经皮椎体成形术后相邻椎体的新发骨折

经皮椎体成形术为治疗椎体溶骨性骨肿瘤及骨质疏松性椎体压缩性骨折等脊柱疾患的重要方法之一,它能迅速缓解疼痛,提高患者的生活质量,但也存在并发症。越来越多的文献报道椎体成形术后其相邻椎体发生了新发骨折,但两者之间究竟是否存在因果关系,目前尚无定论。因为接受椎体成形术的患者本身即患有转移性骨肿瘤、骨质疏松等基础疾病,新发骨折可能并不是椎体成形术引起的并发症,而可能仅仅是原有基础疾病的进展。本文结合相关文献,重点讨论椎体成形术后是否容易导致新发骨折,新发骨折的发生率是否高于无椎体成形术者,从支持及反对椎体成形术与新发骨折之间存在因果关系两个方面作一综述。     

PMMA剂量和分布对重度骨质疏松人工骨中椎弓根螺钉稳定性的作用研究

目的比较骨水泥(PMMA)的不同注射剂量和分布规律对重度骨质疏松(OP)人工骨中可注射螺钉固定强度的作用,分析螺钉固定强度与PMMA注射剂量、分布规律之间的相关关系。方法重度OP人工骨模块随机分为A(180°-4孔螺钉),B(180°-6孔螺钉),C(180°-间隔4孔螺钉),D(普通椎弓根螺钉)4个螺钉组,每组又随机分为0、1、2、3剂量组(0、2.0、2.5、3.0 m L PMMA)。同法制备钉道后,A、B、C组中分别拧入A、B、C 3种可注射螺钉并注射不同剂量PMMA,D组向钉道内注射不同剂量PMMA后再拧入普通椎弓根螺钉。X线检查PMMA分布情况,测量螺钉的最大轴向拔出力(F_(max))。结果 X线检查显示,A1～A3组中PMMA包裹螺钉的前1/3,B1～B3组和C1～C3组中PMMA包裹螺钉的中1/3,D1～D3组中PMMA相对均匀地包裹螺钉的全长。两因素方差分析显示,PMMA剂量和分布两个因素对F_(max)均有影响(P<0.05),但PMMA剂量和分布两者之间无明显的相互作用(P>0.05)。在相同螺钉组间,2.0 m L和2.5 m L PMMA组、2.5 m L和3.0 m L PMMA组的F_(max)比较差异均无统计学差异(P>0.05),但3.0 m L PMMA组的F_(max)高于2.0 m L PMMA组(P<0.05)。A1组中F_(max)低于D1组(P<0.05),其余相同剂量组间的F_(max)比较差异均无统计学意义(P>0.05)。结论 PMMA可提高重度OP人工骨中椎弓根螺钉的稳定性,PMMA的剂量及分布对螺钉稳定性有影响。在重度OP人工骨模块中,推荐使用A组的180°-4孔螺钉或B组的180°-6孔螺钉,可注射螺钉注射3.0 m L PMMA来强化螺钉的稳定性。     

Biomechanical evaluation of kyphoplasty and vertebroplasty with calcium phosphate cement in a simulated osteoporotic compression fracture

 Kyphoplasty and vertebroplasty with polymethylmethacrylate (PMMA) have been used for the treatment of osteoporotic vertebral compression fractures. We performed kyphoplasty and vertebroplasty with α-tricalcium phosphate cement (CPC) and PMMA to compare the biomechanical properties. Thirty osteoporotic vertebrae were harvested from nine embalmed cadavers. We randomized the vertebrae into four treatment groups: (1) kyphoplasty with CPC; (2) kyphoplasty with PMMA; (3) vertebroplasty with CPC; and (4) vertebroplasty with PMMA. Prior to injecting the cement, all vertebrae were compressed to determine their initial strength and stiffness. They were then recompressed to determine their augmented strength and stiffness. Although the augmented strength was greater than the initial strength in all groups, there was no significant difference between the two bone cements for either kyphoplasty or vertebroplasty. The augmented stiffness was significantly less than the initial stiffness in the kyphoplasty groups, but the difference between the two cements did not reach significance. In the vertebroplasty groups, the augmented stiffness was not significantly different from the initial stiffness. There was no significant difference between the two bone cements for either procedure when cement volume and restoration of anterior height were assessed. We concluded that kyphoplasty and vertebroplasty with CPC were viable treatment alternatives to PMMA for osteoporotic vertebral compression fractures. Received: July 18, 2002 / Accepted: November 6, 2002 Offprint requests to: S. Tomita     

Complications following cranioplasty using autologous bone or polymethylmethacrylate—Retrospective experience from a single center

Objective

A decompressive hemicraniectomy is a potentially life-saving intervention following head trauma. Once performed patients are obliged to undergo a second procedure with cranioplasty. Two of the most commonly used materials are autologous bone and polymethylmethacrylate (PMMA). We have now evaluated complications following a cranioplasty using these materials.

