MLK3 silence suppressed osteogenic differentiation and delayed bone formation via influencing the bone metabolism and disturbing MAPK signaling.

Background: Mixed lineage kinase 3 (MLK3) is a member of a serine/threonine MAP3K family, and it has been demonstrated to play critical roles in various biological activities and disease progression. Previous studies showed that impaired skeletal mineralization and spontaneous tooth fracture in the MLK3-deficient mice, suggesting MLK3 actively participated in the bone formation. However, the detailed function and underlying mechanisms remain obscure. Methods: The MLK3 knockout (KO) mouse was applied in the present study, and multi-omics were performed to compare the metabolites and gene expression between wild type (WT) and KO mice. The bone fracture model was successfully established, and the healing process was evaluated by X-ray, micro-CT examination, histomorphometry and immunohistochemistry (IHC) staining. On the other hand, the effects of MLK3 on osteogenic differentiation were assessed by alkaline phosphatase (ALP) activity, Alizarin red S (ARS) staining and qRT-PCR examination. Finally, the downstream signaling pathways were screened out by RNA-sequencing (RNA-seq) and then validated by Western blotting. Results: In the present study, imbalanced bone metabolism was observed in these MLK3 KO mice, suggesting MLK3 may participate in bone development. Moreover, MLK3 -/- mice displayed abnormal bone tissues, impaired bone quality, and delayed fracture healing. Further investigation showed that the inhibition of MLK3 attenuated osteoblast differentiation in vitro. According to the RNA-seq data, MAPK signaling was screened out to be a downstream pathway, and its subfamily members extracellular signal-regulated kinase (ERK), p38 and Jun N-terminal protein kinase (JNK) were subjected to Western blotting examination. The results revealed that although no differences in their expression were observed between MSCs derived from WT and KO mice, their phosphorylated protein levels were all suppressed in MLK3 -/- MSCs. Conclusion: In conclusion, our results demonstrated that loss of MLK3 suppressed osteoblast differentiation and delayed bone formation via influencing metabolism and disturbing MAPK signaling. The translational potential of this article: The findings based on the current study demonstrated that MLK3 promoted osteogenesis, stimulated new bone formation and facilitated fracture healing, suggesting that MLK3 may serve as a potential therapeutic target for bone regeneration. MLK3 activator therefore may be developed as a therapeutic strategy for bone fracture.

Troxerutin Stimulates Osteoblast Differentiation of Mesenchymal Stem Cell and Facilitates Bone Fracture Healing.

Troxerutin (TRX), a semi-synthetic derivative of the natural bioflavonoid rutin, is a bioactive flavonoid widely abundant in various fruits and vegetables. Known as vitamin P4, TRX has been demonstrated to have several activities including anti-inflammation, anti-oxidants, vasoprotection, and immune support in various studies. Although rutin, the precursor of troxerutin, was reported to have a protective role against bone loss, the function of TRX in skeletal system remains unknown. In the present study, we found that TRX promoted osteogenic differentiation of human mesenchymal stem cells (MSCs) in a concentration-dependent manner by stimulating the alkaline phosphatase (ALP) activity, calcium nodule formation and osteogenic marker genes expression in vitro. The further investigation demonstrated that TRX stimulated the expression of the critical transcription factor ß-catenin and several downstream target genes of Wnt signaling, thus activated Wnt/ß-catenin signaling. Using a femur fracture rats model, TRX was found to stimulate new bone formation and accelerate the fracture healing in vivo. Collectively, our data demonstrated that TRX could promote osteogenesis in vitro and facilitate the fracture healing in vivo, indicating that TRX may be a promising therapeutic candidate for bone fracture repair.

TGF-ß1, in association with the increased expression of connective tissue growth factor, induce the hypertrophy of the ligamentum flavum through the p38 MAPK pathway.

