Osteoarticular infections at a pediatric emergency core hospital in Japan.

OBJECTIVES: Osteomyelitis (OM) and septic arthritis (SA) in childhood might cause complications, sequelae, or even death if diagnosis and treatment are delayed. Here, we examined the outcomes of OM/SA at a pediatric emergency core hospital in Japan. METHODS: This was a single-center, retrospective, observational cohort study at a pediatric emergency core hospital in Japan. Pediatric outpatients who underwent magnetic resonance imaging at the hospital in the period 2012?2020 were recruited. Primary outcomes were sequelae, recurrent symptoms, chronicity, and death. RESULTS: Fifteen OM/SA patients (9 OM, 4 SA, 2 OM+SA) were recruited. The identified major pathogens included methicillin-susceptible Staphylococcus aureus (40.0 %, n=6) and methicillin-resistant S. aureus (13.3 %, n=2). Mean time from onset to first hospital visit, hospitalization, and initiation of effective antibiotics was 2 days, 3.9?±?1.8 days, and 4.9±2.2 days, respectively. All OM/SA patients recovered without complications or sequelae. CONCLUSIONS: In this study, all patients with OM/SA showed a good prognosis. Despite the small sample size, this pilot study suggests that the pediatric emergency core system in Japan provides early treatment and a good prognosis for patients diagnosed with OM/SA. J. Med. Invest. 70 : 236-240, February, 2023.

An anterolateral dislocated monteggia lesion with plastic lateral bowing of the ulna associated with ipsilateral epiphyseal fracture of the distal radius: a case report with 4 years of follow-up.

We encountered a rare presentation of anterolateral dislocation of the radial head with plastic lateral bowing of the ulna associated with ipsilateral epiphyseal fracture of the distal radius in a child. The patient was treated surgically and reached skeletal maturity 4 years later with no functional or growth deficiency.

Open pelvic fracture with bilateral common iliac arteriovenous injury successfully treated with hemicorporectomy following damage control interventional radiology in a hybrid emergency room.

BACKGROUND: In severe pelvic fracture, keys of successful treatment are early hemostasis and timely definitive care. We present a case in which the patient was treated by fast and reliable hemostasis and subsequent comprehensive hemicorporectomy. CASE PRESENTATION: We describe the case of a 47-year-old man with severe pelvic trauma. He received early intervention by the helicopter emergency medical service, which included rapid transarterial embolization as damage control interventional radiology in the hybrid emergency room, and hemicorporectomy as a multidisciplinary approach. This series of treatments saved his life and he was discharged home. CONCLUSION: Hemicorporectomy could be the only treatment option in patients with severe pelvic injury when there are no reconstruction options. To the best of our knowledge, this is the first case of severe open pelvic fractures with blood vessel damage, successfully treated by initial hemostasis using the helicopter emergency medical service, hybrid emergency room system, and following hemicorporectomy as a definitive care.

Insufficient Postoperative Rehabilitation in Patients with Both Proximal Femoral Fracture and Antecedent Mental Illness.

INTRODUCTION: Though a combination of proximal femoral fracture and mental illness is likely, the management of this combination is not well established. The aim of this study was to clarify the current disposition of acute care and rehabilitation for patients with this combination of conditions at our institution. METHODS: We retrospectively analyzed the records of 192 patients hospitalized in the psychiatric ward who present with a proximal femoral fracture and an antecedent mental illness. We investigated walking ability prior to injury and after surgery, at discharge from our institution, using the Functional Independence Measure (FIM) score. RESULTS: Although patients in the psychiatric ward demonstrated postoperative hospital stays approximately 10 days longer than those in the orthopedic ward, more than half of the patients in the psychiatric ward were discharged from our institution with a functional level of complete dependence for walking ability. In addition, nearly 90% of the patients studied were transferred to a psychiatric hospital where no physical therapy or rehabilitation was provided to the inpatients. CONCLUSIONS: At our institution, patients with proximal femoral fracture and antecedent mental illness tended to be discharged with complete dependence in walking ability, often to a psychiatric hospital without physical therapy or rehabilitation. We hope this paper will draw attention to the need for rehabilitation in these patients.

