2011年06月28日10:47  来源:好医生网站

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 elements, stabilize the motion segment, and/or realign the spinal column according to the needs of the individual patient. This article is an overview of the current state of minimally invasive spine surgery and a discussion of the key biologic concepts of posterior lumbar decompression as well as posterior and lateral fusion techniques.


Key Concepts


Minimally invasive posterior lumbar surgery is based on the following key concepts: (1) avoid muscle crush injury by self-retaining retractors, (2) 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.


One of the main goals of minimally invasive spine surgery is to reduce trauma to the two posterior paraspinal muscle groups—(1) the deep paramedian transversospinalis muscle group, including the multifidus, interspinales, intertransversarii, and short rotators, and (2) the more superficial and lateral erector spinae muscles including the longissimus and iliocostalis (Fig. 1). These muscles run along the thoracolumbar spine and attach caudally. The multifidus muscle in particular is important for dynamic stability of the spine (see Appendix).



图1 A:经L4-L5椎间盘的MRI轴位T2加权图像显示多裂肌(MU),髂肋肌(IL),最长肌(LO),腰方肌(QL),横突间肌(IT),腰大肌(PS)。B:57 岁男性L5-S1滑脱术前MRI轴位T2加权图像(L5椎弓根水平)。C:45岁女性,L4-L5中线开放式经椎间孔腰椎体间融合术后MRI轴位T2加权图像(L5椎弓根水平),显示椎旁肌被脂肪取代。D:同一患者(如B图所示)行L5-S1微创经椎间孔腰椎体间融合术后轴位T2加权图像,显示椎旁肌结构得以保留。

The traditional midline posterior approach for lumbar decompression and fusion traumatizes some paraspinous tissue. The tendon origin of the multifidus muscle is detached, the surgical site is wide, and muscle crush injury may occur with the use of self-retaining retractors, all of which may result in muscle atrophy1-9. Atrophy, in turn, leads to decreased force-production capacity of the muscle10,11. Kim et al. compared trunk muscle strength between patients treated with open posterior spinal instrumentation and those managed with percutaneous instrumentation12. Patients who had undergone percutaneous instrumentation had >50% improvement in lumbarextension strength, whereas those treated with open surgery had no improvement.


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‘moth-eaten’appearance of muscle fibers13. While there may be several causes, 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 extremities6,14-17. During the application of self-retaining retractors, elevated pressures lead to decreased intramuscular perfusion18,19. The severity of the muscle injury is affected by the degree of the intramuscular pressure and the length of the retraction time. Using MRI (magnetic resonance imaging), Stevens et al. assessed the post-surgical appearance of the multifidus muscle20. Patients treated with a traditional open posterior transforaminal lumbar interbody fusion technique showed marked intramuscular edema on postoperative MRI six months after the surgery, while patients treated with a mini-open transforaminal lumbar interbody fusion had nearly normal findings on MRI. Tsutsumimoto et al. used MRI to assess the multifidus muscle in patients treated with a posterior lumbar interbody fusion21. They compared 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 mini-open posterior lumbar interbody fusion were significantly lower than those following open posterior lumbar interbody fusion.


Another mechanism leading to degeneration and atrophy following traditional open surgery is muscle denervation. The nerve supply to the multifidus is monosegmental, making it especially vulnerable to injury22,23.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 denervation24.


Soft-tissue trauma can have widespread regional and systemic effects. 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 surgery25. The levels of creatinine kinase, aldolase, pro-infiammatory cytokines (IL-6 [interleukin-6] and IL-8), and anti-infiammatory cytokines (IL-10 and IL-1 receptor antagonist) in the paients treated 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 surgery. Glycerol is an important component of glycerophospholipid, the basic structure of the cell plasma membrane. When the integrity of a cell membrane is destroyed, glycerol is released into the interstitial fiuid. Ren 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 patients26.

