Long-Term Effects of Sglt2 Deletion on Bone and Mineral Metabolism in Mice

Sodium‐glucose cotransporter 2 (SGLT2) inhibitors improve kidney and cardiovascular outcomes in patients with type 2 diabetes mellitus (T2DM). However, bone fragility has emerged as a side effect in some but not in all human studies. Because use of SGLT2 inhibitors in humans affects mineral metabolism, we investigated the long‐term effects of genetic loss of Sglt2 function on bone and mineral metabolism in mice. Slc5a2 nonsense mutation in Sweet Pee (SP) mice results in total loss of Sglt2 function. We collected urine, serum, and bone samples from 15‐week‐old and 25‐week‐old wild‐type (WT) and SP mice fasted from food overnight. We measured parameters of renal function and mineral metabolism and we assessed bone growth, microarchitecture, and mineralization. As expected, 15‐week‐old and 25‐week‐old SP mice showed increased glucosuria, and normal kidney function compared to age‐matched WT mice. At 15 weeks, SP mice did not show alterations in mineral metabolism parameters. At 25 weeks, SP mice showed reduced fasting 24‐hour urinary calcium excretion and increased fractional excretion of phosphate, but normal serum calcium and phosphate, parathyroid hormone (PTH), vitamin D (1,25(OH)₂D), and fibroblast growth factor (FGF23) levels. At 25 weeks, but not at 15 weeks, SP mice showed reduced body weight compared to WT. This was associated with reduced femur length at 25 weeks, suggesting impaired skeletal growth. SP mice did not show trabecular or cortical bone microarchitectural modifications but showed reduced cortical bone mineral density compared to WT mice at 25 weeks. These results suggest that loss of Sglt2 function in mice in the absence of T2DM does not alter regulatory hormones FGF23, PTH, and 1,25(OH)₂D, but may contribute to bone fragility over the long term. Future studies are required to determine how loss of Sglt2 function impacts bone fragility in T2DM. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Risk factors and interventions associated with mortality or survival in adult COVID-19 patients admitted to critical care: a systematic review and meta-analysis

Background: Patients with confirmed COVID-19 admitted to intensive care units have a high mortality rate, which appears to be associated with increasing age, male sex, smoking history, hypertension and diabetes mellitus. Methods: A systematic review to determine risk factors and interventions associated with mortality/survival in adult patients admitted to an intensive care unit (ICU) with confirmed COVID-19/SARS-CoV-2 infection. The protocol was registered with PROSPERO (CRD42020181185). Results: The search identified 483 abstracts between 1 January and 7 April 2020, of which nine studies were included in the final review. Only one study was of low bias. Advanced age (odds ratio [OR] 11.99, 95% confidence interval [CI] 5.35–18.62) and a history of hypertension were associated with mortality (OR 4.17, 95% CI 2.90–5.99). Sex was not associated with mortality. There was insufficient data to assess the association between other comorbidities, laboratory results or critical care risk indices and mortality. The critical care interventions of mechanical ventilation (OR 6.25, 95% CI 0.75–51.93), prone positioning during ventilation (OR 2.06, 95% CI 0.20–21.72), and extracorporeal membrane oxygenation (ECMO) (OR 8.00, 95% CI 0.69, 92.33) were not associated with mortality. The sample size was insufficient to conclusively determine the association between these interventions and ICU mortality. The need for inotropes or vasopressors was associated with mortality (OR 6.36, 95% CI 1.89–21.36). Conclusion: The studies provided little granular data to inform risk stratification or prognostication of patients requiring intensive care admission. Larger collaborative research is needed to address this limitation.

Genetic background influences cardiac phenotype in murine chronic kidney disease

Background

Levels of fibroblast growth factor 23 (FGF23) increase early in chronic kidney disease (CKD) and are independently associated with left ventricular hypertrophy (LVH), heart failure and death. Experimental models of CKD with elevated FGF23 and LVH are needed. We hypothesized that slow rates of CKD progression in the Col4a3 knockout (Col4a3KO) mouse model of CKD would promote development of LVH by prolonging exposure to elevated FGF23.

Methods

We studied congenic Col4a3KO and wild-type (WT) mice with either 75% 129X1/SvJ (129Sv) or 94% C57Bl6/J (B6) genomes.

Results

B6-Col4a3KO lived longer than 129Sv-Col4a3KO mice (21.4 ± 0.6 versus 11.4 ± 0.4 weeks; P < 0.05). 10-week-old 129Sv-Col4a3KO mice showed impaired renal function (blood urea nitrogen 191 ± 39 versus 34 ± 4 mg/dL), hyperphosphatemia (14.1 ± 1.4 versus 6.8 ± 0.3 mg/dL) and 33-fold higher serum FGF23 levels (P < 0.05 versus WT for each). Consistent with their slower CKD progression, 10 week-old B6-Col4a3KO mice showed milder impairment of renal function than 129Sv-Col4a3KO mice and modest FGF23 elevation without other alterations of mineral metabolism. At 20 weeks, further declines in renal function in B6-Col4a3KO mice was accompanied by hyperphosphatemia and 8-fold higher FGF23 levels (P < 0.05 versus WT for each). Only the 20-week-old B6-Col4a3KO mice developed LVH (LV mass 125 ± 3 versus 98 ± 6 mg; P < 0.05 versus WT) in association with significantly increased cardiac expression of FGF receptor 4 (FGFR4) messenger RNA and protein and markers of LVH (Atrial natriuretic peptide (ANP), B-type natriuretic peptide (BNP), beta-myosin heavy chain (β-MHC); P < 0.05 versus WT for each).

Conclusions

In conclusion, B6-Col4a3KO mice manifest slower CKD progression and longer survival than 129Sv-Col4a3KO mice and can serve as a novel model of cardiorenal disease.

Ferric citrate reduces fibroblast growth factor 23 levels and improves renal and cardiac function in a mouse model of chronic kidney disease

Iron deficiency, anemia, hyperphosphatemia, and increased fibroblast growth factor 23 (FGF23) are common and interrelated complications of chronic kidney disease (CKD) that are linked to CKD progression, cardiovascular disease and death. Ferric citrate is an oral phosphate binder that decreases dietary phosphate absorption and serum FGF23 concentrations while increasing iron stores and hemoglobin in patients with CKD. Here we compared the effects of ferric citrate administration versus a mineral sufficient control diet using the Col4a3 knockout mouse model of progressive CKD and age-matched wild-type mice. Ferric citrate was given to knockout mice for four weeks beginning at six weeks of age when they had overt CKD, or for six weeks beginning at four weeks of age when they had early CKD. Ten-week-old knockout mice on the control diet showed overt iron deficiency, anemia, hyperphosphatemia, increased serum FGF23, hypertension, decreased kidney function, and left ventricular systolic dysfunction. Ferric citrate rescued iron deficiency and anemia in knockout mice regardless of the timing of treatment initiation. Circulating levels and bone expression of FGF23 were reduced in knockout mice given ferric citrate with more pronounced reductions observed when ferric citrate was initiated in early CKD. Ferric citrate decreased serum phosphate only when it was initiated in early CKD. While ferric citrate mitigated systolic dysfunction in knockout mice regardless of timing of treatment initiation, early initiation of ferric citrate also reduced renal fibrosis and proteinuria, improved kidney function, and prolonged life span. Thus, initiation of ferric citrate treatment early in the course of murine CKD lowered FGF23, slowed CKD progression, improved cardiac function and significantly improved survival.

