Subsidence of Interbody Cage Following Oblique Lateral Interbody Fusion: An Analysis and Potential Risk Factors

Study Design Retrospective cohort study Objectives This study aimed to report the incidence and potential risk factors of polyetheretherketone (PEEK) cage subsidence following oblique lateral interbody fusion (OLIF) for lumbar degenerative diseases. We proposed also an algorithm to minimize subsidence following OLIF surgery. Methods The study included a retrospective cohort of 107 consecutive patients (48 men and 59 women; mean age, 67.4 years) who had received either single- or multi-level OLIF between 2012 and 2019. Patients were classified into subsidence and non-subsidence groups. PEEK cage subsidence was defined as any violation of either endplate from the computed tomography scan in both sagittal and coronal views. Preoperative variables such as age, sex, body mass index, bone mineral density (BMD) measured by preoperative dual-energy X-ray absorptiometry, smoking status, corticosteroid use, diagnosis, operative level, multifidus muscle cross-sectional area, and multifidus muscle fatty degeneration were collected. Age-related variables (height and length) were also documented. Univariate and multivariate logistic regression analyses were used to analyze the risk factors of subsidence. Results Of the 107 patients (137 levels), 50 (46.7%) met the subsidence criteria. Higher PEEK cage height had the strongest association with subsidence (OR = 9.59, P < .001). Other factors significantly associated with cage subsistence included age >60 years (OR = 3.15, P = .018), BMD <−2.5 (OR = 2.78, P = .006), and severe multifidus muscle fatty degeneration (OR = 1.97, P = .023). Conclusions Risk factors for subsidence in OLIF were age >60 years, BMD < −2.5, higher cage height, and severe multifidus muscle fatty degeneration. Patients who had subsidence had worse early (3 months) postoperative back and leg pain.

Biomechanical analysis of stand-alone lumbar interbody cages versus 360° constructs: an in vitro and finite element investigation

OBJECTIVE Low fusion rates and cage subsidence are limitations of lumbar fixation with stand-alone interbody cages. Various approaches to interbody cage placement exist, yet the need for supplemental posterior fixation is not clear from clinical studies. Therefore, as prospective clinical studies are lacking, a comparison of segmental kinematics, cage properties, and load sharing on vertebral endplates is needed. This laboratory investigation evaluates the mechanical stability and biomechanical properties of various interbody fixation techniques by performing cadaveric and finite element (FE) modeling studies. METHODS An in vitro experiment using 7 fresh-frozen human cadavers was designed to test intact spines with 1) stand-alone lateral interbody cage constructs (lateral interbody fusion, LIF) and 2) LIF supplemented with posterior pedicle screw-rod fixation (360° constructs). FE and kinematic data were used to validate a ligamentous FE model of the lumbopelvic spine. The validated model was then used to evaluate the stability of stand-alone LIF, transforaminal lumbar interbody fusion (TLIF), and anterior lumbar interbody fusion (ALIF) cages with and without supplemental posterior fixation at the L4–5 level. The FE models of intact and instrumented cases were subjected to a 400-N compressive preload followed by an 8-Nm bending moment to simulate physiological flexion, extension, bending, and axial rotation. Segmental kinematics and load sharing at the inferior endplate were compared. RESULTS The FE kinematic predictions were consistent with cadaveric data. The range of motion (ROM) in LIF was significantly lower than intact spines for both stand-alone and 360° constructs. The calculated reduction in motion with respect to intact spines for stand-alone constructs ranged from 43% to 66% for TLIF, 67%–82% for LIF, and 69%–86% for ALIF in flexion, extension, lateral bending, and axial rotation. In flexion and extension, the maximum reduction in motion was 70% for ALIF versus 81% in LIF for stand-alone cases. When supplemented with posterior fixation, the corresponding reduction in ROM was 76%–87% for TLIF, 86%–91% for LIF, and 90%–92% for ALIF. The addition of posterior instrumentation resulted in a significant reduction in peak stress at the superior endplate of the inferior segment in all scenarios. CONCLUSIONS Stand-alone ALIF and LIF cages are most effective in providing stability in lateral bending and axial rotation and less so in flexion and extension. Supplemental posterior instrumentation improves stability for all interbody techniques. Comparative clinical data are needed to further define the indications for stand-alone cages in lumbar fusion surgery.

