Luxaciones periastragalinas: análisis de una serie de casos. Nuestro algoritmo de tratamiento urgente / Subtalar dislocations: Analysis of a case series. Our urgent treatment algorithm

Introducción y objetivos: Las luxaciones periastragalinas son una entidad poco frecuente (<1%) de las lesiones traumáticas del pie. Se produce una pérdida de relación anatómica entre astrágalo, calcáneo y escafoides. Solo hay pequeñas series publicadas. Material y métodos: Presentamos los casos de una serie de pacientes (N=13) con luxaciones periastragalinas en los que se realizó un análisis descriptivo de las principales variables epidemiológicas, clínicas y radiológicas, a partir de las cuales se propone un algoritmo de tratamiento urgente. Se excluyeron los casos con fracturas del cuello del astrágalo, cuerpo del calcáneo o fracturas-luxación de Chopart aisladas. Resultados: La mediana de edad fue de 48,5 años con predominio del sexo masculino (69,23%). Cinco pacientes sufrieron caídas-entorsis sobre el tobillo y los 8 restantes mecanismos de alta energía. Las luxaciones mediales (9) predominaron sobre las laterales (4). Además, 4 pacientes presentaron luxaciones abiertas, 2 de ellas tipo IIIC que precisaron amputación. Se solicitó TC en un 76,93% de pacientes y 10 presentaron lesiones óseas asociadas del pie. Se realizó cirugía mediante reducción abierta en todas las lesiones abiertas y en un caso en el que fracasó la reducción cerrada. Cinco pacientes precisaron fijador externo tipo delta. Se objetivó esclerosis subcondral articular en un 77,77% de los casos; si bien solo uno precisó artrodesis subtalar. Conclusiones: Las luxaciones periastragalinas son una urgencia traumatológica y precisan una reducción precoz e inmovilización posterior. La fijación externa temporal transarticular es una buena opción de inmovilización en luxaciones abiertas. Son lesiones graves con alta probabilidad de artrosis precoz.(AU)

Introduction and objectives: Subtalar dislocations are a rare entity (<1%) in traumatic foot injuries. There is a loss of anatomical relationship between the talus, calcaneus and scaphoid. There are only small-published series. Material and methods: We present a series of patients (N=13) with subtalar dislocations in which a descriptive analysis of the main epidemiological, clinical and radiological variables was carried out, from which an urgent treatment algorithm is proposed. Cases with fractures of the neck of the talus, body of the calcaneus, or isolated Chopart fracture-dislocations were excluded. Results: The median age was 48.5 years with a predominance of males (69.23%). Five patients suffered falls or sprained ankles and the other eight suffered high-energy mechanisms. The medial dislocations (nine) predominated over the lateral ones (four). In addition, four patients presented open dislocations, two of them type IIIC that required amputation. CT scans were requested in 76.93% of patients and 10 presented associated bone lesions of the foot. Open reduction surgery was performed in all open lesions and in one case in which closed reduction failed. Five patients required a delta-type external fixator. Subchondral articular sclerosis was observed in 77.77% of cases; although only one required subtalar arthrodesis. Conclusions: Subtalar dislocations are a traumatic emergency that require early reduction and subsequent immobilization. Transarticular temporary external fixation is a good immobilization option in open dislocations. They are serious lesions with a high probability of early osteoarthritis.(AU)

[Translated article] Subtalar dislocations: Analysis of a case series. Our urgent treatment algorithm / Luxaciones periastragalinas: análisis de una serie de casos. Nuestro algoritmo de tratamiento urgente

Introducción y objetivos: Las luxaciones periastragalinas son una entidad poco frecuente (<1%) de las lesiones traumáticas del pie. Se produce una pérdida de relación anatómica entre astrágalo, calcáneo y escafoides. Solo hay pequeñas series publicadas. Material y métodos: Presentamos los casos de una serie de pacientes (N=13) con luxaciones periastragalinas en los que se realizó un análisis descriptivo de las principales variables epidemiológicas, clínicas y radiológicas, a partir de las cuales se propone un algoritmo de tratamiento urgente. Se excluyeron los casos con fracturas del cuello del astrágalo, cuerpo del calcáneo o fracturas-luxación de Chopart aisladas. Resultados: La mediana de edad fue de 48,5 años con predominio del sexo masculino (69,23%). Cinco pacientes sufrieron caídas-entorsis sobre el tobillo y los 8 restantes mecanismos de alta energía. Las luxaciones mediales (9) predominaron sobre las laterales (4). Además, 4 pacientes presentaron luxaciones abiertas, 2 de ellas tipo IIIC que precisaron amputación. Se solicitó TC en un 76,93% de pacientes y 10 presentaron lesiones óseas asociadas del pie. Se realizó cirugía mediante reducción abierta en todas las lesiones abiertas y en un caso en el que fracasó la reducción cerrada. Cinco pacientes precisaron fijador externo tipo delta. Se objetivó esclerosis subcondral articular en un 77,77% de los casos; si bien solo uno precisó artrodesis subtalar. Conclusiones: Las luxaciones periastragalinas son una urgencia traumatológica y precisan una reducción precoz e inmovilización posterior. La fijación externa temporal transarticular es una buena opción de inmovilización en luxaciones abiertas. Son lesiones graves con alta probabilidad de artrosis precoz.(AU)

