Patellar development after patella instability and early reduction in growing rabbits.

BACKGROUND: Patella-shaped disorder has been considered as a predisposing factor for patella instability. But the influence of early patella reduction for patellar development remains unclear. This study aimed to evaluate whether early operation in patella instability could improve patella morphology in growing rabbits. METHODS: Fifty rabbits (1-month-old) were included in the study. The control group underwent no surgical procedures. The two experimental groups (reduction group and non-reduced group), underwent medial soft tissue restraint release surgery. The reduction group, rabbits underwent the medial soft tissue sutura surgery in order to stabilize the patella 2 months after release surgery. The non-reduced group, rabbits did not undergo suture surgery. Computed Tomography (CT) scans analysis in two experimental endpoints (2, 5 months after release surgery) were selected to evaluate the transverse diameter, thickness, Wiberg index and Wiberg angle. Gross observation was conducted to assess morphological changes of the patella. RESULTS: CT scans showed significant difference in the mean transverse diameter, Wiberg angle between the two experimental groups and the control group 2 months after release surgery. 5 months after release surgery, the indices of patella were found no statistically difference in the reduction group versus the control group. However, the transverse diameter, Wiberg angle in the non-reduced group were significantly differences than that in the reduction group (P < 0.05). Gross observation showed a flattened articular surface of the patella in the non-reduced group. CONCLUSIONS: The results indicated that patella instability may lead to patella-shaped disorder, showing a flattened morphology. Early patella reduction can improve the patella morphology in growing rabbits.

Systematic Isolation of Key Parameters for Estimating Skeletal Maturity on Knee Radiographs.

BACKGROUND: The ability to estimate skeletal maturity using a knee radiograph would be useful in anterior cruciate ligament (ACL) injuries and limb-length discrepancy in immature patients. Currently, a quick, accurate, and reproducible method is lacking. METHODS: Serial knee radiographs made 3 years before to 2 years following the chronologic age associated with 90% of final height (an enhanced skeletal maturity gold standard compared with peak height velocity) were analyzed in 78 children. The Pyle and Hoerr (PH) knee method was simplified by developing discrete stages for the distal part of the femur, the proximal part of the tibia, the proximal part of the fibula, and the patella. The Roche-Wainer-Thissen (RWT) knee method was simplified from the 36 original parameters to 14 parameters by removing parameters that were poorly defined, were not relevant to the peripubertal age range, were poorly correlated with 90% final height, or were poorly reliable on a 20-radiograph pilot analysis. We also compared the recently described central peak value (CPV) of the distal part of the femur. The Greulich and Pyle (GP) left-hand bone age was included for comparison. RESULTS: In this study, 326 left knee radiographs from 41 girls (age range, 7 to 15 years) and 37 boys (age range, 9 to 17 years) were included. Stepwise linear regression showed higher correlation in predicting years from 90% final height using the modified RWT and demographic characteristics (R2 = 0.921) compared with demographic characteristics alone (R2 = 0.840), CPV and demographic characteristics (R2 = 0.866), GP and demographic characteristics (R2 = 0.899), and PH and demographic characteristics (R2 = 0.902). Seven parameters were excluded from the RWT and demographic characteristics model using stepwise linear regression and generalized estimating equations analysis, leaving 7 parameters (2 femoral, 4 tibial, and 1 fibular) in the final model. Compared with RWT and demographic characteristics (R2 = 0.921), there were minimal incremental increases by adding CPV (R2 = 0.921), GP (R2 = 0.925), or PH (R2 = 0.931). CONCLUSIONS: This large analysis of knee skeletal maturity systems isolated 7 discrete radiographic knee parameters that theoretically outperform the GP bone age in estimating skeletal maturity. CLINICAL RELEVANCE: We present a modified knee skeletal maturity system that can potentially preclude the need for additional imaging of the hand and wrist in reliably estimating skeletal maturity.

Patellar-Trochlear Morphology in Pediatric Patients From 2 to 11 Years of Age: A Descriptive Analysis Based on Computed Tomography Scanning.

