Failure of tacrolimus to prevent aspirin-induced respiratory reactions in patients with aspirin-exacerbated respiratory disease

BACKGROUND

In patients with aspirin-exacerbated respiratory disease (AERD), pretreatment with asthma controller medications (leukotriene modifiers, inhaled or systemic corticosteroids, and salmeterol) partially modifies the severity of aspirin-induced asthmatic reactions.

OBJECTIVE

A recent study showed that pretreatment with tacrolimus completely prevented aspirin-induced respiratory reactions and might allow silent aspirin desensitization.

METHODS

Ten patients with rhinosinusitis, nasal polyps, and asthma had a history of asthma attacks after ingesting aspirin and nonsteroidal anti-inflammatory drugs. All underwent baseline oral aspirin challenges and had typical respiratory reactions. They were then randomized to receive tacrolimus (0.1 mg/kg weight; 8 patients) or placebo (2 patients) in a double-blind protocol before rechallenge with aspirin using the previous provoking dose of aspirin. In addition, respiratory reactions sustained by 50 consecutive patients with AERD during 2004 were recorded, analyzed, and compared with the tacrolimus/placebo-treated patients to determine whether there were any differences.

RESULTS

Tacrolimus pretreatment failed to block respiratory reactions to provoking doses of aspirin in 5 of 8 patients with AERD, and in the other 3 patients did not block higher doses of aspirin. The results of oral aspirin challenges in the control population of 50 patients were compared with either the baseline or postchallenge data from the tacrolimus-pretreated or placebo-pretreated patients with AERD, and there were no significant differences.

CONCLUSIONS

Use of tacrolimus as add-on pretreatment to prevent reactions to aspirin in patients with AERD or to achieve the goal of silent aspirin desensitization could not be accomplished.

Cause and Effect Analysis of Closed Claims in Obstetrics and Gynecology

BACKGROUND

Identifying the etiologies of real or perceived adverse clinical events and undesired outcomes is an important step in improving patient safety and reducing malpractice risks. Systematic analysis of obstetrics and gynecology-related risk management files allows a more complete examination of ways that human and systems factors may contribute to adverse events.

OBJECTIVE

To learn the medical complaints of patients who experienced apparent adverse events, the general causes of those adverse events, and the significant specific causal factors involved in obstetrics and gynecology-related risk management cases.

METHODS

This was a retrospective analysis of 90 consecutive obstetrics and gynecology-related internal review files opened by a medical center's risk managers between 1995 and 2001. Each file was analyzed to identify factors that may have contributed to or caused unanticipated adverse events. The main outcome was the pattern of contributing factors when they were aggregated into categories.

RESULTS

Fifty percent of cases were associated with inpatient obstetrics. Factors that may have contributed to adverse events were identified in 78% of cases, and most had more than one contributing factor. Thirty-one percent of adverse events were associated with apparent communication problems. Clinical performance issues were identified in 31% of cases, diagnostic issues in 18% of cases, and patient behavior contributed to 14% of adverse events.

CONCLUSION

Diagnostic, therapeutic, and communication issues were the most common factors identified. Although the generalizability of these data are unknown, all obstetrics and gynecology departments face multiple challenges in assuring consistent quality care. Analysis of claims files may help identify opportunities for improvement.

Cause-and-effect analysis of risk management files to assess patient care in the emergency department

OBJECTIVES

Identifying the etiologies of adverse outcomes is an important first step in improving patient safety and reducing malpractice risks. However, relatively little is known about the causes of emergency department-related adverse outcomes. The objective was to describe a method for identification of common causes of adverse outcomes in an emergency department. This methodology potentially can suggest ways to improve care and might provide a model for identification of factors associated with adverse outcomes.

METHODS

This was a retrospective analysis of 74 consecutive files opened by a malpractice insurer between 1995 and 2000. Each risk-management file was analyzed to identify potential causes of adverse outcomes. The main outcomes were rater-assigned codes for alleged problems with care (e.g., failures of communication or problems related to diagnosis).

RESULTS

About 50% of cases were related to injuries or abdominal complaints. A contributing cause was found in 92% of cases, and most had more than one contributing cause. The most frequent contributing categories included failure to diagnose (45%), supervision problems (31%), communication problems (30%), patient behavior (24%), administrative problems (20%), and documentation (20%). Specific relating factors within these categories, such as lack of timely resident supervision and failure to follow policies and procedures, were identified.

