According to new research, certain ratios of correction of cervical parameters contribute to improving neck disability. The study, authored by Katherine E Pierce (NYU Langone Medical Centre, New York, USA) and colleagues, was recently nominated for Best Paper at the 34th Annual Meeting of the North American Spine Society (NASS 2019; 25–28 September, Chicago, USA), where Pierce presented the group’s findings.
The authors—Pierce and colleagues, including senior author Peter G Passias—note that certain cut-offs of radiographic differences from baseline to one year were found prioritising C2–T3 angle, followed by cervical lordosis, C2 slope, C2–C7 plumb line, and McGregor’s slope, all strongly associated with meeting the minimal clinically important difference for the neck disability index score. They conclude: “Prioritising these radiographic alignment parameters will optimise patient-reported outcomes for patients undergoing cervical deformity surgery.
The investigators note that many patients are unable to undergo a major cervical deformity corrective surgery due to deformity severity, age, comorbidities, and overall frailty status. Therefore, “in order to optimise quality of life in patients with cervical deformity, there may be alignment targets to prioritise,” they suggest. The purpose of the present study, a retrospective review of a multicentre prospective cervical deformity database, was to prioritise the cervical parameter targets for alignments.
A total of 77 patients undergoing cervical deformity corrective surgery were included in the study. Outcome measures included cervical regional alignment parameters—namely the cervical sagittal vertical axis (cSVA), cervical lordosis (CL), T1 Slope minus CL(TS–CL), chin brow vertical angle (CBVA), McGregor’s slope (MGS), C2–T3 plumb line (C2–T3 SVA), C2–T3 angle, and C2 slope—as well as health-related quality of life measures such as the neck disability index (NDI).
A backwards linear regression model, including radiographic differences as predictors from baseline to one year for meeting the minimal clinically important difference (MCID) for NDI, demonstrated an R2 of 0.820 (p=0.032). By primary Ames driver, 67.5% of patients were categorised as C, and 32.5% as CT.
Ratios of change in predictors for MCID NDI patients for C driver patients was 260.8% MGS, 140.3% CL, 121.2% C2–T3 angle, 49.6% C2 slope, 41.1% cSVA, 20.5% TS–CL, 3.1% cSVA, 27.5% C2 slope, 24.9% TS–CL, and 13.7% C2–T3 SVA.
The authors comment: “The ratios were not significant between the two groups [p>0.05].” They note that decision tree analysis determined cut-offs for radiographic change, prioritising in the following order (based upon original regression values): a correction ≤42.5 degrees C2–T3 angle (OR: 5.667 [1.074–29.891], p=0.041), <35.4 degrees CL (OR: 4.636 [0.857–25.071], p=0.075), >-31.76 degrees C2 slope (OR: 3.2 [0.852–12.026], p=0.085), >-11.57mm cSVA (OR: 3.185 [1.137–8.917], p=0.027), >-2.16 degrees MGS (OR: 2.724 [0.971–7.636], p=0.057).
The investigators included cervical deformity patients with full baseline and one year radiographic parameters and NDI scores, as well as patients with cervical or cervicothoracic Primary Driver Ames type. Patients with baseline Ames classified as low cervical deformity for both parameters of cSVA and TS–CL were excluded.
The patients included in the study had an average age of 62.1 years and 64% of the cohort were female. Average charlson comorbidity index (CCI) was 0.94 and 7% were current smokers. By approach, the majority of cases were posterior (41.6%), followed by a combined approach (39%), and finally anterior (19.4%). The mean number of anterior levels fused was 3.5, while the figure for posterior was 8.3. Average operation time was 553.1 minutes and mean estimated blood loss (EBL) was 1128.1 cubic centimetres (ccs).
The authors comment: “The goal was to establish an order of targeting alignment parameters and [the patients’] projected minimal corrective degree to benefit operative decision making and inherently improve Health Related Quality of Life (HRQL) management”.
They conclude: “The analysis determined that prioritising regional cervical radiographic alignment parameters in a certain order to a specific degree optimised reaching the minimal clinically important difference in a patient’s self-reported neck disability. Addressing the intertwined cervical parameters in a specific order to a certain degree of correction can contribute to improved patient-reported neck disability.
Looking forward, Pierce and colleagues suggest that future studies should investigate the proposed prioritisation and thresholds on a prospective trial with a larger, homogenous population of patients undergoing cervical deformity corrective surgery.