软组织创伤可造成广泛的局部和全身性影响。Kim等对比了行开放式脊柱融合术和微创脊柱手术患者血清软组织损伤标记物水平25。与接受微创术式的患者相比,行开放式手术的患者其肌酐激酶、醛缩酶、促炎细胞因子(IL-6 [白介素-6] 和IL-8)以及抗炎细胞因子(IL-10和IL-1 受体拮抗物)水平呈数倍改变。行微创手术患者的大多数标记物于术后3天恢复至基线水平,而开放式手术后患者恢复至基线水平需要7天。甘油是细胞质膜基本结构甘油磷脂的重要组份。当细胞膜的完整性受到破坏,甘油即释放至间质液内。Ren等证实,同样一组行后外侧入路腰椎融合内固定的患者,其椎旁肌内甘油浓度要高于三角肌内浓度26。

Another goal of minimally invasive spine surgery is to limit the amount of osseous resection to minimize postoperative spinal instability27,28. The disruption of facet joint integrity combined with loss of the midline interspinous ligament-tendon complex associated with traditional laminectomy can contribute to fiexion instability29-31. 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 finite element analysis demonstrated that minimizing bone and ligament removal resulted in greater preservation of normal motion of the lumbar spine after surgery32.


Minimally Invasive Lumbar Decompression


Minimally Invasive Tubular Microdiscectomy


The 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 length33-35. The tube, typically 18 mm in diameter,circumferentially defines a surgical corridor. Surgery is typically performed with use of an operating microscope. Several recent studies have compared minimally invasive lumbar discectomy with the traditional open approach and have demonstrated that the minimally invasive approach 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 work36-40.Randomized controlled trials comparing traditional open microdiscectomy with minimally invasive tubular microdiscectomy41-43 all showed that tubular microdiscectomy is safe and efficacious.


The surgical corridor is defined by the specific pathological entity. Minimally invasive lumbar decompression can adequately decompress the central, lateral, and foraminal zones of the spinal canal and can be used to remove disc material from the extraforaminal region. However, the access strategy for decompression of each region of the spine should be planned preoperatively. Extraforaminal neural compression may be approached from outside of the spinal canal by inserting the tubular retractor over the intertransverse membrane between the transverse processes. The intertransverse membrane is identified and released to expose the exiting nerve root. Once the root is identified, the disc material in the extraforaminal zone can be accessed deep to the nerve root.


Minimally Invasive Lumbar Hemilaminectomy


The key principle in minimally invasive spine decompression is maintenance of the multifidus tendon attachment to the spinous process. During a traditional laminectomy, the spinous process is removed and the multifidus muscle is retracted laterally. On wound closure, the multifidus origin cannot be repaired to the spinous process. However, a thorough decompression can be achieved through a unilateral portal via a hemi-laminectomy technique44. The 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 (Fig. 2). The dural tube can be gently pushed down, and the ligamentum fiavum and the contralateral superior articular process are resected to achieve a bilateral decompression. The upper lumbar spine anatomy differs from the lower lumbar spine anatomy. At L3 and above, the lamina between the spinous process and the facet joint can be narrow (Fig. 2). With a unilateral approach, it may be difficult to reach the ipsilateral recess without removing an excessive amount of the ipsilateral inferior articular process. An option is to utilize a bilateral cross-over technique to reach the right lateral recess from a left-sided hemi-laminectomy and vice versa. In a small preliminary study of four patients and seven levels of decompression performed with this technique, the total operating time averaged thirty-two minutes per level and the estimated blood loss averaged 75 mL. The average postoperative stay was 1.2 days. All patients had resolution of neurogenic claudication, and there were no complications45.



图2 经L2-L3 (A),L3-L4 (B),L4-L5 (C)和L5-S1 (D)椎间隙的MRI轴位T2加权图像。每张图像均标有管状牵开器示意图,虚线示到达手术目标位置的轨迹。在更高位腰椎,注意靠近同侧关节突关节。L3-L4和以上节段,必须谨慎操作以避免因疏忽导致的同侧关节突关节损伤。利用双侧入路(E)可于对侧进行侧隐窝减压(F)。

The efficacy and safety of minimally invasive posterior lumbar decompression have been assessed44,46-55. The learning curve for minimally invasive spine surgery is a concern, as the patients who had been treated during the initial phases of some studies had higher complication rates53,55. In a study of their experience with a minimally invasive unilateral approach to bilateral lumbar decompression for treatment of lumbar stenosis, Ikuta et al. reported good short-term results in thirty-eight of forty-four patients53. 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, the patients had decreased intraoperative blood loss, decreased pain medication requirements, and shorter hospital stays. The authors reported a 25% complication rate, including four dural tears, three fractures of the inferior facet on the approach side, one postoperative cauda equine syndrome requiring a reoperation, and one postoperative epidural hematoma requiring a reoperation.


