Management of suprapatellar synovial plica, a common cause of anterior knee pain: a clinical review

BACKGROUND AND AIM OF THE WORK

Suprapatellar synovial plica is caused by a congenital thickening of the synovial membrane and is generally asymptomatic. In the literature, suprapatellar plicae are described as one of the causes of anterior knee pain however, their real role in determining symptoms is controversial. The aim of the current paper is to describe the anatomy, classifications, pathophysiology, symptoms and management of suprapatellar plica syndrome, as well as the differential diagnosis from other causes of anterior knee pain.

METHOD

Via a search within the MEDLINE/PubMed database, a current review was conducted, and the results summarized.

RESULTS

Due to idiopathic, traumatic or inflammatory conditions, plicae can become pathological, causing anterior knee pain with possible knee clicking, swelling, giving way and locking after prolonged flexion of the knee. The diagnosis should be formulated based on an accurate medical history and clinical examination, followed by an appropriate imaging study. However, arthroscopy remains the "golden standard" for detecting all synovial plica.

CONCLUSIONS

In patients with anterior knee pain, where doubt is present in the imaging investigation for intraarticular or periarticular lesions, pathological suprapatellar synovial plica must be suspected. The treatment should initially be conservative, but in cases where symptoms persist, patients should undergo arthroscopy to confirm diagnosis and to determine a suitable treatment. In the presence of pathological plica associated with cartilage damage of the femoral condyle or patella at the time of diagnostic arthroscopy, plicae excision leads to favourable results in a high number of cases.

Anatomy and histology of the human temporomandibular joint

1. The anatomy and histology of the human temporomandibular joint indicates that the meniscus is firmly attached to the mandibular condyle and that during translatory movements the meniscus and condyle move concomitantly. The lateral pterygoid muscle, both inferior and superior heads insert into the meniscus and the pterygoid fovea of the condyle. 2. The structure of the gracilis and pars posterior indicate that these are the parts of the meniscus that are exposed to friction during jaw movement. It is suggested that during hinge movement the sagittal crest of the condyle moves from underneath the pars posterior to underneath the pars gracilis. 3. The restraining ligament for the articulation appears to be the lateral ligament. Its function is to keep the articular surfaces relatively close together during movement and to restrain lateral and posterior movements of the condyle. Its intimate association with the deep fibres of the masseter muscle appears to be important. 4. The fact that the meniscus is thicker medially than laterally would indicate that its major function is to smooth out the incongruities between the joint surfaces. 5. The sphenomandibular ligament as well as being a 'guy' ligament is intimately associated with the postero-superior medial capsular meniscal complex. The medial capsular complex would seem to contribute to the major part of the anterior ligament to the malleus. 6. Remodelling of the articular surfaces occur throughout life by progressive and regressive remodelling. However, if the remodelling processes increase, either the medio-lateral or antero-posterior dimensions of the joint an osteoarthritic condition prevails. 7. Excessive progressive remodelling appears to be due to abnormal positions of the condyle in the maximal intercuspal position. It can be caused by orthodontic procedures or by experimental displacement of the condyle. 8. The transitional zone appears to be important in the aetiology of osteoarthritis since when this zone comes under pressure proliferation of cartilage cells occur which may be transformed into bone, resulting in the hooked condyle.

Functional anatomy of the temporomandibular joint (I)

Jaw movement is analyzed as the action between two rigid components jointed together in a particular way, the movable mandible against the stabilized cranium. Jaw articulation distinguishes form most other synovial joints of the body by the coincidence of certain characteristic features. Its articular surfaces are not covered by hyaline cartilage as elsewhere. The two jointed components carry teeth the shape, position and occlusion of which having a unique influence on specific positions and movements within the joint. A fibrocartilaginous disc is interposed between upper and lower articular surfaces; this disc compensates for the incongruities in opposing parts and allows sliding, pivoting, and rotating movements between the bony components. These are the reasons for our review of the functional anatomy of the temporomandibular joint.

The retinacula of Weitbrecht in the adult hip

PURPOSE

The aim of the study was to describe the retinacula of Weitbrecht in the adult hip.

MATERIALS AND METHODS

Specimens were obtained from 30 adult hips, average age was 77 years (age range 43-91 years), 8 specimens were fixed by formalin solution and 22 were not fixed.

RESULTS

Anterior retinaculum was found in 40% of examined specimens. The anterior retinaculum was in 83% of cases formed by a flat plate and in 17% by two to three parallel bands. Medial retinaculum was present constantly, extending from the attachment of the articular capsule at the base of the lesser trochanter towards the fovea capitis femoris as far as the edge of the articular cartilage. Typically, the retinaculum had the form of an inverted "T". Of the three retinacula, the medial one was the strongest. Lateral retinaculum was also present constantly. In 89% of cases, it had the form of a quadrilateral plate adjacent to the upper surface of the femoral neck. This plate arises from the insertion of the articular capsule on the upper part of the femoral neck at the base of the greater trochanter close to the trochanteric fossa. The plate extended along the upper edge of the femoral neck as far as the edge of the articular cartilage. Microscopic examination revealed fine blood vessels running through the retinacula.

CONCLUSION

Lateral retinaculum and medial retinaculum are constant synovial plicae in terms of both occurrence and localization. Nutritive arteries run through both the plicae to supply the femoral head.

Imaging of normal and pathologic joint synovium using nonlinear optical microscopy as a potential diagnostic tool

An estimated 1.3 million people in the United States suffer from rheumatoid arthritis (RA). RA causes profound changes in the synovial membrane of joints, and without early diagnosis and intervention, progresses to permanent alterations in joint structure and function. The purpose of this study is to determine if nonlinear optical microscopy (NLOM) can utilize the natural intrinsic fluorescence properties of tissue to generate images that would allow visualization of the structural and cellular composition of fresh, unfixed normal and pathologic synovial tissue. NLOM is performed on rabbit knee joint synovial samples using 730- and 800-nm excitation wavelengths. Less than 30 mW of excitation power delivered with a 40×, 0.8-NA water immersion objective is sufficient for the visualization of synovial structures to a maximum depth of 70 μm without tissue damage. NLOM imaging of normal and pathologic synovial tissue reveals the cellular structure, synoviocytes, adipocytes, collagen, vascular structures, and differential characteristics of inflammatory infiltrates without requiring tissue processing or staining. Further study to evaluate the ability of NLOM to assess the characteristics of pathologic synovial tissue and its potential role for the management of disease is warranted.

[Is the posterior segment of the temporomandibular joint capsule well defined?]

