Freedman, Brett A.

Study Design: Retrospective. Objective: To examine the long-term perioperative changes in lumbar bone quality, paraspinal muscle size and fat content, and facet degeneration after hemipelvectomy (HP) and hip disarticulation (HD). Summary of Background Data: Emerging evidence shows that transfemoral (TFA) and transtibial (TTA) amputations may accelerate lumbar modic changes and precipitate axial back pain. TFA and TTA amputation studies demonstrate that the severity of postamputation lower back pain is associated with the amputation type (TFA > TTA) and the degree of alteration in lumbopelvic kinematics. Methods: All patients who underwent HP or HD for malignancy or infection at an academic center between 2003 and 2022 were retrospectively identified. Preoperative to postoperative changes in multifidus, erector spinae, quadratus lumborum, and psoas cross-sectional area (CSA), and Hounsfield units (HU) were calculated on CT for the amputated and contralateral side at the level of the L3–4 disc space. Paired univariate analysis was utilized to compare preoperative and postoperative outcomes. Results: A total of 16 patients (8 HP, 8 HD) met the inclusion/exclusion criteria. The preoperative to postoperative changes in HUs in the L1, L3, and L5 vertebral bodies were −27.0 ( P =0.004), −51.5 ( P =0.002), and −48.1 ( P =0.001), respectively. The decrease in L1 HU was greater for prosthesis nonusers (user: −16.50, nonuser: −51.32, P =0.021). L5–S1 segment facet degeneration increased postoperatively ( P =0.030, n=7 progressed). There were significant preoperative to postoperative changes in psoas CSA (preop: 1063.4, postop: 586.5, P =0.005) and psoas HU (preop: 50.95, postop: 33.55, P <0.001) on the amputated but not the contralateral side. Conclusion: Hind-quarter amputations were associated with decreased lumbar bone quality, progression of facet degeneration, and loss of amputated side psoas muscle tone. Daily prosthesis use was moderately protective for lumbar bone quality following amputation. HP but not HD was associated with postoperative loss of amputated side quadratus lumborum tone. Level of Evidence: Level III.

Background. Negative pressure wound therapy promotes wound healing through fluid removal, edema reduction, and mechanical contraction. A novel thermoplastic elastomer (TPE) dressing has been developed to improve exudate evacuation and reduce tissue ingrowth, but its effect on wound contraction compared with reticulated open cell foam (ROCF) remains unclear. Objective. To compare the degree of wound contraction with the TPE dressing, ROCF, or no filler at different wound depths and negative pressure settings in a porcine explant model. Materials and Methods. The effect of the materials or lack thereof on wound contraction was investigated at 2 wound depths (shallow, deep) and 3 negative pressure settings (−50 mm Hg, −80 mm Hg, and −125 mm Hg). Wound width was measured at 3 standardized locations before and during therapy. Univariable and multivariable linear regression analyses were performed to identify factors associated with contraction. Results. A total of 810 measurements were obtained. Both the TPE dressing and ROCF demonstrated statistically significantly greater contraction than no filler. In deep wounds, greater contraction was noted with the TPE dressing compared with ROCF. Higher negative pressure and increased wound depth were independently associated with greater contraction. Absolute differences in contraction between dressings were small (<3 mm across all conditions). Conclusion. The TPE dressing provides equivalent or greater wound contraction compared with ROCF, particularly in deep wounds, without impairing macrodeformation. Given the small magnitude of differences, the clinical relevance of this finding likely depends on additional factors, which should be evaluated in future in vivo studies.

