The effect of lumbar spinal fusion on native acetabular anteinclination in standing position.

PURPOSE: The complex and dynamic spinopelvic interplay is not well understood. The aims of the present study were to investigate the following: (1) whether native acetabular anteinclination (AI) in standing position changes following lumbar spinal fusion (LSF); (2) potential correlations between AI change (ΔAI) and several spinopelvic parameters such as the change in lumbar lordosis (ΔLL), pelvic tilt (ΔPT), and anterior pelvic plane angle (ΔaPP). METHODS: A total of 485 patients (Males: 262, Females: 223) with an average age of 64 ± 13 years who underwent a primary LSF were identified from our institutional database. The difference (Δ) between pre-and postoperative acetabular anteinclination (AI), lumbar lordosis (LL), anterior pelvic plane angle (aPP), sacral slope (SS), and pelvic tilt (PT) were measured on a standing lateral radiograph (EOS®) and compared to find the effect of LSF on the lumbopelvic geometry. RESULTS: Following LSF, the average absolute ΔAI was 5.4 ± 4 (0 to 26)°, ΔLL: 5.5 ± 4 (0 to 27)°, ΔaPP: 5.4 ± 4 (0 to 38)°, ΔPT: 7 ± 5 (0 to 33)° and ΔSS: 5.3 ± 4 (0 to 33)°. No significant differences were observed between LSF levels. A ΔAI ≥ 10° was observed in 66 (13.6%) and ΔAI ≥ 20° in 5 (1%) patients. The Pearson correlation demonstrated a strong negative correlation of ΔAI with ΔLL (r = 0.72, p < .001). CONCLUSION: Clinical decision-making should consider the relationship between native anteinclination and lumbar lordosis to reduce the risk of functional acetabular component malalignment in patients with concomitant hip and spine pathology. LEVEL OF EVIDENCE: Retrospective case-control study, Level III.

Involvement of glutamine synthetase 2 (GS2) amplification and overexpression in Amaranthus palmeri resistance to glufosinate.

MAIN CONCLUSION: Amplification and overexpression of the target site glutamine synthetase, specifically the plastid-located isoform, confers resistance to glufosinate in Amaranthus palmeri. This mechanism is novel among glufosinate-resistant weeds. Amaranthus palmeri has recently evolved resistance to glufosinate herbicide. Several A. palmeri populations from Missouri and Mississippi, U.S.A. had survivors when sprayed with glufosinate-ammonium (GFA, 657 g ha-1). One population, MO#2 (fourfold resistant) and its progeny (sixfold resistant), were used to study the resistance mechanism, focusing on the herbicide target glutamine synthetase (GS). We identified four GS genes in A. palmeri; three were transcribed: one coding for the plastidic protein (GS2) and two coding for cytoplasmic isoforms (GS1.1 and GS1.2). These isoforms did not contain mutations associated with resistance. The 17 glufosinate survivors studied showed up to 21-fold increase in GS2 copies. GS2 was expressed up to 190-fold among glufosinate survivors. GS1.1 was overexpressed > twofold in only 3 of 17, and GS1.2 in 2 of 17 survivors. GS inhibition by GFA causes ammonia accumulation in susceptible plants. Ammonia level was analyzed in 12 F1 plants. GS2 expression was negatively correlated with ammonia level (r = - 0.712); therefore, plants with higher GS2 expression are less sensitive to GFA. The operating efficiency of photosystem II (ϕPSII) of Nicotiana benthamiana overexpressing GS2 was four times less inhibited by GFA compared to control plants. Therefore, increased copy and overexpression of GS2 confer resistance to GFA in A. palmeri (or other plants). We present novel understanding of the role of GS2 in resistance evolution to glufosinate.

Lumbar spinal fusion does not increase early dislocation risk in primary total hip arthroplasty through the direct anterior approach.

