Fadi Taher

Nerve injury after lateral lumbar interbody fusion: a review of 919 treated levels with identification of risk factors

BACKGROUND CONTEXT Lateral lumbar interbody fusion (LLIF) has become an increasingly common minimally invasive procedure for selective degenerative deformity correction, reduction of low-grade spondylolisthesis, and indirect foraminal decompression. Concerns remain about the safety of the transpsoas approach to the spine due to proximity of the lumbosacral plexus. PURPOSE To address risk factors for iatrogenic nerve injury in a large cohort of patients undergoing LLIF. STUDY DESIGN Retrospective analysis of 919 LLIF procedures to identify risk factors for lumbosacral plexus injuries. METHODS The medical charts of patients who underwent transpsoas interbody fusion with or without supplemental posterior fusion for degenerative spinal conditions over a 6-year period were retrospectively reviewed. Patients with prior lumbar spine surgery or follow-up of less than 6 months were excluded. Factors that may affect the neurologic outcome were investigated in a subset of patients who underwent stand-alone LLIF. RESULTS Four hundred fifty-one patients (males/females: 179/272) met the inclusion criteria and were followed for a mean of 15 months (range, 6-53 months). Average age at the time of surgery was 63 years (range, 24-90 years). Average body mass index was 29 kg/m(2) (range, 17-65 kg/m(2)). A total of 919 levels were treated (mean, 2 levels per patient). Immediately after surgery, 38.5% of the patients reported anterior thigh/groin pain, whereas sensory and motor deficits were recorded in 38% and 23.9% of the patients, respectively. At the last follow-up, 4.8% of the patients reported anterior thigh/groin pain, whereas sensory and motor deficits were recorded in 24.1% and 17.3% of the patients, respectively. When patients with neural deficits present before surgery were excluded, persistent surgery-related sensory and motor deficits were identified in 9.3% and 3.2% of the patients, respectively. Among 87 patients with minimum follow-up of 18 months, persistent surgery-related sensory and motor deficits were recorded in 9.6% and 2.3% of the patients, respectively. Among patients with stand-alone LLIF, the level treated was identified as a risk factor for postoperative lumbosacral plexus injury. The use of recombinant human bone morphogenetic protein 2 was associated with persistent motor deficits. CONCLUSIONS Although LLIF is associated with an increased prevalence of anterior thigh/groin pain as well as motor and sensory deficits immediately after surgery, our results support that pain and neurologic deficits decrease over time. The level treated appears to be a risk factor for lumbosacral plexus injury.

Lumbar Degenerative Disc Disease: Current and Future Concepts of Diagnosis and Management

Low back pain as a result of degenerative disc disease imparts a large socioeconomic impact on the health care system. Traditional concepts for treatment of lumbar disc degeneration have aimed at symptomatic relief by limiting motion in the lumbar spine, but novel treatment strategies involving stem cells, growth factors, and gene therapy have the theoretical potential to prevent, slow, or even reverse disc degeneration. Understanding the pathophysiological basis of disc degeneration is essential for the development of treatment strategies that target the underlying mechanisms of disc degeneration rather than the downstream symptom of pain. Such strategies ideally aim to induce disc regeneration or to replace the degenerated disc. However, at present, treatment options for degenerative disc disease remain suboptimal, and development and outcomes of novel treatment options currently have to be considered unpredictable.

Lower preoperative Hounsfield unit measurements are associated with adjacent segment fracture after spinal fusion.

Study Design. Retrospective case-control study. Objective. To determine the association of Hounsfield unit (HU) measurements with adjacent segment fractures after spinal fusion. Summary of Background Data. Adjacent segment fracture is a potentially devastating complication after spinal fusion surgery in osteoporotic patient. Recently, a technique for assessing bone mineral density using HU measurements from computed tomography was described and correlated with both dual-energy x-ray absorptiometry–assessed bone mineral density and compressive strength in an osseous model. Methods. Patients with adjacent segment fractures after spinal fusion were identified from a prospectively collected patient database and matched 1:1 with nonfracture controls on the basis of age, sex, and fusion construct. Minimum follow-up was 6 months. Patients with metabolic bone disease other than osteoporosis or those taking medications known to negatively alter bone strength were excluded. HU assessment was done according to the previously published protocol using the preoperative computed tomography. Results. Twenty patients had complete imaging data and could be matched to nonfracture controls. The groups were well matched with respect to age, sex, body mass index, and number of levels fused. Following the index surgical procedure, the fracture group had more positive sagittal balance than the control group (10.7 cm vs. 9.1 cm). Analysis of HU values at the fracture level showed a significantly lower value in the fracture group than in the controls (145.6 vs. 199.4, P = 0.006). Similarly, global assessment of HU across the thoracic and lumbar spines was significantly lower in the fracture group (139.9 vs. 170.1, P = 0.032). Conclusion. HU was significantly lower both locally and globally in the fracture cohort. Because computed tomographic scans are frequently part of preoperative planning for spinal fusion, this information should be incorporated in preoperative planning. Studies to prospectively validate HU as a predictor of adjacent segment fracture risk and to assess the effect of increasing HU preoperatively with medications for osteoporosis are needed. Level of Evidence: 3

2013 Young Investigator Award winner: how safe is lateral lumbar interbody fusion for the surgeon? A prospective in vivo radiation exposure study.

