Aims. There is evidence that prior lumbar fusion increases the risk of dislocation and revision after total hip arthroplasty (THA). The relationship between prior lumbar fusion and the effect of femoral head diameter on THA dislocation has not been investigated. We examined the relationship between prior lumbar fusion or discectomy and the risk of dislocation or revision after THA. We also examined the effect of femoral head component diameter on the risk of dislocation or revision. Methods. Data used in this study were compiled from several Finnish national health registers, including the Finnish Arthroplasty Register (FAR) which was the primary source for prosthesis-related data. Other registers used in this study included the Finnish Health Care Register (HILMO), the Social Insurance Institutions (SII) registers, and Statistics Finland. The study was conducted as a prospective retrospective cohort study. Cox proportional hazards regression and Kaplan-Meier survival analysis were used for analysis. Results. Prior lumbar fusion surgery was associated with increased risk of prosthetic dislocation (hazard ratio (HR) = 2.393, p < 0.001) and revision (HR = 1.528, p < 0.001). Head components larger than 28 mm were associated with lower dislocation rates compared to the 28 mm head (32 mm: HR = 0.712, p < 0.001; 36 mm: HR = 0.700, p < 0.001; 38 mm: HR = 0.808, p < 0.140; and 40 mm: HR = 0.421, p < 0.001). Heads of 38 mm (HR = 1.288, p < 0.001) and 40 mm (HR = 1.367, p < 0.001) had increased risk of revision compared to the 28 mm head. Conclusion. Lumbar fusion surgery was associated with higher rate of hip prosthesis dislocation and higher risk of revision surgery. Femoral head component of 32 mm (or larger) associates with lower risk of dislocation in patients with previous lumbar fusion. Cite this article: Bone Joint J 2020;102-B(8):1003–1009

Aims. Concurrent hip and spine pathologies can alter the biomechanics of spinopelvic mobility in primary total hip arthroplasty (THA). This study examines how differences in pelvic orientation of patients with spine fusions can increase the risk of dislocation risk after THA. Patients and Methods. We identified 84 patients (97 THAs) between 1998 and 2015 who had undergone spinal fusion prior to primary THA. Patients were stratified into three groups depending on the length of lumbar fusion and whether or not the sacrum was involved. Mean age was 71 years (40 to 87) and 54 patients (56%) were female. The mean body mass index (BMI) was 30 kg/m. 2. (19 to 45). Mean follow-up was six years (2 to 17). Patients were 1:2 matched to patients with primary THAs without spine fusion. Hazard ratios (HR) were calculated. Results. Dislocation in the fusion group was 5.2% at one year versus 1.7% in controls but this did not reach statistical significance (HR 1.9; p = 0.33). Compared with controls, there was no significant difference in rate of dislocation in patients without a sacral fusion. When the sacrum was involved, the rate of dislocation was significantly higher than in controls (HR 4.5; p = 0.03), with a trend to more dislocations in longer lumbosacral fusions. Patient demographics and surgical characteristics of THA (i.e. surgical approach and femoral head diameter) did not significantly impact risk of dislocation (p > 0.05). Significant radiological differences were measured in mean anterior pelvic tilt between the one-level lumbar fusion group (22°), the multiple-level fusion group (27°), and the sacral fusion group (32°; p < 0.01). Ten-year survival was 93% in the fusion group and 95% in controls (HR 1.2; p = 0.8). Conclusion. Lumbosacral spinal fusions prior to THA increase the risk of dislocation within the first six months. Fusions involving the sacrum with multiple levels of lumbar involvement notably increased the risk of postoperative dislocation compared with a control group and other lumbar fusions. Surgeons should take care with component positioning and may consider higher stability implants in this high-risk cohort