The temporomandibular joint (TMJ) is a complex joint due its development and filogeny. This complexity explains the lack of descriptions of the posterior joint capsule. Nowadays it is necessary to establish the limits of this joint part owing to a correct arthroscopic access. Dissecting human cadavers it will determine this joint segment and describe its anatomic relations.

Arthroscopic, macroscopic, and microscopic anatomy of the synovial fold of the elbow joint in correlation with the common extensor origin

PURPOSE

The objective of our study was to clarify the arthroscopic, macroscopic, and microscopic anatomy of the radiocapitellar synovial fold of the elbow joint in correlation with the common extensor origin.

METHODS

We performed arthroscopy in 14 fresh-frozen cadaveric elbows and found the synovial fold covering the radial head or interposing in the radiocapitellar joint in 6. The fold was tagged with loop suture under arthroscopy to identify its exact location in gross anatomy. The radiocapitellar joint capsule was then resected without disturbing the continuity of the common extensor and lateral epicondyle. Macroscopic and histologic evaluation was performed for the lateral elbow capsular complex.

RESULTS

The synovial fold was found to be a triangular-shaped thickening of the capsule located on the proximal edge of the annular ligament. The mean distance between the lateral epicondyle and the base of the fold at the anterior edge, middle part, and posterior edge was 23 mm, 8 mm, and 13 mm, respectively. This structure was distinct from the annular ligament but was continuous with the radiocapitellar joint capsule. The joint capsule and the common extensor tendon blended with each other imperceptibly and formed a single enthesis at the lateral epicondyle.

CONCLUSIONS

The synovial fold identified by arthroscopy is a physiologic capsular tissue located on the proximal edge of the annular ligament. It is distinct from the annular ligament but has a close correlation with the common extensor tendon enthesis at the lateral epicondyle.

CLINICAL RELEVANCE

The synovial fold belongs to the lateral epicondyle enthesis, which is a composite of the common extensor tendon, undersurface capsule, and bone. Therefore, lateral epicondylitis with degenerative lesions in the area of the common extensor origin may involve the synovial fold and induce hypertrophic changes.

Effect of surface roughness on squeeze film poroelastic bearings with special reference to synovial joints

A simplified mathematical model has been developed for understanding the combined effects of surface roughness and couple stresses on lubrication aspects of synovial joints. The modified Reynolds equation which incorporates the elastic as well as randomized surface roughness structure of cartilage with couple-stress fluid as lubricant is derived. The mean pressure, load carrying capacity and time of approach as functions of film thickness during normal articulation of joints are obtained by using Christensen stochastic theory with the assumption that the roughness asperity heights are to be small compared to the film thickness. The effects of surface roughness and elasticity are considerably pronounced for the poroelastic bearings with couple-stress fluid as lubricant compared with classical case.

Anatomy of the temporomandibular joint

The temporomandibular joint (TMJ), also known as the mandibular joint, is an ellipsoid variety of the right and left synovial joints forming a bicondylar articulation. The common features of the synovial joints exhibited by this joint include a fibrous capsule, a disk, synovial membrane, fluid, and tough adjacent ligaments. Not only is the mandible a single bone but the cranium is also mechanically a single stable component; therefore, the correct terminology for the joint is the craniomandibular articulation. The term temporomandibular joint is misleading and seems to only refer to one side when referring to joint function. Magnetic resonance imaging has been shown to accurately delineate the structures of the TMJ and is the best technique to correlate and compare the TMJ components such as bone, disk, fluid, capsule, and ligaments with autopsy specimens.

Anatomic study of the synovial folds of the occipito-atlanto-axial joints

This study was performed to observe and measure synovial folds of the occipito-atlanto-axial joints and to explore their clinical significance. Two hundred ninety eight occipito-atlanto-axial joints from 30 embalmed cadavers of children and 20 of adults were dissected to find the incidence, quantity, distribution, forms, dimension, and histology of synovial folds. Synovial folds were found in most joints in both groups except for the posterior median atlantoaxial joints. Most of synovial folds were crescent-shaped, distributed on the superior aspects of the anterior median atlantoaxial joints, or in the antero-lateral aspects of the atlantooccipital joints and the lateral atlantoaxial joints. Compared to the adult group, the child group had a higher incidence of synovial folds (72.5% joints). The adult incidence was found to be 58.5%. 54.3% of the synovial folds in child were medium size or large size, but only 30.1% of the synovial folds in adult were medium size and there were no large ones. Microscopically, there were three histologic types synovial folds in these cervical joints, and 78.9% of them belonged to adipose type or fibro-adipose type in child, but only 45.8% belonged to the two types in adult. Our data suggest that the larger synovial folds in children may predispose them to an increased rate of entrapment with resultant edema and subluxation of the associated joint complex. This may be the cause why some cervical spine diseases preferentially take place in children rather than in adult, such as benign paroxysmal torticollis'atlantoaxial rotatory deformity and Grisel's syndrome.

Ultrasonographic examination of the synovial fold of the radiohumeral joint

This report describes the anatomy of the synovial fold of the radiohumeral joint and assesses its visibility by ultrasonography. Forty-nine fresh cadaver radiohumeral joints were examined by ultrasonography before and after intraarticular saline injection and then dissected. Digital photos were taken before and after the joint capsule was excised. The relative coverage of the radial head by the fold was calculated. Synovial folds were observed in all specimens. Forty-three had anterior and posterior lobes. The synovial fold covered an average of 28% of the radiocapitellar joint surface of the radial head. The sensitivity of the ultrasonography was 81%, 46%, and 85% from the anterior, lateral, and posterior aspects of the radiohumeral joint, respectively. Intraarticular saline injection improved the sensitivity to 96%, 67%, and 94%, respectively. The synovial fold is a consistent anatomic structure, and ultrasonography can be a useful preoperative diagnostic tool.

The synovial joints of the human foot

The human foot is considered an organ with an assortment of tissues with different morphological characteristics and well defined limits, but effectively has a simple functionality when static that becomes extremely complex when in movement. Its complex structure, comprised of an elastic and resistant skin covering a bone framework, joints, muscles, tendons, veins and nerves, can be compared to an efficient mechanical assembly. After a long and extraordinary evolutive journey, the human foot has undergone numerous changes to perfect its function; it has lost most of its grabbing function whilst gaining new characteristics that have ultimately allowed the modern man to stand upright. The complex articular structure of the human foot consists of thirty four synovial joints, of which eighteen have curved surfaces and sixteen plane surfaces. Following the criteria set by the systematic, radiological and clinical anatomy, the Authors contribute further to the current knowledge on the ankle, tarsal (anatomic subtalar, transverse tarsal, cuneonavicular, intercuneiform and cuneocuboid), tarsometatarsal, intermetatarsal, metatarsophalangeal and interphalangeal joints and dorsal, plantar and interosseous ligaments of the human foot. The articular lines of the transverse tarsal (Chopart) and tarsometatarsal (Lisfranc) joints are particularly interesting and not only from a surgical point of view; through a straightforward identification of few reference points, it is possible to find the medial and lateral extremities of the Chopart's and Lisfranc's lines, the former pinpoints the boundary between the hindfoot and midfoot and the latter between the midfoot and forefoot.

