Reoperation rates and risk factors for revision 4 years after dynamic stabilization of the lumbar spine

Background Context

The concept of dynamic stabilization (DS) of the lumbar spine for treatment of degenerative instability has been introduced almost two decades ago. Dynamic stabilization follows the principle of controlling movement in the coronal plane by providing load transfer of the spinal segment without fusion and, at the same time, reducing side effects such as adjacent segment disease (ASD). So far, only little is known about revision rates after DS due to ASD and screw loosening (SL).

Particulate endocytosis mediates biological responses of human mesenchymal stem cells to titanium wear debris.

Continual loading and articulation cycles undergone by metallic (e.g., titanium) alloy arthroplasty prostheses lead to liberation of a large number of metallic debris particulates, which have long been implicated as a primary cause of periprosthetic osteolysis and postarthroplasty aseptic implant loosening. Long-term stability of total joint replacement prostheses relies on proper integration between implant biomaterial and osseous tissue, and factors that interfere with this integration are likely to cause osteolysis. Because multipotent mesenchymal stem cells (MSCs) located adjacent to the implant have an osteoprogenitor function and are critical contributors to osseous tissue integrity, when their functions or activities are compromised, osteolysis will most likely occur. To date, it is not certain or sufficiently confirmed whether MSCs endocytose titanium particles, and if so, whether particulate endocytosis has any effect on cellular responses to wear debris. This study seeks to clarify the phenomenon of titanium endocytosis by human MSCs (hMSCs), and investigates the influence of endocytosis on their activities. hMSCs incubated with commercially pure titanium particles exhibited internalized particles, as observed by scanning electron microscopy and confocal laser scanning microscopy, with time-dependent reduction in the number of extracellular particles. Particulate endocytosis was associated with reduced rates of cellular proliferation and cell-substrate adhesion, suppressed osteogenic differentiation, and increased rate of apoptosis. These cellular effects of exposure to titanium particles were reduced when endocytosis was inhibited by treatment with cytochalasin D, and no significant effect was seen when hMSCs were treated only with conditioned medium obtained from particulate-treated cells. These findings strongly suggest that the biological responses of hMSCs to wear debris are triggered primarily by the direct endocytosis of titanium particulates, and not mediated by secreted soluble factors. In this manner, therapeutical approaches that suppress particle endocytosis could reduce the bioreactivity of hMSCs to particulates, and enhance long-term orthopedic implant prognosis by minimizing wear-debris periprosthethic osteolysis.     

降钙素防治骨质疏松模型兔的人工假体无菌性松动的实验研究

[目的]探讨降钙素对已行人工假体植入骨质疏松模型免的假体无菌性松动防治作用的实验研究。[方法]将30只假体植入模型的骨质疏松症兔随机分成实验组和对照组，各15只。实验组给予鲑鱼降钙素治疗（6U／kg，肌注，隔日1次），而对照组给予等量的生理盐水肌注，持续治疗半年。两组均分别于术前、术后4、8、12和24周检测假体周围感应区（ROI）骨密度（BMD）；于术前及术后4、12、24周行血清骨代谢指标检测：骨特异性碱性磷酸酶（BALP）、骨钙素（BGP）、抗酒石酸酸性磷酸酶-5b（TRAP-5b）；所有动物于术后24周处死，分别行假体拔出实验与扭转实验测定和假体周围骨组织形态计量学分析。[结果]术后24周，实验组假体周围局部感兴趣区BMD增加近5％，而对照组假体周围局部感兴趣区BMD下降了6％，两组比较有显著性差异（P〈0．01）；骨代谢指标中，术后24周实验组的BALP、BGP稍有下降，但组内无显著性差异（P〉0．05），而TRAP-5b有明显下降（P〈0．05），这些指标与对照组比较差异显著（P〈0．05或P〈0．01）；生物力学检测显示，实验组的假体拔出实验较对照组提高了约50％，扭转实验提高近1倍，且两组比较差异显著（P〈0．01）；骨组织形态计量学显示，实验组中反映骨吸收的Oc．No／Tb．Pm、ES／BS明显减少；反映骨量和微结构的％Tb．Ar、Tb．N明显增多，而Tb．Sp明显变窄：反映骨形成与骨矿化的OS／BS、MAR、BFR／TV及％L．Pm也均明显增多；这些指标与对照组比较差异显著（P〈0．01或P〈0．05）。[结论]鲑鱼降钙素能明显减少人工假体周围骨量的丢失和抑制骨溶解；并加快假体周围的骨形成，提高骨密度，促进生理性骨矿化；还能改善骨质量，促进骨微结构改变，提高骨的生物力学特性并增加假体四周的支撑力。其对骨质疏松症兔的假体松动有明显的预防和治疗作用。这对临床预防和治疗人工关节的无菌性松动有很好的指导意义。     

