Fusion of two or more vertebrae stabilizes the spine, and it is a popular orthopedic and neurosurgical operation. Spinal fusion eliminates abnormal vertebral motion to reduce discomfort, correct deformity, and improve function [1]. Over the past few decades, surgical techniques, equipment, imaging modalities, and perioperative care have expanded spinal fusion surgery indications and success rates [2]. Even with these advances, spinal fusion is still difficult and unpredictable, thus patient-specific and procedure-related variables must be monitored.

Degenerative disc disease, spondylolisthesis, instability, trauma, scoliosis, spinal stenosis, and birth abnormalities or injuries are the most common reasons for spinal fusion surgery [3]. As discs degrade, degenerative disc disease reduces movement and causes back discomfort, which is a typical cause [4]. In spondylolisthesis, which involves the anterior displacement of one vertebral body over another, fusion is usually needed to restore stability and prevent neurological damage [5]. Scoliosis and other spinal deformities may require fusion for correction and long-term alignment, while traumatic spinal injuries may require fusion for mechanical stabilization and neurological rehabilitation [6].

Based on the patient's condition, anatomy, and surgeon preference, spinal fusion techniques include posterolateral fusion, anterior lumbar interbody fusion (ALIF), transforaminal lumbar interbody fusion (TLIF), and posterior lumbar interbody fusion (PLIF) [7]. Hardware failure, surrounding segment disease, and pseudoarthrosis are new risks of bone grafts, biologics, cages, and pedicle screw instrumentation, which have increased fusion rates [8]. Patient variables, including age, obesity, smoking status, osteoporosis, and concurrent conditions, affect surgical healing and long-term success [9].

Over the past 20 years, spinal fusion surgery has become worldwide [10]. In industrialized nations, mainly Europe and North America, spinal fusion rates have increased because of an aging population, more degenerative spinal disease diagnoses, and more surgical justifications [11]. Spine fusion surgery is increasingly performed in developing regions including Africa, the Middle East, and Asia because to increased knowledge of spine illnesses and better access to specialized medical treatment [12]. Institution-specific outcome evaluations are needed due to geographical variability in surgical procedures, patient selection criteria, and postoperative outcomes.

Despite its high risk of complications and relatively good pain relief, spinal fusion surgery has mixed results. Most people improve, but a small percentage may endure extended discomfort, limited movement, infection, neurological damage, implant failure, or the need for further treatment. Patient-related factors like age and comorbidities and surgical factors like fusion type, levels fused, and instrumentation are discussed in deciding results. Single-center analyses are limited, but large multicenter studies often lack clinical data. This retrospective study examines outcomes, complications, and success predictors at single-center (2024–2025) to improve clinical decision-making and patient care.

Objectives

• To evaluate spinal fusion surgery outcomes under the postoperative clinical setting.

• To find the factors influencing success is clinical, surgical and demographic.
• To calculate revision surgery needs and complication rates.

Study design and setting: A cross-sectional, observational study was conducted among apparently healthy young adults to evaluate the association between habitual sleep duration HRV. The study was carried out in a controlled academic research setting over a six-month period.

Study population: Participants were recruited from undergraduate and postgraduate programs through notice-board announcements and direct invitations. Individuals aged 18–25 years of either sex were considered eligible.

Inclusion criteria

• Age between 18 and 25 years
• Self-reported regular sleep–wake schedule for at least the preceding three months
• No history of diagnosed cardiovascular, respiratory, neurological, endocrine, or sleep disorders
• Not on medications known to affect autonomic function (e.g., beta-blockers, antidepressants)

Exclusion criteria

• Current smokers or tobacco users
• Regular alcohol intake (>7 standard drinks/week)
• Shift workers or individuals with frequent trans-meridian travel in the past three months
• Acute illness within two weeks prior to assessment

Sample size estimation:Sample size was calculated assuming a moderate effect size (f = 0.25) for differences in HRV parameters across sleep duration categories, with a power of 80% and a two-sided alpha of 0.05. Based on these assumptions, a minimum of 108 participants was required. To account for potential dropouts and incomplete recordings, 120 participants were enrolled.

Assessment of sleep duration: Habitual sleep duration was assessed using a structured, interviewer-administered sleep questionnaire adapted from validated sleep assessment tools. Participants reported average nightly sleep duration over the previous four weeks. Based on reported sleep duration, participants were categorized into three groups:

• Short sleep: <6 hours per night
• Normal sleep: 6–8 hours per night
• Long sleep: >8 hours per night

Participants were instructed to maintain their usual sleep habits prior to physiological assessment.

Heart rate variability recording: HRV was recorded using a validated digital electrocardiography (ECG) system. All recordings were performed in the morning between 08:00 and 10:00 hours to minimize circadian variation. Participants were advised to avoid caffeine, strenuous physical activity, and heavy meals for at least 12 hours prior to recording.

