Dual Incision Research Articles

Molecular architecture and functional dynamics of the pre-incision complex in nucleotide excision repair

Nucleotide excision repair (NER) is vital for genome integrity. Yet, our understanding of the complex NER protein machinery remains incomplete. Combining cryo-EM and XL-MS data with AlphaFold2 predictions, we build an integrative model of the NER pre-incision complex(PInC). Here TFIIH serves as a molecular ruler, defining the DNA bubble size and precisely positioning the XPG and XPF nucleases for incision. Using simulations and graph theoretical analyses, we unveil PInC’s assembly, global motions, and partitioning into dynamic communities. Remarkably, XPG caps XPD’s DNA-binding groove and bridges both junctions of the DNA bubble, suggesting a novel coordination mechanism of PInC’s dual incision. XPA rigging interlaces XPF/ERCC1 with RPA, XPD, XPB, and 5′ ssDNA, exposing XPA’s crucial role in licensing the XPF/ERCC1 incision. Mapping disease mutations onto our models reveals clustering into distinct mechanistic classes, elucidating xeroderma pigmentosum and Cockayne syndrome disease etiology.

Compartment Syndrome in Association with Tibial Plateau Fracture: Standardized Protocols Ensure Optimal Outcomes.

The purpose of this study was to report on the treatment, results, and longer-term outcomes of patients who sustained a tibial plateau fracture with an associated leg compartment syndrome (CS). A total of 766 patients who sustained 766 tibial plateau fractures met inclusion criteria. Fourteen patients (1.8%) were diagnosed with CS in association with a tibial plateau fracture during their initial hospitalization, 13 at the time of presentation and 1 delayed. The treatment protocol consisted of initial external fixation and fasciotomy, followed by irrigation and debridement, and eventual closure. Fasciotomy cases included 2/14 (14.3%) single incision approaches and 12/14 (85.7%) dual incision approaches. Operative treatment of the tibial plateau fracture was performed at the time of final closure or once soft tissues were permitted. One case of CS that developed following definitive fixation was treated with fasciotomy and delayed primary closure after initial stabilization. Ten (71.4%) were available at 1-year follow-up. We compared these 10 cases to the patients with operative tibial plateau fractures without CS to assess for surgical, radiographic, clinical, and functional outcomes. We used a propensity match based on age, body mass index, sex, Charleson comorbidity index, and fracture type to reduce the presence of confounding biases. Standard statistical methods were employed. Those in the CS cohort were younger males (p < 0.05). At latest follow-up, function did not differ between those in the CS group compared with the non-CS cohort (p > 0.05). Clinically, knee flexion (130.7 vs. 126; p = 0.548), residual depression (0.5 vs. 0.2; p = 0.365), knee alignment (87.7 vs. 88.3; p = 0.470), and visual analog scale pain scores (3.0 vs. 2.4; p = 0.763) did not differ between the cohorts. Although infection was higher in the CS cohort, the overall complication rates did not differ between the CS patients and non-CS cohort (p > 0.05). Early identification and standardized treatment protocols for the management of CS that develops in association with a tibial plateau fracture lead to outcome scores that were not significantly different from patients who did not develop CS.

Schatzker IV tibial plateau fractures: are they always unicondylar?

The objectives of this study were to describe the incidence and morphology of medial tibial plateau fractures that extend into the lateral articular surface and to describe trends in their management. Retrospective. Level I Urban Trauma Center. Seventy consecutive patients sustaining OTA/AO 41 B1 and B3 fractures. Open reduction internal fixation of medial tibial plateau fractures. Incidence of medial tibial plateau fractures that extend into the lateral articular surface. Secondary outcomes include localization of lateral articular surface depression, neurovascular injury, and trends in surgical management. Seventy patients were included with 9 fractures (12.9%) isolated to the medial condyle (MC) and 61 fractures (87.1%) extending to the lateral condyle (LC). Compartment syndrome was present in 2 patients (2.9%), peroneal nerve palsy in 2 (2.9%), and arterial injury in 1 (1.4%). Initial external fixation was used more frequently in the LC group compared with the MC group (P = 0.028). Of the 61 fractures in the LC group, 49 (80.3%) included lateral articular surface depression which localized to the posteromedial quadrant of the lateral articular surface in 36 of 49 fractures (73.5%). Lateral articular surface depression depth ≥10.6 mm was associated with the use of dual incisions (P < 0.001). Schatzker IV fractures frequently extend to the lateral condyle and often present with depression of the posteromedial lateral articular surface. Fractures with lateral articular surface depression depth ≥10.6 mm were more likely to undergo fixation with dual incisions. Therapeutic level IV.

