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  • Author or Editor: Roger Härtl x
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Justin F. Fraser and Roger Härtl

Object

Anterior cervical discectomy (ACD), ACD with interbody fusion (ACDF), ACDF with placement of an anterior plate system (ACDFP), corpectomy, and corpectomy with plate placement are used to fuse the cervical spine. The authors conducted a metaanalysis of studies published after 1990 in which fusion rates achieved with each procedure were reported for patients with degenerative disease at one, two, and three disc levels.

Methods

Twenty-one papers each included data on at least 25 patients. In each of the 21 studies the average clinical follow up was more than 12 months, and the results were evaluated according to radiographic evidence of fusion and delineated by the number of levels fused. Chi-square and Fisher exact tests were used for comparisons. The mean age of the patients was 46.7 years, 46.6% were female, and the mean follow-up period was 39.6 months. The studies included 2682 patients and the overall fusion rate was 89.5%. For single disc–level disease, fusion rates were 84.9% for ACD, 92.1% for ACDF, and 97.1% for ACDFP (p = 0.0002). For two disc–level disease, fusion rates were 79.9% for ACDF, 94.6% for ACDFP, 95.9% for corpectomy, and 92.9% for corpectomy with plate placement (p = 0.0001). For three disc–level disease, fusion rates were 65.0% for ACDF, 82.5% for ACDFP, 89.8% for corpectomy, and 96.2% for corpectomy with plate placement (p = 0.0001). The use of anterior plates significantly improved fusion for one-level (p < 0.0001), two-level (p < 0.0001), and three-level (p < 0.05) ACDF. There was no significant difference in fusion rates between two-level ACDF and corpectomy with plate placement.

Conclusions

The anticipated fusion rate is one of several factors that may guide surgical decision making. Anterior cervical decompression and fusion results in high fusion rates. The results of the authors' study show that regardless of the number of levels fused, the use of an anterior cervical plate system significantly increases the fusion rate. For two-disc–level disease, there was no significant difference between ACD with a plate system or corpectomy with a plate system. For three-disc–level disease, however, the evidence suggests that corpectomy with plate placement is associated with higher fusion rates than discectomy with plate placement.

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W. Bradford DeLong

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Robert F. Heary

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Dean Chou, Roger Hartl and Volker K. H. Sonntag

✓ Conus medullaris injury from burst fractures is known to occur in conjunction with other neurological deficits, including lower-extremity motor weakness or sensory changes. Rarely does an isolated conus medullaris injury occur from an extradural cause without other neurological deficits. The authors report four cases of L-1 burst fractures in which conus medullaris dysfunction was the sole neurological injury in the absence of lower-extremity involvement.

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Andre Tomasino, Harry Gebhard, Karishma Parikh, Christian Wess and Roger Härtl

Object

The authors present the radiological and clinical outcome data obtained in patients who underwent single-level anterior cervical discectomy and fusion (ACDF) for cervical spondylosis and/or disc herniation; bioabsorbable plates were used for instrumentation. The use of metallic plates in ACDF has gained acceptance as a stabilizing part of the procedure to increase fusion rates, but when complications occur with these devices, the overall effectiveness of the procedure is compromised. As a possible solution, bioabsorbable implants for ACDF have been developed. This study investigates the feasibility and radiological and clinical outcomes of the bioabsorbable plates for ACDF.

Methods

The radiological and clinical outcomes of 30 patients were investigated retrospectively. All patients presented with cervical radiculopathy or myelopathy and underwent single-level ACDF in which a bioabsorbable anterior cervical plate and an allograft bone spacer were placed at a level between C-3 and C-7. Radiological outcome was assessed based on the fusion rate, subsidence, and Cobb angle of the surgical level. Clinical outcome was determined by using a visual analog scale, the Neck Disability Index, and the Odom criteria.