After a 10-minute acclimatization period in the supine position in a quiet, temperature-controlled room (22–24 °C), a continuous 5-minute ECG recording was obtained at a sampling rate of 1000 Hz. Artefacts and ectopic beats were identified and corrected using automated filtering followed by manual verification.

HRV analysis: Time-domain and frequency-domain HRV parameters were analyzed in accordance with established guidelines. Time-domain measures included:

• Mean RR interval
• Standard deviation of normal-to-normal intervals (SDNN)
• Root mean square of successive differences (RMSSD)

Frequency-domain analysis was performed using fast Fourier transformation, yielding:

• Low-frequency power (LF; 0.04–0.15 Hz)
• High-frequency power (HF; 0.15–0.40 Hz)
• LF/HF ratio

All HRV parameters were expressed in milliseconds or normalized units, as appropriate.

Anthropometric and physiological measurements: Height and weight were measured using standardized techniques, and body mass index (BMI) was calculated as weight (kg)/height (m²). Resting heart rate and blood pressure were recorded prior to HRV acquisition using an automated sphygmomanometer.

Statistical analysis: Data were entered into a predesigned database and analyzed using standard statistical software. Continuous variables were initially assessed for normality using the Shapiro–Wilk test. Variables demonstrating a normal distribution were summarized as mean ± standard deviation, while categorical variables were expressed as frequencies and percentages. Comparisons of baseline demographic and physiological characteristics across the three sleep duration categories were performed using one-way analysis of variance (ANOVA) for continuous variables. Sex distribution among groups was evaluated using the chi-square test. For heart rate variability parameters, intergroup differences in both time-domain and frequency-domain indices were analyzed using one-way ANOVA. When a significant overall effect was observed, post-hoc pairwise comparisons were conducted with Bonferroni adjustment to control for multiple testing. The relationship between habitual sleep duration and HRV indices was examined using Pearson’s correlation coefficient. In instances where variables did not satisfy normality assumptions, the Spearman rank correlation test was applied as an alternative. All statistical tests were two-tailed, and a p-value <0.05 was considered indicative of statistical significance.

Study Design

This study design is a retrospective observational analysis that evaluates postoperative outcomes and factors influencing spinal fusion surgery. The study period was defined over the patient's medical records, and a retrospective approach was selected to analyze real-world clinical data.

Study Setting and Duration

A study directed at a tertiary care Hospital provides specialized orthopedic and spinal surgery services. From July 2024 to July 2025 medical records of patients who underwent spinal fusion surgery were examined. They experienced that all the procedures were performed by spine surgeons which follows the standardized surgical and postoperative protocols.

Sample Size

In this study total of 45 patients who were eligible were involved. The sample is selected using a consecutive sampling method, in which case all qualified patients who underwent spinal fusion surgery during the study period were included. This method minimized selection bias and representative sampling can be specified for a timeframe.

Inclusion Criteria

• Patients age was up to 18 years.
• During the study period patients who underwent spinal fusion surgery.
• Accessibility of complete medical records:
• Preoperative data
• Intraoperative data
• Postoperative data
• A six-month follow-up duration is a minimum to allow the proper assessment of radiological and clinical outcomes.

Exclusion Criteria

• Patients with incomplete medical records.
• Patients who had undergone spinal fusion surgery.
• Presence of active spinal infection during the surgery.
• Presence of spinal malignancy at the time of surgery.

Data Collection

The data was retrieved from hospital computerized medical records using a predetermined method. Demographic factors included BMI, age, and sex. Clinical factors such as diabetes, hypertension, osteoporosis, main diagnosis, and surgical purpose were most important. Surgery variables were the number of fused spinal levels, the fusion method (posterolateral, anterior, transforaminal, or posterior lumbar interbody), and the equipment used.

It can be measured pain intensity using the Visual Analog Scale (VAS) and functional outcomes with the Oswestry Disability Index (ODI) or the SF-36 questionnaire, whichever is easier. Postoperative imaging assessed radiological fusion. Postoperative complications included surgical site infection, hardware failure, pseudoarthrosis, and a second operation.

Statistical Analysis

The SPSS statistical package was used for the analysis. To describe patient characteristics and outcomes, means with standard deviations or frequencies and percentages were used. Independent t-tests were employed for continuous variables and Fisher's exact or chi-square tests for categorical data. Multivariate logistic regression analysis was performed to identify independent predictors of surgical success. A p-value < 0.05 was considered statistically significant. 

Ethical Considerations

The study was permitted by the Institutional Ethics Committee of the Tertiary care Hospital. In the study, severely maintain the patient's confidentiality and all the data prior to the analysis. These existing records, based on the retrospective study, accordingly obtained a waiver of informed consent with institutional and ethical guidelines.

