Patterns of premature physeal arrest: MR imaging of 111 children

OBJECTIVE: The purpose of this study was to use MR imaging, especially fat-suppressed three-dimensional (3D) spoiled gradient-recalled echo sequences, to identify patterns of growth arrest after physeal insult in children. MATERIALS AND METHODS: We evaluated 111 children with physeal bone bridges (median age, 11.4 years) using MR imaging to analyze bridge size, location in physis, signal intensity, growth recovery lines, avascular necrosis, and metaphyseal cartilage tongues. Fifty-eight patients underwent fat-suppressed 3D spoiled gradient-recalled echo imaging with physeal mapping. The cause, bone involved, radiographic appearance, and surgical interventions (60/111) were also correlated. Data were analyzed with the two-tailed Fisher's exact test. RESULTS: Posttraumatic bridges, accounting for 70% (78/111) of patients, were most often distal, especially of the tibia (n = 43) and femur (n = 14), whereas those due to the other miscellaneous causes were more frequently proximal (p < 0.0001). The position of the bridge in the physis was related to the bone involved (p < 0.0001). Sixty-five percent of distal tibial bridges involved the anteromedial physis, whereas 60% of the distal femoral arrests were central. Larger bridges had higher T1 signal intensity (p < 0.008). Oblique growth recovery lines were seen exclusively with bridges involving the peripheral physis (p = 0.002) and smaller, more potentially resectable bridges. Metaphyseal cartilaginous tongues were seen with all causes, but avascular necrosis was exclusively posttraumatic (p = 0.03). Signal characteristics and bridge size did not vary with the cause. CONCLUSION: Premature physeal bony bridging in children is most often posttraumatic and disproportionately involves the distal tibia and femur where bridges tend to develop at the sites of earliest physiologic closure, namely anteromedially and centrally, respectively. MR imaging, especially with the use of fat-suppressed 3D spoiled gradient-recalled echo imaging, exquisitely shows the growth disturbance and associated abnormalities that may follow physeal injury and guides surgical management.     

Rapidly acquired valgus deformity of the knee after osteochondroma resection in multiple hereditary exostoses pediatric patients: A report of two cases

Patients with multiple hereditary exostoses (MHE) often develop leg length discrepancies and limb alignment deformity around the knee as part of the natural course of the disease. Limb alignment deformity occurring post-resection of an osteochondroma has been described in one case report and only pertaining to the proximal medial tibia location. Here we describe the case of 2 patients with MHE, a 7-year-old female who underwent resection of distal femur and proximal tibia osteochondromas and a 9-year-old female who had a distal femur osteochondroma resected. Both patients developed rapidly progressive valgus knee deformity requiring surgical intervention. Excision of osteochondromas near the physis of a skeletally immature patient can cause overgrowth from the involved side of the growth plate resulting in a rapidly progressing unilateral coronal plane deformity. Surgeons should be aware of this potential complication and closely follow growing patients with serial alignment radiographs and counsel the family regarding the potential of acquired limb deformity and subsequent surgeries.     

Proximal fibular growth deformities

Several congenital and acquired conditions may cause relative disparity between the length of the tibia and fibula, with alteration of the proximal tibiofibular joint and concomitant (or consequent) alteration of the distal tibiofibular relationships at both the malleoli and syndesmosis. Hypoplasia of the fibula may occur in association with neuromuscular disorders (e.g., poliomyelitis, arthrogryposis) or osteomyelitis, and is frequently accompanied by valgus deformity of the ankle because of proximal displacement of the lateral malleolus. The physes of the distal fibula and tibia may be level, rather than the fibular physis being adjacent to the tibial articular surface. Hyperplasia of the fibula may be associated with congenital subluxation or dislocation of the knee, various short stature syndromes (e.g., achondroplasia, spondyloepiphyseal dysplasia), and hypoplasia, or aplasia of the tibia. The increased mobility of the proximal tibiofibular joint during the first eight to ten years of growth appears to be a major factor tendering the proximal end of the fibula susceptible to displacement secondary to relative longitudinal growth variations between the fibula and tibia. Recognition of such disparities at the proximal tibiofibular joint, especially during roentgenography, should aleri the clinician to further evaluate possible accompanying deformity at the distal tibiofibular syndesmosis.     

