Aims. To determine the major risk factors for unplanned reoperations (UROs) following corrective surgery for adult spinal deformity (ASD) and their interactions, using machine learning-based prediction algorithms and game theory. Methods. Patients who underwent surgery for ASD, with a minimum of two-year follow-up, were retrospectively reviewed. In total, 210 patients were included and randomly allocated into training (70% of the sample size) and test (the remaining 30%) sets to develop the machine learning algorithm. Risk factors were included in the analysis, along with clinical characteristics and parameters acquired through diagnostic radiology. Results. Overall, 152 patients without and 58 with a history of surgical revision following surgery for ASD were observed; the mean age was 68.9 years (SD 8.7) and 66.9 years (SD 6.6), respectively. On implementing a random forest model, the classification of URO events resulted in a balanced accuracy of 86.8%. Among machine learning-extracted risk factors, URO, proximal junction failure (PJF), and postoperative distance from the posterosuperior corner of C7 and the vertical axis from the centroid of C2 (SVA) were significant upon Kaplan-Meier survival analysis. Conclusion. The major risk factors for URO following surgery for ASD, i.e. postoperative SVA and PJF, and their interactions were identified using a machine learning algorithm and game theory. Clinical benefits will depend on patient risk profiles. Cite this article: Bone Joint Res 2023;12(4):245–255

Currently, between 17% of patients undergoing surgery for adult spinal deformity experience severe instrumentation related problems such as screw pullout or proximal junctional failure necessitating revision surgery. Cables may be used to reinforce pedicle screw fixation as an additive measure or may provide less rigid fixation at the construct end levels in order to prevent junctional level problems. The purpose of this study is to provide insight into the maximum expected load during flexion in UHMWPE cable in constructs intended for correction of adult spine deformity (degenerative scoliosis) in the PoSTuRe first-in-man clinical trial. Following the concept of toppinoff, a new construct is proposed with screw/cable fixation of rods at the lower levels and standalone UHMWPE cables at the upper level (T11). A parametric FE model of the instrumented thoracolumbar spine, which has been previously validated, was used to represent the construct. Pedicle screws are modeled by assigning a rigid tie constraint between the rod and the lamina of the corresponding spinal level. Cables are modeled using linear elastic line elements, fixing the rod to the lamina medially at the cranial laminar end and laterally at the caudal laminar end. A Youngs modulus was assigned such that the stiffness of the line element was the same as that of the cable. An 8 Nm flexion moment was applied to the cranial endplate. The maximum value of the force in the wire (80 N) is found at the T11 (upper) level. At the other levels, forces in the cable are very small because most of the force is carried by the screw (T12) or because the wires are force shielded by the contralateral and adjacent level pedicle screws (L2, L3). The model provides first estimates of the forces that can be expected in the UHMWPE cables in constructs for kyphosis correction during movement. It is expected that this approach can help in defining the number of wires for optimal treatment

