Josue P. Gabriel

A novel crossed rod configuration incorporating translaminar screws for occipitocervical internal fixation: an in vitro biomechanical study

BACKGROUND CONTEXT Occipitocervical (OC) spinal instrumentation involving the axis (C2) entails the use of transarticular screws through C1-C2 or lateral mass screws at C1 and pedicle screws at C2 to achieve fusion. Because of the anatomical complexity, interpatient anomalous variation, and danger to the vertebral artery injury, there has been an increased interest in alternate sites for fixation. Recent studies have involved the placement of screws bilaterally into the C2 lamina. Several biomechanical studies have been carried out to evaluate the performance of C2 translaminar screws (TLSs). PURPOSE The aim of the study was to compare the biomechanics of an OC2 rigid construct using C2 pedicle screws and C2 TLSs. Also, this study included a new construct in which the OC2 fixation was carried out by connecting rods to the contralateral TLS. STUDY DESIGN Human cadaveric cervical spines were tested in an in vitro biomechanical flexibility experiment to investigate the biomechanical stability provided by a novel crossed rod (CR) configuration incorporating TLSs for OC2 internal fixation. METHODS Seven fresh human cadaver occipitocervical spines (occiput-C3) were tested by applying pure moments of ±1.5 Nm. After intact specimen testing, an occipital plate was implanted. Each specimen was then tested in the following modes: bilateral pedicle screws (BPSs) and rods at C2; TLSs at C2 with rods in parallel configuration (TLS+parallel rod); and TLSs at C2 with rods in crossed configuration (TLS+CR). OC2 range of motion (ROM) for each construct was obtained by applying pure moments in flexion-extension, lateral bending, and axial rotation. RESULTS All three instrumented constructs significantly reduced ROM in all physiological planes when compared with the intact spine. The BPS construct similarly reduced ROM when compared with both the translaminar constructs. There was no significant difference in ROM between the translaminar constructs in all loading modes. CONCLUSIONS A cadaveric model was used to investigate the stability offered by a novel CR construct by using TLS fixation in an OC2 fusion construct. The results were compared with BPS fixation. All three constructs significantly decreased motion as compared with the intact state. There was no statistically significant difference in flexibility among any of the constructs. The novel CR construct provides as much stability as traditional constructs and may be a viable alternative for clinical use.

Biomechanics of posterior instrumentation in L1-L3 lateral interbody fusion: Pedicle screw rod construct vs. transfacet pedicle screws.

BACKGROUND The use of pedicle screws is the gold standard for supplemental posterior fixation in lateral interbody fusion. Information about the performance of transfacet pedicle screws compared to standard pedicle screws and rods in the upper lumbar spine with or without a lateral interbody fusion device in place is limited. METHODS Fifteen fresh frozen human cadaveric lumbar spine segments (T12-L4) were studied using standard pure moment flexibility tests. Specimens were divided into two groups to receive either bilateral transfacet pedicle screws (n=8) or bilateral pedicle screws (n=14). Stability of each motion segment (L1-L2 and L2-L3) was evaluated intact, with posterior instrumentation with an intact disc, with posterior instrumentation and a lateral interbody fusion device in place, and following cyclic loading with the interbody device and posterior instrumentation still in place. Both raw values of motion (range of motion, lax zone and stiff zone) and normalized mobility (ratios to intact) were analyzed for each case. FINDINGS In terms of immediate stability, transfacet pedicle screws performed equivalent to similarly sized pedicle screws, both with intact disc and with lateral interbody fusion device in all directions of loading. Stability following cyclic loading decreased significantly during lateral bending and axial rotation. INTERPRETATION Posterior fixation with transfacet pedicle screws provides equivalent immediate stability to similarly sized pedicle screws. However, in the presence of a lateral interbody fusion device, pedicle screws seem to resist loosening more and may be a better option for fusion in the upper lumbar spine.

Artrodese lombar intersomática anterior multinível combinada com estabilização posterior em discopatia – Análise clínico‐funcional prospectiva

Objective  This was a prospective controlled study with lumbar degenerative disc disease patients submitted to instrumented anterior lumbar interbody fusion (ALIF) combined with posterior stabilization. Methods  A sample with 64 consecutive patients was operated by the same surgeons over 4 years. Half of the ALIFs occurred at 2 levels, 43.8% at 3 levels, and 6.25% at 1 level. Interbody cages with integrated screws, filled with bone matrix and bone morphogenetic protein 2, were used. Results  Half of the patients had undergone previous lumbar spine surgeries, 75% presented with associated degenerative listhesis, and 62.5% had posterior lumbar compression disease. Approximately 56% of the sample had at least 1 risk factor for nonunion. The Oswestry index changed from 71.81 ± 7.22 at the preoperative assessment to 24.75 ± 7.82 at the final follow-up evaluation, while the visual analogue pain scale changed from 7.88 ± 0.70 to 2.44 ± 0.87 ( p  < 0.001). Clinical and functional improvements increased with the number of operated levels, proving the efficacy of multilevel ALIF, performed in 93.75% of the sample. The global complication rate was of 7.82%, with no major complications. No cases of nonunion were observed. Conclusion  Instrumented ALIF combined with posterior stabilization is a successful option for uni- and multilevel degenerative disc disease of the L3 to S1 segments, even in the significant presence of risk factors for nonunion and of previous lumbar surgeries, assuring very satisfactory clinical-functional and radiographic outcomes with a low medium-term complication rate.

Limiting fusion levels by combining anterior cervical decompression and fusion with posterior laminectomy: Technical note

Background Authors aim to report on the outcomes of combining selective anterior cervical decompression and fusion (ACDF) with laminectomy in patients with cervical spondylotic radiculomyelopathy (CSR). Methods 10 patients with ACDF and posterior laminectomy reviewed. Results 60% female population, mean age 61 ± 3 years, mean BMI 24.7 ± 3.4 kg/m2. VAS and NDI showed significant improvement, p < 0.001, p = 0.02 respectively. Mean PCS 31.9 ± 2.7, MCS 38.9 ± 3.4 improved to mean PCS 42.2 ± 5.1, MCS 51.0 ± 4.7, p = 0.09 and 0.06 respectively. At final follow up fusion rate was 90% and all patients had Nurick Grade 0. Conclusion In this pilot study, procedure shown to be safe with improved symptoms.