CONCLUSIONS

This project documented that an aggregate analysis of risk-management files has the potential to identify shared causes related to real or perceived adverse outcomes. Several potentially correctable systems problems were identified using this methodology. These simple, descriptive management tools may be useful in identifying issues for problem solving and can be easily learned by physicians and managers.

The role of the CD4 receptor versus HIV coreceptors in envelope-mediated apoptosis in peripheral blood mononuclear cells

We examined the role of CD4, CXCR4, and CCR5 in HIV envelope-mediated apoptosis by measuring the response of activated PBMCs to recombinant envelope proteins derived from CXCR4- and CCR5-utilizing viruses. Apoptosis of T cells was assessed by annexin-V staining and TdT-mediated dUTP-biotin nick-end labeling. Treatment of CCR5Delta32 homozygote PBMCs with a CCR5-specific envelope induced apoptosis in T cells, demonstrating that envelope--CD4 interactions are sufficient to induce apoptosis. However, a CXCR4-specific envelope induced higher levels of apoptosis than a CCR5-specific envelope, suggesting that envelope-mediated apoptosis can be enhanced by envelope--CXCR4 interactions. We conclude that envelope can induce apoptosis in T cells independently of the coreceptor specificity of a given envelope, or the expression profile of CXCR4 or CCR5 on a target cell. However, envelope--coreceptor interactions, and in particular, envelope--CXCR4 interactions, can contribute to this process.

Biomechanical analysis of clinical stability in the cervical spine

This study was undertaken because there is a dearth of objective information in the literature on the clinical instability of the cervical spine below C2. To our knowledge, it is the first biomechanical investigation designed to analyze clinical stability. We have carried out a quantitative analysis of the behavior of the spine as a function of the systematic destruction of various anatomic elements. Under controlled conditions designed to maintain the biological integrity of the specimens, 17 motion segments from 8 cervical spines were analyzed. The spines were studied with either flexion or extension simulated using physiologic loads. Some of the more important findings are: (1) In sectioning the ligaments, one observes small increments of change followed without warning by sudden, complete disruption of the spine; (2) Removal of the facets alters the motion segment such that in flexion, there is less angular displacement and more horizontal displacement; (3) The anterior ligaments contribute more to stability in extension than the posterior ligaments and in flexion, the converse is true; (4) The adult cervical spine is unstable, or on the brink of instability, when any of the following conditions are present: a) All the anterior or all the posterior elements are destroyed or unable to function. b) More than 3.5 mm horizontal displacement of one vertebra in relation to an adjacent vertebra measured on lateral roentgenograms (resting or flexion-extension). c) More than 11 degrees of rotation difference to that of either adjacent vertebra measured on a resting lateral or flexion-extension roentgenogram. These findings can be aptly applied to clinical situations and when instability as determined by the above criteria is present, surgical fusion or some other method to achieve stability should be seriously considered. Work is continuing on this problem as we do not consider this to be altogether complete or definitive. Hopefully, this initial study will stimulate further scientific and clinical investigations.

Exploring spatial patterns of mortality: the new atlas of United States mortality

The National Center for Health Statistics, CDC, has produced an Atlas of United States Mortality which includes maps of rates for the leading causes of death in the United States for the period 1988-1992. As part of this project, many aspects of statistical mapping have been re-examined to maximize the atlas's effectiveness in conveying accurate mortality patterns to epidemiologists and public health practitioners. Because recent cognitive research demonstrated that no one map style is optimal for answering many different map questions, maps and graphs of several different mortality statistics are included for each cause of death. New mixed effects models were developed to provide predicted rates and improved variance estimates. Results from these models were smoothed using a weighted head-banging algorithm to produce maps of general spatial trends free of background noise. Maps of White female lung cancer rates from the new atlas are presented here to illustrate how this innovative combination of maps and graphs permits greater exploration of the underlying mortality data than is possible from previous single-map atlas designs. Published in 1999 by John Wiley & Sons, Ltd. This article is a U.S. Government work and is in the public domain in the United States.