Introduction. Treatment of spinal metastatic disease has evolved with the advent of advanced interventional, surgical and radiation techniques. Spinal Oligometastatic disease is a low volume disease state where en bloc resection of the tumour, based on oncological principles, can achieve maximum local control (MLC). Hybrid therapy incorporating Separation surgery (>2mm clearance of the thecal sac) and Stereotactic Ablative Radiotherapy (SABR) offer an alternative approach to achieving MLC. Hybrid therapy is also a viable option in patients eligible for SBRT who have failed conventional radiation therapy. En-bloc surgery may be a suitable option for those patients who are ineligible for or have failed SBRT. A multidisciplinary approach is particularly important in the decision-making process for these patients. Metal free instrumentation is aiding the optimization of these surgeries. The authors present a supra-regional centre's experience in managing spinal oligometastases. Methods. Retrospective review of oligometastatic spinal disease at a supra-regional centre between 2017 and 2021. Demographics, operative course, complications and Instrument type are examined. Results. Demographics: 24 patients with mean age 53.8y (range 12–77), 44% (40y–59y), 40% (60y–69y); 51% Male. Histology: Breast, Renal and Sarcoma accounted for 16.7% each; Thyroid, Prostate and Chordoma accounted for 8.3% each. Primary disease 7%, Synchronous 15%, Metachronous 78%. Instrumentation: Carbon-fibre (85%), TiAl (11%), Non-Instrumented (3%). Separation Surgery (70%), En-bloc resection/Tomita surgery (30%); SABR/Proton Beam Planned: 70%. Average length of hospital stays 19.1 days; twenty patients required intensive care admission for an average 2.7 days. 30 Day Mortality 8.3% (n=2: COVID-19 during admission and ventriculitis post discharge), 1y Mortality – 16.7%, 3y Mortality – 25%; Synchronous Mortality 75% (n=3) at 3 years. 30 Day infection rate 3%; 1y infection rate 7%. 1 Non-instrumented case developed proximal junctional failure post proton beam therapy and required a vascularised fibular strut graft. 2-year Revision for Local Recurrence 5% (Revision at 23 months). Conclusion. There are very few case series of oligometastatic spinal disease due to the relatively new concept of adjuvant SABR and its limited availability. Solid tumours pre-dominated the histology in our series with metachronous disease being the most commonly operated disease state. 92% of cases were eligible for SABR. The majority (85%) of cases were performed with Carbon-fibre instrumentation and has been shown to be safe with no mechanical failures in this series. Infection rates are in keeping with patients requiring radical radiotherapy with 3% early and 7% late. 30-day mortality was 8.3%, 1y=16.7% and 25% at last follow up. Mortality, as expected, is highest within the synchronous disease group and should be operated on sparingly. With the current management strategy, there was no local recurrence at 1 year and excellent local recurrence rate at 2 years (5%). Although radical en bloc surgery carries significant morbidity, it should be considered in selective cases to achieve MLC. All Oligometastatic cases deserve extra consideration and specialist MDT as not all are suitable for SABR. Multimodal Hybrid therapy, incorporating less invasive surgical techniques and SABR, represents a paradigm shift in achieving MLC in oligometastatic spinal disease

The current trend in kyphosis correction is for “every level” instrumentation to achieve intraoperative stability, correction, fusion and implant longevity. We evaluate the medium term follow up of a low implant density (LID) construct. All patients with adolescent kyphosis (idiopathic or Scheurmann's) on our deformity database were identified. Radiographs and records were analysed for neurological complications, correction and revision. The constructs included were all pedicle screw anchors with multiple apical chevron osteotomies and a proximal and distal “box” of 6 to 8 screws. A four rod cantilever reduction manoeuvre with side to side connectors completed the construct. Kyphosis for any other cause was excluded. Follow up less than 12 months was excluded. 23 patients were identified with an average follow up 27 months (72 to 12 months) and a mean implant density of 1.1 (53.5% of “available” pedicles instrumented). There was 1 false positive neurophysiological event without sequelae (4%). There were no proximal junctional failures (0%). There were no pseudarthroses or rod breakages (0%). There was 1 loss of distal rod capture (early set screw failure) (4%). This was revised uneventfully. There were 4 infections requiring debridement (early series). Average initial correction was 44% (77.7 degrees to 43.5 degrees) with a 1% loss of correction at final follow up (43.5 to 44.0 degrees). The fulcrum bending correction index was 107% (based on fulcrum extension radiographs). 85% of curves had a fulcrum flexibility of less than 50%. The average cost saving compared to “every level “instrumentation was £5700 per case. This paper shows that a LID construct for kyphosis has technical outcomes as good as high density constructs. The obvious limitation of the study is the small number of patients in the cohort. The infection rates have improved with changes to perioperative process in the later series of patients. We do not believe these are a consequence of the construct itself

Aims

With recent progress in cancer treatment, the number of advanced-age patients with spinal metastases has been increasing. It is important to clarify the influence of advanced age on outcomes following surgery for spinal metastases, especially with a focus on subjective health state values.