Physeal Growth Plate Research Articles

Anterior Talo-Fibular Ligament Reconstruction With InternalBrace™ for Chronic Lateral Ankle Instability in Pediatric Patients.

Ankle injuries and instability in a pediatric age group are common problems and often underreported. The injuries can range from a relatively benign ankle sprain to pain-limiting ankle instability that can inhibit the child from participating in sporting activities. However, conservative management and physiotherapy are the mainstay of treatment; a small group of patients present with persistent instability and benefit from surgical intervention in lateral ligament reconstruction. Our study looked at pediatric patients who had instability following failed conservative management. Retrospective analysis of 14 patients with Chronic lateral Ankle instability (CLAI) who underwent Modified Brostrom-Gould repair( MBG) with or without Internal brace augmentation between January 2015 and October 2020. Patients were evaluated for the visual analogue scale (VAS), Manchester-oxford foot questionnaire (MOxFQ), subjective satisfaction, and return to preinjury activity level. Pain score improved from 8 (average 5-9) to 1 (average 0-3) following surgery. Functional assessment was made by assessing the Manchester Oxford questionnaire pre-and postoperatively. MOxFQ scores improved from 64 (8 SD) to 7 (15 SD). Thirteen of fourteen patients returned to normal sporting activities at the final follow-up. Modified Brostrom-Gould with InternalBrace™ augmentation is an excellent procedure for chronic lateral ligament injuries in the Paediatric population. It can be safely performed if we respect the anatomy and the physeal growth plate. It allows faster rehabilitation and return to preinjury activity level.

Anterior Malleolar Fractures: Pathoanatomy, Classification and Treatment Options

Category: Trauma; Ankle Introduction/Purpose: The anterior distal tibial tubercle (Tillaux-Chaput tubercle) frequently fractures in the wake of malleolar fractures. It provides attachment to the anterior tibiofibular syndesmosis and may be considered a fourth or anterior malleolus (AM). In analogy to posterior malleolar fractures, AM fractures may extend into the tibial incisura and tibial plafond. We analyzed the pathoanatomy of AM fractures and associated injuries in ankle fractures in adults. Methods: Over a course of 9 years, 140 patients (average age 58.3 years) with 140 acute malleolar fractures (OTA/AO 44) involving the anterolateral distal tibial rim were analyzed with CT imaging. All components of the malleolar fractures were analyzed and classified. Fracture patterns were compared with those of all 1,379 patients treated for malleolar fractures at our institution during the same 9-year period. Patients with fractures of the tibial pilon (OTA/AO 43) and patients aged less than 18 years were excluded as the frequent anterolateral distal tibial fractures along the physeal growth plate in adolescents are beyond the scope of this analysis. Fractures were classified according to the most frequent patterns and possible treatment options. Results: Of the 140 AM fractures, 52.9% were classified type 1 (extra-articular avulsion), 35.7% type 2 (incisura and plafond involvement), and 11.4% type 3 (impaction of the anterolateral plafond). The fibula was fractured in 87.1%, the medial malleolus in 67.1%, and the posterior malleolus in 69.3%. Isolated AM fractures were seen in only 6 cases (4.3%). The severity of AM fractures correlated negatively with that of posterior malleolar fractures (p<0.001). The proportion of pronation-abduction fractures increased and the proportion of supination external rotation fractures decreased with increasing severity of AM fractures (p=0.055). Fractures involving the AM had a prevalence of 12.6% of all ankle fractures and occurred significantly more frequently in pronation-type injuries (p<0.001). No supination-abduction fractures were seen with AM involvement. The interclass correlation coefficient for the proposed classification of AM fractures was 0.961 (95% CI 0.933-0.980) for interobserver agreement and 0.941 (95% CI 0.867-0.974) for intraobserver agreement. Conclusion: Knowledge of the 3D pathoanatomy of AM fractures and associated injuries may help with surgical planning. CT imaging should be employed generously in the assessment of complex ankle fractures, particularly with pronation injuries. In analogy to posterior malleolar fractures, fixation of displaced AM fractures potentially restores syndesmotic stability, congruity of the tibial incisura thus facilitating fibular reduction and joint congruity at the anterolateral tibial plafond. Proposed treatment options include transosseous suture for syndesmotic avulsions (type 1), screw fixation for fractures involving the incisura and plafond (type 2), and elevation of the impacted plafond with buttress plating for type 3 fractures.

