More anatomic tunnel placement for anterior cruciate ligament reconstruction by surgeons with high volume compared to low volume.

PURPOSE: Correct placement of the femoral and tibial tunnels in the anatomic footprint during anterior cruciate ligament reconstruction (ACLR) is paramount for restoring rotatory knee stability. Recent studies have looked at surgeon volume and its outcomes on procedures such as total knee arthroplasty and infection rates, but only few studies have specifically examined tunnel placement after ACLR based on surgeon volume. The purpose of this study was to compare the placement of femoral and tibial tunnels during ACLR between high-volume and low-volume surgeons. It was hypothesized that high-volume surgeons would have more anatomic tunnel placement compared with low-volume surgeons. METHODS: A retrospective review of all ACLR performed between 2015 and 2019 at an integrated health care system consisting of both academic and community hospitals with 68 orthopaedic surgeons was conducted. Surgeon volume was categorized as less than 35 ACLR per year (low volume) and 35 or more ACLR per year (high volume). Femoral tunnel placement for each patient was determined using an exact strict lateral radiograph (less than 6 mm of offset between the posterior halves of the medial and lateral condyles) taken after the primary ACLR using the quadrant method. The centre of the femoral tunnel was measured in relation to the posterior-anterior (PA) and proximal-distal (PD) dimensions (normal centre of anatomic footprint: PA 25% and PD 29%). Tibial tunnel placement for each patient was determined on the same lateral radiographs by measuring the mid-sagittal tibial diameter and the centre of the tibial attachment area of the ACL from the anterior tibial margin (normal centre of anatomic footprint: 43%). Each lateral radiograph was reviewed by one of two blinded reviewers. RESULTS: A total of 4500 patients were reviewed, of which 645 patients met all the inclusion/exclusion criteria and were included in the final analysis. There were 228 patients in the low-volume group and 417 patients in the high-volume group. Low-volume surgeons performed a mean of 5 ACLRs per year, whereas surgeons in the high-volume group performed a mean of 40 ACLRs per year. In the PA dimension, the low-volume group had significantly more anterior femoral tunnel placement compared with the high-volume group (32 ± 10% vs 28 ± 9%, p < 0.01). In the PD dimension, the low-volume group had statistically significant more proximal femoral tunnel placement compared to the high-volume group (32 ± 9% vs 35 ± 9%, p < 0.01). For the tibial tunnel, the low-volume group had significantly more posterior tibial tunnel placement compared with the high-volume group (41 ± 10% vs 38 ± 7%, p < 0.01). CONCLUSION: Low-volume surgeons placed their femoral tunnels significantly more anterior and proximal (high) during ACLR, and placed their tibial tunnels significantly more posterior, compared with high-volume surgeons. Prior research has indicated that anatomic placement of the femoral and tibial tunnels during ACLR leads to improved rotatory knee stability. The findings of this study demonstrate the importance of surgical volume and experience during ACLR. LEVEL OF EVIDENCE: III.

Prevalence, severity, and neurosurgical management of abusive head trauma during the COVID-19 pandemic.

OBJECTIVE: Reports published during the severe acute respiratory syndrome coronavirus 2 (Sars-CoV-2) pandemic suggest that hospitals potentially experienced an increased incidence in the presentation of abusive head trauma (AHT) in children; however, it remains unknown if the pandemic influenced the severity or need for neurosurgical intervention during this time. METHODS: This study is a post hoc analysis of a prospectively collected database of pediatric patients who sustained traumatic head injuries from 2018 to 2021 and were treated at the Children's Hospital of Pittsburgh that was screened for concern of AHT at the time of presentation. Pairwise univariate analysis of AHT prevalence, Glasgow Coma Scale (GCS) score, intracranial pathology, and neurosurgical interventions was performed to investigate differences before, during, and after the initial lockdown in Pennsylvania, which was defined as March 23, 2020, to August 26, 2020. RESULTS: Of 2181 pediatric patients who presented with head trauma, 263 (12.1%) with AHT were identified. Prevalence of AHT did not differ during (12.4% before vs 10.0% during, p = 0.31) or following (12.2% after, p = 0.92) lockdown. Need for neurosurgery after AHT remained unchanged during lockdown (10.7% before vs 8.3% during, p = 0.72) and after (10.5% after, p = 0.97). Patients did not differ in terms of sex, age, or race between periods. Average GCS score was lower after lockdown (13.9 before vs 11.9 after, p = 0.008) but not during (12.3, p = 0.062). In this cohort, mortality associated with AHT was 4.8 times higher during lockdown (4.3% before vs 20.8% during, p = 0.002) and returned to pre-lockdown rates thereafter (7.8%, p = 0.27). The primary contributor to mortality was ischemic brain injury (5% before vs 20.8% during, p = 0.005). Patients were 5.5 times more likely to undergo decompressive hemicraniectomy in the months after lockdown compared with prior (1.2% vs 6.6%, p = 0.035). CONCLUSIONS: The authors have presented the findings of the first study to examine the prevalence and neurosurgical management of AHT during the Sars-Cov-2 lockdown in Pennsylvania. The overall prevalence of AHT was not affected by lockdown; however, patients were more likely to experience mortality or traumatic ischemia during lockdown. The GCS score of AHT patients was significantly lower, and these patients were more likely to require decompressive hemicraniectomy after the initial lockdown period.

