Federico P. Girardi

The biology of bone grafting.

Abstract Many approaches are used to repair skeletal defects in reconstructive orthopaedic surgery, and bone grafting is involved in virtually every procedure. The type of bone graft used depends on the clinical scenario and the anticipated final outcome. Autogenous cancellous bone graft, with its osteogenic, osteoinductive, and osteoconductive properties, remains the standard for grafting. However, the high incidence of morbidity during autogenous graft harvest may make the acquisition of grafts from other sources desirable. The clinical applications for each type of bone graft are dictated by the structure and biochemical properties of the graft. An elegant cellular and molecular cascade follows bone transplantation. Bone graft incorporation within the host, whether autogenous or allogeneic, depends on many factors: type of graft (autogenous versus allogeneic, vascular versus nonvascular), site of transplant, quality of transplanted bone and host bone, host bed preparation, preservation techniques, systemic and local disease, and mechanical properties of the graft.

Results of the prospective, randomized, multicenter Food and Drug Administration investigational device exemption study of the ProDisc-L total disc replacement versus circumferential fusion for the treatment of 1-level degenerative disc disease.

Study Design. A prospective, randomized, multicenter, Food and Drug Administration-regulated Investigational Device Exemption clinical trial. Objective. To evaluate the safety and effectiveness of the ProDisc®-L (Synthes Spine, West Chester, PA) lumbar total disc replacement compared to circumferential spinal fusion for the treatment of discogenic pain at 1 vertebral level between L3 and S1. Summary of Background Data. As part of the Investigational Device Exemption clinical trial, favorable single center results of lumbar total disc replacement with the ProDisc®-L have been reported previously. Methods. Two hundred eighty-six (286) patients were treated on protocol. Patients were evaluated before and after surgery, at 6 weeks, 3, 6, 12, 18, and 24 months. Evaluation at each visit included patient self-assessments, physical and neurologic examinations, and radiographic evaluation. Results. Safety of ProDisc®-L implantation was demonstrated with 0% major complications. At 24 months, 91.8% of investigational and 84.5% of control patients reported improvement in the Oswestry Low Back Pain Disability Questionnaire (Oswestry Disability Index [ODI]) from preoperative levels, and 77.2% of investigational and 64.8% of control patients met the ≥15% Oswestry Disability Index improvement criteria. Overall neurologic success in the investigational group was superior to the control group (91.2% investigational and 81.4% control; P = 0.0341). At 6 weeks and 3 months follow-up time points, the ProDisc®-L patients recorded SF-36 Health Survey scores significantly higher than the control group (P = 0.018, P = 0.0036, respectively). The visual analog scale pain assessment showed statistically significant improvement from preoperative levels regardless of treatment (P < 0.0001). Visual analog scale patient satisfaction at 24 months showed a statistically significant difference favoring investigational patients over the control group (P = 0.015). Radiographic range of motion was maintained within a normal functional range in 93.7% of investigational patients and averaged 7.7°. Conclusions. ProDisc®-L has been found to be safe and efficacious. In properly chosen patients, ProDisc®-L has been shown to be superior to circumferential fusion by multiple clinical criteria.

Incidental Durotomy in Spine Surgery

Study Design. Retrospective review of a large series of patients who underwent spinal surgery at a single institution during a 10-year period. Objectives. To further clarify the frequency of incidental durotomy during spine surgery, its treatment, associated complications, and results of long-term clinical follow-up. Summary of Background Data. Incidental durotomy is a relatively common occurrence during spinal surgery. There remains significant concern about it despite reports of good associated clinical outcomes. There have been few large clinical series on the subject. Methods. A retrospective review was conducted of clinical and surgical records and radiographic data for consecutive patients who underwent spinal surgery performed by the two senior surgeons from January 1989 through December 1998. Results. A total of 2144 patients were reviewed, and 74 were found to have dural tears occurring during or before surgery. Incidental durotomy occurred at the time of surgery in 66 patients (3.1% overall incidence). Incidence varied according to the specific procedure performed but was highest in the group that underwent revision surgery. The incidence of clinically significant durotomies occurring during surgery but not identified at the time was 0.28%. All dural tears that occurred during surgery and were recognized (60 of 66) were repaired primarily. Pseudomeningoceles developed in five of the remaining six patients. All six patients had subsequent surgical repair of dural defects because of failure of conservative therapy. A mean follow-up of 22.4 months was available and showed good long-term clinical results for all patients. Conclusions. Incidental durotomy, if recognized and treated appropriately, does not lead to long-term sequelae.

