Evaluation of reliability test and clinical application of monosegment thoracic and lumbar fracture dislocation classification / 中华骨科杂志

Objective:To propose a monosegment thoracic and lumbar fracture dislocation (mTLFD) classification, and to evaluate its reliability and clinical application.Methods:All of 298 cases of thoracic and lumbar fracture dislocation who received surgical management in our hospital from January 2014 to December 2019 were retrospectively analyzed. 123 cases were included in the study according to inclusion and exclusion criteria. mTLFD classification was proposed based on the imaging characteristics: type I (intervertebral disc injury mainly) and type II (vertebral burst fracture mainly). The type II was classified based on distribution of injury segment: type IIa (T 11 and above) and Ttype IIb (below T 11). Six spinal surgeons (3 residents, 3 associate chief physicians) were selected to classify the 123 cases according to preoperative imaging data, and to perform reliability test of each type. The repeatability and reliability of the classification were evaluated by ICC index. Different management strategies were performedf or each type: type I was managed with posterior decompression interbody fusion and internal fixation; type IIa underwent posterior decompression and fixation, subtotal vertebral resection and fusion was performed if bony compromise was still present through intra-operative exploration. Type IIb underwent posterior decompression, posterolateral fusion and internal fixation on the first stage, while anterior subtotal vertebral resection and reconstruction was performed on the second stage if the bony compromise was still present based on post-operative CT examination. The American Spinal Injury Association (ASIA) grading of all patients was recorded, and the visual analogue scale (VAS), Oswetry disability Iindex (ODI) and local Cobb angle of each type was compared between pre-operation and final follow-up. Results:The average follow-up time of all patients was 10.4±1.8 months. The average repeatability and reliability ICC index of mTLFD of 3 residents and 3 deputy chief physicians were 0.926 and 0.964, respectively, and 0.746 and 0.907, respectively. The reliability ICC index of type I, type IIa and type IIb was 0.918, 0.947 and 0.962, respectively, and the repeatability ICC index was 0.930, 0.940 and 0.966, respectively. The neurological function recovery was obtained in 56 patients. The preoperative VAS of type I, type IIa and type IIb were 8.5±1.0, 8.4±1.0 and 8.3±0.9, and 2.0±1.1, 1.8±1.0 and 1.8±0.9 at the final follow-up (all P<0.001). The ODI of type I, type IIa and type IIb were 97.0%±2.1%, 97.1%±1.9% and 97.3%±2.1% before surgery, and 29.5%±6.8%, 27.0%±6.0% and 29.0%±6.7% at the final follow-up (all P<0.001). The local Cobb angles of type I, type IIa and type IIb were 20.9°±7.1°, 29.0°±9.1° and 26.4°±6.9° before surgery, and 12.5°±5.4°, 18.0°±9.1° and 13.1°±5.1° at the final follow-up (all P<0.001). Conclusion:The mTLFD classification proposed in this study has strong repeatability and reliability, and management strategy of each type have achieved satisfactory clinical efficacy, indicating that the classification has certain significance for management of thoracic and lumbar spine fracture dislocation.

Contralateral radiculopathy after unilateral transforaminal lumbar interbody fusion / 中华骨科杂志

Objective To analyze the incidence and risk factors of contralateral radiculopathy in patients after unilateral transforaminal lumbar interbody fusion (TLIF) surgery.Methods A retrospective study was conducted within 587 patients (average age 57.1 years,range 19-71 years) who underwent unilateral TILF from January 2010 to January 2014 in our hospital,including 334 males and 253 females.Patients were divided into a symptomatic group and an asymptomatic group.The causes of contralateral neurological symptom were evaluated according to the radiological data.The difference of pre-and post-operative contralateral foramen area (CFA),segmental angle (SA) and the clinical treatment outcomes (VAS,JOA score) were compared between two groups.Results Patients were followed up for 9-21 months,average 15.1 months.Post-operative contralateral radiculopathy occurred in 28 (4.8％) of the patients who underwent unilateral TLIF,including contralateral foraminal stenosis in 16 (57.1％,16/28),screw malposition in 5 (17.9％,5/28),contralateral lateral recess stenosis and/or newly developed disc herniation in 3 (10.7％,3/28),hematoma in 1 (3.6％,1/28),cement compression in 1 (3.6％,1/28),and unknown origin in 2 patients (7.1％,2/28).Nineteen (3.2％,19/587) of the 28 patients received revision surgery because of ineffective conservative treatment.Compared with the asymptomatic group,the difference of pre-and post-operative CFA was significantly smaller (-13.8±13.2 mm2) in symptomatic group,while the SA was significantly greater (7.0°±9.8°) in symptomatic group.The JOA score at 3 months after the surgery was significantly improved in asymptomatic group (63.0％±18.1％,P＜0.05).Conclusion The incidence rate of contralateral neurological symptom was 4.8％ in the present study.The potential risk factors associated with contralateral radiculopathy were predominantly contralateral foraminal stenosis and screw malposition.The excessive restoration of SA might have an effect on contralateral nerve compression,which should arouse the attention of the surgeon.

