Impact of Elderly Age on Complications and Clinical Outcomes Following Anterior Lumbar Interbody Fusion Surgery

Accepted Manuscript Impact of Elderly Age on Complications and Clinical Outcomes following Anterior Lumbar Interbody Fusion Surgery Kevin Phan, BS MPhil, Vignesh Ramachandran, BS, Tommy Tran, BS, Steven Phan, Prashanth J. Rao, MBBS PhD, Ralph J. Mobbs, MD PII:

S1878-8750(17)30755-6

DOI:

10.1016/j.wneu.2017.05.056

Reference:

WNEU 5750

To appear in:

World Neurosurgery

Received Date: 25 March 2017 Revised Date:

9 May 2017

Accepted Date: 11 May 2017

Please cite this article as: Phan K, Ramachandran V, Tran T, Phan S, Rao PJ, Mobbs RJ, Impact of Elderly Age on Complications and Clinical Outcomes following Anterior Lumbar Interbody Fusion Surgery, World Neurosurgery (2017), doi: 10.1016/j.wneu.2017.05.056. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Impact of Elderly Age on Complications and Clinical Outcomes following Anterior Lumbar Interbody Fusion Surgery

Kevin Phan, BS MPhil1, Vignesh Ramachandran, BS3, Tommy Tran, BS3, Steven Phan1, 2*

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Prashanth J Rao MBBS PhD1,2, Ralph J Mobbs, MD1,

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1. NeuroSpine Surgery Research Group (NSURG), Prince of Wales Private Hospital, Sydney, Australia 2. Department of Neurosurgery, Prince of Wales Hospital, Randwick, Sydney, Australia 3. Baylor College of Medicine, Houston, Texas

Running head: Elderly age and ALIF outcomes

Correspondence: Dr Ralph J Mobbs, [email protected] . NeuroSpine Clinic, Prince of

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Wales Hospital, Barker St, Randwick NSW 2031; Phone: (02) 9650 4766

Conflicts of interest: none declared

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Funding: none declared

Acknowledgements: none declared

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Key words: anterior lumbar interbody fusion; fusion; subsidence; pseudoarthrosis; lumbar

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Abstract Background: Anterior Lumbar Interbody Fusion (ALIF) is a surgical technique used to treat patients with a variety of lumbar pathologies. Identification of risk factors leading to complication

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following ALIF surgery may allow surgeons to better judge candidacy and optimize care for high-risk patients.

Methods: A retrospective analysis was conducted on a prospectively collected database of 137

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patients who all underwent ALIF surgery by a single primary spine surgeon. Patients were

separated into age-based cohorts (≤49, 50-63, and ≥64 years of age). Chi-squared, Fisher’s

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exact test, and multivariate logistic regression models were used to identify independent risk factors.

Results: A total of 137 patients met the inclusion criteria. Patients were divided into age-based tertiles as following: Group 1 (<49 years old, n=45, 32.8%), Group 2 (50-63 years old, n=46,

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33.6%), and Group 3 (64 years old, n=46, 33.6%). Univariate analysis revealed increasing age (relative to Group 1) to be an independent risk factor for postoperative hematoma, and delayed subsidence at 6 weeks and 12 weeks post-operatively compared to immediately post-operation

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(all p<0.05). No significant differences were found among the groups in terms of clinical outcome. Multivariate analysis also demonstrated increased age to be independently associated

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with greater prevalence of delayed subsidence (OR 9.174, p=0.029). Conclusions: Increased age was not associated with adverse perioperative outcomes and complications of ALIF. However, there was an increased incidence of delayed subsidence in patients ≥64 years old.

