Spatial distribution of hip capsule structural and material properties

Contemporary computational models potentially allow the practical incorporation of the effects of a joint capsule on both motion and the loads transmitted to the other parts of the joint. However, the required material properties have not been available for this purpose. To determine these properties we took both hip joints from five fresh-frozen, nondiseased cadavers. Following dissection and potting of the hemi-pelvis, distraction of the intact joint was conducted to measure the structural tangent stiffness of the joint capsule. Anatomical insertion points of the hip capsule were then recorded, and a complete capsulectomy was performed. Once excised, the capsule was sectioned into eight, approximately even sectors, and initial geometrical measurements were recorded for material property calculations. Material properties (i.e., structural tangent stiffness, failure load, ultimate strength, tangent modulus) were calculated using the load-displacement and geometric data collected for each of the sectors. This specimen-to-specimen thickness variability reveals significantly lower (p<0.01) average tangent structural stiffness values in the posterior-inferior portion of the capsule. Explorations of hip stability using numerical models can now be enhanced by incorporation of these experimental capsule data.

Development of a noninvasive measure of pelvic and hip angles in seated posture

OBJECTIVE

To develop a valid noninvasive means to measure pelvic tilt and hip angle in seated posture.

DESIGN

Validation cohort study using radiographs as a criterion standard for pelvic posture.

SETTING

Rehabilitation hospital.

PARTICIPANTS

Volunteer sample of 10 adult men with no known physical disability.

INTERVENTIONS

Radiographs were taken as subjects sat in erect, anterior, and posterior postures. An electromagnetic tracking device was as a pointer to digitize the anterior superior and posterior superior iliac spines and as a 6 degrees of freedom (df) sensor mounted on the thigh and sacrum.

MAIN OUTCOME MEASURES

Variables included pelvic tilt and hip flexion angle. Intra- and interrater reliability of radiographic measures was determined by using intraclass correlation coefficient comparison of the results from 2 investigators. Validity was determined by comparing noninvasive measures of pelvic and hip angles to radiographic measures by using correlation, analysis of variance (ANOVA), and regression.

RESULTS

Reliability of radiographic measures of pelvic tilt and hip angles were >/=.98. Pelvic tilt comparison: pointer: r=.89, R(2)=.80; 6-df sensor: r=.91, R(2)=.83; hip angle comparison using 6-df sensor: r=.78 with average difference of 4.25 degrees. ANOVA showed that differences between all invasive and noninvasive measures did not differ significantly (P>.05).

CONCLUSION

Results indicated excellent reliability of radiographic analysis techniques and represented an improvement over previously published techniques. Noninvasive measures of pelvic tilt and hip angle were shown to be valid.

The Maka femur and its bearing on the antiquity of human walking: applying contemporary concepts of morphogenesis to the human fossil record

MAK-VP-1/1, a proximal femur recovered from the Maka Sands (ca. 3.4 mya) of the Middle Awash, Ethiopia, and attributed to Australopithecus afarensis, is described in detail. It represents the oldest skeletal evidence of locomotion in this species, and is analyzed from a morphogenetic perspective. X-ray, CT, and metric data are evaluated, using a variety of methods including discriminant function. The specimen indicates that the hip joint of A. afarensis was remarkably like that of modern humans, and that the dramatic muscle allocation shifts which distinguish living humans and African apes were already present in a highly derived form in this species. Its anatomy provides no indication of any form of locomotion save habitual terrestrial bipedality, which very probably differed only trivially from that of modern humans.

Revision total hip arthroplasty

Endoscopic visualization and pneumatically-powered ballistic chisels that can be used to remove cement and cementless prostheses are recent developmental improvements for revision total hip arthroplasty (THA). Use of these new tools facilitates the revision procedure, reduces tissue trauma, and may reduce surgical time. Understanding the anatomy of the hip joint, pathophysiology that leads to the need for joint replacement, and the implant selection process can assist perioperative nurses in caring for and teaching patients who require revision THA and their family members. This article describes implant choices based on the type of bone deformity present and the use of the ballistic chiseling system during revision THA. Potential postoperative complications also are described.

Pelvic and hindlimb musculature of Tyrannosaurus rex (Dinosauria: Theropoda)

In this article, we develop a new reconstruction of the pelvic and hindlimb muscles of the large theropod dinosaur Tyrannosaurus rex. Our new reconstruction relies primarily on direct examination of both extant and fossil turtles, lepidosaurs, and archosaurs. These observations are placed into a phylogenetic context and data from extant taxa are used to constrain inferences concerning the soft-tissue structures in T. rex. Using this extant phylogenetic bracket, we are able to offer well-supported inferences concerning most of the hindlimb musculature in this taxon. We also refrain from making any inferences for certain muscles where the resulting optimizations are ambiguous. This reconstruction differs from several previous attempts and we evaluate these discrepancies. In addition to providing a new and more detailed understanding of the hindlimb morphology of T. rex--the largest known terrestrial biped--this reconstruction also helps to clarify the sequence of character-state change along the line to extant birds.

[The development and clinical application of acoustic diagnostic technique in hip joint]

This study aimed to develop a non-invasive diagnostic technique for the measurement of acoustic transmission in hip joints to reflect the dynamic response of the observed structure. This instrument consists of three sub-systems. An stimulation system applied a vibratory force at the sacrum of the test subject. A transduction system included a pair of identical microphones was installed in the tubes of two stethoscopes, which were placed at the greater trochanters on both sides for picking up the acoustic signals transmitting across the hip joints. The data acquisition and analysis system was a portable frequency analyser with a program of dual channel digital filter for measuring the power of acoustic signals in 1/3-octoscn frequency bands. Twenty-seven normal adults, 20 normal pre-school children and 40 normal neonates were recruited for the testing. Coherence function (CF) of the signal and the discrepancy (D) of bilateral hips were measured during the testing. The results from the three groups showed that there was a high coherence of the signals (CF > 0.9) and a small discrepancy (D < 3 dB) between bilateral hips in the frequency range of 200-315 Hz. For normal neonates, the frequency range (160-315 Hz) was wider in which the acoustic signals maintained a high coherence (CF > 0.94) and a smaller discrepancy (D < 2 dB) were observed between bilateral hips. This study has shown that the development of the acoustical diagnostic technique could provide a practical method with objective parameters. The results obtained in this study can offer a base for further investigation of hip disorders, particularly those related to structural abnormalities of hip joints.