Introduction and objectives: Subtalar dislocations are a rare entity (<1%) in traumatic foot injuries. There is a loss of anatomical relationship between the talus, calcaneus and scaphoid. There are only small-published series. Material and methods: We present a series of patients (N=13) with subtalar dislocations in which a descriptive analysis of the main epidemiological, clinical and radiological variables was carried out, from which an urgent treatment algorithm is proposed. Cases with fractures of the neck of the talus, body of the calcaneus, or isolated Chopart fracture-dislocations were excluded. Results: The median age was 48.5 years with a predominance of males (69.23%). Five patients suffered falls or sprained ankles and the other eight suffered high-energy mechanisms. The medial dislocations (nine) predominated over the lateral ones (four). In addition, four patients presented open dislocations, two of them type IIIC that required amputation. CT scans were requested in 76.93% of patients and 10 presented associated bone lesions of the foot. Open reduction surgery was performed in all open lesions and in one case in which closed reduction failed. Five patients required a delta-type external fixator. Subchondral articular sclerosis was observed in 77.77% of cases; although only one required subtalar arthrodesis. Conclusions: Subtalar dislocations are a traumatic emergency that require early reduction and subsequent immobilization. Transarticular temporary external fixation is a good immobilization option in open dislocations. They are serious lesions with a high probability of early osteoarthritis.(AU)

[Translated article] SCIWORA in children. A rare clinical entity: Ambispective study / SCIWORA. Una rara entidad clínica en la población pediátrica. Estudio ambispectivo

Introducción y objetivos: Las luxaciones periastragalinas son una entidad poco frecuente (<1%) de las lesiones traumáticas del pie. Se produce una pérdida de relación anatómica entre astrágalo, calcáneo y escafoides. Solo hay pequeñas series publicadas. Material y métodos: Presentamos los casos de una serie de pacientes (N=13) con luxaciones periastragalinas en los que se realizó un análisis descriptivo de las principales variables epidemiológicas, clínicas y radiológicas, a partir de las cuales se propone un algoritmo de tratamiento urgente. Se excluyeron los casos con fracturas del cuello del astrágalo, cuerpo del calcáneo o fracturas-luxación de Chopart aisladas. Resultados: La mediana de edad fue de 48,5 años con predominio del sexo masculino (69,23%). Cinco pacientes sufrieron caídas-entorsis sobre el tobillo y los 8 restantes mecanismos de alta energía. Las luxaciones mediales (9) predominaron sobre las laterales (4). Además, 4 pacientes presentaron luxaciones abiertas, 2 de ellas tipo IIIC que precisaron amputación. Se solicitó TC en un 76,93% de pacientes y 10 presentaron lesiones óseas asociadas del pie. Se realizó cirugía mediante reducción abierta en todas las lesiones abiertas y en un caso en el que fracasó la reducción cerrada. Cinco pacientes precisaron fijador externo tipo delta. Se objetivó esclerosis subcondral articular en un 77,77% de los casos; si bien solo uno precisó artrodesis subtalar. Conclusiones: Las luxaciones periastragalinas son una urgencia traumatológica y precisan una reducción precoz e inmovilización posterior. La fijación externa temporal transarticular es una buena opción de inmovilización en luxaciones abiertas. Son lesiones graves con alta probabilidad de artrosis precoz.(AU)

