Mustafa H. Khan

Postoperative management protocol for incidental dural tears during degenerative lumbar spine surgery: a review of 3,183 consecutive degenerative lumbar cases.

Study Design. Retrospective review. Objectives. To review the experience of a single institution with degenerative lumbar surgery and to identify cases of incidental dural tears (DTs); and to report on the efficacy of our postoperative management protocol for DT, which relies on early mobilization. Summary of Background Data. DTs are a common complication of degenerative lumbar spine surgery. However, the management strategies for this complication vary from one surgeon to another. Methods. A total of 3,183 degenerative lumbar spine cases (decompression and/or fusion) were reviewed. Cases complicated by an incidental DT were identified. Patients who required a return to the operating room for a second procedure were identified and the operative findings were reviewed. Results. The incidence of DT during primary lumbar surgeries was 7.6% (153 of 2,024 cases), which compares to an incidence of 15.9% for revision cases (185 of 1,159 cases). If recognized during the index procedure, all DTs were repaired using a 4-0 silk suture. Six patients (4 primary, 2 revisions) who did not improve despite our postoperative management protocol were taken to the operating room for irrigation and debridement, repair of the defect, and placement of a subfascial drain to closed suction. All 6 patients went on to do well and did not have any further complications. Conclusions. DTs are common during degenerative lumbar spine surgery. Revision surgery is twice as likely as primary surgery to result in this complication. Our postoperative early mobilization protocol appears to be an effective and safe management strategy for treating this complication (98.2% success rate). Very few patients (6 of 338, or 1.8%) needed a reoperation.

Inflammatory response of human tendon fibroblasts to cyclic mechanical stretching.

Background The cellular and molecular mechanisms for the development of tendinopathy are not clear, but inflammatory mediators produced by tendon fibroblasts in response to repetitive mechanical loading may be an important factor. Hypotheses (1) Cyclic stretching of tendon fibroblasts affects the production of leukotriene B4 and the expression of 5-lipoxygenase; and (2) the production level of leukotriene B4 is inversely related to that of prostaglandin E2. Study Design Controlled laboratory study. Methods Human patellar tendon fibroblasts were uniaxially stretched in the presence of indomethacin (25 μM) or MK-886 (10 μM). After stretching for 4 hours, followed by 4 hours rest, levels of prostaglandin E2, leukotriene B4, and expression of 5-lipoxygenase were measured. Results Stretched tendon fibroblasts increased the levels of leukotriene B4 but did not appreciably change the expression of 5-lipoxygenase. Indomethacin decreased the cellular production of prostaglandin E2 but caused increased leukotriene B4 levels. MK-886 caused decreased production of leukotriene B4 but increased production of prostaglandin E2. Conclusions Cyclic stretching of human tendon fibroblasts increases the production of prostaglandin E2 and leukotriene B4. Blocking prostaglandin E2 production leads to increased leukotriene B4 levels and vice versa. Clinical Relevance The use of nonsteroidal anti-inflammatory drugs for the treatment of tendon inflammation might increase the levels of leukotriene B4 within the tendon, potentially contributing to the development of tendinopathy.

Cerebrospinal Fluid Leaks Following Cervical Spine Surgery

BACKGROUND A cerebrospinal fluid leak during cervical spine surgery is a feared complication. However, little is known about the prevalence, management, and long-term course of these events. METHODS The medical records of 1994 patients who had elective cervical spine surgery during an eleven-year period (1994 through 2005) were reviewed. Patients with cervical cerebrospinal fluid leaks identified at the time of surgery were followed both clinically and radiographically for an average of 5.4 years postoperatively. The prevalence, etiology, management, and outcome of all of the cervical cerebrospinal fluid leaks were analyzed. RESULTS The overall prevalence of cerebrospinal fluid leaks was 1%. The prevalence of cerebrospinal fluid leaks was higher in patients with a diagnosis of ossification of the posterior longitudinal ligament (12.5%), patients having a revision anterior procedure (1.92%), men (1.56%), and patients undergoing an anterior cervical corpectomy and arthrodesis (1.77%). CONCLUSIONS Many cervical dural tears can be managed by observation alone or by placement of a lumbar cerebrospinal fluid shunt either during the index procedure or in the postoperative period. At an average follow-up of 5.4 years, there were no long-term sequelae of the cervical dural tears in our series.

