Light microscopic histology of quadriceps tendon ruptures

PURPOSE

To assess histological changes and possible differences in the quadriceps of patients undergoing open repair of the tendon after spontaneous rupture, and subjects with no history of tendon pathology.

MATERIALS

Biopsies were harvested from the quadriceps tendon of 46 patients (34 men, 12 women) who had reported unilateral atraumatic quadriceps tendon rupture and had undergone surgical repair of the tendon. Samples were also harvested from both the tendons in 11 (N = 11 × 2) patients, nine males and two females, dying from cardiovascular disorders. For each tendon, three slides were randomly selected and examined under light microscopy, and assessed using a semiquantitative grading scale (range 0-21) which considers fibre structure, fibre arrangement, rounding of the nuclei, regional variations in cellularity, increased vascularity, decreased collagen stainability, and hyalinisation.

RESULTS

The pathological sum-score averaged 19.2 ± 3.7 in ruptured tendons and 5.6 ± 2.0 in controls, and all variables considered were significantly different between the two groups, showing an association between tendon abnormalities and rupture (0.05 < P < 0.001).

CONCLUSION

This study confirms that the presence of histological degenerative changes in torn quadriceps tendons increases the risk of rupture.

Cytokines in rotator cuff degeneration and repair

The pathogenesis of rotator cuff degeneration remains poorly defined, and the incidence of degenerative tears is increasing in the aging population. Rates of recurrent tear and incomplete tendon-to-bone healing after repair remain significant for large and massive tears. Previous studies have documented a disorganized, fibrous junction at the tendon-to-bone interface after rotator cuff healing that does not recapitulate the organization of the native enthesis. Many biologic factors have been implicated in coordinating tendon-to-bone healing and maintenance of the enthesis after rotator cuff repair, including the expression and activation of transforming growth factor-β, basic fibroblast growth factor, platelet-derived growth factor-β, matrix metalloproteinases, and tissue inhibitors of metalloproteinases. Future techniques to treat tendinopathy and enhance tendon-to-bone healing will be driven by our understanding of the biology of this healing process after rotator cuff repair surgery. The use of cytokines to provide important signals for tissue formation and differentiation, the use of gene therapy techniques to provide sustained cytokine delivery, the use of stem cells, and the use of transcription factors to modulate endogenous gene expression represent some of these possibilities.

Emerging ideas: the effect of hypercholesterolemia on tendons

BACKGROUND

High levels of total cholesterol, triglycerides, and low-density lipoprotein are toxic to the vascular endothelium and thus have long been associated with atherosclerosis. Several clinical studies have suggested that elevated cholesterol also has a negative effect on tendon structure and function. Data from our preliminary studies show that the patellar tendons of hypercholesterolemic knockout mice exhibit reduced baseline elastic modulus and strength postinjury compared with controls.

QUESTIONS/HYPOTHESES

We therefore hypothesized elevated cholesterol would be associated with diminished tendon mechanical properties.

METHOD OF STUDY

Using hypercholesterolemic (B6.129P2-Apoetm1Unc/J) mice, patellar tendons from control (C57BL/6) and knockout mice will be injured surgically at two different times. Subsequently, mechanical testing will be performed and data evaluated for differences in baseline and in healing between cholesterol groups. For healing assessment, data from the injured limb of each animal will be normalized to that of the sham-operated contralateral limb.

SIGNIFICANCE

We anticipate that such studies eventually will enable us to elucidate the link between elevated cholesterol and tendon disease. If a mechanistic cause of hypercholesterolemia causing tendon disease is clarified, then potentially therapeutic interventions such as the use of pharmacotherapy may be used to help combat this. In the future, it may become worthwhile to consider the presentation of tendinopathy as a trigger to measure serum cholesterol just as one might consider measuring serum glucose in patients presenting with adhesive capsulitis.

Is compressive load a factor in the development of tendinopathy?

Tendons are designed to take tensile load, but excessive load can cause overuse tendinopathy. Overuse tendinopathy results in extensive changes to the cells and extracellular matrix, resulting in activated cells, increase in large proteoglycans and a breakdown of the collagen structure. Within these pathological changes, there are areas of fibrocartilaginous metaplasia, and mechanotransduction models suggest that this response could be due to compressive load. As load management is a cornerstone of treating overuse tendinopathy, defining the effect of tensile and compressive loads is important in optimising the clinical management of tendinopathy. This paper examines the potential role of compressive loads in the onset and perpetuation of tendinopathy, and reviews the anatomical, epidemiological and clinical evidence that supports consideration of compressive loads in overuse tendinopathy.

