Postnatal development of the cruciate ligament insertions in the rat knee. morphological evaluation and immunohistochemical study of collagens types I and II

The postnatal structural remodelling and calcification patterns in the insertions (entheses) of both cruciate ligaments were studied in a rat model with histology and immunohistochemical analysis of collagens types I and II. In the neonate, both ligaments which labelled only for type I collagen attached to epiphyseal cartilage which solely labelled for collagen type II. The entheses calcified between days 20 and 35, and a subchondral bone plate formed under the entheses between days 30 and 55. Thus, within a period of 35 days the tissue to which the ligaments attached increased multifold in stiffness. Interestingly, the process of enthesial calcification and formation of compact bone did not happen simultaneously in both ligaments, not even synchronous at both ends of the same ligament or within a single insertion. This asynchronous calcification of the different knee ligament insertions may make the sudden change in mechanical environment at the entheses less dramatic for the ligaments and knee joint surfaces as anticipated from mechanical models. In addition, a fibrocartilaginous tissue, rich in collagen type II, formed in the ligament at a time when the epiphyseal cartilage was replaced by bone, and grew wider with time. The interposition of a fibrocartilaginous zone in the insertion may diminish the sudden change in stiffness between ligament soft tissue and hard bone.

The menisci of the knee joint. Anatomical and functional characteristics, and a rationale for clinical treatment

The menisci and their insertions into bone (entheses) represent a functional unit. Thanks to their firm entheses, the menisci are able to distribute loads and therefore reduce the stresses on the tibia, a function which is regarded essential for cartilage protection and prevention of osteoarthrosis. The tissue of the hypocellular meniscal body consists mainly of water and a dense elaborate type I collagen network with a predominantly circumferential alignment. The content of different collagens, proteoglycans and nonproteoglycan proteins shows significant regional variations probably reflecting functional adaptation. The meniscal horns are attached via meniscal insertional ligaments mainly to tibial bone. At the enthesis, the fibres of the insertional ligaments attach to bone via uncalcified and calcified fibrocartilages. This anatomical configuration of gradual transition from soft to hard tissue, which is identical to other ligament entheses, is certainly essential for normal mechanical function and probably protects this vulnerable transition between 2 biomechanically different tissues from failure. Clinical treatment of meniscal tears needs to be based on these special anatomical and functional characteristics. Partial meniscectomy will preserve some of the load distribution function of the meniscus only when the meniscal body enthesis entity is preserved. Repair of peripheral longitudinal tears will heal and probably preserve the load distribution function of the meniscus, whereas radial tears through the whole meniscal periphery or more central and complex tears may be induced to heal, but probably do not preserve the load distribution function. There is no proof that replacement of the meniscus with an allograft can reestablish some of the important meniscal functions, and thereby prevent or reduce the development of osteoarthrosis which is common after meniscectomy. After implantation, major problems are the remodelling of the graft to inferior structural, biochemical and mechanical properties and its insufficient fixation to bone which fails to duplicate a normal anatomical configuration and therefore a functional meniscal enthesis.

Regional differences in cell shape and gap junction expression in rat Achilles tendon: relation to fibrocartilage differentiation

Tendon cells have complex shapes, with many cell processes and an intimate association with collagen fibre bundles in their extracellular matrix. Where cells and their processes contact one another, they form gap junctions. In the present study, we have examined the distribution of gap junction components in phenotypically different regions of rat Achilles tendon. This tendon contains a prominent enthesial fibrocartilage at its calcaneal attachment and a sesamoid fibrocartilage where it is pressed against the calcaneus just proximal to the attachment. Studies using DiI staining demonstrated typical stellate cell shape in transverse sections of pure tendon, with cells withdrawing their cell processes and rounding up in the fibrocartilaginous zones. Coincident with change in shape, cells stopped expressing the gap junction proteins connexins 32 and 43, with connexin 43 disappearing earlier in the transition than connexin 32. Thus, there are major differences in the ability of cells to communicate with one another in the phenotypically distinct regions of tendon. Individual fibrocartilage cells must sense alterations in the extracellular matrix by cell/matrix interactions, but can only coordinate their behaviour via indirect cytokine and growth factor signalling. The tendon cells have additional possibilities--in addition to the above, they have the potential to communicate direct cytoplasmic signals via gap junctions. The formation of fibrocartilage in tendons occurs because of the presence of compressive as well as tensile forces. It may be that different systems are used to sense and respond to such forces in fibrous and cartilaginous tissues.