Inhibition of autophgay enhances resveratrol-induced apoptosis of human chondrosarcoma cells / 中国病理生理杂志

AIM:Toinvestigatewhetherautophagyisup-regulatedwhenresveratrol(Res)inducesapoptosis in chondrosarcoma , and to study the effects of autophagy inhibitor combined with Res on chondrosarcoma .METHODS:SW1353 cells were divided into 4 groups: control group, Res group, 3-methyladenine (3MA) group, and Res +3MA group.Electron microscopy was used to observe the autophagyosomes in control group and Res group .At the same time, the viability of the cells in the 4 groups was detected by CCK-8 assay.TUNEL staining and Western blotting (for determi-ning the levels of cleaved caspase-3, Bax and Bcl-2) were used to reflect levels of apoptosis in all groups .The expression of autophagy-related proteins Beclin 1, LC3-Ⅱ and p62 was detected by Western blotting .RESULTS: Exposure of the cells to Res resulted in a decrease in cell viability and an increase in the level of apoptosis ( P<0.05 ) .Compared with control group, the level of apoptosis was increased but the autophagy was decreased (P <0.05).Compared with Res group, the cell viability and the level of autophagy were decreased and the level of apoptosis was increased ( P<0.05 ) . CONCLUSION:Resveratrol induces apoptosis and autophagy , and inhibition of autophgay enhances resveratrol-induced apoptosis in chondrosarcoma .

Complete L₅ burst fracture treated by 270-degree decompression and reconstruction using titanium mesh cage via a single posterior vertebrectomy / 中华创伤杂志(英文版)

Complete burst fractures of the L₅ is relatively uncommon. How to accomplish a rigid internal fixation as well as preserve motor function is an enormous challenge. We report such a case treated via a single posterior vertebrectomy with 270-degree decompression and reconstruction using titanium mesh cage. The disc between L₅/S₁ was preserved by placing the titanium mesh cage on the inferior endplate of the L₅. We hope this method can offer a possible solution for other surgeons when they meet a similar fracture pattern.

Finite element analysis of biomechanical features of percutaneous C1-2 anterior and posterior transarticular screws / 中华创伤杂志

Objective To develop a three-dimensional finite element model of atlantoaxial instability and compare the biomechanical properties of percutaneous anterior transarticular screw (ATS) and posterior transarticular screw (PTS) fixations.Methods A pathologic three-dimensional finite element model of atlantoaxial instability was developed from CT images of the upper cervical spine of volunteers with the aid of softwares,such as Mimics,Freeform,and Ansys.Percutaneous C1-2 ATS and PTS fixation modes were simulated and implanted to the model.Under the preload of 40 N and force moment of 1.5 Nm in anterior flexion,posterior extension,lateral bending,and axial rotation,biomechanical properties of the two fixation modes were compared.Results Under the four loading modalities,both fixation techniques provided maximal inhibition on C1-2 movement.The maximal stress for ATS was larger than that for PTS and maximal displacement for ATS was smaller than that for PTS.Conclusions Both ATS and PTS provide similar outlook and are effective to stabilize the atlantoaxial joint.Biomechanical performance of percutaneous C1-2 ATS is better than that of percutaneous C1-2 PTS.

