Subchondral fracture after ischemic osteonecrosis of the immature femoral head in piglet model

This experimental investigation was performed to study the development of a subchondral fracture after ischemic osteonecrosis of the immature femoral head using a piglet model. Forty-eight male piglets were studied after placing a ligature tightly around the femoral neck to disrupt the blood supply to the femoral head. Animals were euthanized 2-8 weeks after the induction of ischemia. Radiographic, histologic, and histomorphometric assessments were made. A subchondral fracture was seen in 12 out of 32 infarcted femoral heads (38%) that were in the initial radiographic stage of ischemic osteonecrosis. The fracture was seen mainly in those femoral heads that had a prolonged period of the initial stage where the initiation of revascularization and repair was delayed. Histomorphometric assessment showed decreased trabecular thickness and volume in the subchondral region of the infarcted femoral heads compared with the contralateral normal heads. After ischemic osteonecrosis, the trabecular bone in the subchondral region is thinner and less bone volume is present because of a lack of new bone formation. The results of this study support the hypothesis that a subchondral fracture in the immature femoral head develops as a result of mechanic failure of the trabecular bone in the subchondral region.     

Biomechanical properties of bone and cartilage in growing femoral head following ischemic osteonecrosis.

Legg-Calve-Perthes disease (LCPD) is one of the most common causes of a permanent deformity of the femoral head among pediatric hip disorders. Mechanical loading of the osteonecrotic femoral head undergoing repair is thought play a significant role in the development of the femoral head deformity. This study measured the mechanical properties in uniaxial unconfined compression tests of epiphyseal bone and cartilage from immature femoral heads following surgical induction of osteonecrosis using an established piglet model. Both the modulus and yield strength of bone cores from the infarcted heads were significantly lower by 50%-60% than those of the contralateral normal control heads by 2 weeks after surgery and they remained this low for 8 weeks. No consistent difference in the bone mineral or collagen content per dry weight in the bone cores was observed. Cartilage modulus and yield strength were significantly lower at 2 weeks and remained low for 8 weeks. Cartilage collagen and glycosaminoglycan content per dry weight did not differ significantly between control and infarcted heads at any time point. However, the relative proportion of chondroitin 6-sulfate increased significantly over the 8-week postoperative period, which correlated with an increase in cartilage thickness. These results indicate that the deterioration of the mechanical properties of the epiphyseal bone and cartilage likely plays a significant role in the pathogenesis of the femoral head deformity in LCPD. (     

Material properties of bone in the femoral head treated with ibandronate and BMP‐2 following ischemic osteonecrosis

Bone morphogenetic protein (BMP)‐2 and ibandronate (IB) decrease the femoral head deformity following ischemic osteonecrosis of the femoral head (ONFH). The purpose of this study was to determine the effects of BMP‐2 and IB on the mineral content and nanoindentation properties of the bone following ONFH. ONFH was surgically induced in the femoral head of piglets. There were five groups: normal control, untreated, IB, BMP, and BMP + IB (n = 5/group). Backscattered electron imaging, Raman spectroscopy, and nanoindentation testing were performed. Both BMP and BMP + IB groups showed calcium content in the trabecular bone similar to the normal group, while the IB and no‐treatment groups showed a significant increase in the calcium content compared to the normal group. The carbonate content relative to phosphate was significantly increased in the IB and BMP + IB groups (p < 0.01) compared to the normal group. No significant difference was found between the BMP and the normal group. The nanoindentation modulus of the bone in the IB group was significantly increased compared to the normal group (p < 0.05). No significant differences were observed between the BMP and BMP + IB groups compared to the normal group. The nanoindentation hardness measurements in the IB group were also significantly increased compared to the BMP and BMP + IB groups (p < 0.05). In summary, trabecular bone treated with BMP or BMP + IB had material properties comparable to normal bone whereas the bone in the IB group retained the increased mineral content and the nanoindentation hardness found in the necrotic bone. Hence, BMP or BMP + IB better restores the normal mineral content and nanomechanical properties after ONFH than IB treatment alone. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1453–1460, 2017.

     

Structural consequences of subchondral bone involvement in segmental osteonecrosis of the femoral head.

