Comparison of reamed long and short intramedullary nail constructs in unstable intertrochanteric femur fractures: A biomechanical study

OBJECTIVES

There is no definitive evidence to guide clinicians in their decision-making for implant choice regarding long or short intramedullary nails for unstable fracture patterns. Historically short nails were associated with higher rates of perisprothetic fractures which seem to have improved with newer designs. Long intramedullary nails have higher blood loss and time under anesthesia. The purpose of this study was to assess stability of long and short intramedullary nail constructs in unstable intertrochanteric fracture patterns to better elucidate if unstable intertrochanteric fractures are amenable to treatment with short intramedullary nails.

METHODS

This study utilized composite model femurs which were assigned to either a comminuted or reverse obliquity fracture pattern, then subsequently assigned to implantation with either a long or short intramedullary nail. All the samples were reamed to the level of the distal femur and instrumented with the appropriate nail. Axial and torsional stiffness as well as axial load to failure values were determined using a servohydraulic loading system.

RESULTS

Short nail constructs exhibited significantly greater axial stiffness in A1 fractures and torsional stiffness in A3 fractures when compared with long nails. There was no significant difference between axial load to failure between long nails and short nails.

DISCUSSION

We found no significant difference in axial load to failure values between long and short intramedullary nail fixation in 2 unstable intertrochanteric fracture patterns in a composite femur model. Short nails exhibited greater stiffness in axial loads in the A1 pattern and torsional stiffness in the A3 pattern. This suggests short or long intramedullary nails could be appropriately employed for fixation of unstable intertrochanteric hip fracture patterns.

Not Further Specified: Unclassified Orthopedic Injuries in Trauma Registries, Cause for Concern?

BACKGROUND

Data accuracy is essential to obtaining correct results and making appropriate conclusions in outcomes research. Few have examined the quality of data that is used in studies involving orthopedic surgery. A nonspecific data entry has the potential to affect the results of a study or the ability to appropriately risk adjust for treatments and outcomes. This study evaluated the proportion of Not Further Specified (NFS) orthopedic injury codes found into two large trauma registries.

MATERIALS

Data from the National Trauma Data Bank (NTDB) from 2011 to 2015 and from the Michigan Trauma Quality Improvement Program (MTQIP) 2011-2017 were used. We selected multiple orthopedic injuries classified via the Abbreviated Injury Scale, version 2005 (AIS2005) and calculated the percentage of NFS entries for each specific injury.

RESULTS

There were a substantial proportion of fractures classified as NFS in each registry, 18.5% (range 2.4%-67.9%) in MTQIP and 27% (range 6.0%-68.5%) in the NTDB. There were significantly more NFS entries when the fractures were complex versus simple in both MTQIP (34.5% versus 9.6%, P < 0.001) and the NTDB (41.8% versus 15.7%, P < 0.001). The level of trauma center affected the proportion of NFS codes differently between the registries.

CONCLUSIONS

The proportion of nonspecific entries in these two large trauma registries is concerning. These data can affect the results and conclusions from research studies as well as impact our ability to truly risk adjust for treatments and outcomes. Further studies should explore the reasons for these findings.

Variation in Optimal Sagittal Alignment of the Femoral Component in Total Knee Arthroplasty

Accurate sagittal alignment of the femoral component in total knee arthroplasty is crucial for prosthesis longevity, improved function, and patient satisfaction. However, there is variation in the techniques used to attain optimal sagittal femoral component placement in total knee arthroplasty. Femoral component flexion in imageless navigation is based on the mechanical axis rather than the distal femoral anatomy, and there is significant variability in the anatomy of the distal femur. The purpose of this study was to accurately determine the mean distal femoral flexion angle of a representative population and whether variability of the distal femoral flexion angle correlates with race, femur length, or radius of curvature. The mean degree of distal femoral flexion was determined by assessing distal femoral anatomy on computed tomography scans of paired femurs of 1235 patients without evidence of previous fracture, deformity, or surgical implants. The mean±SD distal femoral flexion angle was 2.90°±1.52°, with 80.2% of knees within 3°±2°. Therefore, placing the component in 3° of flexion from the mechanical axis would attain a satisfactory position in most cases. However, further analysis of the patient data revealed 11.4% of Asians, 7.3% of African Americans, and 8.3% of whites had a distal femoral flexion angle greater than 5°. Additionally, the data revealed a moderately strong negative correlation between the distal femoral flexion and the overall radius of curvature of the femur. This preliminary study highlights the need for improved methods for selecting femoral component position in the sagittal plane when using navigation for total knee arthroplasty. [Orthopedics. 2017; 40(2):102-106.].

Own the Bone, a System-Based Intervention, Improves Osteoporosis Care After Fragility Fractures

BACKGROUND

The goal of this study was to evaluate the effectiveness of the American Orthopaedic Association's Own the Bone secondary fracture prevention program in the United States.

METHODS

The objective of this quality improvement cohort study was dissemination of Own the Bone and implementation of secondary prevention (osteoporosis pharmacologic and bone mineral density [BMD] test recommendations). The main outcome measures were the number of sites implementing Own the Bone and implementation of secondary prevention, i.e., orders for BMD testing and/or pharmacologic treatment. The 177 sites participating in the program were academic and community hospitals, orthopaedic surgery groups, and a health system; data were obtained from the first 125 sites utilizing its registry, between January 1, 2010, and March 31, 2015. It included all patients, aged 50 years or older, presenting with fragility fractures (n = 23,132) who were enrolled in the Own the Bone web-based registry. The interventions were education, development of program elements, dissemination, implementation, and evaluation of the Own the Bone program at participating sites.

RESULTS

A growing number of institutions implemented Own the Bone (14 sites in 2005-2006 to 177 sites in 2015). After consultation, 53% of patients had a BMD test ordered and/or pharmacologic therapy for osteoporosis.

CONCLUSIONS

The Own the Bone intervention has succeeded in improving the behaviors of medical professionals in the areas of osteoporosis treatment and counseling, BMD testing, initiation of pharmacotherapy, and coordination of care for patients who have experienced a fragility fracture.

Fat Thickness as a Risk Factor for Infection in Lumbar Spine Surgery

Body mass index does not account for body mass distribution. This study tested the hypothesis that subcutaneous fat thickness is a better indicator than body mass index of the risk of surgical site infection in lumbar spine procedures performed through a midline posterior approach. Charts were reviewed for previously identified risk factors for surgical site infection (age, diabetes, smoking, obesity, albumin level, multilevel procedures, previous surgery, and operative time) in 149 adult patients who underwent lumbar spine procedures through a midline posterior approach. Subcutaneous fat thickness was measured with a novel automated technique. Regression analysis was used to determine associations between risk factors and fat thickness with surgical site infection. In the study group, 15 surgical site infections occurred (10.1%). Bivariate analysis showed a significant association between surgical site infection and body mass index (P=.01), obesity (P=.02), and fat thickness (P=.002). With multivariate analysis, body mass index and obesity did not show significance, but fat thickness remained significant (P=.026). For every 1-mm thickness of subcutaneous fat there was a 6% (odds ratio, 1.06; 95% confidence interval, 1.02-1.10) increase in the odds of surgical site infection, and patients with fat thickness of greater than 50 mm had a 4-fold increase in the odds of surgical site infection compared with those with fat thickness of less than 50 mm. Body mass index and fat thickness were moderately correlated (r²=0.44). These results confirm the hypothesis that local subcutaneous fat thickness is a better indicator than body mass index of the risk of surgical site infection in lumbar spine procedures. [Orthopedics. 2016; 39(6):e1124-e1128.].