Visualisation of the pisotriquetral joint through standard portals for arthroscopy of the wrist

Disorders of the pisotriquetral joint are well recognised as the cause of pain on the ulnar side of the wrist. The joint is not usually examined during routine arthroscopy because it is assumed to have a separate joint cavity to the radiocarpal joint, although there is often a connection between the two.

We explored this connection during arthroscopy and in fresh-frozen cadaver wrists and found that in about half of the cases the pisotriquetral joint could be visualised through standard wrist portals. Four different types of connection were observed between the radiocarpal joint and the pisotriquetral joint. They ranged from a complete membrane separating the two, to no membrane at all, with various other types of connection in between.

We recommend that inspection of the pisotriquetral joint should be a part of the protocol for routine arthroscopy of the wrist.

MR Imaging of Synovial Disorders of the Knee: An Update

Synovial disorders often affect the knee joint and are a common cause of morbidity. Before MR imaging, radiologists were limited in their ability to provide information about the presence or absence of synovial disease. With the advent of MR imaging, useful information can now be provided to referring clinicians, often at a time when the initiation of therapy may mitigate significantly the long-term sequelae of synovial disorders. MR imaging, owing to its superior soft-tissue contrast, is the imaging modality of choice for demonstrating and quantifying pathologic changes of the synovium. MR imaging provides invaluable information to the clinician regarding the need to either initiate or modify therapy in those patients suffering from diseases of, or affecting, the synovium.

Fluid collection within the synovial sheath of the tendon of the flexor hallus longus muscle in the tarsal joint of rats: an anatomic variant detectable with magnetic resonance imaging

Magnetic resonance (MR) images of the right tarsal joint of 22 normal male Han:Wistar rats were acquired using a 4.7 T magnet. An intermediate-high signal area associated with the tendon of the flexor hallus longus muscle was noticed in three rats on T2-weighted images. These areas appeared as an intermediate-high signal on lightly T2-weighted images, but appeared as an iso-signal to muscle structure on proton density weighted images. Histology preparations showed that such areas were caused by a sizable fluid collection within the synovial sheath of the tendon of the flexor hallus longus muscle, with all other joint structures appearing normal. This anatomic variant could be potentially regarded as a lesion on T2-weighted MR images, such as inflamed tissue with oedema, especially when the spatial resolution and/or signal-to-noise ratio are not optimal.

Anatomy of the proximal tibiofibular joint

This paper describes the anatomy and function of the proximal tibiofibular joint (PTFJ). The physical dimensions of the joint and the topology of the articular surfaces are described. It is noted that the inclination of the joint is variable, and that joints with a steeper slope away from the transverse plane are less mobile. The ligamentous and tendinous attachments are described. Finally, the histological features of the articular surfaces are presented. The clinical importance of the anatomical features is discussed.

Enlarged perforating branch of peroneal artery and extra crural fascia in close relationship with the tibiofibular syndesmosis

We found an extremely large perforating branch of peroneal artery in an 89-year-old female cadaver's left ankle. The anterior tibial artery could not reach to supply the ankle and dorsum of the foot. The perforating branch of peroneal artery continued as the dorsalis pedis after giving off an anterior lateral malleolar artery branch. The posterior tibial artery was thinner than usual. On the anterior side of the ankle, there was an extra crural fascia in addition to the regular crural fascia, under the anterior crural muscles. This strong fascia was tightly overlying the perforating branch of peroneal artery and anterior tibiofibular ligament. It is important to know the relationship of these vessels to the surrounding structures. Surgeons must be careful while dissecting this area since the perforating branch of peroneal artery might be anomalously enlarged as well as crossing in front of the tibiofibular syndesmosis in order to prevent vascular injury.

Anatomical variations of the extensor pollicis brevis tendon and abductor pollicis longus tendon--relation to tenosynovectomy

Sufficient improvement in De Quervain disease, is not always archieved even by tenosynovectomy, and the reason for this appears to be anatomical variation in the first extensor compartment of the hand. In this study we examined the first extensor compartment of 159 hands of 80 human cadavers. Hiranuma and colleagues documented four anatomical types of first compartment, and in this study type A was observed in 76 (47.8%) of the 159 hands, type B in 49 (30.8%), and type C in 21 (13.2%). No type D compartments in which the extensor pollicis brevis tendon is absent, were observed. There were 13 hands that did not fit any of Hiranuma's categories, and we classified them into three new types: E, F, and G. The numbers of extensor pollicis brevis tendons in the first compartment varied from one to three, and the number of abductor pollicis longus tendons varied from one to seven. Successful tenosynovectomy in the treatment of De Quervain disease requires to pay close attention to accessory tendons of the extensor pollicis brevis tendon and abductor pollicis longus tendon, branching of the tendons, and the presence of an atypical septum in the first compartment.

Anatomy, biomechanics, and surgical approach to synovial folds within the joints of the foot

The presence of synovial folds in various joints of the foot has been previously documented. The function and clinical significance of these structures within the joint have not been established. Histologically they are considered anatomically different from a meniscus primarily owing to their makeup of loose connective tissue with nerve fibrils and several synovial cell layers. We hypothesize that the function of these folds is similar to that of the menisci: to increase joint congruity and stability. We further hypothesize that these folds will be present in joints of the foot that require greater stability. To demonstrate this, 41 fixated cadaveric feet were sectioned in the sagittal plane and the incidence and locations of the synovial folds were documented. Three fixated cadaveric feet were evaluated using a materials testing machine. The first metatarsophalangeal joint was incised, and the presence of the synovial fold was documented. The joint was then taken through its range of motion with and without the synovial fold while data on the force and displacement were collected. The steps were then repeated for the ankle joint. The results showed statistically stiffer ankle and first metatarsophalangeal joints with the synovial fold present, as determined by the stress-strain curve. On the basis of the presence and location of these synovial folds, we demonstrated arthroscopic surgical approaches to many of the documented joints that contain these folds. Because the folds contain synovial cells and vascular tissue, damage to them can result in considerable pain. In such cases, arthroscopic surgery would be of benefit. Further research may indicate whether they need to be salvaged during joint procedures to facilitate normal joint function or should be removed to reduce postoperative complications.

