Growing skull fracture with an atypical mechanism: a case report.

Growing skull fractures (GSFs) are well-known but rare causes of pediatric head trauma. They generally occur several months after a head injury, and the main lesion is located under the periosteum. We herein report a case involving a 3-month-old boy with GSF that developed by a different mechanism than previously considered. It developed 18 days after the head injury. A large mass containing cerebrospinal fluid and brain tissue was present within the periosteum. A good outcome was obtained with early strategic surgery. Injury to the inner layer of the periosteum and sudden increase in intracranial pressure might be related to GSF in this case.

Development of a novel murine delayed secondary fracture healing in vivo model using periosteal cauterization.

INTRODUCTION: Delayed union and nonunion development remain a major clinical problematic complication during fracture healing, with partially unclear pathophysiology. Incidences range from 5 to 40% in high-risk patients, such as patients with periosteal damage. The periosteum is essential in adequate fracture healing, especially during soft callus formation. In this study, we hypothesize that inducing periosteal damage in a murine bone healing model will result in a novel delayed union model. MATERIALS AND METHODS: A mid-shaft femoral non-critically sized osteotomy was created in skeletally mature C57BL/6 mice and stabilized with a bridging plate. In half of the mice, a thin band of periosteum adjacent to the osteotomy was cauterized. Over 42 days of healing, radiographic, biomechanical, micro-computed tomography and histological analysis was performed to assess the degree of fracture healing. RESULTS: Analysis showed complete secondary fracture healing in the control group without periosteal injury. Whereas the periosteal injury group demonstrated less than half as much maximum callus volume (p < 0.05) and bridging, recovery of stiffness and temporal expression of callus growth and remodelling was delayed by 7-15 days. CONCLUSION: This paper introduces a novel mouse model of delayed union without a critically sized defect and with standardized biomechanical conditions, which enables further investigation into the molecular biological, biomechanical, and biochemical processes involved in (delayed) fracture healing and nonunion development. This model provides a continuum between normal fracture healing and the development of nonunions.

Fracture Pattern and Periosteal Entrapment in Adolescent Displaced Distal Tibial Physeal Fractures: A Magnetic Resonance Imaging Study.

OBJECTIVES: To investigate the fracture pattern and periosteal entrapment in adolescent distal tibial physeal fractures. DESIGN: Retrospective case series. SETTING: Level I academic trauma center. PATIENTS/PARTICIPANTS: Fifty patients (10-16 years of age) with displaced Salter-Harris type II, III, or IV distal tibial physeal fractures were retrospectively reviewed. INTERVENTION: Periosteal involvement, fracture pattern. MAIN OUTCOME MEASUREMENTS: We investigated the incidence and location of periosteal entrapment in those fractures and the angle of the fracture plane of metaphyseal fragments on axial plane by using magnetic resonance imaging. RESULTS: Of the 15 type II, 12 type III (4 malleolar and 8 Tillaux), and 23 type IV (2 malleolar and 21 triplane) fractures, 72.0% (36/50) presented with periosteal entrapment. Among all type II and triplane fractures, periosteal entrapment was observed in the anterolateral corner when there was any displacement on that corner. By contrast, only 1 of 8 Tillaux fractures presented with periosteal entrapment. In almost all supinated foot injuries of type II and triplane fractures, the metaphyseal fracture line was parallel to the intermalleolar axis on axial plane. CONCLUSIONS: Salter-Harris type II and triplane fractures have a high risk of periosteal entrapment especially in the anterolateral corner. Therefore, even without preoperative magnetic resonance imaging, surgical repositioning of entrapped periosteum should be considered after failed closed reduction. In cases of supinated foot injuries of type II or triplane fractures requiring surgical fixation, a metaphyseal fracture plane parallel to the oblique coronal plane connecting the medial and lateral malleoli may assist surgeons in achieving appropriate metaphyseal fixation. LEVEL OF EVIDENCE: Diagnostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Comparison of Negative Pressure Wound Therapy and Conventional Therapy for Cranial Bone-exposed Wounds in Rabbits.

