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.

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.

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.

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.

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.

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.

Metal-binding and circular permutation-dependent thermodynamic and kinetic stability of azurin.

Native topology is known to determine the folding kinetics and the energy landscape of proteins. Furthermore, the circular permutation (CP) of proteins alters the order of the secondary structure connectivity while retaining the three-dimensional structure, making it an elegant and powerful approach to altering native topology. Previous studies elucidated the influence of CP in proteins with different folds such as Greek key ß-barrel, ß-sandwich, ß-α-ß, and all α-Greek key. CP mainly affects the protein stability and unfolding kinetics, while folding kinetics remains mostly unaltered. However, the effect of CP on metalloproteins is yet to be elaborately studied. The active site of metalloproteins poses an additional complexity in studying protein folding. Here, we investigate a CP variant (cpN42) of azurin-in both metal-free and metal-bound (holo) forms. As observed earlier in other proteins, apo-forms of wild-type (WT) and cpN42 fold with similar rates. In contrast, zinc-binding accelerates the folding of WT but decelerates the folding of cpN42. On zinc-binding, the spontaneous folding rate of WT increases by >250 times that of cpN42, which is unprecedented and the highest for any CP to date. On the other hand, zinc-binding reduces the spontaneous unfolding rate of cpN42 by ~100 times, making the WT and CP azurins unfold at similar rates. Our study demonstrates metal binding as a novel way to modulate the unfolding and folding rates of CPs compared to their WT counterparts. We hope our study increases the understanding of the effect of CP on the folding mechanism and energy landscape of metalloproteins.

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.

The distal metatarsal screw is not always necessary in third-generation MICA: a case-control study.

INTRODUCTION: To evaluate the clinical and radiological results after fixation of the first metatarsal head (MTH) with one or two screws as part of the third-generation minimally invasive Chevron-Akin osteotomy (MICA) for hallux valgus deformities. MATERIALS AND METHODS: Between August 2020 and November 2021, 55 MICA procedures (50 patients, male:female = 7:43), 22 with two (MICA2), 33 with one screw (MICA1) were performed for mild to severe hallux valgus deformities. Exclusion criteria were a concomitant pes adductus (Sgarlato angle > 20°) or hindfoot/midfoot deformities requiring treatment. In 27 cases, additional procedures on the forefoot (small toe corrections or metatarsal osteotomies II-V) were necessary. Pre- and post-operatively, hallux valgus angle (HVA) and intermetatarsal I/II angle (IMA) were measured. Clinically, subjective satisfaction, range of motion (ROM) of the first metatarsophalangeal joint (MTPJ), and pain level (NRS score) were evaluated. The minimum follow-up was 12 months. RESULTS: Displacement of MTH was 70-90% on average, all osteotomies showed full consolidation at latest follow-up. In one case of either group, a slight subsidence of MTH was documented. The radiological and clinical parameters showed no differences between the groups. The pain level improved by an average of three points. The mobility of the MTPJ showed a slight reduction in nine cases after three months (4 MICA2, 5 MICA1) which persisted in three cases. Fifty-two of 55 patients (95%) would opt again for the operation. CONCLUSIONS: Fixation of the first MTH with a single bicortical screw in MICA with moderate lateralization of MTH shows stable anchoring and good clinical results. The routine use of a second metatarsal screw can be omitted.

A modified minimally invasive osteotomy for hallux valgus enables reduction of malpositioned sesamoid bones.

BACKGROUND: The current minimally invasive distal metatarsal osteotomy for hallux valgus (HV) is V-shaped, which prevents the correction of the rotational metatarsal head deformity and reduction of the sesamoid bones. We sought to determine the optimal method for sesamoid bone reduction during HV surgery. METHODS: We reviewed the medical records of 53 patients who underwent HV surgery between 2017 and 2019 using one of three techniques: open chevron osteotomy (n = 19), minimally invasive V-shaped osteotomy (n = 18), and a modified straight minimally invasive osteotomy (n = 16). The sesamoid position was graded using the Hardy and Clapham method on weight-bearing radiographs. RESULTS: When compared to open chevron and V-shaped osteotomies, the modified osteotomy resulted in significantly lower postoperative sesamoid position scores (3.74 ± 1.48, 4.61 ± 1.09, and 1.44 ± 0.81, respectively, P < 0.001). Furthermore, the mean change in postoperative sesamoid position score was greater (P < 0.001). CONCLUSION: The modified minimally invasive osteotomy was superior to the other two techniques in correcting HV deformity in all planes, including sesamoid reduction.

