Functional integrative analysis of the human hip joint: the three-dimensional orientation of the acetabulum and its relation with the orientation of the femoral neck

Comparing Hip Dysplasia in Dogs and Humans: A Review

Hip dysplasia (HD) is common in both humans and dogs. This interconnection is because humans and dogs descended from a common ancestor and therefore have a similar anatomy at micro- and macroscopic levels. Furthermore, dogs are the animals of choice for testing new treatments for human hip dysplasia and orthopedic surgery in general. However, little literature exists comparing HD between the two species. Therefore, the aim of this review is to describe the anatomy, etiology, pathogenesis, diagnostics, and treatment of HD in humans and dogs. HD as an orthopedic condition has many common characteristics in terms of etiology and pathogenesis and most of the differences can be explained by the evolutionary differences between dogs and humans. Likewise, the treatment of HD shows many commonalities between humans and dogs. Conservative treatment and surgical interventions such as femoral osteotomy, pelvic osteotomy and total hip arthroplasty are very similar between humans and dogs. Therefore, future integration of knowledge and experiences for HD between dogs and humans could be beneficial for both species.

[Lumbo-pelvino-acetabular alignment-basics and clinical consequences]

The spinal shape and the pelvic ante-/retroversion of an individual are determined by its innate, genetically fixed lumbosacral angulation. This can be measured with little effort in the lateral standing radiograph of the patient. In spinal surgery, there are a lot of original papers on the topic. In hip surgery, however, the individual pelvic version and its consequences for the acetabular orientation have not received the same attention so far.This review focuses on previous data on the relationship between lumbosacral angulation and pelvic ante-/retroversion. Four anatomically definable pelvic types can be distinguished; three of those have to be considered as facultatively pathogenetic. Clinical consequences arise for the clinical pictures of spondylolisthesis, non-specific lower back pain, acetabular retroversion and developmental dysplasia of the hip, as well as for acetabular cup positioning in total hip arthroplasty.

Trabecular architecture of the great ape and human femoral head

Studies of femoral trabecular structure have shown that the orientation and volume of bone are associated with variation in loading and could be informative about individual joint positioning during locomotion. In this study, we analyse for the first time trabecular bone patterns throughout the femoral head using a whole-epiphysis approach to investigate how potential trabecular variation in humans and great apes relates to differences in locomotor modes. Trabecular architecture was analysed using microCT scans of Pan troglodytes (n = 20), Gorilla gorilla (n = 14), Pongo sp. (n = 5) and Homo sapiens (n = 12) in medtool 4.1. Our results revealed differences in bone volume fraction (BV/TV) distribution patterns, as well as overall trabecular parameters of the femoral head between great apes and humans. Pan and Gorilla showed two regions of high BV/TV in the femoral head, consistent with hip posture and loading during two discrete locomotor modes: knuckle-walking and climbing. Most Pongo specimens also displayed two regions of high BV/TV, but these regions were less discrete and there was more variability across the sample. In contrast, Homo showed only one main region of high BV/TV in the femoral head and had the lowest BV/TV, as well as the most anisotropic trabeculae. The Homo trabecular structure is consistent with stereotypical loading with a more extended hip compared with great apes, which is characteristic of modern human bipedalism. Our results suggest that holistic evaluations of femoral head trabecular architecture can reveal previously undetected patterns linked to locomotor behaviour in extant apes and can provide further insight into hip joint loading in fossil hominins and other primates.

[The great apophyses: Functional strain and relevance]

BACKGROUND

The structure of apophyses and apophyseal growth plates is not substantially different from those of epiphyses and epiphyseal growth plates. In contrast to epiphyseal growth plates, apophyses and apophyseal growth plates do not contribute to the longitudinal growth of the extremity. They are associated with their adjacent joints, triggering the lengths of their lever arms and influencing their external shape and internal architecture. The formative stimulus on apophyses is given by muscles and tendons inserting at the apophysis or canopying the apophsis.

APOPHYSIS OF THE GREATER TROCHANTER

The apophysis of the greater trochanter significantly contributes to the lever arm length of the hip joint. Its growth activity triggers the neck-shaft angle and finally the centration of the hip joint.

TIBIAL APOPHYSIS

The tibial apophysis interacts with the slope of the proximal tibia and hereby influences the sagittal stability of the knee joint. A damage to the growth plate of the tibial tubercle leads to an anteverted tibial slope and a genu recurvatum difficult to treat.

CALCANEAL APOPHYSIS

The calcaneal apophysis determines the length and position of the calcaneus and herewith influences the torque of the ankle joint. In a nutshell you may regard the apophyses as adjusting screws acting on their adjacent joints and influencing their growth, form and structure.

The underused hip in ipsilaterally orthotics-dependent children

BACKGROUND

The aim of this investigation is the development of primarily healthy hips in children who have required orthoses/protheses over the long term due to ipsilateral distally located deformities of the leg. These children show ipsilateral in-toeing gait and Duchenne's limping followed by a coxa valga antetorta and facultative hip decentration. A practical question is whether these hips are in danger of decompensation. An additional theoretical question is how the external shape and internal architecture changes if a primarily healthy hip is underused.

METHODS

Ten children with healthy hips who are unilaterally long-term orthotics/prosthetics-dependent agreed to undergo an instrumental gait analysis. The results were analyzed and correlated with clinical findings, a common activity score and planimetric radiographic data.

RESULTS

The intra-individual comparison revealed a number of significant changes in the hip of the deformed leg (p < 0.05). Clinically, the internal rotation was increased (15° ± 4.2°), while the external rotation was diminished (13° ± 1.3°). Radiologically, the projected caput-collum-diaphyseal angle, the lesser trochanter to articular surface distance and the head-shaft angle were increased by 11.1° ± 15.4°, 5.8 ± 4.2 mm and 11.9° ± 0.6°, respectively. Both the Sharp and acetabular angles were increased, the former by 3.6° ± 0.6° and the latter by 3.2° ± 0.6°. Kinetic gait analysis showed increased stride length (6.8 ± 3.7 cm), shortened stance phase (6.6 ± 1.6 %) and reduced forces transmitted to the ground (92.2 ± 34.3 N). The kinematic analysis showed increased hip abduction (14.0° ± 8.2°), while the pelvic obliquity was not significantly changed (0.01° ± 0.01°).

CONCLUSIONS

Duchenne's limp and lack of weight-bearing stress are the decisive pathogenic factors of the underused coxa valga and acetabular dysplasia. These changes follow the mechanobiological concept of "function modifies design", which means function influences external shape and internal architecture of bones and joints. As a practical consequence we recommend that one pelvic radiograph be performed as a precaution at the end of puberty of children with these conditions.

LEVEL OF EVIDENCE

Level II retrospective study.