Clinical utility of (18)F-fluoride PET/CT in benign and malignant bone diseases

¹⁸F labeled sodium fluoride is a positron-emitting, bone seeking agent with more favorable skeletal kinetics than conventional phosphate and diphosphonate compounds. With the expanding clinical usage of PET/CT, there is renewed interest in using ¹⁸F-fluoride PET/CT for imaging bone diseases. Growing evidence indicates that ¹⁸F fluoride PET/CT offers increased sensitivity, specificity, and diagnostic accuracy in evaluating metastatic bone disease compared to ^99mTc based bone scintigraphy. National Oncologic PET Registry (NOPR) has expanded coverage for ¹⁸F sodium fluoride PET scans since February 2011 for the evaluation of osseous metastatic disease. In this article, we reviewed the pharmacological characteristics of sodium fluoride, as well as the clinical utility of PET/CT using ¹⁸F-fluoride in both benign and malignant bone disorders.     

Precision of 18F-fluoride PET skeletal kinetic studies in the assessment of bone metabolism

Summary

We assessed the precision of lumbar spine ¹⁸F-PET measurements based on 58 scans performed on 20 postmenopausal women. The percentage coefficient of variation (%CV) (95% confidence interval) was 9.2% (7.5–11.8) for standardised uptake values, 11.7% (9.5–14.9) for plasma clearance measurements using the Patlak method and 14.5% (11.7–18.5) for plasma clearance measurements using the Hawkins three-compartment model.

Introduction

¹⁸F-Fluoride positron emission tomography (¹⁸F-PET) is a non-invasive technique that allows the assessment of regional bone turnover in patients with metabolic bone disease. Knowledge of the precision errors of ¹⁸F-PET measurements is important for planning the number of subjects required for research studies.

Methods

Twenty osteoporotic postmenopausal women had ¹⁸F-PET scans of the lumbar spine at 0, 6 and 12?months after stopping long-term bisphosphonate treatment. No significant changes in the PET measurements were seen over the 12-month period, and the data were deemed suitable for a precision study. Precision errors were evaluated for standardised uptake values (SUVs) and for the fluoride plasma clearance to bone mineral (K _i) determined using the Patlak and Hawkins methods. Precision errors were expressed as the %CV and were calculated for the mean L1–L4 region and for individual vertebrae.

Results

%CV (95% confidence interval) for the L1–L4 region was 9.2% (7.5–11.8) for SUV, 11.7% (9.5–14.9) for K _i measured using the Patlak method and 14.5% (11.7–18.5) for K _i measured using the Hawkins method. There was no significant difference between precision errors obtained for the L1–L4 region and those obtained for a single vertebra.

Conclusions

SUV measurements showed the smallest precision error followed by the Patlak method, while the Hawkins method gave the largest error. Measuring a smaller region of interest did not increase the precision error, suggesting that the factor determining the errors may be scanner calibration.     

Customized tantalum-augmented reverse shoulder arthroplasty for glenoid bone defect and excessive medialization: description of the technique

Background

Glenoid bone defect and excessive medialization could represent challenging issues during reverse shoulder arthroplasty, especially in the setting of revision surgery. Although a solution is offered by the Boileau’s BIO-RSA technique in primary cases, only autologous iliac crest bone graft and homologous graft from bone banks are available for revision surgeries, with known disadvantages and risk of graft resorption and implant failure.

Materials and methods

We describe in this work a new technique based on a customized porous tantalum device to be used in salvage situations, aimed at lateralization of the glenoid component of a reverse shoulder arthroplasty. Between 2014 and 2015, five patients received a customized tantalum-augmented RSA at our institution. The augments we applied are actually on the market for acetabular bone loss management: these were opportunely prepared and fixed to the metal back of the glenoid component before implantation.

Results

In the five cases treated, no major or minor complications have been recorded to date. Despite the short follow-up, all the implants are still in situ. All of the patients referred complete subjective satisfaction and return to their daylife activities without pain within 4 months after surgery.

Conclusions

The customized tantalum-augmented RSA technique represents in our experience a useful and safe solution in managing glenoid bone loss and medialization. Adaptability to virtually every device in the market should be regarded as important point of strength of this technique.