Results

There were no intraoperative complications, and no hardware failure was observed. No signs or symptoms of adverse tissue reaction caused by the implant were seen. Two reoperations were necessary due to postoperative blood collections. The overall complication rate was 16.7%. After 6 months, radiographic fusion was seen in 92.3% of patients. Subsidence at 11.3 ± 7.2 months was 3.1 ± 5.8 mm (an 8.2% change over the immediately postoperative results), and the change in the sagittal curvature was –2.7 ± 2.7°. The visual analog scale score for neck and arm pain and Neck Disability Index improved significantly after surgery (p < 0.001). Overall at 19.5 months postoperatively, 83% of the patients had favorable outcomes based on the Odom criteria.

Conclusions

Absorbable instrumentation provides better stability than the absence of a plate but graft subsidence and deformity rates may be higher than those associated with metal implants. There were no device-related complications, but adverse late effects cannot be excluded. The fusion rate and outcome are comparable to the results achieved with metallic plates. The authors were satisfied with the use of bioabsorbable plates as a reasonable alternative to metal, avoiding the need for lifelong metallic implants.

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Benjamin J. Shin, Innocent U. Njoku, A. John Tsiouris and Roger Härtl

Object

Three-dimensional spinal navigation increases screw accuracy, but its implementation in clinical practice has been difficult, mainly because of surgeons' concerns about increased operative times, disturbance of workflow, and safety. The authors present a custom-designed navigated guide that addresses some of these concerns by allowing for drilling, tapping, and placing the final screw via a minimally invasive approach without the need for K-wires. In this paper, the authors' goal was to describe the technical aspects of the navigated guide tube as well as pedicle screw accuracy.

Methods

The authors present the technical details of a navigated guide that allows drilling, tapping, and the placement of the final screw without the need for K-wires. The first 10 patients who received minimally invasive mini-open spinal pedicle screws are presented. The case series focuses on the immediate postoperative outcomes, pedicle screw accuracy, and pedicle screw–related complications. An independent board-certified neuroradiologist determined pedicle screw accuracy according to a 4-tiered grading system.

Results

The navigated guide allowed successful placement of mini-open pedicle screws as part of posterior fixation from L-1 to S-1 without the use of K-wires. Only 7-mm-diameter screws were placed, and 72% of screws were completely contained within the pedicle. Breaches less than 2 mm were seen in 23% of cases, and these were all lateral except for one screw. Breaches were related to the lateral to medial trajectory chosen to avoid the superior facet joint. There were no complications related to pedicle screw insertion.

Conclusions

A novel customized navigated guide tube is presented that facilitates the workflow and allows accurate placement of mini-open pedicle screws without the need for K-wires.

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Marjan Alimi, Christoph P. Hofstetter, Se Young Pyo, Danika Paulo and Roger Härtl

OBJECT

Surgical decompression is the intervention of choice for lumbar spinal stenosis (LSS) when nonoperative treatment has failed. Standard open laminectomy is an effective procedure, but minimally invasive laminectomy through tubular retractors is an alternative. The aim of this retrospective case series was to evaluate the clinical and radiographic outcomes of this procedure in patients who underwent LSS and to compare outcomes in patients with and without preoperative spondylolisthesis.

METHODS

Patients with LSS without spondylolisthesis and with stable Grade I spondylolisthesis who had undergone minimally invasive tubular laminectomy between 2004 and 2011 were included in this analysis. Demographic, perioperative, and radiographic data were collected. Clinical outcome was evaluated using the Oswestry Disability Index (ODI) and visual analog scale (VAS) scores, as well as Macnab's criteria.

RESULTS

Among 110 patients, preoperative spondylolisthesis at the level of spinal stenosis was present in 52.5%. At a mean follow-up of 28.8 months, scoring revealed a median improvement of 16% on the ODI, 2.75 on the VAS back, and 3 on the VAS leg, compared with the preoperative baseline (p < 0.0001). The reoperation rate requiring fusion at the same level was 3.5%. Patients with and without preoperative spondylolisthesis had no significant differences in their clinical outcome or reoperation rate.

CONCLUSIONS

Minimally invasive laminectomy is an effective procedure for the treatment of LSS. Reoperation rates for instability are lower than those reported after open laminectomy. Functional improvement is similar in patients with and without preoperative spondylolisthesis. This procedure can be an alternative to open laminectomy. Routine fusion may not be indicated in all patients with LSS and spondylolisthesis.

