Contribution of Round vs. Rectangular Expandable Cage Endcaps to Spinal Stability in a Cadaveric Corpectomy Model

Risk factors affecting spinal fusion: A meta-analysis of 39 cohort studies

PURPOSE

We performed a meta-analysis to identify risk factors affecting spinal fusion.

METHODS

We systematically searched PubMed, Embase, and the Cochrane Library from inception to January 6, 2023, for articles that report risk factors affecting spinal fusion. The pooled odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using fixed-effects models for each factor for which the interstudy heterogeneity I2 was < 50%, while random-effects models were used when the interstudy heterogeneity I2 was ≥ 50%. Using sample size, Egger's P value, and heterogeneity across studies as criteria, we categorized the quality of evidence from observational studies as high-quality (Class I), moderate-quality (Class II or III), or low-quality (Class IV). Furthermore, the trim-and-fill procedure and leave-one-out protocol were conducted to investigate potential sources of heterogeneity and verify result stability.

RESULTS

Of the 1,257 citations screened, 39 unique cohort studies comprising 7,145 patients were included in the data synthesis. High-quality (Class I) evidence showed that patients with a smoking habit (OR, 1.57; 95% CI, 1.11 to 2.21) and without the use of bone morphogenetic protein-2 (BMP-2) (OR, 4.42; 95% CI, 3.33 to 5.86) were at higher risk for fusion failure. Moderate-quality (Class II or III) evidence showed that fusion failure was significantly associated with vitamin D deficiency (OR, 2.46; 95% CI, 1.24 to 4.90), diabetes (OR, 3.42; 95% CI, 1.59 to 7.36), allograft (OR, 1.82; 95% CI, 1.11 to 2.96), conventional pedicle screw (CPS) fixation (OR, 4.77; 95% CI, 2.23 to 10.20) and posterolateral fusion (OR, 3.63; 95% CI, 1.25 to 10.49).

CONCLUSIONS

Conspicuous risk factors affecting spinal fusion include three patient-related risk factors (smoking, vitamin D deficiency, and diabetes) and four surgery-related risk factors (without the use of BMP-2, allograft, CPS fixation, and posterolateral fusion). These findings may help clinicians strengthen awareness for early intervention in patients at high risk of developing fusion failure.

Technical nuances and approach-related morbidity of anterolateral and posterolateral lumbar corpectomy approaches-a systematic review of the literature

Purpose

Approaches for lumbar corpectomies can be roughly categorized into anterolateral (AL) and posterolateral (PL) approaches. It remains controversial to date whether one approach is superior to the other, and no comparative studies exist for the two approaches for lumbar corpectomies.

Methods

A systematic review of the literature was performed through a MEDLINE/PubMed search. Studies and case reports describing technique plus outcomes and possible complications were included. Thereafter, estimated blood loss (EBL), length of operation (LOO), utilized implants, neurological outcomes, complication rates, and reoperation rates were analyzed.

Results

A total of 64 articles reporting on 702 patients including 513 AL and 189 PL corpectomies were included in this paper. All patients in the PL group were instrumented via the same approach used for corpectomy, while in the AL group the majority (68.3%) of authors described the use of an additional approach for instrumentation. The EBL was higher in the AL group (1393 ± 1341 ml vs. 982 ± 567 ml). The LOO also was higher in the AL group (317 ± 178 min vs. 258 ± 93 min). The complication rate (20.5% vs. 29.1%, p = 0.048) and the revision rate (3.1% vs. 9.5%, p = 0.004) were higher in the PL group. Neurological improvement rates were 43.8% (AL) vs. 39.2% (PL), and deterioration was only noted in the AL group (6.0%), while 50.2% (AL) and 60.8% (PL) showed no change from initial presentation to the last follow-up.

Conclusion

While neurological outcomes of both approaches are comparable, the results of the present review demonstrated lower complication and revision rates in anterolateral corpectomies. Nevertheless, individual patient characteristics must be considered in decision-making.

