Technique and complications of callus distraction in the treatment of bone tumors

Introduction: This study investigated the effects of chemotherapy, defect length, and patient age on the outcome and complications of callus distraction as a limb salvage technique in 17 patients. Materials and methods: The mean patient age was 18.4 years (range 7–47). Of 17 patients, 8 received chemotherapy and the remaining 9 patients did not. The mean defect length after excision of the lesion was 13 cm (range 8–20). The mean follow-up period for the patients whose treatments were completed was 55 months (range 20–90), the mean distraction index was 12.55 days/cm (range 11–15.7), and the mean external fixation index was 34.73 days/cm (range 30–41). Results: In two patients, local recurrence occurred before distraction was completed. Two patients died, and one of them was a patient in whom local recurrence had occurred. Complications included non-union in one patient, osteomyelitis in one patient, and premature callus, osseous bridge, and varus of the femur in one patient. The extremity functional score was 80% (range 26–100). Chemotherapy and defect length had no significant effect on the distraction or external fixation indices. In contrast, the increase in the external fixation index in those over 20 years old was significant (P=0.043). Conclusion: We found that chemotherapy and defect length have no significant effect on the outcome and complications with this technique, which was more successful in patients younger than 20 years.     

Bilaterally increased VEGF-levels in muscles during experimental unilateral callus distraction.

Angiogenesis is essential for wound healing and proliferative processes such as bone formation and repair. Since increased expression of the vascular endothelial growth factor (VEGF) stimulates bone formation, it can be hypothesized that surgical procedures leading to a systemic increase of VEGF for instance during wound healing, influence enchondral ossification processes and might be responsible for observed growth phenomena during callus distraction. To study the mechanisms of angiogenesis in soft tissue during unilateral callus distraction, lengthening of the right tibia was performed in 12 beagles. After osteotomy, application of a ring fixator and after five latency days, distraction was started for 25 days. A control group of four additional beagles underwent no surgical procedure. Subsequent to the distraction period (Group A), muscle samples from six beagles were taken from the distracted side (ds) and the contralateral non-distracted side (n-ds), six beagles underwent an additional consolidation period of 25 days (Group B). Samples were analyzed for VEGF, VEGFR-1 and VEGFR-2 mRNA expression using real-time PCR and protein expression using Western Blot analysis. Muscles from both extremities showed significantly increased expression of VEGF and its cognate receptors VEGFR-1/2. Expression decreased significantly after the consolidation period, whereby the level at the non-distracted side decreased more than the level at the distracted side. Interestingly VEGF and VEGFR-1 levels at the non-distracted side were significantly higher than at the distracted side. In contrast VEGFR-2, the receptor that mediates endothelial cell proliferation, showed higher levels at the distracted than at the non-distracted side. These findings indicate that callus distraction results not only in locally increased expression of VEGF and its receptors, but leads also to increased VEGF and VEGFR-1/2 levels at distant sides and might therefore be responsible for the observed growth phenomena during callus distraction.     

Histomorphometric analysis of the epiphyseal growth plate in rats after prenatal alcohol exposure.

We studied the effect of prenatal alcohol exposure on growth in the proximal tibial growth plate in 0- and 15-day-old rats, using histomorphometric methods. Body weight and tibial length were reduced in all alcohol-exposed rats. In 15-day-old rats, these parameters were lower than in the 15-day-old controls, thus showing a persistence of the effects of ethanol. The proximal tibial growth plate showed alterations, principally in 15-day-old rats. The most notable of these was a decrease in growth plate height produced by a significant reduction in hypertrophic zone height. Likewise, there were fewer cells in this zone in alcohol-exposed rats than in controls. This work shows that prenatal ethanol exposure induces growth retardation which may be due to growth plate alterations that might reflect impaired cell function.     

The role of soft-tissue traction forces in bone segment transport for callus distraction: A force measurement cadaver study on eight human femora using a novel intramedullary callus distraction system

Callus distraction using bone segment transport systems is an applied process in the treatment of bone defects. However, complications such as muscle contractures, axial deviation and pin track infections occur in the treatment process using the currently available devices. Since successful treatment is influenced by the applied distraction force, knowledge of the biomechanical properties of the involved soft tissues is essential to improve clinical outcome and treatment strategies. To date, little data on distraction forces and the role of soft-tissue traction forces are available. The aim of this study was to assess traction forces generated by soft tissues during bone segment transport using a novel intramedullary callus distraction system on eight human femora. For traction force measurements, bone segment transport over 60-mm femoral defects was conducted under constant load measurement using 40- and 60-mm bone segments. The required traction forces for 60-mm bone segments were higher than forces for 40-mm bone segments. This study demonstrates that soft tissues are of relevance biomechanically in bone segment transport. The size of the bone segment and the selection of the region for osteotomy are of utmost importance in defining the treatment procedure.     