Comparison of constrained and non-constrained titanium plates in the anterior cervical corpectomy in elderly cervical spondylosis / 中华老年医学杂志

Objective To compare the clinical efficacy and radiologic changes between constrained and non-constrained titanium plate in anterior cervical corpectomy and fusion (ACCF) in elderly cervical spondylosis patients.Methods A total of 58 elderly cervical spondylosis patients who underwent ACCF were divided into group 1 (patients treated with constrained titanium plates,n =30) and group 2 (patients treated with non-constrained titanium plates,n=28).The Japanese Orthopedic Association (JOA) score,fusion rate,the loss of segmental height and cervical lordosis were recorded.The clinical efficacy and imaging features were compared between the two groups.Results The improvement rate of JOA score had no significant differences between group 1 and group 2 [(77.7±18.6)％ vs.(75.8±23.2)％,t=0.340,P＞0.05].At 3 months after operation,the fusion rate was higher in group 2 than in group 1 (89.3％ vs.63.3％,x2 =5.327,P＜0.05).At 3,6 and 12 months after operation,there were no significant differences in the loss of segmental cervical height and lordosis between group 1 and group 2 [(2.42±3.05)mm vs.(0.98±2.86)mm,(3.95±3.65)mm vs.(2.34±2.97)mm,(3.60±4.33)mm vs.(2.40±2.96)mm,(1.64±2.33)° vs.(0.66 ± ±2.14)°,(2.13∧±±3.79)° vs.(0.70±2.99)°,(2.39±4.26)° vs.(0.86±3.25)°,respectively,all P ＞0.05].Conclusions The clinical efficacy is similar in ACCF with the two types of titanium plates.The non-constrained titanium plate can increase the fusion rate in early time,but may aggravate the loss of segmental cervical height and lordosis,which should be used with caution in elderly osteoporosis patients.

Biocompatibility of alpha-calcium sulfate hemihydrate (CSH)/multi-walled carbon nanotube (MWCNT) composites for bone reconstruction application / 生物工程学报

We examined the biocompatibility and the safety of a-calcium sulfate hemihydrate (CSH)/multi-walled carbon nanotube (MWCNT) composites for bone reconstruction application. The biocompatibility of the CSH/MWCNT composites was evaluated by the measures which taking L929 fibroblast cells cultured in the extracted liquid of the composite soaking solution and putting bone marrow stromal cells planted on the composite pellets in vitro, respectively. The cell proliferation was evaluated by MTT test and further observed using an inverted optical microscope and a scanning electric microscope. The toxicity of the composites was evaluated by acute and subacute systemic toxicity test. Long-term muscle and bone implantation in vivo tests were also conducted. L929 fibroblast cells grew well in the extracted liquid, as well as bone marrow stromal cells that could adhere on the surface of sample pellets and proliferated rapidly. MTT test showed that there were no significant differences between the experimental and control groups (P > 0.05). In vivo test manifested that the composites were no toxicity, no irritation to skin and good for bone defect reconstruction. It was proved that a-calcium sulfate hemihydrate (CSH)/multi-walled carbon nanotube (MWCNT) composites exhibited excellent biocompatibility for the potential application in bone tissue engineering.

Clinical evaluation of complications related to Coflex interspinous process device for degenerative lumbar disc diseases / 中华骨科杂志

Objective To investigate complications associated with Coflex interspinous process device for degenerative lumbar disc diseases and methods to treat.Methods Clinical data of 121 patients with degenerative lumbar disc diseases,who had undergone surgical decompression and additional fixation of Coflex between November 2007 and June 2011,was analyzed retrospectively.There were 76 males and 45 females,aged from 37 to 75 years (average,54.6 years).Surgery-related complications and sequelae were recorded and analyzed.Results Surgery-related complications occurred in 10 patients,and the incidence was 8.3％ (10/121).There were 3 cases of device-related complications,including wing break in 1 case,prosthetic loosening in 1 case and spinal process fracture in 1 case; all 3 cases were treated conservatively and received good results.There were 7 cases of non-device-related complications,including dura mater dilaceration in 2 cases,superficial wound infection in 1 case,insufficient decompression of spinal canal in 2 cases,recurrence of disc herniation in 1 case,and intraspinal hematoma in 1 case; the former 3 patients recovered after corresponding treatment,and the latter 4 patients also recovered after re-operation.Conclusion The incidences of complications and re-operation associated with application of Coflex are low,and the incidence of device-related complications is also low.The precise intraoperative manipulation is the key to reduce incidence of device-related complications.It's absolutely necessary to strictly master surgical indications and perform sufficient decompression in order to receive good surgical results and avoid non-device-related complications.