Gustilo Type III Open and Comminuted Tibial Fractures Managed by Simultaneous Combination of a Free Latissimus Dorsi Muscle Flap and Ilizarov External Fixation: A Case Report.

CASE: A 70-year-old woman who sustained Gustilo type III open and comminuted tibial fractures presented with extensive soft-tissue defect. Definitive surgery was performed using a free latissimus dorsi muscle flap for the extensive soft-tissue defect and Ilizarov external fixation (IEF) to stabilize the fractures and arthrodese the ankle. Ankle arthrodesis was accomplished by the wires penetrating the implanted muscle flap. CONCLUSION: The combined free flap and IEF management protocol described in this report was effective in achieving early weight-bearing and prompt bone healing in an elderly patient with poor bone quality and extensive open and comminuted fractures.

Vertebral Lateral Notch as Optimal Entry Point for Lateral Mass Screwing Using Modified Roy-Camille Technique.

STUDY DESIGN: Retrospective study of 37 consecutive female patients with cervical spondylotic myelopathy who underwent reconstructed computed tomography (CT) scanning of the cervical spine. PURPOSE: The purpose of this study was to investigate whether the vertebral lateral notch of the cervical spine is an effective landmark to determine the entry point for lateral mass screwing. A modified Roy-Camille technique was used to determine the entry point associated with the lateral notch of the cervical spine. OVERVIEW OF LITERATURE: The Roy-Camille technique has been a popular technique for the posterior fixation of the cervical spine. A problem with this technique is determining the entry point on the lateral mass via visual inspection, such as in cases with degenerative or destructive cervical facet joints. METHODS: Thirty-three female patients with cervical spondylotic myelopathy underwent reconstructed CT scanning of the cervical spine. Overall, 132 vertebrae from C3 to C6 were reviewed using reconstructed CT. The probable trajectory using a modified Roy-Camille technique was determined using reconstructed CT scans, and the optimal entry point was identified. Horizontal and vertical distances from the vertebral lateral notch were measured. RESULTS: The entry point determined using the modified Roy-Camille technique was significantly superior and medial compared with that determined using the conventional Roy-Camille technique. At C3 and C4 levels, the entry point using the modified technique was 1.4 mm below and 4.4 mm medial to the lateral notch, and at C5 and C6 levels, it was 2.3 mm below and 4.9 mm medial to the lateral notch. CONCLUSIONS: The vertebral lateral notch of the cervical spine was an effective landmark to determine the entry point for lateral mass screwing. The modified Roy-Camille technique proposed here may prevent surgical complications and poor outcomes.

Proteomic Analysis of Human Tendon and Ligament: Solubilization and Analysis of Insoluble Extracellular Matrix in Connective Tissues.

Connective tissues such as tendon, ligament and cartilage are mostly composed of extracellular matrix (ECM). These tissues are insoluble, mainly due to the highly cross-linked ECM proteins such as collagens. Difficulties obtaining suitable samples for mass spectrometric analysis render the application of modern proteomic technologies difficult. Complete solubilization of them would not only elucidate protein composition of normal tissues but also reveal pathophysiology of pathological tissues. Here we report complete solubilization of human Achilles tendon and yellow ligament, which is achieved by chemical digestion combined with successive protease treatment including elastase. The digestion mixture was subjected to liquid chromatography-mass spectrometry. The low specificity of elastase was overcome by accurate mass analysis achieved using FT-ICR-MS. In addition to the detailed proteome of both tissues, we also quantitatively determine the major protein composition of samples, by measuring peak area of some characteristic peptides detected in tissue samples and in purified proteins. As a result, differences between human Achilles tendon and yellow ligament were elucidated at molecular level.

Assessment of maximal insertional torque of cervical and thoracic screws during posterior spinal surgery.