Plica humeroradialis: Inzidenz und MR-tomographische Darstellbarkeit

PURPOSE

To determine frequency and size of a humeroradial plica and correlate it with degenerative changes, and to determine frequency of the visualization of a synovial fold on MR-Images (T1-weighted spin-echo and STIR sequences) and correlate it with degenerative changes.

MATERIALS AND METHODS

Forty-two elbow specimens were dissected and studied for humeroradial synovial folds (small, medium, large) and degenerative changes (absent, medium, strong), and 88 elbow MR-images were analyzed for a synovial fold (not visible, small, large) and degenerative changes (absent, medium, strong). Comparison was performed using the chi (2) test.

RESULTS

Dissections revealed a synovial fold in all cases. The sizes were small in n = 13 (31 %), medium in n = 24 (57 %), and large in n = 5 (12 %). Degenerative changes were absent in n = 9 (21.4 %), medium in n = 29 (69 %), and strong in n = 4 (9.6 %). On MRI the synovial fold was not visible in n = 67 (76 %), small in n = 12 (14 %), and large in n = 9 (10 %). Degenerative changes on MRI were absent in n = 65 (74 %), medium in n = 15 (17 %), and strong in n = 8 (9 %). The size of the fold correlated positively with degenerative changes in the specimen but not with degenerative changes on MRI. The T1-SE sequence was superior to the STIR sequence in revealing the synovial fold.

DISCUSSION

A humeroradial plica is a regular finding, but visualized by MRI in only approximately 20 %, probably due to its variable size. Its visualization succeeds best with T1-spin-echo sequences.

Patellar 'entry' feature: a new arthroscopic anatomic finding

The purpose of this paper is to report a frequently noticed anatomical feature on the soft synovial floor of the suprapatellar pouch in the knee, which has not been reported before. Four hundred and fifty-seven consecutive knee arthroscopies were carried out. The patellar entry feature was present in 294 and not noticed in 163. There was not a concurrent control group. During arthroscopy the presence or absence of the patellar entry feature was noted and entered on a database consecutively and prospectively. All arthroscopies were carried out by the senior author. The ages of the patients undergoing arthroscopy ranged from 8 to 96 years with a mean age of 39.4 years. Out of 457 there were 318 males and 139 females. Where the patellar entry feature was found, there was an average of 40% female; where there was not, there was an average of 27% female. The patellofemoral articulation has been a focus of interest mainly because of the poorly understood and extremely common anterior knee pain syndrome (AKPS). We hypothesise that the patellar entry feature is the area where the patella rests, with the knee in full extension and the quadriceps relaxed and is thus the starting point before flexion is initiated.

Microarchitecture and protective mechanisms in synovial tissue from clinically and arthroscopically normal knee joints

BACKGROUND

Synovial biopsies are used to study synovial immunopathology and are increasingly applied for the evaluation of new therapeutic strategies in chronic arthritis. Therefore, it is essential to be informed on the complete spectrum of synovial immunopathology.

OBJECTIVE

To describe the cellular content, cytokine and cell adhesion molecule expression in synovial tissue from clinically and arthroscopically normal knees.

METHODS

Synovial tissue was obtained from 20 normal subjects at the time of knee joint arthroscopy for unexplained knee pain. Tissue sections were studied for basic histopathology and for a range of cell surface markers, cytokines, and cell adhesion molecules by immunoperoxidase staining. Stained sections were evaluated by semiquantitative scoring and digital image analysis.

RESULTS

Normal synovial tissue is composed predominantly of fibrofatty areolar tissue, with a variable thickness of intimal lining, composed of both CD68 positive macrophages and CD55 positive fibroblast-like synoviocytes. Interleukin 1 receptor antagonist (IL1Ra) was frequently detected in the synovial membrane of normal subjects (mean (SD) integrated optical density (IOD)=3809.6 (3893.9)), but both tumour necrosis factor alpha (TNFalpha) and interleukin 1beta (IL1beta) were rarely detected. In addition, cell adhesion molecules were rarely detected in the normal synovial membrane, with the exception of intercellular cell adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1). Osteoprotegerin (OPG) expression was abundant on synovial lining macrophages (mean (SD) IOD=5276 (4716) as well as endothelial cells (mean (SD) IOD=557 (226)), but receptor activator of nuclear factor kappa ligand (RANKL) expression was rarely seen.

CONCLUSIONS

The normal synovial membrane has a variable architecture, including thickness of the lining and the subintimal cell infiltrate, with little inflammatory cytokine production or expression of cell adhesion molecules. The excess of OPG expression over RANKL and IL1Ra over IL1 may be important for protection against joint damage

[A study on puncturing the temporomandibular joint cavity of rabbits and withdrawing synovia]

OBJECTIVE

The purpose of this study was to study the methods of how to puncture the temporomandibular joint (TMJ) cavity of rabbits and get the synovia.

METHODS

The authors punctured joint cavity and withdrew the synovia from bilateral TMJ cavities of 12 New Zealand rabbits with different methods, such as the traditional puncture method, improved puncture, puncture under X ray, puncture guided by ultrasonography and spiral CT, and withdrawing synovia by micropump.

RESULTS

Only one cavity was successfully punctured using the traditional puncture method. A total of 4 cases were successfully punctured using the improved method. X ray and ultrasonography did not locate the TMJ cavity precisely. The spiral CT helped observation and puncture. However, the above methods did not work in collecting synovia. The method of micropump withdrew synovia successfully.

CONCLUSION

The improved method and spiral CT are efficient methods to precisely puncture TMJ cavity. The technique of micropump successfully resolves the problem of withdrawing synovia.