Analysis of a radiographic assessment method of acetabular cover in developmental dysplasia of the hip

The aim of this study was to analyse a radiographic assessment method of acetabular cover (Ogata et al.) in developmental dysplasia of the hip (DDH). Intraobserver and interobserver reliabilities of the method were found to be 'substantial' (agreement ratio 85%, kappa coefficient 0.76) and 'moderate' (agreement ratio 71%, kappa coefficient 0.54), respectively. The percentage of hips considered pathological was significantly higher following the use of the acetabular roof shape classification system (15%) than following the measurement of the centre-edge (CE) angle of Wiberg (3%) in the same hips ( p=0.000). The average CE angle of Ogata values of types 1&2, 3 and 4 acetabula were significantly different, whereas the CE angle of Wiberg ones were not. It was concluded that this classification system was a reliable and reproducible radiological indicator for reflecting the acetabular cover. A careful assessment is needed in types 3 and 4 acetabula, because the use of classical angle measurements on plain radiographs such as the CE angle of Wiberg may carry the risk of overestimation of the radiological hip anatomy in such hips.

The three-dimensional structure of trabecular bone in the femoral head of strepsirrhine primates

It has been hypothesized for over a hundred years that trabecular bone plays an important structural role in the musculoskeletal system of animals and that it responds dynamically to applied loads through growth. The objectives of this study are to quantify the three-dimensional structure of femoral head trabecular bone in a sample of extant strepsirrhines and to relate patterns of interspecific variation to locomotor behavioral differences. The bone volume fraction (BV/TV) and fabric anisotropy of trabecular bone in the femoral heads of Cheirogaleus major, Avahi laniger, Galago senegalensis, Galago alleni, Loris tardigradus, Otolemur crassicaudatus, and Perodicticus potto were quantified in three dimensions using serial high-resolution X-ray computed tomography scan data. A volume based method was used to quantify the structural anisotropy in three cubic samples located inside the central portion of the femoral head. Significant structural differences were found between the predominantly leaping galagines and indriids and the nonleaping lorisines and cheirogaleids. The leapers in general have relatively anisotropic trabecular bone. The galagines display a unique pattern of decreasing bone volume and increasing anisotropy moving from the superior to the inferior half of the femoral head. By contrast, the nonleaping taxa possess relatively uniform and isotropic bone throughout the femoral head. The differences in femoral head trabecular structure among these taxa seem to be related to locomotor behavioral differences, reflecting variation in the use and loading of the hip joint during normal locomotion.

Sonographic investigation of anatomical specimens of infant hip joints

The anatomical foundations of infant hip sonography techniques are ill-defined. We investigated anatomical specimens of infant hip joints in a water bath, with Graf's and Terjesen's methods. Acetabular position was varied in defined increments, with respect to the ultrasound beam. The alpha angles and the femoral head coverage were measured. Plastic acetabular casts were sawn along the sonographic section planes, and the cut sections compared with the sonographic sections. For images to be obtained, which were analysable by the two methods, the ultrasound beam had to intersect with the acetabular inlet plane at defined angles. The acetabular notch had to be anteriorly rotated from the ultrasound beam plane by at least 20 degrees. Beam entry within a 50 degrees sector posterior to the perpendicular on the inlet plane gave analysable images. The alpha angles and femoral head coverage were much affected by coronal-plane transducer tilt. Caudad tilts were associated with lesser values, a fact that should be borne in mind in clinical ultrasound investigations.

Introduction of intracapsular hip fractures: anatomy and pathologic features

The morbidity, mortality, and financial burden related to intracapsular hip fractures in elderly patients in the United States will continue to increase as the population ages. An appreciation of the anatomy and pathologic features of intracapsular hip fractures is necessary for successful treatment.

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.

Management of hip disorders in patients with cerebral palsy

Hip disorders are common in patients with cerebral palsy and cover a wide clinical spectrum, from the hip at risk to subluxation, dislocation, and dislocation with degeneration and pain. Although the hip is normal at birth, a combination of muscle imbalance and bony deformity leads to progressive dysplasia. The spasticity or contracture usually involves the adductor and iliopsoas muscles; thus, the majority of hips subluxate in a posterosuperior direction. Many patients with untreated dislocations develop pain by early adulthood. Because physical examination alone is unreliable, an anteroposterior radiograph of the pelvis is required for diagnosis. Soft-tissue lengthening is recommended for children as soon as discernable hip subluxation (hip abduction <30 degrees, migration index >25%) is recognized. One-stage comprehensive hip reconstruction is effective treatment for children 4 years of age or older who have a migration index >60% but who have not yet developed advanced degenerative changes of the femoral head. Salvage options for the skeletally mature patient with a neglected hip are limited.

Development of the femoral bicondylar angle in hominid bipedalism

The bicondylar angle is the angle between the diaphysis of the femur and a line perpendicular to the infracondylar plane. The presence of a femoral bicondylar angle in Australopithecus afarensis indicates that these 3.5-million-year-old hominids were bipedal. Many studies have linked the formation of the femoral bicondylar angle with bipedality, but the mechanism for the formation of the angle is poorly understood. Mechanical factors, such as stresses and strains, influence the growth process. In particular, previous studies have demonstrated that hydrostatic compressive stress inhibits growth and ossification, and octahedral shear stress promotes growth and ossification. In this study we implemented these mechanobiological principles in a three-dimensional finite-element model of the distal femur. We applied loading conditions to the model to simulate loading during the single-leg stance phase of bipedal gait. The stresses in the physis of the distal femur that result from bipedal loading conditions promote growth and ossification more on the medial side than on the lateral side of the femur, forming the bicondylar angle. This model explains the presence of the bicondylar angle in hominid bipedalism and also the ontogenetic development of the bicondylar angle in growing children. The mechanobiological relationship between endochondral ossification and mechanical loading provides valuable insight into bone development and morphology.