Measurement error of lumbar total disc replacement range of motion.

Study Design. A retrospective review of lumbar total disc replacement (TDR) radiographs. Objective. To determine the error and variability in measuring TDR radiographic range of motion (ROM). Summary of Background Data. Motion preservation is the driving force behind lumbar TDR technology. In the recent literature, sagittal radiographic TDR ROM as low as 2° has been reported. In these studies, ROM was determined by using the Cobb method to measure TDR sagittal alignment angles in flexion-extension lateral radiographs. However, previous studies in the spinal deformity literature have shown that the Cobb method is very susceptible to measurement error. Methods. There were 5 observers, including 2 attending orthopedic spine surgeons, 1 spine fellow, 1 fifth-year resident, and 1 fourth-year resident, who measured the ROM of 50 ProDisc II (Synthes Spine Solutions, New York, NY) TDRs on standard flexion-extension lumbar spine radiograph sets. Repeated measurements were made on 2 occasions using the Cobb method. Measurement variability was calculated using 3 statistical methods. Results. The 3 statistical methods resulted in extremely similar values for TDR ROM observer variability. Overall, the intraobserver variability of TDR ROM measurement was ±4.6°, and interobserver variability was ±5.2°. Conclusions. To be 95% certain that an implanted TDR prosthesis has any sagittal motion, a ROM of at least 4.6° must be observed, which is the upper limit of intraobserver measurement variability for a TDR with a true ROM of 0°. To be 95% certain that a change in TDR ROM has occurred between 2 measurements by the same observer, a change in ROM of at least 9.6° must be observed (the entire range of ±4.6° intraobserver variability). ROM measurement variability should be considered when evaluating the success or failure of motion preservation in lumbar TDR.

Factors predicting hospital stay, operative time, blood loss, and transfusion in patients undergoing revision posterior lumbar spine decompression, fusion, and segmental instrumentation.

Study Design. A retrospective chart review was conducted for 112 patients who underwent revision posterior lumbar spine decompression, fusion, and segmental instrumentation. Objective. To ascertain factors predicting hospital stay, operative time, blood loss, and transfusion in patients undergoing revision posterior lumbar spine decompression, fusion, and segmental instrumentation. Summary of Background Data. Posterior lumbar spine decompression and fusion with segmental instrumentation is a common procedure in the treatment of degenerative lumbar spine disorders. Many patients undergoing this procedure have had previous lumbar spine surgery, yet little is known about the factors predicting hospital stay, operative time, blood loss, and transfusion. Methods. The charts of 112 patients (53 men and 59 women) with degenerative lumbar spinal stenosis who underwent revision surgery from March 1992 to June 1999 were reviewed. Their average age was 54 years (range, 27–84 years). All the surgeries included decompression and fusion with segmental instrumentation. The patients’ demographics, comorbid conditions, factors related to previous lumbar spine surgery, diagnosis, number of levels fused, and preoperative hemoglobin and hematocrit were collected and used as the independent variables. Multiple regression analysis was used to ascertain factors predicting length of hospital stay, operative time, intraoperative blood loss, and transfusion. Results. The mean length of hospital stay was 6 ± 2.4 days, the operative time 280 ± 62 minutes, the estimated intraoperative blood loss 1073 ± 716 mL, and the total volume of blood transfused 1.04 ± 1.17 U. For 63% of the patients, a blood transfusion was needed. Increasing age was the significant predictor for hospital stay (P < 0.001). The factors predicting operative time were number of levels fused (P < 0.001), diagnosis of degenerative scoliosis (P < 0.05), and excessive body weight (P < 0.01). The factors predicting intraoperative blood loss were number of levels fused (P < 0.01), body weight (P < 0.001), and high preoperative hemoglobin (P < 0.001). Both logistic and linear regression analysis showed that the factors predicting blood transfusion were number of levels fused (P < 0.01), age (P < 0.05), and low preoperative hemoglobin (P < 0.001). Other factors associated with hospital stay and blood transfusion were unemployment associated with three or more comorbid conditions and compli-cations. The women had less intraoperative blood loss (P < 0.01), but received more transfused blood than the men (P < 0.01). Conclusions. Number of levels fused and age seem to be the most significant factors predicting hospital stay, operative time, intraoperative blood loss, and transfusion in patients undergoing revision posterior lumbar spine decompression, fusion, and segmental instrumentation.

