Importance of the cervical paraspinal muscles in postoperative patient-reported outcomes and maintenance of sagittal alignment after anterior cervical discectomy and fusion

OBJECTIVE

The aim of this study was to investigate the influence of preoperatively assessed paraspinal muscle parameters on postoperative patient-reported outcomes and maintenance of cervical sagittal alignment after anterior cervical discectomy and fusion (ACDF).

METHODS

Patients with preoperative and postoperative standing cervical spine lateral radiographs and preoperative cervical MRI who underwent an ACDF between 2015 and 2018 were reviewed. Muscles from C3 to C7 were segmented into 4 functional groups: anterior, posteromedial, posterolateral, and sternocleidomastoid. The functional cross-sectional area and also the percent fat infiltration (FI) were calculated for all groups. Radiographic alignment parameters collected preoperatively and postoperatively included C2-7 lordosis and C2-7 sagittal vertical axis (SVA). Neck Disability Index (NDI) scores were recorded preoperatively and at 2 and 4-6 months postoperatively. To investigate the relationship between muscle parameters and postoperative changes in sagittal alignment, multivariable linear mixed models were used. Multivariable linear regression models were used to analyze the correlations between the changes in NDI scores and the muscles' FI.

RESULTS

A total of 168 patients with NDI and 157 patients with sagittal alignment measurements with a median follow-up of 364 days were reviewed. The mixed models showed that a greater functional cross-sectional area of the posterolateral muscle group at each subaxial level and less FI at C4-6 were significantly associated with less progression of C2-7 SVA over time. Moreover, there was a significant correlation between greater FI of the posteromedial muscle group measured at the C7 level and less NDI improvement at 4-6 months after ACDF.

CONCLUSIONS

The findings highlight the importance of preoperative assessment of the cervical paraspinal muscle morphology as a predictor for patient-reported outcomes and maintenance of C2-7 SVA after ACDF.

Association Between Cervical Sagittal Alignment and Subaxial Paraspinal Muscle Parameters

STUDY DESIGN

Retrospective review of prospectively collected data.

OBJECTIVE

The authors aim to investigate the association between muscle functional group characteristics and sagittal alignment parameters in patients undergoing anterior cervical discectomy and fusion.

SUMMARY OF BACKGROUND DATA

The relationship between the morphology of cervical paraspinal muscles and sagittal alignment is not well understood.

MATERIALS AND METHODS

Patients with preoperative cervical magnetic resonance imaging and cervical spine lateral radiographs in standing position who underwent anterior cervical discectomy and fusion between 2015 and 2018 were reviewed. Radiographic alignment parameters included C2 to 7 lordosis, C2 to 7 sagittal vertical axis (SVA), C2 slope, neck tilt, T1 slope, and thoracic inlet angle. Muscles from C3 to C7 were categorized into four functional groups: sternocleidomastoid group, anterior group, posteromedial group, and posterolateral group (PL). A custom-written Matlab software was used to assess the functional cross-sectional area (fCSA) and percent fat infiltration (FI) for all groups. Multivariable linear regression analyses were conducted and adjusted for age, sex, and body mass index.

RESULTS

A total of 172 patients were included. Regression analyses demonstrated that a greater C2 to 7 SVA was significantly associated with a greater FI of the anterior group from C3 to C5 and with a higher fCSA of the PL group at C3 to C4, and C6 to 7. A larger C2 slope was significantly correlated with a greater FI of the anterior group at C3 to C4 and a higher fCSA of the PL group from C3 to C5.

CONCLUSION

This work proposes new insights into the complex interaction between sagittal alignment and cervical paraspinal muscles by emphasizing the importance of these muscles in sagittal alignment. The authors hypothesize that with cervical degeneration, the stabilizing function of the anterior muscles decreases, which may result in an increase in the compensatory mechanism of the PL muscles. Consequently, there may be a corresponding increase in the C2 to C7 SVA and a larger C2 slope.

Association Between Severity of Cervical Central Spinal Stenosis and Paraspinal Muscle Parameters in Patients Undergoing Anterior Cervical Discectomy and Fusion

STUDY DESIGN

Retrospective study.

OBJECTIVE

The aim of this study was to evaluate the association between severity and level of cervical central stenosis (CCS) and the fat infiltration (FI) of the cervical multifidus/rotatores (MR) at each subaxial levels.

SUMMARY OF BACKGROUND DATA

The relationship between cervical musculature morphology and the severity of CCS is poorly understood.

METHODS

Patients with preoperative cervical magnetic resonance imaging (MRI) who underwent anterior cervical discectomy and fusion (ACDF) were reviewed. The cervical MR were segmented from C3 to C7 and the percent FI was measured using a custom-written Matlab software. The severity of the CCS at each subaxial level was assessed using a previously published classification. Grade 3, representing a loss of cerebrospinal fluid space and deformation of the spinal cord > 25%, was set as the reference and compared to the other gradings. Multivariable linear regression analyses were conducted and adjusted for age, sex, and body mass index.

RESULTS

156 consecutive patients were recruited. A spinal cord compression at a certain level was significantly associated with a greater FI of the MR below that level. After adjustment for the above-mentioned confounders, our results showed that spinal cord compression at C3/4 and C4/5 was significantly associated with greater FI of the MR from C3 to C6 and C5 to C7, respectively. A spinal cord compression at C5/6 or C6/7 was significantly associated with greater FI of the MR at C7.

CONCLUSION

Our results demonstrated significant correlations between the severity of CCS and a greater FI of the MR. Moreover, significant level-specific correlations were found. A significant increase in FI of the MR at the levels below the stenosis was observed in patients presenting with spinal cord compression. Given the segmental innervation of the MR, the increased FI might be attributed to neurogenic atrophy.

LEVEL OF EVIDENCE

3.