Complicated Outcomes After Emergent Lower Extremity Surgery in Patients With Solid Organ Transplants

The complications of emergent or urgent surgery in solid organ transplant recipients are unclear. The goal of this nonrandomized retrospective case study, conducted at a large public university teaching hospital, was to determine the following: (1) 90-day postsurgical complications in solid organ transplant recipients who undergo fracture surgery of the lower extremities; (2) 90-day and 1-year mortality rates for this cohort; (3) correlation of particular postsurgical complications with the 90-day or 1-year mortality rate; and (4) correlation of body mass index with the 90-day or 1-year mortality rate. Subjects included 36 solid organ transplant recipients who underwent surgical treatment for 37 emergent or urgent lower extremity fractures within 72 hours of presentation to the emergency department. Patients were followed for all medical and surgical complications for 90 days and for all-cause mortality for 1 year. Within 90 days of surgery, patients had complications that included acute renal failure (15, 40.5%), deep venous thrombosis (3, 8.1%), pulmonary embolus (2, 5.4%), pneumonia (7, 18.9%), superficial surgical site infection (3, 8.1%), and nonorthopedic sepsis (4, 10.8%). In addition, 3 (8.1%) and 5 (13.9%) patients died within 90 days and 1 year, respectively. Hospital readmission correlated with a higher 1-year mortality rate (odds ratio, 14.000; P=.016). Higher body mass index correlated with higher 90-day (odds ratio, 1.425; P=.035) and 1-year (odds ratio, 1.334; P=.033) mortality rates. Solid organ transplant recipients with lower extremity fracture have high 90-day and 1-year mortality rates and may have multiple complications within 90 days of treatment. [Orthopedics. 2016; 39(6):e1063-e1069.].

Previous arthroscopic repair of femoro-acetabular impingement does not affect outcomes of total hip arthroplasty

BACKGROUND

Total hip arthroplasty (THA) is commonly elected following failed arthroscopic treatment of femoro-acetabular impingement (FAI). The purpose of this study was to evaluate post-operative outcomes of primary THA in patients who had previously undergone arthroscopic treatment for FAI.

METHODS

A retrospective, matched case-control study was conducted. The case group included 39 patients who underwent THA after previous hip arthroscopy for FAI. Thirty-nine patients who had a primary THA without previous hip arthroscopy served as a control group and were matched for age, sex and body mass index. Surgical outcomes were assessed based on inpatient hospital metrics and outpatient complication measures. Statistical analyses were performed to identify the significance of outcome variables between case and control groups.

RESULTS

No statistically significant differences were observed between groups in terms of operative time, haemoglobin drop, intra-operative estimated blood loss, transfusion requirements, amounts of opioids provided, functional mobility assessments on post-operative days one and two, length of hospitalization, discharge location, emergency department visits, post-operative superficial or deep periprosthetic infection, revision rates for dislocation or formation of heterotopic bone (p-values = 0.1-0.8). A statistically significant difference was found between the walking scores on the third post-operative day (p = 0.015).

CONCLUSIONS

These findings, while underpowered, are consistent with other previously published reports. Previous hip arthroscopy for FAI does not appear to impact post-operative outcomes of a subsequent THA. Larger datasets from different surgeons and centers are needed to further assess these conclusions.

LEVEL OF EVIDENCE

Case-control level-III.

Publication Productivity of Early-Career Orthopedic Trauma Surgeons

The goals of this study were to: (1) define the publication productivity of early-career orthopedic trauma surgeons over time; (2) compare the early-career publication productivity of recent orthopedic trauma fellowship graduates vs their more senior colleagues; and (3) determine the proportion of fellowship graduates who meet the Orthopaedic Trauma Association (OTA) publication criteria for active membership early in their careers. Orthopedic trauma fellowship graduates from 1982 to 2007 were analyzed. A literature search was performed for each fellow's publications for the 6-year period beginning the year of fellowship graduation. Publication productivity was compared between early and recent groups of graduates, 1987 to 1991 and 2003 to 2007, respectively. Fulfillment of OTA publication criteria was determined. Seventy-nine percent of graduates contributed to 1 or more publications. The recent group produced more total publications per graduate (4.06 vs 3.29, P=.01) and more coauthor publications (2.60 vs 2.04, P=.019) than the early group. The number of first-author publications did not differ between groups (1.46 vs 1.25, P=.26). A greater percentage of the recent group met current OTA publication criteria compared with the early group (51% vs 35%, P=.04). The findings showed that recent orthopedic trauma graduates had increased publication productivity compared with their more senior colleagues, although a proportion had not qualified for active OTA membership 6 years into their career. Overall, these data are encouraging and suggest that young orthopedic trauma surgeons remain committed to sustaining a high level of academic excellence.

Open Reduction and Internal Fixation of the Tibial Plateau Through the Anterolateral Approach

Fractures of the tibial plateau are challenging injuries to treat. The lateral tibial plateau is fractured more commonly than the medial plateau and the workhorse approach for these fractures is the anterolateral approach. This approach allows visualization of the lateral joint, metaphysis, and can be extensile if there is shaft extension. We present our technique for performing the anterolateral approach while treating a Schatzker III tibial plateau fracture. Special attention is given to performing a submeniscal arthrotomy to view the joint surface and judge the reduction. A femoral distractor is placed to assist with elevation the joint surface and visualization of the lateral plateau. A cortical window is created using a triple reamer from the sliding hip screw set. The reduction is performed and supported with cancellous bone chips. Finally, a lateral locking plate with rafting screws is placed. Knowledge of this approach and the strategies needed to address lateral and some bicondlar tibial plateau fractures are crucial to good patient outcomes.

A Computed Tomography Study of Gender Differences in Acetabular Version and Morphology: Implications for Femoroacetabular Impingement

PURPOSE

To assess the prevalence of acetabular retroversion in a large population of patients with asymptomatic hips. Furthermore, we sought to identify gender differences in acetabular morphology to address the current thinking that retroversion and pincer-type femoroacetabular impingement (FAI) are more common in women.

METHODS

We retrospectively reviewed morphologic features of acetabula from a consecutive series of trauma-protocol computed tomography scans of patients without pelvis injury. An automated algorithm determined the acetabular rim profile and center of the femoral head, normalized the frontal plane of the pelvis, and calculated version and coverage. We then compared male and female rim profiles, specifically focusing on version and acetabular wall coverage in the 1-o'clock (anterosuperior), 2-o'clock (central), and 3-o'clock (inferior) positions.