BACKGROUND: Despite the critical role the trochlea plays in patellofemoral (PF) pathology, the development of the trochlea is poorly understood. The purpose of this study was 2-fold: (1) Describe quantitative osseous and soft tissue anatomy of the patella and trochlea in skeletally immature cadaveric specimens utilizing known measurements used in PF instability, and (2) evaluate additional measurement techniques in the sagittal plane as they relate to PF morphologic development. METHODS: Thirty-one skeletally immature fresh frozen cadaveric knees between the ages of 2 and 11 years old were evaluated using 0.625 mm computed tomography scans. In the axial plane, measurements included condylar height asymmetry, trochlear facet asymmetry, trochlear depth, osseous sulcus angle, cartilaginous sulcus angle, patella sulcus angle, and tibial tubercle-trochlear groove distance. In the sagittal plane, measurements included previously undescribed measurements of trochlear length and condylar height asymmetry which are based on the anterior femoral cortex. RESULTS: Analysis of trochlear morphology using condylar height asymmetry (both axial and sagittal), trochlear facet asymmetry, and trochlear depth and length demonstrated an increase in the size of the medial and lateral trochlea as age increased. There was more variability in the change of size of the medial trochlea (height, length, and facet length) than the lateral trochlea. The osseous sulcus angle, cartilaginous sulcus angle, and patella sulcus angle decreased (became deeper) with age until after 8 years and then plateaued. CONCLUSIONS: This cadaveric analysis demonstrated that there is an increase in the medial and lateral trochlear height as age increased by all measurements analyzed. The findings also demonstrate that the shape of the patella and trochlea change concurrently, which suggests that there may be interplay between the 2 during development. These new sagittal measurement techniques evaluating the medial, central, and lateral trochlear height and length with respect to age may help guide clinicians when investigating patellar instability in skeletally immature patients. LEVELS OF EVIDENCE: Level IV.

Common cellular origin and diverging developmental programs for different sesamoid bones.

Sesamoid bones are small auxiliary bones that form near joints and contribute to their stability and function. Thus far, providing a comprehensive developmental model or classification system for this highly diverse group of bones has been challenging. Here, we compare our previously reported mechanisms of patella development in the mouse with those of two anatomically different sesamoids, namely lateral fabella and digit sesamoids. We show that all three types of sesamoid bones originate from Sox9+ /Scx+ progenitors under the regulation of TGFß and independently of mechanical stimuli from muscles. Whereas BMP2 regulates the growth of all examined sesamoids, the differentiation of lateral fabella or digit sesamoids is regulated redundantly by BMP4 and BMP2. Next, we show that whereas patella and digit sesamoids initially form in juxtaposition to long bones, lateral fabella forms independently and at a distance. Finally, our evidence suggests that, unlike the synovial joint that separates patella from femur, digit sesamoids detach from the phalanx by formation of a fibrocartilaginous joint. These findings highlight both common and divergent molecular and mechanical features of sesamoid bone development, which underscores their evolutionary plasticity.

Spatial variation of T2 relaxation times of patellar cartilage and physeal patency: an in vivo study in children and young adults.

OBJECTIVE: The purpose of this study was to determine whether the T2 spatial variation of patellar cartilage is different between children and young adults with open and closed physes. MATERIALS AND METHODS: Fifty-two subjects in two age ranges were included; 13 girls and 13 boys from 5 to 11 years old, and 13 female young adults and 13 male young adults from 17 to 22 years old. T2 maps of patellar cartilage were generated at 1.5 T. Physeal patency and mean T2 relaxation times as a function of normalized distance (T2 spatial variation) were evaluated in each group and sex. RESULTS: All the subjects from 5 to 11 years old had open physes and all the subjects from 17 to 22 years old had closed physes. Mean T2 relaxation times of patellar cartilage in the open physis group were significantly longer than in the closed physis group throughout all normalized distances across patellar cartilage (p<0.05). There were significant differences in T2 spatial variation between the two groups (p<0.05). The open physis group had longer mean T2 relaxation times at the osteochondral area and articular cartilage than in the central portion. The closed physis group had shorter mean T2 relaxation times in the osteochondral area, with a gradual increase to longer values at the articular surface. Differences in T2 spatial variation were greatest at the osteochondral junction (p<0.05). There was no statistically significant sex difference in T2 spatial variation in either group. CONCLUSION: T2 spatial variation is different between skeletally immature and mature patellar cartilage. This difference is most prominent at the osteochondral junction and likely relates to the presence or absence of ongoing endochondral ossification.

The patellofemoral joint: do age and gender affect skeletal maturation of the osseous morphology in children?

