Improved healing of ligament to bone with point fixation in rabbits

Background?Secure healing of soft tissue to bone is a prerequisite for many orthopedic operations. This healing can be achieved either by pressing the tissue against the bone (press fixation) or by suturing the soft tissue to the bone (point fixation).

Experiments and findings?We tested the hypothesis that point fixation of soft tissue to bone results in better mechanical properties than press fixation. 10 skeletally mature New Zealand White rabbits were operated on bilaterally at the knees. The medial collateral ligaments were fixated to the bone just above the original insertion on the tibia. Two types of plates were used for this purpose, one with flat undersurface (left knee) and the other one with a pegged undersurface (right knee). The pegged plate was thought to mimic fixation achieved with suture anchors. After 4 weeks, mechanical testing revealed an almost doubled force at failure, stiffness and energy uptake in the knees operated with the pegged plates.

Interpretation?Suture anchors or devices with a pegged undersurface are better for soft tissue fixation to bone than devices with a flat surface, such as screws with washers or staples.     

Improved healing of experimental long bone fractures in rabbits by delayed internal fixation.

Experiments in rabbits were conducted to test the clinical propositions that a) the risk of nonunion in certain long bone fractures can be sharply reduced by open reduction and internal fixation, and b) that there is an optimum critical period following trauma in which this procedure should be carried out to facilitate healing. Bilateral standard open fractures of rabbit radii were internally fixed by intramedullary K-wires immediately or at 5, 10, and 17 days after trauma. These bones were subjected to stress and histometric analyses at 4-56 days after the initial fractures. The observations suggested that the pace of fracture healing could be optimized by time-delay surgery. The most exuberant and strongest calluses developed when the bones were fixed 10 days after fracture, and the rate of healing was improved. Delay times of 5 or 17 days did not provide better healing than that achieved by an immediate operation. Callus quality, in terms of the proportion of fiber bone, lamellar bone, and cartilage, was similar in all groups. The tensile strengths of the bones during callus formation were highly correlated with the ratio of callus/cortical bone areas (p less than 0.01).     

Impaired bone healing in rabbits with steroid-induced osteonecrosis

Corticosteroids are prescribed for the treatment of many medical conditions and their adverse effects on bone, including steroid-associated osteoporosis and osteonecrosis, are well documented. Core decompression is performed to treat osteonecrosis, but the results are variable. As steroids may affect bone turnover, this study was designed to investigate bone healing within a bone tunnel after core decompression in an experimental model of steroid-associated osteonecrosis. A total of five 28-week-old New Zealand rabbits were used to establish a model of steroid-induced osteonecrosis and another five rabbits served as controls. Two weeks after the induction of osteonecrosis, core decompression was performed by creating a bone tunnel 3 mm in diameter in both distal femora of each rabbit in both the experimental osteonecrosis and control groups. An in vivo micro-CT scanner was used to monitor healing within the bone tunnel at four, eight and 12 weeks postoperatively. At week 12, the animals were killed for histological and biomechanical analysis. In the osteonecrosis group all measurements of bone healing and maturation were lower compared with the control group. Impaired osteogenesis and remodelling within the bone tunnel was demonstrated in the steroid-induced osteonecrosis, accompanied by inferior mechanical properties of the bone. We have confirmed impaired bone healing in a model of bone defects in rabbits with pulsed administration of corticosteroids. This finding may be important in the development of strategies for treatment to improve the prognosis of fracture healing or the repair of bone defects in patients receiving steroid treatment.     

接骨板内固定与骨折愈合

骨折愈合是一个极其复杂的生物学过程,在影响骨折愈合多种因素中,以骨折局部力学环境和血液供应最为重要。接骨板内固定是治疗四肢长骨骨折的重要手段之一,但接骨板的置入势必会引起骨折环境中的生物学反应（如应力和血供）,扰乱骨折愈合所必需的生物学环境。因此,接骨板对骨折局部血供和力学环境的影响成为衡量接骨板质量及设计是否合理等的重要参数。如何既保证骨折段稳定,又能使骨折端承受一定的应力刺激,同时,又尽可能减少接骨板置入对骨折局部血供的损害,一直是人们针对接骨板内固定研究和探索的热点。多年来,学者们围绕上述…     

Electrical stimulation of ligament healing. An experimental study of the patellar ligament of rabbits

To examine the effects of direct electric current on ligament healing in rabbits, a full-thickness defect of the patellar ligament was electrically stimulated for time periods of up to seven weeks. The rabbits were randomly assigned to biomechanical and biochemical studies, and healing was evaluated by these parameters. Electrical stimulation was shown to restore tensile stiffness in a short period of time and to decrease the relative proportion of Type III collagen more rapidly than in the control group. However, electrical stimulation did not change the collagen content of newly formed tissue. Electricity enhances the repair process of the ligament by changing the ratio of collagen types.     