In a prospective study, Yagi et al. randomly assigned forty-one patients with lumbar stenosis to undergo either a minimally invasive microendoscopic decompression (twenty patients) or a conventional laminectomy (twenty-one patients)56. The duration of follow-up averaged eighteen months. 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 visualanalog 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. Castro-Menfiendez et al. treated fifty patients with lumbar spinal stenosis with a microendoscopic decompression using an 18-mm tubular retractor57. The authors reported good or excellent results in 72% of the patients, with 68% expressing good subjective satisfaction, at a mean of four years. The mean decrease in the Oswestry Disability Index was 30.23, and the mean decrease in the visual analog scale score for leg pain was 6.02.


Asgarzadie and Khoo reported on forty-eight patients who had undergone minimally invasive lumbar decompression for lumbar stenosis58. Twenty-eight patients underwent a one-level decompression, and twenty patients underwent a two-level decompression. Compared with a control group treated with a traditional open laminectomy, the group with minimally invasive surgery had, on average, less intraoperative blood loss (25 versus 193 mL) and a shorter hospital stay (thirty-six versus ninety-four hours). Four-year clinical outcomes were available for thirty-two of the forty-eight patients. All patients reported improvement in walking endurance at six months following surgery, and 80% of the patients had maintained improvement in walking endurance at a mean of thirty-eight months. Improvements in both the Oswestry Disability Index and the Short Form-36 (SF-36) score had been sustained during the follow-up period. There were no neurological complications.

Asgarzadie和Khoo报道了48名行微创腰椎减压的腰椎管狭窄患者58。28名患者行单节段减压,20名患者行双节段减压。与行传统开放式椎扳切除术的对照组患者相比,微创手术组患者平均术中失血量更少(25 vs 193ml)、住院时间更短(36小时vs94小时)。48名患者中的32名4年临床结果可用于评估。术后6个月时,全部患者行走耐力获得改善,80%患者平均38个月后行走耐力改善程度仍获得维持。Oswestry失能指数和简表-36(SF-36)评分改善情况随访期内维持不变。无神经系统并发症发生。

The use of minimally invasive techniques for spine surgery may be advantageous in patients who are elderly, medically frail, or obese40,59-61. In a retrospective case study, Tomasino et al.compared operative results and patient outcomes between obese and nonobese patients who had undergone a one-level lumbar microdiscectomy or a laminectomy with use of tubular retractors62. Of 115 patients, 31% were obese. No significant differences were seen between obese and nonobese patients in terms of incision length, operative time, blood loss, or complications.


Minimally invasive decompression without fusion may be efficacious in patients with degenerative spondylolisthesis. Pao et al. performed a micro-decompression on thirteen patients with stenosis from a grade-I spondylolisthesis63. There was no progression of vertebral slippage, and all patients reported a good outcome. Sasai et al. performed a unilateral approach with bilateral decompression in twenty-three patients with degenerative spondylolisthesis and twenty-five patients with degenerative spinal stenosis64. At two years, the Neurogenic Claudication Outcome Scores and Oswestry Disability Indices were similar between the two groups, although the patients with spondylolisthesis had a somewhat worse outcome. A progression of vertebral slippage of≥5% was found in three of the twenty-three patients with degenerative spondylolisthesis. Kleeman et al. performed a spinous process and interspinous ligament-preserving decompression to treat spinal stenosis in fifteen patients who had an average degenerative spondylolisthesis of 6.7 mm65. After an average of four years of follow-up, two patients had an increase in the slip, with associated worsening of their symptoms, while twelve reported good to excellent results.

