Ischiofemoral Ligaments Research Articles

Reconstruction of soft noncontractile tissue in the derived therizinosaur Nothronychus: The interplay of soft tissue and stress on hindlimb ossification and posture.

Nothronychus graffami was a large therizinosaur from the Upper Cretaceous of North America. Much of the skeleton is well-preserved and relatively undistorted. The synovial capsule, extracapsular, and intracapsular tendons are reconstructed in N. graffami using existing scars and comparison with the hips of extant theropods and models of extinct theropods. The iliofemoral, pubofemoral, and ischiofemoral ligaments are all modeled. Soft tissue, especially the ischiofemoral and pubofemoral ligaments reduced possible protraction/retraction of the femur at the hip while stabilizing the joint. Therefore, most hindlimb movements took place at the knee. Weight-bearing function in Nothronychus was transferred from the supra-acetabular crest to the pubic peduncle and associated labrum at rest. The femur possessed an intermediately angled neck, convergent with titanosaurs. Therefore, some lateral abduction is proposed, requiring a well-developed meniscus at the knee. Such a posture would result in considerable mediolateral stress along the femoral shaft, resulting in increased transverse ossification. The femur is considered somewhat abducted from the midline, especially when maximally pronated, as the preacetabular ala is more extensive than the post-acetabular ala. This trait would probably result in a laterally divergent femur, as in many birds, resulting in a broad-gauge trackway with wider separation between left and right footprints than observed in many theropod trackways. Limb ratios and ossification patterns suggest a slow, waddling gait. A standard digitiform pose is reconstructed as is common for theropods, but a plantigrade stance cannot be firmly rejected.

89 Do Corticosteroid and Local Anaesthetic Hip Injections Administered Proximal or Distal to The Zona Orbicularis Have an Effect on Patient Satisfaction?

Abstract Aim Pubofemoral and ischiofemoral ligaments blend to make zona orbicularis. Zonaorbicularis has been suggested to force fluid from peripheral compartment to central compartment in unidirectional flow. This study aims to assess whether injection of corticosteroid with local anaesthetic injected either proximal or distal to the zona orbicularis has effect on patient satisfaction. Method This retrospective study investigated consecutive patients undergoing ultrasound guided hip injections at a single centre in the UK between November 2018 and March 2019. Patients were identified using IMPAX© picture archiving and communications system. Radiographs were assessed to see if radiopaque dye and therefore corticosteroid and local anaesthetic had been injected proximal or distal to the zona orbicularis. Clinic letters were accessed on the electronic patient record and we recorded whether patients had pain relief at 24 hours and 2 weeks following hip injection. Results 133 Patients were identified during the study period, of which 40 were included. At 24 hours post-injection 72% of patients were satisfied and 28% were unsatisfied, for which there was 76% and 70% satisfaction for proximal and distal injections respectively (p = 0.63). At 2 weeks post-injection 45% of patients were satisfied and 55% of patients unsatisfied, for which there was 47% and 44% satisfaction for proximal and distal injections respectively (p = 0.9). Conclusions Overall patient satisfaction is high following hip corticosteroid and local anaesthetic injection. No difference was found between injections proximal and distal to the zona orbicularis. Further research is needed to quantify the association between proximal and distal injections.

Biomechanical Comparison of Capsular Repair, Capsular Shift, and Capsular Plication for Hip Capsular Closure: Is a Single Repair Technique Best for All?

