Fluoroscopic Radiation Exposure in Spinal Surgery: In Vivo Evaluation for Operating Room Personnel.

STUDY DESIGN: Prospective in vivo investigation of fluoroscopic radiation exposure during spinal surgery. OBJECTIVE: To quantify the total amount of radiation dosage and identify techniques to maintain safe levels of fluoroscopic exposure in the operating room. SUMMARY OF BACKGROUND DATA: No previous study has performed an in vivo examination of fluoroscopic radiation exposure to the spinal surgeon and operating room personnel. Previous similar studies were in vitro, used older versions of fluoroscopy, and increased fluoro times associated with pedicle screw placement. METHODS: Thirty-five surgeries were evaluated in 18 males and 17 females (mean age 52.4 y; range, 26.0-79.4). Surgeries included 37 lumbar levels fused, 45 lumbar decompressions, 8 anterior cervical fusions, and 19 transforaminal lumbar interbody fusion procedures. Spinal instrumentation was implemented in all fusion procedures (104 lumbar pedicle screws, 14 iliac, 22 anterior cervical). Radiation dosimetry was obtained through unprotected badges placed on surgeon's chest, first assistant chest, cranial and caudal end of operating table. RESULTS: Total fluoroscopic time was 37.01 minutes. Mean fluoroscopic time with lumbar spine instrumentation was greater than decompression alone (1.74 vs. 0.22 min). Total fluoroscopic radiation exposure was obtained for surgeon (1225 mrem), first assistant (369 mrem), cranial table (92 mrem), and caudal table (150 mrem). Mean dose/min (mrem/min) was calculated for surgeon (33.1), first assistant (9.97), cranial table (2.48), and caudal table (4.05). To remain below the maximum yearly permissible level of radiation, the estimated total number of minutes for the surgeon would be 453. CONCLUSIONS: The results of this in vivo study indicate fluoroscopic dosage to the spine surgeon remains below the annual maximum limit of radiation exposure. Increasing distance from radiation source led to a significantly diminished in vivo dosimetry reading. Monitoring fluoroscopic time and maintaining a distance from the beam source, radiation exposure to the spine surgeon may be kept within current safety standards.

Role of pelvic incidence, thoracic kyphosis, and patient factors on sagittal plane correction following pedicle subtraction osteotomy.

STUDY DESIGN: An analysis of clinical and radiographic data of 40 consecutive patients with fixed sagittal imbalance. OBJECTIVE: To determine the effect of mid lumbar pedicle subtraction osteotomy (PSO), pelvic incidence (PI), thoracic kyphosis (TK), and patient characteristics on correction obtained in patients with fixed sagittal imbalance. SUMMARY OF BACKGROUND DATA: PSO is commonly performed for spinal reconstruction in patients with fixed sagittal imbalance. Prior studies have not investigated the role that osteotomy location, PI, TK, and presenting patient characteristics may play in the correction obtained after PSO. METHODS: Forty consecutive patients were identified who underwent PSO with minimum 2-year clinical and radiographic follow-up at a single institution. Data were analyzed before surgery and at 2 and 24 months after surgery to identify the magnitude and durability of correction and associated variables. RESULTS.: C7 plumb line improved from mean 15 cm anterior to the sacrum before surgery to 3.0 cm after surgery and 4.5 cm at 24 months (P < 0.0001); mean PSO wedge size was 32.4 degrees . Patients treated for idiopathic deformity (typically following prior Harrington rod fusions) had better maintenance of correction than patients with degenerative sagittal imbalance, although not statistically significant (P = 0.06). Fusion to the upper thoracic spine preserved correction better than fusion to the thoracolumbar junction. Sagittal plane correction, SRS outcome scores and Oswestry scores were equivalent comparing PSO's performed at L2 and L3.Using our patient data, we tested models of PI and TK to predict the lumbar lordosis needed to achieve ideal sagittal balance. The formula PI + LL + TK < or =45 degrees showed 91% sensitivity for predicting ideal sagittal balance at 24 months (P = 0.001). CONCLUSION: PI and TK can predict the lumbar lordosis necessary to correct sagittal imbalance in patients under-going PSO with high sensitivity. Sagittal correction and clinical outcome scores were equivalent comparing PSO's performed at L2 and L3. Patients with degenerative sagittal imbalance and those with shorter fusions are more likely to lose correction with time.

Pedicle screw instrumentation for adult idiopathic scoliosis: an improvement over hook/hybrid fixation.