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Introduction Many techniques are utilized for interbody fusion of the lumbar spine to treat degenerative pathologies, trauma, infections, and neoplasms.1 Anterior Lumbar Interbody Fusion (ALIF) has

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gained popularity in recent years, and can be performed in patients with lumbar pathologies including spondylolisthesis and degenerative disc disease, with effective and safe outcomes.2 The anterior approach allows for more direct access to the intervertebral discs, permits the

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surgeon to add further lordosis to the spine, and decreases the need to manipulate nerves.3 However, the ALIF approach requires mobilization of anteriorly-located major abdominal and

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pelvic vessels in order to gain access to the disc spaces, which increases risk for vascular injury.4 Furthermore, retrograde ejaculation, postoperative ileus, and abdominal wall complications have also been documented in association with ALIF.5, 6, 7

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There is currently inadequate comparative evidence to suggest one surgical approach is superior to other techniques in terms of fusion rates and clinical outcomes.8 Thus, it is important to elucidate risk factors for complications and poor outcomes after ALIF surgery. Identification of

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risk factors for ALIF may allow surgeons to appropriately judge candidacy for the procedure and to better optimize perioperative care for high-risk patients. Prior studies have showed increased

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body mass index (BMI), alcohol use, frailty, and chronic obstructive pulmonary disease (COPD) to correlate with poor outcomes and increased complications following ALIF surgery. 4, 9, 10, 11

Age is another characteristic that has been studied in relation to spine surgery outcomes. Prior studies have shown that increased age is an independent risk factor of complications (increased length of stay, urinary tract infection (UTI), transfusion, readmission, renal) within 30 days of adult spinal deformity surgery.12 Similarly, Murphy et al. demonstrated that elderly age after

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lumbar decompression without fusion is associated with more complex operations, leading to increased length of stay and minor complications.13 In clinical studies, the median age of patients undergoing ALIF ranges anywhere from 38.2 years to 68.4 years.14 Furthermore, the

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individual age of patients in single studies range from as young as 25-years old to as old as 83years old.15 Despite the wide age range of ALIF surgical patients, studies investigating age as it relates to outcomes of the procedure are lacking. In order to address this gap in the literature,

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we conducted a prospective observational study to determine the influence of age on

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complications and clinical outcomes of patients undergoing ALIF.

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Methods

Study population

The present study was a retrospective analysis from a prospective database of 137 patients, all of whom underwent surgery by the same senior neurosurgeon across two hospitals. Clearance

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for the prospective study was obtained through the Human Research Ethics Committee of New South Wales Health (reference No. 11/183). Patients who underwent ALIF surgery were

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included in the study with indications: degenerative disc disease without radiculopathy, degenerative disc disease with radiculopathy, spondylolisthesis, failed posterior fusion, and adjacent segment disease. Exclusion criteria were patients with concurrent local or systemic infection, neoplasia, significant cardiac disease, fever (>38.5°C), or metal allergy; as well as

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patients who were pregnant or breast-feeding, who were mentally incompetent, who had a history of alcohol or drug abuse, and who were at increased risk of vascular or bowel complications related to the anterior approach. Patients were divided into age-based tertiles as

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Procedural details

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following: Group 1(≤49 years old), Group 2 (50-63 years old), and Group 3 (≥64 years old).

All patients underwent ALIF surgery by a primary spine surgery (R.J.M) with and a vascular “access” surgeon. Prior studies have demonstrated no difference between ALIF performed with or without an “access” surgeon.16 Patients received stand-alone Polyetheretherketone (PEEK) integral cage devices. All patients received the SynFix-LR PEEK integral cage device (DePuy Synthes, West Chester, PA, USA) with four diverging intrinsic screws and anterior locking plate, without anterior tension band plating nor posterior instrumentation. The implant sizing varied

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across patients in accordance with the disc height of neighbouring healthy lumbar discs, ranging from 12-19mm height with either 8° or 12° lordotic angle to ensure sufficient distraction. Bone graft substitute i-FACTOR (Cerapedics, Westminster, CO, USA) was used for all patients and is

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comprised of anorganic bone matrix bound to anorganic P-15 small peptide, together facilitating attachment of osteogenic cells.