Lumbar Total Disc Replacement: Seven to Eleven-year Follow-up

BACKGROUND Symptomatic lumbar degenerative disc disease is a challenging entity to treat. The results of arthrodesis may be compromised in the short term by pseudarthrosis and in the long term by pain at the iliac-crest donor site and by junctional degeneration. Total disc replacement has the potential to provide long-lasting relief to these patients. The purpose of this study was to present the clinical and radiographic results assessed seven to eleven years following a Prodisc total lumbar disc replacement. METHODS Sixty-four patients had single or multiple-level implantation of a total lumbar disc replacement between 1990 and 1993. The mean duration of follow-up was 8.7 years. Clinical results were evaluated by assessing preoperative and postoperative lumbar pain, radiculopathy, disability, and modified Stauffer-Coventry scores. Preoperative and postoperative radiographs were evaluated as well. Subgroup analysis was performed to determine if gender, an age of less than forty-five years, previous surgery, or multilevel surgery had an effect on outcome. RESULTS At an average of 8.7 years postoperatively, there were significant improvements in the back-pain, radiculopathy, disability, and modified Stauffer-Coventry scores. Thirty-three of the fifty-five patients with sufficient follow-up had an excellent result, eight had a good result, and fourteen had a poor result. Neither gender nor multilevel surgery affected outcome. An age of less than forty-five years and prior lumbar surgery had small but significant negative effects on outcome. Radiographs did not demonstrate loosening, migration, or mechanical failure in any patient. Five patients had approach-related complications. CONCLUSIONS The Prodisc lumbar total disc replacement appears to be effective and safe for the treatment of symptomatic degenerative disc disease. Gender and multilevel surgery did not affect the outcomes, whereas prior lumbar surgery or an age of less than forty-five years was associated with slightly worse outcomes. Longer follow-up of this cohort of patients and randomized trials comparing disc replacement with arthrodesis are needed.

Long-term flexion-extension range of motion of the prodisc total disc replacement.

The rationale for total disc replacement is avoidance of the junctional degeneration seen after arthrodesis by preservation of segmental motion. To justify the use of disc prostheses, it is essential to document maintained range of motion (ROM) and sagittal alignment at long-term follow-up. This is a retrospective radiographic study of 42 patients who had placement of 58 first-generation Prodisc prostheses at a mean follow-up of 8.7 years. Flexion-extension ROM was measured by Cobbs method. Junctional levels were evaluated for junctional degeneration. Pre- and postoperative global and segmental lordosis were measured. Prognostic patient factors predicting ROM of <2° were evaluated. We observed ROM of at least 2° in 66% of Prodisc prostheses at 8.7-year follow-up, although ROM was less than that reported in asymptomatic normal individuals. Mean ROM for disc prostheses with motion was 7.5° at L3–L4, 6.2° at L4–L5, and 4.1° at L5–S1. Mean ROM for all prostheses was 3.8°. The incidence of radiographic junctional degeneration was 24%, although no patients required surgery for symptomatic junctional degeneration. Mean ROM of prostheses below a degenerated junctional disc was 1.6° compared with 4.7° below a normal junctional disc (P < 0.035). Females were 3.5 times more likely to have ROM of <2°. This is the longest published follow-up study of a lumbar disc replacement. The data show that ROM is preserved at long-term follow-up in the majority of patients. Global and segmental sagittal alignment improve after surgery. Furthermore, there is an association between ROM of disc prostheses and the development of junctional degeneration.

Risk factors for postoperative infection following posterior lumbar instrumented arthrodesis.

BACKGROUND Surgical site infection in the spine is a serious postoperative complication. Factors such as posterior surgical approach, arthrodesis, use of spinal instrumentation, age, obesity, diabetes, tobacco use, operating-room environment, and estimated blood loss are well established in the literature to affect the risk of infection. The goal of this study was to analyze and identify independent risk factors for surgical site infection among spine patients undergoing posterior lumbar instrumented arthrodesis. METHODS The medical records of 3218 patients who underwent posterior lumbar instrumented arthrodesis from January 2000 to December 2006 were reviewed to identify those who developed a postoperative infection (eighty-four patients; 2.6%). The size of this single-institution patient group allowed construction of a multivariate logistic regression model to evaluate the independent associations of potential risk factors for surgical site infection in the spine. RESULTS In the final regression model, obesity, estimated intraoperative blood loss, ten or more people in the operating room, a dural tear, history of diabetes, chronic obstructive pulmonary disease, coronary heart disease, and osteoporosis were critical risk factors for the onset of spinal surgical site infection. Obesity and a history of chronic obstructive pulmonary disease were the strongest risk factors for postoperative spinal infection after adjusting for all other variables. The most common pathogen was methicillin-resistant Staphylococcus aureus with a prevalence of 34.5%. This study established a single institution infection rate for posterior lumbar instrumented arthrodesis at 2.6%. CONCLUSIONS This analysis confirms previously demonstrated risk factors for postoperative infection while reporting on new potential independent risk factors of osteoporosis, chronic obstructive pulmonary disease, and dural tears in the setting of posterior lumbar instrumented arthrodesis. Areas of new research can focus on the roles these novel factors may play in the pathogenesis of surgical site infections in the spine.