Appearance of a crescent sign usually marks the onset of necrotic femoral head collapse, but very little is known about which local factors contribute most critically to avoiding or postponing fracture of at-risk juxtaarticular cancellous bone. A three-dimensional finite element model was used to test the hypothesis that an initially mechanically uncompromised subchondral plate could provide a substantial degree of stress protection to a weakened underlying segmental infarction. The computational simulation of osteonecrosis showed that the principal stress distribution for an assumption of subchondral plate weakening (given also an underlying, comparably weakened segmental infarction) differed inappreciably from that of a normal femoral head. However, the tendency for local structural failure, as reflected in the ratio of stress to strength, was substantially higher in the former instance. If, instead, the mechanical integrity of the subchondral plate overlying the weakened segmental infarction was assumed to be preserved, computed stress levels in the at-risk subjacent necrotic cancellous bone were still over 70% as high as for the weakened-plate case. The data thus indicate that even a fully normal subchondral plate can provide only modest stress protection of a weakened underlying segmental infarction, whereas weakening of the necrotic cancellous bone throughout the infarction induces marked stress increase in the overlying subchondral plate. These findings suggest that the onset of collapse is probably dominated much more strongly by the degree of structural degradation of the cancellous bone within the main infarct body, than by the degree of structural degradation within the subchondral plate.     

Indentation properties of growing femoral head following ischemic necrosis.

Little is known about the mechanical properties of the growing femoral head as it develops deformity following ischemic injury. The purpose of this study was to determine the indentation stiffness of growing femoral head following ischemic injury and to correlate the changes in stiffness with radiographic and histopathologic changes in the femoral head as it develops deformity. Following the induction of ischemia in 24 piglets, indentation testing of whole femoral heads was performed at 2, 4, and 8 weeks, as well as on femoral heads from eight sham operated animals. At 2 weeks, a 52% reduction of indentation stiffness was observed in the infarcted femoral heads compared to the control heads (p=0.004). The bony epiphyses in infarcted femoral heads were smaller due to growth arrest but they were not deformed. Histologically, no evidence of repair was seen. At 4 and 8 weeks, the indentation stiffness in the infarcted femoral heads was reduced by 75% (p<0.000001) and 72% (p=0.001) respectively compared to the control heads. Variable degree of femoral head deformity and repair was observed at 4 weeks. Severe deformity with extensive revascularization and repair were observed at 8 weeks. Although epiphyseal cartilage was thickened on the infarcted femoral heads only a weak correlation was found between the increase in the cartilage thickness and the decrease in the indentation stiffness (R(2)=0.55). These results indicate that the indentation properties of growing femoral head were significantly affected by ischemic injury, prior to the presence of repair process and deformity. A further decrease in the indentation stiffness was concomitant with repair of the infarcted head. These findings suggest that a reduction in the mechanical properties of the infarcted femoral head include both a cartilage and a bony component, which cannot be differentiated at this point. The study validates early institution of treatments that are aimed at limiting the mechanical loading of the affected hip. The study also suggests that in order to minimize the mechanical compromise of the infarcted femoral head, early institution of treatments aimed at stimulating new bone formation and retarding osteoclastic bone resorption may be beneficial.     

Contrast-enhanced MR imaging of subchondral insufficiency fracture of the femoral head: a preliminary comparison with that of osteonecrosis of the femoral head

Introduction  Subchondral insufficiency fracture of the femoral head (SIF) may be confused with osteonecrosis of the femoral head (ON) due to clinical and imaging similarities. Materials and methods  Contrast-enhanced MR images in patients with SIF (ten hips in ten patients) were retrospectively reviewed and compared with those from patients with ON (ten hips in six patients). Results  Low-signal intensity bands on T1-weighted images were present within the femoral head in all hips examined. The segment proximal to the band was contrast-enhanced following IV gadolinium administration in nine of ten hips (90%) with SIF and in none of the 10 hips with ON. Conclusion  These results suggest that the presence of contrast enhancement in the segment proximal to the low-signal intensity band in the femoral head may serve as a supplemental diagnostic measure for the differentiation of SIF from ON.     

Aseptic osteonecrosis of acetabulum following prosthetic replacement of the femoral head

Summary Acetabular osteonecrosis is a rare condition. Only five cases with histological analysis have been reported in the literature, and these patients had previously received radiotherapy. The 67-year-old woman reported on here, who had had no major systemic disorder or local radiotherapy, and who had never consumed alcohol, developed aseptic osteonecrosis of the acetabulum after femoral head replacement with a cemented Austin-Moore prosthesis for aseptic osteonecrosis of the femoral head following femoral neck fracture. The necrosis was found during surgery to go so deeply into each bone composing the acetabulum that the hip joint could not be revised, and we had to perform a Girdlestone resection arthroplasty. The radiographic and histological findings resembled those reported in cases of aseptic osteonecrosis of the acetabulum after radiotherapy.     

