Abstract
Background Structural femoral allografts possess favorable biomechanical properties and may serve as an effective and potentially less costly alternative to synthetic implants for anterior spinal column reconstruction. This study aims to describe the time to fusion and long-term outcomes of using fresh frozen femoral structural allografts for vertebral body reconstruction following en bloc spinal tumor resection.
Methods This retrospective case series included patients who underwent en bloc vertebrectomy with anterior column reconstruction using fresh frozen femoral structural allografts between 1994 and 2019. Each allograft was prepared with a preinserted pedicle screw to allow connection to the posterior pedicle screw–rod construct. Demographic, oncological, and surgical data were collected. The primary outcome was graft fusion and time to fusion, assessed primarily using computed tomography.
Results Fourteen patients were treated, with a mean age of 38 years (range 11–63 years). Nine patients had primary spinal tumors, and 5 patients had oligometastatic spinal metastases. Median follow-up was 78 months (range 24–324 months). An all-posterior approach was utilized in 13 of 14 patients. Iliac crest bone graft was used to pack the allograft in 12 patients, while cement was used in 2 patients.
Mean time to fusion was 11 months (range 6–18 months). One patient developed rod breakage secondary to delayed union requiring revision posterior instrumentation and posterolateral bone grafting, with subsequent fusion achieved. One intraoperative femoral allograft fracture occurred during screw insertion prior to implantation and was successfully treated with cerclage fixation.
Conclusions Structural femoral allografts represent a viable option for anterior spinal column reconstruction following en bloc spinal tumor resection. Posterior stabilization of the allograft using pedicle screws provides mechanical stability while avoiding the need for additional anterior instrumentation.
Level of Evidence 4
Introduction
En bloc surgical resection with Enneking-appropriate margins is the primary treatment for primary spinal tumors,1 significantly reducing local recurrence and improving survival.2–5 While spinal metastases are more common, advances in chemotherapy, radiotherapy, and surgical techniques such as separation surgery have reduced the need for en bloc resection in spinal metastases.6 However, it remains indicated for solitary radioresistant spinal metastases with good survival prognosis.7 In a systematic review, Kieser et al8 found that en bloc resection of solitary spinal metastases provided effective local control and maintained functional independence.
For primary spinal tumors, curative surgery requires stable constructs with early fusion for long-term stability. However, removing load-bearing structures in a biologically compromised environment presents challenges.9–12 In patients with spinal metastases and favorable prognoses, ensuring mechanical stability and durable fusion remains a key surgical goal.7
Various methods have been used for anterior reconstruction, including vascularized and nonvascularized autografts, allografts, polymethylmethacrylate (PMMA) cement, and prefabricated cages.13,14 While there have been previous publications describing the use of femoral allograft in anterior reconstruction after spinal tumor resection, their use remains uncommon, and data on time to fusion and long-term outcomes are unknown.15,16 To our knowledge, this article is one of the first to describe the time to fusion and long-term outcomes when using femoral allograft to reconstruct the spinal column after spinal tumor resection. We also sought to report our technique of stabilization of the allograft by preinserting a pedicle screw, which is then connected to the posterior pedicle screw and rod construct.
Methods
This retrospective review includes patients who underwent en bloc vertebrectomy for primary spinal tumors or solitary spinal metastases in the thoracolumbar spine, followed by anterior column reconstruction with fresh frozen femoral structural allografts and posterior pedicle screw instrumentation. Data was collected from operating room records and physical and electronic medical records. Ethics approval was obtained from the Galeazzi Hospital-San Raffaele Hospital Ethics Committee (authorization number 182/2019). This retrospective study was conducted under ethics approval obtained in 2019 and included patients treated by the senior author from January 1994 to December 2019. Each patient underwent a transpedicular biopsy for histological confirmation. Preoperative imaging (radiographs, computed tomography [CT], magnetic resonance imaging [MRI], and positron emission tomography-CT) was reviewed and discussed at a multidisciplinary tumor board meeting. Chemotherapy and radiotherapy were administered based on multidisciplinary team consensus.