Finite element analysis of cement volume affecting adjacent vertebral endplate in percutaneous kyphoplasty / 中华创伤杂志

ObjectiveTo analyze the stress contribution of different cement volume to the adjacent vertebral endplates in percutaneous kyphoplasty (PKP) so as to explore the possible mechanism of adjacent vertebral fractures after PKP.Methods The three-dimensional finite element model of osteoporotic thoracolumbar vertebral compression fractures was established to simulate vertebral body partial restoration (80％) with PKP.During the process,two doses of bone cement ( polymethylmethacrylate,PMMA) were filled in the vertebral body (4.0 ml bone cement filling 15％ of the vertebral body volume and 8.0 ml bone cement filling 30％ of the vertebral body volume).Endplate stress under conditions of axial compression,flexion and extension was analyzed. ResultsRegarding the two filling doses in PKP,the adjacent vertebral endplate stress under the above-mentioned conditions was all increased at T11 and L1 vertebral body compared with that before operation.Meanwhile,endplate stress had positive correlation with the cement volume and the stress concentrated largely in the anterior and middle parts of endplate.ConclusionsThe stress of adjacent vertebral endplate is positively correlated with cement volume,with anterior and middle parts of endplate as the stress concentration.The probability of adjacent vertebral fractures shows a rising trend with the increase of cement volume in PKP.

Preparation of glial cell line-derived neurotrophic factor loaded microspheres and their in vitro releasing character / 中华创伤杂志

Objective To evaluate the effect of different preparation processes on preparation of the glial cell line-derived neurotrophic factor(GDNF)loaded microspheres and observe the biological activity of GDNF.Methods With polylactide-co-glycolide(PLGA)as the coating material,the GDNF-loaded microspheres were prepared by using double emulsion(W1/O/W2).Two-factor factorial design variance analysis was done to analyze the effects of the composition proportion of lactic acid(LA)and glycolic acid(GA)in PLGA and the stirring speed of multiple emulsion on particle size,entrapment efficiency,burst release and in vitro release characteristics of the GDNF-loaded microspheres.PC-12 bioassay was employed to detect the biological activity of the released GDNF so as to determine the optimal preparation process.Results The composition proportion of PLGA could affect the microspheres'burst release(P ＜ 0.05),with no effect on particle size and entrapment efficiency.with the higher.With higher proportion of GA,the release speed of GDNF in the microspheres was increased.When the stirring speed of multiple emulsion was increased from 1 000 r/min to 3 000 r/min,the particle size of the microspheres was decrease significantly(P ＜ 0.01),the burst release was increased markedly(P ＜ 0.01)and the in vitro release rate was accelerated.The activity of GDNF in the microspheres could last for about 20 days at 37℃,which was 10 days longer than that of single GDNF.Conclusions Double emulsioncan prepare the GDNF-loaded microspheres with high entrapment efficiency and suitable in vitro release time.In the meantime,the microspheres can extend the validity of GDNF.

Clinical evaluation of interspinous dynamic internal fixation for low back pain / 中华骨科杂志

Objective To evaluate the mid-term clinical effects and the imaging changes of Coflex interspinous dynamic internal fixation for low back pain. Methods From February 2007 to June 2009,Coflex interspinous dynamic internal fixation was performed in a consecutive 45 patients. They included 26 males and 19 females, with an average of 51.4 years ranging in age from 45 to 70 years. Thirty-two cases were in L4.5 level, 11 in L5S1 level and 2 in both two levels. The patients were treated with limited laminectomy and implanted with Coflex device. Clinical outcomes were assessed by Oswestry disability index (ODI)scores and Japanese Orthopaedic Association (JOA) questionnaires before and after operation. The imaging examination was obtained to assess height of the intervertebral space, area of the intervertebral foramen,segment movement of the operation level, low lumbar curvature and signal of the lumbar disc on MRI. Results The follow-up time ranged from 10 to 34 months, with an average of 24 months. The ODI scores decreased significantly from 62.82±10.42 preoperatively to 11.80±3.35 postoperatively. The JOA scores were improved remarkably from 9.00±2.63 preoperatively to 24.65±1.86 postoperatively. The proportion with optimal effect was 89% (40 cases). The Cobb angle after operation of L4.5 and L5S1 level was 15.1°±3.9° and 16.3°±3.8° respectively, which was significantly decreased after operation. The range of motion of the L4.5 level increased from 6.5°±1.5° to 8.4°±2.6° while the L5S1 level did not change notedly. The heights of the dorsal intervertebral disc, distance of the spinous processes, intervertebral foramen height and area were significantly higher than those before operation. Conclusion The Coflex interspinous dynamic internal fixation is available to reserve segment movement, to increase intervertebral space height and foramen area. Meanwhile,it is effective to self-repair and prevent degeneration for the disc in adjacent levels.

