The effects of femoral intramedullary reaming on pulmonary function in a sheep lung model

Reaming the intramedullary canal during tibial nailing does not affect in vivo intramuscular pH of the anterior tibialis

Many investigations have evaluated local and systemic consequences of intramedullary (IM) reaming and suggest that reaming may cause, or exacerbate, injury to the soft tissues adjacent to fractures. To date, no study has examined the effect on local muscular physiology as measured by intramuscular pH (IpH). Here, we observe in vivo IpH during IM reaming for tibia fractures.

Methods

Adults with acute tibia shaft fractures (level 1, academic, 2019-2021) were offered enrollment in an observational cohort. During IM nailing, a sterile, validated IpH probe was placed into the anterior tibialis (<5 cm from fracture, continuous sampling, independent research team). IpH before, during, and after reaming was averaged and compared through repeated measures ANOVA. As the appropriate period to analyze IpH during reaming is unknown, the analysis was repeated over periods of 0.5, 1, 2, 5, 10, and 15 minutes prereaming and postreaming time intervals.

Results

Sixteen subjects with tibia shaft fractures were observed during nailing. Average time from injury to surgery was 35.0 hours (SD, 31.8). Starting and ending perioperative IpH was acidic, averaging 6.64 (SD, 0.21) and 6.74 (SD, 0.17), respectively. Average reaming time lasted 15 minutes. Average IpH during reaming was 6.73 (SD, 0.15). There was no difference in IpH between prereaming, intrareaming, and postreaming periods. IpH did not differ regardless of analysis over short or long time domains compared with the duration of reaming.

Conclusions

Reaming does not affect IpH. Both granular and broad time domains were tested, revealing no observable local impact.

Quantitative Evaluation of Embolic Load in Femoral and Tibial Shaft Fractures Treated With Reamed Intramedullary Fixation

OBJECTIVES

To compare the volume of embolic load during intramedullary fixation of femoral and tibial shaft fractures. Our hypothesis was that tibial intramedullary nails (IMNs) would be associated with less volume of intravasation of marrow than IM nailing of femur fractures.

DESIGN

Prospective observational study.

SETTING

Urban Level I trauma center.

PATIENTS/PARTICIPANTS

Twenty-three patients consented for the study: 14 with femoral shaft fractures and 9 with tibial shaft fractures.

INTERVENTION

All patients underwent continuous transesophageal echocardiography, and volume of embolic load was evaluated during 5 distinct stages: postinduction, initial guide wire, reaming (REAM), nail insertion, and postoperative.

MAIN OUTCOME MEASUREMENTS

Volume of embolic load was measured based on previously described luminosity scores. The embolic load based on fracture location and procedure stage was evaluated using a mixed effects model.

RESULTS

The IMN procedure increased the embolic load by 215% (-12% to 442%, P = 0.07) in femur patients relative to tibia patients after adjusting for baseline levels. Of the 5 steps measured, REAM was associated with the greatest increase in embolic load relative to the guide wire placement and controlling for fracture location (421%, 95% confidence interval: 169%-673%, P < 0.01).

CONCLUSIONS

Femoral shaft IMN fixation was associated with a 215% increase in embolic load in comparison with tibial shaft IMN fixation, with the greatest quantitative load during the REAM stage; however, both procedures produce embolic load.

LEVEL OF EVIDENCE

Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Are the unreamed nails indicated in diaphyseal fractures of the lower extremity? A biomechanical study

INTRODUCTION

Intramedullary nailing is generally accepted as the first choice for the treatment of diaphyseal fractures of femur and tibia, with a gradual incease in the use of unreamed nails. Different studies during last years show controversial outcomes. Some authors strongly favor unreamed nailing, but most of the authors conclude that reamed nailing have proved to be more successful.

MATERIAL AND METHODS

This study simulates unreamed intramedullary nailing of four femoral and three tibial fracture types by means of Finite Element (FE) models, at early postoperative stages with a fraction of physiological loads, in order to determine whether sufficient stability is achieved, and if the extent of movements and strains at the fracture site may preclude proper consolidation.

RESULTS

The behavior observed in the different fracture models is very diverse. In the new biomechanical situation, loads are only transmitted through the intramedullary nail. Mean relative displacement values of fractures in the femoral bone range from 0.30 mm to 0.82 mm, depending on the fracture type. Mean relative displacement values of the tibial fractures lie between 0.18 and 0.62 mm, depending on the type of fracture. Concerning mean strains, for femoral fractures the maximum strains ranged between 12.7% and 42.3%. For tibial fractures the maximum strains ranged between 10.9% and 40.8%.

CONCLUSIONS

The results showed that unreamed nailing provides a very limited mechanical stability, taking into account that analyzed fracture patterns correspond to simple fracture without comminution. Therefore, unreamed nailing is not a correct indication in femoral fractures and should be an exceptional indication in open tibial fractures produced by high-energy mechanism.

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.

Does Intramedullary Nail Fixation of the Tibia Pose the Same Risk of Pulmonary Complications as Intramedullary Nail Fixation of the Femur? A Propensity Score-Matched Analysis

OBJECTIVES

To compare duration of mechanical ventilation and pulmonary outcomes in patients treated with intramedullary nail (IMN) fixation of the tibia versus the femur.

DESIGN

Retrospective cohort study.

SETTING

Level I trauma center.

PATIENTS

One thousand thirty patients were categorized based on treatment: those treated with IMN of the tibia (n = 515) and those treated with IMN of the femur (n = 515).

INTERVENTION

IMN fixation of tibial and femoral fractures.

OUTCOME MEASUREMENTS

The primary outcome was duration of mechanical ventilation. Secondary outcomes included length of intensive care unit (ICU) stay and risk of tracheostomy, pulmonary embolism (PE), acute respiratory distress syndrome (ARDS), and mortality.