钛颗粒负荷对切应力作用下骨髓间质干细胞F-actin表达和DNA含量的影响

假体磨损碎屑颗粒是引起假体一骨界面无菌性炎症和骨溶解而致全关节置换术失败的主要原因之一。磨屑颗粒所诱发的骨溶解须有周围骨组织中成骨细胞分泌足够的骨基质以弥补丢失的骨量，而成骨细胞正常的数量和质量有赖于其来源骨髓祖细胞—骨髓问质干细胞的正常增殖分化能力的维持。为了探讨磨屑钛颗粒对大鼠骨髓间质干细胞(Rat MSCs，rMSCs)产生细胞毒性的可能细胞分子机制，选用健康3月龄SD雄性大鼠，采用Percoll等密度梯度离心法分离获取rMSCs，经体外传代纯化培养后，与不同直径、不同负荷浓度、不同负荷作用时间的钛颗粒悬液共孵育，再采用精准的流室系统对钛颗粒负荷的rMSCs施加一定的流体剪切应力(Fluid shear stress，FSS)后立刻固定细胞，经免疫荧光抗体染色，结合激光共聚焦显微镜技术和图像分析软件定性定量分析rMSCs F—actin表达和DNA含量的变化情况。同时设置相应的未经钛颗粒孵育的rMSCs细胞为对照组细胞。结果显示，切应力作用可上调rMSCs胞内F—actin的表达。亚微(Submieron)直径(0．9μm)的钛颗粒负荷对rMSCs F—actin表达和DNA含量的抑制作用最为显著，并伴有凋亡小体出现；直径为2．7μm的钛颗粒负荷产生的抑制作用略为减弱，而较大直径(6．9μm)的抑制效应最弱。相同条件下，钛颗粒负荷对F—actin的抑制效应有一定的时间和浓度依赖性：以0．1wt％浓度对F—actin表达和DNA含量的抑制效应最为明显，亦有凋亡小体的出现；随着浓度的降低，抑制作用亦减弱，以0．01wt％浓度最弱；随着作用时间的延长，F—actin表达和DNA含量逐渐降低，至实验中的32h达到最低值。提示：磨屑颗粒对rMSCs活力的抑制作用是假体无菌性松动的可能分子机制，对其具体细胞分子机制进行深入研究，必将有助于有效防治假体松动药物的研发应用以及人工关节材料的优化设计，从而为全关节置换术患者真正带来福音。     

Risk Factor Analysis of Facet Fusion Following Cervical Lateral Mass Screw Fixation with a Minimum 1-Year Follow-up: Assessment of Maximal Insertional Screw Torque and Incidence of Loosening