The synovial fold of the humeroradial joint: anatomical and histological features, and clinical relevance in lateral epicondylalgia of the elbow

The synovial fold of the humeroradial joint is known, and sometimes considered as a meniscus that could be injured by chronic repeated trauma related to pronation and supination. The aims of this study were to determine the gross anatomy and histological structure of this fold, and to clarify its participation in the painful lateral syndromes of the elbow. Fifty elbows from adult cadavers were dissected. The capsule of the humeroradial part of the elbow joint was resected with the annular ligament. The presence of a synovial fold, and its location relative to the cranial edge of the annular ligament divided into five sectors (ventral, ventrolateral, lateral, laterodorsal and dorsal) were noted; morphological parameters such as thickness, width and length were measured. The histological examination determined the structure of the folds. Five synovial folds were resected during surgery for epicondylalgia in five patients who suffered from pain precisely at the level of the joint between the capitulum and the fovea radialis, and were also examined. A fold was present in 43 cases, and in two cases two folds were seen at the deep side of the junction between the capsule and the annular ligament. The most frequent positions were: dorsal ( n=11), laterodorsal and dorsal ( n=6;), lateral to dorsal ( n=5), lateral ( n=5), ventral ( n=4) and circular ( n=4). The mean length was 21.4 mm (range from 9-51 mm). The mean width was 2.9 mm (range 1-10 mm), and the mean maximal thickness 1.7 mm (range 1-4 mm). The histological study showed two types of folds: a rigid structure, with oriented fibrous tissue, triangular with a peripheral capsular base, covered on its two sides and along the free edge by a synovial layer; and a pliable structure, formed of two synovial layers that surrounded a thin fatty tissue, with a villous appearance of the free edge. No fibromyxoid structure, as in a real meniscus, was observed. Some nerve fibers were seen in the folds. The five folds resected in operated patients were hypertrophic, and showed an increased number of nerve fibers, along the capsule but also close to the synovial layer. Some painful syndromes of the lateral side of the elbow are not related to tendinitis or to posterior interosseous nerve compression, but have an intra-articular origin. This study showed that the synovial fold is not a meniscus, and may be involved in the etiology of lateral epicondylalgia.

Cellular architecture of the synovium in the tendon sheath of horses: an immunohistochemical and scanning electron microscopic study

The intimal lining cells of the synovium in joints have been studied morphologically and histochemically and shown to consist of macrophagic cells (type A) and fibroblast-like cells (type B). It is believed that the structure of the synovium in the tendon sheath is similar to that in the joint, but there have been only a few morphological studies of the tendon sheath. The present study revealed the cellular architecture of synovium in the tendon sheath of horses by histochemistry and scanning electron microscopy (SEM). Like the joint, the inner surface of the tendon sheath was covered with a cell-rich intimal layer. Acid phosphatase-positive A cells accumulated in the mesotendon but few in other regions. B cells were selectively immunolabeled with protein gene product (PGP) 9.5 antiserum and distributed in the entire length of the synovial intima in the tendon sheath. The synovial intima consisted of a surface layer rich in the processes of B cells and a deep layer containing cell bodies of B cells. Using SEM, B cells could be classified into two types according to the morphology of their processes. B cells of dendritic type were located mainly in the joint-side of the tendon sheath and extended branched processes to form a meshwork on the intimal surface. B cells of flat type were located in the skin-side of the tendon sheath and in the mesotendon. Their membranous processes extended in a horizontal direction and covered the intimal surface, resembling epithelium. It appears likely that the morphology and distribution of synovial intimal cells are influenced by various factors, such as the nature of the underlying tissues and the magnitude of mechanical stress.

Anatomy and MR imaging appearances of synovial plicae of the knee

Synovial plicae are normal anatomic structures of the knee that sometimes become symptomatic. Magnetic resonance (MR) imaging and MR arthrography are useful tools in the evaluation of synovial plicae and allow differentiation of these entities from other causes of knee pain. At MR imaging, synovial plicae appear as bands of low signal intensity within the high-signal-intensity joint fluid. Gradient-echo T2-weighted and fat-suppressed T2-weighted or proton density-weighted MR images are optimal for the evaluation of plicae. Plica syndrome, the painful impairment of knee function in which the only finding that helps explain the symptoms is the presence of a thickened and fibrotic plica, should be included in the differential diagnosis of internal derangement of the knee. A diffusely thickened synovial plica, perhaps associated with synovitis or erosion of the articular cartilage of the patella or femoral condyle, in a patient with no other significant MR imaging findings suggests the diagnosis of plica syndrome. Once the diagnosis has been made, nonsurgical treatment is preferable initially. Failure of the patient to improve with conservative treatment leaves arthroscopic excision of the pathologic plica as the treatment of choice.

Hip arthroscopy without traction: In vivo anatomy of the peripheral hip joint cavity

PURPOSE

To describe the in vivo anatomy of the peripheral compartment of the hip joint using a systematic sequence of examination without traction.

TYPE OF STUDY

Case series.

METHODS

We performed 35 hip arthroscopies without traction from an anterolateral portal in the supine position. Free draping and a good range of movement of the hip joint were used to relax parts of the capsule and increase the intra-articular volume of the area that was inspected. Each procedure was documented on a standard protocol including detailed information on technical features and normal and pathologic intra-articular findings.

RESULTS

A comprehensive inspection of the peripheral compartment was obtained from the anterolateral portal. A systematic sequence of examination was developed separating the periphery of the hip joint into 7 areas: anterior neck area, medial neck area, medial head area, anterior head area, lateral head area, lateral neck area, and posterior area. The arthroscopic in vivo anatomy of each area is described. In 3 patients, 1 to 3 loose bodies were removed. In 1 patient with a synovial chondromatosis, 40 chondromas were retrieved. In osteoarthritis, impinging osteophytes were trimmed in 3 cases and partial synovectomy was performed in 10 patients. The following complications were observed: a temporary sensory deficit of the lateral femoral cutaneus nerve in 1 patient, scuffing of the anterior surface of the femoral head in 3 patients, detaching of an osteophyte in 1 patient, and partial tears of the anterior synovial fold in 10 patients.

CONCLUSIONS

Arthroscopy without traction allows for a complete evaluation of hip anatomy without the loaded articular surfaces, the acetabular fossa, and the ligamentum teres. For a complete overview of both the central and peripheral part of the hip, traction is necessary for the central part.

Types of synovial fold in the cervical facet joint

Few detailed studies of synovial folds of cervical facet joints exist at the moment. This study was performed to provide anatomical data for each synovial fold in the cervical facet joints, using 20 cervical spines from C2 to C7 for dissection. Anatomic evaluation of the synovial folds included the gross morphology, in three dimensions, and the histology. Also, degenerative changes of the lower facet surface on which synovial folds occurred were evaluated. On the basis of gross morphology and histological composition, three types of synovial folds were identified. Type-1 synovial folds, shaped like a crescent, consisted principally of adipose tissue. Type-2 synovial folds had an apical region made up of dense fibrous tissue, with the base and middle region consisting of adipose tissue. In type-2 folds, the size and shape varied, including some elliptic-shaped synovial folds projecting well into the joint cavity. Type-3 synovial folds were thin with ragged free borders, and were formed exclusively of fibrous tissue. This study shows the variable appearance of synovial folds. Speculation was raised that the articular facet impingement of a large synovial fold and the subluxation of a smaller structure may play a possible role in the pathology of some disorders of the neck.

