Utilisation of the minimally invasive chevron akin (mica) osteotomy for severe hallux valgus: a systematic review.

BACKGROUND AND AIM: Hallux valgus is the most common forefoot disease that can cause pain and be disabling for the patient. Many surgical procedures have been described to correct this deformity; over the last years, the minimally invasive Chevron and Akin osteotomies (MICA) technique has become very popular. The aim of this review was to assess if MICA technique is a reliable procedure for treating severe hallux valgus. METHODS: A systematic review was performed according to the Preferred Reporting Items for systematic Reviews and Meta-Analysis (PRISMA) guidelines. The keywords were searched in PubMed Medline and Cochrane library. To minimise the number of missed studies, no filters were applied to the search strategy. To be considered for this review, the articles needed to comply with the following inclusion criteria: Minimally invasive Chevron and Akin osteotomy (MICA) for severe hallux valgus (HVA > 40°, IMA > 16°), patient age over 18 years and minimum follow-up of 6 months. RESULTS: Following the PRISMA flow chart 7 studies met the inclusion criteria and were taken into consideration in the review. We reached a population of 582 patients for a total of 676 feet. Males and females were 64 and 518, respectively. The mean age was 54.15 ± 8.25. The mean follow-up was 23.74 ± 9.60 months. All the studies reported an improvement in clinical results, in terms of function and quality of life. Radiological variables, mostly IMA and HVA, assessed pre- and postoperatively showed significant improvement in all studies included. CONCLUSIONS: Despite the limited number of published studies in the literature, the available evidence reveals good clinical outcomes and high levels of patient satisfaction. Percutaneous surgery for severe hallux valgus can achieve great deformity correction with reasonable rates of residual deformity. Patient satisfaction and quality of life following third-generation MICA surgery is very high.

The Overturning of Chevron Deference: Implications for the US Healthcare System.

In 1984, Chevron deference was established by the US Supreme Court in Chevron U.S.A., Inc. v. Natural Resources Defense Council, Inc., granting administrative agencies broad powers to interpret ambiguous laws passed by Congress. This landmark decision has fostered decades of controversy among legal scholars. Opponents argued it deprived courts of their constitutional duty and inappropriately expanded the power of the administrative state, while proponents claimed federal agencies, staffed by experts in their field, possess specialized knowledge to most effectively accomplish the goals of Congress. In June 2024, the Supreme Court's ruling in Loper Bright Enterprises v. Raimondo effectively ended Chevron deference, altering the judicial landscape with significant implications for US healthcare. In this commentary, we discuss the various potential benefits and challenges that the US healthcare system will face in a post-Chevron landscape while also considering the ways in which clinicians will be expected to help address these obstacles.

Evaluating the learning curve of Minimally Invasive Chevron and Akin Osteotomy for correction of hallux valgus deformity: a systematic review.

BACKGROUND: One procedure that has gained popularity in the surgical management of hallux valgus is the minimally invasive Chevron and Akin osteotomy (MICA). The purpose of this systematic review was to evaluate the learning curve associated with this technically demanding procedure. METHODS: A search of the EMBASE and PubMed databases was performed to identify all clinical studies that assessed the learning curve associated with the MICA procedure. Studies where patients were not diagnosed with hallux valgus, did not undergo MICA, or did not report data on operation time, fluoroscopy exposure, or complications were excluded. A risk of bias assessment was conducted to assess the validity of the studies. RESULTS: The initial literature search yielded 287 studies, and seven studies were included in the final analysis. A quantitative comparative analysis could not be performed as the included studies used different statistical methods to quantify the learning curve. Lewis et al. determined that after 38 operations, there was a decrease in operation time and fluoroscopy exposure (p < .001). Merc et al. found that it took 29 and 30 operations to reach a plateau for operation time and fluoroscopy exposure, respectively (p < .001). Palmanovich et al. found that it took 20 and 26 operations to reach a plateau for operation time and fluoroscopy exposure, respectively (p < .001). Toepfer and Strässle found there was a significant decrease in operation time and fluoroscopy exposure after the first 19 procedures in their series (p < .001). With respect to complications, one study found a significant difference after the 42nd operation (p = .007). However, the remaining studies found that complication rates did not significantly change with increased technical proficiency. All seven studies were deemed to have a moderate risk of bias. CONCLUSIONS: Surgeons can expect a learning curve of 20 to 40 operations before reaching technical proficiency with the MICA procedure. After the learning curve is achieved, surgeons can expect to see a significant decrease in both operation times and fluoroscopy exposure. No consistent significant difference was found in complications as one becomes more technically proficient with the procedure.