Infection Rates and Surgical Procedures Associated With Isolated Open Talar Neck and Body Fractures.

Open fractures of the talar body and neck are uncommon. Previous reports of associated deep infection rates and resulting surgical requirements vary widely. The primary objective of this study is to report the incidence of deep infections for isolated open talar body and neck fractures, and secondarily the incidence and number of total surgeries performed (TSP), secondary salvage procedures (SSPs), and nonsalvage procedures (NSPs). Retrospective case-control study of 32 consecutive isolated open talus fracture patients (22 neck, 10 body) were followed for an average of 39.2 months. Five (15.6%) fractures developed deep infections. Fifty percent of open body fractures became infected compared with 0% of neck fractures (P < .001). There was no difference between infected group (IG) and uninfected fracture group (UG) with respect to age, sex, body mass index, tobacco, diabetes, vascular disease, open fracture type, wound location, hours to irrigation and debridement, or definitive treatment. The majority (92.6%) of UG fractures used a dual incision with open wound extension. There were more single extensile approaches in the IG group (P = .04). The IG required 5.8 TSP per patient compared with 2.1 in the UG (P = .004). All (100%) of the IG required an SSP compared with 29.6% of the UG (P = .006). All (100%) of the IG required an NSP compared to 40.7% of the UG (P = .043). In the IG, 2.8 NSPs per patient were required after definitive surgery compared with 1.18 in the UG (P = .003). Of those followed 1 year, the incidence of SSP remained higher in the IG (P = .016). The incidence of deep infection following isolated open talar fractures is high and occurs disproportionally in body fractures. Infected fractures required nearly 6 surgeries, and all required SSP. Level IV, prognostic.

Modified triple pelvic osteotomy for residual acetabular dysplasia through double incisions: Technical note and review of short-term results.

To assess validity, safety, and efficacy of the modified triple pelvic osteotomy (TPO) approach for correction of residual acetabular dysplasia. This is a retrospective case series conducted on 15 hips in 15 patients from 2019 to 2023 with residual acetabular dysplasia treated by modified TPO as described by Tonnis with two modifications. The first modification is using a single medial incision for pubic and ischial cuts (the Vladimirov modification). The second modification is having the ischial cut closer to the acetabulum (Li modification) allowing free movement of the acetabular fragment for better femoral head coverage. The mean age at the time of surgery was 11.85years, (range 8-23). Cases presenting were 10 males (66.7%) and 5 females (33.3%). The mean follow-up period was 36.533 months (24-60 months). Our study revealed significant clinical and radiological improvement. The CE angle improved from a mean value of 10° (range 2-17) pre-operatively to 32.785° (range 18°-40°) post-operatively. The AI improved from a mean value of 32° pre-operatively to a mean value of 13.89° post-operatively. HHS increased from a preoperative mean value of 74.80° to a post-operative mean value of 90.67°. Also, there was a significant improvement in ROM (abduction and internal rotation). LLD improved from a mean value of 2.60cm preoperatively to a mean value of 0.37cm postoperatively. Delayed union was found in 3 cases. No cases of osteonecrosis or neurovascular complication were encountered in our study. The modified TPO technique using dual incisions can be considered safe and effective, providing adequate coverage of the femoral head in acetabular dysplasia with less surgical time, satisfactory functional outcomes, and minimal complications. IV.