Study Design. Prospective in vivo radiation exposure study. Objective. To assess surgeon exposure to ionizing radiation in the setting of lateral lumbar interbody fusion (LLIF). Summary of Background Data. Minimally invasive spine surgery relies heavily on image guidance. Rapid popularization of minimally invasive spine surgery procedures, such as LLIF, is appropriately accompanied by concern regarding occupational radiation exposure related to intraoperative fluoroscopy. Methods. Optically stimulated luminescence technology dosimeters were used to record radiation exposure prospectively at 5 anatomic locations during 18 LLIF procedures: (1) eye, (2) thyroid, (3) chest, (4) axilla, and (5) gluteal region. Additionally, a ring dosimeter was worn during 13 of the LLIF cases. Results. Average fluoroscopy time was 88.7 ± 36.8 seconds and skin dose to the patient was 25.2 ± 21.1 mGy. The chest dosimeter protected by lead recorded the lowest readings per procedure (0.44 ± 0.49 mrem). The gluteal dosimeter recorded an average exposure of 2.31 ± 4.50 mrem and the dosimeter at the axilla recorded an average of 4.20 ± 7.76 mrem per procedure. Exposure to the thyroid and eye were 2.19 ± 2.07 mrem and 2.64 ± 2.76 mrem, respectively. With the exception of the gluteal region, dosimeter readings from all unprotected areas were significantly higher than those from the chest dosimeter (P < 0.0125). In the course of 13 procedures, 190 mrem of exposure to the hand was recorded by the ring dosimeters. More than 2700 LLIF procedures may be performed annually before occupational limits are exceeded. Conclusion. Prolonged exposure to “low-level” radiation as an occupational risk remains a concern for medical personnel. Radiation exposures to unprotected, radiosensitive locations, such as the axilla or eye, are worrisome. However, following radiation safety guidelines, 2700 LLIF procedures can be performed per year before exceeding occupational dose limits. Adherence to radiation safety guidelines is necessary to avoid sequelae related to an invisible but potentially deadly risk of minimally invasive spine surgery procedures.

Rate of revision surgery after stand-alone lateral lumbar interbody fusion for lumbar spinal stenosis.

Study Design. Retrospective case series. Objective. To examine the reoperation rate, specifically the need for posterior decompression and/or fusion, in a cohort of patients who underwent stand-alone lateral lumbar interbody fusion for symptomatic spinal stenosis with instability or deformity. Summary of Background Data. Lateral lumbar interbody fusion provides a minimally invasive means of achieving interbody arthrodesis and indirect foraminal decompression while avoiding the potential morbidity of traditional anterior or posterior approaches. The revision rate for formal posterior decompression after isolated lateral lumbar interbody fusion for spinal stenosis is unknown. Methods. One hundred seventeen patients who underwent stand-alone lateral lumbar interbody fusion for symptomatic spinal stenosis with an indication for fusion were included in the analysis. Detailed demographic and intraoperative data were collected. Clinical evaluation was done both preoperatively and at the final follow-up, and radiographical evaluation was done preoperatively and with the first postoperative standing radiographs. Results. A total of 10.3% of patients who underwent stand-alone lateral lumbar interbody fusion ultimately required revision surgery, most commonly for persistent radiculopathy and symptomatic implant subsidence. Average time to revision was 10.8 months. There was no difference in radiographical correction between patients who did and did not require revision surgery. Conclusion. Lateral lumbar interbody fusion provides a minimally invasive means to treat lumbar spinal stenosis with an acceptable revision rate for formal posterior decompression at early follow-up. Level of Evidence: 4

Contralateral psoas seroma after transpsoas lumbar interbody fusion with bone morphogenetic protein-2 implantation

