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Joseph T. Alexander, Charles L. Branch Jr., Brian R. Subach, and Regis W. Haid Jr.

✓ Polyhydroxy acids are a promising class of resorbable materials with potential applications in spinal surgery. One such polymer, MacroPore (MacroPore Biosurgery, Inc.), offers a balance of strength, predictable degradation, lack of stimulus of foreign body reaction, and biocompatibility with neural tissue. MacroPore can be formed into an array of shapes and can be manufactured, sterilized, and stored using conventional techniques. Limited clinical experience has been gained with resorbable implants used as load-sharing devices in a posterior lumbar interbody fusion construct.

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Prithvi Narayan, Regis W. Haid, Brian R. Subach, Christopher H. Comey, and Gerald E. Rodts

Object. Pedicle screw fixation with transverse process fusion has gained widespread acceptance since its inception. Improved rates of arthrodesis have been demonstrated when this technique is used. The authors present one of the largest series of patients to undergo this procedure at a single center; one of the goals was to correlate construct length and spinal disease with rates of successful arthrodesis by conducting a prospective analysis of lumbar fusion in which pedicle screws were placed.

Methods. During a 7-year period, the senior author performed pedicle screw fixation with posterolateral fusion in 457 patients; the mean follow-up period was 28.4 months. Indications for fusion included metastatic tumor, single-level degenerative disc disease (DDD), trauma, degenerative scoliosis, and translational vertebral instability. Successful fusion was based on the radiographic demonstration of a bilateral contiguous osseous bridge over the transverse processes and absence of movement on dynamic x-ray films.

Fusion rates were lowest in cases of tumors (54%) and highest in cases of trauma (96%). In patients with single-level DDD the rate was 91%, and in those with translational instability it was 89%. Fusion rates, however, declined steeply in relation to each additional motion segment in the translational instability group. In this group a strong linear trend for proportion was demonstrated (p < 0.001). The overall fusion rate in patients with degenerative scoliosis was 70%. The overall fusion rate for the entire group was 86%.

Conclusions. The data in this study can be used as a benchmark with which to compare newer technologies. Although overall pedicle screw—assisted fusion rate in cases of trauma or selected degenerative lesions approached 90%, the arthrodesis rates are not uniform for the different diagnoses. This appears to be related to the underlying spinal disease and the number of segments included in the fusion.

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Amory J. Fiore, Regis W. Haid, Gerald E. Rodts, Brian R. Subach, Praveen V. Mummaneni, Charles J. Riedel, and Barry D. Birch

Object

A variety of techniques may be used to achieve fixation of the upper cervical spine. Transarticular atlantoaxial screws, posterior interspinous cable and graft constructs, and interlaminar clamps have been used effectively to achieve atlantoaxial fixation. Various anatomical factors, however, may preclude the successful application of these techniques. These factors include aberrant vertebral artery anatomy, irreducible atlantoaxial subluxation, exaggerated cervicothoracic kyphosis, and the absence of the osseous substrate for fixation. In these cases, an alternative method of fixation must be performed. The authors present an alternative method to achieve fixation of the atlas in which lateral mass screws can be applied to atlantoaxial and occipitocervical fixation.

Methods

Between February 1998 and November 2001, eight patients who ranged in age from 16 to 74 years underwent posterior fixation for upper cervical instability. Diagnoses included C-2 metastastic disease in two patients, irreducible odontoid fractures in two patients, atlantoaxial subluxation in two patients, and transverse ligament synovial cyst in two patients. Various anatomical factors precluded transarticular atlantoaxial screw fixation in seven patients. One patient with a highly unstable spine due to a C-2 metastasis and pathological fracture underwent occipitocervical fusion.

Atlantocervical fixation was achieved in seven patients by using varying constructs incorporating C-1 lateral mass screws. Occipitocervical fixation was achieved in one patient by incorporating C-1 lateral mass screws as an additional fixation point. A total of 14 C-1 lateral mass screws were placed in eight patients. There were no intraoperative complications. In all patients rigid fixation was achieved as demonstrated on postoperative radiographs. One patient died on postoperative Day 9 of aspiration pneumonia. At a mean follow-up time of 7.4 months, rigid fixation was maintained in all patients.

Conclusions

Atlantal lateral mass screws can be used to provide a safe and efficacious means of achieving atlantoaxial fixation when anatomical constraints preclude the use of a more traditional procedure. Atlantal lateral mass screws may also be incorporated in occipitocervical constructs to provide additional fixation points which may prevent construct failure.

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Matthew T. Mayr, Brian R. Subach, Christopher H. Comey, Gerald E. Rodts, and Regis W. Haid Jr.

Object. The authors undertook a retrospective single-institution review of 261 patients who underwent anterior cervical corpectomy, reconstruction with allograft fibula, and placement of an anterior plating system for the treatment of cervical spinal stenosis to assess fusion rates and procedure-related complications.

Methods. Between October 1989 and June 1995, 261 patients with cervical stenosis underwent cervical corpectomy, allograft fibular bone fusion, and placement of instrumentation for spondylosis (197 patients), postlaminectomy kyphosis (27 patients), acute fracture (25 patients), or ossification of the posterior longitudinal ligament (12 patients). All patients suffered neck pain and cervical myelopathy or radiculopathy refractory to medical management. Of the procedures, 133 involved a single vertebral level (two disc levels and one vertebral body), 96 involved two levels, 31 involved three levels, and a single patient underwent a four-level procedure. Clinical and radiographic outcomes were assessed postoperatively and at 6-month intervals. The mean follow-up period was 25.7 months (range 24–47 months).