Repeated exposure of tendon to prostaglandin-E2 leads to localized tendon degeneration.

Objective: To determine whether repeated exposure of rabbit patellar tendon to prostaglandin-E2 leads to degenerative changes in the tendon. Setting: Laboratory animal study. Main Outcome Measures: Intratendinous changes including cellularity, matrix organization, collagen fibril packing, and diameter. Methods: Skeletally mature New Zealand White rabbits (n = 10) were transcutaneously injected in the midsubstance of the patellar tendon with prostaglandin-E2 (PGE2; 50 ng or 500 ng). The contralateral tendons were used as 3 different controls (no injection, saline injection, and needlestick only). The injection was repeated once a week for 4 weeks, and the rabbits were killed 1 week after the last injection. The patellar tendons were harvested and examined using hematoxylin and eosin staining and transmission electron microscopy. Results: Compared with the control groups, tendons exposed to PGE2 by injection showed focal areas of hypercellularity, loss of normal tissue architecture, and focal areas of tendon disorganization and degeneration. Tendons injected with PGE2 exhibited loosely organized collagen fibrils and had thinner collagen fibril diameter compared with control tendons (P < 0.005). Tendons injected with 500 ng PGE2 appeared to be more disorganized and degenerated than those injected with 50 ng PGE2. Conclusions: Repeated exposure of the tendon to PGE2 leads to degenerative changes within the tendon. Clinical Relevance: It is known that human tendon fibroblasts produce PGE2 in vitro and in vivo in response to repetitive mechanical loading. This study demonstrates that repetitive exposure of the tendon to PGE2 can result in degenerative changes within the tendon. Therefore, PGE2 produced by tendon fibroblasts in response to repetitive mechanical loading in vivo might contribute to the development of exercise-induced tendinopathy.

Prostaglandin E2 affects proliferation and collagen synthesis by human patellar tendon fibroblasts.

Objective:To determine the effect of prostaglandin E2 on proliferation and collagen synthesis by human patellar tendon fibroblasts. Design and Setting:Controlled laboratory study. Methods:Human patellar tendon fibroblasts were treated with different concentrations (1, 10, 100 ng/mL) of prostaglandin E2 in cultures. Fibroblasts without prostaglandin E2 treatment were used as the control group. The fibroblast proliferation and collagen synthesis were measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay and Sircol collagen assay, respectively. Main Outcome Measured:Changes in proliferation and collagen production of human patellar tendon fibroblasts. Results:At 1 ng/mL of prostaglandin E2, there was no significant effect on fibroblast proliferation compared with the control group. At concentrations of 10 ng/mL and 100 ng/mL prostaglandin E2, however, fibroblast proliferation significantly decreased, by 7.3% (P = 0.002) and 10.8% (P < 0.0001), respectively, compared with the control group. At 1 ng/mL of prostaglandin E2, collagen production of the tendon fibroblasts was unaffected. However, at both 10 ng/mL and 100 ng/mL prostaglandin E2, collagen production was significantly decreased, by 45.2% (P < 0.0001) and 45.7% (P < 0.0001), respectively, compared with the control group. The levels of collagen production between these 2 dosages did not differ significantly. Conclusions:Prostaglandin E2 affects the proliferation of and collagen production by human patellar tendon fibroblasts in a dosage-dependent manner. Clinical Relevance:Based on these in vitro findings, we speculate that production of prostaglandin E2 in tendons might play some role in the acellularity and matrix disorganization seen in exercise-induced tendinopathy.

