Techniques to improve the shear strength of impacted bone graft: the effect of particle size and washing of the graft

BACKGROUND: When fresh morselized graft is compacted, as in impaction bone-grafting for revision hip surgery, fat and marrow fluid is either exuded or trapped in the voids between particles. We hypothesized that the presence of incompressible fluid damps and resists compressive forces during impaction and prevents the graft particles from moving into a closer formation, thus reducing the graft strength. In addition, viscous fluid such as fat may act as an interparticle lubricant, thus reducing the interlocking of the particles. METHODS: We performed mechanical shear testing in the laboratory with use of fresh-frozen human femoral-head allografts that had been passed through different orthopaedic bone mills to produce graft of differing particle-size distributions (grading). RESULTS: After compaction of fresh graft, fat and marrow fluid continued to escape on application of normal loads. Washed graft, however, had little lubricating fluid and better contact between the particles, increasing the shear resistance. On mechanical testing, washed graft was significantly (p < 0.001) more resistant to shearing forces than fresh graft was. This feature was consistent for different bone mills that produced graft of different particle-size distributions and shear strengths. CONCLUSIONS: Removal of fat and marrow fluid from milled human allograft by washing the graft allows the production of stronger compacted graft that is more resistant to shear, which is the usual mode of failure. Further research into the optimum grading of particle sizes from bone mills is required.     

Percentage of graft viability versus injected volume in adipose autotransplants

An adipose tissue graft's ability to obtain nutrition through plasmatic imbibition occurs approximately 1.5 mm from the vascularized edge. This and the observation that only 40% of this peripheral margin is viable led the authors to create spherical and cylindroid models to correlate the volume and the percentage of graft viability to the initial injected volume in adipose autotransplants. The authors concluded that the percentage of graft viability depends on the thickness and the geometrical shape and is inversely proportional to the graft diameter if grafts with a diameter greater than 3 mm are considered.     

Study of the histologic alterations and viability of the adipose graft in humans

The authors describe a series of sections of adipose autografts in humans, focusing on the histological viability and the alterations observed in a postgraft followup. Five female patients aged 29 to 43 years were subjected to seven grafting sessions prior to a classic abdominoplasty. The autologous adipose tissue was grafted in the infraumbilical region. The grafting intervals were 60, 30, 21, 15, 8, 5, and 2 days before the surgical procedure. The grafted tissue of all groups was surrounded by a collagen capsule. The viable tissue was observed in the peripheral zone approximately 1.5 ± 0.5 mm from the edge of the graft. A loss of approximately 60% of the grafted tissue was still noticed in this viable zone.     

离心对脂肪颗粒活性影响的研究

目的:明确离心对脂肪颗粒活性的影响,为脂肪移植术中纯化脂肪颗粒时是否采用离心以及选择最佳离心速率提供参考。方法:将脂肪颗粒经不同高速率(1　000、2　000、3　000、4　000rpm)及不同低速率(600、800、1　000rpm)离心后,即刻进行葡萄糖转移实验——即将每组脂肪颗粒样本分为 12 个标本,每个标本 5ml,置入 10ml 含糖 DMEM 中孵育,1h 后检测其葡萄糖转移量,此值代表各标本的活性,方差分析检验比较各组样本葡萄糖转移量即活性大小。将经不同速率 (600、1　000、2　000、3　000rpm)离心的脂肪颗粒放置 4.5h 后再进行葡萄糖转移实验(方法同上),方差分析检验比较各组脂肪颗粒葡萄糖转移量即活性变化。经静置、3　000rpm 离心的两组脂肪颗粒分别植入 6 只裸鼠背部皮下,每只注射 4 点,每点 0.2ml。15 周后取出移植物,测量残留体积、重量并比较之。每组取两个移植物送病理学检查。结果:脂肪颗粒经不同高、低离心速率处理后的即刻活性随离心速率的增大而显著降低(P<0.05),而经不同高、低离心速率处理再放置 4.5h 后,各离心组样本活性变得差异不显著(P>0.05),但仍较对照组(静置组)明显降低(P<0.05)。静置悬浮和 3　000rpm 离心的两组样本植入裸鼠背部皮下 15 周后,残留体积、重量差异不显著(P>0.05),　组织病理     

Reverse-flow vascularized fibular graft: a new method

The reverse-flow island flap is a relatively recent concept. We have applied this concept to the vascularized bone graft. We report a new method of the reverse-flow vascularized fibular graft for two patients with a pseudarthrosis and massive bone defect of the tibia. The peroneal artery and venae comitantes were severed proximally and elevated with the fibula while maintaining distal vascular continuity. The reverse-flow vascularized fibula was grafted to the posterior aspect of the bone defect of the tibia. Bony union was obtained in both cases. The reverse-flow vascularized fibular graft has many advantages compared with free vascularized fibular graft.     

Telescoping vascularized fibular graft: a new method

The authors describe a case of congenital pseudarthrosis of the tibia treated with a telescoping vascularized fibular graft. The advantages of this new method are that bone union and leg-length discrepancy may be corrected simultaneously.     

