Abstract
Background Advancements in 3-dimensional (3D) printing have enabled the development of patient-specific implants tailored to complex anatomical and biomechanical challenges in spine surgery. This technology is especially valuable in disorders such as dysplastic spondylolisthesis, where congenital lumbosacral anomalies create severe challenges for standard interbody implant placement. We present the first use of a Puri-Ti (DeGen Medical, Florence, SC, USA) patient-specific anterior lumbar interbody fusion (ALIF) cage system. The implant was utilized under the Food and Drug Administration (FDA) Expanded Access (Compassionate Use) pathway with Institutional Review Board approval. This case demonstrates the feasibility and potential advantages of custom 3D-printed implants in addressing complex lumbosacral deformity.
Case Presentation A 38-year-old man presented with progressive low-back and bilateral lower-extremity symptoms secondary to high-grade dysplastic spondylolisthesis at L5 to S1. Imaging demonstrated severe anterior translation of L5, dome-shaped sacral morphology, and bilateral foraminal stenosis. Owing to the patient’s severe dysplastic anatomy, standard ALIF cages could not be safely implanted without extensive osteotomy. A patient-specific 3D-printed titanium ALIF implant was designed in collaboration with the manufacturer. The device was inserted via an anterior retroperitoneal approach, followed by posterior percutaneous instrumentation and decompression. Postoperative radiographs and computed tomography imaging confirmed appropriate implant seating, partial reduction of the spondylolisthesis, and restoration of foraminal height. The patient experienced resolution of preoperative radiculopathy and returned to full function by 1 year.
Conclusions Patient-specific 3D-printed implants offer a promising solution for spinal pathology in which conventional implants cannot achieve adequate fit, biomechanical stability, or safe insertion. The successful outcome in this case supports the role of personalized interbody implants in carefully selected patients with dysplastic anatomy and highlights the need for further study in larger cohorts.
Clinical Relevance Standard interbody implants often fail to accommodate the distorted sacral dome morphology characteristic of high-grade dysplastic spondylolisthesis, frequently requiring complex and high-risk bone osteotomies to achieve adequate seating. This case report demonstrates that a patient-specific, 3D-printed titanium ALIF cage can successfully restore alignment, promote stable fusion, and resolve radicular symptoms by matching the patient's unique anatomy exactly. Utilizing custom 3D-printed implants provides a safe, highly conforming, and effective surgical alternative for complex spinal deformities where off-the-shelf devices are anatomically incompatible.
Level of Evidence 5.
Introduction
Advancements in 3-dimensional (3D) printing, also known as additive manufacturing, have enabled the creation of patient-specific implants designed to accommodate complex spinal anatomy and biomechanical requirements.1 The clinical adoption of patient-specific 3D-printed implants has expanded over the past decade, with custom devices now utilized for spinal deformity, infection, degeneration, trauma, and oncological reconstruction across all spinal regions.2 Custom 3D-printed interbody devices offer the potential to improve surgical precision, promote osseointegration, and optimize patient outcomes in cases where standard implants are inadequate.
Dysplastic spondylolisthesis is a rare congenital disorder characterized by anterior vertebral body translation due to malformations at the lumbosacral junction.3 These anatomic abnormalities predispose patients to progressive displacement, often resulting in high-grade spondylolisthesis associated with instability and radiculopathy. Surgical intervention is indicated in symptomatic patients with progressive deformity and clinical symptoms.4 When the deformity is corrected, support for reduction with an interbody implant is paramount.4 When surgical reduction is pursued, interbody support is critical to maintain alignment and achieve fusion, typically via posterior lumbar interbody fusion or anterior lumbar interbody fusion (ALIF) approaches. However, the dome-shaped sacral anatomy characteristic of dysplastic deformities creates significant challenges for placing standard interbody cages without significant bone resection.
We report the first-ever use of a Puri-Ti (DeGen Medical, Florence, SC, USA) 3D-printed, patient-specific ALIF cage in the treatment of high-grade dysplastic spondylolisthesis. Because the device had not yet received FDA clearance at the time of treatment, it was utilized under the FDA Expanded Access (Compassionate Use) pathway with Institutional Review Board (IRB) approval. This case highlights the potential advantages of patient-specific implants in managing severe dysplastic lumbosacral anatomy not amenable to conventional interbody solutions.
