Dislodgment Effects of Different Cage Arrangements in Posterior Lumbar Interbody Fusion: A Finite Element Study.

The vertebral cage has been widely used in posterior lumbar interbody fusion. The risk of cage dislodgment is high for patients undergoing lumbar fusion surgery. Therefore, the main objective of this study was to use a lumbar fusion model to investigate the effects of cage dislodgment on different cage arrangements after PLIF. Finite element analysis was used to compare three PEEK cage placements, together with the fibula-type cage, with respect to the four kinds of lumbar movements. The results revealed that a horizontal cage arrangement could provide a better ability to resist cage dislodgment. Overall lumbar flexion movements were confirmed to produce a greater amount of cage slip than the other three lumbar movements. The lower part of the lumbar fusion segment could create a greater amount of cage dislodgment for all of the lumbar movements. Using an autograft with a fibula as a vertebral cage cannot effectively reduce cage dislodgment. Considering the maximum movement type in lumbar flexion, we suggest that a horizontal arrangement of the PEEK cage might be considered when a single PEEK cage is placed in the fusion segment, as doing so can effectively reduce the extent of cage dislodgment.

Interim Use of Antibiotic-Loaded Cement Spacer for Patients with Infected Cervical Fusion.

OBJECTIVE: The management of postoperative deep infection after anterior cervical discectomy and fusion (ACDF) remains challenging for spine surgeons. Our institution uses handmade antibiotic-loaded cement spacers to treat these complex cases. This study aimed to determine the efficacy and feasibility of this treatment. METHODS: This study included 4 patients with deep cervical spine infections after ACDF who underwent our treatment between March 2012 and January 2022. Patients' laboratory data, visual analog scale scores, comorbidities, complications, and neurological status were recorded. Their clinical conditions were also evaluated based on the Neck Disability Index, Japanese Orthopaedic Association score, and Odom criteria. RESULTS: Infection eradication was achieved in all patients after treatment. The average preoperative visual analog scale score was 7.5 (range: 7-8); this decreased to 1.25 (range: 1-2) at 1 year postoperatively. None of the patients experienced severe complications, such as neurological deterioration or bone graft dislodgement. The Neck Disability Index improved from a preoperative value of 54% (range: 48-60%) to 6% (range: 4-8%) at 1 year postoperatively. The Japanese Orthopaedic Association score improved from a preoperative score of 10.25 (range: 10-11)-14.75 (range: 14-16) at 1 year postoperatively. All patients achieved excellent outcomes based on Odom criteria at 1 year postoperatively. CONCLUSIONS: Good clinical outcomes were achieved in this study. Although 2-stage surgery is required, this technique could be an alternative for patients with postoperative deep infection after ACDF.

Differences in Pain Assessments Between Inpatients and Nurses Leads to Considerable Misestimated Pain.

BACKGROUND: Pain assessments are an important aspect of health care quality because the high prevalence of pain in inpatients may contribute to complications. Several studies revealed a gap in the pain intensity evaluated by nurses (PEN) and patients (PEP). The aim of the present study was to analyze the correlation and agreement between pain assessments conducted by nurses and patients, and to determine patients at high risk of misestimated pain. OBJECTIVES: To compare the difference of pain intensity between the questionnaires conducted by additional assessors and electronic records by nursing staff. STUDY DESIGN: A retrospective study. SETTING: A medical center in Taichung, Taiwan. METHODS: We approached 1,034 patients admitted from January 1, 2018 to December 31, 2018 in our hospital. We compared the assessments of pain intensity using questionnaires conducted by additional assessors with those entered into electronic records by nursing staff. Continuous data were reported as the mean (± standard deviation). The analysis of agreement and correlation were performed by kappa statistics or weighted kappa statistics, and correlation (Spearman rank correlation method). RESULTS: Among the 1,034 patients, 307 patients were excluded. Thus, the final analysis included 686 patients. Patients' median pain intensity was 5 in PEP and 1 in PEN. The patients' pain intensity was underestimated (PEN < PEP) in 539 patients (78.6%), matched (PEN = PEP) in 126 patients (18.3%), and overestimated (PEN > PEP) in 21 patients (3.1%). The surgical interventions (chi squared = 7.996, and P = 0.018) and pain in the past 24 hours (chi squared = 17.776, and P < 0.001) led to a significant difference. LIMITATIONS: The limitation of the study was the single-center and retrospective design. CONCLUSIONS: The gap in pain assessments between inpatients and nurses is an important issue in daily practice. The underestimations of pain were more common than overestimations (78.6% vs 3.1%). Surgical interventions and persistent pain lasting over 24 hours were high risk factors for underestimation, but patients' gender, receiving anesthesia, type of anesthesia, and patient-controlled analgesia did not contribute significantly to differences in pain estimation.