Despite the increasing prevalence of sleep apnoea, little information is available regarding its impact on the peri-operative outcome of patients undergoing posterior lumbar fusion. Using a national database, patients who underwent lumbar fusion between 2006 and 2010 were identified, sub-grouped by diagnosis of sleep apnoea and compared. The impact of sleep apnoea on various outcome measures was assessed by regression analysis. The records of 84 655 patients undergoing posterior lumbar fusion were identified and 7.28% (n = 6163) also had a diagnostic code for sleep apnoea. Compared with patients without sleep apnoea, these patients were older, more frequently female, had a higher comorbidity burden and higher rates of peri-operative complications, post-operative mechanical ventilation, blood product transfusion and intensive care. Patients with sleep apnoea also had longer and more costly periods of hospitalisation. . In the regression analysis, sleep apnoea emerged as an independent risk factor for the development of peri-operative complications (odds ratio (OR) 1.50, confidence interval (CI) 1.38;1.62), blood product transfusions (OR 1.12, CI 1.03;1.23), mechanical ventilation (OR 6.97, CI 5.90;8.23), critical care services (OR 1.86, CI 1.71;2.03), prolonged hospitalisation and increased cost (OR 1.28, CI 1.19;1.37; OR 1.10, CI 1.03;1.18). . Patients with sleep apnoea who undergo posterior lumbar fusion pose significant challenges to clinicians. . Cite this article: Bone Joint J 2014;96-B:242–8

We studied the effects of hyperbaric oxygen (HBO) and zoledronic acid (ZA) on posterior lumbar fusion using a validated animal model. A total of 40 New Zealand white rabbits underwent posterior lumbar fusion at L5–6 with autogenous iliac bone grafting. They were divided randomly into four groups as follows: group 1, control; group 2, HBO (2.4 atm for two hours daily); group 3, local ZA (20 μg of ZA mixed with bone graft); and group 4, combined HBO and local ZA. All the animals were killed six weeks after surgery and the fusion segments were subjected to radiological analysis, manual palpation, biomechanical testing and histological examination. Five rabbits died within two weeks of operation. Thus, 35 rabbits (eight in group 1 and nine in groups 2, 3 and 4) completed the study. The rates of fusion in groups 3 and 4 (p = 0.015) were higher than in group 1 (p < 0.001) in terms of radiological analysis and in group 4 was higher than in group 1 with regard to manual palpation (p = 0.015). We found a statistically significant difference in the biomechanical analysis between groups 1 and 4 (p = 0.024). Histological examination also showed a statistically significant difference between groups 1 and 4 (p = 0.036). Our results suggest that local ZA combined with HBO may improve the success rate in posterior lumbar spinal fusion

1. Anterior transperitoneal lumbar fusion is a successful method of stabilising painful mechanical derangements which have not responded to the usual conservative measures. 2. The operation in this series was done mainly for backache; it should not be contemplated if there is definite evidence of nerve root compression, because sequestrated disc material cannot be removed from the spinal canal from the anterior route. 3. Careful technique has resulted in few complications attributable to the operation. 4. This method is sometimes thought to be inapplicable in cases of spondylolisthesis with a displacement of more than one-third. However, in this series we have seen the block type of graft used with a good measure of clinical and radiological success. 5. There is no doubt that for those patients who have had previous unsuccessful laminectomies or posterior fusions anterior interbody fusion offers an excellent prospect of recovery

We examined the differences in post-operative functional disability and patient satisfaction between 56 patients who underwent a lumbar fusion at three or more levels for degenerative disease (group I) and 69 patients, matched by age and gender, who had undergone a one or two level fusion (group II). Their mean age was 66 years (49 to 84) and the mean follow-up was 43 months (24 to 65). The mean pre-operative Oswestry Disability Index (ODI) and visual analogue scale (VAS) for back and leg pain, and the mean post-operative VAS were similar in both groups (p >  0.05), but post-operatively the improvement in ODI was significantly less in group I (40.6%) than in group II (49.5%) (p < 0.001). Of the ten ODI items, patients in group I showed significant problems with lifting, sitting, standing, and travelling (p < 0.05). The most significant differences in the post-operative ODI were observed between patients who had undergone fusion at four or more levels and those who had undergone fusion at less than four levels (p = 0.005). The proportion of patients who were satisfied with their operations was similar in groups I and II (72.7% and 77.0%, respectively) (p = 0.668). The mean number of fused levels was associated with the post-operative ODI (r = 0.266, p = 0.003), but not with the post-operative VAS or satisfaction grade (p > 0.05). Post-operative functional disability was more severe in those with a long-level lumbar fusion, particularly at four or more levels, but patient satisfaction remained similar for those with both long- and short-level fusions