Background/Objectives: To identify predictors of successful fusion and adjacent segment disease (ASD) following ALIF. Methods: Records of patients undergoing one- or two-level ALIF were queried for baseline and postoperative radiographic data, demographics, operative notes, and implant characteristics. All had ≥1 year of follow-up with CT, and multivariable Cox regression was used to identify predictors of radiographic fusion through the interbody, ASD, and ASD requiring reoperation. Results: In total, 177 patients (median 59 yr; 52.5% male) were treated at 245 unique levels, of which 193 fused (81.3% with posterior fixation and 59.6% with standalone), 43 had ASD (17.6%), and 14 had ASD requiring reoperation (5.7%). Fusion was predicted by anterior cage placement (HR 0.94/mm; 95% CI [0.90, 0.98]; p = 0.003) and BMP use (HR 1.92; [1.15, 3.18]; p = 0.012). Radiographic ASD was predicted by older age (HR 1.08 per year; [1.03, 1.14]; p < 0.001), undergoing a revision [vs. index] fusion operation (HR 3.51; [1.44; 8.59]; p = 0.006), lower preoperative disc height (HR 0.83/mm; [0.74, 0.94]; p = 0.003), and preoperative facet vacuum phenomenon (HR 2.46; [1.18, 5.15]; p = 0.017). None of the extracted variables predicted reoperation for ASD. Conclusions: BMP use along with anterior cage placement and posterior fixation may improve the odds of fusion through the interbody following one- or two-level ALIF. Adjacent segment pathology is more common in patients with greater preoperative degenerative pathology (vacuum sign; more collapsed disc) and advanced age. Pelvic fixation did not improve fusion odds, but the data highlight the benefits of supplementary posterior fixation vs. standalone ALIF.

ABSTRACT Negative pressure wound therapy relies on suction, commonly set to −125 mmHg, to evacuate wound fluid, but dysvascular and pressure injuries often respond unpredictably. Newton's third law indicates that negative pressure applies an equal and opposite contact pressure on the wound surface, and this study quantified this contact pressure across dressing types, wound configurations and suction levels. Using a porcine explant model, central and peripheral contact pressure measurements were obtained beneath black reticulated open cell foam, white foam and a novel thermoplastic elastomer dressing across plexiglass, intact skin, shallow and deep wounds under −50, −75 and −125 mmHg. Contact pressure increased proportionally with negative pressure, and multivariable modelling demonstrated that dressing type, wound type and suction level significantly influenced pressure, with negative pressure explaining most of the variance (0.77 and 0.68). Thermoplastic elastomer at −50 mmHg in deep wounds produced the lowest contact pressure, whereas black reticulated open cell foam and white foam at −125 mmHg generated elevated contact pressures of approximately +125 to +195 mmHg. These findings show that black reticulated open cell foam at conventional −125 mmHg can create hypoperfusion conditions, whereas thermoplastic elastomer consistently produces the lowest pressures and may enhance perfusion at lower suction levels, offering a physiologic explanation for improved clinical outcomes in dysvascular and pressure injuries treated with reduced negative pressure.

Study Design. Finite element (FE) analysis of retrospective clinical cohort. Objective. To determine whether preoperative CT-derived FE model outputs can improve subsidence prediction compared with conventional clinical measurements alone in patients undergoing transforaminal lumbar interbody fusion (TLIF). Summary of Background Data. Cage subsidence occurs in ∼20% of spinal fusion patients and can lead to complications requiring reoperation. While individual risk factors are known, no validated tool integrates patient anatomy, bone quality, and implant characteristics to predict subsidence. Finite element models have been hypothesized to predict subsidence but lack clinical validation. Materials and Methods. Patient-specific FE models were created from preoperative CT scans of 42 TLIF patients: N=22 severe subsidence (≥4 mm); N=20 nonsevere subsidence (<4 mm). Vertebral geometries were segmented, and bone material properties were assigned based on Hounsfield units (HU). Cage positions from postoperative scans were registered to preoperative anatomy. Endplate and trabecular stresses and strains from FE models were compared with clinical measures using receiver operating characteristic analysis. Results. Fifteen principal stresses and strains of the FE simulations showed significantly higher values in severely subsided patients compared with the nonsevere group. Average trabecular intermediate strain achieved the highest area under the curve score (AUC=0.809), outperforming all clinical metrics. Peak endplate minimum principal stress (AUC=0.775) was the second-best FE classifier. Traditional clinical measures showed lower discriminative ability: cage length (AUC=0.797), cage width (AUC=0.750), and cage height (AUC=0.698). Conclusion. Patient-specific FE model outputs significantly correlate with clinical subsidence outcomes and outperform several traditional metrics in classifying severe subsidence. Both endplate and trabecular stresses and strains are important predictors, with average values showing comparable or superior performance to peak values. Integration of FE models into the clinical workflow could provide a comprehensive preoperative subsidence prediction tool.