Posterior stabilization is a common surgical procedure, which aims for rigid stabilization by facet fusion. Facet non-union has a potential risk of the screw loosening and malalignment. Although some authors have reported the influencing factors about screw loosening in the lumbar spine, there are few reports about the risk factor contributing to the facet non-union in the cervical spine. In all, 22 patients (78 facets and 122 screws) with degenerative cervical kyphosis or spondylolisthesis who underwent decompression and lateral mass screw (LMS) fixation were analyzed. Age, gender, smoking, bone mineral density (BMD), the degree of facet decortication with bone packing, and screw loosening were investigated as risk factors contributing to the facet non-union at each segmental fused level. Facet fusion rate was 85.9% (67/78 facets) and the incidence of loosening was 4.9% (6/122 screws, 4 patients). Insufficient facet decortication with bone packing is a significant risk factor of facet non-union (p <0.05, odds ratio: 26.5). All six loosened screws were associated with bony non-union of the facet and were located in the uppermost or lowermost vertebrae. Comparing loosened screws and stable screws, the average maximal insertional screw torque (MIT) was 9.8 cNm and 39.5 cNm, respectively (p <0.05). Additionally, the length of the stable screws was significantly longer versus the loosened screws (p <0.05). Lower MIT and shorter screw length located near the ends of the lateral mass may predict loosening, which can lead to facet non-union. Sufficient facet decortication with bone packing is one of the important factors contributing to the facet fusion.     

Conical Primary Cementless Stem in Revision Hip Arthroplasty: 94 Consecutive Implantations at a Mean Follow-Up of 12.7 years

BackgroundRevision of a failed total hip arthroplasty (THA) poses technical challenges. The use of primary stems for revision can be advantageous for maintaining bone stock and reducing complications: small case series have reported promising results in the short-term to mid-term follow-up. The aim of this study was to evaluate the long-term clinical and functional results and survivorship of a consecutive series of THA femoral component revisions using a conical primary cementless stem (PCS).MethodsNinety-four stem revisions with a preoperative Paprosky I or II defect were analyzed at an average follow-up of 12.7 ± 5.4 years. Aseptic loosening was the reason for revision in 92.5% of cases. Twenty patients were lost to follow-up. Two subgroups were created: Group 1 (n = 59) underwent isolated stem revision; Group 2 (n = 15) underwent complete THA revision. All were evaluated preoperatively and postoperatively based on the Harris Hip Score (HHS), the Western Ontario and McMaster Universities Index (WOMAC) score, and the visual analog scale for pain (VAS). Residual trochanteric pain and length discrepancies were recorded. Radiographic evaluation included signs of osteolysis, subsidence, loosening, and heterotopic ossification.ResultsPCS survivorship was 100% at 5 years and 95.9% at 10 years. Overall, significant postoperative improvements (P < .01) were observed on the HHS (44.3 vs 86.9), WOMAC (42.8 vs 82.8), and VAS (7.0 vs 3.0). Postoperative scores on all scales were higher for Group 1 (P < .01). Three patients (4.1%) underwent further stem revision. Demarcation lines (1 mm) were found in 12 (16.2%) patients and significant heterotopic ossifications in 22 (29.7%).ConclusionThe use of PCS for stem revision in failed THA with a limited femoral bone defect is a reliable option for both isolated stem revision and concomitant cup revision in well-selected patients.     

Survivorship and Patient-Reported Outcomes of an Uncemented Vitamin E–Infused Monoblock Acetabular Cup: A Multicenter Prospective Cohort Study

BackgroundAddition of vitamin E to polyethylene is theorized to reduce the potential for oxidative wear in acetabular components. This paper presents a multicenter prospective cohort study that reports on outcomes from use of a Vitamin E–infused highly cross-linked polyethylene acetabular cup.MethodsPatients were recruited across nine medical institutions. Clinical outcome measures recorded were the Harris Hip Score, visual analogue score for pain and satisfaction. Evidence of implant loosening or osteolysis was collected radiologically. Cup survival and reasons for revision in relevant cases were also recorded. Data collection was undertaken preoperatively, at 6-12 weeks, 6 months, 1 year, 2 years, and 5 years. A total of 675 patients were recruited, with 450 cases available at final review. Data regarding cup survival was available to 8 years and 9 months postoperatively.ResultsImprovements in both the Harris Hip Score and visual analogue score for pain and satisfaction were recorded at all time points, with these being maintained through the length of follow-up. In total, 89% of cups were implanted within the Lewinnek safe zone. A lucent line was identified in one case, with no evidence of acetabular osteolysis observed throughout the follow-up period. Cup survival was 98.9% at 8 years and 9 months. No revisions for aseptic loosening were observed.ConclusionsThe use of a vitamin E–infused polyethylene acetabular cup demonstrates reassuring patient-reported outcomes, radiological measures, and cup survival at medium to long-term follow-up.     