Achilles tendinosis: a morphometrical study in a rat model

This study addresses the morphopathogenesis of Achilles tendinosis, using a rat model and presenting quantitative analysis of time-dependent histological changes. Thirty Wistar rats were used, randomly split in experimental and control groups. Animals of the experimental group were submitted to a treadmill running scheme. Five animals of each group were euthanized at four, eight and sixteen weeks. Achilles tendons were collected and processed routinely for histopath sections. Slides were stained by Hematoxylin-Eosin, Picrosirius Red, Alcian Blue, AgNOR, TUNEL and evaluated morphometrically. Cellular density decreased slightly along the time and was higher in the experimental group than in controls at fourth, eighth and sixteenth weeks. Fiber microtearing, percentual of reticular fibers and glycosaminoglycans content increased along the time and were higher in experimental group than in controls at all-time intervals. AgNOR labeling here interpreted as a marker of transcription activity was higher in the experimental groups than in controls at all-time intervals. Apoptotic cells were more frequent and diffusely distributed in tendinosis samples than in control groups. These results suggest that as mechanical overload is becoming chronic, cellular turnover and matrix deposition increases leading to tendinosis. The combination of staining techniques and morphometry used here to describe the evolution of lesions occurring in a rat model system has proved to be suited for the study of induced Achilles tendinosis.

Radial extracorporeal shock wave therapy in the treatment of shoulder calcific tendinitis

Shoulder calcific lesions of the rotator cuff are a common problem in physiatric and orthopedic practice. The lesions are mostly located in the supraspinatus tendon, close to the insertion area in the critical zone. Patients are usually treated conservatively by nonsteroid antiinflammatory drugs, analgesic drugs, local injections, physiotherapy and rarely by applying surgical procedures. Painful shoulder gives rise to functional disabilities and may sometimes lead to pharmacological overuse. In the last twenty years, extracorporeal shock wave therapy (ESWT) has been frequently used in the treatment of calcific tendinopathies. We have evaluated the effectiveness of radial ESWT on the group of 30 patients, aged between 28 and 58 years, with calcific tendinitis of the shoulder. Criotherapy, medical exercises and radial ESWT were applied. We used the radial ESWT device (BTL-5000 SWT, Columbia, USA), 3 bars pressure, 10 Hz frequency, 2000 shocks. Patients were examined before the beginning of the treatment, immediately after the treatment, and 6 months later. The treatment included measurement of the range of motion (ROM), measurement of voluntary isometric contraction of shoulder muscles with manual muscle test (MMT), and subjective assessment of pain intensity with visual analogue scale (VAS). X-ray was done before and 6 month after treatment. The study has shown the efficiency of the treatment with radial ESWT. The level of statistical significance was determined with student t-test. Radial ESWT applied to patients with shoulder calcific lesions of the rotator cuff resulted in pain relief increase in the range of motion and increase in the muscular strength. As shown by X-ray, these results were followed by the decrease in the size of the rotator cuff calcifications.

Pain mapping for common shoulder disorders

We conducted a study to ascertain specific patterns of pain in patients with common shoulder disorders and to describe a comprehensive shoulder pain map. We prospectively studied 94 cases involving an upper limb pain map and correlated the maps with the final diagnoses made by 2 clinicians who were blinded to the pain map findings. Pattern, severity, and type of pain were specific to each common shoulder disorder. In subacromial impingement, pain was predominantly sharp, occurred around the anterior aspect of the shoulder, radiated down the arm, and was associated with dull, aching pain radiating to the hand. A similar pain pattern was found in rotator cuff tears. In acromioclavicular joint pathology, pain was sharp, stabbing, and well localized to the anterosuperior shoulder area. Glenohumeral joint arthritis was marked by the most severe pain, which occurred in a mixed pattern and affected the entire arm. Whereas the pain of instability was a mixture of sharp and dull pain, the pain of calcific tendonitis was severe and sharp. Both pains were limited to the upper arm and shoulder. Pain mapping revealed definitive patterns for shoulder pathologies. We advocate using pain maps as useful diagnostic guides and research tools.

