Validation of ultrasound imaging for Achilles entheseal fibrocartilage in bovines and description of changes in humans with spondyloarthritis.

BACKGROUND: Entheseal fibrocartilage (EF) derangement is hypothesised to be pivotal to the pathogenesis of spondyloarthritis. Ultrasound is useful for visualisation of the enthesis but its role in EF visualisation is uncertain. This work aimed to demonstrate face and content validity of ultrasound for EF visualisation both by bovine histological evaluation and EF imaging in spondyloarthritis. METHODS: Achilles enthesis of 18 bovine hindfeet was visualised using a MyLab 70 ultrasound machine. The presence of tissue with EF characteristics was documented and histological confirmation was performed on five randomly selected sections using Masson trichrome staining. Ultrasound of the Achilles tendon (AT) was performed in 19 patients with spondyloarthritis and 21 healthy controls (HC). RESULTS: The bovine EF could be visualised in all cases and seen as a thin, uncompressible, well-defined, anechoic layer between the hyperechoic bone and the hyperechoic fibrils of the enthesis both in longitudinal and transverse scans. This region corresponded to EF on histological examination. The same pattern of low signal corresponding to EF location was seen in 17/19 patients and all HC. Discontinuities of the anechoic layer around the erosions and enthesophytes were observed in the spondyloarthritis group. The thickness of the anechoic layer was not significantly different in spondyloarthritis and HC (0.5 ± 0.1 vs 0.5 ± 0.2 mm, p=0.9) whereas the thickness of the EF was greater in men (0.6 ± 0.2 vs 0.5 ± 0.1 mm; p=0.009) compared with women. CONCLUSION: Ultrasound can visualise EF of the AT insertion, which can be abnormal in cases of spondyloarthritis. This has implications for a better understanding of enthesopathy.

The fascia of the limbs and back--a review.

Although fasciae have long interested clinicians in a multitude of different clinical and paramedical disciplines, there have been few attempts to unite the ensuing diverse literature into a single review. The current article gives an anatomical perspective that extends from the gross to the molecular level. For expediency, it deals only with fascia in the limbs and back. Particular focus is directed towards deep fascia and thus consideration is given to structures such as the fascia lata, thoracolumbar fascia, plantar and palmar fascia, along with regional specializations of deep fascia such as retinacula and fibrous pulleys. However, equal emphasis is placed on general aspects of fascial structure and function, including its innervation and cellular composition. Among the many functions of fascia considered in detail are its ectoskeletal role (as a soft tissue skeleton for muscle attachments), its importance for creating osteofascial compartments for muscles, encouraging venous return in the lower limb, dissipating stress concentration at entheses and acting as a protective sheet for underlying structures. Emphasis is placed on recognizing the continuity of fascia between regions and appreciating its key role in coordinating muscular activity and acting as a body-wide proprioceptive organ. Such considerations far outweigh the significance of viewing fascia in a regional context alone.

New insights into the function of the vastus medialis with clinical implications.

PURPOSE: To investigate the gross anatomy of the distal portion of the quadriceps, and to compare the relative contributions of the vastus medialis oblique (VMO) and vastus lateralis (VL) during dynamic weight-bearing conditions. METHODS: Dissection was carried out on 10 cadavers by a longitudinal incision from the anterior superior iliac spine to the patella and completed with upper and lower transverse cuts to reinvestigate the gross anatomy and innervation patterns of the quadriceps femoris. A biomechanical test of knee kinematics was conducted on 10 healthy male volunteers. Maximal isometric force, squat jump, and drop movement jump exercises were performed on a force plate and filmed using a Saga-3 3D system, and surface EMG activity was recorded for the VMO and the VL. RESULTS: The oblique fibers of the vastus medialis (VM) are not only attached to the medial border of the patella, but they also have a small region of direct continuity with the patellar tendon. Furthermore, VMO fibers in the middle and proximal thirds of the thigh attached to vastus intermedius, whereas distally, the fibers were independent. Both parts of the VM (proximal and distal) had independent motor points. During jumping exercises, the VMO and VL were activated in a coordinated manner in a squat jump using both legs. However, in a single-leg squat jump (which challenged the stability of the knee joint more acutely), VMO activation was higher during landing. CONCLUSION: VMO activity was pronounced during the weight-bearing conditions, with increased medial and lateral knee movements. This suggests that the VM should not be considered simply as a knee extensor or as a muscle whose main role is to maintain normal patellar tracking.