Glenoid loosening and migration in reverse shoulder arthroplasty

Aims

The aim of this study was to report the outcomes of different treatment options for glenoid loosening following reverse shoulder arthroplasty (RSA) at a minimum follow-up of two years.

Patients and Methods

We retrospectively studied the records of 79 patients (19 men, 60 women; 84 shoulders) aged 70.4 years (21 to 87) treated for aseptic loosening of the glenosphere following RSA. Clinical evaluation included pre- and post-treatment active anterior elevation (AAE), external rotation, and Constant score.

Results

From the original cohort, 29 shoulders (35%) were treated conservatively, 27 shoulders (32%) were revised by revision of the glenosphere, and 28 shoulders (33%) were converted to hemiarthroplasty. At last follow-up, conservative treatment and glenoid revision significantly improved AAE, total Constant score, and pain, while hemiarthroplasty did not improve range of movement or clinical scores. Multivariable analysis confirmed that conservative treatment and glenoid revision achieved similar improvements in pain (glenoid revision vs conservative, beta 0.44; p = 0.834) but that outcomes were significantly worse following hemiarthroplasty (beta -5.00; p = 0.029).

Conclusion

When possible, glenoid loosening after RSA should first be treated conservatively, then by glenosphere revision if necessary, and last by salvage hemiarthroplasty Cite this article: Bone Joint J 2019;101-B:461–469.

Incidence and Progression of Chronic Kidney Disease in Black and White Individuals with Type 2 Diabetes

BACKGROUND AND OBJECTIVES

Type 2 diabetes and associated CKD disproportionately affect blacks. It is uncertain if racial disparities in type 2 diabetes-associated CKD are driven by biologic factors that influence propensity to CKD or by differences in type 2 diabetes care.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We conducted a post hoc analysis of 1937 black and 6372 white participants of the Action to Control Cardiovascular Risk in Diabetes (ACCORD) trial to examine associations of black race with change in eGFR and risks of developing microalbuminuria, macroalbuminuria, incident CKD (eGFR<60 ml/min per 1.73m2, ≥25% decrease from baseline eGFR, and eGFR slope <-1.6 ml/min per 1.73 m2 per year), and kidney failure or serum creatinine >3.3 mg/dl.

RESULTS

During a median follow-up that ranged between 4.4 and 4.7 years, 278 black participants (58 per 1000 person-years) and 981 white participants (55 per 1000 person-years) developed microalbuminuria, 122 black participants (16 per 1000 person-years) and 374 white participants (14 per 1000 person-years) developed macroalbuminuria, 111 black participants (21 per 1000 person-years) and 499 white participants (28 per 1000 person-years) developed incident CKD, and 59 black participants (seven per 1000 person-years) and 178 white participants (six per 1000 person-years) developed kidney failure or serum creatinine >3.3 mg/dl. Compared with white participants, black participants had lower risks of incident CKD (hazard ratio, 0.73; 95% confidence intervals, 0.57 to 0.92). There were no significant differences by race in eGFR decline or in risks of microalbuminuria, macroalbuminuria, and kidney failure or of serum creatinine >3.3 mg/dl.

CONCLUSIONS

Black participants enrolled in a randomized controlled trial had lower rates of incident CKD compared with white participants. Rates of eGFR decline, microalbuminuria, macroalbuminuria, and kidney failure did not vary by race.

Revision rate after screw or plate arthrodesis of the glenohumeral joint

INTRODUCTION

Glenohumeral arthrodesis is a rare salvage procedure for selected patients with different shoulder pathologies. Among a variety of surgical techniques, compression screws or plate fixation are most widely used. Minimally invasive screw fixation has become more popular, although it has been shown to be biomechanically inferior to plate arthrodesis.

HYPOTHESIS

Screw arthrodesis would lead to a higher revision rate than plate arthrodesis.

MATERIAL AND METHODS

Twenty-seven plate and 7 screw arthrodesis of the glenohumeral joint in 19 male and 15 female patients of a mean age of 50years (range, 16-85years) were reviewed in a retrospective multicenter study with at a follow-up of 43months (range, 11-152months) to compare their clinical and radiographic outcome with special focus on revision rate.

RESULTS

Constant score did not change, but its subscore for pain significantly improved from 4.5 points (range, 0-15 points) to 11 points (range, 6-15 points). The subjective shoulder value increased significantly from 19% (range, 0-70%) to 41% (range, 10-80%) and 81% of the patients were satisfied. In 14 patients (41%), the arthrodesis had to be revised either for non-union (11) or malunion (3) at a mean of 12months (range, 0-47months). The 2 groups did not differ in terms of demographic data, nor of preoperative and postoperative clinical data. There were more revisions after screw than plate fixation. If revision was performed for non-union, this difference was significant.

DISCUSSION/CONCLUSION

In selected patients, glenohumeral arthrodesis can significantly reduce pain and achieve at best a reasonable function and subjective satisfaction rate. Revision rates favor plate over isolated screw fixation.

LEVEL OF EVIDENCE

IV retrospective series.

The acromiohumeral distance and the subacromial clearance are correlated to the glenoid version

BACKGROUND

The acromiohumeral distance (ACHD) is a radiographic parameter for evaluating the presence of a rotator cuff rupture. Previous investigations have demonstrated that several factors may influence the magnitude of the acromiohumeral distance, but glenoid version has not yet been considered.

HYPOTHESIS

Our hypothesis was that there is a direct correlation between glenoid version and acromiohumeral distance as well as subacromial clearance.

METHODS

Four right glenohumeral joints from adult fresh cadavers were anatomically dissected to the level of the rotator cuff. After fixation to a board and positioning of the humeral head in neutral position, an osteotomy of the glenoid neck was carried out and the version was altered in steps of 5°. The ACHD as well as the subacromial clearance (SAC) were measured for every degree of glenoid version.