Assessing paraspinal muscle atrophy with electrical impedance myography: Limitations and insights

Paraspinal muscle atrophy is gaining attention in spine surgery due to its link to back pain, spinal degeneration and worse postoperative outcomes. Electrical impedance myography (EIM) is a noninvasive diagnostic tool for muscle quality assessment, primarily utilized for patients with neuromuscular diseases. However, EIM's accuracy for paraspinal muscle assessment remains understudied. In this study, we investigated the correlation between EIM readings and MRI-derived muscle parameters, as well as the influence of dermal and subcutaneous parameters on these readings. We retrospectively analyzed patients with lumbar spinal degeneration who underwent paraspinal EIM assessment between May 2023 to July 2023. Paraspinal muscle fatty infiltration (FI) and functional cross-sectional area (fCSA), as well as the subcutaneous thickness were assessed on MRI scans. Skin ultrasound imaging was assessed for dermal thickness and the echogenicities of the dermal and subcutaneous layers. All measurements were performed on the bilaterally. The correlation between EIM readings were compared with ultrasound and MRI parameters using Spearman's correlation analyses. A total of 20 patients (65.0% female) with a median age of 69.5 years (IQR, 61.3-73.8) were analyzed. The fCSA and FI did not significantly correlate with the EIM readings, regardless of frequency. All EIM readings across frequencies correlated with subcutaneous thickness, echogenicity, or dermal thickness. With the current methodology, paraspinal EIM is not a valid alternative to MRI assessment of muscle quality, as it is strongly influenced by the dermal and subcutaneous layers. Further studies are required for refining the methodology and confirming our results.

The relationship between paraspinal muscle atrophy and degenerative lumbar spondylolisthesis at the L4/5 level

BACKGROUND/CONTEXT

Degenerative lumbar spondylolisthesis (DLS) is a prevalent spinal condition that can result in significant disability. DLS is thought to result from a combination of disc and facet joint degeneration, as well as various biological, biomechanical, and behavioral factors. One hypothesis is the progressive degeneration of segmental stabilizers, notably the paraspinal muscles, contributes to a vicious cycle of increasing slippage.

PURPOSE

To examine the correlation between paraspinal muscle status on MRI and severity of slippage in patients with symptomatic DLS.

STUDY DESIGN/SETTING

Retrospective cross-sectional study at an academic tertiary care center.

PATIENT SAMPLE

Patients who underwent surgery for DLS at the L4/5 level between 2016-2018 were included. Those with multilevel DLS or insufficient imaging were excluded.

OUTCOME MEASURES

The percentage of relative slippage (RS) at the L4/5 level evaluated on standing lateral radiographs. Muscle morphology measurements including functional cross-sectional area (fCSA), body height normalized functional cross-sectional area (HI) of Psoas, erector spinae (ES) and multifidus muscle (MF) and fatty infiltration (FI) of ES and MF were measured on axial MR. Disc degeneration and facet joint arthritis were classified according to Pfirrmann and Weishaupt, respectively.

METHODS

Descriptive and comparative statistics, univariable and multivariable linear regression models were utilized to examine the associations between RS and muscle parameters, adjusting for confounders sex, age, BMI, segmental degeneration, and back pain severity and symptom duration.

RESULTS

The study analyzed 138 out of 183 patients screened for eligibility. The median age of all patients was 69.5 years (IQR 62 to 73), average BMI was 29.1 (SD±5.1) and average preoperative ODI was 46.4 (SD±16.3). Patients with Meyerding-Grade 2 (M2, N=25) exhibited higher Pfirrmann scores, lower MFfCSA and MFHI, and lower BMI, but significantly more fatty infiltration in the MF and ES muscles compared to those with Meyerding Grade 1 (M1). Univariable linear regression showed that each cm2 decrease in MFfCSA was associated with a 0.9%-point increase in RS (95% CI -1.4 to - 0.4, p<.001), and each cm2/m2 decrease in MFHI was associated with an increase in slippage by 2.2%-points (95% CI -3.7 to -0.7, p=.004). Each 1%-point rise in ESFI and MFFI corresponded to 0.17%- (95% CI 0.05-0.3, p=.01) and 0.20%-point (95% CI 0.1-0.3 p<.001) increases in relative slippage, respectively. Notably, after adjusting for confounders, each cm2 increase in PsoasfCSA and cm2/m2 in PsoasHI was associated with an increase in relative slippage by 0.3% (95% CI 0.1-0.6, p=.004) and 1.1%-points (95% CI 0.4-1.7, p=.001). While MFfCSA tended to be negatively associated with slippage, this did not reach statistical significance (p=.105). However, each 1%-point increase in MFFI and ESFI corresponded to increases of 0.15% points (95% CI 0.05-0.24, p=.002) and 0.14% points (95% CI 0.01-0.27, p=.03) in relative slippage, respectively.

CONCLUSION

This study found a significant association between paraspinal muscle status and severity of slippage in DLS. Whereas higher degeneration of the ES and MF correlate with a higher degree of slippage, the opposite was found for the psoas. These findings suggest that progressive muscular imbalance between posterior and anterior paraspinal muscles could contribute to the progression of slippage in DLS.

Asymmetrical atrophy of the paraspinal muscles in patients undergoing unilateral lumbar medial branch radiofrequency neurotomy

ABSTRACT

Lumbar medial branch radiofrequency neurotomy (RFN), a common treatment for chronic low back pain due to facet joint osteoarthritis (FJOA), may amplify paraspinal muscle atrophy due to denervation. This study aimed to investigate the asymmetry of paraspinal muscle morphology change in patients undergoing unilateral lumbar medial branch RFN. Data from patients who underwent RFN between March 2016 and October 2021 were retrospectively analyzed. Lumbar foramina stenosis (LFS), FJOA, and fatty infiltration (FI) functional cross-sectional area (fCSA) of the paraspinal muscles were assessed on preinterventional and minimum 2-year postinterventional MRI. Wilcoxon signed-rank tests compared measurements between sides. A total of 51 levels of 24 patients were included in the analysis, with 102 sides compared. Baseline MRI measurements did not differ significantly between the RFN side and the contralateral side. The RFN side had a higher increase in multifidus FI (+4.2% [0.3-7.8] vs +2.0% [-2.2 to 6.2], P = 0.005) and a higher decrease in multifidus fCSA (-60.9 mm2 [-116.0 to 10.8] vs -19.6 mm2 [-80.3 to 44.8], P = 0.003) compared with the contralateral side. The change in erector spinae FI and fCSA did not differ between sides. The RFN side had a higher increase in multifidus muscle atrophy compared with the contralateral side. The absence of significant preinterventional degenerative asymmetry and the specificity of the effect to the multifidus muscle suggest a link to RFN. These findings highlight the importance of considering the long-term effects of lumbar medial branch RFN on paraspinal muscle health.

