Meta-analysis of the efficacy of volar plate internal fixation versus closed reduction and external fixation in the treatment of adult distal radius fractures

Objective:To compare the efficacy of open reduction and volar locking plate internal fixation with closed reduction and external fixation in the treatment of distal radius fractures by using meta analysis.Methods:The databases of CNKI,Wanfang,Weipu,Chinese biomedical literature,Pubmed,Embase,and Cochrane Library were retrieved,and the randomized controlled studies that directly compared the efficacy of plate internal fixation and closed reduction external fixation in the treatment of distal radius fractures published publicly from the establishment of the database to April 2023 were collected.The two researchers independently screened the retrieved literature according to the inclusion and exclusion criteria,extracted data,used Cochrane risk bias assessment tool for quality assessment,and used RevMan 5.4 software for meta analysis.Results:A total of 10 randomized controlled trials were included,all of which were in English.There were 1042 patients in total,and 9 of them were rated as low risk.Meta analysis results showed that one year after the treatment of distal radius fracture with volar locking plate internal fixation,DASH score[MD=-5.64,95%CI(-7.21,-4.06),P<0.00001];One year later,PRWE score[MD=-5.90,95%CI(-8.88,-2.92),P=0.001];Palm flexion[MD=5.92,95%CI(1.29,10.55),P=0.01];Pronation[MD=2.48,95%CI(0.59,4.36),P=0.01];Postrotation[MD=4.73,95%CI(2.15,7.31),P=0.0003];Grip strength[MD=0.61,95%CI(0.12,1.10),P=0.02];palmar tilt angle[MD=9.84,95%CI(5.66,14.02),P<0.00001];Radial inclination[MD=4.33,95%CI(2.97,5.69),P<0.00001]was superior to closed reduction plaster or splint external fixation.One year later,the European Five dimensional Health Scale(EQ-5D-5L)score[MD=0.02,95%CI(-0.01,0.05),P=0.27];Back extension[MD=2.22,95%CI(-4.15,8.59),P=0.49];Ulnar deviation[MD=3.49,95%CI(-0.80,7.78),P=0.11];Radial deviation[MD=2.05,95%CI(-2.39,6.50),P=0.37];Ulnar variance[MD=-1.14,95%CI(-3.16,0.88),P=0.27];There was no significant difference in complications[MD=0.77,95%CI(0.54,1.10),P=0.16](P>0.05).Conclusion:Based on the current clinical data,internal fixation with volar locking plate is more conducive to mid-term DASH score and grip strength recovery than closed reduction plaster or splint external fixation,but there is no significant difference in the quality of life and complications of patients.For adult distal radius fractures,surgical indications should be carefully grasped,and non operative treatment should be given priority.

Dynamic External Fixator Combined with Volar Locking Plate Fixation for the Treatment of AO Type C3 Distal Radius Fractures

Background: AO type C3 distal radius fracture (DRF) is the most difficult-to-treat fracture type because of a tendency to shorten and collapse. The purpose of this study is to investigate the clinical and radiographic outcomes of comminuted intra-articular DRFs treated with a dynamic external fixator combined with a volar locking plate (VLP). Methods: Eleven patients (mean age, 61 years) with comminuted intra-articular DRFs were treated with a dynamic type of external fixator combined with a VLP. Following reduction and fixation with a VLP, the dynamic external fixator was applied and the distal ball joint of the fixator was aligned with the lunate-capitate line. The ball joint was unlocked approximately 2 weeks after surgery to allow wrist mobilization. The fixator was removed 3 - 6 weeks (mean, 5 weeks) after surgery. Consequently, clinical and radiographic assessments were carried out at the final follow-up. Results: At the final follow-up, the mean range values of wrist extension and flexion were 76&deg;and 64&deg;, respectively. Compared with the contralateral side, the mean grip strength was 84%. The mean Modified Mayo Wrist Score and the Disabilities of the Arm, Shoulder and Hand score were 88 and 9, respectively. No significant differences in the radiographic parameters exist between after surgery and final follow-up. Conclusions: This study indicated that the dynamic wrist fixator combined with a VLP is effective for the treatment of AO type C3 DRFs.

