioid prescribers, prescribers, and MME. There were no differences in postoperative opioid prescriptions when assessing patients based on operative duration.

Better Functional Recovery After Single-Level Compared With Two-Level Posterolateral Lumbar Fusion.

BackgroundMultiple studies describe the outcomes of patients undergoing single-level and multilevel posterolateral lumbar fusion (PLF). However, a comparison of outcomes between single-level and two-level PLF is lacking. The aim of this prospective cohort study was to compare outcomes between single-level and two-level instrumented PLF.MethodsA total of 42 patients were enrolled at nine US centers between October 2015 and June 2017. Data included radiologic outcomes, visual analog scale (VAS) Back and Leg Pain, disability per the Oswestry Disability Index (ODI), and health-related quality of life (QoL) per 36-Item Short Form Survey version 2.0 (SF-36v2) at six weeks and three, six, 12, and 24 months.ResultsTwelve-month and 24-month follow-ups were completed by 38 (90.5%) and 32 (76.2%) subjects, respectively. The average age was 67 years, and 54.8% were female. Twenty-six received single-level PLF, and 16 received two-level PLF. In the single-level group, there was one reoperation, two postoperative infections, and one dural tear. In the two-level group, there was one postoperative infection. The surgeon computed tomography (CT)-based evaluation of fusion rate was 67.6% (25/37) at 12-month follow-up and 94.1% (32/34) at 24-month follow-up. The third-party evaluation of fusion rate was 52.8% (19/36) at six months, 81.1% (30/37) at 12 months, and 86.5% (32/37) at 24 months. There was a tendency toward a higher fusion rate in single-level compared with two-level PLF. The ODI, SF-36v2 Mental Component Score (MCS), and VAS Back Pain and Leg Pain outcomes improved by the first follow-up visit in both the single-level and two-level groups. Improvement in the ODI was 5.86 (95% confidence interval (CI): 0.03-11.69) points greater in the single-level group compared with the two-level group.ConclusionsCompared with the two-level PLF subjects, single-level PLF subjects had better functional outcomes and reported higher satisfaction with the outcome of surgery but showed similar fusion, pain, and generic health-related quality of life outcomes. Both single-level and two-level PLF subjects demonstrated high fusion rates in association with improvements in pain, functional, and quality of life outcomes, as well as high satisfaction levels.

Does fusion status following posterolateral lumbar fusion in the treatment for stable lumbar degenerative spondylolisthesis affect the long-term surgical outcomes? A propensity score-weighted analysis of consecutive patients

BackgroundThe surgical strategy of lumbar degenerative spondylolisthesis (LDS) is controversial, especially regarding whether or not fusion should be used. Although some reports have indicated that decompression combined with fusion may be better than decompression alone in the treatment of LDS, the effect of fusion status after uninstrumented posterolateral lumbar fusion (PLF) on the outcomes of patients with stable LDS remains unknown. This study aimed to evaluate the surgical outcomes of uninstrumented PLF for stable LDS and clarify whether radiographic fusion status could affect surgical outcomes. MethodsA total of 93 consecutive patients who had undergone single-level uninstrumented PLF for Meyerding grade I LDS without preoperative dynamic instability with a minimum follow-up period of 5 years were retrospectively studied. Patients were divided into two groups: nonunion (52 patients) and union (41 patients). The primary outcomes were the 5-year percent recovery of postoperative Japanese Orthopaedic Association (JOA) scores, Oswestry Disability Index (ODI), Visual analog scale (VAS) scores, and reoperation rate. The outcome scores were compared between the groups using the inverse probability weighting method using propensity scores. ResultsThe union and nonunion groups had comparable weighted means of the 5-year postoperative clinical score for the percent recovery of the JOA score (70.2% vs. 71.1%, P = 0.86), ODI (14.5 vs.14.6, P = 0.98), VAS of low back pain (20.3 vs. 18.7 mm, P = 0.72), and VAS of leg pain (24.0 vs. 19.4 mm, P = 0.43). The reoperation rate was 2.4% (one case of adjacent segment pathology) in the union group and 0% in the nonunion group (P = 0.44). ConclusionThe fusion status following uninstrumented PLF had no significant effect on the 5-year postoperative clinical outcomes and reoperation rate in patients with Meyerding grade I LDS without dynamic instability.

