Femoral head viability after Birmingham resurfacing hip arthroplasty: assessment with use of [18F] fluoride positron emission tomography

Assessment of Orthopedic Surgical Implants in Dogs Using 18F-Sodium Fluoride Positron Emission Tomography and Computed Tomography

Failure of fixation is a potential complication associated with surgical implants, and early detection is important but challenging. Positron emission tomography (PET) has the potential to detect lesions that may exhibit little to no visible findings on other commonly used diagnostic imaging modalities. The aim of this retrospective descriptive study was to assess 18F-Sodium Fluoride (18F-NaF) uptake associated with surgical implants in dogs. Medical records were searched for canine patients with orthopedic metallic implants in place imaged with 18F-NaF PET/CT. PET images were reviewed blinded to clinical history, with each surgical implant assessed for the presence of increased radiopharmaceutical uptake (IRU). IRU was graded subjectively regarding the severity (absent, mild, moderate, severe) and the extent area (focal, multifocal, extensive), and objectively by measuring maximal standardized uptake values (SUVmax). Seven patients were included, with a total of 39 metallic implants used in eight surgical procedures (three total hip replacements, three humeral fractures, one tibial plateau leveling osteotomy, and one tibial tuberosity advancement). In 24 of 39 implants (62%), no IRU was displayed. Fifteen implants (38%) displayed IRU (five mild, five moderate, five severe). The highest SUVmax (24) was associated with confirmed sepsis of a total hip replacement implant. The remaining implants with severe IRU were articular implants with associated marked degenerative joint pathology. This study confirms that most implants displayed no IRU with 18F-NaF PET. The presence of implant-associated IRU may indicate implant failure; however, IRU may also be due to regional bone pathology, including both degenerative joint disease and sepsis.

Evaluation of bone viability in patients after girdlestone arthroplasty: comparison of bone SPECT/CT and MRI

PURPOSE

To test the diagnostic performance of bone SPECT/CT and MRI for the evaluation of bone viability in patients after girdlestone-arthroplasty with histopathology used as gold standard.

MATERIALS AND METHODS

In this cross-sectional study, patients after girdlestone-arthroplasty were imaged with single-photon-emission-computed-tomography/computed-tomography (SPECT/CT) bone-scans using 99mTc-DPD. Additionally, 1.5 T MRI was performed with turbo-inversion-recovery-magnitude (TIRM), contrast-enhanced T1-fat sat (FS) and T1-mapping. All imaging was performed within 24 h prior to revision total-hip-arthroplasty in patients with a girdlestone-arthroplasty. In each patient, four standardized bone-tissue-biopsies (14 patients) were taken intraoperatively at the remaining acetabulum superior/inferior and trochanter major/minor. Histopathological evaluation of bone samples regarding bone viability was used as gold standard.

RESULTS

A total of 56 bone-segments were analysed and classified as vital (n = 39) or nonvital (n = 17) by histopathology. Mineral/late-phase SPECT/CT showed a high sensitivity (90%) and specificity (94%) to distinguish viable and nonviable bone tissue. TIRM (sensitivity 87%, specificity 88%) and contrast-enhanced T1-FS (sensitivity 90%, specificity 88%) also achieved a high sensitivity and specificity. T1-mapping achieved the lowest values (sensitivity 82%, specificity 82%). False positive results in SPECT/CT and MRI resulted from small bone fragments close to metal artefacts.

CONCLUSIONS

Both bone SPECT/CT and MRI allow a reliable differentiation between viable and nonviable bone tissue in patients after girdlestone arthroplasty. The findings of this study could also be relevant for the evaluation of bone viability in the context of avascular bone necrosis.

MRI Evaluation of Femoroacetabular Impingement After Hip Preservation Surgery

OBJECTIVE

This article reviews the surgical treatment options for femoroacetabular impingement (FAI), including labral repair and osteochondroplasty, and the expected postoperative appearance on MRI. Complications, including residual osseous deformities, chondral injury, adhesions, femoral neck stress fractures, osteonecrosis, instability, malpositioned suture anchors, and infection, will also be discussed.

