osteonecrosis of the femoral head is a progressive clinical condition primarily affecting 
 young and middle - aged patients and is the endpoint of a disease process that results from 
 insufficient circulation and bone - tissue necrosis1 , 
 2 . untreated symptomatic osteonecrosis 
 of the femoral head usually leads to joint instability , collapse of the load - bearing segment 
 of the femoral head , severe osteoarthrosis , and permanent deformity of the femoral head3 . the severity of the femoral head deformity 
 is the key factor that determines the long - term outcome of a hip joint . both nonsurgical and surgical treatment options have been used in 
 the treatment of osteonecrosis of the femoral head , such as conservative treatment with 
 analgesics , core decompression , intertrochanteric osteotomy , bone transplants with vascular 
 pedicles , and total hip replacement . most treatment methods have confirmed limited effects 
 in selected series , but none has demonstrated uniform success5,6,7 . therefore , a new effective and noninvasive alternative method of 
 treatment would be preferable over the current standard of care . they 
 have been shown to be effective in improving bone healing and increasing bone mass and bone 
 strength8 . when shock waves are directed 
 at the bone , the reflection and deposition of shock wave energy can stimulate osteogenesis 
 and angiogenesis9 . shock wave treatment 
 can lead to new bone formation in physiological as well as acutely fractured and 
 pseudarthrotic bone8 , 10 , 11 . shock wave treatment 
 has been used for the treatment of nonunion in europe and asia since the early 1990s11 . recently , the results of extracorporeal 
 shock wave treatment for osteonecrosis of the femoral head have been encouraging . shock wave 
 treatment appeared to be more effective than core decompression and nonvascularized fibular 
 grafting in patients with early - stage osteonecrosis of the femoral head , although the 
 underlying working mechanism of shock wave inducing bone repair remains to be fully 
 established12 . the aim of this 
 experimental study was investigate changes in the microarchitecture and bone remodeling in 
 necrotic femoral head of rabbits following shock wave treatment with quantitative bone 
 histomorphometric examination . all procedures performed in the experiment were approved by the local animal care and use 
 committee . eight new zealand white rabbits with a body weight ranging from 3.0 to 4.0  kg 
 were used in this study . using lipopolysaccharide and methylprednisolone , we induced 
 bilateral femoral head necrosis in these animals according to yamamoto et al13 . shock wave treatment was applied to the 
 femoral head of the left limb 6 weeks after injection of methylprednisolone . the right limb 
 received no shock wave treatment and was designated as the control side . on the left side , the femoral head received 2000 shock wave impulses at 0.26  mj / mm using an 
 orthospec ( medispec , gaithersburg , md , usa ) . the shock wave dosage was based on the results 
 of previous studies in animals8 , 14 . on days 7 and 2 before necropsy , all rabbits were given 
 intramuscular injections of tetracycline hydrochloride ( 30  mg / kg ; sigma ) , which was used as 
 fluorochrome bone markers for histomorphometry . the animals were sacrificed with an overdose 
 of pentobarbital at 12 weeks after shock wave treatment . they were bisected along the coronal plane 
 and assigned for undecalcified bone processing . quantitative bone histomorphometric analysis the rabbits were given intravenous injection of 10  g / kg 
 lipopolysaccharide twice at an interval of 24 hours , and after the second injection of 
 lipopolysaccharide , they were injected intramuscularly with 40  mg / kg of methylprednisolone 
 thrice at intervals of 24 hours . osteonecrosis of the femoral head occurred at 6 weeks after 
 the third injection of methylprednisolone15 . the specimens were fixed with 70% ethanol solution at 4  c for 2 days , run through the 
 alcohol series for dehydration , embedded in methylmethacrylate , and cut into 7- and 15-m 
 slices parallel to the coronal plane from the center of the specimen . we evaluated the histomorphometric parameters with semiautomatic simple pci 
 image analyzer ( compix , usa ) . all parameters were expressed according to standardized 
 nomenclature16 . for general bone 
 structure , bone volume per tissue volume ( bv / tv , % ) , trabecular thickness ( tb.th , m ) , 
 trabecular separation ( tb.sp , m ) , and trabecular number ( tb.n ,  mm ) were 
 measured and calculated . for bone formation , the following parameters were measured and 
 calculated : osteoid surface / bone surface ( os / bs , % ) , osteoid thickness ( o.th , m ) , 
 mineralizing apposition rate ( mar , m / day ) , mineralizing surface / bone surface ( ms / bs , % ) , 
 bone formation rate / bone surface ( bfr / bs , m/m / day ) , and osteoblast 
 surface / bone surface ( ob.s / bs , % ) . for bone resorption , eroded surface / bone surface ( es / bs , 
 % ) and osteoclast surface / bone surface ( oc.s / bs , % ) were measured . the indices of histomorphometry were 