[Early effectiveness of modified minimally invasive Chevron-Akin osteotomy for moderate to severe hallux valgus].

Objective: To explore early effectiveness of modified minimally invasive Chevron-Akin (MICA) osteotomy in the treatment of moderate to severe hallux valgus. Methods: A clinical data of 49 patients (61 feet) with moderate to severe hallux valgus, who met the selection criteria between December 2019 and October 2022, was retrospectively analyzed. There were 7 males (8 feet) and 42 females (53 feet) with an average age of 38.0 years (range, 15-59 years), including 37 of unilateral foot and 12 of bilateral feet. There were 41 feet of moderate hallux valgus [hallux valgus angle (HVA) 20°-40°] and 10 feet of severe hallux valgus (HVA>40°). All patients underwent modified MICA osteotomy. A transverse osteotomy on the distal end of the first metatarsal bone was performed to replaced the traditional Chevron osteotomy, and three Kirschner wires were used to assist in three-dimensional correction. The other treatments were the same as traditional MICA osteotomy. The HVA, inter metatarsal angle (IMA), Hardy score of the sesamoid, and American Orthopaedic Foot and Ankle Society (AOFAS) score of 61 feet before operation and at last follow-up were recorded, and the results were compared between the various severity of hallux valgus. Results: All patients were followed up 6-24 months with an average of 12.0 months. After operation, the redness and swelling around the incision occurred in 1 foot; limited mobility of the metatarsophalangeal joint occurred in 2 feet; mild numbness of the skin occurred in 5 feet; mild inversion of the great toe occurred in 2 feet. No complication such as tendon injury was found. X-ray films showed no abnormal healing, nonunion, or necrosis of the metatarsal head after osteotomy. The healing time of osteotomy ranged from 3 to 4 months, with an average of 3.2 months. At last follow-up, the HVA, IMA, Hardy score of sesamoid, and AOFAS scores all significantly improved when compared with preoperative levels ( P<0.05). The AOFAS scores were excellent in 45 feet, good in 15 feet, and fair in 1 foot, with an excellent and good rate of 98.4%. The above indicators for moderate or severe hallux valgus patients were significantly improved when compared with preoperative levels ( P<0.05). The changes between pre- and post-operation in HVA, IMA, and Hardy scores of severe hallux valgus were all greater than those of moderate hallux valgus, with significant difference in HVA change between groups ( P<0.05), while there was no significant difference in the other two changes ( P>0.05). Conclusion: Modified MICA osteotomy can achieve good orthopedic effects and early functional improvement in the treatment of moderate to severe hallux valgus.

Chevron osteotomy and scarf osteotomy for hallux valgus angle and intermetatarsal angle correction: a systematic review and meta-analysis of randomized controlled trials.

BACKGROUND: This systematic review and meta-analysis aimed to investigate the differences in hallux valgus angle (HVA), intermetatarsal angle (IMA), American Orthopedic Foot and Ankle Society (AOFAS) scores, and complication rates between chevron osteotomy and scarf osteotomy for correcting hallux valgus. METHODS: Two investigators independently searched for randomized controlled trials (RCTs) published from 2007 to 2018 on PubMed, Web of Science, and Cochrane Library databases. Next, chevron and scarf osteotomies were compared for their postoperative outcomes using HVA, IMA, and AOFAS scores and their complication rates. Meta-analysis was performed using Review Manager (version 5.3). RESULTS: Six RCTs-comprising 507 feet, of which 261 and 246 underwent chevron and scarf osteotomies, respectively-were included. The meta-analysis revealed that chevron osteotomy led to significantly smaller postoperative HVAs than scarf osteotomy (weighted mean difference [WMD] = -1.94, 95% CI = - 2.65 to - 1.29, P < .00001). However, the differences in postoperative IMA (WMD = - 0.44, 95% CI = - 1.10 to 0.22, P = .19), postoperative AOFAS scores (WMD = 0.75; 95% CI = - 5.32 to 6.82; P = .81), and complication rates (risk ratio = 1.22, 95% CI = 0.65-2.27, P = .53) between feet that underwent chevron and scarf osteotomies were nonsignificant. CONCLUSIONS: Compared with scarf osteotomy, chevron osteotomy had significantly more favorable postoperative outcomes in terms of HVA correction, but not in terms of IMA, AOFAS scores, or complication rates. LEVEL OF EVIDENCE: Level I, systemic review and meta-analysis.