[Hip anatomy and imagery]

Since the advent of new imaging methods (CT, MRI), plain radiographs still play a central role in the evaluation of the non-traumatic painful hip. In rheumatologic practice, standing antero-posterior views of the pelvis, bilateral antero-posterior views of the hips and bilateral lateral view of Lequesne should be performed. This first radiographic evaluation can be completed by a CT arthrogram in the first stage of osteoarthritis or by MRI in synovitis and epiphyseal disorders involving the femoral head (osteonecrosis, transient osteoporosis, subchondral fracture). The physician must be aware of the performance of each imaging in order to use the appropriate radiological exam in each situation.

Joint magnetic resonance imaging: normal variants and pitfalls related to sports injury

MR imaging abnormalities, such as increased signal within normally hypointense structures, form and attachment abnormalities, fluid collections in joints, tendon sheaths and bursa, or even tumors, such as Morton's neuromas, are common in asymptomatic volunteers. They may be explained by normal physiology, anatomic variability, MR imaging artifacts, or true abnormalities without clinical importance. Although it is not always possible to differentiate such variants or artifacts from clinically relevant findings, it is important to know their potential cause and clinical importance and not to over-report them as abnormality requiring additional imaging or treatment. Thorough knowledge of normal anatomy is crucial in this situation.

Imaging of hip disorders in athletes

Normal hip joint function is fundamental in running-, jumping-, and kicking-based sporting activities. Hip disorders do not account for a large portion of exercise-related injuries, but they can pose a clinical dilemma since symptoms tend to be non-specific. Conventional radiographs may demonstrate some causes of hip pain, such as stress fractures and degenerative joint disease. Magnetic resonance (MR) imaging of the hip has proven valuable in the diagnosis of radiographically occult osseous abnormalities and periarticular soft tissue disorders such as stress fractures, avulsion injuries, musculotendinous abnormalities, and bursitis. Conventional MR imaging has been less useful in the evaluation of intra-articular lesions including acetabular labral tears, intra-articular loose bodies, and cartilage lesions. The visualization of intra-articular structures and their abnormalities can be improved by the injection of diluted Gadolinium, which distends the capsule and leaks into labral tears. This article will focus on the use of conventional radiography and MR imaging in recreational and professional athletes with painful hip joints, and where possible it will compare MR imaging with other diagnostic modalities such as bone scan and CT.

Posterior pelvic tilt in patients with decreased lumbar lordosis decreases acetabular femoral head covering

The relationship between pelvic tilt and acetabular femoral head covering was determined in 38 patients with decreased lumbar lordosis. Posterior pelvic tilt and acetabular femoral head covering were measured on radiographs taken in both supine and standing positions. Previously reported normal values obtained from 96 patients were used as controls. Posterior pelvic tilt increased (P<.01) in patients with decreased lumbar lordosis and anterior acetabular femoral head covering decreased (P<.0001) compared with the controls. These differences were more remarkable in the standing position than in the supine position. Patients with decreased lumbar lordosis have decreased femoral head covering, especially in the standing position.

Effect of display modality on spatial accuracy of orthopaedic surgery pre-operative planning applications

Graphical representation of a patient's anatomy is fairly similar in the majority of orthopaedic surgery planning programs. The position of implantable devices is usually established using a three-pane window showing 2D cross sections of the CT data set taken on three user-selectable orthogonal planes. In some cases this orthogonal-plane representation is replaced or extended by interactive 3D visualization, obtained using surface rendering techniques. These ways to represent the CT data come naturally and easily to the programmer. However, the efficacy of these display strategies is questionable. The present study aims to assess if the display modality used to visualize CT data affects the inherent spatial accuracy achievable in a surgical planning application. A group of users was asked to perform repeatedly a specific planning task using various display interfaces to the same underlying software application. The planning task was designed to allow an assessment of the accuracy with which each user was able to position the prosthetic component. A specialized interface, called multimodal display, presented a peak error of 0.45 mm and 0.95 deg, significantly lower than the 2.4 mm and 4 deg for the othogonal slices interface, and the 3.8 mm and 16.7 deg for the 3D-rendering interface. The results of this study indicate an important effect of the type of visualization modality used to represent CT data on final accuracy of the planning operation.

In vivo measurement of fascicle length and pennation angle of the human biceps femoris muscle

The purpose of this investigation was to measure in vivo fascicle length (L(fas)) and pennation angle (PA) of the long head of the biceps femoris muscle (BF(lh) m.) at different hip and knee angles while the muscle was relaxed using ultrasonography (US). Data were collected from 18 healthy females (23.0 +/- 1.8 years). To validate the measurements of the L(fas) and PA, the US measurements on cadavers (n = 5), embalmed with the hip and knee in anatomical position, were compared to actual fiber lengths and PA from the dissected muscles. US images from volunteer subjects were recorded when the hip joint was positioned at 0 degrees, 45 degrees and 90 degrees of hip flexion, and at each hip position, the knee joint was placed at 0 degrees, 45 degrees and 90 degrees from full extension. The images were digitized to measure L(fas) and PA. Results showed no significant differences between US and direct measurements of the L(fas) and PA on the cadaver BF(lh) m. (p > 0.05). L(fas) and PA changed significantly between the different hip and knee positions in volunteer subjects (p < 0.05). Changes in the L(fas) and PA are more sensitive to changes in hip position with the knee position constant than to changes in knee position with the hip position constant. This difference may be related to the larger muscle moment arm at the hip resulting in greater excursion of the muscle with changing hip position. Based on the changes in L(fas) with changing joint positions, BF(lh) sarcomere length was estimated to occupy a portion of the ascending limb, the plateau and descending limb of the length-tension relationship over the range of motion studied. US scanning is valid and reliable for measuring L(fas) and PA of the BF(lh) m. An understanding of the dynamic nature of muscle architecture will assist in determining effective and efficient clinical evaluation and rehabilitation techniques.

