David Christopher Kieser, Derek Thomas Cawley, Takashi Fujishiro, Simon Mazas, Louis Boissière, Ibrahim Obeid, Vincent Pointillart, Jean-Marc Vital and Olivier Gille
The objective of this study was to identify the risk factors of anterior bone loss (ABL) in cervical disc arthroplasty (CDA) and the subsequent effect of this phenomenon.
The authors performed a retrospective radiological review of 185 patients with a minimum 5-year follow-up after CDA (using Bryan, Discocerv, Mobi-C, or Baguera C). Postoperative radiographs were examined and compared to the initial postoperative films to determine the percentage of ABL. The relationship of ABL to potential risk factors was analyzed.
Complete radiological assessment was available in 145 patients with 193 CDRs and 383 endplates (average age 45 years, range 25–65 years, 54% women). ABL was identified in 63.7% of CDRs (48.7% mild, 11.9% moderate, 3.1% severe). Age (p = 0.770), sex (p = 0.200), postoperative alignment (p = 0.330), midflexion point (p = 0.509), maximal flexion (p = 0.080), and extension (p = 0.717) did not relate to ABL. There was no significant difference in the rate of severe ABL between implants. Multilevel surgery conferred an increased risk of any and severe ABL (p = 0.013 for both). The upper endplate, defined as superior to the CDA, was more commonly involved (p = 0.008), but there was no significant difference whether the endplate was between or not between implants (p = 0.226). The development of ABL did not affect the long-term range of movement (ROM) of the CDA, but did increase the overall risk of autofusion. ABL was not associated with pain or functional deficits. No patients required a reoperation or revision of their implant during the course of this study, and there were no cases of progressive ABL beyond the first year.
ABL is common in all implant types assessed, although most is mild. Age, sex, postoperative alignment, ROM, and midflexion point do not relate to this phenomenon. However, the greater the number of levels operated, the higher the risk of developing ABL. The development of ABL has no long-term effect on the mechanical functioning of the disc or necessity for revision surgery, although it may increase the rate of autofusion.
Caglar Yilgor, Nuray Sogunmez, Yasemin Yavuz, Kadir Abul, Louis Boissiére, Sleiman Haddad, Ibrahim Obeid, Frank Kleinstück, Francisco Javier Sánchez Pérez-Grueso, Emre Acaroğlu, Anne F. Mannion, Ferran Pellise, Ahmet Alanay and the European Spine Study Group
The subtraction of lumbar lordosis (LL) from the pelvic incidence (PI) offers an estimate of the LL required for a given PI value. Relative LL (RLL) and the lordosis distribution index (LDI) are PI-based individualized measures. RLL quantifies the magnitude of lordosis relative to the ideal lordosis as defined by the magnitude of PI. LDI defines the magnitude of lower arc lordosis in proportion to total lordosis. The aim of this study was to compare RLL and PI − LL for their ability to predict postoperative complications and their correlations with health-related quality of life (HRQOL) scores.
Inclusion criteria were ≥ 4 levels of fusion and ≥ 2 years of follow-up. Mechanical complications were proximal junctional kyphosis/proximal junctional failure, distal junctional kyphosis/distal junctional failure, rod breakage, and implant-related complications. Correlations between PI − LL, RLL, PI, and HRQOL were analyzed using the Pearson correlation coefficient. Mechanical complication rates in PI − LL, RLL, LDI, RLL, and LDI interpreted together, and RLL subgroups for each PI − LL category were compared using chi-square tests and the exact test. Predictive models for mechanical complications with RLL and PI − LL were analyzed using binomial logistic regressions.
Two hundred twenty-two patients (168 women, 54 men) were included. The mean age was 52.2 ± 19.3 years (range 18–84 years). The mean follow-up was 28.8 ± 8.2 months (range 24–62 months). There was a significant correlation between PI − LL and PI (r = 0.441, p < 0.001), threatening the use of PI − LL to quantify spinopelvic mismatch for different PI values. RLL was not correlated with PI (r = −0.093, p > 0.05); therefore, it was able to quantify divergence from ideal lordosis for all PI values. Compared with PI − LL, RLL had stronger correlations with HRQOL scores (p < 0.05). Discrimination performance was better for the model with RLL than for PI − LL. The agreement between RLL and PI − LL was high (κ = 0.943, p < 0.001), moderate (κ = 0.455, p < 0.001), and poor (κ = −0.154, p = 0.343), respectively, for large, average, and small PI sizes. When analyzed by RLL, each PI − LL category was further divided into distinct groups of patients who had different mechanical complication rates (p < 0.001).
Using the formula of PI − LL may be insufficient to quantify normolordosis for the whole spectrum of PI values when applied as an absolute numeric value in conjunction with previously reported population-based average thresholds of 10° and 20°. Schwab PI − LL groups were found to constitute an inhomogeneous group of patients. RLL offers an individualized quantification of LL for all PI sizes. Compared with PI − LL, RLL showed a greater association with both mechanical complications and HRQOL. The use of RLL and LDI together, instead of PI − LL, for surgical planning may result in lower mechanical complication rates and better long-term HRQOL.