An interventional study of Low-Dose External Beam Irradiation and Hinged Revision Total Knee Arthroplasty in Arthrofibrosis of Knee, sponsored by Mount Sinai Hospital, Canada. Recruiting at 4 sites in 2 countries. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-08-17.
Sponsored by Mount Sinai Hospital, Canada · Not applicable, Interventional, and Treatment
Acquired idiopathic stiffness (AIS) is a common complication following total knee arthroplasty (TKA). It is caused by excessive scar formation, which leads to pain, loss of motion, and functional impairment. When early noninvasive treatments fail, some patients require more surgery. In these cases, surgeons often use a special type of replacement called a hinged prosthesis, which allows more thorough removal of scar tissue and stiffened ligaments. Unfortunately, even after more surgery, many patients continue to struggle with stiffness, pain, and impaired function. Low-dose irradiation (LDI) is a safe, established therapy for conditions with abnormal scar formation. Its role in the setting of AIS has not been defined. The goal of this study is to compare outcomes of revision TKA with or without the addition of LDI. The primary outcome is range of motion at one year following surgery. Secondary outcomes include patient-reported functional scores, repeat surgeries, and complications like wound breakdown or infection. This project has the potential to address a common, debilitating complication after TKA, improve outcomes, reduce repeat interventions and healthcare costs, and broader implementation and standardization of care.
Acquired idiopathic stiffness (AIS), or arthrofibrosis, is a rare but potentially devastating complication after total knee arthroplasty (TKA), occurring in approximately 1-6% of cases. It is characterized by pathological fibroblast and myofibroblast proliferation leading to excessive scar tissue deposition within and around the knee joint, resulting in restricted range of motion (ROM), pain, and functional impairment.
When conservative management (physiotherapy, manipulation under anesthesia) fails, operative intervention is required. Full component revision to a hinged prosthesis - which permits complete synovectomy, posterior capsule release, and debridement of fibrosed collateral ligaments - has demonstrated superior ROM outcomes compared to partial revision strategies.
Perioperative low-dose irradiation (LDI) has an established role in the prophylaxis of heterotopic ossification following total hip arthroplasty and is used as adjunctive therapy for keloid prevention. Mechanistically, LDI at 700-800 cGy inhibits myofibroblast proliferation and modulates fibrotic signaling pathways, addressing the underlying pathophysiology of arthrofibrosis. A retrospective review of 60 patients undergoing hinged revision TKA with LDI demonstrated a median ROM improvement of 60°, with acceptable complication rates.
Despite this evidence, no prospective randomized controlled trial has compared hinged revision TKA with and without LDI.
Mount Sinai Hospital, Canada is the lead sponsor of 158 studies on the registry; 32 are open to participants now.
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Patients undergo hinged revision total knee arthroplasty (TKA) with a rotating hinge prosthesis, followed by a single session of external beam low-dose irradiation (LDI) delivering 800 cGy to the operative knee on post-operative day 1 (or post-operative day 2 if medically necessary), coordinated with radiation oncology.
Radiation: Low-Dose External Beam Irradiation · Procedure: Hinged Revision Total Knee Arthroplasty
Patients undergo hinged revision total knee arthroplasty (TKA) with a rotating hinge prosthesis and receive standard postoperative care without low-dose irradiation. All perioperative care, rehabilitation, and follow-up protocols are identical to the experimental arm.
Procedure: Hinged Revision Total Knee Arthroplasty
A single session of external beam irradiation (800 cGy) delivered to the operative knee on post-operative day 1 (or post-operative day 2 if medically necessary). At Mount Sinai Hospital and Humber River Hospital, LDI is delivered at Princess Margaret Cancer Centre. US sites coordinate through local radiation oncology departments.
Full component revision to a rotating hinge knee prosthesis, including synovectomy, posterior capsule debridement, and release of fibrosed collateral ligaments, performed by the treating orthopaedic surgeon at each participating site.
Total arc of knee range of motion (ROM)
Goniometric measurement of total arc of motion (flexion minus extension deficit) performed by treating surgeon at each follow-up visit, per standard clinical protocol.
Time frame: Baseline (pre-operative), intraoperative, 2 weeks, 6 weeks, 3 months, and1 year post-operatively.
Oxford Knee Score (OKS)
Time frame: Pre-op, 2 weeks, 6 weeks, 3 months, 1 year
EQ-5D-5L (health-related quality of life)
Time frame: Pre-op, 2 weeks, 6 weeks, 3 months, 1 year
Visual Analogue Scale (VAS) - Pain
Time frame: Pre-op, 2 weeks, 6 weeks, 3 months, 1 year
Patient Satisfaction (numeric rating)
Time frame: 6 weeks, 3 months, 1 year
Wound complications (requiring intervention)
Time frame: 2 weeks, 6 weeks, 3 months, 1 year
Infection rate
Time frame: 2 weeks, 6 weeks, 3 months, 1 year
Reoperation Rate
Time frame: 2 weeks, 6 weeks, 3 months, 1 year
Medical complications
Time frame: 2 weeks, 6 weeks, 3 months, 1 year
Plan to share: No — Individual participant data will not be shared publicly. De-identified aggregate data supporting the findings of this study will be available upon reasonable request to the corresponding author following publication of primary results.
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