 compared by two - tailed t - test analysis of variance between the shock wave - treated femoral 
 heads and the controls . the histomorphometric indices of general trabecular structure are presented in table 1table 1.bone structural parameters of shock wave - treated and control femoral heads of 
 rabbitsbone structural parameterscontrol group ( n=8)shock wave - treated group ( n=8)bv / tv ( % ) 36.4  4.150.5  6.3**tb.th ( m)113.3  10.4145.0  13.2**tb.sp ( m)167.1  14.9130.6  11.5**tb.n ( mm)3.01  0.284.06  0.81*results are shown as mean  sd . bv / tv : bone volume per tissue volume , tb.th : 
 trabecular thickness , tb.sp : trabecular separation , tb.n : trabecular number , 
 * p<0.05 , * * p<0.01 . the bv / tv , tb.th , and tb.n were significantly higher in shock wave - treated 
 femoral heads than controls . tb.sp was significantly lower in shock wave - treated 
 femoral heads ( fig . 1fig . 1.representative photomicrographs of goldner - stained bone for untreated control ( a ) and 
 shock wave  treated ( b ) necrotic femoral heads . ( a ) bone of the necrotic femoral heads 
 untreated with shock waves was sparse and osteoid ( arrows ) was scarce . ( b ) bone of the 
 necrotic femoral heads treated with shock waves had greater bone volume . bv / tv : bone volume per tissue volume , tb.th : 
 trabecular thickness , tb.sp : trabecular separation , tb.n : trabecular number , 
 * p<0.05 , * * p<0.01 representative photomicrographs of goldner - stained bone for untreated control ( a ) and 
 shock wave  treated ( b ) necrotic femoral heads . ( a ) bone of the necrotic femoral heads 
 untreated with shock waves was sparse and osteoid ( arrows ) was scarce . ( b ) bone of the 
 necrotic femoral heads treated with shock waves had greater bone volume . parameters reflecting bone formation are given in table 2table 2.bone formation parameters of shock wave - treated and control femoral heads of 
 rabbitsbone formation parameterscontrol group ( n=8)shock wave - treated group ( n=8)os / bs ( % ) 2.55  0.436.13  1.53**o.th ( m)2.99  0.464.14  0.69*mar ( m / day)1.43  0.242.23  0.36**ms / bs ( % ) 6.51  0.5220.08  2.87**bfr / bs ( m/m / day)0.045  0.0090.126  0.020**ob.s / bs ( % ) 2.15  0.357.52  1.40**results are shown as mean  sd . os / bs : osteoid surface / bone surface , o.th : osteoid 
 thickness , mar : mineral apposition rate , ms / bs : mineralizing surface / bone surface , 
 bfr / bs : bone formation rate / bone surface , ob.s / bs : osteoblast surface / bone surface , 
 * p<0.05 , * * p<0.01 . 1 ) , ms / bs , 
 ob.s / bs , mar , and bfr / bs ( fig . 2fig . 2.representative micrographs demonstrating vital stain of bone in untreated control ( a ) 
 and shock wave  treated ( b ) necrotic femoral heads . ( a ) narrow distances between double 
 fluorescent tetracycline labels in untreated femoral heads were observed . ( b ) 
 remarkable distances between double fluorescent tetracycline labels in shock 
 wave  treated femoral heads were marked . ( original magnification 100 ) . ) significantly increased in shock wave - treated femoral heads compared with 
 controls . os / bs : osteoid surface / bone surface , o.th : osteoid 
 thickness , mar : mineral apposition rate , ms / bs : mineralizing surface / bone surface , 
 bfr / bs : bone formation rate / bone surface , ob.s / bs : osteoblast surface / bone surface , 
 * p<0.05 , * * p<0.01 representative micrographs demonstrating vital stain of bone in untreated control ( a ) 
 and shock wave  treated ( b ) necrotic femoral heads . ( a ) narrow distances between double 
 fluorescent tetracycline labels in untreated femoral heads were observed . ( b ) 
 remarkable distances between double fluorescent tetracycline labels in shock 
 wave  treated femoral heads were marked . parameters related to bone resorption are shown in table 3table 3.bone resorption parameters of shock wave - treated and control femoral heads of 
 rabbitsbone resorption parameterscontrol group ( n=8)shock wave  treated group ( n=8)es / bs ( % ) 15.6  3.312.5  2.9***oc.s / bs ( % ) 3.3  0.72.9  0.5***results are shown as mean  sd . es / bs : eroded surface / bone surface , oc.s / bs : 
 osteoclast surface / bone surface , * * * p>0.05 . there was no significant difference between the two groups in oc.s / bs and 
 es / bs . es / bs : eroded surface / bone surface , oc.s / bs : 
 osteoclast surface / bone surface , * * * p>0.05 current treatment practices vary among conservative treatment , joint - preserving procedures , 
 and total hip replacement . both conservative and surgical treatment modalities have been 
 used with limited effects5,6,7 , 9 . extracorporeal shock wave therapy is a promising technology that 
 has been used in the treatment of various musculoskeletal afflictions , such as 
 tendinopathies , delayed bone healing , pseudarthrosis , and osteonecrosis of the femoral 
 head11 , 12 , 
 17 . mechanistic studies demonstrated 
 that extracorporeal shock waves have positive influence on osseous biology through enhanced 
 biomechanical properties , angiogenesis , and augmented osteogenetic differentiation of 
 mesenchymal stem cells8 , 18 , 19 . however , the 