Materials and methods

During a 7-year period (2002–2008) 49 patients were operated with a decompressive craniectomy following head trauma. Patients received a cranioplasty consisting of autologous bone (30 patients, 61.2%) or PMMA (19 patients, 38.8%) and were followed at least 24 months. Patient data were collected retrospectively.

Results

Twenty patients (20/49, 40.8%) experienced a complication that prompted a re-operation. There was a significantly higher rate of complications leading to a re-operation (53.3% vs. 21.1%, p = 0.03) and a shorter survival time of the cranioplasty (mean 48.1 ± 7.8 vs. 79.5 ± 9.0 months, p = 0.035) in patients with autologous bone compared to PMMA. Bone resorption and the presence of postoperative hematomas were significantly more common in patients with autologous bone. The material used for cranioplasty was the only variable that significantly correlated to the rate of complications.

Conclusions

In our series we had a high percentage of patients needing re-operation due to complications following a cranioplasty. Though generally considered a straightforward procedure, complications and associated morbidity in patients undergoing cranioplasty should not be underestimated.     

Strength reduction and the effects of treatment of long bones with diaphyseal defects involving 50% of the cortex

Currently, three criteria are accepted as indications for prophylactic internal fixation of metastatic disease in long bone, including lesions (a) destroying 50% or more of the cortex; (b) 2.5 cm or greater in diameter; or (c) with pain unrelieved by radiation therapy. Using an oblong defect configuration in which one half of the cross-sectional area was destroyed, canine femora were torsion-tested at high speed to determine (a) the actual strength reduction incurred by a lesion destroying 50% of the cortical circumference, and (b) the effects and benefits of internal fixation using polymethylmethacrylate and/or a six-hole compression plate on such a defect. The femurs with a 50% circumferential cortical defect demonstrated only 12.7 +/- 3.8% of intact strength. Defects treated with a combination of plating (all screws bicortical) and polymethylmethacrylate (torque to failure 4.39 +/- 0.90 times greater than the defect alone or TE/TD = 4.39 +/- 0.90) were statistically stronger than defects treated with polymethylmethacrylate alone (TE/TD = 2.48 +/- 0.66; p less than 0.025) or by plating alone (TE/TD = 2.61 +/- 0.91; p less than 0.025), but torque-to-failure was only increased to approximately 56% of an intact bone. Plated intact bones (TE/TD = 5.33 +/- 0.41) were significantly weaker than intact bones (TE/TD = 8.50 +/- 2.52; p less than 0.001). Our results substantiate the need for using polymethylmethacrylate and internal fixation in combination when prophylactically fixing pathologic lesions of this proportion.     

经皮椎体成形术的临床应用

目的　探讨经皮椎体成形术 (PVP)治疗椎体病变引起的压缩骨折的技术操作和临床效果。资料与方法　对 30例共 4 6个椎体行PVP ,其中骨质疏松 2 0例 ,血管瘤 1例 ,多发性骨髓瘤 1例 ,转移瘤 8例。年龄 31～ 98岁 ,平均 5 8岁。穿刺方法为患者俯卧 ,影像增强器向矢状面足侧成角 10°～ 15° ,椎体上下缘没有双边影 ,使欲穿刺侧的椎弓根投影在椎体的中外 1/ 3处 ,将穿刺针、X线管、椎弓根成一直线进针 ,穿刺成功后将聚甲基丙烯酸甲酯 (PM MA ,骨水泥 )按粉液比 3∶2 (g/ml)混合成糊状 ,在透视下用 1ml注射器均匀缓慢注入病变椎体。如骨水泥弥散不良再行对侧穿刺。术后当天、7天、1个月、3个月CT检查注射椎体 ,随访病情变化。结果　所有病例均成功施行了PVP ,单侧穿刺 32个椎体 (胸椎 8个 ,腰椎 2 4个 ) ,双侧穿刺 14个椎体 (胸椎 8个 ,腰椎 6个 )。单侧穿刺胸椎骨水泥平均用量 2 .5ml,腰椎 3.7ml;双侧穿刺胸椎骨水泥平均用量 3.2ml,腰椎 4 .7ml。治疗效果同骨水泥的注射量无关 ,同单双侧穿刺无关。 2 1例良性病例疼痛完全缓解 (CR) 14例 ,部分缓解 (PR) 7例 ;9例恶性病例中PR 7例 ,2例无效(NR) ;随访 6个月良性病例止痛效果良好 ,恶性病例 3个月后止痛效果下降。CT、X线随访骨水泥术后形态无变化 ,未见椎体     

