Pelvic Reconstruction Surgery Using a Dual-Rod Technique with Diverse U-Shaped Rods After Posterior En Bloc Partial Sacrectomy for a Sacral Tumor: 2 Case Reports and a Literature Review

The biomechanical effect of lumbopelvic distance reduction on reconstruction after total sacrectomy: a comparative finite element analysis of four techniques

BACKGROUND CONTEXT

Following total sacrectomy, lumbopelvic reconstruction is essential to restore continuity between the lumbar spine and pelvis. However, to achieve long-term clinical stability, bony fusion between the lumbar spine and the pelvic ring is crucial. Reduction of the lumbopelvic distance can promote successful bony fusion. Although many lumbopelvic reconstruction techniques (LPRTs) have been previously analyzed, the biomechanical effect of lumbopelvic distance reduction (LPDR) has not been investigated yet.

PURPOSE

To evaluate and compare the biomechanical characteristics of four different LPRTs while considering the effect of LPDR.

STUDY DESIGN/SETTING

A comparative finite element (FE) study.

METHODS

The FE models following total sacrectomy were developed to analyze four different LPRTs, with and without LPDR. The closed-loop reconstruction (CLR), the sacral-rod reconstruction (SRR), the four-rod reconstruction (FRR), and the improved compound reconstruction (ICR) techniques were analyzed in flexion, extension, lateral bending, and axial rotation. Lumbopelvic stability was assessed through the shift-down displacement and the relative sagittal rotation of L5, while implant safety was evaluated based on the stress state at the bone-implant interface and within the rods.

RESULTS

Regardless of LPDR, both the shift-down displacement and relative sagittal rotation of L5 consistently ranked the LPRTs as ICR

CONCLUSIONS

LPDR significantly improved both lumbopelvic stability and implant safety in all reconstruction techniques after total sacrectomy. LPDR reduced the shift-down displacement of L5, the relative sagittal rotation of L5, and the stress values at the bone-implant interface. Furthermore, in the ICR and SRR techniques, LPDR decreased the peak stress values within the rods. All four investigated LPRTs demonstrated suitability for lumbopelvic reconstruction, with the ICR technique exhibiting the highest lumbopelvic stiffness.

CLINICAL SIGNIFICANCE

LPDR creates a biomechanically advantageous environment following total sacrectomy; therefore, it has the potential to impact the design of custom-made 3D-printed or traditional LPRTs. However, to confirm the findings of the current FE study, long-term clinical trials are recommended.

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Key Words

• Biomechanics
• Finite element analysis
• Lumbopelvic distance reduction
• Lumbopelvic fixation
• Lumbopelvic reconstruction
• Lumbopelvic stabilization
• Total sacrectomy

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MESH Headings

• Humans
• Finite Element Analysis
• Biomechanical Phenomena
• Sacrum/surgery
• Plastic Surgery Procedures/methods
• Lumbar Vertebrae/surgery
• Male
• Range of Motion, Articular
• Spinal Fusion/methods

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Affiliation(s)

Mate Turbucz School of PhD Studies, Semmelweis University, Üllői Str. 26, Budapest, Hungary; In Silico Biomechanics Laboratory, National Center for Spinal Disorders, Királyhágó Str. 1-3, Budapest, Hungary
Agoston Jakab Pokorni School of PhD Studies, Semmelweis University, Üllői Str. 26, Budapest, Hungary; In Silico Biomechanics Laboratory, National Center for Spinal Disorders, Királyhágó Str. 1-3, Budapest, Hungary
Benjamin Hajnal School of PhD Studies, Semmelweis University, Üllői Str. 26, Budapest, Hungary; In Silico Biomechanics Laboratory, National Center for Spinal Disorders, Királyhágó Str. 1-3, Budapest, Hungary
Kristof Koch School of PhD Studies, Semmelweis University, Üllői Str. 26, Budapest, Hungary; National Center for Spinal Disorders, Királyhágó Str. 1-3, Budapest, Hungary
Zsolt Szoverfi National Center for Spinal Disorders, Királyhágó Str. 1-3, Budapest, Hungary
Peter Pal Varga National Center for Spinal Disorders, Királyhágó Str. 1-3, Budapest, Hungary
Aron Lazary National Center for Spinal Disorders, Királyhágó Str. 1-3, Budapest, Hungary; Department of Spine Surgery, Department of Orthopaedics, Semmelweis University, Üllői Str. 78/b, Budapest, Hungary
Peter Endre Eltes In Silico Biomechanics Laboratory, National Center for Spinal Disorders, Királyhágó Str. 1-3, Budapest, Hungary; National Center for Spinal Disorders, Királyhágó Str. 1-3, Budapest, Hungary; Department of Spine Surgery, Department of Orthopaedics, Semmelweis University, Üllői Str. 78/b, Budapest, Hungary.

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Lumbopelvic shortening and local host bone-to-host bone reconstruction: a surgical method for lumbopelvic fusion following total sacrectomy

PURPOSE

Primary sacral tumors are rare, representing fewer than 7% of spinal neoplasms. Following total sacrectomy, lumbopelvic instrumentation and fusion carries a high risk of non-union with no current consensus on fixation techniques to augment bony defects. We aim to describe the outcome of a reconstruction technique following total sacrectomy whereby lumbopelvic shortening is performed and the posterior pelvic ring is compressed to enable contact with the native L5 vertebra.

METHODS

Retrospective chart review of 2 patients with 2 and 7 years post-operative follow-up. A review of hospital records including clinical assessments, complications, pathology and imaging reports.

