Association between psoas major muscle mass and CPET performance and long-term survival following major colorectal surgery: A retrospective cohort study

OBJECTIVES

To evaluate whether computed tomography (CT)-derived psoas major muscle measurements could predict preoperative cardiopulmonary exercise testing (CPET) performance and long-term mortality in patients undergoing major colorectal surgery and to compare predictive performance of psoas muscle measurements using 2D approach and 3D approach.

METHODS

A retrospective cohort study compliant with STROCSS standards was conducted. Consecutive patients undergoing major colorectal surgery between January 2011 and January 2017 following CPET as part of their preoperative assessment were included. Regression analyses were modelled to investigate association between the CT-derived psoas major muscle mass variables [total psoas muscle area (TPMA), total psoas muscle volume (TPMV) and psoas muscle index (PMI)] and CPET performance and mortality (1-year and 5-year). Discriminative performances of the variables were evaluated using Receiver Operating Characteristic (ROC) curve analysis.

RESULTS

A total of 457 eligible patients were included. The median TPMA and TPMV were 21 ​cm2 (IQR: 15-27) and 274 ​cm3 (IQR: 201-362), respectively. The median PMI measured via 2D and 3D approaches were 7 ​cm2/m2 (IQR: 6-9) and 99 ​cm3/m2 (IQR: 76-120), respectively. The risks of 1-year and 5-year mortality were 7.4% and 27.1%, respectively. Regression analyses showed TPMA, TPMV, and PMI can predict preoperative CPET performance and long-term mortality. However, ROC curve analyses showed no significant difference in predictive performance amongst TPMA, TPMV, and PMI.

CONCLUSION

Radiologically-measured psoas muscle mass variables may predict preoperative CPET performance and may be helpful with informing more objective selection of patients for preoperative CPET and prehabilitation.

Development and validation of a reliable method for automated measurements of psoas muscle volume in CT scans using deep learning-based segmentation: a cross-sectional study

OBJECTIVES

We aimed to develop an automated method for measuring the volume of the psoas muscle using CT to aid sarcopenia research efficiently.

METHODS

We used a data set comprising the CT scans of 520 participants who underwent health check-ups at a health promotion centre. We developed a psoas muscle segmentation model using deep learning in a three-step process based on the nnU-Net method. The automated segmentation method was evaluated for accuracy, reliability, and time required for the measurement.

RESULTS

The Dice similarity coefficient was used to compare the manual segmentation with automated segmentation; an average Dice score of 0.927 ± 0.019 was obtained, with no critical outliers. Our automated segmentation system had an average measurement time of 2 min 20 s ± 20 s, which was 48 times shorter than that of the manual measurement method (111 min 6 s ± 25 min 25 s).

CONCLUSION

We have successfully developed an automated segmentation method to measure the psoas muscle volume that ensures consistent and unbiased estimates across a wide range of CT images.

Pre-sarcopenia is the prognostic factor of overall survival in early-stage hepatoma patients undergoing radiofrequency ablation

Sarcopenia might have impact on the outcome of patients with hepatoma carcinoma (HCC). This study was to determine whether pre-sarcopenia is associated with the outcome of HCC patients undergoing radiofrequency ablation (RFA).Patients with newly diagnosed HCC undergoing RFA were enrolled. We excluded patients without pre-RFA abdominal computed tomography or with incomplete ablation. Psoas muscle area index was calculated at the mid-lumbar 3 level of computed tomography images with the manual trace method. Pre-sarcopenia was defined as psoas muscle area index less than 4.24 and 2.50 cm/m for males and females respectively. The demographics and clinical characteristics were recorded before RFA.All patients were followed regularly until death or end of 2018. A total of 136 patients, including - BCLC stage 0 (n = 44, 32.4%) and - stage A (n = 92, 67.6%), were enrolled (males/females: 78/58, age: 65.4 years) with a mean follow-up period of 3.84 years. There were 75 patients (55.1%) with HCC recurrence and 47 patients (34.6%) with mortality during follow-up. Twenty-two (16.2%) patients were diagnosed with pre-sarcopenia. Multivariate analysis showed pre-sarcopenia (HR: 2.110 (1.092-4.078); P = .026) was the only factor significantly associated with overall survival (OS); however, there were no factors associated with HCC recurrence.For patients without and with pre-sarcopenia, the 1-, 3-, and 5-year OS rates were 92.0%, 77.6%, 68.9%, and 81.8%, 54.5%, 44.1% respectively (P = .007). For early-stage HCC patients undergoing RFA, pre-sarcopenia is the prognostic factor of OS, but not of recurrence, with a worse 5-year OS rate of 44.1%.

Meta-Analysis of the Prognostic Value of Psoas-Muscle Area on Mortality in Patients Undergoing Transcatheter Aortic Valve Implantation

We performed a meta-analysis of currently available studies assessing prognostic value of psoas-muscle area (PMA) on mortality in patients who underwent transcatheter aortic valve implantation (TAVI). MEDLINE and EMBASE were searched through May 2018 to identify studies reporting ≥1-year all-cause mortality in PMA-stratified TAVI patients. A hazard ratio of follow-up (including early) mortality for "lowest-quantile" versus "higher-quantiles" PMA. Study-specific estimates were combined in the random-effects model. Our search identified 6 eligible studies enrolling a total of 1,237 TAVI patients with 1-year to 2-year (midterm) follow-up. A primary meta-analysis pooling all hazard ratios for "lowest-quantile versus higher-quantiles" PMA demonstrated significantly higher mortality in "lowest-quantile" than "higher-quantiles" patients (p <0.0001). A subgroup meta-analysis indicated no significant difference in mortality between "<50th- and ≥50th-percentile" patients (p = 0.95), but significantly higher mortality in "lowest-tertile" than "higher-tertiles" patients (p = 0.0009) and in "lowest-quartile" than "higher- quartiles" patients (p = 0.0003). A secondary meta-analysis revealed significantly higher mortality in "lowest-tertile" than "mid-tertile" patients (p = 0.01) and in "lowest-tertile" than "highest-tertile" patients (p = 0.01). A gender-stratified meta-analysis showed significantly higher mortality in "lowest-quantile" than "higher-quantiles" patients in both men (p = 0.0008) and women (p = 0.01). In conclusion, low PMA, especially "lowest-tertile/quartile" PMA, is a predictor of high all-cause mortality at midterm follow-up after TAVI for both men and women. However, PMA categorization into 50th percentiles may be invalid to predict mortality.

Morphometric Assessment as a Predictor of Outcome in Older Vascular Surgery Patients

BACKGROUND

Frailty is a recognized predictor of poor outcome in patients undergoing surgical intervention. Frailty is intricately linked with body morphology, which can be evaluated using morphometric assessment via computerized tomographic (CT) imaging. We aimed to assess the predictive power of such objective assessments in a broad cohort of vascular surgical patients.

METHODS

A consecutive series of patients aged over 65 years admitted to a vascular unit, who had undergone CT imaging of the abdomen, were analyzed. Demographic and patient-specific data were collated alongside admission relevant information. Outcomes included mortality, length of stay, health care-related costs, and discharge destination. Images were analyzed for 4 morphometric measurements: (1) psoas muscle area, (2) mean psoas density, (3) subcutaneous fat depth, and (4) intra-abdominal fat depth, all taken at the level of the fourth lumbar vertebra.

