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.     

Radiographic evaluation of posterolateral lumbar fusion for degenerative spondylolisthesis: long-term follow-up of more than 10 years vs. midterm follow-up of 2–5 years

Although posterolateral fusion of the lumbar spine without instrumentation has been widely performed for spinal instability caused by degenerative spondylolisthesis in the lumbar spine, few long-term follow-up studies have been reported. We studied ten patients who underwent posterolateral fusion for degenerative spondylolisthesis in the lumbar spine without instrumentation in our hospital, five of whom were followed up for more than 10 years and the other five for 2–5 years. We used radiography to examine their fusion status, instability and degenerative changes at the fusion level, change in the slip, change in lumbar lordosis, and instability and degenerative changes one level above and one level below the fusion. In most of the ten patients, radiographic evaluation demonstrated solid fusion, minimal degenerative changes, and preservation of lumbar lordosis and spinal mobility. Posterolateral lumbar fusion for degenerative spondylolisthesis in the lumbar spine seems promising for obtaining not only good radiographic features but also good clinical results lasting over more than 10 years. Electronic Publication     

Surgical outcomes of degenerative lumbar spondylolisthesis with anterior vacuum disc: Can the intervertebral cage overcome intradiscal vacuum phenomenon and enhance posterolateral fusion?

Background The vacuum phenomenon within an intervertebral disc is not an uncommon radiographic finding in the elderly. However, no reports in the English literature have focused on the effect of an anterior vacuum disc in relation to surgical outcome of same-segment spondylolisthesis. We hypothesized that instrumented posterolateral fusion is not adequate in this situation and that additional interbody fusion with cages would provide better radiographic and clinical outcomes.Methods The medical records of 72 patients who underwent instrumented fusion for one-segment degenerative lumbar spondylolisthesis with a vacuum disc were reviewed. Thirty-three patients were placed in the noncage group and 39 in the cage group based on whether or not augmentation with an intervertebral cage was carried out. Radiographic parameters (disc height, translation, intradiscal angle, segmental angle, and fusion) on preoperative, postoperative, and final radiographs were compared between groups. The Oswestry Disability Index (ODI) and Brosky criteria were used to evaluate clinical outcomes.Results Blood loss and operation time were greater in the cage group but without a significant difference (p = 0.271, p = 0.108, respectively). Preoperative radiographic data were similar between groups, but the cage group had more intradiscal lordosis, less translation, a higher disc height after surgery, and maintained these advantages at the final follow-up. In addition, the posterolateral fusion rate was significantly higher in the cage group (92.3 % vs. 56.1 %, p < 0.001), and they obtained more ODI improvement (30.62 vs. 26.39, p = 0.369) and a higher final satisfaction rate (79.5 % vs. 57.6 %, p = 0.044). There was no decrease in the incidence of developed adjacent segmental disease in the noncage group.Conclusions The vacuum sign at the spondylolisthesis segment should be regarded as another sign of instability. We suggest that instrumented posterolateral fusion simultaneous with intervertebral fusion with a cage can overcome this situation.     

Posterior lumbar interbody fusion for aged patients with degenerative spondylolisthesis: is intentional surgical reduction essential?

Background context

Surgical reduction and posterior lumbar interbody fusion (PLIF) is commonly used to recover segmental imbalance in degenerative spondylolisthesis. However, whether intentional reduction of the slipped vertebra during PLIF is essential in aged patients with degenerative spondylolisthesis remains controversial.

Purpose

We compared the outcomes of surgical reduction and fusion in situ among aged patients who underwent PLIF for degenerative spondylolisthesis.

Study design

A prospective randomized clinical trial on the surgical treatment of degenerative spondylolisthesis patients aged older than 70 years.

Patient sample

Between January 2006 and December 2009, 73 patients aged 70 years or older with single-level degenerative spondylolisthesis requiring surgical treatment were included in this study.

Outcome measures

Clinical outcomes were assessed using the visual analog scale, Oswestry Disability Index, and Japanese Orthopedic Association scores. Radiographic outcomes included percentage of vertebral slippage, focal lordosis, and disc height.