Does Lumbar Facet Fluid Detected on Magnetic Resonance Imaging Correlate With Radiographic Instability in Patients With Degenerative Lumbar Disease

Study Design. Retrospective radiographic/imaging study. Objective. The purpose of this study was to analyze the association between lumbar facet fluid on MRI and sagittal instability on flexion lumbar radiographs in patients with degenerative disease at L4–L5. We hypothesized that the amount of facet fluid on MRI correlates with instability on the flexion radiograph. Summary of Background Data. Although never formally studied, it has been suggested that lumbar facet fluid detected on MRI is indicative of spinal segment instability. Methods. Patients who underwent laminectomy or laminectomy and fusion for the treatment of degenerative lumbar disease at L4–L5 at our institution between 2002 and 2004 and who had preoperative lumbar MRI and anteroposterior and flexion-extension radiographs available for review were study eligible. Axial T2 MRI images through the L4–L5 facets were analyzed for facet fluid. The facet fluid index was calculated, i.e., the ratio of the sum of the width of fluid in each facet (bilateral) to the sum of the width of each facet (bilateral). Instability on the flexion radiograph was measured as percent anterior slip at L4–L5. Results. Fifty-one patients were included in the study, 28 (55%) of whom had facet fluid noted on MRI. Of those patients who did have facet fluid on the MRI, 23 of 28 had instability on the flexion lumbar radiograph and 5 of 28 had no instability. The mean facet fluid index and percent anterior slip for the 28 patients with MRI facet fluid was 0.12% and 11.1%, respectively. There was a positive linear association between these values (Pearson correlation coefficient of 0.90, P < 0.001). The positive predictive value of L4–L5 facet fluid on MRI as an indicator of radiographic instability was 82%. Conclusions. There is a close linear association between the facet fluid index and the amount of radiographic instability at L4–L5. Facet fluid on MRI should raise high suspicion of lumbar instability.

Repetitively stretched tendon fibroblasts produce inflammatory mediators

We studied the expression of cytosolic phospholipase-A2 and activity of secretory phospholipase-A2 by human patellar tendon fibroblasts subjected to cyclic mechanical stretching. The effect of different stretching frequencies on the production of prostaglandin-E2 and expression of cyclooxygenase enzyme were also examined. An in vitro system that can control alignment, shape, and mechanical loading conditions of tendon fibroblasts was used for this study. Cyclic stretching of fibroblasts increased the expression level of cytosolic phospholipase-A2 by 88% and activity level of secretory phospholipase-A2 by 190%, compared with those of nonstretched fibroblasts. Cyclic stretching of tendon fibroblasts at 0.1 Hz and 1.0 Hz also increased prostaglandin-E2 production by 40% and 69%, respectively. Furthermore, cyclooxygenase-1 and cyclooxygenase-2 expression levels were increased in a stretching frequency-dependent manner, but cyclooxygenase-2 expression was increased more than that of cyclooxygenase-1. Because cytosolic phospholipase-A2 and secretory phospholipase-A2 are involved in the production of prostaglandin-E2 and other inflammatory mediators, this study suggests that regulation of phospholipase-A2 expression level may be an alternative approach to control in vivo tendon inflammation. The results of this study also may explain in part why activities that involve repetitive motion and high frequency loading of tendons are more likely to result in tendon inflammation.

Intraoperative somatosensory evoked potential monitoring during cervical spine corpectomy surgery: experience with 508 cases.

Study Design. Retrospective review. Objectives. To review consecutive cases of cervical spine corpectomy surgery performed with intraoperative somatosensory-evoked potential (SSEP) monitoring. Summary of Background Data. There is controversy about the utility of SSEP monitoring during anterior cervical spine surgery. There is no study in the literature that has specifically evaluated the utility of SSEP monitoring for cervical spine corpectomy surgery. Methods. Intraoperative SSEP tracings for 508 patients (average age, 55.7 years; 268 male, 240 female) who underwent anterior cervical fusion with single-level or multilevel corpectomies were reviewed. Intraoperative and postoperative records were analyzed to determine if any new neurologic deficits developed when the patients woke up from anesthesia. Results. The overall incidence of a new postoperative neurologic deficit in this series of patients was 2.4% (11 with nerve root injury, 1 with quadriplegia). The incidence of significant SSEP changes was 5.3% (27 of 508 patients). The most common identifiable cause of SSEP changes was hypotension, and the most common neurologic deficit was deltoid (C5) weakness. One patient had irreversible SSEP changes, and he woke up with new-onset quadriplegia. The calculated sensitivity and specificity of intraoperative SSEP monitoring for detecting impending or resultant intraoperative iatrogenic neurologic injury were 77.1% and 100%, respectively. However, if the isolated nerve root injuries are removed from the analysis, then both the calculated sensitivity and the negative predictive values were 100%. Conclusions. Intraoperative SSEP monitoring can alert the surgeon to adverse iatrogenic intraoperative events with potential for neurologic injury. Most SSEP signal changes are reversible and do not result in a clinical deficit. Isolated nerve root injury appears to be the most common iatrogenic intraoperative injury during cervical spine corpectomy surgery.