Is headless screw a valid alternative for the fixation of Chevron olecranon osteotomy? A biomechanical comparison of 4 fixation methods.

BACKGROUND: Chevron osteotomy is a popular technique for repairing complex distal humerus intra-articular fractures. However, refixation presents challenges like hardware prominence and soft tissue damage. Headless cannulated screws are gaining popularity for fixation due to better bone purchase and less irritation. This study aims to compare different fixation strategies with headless screws for Chevron osteotomy fixation. METHODS: This study utilized 32 polyurethane foam ulna specimens for biomechanical testing. The Chevron osteotomy was performed with an oscillating saw for all specimens. Four different techniques were used for refixation: modified tension band wire fixation, plate-screw fixation, cannulated screw fixation, and headless cannulated screw fixation. The constructs were mounted to the testing machine, simulating the elbow in 90 degrees of flexion. All specimens were tested under axial traction. Displacements at 350N and 500N and loads at the failure were recorded. RESULTS: At the load of the implant failure, headless cannulated screw fixation revealed higher force values when compared to the other constructs, and modified tension band wire fixation showed lower force values compared to the other 3 groups (P < .001). The headless cannulated screw fixation group showed no significant differences in osteotomy displacements when tested to a 350N load. There were no significant differences in displacements at a 500N load between the four groups (P = .275). CONCLUSION: This study suggests that headless cannulated screw fixation is a viable and effective option for Chevron osteotomies. Headless cannulated screw fixation makes it a promising alternative to traditional fixation methods. This technique may be a more reliable fixation technique during daily activities and moderate elbow motions, indicating that it has the potential to succeed.

Minimally Invasive Chevron Akin (MICA) Osteotomy Corrects Radiographic Parameters but Not Central Metatarsal Loading in Moderate to Severe Hallux Valgus without Metatarsalgia.

BACKGROUND: Central metatarsal pressure is increased in patients with hallux valgus, but the pedographic outcomes after hallux valgus (HV) correction are inconclusive. No known literature has reported the pedographic outcomes after HV correction with Minimally Invasive Chevron and Akin Osteotomy (MICA). METHODS: A prospective cohort of 31 feet from 25 patients with moderate-to-severe symptomatic HV but without metatarsalgia underwent MICA and was evaluated using radiographic parameters and pedographic measurements (Footscan®, RSscan International, Olen, Belgium). Data were collected preoperatively and 3 months after surgery. RESULTS: The radiographic parameters of the hallux valgus angle, intermetatarsal angle, distal metatarsal articular angle, first metatarsal head lateral shape, and lateral sesamoid grade significantly improved after MICA. The corrected first metatarsal length was significantly shortened by 2.3 mm, with consistent second metatarsal protrusion distance, lateral Meary's angle, and calcaneal pitch angle. Max force, max pressure, cumulative force, and cumulative pressure on the central metatarsals did not show significant changes between pre- and post-operative measurements, while these parameters significantly decreased in the hallux and first metatarsal area. CONCLUSION: MICA effectively corrects radiographic parameters but does not reduce central metatarsal loading in patients with moderate-to-severe HV without metatarsalgia.

Percutaneous distal chevron osteotomy is associated with lower immediate postoperative pain and a greater range of motion than the open technique: A prospective randomized study.

