Effect of stress-shielding-induced bone resorption on glenoid loosening in reverse total shoulder arthroplasty

Aseptic loosening of the glenoid component is one of the main reasons for the high revision rates of reverse total shoulder arthroplasty (RTSA). It has been reported that the bulky implant designs may lead to stress shielding. However, it is uncertain whether the shielding effect is severe enough to lead to bone resorption and glenoid loosening. The purpose of this study was to evaluate the level of stress-shielding and assess whether bone resorption plays a role in aseptic glenoid loosening following RTSA. A cadaveric in vitro test model was used to validate a finite element model (FEM) of the scapula. The FEM of the scapula, incorporating adaptive bone remodeling algorithms, was used to predict changes in postoperative bone density after RTSA. Changes in bone strength after implantation were also analyzed. The strain values predicted from the FEM of the scapula were in agreement with the in vitro measurements. Analysis of postoperative bone adaptation revealed that strain-induced bone resorption began at the peg of the implant and around the resected bone surface and then gradually expended to the peripheral regions. The bone strength also reduced postoperatively and appeared particularly around the implant peg. Strain-induced bone resorption is a likely source of the bone loss commonly observed in RTSA. The finite element glenoid bone remodeling simulation may be used as a tool to evaluate glenoid implant design.     

Baseplate augmentation strategies: optimizing range of motion with reverse shoulder arthroplasty based upon variable glenoid deformity

IntroductionVarious operative strategies exist to address glenoid deformity in patients undergoing reverse shoulder arthroplasty (RSA). There is lack of guidance in pairing operative strategies with type and severity of deformity especially with regard to glenoid lateralization, humeral lateralization, and global lateralization. The purpose of this study is to compare different glenoid baseplates on their ability to provide optimal glenoid lateralization and improve range-of-motion based upon pattern and severity of deformity in glenohumeral osteoarthritis.MethodsCT scans were chosen from a large database of osteoarthritic shoulders until ten from each of the following three cohorts were identified: 1) no deformity: retroversion <10° and inclination deformity <5°, 2) Uniplanar deformity: retroversion >15° and inclination <10° or, 3) biplanar deformity: retroversion >15° and inclination >15°. Imascap SAS (Wright Medical) was used to quantify deformities and plan RSA placement. Each case was planned with the following baseplates: standard implant, three mm lateralized, wedge augment, and patient-specific implant. Each baseplate was placed in 5° of retroversion and neutral inclination and medialized to 70% seating. Percent seating, amount of reaming, global lateralization, and simulated range of motion (ROM) was recorded for each scenario.ResultsThe average patient age was 65.4 (49-78) and 14 (47%) were women. Ten of thirty (33%) were classified as Walch A1 or A2, 19/30 (63%) were B1, B2, or B3, and 1/30 (5%) was a C. The normal, uniplanar, and biplanar groups had mean retroversion deformities of 2.1° (-3- 8°), 28.4° (22-36°), and 29.3° (19-39°) respectively. Across the three cohorts, increased global lateralization through glenoid-sided lateralization provided improved ROM most significantly in adduction (R = 0.82; P <.001), flexion (R = 0.78; P <.001), and external rotation (R = 0.76; P <.001). In the nodeformity cohort, less global lateralization was needed for improved range of motion compared to uniplanar and biplanar cohorts. In uniplanar deformities, the wedge augment provided similar amounts of added global lateralization as the patient-specific augment (7.2 mm vs 8.5mm; P = .06) and was equally able to improve range of motion. In the biplanar group, the patient-specific provided greater global lateralization than wedge augment when compared to standard implants (10.1mm vs 7.1mm; P = .002) and improved ROM.ConclusionWhen RSA is used in the treatment for glenohumeral arthritis, the degree of deformity should be considered when choosing baseplate implants. Increased global lateralization is needed to optimize ROM in the setting of severe deformities and in select cases an augment wedge or patient-specific implant construct should be considered.Level of EvidenceLevel III, retrospective comparative study.     

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.     

Mid-term outcomes of reverse shoulder arthroplasty using the alternate scapular line baseplate orientation for glenoid bone loss

BackgroundGlenoid-sided bone loss poses a challenge when performing reverse shoulder arthroplasty. Placing the baseplate in an anteverted position along the alternate scapular line is an option when dealing with glenoid erosion or cavitary defects. Although this allows for stable initial baseplate fixation, questions remain about the effects of placing the baseplate in a more anteverted position relative to the standard glenoid center line. The purpose of this study was to evaluate the mid-term outcomes of patients treated with reverse shoulder arthroplasty using an alternate scapular line baseplate orientation in the setting of glenoid bone loss.Materials and methodsFrom September 2007 to March 2014, 71 patients underwent reverse shoulder arthroplasty using the alternate scapular line baseplate orientation and had a minimum of 5 years of follow up. Patients with no prior surgery, prior nonarthroplasty surgery, and prior arthroplasty surgery were included in this analysis. Patients were followed clinically (American Shoulder and Elbow Surgeons score, Simple Shoulder Test score, range of motion analysis, patient satisfaction) as well as radiographically, with data recorded at the 2-year point and their last recorded follow-up after a minimum of 60 months.ResultsAt the final follow-up point (average 78 months) patients had maintained their improvement in American Shoulder and Elbow Surgeons score (75 [P<.0001]), Simple Shoulder Test score (7.8 [P < .0001]), forward elevation (1300 [P < .0001]), external rotation (310 [P < .0001]) with no change in internal rotation (62% with full IR [P = 1.0]). No significant deterioration in outcome scores or motion was noted between the 2-year and final follow-up time point. At final follow-up, 92% remained satisfied with their outcome. There was a 7% complication rate (3 acromial fractures, 1 hematoma, 1 dislocation), with 1 patient requiring revision surgery secondary to instability.ConclusionUtilizing the alternate scapular line baseplate orientation in cases with glenoid bone loss resulted in clinical improvements with no deterioration in outcome scores, range of motion or patient satisfaction at a minimum of 5 years of follow-up. Anteverting the baseplate in this position allowed for stable glenoid-sided fixation with no mechanical failures of the baseplate and did not appear to compromise the patient's functional outcomes. In patients with significant glenoid bone loss, where adequate bone stock along the standard glenoid line may be in question, use of the alternate scapular line for baseplate orientation is an effective option yielding sustained clinical improvements and a low rate of complications.Level of evidenceLevel IV; Case Series; Treatment Study     

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.