A Cam Morphology Develops in the Early Phase of the Final Growth Spurt in Adolescent Ice Hockey Players: Results of a Prospective MRI-based Study.

Cam morphologies seem to develop with an increased prevalence in adolescent boys performing high-impact sports. The crucial question is at what age the cam morphology actually develops and whether there is an association with an aberration of the shape of the growth plate at the cam morphology site. (1) What is the frequency of cam morphologies in adolescent ice hockey players, and when do they appear? (2) Is there an association between an extension of the physeal growth plate and the development of a cam morphology? (3) How often do these players demonstrate clinical findings like pain and lack of internal rotation? A prospective, longitudinal MRI study was done to monitor the proximal femoral development and to define the appearance of cam morphologies in adolescent ice hockey players during the final growth spurt. Young ice hockey players from the local boys' league up to the age of 13 years (mean age 12 ± 0.5 years) were invited to participate. From 35 players performing on the highest national level, 25 boys and their parents consented to participate. None of these 25 players had to be excluded for known disease or previous surgery or hip trauma. At baseline examination as well as 1.5 and 3 years later, we performed a prospective noncontrast MRI scan and a clinical examination. The three-dimensional morphology of the proximal femur was assessed by one of the authors using radial images of the hip in a clockwise manner. The two validated parameters were: (1) the alpha angle for head asphericity (abnormal > 60°) and (2) the epiphyseal extension for detecting an abnormality in the shape of the capital physis and a potential correlation at the site of the cam morphology. The clinical examination was performed by one of the authors evaluating (1) internal rotation in 90° of hip and knee flexion and (2) hip pain during the anterior impingement test. Cam morphologies were most apparent at the 1.5-year follow-up interval (10 of 25; baseline versus 1.5-year follow-up: p = 0.007) and a few more occurred between 1.5 and 3 years (12 of 23; 1.5-year versus 3-year follow-up: p = 0.14). At 3-year follow-up, there was a positive correlation between increased epiphyseal extension and a high alpha angle at the anterosuperior quadrant (1 o'clock to 3 o'clock) (Spearman correlation coefficient = 0.341; p < 0.003). The prevalence of pain on the impingement test and/or restricted internal rotation less than 20° increased most between 1.5-year (1 of 25) and the 3-year follow-up (6 of 22; 1.5-year versus 3-year follow-up: p = 0.02). Our data suggest that a cam morphology develops early during the final growth spurt of the femoral head in adolescent ice hockey players predominantly between 13 to 16 years of age. A correlation between an increased extension of the growth plate and an increased alpha angle at the site of the cam morphology suggests a potential underlying growth disturbance. This should be further followed by high-resolution or biochemical MRI methods. Considering the high number of cam morphologies that correlated with abnormal clinical findings, we propose that adolescents performing high-impact sports should be screened for signs of cam impingement, such as by asking about hip pain and/or examining the patient for limited internal hip rotation. Level I, prognostic study.

RADIOGRAPHIC ANATOMY OF THE FORELIMB IN THE NORTHERN TAMANDUA (TAMANDUA MEXICANA).