PURPOSE: The results of past studies comparing percutaneous techniques with traditional open techniques for hallux valgus are controversial. Therefore, this study aimed to compare the radiologic and clinical outcomes of percutaneous and open distal chevron osteotomies. METHODS: Seventy-one patients with mild to severe hallux valgus deformity were randomized to undergo percutaneous distal chevron osteotomy (percutaneous group, n = 36) or open distal chevron osteotomy (open group, n = 35) between October 2019 and September 2020. Radiological and clinical outcomes were assessed preoperatively and postoperatively. Outcome measures included the foot and ankle outcome score, foot functional index, visual analogue scale (VAS) scores for pain, range of motion (ROM) of the first metatarsophalangeal (MTP) joint, hallux valgus angle, intermetatarsal angle, and first metatarsal shortening. Additionally, the first metatarsal declination angle was measured to evaluate sagittal malunion. RESULTS: The mean first metatarsal declination angle decreased significantly at 12 months postoperatively in both groups (p = 0.021 and p < 0.001 in the percutaneous and open groups, respectively), and the decrement was significantly greater in the open group (p = 0.033). The mean VAS score for pain on postoperative day one was 4.2 ± 1.9 and 5.3 ± 1.7 in the percutaneous and open groups, respectively (p = 0.019). The mean ROM of the first MTP joint did not change significantly after surgery, from 72.5 ± 7.5 preoperatively to 71.0 ± 9.5 at 12 months postoperatively in the percutaneous group (p = 0.215); however, it decreased significantly from 70.6 ± 7.3 preoperatively to 63.4 ± 10.4 at 12 months postoperatively in the open group (p < 0.001). There were no significant differences between the groups regarding other clinical outcomes. CONCLUSION: The percutaneous group showed a lower immediate pain level at postoperative day 1 and better ROM of the first MTP joint at 12 months postoperatively.

Biomechanical Consequences of Proximal Screw Placement in Minimally Invasive Surgery for Hallux Valgus Correction.

Hallux valgus is one of the most common surgically corrected forefoot deformities. Studies evaluating clinical outcomes of minimally invasive chevron and akin (MICA) procedure have shown shorter operation time, faster recovery, and smaller scars compared to the open approach. Previous biomechanical cadaveric studies have largely focused on the open approach with minimal on MICA. To our knowledge, no studies have compared different proximal screw placements in MICA which can either be three-point fixation or intramedullary. This study aims to compare the biomechanical properties of fixation between these 2 techniques in MICA. Six matched pairs of human fresh frozen cadaveric feet were randomized to either 3-point fixation or intramedullary groups. Both procedures were performed by a single fellowship-trained orthopedic foot and ankle surgeon. Using a material testing machine, each specimen underwent 1000 cycles of plantar-to-dorsal uniaxial loads from 0 to 31 N in cantilever configuration while monitoring bending stiffness and distal fragment dorsal angulation. They were then subjected to load until failure at a compression rate of 10 mm/min. Specimens from both groups tolerated the walking fatigue test. Mean bending stiffness of 3-point fixation was 84% higher than intramedullary constructs (p = .002). Mean dorsal angulation of intramedullary was thrice that of 3-point fixation constructs (p = .008). Mean load to failure of 3-point fixation was 30% higher than intramedullary constructs (p = .001). Three-point fixation provide superior biomechanical stability compared to intramedullary proximal screw placement. The surgical technique using 3-point proximal screw fixation can offer robust fixation and lead to better clinical outcomes.

Outcome comparison of minimally invasive proximal and distal chevron Akin osteotomies in patients with severe hallux valgus deformity: A randomized prospective study.