Inclusion criteria for en bloc resection were (1) primary tumors with appropriate histology, staging, and surgical feasibility; (2) spinal metastases with no other metastatic lesions, a favorable tumor type, predicted survival exceeding 2 years, histological confirmation matching the primary tumor, and surgical feasibility. Exclusion criteria were (1) tumors with widespread metastatic disease; (2) tumors lacking histological confirmation; (3) patients with incomplete records or inadequate follow-up for outcome assessment.
Collected data included demographics, tumor histology, location, Enneking classification, and prior treatments. Surgical details recorded were approach, levels resected, instrumentation type, and perioperative complications. Primary outcomes assessed were fusion and time to fusion, while secondary outcomes included local recurrence, recurrence-free survival, overall survival, and postoperative complications.
Preoperative Management and Planning
Each patient was assessed for cardiopulmonary fitness and reviewed by an anesthetist. Preoperative angiography was used to evaluate vascular anatomy, with embolization performed when feasible. CT/MRI measured anterior-posterior, medial-lateral, and cranial-caudal vertebral and disc dimensions for allograft sizing as shown in Figure 1. Informed consent discussions covered surgical alternatives and potential complications.
Preoperative sagittal and axial magnetic resonance imaging of patient 12 with L1 Ewing's sarcoma.
Surgical Technique
Tumor Resection
En bloc resection was performed under general hypotensive anesthesia. If needed, iliac crest bone grafts (ICBGs) were harvested in the supine position and preserved. Patients were then positioned prone for an open posterior longitudinal approach, exposing at least 2 vertebral levels cranial and caudal to the tumor. Lateral exposure extended to the transverse processes, which were amputated with a bone cutter. In thoracic cases, affected ribs were osteotomized 4–5 cm lateral to the costotransverse joint, with medial rib portions removed unless tumor involvement was present.
Nerve root ligation and vascular resection were performed as needed. Adherent structures were bluntly dissected to ensure the vertebrae and discs were circumferentially free. This was confirmed by palpating the vertebrae anteriorly and ensuring both fingertips could meet and move freely along the resected area. Pedicle screws were inserted cranial and caudal to the resection site, with at least 2 levels instrumented except in 1 case. Complete laminectomy of affected levels and partial laminectomy of adjacent levels were performed using an ultrasonic bone scalpel, either piecemeal or en bloc. Pedicles were amputated unless tumor involvement was present. Care was taken to avoid breaching the tumor.
The dura mater was carefully separated from the posterior longitudinal ligament and vertebral body. Hoffman ligaments were divided to facilitate dura mobilization. Tumor tissue in contact with the dura was delicately separated to avoid breaching the tumor capsule. The spinal cord was confirmed to be circumferentially free by passing a right-angled nerve hook under the dura to check for residual adhesions. Malleable retractors were positioned to protect anterior structures. The dura was gently retracted while the cranial and caudal discs and anterior longitudinal ligament were severed using a scalpel, ultrasonic scalpel, and scissors.
A temporary rod was placed to maintain spinal stability. Once the segment was circumferentially free of attachments, it was gently rotated around the spinal cord and delivered. Endplates were prepared, and the required allograft length was measured.
Allograft Preparation
A femoral allograft segment was selected, measured with a caliper, and cut to size using an oscillating saw. Its circumference was adjusted by trimming with an oscillating saw, and a bicortical pilot tract was drilled and tapped to the same diameter as the pedicle screw to be placed. This pedicle screw was placed in a posterior-to-anterior direction to allow for the pedicle screw head to be connected to the rods of the posterior spinal implant construct. Tapping before screw insertion was essential to prevent graft fracture. Harvested ICBGs were morselized and packed into the allograft. The amount of harvested ICBGs were sufficient to fill the entire cavity, and no additional bone substitute was used. In 2 cases (patients 4 and 7), the allograft was packed with cement instead.
Anterior Reconstruction
The pedicle screw inserted into the allograft was used as an “inserter” to maneuver the allograft laterally, then anterior to the cord, and between the superior and inferior vertebrae, ensuring maximal endplate contact. It was inspected to ensure no dural sac compression. A rod was then contoured and secured on the contralateral side, and compression was performed to further secure the allograft between the superior and inferior vertebrae. Then, a second rod was contoured and secured to the pedicle screws on the side of allograft insertion as well as the pedicle screw within the allograft to further augment the stability of the construct, as visualized in the model seen in Figure 2. In 1 case (patient 8), involving L5 tumor resection, additional cortical screws were placed for anterior stabilization, securing the allograft to the inferior endplate of the cranial vertebra and the superior endplate of the caudal vertebra.