     

Intraoperative joint load evaluation of shoulder postures after reverse total shoulder arthroplasty: a cadaveric study using a humeral trial sensor

BackgroundThe effect of improper tension in reverse total shoulder arthroplasty (RTSA) can cause both joint looseness potentially leading to instability and dislocation and joint tightness potentially leading to limited joint motion and acromial or scapular spine stress fractures. Intra-articular load sensors offer an innovative technology providing information on real-time joint load parameters. The objective of this study is to evaluate a novel load sensor in a cadaveric RTSA model, to measure joint loads in shoulder positions required for activities of daily living (ADLs), with and without subscapularis repair. Our hypothesis is that an in situ joint load sensor can reliably measure the magnitude of joint load, and that subscapularis repair both increases joint load magnitude and improves the concentricity of the articulation at end range motion.MethodsNine freshly frozen full body cadaver shoulders were selected for this study. All shoulders were implanted with RTSA implants with the humeral insert incorporating a wireless load measuring sensor. Three ADL postures (“across chest”, “behind back”, and “overhead reach”) were each evaluated 5 times by a single observer that was blinded to the real time loads displayed by the sensor software interface. Joint load magnitude and resultant location of the load (centroid) were recorded for each ADL posture. The subscapularis was then repaired in the native location, and the ADL posture and load measurement protocol were repeated.ResultsAll 3 postures demonstrated an intra-class correlation coefficient of over 0.9, indicating high repeatability of the load magnitude measured on the same specimen. Load magnitudes ranged from 5 lbf to 70 lbf “where 1lbf = .454kgf” depending on the posture and position. Subscapularis repair statistically significantly increased mean joint loads in the behind back position (P = .046) and the “overhead reach” posture (P < .001). The centroid location differed between the “behind back” and “overhead reach” postures for both radial distance (R) and angular position (θ) (P < .05). Subscapularis repair did not change R or theta for any of the three ADL postures compared to testing with subscapularis unrepaired.DiscussionSensors placed within the trial insert can reliably measure joint loads in selected ADL postures. Subscapularis tendon repair increases the magnitude of joint load but does not appear to improve concentricity of resultant load when the shoulder is placed in ADL postures. Future work will involve sensor usage in a clinical setting to evaluate if measured joint load parameters correlate with improved clinical outcomes.Level of EvidenceBasic Science Study; Biomechanics     

A biomechanical assessment of superior shoulder translation after reconstruction of anterior glenoid bone defects: The Latarjet procedure versus allograft reconstruction

Background:

The coracoacromial ligament (CAL) is an important restraint to superior shoulder translation. The effect of CAL release on superior stability following the Latarjet is unknown; therefore, our purpose was to compare the effect of two Latarjet techniques and allograft reconstruction on superior instability.

Materials and Methods:

Eight cadaveric specimens were tested on a simulator. Superior translation was monitored following an axial force in various glenohumeral rotations (neutral, internal, and external) with and without muscle loading. Three intact CAL states were tested (intact specimen, 30% glenoid bone defect, and allograft reconstruction) and two CAL deficient states (classic Latarjet (classicLAT) and congruent-arc Latarjet (congruentLAT)).

Results:

In neutral without muscle loading, a significant increase in superior translation occurred with the classicLAT as compared to 30% defect (P = 0.046) and allograft conditions (P = 0.041). With muscle loading, the classicLAT (P = 0.005, 0.002) and the congruentLAT (P = 0.018, 0.021) had significantly greater superior translation compared to intact and allograft, respectively. In internal rotation, only loaded tests produced significant results; specifically, classicLAT increased translation compared to all intact CAL states (P < 0.05). In external rotation, only unloaded tests produced significant results with classicLAT and congruentLAT allowing greater translations than intact (P ≤ 0.028). For all simulations, the allograft was not significantly different than intact (P > 0.05) and no differences (P = 1.0) were found between classicLAT and congruentLAT.

Discussion:

In most simulations, CAL release with the Latarjet lead to increased superior humeral translation.

Conclusion:

The choice of technique for glenoid bone loss reconstruction has implications on the magnitude of superior humeral translation. This previously unknown effect requires further study to determine its clinical and kinematic outcomes.