The utility of intraoperative neuromonitoring on simple posterior lumbar fusions—analysis of the National Inpatient Sample

Several studies have demonstrated the utility of intraoperative neuromonitoring (IOM) including somatosensory evoked potentials (SSEPs), motor-evoked potentials (MEPs), and electromyography (EMG), in decreasing the risk of neurologic injury in spinal deformity procedures. However, there is limited evidence supporting the routine use of IOM in elective posterolateral lumbar fusion (PLF). The National Inpatient Sample (NIS) was analyzed for the years 2012-2015 to identify patients undergoing elective PLF with (n=22,404) or without (n=111,168) IOM use. Statistical analyses were conducted to assess the impact of IOM on length of stay, total charges, and development of neurologic complications. These analyses controlled for age, gender, race, income percentile, primary expected payer, number of reported comorbidities, hospital teaching status, and hospital size. The overall use of IOM in elective PLFs was found to have increased from 14.6% in the year 2012 to 19.3% in 2015. The total charge in hospitalization cost for all patients who received IOM increased from $129,384.72 in 2012 to $146,427.79 in 2015. Overall, the total charge of hospitalization was 11% greater in the IOM group when compared to those patients that did not have IOM (P<0.001). IOM did not have a statistically significant impact on the likelihood of developing a neurological complication. While there may conceivably be benefits to the use of this technology in complex revision fusions or pathologies, we found no meaningful benefit of its application to single-level index PLF for degenerative spine disease.

Examination of the Role of Cells in Commercially Available Cellular Allografts in Spine Fusion: An in Vivo Animal Study.

Despite the extensive use of cellular bone matrices (CBMs) in spine surgery, there is little evidence to support the contribution of cells within CBMs to bone formation. The objective of this study was to determine the contribution of cells to spinal fusion by direct comparisons among viable CBMs, devitalized CBMs, and cell-free demineralized bone matrix (DBM). Three commercially available grafts were tested: a CBM containing particulate DBM (CBM-particulate), a CBM containing DBM fibers (CBM-fiber), and a cell-free product with DBM fibers only (DBM-fiber). CBMs were used in viable states (CBM-particulatev and CBM-fiberv) and devitalized (lyophilized) states (CBM-particulated and CBM-fiberd), resulting in 5 groups. Viable cell counts and bone morphogenetic protein-2 (BMP-2) content on enzyme-linked immunosorbent assay (ELISA) within each graft material were measured. A single-level posterolateral lumbar fusion was performed on 45 athymic rats with 3 lots of each product implanted into 9 animals per group. After 6 weeks, fusion was assessed using manual palpation, micro-computed tomography (μ-CT), and histological analysis. The 2 groups with viable cells were comparable with respect to cell counts, and pairwise comparisons showed no significant differences in BMP-2 content across the 5 groups. Manual palpation demonstrated fusion rates of 9 of 9 in the DBM-fiber specimens, 9 of 9 in the CBM-fiberd specimens, 8 of 9 in the CBM-fiberv specimens, and 0 of 9 in both CBM-particulate groups. The μ-CT maturity grade was significantly higher in the DBM-fiber group (2.78 ± 0.55) compared with the other groups (p < 0.0001), while none of the CBM-particulate samples demonstrated intertransverse fusion in qualitative assessments. The viable and devitalized samples in each CBM group were comparable with regard to fusion rates, bone volume fraction, μ-CT maturity grade, and histological features. The cellular component of 2 commercially available CBMs yielded no additional benefits in terms of spinal fusion. Meanwhile, the groups with a fiber-based DBM demonstrated significantly higher fusion outcomes compared with the CBM groups with particulate DBM, indicating that the DBM component is probably the key determinant of fusion. Data from the current study demonstrate that cells yielded no additional benefit in spinal fusion and emphasize the need for well-designed clinical studies on cellular graft materials.

P122. Use of a novel allograft in single- and two-level posterolateral lumbar spinal fusion: two-year clinical and radiographic results from a prospective multicenter study