RESULTS

Of 1,088 patients in the database, 878 had complete data (i.e., age, ethnicity, and body mass index) and were therefore included in the final analysis. Of these, 34.3% were women and 65.7% were men. Mean global acetabular version was 19.1° for men and 22.2° for women (P < .001). Mean acetabular version for men and women was 15.5° and 18.3°, respectively, in the 1-o'clock position; 21.5° and 24.0°, respectively, in the 2-o'clock position; and 20.2° and 24.3°, respectively, in the 3-o'clock position (P < .001 for all 3). True retroversion (<0°) was observed only in the 1-o'clock position. The prevalence of true acetabular retroversion in the 1-o'clock position for men and women was 4.3% and 3%, respectively (P = .36).

CONCLUSIONS

Mean global and focal acetabular anteversion was greater in women, and the prevalence of focal cephalad retroversion in the 1-o'clock position was not significantly different compared with men. Acetabular retroversion and anterior overcoverage are not more prevalent in women in the anterosuperior acetabulum, where femoroacetabular impingement most commonly occurs.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Transsacral screw safe zone size by sacral segmentation variations

Variations in sacral segmentation may preclude safe placement of transsacral screws for posterior pelvis fixation. We developed a novel automated 3D technique to determine the safe zone size for transsacral screws in the upper two sacral segments in 526 adult pelvis computed tomography scans. Safe zone sizes were then compared by gender and sacral segmentation variations (number of neuroforamen and the presence/absence of lumbosacral transitional vertebrae, ± LSTV). Ten millimeters was used as the safety threshold for a large screw. 3 (0.6%), 366 (70%), and 157 (30%) sacra had 3, 4, or 5 neuroforamen, respectively. Eighty-eight (17%) were +LSTV. Safe zone size depended on gender, number of neuroforamen in -LSTV sacra and presence of LSTV (p < 0.001) but not on the uni- or bilateral nature of the LSTV. 17% of -LSTV sacra were below the safety threshold in S1, 27% in S2, whereas 3% of +LSTV sacra were below in S1, 74% in S2. Of -LSTV sacra that cannot take an S1 screw safely, 77% can do so in S2, leaving only 4% of sacra that cannot accommodate a screw safely in either upper segment. The results demonstrate a predictable pattern of safe zone size based on gender and sacral segmentation variations.

Analysis of the orthopedic in-training examination (OITE) musculoskeletal trauma questions

OBJECTIVES

Residency program directors are responsible for providing assessment and feedback about resident performance and for developing a comprehensive resident curriculum in orthopedic surgery. One measure of resident knowledge is the Orthopedic In-Training Examination (OITE). Scores of the OITE examination have been found to correlate with the American Board of Orthopedic Surgery Part 1 Certifying Examination. The purpose of this study was to identify commonly tested orthopedic trauma topics, the taxonomic distribution of questions, and literature references in the OITE to aid curriculum development and individual test preparation.

METHODS

The musculoskeletal trauma-related questions on the OITE during a 5-year period (2004-2008) were reviewed, and the number of questions, topics, taxonomic classification, and educational references associated with each question were analyzed.

RESULTS

Nearly 30% of questions each year consist of musculoskeletal trauma-related topics. Femur, tibia, and hip fractures were the most commonly tested topics. The majority (65.6%) of musculoskeletal trauma questions tested recall of specific facts. Examiners referenced primary literature sources (74.9%) more than textbooks (25.1%). The Journal of Bone and Joint Surgery (American) and the Journal of Orthopaedic Trauma were cited most, accounting for 44.3% of all journal references. Forty-seven percent of the primary references were published within 5 years of the test administration.

CONCLUSIONS

One method for assessing orthopedic knowledge is the OITE examination. Longitudinal analysis of trauma-related questions shows a consistent pattern of both topics and primary literature citation. This information may be used to help guide structured review for future OITE examinations and develop an orthopedic trauma curriculum for a residency program.

Patterns of acetabular femoral head coverage

The size and shape of the acetabulum and of the femoral head influence the injury tolerance of the hip joint. The aim of this study is to quantify changes in acetabular cup geometry that occur with age, gender, height, and weight. Anonymized computed tomography (CT) scans of 1,150 individuals 16+ years of age, both with and without hip trauma, were used to describe the acetabular rim with 100 equally spaced points. Bilateral measurements were taken on uninjured patients, while only the uninjured side was valuated in those with hip trauma. Multinomial logistic regression found that after controlling for age, height, weight, and gender, each 1 degree decrease in acetabular anteversion angle (AAA) corresponded to an 8 percent increase in fracture likelihood (p<0.001). Age, weight, and gender were found to influence anteversion angle significantly, with each 10 years in age increasing AAA by 1.07 degrees, each 10 kg of weight decreasing AAA by 0.45 degrees, and being female resulting in 1.42 degrees greater AAA than males. Height was not found to relate significantly to AAA after other anthropometric factors were controlled for. Height, age, and weight, however, correlated with femoral head radius, thus establishing a relationship with acetabular rim size independent of rim shape. A parametric model of the 3D acetabular rim landmark points is reported, allowing for the creation of individualized acetabular geometry for any given age, gender, height, and weight. A custom-built tool to produce such geometry programmatically is also provided.

Do higher hospital-wide nurse staffing levels reduce in-hospital mortality in elderly patients with hip fractures: a pilot study

BACKGROUND

There is increasing recognition that lower nurse staffing levels are associated with higher morbidity and mortality among medical and surgical patients. The degree to which this applies to elderly patients with hip fractures is unclear.

QUESTIONS/PURPOSES

We conducted a pilot study using administrative data as an initial step in investigating the relationship between nurse staffing levels and in-hospital mortality among elderly patients with hip fractures.

PATIENTS AND METHODS

We retrospectively reviewed administrative data for 13,343 patients 65 years or older with a primary diagnosis of hip fracture admitted to 39 Michigan hospitals between 2003 and 2006. We used logistic regression to calculate the change in predicted probability of in-hospital death conferred by differences in the hospitals' overall number of full-time equivalent registered nursing staff (FTE-RN) per patient day. Regression models controlled for patient age, gender, and comorbid conditions; hospital characteristics including teaching status, hip fracture volume, and income/racial composition of the hospital's zip code; and seasonal influenza.

RESULTS

We found an association between hospital-wide nurse staffing levels and in-hospital mortality among patients with hip fractures. The odds of in-hospital mortality decreased by 0.16 for every additional FTE-RN added per patient day, even after controlling for covariates. This association suggests the absolute risk of mortality increases by 0.35 percentage points for every one unit decrease of FTE-RN per patient day, a 16% increase in the risk of death.

CONCLUSIONS

Decreased hospital-wide nurse staffing levels are associated with increased in-hospital mortality among patients admitted with hip fractures. These observations indicate the need for further studies to characterize this relationship for staffing of units caring for patients with hip fractures.