Percutaneous Sacroplasty for Symptomatic Sacral Pedicle Screw Loosening.

Background: This study aimed to evaluate the efficacy of fluoroscopy-guided percutaneous sacroplasty in patients with sacral pedicle screws loosening after instrumented spinal fusion. Methods: We retrospectively reviewed the medical records of 18 patients who underwent percutaneous sacroplasty to treat sacral pedicle screws loosening from January 2016 to December 2019. Imaging studies, visual analog scale (VAS), length of hospital stay, and complications were recorded. The clinical outcomes based on the Oswestry disability index (ODI) and the modified Brodsky's criteria (MBC) were also evaluated to determine the efficacy of percutaneous sacroplasty. Results: All patients had undergone at least 1 year of follow-up in our institute (range, 12-24 months). The average VAS score was 5.6 (range, 4-7) before surgery and decreased to 1.7 (range, 1-3) at the final visit. All patients were discharged on the next day after surgery. No patients experienced complications, such as cement leakage, deep infection, or neurologic deterioration. All patients achieved good or excellent outcomes based on the MBC. The ODI scores improved from 51.8 preoperatively to 25.6 postoperatively. Conclusion: Percutaneous sacroplasty was an effective treatment approach for relieving the patient's symptoms caused by sacral pedicle screws loosening and could be a valuable treatment alternative to extensive revision surgery. Level of clinical evidence: IV.

Single Posterior Approach for Circumferential Debridement and Anterior Reconstruction Using Fibular Allograft in Patients With Skipped Multifocal Pyogenic Spondylodiscitis.

OBJECTIVE: Skipped multifocal pyogenic spondylodiscitis is a rare presentation of spinal infection. In our institution, we used the single posterior approach for circumferential debridement and anterior reconstruction with fibular allograft for treatment. This study aimed to ascertain the viability and reliability of this technique for these difficult cases. METHODS: Nine patients with skipped pyogenic spondylodiscitis who received our treatment method from January 2012 to December 2019 were enrolled in this study. Visual analog scale scores, causative agents, laboratory data, comorbidities, and complications were recorded. The patients' clinical conditions were evaluated based on modified Brodsky's criteria, visual analogue scale, and Oswestry Disability Index. RESULTS: All the patients achieved infection eradication without repeat surgical treatment. The average visual analog scale score was 8.4 (range, 8-9) before operation, which decreased to 1.9 (range, 1-3) 1 year after the surgery. No patient experienced severe complications such as neurologic deterioration or fixation failure. All patients achieved a good or excellent outcome based on modified Brodsky's criteria. The Oswestry Disability Index improved from 80.4 (range, 70-86) preoperatively to 25.1 (range, 20-32) 1 year after the surgery. CONCLUSIONS: In our case series, good clinical outcomes and high successful rates could be achieved through the single-stage posterior-only approach. This could be considered an alternative method to manage patients with skipped pyogenic spondylodiscitis.

Single posterior approach for circumferential debridement and anterior reconstruction using fibular allograft in patients with skipped multifocal spinal tuberculosis.

BACKGROUND: Skipped multifocal spinal tuberculosis (TB) is an atypical presentation of spinal TB. Surgical treatment for these unusual cases remains a challenge for spine surgeons. In our institute, we used single-stage circumferential debridement and anterior reconstruction with fibular allograft followed by posterior instrumentation through posterior-only approach for these patients. This study aimed to determine the efficacy and feasibility of this technique. METHODS: Twelve patients with skipped multifocal spinal TB who received our treatment method from January 2012 to June 2020 were enrolled in this study. The visual analog score (VAS), laboratory data, comorbidities, complications, and neurologic status based on Frankel scale were recorded. The patients' clinical conditions were evaluated based on modified Brodsky's criteria and Oswestry Disability Index (ODI). RESULTS: All the patients were infection free at the end of the treatment. The average VAS score was 7.5 (range, 7-8) before surgery and decreased to 2.1 (range, 1-3) one year postoperatively. No one experienced any severe complications such as neurologic deterioration, fixation failure, or bone graft dislodgement. Out of the three patients requiring debridement surgery, two had wound infection and one had seroma formation. The ODI score improved from 76.8 (range, 70-84) preoperatively to 25.5 (range, 22-28) one year after surgery. All patients achieved good or excellent outcome based on modified Brodsky's criteria one year postoperatively. CONCLUSIONS: In our study, the patients could achieve a good clinical outcome. This technique could be an alternative for patients with skipped spinal TB.

