Callus Diameter Research Articles

Androgenic response of tomato (Lycopersicon esculentum Mill.) lines and their hybrids to anther culture

The androgenic ability of four tomato (Lycopersicon esculentum Mill.) lines (Micro-Tina, Micro-Gemma, Moneymaker and MsK8 as parents) and their hybrids (obtained as half diallel crosses) were studied through anther culture, The isolated anthers were cultured on three culture media including M1 (Park et al., 2001), M2 (Summers, 1997) and M3 (Evans et al. 1986) exposed to two pretreatments (26 ± 2°C as a control and at 4°C for 48 h as a cold pretreatment). Callus formation and callus growth (measured by callus diameter) occurred in the both pretreated anthers, but no callus produced shoot regeneration on the non-pretreated anthers. Statistical analysis showed significant differences between genotypes, culture media and their interactions for the studied traits. The highest callus formation was on M1 and M2 media, among which the longest callus diameter and the highest shoot regeneration were on M1 medium. The lines MsK8 and Micro-Gemma had a considerably higher frequency of callus formation and shoot regeneration and longer callus diameters than the other parents. On M1 medium, the highest frequency of callus formation and shoot regeneration belonged to hybrid MsK8 × Micro-Tina, and the longest callus diameter observed on hybrid Micro-Tina × Micro-Gemma. The mean values of callus formation, callus diameter, and shoot regeneration of hybrids in different culture media were significantly higher than those of the parents. In other words, heterosis (hybrid vigor) for the mentioned traits was observed on different culture media. Therefore, heterozygous genotypes (the hybrids) had a higher frequency of androgenic response than their parents.

Improved growth and quality of Siraitia grosvenorii plantlets using a temporary immersion system

The effects of temporary immersion system (TIS) culture on the growth and quality of Siraitia grosvenorii plantlets were investigated. The TIS promoted the growth and quality of S. grosvenorii plantlets. Proliferation rate, shoot length, fresh weight (FW) and dry weight (DW) of shoots, and total biomass production were significantly (P ≤ 0.05) higher in the TIS than in gelled and liquid medium, respectively. The TIS also decreased callus formation at the base of shoots. Callus diameter was significantly (P ≤ 0.05) lower in the TIS (3.30 mm) than in gelled medium (6.31 mm) and liquid medium (6.77 mm), respectively. FW (50.83 mg) and DW (7.08 mg) of callus in the TIS were also significantly (P ≤ 0.05) lower than those in gelled medium (80.00 and 10.56 mg, respectively) and liquid medium (218.75 and 23.75 mg, respectively). During rhizogenesis, minimal callus was evident at the base of shoots in the TIS, with a well-developed root system. However, the plantlets in gelled medium just produced thick, brown and easily broken roots with obvious callus and fewer secondary roots. The natural-like plantlets of S. grosvenorii obtained in the TIS would probably have positive effects on ex vitro rooting and transplanting in large-scale commercial production.

Inhibition of angiotensin‐converting enzyme stimulates fracture healing and periosteal callus formation – role of a local renin‐angiotensin system

The renin-angiotensin system (RAS) regulates blood pressure and electrolyte homeostasis. In addition, 'local' tissue-specific RAS have been identified, regulating regeneration, cell growth, apoptosis, inflammation and angiogenesis. Although components of the RAS are expressed in osteoblasts and osteoclasts, a local RAS in bone has not yet been described and there is no information on whether the RAS is involved in fracture healing. Therefore, we studied the expression and function of the key RAS component, angiotensin-converting enzyme (ACE), during fracture healing. In a murine femur fracture model, animals were treated with the ACE inhibitor perindopril or vehicle only. Fracture healing was analysed after 2, 5 and 10 weeks using X-ray, micro-CT, histomorphometry, immunohistochemistry, Western blotting and biomechanical testing. ACE was expressed in osteoblasts and hypertrophic chondrocytes in the periosteal callus during fracture healing, accompanied by expression of the angiotensin type-1 and type-2 receptors. Perindopril treatment reduced blood pressure and bone mineral density in unfractured femora. However, it improved periosteal callus formation, bone bridging of the fracture gap and torsional stiffness. ACE inhibition did not affect cell proliferation, but reduced apoptotic cell death. After 10 week treatment, a smaller callus diameter and bone volume after perindopril treatment indicated an advanced stage of bone remodelling. Our study provides evidence for a local RAS in bone that influenced the process of fracture healing. We show for the first time that inhibition of ACE is capable of accelerating bone healing and remodelling.