RESULTS

Two hundred and ten patients were initially analyzed. Forty-four patients had significant retroperitoneal and abdominal abnormalities that limited appropriate CT analysis. Decreased subcutaneous fat depth was significantly associated with mortality, readmission within 12 months, and increased cost of health care (P < 0.01, adjusted for confounders). Psoas muscle area was significantly associated with readmission-free survival.

CONCLUSIONS

Morphometric analysis predicts poorer outcome in a broad cohort of vascular surgery patients. Such assessment is likely to enhance patient counseling regarding individual risk as well as enhancing the ability to undertake risk-modified surgical audit.

Proposal for new diagnostic criteria for low skeletal muscle mass based on computed tomography imaging in Asian adults

OBJECTIVES

Low skeletal muscle, referred to as sarcopenia, has been shown to be an independent predictor of lower overall survival in various kinds of diseases. Several studies have evaluated the low skeletal muscle mass using computed tomography (CT) imaging. However, the cutoff values based on CT imaging remain undetermined in Asian populations.

METHODS

Preoperative plain CT imaging at the third lumbar vertebrae level was used to measure the psoas muscle mass index (PMI, cm(2)/m(2)) in 541 adult donors for living donor liver transplantation (LDLT). We analyzed PMI distribution according to sex or donor age, and determined the sex-specific cutoff values of PMI to define low skeletal muscle mass.

RESULTS

PMI in men was significantly higher than observed in women (8.85 ± 1.61 cm(2)/m(2) versus 5.77 ± 1.21 cm(2)/m(2); P < 0.001). PMI was significantly lower in individuals ≥50 y than in younger donors in both men and women (P < 0.001 and P < 0.001, respectively). On the basis of the younger donor data, we determined the sex-specific cutoff values for the low skeletal muscle mass were 6.36 cm(2)/m(2) for men and 3.92 cm(2)/m(2) for women (mean - 2 SD).

CONCLUSION

Data from healthy young Asian adults were used to establish new criteria for low skeletal muscle mass that would be applicable for defining sarcopenia in Asian populations.

Motor evoked potentials for femoral nerve protection in transpsoas lateral access surgery of the spine

Detecting potential intraoperative injuries to the femoral nerve should be the main goal of neuromonitoring of lateral lumber interbody fusion (LLIF) procedures. We propose a theory and technique to utilize motor evoked potentials (MEPs) to protect the femoral nerve (a peripheral nerve), which is at risk in LLIF procedures. MEPs have been advocated and widely used for monitoring spinal cord function during surgical correction of spinal deformity and surgery of the cervical and thoracic spine, but have had limited acceptance for use in lumbar procedures. This is due to the theoretical possibility that MEP recordings may not be sensitive in detecting an injury to a single nerve root considering there is overlapping muscle innervation of adjacent root levels. However, in LLIF procedures, the surgeon is more likely to encounter lumbar plexus elements than nerve roots. Within the substance of the psoas muscle, the L2, L3, and L4 nerve roots combine in the lumbar plexus to form the trunk of the femoral nerve. At the point where the nerve roots become the trunk of the femoral nerve, there is no longer any alternative overlapping innervation to the quadriceps muscles. Insult to the fully formed femoral nerve, which completely blocks conduction in motor axons, should theoretically abolish all MEP responses to the quadriceps muscles. On multiple occasions over the past year, our neuro-monitoring groups have observed significantly degraded amplitudes of the femoral motor and/or sensory evoked potentials limited to only the surgical side. Most of these degraded response amplitudes rapidly returned to baseline values with a surgical intervention (i.e., prompt removal of surgical retraction).

Anatomic relationships of psoas muscle: clinical applications to psoas hitch ureteral reimplantation

OBJECTIVE

The objective of the study was to examine the anatomic relationship of the genitofemoral and femoral nerves to the psoas major muscle.

STUDY DESIGN

Dissections were performed in 17 unembalmed female cadavers. Point A was used as the approximate location for placement of psoas hitch sutures and as the reference point from which all measurements were taken. Measurements included the width of the psoas major muscle, psoas minor tendon, genitofemoral nerve branches, and femoral nerve. The relative location of the genitofemoral and femoral nerves to point A and the presence or absence of a psoas minor tendon were documented.

RESULTS

The psoas minor tendon was absent on at least 1 side in 11 specimens (64.7%). The median width of the psoas minor tendon was 7 mm (range, 3-11.5 mm). The median width and depth of the psoas major muscle was 21.5 mm (range, 10-35 mm) and 20.0 mm (range, 11.5-32 mm), respectively. The median width of the genitofemoral nerve was 2 mm (range, 1-4.5 mm) and that of the femoral nerve was 6.3 mm (range, 5-10.5 mm). Overall, 54 genitofemoral nerve branches were identified in 17 cadavers, 30 medial (55.5%), 22 lateral (40.7%), and 2 directly overlying point A (3.7%).

CONCLUSION

The exact location for the placement of the psoas hitch sutures will vary, depending on the location of the ureteral injury and the anatomy of the psoas muscle and surrounding structures. A thorough understanding of this regional anatomy should optimize the placement of psoas hitch sutures during ureteral reimplantation procedures and help avoid nerve and vessel injury.

Analytic morphomics corresponds to functional status in older patients

BACKGROUND

Older patients account for nearly half of the United States surgical volume, and age alone is insufficient to predict surgical fitness. Various metrics exist for risk stratification, but little work has been done to describe the association between measures. We aimed to determine whether analytic morphomics, a novel objective risk assessment tool, correlates with functional measures currently recommended in the preoperative evaluation of older patients.

MATERIALS AND METHODS

We retrospectively identified 184 elective general surgery patients aged >70 y with both a preoperative computed tomography scan and Vulnerable Elderly Surgical Pathways and outcomes Assessment within 90 d of surgery. We used analytic morphomics to calculate trunk muscle size (or total psoas area [TPA]) and univariate logistic regression to assess the relationship between TPA and domains of geriatric function mobility, basic and instrumental activities of daily living (ADLs), and cognitive ability.

RESULTS

Greater TPA was inversely correlated with impaired mobility (odds ratio [OR] = 0.46, 95% confidence interval [CI] 0.25-0.85, P = 0.013). Greater TPA was associated with decreased odds of deficit in any basic ADLs (OR = 0.36 per standard deviation unit increase in TPA, 95% CI 0.15-0.87, P <0.03) and any instrumental ADLs (OR = 0.53, 95% CI 0.34-0.81; P <0.005). Finally, patients with larger TPA were less likely to have cognitive difficulty assessed by Mini-Cog scale (OR = 0.55, 95% CI 0.35-0.86, P <0.01). Controlling for age did not change results.

CONCLUSIONS

Older surgical candidates with greater trunk muscle size, or greater TPA, are less likely to have physical impairment, cognitive difficulty, or decreased ability to perform daily self-care. Further research linking these assessments to clinical outcomes is needed.

Temporalis muscle morphomics: the psoas of the craniofacial skeleton

BACKGROUND

The psoas muscle has been shown to predict patient outcomes based on the quantification of muscle area using computed tomography (CT) scans. The accuracy of morphomic analysis on other muscles has not been clearly delineated. In this study, we determine the correlation between temporalis muscle mass, psoas muscle area, age, body mass index (BMI), and gender.