CONCLUSION

Knowledge of the surgical treatment of FAI can assist in improving our understanding of the expected postoperative MRI appearance and in evaluating surgical complications.

¹⁸F-fluoride PET and PET/CT in children and young adults

18F-fluoride PET/CT has been used for a wide variety of indications in children and young adults. Nearly all pediatric 18F-fluoride PET/CTs are performed to evaluate benign conditions. The most common indication is the evaluation of back pain in a wide variety of circumstances, including patients with sports injuries, scoliosis, trauma, and back pain after surgery. The high image quality of 18F-fluoride PET/CT can make it particularly useful for evaluating benign skeletal lesions such as osteoid osteoma and Langerhans cell histiocytosis. Quantitative assessment of bone turnover with 18F-fluoride PET/CT may make it useful for assessing the skeleton in patients with metabolic bone diseases, eating disorders, and avascular necrosis. There is little pediatric experience using 18F-fluoride PET/CT for evaluation of skeletal or soft tissue disease in childhood cancers.

A comprehensive five-phase rehabilitation programme after hip arthroscopy for femoroacetabular impingement

PURPOSE

Recent advancements in the understanding of hip biomechanics have led to the development of techniques to remove bony impingement and repair and/or preserve the labrum during hip arthroscopy. Although much attention in the literature is devoted to diagnosis and treatment, there is little information about post-operative rehabilitation. Therefore, the purpose of this review is to (1) provide a five-phase rehabilitation protocol following arthroscopic treatment for FAI and (2) report clinical and functional outcomes of patients following this protocol at minimum 1-year follow-up, in order to provide the surgeon and therapist with a protocol that is supported by clinical data.

METHODS

All consecutive patients undergoing hip arthroscopy and subsequent five-phase rehabilitation protocol at a single institution from 1 April 2011 to 1 April 2012 were analysed. Inclusion criteria were as follows: no prior ipsilateral hip surgery, completion of the five-phase rehabilitation protocol, minimum 1-year follow-up, and documented outcome scores. Prospective outcomes were assessed with modified Harris hip score (MHHS) and hip outcome score (HOS).

RESULTS

Fifty-two patients (19 male and 33 female) met the inclusion criteria with a median age of 42 (range 16-59) years. Mean MHHS, HOS-ADL, and HOS-sport scores at a mean 12.5 (range 12-15) months were 80.1 ± 19.9 (0-100), 83.6 ± 19.2 (13.2-100), and 70.3 ± 27.0 (0-100), respectively.

CONCLUSION

This five-phase rehabilitation programme provides a framework where progression from surgery to increasing post-operative activity level can take place in a predictable manner. Patients following this rehabilitation protocol after hip arthroscopy demonstrated satisfactory clinical and functional outcomes, validating its implementation.

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.

The effect of surgical approach on the histologyof the femoral head following resurfacing of the hip: Analysis of retrieval specimens

OBJECTIVES

We aimed to determine the effect of surgical approach on the histology of the femoral head following resurfacing of the hip.

METHODS

We performed a histological assessment of the bone under the femoral component taken from retrieval specimens of patients having revision surgery following resurfacing of the hip. We compared the number of empty lacunae in specimens from patients who had originally had a posterior surgical approach with the number in patients having alternative surgical approaches.

RESULTS

We found a statistically significant increase in the percentage of empty lacunae in retrieval specimens from patients who had the posterior approach compared with other surgical approaches (p < 0.001).

CONCLUSIONS

This indicates that the vascular compromise that occurs during the posterior surgical approach does have long-term effects on the bone of the femoral head, even if it does not cause overt avascular necrosis. Cite this article: Bone Joint Res 2013;2:200-5.

Intralesional autologous mesenchymal stem cells in management of osteonecrosis of femur: a preliminary study

BACKGROUND

Management of early stages of osteonecrosis aims to prevent the collapse of the femoral head by attempts at restoring the vascularity of femoral head. Bone marrow-derived mononuclear cells with their angiogenic and osteogenic properties appear to have the potential to halt the disease process when injected intralesionally following core decompression.

