An optimized medial parapatellar approach to the goat medial femoral condyle

Goats or sheep are the preferred animal model for the preclinical evaluation of cartilage repair techniques due to the similarity of the goat stifle joint to the human knee.The medial femoral condyle of the stifle joint is the preferred site for the assessment of articular cartilage repair,as this is the primary location for this type of lesion in the human knee.Proper surgical exposure of the medial femoral condyle is paramount to obtain reproducible results without surgical error.When applying the standard human medial arthrotomy technique on the goat stifle joint,there are some key aspects to consider in order to prevent destabilization of the extensor apparatus and subsequent postoperative patellar dislocations with associated animal discomfort.This paper describes a modified surgical technique to approach the medial femoral condyle of the caprine stifle joint.The modified technique led to satisfactory exposure without postoperative incidence of patellar luxations and no long-term adverse effects on the joint.

The Correlation between Femoral Anteversion and Femoral Condyle Rotation in Patients with Osteoarthritis of the Hip Joint: Investigation about the Asian Female Patients

An abnormality of femoral anteversion (FA) is often recognized in patients with osteoarthritis of the hip joint (hip OA). And it is considered that rotation abnormality in the knee and the lower leg occurs as compensation, in cases of FA abnormality. The purpose of this study was to assess the magnitude and variability of FA and femoral condyle rotation (FCR) in order to identify the association between FA and FCR in female patients with hip OA who require total hip arthroplasty. A total of 174 hips from 174 hip OA patients undergoing THA were included in this study. All patients were Asian women (average age: 71.1 years). An equilateral correlation was accepted in FA and FCR. It was thought that FA abnormality might be accompanied by morphological rotation abnormalities of the knee joint. Caution is needed in considering femoral anteversion using the posterior condylar line. We must consider FA in patients undergoing THA after having considered the whole leg rotation.

Classification and Management of Mandibular Condyle Fractures in a Tertiary Health Center

Background: Condyle fractures are not common but could lead to detrimental effects of growth disturbance of the mandible, ankylosis of temporomandibular joint and facial asymmetry especially in children, if not promptly and adequately managed, the aim of this study was to document our experience in the management of mandibular condyle fractures. Method: The fractures were classified based on the age of the patient, unilateral/bilateral, location on the condyle, presence of displacement and dislocation, for those displaced, whether there was medial or lateral overlap, and features presented. Treatment done for each patient was documented. Both clinical and radiological assessments were done to ascertain the outcome of treatment. Result: 11 patients presented with 14 condyle fractures, 3 patients with bilateral and 8 with unilateral condyle fractures out of which 5 cases were on the right side. Age range of patients was between 13 and 44 years with a mean (SD) of 25.3 (10.7) years. Nine (81.8%) of the patients were males and 2 (18.2%) were females. Eight (72.7%) of the patients with condyle fracture had associated fractures affecting other sites of the mandible while 3 (27.3%) patients had isolated condyle fractures. Intracapusular fractures recorded were 2 (14.2%), while extracapsular accounted for 12 (85.8%) cases. Conservative treatment was not applied in any patient, 9 (81.8%) patients had IMF and 2 (18.2%) patients had ORIF. Conclusion: Most fractures of the condyle were extracapsular and, closed surgical treatment (IMF) was very useful to manage most of the cases.

Loss of Masticatory Function Affects Growth and Development of the Mandibular Condyle in Rats

The effects of childhood masticatory function loss and soft foods on the mandibular condyle have been the subject of much research. However, the corresponding bone turnover is not fully understood. The purpose of the present study was to clarify the effects of a lack of teeth and a soft food diet during the growth period on bone turnover in the mandibular condyle. We divided 3-week-old Wistar rats into the following three groups: 1) Extraction group: The maxillary molars were extracted at the age of 4 weeks, and animals were fed powdered standard feed. 2) Powder group: Animals were fed powdered standard feed without tooth extraction. 3) Control group: Animals were fed solid standard feed without tooth extraction. Non-decalcified thin-slice specimens of sagittal sections of the mandibular condyle were obtained at the age of 20 weeks for histological analysis. We used micro-CT analysis and bone histomorphometry to measure bone volume (BV), bone mineral content (BMC), bone mineral density (BMD), bone microstructure, bone resorption, and osteogenesis in the mandibular condyle, and we compared the results among groups. In the extraction and the powder groups, we found deformation and disruption of the arrangement of chondrocytes, coagulation of chondrocytes, and duplication of the tidemark in the cartilage. We also found an increase in multinuclear osteoclasts in the cancellous bone. We found a reduction in BV, BMC, and BMD in the extraction and powder groups compared to the control group, as well as a reduction of bone volume, a lowering of osteogenesis parameters, and an increase in bone resorption parameters in the secondary cancellous bone. These results suggest that a lack of teeth and a soft food diet during the growth period cause a decline in bone microstructure, a decrease in osteogenesis, and an increase in bone resorption.

