Pneumocystis jiroveci pneumonia after total hip arthroplasty in a dermatomyositis patient:A case report

BACKGROUND Pneumocystis jiroveci pneumonia(PJP)is a serious opportunistic infection that occurs mostly in patients with immunodeficiency and long-term immunosuppressive therapy.In non-human immunodeficiency virus-infected patients,the most important risk factor for PJP is the use of glucocorticoids in combination with other immunosuppressive treatments.The management of glucocorticoids during the perioperative period in patients with dermatomyositis requires special care.CASE SUMMARY We report a case of PJP in the perioperative period.A 61-year-old woman with a history of anti-melanoma differentiation-associated gene 5(MDA5)-positive dermatomyositis and interstitial pneumonia was administered with long-term oral methylprednisolone and cyclosporine.The patient underwent right total hip arthroplasty in the orthopaedic department for bilateral osteonecrosis of the femoral head.She was given intravenous drip hydrocortisone before anesthesia and on the first day after surgery and resumed oral methylprednisolone on the second postoperative day.On the fifth day after surgery,the patient suddenly developed dyspnea.The computed tomography scan showed diffuse grid shadows and ground glass shadows in both lungs.Polymerase chain reaction testing of bronchoalveolar lavage fluid was positive for Pneumocystis jiroveci.The patient was eventually diagnosed with PJP and was administered with oral trimethoprim-sulfamethoxazole.At the 6-mo review,there was no recurrence or progression.CONCLUSION Continued perioperative glucocorticoid use in patients with anti-MDA5-positive dermatomyositis may increase the risk of PJP.

Finite Element Analysis of Mobile-bearing Unicompartmental Knee Arthroplasty： The Influence of Tibial Component Coronal Alignment

Background： Controversies about the rational positioning of the tibial component in unicompartmental knee arthroplasty （UKA） still exist. Previous finite element （FE） studies were rare, and the results varied. This FE study aimed to analyze the influence of the tibial component coronal alignment on knee biomechanics in mobile-bearing UKA and find a ration range of inclination angles. Methods： A three-dimensional FE model of the intact knee was constructed from image data of one normal subject. A 1000 N compressive load was applied to the intact knee model for validating. Then a set of eleven UKA FE models was developed with the coronal inclination angles of the tibial tray ranging from 10° valgus to 10° varus. Tibial bone stresses and strains, contact pressures and load distribution in all UKA models were calculated and analyzed under the unified loading and boundary conditions. Results： Load distribution, contact pressures, and contact areas in intact knee model were validated. In UKA models, von Mises stress and compressive strain at proximal medial cortical bone increased significantly as the tibial tray was in valgus inclination 〉4°, which may increase the risk of residual pain. Compressive strains at tibial keel slot were above the high threshold with varus inclination 〉4°, which may result in greater risk of component migration. Tibial bone resection comer acted as a strain-raiser regardless of the inclination angles. Compressive strains at the resected surface slightly changed with the varying inclinations and were not supposed to induce bone resorption and component loosening. Contact pressures and load percentage in lateral compartment increased with the more varus inclination, which may lead to osteoarthritis progression. Conclusions： Static knee biomechanics after UKA can be greatly affected by tibial component coronal alignment. A rauge from 4° valgus to 4° varus inclination oftibial component can be recommended in mobile-bearing UKA.

Effects of Lower Limb Alignment and Tibial Component Inclination on the Biomechanics of Lateral Compartment in Unicompartmental Knee Arthroplasty

Background： Lateral compartmental osteoarthritis （LCOA）, a major complication after medial mobile-bearing unicompartmental knee arthroplasty （UKA）, is highly associated with the increased stress of the lateral compartment. This study aimed to analyze the effects on the stress and load distribution of the lateral compartment induced by lower limb alignment and coronal inclination of the tibial component in UKA through a finite element analysis. Methods： Eight three-dimensional models were constructed based on a validated model for analyzing the biomechanical effects of implantation parameters on the lateral compartment after medial Oxford UKA： postoperative lower limb alignment of 3° valgus, neutral and 3° varus, and the inclination of tibial components placed in 4°, 2° valgus, square, and 2° and 4° varus. The contact stress of femoral and tibial cartilage and load distribution were calculated for all models. Results： In the 3° valgus lower limb alignment model, the contact stress of femoral （3.38 MPa） and tibial （3.50 MPa） cartilage as well as load percentage （45.78%） was highest compared to any other model, and was increased by 36.75%, 47.70%, and 27.63%, respectively when compared to 3° varus. In the condition of a neutral position, the outcome was comparable for the different tibial tray inclination models. The inclination did not greatly affect the lateral compartmental stress and load distribution. Conclusions： This study suggested that slightly varus （undercorrection） lower limb alignment might be a way to prevent LCOAin medial mobile-bearing UKA. However, the inclination （4° varus to 4° valgus） of the tibial component in the coronal plane would not be a risk factor for LCOA in neutral position.