The development and clinical application of acoustical technique in hip joint

A non-invasive acoustical system was developed for the measurement of transmission properties of acoustic waves in the hip joints. The instrumentation consisted of three sub-systems. An excitation system employed a vibratory force at the sacrum of the test subjects. A transduction system included a pair of identical microphones installed in the tubes of two stethoscopes, which were placed at the greater trochanters on both sides for picking up the acoustical signals transmitted across the hip joints. The data acquisition and analysis system was a portable signal analyzer with a program of dual channel digital filter for measuring the power of acoustical signal in 1/3-octave frequency bands. 27 normal adults, 20 normal pre-school children and 40 normal neonates were randomly selected for testing. Coherence function (CF) and discrepancy (D) was measured during the testing. Results from the three groups showed that there was a high coherence of the signals (CF > 0.9) and a small discrepancy (D < 3 dB) between bilateral hips in the frequency range of 200-315 Hz. For normal neonates, there was a wider frequency range of 160-315 Hz in which the acoustical signals maintained a high coherence (CF > 0.93) and a smaller discrepancy (D < 2 dB) was observed. This study showed that the development of the acoustical technique provided a practical method with objective parameters. The results obtained in this study can offer a baseline for further investigation of hip disorders particularly those related to structural abnormalities of the hip.

Morphometric assessment of the canine hip joint using the dorsal acetabular rim view and the centre-edge angle

The dorsal acetabular rim (DAR) view of the hip joint can be used to assess the weightbearing portion of the acetabulum and the acetabular coverage, providing an adjunct to the conventional ventrodorsal (VD) view in the radiographic evaluation of hip dysplasia in the dog. A quantitative index of acetabular coverage in the DAR view, the acetabular slope (AS) angle, was originally proposed in 1990. The aim of the present study was to make a prospective, comparative assessment of a new parameter, the centre-edge (CE) angle, with the AS angle, for the evaluation of the acetabular coverage of the femoral head in the DAR view. The reliability and repeatability of the two parameters was assessed using the r(I) value of intraclass correlation coefficient (ICC) in a prospective study of 208 hip joints in large and giant breed dogs. An estimation of the added value of using the DAR view, compared with that of the VD standard view alone, was also assessed. The CE angle showed a higher r(I) value compared with the AS angle; in 26 per cent of hips of FCI classes A, B and C, the DAR view provided additional diagnostic information compared with the VD view, with respect to lateralisation and/or initial changes to the dorsal rim. It is concluded that the CE angle is more reliable than the AS angle in the evaluation of acetabular coverage, and that the DAR view provides valuable data compared with the VD view alone in the early stages of canine hip dysplasia.

Differences in bone mineral density, bone mineral content, and bone areal size in fracturing and non-fracturing women, and their interrelationships at the spine and hip

Osteoporotic fractures are a major public health problem, particularly in women. Bone mineral density (BMD), bone mineral content (BMC), and bone size have been regarded as important determinants of osteoporotic fractures. In 1449 women over age 30 years, we studied the detailed relationship, at the spine and hip, between BMD, BMC, and bone areal size (all measured by dual-energy X-ray absorptiometry) and compared their relative magnitudes in fracturing and non-fracturing individuals. We find that, (1) BMD and BMC are significantly higher at the spine and hip in non-fracturing women. Bone areal size is significantly larger at the spine in non-fracturing women; however, the significance disappears when adjustment is made for the significant difference of height (stature) between fracturing and non-fracturing women. In contrast to the spine, bone areal size is always significantly largerin fracturing women at the hip. (2) The relationship among BMD, BMC, and bone areal size is different at the spine and hip. Specifically, at the spine, BMD increases with bone areal size linearly. At the hip, BMD has a quadratic relationship with bone areal size, so that BMD increases at lower bone areal sizes, then (after an intermediate zone of values) decreases with increasing bone areal size. However, BMD adjusted for BMC always decreases with increasing bone areal size, as expected by the definition of BMD. With no adjustment for BMC, the increase in BMD with bone areal size is due to a more rapid increase of BMC than increasing bone areal size, thus explaining the observations of association of both larger BMD and larger bone areal size with stronger bone. (3) At the spine, 86.2% of BMD variation is attributable to BMC and 12.6% to bone areal size. At the hip, 98.0% of BMD variation is due to BMC and 1.1% due to bone areal size. The current study may be important in understanding the relationship among BMD, BMC, and bone size as risk determinants of osteoporotic fractures.

Radiographic associations for "primary" hip osteoarthrosis: a retrospective cohort study of 47 patients

This radiographic retrospective cohort study aims to identify relations between the prearthrotic anatomy of the hip joint and the type of subsequent osteoarthrosis (OA). Radiographs of 64 hips in 47 patients were evaluated. Several anatomical indices were measured on radiographs obtained before the onset of OA. The location, type and grade of OA were recorded on subsequent radiographs. Due to the small number of hips available, only three potential risk factors could be considered for both OA location and OA type (weight-bearing surface angle, spherical sector and neck shaft angle for both outcomes). The only variable that was found to be a significant predictor of OA location was the degree of inclination of the acetabular sourcil. Patients with craniomedial sourcils were more likely to have medial OA. No predictors of OA type could be identified. Our results suggest that the anatomy of the hip joint is a factor determining the location of developing osteoarthrosis.