微创非融合减压亦可有效用于退变性脊柱滑脱患者。Pao等对13名I度脊柱滑脱的腰椎管狭窄患者进行微创减压63。全部患者均取得良好的临床结果,无椎体滑脱进展发生。Sasai等对23名退变性脊柱滑脱和25名退变性椎管狭窄患者进行单侧入路双侧减压64。术后2年时,两组间的神经性破行结果评分和Oswestry失能指数类似,尽管滑脱患者结果稍差。23名退变性脊柱滑脱患者中有3名出现椎体滑脱≥5%的进展。Kleeman等应用保留棘突和棘间韧带方式减压治疗15名平均椎体滑脱6.7 mm的椎管狭窄患者65。术后平均随访4年,2名患者滑脱程度增加,其临床症状亦进一步恶化,12名患者结果优良。

Transforaminal Lumbar Interbody Fusion


Transforaminal lumbar interbody fusion, originally described by Blume and Rojas and later popularized by Harms and Jeszensky, is an adaptation of the posterior lumbar interbody fusion technique first described by Cloward66-68. In contrast to posterior lumbar interbody fusion, which requires a wide decompression and bilateral nerve-root retraction to access the disc space, transforaminal lumbar interbody fusion is done via a unilateral approach to the disc space through the intervertebral foramen (Fig. 3). Compared with bilateral posterior lumbar interbody fusion, transforaminal lumbar interbody fusion requires less neural retraction69-71. One of its main advantages is that the approach allows pathological conditions such as spinal stenosis to be treated concurrently with an anterior interbody fusion through a single posterior incision(Fig. 4).



图3 A:L4-L5节段MRI轴位T2加权图像显示应用管状牵开器的手术通路(白色实线)和到达手术目标位置的轨迹(虚线)。B:L4-L5手术目标位置人造模型,L4棘突底部和下关节突标记为红色,L5上关节突突出部分标记为黑色。C:通过管状牵开器所见的术中微缩图像,显示手术目标位置类似于B图所示,L4棘突和下关节突轮廓以橙色描绘,L5上关节突突出部分轮廓以蓝色描绘。


图4 微创经椎间孔腰椎体间减压融合术显示A:术中图像显示硬脊膜,探针到达对侧部位。B:CT轴位图像显示手术通路。C:术中图像显示切除后的手术目标位置,硬脊膜和神经根轮廓以黄色描绘,行后方椎体融合的环形切开窗以白色虚线描绘。D:手术目标位置的相应草图。E:术中滑脱复位的连续侧位图像,以操作杆状牵引器松动椎间隙,以连接杆异径接头自后方牵拉L4椎体,黄色虚线显示椎体后缘。

Peng et al. compared the clinical and radiographic outcomes of minimally invasive transforaminal lumbar interbody fusion with those of traditional open transforaminal lumbar interbody fusion72. At two years, the outcomes were similar, but the patients who had had the minimally invasive surgery had the additional benefits of less initial postoperative pain, early rehabilitation, shorter hospitalization, and fewer complications. Dhall et al. retrospectively compared the outcomes of twenty-one patients who had undergone a miniopen transforaminal lumbar interbody fusion with those of twenty-one patients treated with a traditional open transforaminal lumbar interbody fusion and reported that there was significantly more blood loss and a longer hospital stay after the open transforaminal lumbar interbody fusion, although there was no difference in the clinical outcomes at two years73. Selznick et al. reported that minimally invasive transforaminal lumbar interbody fusion is technically feasible in revision cases and is not associated with more blood loss or neurological morbidity than are found with primary procedures74. However, there was a higher rate of incidental durotomy. Minimally invasive transforaminal lumbar interbody fusions in the revision setting are challenging procedures and should be performed by surgeons with experience using minimally invasive techniques.


In a prospective study, Kasis et al. found that limited-exposure posterior lumbar interbody fusion provided better clinical outcomes and shorter hospital stays when compared with a traditional open approach75. The authors noted that (1) preservation of posterior elements, (2) avoidance of far lateral dissection over the transverse processes, (3) a bilateral total facetectomy, (4) fewer neurological complications, and (5) an avoidance of iliac crest autograft were all responsible for the improved outcomes.