Copper-dependent depolymerization of lignin in the presence of fungal metabolite, pyridine

Thus far, it has not been recognized that copper complexes are able to depolymerize lignin under physiological conditions of white rot decay. However, we have found that both phenolic and non-phenolic synthetic lignins were intensively depolymerized by Cu(II) and lipid hydroperoxide model compounds in the presence of a metabolite of ligninolytic fungi, pyridine at room temperature in aqueous media. Treatment of 14C-labeled oxygen-prebleached kraft pulp (OKP) by the copper-dependent reaction evidenced effectiveness of this reaction for the delignification of kraft pulps. In contrast to the organic peroxide system, Cu(II)/pyr/H2O2 system was much less effective for the lignin depolymerization. However, treatment of unbleached kraft pulp (UKP) by Cu(II)/H2O2 and Cu(II)/pyr/H2O2 systems demonstrated that the damage of cellulose was suppressed by the coordination of pyridine although high brightness gain was obtained independently of the presence of the coordinator. Spin trapping experiments demonstrated that not hydroxyl radical but superoxide anion is involved in the Cu(II)/pyr/H2O2 system. This finding not only introduces a new concept of non-enzymatic lignin biodegradation by wood-degrading fungi but also presents a new strategy for decomposing lignin and lignin-related compounds by copper complexes and peroxide-producing system.

Oxidation of phenanthrene by a fungal laccase in the presence of 1-hydroxybenzotriazole and unsaturated lipids

Phenanthrene, a polycyclic aromatic hydrocarbon, was efficiently oxidized by laccase in the presence of both 1-hydroxybenzotriazole and unsaturated lipids. 73% of initially added phenanthrene was degraded within 182 hours to give phenanthrene-9,10-quinone and 2,2'-diphenic acid as the major products. The system was also able to peroxidize linoleic acid to its corresponding hydroperoxides suggesting the involvement of lipid peroxidation in laccase catalyzed phenanthrene oxidation. Lipid peroxidation by laccase required 1-hydroxybenzotriazole and did not depend on Mn2+ and H2O2 suggesting that the chemical reactions involved differ from those previously reported for manganese peroxidase.

Healing of the anterior attachment of the rabbit meniscus to bone

In a rabbit model the healing process of the anterior attachment of the medical meniscus was observed during the first 12 weeks after sharp transection and refixation in a tibial bone channel. Evaluations of the healing tissue were histologic analysis, application of immunohistochemical methods to show collagen types and nerve regeneration, and mechanical load to failure tests. Secondary changes to knee joint cartilage, as signs of eventual dysfunction of the refixed meniscus, were evaluated by analysis of proteoglycan fragment concentration in joint fluid and histologic analysis of knee joint articular cartilage and synovium. The healing tissue between the refixed attachment and bone matured from highly cellular, nonspecific granulation tissue at 1 week, to bone, fibrocartilaginous, and fibrous tissues, which at some sites developed an insertion specific tissue arrangement within a 12-week period. However, the irregular interface between the fibrocartilaginous tissue and the underlying bone, which is typical for a normal insertion, was not reestablished. Labeling for collagen Types I and II in the newly formed insertion did not return to normal. In addition a few collagen fibers connected the refixed attachment tissue to bone. New bone formation turned the initially cancellous bone tunnel walls into more solid cortical bone. However, new bone formation did not fill the distal part of the channel. The refixed meniscal attachment underwent necrosis and was revitalized by cell ingrowth from the periphery. Nerve fibers were found in the newly formed insertion by 12 weeks. The failure load at tensile testing never reached more than 20% that of a normal attachment. Degeneration of articular cartilage and increased proteoglycan fragment in the joint fluid were common after this procedure. These data suggest that, despite the focal appearance of insertion specific tissues and healing of collagen fibers to bone, the tissue architecture of a normal meniscal insertion and a normal meniscal joint protective function were not reestablished.