Contribution of acetabular labrum to articulating surface area and femoral head coverage in adult hip joints: an anatomic study in cadavera

The purpose of our study was to describe the gross anatomy of the adult acetabular labrum and to determine its contribution to the depth, surface area, and volume of the acetabulum. Fifty-five embalmed hips were studied. Each hip was disarticulated, and standardized measurements were taken. Calculations of the acetabular articulating surface area and volume, with and without the labrum, were performed based on these measurements. Average width of the acetabular labrum was 5.3 mm (SD, 2.6 mm). The labrum was wider anteriorly and superiorly than posteriorly. The surface area of the acetabulum without the labrum was 28.8 cm2; with the labrum, it was 36.8 cm2 (P < .0001). The volume of the acetabulum without the labrum was 31.5 cm3; with the labrum, it was 41.1 cm3 (P < .0001). There was no side-to-side difference in contribution of the labrum to either surface area or volume between right and left hips. Comparison of these indices for males and females showed statistically significant differences in absolute but not relative increases.

Effects of current and discontinued estrogen replacement therapy on hip structural geometry: the study of osteoporotic fractures

It is assumed that estrogen influences bone strength and risk of fractures by affecting bone mineral density (BMD). However, estrogen may influence the mechanical strength of bones by altering the structural geometry in ways that may not be apparent in the density. Repeated dual energy X-ray absorptiometry (DXA) hip scan data were analyzed for bone density and structural geometry in elderly women participating in the Study of Osteoporotic Fractures (SOF). Scans were studied with a hip structural analysis program for the effects of estrogen replacement therapy (ERT) on BMD and structural geometry. Of the 3,964 women with ERT-use data, 588 used ERT at both the start and end of the approximately 3.5-year study, 1,203 had past use which was discontinued by clinic visit 4, and 2,163 women had never used ERT. All groups lost BMD at the femoral neck, but the reduced BMD among users of ERT was entirely due to subperiosteal expansion and not bone loss, whereas both bone loss and expansion occurred in past or nonusers. BMD increased 0.8%/year at the femoral shaft among ERT users but decreased 0.8%/year among nonusers. Section moduli increased at both the neck and shaft among ERT users but remained unchanged in past and nonusers. Current, but not past, use of estrogen therapy in elderly women seems to increase mechanical strength of the proximal femur by improving its geometric properties. These effects are not evident from changes in femoral neck BMD.

Hip arthroscopy without traction: In vivo anatomy of the peripheral hip joint cavity

PURPOSE

To describe the in vivo anatomy of the peripheral compartment of the hip joint using a systematic sequence of examination without traction.

TYPE OF STUDY

Case series.

METHODS

We performed 35 hip arthroscopies without traction from an anterolateral portal in the supine position. Free draping and a good range of movement of the hip joint were used to relax parts of the capsule and increase the intra-articular volume of the area that was inspected. Each procedure was documented on a standard protocol including detailed information on technical features and normal and pathologic intra-articular findings.

RESULTS

A comprehensive inspection of the peripheral compartment was obtained from the anterolateral portal. A systematic sequence of examination was developed separating the periphery of the hip joint into 7 areas: anterior neck area, medial neck area, medial head area, anterior head area, lateral head area, lateral neck area, and posterior area. The arthroscopic in vivo anatomy of each area is described. In 3 patients, 1 to 3 loose bodies were removed. In 1 patient with a synovial chondromatosis, 40 chondromas were retrieved. In osteoarthritis, impinging osteophytes were trimmed in 3 cases and partial synovectomy was performed in 10 patients. The following complications were observed: a temporary sensory deficit of the lateral femoral cutaneus nerve in 1 patient, scuffing of the anterior surface of the femoral head in 3 patients, detaching of an osteophyte in 1 patient, and partial tears of the anterior synovial fold in 10 patients.

CONCLUSIONS

Arthroscopy without traction allows for a complete evaluation of hip anatomy without the loaded articular surfaces, the acetabular fossa, and the ligamentum teres. For a complete overview of both the central and peripheral part of the hip, traction is necessary for the central part.

Greater trochanter of the hip: attachment of the abductor mechanism and a complex of three bursae--MR imaging and MR bursography in cadavers and MR imaging in asymptomatic volunteers

PURPOSE

To evaluate trochanteric anatomy with magnetic resonance (MR) imaging, bursography, MR bursography, and anatomic analysis.

MATERIALS AND METHODS

T1-weighted and fat-saturated T2-weighted (transverse, sagittal, coronal, and coronal oblique planes) MR imaging of the greater trochanter was performed in 10 cadaveric hips and 12 hips of asymptomatic volunteers. Three bursae comprising the trochanteric bursa complex were injected, and conventional radiography and MR imaging were performed. The specimens were sectioned for anatomic analysis, corresponding to the MR imaging planes. Tendon attachments and bursal localization were related to the facets of the greater trochanter.

RESULTS

The bony surface of the greater trochanter consists of four facets: anterior, lateral, posterior, and superoposterior. The gluteus medius muscle attaches to the superoposterior and lateral facets. The gluteus minimus muscle attaches to the anterior facet. The trochanteric bursa covered the posterior facet and the lateral insertion of the gluteus medius muscle. The subgluteus medius bursa was located in the superior part of the lateral facet, underneath the gluteus medius tendon. The subgluteus minimus bursa lies in the area of the anterior facet, underneath the gluteus minimus tendon, medial and cranial to its insertion, and extends medially covering the distal anterior part of the hip joint capsule. The trochanteric bursa is delineated with fat on both sides and can be seen on transverse nonenhanced T1-weighted images as a fine line curving around the posterior part of the trochanter.

CONCLUSION

MR imaging and bursography provide detailed information about the anatomy of tendinous attachments of the abductor muscles and the bursal complex of the greater trochanter.

Arthroscopy of the hip. Anatomy and portals

Establishing the three portals for hip arthroscopy in the correct sequence is crucial, as is use of the image intensifier for location and passage of needles. Patient position for hip arthroscopy can be either lateral decubitus or supine. Gentle techniques are essential to avoid scuffing of the articular surface. The 70 degrees scope is the "workhorse" in this procedure. Location of portals is essential to successful hip arthroscopy.

