Safdar N. Khan

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.

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.

CLINICAL APPLICATIONS OF BONE GRAFT SUBSTITUTES

Autogenous bone grafting remains the gold standard for osseous reconstruction in clinical practice. It is associated with several limitations. The search for an alternative bone graft substitute with combined osteoinductive, osteoconductive, and osteogenic properties continues. This article highlights the properties of the various bone grafting materials currently available and discusses their efficacy in clinical practice.

Bisphosphonate therapy in fibrous dysplasia.

Fibrous dysplasia is proliferation of fibrous tissue within the bone marrow causing osteolytic lesions and pathologic fractures. Recently, second generation bisphosphonates have shown promise in the treatment of patients with fibrous dysplasia. In the current study, six patients with fibrous dysplasia were treated with either oral alone or oral and intravenous bisphosphonates. The participants were observed for changes in N-telopeptide, pain score, and radiographic changes. In the current study, the combination bisphosphonate therapy diminished pain, prevented fractures, lowered N-telopeptide values, and led to partial resolution of fibrous dysplasia lesions.

Bone growth factors.

Osteoblastic culture models, experimental, and clinical models have revealed that bone growth factors influence cellular activity. Growth factors including bone morphogenetic proteins, transforming growth factor beta, platelet-derived growth factor, insulin-like growth factors I and II, and acidic and basic fibroblast growth factors, are powerful tools for fracture healing and bone grafting. Understanding the role that bone growth factors play in bone repair is necessary to apply these factors in a clinical setting.

Alendronate inhibits spine fusion in a rat model.

Study Design. A posterolateral lumbar fusion model in rats. Objective. To study the effects of alendronate on posterolateral lumbar fusion in rats. Summary of Background Data. To our knowledge, there are no studies that show a significant inhibition of manual palpation-assessed spine fusion by alendronate. Methods. A total of 75 Sprague-Dawley rats underwent intertransverse fusion with 7-tailbone autograft at L4–L5. Animals received saline (control), alendronate equivalent to human dose (dose1, 5 &mgr;g/kg/day), or 10 times the human dose (dose10, 50 &mgr;g/kg/day) via subcutaneous osmotic pumps starting the day of surgery. Eight weeks after surgery, animals were euthanized, and fusion was assessed by manual palpation. Radiographic area and optical density of fusion masses were calculated. Histomorphometry was used to assess the percentage area of fusion masses occupied by bone or marrow tissues. Results. Manual palpation fusion rates were lower in alendronate groups (50% and 40%, respectively) than in the control group (95%, P = 0.002). Interobserver and intraobserver kappa values were high (0.97−1.00). There were dose-dependent and statistically significant (P < 0.001) increases in fusion mass area and optical density with increasing alendronate dose. Fusion masses in dose10 animals had significantly higher percent area of bone tissue (P = 0.01) and lower percent area of marrow elements (P < 0.001) when compared to control animals. Conclusions. Alendronate inhibits spine fusion in rats. Fusion masses in alendronate-treated animals appeared radiographically larger and denser than those in control animals despite lower fusion rates. Quantitative histomorphometry confirmed that alendronate inhibited bone graft resorption and incorporation. We recommend that patients undergoing spine arthrodesis should not take alendronate until fusion is achieved.

THE USE OF GROWTH FACTORS IN CARTILAGE REPAIR

Articular cartilage, which enables smooth gliding of joints during skeletal motion, is vulnerable to injuries and degenerative diseases over time. Bone growth factors have a role in the preservation of the cartilage matrix. This article reviews the potential to treat cartilage damage for bone morphogenetic proteins, insulin-like growth factors, hepatocyte growth factor, basic fibroblast growth factor, and transforming growth factor beta.

Minimally invasive options for the treatment of osteoporotic vertebral compression fractures

The recent introduction of vertebroplasty and kyphoplasty provide minimally invasive methods to alleviate symptoms from vertebral fractures. While both methods are successful in addressing fracture related pain, only the kyphoplasty can partially restore structural alignment and height.

A proposed set of metrics for standardized outcome reporting in the management of low back pain

Background and purpose — Outcome measurement has been shown to improve performance in several fields of healthcare. This understanding has driven a growing interest in value-based healthcare, where value is defined as outcomes achieved per money spent. While low back pain (LBP) constitutes an enormous burden of disease, no universal set of metrics has yet been accepted to measure and compare outcomes. Here, we aim to define such a set. Patients and methods — An international group of 22 specialists in several disciplines of spine care was assembled to review literature and select LBP outcome metrics through a 6-round modified Delphi process. The scope of the outcome set was degenerative lumbar conditions. Results — Patient-reported metrics include numerical pain scales, lumbar-related function using the Oswestry disability index, health-related quality of life using the EQ-5D-3L questionnaire, and questions assessing work status and analgesic use. Specific common and serious complications are included. Recommended follow-up intervals include 6, 12, and 24 months after initiating treatment, with optional follow-up at 3 months and 5 years. Metrics for risk stratification are selected based on pre-existing tools. Interpretation — The outcome measures recommended here are structured around specific etiologies of LBP, span a patient’s entire cycle of care, and allow for risk adjustment. Thus, when implemented, this set can be expected to facilitate meaningful comparisons and ultimately provide a continuous feedback loop, enabling ongoing improvements in quality of care. Much work lies ahead in implementation, revision, and validation of this set, but it is an essential first step toward establishing a community of LBP providers focused on maximizing the value of the care we deliver.

CURRENT CONCEPTS IN INTERVERTEBRAL DISK RESTORATION

A current focus of treatment for degenerative disk disease is the restoration of the intervertebral disk. This article summarizes the structure and function of the intervertebral disk, the pathogenesis of its degeneration, and the clinical relevance of degenerative disk disease. Current literature relating to intervertebral disk replacement and regeneration is reviewed.