Demographic and Baseline Characteristics

The study included 45 patients with spinal fusion from 2024 to 2025. The ages of the participants ranged from 28 to 76, with an average age of 54.6 ± 11.8 years. Most of the patients were between 50 and 65 years old. The included patients were 27 men (60%) and 18 women (40%).

Osteoporosis and smoking were less common, but hypertension, diabetes, and obesity were more prevalent.

Table 1 Demographic and Baseline Characteristics

Surgical Characteristics

Degenerative disc disease (40%), spondylolisthesis (26.7%), and traumatic spinal instability (17.8%) were the top three spinal fusion explanations.

The most prevalent surgical procedure was transforaminal spinal interbody fusion. Single-level fusion outnumbered multilayer fusion.

Table 2 Surgical Characteristics

Clinical Outcomes

In the surgery significantly reduced and improved with the fusion. After surgery, the average VAS pain score decreased dramatically (p < 0.001) from 7.8 ± 1.1 to 2.6 ± 1.3 at the end of follow-up. The Oswestry Disability Index (ODI) showed significant improvement in functional outcomes, with mean scores decreasing from 56.4 ± 9.5 to 24.8 ± 8.7 post-surgery. Radiologically, 38 patients (84.4%) had successful spinal fusions.

Table 3 Clinical Outcomes

Complications and Revisions

Postoperative difficulties were observed in 10 patients (22.2%). Ten patients (22.2%) had post-op issues. Six patients developed superficial surgical site infections and transient neurological symptoms within 30 days. Later issues included hardware failure and pseudoarthrosis.

Five patients (11.1%) underwent revision surgery, mostly due to implant or union-related issues.

Table 4 Complications and Revision Surgery

Factors Influencing Surgical Success

Multivariate logistic regression study shows that being younger than 60, having few comorbidities, undergoing single-level fusion, and using interbody fusion methods predict positive results. Patients with multilayer fusion or several comorbidities reported lower fusion success rates.

Table 5 Factors Influencing Surgical Success

This retrospective study examined 45 patients over a year to determine spinal fusion surgery success factors. The study found 84.4% fusion success and significant improvements in functional outcomes and pain. In both symptoms and function, the ODI and mean postoperative VAS pain scores improved significantly from preoperative values. As in other spinal fusion groups, 22.2% of patients had problems and 11.1% needed revision surgery.

The prognostic factors of good outcomes in series were younger age (<60 years), absence of multiple comorbidities, single-level fusion, and performing interbody fusion (TLIF/PLIF), which correlated with successful interbody fusion as well as achieving better clinical outcomes. In contrast, advanced age, comorbidities, and multilevel fusion were correlated with the lower success rate and increased risk of complications. These results illustrate the complex interaction of factors in spinal fusion and underscore the importance of appropriate patient selection and surgical intervention planning.

 Comparison with Existing Literature

The success rate achieved in this study is consistent with the targeted fusion rates based on prior literature which 80–95% depending on surgical technique, patient population, and follow-up length. Study 1 demonstrated the efficacy of fusion in selected patients for decreasing pain and disability. In terms of increase in VAS and ODI scores, this current study is comparable to large observational and registry-based studies.

Earlier studies found that age and comorbidities were standard as significant factors influencing surgical success. Study 2 showed that elderly patients and those with multiple medical comorbidities experience higher rates of complications, delayed recovery, and non-union. Multilevel fusion has been associated with mechanical stress, extended operating times and pseudoarthrosis, as it has also proved the study.

The highest success rate was found in association with interbody fusion procedures mostly TLIF, PLIF when compared to posterolateral fusion alone. Study 3 supported by the evidence to date, which shows interbody procedures provide greater biomechanical stability in addition to improving rates of fusion and disc height, as well as sagittal alignment. Study results may difference in expertise, patient populations, follow-up period and modalities used to assess outcomes.

 Table 6  Comparison of Present Study with Existing Studies

Clinical Implications 

Selective patient selection, especially for older and multi-healthy patients, improves surgical results, according to this study. Glycemic control, diet, and smoking cessation should be optimized preoperatively. The study also recommends preoperative preparation, including choosing a fusion technique and number of levels to attached. Interbody operations and restricted fusions may produce the best clinical and radiological results.

Strengths of the Study

This study is one of the main strength supports on real world clinical data which reflected routine of postoperative care and surgical practice. In the single institution performed all procedures using consistent surgical protocols can reduce the variability of related operative technique and postoperative management. Moreover, both clinical and radiological outcomes use to measure provide a comprehensive assessment of surgical success.

Limitations

This study has several limitations that should be approved but it’s despite the contributions. The small sample size limits the statistical power and generalizability of the findings. The retrospective design introduces the potential for selection bias and incomplete data capture. Additionally, as single-center study results can reflect the institutions-specific procedures and might not be applicable to other healthcare systems or demographics. The assessment of long-term outcomes, such as adjacent segment disease, is also limited by the relatively short follow-up period.