在一项前瞻性研究中,Kasis等发现,与传统开放式手术相比,经有限暴露方式行后路腰椎体间融合术可获得更好的临床结果、更短的住院时间75。作者指出,(1) 保留后方结构,(2) 避免向横突上远侧方剥离,(3) 双侧全部关节突关节切除,(4) 神经系统并发症更少,(5) 避免取自体髂嵴植骨,这些方法均有助于改善临床结果。

Direct Lateral Interbody Fusion


Interbody lumbar fusion is a popular technique with touted benefits that include eliminating the disc as a potential pain generator, high rates of fusion, and restoration of intervertebral disc height and lumbar lordosis76-78. These benefits can be achieved with anterior lumbar interbody fusion, posterior or transforaminal lumbar interbody fusion, or an endoscopic lateral retroperitoneal approach79. A minimally invasive retroperitoneal direct lateral transpsoas approach to interbody arthrodesis has been described80,81. This technique involves a minimally invasive approach through the retroperitoneal space and the psoas muscle, with reliance on neural monitoring and fiuoroscopy to provide the ability to achieve an interbody fusion (Figs. 5 and 6).



图5 A:术中图像显示直接经腰大肌入路的适当体位,脊柱和骨盆描绘以黑色,手术台可折叠出标记为黑色椭圆形。B:术中前后位图像,髂嵴以黑色虚线描绘。C:术中侧位图像,髂嵴以黑色虚线描绘,黑色圆形示椎间盘中心的手术目标位置。


图6 直接侧方经腰大肌入路安全区域。A:L4-L5节段MRI轴位T2加权图像显示解剖界面(白色虚线)。B:L4-L5节段MRI轴位T2加权图像显示扩张腰大肌的顺序,首先插入导丝(白线),随后插入扩张器(黄色导管)。C:MRI轴位T1加权图像显示安全区域,后界为神经根(NR),前界为腔静脉(VC),主动脉(Ao)在其前方。D:图表显示L4-L5至L1-L2安全区域的界限,L4-L5节段安全界限实际上较其它节段狭窄,使得L4-L5成为直接外侧入路最具挑战性的节段。AP=前后位,NR/VTB=神经根/椎体,RV/VTB=腔静脉/椎体。E:术中图像显示应用球尖探针进行神经生理监测(箭头)。F:术中前后位图像显示穿过牵开器通道的球尖探针的位置(箭头)。

The iliac wing blocks minimally invasive lateral exposure below L4-L5 (Fig. 5). Limiting the dissection to the anterior third to anterior half of the psoas muscle reduces the risk of neural injury because the lumbar plexus is in the posterior half of the psoas muscle80,82,83. The use of intraoperative electromyographic (EMG) monitoring helps reduce the risk of neural injury(Fig. 6)84. While preparing the disc space for interbody fusion and inserting the interbody device, one should not violate the end plates and should confirm the orientation with both anteroposterior and lateral imaging (Fig.7).Indirect foraminal decompression is possible by restoring the neuroforaminal height and sagittal alignment during the interbody fusion. The decision whether to include a posterior spinal fusion or decompression is individualized (Fig. 8).



图7 直接侧方椎间盘切除椎体间cage植入。术中前后位图像显示应用骨膜起子松解对侧纤维环(A);插入钝性扩张器/仪(B和C);植入合成型椎间cage,自皮质边缘完全跨越整个椎间隙(D, E, F)。术中图像显示手术通路和椎间盘切除后(G)以及cage植入后(H)的手术部位。


图8 68岁女性,长期背痛和大腿左前方疼痛病史,术前(A、C)和术后(B、D)X线图像证实畸形矫正程度。患者行直接侧方L2-L3、L3-L4和L4-L5椎间盘切除椎间融合,间接获得了神经根管减压。随后在患者侧卧位下进行单侧椎弓根螺钉内固定,避免了改变患者体位的需要。

Knight et al. reported the early complications in forty-three female and fifteen male patients who had undergone minimally invasive direct lateral interbody fusion85: six patients had postoperative meralgia paresthetica, and two had L4 nerve-root injuries.