Intramedullary fixation of cortical bone osteotomies with self-reinforced polylactic rods in rabbits

Summary Osteotomies of the femoral shaft in rabbits were fixed with intramedullary rods made of poly-L-lactic acid (SR-PLLA) and poly-DL/L-lactic acid (SR-PDLLA/PLLA). Follow up was from one week to 2 years. In the PLLA group, in 37 out of 40 osteotomies the fixation was firm and the bone was united. In the PDLLA/PLLA group, the fixation was firm in 30 out of 45, but in 13 of these angular deformity of more than 10° had occurred. The fixation had failed in 15. No inflammatory or foreign body reaction was seen in either group. This study demonstrates that SR-PLLA rods are suitable fixation for cortical osteotomies in rabbits.

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Résumé Les auteurs ont réalisé des ostéotomies de la diaphyse fémorale chez le lapin, qu'ils ont fixées par des tiges intramédullaires faites d'acide poly-L-lactique (APLL) et d'acide poly-DL-L-lactique (APDLL). Les animaux ont été suivis de 1 mois à 2 ans. Dans le groupe APLL, la fixation a été solide et la consolidation obtenue dans 37 des 40 ostéotomies. Dans le groupe APDLL, la fixation a été solide 30 fois sur 45, mais dans 13 de ces cas il s'est produit une angulation de plus de 10°. Il y a eu 15 échecs de fixation. Dans aucun des deux groupes il n'a été observé de phénomènes inflammatoires ni de réactions à corps étranger. Cette étude montre que les tiges d'APLL permettent une fixation efficace de l'ostéotomie corticale chez le lapin.

     

Tripled semitendinosus-cancellous bone anterior cruciate ligament reconstruction with bioscrew fixation.

A prospective evaluation of a tripled semitendinosus-autologous cancellous bone plug ACL reconstruction, secured with bioabsorbable interference screws (Bioscrew; Linvatec, Largo, FL) made of polyL-lactic acid, was undertaken from July 1994 through August 1995. A total of 21 patients with 22 anterior cruciate ligament (ACL) reconstructions were followed-up an average 29 months (range, 20 to 45). The average age was 38 years (range, 24 to 48 years). Tegner and Lysholm scores were 2.1 and 46, respectively, preoperatively and increased postoperatively to 4.4 and 90. KT tests at 24 months follow-up showed an average 20-lb laxity of 1.4 mm, an average 30-lb laxity of 2.1 mm, and an average KT maximum manual side-to-side difference of 2.9 mm. A pivot shift was absent in all but two patients at final follow-up. Full extension was rapidly achieved in all cases and flexion averaged 135 degrees at follow-up. No problems with the poly L-lactic acid interference screws occurred. These data support the effectiveness of Bioscrew fixation of the tripled semitendinosus-cancellous bone graft ACL reconstruction, which achieves both anatomic graft position and anatomic graft fixation.     

Biomechanical comparison of quadriceps tendon fixation with patellar tendon bone plug interference fixation in cruciate ligament reconstruction

Purpose: The purpose of this study was to use current fixation techniques and compare the stiffness and ultimate tensile failure of the tendinous end of the quadriceps tendon (QT) with the bone plug end of the bone–patellar tendon–bone (BPTB) graft using current techniques of fixation. Type of Study: Randomized trial of elderly cadaver knees. Materials and Methods: Tibial and femoral biodegradable interference fixation and femoral EndoButton (Smith & Nephew, Acufex, Mansfield, MA) fixation in bone tunnels with the QT and the BPTB graft were compared by using 10 pairs of elderly cadavers and biomechanical testing. Two groups, fixation at time zero (simulating fixation in the operating room) and testing after 1,000 loading cycles (simulating patient rehabilitation exercises), were used. Results: At time zero fixation, stiffness of the soft tissue QT tibial tunnel interference fixation was 59% less stiff than the stiffness of the interference fixation of a BPTB plug in a femoral tunnel (P = .11). The EndoButton femoral fixation resulted in a decrease in stiffness at time zero compared with femoral tunnel interference fixation of the soft tissue QT (P = .03). All groups improved stiffness with cycling the construct to 1,000 cycles. Conclusions: Placement of the QT tendinous end of the graft in the femoral bone tunnel when using a interference fixation will approximate the stiffness of a bone plug in the tibial bone tunnel with interference fixation. The EndoButton fixation is not as stiff as either of the femoral interference fixation options. The addition of more than 20 loading cycles could remove laxity from the graft fixation–graft cruciate ligament complex and improve its stiffness.     

