결정론적 스케쥴링을 이용하여 동시성 버그를 재현하는 커널 퍼져 제작

학위논문(석사) -- 서울대학교대학원 : 공과대학 전기·정보공학부, 2022. 8. 이병영.커널 퍼져들이 최근 몇 년간 발전해오면서 퍼져에 의해 보고되는 버그들의 수가 늘어났다. 커널 개발자들이 이런 버그들을 모두 분석할 수 없기 때문에 이런 상황은 디버깅 정보를 제공해줄 수 있는 버그 재현의 중요성을 더욱 중요하게 만든다. 불행 히도, 퍼져는 종종 버그 재현에 실패하는데 재현이 힘든 버그 중 하나가 바로 동시성 버그다. 동시성 버그는 여러 스레드 사이의 특정한 조건을 만족할때 발생하는데 커 널 스케쥴링의 비결정적인 스레드 간섭은 동시성 버그의 재현을 막는다. 그 결과, 일부 동시성 버그들은 버그의 재현에 실패한 뒤 고쳐지지 않은채 버려진다. 이 논문에서는, 퍼져에 의해 발견된 버그를 결정적으로 재현할 수 있도록 도와주 는 REPFUZZER 를 소개한다. 이는 선택적 스레드 추적과 결정적 스케쥴러를 통해 문 제를 해결한다. 선택적 스레드 추적을 통해 REPFUZZER 는 퍼져에 있어서 흥미로운 스레드에만 집중할 수 있도록 한다. 그리고 REPFUZZER 는 결정적 스케쥴러를 통해 선택된 스레드를 스케쥴 해주며 결정적인 스레드 간섭을 만들어 낸다. 퍼징 단계와 재현 단계 모두에서 REPFUZZER 를 사용함으로써 퍼져는 찾아낸 버그를 재현해낼 수 있게 된다. 결과적으로 REPFUZZER 는 15개의 실제 동시성 버그를 재현하면서 효율성을 보여줬으며, 버그 중 일부는 비결정적인 커널 스케쥴링으로 재현해내기 위해 엄청난 시간을 필요로 했다.As kernel fuzzer has been studied and becomes better for years, the number of reported bugs from the fuzzer increased. Since kernel developers could not analyze all of the bugs, the situation emphasizes the importance of bug reproduce which can provide debug information. Unfortunately, the fuzzer often fails to reproduce bug, and one of the most difficult bug type is concurrency bug. The concurrency bug requires certain conditions between several threads, and non-deterministic thread interleavings from kernel scheduling prevent reproducing. As a result, some concurrency bugs are left unpatched after failures of reproduce. In this thesis, we presents REPFUZZER which enables deterministic reproduce for bugs found by fuzzer. It solves the problem with selective thread tracing and deterministic scheduler. With selective thread tracing, REPFUZZER can focus on only interesting thread in fuzzing context. Then REPFUZZER schedules the selected threads with deterministic scheduler and produces deterministic thread interleavings. Using REPFUZZER’s scheduling at both fuzzing and reproduce phase, the fuzzer can reproduce bugs found at fuzzing phase. As a result, REPFUZZER shows its effectiveness for reproducing concurrency bugs with 15 real-world bugs, and some of the bugs require enormous times to be reproduced with non-deterministic kernel scheduling.Abstract i Contents ii List of Tables iv List of Figures v 1 INTRODUCTION 1 2 BACKGROUND 5 2.1 Fuzzing 5 2.2 Concurrency Bug 6 3 DESIGN 7 3.1 Design 7 3.1.1 Selective Thread Tracing 9 3.1.2 Deterministic Scheduler 12 3.2 Implementation 18 4 EVALUATION 20 4.1 Effectiveness of Deterministic Scheduler 20 4.2 Statistics of Deterministic Scheduler 23 4.3 Overhead of Deterministic Scheduler 25 5 DISCUSSION 27 6 RELATED WORKS 29 6.1 Kernel Concurrency Bugs 29 6.2 Reproducing Bugs 30 7 CONCLUSION 32 Abstract (In Korean) 37석

Evaluation of Interfacial Properties of Thin film considering Constraint Effect between Film and Substrate using Flat-end Vickers Indenter