Our study establishes a rabbit model of disc degeneration which requires neither a chemical nor physical injury to the disc. Disc degeneration similar to that seen in man was created at levels proximal (L4-L5) and caudal (L7-S1) to a simulated lumbar fusion and was studied for up to nine months after arthrodesis. Loss of the normal parallel arrangement of collagen bundles within the annular lamellae was observed in intervertebral discs adjacent to the fusion at three months. By six months there was further disorganisation as well as loss of distinction between the lamellae themselves. By nine months the structure of the disc had been replaced by disorganised fibrous tissue, and annular tears were seen. There was an initial cellular proliferative response followed by loss of chondrocytes and notochordal cells in the nucleus pulposus. Degeneration was accompanied by a decrease in the monomer size of proteoglycans. Narrowing of the disc space, endplate sclerosis and the formation of osteophytes at adjacent disc spaces were observed radiologically

Aims. Dual-mobility (DM) components are increasingly used to prevent and treat dislocation after total hip arthroplasty (THA). Intraprosthetic dissociation (IPD) is a rare complication of DM that is believed to have decreased with contemporary implants. This study aimed to report incidence, treatment, and outcomes of contemporary DM IPD. Methods. A total of 1,453 DM components were implanted at a single academic institution between January 2010 and December 2021: 695 in primary and 758 in revision THA. Of these, 49 presented with a dislocation of the large DM head and five presented with an IPD. At the time of closed reduction of the large DM dislocation, six additional IPDs occurred. The mean age was 64 years (SD 9.6), 54.5% were female (n = 6), and mean follow-up was 4.2 years (SD 1.8). Of the 11 IPDs, seven had a history of instability, five had abductor insufficiency, four had prior lumbar fusion, and two were conversions for failed fracture management. Results. The incidence of IPD was 0.76%. Of the 11 IPDs, ten were missed either at presentation or after attempted reduction. All ten patients with a missed IPD were discharged with a presumed reduction. The mean time from IPD to surgical treatment was three weeks (0 to 23). One patient died after IPD prior to revision. Of the ten remaining hips with IPD, the DM head was exchanged in two, four underwent acetabular revision with DM exchange, and four were revised to a constrained liner. Of these, five (50%) underwent reoperation at a mean 1.8 years (SD 0.73), including one additional acetabular revision. No patients who underwent initial acetabular revision for IPD treatment required subsequent reoperation. Conclusion. The overall rate of IPD was low at 0.76%. It is essential to identify an IPD on radiographs as the majority were missed at presentation or after iatrogenic dissociation. Surgeons should consider acetabular revision for IPD to allow conversion to a larger DM head, and take care to remove impinging structures that may increase the risk of subsequent failure. Cite this article: Bone Joint J 2024;106-B(5 Supple B):98–104

