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At least 271 records · Page 15Linked to original sources
PubMed1998

Contact areas and pressures between native patellas and prosthetic femoral components.

Contact areas and pressures between native patellas and a prosthetic condylar design femoral component were measured at flexion angles of 30 degrees, 60 degrees, and 90 degrees. These were compared to measurements obtained with a domed all-polyethylene patellar component. Mean native patellar contact areas were found to be fourfold greater than seen with the prosthetic patellar component. Contact stresses in the native patellas were below the yield strength of articular cartilage in 80% of the contact area. By contrast, stresses measured in the prosthetic patella exceeded the yield strength of ultrahigh molecular weight polyethylene in 64% of the measured contact area. Contact areas and stresses were not significantly effected by flexion angle. Although contact areas and stresses reflect only a part of the dynamics of the patellofemoral articulation this information would support the selective retention of the native patella in total knee arthroplasty.

Aged↗
PubMedDate not supplied

Osteonecrosis of the patella: imaging features.

Osteonecrosis of the patella, although uncommon, has become important to recognize because it can be a cause of pain in the knee. We describe the imaging manifestations of nontraumatic osteonecrosis of the patella in seven clinical cases. The lesions uniformly involved the superior aspect of the patella. Conventional radiography displayed increased radiodensity, subchondral radiolucent areas, and typical demarcation line surrounding the ischemic region. MR imaging and bone scintigraphy demonstrated the characteristic features of osteonecrosis. Recognition of the imaging findings of osteonecrosis involving the patella can preclude misdiagnosis and may obviate unproductive invasive diagnostic procedures.

Adult↗
PubMed2001

Topography, structure and function of the patella and the patelloid in marsupials.

The patella is a sesamoid bone that is found in most mammals and is regularly located in the insertion tendon of the quadriceps femoris muscle. Up to now, only a little has been known about the topography, structure and function of the patella in marsupials. Therefore the stifles of 61 marsupials of 30 different species were studied by radiography, necropsy and light microscopy. It was found that only the family of bandicoots (Peramelidae) possessed a typical patella. The other species revealed a patelloid consisting of fibrocartilage. The structure of the patelloid revealed common characteristic features in the following families of marsupials: (1) Dasyuridae, Phalangeridae. Pseudocheriidae, and Potoroidae; (2) Burramyidae; (3) Phascolarctidae, Vombatidae, and Dendrolagus; and (4) Superfamily Macropodoidea (except Dendrolagus and Potoroidae). Our results imply that the degree of differentiation in the fibrocartilage of the patelloid was strongly correlated to the mechanical forces acting on the patelloid which are a result of the specific kind of locomotion and the way of life. Generally the bony patella does not belong to the phylogenetic programme of the marsupials--with the exception of the bandicoots which are very closely related to the subclass of placental mammals (Eutheria).

Animals↗
PubMed1997

Fetal and postnatal development of the patella, patellar tendon and suprapatella in the rabbit; changes in the distribution of the fibrillar collagens.

The development of the patella, its associated tendons, and suprapatella of the rabbit knee joint is described from the 17 d fetus to the mature adult. The patellar tendon (ligament) with the patella on its posterior surface is seen in the 17 d fetus and is fully developed by 1 postnatal wk. It is composed of bundles of types I and V collagens separated by endotenons of types III and V collagens. Anteriorly there is an epitenon of types III and V collagens while synovium and a fat pad cover its posterior surface. In the 25 d fetus, the patella is cartilaginous and is separated from the femoral condyles. The cartilage contains type II collagen, but types I, III and V collagens are found along the articular surface. Ossification starts 1 postnatal wk and at 6 wk only the articular cartilage remains. In addition to type II, types III and V collagens are located around the chondrocyte lacunae. The long anterior junction between the patella and its tendon is fibrocartilaginous at 1 wk, but as ossification proceeds this is replaced by bone. Types I and V collagens are found in this region. The suprapatella on the posterior surface of the quadriceps tendon is first seen 1 wk postnatally as an area of irregularly organised fibres and chondrocyte-like cells. Types I, II, III and V collagens are present from 3 wk onwards. It is compared with the fibrocartilage of other tendons that are under compression. The arrangement of the collagens in the patellar tendon is discussed in relation to its use as a replacement for injured anterior cruciate ligaments. It is suggested that the structural differences between the patellar tendon and anterior cruciate ligament preclude the translocated tendon acquiring mechanical strength similar to that of a normal cruciate ligament. The designation 'patellar ligament' as opposed to 'patellar tendon' is questioned. It is argued that the term patellar tendon reflects its structure more accurately than patellar ligament.

Animals↗
PubMedDate not supplied

Arthroscopic-assisted surgical technique for treating patella fractures.