Comparison of effects of alfacalcidol and alendronate on mechanical properties and bone collagen cross-links of callus in the fracture repair rat model

Both bone density and quality are important determinants of bone strength. Bone quality is prescribed by matrix characteristic including collagen cross-linking and bone structural characteristics and is important in reinforcement of bone strength. We investigated the effects of alfacalcidol (ALF), a prodrug of calcitriol, and alendronate (ALN), a bisphosphanate, on the mechanical properties and content of enzymatic cross-links in femoral bone using a fracture repair rat model. Forty 3-month-old female Wistar–Imamichi rats were randomized into 4 groups: SHAM (sham-operated+vehicle), OVX (ovariectomy+vehicle), ALF (ovariectomy+ALF, 0.1 μg/kg/d, p.o.) and ALN (ovariectomy+ALN, 10 μg/kg/d, s.c.). Treatment began immediately after SHAM or OVX surgery. Three weeks later, all animals underwent transverse osteotomies at the midshaft of the left femur. Treatment was continued and rats were sacrificed at 12 weeks post-fracture for evaluation by X-ray radiography, micro-CT, pQCT, biomechanical testing and bone histomorphometry. In the ALN group, no new cortical shell appeared and the callus diameter was significantly larger than in the OVX group ( p < 0.05). Stiffness of fractured callus in the ALF group, but not in the ALN group, was significantly higher than in the OVX group. Young's modulus in the ALN group was significantly decreased compared to the OVX group. Moreover, micro-CT analysis showed that ALN treatment increased the lowly mineralized bone in the callus by, resulting in the highest content of woven bone area and lowest content of lamellar bone. The total amount of enzymatic cross-links in both the ALF and ALN groups was significantly higher than in the OVX control group. Of particular interest, the Pyr-to-Dpyr ratio was significantly decreased by ALF administration, suggesting that ALF but not ALN normalized the enzymatic cross-link patterns in fractured bone to the control level. In conclusion, ALN and ALF treatment increased bone strength via the distinctive effect on bone mass and quality. ALN formed larger calluses and increased enzymatic cross-links despite delayed woven bone remodeling into lamellar bone, whereas ALF treatment induced lamellar bone formation coincided with increasing in the enzymatic cross-linking and normalizing the cross-link pattern in callus to native bone pattern.

An internal locking plate to study intramembranous bone healing in a mouse femur fracture model

In most murine fracture models, the femur is stabilized by an intramedullary implant and heals predominantly through endochondral ossification. The aim of the present study was to establish a mouse model in which fractures heal intra-membraneously. Femur fractures of 16 SKH-mice were stabilized by an internal locking plate. Femur fractures of another 16 animals were stabilized by an intramedullary screw. Bone repair was analyzed by radiographic, biomechanical, and histological methods. At 2 weeks, histological analysis showed a significantly smaller callus diameter and callus area after locking plate fixation. Cartilage formation within the callus could only be observed after screw fixation, but not after fracture stabilization with the locking plate. Radiological and biomechanical analysis after 2 and 5 weeks showed a significantly improved healing and a higher bending stiffness of fractures stabilized by the locking plate. Fractures stabilized by the locking plate healed exclusively by intramembranous ossification, which is most probably a result of the anatomical reduction and stable fixation. The fractures that healed by intramembranous ossification showed an increased stiffness compared to fractures that healed by endochondral ossification. This model may be used to study molecular mechanisms of intramembranous bone healing.