Epidemiologic investigation of pediatric distal humerus fractures: An American insurance claims database study

BACKGROUND Distal humerus elbow fractures are one of the most common traumatic fractures seen in pediatric patients and present as three main types:Supracondylar(SC),lateral condyle(LC),and medial epicondyle(ME)fractures.AIM To evaluate the epidemiology of pediatric distal humerus fractures(SC,LC,and ME)from an American insurance claims database.METHODS A retrospective review was performed on patients 17 years and younger with the ICD 9 and 10 codes for SC,LC and ME fractures based on the IBM Truven MarketScan®Commercial and IBM Truven MarketScan Medicare Supplemental databases.Patients from 2015 to 2020 were queried for treatments,patient age,sex,length of hospitalization,and comorbidities.RESULTS A total of 1133 SC,154 LC,and 124 ME fractures were identified.SC fractures had the highest percentage of operation at 83%,followed by LC(78%)and ME fractures(41%).Male patients were,on average,older than female patients for both SC and ME fractures.CONCLUSION In the insurance claims databases used,SC fractures were the most reported,followed by LC fractures,and finally ME fractures.Age was identified to be a factor for how a pediatric distal humerus fractures,with patients with SC and LC fractures being younger than those with ME fractures.The peak age per injury per sex was similar to reported historic central tendencies,despite reported trends for younger physiologic development.

Femoral Condyles Tangential Views： An Effective Method to Detect the Screw Penetration of Femoral Condyles After Retrograde Nailing

Background： Postoperative knee soft tissue irritation is a common complication after retrograde nail fixation of femoral fractures. Distal locking screw prominence is one of the causes for soft tissue irritation. This study aimed to determine whether the use of the femoral condyles tangential views improve the diagnostic accuracy compared with anteroposterior （A-P） view in detecting distal locking screw penetrations during retrograde femoral nailing. Methods： The angle between the sagittal plane and lateral aspect of the condyle and the angle between the sagittal plane and medial aspect of condyle were measured on computed tomography （CT） images. After the angles were measured and recorded, cadaveric femurs were used in a simulated surgical procedure. The retrograde femoral nail was inserted into the femur and placed distal locking screws, which were let1 2, 4, and 6 mm proud of the medial and lateral condyles for each femur. A-P view, lateral condyle tangential view and medial condyle tangential view were obtained. All fluoroscopic images were recorded and sent to three observers blinded to the experimental procedure to determine whether screws penetrated the condyle cortex or not. Results： According to the results of CT scan, the lateral condyle view was 20.88 ＋ 0.98± and the medial condyle view was 40.46 ± 3.14°. In the A-P view, we detected 0% at 2 mm penetration, 16.7% （lateral condyle screw） and 25.0% （medial condyle screw） at 4 mm, and 41.7% （lateral condyle screw） and 58.3% （medial condyle screw） at 6 mm. In the lateral tangential view, we detected 91.7% at 2 mm penetration of the lateral condyle and 100% at 4 mm and 6 ram. In the medial tangential view, we detected 66.7% at 2 mm penetration of the medial condyle and 100% at 4 mm and 6 ram. The femoral condyle tangential views provided significant improvement in detecting screw penetrations at all lengths （2, 4, and 6 mm） compared with the A-P view （P 〈 0.05）. Conclusions： The femoral condyles tangential views increased the accuracy of detecting screw penetrations on the medial and lateral condyles. Routine clinical use of the femoral condyles tangential views has the potential to increase accuracy in detecting distal locking screw penetration during retrograde femoral nailing.

