Damage to and repair of the acetabular labral-chondral complex are areas of clinical interest in the treatment of young adults with pain in the hip and in the prevention of degenerative arthritis of the hip. There are varying theories as to why most acetabular tears are located anterosuperiorly. We have studied the prenatal development of the human acetabular labral-chondral complex in 11 fetal hips, aged from eight weeks of gestation to term. There were consistent differences between the anterior and posterior acetabular labral-chondral complex throughout all ages of gestation. The anterior labrum had a somewhat marginal attachment to the acetabular cartilage with an intra-articular projection. The posterior labrum was attached and continuous with the acetabular cartilage. Anteriorly, the labral-chondral transition zone was sharp and abrupt, but posteriorly it was gradual and interdigitated. The collagen fibres of the anterior labrum were arranged parallel to the labral-chondral junction, but at the posterior labrum they were aligned perpendicular to the junction. We believe that in the anterior labrum the marginal attachment and the orientation of the collagen fibres parallel to the labral-chondral junction may render it more prone to damage than the posterior labrum in which the collagen fibres are anchored in the acetabular cartilage. The anterior intra-articular projection of the labrum should not be considered to be a pathological feature

1. The surface of mature adult human articular cartilage from the knee has been studied by electron microscopy in eleven patients ranging in age from thirty-seven to eighty-three years. The ultrastructural appearance varies from person to person and often from area to area in the same specimen. These variations range from an intact surface to one showing overt fibrillation visible with the light microscope. 2. In areas where the articular surface appears intact the underlying superficial matrix consists of closely packed collagen fibres with only a small amount of interfibrillary ground substance. The collagen fibres show a predominantly tangential orientation in this region of the cartilage. Osmophilic lipidic bodies are sometimes seen in the matrix very close to the joint surface. 3. The appearances under the electron microscope are altered in what is interpreted as an early ultrastructural change in the development of cartilage fibrillation. In the affected areas the collagen fibres show abnormally wide separation by an excessive amount of interfibrillary matrix. Collagen fibres become directly exposed to the joint cavity, and the surface can also show accumulations of finely granular material and sometimes tuft-like projections containing collagen fibres and fine fibrils. At a slightly later stage shallow clefts and steeply sloping curves are apparent at the surface. It is suggested that these various alterations precede the development of overt fibrillation visible under the light microscope. 4. Electron micrographs occasionally show small "blisters" at the articular surface. Electron microscopy has not given evidence of shedding of cells into the joint cavity from non-fibrillated areas of adult human articular cartilage. Cells can, however, sometimes become exposed at the surface in fibrillated areas

We examined the mechanical properties of Vicryl (polyglactin 910) mesh in vitro and assessed its use in vivo as a novel biomaterial to attach tendon to a hydroxyapatite-coated metal implant, the interface of which was augmented with autogenous bone and marrow graft. This was compared with tendon re-attachment using a compressive clamp device in an identical animal model. Two- and four-ply sleeves of Vicryl mesh tested to failure under tension reached 5.13% and 28.35% of the normal ovine patellar tendon, respectively. Four-ply sleeves supported gait in an ovine model with 67.05% weight-bearing through the operated limb at 12 weeks, without evidence of mechanical failure. Mesh fibres were visible at six weeks but had been completely resorbed by 12 weeks, with no evidence of chronic inflammation. The tendon-implant neoenthesis was predominantly an indirect type, with tendon attached to the bone-hydroxyapatite surface by perforating collagen fibres

We used an in vivo model to assess the use of an autogenous cancellous bone block and marrow graft for augmenting tendon reattachment to metallic implants. We hypothesised that augmentation of the tendon-implant interface with a bone block would enable retention of the graft on the implant surface, enhance biological integration, and result in more consistent functional outcomes compared with previously reported morcellised graft augmentation techniques. A significant improvement in functional weight-bearing was observed between six and 12 weeks. The significant increase in ground reaction force through the operated limb between six and 12 weeks was greater than that reported previously with morcellised graft augmented reconstructions. Histological appearance and collagen fibre orientation with bone block augmentation more closely resembled that of an intact enthesis compared with the morcellised grafting technique. Bone block augmentation of tendon-implant interfaces results in more reliable functional and histological outcomes, with a return to pre-operative levels of weight-bearing by 24 weeks