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Benjamin J. Shin, Andrew R. James, Innocent U. Njoku and Roger Härtl

Object

In this paper the authors' goal was to compare the accuracy of computer-navigated pedicle screw insertion with nonnavigated techniques in the published literature.

Methods

The authors performed a systematic literature review using the National Center for Biotechnology Information Database (PubMed/MEDLINE) using the Medical Subject Headings (MeSH) terms “Neuronavigation,” “Therapy, computer assisted,” and “Stereotaxic techniques,” and the text word “pedicle.” Included in the meta-analysis were randomized control trials or patient cohort series, all of which compared computer-navigated spine surgery (CNSS) and nonassisted pedicle screw insertions. The primary end point was pedicle perforation, while the secondary end points were operative time, blood loss, and complications.

Results

Twenty studies were included for analysis; of which there were 18 cohort studies and 2 randomized controlled trials published between 2000 and 2011. Foreign-language papers were translated. The total number of screws included was 8539 (4814 navigated and 3725 nonnavigated). The most common indications for surgery were degenerative disease, spinal deformity, myelopathy, tumor, and trauma. Navigational methods were primarily based on CT imaging. All regions of the spine were represented. The relative risk for pedicle screw perforation was determined to be 0.39 (p < 0.001), favoring navigation. The overall pedicle screw perforation risk for navigation was 6%, while the overall pedicle screw perforation risk was 15% for conventional insertion. No related neurological complications were reported with navigated insertion (4814 screws total); there were 3 neurological complications in the nonnavigated group (3725 screws total). Furthermore, the meta-analysis did not reveal a significant difference in total operative time and estimated blood loss when comparing the 2 modalities.

Conclusions

There is a significantly lower risk of pedicle perforation for navigated screw insertion compared with nonnavigated insertion for all spinal regions.

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Christoph P. Hofstetter, Benjamin Shin, Apostolos John Tsiouris, Eric Elowitz and Roger Härtl

Object

The paracoccygeal approach allows for instrumentation of L5/S1 and L4/5 by using a transsacral rod (AxiaLIF; TransS1, Inc.). The authors analyzed clinical and radiographic outcomes of 1- or 2-level AxiaLIF procedures with focus on durability of the construct.

Methods

This was a retrospective study of 38 consecutive patients who underwent either 1-level (32 patients) or 2-level (6 patients) AxiaLIF procedures at the authors' institution. The Oswestry Disability Index (minimum clinically important difference [MCID] ≥ 12) and visual analog scale ([VAS]; MCID ≥ 3) scores were collected. Disc height and Cobb angles were measured on pre- and postoperative radiographs. Bony fusion was determined on CT scans or flexion/extension radiographs.

Results

Implantation of a transsacral rod allowed for intraoperative distraction of the L5/S1 intervertebral space and resulted in increased segmental lordosis postoperatively. At a mean follow-up time of 26.2 ± 2.4 months, however, graft subsidence (1.9 mm) abolished partial correction of segmental lordosis. Moreover, subsidence of the construct reduced L5/S1 lordosis in patients with 1-level AxiaLIF by 3.2° and L4–S1 lordosis in patients with 2-level procedures by 10.1° compared with preoperative values (p < 0.01). Loss of segmental lordosis predicted failure to improve VAS scores for back pain in the patient cohort (p < 0.05). Overall, surgical intervention led to modest symptomatic improvement; only 26.3% of patients achieved an MCID of the Oswestry Disability Index and 50% of patients an MCID of the VAS score for back pain. At last follow-up, 71.9% of L5/S1 levels demonstrated bony fusion (1-level AxiaLIF 80.8%, 2-level AxiaLIF 33.3%; p < 0.05), whereas none of the L4/5 levels in 2-level AxiaLIF fused. Five constructs developed pseudarthrosis and required surgical revision.

Conclusions

The AxiaLIF procedure constitutes a minimally invasive technique for L5/S1 instrumentation, with low perioperative morbidity. However, the axial rod provides inadequate long-term anterior column support, which leads to subsidence and loss of segmental lordosis. Modification of the transsacral technique to allow for placement of a solid interposition graft may counteract subsidence of the construct.