Aims. The aim of this study was to reassess the rate of neurological, psoas-related, and abdominal complications associated with L4-L5 lateral lumbar interbody fusion (LLIF) undertaken using a standardized preoperative assessment and surgical technique. Methods. This was a multicentre retrospective study involving consecutively enrolled patients who underwent L4-L5 LLIF by seven surgeons at seven institutions in three countries over a five-year period. The demographic details of the patients and the details of the surgery, reoperations and complications, including femoral and non-femoral neuropraxia, thigh pain, weakness of hip flexion, and abdominal complications, were analyzed. Neurological and psoas-related complications attributed to LLIF or posterior instrumentation and persistent symptoms were recorded at one year postoperatively. Results. A total of 517 patients were included in the study. Their mean age was 65.0 years (SD 10.3) and their mean BMI was 29.2 kg/m. 2. (SD 5.5). A mean of 1.2 levels (SD 0.6) were fused with LLIF, and a mean of 1.6 (SD 0.9) posterior levels were fused. Femoral neuropraxia occurred in six patients (1.2%), of which four (0.8%) were LLIF-related and two (0.4%) had persistent symptoms one year postoperatively. Non-femoral neuropraxia occurred in nine patients (1.8%), one (0.2%) was LLIF-related and five (1.0%) were persistent at one year. All LLIF-related neuropraxias resolved by one year. A total of 32 patients (6.2%) had thigh pain, 31 (6.0%) were LLIF-related and three (0.6%) were persistent at one year. Weakness of hip flexion occurred in 14 patients (2.7%), of which eight (1.6%) were LLIF-related and three (0.6%) were persistent at one year. No patients had bowel injury, three (0.6%) had an intraoperative vascular injury (not LLIF-related), and five (1.0%) had ileus. Reoperations occurred in five patients (1.0%) within 30 days, 37 (7.2%) within 90 days, and 41 (7.9%) within one year postoperatively. Conclusion. LLIF involving the L4-L5 disc level has a low rate of persistent neurological, psoas-related, and abdominal complications in patients with the appropriate indications and using a standardized surgical technique. Cite this article: Bone Joint J 2024;106-B(1):53–61

1. Intertransverse fusion in the lumbar spine appears to have many advantages over previously described techniques.

2. The disadvantage of profuse bleeding can be overcome by the use of a Hastings frame and by an operative technique designed to demonstrate constant muscular and articular branches of the lumbar arteries.

3. Coagulation of these vessels by cautery and avoidance of dissection anterior to the plane of the transverse processes ensure that the operative procedure can be carried out with a blood loss averaging less than 500 millilitres.

In a prospective observational study we compared the two-year outcome of lumbar fusion by a simple technique using translaminar screws (n = 57) with a more extensive method using transforaminal lumbar interbody fusion and pedicular screw fixation (n = 63) in consecutive patients with degenerative disease of the lumbar spine. Outcome was assessed using the validated multidimensional Core Outcome Measures Index. Blood loss and operating time were significantly lower in the translaminar screw group (p < 0.01). The complication rates were similar in each group (2% to 4%). In all, 91% of the patients returned their questionnaire at two-years. The groups did not differ in Core Outcome Measures Index score reduction, 3.6 (. sd. 2.5) (translaminar screws) vs 4.0 (. sd. 2.8) (transforaminal lumbar interbody fusion) (p = 0.39); ‘good’ global outcomes, 78% (translaminar screws) vs 78% (transforaminal lumbar interbody fusion) (p = 0.99) or satisfaction with treatment, 82% (translaminar screws) vs 86% (transforaminal lumbar interbody fusion) (p = 0.52). The two fusion techniques differed markedly in their extent and the cost of the implants, but were associated with almost identical patient-orientated outcomes. Extensive three-point stabilisation is not always required to achieve satisfactory patient-orientated results at two years

Aims. We compared the clinical and radiological outcomes of using a polyetheretherketone cage with (TiPEEK) and without a titanium coating (PEEK) for instrumented transforaminal lumbar interbody fusion (TLIF). Materials and Methods. We conducted a randomised clinical pilot trial of 40 patients who were scheduled to undergo a TLIF procedure at one or two levels between L2 and L5. The Oswestry disability index (ODI), EuroQoL-5D, and back and leg pain were determined pre-operatively, and at three, six, and 12 months post-operatively. Fusion rates were assessed by thin slice CT at three months and by functional radiography at 12 months. Results. At final follow-up, one patient in each group had been lost to follow-up. Two patients in each of the PEEK and TiPEEK groups were revised for pseudarthrosis (p = 1.00). The rate of complete or partial fusion at three months was 91.7% in both groups. Overall, there were no significant differences in ODI or in radiological outcomes between the groups. Conclusion. Favourable results with identical clinical outcomes and a high rate of fusion was seen in both groups. The titanium coating appears to have no negative effects on outcome or safety in the short term. A future study to determine the effect of titanium coating is warranted. Cite this article: Bone Joint J 2017;99-B:1366–72

