Pediatric spinal surgery has entered a transformative era with the introduction of resorbable fixation devices. Unlike traditional metal implants that remain permanently or require a second surgery for removal, these advanced implants are engineered to provide mechanical support during the critical healing phase and then gradually dissolve within the body. This eliminates the need for hardware removal, reduces the risk of long-term complications, and allows the growing spine to develop without interference from permanent foreign materials. The development of resorbable spinal fixation devices represents a convergence of polymer science, biomechanical engineering, and clinical pediatric orthopedics, offering young patients a more physiologic and less invasive path to recovery.

Clinical Need for Resorbable Spinal Fixation in Pediatric Patients

Children and adolescents with spinal deformities, fractures, or congenital anomalies often require surgical stabilization. Conditions such as idiopathic scoliosis, kyphosis, spondylolisthesis, and traumatic vertebral fractures are common indications. Traditional metal implants—typically made from titanium or stainless steel—have a long history of success but present unique challenges in the pediatric population. The spine in children is still growing, and rigid metal constructs can restrict that growth, leading to issues such as “crankshaft” deformity in scoliosis correction. Metal implants also interfere with postoperative imaging, causing artifact on MRI and CT scans that can obscure assessment of fusion or residual pathology. Perhaps most significantly, metal implants often require a secondary removal procedure once fusion is achieved, exposing the child to additional anesthesia, surgical risk, and recovery time.

Resorbable devices address these concerns by providing temporary stabilization that gradually transfers load to the healing bone. As the implant degrades, it does not impede growth or imaging, and no removal surgery is needed. This is particularly beneficial in very young children, where growth potential is highest and the consequences of hardware-related complications are most severe. The clinical need for such devices is growing as surgeons seek to minimize the lifetime surgical burden on pediatric patients.

Biomaterials for Resorbable Spinal Implants

The foundation of resorbable fixation is a class of biocompatible polymers known as poly(α-hydroxy acids). The most commonly used materials are polylactic acid (PLA), polyglycolic acid (PGA), and their copolymers (PLGA). Each has distinct degradation kinetics and mechanical properties that can be tailored for specific applications.

Polylactic Acid (PLA)

PLA is a semi-crystalline polymer derived from renewable sources such as corn starch or sugarcane. It has a relatively high tensile strength and a degradation time ranging from 18 months to several years, depending on crystallinity and molecular weight. L- and D-isomers are used to control degradation rate; PLLA (poly-L-lactide) is slower-degrading and retains strength longer, making it suitable for load-bearing spinal applications. The degradation byproduct is lactic acid, which is metabolized naturally by the body.

Polyglycolic Acid (PGA)

PGA degrades more rapidly than PLA, typically losing mechanical strength within 4–8 weeks. Its rapid absorption can be advantageous in non-load-bearing areas, but for spinal fixation, it is often combined with PLA in copolymers to achieve a balance of strength and degradation rate. PGA degrades into glycolic acid, which is also safely metabolized.

Copolymers and Blends

PLGA copolymers allow fine-tuning of degradation time by adjusting the ratio of lactide to glycolide. For example, a 85:15 PLGA copolymer degrades faster than pure PLA but slower than 50:50 PLGA. Other materials such as polycaprolactone (PCL) and poly(trimethylene carbonate) (PTMC) are sometimes used for slower degradation or increased flexibility. Composite materials that combine these polymers with bioactive ceramics like hydroxyapatite (HA) or β-tricalcium phosphate (β-TCP) are being developed to improve osteoconductivity and mechanical stiffness.

Design and Engineering Challenges

Designing resorbable spinal fixation devices that perform reliably in the demanding environment of the pediatric spine involves several trade-offs. The implant must have enough initial strength to stabilize the spine and resist forces from weight-bearing, muscle contraction, and patient activity. At the same time, it must degrade at a controlled rate so that load is gradually transferred to the healing bone, avoiding sudden loss of support that could lead to nonunion or deformity recurrence.

Mechanical Performance Under Load

Traditional metal implants have significantly higher modulus (stiffness) than bone, leading to stress shielding—where the implant bears most of the load and the underlying bone is under-stimulated, potentially weakening it. Resorbable polymers have a modulus closer to that of cancellous bone, which reduces stress shielding and may promote better bone remodeling. However, this lower modulus can be a disadvantage in situations requiring rigid fixation, such as in long-segment scoliosis constructs. To address this, researchers have developed reinforced composites—for example, self-reinforced PLA fibers or HA-reinforced polymers—that increase stiffness without compromising biocompatibility. Manufacturing techniques such as injection molding, compression molding, and 3D printing (fused deposition modeling, selective laser sintering) allow precise control over porosity, fiber orientation, and internal architecture to optimize strength and degradation behavior.