RESULTS

The ACHD increased with increased anteversion and consistently decreased with increased retroversion of the glenoid. The SAC also depended on glenoid version. Neutral version was associated with a minimal clearance under the anterior third of the acromion, retroversion transferred the minimal SAC posteriorly and anteversion transferred minimal SAC under the coracoacromial ligament.

CONCLUSION

Our results indicate that glenoid version correlates directly with the magnitude of ACHD and SAC. Therefore, variations of glenoid version can lead to false interpretations of cuff integrity.

TYPE OF STUDY

Biomechanical investigation.

LEVEL OF EVIDENCE

Not possible to define.

Proximal tubule proteins are significantly elevated in bladder urine of patients with ureteropelvic junction obstruction and may represent novel biomarkers: A pilot study

PURPOSE

Ureteropelvic junction obstruction (UPJO) is the major cause of hydronephrosis in children and may lead to renal injury and early renal dysfunction. However, diagnosis of the degree of obstruction and severity of renal injury relies on invasive and often inconclusive renal scans. Biomarkers from voided urine that detect early renal injury are highly desirable because of their noninvasive collection and their potential to assist in earlier and more reliable diagnosis of the severity of obstruction. Early in response to UPJO, increased intrarenal pressure directly impacts the proximal tubule brush border. We hypothesize that single-pass, apically expressed proximal tubule brush border proteins will be shed into the urine early and rapidly and will be reliable noninvasive urinary biomarkers, providing the tools for a more reliable stratification of UPJO patients.

MATERIALS AND METHODS

We performed a prospective cohort study at Connecticut Children's Medical Center. Bladder urine samples from 12 UPJO patients were obtained prior to surgical intervention. Control urine samples were collected from healthy pediatric patients presenting with primary nocturnal enuresis. We determined levels of NGAL, KIM-1 (previously identified biomarkers), CD10, CD13, and CD26 (potentially novel biomarkers) by ELISA in control and experimental urine samples. Urinary creatinine levels were used to normalize the urinary protein levels measured by ELISA.

RESULTS

Each of the proximal tubule proteins outperformed the previously published biomarkers. No differences in urinary NGAL and KIM-1 levels were observed between control and obstructed patients (p = 0.932 and p = 0.799, respectively). However, levels of CD10, CD13, and CD26 were significantly higher in the voided urine of obstructed individuals when compared with controls (p = 0.002, p = 0.024, and p = 0.007, respectively) (Figure).

CONCLUSIONS

Targeted identification of reliable, noninvasive biomarkers of renal injury is critical to aid in diagnosing patients at risk, guiding therapeutic decisions and monitoring treatment efficacy. Proximal tubule brush border proteins are reliably detected in the urine of obstructed patients and may be more effective at predicting UPJO.

Phosphorylation state-dependent interaction between AKAP7δ/γ and phospholamban increases phospholamban phosphorylation

Changes in heart rate and contractility in response to sympathetic stimulation occur via activation of cAMP dependent protein kinase A (PKA), leading to phosphorylation of numerous substrates that alter Ca(2+) cycling. Phosphorylation of these substrates is coordinated by A-kinase anchoring proteins (AKAPs), which recruit PKA to specific substrates [1]. Phosphorylation of the PKA substrate phospholamban (PLB) is a critical determinant of Ca(2+) re-entry into the sarcoplasmic reticulum and is coordinated by AKAP7δ/γ [2,3]. Here, we further these findings by showing that phosphorylation of PLB requires interaction with AKAP7δ/γ and that this interaction occurs only when PLB is unphosphorylated. Additionally, we find that two mutants of PLB (R9C and Δ14), which are associated with dilated cardiomyopathy in humans, prevent association with AKAP7δ/γ and display reduced phosphorylation in vitro. This finding implicates the AKAP7δ/γ-PLB interaction in the pathology of the disease phenotype. Further exploration of the AKAP7δ/γ-PLB association demonstrated a phosphorylation state-dependence of the interaction. Computational modeling revealed that this mode of interaction allows for small amounts of AKAP and PKA (100-200nM) to regulate the phosphorylation of large quantities of PLB (50μM). Our results confirm that AKAP7γ/δ binding to PLB is important for phosphorylation of PLB, and describe a novel phosphorylation state-dependent binding mechanism that explains how phosphorylation of highly abundant PKA substrates can be regulated by AKAPs present at ~100-200 fold lower concentrations.

Molecular mechanisms regulating CD13-mediated adhesion

CD13/Aminopeptidase N is a transmembrane metalloproteinase that is expressed in many tissues where it regulates various cellular functions. In inflammation, CD13 is expressed on myeloid cells, is up-regulated on endothelial cells at sites of inflammation and mediates monocyte/endothelial adhesion by homotypic interactions. In animal models the lack of CD13 alters the profiles of infiltrating inflammatory cells at sites of ischaemic injury. Here, we found that CD13 expression is enriched specifically on the pro-inflammatory subset of monocytes, suggesting that CD13 may regulate trafficking and function of specific subsets of immune cells. To further dissect the mechanisms regulating CD13-dependent trafficking we used the murine model of thioglycollate-induced sterile peritonitis. Peritoneal monocytes, macrophages and dendritic cells were significantly decreased in inflammatory exudates from global CD13^KO animals when compared with wild-type controls. Furthermore, adoptive transfer of wild-type and CD13^KO primary myeloid cells, or wild-type myeloid cells pre-treated with CD13-blocking antibodies into thioglycollate-challenged wild-type recipients demonstrated fewer CD13^KO or treated cells in the lavage, suggesting that CD13 expression confers a competitive advantage in trafficking. Similarly, both wild-type and CD13^KO cells were reduced in infiltrates in CD13^KO recipients, confirming that both monocytic and endothelial CD13 contribute to trafficking. Finally, murine monocyte cell lines expressing mouse/human chimeric CD13 molecules demonstrated that the C-terminal domain of the protein mediates CD13 adhesion. Therefore, this work verifies that the altered inflammatory trafficking in CD13^KO mice is the result of aberrant myeloid cell subset trafficking and further defines the molecular mechanisms underlying this regulation.

Age, trauma and the critical shoulder angle accurately predict supraspinatus tendon tears

BACKGROUND

The pathogenesis of full-thickness tears of the rotator cuff remains unclear. Apart from age and trauma, distinct scapular morphologies have been found to be associated with rotator cuff disease. The purpose of the present study was to evaluate whether a score formed using these established risk factors was able to predict the presence of a rotator cuff tear reliably.