Methods

The 73 patients were randomly assigned to two groups treated using surgical reduction (Group A, n=36) and fusion in situ (Group B, n=37). Both groups were followed up for an average of 33.2 months (range, 24–54 months). The clinical and radiographic outcomes were compared between the two groups.

Results

Surgical complications were similar in the two groups. The average operative time and blood loss during surgery did not insignificantly differ (p>.05) between the two groups. Spondylolisthesis, disc height, and focal lordosis were significantly improved postoperatively in both groups. There was no obvious difference in clinical outcomes, as assessed using the visual analog scale, Oswestry Disability Index, and Japanese Orthopedic Association scores, although the radiographic outcomes were considerably better in Group A than in Group B.

Conclusions

Posterior lumbar interbody fusion with pedicle screws fixation, with or without intraoperative reduction, provides good outcomes in the surgical treatment of aged patients with degenerative spondylolisthesis. Better radiological outcomes by intentional reduction do not necessarily indicate better clinical outcomes.     

Can cantilever transforaminal lumbar interbody fusion (C-TLIF) maintain segmental lordosis for degenerative spondylolisthesis on a long-term basis?

Purpose

To determine if cantilever transforaminal lumbar interbody fusion (C-TLIF) using the crescent-shaped titanium interbody spacer (IBS) favors acquisition of segmental and lumbar lordosis even for degenerative spondylolisthesis (DS) on a long-term basis.

Methods

We analyzed 23 consecutive patients who underwent C-TLIF with pedicle screw instrumentations fixed with compression for a single-level DS. Measurements on the lateral radiographs taken preoperatively, 2 weeks postoperatively and at final follow-up included disc angle (DA), segmental angle (SA), lumbar lordosis (LL), disc height (%DH) and slip rate (%slip).

Results

There was a good functional recovery with 100 % fusion rate at the mean follow-up of 62 months. Segmental lordosis (DA and SA) and  %DH initially increased, but subsequently decreased with the subsidence of the interbody spacer, resulting in a significant increase (p = 0.046) only in SA from 13.2° ± 5.5° preoperatively to 14.7° ± 6.4° at the final follow-up. Changes of LL and  %slip were more consistent without correction loss finally showing an increase of LL by 3.6° (p = 0.005) and a slip reduction by 6.7 % (p < 0.001).

Conclusions

Despite the inherent limitation of placing the IBS against the anterior endplate of the upper vertebra in the presence of DS, the C-TLIF helped significantly restore segmental as well as lumbar lordosis on a long-term basis, which would be of benefit in preventing hypolordosis-induced back pain and the adjacent level disc disease.     

Can facet joint fluid on MRI and dynamic instability be a predictor of improvement in back pain following lumbar fusion for degenerative spondylolisthesis?

Purpose

To investigate the relationship between lumbar facet fluid and dynamic instability in degenerative spondylolisthesis (DS), as well as the relationship between facet fluid and patient-reported outcomes following a posterior lumbar fusion.

Methods

We analyzed consecutive patients with degenerative spondylolisthesis undergoing single level posterior lumbar fusion from December 2010 to January 2013 at a single academic institution. We investigated the relationship between fluid in the facet joint as measured on axial MRI and the presence of dynamic instability. We investigated the impact of facet fluid, Modic changes, and dynamic instability on patient-reported outcomes.

Results

There was a significant association between the amount of facet joint fluid and the presence of dynamic instability (p = 0.03); as facet fluid increases, the probability of dynamic instability also increases. For every 1 mm of facet fluid, there was a 41.6 % increase (95 % CI 1.8–97) in the odds of dynamic instability. A facet fluid amount less than 0.5 mm gave a 90 % probability that there was no dynamic instability. The presence of facet fluid and dynamic instability were associated with achieving minimal clinical important difference (MCID) in low back pain following lumbar fusion (p = 0.04 and 0.05, respectively).

Conclusion

Facet joint fluid is associated with the presence of dynamic instability in DS. The presence of facet fluid and dynamic instability may predict increased likelihood of achieving MCID for improvement in back pain following posterior lumbar fusion.