Tendon tissue engineering: progress, challenges, and translation to the clinic

The tissue engineering field has made great strides in understanding how different aspects of tissue engineered constructs (TECs) and the culture process affect final tendon repair. However, there remain significant challenges in developing strategies that will lead to a clinically effective and commercially successful product. In an effort to increase repair quality, a better understanding of normal development, and how it differs from adult tendon healing, may provide strategies to improve tissue engineering. As tendon tissue engineering continues to improve, the field needs to employ more clinically relevant models of tendon injury such as degenerative tendons. We need to translate successes to larger animal models to begin exploring the clinical implications of our treatments. By advancing the models used to validate our TECs, we can help convince our toughest customer, the surgeon, that our products will be clinically efficacious. As we address these challenges in musculoskeletal tissue engineering, the field still needs to address the commercialization of products developed in the laboratory. TEC commercialization faces numerous challenges because each injury and patient is unique. This review aims to provide tissue engineers with a summary of important issues related to engineering tendon repairs and potential strategies for producing clinically successful products.

Models for the study of tendinopathy

Tendinopathy refers to the clinical presentation of activity-related pain, focal tendon tenderness, and intratendinous imaging changes. The underlying pathology was once thought to be due to inflammation ('tendinitis'), but is now considered to predominantly result from degeneration ('tendinosis'). While some progress has been made in understanding tendinosis, the condition remains poorly understood and a need exists for suitable exploratory preclinical models. It is unlikely that one suitable model exists because of the complexity of the underlying pathology and myriad of possible causes. This paper provides an overview of current models utilized in tendinopathy research. It progresses hierarchically from in vitro and ex vivo models to in vivo models. For each model, rationale for use, pertinent findings, and advantages and disadvantages are discussed. By improving on these models, new methods for the prevention and treatment of tendinopathy may be explored with the ultimate outcome being a reduction in the occurrence and effects of the condition in humans.

Rotator cuff tears: what have we learned from animal models?

Rotator cuff tendon tears are among the most common soft tissue injuries that occur at the shoulder. Despite advancements in surgical repair techniques, rotator cuff repairs experience a high rate of failure. The common occurrence of tears and the frequency of re-tears require a further understanding of the mechanisms associated with injuries, healing, and regeneration of the rotator cuff. This paper reviews in vivo studies using the various animal shoulder models of the rat, rabbit, sheep, canine, and primate. These animal models have been used to study intrinsic and extrinsic factors leading to shoulder degeneration, various suture techniques, effects of post-surgical treatment, numerous biologic and synthetic scaffolds, and an assortment of biologic augmentations used to accelerate healing. These effects can be examined in a controlled manner using animal models without other confounding factors that sometimes limit clinical studies. The clinically impactful results will be explained to highlight the specific knowledge gained from using animal models in rotator cuff research.

In vivo investigation of tendon responses to mechanical loading

Tendons transmit skeletal muscle forces to bone and are essential in all voluntary movement. In turn, movement appears to affect tendon properties, and in recent years considerable effort has been put into discovering how tendon tissue responds to mechanical stimuli in vivo. Months and years of mechanical loading can influence the gross morphology of tendon, seen as an increase tendon cross sectional area (CSA). Similarly, tendon stiffness appears to be affected by weeks to months of loading. Increased stiffness can relate to changes in CSA and/or tendon material properties (modulus), though the relative contribution of these parameters is largely unclear. The possible mechanisms behind alterations in tendon material properties include changes in collagen fibril morphology and levels of cross-linking between collagen molecules. Furthermore, increased levels of collagen synthesis and expression are seen as a response to acute exercise and training, and may be a central parameter in tendon adaptation to loading. There are indications that this collagen-induction relates to the auto-/paracrine action of collagen-stimulating growth factors, such as TGFβ-1 and IGF-I, which are expressed in response to mechanical stimuli.