PURPOSE: To date, the surgical treatment of severe hallux valgus deformity remains challenging despite the various methods presented. This study aimed to compare the effectiveness of minimally invasive distal chevron Akin osteotomies (d-MICA) and minimally invasive proximal chevron Akin osteotomies (p-MICA) in correcting severe hallux valgus deformities. METHODS: This prospective follow-up study included patients randomly assigned to undergo p-MICA or d-MICA for hallux valgus deformities with a preoperative hallux valgus angle (HVA) ≥ 40° and/or a first to second intermetatarsal angle (IMA) ≥ 16°. After a minimum follow-up period of two years, we compared various clinico-radiographic parameters of patients whose HVA exceeded 15° at the final follow-up. RESULTS: In the p-MICA and d-MICA groups, seven of 40 cases (17.5%) and 16 of 41 cases (39.0%), respectively, exhibited HVA > 15° at the final follow-up (P = 0.048). The preoperative parameters showed no significant differences. However, at the first weight-bearing assessment, the HVA, IMA, and relative second metatarsal length were significantly smaller, and the distal metatarsal articular angle (DMAA) was greater in the p-MICA group (all P < 0.05) compared with the d-MICA group. Postoperatively, both groups exhibited significant decreases in HVA and IMA at the final follow-up (P < 0.001 for all parameters). The p-MICA group showed no significant changes in DMAA and the relative length of the second metatarsal (P = 0.253 and 0.185, respectively). However, the d-MICA group showed a significant decrease in DMAA (P < 0.001) and an increase in the relative length of the second metatarsal at the final follow-up (P = 0.01). CONCLUSIONS: p-MICA and d-MICA procedures demonstrated effective correction potential for severe hallux valgus deformities; however, the d-MICA procedure exhibited a notably higher incidence of unsatisfactory correction at the final follow-up than p-MICA. Therefore, d-MICA may be less predictable in achieving successful outcomes than p-MICA in treating severe hallux valgus deformities.

Changes in Foot Width in Minimally Invasive Bunionectomy.

BACKGROUND: Minimally invasive bunionectomy (MISB) has emerged as a popular approach to treat symptomatic hallux valgus deformity. Although previous studies focused on distal foot width changes postsurgery, this research introduces a novel midshaft measurement to evaluate proximal transverse midfoot width, aiming for a comprehensive understanding of foot changes post-MISB. METHODS: A retrospective review of 44 HV patients from an institutional registry was conducted. Demographic data, surgical details, radiographs, and foot width measurements were collected. Changes in hallux valgus angle (HVA) and intermetatarsal angle (IMA) were also measured. RESULTS: Intraclass correlation coefficients (ICCs) demonstrated good to excellent interobserver reliability (all ICCs > 0.70) for all measurements. MISB resulted in a consistent reduction in distal foot width (P < .001). These reductions correlated with changes in HVA and IMA, suggesting that the extent of deformity correction influenced distal foot width: distal bone width decreased an average of 8 mm, P < .001). However, midshaft bony width increased an average of 4 mm, P < .001). Changes in midshaft foot width showed no correlation with HVA or IMA alterations. CONCLUSION: We found in this cohort of 44 patients that MISB for HV leads to an expected decrease in distal bony foot width but, on average, an increase in midshaft foot width.

Improvement of Valgus Deviation of the Lesser Toes of Moderate to Severe Hallux Valgus After Proximal Chevron Metatarsal Osteotomy and Akin Osteotomy.

BACKGROUND: This study examines the correction of lesser toe valgus deviation following proximal chevron metatarsal osteotomy (PCMO) and Akin osteotomy in moderate to severe hallux valgus patients, while identifying influencing factors. METHOD: Among 89 patients (116 feet), those with moderate to severe hallux valgus underwent PCMO and Akin osteotomy. Radiologic assessments included preoperative metatarsus adductus angle (MAA), hallux valgus angle (HVA), intermetatarsal angle (IMA), valgus angles of the second to fourth metatarsophalangeal joints, and hallux valgus recurrence. Assessments included visual analog scale (VAS) pain scores, American Orthopaedic Foot & Ankle Society (AOFAS) scores, and patient satisfaction over an average follow-up of 30.6 ± 21.2 (range, 12-99) months. RESULTS: The mean preoperative HVA of 34.4 degrees decreased to 8.7 degrees at final follow-up. The valgus angles of the second, third, and fourth toes improved by 37.1%, 27%, and 44.5%, respectively. In metatarsus adductus patients, lesser toe valgus angles were significantly higher both preoperatively and at final follow-up. Hallux valgus recurrence patients had higher preoperative and final follow-up IMA and valgus angles in the second and third toes. Nonrecurrence patients showed greater decreases in these angles. A larger HVA correction corresponded to a greater decrease in lesser toe valgus deviation. VAS and AOFAS scores improved significantly at the last follow-up. CONCLUSION: The study found a significant reduction in the valgus angle of the second, third, and fourth toes after PCMO and Akin osteotomy in moderate to severe hallux valgus cases, without additional surgeries on lesser toes. The lesser toe angular reductions were less pronounced in patients with metatarsus adductus or with hallux valgus recurrence. LEVEL OF EVIDENCE: Level IV, case series.