Safety and efficacy of intraarticular hip injection using anatomic landmarks

This study tests the hypotheses that the hip can be injected safely and reliably, using anatomic landmarks, without fluoroscopic guidance. Fifteen human cadavers (30 hips) were injected, each receiving one anterior hip injection and one lateral hip injection with methylene blue dye. Anatomic dissections were done on all 30 specimens to determine the rate of success and the proximity of the needle to the neurovascular structures about the hip with each approach. Neither the anterior nor the lateral injection approach, using published techniques based on anatomic landmarks, was sufficiently reliable to recommend for clinical use without radiographic guidance; the anterior approach was successful in only 60% of injections, and the lateral technique was successful in 80% of injections. In addition, the anterior approach, which is recommended in more reference works than any other approach, resulted in significantly more risk to the femoral nerve than did the lateral approach. The needle pierced or contacted the femoral nerve in 27% of anterior injections and was within 5 mm of the femoral nerve in 60% of anterior attempts. The anterior injection approach also resulted in needle placements significantly closer to the femoral artery and the lateral femoral cutaneous nerve than did the lateral approach. Using the lateral approach, the needle was never within 25 mm of any neurovascular structure in any injection. Some form of radiographic or sonographic guidance is recommended for needle placement during hip injections and aspirations; the lateral approach for needle placement seems safer than the anterior approach, with respect to the possibility of neurovascular injury.

Hip arthroscopy. The supine position

Hip arthroscopy is an effective technique. It can be performed successfully either supine or in the lateral position, but there appear to be modest advantages of the supine approach. Arthroscopy offers a less invasive alternative to arthrotomy for traditionally recognized forms of hip pathology, such as loose bodies or impinging osteophytes. Arthroscopy also offers a method of treatment for many conditions (including labral tears, acute articular injuries, and damage to the ligamentum teres) that previously went unrecognized and untreated. In the past, these patients were simply resigned to living within the constraints of their symptoms. Several dictums about hip arthroscopy must be acknowledged. First, the key to a successful outcome lies in proper patient selection. A technically well-executed procedure will fail when performed for the wrong reason, or when the outcome fails to meet the patient's expectations. Second, the patient must be properly positioned for the procedure to go well. Poor positioning will assure a difficult procedure. Third, simply gaining access to the hip joint is not an outstanding technical accomplishment. The paramount issue is accessing the joint in as atraumatic a fashion as possible. Due to its constrained architecture and dense soft tissue envelope, the potential for inadvertent iatrogenic scope trauma is significant and, perhaps unavoidable to some extent. Therefore, every reasonable step should be taken to keep this concern to a minimum. Perform the procedure as carefully as possible and be certain that it is being performed for the right reason. After accessing the joint, the techniques of operative arthroscopy for the hip employ existing strategies established in other joints. Because of the restraints imposed by the hip, however, technical deficiencies may be more apparent.

Injury to the ligamentum teres. Mechanism, findings, and results of treatment

In this article we discuss the role of the ligamentum teres in relation to the hip joint. The anatomy of the ligamentum teres is used to help with an understanding of the mechanism of the ligament's actions. This action and the modes of injury to the ligament are explored. We describe a simple classification system for injuries to the ligamentum teres, such that Group I are complete tears to the ligament; Group II are partial tears; and Group III are degenerative tears. As more experience is gained with the diagnosis and treatment of injuries to this integral structure, the clearer will be our understanding of the role of the ligamentum teres in the hip joint.

Hip arthroscopy. The lateral approach

The lateral approach provides an easy and safe access to the hip joint. The line from skin to the joint itself is a straight, downward drop (Fig. 18). The vital arteries and nerves are a safe distance from the portal sites. The potential problems that can arise from this procedure are from the traction applying a compression force on the branches of the pudendal nerve as they cross the ischium (Fig. 19) and traction force on the sciatic nerve. I have always maintained that traction should be treated like a tourniquet; that is, it should be applied for no more then 2 hours. [figure: see text] Furthermore, the amount of traction should not exceed 75 pounds. I use a tensiometer, but it is not mandatory because the major issue with traction is the duration of application. I have monitored the sciatic nerve using both evoke potentials and, in some cases, motor potentials in over 50 cases in the past year, and the poundage and time limits of the traction (75 pounds and 2 hours) were verified. In addition, if the fracture [figure: see text] table has a vertical post as well as a peroneal post, set the vertical post in the back of the patient, and not in the front. Flexing the hip around that post will greatly increase the traction and at the same time will place an extreme stretch on the sciatic nerve, setting up the chance of a significant sciatic nerve neuropraxia. To protect the pudendal nerve, Lyon et al suggest that the perineal post be at least 9 cm in diameter to distribute the forces in a wide area on the ischium and make sure that the pelvis is well supported so the pressure of the post is not placed directly on the this nerve. The perineal posts on most fracture tables are only 3 cm in diameter. These can be made larger by wrapping them with padding. In some fracture tables, the slats that support the lower leg can be removed, and consequently the support on the pelvis is lost. For hip arthroscopy, the slats do not have to be removed. The lateral approach provides a safe and simple way of performing hip arthroscopy. The instruments can be manipulated easily so that the entire confines of the joint can be visualized with the arthroscope and reached with operative instruments.

Radiographic imaging for treatment and follow-up of developmental dysplasia of the hip

Developmental dysplasia of the hip (DDH) is a spectrum of abnormalities that can range from a very mild disturbance to a very severe process that is incapacitating later in life. This article considers the causative factors and natural history of DDH, as well as anatomic abnormalities, physical examination findings, and both surgical and nonsurgical treatment options. The goal of this article is to place in perspective the use of advanced imaging techniques in the diagnosis and follow-up of patients with DDH. Ultrasound, computed tomography (CT), and magnetic resonance (MR) findings are reviewed with respect to the diagnosis of DDH, treatment complications, and long-term problems that may occur in treated and untreated patients.

