Radiological Assessment of Postoperative Paraspinal Muscle Changes After Lumbar Interbody Fusion With or Without Minimally Invasive Techniques.

STUDY DESIGN: Retrospective cohort study. BACKGROUND: Percutaneous pedicle screws (PPS) have the advantage of being able to better preserve the paraspinal muscles when compared with a traditional open approach. However, the nature of changes in postoperative paraspinal muscle after damage by lumbar fusion surgery has remained largely unknown. It is clinically important to clarify and compare changes in paraspinal muscles after the various surgeries. OBJECTIVE: (1) To determine postoperative changes of muscle density and cross-sectional area using computed tomography (CT), and (2) to compare paraspinal muscle changes after posterior lumbar interbody fusion (PLIF) with traditional open approaches and minimally invasive lateral lumbar interbody fusions (LLIF) with PPS. METHODS: We included data from 39 consecutive female patients who underwent open PLIF and 23 consecutive patients who underwent single-staged treatment with LLIF followed by posterior PPS fixation at a single level (L4-5). All patients underwent preoperative, 6 months postoperative, and 1-year postoperative CT imaging. Measurements of the cross-sectional area (CSA) and muscle densities of paraspinal muscles were obtained using regions of interest defined by manual tracing. RESULTS: We did not find any decrease of CSA in any paraspinal muscles. We did find a decrease of muscle density in the multifidus at 1 year after surgery in patients in the PILF group, but not in those in LLIF/PPS group. CONCLUSIONS: One year after surgery, a significant postoperative decrease of muscle density of the multifidi was observed only in patients who underwent open PLIF, but not in those who underwent LLIF/PPS.

Upper Extremity Skeletal Muscle Mass Asymmetry Exacerbated by Shoulder Imbalance in Lenke1A Adolescent Idiopathic Scoliosis.

Limb muscle strength asymmetry affects many physical abilities. The present study (1) quantified limb muscle asymmetry in patients with adolescent idiopathic scoliosis (AIS); (2) compared AIS patients with major thoracolumbar/lumbar (TL/L) or major thoracic (MT) curves; (3) examined correlations between limb muscle asymmetry and radiographic parameters. Patients with AIS with major TL/L curves (Lenke type 5C) and MT curves (Lenke Type 1A) who underwent posterior spinal fusion at our university hospitals were included. Patients with left hand dominance were excluded. Body composition was measured using whole-body dual-energy X-ray absorptiometry and asymmetry of left and right side skeletal muscles were evaluated. Upper extremity skeletal muscles on the dominant side were significantly larger than those on the nondominant side in both Lenke1A and 5C groups. The asymmetry of upper extremity skeletal muscles was significantly greater in the Lenke1A group than in the Lenke5C group. Additionally, the size of the asymmetry did not correlate with the magnitude of the major curve and rotational deformation but did correlate with a right shoulder imbalance in the Lenke1A group. These results suggest that in AIS with a constructive thoracic curve, right shoulder imbalance is an independent risk factor for upper extremity skeletal muscle asymmetry.

Potential Role of Paraspinal Musculature in the Maintenance of Spinopelvic Alignment in Patients With Adult Spinal Deformities.

STUDY DESIGN: A retrospective observational study. OBJECTIVES: To (1) compare skeletal muscle mass index (SMI) and the composition of paraspinal muscles between patients with lumbar spinal stenosis (LSS) and adult spinal deformity (ASD) who underwent spinal surgery, (2) determine whether paraspinal muscles influence low back pain in ASD, and (3) ascertain which radiographic spinal parameters of ASD are predominantly influenced by paraspinal muscles. SUMMARY OF BACKGROUND DATA: Relative muscle cross-sectional area (rmCSA; total CSA minus intramuscular fat CSA) determined using magnetic resonance imaging (MRI) is useful when evaluating not only muscle volume but also muscle quality. Currently, no study has examined paraspinal muscles using rmCSAs to determine which radiographic spinopelvic parameters identified in patients with severe spinal deformities make them candidates for thoracolumbar corrective surgery. MATERIALS AND METHODS: Paraspinal muscle rmCSAs were calculated using preoperative T2-weighted MRIs at the L3/4 axial level. Whole-body bone mineral density and lean, soft tissue mass were measured using dual-energy x-ray absorptiometry. SMI was calculated as appendicular (upper and lower limbs) lean, soft tissue mass (kg/m). Correlations between low back pain according to the Roland-Morris Disability Questionnaire, Oswestry Disability Index, spinopelvic parameters, and rmCSA were evaluated for 110 consecutive patients with ASD and 50 consecutive patients with LSS who underwent spinal surgery. RESULTS: There was no significant difference in the total SMI and morbidity rate of sarcopenia between patients with ASD and LSS. A significant negative correlation between Oswestry Disability Index and the rmCSA of the multifidus muscles and the rmCSA of the erector muscles were observed. There was a significant positive correlation between pelvic tilt/sacral slope and multifidus/erector muscles. CONCLUSIONS: Paraspinal muscles evaluated with MRI were more significantly associated with the pathology of ASD compared with appendicular skeletal muscle evaluations with dual-energy x-ray absorptiometry. The present study indicates that multifidus and erector muscles significantly influenced the maintenance of the pelvic alignment. LEVEL OF EVIDENCE: Level III.

Comparative study of the paraspinal muscles after OVF between the insufficient union and sufficient union using MRI.

BACKGROUND: Identification of poor prognostic factors for OVF is important but has not yet been clearly established. Despite paraspinal muscles could play an important role in the etiology of OVF, what influence time-dependent changes in paraspinal muscles have after OVF, and the impact on conservative treatments for patients who have an OVF remain largely unknown. The purposes of this study were to (1) evaluate time-dependent changes of the paraspinal musculature using MRI after injury in patients with osteoporotic vertebral fractures (OVFs), and (2) compare paraspinal muscles between conservatively treated patients with OVF who have successful union and those failed to conservative treatment. METHODS: A total of 115 consecutive patients who had sustained a recent OVF injury in the thoracolumbar region were assessed for eligibility using medical records and all required data were available from 90 patients who had been followed up for at least 6 months. Patients who needed to undergo surgery and patients who were diagnosed as having insufficient union after 6 months of follow-up were assigned to a group with insufficient union. Lumbar trunk parameters, relative cross-sectional area (rCSA) and proportion of fat infiltration (FI%) were calculated from MRI. To evaluate the time-dependent changes in the paraspinal muscle in patients after OVF injury, correlations between the timing of MRI and rCSA, FI% were determined. To clarify the impact of paraspinal muscles on the outcome of conservative treatments of patients with OVF, we compared rCSA between the groups. RESULTS: Sixty-five patients were assigned to a group with insufficient union and 25 patients were assigned to a group with successful union. FI% of the multifidus and erector spinae in the group with insufficient union were significantly greater than in the group with union. The timing of MRI in relation to initial injury was significantly correlated with FI% of the multifidus and erector spinae. rCSA of the erector spinae was significantly larger in the group with successful union than in the group with insufficient union. CONCLUSIONS: These findings indicated a time-dependent increase of fatty degeneration of the multifidus and erector muscles, but no change in the rCSA and larger rCSAs of spinal erectors may play a role in successful union in patients with OVF.