***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
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    Input: OBJECTIVE To explore current beliefs among senior physiotherapy ( PT ) students and orthopedic surgeons on the clinical utility of therapeutic ultrasound for assisting fracture healing . DESIGN Cross-sectional survey . SETTING University . PARTICIPANTS Orthopedic surgeons , senior orthopedic surgery residents , and PT students in their final 6 months of study . INTERVENTIONS Not applicable . Main outcome measures Percentage of respondents reporting specific perceptions on ( 1 ) the role of therapeutic ultrasound in fracture healing , ( 2 ) clinical use of therapeutic ultrasound for fracture healing , ( 3 ) rationale for not using therapeutic ultrasound  for healing fractures , and ( 4 ) what constitutes a clinical ly significant difference in fracture healing time . Between-group comparisons were conducted for survey responses . RESULTS The response rate was 20 of 22 ( 90.9 % ) orthopedic surgeons , 5 of 5 ( 100 % ) senior orthopedic residents , and 34 of 50 ( 68.0 % ) senior PT students . The majority of senior PT students ( 58.8 % ) and orthopedic residents and surgeons ( 60.0 % ) surveyed reported the belief that therapeutic ultrasound may help in assisting fracture healing in some cases . However , the majority of respondents do not use this modality ( 60.0 % of surgeons , 88.2 % of Senior PT students ) , with most surgeons ( 32.0 % ) citing lack of evidence and most senior PT students ( 58.8 % ) indicating lack of availability as the predominant barrier . Thirty-two percent of surgeons felt that ultrasound was contraindicated and harmful to healing fractures , or that it was of no use , and 20.5 % of PT students reported the belief that ultrasound was contraindicated and was , or may be , harmful to healing bone . Most orthopedic residents and surgeons ( 52.0 % ) reported that a reduction in fracture healing time of 4 weeks would be clinical ly significant versus senior PT students , the majority of whom ( 64.7 % ) indicated that a reduction of 2 weeks would be clinical ly significant . CONCLUSIONS Some surgeons and PT students believed that therapeutic ultrasound is contraindicated and harmful to healing bone ; however , most believed that therapeutic ultrasound may help in assisting fracture healing , in at least some cases . Current usage of this modality is rare , primarily due to the perceived lack of evidence and lack of availability . Large r and omized trials are needed to define further the role of ultrasound in fracture healing AIM The management of  pseudarthrosis  remains a challenge . Several in vivo animal and controlled clinical studies have demonstrated that low-intensity pulsed ultrasound can influence fracture healing . METHODS A prospect i ve longitudinal design was used . Fifteen patients ( 12 males and 3 females ; mean age 35.5+/-12.9 , range 18 to 60 ) , all amateur athletes , under treatment for pseudarthrosis at different sites ( average fracture age : of 336.6+/-60.1 days ) were treated with a single 20 min daily application of low-intensity pulsed ultrasound ( frequency 1.5 MHz and intensity 30 mW/cm2 ) . All patients underwent clinical examination and plain radiography at the beginning of treatment and were followed up clinical ly and radiographically at 4 , 8 , 12 , 16 , 20 and 24 weeks until the fracture healed . RESULTS All fractures healed with a mean healing time of 94.7+/-43.8 days . CONCLUSION Low-intensity pulsed ultrasound is effective in the management of long st and ing fracture non-unions . Prospect i ve r and omized studies are needed to confirm the value of this modality of treatment BACKGROUND Established fracture nonunions rarely heal without secondary intervention . Revision surgery is the most common intervention , though non-surgical options for nonunion would be useful if they could overcome nonunion risk factors . Our hypothesis is that low-intensity pulsed ultrasound ( LIPUS ) can enhance heal rate ( HR ) in fractures that remain nonunion after one year , relative to the expected HR in the absence of treatment , which is expected to be negligible . METHODS We collated outcomes from a prospect i ve patient registry required by the U.S. Food & Drug Administration . Patient data were collected over a 4-year period beginning in 1994 and were individually review ed and vali date d by a registered nurse . Patients were only included if they had four data points available : date when fracture occurred ; date when LIPUS treatment began ; date when LIPUS treatment ended ; and a dichotomous outcome of healed vs. failed , assessed by clinical and radiological criteria . Data were used to calculate two derived variables : days to treatment ( DTT ) with LIPUS , and days on treatment ( DOT ) with LIPUS . Every vali date d chronic nonunion patient ( DTT>365 days ) with