Exsanguinous metabolic support perfusion--a new strategy to improve graft function after kidney transplantation

BACKGROUND: The compounding damage of warm ischemia (WI) followed by cold preservation is a major barrier in renal transplantation. Although the relative effect of WI is not yet well understood, therapeutic strategies have mostly focused on minimizing the pathology seen upon reperfusion from the cold. Our study was designed to examine the effect of restoration of renal metabolism by warm perfusion on graft survival and to investigate the compounding damage of WI. METHODS: Using a known critical canine autotransplantation model (1), kidneys were exposed to 30 min WI followed by 24 hr cold storage in Viaspan. They were then either reimplanted directly or first transitioned to 3 hr of warm perfusion with an acellular perfusate before reimplantation. Contralateral kidneys were subjected to 0, 30, or 60 min WI; 24 hr cold storage, and 3 hr warm perfusion. RESULTS: Transplanted kidneys that were warm perfused before reimplantation had both lower 24 hr posttransplant serum creatinine (median of 3.2 vs. 4.1 mg/dl) and lower peak serum creatinine (median of 4.95 vs. 7.1 mg/dl). Survival rate for warm perfused kidneys was 90% (9/10) vs. 73% (8/11). In the contralateral kidneys, metabolism was affected by the compounding damage of WI. Renal oxygen and glucose consumption diminished significantly, whereas vascular resistance and lactate dehydrogenase-release rose significantly with increasing WI. CONCLUSIONS: The results demonstrate a reduction of reperfusion damage by an acellular ex vivo restoration of renal metabolism. Furthermore, data from the contralateral kidneys substantiates the relative role of WI on metabolism in renal transplantation.     

A new training method to improve deep microsurgical skills using a mannequin head

Neurosurgeons need fine and special microsurgical techniques, such as the ability to suture deep microvasculature. Intensive training is required to perform microsurgery, especially in deep microvascular anastomosis. There have been many previous reports of training methods for typical microsurgical techniques, including suturing of surgical gloves, Silastic tubes, living animals, and chicken wing arteries. However, there have been no reports of training methods to improve deep microsurgical skills under the various hand positions specific to neurosurgical operation. Here, we report a new training method using a mannequin head, water balloons, and clay to mimic actual deep microsurgery in the brain. This method allows trainees to experience microsurgery under various hand positions to approach the affected areas located at various depths in the brain from various angles.     

Effect of aprotinin to improve myocardial viability in myocardial preservation followed by reperfusion.

Isolated canine hearts were preserved at 4 degrees C with multi-dose cardioplegic solution every hour for 6 hours. Reperfusion was observed for 2 hours under cross-circulation without cardiotonic drugs. The aprotinin group (n = 8), which received cardioplegic solution with added aprotinin (150 KIU/mL), was compared with the control group (n = 6). The increase in tissue adenosine triphosphate and total adenine nucleotide content during reperfusion was significant in the aprotinin group; there was no change in the control group, and the levels at the end of reperfusion tended to be higher in the aprotinin group than in the control group. Tissue adenosine diphosphate levels remained unchanged in both groups. Tissue adenosine monophosphate levels declined during reperfusion in both groups and were slightly lower in the control group. Tissue levels of cyclic adenosine monophosphate remained unchanged in the aprotinin group whereas they increased during ischemia and declined significantly during reperfusion in the control group. Tissue levels of cyclic guanosine monophosphate declined during reperfusion in both groups without difference. Creatine phosphate levels recovered in both groups without difference. Serum cyclic guanosine monophosphate concentration tended to be lower in the aprotinin group than in the control group. Serum creatine kinase-MB level increased slightly during reperfusion in both groups without difference. N-acetyl-beta-D-glucosaminidase levels were significantly suppressed during reperfusion in the aprotinin group as compared with the control group. These results suggest that aprotinin is effective in preserving adenine nucleotide and adenosine triphosphate levels and in stabilizing tissue cyclic adenosine monophosphate levels in prolonged hypothermic cardioplegic preservation followed by reperfusion.     

A new method of external cardiac massage to improve diastolic augmentation and prolong survival time.

Experiments were performed on 50 dogs to determine the reason for unsatisfactory survival rates following closed-chest cardiac massage and to help develop new means for increasing survival following acute myocardial infarction and other causes of cardiac arrest. A new technique, named the countermassage method, was subsequently developed. Coronary and carotid flows after use of countermassage following cardiac arrest were increased 1.4 and 2 times, respectively, in contrast to flows obtained during manual closed-chest cardiac massage. These increases brought flows up to normal levels. We also tried to determine whether survival could be extended by this method to facilitate clinical treatment such as defibrillation or placing a temporary pacemaker catheter under fluoroscopic control, which are hard to accomplish during the brief time permitted by conventional closed-chest cardiac massage.     

A multidisciplinary process to improve the efficiency of cardiac operating rooms

OBJECTIVE: To alter the approach to cardiac operating room services in an attempt to remain competitive in a cost-driven market. DESIGN: Study of processes and strategies for tracking and decreasing the times required for the multiple components of the operating room period. SETTING: Cardiac operating rooms in a tertiary care, university-affiliated hospital. PARTICIPANTS: All patients undergoing primary coronary artery bypass grafting during December 1996 (baseline) and the following year (1997). INTERVENTIONS: After participation in cost-containment meetings, site visits, and development of a working group, data collection was begun detailing the times of the various components of the operating room period. Changes of process were made to reduce operating room times. Most of these changes involved multitasking care: multiple people performing various tasks at the same time. All measured operating room intervals were decreased. There was no difference in morbidity and mortality over this time period. CONCLUSION: Development of a working group, with support from the hospital administration, can significantly decrease the time of tasks in a cardiac surgery operating room without adversely affecting morbidity and mortality.