Degradation Kinetics and Biocompatibility

The degradation of resorbable polymers occurs through hydrolysis, breaking long polymer chains into smaller molecules that are then metabolized. The process must not generate a local acidic environment that could cause inflammation or delayed healing. Copolymer composition, molecular weight, crystallinity, and implant geometry all influence degradation rate. In vivo, factors such as blood supply, pH, and mechanical stress also affect degradation. Extensive preclinical testing in animal models is necessary to ensure that the degradation profile is appropriate for the intended clinical scenario. The byproducts—lactic acid and glycolic acid—are natural metabolites and are safely cleared, but high concentrations can temporarily lower local pH. Modern formulations are designed to buffer this via the inclusion of basic salts or by using slower-degrading polymers to spread the acid release over a longer period.

Sterilization and Shelf Life

Resorbable polymers are sensitive to heat and radiation, which can cause premature degradation. Gamma irradiation, a common sterilization method for metal implants, can break polymer chains and accelerate degradation. Ethylene oxide (EtO) gas sterilization is often used instead, but it leaves residues that must be carefully removed. Newer sterilization techniques such as low-temperature hydrogen peroxide plasma are being explored. Shelf life is another consideration, as these materials may degrade during storage. Therefore, packaging and storage conditions (controlled temperature and humidity) are critical, and expiration dates must be strictly observed.

Current Clinical Applications and Devices

Several resorbable spinal fixation devices have received regulatory approval and are now in clinical use for pediatric patients. These include resorbable screws, plates, cages, and rods, primarily used in anterior cervical discectomy and fusion (ACDF), corpectomy, and certain posterior fixation procedures.

Resorbable Screws and Plates

Resorbable screws made from PLLA or PLGA are commonly used for fixation of bone grafts or osteotomies in the cervical and thoracic spine. They eliminate artifact on postoperative MRI and CT, which is especially important in pediatric oncology patients where imaging surveillance is critical. Plates made from resorbable materials are used for anterior cervical plating and for reconstruction after tumor resection. Clinical studies have shown fusion rates comparable to metal implants with no increase in complication rates. A link to a clinical study is provided below.

Resorbable Interbody Cages

Interbody cages made from PLLA or PLLA/HA composites are used to restore disc height and promote fusion. These cages gradually degrade, allowing more natural load transfer to the bone graft. Some designs incorporate a radiolucent property that improves visualization of bony fusion on plain radiographs. Early results in pediatric patients with symptomatic disc degeneration or trauma are promising.

Resorbable Rods and Constructs

For growing children, resorbable rods are being developed as alternatives to traditional metal growing rods for scoliosis treatment. These rods provide temporary scoliosis correction and allow for growth without the need for repeated lengthening surgeries. However, their mechanical strength is currently insufficient for heavier, older children, and most applications remain experimental. Research is ongoing to improve the fatigue resistance and load-bearing capacity of resorbable rods through fiber reinforcement and novel polymer blends.

Future Directions and Emerging Technologies

The field of resorbable spinal fixation is rapidly evolving, with several promising innovations on the horizon.

Bioactive and Drug-Eluting Coatings

Coatings that release growth factors (e.g., BMP-2, BMP-7) or antimicrobial agents from the implant surface could enhance bone fusion and reduce infection risk. Controlled release from resorbable polymers is already used in other orthopedic applications, and adapting this to spinal implants is an active area of research. These coatings would be fully resorbable, leaving no residual material.

Smart Materials and Responsive Degradation

Materials that respond to physiological cues—such as pH changes from inflammation or local mechanical loading—could adjust their degradation rate to optimize healing. For example, a polymer that degrades faster under tensile load might accelerate resorption once bone healing reduces the need for support. While still in the early stages, such “smart” resorbable implants could personalize treatment without active intervention.

Patient-Specific 3D Printing

Additive manufacturing allows the creation of patient-specific resorbable implants with complex geometries matched to individual anatomy. This is particularly valuable in congenital spinal deformities or revision surgeries where standard sizes do not fit. 3D-printed resorbable implants can incorporate porous structures to promote osteointegration and can be produced with graded mechanical properties. Clinical trials for custom resorbable implants in pediatric spine are beginning to report positive outcomes.

Improved Imaging Compatibility

One of the key advantages of resorbable implants is their compatibility with advanced imaging. Future materials may be engineered to be completely radiolucent or to incorporate MRI-visible markers for non-invasive monitoring of degradation and fusion without artifact. This would allow surgeons to assess healing with high-quality imaging throughout the postoperative period.

Conclusion

The development of resorbable spinal fixation devices for pediatric patients represents a significant step forward in reducing the long-term burden of spinal surgery on children. By providing temporary stabilization that gives way to natural bone healing and growth, these implants avoid the complications associated with permanent or removable metal hardware. Current materials such as PLLA and PLGA, along with advances in composite technology and manufacturing, have brought resorbable devices into clinical reality for certain applications. Ongoing research into bioactive coatings, smart materials, and patient-specific 3D printing promises to expand their utility to more complex spinal reconstructions. As the technology matures, it will likely become an integral part of the pediatric spine surgeon’s toolkit, offering young patients a less invasive, more physiologic path to a stable and healthy spine.

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