About

Jaimo Ahn, MD, PhD, is an Adjunct Associate Professor of Orthopaedic Surgery at the University of Pennsylvania and an attending orthopaedic surgeon at the Hospital of the University of Pennsylvania, Pennsylvania Hospital, and Penn-Presbyterian Medical Center in Philadelphia, PA. He serves as the Assistant Director of the Orthopaedic Surgery Residency Program and is Co-Director of Penn Orthopaedic Trauma and Fracture Reconstruction. Dr. Ahn's research interests focus on the outcomes of orthopaedic trauma and fracture treatment, as well as the molecular enhancement of bone formation and fracture healing. He works with interdisciplinary teams including biologists, engineers, surgeons, veterinarians, and clinical investigators to improve orthopaedic care. His scientific work delves into gene regulation in bone healing, utilizing mouse models to study pathways related to thrombospondins, Wnt, and Notch, with particular attention to geriatric conditions such as fractures and bone loss. Additionally, Dr. Ahn investigates medical decision-making paradigms, analyzing orthopaedic outcomes data and exploring evidence-based medicine to refine clinical decision processes. He is also dedicated to advancing medical education, especially for clinician-scientists, advocating for data-driven training and resource allocation from undergraduate through graduate levels. His contributions aim to enhance patient care, surgical outcomes, and the training of future medical scientists.

Research topics

• Medicine
• Pathology
• Cancer research
• Biology
• Cell biology
• Endocrinology
• Family medicine
• Anatomy
• Immunology
• Internal medicine
• Biochemistry
• Chemistry
• Surgery
• Genetics

Selected publications

• My Lucky Break

  Journal of Bone and Joint Surgery · 2026-04-23

  articleSenior author
  PublisherDOI

• What are the effects of early versus delayed weight-bearing following surgical fixation of ankle fractures in adults?

  Cochrane Clinical Answers · 2025-06-02

  article1st authorCorresponding
  PublisherDOI

• Prevalence and Impact of MD PHD Training in Academic Orthopedic Surgery

  Journal of Orthopaedic Research® · 2025-12-16

  article

  The prevalence of surgical scientists is decreasing due to rising complexities associated with these careers. This study determines the prevalence and impact of MD PhD training in academic orthopedic surgery. This was a cross-sectional study of faculty with MD PhD training at departments of orthopedic surgery in the United States. A control group of MD-only faculty was generated via propensity matching in a 3:1 ratio based on MD degree, institutional affiliation, academic rank, and subspecialty training. Study outcomes were peer-reviewed publication volume, h-index, National Institutes of Health (NIH) grant funding totals, and obtainment of department leadership positions. Comparisons were made with non-parametric and Chi-squared tests. There were 108 clinical faculty with MD PhD training at departments of orthopedic surgery (108/2775, 3.9%). In aggregate, MD PhD trained faculty had more peer-reviewed publications (55, IQR (114) vs. 42, IQR (94), p = 0.024), citations (1521, IQR (3122) vs. 738, IQR (2168), p < 0.001), and higher h-index values (18.0, IQR (23) vs. 14.0, IQR (19), p = 0.005) than controls. MD PhD faculty were more likely to obtain NIH research funding (27.8% vs. 3.7%, p < 0.001) and had higher NIH grant funding totals than MD faculty ($131,347,304 vs. $41,964,766). There were similar rates of promotion to department chair, service line chief, residency program director, and fellowship program director between the two cohorts (p > 0.05). Surgical scientists with MD PhD training account for a small percentage of clinical faculty at departments of orthopedic surgery, but have outsized scholarly influence as measured by peer-reviewed publication volume and NIH research grant funding totals.