BACKGROUND: Bone-exposed wounds with intact or defected periosteum are difficult to heal. To provide relevant experimental evidence for guidance of clinical therapy, we established a rabbit model to compare the efficacies of negative pressure wound therapy (NPWT) and conventional guaze dressing therapy on the healing of cranial bone-exposed wounds. METHODS: Full-thickness excisional circular wounds of 2.0 cm in diameter with exposed bones covered with or without periosteum were created at the parietal regions in 88 rabbits that were further randomly divided into the following treatment groups: periosteum-intact wounds treated with conventional vaseline gauze dressings (P + Control group), periosteum-intact wounds treated with NPWT (P + NPWT group), periosteum-lacking wounds treated with conventional vaseline gauze dressings (P-Control group), and periosteum-lacking wounds treated with NPWT (P-NPWT group). The wounds of NPWT groups were treated using a negative pressure therapy assembly that was set at a continuous pressure of -125 mm Hg for 7 days, then covered with vaseline gauze. The wound healing rates, wound infection rates, hydroxyproline content, and wound tissue histology were determined and evaluated. RESULTS: The NPWT shortened the wound healing time by approximately 5 days when compared with the conventional gauze therapy. The histological characterization of wound tissues showed that NPWT decreased the inflammatory cells infiltration, accelerated reepithelialization and facilitated the organization of collagen fibers into neat layers on postoperative day (POD) 10. The NPWT enhanced bacterial clearances, reduced infection rates and increased the hydroxyproline contents in both types of wounds on PODs 10 and 15. The immunohistochemical staining of CD31 showed the NPWT treatment resulted in a significantly increased and persistent angiogenesis, and the wounds treated with NPWT showed well developed and more functional vessels at POD 7 compared with control. CONCLUSIONS: The NPWT is a more effective therapy for bone-exposed wounds than conventional guaze dressing therapy. The NPWT can promote bone-exposed wounds healing by increasing collagen contents and vessels densities while reducing inflammatory cells infiltration, reducing wound infection rates, and inducing an ordered collagen arrangement.

Traumatic avulsion of the superior extensor retinaculum of the ankle as a cause of subperiosteal haematoma of the distal fibula in children. A retrospective study of 7 cases.

OBJECTIVE: To describe a new sonographic feature for a traumatic lesion of the ankle in children. MATERIALS AND METHODS: We present a retrospective review of superior extensor retinaculum (SER) avulsions diagnosed by ultrasound (US) as a cause of subperiosteal haematoma (SPH) and periosteal apposition of the distal fibula in seven children (3 girls and 4 boys, mean age 13.4 years; age range 10-15 years) after an inversion trauma of the ankle. Two children were subsequently examined with magnetic resonance imaging (MRI). RESULTS: At the acute phases (6 children), US showed a hypoechoic collection with periosteal elevation at the fibular insertion of the SER. The fibular cortex and growth plate were unremarkable. The SPH was isolated in three cases and associated with an anterior talofibular ligament sprain in four. In two cases, MRI confirmed the SER periosteal avulsion and the integrity of the distal fibula. At the later phase (one child), US showed a periosteal apposition at the fibular insertion of the SER with hypoechoic thickening of the SER and power Doppler hyperaemia. CONCLUSION: This is the first sonographic description of SER avulsion as cause of SPH of the distal fibula in children. SPH in children should not be considered as pathognomonic of a Salter-Harris type 1 lesion of the distal fibula. Later, it may be responsible for persistent ankle pain. Therefore, SER may be systematically explored in children during US examination of the ankle after trauma.

A bio-artificial poly([D,L]-lactide-co-glycolide) drug-eluting nanofibrous periosteum for segmental long bone open fractures with significant periosteal stripping injuries.