LEVEL OF EVIDENCE

Level III, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

Indometacin as prophylaxis for heterotopic ossification after the operative treatment of fractures of the acetabulum

Our study was designed to compare the effect of indometacin with that of a placebo in reducing the incidence of heterotopic ossification in a prospective, randomised trial. A total of 121 patients with displaced fractures of the acetabulum treated by operation through a Kocher-Langenbeck approach was randomised to receive either indometacin (75 mg) sustained release, or a placebo once daily for six weeks. The extent of heterotopic ossification was evaluated on plain radiographs three months after operation. Significant ossification of Brooker grade III to IV occurred in nine of 59 patients (15.2%) in the indometacin group and 12 of 62 (19.4%) receiving the placebo. We were unable to demonstrate a statistically significant reduction in the incidence of severe heterotopic ossification with the use of indometacin when compared with a placebo (p = 0.722). Based on these results we cannot recommend the routine use of indometacin for prophylaxis against heterotopic ossification after isolated fractures of the acetabulum.

Delayed unions of the tibia

Delayed union of the tibia represents a diverse group of clinical problems that can at times be challenging for even the most experienced surgeon to treat. Early recognition and treatment can help patients avoid prolonged periods of pain and disability. Many factors have been associated with delayed union or nonunion; most of these factors are dictated by the injury and patient factors but others are within the surgeon's control. Although high rates of union are obtained in many series of tibial fractures using simple treatment methods, nonunion is seen by all practitioners treating tibial fractures. Early intervention to prevent nonunion seems to be in the best interest of patients and surgeons. Treatment must take into account the biologic and mechanical factors contributing to delay in fracture union.

Operative treatment of unstable pediatric pelvis and acetabular fractures

The management of unstable pediatric pelvic and acetabular fractures continues to be controversial. Recent reports have suggested that closed management of unstable pelvic and acetabular fractures can result in significant long-term morbidity. The purpose of this study was to evaluate the results of operative stabilization of unstable pelvic and acetabular fractures in children and adolescents. Eighteen patients less than 16 years of age with unstable pelvic and acetabular fractures were treated operatively over a 7-year period. Fracture healing, time to union, complications, and functional outcome were assessed. All fractures healed by 10 weeks. No patients suffered wound complications, infection, or growth arrest at an average follow-up of 30 months. These results support operative fixation of unstable pediatric pelvic and acetabular fractures to restore pelvic symmetry and periarticular anatomy. Favorable clinical results can be achieved with a low incidence of complications.

Pelvic fracture patterns and their corresponding angiographic sources of hemorrhage

The association between pelvic arterial injuries and associated fracture patterns has been investigated directly in a post mortem study and indirectly in an earlier clinical study evaluating an overall management approach to pelvic fractures. One previous report has correlated the angiographic findings of a group of patients with pelvic ring disruptions. The authors' study was designed to further define the anatomic sites of hemorrhage associated with specific pelvic ring injury patterns and evaluate patient survival in each of these groups.

The tolerance of the human hip to dynamic knee loading

Based on an analysis of the National Automotive Sampling System (NASS) database from calendar years 1995-2000, over 30,000 fractures and dislocations of the knee-thigh-hip (KTH) complex occur in frontal motor-vehicle crashes each year in the United States. This analysis also shows that the risk of hip injury is generally higher than the risks of knee and thigh injuries in frontal crashes, that hip injuries are occurring to adult occupants of all ages, and that most hip injuries occur at crash severities that are equal to, or less than, those used in FMVSS 208 and NCAP testing. Because previous biomechanical research produced mostly knee or distal femur injuries, and because knee and femur injuries were frequently documented in early crash investigation data, the femur has traditionally been viewed as the weakest part of the KTH complex. However, the relative risk of hip injuries to the risks of knee and thigh injuries in frontal crashes of late-model vehicles suggests that this may not be the case. This study investigated the frontal-impact fracture tolerance of the hip in nineteen tests performed on the KTH complexes from sixteen unembalmed human cadavers. In each test, the pelvis was rigidly fixed by gripping the iliac wings with the thigh-to-pelvis angle set to correspond to a standard automotive-seated posture. A dynamic load was applied to the knee along the axis of the femur at loading rates that are representative of knee-to-knee bolster impacts in frontal crashes. Rigidly fixing the pelvis minimizes inertial effects along the KTH complex, which results in similar force levels along the KTH complex. Consequently, in these tests, the weakest part of the KTH complex failed first. All seventeen fixed pelvis tests that produced usable data resulted in acetabular fractures at an average applied force of 5.70 kN (sd = 1.38 kN). The lack of injuries to the femoral shaft and distal femur in these tests indicates that the tolerance of the hip is less than that of the femur under frontal-impact loading. To further explore the tolerance of the femur relative to the hip, thirteen uninjured knee/femur specimens from seven cadavers previously used in hip tolerance tests were dynamically loaded. In these tests, the head of the femur was supported in a fixed "acetabular cup" to minimize inertial effects, and load was applied at the knee along the axis of the femur. All of these tests resulted in femoral neck fractures. Two tests also resulted in fractures to the femoral shaft. The average tolerance of the femoral neck from these tests is 7.59 kN (sd = 1.58 kN), which is significantly higher (p < 0.05) than the tolerance of the acetabulum. These results suggest that the mid and distal portions of the femur have a higher tolerance under these loading conditions than the pelvic and femoral portions of the hip.

Increased distraction rates influence precursor tissue composition without affecting bone regeneration

The effect of increased distraction rate on bony tissue differentiation was studied using a paired bilateral model of rat femur lengthening. After a 6-day latency period, one randomly selected femur for each rat was distracted at 0.5 mm/day (normal rate) for 12 days, and the contralateral femur was distracted at 1.5 mm/day (increased rate) for 4 days. Femoral lengthening for each side was 6.0 mm, leaving the increased rate leg with an extra 8 days of consolidation compared with the normal rate limb. Group I rats (n = 9) were killed at day 18 postsurgery and analyzed for cartilage tissue composition and distribution. Group II rats (n = 7) were killed on day 36 postsurgery and analyzed by three-dimensional microcomputed tomography (MCT) for changes in new bone volume. Digital color analysis of slides stained with type II collagen antibody showed increases in cartilaginous tissue formation on the increased rate side (1.51 mm2 vs. 0.83 mm2; p = 0.10). No differences in new bone volume were detected between increased rate limbs and their contralateral controls (46.13 mm3 vs. 42.69 mm3; p = 0.63). These findings suggest that intermediate distraction rates may influence precursor tissue composition without affecting the final amount of new bone formed. Because damage to the tissue was not detected at either time point, these changes in chondrogenesis may reflect sensitivity of the pluripotential gap tissue to tension accumulation during lengthening. Future work with this in vivo model is focused on improving our understanding of the mechanisms behind this strain sensitivity.

Success of exchange reamed intramedullary nailing for femoral shaft nonunion or delayed union

OBJECTIVES

To investigate the success of exchange reamed femoral nailing in the treatment of femoral nonunion after intramedullary (IM) nailing, and to analyze factors that may contribute to failure of exchange reamed femoral nailing.