INTRODUCTION: Patients with total hip arthroplasty (THA) and a concomitant lumbar spinal fusion (LSF) might have an increased incidence of revision surgery and postoperative complications such as early THA dislocation. The direct anterior approach (DAA) has gained popularity in THA due to its soft tissue-preserving nature and the relatively low dislocation risk. The purpose of the present study was to examine whether LSF patients undergoing minimally invasive THA through the DAA might have an increased risk of prosthetic-related complications compared to matched-control patients without a LSF. MATERIALS AND METHODS: Patients who underwent THA through the DAA in our institution from January 2014 to December 2018 were identified. A total of 30 primary THA also underwent LSF within 3 months from the initial operation. These patients were randomly matched (1:3) for sex, age, and body mass index with patients who underwent primary THA in our institution without a history of LSF (control group). Peri and postoperative complications, revisions, radiographic and clinical outcomes were assessed retrospectively. RESULTS: LSF patients who underwent THA through the DAA did not have an increased risk of prosthetic-related complications compared to matched-control subjects without a LSF (6.6% versus 4.4%, P < 0.05). The functional and radiological outcomes were similar between groups. CONCLUSION: LSF patients undergoing THA could benefit from the DAA similarly to patients without LSF and without increased rate of early THA dislocation. Although the complex interplay between the lumbar spine and hip in THA patients warrants further investigation, the outcomes of THA through the DAA in LSF patients appear promising. LEVEL OF EVIDENCE: Retrospective case-control study, III.

Biomechanical performance of bicortical versus pericortical bone trajectory (CBT) pedicle screws.

PURPOSE: The cortical bone trajectory (CBT) is an alternative to the traditional pedicle screw trajectory (TT) in posterior spinal instrumentation, enhancing screw contact with cortical bone and therefore increasing fixation strength. Additional to the trajectory, insertion depth (pericortical vs. bicortical placement) could be a relevant factor affecting the fixation strength. However, the potential biomechanical benefit of a bicortical placement of CBT screws is unknown. Therefore, the aim of this study was to quantify the fixation strength of pericortical- versus bicortical-CBT (pCBT versus bCBT) screws in a randomized cadaveric study. METHODS: Pedicle screws were either placed pericortical or bicortical with a CBT in 20 lumbar vertebrae (2 × 20 instrumented pedicles) from four human spine cadavers by using patient-specific templates. Instrumented specimens underwent physiological cyclic loading testing (1'800'000 cycles, 10 Hz), including shear and tension loads as well as bending moments. Translational and angular displacements of the screws were quantified and compared between the two techniques. RESULTS: There was a slight decrease in translational (0.2 mm ± 0.09 vs. 0.24 mm ± 0.11) and angular displacements (0.06° ± 0.05 vs. 0.13° ± 0.11) of bCBT screws when compared with pCBT screws after 1'800'000 cycles. However, the results were non-significant (p > 0.05). CONCLUSION: The authors do not recommend placing CBT screws bicortically, as no relevant biomechanical advantage is gained while the potential risk for iatrogenic injury to structures anterior to the spine is increased.

Osteoarticular infections: a specific program for older patients?

BACKGROUND: With the increasing number of elderly patients, arthroplasties, fractures and diabetic foot infections, the worldwide number of osteoarticular infections (OAI) among the elderly is concomitantly expected to rise. AIMS: We explore existing scientific knowledge about OAI in the frail elderly population. METHODS: We performed a literature search linking OAIs to geriatric patients and comparing elderly patients (> 65 years) with average adults (range 18-65 years). RESULTS: In this literature, financial aspects, comparison of diverse therapies on quality of life, reimbursement policies, or specific guidelines or nursing recommendations are missing. Age itself was not an independent factor related to particular pathogens, prevention of OAI, nursing care, and outcomes of OAI. However, geriatric patients were significantly more exposed to adverse events of therapy. They had more co-morbidities and more conservative surgery for OAI. CONCLUSION: Available literature regarding OAI management among elderly patients is sparse. In recent evaluations, age itself does not seem an independent factor related to particular epidemiology, pathogens, prevention, nursing care, rehabilitation and therapeutic outcomes of OAI. Future clinical research will concern more conservative surgical indications, but certainly reduce inappropriate antibiotic use.

Reducing the kyphosis effect of anterior short thoracolumbar/lumbar scoliosis correction with an autograft fulcrum effect.

