Goutallier grading of psoas major and lumbar extensor muscles as a predictor of cage subsidence and reoperation following transforaminal and posterior lumbar interbody fusion.

Background context: Cage subsidence after transforaminal or posterior lumbar interbody fusion (TLIF/PLIF) is a complication that can lead to recurrence of radiculopathy, loss of correction, and poor patient outcomes. A reliable method to predict subsidence has not yet been established. One recently proposed method involves measuring the degree of fatty degeneration and Goutallier grading of the psoas major (PM) and lumbar extensors (LE) muscle groups, as well as the cross-sectional area (CSA) ratio between these muscle groups and the corresponding vertebrae.

Purpose: The purpose of this study was to determine the relationship between (1) Goutallier grading of PM/LE and subsidence, (2) CSA ratio and subsidence, (3) identify the most predictive vertebral level, (4) examine the relationship between these measurements and rates of reoperation, and (5) examine the relationship between these measurements and patient-reported outcome measures (PROMs).

Study design/setting: This study is a retrospective chart review.

Patient sample: This study included one hundred and sixty-two patients who underwent elective single level TLIF/PLIF from 2007 to 2022.

Outcome measures: Outcome data collected included cage subsidence rates, reoperation rates, Oswestry disability index (ODI), and Patient-Reported Outcomes Measurement Information System (PROMIS) Global scores.

Methods: A retrospective analysis was performed identifying patients who underwent elective single level TLIF/PLIF from 2007 to 2022. Muscle parameters collected include the CSA ratio and Goutallier grade of the PM/LE muscle groups at L3/L4, L4/L5, and L5/S1 based on axial CT and MRI. Clinical and radiographic data collected include cage subsidence, osteoporosis diagnosis, reoperation rates, and PROMs.

Results: One hundred sixty-two patients met inclusion criteria. Average follow-up time was 1.6±1.1 years (range:0.13-7.3 years). Eighty-one (50%) patients experienced cage subsidence. Compared to the non-subsidence group, the subsidence group had higher mean Goutallier grade at L3/4 measured in the PM (1.10±1.05 vs. 0.60±0.84, p<.001) and LE (1.40±0.89 vs. 1.18±0.76, p=.047) muscle groups. A Goutallier grade ≥ 2 at L3/4 was associated with an increased risk of subsidence based on PM (OR=4.585, p<.001; AUC=0.635; r=0.258, p=.001) measurements. Increased risk of reoperation was observed in patients with higher Goutallier grades at L3/L4, L4/L5, and L5/S1 based on PM parameters (OR=3.997, p=.004; OR=3.516, p=.008; and OR=3.124, p=.016, respectively), and at L3/4 based on LE parameters (OR 3.462, p=.009). A significant correlation was found between worse ODI and a higher Goutallier grade at L3-L4 for PM (B=2.105, p=.043). Worse PROMIS Global scores were significantly correlated with higher Goutallier grades at L3-L4 for LE (B= -4.455, p=.002). CSA ratios for PM/LE were not strongly correlated with subsidence, PROMs, or reoperation.

Conclusion: Our results demonstrated that the degree of fat degeneration of PM and LE is correlated with increased risk of cage subsidence, worse PROMs, and reoperation rates following single level TLIF/PLIF. A Goutallier grade of ≥ 2 of both PM and LE parameters at L3/4 was found to be most predictive of subsidence risk. CSA ratios were not as strongly correlated nor predictive of subsidence. These findings suggest that Goutallier grading of PM and LE show promise as a tool to predict risk of cage subsidence and the need for potential reoperation.