In vitro and ex vitro rooting of Siratia grosvenorii, a traditional medicinal plant

Since a decade, the large-scale commercial production of Siratia grosvenorii plantlets is being practiced through in vitro culture of its microcuttings, but it has some drawbacks such as handling of plantlets, low transplant-survival rate, development of massive callus, low yield after transplantation, etc. An experiment has been conducted to improve the prevailing technique as well as to develop a new ex vitro technique to overcome these drawbacks. Several concentrations of naphthalene acetic acid (NAA) (0–4.0 mg/l) have been tried with the MS (Murashige and Skoog in Physiol Plant 15:473–479, 1962) basal medium containing 3% (w/v) sucrose and 4.0 g/l agar, out of which 0.1 mg/l NAA was found best in terms of smaller diameter of callus and maximum rooting and transplant survival rate. Further, use of perlite instead of agar medium also showed possibilities for future research on commercial-scale plantlet production. Ex vitro rooting technique was found superior to the in vitro one as plantlets developed through this method had lateral roots without any callus at the base of microcuttings, just like the natural root system and of course with higher root length, rooting rates, and transplant survival rate compared to the in vitro developed plantlets. Further, this technique is economical in terms of labor and time saving and gives rise to vigorous plants which ultimately bring higher yields and profits.

In vitro micropropagation from plumular apices of Turkish cowpea ( Vigna unguiculata L.) cultivar Akkiz

Multiple shoot formation from the plumular apices excised from mature embryos of cowpea cv. Akkiz was obtained after pulse treatment with 10 mg/l BAP for 5 days followed by culture on MS medium containing 0.25, 0.50, 0.75 and 1.00, 1.25 mg/l BAP – with or without 0.10 mg/l NAA. Callus induction and shoot regeneration was recorded on all cultures containing BAP with or without NAA. However, inclusion of 0.1 mg/l NAA had positive effect on callus diameter and shoot length. Maximum mean number of 7.11 shoots per explant were obtained on MS medium containing 1.00 mg/l BAP. Longer shoots were recorded on MS medium containing various concentration of BAP+ 0.1 mg/l NAA compared to those containing various concentrations of BAP singly. All shoots cultured on MS medium containing 1 mg/l BAP were rooted on MS medium containing 0.50 mg/l IBA. Rooted plants were acclimatized at room temprature in soil contained in pots. All plants flowered and set seeds in the greenhouse after 3 months.

Hyperhomocysteinemia Is Associated with Impaired Fracture Healing in Mice

Hyperhomocysteinemia (HHCY) has been shown to disturb bone metabolism and to increase the incidence of osteoporosis and osteoporotic fractures. However, there is a complete lack of information on whether these metabolic alterations affect bone repair. The aim of this study was to analyze the impact of HHCY on fracture healing. One group of mice was fed a homocystine-supplemented diet (n = 12), whereas another group received the accordant standard diet for control (n = 13). Four weeks after the stable fixation of a closed femoral fracture, animals were killed to prepare bones for histomorphometric and biomechanical analyses. In addition, blood samples were obtained to evaluate serum concentration of homocysteine (HCY). Quantitative analysis of blood samples revealed severe HHCY as indicated by significantly increased serum concentrations of HCY in animals fed the homocystine-supplemented diet (102.2 +/- 64.5 micromol/l) compared to controls (2.8 +/- 1.5 micromol/l). Biomechanical evaluation of bone repair revealed significantly decreased bending stiffness of the femora of homocystine-fed animals (45.5 +/- 18.2 N/mm) compared with controls (64.6 +/- 15.8 N/mm). Histomorphometric analysis demonstrated a slightly smaller callus diameter in HHCY animals but no significant differences in the tissue composition of the callus. In conclusion, the homocystine-supplemented diet leads to severe HHCY, which is associated with an impaired biomechanical quality of the healing bone.