Functional outcome with special attention to the DASH questionnaire following callus distraction and phalangization of the thumb after traumatic amputation in the middle one-third

Introduction Aim of this retrospective study was to obtain a functional outcome following callus distraction and phalangization of the thumb after traumatic amputation in the middle one-third.Materials and methods From January 1998 to June 2001, 12 patients were treated in a staged procedure starting with corticotomy and continuous distraction (1 mm/day) of the first metacarpal bone using a unilateral external fixator device. After distraction until day 31 (range 25–35 days), the first metacarpal bone was stabilized with a plate, and phalangization was performed.Results At follow-up 1 year after surgery, the thumb was lengthened to 25–35 mm (average 28 mm) in all but 1 patient. In 1 patient a bone graft from the iliac crest had to be interposed. Pinch grip improved by 45%; grip strength improved by 55%. The function/symptom score from the DASH questionnaire was 25 points (range 16–38 points). In a 'pick-up test' all patients were able to pick up a pencil, they were able to write and could hold a full cup of water. Nine patients were able to pick up a paper clip, and 8 patients could hold a 1-liter bottle of water.Conclusion Callus distraction can be considered a suitable procedure to reconstruct an amputated thumb levelled at the middle one-third. Additional phalangization proved essential as it deepened the first web space, enabling good motion and grasp. Callus formation was delayed in elderly patients, but adequate lengthening and bone healing also occurred in this age group. The procedure will not be as beneficial in cases of osteoarthritis of the trapezometacarpal joint or when coverage of the stump is insufficient. The DASH questionnaire is very helpful in evaluating the effect of thumb reconstruction on the entire upper limb.     

Limb lengthening by diaphyseal corticotomy, callus distraction, and dynamic axial fixation. An experimental study in the ovine femur

Limb lengthening of the left femur was performed in 12 sheep, 7-8 months of age. After weakening of the cortex by drill holes, a controlled fracture was created in the diaphysis. The bone segments were fixed in reduced position using a unilateral external fixation device. The fixator was left in neutral position for 10 days postoperatively when lengthening started. By means of daily distraction at a rate of 1.0 mm once a day for 3 weeks, an average lengthening of 1.9 cm (11.9%) was obtained. Two weeks after distraction had been discontinued, distinct callus bridging of the lengthening zone was confirmed radiographically in all animals. At this time the rigid state of fixation was converted to a system allowing axial compression by loading in half the animals. The other half of the animals served as controls with the fixator remaining unchanged. The external device was left on until 5 weeks after the end of distraction. At this time the animals were killed. Both femora of all animals were tested mechanically in torsion. The average ultimate torsional strength of the elongated femur compared with control was 71% in the group with dynamic axial fixation and 65% in the control group. No significant difference in relative strength of the tested bones in the two groups was found. We conclude that intermittent axial compression by loading during consolidation had no significant effect on the bone-healing process evaluated by radiography and mechanical testing.     

Effects of botulinum toxin A on functional outcome during distraction osteogenesis.