Imaging of growth disturbance in children

Growth disturbance of the long bones in children is frequently post-traumatic but also occurs because of physeal, epiphyseal, or metaphyseal ischemia. The imaging features of growth arrest depend more on the anatomic site involved than on the cause. The physes of the distal tibia and femur and proximal tibia are disproportionately at risk because of their complex geometry. The central undulation in the distal femur and the bump in the anteromedial physis (Kump's bump) in the distal tibia are the sites of initial physiologic closure and the most frequent areas of premature fusion. The MR imaging features of growth disturbance are characteristic. T1-weighted images show low signal intensity GRL and variable signal intensity bony bridges. On GRE sequences, a bridge appears as low signal intensity interruption in the otherwise high signal intensity physeal cartilage. Physeal widening on GRE and T2-weighted images implies physeal dysfunction without bridge formation. Proton density and T2-weighted images best reveal associated metaphyseal and soft tissue changes. Regardless of the cause, MR imaging exquisitely depicts cartilaginous pathology at the physis. MR evaluation should be considered in patients at high risk for growth disturbance including young children with extensive residual growth potential; those with involvement of particularly vulnerable growth plates; and those with severe, complex fractures.     

The anatomy of the proximal tibia in pediatric and adolescent patients: implications for ACL reconstruction and prevention of physeal arrest

Although the treatment of anterior cruciate ligament (ACL) tears in skeletally immature patients is still controversial, several studies have advocated ACL reconstruction in selected patients to prevent secondary injury. The proximal tibial physis is a structure at risk during ACL reconstruction in young patients, and physeal growth complications have been reported after surgery in this area. The relationship between the ACL and the proximal tibial physeal/apophyseal regions is poorly understood. This study examined the MRI anatomy of the ACL and the proximal tibia apophysis and epiphysis. MRIs of 59 skeletally immature knees were reviewed (Average age = 12.75 years, range 6–15) to define the anatomy of the epiphyseal and apophyseal regions. Measurements were recorded in three parasagittal planes: (1) at the lateral border of the patellar tendon, (2) the lateral edge of the ACL insertion, and (3) the medial edge of the ACL insertion. A single three-dimensional (3D) computed tomography (CT) scan was used to evaluate the position of standard drill holes used in ACL reconstruction to assess for potential degree of injury to the epiphyseal and apophyseal growth plates. In the parasagittal planes, the average height of the epiphysis was 19.6, 20.7, and 21.5 mm at the lateral border of the patellar tendon, the lateral border of the ACL, and the medial border of the ACL, respectively. At the level of the same landmarks, the apophysis extended below the physis at an average of 20.2, 16.8, and 7.0 mm, respectively. Expressed as a percentage of epiphysis height this was an average of 104, 82, and 33%, respectively. Examination of 3D CT images revealed that variations in drill hole placement had effects on the volume of injury to the proximal tibial physis and apophysis. Drill holes that started more medial, distal, and with a steeper angle of inclination reduced the amount of physis and apophysis violated when compared with holes placed more lateral, proximal, and with a shallow angle of inclination. The proximal tibial physis and apophysis is vulnerable to injury by drill hole placement during ACL reconstruction in skeletally immature patients. This paper defines the anatomic relationship of the apophyseal and epiphyseal regions of the physis in the proximal tibia. The volume of injury to the physis can be reduced by avoiding tunnel placement that is too lateral or too proximal on the tibia. A better understanding of these relationships may guide the placement of tibial drill holes, which have a lower risk of producing significant physeal damage. The preliminary work on this topic was presented at the 2000 Meeting of the Pediatric Orthopaedic Society of North America, Vancouver, Canada, and the 2001 American Academy of Orthopaedic Surgeons Annual Meeting in San Francisco.     