Minimally invasive Chevron Akin (MICA) osteotomy for severe hallux valgus.

INTRODUCTION: The minimally invasive Chevron Akin (MICA) osteotomy has been widely used to treat hallux valgus (HV). The purpose of this study was to present a case series of patients with severe HV undergoing surgical treatment using the MICA procedure and to evaluate the clinical and radiographic outcomes. MATERIALS AND METHODS: Retrospective study including 60 consecutive feet (52 patients) undergoing MICA for severe HV. The data were collected pre- and post-operatively at the last follow-up. Patients were clinically evaluated by the visual analog pain scale (VAS) and AOFAS hallux MTP-IP score. Radiographic assessments included measurements of hallux valgus angle (HVA), intermetatarsal angle (IMA), metatarsal (MT) length, distal metatarsal articular angle (DMAA), and plantar translation of MT head. The complications were recorded during the follow-up. RESULTS: The mean age was 59.9 years, and the mean follow-up was 20.5 months. The average AOFAS increased from 41.2 to 90.9 points, and the VAS from 8.1 to 1.3 at the last follow-up. The average HVA decreased from 41.2º to 11.6º, the IMA from 17.1º to 6.9º, and the DMAA from 17.9º to 7.8º. The average shortening of the first metatarsal and the plantar translation of the MT head was 5.1 mm and 2.8 mm, respectively. The most observed complication was hardware discomfort, observed in 5 feet (8.3%). There were two cases of recurrence (3.3%). CONCLUSION: MICA technique was demonstrated in this series of cases to be an effective procedure for severe HV, with a low rate of recurrence and an acceptable rate of complications. LEVEL OF EVIDENCE: IV; case series.

The chevron bunionectomy for moderate to severe hallux valgus deformity: Effects of procedural factors on hallux valgus correction.

BACKGROUND: Effects of procedural factors on chevron bunionectomy outcomes were studied. METHODS: Included were 109 feet with distal chevron osteotomy and preoperative intermetatarsal angle (IMA) greater than 15 degrees. IMA and hallux valgus angles (HVA), release type, fixation, second-digit procedures, and risk factors were evaluated. RESULTS: Eighty-three percent (91/109 feet) had satisfactory outcomes; nine had moderate pain. From preoperative, IMA improved 7.2 and HVA 20.5 degrees. Risk factors or second-digit procedures had no effect. Lateral release improved IMA (p < 0.01), with no difference between open lateral and transarticular release; 86% percent (64/74) were satisfied with open lateral release compared with 83% (19/23) and 66% (8/12) with no release and transarticular release, respectively. Fixation did not affect outcomes. CONCLUSION: Chevron bunionectomy corrected IMA and HVA to normal with few complications. Lateral release increased IMA correction. Transarticular release had lower satisfaction than open lateral release or no release. LEVEL OF EVIDENCE: Level III, retrospective.

Comparison of modified Mitchell and Chevron osteotomies for hallux valgus.

BACKGROUND: Good clinical and radiological outcomes in mild-moderate hallux valgus (HV) can be achieved with Chevron osteotomy (CO) and modified-Mitchell osteotomy (MMO). The main goal of the present study was to compare the clinical and radiological outcomes after CO and MMO in HV. METHODS: The study included 45 patients, comprising 40 females with a mean follow-up of 87.5 ± 27.8 months. The outcome measurements of metatarsal length (MT1), HV angle (HVA), intermetatarsal angle (IMA), clinical outcomes, and metatarsalgia were evaluated pre- and postoperatively. RESULTS: No significant difference was determined between the MMO and CO groups in respect of metatarsalgia and AOFAS scores. The CO resulted in a significantly larger decrease in the MT1. The mean HVA and IMA correction was significantly greater after MMO than after CO. CONCLUSION: Since MMO may prevent MT1 shortening, which is a typical problem in the Mitchell osteotomy, MMO may be preferred over CO in patients with preoperative shortened first metatarsal.