The thoracic limb anatomy of anteaters in the family Myrmecophagidae is specialized for accessing termite and ant nests and for defense purposes. In the case of the northern tamandua (Tamandua mexicana), the forelimbs are also adapted for arboreal and terrestrial locomotion. Unfortunately, this species faces many conservation threats, such as habitat loss and traffic accidents, and injured individuals are frequently taken to wildlife rehabilitation centers. However, lack of knowledge of the radiographic osteoanatomy of this species may prevent appropriate management of injuries and thereby reduce the chances of successful release and survival. In order to fill this knowledge gap, this article describes for the first time the radiographic anatomy of the thoracic limb of the northern tamandua using four standard views and one additional view. The additional orthogonal view helps visualize structures, such as the hamatus process and the sesamoid bone, that are otherwise difficult to visualize due to the natural forearm position of anteaters. Additionally, some fractures and physeal growth plates were identified in one juvenile individual. Further radiographic investigations should be conducted on anteaters to provide more tools for diagnosis, treatment, and rehabilitation of these animals.

Maturation of the equine medial femoral condyle osteochondral unit

The juvenile equine medial femoral condyle (MFC) is frequently affected with radiographic changes (sclerosis and subchondral lucencies) that arise at a similar site to juvenile osteochondritis dissecans (JOCD) in children. There is little information on maturation of the MFC. To describe the normal development of the equine MFC osteochondral unit from birth to 2 years. Micro CT, histology and immunohistochemistry were performed on healthy equine MFCs (n=29) at sites where lesions occur. Parameters assessed included: cartilage thickness; the epiphyseal growth plate cartilage organization; the osteochondral junction and progression of endochondral ossification. From 0 to 6 months, chondrocytes near the articular surface are small and flat and have a characteristic hypertrophic appearance near the osteochondral junction but are not arranged in columns like physeal growth plates. The osteochondral junction is also crossed by cartilage canals containing vessels giving a porous appearance on 3D μCT images. At 7 months of age, a subchondral bone plate compact structure emerged histologically coincident with the end of endochondral ossification (absence of type X collagen immunostain and chondrocyte hypertrophy). New information is provided on MFC osteochondral unit maturation that will improve our understanding of the development of juvenile equine orthopaedic disease. Equine MFC endochondral ossification is complete at 6 months of age. The immature osteochondral junction may be structurally fragile because of its microarchitecture and susceptible to focal traumatic events that induce developmental lesions.

Le fratture di polso e la lesione di Galeazzi

Fractures of the distal radius are the most common fractures in children and adolescents, accounting for 40% of all fractures. Distal radius fractures occur most frequently during early adolescence. The mechanism of injury is usually a fall on a hyperextended wrist. Fractures of the distal radius usually involve the metaphysis. Although physeal (growth plate) injuries are relatively rare, they must be considered carefully because they can result in premature growth arrest. Shortening of the radius can lead to ulnar impaction and triangular fibrocartilage complex (TFCC) tears. The two most common types of distal radial metaphyseal fractures are torus fractures and greenstick fractures. A complete fracture passes through both cortices of the distal metaphysis (distal third) of the radius and/or ulna, often with displacement. A Galeazzi fracture is a fracture of the distal third of the radius along with dislocation of the distal radioulnar joint or ulnar physeal separation (Galeazzi-equivalent fracture). This article reviews current concepts regarding distal forearm fractures in children and adolescents, with particular attention to classification, recommended treatment options and long term complications.