Background:In hip arthroscopy, the best capsular closure technique to prevent microinstability in some patients while preventing overconstraints in other patients has yet to be determined.Purpose:To evaluate the biomechanical effects of capsular repair, capsular shift, and combination capsular shift and capsular plication for closure of the hip capsule.Study Design:Controlled laboratory study.Methods:Eight cadaveric hips (4 male and 4 female hips; mean age, 55.7 years) were evaluated in 7 conditions: intact, vented, capsulotomy, side-to-side repair, side-to-side repair with capsular plication (interval closure between iliofemoral and ischiofemoral ligaments), capsular shift repair, and capsular shift repair with plication. Measurements, via a 360° goniometer, included internal and external rotation with 1.5 N·m of torque at 5° of extension and 0°, 30°, 60°, and 90° of flexion. In addition, the degree of maximum extension with 5 N·m of torque and the amount of femoral distraction with 40 N and 80 N of force were obtained. Repeated-measures analysis of variance and Tukey post hoc analyses were used to analyze differences between capsular conditions.Results:At lower hip positions (5° of extension, 0° and 30° of flexion), there was a significant increase in external rotation and total rotation after capsulotomy versus the intact state (P < .05). At all hip flexion angles, there was a significant increase in external rotation, internal rotation, and total rotation as well as a significant increase in maximum extension after capsulotomy versus capsular shift with plication (P < .05 for all). At all flexion angles, both capsular closure with side-to-side repair (with or without plication) and capsular shift without capsular plication were able to restore rotation, with no significant differences compared with the intact capsule (P > .05). Among repair constructs, there were significant differences in range of motion between side-to-side repair and combined capsular shift with plication (P < .05).Conclusion:At all positions, significantly increased rotational motion was seen after capsulotomy. Capsular closure was able to restore rotation similar to an intact capsule. Combined capsular shift and plication may provide more restrained rotation for conditions of hip microinstability but may overconstrain hips without laxity.Clinical Relevance:More advanced closure techniques or a combination of techniques may be needed for patients with hip laxity and microinstability. At the same time, simple repair may suffice for patients without these conditions.

THE DEVELOPMENT OF EXTRA-ARTICULAR LIGAMENTS OF THE HIP JOINT DETERMINE ANGULAR VALUES OF THE PROXIMAL FEMUR

There are practically no data on the quantitative aspects of prenatal morphogenesis and the growth rates of the ligaments of the hip joint in humans, as well as information on the correspondence of the shape and structure of the ligaments to the bones forming the joint. The aim of the study was to reveal the features of the growth of the extra-articular ligaments of the hip joint in the prenatal period and to establish correlations between the structure of the ligaments and the structures of the proximal end of the femur. The material of the study is based on the analysis of 175 cases without pathology of the musculoskeletal system. The dimensions of the ilio-femoral, pubic-femoral, ischio-femoral ligaments and the cervico-diaphyseal angle and angle of rotation of the femoral neck in relation to the distal epiphysis of the bone were studied. As a result of the study, it was found that in the process of prenatal development with increasing age, the distance between the distal fixation points and the angle between the parts of the ilio-femoral ligament increases. Both legs have fibers that are woven into the fibrous membrane of the joint capsule. A correlation was found between the growth of morphometric parameters of the ilio-femoral ligament and the angular values ​​of the proximal femur. In contrast to the ilio-femoral ligament, the pubo-femoral and ischio-femoral ligaments show low signs of differentiation at different stages of prenatal ontogenesis. The pubo-femoral ligament becomes available for macroscopic examination from the beginning of the second half of the prenatal period. It is defined as a thickening of the medial fibrous membrane of the joint capsule, has its origin on the superior branch of the pubic bone and the iliac part of the acetabulum and is attached to the intertrochanteric line in the medial segment. The sciatic-femoral ligament is macroscopically defined as a thickening of the posterior part of the joint capsule. The ligament has a triangular shape, with a base in the region of the ischial part of the acetabulum and the ischial tubercle, its apex facing the trochanteric fossa at the antero-inner edge of the greater trochanter. It was found that the growth rate of morphometric parameters of different parts of the hip joint ligaments at different stages is not the same, which determines the change in the shape of the ligaments. The greatest transformations occur in the ilio-femoral ligament, the smallest in the pubic-femoral and sciatic-femoral ligaments. There is a correlation between the anatomical structure of the extra-articular ligaments of the hip joint and the corresponding angular values ​​of the proximal femur.

Anatomic evaluation of the insertional footprints of the iliofemoral and ischiofemoral ligaments: a cadaveric study

