Fat embolism and related effects during reamed and unreamed intramedullary nailing in a pig model

Early myocardial damage (EMD) and valvular dysfunction after femur fracture in pigs

Musculoskeletal injuries are the most common reason for surgery in severely injured patients. In addition to direct cardiac damage after physical trauma, there is rising evidence that trauma induces secondary cardiac structural and functional damage. Previous research associates hip fractures with the appearance of coronary heart disease: As 25% of elderly patients developed a major adverse cardiac event after hip fracture. 20 male pigs underwent femur fracture with operative stabilization via nailing (unreamed, reamed, RIA I and a new RIA II; each group n = 5). Blood samples were collected 6 h after trauma and the concentration of troponin I and heart-type fatty acid binding protein (HFABP) as biomarkers for EMD were measured. At baseline and 6 h after trauma, transesophageal ECHO (TOE) was performed; and invasive arterial and left ventricular blood pressure were measured to evaluate the cardiac function after femur fracture. A systemic elevation of troponin I and HFABP indicate an early myocardial damage after femur fracture in pigs. Furthermore, various changes in systolic (ejection fraction and cardiac output) and diastolic (left ventricular end-diastolic pressure, mitral valve deceleration time and E/A ratio) parameters illustrate the functional impairment of the heart. These findings were accompanied by the development of valvular dysfunction (pulmonary and tricuspid valve). To the best of our knowledge, we described for the first time the development of functional impairment of the heart in the context of EMD after long bone fracture in pigs. Next to troponin and HFABP elevation, alterations in the systolic and diastolic function occurred and were accompanied by pulmonary and tricuspid valvular insufficiency. Regarding EMD, none of the fracture stabilization techniques (unreamed nailing, reaming, RIA I and RIA II) was superior.

Reamed Intramedullary Nailing of a Femur Fracture in a Polytraumatized Patient on Extracorporeal Membrane Oxygenation: A Case Report

CASE

We present the case of a young adult with blunt lung trauma and acute respiratory distress syndrome requiring extracorporeal membrane oxygenation (ECMO) after a motor vehicle crash with a concomitant diaphyseal femur fracture who underwent reamed intramedullary nailing (IMN) while on ECMO support.

CONCLUSION

This case is important because it demonstrates that reamed IMN of the femur has been performed safely in a critically ill patient on ECMO.

Healing, nonunion, and re-operation after internal fixation of diaphyseal and distal femoral fractures: a systematic review and meta-analysis

PURPOSE

Nonunion is a highly morbid complication that exacerbates the pain, disability and financial burden of distal and diaphyseal femur fractures. This study examined the modern rates of healing, nonunion, and other complications requiring reoperation of different fixation methods for distal and diaphyseal femur fractures.

METHODS

A systematic review and meta-analysis of all records from PubMed, Embase and the Cochrane Review system was performed. Included studies had >20 acute, non-pathologic distal or diaphyseal femur fractures treated with primary internal fixation. Excluded were studies on abnormal patient/fracture populations, external fixation, or cement/bone graft use.

RESULTS

Thirty-eight studies with 2,829 femoral shaft fractures and 11 studies with 505 distal femur fractures were included. Distal fractures had a lower healing rate (86.6% vs. 93.7%) and a higher re-operation rate (13.4% vs 6.1%) than shaft fractures (p < 0.00001), primarily due to higher rates of mechanical failure (p < 0.00001). Nonunion was the most frequent complication, occurring in 4.7% of distal fractures and 2.8% of shaft fractures. There was no difference between plate and nail fixation of distal fractures in healing, nonunion, or other causes of re-operation. Shaft fractures developed nonunion in 6.6% of unreamed nails and 2.1% of reamed nails (p = 0.002). Nonunion occurred in 2.3% of antegrade nailed fractures and 1.5% of retrograde nailed fractures (p = 0.66).

CONCLUSIONS

Approximately one out of every eight distal fractures and one of every 16 shaft fractures requires re-operation. The most common cause of fixation failure is nonunion. Further research is needed to improve outcomes, particularly in distal femur fractures.