STUDY DESIGN: Multicenter intraoperative biomechanical analysis. PURPOSE: This study aimed to assess the maximal insertional torque (MIT) of lateral mass screw (LMS) and pedicle screw (PS) in the cervical or thoracic vertebrae during surgery. METHODS: During posterior spinal fusion, cervical or thoracic multi-axial screws were placed at different cervical or thoracic levels and the MIT was recorded for each screw revolution using an analogue torque wrench. Screw number was as follows: 11 PS at C7, 134 LMS (C3-6) (Magerl technique, 70; Roy-Camille technique, 64), and 33 PS in the thoracic region. RESULTS: Average MIT values (cNm) were as follows: for PS (diameter: 3.5 mm) at C7, 45.3 ± 21.9 in men and 60.0 ± 20.1 in women (p=0.28); for Magerl screws, 69.0 ± 20.5 in men and 58.6 ± 15.7 in women (p=0.13); and for Roy-Camille screws, 51.0 ± 17.9 in men and 42.4 ± 15.9 in women (p=0.52). The average MIT for Magerl screws was significantly higher than that for Roy-Camille screws in men and women (both p<0.01). CONCLUSIONS: Intraoperative insertional torque could be a good indicator to evaluate the purchase and help guide decisions on screw type and insertion technique. Further postoperative assessments with sequential X-rays are needed to reveal the significance of MIT during posterior spinal fusion.

Hybrid technique of cortical bone trajectory and pedicle screwing for minimally invasive spine reconstruction surgery: a technical note.

The pedicle screw (PS) system is widely used for spinal reconstruction. Recently, screw insertion using the cortical bone trajectory (CBT) technique has been reported to provide increased holding strength of the vertebra, even in an osteoporotic spine. CBT is also beneficial due to its low invasiveness. We have been performing hybrid reconstruction with CBT at the cranial level and PS at the caudal level based on the concept of minimal invasiveness. We applied this hybrid technique to 6 cases of degenerative spondylolisthesis. Surgery was completed with a small skin incision of around 5-6 cm, which is shorter than that of the conventional PS procedure. The mean percent slippage before surgery was 19.8%, and this was reduced to 3.9% after surgery and almost maintained 3 months after surgery. Furthermore, no major surgical complications were observed. Here, we introduce the minimally invasive hybrid technique of CBT-PS. Surgeons should be aware of the procedure as an option for minimally invasive lumbar spine reconstructive surgery.

Long-term outcomes of lumbar posterior apophyseal end-plate lesions in children and adolescents.

BACKGROUND: A lesion of the lumbar posterior apophyseal end plate in children and adolescents causes symptoms similar to those associated with a herniated disc. However, the end-plate lesion and the herniated disc differ in terms of pathology. The purpose of this study was to clarify the long-term clinical and radiographic outcomes in children and adolescents who were treated either surgically or conservatively for a lumbar posterior apophyseal end-plate lesion. METHODS: We identified twenty-four consecutive patients who had been treated in the sports clinic of our hospital. The mean age at the first medical examination was 14.5 years. The mean follow-up time was 13.8 years. The mean age at the time of final follow-up was 28.4 years. All twenty-four patients had symptomatic low back pain with sciatica. All but two were active in sports. Sixteen patients were treated conservatively, and eight patients underwent surgical intervention. Skeletal maturity was evaluated on the basis of the appearance of the secondary ossification center of L3. RESULTS: The apophyseal stage ("A" stage), which was assigned when the secondary ossification center of the vertebral body was visible on radiographs, was seen most frequently. Both the surgically treated group and the conservatively treated group demonstrated progressive disc degeneration at the involved level. The average Roland-Morris Disability Questionnaire (RDQ) score was 1.3 for the patients treated conservatively and 1.8 for those treated surgically, a nonsignificant difference. One patient developed spinal stenosis after twelve years of conservative treatment. One patient treated surgically demonstrated severe lumbar instability. There were no significant associations between the magnetic resonance imaging (MRI) findings and RDQ scores. Histological examination of surgical specimens showed irregular alignment of the anulus fibrosus, with degenerative matrix and chondrocytes without a nucleus. CONCLUSIONS: The long-term outcome for patients with a posterior end-plate lesion is favorable, regardless of whether it is treated surgically or nonsurgically.