Hypertrophy of the ligamentum flavum (LF) is one of the key pathomechanisms of lumbar spinal stenosis (LSS). Transforming growth factor (TGF)-ß1 is abundantly expressed in hypertrophied degenerative LF tissues from LSS. However, the molecular mechanisms underling the association between TGF-ß1 and LF hypertrophy have not yet been fully elucidated. In this study, we investigated the important role of the mitogen-activated protein kinase (MAPK) pathway in the pathogenesis of LSS by analyzing the expression of connective tissue growth factor (CTGF) and extracellular matrix (ECM) components (collagen I and collagen III) in TGF-ß1-treated LF cells. Cell growth assay revealed that TGF-ß1, in association with CTGF, enhanced the the proliferation of LF cells, and we found that TGF-ß1 also elevated CTGF expression and subsequently enhanced the mRNA expression of collagen I and collagen III. The increased mRNA expression levels of CTGF, collagen I and collagen III were abolished by p38 inhibitors. Both immunofluorescence imaging and western blot analysis of p38 and p-p38 revealed the increased expression and phosphorylation of p38. Silencing the expression of p38 by siRNA in LF cells decreased the protein expression of p38, p-p38 and CTGF, as well as the mRNA expression of CTGF, collagen I and collagen III. Taken together, our findings indicate that TGF-ß1, in association with the increased expression of CTGF, contribute to the homeostasis of the ECM and to the hypertrophy of LF through the p38 MAPK pathway.

PLK2 phosphorylates and inhibits enriched TAp73 in human osteosarcoma cells.

TAp73, a member of the p53 tumor suppressor family, can substitute for p53 function, especially in p53-null and p53-mutant cells. However, TAp73 enrichment and phosphorylation change its transcriptional activity. Previously, we found that the antitumor function of TAp73 was reactivated by dephosphorylation. Polo-like kinase 2 (PLK2) plays an important role in bone development. Using a biological information database and phosphorylation prediction software, we hypothesized that PLK2 phosphorylates TAp73 and inhibits TAp73 function in osteosarcomas. Actually,we determined that PLK2 physically binds to and phosphorylates TAp73 when TAp73 protein abundance is up-regulated by cisplatin. PLK2-phosphorylated TAp73 at residue Ser48 within the TA domain; phosphorylation of TAp73 was abolished by mutating this residue. Moreover, PLK2 inhibition combined with cisplatin treatment in osteosarcoma Saos2 cells up-regulated p21 and puma mRNA expression to a greater extent than cisplatin treatment alone. Inhibiting PLK2 in TAp73-enriched Saos2 cells resulted in inhibited cell proliferation, increased apoptosis, G1 phase arrest, and decreased cell invasion. However, these changes did not occur in TAp73 knockdown Saos2 cells. In conclusion, these findings reveal a novel PLK2 function in the phosphorylation of TAp73, which prevents TAp73 activity in osteosarcoma cells. Thereby, this research provides an insight into the clinical treatment of malignant tumors overexpressing TAp73.

Anatomical basis of a proximal fasciocutaneous extension of the distal-based posterior interosseous flap that allows exclusion of the proximal posterior interosseous artery.

OBJECTIVE: The objective of this study was to provide anatomical information for the repair of small tissue defects in the hand with posterior interosseous artery chain-link perforator flaps, a proximal fasciocutaneous extension of the distal-based posterior interosseous flap, which allows the exclusion of the proximal posterior interosseous artery. METHODS: Fourteen posterior interosseous artery chain-link perforator flaps taken from human cadavers were studied by the following three methods: latex perfusion for microanatomy analysis, denture material and vinyl chloride mixed packing for cast analysis, and latex perfusion for the production of clearance specimens. Statistical analysis was performed on cutaneous perforators coming from the intermuscular septum of the extensor carpi ulnaris and the extensor digitorum communis. A cluster analysis was conducted to determine the overall distribution of perforators. RESULTS: There are two main clusters of perforators at a relative distance of 21% and 48% along the ulnar head-to-lateral epicondyle interval. On average, the posterior interosseous artery extends six cutaneous perforators through the intermuscular septum of the extensor carpi ulnaris and the extensor digitorum communis. Of these six arteries, two are clinically significant perforators (0.5 mm or more in diameter) and are located 6 ± 2 cm proximal to the head of the ulna and 10 ± 1 cm distal to the lateral epicondyle of the humerus. Their mean diameters are 0.5 ± 0.1 and 0.6 ± 0.1 mm, with pedicle lengths of 16.8 ± 5.1 and 21.2 ± 12.3 mm, respectively. At the two main clusters of perforator-intensive sites, the vessel chains formed by adjacent perforators are parallel to the intermuscular septum of the extensor carpi ulnaris and the extensor digitorum communis. CONCLUSIONS: This study demonstrates that the posterior interosseous artery has two main clusters of perforators in the middle and distal one-fifth of the forearm, which can be used for repairing hand defects with posterior interosseous artery chain-link perforator flaps.