BACKGROUND: Anterior scoliosis correction is a powerful technique with the disadvantage of a kyphotic effect on lumbar and thoracolumbar curves. We aimed to investigate whether a cognizant interposition of a rib graft anteriorly and at the concave side of the scoliotic curve causes significant fulcrum effect to enforce scoliosis correction and to reduce interfusional kyphosis in anterior scoliosis corrections. METHODS: Twenty otherwise comparable patients with lumbar and thoracolumbar adolescent idiopathic scoliosis (AIS) curves undergoing anterior short scoliosis correction with (n = 10) or without (n = 10, matched for age, gender and degree of deformity) fulcrum effect were retrospectively compared by means of radiographic measurements (sagittal and coronal profile, Cobb angles and intersegmental deformity correction angles) to evaluate the effect of this modified surgical technique. RESULTS: The overall amount of scoliosis correction was similar with 74 and 60% of initial curves of 57° and 53° in the case and control group respectively with a mean of 3 fused segments (4 screws). Statistically relevant differences were found for intersegmental coronal cobb angles at the apex of 20° to 3° and 17° to 9° with and without fulcrum, respectively (p < 0.05). Creation of kyphosis in the fused segments was reduced with an interfusional kyphotic sagittal cobb angle of 15° pre-operatively vs. 3° post-operatively compared to the control group (13° pre-operatively vs. 18° post-operatively), (p < 0.05). CONCLUSIONS: Interfusional hyperkyphosis associated with anterior scoliosis correction for thoracolumbar/lumbar curves can be reduced with cognizant positioning of the bone autograft at the antero-lateral (concave) site in the intervertebral region to create a fulcrum effect. TRIAL REGISTRATION: Registered at swissethics: BASEC No.: 2018-00180 .

Hand or foot train-of-four tests and surgical site muscle relaxation assessed with multiple motor evoked potentials: A prospective observational study.

BACKGROUND: Intra-operative muscle relaxation is often required in orthopaedic surgery and the hand train-of-four (TOF) test is usually used for its quantification. However, even though full muscle relaxation is claimed by anaesthesiologists based on a TOF count of zero, surgeons observe residual muscle activity. OBJECTIVE: The aim of the study was to assess if hand or foot TOF adequately represents intra-operative muscle relaxation compared with multiple motor evoked potentials. DESIGN: Prospective observational study. SETTING: A single-centre study performed between February 2016 and December 2018 at the Balgrist University Hospital, Zurich, Switzerland. PATIENTS: Twenty patients scheduled for elective lumbar spinal fusion were prospectively enrolled in this study after giving written informed consent. INTERVENTIONS: To assess neuromuscular blockade (NMB) with the intermediate duration nondepolarising neuromuscular blocking agent rocuronium, hand TOF (adductor pollicis) and foot TOF (flexor hallucis brevis) monitoring, and muscle motor evoked potentials (MMEPs) from the upper and lower extremities were assessed prior to surgery under general anaesthesia. Following baseline measurements, muscle relaxation was performed with rocuronium until the spinal surgeon observed sufficient relaxation for surgical intervention. At this timepoint, NMB was assessed by TOF and MMEP. MAIN OUTCOME MEASURES: The primary outcome was to determine the different effect of rocuronium on muscle relaxation comparing hand and foot TOF with the paraspinal musculature assessed by MMEP. RESULTS: Hand TOF was more resistant to NMB and had a shorter recovery time than foot TOF. When comparing MMEPs, muscle relaxation occurred first in the hip abductors, and the paraspinal and deltoid muscles. The most resistant muscle to NMB was the abductor digiti minimi. Direct comparison showed that repetitive MMEPs simultaneously recorded from various muscles at the upper and lower extremities and from paraspinal muscles reflect muscle relaxation similar to TOF testing. CONCLUSION: Hand TOF is superior to foot TOF in assessing muscle relaxation during spinal surgery. Hand TOF adequately represents the degree of muscle relaxation not only for the paraspinal muscles but also for all orthopaedic surgical sites where NMB is crucial for good surgical conditions. TRIAL REGISTRATION: ClinicalTrials.gov (NCT03318718).

