Expandable Intravertebral Implants: A Narrative Review on the Concept, Biomechanics, and Outcomes in Traumatology.

Expandable intravertebral implants are self-expanding devices applied percutaneously by the posterior transpedicular approach. These devices introduce the concept of anatomical restoration of vertebral body endplates and direct anatomical reduction performed from the interior of the vertebral body with a compression fracture. This paper aims to provide a narrative review on the concept, indications, biomechanical characteristics, as well as functional and radiographic outcomes of the main expandable intravertebral implants currently available, in terms of their application to thoracolumbar spine traumatology. To this end, we performed a search in July 2021 on the MEDLINE/PubMed platform with the words "expandable intravertebral implant", "armed kyphoplasty", "Vertebral Body Stenting" or "stentoplasty" and "SpineJack". The search yielded 144 papers, and of those, we included 15 in this review. We concluded that percutaneous transpedicular posterior access, the ability to reduce vertebral body fractures, particularly of the vertebral endplates and to maintain the vertebral body height, makes the application of expandable intravertebral implants an attractive option in the treatment of thoracolumbar vertebral compression fractures. However, more prospective, randomized, and large-scale blinded studies are still warranted, especially comparative studies between treatments and about the preferential use of an expansive implant over others, in order to gain definitive insights into the effectiveness and indications of each of these devices.

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 ±â€¯3 years, mean BMI 24.7 ±â€¯3.4 kg/m2. VAS and NDI showed significant improvement, p < 0.001, p = 0.02 respectively. Mean PCS 31.9 ±â€¯2.7, MCS 38.9 ±â€¯3.4 improved to mean PCS 42.2 ±â€¯5.1, MCS 51.0 ±â€¯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.

Stability of transforaminal lumbar interbody fusion in the setting of retained facets and posterior fixation using transfacet or standard pedicle screws.

BACKGROUND CONTEXT: The transforaminal lumbar interbody fusion (TLIF) technique supplements posterior instrumented lumbar spine fusion and has been tested with different types of screw fixation for stabilization. Transforaminal lumbar interbody fusion is usually placed through a unilateral foraminal approach after unilateral facetectomy, although extraforaminal entry allows the facet to be spared. PURPOSE: To characterize the biomechanics of L4-L5 lumbar motion segments instrumented with bilateral transfacet pedicle screw (TFPS) fixation versus bilateral pedicle screw-rod (PSR) fixation in the setting of intact facets and native disc or after discectomy and extraforaminal placement of a TLIF technology graft. STUDY DESIGN: Human cadaveric lumbar spine segments were biomechanically tested in vitro to provide a nonpaired comparison of four configurations of posterior and interbody instrumentation. METHODS: Fourteen human cadaveric spine specimens (T12-S1) underwent standard pure moment flexibility tests with intact L4-L5 disc and facets. Seven were studied with intact discs, after TFPS fixation, and then with TLIF and TFPS fixation. The others were studied with intact discs, after PSR fixation, and then combined with extraforaminally placed TLIF. Loads were applied about anatomic axes to induce flexion-extension, lateral bending, and axial rotation. Three-dimensional specimen motion in response to applied loads during flexibility tests was determined. A nonpaired comparison of the four configurations of posterior and interbody instrumentation was made. RESULTS: Transfacet pedicle screw and PSR, with or without TLIF, significantly reduced range of motion during all directions of loading. Transfacet pedicle screw provided greater stability than PSR in all directions of motion except lateral bending. In flexion, TFPS was more stable than PSR (p=.042). A TLIF device provided less stability than the intact disc in constructs with TFPS and PSR. CONCLUSIONS: These results suggest that fixation at L4-L5 with TFPS is a promising alternative to PSR, with or without TLIF. A TLIF device was less stable than the native disc with both methods of instrumentation presumably because of a fulcrum effect from a relatively small footplate. Additional interbody support may be considered for improved biomechanics with TLIF.

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.

Degenerative spondylolisthesis of the cervical spine: analysis of 58 patients treated with anterior cervical decompression and fusion.

