Simulated Weightbearing and Articular Injury From Transarticular Screws in a Ligamentous Lisfranc Injury Model.

BACKGROUND: Transarticular screw fixation is a common surgical treatment for tarsometatarsal ligamentous (Lisfranc) injuries. Iatrogenic damage to articular cartilage from screw placement, however, has been thought to potentially lead to increased risk of tarsometatarsal (TMT) joint arthritis after initial injury. To date, no study has evaluated the effect of weightbearing on articular cartilage after screw fixation. The aim of this study was to create a Lisfranc injury and quantify and compare articular damage due to screw fixation before and after simulated weightbearing. METHODS: A ligamentous Lisfranc injury was created in 10 cadaveric specimens and treated with transarticular screws. Specimens were cycled for 1000 cycles at 250 N to simulate 2 weeks of physiologic weightbearing. Rotation and diastasis across the Lisfranc complex were measured. Articular injury as a percentage of total articular surface was measured using digital imaging of the first and second TMT joint before and after simulated weightbearing. Comparisons between articular damage were made and statistical analysis was performed. RESULTS: Simulated partial weightbearing increased articular injury 1.44-fold (P < .001). The second metatarsal (M2) showed the greatest increase (1.54-fold, P = .0047), whereas the first (M1) showed the least (1.35-fold, P = .0083). Increases seen at the medial (1.43-fold, P = .0387) and middle cuneiform (1.44-fold, P = .0292) were intermediate between the values seen at M2 and M1. CONCLUSION: Articular damage from transarticular screw fixation significantly increased after simulated partial weightbearing. This may increase the risk of arthritis and future morbidity when using transarticular screws for the treatment of ligamentous Lisfranc injuries. CLINICAL RELEVANCE: Iatrogenic damage to articular cartilage due to screw fixation of ligamentous Lisfranc injuries may be increased with weightbearing.

The Arthroscopic Surgery Skill Evaluation Tool Global Rating Scale is a Valid and Reliable Adjunct Measure of Performance on a Virtual Reality Simulator for Hip Arthroscopy.

PURPOSE: The purpose of this study is to further evaluate the construct validity and interobserver reliability of a hip arthroscopy virtual simulator using the Arthroscopic Surgery Skill Evaluation Tool (ASSET) global rating scale. METHODS: Thirty participants (23 male/7 female) completed a diagnostic arthroscopy and a loose body retrieval simulation on the VirtaMed Arthros Hip Simulator (Zurich, Switzerland) twice at a minimum of 1 week apart. Subjects consisted of 12 novices (medical students, postgraduate year [PGY] 1-2), 5 intermediate trainees (PGY3-4), 9 senior trainees (PGY5 and fellows), and 4 attending faculty. Simulator metrics were recorded and then compiled to generate a total simulator score (TSS). The loose body retrieval was graded using the ASSET scoring tool. Inter-rater and intrarater reliability for the ASSET for 2 blinded raters and construct validity of the ASSET and the TSS were calculated. Correlation between the TSS, ASSET and individual simulator metrics was determined. RESULTS: Prior simulation experience (P ≤ 0.01) correlated with higher TSS and higher ASSET, while video game experience correlated with higher TSS on the diagnostic module only (P = 0.004). There was a significant difference in ASSET score among all experience groups (P < 0.04). Novices had the lowest mean ASSET whereas experts had the highest mean ASSET with a difference of 17.4 points. Overall performance on the surgical module significantly correlated with the ASSET score (r = 0.444, P = 0.016). There was a significant positive correlation among higher ASSET and number of loose bodies retrieved, operation time, camera path and grasper path length, and percentage of cartilage injury. ASSET demonstrated excellent intrarater reliability and showed substantial or better inter-reliability in 8 of 9 domains. CONCLUSION: The VirtaMed hip arthroscopy simulator demonstrated good construct validity and excellent reliability for simulator-based metrics and ASSET score. Use of both simulator metrics and ASSET offers a more comprehensive performance assessment on hip arthroscopy simulation than either measure alone. CLINICAL RELEVANCE: As virtual reality simulation for arthroscopy becomes more commonplace in orthopaedic training, evaluation of the most effective objective and subjective measures of performance is necessary to optimize simulation training.

Depletion of WRN enhances DNA damage in HeLa cells exposed to the benzene metabolite, hydroquinone.

Werner syndrome is a progeroid disorder caused by mutations of the WRN gene. The encoded WRN protein belongs to the family of RecQ helicases that plays a role in the maintenance of genomic stability. Single nucleotide polymorphisms in WRN have been associated with an increased risk for some cancers and were recently linked to benzene hematotoxicity. To further address the role of WRN in benzene toxicity, we employed RNA interference (RNAi) to silence endogenous WRN in HeLa cells and examined the susceptibility of these WRN-depleted cells to the toxic effects of the benzene metabolite hydroquinone. HeLa cells were used as the experimental model because RNAi is highly effective in this system producing almost complete depletion of the target protein. Depletion of WRN led to a decrease in cell proliferation and an enhanced susceptibility to hydroquinone cytotoxicity as revealed by an increase in necrosis. WRN-depleted HeLa cells treated with hydroquinone also displayed an increase in the amount of DNA double-strand breaks as determined by the Comet assay, and an elevated DNA damage response as indicated by the sevenfold induction of gammaH2AX and acetyl-p53 (Lys373 and Lys382) over control levels. Together, these results show that WRN plays an important role in the protection of HeLa cells against the toxicity of the benzene metabolite hydroquinone, specifically in mounting a normal DNA damage response following the induction of DNA double-strand breaks. Further studies in bone marrow-derived stem or progenitor cells are required to confirm our findings in HeLa cells and expand our ability to extrapolate the results to benzene toxicity in humans.