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Nitin Agarwal, Robert F. Heary and Prateek Agarwal

OBJECTIVE

Pedicle screw fixation is a technique widely used to treat conditions ranging from spine deformity to fracture stabilization. Pedicle screws have been used traditionally in the lumbar spine; however, they are now being used with increasing frequency in the thoracic spine as a more favorable alternative to hooks, wires, or cables. Although safety concerns, such as the incidence of adjacent-segment disease (ASD) after cervical and lumbar fusions, have been reported, such issues in the thoracic spine have yet to be addressed thoroughly. Here, the authors review the literature on ASD after thoracic pedicle screw fixation and report their own experience specifically involving the use of pedicle screws in the thoracic spine.

METHODS

Select references from online databases, such as PubMed (provided by the US National Library of Medicine at the National Institutes of Health), were used to survey the literature concerning ASD after thoracic pedicle screw fixation. To include the authors’ experience at Rutgers New Jersey Medical School, a retrospective review of a prospectively maintained database was performed to determine the incidence of complications over a 13-year period in 123 consecutive adult patients who underwent thoracic pedicle screw fixation. Children, pregnant or lactating women, and prisoners were excluded from the review. By comparing preoperative and postoperative radiographic images, the occurrence of thoracic ASD and disease within the surgical construct was determined.

RESULTS

Definitive radiographic fusion was detected in 115 (93.5%) patients. Seven incidences of instrumentation failure and 8 lucencies surrounding the screws were observed. One patient was observed to have ASD of the thoracic spine. The mean follow-up duration was 50 months.

CONCLUSIONS

This long-term radiographic evaluation revealed the use of pedicle screws for thoracic fixation to be an effective stabilization modality. In particular, ASD seems to be less of a problem in the relatively immobile thoracic spine than in the more mobile cervical and lumbar spines.

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Robert F. Heary, Naresh K. Parvathreddy, Zainab S. Qayumi, Naiim S. Ali and Nitin Agarwal

OBJECTIVE

Fibular allograft remains a widely used strut for corpectomy surgeries. The amount of graft material that can be packed into an allograft strut has not been quantified. Cages are an alternative to fibular allograft for fusion surgeries. The authors of this study assessed the suitability of carbon fiber–reinforced polyetheretherketone (CFRP) cages for anterior corpectomy surgeries. They further explored the parameters known to affect fusion rates in clinical practice.

METHODS

Six fibular allografts were tested at standard lengths. Three sets of carbon fiber cages (Bengal, DePuy Spine), each with a different footprint size but the same lengths, were tested. The allografts and cages were wrapped in adhesive, fluid-tight transparent barriers and filled with oil. The volume and weight of the oil instilled as well as the implant footprints were measured. The fibular allografts and cages were tested at 20-, 40-, and 50-mm lengths. Two investigators independently performed all measurements 5 times. Five CFRP cubes (1 × 1 × 1 cm) were tested under pure compression, and load versus displacement curves were plotted to determine the modulus of elasticity.

RESULTS

Significantly more oil fit in the CFRP cages than in the fibular allografts (p < 0.0001). The weight and volume of oil was 4–6 times greater in the cages. Interobserver (r = 0.991) and intraobserver (r = 0.993) reliability was excellent. The modulus of elasticity for CFRP was 16.44 ± 2.07 GPa.

CONCLUSIONS

Carbon fiber–reinforced polyetheretherketone cages can accommodate much more graft material than can fibular allografts. In clinical practice, the ability to deliver greater amounts of graft material following a corpectomy may improve fusion rates.

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Robert F. Heary, Ira M. Goldstein, Katarzyna M. Getto and Nitin Agarwal

Cervical disc arthroplasty (CDA) has been gaining popularity as a surgical alternative to anterior cervical discectomy and fusion. Spontaneous fusion following a CDA is uncommon. A few anecdotal reports of heterotrophic ossification around the implant sites have been noted for the BRYAN, ProDisc-C, Mobi-C, PRESTIGE, and PCM devices. All CDA fusions reported to date have been in devices that are semiconstrained.

