Surgical resection and reconstruction after resection of tumors involving the sacropelvic region

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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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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Axial Axis Metastasis

Axial axis metastasis remains a challenge for surgical as well as other treatment modalities, like chemotherapy, immunotherapy, and radiotherapy. It is unequivocal that surgery provides pain improvements and preservation of neurological status, but this condition remains when associated with radiotherapy and other treatment modalities. In this review, we emphasize the current forms of surgical treatment in the different regions of the spine and pelvis. The evident possibility of percutaneous treatments is related to early or late cases, and in cases in which there are greater risks and instability to conventional surgeries associated with radiotherapy and have been shown to be the appropriate option for local control of metastatic disease.

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.

COMPLICATIONS AFTER PARTIAL, TOTAL OR EXTENDED SACRECTOMY: A CASE SERIES

ABSTRACT Objective The aim of this study was to conduct a survey of the different complications of partial, total or extended sacrectomy for the treatment of spinal tumors. Method This study is a descriptive analysis of medical records from a series of 18 patients who underwent sacrectomy between 2010 and 2019 at a tertiary center specializing in spinal tumor surgeries. The variables analyzed were sex, age, hospitalization time, oncologic diagnosis, posterior fixation pattern, rate of complications, and Frankel, ASA and ECOG scales. Results Of the 18 patients, 10 (55.5%) were male and 8 (44.5%) were female, and the mean age was 48 years. The mean hospitalization time was 23 days. Of the 18 patients, 8 (44.5%) contracted postoperative infections requiring surgery. Perioperative complications included liquoric fistula (22.25%), hemodynamic instability requiring vasoactive drugs in the immediate postoperative period (22.25%), wound dehiscence (11.1%), acute obstructive abdomen (11.1%), occlusion of the left external iliac artery (11.1%), immediate postoperative death due to acute myocardial infarction (11.1%), and intraoperative death due to hemodynamic instability (11.1%). Conclusions Partial, total or extended sacrectomy is a complex procedure with high morbidity and mortality, even in centers specializing in the treatment of spinal tumors. Level of evidence IV; case series study.

One-Step Reconstruction with a Novel Suspended, Modular, and 3D-Printed Total Sacral Implant Resection of Sacral Giant Cell Tumor with Preservation of Bilateral S1-3 Nerve Roots via a Posterior-Only Approach

Objective

To investigate the efficacy and safety of spinopelvic reconstruction based on a novel suspended, modular, and 3D‐printed total sacral implant after total piecemeal resection of a sacral giant cell tumor (SGCT) with the preservation of bilateral S_1–3 nerve roots via a posterior‐only approach.

Methods

Five patients who had undergone total piecemeal resection of SGCT involving upper sacral segments (S₁ and S₂) and the midline with the preservation of bilateral S_1–3 nerve roots via a posterior‐only approach between September 2017 and July 2018 were retrospectively reviewed. A novel suspended, modular, and 3D‐printed total sacral implant had been used for reconstruction. This series included two female and three male patients, with a mean age of 42.2 years (range, 31–53 years). Surgical time, blood loss, complications, preoperative and postoperative neurological function, instrumentation failure, and local control were presented and analyzed.

Results

All patients underwent the operation without death or serious complications. The implant was installed on the defect, connecting the ilium and lumbar vertebrae, and fixed with a screw–rod system up to the level of L_3–4 or L_4–5. The mean operative time was 502 min (range, 360–640 min) and the mean operative blood loss 4400 mL (range, 3000–7000 mL). The mean follow‐up was 15 months. After the operation, pain was significantly relieved, and the patients resumed walking as early as 2 weeks later. The patients showed no neurogenic bladder dysfunction and no fecal incontinence or gait disturbance. Wound healing was poor in one patient. Patients recovered well without evidence of local recurrence. No implant failures or related clinical symptoms were detected during follow up. Satisfactory bone ingrowth and osseointegration at the bone‐implant junctions was found in follow‐up CT.

Conclusion

Although technically challenging, it is feasible and safe to use a suspended, modular, and 3D‐printed implant for reconstruction after total piecemeal resection with the preservation of bilateral S_1–3 nerve roots in patients with SGCT. We believe that this implant can be applied to sacral reconstruction in a wide variety of diseases.

Factors Associated With Spinopelvic Fixation Mechanical Failure After Total Sacrectomy

STUDY DESIGN

We retrospectively analyzed factors associated with spinopelvic mechanical failure after total sacrectomy.

OBJECTIVE

To find the rate and type of mechanical fixation failure after total sacrectomy and to identify the associated risk factors.

SUMMARY OF BACKGROUND DATA

Although rigid fixation has been achieved, mechanical failure is sometimes encountered in reconstruction after total sacrectomy. The incidence and factors associated with spinopelvic fixation mechanical failure after total sacrectomy are still not clear.