학위논문 (박사) -- 서울대학교 대학원 : 공과대학 재료공학부, 2020. 8. 권동일.Delamination of thin-coating films on substrates has become a critical issue for the reliability of micro- and nanoelectronic devices. Since failures of the interface may eventually lead to total system failure, evaluation of the interface between its film and substrate becomes an important problem and several testing methods such as a scratch test, pull-off test and peel test have been proposed. However, these conventional tests have limitations as a universal test methods because of limitations of the film characteristics and requirements such as specially designed specimen. In this thesis, nanoindentation test was developed to overcome the limitations of conventional test methods. In general, nanoindentation testing has been widely applied to evaluate the mechanical properties of thin films such as hardness and elastic modulus at small scale. It was initially used only to evaluate hardness and elastic modulus from the loading/unloading curve of the indentation testing, but has now been extended to evaluate residual stress, tensile, fracture properties and so on. The nanoindentation test has the advantage that local and thin-film properties can be evaluated through only a single indentation, and no specially designed specimen is needed. When an indentation is made in nanoindentation testing, the amount of elastic-plastic deformation beneath the indent increases as the indentation load increases. In addition, in the case of a thin film, which is a bond-type heterogeneous material, the total amount of work involved in indentation testing can be expressed as the sum of the work in the film, work in the substrate, and work at the interface. The work at the interface generated by indentation testing can be defined as the resistance to interaction between the film and the substrate, which can be expressed as adhesion at the interface. As a result, in order to evaluate the adhesive force at the interface, the work at the interface is evaluated by a quantitative evaluation of the work in the composite film-substrate structure and the work occurring in the film and the substrate in an independent situation. If a film of differing hardness and elastic modulus is placed on the substrate and the composite structure is indented, the plastic deformation in the film is expected to differ from the plastic deformation of the substrate. The stress-strain field of the film and substrate can be determined based on elastic-plastic theory, and the expanding spherical cavity model for indentation gives the individual radial strain components. If there is no adhesion between film and substrate, the radial strain profile exhibits strain discontinuity, but if there is strong adhesion between them, the strain continuity will act strongly. Eventually, the strain continuity across the film and the substrate causes the shape of the strain to bend and the deformation geometry will be distorted. In addition, the relatively soft material will be constrained to the hard material side. As a result, the constraint on film and substrate will depend on the degree of adhesion at the interface between the film and the substrate, and the extent of the constraint can be explained by the change in constraint according to indentation testing. It is thus possible to quantitatively evaluate the amount of constraint change through indentation testing on the film and substrate structure system, and to evaluate the adhesion at the interface using this quantitative evaluation.