No benefit of early versus late ambulation after incidental durotomy in lumbar spine surgery: a randomized controlled trial.

PURPOSE: Incidental durotomy (ID) is a complication occurring in 4-17% of decompressive spinal surgeries. Persisting CSF leakage can occur even after ID repair and requires revision surgery. Prolonged flat bed rest (BR) to reduce the incidence of persisting CSF leakage is frequently applied but highly debated. A randomized controlled trial comparing prolonged BR versus early ambulation after ID repair is lacking. The aim of this study was to investigate the incidence of revision surgery as a result of persistent cerebro-spinal fluid (CSF) leakage and medical complications after immediate or late post-operative ambulation following ID during decompressive spinal surgery. METHODS: Ninety-four of 1429 consecutive cases undergoing lumbar spine surgery (6.58%) were complicated by an ID. Sixty patients (mean age of 64 ± 13.28 years) were randomized to either early post-operative ambulation (EA, n = 30) or flat BR for 48 h (BR, n = 30). The incidence of CSF leakage resulting in revision surgery, medical complications and duration of hospitalization were compared between groups. RESULTS: Two patients in the BR group and two patients in the EA group underwent revision surgery as a result of persisting CSF leakage. Four patients in the BR group experienced medical complications associated with prolonged immobilization. The duration of hospitalization was 7.25 ± 3.0 days in the BR group versus 6.56 ± 2.64 days in the EA group, p = 0.413. CONCLUSION: The results of this study indicate no benefit of prolonged BR after an adequately repaired ID in lumbar spine surgery. LEVEL OF EVIDENCE: Level 1b (individual randomized controlled trial). These slides can be retrieved under Electronic Supplementary Material.

Clinical and structural outcome 20 years after repair of massive rotator cuff tears.

BACKGROUND: Short- and mid-term outcomes after massive cuff tear repair are well reported, but there is no documentation of the clinical and structural outcomes at 20 years of follow-up. The hypothesis of the present study was that at 20 years, deterioration of the shoulder would have occurred and led to a substantial number of reoperations. METHODS: The authors retrospectively recalled all 127 patients operated for massive rotator cuff tears in 1994 at 6 different centers. At the 20-year follow-up, 26 patients died and 35 were lost to follow-up. Thirteen (10.2%) had been reoperated. This left 53 patients for personal clinical assessment. Forty-nine consented to standardized radiographic evaluation for assessment of osteoarthritis, 36 patients underwent magnetic resonance imaging, allowing assessment of tendon healing, atrophy, and fatty infiltration (FI) of the cuff muscles. RESULTS: The final Constant-Murley score (CS) was 68 ± 17.7 (range, 8-91) vs. 44 ± 15.3 (range, 13-74) preoperatively (P < .05). The final Subjective Shoulder Value (SSV) was 73% ± 23% (range, 0-100). Retears (Sugaya IV and V) were found in 17 cases (47%). Nine patients (17%) had cuff tear arthropathy (Hamada stage 4). The CS and SSV for the shoulders with FI stages III or IV were significantly inferior (53 ± 19 points and 65% ± 14% respectively) than for those with FI stages 0-II (respectively, 71.6 ± 6 points and 73% ± 4%) (P < .05). CONCLUSIONS: Twenty years after surgical repair of massive rotator cuff tears, the functional scores remain satisfactory, and the rate of revision is low.

Clinical and structural outcome twenty years after repair of isolated supraspinatus tendon tears.