Treatment choices for unilateral cervical facet locking / 中华创伤杂志

Objective To explore different treatment choices for unilateral cervical facet locking. Methods The study involved 32 patients with cervical unilateral facet locking. Successful reduction by the skull traction was done in eight patients, of whom three were fixated by the head and neck chest plas-ter after a month of traction. Five patients were treated with anterior decompression and internal fusion fixation. The other 23 patients resulted in failure of traction and then were treated with anterior reduction, discectomy and internal fusion fixation in 14 patients, subtotal vertebral decompression and bone graft fix-ation in three, posterior open reduction and anterior bone graft fixation in one, posterior reduction, fixation and internal fusion fixation in three and posterior reduction and decompression plus anterior discectomy decompression and bone graft fixation in two. Due to misdiagnosis, one patient was treated with anterior decompression and fusion eight months after injury. Results A follow-up for average 18 months showed cervical instability in two patients who were treated with only traction, without fusion. The patients treated with anterior cervical fusion obtained bone union after 12 weeks, with satisfactory cervical physiological curvature and vertebral height. There were no internal fixation complications or neurological complications. Conclusions The treatment of lower cervical unilateral facet locking needs a compre-hensive considerations on whether there associates with disc injury, posterior column fractures or spinal cord injuries. As for patients with lower cervical unilateral facet locking combined with traumatic cervical disc herniation, the anterior reduction and decompression is the choice of treatment. While for those with-out disc herniation, traction or posterior open reduction and fixation can be carried out directly.

Clinical characteristics and treatment of upper cervical spine injuries in the elderly / 中华创伤杂志

Objective To discuss the clinical characteristics and treatment of upper cervical spine injuries in the elderly. Methods A retrospective study was done on clinical data of 28 elderly patients ( > 60 years old) with upper cervical spine injuries treated from January 2003 to December 2007. There were 20 males and 8 females, at age range of 60-86 years (mean 68.1 years). Injury causes included slip in 16 patients, traffic injury in eight and fall from height in four. Atlas fractures occurred in five patients and axis ones in 15,of which there were eight patients with odontoid fractures, six with C2 vertebral arch fractures and one with C2 body fractures. Upper cervical spine injury was combined with lower cervical spine injuries in five patients. There were combined atlantoaxial injuries including odontoid fractures combined with lateral atlas fracture in one and edontoid fractures combined with anterior atlas arch fracture in one. Atlantoaxial dislocation occurred in one patient and combined spinal injury in four. Of all, eight patients were treated conservatively, eight with open surgical operation and 12 with minimally invasive surgery. Results The average hospital stay was 16.5 days, with no statistical difference be-tween conservative treatment group and open surgical operation group ( P > 0.05 ). While the average hos-pital stay in minimally invasive surgery group was shorter than that in conservative treatment and open sur-gical operation groups ( P < 0.05 ). Of all, two patients in conservative treatment group and one in open surgical operation group died and the other 25 patients were followed up for average 16.8 months (9-56 months). The satisfaction rate was 50% in conservative treatment group, 72% in open surgical operation group and 75% in minimally invasive surgery group. Complications occurred in four patients in conserva-tive treatment group, three in open surgical operation group and two in minimally invasive surgery group. Conclusions With odontoid fracture the most common injury type, upper cervical spine injuries arema-inly caused by low-energy force and characterized by low mobidity of spinal cord injuries and high possi-bility of missed diagnosis in the elderly patients. The surgical treatment especially minimally invasive surgery can bring good results compared with conservative methods.