Site-Dependent Osseointegration of Biodegradable High-Purity Magnesium for Orthopedic Implants in Femoral Shaft and Femoral Condyle of New Zealand Rabbits

Magnesium （Mg） has been widely accepted as osteoconductive biomaterial, but osseointegration of Mg device at different implantation sites is still unclear. In the present study, high-purity magnesium （HP Mg） pins were implanted into femoral shaft and condyle of New Zealand rabbits concurrently. 2, 8, 12 and 16 weeks after surgery, rabbit femurs were harvested for micro-computed tomography （micro-CT） scanning and subsequent histological examinations. HP Mg pins were retrieved for scanning electron microscope and energy dispersive spectrum （SEM/EDS） analyses. HP Mg pins at both implantation sites performed stable corrosion with mineral deposition and bone incorporation on surface. However, difference in distribution of contact osteogenesis centers and biological properties of peri-implant bone tissues was detected between femoral shaft and femoral condyle. In femoral condyle, contact osteogenesis centers originated from both periosteum and cancellous bones and the whole HP Mg pin was encapsuled in trabecular bone at 16 weeks. Meanwhile, bone volume to total bone volume （BV/TV） and bone mineral density （BMD） of peri-implant bone tissues were above those of normal bone tissues. In femoral shaft, contact osteogenesis centers were only from periosteum and direct bone contact was confined in cortical bone, while BV/TV and BMD kept lower than normal. Furthermore, new formation of peri-implant bone tissues was more active in femoral condyle than in femoral shaft at 16 weeks. Therefore, although HP Mg performed good biocompatibility and corrosion behavior in vivo, its bioadaption of osseointegration at different implantations sites should be taken into consideration. Bone metaphysic was suitable for Mg devices where peri-implant bone tissues regenerated rapidly and the biological properties were close to normal bone tissues.

Evaluation of the performance of Ca-deficient hydroxyapatite(CDHA)/MgF_(2)bilayer coating on biodegradable high-purity magnesium in a femoral condyle defect model in rabbits

The two most critical factors in promoting the clinical translation of magnesium(Mg)are reducing its degradation rate and improving its osteogenesis.In this study,a Ca-deficient hydroxyapatite(CDHA)/MgF_(2)bilayer coating was prepared on high-purity magnesium(HP Mg)rods by fluorination and hydrothermal treatment.Scanning electron microscope showed that the thickness of the bilayer coating was 3.78 lm and that the surface morphology was nanoscale.In an in vivo experiment on femoral condyle defects in rabbits,the serum magnesium ion levels of rabbits were always in the normal range after surgery,and the liver and kidney functions were not abnormal,which indicated that the CDHA/MgF_(2)bilayer coating has good biosafety.Micro-CT showed that the CDHA/MgF_(2)bilayer coating significantly reduced the degradation rate of the HP Mg rods and enhanced the promotion of bone formation.Hard tissue sections showed that the CDHA/MgF_(2)bilayer coating gave the bone tissue a tight contact interface with the HP Mg rod and improved the bone mass.Immunohistochemistry showed that the expression of vascular endothelial growth factor and BMP-2 was more obvious.These results confirm that the CDHA/MgF_(2)bilayer coating can improve the properties of HP Mg and provide a basis for the further transformation of HP Mg in the future.It also provides a new reference for the surface modification of magnesiummetal.

Anatomic variability of the vascularized composite osteomyocutaneous fl ap from the medial femoral condyle: an anatomical study

Aim:The anatomical study and clinical application for the vascularized corticoperiosteal fl ap from the medial femoral condyle have been performed and described previously.Although prior studies have described the composite osteomyocutaneous fl ap from the medial femoral condyle,a detailed analysis of the vascularity of this region has not yet been fully evaluated.Methods:This anatomical study described the variability of the arteries from the medial femoral condyle in 40 cadaveric specimens.Results:The descending genicular artery(DGA)was found in 33 of 40 cases(82.5%).The superomedial genicular artery(SGA)was present in 10 cases(25%).All 33 cases(100%)of the DGA had articular branches to the periosteum of the medial femoral condyle.Muscular branches and saphenous branches of the DGA were present in 25 cases(62.5%)and 26 cases(70.3%),respectively.Conclusion:The current study demonstrates that the size and length of the vessels to the medial femoral condyle are suffi cient for a vascularized bone fl ap.A careful preoperative vascular assessment is essential prior to use of the vascularized composite osteomyocutaneous fl ap from the medial femoral condyle,because of the considerable anatomical variations in different branches of the DGA.