BACKGROUND: This study evaluated the clinical and structural outcome 20 years after repair of isolated supraspinatus tendon tears. We hypothesized that the results would deteriorate over time. MATERIALS AND METHODS: For this retrospective multicenter study, 137 patients were recalled for a clinical and imaging assessment. Six patients (4.3%) had died from unrelated causes, 52 (38.0%) were lost to follow-up, and 13 (9.5%) had undergone reoperations. This left 66 patients for clinical evaluation. Radiographs and magnetic resonance imaging were additionally performed for 45 patients, allowing assessment of osteoarthritis, tendon healing, fatty infiltration (FI), and muscle atrophy. RESULTS: The Constant Score (CS) improved from 51.5 ± 14.1 points preoperatively to 71 points (P < .05) with a mean Subjective Shoulder Value (SSV) of 77.2% ± 22%. Tendon discontinuity (Sugaya IV-V) was present in 19 of 45 patients (42 %), and there was advanced FI (Goutallier III-IV) of the supraspinatus in 12 (27%) and of the infraspinatus muscle in 16 (35%). Supraspinatus atrophy was present in 12 patients (28%), advanced arthritis in 6, and cuff tear arthropathy in 12 (30%). The CS and SSV were significantly inferior for shoulders with FI of stages III to IV (P < .05). The CS was lower in cuff tear arthropathy and correlated with infraspinatus FI. CONCLUSIONS: At 20 years after surgical repair of isolated supraspinatus tears, the clinical outcome remains significantly above the preoperative state. FI of the infraspinatus is the most influential factor on long-term clinical outcome.

Texture analysis of paraspinal musculature in MRI of the lumbar spine: analysis of the lumbar stenosis outcome study (LSOS) data.

OBJECTIVE: To evaluate association of fatty infiltration in paraspinal musculature with clinical outcomes in patients suffering from lumbar spinal stenosis (LSS) using qualitative and quantitative grading in magnetic resonance imaging (MRI). MATERIALS AND METHODS: In this retrospective study, texture analysis (TA) was performed on postprocessed axial T2 weighted (w) MR images at level L3/4 using dedicated software (MaZda) in 62 patients with LSS. Associations in fatty infiltration between qualitative Goutallier and quantitative TA findings with two clinical outcome measures, Spinal stenosis measure (SSM) score and walking distance, at baseline and regarding change over time were assessed using machine learning algorithms and multiple logistic regression models. RESULTS: Quantitative assessment of fatty infiltration using the histogram TA feature "mean" showed higher interreader reliability (ICC 0.83-0.97) compared to the Goutallier staging (κ = 0.69-0.93). No correlation between Goutallier staging and clinical outcome measures was observed. Among 151 TA features, only TA feature "mean" of the spinotransverse group showed a significant but weak correlation with worsened SSM (p = 0.046). TA feature "S(3,3) entropy" showed a significant but weak association with worsened WD over 12 months (p = 0.046). CONCLUSION: MR TA is a reproducible tool to quantitatively assess paraspinal fatty infiltration, but there is no clear association with the clinical outcome in asymptomatic LSS patients.

Arthroscopic Correction of the Critical Shoulder Angle Through Lateral Acromioplasty: A Safe Adjunct to Rotator Cuff Repair.

PURPOSE: To investigate whether arthroscopic lateral acromioplasty reliably decreases the critical shoulder angle (CSA) and whether it is associated with damage to the deltoid or other complications. METHODS: Patients undergoing arthroscopic rotator cuff repair (RCR) with lateral but without anterior acromioplasty for degenerative, full-thickness rotator cuff tears and a CSA of 34° or greater were retrospectively reviewed. Patients with traumatic or irreparable rotator cuff tears, osteoarthritis, or previous surgery were excluded. Clinical and radiographic outcomes were assessed at a minimum of 12 months' follow-up. RESULTS: We reviewed 49 consecutive patients (mean age, 56 years; age range, 39-76 years) at a mean of 30 months (range, 12-47 months). There were 7 RCR failures (14%). The mean CSA was reduced from 37.5° preoperatively (95% confidence interval [CI], 36.7°-38.3°) to 33.9° postoperatively (95% CI, 33.3°-34.6°; P < .001). There were no cases of dehiscence, increases in fatty infiltration, or significant atrophy of the deltoid. Scarring at the deltoid origin was noted in 18 patients (37%). The mean absolute and relative Constant scores increased from 59 points (95% CI, 54-64 points) to 74 points (95% CI, 70-78 points) and from 66% (95% CI, 61%-71%) to 83% (95% CI, 79%-87%) respectively, and the Subjective Shoulder Value increased from 45% (95% CI, 39%-50%) to 80% (95% CI, 74%-86%) (P < .001 for all 3 improvements). The postoperative CSA was significantly larger in failed than in healed repairs (P = .026). Patients with a healed RCR and a CSA corrected to 33° or less (n = 22) had 25% more abduction strength than patients with a healed cuff and a CSA corrected to 35° or greater (n = 14, P = .04). CONCLUSIONS: Arthroscopic lateral acromioplasty performed in addition to arthroscopic RCR can reduce the CSA without significantly compromising the deltoid origin, deltoid muscle, or function. It is not associated with any additional complications of arthroscopic RCR. Insufficiently corrected, abnormally large CSAs are associated either with a higher retear rate or with inferior strength of abduction if the tears heal. LEVEL OF EVIDENCE: Level IV, case series, treatment study.