Biomechanical evaluation of the proximal chevron osteotomy in comparison to the Lapidus arthrodesis for the correction of hallux valgus deformities.

PURPOSE: The proximal chevron osteotomy and the modified Lapidus arthrodesis are both procedures utilized for deformity correction in patients with severe symptomatic hallux valgus. The aim of the current study was to compare their biomechanical stability when using locking plate fixation. METHODS: Twelve matched pairs of human anatomical lower leg specimens underwent on one side a proximal chevron osteotomy with a medial locking plate and on the other side a modified Lapidus arthrodesis with a plantar locking plate utilizing an interfragmentary compression screw. All specimens underwent bone mineral density (BMD) assessment and were tested in a servohydraulic load frame which applied a load on the centre of the metatarsal head over 1000 loading cycles with subsequently ultimate load testing. Displacement of the proximal and distal bone segment, ultimate load, and bending stiffness were analyzed. RESULTS: Mean displacement of both procedures showed no statistically significant difference throughout all the loading cycles (0.213 ≤ p ≤ 0.834). The mean ultimate load of the proximal chevron osteotomy was 227.9 N (± 232.4) and of the modified Lapidus arthrodesis 162.9 N (± 74.6) (p = 0.754). The proximal chevron osteotomy (38.2 N/mm (± 24.9)) had a significantly higher bending stiffness compared to the modified Lapidus arthrodesis (17.3 N/mm (± 9.9)) (p = 0.009). There was no correlation between BMD and displacement in all loading cycles, ultimate load, and bending stiffness of either procedure (p > 0.05). CONCLUSION: Although the bending stiffness of the chevron osteotomy was higher, there was no statistically significant difference between the surgical techniques in mean displacement and ultimate load. The BMD did not influence the overall stability of either reconstruction. Locking plate fixation increases the clinical value of the modified Lapidus arthrodesis by outweighing most of the biomechanical disadvantages in comparison to the proximal chevron osteotomy.

Correlation of Loss of Correction With Postoperative Radiological Factors After Distal Chevron Osteotomy in Dependence of Concomitant Akin Osteotomy.

Loss of correction is frequently observed following hallux valgus correction and is associated with recurrence of a hallux valgus deformity. The purpose of this study was to correlate loss of correction and radiological parameters following distal chevron (Group C) and combined chevron/akin (Group AC) osteotomy. A total of 859 feet were included for analysis and grouped according to treatment with a distal chevron osteotomy alone or a combined chevron/akin osteotomy. Radiographs were evaluated preoperatively, postoperatively, after 6 weeks, 3 months and, if available, at long term follow-up with a mean of 34.2 (range 7.5-155.3) months. With the exception of the proximal to distal phalangeal articular angle (PDPAA), preoperative deformity was comparable between both groups. Significant correction of all examined parameters (p < .001) was seen. Loss of correction at 6 weeks with minor deterioration until follow-up was also detected, with group AC somewhat better than Group C. A strong correlation with loss of correction was found for the postoperative hallux valgus angle (HVA) (p < .002), intermetatarsal angle (IMA) (p < .001), distal metatarsal articular angle (DMAA) (p < .002), positioning of the sesamoids (p < .002) and joint congruity (p < .035) in Group C and for the DMAA (p < .033) and HVA (p < .046) in Group AC. Multiple postoperative radiological parameters correlated with loss of correction following distal chevron osteotomy. In Group AC only postoperative HVA and DMAA determined loss of correction. Correction of the deformity in Group AC showed greater stability.

Comparison of Fixation Techniques in Oblique and Biplanar Chevron Medial Malleolar Osteotomies; a Finite Element Analysis.