Justifications and needs for diversity in orthopaedics

America is founded on high humanitarian, democratic ideals. The historic facts of slavery, discrimination, and segregation challenge and taint these democratic principles. Although progress has been made, serious racial problems remain. In 1997, the United States had 474 active hate groups, up 20% from 1996. African American males who have the same education as white males doing the same work earn approximately 75% of what their white counterparts earn. America, as predicted by the Kerner Commission Report, is two societies: black and white, separate, and unequal. Some astonishing disparities in healthcare exist. Peer reviewed medical literature documents that African Americans have higher infant mortality rates, shorter life expectancies, fewer joint replacements, and more amputations than whites. Communications within a diverse group of students and teachers enriches the educational experience. The late Supreme Court Justice Lewis Powell, LLD, asserted that a medical student from a particular background may enrich classmates' understanding of people whose cultures are different from their own, and improve their ability to serve a heterogeneous patient population. Diversity on clinical teams can enhance rapport between patient and physician, and can diminish unthinking insults to patients, born of physician ethnic insensitivity. Healthcare facilities with diverse staffs are more likely than homogeneous facilities to attract and successfully serve the nation's diverse population. A University of California at Davis School of Medicine study showed that diversity can be achieved without compromising quality of patient care. Clinically and ideologically, diversity in orthopaedics is good for patients and for the country.

Compassionate patient care and personal survival in orthopaedics. A 35-year perspective

Orthopaedic surgeons can enjoy good patient and physician relationships and be happy in the work setting. Here's how. It is important to know oneself. Explore one's spirituality. Maintain humor, humility, and humanity. Make only original mistakes. Attend to one's mental health. Invest time, thought, and energy in interpersonal relationships with patients, colleagues, and loved ones. Apologize when one causes pain to patients or keeps them waiting. Treat them with respect and answer their questions. Educate patients, listen to them, serve them. Provide informed consent, identify congruent outcome goals for patient and surgeon. In surgery, let thought precede action. Plan the surgery, review the anatomy, avoid excessive force, triple-check the anatomy, and control the bleeding. Orchestrate the operating theater to manifest the values of patient care, excellent surgery, team spirit, and mutual respect. Maintain equanimity. Find things to enjoy at work every day, and then enjoy them. These suggestions may be discussed, refined, and learned. They may stimulate the generation of more and better ways than are presented in this article for the orthopaedist to help patients and be fulfilled in his or her work.

Role of IL-6 and TNF in thermoregulation and survival during sepsis in mice

Interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) have been implicated as key mediators in inflammation, morbidity, and mortality associated with sepsis. We examined the role of IL-6 and TNF-alpha signaling on hypothermia, fever, cachexia, anorexia, and survival during sepsis induced by cecal ligation and puncture (CLP) in male and female gene knockout mice. Male wild-type mice developed an initial hypothermia and subsequent fever during sepsis. Male IL-6 knockout mice did not develop fever; rather, they maintained a profound hypothermia during sepsis. Male TNF p55/p75 receptor (TNFR) knockout mice had attenuated hypothermia, but developed a virtually identical fever as wild-type mice. Cachexia did not differ between male wild-type and IL-6 or TNFR knockout mice, whereas anorexia was prolonged in IL-6 knockout mice. Due to the rapid lethality of sepsis in female mice, survival was the only variable we were able to statistically compare among female genotypes. Female wild-type mice had significantly decreased survival compared with male wild-type mice. Survival was significantly enhanced in male and female TNFR knockout mice compared with their wild-type controls. Lack of IL-6 did not affect male or female lethality. These data support the hypothesis that IL-6 is a key mediator of fever and food intake, whereas TNF is responsible for the initial hypothermia and lethality of sepsis in both sexes of mice. The enhanced lethality of CLP-treated female mice supports a role for sex steroids during sepsis.

Outcomes of surgeons who have undergone spine surgery

The objective of this study was to examine the prevalence, characteristics, and outcomes of spine surgery among a membership of American orthopaedic surgeons with a particular interest in spine care [North American Spine Society (NASS)] and a general membership of Canadian orthopaedic surgeons [Canadian Orthopaedic Association (COA)]. A 25-item multiple choice questionnaire was developed and mailed to both memberships. The COA response rate was 45.9%; the NASS response rate was 45.8%. Of those who replied, 17.2% had undergone spinal surgery, and the results differed significantly between the COA at 12.9% and NASS at 21.9%. As a percentage of the total mailing, 7.7% had undergone spinal surgery. These results differed significantly between the COA at 5.9% and NASS at 9.7%. Although the surgery rate for NASS respondents was more than 1.5 times that of COA respondents, they had strikingly similar outcomes. They are a highly motivated, self-employed group who missed little work before and after having surgery.

The anatomy of the human lumbar ligamentum flavum. New observations and their surgical importance

STUDY DESIGN

An anatomic study was performed to investigate the ligamentum flavum of the human lumbar spine.