Influence of Surgical Approach and Fixation on Complications in Talus Fractures: A Multicenter Review

Fractures of the talus are infrequent injuries often associated with substantial morbidity and imperfect outcomes. We undertook a retrospective review of talus fractures at multiple level 1 trauma centers in order to identify common treatment patterns and potential predictors of complications. All cases of talar fractures meeting inclusion criteria at our institution were reviewed. 54 of 103 talus fractures met inclusion criteria. 33 (61.1%) involved the talar neck, 13 (24.1%) the talar body, and 6 (9.2%) involved the lateral process. The most common etiology was motor vehicle accidents, accounting for 27 (50.0%). Mean follow up was 13.6 months (range 8-52 months). 37 (68.5%) fractures were fixated with screws, and 17 (31.5%) were fixated with a plate construct. Single and dual incisions were used in 63.0% and 25.9% of cases, respectively. Complications were seen in 46.3% of cases, with post-traumatic osteoarthritis being the most common complication (35.1%). Avascular necrosis occurred in 4 (7.4%) patients. No independent variables met the statistical threshold to be associated with complications. The present data alludes to possibility of over-reporting complications due to historical literature and the need for further studies.

Single and dual limbal relaxing incisions in correcting corneal astigmatism during cataract surgery

Introduction: Correcting astigmatism during cataract surgery to achieve optimal visual outcomes is important. Various techniques, such as limbal relaxing incisions (LRIs), are used to correct astigmatism. LRIs are effective for mild to moderate astigmatism but have limitations in correcting larger astigmatism. This study aimed to review the effectiveness of single and dual LRI in correcting astigmatism during cataract surgery. Methods: This literature review utilized databases from 2010 until 2022. The keywords “corneal astigmatism”, “limbal relaxing incision”, and “cataract surgery” were used to collect 12 journals that had relevant topics. Results: LRIs are a form of partial-thickness keratotomy used to correct astigmatism during cataract surgery. The incisions for LRIs are made in the peripheral cornea, following a nomogram based on the patient's astigmatism, age, and the location of the steep axis of astigmatism. LRIs can be performed as single or dual incisions, with dual LRIs offering greater astigmatism correction. In the case of irregular astigmatism, LRIs can be adjusted to the topography of the cornea because the lengths of coupled incisions can vary. Conclusion: The effectiveness between single and dual LRIs was the same, but paired LRIs have a superior effect in correcting greater astigmatism. LRIs remain a valuable tool for cataract surgeons to manage astigmatism and improve visual outcomes in cataract surgery patients.

Single-Incision Fasciotomy Decreases Infection Risk Compared with Dual-Incision Fasciotomy in Treatment of Tibial Plateau Fractures With Acute Compartment Syndrome.

Comparison of surgical site infection (SSI) rates in tibial plateau fractures with acute compartment syndrome treated with single-incision (SI) versus dual-incision (DI) fasciotomies. Retrospective cohort study. Two, Level-1, academic, trauma centers. Between January 2001 and December 2021, one-hundred ninety patients with a diagnosis of tibial plateau fracture and acute compartment syndrome met inclusion criteria (SI: n = 127, DI: n = 63) with a minimum of 3-month follow-up after definitive fixation. Emergent 4-compartment fasciotomy, using either SI or DI technique, and eventual plate and screw fixation of the tibial plateau. The primary outcome was SSI requiring surgical debridement. Secondary outcomes included nonunion, days to closure, method of skin closure, and time to SSI. Both groups were similar in demographic variables and fracture characteristics (all P > 0.05). The overall infection rate was 25.8% (49 of 190), but the SI fasciotomy patients had significantly fewer SSIs compared with the DI fasciotomy patients [SI 18.1% vs. DI 41.3%; P < 0.001; OR 2.28, (confidence interval, 1.42-3.66)]. Patients with a dual (medial and lateral) surgical approach and DI fasciotomies developed an SSI in 60% (15 of 25) of cases compared with 21.3% (13 of 61) of cases in the SI group ( P < 0.001). The nonunion rate was similar between the 2 groups (SI 8.3% vs. DI 10.3%; P = 0.78). The SI fasciotomy group required fewer debridement's ( P = 0.04) until closure, but there was no difference in days until closure (SI 5.5 vs. DI 6.6; P = 0.09). There were zero cases of incomplete compartment release requiring return to the operating room. Patients with DI fasciotomies were more than twice as likely to develop an SSI compared with SI patients despite similar fracture and demographic characteristics between the groups. Orthopaedic surgeons should consider prioritizing SI fasciotomies in this setting. Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

