Elsevier

Spine Deformity

Volume 4, Issue 4, July 2016, Pages 323-329
Spine Deformity

Case Series
Adult Spinal Deformity Surgeons Are Unable to Accurately Predict Postoperative Spinal Alignment Using Clinical Judgment Alone

https://doi.org/10.1016/j.jspd.2016.02.003Get rights and content

Abstract

Object

Adult spinal deformity (ASD) surgery seeks to reduce disability and improve quality of life through restoration of spinal alignment. In particular, correction of sagittal malalignment is correlated with patient outcome. Inadequate correction of sagittal deformity is not infrequent. The present study assessed surgeons' ability to accurately predict postoperative alignment.

Methods

Seventeen cases were presented with preoperative radiographic measurements, and a summary of the operation as performed by the treating physician. Surgeon training, practice characteristics, and use of surgical planning software was assessed. Participants predicted if the surgical plan would lead to adequate deformity correction and attempted to predict postoperative radiographic parameters including sagittal vertical axis (SVA), pelvic tilt (PT), pelvic incidence to lumbar lordosis mismatch (PI-LL), thoracic kyphosis (TK).

Results

Seventeen surgeons participated: 71% within 0 to 10 years of practice; 88% devote >25% of their practice to deformity surgery. Surgeons accurately judged adequacy of the surgical plan to achieve correction to specific thresholds of SVA 69% ± 8%, PT 68% ± 9%, and PI-LL 68% ± 11% of the time. However, surgeons correctly predicted the actual postoperative radiographic parameters only 42% ± 6% of the time. They were more successful at predicting PT (61% ± 10%) than SVA (45% ± 8%), PI-LL (26% ± 11%), or TK change (35% ± 21%; p < .05). Improved performance correlated with greater focus on deformity but not number of years in practice or number of three-column osteotomies performed per year.

Conclusion

Surgeons failed to correctly predict the adequacy of the proposed surgical plan in approximately one third of presented cases. They were better at determining whether a surgical plan would achieve adequate correction than predicting specific postoperative alignment parameters. Pelvic tilt and SVA were predicted with the greatest accuracy.

Introduction

The goals of adult spinal deformity (ASD) surgery include reducing disability and improving quality of life through restoration of spinopelvic alignment and decompression of neural elements. Over the past decade, several studies have highlighted the importance of sagittal spinopelvic alignment in achieving optimal postoperative outcomes [1], [2], [3]. Specifically, Schwab et al. demonstrated significant correlations between specific radiographic parameters and standardized measures of health-related quality of life (HRQOL) [4]. It has become apparent that sagittal spinopelvic malalignment is a key factor influencing patient disability, with significant correlations reported between HRQOL and sagittal vertical axis (SVA), pelvic tilt (PT), and pelvic incidence to lumbar lordosis mismatch (PI-LL) [5], [6]. Furthermore, it has been demonstrated that more complete sagittal plane deformity correction favors the greatest HRQOL benefit [7]. Determining the degree of correction required to restore sagittal alignment and, in turn, selection of suitable osteotomies, soft tissue releases, implants, and levels of instrumentation to achieve the desired correction, represents a significant challenge. Indeed, Moal et al. [8] demonstrated a relatively high rate of incomplete sagittal correction in ASD surgery of up to 50%.

The complexity of surgical planning, which must take into account radiographic and patient factors in addition to surgeon experience, has resulted in multi-faceted efforts to develop appropriate treatment strategies. Several authors have proposed mathematical models to facilitate accurate calculation of the angle required for spinal osteotomies to correct sagittal deformity [9], [10], [11], [12]. Although these formulas represent an important step in improving prediction of postoperative alignment, they may be too complex and thus impractical for routine clinical use [9], [10], [13]. Alternatively, surgical planning software has been developed which allows simulation of a proposed plan and prediction of postoperative alignment. Such software allows the surgeon to measure spinopelvic, sagittal, and coronal alignment parameters. An osteotomy (or set of osteotomies) can then be simulated. Based on the surgical plan simulation, the software provides predicted values for postoperative radiographic parameters that allows surgeons to assess the adequacy of their plan [4], [13].

The accuracy with which surgeons performing ASD are able to predict postoperative alignment in the absence of surgical planning software is currently unknown and represents the central question of the present study. In particular, we sought to determine the extent to which surgeons could judge whether a series of surgical plans would achieve adequate restoration of sagittal spinopelvic alignment without the use of surgical planning software or formula. We also assessed their ability to predict, within a range, the expected values of key postoperative radiographic alignment parameters based on preoperative images and proposed surgical plans. These data may prove useful in assessing the potential value of adjuncts to surgical planning as a means of optimizing the postoperative alignment and outcomes.