Models of femoral allograft.
Postoperative Care
After surgical treatment, patients were followed at 3, 6, 9, 12, and 24 months postoperatively, then every 6 months for 2 years and annually thereafter. At each time point, standard radiographs (Figure 3) and CT images were obtained to assess for bony fusion, allograft and construct failure, loosening, or dislocation.
Postoperative anterior-posterior and lateral radiograph of patient 12.
Fusion was primarily assessed by CT scan, interpreted by musculoskeletal radiologists. Fusion was defined as continuous trabecular bone bridging across both the cranial and caudal graft–vertebral interfaces on multiplanar CT, with the absence of a radiolucent gap. Representative CT images are shown in Figures 4 and 5. Once bone union was confirmed, follow-up CTs were discontinued.
Postoperative 12 months coronal computed tomography of patient 12 showing growth of native vertebral bone (T12 and L2) into the graft, indicating initial fusion.
Postoperative 6 years coronal and sagittal computed tomography of patient 12 showing graft fusion.
MRI was used to detect local recurrence, while oncologists performed periodic thorax, abdomen, pelvis, and positron emission tomography CT to monitor for metastatic spread.
Results
A total of 14 patients (7 females and 7 males) were treated, with a mean age of 38 years (11–63 years). Nine patients had primary spinal tumors, including Ewing sarcoma (2), epithelioid hemangioendothelioma (3), giant cell tumor (2), benign fibrous histiocytoma (1), and chordoma (1). Five patients had spinal metastases with either renal cell carcinoma (3) or thyroid cancer (2). Tumor locations were evenly distributed between the thoracic and lumbar spine. A total of 10 patients had single-level involvement (Table 1).
Demographics, tumor characteristics, and preoperative treatment of patients undergoing structural femoral allograft reconstruction after en bloc thoracolumbar spinal tumor resection.
A posterior approach was used in 13 of the 14 cases, with only patient 8 requiring a combined anterior and posterior approach. The first 2 patients received posterior stabilization using a Roy-Camille plate and a Steffee plate, respectively, while subsequent patients received conventional titanium rods. ICBGs were used to pack the allograft in all but 2 cases (patients 4 and 7), where cement was used instead (Table 2).
Surgical approach, instrumentation, grafting strategy, complications, revision surgery, and adjuvant treatment following structural femoral allograft reconstruction after en bloc thoracolumbar spinal tumor resection.
Postoperatively, only patient 3 had neurological symptoms, experiencing persistent unstable gait that required a crutch. Intraoperative complications occurred in patients 2 and 6. In patient 2, a fracture occurred while the pedicle screw was being placed before insertion of the femoral allograft. The femoral graft was cerclaged with a cable and a second pedicle screw inserted in a new track. Fusion occurred at 8 months with no further postoperative fracture of the allograft. Patient 6 experienced significant intraoperative blood loss, leading to hypotension and massive allogeneic transfusion.
Two patients required revision surgery. Patient 7 developed a deep wound infection requiring surgical debridement and intravenous antibiotics. Patient 8 experienced rod breakage at 8 months, secondary to nonunion of the allograft, necessitating revision posterior instrumentation with additional sacral screws and posterolateral bone grafting. Fusion was achieved at 12 months postinitial surgery.
The median follow-up was 78 months (24–324 months). Mean fusion time was 11 months (6–18 months), and there were no cases of persistent pseudarthrosis at final follow-up. Fusion of the autograft and allograft to the cranial and caudal vertebrae and incorporation of the structural allograft was confirmed in all cases. Local recurrence occurred in 2 patients: patient 4 (renal cell carcinoma) at 84 months and patient 9 (chordoma) at 24 months. Mean local recurrence-free survival was 114 months (24–324 months).
By study end, all patients with spinal metastasis had passed away, with a mean survival of 47 months (24–84 months). Among primary tumor patients, 3 had died: patient 6 from breast cancer and patients 9 and 14 from cancer-related causes. Mean survival in the primary tumor group was 155 months (36–324 months; Table 3).
Postoperative neurological, union, recurrence, and survival outcomes following structural femoral allograft reconstruction after en bloc thoracolumbar spinal tumor resection.