Effect of compression on fracture healing. Plate fixation studied in rabbits

Bilateral osteotomies in rabbit tibiae were secured with six-hole rigid plates, using axial compression on the right and no compression on the left side. Histological, histomorphometric and torsiometric analysis was performed up to 24 weeks postoperatively. Histological analysis showed end-to-end primary bone healing regardless of treatment. The fracture gaps tended to be smaller in the compression osteotomies, but union was achieved within the same time on both sides, and at 6 weeks torsiometric analysis of the paired specimens revealed similar mechanical properties. By the time the fracture had united both groups of bones showed similar degrees of subendosteal resorption. As a result of this porotic transformation the strength of the cortical bone was slightly impaired from 6 weeks onward, whether or not compression had been applied. The results suggest that axial compression does not augment fracture healing of plated cortical bone.     

Medial collateral knee ligament healing: Combined medial collateral and anterior cruciate ligament injuries studied in rabbits

We examined the histological appearance and biochemical properties of the healing medial collateral ligament (MCL) of a rabbit knee after combined MCL and anterior cruciate ligament (ACL) injury treated with ACL reconstruction and with or without MCL repair. By so doing, we hoped to understand better our previous biomechanical observations (Ohno et al. 1995) and possibly learn where to focus future investigation into improving the quality of the healing MCL.

Ligaments were examined at 6 and 12 weeks of healing. We found healing of all ligaments with hypercellularity and fibroblast elongation along the axis of loading, as expected. Unexpected, however, was the finding of multiple osteophytes in both the repaired and nonrepaired specimens at the medial borders of the joint and at the MCL insertions. These were felt to affect possibly the biomechanics of the MCL by causing stress risers at the point where they undermine the ligament. Biochemically, we demonstrated a correlation between collagen content and hydroxypyridinium crosslinks and modulus of elasticity. While this implies that the modulus is dependent on collagen content and hydroxypyridinium crosslink density, modulus is also probably dependent on other factors such as collagen organization, type and internal structure. Overall, the detailed characterization and correlation between the histological, biochemical, and biomechanical properties of the healing MCL in the severe knee injury model provide insight into the functional behavior of the healing MCL.     

参考骨质移行转换点改良椎弓根螺钉置入法行腰椎内固定术

目的 探讨采用以骨质移行转换点为参考标志的改良椎弓根螺钉徒手置钉法行腰椎内固定术的疗效。方法 2017年1月—2018年3月,采用内固定术治疗腰椎疾病患者60例,采用随机数字表法分为2组,每组30例,改良组采用骨质移行转换点为参考标志徒手置钉,对照组采用传统方法徒手置钉。术后行CT多平面重建（MPR）对螺钉进行椎弓根层面扫描,采用Neo分级评估螺钉位置。结果 所有手术顺利完成。改良组共置入椎弓根螺钉154枚,置钉准确率为96.10%;对照组共置入椎弓根螺钉150枚,置钉准确率为88.67%;2组置钉准确率差异有统计学意义（P<0.05）。结论 以骨质移行转换点为参考标志的改良椎弓根螺钉徒手置钉法相较于传统徒手置钉法有更高的置钉准确率,可一定程度上实现椎弓根置钉的个体化,值得临床推广。     

Graft healing in the bone tunnel in anterior cruciate ligament reconstruction

The histologic sequence in the bone tunnel after anterior cruciate ligament reconstruction using the bone-patellar tendon-bone graft was investigated in this study. Eighteen adult mongrel dogs were used. After excision of the anterior cruciate ligament, the graft was routed through the bone tunnels and fixed with interference fit screws. After the dogs were sacrificed at intervals, the bone blocks containing the bone tunnels were isolated and processed for histologic examination. At the bone-bone interface, incorporation of the bone plug at each end of the graft was completed at 12 weeks. The structure of the tendon insertion of the grafted patellar tendon, consisting of four distinct zones, was observed without apparent necrotic and degenerative change for as long as 12 weeks. Between the tendon and the bone tunnel, a layer of hypercellular fibrous tissue gradually became mature with time. Thus, it appeared the morphologic characteristics and location of the reestablished attachment of the bone-patellar tendon-bone graft were more similar to those of the native anterior cruciate ligament compared with the graft to bone healing in the hamstring tendon graft.     