The microanatomy of the rhesus monkey temporomandibular joint

PURPOSE

The objective of this study was to describe and compare the histology of the rhesus monkey temporomandibular joint (TMJ) with that of the human joint.

MATERIALS AND METHODS

Seventeen rhesus monkeys (Macaca mulatta) with an age range from 4 to 11 years were used. Both TMJs of the first animal and the left TMJs of the remaining 16 animals were used for this study. The joint specimens were sectioned sagittally and processed for light and electron microscopic studies.

RESULTS

The rhesus monkey TMJ consists of the condylar, glenoid fossa, and articular disc components. The histology of these components is described at the light and electron microscopic level.

CONCLUSIONS

The monkey TMJ was found to be anatomically similar to the human joint. It was concluded that the rhesus monkey is one of the most suitable animal models for studies involving the TMJ.

Coaxial portals for posterior ankle arthroscopy: An anatomic study with clinical correlation on 29 patients

PURPOSE

The authors performed a cadaveric study on 10 ankles and retrospectively reviewed 29 arthroscopic synovectomies to determine the trajectory, minimal safe distances, and complications using a new approach for posterior ankle arthroscopy.

TYPE OF STUDY

Anatomic study and case series.

MATERIALS AND METHODS

A posterolateral portal was established immediately posterior to the peroneal tendon sheath. While staying within the posterior ankle capsule, an inside-out technique was then used to establish the posteromedial portal directly behind the medial malleolus adjacent to the posterior tibial tendon. The cadaveric ankles were frozen, sectioned, and photographed to measure the proximity of neurovascular structures to these coaxial portals. From 1988 to 1994, arthroscopic synovectomy was performed on 23 patients (29 ankles) with hemophilia using these modified portals.

RESULTS

Results of the anatomic study showed that the posterior tibial nerve and posterior tibial artery were located a mean distance of 5.7 mm (SEM, 0.6 mm) and 6.4 mm (SEM, 0.7 mm) from the edge of the cannula, respectively. Neither penetration nor contact of nerve or vessel was observed at either posterior portal. In the 29 clinical cases, posterior capsular synovectomy was achieved arthroscopically with no detectable complications at an average 45-month follow-up.

CONCLUSIONS

Our anatomic data show that the coaxial portals described here are essentially equidistant to the neurovascular structures compared with conventional portals. Our clinical results suggest that his technique for posteromedial and posterolateral portals is safe, effective, and reproducible.

Posterior cruciate ligament architecture: evaluation under microsurgical dissection

PURPOSE

Our objective was to verify the fiber anatomy of the posterior cruciate ligament (PCL) and to measure the main dimensions and the femoral and tibial attachment site distances of the ligament after microsurgical dissection. We hypothesized that PCL anatomy is more complex than the 2 traditionally characterized bands.

TYPE OF STUDY

This is a purely anatomic description of microdissections of the PCL, focused on the fine anatomy of the ligament.

MATERIALS AND METHODS

Twenty-four fresh-frozen cadaveric knees were dissected using magnifying loupes and an operative microscope, being careful to avoid creating artificially separated bundles. The main dimensions of the PCL were measured using a micrometer.

RESULTS

The anterior, central, posterior-longitudinal, and posterior-oblique were the 4 fiber regions identified based on their orientation and the osseous sites of their insertions. These were partially separable anatomically but were functionally distinct. The anterior and central fiber regions made up the bulk of the ligament, while the remaining 15% consisted of the posterior fiber regions. During manual joint motion, the behavior of these fiber regions was observed. The anterior fiber region appeared to be the most nonisometric and remained in tension mainly between 30 degrees and 90 degrees of flexion. The posterior fiber regions appeared to be the most isometric (especially the posterior-oblique) and remained in tension mainly in extension and partially in deep flexion. The central fiber region appeared to have an intermediate behavior and remained in tension mainly between 30 degrees and 120 degrees of flexion. Additionally, it appeared to be the widest of all fiber regions.

CONCLUSIONS

These findings should be of interest and help in interpreting some of the anatomy encountered during arthroscopic examination of the PCL, both from the anterior and posterior lateral portals. Furthermore, this information should prove useful in selecting treatment for the PCL.

Anatomical study of the synovial plicae of the hip joint

Observations and measurements of the synovial plicae of the hip joints were made on 63 embalmed cadavers. The cadavers were divided equally among three age groups (fetuses, children, and adults). Our observations showed that the plicae appeared in two forms (flat and villous) and were mainly confined to the external surface of the lower medial part of the acetabular labrum (labral plicae), the base of the ligament of the head of the femur (ligamental plicae), and along the reflecting line of the synovial membrane on the base of the femoral neck (neck plicae). The ligamental plicae were well padded with a fibroelastic pad of fat filling the acetabular fossa, and the neck plicae were far away from the articular surfaces of the joint; as a result, neither was likely to be injured or entrapped during joint movements. The labral plicae were larger than the ligamental or neck plicae and had an incidence of 73.8% in the fetal group. The fetal plicae were found only after the fetal age of 5 months. In nine cases of the child and adult groups, the labral plicae extended between the articular surface of the femoral head and the lower part of the acetabulum during medial rotation of the thigh. When the thigh was rotated laterally, the plicae in six of the same cases could be returned to their original positions. In the remaining three cases, there was continual impingement.

The normal width of anterior hip synovial recess in children

To establish the diagnostic criteria for hip joint effusion, the normal width of the anterior hip synovial recess in children and the difference between both hips of the same child were examined in this study. Eight kindergarten schools were randomly selected for study in Kaohsiung City. The width of anterior hip synovial recess of 1,568 hips in 784 children (421 boys, 363 girls) was measured by ultrasound scanner with 7.5-MHz linear probe. The age of children ranged from 2.5 to 6.6 years old. During measurement, the children were put in supine position with hips and knees in extension and patella facing up. The results revealed that the mean width of the anterior synovial recess was 7.29+/-1.15 mm. Linear correlation of the width of synovial recess to age and height was disclosed and expressed as follows: width (millimeters) equal to 6.52+0.013x age (months), or width (millimeters) equal to 3.97+0.030x height (centimeters). The mean difference between both hips of the same child was 0.611+/-0.523 mm, and the difference was independent from the factors of age, gender, height, or weight (p>0.05). Ninety-five percent of the differences should be < or =1.46 mm, so that if the difference between hips is >1.46 mm, hip joint effusion should be suspected.