Discussion
Various methods of anterior column reconstruction following en bloc spondylectomy have been described, including titanium mesh cages, expandable cages, structural allografts, and PMMA constructs. Each technique balances mechanical stability, fusion potential, and imaging compatibility. Structural femoral allografts offer the advantage of biological incorporation and reduced imaging artifact compared with metallic implants.
Structural femoral allografts have been used for anterior column reconstruction in spinal deformity, degeneration, infection, and trauma.17–24 However, reports on their use after spinal tumor en bloc resection are limited.15,16 The largest case series, by Lewandrowski et al,15 reported 12 patients treated with femoral allografts and ICBGs, all achieving union, though time to union and long-term outcomes were not detailed. Villavicencio et al16 reported 16 patients receiving femoral allografts for metastatic spine tumors; none required revision, but fusion details were not provided. Both studies employed anterior instrumentation for stability.
Despite these gaps in tumor reconstruction research, femoral allografts have demonstrated advantages over synthetic implants in other spinal applications.25–27 In a randomized controlled trial comparing structural femoral grafts and titanium cages for anterior lumbar interbody fusion, McKenna et al25 found that they provided better Oswestry Disability Index, Short Form-36, and visual analog scale scores than titanium cages, with similar complication and revision rates. Freeman et al26 highlighted their cost-effectiveness, reporting higher quality-adjusted life years and improved return-to-work rates. Fatima et al’s meta-analysis27 further supported femoral allografts, noting higher fusion success and lower reoperation rates compared to polyetheretherketone (PEEK) implants, likely due to their osteoconductive and weakly osteoinductive properties, as well as their autograft packing capacity. In another case series, Chang et al23 explored the use of structural femoral shaft allografts for the reconstruction of the anterior spinal column in osteoporotic patients. It found that femoral shaft allografts improved kyphosis and resulted in minimal subsidence, recommending it as an effective treatment option for osteoporotic spines.
Mechanically, femoral allografts withstand thoracolumbar compressive forces better than other autografts.24,28 Their variable diameter and circumference along the length of the allograft enable cortical ring alignment for stronger apposition with the cortical region of the peripheral endplate, reducing allograft subsidence risk.29,30 Their elasticity closely matches native bone, minimizing stress shielding, bone density loss, and nonunion.23,29 Additionally, their length allows anterior reconstruction for up to 2 vertebral levels.
Potential disadvantages include theoretical disease transmission, fracture risk, and slower union compared to autografts.31 In recent years, improved donor screening and sterilization and preparation techniques have minimized transmission risk,32 with no cases in our cohort. While fractures of structural femoral allografts are a common complication in long-bone defects grafting due to resorption secondary to creeping substitution and immune response,33 there is a much lower rate in spinal anterior column reconstruction. In 2 studies of anterior column reconstruction, Singh et al34 reported 100% fusion with no allograft fractures or collapse in 41 patients, while Chang et al23 observed no allograft fractures in 21 osteoporotic patients. Similarly, our series had no fractures, with all cases achieving fusion.
Achieving fusion and incorporation after en bloc resection is challenging due to spinal instability and biological compromise from tumor excision, soft tissue defects, chemotherapy, and radiotherapy.11–14 In a systematic review, Altaf et al14 reported a mean construct failure rate of 7.5% (0%–55%) and a mean revision rate of 2.5% (0%–24%) after circumferential reconstruction. Moreover, radiotherapy reduces osteogenic cell numbers and osteoblastic activity, delaying bone remodeling and fusion.11–13 Radiotherapy also reduces bone mineral density,13 increasing subsidence risk. In a study of 136 en bloc spondylectomies by Shimizu et al,35 instrumentation failure occurred in 32.4% of patients. Most commonly 2 to 3 years postoperatively, with cage subsidence as a risk factor. Femoral allografts can provide early stability with potential for incorporation and fusion, preventing implant failure.