Fat embolism syndrome in a child with dystonia musculorum deformans

A 16-year-old boy with dystonia musculorum deformans underwent an operation for removal of femoral implants and excision of the prominence at the greater trochanter of the left hip. He was found to have fat embolism syndrome at postoperative day 1 as evidenced by confusion, respiratory symptoms, chest radiograph changes, raised erythrocyte sedimentation rate, thrombocytopenia and fat in the urine and sputum.

Use of the reamer-irrigator-aspirator may reduce tumor dissemination during intramedullary fixation of malignancies

Intramedullary nail fixation is the treatment of choice for impending and pathologic fractures secondary to metastatic cancer; however, this procedure has been shown to cause systemic embolization of intramedullary contents. This article reports the use of the reamer-irrigator-aspirator (RIA) (Synthes, Paoli, Pennsylvania) instead of a standard femoral reamer to decrease tumor intravasation during femoral intramedullary nail fixation for impending or pathologic fractures.Twenty-one consecutive patients indicated for fixation of malignant femoral lesions were treated with intramedullary nail placement. The RIA was used for canal preparation, and solid reamings were collected and submitted for analysis by a single pathologist. The volume of each specimen was recorded, and representative samples were examined histologically to determine their percent tumor content. These data were then used to estimate the volume of tumor retrieved by the RIA in each case. The mean volume of reamings collected by the RIA was 75.0 cc per case (range, 23.4-196.0 cc), and the mean tumor content was 24.8% (range, 1.0%-60.0%). The mean estimated volume of tumor retrieved in each case was 16.7 cc (range, 0.35-36.0 cc). In 2 cases, the tip of the RIA dissociated from the device intraoperatively but was retrieved without adverse consequence to the patient. Use of the RIA in cases of femoral intramedullary nail fixation for pathologic lesions or fractures effectively retrieves variable amounts of intramedullary contents, including tumor. By preventing the systemic dissemination of malignant cells, this technique may reduce the risk of distant metastases.

Pulmonary fat embolism after reamed and unreamed nailing of femoral fractures

BACKGROUND

To determine whether reamed or unreamed intramedullary nailing of femoral fractures results in higher incidence of pulmonary fat embolism, three different methods of intramedullary nailing were compared in sheep. To analyze the presence of bone marrow fat embolism in pulmonary arteries, histological evaluation was undertaken using a quantitative computer-assisted measurement system.

METHODS

In this experimental model of 27 female Swiss alpine sheep, an osteotomy of the proximal femur was conducted in each animal. Then, the animals were divided into three groups according to the method of treatment: two different reamed intramedullary nailing techniques and an unreamed nailing technique were used. In the first group "ER" (experimental reamer; n=9), the nail was inserted after reaming with an experimental reamer; in the second group "CR" (conventional reamer; n=7), the intramedullary nail was inserted after reaming with the conventional AO-reamer. In the third group "UN" (unreamed; n=8) unreamed nailing was performed. During the operation procedure intramedullary pressure was measured in the distal fragment. After sacrificing the animals, quantitative histological analyses of bone marrow fat embolism in pulmonary arteries were done using osmium tetroxide fixation and staining of the fat.

RESULTS

The measurement of intramedullary pressure showed significantly lower values for reamed nailing than for the unreamed technique. The quantitative histological evaluation of lung vessels concerning bone marrow fat embolism revealed a statistically significant difference between reamed and unreamed insertion of the nail: 7.77%±6.93 (ER) and 6.66%±5.61 (CR) vs. 16.25%±10.05 (UN) (p<0.05) of the assessed lung vessels were filled with fat emboli. However, no difference was found between the traditional and experimental reamer.

CONCLUSIONS

Intramedullary nailing after reaming is a safe procedure with low systemic embolisation when compared to the unreamed insertion of the nail.