Ozgur et al. reported on thirteen patients treated with a single or multi-level extreme lateral interbody fusion80.The patients had significant relief of pain and improvement in functional scores without any complications. Anand et al. reported on twelve patients treated with direct lateral interbody fusion in combination with a transsacral interbody fusion technique at L5-S186. The patients had an average of 3.6 levels fused, and the correction of the Cobb angle was from an average of 18.9° preoperatively to an average of 6.2° postoperatively86. Pimenta et al. reported on thirty-nine patients treated with direct lateral interbody fusion at an average of 2.0 levels. Scoliosis improved from an average of 18°preoperatively to an average of 8° postoperatively and lumbar lordosis increased from an average of 34° preoperatively to an average of 41° postoperatively81. All patients were walking and tolerating a regular diet on the day of the surgery.The average blood loss was <100 mL, and the average operative time was 200 minutes. The average duration of hospitalization was 2.2 days. Pain scores and functional scores improved. In a larger series, Wright reported the results of extreme lateral interbody fusion in 145 patients treated for degenerative disc disease at multiple institutions87. The number of levels treated ranged from one to four (72% of the procedures were at a single level; 22%, at two levels; 5%, at three levels; and 1%, at four levels). Interbody spacers (polyetheretherketone [PEEK] in 86%, allograft in 8%, and a cage in 6%) were used in conjunction with bone morphogenetic protein (52%), demineralized bonematrix (39%), or autograft (9%). Twenty percent of the operations were stand-alone interbody fusions, 23% used a lateral rod-screw construct, and 58% used posterior pedicle screws. The average operative time was seventy-four minutes, and the average blood loss was 88 mL. There were two transient genitofemoral injuries, and five patients experienced transient hip fiexor weakness. Most patients walked on the day of surgery and were discharged on the first postoperative day.

Ozgur等报道了13名行单节段或多节段极外侧椎间融合治疗的患者80。这些患者具有显著的疼痛缓解程度和功能评分改善程度而无并发症发生。Anand等报道了12名行直接侧方椎间融合并对L5-S1联合应用经骶骨椎间融合技术的患者86。患者平均融合3.6个节段,Cobb角由术前的平均18.9°矫正至术后的平均6.2°86。Pimenta等报道了39名行直接侧方椎间融合平均2个节段的患者。侧凸由术前的平均18°矫正至术后的平均8°,腰椎生理前凸由术前的平均34°增加至术后的平均41°81。所有患者在手术当日均可步行并耐受普通膳食。平均失血量<100 mL,平均手术时间为200分钟。平均住院时间为2.2天。疼痛评分和功能评分均获得改善。在一项大型系列研究中,Wright报道145名退变性椎间盘疾病患者在多个机构行极外侧椎间融合的临床结果87。进行治疗的节段数1~4不等(72% 为单节段;22%双节段;5%为3节段;1%为4节段)。椎间装置(聚醚醚酮[PEEK]占86%;同种异体移植物占8%;cage占6%)联合应用骨形态发生蛋白(52%)、脱钙骨基质(39%)或自体植骨块(9%)。20%的手术为单纯椎间融合,23%应用侧方钉棒系统,58%应用后方椎弓根螺钉。平均手术时间74分钟,平均失血量88mL。2名患者出现暂时性生殖股神经损伤表现,5名出现短暂性屈髋肌力减弱。大多数患者手术当日可行走并于术后第1日出院。

Akbarnia et al. reported on thirteen patients who had had multilevel extreme lateral interbody fusion for the treatment of adult lumbar scoliosis of >30°88. A mean of three levels were treated, and all procedures were combined with posterior spinal fusion and instrumentation. Substantial improvements in lumbar scoliosis and lordosis were found at a mean of nine months. One graft required revision because of migration, and one hernia occurred at the level of the incision for the extreme lateral interbody fusion. All cases of psoas muscle weakness or thigh numbness or pain resolved within six months.Short-term postoperative visual analog scale, Scoliosis Research Society-22, and Oswestry Disability Index scores were improved compared with preoperative scores. Similar results were shown by Anand et al., in a series of twelve patients86. The number of levels treated ranged from two to eight (mean, 3.64). The mean blood loss was 163.89mL (SD [standard deviation], 105.41 mL) for anterior procedures and 93.33 mL (SD, 101.43 mL) for posterior percutaneous pedicle screw fixation. The mean surgical time was 4.01 hours (SD, 1.88 hours) for anterior procedures and 3.99 hours (SD, 1.19 hours) for posterior procedures. The mean Cobb angle improved significantly from 18.93° (SD, 10.48°) preoperatively to 6.19°(SD, 7.20°) at a mean of seventy-five days postoperatively.

