EndoLimb is developing the EndoThumb—an implantable, skin-covered prosthetic thumb that restores natural appearance, touch sensation, and critical hand function for thumb amputation patients.
EndoLimb Orthoplastic Solutions, Inc. is advancing the EndoThumb, a transformative implantable device designed to address the significant unmet need in thumb amputation reconstruction.
The Clinical Challenge
Thumb amputation causes profound disability—the thumb accounts for:
- 40% of hand function
- 36% of upper extremity function
- 22% of whole-person function
Each year, approximately 6,500 patients in the US and 153,400 worldwide suffer thumb amputations without replantation. Current solutions fall short:
- External prostheses restore length and grasp but are bulky, unnatural-looking, and lack sensation.
- Percutaneous osseointegrated devices offer some sensation via osseoperception but carry ongoing infection risk.
- Surgical reconstructions (toe/finger transfer, bone grafts, distraction lengthening) are complex, lengthy, painful, and often require sacrificing healthy digits—many patients decline them.
The EndoThumb Solution
The EndoThumb is a fully implantable, skin-covered endoprosthesis that restores:
- Thumb length for pinch and opposition grasp
- Natural touch sensation for object manipulation, temperature, and pain detection
- Cosmetic appearance with autologous skin coverage
By eliminating external components and infection-prone skin breaches, the EndoThumb offers superior function, aesthetics, and quality of life with lower complexity and morbidity than existing options.
Founding Team
- Dr. Dustin L. Crouch – Founder & Primary Inventor
Associate Professor of Biomedical Engineering at the University of Tennessee. Principal investigator on NSF- and NIH-funded projects proving EndoLimb feasibility. Over 11 years of dedicated prosthesis research focused on improving patient outcomes. - Dr. David E. Anderson – Co-Founder
Professor of Large Animal Clinical Sciences at UT. Performed animal surgeries in proof-of-concept studies and provides essential clinical perspective. - Dr. Katrina L. Easton – Research Lead
Research Assistant Professor and veterinarian with PhD in bioengineering. Managed and executed proof-of-concept studies; ideal expertise to drive technology development.
The team is supported by enthusiastic hand surgeon collaborators and experienced business mentors.
Regulatory & Development Pathway
Guided by FDA meetings (Jan 2024), MCRA regulatory consultants (2024–2025), and NSF I-Corps programs:
- Exploring FDA 510(k) clearance; if not eligible, pursuing De Novo Class II with potential Breakthrough Device Designation for expedited review.
- Pre-clinical testing with medical device partners to support IDE (if required) and final submission.
- Manufacturing via established contract manufacturers with orthopedic implant expertise and quality systems.
Commercial Strategy
- Primary channels: Journal ads, conference presentations, and direct engagement with hand surgeons and key opinion leaders already expressing collaboration interest.
- Initial sales: Direct to specialty hand reconstruction hospitals via medical device sales subcontractors.
- Future expansion: Academic centers, large/mid-sized hospitals, and international markets with strong reimbursement (Canada, EU, Japan, South Korea, Australia, Brazil).
Revenue will be generated through direct sales of implantable devices and supporting surgical tools/supplies.
Market Opportunity
- Flagship product: EndoThumb addresses ~80% of thumb amputations by level.
- Beachhead market: US specialty hand reconstruction hospitals with existing expertise and patient volume.
- Pricing: $20,000–$30,000 per unit (aligned with niche orthopedic implants).
- Projected revenue (at 30% market share, including current + prior-year patients):
$50M annually in the US
$130M annually in select international markets
Investment Ask
Seeking $1M to advance critical milestones over the next 2 years.
Use of Proceeds
| Timeline | Key Activities |
|---|---|
| Year 1 |
|
| Year 2 |
|
| Ongoing (Both Years) |
|
Personnel Support
- Full-time: Dr. Katrina Easton + staff engineer
- Part-time: Tim Rinks (COO) – 30+ years orthopedic device experience, former NSF I-Corps Industry Mentor
Funds will also cover direct activity costs, office/resources, and travel.
Proof-of-Concept & Validation
- Live-animal studies: 10 skin-covered endoprostheses implanted in rabbit model (8–24 weeks). Animals bore full weight with no skin issues; jointed versions recovered near-normal motion.
- Customer discovery: NSF I-Corps Regional & National programs – interviewed 120+ stakeholders (surgeons, therapists, patients). Confirmed clinical need and target population (amputation at/near metacarpal joint).
- Design progress: Multiple refinement iterations, FDA design controls initiated, computational modeling, cadaver testing with surgeon collaborators (Summer 2025), custom mechanical test fixture (Fall 2025).
These milestones de-risk the technology and position EndoLimb for pre-clinical testing and regulatory submission.
The startup has not yet received direct funding. Development has been supported through grants to Dr. Dustin Crouch’s academic lab:
| Source | Amount | Period |
|---|---|---|
| University of Tennessee Chancellor’s Innovation Fund | $50,000 | 2025–2026 |
| University of Tennessee Research Foundation Entrepreneurial Fellowship | $80,000 | — |
| NIH R33AR078096 | $331,701 | 2023–2025 |
| NIH R61AR078096 | $667,990 | 2020–2023 |
| NSF CAREER Award #1944001 | $504,459 | 2020–2025 |
| University of Tennessee Seed Grant | $45,000 | 2019–2020 |