Wage and Employment Growth in America's Drug Epidemic: Is All Growth Created Equal?

The rise in drug overdose deaths in the United States since the turn of the millennium has been extraordinary. A popular narrative paints a picture whereby opioid overdoses among white, male, less-educated, rural workers have been caused by reduced economic opportunities borne by such people. In this article, we causally test the validity of this theory by using Bartik-type variables to explore the relationship between local economic conditions and county opioid overdose death rates. We add to the literature by exploring how both employment and wage growth in different types of industries are related to opioid overdose deaths for the population as a whole, as well as for rural (vs. urban), male (vs. female) and white (vs. black) populations. We find mixed evidence. Our results confirm that wage and employment growth in industries more likely to employ low-skill workers are important protective factors for rural, white males. However, we also find evidence that economic improvements in low-skill industries are just as important in protecting blacks and women against opioid overdoses, and for workers in metro counties. We also find evidence that employment growth in high-paying industries has led to increases in opioid overdoes rates.

Reliability of postoperative MR imaging in the determination of level and side of lumbar spinal decompression surgery.

Background Magnetic resonance imaging (MRI) is the diagnostic modality of choice in defining soft tissue compromise of the spinal canal. Purpose To evaluate the reliability of postoperative MRI in the determination of level and side of lumbar spinal decompression surgery, investigated by two reviewers, in different levels of training and specialization. Material and Methods Postoperative MR images of 86 patients who underwent spinal decompression (single level, n = 70; multilevel, n = 16; revision decompression, n = 9) were reviewed independently by an experienced musculoskeletal radiologist and a fourth-year orthopedic surgery resident. The level (single or multiple) and side of previous surgical decompression were determined and compared to the surgical notes. We examined factors that may have influenced the reliability, including demographics, type of surgical decompression, use of a drain, and time interval from surgery to MRI. Results Significantly fewer levels were correctly determined by the resident (77/86 cases, 89.5%) compared with the radiologist (84/86 cases, 97.7%) ( P = 0.014). The resident interpreted significantly more MR images incorrectly in cases where a drain was used (n = 8; P < 0.001). Re-decompression cases were interpreted incorrectly significantly more often by both the radiologist (n = 2, P = 0.032) and the resident (n = 4, P = 0.014). Conclusion Determination of the level and side operated on in previous lumbar spinal decompression surgery on MRI has a high reliability, especially when performed by a musculoskeletal radiologist. However, this reliability is decreased in cases involving surgical drainage and same-level revision surgery.

Accuracy of patient-specific template-guided vs. free-hand fluoroscopically controlled pedicle screw placement in the thoracic and lumbar spine: a randomized cadaveric study.