Intraorgan biodistribution and dosimetry of 153Sm-ethylenediaminetetramethylene phosphonate in juvenile rabbit tibia: implications for targeted radiotherapy of osteosarcoma.

Targeted radiotherapy using 153Sm-ethylenediaminetetramethylene phosphonate (153Sm-EDTMP) is currently under investigation for treatment of primary osteosarcoma. Human osteosarcoma most frequently occurs in skeletally immature individuals, and previous studies in a juvenile rabbit model demonstrated that clinically significant damage to developing physeal cartilage might occur as a result of systemic 153Sm-EDTMP therapy. The aim of this study was to determine the distribution of 153Sm-EDTMP within the tibias of juvenile rabbits and estimate the radiation-absorbed doses delivered to the physeal cartilage. METHODS: Eight-week-old New Zealand White rabbits were injected intravenously with 7.57 kBq (280 microCi) of 153Sm-EDTMP. At 21 h after injection, the biodistribution of 153Sm in the epiphysis, metaphysis, diaphysis, and red marrow of the tibia was obtained. Two-dimensional digital autoradiography was performed on 2-mm sections of tibias for qualitative comparison with the biodistribution data. Self-tissue and cross-tissue absorbed doses were calculated using absorbed fractions generated by the Monte Carlo particle transport code MCNP-4C. RESULTS: The highest uptakes (percentage injected dose per gram [%ID/g] of tissue) of 153Sm, 1.99-2.56 %ID/g, were found in the proximal and distal metaphyses, 70%-73% of which localized within 3 mm of the physeal cartilage. The second highest tissues of uptake were the proximal and distal epiphyses, at 0.33-0.62%ID/g. Digital autoradiography imaging confirmed that the majority of 153Sm deposited in the tibia localized to these tissues. Radiation-absorbed doses to the proximal and distal metaphyses were 183 and 130 mGy/MBq, respectively, and those to the proximal and distal epiphyses were 141 and 43.4 mGy/MBq, respectively. These tissues represented the only source compartments contributing to the physeal cartilage doses of 50.0 mGy/MBq for the proximal physis and 39.2 mGy/MBq for the distal physis. CONCLUSION: The 153Sm absorbed doses to the physeal cartilage were consistent with values that can cause dose-limiting damage to rapidly proliferating and differentiating chondrocytes. The pronounced uptake in the juvenile epiphysis indicates that the proliferating zone of the physis can be irradiated from multiple areas, which could increase the expression and degree of radiation damage. Further investigation of the effects of 153Sm-EDTMP on immature physeal cartilage is warranted to develop optimized treatment regimens.     

新战士胫骨近端生长板闭合程度MRI调查

目的 了解新战士长骨生长板闭合程度与MRI表现.方法 采用Tanner二次骨化中心闭合分级标准,对武警某部新兵连230名战士胫骨近段X线照片进行胫骨近端生长板闭合情形观察与分析,对照和归纳胫骨近端干骺端生长板MRI表现.结果 230名新兵胫骨近端X线照片显示干骺端生长板Tanner分级中未完全闭合生长板（即1～3级）129例（56.09%,129/230）,4级即生长完全闭合101例（43.91%,101/230）;对胫骨近端干骺端生长板闭合程度MRI评价,MRI判断完全闭合生长板67例（29.13%,67/230）;生长板含有A、B、C、D信号三种以上,或只要含有C、D信号中的任何一种和（或）两种,MRI判断未完全闭合生长板163例（70.87%,163/230）,则X线片Tanner分级与MRI评价完全与未完全闭合闭合生长板两者有一定的差异（χ2=37.24,P=0.046,P＜0.05）;如MRI参照Tanner分级骨化生长板覆盖干骺端小于或大于1/2标准,则Tanner分级X线2～3级120名,MRI判断级别显著低于X线分级（χ2=17.21,P=0.0018,P＜0.01）.结论 新战士胫骨近端干骺端生长板闭合程度不同,MRI能较好地显示正常生长板闭合程度、形态及其信号特征.     

