Hemodynamic measurement in the femoral head using laser Doppler

Methods to predict osteonecrosis of femoral head after femoral neck fracture: a systematic review of the literature

BACKGROUND

Femoral neck fracture (FNF) is a very common traumatic disorder and a major cause of blood supply disruption to the femoral head, which may lead to a severe long-term complication, osteonecrosis of femoral head (ONFH). Early prediction and evaluation of ONFH after FNF could facilitate early treatment and may prevent or reverse the development of ONFH. In this review paper, we will review all the prediction methods reported in the previous literature.

METHODS

Studies on the prediction of ONFH after FNF were included in PubMed and MEDLINE databases with articles published before October 2022. Further screening criteria were conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. This study highlights all the advantages and disadvantages of the prediction methods.

RESULTS

There were a total of 36 studies included, involving 11 methods to predict ONFH after FNF. Among radiographic imaging, superselective angiography could directly visualize the blood supply of the femoral head, but it is an invasive examination. As noninvasive detection methods, dynamic enhanced magnetic resonance imaging (MRI) and SPECT/CT are easy to operate, have a high sensitivity, and increase specificity. Though still at the early stage of development in clinical studies, micro-CT is a method of highly accurate quantification that can visualize femoral head intraosseous arteries. The prediction model relates to artificial intelligence and is easy to operate, but there is no consensus on the risk factors of ONFH. For the intraoperative methods, most of them are single studies and lack clinical evidence.

CONCLUSION

After reviewing all the prediction methods, we recommend using dynamic enhanced MRI or single photon emission computed tomography/computed tomography in combination with the intraoperative observation of bleeding from the holes of proximal cannulated screws to predict ONFH after FNF. Moreover, micro-CT is a promising imaging technique in clinical practice.

Changes in intraarticular pressure on the blood supply in the retinaculum of the femoral neck

BACKGROUND

This study aimed to analyze the effects of intracapsular pressure (IAP) on blood flow in the femur after a femoral neck fracture.

METHODS

Four simplified vascular models were used to measure the effect of vessel length on arterial blood flow in 10 New Zealand white rabbits. Ten models were evaluated under 10 different blood pressures.

FINDINGS

IAP increased following fracture of the femoral neck, and deformation had the greatest potential effect on blood flow in the retinacular artery. When blood pressure was fixed at 60 mm Hg, an increase in IAP caused a reduction in blood flow. When the IAP was relatively high (above 60 mm Hg), and higher than the blood pressure, blood flow continued to drop as intracapsular pressure increased. Shortening of blood vessels had no significant effect on blood supply. However, the p-value was uniformly significant (<0.05) when stretched and twisted blood vessels were compared with normal blood vessels.

INTERPRETATION

The results of computational fluid-structure interaction similarly indicated that a smaller blood vessel diameter and twisted blood vessels will result in decreased flow velocity when IAP increases. This study also revealed a close relationship between IAP and the hip joint's position and traction.

Using Naive Bayes Classifier to predict osteonecrosis of the femoral head with cannulated screw fixation

Predictive models permitting personalized prognostication for patients with cannulated screw fixation for the femoral neck fracture before operation are lacking. The objective of this study was to train, test, and cross-validate a Naive Bayes Classifier to predict the occurrence of postoperative osteonecrosis of cannulated screw fixation before the patient underwent the operation. The data for the classifier model were obtained from a ambispective cohort of 120 patients who had undergone closed reduction and cannulated screw fixation from January 2011 to June 2013. Three spatial displaced parameters of femoral neck: displacement of centre of femoral head, displacement of deepest of femoral head foveae and rotational displacement were measured from preoperative CT scans using a 3-dimensional software. The Naive Bayes Classifier was modelled with age, gender, side of fractures, mechanism of injury, preoperative traction, Pauwels angle and the three spatial parameters. After modelling, the ten-fold cross-validation method was used in this study to validate its performance. The ten-fold cross-validation method uses the whole dataset to be trained and tested by the given algorithm. Two of the three spatial parameters of femoral neck (displacement of center of femoral head and rotational displacement) were included successfully in the final Naive Bayes Classifier. The Classifier achieved good performance of the accuracy (74.4%), sensitivity (74.2%), specificity (75%), positive predictive value (92%), negative predictive value (42.9%) and AUC (0.746). We showed that the Naive Bayes Classifier have the potential utility to be used to predict the osteonecrosis of femoral head within 5 years after surgery. Although this study population was restricted to patients treated with cannulated screws fixation, Bayesian-derived models may be developed for application to patients with other surgical procedures at risk of osteonecrosis.