Radiological Evaluation of Combined Anteroposterior Fusion with Vertebral Body Replacement Using a Minimally Invasive Lateral Approach for Osteoporotic Vertebral Fractures: Verification of Optimal Surgical Procedure

The combined anteroposterior fusion with vertebral body replacement (VBR) using a wide footplate expandable cage with a minimally invasive lateral approach has been widely used for pseudoarthrosis after osteoporotic vertebral fractures. The purpose of this study is to evaluate the radiological results of combined anteroposterior surgery using VBR and to recommend the optimal procedure. Thirty-eight elderly patients were included in this study. The mean preoperative local kyphosis angle was 29.3°, and the mean correction loss angle was 6.3°. Cage subsidence was observed in ten patients (26.3%), and UIV or LIV fracture in twelve patients (31.6%). Patients with cage subsidence were compared to those without cage subsidence to determine the causal factors. The mean number of fixed vertebrae was 5.4 vertebrae with cage subsidence and 7.4 vertebrae without cage subsidence. In addition, to precisely clarify the optimal number of fixed vertebrae, those patients with two above–two below fixation were compared to those with less than two above–two below fixation, which revealed that the correction loss angle was significantly less in two above–two below fixation (p = 0.016). Based on these results, we recommend at least two above–two below fixation with VBR to minimize the correction loss angle and prevent cage subsidence.

Comparison of Outcomes between Minimally Invasive Lateral Approach Vertebral Reconstruction Using a Rectangular Footplate Cage and Conventional Procedure Using a Cylindrical Footplate Cage for Osteoporotic Vertebral Fracture

The aim of the current study was to compare outcomes between lateral access vertebral reconstruction (LAVR) using a rectangular footplate cage and the conventional procedure using a cylindrical footplate cage in patients with osteoporotic vertebral fracture (OVF). We included 46 patients who underwent anterior-posterior combined surgery for OVF: 24 patients underwent LAVR (Group L) and 22 underwent the conventional procedure (Group C). Preoperative, postoperative, and 1- and 2-year follow-up X-ray images were used to measure local lordotic angle, correction loss, and cage subsidence (>2 mm in vertebral endplate depression). In anterior surgery, the operation time was significantly shorter (183 vs. 248 min, p < 0.001) and the blood loss was significantly less (148 vs. 406 mL, p = 0.01) in Group L than in Group C. In Group C, two patients had anterior instrumentation failure. Correction loss was significantly smaller in Group L than in Group C (1.9° vs. 4.9° at 1 year, p = 0.02; 2.5° vs. 6.5° at 2 years, p = 0.04, respectively). Cage subsidence was significantly less in Group L than in Group C (29% vs. 80%, p < 0.001). LAVR using a rectangular footplate cage is an effective treatment for OVF to minimize surgical invasiveness and postoperative correction loss.

Lag-Screw Osteosynthesis in Thoracolumbar Pincer Fractures

STUDY DESIGN

Biomechanical.

OBJECTIVE

This study evaluates the biomechanical properties of lag-screws used in vertebral pincer fractures at the thoracolumbar junction.

METHODS

Pincer fractures were created in 18 bisegmental human specimens. The specimens were assigned to three groups depending on their treatment perspective, either bolted, with the thread positioned in the cortical or cancellous bone, or control. The specimens were mounted in a servo-hydraulic testing machine and loaded with a 500 N follower load. They were consecutively tested in 3 different conditions: intact, fractured, and bolted/control. For each condition 10 cycles in extension/flexion, torsion, and lateral bending were applied. After each tested condition, a computed tomography (CT) scan was performed. Finally, an extension/flexion fatigue loading was applied to all specimens.

RESULTS

Biomechanical results revealed a nonsignificant increase in stiffness in extension/flexion of the fractured specimens compared with the intact ones. For lateral bending and torsion, the stiffness was significantly lower. Compared with the fractured specimens, no changes in stiffness due to bolting were discovered. CT scans showed an increasing fracture gap during axial loading both in extension/flexion, torsion, and lateral bending in the control specimens. In bolted specimens, the anterior fragment was approximated, and the fracture gap nullified. This refers to both the cortical and the cancellous thread positions.