Case Presentation
A 38-year-old man presented with progressive low back and leg pain. His symptoms began in 2013 after a significant fall while on duty in the military; initial evaluation did not result in further diagnostic imaging or intervention. He managed chronic back pain until 2019, when it worsened during a deployment that required regular heavy lifting. The patient reported that after standing for more than 20 minutes, he developed numbness in his toes and legs. On several occasions, his legs became weak enough that he felt unable to maintain an upright posture. He denied any bowel or bladder dysfunction.
On examination, the patient appeared well. He ambulated with a normal gait and was able to heel-toe walk without difficulty. He appeared balanced in the coronal and sagittal planes when standing. There was no tenderness upon direct palpation of the midline and paraspinal musculature. He reported no pain at the sacroiliac joint or sciatic notch. He had full strength and normal sensation to testing in the bilateral lower extremities. He had a negative straight leg raise bilaterally, and no clonus was observed.
Full spine radiographs (Figure 1), a computed tomography (CT) image (Figure 2), and magnetic resonance images (Figure 3) were obtained, and all demonstrated high-grade dysplastic spondylolisthesis at L5 to S1. Imaging showed severe anterior translation of the L5 vertebral body relative to S1 and a markedly dysplastic, dome-shaped anterior sacrum (Figure 2). The neural foramina were severely narrowed, and there was severe bilateral foraminal stenosis at L5 to S1 (Figure 3).
Preoperative lateral and anteroposterior standing fluoroscopy images demonstrating high-grade dysplastic spondylolisthesis and anterior translation of L5 vertebral body.
Preoperative computed tomography displaying sacral dome defect and narrowed posterior disc space.
Preoperative T2-weighted magnetic resonance imaging demonstrating severely narrowed neural foramen and bilateral foraminal stenosis at L5–S1.
The patient previously completed conservative treatments, including physical therapy, epidural steroid injections, nonsteroidal anti-inflammatories, and activity modifications. Given the chronicity and neurological nature of his symptoms (numbness and weakness when standing), surgical treatment options were discussed. The patient underwent extensive shared decision-making counseling. He was informed that his unique anatomy may create surgical challenges if using a standard off-the-shelf interbody implant and may require substantial bone modifications. Standard rectangular and trapezoidal ALIF cages could not be adequately seated or anchored due to the sacral dome morphology and deficient anterior sacral endplate. Furthermore, a standard posterior-based interbody (posterior lumbar interbody fusion and transforaminal lumbar interbody fusion) may rest in a anterior sacral defect and not sufficiently support the L5 vertebra and achieve surgical goals. Given these challenges, an implant manufacturer with capabilities to create custom implants was contacted to design a 3D patient-specific design intended to fit and fill the dysplastic defect, requiring no bony modifications. The patient was counseled on the FDA Expanded Access (Compassionate Use) process and the requirement for IRB approval.
After this discussion, the patient elected to proceed with L5 to S1 ALIF, followed by posterior spinal instrumentation and fusion L5 to S1, using robot-assisted navigation. A potential laminectomy and foraminotomy were also planned at the L5 to S1 level for possible neural decompression, and the necessity for these procedures would be determined intraoperatively based on the spondylolisthesis reduction after the ALIF and posterior instrumentation.
A patient-specific implant was designed collaboratively between the surgical team and the manufacturer using fine-cut preoperative CT imaging. The morphology of the implant was customized to match the dysplastic sacral dome and maximize endplate conformity (Figure 4). Small, medium, and large implant sizes were produced, each maintaining identical geometric features while varying in height to optimize intraoperative flexibility. These models included integrated fixation screw trajectories and a porous titanium architecture intended to promote osseointegration. Representative design renderings and 3D models of the seated implant (Figure 5) were reviewed and approved by the treating surgeon.
3-Dimensional render of patient-specific implant. Unique endplate morphology is matched by the implant, maximizing contact area and preventing the need for osteotomy.