     

Circumferential fusion: a comparative analysis between anterior lumbar interbody fusion with posterior pedicle screw fixation and transforaminal lumbar interbody fusion for L5–S1 isthmic spondylolisthesis

Background Context

Transforaminal lumbar interbody fusion (TLIF) or anterior lumbar interbody fusion with percutaneous pedicle screws (ALIFPS) offer significantly higher radiographic fusion rates than other fusion techniques for L5–S1 isthmic spondylolisthesis (IS). As it stands, there is a relative paucity of comparative data of the two techniques.

Radiological factors affecting functional outcome after the implantation of BDYN™ dynamic stabilization system for low-grade lumbar degenerative spondylolisthesis

BackgroundThe objectives of this study are to identify radiological factors associated with good functional outcomes after the implantation of BDYN™ dynamic stabilization system in the setting of painful low-grade degenerative lumbar spondylolisthesis (DLS).Material and methodsIn this monocentric, retrospective study, we followed 50 patients, a 5-years period, with chronic lower back pain, radiculopathy and/or neurogenic claudication evolving for at least one year that failed conservative treatment. All patients presented low-grade DLS and underwent lumbar dynamic stabilization. Radiological and clinical outcomes were assessed preoperatively and 24 months after surgery. Functional evaluation was based on the Oswestry Disability Index (ODI), the Numerical Rating Scale (NRS), and the Walking Distance (WD). Radiological analysis was based on lumbar X-rays and MRI parameters. Patients were divided into two groups according to the reduction in the postoperative ODI score (more or less than 15 points), and statistical analysis was performed between both groups to find predictive radiological factors for a satisfying functional outcome.ResultsClinically, 80% (40 patients) had a satisfying functional result, and 20% (10 patients) were considered having a poor outcome according to the ODI score. Radiologically, the loss in segmental lordosis was statistically associated with bad functional outcomes (18° for ODI decrease > 15 versus 11° for ODI decrease < 15). There is also a tendency showing that a higher Pfirmann disc signal grade (grade IV) and a severe canal stenosis according to Schizas classification (grade C & D) are predictive of a poor clinical result, but that must be confirmed in future studies.ConclusionsBDYN™ appears safe and well-tolerated. This new device should be effective for the treatment of patients with low-grade DLS. It provides significant improvement in terms of daily life activity and pain. Moreover, we have been able to deduce that a kyphotic disc is associated with a bad functional outcome after BDYN™ device implantation. It may represent a contraindication for the implantation of such DS device. Moreover, it seems that it is better to implant BDYN™ in DLS with mild or moderate disc degeneration and canal stenosis.     

Potential pathological mechanisms of L3 degenerative spondylolisthesis in lumbar spinal stenosis patients: A case–control study

BackgroundDegenerative spondylolisthesis (DS) occurs mostly at L4. However, there are a small number of patients in whom it occurs only at L3. Accordingly, past reports elucidating the factors of DS have been primarily concerned with L4 DS, and few reports are available on DS at L3. The objective of this study was to compare the differences between lumbar spinal stenosis patients with or without L3 DS and to identify the possible pathological mechanisms of their L3 DS.MethodsAmong the 369 patients with lumbar spinal stenosis who underwent lumbar surgery, we assessed 25 patients who had DS only at L3 and compared them against 50 other age- and gender-matched lumbar spinal stenosis patients without any DS. The following radiographic parameters: pelvic incidence, sacral slope, pelvic tilt, L3 slope, L4 slope, L5 slope, and lumbar lordosis were measured on radiographs. The orientation of facet joints and disc heights were measured via computed tomography.ResultsImaging findings showed that the L3, L4, and L5 slopes in the L3 DS group were significantly greater than in the non-DS group, and only L3/4 facet joints in the L3 DS group were significantly more sagittally oriented than in the control group. The number of patients with low disc heights at L4/5 in the L3 DS group was significantly greater than in the control group.ConclusionsThe results suggested that the greater lumbar slope, including L3 together with more sagittally oriented facet joints only at L3/4 and not at L4/5, may lead to DS only at L3.     