[Pullout test in expansive unilateral open-door laminoplasty of the cervical spine with OsteoMed M3 plate and screws: the screw orientation matters].

OBJECTIVE: To study the impact of screw orientation on the pullout strength of OsteoMed M3 titanium screws in expansive unilateral open-door laminoplasty of the cervical spine. METHODS: Six fresh human cervical spine specimens were randomly numbered and OsteoMed M3 plate and screws were used for an expansive unilateral open-door laminoplasty. The screws were inserted in the lateral mass at different extraversion angles (0°, 30° and 45°). The maximum pullout strength was tested on the ElectroForce material testing machine. RESULTS: The maximum pullout strength was 81.60∓7.33 N, 150.05∓15.57 N, and 160.08∓17.77 N in extraversion angle 0°, 30°, and 45° groups, respectively. The maximum pullout strength was significantly less in extraversion angle 0° group than in 30° and 45° groups (P<0.05), but similar in the latter two groups. CONCLUSION: The pullout strength of the screws inserted at an extraversion angle over 30° provides stronger fixation than an angle of 0° in the unilateral open-door laminoplasty using OsteoMed M3 titanium plate and screws.

Posterior cervical fixation following laminectomy: a stress analysis of three techniques.

The aim of this study was to compare the following three main fixation techniques: pedicle screw (PS) technique, lateral mass screw (LS) technique, and transarticular screw (TS) technique. A detailed, geometrically accurate, nonlinear C3-C7 FE model had been successfully developed and validated. Then three finite element (FE) models were reconstructed by different fixation techniques following C4-C6 level laminectomy. A compressive preload of 74 N combined with a pure moment of 1.8 Nm in flexion, extension, left-right lateral bending, and left-right axial rotation was applied to the models. The results showed that maximum von Mises stress on the fixation devices was much higher in the FE models of TS technique, compared with the models of PS and LS techniques. Furthermore, the screws inserted by TS technique had high stress concentration at the middle part of the screws. Screw inserted by PS and LS techniques had high stress concentration at the actual cap-rod-screw interface. The highest level of maximal stress was obtained with the fixation device of the TS technique. TS technique induces noticeable differences in the stress compared to the posterior cervical fixation technique, regarding the higher stress level on fixation devices.

[Placement of short iliac screw using Galveston technique in lumbosacral fusion].

OBJECTIVE: To evaluate the effect of placement of short iliac screw using Galveston technique in lumbosacral fusion. METHODS: From October 2003 to August 2007, 18 consecutive patients (mean age 46 years ranging from 25 to 62 years) received placement of short iliac screw in lumbosacral fusion. The patients were followed up for a mean of 18 months (12-23 months), and the effect of lumbosacral fusion was evaluated according to standing anterior-posterior and lateral plain films taken before and after the operation and at the follow-up and also on the basis of symptom relief. RESULTS: The mean time of surgery was 210 min (180-290 min). No complications occurred during and after the operation. According to the evaluation criteria of surgical treatment of low back pain formulated by the spine group of Chinese Orthopedic Association, excellent clinical outcome was achieved in 12 cases, good outcome in 3 cases, and tolerable outcome in 2 cases, with the excellent and good outcome rate of 83%. CONCLUSION: The Galveston technique for short iliac screw placement can obtain satisfactory outcome in the lumbosacral fusion.

[Effect of continuous passive motion on basic fibroblast growth factor expression during tendon-bone repair after surgical repair of acute rupture of the supraspinatus tendon in rabbits].

OBJECTIVE: To study the effect of continuous passive motion (CPM) on basic fibroblast growth factor (b-FGF) expression during tendon-bone repair in rabbits and explore the role of stress in the postoperative repair after acute rotator cuff injury. METHODS: Sixteen rabbits randomized into CPM group (n=8) and non-CPM group (n=8) were subjected to surgically induced acute rupture of the supraspinatus tendon and subsequent surgical repair, with another two rabbits serving as the control. Two weeks after the operation, the rabbits in CPM group underwent CPM training, and those in non-CPM group were normally fed only. At 2, 4, 6, and 8 weeks after the operation, 2 rabbits from each group were sacrificed and the tissue samples were obtained for detecting the changes in b-FGF expression. RESULTS: Two weeks after the operation, b-FGF expression was detected in both groups, and the CPM group showed slightly higher and more diffusive expression. At 4 weeks, b-FGF expression was significantly higher and distributed over a greater area in CPM group and in the non-CPM group. A large number of fibroblasts positive for b-FGF expression were identified in CPM group, aligning in parallel with the tendon membrane. At 6 weeks, b-FGF in the CPM group showed no obvious changes but that in the non-CPM group became lightened. At 8 weeks, b-FGF expression was reduced in both groups, which was more obvious in the non-CPM group. CONCLUSION: CPM can promote b-FGF expression to enhance type III collagen synthesis at the tendon-bone interface in early stage of tendon-bone repair following acute rupture of supraspinatus tendon in rabbits, thereby contributing to tendon-bone recovery after rotator cuff injury.