Amplified inflammatory response to sequential hemorrhage, resuscitation, and pulmonary fat embolism: an animal study

BACKGROUND

The objective of this study was to assess the role of pulmonary fat embolism caused by intramedullary pressurization of the femoral canal in the development of acute lung injury in the setting of acute hemorrhagic shock and resuscitation.

METHODS

Thirty New Zealand White rabbits were randomly assigned to one of four groups: (1) nine animals in which hemorrhagic shock was induced by carotid bleeding, resuscitation was performed, and the femoral canal was reamed and pressurized with bone cement to induce fat embolism (hemorrhagic shock and resuscitation/fat embolism [HR/FE] group); (2) six animals in which shock was induced by carotid bleeding, resuscitation was performed, and a sham knee incision was made and closed without drilling, reaming, or pressurization (hemorrhagic shock and resuscitation [HR] group); (3) eight animals in which no hemorrhage or shock was induced but the femoral canal was reamed and pressurized with bone cement to induce fat embolism (fat embolism [FE] group); and (4) seven animals that had a three-hour ventilation period followed by a sham knee incision (control group). The animals were ventilated for four hours following closure. Flow cytometry with use of antibodies against CD45 and CD11b was performed to test neutrophil activation in whole blood. Histological examination of lung specimens was also performed. Plasma and bronchoalveolar lavage fluid were analyzed for monocyte chemotactic peptide-1 and interleukin-8 levels with use of the ELISA (enzyme-linked immunosorbent assay) method.

RESULTS

Three animals in the HR/FE group died immediately after canal pressurization and were excluded. CD11b mean channel fluorescence was significantly elevated, as compared with baseline, only in the HR/FE group at two hours (p = 0.025) and four hours (p = 0.024) after knee closure. Histological analysis showed that only the HR/FE (p < 0.001) and HR (p = 0.010) groups had significantly greater infiltration of alveoli by polymorphonuclear leukocytes as compared with that in the controls. No significant differences in plasma cytokine levels were found between the groups. Only the HR/FE group had significantly higher interleukin-8 (p = 0.020) and monocyte chemotactic peptide-1 (p = 0.004) levels in the bronchoalveolar lavage fluid as compared with those in the controls.

CONCLUSIONS

Fat embolism from canal pressurization alone did not activate a pulmonary inflammatory response. The combination of hemorrhagic shock, resuscitation, and fat embolism elicited neutrophil activation, infiltration of alveoli by polymorphonuclear leukocytes, and inflammatory cytokine expression in bronchoalveolar lavage fluid.

The stress response to bilateral femoral fractures: a comparison of primary intramedullary nailing and external fixation

OBJECTIVES

Concern has recently been expressed with regard to the physiologic effects of primary intramedullary femoral nailing in seriously injured patients. "Damage control orthopaedics" techniques have been proposed, which comprise principally the use of primary external fixation. The aim of this study was to compare the physiologic effects of external femoral fixation with those of intramedullary stabilization over the first 24 hours after femoral fracture using an established large animal (ovine) trauma model.

METHODS

Under terminal anesthesia, bilateral high-energy femoral fractures and hypovolemic shock were produced using a pneumatic actuator. Twenty-four sheep were randomized into 4 groups and monitored for 24 hours. Group 1--control, group 2--trauma only, group 3--trauma and external fixation, and group 4--trauma and reamed intramedullary nailing. Outcome measures included the following: pulmonary embolic load (transesophageal echocardiography), metabolic base excess, plasma coagulation markers, and polymorphonuclear cell counts obtained from bronchoalveolar lavage samples.

RESULTS

The total embolic load was significantly higher (P < 0.001) in the intramedullary nailing group. All trauma groups had a significant increase (P < 0.05) in prothrombin times with a fall in antithrombin III and fibrinogen levels. However, the type of fracture stabilization used did not significantly affect any of the other outcome measurements.

CONCLUSIONS

A higher pulmonary embolic load can be expected during early intramedullary femoral fracture stabilization compared with primary external fixation. However, the degree of stimulation to systemic coagulation and pulmonary inflammation by each type of surgery was comparable.