METHODS

Temporalis and psoas muscle dimensions were determined on all trauma patients who had both abdominal and maxillofacial CT scans at the University of Michigan between 2004 and 2011. Age, BMI, and gender were obtained through chart review. Univariate and multivariate analyses were performed to determine the relative relationship between morphomic data of the temporalis and psoas muscles and the ability of such information to correspond with clinical variables, such as BMI, age, and gender.

RESULTS

A total of 646 patients were included in the present study. Among the 249 (38.5%) women and 397 (61.5%) men, the average age was 49.2 y. Average BMI was 27.9 kg/m². Total psoas muscle area directly correlated with mean temporalis muscle thickness (r = 0.57, P < 0.001). There was an indirect correlation between age and psoas muscle area (r = -0.52, P < 0.001) and temporalis muscle thickness (r = -0.36, P < 0.001). Neither psoas nor temporalis measurements correlated strongly with BMI (r = 0.18, P < 0.001; r = 0.14, P = 0.002), although stronger correlations were found in a more "frail," subgroup as defined by a BMI of <20 (r = 0.59, P = 0.002).

CONCLUSIONS

We demonstrate that dimensions of the temporalis muscle can be quantified and may serve as a proxy for age. Going forward, we aim to assess the utility of temporalis and psoas morphomics in predicting complication rates among trauma patients admitted to the hospital to predict outcomes in the future.

Automated segmentation of psoas major muscle in X-ray CT images by use of a shape model: preliminary study

Our motivation was to provide an automatic tool for radiologists and orthopedic surgeons for improving the quality of life of an aging population. We propose a method for generating a shape model and a fully automated segmenting scheme for the psoas major muscle in X-ray CT images by using the shape model. Our approach consists of two steps: (1) The generation of a shape model and its application to muscle segmentation. The shape model describes the muscle's outer shape and has two parameters, an outer shape parameter and a fitting parameter. The former was determined by approximating of the outer shape of the muscle region in training cases. The latter was determined for each test case in the recognition process. (2) Finally, the psoas major muscle was segmented by use of the shape model. To evaluate the performance of the method, we applied it to CT images for constructing the shape models by using 20 cases as training samples; 80 cases were used for testing. The accuracy of this method was measured by comparison of the extracted muscle regions with regions that were identified manually by an expert radiologist. The experimental results of the segmentation of the psoas major muscle gave a mean Jaccard similarity coefficient of 72.3%. The mean true segmentation coefficient was 76.2%. The proposed method can be used for the analysis of cross-sectional area and muscular thickness in a transverse section, offering radiologists an alternative to manual measurement for saving their time and improving the reproducibility of segmentation.

Validity of gait parameters for hip flexor contracture in patients with cerebral palsy

BACKGROUND

Psoas contracture is known to cause abnormal hip motion in patients with cerebral palsy. The authors investigated the clinical relevance of hip kinematic and kinetic parameters, and 3D modeled psoas length in terms of discriminant validity, convergent validity, and responsiveness.

METHODS

Twenty-four patients with cerebral palsy (mean age 6.9 years) and 28 normal children (mean age 7.6 years) were included. Kinematic and kinetic data were obtained by three dimensional gait analysis, and psoas lengths were determined using a musculoskeletal modeling technique. Validity of the hip parameters were evaluated.

RESULTS

In discriminant validity, maximum psoas length (effect size r = 0.740), maximum pelvic tilt (0.710), maximum hip flexion in late swing (0.728), maximum hip extension in stance (0.743), and hip flexor index (0.792) showed favorable discriminant ability between the normal controls and the patients. In convergent validity, maximum psoas length was not significantly correlated with maximum hip extension in stance in control group whereas it was correlated with maximum hip extension in stance (r = -0.933, p < 0.001) in the patients group. In responsiveness, maximum pelvic tilt (p = 0.008), maximum hip extension in stance (p = 0.001), maximum psoas length (p < 0.001), and hip flexor index (p < 0.001) showed significant improvement post-operatively.

CONCLUSIONS

Maximum pelvic tilt, maximum psoas length, hip flexor index, and maximum hip extension in stance were found to be clinically relevant parameters in evaluating hip flexor contracture.

The reliability of paraspinal muscles composition measurements using routine spine MRI and their association with back function

This study examines the reliability of quantitative and qualitative muscle composition measurements of paraspinal muscle cross-sectional areas (CSAs) from routine lumbar spine magnetic resonance images and their association with maximal isokinetic lifting performance. The extent of paraspinal muscle composition reflects back function is currently not known. Measurements were repeated 4-8 weeks apart and different measurements of related constructs were compared. Participants were a population-based sample of 169 males, 35-67 years old, without considering the presence or absence of a history of low back pain or related problems in the selection of subjects. The quantitative and qualitative muscle composition measurements for axial magnetic resonance (MR) images of paraspinal muscles at the L3-L4 lumbar spine level, isokinetic lifting force and work, and body fat percentage were the main outcome measures. Results showed that the reproducibility of different paraspinal muscle composition measurements at the L3-L4 level was excellent for CSAs (ICC=0.95-0.99) and quantitative muscle composition measurements using cerebrospinal fluid adjusted signal intensity (ICC=0.96-0.99), and moderate for qualitative muscle composition ratings (Kappa=0.54-0.76). The correlations of the quantitative and qualitative muscle composition measurements with isokinetic lifting force and work were generally low (r=0.02-0.41), and favoured the qualitative assessments. In conclusion, quantitative and qualitative muscle composition measurements of paraspinal muscles are highly reproducible tissue measures, have low associations with body fat and isokinetic lifting performance, and show that paraspinal muscle morphology using routine spine magnetic resonance imaging (MRI) is poorly related to back function.

Different changes of quantity due to aging in the psoas major and quadriceps femoris muscles in women

Bone fractures cause disabilities that leave the elderly bedridden and strengthening the muscles of the lower limbs, especially the quadriceps femoris, is the main kinematical method of preventing falls. Recently, however, it has become clear that the psoas major is critical for walking ability. We examined changes due to aging in the size of the psoas major compared with changes in the quadriceps femoris. Bone fractures are more frequent in women than in men; our participants (n=210) were therefore exclusively women ranging in age from 20 to 79 and divided into 6 age groups (n=35 each) in 10-year increments. Cross-sectional areas of the two muscles were measured by an MR scanner for a comparative estimation of muscle size. The psoas major showed the greatest quantity in subjects in their 20s, after which it declined steadily until the 60s and dramatically in the 70s, while the area of the quadriceps femoris was preserved until the 40s and showed no dramatic later decline. Exercise beyond regular daily activities is recommended to prevent the psoas major from decreasing in volume. We also recommend the development of a method of maintaining its muscle volume which would target women younger than 40 and older than 60.

Bilateral variations of the psoas major and the iliacus muscles and presence of an undescribed variant muscle – accessory iliopsoas muscle

Inspite of the detailed description of the iliopsoas muscle complex, interesting variations of its main parts--the psoas major and the iliacus muscles can still be encountered. These variations may clarify some aspects of the embryological development of the iliopsoas and have certain clinical importance because of the frequent co-existence with an unusual femoral nerve by its formation and course. We present in our report a case of bilateral variations of the psoas major and the iliacus muscles combined with variations of the left and the right femoral nerves, which were found during the anatomical dissection of a female human cadaver. The most remarkable finding was noted on the left side, where an undescribed variant muscle accessory iliopsoas, was observed. It was the only finding of such a muscle among 108 human cadavers examined over a period of 22 years. The accessory iliopsoas was formed by the connection of two accessory muscles--accessory psoas major and accessory iliacus. The clinical significance of the described variant muscles and their importance as an additional factor in the femoral neuropathy are also a matter of discussion in our report.