CONCLUSION

The results of this study concerning the effect of lag-screws on pincer fractures appear promising. Though there was little effect on stiffness, CT scans reveal a bony contact in the bolted specimens, which is a requirement for bony healing.

Prone transpsoas lumbar corpectomy: simultaneous posterior and lateral lumbar access for difficult clinical scenarios

OBJECTIVE

Lateral lumbar corpectomy with interbody fusion has been well described via a transpsoas approach in the lateral position, as has lumbar interbody fusion with posterior fixation in the prone position. However, no previous report has described the use of both an open posterior approach and a lateral transpsoas approach simultaneously in the prone position. Here, the authors describe their technique of performing transpsoas lumbar corpectomy in the prone position in order to have simultaneous posterior and lateral access for difficult clinical scenarios, and they report their early clinical experience.

METHODS

The surgical technique for simultaneous posterior and lateral transpsoas access to the lumbar spine was reviewed and described in detail. The cases of 2 patients who underwent simultaneous posterior and lateral access in the prone position for complex lumbar pathology were retrospectively reviewed. Clinical presentation, preoperative radiographs, postoperative course, and postoperative radiographs were reviewed.

RESULTS

The first patient presented after previous transforaminal lumbar interbody fusion that was complicated by significant subsidence of the intervertebral cage, vertebral body split fracture, rotational instability, and resulting spinal stenosis. A simultaneous posterior and lateral transpsoas approach in the prone position allowed for removal of the previous cage, lumbar corpectomy, and rigid posterior fixation with direct decompression. The second patient had a significant pathologic burst fracture secondary to a plasmacytoma with retropulsion, resulting in vertebra plana and significant canal stenosis. Simultaneous approaches allowed for complete resection of the plasmacytoma, restoration of lumbar alignment, rigid fixation, and direct posterior decompression. There were no short-term complications, and both patients had resolution of their preoperative symptoms.

CONCLUSIONS

Simultaneous posterior and lateral transpsoas access to the lumbar spine in the prone position is a previously unreported technique that allows a safe surgical approach to difficult clinical scenarios.

Thoracolumbar Vertebral Column Resection With Rectangular Endplate Cages Through a Posterior Approach: Surgical Techniques and Early Postoperative Outcomes

BACKGROUND

Thoracolumbar pathology can result in compression of neural elements, instability, and deformity. Circumferential decompression with anterior column reconstruction is often required to restore biomechanical stability and minimize the risk of implant failure.

OBJECTIVE

To assess the safety and viability of wide-footprint rectangular cages for vertebral column resection (VCR).

METHODS

We performed VCR with wide-footprint rectangular endplate cages, which were designed for transthoracic or retroperitoneal approaches. We present our technique using a single-stage posterior approach.

RESULTS

A total of 45 patients underwent VCR with rectangular endplate cages. Mean age was 58 yr. Diagnoses included 23 tumors (51%), 14 infections (31%), and 8 deformities (18%). VCRs were performed in 10 upper thoracic, 17 middle thoracic, 14 lower thoracic, and 4 lumbar levels. Twenty-four cases involved a single level VCR (53%) with 18 two-level (40%) and 3 three-level (7%) VCRs. Average procedure duration was 264 min with mean estimated blood loss of 1900 ml. Neurological outcomes were stable in 27 cases (60%), improved in 16 (36%), and worse in 2 (4%). There were 7 medical and 7 surgical complications in 11 patients. There were significant decreases in postoperative thoracic kyphosis (47° vs 35°, P = .022) and regional kyphosis (34° vs 10°, P < .001). There were 2 cases of cage subsidence due to intraoperative endplate violation, neither of which progressed on CT scan at 14 and 35 mo.

CONCLUSION

Posterior VCR with rectangular footprint cages is safe and feasible. This provides improved biomechanical stability without the morbidity of a lateral transthoracic or retroperitoneal approach.