A Prophylactic Tibial Stem Reduces Rates of Early Aseptic Loosening in Patients with Severe Preoperative Varus Deformity in Primary Total Knee Arthroplasty

BackgroundPatients with a preoperative varus deformity >8 degrees are at increased risk of aseptic loosening after total knee arthroplasty. This study analyzes the effect of a tibial stem on the rate of aseptic loosening in patients with a severe preoperative varus deformity.MethodsPatients with a preoperative varus deformity of >8 degrees and 2-year minimum follow-up with a stemmed tibial component (n = 67) were matched 1:2 to patients with a similar preoperative varus deformity with a standard tibial component (n = 134). Radiolucent lines were measured on the tibia at 6 weeks, 1 year, and 2 years postoperatively using the Knee Society Radiographic Evaluation System. Failure was defined as revision due to aseptic loosening of the tibial component. Outcomes were evaluated using Student’s t-tests and log-rank tests.ResultsPatients with tibial stems had greater preoperative deformity (12.9 vs 11.3 degrees, P = .004). There was no difference in postoperative alignment (1.7 vs 2.1 degrees varus, P = .25) or tibial component angle (1.8 vs 2.1 degrees varus, P = .33). Patients with stems were more likely to have more constraint (44.8% vs 1.5%, P < .001). Progression of radiolucent lines >2 mm was observed in 17.6% (23/134) vs 5.97% (4/67) of patients in the stem group (P = .03). Rates of aseptic loosening were lower in the stem group (0% vs 5.15%, P = .05).ConclusionDespite worse preoperative deformity and higher utilization of constraint, tibial stem use in patients with severe preoperative varus deformity resulted in lower rates of aseptic loosening. Prophylactic use of stems in these patients may help increase implant survival.     

Utility and Prognostic Ability of a Diagnostic Injection Before Revision Total Knee Arthroplasty

BackgroundDiagnostic injections are commonly utilized in the workup of painful total knee arthroplasties (TKA), particularly when the diagnosis remains unclear. However, current literature provides limited evidence regarding the utility and prognostic capability of anesthetic injections in this scenario. This study sought to establish the role of diagnostic injections in predicting successful revision TKA.MethodsA retrospective review was conducted on 144 consecutive aseptic revision TKAs receiving diagnostic anesthetic injections. Instability (57.6%) and aseptic loosening (33.3%) comprised most revision etiologies. Patient-reported percentage pain relief after the injection was statistically correlated with KOOS JR, Knee Society Score, UCLA Activity Level, and satisfaction scores.ResultsAbout 74.3% (107/144) of revision TKAs reported >50% pain relief after injection. There were no differences in pain relief based on revision indication (P = .841). Improvement from preoperative activity level was greater in the >50% pain relief group (P = .024). Four-month patient satisfaction did not differ between patients who reported >50% and ≤50% pain relief (67% vs. 66%, P = .130). About 64% of patients who reported >50% pain relief were satisfied at minimum 1-year follow-up, compared with only 47% of those who reported ≤50% pain relief after diagnostic injection (P < .001).ConclusionStudy results show that patients reporting >50% pain relief after diagnostic injection have improvements in activity level and maintain greater satisfaction at minimum 1-year than those reporting ≤50% pain relief. Expectations for improvement after revision TKA should be tempered if diagnostic anesthetic injection yields minimal subjective pain relief.