OBJECTIVES

To describe accurately the interlaminar portion of ligamentum flavum, and to determine if there is an insertion onto the anterosuperior surface of the caudal lamina.

SUMMARY OF BACKGROUND DATA

The insertions of the ligamentum flavum onto its adjacent laminas were classically described by Naffzinger. His description has been recounted by others. It has been the authors' observation that there is a slip of inferior ligamentum flavum that inserts onto the anterosuperior surface of the caudal lamina. Review of the literature revealed only anecdotal observations that support the authors' finding. A clear anatomic description of this structure is important to the surgeon who frequently enters the spinal canal at this anatomic site.

METHODS

Thirty human lumbar ligamenta flava from six fresh frozen lumbar spines were studied macroscopically, with particular attention paid to the insertions onto the adjacent laminas.

RESULTS

The ligamentum flavum consists of a superficial and a deep component. It is continuous in the midline. The superficial ligamentum flavum inserts onto the superior edge and posterosuperior surface of the caudal lamina. The deep ligamentum flavum inserts for a variable distance onto the anterosuperior surface of the caudal lamina.

CONCLUSIONS

There is an inferoventral slip of the ligamentum flavum that attaches to the anterosuperior surface of the caudal lamina. This slip is the inferior portion of the deep ligamentum flavum. When the ligamentum flavum's superficial layer is selectively released, the inferoventral slip of the ligamentum flavum's deep layer remains attached to the anterosuperior surface of the caudal lamina and remains between the surgeon and the dura.

Radiographic appearance of the odontoid lateral mass interspace in the occipitoatlantoaxial complex

STUDY DESIGN

This is an anatomic study in which the odontoid lateral mass interspace is evaluated radiographically in various positions of upper cervical spine rotation.

OBJECTIVES

The objectives are to determine whether odontoid lateral mass interspace asymmetry exists in the ligamentously intact cervical spine and to define odontoid lateral mass interspace behavior during atlantoaxial rotation.

SUMMARY OF BACKGROUND DATA

Controversy exists regarding the behavior of the odontoid lateral mass interspace during atlantoaxial rotation. The meaning of interspace asymmetry varies depending on the author and the method of study. Atlas fractures account for 7% of cervical spine fractures and are frequently associated with other cervical fractures, so an understanding of the radiographic anatomy is crucial to the evaluation of these patients.

METHODS

Ten human cadaveric cervical spines were dissected of all but ligamentous soft tissue and were mounted and prepared for radiographic study in neutral position and in varying degrees of right and left rotation. Radiographs were evaluated for odontoid lateral mass interspace asymmetry in neutral and in rotated positions, and data were analyzed.

RESULTS

Measurable asymmetry could be shown when comparing neutral positions and when comparing rotated with neutral positions. A statistically significant difference could not be proven in this asymmetry, although clinical significance is suggested by the analysis of the data.

CONCLUSION

Measurable asymmetry can be present in the neutrally positioned, ligamentously intact atlanto-axial complex and is not necessarily indicative of instability. This agrees with the concept of the "neutral zone" as described by White and Panjabi in Clinical Biomechanics of the Spine. There is a trend for increasing odontoid lateral mass interspace on the side to which the head is rotated, and this odontoid lateral mass interspace is measurably different from the contralateral odontoid lateral mass interspace, indicating that odontoid lateral mass interspace asymmetry is not a good indicator for cervical instability in the otherwise asymptomatic individual.

Optimization technique for the calculation of in vitro three-dimensional vertebral motion

A method for the calculation of translations and Eulerian rotations of an orthogonal axis system with respect to a fixed reference is described with application to the measurement of position in a vertebral motion segment. Kinematic equations were derived to compute the three-dimensional motion of a moving vertebra relative to an adjacent fixed body, without the requirement of a direct physical link between the two bodies. For this calculation, the quadratic error of the lengths of six position vectors was minimized to obtain a mathematically optimal estimate of the translations and rotations. Tests with a rigid model resulted in mean maximum overall system errors of 2.8 percent for the measurement of translation (translations less than 3.5 mm) and 6.1 percent for the measurement of rotations (rotations less than 10 deg) limited by transducer accuracy. The mathematical techniques presented for the quantitative description of rigid body motion, based on the measurement of three reference vectors, may be extended to a broad range of kinematic problems.