MATERIALS AND METHODS

Forty patients (60 hips) with stage I, II or III (ARCO system) osteonecrosis of femoral head were treated by either core decompression and isolated mononuclear cells (group A) or core decompression and unprocessed bone marrow injection (group B). The patients were followed up clinically and radiologically for a minimum of 2 years. The functional outcome was assessed in terms of Harris hip score, and disease progression was assessed radiologically by comparing the preoperative and follow-up MRI at the end of 2 years.

RESULTS

On 2-year follow-up, there was considerable improvement in the hip function as measured by the Harris hip score in both the groups (p = 0.031). On MRI, there was a decrease in the size of the lesion in group A (p = 0.03). Three of 30 hips (10.0 %) in group B required total hip replacement.

CONCLUSIONS

Implantation of autologous bone marrow stem cells in avascular necrosis of femoral head is a safe and effective procedure and has better outcome than bone marrow for early stage of avascular necrosis of femoral head.

The distribution of vascular foramina at the femoral head/neck junction: implications for resurfacing arthroplasty

Reaming for resurfacing arthroplasty may endanger the blood supply at the head-neck junction, possibly predisposing to osteonecrosis and femoral neck fracture. The current study hypothesizes that reaming endangers femoral head vasculature. Vascular foramina were identified on 16 cadaveric femora and registered on computed tomographic models. Virtual reaming was performed after templating of resurfacing components. Almost half (41.8%) of foramina was located in the anterosuperior quadrant. Loss of foramina after reaming averaged 28% (P = .03), with up to 34.6% and 33.1% loss in the anterosuperior and posterosuperior quadrants, respectively. Reaming for resurfacing arthroplasty endangers a substantial number of vascular foramina. Notching or malpositioning of components may worsen injury to the vascular supply and could subsequently increase the risk of implant failure.

Scintigraphic assessment of bone status at one year following hip resurfacing: Comparison of two surgical approaches using SPECT-CT scan

Objectives

To study the vascularity and bone metabolism of the femoral head/neck following hip resurfacing arthroplasty, and to use these results to compare the posterior and the trochanteric-flip approaches.

Methods

In our previous work, we reported changes to intra-operative blood flow during hip resurfacing arthroplasty comparing two surgical approaches. In this study, we report the vascularity and the metabolic bone function in the proximal femur in these same patients at one year after the surgery. Vascularity and bone function was assessed using scintigraphic techniques. Of the 13 patients who agreed to take part, eight had their arthroplasty through a posterior approach and five through a trochanteric-flip approach.

Results

One year after surgery, we found no difference in the vascularity (vascular phase) and metabolic bone function (delayed phase) at the junction of the femoral head/neck between the two groups of patients. Higher radiopharmaceutical uptake was found in the region of the greater trochanter in the trochanteric-flip group, related to the healing osteotomy.

Conclusions

Our findings using scintigraphic techniques suggest that the greater intra-operative reduction in blood flow to the junction of the femoral head/neck, which is seen with the posterior approach compared with trochanteric flip, does not result in any difference in vascularity or metabolic bone function one year after surgery.

Metabolic development of necrotic bone in the femoral head following resurfacing arthroplasty. A clinical [18F]fluoride-PET study in 11 asymptomatic hips

BACKGROUND AND PURPOSE

One concern regarding resurfacing arthroplasty is the viability of the diminished femoral head and the postoperative risk of collapse, or a femoral neck fracture. (18)F-fluoride positron emission tomography (F-PET) enables us to assess bone viability despite there being a covering metal component. By F-PET studies, we recently showed the absence of metabolism in the remaining part of femoral heads, 1-4 years after surgery in 11 of 46 consecutive cases. We now present the further development of bone metabolism in these 11 cases.

PATIENTS AND METHODS

10 patients (11 chips) with previously shown loss of femoral head metabolism were evaluated by radiography and repeated F-PET scans, 3-6.5 years after surgery. The size of the area with low (18)F-fluoride PET uptake in the femoral head was compared to that in earlier PET images.

RESULTS

No patients had any clinical symptoms; nor was any necrotic bone area visible in plain radiographs. On F-PET scans, 2 patients showed a diminished area with low uptake, 4 were unchanged, and 5 had enlarged areas.