RESULTS

In an unadjusted analysis, femoral fractures were associated with increase in ventilator days (mean difference, 1.4; P < 0.001), ICU days (mean difference, 1.8; P < 0.001), and odds of tracheostomy (odds ratio, 1.7; P < 0.01). No difference was shown in likelihood of PE, ARDS, or mortality (P > 0.2). Propensity score-matched estimates showed no differences in any measured outcomes (P > 0.40). In patients with Injury Severity Scores >17, we found no difference in length of ventilator or ICU days or likelihood of tracheostomy, PE, ARDS, or mortality in the unadjusted (P > 0.2) or propensity score-matched estimates (P > 0.3).

CONCLUSIONS

These findings suggest that IMN fixation of the tibia is associated with duration of mechanical ventilation and risk of poor pulmonary outcomes similar to those of femoral nailing, after adjustment for baseline characteristics.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Comparison of an Accelerometer-Based Portable Navigation System, Patient-Specific Instrumentation, and Conventional Instrumentation for Femoral Alignment in Total Knee Arthroplasty

Purpose

The KneeAlign2 (KA2, OrthoAlign Inc.) accelerometer-based portable navigation system and patient-specific instrumentation (PSI; Signature, ZimmerBiomet) are widely used for ideal femoral component alignment in total knee arthroplasty (TKA). However, there has been no comparative study of the KA2 system, PSI, and conventional intramedullary instrumentation (CON). The purpose of this study was to compare the accuracy in achieving proper femoral component alignment and clinical features by using the KA2 navigation system, PSI, and CON.

Materials and Methods

We retrospectively compared the accuracy of femoral component alignment of 34 TKAs performed with the KA2 system for implantation of the femoral component, 32 TKAs with PSI, and 33 TKAs with CON.

Results

In the coronal plane, use of the KA2 system was more likely to result in optimal femoral component alignment than the CON and PSI (p<0.01). In the sagittal plane, use of the KA2 system was more likely to result in optimal component alignment than PSI, but the difference between the KA2 and CON was insignificant.

Conclusions

The portable accelerometer-based KA2 navigation system enabled ideal femoral implantation in the coronal and sagittal planes, as compared to the PSI or CON.

Fat embolism syndrome: What have we learned over the years?

Although its original clinical description dates from the nineteenth century, fat embolism syndrome remains a diagnostic challenge for clinicians. Fat emboli occur in all patients with long-bone fractures, but only few of them develop a multisystem disorder affecting the lung, brain, and skin, also known as fat embolism syndrome (FES). The incidence of FES varies and is often underestimated. Mechanical and biochemical theories have been proposed for the pathophysiology of FES. Clinical manifestations consist of respiratory and cerebral dysfunction and a petechial rash. Diagnosis of FES is difficult and based mainly on clinical criteria. FES is a self-limiting disease and treatment needs to be mainly supportive. Surgical treatment of the coexistent injuries is still obscured by controversies and the treatment methods used provide inconclusive results. In this context, prevention focuses on the early identification of predisposing factors.

Limits of internal fixation in long-bone fracture

Alternatives to internal fixation of long-bone fracture comprise, depending on location, external fixation or joint replacement. Limitations comprise risk of infection and functional outcome quality, which vary according to technique. The present study examines these limitations, based on comparative or large-scale studies from which certain significant results emerge. Four main questions are dealt with: (1) the present role of locking plates; (2) conditions for intramedullary nailing in Gustilo grade IIIb open fracture; (3) the limitations of conversion from external fixation to intramedullary nailing in open lower leg fracture; (4) and the limitations of definitive anterograde femoral nailing in multiple trauma. Locking plate fixation has yet to prove clinical superiority in any of the anatomic sites for which good-quality comparative analyses are available. Infection risk in Gustilo grade IIIb open lower leg fracture is equivalent when treated by intramedullary nailing or external fixation, if wound care and debridement are effective, antibiotherapy is initiated rapidly and skin cover is restored within 7days. Conversion from primary external fixation to intramedullary nailing is possible if the external fixator was fitted less than 28days previously and skin cover was restored within 7days. The pulmonary and systemic impact of peripheral lesions or definitive anterograde intramedullary nailing of femoral fracture in multiple trauma calls for caution and what is known as "damage-control orthopedics" (DCO), a term covering the general consequences of both the initial trauma and its treatment. Femoral intramedullary nailing is thus contraindicated in case of hemorrhagic shock (blood pressure<90mmHg), hypothermia (<33°C), coagulation disorder (platelet count<90,000) or peripheral lesions such as multiple long-bone fractures, crushed limb or primary pulmonary contusion. In such cases, external fixation or retrograde nailing with a small-diameter nail and without reaming are preferable.

A prospective randomized study to compare systemic emboli using the computer-assisted and conventional techniques of total knee arthroplasty

BACKGROUND

Conventional total knee arthroplasty is performed with use of an intramedullary alignment guide, which produces elevated intramedullary pressure that can create fat emboli. Total knee arthroplasty performed via computer-assisted surgery does not require an intramedullary femoral rod, raising the question of whether computer-assisted surgery generates less embolic material than conventional total knee arthroplasty. The purpose of this study was to compare the emboli produced in the two techniques.

METHODS

Fifty-seven patients were randomized into two groups: the computer-assisted surgery group (n = 29) and the conventional total knee arthroplasty group (n = 28). An intramedullary femoral alignment jig was used in the conventional total knee arthroplasty group but not in the computer-assisted surgery group. Intraoperative invasive monitoring was performed with use of transesophageal echocardiography and a pulmonary artery catheter.

RESULTS

The mean embolic score was 6.21 points for the conventional technique group and 5.48 points for the computer-assisted surgery group (p = 0.0161). After tourniquet deflation, fat emboli were observed in the blood of five patients in the conventional surgery group and one patient in the computer-assisted surgery group.

CONCLUSIONS

The patients in the computer-assisted surgery group had lower embolic loads compared with the patients in the conventional total knee arthroplasty group. In patients with an uncompromised cardiopulmonary system, the embolic load difference between the techniques was not clinically relevant.

