Hollow cylindrical polymethylmethacrylate strut for spinal reconstruction after single-level cervical corpectomy

Developments of nano-TiO2 incorporated hydroxyapatite/PEEK composite strut for cervical reconstruction and interbody fusion after corpectomy with anterior plate fixation

The technique of anterior cervical corpectomy and fusion (ACCF) for strut grafting has become a widespread and actively applied for many cervical complaints including cervical degeneration of the intervertebral disks, cervical trauma, cancer, rheumatoid arthritis and multilevel cervical spondylotic diseases. To avoid the complications of the old techniques, the construct stability and long anterior screw-plate designs of the bone strut have been improved by using effective biomaterials. The nanostructured hydroxyapatite (HAp) incorporated with biocompatible polymer matrixes is an effective biomedical material and creating a functional properties applied for different tissue replacements such as dental, hips, knees, tendon and ligaments and tissue repair for maxillofacial reconstruction, stabilization of the jaw bone and spinal fusion. In the present investigation, we have successfully designed cylindrical nano titanium dioxide (n-TiO₂) interbody fusion with anterior plate fixation. The n-TiO₂ incorporated HAp/ Polyetheretherketone (PEEK) nanocomposite strut has a superior mechanical properties and larger contact area with high fusion rates as compared with the HAp/PEEK strut in the absence of n-TiO₂ nanoparticles. It is highly able to provide appropriate strength and biological activity similar to the conventional titanium cage and also mainly it has been minimizes subsidence value. The synthesized novel material of n-TiO2 incorporated HAp/PEEK nanocomposite strut is scientifically given effective outcomes for fusion and reconstruction of the ACCF.

Vertebral body replacement with PEEK-cages after anterior corpectomy in multilevel cervical spinal stenosis: a clinical and radiological evaluation

INTRODUCTION

A growing number of industrially manufactured implants have been developed in the last years for vertebral replacement in anterior cervical corpectomy and fusion (ACCF). Polyetheretherketone (PEEK)-cages are used in many centers, but outcome reports are scarce. This study assesses the clinical and radiological outcome after one- or two-level ACCF by the use of a PEEK-cage augmented by a plate-screw osteosynthesis.

METHODS

A total of 21 patients received one-level (18 patients) or two-level (3 patients) ACCF by a PEEK-cage and plate-screw osteosynthesis for multilevel degenerative stenosis. The Visual Analogue Scale, Nurick Score, Neck Disability Index and European Myelopathy Score were used for clinical assessment. Radiological outcome-osseous fusion and loss of height-was evaluated by CT.

RESULTS

The mean follow-up was 28 ± 12 months. In 19 patients, bony fusion was achieved after the primary operation. Graft failure that required surgical revision occurred in two patients. In these patients, osseous fusion was achieved after the second operation. Myelopathy improved significantly. The loss of height was 2.2 ± 2.3 and 5.3 ± 2.1 mm after one- and two-level ACCF, respectively.

CONCLUSION

Anterior corpectomy and fusion by a PEEK-cage and plate-screw osteosynthesis resulted in clinical improvement in all patients. Bony fusion was achieved in all patients in the long run. PEEK cages are allegedly less rigid than other xenografts. Similar to those, however, their use bears the risk of early cage-dislocation and subsidence. A comparison of industrial xenografts and autologous bone implants is required to challenge the different fusion techniques.

Outcome of single level anterior cervical discectomy and fusion using nano-hydroxyapatite/polyamide-66 cage

BACKGROUND

Cages have been widely used for the anterior reconstruction and fusion of cervical spine. Nonmetal cages have become popular due to prominent stress shielding and high rate of subsidence of metallic cages. This study aims to assess fusion with n-HA/PA66 cage following one level anterior cervical discectomy.

MATERIALS AND METHODS

Forty seven consecutive patients with radiculopathy or myelopathy underwent single level ACDF using n-HA/PA66 cage. We measured the segmental lordosis and intervertebral disc height on preoperative radiographs and then calculated the loss of segmental lordosis correction and cage subsidence over followup. Fusion status was evaluated on CT scans. Odom criteria, Japanese Orthopedic Association (JOA) and Visual Analog Pain Scales (VAS) scores were used to assess the clinical results. Statistically quantitative data were analyzed while Categorical data by χ(2) test.

RESULTS

Mean correction of segmental lordosis from surgery was 6.9 ± 3.0° with a mean loss of correction of 1.7 ± 1.9°. Mean cage subsidence was 1.2 ± 0.6 mm and the rate of cage subsidence (>2 mm) was 2%. The rate of fusion success was 100%. No significant difference was found on clinical or radiographic outcomes between the patients (n=27) who were fused by n-HA/PA66 cage with pure local bone and the ones (n=20) with hybrid bone (local bone associating with bone from iliac crest).

