Study Design
The study was designed as a retrospective clinical study.
Purpose
This study aimed to demonstrate that solid fusion and favorable outcomes can be achieved even without fusion extension through the application of an allograft bone chip insertion technique. Overview of Literature: Screw loosening and nonunion are common complications following lumbar posterior fixation, often resulting from fusion failure. The optimal surgical strategy remains controversial, and most surgeons prefer extending fusion levels above or below the affected segment.
Methods
Twelve patients who underwent revision surgery for screw loosening and nonunion by a single surgeon were retrospectively analyzed. Allograft bone chips were inserted into loosened screw holes to enhance fixation and promote fusion. Radiologic outcomes were evaluated at 1 year using dynamic flexion–extension X-ray and computed tomography (CT). Solid fusion was defined as ≤3° of motion on X-ray and, in eight patients with CT, as a continuous trabecular bone bridge. Clinical outcomes were assessed using the numerical rating scale (NRS) for back and leg pain and the Oswestry Disability Index (ODI).
Results
From January 2020 to February 2022, 12 patients (7 men, 5 women; mean age, 65.8 years) underwent surgery. Eight were treated without fusion extension, three required one-level extension for adjacent segmental disease, and one for deformity correction. At 1 year, all patients achieved solid fusion with ≤3° motion, and CT confirmed a trabecular bone bridge in eight cases. Mean NRS scores for back and leg pain improved by 6.9 and 5.1 points, respectively, and ODI showed marked functional recovery.
Conclusion
The allograft bone chip insertion technique appears to be a practical revision option for managing screw loosening and nonunion in selected patients. It can achieve solid fusion and favorable outcomes without fusion extension, thereby minimizing surgical morbidity and preserving motion segments.