산업화가 다양해지고 고도화가 될수록 국가기간 산업에서는 다양한 역할 및 특성을 가지고 있는 소재를 요구하고 있다. 특히 전자, 디스플레이 등 첨단 산업에서는 이종소재를 접합시킨 다기능성 소재의 활용이 증가하고 있다. 하지만 이러한 이종소재의 접합은 물리, 화학적인 인위적 접합으로서 발생되는 계면은 박막과 모재에 비해 기계적인 특성이 상대적으로 취약한 부분으로 나타나며, 외부에서 응력이 가해지는 상황 또는 환경적 요인에 의해 박리와 파손이 우선적으로 발생한다. 그렇기 때문에 이러한 계면의 특성은 박막시스템의 신뢰성을 평가하는 최우선 요소로서 정량적으로 평가하기 위한 연구와 다양한 시험법들이 개발되었다. 그러나 기존의 시험법은 정량적으로 접착력을 평가하기에 몇가지 한계점을 가지고 있다. 첫 번째로, 박막과 모재의 영향이다. 기존에 사용되어왔던 접착력 평가 시험법의 경우 시험법상 특수성으로 인해 필수불가결하게 박막과 모재의 특성이 결과값에 주도적으로 작용하게 된다. 하지만 아직까지 박막과 모재의 영향을 정량적으로 해석하는 연구가 미비하여 정확한 접착력을 평가하는데 문제점을 가지고 있다. 두 번째로는, 기존의 시험법이 해당 소재의 파괴를 가져온다는 점이다. 파괴 시험법으로서 가지는 한계점으로 수 나노미터 수준으로 경박화 되고 있는 박막시스템에서 정확한 계면 박리 시점 및 광학 장비를 통한 파손 영역의 관찰이 필수적이라는 점이다. 결국 정확한 박리 시점의 선택의 어려움과 매우 좁은 영역의 정확한 관찰이 동반되어야 목적으로 하는 접착력의 정확한 평가가 가능하다는 문제점을 가지고 있다. 세 번째로, 시험법에 따라 적용할 수 있는 소재가 제한되어 있어 적용상의 한계가 있다. 산업에서 필요로 하는 소재는 시간이 지날수록 다양해지고 있다. 하지만 기존의 시험법이 적용 가능한 소재에 한계를 가지고 있으며, 결국 하나의 시험법을 통하여 다양한 소재에 대한 접착력 평가 및 결과 비교에 문제점을 가지고 있다고 할 수 있다. 본 학위 논문에서는 기존의 시험법들이 가지는 한계점을 극복하고자 비파괴 시험이 가능하고 박막과 기판의 영향을 정량화 시키기 위해 압입시험을 이용하여 접착력을 평가하는 모델을 연구하였다. 압입시험은 간단한 시험을 통해 압입자 하부의 응력 분포 및 상태를 해석함으로써 다양한 역학특성을 평가하는 최신의 기계적 시험법이다. 또한 높은 하중 분해능과 변위 분해능을 가지는 장비 개발을 통해 매크로, 마이크로 스케일 뿐만 아니라 나노 스케일 박막까지의 기계적 물성을 평가하는데 활용성이 증가하고 있다. 박막시스템에 압입시험을 수행하면 박막과 모재의 개별적인 하중변위 곡선을 얻을 수 있으며 이와 함께 계면의 영향이 복합적으로 반영이 된 압입 하중변위 곡선을 획득할 수 있다. 하지만 단순히 이렇게 얻은 곡선에서 박막과 모재의 영향을 실험적으로 구분하여 분리해 낼 수 없었기 때문에 이론적 모델링을 통해서 각각의 영향을 구분하였다. 본 연구에서는 압입시험 시 발생되는 에너지의 총합을 박막/계면/모재의 합으로 정의하고, 가해진 하중과 면적의 비로 정의되는 경도를 압입시험 시 발생된 에너지와 압입자 하부의 소성변형에 동반되는 부피의 비로 확장시킨 개념을 인용하였다. 확장된 경도를 바탕으로 박막과 모재의 변형에 의해 발생된 일을 각각 해석하였다. 또한 계면에 의해서 압입자 하부에 확장되는 소성역이 구속되는 상황을 해석하였다. 박막과 모재 중 상대적으로 연질의 재료가 경질의 재료에 의해 소성역이 구속됨을 가정하였고, 수치화를 위해 공극확장모델을 사용하여 수식을 전개하였다. 이를 통해 계면에 의해 상대적으로 연질 재료의 구속되는 부피의 양을 표현하는 계면인자를 정의하였고, 계면인자를 재료 인자를 이용하여 수학적으로 도출하였다. 압입시험에서 계면에 의한 구속효과를 해석하여 계면의 일의 양을 정량적으로 평가하는 수식을 제안하였으며, 압입깊이에 따라 달라지는 일의 양을 구속되는 부피로 정규화 하여 최종적으로 접착강도를 평가하는 수식을 제안하였다. 제안한 접착력 평가 모델의 타당성을 검증하기 위해 기존의 박리시험을 통해 얻어진 결과와 압입시험을 이용하여 도출된 접착강도를 비교하여 유사한 경향성을 확인하였다.Chapter 1. Introduction 1 1.1. Objective of the Thesis 2 1.2. Organization of the Thesis 7 Chapter 2. Research Background 11 2.1. Adhesion evaluation method 12 2.1.1. True work of adhesion 12 2.1.2. Practical Work of Adhesion 14 2.2. Instrumented indentation tests 17 2.2.1. Elastic Contact mechanics 19 2.2.2. Elastic-Plastic Contact mechanics 23 2.3. Nanoindentation 29 2.3.1. Development 29 2.3.2. Application 31 Chapter 3. Theoretical Modeling 68 3.1. Thin-film indentation 69 3.2. Interfacial Constraint Effect 71 3.3. Interface parameter 76 3.4. Factor analysis 79 3.5. Modeling 81 3.5.1 Film constraint 82 3.5.2 Substrate constraint 83 3.6 Physical meaning of equation 85 Chapter 4. Verification of models 98 4.1. Experimental Details 99 4.1.1. Sample preparation 101 4.1.2. Experiment conditions 103 4.2. Results & Discussion 103 4.2.1. Comparison with scratch and pull-off 103 4.2.2. Indentation parameter 104 4.2.3. Indentation adhesion strength 105 4.2.4. Experimental results 107 Chapter 5. Conclusion 127 Reference 133 Abstract in Korean 141 List of publications 147Docto