This study aimed to evaluate different fixation techniques and implants in oblique and biplanar chevron medial malleolar osteotomies using finite element analysis. Both oblique and biplanar chevron osteotomy models were created, and each osteotomy was fixed with 2 different screws (3.5 mm cortical screw and 4.0 mm malleolar screw) in 2 different configurations; (1) 2 perpendicular screws, and (2) an additional third transverse screw. Nine simulation scenarios were set up, including 8 osteotomy fixations and the intact ankle. A bodyweight of 810.44 N vertical loading was applied to simulate a single leg stand on a fixed ankle. Sliding, separation, frictional stress, contact pressures between the fragments were analyzed. Maximum sliding (58.347µm) was seen in oblique osteotomy fixed with 2 malleolar screws, and the minimum sliding (17.272 µm) was seen in chevron osteotomy fixed with 3 cortical screws. The maximum separation was seen in chevron osteotomy fixed with 2 malleolar screws, and the minimum separation was seen in oblique osteotomy fixed with 3 cortical screws. Maximum contact pressure and the frictional stress at the osteotomy plane were obtained in chevron osteotomy fixed with 3 cortical screws. The closest value to normal tibiotalar contact pressures was obtained in chevron osteotomy fixed with 3 cortical screws. This study revealed that cortical screws provided better stability compared to malleolar screws in each tested osteotomy and fixation configuration. The insertion of the third transverse screw decreased both sliding and separation. Biplanar chevron osteotomy fixed with 3 cortical screws was the most stable model.

Outcomes of modified chevron osteotomy for hallux valgus.

PURPOSE: This study aimed to detect the effect of a modified chevron osteotomy on hallux valgus (HV) deformity at five-year follow up. METHODS: Twenty patients with symptomatic HV who underwent modified chevron osteotomy between June 2014 and January 2016 were included in the present study. The minimum follow-up duration was five years. Each patient was evaluated preoperatively, six weeks postoperatively and five years postoperatively using the visual analog scale (VAS) pain score, the American Orthopedic Foot & Ankle Society (AOFAS) score and cosmetic and radiological outcomes. RESULTS: The AOFAS score improved from 54.40 ( ± 4.58) preoperatively to 94.30 ( ± 2.15) six weeks postoperatively (p < 0.001) and 96.95 ( ± 1.54) five years postoperatively (p < 0.001). The VAS scores decreased from 6.30 ( ± 1.17) preoperatively to 0.15 ( ± 0.37) five years postoperatively (p < 0.001). The mean intermetatarsal angle improved from 16.00° ( ± 2.20°) preoperatively to 4.15° ( ± 1.22°) six weeks postoperatively (p < 0.001) and 4.40° ( ± 1.39°) five years postoperatively (p < 0.001). The mean HV angle also improved, from 32.70° ( ± 5.34°) preoperatively to 4.80° ( ± 1.40°) six weeks postoperatively (p < 0.001) and 5.20° ( ± 1.32°) five years postoperatively (p < 0.001). The cosmetic results were either excellent or good in 19 patients (95%). There was no recurrence in this study during the five postoperative years. CONCLUSION: A modified chevron osteotomy can achieve successful correction of moderate-to-severe HV, with excellent outcomes at five-year follow up.

The percutaneous learning curve of 3rd generation minimally-invasive Chevron and Akin osteotomy (MICA).

BACKGROUND: Minimally-invasive Chevron and Akin osteotomy (MICA) represents the third-generation percutaneous hallux valgus surgery which is characterized by an extra-articular osteotomy, stable internal fixation and a high potential for correction. Compared to other percutaneous techniques of the foot, MICA is generally regarded as an advanced and demanding surgical procedure with a flat learning curve. The aim of this study is to analyze a single-surgeons experience with his first 50 consecutive MICA procedures. METHODS: Between May 2018 and February 2021, 50 consecutive MICA procedures performed by the author with the "K-wires-First technique" were prospectively analyzed focusing on surgery duration, number of fluoroscopies, correction results and surgery-associated complications. A modification of the original MICA technique as described by its inaugurators Redfern and Vernois allows the use of a standard-sized C-arm and aims to reduce revison rates and conversion to open surgery by placing the guidewires prior to performing the osteotomy. RESULTS: The average surgery time for all MICA procedures was 46.8 min (SD 12.1, range 31-90 min). The average amount of fluoro shots required to perform MICA was n = 126.6 (SD 40.8, range 65-231). Comparing the preoperative and 6-week postoperative radiographs, the IMA decreased after MICA by a mean of 10.8° from 16.2° to 5.4° and the HVA by a mean of 22.1° from 30.6° to 8.5°. One case required intraoperative conversion to open hallux correction. There were 4 feet in three patients with secondary screw removal of the Chevron fixation due to prominent proximal screw tips. CONCLUSIONS: Although the learning curve of 3rd generation MICA is flat and requires specific training and intensive practice, the rate of complications is not elevated compared to other percutaneous hallux valgus techniques. Strict adherence to the principles of 3rd generation MICA with stable fixation and meticulous intraoperative control of each surgical step helps to reduce surgery-associated complications. The learning curve showed a continous improvement in regard to surgery time and use of fluoroscopy. After 40 procedures, the surgery time consistently dropped under 45 min and required less than 100 fluoro-shots. The modified surgical technique may help reduce Chevron screw mal-positioning when using large C-arm fluoroscopy for this procedure.

