title: Which patients risk segmental kyphosis after short segment thoracolumbar fracture fixation with intermediate screws?
abstract: BACKGROUND
  The use of intermediate screws in fractured vertebrae has been proposed to decrease the number of fused levels in thoracolumbar fractures and to enable short fixations. The aim of this study was to evaluate the results of this technique and to establish predictive factors involved in loss of segmental kyphosis correction (LKC).
  
  
  METHODS
  Forty-three patients who underwent short-segment spinal fixation with intermediate screws for a thoracolumbar spine fracture in a two-year time period were enrolled in the study. Patients had AO-type A3, A4 and B2 thoracolumbar fractures. Radiological parameters included segmental kyphosis (SK), vertebral wedge angle (VWA) and loss of anterior and posterior vertebral body height. Patients were evaluated up to one-year follow-up. The correlation between LKC and potential risk factors, such as smoking habit, sex, age, neurological status and BMI was evaluated.
  
  
  RESULTS
  Mean preoperative SK was 16.5°±6.5°, and it decreased to 3.4°±3.5° postoperatively (P<0.01). At the one-year follow-up mean SK dropped to 5.5°±3.9° (P<0.01). Mean preoperative VWA was 20.0°±8.1°, and significantly improved to 6.3°±3.1° after surgery (P<0.01). There was a mean LKC of 1.8°±2.1°at one year. LKC mildly correlated with body mass index (BMI, r: +0.31), and obese patients (BMI>30) had an increased risk of LKC at the one-year follow-up (P=0.03; odds ratio [OR]=3.2).
  
  
  CONCLUSIONS
  Analysis of the radiological data at one-year follow-up showed that all the evaluated parameters were associated with a mild loss of correction, with no impact on the clinical outcomes or implant failure. These findings confirm the trends reported in the literature. The correlation between LKC and clinical features, such as BMI, age, sex, smoking habit and preoperative neurological status was investigated. Interestingly, a positive correlation was observed between BMI and LKC, and obese patients with BMI>30 had an increased risk of LKC at one-year follow-up (OR 3.2); to our knowledge this finding has never before been reported.
  
  
  CONCLUSIONS
  Short-segment fixation with intermediate screws is a viable technique with positive clinical and radiological outcomes at one-year follow-up. However, surgeons should be aware that in obese patients (BMI>30) this technique is associated with an increased risk of LKC.
  
  
  METHODS
  3.
authors: Clinica Ortopedica, IRCCS Azienda Ospedaliera Universitaria San Martino, IST, Istituto Nazionale per la Ricerca sul Cancro, Largo Rosanna Benzi, 10 16132 Genova, GE, Italy. Electronic address: matteo.formica@unige.it.
authors: Matteo
authors: M
authors: Formica
authors: Clinica Ortopedica, IRCCS Azienda Ospedaliera Universitaria San Martino, IST, Istituto Nazionale per la Ricerca sul Cancro, Largo Rosanna Benzi, 10 16132 Genova, GE, Italy.
authors: Luca
authors: L
authors: Cavagnaro
authors: Clinica Ortopedica, IRCCS Azienda Ospedaliera Universitaria San Martino, IST, Istituto Nazionale per la Ricerca sul Cancro, Largo Rosanna Benzi, 10 16132 Genova, GE, Italy.
authors: Marco
authors: M
authors: Basso
authors: Clinica Ortopedica, IRCCS Azienda Ospedaliera Universitaria San Martino, IST, Istituto Nazionale per la Ricerca sul Cancro, Largo Rosanna Benzi, 10 16132 Genova, GE, Italy.
authors: Andrea
authors: A
authors: Zanirato
authors: Clinica Ortopedica, IRCCS Azienda Ospedaliera Universitaria San Martino, IST, Istituto Nazionale per la Ricerca sul Cancro, Largo Rosanna Benzi, 10 16132 Genova, GE, Italy.
authors: Lamberto
authors: L
authors: Felli
authors: IRCCS Istituto Ortopedico Galeazzi, Via Riccardo Galeazzi 4, 20161 Milan, MI, Italy.
authors: Carlo
authors: C
authors: Formica
authors: Department of Orthopaedics and Trauma Surgery, University Campus Bio-Medico of Rome, Via Álvaro del Portillo, 200, Roma, Italy.
authors: Alberto
authors: A
authors: Di Martino
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D015992:Body Mass Index; D002648:Child; D005260:Female; D005500:Follow-Up Studies; D005593:Fracture Fixation, Internal / Q000009:adverse effects* / Q000295:instrumentation; D006801:Humans; D007558:Italy; D007738:Kyphosis / Q000000981:diagnostic imaging / Q000209:etiology / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000293:injuries* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D065289:Pedicle Screws; D011184:Postoperative Period; D011859:Radiography; D012189:Retrospective Studies; D018570:Risk Assessment; D017678:Sex Distribution; D016103:Spinal Fractures / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging / Q000293:injuries* / Q000601:surgery; D016896:Treatment Outcome; D055815:Young Adult
keywords: BMI; Injury; Intermediate screw; Pedicle screw fixation; Post-traumatic kyphosis; Short-segment fixation; Spine; Thoracolumbar fractures; Trauma