Major vascular injury during anterior lumbar spinal surgery: incidence, risk factors, and management.

Study Design. Retrospective chart review. Objective. To examine the incidence of major vascular injury during anterior lumbar spinal surgery, attempt to identify predisposing risk factors, and to discuss management techniques. Summary of Background Data. Major vascular injury can be a catastrophic complication of anterior lumbar spinal surgery. Methods. Current procedural terminology codes were used to identify the occurrence of major vascular injury, defined as injury to the iliac vessels, vena cava, and aorta. Once identified, the office record, hospital chart, operative note, and diagnostic test results were reviewed in detail. Results. Three hundred forty-five operations were performed on 338 patients. Incidence of major vascular complication was 2.9% (10 of 345). There were 9 injuries of the common iliac vein and a single aortic injury. Risk factors identified in patients with major vascular injury were current or previous osteomyelitis or discogenic infection (n = 3), previous anterior spinal surgery (n = 2), spondylolisthesis (n = 2; 1 isthmic Grade II, 1 iatrogenic Grade II), large anterior osteophyte (n = 2), transitional lumbosacral vertebra (n = 1), and anterior migration of interbody device (n = 1). Lateral venorrhaphy by suture (n = 6) and hemoclip application (n = 2) was augmented by topical agents, which constituted the sole method of repair on 1 occasion. Magnetic resonance venography demonstrated iliac vein thrombosis in 1 patient. Conclusion. Current or previous osteomyelitis or discogenic infection, previous anterior spinal surgery, spondylolisthesis, osteophyte formation, transitional lumbosacral vertebra and anterior migration of interbody device point to an increased risk of vascular injury during anterior lumbar spinal surgery. Careful handling of the vascular structures and liberal use of topical hemostatic agents can lead to control of hemorrhage and preservation of vascular patency. Routine postoperative surveillance for proximal deep vein thrombosis, by magnetic resonance venography of the pelvic veins and inferior vena cava, should be performed after venorrhaphy.

Correlation between range of motion and outcome after lumbar total disc replacement : 8.6-year follow-up

Study Design. Retrospective radiographic and chart review. Objective. To examine the relationship between lumbar total disc replacement (TDR) range of motion (ROM) and clinical outcome at 8.6-year follow-up. Summary of Background Data. There are no studies on the relationship between TDR motion and clinical outcomes. Methods. We reviewed 38 patients who underwent 1 or 2-level TDR implantation with 51 TDR. Flexion-extension ROM was measured on lateral radiographs. Clinical outcomes were measured at 8.6 years by modified Stauffer-Coventry scores, Oswestry Disability Questionnaires (ODQ), and subjective ratings of back pain, leg pain, and disability. Spearman rank correlation coefficient was used to determine if ROM was correlated with clinical outcome. Patients were divided into 2 groups by motion (≤5° and >5°). Statistical differences in outcome were sought. Results. Spearman rank correlation coefficient revealed weak-to-moderate but statistically significant associations between ROM and outcome for postoperative back pain (r = −0.35, P = 0.034), ODQ (r = −0.33, P = 0.046), and modified Stauffer-Coventry scores (r = 0.42, P = 0.0095). Patients with motion of >5° had superior outcomes in ODQ (mean difference 12.6 points, P = 0.026) and Stauffer-Coventry scores (mean difference 2.2 points, P = 0.015). Conclusions. The radiographic ROM at 8.6-year follow-up was positively correlated with several outcomes measures. Patients with motion >5° had clinically modest but statistically better outcomes in ODQ and modifiedStauffer-Coventry scores. Longer follow-ups will be necessary to measure fully the impact of TDR ROM on outcome.