PURPOSE: Dorsal spinal instrumentation with pedicle screw constructs is considered the gold standard for numerous spinal pathologies. Screw misplacement is biomechanically disadvantageous and may create severe complications. The aim of this study was to assess the accuracy of patient-specific template-guided pedicle screw placement in the thoracic and lumbar spine compared to the free-hand technique with fluoroscopy. METHODS: Patient-specific targeting guides were used for pedicle screw placement from Th2-L5 in three cadaveric specimens by three surgeons with different experience levels. Instrumentation for each side and level was randomized (template-guided vs. free-hand). Accuracy was assessed by computed tomography (CT), considering perforations of <2 mm as acceptable (safe zone). Time efficiency, radiation exposure and dependencies on surgical experience were compared between the two techniques. RESULTS: 96 screws were inserted with an equal distribution of 48 screws (50 %) in each group. 58 % (n = 28) of template-guided (without fluoroscopy) vs. 44 % (n = 21) of free-hand screws (with fluoroscopy) were fully contained within the pedicle (p = 0.153). 97.9 % (n = 47) of template-guided vs. 81.3 % (n = 39) of free-hand screws were within the 2 mm safe zone (p = 0.008). The mean time for instrumentation per level was 01:14 ± 00:37 for the template-guided vs. 01:40 ± 00:59 min for the free-hand technique (p = 0.013), respectively. Increased radiation exposure was highly associated with lesser experience of the surgeon with the free-hand technique. CONCLUSIONS: In a cadaver model, template-guided pedicle screw placement is faster considering intraoperative instrumentation time, has a higher accuracy particularly in the thoracic spine and creates less intraoperative radiation exposure compared to the free-hand technique.

Thermodynamic signatures of fragment binding: Validation of direct versus displacement ITC titrations.

BACKGROUND: Detailed characterization of the thermodynamic signature of weak binding fragments to proteins is essential to support the decision making process which fragments to take further for the hit-to-lead optimization. METHOD: Isothermal titration calorimetry (ITC) is the method of choice to record thermodynamic data, however, weak binding ligands such as fragments require the development of meaningful and reliable measuring protocols as usually sigmoidal titration curves are hardly possible to record due to limited solubility. RESULTS: Fragments can be titrated either directly under low c-value conditions (no sigmoidal curve) or indirectly by use of a strong binding ligand displacing the pre-incubated weak fragment from the protein. The determination of Gibbs free energy is reliable and rather independent of the applied titration protocol. CONCLUSION: Even though the displacement method achieves higher accuracy, the obtained enthalpy-entropy profile depends on the properties of the used displacement ligand. The relative enthalpy differences across different displacement experiments reveal a constant signature and can serve as a thermodynamic fingerprint for fragments. Low c-value titrations are only reliable if the final concentration of the fragment in the sample cell exceeds 2-10 fold its K(D) value. Limited solubility often prevents this strategy. GENERAL SIGNIFICANCE: The present study suggests an applicable protocol to characterize the thermodynamic signature of protein-fragment binding. It shows however, that such measurements are limited by protein and fragment solubility. Deviating profiles obtained by use of different displacement ligands indicate that changes in the solvation pattern and protein dynamics most likely take influence on the resulting overall binding signature.

Impact of Surface Water Layers on Protein--Ligand Binding: How Well Are Experimental Data Reproduced by Molecular Dynamics Simulations in a Thermolysin Test Case?

Drug binding involves changes of the local water structure around proteins including water rearrangements across surface-solvation layers around protein and ligand portions exposed to the newly formed complex surface. For a series of thermolysin-binding phosphonamidates, we discovered that variations of the partly exposed P2'-substituents modulate binding affinity up to 10 kJ mol(-1) with even larger enthalpy/entropy partitioning of the binding signature. The observed profiles cannot be completely explained by desolvation effects. Instead, the quality and completeness of the surface water network wrapping around the formed complexes provide an explanation for the observed structure-activity relationship. We used molecular dynamics to compute surface water networks and predict solvation sites around the complexes. A fairly good correspondence with experimental difference electron densities in high-resolution crystal structures is achieved; in detail some problems with the potentials were discovered. Charge-assisted contacts to waters appeared as exaggerated by AMBER, and stabilizing contributions of water-to-methyl contacts were underestimated.

Replacement of water molecules in a phosphate binding site by furanoside-appended lin-benzoguanine ligands of tRNA-guanine transglycosylase (TGT).