Direct adenovirus-mediated gene delivery to the temporomandibular joint in guinea-pigs

Adenovirus vector system is expected to be useful for direct gene therapy for joint disease. This study first sought to confirm that foreign genes can be transferred to articular chondrocytes in primary culture. Next, recombinant adenovirus vectors harbouring beta-galactosidase gene (LacZ) was injected directly into the temporomandibular joints of Hartley guinea-pigs to clarify the in vivo transfer availability of the adenovirus vectors. Specifically, recombinant adenovirus harbouring LacZ gene (AxlCALacZ) was injected into the upper joint cavities of both mandibular joints of four male 6-week-old Hartley guinea-pigs. Either the same amount of recombinant adenovirus without LacZ gene (Axlw) suspension (placebo) or the same amount of phosphate-buffered saline solution (control) were injected into the upper joint cavities of both joints of another four male guinea-pigs. At 1, 2, 3 and 4 weeks after injection, the joints were dissected and the expression of delivered LacZ was examined by 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside (X-gal) staining and reverse transcriptase-polymerase chain reaction (RT-PCR). To investigate the expression of transferred gene in other organs, total RNA was extracted from liver, kidney, heart and brain and the expression of LacZ mRNA and 18 S ribosomal RNA were analysed by RT-PCR. Clear expression of LacZ was observed in the articular surfaces of the temporal tubercle, articular disc and synovium of the temporomandibular joints even 4 weeks after injection in the AxlCALacZ-injected group, while no expression was detected in placebo and control groups. Histological examination confirmed that LacZ activity was clearly detected in a few cell layers of the articular surface tissues, which is much more efficient than in a previously study of the knee joint. In the other organs, expression of the delivered transgene was not observed. Based on these findings, direct gene delivery into the articular surface of the temporomandibular joint using the adenovirus vector is feasible as an effective in vivo method.

Anatomy of the distal knee joint and pyarthrosis following external fixation

OBJECTIVE

To determine the limits of the distal synovial reflection of the human knee joint.

SPECIMENS

Six paired knees studied by magnetic resonance imaging (MRI), fluoroscopic arthrography, and gross dissection. The right knees of five patients with chronic idiopathic knee effusions were studied by MRI. Cadaveric knees were injected with saline prior to MRI. The joint capsules were dissected to visualize local anatomy and check for capsular tears. In each modality (MRI, fluoroscopy, and dissection), the most distal extent of knee synovial fluid was measured.

RESULTS

The right versus left agreement for paired specimens was generally two to three millimeters. Some specimens showed asymmetric capsular reflection. Medial fluid was identified at distances greater than forty-nine millimeters from the subchondral bone in seven knees and less than fifteen millimeters in four knees (range 0 to 70 millimeters, mean thirty-three millimeters). Laterally, the range was ten to thirty-five millimeters (mean twenty-three millimeters). In six of the twelve cadaveric specimens, there was evidence of a communication between the knee joint and the proximal tibiofibularjoint. In the knees of volunteers, joint fluid tracked medially to a range of ten to fifty millimeters and laterally to a range of six to fifteen millimeters, with means of twenty-six and eleven millimeters, respectively. The knees of the volunteers had no evidence of tibiofibular joint communication with the knee.

CONCLUSION

Insertion of external fixation pins within sixty to seventy millimeters of the proximal articular surface of the tibia is associated with a high probability of synovial penetration and possibly provides a conduit for the introduction of bacteria, which may be etiologic in iatrogenic pyarthrosis.

Cartilage and synovium of the peroneocuboid joint: an anatomic and histological study

The surface area, thickness, and composition of the articular cartilage of the peroneocuboid articulation and the location of the synovium were investigated in 15 cadaver foot specimens. The articulations of the medial side of the peroneus longus tendon and lateral side of the cuboid were covered with fibrous and hyaline cartilages, respectively. On the lateral tuberosity of the cuboid, there is a facet that has 79.37+/-20.24 mm2 articular cartilage area with an oval shape to conform to that of the articular surface of the peroneus longus tendon (articular cartilage area, 67.35+/-28.53 mm2) with which it articulates. The mean thickness of the articular cartilage of the peroneus longus tendon and cuboid was 0.34+/-0.08 and 0.52+/-0.07 mm, respectively. The peroneocuboid joint has its own joint capsule. The synovial cavity does not communicate with the sheath of the peroneus longus tendon. Synovial membranes were attached to the margins of the articular surfaces of the cuboid immediately peripheral to the cartilage region.

The MR appearance of the infrapatellar plica

OBJECTIVE

Our purpose is to describe the MR appearance and clinical relevance of the infrapatellar plica of the knee and to assess possible imaging pitfalls resulting from lack of recognition of this normal structure. Seven patients--four from our institution and three from our teaching file from outside institutions--were selected because they displayed the imaging features of the infrapatellar plica.

CONCLUSION

The infrapatellar plica is readily appreciated on sagittal MR images of the knee as a low-signal-intensity structure in the intercondylar notch just anterior to the anterior cruciate ligament (ACL). The infrapatellar plica is important to recognize for the following reasons: It may be confused with an intact ACL because of its proximity and similar signal characteristics; it may pose difficulty to the arthroscopist when attempting to move instruments from the medial to lateral compartments of the knee; it can block clear visualization of the ACL during arthroscopy; and it can impair retrieval of loose bodies in the intercondylar notch. Familiarity with the infrapatellar plica should allow one to differentiate this normal structure from other structures in the knee and aid in preoperative planning.

Electron microscopy of the human synovial membrane

The structure of the lining cells at the surface of the synovial membrane facing the joint cavity has been studied by electron microscopy. The long cytoplasmic processes of these cells appear to be oriented toward the surface of the membrane, where they overlap and intertwine. The matrix of the lining cells contains dense material but no fibers with the periodicity of collagen. The lining cells are divided into two cell types or states of activity on the basis of their cytoplasmic contents. Type A is more numerous and contains a prominent Golgi apparatus, numerous vacuoles (0.4 to 1.5 microns in diameter) containing varying amounts of a dense granular material, many filopodia, mitochondria, intracellular fibrils, and micropinocytotic-like vesicles. Type B contains large amounts of ergastoplasm with fewer large vacuoles, micropinocytotic-like vesicles, and mitochondria. The probable functions of these cells are discussed in the light of current knowledge of the metabolism and function of the synovial membrane.