STUDY DESIGN: A matched cohort comparison of adult idiopathic scoliosis (AdIS) patients treated with all pedicle screw constructs compared to hook/hybrid constructs. OBJECTIVE: To compare clinical and radiographic results of AdIS treatment using all pedicle screw constructs versus hook/hybrid constructs. SUMMARY OF BACKGROUND DATA: Pedicle screw instrumentation has demonstrated excellent clinical efficacy in the treatment of pediatric spinal deformity. No prior reports have compared the outcomes of pedicle screw only constructs to hook/hybrid constructs in the treatment of AdIS. METHODS: We analyzed 34 consecutive patients undergoing posterior-only correction for AdIS, using pedicle screw instrumentation at minimum 2-year follow-up. Thirty-four matching patients (11 with anterior releases) were selected from a cohort of 58 patients treated with hook/hybrid constructs based on similar age, curve type, magnitude, and fusion levels. RESULTS: Significantly greater curve correction was seen in the pedicle screw compared to the hook/hybrid group (56 vs. 40%, P < 0.01). Coronal and sagittal imbalance were equivalent between the groups (P = 0.91 and 0.23, respectively). Thoracic kyphosis (T5-T12) was maintained in the pedicle screw patients but significantly increased in the hybrid/hook patients over time (P < 0.05). Scoliosis Research Society outcome scores significantly improved in both groups. Blood loss was equivalent but operative time was longer in the hook/hybrid patients.No pedicle screw patients were revised for instrumentation complications with 1 lumbosacral nonunion revised at 5 years postoperative (3% revision rate). Eight of 58 patients among the hook/hybrid cohort underwent 9 revisions for instrumentation failure (n = 3) or nonunion (n = 6) (14% revision rate; P = 0.04). CONCLUSION: Pedicle screw correction of AdIS is safe and effective. Compared to hook/hybrid constructs, these patients displayed significantly improved correction of the major curve (even in the absence of anterior releases), maintenance of thoracic kyphosis, and a lower revision rate. Similar SRS scores and blood loss were noted. The hook/hybrid patients had significantly longer operative times. The use of BMP-2 in 7 patients and TLIF/ALIF also in 7 of the pedicle screw patients may have decreased the need for revision surgery up to the latest follow-up.

Bone morphogenetic protein (RhBMP-2) as a substitute for iliac crest bone graft in multilevel adult spinal deformity surgery: minimum two-year evaluation of fusion.

STUDY DESIGN: Prospective, single center, nonblinded radiographic analysis of anterior and posterior adult spinal deformity fusions performed with bone morphogenetic protein (rhBMP-2). OBJECTIVE: To determine the ability of rhBMP-2 to achieve multilevel spinal fusion in the deformity patient. SUMMARY OF BACKGROUND DATA: No previous study has evaluated rhBMP-2 for multilevel adult spinal deformity fusion with 2-year results. We postulated fusion could be achieved without distant autogenous graft harvest. METHODS: Prospective analysis was performed for 98 patients (308 levels; mean age, 51.4 years) who underwent multilevel anterior or posterior spinal fusion (PSF) with minimum 2-year follow-up (average, 2.6 years). Group 1 (10 mg/level) contained 47 patients (109 levels; 2.33 levels/patient) who underwent anterior spinal fusion (ASF): BMP on an absorbable collagen sponge (ACS) with a titanium mesh cage. Group 2 (20 mg/level) included 43 patients (156 levels; 3.63 levels/patient) with PSF: BMP on an ACS with local bone graft (LBG) and bulking agent [tricalcium phosphate/hydroxyapatite (TCP-HA)]. Group 3 (40 mg/level) contained 8 patients (43 levels; 5.38 levels/patient) with PSF: rhBMP-2 and TCP-HA with no autologous bone. Confounding negative factors were present in the study population: medical comorbidities (26%), tobacco use (17%), revision surgery (34%), previous laminectomy (51%), and preoperative pseudarthrosis (27%). Postoperative films (AP, lateral, oblique) were evaluated by independent observers. Average fusion grade was based on a published scale. RESULTS: Overall fusion rate was 95%. (group 1 91%, group 2 97%, group 3 100%). No confounding factor demonstrated a detrimental statistical significance to fusion. CONCLUSION: In multilevel ASF, BMP (10 mg/level) generates fusion without autogenous bone. In multilevel PSF, BMP (20 mg/level) with LBG and TCP-HA produced fusion. BMP (40 mg/level) and TCP-HA without LBG achieved fusion. In multilevel spinal fusion, rhBMP-2 eliminated the necessity for iliac crest bone graft and yielded an excellent fusion rate.

Transpedicular hemiepiphysiodesis and posterior instrumentation as a treatment for congenital scoliosis.

Anterior and posterior hemiepiphysiodesis using a transpedicular approach is an effective alternative treatment when compared with the traditional convex hemiepiphysiodesis or hemivertebrae excision. No study has reported the results of instrumentation with transpedicular hemiepiphysiodesis. Our study was a retrospective radiographic evaluation to assess the efficacy of transpedicular convex hemiepiphysiodesis with short segment instrumented posterior spinal fusion for congenital scoliosis. Ten hemivertebrae in 9 patients were evaluated. The average patient age was 10.5 years (range, 2.9-14.5 years). The average follow-up was 29.7 months. Cobb angles were recorded for the instrumented segment (segmental main curve) and the global or entire curve (total main curve). These values were compared preoperatively, postoperatively, and at 2-year follow-up. The average total main curve improved in 6 of 10 curves, from 35.0 to 29.6 degrees (15.4%). The average segmental main curve improved in 8 of 10 curves, from 30.0 to 21.5 degrees (28.3%). Seven of 10 curves demonstrated either no progression or improvement at the average 2-year follow-up. Two curves in older patients (greater than 9 years, 10 months) progressed until a comprehensive posterior spinal fusion was required. Multiple surgical techniques have been developed to provide treatment for progressive congenital scoliosis. Transpedicular hemiepiphysiodesis with a short segment instrumented posterior spinal fusion is a safe and effective treatment method to halt the progression of congenital scoliosis due to a hemivertebra in patients who are skeletally immature.