Stabilizing effect of the rib cage on adjacent segment motion following thoracolumbar posterior fixation of the human thoracic cadaveric spine: A biomechanical study

BACKGROUND

Although the rib cage provides substantial stability to the thoracic spine, few biomechanical studies have incorporated it into their testing model, and no studies have determined the influence of the rib cage on adjacent segment motion of long fusion constructs. The present biomechanical study aimed to determine the mechanical contribution of the intact rib cage during the testing of instrumented specimens.

METHODS

A cyclic loading (CL) protocol with instrumentation (T4-L2 pedicle screw-rod fixation) was conducted on five thoracic spines (C7-L2) with intact rib cages. Range of motion (±5 Nm pure moment) in flexion-extension, lateral bending, and axial rotation was captured for intact ribs, partial ribs, and no ribs conditions. Comparisons at the supra-adjacent (T2-T3), adjacent (T3-T4), first instrumented (T4-T5), and second instrumented (T5-T6) levels were made between conditions (P ≤ 0.05).

FINDINGS

A trend of increased motion at the adjacent level was seen for partial ribs and no ribs in all 3 bending modes. This trend was also observed at the supra-adjacent level for both conditions. No significant changes in motion compared to the intact ribs condition were seen at the first and second instrumented levels (P > 0.05).

INTERPRETATION

The segment adjacent to long fusion constructs, which may appear more grossly unstable when tested in the disarticulated spine, is reinforced by the rib cage. In order to avoid overestimating adjacent level motion, when testing the effectiveness of surgical techniques of the thoracic spine, inclusion of the rib cage may be warranted to better reflect clinical circumstances.

Influence of additional cement augmentation on endplate stability in circumferential stabilisation of osteoporotic spine fractures

BACKGROUND

Anterior stabilisation of osteoporotic spine fractures is uncommon but necessary in the case of complex vertebral body comminution. The purpose of this study was to investigate the effect of additional cement-augmentation on the endplate stability.

METHODS

Twelve human cadaveric lumbar spines were divided in two groups: (A) posterior cement-augmented pedicle screw/rod-based instrumentation of L3 to L5, posterior decompression of L4/5 and partial corpectomy of L4 and (B) same experimental setup with additional cement-augmentation of the adjacent endplates. A cyclic loading test was performed at a frequency of 3 Hz, starting with a peak of 500 N for the first 2.000 cycles, up to 950 N for 100.000 cycles under a general preload with 50 N. All specimens were evaluated with regard to a potential collapse of the adjacent endplates. Subsequently, the maximum zero-time failure load of all specimens was determined using a universal testing machine.

FINDINGS

The median T-score of bone density was -4.32 (range -2.97 to -5.59), distributed equally in the two groups (average age 83 years). The specimen of the endplate-augmented group showed a significant higher failure load compared to non-endplate-augmented cadavers (group A: 2038 N, group B: 2990 N, p = 0.03). All specimens passed the full cyclic loading protocol with 100.000 cycles. No significant difference was observable regarding the adjacent endplate subsidence.

INTERPRETATION

Additional cement augmentation in circumferential stabilisation resulted in a significant enhancement of the endplate stability regarding the maximum axial load, while the cyclic loading did not significantly enhance the fatigue endurance of the vertebral endplates over the 100,000 cycles tested.

Application value of expansive pedicle screw in the lumbar short-segment fixation and fusion for osteoporosis patients