Iatrogenic Lateral Plantar Nerve Injury After Endoscopic Plantar Fascia Release: A Case Report.

We present a 57-year-old female patient with iatrogenic lateral plantar nerve injury caused by endoscopic surgery for plantar fasciitis. Nerve grafting surgery was recommended, but the patient refused further surgical intervention because of personal reasons. After 1-year follow-up in outpatient clinics, she achieved only slight improvement in the lateral foot symptoms and still required oral analgesics for pain control. The purpose of this case report is to remind physicians of such a rare and serious complication that can occur after endoscopic surgery for plantar fasciitis. Good knowledge of anatomy and skilled surgical technique could decrease this type of complication.

A cost and efficacy analysis of performing arthroscopic excision of wrist ganglions under wide-awake anaesthesia versus general anaesthesia.

BACKGROUND: Arthroscopic excision has currently become popular for the treatment of wrist ganglions. The objective of this study was to evaluate the clinical outcomes and cost effectiveness of arthroscopic wrist ganglion excisions under Wide-Awake Local Anaesthesia No Tourniquet versus general anaesthesia. METHODS: We retrospectively reviewed patients who underwent arthroscopic ganglionectomy from April 2009 to October 2016 at our institute. They were separated into two groups according to anaesthesia techniques: general anaesthesia and Wide-Awake Local Anaesthesia No Tourniquet. We compared the clinical outcomes and cost-effectiveness of the two groups. RESULTS: Seventy-four patients were included. Both groups were matched with regard to the demographics and preoperative clinical assessments. We found no significant differences between groups in postoperative visual analog scale, modified Mayo wrist score, Disabilities of Arm, Shoulder and Hand score, recurrence, residual pain, or complications. Recurrence was found in five of 74 patients, one (4.3%) in the Wide-Awake Local Anaesthesia No Tourniquet group and four (7.8%) in the general anaesthesia group. One extensor tendon injury and four extensor tenosynovitis cases occurred in the general anaesthesia group. Regarding cost effectiveness, the mean operating time in the Wide-Awake Local Anaesthesia No Tourniquet and general anaesthesia groups were 88.7 ± 24.51 and 121.5 ± 25.75 min, respectively (p < 0.001). The average total costs of the Wide-Awake Local Anaesthesia No Tourniquet and general anaesthesia groups were €487.4 ± 89.15 and €878.7 ± 182.13, respectively (p < 0.001). CONCLUSIONS: For arthroscopic wrist ganglion resections, both anaesthesia techniques were effective and safe regarding recurrence rates, complications, and residual pain. The most important finding of this study was that arthroscopic ganglionectomy under Wide-Awake Local Anaesthesia No Tourniquet was superior to that under general anaesthesia for cost-effectiveness. LEVEL OF EVIDENCE: Level III, Retrospective comparative study.

Using antibiotic cement nail with multiple screws fixation as a single-stage salvage procedure for patient with infected tibiotalocalcaneal arthrodesis: A case report.

Tibiotalocalcaneal (TTC) arthrodesis with retrograde nail is a widely used treatment option for severe ankle arthropathy. With inherent biomechanical benefits in axial loading and strong bending stiffness, high union rate and good clinical outcomes have been reported in the literature. However, some undesired complications, such as osteomyelitis or implant failure, can develop after this procedure. Herein, we report the case of an 86-year-old man with right ankle osteomyelitis after TTC arthrodesis with retrograde nail. After removing the previous implants and extensive debridement, we used an antibiotic cement nail with multiple screws fixation as a salvage procedure in the same operation. The patient fully recovered without further surgical treatment.

Investigation of pullout strength in different designs of pedicle screws for osteoporotic bone quality using finite element analysis.