The genetic contribution to hip joint morphometry and relationship to hip cartilage thickness

A twin study approach was used to explore the genetic determinants of hip joint morphometry and their relationship to hip cartilage thickness. Our analysis used data on anthropometric characteristics and radiographic features of a group of 222 monozygotic (MZ) and 240 dizygotic (DZ) twins. We confirmed that genetic factors account for most of the variation in minimal joint space (MJS) and acetabular anatomy. This genetic variation was largely due to factors unique to MJS itself and not explained by anthropometric variables or measurements of acetabular morphology. Only a small proportion was shared with genetic factors underlying acetabular shape, mainly the centre edge angle.

MR arthrography for evaluation of the acetabular labrum

MR arthrography of the hip has provided new insights into the lesions underlying mechanical hip pain. Until now evaluation of these structures, especially the acetabular labrum, has been limited. With the joint distention provided by MR arthrography, labral detachments and intrasubstance tears can be identified and differentiated from the many varied appearances of the asymptomatic labrum. This article reviews the normal anatomy of the hip, the clinical presentation of internal derangement and the technique for performing MR arthrography. The variations in morphology and signal of the asymptomatic labrum are reviewed as well as the appearance of the abnormal labrum.

[Images of growth zones of the femoral head, neck and greater trochanter in MR examination]

The possibilities of MR imaging were evaluated in 36 children with 58 normal hips. The analysed children were divided into 3 groups, basing on age at the time of investigation i.e. children less than 5 years old, age ranging from 5 to 12 years, and over 12 years of age. MRI allowed visualisation of all growth zones of the proximal femur. On T-1 weighted images the growth cartilage of the femoral head, neck, and greater trochanter were of intermediate signal intensity. On sequences using fat saturation and on gradient echo images the cartilage was of high signal intensity. The growth zone of the subtrochanteric cartilage was of low signal intensity on T-1 weighted images and high signal intensity on sequences using fat saturation and on gradient echo images. T-1 weighted images together with FLASH 3D FAT SAT seem to be sufficient for the analysis of the growth zones of the proximal femur.

Does body size account for gender differences in femur bone density and geometry?

The extent to which greater bone strength in men is caused by proportionately greater bone mass versus bigger bone size is not clear, primarily because the larger overall body size of men has made direct comparisons of skeletal measures difficult. We examined gender differences in femur neck (FN) areal bone mineral density (BMD) values collected from 5,623 non-Hispanic whites aged 20+ years in the third National Health and Nutrition Examination Survey (NHANES III, 1988-1994) before and after correction for measured height and weight. We supplemented the conventional areal BMD data (Hologic QDR 1000) with measurements of areal BMD and geometric properties (subperiosteal width, section modulus, and cortical thickness) made at narrow "cross-sectional" regions traversing the FN and the proximal shaft using a structural analysis program. Before body size adjustment, men had significantly higher values than women for all variables at the three measurement sites (p < 0.0001). Adjustment for body size reduced the differences between the sexes for all variables but had a greater effect on BMD (1-8% higher in men) than on geometry (5-17% higher in men). When examined by age, the sex discrepancy was significantly greater in the older group for all variables except subperiosteal widths. We conclude that although body size difference may account for most of the areal BMD difference between men and women, male bones are still bigger in ways that suggest greater bone strength. These differences may contribute importantly to lower fracture risk in men.

Musculo-skeletal loading conditions at the hip during walking and stair climbing

Musculo-skeletal loading plays an important role in the primary stability of joint replacements and in the biological processes involved in fracture healing. However, current knowledge of musculo-skeletal loading is still limited. In the past, a number of musculo-skeletal models have been developed to estimate loading conditions at the hip. So far, a cycle-to-cycle validation of predicted musculo-skeletal loading by in vivo measurements has not been possible. The aim of this study was to determine the musculo-skeletal loading conditions during walking and climbing stairs for a number of patients and compare these findings to in vivo data. Following total hip arthroplasty, four patients underwent gait analysis during walking and stair climbing. An instrumented femoral prosthesis enabled simultaneous measurement of in vivo hip contact forces. On the basis of CT and X-ray data, individual musculo-skeletal models of the lower extremity were developed for each patient. Muscle and joint contact forces were calculated using an optimization algorithm. The calculated peak hip contact forces both over- and under-estimated the measured forces. They differed by a mean of 12% during walking and 14% during stair climbing. For the first time, a cycle-to-cycle validation of predicted musculo-skeletal loading was possible for walking and climbing stairs in several patients. In all cases, the comparison of in vivo measured and calculated hip contact forces showed good agreement.Thus, the authors consider the presented approach as a useful means to determine valid conditions for the analysis of prosthesis loading, bone modeling or remodeling processes around implants and fracture stability following internal fixation.

Accuracy of the functional method of hip joint center location: effects of limited motion and varied implementation

Accurate location of the hip joint center is essential for computation of hip kinematics and kinetics as well as for determination of the moment arms of muscles crossing the hip. The functional method of hip joint center location involves fitting a pelvis-fixed sphere to the path traced by a thigh-fixed point while a subject performs hip motions; the center of this sphere is the hip joint center. The aim of the present study was to evaluate the potential accuracy of the functional method and the dependence of its accuracy on variations in its implementation and the amount of available hip motion. The motions of a mechanical linkage were studied to isolate the factors of interest, removing errors due to skin movement and the palpation of bony landmarks that are always present in human studies. It was found that reducing the range of hip motion from 30 degrees to 15 degrees did significantly increase hip joint center location errors, but that restricting motion to a single plane did not. The magnitudes of these errors, however, even in the least accurate cases, were smaller than those previously reported for either the functional method or other methods based on pelvis measurements of living subjects and cadaver specimens. Neither increasing the number of motion data observations nor analyzing the motion of a single thigh marker (rather than the centroid of multiple markers) was found to significantly increase error. The results of this study (1) imply that the limited range of motion that is often evident in subjects with hip pathology does not preclude accurate determination of the hip joint center when the functional method is used; and (2) provide guidelines for the use of the functional method in human subjects.