LEVEL OF EVIDENCE

Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Non-osteotomy and osteotomy large animal fracture models in orthopedic trauma research

Large animal fracture models are important in the field of orthopedic trauma research. New implants are tested in animals before being implanted into humans. Large animals like sheep or swine often are more properly to simulate conditions in humans, e.g. biomechanical demands, compared to rodents. Cited articles mainly analyze shock or fracture healing. Both osteotomy and non-osteotomy fracture models have been used in the past. However, comparative studies are rare and clear recommendation when to use which model are missing. This review will summarize large animal fracture models putting special emphasis on non-osteotomy fracture models.

Fat embolism in pediatric patients: an autopsy evaluation of incidence and etiology

INTRODUCTION

Little is known about the incidence and etiology of fat embolism in pediatric patients. We sought to determine the incidence, time course, and associated factors of pulmonary fat embolism (PFE), cerebral fat embolism (CFE), and kidney fat embolism (KFE) in trauma and nontrauma pediatric patients at the time of autopsy.

METHODS

Retrospectively, a convenience sample of consecutive pediatric patients (age, ≤10 years) who had undergone autopsy between 2008 and 2012 were evaluated for fat embolism. Patients who had no documented cause of death or who were hospital births and died during the same hospitalization were excluded. Formalin-fixed paraffin sections were reviewed by a forensic pathologist for evidence of fat embolism and nuclear elements. Autopsy reports were used to determine cause of death, injuries, resuscitative efforts taken, sex, height, weight, and age.

RESULTS

Sixty-seven decedents were evaluated. The median age was 2.0 years (interquartile range, 0.75-4), median body mass index (BMI) was 18.0 kg/m(2) (interquartile range, 15.7-19.0 kg/m(2)), and 55% of the patients were male. Pulmonary fat embolism, CFE, and KFE were present in 30%, 15%, and 3% of all patients, respectively. The incidence of PFE was not significantly different by cause of death (trauma 33%, drowning 36%, burn 14%, medical 28%). Patients with PFE but not CFE had significantly higher age, height, weight, and BMI. Half of the PFE and 57% of the CFE occurred in patients who lived less than 1 hour after beginning of resuscitation. Seventy-one percent of patients with CFE did not have a patent foramen ovale. Multivariate regression revealed an increased odds ratio of PFE based on BMI (1.244 [95% confidence interval, 1.043-1.484], P = .015). None of the samples evaluated demonstrated nuclear elements.

CONCLUSIONS

Pulmonary fat embolism, CFE, and KFE are common in pediatric trauma and medical deaths. Body mass index is independently associated with the development of PFE. Absence of nuclear elements suggests that fat embolism did not originate from intramedullary fat.

The physiologic and pathologic effects of the reamer irrigator aspirator on fat embolism outcome: an animal study

OBJECTIVES

Intramedullary reaming of long bones before nail insertion has been known to cause an increase in fat emboli introduction into the bloodstream, which is a potentially fatal phenomenon. The goal of this study was to assess whether the reamer irrigator aspirator (RIA) reamer can reduce fat embolic load compared with the standard AO reamer.

METHODS

Fifteen pigs were prepared using an intravenous catheter inserted into the marginal ear vein for fluid balance and drug administration. One third of the pig's blood volume was withdrawn to simulate hemorrhagic shock. Each animal underwent bilateral retrograde femoral reaming, cementing, and nailing using either an RIA or AO reamer. Assignment of a reamer type to the left or right side was done randomly and allowed for direct comparison of matching femur results. Outcome measures were obtained, namely, pulmonary arterial pressure, mean arterial pressure, partial pressure of arterial oxygen, and cardiac output. Staining techniques were used to ascertain fat emboli counts from lung tissue samples.

RESULTS

For mean arterial pressure, partial pressure of arterial oxygen, and cardiac output after cement injection, the RIA reamer group showed statistically higher values than the AO reamer group. In corollary, the RIA showed statistically lower pulmonary arterial pressure levels. No differences were noted at baseline, during hypovolemia, and post resuscitation. With the Student t test, no statistical differences were found between reamers regarding fat emboli counts for both staining methods. With the Mann-Whitney test, the RIA reamer showed statistically fewer emboli (7.0 versus 74.5) (P = 0.02, Z = 2.33) using Oil Red "O" staining.

CONCLUSIONS

The RIA reamer demonstrated superior results with respect to physiologic measures and fat emboli counts and may provide optimal results compared with the AO reamer.

Cerebral fat embolism without intracardiac shunt: A novel presentation

Fat embolism syndrome (FES) is defined as an uncommon life-threatening disease process consisting of pulmonary, central nervous system (CNS), and cutaneous manifestations. The pathophysiology of this secondary injury is poorly understood. In the setting of the multiply injured patient, the diagnosis of FES is difficult to ascertain. A case report of a posttraumatic death caused by acute dissemination of diffuse fat emboli to the brain and lungs in the absence of a right-to-left heart defect after femur fracture is presented. The transesophageal echo cardiogram with bubble study failed to demonstrate an intracardiac defect or AV malformation in the lung further supporting a biochemical process. The acute decompensation of the patient within 2 h of the injury would favor mechanical emboli. Supportive care continues to be the mainstay of treatment for FES. Cerebral fat embolism should be considered in traumatically injured patients with unexplained decline in their neurologic examination. Cerebral fat embolism may occur without an intracardiac shunt.

Pathophysiology of fat embolism: a rabbit model

OBJECTIVES

The objective of this study was to assess the effects of fat embolism on rabbit physiology.

METHODS

After anesthetic administration, both femoral condyles of the right knee only of 23 New Zealand white rabbits were exposed through a medial parapatellar approach to the knee. In the pulmonary fat embolism group (n = 15), the femoral canal was drilled in a retrograde fashion and then reamed and pressurized with a 1- to 1.5-mL cement injection. In the no-pressurization group (n = 4), after reaming, no cement was injected. In the control group (n = 4), the knee incision was immediately closed. Animals were then observed for 5 hours. Hemodynamics and blood gases were recorded at standard intervals. Postmortem, the lungs were removed en bloc and fixed for histologic assessment and quantitative histomorphometry.