DESIGN

Retrospective consecutive clinical series.

SETTING

Level I trauma center and tertiary university hospital.

PATIENTS

Twenty-three patients were identified whose radiographs failed to show progression of healing for four months after treatment with a reamed IM femoral nail. Nineteen patients had undergone primary IM nailing of an acute femoral shaft fracture, one patient had been converted to an IM nail after initially being treated in an external fixator, and three patients had previously undergone an unsuccessful exchange reamed nailing.

INTERVENTION

All patients were treated by exchange reamed femoral nailing. The diameter of the new nail was one to three millimeters larger than that of the previous nail (the majority were two millimeters larger). The intramedullary canal was overreamed by one millimeter more than the diameter of the nail. Most of the nails were statically locked, and care was taken to avoid distraction of the nonunion site by reverse impaction after distal interlocking was performed or by applying compression with a femoral distractor.

MAIN OUTCOME MEASUREMENTS

Radiographic evaluation of union was determined by the presence of healing on at least three of four cortices. Factors reviewed included the patient's age, smoking history, mechanism of injury, associated injuries, whether the initial fracture was open or closed, the pattern and location of the fracture, the type of nonunion, the increase in nail diameter, whether the nail was dynamically or statically locked, and the results of any intraoperative cultures.

RESULTS

Tobacco use was found to have a detrimental impact on the success of exchange reamed nailing. All eight of the nonsmokers healed after exchange reamed nailing, whereas only ten of the fifteen smokers (66.7 percent) healed after exchange reamed nailing. Overall, exchange reamed femoral nailing was successful in eighteen cases (78.3 percent). Three patients achieved union with additional procedures. Intramedullary cultures were positive in five cases; all of these achieved successful union.

CONCLUSIONS

Exchange reamed nailing remains the treatment of choice for most femoral diaphyseal nonunions. Exchange reamed IM nailing has low morbidity, may obviate the need for additional bone grafting, and allows full weight-bearing and active rehabilitation. Tobacco use appears to have an adverse effect on nonunion healing after exchange reamed femoral nailing.

Temporal and spatial characterization of regenerate bone in the lengthened rabbit tibia

A rabbit model of bilateral tibial lengthening was used to investigate temporal and spatial changes in new bone volume and architecture during regenerate bone formation. Tibiae were lengthened 9.0 mm at 0.75 mm/day after a 6-day latency period. Animals were euthanized at four time points, and new bone volume and architecture within the distraction gap were assessed by microcomputed tomography and histomorphometry. New bone formation began before day 18 postsurgery and increased markedly between day 18 (completion of distraction) and day 24. This period of high bone formation activity might therefore be optimal for biologic and mechanical interventions aimed at enhancing bone regeneration. Regions of both endochondral and intramembranous bone formation were observed throughout the consolidation period. Significant increases in bone volume fraction were observed early in the consolidation period and were attributed to significant increases in trabecular thickness. This suggested that increased mineral density in the gap tissue with time was a consequence of increased osteoblast activity and associated trabecular thickening. New bone formation was shown to be highly oriented toward the distraction axis throughout lengthening. More bone formed consistently in lateral and proximal regions of the distraction gap, perhaps due to improved blood supply or progenitor cell availability in these areas. No differences in trabecular architecture were detected between regions having more or less bone volume, suggesting that bony tissue differentiation in all regions of the distraction gap was similar. Homotypical variations in measures of bone architecture were small; thus, these outcome variables seem appropriate for determining the effects of biological and mechanical interventions on bone regeneration in this animal model.

Marrow-derived progenitor cell injections enhance new bone formation during distraction

Bilateral femoral distraction was performed in rats to investigate whether injections of marrow-derived mesenchymal progenitor cells could be used to facilitate new bone formation. The cells were isolated from whole marrow of 2-6-month-old Sprague-Dawley rats. One-year-old recipient Sprague-Dawley rats were divided into five experimental groups. Rats in groups I, II, and III received injections of mesenchymal progenitor cells on days 6 (beginning), 12 (middle), and 18 (end of distraction) after surgery, respectively. Those in group IV received injections of serum and carrier gel alone, and those in group V received no injections. Distraction zones were harvested at 36 days and analyzed for new bone volume within the distraction gap by three-dimensional microcomputed tomography. Significant increases in new bone volume were observed for femora injected with marrow-derived progenitor cells compared with contralateral femora and controls (no injection). The timing of the cell injections appeared to have no effect on the experimental outcome. Histologic analyses demonstrated active formation of new trabecular bone with marked osteoblastic activity and osteoid production. No qualitative differences in histologic appearances of new bone among rats in any of the five groups were seen. The results of in vitro lysis assays indicated that donor and recipient rats were not completely syngenic, leaving some doubt as to the reasons for observed increases in new bone formation. Future work will focus on attempting to repeat these experiments in a fully syngenic rat model. This rat distraction model can be used to explore the molecular and cellular behavior of these progenitor cells in a clinically relevant in vivo environment.

Severity of injuries associated with traumatic hip dislocation as a result of motor vehicle collisions

BACKGROUND

Previous reports have shown a high rate of associated injuries in patients who sustain traumatic hip dislocation. Since these earlier reports appeared, improvements have been made in passenger safety systems and the rate of restraint usage has increased. The purpose of this study was to review the associated injuries present in a current series of patients who sustained traumatic hip dislocation as a result of motor vehicle collisions.

METHODS

We retrospectively reviewed our trauma registry and identified 66 patients who sustained traumatic hip dislocation as a result of motor vehicle collisions. Thirty patients (45%) were restrained and 36 (55%) were unrestrained. Airbags were known to have deployed in 14 cases.

RESULTS

The incidence of associated injuries was 95% (63 patients). Orthopedic injuries alone were seen in 22 patients (33%), whereas associated injuries were seen in 44 patients (67%). Abdominal injuries were present in 10 patients (15%), thoracic injuries were present in 14 patients (21%), closed head injuries were present in 16 patients (24%), and craniofacial injuries were present in 14 patients (21%). Acetabular fractures were seen in 46 patients (70%), femoral head fractures were identified in 9 patients (14%), and other extremity fractures occurred in 26 patients (39%). The average Injury Severity Score for all patients was 17.4 (range, 9-59). The average Injury Severity Score of the restrained patients was not statistically different from that of the unrestrained patients (p = 0.491).

CONCLUSION

Although improvements in automotive safety features and restraint usage have occurred since previous reports appeared, there continues to be a high rate of severe injuries associated with traumatic hip dislocation that occur in motor vehicle collisions. We believe that all patients who sustain traumatic hip dislocation warrant a general surgery trauma evaluation to rule out any potential associated injuries.