The presacral retroperitoneal approach for axial lumbar interbody fusion (presacral ALIF) is not widely reported, particularly with regard to the mid-term outcome. This prospective study describes the clinical outcomes, complications and rates of fusion at a follow-up of two years for 26 patients who underwent this minimally invasive technique along with further stabilisation using pedicle screws. The fusion was single-level at the L5-S1 spinal segment in 17 patients and two-level at L4–5 and L5-S1 in the other nine. The visual analogue scale for pain and Oswestry Disability Index scores were recorded pre-operatively and during the 24-month study period. The evaluation of fusion was by thin-cut CT scans at six and 12 months, and flexion-extension plain radiographs at six, 12 and 24 months. Significant reductions in pain and disability occurred as early as three weeks postoperatively and were maintained. Fusion was achieved in 22 of 24 patients (92%) at 12 months and in 23 patients (96%) at 24 months. One patient (4%) with a pseudarthrosis underwent successful revision by augmentation of the posterolateral fusion mass through a standard open midline approach. There were no severe adverse events associated with presacral ALIF, which in this series demonstrated clinical outcomes and fusion rates comparable with those of reports of other methods of interbody fusion

Aims. Minimally invasive transforaminal lumbar interbody fusion (MITLIF) has been well validated in overweight and obese patients who are consequently subject to a higher radiation exposure. This prospective multicentre study aimed to investigate the efficacy of a novel lumbar localisation system for MITLIF in overweight patients. Patients and Methods. The initial study group consisted of 175 patients. After excluding 49 patients for various reasons, 126 patients were divided into two groups. Those in Group A were treated using the localisation system while those in Group B were treated by conventional means. The primary outcomes were the effective radiation dosage to the surgeon and the exposure time. Results. There were 62 patients in Group A and 64 in Group B. The mean effective dosage was 0.0217 mSv (standard deviation (. sd. ) 0.0079) in Group A and 0.0383 mSv (. sd. 0.0104) in Group B (p <  0.001). The mean fluoroscopy exposure time was 26.42 seconds (. sd. 5.91) in Group A and 40.67 seconds (. sd. 8.18) in Group B (p < 0.001). The operating time was 175.56 minutes (. sd. 32.23) and 206.08 minutes (. sd. 30.15) (p < 0.001), respectively. The mean pre-operative localisation time was 4.73 minutes (. sd. 0.84) in Group A and 7.03 minutes (. sd. 1.51) in Group B (p < 0.001). The mean screw placement time was 47.37 minutes (. sd. 10.43) in Group A and 67.86 minutes (. sd. 14.15) in Group B (p < 0.001). The pedicle screw violation rate was 0.35% (one out of 283) in Group A and 2.79% (eight out of 287) in Group B (p = 0.020). Conclusion. The study shows that the localisation system can effectively reduce radiation exposure, exposure time, operating time, pre-operative localisation time, and screw placement time in overweight patients undergoing MITLIF. Cite this article: Bone Joint J 2017;99-B:944–50

Methods

In this study of patients who underwent internal fixation without fusion for a burst thoracolumbar or lumbar fracture, we compared the serial changes in the injured disc height (DH), and the fractured vertebral body height (VBH) and kyphotic angle between patients in whom the implants were removed and those in whom they were not. Radiological parameters such as injured DH, fractured VBH and kyphotic angle were measured. Functional outcomes were evaluated using the Greenough low back outcome scale and a VAS scale for pain.