BackgroundAn understanding of the insertional footprints of the capsular ligaments of the hip is important for preserving hip function and stability given the increasing number of minimally invasive hip surgeries being performed under a limited surgical view. However, it is difficult to detect these ligaments intraoperatively and many surgeons may not fully appreciate their complex anatomy. The aims of this study were to quantify the proximal and distal footprints of the iliofemoral ligament (ILFL) and ischiofemoral ligament (ISFL) and to estimate the location of the corresponding osseous landmarks on the proximal femur, which can be detected easily during surgery.MethodsTwelve hip joints from Japanese fresh frozen cadavers were used. All muscle, fascia, nerve tissue, and vessels were removed to expose the intact capsular ligaments of the hip. The length and width of the proximal and distal footprints of the ILFL and ISFL were measured and their relationship to osseous structures was evaluated, including the intertrochanteric line, femoral neck, and lesser trochanter.ResultsThe mean length of the distal medial arm of the ILFL footprint was 17.9 mm and the mean width was 9.0 mm. The mean length of the distal lateral arm of the ILFL footprint was 23.0 mm and the mean width was 9.7 mm. For the footprint of the medial arm, the insertion was in the distal third of the intertrochanteric line and that of the lateral arm was in the proximal 42% of this line. The mean distance from the lesser trochanter to the footprint of the medial arm was 24.6 mm. The mean length of the distal ISFL footprint was 11.3 mm and the mean width was 6.9 mm. The footprint of the distal ISFL was located forward of the femoral neck axis in all specimens.ConclusionsUnderstanding the size and location of each capsular ligament footprint in relation to an osseous landmark may help surgeons to manage the hip capsule intraoperatively even under a narrow surgical view. The findings of this study underscore the importance of recognizing that the distal ISFL footprint is located relatively forward and very close to the distal lateral arm footprint.

A three-dimensional finite element analysis of the human hip

A three-dimensional hip model was created from the MRI scans of one human subject based on constructing the entire pelvis and femur. The ball and socket joint was modelled between the hip’s acetabulum and the femoral head to analyse the multiaxial loads applied in the hip joint. The three key ligaments that reinforce the external surface of the hip to help to stabilise the joint were also modelled which are the iliofemoral, the pubofemoral and ischiofemoral ligaments. Each of these ligaments wraps around the joint connection to form a seal over the synovial membrane, a line of attachment around the head of the femur. This model was tested for different loading and boundary conditions to analyse their sensitivities on the cortical and cancellous tissues of the human hip bones. The outcomes of a one-legged stance finite element analysis revealed that the maximum of 0.056 mm displacement occurred. The stress distribution varied across the model which the majority occurring in the cortical femur and dissipating through the cartilage. The maximum stress value occurring in the joint was 110.1 MPa, which appeared at the free end of the proximal femur. This developed finite element model was validated against the literature data to be used as an asset for further research in investigating new methods of total hip arthroplasty, to minimise the recurrence of dislocations and discomfort in the hip joint, as well as increasing the range of movement available to a patient after surgery.

Does Capsular Laxity Lead to Microinstability of the Native Hip?

Background: Hip “microinstability” is commonly cited as the cause of symptoms that occur in the presence of translation of the femoral head away from conformity with the acetabular fossa. However, there is still no consistent objective criteria defining its presence and biomechanical basis. One hypothesis is that abnormal motion of the articular surfaces occurs because of capsular laxity, ultimately leading to clinical symptoms. Purpose: To determine the relationship between capsular laxity and abnormal rotation and translation of the hip. Study Design: Controlled laboratory study. Methods: Eight cadaveric hips were dissected down to the capsule and mounted in a customized multiaxial hip activity simulator. Each specimen was loaded with 5 N·m of internal and external rotational torque in full extension and 0°, 30°, 60°, and 90° of flexion. During testing, the relative position and rotation of the femur and the pelvis were monitored in real time with a 6-camera motion analysis system. The testing was repeated after capsular laxity was generated by placing a regular array of incisions (“pie crusting”) in the iliofemoral, pubofemoral, and ischiofemoral ligaments. Joint rotation and femoral head translation were calculated with specimen-specific models. A hip microinstability index was defined as the ratio between the length of the locus of the femoral head center and the radius of the femoral head during rotation from extension to 90° of flexion. Results: In intact hips, the components of femoral head translation were within 0.5 mm in positions close to neutral (<30° of flexion). Capsular modification led to significant increases in internal and external rotation (P < .01) and in the translation of the femoral head center at different positions (P < .05). Compared with intact hips, the femoral head was inferiorly displaced during external rotation and anteroinferiorly during internal rotation. The length of the locus of the femoral head center increased from 3.61 ± 1.30 mm to 5.35 ± 1.83 mm for external rotation (P < .05) and from 6.24 ± 1.48 mm to 8.21 ± 1.42 mm for internal rotation (P < .01). The correlations between rotational laxity and the total translation of the femoral head were not significant, with coefficients of 0.093 and 0.006 in external and internal rotation, respectively. In addition, the hip microinstability index increased from 0.40 ± 0.08 for intact hips to 0.55 ± 0.09 for modified hips (P < .01). Conclusion: The native hip approximates a concentric ball-and-socket joint within 30° of flexion; however, beyond 30° of flexion, the femoral head translation reached as high as 4 mm. Capsular laxity leads to microinstability of the hip, as indicated by significantly increased joint rotations and femoral head translations and an abnormal movement path of the femoral head center. However, there was no correlation between rotational laxity and the increase in femoral head translation. Clinical Relevance: Capsular laxity alters normal kinematics (joint rotation and femoral head translation) of the hip, potentially leading to abnormal femoral-acetabular contact and joint degeneration.