Histopathological and biochemical changes following fat embolism with administration of corn oil micelles

Several experimental models have been used to produce intravascular fat embolism. We have developed a simple technique to induce fat embolism using corn oil emulsified with distilled water to form fatty micelles. Fat embolism was produced by intravenous administration of these fatty micelles in anaesthetised rats, causing alveolar oedema, haemorrhage and increased lung weight.

Histopathological examination revealed fatty droplets and fibrin thrombi in the lung, kidney and brain. The arteriolar lumen was filled with fatty deposits. Following fat embolism, hypoxia and hypercapnia occurred. The plasma phospholipase A2, nitrate/nitrite, methylguidanidine and proinflammatory cytokines were significantly increased. Mass spectrometry showed that the main ingredient of corn oil was oleic acid.

This simple technique may be applied as a new animal model for the investigation of the mechanisms involved in the fat embolism syndrome.

Post-traumatic cerebral fat embolism prior to operative repair of femoral and tibial fractures

Rare cases of primary cerebral fat embolism as a postoperative complication have been reported. In addition, cerebral fat embolism occurring before operative repair without shunt lesion are more rarely reported. We report a patient with a posttraumatic cerebral fat embolism resulting in severe neurologic dysfunction without right to left shunt. A 25-year-old man was brought to the hospital immediately after a traffic accident. He sustained a right segmental femoral shaft fracture and a left tibial shaft fracture. The patient was alert with no neurological deficits. Approximately 13 hours after injury, the patient developed acute mental status deterioration and dyspnea. Magnetic resonance imaging of the brain revealed extensive multifocal infarction owing to embolic showering throughout nearly the entire brain parenchyma. Computed tomography with intravenous contrast revealed no evidence of embolism in the lung, abdomen, and pelvis. Transthoracic and transesophageal echocardiogram revealed no circulating embolic particles or intracardiac shunt. The patient underwent closed reduction and internal fixation with a reamed intramedullary nail in the tibia and underwent open reduction and internal fixation with a reamed nail in the femur at 5 days after injury. We performed decompression of a hematoma containing a large number of lipid droplets via a small incision in the femur shaft fracture, established suction drainage of the tibia medullar cavity, and applied a tourniquet to the thigh in the tibia shaft fracture. Supportive medical treatment included endotracheal ventilatory support and tracheostomy. The patient was discharged from the hospital 50 days after admission. On follow-up 2 months later, he had returned to activities of daily living, however a speech disturbance remained.

Effect of re-implanted particles from intramedullary reaming on mechanical properties and callus formation

This study investigated the quality and quantity of healing of a bone defect following intramedullary reaming undertaken by two fundamentally different systems; conventional, using non-irrigated, multiple passes; or suction/irrigation, using one pass. The result of a measured re-implantation of the product of reaming was examined in one additional group. We used 24 Swiss mountain sheep with a mean tibial medullary canal diameter between 8 mm and 9 mm. An 8 mm ‘napkin ring’ defect was created at the mid-diaphysis. The wound was either surgically closed or occluded. The medullary cavity was then reamed to 11 mm. The Reamer/Irrigator/Aspirator (RIA) System was used for the reaming procedure in groups A (RIA and autofilling) and B (RIA, collected reamings filled up), whereas reaming in group C (Synream and autofilling) was performed with the Synream System. The defect was allowed to auto-fill with reamings in groups A and C, but in group B, the defect was surgically filled with collected reamings. The tibia was then stabilised with a solid locking Unreamed Humerus Nail (UHN), 9.5 mm in diameter. The animals were killed after six weeks. After the implants were removed, measurements were taken to assess the stiffness, strength and callus formation at the site of the defect.

There was no significant difference between healing after conventional reaming or suction/irrigation reaming. A significant improvement in the quality of the callus was demonstrated by surgically placing captured reamings into the defect using a graft harvesting system attached to the aspirator device. This was confirmed by biomechanical testing of stiffness and strength. This study suggests it could be beneficial to fill cortical defects with reaming particles in clinical practice, if feasible.