Radiology of postnatal skeletal development

Initially the distal tibial physis is a relatively transverse structure. As the epiphysis matures, undulations develop within the physis and lappet formation occurs peripherally. Within the first two years a significant physeal undulation develops anteriorly above the medial malleolus. This undulation must not be misinterpreted as premature epiphyseodesis following distal tibial fracture. Secondary ossification in the distal tibia begins centrally and initially expands to fill the area over the tibial plafond. At the lateral side of the tibial epiphysis the ossification center may be wedgeshaped. The medial margin adjacent to the medial malleolus is often irregular and may show small peripheral foci of ossification. By seven to eight vears, the secondary center extends into the medial malleolus, with complete distal extension often not occurring until adolescence (although usually complete by ten to eleven years). The malleolar tip may exhibit an accessory ossification center. However, this center also may be a traumatic avulsion in the symptomatic patient. Physiologic epiphyseodesis begins over the medial malleolus and subsequently extends laterally. This pattern of closure appears to predispose to fracture of the lateral portion of the distal tibial epiphysis (fracture of Tillaux), as well as to triplane fractures. The articular surface curves onto the lateral side of the distal tibia to form an articulation with the lateral malleolus (distal tibiofibular joint). A similar extension occurs along the medial side of the fibula. These surfaces extend proximally as a recess to the level of the distal tibial physis, at which point the syndesmosis begins. The initially transverse distal fibular physis becomes a convoluted structure, with extensive peripheral lappet formation. Within these regions of physeal overlap there may be small areas of accessory ossification (both medially and laterally) that should not be misinterpreted as fractures. This overlapping also minimizes specific physeal separation and displacement (especially when compared to the incidence of distal tibial physeal injuries). Stress views may be necessary to show such an undisplaced fracture. The fibular physis normally is level with the tibial articular surface or distal extent of the tibial ossification center, especially after the second year of life (however, it may be more proximal in infants). As in the medial malleolus, there may be accessory ossification at the tip of the fibula. While this usually is a normal variant of secondary ossification, occasionally it also may result from trauma. Extensive porosity of the distal fibular metaphysis predisposes to buckling or torus injuries that may have severe, multiangular deformation.     

Epiphysiodesis for bilateral irregular closure of the distal radial physis in a gymnast

Wrist pain is a common complaint in gymnasts. Repetitive stress on the distal radial physis may lead to either gradual slipping of the epiphysis or growth disturbances. In some cases growth disturbances of the distal radial physis lead to triangulation of the distal radius and secondary ulnar overgrowth, and eventually a Madelung-like deformity. The present case report is the first to describe the outcome of epiphysiodesis of the distal radial and ulnar growth dates in a skeletally immature gymnast as a surgical treatment to irevent-Madelung's deformity.     

Patterns of red marrow in the adult femur

PURPOSE: Conversion of red marrow (RM) to fatty marrow in the skeleton of the lower extremities begins at the distal end, ie, feet, and progresses proximally with distal bone marrow (ie, tibia) being converted more rapidly than proximal bone marrow (ie, femur). However, in an individual long bone, conversion begins in the diaphysis and progresses both distally and proximally (more rapidly toward the distal side). In a normal adult's femur, RM is present in the proximal one third or less. Reconversion of fatty marrow to RM is reported to occur in the reverse order of conversion. We assessed the frequency of various patterns of RM in the adult femur on In-111 leukocyte scans for a better understanding of the bone marrow regeneration process in individual long bones. METHODS: The patterns of marrow activity in the femur shown on In-111 leukocyte scans performed in 354 adults were divided into a) RM limited to the proximal one third or less, b) to the proximal two thirds, c) to the proximal one third and distal one third with no activity in the middle shaft, and d) in the entire femur. RESULTS: There were 207 patients with pattern A, 91 pattern B, 14 pattern C, and 42 pattern D. CONCLUSIONS: A considerably higher number of adults showed pattern B than pattern C. This suggests that regeneration of diaphyseal marrow precedes that of the distal marrow in an individual long bone or possibly that conversion of the latter precedes the former, which is different from that proposed in the literature.     