Does the Presence of Asymptomatic Flatfoot Deformity Impact the Clinical and Radiographic Outcomes of the Minimally Invasive Chevron and Akin Bunionectomy?

BACKGROUND: Flatfoot deformity is believed to play a role in hallux valgus development and recurrence. While symptomatic flatfoot deformity can be treated with separate procedures at the time of hallux valgus correction, the question remains whether the patient undergoing correction of a symptomatic hallux valgus deformity should have their asymptomatic flatfoot concurrently addressed. We aimed to investigate whether the presence of asymptomatic flatfoot influences patient-reported and radiographic outcomes of the minimally invasive chevron and Akin bunionectomy. METHODS: A total of 104 patients were included in this study. Forty-two asymptomatic patients met the radiographic criteria for flatfoot while 62 had a normal arch. Patient-reported outcomes were evaluated and compared between the two groups using validated PROMIS measures preoperatively and at a minimum one-year postoperatively. Radiographic outcomes including hallux valgus angle (HVA), intermetatarsal angle (IMA), Meary's angle, calcaneal pitch (CP), and talonavicular coverage angle (TNCA) were measured and compared preoperatively and minimum six-months postoperatively. RESULTS: Both groups demonstrated similar preoperative and postoperative PROMIS scores with significant improvements in physical function, pain interference, pain intensity, and global physical health. Preoperatively, HVA was similar between both groups, however the flatfoot group showed a greater IMA, Meary's angle, TNCA, and lower CP. Postoperatively, HVA and IMA were similar between groups, although patients in the flatfoot group retained a significantly greater Meary's angle, TNCA, and lower CP. Both groups showed significant improvements in HVA, IMA, and TNCA. CONCLUSION: Our study indicates that the minimally invasive chevron and Akin bunionectomy leads to improved clinical and radiographic hallux valgus outcomes without adversely impacting radiographic flatfoot parameters. Therefore, the MIS bunionectomy may be an effective option for hallux valgus correction in patients with mild, asymptomatic flatfoot. LEVEL OF EVIDENCE: Level III, retrospective cohort.

Radiographic Comparison of Open and Minimally Invasive Distal Chevron Metatarsal Osteotomy in Patients With Hallux Valgus.

This study aimed to compare radiographic outcomes of open and minimally invasive surgery (MIS) in patients with hallux valgus. We reviewed data of patients with hallux valgus who underwent open or minimally invasive distal chevron osteotomy at our institution. Radiographic assessment was completed preoperatively, immediate postoperatively, and one year postoperatively using eight weight bearing parameters . The classic distal chevron osteotomy method was used for open surgery and a modified method that added percutaneous K-wire fixation to the minimal invasive Chevron-Akin (third-generation MIS) was used for correction of the distal metatarsal articular angle (DMAA). A total of 65 feet (33 open surgeries and 32 MIS) were included. The HVA, IMA, and DMAA improved significantly following surgery regardless of surgical method (p<0.001). Other radiographic indicators showed no statistically significant differences after surgery. DMAA improved by 71.0±14.2% after surgery, and the open surgery group showed less significant reduction in DMAA (49.7±25.7%, p<0.001). Other parameters showed no difference between the two groups regarding relative postoperative changes. The MIS group showed shorter operation time (p<0.001) and hospitalization period (p=0.034) than did the open surgery group. Therefore, the MIS group is expected to be cost-effective. Radiographic measurements revealed comparable outcomes of MIS compared with open surgery. Additionally, adding percutaneous K-wire fixation during MIS had an advantage in correcting DMAA compared with open surgery. Furthermore, the correction of DMAA could reduce recurrence of valgus deformity of the hallux.

Judicial Threats to Olmstead and the Americans With Disabilities Act.