Low risk of cardiac events during intramedullary instrumentation of lung cancer metastases

BACKGROUND

Instrumentation, particularly reaming, of the long bones carries the risk of embolic phenomenon. Emboli may result in pulmonary injury, which is usually manifested by desaturation. This pulmonary injury may be particularly relevant if there is diminished pulmonary reserve due to pre-existing lung disease such as lung carcinoma. In extreme cases, this can result in cardiac arrest intraoperatively.

PATIENTS AND METHODS

We reviewed 34 consecutive operations that involved instrumentation of long bones for metastases of lung carcinoma.

RESULTS

Desaturation developed during 1 procedure, and there was hypotension in 5 patients. In addition, cardiac arrest occurred intraoperatively in 1 patient, which was the only fatality.

INTERPRETATION

This study has shown that while emboli during femoral instrumentation may be common, significant clinical manifestations of this phenomenon are uncommon.

Intramedullary nailing of the lower extremity: biomechanics and biology

The intramedullary nail or rod is commonly used for long-bone fracture fixation and has become the standard treatment of most long-bone diaphyseal and selected metaphyseal fractures. To best understand use of the intramedullary nail, a general knowledge of nail biomechanics and biology is helpful. These implants are introduced into the bone remote to the fracture site and share compressive, bending, and torsional loads with the surrounding osseous structures. Intramedullary nails function as internal splints that allow for secondary fracture healing. Like other metallic fracture fixation implants, a nail is subject to fatigue and can eventually break if bone healing does not occur. Intrinsic characteristics that affect nail biomechanics include its material properties, cross-sectional shape, anterior bow, and diameter. Extrinsic factors, such as reaming of the medullary canal, fracture stability (comminution), and the use and location of locking bolts also affect fixation biomechanics. Although reaming and the insertion of intramedullary nails can have early deleterious effects on endosteal and cortical blood flow, canal reaming appears to have several positive effects on the fracture site, such as increasing extraosseous circulation, which is important for bone healing.

Similar Central Hemodynamics but Increased Postoperative Oxygen Consumption in Unreamed Versus Reamed Intramedullary Nailing of Femoral Fractures

BACKGROUND

Patients undergoing intramedullary nailing of long bone fractures have pathologically altered pulmonary vascular tone, right heart strain, and transient impairment of pulmonary gas exchange. The purpose of this study was to examine the acute differences in cardiopulmonary variables between reamed and unreamed nailing techniques in 18 (9 + 9) healthy patients with unilateral femoral shaft fractures.

METHODS

Intramedullary nailing was performed under general anesthesia within 12 hours after the trauma. For blood sampling, recording, and measurements, the patients were cannulated with radial artery and pulmonary artery catheters. Changes in central hemodynamics and oxygenation were studied pre-, peri-, and postoperatively for 16 to 20 hours.

RESULTS

Abnormally high pulmonary shunting (23 +/- 12% in the reamed and 27 +/- 11% in the unreamed group) was observed before the operation. The trends of all variables were very similar in both groups except for the last phase in which the mixed venous oxygen saturation tended to be lower (65 +/- 8 vs. 70 +/- 5%) and the oxygen consumption index was higher (186 +/- 21 vs. 151 +/- 20 mL/min/m) in the unreamed group than in the reamed group (p < 0.05). The timepoints most strenuous to the heart were at the end of operation and in the recovery room.

CONCLUSIONS

The unreamed intramedullary nailing technique does not offer any advantage in cardiopulmonary variables over the reamed technique. In both groups, there was considerable deviation in over 10 cardiopulmonary variables from normal reference values during the study. We suggest the use of invasive monitoring on patients with a long bone fracture and poor preoperative oxygenation or a history of cardiopulmonary or cardiac disease.

Physical and technical aspects of intramedullary reaming

Intramedullary pressure during reaming is influenced by various factors, including those of the patient, such as bone morphology and location and type of fracture, and those related to reaming technique and instruments. Through intensive research, technical developments and the use of modern materials, intramedullary pressure caused by modern reaming systems can be reduced to a minimum and, perhaps, completely avoided through use of the reaming-irrigation-aspiration system.