Introduction and objectives: Subtalar dislocations are a rare entity (<1%) in traumatic foot injuries. There is a loss of anatomical relationship between the talus, calcaneus and scaphoid. There are only small-published series. Material and methods: We present a series of patients (N=13) with subtalar dislocations in which a descriptive analysis of the main epidemiological, clinical and radiological variables was carried out, from which an urgent treatment algorithm is proposed. Cases with fractures of the neck of the talus, body of the calcaneus, or isolated Chopart fracture-dislocations were excluded. Results: The median age was 48.5 years with a predominance of males (69.23%). Five patients suffered falls or sprained ankles and the other eight suffered high-energy mechanisms. The medial dislocations (nine) predominated over the lateral ones (four). In addition, four patients presented open dislocations, two of them type IIIC that required amputation. CT scans were requested in 76.93% of patients and 10 presented associated bone lesions of the foot. Open reduction surgery was performed in all open lesions and in one case in which closed reduction failed. Five patients required a delta-type external fixator. Subchondral articular sclerosis was observed in 77.77% of cases; although only one required subtalar arthrodesis. Conclusions: Subtalar dislocations are a traumatic emergency that require early reduction and subsequent immobilization. Transarticular temporary external fixation is a good immobilization option in open dislocations. They are serious lesions with a high probability of early osteoarthritis.(AU)

[Translated article] Subtalar dislocations: Analysis of a case series. Our urgent treatment algorithm.

INTRODUCTION AND OBJECTIVES: Subtalar dislocations are a rare entity (<1%) in traumatic foot injuries. There is a loss of anatomical relationship between the talus, calcaneus and scaphoid. There are only small-published series. MATERIAL AND METHODS: We present a series of patients (N=13) with subtalar dislocations in which a descriptive analysis of the main epidemiological, clinical and radiological variables was carried out, from which an urgent treatment algorithm is proposed. Cases with fractures of the neck of the talus, body of the calcaneus, or isolated Chopart fracture-dislocations were excluded. RESULTS: The median age was 48.5 years with a predominance of males (69.23%). Five patients suffered falls or sprained ankles and the other eight suffered high-energy mechanisms. The medial dislocations (nine) predominated over the lateral ones (four). In addition, four patients presented open dislocations, two of them type IIIC that required amputation. CT scans were requested in 76.93% of patients and 10 presented associated bone lesions of the foot. Open reduction surgery was performed in all open lesions and in one case in which closed reduction failed. Five patients required a delta-type external fixator. Subchondral articular sclerosis was observed in 77.77% of cases; although only one required subtalar arthrodesis. CONCLUSIONS: Subtalar dislocations are a traumatic emergency that require early reduction and subsequent immobilisation. Transarticular temporary external fixation is a good immobilisation option in open dislocations. They are serious lesions with a high probability of early osteoarthritis.

Subtalar dislocations: Analysis of a case series. Our urgent treatment algorithm. / Luxaciones periastragalinas: análisis de una serie de casos. Nuestro algoritmo de tratamiento urgente.

INTRODUCTION AND OBJECTIVES: Subtalar dislocations are a rare entity (<1%) in traumatic foot injuries. There is a loss of anatomical relationship between the talus, calcaneus and scaphoid. There are only small-published series. MATERIAL AND METHODS: We present a series of patients (N=13) with subtalar dislocations in which a descriptive analysis of the main epidemiological, clinical and radiological variables was carried out, from which an urgent treatment algorithm is proposed. Cases with fractures of the neck of the talus, body of the calcaneus, or isolated Chopart fracture-dislocations were excluded. RESULTS: The median age was 48.5 years with a predominance of males (69.23%). Five patients suffered falls or sprained ankles and the other eight suffered high-energy mechanisms. The medial dislocations (nine) predominated over the lateral ones (four). In addition, four patients presented open dislocations, two of them type IIIC that required amputation. CT scans were requested in 76.93% of patients and 10 presented associated bone lesions of the foot. Open reduction surgery was performed in all open lesions and in one case in which closed reduction failed. Five patients required a delta-type external fixator. Subchondral articular sclerosis was observed in 77.77% of cases; although only one required subtalar arthrodesis. CONCLUSIONS: Subtalar dislocations are a traumatic emergency that require early reduction and subsequent immobilization. Transarticular temporary external fixation is a good immobilization option in open dislocations. They are serious lesions with a high probability of early osteoarthritis.

Ipsilateral proximal and shaft femoral fractures: Results of two treatment strategies. / [Artículo traducido] Fracturas ipsilaterales proximales y diafisarias del fémur: resultados de dos estrategias de tratamiento.