Significance of Lateral Pillar in Osteonecrosis of Femoral Head:A Finite Element Analysis

Background： The lateral pillar of the femoral head is an important site for disease development such as osteonecrosis of the femoral head. The femoral head consists of medial, central, and lateral pillars. This study aimed to determine the biomechanical effects of early osteonecrosis in pillars of the femoral head via a finite element （FE） analysis. Methods： A three-dimensional FE model of the intact hip joint was constructed from the image data of a healthy control. Further, a set of six early osteonecrosis models was developed based on the three-pillar classification. The von Mises stress and surface displacements were calculated for all models. Results： The peak values of von Mises stress in the cortical and cancellous bones of normal model were 6.41 MPa and 0.49 MPa, respectively. In models with necrotic lesions in the cortical and cancellous bones, the von Mises stress and displacement of lateral pillar showed significant variability： the stress of cortical bone decreased from 6.41 MPa to 1.51 MPa （76.0% reduction）, while cancellous bone showed an increase from 0.49 MPa to 1.28 MPa （159.0% increase）; surface displacements of cortical and cancellous bones increased from 52.4 μm and 52.1 μm to 67.9 μm （29.5%） and 61.9 μm （18.8%）, respectively. In addition, osteonecrosis affected not only pillars but also adjacent structures in terms of the von Mises stress and surface displacement levels. Conclusions： This study suggested that the early-stage necrosis in the femoral head could increase the risk of collapse, especially in lateral pillar. On the other hand, the cortical part of lateral pillar was found to be the main biomechanical support of femoral head.

Glucocorticoids Significantly Influence the Transcriptome of Bone Microvascular Endothelial Cells of Human Femoral Head

Background： Appropriate expression and regulation of the transcriptome, which mainly comprise ofmRNAs and lncRNAs, are important for all biological and cellular processes including the physiological activities of bone microvascular endothelial cells （BMECs）. Through an intricate intraeellular signaling systems, the transcriptome regulates the pharmacological response of the cells. Although studies have elucidated the impact of glucocorticoids （GCs） cell-specific gene expression signatures, it remains necessary to comprehensively characterize the impact of lncRNAs to transcriptional changes. Methods： BMECs were divided into two groups. One was treated with GCs and the other left untreated as a paired control. Differential expression was analyzed with GeneSpring software V12.0 （Agilent, Santa Clara, CA, USA） and hierarchical clustering was conducted using Cluster 3,0 software. The Gene Ontology （GO） analysis was performed with Molecular Annotation System provided by CapitalBio Corporation. Results： Our results highlight the involvement of genes implicated in development, differentiation and apoptosis following GC stimulation. Elucidation of differential gene expression emphasizes the importance of regulatory gene networks induced by GCs. We identified 73 up-regulated and 166 down-regulated long noncoding RNAs, the expression of 107 of which significantly correlated with 172 mRNAs induced by hydrocortisone. Conclusions： Transcriptome analysis of BMECs from human samples was performed to identify specific gene networks induced by GCs. Our results identified complex RNA crosstalk underlying the pathogenesis of steroid-induced necrosis of femoral head.

Local Administration of Bisphosphonate-soaked Hydroxyapatite for the Treatment of Osteonecrosis of the Femoral Head in Rabbit