Tendon fatigue in response to mechanical loading

Tendinopathies are commonly attributable to accumulation of sub-rupture fatigue damage from repetitive use. Data is limited to late stage disease from patients undergoing surgery, motivating development of animal models, such as ones utilizing treadmill running or repetitive reaching, to investigate the progression of tendinopathies. We developed an in vivo model using the rat patellar tendon that allows control of the loading directly applied to the tendon. This manuscript discusses the response of tendons to fatigue loading and applications of our model. Briefly, the fatigue life of the tendon was used to define low, moderate and high levels of fatigue loading. Morphological assessment showed a progression from mild kinks to fiber disruption, for low to high level fatigue loading. Collagen expression, 1 and 3 days post loading, showed more modest changes for low and moderate than high level fatigue loading. Protein and mRNA expression of Ineterleukin-1β and MMP-13 were upregulated for moderate but not low level fatigue loading. Moderate level (7200 cycles) and 100 cycles of fatigue loading resulted in a catabolic and anabolic molecular profile respectively, at both 1 and 7 days post loading. Results suggest unique mechanisms for different levels of fatigue loading that are distinct from laceration.

Terminology for Achilles tendon related disorders

The terminology of Achilles tendon pathology has become inconsistent and confusing throughout the years. For proper research, assessment and treatment, a uniform and clear terminology is necessary. A new terminology is proposed; the definitions hereof encompass the anatomic location, symptoms, clinical findings and histopathology. It comprises the following definitions: Mid-portion Achilles tendinopathy: a clinical syndrome characterized by a combination of pain, swelling and impaired performance. It includes, but is not limited to, the histopathological diagnosis of tendinosis. Achilles paratendinopathy: an acute or chronic inflammation and/or degeneration of the thin membrane around the Achilles tendon. There are clear distinctions between acute paratendinopathy and chronic paratendinopathy, both in symptoms as in histopathology. Insertional Achilles tendinopathy: located at the insertion of the Achilles tendon onto the calcaneus, bone spurs and calcifications in the tendon proper at the insertion site may exist. Retrocalcaneal bursitis: an inflammation of the bursa in the recess between the anterior inferior side of the Achilles tendon and the posterosuperior aspect of the calcaneus (retrocalcaneal recess). Superficial calcaneal bursitis: inflammation of the bursa located between a calcaneal prominence or the Achilles tendon and the skin. Finally, it is suggested that previous terms as Haglund's disease; Haglund's syndrome; Haglund's deformity; pump bump (calcaneus altus; high prow heels; knobbly heels; cucumber heel), are no longer used.

Changes in collagen fibril pattern and adhesion force with collagenase-induced injury in rat Achilles tendon observed via AFM

The Achilles tendon consists mainly of type I collagen fibers that contain collagen fibrils. When the Achilles tendon is injured, it is inflamed. The collagenase-induced model has been widely used to study tendinitis. The major advantages of atomic force microscopy (AFM) over conventional optical and electron microscopy for bio-imaging include its non-requirement of a special coating and vacuum, and its capability to perform imaging in all environments. AFM force-distance measurements have become a fundamental tool in the fields of surface chemistry, biochemistry and materials science. Therefore, the changes in the ultrastructure and adhesion force of the collagen fibrils on the Achilles tendons of rats with Achilles tendinitis were observed using AFM. The changes in the structure of the Achilles tendons were evaluated based on the diameter and D-banding of the collagen fibrils. Collagenase-induced Achilles tendinitis was induced with the injection of 30 microl crude collagenase into 7-week-old male Sprague-Dawley rats. The animals were each sacrificed on the first, second, third, fifth and seventh day after the collagenase injection. The normal and injured Achilles tendons were fixed in 4% buffered formalin and dehydrated with increasing concentrations of ethanol. AFM was performed using the non-contact mode at the resolution of 512 x 512 pixels, with a scan speed of 0.8 line/sec. The adhesion force was measured via the force-distance curve that resulted from the interactions between the AFM tip and the collagen fibril sample using the contact mode. The diameter of the collagen fibrils in the Achilles tendons significantly decreased (p < 0.05) after the collagenase injection, and the pattern of the D-banding of the collagen fibrils was similar to that of the diameter changes. The adhesion force decreased until the fifth day after the collagenase injection, but increased on the seventh day after the collagenase injection (p < 0.0001).

Patellar tendinopathy: histopathological examination and follow-up of surgical treatment

PURPOSE OF THE STUDY

The aim of this study was to determine the exact localization of the histopathological process (bone, bone-tendon junction or tendon), and to determine whether the underlying pathologic process is predominantly of inflammatory or degenerative nature, then to evaluate the outcome of the surgical treatment of patellar tendinopathy.