Light microscopy and image analysis of thin filament lengths utilizing dual probes on beef, chicken, and rabbit myofibrils

Image analysis procedures for immunofluorescence microscopy were developed to measure muscle thin filament lengths of beef, rabbit, and chicken myofibrils. Strips of beef cutaneous trunci, rectus abdominis, psoas, and masseter; chicken pectoralis; and rabbit psoas muscles were excised 5 to 30 min postmortem. Fluorescein phalloidin and rhodamine myosin subfragment-1 (S1) were used to probe the myofibril structure. Digital images were recorded with a cooled charge-coupled device controlled with IPLab Spectrum software (Signal Analytics Corp.) on a Macintosh operating system. The camera was attached to an inverted microscope, using both the phase-contrast and fluorescence illumination modes. Unfixed myofibrils incubated with fluorescein phalloidin showed fluorescence primarily at the Z-line and the tips of the thin filaments in the overlap region. Images were processed using IPLab and the National Institutes of Health's Image software. A region of interest was selected and scaled by a factor of 18.18, which enlarged the image from 11 pixels/microm to approximately 200 pixels/microm. An X-Y plot was exported to Spectrum 1.1 (Academic Software Development Group), where the signal was processed with a second derivative routine, so a cursor function could be used to measure length. Fixation before phalloidin incubation resulted in greatest intensity at the Z lines but a more-uniform staining over the remainder of the thin filament zone. High-resolution image capture and processing showed that thin filament lengths were significantly different (P < 0.01) among beef, rabbit, and chicken, with lengths of 1.28 to 1.32 microm, 1.16 microm, and 1.05 microm, respectively. Measurements using the S1 signal confirmed the phalloidin results. Fluorescent probes may be useful to study sarcomere structure and help explain species and muscle differences in meat texture.

Femoral muscle attachment locations in children and adults, and their prediction from clinical measurement

Accurate representation of children's musculo-skeletal anatomy is becoming increasingly important to biomechanical techniques such as gait analysis. This study used magnetic resonance imaging to examine the locations of the femoral insertions of the psoas, vastus medialis and gastrocnemius muscles in five adults and 17 children (including 7 children with cerebral palsy). The relationship of muscle attachment locations with age and bone geometry was then determined. Scaling techniques and external measurements of parameters such as femoral anteversion/antetorsion were shown to have potential for prediction of the locations of femoral muscle attachment points. It was shown that femoral anteversion can be modelled geometrically as occurring proximal to the lesser trochanter.

Examination of the variations of lateral femoral cutaneous nerves: report of two cases

The origins, courses and relations of lateral femoral cutaneous nerves (LFCNs) were examined bilaterally in 28 cadavers, and the variations were observed in two. On the right side of one cadaver, the ventral rami of the first and second lumbar spinal nerves were united and then this nerve was divided into four branches. From medial to lateral, these branches were the obturator nerve, the femoral nerve, the medially located LFCN and the laterally located LFCN. On the left side of another cadaver, there were three LFCNs. All of these nerves pierced the psoas major muscle anterolaterally. Two of these nerves, which pierced the psoas major muscle more proximally than the third, united with each other by a communicating branch anterior to the iliacus muscle. These types of variations are very important, especially in the presence of paresthesias or pain in the anterior thigh, lateral thigh and gluteal region. In these cases, surgeons must always remember the possible variations of the LFCN during surgical procedures in order to prevent injury and the occurrence of meralgia paresthetica.

Anatomical study of lumbar spine innervation

To precisely evaluate low back pain, identification of the detailed innervation of the lumbar spine is necessary. On twenty-five sides of adult cadavers we investigated various patterns of rami communicantes (RC) and their relationship to the psoas major muscle (PM). In ten sides, we focused our dissection on the minute nerve supply of the anterior (ALL) and posterior longitudinal ligaments (PLL), vertebral bodies and the intervertebral discs (IVD). According to the mode of piercing PM, two types of RC were observed: superficial oblique rami (SOR) and deep transverse rami (DTR). SOR ran obliquely between superficial heads of PM, connecting sympathetic trunk (ST) and T12-L2 (3) spinal nerves non-segmentally. DTR ran segmentally close to the vertebral bodies and were situated deep to the PM slips. On the lateral side of the lumbar spine, the vertebral bodies and IVD received branches from DTR and ventral rami segmentally, as well as branches from the sympathetic trunk (ST) and, in the upper lumbar region, SOR non-segmentally. On the anterior aspect of the lumbar spine, ALL received branches from ST and splanchnic nerves non-segmentally. Within the vertebral canal, the posterior aspect of IVD and PLL received the sinu-vertebral nerves originating from DTR. These findings suggest the coexistence of two different types of innervation: one originating directly from the spinal nerve segmentally, and one reaching vertebral structures via the sympathetic nerves non-segmentally. Therefore, sympathetic nerves are likely involved in the proprioception of the spinal column.

Gadolinium-enhanced T1-weighted renal and abdominal MR imaging: quantitative discrepancy between clinical and in vitro findings

RATIONALE AND OBJECTIVES

This study was conducted to compare the magnetic resonance (MR) contrast medium enhancement of abdominal organs in vivo with the signal intensity (SI) values of known in vitro gadolinium solutions.

MATERIALS AND METHODS

A phantom was imaged with the MR contrast medium gadodiamide (Omniscan; Nycomed, Princeton, NJ) of solutions at full-strength (0.5 mmol/mL), one-third, 1/10, and 1/100 concentrations. A fat-suppressed fast spoiled gradient-echo pulse sequence with flip angles ranging from 10 degrees to 170 degrees (at 20 degrees increments) was performed with a 1.5-T magnet. In 12 subjects, the SIs of abdominal organs were determined with identical imaging parameters, before and after administration of gadodiamide injection at 0.1 mmol/kg.

RESULTS

As anticipated, the plot of SI in relation to gadodiamide concentration is nonlinear, with a decrease in SI due to T2 effects at concentrations above 0.05 mmol/mL. The kidney showed the highest SI after gadodiamide enhancement (125.2 +/- 11.6 [standard error] at 2.5 minutes), followed by the liver (76.5 +/- 11.5 at 1 minute) and spleen (57.26 +/- 9.35 at 30 seconds). The SI of the renal medulla (114.2 +/- 9.8 at 4.5 minutes) was approximately one-third that in phantom observations.

CONCLUSION

The authors observed a marked discrepancy between empirical contrast medium performance in abdominal organs and SI values for comparable gadodiamide concentrations in vitro. One possible reason is the intracellular compartmentalization of water molecules in vivo. These results suggest a need for a better understanding of MR contrast medium performance in vivo.