No correlation between patient outcome and abnormal lumbar MRI findings 21 years after posterior or posterolateral fusion for isthmic spondylolisthesis in children and adolescents

Between 1977 and 1987, posterior (n=29) or posterolateral (n=73) fusion was performed for mild to moderate (slip <50%) isthmic spondylolisthesis on 102 patients (46 females, 56 males). The patients average age at the time of operation was 15.9 (range, 8.1–19.8) years. Clinical (physical examination and Oswestry disability index (ODI)) and radiological (MRI and plain radiographs) examinations were performed on these patients after an average follow-up time of 21.0 (range, 26.2–15.1) years. In the radiographs, the mean slip preoperatively was 27% (range, 5–50%) and at the last follow-up visit 26% (range, 5–78%). Inside the fusion, there were a total of 148 intervertebral discs, 121 (82%) of them had decreased signal intensity in T2-weighted MR images and 113 (76%) were narrowed. Above the fusion level, 27 (27%) discs were speckled and 27 (27%) were black; 21 (21%) intervertebral disc spaces were narrowed. Two levels above the fusion level the numbers were 8 (8%), 16 (16%) and 16 (16%), respectively. Six (6%) patients had a prolapse. Degenerative facet joint hypertrophy above fusion was seen at 80 (79%) of the levels studied. When compared to healthy subjects higher frequency of disc and facet joint degeneration was found. In MR images, none of the patients had lumbar spinal stenosis inside or above the fusion. Narrowing of one or both of the neural foramina at the level of the L5–S1 interververtebral disc was noted in 32 (31%) patients. Seventeen (17%) of the patients had, usually mild, muscular atrophy of the psoas and 33 (32%) of the paraspinal muscles. There was no difference in frequency of abnormal MRI findings between patients (n=93) with ODI 20 or less compared with patients (n=9) with ODI more than 20. In situ fusion due to isthmic spondylolsthesis at adolescence is associated with moderate degenerative changes in the lumbar spine during a 20-year follow-up. Changes were most commonly found at the level of the spondylolisthesis and above fusion level. Neural foramina stenosis seems to be associated with spondylolisthesis and its severity to severity of the slip. Muscle atrophy tended to be mild. However, there was no correlation between patient outcome (ODI) and abnormal lumbar MRI findings.     

Clinical and radiological outcome of anterior–posterior fusion versus transforaminal lumbar interbody fusion for symptomatic disc degeneration: a retrospective comparative study of 133 patients

Abundant data are available for direct anterior/posterior spine fusion (APF) and some for transforaminal lumbar interbody fusion (TLIF), but only few studies from one institution compares the two techniques. One-hundred and thirty-three patients were retrospectively analyzed, 68 having APF and 65 having TLIF. All patients had symptomatic disc degeneration of the lumbar spine. Only those with one or two-level surgeries were included. Clinical chart and radiologic reviews were done, fusion solidity assessed, and functional outcomes determined by pre- and postoperative SF-36 and postoperative Oswestry Disability Index (ODI), and a satisfaction questionnaire. The minimum follow-up was 24 months. The mean operating room time and hospital length of stay were less in the TLIF group. The blood loss was slightly less in the TLIF group (409 vs. 480 cc.). Intra-operative complications were higher in the APF group, mostly due to vein lacerations in the anterior retroperitoneal approach. Postoperative complications were higher in the TLIF group due to graft material extruding against the nerve root or wound drainage. The pseudarthrosis rate was statistically equal (APF 17.6% and TLIF 23.1%) and was higher than most published reports. Significant improvements were noted in both groups for the SF-36 questionnaires. The mean ODI scores at follow-up were 33.5 for the APF and 39.5 for the TLIF group. The patient satisfaction rate was equal for the two groups. This work is dedicated to the memory of Grace and Julia Hanson.     

Factors affecting disability and physical function in degenerative lumbar spondylolisthesis of L4–5: evaluation with axially loaded MRI