MATERIALS

A prospective cohort study was performed in order to analyze the outcome of surgical treatment of patellar tendinopathy, as well as to document histopathological changes in bone, bone-tendon junction, and in the patellar ligament in 34 professional athletes treated with patellar apicotomy. All the patients included in the study were classified as stage 3 according to Blazina and showed no improvement after at least 6 months of conservative treatment. The postoperative follow-up was from 1 to 8 years with a mean value of 4.7 years.

METHODS

The postoperative results were analyzed using a semiquantitative scoring system where the functional outcome was classified as very good if the athlete returned to his sporting activity without any negative side effects, good if the athlete resumed his sporting activities with modest painful sensations present only at the maximum level of physical exertion, and poor if any reduction of athletic activity was present. In twenty patients a histopathological examination of resected bone and tendon tissue was performed. The specimens were stained with hematoxylin-eosin and examined under a light microscope using polarization. Special stains used were Alcian blue, to detect any increase in ground substance, and Prussian blue which enhances conspicuity of hyaline degeneration and enables detection of hemosiderin. Immunohistochemistry was performed in order to analyze presence of blood vessels, leukocytes and histiocytes.

RESULTS

Very good results were achieved in 20 of operated knees, good results were achieved in 12 of knees and poor results were achieved in 2 of operated knees. Pathological changes in the bone were found in 35% of analyzed specimens, abnormality at the bone-tendon junction were found in 75% of the specimens, and changes in the patellar tendon were found in all extracted specimens. The histopatholological nature of the lesions found within the tendon tissue in all of the analyzed specimens belongs to the group of degenerative changes.

DISCUSSION

Currently a consenus has been established that the expression tendinitis is "out", and the term tendinopathy should be used instead. No inflammatory cells and no increase in prostaglandins can be detected in the tendons. Histopathological studies of the tissue fibrils affected by tendinosis characteristically demonstrate hypercellularity, hypervascularity, lack of inflammatory infiltrates, and disorganization and loosening of collagen fibers.

CONCLUSION

The clinical results and histopathological examination in our series justified our operative method. In the chronic stage these lesions are irreversible and constitute permanent intratendinous lesions. It thus seems logical to excise these lesions from their origin at the apex of the patella and entry into the adjacent tendon. It is also recommended on the basis of our and other authors' research that the term patellar tendinopathy should be used instead of tendonitis/tendinitis.

Proximal humerus fracture after keyhole biceps tenodesis

A biceps tenodesis is a common surgical procedure that is often carried out in conjunction with other surgical shoulder repairs to relieve biceps tendonitis. This case presents a 50-year-old woman who suffered a humerus fracture following an open keyhole biceps tenodesis. The potential reasons for the fracture as well as a brief analysis of the technique itself are presented. To our knowledge, this is the first case report of a humerus fracture following keyhole biceps tenodesis in the English-language literature.

Coracoid pain test: a new clinical sign of shoulder adhesive capsulitis

Patients with adhesive capsulitis were clinically evaluated to establish whether pain elicited by pressure on the coracoid area may be considered a pathognomonic sign of this condition. The study group included 85 patients with primary adhesive capsulitis, 465 with rotator cuff tear, 48 with calcifying tendonitis, 16 with glenohumeral arthritis, 66 with acromioclavicular arthropathy and 150 asymptomatic subjects. The test was considered positive when pain on the coracoid region was more severe than 3 points (VAS scale) with respect to the acromioclavicular joint and the anterolateral subacromial area. The test was positive in 96.4% of patients with adhesive capsulitis and in 11.1%, 14.5%, 6.2% and 10.6% of patients with the other four conditions, respectively. A positive result was obtained in 3/150 normal subjects (2%). With respect to the other four diseases, the test had a sensitivity of 0.96 and a specificity ranging from 0.87 to 0.89. With respect to controls, the sensitivity and specificity were 0.99 and 0.98, respectively. The coracoid pain test could be considered as a pathognomonic sign in physical examination of patients with stiff and painful shoulder.

Lameness associated with foot pain: results of magnetic resonance imaging in 199 horses (January 2001-December 2003) and response to treatment

REASONS FOR PERFORMING STUDY

The diagnosis of foot-related lameness often remains elusive and it can be difficult to offer rational treatment, or to predict outcome.