Future Research Directions

Future research findings can be generalized across patient populations and surgical settings, and future large multi-institution studies are necessary. The durability of fusion results and the late complications will have to be evaluated in studies with longer follow-up duration. In addition, further prospective studies using standardized outcome measures and advance imaging techniques may present stronger evidence on predictors of success and choice of surgical intervention for spinal fusion.

This retrospective study shows that spinal fusion surgery improves pain alleviation, functional results, and radiological fusion rates in suitable individuals. Most patients had good clinical and radiological outcomes during follow-up in this study. Younger age, reduced comorbidity burden, single-level fusion, and TLIF/PLIF interbody fusion predicted success. Multilevel fusion, advanced age, and many comorbidities were associated with worse outcomes and more complications. The findings highlight the complexity of spinal fusion success and the need for patient assessment and surgical plan customization. To improve patient outcomes and reduce postoperative complications, preoperative risk assessment, optimization of controllable risk factors, and careful surgical method selection are crucial. This study provides valuable real-world facts to help spine surgeons make decisions, educate patients, and improve spinal fusion surgery.

• Yang et al., “Risk factors affecting spinal fusion: A meta-analysis of 39 cohort studies,” PLoS One, vol. 19, no. 6, Art. no. e0304473, 2024.
• Shahrestani et al., “The influence of modifiable risk factors on short-term postoperative outcomes following cervical spine surgery: A retrospective propensity score matched analysis,” EClinicalMedicine, vol. 36, 2021.
• Inculet et al., “Factors associated with using an interbody fusion device for low-grade lumbar degenerative versus isthmic spondylolisthesis: A retrospective cohort study,” J. Neurosurg. Spine, vol. 35, no. 3, pp. 299–307, 2021.
• Oezel et al., “Procedure-specific complications associated with ultrasound-guided erector spinae plane block for lumbar spine surgery: A retrospective analysis of 342 consecutive cases,” J. Pain Res., vol. 15, pp. 655–661, 2022.
• Yoshimura et al., “High body mass index is a strong predictor of intraoperative acquired pressure injury in spinal surgery patients when prophylactic film dressings are applied: A retrospective analysis prior to the BOSS trial,” Int. Wound J., vol. 17, no. 3, pp. 660–669, 2020.
• Odonkor et al., “Fantastic four: Age, spinal cord stimulator waveform, pain localization and history of spine surgery influence the odds of successful spinal cord stimulator trial,” Pain Physician, vol. 23, no. 1, pp. E19–E28, 2020.
• Wang et al., “Retrospective data analysis for enhanced recovery after surgery (ERAS) protocol for elderly patients with long-level lumbar fusion,” World Neurosurg., vol. 164, pp. e397–e403, 2022.
• Hiyama et al., “Impact of osteoporosis on short-term surgical outcomes in lumbar degenerative disease patients undergoing lateral lumbar interbody fusion: A retrospective analysis,” World Neurosurg., vol. 188, pp. e424–e433, 2024.
• N. Kurnutala et al., “Enhanced recovery after surgery protocol for lumbar spinal surgery with regional anesthesia: A retrospective review,” Cureus, vol. 13, no. 9, 2021.
• Gupta et al., “Comparison of functional outcomes between lumbar interbody fusion surgery and discectomy in massive lumbar disc herniation: A retrospective analysis,” Global Spine J., vol. 11, no. 5, pp. 690–696, 2021.
• Fan et al., “Unilateral biportal endoscopic lumbar interbody fusion (ULIF) versus endoscopic transforaminal lumbar interbody fusion (Endo-TLIF) in the treatment of lumbar spinal stenosis along with intervertebral disc herniation: A retrospective analysis,” BMC Musculoskelet. Disord., vol. 25, no. 1, Art. no. 186, 2024.
• Park et al., “Factors affecting successful immediate indirect decompression in oblique lateral interbody fusion in lumbar spinal stenosis patients,” North Am. Spine Soc. J., vol. 16, Art. no. 100279, 2023.
• H. Park, S. Park, and S. A. Choi, “Incidence and risk factors of spinal epidural hemorrhage after spine surgery: A cross-sectional retrospective analysis of a national database,” BMC Musculoskelet. Disord., vol. 21, no. 1, Art. no. 324, 2020.
• D. Bao et al., “Factors related to instrumentation failure in titanium mesh reconstruction for thoracic and lumbar tumors: Retrospective analysis of 178 patients,” Cancer Manag. Res., vol. 13, pp. 3345–3355, 2021.
• Mooney et al., “Minimally invasive versus open lumbar spinal fusion: A matched study investigating patient-reported and surgical outcomes,” J. Neurosurg. Spine, vol. 36, no. 5, pp. 753–766, 2021.