Leg lengthening by distraction osteogenesis using the Ilizarov apparatus: a novel concept of tibia callus subsidence and its influencing factors

This article studies the incidence and magnitude of delayed callus subsidence, which will also help in study the hypothesis of three cortex corticalisation to determine the time of fixator removal during distraction osteogenesis (DO). Eighty-one tibia segments with mean lengthening of 7.7 +/- 2.9 cm were studied with age, gender, skeletal maturity, amount and percentage of lengthening, callus pattern, callus shape, number of cortices seen at the time of fixator removal, bone mineral density (BMD) ratio, and callus diameter ratio analysed for their effect on callus subsidence. All segments had tibia callus subsidence ranging from 4 mm to 3.2 cm with 54% having significant subsidence of more than 1 cm. Multivariate regression analysis revealed only the amount of lengthening and callus patterns to be significant. In conclusion, we can say that tibia callus subsidence is a significant delayed complication and factors affecting it can be used to determine the time of fixator removal.

The Influence of Soft Tissue Trauma on Bone Regeneration after Acute Limb Shortening

Reconstructing posttraumatic tibial defects is often challenging. Some authors recommend acute limb shortening. We determined whether soft tissue trauma affects the formation of regenerated bone after acute shortening and monofocal lengthening. Twenty-two rabbits were divided into two equal groups. In the test group, 90 minutes of ischemia and 30 minutes of tibialis anterior muscle contusion at 100 kPa induced substantially elevated pressure as an onset of compartment syndrome. The untreated hind limb acted as the paired control. An external fixator was applied and the limb was shortened 10 mm through bone resection. After a latency period, distraction was performed for 10 days until the natural length was restored. New bone formation was evaluated mechanically, radiographically, and histomorphometrically. Osseous consolidation occurred in all animals. Normalized mechanical values of the newly reconstructed tibia indicated torsional strength was lower in the trauma group than in controls (46% +/- 18.5% versus 64% +/- 16.7%). Average normalized callus diameters were smaller in the trauma group than in controls (1.27 +/- 0.14 versus 1.6 +/- 0.16), as were callus volumes (37% +/- 5.9% versus 44% +/- 10.3%). Although soft tissue trauma affected the formation of regenerated bone, our results suggest reconstruction of tibial defects using a monofocal technique is consistent, even in the presence of blunt trauma and elevated compartment pressure.

Accelerated bone healing and excessive callus formation in patients with femoral fracture and head injury

The effect of head injury on systemic physiology, including bone healing is still a topic of vivid discussion. Whether the observed changes genuinely represent accelerated fracture healing or are a form of local heterotopic ossification remains unclear. We aimed to investigate whether in patients with long bone fractures the presence of head injury is associated with accelerated bone healing and excessive callus formation. In total 67 patients were studied 17 with head injury and 50 without head injury (25 treated with reamed and the other 25 with the unreamed nailing technique). Both groups were comparable in terms of age, sex, ISS. All underwent stabilisation of their femoral fracture with intramedullary nailing. The quantification of fracture healing response was estimated by taking the radiological ratio of the largest diameter of callus formed into two planes and the adjacent normal diameter of femoral canal. The minimum follow up of the patients was 12 months. In patients with head injury, the mean time to fracture union was significantly shorter than either the reamed or unreamed group (10.5 weeks compared with 20.5 and 26.9 weeks, p<0.001). The difference between the mean callus to diaphyseal ratio was statistically significant for both the AP and Lateral projections (AP: mean difference 0.462, 95% CI 0.312 to 0.602, p<0.0001, LAT: mean difference 0.289, 95% CI 0.142 to 0.436, p<0.001) with the head injured patients having more florid callus compared to the control group.