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Assessment of fusion and subsidence

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Fusion rates were assessed using reconstructed axial and coronal fine-cut computed tomography (CT) scans by 2 neurosurgeons (R.M., P.J.R.). Criteria for established fusion were bridging trabecular formation across the intervertebral disc space with the absence of radiolucency spanning more than half of the implant. The anterior and posterior intervertebral disc heights were measured and averaged. Endplate levels were taken as a straight-line

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average of the endplate as seen on the most central image in all planes, using the most anterior and posterior points excluding osteophytes. Osteophytes were identified as superficial extrusions of bone anteriorly or posteriorly beyond the main vertebral body. Subsidence was

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defined as greater than or equal to 2 mm mean loss of height. Delayed subsidence was defined

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as occurring within after 6 weeks postoperatively.

Assessment of clinical outcomes Clinical outcome was measured preoperatively and postoperatively using the Oswestry Disability Index (ODI). Questionnaire data from the Short Form 12 Item survey (SF-12) were compiled in a custom-designed database. Preoperative and 1-year postoperative clinical outcomes were compared.

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Statistical analysis

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Descriptive and comparative statistics of demographics, comorbidities, operative parameters, and postoperative complications were analysed for all patients. For univariate analysis,

categorical variables were assessed using Pearson's chi-square or Fisher's exact test where appropriate. Continuous variables were examined using 1-way analysis of variance (ANOVA)

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test. Multivariate analysis was performed by adjustment for confounders, determined by

significant differences discovered on univariate analysis. This was presented as odds ratio (OR)

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and 95% confidence interval (CI). Analyses were based on 2-sided tests with values of p<0.05 considered significant. Data analysis and statistical evaluation was conducted using IBM SPSS

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Statistics 24 (IBM Corporation, Armonk, NY, USA).

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Results The study identified 137 patients for analysis following application of initial inclusion and exclusion criteria (Table 1). Patients were divided into age-based tertiles as following: Group

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1(≤49 years old), Group 2 (50-63 years old), and Group 3 (≥64 years old). Age groups 1, 2, and 3 consisted of 45 (32.8%), 46 (33.6%), and 46 (33.6%) patients respectively. Among patient characteristics, gender and BMI were not significantly different among groups. Only patients

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<64 years old had worker’s compensation (p<0.001). Among medical comorbidities, smoking was most prevalent among patients ≤49 years old (26%) (p=0.010), while hypertension was

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most prevalent among patients ≥50 years old (13% in Group 1, 15.2% in Group 2, p=0.028). History of diabetes, asthma/COPD, coronary artery disease, and depression were found to not be significantly different among the groups.

Indications for ALIF in patients ≤49 years old was most prevalently due to DDD (p<0.001), while indications for patients ≥64 years old was mostly due to spondylolisthesis (p=0.009). Among

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surgical risk factors, history of prior spine surgery, posterior fusion, or ALIF did not differ significantly among the groups. In terms of spinal level pathology, L4/5 pathology was most prevalent in patients ≥64 years (63%, p=0.048), while L5/S1 pathology was most prevalent in

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patients ≤49 years old (75.5%, p=0.048). Prevalence of L3/4 pathology did not differ significantly. The percentage of patients undergoing multilevel operation were not statistically

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different among the groups. Univariate analysis

Surgical parameters associated the operation such as operation duration, blood loss, and hospital stay did not differ significantly among the groups. The total number of complications did not differ significantly among the three groups (p=0.258), however a greater proportion of patients ≥64 years old developed postoperative hematoma (6.5%, p=0.048) and delayed

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subsidence (21.7%, p=0.007). Postoperative complications such as wound infection, DVT, postoperative ileus, vessel injury, pneumonia, wound dehiscence, pseudarthrosis, and death were not significantly different among the groups.

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Preoperative and immediate postoperative radiographic findings among the three groups

showed no significant differences (Table 3). However, 6-week postoperative radiographs of patients ≥64 years showed a significantly greater decrease in anterior, posterior, and average

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disk heights compared to other groups (17.9%, 15.4%, 16.7% respectively; all p<0.05).