Biodegradable poly([D,L]-lactide-co-glycolide) (PLGA) nanofibrous membrane embedded with two drug-to-polymer weight ratios, namely 1:3 and 1:6, which comprised PLGA 180 mg, lidocaine 20 mg, vancomycin 20 mg, and ceftazidime 20 mg, and PLGA 360 mg, lidocaine 20 mg, vancomycin 20 mg, and ceftazidime 20 mg, respectively, was produced as an artificial periosteum in the treatment of segmental femoral fractures. The nanofibrous membrane's drug release behavior was assessed in vitro using high-performance liquid chromatography and the disk-diffusion method. A femoral segmental fracture model with intramedullary Kirschner-wire fixation was established for the in vivo rabbit activity study. Twenty-four rabbits were divided into two groups. Twelve rabbits in group A underwent femoral fracture fixation only, and 12 rabbits in group B underwent femoral fracture fixation and were administered the drug-loaded nanofibers. Radiographs obtained at 2, 6, and 12 weeks postoperatively were used to assess the bone unions. The total activity counts in animal behavior cages were also examined to evaluate the clinical performance of the rabbits. After the animals were euthanized, both femoral shafts were harvested and assessed for their torque strengths and toughness. The daily in vitro release curve for lidocaine showed that the nanofibers eluted effective levels of lidocaine for longer than 3 weeks. The bioactivity studies of vancomycin and ceftazidime showed that both antibiotics had effective and sustained bactericidal capacities for over 30 days. The findings from the in vivo animal activity study suggested that the rabbits with the artificial drug-eluting periosteum exhibited statistically increased levels of activity and better clinical performance outcomes compared with the rabbits without the artificial periosteum. In conclusion, this artificial drug-eluting periosteum may eventually be used for the treatment of open fractures.

Establishment and characterization of the Masquelet induced membrane technique in a rat femur critical-sized defect model.

The Masquelet induced membrane technique for reconstructing large diaphyseal defects has been shown to be a promising clinical treatment, yet relatively little is known about the cellular, histological and biochemical make-up of these membranes and how they produce this positive clinical outcome. We compared cellular make-up, histological changes and growth factor expression in membranes induced around femur bone defects and in subcutaneous pockets at 2, 4 and 6 weeks after induction, and to the periosteum. We found that membranes formed around bone defects were similar to those formed in subcutaneous pockets; however, both were significantly different from periosteum with regard to structural characteristics, location of blood vessels and overall thickness. Membranes induced at the femur defect (at 2 weeks) and in periosteum contain mesenchymal stem cells (MSCs; STRO-1+ ) which were not found in membranes induced subcutaneously. BMP-2, TGFß and VEGF were significantly elevated in membranes induced around femur defects in comparison to subcutaneously induced membranes, whereas SDF-1 was not detectable in membranes induced at either site. We found that osteogenic and neovascular activity had mostly subsided by 6 weeks in membranes formed at both sites. It was conclude that cellular composition and growth factor content in induced membranes depends on the location where the membrane is induced and differs from periosteum. Osteogenic and neovascular activity in the membranes is maximal between 2 and 4 weeks and subsides after 6. Based on this, better and quicker bone healing might be achieved if the PMMA cement were replaced with a bone graft earlier in the Masquelet technique. Copyright © 2013 John Wiley & Sons, Ltd.

Association of a Subperiosteal Hematoma With Minor Injury.

An intraorbitalsubperiosteal hematoma is a rare clinical entity that is usually caused by head trauma. The authors experienced a patient involving an intraorbital hemorrhage that was associated with minor injury in the forehead and that required surgical decompression. The authors describe this rare case involving an intraorbitalsubperiosteal hematoma that occurred in a conscious young boy who had no remarkable head injury and who had sudden onset of proptosis. Three-dimensional computed tomography, which was conducted with a volume-rendering method, was very useful, and the transorbital approach that was used to remove the hematoma was very effective. The patient showed good recovery. The pathogenesis of the intraorbitalsubperiosteal hemorrhage could not be fully explained, and, thus, the authors suggest that a possible pathogenesis involved the migration of the hemorrhage from the forehead into the intraorbital region.

Evaluation of oriented electrospun fibers for periosteal flap regeneration in biomimetic triphasic osteochondral implant.

Osteochondral defects represent a serious clinical problem. Although the cell-scaffold complexes have been reported to be effective for repairing osteochondral defects, a periosteal flap is frequently needed to arrest leakage of the implanted cells into the defect and to contribute to the secretion of cytokines to stimulate cartilage repair. The electrospun mesh mimicking the function of the flap assists tissue regeneration by preventing cell leakage and merits favorable outcomes in the cartilaginous region. In this study, an oriented poly(ε-caprolactone) (PCL) fibrous membrane (OEM) was fabricated by electrospinning as a periosteal scaffold and then freeze-dried with a collagen type I and hyaluronic acid cartilage scaffold (CH) and finally, freeze-dried with a tricalcium phosphate (TCP) bone substratum. Scanning electron microscopic images show obvious microstructure formation of the trilayered scaffolds, and electrospun fibrous membranes have an oriented fibrous network structure for the periosteal phase. Also shown are opened and interconnected pores with well designed three-dimensional structure, able to be bound in the CH (chondral phase) and TCP (osseous phase) scaffolds. In vitro results showed that the OEM can promote the orientation of bone marrow mesenchymal stem cell (BMSCs) and BMSCs can penetrate into the CH and TCP. After successfully combining the BMSCs, the tissue-engineered cartilage which contained the OEM and TCP complex was successfully used to regenerate the osteochondral defects in the rabbit model with greatly improved repair effects.