Effect of cement pressure and bone strength on polymethylmethacrylate fixation

The effect of the quality of the bone and of the cement pressurization magnitude and duration on the fixation achieved with polymethylmethacrylate (PMMA) bone cement is studied in vitro. Seventy-one cementbone interface specimens, prepared under various conditions of pressurization of low-viscosity bone cement, are tested in tension. The load at failure and the maximum cement penetration are measured to assess the fixation achieved, and the quality of the bone is assessed by determining the compressive strength of each of the bone specimens. Statistical analysis of the data indicates that the pressure magnitude is the most influential of the factors considered in the cement penetration behavior and in the development of failure load capacity. The duration of the pressure does not appear to be a significant factor. The cement penetration is a decreasing function of the bone strength, reflecting a decrease in the porosity and an increase in the area fraction. Although not directly measured in these tests, these latter bone properties are indirectly measured by the bone compressive strength. The effect of increasing bone strength on the failure load is nonlinear. The development of adequate failure load capacity is the result of a balance between the cement penetration allowed by the porosity of the bone and the inherent strength of the cancellous bone itself. Weak bone, although adequately penetrated by cement, cannot provide strong fixation. Stronger, denser bone limits cement penetration, but pressurization enhances development of failure load capacity through more complete infusion and interlocking of the cement in the available pore space. The strength of the fixation achievable for any bone is limited by the intrinsic strength of the bone. An optimal depth of cement penetration of 4 mm and an optimal bone area fraction of 0.20 are suggested for the most effective fixation.     

Antibiotic-releasing porous polymethylmethacrylate/gelatin/antibiotic constructs for craniofacial tissue engineering

An antibiotic-releasing porous polymethylmethacrylate (PMMA) construct was developed to maintain the bony space and prime the wound site in the initial step of a two-stage regenerative medicine approach toward reconstructing significant bony or composite craniofacial tissue defects. Porous PMMA constructs incorporating gelatin microparticles (GMPs) were fabricated by the sequential assembly of GMPs, the antibiotic colistin, and a clinically used bone cement formulation of PMMA powder and methylmethacrylate liquid. PMMA/gelatin/antibiotic constructs with varying gelatin incorporation and drug content were investigated to elucidate the relationship between material composition and construct properties (porosity and drug release kinetics). The porosity of PMMA/gelatin/antibiotic constructs ranged between 7.6 ± 1.8% and 38.4 ± 1.4% depending on the amount of gelatin incorporated and the drug solution added for gelatin swelling. The constructs released colistin over 10 or 14 days with an average release rate per day above 10 μg/ml. The porosity and in vitro colistin release kinetics of PMMA/gelatin/antibiotic constructs were tuned by varying the material composition and fabrication parameters. This study demonstrates the potential of gelatin-incorporating PMMA constructs as a functional space maintainer for both promoting tissue healing/coverage and addressing local infections, enabling better long-term success of the definitive regenerated tissue construct.     

Minimally invasive decompression with posterior column reinforcement for the treatment of symptomatic osteoporotic fracture with spinal stenosis in lumbar vertebrae

An osteoporotic fracture (OF) in the second to fifth lumbar vertebrae with spinal stenosis may be an indication for surgical treatment, but carries the risks of instability or instrumentation failure. Modified surgical procedures have been developed to manage patients with challenging OF. We retrospectively studied 12 patients (three male, nine female; mean age±standard deviation=73.5±7.2 years) who underwent minimally invasive decompression and posterior column reinforcement with polymethylmethacrylate. During a mean follow-up period of 24.8±3.1 months, pain severity and functional impairment were both significantly reduced, as measured by the visual analog scale and the Oswestry disability index. Nine patients (75%) experienced a satisfactory outcome while the other three (25%) were unchanged. Plain radiographs showed stable spinal alignment and immobilization of flexion-extension within the PMMA construct. Five complications were managed successfully, including one by revision surgery. These procedures are a feasible surgical option in the elderly population studied.     

Fenestrated pedicle screws for cement-augmented purchase in patients with bone softening: a review of 21 cases

Background  

This prospective mixed cohort study was designed to evaluate the middle- to long-term purchase of cement-augmented pedicular screws in patients with poor bone quality. The growing number of surgical procedures performed in the spine has highlighted the problem of screws loosening in patients with poor bone stock due to osteoporosis and/or tumors. Different methods of increasing screw purchase have been reported in the literature, including polymethylmethacrylate (PMMA) augmentation.