We have examined the process of fusion of the intertransverse processes and bone graft in the rabbit by in situ hybridisation and evaluated the spatial and temporal expression of genes encoding pro-α1 (I) collagen (COL1A1), pro-α1 (II) collagen (COL2A1) and pro-α1 (X) collagen (COL10A1).

Beginning at two weeks after operation, osteogenesis and chondrogenesis occurred around the transverse process and the grafted bone at the central portion of the area of the fusion mass. Osteoblasts and osteocytes at the newly-formed woven bone expressed COL1A1. At the cartilage, most chondrocytes expressed COL2A1 and some hypertrophic chondrocytes COL10A1. In some regions, co-expression of COL1A1 and COL2A1 was observed. At four weeks, such expressions for COL1A1, COL2A1 and COL10A1 became prominent at the area of the fusion mass. From four to six weeks, bone remodelling progressed from the area of the transverse processes towards the central zone. Osteoblasts lining the trabeculae expressed a strong signal for COL1A1. At the central portion of the area of the fusion mass, endochondral ossification progressed and chondrocytes expressed COL2A1 and COL10A1.

Our findings show that the fusion process begins with the synthesis of collagens around the transverse processes and around the grafted bone independently. Various spatial and temporal osteogenic and chondrogenic responses, including intramembranous, endochondral and transchondroid bone formation, progress after bone grafting at the intertransverse processes. Bone formation through cartilage may play an important role in posterolateral spinal fusion.

Aims. To determine whether obesity and malnutrition have a synergistic effect on outcomes from skeletal trauma or elective orthopaedic surgery. Methods. Electronic databases including MEDLINE, Global Health, Embase, Web of Science, ScienceDirect, and PEDRo were searched up to 14 April 2024, as well as conference proceedings and the reference lists of included studies. Studies were appraised using tools according to study design, including the Oxford Levels of Evidence, the Institute of Health Economics case series quality appraisal checklist, and the CLARITY checklist for cohort studies. Studies were eligible if they reported the effects of combined malnutrition and obesity on outcomes from skeletal trauma or elective orthopaedic surgery. Results. A total of eight studies (106,319 patients) were included. These carried moderate to high risk of bias. Combined obesity and malnutrition did not lead to worse outcomes in patients undergoing total shoulder arthroplasty or repair of proximal humeral fractures (two retrospective cohort studies). Three studies (two retrospective cohort studies, one case series) found that malnourishment and obesity had a synergistic effect and led to poor outcomes in total hip or knee arthroplasty, including longer length of stay and higher complication rates. One retrospective cohort study pertaining to posterior lumbar fusion found that malnourished obese patients had higher odds of developing surgical site infection and sepsis, as well as higher odds of requiring a revision procedure. Conclusion. Combined malnutrition and obesity have a synergistic effect and lead to poor outcomes in lower limb procedures. Appropriate preoperative optimization and postoperative care are required to improve outcomes in this group of patients. Cite this article: Bone Joint J 2024;106-B(10):1044–1049