We examined whether enamel matrix derivative (EMD) could improve healing of the tendon–bone interface following reconstruction of the anterior cruciate ligament (ACL) using a hamstring tendon in a rat model. ACL reconstruction was performed in both knees of 30 Sprague-Dawley rats using the flexor digitorum tendon. The effect of commercially available EMD (EMDOGAIN), a preparation of matrix proteins from developing porcine teeth, was evaluated. In the left knee joint the space around the tendon–bone interface was filled with 40 µl of EMD mixed with propylene glycol alginate (PGA). In the right knee joint PGA alone was used. The ligament reconstructions were evaluated histologically and biomechanically at four, eight and 12 weeks (n = 5 at each time point). At eight weeks, EMD had induced a significant increase in collagen fibres connecting to bone at the tendon–bone interface (p = 0.047), whereas the control group had few fibres and the tendon–bone interface was composed of cellular and vascular fibrous tissues. At both eight and 12 weeks, the mean load to failure in the treated specimens was higher than in the controls (p = 0.009). EMD improved histological tendon–bone healing at eight weeks and biomechanical healing at both eight and 12 weeks. EMD might therefore have a human application to enhance tendon–bone repair in ACL reconstruction

Bone samples from the iliac crest of patients with no signs of bone disorder were treated with collagenase to remove the collagen component and so allow detailed observation of the mineral hydroxyapatite. Both polished and unpolished surfaces were studied in the scanning electron microscope and they showed that the mineral component of bone is composed of small rounded units about 10 nm across which are fused together to form larger spheroidal units roughly 100 nm in diameter. In the unpolished surfaces these 100 nm units are seen to aggregate to form columns approximately parallel to their neighbours and with numerous interconnections forming a continuous mineral phase. The polished sections also show the hydroxyapatite as a continuous phase of contiguous spheroids and the holes from which the collagen fibres were removed are clearly revealed. Lamellations in the surface are interpreted as resulting from adjacent layers of collagen fibres having orientations approximately perpendicular to each other

While the evolution of the bony skeleton of the shoulder girdle is well described, there is little information regarding the soft tissues, in particular of the rotator cuff. We dissected the shoulders of 23 different species and compared the anatomical features of the tendons of the rotator cuff. The alignment and orientation of the collagen fibres of some of the tendons were also examined histologically. The behaviour of the relevant species was studied, with particular reference to the extent and frequency of forward-reaching and overhead activity of the forelimb. In quadrupedal species, the tendons of supraspinatus, infraspinatus and teres minor were seen to insert into the greater tuberosity of the humerus separately. They therefore did not form a true rotator cuff with blending of the tendons. This was only found in advanced primates and in one unusual species, the tree kangaroo. These findings support the suggestion that the appearance of the rotator cuff in the evolutionary process parallels anatomical adaptation to regular overhead activity and the increased use of the arm away from the sagittal plane

1. A clinical, radiological and histological description of a patient with fibrogenesis imperfecta ossium is given. We think that this is the first case in which diagnosis has been made during the life of the patient. 2. The disease is characterised by a defect in the formation of the collagen fibres of the bone matrix. There is also a failure of normal calcification of the matrix, giving rise to the appearance of wide "osteoid" seams. When examined with the polarising microscope and when stained with Gomori's reticulin stain the collagen fibres can be seen to be grossly deficient and abnormal. 3. The patient presented at the age of fifty-four years with bone pain and multiple fractures. The only biochemical abnormality detected in the plasma was an elevated alkaline phosphatase. He was also in negative calcium balance. 4. Treatment with vitamin D. 2. , later changed to dihydrotachysterol, appears to have produced clinical, biochemical and radiological improvement. It appears that a direct action of the vitamin on the abnormal bone collagen must be postulated, in addition to its known actions on the calcifying mechanisms. 5. An unusual feature of the case was the slow development of a total unresponsiveness to large doses of vitamin D. 2. , in spite of a markedly elevated level of vitamin D in the plasma. There was later a response to a much smaller dose of dihydrotachysterol, which is being maintained to date

1. A description is given of the pathology of a generalised skeletal disease characterised by a defect in the formation of the collagen fibres of the bone matrix—"fibrogenesis imperfecta ossium.". 2. Material from two cases, a woman of fifty-six and a man of sixty-four, was examined. All the samples of bone from both patients showed the same defect, which was severe in most of the specimens, and there was radiographic evidence of similar widespread bone changes in both cases. 3. The defect is clear-cut and striking histologically, provided that sections are examined with a polarising microscope, and/or by reticulin methods. 4. As a result of the defect in the bone matrix this fails to calcify, or calcifies imperfectly, showing wide osteoid borders as in severe osteomalacia. But the fibre defect separates it quite clearly from osteomalacia, in which the fibre structure of the osteoid tissue is normal. Moreover neither the biochemical findings (Case 2) nor the radiographic appearances correspond with those of osteomalacia. 5. The collagen fibre defect is confined to the bone matrix; no defect was found in the soft tissue collagen, and even the periosteum shows a normal fibre structure. 6. Both the clinical and the histological evidence indicate that the disease is not congenital, but was, in these two patients, apparently acquired during middle age. There was no family history of bone disease. 7. The cause of the condition is quite obscure. It is not inflammatory or neoplastic, nor is there histological or clinical evidence of a toxic origin. If it is a deficiency disease it is unlike any known vitamin or other chemical deficiency