BACKGROUND CONTEXT The lateral transpsoas approach to interbody fusion of the lumbar spine (lateral lumbar interbody fusion [LLIF]) with recombinant human bone morphogenetic protein-2 (BMP-2) augmentation has been increasingly performed in recent years. Potential side effects and adverse sequelae of BMP-2 in the acute setting remain to be fully elucidated. PURPOSE To review the literature for reports of complications related to BMP-2 implantation in lumbar spinal surgery and present a case of a contralateral psoas muscle seroma after LLIF with BMP-2 implantation. STUDY DESIGN Case report and literature review. METHODS The PubMed database was searched for articles related to adverse events to BMP-2 in lumbar spinal surgery. We report the case of a 57-year-old woman who underwent routine right-sided transpsoas approach for LLIF with the use of BMP-2 at our institution and developed a left-sided psoas muscle fluid accumulation 2 weeks postoperatively. RESULTS No reports of complications contralateral to an LLIF approach attributable to an inflammatory response to BMP-2 were identified in the English literature. In the presented patient, a large (4.2×6.5×2.7 cm) left-sided sterile intramuscular psoas fluid collection was seen on a magnetic resonance imaging study obtained on postoperative day 14. At a 6-month follow-up, left-sided L5 radiculopathy resulting in 4/5 foot drop was confirmed by electromyography. The patient reported here represents the only case of a contralateral psoas seroma with suspected association to BMP-2 utilization in LLIF encountered at our institution. CONCLUSIONS A serous psoas muscle fluid accumulation after BMP-2 implantation may rarely occur contralateral to the surgical approach for LLIF. Further characterization of complications related to BMP-2 implantation after lumbar spinal surgery will help guide preoperative informed decision making and the management of this unusual postoperative adverse event.

Evaluation of a new formulation of demineralized bone matrix putty in a rabbit posterolateral spinal fusion model

BACKGROUND CONTEXT Alternatives to autologous bone graft (ABG) with osteoconductive, osteoinductive, and osteogenic potential continue to prove elusive. Demineralized bone matrix (DBM) however, with its osteoconductive and osteoinductive potential remains a viable option to ABG in posterolateral spine fusion. PURPOSE To compare the efficacy of a new formulation of DBM putty with that of ABG in a rabbit posterolateral spinal fusion model. STUDY DESIGN Efficacy of a new formulation of DBM was studied in an experimental animal posterolateral spinal fusion model. METHODS Twenty-four male New Zealand White rabbits underwent bilateral posterolateral spine arthrodesis of the L5-L6 intertransverse processes, using either ABG (control group, n=12) or DBM (DBM made from rabbit bone) putty (test group, n=12). The animals were killed 12 weeks after surgery and the lumbar spines were excised. Fusion success was evaluated by manual palpation, high resolution X-rays, microcomputed tomography imaging, biomechanical four-point bending tests, and histology. RESULTS Two animals were lost because of anesthetic related issues. Manual palpation to assess fusion success in the explanted lumbar spines showed no statistical significant difference in successful fusion in 81.8% (9/11) of DBM group and 72.7% (8/11) of ABG group (p=.99). Reliability of these assessments was measured between three independent observers and found near perfect agreement (intraclass correlation cofficient: 0.92 and 0.94, respectively). Fusion using high resolution X-rays was solid in 10 of the DBM group and 9 of the ABG group (p=.59). Biomechanical testing showed no significant difference in stiffness between the control and test groups on flexion, extension, and left lateral and right lateral bends, with p values accounting for .79, .42, .75, and .52, respectively. The bone volume/total volume was greater than 85% in the DBM treated fusion masses. Histologic evaluation revealed endochondral ossification in both groups, but the fusion masses were more mature in the DBM group. CONCLUSIONS The DBM putty achieved comparable fusion rates to ABG in the rabbit posterolateral spinal fusion model.

Contralateral motor deficits after lateral lumbar interbody fusion.

Study Design. Retrospective case series. Objective. To report on the rare finding of motor deficits contralateral to the transpsoas approach in patients who underwent lateral lumbar interbody fusion (LLIF). Summary of Background Data. Although sensorimotor deficits occurring ipsilaterally to a transpsoas approach have more fully been elucidated, there seems to be a paucity of data on motor deficits contralateral to an LLIF approach. Methods. The electronic medical records and radiographical studies of 244 patients who underwent LLIF at a single institution between 2006 and 2009 were retrospectively reviewed for reports on motor deficits contralateral to the surgical approach. Results. Of the patients reviewed, 2.9% (7/244) presented with a postoperative contralateral motor deficit, the most severe of which was a 1/5 weakness of the quadriceps muscle. An average of 3 levels (range: 2–4) was fused in 7 patients who developed a contralateral motor deficit, and in 3 of the 7 patients, an anterior lumbar interbody fusion (ALIF) was performed in addition to the LLIF. At 1 year follow-up, 3 patients presented with complete resolution of their muscle weakness, 1 patient still had mild weakness, 1 patient had decreased range of motion in the affected joint, and 1 patient had a 2/5 foot drop. One patient was lost to follow-up. Conclusion. These data are among the largest reports of contralateral motor deficits after LLIF. Among possible underlying mechanisms are entrapment of the contralateral nerve root through translational correction of spondylolisthesis, front-to-back misalignment of the cage resulting in contralateral nerve root impingement, pressure on the contralateral peroneal nerve during positioning, and overdistraction neurapraxia when using ALIF at L5–S1 concomitantly. Awareness of the possibility of this rare complication can play an important role in surgical consideration and preoperative patient counseling. Level of Evidence: 4

Incidence, diagnosis, and management of sacral fractures following multilevel spinal arthrodesis.