Strength Training Safety for Younger Children

Cordelia W. Carter, MD, is a Clinical Assistant Professor, Department of Orthopedics, Seattle Children’s Hospital. She completed a fellowship in pediatric orthopaedic surgery at Children’s Hospital Los Angeles in 2010, followed by another fellowship in pediatric sports medicine at Children’s Hospital Boston in 2011. She can be contacted at Seattle Children’s Hospital, 4800 Sand Point Way NE, Seattle, WA 98105; email: cordelia.carter@ seattlechildrens.org. Lyle J. Micheli, MD, is the Director, Division of Sports Medicine, Boston Children’s Hospital; and Clinical Professor of Orthopaedic Surgery, Harvard Medical School. He is the past President of the American College of Sports Medicine and is currently the Secretary General of the International Federation of Sports Medicine. He can be contacted at Boston’s Children Hospital, 319 Longwood Avenue, Boston, MA 02115; email: l.micheli62@gmail.com Disclosure: The authors have no relevant financial relationships to disclose. doi: 10.3928/00904481-20120727-03 Q: IS STRENGTH TRAINING SAFE FOR YOUNGER CHILDREN? A: Yes. Resistance training was traditionally discouraged for children and adolescents as a result of unfounded concerns that it was unsafe for the skeletally immature population.1 However, there is now an abundance of scientific literature demonstrating that resistance training is not only safe for the young athlete, but is routinely associated with increased muscle strength, and in fact may play a role in the prevention of sports-related injuries.2 A recent meta-analysis of the available literature on resistance training in children and adolescents reviewed 27 studies that employed a resistance training intervention in youth aged 6 to 18 years.2 Only three instances of injury were reported in this group: 1) shoulder pain that resolved with one week of rest; 2) a shoulder strain that resulted in one missed training session; and 3) thigh pain that resolved with 5 minutes of rest. The estimated injury rates for these studies were 0.176, 0.053 and 0.055 per 100 participant hours, respectively (compared with rugby, for example, which has been reported to have an injury rate of 0.800 per 100 participant hours).2 While there have been several case reports of physeal (growth plate) injury related to resistance training, it has been noted that these injuries were almost exclusively the result of improper technique, inappropriate training load or lack of qualified supervision. In addition to its proven safety, there is good evidence demonstrating the efficacy of resistance training in child and adolescent athletes for improving muscle strength, with strength gains of up to 74% reported in one study after 8 weeks of progressive resistance training.3 As summarized by Faigenbaum and Myer,1 two meta-analyses evaluating the effectiveness of resistance training in youth demonstrated a significant positive association between resistance training and strength gains, with effect sizes of 0.57 and 0.75, respectively.3 It is now almost universally accepted that resistance training, when performed under the close supervision of a qualified instructor, using appropriate training equipment, and a stepwise progression of loads and skills can be both safe and effective for the young athlete.

Adolescent Segond Fracture With an Intact Anterior Cruciate Ligament

Segond fractures, or avulsion fractures of the proximal lateral tibial plateau, have been well documented and studied since their original description in 1878. Segond fractures have a widely recognized pathognomonic association with anterior cruciate ligament (ACL) injuries and often prompt orthopedic surgeons to consider reconstruction following radiographic and clinical evaluation. Adolescent patients are particularly vulnerable to these fractures due to the relative weakness of their physeal growth plates compared with the strength of their accompanying ligamentous structures. This article describes a case of a 13-year-old boy who sustained a Segond fracture that was not coupled with an ACL avulsion or tear. The patient sustained a twisting injury to his knee. He presented to the emergency room with an effusion and radiographic findings consistent with a Segond fracture. On follow-up examination 1 week after injury, the ACL was intact. The patient was followed for 5 months of conservative treatment. At final follow-up, the patient had reestablished his previous level of activity. This article describes the history, physical examination, and radiographic findings necessary to care for patients who present with a Segond fracture. Although considered pathognomonic for an associated ACL injury, this article describes a Segond fracture that occurred in isolation.

Subacute physeal abscess: case report to illustrate treatment with a minimally invasive incision and drainage technique

Brodie's abscess is a form of subacute osteomyelitis characterised by a low grade pyogenic abscess found most commonly in the metaphysis. One rare form found in children crosses the physeal growth plate and into the epiphysis. Due to the rarity of this subtype and apprehension associated with treatment of the transphyseal abscess, no clear guidance exists on its management. We present a case of delayed diagnosis of Brodie's abscess crossing the physis in a 14-year-old boy. He gave a one-year history of pain in the right knee and early x-rays had shown lucent areas in the tibia. However, these were only noted to be significant at presentation one year later. We also describe an improvised minimally invasive and atraumatic technique of modifying a laminar suction catheter for accessing and draining the abscess. From our experience and reports in the literature it is clear that antibiotic treatment is generally advocated with varying degrees of surgical intervention. Outcomes are largely favourable. Nevertheless, initial drainage allows samples to be sent for microbiological and histological assessment to aid subsequent management and may prevent subsequent leg length discrepancy from failed conservative treatment. We believe that management of a transphyseal abscess must include early drainage and a prolonged course of antibiotics. The antibiotic choice and duration will be governed by culture results and local policy but is commonly given for up to six weeks in the literature and must include one antistaphylococcal drug.