TFIIH central activity in nucleotide excision repair to prevent disease

The heterodecameric transcription factor IIH (TFIIH) functions in multiple cellular processes, foremost in nucleotide excision repair (NER) and transcription initiation by RNA polymerase II. TFIIH is essential for life and hereditary mutations in TFIIH cause the devastating human syndromes xeroderma pigmentosum, Cockayne syndrome or trichothiodystrophy, or combinations of these. In NER, TFIIH binds to DNA after DNA damage is detected and, using its translocase and helicase subunits XPB and XPD, opens up the DNA and checks for the presence of DNA damage. This central activity leads to dual incision and removal of the DNA strand containing the damage, after which the resulting DNA gap is restored. In this review, we discuss new structural and mechanistic insights into the central function of TFIIH in NER. Moreover, we provide an elaborate overview of all currently known patients and diseases associated with inherited TFIIH mutations and describe how our understanding of TFIIH function in NER and transcription can explain the different disease features caused by TFIIH deficiency.

Lesion recognition by XPC, TFIIH and XPA in DNA excision repair.

Nucleotide excision repair removes DNA lesions caused by ultraviolet light, cisplatin-like compounds and bulky adducts1. After initial recognition by XPC in global genome repair or a stalled RNA polymerase in transcription-coupled repair, damaged DNA is transferred to the seven-subunit TFIIH core complex (Core7) for verification and dual incisions by the XPF and XPG nucleases2. Structures capturing lesion recognition by the yeast XPC homologue Rad4 and TFIIH in transcription initiation or DNA repair have been separately reported3-7. How two different lesion recognition pathways converge and how the XPB and XPD helicases of Core7 move the DNA lesion for verification are unclear. Here we report on structures revealing DNA lesion recognition by human XPC and DNA lesion hand-off from XPC to Core7 and XPA. XPA, which binds between XPB and XPD, kinks the DNA duplex and shifts XPC and the DNA lesion by nearly a helical turn relative to Core7. The DNA lesion is thus positioned outside of Core7, as would occur with RNA polymerase. XPB and XPD, which track the lesion-containing strand but translocate DNA in opposite directions, push and pull the lesion-containing strand into XPD for verification.

Structural and functional insights into the activation of the dual incision activity of UvrC, a key player in bacterial NER.

Bacterial nucleotide excision repair (NER), mediated by the UvrA, UvrB and UvrC proteins is a multistep, ATP-dependent process, that is responsible for the removal of a very wide range of chemically and structurally diverse DNA lesions. DNA damage removal is performed by UvrC, an enzyme possessing a dual endonuclease activity, capable of incising the DNA on either side of the damaged site to release a short single-stranded DNA fragment containing the lesion. Using biochemical and biophysical approaches, we have probed the oligomeric state, UvrB- and DNA-binding abilities and incision activities of wild-type and mutant constructs of UvrC from the radiation resistant bacterium, Deinococcus radiodurans. Moreover, by combining the power of new structure prediction algorithms and experimental crystallographic data, we have assembled the first model of a complete UvrC, revealing several unexpected structural motifs and in particular, a central inactive RNase H domain acting as a platform for the surrounding domains. In this configuration, UvrC is maintained in a 'closed' inactive state that needs to undergo a major rearrangement to adopt an 'open' active state capable of performing the dual incision reaction. Taken together, this study provides important insight into the mechanism of recruitment and activation of UvrC during NER.

Bicondylar tibial plateau fracture dislocations with an intact anterolateral cortical rim: A surgical technique

A displaced medial tibial plateau fracture with central and lateral impaction, but an intact anterolateral cortical rim, is an uncommon variant of bicondylar tibial plateau fracture that presents a number of challenges. Without a lateral metaphyseal fracture line to work through, it is challenging to address central and lateral impaction. Previously published techniques for addressing this fracture pattern describe an intra-articular osteotomy of the lateral plateau to aid visualization and reduction, or use a posterolateral approach to the proximal tibia with or without an osteotomy of the proximal fibula. This study presents a technique which utilizes standard dual incision approaches and does not involve an intra-articular osteotomy of the lateral tibial plateau or a posterolateral approach. A case series was conducted evaluating radiographic and functional outcomes of 8 patients.

Unscheduled DNA Synthesis at Sites of Local UV-induced DNA Damage to Quantify Global Genome Nucleotide Excision Repair Activity in Human Cells.