Fat embolism: the reaming controversy

Intramedullary nailing is the preferred treatment method for stabilizing femoral diaphyseal fractures. Despite its superior biomechanical advantages over other implants, its use, particularly in selected groups of patients, has been questioned because of the possible harmful systemic effects of intramedullary reaming. The increase in intramedullary canal pressure during intramedullary nailing can result in intravasation of bone marrow and fat into the venous blood system. The subsequent consequences can be fat embolism syndrome (FES), adult respiratory distress syndrome (ARDS), and multiple organ failure. The lung seems to be the primary target for fat embolization and for the mediated effects primed by inflammatory reactions. In laboratory studies, both reamed and unreamed intramedullary nailing has been shown to alter selected pulmonary variables. Although transient, this effect appears to be more prominent with reamed than unreamed techniques. Additional studies are required to determine whether a subgroup of trauma patients is adversely affected by intramedullary reaming, thus necessitating other fixation techniques.

Pathophysiological advantages of rinsing-suction-reaming (RSR) in a pig model for intramedullary nailing

Although reamed intramedullary nailing has been one of the greatest advances in modern fracture care, the concomitant increase in medullary cavity pressure leads to intravasation of bone marrow content into the blood stream, an effect that can evoke serious systemic reactions. A newly developed rinsing-suction-reamer (RSR) was able to substantially reduce the pressure and bone marrow intravasation content during experimental femoral nailing. We investigated the pathophysiological effects using the RSR, testing the hypothesis that by reducing marrow fat embolization, RSR would also reduce the activation of coagulation compared with the universal AO-Reamer (AOR) and comparable to external fixation. Twenty-two pigs were treated with either simulated external fixation or reamed femoral nailing using AOR or RSR. During surgery, the intramedullary pressure was measured and intravasation of medullary material was quantified. After surgery, the pigs were kept anaesthetised and monitored for 6 h. At defined intervals, serological, hematological, and hemodynamic parameters were evaluated. The RSR was significantly superior when compared to AOR with regard to the generation of intramedullary pressure and fat embolization; however, with external fixation the values were even lower. The evaluation of other parameters revealed no clear differences between the two reamers and the external fixator. The pig model showed that RSR led to a significant reduction of the intramedullary increase in pressure and fat intravasation compared to AOR. Although the reduction of fat embolism by RSR is not associated with pathophysiological changes, RSR can have advantages for the treatment of femoral fractures.

Evolving trends in the care of polytrauma patients

Management of polytrauma patients has changed considerably in recent years. This is in keeping with the developments that have occurred in the fields of fracture fixation techniques and intensive care. Prior to the 1970s, patients with multiple injuries were treated non-operatively, as it was believed that they were too ill to withstand surgery. Around this time, literature appeared to suggest that these patients had high rates of complications as a result of prolonged recumbency. Fracture fixation techniques were also developing rapidly, and these events led to the advent of early fracture stabilisation of multiply injured patients, known as early total care. In the following decade, the surgical world came to recognise that early stabilisation of skeletal injuries produced poor results in certain patients. The concept of 'damage control' surgery was introduced for multiply injured patients. The current era may give way to new methods as our understanding of the pathophysiology of polytrauma improves.

Cardiopulmonary complications of intramedullary fixation of long bone metastases

Intramedullary fixation of long bone metastases is an effective method of treating or preventing pathologic fractures. An important complication of this technique is the development of pulmonary embolism, which may occur at any number of steps during bone manipulation. Passage of normal marrow contents or tumor into the pulmonary circulation is thought to cause various biochemical, hemodynamic, or physical responses that lead to hypotension, arrythmia, and O2 desaturation. Death is a known risk of this procedure. Numerous surgical and anesthetic strategies have been developed to prevent or treat pulmonary embolic phenomena; however, the most important prophylaxis may be a heightened awareness of this possibility during any procedure that involves intramedullary manipulation of tumor containing bone.