The authors examine the U.S. Supreme Court decision in Olmstead v L.C. ex rel. Zimring and related Supreme Court rulings that could raise questions about the Americans With Disabilities Act's guarantee of care in integrated settings and about which governmental entity's interpretation should be respected when deciding whether a state has met its integration obligation. After reviewing statutes, administrative regulations, and judicial decisions, the authors conclude that Olmstead's integration mandate will likely stand, but actions should be taken to codify the rule in federal and state statutes so that governmental agencies will continue to have the authority to ensure compliance with the mandate.

Numerical study of critical straight, frown, and chevron incisions in small incision cataract surgery.

Introduction: When an intraocular lens (IOL) injector is inserted through a pre-cut corneal incision (e.g., an empirical size of 2.2 mm) during small incision cataract surgery, uncontrollable tearing to the corneal tissue may occur, which is highly associated with the incision shape, size, and location. The goal of this numerical study was to investigate the optimal incision scheme amongst three typical shapes, i.e., straight, frown, and chevron incisions using mechanical modeling and finite element analysis. Methods: Assuming that the damage is caused by the tissue fracture at the incision tips and is governed by the classical energy release rate (ERR) theory which compares the current ERR value subject to IOL injection and the material's intrinsic parameter, critical ERR G c. Results: It was found that for chevron incisions, the incision shape with an angle of 170° was superior which induced minimal ERR value, while for frown incisions, the shape with a central angle of 6° was optimal. Both chevron and frown incisions could allow a larger size of injector to inject through than a straight pre-cut. In particular, the frown incision performed the best due to its lowest corresponding ERR and easy operation. Discussion: It was also observed that regions where the embedded fibrils are more dispersed and exhibit high isotropy were more favorable. If necessary, the chevron incision was recommended to be more aligned with the direction exhibiting a larger modulus, for example, along the circumferential direction near the limbus. This study provides useful knowledge in operation design and a deep insight into mechanical damage to corneal wounds in small incision cataract surgery.

Circular permutation at azurin's active site slows down its folding.

Circular permutation (CP) is a technique by which the primary sequence of a protein is rearranged to create new termini. The connectivity of the protein is altered but the overall protein structure generally remains unperturbed. Understanding the effect of CP can help design robust proteins for numerous applications such as in genetic engineering, optoelectronics, and improving catalytic activity. Studies on different protein topologies showed that CP usually affects protein stability as well as unfolding rates. Though a significant number of proteins contain metals or other cofactors, reports of metalloprotein CPs are rare. Thus, we chose a bacterial metalloprotein, azurin, and its CP within the metal-binding site (cpF114). We studied the stabilities, folding, and unfolding rates of apo- and Zn2+-bound CP azurin using fluorescence and circular dichroism. The introduced CP had destabilizing effects on the protein. Also, the folding of the Zn2+-CP protein was much slower than that of the Zn2+-WT or apo-protein. We compared this study to our previously reported azurin-cpN42, where we had observed an equilibrium and kinetic intermediate. cpF114 exhibits an apparent two-state equilibrium unfolding but has an off-pathway kinetic intermediate. Our study hinted at CP as a method to modify the energy landscape of proteins to alter their folding pathways. WT azurin, being a faster folder, may have evolved to optimize the folding rate of metal-bound protein compared to its CPs, albeit all of them have the same structure and function. Our study underscores that protein sequence and protein termini positions are crucial for metalloproteins. TOC Figure. (Top) Zn2+-azurin WT structure (PDB code: 1E67) and 2-D topology diagram of Zn2+-cpF114 azurin. (Bottom) Cartoon diagram representing folding (red arrows) and unfolding (blue arrows) of apo- and Zn2+- WT and cpF114 azurins. The width of the arrows represents the rate of the corresponding processes.

A Modified 90-Degree Distal Chevron Metatarsal Osteotomy for Correcting Moderate Hallux Valgus Deformity.