Anatomy of intervertebral disc and pathophysiology of herniated disc disease

This discussion reviews developments in normal and abnormal disc biology over the past decade. The anatomic and biochemical structure of the disc is reviewed. Emphasis is placed on recent neurochemical changes identified in disc degeneration and disc herniation. Biomechanical considerations for the normal disc are presented. Influence of mechanical factors on disc nutrition, disc degeneration and disc herniation is reviewed. Biologic events underlying the diagnostic methods used in evaluating disorders of the intervertebral disc are presented. The biologic consequences of iatrogenic disc injury in discectomy are also discussed.

Effects of the choice of age-adjustment method on maps of death rates

Maps of morbidity or mortality rates, whether considered individually or as a layer in a geographic information system application, invite multiple comparisons of area rates. However, comparisons of rates across different populations require standardization of the age-specific rates to account for differences in population age structures. The indirect standardization method, or equivalently the standardized mortality ratio (SMR), has been recommended for small areas where age-specific rates can be quite variable. Although theoretically equivalent to directly adjusted rates under the assumption of independent age and area effects, indirect summary measures are not comparable across areas when this assumption is violated. We tested the validity of this assumption for the 10 most common causes of death in the United States during 1980-84 and examined the geographic clustering apparent when categorized death rates, adjusted by different methods, are presented as thematic maps. Although overall agreement between the methods was good (rank correlation coefficient > 82 per cent for each cause), when the adjusted rates were classified into quintiles 18 per cent of the states fell into different categories depending on the method of adjustment. Using an internal standard for the indirect method reduced this discrepancy to 4.9 per cent. However, both traditional chi-square tests and a generalized logistic spline model identified significant interactions between age and area for each cause of death, a violation of the assumption required for equivalence of the methods. Potential variation in geographic inferences is illustrated by maps of direct and indirect rates and an empirical Bayes posterior mean, which is a function of these traditionally adjusted rates. Based on these results, we recommend the direct age-adjustment method for rate maps.

A comparison of the effects of automated percutaneous diskectomy and conventional diskectomy on intradiscal pressure, disk geometry, and stiffness

Diskectomy, chemonucleolysis, percutaneous diskectomy, and laser ablation are used to treat patients with sciatica. The effects of percutaneous diskectomy on the intradiscal pressure of the human disk are not known. Our aims were to determine (a) whether removal of nucleus through automated percutaneous diskectomy significantly reduces intradiscal pressure without altering the disk geometry and stiffness, and if so, how much nucleus removal is required to achieve these goals; and (b) whether the effects of conventional diskectomy on these same parameters are equivalent to removal of nucleus through automated percutaneous diskectomy. Cyclic compressive loads of 20-900 N were applied to lumbar disks. Conventional diskectomy or automated percutaneous diskectomy (performed for 40 min with biomechanical measurements made four times at 10-min intervals) was then performed under zero load and the specimens retested under the same cyclic compressive loading. There were significant (p < 0.01) decreases in intradiscal pressure (by 7% under 900 N) after 10 min of automated percutaneous lumbar diskectomy. There were no further significant decreases in pressure during the next 30 min of percutaneous diskectomy. There were also significant decreases in pressure due to a puncture hole made with the Nucleotome trephine alone, without removal of disk material, and there was no difference in pressure after trephining alone and after percutaneous diskectomy. Decreases in disk height were significant, ranging from 5% at 10 min to 7% at 40 min of treatment. There were equivalent decreases in intradiscal pressure and disk height due to removal of similar amounts of nucleus during conventional diskectomy and during 40 min of percutaneous diskectomy.(ABSTRACT TRUNCATED AT 250 WORDS)

The discectomy membrane (nerve root fibrovascular membrane): its anatomic description and its surgical importance

The positive identification and protection of the nerve root is crucial prior to addressing the disc during lumbar discectomy. We report here our observation that there exists a membrane which lies immediately posterior to the annulus fibrosus at the level of the disc and connects to the dura of the nerve root at that level. This is a constant anatomic finding during the approach to the disc, and we refer to it as the "discectomy membrane". We found this tissue present at all lumbar levels of five fresh frozen cadaver spines. Its consistency varied from thin wisps of nearly transparent tissue to tissue strong enough to tether the nerve root laterally.