Cranial subdural migrating to lumbar subdural space in a toddler.

Migrated spinal subdural haematoma (sSDH) is a significantly uncommon finding. This case involves a paediatric patient representing after cranial trauma with new abnormal gait and leg pain who was found to have a migrated sSDH. Literature review for reported cases of pathogenesis theories, causes and management was performed and summarised in this report. The authors concluded that new abnormal gait and leg pain in a paediatric patient with previous cranial trauma is an indication for spinal MRI if migrated subdural haematoma is suspected. Non-surgical management is generally tolerated, and steroids can be trialled for radiculopathy if clinically indicated.

Quantification of reactive oxygen species production by the red fluorescent proteins KillerRed, SuperNova and mCherry.

Fluorescent proteins can generate reactive oxygen species (ROS) upon absorption of photons via type I and II photosensitization mechanisms. The red fluorescent proteins KillerRed and SuperNova are phototoxic proteins engineered to generate ROS and are used in a variety of biological applications. However, their relative quantum yields and rates of ROS production are unclear, which has limited the interpretation of their effects when used in biological systems. We cloned and purified KillerRed, SuperNova, and mCherry - a related red fluorescent protein not typically considered a photosensitizer - and measured the superoxide (O2•-) and singlet oxygen (1O2) quantum yields with irradiation at 561 nm. The formation of the O2•--specific product 2-hydroxyethidium (2-OHE+) was quantified via HPLC separation with fluorescence detection. Relative to a reference photosensitizer, Rose Bengal, the O2•- quantum yield (ΦO2•-) of SuperNova was determined to be 1.5 × 10-3, KillerRed was 0.97 × 10-3, and mCherry 1.2 × 10-3. At an excitation fluence of 916.5 J/cm2 and matched absorption at 561 nm, SuperNova, KillerRed and mCherry made 3.81, 2.38 and 1.65 µM O2•-/min, respectively. Using the probe Singlet Oxygen Sensor Green (SOSG), we ascertained the 1O2 quantum yield (Φ1O2) for SuperNova to be 22.0 × 10-3, KillerRed 7.6 × 10-3, and mCherry 5.7 × 10-3. These photosensitization characteristics of SuperNova, KillerRed and mCherry improve our understanding of fluorescent proteins and are pertinent for refining their use as tools to advance our knowledge of redox biology.

Mitochondrial Reactive Oxygen Species Generated at the Complex-II Matrix or Intermembrane Space Microdomain Have Distinct Effects on Redox Signaling and Stress Sensitivity in Caenorhabditis elegans.

Aims: How mitochondrial reactive oxygen species (ROS) impact physiological function may depend on the quantity of ROS generated or removed, and the subcellular microdomain in which this occurs. However, pharmacological tools currently available to alter ROS production in vivo lack precise spatial and temporal control. Results: We used CRISPR/Cas9 to fuse the light-sensitive ROS-generating protein, SuperNova to the C-terminus of mitochondrial complex II succinate dehydrogenase subunits B (SDHB-1::SuperNova) and C (SDHC-1::SuperNova) in Caenorhabditis elegans to localize SuperNova to the matrix-side of the inner mitochondrial membrane, and to the intermembrane space (IMS), respectively. The presence of the SuperNova protein did not impact complex II activity, mitochondrial respiration, or C. elegans development rate under dark conditions. ROS production by SuperNova protein in vitro in the form of superoxide (O2˙-) was both specific and proportional to total light irradiance in the 540-590 nm spectra, and was unaffected by varying the buffer pH to resemble the mitochondrial matrix or IMS environments. We then determined using SuperNova whether stoichiometric ROS generation in the mitochondrial matrix or IMS had distinct effects on redox signaling in vivo. Phosphorylation of PMK-1 (a p38 MAPK homolog) and transcriptional activity of SKN-1 (an Nrf2 homolog) were each dependent on both the site and duration of ROS production, with matrix-generated ROS having more prominent effects. Furthermore, matrix- but not IMS-generated ROS attenuated susceptibility to simulated ischemia reperfusion injury in C. elegans. Innovation and Conclusion: Overall, these data demonstrate that the physiological output of ROS depends on the microdomain in which it is produced. Antioxid. Redox Signal. 31, 594-607.