Hemorrhagic facet cyst in the lumbar spine causing contralateral leg symptoms: a case report.

Here we present a case of hemorrhagic lumbar facet cyst presenting with progressive radiculopathy only on the contralateral side. If a patient has previous back pain or neuropathy for several months and then suddenly deteriorates, hemorrhagic facet cyst of the lumbar spine should be part of the differential diagnosis. However, as in the present case, we should be aware that there is a possibility of a contralateral lesion.

Osseous erosion by herniated nucleus pulposus mimicking intraspinal tumor: a case report.

Erosion of spinal osseous structure, so-called scalloping, has been rarely reported associated with herniated nucleus pulposus (HNP). We report a rare case of HNP causing erosion of the spinal osseous structure (including lamina). The patient was an 81-year-old woman with 3-year history of low-back pain and left leg radiating pain. Muscle weakness of the left leg was also apparent. Computed tomography following myelography showed severe compression of the dural sac at the level of L3-L4; furthermore, erosion of the lamina, pedicle, and vertebral body was noted, indicating that the space-occupying mass was most probably a tumorous lesion. The mass also showed calcification inside. During the surgery, the mass was confirmed to be an HNP with calcification. Following resection, the pain disappeared. Surgeons should be aware of the possibility of scalloping of the vertebrae caused by HNP mimicking a tumorous lesion.

Adolescents with symptomatic laminolysis: report of two cases.

Retroisthmic cleft refers to a cleft in the lamina and is rarely reported. It was first described by Brocher, and later Wick et al. proposed the term "laminolysis" to describe the retroisthmic cleft by analogy with the nomenclature of the applied stress fracture of the pars interarticularis (spondylolysis) and the pedicle (pediculolysis). In this paper, we describe two adolescent sports players with symptomatic lumbar laminolysis. Both improved significantly after adequate conservative treatment. Knowledge of laminolysis in adolescent patients with low back pain is necessary to avoid overlooking it and late diagnosis. For correct diagnosis, multidetector three-dimensional computed tomography (CT) is suggested. In addition, magnetic resonance imaging (MRI) also allows detection of inflammation in the defects.

Incidence and etiology of lumbar spondylolysis: review of the literature.

BACKGROUND: Lumbar spondylolysis is a defect of the pars interarticularis known to occur as a stress fracture. Its incidence varies considerably depending on ethnicity, sex, and sports activity. However, there are few literature reviews describing its incidence in different ethnic groups or in people who engage in different sports. METHODS: We reviewed the most relevant articles on spondylolysis published in scientific journals. First, we focused on its incidence in various ethnic groups distributed by sex, the familial occurrence, and in patients with relevant diseases. Second, we focused on the incidence of spondylolysis in relation to the sports practiced by the patients. Although placing special emphasis on the incidence of lumbar spondylolysis in the general population in Japan, we also reviewed the Japanese and English literature to investigate its incidence among those who engage in different sports. RESULTS: The incidence of lumbar spondylolysis in the general Japanese population was 5.9%. Most studies report that the incidence in higher in male subjects than in female subjects. We found that Japanese rugby and judo players were prone to suffer lumbar spondylolysis, at an incidence of about 20%. However, the incidence for Japanese professional soccer and baseball players was much higher, at 30%, which was more than five times the incidence in the general Japanese population. CONCLUSIONS: The incidence of lumbar spondylolysis varies depending on ethnicity, sex, family history, relevant disease, and sports activity.

Diffuse arachnoid ossification and multiple arachnoid cysts presenting with progressive thoracic myelopathy.