[Three-dimensional visualization of the structures related to the anterior cervical segment approach].

OBJECTIVE: To establish a digital model allowing three-dimensional visualization of the structures involved in the anterior cervical segment approach. METHODS: Based on the imaging data obtained from CT angiography (CTA), magnetic resonance myelography (MRM) and continuous magnetic resonance imaging (MRI) of a healthy volunteer (scanning from the center of the head to the inferior border of the T3 level), image segmentation and reconstruction for the skeleton, arteries, veins, and spinal cord was conducted semi-automatically using the Mimics software according to the different thresholds of the tissues. The cervical plexus, brachial plexus and muscles of the neck were reconstructed with the Nerves pipe editor and the Med CAD module to establishing the three-dimensional model for displaying the structures involved in the anterior cervical segment approach. RESULTS: A three-dimensional digital model of the structures involved in the anterior cervical segment anterior approach was established, which allowed the display of anatomical relations of the skeletal structure, aorta, superior vena cava, thyroid gland, hyoid bone, laryngeal cartilages, trachea, lung, 12 neck muscle groups, as well as the spinal cord, spinal nerves, cervical plexus, brachial plexus, and intervertebral disk of the neck. CONCLUSION: The three-dimensional model established can allow the visualization of the important structures for the anterior cervical segment approach, and provides a medical teaching platform for anatomy and surgical training.

[Indication of fusion for degenerative lumbar spinal stenosis treated by "windows technique" laminoforaminotomy].

OBJECTIVE: To explore the indications of fusion for degenerative lumbar spinal stenosis treated by "windows technique". METHODS: From December 1999 to December 2005, 145 consecutive patients who were treated by primary decompression with "windows technique" laminoforaminotomy for degenerative lumbar spinal stenosis, a retrospective study, were divided into 3 groups (A and B and C) by preoperative lumbar conditions and surgical methods. In group A, 39 patients with spinal instability or degenerative lumbar spondylolisthesis or scoliosis underwent decompression and fusion; in group B, 31 patients with spinal instability or degenerative lumbar spondylolisthesis or scoliosis underwent decompression alone; In group C, 75 patients without spinal instability or degenerative lumbar spondylolisthesis or scoliosis were treated by decompression without fusion. On hospital medical records to review, they were followed up by telephone and out-patient referral. Statistics the duration of hospitalization, operative time, estimated blood loss; Observed recrudescence and reoperation and complication; and using Oswestry Disability Index and Visual Analog Scale and satisfaction rate for efficacy assessment, application SPSS 13.0 software. RESULTS: All 145 patients had at least a 3-year follow-up (ranging 37 to 108 months). In the group C, the duration of hospitalization less than in the group A or B (P < 0.05); In the group A, the operative time and estimated blood loss greater than in the group B or C (P < 0.05); The group B treated by decompression alone in the presence of instability or spondylolisthesis or scoliosis showed the worst results by the Oswestry Disability Index or Visual Analog Scale or ate of satisfaction (P < 0.05). The same good results can be obtained in the group A and C. There were not different about recrudescence or reoperation or complication in the three groups. CONCLUSIONS: Fusion should be performed on patients with instability or degenerative lumbar spondylolisthesis or scoliosis after primary decompression with "windows technique" laminoforaminotomy. The patient with simple lumbar spinal stenosis undergone primary surgery does not require fusion.

[Biomechanical evaluation of asymmetrical posterior internal fixation for transforaminal lumbar interbody fusion with transfacetopedicular screws].