Deferoxamine-induced bone dysplasia in the distal femur and patella of pediatric patients and young adults: MR imaging appearance

OBJECTIVE: We investigated the MR imaging appearance of deferoxamine-induced bone dysplasia in the distal femur and patella in patients with thalassemia major. MATERIALS AND METHODS: Thirty-five patients with homozygous ss-thalassemia major who were undergoing regular transfusions and chelation therapy underwent coronal T1-weighted MR imaging of the femur, including the femoral head and the distal femoral epiphysis. Additional coronal fat-saturated dual-echo and sagittal T1-weighted images of the distal femur and patella were obtained in 11 patients who were suspected of having distal femoral lesions on the basis of the coronal T1-weighted images of the entire femur. RESULTS: No dysplastic change was detected in the proximal femur on coronal T1-weighted images. In 22 distal femurs of 11 patients, the following abnormalities were detected on MR imaging: blurred physeal-metaphyseal junction (n = 22), distal metaphyseal areas of hyperintensity (n = 21), physeal widening (n = 18), metadiaphyseal lesions (n = 11), epiphyseal lesions (n = 10), and patellar lesions (n = 2). Physeal widening and distal metaphyseal hyperintense areas were all more pronounced peripherally. Of the 21 distal metaphyseal hyperintensities, lateral abnormalities were larger than medial abnormalities in 16. Of the 18 distal femurs in which physeal widening was detected, the lateral widening was more marked than the medial widening in 12. Patients with MR imaging evidence of bone dysplasia have a significantly (p = 0.003) greater height reduction than patients without such evidence of bone dysplasia. CONCLUSION: Deferoxamine-induced bone dysplasia in the distal femur and patella is represented by a spectrum of morphologic changes in the epiphysis, physis, metaphysis, and metadiaphysis on MR imaging.     

Ankle injuries in the young athlete

Ankle injuries in the young athlete are quite different from those of an adult. Because the epiphyseal plates of the distal tibia and fibula are significantly weaker than surrounding ligaments, failure on stress occurs through the growth plates rather than through soft tissue. Growth-plate injuries can assume a distinct pattern based on the maturity of the physis. Leg length inequality and angular deformity are potential sequelae from significant injury to the ankle in the skeletally immature but, fortunately, occur infrequently. Soft-tissue injuries about the ankle are rare, but with advanced, rigorous training techniques a new pattern of overuse injuries appears to be emerging.     

The anterior tilt angle of the proximal tibia epiphyseal plate: A significant radiological finding in young children with trampoline fractures

Objective

Evaluation of the anterior tilt angle of the proximal tibia epiphyseal plate in young children, which suffered a trampoline fracture in comparison with a normal population.

Materials and methods

62 children (31 females, 31 males) between 2 and 5 years of age (average 2 years 11 months, standard deviation 11 months) with radiographs in two views of the tibia were included in this retrospective study. 25 children with proximal tibia fractures were injured with a history of jumping on a trampoline. All other causes for tibia fractures were excluded. A normal age-mapped control cohort of 37 children was compared. These children had neither evidence of a trampoline related injury nor a fracture of the tibia. The anterior tilt angle of the epiphyseal plate of the tibia was defined as an angle between the proximal tibia physis and the distal tibia physis on a lateral view. Two radiologists evaluated all radiographs for fractures and measured the anterior tilt angle in consensus. An unpaired Student's t-test was used for statistical analysis (SPSS). Original reports were reviewed and compared with the radiological findings and follow-up radiographs.

Results

In the normal control group, the average anterior tilt angle measured −3.2°, SD ± 2.8°. The children with trampoline fractures showed an anterior tilt of +4.4°, SD ± 2.9°. The difference was statistically significant, P < 0.0001. In 6 patients (24% of all patients with confirmed fractures) the original report missed to diagnose the proximal tibial fracture.

Conclusion

Young children between 2 and 5 years of age are at risk for proximal tibia fractures while jumping on a trampoline. These fractures may be very subtle and difficult to detect on initial radiographs. Measurement of the anterior tilt angle of the proximal tibia epiphyseal plate on lateral radiographs is supportive for interpreting correctly trampoline fractures.     