An ossified arachnoid membrane combined with cystic formation is rarely reported as a cause of spinal cord compression. We report the case of a 60-year-old man who presented with diffuse ossification of the arachnoid membrane (arachnoid ossification) and multiple cystic changes (arachnoid cyst) at the thoracic and lumbar spine. The lesions were surgically removed and progressive deterioration was prevented, although no marked improvement of neurological symptoms was attained.

Treatment of dysplastic osteoarthritis with labral tear by Chiari pelvic osteotomy: outcomes after more than 10 years follow-up.

INTRODUCTION: The presence of a damaged labrum is one of many factors influencing the outcomes of Chiari pelvic osteotomy. However, there are few previous papers describing the long-term outcomes of Chiari pelvic osteotomy with labrectomy. The purpose of this study was to evaluate the long-term clinical and radiological outcomes of Chiari pelvic osteotomy for dysplastic hips with labral tears. We compared outcomes between labrectomy (+) and labrectomy (-) groups. PATIENTS AND METHODS: Chiari pelvic osteotomies were performed by one surgeon on 34 dysplastic hips with labral tears between 1983 and 1996, in which labrectomy was performed on 23 hips but not on 11 hips. Three patients undergoing labrectomy were lost to follow-up evaluation within 5 years after surgery. The average age of the remaining 31 patients was 35.5 years (range, 16-54 years). The clinical and radiographic surveillance averaged 16.0 years (range, 10-23.3 years). RESULTS: In all patients, pain disappeared after the operation. At the end of the study, 8 of the 31 patients displayed clinical deterioration. Progression of osteoarthritis (OA) was observed in 11 hips. Patients with poor results have not opted for revision surgery except for one patient. In the labrectomy (+) group, 10 of the 20 hips showed progression of OA and the clinical outcomes of 6 patients deteriorated. In the labrectomy (-) group, 1 of the 11 hips showed progression of OA and 2 patients deteriorated clinically. Radiological outcomes differed significantly between the two groups. CONCLUSION: Labrectomy accompanying Chiari pelvic osteotomy is an acceptable procedure for relieving pain caused by the damaged labrum, but the outcomes have a tendency to deteriorate after 10 or more years postoperatively.

Pathomechanism of loss of elasticity and hypertrophy of lumbar ligamentum flavum in elderly patients with lumbar spinal canal stenosis.

STUDY DESIGN: A histologic, biologic, and immunohistochemical assessment using human samples of lumbar ligamentum flavum. OBJECTIVE: To clarify the pathomechanism of loss of elasticity and hypertrophy of the lumbar ligamentum flavum (LF) in the elderly population. SUMMARY OF BACKGROUND DATA: The most common spinal disorder in elderly patients is lumbar spinal canal stenosis, causing low back and leg pain, and paresis. Canal narrowing, in part, results from hypertrophy of the LF. Although histologic and biologic literature on this topic is available, the pathomechanism of loss of elasticity and hypertrophy of the LF is still unknown. METHODS: One fetus, 5 young, and 5 elderly LF were obtained for histologic study. Hematoxylin and eosin, Alcian blue, Masson Trichrome, and Elastica Van Gieson stains were performed for each LF. Nine LF were collected and were used for biologic study of real time RT-PCR to quantitatively measure mRNA expression of Type I collagen and elastin in each LF. RESULTS: In the LF of the fetus, elastic fibers accounted for about 75% of the entire area. In the dural aspect of the LF in the young and elderly group, the ratio was also around 75%; however, the ratio of the dorsal aspect decreased with age. Almost half of the area showing loss of elastic fibers was shown to be converted to cartilaginous tissue producing Type II collagen and proteoglycan by Alcian blue and Type II collagen immunohistochemistry. The area, which did not stain black with EV nor blue with AB stain, was positively stained blue with T stain, indicating scarring. The area of the normal dural layer was 18.0 +/- 2.3 and 33.8 +/- 4.3 (mm2), for young and elderly group, respectively. Accordingly, it was 3.2 +/- 0.8 and 18.0 +/- 10.2 (mm2), for the dorsal abnormal layer. Elastin mRNA showed a relatively strong correlation (r = 0.44) with age; however, the slope was very gentle. Type I collagen mRNA showed a very strong correlation (r = 0.80) with age. The slope was steeper, and the value reached at 1000% (10-fold) around 65 years old when compared with the LF from younger patient. Elastin mRNA showed a weak correlation (r = 0.36) with thickness, and the slope was gentle. Type I collagen mRNA showed relatively strong correlation (r = 0.52) with thickness. The slope was steeper, and the line reached at 1000% (10-fold) around 6.5 (mm) when compared with a thin LF. CONCLUSION: Decreased elasticity of LF in the elderly is due to the loss of elastic fibers and a concomitant increase of collagenous fibers in the dorsal aspect. LF hypertrophy could be due to the thickening of the normal elastic layer as well as of the abnormal collagenous layer.