Distraction osteogenesis is useful for correcting limb length inequality, deformities, or short stature. Despite success with bone formation, soft tissue maladaptations including muscle and joint contracture may lead to undesirable results. Botulinum toxin A has been useful in treating spasticity in cerebral palsy, and has been used clinically in select cases to allay contracture in distraction osteogenesis. This study examines the toxin's efficacy in preventing distraction-induced loss of muscle strength and range of motion. The left tibias of 15 New Zealand White rabbits were distracted 1.5 mm/day until approximately a 20% gain was achieved. Each treatment group was divided into animals injected with saline or botulinum toxin in either the gastrocnemius or tibialis anterior muscles. A control group of two additional animals underwent no surgical procedure. Strength and range of motion were assessed prior to, and following, the experiment. At the study's end, animals were euthanized and muscles were harvested, when lengths and weights were recorded. All muscles injected with botulinum toxin showed decreased wet weight and persistent weakness upon completion of the study. Range of motion decreased in all distracted animals. When the gastrocnemius was injected, its strength was reduced but the tibialis anterior strength was preserved, and the limb achieved 22% greater dorsiflexion than saline controls (p = 0.016). When the tibialis anterior received the toxin, plantarflexion was increased by 23% (p = 0.049). Botulinum toxin injection prior to limb distraction increases the "post-lengthened" excursion of the injected muscle and this increased length may have a protective effect on its antagonist. In toxin-injected gastrocnemius muscles, the level of equinus contracture is reduced due to length gains in the Achilles tendon while the anterior tibialis maintains its ability to generate torque. Injection of botulinum toxin in the gastrocnemius may minimize equinus contracture and protect the anterior tibialis from damage during human tibial lengthening. Longer follow-up studies are needed to ensure that toxin-induced muscle weakness resolves with time.     

Reimplantation of growth plate chondrocytes into growth plate defects in sheep

Defects in growth plates due to trauma, infection, or genetic causes can result in bone formation across the defect, bridging the epiphysis and metaphysis, resulting in growth arrest and limb deformation. We have investigated the capacity of implanted chondrocyte cultures to prevent this process. Sheep growth plate chondrocytes were isolated, and after culture at high density produced easily manipulated cartilaginous discs. The tissue was implanted into growth plate defects produced in lambs and the response was assessed histologically. Following implantation, cultures continued to proliferate and maintain a cartilage-like matrix. After 8 to 12 weeks, hypertrophic maturation chondrocyte columnation, and associated endochondral calcification were observed. Culture implantation was always associated with local immune inflammatory reaction, which continued throughout the course of investigation. Cellular survival was variable and resulted in the presence of viable implants as well as residual cartilage matrix devoid of chondrocytes; however, implanted chondrocyte discs always prevented bone bridge formation. These findings encourage the expectation that cultured chondrocytes may provide a useful replacement for the inert interpositional materials currently used in the treatment of growth arrest. The potential of this technique for growth plate replacement, however, requires a more predictable rate of implant survival. The likely reasons for implant loss are discussed.     

Limb lengthening by low rate epiphyseal distraction. An experimental study in the caprine tibia

Low-rate epiphyseal distraction of the left proximal tibia using a modified bilateral Hoffmann external fixation device, was accomplished in 14 goats (age 6-7 months). Daily distraction at a rate of 0.5 mm was continued for 5.5 weeks. Epiphysiolysis occurred after 5-9 days. After distraction had been discontinued, the external device was left in situ for fixation for 4 weeks. The animals in group 1 (n = 6), group 2 (n = 3), and group 3 (n = 5) were killed at 4, 16, and 32 weeks, respectively, from the end of the distraction period. The proximal growth plate of the elongated tibia appeared radiolucent at the conclusion of the study but was less distinct and reduced in height as compared with the control leg. The gained length at the end of the distraction period was on the average 2.2 cm (11.9%). This gain in length was reduced with further growth. In group 3, the final gain in length was reduced to half. A reduced cortical thickness of the bone within the area subjected to distractional force was observed. This finding is attributable to stress protection. An interesting observation comparing control and operated tibia was an increase of the cross-sectional diameter of the elongated bone. Both tibiae of all animals were tested mechanically. The torsional strength of the elongated tibiae as compared with controls was on the average 29% in group 1, 79% in group 2, and 95% in group 3. We conclude that leg lengthening by low-rate epiphyseal distraction in the proximal tibia is a justifiable alternative to other lengthening procedures in individuals approaching adolescence. In juveniles, lengthening by epiphyseal distraction may result in reduction in the longitudinal growth.     

Low-intensity pulsed ultrasound shortens the treatment time in tibial distraction osteogenesis

Purpose

Low-intensity pulsed ultrasound (LIPUS) has been used successfully to accelerate healing of fresh fractures and non-unions. It also improved callus maturation with distraction osteogenesis in animal trials. However, only few clinical studies are available to support its widespread use for the latter indication in humans.