BACKGROUND: The osseous morphology of the patellofemoral joint is an independent factor that affects the biomechanics of patellofemoral instability. OBJECTIVE: The purpose of this study is to determine age- and gender-related differences in the osseous morphology of the patellofemoral joint in children during skeletal maturation. MATERIALS AND METHODS: This study was approved by the institutional review board and was HIPAA-compliant. We included 97 children and young adults (age range 5-22 years; 51 girls and 46 boys, mean ages 14.3 years and 13.7 years, respectively). We studied 1.5-T knee MR exams, measuring the osseous morphology of the patellofemoral joint (lateral trochlear inclination, trochlear facet asymmetry, trochlear depth, patellar height ratio, tibial tubercle-trochlear groove distance, and lateral patellofemoral angle) for each MR exam. We compared measurements to published values for patellofemoral instability. Physeal patency (open or closing/closed) was determined on MR. We assessed the associations between MR osseous measurements and gender, age and physeal patency using Wilcoxon rank sum test and least square means regression models. RESULTS: The osseous patellofemoral joint morphology measurements were all within a normal range. There were no significant correlations between MR osseous measurements and age, gender or physeal patency. CONCLUSION: During skeletal maturation, age and gender do not affect the osseous morphology or congruency of the patellofemoral joint.

Change of patellar height with age and sex.

Patellar height is one of the important parameter in patellar stability. Growth spurt or excessive physical strain can lead to high-riding patella or patella alta. But this is not yet proved. This study was mainly targeted at eliciting the influence of age on Insall-Salvati index, one of the important index to measure patellar height. As the present study is meant for measuring the patellar height separately in male and female, it is also to find out the effect of gender on patellar height if any. The study was been conducted in North Bengal Medical College and Hospital among 93 subjects covering both adult and adolescent age groups. Patellar height of respective subjects was measured radiologically using Insall-Salvati Index; results were extrapolated for statistical analysis. It revealed that value of Insall-Salvati index was higher in adult compared to adolescent group but the difference was not statistically significant. Statistical tests shows no significant difference in Insall-Salvati index according to sex. While screening the athletes patella alta must be kept in mind as this can be associated with patellofemoral pain syndrome, chondromalacia patellae, knees with apophysitis of tibial tubercle (Osgood-Schiatter disease). Not only that, significant cause of recurrent patellar dislocation can be associated with patella alta

Vastus medialis cross-sectional area is positively associated with patella cartilage and bone volumes in a pain-free community-based population.

INTRODUCTION: Although vastus medialis and lateralis are important determinants of patellofemoral joint function, their relationship with patellofemoral joint structure is unknown. The aim of this study was to examine potential determinants of vastus medialis and lateralis cross-sectional areas and the relationship between the cross-sectional area and patella cartilage and bone volumes. METHODS: Two hundred ninety-seven healthy adult subjects had magnetic resonance imaging of their dominant knee. Vastus medialis and lateralis cross-sectional areas were measured 37.5 mm superior to the quadriceps tendon insertion at the proximal pole of the patella. Patella cartilage and bone volumes were measured from these images. Demographic data and participation in vigorous physical activity were assessed by questionnaire. RESULTS: The determinants of increased vastus medialis and lateralis cross-sectional areas were older age (P

Growth kinetics and integrin expression of fibroblasts infiltrating devitalised patellar tendons are different from those of intrinsic fibroblasts.

We compared the biological characteristics of extrinsic fibroblasts infiltrating the patellar tendon with those of normal, intrinsic fibroblasts in the normal tendon in vitro. Infiltrative fibroblasts were isolated from the patellar tendons of rabbits six weeks after an in situ freeze-thaw treatment which killed the intrinsic fibroblasts. These intrinsic cells were also isolated from the patellar tendons of rabbits which had not been so treated. Proliferation and invasive migration into the patellar tendon was significantly slower for infiltrative fibroblasts than for normal tendon fibroblasts. Flow-cytometric analysis indicated that expression of alpha5beta1 integrin at the cell surface was significantly lower in infiltrative fibroblasts than in normal tendon fibroblasts. The findings suggest that cellular proliferation and invasive migration of fibroblasts into the patellar tendon after necrosis are inferior to those of the normal fibroblasts. The inferior intrinsic properties of infiltrative fibroblasts may contribute to a slow remodelling process in the grafted tendon after ligament reconstruction.

Relationship between the patellar height and the disorder of the knee extensor mechanism in immature athletes.

SUMMARY: The purposes of this study were to evaluate the outcome of longitudinal research on the patellar height of immature athletes, and to clarify the relationship with disorders of the knee extensor mechanism. The patellar height of 40 young male soccer players (80 knees) was observed with radiographs of the bilateral knee joint for 2 years. The patellar height was measured using the epiphyseal line method. No subject showed patella alta before the occurrence of the disorder. Of the 12 knees in which the disorder occurred during the observation period, 10 knees (83%) had higher patella after the onset of symptoms than before. The patellar height in the painful stage was considered significant compared with the normal group. Although the patellar position in the predisorder stage was relatively high, this state was considered within the normal scope of physiologic variation, such as the growth spurt.