Background：Systemic administration ofbisphosphonates has shown promising results in the treatment ofosteonecrosis of the femoral head （ONFH）.However,few studies have evaluated the efficacy of local zoledronate （ZOL） administration in the treatment of ONFH.The purpose of this study was to investigate whether local administration of bisphosphonate-soaked hydroxyapatite （HA） could improve bone healing in an experimental rabbit model of ONFH.Methods：This experimental study was conducted between October 2014 and June 2015.Forty-five rabbits underwent simulated ONFH surgery.Immediately following surgery,they were divided into three groups：model （untreated,n =15）,HA （treated with HA alone,n =15）,and HA ＋ ZOL （treated with HA soaked in a low-dose ZOL solution,n =15）.Histological,immunohistochemical,and quantitative analyses were performed to evaluate bone formation and resorption 2,4,and 8 weeks after surgery.Results：Gross bone matrix and hematopoietic tissue formation were observed in the HA ＋ ZOL group 4 weeks after surgery.The immunohistochemical staining intensities for 5-bromodeoxyuridine,runt-related transcription factor 2,osteocalcin,osteopontin,and osteoprotegerin were significantly higher in the HA ＋ ZOL group than that in the model （P 〈 0.001,P 〈 0.001,P 〈 0.001,P 〈 0.001,and P =0.018,respectively） and HA groups （P =0.003,P =0.049,P 〈 0.00l,P =0.020,and P =0.019,respectively）,whereas receptor activator of the nuclear factor-κB ligand staining intensity was significantly lower in the HA ＋ ZOL group than that in the model and HA groups （P =0.029 and P =0.015,respectively） 4 weeks after surgery.No significant differences in bone formation or bone resorption marker expression were found between the three groups 2 or 8 weeks after surgery （P 〉 0.05）.Conclusions：Local administration of HA soaked in a low-dose ZOL solution increased new bone formation while inhibiting bone resorption in an animal model of ONFH,which might provide new evidence for joint-preserving surgery in the treatment of ONFH.

An Innovative Three-Dimensional Method for Identifying a Proper Femoral Intramedullary Entry Point in Total Knee Arthroplasty

Background： Identification of the proper femoral intramedullary （IM） access point is an important determinant of final implant position in IM-guided total knee arthroplasty （TKA）. The aim of this study was to identify the optimal entry point in Chinese participants using a new three-dimensional method. Methods： A series of computed tomography scans of 44 femurs in Chinese participants from October 2014 to October 2015 were imported into Mimics 17.0 software to identify the optimal entry point. The apex of the intercondylar notch （AIN） was used as the reference bony anatomical landmark to identify the proper entry point to insert the IM rod. The statistical significance was calculated on the basis of a 5% level （P 〈 0.05） using the Student＇s t-test. Results： For the males, the average ideal entry point was 1.49 mm medial and 13.39 mm anterior to the AIN. The values were 1.77 mm medial and 15.29 mm anterior to the AIN in females. A significant difference was present between males and females （13.39 ±2.46 mm vs. 15.29 ± 3.44 mm, t = 2.124, P = 0.040）. When using the recommended location as the entry point for the IM rod, the mean potential error differed significantly from the femoral trochlear groove （the potential error of IM in males in coronal plane： 0.93~ ±0.24~ vs. 1.27~ ± 0.32~, t = -4.166, P 〈 0.001; the potential error of 1M in males in sagittal plane： 1.40° ± 0.42° vs. 2.79° ± 0.70°, t = -7.155, P 〈 0.001; the potential error oflM in females in coronal plane： 0.73° ± 0.28° vs. 1.15° ± 0.35°, t = -3.940, P 〈 0.001 ： and the potential error of 1M in females in sagittal plane： 1.48° ±0.47° vs. 2.76° ± 0.83°, t = -5.574, P 〈 0.001 ）. A significant difference was present between the recommended point and the point 10 mm anterior to the origin of the posterior cruciate ligament （the potential error of IM in males in coronal plane： 0.93° ± 0.24° vs. 1.53° ±0.43°, t = -5.948, P 〈 0.001 ; the potential error of IM in males in sagittal plane： 1.40° ± 0.42° vs. 2.15°± 0.75°, t = -3.152, P = 0.003; the potential error of IM in females in coronal plane： 0.73° ± 0.28° vs. 1.28° ±0.42°, t = -4.632, P 〈 0.001; and the potential error oflM in females in sagittal plane： 1.48°± 0.47° vs. 2.40°± 0.93°, t = -3.763, P = 0.001）. Conclusions： The technique described here is an innovative method for swift, easy, and accurate access to the medullary canal during TKA, and it can optimize the position and orientation of the prosthetic components in knee arthroplasty.