Distal Chevron Osteotomy with One BOLD ScrewⓇ Fixation in Hallux Valgus

Purpose: To present our experience of distal chevron osteotomy utilizing one BOLD screwⓇ as an alternative fixation method which has advantages over the Kirschner (K)-wire fixation. Materials and Methods: Between January 2001 and June 2003, 19 patients with a symptomatic hallux valgus deformity underwent 20 distal metatarsal chevron osteotomies with one BOLD screwⓇ fixation. The mean age was 55.6 years with a minimum follow up period 12 months. For radiographical evaluation, hallux valgus angle (HVA) and intermetatarsal angle (IMA) were used. For clinical evaluation, we used AOFAS hallux metatarsophalangeal interphalangeal scale and overall satisfaction of the patients. Results: The AOFAS scores improved from mean 47.5 points to mean 68.1 points at postoperative 3 months and mean 86.0 points at last follow-up. The average HVA corrected from 25.3 degrees to 12.7 degrees. The IMA was corrected from 11.6 degrees to 7.6 degrees. The overall satisfaction of the patients was 85%. There was no major complication. Conclusion: We demonstrated that distal chevron osteotomy with one BOLD screwⓇ fixation has advantages such as no additional procedure, no loss of correction, early rehabilitation, no prominent hardware and skin irritation. This method also showed excellent bone union, correction and patient satisfaction.ope

Peroxisome Proliferator-Activated Receptor γ Activation Promotes Adipogenesis in Human Mesenchymal Stem Cells

Purpose: In this study, we determined that the troglitazones could induce uniform adipogenesis of human mesenchymal stem cells (MSCs) within a short time in a dose- and a time-dependent manners. Materials and Methods: Human MSCs were isolated from bone marrow and cultured in basal or adipogenic medium in the presence of 0 50 μM troglitazone for 5 days. Then we performed flow cytometry, RT-PCR and western blot analysis. Results: In FACS assay, troglitazone induced adipocyte differentiation in a dose-dependent manner. At concentration of 25 μM troglitazone in adipogenic medium, over 50% of the cells differentiated into adipocytes at day 5. This was accompanied by increased mRNA levels for the adipocyte gene markers (LPL, aP2 and PPARγ) in RT-PCR. In western blot analysis, we found that ERK phosphorylation was inhibited in the early stage of adipogenesis. Conclusion: Through the addition of troglitazone as a PPAR γ agonist, we could get the uniform adipogenic differentiation within a short time. Thus, troglitazone directly regulates differentiation of human MSCs into adipocytes; induced PPAR γ expression may play a key regulatory role in this process. And we suggest a role for ERK as a regulatory switch for these differentiation pathwaysope

Spectral ratio method를 이용한 탄성파 감쇠 특성 연구

탄성파 감쇠는 탄성파 자료의 해상도의 향상과 직접적인 탄화수소 지시자로써 유용하게 사용된다. 이론적으로 탄화수소가 매장된 저류층은 물로 포화된 다공질 암석보다 감쇠가 잘 일어나며, 이는 매질을 통과하는 탄성파의 속도와 진폭의 감쇠가 지각을 구성하는 매질과 공극 내부의 공극수 및 그 상호간의 작용에 의하여 영향을 받는 것이 원인이다. 본 연구에서는 탄성파 감쇠와 반비례 관계를 가지는 Quality factor 를 Spectral ratio method를 이용하여 축소모형실험, 수치모형실험 그리고 현장자료에 적용하여 분석하였다. 축소모형실험에서는 일반적으로 실내분석방법에서 기준 시료로 사용하는 알루미늄에 대하여 아크릴의 를 산출하였고, 수치모형실험에서는 탄성파 반사법과 수직입사 탐사법을 이용하여 지층의 물성 변화와 그 경계에서 발생하는 탄성파 감쇠영향을 분석하여 를 도출하였다. 마지막으로 현장자료의 적용은 남해안 거제도에서 취득한 탄성파 반사법 자료에 대하여 각 층의 반사면에 따른 감쇠 정도를 파악하였다. Quality factor의 분석은 저류층 특성과 탄화수소 탐지를 위한 예측 수단이며, AVO의 효과적인 해석, 탄성파 영상의 해상도 향상과 매질의 특성 연구를 위해 매우 중요하다.1. 서 론 1 1.1 개요 1 2. 탄성파 감쇠 이론 3 2.1 탄성파 감쇠의 정의 3 2.2 탄성파 Quality factor, 와 Spectral ratio method 6 3. 탄성파 감쇠 모형실험 및 적용 15 3.1 탄성파 감쇠 축소모형실험 15 3.1.1 탄성파 감쇠 축소모형실험 구성 15 3.1.2 탄성파 감쇠 축소모형실험 방법 19 3.1.3 탄성파 감쇠 축소모형실험 결과 22 3.2 탄성파 감쇠 수치모형실험 27 3.2.1 탄성파 감쇠 수치모형실험 구성 27 3.2.2 탄성파 감쇠 수치모형실험 방법 29 3.2.3 탄성파 감쇠 수치모형실험 결과 31 3.2.3.1 1번 모델 31 3.2.3.2 2번 모델 37 3.2.3.3 3번 모델 39 3.2.3.4 4번 모델 42 3.3 현장 자료 적용 47 3.3.1 현장 자료 취득 및 처리 47 3.3.2 현장 자료 적용 및 분석 49 4. 결론 52 감사의 글 54 References 56 Bibliography 6