Ischemic femoral head osteonecrosis in a piglet model causes three dimensional decrease in acetabular coverage

Legg‐Calve‐Perthes disease (LCPD) is a childhood form of ischemic osteonecrosis marked by development of severe femoral head deformity and premature osteoarthritis. The pathogenesis of femoral head deformity has been studied extensively using a piglet model of ischemic osteonecrosis, however, accompanying acetabular changes have not been investigated. The purpose of this study was to determine if acetabular changes accompany femoral head deformity in a well‐established piglet model of LCPD and to define the acetabular changes using three dimensional computed tomography (3‐D CT) and modeling. Twenty‐four piglets were surgically induced with ischemic osteonecrosis on the right side. The contralateral hip was used as control. At 8 weeks postoperative, pelvi were retrieved and imaged with CT. Custom software was used to measure acetabular morphologic parameters on 3‐D CT images. Moderate to severe femoral head deformities were present in all animals. Acetabula with accompanying femoral head deformity had a significant decrease in acetabular version and tilt (p < 0.001) and in coverage angle in the superior, posterior, and inferior quadrants (p < 0.05). These findings indicate that the development of femoral head deformity following ischemic osteonecrosis produces specific and predictable changes to the shape of the acetabulum. Acetabular changes described in patients with LCPD were observed in the piglet model. This model may serve as a valuable tool to elucidate the relationship between femoral head and acetabular deformities. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1173–1177, 2018.

     

Drug therapy increases bone density in osteonecrosis of the femoral head in canines

Although many different pathogenetic mechanisms have been proposed for osteonecrosis of the femoral head, the repair process leads to structural collapse when bone resorption exceeds production. The purpose of the current study was to determine the effects of two agents with known bone-altering qualities, alendronate and simvastatin, on the healing response of a cryosurgically induced necrotic lesion of the femoral head in canines. Eighteen beagles had cryosurgical necrosis of the right femoral head. After 2 weeks, in a blinded, placebo-controlled, randomized fashion, a 10-mg dose of oral alendronate (n = 6), a 40 mg dose of simvastatin (n = 6), or a placebo (n = 6) was administered daily for 12 weeks. At sacrifice, bone densitometry and histomorphometry quantified bone in the femoral head. In the alendronate-treated animals, a 16% increase in bone mineral density of the femoral head with induced osteonecrosis was found compared with the placebo group. Increases in bone volume and trabecular thickness also were detected in the alendronate and simvastatin groups, with alendronate having the greatest effect. Clinically, increasing the amount of bone in the femoral head may forestall mechanisms leading to joint collapse characteristic of advanced osteonecrosis of the femoral head.     

The utility of clinical features for distinguishing subchondral insufficiency fracture from osteonecrosis of the femoral head

Purpose

Subchondral insufficiency fractures of the femoral head (SIF) need to be differentiated from osteonecrosis of the femoral head (ON), since these two conditions have several overlapping characteristics especially in their radiological findings. The purpose of this study was to determine the useful clinical features for differentiating SIF from ON.

Methods

This study reviewed 44 consecutive patients, aged 60 years or older with a radiological evidence of subchondral collapse of the femoral head. According to the histopathological diagnosis, 22 patients were grouped as SIF and 22 patients as ON. A 2 × 2 contingency table analysis was used to obtain the odd ratios (ORs) for SIF compared to ON.

Results

The age, proportion of females, the rate of a history of either corticosteroid intake or alcohol abuse, and the presence of vertebral compression fracture in subchondral insufficiency fracture were significantly higher than those with osteonecrosis (p = 0.0001, 0.0212, 0.0001, and 0.0040, respectively). ORs for SIF were 12.01 [95 % confidence intervals (CI) 1.35–106.80] and 7.29 (95 % CI 1.91–27.86), if the patient were female and 70 years of age or older, respectively. In addition, OR for SIF was extremely high (OR 56.01, 95 % CI 6.12–512.87) compared to ON, if the patients have a history of either corticosteroid intake or alcohol abuse.

Conclusion

The results of this study indicate that osteoporotic elderly women without any history of corticosteroid intake or alcohol abuse need to first be considered to have subchondral insufficiency fracture when radiographs show a collapse of the femoral head.     