The enzyme tRNA-guanine transglycosylase has been identified as a drug target for the foodborne illness shigellosis. A key challenge in structure-based design for this enzyme is the filling of the polar ribose-34 pocket. Herein, we describe a novel series of ligands consisting of furanoside-appended lin-benzoguanines. They were designed to replace a conserved water cluster and differ by the functional groups at C(2) and C(3) of the furanosyl moiety being either OH or OMe. The unfavorable desolvation of Asp102 and Asp280, which are located close to the ribose-34 pocket, had a significant impact on binding affinity. While the enzyme has tRNA as its natural substrate, X-ray co-crystal structures revealed that the furanosyl moieties of the ligands are not accommodated in the tRNA ribose-34 site, but at the location of the adjacent phosphate group. A remarkable similarity of the position of the oxygen atoms in these two structures suggests furanosides as a potential phosphate isoster.

Increased risk of joint failure in hip prostheses infected with Staphylococcus aureus treated with debridement, antibiotics and implant retention compared to Streptococcus.

PURPOSE: The debridement, antibiotic and implant retention (DAIR) procedure is an option for patients with prosthetic hip joint infections for whom arthroplasty removal is problematic. Unfortunately, some of the guidelines proposed for deciding on DAIR management of arthroplasty infections fail to take into consideration the role of the infecting pathogen. While Staphylococcus aureus and streptococci are major contributors to infected hip arthroplasties, their respective contributions to treatment success or failure rates with the DAIR procedure have not been thoroughly analysed from a microbiological perspective. METHODS: This retrospective study included all patients who were hospitalised in Geneva University Hospitals between 1996 and 2012 and were initially treated with DAIR for prosthetic hip joint monomicrobial infection due to S. aureus or Streptococcus spp. The outcome of DAIR treatment was evaluated after a minimal follow-up of two years. A literature search was also performed to retrieve data from additional DAIR-treated cases in other institutions. RESULTS: In our institution, 38 DAIR-treated patients with hip arthroplasty monomicrobial infections underwent at least one surgical debridement (median two, range one to five), exchange of mobile parts and concomitant targeted antibiotic therapy for several weeks or months. A literature search identified outcome data in other institutions from 52 additional DAIR-treated cases according to our study criteria. After merging our own data with those retrieved from other reports, we found a failure rate of 21 % instead of 24 % for S. aureus-infected, DAIR-treated patients, but no failure in 14 streptococcal-infected patients. In the pooled data, the failure rate linked with S. aureus infections was significantly higher than that with Streptococcus ssp. (19/90 vs 0/14 episodes; Fisher's exact test, P = 0.07). CONCLUSIONS: DAIR-treated patients with prosthetic hip joint infections due to S. aureus tended to have worse outcomes than those infected with Streptococcus spp. The specific influence of the infecting pathogen should be considered in future guidelines and recommendations.

Identification of a novel polyfluorinated compound as a lead to inhibit the human enzymes aldose reductase and AKR1B10: structure determination of both ternary complexes and implications for drug design.

Aldo-keto reductases (AKRs) are mostly monomeric enzymes which fold into a highly conserved (α/ß)8 barrel, while their substrate specificity and inhibitor selectivity are determined by interaction with residues located in three highly variable external loops. The closely related human enzymes aldose reductase (AR or AKR1B1) and AKR1B10 are of biomedical interest because of their involvement in secondary diabetic complications (AR) and in cancer, e.g. hepatocellular carcinoma and smoking-related lung cancer (AKR1B10). After characterization of the IC50 values of both AKRs with a series of polyhalogenated compounds, 2,2',3,3',5,5',6,6'-octafluoro-4,4'-biphenyldiol (JF0064) was identified as a lead inhibitor of both enzymes with a new scaffold (a 1,1'-biphenyl-4,4'-diol). An ultrahigh-resolution X-ray structure of the AR-NADP(+)-JF0064 complex has been determined at 0.85 Šresolution, allowing it to be observed that JF0064 interacts with the catalytic residue Tyr48 through a negatively charged hydroxyl group (i.e. the acidic phenol). The non-competitive inhibition pattern observed for JF0064 with both enzymes suggests that this acidic hydroxyl group is also present in the case of AKR1B10. Moreover, the combination of surface lysine methylation and the introduction of K125R and V301L mutations enabled the determination of the X-ray crystallographic structure of the corresponding AKR1B10-NADP(+)-JF0064 complex. Comparison of the two structures has unveiled some important hints for subsequent structure-based drug-design efforts.