The canine trochanteric fossa: a radiographic and anatomic study

Radiographic features of the region of the trochanteric fossa were evaluated bilaterally on 175 ventrodorsal radiographs of canine hip joints and findings were compared to anatomic specimens. The fossa showed a variable radiographic appearance, which was affected by positioning and anatomic diversity. On a small number of radiographs (n = 12), the trochanteric fossa was clearly defined as a circular area of radiopacity surrounded by a radiolucent halo. This appearance was significantly influenced by medial rotation of the femur (P < 0.001). On some anatomic specimens an irregular protuberance representing the site of attachment of the gemelli, internal and external obturator muscles was seen within the fossa, surrounded by a variable number of small openings, which were thought to be nutrient foramina. Dissection identified a small number of minor branches of the medial circumflex femoral artery entering these.

Normal hip joint contact pressure distribution in single-leg standing--effect of gender and anatomic parameters

A practical and easy-to-use analysis technique that can study the patient's hip joint contact force/pressure distribution would be useful to assess the effect of abnormal biomechanical conditions and anatomical deformities on joint contact stress for treatment planning purpose. This technique can also help to establish the normative database on hip joint contact pressure distribution in men and women in different age groups. Twelve anatomic parameters and seven biomechanical parameters of the hip joint in a normal population (41 females, 15 males) were calculated. The inter-parameter correlations were investigated. The pressure distribution in the hip joint was calculated using a three-dimensional discrete element analysis (DEA) technique. The 3D contact geometry of the hip joint was estimated from a 2D radiograph by assuming that the femoral head and the acetabular surface were spherical in shape. The head-trochanter ratio (HT), femoral head radius, pelvic height, the joint contact area, the normalized peak contact pressure, abductor force, and the joint contact force were significantly different between men and women. The normalized peak contact pressure was correlated both with acetabular coverage and head-trochanter ratio. Change of abductor force direction within normal variation did not affect the joint peak contact pressure. However, in simulated dysplastic conditions when the CE angle is small or negative, abductor muscle direction becomes very sensitive in joint contact pressure estimation. The models and the results presented can be used as the reference base in computer simulation for preoperative planning in pelvic or femoral osteotomy.

Regional material properties of the human hip joint capsule ligaments

The hip joint capsule functions to constrain translation between the femur and acetabulum while allowing rotational and planar movements. Despite the crucial role it plays in the pathogenesis of hip instability, little is known about its biomechanical properties. The goal of this study was to determine the regional material properties of the iliofemoral and ischiofemoral ligaments of the capsule. Ten human cadaveric specimens of each ligament were tested to failure in tension. The stress at failure, strain at failure, strain energy density at failure, toe- and linear-region elastic moduli, and the Poisson's ratio were measured for each ligament. The strain to failure was greatest in the ischiofemoral ligament, while no significant difference was noted in failure stress by region or ligament. The Young's moduli of elasticity ranged from 76.1 to 285.8 MPa among the different ligaments, and were generally consistent with properties previously reported for the shoulder capsule. The elastic moduli and strain energy density at failure differed by region. No significant differences in Poisson's ratio were found by region or ligament. The average Poisson's ratio was approximately 1.4, consistent with anisotropic behavior of ligamentous tissues. Understanding the material properties of the hip capsule may help the orthopaedic surgeon better understand normal ligament function, and thereby choose a surgical approach or strategy of repair. Furthermore, knowledge of the normal mechanical function of the hip capsule ligaments could assist in the evaluation of the success of a repair.

Alveolar process fractal dimension and postcranial bone density

OBJECTIVES

Our goal was to determine whether the radiographic fractal dimension of the maxillary and mandibular alveolar processes is related to bone density of the alveolar processes, spine, hip, and radius in healthy women.

STUDY DESIGN

Thirty-seven dentate healthy white women aged 20 to 78 years underwent assessment of systemic and alveolar process bone. After a periodontal examination, D-speed vertical bite-wing and periapical radiographs with aluminum step wedges and a density correction algorithm were used to make alveolar process fractal dimension and density calculations within regions of interest that avoided crestal bone and intrabony defects. Anteroposterior (L1-L4) and lateral (L2-L4) lumbar spine, total hip, and total wrist densities were determined by means of dual energy x-ray absorptiometry.

RESULTS

Correlation analysis revealed significant relationships between maxillary alveolar process fractal dimension and maxillary alveolar process density (r = 0.47, P < or =.01), mandibular alveolar process density (r = 0.48, P < or =.01), and mandibular alveolar process fractal dimension (r = 0.44, P < or =.05); and between mandibular alveolar process fractal dimension and maxillary alveolar process density (r = 0.54, P < or =.01) and mandibular alveolar process density (r = 0.58, P < or =.001). No significant relationships were found between the maxillary alveolar process or the mandibular alveolar process fractal dimension and the density of any postcranial regions.

CONCLUSIONS

In healthy women, the alveolar process radiographic fractal dimension is significantly related to the alveolar process density but is not related to the density of the spine, hip, or radius.

Shelf acetabuloplasty for Perthes' disease: 12-year follow-up

The goal of all therapies for Perthes' disease is to achieve an optimal shape of the acetabulum and an optimal coverage of the femoral head. Thirty patients who were included in this follow-up study (mean follow-up 12 years) underwent a shelf acetabuloplasty for Catterall group III or IV. The mean IOWA hip score at follow-up was 96 (max. 100 points, range 74-100). The mean acetabular-head quotient increased from 82.9% pre-operatively to 107.9% postoperatively, and remained 102.4% at follow-up. There was a decrease in mean lateral subluxation ratio from 1.44 pre-operatively to 1.27 postoperatively, which remained 1.23 at follow-up. According to the Stulberg classification in the 18 adult hips, 6 hips had a good result (Stulberg 1 or 2), 10 hips had a fair result (Stulberg 3), and 2 hips had a poor result (Stulberg 4 or 5). These results appear to be better than the natural history as described by Stulberg. Shelf acetabuloplasty can be considered as an appropriate surgical treatment for severe cases of Perthes' disease.