The study will examine if variability in created value (outcome/costs) over the care cycle for ASD patients can be explained by patient and treatment characteristics.

Due to budget restrictions in health care, cost is a major challenge, particularly in chronic disorders affecting the ageing population for which advanced but often expensive medical technologies offer benefit. Stakeholders strive to define, assess and improve the so-called "value in healthcare" to achieve the best outcome at the lowest cost of care.

First and foremost, the investigator will try to examine if we can explain variability in the created value over the care cycle by patient and treatment characteristics. This knowledge can be used to optimize the value for the patients. Also, the investigator will try to compare the psychometric properties between the different versions of value equations, resulting from the use of different outcome tools to measure value.

Adult Spinal Deformity patients can take part in the study. This will be decided by clinical examination and radiographic evaluation and is based on at least one of the following criteria: 1) Coronal spinal curvature ≥20°, 2)Sagittal vertical axis (SVA) >5 cm, 3) Pelvic tilt >25°, 4) Thoracic kyphosis >60°. The patients have to be older than or equal to 18 years old at the time of surgery.

In line with the standard of care, the patients will be seen after 3 months, 6 months, 1 year and 2 years postoperatively. Pre- and post-operatively, questionnaires will be completed by the patients. The patient questionnaires EuroQol 5D (EQ-5D-3L and EQ-5D-5L) , Scoliosis Research Society 22 score (SRS-22), Oswestry disability Index, Core Outcome Measures Index score (COMI) and Work status will be completed by the patients during the baseline visit and on each follow-up moment at 3 months, 6 months, 1 year and 2 years.

Inclusion Criteria:

• Adult Spinal Deformity patients
• Index Surgery from 15/03/2020 and 15/03/2022
• Age of 18 years old or older at the moment of the index surgery
• Patients treated in University Hospitals Leuven
• Patient has full understanding and is willing to participate (Informed consent)

Exclusion Criteria:

• • Patients younger than 18 years old at the moment of index surgery

  • Patients with an index surgery before 15/03/2020
  • Patients treated in other centers outside of University Hospitals Leuven

Population of patients, diagnosed with ASD, with an index surgery between 15 march 2020 and 15 march 2022 at University Hospitals Leuven.