Methods

Twenty-one patients undergoing callus distraction for posttraumatic tibial defects were randomized into two groups: the trial group (12 men; mean age 32 years) which received 20 minutes LIPUS daily during treatment and the control group (six men and three women; mean age 29 years) without LIPUS treatment. The Ilizarov ring fixator was used in all cases. Results were examined clinically and radiologically, analysing callus maturation with a computer-assisted measurement.

Results

Patients in the LIPUS group needed a mean of 33 days to consolidate every 1 cm of new bone in comparison to 45 days in the control group. The healing index was therefore shortened by 12 days/cm in the LIPUS group. This means that callus maturation was 27 % faster in the LIPUS group. The fixator time was shortened by 95 days in the LIPUS group. The overall daily increase in radiographic callus density was 33 % more in the LIPUS group than in the control group.

Conclusions

LIPUS treatment is an effective non-invasive adjuvant method to enhance callus maturation in distraction osteogenesis. With the help of this treatment, the healing time and the duration of external fixation can be reliably shortened.     

组织工程软骨移植修复兔生长板缺损

目的探讨一种新的修复生长板缺损的方法,应用组织工程软骨治疗生长板缺损并发肢体畸形。方法分离收集1月龄兔关节软骨,于离心管内培养2周形成组织工程软骨。36只6周龄新西兰白兔随机分为3组,于右侧胫骨上端生长板内侧造成1/3～1/2缺损,A组即刻植入培养软骨,B组及C组分别于术后4周、术后8周再次手术,切除缺损内修复组织后再移植培养软骨。左侧胫骨经相同手术造成缺损,但无植入物充填,仅作为对照组。A组于手术后16周、B组于再手术后12周、C组于再手术后8周进行双下肢X线、组织学及免疫组织化学等检查,测量双侧胫骨长度和胫骨角,观察生长板缺损修复情况。结果培养软骨呈圆盘状,直径8mm,厚1.5mm。A、B组右侧胫骨生长显著优于左侧,内翻和短缩畸形右侧较左侧轻(P<0.01)。A、B组右侧生长板缺损经组织修复后恢复正常生长板结构和性质,Ⅱ型胶原和IGF-IRa免疫组织化学染色呈阳性;左侧胫骨生长板缺损由新生骨充填。C组双侧胫骨均发生严重畸形(P>0.05),生长板闭合或接近闭合。结论离心管培养组织工程软骨移植可以有效防止4周内生长板缺损并发早期肢体畸形,但对生长板缺损8周已形成畸形者无效。     

重度僵硬型脊柱侧凸分期手术矫形不同撑开次数的效果及意义

【摘要】 目的：探讨分期前路松解、后路撑开联合后路固定融合治疗重度僵硬型脊柱侧凸患者侧弯及躯干平衡的改善情况,通过对不同撑开次数的手术效果及卫生经济学指标对比来评价第二次撑开的意义。方法：2010年1月～2014年1月共收治重度僵硬型脊柱侧凸（Cobb角＞90°,柔韧度＜30%）患者23例,根据后路撑开次数分为一次撑开组及两次撑开组。所有患者一期手术均为前路松解和第一次撑开,两次撑开组患者第二次撑开在第一次撑开后10d进行,两组患者均在撑开术后2周行后路融合固定术。分析比较两组患者术前、术后影像学躯干平衡参数;同时对两组患者并发症发生率、手术时间、手术出血量、住院时间、住院花费等卫生经济学指标进行对比。结果：总共有23例患者纳入研究,一次撑开组11例,两次撑开组12例。术前两组患者主弯Cobb角、主弯柔韧度、冠状位平衡、矢状位平衡、胸椎后凸、腰椎前凸差异无显著性（P＞0.05）。融合术后,两组患者主弯Cobb角、冠状位平衡、矢状位平衡较术前均有明显改善,差异有显著性（P<0.05）;但两组间比较差异无显著性（P>0.05）。两次撑开组中第一次与第二次撑开后除主弯Cobb角有明显改善外（P＜0.05）,其他指标间差异均无显著性（P>0.05）。一次撑开组手术失血量、平均手术时间、住院时间、住院总费用均显著少于两次撑开组（P<0.05）。两次撑开组围术期共有2例手术并发症发生（1例胸腔大量积液,1例术后下肢麻木,均通过相应治疗后恢复）,一次撑开组无相关并发症发生。结论：前路松解、后路撑开联合后路固定融合是一种治疗重度僵硬型脊柱侧凸有效安全的方法,两次撑开次能有限增加的躯干平衡的矫形效果,但可能会带来较高的手术费用及增加并发症发生率;从卫生经济学角度出发,临床上对于第二次的撑开应慎重进行。     