Emergent and delayed hybrid external fixation management of tibial pilon fractures: A multicentric retrospective analysis of 80 patients

Objective:To report our experience with the hybrid external fixator in emergency.Methods:We assessed 80 cases of pilon fracture treated with the external fixator during the period of January 2009 and December 2016:55 men (69%) and 30 women (33%) with a mean age of 40 years (range between 16 and 70 ). About 45 occurred as isolated trauma, 35 instead were politrauma. Each patient underwent standard radiographic examination and a CT examination. There were 28 open fractures (35%), (Gustilo type 1, 2 and 3) while closed fractures showed soft tissue involvement of various grade (2-3 Tscherne classification). In all cases, the external fixation, sometimes associated with other reduction and synthesis techniques, was used. The timing of surgery was dictated by the condition of the soft tissues. For clinical evaluation, the Mazur score with mean follow-ups at 12 months was utilized.Results:The final range of ankle motion was 15 dorsal and 10 plantar flexion. In about 80 cases there was an average Mazur score of83. The mean score was 90;in open fractures 85 to 72. Radiographic healing of fractures in 60 patients occurred in 120 days (mean 105 days), at the time when the external fixator was removed.Conclusion:Pilon fractures are complex and often present complications;the definitive treatment, in emergency or delayed, with hybrid external fixator permits a stable synthesis with minimal soft tissue damage. Weight bearing maybe allowed early and functional recovery is generally good.

External fixation is more suitable for intra-articular fractures of the distal radius in elderly patients

The purpose of this study was to compare the functional outcomes, psychological impact, and complication rates associated with external fixation and volar or dorsal plating in relation to the functional parameters following treatment of intra-articular fractures of the distal radius （IFDR） in patients older than 65 years. We hypothesized that using volar or dorsal plating would improve functional outcomes, but that it would be associated with more complications and equivalent functional outcomes when compared with the external fixation group. A total of 123 consecutive patients suffering from IFDR were recruited into the study. The patients were measured for clinical, radiological, and psychosocial functioning outcomes and were followed up after I week and 3, 6 and 12 months. After 3 months, the plating group had better pronation （P = 0.001）, supination, （P = 0.047） and extension （P = 0.043） scores. These differences were somewhat attenuated by 6 months and disappeared at I year. The plating group had a greater occurrence of wound infection （P = 0.043）, tendonitis, （P = 0.024） and additional surgery compared with the external fixation group. The only TNO-AZL Adult Quality of Life scores in the plating group that were lower than those in the external fixation group were in the ＂gross motor＂ category （walking upstairs, bending over, walking 500 yards; P = 0.023）. Internal fixation was more advantageous than external fixation in the early rehabilitation period; after I year the outcomes were similar. The plating group showed significantly higher levels of wound infection and tendonitis and had a greater need for additional surgeries.

Advantages of Ilizarov External Fixation in an Elderly Patient with Pilon Fracture with Severe Soft Tissue Injury and Severe Osteoporosis: A Case Report

Introduction: Pilon fracture in elderly individuals is characterized by senile skin atrophy, poor dermal extensibility, and thin subcutaneous tissue. The use of bulky internal fixation material can thus cause the swelling that accompanies the fracture to induce secondary injury to skin tissue. In addition, initiation of postoperative weight-bearing is delayed due to bone fragility and difficulties with partial weight-bearing, causing a tendency toward prolonged hospitalization. Mean duration of hospitalization after pilon fracture for elderly patients in our department was 79.2 days. Case Presentation: An 80-year-old woman with pilon fracture with soft tissue injury and severe osteoporosis was transferred to our department. The fracture was treated using Ilizarov external fixation. Fourteen days postoperatively, walking with full weight-bearing was permitted. The hospital stay was 28 days. The external fixator of the ankle was removed 87 days postoperatively, at which time the patient was anatomically and functionally recovered and able to walk unaided. Conclusion: Ilizarov external fixation may represent a useful option in elderly patients with pilon fracture showing severe soft tissue injury and severe osteoporosis. The present case provides evidence that this procdure can be successfully applied to the management of such pilon fractures in elderly patients.