INTERPRETATION

Bone metabolism surrounding a volume of bone with no metabolic activity changes dynamically even 5 years after surgery. The presence of bone with minor uptake of F-tracer, indicating low or no bone metabolism, with further progression in 5 of 11 cases leads us to conclude that resurfacing THA should be used restrictively.

Complications after metal-on-metal hip resurfacing arthroplasty

This article determines the incidence and cause of the complications commonly associated with metal-on-metal hip resurfacing implants and the proposed methods to prevent these complications. The literature available in PubMed was reviewed. Complication rates after hip resurfacing are low, and the procedure has shown both safety and efficacy in the hands of surgeons trained in specialized centers. Proper surgical technique can further reduce the incidence of femoral neck fracture, component loosening, and abnormal wear of the prosthesis. A more systematic detection of adverse local tissue reactions is needed to provide accurate assessments of their prevalence.

Total hip arthroplasty in advanced osteonecrosis: the short-term results by metal-on-metal hip resurfacing

BACKGROUND

Characteristically, osteonecrosis affects younger patients who typically refer to the orthopedic surgeon for the first time in the third to fifth decades of life, in the late stages of the disease. Femoral metal-on-metal hip resurfacing is as an alternative to conventional total hip arthroplasty in treating osteoarthritis of the hip. Since there are already many reports regarding the successful outcome of resurfacing in advanced osteoarthritis, the purpose of this study was to analyze the clinical outcomes of this procedure in patients with osteonecrosis of the femoral head and to compare them with a matched group of patients with osteoarthritis.

MATERIAL/METHODS

This retrospective cohort study evaluated a consecutive series of 52 patients with end-stage osteonecrosis (28 patients) and osteoarthritis (24 patients) of the femoral head, managed by metal-on-metal hip resurfacing in a referral orthopedic center from Feb 2002 to May 2007. Pain, function and deformity were evaluated with the use of the Harris hip score after the operation. Patients were clinically followed for a mean of 41 months.

RESULTS

The patients in the osteoarthritis group had a significantly higher mean age than those in the osteonecrosis group (47.88 ± 12.6 vs 30.86 ± 7.5, p=0.003). The clinical outcomes were similar for both groups. There was no significant difference in mean Harris hip score (p=0.347) and hip joint range of motion (p=0.346) between osteonecrosis and osteoarthritis groups after surgery.

CONCLUSIONS

On the basis of these initial findings, we recommend MOM resurfacing as a viable treatment option for patients with advanced stages of osteonecrosis.

Birmingham hip resurfacing: the prevalence of failure

Despite the increasing interest and subsequent published literature on hip resurfacing arthroplasty, little is known about the prevalence of its complications and in particular the less common modes of failure. The aim of this study was to identify the prevalence of failure of hip resurfacing arthroplasty and to analyse the reasons for it. From a multi-surgeon series (141 surgeons) of 5000 Birmingham hip resurfacings we have analysed the modes, prevalence, gender differences and times to failure of any hip requiring revision. To date 182 hips have been revised (3.6%). The most common cause for revision was a fracture of the neck of the femur (54 hips, prevalence 1.1%), followed by loosening of the acetabular component (32 hips, 0.6%), collapse of the femoral head/avascular necrosis (30 hips, 0.6%), loosening of the femoral component (19 hips, 0.4%), infection (17 hips, 0.3%), pain with aseptic lymphocytic vascular and associated lesions (ALVAL)/metallosis (15 hips, 0.3%), loosening of both components (five hips, 0.1%), dislocation (five hips, 0.1%) and malposition of the acetabular component (three hips, 0.1%). In two cases the cause of failure was unknown. Comparing men with women, we found the prevalence of revision to be significantly higher in women (women = 5.7%; men = 2.6%, p < 0.001). When analysing the individual modes of failure women had significantly more revisions for loosening of the acetabular component, dislocation, infection and pain/ALVAL/metallosis (p < 0.001, p = 0.004, p = 0.008, p = 0.01 respectively). The mean time to failure was 2.9 years (0.003 to 11.0) for all causes, with revision for fracture of the neck of the femur occurring earlier than other causes (mean 1.5 years, 0.02 to 11.0). There was a significantly shorter time to failure in men (mean 2.1 years, 0.4 to 8.7) compared with women (mean 3.6 years, 0.003 to 11.0) (p < 0.001).