Use of near-infrared systems for investigations of hemodynamics in human in vivo bone tissue: A systematic review

A range of technologies using near infrared (NIR) light have shown promise at providing real time measurements of hemodynamic markers in bone tissue in vivo, an exciting prospect given existing difficulties in measuring hemodynamics in bone tissue. This systematic review aimed to evaluate the evidence for this potential use of NIR systems, establishing their potential as a research tool in this field. Major electronic databases including MEDLINE and EMBASE were searched using pre-planned search strategies with broad scope for any in vivo use of NIR technologies in human bone tissue. Following identification of studies by title and abstract screening, full text inclusion was determined by double blind assessment using predefined criteria. Full text studies for inclusion were data extracted using a predesigned proforma and quality assessed. Narrative synthesis was appropriate given the wide heterogeneity of included studies. Eighty-eight full text studies fulfilled the inclusion criteria, 57 addressing laser Doppler flowmetry (56 intra-operatively), 21 near infrared spectroscopy, and 10 photoplethysmography. The heterogeneity of the methodologies included differing hemodynamic markers, measurement protocols, anatomical locations, and research applications, making meaningful direct comparisons impossible. Further, studies were often limited by small sample sizes with potential selection biases, detection biases, and wide variability in results between participants. Despite promising potential in the use of NIR light to interrogate bone circulation, the application of NIR systems in bone requires rigorous assessment of the reproducibility of potential hemodynamic markers and further validation of these markers against alternative physiologically relevant reference standards. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2595-2603, 2018.

Focal osteonecrosis in the femoral head following stable anatomic fixation of displaced femoral neck fractures

INTRODUCTION

Femoral head (FH) osteonecrosis (ON) and subsequent segmental collapse is a major concern following displaced femoral neck fractures (FNF). We aimed to quantify residual perfusion to the FH following FNF and evaluate the viability of the FH overtime after surgical fixation.

MATERIALS AND METHODS

Twenty-three patients with FNF underwent dynamic contrast-enhanced (DCE)-MRI to estimate bone perfusion in the FH, using the contralateral side as control. Following open anatomic reduction and a length/angle-stable fixation, a special MRI sequence evaluated the FH for ON changes over time at 3 and 12 months after surgery.

RESULTS

We found significant compromise of both arterial inflow [83.1%-initial area under the curve (IAUC) and 73.8%-peak) and venous outflow (243.2%-elimination rate (K _el)] in the FH of the fractured side. The supero-medial quadrant suffered the greatest decrease in arterial inflow with a significant decrease of 71.6% (IAUC) and 68.5% (peak). Post-operative MRI revealed a high rate (87%-20/23) of small ON segments within the FH, and all developed in the anterior aspect of the supero-medial quadrants. Fracture characteristics, including subcapital FNF, varus deformity, posterior roll-off ≥20° and Pauwel's angle of 30°-50° demonstrated a greater decrease in perfusion compared to contralateral controls.

CONCLUSION

FNF significantly impaired the vascular supply to the FH, resulting in high incidence of small ON segments in the supero-medial quadrant of the FH. However, maintained perfusion, probably through the inferior retinacular system, coupled with urgent open anatomic reduction and stable fixation resulted in excellent clinical and radiographic outcomes despite a high rate of small ON segments noted on MRI.

LEVEL OF EVIDENCE

Level I: Prognostic Investigation.