Association between severity of the cervical foraminal stenosis and paraspinal muscle parameters in patients undergoing anterior cervical discectomy and fusion

OBJECTIVE

The cervical multifidus and rotatores muscles are innervated by the posterior rami of the spinal nerves of the corresponding level, and it has been hypothesized that cervical foraminal stenosis (CFS) affecting the spinal nerves results in changes in these muscles. The purpose of this study was to evaluate the relationship between the severity of CFS and fat infiltration (FI) of the multifidus and rotatores muscles.

METHODS

Patients who received preoperative cervical MRI, underwent anterior cervical decompression and fusion between 2015 and 2018, and met inclusion and exclusion criteria were included. Multifidus and rotatores muscles were segmented bilaterally from C3 to C7, and the percent FI was measured using custom-written MATLAB software. The severity of the CFS was assessed by the Kim classification. Multivariable linear mixed models were conducted and adjusted for age, sex, BMI, and repeated measures.

RESULTS

In total, 149 patients were included. Linear mixed modeling results showed that a more severe CFS at C3-4 was correlated with a greater FI of the multifidus and rotatores muscles at C4 (estimate 0.034, 95% CI 0.003-0.064; p = 0.031), a more severe CFS at C4-5 was correlated with a greater FI of the multifidus and rotatores muscles at C5 (estimate 0.037, 95% CI 0.015-0.057; p < 0.001), a more severe CFS at C5-6 was correlated with a greater FI of the multifidus and rotatores muscles at C6 (estimate 0.041, 95% CI 0.019-0.062; p < 0.001) and C7 (estimate 0.035, 95% CI 0.012-0.058; p = 0.003), and a more severe CFS at C6-7 was correlated with a greater FI of the multifidus and rotatores muscles at C7 (estimate 0.049, 95% CI 0.027-0.071; p < 0.001).

CONCLUSIONS

These results demonstrated level- and side-specific correlations between the FI of the multifidus and rotatores muscles and severity of CFS. Given the segmental innervation of the multifidus and rotatores muscles, the authors hypothesize that the observed increased FI could be reflective of changes due to muscle denervation from CFS.

Association between lumbar intervertebral vacuum phenomenon severity and posterior paraspinal muscle atrophy in patients undergoing spine surgery

PURPOSE

Intervertebral vacuum phenomenon (IVP) and paraspinal muscular atrophy are age-related changes in the lumbar spine. The relationship between both parameters has not been investigated. We aimed to analyze the correlation between IVP and paraspinal muscular atrophy in addition to describing the lumbar vacuum severity (LVS) scale, a new parameter to estimate lumbar degeneration.

METHODS

We analyzed patients undergoing spine surgery between 2014 and 2016. IVP severity was assessed utilizing CT scans. The combination of vacuum severity on each lumbar level was used to define the LVS scale, which was classified into mild, moderate and severe. MRIs were used to evaluate paraspinal muscular fatty infiltration of the multifidus and erector spinae. The association of fatty infiltration with the severity of IVP at each lumbar level was assessed with a univariable and multivariable ordinal regression model.

RESULTS

Two hundred and sixty-seven patients were included in our study (128 females and 139 males) with a mean age of 62.6 years (55.1-71.2). Multivariate analysis adjusted for age, BMI and sex showed positive correlations between LVS-scale severity and fatty infiltration in the multifidus and erector spinae, whereas no correlation was observed in the psoas muscle.

CONCLUSION

IVP severity is positively correlated with paraspinal muscular fatty infiltration. This correlation was stronger for the multifidus than the erector spinae. No correlations were observed in the psoas muscle. The lumbar vacuum severity scale was significantly correlated with advanced disc degeneration with vacuum phenomenon.

Decision-making Algorithm for the Surgical Treatment of Degenerative Lumbar Spondylolisthesis of L4/L5

STUDY DESIGN

A retrospective analysis of prospectively collected data.

OBJECTIVE

To report the decision-making process for decompression alone (DA) and decompression and fusion (DF) at a tertiary orthopedic center and compare the operative outcomes between both groups.

BACKGROUND

Controversy exists around the optimal operative treatment for DLS, either with DF or DA. Although previous studies tried to establish specific indications, clinical decision-making algorithms are needed.

MATERIALS AND METHODS

Patients undergoing spinal surgery for DLS at L4/5 were retrospectively analyzed. A survey of spine surgeons was performed to identify factors influencing surgical decision-making, and their association with the surgical procedure was tested in the clinical data set. We then developed a clinical score based on the statistical analysis and survey results. The predictive capability of the score was tested in the clinical data set with a receiver operating characteristic (ROC) analysis. To evaluate the clinical outcome, two years follow-up postoperative Oswestry Disability Index (ODI), postoperative low back pain (LBP) (Numeric Analog Scale), and patient satisfaction were compared between the DF and DA groups.

RESULTS

A total of 124 patients were included in the analysis; 66 received DF (53.2%) and 58 DA (46.8%). Both groups showed no significant differences in postoperative ODI, LBP, or satisfaction. The degree of spondylolisthesis, facet joint diastasis and effusion, sagittal disbalance, and severity of LBP were identified as the most important factors for deciding on DA or DF. The area under the curve of the decision-making score was 0.84. At a cutoff of three points indicating DF, the accuracy was 80.6%.

CONCLUSIONS

The two-year follow-up data showed that both groups showed similar improvement in ODI after both procedures, validating the respective decision. The developed score shows excellent predictive capabilities for the decision processes of different spine surgeons at a single tertiary center and highlights relevant clinical and radiographic parameters. Further studies are needed to assess the external applicability of these findings.

Relationship between lumbar spinal stenosis and axial muscle wasting

BACKGROUND CONTEXT

Although the effect of lumbar spinal stenosis (LSS) on the lower extremities is well documented, limited research exists on the effect of spinal stenosis on the posterior paraspinal musculature (PPM). Similar to neurogenic claudication, moderate to severe spinal canal compression can also interfere with the innervation of the PPM, which may result in atrophy and increased fatty infiltration (FI).

PURPOSE

This study aims to assess the association between LSS and atrophy of the PPM.

STUDY DESIGN

Retrospective cross-sectional study.

PATIENT SAMPLE

Patients undergoing MRI scans at a tertiary orthopedic center for low back pain or as part of a preoperative evaluation.

OUTCOME MEASURES

The functional cross-sectional area (fCSA) and percent fatty infiltration (FI) of the PPM at L4.