METHODS

We retrospectively assessed a consecutive series of patients with a minimal age of 40 years old, who had true antero-posterior (AP) radiographs of their shoulders, as well as a magnetic resonance (MR) gadolinium-arthrography, between January and December 2011. In all of these patients, the critical shoulder angle (CSA) was determined, and MR images were assessed for the presence of rotator cuff tears. Additionally, the patients' charts were reviewed to obtain details of symptom onset. Based on these factors, the so-called rotator cuff tear (RCT) score was calculated.

RESULTS

Patients with full-thickness RCTs were significantly older and had significantly larger CSAs than patients with intact rotator cuffs. Multiple logistic regression, using trauma, age and CSA as independent variables, revealed areas under the curve (AUCs) for trauma of 0.55, for age of 0.65 and for CSA of 0.86. The combination of all three factors was the most powerful predictor, with an AUC of 0.92.

CONCLUSION

Age, trauma and the CSA can accurately predict the presence of a posterosuperior RCT.

LEVEL OF EVIDENCE

Level IV. Case series with no comparison groups.

Is there an association between the individual anatomy of the scapula and the development of rotator cuff tears or osteoarthritis of the glenohumeral joint?: A radiological study of the critical shoulder angle

We hypothesised that a large acromial cover with an upwardly tilted glenoid fossa would be associated with degenerative rotator cuff tears (RCTs), and conversely, that a short acromion with an inferiorly inclined glenoid would be associated with glenohumeral osteoarthritis (OA). This hypothesis was tested using a new radiological parameter, the critical shoulder angle (CSA), which combines the measurements of inclination of the glenoid and the lateral extension of the acromion (the acromion index). The CSA was measured on standardised radiographs of three groups: 1) a control group of 94 asymptomatic shoulders with normal rotator cuffs and no OA; 2) a group of 102 shoulders with MRI-documented full-thickness RCTs without OA; and 3) a group of 102 shoulders with primary OA and no RCTs noted during total shoulder replacement. The mean CSA was 33.1° (26.8° to 38.6°) in the control group, 38.0° (29.5° to 43.5°) in the RCT group and 28.1° (18.6° to 35.8°) in the OA group. Of patients with a CSA > 35°, 84% were in the RCT group and of those with a CSA < 30°, 93% were in the OA group. We therefore concluded that primary glenohumeral OA is associated with significantly smaller degenerative RCTs with significantly larger CSAs than asymptomatic shoulders without these pathologies. These findings suggest that individual quantitative anatomy may imply biomechanics that are likely to induce specific types of degenerative joint disorders.

Tyrosine phosphorylation of CD13 regulates inflammatory cell-cell adhesion and monocyte trafficking

CD13 is a large cell surface peptidase expressed on the monocytes and activated endothelial cells that is important for homing to and resolving the damaged tissue at sites of injury. We showed previously that cross-linking of human monocytic CD13 with activating Abs induces strong adhesion to endothelial cells in a tyrosine kinase- and microtubule-dependent manner. In the current study, we examined the molecular mechanisms underlying these observations in vitro and in vivo. We found that cross-linking of CD13 on U937 monocytic cells induced phosphorylation of a number of proteins, including Src, FAK, and ERK, and inhibition of these abrogated CD13-dependent adhesion. We found that CD13 itself was phosphorylated in a Src-dependent manner, which was an unexpected finding because its 7-aa cytoplasmic tail was assumed to be inert. Furthermore, CD13 was constitutively associated with the scaffolding protein IQGAP1, and CD13 cross-linking induced complex formation with the actin-binding protein α-actinin, linking membrane-bound CD13 to the cytoskeleton, further supporting CD13 as an inflammatory adhesion molecule. Mechanistically, mutation of the conserved CD13 cytoplasmic tyrosine to phenylalanine abrogated adhesion; Src, FAK, and ERK phosphorylation; and cytoskeletal alterations upon Ab cross-linking. Finally, CD13 was phosphorylated in isolated murine inflammatory peritoneal exudate cells, and adoptive transfer of monocytic cell lines engineered to express the mutant CD13 were severely impaired in their ability to migrate into the inflamed peritoneum, confirming that CD13 phosphorylation is relevant to inflammatory cell trafficking in vivo. Therefore, this study identifies CD13 as a novel, direct activator of intracellular signaling pathways in pathophysiological conditions.

Reamed intramedullary nailing of diaphyseal tibial fractures: comparison of compression and non-compression nailing

BACKGROUND

Modern intramedullary implants provide the option to perform compression at the fracture gap in long bone fractures via a compression screw mechanism. The aim of this study was to assess if the application of interfragmentary compression in the intramedullary nailing of tibia fractures could increase the union rate and speed of fracture healing.

METHODS

Sixty-three patients who suffered from an AO-type 42-A3 or 42-B2 fracture that was treated by reamed intramedullary nailing between 2003 and 2008 were included in this retrospective study. Twenty-five patients were treated with dynamic interlocking without compression while 38 were treated with compression nailing. The compression load of the dynamic proximal screw was calculated by postoperative X-ray and radiographs taken four weeks after operation. Healing was assessed by radiological evaluation until the completion of bony healing or the disappearance of clinical symptoms. Nonunion was defined as the absence of radiological union and the persistence of clinical symptoms after six months.

RESULTS

Postoperative compression was applied at a mean load of 1,852 N, and 980 N remained after four weeks. In the compression group, 19 open and 19 closed fractures occurred. In the non-compression group, 25 patients were included (14 closed and 11 open cases). Active compression decreased healing time significantly. Nonunion occurred in one compression patient and three non-compression patients.

CONCLUSION

The results show that additional compression of the fracture gap can improve healing outcome in simple transverse tibial shaft fractures treated with reamed nailing.

Antimicrobial activity of lemongrass oil against Salmonella enterica on organic leafy greens

AIMS

We investigated the antimicrobial effectiveness of lemongrass essential oil on organic leafy greens, romaine and iceberg lettuces and mature and baby spinach, inoculated with Salmonella Newport. The influences of exposure times and abuse temperatures on bacterial survival were also investigated.

METHODS AND RESULTS

Leaf samples were washed, inoculated with Salm. Newport (6-log CFUml(-1) ) and dried. Inoculated leaves were immersed in solutions containing 0·1, 0·3 or 0·5% lemongrass oil in phosphate-buffered saline for 1 or 2min and then individually incubated at 4 or 8°C. Samples were taken at day 0, 1 and 3 for the enumeration of survivors. Compared to the PBS control, romaine and iceberg lettuces, and mature and baby spinach samples showed between 0·6-1·5-log, 0·5-4·3-log, 0·5-2·5-log and 0·5-2·2-logCFUg(-1) reductions in Salm. Newport by day 3, respectively.

