[Zeta-focal bone lengthening for bone defects after fracture-related infection: a two-case based research].

Objective: To summarize the clinical experiences of using Zeta-focal bone lengthening to treat bone defects caused by fracture-related infection (FRI) in two cases, and to preliminarily explore its feasibility and efficacy. Methods: In 2023, two male patients with bone defects caused by FRI were treated, aged 19 and 40 years, respectively. After admission, stage Ⅰ treatment consisted of thorough debridement and infection control based on bacterial culture and drug susceptibility test results. The lengths of bone defects were 6 cm and 22 cm, respectively. When the erythrocyte sedimentation rate and inflammatory markers returned to normal ranges, stage Ⅱ treatment (debridement and reconstruction with Zeta-focal bone lengthening) was performed. Distraction was initiated at 7 days after the second-stage operation. Docking of the bone segments was achieved at 11 and 40 days of distraction, respectively, and obvious mineralization in the distraction zones was observed at 65 and 104 days postoperatively. The external fixator was removed after radiographic evidence of cortical continuity at four sites was confirmed on anteroposterior and lateral X-ray films. The external fixation time was 112 and 357 days, respectively, and the external fixation indexes were 18.5 and 17.9 days/cm, respectively. Complications during the distraction period were observed. During follow-up, bone healing and functional recovery were evaluated with the Paley D score, the Association for the Study and Application of the Method of Ilizarov (ASAMI) score, the Lower Extremity Functional Scale (LEFS), and the American Orthopaedic Foot & Ankle Society (AOFAS) score. Results: Both patients completed the two-stage treatment. Their hospital stays were 21 and 16 days, respectively. Only mild pin-tract reactions occurred during the distraction period. Both patients were followed up for 18 months. At last follow-up, 2 patients achieved excellent functional results according to the ASAMI score, and bone healing was rated as excellent by the Paley D score. In 1 patient, the LEFS score was 76 and the AOFAS score was 95. The other patient was not scored because of knee arthrodesis. Conclusion: Under the prerequisites of strict infection control and individualized segmental design, Zeta-focal bone lengthening can achieve effective reconstruction of infectious bone defects and significantly reduce the external fixation time and the external fixation index.