Nucleotide excision repair (NER) removes a wide variety of structurally unrelated lesions from the genome, including UV-induced photolesions such as 6-4 pyrimidine-pyrimidone photoproducts (6-4PPs) and cyclobutane pyrimidine dimers (CPDs). NER removes lesions by excising a short stretch of single-stranded DNA containing the damaged DNA, leaving a single-stranded gap that is resynthesized in a process called unscheduled DNA synthesis (UDS). Measuring UDS after UV irradiation in non-dividing cells provides a measure of the overall NER activity, of which approximately 90% is carried out by the global genome repair (GGR) sub pathway. Here, we present a protocol for the microscopy-based analysis and quantification of UDS as a measurement for GGR activity. Following local UV-C irradiation, serum-starved human cells are supplemented with the thymidine analogue 5-ethynyl-2'-deoxyuridine (EdU), which is incorporated into repair patches following NER-dependent dual incision. The incorporated nucleotide analogue is coupled to a fluorophore using Click-iT chemistry, followed by immunodetection of CPD photolesions to simultaneously visualize both signals by fluorescence microscopy. Accompanying this protocol is a custom-built ImageJ plug-in to analyze and quantify UDS signals at sites of CPD-marked local damage. The local UDS assay enables an effective and sensitive fluorescence-based quantification of GGR activity in single cells with application in basic research to better understand the regulatory mechanism in NER, as well as in diagnostics to characterize fibroblasts from individuals with NER-deficiency disorder. Graphical abstract.

An Unusual Inverted Talar Neck Fracture–Dislocation

Talar neck fractures occur on a continuum of injury severity. Hawkins classification, later modified by Canale, is the gold standard method of describing talar neck fractures by the degree of dislocation. It has proven to be clinically relevant in predicting risk of osteonecrosis. Despite its merits, talar neck fractures present on a wide spectrum of involvement of the body and neck, dislocation, and concomitant injuries, making every situation a challenge in treatment. We present a unique case of a talar neck fracture in which the talar dome had dislocated and inverted 180°, which is not described in the widely used Hawkins classification. We recommend urgent open reduction, low threshold for use of a transcalcaneal traction pin and dual incisions, and guarded prognosis of osteonecrosis and posttraumatic arthritis.

Results of a shuttle catheter technique for surgical repair of acute extensor hallucis longus tears

The proximal end of a torn Extensor hallucis longus (EHL) is usually so retracted that a proximal wound extension is always required to retrieve it; leading to more adhesions and stiffness. This study aims at assessment of a novel technique for proximal stump retrieval and repair of acute EHL injuries with no need for wound extension. Thirteen patients with acute EHL tendon injuries at zones III, IV were prospectively included in our series. Patients with underlining bony injuries, chronic tendon injuries and previous nearby skin lesions were excluded. Dual Incision Shuttle Catheter (DISC) technique was applied with subsequent evaluation by the American Orthopedic Foot and Ankle Society (AOFAS) hallux scale, Lipscomb and Kelly score, range of motion and muscle power. Dorsiflexion at the metatarsophalangeal (MTP) joint significantly improved from a mean of 38.4±6.2º at one month to 58±9.6º at three months to 78.8±3.1º at one year postoperatively (P=0.0004). Plantar flexion at MTP joint significantly inclined from 16±3.8º at 3 months to 30.6±7.8º at the last follow-up (P=0.006). The big toe dorsiflexion power surged from 6.1±0.9N to 11.1±2.5N to 19.7±3.4N at 1 month, 3 months and one-year follow-up periods respectively (P=0.013). As per the AOFAS hallux scale, pain score was 40 of 40 points. The mean functional capability score was 43.7 out of 45 points. On Lipscomb and Kelly scale, all were graded "good" except for one patient who was graded "fair". Dual Incision Shuttle Catheter (DISC) technique represents a reliable method for repair of acute EHL injury at zones III, IV.

Single incision simultaneous liver kidney transplantation: Feasibility and outcomes.