Percutaneous C2 pedicle lag screw for treatment of Hangman's fractures / 中华创伤杂志

Objective To study the feasibility and clinical effect of percutaneous C2 pedicle lag screw in treatment of Hangman's fracture and define the indications of the technique. Methods There were 9 patients including 5 males and 4 females at average age of 36 years (26-68 years). According to a Levine and Edwards System, there were 5 patients with type Ⅰ hangman' s fracture, 3 with type Ⅱ hangman' s fracture and 1 with type Ⅱ A hangman' s fracture. According to American spinal injury association (ASIA) system, the spinal cord function was ranked at Type D in 2 patients and Type E in 7. All patients achieved anatomic reduction by skull traction. Under general anesthesia, 9 patients were fixed with percutaneons C2 pedicle lag screw. The whole procedure was done under monitoring of "C"-arm fluoroscopy for safety and accuracy. Results All patients obtained bony fusion within 2-3 months, with no infection, neurological deficits, vertebra artery injury or other complications. CondusionsThe percutaneous C2 pedicle lag screw fixation is minimally invasive and effective for treatment of Hangman's fracture. During the course of treatment, the function of upper cervical spine remains unaffected.

Influence of continuous pressure on the function of rabbit bone marrow stromal cells proliferation / 中国矫形外科杂志

[Objective]To investigate the influence of pressure on the proliferation of rabbit bone marrow stromal cells(MSCs) and explain the relationship of the hip prosthesis submerge and loosening with continuous pressure after revision of total hip replacement.[Method]A unit of MSCs pressure model was set up to load different pressures on MSCs cultured in vitro.[Result]MSCs showed more proliferation capacity under discontinuous pressure.MTT assay was used to determine the cell proliferation of primarily cultured MSCs under discontinuous pressure.The MSCs OD value of pressured groups was much smaller than the control group at different times.Various magnitudes and durations of the discontinuous pressure could significantly suppress MSCs proliferation with the magnitude-dependent.[Conclusion]At the early period after revision of total hip replacement,patients should lie and exercise on the bed until 6 weeks.Otherwise,the weight-bearing pressure may restrain MSCs proliferation which is harmful to union and may cause prosthesis submerge and loose.

Stability analysis of an enhanced load sharing dynamic pedicle screw fixation device and its equivalent rigid device / 中华外科杂志

<p><b>OBJECTIVES</b>To compare the stability of an enhanced load sharing dynamic pedicle screw fixation device with its equivalent rigid device and to evaluate biomechanical roles of the dynamic fixation.</p><p><b>METHODS</b>A model of L(1) body fracture was produced on seven specimens of fresh adult cadaver spine from T(10) to L(4). Both dynamic and rigid devices were applied in the specimens to strength the injured level. Ranges of three dimensional movements and stiffness under flexion-compression were measured in intact, injured and stabilized specimens.</p><p><b>RESULTS</b>Both dynamic and rigid devices were found to provide significant stability for injured segment in flexion-extension and lateral bending. In axial rotation, the devices could restore the stability to levels similar to those in an intact spine. Results indicated 40% increase in range of motion in flexion-extension and 24.1 Nmm reduction in stiffness of flexion-compression for dynamic device, compared with the rigid device.</p><p><b>CONCLUSION</b>The dynamic device offers a design that may enhance load sharing without sacrificing the stability and will decrease stress-shielding and stress concentration.</p>

The effect of an enhanced load sharing dynamic pedicle screw fixation device on the bone mineral density and bone structure of vertebrae / 中华骨科杂志

Objective To compare the influence of the dynamic device(DD) of pedicle screw fixation and its equivalent rigid device (RD) on bone mineral density and bone structure of the vertebrae. Methods 24 goats were randomly divided into 4 groups: control group, single posterolateral fusion group, dynamic device with posterolateral fusion group and rigid device with posterolateral fusion group. After 24 weeks postoperative observation, the animals were sacrificed and the fixed lumbar spines were harvested. The bone mineral density (BMD) of these harvested specimens was measured by quantitative computed tomography (QCT). Then the L3 segment was embedded in methyl methacrylate and sectioned after alcoholic dehydration. Undecalcified slides (50 ?m in thickness) were stained with toluidine blue. Quantitative histologic analysis was performed in a semiautomatic way. The static parameters consisted of trabecular bone volume (TBV), the mean trabecular plate thickness (MTPT) and mean trabecular spacing (Tb.Sp). The main dynamic histomorphometric parameter, bone mineralization rate (MAR), was calculated by measuring the mean distance between two flurochrome labelings. Results The BMD in the rigid device group decreased significantly compared with control group (P