METHODS

Lumbar MRIs of patients at a tertiary orthopedic center indicated due to lower back pain (LBP) or as a presurgical workup were analyzed. Patients with previous spinal fusion surgery or scoliosis were excluded. LSS was assessed according to the Schizas classification at all lumbar levels. The cross-sectional area of the PPM was measured on a T2-weighted MRI sequence at the upper endplate of L4. The fCSA and fatty infiltration (FI) were calculated using custom software. Crude differences in FI and fCSA between patients with no stenosis and at least mild stenosis were tested with the Wilcoxon signed-rank test. To account for possible confounders, a multivariable linear regression model was used to adjust for age, sex, body mass index (BMI), and disc degeneration. A subgroup analysis according to MRI indication was performed.

RESULTS

A total of 522 (55.7% female) patients were included. The median age was 61 years (IQR: 51-71). The greatest degree of moderate and severe stenosis was found at L4/5, 15.7%, and 9.2%, respectively. Stenosis was the least severe at L5/S1 and was found to be 2% for moderate and 0.2% for severe stenosis. The Wilcoxon test showed significantly increased FI of the PPM with stenosis at any lumbar level (p<.001), although no significant decrease in fCSA was observed. The multivariable regression model showed a significant increase in FI with increased LSS at L1/2, L2/3, and L3/4 (p=.013, p<.01 and p=.003). The severity of LSS at L4/5 showed a positive association with the fCSA (p=.019). The subgroup analysis showed, the effect of LSS was more pronounced in nonsurgical patients than in patients undergoing surgery.

CONCLUSIONS

In this study, we demonstrated a significant and independent association between LSS and the composition of the PPM, which was dependent on the level of LSS relative to the PPM. In addition to neurogenic claudication, patients with LSS might be especially susceptible to axial muscle wasting, which could worsen LSS due to increased spinal instability, leading to a positive feedback loop.

Association of abdominal aortic calcification and lower back pain in patients with degenerative spondylolisthesis

ABSTRACT

Abdominal aortic calcification (AAC) is hypothesized to lead to ischemic pain of the lower back. This retrospective study aims to identify the relationship between AAC and lower back pain (LBP) in patients with degenerative lumbar spondylolisthesis. Lower back pain was assessed preoperatively and 2 years after surgery using the numeric analogue scale. Abdominal aortic calcification was assessed according to the Kauppila classification and was grouped into no, moderate, and severe. A multivariable regression, adjusted for age, sex, body mass index, hypertension, and smoking status, was used to assess the association between AAC and preoperative/postoperative LBP as well as change in LBP after surgery. A total of 262 patients were included in the final analysis. The multivariable logistic regression demonstrated an increased odds ratio (OR) for preoperative LBP ≥ 4 numeric analogue scale (OR = 9.49, 95% confidence interval [CI]: 2.71-40.59, P < 0.001) and postoperative LBP ≥ 4 (OR = 1.72, 95% CI: 0.92-3.21, P = 0.008) in patients with severe AAC compared with patients with no AAC. Both moderate and severe AAC were associated with reduced improvement in LBP after surgery (moderate AAC: OR = 0.44, 95% CI: 0.22-0.85, P = 0.016; severe AAC: OR = 0.41, 95% CI: 0.2-0.82, P = 0.012). This study demonstrates an independent association between AAC and LBP and reduced improvement after surgery. Evaluation of AAC could play a role in patient education and might be considered part of the differential diagnosis for LBP, although further prospective studies are needed.

Predicting postoperative outcomes in lumbar spinal fusion: development of a machine learning model

BACKGROUND CONTEXT

Degenerative lumbar spondylolisthesis (DLS) is a prevalent spinal disorder, often requiring surgical intervention. Accurately predicting surgical outcomes is crucial to guide clinical decision-making, but this is challenging due to the multifactorial nature of postoperative results. Traditional risk assessment tools have limitations, and with the advent of machine learning, there is potential to enhance the precision and comprehensiveness of preoperative evaluations.

PURPOSE

We aimed to develop a machine-learning algorithm to predict surgical outcomes in patients with degenerative lumbar spondylolisthesis (DLS) undergoing spinal fusion surgery, only using preoperative data.

STUDY DESIGN

Retrospective cross-sectional study.

PATIENT SAMPLE

Patients with DLS undergoing lumbar spinal fusion surgery.

OUTCOME MEASURES

This study aimed to predict the occurrence of lower back pain (LBP) ≥4 on the numeric analogue scale (NAS) 2 years after surgery. LBP was evaluated as the average pain patients experienced at rest in the week before questioning. NAS ranges from 0 to 10, 0 representing no pain and 10 representing the worst pain imaginable.

METHODS

We conducted a retrospective analysis of prospectively enrolled patients who underwent spinal fusion surgery for degenerative lumbar spondylolistheses at our institution in the United States between January 2016 and December 2018. The initial patient characteristics to be included in the training of the model were chosen by clinical expertise and through a literature review and included demographic characteristics, comorbidities, and radiologic features. The data was split into a training and validation datasets using a 60/40 split. Four different machine learning models were trained, including the modern XGBoost model, logistic regression, random-forest, and support vector machine (SVM). The models were evaluated according to the area under the curve (AUC) of the receiver operating characteristics (ROC) curve. An AUC of 0.7 to 0.8 was considered fair, 0.8 to 0.9 good, and ≥ 0.9 excellent. Additionally, a calibration plot and the Brier score were calculated for each model.

RESULTS

A total of 135 patients (66% female) were included. A total of 38 (28%) patients reported LBP ≥ 4 after 2 years, representing the positive class. The XGBoost model demonstrated the best performance in the validation set with an AUC of 0.81 (95% CI 0.67-0.95). The other machine learning models performed significantly worse: with an AUC of 0.52 (95% CI 0.37-0.68) for the SVM, 0.56 (95% CI 0.37-0.76) for the logistic regression and an AUC of 0.56 (95% CI 0.37-0.78) for the random forest. In the XGBoost model age, composition of the erector spinae, and severity of lumbar spinal stenosis as were identified as the most important features.

CONCLUSIONS

This study represents a novel approach to predicting surgical outcomes in spinal fusion patients. The XGBoost demonstrated a better performance compared with classical models and highlighted the potential contributions of age and paraspinal musculature atrophy as significant factors. These findings have important implications for enhancing patient care through the identification of high-risk individuals and modifiable risk factors. As the incorporation of machine learning algorithms into clinical decision-making continues to gain traction in research and clinical practice, our insights reinforce this trajectory by showcasing the potential of these techniques in forecasting surgical results.