Aims. Lumbar fusion is known to reduce the variation in pelvic tilt between standing and sitting. A flexible lumbo-pelvic unit increases the stability of total hip arthroplasty (THA) when seated by increasing anterior clearance and acetabular anteversion, thereby preventing impingement of the prosthesis. Lumbar fusion may eliminate this protective pelvic movement. The effect of lumbar fusion on the stability of total hip arthroplasty has not previously been investigated. Patients and Methods. The Medicare database was searched for patients who had undergone THA and spinal fusion between 2005 and 2012. PearlDiver software was used to query the database by the International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) procedural code for primary THA and lumbar spinal fusion. Patients who had undergone both lumbar fusion and THA were then divided into three groups: 1 to 2 levels, 3 to 7 levels and 8+ levels of fusion. The rate of dislocation in each group was established using ICD-9-CM codes. Patients who underwent THA without spinal fusion were used as a control group. Statistical significant difference between groups was tested using the chi-squared test, and significance set at p < 0.05. Results. At one-year follow-up, 14 747 patients were found to have had a THA after lumbar spinal fusion (12 079 1 to 2 levels, 2594 3 to 7 levels, 74 8+ levels). The control group consisted of 839 004 patients. The dislocation rate in the control group was 1.55%. A higher rate of dislocation was found in patients with a spinal fusion of 1 to 2 levels (2.96%, p < 0.0001) and 3 to 7 levels (4.12%, p < 0.0001). Patients with 3 to 7 levels of fusion had a higher rate of dislocation than patients with 1 to 2 levels of fusion (odds ratio (OR) = 1.60, p < 0.0001). When groups were matched for age and gender to the unfused cohort, patients with 1 to 2 levels of fusion had an OR of 1.93 (95% confidence interval (CI) 1.42 to 2.32, p < 0.001), and those with 3 to 7 levels of fusion an OR of 2.77 (CI 2.04 to 4.80, p < 0.001) for dislocation. Conclusion. Patients with a previous history of lumbar spinal fusion have a significantly higher rate of dislocation of their THA than age- and gender-matched patients without a lumbar spinal fusion. Cite this article: Bone Joint J 2017;99-B:585–91

Increasing numbers of posterior lumbar fusions are being performed. The purpose of this study was to identify trends in demographics, mortality and major complications in patients undergoing primary posterior lumbar fusion. We accessed data collected for the Nationwide Inpatient Sample for each year between 1998 and 2008 and analysed trends in the number of lumbar fusions, mean patient age, comorbidity burden, length of hospital stay, discharge status, major peri-operative complications and mortality. An estimated 1 288 496 primary posterior lumbar fusion operations were performed between 1998 and 2008 in the United States. The total number of procedures, mean patient age and comorbidity burden increased over time. Hospital length of stay decreased, although the in-hospital mortality (adjusted and unadjusted for changes in length of hospital stay) remained stable. However, a significant increase was observed in peri-operative septic, pulmonary and cardiac complications. Although in-hospital mortality rates did not change over time in the setting of increases in mean patient age and comorbidity burden, some major peri-operative complications increased. These trends highlight the need for appropriate peri-operative services to optimise outcomes in an increasingly morbid and older population of patients undergoing lumbar fusion.

Aims. As the population ages and the surgical complexity of lumbar spinal surgery increases, the preoperative stratification of risk becomes increasingly important. Understanding the risks is an important factor in decision-making and optimizing the preoperative condition of the patient. Our aim was to determine whether the modified five-item frailty index (mFI-5) and nutritional parameters could be used to predict postoperative complications in patients undergoing simple or complex lumbar spinal fusion. Methods. We retrospectively reviewed 584 patients who had undergone lumbar spinal fusion for degenerative lumbar spinal disease. The 'simple' group (SG) consisted of patients who had undergone one- or two-level posterior lumbar fusion. The 'complex' group (CG) consisted of patients who had undergone fusion over three or more levels, or combined anterior and posterior surgery. On admission, the mFI-5 was calculated and nutritional parameters collected. Results. Complications occurred in 9.3% (37/396) of patients in the SG, and 10.1% (19/167) of patients in the CG. In the SG, the important predictors of complications were age (odds ratio (OR) 1.036; p = 0.002); mFI-5 (OR 1.026 to 2.411, as score increased to 1 ≥ 2 respectively. ;. p = 0.023); albumin (OR 11.348; p < 0.001); vitamin D (OR 2.185; p = 0.032); and total lymphocyte count (OR 1.433; p = 0.011) . In the CG, the predictors of complications were albumin (OR 9.532; p = 0.002) and vitamin D (OR 3.815; p = 0.022). Conclusion. The mFI-5 and nutritional status were effective predictors of postoperative complications in the SG, but only nutritional status was successful in predicting postoperative complications in the CG. The complexity of the surgery, as well as the preoperative frailty and nutritional status of patients, should be considered when determining if it is safe to proceed with lumbar spinal fusion. Cite this article: Bone Joint J 2020;102-B(12):1717–1722