CONCLUSIONS

The antimicrobial activity of lemongrass oil against Salm. Newport was concentration and time dependent. The antimicrobial activity increased with exposure time; iceberg samples treated for 2min generally showed greater reductions (P<0·05) than those treated for 1min (c.1-log reduction difference for 0·3 and 0·5% treatments). Few samples showed a difference between refrigeration and abuse temperatures.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study demonstrates the potential of lemongrass oil solutions to inactivate Salm. Newport on organic leafy greens.

Anabolic steroids reduce muscle damage caused by rotator cuff tendon release in an experimental study in rabbits

BACKGROUND

Muscles of the rotator cuff undergo retraction, atrophy, and fatty infiltration after a chronic tear, and a rabbit model has been used to investigate these changes. The purpose of this study was to test the hypothesis that the administration of anabolic steroids can diminish these muscular changes following experimental supraspinatus tendon release in the rabbit.

METHODS

The supraspinatus tendon was released in twenty New Zealand White rabbits. Musculotendinous retraction was monitored over a period of six weeks. The seven animals in group I had no additional intervention, the six animals in group II had local and systemic administration of nandrolone decanoate, and the seven animals in group III had systemic administration of nandrolone decanoate during the six weeks. Two animals (group III) developed a postoperative infection and were excluded from the analysis. At the time that the animals were killed, in vivo muscle performance as well as imaging and histological muscle changes were investigated.

RESULTS

The mean supraspinatus retraction was higher in group I (1.8 cm; 95% confidence interval: 1.64, 2.02 cm) than in group II (1.5 cm; 95% confidence interval: 1.29, 1.81 cm) or III (1.2 cm; 95% confidence interval: 0.86, 1.54 cm). Histologically, no fatty infiltration was measured in either treated group II (mean, 2.2%; range, 0% to 8%) or III (mean, 1%; range, 0% to 3.4%), but it was measured in the untreated group I (mean, 5.9%; range, 0% to 14.1%; p = 0.031). The radiographic cross-sectional area indicating atrophy and the work of the respective muscle during one standardized contraction with supramaximal stimulation decreased in all groups, but the work of the muscle was ultimately highest in group III.

CONCLUSIONS

To our knowledge, this is the first documentation of partial prevention of important muscle alterations after retraction of the supraspinatus musculotendinous unit caused by tendon disruption. Nandrolone decanoate administration in the phase after tendon release prevented fatty infiltration of the supraspinatus muscle and reduced functional muscle impairment caused by myotendinous retraction in this rabbit rotator cuff model, but two of seven rabbits that received the drug developed infections.

A Biomechanical Evaluation of Orthopaedic Implants for Hip Fractures by Finite Element Analysis and In-Vitro Tests

The aim of this study was to test the hypothesis that a reinforced gamma nail for the fixation of subtrochanteric fractures would experience less stress during loading compared with a common gamma nail. The issue of whether the use of the stronger implant would result in more stress shielding in the surrounding bone was also addressed.

A finite element analysis (FEA) of a synthetic bone was employed to calculate the stress distribution in implant and bone for two fracture types (AO 31-A3.1 and AO 31-A3.3). The FEA was validated by mechanical tests on six synthetic femurs. To test the hypothesis in vitro, mechanical tests on six pairs of fresh-frozen human femurs were conducted. The femurs were supplied with a common or a reinforced gamma nail in a cross-over study design. Strains were measured on the nail shaft to quantify the loading of the nail.

The FEA resulted in 3—51 per cent lower stresses for the reinforced gamma nail. No increase in stress shielding could be observed. In the in-vitro tests, the reinforced gamma nail experienced less strain during loading ( p < 0.016). The study demonstrated the benefit of a reinforced gamma nail in subtrochanteric fractures. It experienced less stress but did not result in more stress shielding.

The stability of a hip fracture determines the fatigue of an intramedullary nail

The purpose of this study was to address the question of how the stability of a proximal hip fracture determines the fatigue and failure mechanism of an intramedullary implant. To answer this question, mechanical experiments and finite element simulations with two different loading scenarios were conducted. The two load scenarios differed in the mechanical support of the fracture by an artificial bone sleeve, representing the femoral head and neck. The experiments confirmed that an intramedullary nail fails at a lower load in an unstable fracture situation in the proximal femur than in a stable fracture. The nails with an unstable support failed at a load 28 per cent lower than the nails with a stable support by the femoral neck. Hence, the mechanical support of a fracture is crucial to the fatigue failure of an implant. The simulation showed why the fatigue fracture of the nail starts at the aperture of the lag screw. It is the location of the highest von Mises stress, which is the failure criterion for ductile materials.

Non-operative treatment of large anterior glenoid rim fractures after traumatic anterior dislocation of the shoulder

The generally-accepted treatment for large, displaced fractures of the glenoid associated with traumatic anterior dislocation of the shoulder is operative repair. In this study, 14 consecutive patients with large (> 5 mm), displaced (> 2 mm) anteroinferior glenoid rim fractures were treated non-operatively if post-reduction radiographs showed a centred glenohumeral joint. After a mean follow-up of 5.6 years (2.8 to 8.4), the mean Constant score and subjective shoulder value were 98% (90% to 100%) and 97% (90% to 100%), respectively. There were no redislocations or subluxations, and the apprehension test was negative. All fragments healed with an average intra-articular step of 3.0 mm (0.5 to 11). No patient had symptoms of osteoarthritis, which was mild in two shoulders and moderate in one. Traumatic anterior dislocation of the shoulder, associated with a large displaced glenoid rim fracture can be successfully treated non-operatively, providing the glenohumeral joint is concentrically reduced on the anteroposterior radiograph.

Clinical and structural outcomes of nonoperative management of massive rotator cuff tears

BACKGROUND

The natural history of massive rotator cuff tears is not well known. The purpose of this study was to determine the clinical and structural mid-term outcomes in a series of nonoperatively managed massive rotator cuff tears.

METHODS

Nineteen consecutive patients (twelve men and seven women; average age, sixty-four years) with a massive rotator cuff tear, documented by magnetic resonance imaging, were identified retrospectively. There were six complete tears of two rotator cuff tendons and thirteen complete tears of three rotator cuff tendons. All patients were managed exclusively with nonoperative means. Nonoperative management was chosen when a patient had low functional demands and relatively few symptoms and/or if he or she refused to have surgery. For the purpose of this study, patients were examined clinically and with standard radiographs and magnetic resonance imaging.