Barriers to implementing a quality improvement program

Critical barriers can prevent the implementation of an effective quality improvement (QI) program in the health care setting, including organizational culture, restructuring, quality assurance/quality control functions, QI teams and costs. Common pitfalls encountered that cause QI programs to falter--or worse, to fail--are discussed.

Age- and injury-dependent concentrations of transforming growth factor-beta 1 and proteoglycan fragments in rabbit knee joint fluid

OBJECTIVE

The purpose of the study was to characterize maturation-related changes of TGF-beta 1 and proteoglycan fragment (PG) concentrations in joint fluid of healthy rabbit knees, and to investigate changes associated with osteochondral injury and spontaneous repair.

METHODS

In 26 young (age range: 12-15 weeks), 26 adolescent (18-25 weeks), and 26 adult (33-44 weeks) New Zealand white rabbits, TGF-beta 1 and PG concentrations were analyzed in joint fluid samples which were taken before, and at several time intervals (max. 1 year) after creation of a osteochondral defect in the knee medial femoral condyle. At death, the characteristics of the regenerated tissue in the defect and any signs of degeneration of adjacent cartilage were recorded and graded.

RESULTS

In preoperative samples, TGF-beta 1 and PG concentrations decreased with maturation (P < 0.01), and were moderately correlated (r = 0.51, P < 0.001). Shortly after trauma, the concentrations of both substances were found increased, which was followed by a decrease up to 3 months, and then again an increase up to 1 year. However, meanwhile PG concentrations had similar magnitude irrespective of age, TGF-beta 1 concentrations never reached similarly high levels in adulthood as in infancy or adolescence. The cartilage adjacent to the defect had more signs for degeneration in younger rabbits, and also osteophytes were more common in young than adult animals.

CONCLUSION

The similar pattern for TGF-beta 1 and PG concentrations during postnatal maturation may reflect the stimulatory effect of TGF-beta 1 on proteoglycan synthesis. The higher TGF-beta 1 concentrations in younger animals may be a reason for their better healing capacity, but also for their higher susceptibility to osteoarthritic change compared to adult animals.

Ten-year prognosis of isolated and combined medial collateral ligament ruptures. A matched comparison in 40 patients using clinical and radiographic evaluations

In a matched-pair study of 40 patients, the prognoses of patients with acute isolated partial medial collateral ligament injuries and acute combined medial collateral and anterior cruciate ligament injuries were compared 10 years after initial treatment. All patients in the first group were treated nonoperatively. In the latter group, most medial collateral ligament injuries were total ruptures, which were thoroughly repaired; the torn anterior cruciate ligament was repaired with augmentation in half of the cases. At the follow-up evaluation, both patient groups had similarly high knee functions according to the Lysholm score and similar activity levels (recreational team sports). Knees with combined injuries had increased sagittal laxity at manual and instrumented assessment. Radiographic signs of knee osteoarthritis were present in half of the knees with combined injuries, but they were absent in knees with isolated injuries. The long-term functional prognosis was similarly good after isolated or combined medial collateral ligament injuries, but patients with combined ruptures had more reinjuries and repeat surgeries, increased sagittal laxity, and a higher incidence of radiographic osteoarthritis.

Maturation-dependent repair of untreated osteochondral defects in the rabbit knee joint

Repair of untreated full-thickness cartilage defects in the medial femoral knee condyle was studied in 17 young, 21 adolescent, and 19 adult rabbits. At 6 weeks, the defect was completely filled by tissue regeneration in all young and adolescent animals, but in only few of the adults (p < 0.05). The morphology of all repairs improved from fibrous tissue to hyaline-like cartilage over time (p < 0.05), but at 3 and 6 weeks, the repair tissue in young and adolescent rabbits was more cartilage-like than in the adults (p < 0.05). In addition, bonding of the repair tissue to the adjacent cartilage was better in the young and adolescent than in the adult animals (p < 0.05). At 12 weeks, subchondral bone had formed in some young and adolescent repairs, but in no case in the adults. None of the repairs showed normal cartilage appearance, but formation of hyaline-like cartilage was common at 12 weeks. Irrespective of age or observation time, the repair site showed decreased stiffness and larger strain values compared to adjacent or control cartilage (p < 0.001) with no tendency for improvement over time. Younger animals showed a faster filling of the defect and an earlier specialization of the repair tissue than adult animals, but the mechanical quality of the regenerated tissue remained inferior to normal.