Computational simulation of fracture healing: Influence of interfragmentary movement on the callus growth

Bone fractures heal through a complex process involving several cellular events. This healing process can serve to study factors that control tissue growth and differentiation from mesenchymal stem cells. The mechanical environment at the fracture site is one of the factors influencing the healing process and controls size and differentiation patterns in the newly formed tissue. Mathematical models can be useful to unravel the complex relation between mechanical environment and tissue formation. In this study, we present a mathematical model that predicts tissue growth and differentiation patterns from local mechanical signals. Our aim was to investigate whether mechanical stimuli, through their influence on stem cell proliferation and chondrocyte hypertrophy, predict characteristic features of callus size and geometry. We found that the model predicted several geometric features of fracture calluses. For instance, callus size was predicted to increase with increasing movement. Also, increases in size were predicted to occur through increase in callus diameter but not callus length. These features agree with experimental observations. In addition, spatial and temporal tissue differentiation patterns were in qualitative agreement with well-known experimental results. We therefore conclude that local mechanical signals can probably explain the shape and size of fracture calluses.

Identification of Callus Induction Potential of 15 Indonesian Rice Genotypes

The callus induction potential of 15 indica rice genotypes from Indonesia was examined in comparison with that of the japonica rice Nipponbare. Callus was induced from embryos of mature seeds and root segments on MS and CI media. There was genotype × medium × explant interaction for inducing white/cream/yellow callus with an organized structure (callus type I and II) and for callus browning, but not for callus induction ability and diameter of callus. Genotypes significantly differed in inducing high quality of calluses depending on medium and explant used. Four indica types, Fatmawati, Ciapus, BP-23 and BP-360-3, had callus induction-related traits similar to those of Nipponbare. These genotypes would be useful for tissue-culture based research and for crop improvement, particularly for genetic transformation. Culturing seed explant on MS was more suitable for callus induction than either root explant on MS or both explants on CI medium.

Influência da concentração de BAP e AG3 no desenvolvimento in vitro de mandioquinha-salsa

Foram realizados dois experimentos com o objetivo de avaliar o efeito das concentrações de BAP e de AG3 no desenvolvimento in vitro de mandioquinha-salsa. Foram avaliadas as concentrações de 0,0; 0,2 e 0,4 mg L-1 de BAP e de 0,0; 0,125 e 0,250 mg L-1 de AG3 no desenvolvimento de ápices caulinares com cerca de 2 mm das cultivares Amarela de Senador Amaral e Amarela Comum. A interação cultivares x concentração de BAP não foi significativa para nenhuma das características avaliadas (P&gt;0,0617). O aumento na concentração de BAP reduziu a formação de calos; entretanto, promoveu proporcionalmente redução no desenvolvimento da parte aérea. A concentração de BAP que apresentou os melhores resultados foi em torno de 0,3 mg L-1 de BAP, conciliando diâmetro de calo relativamente reduzido e bom desenvolvimento da parte aérea, cerca de 4,5 brotos com altura média de 43 mm. A interação cultivares x concentração de AG3 não foi significativa para nenhuma das características avaliadas (P&gt;0,4310). O aumento na concentração de AG3 promoveu elevação significativa na altura média e máxima das brotações e aumento no tamanho de calos. Nos dois experimentos, observou-se maior número de brotações na cultivar Amarela Comum.

