Porous Cage Macro-Topography Improves Early Fusion Rates in Anterior Cervical Discectomy and Fusion.

Objectives: Anterior cervical discectomy and fusion (ACDF) aims to improve pain, relieve neural compression, achieve rapid solid bony arthrodesis, and restore cervical alignment. Bony fusion occurs as early as 3 months and up to 24 months after ACDF. The correlations between bony fusion and clinical outcomes after ACDF remain unclear. Macro-topographic and porous features have been introduced to interbody cage technology, aiming to improve the strength of the bone-implant interface to promote early fusion. In this study, we aimed to compare clinical outcomes and CT-evaluated fusion rates in patients undergoing ACDF using one of two different interbody cages: traditional NanoMetalene™ (NM) cages and NM cages with machined porous features (NMRT). Methods: This was a prospective, observational, nonrandomised, cohort study of consecutive patients undergoing ACDF. The NM cage cohort was enrolled first, then the NMRT cohort second. The visual analogue scale, neck disability index, and 12-item Short Form Survey scores were evaluated preoperatively and at 6 weeks, 3 months, and 6 months. The minimum clinical follow-up period was 12 months. Plain radiographs were obtained on postoperative day 2 to assess instrumentation positioning, and computed tomography (CT) was performed at 3 and 6 months postoperatively to assess interbody fusion (Bridwell grade). Results: Eighty-nine (52% male) patients with a mean age of 62 ± 10.5 years were included in this study. Forty-one patients received NM cages, and 48 received NMRT cages. All clinical outcomes improved significantly from baseline to 6 months. By 3 months, the NMRT group had significantly higher CT fusion rates than the NM group (79% vs 56%, p=0.02). By 6 months, there were no significant differences in fusion rates between the NMRT and NM groups (83% vs 78%, p=0.69). The mean Bridwell grade at 6 months was 1.4 ± 0.7 in the NMRT group and 1.8 ± 1.0 in the NM group (p=0.08). Conclusions: With both NM and NMRT cages, serial improvements in postoperative clinical outcomes were associated with fusion progression on CT. NMRT cages demonstrated significantly better fusion at 3 months and a trend toward higher quality of fusion at 6 months compared with NM cages, suggesting earlier cage integration with NMRT. An early 3-month postoperative CT is adequate for fusion assessment in almost 80% of patients undergoing ACDF with an NMRT cage, permitting an earlier return to activity.

Who bleeds during elective anterior lumbar surgery?

Background: Blood loss (BL) during elective anterior lumbar access for interbody fusion or disc replacement is a potentially major complication. This study sought to identify factors other than major vascular injury which contribute to BL and therefore this risk. Factors suggested to effect blood loss include age, increasing body mass index (BMI), sex, prothesis, intraoperative heparinization and continuation of low-dose aspirin (LD-ASA). Methods: A Cell Saver was used in all cases with BL measured and recorded by an independent autotransfusionist. Heparin was administered intravenously when one or both of 2ndtoe saturation metre signal/s lost pulsatility indicating lower limb arterial flow was interrupted. Results: The mean age of the 364 patients was 47 ± 13.2 yrs. [95% CI: 45 - 48]; and 191 (52%) were male. Age, BMI and heparinization showed a positive correlation with increased BL. There was no significant association with continuation of low-dose ASA with increased BL. Most patients underwent an ALIF - 265 (72%), 52 (14%) had a TDR, and 47 (13%) had a hybrid operation. There was a significant increase in mean BL between single- and two-level procedures in the non-heparinised group (48 vs 83 mls, p = 0.003). Intraoperative heparinization was administered in 102 patients (28%). The total mean BL for the heparin group (104 ml) which was significantly higher than for the non-heparin group (53 ml) (p = 0.001). Heparinisation did not significantly increase the mean BL in single or double level ALIF patients but did significantly increase the BL in single level TDR (57 vs 151 mls, p = 0.039). Conclusions: Younger, leaner, non-heparinized, single level ALIF patients represented the lowest bleeding risk in anterior lumbar surgery. Conversely, older, increasing BMI, two operative levels, TDR prosthesis and heparinization represent the highest bleeding risk. Continuation of LD-ASA was not associated with an increase in BL.

Surface landmarks for anterior lumbar access: is fluoroscopy necessary?

BACKGROUND CONTEXT: Anterior lumbar fusion surgery is increasing by an estimated 24% annually in the United States. There is a paucity of precise anatomic guidelines to help surgeons determine the appropriate anterior access incision site. PURPOSE: The purpose of this study is to compare the available anterior surface landmarks for the L4/L5 and L5/S1 disk levels to the disk levels determined by fluoroscopy, with the goal of creating a guide for surgical incision sites in anterior lumbar access surgery. STUDY DESIGN: A prospective, observational cohort study of consecutive patients undergoing anterior lumbar spinal exposure for anterior lumbar interbody fusion (ALIF), total disk replacement (TDR), or a combination of the two procedures at levels L4/L5 and/or L5/S1. PATIENT SAMPLE: All patients (n=183) undergoing primary ALIF and/or TDR surgery from June 2018 to April 2021 at the study sites were assessed for inclusion, and 18 patients were excluded. The remaining 165 patients were included in the study, and a total of 208 surgical levels were exposed. OUTCOME MEASURES: Mean, standard deviation, and 95% confidence interval (CI) were calculated. At each level, the distance from the symphysis pubis to the target disk level (SD distance) and the distance from the symphysis pubis to the umbilicus (SU distance) were measured, and the SD/SU ratio was calculated. Paired 2-tailed t tests were used to assess significant differences (p<.05). An R2 (coefficient of determination) test was used to assess variability of the SD distance, SU distance, and SD/SU ratio at each level. METHODS: All physiologic and anatomic measures were collected prospectively by the investigators, including intraoperative measurements of SD and SU. Demographic and previous health history data were collected at the time of study enrollment. RESULTS: The mean age of the 165 study participants was 48±14 years (range 18-80 years), and 97 (61%) were male. A total of 208 disk levels were exposed: 140 at L5/S1 and 68 at L4/L5. For the L5/S1, the SD ranged from 0 to 12.5 cm, with a mean of 5.2±1.9 cm (95% CI 4.88-5.52). For the L4/L5 level, the SD ranged from 6 to 15.5 cm, with a mean of 10.7±2.3 cm (95% CI 10.2-11.2). SD/SU ratios at both levels were lower in overweight (body mass index [BMI] 25-29.9) and obese (BMI 30-34.9) groups than in normal body mass index groups. There was no significant difference in SD/SU ratios between females and males at either L5/S1 (p=.39) or L4/L5 (p=.66). CONCLUSION: Clinically important variability in SD distances (≥9.5 cm) was observed for both the L5/S1 and L4/L5 disk levels. SD/SU ratios provided more consistent estimates of disk location than SD distance alone, but they still displayed substantial variability. Thus, intraoperative fluoroscopy remains mandatory to accurately plan the surgical incision for anterior lumbar access surgery.