Reduced gap strains induce changes in bone regeneration during distraction

A bilateral New Zealand white rabbit model of distraction osteogenesis (DO) was used to investigate the relationship between strain environment and bone regeneration during limb lengthening. In seven (n = 7) rabbits, a stiffener was applied to the fixator on one side to reduce strains within the gap tissue after lengthening was completed. Animals were euthanized six days later and their distraction zones were harvested and analyzed for changes in new bone volume and architecture. Nonlinear finite element analyses (FEA) were performed to predict changes in the gap strain environment. FEA results predicted a nearly uniform sevenfold decrease in average strain measures within the distraction zone. No change in total average new bone volume and significant decreases in both bone volume fraction (BV/TV) and trabecular thickness (Tb.Th) were observed in tibiae in which gap strains were reduced experimentally, compared to contralateral controls. These results suggest that fixator stiffening influenced the architecture but not the amount of newly formed bone. This animal model of distraction might be used to study the mechanisms by which strain fields affect events in bone repair and regeneration, such as cell proliferation, precursor tissue differentiation, and altered growth factor and nutrient delivery to tissues.

Viscoelastic characterization of mesenchymal gap tissue and consequences for tension accumulation during distraction

Nonlinear viscoelastic analysis was used to characterize the time-dependent behavior of mesenchymal gap tissue generated during distraction osteogenesis. Six (n = 6) lengthened tibiae were harvested from New Zealand white rabbits at 18 days. This gap tissue was subjected to a series of step displacement tests of increasing magnitude, and force relaxation behavior was monitored. Isochrones in stress-strain space were fit to odd cubic functions of strain. An analytic expression, linear in both e and e3, was developed to predict stress accumulation within the gap tissue as a function of time during distraction. Stress relaxation functions were described well by two-term Prony series. The two time constants determined from mechanical testing results were consistent, suggesting the presence of two fundamental physiologic relaxation processes. Gap tissue stresses were predicted to rise considerably during early stages of lengthening when distraction magnitudes exceeded the clinical norm of 0.25 mm. These differences in tension accumulation were less pronounced by the time lengthening was completed. Specifically, these results may in part explain clinical observations of decreased bone regeneration and altered tissue proliferation and differentiation at higher distraction rates. More generally, this work provides a framework for the rigorous characterization of the viscoelastic properties of biologic tissues ordinarily exposed to step strains.

Bone regeneration and fracture healing. Experience with distraction osteogenesis model

The relation between physical forces and the processes of bone regeneration and healing remains incompletely understood. Gaps in understanding of these processes stem in part from models that produce inadequate amounts of new bone for study. Bone created through the use of distraction osteogenesis provides an attractive substrate for the study of mechanical forces and their effects on bone formation because this technique produces large volumes of new bone in a controlled fashion. The optimal mechanical environment in which bone formation occurs clinically has not been fully determined. In laboratory studies, however, the mechanical environment can be manipulated, and resultant changes in bone formation can be measured. To investigate how changes in strain environment influence patterns of bone formation, a bilateral New Zealand White rabbit model of bilateral distraction osteogensis was implemented. When a stiffener was applied to the external distractor, computation analyses predicted a sevenfold to eightfold decrease in all strain measures. These reductions in gap strains appeared to induce significant decreases in bone volume fraction and mean trabecular thickness. When osteotomies were created at a 30 degrees angle to the bony axis to generate more shear within the gap tissue, changes in the distribution of gap strains and resultant new bone architecture were observed. Specific correlations between changes in tissue level strains and the pattern of bone regeneration were seen in both experiments. These results provide direct in vivo evidence that pluripotential gap tissues are sensitive to their physical surroundings. Mechanisms responsible for this sensitivity might include vascularity, stem cell supply, and scaffolding architecture. The process of bone formation in distraction osteogenesis appears to be related to bone formation processes associated with more common conditions. The distraction osteogenesis model described suggests a mechanism for bone formation that seems applicable to other more common processes associated with bone formation, including fracture healing and impaired fracture healing.

Evaluation of the mechanical environment during distraction osteogenesis

Physical forces have been hypothesized to direct the process of bone regeneration during distraction osteogenesis. However, despite significant clinical experience, relatively little is known about how the mechanics of distraction influence bone formation. This study investigated net fixator forces and strains in the distraction callus during bilateral lengthening of tibiae in New Zealand White rabbits. Distractions yielded a classic viscoelastic response with a sharp increase in fixator force, followed immediately by significant relaxation. Tension acting on mesenchymal gap tissue caused by distraction was estimated to reach more than 30 N by the time full lengthening was achieved. Average maximum cyclic strains within the distraction zone during ambulation were estimated to be 14% to 15% and supported by the results of fluoroscopic imaging. Paradigms for fracture healing have hypothesized that such strains are incompatible with new bone formation. The documented clinical success of distraction osteogenesis at stimulating large volumes of new bone suggests that other mechanisms that warrant additional investigation may be at work during distraction.

Hip screw augmentation with an in situ-setting calcium phosphate cement: an in vitro biomechanical analysis

OBJECTIVES/HYPOTHESIS

This study was performed to determine whether a new, in situ-setting calcium phosphate cement would have sufficient mechanical integrity to reinforce compression screw fixation of unstable intertrochanteric fractures. We compared the cut-out resistance of screws augmented with calcium phosphate cement to the cut-out resistance of screws augmented with polymethylmethacrylate (PMMA). We used PMMA as the standard for comparison because it is currently used clinically. Our hypothesis was that initial fixation strength with PMMA and calcium phosphate cement augmentation would not be significantly different from one another.

STUDY DESIGN

Cut-out testing of compression hip screws in paired human cadaveric proximal femurs was performed before and after augmentation with PMMA or calcium phosphate cement. Bilateral testing was performed to allow pairwise comparisons of the materials used for augmentation, and repeated testing was done to provide an internal control for the effects of bone quality. The initial fixation of screws augmented with calcium phosphate cement was compared with that of screws augmented with PMMA.

METHODS

Ten paired human femurs (mean age, 75 +/- 9.2 years) were implanted with Richards AMBI compression hip screws. Basicervical osteotomies were then performed, yielding isolated proximal fragments for mechanical testing. Preaugmentation cut-out tests were performed under displacement control, with cut-out continuing to five millimeters at two millimeters per second. The screws were then removed, and the screw tracks were filled with 2.0 cubic centimeters of PMMA (one side) or calcium phosphate cement (contralateral side). After augmentation, the screws were reinserted and the cements were allowed to harden for twenty-four hours. Postaugmentation testing followed the protocols for preaugmentation testing, and the initial fixation strength of screws augmented with calcium phosphate cement was compared with the initial fixation strength of screws augmented with PMMA using a two-way repeated measures analysis of variance.

RESULTS

The cut-out behavior of screws augmented with calcium phosphate cement was not significantly different from the cut-out behavior of screws augmented with PMMA. With calcium phosphate cement, yield strength increased by 15.8 percent (from 1,354 +/- 632 newtons to 1,568 +/- 320 newtons); with PMMA, the yield strength increased by 26.8 percent (from 1,477 +/- 526 newtons to 1,834 +/- 225 newtons). However, only the increase with PMMA augmentation was significant at p < 0.05). The energy to yield increased significantly (41 percent, p < 0.05) with both types of augmentation (from 2,399 +/- 1,186 newton-millimeters to 3,378 +/- 857 newton-millimeters for calcium phosphate cement, and from 2,635 +/- 1,113 newton-millimeters to 3,741 +/- 426 newton-millimeters for PMMA), whereas the stiffness increased only slightly with PMMA augmentation (6.2 percent, from 481 +/- 180 newtons per millimeter to 511 +/- 92 newtons per millimeter) and fell slightly with calcium phosphate cement augmentation (10 percent, from 457 +/- 201 newtons per millimeter to 411 +/- 663 newtons per millimeter).