Management of femoral neck fractures in the young patient: A critical analysis review

Femoral neck fractures account for nearly half of all hip fractures with the vast majority occurring in elderly patients after simple falls. Currently there may be sufficient evidence to support the routine use of hip replacement surgery for low demand elderly patients in all but non-displaced and valgus impacted femoral neck fractures. However, for the physiologically young patients, preservation of the natural hip anatomy and mechanics is a priority in management because of their high functional demands. The biomechanical challenges of femoral neck fixation and the vulnerability of the femoral head blood supply lead to a high incidence of non-union and osteonecrosis of the femoral head after internal fixation of displaced femoral neck fractures. Anatomic reduction and stable internal fixation are essentials in achieving the goals of treatment in this young patient population. Furthermore, other management variables such as surgical timing, the role of capsulotomy and the choice of implant for fixation remain controversial. This review will focus both on the demographics and injury profile of young patients with femoral neck fractures and the current evidence behind the surgical management of these injuries as well as their major secondary complications.

Increased post-operative ischemia in the femoral head found by microdialysis by the posterior surgical approach: a randomized clinical trial comparing surgical approaches in hip resurfacing arthroplasty

BACKGROUND

Hip resurfacing arthroplasty (HRA) is associated with osteonecrosis of the femoral head and femoral neck fracture, which may be caused by a decrease in the perfusion of the bone initiated at surgery. Several studies have demonstrated a decreased blood flow during surgery depending on the choice of surgical approach. We investigated the effect of the surgical approach on the blood flow and metabolism in the femoral head and neck in HRA by Laser Doppler flowmetry (LDF) and microdialysis.

MATERIALS AND METHODS

We conducted a randomized clinical trial on 38 patients, allocated to HRA by either the posterior (Post) or the antero-lateral (AntLat) surgical approach. LDF was performed during surgery and microdialysis after surgery to assess the concentration of the following metabolic markers: glucose, lactate, pyruvate and glycerol.

RESULTS

At 44-50 h after surgery, the mean lactate/pyruvate (L/P) and lactate/glucose (L/G) ratio was higher in the Post group compared to the AntLat group; L/P 195.3 (SEM 123) in Post and 128.5 (108.0) in AntLat; L/G 16.9 (6.5) in Post and 8.9 (3.7) in AntLat (p L/P = 0.02 and p L/G = 0.03). There was no difference in the LDF measurements (p = 0.74).

INTERPRETATION

HRA in the posterior approach results in increased post-operative ischemia in the femoral head and neck although during surgery, no difference in the blood flow was found. Still, the antero-lateral approach also causes considerable ischemia and other possible explanations, such as damage to the retinacular vessels during surgery or altered microcirculation because of heating from the cementation process, needs to be investigated.

Early prediction of femoral head avascular necrosis following neck fracture

Femoral neck fracture puts at risk functional prognosis in young patients and can be life-threatening in the elderly. The present study reviews methods of femoral head vascularity assessment following neck fracture, to address the following issues: what is the risk of osteonecrosis? And what, in the light of this risk, is the best-adapted treatment to avoid iterative surgery? Femoral head vascularity depends on retinacular vessels and especially the lateral epiphyseal artery, which contributes from 70 to 80% of the femoral head vascular supply. Fracture causes vascular lesions, which are in turn the prime cause of necrosis. Other factors combine with this: hematoma tamponade effect, reduced joint space and increased pressure due to lower extremity positioning in extension/internal rotation/abduction during surgery. Head deformity is not due to direct cell death but to the repair process originating from the surrounding living bone. In post-traumatic necrosis, proliferation rapidly invades the head, with significant osteogenesis. Pathologic fractures occur at the boundary between the new and dead bone. Many techniques have been reported to help assess residual hemodynamics and risk of necrosis. Some are invasive: superselective angiography, intra-osseous oxygen pressure measurement, or Doppler-laser hemodynamic measurement; others involve imaging: scintigraphy, conventionnal or dynamic MRI. The future seems to lie with dynamic MRI, which allows a new classification of femoral neck fractures, based on a non-invasive assessment of femoral head vascularity.