Meningococcal purpura fulminans in children. II: Late orthopedic sequelae management

Purpura fulminans is a rare and extremely severe infection, mostly due to Neisseria meningitidis. Nineteen patients were followed up immediately after the initial multivisceral failure in order to diagnose late-onset orthopedic sequelae. We report our experience with these 19 patients, in light of our medical follow-up protocol and surgical management. Nineteen patients were referred for acute purpura fulminans between 1987 and 2005 to our institution and followed up prospectively until the present. We collected information on all diagnosed orthopedic sequelae, all surgical procedures performed, and the actual orthopedic outcome. Fourteen patients developed at least one orthopedic sequel after a mean of 2years delay, with a mean of 8.65years follow-up (range 3-22years). The most common presentation was lower limb physeal growth plate arrest in eight patients involving 18 growth plates, leading to five limb length discrepancies and 12 significant knee and/or ankle deviations. Patients were treated by completing epiphysiodesis in addition to limb lengthening and/or reaxation osteotomies, except for two patients, in which epiphysiolysis was performed. All outcomes are, to date, satisfactory, with both knee and ankle axes within the physiological range. Among the seven patients who underwent below-knee amputation, six needed stump revision because of skin conflict (4) or prosthetics misadaptation due to upper tibial varus (2). Regarding the upper limb, three patients presented with four cicatricial scar bands, one located on a ring finger, two at the first commissure, and one at the wrist (all were successfully treated by enlargement Z-plasties). Two patients developed hip avascular necrosis. It is important for children diagnosed with meningococcal purpura fulminans to be followed up closely starting from the very beginning by a pediatric orthopedic surgeon. It ensures that late-onset orthopedic sequelae will be diagnosed early. In accordance to the literature, this study highlights the high rate of lower limb epiphysiodesis, above all other types of sequelae. This study reports a possible link between purpura fulminans and avascular necrosis of the hip.

Cranioectodermal dysplasia: A probable ciliopathy

Cranioectodermal dysplasia (CED), also known as Sensenbrenner syndrome, is a rare autosomal recessive genetic disorder characterized by typical craniofacial, skeletal and ectodermal defects, and tubulointerstitial nephritis leading to early end-stage renal failure. We report on a new familial case of a 9-year-old patient and two fetuses of 23 and 19 weeks of gestation respectively. Hypohidrosis was an additional ectodermal finding is the patient with CED. Postmortem findings in the two fetuses included acromesomelic shortening, craniofacial characteristics with absence of craniosynostosis, small kidneys with tubular and glomerular microscopic cysts, persistent ductal plate with portal fibrosis in the liver, small adrenals and roughly unremarkable histopathology of the physeal growth plate. Posterior fossa anomalies were additional findings in this patient and included an enlarged cisterna magna and a posterior fossa cyst. The above findings, in association with renal cysts, persistent ductal plate and portal fibrosis, introduce CED, a nonlethal genetic skeletal disorder of yet unknown molecular origin, as a possible member of the expanding group of ciliopathies.

Radiographic pelvimetry and evaluation of radiographic findings of the pelvis in cats with dystocia