3-Dimensional computed tomography render of implanted device and predicted change to spinal alignment.
As this procedure was the first human use of the implant, appropriate regulatory and ethical approvals were obtained under the FDA Expanded Access (Compassionate Use) pathway. A formal submission to the FDA included clinical justification, anatomical limitations of standard implants, proposed surgical plan, and follow-up protocol. An IRB-approved treatment plan outlining the procedure, risks, and follow-up protocols was secured. An independent spine surgeon not involved in the patient’s care confirmed the clinical necessity of the device.
Upon review, the FDA granted authorization for single-patient compassionate use under submission number U240004. Informed consent was obtained from the patient using an IRB-approved consent document specifically developed for investigational device use. All regulatory milestones, including FDA and IRB approval, were completed prior to the scheduled surgery.
The patient was taken to the operating room and placed supine on the operating table. An anterior retroperitoneal exposure was performed by a senior vascular surgeon. Lateral fluoroscopy confirmed the operative level. A full discectomy was performed while taking care to avoid violation of the bony end plates to ensure proper seating of the custom implant. Once the disc space was prepared and the appropriate size implant selected, the device was packed with recombinant human bone morphogenic protein-2 (Infuse, Medtronic Corp, Minneapolis, MN, USA) and fresh frozen allograft. It was inserted under direct fluoroscopic imaging. Lateral fluoroscopy confirmed implant positioning, partial reduction of the spondylolisthesis, and restoration of foraminal height (Figure 6). Two integrated fixation screws were placed through the cage into the L5 vertebral body.
Intraoperative lateral and anteroposterior fluoroscopy confirmed implant positioning, partial spondylolisthesis reduction, and restoration of foraminal height.
After completion of the ALIF, the patient was transferred to the prone position on a radiolucent Jackson table. Bilateral pedicle screws at L5 and S1 were placed using robotic navigation and a minimally invasive approach. Rods were then inserted, and all implants confirmed fluoroscopically. Given the spondylolisthesis was partially reduced and foraminal height restored, the laminectomy and foraminotomy procedures were deferred. All incisions were closed in layers, and sterile dressings were applied. The patient was extubated and transferred to the postanesthesia care unit, where they reported resolution of the preoperative radicular leg pain. The patient ambulated 600 feet and was discharged home on postoperative day 2. At his 2-week postoperative visit, he reported continued resolution of his preoperative radicular pain and had a stable motor and sensory examination.
At his 1-month postoperative visit, the patient reported improved leg pain, and he was able to perform all daily tasks. Radiographs from the 1-month visit demonstrated an intact anterior lumbar interbody cage and instrumentation with no evidence of subsidence, loosening, or failure. No changes were observed at the standard 6-month follow-up, and implants remained stable. At the 1-year postoperative visit, the patient reported complete resolution of his preoperative symptoms. One-year radiographs confirmed stable instrumentation (Figure 7), and 1-year CT showed successful fusion at L5 to S1 (Figure 8). There was no evidence of implant fracture, failure, or particulate debris on CT imaging. Direct comparison of preoperative to 1-year 3D CT reconstructions highlights the fit of the implant in the bony defect and restoration of sagittal alignment (Figure 9).
One-year postoperative radiographs confirming stable instrumentation with no signs of subsidence, loosening, or failure.
One-year postoperative computed tomography imaging showing anterior fusion with bony growth spanning L5 to S1 disc space.
Preoperative and 1-year 3-dimensional computed tomography reconstructions displaying change in sagittal alignment and positioning of interbody implant.
Discussion
There is an ongoing debate regarding the optimal treatment strategy for dysplastic spondylolisthesis. Fusion can be achieved via posterolateral fusion or combined anterior-posterior, but the role of reduction in these cases is debated.5 In situ fusion is often considered to reduce the risks of neurologic injury. For surgeons pursuing posterior-approach reduction, sacral dome osteotomy is often utilized to facilitate alignment restoration, tension reduction on the exiting nerve roots, and to improve endplate contact with posterior-based interbody devices (when used).5 In anterior approach cases, the high sacral slope associated with isthmic and dysplastic spondylolisthesis can make visualization during disc preparation difficult. Resection of the anterior-inferior lip of the L5 vertebral body may also be performed to enhance anterior disc space visualization and improve interbody-endplate contact with traditional cage designs.5 However, both posterior and anterior osteotomy techniques add inherent surgical risk and complexity.