The authors reported the case of a 56-year-old man who presented with left C-7 radiculopathy and neck pain for 10 weeks after an assault injury. There was evidence of disc herniation at the C6–7 level. He was otherwise healthy with functional scores on the visual analog scale (VAS, 4.2); neck disability index (NDI, 16); and the 36-item short form health survey (SF-36; physical component summary [PSC] score 43 and mental component summary [MCS] score 47). The patient underwent total disc replacement in which the DISCOVER Artificial Cervical Disc (DePuy Spine, Inc.) was used. The patient was seen at regular follow-up visits up to 60 months. At his 60-month follow-up visit, he had complete radiographic fusion at the C6–7 level with bridging trabecular bone and no motion at the index site on dynamic imaging. He was pain free, with a VAS score of 0, NDI score of 0, and SF-36 PCS and MCS scores of 61 and 55, respectively.

Conclusions

This is the first case report that identifies the phenomenon of fusion around a nonconstrained cervical prosthesis. Despite this unwanted radiographic outcome, the patient's clinical outcome was excellent.

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Robert F. Heary, Nitin Agarwal, James C. Barrese, Maureen T. Barry and Ada Baisre

Lesions metastatic to the site of a meningioma resection from a different primary tumor are rare. Metastasis of a tumor without a known primary tumor is also rare. Metastasis of a renal cell carcinoma, without an identifiable primary tumor, to the bed of a meningioma resection has not been previously reported.

The authors describe the case of a 54-year-old man who presented with decreased sensory and motor function in the lower extremities. He underwent T3–5 laminectomies and gross-total removal of an intradural, extramedullary meningioma. The postoperative course was uneventful, and the patient regained full neurological function. After a 3-year period, he developed progressive upper thoracic pain and lower-extremity paresthesias. Imaging studies showed an epidural mass at the T2–4 levels and what appeared to be blastic involvement of the T2–4 vertebrae. A metastatic workup was negative. Emergency revision laminectomies yielded a fibrous, nonvascular mass. Neuropathology was consistent with metastatic renal cell carcinoma. After 6 months, the patient's symptoms of pain and paresthesias recurred. Repeat excision, with decompression of the spinal cord, revealed tumor cells morphologically and immunophenotypically similar to those obtained from the prior surgery. Cytogenetic analysis confirmed the presence of metastatic renal cell carcinoma.

A novel case of an epidural metastatic renal cell carcinoma, of unknown primary origin, in the same operative bed of a previously resected intradural, extramedullary meningioma of the thoracic spine is reported.

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Nitin Agarwal, Daniel P. Feghhi, Raghav Gupta, David R. Hansberry, John C. Quinn, Robert F. Heary and Ira M. Goldstein

Object

The Internet has become a widespread source for disseminating health information to large numbers of people. Such is the case for spine surgery as well. Given the complexity of spinal surgeries, an important point to consider is whether these resources are easily read and understood by most Americans. The average national reading grade level has been estimated to be at about the 7th grade. In the present study the authors strove to assess the readability of open spine surgery resources and minimally invasive spine surgery resources to offer suggestions to help improve the readability of patient resources.

Methods

Online patient education resources were downloaded in 2013 from 50 resources representing either traditional open back surgery or minimally invasive spine surgery. Each resource was assessed using 10 scales from Readability Studio Professional Edition version 2012.1.

Results

Patient education resources representing traditional open back surgery or minimally invasive spine surgery were all found to be written at a level well above the recommended 6th grade level. In general, minimally invasive spine surgery materials were written at a higher grade level.

Conclusions

The readability of patient education resources from spine surgery websites exceeds the average reading ability of an American adult. Revisions may be warranted to increase quality and patient comprehension of these resources to effectively reach a greater patient population.