Successful allograft incorporation depends on autologous bone grafting, preservation methods, and mechanical stability.16 Autologous bone graft remains the gold standard for achieving spinal fusion, with ICBG being the most commonly used.36 Despite donor-site morbidity and increased operating time, we believe that ICBG allows earlier fusion, thereby preventing allograft fracture and pseudoarthrosis. ICBG was used in 12 out of 14 of our cases, achieving a mean fusion time of 10 months (6–18 months). In patients 4 and 7, PMMA was used due to poor survival prognosis, with fusion at 12 and 14 months, respectively. PMMA offers immediate stability, radiation resistance, imaging compatibility, and cost-effectiveness while preventing cement leakage. Altaf et al14 reported a construct failure rate of 0% to 10.7% and a revision rate of 0% to 4.3% for PMMA reconstructions. Fresh frozen allografts achieve higher fusion rates than freeze-dried ones,37 likely due to denaturation of osteoinductive factors in the preservation process. For this reason, we consistently use fresh frozen allografts.
In 13/14 patients, we used at least 2 levels of pedicle screw instrumentation cranial and caudal, with no cases of implant failure. The only mechanical failure occurred in a patient who underwent short-segment fixation with anterior screws, aligning with biomechanical literature.38–40 In biomechanical in vitro testing on a spine simulator, Disch et al39 found that after en bloc spondylectomy, posterior fixation spanning more than 1 adjacent segment was the primary determinant of stability. Short-segment fixation with supplementary anterior fixation was insufficient to restore stability. Our technique of stabilizing the structural allograft with a posterior pedicle screw obviates the need for an anterior approach and instrumentation. Additional anterior or lateral fixation may increase stress shielding,41 does not significantly enhance stability, and may lead to increased surgical morbidity.
Alternatives to allografts include synthetic implants and autografts. Traditional metallic implants cause imaging artifacts that hinder radiotherapy planning and tumor surveillance. Carbon composite cages, which avoid these issues and have bone-like mechanical properties, are gaining popularity.42,43 Disch et al44 reported no implant breakage or loosening at 25-month follow-up with a modular carbon composite system, including stackable cages and artificial titanium pedicles. Composite PEEK/carbon fiber vertebral body replacement and PEEK/carbon fiber posterior instrumentation systems are also under study.45 However, carbon composite implants remain costly and less widely available. Another alternative to stabilize the anterior column after en bloc spondylectomy is the use of a titan mesh cage. Pokorni et al46 used finite element analysis to compare posterior-only vs combined anterior-posterior constructs. Posterior-only fixation transmitted more stress to the bone graft, potentially promoting fusion, while anterior instrumentation led to stress shielding. This suggests that omitting anterior support may enhance graft incorporation in selected cases. PMMA replacement is another alternative to stabilize the anterior column as well. In a retrospective study by Eleraky et al47 comparing the 2 following single-stage posterior corpectomy, both PMMA and expandable cages achieved similar outcomes in kyphosis correction, pain relief, and functional status in the lumbar and thoracolumbar spine. While expandable cages showed a trend toward better kyphosis correction, the difference was not statistically significant. These findings support the use of either approach as viable options for anterior support, with PMMA offering a cost-effective alternative. Our technique provides a viable alternative when these implants are unavailable or when size constraints exist, such as in pediatric cases.
The main limitation of our study is the relatively small number of patients and the heterogeneity of techniques and instruments used, with an anterior approach and additional anterior screws in 1 patient, and bone cement instead of ICBG in 2 patients. However, despite this, the allograft proceeded to fuse in every patient. Larger prospective case series are needed to further validate this technique. The appropriateness of analyzing pediatric and adult cases together is another limitation of this study. While fusion rates may differ between these groups, en bloc vertebrectomy is a rare procedure, and both cohorts shared comparable factors influencing bone union. All patients underwent a similar surgical technique and received adjuvant chemotherapy and radiotherapy, both of which are recognized to impair bone healing.
Conclusion
Structural femoral allograft is suitable for anterior column reconstruction after spinal tumor en bloc resection due to its biomechanical properties. In spinal tumor patients, its compatibility with imaging modalities makes it ideal for postoperative surveillance and radiotherapy. Our technique of posterior stabilization with pedicle screws ensures mechanical stability and removes the need for an anterior approach and stabilization. While our favored technique is packing the allograft with ICBG to encourage early fusion, this technique can be adapted for the use of PMMA cement. While technically challenging to perform, we believe that our technique is a viable alternative to carbon composite implants, with reliable fusion and complication rates.
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.
Disclosures There are no disclosures to be made
- 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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