The purpose of this study was to describe and report preliminary results of an arthroscopic-assisted surgical technique for the treatment of displaced transverse patella fractures with percutaneous internal fixation. We applied this technique in 5 patients who presented a displaced transverse patella fracture and were followed-up for an average of 18 months. Under an image-intensifier fluoroscope, the fracture was closely reduced with a percutaneously reduction clamp while the congruence of the articular surface was monitored arthroscopically. Two Kirschner wires were inserted perpendicular to the fracture line followed by 2 cannulated lag screws obtaining interfragmentary compression. By using a cannulated guide, 2 wires were threaded through both cannulated screws and percutaneously were crossed over the top of the patella creating a figure-8 pattern tension band. At final follow-up, radiographic consolidation was achieved in all patients obtaining full range of motion and returning to the activity level previous to the fracture. Arthroscopic internal fixation is a valid alternative for the treatment of intra-articular displaced and noncomminuted patella fractures. This technique allows healing of the fracture with low patient morbidity, a short hospitalization period, and an accelerated rehabilitation of the affected knee.

Adult↗
PubMed2002

Patella inversion method for exposure in revision total knee arthroplasty.

Satisfactory performance of revision total knee arthroplasty (TKA) requires adequate exposure. This article shows the patella inversion method of exposure in a large consecutive series of revision TKAs.Between 1987 and 1999, 420 revision TKAs were performed. Exposure was facilitated by the patella inversion method. No attempt was made to evert the patella. This technique of exposure was used in 95% (397 of 420) of patients. There were no episodes of patellar tendon avulsion in this series. Multiple exposure options are available in revision TKA. Extensile techniques violate the extensor mechanism. For most patients, these methods were unnecessary. The patella inversion method afforded adequate exposure in most patients without violating the extensor mechanism.

Arthroplasty, Replacement, Knee↗
PubMed2004

Results of resurfacing a native patella in patients with a painful total knee arthroplasty.

Between 1990 and 2003, 24 patients (28 knees) who had a total knee arthroplasty (TKA) and underwent subsequent patella resurfacing without revision of the tibial or femoral components to alleviate pain were identified. Patient charts were reviewed retrospectively and patients were interviewed after average 2.9-year follow-up (range: 1-12 years) to assess function, pain, and satisfaction with the procedure. Average patient age at revision surgery was 68 years, and the average time from the index TKA was 9.8 years. Mean Knee Society function and pain scores were 68+/-28 and 45+/-16, respectively. Average preoperative range of motion was 102 degrees (range: 65 degrees-130 degrees), and average postoperative range of motion was 106 degrees (range: 65 degrees-130 degrees). Only 52% of patients would undergo revision surgery again given their current levels of pain and function. Revision of only the patella for patients with a painful TKA who did not undergo patella resurfacing at the initial surgery provides 52% satisfactory results. Surgeons should look for other causes of pain in this patient population and reconsider their indications for not resurfacing the patella in TKA.

Aged↗
PubMed2000

Bilateral accessory iliac horns: pathognomonic findings in Nail-patella syndrome. Scintigraphic evidence on bone scan.

Nail-patella syndrome is a rare hereditary (autosomal dominant) disorder, also called hereditary osteo-onychodysplasia and Fong's syndrome. Its incidence is 4.5 per million population in the United States. Patients have a characteristic tetrad of pathologic symptoms including fingernail dysplasia, hypoplastic or absent patellas, radial head dislocation, and iliac horns. Soft-tissue changes and renal dysplasia have also been associated with the syndrome. Iliac horns are bilateral accessory outgrowths consisting of cortex and medulla continuous with the iliac bone. They are located at the site of attachment of the gluteus medius muscles and project posterolaterally. These smooth bony outgrowths are asymptomatic, frequently palpable, and, because they have no effect on gait, they need not be treated. Iliac horns are the pathognomonic feature of Nail-patella syndrome; that is, they occur in approximately 80% of cases and are observed only in this condition. Four patients (two female, two male) with Nail-patella syndrome have been examined in the authors' department: three family members, including a 37-year-old woman, her 18-year-old son, and her 15-year-old daughter, and an unrelated 26-year-old man. All patients, regardless of age or sex, had similar pelvic findings on their bone scans. Although whole-body scans were obtained in all patients, significant scintigraphic findings were observed only in the pelvis in all the patients examined. This is most likely the result of the mild nature of the related deformities, which do not yield scintigraphically detectable osteoblastic changes. A representative image showing these independent ossification on a Tc-99m MDP bone scan is presented. A conventional pelvic radiographic image of the same patient's pelvis is presented for comparison.

Adolescent↗
PubMed2001

Increased accumulation of Tl-201 in monostotic Paget's disease of the patella: evaluation with quantitative analysis.