The capsular ligaments provide more hip rotational restraint than the acetabular labrum and the ligamentum teres : an experimental study.

In this in vitro study of the hip joint we examined which soft tissues act as primary and secondary passive rotational restraints when the hip joint is functionally loaded. A total of nine cadaveric left hips were mounted in a testing rig that allowed the application of forces, torques and rotations in all six degrees of freedom. The hip was rotated throughout a complete range of movement (ROM) and the contributions of the iliofemoral (medial and lateral arms), pubofemoral and ischiofemoral ligaments and the ligamentum teres to rotational restraint was determined by resecting a ligament and measuring the reduced torque required to achieve the same angular position as before resection. The contribution from the acetabular labrum was also measured. Each of the capsular ligaments acted as the primary hip rotation restraint somewhere within the complete ROM, and the ligamentum teres acted as a secondary restraint in high flexion, adduction and external rotation. The iliofemoral lateral arm and the ischiofemoral ligaments were primary restraints in two-thirds of the positions tested. Appreciation of the importance of these structures in preventing excessive hip rotation and subsequent impingement/instability may be relevant for surgeons undertaking both hip joint preserving surgery and hip arthroplasty.Cite this article: Bone Joint J 2015; 97-B:484–91.

Ligament strain on the iliofemoral, pubofemoral, and ischiofemoral ligaments in cadaver specimens: biomechanical measurement and anatomical observation.

The iliofemoral, pubofemoral, and ischiofemoral ligaments are major structures that stabilize the hip joint. We have sought evidence on which to base more effective hip stretching positions. The purpose of this study was to measure strains on these ligaments and to observe them. Eight fresh/frozen translumbar cadaver specimens were used. Clinically available stretching positions for these ligaments were adopted. Strain on each ligament was measured by a displacement sensor during passive torque to the hip joint. Hip motion was measured using an electromagnetic tracking device. The strained ligaments were captured on clear photographs. Significantly, high strains were imposed on the superior iliofemoral ligament by external rotation of the hip (3.48%); on the inferior iliofemoral ligament by maximal extension and 10° or 20° of external rotation with maximal extension (1.86%, 1.46%, 1.25%); on the pubofemoral ligament by maximal abduction and 10°, 20°, or 30° of external rotation with maximal abduction (3.18%, 3.28%, 3.11%, 2.99%); and on the ischiofemoral ligament by 10° or 20° of abduction with maximal internal rotation (7.11%, 7.83%). Fiber direction in each ligament was clearly identified. Significantly, high strains on hip ligaments corresponded with the anatomical direction of the ligament fibers. Positions were identified for each ligament that imposed maximal increase in strain on it.