INTRODUCTION: Ipsilateral proximal and shaft femoral fractures typically occur in young adults after high-energy trauma. No consensus exists regarding the optimal internal fixation device or surgical strategy for these complex fractures. Our main objective is to identify differences on outcomes and complications between patients treated with one or combined implants. MATERIAL AND METHOD: This is a single-center retrospective cohort study in patients with associated fractures of the proximal (31 AO) and shaft femur (32 AO). We divided the patients into two groups according to the use of single (GroupI) or combined implants (GroupII). Demographic, clinical, radiological, surgical data and development of complications were collected. RESULTS: We identified 28 patients (19 men and 9 women) with an average age of 43years. We used an anterograde femoral nail in GroupI (17 patients) and a retrograde femoral nail or a plate associated with hip lag screws or sliding hip screw in GroupII (11 patients). Patients were followed up for 26.28 (9.12-62.88) months. Osteonecrosis of the femoral head, osteoarthritis, infection or nonunion was found in 9 patients (32%). No significant differences (P=.70) were found in complications between two groups or between definitive surgical fixation before or after the first 24h. CONCLUSIONS: No differences in the development of complications or timing of definitive fixation were found between the use of one or combined implants in ipsilateral proximal femur and shaft fractures. Regardless of the implant chosen, an appropriate osteosynthesis technique is crucial, even so high complication rates are expected.

Ipsilateral proximal and shaft femoral fractures: Results of two treatment strategies.

INTRODUCTION: Ipsilateral proximal and shaft femoral fractures typically occur in young adults after high-energy trauma. No consensus exists regarding the optimal internal fixation device or surgical strategy for these complex fractures. Our main objective is to identify differences on outcomes and complications between patients treated with one or combined implants. MATERIAL AND METHOD: This is a single-center retrospective cohort study in patients with associated fractures of the proximal (31 AO) and shaft femur (32 AO). We divided the patients into two groups according to the use of single (Group I) or combined implants (Group II). Demographic, clinical, radiological, surgical data and development of complications were collected. RESULTS: We identified 28 patients (19 men and 9 women) with an average age of 43 years. We used an anterograde femoral nail in group I (17 patients) and a retrograde femoral nail or a plate associated with hip lag screws or sliding hip screw in Group II (11 patients). Patients were followed up for 26.28 (9.12-62.88) months. Osteonecrosis of the femoral head, osteoarthritis, infection or nonunion was found in 9 patients (32%). No significant differences (p 0.70) were found in complications between two groups or between definitive surgical fixation before or after the first 24h. CONCLUSIONS: No differences in the development of complications or timing of definitive fixation were found between the use of one or combined implants in ipsilateral proximal femur and shaft fractures. Regardless of the implant chosen, an appropriate osteosynthesis technique is crucial, even so high complication rates are expected. LEVEL OF EVIDENCE: IV. Grade of Recommendation: C.

[Femur fracture in a patient with dog-leg deformity secondary to arthrogryposis. Description of a unique osteosynthesis method]. / Fractura de fémur en un paciente con deformidad «dog-leg¼ secundaria a artrogriposis. Descripción de un método único de osteosíntesis.

The concept of arthrogryposis encompasses several conditions that share the presence of multiple congenital contractures. The knee is frequently involved and is an important cause of morbidity in these patients. Flexion contractures of the knee are the most common ones and have a worse prognosis than extension contractures. Different approaches are available to treat flexion contractures of the knee. Distal femoral extension osteotomy effectively corrects fixed flexion, but may lead to residual deformity. This iatrogenic deformity disrupts the anterior convexity of the femoral shaft and leads to serious problems in the subsequent management of orthopedic conditions. This is a case report of a patient with arthrogryposis and a femur deformity who sustained a supracondylar fracture. Managing the fracture was challenging due to a disruption in the normal architecture of the femur. This is a description of the osteosynthesis approach used to treat the fracture and the patients pre-existing deformity.

El concepto «artrogriposis¼ agrupa varias enfermedades cuya característica común es la presencia de múltiples contracturas congénitas. La rodilla se afecta con frecuencia y es causa importante de morbilidad en estos pacientes. Las contracturas en flexión de la rodilla son más comunes y tienen peor pronóstico que las contracturas en extensión. Existen diferentes técnicas de tratamiento para la contractura en flexión de la rodilla; la osteotomía distal de extensión femoral corrige eficazmente la flexión fija, pero puede dar lugar a una deformidad residual. Esta deformidad iatrogénica altera la convexidad anterior de la diáfisis femoral y conlleva problemas graves en el manejo posterior de patología ortopédica. Se presenta el caso de una paciente con artrogriposis y una deformidad en fémur con una fractura en la región supracondílea. El manejo de la fractura fue dificultoso por la presencia de una distorsión de la arquitectura normal del fémur. En nuestro trabajo se describe el método de osteosíntesis utilizado para hacer frente a la fractura y a la deformidad previa de la paciente.