BACKGROUND Fractures of the sacrum are a rare complication following instrumented spinal fusion, with only 34 cases previously reported in the literature. Previous series have generally been limited to less than five cases. PURPOSE The purpose of this study is to determine the incidence of sacral fractures caudal to instrumented spinal fusion constructs, identify risk factors for fracture and for failure of conservative management, and describe strategies for surgical treatment of these fractures. STUDY DESIGN This is a retrospective review. PATIENT SAMPLE Patients undergoing instrumented posterior spinal arthrodesis between 2002 and 2011 were included in the sample. OUTCOME MEASURES Clinical and radiographic data from hospital and surgeon records comprise outcome measures. METHODS Methods include a review of clinical and radiographic data from a prospectively collected patient database recording all adjacent segment fractures during the study period. RESULTS Twenty-four patients developed sacral fractures caudal to instrumented spinal fusion constructs during the study period. The overall incidence was 6.1% and was significantly greater in fusions greater than four levels (14.5%). The mean time from index surgery to fracture was 4.3 months. Only one fracture was evident on plain radiography at the onset of symptoms. Computed tomography, magnetic resonance imaging, and nuclear scintigraphy can all be used to establish the diagnosis. Eight patients were successfully treated conservatively. The mean time to fracture union was 21 weeks. Anterolisthesis of the fracture greater than 2 mm and kyphotic angulation were significantly associated with failure of conservative management. Surgical intervention included posterior extension of the fusion construct to S2 and the iliac wings with sacroiliac joint fusion. In 10 cases, a combined anterior and posterior approach was used that consisted of either revision anterior lumbar interbody fusion or transsacral posterior lumbar interbody fusion. CONCLUSIONS Sacral fractures following instrumented posterior spinal fusion are an uncommon complication; that is often unrecognized on plain radiographs. Risk factors include osteoporosis and long spinal fusions. Anterolisthesis and kyphosis of the fracture is associated with failure of conservative management.

Multiple myeloma exacerbation following utilization of bone morphogenetic protein-2 in lateral lumbar interbody fusion: a case report and review of the literature.

BACKGROUND CONTEXT Recent studies generated antithetic results regarding the safety of bone morphogenetic protein-2 (BMP-2) use in spine surgery, and the effect of this biologic adjunct on myeloma cells remains to be fully elucidated. PURPOSE The purpose of this study was to present a case of multiple myeloma (MM) exacerbation after BMP-2 implantation in the setting of lateral lumbar interbody fusion (LLIF). STUDY DESIGN Case report and literature review. METHODS The medical records, laboratory findings, and radiographic imaging studies of an 86-year-old female patient with exacerbation of previously undiagnosed MM were reviewed. RESULTS The patient presented with a 10-year history of debilitating lower back pain and bilateral lower extremity claudication. Radiographic studies depicted lumbar scoliosis and lateral spondylolisthesis. Preoperative serum immunofixation electrophoresis showed a serum immunoglobulin A kappa paraprotein-peak; however, the patient had never been diagnosed with MM or reported any unexplained fever, night sweats, or weight loss indicative of MM. The patient underwent LLIF from L1-L5 supplemented by BMP-2. On postoperative day 1, the patient was evaluated by the hematology department for paraproteinemia. Serum electrophoresis showed decreased albumin, hypogammaglobulinemia, and suspicious broadening of the complement component in the beta region. Postoperative imaging studies (19 weeks) depicted progression of a previously visible intraosseous lesion, and anterior cortical breakthrough (L5), in addition to a soft tissue mass at the T10 level. Histological examination of iliac crest and T10 vertebral biopsies showed fatty marrow infiltration by plasma cells and plasma cell dyscrasia, proving the diagnosis of MM. The patient died 10 months after surgery due to complications related to a methicillin-resistant Staphylococcus aureus infection. CONCLUSIONS Based on the present case, perhaps one should consider that in patients with abnormal electrophoresis results, even in the absence of a prior diagnosis of MM as well as in the absence of symptoms indicative of MM, BMPs should be administered only after preoperative exclusion of neoplastic disease.