RESULTS

Four intraoperative deaths occurred in the pulmonary fat embolism group immediately after pressurization and may have been associated with hypotension and cardiac arrest. In the pulmonary fat embolism group, pulmonary artery pressure increased, and both mean arterial pressure and PaO2 decreased after pressurization. Approximately 2% of lung volume was occupied by intravascular fat and there were no signs of perivascular inflammation. Control and no-pressurization animals remained stable throughout the experiment.

CONCLUSIONS

This model simulates pulmonary fat embolism after long-bone fractures. Despite cardiorespiratory dysfunction, there was no evidence of fat initiating pulmonary inflammation based on histologic data within the timeframe of the investigation.

Incidence of pulmonary fat embolism at autopsy: an undiagnosed epidemic

BACKGROUND

To determine the incidence, time course, and severity of pulmonary fat embolism (PFE) and cerebral fat embolism (CFE) in trauma and nontrauma patients at the time of autopsy.

METHODS

Prospectively, consecutive patients presenting for autopsy were evaluated for evidence pulmonary and brain fat embolism. The lung sections were obtained from the upper and lower lobe of the patients' lungs on the right and left and brain tissue. This tissue was prepared with osmium tetroxide for histologic evaluation. The number of fat droplets per high power field was counted for all sections. The autopsy reports and medical records were used to determine cause of death, time to death, injuries, if cardiopulmonary resuscitation (CPR) was attempted, sex, height, weight, and age.

RESULTS

Fifty decedents were evaluated for PFE and CFE. The average age was 45.8 years ± 17.4 years, average body mass index was 30.1 kg/cm² ± 7.0 kg/cm², and 68% of the patients were men. The cause of death was determined to be trauma in 68% (34/50) of decedents, with 88% (30/34) blunt and 12% (4/34) penetrating. CPR was performed on 30% (15/50), and PFE was present in 76% (38/50) of all patients. Subjects with PFE had no difference with respect to sex, trauma, mechanism of injury, CPR, external contusions, fractures, head, spine, chest, abdominal, pelvic, and extremity injuries. However, subjects without PFE had significantly increased weight (109 ± 29 kg vs. 86 ± 18 kg; p = 0.023) but no difference in height or body mass index. PFE was present in 82% (28/34) of trauma patents and 63% (10/16) nontrauma patients. Eighty-eight percent of nontrauma patients and 86% of trauma patients who received CPR had PFE. Trauma patients with PFE showed no significant difference in any group. Eighty-eight percent of trauma patients died within 1 hour of injury, and 80% (24/30) of them had PFE at the time of autopsy. CFE was present only in one patient with a severe head and cervical spine injury.

CONCLUSION

PFE is common in trauma patients. CPR is associated with a high incidence of PFE regardless of cause of death. PFE occurs acutely within the "golden hour" and should be considered in traumatically injured patients. Further studies are needed to evaluate the pathogenesis of PFE.

Second hit phenomenon: existing evidence of clinical implications

The last two decades extensive research evidence has been accumulated regarding the pathophysiology of trauma and the sequelae of interventions that follow. Aim of this analysis has been to collect and categorise the existing data on the so-called "second hit" phenomenon that includes the biochemical and physiologic alterations occurring in patients having surgery after major trauma. Articles were extracted from the PubMed database and the retrieved reports were included in the study only if pre-specified eligibility criteria were fulfilled. Moreover, a constructed questionnaire was utilised for quality assessment of the outcomes. Twenty-six articles were eligible for the final analysis, referring to a total of 8262 patients that underwent surgery after major trauma. Sixteen retrospective clinical studies including 7322 patients and 10 prospective ones, including 940 patients were evaluated. Several variables able to reproduce a post-operative second hit were identified; mostly related to pulmonary dysfunction, coagulopathy, fat or pulmonary embolism, and the inflammatory immune system. Indicative conclusions were extracted, as well as the need for further prospective randomised trials. Suggestions on the content and the rationale of future studies are provided.

Prediction of pulmonary morbidity and mortality in patients with femur fracture

BACKGROUND

We aimed to determine the effect of femur fractures on mortality, pulmonary complications, and adult respiratory distress syndrome (ARDS). In addition, we aimed to compare the effect of femur fractures with other major musculoskeletal injuries and to determine the effect of timing to surgery on these complications.

METHODS

All patients were identified from the trauma registries of two Level I trauma centers. Outcomes were defined at mortality in hospital, pulmonary complications, and ARDS in hospital. Regression analysis was used to determine the effect of femur fractures, while controlling for age, Abbreviated Injury Scales, Glasgow Coma Scale, and systolic blood pressure at presentation. We compared femur fractures with other major musculoskeletal injuries in similar models. Within the patients with femur fracture, time to surgery (< 8 hours, 8 hours to 24 hours, and > 24 hours) was evaluated using similar regression analysis.

RESULTS

Of the total 90,510 patients, 3,938 (4.35%) died in the hospital, 2,055 (2.27%) had a pulmonary complication, and 285 (0.31%) developed ARDS. Femur fracture is statistically predictive of mortality (odds ratio [OR], 1.606; 95% confidence interval [CI], 1.288-2.002) and pulmonary complications (OR, 1.659; 95% CI, 1.329-2.070), when controlling for other injury factors. This was comparable with the effect of pelvic fracture and other major musculoskeletal injuries. Femur fracture had a strong relationship with ARDS (OR, 2.129; 95% CI, 1.382-3.278). Patients treated in the 8 hours to 24 hours window had the lowest mortality risk (OR, 0.140; 95% CI, 0.052-0.375), and there was a trend to increased risk of ARDS in a delay to surgery of > 24 hours.

CONCLUSIONS

Femur fractures are a major musculoskeletal injury and increase the risk of mortality and pulmonary complications as much as any other musculoskeletal injuries. There is a unique relationship between ARDS and femur fractures, and this must be considered carefully in treatment planning for these patients.