Various modifications of distal chevron metatarsal osteotomy (DCMO) have been introduced for correcting moderate hallux valgus deformity; however, the amount of correction may be limited, and complications, such as the recurrence of the deformity and avascular necrosis of the metatarsal head, have been a problem. This study aimed to present a modified 90-degree DCMO technique that overcomes the previously reported shortcomings and to report a successful short-term radiographic outcome. Sixty-eight consecutive patients who underwent the operation with our modified DCMO technique and twenty-two consecutive patients with the conventional DCMO technique (control group) were retrospectively analyzed. The radiographic measurements were evaluated preoperatively, at two months post operation, and at the final follow-up. Both groups showed a significant correction of the hallux valgus angle, first-second intermetatarsal angle, distal metatarsal articular angle, and sesamoid position at the final follow-up, while the amount of correction was significantly greater in the modified DCMO group. In both groups, there were no cases of complications such as avascular necrosis of the metatarsal head, nonunion, and surgical site infection appearing throughout the follow-up period. Therefore, the modified 90-degree DCMO technique is effective and safe, which could serve as a favorable option to treat moderate hallux valgus deformity.

Estimation of the Spatial Extent of the Transient Gain Drop in a Microchannel Plate.

The gain of the microchannel plate temporally drops after an ion initiates an electron avalanche. Electron multiplication was expected to deplete the charge from the microchannel wall and produce the depleted charge (wall charge). Moreover, it was reported that the gain drop occurred not only in the activated channels, where the electrons are multiplied, but also in the surrounding channels. One mechanism of the gain-drop spatial extension has been considered as that the wall charges in the activated channels change the electric field in the surrounding channels. Anacker et al. assumed that the wall charge is a uniform line charge; the gain-drop spatial extent should be proportional to the amount of the wall charges. We considered that the wall charges exponentially increased in the channel toward the exit. In this study, the electric field produced by the wall charges was calculated, considering the distribution of the wall charges. The transverse electric field generated by the wall charges was expected to disturb the electron trajectory near the channel exit and decrease the number of secondary electrons emitted per collision (gain per collision), resulting in a gain drop. The gain per collision was calculated to decrease by 22% for the position where the gain decreased significantly in the presence of the transverse electric field of 3×105 V/m. In our model, the gain-drop spatial extent extended proportionally to the square root of the wall charges when the distance from the activated channel exceeded 50 µm.

Changes in Radiographic Alignment Following Metatarsophalangeal Fusion, Distal Metatarsal Osteotomy, and Lapidus.

BACKGROUND: The purpose of this study is to evaluate the effect of the different surgical treatments for hallux valgus on various radiographic measures of bunion correction. METHODS: A retrospective cohort study was conducted at a single academic medical center involving 2 fellowship-trained foot and ankle surgeons. One hundred and nineteen feet (110 patients) were included. Procedures included first metatarsophalangeal (MTP) arthrodesis (n = 88), Chevron and/or Scarf osteotomy (n = 23), and Lapidus (n = 8). Overall, 78.2% of patients were female, mean age was 60.49 (range, 16-81) years, and mean follow-up was 1.20 (range, 0.25-3.92) years. RESULTS: Hallux valgus angle (HVA) significantly differed preoperatively (MTP = 33.33°, Chevron/Scarf = 27.03°, Lapidus = 32.56°; P = .026). There was no difference in distal metatarsal articular angle (DMAA) preoperatively (MTP = 18.87°, Chevron/Scarf = 17.80°, Lapidus = 14.39°; P = .629). At final follow-up, DMAA was significantly greatest among the Lapidus bunionectomy cohort (MTP = 9.63°, Chevron/Scarf = 13.51°, Lapidus = 17.45°; P = .005). There was no difference in infection (MTP = 6.8%, Chevron/Scarf = 4.4%, Lapidus = 0.0%; P = 1.00) or reoperation (MTP = 19.3%, Chevron/Scarf = 21.7%, Lapidus = 12.5%; P = .921) rates between cohorts, although both rates were highest in the first MTP arthrodesis group. CONCLUSION: Among the 3 hallux valgus corrections studied, Lapidus bunionectomy fared the worst regarding DMAA correction at first follow-up and final follow-up, compared with MTP fusion and distal metatarsal osteotomies. Other radiographic measures showed no significant difference among the groups. LEVEL OF EVIDENCE: Level III: Retrospective cohort study.