RESULTS

After a mean duration of follow-up of forty-eight months, the mean relative Constant score was 83% and the mean subjective shoulder value was 68%. The score for pain averaged 11.5 points on a 0 to 15-point visual analogue scale in which 15 points represented no pain. The active range of motion did not change over time. Forward flexion and abduction averaged 136 degrees; external rotation, 39 degrees; and internal rotation, 66 degrees. Glenohumeral osteoarthritis progressed (p = 0.014), the acromiohumeral distance decreased (p = 0.005), the size of the tendon tear increased (p = 0.003), and fatty infiltration increased by approximately one stage in all three muscles (p = 0.001). Patients with a three-tendon tear showed more progression of osteoarthritis (p = 0.01) than did patients with a two-tendon tear. Four of the eight rotator cuff tears that were graded as reparable at the time of the diagnosis became irreparable at the time of final follow-up.

CONCLUSIONS

Patients with a nonoperatively managed, moderately symptomatic massive rotator cuff tear can maintain satisfactory shoulder function for at least four years despite significant progression of degenerative structural joint changes. There is a risk of a reparable tear progressing to an irreparable tear within four years.

The role of the subscapularis in preventing anterior glenohumeral subluxation in the abducted, externally rotated position of the arm

BACKGROUND

Current literature suggests that the subscapularis muscle is the main active stabilizer when the humerus is abducted and externally rotated. Conservative treatment of anterior shoulder instability therefore aims at strengthening this muscle. Empirical models, however, have questioned the role of the subscapularis muscle as it has been observed to potentially support dislocation of the subluxated humeral head.

METHODS

Ten human shoulders were loaded with an anterior dislocating force and the effect of different subscapularis tensions on humeral translation was measured with the Motion Analysis system, for the abducted and externally rotated arm and neutral positions. Also, lines of action of the subscapularis segments were measured on a 3D epoxy model.

FINDINGS

Shoulders in which the humeral head migrated antero-superiorly under an external antero-inferior load were observed to dislocate under simulated active subscapularis tension in both positions. In contrast, shoulders in which the head migrated antero-inferiorly remained stable. Twice as many specimens dislocated in the abducted - externally rotated position than in the neutral position. The change in line of action of the subscapularis may account for this change.

INTERPRETATION

Exercises alone are unlikely to be adequate for all patients with anterior instability symptoms. Passive motion pattern of the humeral head might serve as an indicator as to whether the effect of strengthening the subscapularis might stabilize a shoulder without further operation. Development of a clinical test based on these findings might differentiate the non-operative from operative candidates among patients presenting with anterior instability of the shoulder.

Tendon retracts more than muscle in experimental chronic tears of the rotator cuff

We released the infraspinatus tendons of six sheep, allowed retraction of the musculotendinous unit over a period of 40 weeks and then performed a repair. We studied retraction of the musculotendinous unit 35 weeks later using CT, MRI and macroscopic dissection.

The tendon was retracted by a mean of 4.7 cm (3.8 to 5.1) 40 weeks after release and remained at a mean of 4.2 cm (3.3 to 4.7) 35 weeks after the repair. Retraction of the muscle was only a mean of 2.7 cm (2.0 to 3.3) and 1.7 cm (1.1 to 2.2) respectively at these two points. Thus, the musculotendinous junction had shifted distally by a mean of 2.5 cm (2.0 to 2.8) relative to the tendon. Sheep muscle showed an ability to compensate for approximately 60% of the tendon retraction in a hitherto unknown fashion. Such retraction may not be a quantitatively reliable indicator of retraction of the muscle and may overestimate the need for elongation of the musculotendinous unit during repair.

Single-stage bilateral total shoulder arthroplasty

We compared six patients with a mean age of 70 years (49 to 80) with severe bilateral, painful glenohumeral joint destruction who underwent a single-stage bilateral total shoulder replacement, with eight patients of mean age 61 years (22 to 89) who underwent bilateral total shoulder replacement in two stages, at a mean interval of 18 months (6 to 43).

The overall function, pain and strength improved significantly in both groups. The subjective shoulder value, relative Constant score, active external rotation and the strength were improved significantly more in the single-stage group. Active elevation, abduction and overall function improved, significantly more in the single-stage group. Both the total duration of hospitalisation and the time off work per shoulder were substantially shorter in the single-stage group. The overall rate of complication was lower in the single-stage group.

Our findings indicated that single-stage bilateral total shoulder replacement yielded significantly better clinical results with shorter hospitalisation and rehabilitation than staged replacement, and was not associated with any increase in complications.

Ultrasonically implanted PLA suture anchors are stable in osteopenic bone

We compared the in vitro pullout strengths of a metallic screw-type suture anchor (5-mm Corkscrew) and a new ultrasonically implanted absorbable pin from cadaveric humeral heads with different bone densities. They were assessed quantitatively using microcomputed tomography. Pullout tests were done at four standardized sites and then correlated with the local bone density. The mean pullout strengths for the 5-mm Corkscrew and the 3.5-mm polylactic pin were similar in weak bone (76 +/- 24 N versus 104 +/- 46 N), intermediate quality bone (194 +/- 81 N versus 218 +/- 76 N), and strong bone (349 +/- 127 N versus 325 +/- 100 N). Pullout strength correlated with bone density for both implants (r = 0.76 and r = 0.86 for the Corkscrew and polylactic pin, respectively). The ultrasonically implanted absorbable 3.5-mm polylactic pin achieved equal pullout strength in weak bone as the larger 5-mm titanium Corkscrew. Bone density is highly variable in humeral heads and influenced the pullout strength of both implants.

Treatment of painful pseudoparesis due to irreparable rotator cuff dysfunction with the Delta III reverse-ball-and-socket total shoulder prosthesis

BACKGROUND

The Delta III reverse-ball-and-socket total shoulder implant is designed to restore overhead shoulder function in the presence of irreparable rotator cuff deficiency by using the intact deltoid muscle and the stability provided by the prosthetic design. Our purpose was to evaluate the clinical and radiographic results of this arthroplasty in a consecutive series of shoulders with painful pseudoparesis due to irreversible loss of rotator cuff function.

METHODS

Fifty-eight consecutive patients with moderate-to-severe shoulder pain and active anterior elevation of <90 degrees due to an irreparable rotator cuff tear were treated with a Delta III total shoulder replacement at an average age of sixty-eight years. Seventeen of the procedures were the primary treatment for the shoulder, and forty-one were revisions. The patients were examined clinically and radiographically after an average duration of follow-up of thirty-eight months.

RESULTS

On the average, the subjective shoulder value increased from 18% preoperatively to 56% postoperatively (p < 0.0001); the relative Constant score, from 29% to 64% (p < 0.0001); the Constant score for pain, from 5.2 to 10.5 points (p < 0.0001); active anterior elevation, from 42 degrees to 100 degrees (p < 0.0001); and active abduction, from 43 degrees to 90 degrees (p < 0.0001). The patients for whom the implantation of the Delta III prosthesis was the primary procedure and those who had had previous surgery showed similar amounts of improvement. The total complication rate, including all minor complications, was 50%, and the reoperation rate was 33%. Of the seventeen primary operations, 47% (eight) were associated with a complication and 18% (three) were followed by a reoperation. Of the forty-one revisions, 51% (twenty-one) were associated with a complication and 39% (sixteen) were followed by a reoperation. Subjective results and satisfaction rates were not influenced by complications or reoperations when the prosthesis had been retained.