The Effect of Capsulectomy On Hip Joint Biomechanics

Objectives:Hip arthroscopy is performed in young adult patients with hip pain. During arthroscopy, capsulectomy is performed to improve intraoperative visualization. The stability of the hip joint after capsulectomy is relatively unknown. Our study evaluated anterior hip stability in capsular sectioned states with labral injury. We theorized the load required for anterior translation would decrease with greater capsular injury.Methods:Ten human cadaveric pelvises (20 hips, mean 54.25 years) without radiographic evidence of degeneration or dysplasia were harvested. The hips were prepared and mounted onto a custom built testing fixture. Two pelvises were excluded due to fixation issues for one or both hips. The 16 hips were tested in five states (table 1). Each hip was tested in neutral position with a 20N compressive force. The capsular incision was made in-line with the femoral neck. The labrectomy was made at 2:30 position. The sutured capsule was created using #2 Ethibond suture 1cm apart along the incision. The partial capsulectomy was made by resecting the iliofemoral ligament, leaving the pubofemoral and ischiofemoral ligaments intact. Total capsulectomy state was created by removing the remaining capsule. The load at 12mm of anterior translation was recorded for each state after two preconditioning trials.Results:A repeated measures ANOVA with a Bonferroni adjustment showed no difference between all-intact vs. sutured-intact. It also demonstrated no significant difference between the sutured-intact and the sutured labrectomy states. A repeated measures ANOVA with a Bonferroni adjustment was run to compare the capsular states with a 1cm partial labrectomy (table 2). There was a significant difference between the sutured-labrectomy and the partial capsulectomy (p=0.0146) and between the sutured-labrectomy and the total capsulectomy (p=0.0005). There was also a significant difference when comparing the partial capsulectomy and the total capsulectomy (p=0.0377).Conclusion:The findings demonstrate that both the capsule and labrum play a role in providing anterior hip stability. These results indicate that the iliofemoral ligament is crucial for preventing anterior translation in labral injured states. Intraoperative capsulectomy should be avoided in patients with large irreparable labral tears to prevent postoperative anterior hip instability

Microscopic analysis of the iliofemoral and ischiofemoral ligaments in the hip joint: collagen fiber direction and crimp distribution

Since no previous studies have described the functional significance of the iliofemoral and ischiofemoral ligaments on the basis of microscopic analyses, we examined the direction of collagen fiber alignment and crimp distribution of the collagen fibers in sections cut in different directions. Polarized microscopic images of sections along the longitudinal (L) and transverse (T) planes of each ligament were obtained from 20 cadavers (8 males and 12 females, age at death 81.7 ± 9.4 years old). Results showed that the microscopic direction of collagen fibers in the iliofemoral ligament was parallel to the macroscopic direction, suggesting that this ligament may play a part in restricting extension of the hip joint. In contrast, the microscopic direction of collagen fibers in the ischiofemoral ligament was not parallel to the macroscopic direction, suggesting that this ligament may contribute not only to the restriction of medial rotation but also retstriction of flexion of the hip joint. From the low density of the crimp distribution in the L plane, the iliofemoral ligament may contribute to stability of the hip joint in the standing position in the living body. In conclusion, the microscopic observations of the direction of collagen fibers as well as the crimp distribution shown in the present study provide a better understanding of the functional significance of the iliofemoral and ischiofemoral ligaments.

Defining the Origins of the Iliofemoral, Ischiofemoral, and Pubofemoral Ligaments of the Hip Capsuloligamentous Complex Utilizing Computer Navigation

To use computer navigation software to investigate the specific origins of the hip capsuloligamentous complex. Six fresh frozen cadaver hips were anatomically landmarked utilizing a three-dimensional computer navigation system. The acetabular origins of the iliofemoral, pubofemoral, and ischiofemoral ligaments were statically digitized. Computer software was used to create a 180° (6:00) meridian line positioned over the midpoint of the acetabular notch, and to present the results in a clocklike manner in hours and minutes (00:00) and also degrees relative to the 12 o'clock position. The iliofemoral ligament origin starts at 17° (±31°) from the 12 o'clock position, or 12:35 (±1:02) in hours and minutes, and ends at 69° (±13°) or 2:18 (±0:25), spanning a mean distance of 52° (±19°). The ischiofemoral ligament has the broadest origin, starting at 262° (±12°) or 8:44 (±0:24), and ending at 353° (±17°) or 11:45 (±0:14), spanning a mean distance of 90° (±6°). The pubofemoral ligament origin is the smallest, starting at 121° (±5°) or 4:02 (±0:11), and ending at 163° (±9°) or 5:27 (±0:18), spanning a mean distance of 42° (±5°). The iliofemoral ligament origin demonstrates the greatest anatomic variability with regards to its location and its size (p = 0.002). This study demonstrates that there is significant variability in the size and location of the iliofemoral ligament origin versus the pubofemoral and ischiofemoral ligaments. Level IV anatomic cadaveric study. See the guidelines online for a complete description of level of evidence.