Understanding the Interplay Between Paraspinal Muscle Atrophy and Lumbar Endplate Degeneration: A 3-Year Longitudinal Study

STUDY DESIGN

Retrospective analysis of longitudinal data.

OBJECTIVE

To assess the association between the paraspinal musculature (PM) and lumbar endplate degeneration.

BACKGROUND

The PM is essential for spinal stability, while the vertebral endplate is pivotal for nutrient transport and force distribution. The clinical importance of both has been highlighted in recent literature, though little is known about their interaction.

METHODS

We identified patients with lumbar MRI scans due to low back pain, with a 3-year interval between MRI scans. Endplate damage was assessed by the total endplate score (TEPS) at each lumbar level. The PM was evaluated for its functional cross-sectional area and fatty infiltration (FI) at the L4 level. We used a generalized mixed model to analyze the association between PM parameters and TEPS at timepoint one, adjusting for age, sex, BMI, diabetes, hypertension, and smoking status. The association with the progression of endplate damage was analyzed through an ordinal regression model, additionally adjusted for TEPS at baseline.

RESULTS

In all, 329 patients were included, with a median follow-up time of 3.4 years. Participants had a median age of 59 and a BMI of 25.8 kg/m 2 . In the univariate analysis, FI of the posterior PM was significantly associated with TEPS at baseline (β: 0.08, P <0.001) and progression of TEPS [Odds Ratio (OR): 1.03, P =0.020] after adjustment for confounders. The β and OR in this analysis are per percent of FI. In a binary analysis, patients with FI≥40% had an OR of 1.92 ( P =0.006) for the progression of TEPS.

CONCLUSIONS

This is the first longitudinal study assessing the relationship between PM and endplate degeneration, demonstrating the association between PM atrophy and the progression of endplate degeneration. This insight may aid in identifying patients at risk for degenerative lumbar conditions and guide research into preventive measures.

Risk Factors for Unexpected Conversion From Ambulatory to Inpatient Admission Among One-level or Two-level ACDF Patients

STUDY DESIGN/SETTING

A retrospective observational study.

OBJECTIVE

The aim of this study was to investigate the factors associated with the conversion of patient status from ambulatory anterior cervical discectomy and fusion (ACDF) to inpatient.

SUMMARY OF BACKGROUND DATA

Surgeries are increasingly performed in an ambulatory setting in an era of rising healthcare costs and pressure to improve patient satisfaction. ACDF is a common ambulatory cervical spine surgery, however, there are certain patients who are unexpectedly converted from an outpatient procedure to inpatient admission and little is known about the risk factors for conversion.

MATERIALS AND METHODS

Patients who underwent one-level or two-level ACDF in an ambulatory setting at a single specialized orthopedic hospital between February 2016 to December 2021 were included. Baseline demographics, surgical information, complications, and conversion reasons were compared between patients with ambulatory surgery or observational stay (stay <48 h) and inpatient (stay >48 h).

RESULTS

In total, 662 patients underwent one-level or two-level ACDF (median age, 52 yr; 59.5% were male), 494 (74.6%) patients were discharged within 48 hours and 168 (25.4%) patients converted to inpatient. Multivariable logistic regression analysis demonstrated that females, low body mass index <25, American Society of Anesthesiologists classification (ASA) ≥3, long operation, high estimated blood loss, upper-level surgery, two-level fusion, late operation start time, and high postoperative pain score were considered independent risk factors for conversion to inpatient. Pain management was the most common reason for the conversion (80.0%). Ten patients (1.5%) needed reintubation or remained intubated for airway management.

CONCLUSIONS

Several independent risk factors for prolonged hospital stay after ambulatory ACDF surgery were identified. Although some factors are unmodifiable, other factors, such as procedure duration, operation start time, and blood loss could be potential targets for intervention. Surgeons should be aware of the potential for life-threatening airway complications in ambulatory-scheduled ACDF.

Spine surgery under neuraxial vs. general anesthesia: the current state of comparative outcomes research

PURPOSE OF REVIEW

The impact of primary anesthetic technique on outcomes after spine surgery is controversial. Given frequent calls for well designed prospective comparative studies of neuraxial anesthesia vs. general anesthesia and recent reports of 'awake spine surgery' successes in the surgical literature, an updated evidence review is indicated.

RECENT FINDINGS

Systematic reviews, population-based and retrospective cohort studies suggest few significant differences in important complications or global recovery between anesthetic techniques. On the basis of overall low-to-moderate quality evidence, neuraxial anesthesia is associated with statistically significant benefits for several individual outcomes compared with general anesthesia, including improved intraoperative hemodynamic stability, less postoperative nausea and vomiting, lower early pain scores and shorter length of hospital stay. There are ongoing calls for well designed, adequately powered prospective studies.

SUMMARY

Our understanding of the risks, benefits and comparative outcomes between neuraxial anesthesia and general anesthesia for spine surgery is evolving. Although the results derived from this body of literature suggest specific benefits of neuraxial anesthesia, further research is required before widespread recommendations for either technique can be made. Until then, both neuraxial anesthesia and general anesthesia are reasonable choices for lumbar spine surgery of short duration, in appropriately selected patients.

Abdominal aortic calcification is independently associated with lumbar endplate degeneration

BACKGROUND

Abdominal aortic calcification (AAC) is associated with lower back pain, reduced bone mineral density of the spine. Vascular changes could also affect the already sparsely perfused intervertebral endplate and intervertebral disc.

METHODS

Lumbar MRIs and lateral radiographs of patients with lower back pain were retrospectively analyzed. AAC was assessed on lateral lumbar radiographs according to the Kauppila score, with a maximum score of 24. Patients were grouped into no (AAC = 0), moderate (AAC 1 to ≤ 4), and severe AAC (AAC ≥ 5). Endplate and disc degeneration were classified according to the total endplate score (TEPS) and Pfirrmann classification. The associations between AAC and degenerative changes was analyzed with a generalized mixed model and was adjusted for age, sex, body mass index as well as diabetes mellitus, and smoking status.

RESULTS

A total of 217 patients (47.9% female) were included in the analysis, totaling 1085 intervertebral levels. Of those, 45 (20.7%) patients had moderate, and 39 (18%) had severe AAC. The results of the generalized mixed model showed no significant association between AAC and disc degeneration (p > 0.05). In contrast, a significant positive association between AAC and the severity of TEPS (β: 0.51, 95% CI: 1.92-2.12, p = 0.004) was observed in the multivariable analysis.