PURPOSE: The purpose of this study was to investigate pullout strength of three types of pedicle screws with and without cement augmentation in osteoporotic bone using finite element analysis. METHODS: Twelve 3D finite element models were created to investigate the effect of pullout strength when comparing between pedicle screw types and bone cement clouds. The bottom side of bone block model was constrained and U-shape head was applied 1 mm in direction of longitudinal axis of pedicle screw to perform pullout resistance. The material properties of the FEA was set as linear elastic, homogenous, isotropic condition. The element sensitivity of convergence testing has been performed and variation of the sequential analytical results was less than 3%. RESULTS: The results showed that the maximum total reaction force (133.8 N) was detected in the model of cannulated pedicle screw combined with a central pin with 4 ml cement augmentation, but, in contrast, the minimum total reaction force (106.8 N) was discovered in the model of cannulated pedicle screw without cement. A strong relationship (r = 0.9626) is found in comparison with the biomechanical results between pullout strength of sawbone testing and reaction forces of the FEA. CONCLUSIONS: The study concludes that the cannulated pedicle screw can not only provide an inner guider for cement flow and increase bending resistance (deflection effect) when a central pin is selected, but also can improve the pullout strength in the osteoporotic bone to add cement augmentation. The design of the cannulated pedicle screw is suggested for poor bone quality to change pullout failure.

Erratum - A Novel Model for Studying Voltage-Gated Ion Channel Gene Expression during Reversible Ischemic Stroke.

[This corrects the article DOI: 10.7150/ijms.27442.].

Left stellate ganglion block, a rescue treatment for ventricular arrhythmia refractory to radiofrequency catheter ablation: A care-compliant case report.

RATIONALE: Stellate Ganglion Block (SGB) provides a blockade of sympathetic signals from the sympathetic chain and appears to be a promising method of controlling refractory ventricular arrhythmias, but there are scanty data in the literature. PATIENT CONCERNS: Herein, we describe a 59-year-old male patient with a history of non-ischemic cardiomyopathy and suffering from frequent VT episodes, who received ICD implantation and regular amiodarone medication control. DIAGNOSES: Monomorphic VT refractory to standard medication control and focal extensive catheter ablation. INTERVENTIONS: Left Stellate Ganglion Block (LSGB) was performed under ultrasound-assisted injection at the C6 level using a 10 ml solution of 0.4% lidocaine and 0.5% bupivacaine. OUTCOMES: In our case, refractory VT subsided and sinus rhythm was retained immediately after LSGB. There were no VT episodes for at least 3 hours during the inter-hospital transfer, which did not involve any specific complications. LESSONS: LSGB may provide effective VT control and play an important role in rescue and bridge therapy before catheter ablation.

Topically Applied Cross-Linked Hyaluronan Attenuates the Formation of Spinal Epidural Fibrosis in a Swine Model of Laminectomy.

Epidural fibrosis is an inevitable aspect of the postoperative healing process which is one of the causes of failed back surgery syndrome following spinal surgery. The aim of the present study was to examine the inhibitory effect of 1,4-butanediol diglycidyl ether-crosslinked hyaluronan (cHA) on spinal epidural fibrosis in a swine model. Epidural fibrosis was induced through conduction of hemi-laminotomy (L2 and L3) or laminectomy (L4 and L5), while L1 was assigned as the control group in six pigs. The cHA was applied to L3 and L5 surgical sites. MRI evaluation, histologic examination, expressions of matrix metalloproteinases (MMPs), and cytokines in scar tissue were assessed four months after surgery. cHA treatment significantly decreased the scar formation in both hemi-laminotomy and laminectomy sites. cHA also significantly increased MMP-3 and MMP-9 expression in scar tissue. Further, the epithelial-mesenchymal transition -related factors (transforming growth factor-ß and vimentin) were suppressed and the anti-inflammatory cytokines (CD44 and interleukin-6) were increasingly expressed in cHA-treated sites. The current study demonstrated that cHA may attenuate spinal epidural fibrosis formation after laminectomy surgery by enhancing the expression of MMPs and anti-inflammatory pathways.

Percutaneous endoscopic debridement and drainage for the treatment of instrumented lumbar spine infection.