Time to maximum clinical improvement following minimally invasive chevron and Akin osteotomies (MICA) in hallux valgus surgery.

BACKGROUND: There is increasing evidence of positive improvement in clinical and radiological outcomes following minimally invasive hallux valgus deformity correction surgery (MIS). This study investigated the rate of improvement in clinical patient reported outcome measures (PROMs) following MIS as this is not well understood. METHODS: Between July 2014 and July 2019, data was prospectively collected from consecutive patients pre-operatively and at 6, 12, and 24 months following third-generation minimally invasive chevron and Akin osteotomies (MICA). Radiographic deformity and correction was assessed using weight-bearing radiographs pre-operatively and 6 weeks post-operatively. The primary outcome measure was the change in Manchester Oxford Foot Questionnaire (MOXFQ) score at each time point. Secondary outcomes include radiographic deformity correction, health-related quality of life PROMs and exploration of cases where PROMs did not improve. RESULTS: There were 202 feet with complete PROM data for every time point. There was a statistically significant improvement in MOXFQ Index score at each time point (p < 0.05) following MICA surgery. The majority of the improvement occurred within the first 6 months. A subgroup of 17 feet (8.4%) were identified which had worse MOXFQ Index scores 6 months following MICA. For 14 feet in this subgroup (82.4%), the MOXFQ Index score subsequently improved over time such that by two years, their score had significantly improved compared to their pre-operative score. CONCLUSION: The majority of PROM improvement with MICA is gained by 6 months post-operatively but further significant improvement can be seen up to 2 years. Those patients who have not improved at 6 months, are likely to do so with time. LEVEL OF EVIDENCE: IV.

Minimally invasive surgery for severe hallux valgus in 106 feet.

BACKGROUND: There is widespread variation in the optimal procedure for correction of severe hallux valgus deformity defined as hallux valgus angle (HVA) (≥40°) and/or 1-2 intermetatarsal angle (IMA) (≥20°). There is limited evidence investigating the clinical or radiological outcomes following treatment of severe hallux valgus deformity with third-generation minimally invasive chevron and Akin osteotomies (MICA). METHODS: This was a prospective observational single surgeon series of consecutive patients who underwent primary third-generation MICA with screw fixation for severe hallux valgus. The primary outcome was a validated patient reported outcome measure (PROM), the Manchester-Oxford Foot Questionnaire (MOXFQ), assessed minimum 2 years following MICA. Secondary outcomes were radiographic deformity correction (assessed 6 weeks post-operatively), complication rates and other quality of life PROMs (EQ-5D and Visual Analogue Pain Scale). RESULTS: Between September 2014 and November 2018, 106 consecutive feet (n = 78 patients; 73 female, 5 male) met the inclusion criteria. Prospectively collected pre-operative and 2 year PROM MOXFQ data was available for 86 feet (81.1%). At two years following surgery, the MOXFQ score significantly improved for the Pain, Walking and Standing and Social Interaction domains from 39.2 to 7.5, 38.2 to 5.9 and 48.6 to 5.5, respectively (p < 0.001). Pre- and 6 week post-operative radiographic data was available for all 106 feet. Mean IMA improved from 18.2° to 6.3° (p < 0.001) whilst mean HVA improved from 45.3° to 10.9° (p < 0.001). The complication rate was 18.8% and the screw removal rate was 5.6%. CONCLUSION: This study has demonstrated third-generation MICA for the treatment of severe hallux valgus deformity enables substantial deformity correction and is associated with significant improvements in clinical PROMs 2 years following surgery.