Sequential scintigraphy and orthoradiographic measurement of femoral shortening after femoral neck fracture

The objective of the study was to assess scintigraphic patterns and femoral shortening after femoral neck fracture in order to select predictive parameters for late complications. Eighty-eight patients with osteosynthesized femoral neck fractures were followed for 2 years with regular scintigraphic evaluations and orthoradiographic measurements of femoral length shortening. Four different patient categories were identified with regard to the late outcome two different groups with uneventful healing and two different groups with late complications. Accordingly, a high scintigraphic uptake at 1 month may either point to an uneventful healing if combined with minor femoral shortening or indicate failure if combined with a high degree of femoral shortening. In contrast, low scintigraphic uptake may either reflect primary fracture healing if accompanied by minor femoral shortening or predict failure if a high degree of femoral shortening is present. Compared with using scintigraphy alone, combined scintigraphic evaluation and assessment of femoral shortening increased the accuracy for prediction of late failures from 80% to 93%. Early scintigraphic patterns after osteosynthesis of femoral neck fractures have to be validated with care. Radiographic assessment of femoral shortening, which is less invasive, gives better prognostic accuracy and should therefore be preferred for this purpose.

Evaluation of knee-joint cartilage and menisci ten years after isolated and combined ruptures of the medial collateral ligament. Investigation by weight-bearing radiography, MR imaging and analysis of proteoglycan fragments in the joint fluid

PURPOSE

To compare radiography, MR imaging, and chemical analysis in posttraumatic knees.

MATERIAL AND METHODS

Ten matched pairs with either isolated partial rupture of the medial collateral ligament or combined medial collateral ligament/anterior cruciate ligament rupture were compared with matched controls 10 years after trauma. Weight-bearing radiographs and MR examinations were compared with proteoglycan fragment concentrations in the joint fluid.

RESULTS

The chemical analyses were similar in both trauma groups. The radiographs showed mild signs of arthrosis in half the patients with combined injury. MR images showed almost all injured knees to have degenerative changes of various degrees in the cartilage and menisci. More frequent and more advanced changes were found after combined injury than after isolated injury (p < 0.01). There were no changes in the controls.

CONCLUSION

MR imaging is the best method for detecting and differentiating early posttraumatic knee arthrosis.

An immunohistochemical study of enthesis development in the medial collateral ligament of the rat knee joint

The changing distributions of collagens and glycosaminoglycans have been studied at the attachments of the medial collateral ligament during postnatal development. The ligament is of particular interest because it has a fibrocartilaginous attachment to the femoral epiphysis, but a fibrous one to the tibial metaphysis. Ligaments were examined in rats killed at birth and at 2, 4, 6, 8, 10, 20, 30, 45, 60, 90 and 120 days after birth. Cryosections were immunolabelled with monoclonal and polyclonal antibodies against types I and II collagen, chondroitin 4 and 6 sulfate, dermatan and keratan sulfate. Although the ligament is attached at both ends to bones that develop from cartilage, there was a striking difference in collagen labelling. Type II collagen was only found in spicules of calcified cartilage in bone beneath the tibial enthesis after ossification had commenced, but there was a continuous band of labelling at all stages of development at the femoral enthesis. Initially, the cartilage at the femoral attachment lacked type I collagen, but by 45 days labelling was continuous from ligament to bone. Continuity of labelling was seen much earlier at the tibial enthesis, as soon as bone had formed. There were also marked changes in glycosaminoglycan distribution. Keratan sulfate was present at both entheses up to 45 days, but only at the femoral enthesis thereafter. Both attachments labelled throughout life for dermatan sulfate, but chondroitin 4 and 6 sulfate were only found at the femoral end. The results suggest that enthesial cartilage at the femoral attachment was initially derived from the cartilaginous bone rudiment but was quickly eroded on its deep surface by endochondral ossification as bone formed at the attachment site. It was replaced by fibrocartilage developing in the ligament. This mechanism allows enthesis cartilage/fibrocartilage to contribute to the growth of a bone at a secondary centre of ossification in addition to dissipating stress at the ligament-bone junction.