RESULTS

Patient 1 was a 17-years-old male with recurrent sacral chondrosarcoma, who presented with lumbosacral neuropathic pain and radiculopathy after failed intralesional surgery. Patient 2 was a 51-years-old male with chronic low back pain caused by a large low-grade chondroid sacral chordoma. Reconstruction technique involved mobilizing the L5 vertebra into the pelvis and pelvic ring closure to obtain host-bone-to-bone contact, eliminating the need for alternative grafts. Post-operative complications included superficial abdominal wound drainage, lower limb DVT, pulmonary emboli and deep pelvic infection. Serial CT scans demonstrated bony fusion in both patients. Neither patients had evidence of tumor recurrence and were able to ambulate at recent follow-up. Imaging demonstrated changed acetabular version of - 4.6/- 8.1 and - 14.4/- 14.8 (patient 1/2, R/L, respectively).

CONCLUSION

Primary lumbopelvic shortening represents an alternative local autograft reconstructive technique for management of large sacral defects following total sacrectomy. This technique obviates the additional morbidity and surgical cost associated with the use of previously described techniques.

A Novel Three-Dimensional Computational Method to Assess Rod Contour Deformation and to Map Bony Fusion in a Lumbopelvic Reconstruction After En-Bloc Sacrectomy

Introduction: En-bloc resection of a primary malignant sacral tumor with wide oncological margins impacts the biomechanics of the spinopelvic complex, deteriorating postoperative function. The closed-loop technique (CLT) for spinopelvic fixation (SPF) uses a single U-shaped rod to restore the spinopelvic biomechanical integrity. The CLT method was designed to provide a non-rigid fixation, however this hypothesis has not been previously tested. Here, we establish a computational method to measure the deformation of the implant and characterize the bony fusion process based on the 6-year follow-up (FU) data.

Materials and Methods: Post-operative CT scans were collected of a male patient who underwent total sacrectomy at the age of 42 due to a chordoma. CLT was used to reconstruct the spinopelvic junction. We defined the 3D geometry of the implant construct. Using rigid registration algorithms, a common coordinate system was created for the CLT to measure and visualize the deformation of the construct during the FU. In order to demonstrate the cyclical loading of the construct, the patient underwent gait analysis at the 6th year FU. First, a region of interest (ROI) was selected at the proximal level of the construct, then the deformation was determined during the follow-up period. In order to investigate the fusion process, a single axial slice-based voxel finite element (FE) mesh was created. The Hounsfield values (HU) were determined, then using an empirical linear equation, bone mineral density (BMD) values were assigned for every mesh element, out of 10 color-coded categories (1st category = 0 g/cm³, 10th category 1.12 g/cm³).

Results: Significant correlation was found between the number of days postoperatively and deformation in the sagittal plane, resulting in a forward bending tendency of the construct. Volume distributions were determined and visualized over time for the different BMD categories and it was found that the total volume of the elements in the highest BMD category in the first postoperative CT was 0.04 cm³, at the 2nd year, FU was 0.98 cm³, and after 6 years, it was 2.30 cm³.

Conclusion: The CLT provides a non-rigid fixation. The quantification of implant deformation and bony fusion may help understate the complex lumbopelvic biomechanics after sacrectomy.

Risk Factors Associated with Reconstructive Complications Following Sacrectomy

BACKGROUND

Sacral pathology requiring partial or total sacrectomy is rare, and reconstructing the ensuing defects requires careful decision-making to minimize morbidity. The purpose of this study was to review the experience of a single institution with reconstructing large sacral defects, to identify risk factors for suboptimal outcomes.

METHODS

A retrospective chart review was conducted of all patients who underwent sacrectomy over a 10-year period. Univariate analysis of differences in risk factors between patients with and without various postoperative complications was performed. Multivariate logistic regression was used to identify predictive variables.

RESULTS

Twenty-eight patients were identified. The most common diagnosis leading to sacrectomy was chordoma (39%). Total sacrectomy was performed on 4 patients, whereas 24 patients underwent partial resection. Reconstructive modalities included 15 gluteal advancement flaps, 4 pedicled rectus abdominis myocutaneous flaps, and 9 paraspinous muscle or other flap types. There was an overall complication rate of 57.1% (n = 12) and a 28.6% (n = 8) incidence of major complications. There were significantly more flap-related complications in patients who underwent total sacrectomy (P = 0.02). Large defect size resulted in significantly more unplanned returns to the operating room (P < 0.01).

CONCLUSION

Consistent with other published series', the overall complication rate exceeded 50%. Defect volume and sacrectomy type were the strongest predictors of postoperative complications and return to the operating room, while reconstructive strategy showed limited power to predict patient outcomes. We recommend that patients anticipated to have large sacral defects should be appropriately counseled regarding the incidence of wound complications, regardless of reconstructive approach.

Rare case of a recurrent juvenile ossifying fibroma of the lumbosacral spine

Juvenile ossifying fibroma (JOF) is a rare benign bone tumor that occurs most frequently in the craniofacial bones of children and young adults. There are few case reports that describe its involvement outside the craniofacial skeleton, especially within the spinal column. While JOF is classified as a benign lesion, it may be locally aggressive and demonstrate a high propensity for recurrence, even after resection. Definitive surgical management may be challenging in naive cases, but it is particularly challenging in recurrent cases and when extensive spinal reconstruction is warranted. In this report, the authors describe the diagnosis and surgical management of a 29-year-old man who presented with a large recurrent sacral trabecular-subtype JOF. A review of literature regarding JOFs, management of recurrent primary spinal tumors, and sacral reconstruction are discussed.