Rapamycin retards growth and causes marked alterations in the growth plate of young rats

Rapamycin is a potent immunosuppressant with antitumoral properties widely used in the field of renal transplantation. To test the hypothesis that the antiproliferative and antiangiogenic activity of rapamycin interferes with the normal structure and function of growth plate and impairs longitudinal growth, 4-week-old male rats (n = 10/group) receiving 2 mg/kg per day of intraperitoneal rapamycin (RAPA) or vehicle (C) for 14 days were compared. Rapamycin markedly decreased bone longitudinal growth rate (94 ± 3 vs. 182 ± 3 μm/day), body weight gain (60.2 ± 1.4 vs. 113.6 ± 1.9 g), food intake (227.8 ± 2.6 vs. 287.5 ± 3.4 g), and food efficiency (0.26 ± 0.00 vs. 0.40 ± 0.01 g/g). Signs of altered cartilage formation such as reduced chondrocyte proliferation (bromodeoxiuridine-labeled cells 32.9 ± 1.4 vs. 45.2 ± 1.1%), disturbed maturation and hypertrophy (height of terminal chondrocytes 26 ± 0 vs. 29 ± 0 μm), and decreased cartilage resorption (18.7 ± 0.5 vs. 31.0 ± 0.8 tartrate-resistant phosphatase alkaline reactive cells per 100 terminal chondrocytes), together with morphological evidence of altered vascular invasion, were seen in the growth plate of RAPA animals. This study indicates that rapamycin can severely impair body growth in fast-growing rats and distort growth-plate structure and dynamics. These undesirable effects must be kept in mind when rapamycin is administered to children.     

骨痂延长术治疗桡骨化脓性骨髓炎后继发桡侧球棒手畸形的临床报道

[目的]评价利用镶嵌式双臂外固定器行骨痂延长术治疗桡骨骨髓炎后继发桡侧球棒手畸形的临床效果。[方法]回顾性分析应用镶嵌式骨外固定器行骨痂延长术治疗桡骨化脓性骨髓炎后导致的Heikel’sⅢ型桡侧球棒手畸形的临床资料,男9例,女4例;骨缺损长度3～8 cm,平均5.8 cm;桡偏角度30°～70°,平均55°。术后观察前臂肘、腕关节功能及骨不连的愈合指数,进行统计学分析。[结果]13例患者均获得24～58个月随访,球棒畸形纠正,术后的桡偏角度0～10°,平均5.0°±3.1°,P<0.05有统计学意义;双侧前臂等长,肘腕关节屈曲、伸直功能恢复良好;前臂旋后功能改善至71.8°±13.5°,P<0.05提示结果有统计学差异,所有病例无神经、血管损伤。[结论]利用镶嵌式骨外固定器行骨痂延长术是治疗桡骨骨髓炎后继发桡侧球棒手畸形的一种疗效好,副作用小,操作简单的有效手术。     

The Effects of botulinum toxin A on muscle histology during distraction osteogenesis

Distraction osteogenesis is a highly successful method of bone formation, yet muscle fibrosis and contractures can result in significant morbidity. In the current study, we investigate the efficacy of botulinum toxin A in preventing fibrosis and potentially increasing muscle development in distracted muscles. Fifteen New Zealand White rabbits underwent tibial distraction at 1.5 mm/day until a 20% gain was achieved. Treatment groups were divided by drug (saline or botulinum toxin) and target muscle (gastrocnemius or tibialis anterior). Two additional control animals received no treatment. Bromeodeoxyuridine was delivered continuously throughout the 8‐week experiment, and following muscle harvest. Tissues were stained for BrdU, Pax‐7, vimentin, and haematoxylin and eosin staining. Mitotic activity increased in all distracted animals; however, in the animals receiving botulinum toxin A injections into the gastrocnemius, the antagonist tibialis anterior suffered up to 9% less fibrosis than distraction alone (p = 0.024). Use of botulinum A toxin did not appear to promote or improve neogenesis of muscle fibers, nor did it decrease fibrosis in the injected muscles. It appears from this study, and a previously published study on the effects of this toxin on muscle function, that botulinum A toxin maybe of some benefit in decreasing morbidity in the antagonist muscle but not the muscle injected with the toxin. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:310–317, 2009     