CONCLUSIONS

Total shoulder arthroplasty with the Delta III prosthesis is a salvage procedure for severe shoulder dysfunction caused by an irreparable rotator cuff tear associated with other glenohumeral lesions. Complications were frequent following both primary and revision procedures, but they rarely affected the final outcome. The procedure has a substantial potential to improve the condition of patients with severe shoulder dysfunction, at least in the short term.

A new methodology for the planning of single-cut corrective osteotomies of mal-aligned long bones

BACKGROUND

Corrections of combined torsional and angular deformities of long bones may be performed creating a single osteotomy which is oriented so that rotating the two fragments on the created osteotomy plane allows to correct all deformities in one step. A practical geometrical tool is presented to facilitate the difficult preoperative planning of such osteotomies.

METHODS

The geometrical tool consists of two limbs connected by a mobile disk representing the osteotomy plane. This allows the two limbs to be deliberately bent and rotated against each other. Thereby, the mobile disk will change orientation in such a way that it will indicate the osteotomy plane needed in order to anatomically align the two limbs. The geometrical principle of the tool has been confirmed mathematically and compared with data from the literature. Five deformed test bones have been used to test the effectiveness of the tool.

FINDING

. The geometrical principle of the tool is equivalent with the mathematical data from the literature. The maximal osteotomy angle which can be indicated by the tool is 65 degrees , with an error of +/-3 degrees compared to mathematically calculated values. The five test bones were all aligned anatomically with appropriate accuracy.

INTERPRETATION

The presented tool can be easily used and facilitates largely the preoperative planning of a single cut osteotomy for complex deformities of long bones. It allows to avoid sophisticated mathematical calculations and helps to avoid the risk for errors in planning and performing correctional osteotomies.

Analysis of a retrieved Delta III total shoulder prosthesis

A reversed Delta III total shoulder prosthesis was retrieved post-mortem, eight months after implantation. A significant notch was evident at the inferior pole of the scapular neck which extended beyond the inferior fixation screw. This bone loss was associated with a corresponding, erosive defect of the polyethylene cup. Histological examination revealed a chronic foreign-body reaction in the joint capsule. There were, however, no histological signs of loosening of the glenoid base plate and the stability of the prosthetic articulation was only slightly reduced by the eroded rim of the cup.

Effect of Amine/Sodium Fluoride Rinsing on Toothbrush Abrasion of Softened Enamel in situ

The aim of this study was to test the effect of fluoride rinsing on the prevention of toothbrush abrasion of softened enamel in situ. For softening, the samples were immersed in 0.1 M citric acid (pH 3.5) for 3 min. Eight test subjects had to make 5 runs in which 4 slabs per run were attached to intraoral appliances. They were as follows: (1) no softening, no fluoride rinsing (control 1); (2) softening, no fluoride rinsing (control 2); (3) softening, rinsing in situ with a sodium/amine fluoride rinsing solution (250 ppm F) for 30 s; (4) rinsing in situ with the sodium/amine fluoride rinsing solution (250 ppm F) for 30 s, softening; (5) softening, rinsing in situ with an experimental amine fluoride-containing rinsing solution (250 ppm F) for 30 s. After exposure for 60 min to the oral milieu, the volunteers brushed the samples for 30 s with toothpaste and the loss of tooth substance was determined. For each test person, the secretion rate of resting and paraffin-stimulated saliva, buffering capacity and pH were measured. Toothbrush abrasion in situ was not significantly lower using the fluoride rinsing solutions before or after softening the enamel compared to no rinsing (p > 0.05). Multiple linear regression analyses revealed that 57% of the variation in toothbrush abrasion could be attributed to the severity of softening (p < 0.001) and the pH of stimulated saliva (p < 0.001). It was concluded that a single rinse for 30 s had no statistically significant effect on the prevention of toothbrush abrasion of softened enamel.

Internal fixation of complex fractures of the proximal humerus

We treated 34 consecutive articular fractures of the proximal humerus in 33 patients with good bone quality by open reduction and internal fixation. Anatomical or nearly anatomical reduction was achieved in 30, at a mean follow-up of 63 months (25 to 131), complete or partial avascular necrosis had occurred in 12 cases (35%). Two patients subsequently underwent arthroplasty and six further patients required additional surgery. The 32 patients who did not require arthroplasty obtained a mean Constant score of 78 points or 89% of an age- and gender-matched normal score (66 points or 76% in the presence and 83 points or 96% in the absence of avascular necrosis (p < 0.0005)); 22 were painfree, and seven had mild pain and three moderate pain. The mean active anterior elevation was 156 degrees. Internal fixation of complex fractures of the proximal humerus restored good shoulder function if avascular necrosis did not develop.

Effect of tendon release and delayed repair on the structure of the muscles of the rotator cuff: an experimental study in sheep

BACKGROUND

Ruptures of the tendons of the rotator cuff lead to profound and possibly irreversible changes in the structure and physiological properties of the rotator cuff muscles. Muscle atrophy and fatty infiltration are important prognostic factors that affect the natural history and outcome of treatment. The purpose of this study was to examine the amount of muscle atrophy and fatty infiltration in an animal model and to determine whether the repair of a long-standing tendon tear can reverse these changes.

METHODS

The infraspinatus tendon in six sheep was released and encased in a silicone tube to prevent spontaneous healing. The musculotendinous unit was allowed to retract for forty weeks. Throughout this period, the muscular changes were studied with use of computed tomography, histological analysis, and electron microscopy. At forty weeks, the elasticity, intramuscular pressure, and perfusion were measured intraoperatively and a tendon repair was carried out. The structural changes of the muscle were studied for thirty-five weeks after the repair. The animals were then killed, and the musculotendinous units were examined macroscopically and by computed tomography, histological analysis, and electron microscopy.

RESULTS

At the time of the tendon release, the infraspinatus showed no fatty changes. The force needed to cause a tendon excursion of 1 cm was a mean (and standard deviation) of 6.8 +/- 1 N. The application of tension on the tendon did not alter the perfusion and decreased the intramuscular pressure. After the tendon release, muscular atrophy developed and there was a significant increase (p < 0.001) in interfascicular and intrafascicular fat, representing fatty infiltration rather than fatty degeneration. Furthermore, there was an increase of interstitial connective tissue. At the time of the tendon repair, between forty and forty-two weeks after the release, there was a sevenfold poorer elasticity of the musculotendinous unit but preserved muscle perfusion. The structural changes increased six weeks after the repair and then recovered partially at twelve and thirty-five weeks thereafter but only to the amount demonstrated before the repair.