Insufficiency subchondral fracture of the femoral head

The authors recently encountered a 65-year-old osteoporotic woman who had had intractable pain in the hip joint that was diagnosed clinically as osteonecrosis. She was treated by total hip replacement. Histopathologically, the most striking finding was the presence of a subchondral fracture with associated callus formation and granulation tissue along both sides of the fracture line. There was no evidence of antecedent osteonecrosis. This case was diagnosed histopathologically as insufficiency subchondral fracture of the femoral head. This is the first case report to substantiate the presence of insufficiency subchondral fracture of the femoral head by both gross and microscopic examination. Because the treatment and management of insufficiency subchondral fracture are entirely different from osteonecrosis, it is important to differentiate between these two conditions.     

非创伤性股骨头坏死的国外研究进展

非创伤性股骨头坏死在国内外均被列为尚未解决的难治性疾病之一,本文中作者综合近几年的研究对非创伤性股骨头坏死的病因及手术和非手术治疗方法进行最新的阐述.非创伤性股骨头坏死的发病有遗传学基础,各种危险因素及遗传易感性的相互作用将决定病情的转归.早期诊断及在股骨头出现塌陷之前进行干预是关节保留治疗能否得到良好结果的关键.关节是否保留取决于放射影像学表现.对于股骨头已经塌陷的患者,行关节置换术的满意度优于关节保留治疗.最新的药物治疗方法如生长分化因子可能会改变作者目前的治疗方法,但是有待于临床研究结果及长期的随访.     

Changes of the bone mineral density in proximal femur following total hip resurfacing arthroplasty in osteonecrosis of femoral head

Total hip resurfacing arthroplasty (THRA) is being performed with increasing frequency for osteonecrosis of femoral head (ONFH). To evaluate femoral bone remodeling in ONFH after THRA and determine the impact of stem‐neck angle (SNA) of inserted femoral component on bone remodeling, we monitored the changes in BMD in proximal femur in 23 patients with ONFH after surgery. Patients were divided into group A (SNA ≥ 5°) and group B (SNA < 5°). The BMD was measured in seven Gruen zones and two neck zones using dual‐energy X‐ray absorptiometry preoperatively, then at 3, 6, 12, and 24 months after surgery. At all ROIs, the BMD decreased significantly by 3 months postoperatively. The BMD ceased to decrease and reversed by 6 months. The BMD in neck increased significantly in group A, compared with group B at 24 months. The BMD increased 2% at ROI1 at 24 months in both groups, and at ROI7, the BMD in group A reversed to baseline value by 6 months and increased 5.81% at 24 months. These findings implied that the bone stock of proximal femur in ONFH can be well reserved after total hip resurfacing arthroplasty with valgus positioning of the femoral component. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:453–459, 2008     

Pathology of femoral head collapse following transtrochanteric rotational osteotomy for osteonecrosis

We investigated the pathology of femoral head collapse following transtrochanteric anterior rotational osteotomy. Six femoral heads were obtained during total hip arthroplasty some 2–12 years after osteotomy. In all cases, the preoperatively necrotic lesions exhibited mostly osteonecrosis with accumulation of bone marrow cell debris and trabecular bone with empty lacunae, although repair tissue such as granulation tissue and appositional bone formation were observed in limited areas in some cases. In the transposed intact articular surface of the femoral head, osteoarthritic changes such as fissure penetration to the subchondral bone and osteophyte formation were commonly observed. In newly created subchondral areas at weight-bearing sites, trabecular thickness and the number of trabecular bones had decreased, with few osteoblasts, osteoclasts, and osteocytes being present, resulting in a coarse lamellar structure of the trabecular bone. These findings suggest that transposed areas in cases of failure consist mostly of low-turnover osteoporotic lesions which could cause collapse of the femoral head. Received: 5 October 1999     

Cyclosporin A and osteonecrosis of the femoral head

A vascular osteonecrosis has occurred in 5 to 40 per cent of patients who have undergone transplantation of a kidney and generally has been considered to be a complication of the use of corticosteroids. Currently cyclosporin A is in general use for its immunosuppressive property, so that a lower dose of corticosteroids is needed. We analyzed the cases of a series of our patients who underwent transplantation of a kidney in order to find out if our present regimen, using cyclosporin A, influenced the prevalence of osteonecrosis of the femoral head. Of a total of 270 patients, osteonecrosis of the femoral head developed in fifteen of 174 who received conventional immunosuppressive therapy and in only one of ninety-six who received cyclosporin A (p less than 0.05). During the first two months after transplantation, the mean dose of prednisone was approximately 2.5 milligrams per kilogram of body weight per day in the group that received conventional immunosuppressive therapy and approximately 1.1 milligrams per kilogram of body weight per day in the group that received cyclosporin A (p less than 0.001). We concluded that the pathogenesis of the osteonecrosis in patients who underwent transplantation of a kidney was probably related to the higher doses of corticosteroids that were administered.     