We used demineralised bone matrix (DBM) to augment re-attachment of tendon to a metal prosthesis in an in vivo ovine model of reconstruction of the extensor mechanism at the knee. We hypothesised that augmentation of the tendon-implant interface with DBM would enhance the functional and histological outcomes as compared with previously reported control reconstructions without DBM. Function was assessed at six and 12 weeks postoperatively, and histological examination was undertaken at 12 weeks. A significant increase of 23.5% was observed in functional weight-bearing at six weeks in the DBM-augmented group compared with non-augmented controls (p = 0.004). By 12 weeks augmentation with DBM resulted in regeneration of a more direct-type enthesis, with regions of fibrocartilage, mineralised fibrocartilage and bone. In the controls the interface was predominantly indirect, with the tendon attached to the bone graft-hydroxyapatite base plate by perforating collagen fibres

Surgical treatment for traumatic, anterior glenohumeral instability requires repair of the anterior band of the inferior glenohumeral ligament, usually at the site of glenoid insertion, often combined with capsuloligamentous plication. In this study, we determined the mechanical properties of this ligament and the precise anatomy of its insertion into the glenoid in fresh-frozen glenohumeral joints of cadavers. Strength was measured by tensile testing of the glenoid-soft-tissue-humerus (G-ST-H) complex. Two other specimens of the complex were frozen in the position of apprehension, serially sectioned perpendicular to the plane containing the anterior and posterior rims of the glenoid, and stained with Toluidine Blue. On tensile testing, eight G-ST-H complexes failed at the site of the glenoid insertion, representing a Bankart lesion, two at the insertion into the humerus, and two at the midsubstance. For those which failed at the glenoid attachment the mean yield load was 491.0 N and the mean ultimate load, 585.0 N. At the glenoid region, stress at yield was 7.8 ± 1.3 MPa and stress at failure, 9.2 ± 1.5 MPa. The permanent deformation, defined as the difference between yield and ultimate deformation, was only 2.3 ± 0.8 mm. The strain at yield was 13.0 ± 0.7% and at failure, 15.4 ± 1.2%; therefore permanent strain was only 2.4 ± 1.1%. Histological examination showed that there were two attachments of the anterior band of the inferior glenohumeral ligament at the site of the glenoid insertion. In one, poorly organised collagen fibres inserted into the labrum. In the other, dense collagen fibres were attached to the front of the neck of the glenoid

The experiments were performed to answer three main questions. These and our answers may be summarised as follows. What is the precise mechanism of healing of a raw bony surface in a joint? What cells are involved? Where do they originate?—In all the implant experiments and in the control series the fundamental mechanism of healing was similar. 1. A massive proliferation of fibroblasts occurred from the cut periosteum, from the cut joint capsule, and to a lesser extent from the medullary canal. 2. Fibroblasts grew centripetally in the first few weeks after operation, attempting to form a "fibroblast cap" to the cut bone end. 3. Fibroblasts of this cap near the cut bone spicules metamorphosed to become prechondroblasts, chondroblasts laying down cartilage matrix, and hypertrophied (alkaline phosphatase-secreting) chondrocytes lying in a calcified matrix. 4. This calcified cartilage matrix was invaded by dilated capillaries probably bearing osteoblasts which laid down perivascular (endochondral) bone. 5. Some of the cells of projecting bone spicules died and their matrix was eroded in the presence of many osteoclasts. 6. In the control experiments of simple excision of the radial head new bone was produced at the periphery only by processes (3) and (4). This sealed off the underlying peripheral cortical bone from the superficially placed peripheral articular surface of fibrocartilage. At about a year from operation the central portion of the articular surface was still formed of bare bone, or of bone spicules covered by a thin layer of irregularly arranged collagen fibres. The opposite capitular articular cartilage was badly eroded. Does the introduction of a dead cartilage implant over the raw bone end affect in any way the final constitution of the new articular surface?—In the implant experiments the new bone produced by processes (3) and (4) formed, after about a year, a complete cortical plate which entirely sealed off the cut end of the radius and left a superficially placed articular covering of smooth fibrocartilage, closely resembling a normal joint surface. The opposite capitular articular surface was normal. What is the final fate of such an implant?—Whale cartilage implants underwent replacement by fibroblasts and collagen fibres, and took about nine months to disappear. The cartilage of fixed autotransplants and homotransplants underwent similar gradual replacement, and took about the same time in each case. The dead bone, implanted in association with the cartilage in both cases, acted as a nidus for hyaline cartilage production by chondrocytes derived from fibroblasts. This cartilage underwent endochondral ossification. This observation suggests that induction by non-cellular osseous material is a factor in chondrification and ossification. All the implants functioned as temporary articular menisci or in some cases as temporary radial articular surfaces. They were always replaced by a permanent fibrocartilaginous meniscus, or a fibrocartilaginous articular surface. An implant did, in fact, always act as a temporary protecting cap and mould for the subjacent growth offibroblasts which was necessary for the production of a satisfactory new joint surface