Transcriptomic and proteomic studies of condylar ossification of the temporomandibular joint in porcine embryos

Background:The ossification mechanism of the temporomandibular joint(TMJ)condyle remains unclear in human embryo.The size and structure of TMJ,shape of articular disc and the characteristics of omnivorous chewing in the pig are similar to those of humans.The pig is an ideal animal for studying the mechanism of ossification of the TMJ condyle during the embryonic period.Method:In a previous study by our group,it was found that there was no condylar ossification on embryonic day(E)45,but the ossification of condyle occurred between E75 and E90.In this study,a total of 12 miniature pig embryos on E45 and E85 were used.Six embryos were used for tissue sections(3 in each group).The remaining six embryos were used for transcriptomic and proteomic studies to find differential genes and proteins.The differentially expressed genes in transcriptome and proteomic analysis were verified by QPCR.Results:In total,1592 differential genes comprising 1086 up-regulated genes and 506 down-regulated genes were screened for fold changes of≥2 to≤0.5 between E45 and E85.In the total of 4613 proteins detected by proteomic analysis,there were 419 differential proteins including 313 up-regulated proteins and 106 down-regulated proteins screened for fold changes of≥2 to≤0.5 between E45 and E85.A total of 36 differential genes differing in both transcriptome and proteome analysis were found.QPCR analysis showed that 14 of 15 selected genes were consistent with transcriptome analysis.Conclusion:Condylar transcriptome and proteomic analysis during the development of TMJ in miniature pigs revealed the regulatory genes/proteins of condylar ossification.

Validation of a novel imaging approach using multi-slice CT and cone-beam CT to follow-up on condylar remodeling after bimaxillary surgery

The main goal of this study was to introduce a novel three-dimensional procedure to objectively quantify both inner and outer condylar remodelling on preoperative multi-slice computed tomography （MSCT） and postoperative cone-beam computed tomography （CBCT） images. Second, the reliability and accuracy of this condylar volume quantification method was assessed. The mandibles of 20 patients （11 female and 9 male） who underwent bimaxillary surgery were semi-automatically extracted from MSCT/CBCT scans and rendered in 3D. The resulting condyles were spatially matched by using an anatomical landmark-based registration procedure. A standardized sphere was created around each condyle, and the condylar bone volume within this selected region of interest was automatically calculated. To investigate the reproducibility of the method, inter- and intra-observer reliability was calculated for assessments made by two experienced radiologists twice five months apart in a set of ten randomly selected patients. To test the accuracy of the bone segmentation, the inner and outer bone structures of one dry mandible, scanned according to the clinical set-up, were compared with the gold standard, micro-CT. Thirty-eight condyles showed a significant （P〈O.05） mean bone volume decrease of 26.4%_ 11.4% （502.9 mm3＋ 268.1 mm3）. No significant effects of side, sex or age were found. Good to excellent （ICC〉 0.6） intra- and inter-observer reliability was observed for both MSCT and CBCT. Moreover, the bone segmentation accuracy was less than one voxel （0.4 mm） for MSCT （0.3 mm __. 0.2 mm） and CBCT （0.4 mm _ 0.3 mm）, thus indicating the clinical potential of this method for objective follow-up in pathological condylar resorption.

Enhanced Biocompatibility and Osseointegration of Calcium Titanate Coating on Titanium Screws in Rabbit Femur

This study aimed to examine the biocompatibility of calcium titanate(CaTiO3) coating prepared by a simplified technique in an attempt to assess the potential of CaTiO3coating as an alternative to current implant coating materials. CaTiO3-coated titanium screws were implanted with hydroxyapatite(HA)-coated or uncoated titanium screws into medial and lateral femoral condyles of 48 New Zealand white rabbits. Imaging, histomorphometric and biomechanical analyses were employed to evaluate the osseointegration and biocompatibility 12 weeks after the implantation. Histology and scanning electron microscopy revealed that bone tissues surrounding the screws coated with CaTiO3were fully regenerated and they were also well integrated with the screws. An interfacial fibrous membrane layer, which was found in the HA coating group, was not noticeable between the bone tissues and CaTiO3-coated screws. X-ray imaging analysis showed in the CaTiO3coating group, there was a dense and tight binding between implants and the bone tissues; no radiation translucent zone was found surrounding the implants as well as no detachment of the coating and femoral condyle fracture. In contrast, uncoated screws exhibited a fibrous membrane layer, as evidenced by the detection of a radiation translucent zone between the implants and the bone tissues. Additionally, biomechanical testing revealed that the binding strength of CaTiO3coating with bone tissues was significantly higher than that of uncoated titanium screws, and was comparable to that of HA coating. The study demonstrated that CaTiO3coating in situ to titanium screws possesses great biocompatibility and osseointegration comparable to HA coating.