[The origin of femoral trochlear dysplasia: comparative anatomy, evolution, and growth of the patellofemoral joint]. / Origine des dysplasies de la trochlée fémorale: anatomie comparée, évolution et croissance de l'articulation fémoro-patellaire.

We performed a comparative analysis of the femoropatellar morphology examining the evolutionary aspects to search for the origin of trochelar dysplasia. Trochlear dysplasia is frequent in the human population and, when associated with morphological and positional abnormalities of the patella, can lead to patellar pain syndrome in minor cases or patellar dislocation in severe cases. There is no strict relationship between the observed anomalies and clinical expression. The shape of the articular surfaces is variable in mammals depending on their type of locomotion: unguligrade, digitigrade, plantigrade. In greater apes, the femoral diaphysis is straight and the trochlea is flat and symmetrical. The patella does not tend to dislocate laterally since the knee under load is always flexed. In human adults, the femoral diaphysis has a valgus obliquity angle of 8 degrees to 10 degrees. Consequently, the trochlea has a deepened sulcus and an elevated lateral lip, avoiding lateral patellar dislocation, especially during initial knee flexion. In the human newborn, the femoral diaphysis is vertical. As the child starts walking, the femoral obliquity angle develops between 1 and 7 years of age, inducing a secondary valgus of the extensor apparatus. This obliquity does not develop in non-walking children. Fossil femurs of australopithecus demonstrate that a high obliquity angle had appeared more than 3 million years ago, but also exhibit a poorly deepened trochlea and a slight elevation of the lateral facet. At 1.8 million years, the fossils have the oblique diaphysis, the strongly deepened sulcus and the strongly elevated lateral facet. The obliquity angle of the femoral diaphysis is the leading feature which initiated the later modifications of the patellofemoral joint that over 3 million years were never inscribed in the human genoma. Lateral trochleal lip and deep sulcus are features that were first acquired, then once selected, genetically assimilated, and now appear on the fetal cartilaginous epiphysis.

Growth arrest lines and recurrent patellar dislocation: a new sign.

The phenomenon of growth arrest lines has been widely described in the medical literature. They are usually found at the metaphysis of growing long bones and are the result of short periods of partial growth arrest. Recurrent dislocation of the patella is a well-recognised problem, particularly in adolescents. Several radiological features have been reported in association with patellar dislocation or instability. We have reported a hitherto undescribed radiological sign of patellar growth arrest lines on the skyline radiographs of two patients with this condition. The shape of the patella when symptoms were at their worst corresponded remarkably closely to the outline of the subsequent growth arrest line. We postulated that repeated dislocations adversely affect the process of normal maturation of the patella. With the resolution of symptoms, patella ossification resumes, leaving the telltale sign of previous injury in the form of a growth arrest line and an improvement in bone density once the patella has been stabilised and tracks normally.

A prospective study of quantitative ultrasound in children and adolescents.

The accrual of optimal bone mass during childhood and adolescence is essential for the formation of a skeleton that will meet structural needs throughout life. Assessing bone health of children is becoming increasingly important in order to identify those who require interventions, and quantitative ultrasound (QUS) has appeal for these assessments. The purpose of this prospective study was to characterize changes in QUS values in 328 healthy children and adolescents over a 3-yr period. Measurements of QUS, height, weight, nutrient intake, fracture history, and Tanner stage were made at baseline and 3 yr later. Both females and males experienced significant increases in QUS values during the study. The rate of change of QUS peaked at an earlier age in females than in males, and maximum accumulation rates in both genders occurred at ages at which highest accumulation rates are seen with densitometry. Females exhibited higher QUS values than males during puberty, also similar to results for dual X-ray absorptiometry (DXA). This is the first report of prospective data of QUS in children and adolescents. Our findings that QUS values change during childhood and adolescence in a manner similar to DXA values, the "gold standard," provide support for the validity of using QUS to assess bone health in children and adolescents.

Morphological and histochemical ageing changes in patellar articular cartilage of the rat.

The aim of this study was to investigate the variation in cartilage characteristics with age. Fresh-frozen cryostat sections of the patellar articular cartilage of the rat were used to demonstrate the enzyme activity of succinate dehydrogenase, lactate dehydrogenase, alkaline phosphatase, and acid phosphatase in the different layers and at different ages. Light microscopic techniques were used to analyse quantitative features such as thickness, cell density and the histological characteristics of the articular cartilage. The results indicate that cell density is significantly affected by age. Furthermore, it depends on the distance from the surface. The most marked decline in cell density occurred between months 3 and 6. The thickness of the articular cartilage also varies with age. The reduction in cartilage thickness was most striking between months 3 and 6. Differentiation into the histological layers is obvious after 3 months. Glycolytic enzymes were strongly reactive in all regions and at all ages, whereas aerobic activity declines with age. The metabolic and morphological changes in ageing cartilage contribute to trophic disorders and deterioration of the functional cartilaginous situation in adult cartilage.