Femoral-head vascularity after hip surface arthroplasty

BACKGROUND

iatrogenic devascularization of the femoral head is as an area of concern following hip resurfacing arthroplasty, with probable implications on short-term failure and long-term survival of the implant.

MATERIALS AND METHODS

we assessed the vascularity of 25 resurfaced femoral heads in 20 patients by comparison with preoperative and postoperative Tc-99m methylene diphosphonate (MDP) bone scintigraphy images, the postoperative scans being done 9 months after the surgery.

RESULTS

eight out of 25 hips (32%) showed <55% of their preoperative uptake at a mean of 9 months after surgery and were categorized as showing reduced vascularity.

CONCLUSION

our study reveals reduction in vascularity of the femoral-head remnant as a frequent occurrence after hip resurfacing. Our study also highlights the role of bone scintigraphy as tool in assessing the vascularity of resurfaced femoral heads.

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.

Osteonecrosis following resurfacing arthroplasty

BACKGROUND AND PURPOSE

One of the main concerns regarding resurfacing arthroplasty is the viability of the remaining part of the femoral head, and the postoperative risk of a femoral neck fracture or collapse. In contrast to radiographic methods, positron emission tomography using the radiotracer [18F]-fluoride (Fluoride-PET) enables us to visualize the viability of bone in the remaining part of the head, despite the presence of the covering metal component.

PATIENTS AND METHODS

This is preliminary prospective study of 14 patients who underwent an ASR resurfacing arthroplasty. Apart from clinical and radiographic analyses, all patients were analyzed by PET scan 1 week, 4 months, and 1 year after surgery.

RESULTS

1 patient had a minor region of osteonecrosis on PET scan at 1 week and at 4 months. After 1 year, the necrosis had increased to include most of the head. 2 other patients, normal at 4 months, had developed equally large osteonecrosis at 1 year. A fourth patient had a minor osteonecrosis at 1 year. None of the patients had clinical symptoms, and the necrotic areas were not visible on plain radiographs.

CONCLUSIONS

We found Fluoride PET to be a sensitive and useful method for evaluation of bone metabolism at resurfacing arthroplasty. 3 of the 14 patients had developed osteonecrosis, involving most of the head at 1 year. The late onset of the phenomenon does not support the hypothesis of surgically damaged vascularity. The presence of this complication together with the lack of visibility on plain radiographs gives reason for concern.

Bone density of the femoral neck following Birmingham hip resurfacing

BACKGROUND

Resurfacing is a popular alternative to a standard hip replacement in young arthritic patients. Despite bone preservation around the femoral component, there is little information regarding the bone quality.

PATIENTS AND METHODS

32 patients underwent consecutive Birmingham hip resurfacing. The bone density of the femoral neck was measured preoperatively and then at 6 weeks, 3 months, 1 year, and 2 years. The femoral neck was divided into regions of interest. Results were available for 27 hips in 26 patients.

RESULTS

The overall femoral neck bone density showed a trend towards a decrease at 6 weeks and 3 months but returned to the preoperative level at 1 year, and was maintained at 2 years. The combined superior regions of the neck showed a statistically significant decrease in bone density at 6 weeks and 3 months. This returned to preoperative levels at 1 year and was maintained at 2 years.

INTERPRETATION

Bone density appears to decrease at 6 weeks and 3 months, suggesting that care is necessary until bone density begins to recover.

Evaluation of Musculoskeletal Disorders with PET, PET/CT, and PET/MR Imaging

18F-2-fluoro-2-deoxy-D-glucose-PET has an established role in the evaluation of hip periprosthetic infection and musculoskeletal malignancies. Determination of its role in the management of inflammatory arthritis and diabetic foot complications is ongoing. The reintroduction of fluorine F 18 sodium fluoride as a PET radiotracer may advantageously replace technetium Tc 99 m methylene diphosphonate for some non-oncologic applications, including treatment monitoring of Paget's disease andfibrous dysplasia. The combination of CT or MR imaging with PET imaging synergistically maximizes the diagnostic potential of a combined structural-functional imaging approach for the detection, characterization, and monitoring of myriad musculoskeletal disorders.