Is iliotibial band syndrome really a friction syndrome?

Iliotibial band (ITB) syndrome is regarded as an overuse injury, common in runners and cyclists. It is believed to be associated with excessive friction between the tract and the lateral femoral epicondyle-friction which 'inflames' the tract or a bursa. This article highlights evidence which challenges these views. Basic anatomical principles of the ITB have been overlooked: (a) it is not a discrete structure, but a thickened part of the fascia lata which envelops the thigh, (b) it is connected to the linea aspera by an intermuscular septum and to the supracondylar region of the femur (including the epicondyle) by coarse, fibrous bands (which are not pathological adhesions) that are clearly visible by dissection or MRI and (c) a bursa is rarely present-but may be mistaken for the lateral recess of the knee. We would thus suggest that the ITB cannot create frictional forces by moving forwards and backwards over the epicondyle during flexion and extension of the knee. The perception of movement of the ITB across the epicondyle is an illusion because of changing tension in its anterior and posterior fibres. Nevertheless, slight medial-lateral movement is possible and we propose that ITB syndrome is caused by increased compression of a highly vascularised and innervated layer of fat and loose connective tissue that separates the ITB from the epicondyle. Our view is that ITB syndrome is related to impaired function of the hip musculature and that its resolution can only be properly achieved when the biomechanics of hip muscle function are properly addressed.

Trace elements in human tendons and ligaments.

Tendons and ligaments are key structures in promoting joint movement and maintaining joint stability. Although numerous reviews have detailed their structure, molecular composition, and biomechanical properties, far less attention has been paid to their content of trace elements. Tendons and ligaments are generally rich in calcium, sulfur, and phosphorus, although there are intriguing differences between one tendon/ligament and another. Furthermore, there can be significant regional variations that correlate with the presence or absence of fibrocartilage in the "wrap-around" regions of tendons or ligaments, where they change direction and press against bone. Here, their sulfate and calcium contents are particularly high. This is undoubtedly associated with the high levels of proteoglycans that are found in these cartilaginous tissues and the occasional presence of sesamoid bones within them.

The molecular composition of the extracellular matrix of the human iliolumbar ligament.

BACKGROUND CONTEXT: The human iliolumbar ligament connects the transverse process of L5 to the iliac crest and contributes to lumbosacral stability and has been associated with low back pain. However, different opinions exist regarding the functional relevance of the ligament. PURPOSE: In the present study, we analyze the regional molecular composition of the ligament extracellular matrix. STUDY DESIGN: Special attention is given to the attachment sites, to determine whether the ligament is subjected to a certain mechanical environment. METHODS: Iliolumbar ligament samples, extending from one enthesis to the other, were removed from 11 cadavers and fixed in methanol. Cryosections were immunolabeled with a panel of antibodies directed against collagens, glycosaminoglycans, proteoglycans, matrix proteins, and neurofilament. RESULTS: The mid-substance of the ligament labeled for all the molecules normally found in dense fibrous connective tissue including types I, III, and VI collagen, versican, dermatan -, chondroitin 4 -, and keratan sulfate. However, both entheses were fibrocartilaginous and labeled for type II collagen, aggrecan, and chondroitin 6- sulfate. A common feature was fat between the fiber bundles near the entheses. Occasionally this fat contained nerve fibers. CONCLUSIONS: The existence of fibrocartilaginous entheses suggests that the insertion sites of the ligament are subject to both tensile and compressive loading-probably because of insertional angle changes between ligament and bone during loading. Our findings support the suggestion that the iliolumbar ligament might play an important role in the stabilization of the lumbosacral junction.

Fatigue and muscle-tendon stiffness after stretch-shortening cycle and isometric exercise.