BACKGROUND CONTEXT Instrumented posterolateral lumbar fusion (PLF) surgery is commonly used to alleviate pain and other symptoms associated with degenerative conditions of the lumbosacral spine. Although autologous iliac crest bone graft (ICBG) remains the gold standard graft material for PLF, surgeons have sought alternatives to avoid morbidities associated with ICBG harvest. OSTEOAMP® is a novel allograft bone graft substitute (BGS) that retains multiple endogenous growth factors. Evidence concerning effectiveness of PLF in multi-level fusion is scarce. PURPOSE The purpose of this study was to compare 2-year clinical and radiographic outcomes of OSTEOAMP and ICBG in single- and 2-level PLF. STUDY DESIGN/SETTING This was a prospective multicenter cohort study (level 2 evidence) involving nine centers in the United States. PATIENT SAMPLE A total of 42 patients with Oswestry Disability Index (ODI) score of at least 30 at baseline were prospectively enrolled and underwent a single- (N=26) or two-level (N=16) PLF utilizing the novel BGS. 38/42 (90.5%) and 32/42 (76.2%) subjects attended 12- and 24-month follow-ups, respectively. OUTCOME MEASURES ODI, SF-36v2 PCS, SF-36v2 MCS, back and leg pain. METHODS Data was obtained preoperatively and at 1.5, 3, 6, 12, and 24 months. Radiographic studies were assessed by an independent core lab for evidence of bridging bone and lack of segmental angular ( RESULTS The two-year fusion rate for the novel BGS was 32/37 (86.5%) compared to the literature average of 76% (range 40%-100%) for ICBG. The fusion rate was 90.9% (20/22) in single- and 80% (12/15) in 2-level PLF (p=0.377). While ODI improved in both groups, the improvement was larger in single- than in 2-level subjects (p=0.058). At 24 months, the improvement in ODI was 33.5 and 25.9 in single- and 2-level subjects, respectively. There was a tendency for greater improvements at 24 months in single-level compared to 2-level PLF in SF36 PCS (15.4 vs 12.5) and SF36MCS (7.9 vs 5.6), but these differences did not reach statistical significance. Improvements in pain at back (4.8 vs 4.6) and pain at leg (4.8 vs 4.3) were similar in single- and 2-level surgeries. One secondary surgery was performed at 3 months postoperatively for a symptomatic screw in single-level subject. No product-related treatment complications were reported. CONCLUSIONS Two-level PLF is associated with poorer ODI but similar pain outcomes compared to single-level PLF. OSTEOAMP is safe and effective for use in posterolateral spinal fusion as evidenced by fusion rates higher than for ICBG, good clinical outcomes, and freedom from serious product-related complications. FDA DEVICE/DRUG STATUS OSTEOAMP® is compliant to 21 CFR 1271 and is regulated as a 361 HCT/P.

Does the Number of Levels Fused Affect Spinopelvic Parameters and Clinical Outcomes Following Posterolateral Lumbar Fusion for Low-Grade Spondylolisthesis?

Study Design:Retrospective cohort.Objectives:To determine how the number of fused intervertebral levels affects radiographic parameters and clinical outcomes in patients undergoing open posterolateral lumbar fusion (PLF) for low-grade degenerative spondylolisthesis.Methods:This was a retrospective cohort study on patients who underwent open PLF for low-grade spondylolisthesis at a single institution from 2011 to 2018. Patients were divided into groups based on number of levels fused during their procedure (1, 2, or 3 or more). Preoperative and postoperative spinopelvic radiographic parameters, patient-reported outcomes (Visual Analog Scale [VAS]-back, VAS-leg, Oswestry Disability Index [ODI]), and postoperative complications were compared.Results:Of the 316 patients eligible (203 one-level, 95 two-level, 18 three or more levels), change in initial postoperative to final pelvic incidence-lumbar lordosis was greatest in 2-level fusions (P = .039), while 3 or more level fusions had worse final pelvic tilt measures (P = .021). In addition, multilevel fusions had worse final VAS-back scores (2-level: P = .015; 3 or more levels: P = .011), higher rates of dural tears (2-level: P = .001), reoperation (2-level: P = .039), and discharge to facility (3 or more levels: P = .047) when compared with 1-level fusions.Conclusions:Patients in multilevel fusions experienced less improvement in back pain, had more complications, and were more commonly discharged to a facility compared with single-level PLF patients. These findings are important for operative planning, for setting appropriate preoperative expectations, and for risk stratification in patients undergoing posterior lumbar fusion for low-grade spondylolisthesis.

Treatment of degenerative spondylolisthesis by instrumented posterolateral versus instrumented posterolateral with transforaminal lumbar interbody single-level fusion.