The use of patient-specific 3D-printed titanium interbody implants represents a significant advancement compared with standard ALIF techniques, which typically rely on off-the-shelf polyetheretherketone or solid titanium cages.6 Conventional implants are constrained by fixed geometries and limited ability to accommodate the distorted anatomy observed in dysplastic spondylolisthesis. 3D-printed titanium devices can be tailored to match patient-specific anatomy, improving endplate conformity, optimizing load distribution, and enhancing implant stability. Avoiding osteotomy not only simplifies the anterior approach but may reduce the risks associated with increased blood loss, prolonged operative time, and potentially implant subsidence after resection of the structural endplate.7
3D-printed titanium implants feature porous architecture engineered to mimic trabecular bone, facilitating early osseointegration and biological fixation.8 While porosity lends itself to better osseointegration, there is an inverse relationship with mechanical strength.9 Modern additive manufacturing permits optimization of pore size, distribution, and structural density to balance mechanical integrity with the desired biological response.9 In this case, the patient-specific implant was designed to achieve adequate strength while matching the unique load-bearing requirements of the dysplastic sacrum.
The compassionate use pathway used for this case raises important regulatory and ethical considerations. The use of an investigational device necessitates careful balancing of innovative intent with patient safety, robust informed consent, and transparent reporting of clinical outcomes. Notably, during the follow-up period for this patient, the manufacturer’s patient-specific ALIF system received FDA 510(k) clearance (K241077), supporting the broader regulatory acceptance of custom interbody solutions.
To our knowledge, this is the first reported human use of a patient-specific ALIF implant utilizing the Puri-Ti manufacturing process for high-grade dysplastic spondylolisthesis. The favorable clinical and radiographic outcome observed in this case suggests that patient-specific implants may provide a viable alternative when conventional implants are anatomically incompatible, particularly in severe dysplastic deformities. Further investigation in larger cohorts is needed to validate long-term outcomes, complication profiles, cost-effectiveness, and reproducibility across varied anatomical presentations.
While patient-specific 3D-printed implants represent a significant technical advancement, we acknowledge that the customized design and manufacturing process involve higher costs compared with standard off-the-shelf devices. Given the economic impact on the health care system, we advocate for the judicious use of this technology, reserving it for complex cases where conventional implants are anatomically incompatible or would require high-risk maneuvers, such as extensive osteotomy, to achieve stability. By prioritizing these implants for patients with severe dysplastic anomalies that preclude standard solutions, surgeons can balance the benefits of personalized medicine with the necessity for responsible resource allocation.
Conclusion
This case highlights the clinical utility of patient-specific 3D-printed interbody implants in addressing the anatomic and biomechanical limitations of standard ALIF devices. In cases with unique anatomy, such as dysplastic spondylolisthesis, custom implants may provide safer and more effective correction by improving implant conformity, reducing the need for bone resection, and enhancing endplate contact. The successful outcome in this case supports the ongoing development and clinical integration of personalized implants, underscoring the need for further study in larger patient cohorts to determine long-term durability, complication profiles, and comparative effectiveness.
Footnotes
Funding The authors received no financial support for the research, authorship, and/or publication of this article.
Declaration of Conflicting Interests The authors report no conflicts of interest in this work.
Patient Consent for Publication Patient consent was obtained.
Disclosures Brandon B. Carlson reports IDE study research support from Theradaptive; consulting fees from Globus Medical; speaking honoraria from Globus Medical and AMGEN; support for attending travel as faculty from Spine Base to Summit, Spine Surgery Think Tank, and Spine Safety Summit; serving on the Bone Health Task Force for the National Spine Health Foundation; and stock shares from SpinEM Robotics.
- This manuscript is generously published free of charge by ISASS, the International Society for the Advancement of Spine Surgery. Copyright © 2026 ISASS. To see more or order reprints or permissions, see http://ijssurgery.com.
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