Few studies have investigated the factors related to the disability and physical function in degenerative lumbar spondylolisthesis using axially loaded magnetic resonance imaging (MRI). Therefore, we aimed to investigate the effect of axial loading on the morphology of the spine and the spinal canal in patients with degenerative spondylolisthesis of L4–5 and to correlate morphologic changes to their disability and physical functions. From March 2003 to January 2004, 32 consecutive cases (26 females, 6 males) with degenerative L4–5 spondylolisthesis, grade 1–2, intermittent claudication, and low back pain without sciatica were included in this study. All patients underwent unloaded and axially loaded MRI of the lumbo-sacral spine in supine position to elucidate the morphological findings and to measure the parameters of MRI, including disc height (DH), sagittal translation (ST), segmental angulation (SA), dural sac cross-sectional area (DCSA) at L4–5, and lumbar lordotic angles (LLA) at L1–5 between the unloaded and axially loaded condition. Each patient’s disability was evaluated by the Oswestry Disability Index (ODI) questionnaire, and physical functioning (PF) was evaluated by the Physical Function scale proposed by Stucki et al. (Spine 21:796–803, 1996). Three patients were excluded due to the presence of neurologic symptoms found with the axially loaded MRI. Finally, a total of 29 (5 males, 24 females) consecutive patients were included in this study. Comparisons and correlations were done to determine which parameters were critical to the patient’s disability and PF. The morphologies of the lumbar spine changed after axially loaded MRI. In six of our patients, we observed adjacent segment degeneration (4 L3–L4 and 2 L5–S1) coexisting with degenerative spondylolisthesis of L4–L5 under axially loaded MRI. The mean values of the SA under pre-load and post-load were 7.14° and 5.90° at L4–L5 (listhetic level), respectively. The mean values of the LLA under pre-load and post-load were 37.03° and 39.28°, respectively. There were significant correlations only between the ODI, PF, and the difference of SA, and between PF and the post-loaded LLA. The changes in SA (L4–L5) during axial loading were well correlated to the ODI and PF scores. In addition, the LLA (L1–L5) under axial loading was well correlated to the PF of patients with degenerative L4–L5 spondylolisthesis. We suggest that the angular instability of the intervertebral disc may play a more important role than neurological compression in the pathogenesis of disability in degenerative lumbar spondylolisthesis.     

Is academic department teaching status associated with adverse outcomes after lumbar laminectomy and discectomy for degenerative spine diseases?

BACKGROUND CONTEXTLumbar laminectomy and discectomy surgeries are among the most common procedures performed in the United States, and often take place at academic teaching hospitals, involving the care of resident physicians. While academic institutions are critical for the maturation of the next generation of attending surgeons, concerns have been raised regarding the quality of resident-involved care. There is conflicting evidence regarding the effects of resident participation in teaching hospitals on spine surgery patient outcomes. As the volume of lumbar laminectomy and discectomy increases, it is imperative to determine how academic status impacts clinical and economic outcomes.PURPOSEThe purpose of this study is to determine if lumbar laminectomy and discectomy surgeries for degenerative spine diseases performed at academic teaching centers is associated with more adverse clinical outcomes and increased cost compared to those performed at nonacademic centers.STUDY DESIGN/SETTINGThis study is a multi-center retrospective cohort study using a New York Statewide database.PATIENT SAMPLEWe identified 36,866 patients who met the criteria through the New York Statewide Planning and Research Cooperative System who underwent an elective lumbar laminectomy and/or discectomy in New York State between January 1, 2009 and September 30, 2014.OUTCOME MEASURESThe primary functional outcomes of interest included: length of stay, cost of the index admission; 30-day and 90-day readmission; 30-day, 90-day, and 1-year return to the operating room.METHODSInternational Classification of Diseases, Ninth revision codes were utilized to define patients undergoing a laminectomy and/or discectomy who also had a diagnosis code for a lumbar spine degenerative condition. We excluded patients with a procedural code for lumbar fusion, as well as those with a diagnosis of scoliosis, neoplasm, inflammatory disorder, infection or trauma. Hospital academic status was determined by the Accreditation Council for Graduate Medical Education. Unique encrypted patient identifiers allowed for longitudinal follow-up for readmission and re-operation analyses. We extracted charges billed for each admission and calculated costs through cost-to-charge ratios. Logistic regression models compared teaching and nonteaching hospitals after adjusting for patient demographics and comorbidities.RESULTSCompared to patients at nonteaching hospitals, patients at teaching hospitals were more likely to be younger, male, non-Caucasian, be privately insured and have fewer comorbidities (p<.001). Patients undergoing surgery at teaching hospitals had 10% shorter lengths of stay (2.7 vs. 3.0 days, p<.001), but 21.5% higher costs of admission ($13,693 vs. $11,601 p<.001). Academic institutions had a decreased risk of return to the operating room for revision procedures or irrigation and debridement at 30 days (OR:0.70, 95% confidence interval [CI]: 0.60–0.82, p<.001), 90 days (OR:0.75, 95%CI: 0.66–0.86, p<.001), and 1 year (OR:0.84, 95%CI: 0.77–0.91, p<.001) post index procedure. There was no difference in 30- and 90-day all-cause readmission, or discharge disposition between the two groups.CONCLUSIONSElective lumbar laminectomy and discectomy for degenerative lumbar conditions at teaching hospitals is associated with higher costs, but decreased length of stay and no difference in readmission rates at 30- and 90-days postoperatively compared to nonteaching hospitals. Teaching hospitals had a decreased risk of return to the operating room at 30 days, 90 days and 1 year postoperatively. Our findings might serve as an impetus for other states or regions to compare outcomes at teaching and nonteaching sites.     