Monostotic Paget's disease of the patella was detected with Tc-99m MDP and Tl-201 scans. Diffuse intense uptake of MDP in the left patella was observed on the blood-pool and late phases of the bone scan. Tl-201 imaging was performed to differentiate a malignant process and showed diffuse marked accumulation at the same site. Semiquantitative analysis of the patella region on both Tc-99m MDP and Tl-201 scans did not support a diagnosis of cancer. Radiographs showed the features of Paget's disease of the bone. Findings of a pathologic evaluation were compatible with the diagnosis of osteitis deformans. This case represents the unusual skeletal involvement of monostotic Paget's disease of the bone in the patella. Tl-201 accumulation in the Paget's lesion was suggested to be caused by increased metabolic activity of the lesion but was not indicative of a malignant process.

Aged↗
PubMedDate not supplied

The patella index as a guide to the understanding and diagnosis of patellofemoral instability.

An analysis of 1004 X-rays has demonstrated that the medial patella facet is significantly smaller in patients with patellofemoral instability. There is no such significant difference in the width of the whole patella. Therefore the longitudinal ridge separating the smaller medial facet from the larger lateral facet must be closer to the medial patella border. As this ridge articulates with the groove between the femoral condyles, its medial position is accounted for by the patella being more laterally positioned in patients with patellofemoral instability.

Bone Diseases↗
PubMedDate not supplied

The problem of chondromalacia patellae.

Daily activity subjects the human patella to forces often several times the individual's body weight. Healthy cartilage can adjust to these forces if they are not too excessive, concentrated, or repetitive. Such abnormal stresses most frequently occur with the disturbance of normal patellar mechanical function. Chondromalacia patellae is the result common to a wide variety of unusual traumata. Treatment must be directed primarily not toward the damaged patellar cartilage but toward a correction of the mechanical abnormality causing it. Until proven otherwise, a young female complaining of knee joint pain, particularly if bilateral, should be considered as suffering from a subluxating patella, with or without chondromalacia patellae.

Adolescent↗
PubMed2001

Applied biomechanics of the patella.

Although numerous prominent orthopaedists of the twentieth century considered the patella to be useless, even detrimental, it now is clear that the patella serves an important biomechanical function. It is a complex lever that magnifies the moment arm of the extensor mechanism. The patellofemoral contact area (the fulcrum of the lever) shifts along a proximodistal axis through the knee's arc of motion. As the knee flexes, the force within the patellar tendon diminishes relative to that of the quadriceps tendon. One's interpretation of patellar tracking is dependent on the choice of coordinates. When assessing tracking by way of anatomic coordinates, patellas are seen to be slightly lateralized at 0 degrees flexion and to follow similar paths down the trochlea. The tracking pattern is the result of an elaborate interplay between the quadriceps muscles, patellofemoral ligaments, the geometry of the trochlea, and the quadriceps angle. The articular cartilage of the patella is the thickest in the human body and does not follow the contour of the subchondral bone. Patellar cartilage is softer and more permeable than that of the trochlea. It is insensate. In size, nature, and number, the facets of the patellar articulation vary from person to person.

Biomechanical Phenomena↗
PubMedDate not supplied

Congenital dislocation of the patella. Part I: pathologic anatomy.

There has been considerable confusion between true congenital dislocation of the patella and other patellar instabilities. Only very few papers describing the anatomical features of congenital dislocation of the patella are found in the literature. The purpose of this paper was to describe the anatomical anomalies found in two cadaver specimens of a true permanent and irreducible congenital patellar dislocation. The quadriceps femoris is short and displaced laterally and acts as a knee flexor. The patella is small, articulating with the outer aspect of the lateral condyle, with no possibility of medial reduction onto the trochlea. Many other anomalies involving the bones, muscles, and nervous structures were found. Congenital dislocation of the patella must be distinguished from other patellar dislocations in children. The severity of structural anomalies is mainly owing to its prenatal onset. Congenital

Abnormalities, Multiple↗
PubMed1997

Biomechanical evaluation of current patella fracture fixation techniques.