The vascular network in the femoral head and neck after hip resurfacing

The purpose of this study was to determine whether femoral neck fracture after cemented resurfacing hip arthroplasty (RHA) arises from intraosseous vascularity around the femoral head-neck junction. We implanted a replica of the femoral head component into osteoarthritic femoral heads and compared the intraosseous vascularity network between the femoral heads with and without the RHA procedure using microangiography through a retinacular artery with micro-computed tomography. Our results showed no significant difference in the vascularity around the femoral head-neck junction between the groups with and without the RHA procedure. These results suggest that deterioration of the intraosseous vascular network around the head-neck junction after RHA was not severe enough to induce complete avascularity.

Role of the extraosseus blood supply in osteoarthritic femoral heads?

Blood perfusion to the femoral head might be endangered during the surgical approach or the preparation of the femoral head or both in hip resurfacing arthroplasty. The contribution of the intramedullary blood supply to the femoral head in osteoarthritis is questionable. Therefore, the contribution of the extraosseous blood supply to osteoarthritic femoral heads was measured intraoperatively to question if there is measurable blood flow between the epiphysis and metaphysis in osteoarthritic hips in case of extraosseus vessel damage. At defined points during surgery we acquired the epiphyseal and metaphyseal femoral head perfusion by high-energy laser Doppler flowmetry. Complete femoral neck osteotomy sparing the retinacular vessels to simulate intraosseous blood disruption showed unchanged epiphyseal blood flow compared to initial measurement after capsulotomy. The pulsatile signal disappeared after transection of the retinacular vessels. Based on these acute measurements, we conclude intramedullary blood vessels to the femoral head do not provide measurable blood supply to the epiphysis once the medial femoral circumflex artery or the retinacular vessels have been damaged. We recommend the use of a safe surgical approach for hip resurfacing and careful implantation of the femoral component to respect blood supply to the femoral head and neck region in hip resurfacing arthroplasty.

The influence of surgical approach on outcome in Birmingham hip resurfacing

Various approaches have been described for metal-on-metal hip resurfacing. We compared the posterolateral and direct lateral approaches for complications, pain, function, and implant survival in the short and medium term for two surgeons in a consecutive series of 790 patients (909 hips; July 1997 to July 2004) followed until July 2007. The direct lateral approach group included 135 resurfacing procedures and the posterolateral group included 774 procedures. There was no difference between the two groups for age or gender. The minimum followup for the anterolateral group was 2 years (mean, 5.1 years; range, 2.0-9.4 years) and for the posterolateral group 2 years (mean, 5.5 years; range, 2.0-9.6 years). There were no differences between the two approaches for complications, additional surgery, implant survival, or Oxford hip scores. The 8-year survival rate was 97.9% (95% confidence interval, 89.9-100) for the direct lateral approach and 97.2% (95% confidence interval, 93.9-99.3) for the posterolateral approach. This study indicates both approaches offer excellent pain reduction and return to function after Birmingham hip resurfacing with no difference in survival or in the incidence of complications. An 8-year survival rate of 97% can be achieved using either the posterolateral approach or the direct lateral approach.

LEVEL OF EVIDENCE

Level III, therapeutic study. See the Guidelines for authors for a complete description of levels of evidence.

The blood flow to the femoral head/neck junction during resurfacing arthroplasty

We used Laser Doppler flowmetry to measure the effect on the blood flow to the femoral head/neck junction of two surgical approaches during resurfacing arthroplasty. We studied 24 hips undergoing resurfacing arthroplasty for osteoarthritis. Of these, 12 had a posterior approach and 12 a trochanteric flip approach. A Laser probe was placed under radiological control in the superolateral part of the femoral head/neck junction. The Doppler flux was measured at stages of the operation and compared with the initial flux. In both groups the main fall in blood flow occurred during the initial exposure and capsulotomy of the hip joint.

There was a greater reduction in blood flow with the posterior (40%) than with the trochanteric flip approach (11%).

Does surgical approach influence component positioning with Birmingham Hip Resurfacing?