CONCLUSIONS

This study demonstrates an independent association between AAC and endplate degeneration. These findings expand our knowledge about the degenerative cascade of the lumbar spine and suggest that AAC might be a modifiable risk factor for endplate changes.

Abdominal aortic calcification is independently associated with increased atrophy and fatty infiltration of the lumbar paraspinal muscles: a retrospective cross-sectional study

BACKGROUND

Aortic abdominal calcification (AAC) is associated with spine-related conditions, such as lower back pain and reduced bone mineral density. Similar to peripheral vascular disease, AAC possibly reduces blood flow to the lumbar posterior paraspinal muscles (PPM) which may lead to atrophy and increased fatty infiltration.

METHODS

Imaging of patients with lower back pain was analyzed. AAC was assessed on lateral lumbar radiographs according to the Kauppila classification. The cross-sectional area of the PPM was measured on a T2-weighted axial MRI sequence and the functional cross-sectional area (fCSA) and fatty infiltration (FI) were calculated with custom software. The association of AAC and FI as well as AAC and fCSA was assessed by multivariable linear regression, adjusted for age, sex, body mass index (BMI), diabetes, and smoking.

RESULTS

Two hundred and thirty patients (47.8% female) with a median age of 60 years (IQR 48-68) were analyzed. In patients, without AAC the median FI of the PPM was 33.3% (IQR 29.1-37.6%), compared to 44.6% (IQR 38.5-54.3%) in patients with AAC (p < 0.001). In the multivariable linear regression, both fCSA and FI of the PPM were significantly and independently associated with the degree of AAC (p = 0.037 and p = 0.015, respectively).

CONCLUSIONS

This is the first study to demonstrate a significant and independent association between AAC and PPM morphology. The results of this study improve our understanding of the interaction between AAC and spinal musculature, with AAC being a reason for atrophy of the PPM.

Changes of the posterior paraspinal and psoas muscle in patients with low back pain: a 3-year longitudinal study

PURPOSE

This study aimed to investigate the changes of the posterior paraspinal muscles (PPM) and psoas muscle in patients with low back pain (LBP) over time.

METHODS

Patients with LBP who had a repeat lumbar MRI with a minimum of 3-years apart at a tertiary referral center were analyzed. MRI-based quantitative assessments of the PPM and the psoas muscle were conducted for the baseline and follow-up MRI. The cross sectional area (CSA), the functional cross sectional area (fCSA) and the fat area (FAT) were calculated using a dedicated software program. The fatty infiltration (FI,%) of the regions of interest was calculated. Differences between the 1st and 2nd MRI were calculated for all assessed muscular parameters.

RESULTS

A total of 353 patients (54.4%female) with a median age of 60.1 years and BMI of 25.8 kg/m2 at baseline were analyzed. The mean time between the 1st and 2nd MRI was 3.6 years. The fCSAPPM declined in both sexes significantly from the 1st to the 2nd MRI, whereas the FATPPM increased. In line with this result, the FIPPM increased in both males (29.9%) and females (19.4%). Females had a higher FIPPM and FIPsoas than males in both MRIs. In females, no significant changes were found for the psoas muscle. The CSAPsoas and fCSAPsoas in males were significantly smaller in the 2nd MRI. With increasing age, a significant trend in a decrease in ∆FIPPM was observed for both sexes.

CONCLUSION

The study revealed significant quantitatively muscular changes in males and females, especially in the posterior paraspinal muscles in only three years' time.

Frailty stratification using the Modified 5-item frailty index: Significant variation within frailty patients in spine surgery

BACKGROUND

Frailty status has been associated with higher rates of complications after spine surgery. However, frailty patients constitute an heterogeneous group based on the combinations of comorbidities. The objective of this study is to compare the combinations of variables that compose the modified 5-factor frailty index score (mFI-5) based on the number of comorbidities in terms of complications, reoperation, readmission, and mortality after spine surgery.

METHODS

The American College of Surgeons - National Surgical Quality Improvement Program (ACS-NSQIP) Database from 2009-2019 was used to identify patients who underwent elective spine surgery. The mFI-5 item score was calculated and patients were classified according to number and combination of comorbidities. Multivariable analysis was used to assess the independent impact of each combination of comorbidities in the mFI-5 score on the risk of complications.

RESULTS

A total of 167, 630 patients were included with a mean age of 59.9 ± 13.6 years. The risk of complications was the lowest in patients with diabetes + hypertension (OR=1.2) and highest in those with the combination of CHF, diabetes, COPD, and dependent status (OR=6.6); there was a high variation in complication rate based on specific combinations.

CONCLUSION

There is high variability in terms of relative risk of complications based on the number and combination of different comorbidities, especially with CHF and dependent status. Therefore, frailty status encompasses a heterogeneous group and sub-stratification of frailty status is necessary to identify patients with significantly higher risk of complications.

Continuous erector spinae plane catheters leading to unwanted neuraxial spread after spinal fusion surgery: a report of two cases from a terminated prospective randomized clinical trial

BACKGROUND

Erector spinae plane blocks are used to improve outcomes after spine surgery, but pain frequently outlasts the duration of single injection blocks. We hypothesized continuous erector spinae plane (cESP) catheters would provide superior analgesia. We terminated a prospective double-blinded randomized clinical trial (RCT) comparing outcomes after multilevel spine surgery among patients randomized to saline versus ropivacaine cESP catheters. We present two cases of undesired epidural spread of ropivacaine and discuss etiology, management, and future research directions.

CASE PRESENTATION

Nine out of 44 patients (planned) enrolled in the RCT; 6/9 were randomized to receive ropivacaine infusions via bilateral cESP catheters. Two patients underwent uncomplicated posterior lumbar fusion and were recovering well with minimal pain and opioid requirements through postoperative day 1. Both had new-onset urinary retention and bilateral lower extremity numbness, weakness and paresthesias (24 and 30 hours after infusion-start time, respectively). One patient underwent MRI, which was remarkable for an epidural fluid collection compressing the thecal sac. Infusions were stopped, cESP catheters were removed and symptoms fully resolved over the next 3-5 hours.

CONCLUSIONS

Unwanted neuraxial spread of local anesthetic from cESP catheters may be a unique consideration after spine surgery, accounted for by unpredictable local anesthetic distribution within disrupted surgical planes. Future studies are indicated to determine optimal catheter regimens together with guidance for extended monitoring in parallel with further studies of efficacy in spine surgery cohorts.