Summary Objective: The aim of this study was to determine reference values for pelvic dimensions in radiographically unremarkable native Turkish cats (similar to European Shorthair cats) and to evaluate radiographic findings of the pelvis in cats with dystocia and to compare their pelvimetric measurements with those of radiographically unremarkable cats. Material and methods: Pelvimetry was performed on ventro-dorsal and lateral radiographs of radiographically unremarkable male (n = 34) and female cats (n = 23) with no history of dystocia and cats presented with dystocia. Cats with dystocia were classified in groups according to radiographical findings: cats without obvious radiographical changes, cats with traumatic pelvic stenosis and cats with pelvic narrowing due to metabolic disease. Statistical analyses were performed to find out significant differences between both groups with respect to gender and age. Results: Pelvic dimensions of radiographically unremarkable cats are greater in males compared to females. These differences increase with increasing age, but are not significant in cats older than 2 years. Twenty-five out of 37 queens presented with dystocia had significantly smaller pelvic dimensions compared to radiographically unremarkable queens. Deformation/narrowing of the pelvis in 12 cats (32%) due to old fractures and metabolic bone disease occurred in 7 and 5 cases, respectively. Conclusion: Old, untreated pelvic fractures and metabolic disorders may cause stenosis of the birth canal and dystocia. However, there is a high rate of queens without deformation, but smaller pelvic dimension experiencing dystocia. As 80% of these cats are around 1 year of age they might still be growing or are underdeveloped, despite pelvic physeal growth plates are already closed. Clinical relevance: Pelvic radiographs and pelvimetry before mating enables to identify cats with pelvic narrowing due to traumatic, metabolic, or developmental reasons and may prevent the queen from potential dystocia.

The effect of dietary nutrients on osteochondrosis lesions and cartilage properties in pigs (2006)

A total of 80 gilts (PIC 327 × 1050; 86 lb initial BW) were used in an 84-d study to determine the effect of different nutrients on the occurrence of osteochondrosis (OC) lesions, several cartilage criteria, growth performance, and carcass composition. Eight dietary treatments were formulated, consisting of 1) control (standard corn-soy diet, 3.5% choice white grease (CWG)) or the control diet plus 2) fish oil (3.5%) replaced CWG, 3) proline and glycine (Pro/Gly; 300 and 200% of lysine), 4) leucine, isoleucine, and valine (BCAA; 200, 100, and 100% of lysine, respectively), 5) silicon (1,000 ppm), 6) copper and manganese (Cu/Mn; 250 ppm and 100 ppm, respectively), 7) methionine and threonine (Met/Thr; 150 and 100% of lysine), and 8) combination of ingredients in diets 2 through 7. The diets were formulated slightly in excess of the pig’s requirement for lysine and to meet minimum true ileal digestibility (TID) ratios for the other essential amino acids. The diets were also formulated to be isocaloric by slightly adjusting the fat (CWG) content, and were fed in three phases (1.07, 0.94, and 0.80% TID Lys). Upon completion of the feeding period, pigs were harvested, and the distal aspect of the left femur was evaluated by gross examination for OC lesions. The external surface was evaluated for abnormalities and given a severity score. Then each femur was sliced into 3-mm sections, and lesions were assigned a severity score for the underlying articular cartilage, and physeal growth plate. Overall (d 0 to 84), growth performance was unaffected by dietary treatment (P>0.21). Pigs fed diets containing fish oil or silicon tended (P<0.07) to have a higher severity score for external abnormalities (or defects in cartilage surface), compared with pigs fed the other dietary treatments, with pigs fed the control diet, Pro/Gly, or Cu/Mn intermediate. Pigs fed high Met/Thr, Cu/Mn, or silicon tended (P<0.08) to have lower articular cartilage severity scores than scores of pigs fed the control diet or BCAA, with the other dietary treatments intermediate. The occurrence of OC lesions at the growth plate, total faces with lesions, and total number of abnormalities were not affected by dietary treatment (P>0.23); there was a trend (P<0.14) for pigs fed diets containing high Met/Thr or fed the combination diet to have lower total severity scores than scores of pigs fed the control diet or fish oil, with the other treatments intermediate. Pigs fed additional Cu/Mn, Met/Thr, or

The acrophysis: a unifying concept for understanding enchondral bone growth and its disorders. II. Abnormal growth.