OBJECTIVE: To assess the biomechanical stability of asymmetrical posterior internal fixation for transforaminal lumbar interbody fusion (TLIF) with transfacetopedicular screws (TFPS). METHODS: Range of motion (ROM) testing was performed in 7 fresh-frozen human cadaveric lumbar spine motion segments in flexion/extension, lateral bending, and axial rotation using 10.0 Nm torques at the L3-4 motion segment. The sequential test configurations included intact motion segment, TLIF and ipsilateral pedicle screw (PS), TLIF and ipsilateral PS plus contralateral TFPS according to Boucher technique, and TLIF and bilateral PS. The ROM was determined to assess the construct stability. RESULTS: In flexion/extension, lateral bending, and axial rotation, no measureable difference was found in the ROM between the standard bilateral pedicle screw and the novel asymmetric posterior internal fixation after TLIF. After TLIF, the ipsilateral PS construct provided less segment stability than the novel asymmetric construct with TFPS in flexion, left bending and left rotation. In rotation, the novel asymmetric construct allowed for significant off-axial rotation motions detrimental to the stability and fusion. CONCLUSION: Ipsilateral PS placement plus contralateral TFPS provides stability comparable to that of TLIF with bilateral PS, and can be an alternative in minimal invasive surgery.

[Biomechanical evaluation of the U shape lumbar biological dynamic fixation system].

OBJECTIVE: To evaluate biomechanical characteristics of a new U-shaped lumbar bioelastic internal fixation deuice (UBD). METHODS: Six fresh calf lumbar (L2-L5) samples were divided into 4 groups, namely the normal group, traumatic instability group, instability group with rigid internal fixation and instability group with UBD fixation. The vertebral 3-dimensional range of motion (ROM) and rigidity of the 4 group were tested. RESULTS: Elastic fixation and rigid fixation both significantly increased vertebral segment stability for flexion, extension, lateral curvature and rotations. Compared with rigid fixation, elastic fixation obviously increased the ROM by 2.22 degrees in flexion and extension, but significantly decreased the rigidity in forward bending and backward bending and compression (P<0.01). CONCLUSION: The UBD may enhance the load sharing and decrease stress-shielding and stress concentration without sacrificing lumbar stability.

[Recombinant human bone morphogenetic protein-2 promotes tendon-bone healing after anterior cruciate ligament reconstruction in rabbits].

OBJECTIVE: To observe the effect of recombinant human bone morphogenetic protein-2 (rhBMP-2) in promoting the tendon-bone healing in rabbits after anterior cruciate ligament reconstruction. METHODS: Thirty normal adult New Zealand rabbits were divided into 3 groups for anterior cruciate ligament reconstruction using autologous semitendinosus tendons as the graft material. In the rhBMP-2 group, fibrin glue (FG) containing rhBMP-2 was applied to the interface between the tendon graft and the bone tunnel, while in the FG control group, only FG was applied. The blank control group received no treatment after the surgery. The grafts were collected at 2, 4, 8 weeks after the surgery for gross observation and histological examination of the graft incorporation. RESULTS: In the FG control group, the tendon-bone interface was filled with granulation tissue 2 weeks after the surgery, and the newly generated tissue growing into the bone tunnel and fibroblasts were observed at 4 weeks. Till week 8, Sharpey's fibers were found in the interface with the formation of indirect insertion. In the rhBMP-2 group, the tendon-bone interface was filled with cartilage tissue at 2 weeks, and the four-layer direct insertion was formed at 4 weeks; till week 8, the interface was mainly composed of the direct insertion. CONCLUSION: rhBMP-2 can induce direct insertion formation in the tendon-bone interface after early anterior cruciate ligament reconstruction. The direct insertion possesses better biomechanical properties than indirect insertion.

[Biomechanical reconstruction of the hip in metal-on-metal total hip resurfacing].

OBJECTIVE: To analyze the effect of biomechanical reconstruction of the hip in metal-on-metal total hip resurfacing. METHODS: Thirty patients undergoing hip resurfacing arthroplasties were enrolled in this study. The clinical outcomes of the patients were assessed according to the Harris Hip Score before and after the surgery, X-ray examinations and biomechanical reconstruction evaluations. RESULTS: After the operation, the length of the patients' legs was shortened by a mean of 2.4 mm. and the femoral offset was decreased by a mean of 5.45 mm. No dislocation were be found in these patients. The preoperative Harris Hip Score was 36.69-/+7.16, significantly lower than that postoperative score (89.63-/+3.36, P<0.01). CONCLUSION: Precise biomechanical reconstruction of the hip can be achieved in hip resurfacing arthroplasty, and the stability and functional restoration is guaranteed by large diameter prosthesis design.

[Short-term clinical follow-up of metal-on-metal hip resurfacing arthroplasty].