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.

The biology of intramedullary reaming

In this review we focus on the local biologic and physiologic effects of intramedullary reaming of long bones. Among the topics discussed are the consequences for vascularity, as well as the pathophysiology of intramedullary pressure generation and temperature increase. Reaming techniques and their suggested effects on bone formation are outlined. Moreover, techniques for avoiding local and systemic complications are summarized.

Rationale for reduced pressure reaming when stabilizing actual or impending pathological femoral fractures: a review of the literature

Surgical treatment for impending or actual pathologic femoral fractures due to metastatic carcinoma has been shown to improve pain and quality of life. Surgery usually involves manipulation of the intramedullary (IM) portion of the femur to provide adequate stability and to restore function. IM nailing is generally considered the preferred treatment over plate osteosynthesis for most areas of the femur due to load sharing capabilities. Several reports have shown a high incidence of oxygen desaturation, hypotension, fat or air embolism, and mortality in the surgical treatment of femoral metastatic disease. The patient with a metastatic lesion in the femur is at risk for cardiopulmonary complications associated with entering the IM canal. Complications and mortality reported in the literature are varied. Benefits of IM nailing of femoral lesions and associated complications in the literature are discussed. The theoretical benefit of aspiration and irrigation while reaming is also reviewed. Reaming while irrigating under negative pressure provided through suction may potentially minimize cardiopulmonary and oncologic complications.

Intramedullary nailing as a 'second hit' phenomenon in experimental research: lessons learned and future directions

BACKGROUND

The 'second hit' phenomenon is based on the fundamental concept that sequential insults, which are individually innocuous, can lead to overwhelming physiologic reactions. This response can be expressed in several organic systems and can be examined by measurement of several parameters.

PURPOSES

The purpose of this study was to evaluate the incidence of systemic effects of intramedullary nailing and the role of concurrent head and thoracic injuries as they have been recorded in vivo. We also wanted to determine what would be the optimal animal model for future research and what variables should be investigated.

METHODS

We reviewed the available literature of animal studies that used surgery, and particularly nailing, as a second hit. The reviewed studies were retrieved through an electronic search of the MEDLINE database. We analyzed the methods of creating the first and second hits (nailing), the characteristics of the animal models, the variables examined, and the pathophysiologic responses, which appeared after the second hit.

RESULTS

Second hit reamed intramedullary nailing was found to provoke consumption of coagulation factors, whereas the effect of unreamed nailing on coagulation factors appears inconsistent. Hemodynamic factors were affected only transiently by the second hit, whereas the pulmonary function was affected only when the first hit included lung injury.

CONCLUSIONS

Thoracic and head injuries predispose to an aggravated second hit. Primate animal models are considered to be closer to clinical reality and should be preferred for future studies. Future studies should include measurements of proinflammatory and antiinflammatory markers.

[Unreamed intramedullary nailing]

Reaming and non-reaming of intramedullary nails in long bone fractures was a controversial and even emotional topic in recent decades. This article gives an historical overview of the development in this field and presents the background to the need for unreamed nailing. Furthermore, the current state of knowledge is illustrated by describing the results of a series of randomised controlled trials. Before the year 2000 nearly all German handbooks on orthopaedic and trauma surgery recommended unreamed intramedullary nailing as a more "biological" treatment that causes less harm to vascularity with equal or even better results. Unreamed nailing was in particular advocated for the treatment of open fractures. The tide turned as randomised controlled trials conducted since 2000 gave evidence that unreamed nailing leads to a higher rate of delayed or non-union, while the advantages to blood supply and infection rate could not be proven. According to evidence based medicine isolated femur and tibia fractures should be nailed in a reamed procedure. In a severe multiple injury setting it is safer to stabilize long bone fractures with external fixators, as adverse events are described for reamed and unreamed nailing.

Reaming does not add significant time to intramedullary nailing of diaphyseal fractures of the tibia and femur

BACKGROUND

Reamed intramedullary nailing is the current gold standard for the treatment of diaphyseal fractures of the femur and tibia. Current concepts of orthopedic damage control surgery for patients with multiple injuries have placed an emphasis on appropriate surgical timing, limiting blood loss, and the duration of the initial operative procedure(s). Proponents of unreamed nailing have stated that reaming places polytraumatized patients "at risk," in part because it adds to the length of the surgical procedure and may exacerbate the severity of a patient's pulmonary injury. The purpose of this study was to determine how many minutes reaming actually takes and what percentage of operative time reaming comprises during intramedullary nailing of femoral and tibial shaft fractures.

METHODS

Intraoperative timing data were collected prospectively on a total of 52 patients with 54 fractures (21 femoral and 33 tibial) who underwent reamed intramedullary nailing of acute closed or open femoral or tibial shaft fractures over a 10-month period. Total operating room, surgical, and reaming times were collected.

RESULTS

The average reaming time for femur and tibia fractures was 6.9 minutes and 7 minutes, respectively. On average, reaming accounted for 4.9% of the surgical time and 3.2% of the total operating room time for femur fractures and 4.9% of the surgical time and 3.4% of the total operating room for tibia fractures.

CONCLUSION

Our results show that reaming comprises a small percentage of the operative time and the total time a patient spends in the operating room.

Fat marrow embolism during intramedullary bone endoscopy: an experimental study in sheep

We present a study designed to investigate whether the intramedullary bone endoscopy (IBE) procedure within the cavity of an intact long bone will create embolic loads on the lungs similar to that of other orthopedic procedures (e.g., stem implantation in total hip arthroplasty [THA]). In a sheep model, 10 animals underwent the IBE procedure with complete perioperative anesthesiology monitoring. The lungs were harvested postoperatively and examined for fat embolisms. One animal showed evidence of intraoperative fat embolism with temporary increases in mean pulmonary arterial pressure (MPAD) and the mean CO(2)-gradient. The histological examination in this animal revealed fat embolism with a 2% surface area of the investigated fields covered with fat vacuoles. All peri- and postoperative data on the other nine animals were normal. Our findings indicate that, as with other intramedullary manipulation in intact long bones, there is a potential risk for systemic fat excavation during IBE. However, the embolic load is much lower than the rates reported for other orthopedic interventions.

