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Monoaxial vs. Polyaxial Percutaneous Hybrid Stabilization

Sponsor: Medical University Innsbruck • ClinicalTrials.gov ID: NCT07408726

Registry updated: 2026-10-09

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Description

Vertebral body fractures in older adults mostly affect the thoracolumbar junction and are challenging to treat due to osteoporosis and other comorbidities. Treatment options range from conservative approaches to minimally invasive procedures like vertebroplasty or balloon kyphoplasty, as well as surgical techniques such as posterior or combined stabilization. A common method for more severe fractures (from OF3 onwards) is percutaneous bisegmental hybrid stabilization using cement-augmented pedicle screws and balloon kyphoplasty. Polyaxial screws are easier to implant but offer less biomechanical stability. In contrast, monoaxial screws provide greater stiffness, allowing better correction of kyphosis and restoration of vertebral body height. The study compares radiological and clinical outcomes in patients aged 60 and older with thoracolumbar fractures (T11-L4) between monoaxial and polyaxial hybrid stabilization. The primary goal is to evaluate and compare the degree of kyphosis correction six months after surgery.

Interventions

Monoaxial instrumentation - the M.U.S.T. Monoaxial Pedicle Screw Cannulated (Medacta International SA, Switzerland) (Device)
In this study, fractures between the 11th thoracic (T11) and 4th lumbar (L4) vertebra (both included) will be treated surgically using either monoaxial or polyaxial bisegmental hybrid stabilization. Hybrid stabilization consists of posterior cement-augmented pedicle screw instrumentation combined with balloon kyphoplasty of the fractured vertebral body. For bisegmental hybrid stabilization, standard cannulated and perforated pedicle screws, either monoaxial (M.U.S.T. Monoaxial Pedicle Screw Cannulated (Medacta International SA, Switzerland)) or polyaxial (M.U.S.T. LT Pedicle Screw System (Medacta International SA, Switzerland)), will be placed in the vertebrae adjacent to the fractured vertebral body.
Polyaxial instrumentation - the M.U.S.T. LT Pedicle Screw System (Medacta International SA, Switzerland) (Device)
In this study, fractures between the 11th thoracic (T11) and 4th lumbar (L4) vertebra (both included) will be treated surgically using either monoaxial or polyaxial bisegmental hybrid stabilization. Hybrid stabilization consists of posterior cement-augmented pedicle screw instrumentation combined with balloon kyphoplasty of the fractured vertebral body. For bisegmental hybrid stabilization, standard cannulated and perforated pedicle screws, either monoaxial (M.U.S.T. Monoaxial Pedicle Screw Cannulated (Medacta International SA, Switzerland)) or polyaxial (M.U.S.T. LT Pedicle Screw System (Medacta International SA, Switzerland)), will be placed in the vertebrae adjacent to the fractured vertebral body.

Eligibility criteria

Inclusion Criteria: Patient-related criteria: 1. Age ≥ 60 years (male and female patients) 2. Ability to understand nature, risks, and benefits of study participation and to provide written informed consent. 3. Psychosocially, mentally, and physically capable of complying with all study requirements, including scheduled follow-up visits, completion of forms, and participation in all procedures as defined by the protocol. 4. Ambulatory prior to fracture, with or without the use of assistive devices Fracture-related criteria: 1. Acute vertebral fractures located between T11 and L4 (inclusive) 2. Fractures deemed suitable for bisegmental hybrid stabilization based on clinical and radiological assessment - primarily OF type 3 and type 4 fractures according to DGOU classification; type 2 and 5 fractures may also be included based on individual evaluation, with the final treatment decision left to the discretion of the treating surgeon. Exclusion Criteria: Patient-related criteria: 1. Body mass index (BMI) \> 35 2. Permanent or progressive neurologic deficits (including upper motor neuron disease and myelopathy) 3. Rheumatoid arthritis or known disorders of bone metabolism (excluding osteopenia/osteoporosis, Vitamin D deficiency) 4. History of radiation therapy to the spine 5. History of alcohol or drug abuse within the last 2 years prior to randomization 6. Current therapy with high-dose systemic corticosteroids (e.g., \>10 mg/day prednisone equivalent for more than 3 months) 7. Ongoing or planned treatment with cytotoxic chemotherapy (excluding biologicals, immunotherapy, or targeted agents) at the time of enrollment 8. Known allergy to any component of the spinal instrumentation 9. Participation in other clinical investigations (drug or device) that may interfere with the outcomes of this study Fracture-related criteria: 1. Vertebral fractures associated with neurological deficits 2. Fracture age \> 4 weeks at the time of enrollment 3. Pathological fractures due to spinal infection or metastatic bone disease 4. Planned major spinal surgery within 12 months of enrollment 5. Severe spinal deformities or fusion at the index or adjacent segments 6. Previous spinal surgery involving the index or adjacent vertebrae, with the exception of minor non-instrumented procedures, such as simple sequestrectomies or decompressions

Conditions

Thoracolumbar Fractures in the Elderly

Locations

Univ.-Klinik für Orthopädie und Traumatologie — Innsbruck, Tyrol, Austria

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Official Source

Data sourced from ClinicalTrials.gov, a service of the U.S. National Institutes of Health.

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