OBJECTIVES

To describe the spectrum of injuries of the foot identified using magnetic resonance imaging (MRI), to determine their relative prevalence among MRI diagnoses and to establish the long-term results of treatment.

METHODS

The MR images of horses examined from January 2001--December 2003 were reviewed. Horses were selected for MRI if the pain causing lameness was localised to the foot using perineural analgesia but any clinical, radiological or ultrasonographic abnormalities were insufficient to explain the degree of lameness. The clinical significance of lesions identified using MRI was determined with reference to the results of local analgesia, radiography, ultrasonography and nuclear scintigraphy. Follow-up information was obtained in January 2004 for horses which had been examined 6-36 months previously and the outcome classified as excellent (horse returned to full athletic function without recurrent lameness), moderate (sound, but only in light work), or poor (persistent or recurrent lameness).

RESULTS

One hundred and ninety-nine horses underwent MRI examinations. Deep digital flexor (DDF) tendonitis was the most common injury (59%) with primary injury in 65 horses (33%) and a further 27 horses (14%) having lesions of the DDF tendon and navicular bone. Seventeen percent of horses had injuries to multiple structures, including 24 with DDF tendonitis. Desmitis of a collateral ligament (CL) of the distal interphalangeal (DIP) joint was the second most common injury (62 horses, 31%), with primary injuries in 30 horses (15%) and a further 32 horses (16%) that had CL desmitis in conjunction with other injuries. Prognosis was best for horses with traumatic injuries of the middle or distal phalanges, with 5 of 7 horses (71%) having an excellent outcome. Horses with primary lesions of the DDF tendon or CL of the DIP joint had excellent results in only 13 of 47 (28%) and 5 of 17 horses (29%), respectively. Horses with combined injuries of the DDF tendon and navicular bone, or primary navicular bone abnormalities, had a poor outcome, with the majority of horses suffering persistent lameness.

CONCLUSIONS

A wide variety of lesions associated with foot pain were identified using MRI, a high proportion of which were primary soft tissue injuries with a guarded prognosis for return to full athletic function.

POTENTIAL RELEVANCE

It is now possible to propose more rational treatment strategies for the variety of foot injuries identified using MRI than had previously been possible; however, further information concerning aetiopathogenesis of these injuries is needed to improve their management.

Medical management of superficial digital flexor tendonitis: a comparative study in 219 horses (1992-2000)

REASONS FOR PERFORMING STUDY

There is a lack of long-term follow-up data for outcome of medical treatment of superficial digital flexor (SDF) tendonitis.

OBJECTIVES

To determine whether intralesional injection of hyaluronan, beta aminoproprionitrile fumarate (BAPN) or polysulphated glycosaminoglycans (PSGAG) or systemic administration of PSGAG yielded better results than a controlled exercise programme alone in the management of SDF tendonitis, with a minimum follow-up period of 2 years after resumption of full work; and to determine whether reinjury rate was related to sports discipline and whether fibre alignment score (FAS) at 4 months could predict outcome.

METHODS

In Study 1, 50 horses were managed by controlled exercise alone (Group A), 50 were treated with intralesional injection of hyaluronan (Group B), 20 received intralesional and systemic treatment with PSGAG (Group Ci) and 30 received systemic treatment with PSGAG (Group Cii). Horses in Groups B, Ci and Cii followed the same controlled exercise programme as Group A. In Study 2, 69 horses (Group D) were treated by intralesional injection of BAPN and followed a modified controlled exercise programme. Horses were re-examined clinically and ultrasonographically at intervals. Follow-up data were obtained for horses 2 years after resuming full work and for up to 6 years.

RESULTS

There was no significant difference in reinjury rate of the treated limb(s) between Groups A, B, Ci and Cii (42.5-44.4%) (P>0.9). The reinjury rate (16%) in the treated limb(s) in Group D was significantly lower than in the other groups (P<0.001). However, when injury rate of the uninjured limb was considered, the results were similar to Study 1. In Study 2, the FAS at 4 months after treatment was a good predictor of outcome (P<0.001). Reinjury rates for different disciplines were similar in the 2 studies, with the risk of reinjury ascending from showjumpers to event horses to National Hunt and flat racehorses.