The aim of this study was to compare the component positioning of Birmingham Hip Resurfacings implanted through a posterolateral approach with those inserted via a direct lateral approach. Sixty-four hip resurfacings for osteoarthritis were carried out by a single surgeon: 23 through a direct lateral approach and 41 through a posterolateral approach. No significant differences in implant survival, Oxford Hip Scores or complications were found. The mean abduction angle for the acetabular component was lower (p < 0.007) with a posterior approach (mean: 37.5 degrees ; range 26-50 degrees ) than the lateral approach (mean: 43 degrees ; range 30-56 degrees ). There was no significant difference in stem orientation, either in flexion/extension or varus/valgus, between the two groups. This study demonstrates that components can be implanted in an acceptable orientation through either approach but that the posterior approach results in greater closure of the acetabular component.

Prediction of avascular necrosis of the femoral head by measuring intramedullary oxygen tension after femoral neck fracture

OBJECTIVE

To measure the intramedullary oxygen tension of the proximal femur after a femoral neck fracture and to evaluate the usefulness of that monitoring for prediction of subsequent avascular necrosis.

DESIGN

Prospective case series with comparison group.

SETTING

University hospital.

INTERVENTION

Measurement of intramedullary oxygen tension of the femoral head and neck during internal fixation using the Hansson hook-pin system.

MAIN OUTCOME MEASUREMENTS

Intramedullary oxygen tension was measured directly during surgery in 17 patients with 18 femoral neck fractures treated by internal fixation between October 2000 and February 2002. The intramedullary oxygen tension was measured by using polarographic oxygen electrodes and an oxygen monitor at four points: (A) 1 cm distal from the joint surface; (B) 1 cm proximal from the fracture site; (C) 1 cm distal from the fracture site; and (D) 1 cm proximal from the lateral wall. The presence or absence of avascular necrosis was evaluated by magnetic resonance imaging (MRI) at 2, 6, and 12 months after surgery.

RESULTS

MRI evaluation showed 11 fractures healed without complications, and 7 fractures developed avascular necrosis. We found significant differences in the distribution of intramedullary oxygen tension of the femoral head between points A (1 cm from the joint surface) and B (1 cm proximal from the fracture site) in those patients who developed avascular necrosis (P = 0.039); that is the oxygen tension was lower at point A than at point B. In contrast, in those patients who did not develop avascular necrosis there was no significant differences between point A and B were found (P = 0.059). The sensitivity and specificity for prediction of avascular necrosis were 1.0 and 0.82 (Fischer exact probability test, P = 0.002), respectively, when the cut-off level of oxygen tension differences between points A and B was set at 3.1 mm Hg.

CONCLUSION

We believe that this method of measuring intramedullary oxygen tension is simpler and less invasive than other currently used methods and has the possibility for intraoperatively identifying a risk group that can develop a late segmental collapse of the femoral head secondary to avascular necrosis.

A predictive method for subsequent avascular necrosis of the femoral head (AVNFH) by observation of bleeding from the cannulated screw used for fixation of intracapsular femoral neck fractures

OBJECTIVES

To examine the validity of bleeding from the drill holes used for cannulated screw placement as a method for predicting any subsequent avascular necrosis of the femoral head (AVNFH) after the fixation of intracapsular femoral neck fractures.

DESIGN

Retrospective study.

SETTING

University hospital.

PARTICIPANTS

Forty-four patients (mean age, 51 years; range, 18-76 years) whose femoral neck fractures had been fixed with cannulated screws from March 1999 to January 2001 were enrolled in this study. The fractures were classified according to Garden and included 11 type I, 5 type II, 17 type III, and 11 type IV. The average delay between injury and surgery was 52 hours (< or =24 hours, 26; > or =24 hours, 18; range 7 to 504 hours). The follow-up period was more than 25 months (range, 25-57 months).

INTERVENTION

7.0 mm cannulated screws were used for fracture fixation. Three and 4 screws were used for fixation in 35 and 9 cases, respectively.

