Magnetic Resonance Imaging Characteristics and Age-Related Changes in the Psoas Muscle: Analysis of 164 Patients with Back Pain and Balanced Lumbar Sagittal Alignment

The relationship between the psoas major muscle morphology characteristics with disability index and pain in patients with chronic nonspecific low back pain

BACKGROUND

Chronic nonspecific low back pain (CNLBP) is a common disorder in people of active ages and significantly affects their quality of life. Different structures in the lumbar area can cause LBP. The lumbar muscle disorders, including the psoas major (PM) muscles, have an essential role in LBP. Magnetic Resonance Imaging (MRI) has been introduced as a safe and useful instrument for investigating the morphological properties of skeletal muscle. In general, PM morphology changes may be one reason for the pain and disability experienced in CNLBP patients. Thus, this study aimed to assess the relationship among the PM's Cross-sectional area (CSA), medial-lateral (ML), and anterior-posterior (AP) diameters, with disability index and pain score in patients with CNLBP.

METHOD

One hundred twenty patients with CNLBP (60 men and 60 women) participated in this cross-sectional study. Axial MRIs were obtained from L3/L4 and L4/L5 disc levels. Then, patients filled out Rolland Morris Disability Questionnaires, demographic data forms, and the Numeric Pain Rating Scale (NPRS). Image J software was used to analyze the images. Using Linear Regression and the Pearson test, the correlation between muscle CSA and diameters, as well as data obtained from questionnaires and NPRS, was analyzed.

RESULTS

Results from the statistical analysis showed no statistically significant relationship among morphological characteristics of the psoas major muscle in L3/L4 and L4/L5 disc levels with disability index and pain score (p < 0.05).

CONCLUSIONS

There is no significant relationship between the PM morphological characteristics and disability index and pain score. Therefore, muscle CSA and diameters are insufficient to determine the cause of CNLBP.

Association Between Paravertebral Muscle Mass and Improvement in Sagittal Imbalance After Decompression Surgery of Lumbar Spinal Stenosis

STUDY DESIGN

Retrospective observational study.

OBJECTIVE

This study examined associated factors for the improvement in spinal imbalance following decompression surgery without fusion.

SUMMARY OF BACKGROUND DATA

Several reports have suggested that decompression surgery without fusion may have a beneficial effect on sagittal balance in patients with lumbar spinal stenosis (LSS) through their postoperative course. However, few reports have examined the association between an improvement in sagittal imbalance and spinal sarcopenia.

METHODS

We retrospectively reviewed 92 patients with LSS and a preoperative sagittal vertical axis (SVA) more than or equal to 40 mm who underwent decompression surgery without fusion at a single institution between April 2017 and October 2018. Patients' background and radiograph parameters and the status of spinal sarcopenia, defined using the relative cross-sectional area (rCSA) of the paravertebral muscle (PVM) and psoas muscle at the L4 caudal endplate level, were assessed. We divided the patients into two groups: those with a postoperative SVA less than 40 mm (balanced group) and those with a postoperative SVA more than or equal to 40 mm (imbalanced group). We then compared the variables between the two groups.

RESULTS

A total of 29 (31.5%) patients obtained an improved sagittal imbalance after decompression surgery. The rCSA-PVM in the balanced group was significantly higher than that in the imbalanced group (P = 0.042). The preoperative pelvic incidence (PI)-lumbar lordosis (LL) mismatch (P = 0.048) and the proportion with compression vertebral fracture (P = 0.028) in the balanced group were significantly lower than those in the imbalanced group. A multivariate logistic regression analysis identified PI-LL less than or equal to 10° and rCSA-PVM more than or equal to 2.5 as significant associated factor for the improvement in spinal imbalance following decompression surgery.

CONCLUSION

A larger volume of paravertebral muscles and a lower PI-LL were associated with an improvement in sagittal balance in patients with LSS who underwent decompression surgery.Level of Evidence: 3.

Effects of Total Psoas Area Index on Surgical Outcomes of Single-Level Lateral Lumbar Interbody Fusion

OBJECTIVE

We evaluated the effect of the total psoas area index (TPAI = total psoas muscle area [cm²]/height squared [m²]) on neurological complications and clinical outcomes after lateral lumbar interbody fusion and identified the appropriate TPAI to achieve a substantial clinical benefit (SCB).

METHODS

A consecutive series of 123 patients who had undergone single-level lateral lumbar interbody fusion at a single center with ≥2 years of follow-up were retrospectively reviewed. The patient characteristics and operative data were evaluated. The neurological complications were classified as transient and persistent symptoms. The visual analog scale score for back pain was assessed preoperatively and at 1 and 2 years postoperatively.

RESULTS

The present study included 31 men and 92 women. The mean TPAI was 8.97 cm²/m² for the men and 5.04 cm²/m² for the women. The mean TPAI was not significantly different between the patients with and without perioperative neurological complications. Multiple logistic regression analysis showed that solid interbody fusion was the most significant factor for achieving an SCB regarding back pain in men (odds ratio [OR], 2.453; P = 0.019) and women (OR, 2.906; P = 0.042). The TPAI was one of the predictors for achieving an SCB in men (OR, 1.251; P = 0.038) and women (OR, 1.795; P = 0.023). The optimal cutoff point of the TPAI for an SCB was 8.18 cm²/m² for the men and 4.43 cm²/m² for the women.

CONCLUSIONS

The TPAI had little effect on the incidence of perioperative neurological complications. However, the TPAI was identified as one of the predictors for achieving an SCB regarding back pain.

The Effect of Patient Position on Psoas Morphology and in Lumbar Lordosis

INTRODUCTION

Among the interbody fusions, lateral lumbar interbody fusion allows access to the lumbar spine through the major psoas muscle, which offers several advantages to the spine surgeon. However, some of its drawbacks cause surgeons to avoid using it as a daily practice. Therefore, to address some of these challenges, we propose the prone transpsoas technique, differing mainly from the traditional technique on patient position-moving from lateral to prone decubitus, theoretically enhancing the lordosis and impacting the psoas morphology.

METHODS

Twenty-four consecutive patients were invited to have magnetic resonance imaging examinations in 3 different positions (prone, dorsal, lateral). Two observers measured the following parameters: vertebral body size, psoas diameter, psoas anterior border distance, plexus distance, total lumbar lordosis, distal lumbar lordosis, and proximal lumbar lordosis. Values of P < 0.05 were deemed significant.

RESULTS

The prone position yielded a significant increase in the lumbar lordosis, both in L1-S1 (57° vs. 46.5°) and proximal lordosis (40.4° vs. 36.9°) compared with the lateral position. Regarding the morphologic aspects, patients in the prone position presented lesser psoas muscles forward shift, but no difference was noted in the plexus position neither for L3-L4 nor L4-L5.

CONCLUSIONS

The prone position resulted in a significantly increased lumbar lordosis, both distal and proximal, which may enable the spine surgeon to achieve significant sagittal restoration just by positioning. The prone position also produced a posterior retraction of the psoas muscle. However, it did not significantly affect the position of the plexus concerning the vertebral body.