Effect of microRNA-101 on apoptosis of rabbit condylar cartilage cells by inhibiting target gene SOX9

Objective:To explore the effect of microRNA-101 on apoptosis of condylar cartilage cells and the specific mechanism of molecular biology.Methods:IL-1 was used to stimulate and establish the model of apoptosis of condylar cartilage cells.The expression change of miR-101 in control group was compared with that in IL-1 stimulation group by qRT-PCR.Overexpression and down-regulation models of miR-101 were established by transfecting Mimics and Inhibitor and verified by qRT-PCR.Flow cytometry was used to detect the effect of miR-101 overexpression and down-regulation on apoptosis.Target gene of miR-101 was analyzed and calculated through bioinformatics.Western blot and Luciferase report assay were used to detect whether.Sox9 could become the target gene of miR-101.Results:qRTPCR results showed that IL-1 stimulation could cause the increase of miR-101 expression.After the transfection of rabbit condylar cartilage cells by Mimics and Inhibitor,qRT-PCR results confirmed the significant effect of miR-101 overexpression and down-regulation.It was confirmed by flow cytometry that overexpression of miR-101 could promote the apoptosis of condylar cartilage cells,and down-regulation of miR-101 could reduce the apoptosis.It was confirmed by Western blot and Luciferase report assay that Sox9 was the target gene of miR-101.and miR-101 inhibited SOX9 expression through complementary pairing with 3'UTR of Sox9 mRNA.Conclusions:miR-101 can promote the apoptosis of condylar cartilage cells through inhibiting the protein level of target gene S0X9.

Comparison of computed tomography and magnetic resonance imaging for the detection of mandibular condylar osteochondroma

Objective The purpose of this study was to compare computed tomography(CT) and magnetic resonance imaging(MRI) for the detection of mandibular condylar osteochondroma.Methods Preoperative CT and MRI of 33 patients with unilateral condylar osteochondroma were reviewed. The morphology, location, continuity with the parent bone, cartilage cap, perichondrium of tumors, and changes in soft and hard tissues adjacent to the lesions were investigated by two reviewers. Data were analyzed using Mc Nemar test. A P value < 0.05 was considered significant.Results Among the 33 condylar osteochondromas, 11 were of the diffuse type, 10 were of the sessile type, and 12 were of the pedunculated type. Continuity with the cortex and marrow of the host condyle was observed on both CT and MRI. Both modalities had identical detection rates of surface reconstruction of the temporal bone joint, condylar dislocation, and pseudarthrosis formation. However, MRI showed significantly higher detection rates of the cartilage cap and perichondrium than CT(P < 0.05). Furthermore, MRI showed ipsilateral and contralateral temporo-mandibular joint(TMJ) disc displacement in 4 cases and 6 cases, respectively, and ipsilateral and contralateral TMJ effusion in 20 cases and 14 cases, respectively.Conclusion CT can intuitively display the morphology and spatial location of condylar osteochondromas through three-dimensional reconstruction. MRI may be superior to CT in the detection of cartilage cap, perichondrium of the condylar osteochondroma, and changes in the TMJ and adjacent soft tissues.

Hoffa's fracture in a five-year-old child diagnosed and treated with the assistance of arthroscopy:A case report

BACKGROUND Hoffa’s fracture is a coronal-oriented fracture of the femoral condyle.It is rarely observed in pediatric patients that isolated coronal fracture of the medial femoral condyle accompanies an intact lateral femoral condyle.Only a few cases involving Hoffa’s fracture of the medial femoral condyle have been reported in patients with undeveloped skeletons.Such a fracture cannot be observed by routine imaging examinations,thus resulting in possible misdiagnosis and further treatment challenges.CASE SUMMARY A 5-year-old boy with Hoffa’s fracture of the medial femoral condyle suffered from right knee pain and severe swelling after being hit by a heavy object.The patient was misdiagnosed and initially treated in a local primary healthcare center.No improvement in his right knee’s extension was observed following conservative treatment for 2 wk.The patient was transferred to our hospital,rediagnosed using arthroscopy,and underwent open reduction and internal fixation.The therapeutic outcome was satisfactory with the screws removed 7 mo after fixation.At the final follow-up of 40 mo,the range of motion in the knee had recovered.There was no varus-valgus instability.CONCLUSION Hoffa’s fracture is rarely seen in children aged 5 years,let alone in the medial condyle,and can easily be misdiagnosed due to limited physical and imaging examinations.Suspected Hoffa’s fracture in preschool children should be confirmed based on arthroscopic findings.Open reduction and internal fixation should be performed to protect the articular surface and prevent long-term complications.