Effect of screw diameter, insertion technique, and bone cement augmentation of pedicular screw fixation strength

This study investigated (1) the effect of screw diameter and insertion technique in lumbar vertebrae, and insertion site in the sacrum, on the axial pullout force and transverse bending stiffness of pedicle screws, and (2) the effect of bone cement augmentation using polymethylmethacrylate (PMMA) and the biodegradable composite, poly(propylene glycol-fumarate) on axial pullout force and transverse bending stiffness of pedicle screws inserted into lumbar vertebrae. The axial pullout force and transverse bending stiffness of a 6.25-mm Steffee screw and a 6-mm Kluger screw did not differ significantly in vertebral bodies of similar equivalent bone mineral density. The axial pullout force of Schanz screws was significantly increased with a 1-mm increase in screw diameter. However, there was no significant increase in transverse bending stiffness. In the sacrum, an approach through the S1 facet produced significantly higher axial pullout forces and transverse bending stiffness than the approach described by Harrington and Dickson. PMMA and a biodegradable composite bone cement poly(propylene glycol-fumarate) both increased the axial pullout force. PMMA also increased the transverse bending stiffness.

Cryogenic solvents inhibit the binding of the Escherichia coli heat-stable enterotoxin to intestinal brush border membranes

The cryogenic solvents ethylene glycol, glycerol, dimethyl sulfoxide (Me2SO) and dimethylformamide (Me2FM), with increasing potency, produced concentration-dependent inhibition of the binding of the Escherichia coli heat-stable enterotoxin (STa) to pig intestinal brush border membranes. Inhibition increased with time, and both Me2SO and Me2FM appeared to decrease both the affinity of the STa receptor and the effective receptor number. Both solvents stimulated the release of previously bound 125I-STa (Me2FM > Me2SO), 3 M Me2FM inducing 93% release by 120 min. These effects were reversible, and preincubation of membranes with up to 3 M Me2SO or Me2FM at 37 degrees C for 30 min, followed by washing, did not alter subsequent 125I-STa binding. Also, 125I-STa released from membranes by 3 M Me2FM was shown to rebind to the membranes after 10-fold dilution of Me2FM. Since pretreating membranes with the thiol reagent p-chloromercuribenzenesulfonate had no effect on the release of bound 125I-STa by Me2SO or Me2FM, and since neither of these can reduce disulfide bonds, the formation of mixed disulfides between STa and receptor is unlikely. Me2SO inhibition of 125I-STa binding was greater with membranes than with a partially purified receptor preparation, which may result from the substitution of detergent for the phospholipid normally associated with the receptor(s).

Rehabilitation of athletes following spine injury

We feel that the described system for staging cervical and lumbar spine injuries in the high-performance athlete affords a basic framework for the rehabilitation of those individuals. With spine injuries, one has to exercise care to rule out those injuries and additional pathologies presenting as neck or back pain that could result in catastrophic sequelae. We stress due diligence in the initial and continued follow-up of these patients with careful evaluation to rule out associated fractures, dislocations, and attendant disc pathology. The treatment of the "stinger" or "burner" is controversial. We suggest a conservative approach, although the orthopedic and neurologic literature reports that these individuals have been returned to full contact sports activity without documented subsequent neurologic sequelae. The final decision remains at the discretion of the treating physician. This program provides a rational approach to the rehabilitation of the spine-injured high-performance athlete that will provide for the return of him or her to preinjury activity level in an expeditious manner with the minimal period of interruption in training.

Biomechanics of pin and screw fixation of femoral neck fractures

Using an in vitro cadaveric femoral neck osteotomy model and a paired experimental design, we compared fixation stiffness and yield load for three- and four-pin configurations for both Knowles pins and Asnis screws and for three Asnis screws versus an AO-ASIF sliding hip screw. Repeat measure analyses of variance indicated a significant increase in stiffness (p < 0.05) with the use of three versus four pins; the yield load did not depend significantly on the number of pins. Fixation was significantly stiffer (p < 0.01) and stronger (p = 0.02) for Knowles pins if the osteotomy was oblique rather than transverse to the femoral neck; the opposite was found for Asnis screws. Femoral fixed with hip screws were significantly stiffer (p < 0.01) than the contralateral side fixed with three Asnis screws. No significant difference in yield load was observed, however. Clinically, it appears from these findings that the use of three Asnis screws or three Knowles pins provides modest increases (averaging 4%) in fixation stiffness with no degradation in strength when compared with four screws or pins. Parallel placement of Asnis screws also provides advantages over nonparallel Knowles pins by allowing controlled impaction of the femoral head. While three Asnis screws provide fixation stiffness approximately 40% less than that found with a sliding hip screw, there is no compromise in fixation strength.