Reconstruction of a functional gliding surface with extensor retinaculum in extensor tendon reconstruction in the digits.

BACKGROUND: Tendon gliding is key to optimal recovery of hand function after complex tendon injuries. Gliding is facilitated by a low-friction gliding surface that is normally provided by the periosteum of the underlying bone. However, significant injuries may damage the periosteum, which must be reconstructed to allow uninterrupted tendon excursion. The absence of the periosteum may compromise a tendon's ability to glide freely, thereby limiting the range of motion. METHODS: Six digits in 4 patients with complex, composite soft tissue defects involving tendon, periosteum, and skin of the hand underwent surgical repair. Each digit had disruption of the bony cortex underlying the tendon injury including periosteal loss. Through an incision on the dorsum of the ipsilateral wrist, an extensor retinaculum graft corresponding to the size of the periosteal defect was harvested. It was then sutured into place over the bare cortex to replace the lost periosteum. RESULTS: All the 6 digits in the 4 patients had complete return to function. Additionally, all patients had near normal strength in the repaired hand along with excellent tendon excursion in both flexion and extension. The average time of follow-up of this series of patients was 1.5 years. CONCLUSIONS: Extensor retinaculum grafting to replace lost periosteum is a technique that is easily used, uses locally available autogenous tissues, and produces excellent tendon function. Additionally, the histologic similarities between extensor retinaculum and periosteum add scientific merit to this novel approach. On the basis of our experience, we recommend the use of extensor retinaculum for periosteal reconstruction to provide an adequate gliding surface for a reconstructed tendon.

Arthroscopic findings in the recurrent anterior instability of the shoulder.

BACKGROUND: A recurrent anterior shoulder dislocation consists of a variety of lesion types. OBJECTIVES: To evaluate the pathological classification of recurrent anterior dislocation of the shoulder joint under arthroscopy. METHODS: Thirty-one patients with recurrent anterior shoulder dislocation were inspected by arthroscopy, including 23 males and 8 females, with a mean age of 35.1 (18-46) years. The patients were divided into two groups: 17 with shoulder dislocation and hyper-laxity (the hyper-laxity group) and 14 with only traumatic shoulder dislocation (the trauma group). All the patients were assessed by arthroscopy for pathological changes, and the differences in the pathological changes were compared between the two groups. RESULTS: All these 31 patients suffered from anteroinferior labrum injury. Twenty-five had Hill-Sachs injury; 27, bone or cartilage injury of anteroinferior glenoid; 16, SLAP injury; and 5, rotator cuff injury. Bankart injury occurred more in the trauma group, and anterior labroligamentous periosteal sleeve avulsion injury and glenolabral articular disruption injury were more in the hyper-laxity group. Bone or cartilage injury of anteroinferior glenoid was more noticed in the trauma group. CONCLUSIONS: Significant differences are found under arthroscopy in the pathological changes of recurrent anterior shoulder dislocation between the purely traumatic group and the hyper-laxity group. The pathological changes in the trauma group were more severe than in the hyper-laxity group.

Ossification of subperiosteal hematoma: the potential of periosteal osteogenesis in cranioplasty.

BACKGROUND: Subperiosteal hematoma is the accumulation of blood between the periosteum and the skull, which commonly occurs in the neonatal period but rarely in other ages. Subperiosteal hematoma can be self-absorbed in most cases and occasionally may cause ossification. MATERIALS AND METHODS: This study reports a case of subperiosteal hematoma formed in a 16-year-old adolescent boy after a minor trauma. Because the hematoma did not disappear for more than a month after the trauma, the patient was treated with multiple hematoma punctures. However, the hematoma recurred and led to ossification. Finally, the patient underwent surgical treatment. RESULTS: Finally, the ossification associated with the hematoma was treated through surgery. The head contour recovered normally. CONCLUSIONS: The occurrence of hematoma ossification in the 16-year-old patient suggests that the periosteum has great potential for osteogenesis. This is likely caused by the joint action of some active factors in the blood and a certain tension of the hematoma on the local periosteum. This case provides the following thoughts. (1) A subperiosteal hematoma that has not been absorbed after 1 month should be treated promptly to avoid ossification. Once ossification has occurred, the hematoma should be treated surgically. (2) The potential for periosteal osteogenesis is great, which may provide a new thought for cranioplasty.