Vertebral bone resorption after transforaminal lumbar interbody fusion with bone morphogenetic protein (rhBMP-2).

OBJECTIVE: Bone morphogenetic protein (rhBMP-2) has demonstrated an increased rate of interbody fusion when placed in the intervertebral space. Owing to this advantage, rhBMP-2 is being implanted with increasing frequency in the lumbar spine. The purpose was to quantify and describe the presence of bone resorption within the vertebral body after transforaminal lumbar interbody fusion with placement of rhBMP-2 within the disc space. METHODS: Twenty-six patients were selected from a clinical database. Patients included in the study had undergone a transforaminal lumbar interbody fusion with BMP. Interbody implants included allograft dowels or interbody cages augmented with autograft or allograft bone. A computed tomography study of the lumbar spine a minimum of 3-month postoperatively was another inclusion criterion. Osteolytic defects were grouped into 3 categories on the basis of the size and extent of involvement in the vertebral body. RESULTS: A total of 32 lumbar levels were reviewed. Fourteen males and 12 females with an average age of 46.0 years were included in the study. Bone resorption defects were noted in 22 of the 32 levels reviewed (69%). The defects were characterized as mild in 50% (11 of 22), moderate in 18% (4 of 22), and severe in 31% (7 of 22). CONCLUSIONS: The benefit of rhBMP-2 to promote interbody fusion in the lumbar spine has been well documented. BMP has demonstrated an increased fusion rate and the ability to produce a robust fusion mass. rh-BMP-2's osseous remodeling potential may lead to bone resorption within the vertebral body.

Interobserver reliability in the interpretation of diagnostic lumbar MRI and nuclear imaging.

BACKGROUND CONTEXT: Assessment of patients with complaints of low back or leg pain varies with the subspecialty of the treating physician. The evaluation of the spine patient may include magnetic resonance imaging (MRI), bone scan, or single-photon emission computed tomography (SPECT) imaging. The interpretation of these tests and the examiner's biases will impact the outcome of patient treatment and the cost to the health-care system. PURPOSE: To evaluate interobserver reliability of MRI and nuclear imaging studies and determine the predictability of nuclear medicine results based upon MRI findings. STUDY DESIGN/SETTING: Retrospective radiographic review for patients with low back pain. MRI, planar bone scan imaging, and SPECT imaging techniques were evaluated. PATIENT SAMPLE: Seventeen patients (80 lumbar levels) who presented to an orthopedic spine specialist with a complaint of mechanical low back or leg pain were randomly selected. Inclusion criteria were age greater than 21 years and a workup that included MRI, bone scan, and SPECT scan images. OUTCOME MEASURES: Interobserver reliability was determined using kappa values (0.6 to <0.8=substantial; 0.8-1=perfect). Interobserver reliability was evaluated for all studies and compared with a "group consensus." METHODS: A team of orthopedists and radiologists of varying experience levels were assembled to interpret the imaging studies. All readings were performed independently followed by group interpretation and discussion. The reviewers were asked to assess each lumbar level (L1-L2 through L5-S1). Phase one: Is the level degenerative? Is there a spondylolisthesis present? Does the level have Modic changes on MRI? Phase two: Based on the MRI, will the planar bone scan be positive? After this prediction, was the planar scan positive? Identify the lesion location (anterior column vs. posterior column). Phase three: Based on their assessment and predicted results on planar bone scan, was the SPECT scan able to improve this assessment? RESULTS: High kappa values were demonstrated in the identification of a degenerative disc, spondylolisthesis, and Modic change (0.773, 0.728, and 0.669, respectively). Bone scan and SPECT scan yielded poorer kappa results (0.539 and 0.460, respectively). Reviewer-predicted bone scan results demonstrated a positive predictive value of 68% and a negative predictive value of 84%. Predicated SPECT results were similar (positive predictive value 66% and negative predictive value 84%). SPECT identified 24% more lesions in the lumbar spine when compared with bone scan. CONCLUSIONS: MRI interpretation of the lumbar spine is comparable between specialties. Nuclear imaging studies (bone scan/SPECT) demonstrated a poorer correlation between examiners. The presence of MRI changes enables an accurate prediction of bone scan or SPECT scan findings. SPECT scan demonstrates an increased sensitivity in the detection of spinal abnormalities and the ability to localize a lesion when compared with planar bone scan.