CONCLUSIONS

Treatment with BAPN reduced the risk of reinjury in the treated limb, although the overall rate of subsequent injury was not affected. FAS at 4 months after treatment is a good predictor of outcome in the treated limb(s).

POTENTIAL RELEVANCE

This study provides long-term follow-up data in horses from a variety of sports disciplines that can be used to provide prognostic information.

Survey of the enthesopathy of X-linked hypophosphatemia and its characterization in Hyp mice

X-linked hypophosphatemia (XLH) is characterized by rickets and osteomalacia as a result of an inactivating mutation of the PHEX (phosphate-regulating gene with homology to endopeptidases on the X chromosome) gene. PHEX encodes an endopeptidase that, when inactivated, results in elevated circulating levels of FGF-23, a novel phosphate-regulating hormone (a phosphatonin), thereby resulting in increased phosphate excretion and impaired bone mineralization. A generalized and severe mineralizing enthesopathy in patients with XLH was first reported in 1985; we likewise report a survey in which we found evidence of enthesopathy in fibrocartilaginous insertion sites, as well as osteophyte formation, in the majority of patients. Nonetheless, there has been very little focus on the progression and pathogenesis underlying the paradoxical heterotopic calcification of tendon and ligament insertion sites. Such studies have been hampered by lack of a model of mineralizing enthesopathy. We therefore characterized the involvement of the most frequently targeted fibrocartilaginous tendon insertion sites in Hyp mice, a murine model of the XLH mutation that phenocopies the human syndrome in every detail including hypophosphatemia and elevated FGF-23. Histological examination of the affected entheses revealed that mineralizing insertion sites, while thought to involve bone spur formation, were not due to bone-forming osteoblasts but instead to a significant expansion of mineralizing fibrocartilage. Our finding that enthesis fibrocartilage cells specifically express fibroblast growth factor receptor 3 (FGFR3)/Klotho suggests that the high circulating levels of FGF-23, characteristic of XLH and Hyp mice, may be part of the biochemical milieu that underlies the expansion of mineralizing enthesis fibrocartilage.

Semimembranosus tendonitis after total knee arthroplastyGood outcome after surgery in 6 patients

More than 700 total knee arthroplasties were performed in our Department between 1992-2000. 6 patients developed pain on the postero-medial aspect of the knee, within 1 year of surgery. The pain increased during walking and especially on rising from a chair. All patients were women with good knee motion and good alignment of the implanted prosthesis. We found no signs of low-grade infection. Injection of 1% Xylocaine relieved pain for a short time in all patients. They were all treated with excision of the reflected portion of the semimembranosus tendon which was not cut during the arthroplasty. Pain was completely relieved in 5 cases and improvement occurred in 1.

Changes in the composition of the extracellular matrix in patellar tendinopathy

OBJECTIVE

To compare the chemical levels and mRNA expression of proteoglycan and collagen in normal human patellar tendons and tendons exhibiting chronic overuse tendinopathy.

METHODS

Sulfated glycosaminoglycan and hydroxyproline content were investigated by spectrophotometric measurement using papain-digested samples. Deglycosylated proteoglycan core proteins were analysed by Western blot using specific antibodies. Total mRNA isolated from samples of frozen tendons was assayed by relative quantitative RT-PCR for decorin, biglycan, fibromodulin, versican, aggrecan, and collagens Type I, II and III and normalised to glyceraldehyde-3-phosphate dehydrogenase.

RESULTS

There was a significant increase in sulfated glycosaminoglycan content in pathologic tendons compared to normal. This was attributed to an increased deposition of the large aggregating proteoglycans versican and aggrecan and the small proteoglycans biglycan and fibromodulin, but not decorin. Aggrecan and versican were extensively degraded in both normal and pathologic tendons, biglycan was more fragmented in the pathologic tendons while predominantly intact fibromodulin and decorin were present in normal and pathologic tendons. There was a greater range in total collagen content but no change in the level of total collagen in pathologic tendons. There were no significant differences between the pathologic and normal tendon for all genes, however p values close to 0.05 indicated a trend in downregulation of Type I collagen and fibromodulin, and upregulation in versican and Type III genes in pathologic tissue.

CONCLUSION

The changes in proteoglycan and collagen levels observed in patellar tendinopathy appear to be primarily due to changes in the metabolic turnover of these macromolecules. Changes in the expression of these macromolecules may not play a major role in this process.