The purpose of this study was to compare outcomes of patients with degenerative spondylolisthesis treated by posterolateral lumbar fusion (PLF) versus PLF with transforaminal lumbar interbody fusion (PLF + TLIF). Studies of PLF versus PLF + TLIF have shown either equivalence or support for PLF + TLIF in lumbar spine surgery. Many are heterogeneous in the conditions treated, with few considering only spondylolisthesis of degenerative origin. Radiographic outcomes tend to favor PLF + TLIF, but this has not translated into better clinical outcomes. This was a retrospective cohort study. Forty-nine patients undergoing single-level PLF and seventy patients undergoing single-level PLF + TLIF with two-year follow-up were retrospectively reviewed. Demographics, Oswestry Disability Index (ODI), implant cost, surgical data, and complications were analyzed. There was no difference in ODI improvement at two-year follow-up between the cohorts (P=0.97). Dural tears were more common in the PLF cohort (P<0.01), but otherwise complication and reoperation rates were similar. Implant cost (P<0.01) and operative time (P=0.01) were higher in the PLF + TLIF cohort. The addition of a TLIF to a PLF did not result in a functional improvement in the treatment of degenerative spondylolisthesis as measured by the ODI.

110. Use of a novel allograft in single-level posterolateral lumbar spine fusion surgery: 1-year clinical and radiographic results from a prospective multicenter study with comparison to reported results for ICBG

BACKGROUND CONTEXT Instrumented posterolateral lumbar fusion (PLF) surgery is commonly used to alleviate pain and other symptoms associated with degenerative conditions of the lumbosacral spine. Although autologous iliac crest bone graft (ICBG) remains the “gold standard” grafting material for these procedures, surgeons have sought alternatives to avoid the potential morbidity associated with ICBG harvest. OSTEOAMP is a novel allograft bone graft substitute (BGS) that has been processed to retain multiple endogenous growth factors. A prospective multicenter study was designed to enable comparison of this novel product to available data for autologous bone graft controls from large randomized controlled trials (RCTs). PURPOSE Compare 1-year outcomes from an ongoing study investigating radiographic and clinical outcomes to reported results for ICBG controls from a large RCT. STUDY DESIGN/SETTING Prospective multicenter single-arm study conducted in the United States. PATIENT SAMPLE Consenting patients, 21 to 85 years of age, scheduled for PLF surgery with a diagnosis of degenerative disc disease (DDD), degenerative spondylolisthesis, and/or mild degenerative scoliosis. OUTCOME MEASURES Bilateral radiographic fusion (blinded, multireader with adjudication) was assessed. Additional outcome measures included Oswestry Disability Index (ODI), Short Form-36 (SF-36) physical component summary (PCS) and mental component summary (MCS) scores, and improvement in leg/back pain scores. Product-related serious adverse events (SAEs) and secondary surgeries were also assessed. METHODS Forty-two patients were prospectively enrolled after obtaining IRB approval at each of 9 centers and underwent a 1-level (26 patients) or 2-level (16 patients) PLF procedure utilizing the novel BGS (67% BGS: 33% local bone graft). Clinical outcomes were measured and radiographic studies were obtained preop and postop at 1.5, 3, 6, and 12 months. Radiographic analysis included CT assessment of fusion at 12 months. One-year outcomes were available for 23 of the 26 patients who underwent a 1-level procedure and were compared to 1-year outcomes reported for ICBG controls from a large previously published RCT by estimation of novel BGS:ICBG Risk Ratios (RR) with 95% confidence intervals (CI). RESULTS One-year fusion rates and results for each of the measures (novel BGS vs ICBG) are as follows: bilateral fusion = 73.9% (17/23) vs 82.5% (151/183) with RR 0.90 (0.69, 1.15 CI); ODI (>15 improvement) = 73.9% (17/23) vs 73.9% (150/203), RR 1.00 (0.77, 1.29 CI); leg pain = 95.7% (22/23) vs 87.6% (177/202), RR 1.09 (0.99, 1.21 CI); back pain = 91.3% (21/23) vs 93.1% (180/203), RR 0.98 (0.86, 1.12 CI); SF-36 MCS = 73.9% (17/23) vs 68.7% (138/201), RR 1.08 (0.83, 1.40); SF-36 PCS = 95.7% (22/23) vs 86.6% (174/201), RR 1.10 (1.00, 1.22 CI). No statistically significant difference was found in RR between groups for all comparisons. No product-related SAEs and only one secondary surgery were observed with the novel BGS. CONCLUSIONS One-year clinical and radiographic outcomes following single-level PLF procedures with OSTEOAMP compare favorably to results reported for an ICBG control group from a large RCT. FDA DEVICE/DRUG STATUS OSTEOAMP (Approved for this indication)

Repurposing Human Osteoarthritic Cartilage as a Bone Graft Substitute in an Athymic Rat Posterolateral Spinal Fusion Model.