Fat extravasation due to unreamed and experimentally reamed intramedullary nailing of the sheep femur

AIM

To compare systemic fat extravasation in unreamed and experimentally reamed nailing.

METHODS

An osteotomy was created in the proximal third of the femoral shaft in 16 sheep, and intramedullary pressure increase and fat extravasation were monitored for the two nailing techniques.

RESULTS

The highest intramedullary pressures, median 2700 mm Hg, and highest percentages of fat extravasation, peaking at almost 90% of fat, were found for the unreamed nailing technique. The values for the reamed group were significantly lower.

CONCLUSIONS

The extravasation of intramedullary fat can be attributed to the great increase in intramedullary pressure that occurs during unreamed nailing. Correctly performed intramedullary reaming with the new reaming system produces lower pressures and much less systemic fat extravasation, reducing the risk for fat embolism.

Intramedullary nailing of the femur: current concepts concerning reaming

Intramedullary fixation has advanced to the standard of care for fractures of the femoral shaft. Current controversies center on whether to prepare the intramedullary canal by reaming, particularly in certain subsets of patients. As understanding of the local and systemic effects of reaming deepens, there is a role for maximizing the benefits of intramedullary preparation before nail fixation, while attempting to minimize the major disadvantages of this technique. Several treatment strategies have emerged to address the downsides of intramedullary reaming. The purpose of this review is to discuss the history and current knowledge of intramedullary reaming with respect to problems associated with its use and the evolution of treatment modalities and their clinical applicability for orthopaedic trauma care.

Pathoanatomy and clinical correlates of the immunoinflammatory response following orthopaedic trauma

The natural inflammatory response to major trauma may be associated with the development of a systemic inflammatory state, remote multiorgan failure, and death. Although a controlled inflammatory response is beneficial, an exaggerated response can cause serious adverse systemic effects. Early identification of high-risk patients, based on inflammatory markers and genomic predisposition, should help direct intervention in terms of surgical stabilization and biologic response modification. Currently, two markers of immune reactivity, interleukin-6 and human leukocyte antigen-DR class II molecules, appear to have the most potential for regular use in predicting the clinical course and outcome in trauma patients; however, the ability to measure markers of inflammation is still limited at many hospitals. With improving technology and increasing research interest, understanding of the significance of the immunoinflammatory response system in injured patients will continue to evolve.

Femoral nailing-related coagulopathy determined by first-hit magnitude: an animal study

We asked whether coagulopathy worsened during femoral intramedullary nailing in the presence of lung contusion and hemorrhagic shock and whether reamed or unreamed nailing influenced these results. In 30 Merino sheep, we induced hemorrhagic shock and/or standardized lung contusion followed by femoral nailing. Six groups of five each were assigned as follows: thoracotomy control groups treated with reamed or unreamed nailing, lung contusion groups treated with reamed or unreamed nailing, and shock and lung contusion groups treated with reamed or unreamed nailing. After lung contusion alone (first hit), the serum values of antithrombin III, factor V, and fibrinogen were considerably altered after reamed and unreamed femoral nailing (second hit) 4 hours postoperatively. In the lung contusion and shock groups, we found a substantial reduction for all serum coagulative parameters between baseline and fixation after reamed and unreamed nailing. The magnitude of the first hit is increased if hemorrhagic shock is added to a lung contusion determined by hemostatic reactions. The magnitude of the injury appears equally important as the type of subsequent surgery and should be considered in planning for fracture fixation in patients at high risk for complications.

The biological and physiological effects of intramedullary reaming

This paper summarises the current knowledge on the effects of medullary reaming of long-bone fractures. Following a review of intramedullary vascular physiology, the consequences for vascularity, the autograft effects, the generation of heat, and fat embolism are outlined. Also, alternative reaming techniques are described.

Damage control nailing

The role of intramedullary nailing of the femur and the timing for this procedure in the trauma patient with multiple injuries has been widely debated. Recent literature has advocated the idea of "damage control orthopaedics," promoting temporary external fixation for stabilization of long bone fractures in the acute setting. This paper advances an alternative to damage control orthopaedics, the option of rapidly executed small-diameter unreamed retrograde nailing of the femur for the patient with polytrauma who will be undergoing simultaneous surgery for other injuries. This technique offers the advantages of rapid stabilization performed under controlled circumstances in the operating room, without some of the disadvantages of using external fixation in this situation.

Embolic phenomena during computer-assisted and conventional total knee replacement

Systemic emboli released during total knee replacement have been implicated as a cause of peri-operative morbidity and neurological dysfunction. We undertook a prospective, double-blind, randomised study to compare the cardiac embolic load sustained during computer-assisted and conventional, intramedullary-aligned, total knee replacement, as measured by transoesophageal echocardiography. There were 26 consecutive procedures performed by a single surgeon at a single hospital. The embolic load was scored using the modified Mayo grading system for echogenic emboli.

Fourteen patients undergoing computer-assisted total knee replacement had a mean embolic score of 4.89 (3 to 7) and 12 undergoing conventional total knee replacement had a mean embolic score of 6.15 (4 to 8) on release of the tourniquet. Comparison of the groups using a two-tailed t-test confirmed a highly significant difference (p = 0.004).

This study demonstrates that computer-assisted knee replacement results in the release of significantly fewer systemic emboli than the conventional procedure using intramedullary alignment.

Cortical heat generation using an irrigating/aspirating single-pass reaming vs conventional stepwise reaming

OBJECTIVE

To compare the heat generation and pressure generation of a prototype irrigating aspirating intramedullary reaming system to traditional stepwise reaming.