PURPOSE: The purpose of this study is to evaluate the efficacy of percutaneous endoscopic debridement and drainage (PEDD) in patients with surgical site infection (SSI) following instrumented lumbar fusion. METHODS: We retrospectively reviewed the medical records of 20 patients (6 women and 14 men; average age, 60.1 years) who underwent PEDD at our institute to treat SSI following instrumented lumbar fusion from January 2010 to December 2015. The terminal event, or failure of PEDD treatment, was defined as a shift in treatment methods to open surgery. Risk factors were analyzed to determine their effect on the therapeutic results of PEDD. Clinical outcomes were assessed by careful physical examination, regular serologic testing, and imaging studies to determine whether continued conservative treatment or open surgery was necessary. RESULTS: Causative bacteria was identified in 17 (85%) of the 20 biopsy specimens. Successful infection control through PEDD was identified in 13 patients (65%). Both the visual analog scale and Oswestry disability index significantly improved in these patients. Detection of the causative pathogens was the only risk factor influencing the terminal event in the remaining seven patients (35%). CONCLUSION: In this study, PEDD was an effective treatment approach for obtaining a bacteriological diagnosis, relieving the patient's symptoms, and assisting in eradication of SSI following instrumented lumbar fusion. The use of species-specific antibiotics for the offending pathogens appears to be the most important factor to determine the success rate. The indications of this procedure could be extended to treat patients with SSI after instrumented lumbar fusion.

A Novel Model for Studying Voltage-Gated Ion Channel Gene Expression during Reversible Ischemic Stroke.

The dysfunction of voltage-gated ion channels contributes to the pathology of ischemic stroke. In this study, we developed rat models of transient ischemic attack (TIA) and reversible ischemic neurological deficit (RIND) that was induced via the injection of artificial embolic particles during full consciousness, that allow us to monitor the neurologic deficit and positron emission tomography (PET) scans in real-time. We then evaluated the infarction volume of brain tissue was confirmed by 2,3,5-triphenyl tetrazolium chloride (TTC) staining, and gene expressions were evaluated by quantitative real-time PCR (qPCR). We found that rats with TIA or RIND exhibited neurological deficits as determined by negative TTC and PET findings. However, the expression of voltage-gated sodium channels in the hippocampus was significantly up-regulated in the qPCR array study. Furthermore, an altered expression of sodium channel ß-subunits and potassium channels, were observed in RIND compared to TIA groups. In conclusion, to our knowledge, this is the first report of the successful evaluation of voltage-gated ion channel gene expression in TIA and RIND animal models. This model will aid future studies in investigating pathophysiological mechanisms, and in developing new therapeutic compounds for the treatment of TIA and RIND.

Pullout evaluation of sawbone experiment in different types of pedicle screws combined with bone cement augmentation for severe osteoporotic spine.

PURPOSE: The conventional screw is unable to provide enough screw-bone interface strength for osteoporotic cencellous bone, and complications resulting from loosening or failure of the implants remain a significant clinical problem. Hence, the purpose of this study is to investigate pullout strength and energy in three types of the pedicle screws, including conventional solid pedicle screw, cannulated pedicle screw, and cannulated pedicle screw with a central pin, using osteoporotic sawbone test block with different bone cement volumes through pullout force testing. METHODS: The control group (n = 15) of the osteoporotic sawbone test block includes groups A, B, and C to reflect three types of the pedicle screws without bone cement augmentation. The cemented group (n = 45) of the osteoporotic sawbone test block includes groups D1, D2, D3, E1, E2, E3, F1, F2, and F3 to reflect three types of the pedicle screws with PMMA bone cement of 2, 3, and 4 mL augmentation. RESULTS: The results showed that the pullout strength and energy in the cemented group were significantly larger than that in the control group. Moreover, the best performances of the pullout strength and energy in the cemented group were evidenced obviously in the case of cannulated pedicle screw with a central pin with 4 mL bone cement augmentation. CONCLUSIONS: This study concludes that cement argumentation in the cannulated pedicle screw with a central pin can increase a pullout strength of pedicle screw for severe osteoporotic patients while bone cement of injective volume is limited.

Exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin increases the activation of aryl hydrocarbon receptor and is associated with the aggressiveness of osteosarcoma MG-63 osteoblast-like cells.