Spinal fusion involves both endochondral and intramembranous bone formation. We previously demonstrated that endochondral cartilage grafts that were derived from human osteoarthritic (OA) articular cartilage can be used as a bone graft in mouse models. We hypothesized that OA cartilage could also be recycled and repurposed as a bone graft substitute in a posterolateral lumbar spinal fusion model in athymic rats. OA articular cartilage was obtained from the femoral resection of a healthy 60-year-old man undergoing elective total knee arthroplasty. The chondrocytes recovered from this tissue were dedifferentiated in monolayer tissue culture and then transitioned to culture conditions that promote chondrocyte hypertrophy. The resultant cell pellets were then used as bone graft substitute for single-level posterolateral spinal fusion in 5 athymic rats. Decortication alone was used as the control group. Spinal fusion was assessed with manual palpation, micro-computed tomography, and histologic analysis. In the experimental group, micro-computed tomography at 4 and 8 weeks demonstrated bilateral fusion in 4 of 5 animals and unilateral fusion in 1 animal. At 8 weeks, manual palpation and histologic analysis showed direct correlation with the radiographic findings. Animals undergoing decortication alone failed to generate any spinal fusion. The difference in the fusion rate between groups was statistically significant with respect to both unilateral fusion (P = .047) and bilateral fusion (P = .007). In the absence of additional surgically implanted bone graft, hypertrophic chondrocyte grafts are sufficient for generating single-level posterolateral lumbar fusion in athymic rats. This animal study demonstrates that cartilage harvested from OA knees can be used as a bone graft substitute. Commercially available cell-based bone grafts have previously only used mesenchymal stem cells or osteoblast precursor cells.

Comparison of three calcium phosphate bone graft substitutes from biomechanical, histological, and crystallographic perspectives using a rat posterolateral lumbar fusion model

This study evaluated the effectiveness of three calcium phosphate bone graft substitutes with different chemical compositions on spinal fusion using a rat posterolateral lumbar fusion model. Specifically, two recently developed non-dispersive tetracalcium phosphate/dicalcium phosphate anhydrous-based calcium phosphate cements (CPCs), namely a CPC consisting of equimolar amounts of the two compounds (nd-CPC) and a CPC consisting of a two-fold greater amount of dicalcium phosphate anhydrous (DCP-rich CPC), were compared with a commercial calcium phosphate bone graft (c-CPG) consisting of hydroxyapatite (60%) and β-tricalcium phosphate (40%). Single-level posterolateral lumbar fusion was performed at the L4–L5 vertebrae in fifteen adult rats (n=5 for each group). Spinal fusion was evaluated with radiographs, manual palpation, mechanical testing, micro-CT, and histology 8weeks post-surgery. In particular, the crystallographic phases in the three substitutes were identified before and 8weeks after their implantation. Manual palpation revealed stable constructs in nearly all of the spine specimens. The stiffness and bending load of fused spines in the two CPC groups were comparable to those in the c-CPG group. The radiographs specifically revealed implant resorption and bone remodeling in the DCP-rich CPC group. Analysis of 3D micro-CT images revealed that the bone volume ratio in the DCP-rich CPC group was significantly greater than those in the nd-CPC and c-CPG groups. Histology showed that the DCP-rich CPC group exhibited the highest degree of bone regeneration and osseointegration. Notably, DCP-rich CPC led to a pronounced phase transformation, generating the greatest amount of poorly crystalline apatite among the three groups, which together with adequate resorption may explain the aforementioned positive findings. We therefore conclude that of the bone graft substitutes considered, DCP-rich CPC has the greatest potential to be used in spinal fusion.

Bone Morphogenetic Protein-2 and Bone Marrow Aspirate With Allograft as Alternatives to Autograft in Instrumented Revision Posterolateral Lumbar Spinal Fusion