Donor-site complications of autogenous nonvascularized fibula strut graft harvest for anterior cervical corpectomy and fusion surgery: experience with 163 consecutive cases.

BACKGROUND CONTEXT The fibula is a source of bone graft for reconstruction of the appendicular and axial skeleton. PURPOSE The aim of this study is to determine donor-site complications and morbidity in a large series of patients who underwent autogenous fibula harvesting for anterior cervical corpectomy and fusion (ACCF) surgery. STUDY DESIGN/SETTING Retrospective review (Level III). PATIENT SAMPLE One hundred sixty-three patients over an eight-year period who underwent ACCF with autogenous fibula. OUTCOME MEASURES Donor site complications (such as infection, cellulitis, pain, damage to the superficial peroneal nerve, ankle instability, tibial stress fracture, and so forth), treatment, and final outcome were determined from patient records. METHODS Retrospective study of patients who underwent ACCF with autogenous nonvascularized fibula strut graft over an eight-year period (from 1995 to 2002) was conducted. Donor site complications (such as infection, cellulitis, pain, damage to the superficial peroneal nerve, ankle instability, tibial stress fracture, and so forth), treatment, and final outcome were determined from patient records. RESULTS One hundred sixty-three patients underwent ACCF with autogenous fibula graft during the study period. The most common short-term complication (lasting <3 months) was incisional pain, present in 86 of 163 patients (53%). Incisional pain lasted longer than 3 months in 25 of 163 patients (15%) but resolved in all but two patients by 24 months. Two patients (1.2%) developed superficial peroneal neuromas. Five patients (3%) developed tibial stress fractures. Two patients (1.2%) developed ankle instability. Fifteen (9%) patients developed cellulitis that resolved in all patients after a short course of oral antibiotics, with one additional patient developing a deep infection requiring surgical debridement and intravenous antibiotics. CONCLUSIONS Although autogenous fibula is an excellent graft for multilevel ACCF reconstruction, surgeons should carefully consider the associated morbidity of fibular harvest before surgery. In this series, most complications were of short duration. However, nine patients with long-term complications required five additional surgical procedures. Therefore, patients who are scheduled to undergo autogenous fibula harvest should be advised about these potential complications.

Sacral insufficiency fractures following multilevel instrumented spinal fusion: case report.

Study Design. Case series. Objective. To report a series of patients in whom sacral insufficiency fractures developed following multilevel spinal fusion with instrumentation. Summary of Background Data. Rigid spinal fusion with instrumentation results in abnormal distribution of forces in the spine. These forces have the potential to cause failure of adjacent segments, especially in older, osteopenic individuals. Sacral insufficiency fractures following lumbar-sacral fusion may be the result of these abnormal forces. However, this complication is not well described in the literature. Methods. Three patients who sustained sacral fractures after instrumented lumbar-sacral fusion performed for degenerative disease of the spine are discussed. History, physical examination findings, and radiographic features are presented, along with a brief review of the pertinent literature. Results. All 3 patients in our series started complaining of new-onset buttock pain a few weeks after their operative procedure. Radiographic examination revealed that they had transverse sacral fractures just below the fusion instrumentation. Nonoperative, conservative treatment was performed. At final follow-up, the fractures had healed completely and the patients’ complaints had resolved. Conclusion. Patients who complain of new-onset buttock pain following multilevel lumbar-sacral fusion with instrumentation should be evaluated for sacral insufficiency fractures, especially if they have been sitting for prolonged periods. Conservative treatment seems to be sufficient.