Traditionally, simultaneous liver kidney transplantation (SLK) has been performed using a subcostal incision for the liver allograft and a lower abdominal incision for kidney transplantation (dual incision, DI). At our institution, we performed SLK using a single subcostal incision (SI). The aim of this study was to report the outcomes of single versus dual incisions for SLK. A retrospective cohort study of consecutive SLK procedures performed at our center from January 2015 to April 2021 was performed. The demographic characteristics, complications, intraoperative findings, and complications after SI and DI were statistically compared. A total 37 SLK were performed (19 DI and 18 SI). The age and indications for transplantation were comparable between the two groups. Patient in SI group had significantly higher MELD score (27.0±1.5vs. 31.7±1.5, p=.038). The cold ischemic time of kidney transplantation (599±26min vs. 447±27min, p<.001) and the total surgical time (508±21min vs. 423±22min, p=.008) were significantly shorter in the SI group. The incidence of complications and post-transplant kidney function was comparable between the groups. A slightly higher incidence of surgical site complications was noted in the DI group without any statistically significance (p=.178). Single-subcostal incision SLK is technically feasible and has comparable outcomes to dual-incision SLK. SI was associated with shorter cold ischemic time for kidney transplant, as well as shorter overall operative time.

Tarsometatarsal Joint Preparation using a Modified Dorsal Approach vs Standard Approach: A Cadaver Study

Category: Midfoot/Forefoot Introduction/Purpose: Lisfranc injuries are a relatively common midfoot injury involving the tarsometatarsal (TMT) joint. Surgical fixation typically involves open reduction with internal fixation or primary arthrodesis of the joint(s). The standard surgical approach to the TMT joint involves two dorsal incisions however, a recent study has suggested the use of a modified single dorsal incision approach. The goal of this paper is to compare the total surface area of the joint that can be prepared for primary arthrodesis of the TMT using the standard vs modified single dorsal approach. Methods: Ten fresh frozen below-the-knee cadaver specimens were randomly assigned to receive either the standard or modified dorsal single incision operative approach to the TMT joint. Prior to initiating the study, specimens were inspected with fluoroscopic radiographs for preexisting pathology or prior surgical intervention. The joint surface was visualized and then underwent articular preparation as for a joint fusion. After adequate joint preparation, the TMT joint was disarticulated and the surface was photographed for image analysis. Using ImageJ, articular joint surface preparation areas were measured by two blinded reviewers. to assess the joint surface preparation and this was compared by surgical approach. Results: After ImageJ and Mann-Whitney U statistical analysis, there was no significant difference in the amount of joint prepared when comparing the standard versus modified dorsal approach for the first three TMT joints (p= 0.548, p=0.310, p= 0.548). The percentage of joint preparation utilizing the standard dorsal approach versus the modified dorsal approach for TMT joints one through three are as follows (percentages utilized are listed as the median value with its correlating range): First TMT- 67.6% (range 26%) by the standard approach versus 71.7% (range 9%) by the modified dorsal approach, second TMT- 67.9% (range 24%) versus 65.7% (range 12%), and third TMT- 65.9% (range 42%) versus 59.6% (range 24%). Table 1 summarizes our results between each operative approach. Conclusion: With our findings, we demonstrate that a modified single dorsal approach to the Lisfranc joint provided comparable joint preparation for primary arthrodesis as the standard dual incision approach. However, the modified dorsal approach may be beneficial in that it avoids creating a skin bridge which has potential for necrosis with the standard two incision approach. The authors believe the comparable joint preparation combined with its potential to alleviate soft tissue complications make the modified dorsal approach a viable surgical approach for a TMT arthrodesis.

Two interaction surfaces between XPA and RPA organize the preincision complex in nucleotide excision repair

The xeroderma pigmentosum protein A (XPA) and replication protein A (RPA) proteins fulfill essential roles in the assembly of the preincision complex in the nucleotide excision repair (NER) pathway. We have previously characterized the two interaction sites, one between the XPA N-terminal (XPA-N) disordered domain and the RPA32 C-terminal domain (RPA32C), and the other with the XPA DNA binding domain (DBD) and the RPA70AB DBDs. Here, we show that XPA mutations that inhibit the physical interaction in either site reduce NER activity in biochemical and cellular systems. Combining mutations in the two sites leads to an additive inhibition of NER, implying that they fulfill distinct roles. Our data suggest a model in which the interaction between XPA-N and RPA32C is important for the initial association of XPA with NER complexes, while the interaction between XPA DBD and RPA70AB is needed for structural organization of the complex to license the dual incision reaction. Integrative structural models of complexes of XPA and RPA bound to single-stranded/double-stranded DNA (ss/dsDNA) junction substrates that mimic the NER bubble reveal key features of the architecture of XPA and RPA in the preincision complex. Most critical among these is that the shape of the NER bubble is far from colinear as depicted in current models, but rather the two strands of unwound DNA must assume a U-shape with the two ss/dsDNA junctions localized in close proximity. Our data suggest that the interaction between XPA and RPA70 is key for the organization of the NER preincision complex.