Connections between the tendons of the musculus flexor digitorum profundus involving the synovial sheaths in the carpal tunnel

In the carpal tunnel anatomical interconnections between the tendons of the musculus flexor digitorum profundus are systematically present. These interconnections limit the mutual tendon displacements, which decreases finger independence and may be problematic in a musician's hand. The present study investigates a possible role of the synovial sheaths in the formation of these intertendinous connections in the carpal tunnel. To this end a morphological model is provided which correlates the often distinctly fibrous structure of the deep flexor tendons in the carpal tunnel and the frequent exchange of tendon fibres between the tendons to the different fingers, with the tendency of the synovial membranes to strongly adhere to the tendons. This model is validated by gross dissection results, and by cross sections of the flexor tendons in the carpal tunnel. In agreement with the model, the anatomic data show that the synovial membranes tend to invade and become trapped in tendons made up from individualised tendon strands, and also strongly adhere to the substantial amounts of tendon fibres which may be exchanged between the flexor tendons proximal to the lumbrical origins. These fibres and the synovial membranes may form a strong fabric able to withstand substantial stretching forces of interconnected oppositely pulled flexor tendons.

Structure and physiology of joints and their relationship to repetitive strain injuries

Joints involved in repetitive strain injuries are diathrodial, that is, two bone ends with cartilaginous end plates sheathed by a soft envelope of synovium. The cartilaginous plates, consisting of chondrocytes, ground substance, and at least seven species of collagen, but mostly Type II, cushion the bone ends during repeated elastic compression and enable them to slide with minimal friction. The metabolic needs of the avascular cartilage are met by nutrients and waste products diffusing through the synovial fluid and into and out of the synovium and its blood vessels and lymphatics. Synovial nerves give joint position information. Fat, collagen, and glycosaminoglycans constitute the deformable synovial sheath. Synovial lining cells synthesize joint lubricants, matrix molecules, digestive enzymes, and cytokines, and participate in immunologic processes that can be reparative or degradative especially of cartilage. Heavy repeated forces applied to the upper and lower extremity joints cause degenerative changes that can be documented radiographically. Repeated light loading, such as in computer keyboard use, is evaluated inadequately with current imaging and clinical techniques. Differences in individual's response to repetitive loading may be caused by subtle differences in the interaction and initial conditions of the musculoskeletal structures, including the joint, involved in repetitive strain injuries.

Cartilage and synovium of the human atlanto-odontoid joint. An anatomic and histological study

The surface area, thickness and composition of articular cartilage of the atlanto-odontoid joints were investigated in twenty human cadaveric cervical spine specimens. The specimens were also examined grossly and by light microscopy to determine the location of the synovium. The anterior arch of the atlas and ventral and dorsal articular surfaces of the dens were covered with hyaline cartilage. The mean values of the articular surface areas on the ventral surface of the dens and anterior arch of the atlas were 55.10 and 58.24 mm2, respectively. The mean thickness of the articular cartilage of the anterior arch of the atlas, ventral and dorsal surfaces of the dens was 0.80, 0.81 and 0.82 mm, respectively. Synovial membranes were associated with the joint capsules and surrounding tissues of both anterior and posterior atlanto-odontoid joint spaces, where the synovial membranes were attached to the margins of the articular surfaces of the dens and anterior arch of the atlas anteriorly and the region of the cruciate ligament immediately peripheral to the cartilage region apposed to the dens and dens cartilage itself, posteriorly.

Distribution and origin of nerve fibers in the rat temporomandibular joint capsule

The distribution and origin of nerve fibers containing neuropeptides and NOS projecting to the temporomandibular joint capsule (TMJ) of the rat were studied by retrograde tracing in combination with immunocytochemistry. Numerous nerve fibers were seen in the TMJ as revealed by the neuronal marker protein gene product 9.5. Nerve fibers containing neuropeptide Y (NPY), vasoactive intestinal peptide (VIP), pituitary adenylate cyclase activating peptide (PACAP), substance P (SP), calcitonin gene-related peptide (CGRP), and nitric oxide synthase (NOS) were seen in the synovial membrane, the joint capsule and entering the articular disc. Injection of the retrograde tracer True Blue (TB) into the TMJ resulted in the appearance of numerous labeled nerve cell bodies in the trigeminal and superior cervical ganglia, and moderate numbers in the nodose, the otic, the sphenopalatine, the stellate and the dorsal root ganglia at levels C2-C5. Most of the TB-labeled cell bodies in the superior cervical and stellate ganglia contained NPY. In the trigeminal ganglion, numerous TB labeled cell bodies contained CGRP and a minor population stored SP, a few cell bodies were seen to store NOS or PACAP. In the sphenopalatine and otic ganglia, TB labeled cell bodies contained NOS or VIP. In the nodose ganglion, labeled cell bodies contained CGRP; other labeled cell bodies harbored NOS. In the cervical dorsal root ganglia, the majority of the labeled cell bodies stored CGRP and smaller populations stored SP and PACAP. Thus, the innervation of the TMJ is complex and many different ganglia are involved.

Excursion properties of tendon graft sources: interaction between tendon and A2 pulley

We measured excursion resistance of 4 different tendons (flexor digitorum superficialis, the portion of the extensor indicis proprius tendon beneath the extensor retinaculum, the portion of the extensor indicis proprius tendon distal to the extensor retinaculum, and palmaris longus) beneath the A2 pulley. Intrasynovial tendons (i.e., flexor digitorum superficialis and the portion of the extensor indicis proprius beneath the extensor retinaculum) produced less excursion resistance than extrasynovial tendons (i.e., the portion of the extensor indicis proprius distal to the extensor retinaculum and palmaris longus). The excursion resistance of the intrasynovial portion of the extensor indicis proprius tendon was significantly lower than that of the extrasynovial portion of the same tendon. Intrasynovial tendons may be preferred to extrasynovial tendons when choosing a tendon graft source and graft gliding under a pulley is a consideration.

Flexor tendon-pulley interaction after annular pulley reconstruction: a biomechanical study in a dog model in vivo

The excursion resistance between the canine flexor digitorum profundus tendon and A2 pulley was compared after pulley reconstruction using tendon grafts of either intrasynovial or extrasynovial origin at 10 days, 3 weeks, and 6 weeks after surgery. The changes over time in the underlying flexor digitorum profundus tendon after pulley reconstruction were also evaluated. The excursion resistance for both types of pulley reconstruction was significantly greater than that of the control group at all time periods. The excursion resistance of the extrasynovial tendon graft reconstruction was greater than that of intrasynovial pulley reconstruction at all time periods. In conclusion, pulley reconstruction with intrasynovial tendon grafts may facilitate tendon gliding after surgery.