Deletion of iNOS gene impairs mouse fracture healing

Nitric oxide (NO) is a signaling molecule synthesized from l-arginine by nitric oxide synthases (NOSs). NOS isoforms are either constitutive (endothelial NOS [eNOS] and neuronal NOS [nNOS]) or inducible NOS (iNOS). Previously, our group has reported that NO is expressed during and modulates fracture healing. In this study, we evaluated the specific contribution of iNOS to fracture healing by using iNOS gene therapy in iNOS-deficient mice. Twelve-week-old female wild-type mice and iNOS-KO mice had a right femoral midshaft osteotomy fixed with an intramedullary 0.5-mm-diameter needle. A gelatine sponge was implanted across the fracture site. The gelatine sponge received either Ad5-CMViNOS (in iNOS-deficient mice; n = 16) or Ad5-CMVempty (in wild-type mice; n = 15, and iNOS-deficient mice; n = 15) at a dose of 10 7 pfu. Mice were sacrificed at day 14, and their right and left hind limbs were harvested. Cross-sectional area (CSA) was determined by measuring the callus diameter across the mediolateral and anteroposterior plane using a vernier caliper. Specimens were loaded to failure torsionally in a biaxial INSTRON testing system, and maximum torque, torsional stiffness, and maximal and total energy were determined. Deletion of the iNOS gene decreased the total and maximum energy absorption of the healing femoral fracture by 30% and by 70% ( P < 0.01), respectively, in comparison to the wild-type mice. This reduction in energy absorption was reversed by iNOScDNA administration via adenovirus vector. Furthermore, iNOScDNA caused an increase in torsional failure by 20% ( P = 0.01) in comparison to iNOS(−/−) mice that did not receive the iNOScDNA. There were no significant differences in the biomechanical properties of intact femora. These data indicate that iNOS is important in mouse fracture healing. However, the clinical utility of NOS gene therapy to enhance fracture healing will need further evaluation.

The initial phase of fracture healing is specifically sensitive to mechanical conditions

Interfragmentary movements affect the quality and quantity of callus formation. The mounting plane of monolateral external fixators may give direction to those movements. Therefore, the aim of this study was to determine the influence of the fixator mounting plane on the process of fracture healing. Identically configured fixators were mounted either medially or anteromedially on the tibiae of sheep. Interfragmentary movements and ground reaction forces were evaluated in vivo during a nine week period. Histomorphological and biomechanical parameters described the bone healing processes. Changing only the mounting plane led to a modification of interfragmentary movements in the initial healing phase. The difference in interfragmentary movements between the groups was only significant during the first post-operative period. However, these initial differences in mechanical conditions influenced callus tissue formation significantly. The group with the anteromedially mounted fixator, initially showing significantly more interfragmentary movements, ended up with a significantly smaller callus diameter and a significantly higher callus stiffness as a result of advanced fracture healing. This demonstrates that the initial phase of healing is sensitive to mechanical conditions and influences the course of healing. Therefore, initial mechanical stability of an osteosynthesis should be considered an important factor in clinical fracture treatment.

Effect of recombinant human osteogenic protein-1 on the healing of a freshly closed diaphyseal fracture

Osteogenic protein-1 (OP-1), or bone morphogenetic protein-7, is an osteoinductive morphogen that is involved in embryonic skeletogenesis and in bone repair. In bone defect models without spontaneous healing, local administration of recombinant human OP-1 (rhOP-1) induces complete healing. To investigate the ability of rhOP-1 to accelerate normal physiologic fracture healing, an experimental study was performed. In 40 adult female goats a closed tibial fracture was made, stabilized with an external fixator, and treated as follows: (1) no injection; (2) injection of 1 mg rhOP-1 dissolved in aqueous buffer; (3) injection of collagen matrix; and (4) injection of 1 mg rhOP-1 bound to collagen matrix. The test substances were injected in the fracture gap under fluoroscopic control. At 2 and 4 weeks, fracture healing was evaluated with radiographs, three-dimensional computed tomography (CT), dual-energy X-ray absorptiometry, biomechanical tests, and histology. At 2 weeks, callus diameter, callus volume, and bone mineral content at the fracture site were significantly increased in both rhOP-1 groups compared with the no-injection group. As signs of accelerated callus maturation, bending and torsional stiffness were higher and bony bridging of the fracture gap was observed more often in the group with rhOP-1 dissolved in aqueous buffer than in uninjected fractures. Treatment with rhOP-1 plus collagen matrix did not result in improved biomechanical properties or bony bridging of the fracture gap at 2 weeks. At 4 weeks there were no differences between groups, except for a larger callus volume in the rhOP-1 plus collagen matrix group compared with the control groups. All fractures showed an advanced stage of healing at 4 weeks. In conclusion, the healing of a closed fracture in a goat model can be accelerated by a single local administration of rhOP-1. The use of a carrier material does not seem to be crucial in this application of rhOP-1.