MAIN OUTCOME MEASUREMENTS

The presence or absence of blood drainage from the holes of the proximal cannulated screws was determined by an independent observer and defined as bleeding or no bleeding throughout a 5 minute observation period. According to those findings, patients were classified into 2 groups: the bleeding group (38 cases), and the nonbleeding group (6 cases). The validity of the relationship between the 2 groups and the development of AVNFH was evaluated according to the sensitivity, specificity, positive predictive value, and negative predictive value. A chi test was used for univariate analysis of the relationship between the related factors with the development of AVNFH.

RESULTS

The mean follow-up was 39 months (range, 25-57 months). AVNFH developed in 7 cases (16%). One patient of 38 in the bleeding group (2.6%) and all 6 patients in the nonbleeding group (100%) developed AVNFH. The sensitivity was 86%, specificity 100%, positive predictive value 100%, and negative predictive value 97%. Age (P < 0.734), sex (P < 0.587), the type of the fracture (P < 0.356), procedure interval (P < 0.398), the reduction status of the fracture site (P < 0.3849), the positions of the fixed screws (P < 0.2137), and the existence of osteoporosis (P < 0.4347) were not related to the development of AVNFH.

CONCLUSION

It seems that bleeding from the holes of proximal cannulated screws is a simple and accurate perfusion assessment technique for predicting the development of AVNFH after a femoral neck fracture. Given that assumption, primary arthroplasty might be an appropriate choice as a treatment method in a nonbleeding-group patient whose treatment choice is ambivalent or who might not be able to undergo additional surgery should he or she develop a subsequent AVNFH after internal fixation of femoral neck fracture.

Blood flow and microdialysis in the human femoral head

BACKGROUND

If it would be possible to detect lack of flow and/or the development of ischemia in bone, we might have a way of predicting whether a broken bone will heal. We established microdialysis (MD) and laser Doppler (LD) flow measurement in the human femoral head in order to be able to detect ischemia and measure changes in blood flow.

MATERIAL AND METHODS

In 9 patients undergoing total hip arthroplasty for primary osteoarthrosis, two MD catheters were inserted into the femoral head through two drill holes after the blood flow had been visualized by LD. Then primary samples were collected with the femoral head in situ; thereafter, the head was removed and samples were collected over the following 4 hours ex vivo. The variables obtained by MD were concentrations of glucose, lactate, pyruvate, and glycerol in extracellular fluid.

RESULTS

The results showed development of ischemia with a statistically significant decrease in glucose concentration and elevation of the lactate/pyruvate ratio over time. The LD showed flow with the femoral head in situ and lack of flow when the femoral head was removed.

INTERPRETATION

The use of MD was established in the human femoral head. Ischemic levels were detected within 2 h of cessation of blood flow in most patients.

Vascularity of the femoral head after Birmingham hip resurfacing. A technetium Tc 99m bone scan/single photon emission computed tomography study

To investigate the vascularity of femoral heads after Birmingham hip resurfacing (BHR), we used a visual scale to assess technetium Tc 99m HDP planar and single photon emission computed tomography bone scans of 36 arthroplasties in 32 asymptomatic patients for an average of 26 months after BHR. The validity of this method was demonstrated by comparing levels of radiation detected from within and immediately adjacent to a BHR prosthesis placed on a technetium Tc 99m radioisotope tracer-filled hollow tube and further validated in vivo by comparing radiation levels from bilateral hip scans in human subjects with 2 normal hips and with unilateral BHR. All femoral heads scanned postoperatively appeared vascular. We speculate that preserved femoral head vascularity after BHR may be related to increased intraosseous blood supply from metaphyseal vessels in arthritic hips.

Acetabular blood flow during Bernese periacetabular osteotomy: an intraoperative study using laser Doppler flowmetry

BACKGROUND

The blood flow to the acetabular fragment is of some concern in juxtaarticular pelvic osteotomies used for the treatment of hip dysplasia. No direct measurements have determined the effect of the Bernese periacetabular osteotomy (PAO) on acetabular perfusion.