Hybrid External Fixation for Open Severe Comminuted Fractures of the Distal Femur

Background: The treatment of distal femoral open comminuted fractures is a major problem for orthopedic surgeon. The basic and important aim in treatment of these fractures is to assemble the condylar fragments and then fix the condyles to the femoral shaft by minimum handling of the bone and soft tissues. Objectives: To evaluate the treatment of distal femoral open comminuted fractures (type C2 and C3) with hybrid external fixator. Methods: Thirty-four patients with distal femur open comminuted fracture (type C2 and C3) were treated by hybrid external fixator between January 2005 and December 2008. All of the fractures were opened with extension to joint surface. 30 patients were male and 4 were female. Their average age was 30.5 years (17 to 72 years). Average follow up period was 36 months. 12 patients had isolated fracture and 22 patients had multiple fractures. The bony and functional results were evaluated by the association for the study and application of the method of Ilizarov (ASAMI) protocol and knee society score. Results: 29 out of 34 fractures (85%) had union without bone grafts. Average time of union was 6.1 months (4 - 19 ms). The average knee range of motion was 87.5 degrees (30 - 115 degrees). The bony results were excellent in 24 patients (70.5%), good in 6 (17.7%), fair in 2 (5.9%), and poor in 2 (5.9%), and the functional results were excellent in 10 (29.4%) patients, good in 14 (41.2%), fair in 6 (17.6%), and poor in 4 (11.8%), and the functional results were excellent in 10 (29.4%) patients, good in 14 (41.2%), fair in 6 (17.6%), and poor in 4 (11.8%) according to ASAMI protocol. According to the knee society score the functional results were excellent in 9 (26.44%) patients, good in 13 (38.26%), fair in 7 (20.6%), and poor in 5 (14.7%). Conclusion: Hybrid external fixator is an effective method for treatment of distal femoral open comminuted fractures (type C2 and C3) and may be considered as an alternative surgical methods in the management of these fractures.

Treatment of Vertically Unstable Sacral Fractures with Pelvic External Fixation and Skeletal Traction

Objective: To determine the efficacy in treatment of vertically unstable sacral fractures with pelvic external fixation and skeletal traction. Patients and Methods: The pelvic external fixation and skeletal traction were applied on 12 cases of vertically unstable sacral fracture (eight males and four females, at age of 19 - 52 years, mean 35.2 years) including two cases of Denis Zone I, nine of Zone II, and one of Zone III. All patients were treated with the pelvic external fixation, and pre- and post-operational longitudinal skeletal traction. Results: The mean operation time, skeletal traction time, skeletal traction removal time and full weight bearing time were 38 min, 4.5 weeks, 8.5 weeks, and 10.3 weeks respectively. All these patients were followed up for 12 - 36 months (average, 22.5 months), which showed no associated complication. The function results were rated as excellent in four cases, good in six and fair in two, with a mean score of 84.4 points, according to Majeed scoring system. Conclusion: The anterior pelvic external fixation with continuous skeletal traction can reliably restore and stabilize the vertically unstable sacrum fracture with excellent functional and radiographic outcomes. It is an ideal method to treat unstably vertical sacral fracture.

Assessment of the trauma degree and bone metabolism after external fixation combined with vacuum sealing drainage treatment of open tibiofibula fracture

Objective: To evaluate the effect of external fixation combined with vacuum sealing drainage on the trauma degree and bone metabolism in patients with open tibiofibula fracture. Methods:A total of 116 patients with open tibiofibula fracture who received surgical treatment in Luzhou People's Hospital between February 2015 and January 2017 were divided into control group (n=58) and study group (n=58) by random number table. Control group received debridement + external fixation, and study group received debridement + external fixation +vacuum sealing drainage. The differences in the levels of trauma indexes and bone metabolism indexes were compared between the two groups before and after treatment. Results: Before surgery, there was no statistically significant difference in serum levels of trauma indexes and bone metabolism indexes between the two groups. 1 week after surgery, serum acute phase protein Tf level of study group was higher than that of control group whereas CER, Hp and CRP levels were lower than those of control group;stress indexes NE and Cor levels were lower than those of control group;bone metabolism indexes P1NP, BGP and BALP levels were higher than those of control group whereas β-CTX level was lower than that of control group. Conclusion: External fixation combined with vacuum sealing drainage can effectively reduce fracture trauma and promote fracture end healing in patients with open tibiofibula fracture.

