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Minimally Invasive Spine Surgery The last decade has seen an evolution of minimally invasive spine surgery with new technological developments. Minimally invasive spine surgery is thought to decrease postoperative pain and allow quicker recovery by limiting soft-tissue retraction and dissection. Advances in microscopy, tissue retractors, and specialized instruments have enabled surgeons to perform procedures through small incisions. As with the open approach, the goals of the minimally invasive approach are to adequately decompress the involved neural

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Minimally Invasive Spine SurgeryThe last decade has seen an evolution of minimally invasive spine surgery with new technological developments. Minimally invasive spine surgery is thought to decrease postoperative pain and allow quicker recovery by limiting soft-tissue retraction and dissection. Advances in microscopy, tissue retractors, and specialized instruments have enabled surgeons to perform procedures through small incisions.

As with the open approach, the goals of the minimally invasive approach are to adequately decompress the involved neural elements, stabilize the motion segment, and/or realign the spinal column according to the needs of the individual patient. Key ConceptsMinimally invasive posterior lumbar surgery is based on the following key concepts: avoid muscle crush injury by self-retaining retractors, do not disrupt tendon attachment sites of key muscles, particularly the origin of the multifidus muscle at the spinous process,(3)Utilize known anatomic neurovascular and muscle compartment planes, and (4)Minimize collateral soft tissue injury by limiting the width of the surgical corridor.Kim et al. compared trunk muscle strength between patients treated with open posterior spinal instrumentation and those managed with percutaneous instrumentation. Patients who had undergone percutaneous instrumentation had >50% improvement in lumbar extension strength, whereas those treated with open surgery had no improvement.

Comparison of Multifidus Muscle Atrophy and Trunk Extension Muscle Strength : Percutaneous Versus Open Pedicle Screw Fixation Kim, MD,* Sang-Ho Lee, MD, PhD,* Sang Ki Chung, MD SPINE 2004Significant decrease in the cross-sectional area of multifidus muscle in the OPF group. In contrast, the results in the PPF group showed no statistical difference between preoperative & post operative results. PPF had positive effects on postoperative trunk muscle performance.

Box plot showing the longitudinal changes of crosssectional area of multifidus muscle and extensor muscle strength in the percutaneous and open pedicle screw fixation groups. Box plots show the median value (horizontal line in box), and interquartile range (25%75%) is represented by the box

Muscle biopsy specimens from patients undergoing revision spine surgery have revealed selective type-II fiber atrophy, widespread fiber-type grouping (a sign of reinnervation), and a motheaten appearance of muscle fibers. the most important factor responsible for muscle injury is the use of forceful self retaining retractors.Kawaguchi et al. proposed that injury is induced by a crush mechanism similar to that caused by a pneumatic tourniquet during surgery on the extremities. The severity of the muscle injury is affected by the degree of the intramuscular pressure and the length of the retraction time. Patients treated with a traditional open posterior transforaminal lumbar interbody fusion technique showed marked intramuscular edema on postoperative MRI six months after the surgery.Tsutsumimoto et al. used MRI to compare two groups of patients: those who had had a traditional midline approach and those who had had a mini-open Wiltse approach. The degree of multifidus atrophy and the increase in T2-signal intensity in the multifidus muscle after the miniopen posterior lumbar interbody fusion were significantly lower than those following open posterior lumbar interbody fusion Damage to the neuromuscular junction following prolonged retraction can also lead to muscle denervation. Muscle biopsies in patients with failed back surgery syndrome showed signs of advanced chronic denervation. Kim et al. compared levels of circulating markers of tissue injury in patients who had undergone open spinal fusion with those in patients treated with minimally invasive spine surgery.The levels of creatinine kinase, aldolase, pro-inflammatory cytokines (IL-6 [interleukin-6] and IL-8), and antiinflammatory cytokines (IL-10 and IL-1 receptor antagonist) in the patientstreated with the open surgery were altered several-fold compared with those in the patients treated with the minimally invasive surgery. Most markers returned to baseline levels by three days after the minimally invasive surgery, whereas they required seven days to return to baselines levels after the open surgeryRen et al. demonstrated that the glycerol concentrations in the paraspinal muscles of patients who had undergone posterolateral lumbar fusion with instrumentation were higher than the concentrations in the deltoid muscles of the same patients.Another goal of minimally invasive spine surgery is to limit the amount of osseous resection to minimize postoperative spinal instability. The disruption of facet joint integrity combined with loss of the midline interspinous ligament-tendon complex associated with traditional laminectomy can contribute to flexion instability. A finite element analysis demonstrated that minimizing bone and ligament removal resulted in greater preservation of normal motion of the lumbar spine after surgery.Efforts to limit such potentially destabilizing surgery have been pursued via unilateral laminotomies in which the spinous processes and corresponding tendinous attachments of the multifidus muscle and the supraspinous and interspinous ligaments are preserved.A. Jay Khanna, MD Johns Hopkins Orthopaedics at Good Samaritan HospitalLaminectomy risks and complications In approximately 5 to 10% of cases, postoperative instability of the operated level can be encountered. This complication can be minimized by avoiding the pars interarticularis. Facet joints may have to be removed if they are enlarged with arthritis or are pushing on the spinal nerves, causing instability and may require spinal fusion.