  PublisherDOI

• <i>Prg4</i> + fibroadipogenic progenitors in muscle are crucial for bone fracture repair

  Proceedings of the National Academy of Sciences · 2025-07-29 · 7 citations

  articleOpen access

  Clinically, compromised fracture healing often occurs at sites with less muscle coverage and muscle flaps can provide the necessary healing environment for appropriate healing in severe bone loss. However, the underlying mechanisms are largely unknown. Here, we established a mouse reporter model for studying muscle cell contribution to bone fracture repair. Analyzing skeletal muscle scRNA-seq datasets revealed that Prg4 marks a fibroadipogenic progenitor (FAP) subpopulation. In mice, Prg4 + cells were specifically located in the skeletal muscle, but not at the periosteum or inside cortical bone. These cells expressed FAP markers, responded to muscle injury, and became periosteal cells under normal and muscle injury conditions. Fracture fragmented muscle fibers, rapidly expanded Prg4 + FAPs at the injury site and promoted their migration into the fracture gap. Later, they gave rise to many chondrocytes, osteoblasts, and osteocytes in the outer periphery of callus next to muscle. In repaired bones, the descendants of Prg4 + FAPs were detected as mesenchymal progenitors in the periosteum and osteocytes at the prior fracture site. A second fracture activated those cells and stimulated them to become osteoblasts in the inner part of callus. Importantly, ablation of Prg4 + FAPs impaired fracture healing and functional repair. In an intramembranous bone injury model (drill-hole), Prg4 + FAPs became periosteal cells, but their contribution to bone defect repair was significantly less than in fractures. Taken together, we demonstrate the critical role of FAPs in endochondral bone repair and uncover a mechanism by which mesenchymal progenitors transform from muscle to cortical bone.

  PublisherDOI

• Management of hip fracture patients on direct oral anticoagulants: a survey of orthopaedic trauma surgeons, systematic review, and meta-analysis

  OTA International The Open Access Journal of Orthopaedic Trauma · 2025-01-28 · 1 citations

  articleOpen access

  Objectives: This systematic review examined the literature regarding management of fracture patients who take direct oral anticoagulant (DOAC) medications, with a focus on delay in surgical treatment, and need for transfusions. In addition, a survey of orthopaedic trauma surgeons was conducted to gain insight on current practices. Data Sources: A review of PubMed, Cochrane, Embase, and Scopus databases was performed from inception through March 2024, including English language publications. Study Selection: Studies were included if they reported time to surgery and transfusion rates among fracture patents who were taking DOAC medications. Additional data points were collected on an "if-reported" basis, including mortality, venous thromboembolism, and bleeding complications. Data Extraction: In all, 4546 abstracts were screened. Full-text review was conducted on 86 publications, and 25 articles were included in the final analysis. Each article was independently screened by 2 reviewers, with disputes settled by a third reviewer. Study quality was assessed using the Methodological Index for Non-Randomized Studies (MINORS) tool. Data Synthesis: Descriptive statistics are reported for overall study findings. Meta-analysis was performed for the variables "time to surgery" and "transfusion rate." Conclusions: Our findings indicate that fracture patients taking DOACs experience longer delays before surgery but have equivalent transfusion rates compared with nonanticoagulated patients. Survey results indicate that surgeons do not delay operating on emergent or percutaneous cases, regardless of anticoagulant medications. In circumstances when they do delay, they are more likely to do so for patients taking DOAC medications. Level of Evidence: Level III, systematic review and meta-analysis of Level II and III articles.

  PublisherDOI

• Pelvic Fractures and Associated Urogenital Injuries in Children: A Systematic Review: Erratum

  Journal of Pediatric Orthopaedics · 2025-12-10

  erratum
  PublisherDOI

• Pelvic Fractures and Associated Urogenital Injuries in Children: A Systematic Review