Postoperative radiographs at 12-weeks also showed significant decrease in anterior, posterior,

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and average disk heights from immediate postoperative radiographs (15.4%, 18.7%, 16.7% respectively, all p<0.05). Lordosis angle (˚), lumbar lordosis (˚), cage height (mm), and cage lordosis (˚) measurements did not differ significantly at the final follow-up among the groups. No significant differences were found among the groups in terms of clinical outcome (Table 4). Preoperative and postoperative assessment with regards to physical component summary,

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mental component summary, SF-12 health survey, Oswestry Disability Index, and Patient Satisfaction Index were similar among all groups (all p>0.05).

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Multivariate analysis

A more thorough multivariable analysis was performed to determine if age is a risk factor for

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delayed subsidence following ALIF surgery (Table 5). This analysis demonstrated that with respects to Group 1, Group 3 was independently associated with greater prevalence of delayed subsidence (OR 9.174, p=0.029).

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Discussion The increasing age of the population impacts patient demographics and implores spine surgeons to begin evaluating surgical outcomes in light of patient age.17 In this prospective

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study, 137 patients categorized by age tertiles (Group 1: ≤49 years old, Group 2: 50-63 years old, Group 3: ≥64 years old) underwent ALIF surgery. The total number of complications,

postoperative complications, pre- and immediately postoperative radiographic studies, clinical

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outcomes, and pre- and postoperative assessments were not statistically different between the groups. Interestingly, the age of the most elderly tertile was independently associated with

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greater prevalence of delayed subsidence compared to that of the youngest tertile.

Our study demonstrated that age did not affect perioperative outcomes in ALIF, and suggests that age alone should not be a contraindication to ALIF. In this study, an “access” surgeon

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operated on all patients to expose the necessary surgical field before the neurosurgeon performed the ALIF. However, prior studies have demonstrated no difference reoperation rates or intraoperative and postoperative complicates between ALIF performed with or without an “access” surgeon. In operatives in which exposure may be difficult, assistance from an "access”

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surgeon should be available.16 Investigation of spine surgery outcomes in relation to age have

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produced mixed data depending on the procedure performed. In a retrospective analysis of 52 patients (median age of 61.8 years) who underwent anterior cervical discectomy and fusion (ACDF), Gray et al. report that patient-reported outcomes (NDI and SF-36) of ACDF is not significantly different between older (age over 55) and younger age groups.18 Giannadakis et al. conducted a multi-institutional study utilizing the Norwegian Registry for Spine Surgery to investigate age-related outcomes of laminectomy or microdecompression for lumbar spinal stenosis. The results of the study (N = 1,503), showed that individuals aged 80 and older experienced similar self-reported outcomes as younger individuals and did not have significantly

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increased rates of perioperative complications.19 Contrarily, Winkler et al. utilized the National Sample Program of the National Trauma Data Bank to perform a retrospective analysis of middle-aged (55-69 years) and elderly (≥70 years) patients who had traumatic fracture of the

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lumbar spine. The results of their study reveal that lumbar surgery in the elderly is associated with increased morbidity, including periprocedural complications, prolonged hospitalization, and lowered likelihood for discharge to home.20 In light of these findings, however, our study

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of subsidence, but does not affect clinical outcomes.9

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provides evidence that for ALIF specifically, elderly age (≥64 years old) results in increased rate

Comorbidities and reduced physiologic reserve are documented predictors of adverse surgical outcomes in elderly populations. Frailty, a lack of physiologic reserve across multiple organ systems, is more common in older patients.21 Prior study has shown that frailty is associated with morbidity in adults undergoing elective ALIF surgery. However, in this study, the eldest

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tertile was not necessarily frailer or have more comorbidities.9 This may account for the lack of difference in clinical outcomes between the tertiles. Thus, age alone should not be a contraindication to ALIF surgery, however elderly age along with comorbidities or markers of

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frailty is more likely to result in greater complications.