The interface between bone and tendon at an insertion site: a study of the quadriceps tendon insertion.

Traumatic avulsions of ligament or tendon insertions rarely occur at the actual interface with bone, which suggests that this attachment is strong or otherwise protected from injury by the structure of the insertion complex. In this study we describe the terminal extent of quadriceps tendon fibres where they insert into the patellae of adult rabbits, humans, dogs and sheep. Specimens were examined by scanning electron microscopy (SEM) and light microscopy (LM). To facilitate tracing of tendon fibres the specimens were decalcified for SEM, and polarised light microscopy (PLM) was used in the LM segment of the study. By SEM it was possible to identify mature bone by the presence of osteocytes and a lamellar organisation. PLM and SEM showed that, unlike tendon fibres elsewhere, those in the calcified fibrocartilage were not crimped. No specific cement line was identified by SEM. Tendon fibres interdigitated among separate bone lamellar systems, (osteons or marrow spaces), but did not merge with the collagen systems of individual lamellae. The interdigitation was more extensive and the margin between tendon and bone was less distinct in the anterior third of the insertion. The segment of calcified tendon which interdigitated with bone stained less intensely blue and was less cellular than the more proximal calcified fibrocartilage zone adjacent to the tidemark. Lamellar collagen fibres of the bony trabeculae in the anterior patella were unusually parallel and longitudinal in orientation, making distinction of interposed tendon fibres difficult on LM and PLM sections. LM, SEM and transmission electron microscopy of rabbit patellae at birth revealed that anterior quadriceps tendon fibres extended over the patella in a fibrous cellular layer. By 2 wk of age, this layer had acquired chondroid features (i.e. cell lacunae and metachromasia) and contained vessels extending from patellar marrow. At 6 wk of age, part of this fibrocartilaginous layer was replaced by mature bone and osteoid. In the young adult animal, the quadriceps tension interdigitates extensively with the patellar bone. This segment of the insertion is perhaps the remnant of calcified fibrocartilage which has been remodelled by bone formation.

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.

Patellar ultrasound transmission velocity in healthy children and adolescents.

Apparent velocity of ultrasound (AVU) (Signet, Osteo-Technology Cambridge, MA) at the patella was measured on 568 children and adolescents, aged 8 to 18 years. Trend analysis revealed a significant trend (p < 0.004) toward increasing AVU with increasing age and increasing Tanner stage. Height and weight were positively correlated with AVU in both sexes, while dietary intake of calories, protein, and calcium were positively correlated with AVU in males, but not in females. Multiple linear regression revealed that 29% of the variance of AVU in females was described by Tanner stage (p < 0.002) and height (p < 0.007). The best regression model for males accounted for 48% of the variance in AVU and included age (p < 0.0001) and protein intake (p < 0.01). Bone quality has a distribution in children which is similar to the distribution of bone mass and density. Our patellar AVU values can be used as a baseline for much-needed prospective research with children and adolescents.

Efficacy of lateral retinacular release for painful bipartite patella.

We treated painful bipartite patella with a modified lateral retinacular release technique in 15 patients (16 knees). Bony union of the separated fragment and the patella was obtained in 15 of 16 knees within 8 months of surgery. Sustained traction acting on the patella laterally and proximally is presumed to cause the pain. The surgical technique to reduce this force proved effective not only in relieving the pain but also in achieving bony union. Painful bipartite patella can lead to excessive lateral pressure syndrome or patellar compression syndrome, these complications can be effectively treated by this surgical technique. In contrast to conventional treatments, such as excision of smaller fragments or osteosynthesis to achieve bony union, the modified lateral retinacular release technique is easy to perform and provides an effective means for relieving patellofemoral pain and achieving bony union.

The femoral sulcus in children. An ultrasonographic study.

Both knees of 50 normal children aged from birth to 18 years were examined by ultrasonography to measure the angles of the bony intercondylar and the cartilaginous sulcus on the patellar surface of the femur. The osseous angle was inversely related to the age of the child and was completely flat in the youngest children. During growth it gradually gained depth to assume the shape of the overlying articular cartilage by adolescence. At all ages, however, the angle of the cartilaginous sulcus was between 134 degrees and 155 degrees. This suggests that the configuration of the patellar articulation is already well developed at birth.