Primary resective shortening followed by distraction osteogenesis for limb reconstruction: a comparison with simple lengthening.

Resective distraction osteogenesis is a new approach to treat segmental diaphyseal bone defects by primary limb shortening and secondary distraction osteogenesis from the same site. A rabbit model was introduced to compare the bone-regeneration characteristics of this technique with those of simple lengthening procedures. Twenty-four skeletally mature New Zealand White rabbits were divided into two equal groups. In the test group, limbs were lengthened after a 10-mm segmental diaphyseal bone resection and limb shortening. In the control group, a simple subperiosteal osteotomy for limb lengthening was performed without resection. New bone formation was evaluated mechanically, radiologically, histomorphometrically, and densitometrically. Bone bridging occurred in all animals. Normalized mechanical values for the newly reconstructed tibiae demonstrated similar torsional stiffness (71+/-3.3 compared with 71+/-8.2%; p = 0.95) and strength (64+/-5.3 compared with 68+/-7.3%; p = 0.66) in the two groups. The average normalized callus diameter was significantly greater in the test group than in the control group (p < 0.01). The remodeling index calculated from densitometry, however, showed a significantly less progressed stage of remodeling in the test group (p < 0.05). Histomorphometric analysis of the callus center supported this finding, showing significantly lower values for trabecular thickness (p < 0.05) and total bone volume (p < 0.01) in the test group. The results demonstrated the possibility of new bone formation after resection and monofocal shortening. This suggests a new therapeutic option to treat diaphyseal segmental bone defects.

Changes of callus diameter during axial loading and after fixator removal in leg lengthening.

We retrospectively reviewed nine tibial lengthenings in seven achondroplastic patients. The callotasis method was used, and a unilateral type lengthener, either the Dynamic Axial Fixator (Orthofix, Italy; eight legs) or the High Functional Fixator (Matsumoto Co., Japan; one leg), was applied. The distracted length averaged 14.6 (range 10-18) cm. The minimum diameter of the callus was measured using a ruler on anteroposterior and lateral radiographs. The callus diameter ratio (%) was calculated as the callus diameter divided by the original diaphysis diameter. For periods during axial loading and after removal of the fixator in each patient, a single regression line was drawn on the callus diameter ratio data using the least squares method, and the diameter change rate (%/day) was evaluated by inclination of this line. The diameter change rates during axial loading were negative in six legs, but those after fixator removal were positive in all legs, and the latter were significantly greater than the former. The diameter change rates after fixator removal on the anteroposterior radiographs were negatively correlated with the callus diameter ratio at the time of fixator removal (r = 0.84, P = 0.0008). Simple axial loading may not be a sufficient mechanial environment for restoration of the physiological shape, and it is important to be aware that we cannot expect the callus diameter to increase by this means alone.

Callus response to micromovement during elongation in the rabbit.

The purpose of this investigation was to determine whether induced micromovement during the elongation period could improve the consolidation of diaphyseal elongation obtained by callus distraction. Two series of paired rabbit hindlimbs were studied. The surgical procedure and the waiting period were identical. During elongation, one hindlimb was stimulated, and the other was the control. The consolidation period was 2 days. Reproducible tibial osteotomy and lengthening of the two tibiae was confirmed radiographically. The mineralized callus was quantified by dual-beam x-ray absorptiometry. The callus diameters were measured. Bones were axially compressed to failure. Callus volume, mineral quantity, mineral density, and resistance to failure were not different on the stimulated side compared with the unstimulated side, so micromovement applied during elongation had no effect on bone consolidation. For all tibiae, resistance to failure of the callus was significantly correlated to callus volume, to callus mineral content, and to callus mineral density.