Biocompatibility,bone healing,and safety evaluation in rabbits with an IlluminOss bone stabilization system

Bone healing, biocompatibility, and safety employing the IlluminOss System (IS), comprised of an inflatable balloon filled with photopolymerizable liquid monomer, was evaluated in New Zealand white rabbits. Successful bone healing and callus remodeling over 6 months was demonstrated radiologically and histologically with IS implants in fenestrated femoral cortices. Biocompatibility was demonstrated with IS implants in brushed, flushed femoral intramedullary spaces, eliciting no adverse, local, or systemic responses and with similar biocompatibility to K‐wires in contralateral femurs up to 1 year post‐implant. Lastly simulated clinical failures demonstrated the safety of IS implants up to 1 year in the presence of liquid or polymerized polymer within the intramedullary space. Polymerized material displayed cortical bone and vasculature effects comparable to mechanical disruption of the endosteum. In the clinically unlikely scenario with no remediation or polymerization, a high dose monomer injection resulted in marked necrosis of cortical bone, as well as associated vasculature, endosteum, and bone marrow. Overall, when polymerized and hardened within bone intramedullary spaces, this light curable monomer system may provide a safe and effective method for fracture stabilization. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2181–2190, 2017.

     

Local application of growth-factor IGF-1 to healing bone. Experiments with a titanium chamber in rabbits

In order to study the effects of bone healing, insulin-like growth factor 1 (IGF-1) was continuously applied with a minipump to a healing bone callus located inside a titanium chamber in a rabbit tibia. After 2 weeks, 99mTc-MDP uptake and calcium content were measured. IGF-1 decreased 99mTc-MDP uptake, and thus the mineral turnover rate, but the amount of bone mineral was unchanged. Probably the normal endogenous production of IGF-1 is already optimal for healing in this model.     

Effects of a bioscaffold on collagen fibrillogenesis in healing medial collateral ligament in rabbits

Bioscaffolds have been successfully used to improve the healing of ligaments and tendons. In a rabbit model, the application of porcine small intestine submucosa (SIS) to the healing medial collateral ligament (MCL) resulted in improved mechanical properties with the formation of larger collagen fibrils. Thus, the objective of the study was to find out whether the SIS bioscaffold could improve the gene expressions of fibrillogenesis‐related molecules, specifically, collagen types I, III, V, and small leucine‐rich proteoglycans including decorin, biglycan, lumican, and fibromodulin, as well as collagen fibril morphology and organization, in the healing rabbit MCL at an early time point (6 weeks postinjury). Twenty skeletally mature rabbits were equally divided into two groups. In the SIS‐treated group, a 6‐mm gap was surgically created and a layer of SIS was sutured to cover the gap, whereas the gap was left open in the nontreated group. At 6 weeks postinjury, Masson's trichrome staining showed that the SIS‐treated group had more regularly aligned collagen fibers and cells. Transmission electron microscopy revealed that the SIS‐treated group had larger collagen fibrils with a diameter distribution from 24 to 120 nm, whereas the nontreated group had only small collagen fibrils (ranging from 26 to 87 nm, p < 0.05). Finally, the quantitative real‐time PCR showed that the mRNAs of collagen type V, decorin, biglycan, and lumican in the SIS‐treated group were 41, 58, 51, and 43% lower than those in the nontreated group, respectively (p < 0.05). Such significant reduction in the gene expressions are closely related to the improved morphological characteristics, which are known to be coupled with better mechanical properties, as previously reported in longer term studies. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:1098–1104, 2008     

生物骨传导性骨水泥促进前交叉韧带重建术腱骨愈合的研究进展(英文)

近10年来,应用软组织移植物行前交叉韧带重建术越来越普遍。手术的远期疗效主要取决于肌腱移植物能否在骨隧道内达到坚强的腱-骨愈合。但是,目前面临的问题是肌腱移植物在骨隧道内获得腱-骨愈合所需要的时间相当长。研究发现,在腱-骨界面局部应用生物骨传导性的骨水泥能有效地促进肌腱移植物的骨愈合。这类骨水泥主要是磷酸钙。本文就生物骨传导性骨水泥促进前交叉韧带重建术腱-骨愈合的研究进展作一综述。     