The morphology of ligament insertions after failure at low strain velocity: an evaluation of ligament entheses in the rabbit knee

The morphology of failed rabbit knee entheses is described after in vitro load to failure testing at low strain velocity. Avulsion fracture was the dominant failure mode both for the cruciate ligaments and the medial collateral ligament. The patellar ligament became avulsed in most cases from the patellar insertion. The ligamentous anterior attachment of the medial meniscus failed by a midsubstance rupture and the posterior fibrocartilaginous attachment by a rupture near to the meniscal horn. On histological inspection the failure characteristics usually appeared more elaborate, involving to different degrees all portions of the bone-ligament-bone complexes. Avulsion fracture through subchondral bone was often combined with a partial ligament midsubstance rupture. In few cases avulsion from the cement line was combined with a rupture between the uncalcified fibrocartilage and the ligament. The medial collateral ligament failed in one case entirely at the cement line of its femoral insertion. Horizontal rupture through the calcified fibrocartilage and a vertical cleavage crossing the tidemark were also observed. The superficial portion of the patellar ligament failed with a midsubstance rupture, and the deeper part with an avulsion through the calcified fibrocartilage or an avulsion fracture. The complex failure characteristics may be attributed to uneven loading, nonuniformity of the structure, and specific anatomical location. Subchondral bone beneath femoral and tibial insertions seems to be weaker than the transitional zone between soft tissue and hard bone at the enthesis. The overall inferior structural quality of a ruptured ligament has to be taken into account when parts of the original structure are used for suturing or reconstruction.

In vitro femoral stiffness after femoral neck osteotomy and osteosynthesis with defined surgical errors

In our search for an osteosynthesis device that would tolerate the surgical errors of the inexperienced surgeon, we tested in vitro femoral stiffness in 75 human osteoporotic femora after internal fixation of a cervical neck osteotomy using three commonly used devices: two von Bahr screws (A. Ericsson AB, Sweden), two cannulated screws (Uppsala type, Olmed AB, Sweden), and two hookpins (LiH, PSAB, Sweden). The first device has its main grip in the cancellous bone by threads; the second has grip in cancellous and subchondral bone by threads; and the third, which has no threads, has its grip in cancellous bone by a hook pin. The intact specimen was in all instances stiffer (22-63%) than the osteosynthesized specimen (p < 0.001). An osteosynthesized femur with perfectly reduced bone ends was 14-23% stiffer than when reduction of the bone ends was insufficient, irrespective of device malposition (p < 0.001). Insufficient reduction of the osteotomy leaving a 20 degrees dorsal angulation of the femoral head combined with too far ventrally placed screws resulted in the lowest femoral stiffness. If reduction of osteotomy was sufficient, screws placed too far ventrally or converging screws did not result in decreased stiffness compared with optimal screw placement. Irrespective of the quality of reduction, osteosynthesis with the Uppsala screw resulted in all instances in a higher stiffness than using the other devices (p < 0.01). With the Uppsala screw design, femoral stiffness after optimal osteosynthesis was reduced by 22% compared with the intact femur, and in the most unfavorable position with combined malreduction and malpositioning it was reduced by 42%. Corresponding values for the von Bahr screws were 29% and 46%, respectively, and for the LiH screws 47% and 63%, respectively. Use of a device with threads and grip in the subchondral bone is recommended for fixation of femoral neck fractures in osteoporotic bone. Furthermore, the importance of anatomical reduction for fracture fixation is emphasized.