THE ROLE OF ARTHROSCOPIC THERMAL CAPSULORRHAPHY IN THE HIP

Arthroscopic thermal modification of collagen in the hip capsular tissue appears to be a treatment option for patients with hip instability. Traumatic hip instability is associated with frank dislocation or a subluxation, and labral tears. Atraumatic hip instability is associated with evidence of generalized ligament laxity. It can be associated with bone-collagen type disorders, including Ehlers-Danlos syndrome, Down syndrome, arthrochalasis multiplex congenita, developmental dysplastic hip, and idiopathic type. As previously discussed by Bellabarba et al, capsular laxity may be the underlying cause of dynamic hip instability. The capsule is a fibrous, thick, and strong structure that encircles the proximal femur and the acetabulum. The capsule is thicker anteriorly than posteriorly, and consists of two sets of fibers, circular and longitudinal. The capsule ligaments play a very important role in hip stability. The hip joint capsule is reinforced by the iliofemoral, pubofemoral, and ischiofemoral ligaments. It remains sensitive to stretch and serves as a mechanism for muscular feedback and pain. The iliofemoral ligament limits hyperextension and lateral rotation of the hip joint and is taut in full extension. Full extension of the hip exposes the capsule and ligaments to a twisting and shortening effect that forces the head onto the acetabulum. We are currently studying the effect of iliofemoral ligament deficiency and its relationship to instability. Many of the properties of synovial lubrication depend on contact with articular surfaces, and incongruency due to instability may have some functional role in distribution of synovial fluid, leading to stresses from weightbearing and eventually to rapid deterioration of the articular surfaces. The high-level athletes in this series include two professional baseball players, three professional golfers (PGA), one professional football player (NFL), one figure skater (Olympic gold medalist), one gymnast (Olympic level, bilateral hips), and one ballet dancer; they returned to their pre-injury level of activity. The other patients returned to their pre-injury functional lifestyle. Hip instability appears to present consistently with stable gait abnormalities and painful sensation of instability. Recognizing the various patterns of hip instability is complicated, and therefore management and outcome of these disorders are quite variable. Bellabarba et al concluded that physical therapy alone had been unsuccessful and that temporary success of a posterior capsular "plication" in one patient showed promise. Arthroscopic thermal modification of collagen in the hip capsular tissue appears to be a treatment option for patients with hip instability. The hip joint capsule is predominantly type 1 collagen, and the mechanism of tissue shrinkage through type 1 collagen alteration is well documented in the literature. Short-term results appear promising, however, more studies are required to determine the long-term efficacy of this procedure in the treatment of this challenging disorder.

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.

New aspects of the morphology and function of the human hip joint ligaments

The capsular ligaments of the human hip joint were submitted to exact morphological analysis, and they proved to be multiple and numerous. We have described various ligamentous systems and their interconnections, and have suggested new terminologies and systematics. The ligaments were subjected to functional analysis by means of measuring strips to determine the positions in which the ligaments are taut. The ligament systems were all found to serve a restrictive function, and various parts of the apparatus restricted all possible movements in the hip joint. Extension is restricted by the medial iliofemoral complex, abduction by the pubofemoral ligament, and adduction by the posterior coxal ligaments and by the superior ischiofemoral ligament. Flexion is restricted by the inferior ischiofemoral ligaments, inward rotation by the superior ischiofemoral ligament, and outward rotation by the lateral iliofemoral complex. Only the ligament of the femoral head is unable to exert a restricting function, despite reaching a state of tension in extreme adduction.

THE LOCKING MECHANISM OF THE HIP JOINT.

AbstractThis study is based upon observations made upon the hip joints of 12 embalmed cadavers. Windows were made into the joints and the effects of extension and flexion of the femur, produced both actively and passively, were noted. Particular attention was paid to associated movements. Use was made of x‐rays as well as direct observation.It was determined that, as the femur extends it abducts and medially rotates; a terminal medial rotation takes up the last of the slack in the iliofemoral and ischiofemoral ligaments. The locked position therefore is brought about by these three movements. There is no evidence of any medial displacement or translation of the femoral head on extension, as is commonly stated to occur. The passively extended femur also abducts and tends to rotate medially whereas the flexed femur laterally rotates and falls into a position about midway between abduction and adduction. The same general effects are reproducibile in the skeleton articulated in such a way as to leave hip motion practically unhindered. This would indicate that the ligaments play a passive role, restricting motion within physiological limits. The shape of the acetabulum and the direction toward which it faces, together with the topography of the articular surface of the head of the femur, are no doubt responsible for the associated movements.