The function of the psoas major muscle: passive kinetics and morphological studies using donated cadavers

This study was carried out to analyze the phasic heterogeneity in the function of the psoas major muscle (PMM) depending on the flexion angle at the hip joint. The study design was a passive kinetic experiment using 25 osteoligamentous specimens with the PMM tendon. We measured the flexion angle of the hip joint where the PMM tendon loses contact with the femoral head and pelvic surface. Ten osteoligamentous specimens were used for additional measurements of the tensile force and pressure exerted on the PMM and/or at the bone-tendon interface when the PMM tendon was gently pulled in line with the PMM origin in the supine position. The tension loading the PMM tendon was measured at seven different angled positions of hip joint flexion (0 degrees, 15 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees, and 90 degrees ), using a load cell attached to a traction appliance. The pressure was measured at each of eight sites along the long axis of the PMM, using a pressure sensor. The PMM tendon lost contact with the femoral head at angled positions of 14 degrees (average) hip flexion, and lost contact with the iliopectineal eminence at positions of 54 degrees (average). The tension was stronger at angled positions of 0 degrees -30 degrees at the hip joint. The pressure on the femoral head and pelvic surface were stronger at positions of 0 degrees -30 degrees at the hip joint. The pressure on the femoral head was strongest at a hip flexion of 0 degrees. The tensile force markedly decreased at 45 degrees -60 degrees flexion at the hip joint, while the pressure on the femoral head gradually reduced to zero in the same phases. We concluded that the PMM works phasically: (1) as an erector of the lumbar vertebral column, as well as a stabilizer of the femoral head in the acetabulum at 0 degrees -15 degrees flexion at the hip joint; (2) less as a stabilizer, in contrast to maintaining its erector action, at 15 degrees -45 degrees; and (3) as an effective flexor of the lower extremity, at 45 degrees -60 degrees.

Descriptive anatomy of the femoral portion of the iliopsoas muscle. Anatomical basis of anterior snapping of the hip

Anterior hip snapping is a rare clinical observation. The physiopathological hypothesis currently held is a sudden slip of the iliopsoas tendon over the iliopectineal eminence. For symptomatic cases, a surgical technique is proposed. The aim of this work is to describe the anatomy of the femoral portion of the iliopsoas, which is the target of surgery. We have studied, through dissection of embalmed cadavers, the different components of the musculotendinous complex forming the femoral portion of the muscle and the gliding apparatus associated with it. The psoas major tendon exhibited a characteristic rotation. The iliacus tendon, more lateral, received the most medial iliacus muscular fibers, then fused with the main tendon. The most lateral fibers, starting in particular from the ventral portion of the iliac crest, ended up without any tendon on the anterior surface of the lesser trochanter and in the infratrochanteric region. The most inferior muscular fibers of the iliacus, starting from the arcuate line, joined the principal tendon of the psoas major passing around it by its ventromedial surface. An ilio-infratrochanteric muscular bundle was observed, in a deeper position, under the iliopsoas tendon; it arose from the interspinous incisure and on the anterior inferior iliac spine, ran along the anterolateral edge of the iliacus and inserted without any tendon onto the anterior surface of the lesser trochanter of the femur and in the infratrochanteric area. The iliopectineal bursa was studied on horizontal cross sections of a frozen pelvis and on 5 of the non-frozen preparations after dividing the iliopsoas tendon. The iliopectineal bursa had the shape of a 5 to 6-cm high and 3-cm wide cavity; in its upper part, it was divided into 2 compartments: a medial compartment for the main tendon and a lateral compartment for the accessory tendon.

Anatomic landmarks and time management during retroperitoneoscopic radical nephrectomy

BACKGROUND AND PURPOSE

Retroperitoneoscopy has not been widely considered the preferred approach to laparoscopic radical nephrectomy for cancer, in part because the retroperitoneal anatomic landmarks have not been well defined. The aim of this study is to provide prospective, objective data on retroperitoneoscopic radical nephrectomy with regard to anatomic landmarks and time management of the sequential operative steps.

MATERIALS AND METHODS

A uniform database was devised to record predetermined intraoperative parameters prospectively in 18 consecutive retroperitoneoscopic radical nephrectomies.

RESULTS

A three- or four-port technique was employed to perform 10 left and 8 right retroperitoneoscopic radical nephrectomies. Initial balloon dilation was routinely performed outside of and posterior to Gerota's fascia. The anatomic landmarks visible immediately on initial insertion of the laparoscope were: psoas muscle in 18 cases (100%), Gerota's fascia in 18 (100%), peritoneal reflection in 15 (83%), ureter and/or gonadal vein in 11 (61%), and renal artery pulsations in 10 (56%). Aortic pulsations were seen in 9 of 10 left (90%) and the inferior vena cava in 2 of 8 right (25%) radical nephrectomies. The mean surgical time was 203 +/- 52.9 minutes (range 105-290 minutes). The sequential operative steps and their individual time breakdowns were: port placement 12 +/- 3.9 minutes, hilar dissection 63 +/- 29.1 minutes, adrenal mobilization 49 +/- 12.1 minutes, specimen mobilization 19 +/- 20.8 minutes, and specimen entrapment and exit 23 +/- 18.2 minutes. When the initial balloon dilation resulted in visibility of four or more anatomic landmarks, the hilar dissection time was significantly shorter (P < 0.001).

CONCLUSIONS

Proper development of the retroperitoneal space and identification of adequate anatomic landmarks is important during retroperitoneoscopy. This timed analysis of the sequential operative steps of retroperitoneoscopic radical nephrectomy has served as an important self-assessment tool for us in improving our surgical technique. As a result, our surgical time for retroperitoneoscopic radical nephrectomy has decreased from the earlier 4- to 5-hour range to the current 2- to 3-hour range.

Composition of psoas major muscle fibers compared among humans, orangutans, and monkeys

In primate species the m. psoas major, the only muscle simultaneously controlling the spinal column and lower extremity, is expected to reflect morpho-functional adaptation to diversified locomotor behavior. By using histochemical analysis with Sudan black B staining, composition of different types of muscle fibers in the psoas major was compared between 2 Japanese macaques, 2 hamadryas baboons, 2 anubis baboons, 2 orangutans, and 17 humans. The comparison has revealed unique features of this muscle in humans: 1) Type 1 or red fibers are thicker than Type 2 or white fibers in humans but vice versa in nonhumans; 2) among the species examined the number of the muscle fibers per unit cross-sectional area is largest, implying the fibers are thinnest, in humans; 3) frequency of Type 1 fibers is highest in humans, intermediate in monkeys, and lowest in the orangutan, whereas Type 2 fibers show an inverse trend among the species. These results suggest a correspondence in primates between the composition of the psoas major muscle fibers and difference in substrates inhabited as well as in their positional behaviors.

Psoas muscle and lumbar spine stability: a concept uniting existing controversies. Critical review and hypothesis

Psoas muscle (PM) function with regard to the lumbar spine (LS) is disputed. Electromyographic studies attribute to the PM a possible role as stabilizer. Anatomical textbooks describe the PM as an LS flexor, but not a stabilizer. According to more recent anatomical studies, the PM does not act on the LS, because it tends to pull the LS into more lordosis by simultaneously flexing the lower and extending the upper region, but due to the short moment arms of its fascicles, this would require maximal muscular effort and would expose the LS motion segments to dangerous compression and shear. The findings of the present study indicate that the described opposite action of the PM on upper and lower LS regions, performed passively and requiring minimal muscular effort, may serve to stabilize the LS in an upright stance. It was demonstrated that a vertically placed elastic metal strip, modelled into a lordotic configuration to imitate the LS, will be brought into more lordosis, with maintenance of vertical position, if a string fastened at its upper end is pulled downward in a very specific direction. Conversely, any increase of lordosis of the strip brought about by vertical downward pushing of its top, will be stabilized by tightening the pulling string in the same specific direction. As this direction corresponded with the psoas orientation, the experiments show that the PM probably functions as a stabilizer of the lordotic LS in an upright stance by adapting the state of contraction of each of its fascicles to the momentary degree of lordosis imposed by factors outside the LS, such as general posture, general muscle activity and weight bearing. The presence of multiple PM fascicles, all of about equal length, and attaching to all LS levels, facilitates this function.