The effects of low-level laser therapy on palatal mucoperiosteal wound healing and oxidative stress status in experimental diabetic rats.

OBJECTIVE: The biostimulation effects of low-level laser therapy (LLLT) have recently been demonstrated. In this study, we aimed to investigate the effects of LLLT on palatal mucoperiostal wound healing and oxidative stress status in experimental diabetic rats. MATERIALS AND METHODS: Forty-two male Wistar rats that weighed 250-300 g were used in this study. Experimental diabetes was induced in all of the rats using streptozotocin. A standardized full thickness wound was made in the mucoperiosteum of the hard palates of the rats using a 3 mm biopsy punch. The rats were divided into groups: 1 (control group, non- irradiated), and 2 (experimental group, irradiated). Treatment using a GaAlAs laser at a wavelength of 940 nm and at dose of 10 J/cm(2) began after surgery, and was repeated on the 2nd, 4th, and 6th days post-surgery. Seven animals from each group were killed on the 7th, 14th, and 21st day after surgery. Biopsies were performed for the histological analysis and blood samples were collected by cardiac puncture for biochemical analysis. RESULTS: The histopathological findings revealed reduced numbers of inflammatory cells, and increased mitotic activity of fibroblasts, collagen synthesis, and vascularization in rats in group 2. The total oxidative status was significantly decreased in the laser-treated group on the 21st day. CONCLUSIONS: LLLT elicits a positive healing effect on palatal mucoperiostal wounds, and modulates the oxidative status in experimental diabetic rats.

Complicaciones nasales y orbitarias secundarias al abuso de cocaína inhalada / Orbital and nasal complications secondary to inhaled cocaine abuse

El abuso de cocaína por vía intranasal provoca una sinusopatía química por destrucción y necrosis mediofacial secundaria. Cuando esta necrosis mediofacial ya está establecida, pueden aparecer otras complicaciones relacionadas con la proximidad de estructuras como la órbita o el nervio óptico. Presentamos la evolución de un joven cocainómano con destrucción mediofacial, que en el trascurso de los años ha padecido un absceso subperióstico y una neuritis óptica. Planteamos el diagnóstico diferencial y el manejo de estas complicaciones (AU)

The abuse of inhaled cocaine causes chemical sinus pathology by secondary midfacial destruction and necrosis. When midfacial necrosis is already established, other complications may occur related to the proximity of structures such as the orbit or optic nerve. We present the evolution of a young cocaine addict with midfacial destruction, who has had a subperiosteal abscess and optic neuritis over the course of the years. Differential diagnosis and management of these complications are also discussed (AU)

Validation of MRI classification system for tibial stress injuries.

OBJECTIVE: The purpose of our study was to compare an MRI classification system for tibial stress injuries with semiquantitative MR features of injury severity and clinical outcome. MATERIALS AND METHODS: Two musculoskeletal radiologists retrospectively reviewed in consensus the MR findings of 142 tibial stress injuries to quantify the degree of periosteal and bone marrow edema and grade the injuries using the Fredericson classification system (grade 1 = periosteal edema only, grade 2 = bone marrow edema visible on T2-weighted images, grade 3 = bone marrow edema visible on T1-weighted and T2-weighted images, grade 4a = multiple focal areas of intracortical signal abnormality, and grade 4b = linear areas of intracortical signal abnormality). Kruskal-Wallis tests were used to determine the relationship between the grade of stress injury and the degree of periosteal and bone marrow edema and the time to return to sports activity. RESULTS: Grade 4b injuries had significantly (p < 0.002) more severe and grade 1 injuries less severe periosteal and bone marrow edema than grades 2, 3, and 4a injuries. Grade 4b injuries had significantly (p < 0.002) longer time and grade 1 injuries shorter time to return to sports activity than grades 2, 3, and 4a injuries. There was no significant difference (p = 0.06-0.79) among grades 2, 3, and 4a injuries in the degree of periosteal and bone marrow edema and the time to return to sports activity. CONCLUSION: Grades 2, 3, and 4a stress injuries had similar degrees of periosteal and bone marrow edema and similar time to return to sports activity, which suggests that these three grades can be combined into a single category in an abbreviated Fredericson classification system.

