Intra-osseous and coverage fixation for inferior pole fracture of the patella: a comparative finite element analysis and retrospective cohort study.

Abstract

Inferior pole fracture of the patella (IPFP) is notoriously difficult to manage. Although multiple surgical options are available, the percutaneous cannulated-screw tension-band (PCST) technique remains the conventional choice, despite its high complication rate. The recently introduced technique of tension-band wiring through a cannulated screw with suture anchors (TACS-SA) offers a promising alternative, though its efficacy requires further validation. This study was conceived to compare the biomechanical behaviour and early clinical results of the TACS-SA construct with PCST fixation. This study comprises a finite-element analysis (FEA) and clinical investigation. In the FEA, a knee flexion of 45° under 200 N contact stress was simulated. Three fracture models were constructed for the TACS-SA, PCST with a figure-of-eight tension band (EPCST), and PCST with a figure-of-zero tension band (ZPCST). Fracture fragment stability was assessed by measuring mean displacement (MD-FF) and mean stress (MS-FF). The biomechanical strength of the fixation device was evaluated via its mean displacement (MD-IF) and mean stress (MS-IF). The clinical cohort included 43 patients, with 25 undergoing TACS-SA and 18 undergoing EPCST. Recorded parameters included bone union time, radiographic union time, range of motion (ROM), and follow-up duration. At the final follow-up, functional outcomes were evaluated with the Böstman score, KOOS score, and extension lag. In the FEA, the TACS-SA models consistently showed lower MD-FF, MS-FF, and MD-IF across all three fragment conditions (p < 0.05), with the MS-IF of TACS-SA being moderate but not significant in the one-fragment condition (p > 0.05). In the retrospective cohort, the TACS-SA group achieved radiographic union earlier than the EPCST group (P < 0.05). Similar results were observed in the KOOS score, bone union period, ROM, Böstman score, and extension lag between the groups (P > 0.05). The TACS-SA technique exhibits superior biomechanical properties and clinical outcomes to the conventional PCST technique when treating IPFP.