Influence of occlusal splint thickness on the position of mandible

Objective: To investigate the influence of occlusal splint thickness on mandibular movement. Methods: Stabilization occlusal splints of 3, 5 and 7 mm thickness were respectively used during clenching from light contact in intercuspal position and the movement of condyles and incisor point were recorded in 5 healthy subjects. Results:The condyles moved anteriorly and superiorly without wearing occlusal splint. When wearing the occlusal splints the condyles displaced anteriorly and inferiorly. The distance of displacement increased gradually with raising the thickness of splint, though the significant difference was just found in right condyle in superior- inferior movement. The condyles went again on a path of anterior and superior direction when subjects clenched from the displaced position. In right condyle the displacement was significantly greater at 7 mm splint than that at 3 mm splint both in anterior-posterior and inferior-superior direction, while in left condyle only in anterior-posterior direction. Meanwhile, the incisal point movement was larger at 7 mm splint than at 3 mm splint in inferior-superior direction. In tapping movement there were no significant differences in condyle movement between the different thickness of occlusal splint. However, the coefficient of variation in total cycle time was the greatest when wearing the splint of 7 mm. Conclusion: Occlusal splint of 7 mm has greater effect than that of 3 mm on condyle movement, but no obvious difference with occlusal splint of 5 mm. When occlusal splint of 7 mm is inserted, the stability of condyle might be influenced during tapping movement.

Condylar invasion after postoperative chemotherapy for primary intraosseous squamous cell carcinoma of the mandible: a case report

Primary intraosseous squamous cell carcinoma (PIOSCC) is a rare malignant tumor that occurs predominantly in the jaw. Pathological evidence shows that PIOSCC originates from the residual odontogenic epithelium and a preexisting odontogenic cyst or tumor. Here, we report the case of a 63-year-old man with central squamous cell carcinoma of the mandible. On the basis of imaging and histopathology reports, the patient was diagnosed with PIOSCC of the jaw. Subsequently, he was treated with postoperative adjuvant chemotherapy. During a postoperative follow-up visit in the ninth month, mandibular computed tomography (CT) scanning and bone imaging revealed local recurrence and condylar invasion. Therefore, radiation along with chemotherapy was administered. This case study adds to the literature on PIOSCC and widens the understanding of its diagnosis, treatment, and prognosis.

Morphology of the Temporomandibular Joint (TMJ) of Sheep (<i>Ovis aries</i>)

The detailed anatomy of TMJ of sheep was explored so that it could be used as an experimental animal for study of condylar growth. The experimental animal was a 3 month old sheep, head of which was procured from a local abettor. The results showed that the sheep is an excellent experimental model for the study of condylar growth, with and without the use of functional appliances, because of similarity in anatomy related to size, shape and position of the condyle to that of human beings. Thus, it is concluded that the study will help future investigators in the field of dentistry to consider the sheep as an experimental animal for further research.

Effects of estradiol on proliferation and metabolism of rabbit mandibular condylar cartilage cells in vitro

Objective To investigate the effects in vitro of 17 β-estradiol (E2) on the proliferation and metabolism of rabbit mandibular condylar cartilage cells.Methods Chondrocytes were derived from neonatal rabbit mandibular condylar cartilage using a modified enzyme method. 17p-estradiol was added to the culture medium in a variety of concentrations. Cell growth and DNA, collagen, and proteoglycan synthesis were used as indicators of proliferation and differentiation of condylar chondrocytes. These were measured by cell number, 3H-proline and 35S-incorporation, respectively.Results E2 increased cell number and 3H-thymidine incorporation at 10^(-8) to 10^(-10)mol/L, and 10^(-8) to 10^(-11) mol/L in a dose-dependent manner, peaking at 10^(-8) mol/L and 10^(-9) mol/L, respectively. However, further increase in the concentration of estradiol caused inhibition of both cell number and 3H-thymidine incorporation, and this was significant at 10^(-6) mol/L. The effect of E2 on proteglycan synthesis was similar; the maximum stimulating effect was at 10^(-8) mol/L, and inhibition was significant at 10^(-6) mol/L. There was no obvious stimulatory effect of E2 on 3H-thymidine incorporation observed.Conclusions Estradiol affects condylar chondrocyte cell growth, DNA, and proteoglycan synthesis in a biphasic manner depending on its concentration. This indicates that estrogen may be important in the proliferation and differentiation of mandibular condylar chondrocytes, and could be relevant to some aspects of certain tempormandibular joint diseases by modulating the function of the chondrocytes.