Fractura de fémur en un paciente con deformidad « dog-leg ¼ secundaria a artrogriposis. Descripción de un método único de osteosíntesis / Femur fracture in a patient with dog-leg deformity secondary to arthrogryposis. Description of a unique osteosynthesis method

Resumen: El concepto «artrogriposis¼ agrupa varias enfermedades cuya característica común es la presencia de múltiples contracturas congénitas. La rodilla se afecta con frecuencia y es causa importante de morbilidad en estos pacientes. Las contracturas en flexión de la rodilla son más comunes y tienen peor pronóstico que las contracturas en extensión. Existen diferentes técnicas de tratamiento para la contractura en flexión de la rodilla; la osteotomía distal de extensión femoral corrige eficazmente la flexión fija, pero puede dar lugar a una deformidad residual. Esta deformidad iatrogénica altera la convexidad anterior de la diáfisis femoral y conlleva problemas graves en el manejo posterior de patología ortopédica. Se presenta el caso de una paciente con artrogriposis y una deformidad en fémur con una fractura en la región supracondílea. El manejo de la fractura fue dificultoso por la presencia de una distorsión de la arquitectura normal del fémur. En nuestro trabajo se describe el método de osteosíntesis utilizado para hacer frente a la fractura y a la deformidad previa de la paciente.

Abstract: The concept of arthrogryposis encompasses several conditions that share the presence of multiple congenital contractures. The knee is frequently involved and is an important cause of morbidity in these patients. Flexion contractures of the knee are the most common ones and have a worse prognosis than extension contractures. Different approaches are available to treat flexion contractures of the knee. Distal femoral extension osteotomy effectively corrects fixed flexion, but may lead to residual deformity. This iatrogenic deformity disrupts the anterior convexity of the femoral shaft and leads to serious problems in the subsequent management of orthopedic conditions. This is a case report of a patient with arthrogryposis and a femur deformity who sustained a supracondylar fracture. Managing the fracture was challenging due to a disruption in the normal architecture of the femur. This is a description of the osteosynthesis approach used to treat the fracture and the patient's pre-existing deformity.

Enhancement of osteoinduction by vitamin D metabolites in rachitic host rats.

Diaphyseal bone from normal Sprague-Dawley rats was delipidated in chloroform-methanol and demineralized in 0.6 N HCl at 4 degrees C. The bones were then implanted for 7-28 days into rats made rachitic by a low-phosphate, vitamin D-deficient diet (VDP-) for 3 weeks. Bones from VDP- and normal rats were also implanted into normal hosts. When normal rats were used as the host environment, a consistent sequence of cartilage induction and bone formation was observed. Demineralized rachitic bone (RB) implanted into normal host rats resulted in cartilage and bone induction similar to that seen for normal bone (NB) implants. Transmission electron microscopy of RB in normal hosts revealed morphologically normal chondrocytes and cartilage matrix with normal mineralization. In contrast, implantation of NB in VDP- hosts resulted in delayed chondrogenesis and lack of calcification. Furthermore, similar results were observed when RB was implanted into VDP- hosts. Treatment of VDP- hosts with either 1 alpha-hydroxyvitamin D3 or 24,25-dihydroxyvitamin D3 did not accelerate the sequential appearance of precartilage or cartilage. However, 24,25-(OH)2D3 administered alone or in combination with 1 alpha-OHD3 significantly increased the amount of calcified cartilage observed at 2 weeks postimplantation compared to implants from either untreated VDP-hosts or those treated only with 1 alpha-OHD3. New bone formation was observed at 4 weeks postimplantation in all vitamin D-treated groups as determined by von Kossa staining or direct electron microscope examination. There was no apparent difference in the quantitative or qualitative bone formed within the various vitamin D-treated groups. Serum calcium and phosphorus levels were lower and alkaline phosphatase levels were higher in VDP- hosts compared with normal animals or those treated with vitamin D metabolites. The results of this study show a reduction in the capacity of progenitor cells in VDP- rat hosts to respond to osteoinductive factor(s). This impaired response appears to be corrected by vitamin D metabolites.

Amelioration of lapine osteoarthritis by treatment with glycosaminoglycan-peptide association complex (Rumalon).