1. The orientation of collagen fibres of the menisci of the knee has been demonstrated by polarised light microscopy. 2. As might be supposed from its fibre structure, the ultimate tensile strength of the meniscal tissue is dependent upon the axis of loading. 3. The tensile strength of the meniscus is similar to that of articular cartilage

By polarising microscope and x-ray crystallographic techniques the annulus fibrosus has been shown to consist of regularly oriented sheets of collagen fibres. These results have been interpreted in terms of an elastic mechanism whereby thrust from the nucleus causes increased girth in the annulus. It is suggested that this is accomplished by a change in the angle between the axis of the fibres in adjacent uniaxial layers of the annulus. Furthermore, the loss of elasticity of the intervertebral disc associated with age would seem to be mainly due to changes occurring in the nucleus pulposus

The surface ultrastructure of ganglia has been studied using the scanning electron microscope. This study showed that the ganglion wall consists of multidirectional strata of collagen fibres and has no cellular lining. The wall has a sponge-like appearance and does not appear degenerate or necrotic. Comparison with synovial membrane and adventitious bursa confirmed that these are distinct structures which have a cellular lining. Ganglia probably arise from the multifunctional mesenchymal cells which are found within their walls. The ganglion fluid may also originate from these cells

1. All articulating cartilages are fibrocartilages. 2. The articular cartilages of the synovial joints are largely composed of collagen fibres. 3. These fibres form a dense network, the fibres of which run obliquely between the articular surface and the bone. 4. This network is operative when the parts are at rest and in contact under pressure. It takes the tensile component of the resultant shear stress, and is a postural mechanism of the joint. 5. The articular cartilage is most heavily chondrified at its centre, between the juxta-synovial and juxta-osseous parts. 6. The technique for demonstrating the fibrous structure is described

Thirty cruciate ligaments were retrieved from either cadavers or limbs which had been amputated. Each specimen was sectioned and stained to demonstrate the presence of collagen, nerves and vessels. All 30 specimens contained an interconnecting band of collagen fibres between the anterior and posterior cruciate ligaments. Vascular structures were present in all specimens and nerve fibres were identified in 26 (86%). We have called this structure the ‘intercruciate band’. The anterior and posterior cruciate ligaments should no longer be thought of in isolation, but together as a ‘cruciate complex’

The soft tissue response to carbon fibre was studied histologically one and a half years after being used to reconstruct the lateral collateral ligament of the human knee. A remarkably consistent pattern was seen in the induced ligament. The basic pattern was a "composite unit", consisting of a core of carbon fibre enveloped in a concentric manner by coherent layers of fibroblasts and collagen fibres. This new structure seemed to have been induced by continuous irritation caused by the physical structure of the carbon fibres; it is unlikely ever to acquire the structure of a natural ligament. However, it is biologically compatible and is biomechanically sufficient as long as the entire tow of carbon fibres is preserved

1. The arrangement of collagen fibres in the secondary osteones in human femora and tibiae has been examined. The fibres were observed in paraffin sections stained by Weidenreich's method. 2. Three fibre patterns have been observed. They differ from one another in the relative numbers of longitudinal and circumferential fibres which they contain, and in the degree of lamellation which they exhibit. 3. The incidence of the three fibre patterns has been correlated with the relative ages of the regions of bone in which they occur. 4. The possibility of a correlation between variations in fibre pattern and certain recent microradiographic observations is discussed

1. Human articular cartilage from normal femoral heads and from cases of osteoarthrosis in subjects of various ages has been examined histologically and by electron microscopy. 2. In specimens from middle-aged and old subjects, peculiar "matrix-streaks" have been observed in the deep zone of the pressure areas as oblique bands extending from the pericellubar halos into the adjacent matrix. 3. Ultrastructurally the streaks are correlated with an undulating pattern of the radially oriented collagen fibres. 4. The streaks are considered to result from a focal lack of acid mucopolysaccharide and from natural forces on the articular cartilage. Their appearance is assumed to be an early sign of cartilage disintegration associated with ageing