BACKGROUND CONTEXT: Degenerative spondylolisthesis has been well described as a disorder of the lumbar spine. Few authors have suggested that a similar disorder occurs in the cervical spine. To our knowledge, the present study represents the largest series of patients with long-term follow-up who were managed surgically for the treatment of degenerative spondylolisthesis of the cervical spine. PURPOSE: To describe the clinical presentation and radiographic findings associated with degenerative cervical spondylolisthesis, and to report the long-term results of surgically managed patients. STUDY DESIGN: Analysis of 58 patients treated with anterior cervical decompression and fusion for degenerative spondylolisthesis of the cervical spine. PATIENT SAMPLE: From 1974 to 2003, 58 patients were identified as having degenerative spondylolisthesis of the cervical spine occurring in the absence of trauma, systemic inflammatory arthropathy, or congenital abnormality. These patients were identified from a database of approximately 500 patients with degenerative cervical spine disorders treated by the senior one of us. OUTCOME MEASURES: Patient outcomes were evaluated with regard to neurologic improvement (Nurick grade myelopathy) and osseous fusion. METHODS: The records of 58 patients were reviewed. The average follow-up period was 6.9 years (range, 2-24 years). Seventy-two cervical levels demonstrated spondylolisthesis. In all cases, there was radiographic evidence of facet degeneration and subluxation. All patients were treated with anterior cervical decompression and arthrodesis with iliac crest structural graft. This most commonly involved corpectomy of the caudal vertebrae. Three patients required additional posterior facet fusion. RESULTS: Fifty-eight patients demonstrated 72 levels of involvement. The C4-C5 level was most frequently involved (43%). Two radiographically distinct types of listhesis were observed based on the amount of disc degeneration and the degree of spondylosis at adjacent levels. The average neurologic improvement was 1.5 Nurick grades. The overall fusion rate was 92%. Three patients were treated with combined anterior-posterior arthrodesis. The prevalence of myelopathy and instability pattern was greater in the listheses occurring adjacent to spondylotic levels. CONCLUSIONS: Degenerative spondylolisthesis is relatively common in the cervical spine. Common to all cases is facet arthropathy and neurologic compression. Anterior cervical decompression and arthrodesis appears to yield excellent union rates and neurological improvement in those patients having cervical degenerative spondylolisthesis and significant neurological sequelae who have failed nonoperative treatments.

The treatment of unstable thoracic spine fractures with transpedicular screw instrumentation: a 3-year consecutive series.

STUDY DESIGN: The treatment of unstable thoracic spine fractures remains controversial. Theoretical biomechanical advantages of transpedicular screw fixation include three-column control of vertebral segments and fixation of a vertebral segment in the absence of intact posterior elements. Additionally, pedicle screw constructs may obviate the need for neural canal dissection and potential neural element impingement by intracanal instrumentation. A 3-year consecutive series was performed to evaluate the use of transpedicular screw fixation in the treatment of unstable thoracic spine injuries. OBJECTIVE: This study was performed to evaluate the efficacy of transpedicular screw fixation in the upper, middle, and lower thoracic spine. SUMMARY OF BACKGROUND DATA: The use of rod/hook and rod/wiring techniques has been evaluated in the treatment of thoracic spine injuries. To date, a study evaluating the safety and efficacy of pedicle screw instrumentation in the upper, middle, and lower thoracic spine has not been reported. METHODS: Thirty-two patients with 79 individual vertebral injury levels (T2-L1) treated with transpedicular spinal stabilization and bone fusion were evaluated during a 3-year consecutive series from 1998 to 2001. Patient charts, operative reports, preoperative and postoperative radiographs, computed tomography scans, and postoperative follow-up examinations and radiographs were reviewed from the time of surgery to final follow-up assessment. Radiographic measurements included: sagittal index, Gardner segmental kyphotic deformity, and compression percentage. RESULTS: A total of 252 pedicle screws were placed, of which 222 were placed in segments T2-L1. Clinical examination and plain radiographs were used to determine the presence of a solid fusion. Fracture healing and radiographic stabilization occurred at an average of 4.8 months after the initial operation. There were no reported cases of hardware failure, loss of reduction, or painful hardware removal. Two hundred fifty-two transpedicular screws were successfully placed without intraoperative complications. The mean preoperative sagittal index was 13.9 degrees, whereas the mean follow-up was 5.25 degrees (P < 0.001). The mean final correction of sagittal index achieved was 8.65 degrees, or a 62.2% improvement. The mean Gardner segmental kyphotic angle was 15.9 degrees, whereas the mean follow-up angle was 10.6 degrees (P < 0.0005). The mean compression percentage was 35.4, and at follow-up was 27.4 (P < 0.07). CONCLUSIONS: In carefully selected instances, pedicle screw fixation of upper, middle, and lower thoracic and upper thoracolumbar spinal injuries is a reliable and safe method of posterior spinal stabilization. Transpedicular screw fixation may offer superior three-column control in the absence of posterior element integrity and obviates the need for intracanal placement of hardware. Transpedicular instrumentation provides rigid fixation for upper, middle, and lower unstable thoracic spine injuries and produces early pain-free fusion results. These results provide evidence that with appropriate preoperative radiographic evaluation of pedicular size and orientation using computed tomography as well as radiograph assessment, transpedicular instrumentation is a safe and effective alternative in the treatment of unstable thoracic (T2-L1) spinal injuries.