The chondroprotective potential of glycosaminoglycan-peptide association complex (GP-C) was examined in the medial meniscectomy model of lapine osteoarthritis (OA). Prophylactic treatment with increasing doses of intramuscular GP-C (0.05-0.5 ml/kg) caused a significant reduction in OA lesion area and histologic scores, and the effect on disease activity appeared to be dose related. The DNA and uronic acid contents of OA tissue were unaffected by prophylactic treatment with GP-C. However, levels of hydroxyproline in OA cartilage increased to near control levels with prophylactic treatment. Cartilage levels of active and total metalloproteinases that digest proteoglycans were elevated in rabbits with OA; prophylactic treatment with low-dose GP-C (0.05 ml/kg) produced a significant reduction in active, but not total, enzyme. Cartilage levels of tissue inhibitor of metalloproteinases in animals with OA were comparable with control levels, but rose with increasing doses of GP-C. We also investigated GP-C as a therapeutic treatment in animals that had already developed OA lesions. Carbon black retention and histologic score returned to near-normal after therapeutic treatment with GP-C. Uronic acid and hydroxyproline levels were decreased in OA cartilage. Therapeutic treatment with GP-C had no statistically significant effect on uronic acid levels, but was associated with increased hydroxyproline content in the cartilage. The changes in metalloproteinase and metalloproteinase inhibitor were similar to those found in the studies of prophylactic treatment. The findings in this animal model may help explain some of the beneficial effects of GP-C in human OA.

EHDP-induced rachitic syndrome in rats is not reversed by vitamin D metabolites.

To examine whether either of the two known active vitamin D metabolites 1,25(OH)2D3 or 24,25(OH)2D3 could reverse the mineralization defect induced by 1-hydroxyethylidene-1,1-bis phosphonate (EHDP), a model of EHDP-induced rickets was used. Rats at the age of 31 days were injected for 10 consecutive days with EHDP (10 mg/kg). Other littermates were treated with a combination of EHDP and either 1,25(OH)2D3 or 24,25(OH)2D3 or were treated following 10 days of EHDP, with either of the vitamin D metabolites for an additional 72 hr. Samples of cartilage fluid (Cfl) and of blood were removed prior to sacrifice for biochemical studies of some parameters of calcification. These parameters were correlated with the results of light and electron microscope studies of growth plate cartilage and bone. EHDP-treated rats revealed signs of typical rickets, manifested by widened growth plates and impaired bone mineralization. Transmission electron microscope (TEM) examination revealed matrix vesicles distributed throughout the growth plate; however, there appeared to be an arrest of the spread of the crystals at the provisional zone of calcification. Treatment with either 1,25(OH)2D3 or 24,25(OH)2D3 failed to reverse the rachitic condition of the animals. Serum calcium blood levels were elevated in the 1,25(OH)2D3 and EHDP-treated group. 1,25(OH)2D3 and 24,25(OH)2/D3 further increased the already elevated serum alkaline phosphatase levels observed in EHDP rats, although the increase observed with 1,25(OH)2D3 was not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of vitamin D metabolites on healing of low phosphate, vitamin D-deficient induced rickets in rats.

A model of low-phosphate, vitamin D-deficient rachitic rats was used to compare the effects of 1 alpha(OH)D3, 1,25(OH)2D3, and 24,25(OH)2D3 on cartilage and bone. The rats were maintained for 3 weeks on a high-calcium, low-phosphate, vitamin D-deficient diet, during which period they developed severe rickets. The rachitic rats were injected for 2 or 3 consecutive days with a physiologic dose of either metabolite. Other littermates were given a single dose of 50,000 IU of cholecalciferol in combination with a normal diet. Samples of cartilage fluid (Cfl) and of blood were removed prior to sacrifice for biochemical studies of some parameters of calcification. These parameters were correlated with the results of light and electron microscopic studies of the growth plate cartilage and bone. Treatment with 1 alpha (OH)D3 or with 1,25(OH)2D3, in spite of increasing Ca and P levels in the Cfl, induced only partial healing of the rickets. In contrast, 24,25(OH)2D3 or vitamin D with a normal diet resulted in complete morphologic and biochemical healing of the rickets. Transmission electron microscopic (TEM) studies have shown partial mineralization of the wide hypertrophic zone of the growth plate following treatment with 1 alpha(OH)D3 or with 1,25(OH)2D3. Mineralization was more complete with 24,25(OH)2D3 treatment. The results of this study emphasize the importance of 24,25(OH)2D3 for normal endochondral bone formation and mineralization.