 effects of extracorporeal shock waves on the microarchitecture and bone remodeling of the 
 necrotic femoral heads have not been established . the results of this study showed that 
 shock wave treatment promotes bone formation with increased bone mass in necrotic femoral 
 heads of rabbits . many authors had studied the mechanism of shock wave treatment , and they documented that 
 shock wave therapy was effective in clinical orthopedic practice and basic research because 
 it enhances new bone formation and expression of growth factors8 , 10 , 11 , 20 . our previous 
 studies showed that extracorporeal shock wave treatment significantly upregulated the 
 expression of bone morphogenetic protein 2 and vascular endothelial growth factor in 
 necrotic femoral heads and accelerated the repair process of femoral head necrosis15 , 21 . we applied histomorphometry in the current study to investigate 
 the detailed changes in subchondral bone of necrotic femoral heads treated with 
 extracorporeal shock waves . the results of this study demonstrate significant structural 
 changes in trabecular bone volume , tb.th , tb.sp , and tb.n of subchondral bone of necrotic 
 femoral heads treated with extracorporeal shock waves . increases in tb.th and tb.n and a 
 decrease in tb.sp result in a significant increase in trabecular bone volume . the data 
 provide strong evidence that extracorporeal shock wave therapy promotes marked new bone 
 formation in the necrotic femoral heads . the effectiveness of extracorporeal shock wave therapy in promoting new bone formation 
 observed in our study is similar to that reported for long bone fracture treated with shock 
 waves8 . changes in bone remodeling may 
 be proposed to explain the increased bone mass of the necrotic femoral heads treated with 
 shock waves . in our study , we found that necrotic femoral heads treated with shock waves , 
 when compared to controls , were characterized by higher ob.s / bs , os / bs , and o.th , ms / bs , 
 mar , and bfr . these increases in mar and bfr are indicative of an increase in osteoblastic 
 activity at the cellular level23 . therefore , shock wave treatment appears to have stimulated the proliferation of osteoblasts 
 as well as their activation to produce more and denser bone . moreover , more osteoid observed 
 in shock wave - treated femoral heads also indicates that shock wave treatment promotes new 
 bone formation . however , there was no significant difference between shock wave - treated 
 femoral heads and the controls in es / bs and oc.s / bs . the unchanged resorption of trabecular 
 bone and increased formation of new trabecular bone resulted in increased bone mass and 
 enhanced bone repair in necrotic femoral heads treated with shock waves . the results of this 
 study are identical with those of tamma et al.24 , who showed that shock wave treatment induced bone repair through 
 the proliferation and differentiation of osteoblasts and the reduction of their secretion of 
 pro - osteoclastogenic factors . it is therefore highly likely that the positive effect of 
 shock wave treatment on osteoblasts proliferation and their activation in necrotic femoral 
 heads contribute to the mechanism by which shock waves increase new bone formation and 
 promote repair of necrotic femoral heads . in summary , this study documents the general trabecular structure , trabecular formation , 
 and trabecular resorption changes in necrotic femoral heads treated with extracorporeal 
 shock waves . the results of denser trabecular structure and increased bone remodeling 
 demonstrate increased bone repair in shock wave - treated femoral heads , due to proliferation 
 and activation of osteoblasts .
[ purpose ] this study aimed to determine the effectiveness and mechanisms of 
 extracorporeal shock wave therapy in the treatment of femoral head osteonecrosis . 
 [ subjects and methods ] histomorphometric analysis of necrotic femoral head in rabbits 
 treated with shock waves was performed . 
 bilateral osteonecrosis of femoral heads was 
 induced with methylprednisolone and lipopolysaccharide in eight rabbits . 
 the left limb 
 ( study side ) received shock waves to the femoral head . 
 the right limb ( control side ) 
 received no shock waves . 
 biopsies of the femoral heads were performed at 12 weeks after 
 shock wave therapy . [ results ] necrotic femoral heads treated with shock waves , compared 
 with controls , had higher bone volume per tissue volume , trabecular thickness , trabecular 
 number , osteoblast surface / bone surface , osteoid surface / bone surface , osteoid thickness , 
 mineralizing surface / bone surface , mineralizing apposition rate , and bone formation rate . 
 however , trabecular separation was lower in shock wave - treated femoral heads than in 
 controls 
 . eroded surface / bone surface and osteoclast surface / bone surface did not differ 
 significantly between groups . 
 [ conclusion ] the bone mass of necrotic femoral heads treated 
 with shock waves increases . 
 extracorporeal shock wave may promote bone repair in necrotic 
 femoral heads through the proliferation and activation of osteoblasts .