Analysis of fractal dimensions of rat bones from film and digital images.

OBJECTIVES: (1) To compare the effect of two different intra-oral image receptors on estimates of fractal dimension; and (2) to determine the variations in fractal dimensions between the femur, tibia and humerus of the rat and between their proximal, middle and distal regions. METHODS: The left femur, tibia and humerus from 24 4-6-month-old Sprague-Dawley rats were radiographed using intra-oral film and a charge-coupled device (CCD). Films were digitized at a pixel density comparable to the CCD using a flat-bed scanner. Square regions of interest were selected from proximal, middle, and distal regions of each bone. Fractal dimensions were estimated from the slope of regression lines fitted to plots of log power against log spatial frequency. RESULTS: The fractal dimensions estimates from digitized films were significantly greater than those produced from the CCD (P=0.0008). Estimated fractal dimensions of three types of bone were not significantly different (P=0.0544); however, the three regions of bones were significantly different (P=0.0239). The fractal dimensions estimated from radiographs of the proximal and distal regions of the bones were lower than comparable estimates obtained from the middle region. CONCLUSIONS: Different types of image receptors significantly affect estimates of fractal dimension. There was no difference in the fractal dimensions of the different bones but the three regions differed significantly.     

A physical model for dual-energy X-ray absorptiometry--derived bone mineral density

RATIONALE AND OBJECTIVES: Dual-energy X-ray absorptiometry (DXA)-derived areal bone mineral density (BMD) is an established predictor of osteoporotic fractures and reflects bone strength as well. The goal of this study was to develop and validate a physical model for appropriate interpretation of BMD. METHODS: DXA and peripheral quantitative computed tomography investigations of the distal tibia (n = 45), proximal tibia (n = 12), distal femur (n = 26), and distal radius (n = 34) were carried out. The DXA-derived BMD was analytically modeled as a nonlinear function of volumetric bone mineral apparent density and the cross-sectional area (eCSA) of given bone; ie, BMD(mod) = apparent BMD x square root of eCSA. RESULTS: At every measured skeletal site, the relationship between BMD and BMD(mod) was systematically stronger than that observed separately between BMD and apparent BMD or cross-sectional area. The models (r2) explained 85%, 94%, 87%, and 74% of the variability in BMD at the distal tibia, proximal tibia, distal femur, and distal radius, respectively. CONCLUSIONS: The mutual contributions of bone density and size to BMD can vary to some extent in a site-dependent fashion. This dual nature of BMD on one hand provides a reasonable mechanical explanation for why BMD is a good surrogate of bone strength and a predictor of osteoporotic fractures but on the other hand, complicates its detailed interpretation.     

Activation of the growth plates on three-phase bone scintigraphy: the explanation for the overgrowth of fractured femurs