TRIAL REGISTRATION NUMBER

NCT05494125.

Comparative effectiveness of anesthetic technique on outcomes after lumbar spine surgery: a retrospective propensity score-matched analysis of the National Surgical Quality Improvement Program, 2009-2019

BACKGROUND

The impact of anesthetic technique on spine surgery outcomes is controversial. Using a large national sample of patients, we compared outcomes after lumbar decompression under regional anesthesia (RA: spinal or epidural) or general anesthesia (GA).

METHODS

A retrospective population-based study of American College of Surgeons National Surgical Quality Improvement Program data (2009-2019). Patients were propensity score (PS) matched 3:1 (GA:RA) on demographic and surgical variables. The primary outcome was the association between anesthetic type and any complication (cardiac, pulmonary, renal, transfusion, stroke, infectious, deep vein thrombosis/pulmonary embolus). Secondary outcomes included the association between anesthetic type and individual complications, readmission and length of stay (LOS). Unadjusted comparisons (OR, 95% CI), logistic regression and adjusted generalized linear modeling (parameter estimate, PE, 95% CI) were performed before and after PS matching.

RESULTS

Of 1 51 010 cases, 149 996 (99.3%) were performed under GA, and 1014 (0.67%) under RA. After matching, 3042 patients with GA were compared with 1014 patients with RA. On unadjusted analyses, RA was associated with lower odds of complications (OR 0.43, 0.3 to 0.6, p<0.001), shorter LOS (RA: 1.1±3.8 days vs GA: 1.3±3.0 days; p<0.001) and fewer blood transfusions (RA: 3/1014, 0.3% vs GA: 40/3042, 1.3%; p=0.004). In adjusted analyses, RA was associated with fewer complications (PE -0.43, -0.81 to -0.06, p=0.02) and shorter LOS (PE -0.76, -0.90 to -0.63, p<0.001). There was no significant association between anesthetic type and readmission (PE -0.34, -0.74 to 0.05, p=0.09).

CONCLUSIONS

Compared with GA, RA was associated with fewer complications, less blood transfusion and shorter LOS after spine surgery. Although statistically significant, the magnitude of effects was small and requires further prospective study.

Abstract P2-09-24: Information preferences and short-term psychological responses to multiplex genetic testing among individuals at risk for hereditary breast cancer

Background: Multiplex genetic testing involves the simultaneous analysis of a panel of known cancer susceptibility genes. Although efficient and cost-effective, multiplex testing presents several challenges for patients and clinicians: these tests provide information about high and moderate penetrance genes of varying clinical utility, patients cannot choose which specific genes are tested, and multiple variants of uncertain significance can be identified at once. Multiplex testing is being increasingly integrated into clinical care, yet little is known about patients' preferences, uptake, or psychological responses to these tests.

Methods: To address this gap, we examined two data sources: Sample A) a cross-sectional clinical ascertainment of 189 patients evaluated for hereditary breast and other cancer syndromes (89% female), and Sample B) an ongoing prospective research study of multiplex testing among 194 breast cancer patients and survivors who previously received uninformative BRCA1/2 results (99% female, 84% white, ages 27-76, 60% had BRCA1/2 testing in the past year).

Results: In Sample A, 32% declined clinical multiplex testing in favor of more targeted testing. Female patients were more likely than males to decline (p=0.004). Self-reported reasons for declining included: concerns about uncertain clinical utility of moderate penetrance genes (51% of patients) and variants of uncertain significance (38%), feeling emotionally overwhelmed (23%), and not seeing the value of multiplex testing (20%). In Sample B, participants were allowed to select which information to receive from a multiplex test; 16% chose to learn less than all of the information available (e.g., not genes unrelated to breast/ovarian cancer, not genes without established clinical utility, not CDH1 or TP53). Information preferences were unrelated to demographic (age, race, time since cancer diagnosis and BRCA1/2 testing) and self-reported psychological factors (baseline genetic testing-related distress, uncertainty, and positive experiences; anxiety; depression). Participants who chose to learn all possible information reported greater concerns about their children's cancer risk than did those who chose to learn less information (p=0.01). Participants reported a small increase in both genetic testing-related distress and positive experiences from before testing to 1 week after receiving results (p&lt;0.001). In multivariable analyses controlling for baseline psychological functioning, only non-white race was consistently associated with significantly increased post-result anxiety, depression, and genetic testing-related distress and uncertainty. Participants who had BRCA1/2 testing one or more years ago also reported fewer positive experiences 1 week after receiving results.

Conclusions: Together, these findings demonstrate that a sizable minority of patients have important concerns regarding multiplex tests that may limit their uptake of this novel testing, and suggest that some patients may prefer to customize the specific risk information provided. Results also highlight characteristics of those at risk for poorer emotional outcomes following testing; these individuals may benefit from additional support in this context.

Citation Format: Robson ME, Gaissert P, Salo-Mullen EE, Amoroso K, Sheehan M, Berliner JL, Trottier M, Arnold AG, Sekhri N, Marcell V, Siegel B, Harlan Fleischut M, Hay JL, Walsh MF, Kauff ND, Stadler ZK, Offit K, Hamilton JG. Information preferences and short-term psychological responses to multiplex genetic testing among individuals at risk for hereditary breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-09-24.

Decision Making about Contralateral Prophylactic Mastectomy Among BRCA1/2 Noncarriers with Newly-diagnosed Breast Cancer: Examining Cognitive, Emotional, and Sociodemographic Influences