Does loss of spondylolisthesis reduction impact clinical and radiographic outcomes after minimally invasive transforaminal lumbar interbody fusion?

BACKGROUND CONTEXTMinimally invasive transforaminal lumbar interbody fusion (MI-TLIF) is a common operative approach to address degenerative lumbar stenosis and spondylolisthesis which has failed nonoperative care. Compared to open TLIF, MI-TLIF relies to a greater extent on indirect decompression resulting in a heightened awareness of spondylolisthesis reduction among MI surgeons. To what extent intraoperative reduction is achieved as well as the rate and clinical impact of loss or reduction and slip recurrence remain unknown.PURPOSETo determine the rate and clinical impact of slip recurrence after MI-TLIF with expandable cage technologySTUDY DESIGN/SETTINGRetrospective Cohort StudyPATIENT SAMPLEPatients undergoing MI-TLIF for degenerative spondylolisthesis using an articulating, expandable cageOUTCOME MEASURESPatient-reported outcome measures (PROMs), including the Oswestry Disability Index (ODI), visual analog scale (VAS) for back/leg pain, Short Form-12 (SF-12), and PROMIS Physical Function (PF)METHODSPatients undergoing MI-TLIF for degenerative spondylolisthesis using articulating, expandable cages from 2017 to 2019 were retrospectively studied. Lateral radiographs were reviewed and evaluated for the presence or absence of spondylolisthesis preoperatively, intraoperatively, and at follow-up times including 2 weeks, 6 weeks, 12 weeks, 6 months, and 1 year postoperatively. Spondylolisthesis was measured from the posterior inferior corner of the cephalad vertebra to the posterior superior corner of the caudal vertebra, with any measurement >1 mm classified as spondylolisthesis, and Meyerding grade was noted. Intraoperative reduction was measured, and loss of reduction was defined as >1 mm increase in spondylolisthesis comparing follow-up imaging to intraoperative films. PROMs were recorded at the preoperative and follow-up time points. Fusion was assessed at 1 year postoperatively via CT.RESULTSA total of 63 patients and 70 levels were included, with mean age 59.8 years (SD,13.8). 19 levels (27.1%) had complete reduction intraoperatively, 40 (57.1%) had partial reduction, and 11 (15.7%) had no reduction. Of the 30 levels with loss of reduction (50.8%), 20 (66.7%) occurred by 2 weeks postoperatively and 28 (93.3%) occurred by 12 weeks postoperatively. At 6 months, there were significant differences between those who had loss of reduction and those who did not in VAS back pain (3.0 vs. 0.9, p = .017) and SF-12 PCS (41.5 vs. 50.0, p = .035), but no differences were found between the groups for any instruments at any other time points. The overall fusion rate was 82.1% (32/39) at 1 year postoperatively. There was no significant difference in fusion rate between the loss of reduction (16/20) and no loss of reduction (20/23) groups. Patients with loss of reduction had no difference in reoperation rate (1/28) compared to those without loss of reduction (2/24).CONCLUSIONSWhile a majority of patients demonstrated reduction intraoperatively, 51% had loss of reduction, most commonly in the acute postoperative period. There were few differences in PROMs between patients who had loss of reduction and those who did not, suggesting that radiographic loss of reduction after MI-TLIF in the setting of degenerative spondylolisthesis may not be clinically meaningful.