Length-dependent effects of osmotic compression on skinned rabbit psoas muscle fibers

The goal of this study was to characterize the interrelationship between sarcomere length and interfilament spacing in the control of Ca2+ sensitivity in skinned rabbit psoas muscle fibers. Measurements were made at sarcomere lengths 2.0, 2.7 and 3.4 microm. At 2.7 microm the fiber width was reduced by 17% relative to that at 2.0 microm and the pCa50 for force development was increased by approximately 0.3 pCa units. In the presence of 5% Dextran T-500 the fiber width at sarcomere length 2.0 microm was also decreased by 17% and the Ca2+ sensitivity was increased to the same value as at 2.7 microm. In contrast, at sarcomere length 2.7 microm the addition of as much as 10% Dextran T-500 had no effect on Ca2+ sensitivity. At sarcomere length 3.4 microm there was an additional 7% compression and the Ca2+ sensitivity was increased slightly (approximately 0.1 pCa units) relative to that at 2.7 microm. However at 3.4 microm the addition of 5% Dextran T-500 caused the Ca2+ sensitivity to decrease to the level seen at 2.0 microm. Given that the skinning process causes a swelling of the filament lattice it is evident that the relationship between sarcomere length and Ca2+ sensitivity observed in skinned fibers may not always be applicable to intact fibers. These data are consistent with measurements of Ca2+ in intact fibers which indicate that there might be a decline in Ca2+ sensitivity at long sarcomere lengths.

Difficulties in estimating muscle forces from muscle cross-sectional area. An example using the psoas major muscle

Most biomechanical models use muscle cross-sectional area (CSA) as an indicator of maximum isometric muscle force. In general, there are multiple estimates of CSA for the same muscle. For example, numerous studies have estimated the CSA of the psoas major muscle using different subject populations and positions. However, few studies have combined the available information to obtain an overall estimate of CSA or investigated the effect different subject characteristics may have on CSA. In the present update, nine studies that reported psoas major CSA or physiologic CSA were compared with respect to subject characteristics, methodology, and results. Corrections to cadaveric data were made to adjust physiologic CSA to CSA. Comparison of reported values for living subjects indicated that females have smaller mean CSA than males for the psoas major muscle and that body size does not significantly influence muscle CSA in males. Areas derived from cadaveric data were smaller than similar studies on living subjects, possibly because of subject age, removal of tendinous and fatty components of fascicles, and lack of detailed data for fascicle angles in the supine position. Results indicate that researchers who use muscle CSA in biomechanical models should carefully assess the appropriateness of the data used, particularly in relation to potential sex differences and the influence of postural changes on CSA.

Psoas major and its controversial rotational action

The action of psoas major muscle as a primary flexor of the hip joint is undisputed. However it is also variably reported as being a medial and a lateral rotator of the femur at the hip joint. The psoas and iliacus muscles, along with their common insertion, were isolated by dissection in six adult cadaveric specimens. The action of psoas muscle was assessed by pulling the muscle along its long axis and then observing the effects on rotation of the femur, with a visual estimation of the rotation in degrees. The experiment was repeated with the hip joint capsule removed. In the anatomical position, applied traction along the long axis of the muscle produced hip flexion with no rotational component. With the hip in the abducted position, traction produced flexion, adduction, and lateral rotation of the femur at the hip joint. In adduction of the hip, traction on psoas produced only flexion at the hip joint, with no rotation. In maximal flexion, traction also produced adduction. The results were unaffected by the removal of the joint capsule.

Associations of isometric and isoinertial trunk muscle strength measurements and lumbar paraspinal muscle cross-sectional areas

The relationships of dynamic and static trunk muscle strength measurements and muscle geometry are studied. Physiologically, isometric muscle strength is directly related to muscle cross-sectional area. We measured isometric and isoinertial trunk muscle strength of 111 former elite male athletes, aged 45-68, by Isostation B-200. Paraspinal muscle cross-sectional areas were measured from axial magnetic resonance images at the L3-L4 level. Isometric and isoinertial torques were closely related, but angular velocities were not predicted by isometric maximal torque. The area of the psoas muscles correlated with isometric maximal flexion, as well as with isoinertial maximal torque. angular velocity, and power in flexion (r = 0.24-0.27). The area of the extensor group correlated with isometric maximal extension and with isoinertial maximal torque and power in extension (r = 0.24-0.25). We conclude that dynamic and static strength measurements are closely related, with angular velocity giving additional information on muscle function. Paraspinal muscle cross-sectional area is one determinant of isometric and isoinertial trunk muscle strength.

Variation of rotation moment arms with hip flexion

Excessive flexion and internal rotation of the hip is a common gait abnormality among individuals with cerebral palsy. The purpose of this study was to examine the influence of hip flexion on the rotational moment arms of the hip muscles. We hypothesized that flexion of the hip would increase internal rotation moment arms and decrease external rotation moment arms of the primary hip rotators. To test this hypothesis we measured rotational moment arms of the gluteus maximus (six compartments), gluteus medius (four compartments), gluteus minimus (three compartments) iliopsoas, piriformis, quadratus femoris, obturator internus, and obturator externus. Moment arms were measured at hip flexion angles of 0, 20, 45, 60, and 90 degrees in four cadavers. A three-dimensional computer model of the hip muscles was developed and compared to the experimental measurements. The experimental results and the computer model showed that the internal rotation moment arms of some muscles increase with flexion; the external rotation moment arms of other muscles decrease, and some muscles switch from external rotation to internal rotation as the hip is flexed. This trend toward internal rotation with hip flexion was apparent in 15 of the 18 muscle compartments we examined, suggesting that excessive hip flexion may exacerbate internal rotation of the hip. The gluteus maximus was found to have a large capacity for external rotation. Enhancing the activation of the gluteus maximus, a muscle that is frequently underactive in persons with cerebral palsy, may help correct excessive flexion and internal rotation of the hip.

Anatomical differences in the psoas muscles in young black and white men

The anatomy of the psoas major muscle (PMA) in young black and white men was studied during routine autopsies. The forensic autopsies included 44 fresh male cadavers (21 black, 23 white) with an age span of 14 to 25 y. The range for weight was 66-76 kg and for height 169-182 cm. The PMA was initially measured in its entire length before measuring the diameter and circumference at each segmental level (L1-S1). At each segmental level, the calculated anatomical cross-sectional area (ACSA) was more than 3 times greater in the black group compared with the white (P < 0.001). The psoas minor muscle (PMI) was absent in 91% of the black subjects, but only in 13% of the white subjects. These data show that the PMA is markedly larger in black than white subjects. The marked race specific difference in the size of the PMA may have implications for hip flexor strength, spine function and race specific incidence in low back pathology, and warrants further investigation.