F-18 fluoride positron emission tomography of the hip for osteonecrosis

Osteonecrosis (ON) of the femoral head continues to be a devastating disorder for young patients. We evaluated the F-18 fluoride positron emission tomography (PET) imaging modality for use in detection of the bone involved in ON of the hip. We retrospectively reviewed the records of 60 consecutive patients diagnosed with ON and interviewed all by phone. Eleven patients (17 hips) of those interviewed agreed to participate in the study. We classified the ON using the University of Pennsylvania classification system and compared each patient's plain AP bone scan, single photon emission 3-D computed tomography, and MRI. ON was associated with HIV, alcohol, steroid use, and polycythemia vera in this group. Nine of 17 hips (8 patients) had acetabular increased uptake when using the F-18 fluoride PET scans that were not seen on MRI, single photon emission computed tomography, or bone scans. These data suggest earlier acetabular changes in osteonecrosis may exist that traditional imaging modalities do not reveal.

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.

18F-Fluoride positron emission tomography and positron emission tomography/computed tomography

(18)F-Fluoride is a positron-emitting bone-seeking agent, the uptake of which reflects blood flow and remodeling of bone. Assessment of (18)F-fluoride kinetics using quantitative positron emission tomography (PET) methods allows the regional characterization of lesions of metabolic bone diseases and the monitoring of their response to therapy. It also enables the assessment of bone viability and discrimination of uneventful and impaired healing processes of fractures, bone grafts and osteonecrosis. Taking advantage of the favorable pharmacokinetic properties of the tracer combined with the high performance of PET technology, static (18)F-fluoride PET is a highly sensitive imaging modality for detection of benign and malignant osseous abnormalities. Although (18)F-fluoride uptake mechanism corresponds to osteoblastic activity, it is also sensitive for detection of lytic and early marrow-based metastases, by identifying their accompanying reactive osteoblastic changes, even when minimal. The instant fusion of increased (18)F-fluoride uptake with morphological data of computed tomography (CT) using hybrid PET/CT systems improves the specificity of (18)F-fluoride PET in cancer patients by accurately differentiating between benign and malignant sites of uptake. The results of a few recent publications suggest that (18)F-fluoride PET/CT is a valuable modality in the diagnosis of pathological osseous conditions in patients also referred for nononcologic indications. (18)F-fluoride PET and PET/CT are, however, not widely used in clinical practice. The limited availability of (18)F-fluoride and of PET and PET/CT systems is a major factor. At present, there are not enough data on the cost-effectiveness of (18)F-fluoride PET/CT. However, it has been stated by some experts that (18)F-fluoride PET/CT is expected to replace (99m)Tc-MDP bone scintigraphy in the future.

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.

Femoral neck fractures after metal-on-metal total hip resurfacing: a prospective cohort study

There has been a renewed interest in metal-on-metal resurfacing total hip arthroplasty. Recent studies have reported high success rates at short to midterm follow-up. Despite these excellent early outcomes, femoral neck fractures have been reported as a major complication after this procedure. The purpose of this study was to identify the incidence of this complication in a prospective cohort of patients. In addition, various demographic and radiographic factors such as surgeon experience, age, sex, body mass index, femoral neck notching, and cysts were assessed as potential risk factors. Between November 2000 and August 2006, 550 metal-on-metal total hip resurfacings were performed by a single surgeon. The absolute risk for femoral neck fracture in this cohort was 2.5%. Of the 14 fractures, 12 occurred in the first 69 resurfacings performed. After this time, the incidence of fracture was 0.4%. Women and obese patients were shown to have higher cumulative incidences of fractures. These findings suggest the need for careful patient selection and surgical technique, especially for surgeons during the early learning curve for this technically difficult surgery.