Akbarnia等报道13例成人腰椎侧凸>30°患者行多节段极外侧椎间融合术88。平均治疗3个节段,所有术式均联合后路脊柱融合内固定。1例患者由于内植物移位需要翻修,1例极外侧椎间融合切开节段发生椎间盘脱出。全部病例腰大肌无力、大腿疼痛或麻木均于6月内消退。术后短期视觉模拟评分、侧凸研究学会-22评分和Oswestry失能指数评分与术前相比均获改善。Anand等在一项包括12名患者的研究中得到类似的结果86。治疗节段数范围在2-8个(平均3.64)。平均失血量前路手术163.89mL(SD [标准差],105.41 mL),后路经皮椎弓根螺钉固定为93.33 mL (SD,101.43 mL)。平均手术时间前路手术为4.01小时(SD,1.88小时),后路手术为3.99小时(SD,1.19小时)。Cobb角在平均术后75天时由术前的18.93°(SD,10.48°)矫正为6.19°(SD,7.20°)。

Minimally Invasive Posterior Instrumentation


The rationale for minimally invasive pedicle screw insertion into the spine, which can be performed percutaneously or via a paramedian mini-open technique, is to preserve multifidus muscle function. With the percutaneous technique, the pedicle is entered with use of a Jamshidi-type trocar needle under fiuoroscopic control (see Appendix). Once the needles are within the pedicles, the stylets are removed and guidewires inserted. Sequential soft-tissue dilators are used to create a path for the tap and screw. The outermost dilator can be used as a protective sleeve during pedicle tapping. The guidewire is then used to direct cannulated taps and screws into the pedicle. A cannulated pedicle screw is placed over the guidewire.Rods are inserted percutaneously to minimize soft-tissue trauma (Fig. 9).



图9 微创连接杆植入和畸形矫正。图解显示通过椎弓根螺钉套筒植入连接杆技术(A),使用能够体外操作的单一螺纹套筒复位系统(C),将连接杆推入椎弓根螺钉U型头内(B)。术中X线图像显示前后位(D)和侧位(E)内固定影像。骨盆固定可通过植入与S1螺钉一致的骨盆万象螺钉完成,(F)示其轴位CT图像。术前(G、H)和术后(I、J)站立位X线图像对比显示最终内固定形态和畸形矫正程度。

With the mini-open technique, a longitudinal, paramedian incision is placed slightly lateral to the lateral edge of the pedicles. Dissection is performed through the intermuscular plane between the multifidus and longissimus muscles. A tubular retractor system is subsequently deployed after tissue dilation is performed. The pars interarticularis and the mammillary processes of the cephalad and caudad levels are exposed. A high-speed burr is utilized to create a starting point, and pedicle probes are used to enter the pedicle. Cannulated or non-cannulated pedicle screws can be used with this technique. The exposure allows for decortication of the pars, facet joint, and transverse processes for bone-grafting and fusion.


The mini-open technique offers several advantages over the percutaneous method. It allows direct visualization of the anatomy and the choice of using either cannulated or non-cannulated pedicle-screw systems. The mini-open technique also allows greater access for bone-grafting posteriorly. However, the mini-open technique threatens the medial branch of the dorsal rami, which extends downward to the transverse process of the caudad level. The nerve then curves posteriorly, where it branches to supply the multifidus muscle, the intertransverse muscles and ligaments, and the facet joint of the cephalad level. As a result, insertion of a pedicle screw through the mammillary process at one level can cause injury to the medial branch of the dorsal rami that supplies the adjacent cephalad level. In a cadaveric study comparing these minimally invasive spine techniques, Regev et al. found that the mini-open technique causes injury to the medial branch of the dorsal rami more frequently than does the percutaneous technique89. They recommended that pedicle screw insertion at the cephalad level be performed percutaneously if one desires to minimize denervation of the multifidus complex at the cephalad adjacent level.