Evaluation of a biodegradable novel periosteal distractor.

UNLABELLED: We developed a new device composed of a thin biodegradable mesh (poly-L-lactide/hydroxyapatite composite) for distracting periosteum. The purpose of this study is to evaluate the effect of using this device as a periosteal distractor. MATERIALS AND METHODS: Eight Japanese male rabbits were divided into two groups according to time of sacrifice. The calvarial periosteum was elevated and one side of a biodegradable mesh was fixed to the bone surface with two titanium screws. Seven days after the surgery, an elevating screw was inserted into the other side of the mesh. Then, the calvarial periosteum was elevated at maximum 0.5 mm every 12 h for 5 days. The device was designed to distract the periosteum at different rates along its entire surface. At 4 and 6 weeks of the consolidation, the animals were sacrificed and newly formed bone was histologically and radiographically evaluated. RESULTS: The new device simplified periosteal distraction and reduced its invasiveness. Moreover, it successfully induced new bone formation from two sources; the periosteum and the underlying basal bone. Histomorphometric analysis of the distracted space showed that there is a relation between the rate of distraction and the amount of newly formed bone. We suggest that the optimal speed range for periosteal distraction in rabbit calvarial model could be less than 0.33 mm/day. CONCLUSIONS: The new device is slim, biodegradable and the procedure is simple. Thus, periosteal distraction with this device is potential for vertical and horizontal ridge augmentation in oral cavity.

Preferential recruitment of bone marrow-derived cells to rat palatal wounds but not to skin wounds.

OBJECTIVE: To investigate the contribution of bone marrow-derived cells to oral mucosa wounds and skin wounds. BACKGROUND: Bone marrow-derived cells are known to contribute to wound healing, and are able to differentiate in many different tissue-specific cell types. As wound healing in oral mucosa generally proceeds faster and with less scarring than in skin, we compared the bone marrow contribution in these two tissues. DESIGN: Bone marrow cells from GFP-transgenic rats were transplanted to irradiated wild-type rats. After recovery, 4-mm wounds were made in the mucoperiosteum or the skin. Two weeks later, wound tissue with adjacent normal tissue was stained for GFP-positive cells, myofibroblasts (a-smooth muscle actin), activated fibroblasts (HSP47), and myeloid cells (CD68). RESULTS: The fraction of GFP-positive cells in unwounded skin (19%) was larger than in unwounded mucoperiosteum (0.7%). Upon wounding, the fraction of GFP-positive cells in mucoperiosteum increased (8.1%), whilst it was unchanged in skin. About 7% of the myofibroblasts in both wounds were GFP-positive, 10% of the activated fibroblasts, and 25% of the myeloid cells. CONCLUSIONS: The results indicate that bone marrow-derived cells are preferentially recruited to wounded oral mucosa but not to wounded skin. This might be related to the larger healing potential of oral mucosa.

Periosteal entrapment in distal femoral physeal fractures: harbinger for premature physeal arrest ?

We report on two patients who sustained Salter-Harris II fractures of the distal femur with physeal widening after being tackled in football games. Preoperative MRI indicated entrapped periosteum at the physeal fracture site for both patients. Both patients underwent open reduction of the physeal fracture with removal of the entrapped periosteum and achieving an anatomic reduction. Follow-up MRI's revealed premature physeal arrest. Subsequent procedures were performed to address sequelae of premature physeal arrest. The presence of physeal widening and entrapped periosteum may reflect high-energy trauma to the physis. This can result in injury to both the epiphyseal blood supply and to the physeal cartilage (germinal zone) resulting in physeal arrest despite anatomic reduction after removal of the entrapped periosteum. Upon literature review, pre-operative MRI demonstrating entrapped periosteum has not been previously reported. We hypothesize that the presence of entrapped periosteum following distal femoral physeal fractures may be associated with an increased risk for premature physeal arrest.