Biophysical stimulation in osteonecrosis of the femoral head

Osteonecrosis of the femoral head is the endpoint of a disease process that results from insufficient blood flow and bone-tissue necrosis, leading to joint instability, collapse of the femoral head, arthritis of the joint, and total hip replacement. Pain is the most frequent clinical symptom. Both bone tissue and cartilage suffer when osteonecrosis of the femoral head develops. Stimulation with pulsed electromagnetic fields (PEMFs) has been shown to be useful for enhancing bone repair and for exerting a chondroprotective effect on articular cartilage. Two Italian studies on the treatment of avascular necrosis of the femoral head with PEMFs were presented in this review. In the first study, 68 patients suffering from avascular necrosis of the femoral head were treated with PEMFs in combination with core decompression and autologous bone grafts. The second one is a retrospective analysis of the results of treatment with PEMFs of 76 hips in 66 patients with osteonecrosis of the femoral head. In both studies clinical information and diagnostic imaging were collected at the beginning of the treatment and at the time of follow up. Statistical analysis was performed using chi-square test. Both authors hypothesize that the short-term effect of PEMF stimulation may be to protect the articular cartilage from the catabolic effect of inflammation and subchondral bone-marrow edema. The long-term effect of PEMF stimulation may be to promote osteogenic activity at the necrotic area and prevent trabecular fracture and subchondral bone collapse. PEMF stimulation represents an important therapeutic opportunity to resolve the Ficat stage-I or II disease or at least to delay the time until joint replacement becomes necessary.     

Endoprostheses for osteonecrosis of the femoral head

Summary Eighty-eight hip arthroplasties were carried out in 75 patients, all aged 50 years or less, with osteonecrosis. All the operations were carried out by one surgeon. Four different methods were used: a standard cemented arthroplasty; a cemented THARIES surface replacement; an uncemented surface replacement; a cemented titanium femoral surface hemiarthroplasty. Comparable clinical improvement occurred in all 4 groups initially. Aseptic loosening, with intersurface degradation and osteolytic lesions, was the most common cause of failure in the 3 types which had a polythene bearing. Polyethylene is the major contributor to bone loss around the endoprosthesis and loosening. Fixation of the surface hemiarthroplasty remained intact in every patient and failure was secondary to wear of the acetabular cartilage. We recommend surface hemiarthroplasty as an interim solution for young patients with stage III or early stage IV osteonecrosis because this procedure conserves bone stock, there is little osteolysis and it can easily be revised.

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Résumé Quatre-vingt-huit prothèses de hanche chez 75 patients atteints d'ostéonécrose et âgés de 50 ans ou moins ont été faites par un seul chirurgien. Vingt patients (24 hanches) ont été traités par une prothèse conventionelle cimentée. Il y eut 6 révisions, en moyenne à 87 mois. Trente et un patients (35 hanches) furent traités par une cupule couplée cimentée THARIES. Vingt deux révisions furent nécessaires, en moyenne à 84 mois. Un remplacement de surface sans ciment a été utilisé chez 19 patients, dont 10 furent réopérés à 60 mois en moyenne. Neuf patients (10 hanches) furent traités avec une hémi-arthroplastie fémorale de surface en titane, cimentée. 5 d'entre-eux ont dû être réopérés à un délai moyen de 89 mois. L'amélioration fonctionnelle a été comparable dans les 4 groupes. Dans les 3 groupes ayant une surface de frottement en polyéthylène, le descellement aseptique avec lésions d'ostéolyse fut la cause la plus fréquente d'échec. La fixation de l'hémi-arthroplastic fémorale ne s'est pas dégradée, et les échecs survinrent secondairement à cause de l'usure du cartilage acétabulaire. Ceci suggère que le polyéthylène est le facteur principal de l'ostéolyse péri-prothétique et du descellement. Avec l'avantage de la conservation osseuse, de l'absence d'ostéolyse et la facilité de la reprise, nous recommandons l'hémiarthroplastie de surface comme solution temporaire chez le jeune patient atteint d'une ostéonécrose au stade III ou IV précoce.