Clinical value of expansive pedicle screw in lumbar short-segment fixation and fusion for patients with osteoporosis was investigated. A total of 80 patients with lumbar compression fracture but without obvious nerve compression were selected and divided into the observation group (n=40) and the control group (n=40) using a random number table. The observation group used the expansive pedicle screw, and the control group received conventional pedicle screw fixation and bone graft fusion. In the observation group, the operation and hospitalization time after operation were shorter and the intraoperative bleeding amount was less than that in control group (p<0.05). At 1 week, 1, 3 and 6 months after operation, the observation group had better straight leg raising test (SLRT) scores, higher lower limb sensory scores but lower visual analogue scale (VAS) scores than control group (p<0.05). Besides, the proportions of postoperative infection, dural mater tear, nerve root injury and spinal cord injury during operation in the observation group were lower than those in the control group (p<0.05), and the bone graft fusion rates at 3 and 6 months after operation were obviously superior to those in control group (p<0.05). Moreover, after operation, the spinal stenosis rate in the observation group was lower than that in control group (p<0.05), the vertebral height ratio was larger than that in control group (p<0.05), and the Cobb's angle was smaller than that in the control group (p<0.05). In addition, there was a negative correlation between bone mineral density (BMD) and hospitalization time after operation in the observation group (p<0.05). In conclusion, the internal fixation with expansive pedicle screw for osteoporosis patients with lumbar compression fracture is characterized by short operation time, less intraoperative bleeding, few complications, quick recovery of postoperative neurological function and satisfactory surgical effect. However, reasonable intervention in osteoporosis is also necessary.

Minimally invasive surgery for thoracolumbar spinal trauma

The indications for operative intervention after thoracolumbar spine trauma have been well described. Advances in minimally invasive techniques, including percutaneous pedicle screw fixation and mini-open anterolateral retractor-based approaches can improve surgical outcomes when appropriately applied by reducing blood loss, operative duration and post-operative pain. Moreover, they allow for theoretical advantages by preservation of muscular and skeletal blood supply and innervation that is typically lost during the muscular dissection of open approaches. For thoracolumbar spine fractures, percutaneous fixation allows for internal bracing of unstable fractures during healing while maintaining sagittal alignment. In instances of neurological compromise from fracture retropulsion, corpectomies may be required, and mini-open lateral approaches adopted from degenerative disease applications allow for a minimally invasive manner to treat the defect. These further allow for placement of wide rectangular-footprint expandable vertebral body replacement devices to provide anterior column support. We believe this allows for lower rates of subsidence and helps to maintain the biomechanical integrity necessary to prevent post-traumatic malalignment and kyphosis. Together, these minimally invasive techniques combined supply the spine surgeon with a minimally invasive armamentarium to treat nearly all thoracolumbar spine trauma. Surgeons should be comfortable with the strengths and shortcomings of these approaches in order to successfully apply them for this pathology.

Does pedicle screw fixation of the subaxial cervical spine provide adequate stabilization in a multilevel vertebral body fracture model? An in vitro biomechanical study

BACKGROUND

Cervical vertebral body fractures generally are treated through an anterior-posterior approach. Cervical pedicle screws offer an alternative to circumferential fixation. This biomechanical study quantifies whether cervical pedicle screws alone can restore the stability of a three-column vertebral body fracture, making standard 360° reconstruction unnecessary.

METHODS

Range of motion (2.0 Nm) in flexion-extension, lateral bending, and axial rotation was tested on 10 cadaveric specimens (five/group) at C2-T1 with a spine kinematics simulator. Specimens were tested for flexibility of intact when a fatigue protocol with instrumentation was used to evaluate construct longevity. For a C4-6 fracture, spines were instrumented with 360° reconstruction (corpectomy spacer + plate + lateral mass screws) (Group 1) or cervical pedicle screw reconstruction (C3 and C7 only) (Group 2).

FINDINGS

Results are expressed as percentage of intact (100%). In Group 1, 360° reconstruction resulted in decreased motion during flexion-extension, lateral bending, and axial rotation, to 21.5%, 14.1%, and 48.6%, respectively, following 18,000 cycles of flexion-extension testing. In Group 2, cervical pedicle screw reconstruction led to reduced motion after cyclic flexion-extension testing, to 38.4%, 12.3%, and 51.1% during flexion-extension, lateral bending, and axial rotation, respectively.

INTERPRETATION

The 360° stabilization procedure provided the greatest initial stability. Cervical pedicle screw reconstruction resulted in less change in motion following cyclic loading with less variation from specimen to specimen, possibly caused by loosening of the shorter lateral mass screws. Cervical pedicle screw stabilization may be a viable alternative to 360° reconstruction for restoring multilevel vertebral body fracture.