Limb lengthening by epiphyseal distraction in chondrodystrophic bone: an experimental study in the canine femur

Epiphyseal distraction of the left distal femur was accomplished in 18 chondrodystrophic dogs (age 19-22 weeks). A distraction rate of 0.5 mm/day was applied by means of a unilateral device. Epiphysiolysis occurred after 4 to 9 days. Lengthening was continued for 3 weeks. The animals were killed at 3 (Group 1; n = 5), 19 (Group 2; n = 10), and 71 (Group 3; n = 3) weeks after the end of distraction to verify the magnitude of elongation at removal of the device (Group 1) and at the time of growth cessation (Groups 2 and 3), and to register possible permanent secondary joint changes (Group 3). The average lengthening of 1.2 cm (12.3%) at removal of the device was reduced to 0.7 cm (6.4%) at cessation of growth. The middiaphyseal diameter of the elongated femur was enlarged after the lengthening procedure in all animals. The average torsional strength of the elongated femur compared with the contralateral control was 83% in Group 1, 98% in Group 2, and 107% in Group 3. Degenerative changes were observed in the knee joints of three animals in each group. A two-way analysis of variance was applied for all data sets to test differences between control and elongated bones and between time periods. The reduction in gained length by retardation of residual growth in the distal femur was significant (p less than 0.05). The difference in external diameter between lengthened and control bones was significant in Groups 1 and 3 (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Ultrastructure of the rat epiphyseal growth plate following chronic ethanol ingestion

Summary We have previously demonstrated that ethanol has a direct toxic effect on the rat skeleton characterized by decreased trabecular bone volume. In the present study, we examined the ultrastructure of the distal radial epiphyseal growth plates in these same animals. Eight weeks of ethanol administration to 12 male rats results in serum alcohol levels of 140 mg/dl but did not alter the width or light microscopic appearance of the radial growth plate. Quantitative electron microscopy failed to demonstrate morphologic evidence of toxicity in the skeletal cells. We conclude that although ethanol appears to have a direct effect on rat bone characterized by enhanced resorption, toxicity is not attended by ultrastructural changes in the skeletal cells.     

不对称力学负荷对山羊脊柱生长板影响的组织学观察

目的：观察不对称力学负荷对山羊脊柱生长板的影响，探讨机械性因素调节脊柱生长的可能机制。方法：9只未成年雌性山羊随机分为实验组（n=6）和对照组（n=3），实验组采用单侧椎弓根螺钉不对称拴系的方法建立脊柱侧凸模型；对照组只作相同切口暴露，不进行固定。8周后获取侧凸顶椎（对照组相应节段）上下椎间盘及生长板，聚甲基丙烯酸甲酯（PMMA）包埋，不脱钙切片，Giemsa染色，镜下观察生长板情况。结果：对照组两侧生长板无明显差异；实验组非加压侧生长板增殖肥大层高度明显大于加压侧。实验组加压侧增殖肥大层软骨细胞数量少、形态异常、排列不规则，非加压侧软骨细胞增殖活跃，肥大层明显增厚：加压侧生长板最边缘的骺板内软骨细胞朝应力方向向外排列。结论：不对称力学负荷可导致生长板两侧软骨细胞增殖、肥大、形态及排列等的差异，并改变软骨内成骨方向，最终可能改变脊柱的生长方向。     

Immunolocalization of the angiogenetic factor pleiotrophin (PTN) in the growth plate of mice

The aim of this study was to find out whether and where the angiogenic agent pleiotrophin (PTN) occurs within the growth plate. We investigated paraffin-embedded tissue sections of ten male mice with an antibody directed against the recombinant PTN. Immunostaining for PTN was positive within the cytoplasm and the pericellular matrix of osteoblasts which lined the longitudinal mineralized septae of the epiphyseal plate. Within the zone of hypertrophic chondrocytes, immunolabelling for PTN was positive in the pericellular matrix of hypertrophic chondrocytes and within the opened lacunae of the apoptotic hypertrophic chondrocytes. The resting zone and the proliferation zone were PTN negative. The results of our study suggest that the known angiogenetic peptide PTN plays a role in the process of angiogenesis in the growth plate. Received: 17 November 1999