OBJECTIVE: To evaluate the short-term outcome of patients receiving metal-on-mental hip resurfacing arthroplasty and analyze the factors affecting the result. METHODS: In 13 patients receiving metal-on-metal hip resurfacing arthroplasties with scheduled follow-up, the treatment outcomes were assessed according to the Harris Hip Score. RESULTS AND CONCLUSION: The short-term outcomes of hip resurfacing arthroplasties were encouraging, and intraoperative complications, infections, peripheral nerve palsy, hip dislocations or clinically overt lower limb deep vein thrombosis occurred in none of these cases. All the patients reported complete or major pain relief. Clinical assessment according to the Harris Hip Score revealed an improvement from an average score of 36.69 preoperatively to 89.63 after the surgery. Crutch use lasted for a maximum of 4 weeks postoperatively in these patients, after which the patients were all capable of walking without crutches with full weight-bearing.

[Surgery simulation with a percutaneous and transpedical interbody bone grafting apparatus].

OBJECTIVE: To develop a percutaneous and transpedical interbody bone grafting apparatus for vertebral bone defect reconstruction in thoracolumbar fracture correction via minimally invasive operation. METHODS: The percutaneous and transpedical interbody bone grafting apparatus was designed with CAD software, and the reduction effect, range of bone grafting and surgical complications of the apparatus were investigated in adult cadaveric thoracolumbar body and with computerized surgical simulation. RESULTS: The self-designed apparatus was convenient for percutaneous and transpedical interbody bone grafting that did not give rise to complications. CT showed large bone grafting area with increased density in the vertebral body corrected with this apparatus. CONCLUSION: The designed apparatus allows easy manipulation and efficient bone grafting and repositioning. Minimally invasive interbody bone grafting in thoracolumbar fracture can be easily performed with proper application of the apparatus.

[A digital model for lumbar motion segment reconstruction and three-dimensional visualization].

OBJECTIVE: To establish a digital model for reconstruction and three-dimensional visualization of lumbar motion segment from CT images. METHODS: Based on 64 row spiral CT continuous 2-dimensional images of L4-L5 segments, the lumbar structure and various soft tissues were reconstructed with the Mimics software, followed by validation of this model using finite element analysis software. RESULTS: The established three-dimensional digital model of lumbar motion segment included two vertebral bodies, cortical bone, cancellous bone, endplate, annulus fibrosus, nucleus pulposus and 6 types of ligaments. The output result of the digital model can be used to for research of computer aided design, rapid rototyping and finite element analysis. CONCLUSION: The application of thin-layer CT and Dicom standard ensures more accurate digital model establishment, and Mimics software allows more convenient reconstruction of the human skeleton and various soft tissues to facilitate further research.

[Finite element analysis of a new shape memory alloy cervical hook for atlantoaxial instability].

The mechanics of a new shape memory alloy cervical hook for atlantoaxial instability was analyzed with finite element method on the basis of a three-dimensional model reconstructed from the images of CT scanning of an adult cadaveric upper cervical at 1-mm interval. The stress and displacement of every nodule and element in the course of deformation of the internal fixation were tested, and the results showed that the cervical hook was strong enough against tensile stress, which concentrates in the middle of the device. The pull was 237.58 N at the loading point. With such mechanical performance, this cervical hook can be reliable for correction of atlantoaxial instability.

[Development of an anti-infection nano-hydroxypatite drug delivery microsphere and its drug-release in vitro].

OBJECTIVE: To develop an anti-infection nano-hydroxypatite (nano-HA) microsphere for local drug delivery for treating osteomyelitis. METHODS: The nano-HA was used as the core carrier to load gentamicin (GM) and coated with poly(-hydroxybutyrate-co- hydroxyvalerate)/polyethylene glycol (PHBV/PEG), which was degradable and biocompatible, to prepare nano-HA-PHBV/PEG-GM microsphere. The surface structure and in vitro drug-release of the microsphere were studied. RESULTS: The microsphere had good drug delivery capability. The samples weighing 90 mg each were soaked in PBS and gentamicin release within the first day was 165.2 microg/ml, which maintained a low release rate in the following days. After 28 days, gentamicin release declined to 8.5 microg/ml, which was higher than the minimal inhibitory concentration of gentamicin (2 microg/ml). CONCLUSION: The local drug delivery system has good drug-release performance in vitro and may possess potential value in clinical management of osteomyelitis.