Joseph Hong

The management of spinal injuries in patients with ankylosing spondylitis or diffuse idiopathic skeletal hyperostosis: a comparison of treatment methods and clinical outcomes.

Study Design A retrospective review of 12 patients with ankylosing spondylitis (AS) and 18 patients with diffuse idiopathic skeletal hyperostosis (DISH) treated at a single institution for spinal injuries between the years 2000 and 2006. Objective To independently evaluate patients with these diagnoses who sustained spinal injuries and directly compare their treatment methods and clinical outcomes. Summary of Background Data AS and DISH are disorders characterized by abnormal ossification of the spinal column, which predisposes these patients to spinal injuries with potentially devastating consequences. Methods Patient and surgical data were obtained from medical records and appropriate imaging studies. Neurologic status was recorded using the American Spinal Injury Association (ASIA) impairment scale for spinal cord injuries, and clinical outcomes were assessed using Odom criteria. Results Most of these injuries involved the subaxial cervical spine between C5 and C7. In all, 41.2% of AS patients were considered to be ASIA A, whereas 44.4% of DISH patients were classified as ASIA E. Surgery was performed in 83.3% of AS patients and 66.7% of DISH patients, and the overall complication rates were 41.7% and 33.3%, respectively. There were no statistically significant differences between the survivorship and outcomes of the AS and DISH groups and 81.3% of all respondents were classified as having excellent or good outcomes. There were 4 deaths, all of which were considered to be related to the use of halo-vest immobilization. Conclusions Although the rate of neurologic injury was high for both groups, AS patients were more likely to exhibit neurologic deficits and undergo operative management. Although the majority of these spinal injuries were treated surgically, stable fractures without any associated neurologic deficits were often successfully managed with immobilization. Complications were observed with both operative and nonoperative treatments, although all of the deaths occurred in conjunction with the use of the halo-vest orthosis.

Immunogenicity of bone morphogenetic proteins

OBJECT The object of this paper is to review the immunogenicity of bone morphogenetic proteins (BMPs) and to compare the results of the immunogenicity characterization and clinical consequences between recombinant human (rh)BMP-2 and recombinant human osteogenic protein-1 (rhOP-1/BMP-7). METHODS The immunogenicity of therapeutic proteins and its clinical effects were reviewed. The characteristics of BMPs were also described in terms of immunogenicity. The methods and results of antibody detection in various clinical trials of rhBMP-2 and rhOP-1 were compared, including the most recent studies using a systematic characterization strategy with both a binding assay and bioassay. RESULTS Similar to all recombinant human proteins, rhBMPs induce immune responses in a select subgroup of patients. Adverse effects from this response in these patients, however, have not been reported with antibody formation to either rhBMP-2 or rhOP-1. Overall, the incidence of antibody formation was slightly higher in rhOP-1 trials than in rhBMP-2 trials. CONCLUSIONS Although they occur in a subgroup of patients, the immune responses against rhBMPs have no correlation with any clinical outcome or safety parameter. Clinicians, however, must be aware of the potential complications caused by the immunogenicity of BMPs until more studies clearly elucidate their safety.

A multicenter study to evaluate the safety and efficacy of a stand-alone anterior carbon I/F Cage for anterior lumbar interbody fusion: two-year results from a Food and Drug Administration investigational device exemption clinical trial.

Study Design. Two-year prospective multicenter clinical trial. Objective. To determine the safety and efficacy of the anterior I/F Cage in the primary treatment of single-level degenerative disc disease. Summary of Background Data. A carbon fiber-reinforced polymer cage was designed to replace the traditional allograft/autograft structural graft used in an anterior lumbar interbody fusion (ALIF). Although the outcomes of various types of ALIF cages have previously been reported, the safety and efficacy of the I/F cage are unknown. Methods. Between June 2000 and June 2004, 112 patients were prospectively enrolled at 12 study sites for the current study. Efficacy was evaluated clinically and radiographically. “Patient success” was declared only when the following 4 criteria were present at final follow-up: (1) “clinical success”: improvement of 15 points on Oswestry Disability Index, (2) absence of a new neurologic abnormality, (3) successful radiographic fusion, and (4) no subsequent secondary surgical intervention at 24-month follow-up. Safety was inferred by way of an objective summary of complications and adverse events, as reported at regular intervals throughout the course of the study. Results. A total of 112 patients (mean age: 41.7 years) underwent a single-level ALIF procedure (L5–S1: 95 patients, L4–L5: 17 patients). The mean surgical time was 126 minutes, the mean estimated blood loss was 134 mL, and the mean duration of hospitalization was 3.3 days. There were 80 patients available for 24-month follow-up. Overall patient success was 25% (20/80). Clinical success was present in 46.3% (37/80), fusion success was 57.5% (46/80), and 87.5% of patients (70/80) avoided a subsequent secondary surgical intervention. Disc space height had significantly increased after surgery, and this increase was maintained at 2 years follow-up period. Complications and adverse events included the following: 8 infections (7.1%) (7 superficial, 1 deep), 2 vascular injuries (1.8%) (left common iliac vein), and 12 secondary surgical interventions (15%). Conclusion. This safety and efficacy study suggests that the anterior I/F Cage is a safe surgical option in the treatment of single-level lumbar degenerative disc disease. As a stand-alone construct, the I/F Cage yields suboptimal radiographic and clinical outcomes. Additional benefit may be gained from adjunctive posterior stabilization.