Changes of bioelectric potentials of experimental fracture healed under compressive external fixation

Experimental fracture was inflicted to the Junction of the upper and middle thirds of the tibia of 50 rabbits and the fracture was fixed with a half-ring sulcated external fixator to exert axial compression on the 2 fragments of the fracture. The changes

Early complications of preoperative external traction fixation in the staged treatment of tibial fractures:A series of 402 cases

BACKGROUND Different external skeletal fixators have been widely used in preoperative traction of high-energy tibial fractures prior to a definitive surgical treatment.However,the early complications associated with this staged treatment for traction and soft tissue injury recovery have rarely been discussed.AIM To analyze the early complications associated with preoperative external traction fixation in the staged treatment of tibial fractures.METHODS A total of 402 patients with high-energy tibial fractures treated using preoperative external traction fixation at a Level 1 trauma center from 2014 to 2018 were enrolled in this retrospective study.Data regarding the demographic information,Tscherne soft tissue injury,fracture site,entry point placement,and duration of traction were recorded.Procedure-related complications such as movement and sensation disorder,vessel injury,discharge,infection,loosening,and iatrogenic fractures were analyzed.RESULTS The mean patient age was 42.5(18-71)years,and the mean duration of traction was 7.5(0-26)d.In total,19(4.7%)patients presented with procedure-related complications,including technique-associated complications in 6 patients and nursing-associated complications in 13.Differences in the incidence of complications with respect to sex,affected side,soft tissue injury classification,and fracture sites were not observed.However,the number of complications due to hammer insertion was significantly reduced than those due to drill insertions(2.9%vs 7.4%).CONCLUSION We found a low incidence of early complications related to the fixation.Furthermore,the complications were not significantly associated with the severity of the soft tissue injury and fracture site.Although relatively rough and more likely to cause pain,the number of complications associated with hammer insertion was significantly smaller than that of complications associated with drill insertion.

Establishment and validation of standardized animal models of spinal cord injury by normal external force-caused fracture dislocation

The duplication of animal models plays a key role in spinal cord injury research; however, there has been limited study into normal, external force-derived fracture dislocation. This study adopted experimental devices, designed in-house, to construct standardized ventral and dorsal spinal cord injury animal models of 6 g and 17 g falling from a height of 2, 4, and 10 cm, and 15, 30 or 50 g transversal compression on the spinal cord. The results showed that gradual increases in the degree of histopathological injury led to decreased Tarlov and Basso, Beattie and Bresnahan scores for the behavioral test, and increased Ashworth scores for the hind limb. Furthermore, there was a gradual decline in the slope test in the rats with dorsal spinal cord injury that correlated to increases in the falling substance weight or falling height. Similar alterations were observed in the ventral spinal cord injured rats, proportional to the increase in compression weight. Our experimental findings indicate that the standardized experimental rat models of dorsal and ventral spinal cord injury are stable, reliable and reproducible.

Management of Tibial Metaphyseal Fractures by Hybrid External Fixator

Introduction: The Hybrid External Fixator combines the advantages of the monolateral pin fixators and the circular Ilizarov wire fixators. Principle of early motion has been touted as the functional savior of major intra articular injuries in application of hybrid external fixation. Materials & Methodology: 48 patients were considered for the study with tibial fractures admitted in Mamata General Hospital from May 2011 to May 2013. Results: The union and functional outcome of hybrid external fixator in simple and complex proximal and distal metaphyseal fractures of tibia in adults was evaluated at our centre. The fractures of the proximal tibia united with an average of 13.3 weeks (12 - 16 weeks). The fractures of the distal tibia united with an average of 14.42 weeks (13 - 22 weeks) with minimal complications. Conclusion: Our study shows high satisfaction rate after fixation, provides adequate stability and allows early motion of the joint. It is also effective in extra articular fractures occurring within 5 cm of the joint as the IM nails often do not provide enough stability and plating requires extensive soft tissue dissection.