Vertebral rounding deformity in pediatric spondylolisthesis occurs due to deficient of endochondral ossification of the growth plate: radiological, histological and immunohistochemical analysis of a rat spondylolisthesis model.

STUDY DESIGN: A study using rat spondylolisthesis models. OBJECTIVE: To clarify pathomechanism of vertebral rounding deformity in pediatric spondylolisthesis. SUMMARY OF BACKGROUND DATA: For high-grade slippage, rounding of sacrum surface associated with L5 spondylolisthesis is reported to be the most responsible risk factor. However, the exact pathomechanism of the rounding deformity is yet to be clarified. METHODS: Spondylolisthesis rat model (4-week-old) was used. Radiographs were taken weekly for 5 weeks after the surgery. The lumbar spines were harvested for histology. Hematoxylin and eosin, alcian blue staining, and tartrate-resistant acid phosphatase staining were used. Immunohistochemically, the growth plate cartilage was studied for type II and X collagen. A modified bone histomorphometric analysis was also performed. RESULTS: Radiographs showed slippage 1 week after surgery. Rounding deformity was obvious 2 weeks after surgery. The rounding deformity progressed with time. Three weeks after surgery, the specific columns of growth plate were unclear at the anterior corner, which corresponded to the rounding surface observed on radiographs. Instead, a huge mass of cartilage was observed at that site. Tartrate-resistant acid phosphatase-positive cells were observed in the vicinity of the growth plate except in relation with the anterior corner. The growth plate and cartilage mass at the anterior corner stained positive for type II collagen. Chondrocytes in the hypertrophied layer stained positively for type X collagen; however, staining was faint at the anterior corner. The results suggested that the chondrocytes at the anterior did not form, morphologically and functionally, the normal growth plate. From histomorphometrical analysis, the normal posterior growth plate made endochondral bone growth in 510 +/- 20 microm for a week, whereas the anterior corner in 200 +/- 15 microm. CONCLUSION: Deficient endochondral ossification of the growth plate in the anterior upper corner of the vertebra could be the pathomechanism of the rounding deformity of the sacrum.

Ubiquitin ligase Cbl-b downregulates bone formation through suppression of IGF-I signaling in osteoblasts during denervation.