Successful fusion was documented in 226 patients (86.6%). A stable, fibrous union developed in 33 asymptomatic patients (12.6%), whereas an unstable pseudarthrosis in two patients (0.8%) required reoperation. There were no cases of infection, spinal fluid leakage, or postoperative hematoma. Complications included transient unilateral upper-extremity weakness (two patients), dysphagia (35 transient and seven permanent), and hoarseness (35 transient and two permanent). In 14 patients (5.4%) radiological studies demonstrated evidence of hardware failure.

Conclusions. Cervical corpectomy with fibular allograft reconstruction and anterior plating is an effective means of achieving spinal decompression and stabilization in cases of anterior cervical disease. Symptomatic improvement was achieved in 99.2% of patients. In their series the authors found a fusion rate of 86.6% and rates of permanent hoarseness of 3.4%, dysphagia of 0.7%, and an instrumentation failure rate of 5.4%.

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Praveen V. Mummaneni, Regis W. Haid, Vincent C. Traynelis, Rick C. Sasso, Brian R. Subach, Amory J. Fiore, and Gerald E. Rodts

Object

Standard lateral mass plate and screw systems are of limited use in patients with abnormal cervical anatomy and do not easily allow for extension to either the occipit or the thoracic spine. The objective of this study was to demonstrate the safety, surgical efficacy, and advantages of a new cervical polyaxial screw and rod system for posterior occipitocervicothoracic arthrodesis.

Methods

The authors reviewed a multicenter series of patients who underwent surgery in which they used a new posterior cervical polyaxial screw and rod system. The system was implanted in 32 (20 women and 12 men) adult patients (mean age 56.9 years, range 23–84 years). Twentythree of the patients were treated for spondylostenosis; four for cervical fracture/dislocations; four for kyphosis; and one patient was treated for pseudarthrosis that developed after prior surgery.

The system was successfully implanted in all patients despite the presence of anatomical lateral mass anomalies in the majority of cases. The mean number of levels fused was 3.9 (range one–eight levels). This dynamic system allowed for screw placement into the occiput, C-1 lateral masses, C-2 pars, C3–7 lateral masses, and low cervical as well as upper thoracic pedicles. Selective application of compressive or distractive forces was possible in adjacent segments. Surgery-related complications included one dural tear and one malpositioned screw. There were two cases of wound infection.

Conclusions

Unlike standard lateral mass plate and screw systems, the new cervical polyaxial screw and rod system easily accommodates severe degenerative cervical spondylosis and curvatures. This instrumentation system allows for polyaxial screw placement with subsequent multiplanar rod contouring and offset attachment. The authors have used this system successfully, and without significant complications, to achieve posterior cervical arthrodesis.

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Brian R. Subach, Regis W. Haid, Gerald E. Rodts, and Michael G. Kaiser

The widespread use of fusion procedures in the management of spinal disorders has led investigators to explore the use of growth and differentiation factors in such procedures. As an adjuvant to allograft bone or as a replacement for harvested autograft, bone morphogenetic proteins (BMPs) appear to improve fusion rates after spinal arthrodesis in both animal models and humans, while reducing the donor-site morbidity previously associated with such procedures. The use of recombinant genetic technology in the production of BMP has improved the efficiency, cost effectiveness, and safety of producing and using such materials. Recombinant human BMP-2 (rhBMP-2), as one of the first factors identified in the process of endochondral bone formation, has been extensively researched over the past decade. The efficacy and dose profile of this differentiation factor in the context of various carrier substrates has been investigated. Based on the encouraging results of preliminary studies, the future role of rhBMP-2 may lie in its replacement of autologous bone grafting and, consequently, the reduced need for instrumented fixation, while concurrently improving overall fusion rates. The authors provide an overview of BMP and review its use in clinical and laboratory settings.

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Shushil Shilpakar SK, Mark R. McLaughlin, Regis W. Haid Jr., Gerald E. Rodts Jr., and Brian R. Subach

In this article the authors describe the management of Type II odontoid fractures with special attention to operative technique and avoidance of complication. Anterior odontoid screw fixation is a procedure the authors have performed over the last 8 years in cases with acute Type II and rostral Type III odontoid fractures. In cases of Chronic Type II odontoid fractures and in patients with transverse ligament disruption, the authors prefer to undertake posterior transarticular facet screw fixation supplemented by bone graft and interspinous C1–2 wiring.

The technical aspects of these procedures are described with a focus on operative nuances. Selection criteria and techniques that the authors have refined over the years have helped them to optimize success rates and minimize complications.

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Mark R. McLaughlin, Jonathan Y. Zhang, Brian R. Subach, Regis W. Haid Jr., and Gerald E. Rodts Jr.

In recent years, there has been an unprecedented increase in the number of patients undergoing treatment with interbody fusion devices for degenerative disease of the lumbar spine. These devices can be placed either anteriorly or posteriorly. With the advent of minimally invasive surgery and the increasing ability of general surgeons to perform transperitoneal procedures laparoscopically, a new laparoscopic technique has been developed for placing lumbar interbody fusion devices. Although this procedure has some advantages over posterior lumbar interbody fusion, it is not without significant risk, and the learning curve is steep. The authors review a series of 32 consecutive patients who underwent single-level laparoscopic anterior lumbar interbody fusion at L4–5 or L5–S1 over a 2-year period for the treatment of single-level lumbar degenerative disease. In this report they review the technical aspects of the procedure and the important lessons they have learned through their early experience with this technique.

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