DESIGN

This in vitro study used 8 pairs of fresh-frozen human cadaver tibias. Thermocouples were mounted in the mid-diaphysis and distal diaphysis. A pressure transducer was placed distally to assess intramedullary pressure, a load cell measured axial load was applied by the surgeon, and the entire construct was placed in a 37 degrees C saline bath. One specimen from each pair underwent single-pass reaming with the prototype reamer irrigator aspirator (RIA), and the contralateral limb underwent standard stepwise reaming. All variables were recorded.

RESULTS

There were no significant differences in pressure applied to the load cells during reaming. The maximum temperatures reached in the distal diaphysis in the RIA group (42.0 +/- 9.1 degrees C) were significantly lower (P = 0.025) than in the standard reaming group (58.7 +/- 15.9 degrees C). The maximum pressure generated in the distal tibia in the RIA group (32.7 +/- 39.4 kPa) was significantly higher (P = 0.019) than in the standard reaming group (17.0 +/- 32.6 kPa).

CONCLUSIONS

This study demonstrated substantially decreased temperatures with the RIA prototype when compared with standard stepwise reaming. It appears that the continuous flow of room temperature saline irrigant into the system manages to cool the cortical bone, despite the aggressive nature of a single-pass reaming method. However, in this model, contrary to the findings of other studies, the RIA system did generate higher pressures in the distal tibial metaphysis, perhaps as a result of congestion within the outflow of the RIA system. The results of this study confirm that cortical heat generation is not a problem but definitely indicate further development of this prototype aspirator function is warranted, followed by careful in vivo evaluation.

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.

Experimental background--review of animal studies

Most of the research on the physiological effects of intramedullary nailing is technically difficult or ethically impossible to perform in humans. A substantial range of factors apply in clinical cases, which means that the data obtained from this source may lack the control needed to reveal the basic mechanisms of pathophysiology associated with this surgical procedure. Consequently, animal studies have been relied upon to provide answers that would otherwise be unavailable. This review manuscript summarizes the available literature on animal studies dealing with the local and systemic effects of intramedullary nailing. It focuses on whether these studies have contributed to our clinical knowledge of the procedure's impact on perfusion and fracture healing, as well as the medical relevance of coincident systemic effects.

DATA SOURCES

Medline, personal library of the first author and of the Department of Trauma Surgery, University of Pittsburgh Medical Center.

STUDY SELECTION

All animal studies on intramedullary stabilization published in English, German, and French.

CONCLUSIONS

The relevance of animal studies investigating the impact of a surgical procedure and its influence on concomitant injuries depends on the design and the type of the animal model. If this fact is considered, and if a model is selected that simulates a systemic impact comparable with the clinical situation, then animal studies may provide a valuable source of otherwise unobtainable information. Such an example is the study of fat embolization associated with intramedullary nailing. Animal subjects enable assessment of the intervention's additive surgical impact, measurement of side effects that may have adverse results, and influence of cofactors (eg, thoracic trauma, severe shock, polytrauma) that predispose the individual to postoperative complications.

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.

Prevention of fat embolism syndrome

Fat embolism syndrome is a condition of acute respiratory distress following long-bone trauma. This condition may involve not only the lungs but also a number of other body systems. The pathophysiology is not as yet clearly understood, however, intravasation of fat from long-bone fractures may play a role. Early recognition of the severity of injury both on clinical and biochemical grounds and early surgical stabilization of long bones may help to decrease its incidence. However, the best surgical technique with which to do this stabilization has not yet been clearly determined. Surgical and pharmacological techniques have been developed in an attempt to either decrease the intravasation of fat during long-bone stabilization or block the inflammatory cascade with varying degrees of efficacy. Ongoing research focuses on both the prevention and treatment of this condition.

The early response to major trauma and intramedullary nailing

The stress response to trauma is the summation of the physiological response to the injury (the 'first hit') and by the response to any on-going physiological disturbance or subsequent trauma surgery (the 'second hit'). Our animal model was developed in order to allow the study of each of these components of the stress response to major trauma. High-energy, comminuted fracture of the long bones and severe soft-tissue injuries in this model resulted in a significant tropotropic (depressor) cardiovascular response, transcardiac embolism of medullary contents and activation of the coagulation system. Subsequent stabilisation of the fractures using intramedullary nails did not significantly exacerbate any of these responses.

Damage control: extremities

The principles of fracture management in polytrauma patients continue to be of crucial importance. Over the last five decades, various strategies of fracture treatment in the multiply injured patient have evolved. The various new methodologies remain controversial. In the beginning, early surgical fracture treatment of long bone fractures after multiple trauma was not routinely advocated. It was believed that the polytraumatised patient did not have the physiological reserve to withstand prolonged operations. The introduction of standardised, definitive surgical protocols, led to the concept of early total care (ETC) in the 1980s. This concept was subsequently applied universally, in all patient groups, regardless of injury severity and distribution. Later, it became apparent that certain patients did not appear to benefit from ETC. Indeed, extended operative procedures, during the early phase of multiple trauma recovery, were associated with adverse outcome. This applied for patients with significant thoracic, abdominal and head injuries and those with high injury severity scores (ISS). In response, the concept of damage control orthopaedics (DCO) was developed in the 1990s. DCO methodology is characterised by primary, rapid, temporary fracture stabilization. Secondary definitive management follows, once the acute phase of systemic recovery has passed. We explore the processes underlying the systemic biological impact of fracture fixation, the evolution of operative treatment strategies for major fractures in polytrauma and the current trends toward staged management of these patients.

Pulmonary aspects of treatment of long bone fractures in the polytrauma patient

During the past decade, there have been significant advances in the treatment of long bone fractures in the polytraumatized patient. The major controversy in this area is whether definitive long bone stabilization needs to be done emergently. In general, definitive fixation should be done early in the patient's hospital course after it is determined that the patient is hemodynamically stable and is resuscitated adequately. The major benefits of fixation are: (1). improve mobilization to enhance pulmonary function; (2). decreased narcotic requirements with improved pain control after fixation; and (3). early aggressive fluid resuscitation associated with operative intervention. Patients with multisystem injury who are underresuscitated or are unstable should have early external fixation because temporizing skeletal stabilization until definitive fixation can be done.