Triple Arthrodesis with Internal and External Fixation: Technique Paper

Background: The triple arthrodesis was described early by Myerson in 1923 and has been the gold standard surgical procedure for various conditions with the goal to reduce pain, improve deformity and facilitate function. Methods: The procedure consists of fusion of the subtalar joint, talonavicular joint and calcaneocuboid joint [1]. The procedure is traditionally done with internal fixation, however, Marinet al. has shown it to be performed with external fixation [2]. Dr. Marin and the associates have developed an alternative technique to perform a triple arthrodesis using internal and external fixation. This paper describes a step-by-step technique to perform a triple arthrodesis with both internal and external fixation. It will demonstrate the use of the prefabricated arches on the footplate for more precise and accurate placement of transosseous wires using arch-wire technique [3]. Results/Conclusion: We believe this technique will not only help increase the ability to achieve fusion with a less chance of non-union, but may also decrease healing time, which may allow patients to be mobile from the first week post-operatively and may diminish the risks associated with being non-weightbearing.

Role of coatings and materials of external fixation pins on the rates of pin tract infection:A systematic review and meta-analysis

BACKGROUND Infection at the pin tract is a frequent and feared complication of external fixators(EF).The type of pin material and coatings have been regarded as possibly influencing infection rates.Over the last 20 years,few prospective clinical studies and systematic reviews addressed the role of coated pins on the rate of pin site infection in human clinical studies.AIM To assess the EF literature over the past 20 years on the clinical benefits of pins manufactured from varied materials and coating systems and their possible role in pin tract infection rates.METHODS We performed a systematic review according to the PRISMA and PICOS guidelines using four scientific platforms:PubMed,LiLacs,SciELO,and Cochrane.We searched the literature for related publications over the past 20 years.RESULTS A literature search yielded 29 articles,among which seven met the inclusion criteria.These studies compared stainless-steel pins and pins coated with hydroxyapatite(HA),titanium and silver.The pin tract infection definitions were arbitrary and not standardized among studies.Most studies included a low number of patients in the analysis and used a short follow-up time.Three metaanalyses were carried out,comparing stainless steel vs silver pins,stainless steel vs HA-coated pins,and titanium vs HA-coated pins.None of this analysis resulted in statistically significant differences in pin tract infection rates.CONCLUSION Currently,no clinical evidence supports the advantage of EF pins manufactured with materials other than stainless steel or coated over uncoated pins in reducing the rates of pin tract infections.A standardized definition of pin tract infection in external fixation is still lacking.

Effect of Ilizarov external fixation combined with negative pressure sealing drainage and antibiotics in the treatment of infective tibial nonunion

Objective:Observation on the effect of Ilizarov external fixation combined with vacuum pressure sealing drainage and antibiotics in the treatment of infective tibial nonunion.Methods:79 patients with tibial infective nonunion who were treated in our hospital from August 2016 to August 2018 were divided into two groups according to random number table,with 39 patients in the control group treated with Ilizarov external fixation technology and 40 patients in the study group treated with vacuum pressure sealing drainage and antibiotics on the basis of the control group.Bone healing time and daily walking were recorded.Rasmussen score,serum intercellular adhesion molecule-1(ICAM-1)and IL-6 levels,lower limb Fugl-Meyer motor function score and lower limb BI index score were compared at different time.Results:The daily walking condition of the study group was significantly better than that of the control group(P<0.05),and the healing time of bone was significantly shorter than that of the control group(P<0.05);the Rasmussen score of the study group was higher than that of the control group at 1 month,6 months and 12 months after treatment(P<0.05);the levels of serum ICAM-1 and IL-6 in the two groups after treatment were lower than those before treatment(P<0.05),and the levels of serum ICAM-1 and IL-6 in the study group were lower than those in the control group after treatment(P<0.05).The lower limb Fugl-Meyer motor function score and lower limb BI index score of the two groups after treatment were higher than those before treatment(P<0.05),and the lower limb Fugl-Meyer motor function score and lower limb BI index score of the study group after treatment were higher than those of the control group(P<0.05).Conclusions:Ilizarov external fixation combined with vacuum pressure sealing drainage and antibiotics can promote the bone healing of patients with infective tibial nonunion,significantly improving their daily walking condition,alleviating inflammation,and recovering the knee joint function and lower limb function well.