Claudius Thome (JNS) 2005 success rate of laminectomy is only 64%, failures have been attributed to local tissue trauma and post operative spinal instability, which has led to dramatic increase in lumbar fusion surgery. Carl Lauryssen, MD, Spine 2010, difficulty of accessing a stenotic neural foramen with linear configured decompression instruments during traditional or MIS surgery results in resections of part or the entire facet joint, leading to instability. Destruction of facet joint transfers axial loads to the anulus and anterior longitudinal ligament, which may accelerate disc degeneration. This may cause instability and nonphysiological motion, possibly leading to neural trauma, facet fracture, disc disruption, or spondylolisthesis. In their retrospective study, Hopp and Tsou reported that 57 of 344 (16.6%) of patients who had decompression for stenosis had to undergo additional fusion surgery because of complications mostly due to instability. Minimally Invasive Tubular MicrodiscectomyThe treatment of herniated discs via minimally invasive tubular microdiscectomy is the most common minimally invasive spine technique currently used in the United States. This system, developed by Foley and Smith, consists of a series of concentric dilators and thin walled tubular retractors of variable length. The tube, typically 18 mm in diameter, circumferentially defines a surgical corridor. Surgery is typically performed with use of an operating microscope.Randomized controlled trials comparing traditional open microdiscectomy with minimally invasive tubular microdiscectomy all showed that tubular microdiscectomy is safe and efficacious resulted in less intraoperative tissue damage, nerve irritation, blood loss, and immediate postoperative pain as well as a shorter period of hospitalization and a faster recovery and return to work

8Minimally Invasive Lumbar DecompressionPercutaneous transforaminal endoscopic lumbar discectomy

Ideal for foraminal and extra foraminal lumbar disc herniaitonsSpinal stenosis can be tackled using laser and endoscopic burrs Minimally Invasive Lumbar HemilaminectomyThe central canal and the contralateral recess can be decompressed by angling the tubular retractor dorsally to view the undersurface of the spinous process and the contralateral lamina The dural tube can be gently pushed down, and the ligamentum flavum and the contralateral superior articular process are resected to achieve a bilateral decompression. Ikuta et al. reported good short-term results in thirty-eight of forty-four patients.The mean improvement in the Japanese Orthopaedic Association score was 72%. Postoperative morbidity was relatively low and, compared with a control group treated with open surgery. Yagi el.al The patients treated with the minimally invasive decompression had a shorter mean hospital stay, less blood loss, a lower mean creatine phosphokinase muscle isoenzyme level, a lower visual analog scale score for back pain at one year postoperatively, and a faster recovery rate. Satisfactory neurological decompression and symptom relief were achieved in 90% of the patients, and no patient had spinal instability