Continuous Pulse Oximeter Monitoring for Inapparent Hypoxemia after Long Bone Fractures

BACKGROUND

Continuous pulse oximeter monitoring (CPOM) and daily intermittent arterial blood gas (ABG) were used to define the incidence, pattern, and severity of inapparent hypoxemia after long bone fractures.

METHOD

Twenty long bone fracture patients and 19 normal control patients were studied. CPOM, daily ABG, hypoxic symptoms, and features of fat embolism syndrome were monitored for 72 hours after fractures and after surgical interventions.

RESULTS

CPOM trend curves showed that all fracture patients except one had recurrent desaturations below 90% Sao2 of varying duration and depth. The lowest Sao2 was down to 60% and the longest episode lasted for 1.47 hours. ABG analysis could not show the recurrent phenomena and never detected the corresponding desaturation episodes. Long bone fracture patients had more desaturation episodes, longer total desaturation duration, and larger total area under desaturation curves in both the postfracture and postoperative periods (p < 0.05). The mean Sao2 was significantly lower in the postfracture period. Although most patients remained asymptomatic and recovered spontaneously, two required transient oxygen therapy and one progressed to fat embolism syndrome.

CONCLUSION

Inapparent hypoxia with profound desaturation is common after long bone fractures. CPOM of all patients admitted with long bone fractures is recommended for early detection. In patients who develop inapparent hypoxia, additional pulmonary insult should be avoided or undertaken with care and well timed.

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.

Effects of intramedullary femoral fracture fixation: what is the impact of experimental studies in regards to the clinical knowledge?

This review manuscript summarizes the available literature on animal studies dealing with the local and systemic effects of intramedullary (IM) reamed and unreamed nailing. It focuses on the question of whether the large numbers of studies have contributed to our clinical knowledge about its impact on perfusion, fracture healing, and about the clinical relevance of systemic side effects. The effects of IM contents that are squeezed out of the medullary canal into the venous and the systemic circulation due to reaming and nailing has been a major issue. In addition, the impact of the surgical procedure and the timing of such a major operation as femoral fractures surgery has been a major source of debate within the last decade. The compilation of relevant studies investigating the degree of impact of a surgical procedure and the influence of concomitant injuries depends on the design and the type of the animal model. If this fact is considered and if a model is selected that reflects the systemic impact comparable with the clinical situation, animal studies represent a valuable source of information. In this respect, fat embolization represents an additive surgical impact and can cause clinically relevant side effects if cofactors (e.g., thoracic trauma, severe shock, and polytrauma) are present that set the individual up for postoperative complications.

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

OBJECTIVES

To determine whether reamed or unreamed femoral intramedullary nailing is more adverse to pulmonary function, the authors compared three populations of healthy pigs, analyzing the biochemical and hemodynamic effects related to fat embolism. Likewise, the authors histologically evaluated the presence of bone marrow fat embolism in lungs, heart, kidney, brain, and retina.

DESIGN

Randomized, experimental model.

SETTING

Laboratory.

PARTICIPANTS

Twenty-five male Duroc Jersey adult healthy pigs divided in three groups.

INTERVENTION

Reamed and unreamed intramedullary nailing.

OUTCOME MEASUREMENTS

Biochemical, hemodinamical, and histologic analysis.

METHODS

In the first group of ten pigs, a reamed nail was inserted; in the second group of ten specimens, the authors placed an unreamed nail; and in the third group of five animals (control), only the surgical approach was made without opening the medullary cavity.

RESULTS

The authors did not find statistically significant differences in pulmonary function between the reamed and unreamed group in the hemodynamic, biochemical, and histopathologic parameters evaluated. The histologic analysis of the lung tissue revealed a statistically significant difference between the nailed groups and the control (P < 0.04).

CONCLUSIONS

In this animal model, the results indicate that pulmonary changes and fat embolization during intramedullary nailing occur to the same degree in reamed and in unreamed femurs.

Fat embolism and acute hypotension during vertebroplasty: an experimental study in sheep

STUDY DESIGN

An experimental study of cardiovascular complications that arise during vertebroplasty was conducted.

OBJECTIVE

To investigate the sequential occurrence of fat embolism and hypotension during vertebroplasty.

SUMMARY OF BACKGROUND DATA

Vertebroplasty, the augmentation of vertebrae with polymethylmethacrylate, is a technique for treating osteoporotic compression fractures and achieving prophylactic stabilization of osteoporotic vertebral bodies at risk of fracture. However, there is concern that fat embolism and acute hypotension could occur as in a variety of other orthopedic procedures.

METHODS

In six sheep, 6 mL of polymethylmethacrylate was injected unilaterally into L1. Transesophageal echocardiography monitored the pulmonary artery for echodense particles. Heart rate, arterial and venous pressures, and blood gas values were recorded before and for 25 minutes after injection. The lungs were subjected to postmortem histologic evaluation and compared with lung specimens from two sheep that had not undergone vertebroplasty.

RESULTS

Injection of cement elicited a very rapid decrease in heart rate (within 2 +/- 1 seconds) and a rapid increase in venous pressure (within 3 +/- 1 seconds), which was followed by a fall in arterial pressure (within 5 +/- 2 seconds) (phase 1). Thereafter, showers of echogenic material appeared (within 6 +/- 1 seconds) and lasted for 138 +/- 36 seconds. A second more severe fall in arterial pressure was observed beginning at 18 +/- 2 seconds (phase 2). The injection resulted in an increase in partial pressure of carbon dioxide and a decrease in pH. The histology showed intravascular fat globules and bone marrow cells in lung tissue.

CONCLUSIONS

The results suggest that immediately after cement injection, there was a reflex fall in heart rate and arterial pressure. The second fall in arterial pressure was a consequence of fat emboli passing through the heart and getting trapped in the lungs.