CONCLUSIONS

The in situ-setting calcium phosphate cement investigated in this study compared favorably with PMMA in a single-cycle cut-out test of augmented compression hip screws in senile trabecular bone. Our results suggest that these materials may have promise as substitutes for PMMA in the salvage of compression hip screw fixation in elderly osteopenic patients with complex intertrochanteric fractures and that further study of their use in this application is warranted.

Extracorporeal life support for patients with significant orthopaedic trauma

Extracorporeal life support is a therapeutic modality that can provide cardiorespiratory support for multiply injured patients. Fourteen patients with multiple trauma who sustained pelvic or long bone fractures were referred for treatment with extracorporeal life support at the University of Michigan Medical Center. All patients were considered morlbund secondary to their pulmonary injury. Six of the 14 patients had bilateral pulmonary contusions. The mean Injury Severity Score was 19. Twelve of the 14 patients had femoral or pelvic fractures or both. Eight patients had orthopaedic injuries initially treated with traction. The most common complication during extracorporeal life support management was bleeding, which occurred in eight of 14 patients. Eight of the 14 patients survived. Seven of eight patients with less than 6 days of mechanical ventilation before initiation of extracorporeal life support survived. Only one of six patients with six or more days of mechanical ventilation before initiation of extracorporeal life support survived. Patients with significant orthopaedic trauma and severe pulmonary compromise have an extremely high mortality risk. Appropriate aggressive fracture management remains the most important intervention to decrease the risk of pulmonary compromise. Early initiation of extracorporeal life support can be an additional lifesaving intervention in select patients with orthopaedic trauma who have respiratory failure refractory to conventional mechanical ventilation.

Autogenous iliac crest bone graft. Complications and functional assessment

Functional outcomes and complications experienced by adult patients who underwent iliac crest bone grafting were evaluated to assess the effect of bone grafts on patient function. In addition to retrospective chart reviews, patients completed the Sickness Impact Profile and a detailed questionnaire on pain. One hundred ninety-two patients met study inclusion criteria. Major complications were recorded in four (2.4%) patients in whom infections developed requiring readmission. Thirty-seven (21.8%) patients had minor complications. One hundred nineteen of 170 patients were available for followup; of these 119 patients, 87 (73.1%) returned completed questionnaires. Thirty-three of 87 (37.9%) patients reported pain 6 months postoperatively. The incidence of pain decreased with time, with 16 of 87 (18.7%) patients continuing to report pain more than 2 years postoperatively. Proportionately more spine patients reported pain at all time points. The mean Sickness Impact Profile score for patients completing questionnaires was nine, suggesting most patients were functioning well 2 years postoperatively. The morbidity of iliac crest grafting remains substantial. Pain symptoms in this study sample seemed to last longer in more patients than earlier series have indicated. Minimizing muscle dissection around donor sites and the advent of bone graft substitutes may help alleviate these problems.

Comminuted fractures of the posterior wall of the acetabulum. A biomechanical evaluation of fixation methods

Reproducible simple fractures and osteotomies of the posterior wall of the acetabulum were created in twenty paired hemipelves from fresh human cadavera. Comminution was created with an additional fracture line that was either parallel (concentric comminution) or perpendicular (transverse comminution) to the posterior rim of the acetabulum. Under simulated weight-bearing, the stiffness of fixation of the transversely comminuted fractures that had been achieved with use of a reconstruction plate and screws was significantly higher than that achieved with fixation with screws alone (p < 0.05). The load to failure of the fixation of transversely comminuted fractures treated with a reconstruction plate and screws was also significantly higher than that of fixation of such fractures with screws alone (p = 0.05). The load to failure of the fixation of concentrically comminuted fractures was significantly higher when a reconstruction plate and accessory spring plates had been used than when a reconstruction plate alone had been employed (p < 0.05).

The use of ultrasound mean acoustic attenuation to quantify bone formation during distraction osteogenesis performed by the Ilizarov method. Preliminary results in five dogs

RATIONALE AND OBJECTIVES

Management of distraction during Ilizarov limb lengthening remains primarily clinical and empirical. Estimates of tissue acoustic attenuation were evaluated for their ability to quantify bone formation within the distraction gap.

METHODS

Five dogs had tibias lengthened by the method of Ilizarov. Mean acoustic attenuation measurements at multiple positions across the distraction gap were compared with corresponding x-ray computed tomography attenuation measurements.

RESULTS

Computed tomography and ultrasound attenuation displayed similar quantitative behavior across the gap. Linear correlation between them ranged from R2 = .878 to R2 = .131. Fibrous interzone width estimates based on computed tomography and ultrasound attenuation measurements were correlated, based on our preliminary data with R2 = .519. These estimates are independent of the width of distraction.

CONCLUSIONS

Ultrasound parallels computed tomography as a measure of bone formation within the distraction gap. Future studies are needed to improve acoustic attenuation data acquisition techniques and to evaluate their potential as a tool for optimizing early distraction rates in patients at risk for rate-related complications.

Mortality after fracture of the hip in patients who have end-stage renal disease

Thirteen fractures of the hip in twelve patients who had end-stage renal disease were treated over a ten-year period; these injuries included one intertrochanteric fracture, seven non-displaced fractures of the femoral neck, and five displaced fractures of the femoral neck. Twelve of the thirteen fractures were treated with an operation. Six patients (who had a total of six fractures) died within one year after the fracture. Two patients died as the result of sepsis related to the wound; the other four deaths were not directly related to the operation. Although the mortality rate in this group of patients was higher than that in a group of matched patients who had a fracture of the hip but who did not have end-stage renal disease, we were not able to demonstrate that this difference was significant, perhaps because of the small size of the sample. The mortality rate in these twelve patients was significantly higher, however, than that in matched patients who had end-stage renal disease but who did not have a fracture of the hip (p = 0.01).

Compartment syndrome complicating tibial tubercle avulsion

Avulsion of the tibial tubercle is an uncommon physeal injury. Complications from this fracture are infrequent. Adolescent boys developed compartment syndrome after tibial tubercle avulsion. Injury to the soft tissue surrounding the tibial tubercle avulsion may be more extensive than is usually appreciated. The anatomy of the proximal tibia and the tibial tubercle with nearby branches of the anterior tibial recurrent artery suggest a predisposing factor for the development of compartment syndrome. Compartment syndrome should be added to the list of possible complications of tibial tubercle avulsion fractures.

