The effect of polymethylmethacrylate augmentation on the primary stability of stand-alone implant construct versus posterior stabilization in oblique lumbar interbody fusion with osteoporotic bone quality- a finite element study.

BACKGROUND CONTEXT: Oblique lumbar interbody fusion (OLIF) can provide an ideal minimally invasive solution for achieving spinal fusion in an older, more frail population where decreased bone quality can be a limiting factor. Stabilization can be achieved with bilateral pedicle screws (BPS), which require additional incisions and longer operative time. Alternatively, a novel self-anchoring stand-alone lateral plate system (SSA) can be used, where no additional incisions are required. Based on the relevant literature, BPS constructs provide greater primary biomechanical stability compared to lateral plate constructs, including SSA. This difference is further increased by osteoporosis. Screw augmentation in spinal fusion surgeries is commonly used; however, in the case of OLIF, it is a fairly new concept, lacking a consensus-based guideline. PURPOSE: This comparative finite element (FE) study aimed to investigate the effect of PMMA screw augmentation on the primary stability of a stand-alone implant construct versus posterior stabilization in OLIF with osteoporotic bone quality. STUDY DESIGN: The biomechanical effect of screw augmentation was studied inside an in-silico environment using computer-aided FE analysis. METHODS: A previously validated and published L2-L4 FE model with normal and osteoporotic bone material properties was used. Geometries based on the OLIF implants (BPS, SSA) were created and placed inside the L3-L4 motion segment with increasing volumes (1-6 cm3) of PMMA augmentation. A follower load of 400 N and 10 Nm bending moment (in the three anatomical planes) were applied to the surgical FE models with different bone material properties. The operated L3-L4 segmental range of motion (ROM), the inserted cage's maximal caudal displacements, and L4 cranial bony endplate principal stress values were measured. RESULTS: The nonaugmented values for the BPS construct were generally lower compared to SSA, and the difference was increased by osteoporosis. In osteoporotic bone, PMMA augmentation gradually decreased the investigated parameters and the difference between the two constructs as well. Between 3 cm3 and 4 cm3 of injected PMMA volume per screw, the difference between augmented SSA and standard BPS became comparable. CONCLUSIONS: Based on this study, augmentation can enhance the primary stability of the constructs and decrease the difference between them. Considering leakage as a possible complication, between 3 cm3 and 4 cm3 of injected PMMA per screw can be an adequate amount for SSA augmentation. However, further in silico, and possibly in vitro and clinical testing is required to thoroughly understand the investigated biomechanical aspects. CLINICAL SIGNIFICANCE: This study sheds light on the possible biomechanical advantage offered by augmented OLIF implants and provides a theoretical augmentation amount for the SSA construct. Based on the findings, the concept of an SSA device with PMMA augmentation capability is desirable.

Complication Pattern of Sacral Primary Tumor Resection: A Study on the Risk Factors of Surgical Site Infection and Bowel or Bladder Dysfunction and Their Associations with Length of Hospital Stay.

STUDY DESIGN: Retrospective open cohort study. PURPOSE: The current study aimed to explore the pattern of complications after primary sacral tumor resection, to investigate the possible effect of several perioperative parameters on the development of complications, and to identify which complications are associated with the length of hospital stay (LOS). OVERVIEW OF LITERATURE: Primary sacral tumor (pST) resection is associated with a high complication rate. However, the number of studies on these complications and their effect on LOS is limited. METHODS: The clinical data of 140 patients with pST surgeries and 106 subsequent patients with local recurrence surgeries in four subgroups (index surgery, local recurrence surgery, malignant, and benign tumor) were prospectively collected and analyzed. The prognostic value of several perioperative factors on the development of surgical site infection (SSI), bowel and bladder dysfunction (BBD), and LOS was investigated using the logistic and linear regression models. RESULTS: The overall complication rates were 61.2% after index surgeries and 50.9% after local recurrence surgeries. The most frequent complications were SSI, vegetative dysfunction, urinary tract infections, and neurological deterioration. Age >55 years, malignant tumors, and red blood cell transfusion had a predictive effect on the development of SSI in the logistic model (p<0.01, R2=0.43). Bilateral S2 or S3 resection commonly caused postoperative BBD (chi-square test=62.5, degrees of freedom=4, p<0.001). In the multiple linear regression model, wound dehiscence, BBD, systemic and urinary tract infection, cerebrospinal fluid leak, and neurologic deterioration were associated with a significantly long LOS (p<0.01, R2=0.62). CONCLUSIONS: Surgical resection of pSTs has a high complication rate. Its common complications are SSI and BBD, both of which can have a significant influence on global therapeutic outcome. Malignant tumor diagnosis, old age, and red blood cell transfusion can remarkably increase the risk of SSI. Further, the development of BBD is significantly associated with the number of resected sacral nerve roots. By decreasing perioperative complications, LOS can decrease significantly.

