Predictors of junctional failure following pedicle fixation in thoracolumbar spine in traumatic spinal cord injury at the National Orthopaedic Hospital Dala Kano, Nigeria

INTRODUCTION

Traumatic thoracolumbar fractures are among the most common spinal injuries managed in Nigerian tertiary centres, often resulting from high‑energy mechanisms such as road traffic accidents and falls from height.^1,2 Posterior pedicle screw fixation has become the standard treatment for unstable thoracolumbar fractures, offering rigid segmental stabilisation and facilitating neurological recovery.^3,4 However, a well‑recognised late complication is JF–which includes proximal junctional kyphosis (PJK), distal junctional kyphosis (DJK), screw pullout or implant failure at the ends of the construct.^5,6 Junctional failure can lead to persistent pain, loss of sagittal balance, neurological deterioration and the need for revision surgery.^7,8

The reported incidence of PJK after thoracolumbar fusion ranges from 10% to 40% in the literature, depending on patient factors, surgical technique and follow‑up duration.^9,10 In traumatic settings, JF may be even more common due to associated ligamentous injury and poor bone quality.¹¹ In Nigeria, where routine follow‑up imaging may be limited and osteoporosis screening is not standard, the true burden of JF is unknown.¹² Identifying predictors of JF in this population is essential to guide surgical planning, patient counselling and preventive strategies. This study aimed to determine the incidence of and risk factors for junctional failure following pedicle screw fixation for traumatic thoracolumbar spinal cord injury at the National Orthopaedic Hospital Dala, Kano.

METHODS

This was a retrospective cohort study conducted at the National Orthopaedic Hospital Dala, Kano, Nigeria, covering a 6‑year period from January 2020 to December 2025. Ethical approval was obtained and the requirement for individual patient consent was waived due to the retrospective nature.

All adult patients (≥18 years) who underwent posterior pedicle screw fixation for acute traumatic thoracolumbar fractures (T10–L3) with complete or incomplete spinal cord injury were eligible.

Inclusion criteria

Inclusion criteria traumatic fracture with at least 6 months of follow‑up, availability of pre‑ and postoperative radiographs, no prior spinal surgery at the same levels.

Exclusion criteria

pathological fractures, infection, revision surgery or follow‑up <6 months. A total of 172 patients met the inclusion criteria. Mean age was 39.4±13.8 years; 117 (68%) were male. Road traffic accidents accounted for 81% of injuries.

Surgical technique

All patients underwent posterior pedicle screw fixation using a freehand technique with intraoperative C‑arm fluoroscopy. Screw diameter (5.5–6.5 mm) and length (40–50 mm) were chosen based on preoperative imaging. Rods were contoured to restore physiological thoracic kyphosis (20–40°) and lumbar lordosis (40–60%). The number of fused levels was determined by the fracture pattern and surgeon preference. No interbody fusion or osteotomy was performed unless specifically indicated. All patients received a standardised postoperative rehabilitation protocol.

Data collection

Demographic and clinical data were extracted from medical records: age, sex, body mass index (BMI), smoking status, bone mineral density (when available or surrogate markers such as history of fragility fracture), mechanism of injury, level of fracture, Asia impairment scale grade at admission, time from injury to surgery, number of fused levels, screw density (number of screws÷number of instrumented levels) and preoperative local kyphosis angle (measured from one level above to one level below the fractured vertebra).¹³

Definition of junctional failure

JF was defined as the occurrence of any of the following within 24 months of surgery proximal junctional kyphosis >10° measured on lateral standing radiographs (PJK), distal junctional kyphosis >10° screw loosening or pullout at the cranial or caudal end of the construct rod fracture at the junction or symptomatic implant failure requiring revision surgery.¹⁴

Radiographic measurements were performed by two independent spine surgeons, with the average recorded.

Outcome measures

Primary outcome: occurrence of JF. Secondary outcomes: time to JF, revision surgery rate and functional outcome measured by ODI at final follow‑up.

Statistical analysis

Continuous variables are presented as mean±SD and categorical as frequencies (%). Univariate analysis compared patients with and without JF using independent t‑test or Mann‑Whitney U for continuous variables and chi‑square or Fisher’s exact for categorical variables.

Variables with p<0.10 in univariate analysis were entered into a multivariate logistic regression model to identify independent predictors of JF. Odds ratios (OR) with 95% confidence intervals (CI) were calculated. Statistical significance was set at p<0.05. Analysis used SPSS version 26.

RESULTS

Of 172 patients, 31 (18.0%) developed junctional failure at a mean of 11.2±4.5 months post‑surgery. JF consisted of PJK (n=18, 58.1%), DJK (n=7, 22.6%), screw pullout (n=4, 12.9%) and rod fracture (n=2, 6.5%). Revision surgery was performed in 14 patients (45.2% of JF group). Baseline characteristics are shown in Table 1.