In order to discuss and illustrate the effects common to normal and abnormal enchondral bone at the physes and at all other growth plates of the developing child, the term "acrophysis" was proposed. Acrophyses include the growth plates of secondary growth centers including carpals and tarsals and apophyses, and the growth plates at the nonphyseal ends of small tubular bones. Abnormalities at acrophyseal sites are analogous to those at the physeal growth plates and their metaphyses. For example, changes relating to the zone of provisional calcification (ZPC) are often important to the demonstration of such similarities. Lead lines were an early example of the concept of analogy from abnormality due to physeal and to acrophyseal disturbance. The ZPC is a key factor in understanding patterns of rickets and its healing. Examples (including hypothyroidism, scurvy and other osteoporosis, Ollier disease, achondroplasia, and osteopetrosis, as well as the family of frostbite, Kashin-Beck disease, and rat bite fever) illustrate the acrophysis principle and in turn their manifestations are explained by that principle.

Evaluation of a Method for Biopsy of the Distal Radial Physeal Growth Plate in Neonatal Foals

SummaryA technique was devised for taking biopsies from the distal radial physeal growth plate in neonatal foals to study cartilage morphology. The biopsy taken from the right forelimb of 21 Thoroughbred foals, four to 10 days of age, was performed under inhalation anaesthesia, using a 9 mm diameter trephine on a multi speed drill. Due to their exercise not being adequately restricted postoperatively, five foals (24%) developed excessive incisional granulation tissue at the biopsy site. Nine foals (43%) developed some flexion of the carpus (over at the knee) and 15 (71%) developed outward rotation of the left limb. There was significantly greater carpal valgus in the left limb when compared with the right limb (p &lt;0.005), a situation which was not present in six agematched, unoperated, control foals. Abnormalities in the congruency of the antebrachiocarpal joint were not detected grossly at postmortem at five months of age. However, there were localised gross and histological abnormalities of the distal radial physeal growth plate. Postoperative morbidity, significant changes to conformation, and the unknown long term consequences of the disruption to the biopsied physeal growth plate are likely to make this procedure inappropriate for clinical usage. However, the biopsy procedure was easy to perform, and provided a suitable sample for both histological and histomorphometric examination of the physeal growth plate cartilage. Therefore this technique provides a useful research method for study of growth plate morphology in neonates.A technique was developed for biopsy of the distal radial physeal growth plate in neonatal foals. Additionally, the effects on conformation, and on gross and histological abnormalities at five months of age, were reported. There were significant, mild conformational abnormalities, which self-corrected without intervention, and there were abnormalities detected at postmortem examination, but these abnormalities did not appear to affect the joint. The expected effects of this procedure are stated, and provided that these are accounted for, the technique is useful for harvesting and studying the physeal growth plate of neonates.

Initiation of the bony epiphysis in long bones: chronology of interactions between the vascular system and the chondrocytes.

Many events occur concurrently during the initiation of the secondary ossification center in the cartilaginous epiphyses of long bones. We have investigated the chronology of interactions between the vascular system and epiphyseal chondrocytes by culturing explanted heads of femurs and humeri from pre- and neonatal rabbits on the chorioallantoic membrane (CAM) of growing chick embryos. We confirmed that, on the whole, the epiphyseal cartilage was resistant to vascular invasion, whereas the physeal growth plate was resorbed. However, new CAM-derived cartilage canals occasionally penetrated through the articular surface. This caused death of those chondrocytes in the immediate vicinity of the canal but no further reaction. If explants already contained a bony epiphysis and were halved prior to culture, CAM-derived vessels were attracted to the spongiosa. From there they pushed into the uncalcified cartilage, indicating that calcification was not a prerequisite for vascular invasion. Where at least two vessels were in apposition, a new pseudo-ossification center was initiated: chondrocytes became hypertrophic and the matrix calcified. This suggests that cumulative release of diffusible factors from more than one vessel was the trigger for chondrocyte hypertrophy, which, in turn, led to the initiation of the bony epiphysis. CAM cultures thus provide an experimental model for both the quiescent angiogenesis of cartilage canal formation and the reactionary angiogenesis associated with chondrocyte hypertrophy. By exploiting the different anatomy of CAM-derived vascularity, events that occur concurrently in vivo can be specially separated in CAM culture.