Quality of Life Following Prestige LP Cervical Disc Arthroplasty in a Prospective Multicountry Study.

BACKGROUND: To describe routine surgical practice using Prestige LP Cervical Disc (Prestige disc) and patient outcomes for degenerative cervical disc disease in a multicenter 2-year prospective, observational study. METHODS: Patient demographics and intraoperative data were collected; quality of life (QoL) (EQ-5D, EQ-VAS, and neck disability index), average disc height, and adverse events were assessed pre- and postoperatively at 3, 6, 12, and 24 months. RESULTS: One hundred and ninety-four patients were enrolled (190 patients implanted; female: 67%; mean age: 44.0 years; mean body mass index: 25.6). Disc herniation was the most frequent indication for cervical arthroplasty (80.5%). Thirty-seven percent of patients experienced pain for >1 year prior to baseline assessment. Mean procedure duration was 87.1 minutes, and mean blood loss was 43.8 mL. The majority (71.0%) of Prestige discs were implanted at level C5 to C6, while 16.3% of patients received implants at 2 levels. There was a significant improvement from baseline to 3, 6, 12, and 24 months of follow-up in all QoL assessments. After implantation, the mean disc height at the affected level increased by 0.19 from baseline (0.22) to 3 months (0.41) and remained constant up to 24 months (P < .001). Mean disc height of levels above and below the implant remained comparable at baseline and follow-up. A total of 63 adverse events (44 patients) was recorded, of which 7 (11.1%) were related to the Prestige disc, instrumentation, or procedure; 41 (65.1%) were unrelated; and 15 (23.8%) had an unknown relation. CONCLUSIONS: In line with published findings, our study shows significant improvement in outcomes in the first 3 months after Prestige disc implantation with improvements maintained throughout the study.

[Prognostic factors of primary spinal tumors]. / Primer gerincdaganatok prognosztikai faktorai.

AIMS: Primary spinal tumors are rare diseases and there are less objective data in the international literature. We analyzed the epidemiology and clinical consequences of primary spinal tumors based on the clinical experience of the National Center for Spinal Disorders. METHODS: Demographic and clinical data of 300 patients treated in our institute between 1995 and 2007 was collected retrospectively and analysed. RESULTS: Beyond the relatively more frequent pathologies (chordoma, myeloma multiplex) we treated in our hospital some of the very rare types of tumors (spinal leiomyosarcoma, synovial sarcoma). Primary spinal tumors are most often located in the lumbosacral region causing most frequently (73%) local or radiating pain. Modern therapy of these patologies is based on the surgical intervention. Mean operation time was 130 minutes, mean blood loss was 650 ml in our pratice during these often technically challenging surgeries. We found a significant association among the operation time, the blood loss and the extension of the tumor (p < 0.01). Histology (p < 0.0001), severity of symptomes (p < 0.05) and blood loss (p < 0.05) were significantly related to mortality. Local recurrence was more than 5-fold in case of patients previously operated in another institute (p < 0.0001). CONCLUSIONS: We successfully determined some significant prognostic factor on clinical behavior of primary spinal tumors performing a large scale retrospective study. Long time follow up of the patients and completion of our database with prospective data are planned for the future.