METHODS

Acetabular perfusion was measured by means of laser Doppler flowmetry in 10 patients undergoing a PAO for symptomatic acetabular dysplasia. During the surgical procedure, the intraosseous high energy laser Doppler reliably depicts dynamic changes of small vessel blood flow. Measurements were performed after defined surgical steps to obtain sequential information on the blood perfusion of the acetabular fragment.

RESULTS

After complete separation of the acetabular fragment, nine out of 10 patients had pulsatile signals, but the blood flow (BF) significantly decreased by 77%. Corrective positioning of the fragment induced no further drop of the BF signal but a loss of pulsatility in six patients. After a recovery period of about 30 min following preliminary fixation of the fragment, reestablishment of the pulsatile signal and an increase of the BF signal was seen. At termination of the surgical procedure, five out of eight patients, who could be followed throughout the whole procedure, showed a clear pulsatile signal in the supraacetabular area. Bleeding of the supraacetabular cancellous surface could be observed in all acetabula.

CONCLUSION

Despite careful preservation of soft tissues during the surgical procedure, a significant reduction of the blood flow in the supraacetabular region has been observed. Nevertheless, a pulsatile signal in more than 60% of the fragments after fragment correction and an increasing signal during the recovery period showed ongoing blood perfusion indicating reversible changes in the measured supraacetabular area. All osteotomies healed within eight weeks without showing signs of necrosis during a minimum follow up of 1 year.

Evaluation of femoral perfusion in a non-traumatic rabbit osteonecrosis model with T2*-weighted dynamic MRI

We evaluated femoral perfusion in a non-traumatic rabbit serum sickness osteonecrosis (ON) model, using serial repetitive T2*-weighted (T2*W) dynamic magnetic resonance imaging (MRI) and investigated prediction of ON occurrence in early stages, comparing T2*W dynamic MRI with non-enhanced (T2-, T1- and fat suppression T1-weighted) and contrast-enhanced MRI. Early microcirculatory injury or necrotic lesion was detected in 0% of femora (extravasation, 0/6) at 72 h, 33% (necrotic, 4/12) at 1 week and 100% (necrotic, 14/14) at 3 weeks using non-enhanced MRI, and in 67% of femora (extravasation, 4/6) at 72 h, 58% (necrotic, 7/12) at 1 week and 100% (necrotic, 14/14) at 3 weeks using contrast-enhanced MRI. In contrast, microcirculatory injury or necrotic lesion was detected in 83% of femora (extravasation, 5/6) at 72 h, 92% (necrotic, 11/12) at 1 week and 100% (necrotic, 14/14) at 3 weeks using T2*W dynamic MRI as no transient decrease or less marked transient decrease in signal intensity of regions of interest (ROIs), compared to normal femora, which showed a clear transient decrease in signal intensity of ROIs. These results indicate that T2*W dynamic MRI with optimal imaging parameters and a dose of contrast agent is the most sensitive of these three MRI methods and may be clinically useful for evaluating femoral perfusion in artery phase and predicting ON occurrence.

Avascular necrosis of the femoral head after femoral neck fracture

Trauma-induced avascular necrosis of the femoral head represents the most common femoral head aseptic necrosis. An alteration in blood supply to the femoral head is the cause of the vascular necrosis. Another mechanism in the genesis of femoral head necrosis is the tamponade effect. Femoral head necrosis may be asymptomatic for a long time, even in patients in whom late segmental collapse already is present. Radiography does not allow diagnostic reliability until 6 months after fracture. The presence of a low signal intensity band away from the fracture line on magnetic resonance images clearly delimits the necrotic area. Once segmental collapse has developed, the diagnosis becomes simple using plain radiographs. The treatment of established femoral necrosis complicating fractures of the upper end of the femur is approached as a therapeutic problem lacking an optimal solution. The main therapeutic options are femoral head-preserving procedures and joint reconstruction. Among the procedures that preserve the femoral head are joint unloading, femoral head core decompression, electric stimulation, osteotomy, and bone grafting. Joint reconstruction procedures including cup arthroplasty, hemiresurfacing, total hip resurfacing, femoral head replacement, femoral head endoprosthesis, and total arthroplasty will be reviewed.