Superior pedal function recovery of newly designed three spike insole over total contact insole in refractory plantar fasciitis: A randomized, double-blinded, non-inferiority study

Introduction: Plantar fasciitis is one of the common foot complaints that is chronic and can induce dysfunction. Total contact insole (TCI) is simple but effective in treating plantar fasciitis. Despite its effect, the cost and long duration for production have been the major flaws. Therefore, we developed a newly designed three-spike insole (TSI) that can be commercially productive and compared its clinical outcomes to TCI. Methods: Patients with plantar fasciitis refractory to conservative treatment for more than 6 weeks were candidates. We produced insoles with hardness of 58 ± 5 Shore-A. Twenty-eight patients were randomized with equal allocation to either TSI or TCI. The following assessment tools were used: visual analog scale (VAS), American Orthopaedic Foot and Ankle score, Foot and Ankle Outcome Score, Karlsson-Peterson (KP) score, Short Form-36 for quality of life, and Foot Function Index. Non-inferiority was declared if VAS was within the statistical variability of minimal important difference. A blinded assessor evaluated the groups at baseline and after 6, 12, and 24 weeks. Results: The groups were homogenous for majority of variables at baseline. Overall patient-reported satisfaction showed improvement from mean 5.2 (range, 1-12) weeks of wearing and all clinical outcome scores showed significant improvements in both groups over time on Friedman test (p ≤.032). TSI showed non-inferiority to TCI at each time point. Post hoc analysis revealed that many scales showed significant superiority of TSI at 3 month (p ≤.008) and KP score at 6 month (p < .001). Conclusion: We reaffirmed that semi-rigid insole is effective in refractory plantar fasciitis and showed TSI restores pedal function more rapidly than TCI. TSI can be not only effective in deriving better clinical outcomes but also be manufactured for popularization to lower the price and producing time of orthosis.ope

Tendon transfer with a microvascular free flap for injured feet in children

We reviewed 11 patients who had been treated between January 1986 and June 1994 for severe foot injuries by tendon transfer with microvascular free flaps. Their mean age was 5.6 years (3 to 8). Five had simultaneous tendon transfer and a microvascular free flap and six had separate operations. The mean interval between the tendon transfer and the microvascular free flap was 5.8 months (2 to 15) and the mean time between the initial injury and the tendon transfer was 9.6 months (2 to 21). The anterior tibial tendon was split in five of six cases. The posterior tibial tendon was used three times and the extensor digitorum longus tendon twice. The mean follow-up was 39.7 months (24 to 126). There were nine excellent and two good results. Postoperative complications included loosening of the transferred tendon (2), plantar flexion contracture (1) mild flat foot deformity (1) and hypertrophic scars (2). We recommend tendon transfer with a microvascular free flap in children with foot injuries combined with nerve injury and extensive loss of skin, soft tissue and tendon.ope

Terminology for osteochondral lesions of the ankle: proceedings of the International Consensus Meeting on Cartilage Repair of the Ankle

