Positional effects of transforaminal interbody spacer placement at the L5-S1 intervertebral disc space: a biomechanical study.

BACKGROUND CONTEXT: Transforaminal lumbar interbody fusion (TLIF) is an increasingly used alternative fusion method over anterior and posterior lumbar interbody fusions. There are conflicting results on the optimal positioning of interbody devices. No study has addressed the lumbosacral segment, L5-S1, where the lordotic configuration presents unique challenges. PURPOSE: To determine if there are biomechanical and/or anatomical advantages related to the positioning of an interbody device at L5-S1, either anterior or posterior to the neutral axis. STUDY DESIGN: An in vitro biomechanical study using human cadaveric lumbar specimens. METHODS: Lumbar specimens were biomechanically tested using pure moments with and without compressive axial loading. Testing was performed in intact and after TLIF with the implant posterior (TLIF-post) and anterior (TLIF-ant) to neutral axis. Segmental range of motion (ROM) and stiffness were analyzed at the L5-S1 surgical level and the adjacent L4-L5 level. Neuroforaminal height measurements of L5-S1 were analyzed in neutral and end range positions. RESULTS: Compared with the intact condition, ROM decreased more than 75% at L5-S1 and stiffness increased up to 270% with TLIF. There was no significant difference between anterior or posterior placement for ROM and stiffness. There was a change in L5-S1 neuroforaminal height based on the placement, with posterior placement showing a significant increase compared with anterior placement. There were no relative changes in neuroforaminal height under loading after TLIF. Compressive load did not affect the magnitudes or resulting significance of outcome measures at L5-S1 after either TLIFs. CONCLUSIONS: An interbody spacer with the addition of posterior instrumentation significantly enhances the mechanical stability of L5-S1 regardless of interbody position. There were noticeable increases in terms of construct stability and stiffness after both TLIF-ant and TLIF-post in comparison with the intact condition. A posteriorly placed interbody implant did result in the distraction of the neuroforamin. Positioning an interbody implant at L5-S1 for TLIF with posterior instrumentation should be at the discretion of the surgeon without consequence to biomechanical stability.

Wrong-site Spine Surgery.

Wrong-site spine surgery is an adverse event that has potentially devastating consequences for the patient as well as the surgeon. Despite substantial efforts to prevent wrong-site spine surgery, this complication continues to occur and has the potential for serious medical, personal, and legal repercussions. Although systems-based prevention methods are effective in identifying the proper patient, procedure, and region of the spinal column, they cannot be relied on to establish the correct vertebral level during the operation. The surgeon must design and implement a patient-specific protocol to ensure that the appropriate operation is performed on the correct side and level or levels of the spinal column.

Airway compromise due to laryngopharyngeal edema after anterior cervical spine surgery.

Postoperative airway compromise due to laryngopharyngeal edema is a potentially serious adverse event associated with anterior cervical spine surgery. The reported incidence of this complication has varied from 1.2% to 6.1%, with a higher incidence following multi-level surgery. The relevant literature on airway compromise following anterior cervical spine surgery is reviewed.

Pediatric disk herniation.

Pediatric disk herniation is a rare condition that should be considered in the differential diagnosis of the child with back pain or radiating leg pain. Because pediatric disk herniation is relatively uncommon, there is typically a delay in diagnosis compared with time to diagnosis of adult disk herniation. Pediatric disk herniations are often recalcitrant to nonsurgical care, but such measures should be attempted in patients who present with isolated pain symptoms and have a normal neurologic examination. Twenty-eight percent of adolescent disk herniations involve apophyseal fractures; this presentation has a higher rate of surgical intervention than do herniations without fracture. Surgical management of pediatric disk herniation involves laminotomy and fragment excision. Short-term data demonstrate excellent pain relief, with 1% of children requiring repeat surgery for lumbar disk pathology in the first year. Long-term data suggest that 20% to 30% of patients will require additional surgery later in life.

The role of the oblique popliteal ligament and other structures in preventing knee hyperextension.

BACKGROUND: Ligament restraints to terminal knee extension are poorly understood. HYPOTHESES: (1) As with other motions of the knee, genu recurvatum is limited primarily by a named, identifiable structure. (2) As the largest static structure of the posterior knee, the oblique popliteal ligament is uniquely suited to act as a checkrein to knee hyperextension. STUDY DESIGN: Descriptive laboratory study. METHODS: Twenty fresh-frozen human knees were divided into 3 groups for a ligament sectioning study. Extension moments of 14 and 27 N x m were applied before and after sectioning of each ligament, and motion changes were recorded. In group 1, the oblique popliteal ligament was sectioned first, followed by the fabellofibular ligament, ligament of Wrisberg, anterior cruciate ligament, posterolateral structures, and posterior cruciate ligament. In group 2, the order was altered to section the anterior cruciate ligament first; no other changes were made. Similarly, the cutting order for group 3 was altered to section the posterior cruciate ligament first. The sagittal tibial slope of each specimen was documented off a lateral radiograph. RESULTS: The greatest increase in knee hyperextension was observed after sectioning the oblique popliteal ligament. This was independent of cutting order, consistent across groups, and statistically significant. In all groups, the increase in knee hyperextension after sectioning the oblique popliteal ligament approached or exceeded the increases seen after sectioning the anterior and posterior cruciate ligaments combined. Overall, less knee hyperextension was seen in knees with increased posterior tibial slope. CONCLUSION: The oblique popliteal ligament was found to be the primary ligamentous restraint to knee hyperextension. CLINICAL RELEVANCE: Further studies are needed to determine if surgical repair or reconstruction of the oblique popliteal ligament can restore normal motion limits in patients with symptomatic genu recurvatum. Patients with decreased posterior tibial slope would have increased recurvatum with posterior structure injury, which increases the likelihood of increased symptoms in this population.