An experimental study of the femoral nerve in the long-term periods after modeling lateral interbody spondylodesis of the lumbar spine

Neuropathies of the lumbar plexus trunks, in particular those of the femoral nerve, are the most common complications of lateral interbody spondylodesis of the lumbar spine. Modeling of this surgical intervention in normal animals experimentally makes it possible to assess the degree of its trauma to the nervous structures, and to understand what is the reason for the persistence or aggravation of neurological symptoms iatrogenic injuries or the existing pathology progression. Purpose of the Study. To study histological and morphometric changes in the femoral nerve in the long-term periods after modeling of the lateral interbody spondylodesis of the canine lumbar spine. Design of the Study. An experimental prospective continuous uncontrolled study. Material and Methods. Discectomy via lateral approach was performed in 18 mongrel dogs (aged 2-3 years, mass 13.2-17.6 kg) at the level of L4-5 и L5-6, interbody titanium implants were mounted, the lumbar spine was stabilized with a wire device for external fixation within 30 days. Clinical-and-neurological evaluation was performed, as well as histological investigation of the femoral nerves from the side of surgical approach. Results. In the early postoperative period a temporary decrease in the femoral nerve function was observed, which was manifested by the disorder of the support function and muscle weakness of the pelvic limbs, decrease in the knee reflex, the foot support shift to the metatarsal pad. Later, until the end of the study (18 months), the general condition of all animals was satisfactory, there were no disorders of the limb support function and motor reflexes. After six months, in the femoral nerve there was 4-fold decrease in the proportion of large fast-conducting myelin fibers D 10 m and 3-fold increase in that of the small ones. The mean axon diameter and myelin thickness were 62% and 53% of the norm. After 12-18 months, the dimensional characteristics of myelin fibers were restored. During the entire experiment, 4-6% of myelin fibers were reactively-and-destructively altered. Conclusions. The modeling of the lateral interbody spondylodesis of the lumbar spine in normal animals experimentally demonstrated the absence of neurological symptoms after 6-18 months, which indicated low invasiveness of the surgical intervention. Nevertheless, the subclinical reactive-and-destructive changes in the myelin fibers of the femoral nerve revealed 6 months after the surgery indicated the need for preventive anti-neurotic therapy.

The Role of Hounsfield Unit in Intraoperative Endplate Violation and Delayed Cage Subsidence with Oblique Lateral Interbody Fusion

Study Design Retrospective clinical case series. Objectives To investigate the risk factors for intraoperative endplate violations and delayed cage subsidence after oblique lateral interbody fusion (OLIF) surgery. Secondly, to examine whether low Hounsfield unit (HU) values at different regions of the endplate are associated with intraoperative endplate violation or delayed cage subsidence. Methods 61 patients (aged 65.1 ± 9.5 years; 107 segments) who underwent OLIF with or without posterior instrumentation from May 2015 to April 2019 were retrospectively studied. Intraoperative endplate violation was measured on sagittal reconstructed computerized tomography (CT) images immediate postoperatively, while delayed cage subsidence was evaluated using lateral radiographs and defined at 1-month follow-up or later. Demographic information and clinical parameters such as age, body mass index, bone mineral density, number of surgical levels, cage dimension, disc height restoration, visual analogue scale (VAS), and HU at different regions of the endplate were obtained. Results Total postoperative cage subsidence was identified in 45 surgical levels (42.0%) in 26 patients (42.6%) up till postoperative 1-year follow-up. Low HU value at the ipsilateral epiphyseal ring was an independent risk factor for intraoperative endplate violation ( P = .008) with a cut-off value of 326.21 HUs. Low HU values at the central endplate had a significant correlation with delayed cage subsidence in stand-alone cases ( P = .013) with a cut-off value of 296.42 HUs. VAS scores were not different at 1 week postoperatively in cases with or without intraoperative endplate violation (3.12 ± .73 vs 2.89 ± .72, P = .166) and showed no difference at 1 year with or without delayed cage subsidence (1.95 ± .60 vs 2.26 ± .85, P = .173). Conclusions Intraoperative endplate violation and delayed cage subsidence are not uncommon with OLIF surgery. HUs of the endplate are good predictors for intraoperative endplate violation and cage subsidence since they can represent the regional bone quality of the endplate in contact with the implant. VAS improvements were not affected by intraoperative endplate violation or delayed cage subsidence at 1-year follow-up. Level of Evidence Level III.