HYBRID EXTERNAL FIXATOR FOR THE TREATMENT OF UNICAMERAL BONE CYSTS WITH PATHOLOGICAL FRACTURE IN THE PROXIMAL HUMERUS

Objective: Unicameral bone cyst is a nonneoplasticbone lesion characterized by its tenacity and risk ofrecurrence. Pathological fracture is common and is often the presenting symptom. The objective of the present study was to evaluate the results of hybrid external fixator for thetreatment of a unicameral bone cyst with a pathologicalfracture. Methods: Hybrid external fixator for thetreatment of a unicameral bone cyst was performed intwelve patients. These patients presented with a pathological fracture and were managed immediately with hybridexternal fixator, of whom four had been managedconservatively at other clinics before they were referred toour department. The cyst was located in the proximalhumerus in all patients. The mean age of the patients at the time of surgery was 8.7 years, and the mean duration offollow-up was 32.6 months. Radiographic evaluation wasperformed according to the criteria of Capanna et al., andthe cyst was classified as completely healed, healed withresidual radiolucency (osteolysis), recurred, or having noresponse. Results: The healing period ranged from three to eight months. Eight cysts healed completely, and threehealed with residual radiolucent areas visible onradiographs. There was recurrence of one cyst that hadhealed with residual radiolucency. All of the cysts in thepresent study responded to treatment. A modulation ofhybrid external fixator was necessary in three patients, asthe bars had become too short after bone growth or the pins had been loose. No major complications were observed.Conclusion: Hybrid external fixator provides earlystability, which allows early mobilization and thus obviates the need for a plaster cast. This method of treatment alsoallows for an early return to normal activity.

Step-by-step external fixation of unstable pelvis with separate anterior and posterior modules

Objective: To evaluate the treatment outcomes of patients with pelvic ring injury by applying step-by-step external pelvic fixation and circular external fixation device.Methods: A total of 28 patients suffering from disintegrated pelvic ring injury are involved in the study. Fourteen patients(the treatment group) underwent step-by-step external pelvic fixation by applying anterior(anti-shock) and posterior modules. For the rest 14 patients(the experimental group), the osteosynthesis were conducted by means of a circular external fixation device. The long-term outcomes were evaluated in a year after the injury.Results: The residual deformity of 5(4–7) mm was observed in 10 patients(71.4%) from the experimental group. In the treatment group, the residual deformity was evident only in 4(28.6%) cases being 2.5(2–3) mm(P = 0.000 319) on the average. The functional result(according to the Majeed scale) was statistically better in the treatment group(P = 0.000 319). Nine(64.3%) and five(35.7%) patients in treatment group showed excellent and positive results, respectively. The excellent result was demonstrated by 3patients(21.4%) of the experimental group, the positive outcomes were observed in 6 cases(42.9%) and the unsatisfactory one was displayed by 1 patient(7.1%) of the same group.Conclusions: The modular approach applied is the advantage of the transosseous osteosynthesis allowing for a separate anterior(anti-shock) fixation and final posterior reposition of the pelvic ring preceded by the stabilization of vital functions. The above mentioned method gives an opportunity to increase the amount of techniques applied for the pelvic external fixation in polytrauma cases.