Section snippets

Methods

A survey that included 17 ASD cases was administered to surgeon members of the International Spine Study Group (ISSG). The survey was presented in PowerPoint (Microsoft, Redmond, WA) format and cases were prepared at a central location. Each case included a full-length (36-inch) lateral standing radiograph with standard preoperative radiographic measurements and a summary of the surgery performed by the surgeon who treated that patient. The surgical summary included the upper (UIV) and lower

Results

A total of 17 of 23 (74%) surgeon members of the ISSG completed the survey. Surgeon practice characteristics are shown in Table 1 along with their current use of and opinions regarding the utility of preoperative surgical planning software. The majority of participants were experienced surgeons with a significant focus on spinal deformity. Although most did not regularly use surgical planning software, 88% believed that its use is at least somewhat important.

On average, surgeons appropriately

Discussion

In the present study, surgeons were able to correctly judge the adequacy of a surgical plan to achieve global alignment in approximately two-thirds of survey cases. Thus, surgeons failed to correctly predict the adequacy of the surgical plan in approximately 1 in 3 cases. There was no difference in their success rate in predicting adequacy of correction for any specific radiographic parameter (SVA, PT, or PI-LL). The rate of correct responses was much lower (42% overall) when participants were

Conclusion

Accurate estimation of postoperative alignment after deformity correction represents a significant challenge. Surgeons failed to correctly predict the adequacy of the proposed surgical plan in approximately one in three of the presented cases. Surgeons were better at determining whether a surgical plan would achieve adequate correction than predicting specific postoperative alignment parameters. Pelvic tilt and SVA were predicted with the greatest accuracy. Future study is warranted to assess

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Author disclosures: TA (none); JKS (none); VL (grants from SRS, grants from NIH, grants from DePuy Spine Synthesis, personal fees from Medicrea, personal fees from MSD, personal fees from DePuy Spine Synthesis, personal fees from Nemaris INC, personal fees from Nemaris INC, outside the submitted work); FJS (grants from SRS, grants from AO, grants from DePuy Spine Synthesis, personal fees from Medicrea, personal fees from BiometZimmer, personal fees from NuVasive, personal fees from MSD, personal fees from K2M, personal fees from Nemaris INC, outside the submitted work); EK (grants and personal fees from AO Spine, personal fees from DePuy, personal fees from Stryker, personal fees from K2M, outside the submitted work); DMS (other from Medtronic, DePuy-Synthes, Globus, outside the submitted work); TSP (grants from DePuy-Synthes, during the conduct of the study; personal fees from Globus, personal fees from K2M, outside the submitted work); LZ (personal fees from Ulrich Medical USA, personal fees from Broadwater, personal fees from DePuy, personal fees from K2M, grants from AO Spine Fellowship Grant, grants from DePuy, outside the submitted work); RH (personal fees from DePuy Spine, other from NuVasive, other from Seeger, other from DJO, other from DePuy Spine, other from K2M, outside the submitted work); IO (grants and personal fees from DePuy-Synthes Spine, personal fees from Medtronic, personal fees from Alfatec Spine, outside the submitted work); TK (grants and personal fees from Medtronic, personal fees from NuVasive, personal fees from Spinewave, personal fees from Globus, outside the submitted work); MPK (none); SB (grants from DePuy Synthes, during the conduct of the study; grants and personal fees from K2 Medical, grants and personal fees from NuVasive, grants and personal fees from Innovasis, personal fees from Allosource, grants from Stryker, grants from Medtronic, personal fees from Pioneer, outside the submitted work); CIS (grants from DePuy Synthes, during the conduct of the study; personal fees from Biomet, personal fees from Medtronic, personal fees from NuVasive, personal fees from Stryker, grants from AO Spine, grants from DOD, grants from NACTN, grants from NIH, outside the submitted work); JSS (grants from DePuy, during the conduct of the study; personal fees and other from Biomet, personal fees from NuVasive, personal fees from K2M, personal fees from Cerapedics, personal fees from Globus, grants and personal fees from DePuy, outside the submitted work); CPA (personal fees from DePuy, personal fees from Medtronic, personal fees from Stryker, personal fees from Biomet Spine, personal fees from Stryker, personal fees from Doctors Research Group, personal fees from UCSF, outside the submitted work; In addition, Dr. Ames has a patent Fish & Richardson, P.C. issued).

The ISSG is funded through research grants from DePuy-Synthes and individual donations.

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