Physical therapy management of patients undergoing limb lengthening by distraction osteogenesis

Limb lengthening by distraction osteogenesis and external fixation is used increasingly in the United States for a variety of orthopaedic conditions. Maintenance of joint motion, critical for successful outcomes, can be difficult to achieve. The rate of growth needed for distraction osteogenesis is faster than that of normal growing bone. Histogenesis of soft tissues must also occur to maintain the motion in joints above and below the limb being lengthened. Physical therapists in patients' home communities need to be knowledgeable about the aggressive management needed to prevent the loss of joint motion. This article introduces physical therapists to a commonly used external fixator, the procedure of distraction osteogenesis, and the role of functional loading. To assist in treatment planning, a physical therapy management plan is presented. Two case examples illustrate how therapists can assess a patient's status relative to the goals in the management plan and determine intervention priorities.

Interlocking intramedullary nails. An improved method of screw placement combining image intensification and laser light

Insertion of distal interlocking screws in femoral nails can be technically demanding and may entail substantial exposure. A method of insertion of femoral interlocking screws that uses a laser guiding system in addition to the standard image intensifier was used in an attempt to improve the accuracy of distal screw placement and to limit radiation exposure. Using this technique, 97% of the distal femoral drill holes attempted were successfully made with the first pass of a drill. Little or no resistance to the drill was met from contacting the femoral nail. Average fluoroscopy time was 0.4 minute. Laser-assisted screw placement requires relatively inexpensive modifications of existing equipment and is easy to master. Compared with the more commonly used freehand method, laser-assisted screw placement appears to offer a reduction in the amount of time and radiation exposure required to insert distal interlocking femoral screws.

Deep-vein thrombosis after fracture of the pelvis: assessment with serial duplex-ultrasound screening

Sixty patients who had had a major fracture of the pelvis and were in stable condition on the orthopaedic ward three to five days after the injury were tested serially with duplex ultrasound, beginning approximately seven days after the injury, in order to determine the incidence of deep-vein thrombosis. Contrast venography was performed to confirm all positive non-invasive studies. Deep-vein thrombosis developed in eight patients (approximately 15 per cent). The thrombosis was in the popliteal or a more proximal vein in six of the eight patients, whereas in two it was distal to the popliteal vein. In four patients, evidence of thrombosis developed after one or more normal duplex-ultrasound studies. In one patient, symptoms that were suggestive of deep-vein thrombosis developed fifty-two days after the injury (four days after the fourth normal duplex-ultrasound examination), and ascending venography was entirely normal. Another patient had a pulmonary embolus fifteen days after the injury, and on the same day a duplex-ultrasound study was positive for thrombosis. During six weeks of follow-up after discharge from the hospital, symptoms of deep-vein thrombosis or pulmonary embolism did not develop in any patient in whom serial duplex-ultrasound studies had been negative.

Complex acetabular fractures

Displaced acetabular fractures belonging to the associated fracture group described by Judet and Letournel present a formidable diagnostic and therapeutic challenge. Of 116 acetabular fractures, 31 had associated fracture types with follow-up evaluation of one year or longer. The patients' mean age was 30.7 years, their mean injury severity score was 15, and the average follow-up period was 21 months. Four patients had failed previous acetabular surgery. Operating time averaged 4.5 hours. Mean blood loss was 1150 cc. Clinical results were satisfactory in 77% of cases, with 11 excellent, 13 good, four fair, and three poor results. Complex acetabular fractures can be reduced by a combined anterior and posterior approach designed by the authors. This approach offers significant advantages for visualization and stabilization of these fractures. The combined approach is recommended for the surgeon who has mastered the single-approach techniques for standard, simple fracture patterns.

Intraoperative autologous transfusion in orthopaedic patients

The cases of 175 consecutive patients who had intraoperative autologous transfusion during revision total hip arthroplasty, an elective operation on the spine, repair of trauma to the spine, or open reduction of a fracture of the acetabulum were reviewed to evaluate the applicability of this technique in orthopaedic operations. A separate group of forty-one consecutive patients who had open reduction of a fracture of the acetabulum or the spine before the introduction of the autotransfuser was reviewed and compared with the group that had autotransfusion. An autologous blood predeposit program was used for twenty-five of fifty-two patients who had a procedure on the hip and for fifty-one of fifty-five patients who had an elective procedure on the spine. The mean rate of red blood-cell salvage using the autotransfuser was 60 per cent over-all. The mean transfusion requirements were significantly less (p less than 0.001) in all groups of patients in whom the autotransfuser was used. Use of the autotransfuser reduced the mean requirement for banked blood in patients who had a fracture of the acetabulum from 3.8 to 2.3 units per patient, and significantly reduced the mean need for banked blood in individuals who had trauma to the spine from 2.7 to 1.8 units per patient (p less than 0.01). The use of prebanked autologous blood further reduced the mean requirement for homologous blood from 2.4 to 0.8 unit per patient in those who had revision total hip arthroplasty (p less than 0.005), and from 3.6 to 0.4 unit per patient in those who had an elective procedure on the spine (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Prolonged suppression of infection in total hip arthroplasty

Nineteen periprosthetic infections after total hip arthroplasty were treated with prolonged suppressive antibiotics without removing the components. In 11, antibiotic therapy was monitored with serum bactericidal titers. Eleven had incision and drainage. Indications included patients' refusal of removal or medical contraindications to surgery. Requirements included well-fixed components, highly sensitive organisms, and no systemic sepsis. The follow-up period averaged 4.1 years after treatment. Nine hips showed no deterioration. Seven prostheses failed, five with progressive hip sepsis. Three patients had increasing symptoms without prosthesis removal. Although two-stage reimplantation is preferred, suppressive antibiotics and prosthesis retention can succeed in some patients and may be considered in old, frail patients with an early infection caused by bacteria responsive to oral antibiotic therapy. Suppressive therapy may also be considered for an otherwise compliant patient who refuses removal of an infected prosthesis. The organism must be sensitive to oral antibiotics, and the patient must be tolerant of the antibiotics.

A critical analysis of mechanical factors correlated with bone remodeling following total elbow arthroplasty

Thirty elbows were critically reviewed for quantitative evidence of bone remodeling, with demonstrable bone remodeling noted in more than one half of the ulnae and humerii. Bone remodeling was analyzed statistically with independent variables of age, sex, handedness, diagnosis, implant design considerations, and implant alignment. Only implant design and alignment had a statistically significant impact on bone remodeling. Periarticular (zone 1) bone loss was statistically significantly correlated with a high percentage of diaphyseal medullary canal occupied by prosthesis, the presence of assymetric stem cortical contact, and lack of metaphyseal (zone 1) load transfer. Diaphyseal bone hypertrophy (zone 4) was statistically significantly correlated with a high percentage of diaphyseal medullary canal occupied by prosthesis (zone 4) and assymetric stem tip-to-cortical wall contact. Periarticular bone hypertrophy and diaphyseal bone atrophy did not occur. Fractures through the humeral condyles occurred in three elbows undergoing bone atrophy, but no implant loosening or failure could be correlated with bone remodeling. Bone remodeling does occur in a high percentage of stemmed elbow implants but to date has not been a factor in clinical failure.