骨形态发生蛋白-2在兔骨折愈合过程中的作用

[目的]利用兔骨折动物模型探讨骨形态发生蛋白-2(BMP-2)对骨折愈合的影响以及BMP-2、转化生长因子-β1(TGF-β1)、血管内皮生长因子(VEGF)三者在骨折愈合中的相互关系及机制。[方法]30只新西兰大白兔制作右侧桡骨骨折模型,随机将其分为两组,每组15只。实验组骨折局部注射BMP-2,对照组注射生理盐水。采用X线片、组织形态学检查观察两组骨折愈合的差异,免疫组化染色观察骨折愈合局部BMP-2、TGF-β1及VEGF蛋白的表达变化。[结果]注射BMP-2的实验组兔的骨痂生长、骨质重建、髓腔再通均早于对照组;两组间影像学评分差异有统计学意义(P0.05)。骨折造模后1、2周BMP-2、TGF-β1、VEGF免疫组化染色的积分吸光度值实验组高于对照组,两组间差异有统计学意义(P0.05),3周时BMP-2、TGF-β1及VEGF免疫组化染色积分吸光度值实验组仍明显高于对照组(P0.05),而5、7周时,两组间免疫组化染色积分吸光度值无明显差异(P0.05)。[结论]BMP-2通过促进TGF-β1及VEGF的表达,可促进血管的再生,提高成骨细胞、破骨细胞的数量及活性,促进骨折愈合。     

Modulation of fixation stiffness from flexible to stiff in a rat model of bone healing

Background and purpose — Constant fixator stiffness for the duration of healing may not provide suitable mechanical conditions for all stages of bone repair. We therefore investigated the influence of stiffening fixation on callus stiffness and morphology in a rat diaphyseal osteotomy model to determine whether healing time was shortened and callus stiffness increased through modulation of fixation from flexible to stiff.

Material and methods — An external unilateral fixator was applied to the osteotomized femur and stiffened by decreasing the offset of the inner fixator bar at 3, 7, 14, and 21 days after operation. After 5 weeks, the rats were killed and healing was evaluated with mechanical, histological, and microcomputed tomography methods. Constant fixation stiffness control groups with either stiff or flexible fixation were included for comparison.

Results — The callus stiffness of the stiff group and all 4 experimental groups was greater than in the flexible group. The callus of the flexible group was larger but contained a higher proportion of unmineralized tissue and cartilage. The stiff and modulated groups (3, 7, 14, and 21 days) all showed bony bridging at 5 weeks, as well as signs of callus remodeling. Stiffening fixation at 7 and 14 days after osteotomy produced the highest degree of callus bridging. Bone mineral density in the fracture gap was highest in animals in which the fixation was stiffened after 14 days.

Interpretation — The predicted benefit of a large robust callus formed through early flexible fixation could not be shown, but the benefits of stabilizing a flexible construct to achieve timely healing were demonstrated at all time points.     

Biological fixation of the graft within bone after anterior cruciate ligament reconstruction in rabbits: effects of the duration of postoperative immobilization

To investigate the effects of the duration of postoperative immobilization on the biological fixation of the graft within bone after anterior cruciate ligament (ACL) reconstruction, we performed ACL reconstruction in 27 rabbits, which were divided into five groups — no immobilization and 1-, 2-, 4-, and 6-week immobilization. All animals were killed 6 weeks postoperatively, and the graft-bone tunnel interface was examined biomechanically and histologically. In the groups with immobilization, in tensile failure tests, most specimens failed through the intraarticu-lar portion of the grafts. There was no significant difference in the maximum load between these groups. In the no-immobilization group, all specimens failed through pulling of the grafts out of the femoral tunnel, with a lower maximum load than in the other groups. Histologically, new bone formation and occasional collagen fiber continuity were observed at the interface; which consisted of a fibrous tissue. In the no-immobilization group, the graft was partly separated from the fibrous tissue covering the bony wall. It is concluded that no immobilization delays the biological fixation process in the bone tunnel after ACL reconstruction, and that a certain period of immobilization is necessary for the fixation to proceed smoothly. Received for publication on Oct. 26, 1998; accepted on July 9, 1999