Children with an uncomplicated femoral fracture, treated with superimposition of fragments and intentional shortening, usually develop overgrowth of the fractured femur and the ipsilateral tibia which may compensate for the initial shortening and enable the limb in question to reach a length similar to that on the normal side. The overgrowth is evaluated clinically and by scanography. The increased metabolic activity of the growth plates that support this overgrowth has not been documented by any laboratory method. In order to evaluate the metabolic activity of the growth plates, 18 patients (11 males, seven females; mean age 6.1 years) with fractures of the femur were studied at three different time intervals (2-5 months, 6-12 months and 18-24 months). Three-phase bone scintigraphy was performed in all patients. Ten children (five males, five females; mean age 7.5 years) who had had bone imaging for other reasons were used as the control group. Visual analysis of the flow and equilibrium phases was performed for the distal femoral and proximal tibial growth plates. Visual and semi-quantitative analyses of the delayed images were performed for the distal femoral and proximal and distal tibial growth plates. Semi-quantitative analyses yielded the following activity ratios: (a) the distal femoral growth plate of the fractured femur to the contralateral one (FR); (b) the proximal growth plate of the tibia on the side of the fractured femur to the contralateral one (TpR); (c) the distal growth plate of the tibia on the side of the fractured femur to the contralateral one (TdR); and (d) in the control group, the distal growth plates of both femora (FCG) and the proximal (TCGp) and distal (TCGd) growth plates of the tibiae. Visual analysis of the blood flow, equilibrium and delayed images showed increased activity in the distal femoral growth plates during the first and second time intervals, but not during the third. No significant activity changes were found in the proximal and distal tibial growth plates during any of the phases analysed. The mean and standard deviation for FR in the three time intervals were: FRI=1.22+/-0.27, FRII=1.17+/-0.16 and FRIII=1.09+/-0.20. FR values were significantly higher than in the control group (FCG=0.99+/-0.03) (P=0.033). The mean and standard deviation for TpR in the three time intervals were: TpRI=1.08+/-0.18, TpRII=0.94+/-0.09 and TpRIII=0.96+/-0.20. TpR values were not significantly different from those in the control group (TCGp=1.00+/-0.05). However, TpRI was significantly higher than TpRII (P=0.043). The mean and standard deviation for TdR in the three time intervals were: TdRI=1.10+/-0.41, TdRII=1.05+/-0.15 and TdRIII=1.13+/-0.36. TdR values were not significantly higher than in the control group (TCGd=1.00+/-0.04) (P=0.777). These results support the concept that three-phase bone imaging is able to quantify and determine that activation occurs in the distal femoral and proximal tibial growth plates of fractured femora. This phenomenon may explain the overgrowth observed in this injured bone structure.     

MR imaging of transarticular skip metastases from distal femoral osteosarcoma

We describe a case in which magnetic resonance (MR) imaging of a distal femoral osteosarcoma showed transarticular skip metastases in the proximal tibia. These lesions were not found by conventional radiography, bone scintigraphy, or CT. Since detection of transarticular skip metastases has an important influence on surgical management, MR imaging of metaphyseal osteosarcomas should always include the bone on the opposite side of the joint.     

Gender differences in the knees of Chinese population

The goal of this study was to characterize the geometry of the distal femur and proximal tibia in the Chinese population. Three-dimensional models of twenty female and twenty male knees were constructed using CT images. The morphologic measurements of the distal femur included mediolateral (ML) and anteroposterior dimension of medial and lateral condyles (MAP, LAP), femoral aspect ratio (ML/LAP), medial and lateral condylar width, intercondylar notch width, notch width index (NWI), and trochlear groove orientation. The sagittal profiles of the medial and lateral femoral condyles and tibial plateaus were also characterized. The results showed that the size of the distal femur of the females was significantly smaller than that of the males. Furthermore, when normalized by LAP, the females had a significantly narrower distal femur (ML), and a shorter MAP compared to the males. In the sagittal plane, the radius of the lateral distal circle of the femur was significantly smaller than that of the medial condyle in both genders. There were no significant gender differences in the proximal tibial geometry. The data of the present study may enable suitable modification of total knee prosthesis sizing/geometry for Asia-Pacific patients.     

Carbon-11 labeled cathepsin K inhibitors: Syntheses and preliminary in vivo evaluation

Cathepsin K is a cysteine peptidase primarily located in osteoclasts, cells involved in normal growth and remodeling of bone but that are also responsible for bone loss in osteolytic diseases such as osteoporosis. In vivo imaging of cathepsin K may provide a method to assess changes in osteoclast numbers in such disease states. To that end, two high-affinity and selective cathepsin K inhibitors were radiolabeled with carbon-11. In vivo microPET imaging studies demonstrated uptake and prolonged retention of radioactivity in actively growing or remodeling bone regions (e.g., distal ulnar, carpal, distal and proximal humeral, distal femur, proximal tibia, tail vertebrae). Uptake into bone could be blocked by pre- or co-injection of unlabeled ligand, supporting a specific and saturable binding mechanism for radiotracer localization. These proof-of-concept studies indicate that radiolabeled cathepsin K inhibitors may have potential as in vivo imaging radiotracers for assessing changes of osteoclast numbers in osteolytic diseases.