Univariate analysis

Patients with JF were significantly older (48.2±12.5 vs. 37.5±13.2 years, p<0.001) and had higher BMI (27.8±3.5 vs. 24.5±3.2 kg/m², p=0.01). Fusion length (≥4 levels) was more common in the JF group (64.5% vs. 32.6%, p<0.001). Screw density <0.8 was present in 58.1% of JF vs. 32.6% of non‑JF (p=0.01). Preoperative local kyphosis >25° was seen in 54.8% vs. 24.1% (p=0.002). Time to surgery, smoking and ASIA grade were not significantly different.

Multivariate predictors

Multivariate logistic regression identified four independent predictors of JF as highlighted below. This is shown better in Table 2.

Age>50 years

OR 3.2 (95% CI 1.6–6.4), p=0.001.

Fusion length ≥4 levels

OR 2.8 (95% CI 1.4–5.6), p=0.003.

Preoperative local kyphosis >25°

OR 2.5 (95% CI 1.2–5.2), p=0.01.

Screw density <0.8

OR 2.1 (95% CI 1.0–4.3), p=0.04.

Functional outcomes

At final follow‑up (mean 18.4±7.2 months), patients with JF had significantly worse ODI scores (48.2±15.4 vs. 32.5±14.1, p<0.001). Among the 14 patients who underwent revision surgery, the mean ODI improved from 55.2±12.3 pre‑revision to 38.5±14.0 post‑revision (p=0.02).

DISCUSSION

This retrospective study of 172 Nigerian patients with traumatic thoracolumbar spinal cord injury found that junctional failure occurred in 18.0% of patients after posterior pedicle screw fixation. Independent predictors included age >50 years, fusion length ≥4 levels, preoperative local kyphosis >25°, screw density <0.8 and osteoporosis. These findings have important implications for surgical planning in low‑resource settings. The 18% incidence of JF is consistent with published rates from high‑income countries, which range from 10% to 30%.^9,10,15 However, the high proportion requiring revision surgery (45%) reflects the severity of JF in the cohort and the limited access to routine surveillance that might detect early changes before catastrophic failure.¹²

Age as a predictor

Older age (OR 3.2) is a well‑established risk factor for PJK after spinal fusion, attributed to reduced bone quality, decreased muscle tone and impaired healing capacity.^16,17 In Nigeria, where DXA scanning is not routinely performed, older patients may have undiagnosed osteoporosis, further increasing risk.

Fusion length

Longer fusion constructs (≥4 levels) increased JF risk by nearly threefold. Each additional instrumented level increases the lever arm at the proximal junction, concentrating stress.¹⁸ Whenever possible, limiting fusion to the minimum necessary levels (short‑segment fixation) may reduce JF. In the practice, the traditional preference for long fusion to achieve stability should be re‑evaluated.

Preoperative kyphosis

A preoperative local kyphosis >25° independently predicted JF (OR 2.5). This likely reflects the severity of the initial injury and the difficulty of achieving and maintaining sagittal alignment.¹⁹ Inadequate restoration of lordosis or overcorrection can both predispose to JF. Surgeons should aim to restore physiological alignment without excessive correction.

Screw density

Screw density <0.8 (i.e., not placing screws at every possible level) was associated with higher JF risk. Higher screw density distributes forces more evenly across the construct, reducing stress at the junction.²⁰ In resource‑limited settings where implant costs are high, surgeons may be tempted to use fewer screws, but this study suggests that this practice increases JF risk. The retrospective design introduces selection bias. Bone mineral density was not measured in all patients; relied on clinical diagnosis or historical fragility fractures. Follow‑up radiographs were not standardised in terms of positioning. The sample size, while adequate for identifying major predictors, limited subgroup analyses. Finally, we did not assess the role of interbody fusion or the effect of rod material/design. To reduce JF, we recommend limit fusion length to the shortest possible construct that provides stability achieve screw density ≥0.8, optimize bone health preoperatively, especially in patients >50 years carefully restore sagittal alignment without excessive correction; and counsel high‑risk patients about the possibility of JF and need for long‑term follow‑up. Junctional failure occurs in nearly one in five Nigerian patients after thoracolumbar pedicle fixation for traumatic SCI. Age >50 years, fusion length ≥4 levels, preoperative kyphosis >25°, screw density <0.8 and osteoporosis are independent predictors. These factors should guide surgical decision‑making and patient counselling.

CONCLUSION

Junctional failure after thoracolumbar pedicle fixation is common (18%) in this Nigerian cohort. Older age, longer fusion, inadequate screw density, severe preoperative kyphosis and osteoporosis are independent predictors. Strategies to reduce JF include optimizing bone health, limiting fusion length and achieving high screw density.

Funding: No funding sources

Conflict of interest: None declared

Ethical approval: The study was approved by the Institutional Ethics Committee

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