The purpose of the present study was to compare vertical jump performance after 2 different fatigue protocols. In the first protocol, subjects performed consecutive sets of 10 repetitions of stretch-shortening cycle (SSC) contractions. In the second protocol, successive sets of 10 repetitions of isometric contractions were performed for 10 s with the knee at 90 degrees of flexion. The exercises were stopped when the subjects failed to reach 50% of their maximum voluntary isometric contractions. Maximal isometric force and maximal concentric power were assessed by performing supine leg presses, squat jumps, and drop jumps. Surface EMG was used to determine changes in muscle activation before and after fatigue. In both groups, the fatigue exercises reduced voluntary isometric force, maximal concentric power, and drop jump performance. Kinematic data showed a decrease in knee muscle-tendon stiffness accompanied by a lengthened ground contact time. EMG analysis showed that the squat and drop jumps were performed similarly before and after the fatigue exercise for both groups. Although it was expected that the stiffness would decrease more after SSC than after isometric fatigue (as a result of a greater alteration of the reflex sensitivity SSC), our results showed that both protocols had a similar effect on knee muscle stiffness during jumping exercises. Both fatigue protocols induced muscle fatigue, and the decrease in jump performance was linked to a decrease in the strength and stiffness of the knee extensor muscles.

The functional anatomy of the iliotibial band during flexion and extension of the knee: implications for understanding iliotibial band syndrome.

Iliotibial band (ITB) syndrome is a common overuse injury in runners and cyclists. It is regarded as a friction syndrome where the ITB rubs against (and 'rolls over') the lateral femoral epicondyle. Here, we re-evaluate the clinical anatomy of the region to challenge the view that the ITB moves antero-posteriorly over the epicondyle. Gross anatomical and microscopical studies were conducted on the distal portion of the ITB in 15 cadavers. This was complemented by magnetic resonance (MR) imaging of six asymptomatic volunteers and studies of two athletes with acute ITB syndrome. In all cadavers, the ITB was anchored to the distal femur by fibrous strands, associated with a layer of richly innervated and vascularized fat. In no cadaver, volunteer or patient was a bursa seen. The MR scans showed that the ITB was compressed against the epicondyle at 30 degrees of knee flexion as a consequence of tibial internal rotation, but moved laterally in extension. MR signal changes in the patients with ITB syndrome were present in the region occupied by fat, deep to the ITB. The ITB is prevented from rolling over the epicondyle by its femoral anchorage and because it is a part of the fascia lata. We suggest that it creates the illusion of movement, because of changing tension in its anterior and posterior fibres during knee flexion. Thus, on anatomical grounds, ITB overuse injuries may be more likely to be associated with fat compression beneath the tract, rather than with repetitive friction as the knee flexes and extends.

Heel spur formation and the subcalcaneal enthesis of the plantar fascia.

OBJECTIVE: To describe the structure and significance of subcalcaneal heel spurs associated with the plantar fascia. METHODS: The enthesis of the plantar fascia was removed from 17 elderly cadavers by sagittal saw cuts either side of the medial tuberosity, radiographs were taken, and the tissue was processed for routine histology. Sagittal sections were stained with toluidine blue, Masson's trichrome, or alcian blue, and sections were matched with the corresponding radiographs. RESULTS: Spurs develop on the deep surface of the plantar fascia but their formation is heralded by degenerative changes that occur within it. According to differences between small and large spurs, we propose that there are 3 stages in their development: (1) an initial formation of cartilage cell clusters and fissures at the plantar fascia enthesis; (2) thickening of the subchondral bone plate at the enthesis as small spurs form; (3) development of vertically oriented trabeculae buttressing the proximal end of larger spurs. The spurs grow by a combination of intramembranous and chondroidal ossification. CONCLUSION: Contrary to popular belief, subcalcaneal heel spurs cannot be traction spurs as they do not develop within the plantar fascia itself. They are thus fundamentally different from heel spurs in the Achilles tendon. We suggest instead that they develop as a consequence of degenerative changes that occur in the plantar fascia enthesis.