Oblique Lateral Interbody Fusion Combined with Lateral Plate VS. Combined with Posterior Pedicle Screw Fixation in Lumbar Degenerative Diseases

Background The oblique lateral interbody fusion (OLIF) is a minimally invasive indirect decompression technique for the treatment of degenerative spinal disease. OLIF with posterior pedicle screws fixation frequently is performed, whereas it requires much more surgery time and blood loss. The purpose of this study was to compare the oblique lateral interbody fusion (OLIF) combined with lateral plate (LP) vs. OLIF combined with posterior pedicle screw (PS) fixation for the treatment of lumbar degenerative diseases.Methods The clinical data of 53 patients with lumbar degenerative diseases who underwent OLIF from January 2020 to September 2020 were retrospectively analyzed，24 in OLIF combined with lateral plate (OLIF+LP) group and 29 in OLIF combined with pedicle screw (OLIF+PS) group. All patients completed a minimum 1-year follow-up. The duration of operation, blood loss, fusion rate and complications were recorded. The visual analog scale (VAS) score, Oswestry Disability Index (ODI), disc height (DH), foraminal height (FH) and cross-sectional area (CSA) were also evaluated.Results The operation time was 75.41±11.53 min in the OLIF+LP group, which shorter than that in OLIF+PS group(127.05±5.62min, P<0.01). Also, the blood loss was significantly less in the OLIF+LP group (39.55±5.32 ml ) than in the OLIF+PS group (89.81±9.62, P<0.01). The VAS and ODI scores both significantly reduced after operation in OLIF+LP group. There was no difference either in VAS or ODI scores by 1 year after surgery between two groups (P>0.01). The DH, FH, and CSA parameters were all improved significantly after operation in both groups, however, there was no significant difference at the any follow-up point between the two groups. The total complication rate was 13.21% (7/53) in this study, and there was no siginificant difference between the two groups. The fusion rate was 91.67% in the OLIF+LP group and 93.10% in the OLIF+PS group (P =0.69).Conclusions OLIF+LP fixation seems to be a valuable surgical option for single-segmental lumbar degenerative disease, it can achieve much better clinical outcomes than OLIF+PS group.

Curative Effect of Oblique Lateral Interbody Fusion in the Treatment of Lumbar Tuberculosis

Objective: This research aimed to investigate the curative effect of oblique lateral interbody fusion (OLIF) in the treatment of lumbar tuberculosis. Methods: A total of 32 patients, including 18 males and 14 females (29-58 years old, with the mean age of 47) who were admitted to our hospital from October 2016 to June 2020 and treated with oblique lateral interbody fusion combined with vertebral screw internal fixation, were retrospectively collected. The segmental distribution of lesions was L2- L316 cases, L3-L411 cases and L4-L55 cases. At first, preoperative antituberculous drug treatment was standardized for 2-4 weeks. Furthermore, intraoperative blood loss, operation time, postoperative complications, ESR, CRP, VAS, JOA and ASIA scores were recorded before and after surgery and at the last follow-up. In addition, antituberculous drug therapy was regulated continuously after surgery.Results: All patients were followed up for 12-17 months, with an average of 14 months. ① The average operation time was (132.5±21.4) min, and the intraoperative blood loss was (227.3±43.1) ml. ② Preoperative ESR was (74.56±15.43) mmol/h, and CRP was (43.21±19.37) mg/L. Seven days after surgery, ESR was (42.37±19.26) mmol/h, and CRP was (22.51±18.42) mg/L. In the last follow-up, ESR was (9.25±4.13) mmol/h, and CRP was (8.17±3.21) mg/L. They have statistically significant differences before surgery, seven days after the surgery and in the last follow-up (P<0.05). ③ The average VAS score before surgery was (7.21±1.40) points, the average JOA score was (18.24±4.13) points, the average VAS score seven days after surgery was (2.23±1.32) points, the average JOA score was (24.72±3.19) points, and the average VAS score in the last follow-up was (1.63±0.54) points. JOA score was (27.72±2.61). They have statistically significant differences before surgery, seven days after the surgery and in the last follow-up (P<0.05) ④Six patients had neurologic symptoms with ASIA grade D before surgery, 2 patients recovered to Grade E seven days after surgery, and the remaining 4 patients also recovered to grade E in the last follow-up. Besides, 26 patients were graded as Grade E before surgery, seven days after surgery and in the last follow-up. ⑤ After surgery, 1 patient suffered psoas major muscle damage, which was manifested as reduced hip flexion strength of the lower extremity, and returned to normal three weeks later. Apart from that, none of the patients had complications such as abdominal organ injury and poor wound healing. Conclusion: OLIF is a new minimally invasive method for treating lumbar tuberculosis, with short operation time, less blood loss, convenient operation, thorough removal of lesions, and good long-term follow-up effect. It is worthy of promotion and application.