Kniest dysplasia: Radiologic, histopathological, and scanning electronmicroscopic findings

We describe severe neonatal Kniest dysplasia. Radiological findings in a severe case include short bowed tubular bones with exaggerated metaphyseal flare, moderate platyspondyly with vertical clefts of the vertebral bodies, and characteristically shaped iliac bones. Pathologic findings included a disorganized physeal growth plate, soft crumbly cartilage with a "Swiss-cheese" appearance, and diastase resistant intracytoplasmic inclusions in the resting chondrocytes. Transmission electronmicroscopy showed dilated cisternae of rough endoplasmic reticulum with finely granular material of accumulated protein. Scanning electronmicroscopy documented striking fragmentation and disintegration of collagen fibrils resulting in a web-like pattern and large open cyst-like spaces, and deficiency and disorganization of the collagen fibrils.

Kniest dysplasia: Radiologic, histopathological, and scanning electronmicroscopic findings

We describe severe neonatal Kniest dysplasia. Radiological findings in a severe case include short bowed tubular bones with exaggerated metaphyseal flare, moderate platyspondyly with vertical clefts of the vertebral bodies, and characteristically shaped iliac bones. Pathologic findings included a disorganized physeal growth plate, soft crumbly cartilage with a “Swiss-cheese” appearance, and diastase resistant intracytoplasmic inclusions in the resting chondrocytes. Transmission electronmicroscopy showed dilated cisternae of rough endoplasmic reticulum with finely granular material of accumulated protein. Scanning electronmicroscopy documented striking fragmentation and disintegration of collagen fibrils resulting in a web-like pattern and large open cyst-like spaces, and deficiency and disorganization of the collagen fibrils. © 1996 Wiley-Liss, Inc.

6. Calcification-linked angiogenesis and bone growth

Adult cartilage is normally considered to be an avascular tissue. Certainly, it is a rich source of anti-angiogenic factors and a number of studies have identified anti-invasion factors which may act by inhibition of matrix proteases1,2,3. Despite this, cartilage neovascularisation does occur - most commonly during calcification and ossification associated with long bone growth and fracture repair. Paradoxically, it is its resistance to angiogenesis which makes cartilage so important in the study of its control. Where it does occur, the control of cartilage neovascularisation is both stark and rigid, for example in the normal physeal growth plate (fig. 1). Invasion is through the non-mineralised transverse cartilage septa which separate each chondrocyte. Progress is synchronised to produce an invasive ‘front’ of vessels which resorbs the cartilage at a rate just equal to its synthesis. This can be rapid, averaging 0.3mm per 24 hour, or one chondrocyte plus its matrix every 3 hours, in young rats4. We must ask ourselves, therefore, what is the mechanism by which microvessels are suddenly able to invade and erode cartilage. Inhibitors of matrix degradation-have been implicated in the restraint of invasion and the present thesis is that activation (ie. angiogenesis) is regulated through localised removal of that inhibition.

Two Patterns of Calcification in Primary (Physeal) and Secondary (Epiphyseal) Growth Cartilage

It is generally stated that the process of cartilage calcification and ossification is the same in the physeal (primary growth center) and epiphyseal (secondary growth center) growth plates. Reexamination of osteophyte growth led to the proposal that these growth plates differ. This proposition was tested by examining rabbit and human material from both sites before and after maceration; both tissue preparations were processed for light microscopy, and the macerated tissues were also studied by scanning electron microscopy (SEM). The physis showed the well-recognized, longitudinal calcified tubal structures in which capillaries make direct contact with and resorb the nonmineralized, transverse septal cartilage. In the epiphysis, the transverse septal cartilage was also mineralized, producing a continuous calcified sheet, perforated only by a limited number of channels and susceptible only to osteoclastic removal. This variation in mineral distribution modifies the way in which the primary spongiosa is formed during growth.