Study Design: Retrospective cohort. Objective: This study aims to assess the effects of CT-based subsidence on lumbar sagittal alignment and patient-reported outcome measures (PROMs) after transforaminal lumbar interbody fusion (TLIF), and to determine if subsidence and cage properties are independent predictors of postoperative changes in regional lordosis. Summary of Background Data: Subsidence is a well-known complication following interbody fusion and has previously been associated with recurrence of preoperative symptoms and higher reoperation rates. There is incomplete evidence to characterize the effects of subsidence on lumbar alignment and PROMs following TLIF. Methods: All adult patients who underwent 1- or 2-level TLIF at a multi-institutional academic center between 2017 and 2019 were retrospectively identified. Interbody subsidence at the superior and inferior endplate of each TLIF level was directly measured on both coronal and sagittal CT scans obtained between 6 months and 1 year postoperatively. Patients were grouped based on the maximum subsidence at each operative level: mild-moderate (<4 mm) or severe (≥4 mm). Preoperative, immediate (<3 mo), and intermediate (>6 mo) postoperative radiographic outcomes (local and global lumbar alignment) and PROMs (VAS Back, Oswestry Disability Index, PROMIS Physical Function and Mood) were collected. Univariate and multivariate analysis compared patient demographics, surgical factors, and changes in radiographic measures and PROMs across subsidence groups. Multiple linear regression analyzed independent effects of subsidence and cage characteristics on alignment. Results: Sixty-seven patients with 85 unique fusion levels were included (55 with mild-moderate subsidence, 30 with severe subsidence). Levels with severe subsidence demonstrated significantly less regional lordosis at final follow-up than nonseverely subsided levels (6.4 vs. 9.1 degrees, P =0.032). No PROM significantly differed between severe and nonsevere subsidence subgroups. Linear regression analysis revealed that severe subsidence was a strong independent predictor of regional lordosis ( P =0.029) at final follow-up. Conclusions: Severe subsidence negates perioperative improvements in regional lordosis following TLIF, while changes in regional alignment are maintained in the absence of severe subsidence. Level of Evidence: Level III.