The damage control in tibial pilon open fractures with a new external fixator delta frame

Objective: To evaluate the effectiveness of the damage control, in emergency to treat the open tibial pilon fractures with Dolphix? External Fixator Frame(CITIEFFE?, Calderara di Reno, Bologna, Italy). Methods: From January 2017 to August 2017, at the Department of Orthopedics and Traumatology of Vito Fazzi Hospital Lecce, we treated 23 open tibial pilon fractures with Dolphix? External Fixator Frame(CITIEFFE?, Calderara di Reno, Bologna, Italy). The evaluation criteria of the case series were: the time needed to assemble the external fixator;the time taked to treat the ankle associated lesions;the time of skin healing;the ankle alignment;the subjective/objective Ovadia and Beals score;and complications. The Endpoint assessment was set at the days of the definitive surgery. Results: The results in terms of alignment, biomechanical stability of the frame, healing of soft tissue, complications were as good as the objective and subjective results according Ovadia and Beals score. Conclusion:Pilon fractures are complex and often present complications;the damage control treatment, in emergency, with Dolphix? External Fixator Frame(CITIEFFE?, Calderara di Reno, Bologna, Italy) permits a stable osteotaxis with minimal soft tissue damage and permit the repair of muscles, blood vessels and nerves with a stable bone and the soft tissue healing with vaccum therapy.

Effects of external temperature and dead volume on laboratory measurements of pore pressure and injected volume in a rock fracture

The accurate evaluation of pore pressure and injected volume is crucial for the laboratory characterization of hydromechanical responses of rock fractures. This study reports a series of laboratory experiments to systematically demonstrate the effects of external temperature and dead volume on laboratory measurements of pore pressure and injected volume in a rock fracture. We characterize the hydraulic aperture of the fracture as a function of effective normal stress using the exponential aperture model.This model is then employed to predict the pore pressure change and injected volume in the fracture without the influences of external temperature and dead volume. The external temperature changes in the cyclic loading test due to the Joule-Thompson effect for fluids. The effect of external temperature on pore pressure change in the fracture can be well explained by thermal pressurization of fluids. Our results also show that the external dead volume can significantly lower the pore pressure change in the fracture during the cyclic loading test under undrained conditions. The injected volume can also be substantially enlarged due to the external dead volume in a typical pore pressure system. Internal measurement of the pore pressure in the fracture using a fiber optic sensor cannot exclude the influences of external temperature and dead volume, primarily because of the good hydraulic communication between the fracture and pore pressure system. This study suggests that the effects of external temperature and dead volume on pore pressure response and injected volume should be evaluated for accurate laboratory characterization and inter-laboratory comparison.

Formation process of extension knee joint contracture following external immobilization in rats

BACKGROUND Current research lacks a model of knee extension contracture in rats.AIM To elucidate the formation process of knee extension contracture.METHODS We developed a rat model using an aluminum external fixator.Sixty male Sprague-Dawley rats with mature bones were divided into the control group(n=6)and groups that had the left knee immobilized with an aluminum external fixator for 1,2,and 3 d,and 1,2,3,4,6,and 8 wk(n=6 in each group).The passive extension range of motion,histology,and expression of fibrosis-related proteins were compared between the control group and the immobilization groups.RESULTS Myogenic contracture progressed very quickly during the initial 2 wk of immobilization.After 2 wk,the contracture gradually changed from myogenic to arthrogenic.The arthrogenic contracture progressed slowly during the 1^(st) week,rapidly progressed until the 3^(rd) week,and then showed a steady progression until the 4^(rd) week.Histological analyses confirmed that the anterior joint capsule of the extended fixed knee became increasingly thicker over time.Correspondingly,the level of transforming growth factor beta 1(TGF-β1)and phosphorylated mothers against decapentaplegic homolog 2(p-Smad2)in the anterior joint capsule also increased with the immobilization time.Over time,the cross-sectional area of muscle fibers gradually decreased,while the amount of intermuscular collagen and TGF-β1,p-Smad2,and p-Smad3 was increased.Unexpectedly,the amount of intermuscular collagen and TGF-β1,p-Smad2,and p-Smad3 was decreased during the late stage of immobilization(6-8 wk).The myogenic contracture was stabilized after 2 wk of immobilization,whereas the arthrogenic contracture was stabilized after 3 wk of immobilization and completely stable in 4 wk.CONCLUSION This rat model may be a useful tool to study the etiology of joint contracture and establish therapeutic approaches.