OBJECTIVE: To compare the mechanical effectiveness of three different techniques for stabilization of transverse fractures of the patella. DESIGN: Cadaveric knees were used to model acute fractures of the patella. To test three treatment techniques in pairs of knees, specimen pairs were assigned randomly to a set of predetermined treatment pairs so as to provide equal numbers of paired and unpaired data sets. Results then were analyzed using a two-way analysis of variance. SETTING: The treatment techniques used are widely applicable in the clinical setting for the treatment of transverse fractures of the patella. No specialized equipment or training is required for the general or subspecialized orthopaedic surgeon. PATIENTS/PARTICIPANTS: None. INTERVENTIONS: Fractures were created in eighteen knees (nine pairs) and repaired by one of three techniques: (a) modified tension band (AO technique); (b) two parallel 4.5-millimeter interfragmentary lag screws; or (c) a new technique using four-millimeter cannulated lag screws with a tension band wired through the screws. MAIN OUTCOME MEASURES: In mechanical testing, the amount of interfragmentary separation in simulated knee extension and the maximum load to failure at 45 degrees of flexion were measured. RESULTS: Fractures stabilized with a modified tension band were found to displace significantly more than those fixed with screws alone or screws plus a tension band in simulated knee extensions (p < 0.05). The fractures fixed with the cannulated screws plus the tension band failed at higher loads (mean = 732 newtons) than those stabilized with screws alone (mean = 554 newtons, p = 0.06) or those with a modified tension band (mean = 395 newtons, p < 0.05). CONCLUSIONS: Combining interfragmentary screw fixation with the tension band principle appears to provide improved stability over the modified tension band or screws alone for transverse patella fractures. Cannulated screws allow for simple, reliable addition of a tension band to screw fixation.

Aged↗
PubMed1997

Open reduction internal fixation of displaced transverse patella fractures with figure-eight wiring through parallel cannulated compression screws.

OBJECTIVE: To evaluate the clinical results of transverse patella fracture fixation with a tensioned anterior figure-eight wire placed through parallel cannulated screws. DESIGN: Prospective, clinical. PATIENTS: Ten patients with displaced transverse patella fractures were managed with a standardized rehabilitation protocol that employed early continuous passive knee motion. OUTCOME MEASURES: Time to clinical and radiographic union, Hospital for Special Surgery Knee Scores, and comparisons with literature cohort studies. RESULTS: Clinical union occurred at an of average eight weeks and radiographic union at a mean of thirteen weeks postoperatively. Early continuous passive motion over a restricted are did not compromise the quality of fracture reduction, even though the majority of patients were elderly and had osteopenic bone. Subjective and functional results using Hospital for Special Surgery Knee Scores were comparable to previously published reports, with 70 percent achieving an excellent or good outcome. CONCLUSIONS: The described fixation technique for transverse patella fractures had clinical results equivalent to reports of patella fractures fixed with modified tension band wiring. Advantages included a low-profile construct that caused lesser degrees of implant irritation to local soft tissue structures, was compatible with the use of early restricted motion, and afforded a method to salvage three cases in which traditional tension band wiring failed to maintain an anatomic reduction in oteoporotic bone.

Adult↗
PubMedDate not supplied

Irreducible lateral dislocation of patella due to an intact retinaculum.

Lateral dislocation of the patella is a common injury that can be treated successfully nonoperatively. The authors present a patient with lateral dislocation of the patella in which the patella rotated 90 degrees about its vertical axis. The retinaculum had been avulsed from the anterior aspect of the patella but was otherwise intact. Because the intact retinaculum prohibited closed reduction, open reduction was performed. The patient has returned to full, unrestricted activities.

Adolescent↗
PubMed1992

Incidence, mechanism of injury, and treatment of fractures of the patella in children.

Fractures of the patella in skeletally immature patients are rare. The charts of 185 patients treated for patella fractures at the University of Kentucky Medical Center between 1976 and 1988 were retrospectively reviewed. The 12 patients of these 185 aged 8 to 16 years were included in this study. The incidence was calculated to be 6.5% of all patella fractures. All patients studied were male with an average age of 12.7 years. Sleeve fractures were the most common type of patella fracture observed (five), followed by transverse fractures (four). Ten of the 12 cases required operative management ranging from irrigation and debridement to open reduction and internal fixation. Partial patellectomy was performed when indicated. Indications for operative management in this age group were similar to those for adults. As in adults, the mechanism of injury was predominantly motor vehicle and motorcycle crashes. Laws requiring seatbelt restraints for children should have a positive effect on the incidence of such fractures resulting from dashboard injuries. One mechanism of injury not reported previously was that of a flexed knee striking the gym wall after performing a basketball lay-up because the basket was placed flush with the wall.

Accidents, Traffic↗
PubMed1996

Transverse stress fracture of the patella: a case report.

PURPOSE: A high index of suspicion is necessary to make the diagnosis of stress fractures in athletes. This is a case report of a soccer player who sustained a transverse stress fracture of the patella. CASE SUMMARY: The soccer player experienced mild discomfort to the patella for 1 month. He then developed severe pain after a twisting motion while playing soccer. Radiological examination showed an undisplaced transverse fracture of the patella. After immobilization in a plaster cast and rehabilitation, he returned to normal activity in 3 months. DISCUSSION: Only six cases have been reported in the literature to date. RELEVANCE: This case illustrates the need to consider a stress fracture when pain in the patella persists.

Adult↗