CONCLUSIONS

The n-HA/PA66 cage is a satisfactory reconstructing implant after anterior cervical discectomy, which can effectively promote bone graft fusion and prevent cage subsidence.

Postoperative infection treatment score for the spine (PITSS): construction and validation of a predictive model to define need for single versus multiple irrigation and debridement for spinal surgical site infection

BACKGROUND CONTEXT

There is very little evidence to guide treatment of patients with spinal surgical site infection (SSI) who require irrigation and debridement (I&D) in deciding need for single or multiple I&Ds or more complex wound management such as vacuum-assisted closure dressing or soft-tissue flaps.

PURPOSE

The purpose of this study was to build a predictive model that stratifies patients with spinal SSI, allowing us to determine which patients will need single versus multiple I&D. The model will be validated and will serve as evidence to support a scoring system to guide treatment.

STUDY DESIGN

A consecutive series of 128 patients from a tertiary spine center (collected from 1999 to 2005) who required I&D for spinal SSI were studied based on data from a prospectively collected outcomes database.

METHODS

More than 30 variables were identified by extensive literature review as possible risk factors for SSI and tested as possible predictors of risk for multiple I&D. Logistic regression was conducted to assess each variable's predictability by a "bootstrap" statistical method. A prediction model was built in which single or multiple I&D was treated as the "response" and risk factors as "predictors." Next, a second series of 34 different patients meeting the same criteria as the first population were studied. External validation of the predictive model was performed by applying the model to the second data set, and predicted probabilities were generated for each patient. Receiver operating characteristic curves were constructed, and the area under the curve (AUC) was calculated.

RESULTS

Twenty-four of one hundred twenty-eight patients with spinal SSI required multiple I&D. Six predictors: anatomical location, medical comorbidities, specific microbiology of the SSI, the presence of distant site infection (ie, urinary tract infection or bacteremia), the presence of instrumentation, and the bone graft type proved to be the most reliable predictors of need for multiple I&D. Internal validation of the predictive model yielded an AUC of 0.84. External validation analysis yielded AUC of 0.70 and 95% confidence interval of 0.51 to 0.89. By setting a probability cutoff of .24, the negative predictive value (NPV) for multiple I&D was 0.77 and positive predictive value (PPV) was 0.57. A probability cutoff of .53 yielded a PPV of 0.85 and NPV of 0.46.

CONCLUSIONS

Patients with positive methicillin-resistant Staphylococcus aureus culture or those with distant site infection such as bacteremia were strong predictors of need for multiple I&D. Presence of instrumentation, location of surgery in the posterior lumbar spine, and use of nonautograft bone graft material predicted multiple I&D. Diabetes also proved to be the most significant medical comorbidity for multiple I&D. The validation of this predictive model revealed excellent PPV and good NPV with appropriately chosen probability cutoff points. This study forms the basis for an evidence-based classification system, the Postoperative Infection Treatment Score for the Spine that stratifies patients who require surgery for SSI, based on specific spine, patient, infection, and surgical factors to assess a low, indeterminate, and high risk for the need for multiple I&D.

Surgical treatment of disk-associated wobbler syndrome by a distractable vertebral titanium cage in seven dogs

OBJECTIVE

To evaluate a distractable titanium cage for the treatment of disk-associated wobbler syndrome (DAWS).

STUDY DESIGN

Prospective study.

ANIMALS

Dogs (n = 7) with DAWS.

METHODS

After total discectomy of C5-C6 and C6-C7, the median part of the vertebral body of C6 was removed with preservation of the lateral walls and dorsal cortex. The removed cancellous bone was collected. The implant was placed in the bony defect of C6. After placement, the titanium cage was distracted and affixed by 4 screws. Finally, the implant was filled and covered with cancellous bone. Dogs had follow-up examinations at 1, 3, 6, 12, and 24 months. Six months after surgery, cervical radiographs and computed tomography (CT) were performed.

RESULTS

Although no intraoperative complications occurred, correct placement of the cage was technically challenging. Revision surgery was necessary in 2 dogs because of implant loosening and aggravation of vertebral tilting. All dogs improved after discharge from the hospital. In 1 dog, recurrence of clinical signs caused by articular facet proliferation at an adjacent intervertebral disk space occurred. Radiographs at 6 months demonstrated cage subsidence in 4 dogs. In all dogs, CT was suggestive for fusion of the bone graft with the vertebral body.

CONCLUSIONS

Although results are promising, technical adaptations will be necessary to make this specific surgical technique, designed for humans, suitable for routine use in dogs.

A simple method for making a hollow cylindrical polymethylmethacrylate strut for cervical spinal reconstruction

Object

The purpose of this study was to introduce a method for making a hollow cylindrical polymethylmethacrylate (PMMA) strut for perioperative anterior spinal reconstruction after discectomy and/or corpectomy.