Our study demonstrated that the elderly tertile was independently associated with higher risk of delayed subsidence following ALIF surgery. A possible explanation for the delayed subsidence observed in the most elderly tertile in our study is osteoporosis. Osteoporosis particularly affects the lumbar spine, resulting in an mean bone loss of 44% from the age of 34 throughout life.22 The incidence of osteoporosis progressively increases with age, increasing from 5.1% in individuals between 50-59 to 26.2% in those 80 and above.23 Formby et al. demonstrated

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increased rates of cage subsidence in osteoporotic patients who underwent transforaminal lumbar interbody fusion (TLIF).24 Furthermore, Mi et al. report that lower preoperative Hounsfield Units, indicative of decreased bone mineral density, is associated with cage

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subsidence after unilateral TLIF.25 Therefore, subclinical or undiagnosed osteoporotic patients may have an increased incidence of subsidence. In our study, patients in Group 3 may have had subclinical or clinical osteoporosis resulting in increased incidence of subsidence after

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ALIF. This needs to be confirmed in future studies via assessment of bone mineral density.

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Subsidence rates in lumbar fusion and their risk factors have been investigated in prior studies. Choi and Sung demonstrated that cage subsidence is to be anticipated after ALIF with standalone rectangular cages, reaching 63.4% and 70.7% actuarial rates at 3- and 4-months. However, subsidence had no correlation with symptom recurrence and fusion rates by radiographic study.26 Malham et al. showed that in lumbar fusion, there is increased risk of

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subsidence after MIS LIF at the caudal endplate, so surgeons are advised to take particular care with this portion of the cage insertion. However, the results of the study also show that neither the rate of lateral interbody fusion nor clinical outcomes (assessed by the ODI and SF-

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12) are affected by radiographic subsidence.27 ALIF, posterior lumbar interbody fusion, and transverse lumbar interbody fusion are three different approaches to lumbar fusion. Lee et al.

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showed that one year postoperatively, the rates of subsidence are the same between the three approaches, however two years postoperatively, PLIF has a higher rate of subsidence.28 A few studies have also identified patient characteristics that may serve as risk factors for subsidence in lumbar fusion. The results from Behrbelk et al. identified that there was a statistically significant increase in body mass index of patients with olisthesis who developed subsidence than those who did not (29 ± 2.6 vs. 22 ± 6.5 respectively; p = 0.04).29 Additionally, a statistically significant older patient population with osteoporosis was shown to have an increased rate of

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subsidence, but also no increased likelihood for surgical revision or worse clinical outcomes than the younger, non-osteoporotic group.30 Thus, some of the prior outline literature corroborate the findings in this study. This paper identified an increased rate of subsidence in

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the most elderly tertile group. However, the presence of subsidence did not affect clinical outcomes as evidenced by statistically insignificant variation in the patient-reported outcomes

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results amongst the three age groups.

The study has several limitations. First of all, it is a single center study encompassing patients

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from a similar geographic area. Thus, the results of the study would benefit from replication at other institutes from different geographic areas to be more widely applicable. Additionally, the patient population may have been derived from a particular socioeconomic status depending on the insurance types accepted. The study would benefit from a larger multi-institutional sample size and larger subgroups, which would ensure greater statistical power. This was not controlled

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for in our study, which may restrict the broader application of its findings. Another limitation of the present study was that DEXA scans were not performed on these patients to determine bone mineral density of the vertebrae, particularly in patients who had subsidence, which could

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be a potential explanation for their subsidence. The strengths of our study include its prospective design, multivariate adjustment of potential confounders, use of several domains of

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outcome measures, and follow-up outcomes.

Conclusions

This study utilized a prospective, single-institutional study collected data over two years on patients undergoing ALIF. Increased age was not associated with adverse perioperative

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outcomes and complications of ALIF. There was an increased incidence of delayed subsidence in patients ≥64 years old. While increasing age may raise concern for the possibility of comorbidities, elderly age alone should not serve as a contraindication for ALIF surgery. Thus,

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the surgeon should engage the elderly patient in a discussion of the benefits of ALIF surgery, including pain relief, functional improvement, and independence in conjunction with the risks of subsidence, vascular, urologic, and abdominal complications. Further studies are necessary to

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confirm this study’s findings.