Background: The evidence supporting best practice guidelines in the field of cartilage repair of the ankle is based on both low quality and low levels of evidence. Therefore, an international consensus group of experts was convened to collaboratively advance toward consensus opinions based on the best available evidence on key topics within cartilage repair of the ankle. The purpose of this article is to report the consensus statements on "terminology for osteochondral lesions of the ankle" developed at the 2019 International Consensus Meeting on Cartilage Repair of the Ankle. Methods: Forty-three international experts in cartilage repair of the ankle representing 20 countries were convened and participated in a process based on the Delphi method of achieving consensus. Questions and statements were drafted within four working groups focusing on specific topics within cartilage repair of the ankle, after which a comprehensive literature review was performed, and the available evidence for each statement was graded. Discussion and debate occurred in cases where statements were not agreed on in unanimous fashion within the working groups. A final vote was then held, and the strength of consensus was characterised as follows: consensus, 51%-74%; strong consensus, 75%-99%; unanimous, 100%. Results: A total of 11 statements on terminology and classification reached consensus during the 2019 International Consensus Meeting on Cartilage Repair of the Ankle. Definitions are provided for osseous, chondral and osteochondral lesions, as well as bone marrow stimulation and injury chronicity, among others. An osteochondral lesion of the talus can be abbreviated as OLT. Conclusions: This international consensus derived from leaders in the field will assist clinicians with the appropriate terminology for osteochondral lesions of the ankle.ope

Arthroscopic Debridement for the Osteoarthritic Ankle: Clinical Results and Prognostic Factors

Purpose: To evaluate the clinical results of arthroscopic debridement in osteoarthritic ankle and prognostic factors. Materials and Methods: Between Feb. 2001 and Mar. 2004, twenty-seven patients who had an osteoarthritic ankle disease were managed by arthroscopic debridement. The mean age of the patients was 50.0 years (20-71) and the mean follow-up after operation was 16.2 months (12-36). There were 18 men (66.7%) and 9 women (33.3%). The preoperative radiographic findings were divided into 4 groups according to the classification system by Takakura et al. Preoperative AOFAS ankle-hindfoot scale and subjective satisfaction were checked at the last follow-up visit, and the results were compared. Results: In radiological evaluation, stage Ⅰ was 6 cases (22.2%), stage Ⅱ was 14 cases (51.9%), stage Ⅲ was 4 cases (14.8%), and stage Ⅳ was 3 cases (11.1%). The mean preoperative AOFAS ankle-hindfoot scale was 59.1±16.7 and improved to 66.5±24.3 at last follow-up. Especially, in stage Ⅰ, preoperative AOFAS score was 69.3±18.7 and improved to 74.3±29.7, and in stage Ⅱ, preoperative AOFAS socre was 63.0±9.6 and improved to 77.1±12.9. But in the stage Ⅲ and Ⅳ, preoperative scores were not improved. The preoperative radiographic findings correlated with the outcome at the last follow-up time (p<0.05). The group with loose body and the group without anterior osteophyte showed better AOFAS score compared to the control group, but there was no statistically significant difference between the two-groups. In subjective satisfaction, excellent or good results were achieved in 14 cases (51%). Conclusion: We suggest that arthroscopic debridement is an effective treatment in which preservation of alignment and reasonable articular cartilage can be achieved.ope

Clinical comparison of the osteochondral autograft transfer system and subchondral drilling in osteochondral defects of the first metatarsal head

BACKGROUND: Osteochondral defects of the first metatarsal head can deteriorate to osteoarthritis of the first metatarsophalangeal joint if left untreated. Treatment options for osteochondral defects of the first metatarsal head vary widely. PURPOSE: To compare the clinical outcomes of the osteochondral autograft transfer system with those of subchondral drilling for the treatment of osteochondral defects of the first metatarsal head. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: The authors retrospectively evaluated 24 cases of osteochondral defects of the first metatarsal head treated operatively; 14 patients underwent subchondral drilling (group A), while 10 were treated with the osteochondral autograft transfer system (group B). The association of variables of osteochondral defects with clinical outcomes was assessed in each group. Clinical outcomes were evaluated according to a visual analog scale (VAS) for pain, the American Orthopaedic Foot and Ankle Society (AOFAS) hallux metatarsophalangeal-interphalangeal scale, and the Roles and Maudsley score. The Tegner activity scale and an activity rating scale were used to determine the activity levels. RESULTS: The mean VAS score in both groups was significantly improved (from 6.9 ± 0.9 to 3.9 ± 1.3 in group A and from 7.4 ± 0.8 to 3.4 ± 1.2 in group B; P .05). No association was found between location of the defect area and clinical outcome in either group. CONCLUSION: For osteochondral defects larger than 50 mm(2) or when a subchondral cyst exists, the osteochondral autograft transfer system could potentially be used as a treatment of choice for osteochondral defects of the first metatarsal head to restore functionality of the metatarsophalangeal joint.ope