The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor whose activity is modulated by xenobiotics and physiological ligands. Activation of the AhR by environmental xenobiotics may induce a conformational change in AhR and has been implicated in a variety of cellular processes, including inflammation and tumorigenesis. It is unknown whether the activation of AhR serves a role in modulating the progression of osteosarcoma. The osteosarcoma cell line MG-63, was treated with AhR ligand, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). TCDD treatment degrades AhR expression through activation of the AhR signaling pathway, however there were no survival differences observed in MG-63 cells. There were concomitant elevations of cyclooxygenase-2 and receptor activator of nuclear factor-κB ligand secretion from MG-63 cells upon TCDD treatment on a protein and mRNA level at 24 and 72 h. In addition, TCDD treatment also increases the production of prostaglandin E2 on MG-63 cells, and induces the expression of chemokine receptor CXCR4. However, CXCL12 production was not altered in MG-63 cells when stimulated with TCDD. The AhR antagonist CH-223191, blocks the effects on TCDD-induced RANKL, COX-2, PGE2 and CXCR4 changes. In conclusion, these findings suggest that AhR signal therapy should be further explored as a therapeutic option for the treatment of osteosarcoma.

Comparison of sacroplasty with or without balloon assistance for the treatment of sacral insufficiency fractures.

PURPOSE: Sacral insufficiency fractures (SIFs) can cause severe lower back pain and immobility, which have limited therapeutic options. No previous studies have compared clinical outcomes and radiographic findings of sacroplasty with or without balloon assistance for the treatment of SIFs. METHODS: Forty-five patients with SIFs were divided into two groups. One group had 18 patients treated using sacroplasty with balloon assistance, and the other had 27 patients treated without balloon assistance. The operation time and cement injection volume were compared between these two groups. Clinical outcomes were evaluated using visual analog scale (VAS), Oswestry Disability Index (ODI), and Odom's criteria. Cement leakage rate was examined by postoperative radiography and computed tomography. RESULTS: Sacroplasty with balloon assistance was associated with significantly longer operative time ( p = 0.003) and larger cement injection volume ( p = 0.038). Cement leakages were found in 4 of 18 patients (22.2%) with balloon assistance and 15 of 27 patients (55.6%) without balloon assistance, which showed significant difference ( p = 0.027). No significant differences were observed between sacroplasty with and without balloon assistance with regard to clinical outcomes including improvement in VAS, ODI, and Odom's criteria. CONCLUSIONS: Sacroplasty with balloon assistance was shown to achieve greater cement injection with longer operation time and can decrease the risk of cement leakage. Both sacroplasty with and without balloon assistance showed good-to-excellent clinical outcomes for the treatment of SIFs.

Assessment of thermal necrosis risk regions for different bone qualities as a function of drilling parameters.

BACKGROUND AND OBJECTIVE: During bone drilling, the heat generated by friction depends directly on bone quality and surgical parameters. Excessive bone temperatures may cause thermal necrosis around the pilot hole, weaken the purchase of inserted screws, and in turn reduce the stability of screw fixation. A few studies have addressed the key parameters of drilling, such as the rotation speed of the drill-bit, feed force (axial force), feed rate, tool type, and tip geometry of drill-bits. Nevertheless, in the literature, information on the relationship between bone quality and thermally affected regions is still lacking. This study employed a three-dimensional dynamic elastoplastic finite element model to evaluate the influence of surgical parameters on the bone temperature elevation and assess the risk region of thermal necrosis for different bone qualities as a function of drilling parameters. METHODS: To ascertain the heat generation rate and the high-risk region of thermal necrosis, the effects of bone quality, feed rate, feed force, and drill-bit diameter on the bone temperature elevation were explained using a three-dimensional dynamic elastoplastic finite element model, which was validated through experimental measurements. RESULTS: The bone temperature was affected by the drilling parameters; the maximum temperature was attained at the junction of cancellous and cortical bones. The bone temperature increased with cortical bone thickness, bone density, and drill-bit diameter, and it decreased with the drilling speed and feed force. CONCLUSIONS: The present model could assess the risk region of thermal necrosis by accurately analyzing the bone temperature elevation for various bone qualities, feed forces, and feed rates. The bone temperature increased with the bone mineral density and cortical bone thickness. The highest bone temperature and maximum necrosis region were found near the junction of cortical and cancellous bones. Increasing the drilling speed or feed force can minimize the bone temperature elevation and the risk range of thermal necrosis.