METHODS

The study comprised 63 patients who underwent spinopelvic reconstruction after total sacrectomy. The potential risk factors for fixation mechanical failure after total sacrectomy were evaluated, which included age, sex, body mass index, type of tumor (benign or malignant), and adjuvant treatment received (e.g., chemotherapy, radiation therapy). The surgery-related factors included the classification of tumor resection (en bloc or piecemeal resection) and the type of iliosacral resection. Adoption of anterior spinal column fixation (ASCF), posterior pelvic ring fixation (PPRF), four-rod technique (FRT) of spinopelvic fixation (SPF), and structural or morselized bone grafting after total sacrectomy in patients were considered reconstruction-related factors. Cox regression models were used to analyze associations between postoperative fixation failure and risk factors for all models.

RESULTS

Postoperative fixation mechanical failure occurred in 25% of patients (16/63) who underwent total sacrectomy. Univariate analysis showed that the factors associated with spinopelvic fixation mechanical failure after total sacrectomy were the non-adoption of FRT of SPF and ASCF, the adoption of Type II sacroiliac resection, and female sex, whereas multivariate analysis demonstrated similar results, except for the adoption of Type II sacroilliac resection.

CONCLUSION

FRT connection of SPF and ASCF should be adopted in reconstruction after total sacrectomy, especially in female patients.

LEVEL OF EVIDENCE

3.

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.

Soft Tissue and Bone Defect Management in Total Sacrectomy for Primary Sacral Tumors: A Systematic Review With Expert Recommendations

STUDY DESIGN

Systematic review and expert consensus.

OBJECTIVE

To address the following two questions: (A) Is there a difference in outcomes after spino-pelvic reconstruction of total sacrectomy defects compared with no reconstruction? (B) What constitutes best surgical technique for soft tissue and bony reconstruction after total sacrectomy?

SUMMARY OF BACKGROUND DATA

The management of the soft tissue and bony defect after total sacrectomy for primary sacral tumors remains a challenge due to the complex anatomical relationships and biomechanical requirements. The scarcity of evidence-based literature in this specialized field makes it difficult for the treating surgeon to make an informed choice.

METHODS

A systematic literature review was performed (1950-2015), followed by a meeting of an international expert panel. Medline, Embase, and CINAHL databases and Cochrane Libraries were searched. Using the GRADE guidelines, the panel of experts formulated recommendations based on the available evidence.

RESULTS

Three hundred fifty-three studies were identified. Of these, 17 studies were included and were case series. Seven were evaluated as high quality of evidence and nine were of low quality. There were a total of 116 participants. Three studies included patients (n = 24) with no spino-pelvic reconstruction. One study included patients (n = 3) with vascularized bone reconstruction. Twelve studies included patients (n = 80) with no soft tissue reconstruction, three studies described patients with a local flap (n = 20), and four studies with patients having regional flap reconstruction (n = 16). Patients with or without spino-pelvic reconstruction had similar outcomes with regards to walking; however, most patients in the nonreconstructed group had some ilio-lumbar ligamentous stability preserved. The wound dehiscence and return to theater rates were higher in patients with no soft tissue reconstruction.

CONCLUSION

We recommend spino-pelvic reconstruction be undertaken with soft tissue reconstruction after total sacrectomy.

LEVEL OF EVIDENCE

N/A.

Malignant Pelvic Tumors Involving the Sacrum: Surgical Approaches and Procedures Based on a New Classification

OBJECTIVE

To introduce a new classification of Enneking type IV pelvic tumors involving the sacrum and a corresponding system of standardized surgical approaches and procedures for resection of such tumors, and to investigate the feasibility and therapeutic effect of the new system.

METHODS

Data on 59 patients treated between February 2003 and February 2013 by standardized surgical approaches and procedures were retrospectively reviewed. The study subjects comprised 28 male and 31 female patients with a mean age at diagnosis of 36 years (range, 2-72 years). There are four subtypes in the new classification: (i) subtype IVa, neoplasms invading the ipsilateral sacral wing; (ii) subtype IVb, neoplasms invading the ipsilateral sacral foramina; (iii) subtype IVc, neoplasms invading the contralateral sacral foramina; and (iv) subtype IVd, neoplasms invading the whole of the sacrum. Standardized surgical approaches and procedures were devised for en-bloc resection for each subtype with adequate margins.

RESULTS

Adequate margins were achieved in 43/59 patients (72.9%). The mean operation time was 5.0 h and the mean intraoperative blood loss 2157 mL. At the final follow-up, 27/53 patients (50.9%) who had been followed up were alive and in complete remission. The mean Musculoskeletal Tumor Society 93 score was 17.4 (58%) of a possible 30 points. The mean functional score for patients who had undergone a pelvic zone II resection was 15.2, compared with 19.0 for those with an intact pelvic zone II.

CONCLUSIONS

The proposed standardized protocols should help orthopaedic surgeons to achieve adequate margins, manage risk, achieve better oncologic and functional outcomes, and minimize perioperative complications when treating massive pelvic tumors involving the sacrum.