Methods

For use after anterior cervical discectomy or corpectomy, the authors created a hollow cylindrical PMMA strut using 10- and 3-ml disposable plastic syringes filled with PMMA containing 10% BaSO4 for anterior spinal reconstruction.

Results

With this method, the authors were able to make a PMMA strut that was approximately 50 mm in length with a 14-mm outer diameter and a 10-mm inner diameter. The PMMA strut could easily be cut with a saw to any desired length and molded with a cutting bur. The PMMA strut was used as a substitute for the cortical bone and was filled with bone graft for cervical spinal reconstruction after discectomy and/or corpectomy. The whole process of making the PMMA strut can be completed within 30 minutes, and it reduces costs by at least $1000 US (in 1-level discectomy), making the procedure cost effective.

Conclusions

It is simple to make a hollow cylindrical PMMA strut with plastic syringes during a discectomy and/or corpectomy. The strut can provide adequate support at less cost than other methods. The hollow cylindrical strut is also of suitable size and length for anterior spinal reconstruction. It serves as an alternative for patients who cannot afford the expense of similar instruments or who cannot or do not want to take the risk of a human graft for anterior spinal reconstruction.

Correlation between change in graft height and change in segmental angle following central corpectomy for cervical spondylotic myelopathy

Object

This study was undertaken to examine the correlation between change in graft height and change in angulation across grafted segments (segmental angle) in patients undergoing central corpectomy (CC) with autologous bone reconstruction for cervical spondylotic myelopathy (CSM).

Methods

The authors performed a retrospective analysis of 70 cases in which patients with CSM underwent uninstrumented single- or multilevel CC and had evidence of osseous fusion of their grafts at follow-up. The segmental angles and heights of the grafted segments on preoperative, postoperative, and follow-up radiographs were compared.

Results

The mean change in graft height (± standard deviation) was −7.3 ± 3.8 mm (mean duration of follow-up 19.7 ± 5.4 months, range 13–53 months). There was a mean kyphotic change in segmental angle of −7.3 ± 3.8° (p < 0.001). In patients who had a straight or kyphotic cervical spine (28 patients) or a straight or kyphotic segment (32 patients) preoperatively, there was a significant linear correlation between changes in graft height and changes in segmental angle (Pearson correlation, r = 0.40, p = 0.03; r = 0.40, p = 0.02, respectively). Such a correlation was not seen in the patients who had a lordotic cervical spine (42 patients) or a lordotic segment (38 patients) preoperatively (Pearson correlation, r = −0.04, p = 0.81; r = 0.08, p = 0.62, respectively). The change in segmental angle did not influence improvement in Nurick grade (p = 0.8). The degree of agreement between the 2 observers was almost perfect for measurement of graft height (postoperative intraclass correlation coefficient [ICC] = 0.94, follow-up ICC = 0.90) but was significantly lower for measurement of segmental angles (postoperative ICC = 0.71, follow-up ICC = 0.67).

Conclusions

Among patients undergoing uninstrumented CC for CSM, there is a significant correlation between postoperative settling and kyphotic change across fused segments in those who had straight or kyphotic cervical spines or segments preoperatively but not in those who had lordotic cervical spines or segments preoperatively. A more vigorous surgical correction of the segmental kyphosis than achieved in this study might have caused the kyphotic segments to behave like the lordotic segments. Paraspinal muscles and ligaments may play a role in determining the segmental angle as graft settling in patients with lordotic spines or segments is not linearly correlated with angular change.

[Anterior cervical fusion in the lower cervical spine. Locked vs nonlocked screw plate, pure cancellous bone vs tricortical strut]

Physical alterations in cervical fusions endanger healing. Experimentally we determined less stability loss in fixations using cancellous bone grafts than in those using tricortical grafts. Four hundred eighty-five Patients underwent anterior cervical fusion, for a total of 700 Segments. Patients were divided into four groups: (1) nonlocked H plate with autogenous cancellous bone, (2) nonlocked H plate with autogenous tricortical graft, (3) locked cervical plate with tricortical graft, and (4) stand-alone cage with cancellous bone. Evaluations included X-ray and random CT scan examinations. Our results suggest that anterior cervical fusions using nonlocked H screw plate systems with pure autogenous cancellous bone grafts provide the fastest (6 weeks) and most secure bone healing (P=0.00001), whereas fixations using nonlocked or locked screw plate systems and tricortical autograft require prolonged healing and develop nonunions more frequently. Complete consolidation was achieved using stand-alone cages filled with pure autogenous cancellous bone, but bony healing was delayed due to the cage. Rate of nonunions were: groups 1 and 4 0%, and groups 2 and 3 4.5% and 21%, respectively.