complete data is reported . RESULTS Heal rate for chronic nonunion patients ( N=767 ) treated with LIPUS was 86.2 % . Heal rate was 82.7 % among 98 patients with chronic nonunion ≥5 years duration , and 12 patients healed after chronic nonunion > 10 years ( HR=63.2 % ) . There was more patient loss to follow-up , non-compliance , and withdrawal , comparing chronic nonunion patients to all other patients ( p<0.0001 ) . Patient age was the only factor associated with failure to heal among chronic nonunions ( p<0.004 ) . Chronic nonunion patients averaged 3.1 surgical procedures prior to LIPUS , but some LIPUS-treated patients were able to heal without revision surgery . Among 91 patients who received LIPUS ≥90 days after their last surgery , HR averaged 85.7 % , and the time from last surgery to index use of LIPUS averaged 449.6 days . CONCLUSIONS Low-intensity pulsed ultrasound enhanced HR among fractures that had been nonunion for at least 1 year , and even healed fractures that had been nonunion > 10 years . LIPUS result ed in successful healing in the majority of nonunions without further surgical intervention Background We compared the healing response of tibial delayed unions between subjects treated with low-intensity pulsed ultrasound ( LIPUS ) ( n = 51 ) and subjects treated with a sham device ( n = 50 ) . Fracture age was ≥ 4 months in all cases . Study personnel and participants were blinded to r and om treatment assignment throughout the study . Methods This multi-center r and omized sham-controlled trial was undertaken at six hospitals in Germany . Adult patients who had sustained a tibial shaft fracture that subsequently showed inadequate progress toward healing ( i.e. , delayed union ) were enrolled and r and omized to receive either LIPUS ( Exogen 2000/2000 + , Smith & Nephew GmbH , Schenefeld , Germany ) or an identical nonoperative sham device . The daily treatment duration was 20 minutes , for a period of 16 weeks . Subjects r and omly assigned to active treatment had the ultrasound pressure wave signal set at the following parameters : 1.5 MHz frequency , 1 kHz repetition rate , 200 μs pulse duration , 30 mW/cm2 spatial intensity . Progress toward healing was estimated from changes in bone mineral density ( BMD ) and gap area as determined from computed tomography scans . Intention-to-treat analysis was conducted using a multiple imputation methodology . Results Based on log-transformed data , mean improvement in BMD was 1.34 ( 90 % confidence interval ( CI ) 1.14 to 1.57 ) times greater for LIPUS-treated subjects compared to sham ( p = 0.002 ) . A mean reduction in bone gap area also favored LIPUS treatment ( p = 0.014 ) . Conclusions These findings demonstrate significantly greater progress toward bone healing after LIPUS treatment compared to no LIPUS treatment in subjects with established delayed unions of the tibia Background Postoperative delayed union and nonunion is the most common complication in fracture treatment . Recent studies have shown an accelerating effect of low-intensity pulsed ultrasound ( LIPUS ) on fracture repair . However , the indications for delayed union and nonunion are not clear . To clarify the factors which influence the effects of LIPUS , the data from a previous prospect i ve multicenter study on LIPUS treatment for postoperative delayed union and nonunion of long bone fractures were reanalyzed . Methods Seventy-two cases of long bone fracture , including those of the femur , tibia , humerus , radius , and ulna , were analyzed . The mean time from the most recent operation to the beginning of LIPUS treatment was 11.5 ( 3–68 ) months . The relationship between the background factors and the union rate was analyzed using a logistic regression method . In addition , long bone fractures in an upper extremity or in a lower extremity were analyzed separately . Results The union rate was 75 % in all the cases of long bone fracture . There was a significant relationship between the union rate and the period from the most recent operation to the beginning of LIPUS treatment in all cases and in those that had long bone fracture of an upper extremity . There was also a significant relationship between the union rate and the time when a radiological improvement was first observed after the beginning of the treatment in all cases and in those with fractures in a lower extremity . When LIPUS treatment was started within 6 months of the most recent operation , 89.7 % of all fractures healed . When an improvement in the radiological changes at the fracture site was observed after 4 months in those cases , then the sensitivity and specificity for union were more than 90 % . Conclusions LIPUS treatment should be started within 6 months of the most recent operation . Because LIPUS has been shown to be effective without causing either serious invasiveness or any undue risk to the patient , it may be considered the treatment of first choice for cases of postoperative delayed union or nonunion This article provides an overview of the biology behind the use of electrical stimulation in fracture healing and discusses the current methods of electrical bone growth stimulation . In addition , we review the best available clinical evidence for the use of electrical stimulation in the treatment of delayed and nonunions of fractures . Our search identified 4 meta-analyses on the use of electrical stimulation on fracture healing . The most method ologically rigorous and recent meta- analysis suggests that the current evidence is insufficient to conclude a benefit of electromagnetic stimulation in improving the rate of union in patients with a fresh fracture , osteotomy , delayed union , or nonunion . The other 3 meta-analyses that we identified suggested a more significant treatment effect from electrical stimulation . Although the evidence supporting electrical stimulation does trend in favor of its use to help achieve bony union , further large , multicenter , r and omized , controlled trials are required to resolve the current uncertainty surrounding the use of electrical stimulation and fracture healing BACKGROUND Despite the large number of fracture outcome studies , there remains variability in the definitions of fracture-healing . It is unclear how orthopaedic surgeons are diagnosing and managing delayed unions and nonunions in clinical practice . We aim ed to explore the current opinions of orthopaedic surgeons with regard to defining , diagnosing , and treating delayed unions and nonunions in extremity fractures . METHODS We developed a survey using previous literature , key informants in the field of orthopaedic surgery , and a sample -to-redundancy strategy . Our final survey contained four sections and twenty-nine questions focusing on demographics and surgical experience , definitions of fracture union , prognostic factors for union , and the need for clinical trials . The Internet-based survey and follow-up e-mails were continued until our a priori sample size of a minimum of 320 completed and eligible responses were collected . RESULTS Three hundred and thirty-five surgeons completed the survey . The typical respondent was a North American , male orthopaedic surgeon or consultant over the age of thirty years who had completed trauma fellowship training , worked in an academic practice , supervised residents , and had more than six years of experience in treating orthopaedic injuries . Most surgeons endorsed a lack of st and ardization in definitions for delayed unions ( 73 % ) and nonunions ( 55 % ) ; almost all agreed that defining a delayed union and nonunion should be done on the basis of both radiographic and clinical criteria ( 88 % ) . Most respondents believed that the degree of soft-tissue injury ( approximately 93 % ) , smoking history ( approximately 82 % ) , and vascular disease ( approximately 76 % ) increased the risk of healing complications . CONCLUSIONS Surgeons use similar prognostic factors to define and assess delayed unions and nonunions , but there is a lack of consensus in the definitions of delayed union and nonunion . The need for st and ardization and future r and omized trials was strongly endorsed This prospect i ve consecutive study judges the effectiveness of pulsed low-intensity ultrasound for treatment of  boney healing disorders .  86 out of 100 treatments were successful . Although in these 100 cases 64 delayed unions and 36 nonunions were enrolled ultrasound therapy was performed as an alternative to the indicated operation in every case . Excluding ten cases of ununited fractures of the scaphoid no additional therapy was performed in any case . Stratifying the data no significant differences in healing rate and treatment time were observed between delayed unions and non-unions and between atrophic and hypertrophic healing disorders . Judging the healing rate of 86 % one has to take into consideration that according to our 
    Output:
    
Hypertrophic nonunions benefitted more than biologically inactive atrophic nonunions .
An interval without surgery of < 6months prior to LIPUS was associated with a more favorable result .
Stratification of nonunions by anatomical site revealed no statistically significant differences between upper and lower extremity long bone nonunions .
CONCLUSIONS LIPUS treatment can be an alternative to surgery for established nonunions .
LIPUS may be most useful in patients for whom surgery is high risk , including elderly patients at risk of delirium , or patients with dementia , extreme hypertension , extensive soft-tissue trauma , mechanical ventilation , metabolic acidosis , multiple organ failure , or coma .
With an overall average success rate for LIPUS > 80 % this is comparable to the success of surgical treatment of non-infected nonunions