Retropsoas positioned bowel: incidence and clinical relevance

PURPOSE

Our goal was to assess the incidence of retropsoas positioned large or small bowel in the population and to examine factors predisposing to its formation.

METHOD

The presence of retropsoas positioned bowel was retrospectively studied in 1,852 abdominal CT examinations of 1,055 men and 797 women, 648 younger and 1,204 older than 50 years. All examinations were considered normal or demonstrated findings that were unrelated to the position of the bowel.

RESULTS

Retropsoas positioned colon (RPC) was observed in 51 (2.8%) cases for the ascending and 45 (2.3%) for the descending colon. RPC appeared more frequently in younger (< 50 years) than older patients and in individuals with decreased amount of retroperitoneal fat. Retropsoas position of small bowel loops was observed in 11 (0.6%) patients, all exhibiting paucity of retroperitoneal fat.

CONCLUSION

Because of its prevalence, retropsoas positioned bowel should be considered when performing percutaneous diskectomy or other interventional procedures in the posterior retroperitoneum.

Back extensor and psoas muscle cross-sectional area, prior physical training, and trunk muscle strength--a longitudinal study in adolescent girls

The association between physical training, low back extensor (erector spinae plus multifidus muscles) and psoas muscle cross-sectional areas (CSA) and strength characteristics of trunk extension and flexion were studied in adolescent girls. A group of athletes (n = 49) (age range 13.7-16.3 years) consisting of gymnasts, figure skaters and ballet dancers was age-matched with non-athletes (n = 17) who acted as a sedentary control group. The CSA of psoas muscles and multifidus plus erector spinae muscles were measured from lumbar axial images by magnetic resonance imaging. Maximal trunk extension and flexion forces were measured in a standing position using a dynamometer and trunk musculature endurance was evaluated using static holding tests. When CSA were adjusted with body mass, the athletes showed significantly greater CSA in both muscles studied (psoas P < 0.001; erector spinae plus multifidus P < 0.05) than the non-athletes. The athletes also had a greater absolute psoas muscle CSA (P < 0.01) and trunk flexion force (P < 0.01) compared to the controls. When the forces were expressed relative to body mass, the athletes were superior both in trunk flexion (P < 0.001) and extension (P < 0.001). There was a significant correlation between muscle CSA and strength parameters, but the force per muscle CSA did not differ significantly between the athletes and the non-athletes. In addition, the athletes showed a better body mass adjusted muscle endurance in trunk flexion (P < 0.05) than the non-athletes. Our study indicated that regular physical training enhances trunk musculature hypertrophy, force and endurance in adolescent girls, and that there is an association between muscle CSA and strength parameters.

Lengths of hamstrings and psoas muscles during crouch gait: effects of femoral anteversion

Recent studies of muscle lengths measured by means of gait analysis data and musculoskeletal models have suggested that in many cases of crouch gait in patients with cerebral palsy, the hamstrings are of normal length and the psoas muscles are short. In these studies, however muscle lengths were calculated by applying kinematic data from a child's joint to a normal adult model. Children with cerebral palsy and other disorders generally do not have normal bone architecture but instead have muscle attachment points and muscle paths altered by osseous deformities. In this study, we explored the consequences of using normal adult musculoskeletal models to calculate hamstring and psoas lengths for children with cerebral palsy. Specifically, for a group of subjects with cerebral palsy who walk with a crouch gait, we investigated the changes in muscle lengths that arise when a patient-specific representation of clinically measured femoral anteversion was added to a model of normal musculoskeletal geometry. The calculation of psoas muscle length was found to be very sensitive to femoral anteversion whereas the calculation of hamstrings length was found to be relatively insensitive to this osseous deformity.

Relationship of spinal fracture to bone density, textural, and anthropometric parameters

To investigate risk factors for spinal fracture, we studied the relationship between the prevalence of asymptomatic spinal fracture and various morphological measures including spinal bone mineral density (BMD) in women. A total of 122 women ranging in age from 55 to 79 years were studied. The group consisted of 46 women aged 55-59 years (18 with fracture), 51 women aged 60-69 years (26 with fracture), and 26 women aged 70-79 years (14 with fracture). BMD of cortical and trabecular bone from L1 to L3 was measured using quantitative computed tomography (QCT). Run-length analysis was applied to evaluate the spinal trabecular textural features using CT images; the texture indices which represent the mean width of trabecular (the T-texture) and that of intertrabecular spaces (the I-texture) were obtained. Anthropometric factors including body weight and height, psoas muscle area, and vertebral bone volume were measured using CT images. Among the various factors, trabecular BMD in women aged 55-69 years showed the highest odds ratio for the presence of fracture per standard deviation (SD) decrease in bone density. However, in women aged 70-79 years, the highest odds ratio was observed for trabecular texture index but not for trabecular BMD. The I-texture in women aged 55-59 years, the muscle area in women aged 60-69 years, and cortical BMD and muscle area in women aged 70-79 years were also considered significantly related to the risk of fracture.

Iliopsoas compartment: normal anatomy and pathologic processes

The iliopsoas compartment is an extraperitoneal space that contains the greater psoas, smaller psoas, and iliac muscles. Many pathologic processes may involve the iliopsoas compartment, including inflammatory, hemorrhagic, and neoplastic conditions. Psoas muscle infection is usually due to direct extension from contiguous structures. With the decreasing incidence of tuberculosis, the majority of psoas abscesses now encountered have a pyogenic origin. Hemorrhage into the psoas muscle can be spontaneous or secondary to various conditions. Neoplastic involvement of the psoas muscle is usually due to contiguous spread and is rarely primary. With the refinement of imaging modalities, there has been increased recognition of diseases that involve the iliopsoas compartment. Although these conditions may look similar radiologically, they can be correctly diagnosed by combining the radiologic findings with the clinical history. Biopsy is effective in diagnosis of such conditions; aspiration and drainage are effective in both diagnosis and therapy.

Femoral nerve "sheath" for inguinal paravascular lumbar plexus block is not found in human cadavers

STUDY OBJECTIVE

To determine if a femoral nerve sheath capable of conveying local anesthetic to the lumbar plexus and the obturator nerve exists in human cadavers.

DESIGN

Injection of methylene blue dye into the femoral nerves of human cadavers followed by dissection and observation of dye distribution.

SETTING

University medical center pathology department autopsy room.

PATIENTS

Six fresh adult cadavers about to undergo postmortem examination.

INTERVENTIONS

Both femoral nerves of six fresh cadavers were injected with either 20 ml or 40 ml of dye. The abdomen was opened and distribution of the dye was observed.

MEASUREMENTS AND MAIN RESULTS

In all of the cadavers studied there was no evidence of a femoral nerve sheath capable of conveying methylene blue dye to the lumbar plexus. Both 20 ml and 40 ml of dye injected into the femoral nerve failed to reach the lumbar plexus or the obturator nerve. When 40 ml of dye was injected it always stained the femoral nerves, it usually stained the lateral femoral cutaneous nerves, but it never stained the obturator nerves.