OBJECTIVE Glucagon-like peptide-1 (GLP-1) agonists are established therapeutics for weight loss that are increasingly used for BMI optimization prior to spine surgery. However, emerging evidence has suggested that GLP-1 agonists might reduce bone mineral density (BMD), increasing the risk of postoperative biomechanical complications. CT-based Hounsfield units (HUs) have gained popularity as a method for measuring spinal BMD. The aim of this study was to evaluate the effects of GLP-1 agonist–induced weight loss on spinal BMD as measured by opportunistic CT-based HUs. METHODS Patients who were treated with any GLP-1 agonist (2017–2022) for > 3 months were retrospectively identified. Patient body weight (BW), BMI, and HU measurements in the L1 vertebral body were measured before and after GLP-1 therapy. Patients were grouped according to the percentage of weight loss during GLP-1 therapy. One-way ANOVA was used to compare the mean changes in spinal HUs across the groups. RESULTS Among the 102 included patients, the mean ± standard error of the mean BW reduction was 14.5 ± 2.5 kg over 15.9 ± 1.2 months of GLP-1 agonist therapy. Of these, 7 patients (6.9%) lost > 20% BW (mean decrease of 31.9 ± 7.0 HU, p = 0.011), 14 (13.7%) lost 15%–20% BW (mean decrease of 19.1 ± 8.3 HU, p = 0.038), 14 (13.7%) lost 10%–15% BW (mean decrease of 12.2 ± 5.1 HU, p = 0.036), 24 (23.5%) lost 5%–10% BW (mean decrease of 15.7 ± 3.3 HU, p < 0.0001), 26 (25.5%) lost < 5% BW (mean decrease of 14.7 ± 6.0 HU, p = 0.022), and 17 (16.7%) gained BW during GLP-1 therapy (mean decrease of 6.3 ± 5.0 HU, p = 0.229). One-way ANOVA testing did not show a significant difference in HU reduction across the weight loss groups (F = 1.12, p = 0.355). In addition, there was a significant correlation between the decrease in L1 HUs and the duration of GLP-1 therapy (r = −0.38, p = 0.0001) but not the amount of weight loss (r = −0.18, p = 0.070). In the multivariate analysis, the duration of GLP-1 therapy (p = 0.032) was a significant independent predictor of vertebral HU reduction, but the amount of weight loss (p = 0.664) was not. CONCLUSIONS Despite similar pretreatment BW and HU measurements, all weight loss groups had significant decreases in vertebral HUs following GLP-1 agonist therapy, with a significant correlation observed between HU reduction and treatment duration. This suggests that long-term GLP-1 agonist therapy can significantly diminish spinal BMD regardless of the amount of weight loss achieved.

OBJECTIVE Hundreds of thousands of Americans undergo decompression for lumbar spinal stenosis annually. The mild (minimally invasive lumbar decompression) procedure was developed as a potentially less invasive alternative to open decompression; however, much of the evidence has been gathered from industry-sponsored studies. The present study sought to compare real-world clinical outcomes between the mild procedure and open decompression for lumbar spinal stenosis. METHODS All patients who underwent the mild procedure at a single-institution, multisite, tertiary care center from 2005 to October 2024 were included. One-to-one propensity score matching was used to identify patients who underwent open decompression at the same institution, with age, sex, smoking, and comorbidities as covariates. Primary outcomes were change in pain on the numeric rating scale (NRS), surgical reoperation, and perioperative complications. For pain, the minimal clinically important difference (MCID) was defined as a 30% improvement in NRS score. RESULTS A total of 175 patients who underwent the mild procedure (mean age 76.3 ± 8.7 years; 44.6% female) were matched to 175 patients treated with open decompression (mean age 75.4 ± 8.7 years; 44.0% female). Among patients with at least 60 days of follow-up, those treated with open decompression were more likely to achieve the MCID for pain (43.1% vs 22.2%, p < 0.001). Patients treated with mild were more likely to require reoperation (46.2% vs 29.3%, p = 0.008). Those who underwent the mild procedure experienced lower rates of durotomies (0% vs 2.9%, p = 0.024) but had higher rates of neurological deficits (6.3% vs 0.6%, p = 0.003). CONCLUSIONS For patients with symptomatic lumbar stenosis, those who underwent open decompression were more likely to achieve pain improvement and less likely to require reoperation compared with those who underwent the mild procedure.