Pre-surgical BRCA1/2 genetic testing provides valuable risk information to guide a newly-diagnosed breast cancer patient's decision about whether to have a contralateral prophylactic mastectomy (CPM) to reduce her future risk of cancer in her unaffected breast. Although BRCA1/2 mutation noncarriers face a much lower objective ten-year risk of developing contralateral disease (approximately 3–10%) as compared to the risk of BRCA1/2 mutation carriers (27–37%), some noncarriers still choose to undergo a CPM. The psychosocial factors that motivate this decision are not well understood and warrant investigation. Thus, as part of a prospective study of pre-surgical BRCA1/2 testing, we examined the frequency and psychosocial correlates of the decision to undergo a CPM among newly-diagnosed breast cancer patients who were identified as BRCA1/2 mutation noncarriers. Self-report questionnaire data from 90 BRCA1/2 noncarriers (median age = 43 years, range = 29–59) were analyzed. A sizeable minority of the BRCA1/2 noncarriers (24.4%) chose to undergo a CPM after learning their mutation status (compared to 88% of the 8 BRCA1/2 carriers in the sample). Both bivariate and multivariable analyses indicated that perceiving that one's physician had recommended CPM (OR = 11.17, P = 0.007), perceiving greater risk for contralateral breast cancer (OR = 6.46, P = 0.02), and perceiving greater pros of CPM (OR = 1.37, P = 0.004) were all significantly associated with noncarriers' decision to undergo CPM. However, factors including age, Ashkenazi Jewish ethnicity, breast cancer-related distress, perceived cons of CPM, and decisional conflict regarding CPM were not related to the CPM decision (all ps &gt; 0.05). Results demonstrate that although noncarriers' decision making regarding CPM was unrelated to sociodemographic and emotional factors, their cognitive perceptions of contralateral disease risk, surgical benefits, and physician recommendations were particularly important. Future studies should examine the content of patient-physician communication regarding CPM and hereditary risk in greater detail, and explore how these conversations shape and interact with women's past experiences, emotions, and beliefs to influence their cancer prevention decisions.

Spinal muscular atrophy variant with congenital fractures

A single report of brothers born to first-cousin parents with a form of acute spinal muscular atrophy (SMA) and congenital fractures suggested that this combination represented a distinct form of autosomal recessive SMA. We describe a boy with hypotonia and congenital fractures whose sural nerve and muscle biopsies were consistent with a form of spinal muscular atrophy. Molecular studies identified no abnormality of the SMN(T) gene on chromosome 5. This case serves to validate the suggestion of a distinct and rare form of spinal muscular atrophy while not excluding possible X-linked inheritance.

Breast feeding and the development of juvenile rheumatoid arthritis

OBJECTIVE

To determine if children with juvenile rheumatoid arthritis (JRA) are less likely to have been breast fed than controls.

METHODS

Case-control study of data obtained from a survey of mothers 54 children with JRA and 79 playmates regarding breast feeding. Duration of breast feeding was tabulated and odds ratios (OR) with 95% confidence intervals (CI) were determined.

RESULTS

OR for breast feeding in children with JRA was 0.40 (0.20-0.81, 95% CI) compared to playmates. For pauciarticular JRA (N = 28) OR was 0.31 (0.10-0.93); in polyarticular JRA (N = 24) OR was 0.60 (0.21-1.70). Lower OR for increased durations of breast feeding were noted in children with JRA.

CONCLUSION

Children who have had JRA, especially pauciarticular JRA, are less likely to have been breast fed than controls, suggesting that breast feeding may have a protective effect on the development of JRA.

Frequency of human B cells that differentiate in response to anti-CD3-activated T cells

Activation of T cells by mAb to the CD3 molecular complex induces the differentiation of many more Ig-secreting cells (ISC) from resting human B cells in bulk cultures than do other modes of polyclonal B cell activation. In the current experiments, a limiting dilution assay was used to demonstrate that this increase in ISC generation reflects an increased frequency of responding B cells. Highly purified B cells were cultured at densities of between 1000 cells and 0.5 cell per microwell with fresh, mitomycin C-treated T cells (T mito) or T cell clones stimulated by immobilized mAb to CD3. After 5 days in culture, the number of wells containing ISC was determined, and the frequency of responding B cells was calculated. The proportion of B cells responding to anti-CD3-stimulated T cells was very large (10.7 +/- 2.8%) and greatly surpassed that induced by other polyclonal activators. B cells cultured with anti-CD3-stimulated T cell clones responded better than did those cultured with T mito. The addition of exogenous IL-2 or IL-6 to cultures supported by activated T mito enhanced the frequency of responding B cells, whereas IL-4 did not increase the generation of ISC and inhibited the augmentation of B cell responses induced by IL-2. Supplementation of cultures with mitomycin C-treated B cells as accessory cells had less of an effect. The addition of both accessory cells and IL-2 markedly increased B cell responsiveness, with precursor frequencies of 60 to 80% noted. In some experiments, cultures were carried out for 7 to 14 days and supernatants were analyzed for IgM, IgG, and IgA secretion. B cells activated by anti-CD3-stimulated T cells produced all three Ig isotypes. When the classes of Ig produced by single B cells were examined, it was observed that the stimulation of individual B cell precursors led to the production of multiple Ig isotypes, suggesting that isotype switching occurs in these cultures. These results demonstrate that under optimum culture conditions, T cells stimulated with immobilized anti-CD3 can activate the majority of human peripheral blood B cells to produce Ig and induce isotype switching by many.

Frequency of human B cells that differentiate in response to anti-CD3-activated T cells

Activation of T cells by mAb to the CD3 molecular complex induces the differentiation of many more Ig-secreting cells (ISC) from resting human B cells in bulk cultures than do other modes of polyclonal B cell activation. In the current experiments, a limiting dilution assay was used to demonstrate that this increase in ISC generation reflects an increased frequency of responding B cells. Highly purified B cells were cultured at densities of between 1000 cells and 0.5 cell per microwell with fresh, mitomycin C-treated T cells (T mito) or T cell clones stimulated by immobilized mAb to CD3. After 5 days in culture, the number of wells containing ISC was determined, and the frequency of responding B cells was calculated. The proportion of B cells responding to anti-CD3-stimulated T cells was very large (10.7 +/- 2.8%) and greatly surpassed that induced by other polyclonal activators. B cells cultured with anti-CD3-stimulated T cell clones responded better than did those cultured with T mito. The addition of exogenous IL-2 or IL-6 to cultures supported by activated T mito enhanced the frequency of responding B cells, whereas IL-4 did not increase the generation of ISC and inhibited the augmentation of B cell responses induced by IL-2. Supplementation of cultures with mitomycin C-treated B cells as accessory cells had less of an effect. The addition of both accessory cells and IL-2 markedly increased B cell responsiveness, with precursor frequencies of 60 to 80% noted. In some experiments, cultures were carried out for 7 to 14 days and supernatants were analyzed for IgM, IgG, and IgA secretion. B cells activated by anti-CD3-stimulated T cells produced all three Ig isotypes. When the classes of Ig produced by single B cells were examined, it was observed that the stimulation of individual B cell precursors led to the production of multiple Ig isotypes, suggesting that isotype switching occurs in these cultures. These results demonstrate that under optimum culture conditions, T cells stimulated with immobilized anti-CD3 can activate the majority of human peripheral blood B cells to produce Ig and induce isotype switching by many.