Single versus dual incision approaches for dual plating of bicondylar tibial plateau fractures have comparable rates of deep infection and revision surgery

ObjectivesThe use of one midline incision versus dual medial/lateral incisions for dual plating of bicondylar tibial plateau (BTP) fractures is controversial. This study aimed to compare rates of infection and secondary surgery in patients treated with dual plating for a BTP fracture using a single versus double incisions. DesignRetrospective cohort study. SettingTwo Level-1 trauma centers. Patients/ParticipantsPatients > 18 years with a closed AO/OTA 41-C BTP fracture without compartment syndrome treated with a single midline or dual incision (lateral with medial or posteromedial) approach for dual plating. InterventionDual plating through either a single anterior incision, or dual medial/lateral incisions. Main outcome measurementsRates of deep infection and reoperation were compared using Chi-square analysis (p-value of < 0.05). Results and conclusionsIn total 636 AO/OTA 41-C BTP fractures treated between 1/1/01 and 12/31/18 were identified and assessed. After exclusions for limited follow up, other techniques, open fracture and the need for fasciotomies, 346 patients were studied. Of these 254 had been treated with a single plate / single approach technique while 92 had been dual plated, 41 through a single anterior incision while 51 had dual plating through separate lateral and medial or posteromedial incisions. For these 92 fractures, there was no significant difference in the rate of deep infection (22.0% vs 23.5%, s=0.858) or reoperation (31.7% vs 31.4%, p=0.973) between the single and dual incision groups. Injuries that had been treated with single plating via a single incision had comparably lower rates of deep infection (10.2% vs. 22.8%, p=0.003) and reoperation (12.2% vs. 31.5%, p<0.001). There were no significant differences in any demographic parameters between patients undergoing single versus dual plating. Although retrospective, not randomized and subject to single surgeon bias these data suggest that these complications are more based on injury than the approach. Level of evidenceIII

Inhibiting and Enhancing Effects on DNA Repair of Rare Metal Elements in Cultured Human Lymphoblastoid Cells

Along with increasing relevance of rare earth (RE) elements in industrial technology, the risk of their environmental release and occupational exposure on human health is of concern. Although many toxicological studies were reported for REs, it is not known how they affect DNA repair. In this study, the effects on DNA repair of all RE ions except radioactive promethium (Pm) were studied. Human lymphoblastoid WTK1cells were irradiated to UV followed by 2h exposure to each RE with and without DNA repair inhibitor cytosine-1β-D- arabinofuranoside (araC), and then single strand breaks (SSBs) were detected by the comet assay. UV-induced pyrimidine dimers are removed by nucleotide excision repair (NER) which consists of recognition of the DNA lesion, excision of a 24–32 nucleotide stretch containing the lesion by dual incision of the damaged DNA strand on both sides, and re-synthesis of the resulting gap by DNA polymerase, and ligation of the nick. SSBs are generated in the incision step of nucleotide excision repair (NER) and disappear in the re-synthesis step of NER. Seven REs, Yb, Lu, Dy, Er, Sc, Pr, and Ce, enhanced comet positive response without araC but not with araC, suggesting that araC is antagonistic to the 7 REs. Since araC inhibits re-synthesis of NER, these seven REs would inhibit the re-synthesis step of NER. Six REs, Tm, Sm, Tb, Gd, Eu, and Y suppressed comet positive responses with and without araC, suggesting that they decreased comet assay detectable SSBs. Therefore, these 6 REs are considered to inhibit the incision step of NER. Only La decreased tail length without araC but increased with araC, suggesting that La increased comet assay detectable SSBs and that only La would enhance the incision step of NER. Neither Nd nor Ho affected tail length with or without araC.