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ACCEPTED MANUSCRIPT Table 1. Baseline demographics Baseline

Males, n (%)

Age ≤49 years

Age 50-63

Age ≥64 years

(n=45)

years (n=46)

(n=46)

24

22

19

p-value

0.516 0.991

27

29

29

III

14

14

14

IV

4

3

3

Multi-level operation

10

12

16

L3/4

3

6

9

L4/5

14

23

29

L5/S1

34

28

DDD

43

33

Spondylolithesis

1

Prior spine surgery

8

Prior posterior fusion

1

Prior ALIF

4

Smoker

12

Diabetic

2

Asthma/COPD Coronary artery disease

0.389

0.048*

0.048*

25

<0.001*

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23

6

11

0.009*

3

6

0.262

3

1

0.618

1

2

0.372

4

3

0.010*

4

6

0.349

0

6

7

0.028*

1

0

1

0.599

1

1

1

0.999

1

3

3

0.562

10

0

<0.001*

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Depression

0.395

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HT

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II

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BMI class

Worker’s compensation

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BMI, body mass index; DDD, degenerative disc disease; HT, hypertension; COPD, chronic

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obstructive pulmonary disease. Asterisk* represents significant differences with P<0.05.

ACCEPTED MANUSCRIPT Table 2. Surgical parameters and complications Age ≤49

Age 50-63

Age ≥64

years (n=45)

years (n=46)

years (n=46)

Hospital stay (days)

4.32±1.76

4.25±1.59

5.30±3.21

Blood loss (mL)

104.55±120.83 68.84±43.48

116.79±137.68 0.261

Operation duration

103.18±35.6

96.81±35.94

106.67±35.36

6

2

7

Wound infection

1

0

2

DVT

1

0

0

Postoperative ileus

1

0

Postoperative

0 (0%)

0 (0%)

Total Complications,

0

Pneumonia

1

Wound dehiscence

1

Death

1

Pseudoarthrosis

2 (4.4%)

Delayed subsidence

2 (4.4%)

0.258

0.394

0.386

0.599

3 (6.5%)

0.048*

0

1

0.369

0

0

0.357

0

0

0.357

0

0

0.357

2 (4.3%)

3 (6.5%)

0.675

10 (21.7%)

0.007*

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Vessel injury

0.771

1

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hematoma

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n (%)

0.130

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(mins)

p-value

2 (4.3%)

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EP

DVT, deep venous thrombosis; Asterisk* represents significant differences with P<0.05.

ACCEPTED MANUSCRIPT Table 3. Fusion and radiographic changes Age ≤49

Age 50-63

Age ≥64

years

years (n=46)

years

(n=45) Fused successfully, n (%)

p-value

(n=46)

36

38

39

0.972

Anterior disk height (mm)

8.9±3.3

8.7±3.3

8.3±3.1

0.756

Posterior disk height (mm)

5.5±1.9

4.8±2.1

4.4±1.9

0.122

Average height (mm)

7.2±2.2

6.8±2.4

6.3±2.3

0.382

Anterior disk height (mm)

17.8±5.2

16.4±4.3

16.2±4.4

0.290

Posterior disk height (mm)

9.4±2.8

8.6±2.9

9.1±2.5

0.477

Average height (mm)

13.6±3.7

12.5±3.2

12.6±3.1

0.329

6 weeks postop: Anterior disk height (mm)

16.9±3.7

Posterior disk height (mm)

10.1±3.2

Average height (mm)

13.5±2.9

At final follow-up: 15.6±3.7

SC

15.5±3.3

13.3±3.6

0.006*

10.3±3.5

7.7±3.1

0.020*

13.8±4.7

10.5±2.6

0.006*

16.5±3.2

13.7±2.8

0.042*

TE D

Anterior disk height (mm)