CONCLUSIONS

A femoral nerve sheath capable of conveying a solution to the cadaver lumbar plexus does not exist in human cadavers. Dye injected into the cadaver femoral nerve does not reach either the lumbar plexus or the obturator nerve. When 40 ml of methylene blue dye is injected into the cadaver femoral nerve, some dye usually diffuses under the iliacus muscle fascia to the lateral femoral cutaneous nerve. This study indicates that in patients the "3-in-1 block" always blocks the femoral nerve, it usually blocks the lateral femoral cutaneous nerve, but it probably does not block the lumbar plexus or the obturator nerve.

The psoas major muscle: a three-dimensional geometric study

The purpose of this study was to use anatomical data obtained from cadavers, and geometrical scaling data obtained from MRI scans of living subjects, to assess the line of action and mechanical function of the psoas major muscle in three dimensions about each lumbar spine level. In addition, the line of action of the psoas major was documented as a function of lordosis. A total of seven cadavers were dissected from which fibre/tendon architecture was measured, while MRI scans were performed on 15 males to obtain centroid paths and area scales of the muscle over its length. In this way, the curving path of muscle line of action was accommodated together with force and moment predictions that recognized the presence of a tendon at lower lumbar levels (up to L3 in some subjects) significantly increasing the stress. Results confirm that the mechanics of the psoas cannot be adequately represented with a series of straight line vectors from vertebral origins to insertion. Moreover, the mechanical action of the psoas major does not change as a function of lumbar spine lordosis as the muscle path of action changes in accordance with changes in spine posture. Functionally, contrary to claims, the psoas cannot act as a 'derotator' of the spine, does not impose large shear forces on the spine in any posture except at L5-S1, and cannot have major affects to 'control lordosis'. It has the potential to stabilize the lumbar spine with compressive loading and with bilateral activation, to laterally flex it, and can create large anterior shear forces but only at L5-S1.

Distended iliopsoas bursa: case reports and anatomical dissection

Distension of the iliopsoas bursa is usually seen in association with underlying hip joint disease. The computed tomography (CT) appearance is characteristic and allows a diagnosis to be readily made. Computed tomography will also facilitate needle placement for aspiration of bursa contents and the injection of water-soluble contrast media for CT bursography. Three cases of iliopsoas bursa enlargement of varying underlying aetiology are presented. The dissection of seven cadavers demonstrated the anatomy of the normal bursa and highlighted its important role in the normal functioning of the iliopsoas muscle.

The geometry of the psoas muscle as determined by magnetic resonance imaging

Magnetic resonance images from fifteen physically active and asymptomatic male volunteers were collected to present morphometric parameters on the psoas and its moment arms, which are important in the study of spinal mechanics and models for the investigation of low back pain. The mean age of the subjects was 21.5 +/- 1.8 years. Data were obtained from nine vertebral and/or intervertebral levels (L2, L2/L3, L3, L3/L4, L4, L4/L5, L5, L5/S1, S1). In general, the psoas increased in size as it descended the trunk, moving anteriorly and slightly laterally in relation to the vertebral column. Maximum cross-sectional areas for the psoas (M = 16.3cm2) were observed at the L4/L5 level. Right-left symmetry was apparent in the aforementioned dimension, but not with respect to the mediolateral (X) diameter of the muscle. The length of the X moment arm was significantly (p < .05) greater for the right versus the left psoas from L3 to S1, with the length increasing as the psoas descended the trunk. However, this trend was not noted for the anteroposterior (Y) moment arm where observed values remained relatively small throughout the course of the muscle. These results will contribute to the study of low back pain onset and the design of appropriate rehabilitation interventions by providing accurate morphometric parameters for biomechanical models to predict of the loading conditions of the spine in vivo.

Anatomy of the posterior approach to the lumbar plexus block

The purpose of this study was to describe the relation of the lumbar plexus with the psoas major and with the superficial and deep landmarks close to it. Four cadavers were dissected and 22 computed tomography files of the lumbosacral region studied. Cadaver dissections demonstrated that the lumbar plexus, at the level of L5, is within the substance of the psoas major muscle rather than between this muscle and the quadratus lumborum. The femoral nerve lies between the lateral femoral cutaneous and obturator nerves. However, while the lateral femoral cutaneous nerve is in the same fascial plane as the femoral nerve, the obturator nerve can be found in the same plane as the two other nerves or in its own muscular fold. Radiological data provided the following measurements: the femoral nerve is at a depth of 9.01 +/- 2.43 cm; the psoas major medial border is at 2.73 +/- 0.64 cm from the median sagittal plane; and its lateral border is at 6.41 +/- 1.61 cm from the same plane. It is concluded that the lumbar plexus is within the psoas major, that the obturator nerve localization within the psoas major varies and that computed tomography data define precisely the relationship of the lumbar plexus with superficial and deep landmarks.

The ultrasound appearance of the normal psoas muscle

One hundred and forty-four psoas muscles in 72 subjects were scanned to study the normal ultrasound appearance. For the purpose of description the psoas was divided into three sections. Ten of the 432 sections could not be adequately seen on ultrasound. The psoas demonstrated hyperechoic striations on a hypoechoic background typical of muscle. In addition the upper section, from the origin of the muscle to the lower pole of the kidney, contained echogenic planes in 15 (10%) and the mid section, from the lower pole of kidney to iliac crest, demonstrated prominent echogenic planes and focal areas of increased and decreased echogenicity in 65 (46%). The lower section, from the iliac crest to fusion with the iliacus, demonstrated a single echogenic plane in 96 (70.5%) which was best seen running obliquely in the transverse plane and in 40 (29.5%) there were more complex echogenic planes or focal areas of increased or decreased echogenicity. The cause of the prominent echogenic plane in the lower section was not apparent in the anatomical literature and therefore cadaveric dissection of nine psoas muscles was performed which demonstrated that the echogenic plane was caused by intramuscular tendon fibres formed from the more cranial origins of the psoas. The psoas minor was not identified as a separate structure.

Trunk muscle geometry and centroid location when twisting

The trunk muscles of the lumbar region were studied using magnetic resonance imaging (MRI) in five male volunteers placed in neutral and in two twisted postures. Using a CAD digitizing system, the positions of trunk muscle centroids and the cross-sectional areas of these muscles were measured from the transverse scans at 1 cm intervals from L2 to S1. Muscle lines of action were created by connecting the muscle centroids from the successive sections. Changes in cross-sectional areas and displacements of centroids in a three-dimensional coordinate system and the local two-dimensional coordinate system were estimated at each disc level. In the three-dimensional coordinate system, all muscle centroids were displaced when twisting. Thus, the locations and orientations of all muscle lines of action changed. In the local two-dimensional coordinate system, only the muscle centroids of four abdominal muscles were displaced. Most of these displacements occurred in the first 25 degrees of twisting. Higher up in the lumbar spine, the displacement was greater. The changes in moment arms were sometimes as great as twofold. Only the abdominal oblique muscles (AOM) changed their cross-sectional area significantly; the area of the right AOM ipsilateral to the side of twisting increased, while that of the left AOM was decreased.

Unilateral "vanishing psoas": an anatomic variant

We report five patients found to have obvious asymmetry of the psoas muscles on abdominal computed tomography (CT) examination. In all five patients, the upper portion of the psoas muscle was normal, but the lower portion was significantly reduced in size. In no patient was there neurological or other disease that might explain this finding. No patient exhibited signs or symptoms secondary to psoas asymmetry. Asymmetry of the psoas musculature is apparently a benign anatomical variant that may be recognized on CT examination and must be differentiated from pathological conditions.