Immunogenicity of osteogenic protein 1: results from a prospective, randomized, controlled, multicenter pivotal study of uninstrumented lumbar posterolateral fusion

OBJECT The aim in this study was to detect and quantify antibody responses against recombinant human osteogenic protein 1 (OP-1) and to compare these responses to patient clinical outcomes and safety information. METHODS A controlled, open-label, randomized, prospective, multicenter pivotal study was performed in which patients with single-level Grade I or II degenerative lumbar spondylolisthesis (Meyerding classification) and spinal stenosis underwent decompression and uninstrumented posterolateral spinal arthrodesis. Three hundred thirty-six patients were randomized in a 2:1 fashion to receive either OP-1 Putty or autogenous iliac crest bone graft. Patients were evaluated at regular postoperative intervals for radiographic results, clinical outcomes, and safety parameters for more than 36 months. Serum samples were collected over this period and evaluated for the presence of anti–OP-1 antibodies and neutralizing activity by using a battery of in vitro binding assays (including enzyme-linked immunosorbent assay [ELISA]) and cell-based bioassays, respectively. RESULTS Antibodies were predominantly seen in the OP-1–treated patients, although some responses were recorded preoperatively and in patients receiving autograft alone. Antibody production peaked in the 6-week to 3-month postoperative time frame and diminished thereafter. Neutralizing antibodies (Nabs) were detected at 1 time point at least in 25.6% of the patients treated with OP-1 Putty, but were not found in any patient following the 24-month postoperative time period. A single autograft patient (1.2%) also presented with OP-1 Nabs. An anti–OP-1 antibody status did not correlate with any measure of patient outcomes or adverse events. CONCLUSIONS Recombinant human OP-1 (bone morphogenetic protein 7), like many recombinant human proteins, induces an immune response following its use as a bone graft alternative. This response was transient and diminished over time, and there was no statistical evidence to suggest an association between Nab status and any of the efficacy or safety criteria that were examined.

Evaluation of two novel thoracolumbar trauma classification systems

Background: Despite numerous attempts at classifying thoracolumbar spinal injuries, there remains no consensus on a single unifying algorithm of management. The ideal system should provide diagnostic and prognostic information, exhibit adequate reliability and validity and be easily applicable to clinical practice. The purpose of this study is to assess the reliability and validity of two novel classification systems for thoracolumbar fractures – the Thoracolumbar Injury Severity Score (TLISS) and the Thoracolumbar Injury Classification and Severity Score (TLICS) – and also to discuss potential efforts towards research in the future. Matereials and Methods: Seventy-one patients with thoracolumbar fractures were prospectively assessed by surgeons with different levels of training and experience (attending orthopedic surgeon, attending neurosurgeon, spine fellows, senior level and junior level residents) at a single institution. Plain radiographs, CT and MRI imaging were used to classify these injuries using the TLISS system. Seven months later, 25 consecutive injuries were prospectively assessed with the TLISS and TLICS systems. Unweighted Cohens kappa coefficients and Spearmans correlation values were calculated to assess inter-observer reliability and validity at each point in time. Results: For both the TLISS and TLICS algorithms, the inter-rater kappa statistics for all of the subgroups demonstrated moderate-to-substantial reliability (0.45-0.74), although there were no significant differences among the shared subgroups. The kappa score of the TLISS system was greater than that of the TLICS system for injury mechanism/ morphology. Correlation values were also greater across all subgroups (P ≤0.01). Statistically significant improvements in TLISS inter-observer reliability were observed across all TLISS fields (P <0.05). The TLISS and TLICS schemes both demonstrated excellent validity. Conclusion: The TLISS and TLICS scales both exhibited substantial reliability and validity. However, the TLISS system displayed greater inter-observer correlation than did the TLICS and demonstrated significant improvements in reliability over time.

Patient perception of outcomes following failed spinal instrumentation with polyetheretherketone rods and titanium rods.

Study Design. A structured questionnaire. Objective. The purpose of this study was to determine whether material rod composition and its imaging characteristics can determine patient perceptions of pain, outcome, and need for revision surgery in the context of the failure of spinal instrumentation following lumbar arthrodesis. Summary of Background Data. Patient perceptions of radiographic images in the context of failed spinal instrumentation may influence clinical outcomes and patient satisfaction. Due to radiolucency, failed polyetheretherketone (PEEK) rods may be perceived differently by patients than more traditional materials. Methods. Patients presenting primarily with chief complaints of back pain completed a 2-page, 22-question questionnaire containing 3 alternative radiographic images of failed rod instrumentation following posterolateral lumbar arthrodesis. The images represented failed rods composed of either PEEK, PEEK with a longitudinal radio-opaque marker, or traditional titanium. Statistical analysis with the Cochran Q test was performed to determine whether there were statistical differences in the responses. Results. The responses suggested a preference for the images representing PEEK instrumentation as being associated with superior clinical outcomes, the least pain, the most comfort, and the least likelihood of required revision surgery. Conclusion. PEEK rods possess radiolucent properties that can alter patient perceptions of clinical outcomes when compared with images of other equally unfavorable scenarios. The significance of these patient perceptions must still be demonstrated. However, they may play an important role in clinical outcomes and patient satisfaction.

Complications in the management of Charcot spinal arthropathy.

Charcot spinal arthropathy is a relatively rare, destructive process characterized by a cycle of progressive deformity, destruction, and worsening instability as a result of repetitive trauma and inflammation. It may result from nontraumatic as well as traumatic causes. Historically, patients with severe symptomatic instability have been successfully treated with combined anterior and posterior fusion techniques. The long-term outcomes and potential complications, however, have not been well reported. The authors report on 2 such cases of Charcot spinal arthropathy treated surgically, one with a traumatic and one with a nontraumatic etiology. They include the unique pitfalls encountered while treating these patients, as well as their surgical treatments, complications, and long-term results.