M AN U

Directly postop:

RI PT

Preoperative data:

Posterior disk height (mm)

9.5±3.0

9.4±2.8

7.4±2.3

0.045*

Average height (mm)

12.6±2.8

13.0±2.8

10.0±3.2

0.013*

6.5±4.0

6.9±3.6

6.7±4.4

0.958

37.8±9.9

42.2±10.5

44.7±10.6

0.056

13.3±1.2

13.4±1.4

13.5±1.1

0.782

9.2±1.8

9.0±1.6

8.8±1.4

0.456

Lordosis angle (degrees)

Cage height (mm)

EP

Lumbar lordosis (degrees)

Cage lordosis (degrees)

AC C

Asterisk* represents significant differences with P<0.05.

ACCEPTED MANUSCRIPT Table 4. Clinical outcomes Age ≤49

Age 50-63

Age ≥64

years

years (n=46)

years

(n=45)

p-value

(n=46)

32.4±6.6

31.4±6.8

Postoperative SF-12 PCS

40.8±11.8

41.0±9.1

Change in SF-12 PCS

9.9±12.0

12.5±11.0

Preoperative SF-12 MCS

35.9±11.2

39.7±13.1

Postoperative SF-12 MCS

48.7±9.1

47.9±9.5

Change in SF-12 MCS

15.0±12.9

Preoperative ODI

59.3±20.0

Postoperative ODI

29.3±20.8

Change in ODI Patient satisfaction index

36.3±32.4

0.506

RI PT

Preoperative SF-12 PCS

0.951

6.3±34.0

0.515

39.0±14.0

0.380

50.7±10.4

0.423

11.2±13.0

13.2±17.5

0.574

57.9±20.2

57.0±26.7

0.900

31.8±17.9

25.4±19.4

0.379

29.5±23.8

29.8±21.3

36.1±27.4

0.453

1.7±0.7

1.9±0.8

1.5±0.7

0.134

M AN U

SC

41.6±11.0

PCS, physical component score; MCS, mental component score; SF-12, short-form 12; ODI,

TE D

Oswestry disability index

surgery

Age

AC C

Outcome

EP

Table 5. Multivariate analysis of age as a risk factor for delayed subsidence following ALIF

Odds ratio

Lower

Upper

confidence

confidence

limit

limit

1.103

0.140

8.696

0.927

9.174

1.248

66.67

0.029*

group

Delayed

50-63

subsidence

years vs

P-value

≤49 years ≥64 years vs ≤49 years Asterisk* represents significant differences with P<0.05.

ACCEPTED MANUSCRIPT Highlights 1. Increased age was found to not be associated with adverse perioperative outcomes and complications of ALIF. 2. Increased age was found to be independently associated with greater prevalence of

RI PT

delayed subsidence.

AC C

EP

TE D

M AN U

SC

3. Elderly age alone should not serve as a contraindication for ALIF surgery.

ACCEPTED MANUSCRIPT Kevin Phan, BS MPhil: Conflicts of interest: none Vignesh Ramachandran, BS: Conflicts of interest: none Tommy Tran, BS: Conflicts of interest: none Prashanth J Rao MBBS PhD: Conflicts of interest: none

AC C

EP

TE D

M AN U

SC

RI PT

Ralph J Mobbs, MD: Conflicts of interest: none

ACCEPTED MANUSCRIPT Abbreviations ALIF, anterior lumbar interbody fusion BMI, body mass index COPD, chronic obstructive pulmonary disease UTI, urinary tract infection

RI PT

PEEK, Polyetheretherketone CT, computed tomography ODI, Oswestry disability index SF-12, Short Form 12 Item Survey

SC

ANOVA, analysis of variance OR, odds ratio

M AN U

CI, confidence interval

AC C

EP

TE D

TLIF, transforaminal lumbar interbody fusion