Overall safety and accuracy have been reported for minimally invasive pedicle screw insertion. Ringel et al. assessed 488 pedicle screws implanted in a total of 103 patients via a percutaneous technique90. They found that only 3% of the screws were rated as unacceptable, leading to nine screw-revision surgical procedures. These results mirror a growing body of evidence that refect the safety and efficacy of minimallyinvasive posterior spinal instrumentation91-93. In a meta-analysis of 130 studies and 37,337 pedicle screws placed, the overall screw-placement accuracy was 91.3%94.


Limitations and Drawbacks


Radiation Exposure


There are several techniques for minimally invasive posterior screw insertion, but the percutaneous pedicle screw technique is the least tissue-disruptive and has been adapted by some for single or multilevel fusions. Its use, however, depends on intraoperative multiplanar fiuoroscopy. The operative time for insertion of two screws at the same vertebral level reaches ten minutes or longer with the use of advanced fiuoroscopic techniques, whereas lateral-only fiuoroscopic methods require less than five minutes per level95-97. With increased insertion times associated with advanced fiuoroscopic guidance, the cumulative exposure to radiation increases concomitantly.


Studies have shown that fiuoroscopically guided pedicle screw placement exposes surgeons to a dose of radiation that is ten to twelve times the dose associated with non-spinal musculoskeletal procedures98. Despite these concerns, the convenience of the c-arm, combined with a high degree of accuracy, has made intraoperative fiuoroscopy an increasingly necessary part of advanced minimally invasive spine surgery. Exposure of both the surgeon and the patient to radiation was analyzed in a prospective study of twenty-four consecutive patients who underwent minimally invasive transforaminal lumbar interbody fusion99. The mean fiuoroscopy time was 1.69 minutes (range, 0.82 to 3.73 minutes) per case. The authors concluded that patient exposures were low and compared favorably with those associated with other common interventional fiuoroscopically guided procedures. Kim et al. showed that the use of navigation-assisted fiuoroscopy for minimally invasive transforaminal lumbar interbody fusion markedly decreases direct exposure to radiation by allowing the surgeon to step away from the surgical field during image acquisition100. In addition to reducing radiation exposure, navigation eliminates the need for cumbersome protective lead gear and eliminates the need for fiuoroscopy during surgery.


Learning Curve for Minimally Invasive Spine Surgery


The barriers to widespread adoption of minimally invasive techniques appear to be related to technical difficulties of the procedures and a lack of adequate training opportunities. Webb et al. showed that most spinal surgeons perceive minimally invasive spine surgery to be efficacious and most wish to perform more of the procedures101. However, most surgeons have not pursued minimally invasive spine surgery because of concerns about technical difficulties of the procedure and a lack of adequate training opportunities. Nowitzke evaluated the learning curve for tubular decompression and noted that three of the first seven cases performed in their series, but none of the subsequent twenty-eight, required conversion to open surgery102. Villavicencio et al. noted a higher rate of overall perioperative complications, Dhall et al. found a higher rate of instrumentation-related complications, and Peng et al. reported longer operative times when comparing minimally invasive transforaminal lumbar interbody fusion with open transforaminal lumbar interbody fusion72,73,103. Improving the learning curve for minimally invasive spine surgery requires studies to better the understanding of the specific portions of the procedure that are most challenging and to thus allow for development of appropriate instrumentation and improved training techniques.




The posterior spine is dynamically stabilized by a diverse group of muscles that lie in close proximity to the vertebrae and possess multiple tendon insertion sites. In humans, stability and motion are controlled by active and passive means. The multifidus muscle is a powerful spine stabilizer as it has short and powerful fibers that enable it to produce large forces over short distances. Traditional posterior midline open approaches disrupt the function of this muscle through tendon detachment, devascularization, and crush injury. Minimally invasive spine surgery techniques were developed in an attempt to minimize surgical damage and preserve normal function. The rationale of this approach relies on limiting the surgical corridor to the minimum necessary to safely expose the surgical target site and to minimize injury to the anatomic structures necessary for normal function. The traditional use of self-retaining retractors, which can induce crush injuries to muscle, has been supplanted by table-mounted, tubular-type retractors that minimize pressure on muscles, vessels, and nerves. As minimally invasive spine surgery continues to evolve, it is important to properly evaluate the risks and benefits of various minimally invasive techniques with prospective, long-term clinical studies.


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