OBJECTIVE Lordotic devices have garnered increased attention for improving the segmental lordosis (SL) achieved with transforaminal lumbar interbody fusion (TLIF). However, it is unclear the degree to which surgeons maximize the "ideal" or listed lordosis of the interbody device. METHODS Patients undergoing one- or two-level TLIF for degenerative pathologies were identified and data were extracted on demographics, baseline lumbopelvic radiographic parameters, and TLIF details. The primary outcome of interest was the degree to which postoperative SL approximated the listed cage lordosis (Δtarget). Change in SL was a secondary outcome. Linear mixed-effects modeling was used to identify significant predictors of the percentage of ideal lordosis achieved. RESULTS A total of 239 treated levels were included (median patient age 66.6 years; 56.9% female); 151 levels were part of single-level TLIF constructs. The median segmental corrections were a 2.8° increase in SL and 2.8 mm in disc height. The median difference between listed cage lordosis and postoperative SL (Δtarget) was 0.5°. However, only 56.1% of levels achieved at least the listed cage lordosis. Linear mixed-effects modeling found that independent predictors of Δtarget were lower implant lordosis (estimate −1.01° [95% CI −1.15° to −0.87°] per degree, p < 0.001), greater preoperative SL (estimate 0.38° [95% CI 0.28°–0.48°] per degree, p < 0.001), greater preoperative PI (estimate 0.06° [95% CI 0.02°–0.11°] per degree, p = 0.007), and closer approximation of the anterior apophyseal ring of the caudal vertebrae (estimate −0.27° [95% CI −0.39° to −0.15°] per mm, p < 0.001). Similarly, independent predictors of postoperative SL were larger implant lordosis (estimate 0.16° [95% CI 0.05°–0.27°] per degree, p = 0.004), lower preoperative SL (estimate −0.70° [95% CI −0.79° to −0.62°] per degree, p < 0.001), greater preoperative PI (estimate 0.08° [95% CI 0.04°–0.12°] per degree, p < 0.001), and closer approximation of the anterior apophyseal ring of the cranial vertebrae (estimate −0.15° [95% CI −0.28° to −0.03°] per mm, p = 0.014). CONCLUSIONS The present results suggest that while lordosing, only 56% TLIF operations obtain the listed interbody lordosis ("target" lordosis). Anterior placement within the disc space is the only modifiable intraoperative technical factor for maximizing lordosis for a given interbody, highlighting the importance of effective disc space exenteration.

Study Design: Retrospective cohort analysis. Objective: To determine the effect of long-segment posterior cervical decompression and fusion (PCDF) on perioperative changes in vertebral Hounsfield Units (HUs) and the impact of these changes on radiographic outcomes and fusion status. Summary of Background Data: Low preoperative CT HUs have been associated with adverse outcomes after spinal fusion, including hardware complications and reoperation. No existing studies have investigated the preoperative to postoperative change in HUs after cervical spinal fusion. Stress shielding may decrease bone quality within the fusion construct. Whereas, altered junctional loading and increased segmental mobility may precipitate bony hypertrophy in the terminal and adjacent levels. Methods: All adult patients who underwent C2-T2 PCDF for myelopathy/ myeloradiculopathy at an academic center between 2013 and 2020 were retrospectively identified. Preoperative and postoperative HUs were assessed on axial CT images in the cranial, middle, and caudal C2, C6, T2, and T3 vertebral bodies, outside of the region of instrumentation and artifact by 2 independent reviewers. Paired t test compared preoperative to postoperative changes in HUs. Preoperative and long-term postoperative cervical alignment, fusion, and revision rates were assessed. Univariate and regression analysis compared patient factors and outcomes between groups with perioperative increase versus decrease in vertebral HUs. Results: One hundred patients were included. The average preoperative to postoperative change in HUs in the C2, C6, T2, and T3 vertebral bodies were −19.80 (P=0.008), −52.63 (P<0.001), 15.15 (P=0.014), and 9.41 (P=0.346), respectively. Perioperative increase in C2 HUs was predictive of increased postoperative distal junctional angle (β=3.41, P=0.048) and increased T1–T4 kyphosis (β=6.50, P=0.003). Perioperative increase in C6 HU predicted pseudoarthrosis (fusion odds ratio: 0.19, P=0.007). Conclusions: Significant perioperative decreases in C6 HUs within a long-fused construct may demonstrate stress shielding. The significant association between greater distal kyphosis and an increase in C2 HUs may be attributed to a stress riser effect. Level of Evidence: Level III.