Background: If bone union is expected, conservative treatment is generally selected for lumbar spondylolysis. However, sometimes conservative treatments are unsuccessful. We sought to determine the factors associated with failure of bony union in acute unilateral lumbar spondylolysis with bone marrow edema including contralateral pseudarthrosis. Methods: This study targeted unilateral lumbar spondylolysis treated conservatively in high school or younger students. Conservative therapy was continued until the bone marrow edema disappeared on MRI and bone union was investigated by CT. We conducted a univariate analysis of sex, age, pathological stage, lesion level complicating the contralateral bone defect, lesion level, and intercurrent spina bifida occulta, and variables with p < 0.1 were considered in a logistic regression analysis. An item with p < 0.05 was defined as a factor associated with failure of bony union. Results: We found 92 cases of unilateral spondylolysis with bone marrow edema and 66 cases were successfully treated conservatively. Failure of bony union in unilateral lumbar spondylolysis with bone marrow edema was associated with progressive pathological stage (p = 0.004), contralateral pseudarthrosis (p < 0.001), and L5 lesion level (p = 0.002). The odds ratio was 20.0 (95% CI 3.0–193.9) for progressive pathological stage, 78.8 (95% CI 13–846) for contralateral pseudarthrosis, and 175 (95% CI 8.5–8192) for L5 lesion level. Conclusions: Conservative therapy aiming at bony union is contraindicated in cases of acute unilateral spondylolysis when the pathological stage is progressive, the lesion level is L5, or there is contralateral pseudarthrotic spondylolysis.

The usefulness of minimally invasive posterior fixation without debridement and autogenous bone grafting remains unknown. This multicenter case series aimed to determine the clinical outcomes and limitations of this method for thoracolumbar pyogenic spondylitis. Patients with thoracolumbar pyogenic spondylitis treated with minimally invasive posterior fixation alone were retrospectively evaluated at nine affiliated hospitals since April 2016. The study included 31 patients (23 men and 8 women; mean age, 73.3 years). The clinical course of the patients and requirement of additional anterior surgery constituted the study outcomes. The postoperative numerical rating scale score for lower back pain was significantly smaller than the preoperative score (5.8 vs. 3.6, p = 0.0055). The preoperative local kyphosis angle was 6.7°, which was corrected to 0.1° after surgery and 3.7° at the final follow-up visit. Owing to failed infection control, three patients (9.6%) required additional anterior debridement and autogenous bone grafting. Thus, in this multicenter case series, a large proportion of patients with thoracolumbar pyogenic spondylitis could be treated with minimally invasive posterior fixation alone, thereby indicating it as a treatment option for pyogenic spondylitis.

Background: Factors affecting bone union in the conservative treatment of adolescent lumbar spondylolysis remain controversial. We aimed to examine these factors along with advances in diagnostic imaging using multivariable analysis of a sufficient number of patients and lesions. Methods: In this retrospective study, high-school-aged patients or younger (n = 514) who were diagnosed with lumbar spondylolysis from 2014 to 2021 were investigated. We included patients with acute fractures who showed signal changes around the pedicle on magnetic resonance imaging and who completed conservative treatment. The following factors were investigated at the initial visit: age, sex, level of lesion, main side stage, presence and stage of contralateral side lesion, and presence of spina bifida occulta. The association of each factor with bone union was evaluated through a multivariable analysis. Results: Altogether, 298 lesions in 217 patients (174 boys and 43 girls; mean age: 14.3 years) were included in this study. Multivariable logistic regression analysis of all factors showed that the main side progressive stage was more likely associated with nonunion as compared to the pre-lysis (OR: 5.86; 95% confidence interval [CI]: 2.00–18.8; p = 0.0011) and early stages (OR: 3.77; 95% CI: 1.72–8.46; p = 0.0009). Regarding the contralateral side stage, the terminal stage was more likely to be associated with nonunion. Conclusion: In the conservative treatment of lumbar spondylolysis, the factors affecting bone union were the main and contralateral side stages. Sex, age, level of lesion, or spina bifida occulta had no significant effects on bone union. The main, progressive, and contralateral side terminal stages were negative predictors of bone union. Trial registration This study was retrospectively registered.

Lumbar spondylolysis is a fatigue fracture that occurs most frequently in middle and high school athletes. Conservative treatment is the first choice when the fracture is fresh. Surgical treatment of lumbar spondylolysis is often reported for pseudarthrosis cases, but surgery for cases of fresh fractures is rare. We report a case of a 16-year-old male, high jump athlete, with recurrent non-pseudoarthorotic lumbar spondylolysis. He presented to our hospital with a chief complaint of back pain, and was diagnosed as right L5, pre-lysis-stage lumbar spondylolysis. After 3 months of conservative treatment, bone union was achieved with no obvious worsening of the fracture. His back pain also disappeared and he was able to return to exercise. At 6 months after the first examination, the lesion recurred and he could no longer continue playing sports, so surgical treatment was indicated. Minimally invasive screw fixation was performed by combining Buck's method and the cortical bone trajectory. After the surgery, he started jogging at 5 weeks, resumed jumping practice at 7 weeks, and returned to competition at 2 months. He set a new personal best in a competition 3 months post-surgery. Bone union was achieved at 4 months. This technique is minimally invasive and does not involve debridement or bone grafting, which provides early pain relief and return to sports.