Regional variations of indentation stiffness and thickness of normal rabbit knee articular cartilage

The rabbit knee is frequently used as an experimental model for cartilage repair, but the choice of different joint regions for such studies makes comparisons between methods difficult. Furthermore, there is only limited information available about the regional variations of the biomechanical properties in normal rabbit knee articular cartilage. In the present study in situ indentation tests were used to map the short-term stiffness and thickness of articular cartilage at seven locations (anterior and posterior areas of the medial and lateral femoral condyles, the patellar groove, and the central areas of the medial and lateral tibial plateaus) in nine normal rabbit knee joints. Short-term cartilage stiffness was described by elastic moduli under ramp loading and 15-s creep conditions. The moduli were calculated according to Hayes' single-phase elastic model. A moderate positive correlation (r = 0.54) between cartilage stiffness and thickness was found for rabbit femoral cartilage, but was not confirmed for tibial cartilage, which had the thickest, but also the softest cartilage of all areas. The cartilage in the patellar groove and the medial compartments of both femoral condyles and tibial plateaus was stiffer and thicker than that in the lateral components, similar to previous findings in dogs. However, the dog femoral cartilage was found to be stiffer at the anterior than at the posterior regions, but we found the opposite in the rabbit. These dissimilarities between animal models may be caused by different joint loading characteristics. Accordingly, in rabbits repair processes in the more anterior femoral areas with less stiff cartilage may not be comparable to repairs in more posterior areas where cartilage is stiffer.

Natural healing of anterior and posterior attachments of the rabbit meniscus

The natural healing capacity of the anterior or posterior medial meniscal attachment after radial transection and the effect of such procedures on knee joint cartilage were investigated in 28 skeletally mature New Zealand white rabbits. Either the anterior (n = 14) or the posterior attachment (n = 14) was radially transected in the right knee joint. Fifty percent of the rabbits with each procedure were euthanized at 6 weeks and 50% at 12 weeks. The histologic characteristics of the healing tissue were evaluated, including immunohistochemical demonstration of nerve fibers. Histologic changes in the synovium and articular cartilage were graded for severity and extent. The concentration of proteoglycan fragments in joint fluid was analyzed before operation and at euthanasia. After both procedures, the transected attachment healed in a prolongated position resulting in peripheral displacement of the meniscus. The healing tissue at 6 weeks was composed mainly of granular tissue. By 12 weeks, the healing tissue at the anterior attachment had a ligament like structure, but at the posterior attachment, fibrocartilage like tissue had formed. Nerve fibers were found in the healing tissue, but connections to nerves in normal attachment or meniscal tissues were not found. Increased concentrations of proteoglycan fragments, articular cartilage degeneration, and synovitis were found in the operated knees. These data indicate that although the meniscal attachment can heal in a prolongated position, such a meniscus has lost its mechanical functions. Further, a joint protective function of the neoneurons is doubtful because of the lack of continuity with the adjacent meniscus. Rigid fixation of the attachment seems essential for a functional meniscal substitute.

The effect of partial meniscectomy on the long-term prognosis of knees with localized, severe chondral damage. A twelve- to fifteen-year followup

We retrospectively matched 42 patients with unilateral chondral damage in the weightbearing zone of one knee compartment according to sex, age, location of chondral damage, and follow-up time. Two groups of 21 patients were formed. One group had chondral damage only. The other group had chondral damage and a meniscal tear treated with partial meniscectomy. After 12 to 15 years, all patients were reexamined. Twenty-nine percent (N = 6) of the patients who had a partial meniscectomy needed repeat meniscal surgery during followup. No patients with isolated chondral damage developed meniscal symptoms, and only three patients underwent minor surgeries (P < 0.02). At the follow-up evaluation, both groups had similar knee function with a mean Lysholm score of 87 points. However, most patients had reduced their sports activities from competitive individual sports before injury to noncompetitive physical fitness exercise at followup. At the roentgenologic examination, patients who had partial meniscectomies had more severe roentgenologic signs of osteoarthritis than patients who had chondral damage only (P < 0.03). Meniscectomy, varus knee alignment at the follow-up evaluation (P < 0.04), and age older than 30 years (P < 0.04) at the time of the operation were associated with a higher incidence of osteoarthritis.