A modified technique for tibial bone sparing in unicompartmental knee arthroplasty

Background:Previously,the authors modified the surgical technique to preserve tibial bone mass for Oxford unicompartmental knee arthroplasty(UKA).The purpose of this study was to determine the clinical outcomes and values of this modified technique.Methods:Clinical data of 34 consecutive patients who underwent the unilateral modified UKA technique(modified group,34 knees)were retrospectively analyzed.To compare the outcome,a match-paired control group(conventional group,34 knees)of an equal number of patients using the conventional technique system in the same period were selected and matched with respect to diagnosis,age,pre-operative range of motion(ROM),and radiological grade of knee arthrosis.Clinical outcomes including knee Hospital for Special Surgery(HSS)score,ROM,and complications were compared between the two groups.Post-operative radiographic assessments included hip-knee-ankle angle(HKA),joint line change,implant position,and alignment.Results:The mean follow-up time was 38.2±6.3 months.There was no difference in baseline between the two groups.The amount of proximal tibial bone cut in the modified group was significantly less than that of the conventional group(4.7±1.1 mm vs.6.7±1.3 mm,t=6.45,P<0.001).Joint line was elevated by 2.1±1.0 mm in the modified group compared with-0.5±1.7 mm in the conventional group(t=-7.46,P<0.001).No significant differences were observed between the two groups after UKA with respect to HSS score,VAS score,ROM,and HKA.Additionally,the accuracy of the post-operative implant position and alignment was similar in both groups.As for implant size,the tibial implant size in the modified group was larger than that in the conventional group(x^2=4.95,P=0.035).Conclusions:The modified technique for tibial bone sparing was comparable with the conventional technique in terms of clinical outcomes and radiographic assessments.It can preserve tibial bone mass and achieve a larger cement surface on the tibial side.

One-stage total hip arthroplasty and“light-bulb”procedure for bilateral non-traumatic osteonecrosis of femoral head in different stages

To the Editor:Clinically,it is not rare for patients with bilateral non-traumatic osteonecrosis of femoral head(NONFH)first presenting to an orthopedic surgeon with one hip that requires total hip arthroplasty(THA)and another asymptomatic or less symptomatic one that potentially needs hip preservation surgery.

Glycosaminoglycan Content of the Lateral Compartment Cartilage in Knees Conforming to the Indications for Oxford Medial Unicompartmental Knee Arthroplasty

Background： The quality of the lateral compartment cartilage is important to preoperative evaluation and prognostic prediction of unicompartmental knee arthroplasty （UKA）. Delayed gadolinium-enhanced magnetic resonance imaging of cartilage （dGEMRIC） enables noninvasive assessment of glycosaminoglycan （GAG） content in cartilage. This study aimed to determine the GAG content of the lateral compartment cartilage in knees scheduled to undergo Oxford medial UKA. Methods： From December 2016 to May 2017, twenty patients （20 osteoarthritic knees） conforming to the indications fbr Oxford medial UKA were included as the osteoarthritis （OA） group, and 20 healthy volunteers （20 knees） paired by sex, knee side, age （±3 years）, and body mass index （BMI） （i3 kg/m2） were included as the control group. The GAG contents of the weight-bearing femoral cartilage （wbFC）, the posterior non-weight-bearing femoral cartilage （pFC）, the lateral femoral cartilage （FC）, and tibial cartilage （TC） were detected using dGEMRIC. The dGEMRIC indices （T1Gd） were calculated in the middle three consecutive slices of the lateral compartment. Paired t-tests were used to compare the T1Gd in each region of interest between the OA group and control group. Results： The average age and BMI in the two groups were similar. In the OA group, TIGd of FC and TC was 386.7 ± 50.7 ms and 429.6 ± 59.9 ins, respectively. In the control group, T1Gd of FC and TC was 397.5 ± 52.3 ms and 448.6 ±62.5 ms, respectively. The respective T 1Gd ofwbFC and pFC was 380.0 ± 47.8 ms and 391.0 ± 66.3 ms in the OA group and 400.3 ± 51.5 ms and 393.6 ± 57.9 ms in the control group. Although the T 1Gd ofwbFC and TC tended to be lower in the OA group than the control group, there was no significant difference between groups in the TIGd in any of the analyzed cartilage regions （P value ofwbFC, pFC, FC, and TC was 0.236, 0.857, 0.465, and 0.324, respectively）. Conclusions： The GAG content of the lateral compartment cartilage in knees confonning to indications for Oxford medial UKA is similar with those of age- and BMl-matched participants without OA.