Retrospective cohort study. Compare the efficacy of rhBMP-2 and bone marrow aspirate with allograft (BMAA) as alternatives to autograft in instrumented revision posterolateral lumbar fusion (PLF). The use of autogenous bone graft is the current gold standard in revision PLF; however, this practice is associated with significant donor-site morbidity. Revision PLF pose the additional challenges of a less than ideal fusion environment and a limited quantity of autogenous bone graft. rhBMP-2 and BMAA have been shown to be acceptable bone graft substitutes in several primary orthopedic procedures. The role of these bone graft substitutes in instrumented revision PLF has yet to be determined. Sixty-two patients (125 levels) who underwent instrumented revision PLF with a minimum 2-year follow-up were included. Group 1 contained 24 patients (13 single- [group 1A] and 11 multilevel [group 1B]) who underwent instrumented revision PLF using rhBMP-2 on an absorbable collagen sponge. Group 2 included 18 patients (7 single- [group 2A] and 11 multilevel [group 2B]) with procedures using BMAA. Group 3 consisted of 20 patients (10 single- [group 3A] and 10 multilevel [group 3B]) with procedures using autograft. Demographic, surgical, and clinical data were collected from medical records. Time to solid fusion mass formation, fusion rate, complications, and clinical outcomes were evaluated. The progression of the fusion mass was evaluated by reviewing radiographs. A diagnosis of nonunion was based on exploration during an additional revision surgery or evidence of nonunion on dynamic radiographs or computerized tomography. Clinical outcomes were assessed using a visual analog scale (VAS) before surgery and at 6-week, 6-, 12-, and 24-month follow-ups. Overall fusion rate was 93.5% (58/62). All single-level revision PLF achieved solid fusion. Groups 1B and 3B achieved 100% fusion, (11/11) and (10/10), respectively;whereas group 2B had a fusion rate of 63.6% (7/11). Group 1 also developed a solid fusion mass earlier than the other groups. There was a significant decrease between preoperative and 2-year postoperative VAS scores in all groups, but no significant difference among groups. Three patients in group 2 required an additional revision surgery. rhBMP-2 may be an appropriate alternative to autogenous bone graft in both single- and multilevel revision PLF, whereas BMAA may be appropriate as a substitute in single-level revision PLF. The use of BMAA in single-level revisions may be a more cost-effective option than rhBMP-2.

Wednesday, October 30, 2001 4:42–5:25 pm Concurrent Session 2B: Lumbar Fusion Complications: 4:42 Residual lower extremity pain after decompression and posterolateral fusion for lumbar spondylolisthesis is often related to bone graft harvest

Purpose of study: Posterior decompression and single-level posterolateral fusion is a well-accepted means of treating symptomatic grade 1–2 lumbar spondylolisthesis. Patients often present with lower extremity (LE) radiculopathy in addition to low back pain. This study was performed to determine whether residual LE pain is secondary to continued radiculopathy or to bone graft site harvest.Methods used: A total of 1,225 patients who had undergone lumbar surgery between 1997 and 2000 were retrospectively studied; 137 patients had undergone single-level posterolateral lumbar fusion for grade 1–2 spondylolisthesis that failed conservative treatment and were available for minimum 2-year follow-up. All patients had iliac crest bone graft site harvest contralateral to the side with the more severe radiculopathy preoperatively. Patients with continued LE discomfort were examined postoperatively to determine whether radicular signs were present and whether tenderness was present directly over the bone graft harvest site.of findings: Twenty-three patients (16.8%) continued to have some LE pain postoperatively. In 19 patients (82.6%) this pain was on the bone graft side. Postoperative physical examination demonstrated that in all 19 of these patients, radicular signs were absent, but tenderness localized to the buttock/posterior iliac crest area was present. Only 1 of the 23 patients had true residual radiculopathy. Fisher's exact test showed that the proportion of patients with residual LE pain and bone graft site findings was significantly greater than the proportion of patients with residual LE pain and radiculopathy (p<.01).Relationship between findings and existing knowledge: Excellent fusion rates and clinical outcomes have been reported for single-level posterior decompression and fusion for grade 1–2 spondylolisthesis. Although resolution of radicular symptoms is more reliable than relief of back pain, some patients still do complain of some LE pain postoperatively. Little is known about whether this is the result of true radiculopathy or the result of bone graft site pain.Overall significance of findings: Radiculopathy after single-level decompression and posterolateral fusion for lumbar grade 1–2 spondylolisthesis is rare. Patients with residual LE pain after this surgery most often have symptoms secondary to iliac crest bone graft harvest. The clinician must be aware of this and perform a thorough examination to prevent unnecessary reoperation for residual LE symptoms.Disclosures: No disclosures.Conflict of interest: No conflicts.

Uninstrumented Posterolateral Lumbar Fusion for Single Level Isolated Disc Resorption and/or Degenerative Disc Disease

The limited soft-tissue envelope technique for an uninstrumented single-level posterolateral lumbar fusion has been studied in a group of 23 patients. It resulted in a solid fusion in 21 of 23 (91%) patients. Overall, 18 of 23 (78%) patients had a satisfactory outcome to this fusion technique, which can be performed in any community-based hospital.