  Journal of Pediatric Orthopaedics · 2025-04-07 · 2 citations

  review

  INTRODUCTION: Traumatic pelvic injuries are potentially life-threatening and disabling injuries that often result from high-energy impact. It is well established in the orthopaedic literature that adult pelvic fractures can result in urologic injury, especially posterior urethral injury. Pelvic trauma and associated injuries in children are less characterized than in adults and extrapolated from an older population although there are significant anatomic differences between the skeletally mature and immature pelvis. In this context, long-term urogenital sequelae of pelvic fractures, specifically in children, are not clearly and comprehensively represented in the literature. Therefore, we conducted this systematic review with 3 main objectives: (1) to identify characteristics of pediatric pelvic fractures and urogenital injuries, (2) to understand the relationship between pelvic fractures and associated urogenital injuries with their outcomes, and (3) to elucidate treatment modalities for orthopaedic pelvic injuries. METHODS: A comprehensive literature search of PubMed, Medline, SCOPUS, and Cochrane databases was conducted following the PRISMA guidelines with predefined criteria on September 1st, 2024, yielding 595 papers. The papers were screened using Rayyan QCRI and studies included for data analysis were confirmed by at least 2 reviewers. The final full manuscript review was conducted for 29 studies, encompassing a total of 838 pediatric patients with documented pelvic ring fractures and concurrent urogenital injury. RESULTS: Of the papers reporting on the mechanism of injury, the most common mechanism was motor vehicle collision (325/562 patients, 58%), followed by motor vehicle versus pedestrian collision (215/562, 38%), and fall (22/562, 4%). Among 161 cases where the pelvic fracture was classified, 86 (53%) had rotational or segmental instability of the pelvis, correlating to Torode and Zieg type IV and Tile-type B and C classifications. Forty-eight (30%) patients had multisite pelvic fractures. The most commonly reported urogenital injuries included urethral injury (725/807, 90%), bladder/bladder neck injury (53/807, 6.6%), and vaginal/vulvar laceration (29/807, 3.6%). Among cases where the entire urologic management of the patient was described, nonoperative management was utilized in patients rarely, (38/683, 5.5%), early urethral realignment and repair was utilized (337/683, 49%) and was the most common form of post-traumatic intervention, followed by delayed urethroplasty [284/683 (42%)]. DISCUSSION: Many cases of pediatric pelvic fractures, ranging from 2.4% to 7.5%, present with concomitant urogenital injuries, particularly posterior urethral and bladder injuries. These urogenital injuries were more frequently reported in high-energy pelvic injuries characterized by rotational instability, multisite pelvic fractures, and pelvic ring disruptions. Generally, fractures were conservative unless surgery was indicated. In those cases, surgical fixation and plating were utilized in stabilizing the pelvic ring. Early urethral realignment and repair was the most reported surgical intervention for these associated urologic injuries, followed by cystostomy with delayed urethroplasty (generally 3 mo after injury), but the optimal time to surgery is still debated in the literature. While historically delayed repair has been favored due to the increased risk of incontinence and erectile dysfunction associated with early primary repair, endoscopic techniques have decreased the risk profile of early intervention, thus increasing its popularity.

  PublisherDOI

• What are effects of etidronate for the primary and secondary prevention of osteoporotic fractures in postmenopausal women?

  Cochrane Clinical Answers · 2025-01-30

  article1st authorCorresponding
  PublisherDOI

• Successful Residency Program Transfers in Orthopaedic Surgery: A Guide for Residents and Faculty

  Journal of the American Academy of Orthopaedic Surgeons · 2025-10-27

  articleSenior author

  Some orthopaedic surgery residents may find that another residency program is more appropriate for them to succeed either personally or professionally. Currently, there is a paucity of information on the available avenues for residency program transfers in orthopaedic surgery. In this review, the authors discuss common reasons for orthopaedic surgery residency program transfer including logistical considerations, keys to success, and potential pitfalls during this process.

  PublisherDOI

• Repair of Pediatric LC3 Pelvic Ring Injury

  Journal of Orthopaedic Trauma · 2025-07-18

  reviewSenior author

  SUMMARY: Lateral compression (LC) 3 pelvic ring injuries are high energy, complex patterns that may include a "crescent fracture," which is an important consideration when determining the appropriate fixation tactic. This review discusses the reduction and fixation of a pediatric LC3 pelvic ring injury with particular focus on the open and percutaneous techniques for treatment of a crescent fracture.

  PublisherDOI

Recent grants

• NIH Grant R03AG040670

  NIH · $160k · 2014

Frequent coauthors

• Mara L. Schenker

  143 shared

• Robert L. Mauck

  Philadelphia VA Medical Center

  132 shared

• Samir Mehta

  121 shared

• Joseph Bernstein

  University of Pennsylvania

  63 shared

• David L. Helfet

  Cornell University

  50 shared

• Mark L. Prasarn

  Methodist Hospital

  49 shared

• Dean G. Lorich

  Cornell University

  45 shared

• Yulong Wei

  Union Hospital

  36 shared

Labs

• Orthopaedic Surgery, University of PennsylvaniaPI

Education

• MD, PhD

  University of Pennsylvania Perelman School of Medicine

• BS

  Stanford University