The diagnostic validity of magnetic resonance imaging in acute knee injuries with hemarthrosis. A single-blinded evaluation in 69 patients using high-field MRI before arthroscopy

Sixty-nine patients with traumatic knee hemarthrosis were evaluated an average of 3 days after trauma by high field (1.5T) magnetic resonance imaging (MRI) using sagittal T1, T2-weighted and coronal 3D-gradient echo images. All knees were arthroscopically examined shortly afterwards. The diagnostic validity of MRI for intraarticular pathology was determined using arthroscopy as golden standard. All patients had pathological findings on arthroscopy. The injuries were sports-related in 77% of the cases. MRI was highly sensitive (86%) and specific (92%) for diagnosis of anterior cruciate ligament tears. Diagnosis of medial meniscal tears showed a 74% sensitivity and 66% specificity. MRI detected lateral meniscal tears in 50% with an 84% specificity. As such, MRI missed 10 significant meniscus ruptures requiring surgical treatment. The sensitivity for partial or total medial collateral ligament tears was 56%, the specificity 93%. Rupture of the medial retinaculum in cases with patellar dislocation or significant damage of articular cartilage were only detected by MRI in a few cases (27% and 20% sensitivity, respectively). MRIs low diagnostic validity for intraarticular pathology with hemarthrosis may be attributed to the shifting paramagnetic properties of the blood remains and catabolic processes in meniscal and chondral tissues during the hemoglobin degradation process. Accordingly, MRI, with the technique used, could neither replace arthroscopy in the diagnosis and screening of acute knee injuries, nor select patients with need for immediate arthroscopic meniscal surgery.

The long-term prognosis for severe damage to weight-bearing cartilage in the knee: a 14-year clinical and radiographic follow-up in 28 young athletes

We examined 28 young athletes with isolated severe chondral damage in the weight-bearing area of the knee joint clinically and radiographically 14 years after arthroscopic diagnosis. Except for Pridie drilling in 3 cases and occasional cartilage shaving or removal of free bodies, no special treatment was given initially. 21 patients were able to return to preinjury team sport activity levels. During the follow-up period, only 3 patients needed repeat surgery with removal of free bodies, and another 2 underwent diagnostic arthroscopy because of persistent pain. At the latest follow-up evaluation, 22 patients had excellent or good knee function. At this time, the patients were mainly involved in individual sports on a physical fitness level. 12 cases had radiographic joint space reduction (< 50%) which was limited to the compartment concerned.

Quantitative comparison of soft tissue-bone interface at chondral ligament insertions in the rabbit knee joint

At chondral ligament insertions the calcified fibrocartilage interdigitates deeply with the lamellar bone. The shape of this interface is formed under physiological loading conditions. For the purpose of morphological comparison between different ligament entheses in the rabbit knee, the number and frequency of interdigitations and thickness of calcified fibrocartilage were quantitated at the femoral insertion of the medial collateral ligament, both insertions of the cruciate ligaments, and the tibial insertion of the patellar ligament. Among the insertions, the femoral insertion of the medial collateral ligament showed the lowest frequency and depth of interdigitations at the soft tissue-bone interface, but had the thickest zone of calcified fibrocartilage. An inverse relationship was found at the insertion interface of the cruciate and patellar ligaments. The frequency and depth of interdigations at the bone-soft tissue interface at different chondral entheses seem to be related to the mechanical strength of the respective ligament; meanwhile it may be hypothesised that the thickness of the calcified fibrocartilage might be more related to the amount of motion which takes place at an insertion.

Concentrations of proteoglycan fragments in relation to maturation, sex and time of day: physiologic variations in knee joint fluid of rabbits

We analyzed the concentrations of proteoglycan fragments in knee joint fluid in 142 rabbits to investigate the effect of physiologic variations--i.e., maturation, sex and time of day. The concentrations of proteoglycan fragments differed significantly between young, adolescent and adult animals and showed an inverse correlation to the stage of maturation of the rabbit. Adolescent male rabbits had higher concentrations than age-matched females. Morning and evening samples had similar concentrations. No relation was found between the proteoglycan fragment concentrations in joint fluid and the cartilage mass. The proteoglycan fragment concentrations in knee joint fluid apparently reflect the metabolic status of growing articular cartilage. There are considerable physiologic variations associated with maturation and sex, and these need to be taken into account when using the proteoglycan fragment concentration as a marker for joint diseases.