UNLABELLED: Unloading can prevent bone formation by osteoblasts. To study this mechanism, we focused on a ubiquitin ligase, Cbl-b, which was highly expressed in osteoblastic cells during denervation. Our results suggest that Cbl-b may mediate denervation-induced osteopenia by inhibiting IGF-I signaling in osteoblasts. INTRODUCTION: Unloading, such as denervation (sciatic neurectomy) and spaceflight, suppresses bone formation by osteoblasts, leading to osteopenia. The resistance of osteoblasts to growth factors contributes to such unloading-mediated osteopenia. However, a detailed mechanism of this resistance is unknown. We first found that a RING-type ubiquitin ligase, Cbl-b, was highly expressed in osteoblastic cells after sciatic neurectomy in mice. In this study, we reasoned that Cbl-b played an important role in the resistance of osteoblasts to IGF-I. MATERIALS AND METHODS: Cbl-b-deficient (Cbl-b(-/-)) or wildtype (Cbl-b(+/+)) mice were subjected to sciatic neurectomy. Bone formation in these mice was assessed by calcein labeling and histomorphometric analyses. We examined IGF-I signaling molecules in femora of these mice by Western blot and immunohistochemical analyses. We also examined the mitogenic response of Cbl-b-overexpressing or -deficient osteoblastic cells to various growth factors. RESULTS: In Cbl-b(+/+) mice, denervation decreased femur mass and bone formation, whereas it increased the expression of Cbl-b protein in osteoprogenitor cells and in osteocalcin-positive cells (osteoblastic cells) in hindlimb bone. In contrast, in Cbl-b(-/-) mice, bone mass and bone formation were sustained during denervation. Denervation inhibited the mitogenic response of osteoprogenitor cells most significantly to IGF-I. Therefore, we focused on Cbl-b-mediated modification of IGF-I signaling. Denervation decreased the amounts of insulin receptor substrate-1 (IRS-1), phosphatidly inositol 3-phosphate kinase (PI3K), and Akt-1 proteins in femora of Cbl-b(+/+) mice, whereas the amounts of these IGF-I signaling molecules in femora of Cbl-b(-/-) mice were constant after denervation. On a cellular level, primary osteoblastic cells from Cbl-b(-/-) mice were more stimulated to proliferate by IGF-I treatment compared with those from Cbl-b(+/+) mice. Furthermore, overexpression of Cbl-b increased ubiquitination and degradation of IRS-1 in primary Cbl-b(-/-) osteoblastic cells, leading to their impaired mitogenic response to IGF-I. CONCLUSIONS: These results suggest that Cbl-b induces resistance of osteoblasts to IGF-I during denervation by increasing IRS-1 degradation and that Cbl-b-mediated modification of IGF-I signaling may contribute to decreased bone formation during denervation.

Effects of monofilament nylon coated with basic fibroblast growth factor on endogenous intrasynovial flexor tendon healing.

PURPOSE: We developed a monofilament nylon thread that can release various growth factors to enhance intrinsic reparative processes after flexor tendon injury. We evaluated the properties of this thread in vitro and in vivo. METHODS: Nylon threads were coated with gelatin that subsequently was cross-linked in glutaraldehyde. The thread was soaked in basic fibroblast growth factor (bFGF) solution (400 microg/mL). Exogenous bFGF in the thread was released constantly over the course of 1 week. The biologic activity of bFGF and the biomechanical strength of the thread were examined in vitro and its efficacy was investigated in an in vivo rabbit tendon repair model after early flexion exercises. The sutured sites were examined histologically (hematoxylin-eosin, immunohistochemistry, in situ hybridization), biochemically (Western blot test), and biomechanically (ultimate load) after surgery. RESULTS: This gelatin-coated thread absorbed iodine 125-labeled bFGF in a time-dependent manner. The total amount of bFGF absorbed by the thread within the tendon tissue was between 3 and 15 mug depending on the concentration of bFGF solution. Basic fibroblast growth factor protein was delivered selectively-not in the surrounding scar but in the repaired tendon-for 3 weeks. Histologic analysis showed that the cellular density at the repaired site increased in accordance with the expression of bFGF messenger RNA and protein in the tendon. Endogenous bFGF expression seemed to be enhanced transiently by exogenous bFGF during the first few weeks. The epitenon showed a vigorous fibroblastic response to the coated thread and the ultimate load also was increased significantly at 3 weeks after surgery. CONCLUSIONS: This bFGF-coated nylon suture gave excellent results in delivering a drug selectively to tendon; it also induced an increase of biomechanical strength and a thickening of the epitenon layer in vivo during a 3-week period, thereby accelerating cellular proliferation, initially peripherally and later centrally. This system may become a therapeutic tool to be used in hand surgery.