CONCLUSIONS

Musculotendinous retraction induced by tendon release is associated with profound changes in the structure and function of the affected muscle. Vascularization, intramuscular pressure, and individual fiber composition are not markedly affected, and muscle fibers do not appear to degenerate. However, muscle atrophy, infiltration by fat cells, and an increase of interstitial connective tissue lead to impairment of the physiological properties of the muscle. These changes were irreversible under the conditions of this experiment with the repair technique used.

Subluxation antérieure statique de l’épaule après butée pré-glénoïdienne et transfert du grand pectoral

We report the case of a patient who experienced post-traumatic static anterosuperior subluxation of the shoulder. The displacement worsened after surgical treatment associating a preglenoid bone block and pectoralis major transfer. We studied the lines of action of the conjoint tendon on an anatomic model. The biomechanical study demonstrated that alone, the coracoid bone block did not provoke the anterior glenohumeral subluxation. On the contrary, the compression components of the humeral head into the glenoid cavity increased and could not explain the worsening dislocation. Inversely, the tendon of the pectoralis major passed in front of the conjoint tendon because of the absence of the subscapularis and could have been the cause of the aggravated anterior subluxation.

In vivo tendon force measurement of 2-week duration in sheep

Tendon tension in vivo may be determined indirectly by measuring intratendinous pressure, by using a buckle transducer or by measuring the tendon strain. All of these methods require appropriate calibration, which is highly dependent on various variables. To measure the tendon load in vivo during a period of 2 weeks in sheep, a measurement technique has been developed using a force sensor interposed serially between the humeral head and the tendon end. Within a supporting frame, a flexion-sensitive force transducer is subjected to three-point bending stress. The load is transmitted by sutures from the tendon end through a hole in the sensor frame, orthogonal to the force transducer. In this configuration, the sensor measures the tensile force acting on the tendon, largely independent of the loading direction. The sensor was screwed to the humeral head and connected to the tendon end which was previously released from its insertion site along with a bone chip, using sutures. Connecting wires passed subcutaneously to a skin outlet about 30 cm away from the transducer. The sensor output was linear to the measured load up to 300 N, with maximum hysteresis of 18% full scale. All sensors worked in vivo without drift over a period of up to 14 days with no change in the calibration data. Forces up to 310 N have been recorded in vivo with daily tension measurements. This study shows that serial tendon tension measurement is feasible and allows for reliable, repeatable recording of the absolute tendon tension at the expense of tendon integrity.

Levator scapulae and rhomboid transfer for paralysis of trapezius. The Eden-Lange procedure

Spinal accessory nerve palsy leads to painful disability of the shoulder, carrying an uncertain prognosis. We reviewed the long-term outcome in 16 patients who were treated for pain, weakness of active elevation and asymmetry of the shoulder and the neck due to chronic paralysis of the trapezius muscle, as a result of nerve palsy. Of four patients who were treated conservatively, none regained satisfactory function, although two became pain-free. The other 12 patients were treated operatively with transfer of the levator scapulae to the acromion and the rhomboid muscles to the infraspinatus fossa (the Eden-Lange procedure). At a mean follow-up of 32 years, the clinical outcome of the operatively treated patients was excellent in nine, fair in two, and poor in one patient, as determined by the Constant score. Pain was adequately relieved in 11 and overhead function was restored in nine patients. Pre-operative electromyography had been carried out in four patients. In two, who eventually had a poor outcome, a concomitant long thoracic and dorsal scapular nerve lesion had been present. The Eden-Lange procedure gives very satisfactory long-term results for the treatment of isolated paralysis of trapezius. In the presence of an additional serratus anterior palsy or weak rhomboid muscles, the procedure is less successful in restoring shoulder function.

Influence of peg design and cement mantle thickness on pull-out strength of glenoid component pegs

Fixation of the glenoid component is critical to the outcome of total shoulder arthroplasty. In an in vitro study, we analysed the effect of surface design and thickness of the cement mantle on the pull-out strength of the polyethylene pegs which are considered essential for fixation of cemented glenoid components. The macrostructure and surface of the pegs and the thickness of the cement mantle were studied in human glenoid bone. The lowest pull-out forces, 20 ± 5 N, were for cylindrical pegs with a smooth surface fixed in the glenoid with a thin cement mantle. The highest values, 425 ± 7 N, were for threaded pegs fixed with a thicker cement mantle. Increasing the diameter of the hole into which the peg is inserted from 5.2 to 6.2 mm thereby increasing the thickness of the cement mantle, improved the mean pull-out force for the pegs tested.

Influence of peg design and cement mantle thickness on pull-out strength of glenoid component pegs

Fixation of the glenoid component is critical to the outcome of total shoulder arthroplasty. In an in vitro study, we analysed the effect of surface design and thickness of the cement mantle on the pull-out strength of the polyethylene pegs which are considered essential for fixation of cemented glenoid components. The macrostructure and surface of the pegs and the thickness of the cement mantle were studied in human glenoid bone. The lowest pull-out forces, 20 +/- 5 N, were for cylindrical pegs with a smooth surface fixed in the glenoid with a thin cement mantle. The highest values, 425 +/- 7 N, were for threaded pegs fixed with a thicker cement mantle. Increasing the diameter of the hole into which the peg is inserted from 5.2 to 6.2 mm thereby increasing the thickness of the cement mantle, improved the mean pull-out force for the pegs tested.

The use of acrylic bone cement for suture anchoring

Healing of tendon or ligament sutured to bone depends among other parameters on the mechanical stability of the suture fixation in or to the bone. The authors propose a method of anchoring suture material using bone cement as a substitute for conventional suture anchors. Conditions for secure fixation of suture material in bone cement were assessed and the technique of anchoring suture material with acrylic cement in bone was developed. Mechanical testing and microcomputed tomography of the suture-cement-bone compound were done. It was found that the suture always should be knotted before embedding it at least 2 mm deep in the bone cement. The holes drilled into the bone in which the sutures are secured with cement should be at least 3.5 mm in diameter and 10 mm deep; in cortical bone a tapped thread is required. Sutures can be secured safely using cement anchors which provide higher pull-out strength of a factor two to five than conventional metallic suture anchors of comparable size. They also adapt to anatomic situations where conventional anchors cannot be used and are more favorable in osteoporotic bone. Cement anchoring of sutures seems to be a cost-effective and valuable alternative when there is poor bone quality or extraordinarily high mechanical load.