Introduction A semiknee mega endoprosthesis (SKMEP) was used to replace the resected distal femur or proximal tibia in skeletally immature bone sarcoma patients. This study investigated the surgical technique, endoprosthesis survival rate, functional outcome, complications, and approaches to resolve limb-length discrepancy (LLD) following this procedure.

Patients and Methods In total, 15 girls and 16 boys with a mean age of 9.1 years (range, 4–12) and 8.9 years (range, 5–13), respectively, were included in this study. The mean length of the resected distal femur (15 cases) and proximal tibia (16) was 145.0 and 122.8 mm, respectively. Altogether, 19 custom-made SKMEPs and 12 modular units were used to reconstruct the bone and joint defects.

Results The average follow-up was 82.8 months (range, 4–225 months). Five patients died of disease. Seven SKMEPs were revised to total knee endoprosthesis after a mean of 40.3 months. Nineteen patients retained the original SKMEP, and the mean LLD was 4.3 cm (range, 0–10 cm). One case each of Henderson type 1B, type 2A, type 2B, and type 5B failures was observed. Knee subluxation occurred in two cases. Although a slight laxity of the knee was identified on physical examination, the average Musculoskeletal Tumor Society 93(MSTS93) functional score was 84.5% (range, 57–97%). The estimated implant survival was 70.5% at 5 years.

Conclusion This was the largest retrospective study reporting the application of SKMEP in bone sarcoma patients. For selected skeletally immature bone sarcoma patients, SKMEP is an option with satisfactory functional outcomes and survival rates. However, heightening pads or shoes to compensate the LLD were indispensable before subsequent LLD was adjusted by further operation(s).

简介 半膝巨型内置假体 (SKMEP) 用于替代骨骼未成熟骨肉瘤患者切除的股骨远端或胫骨近端。本研究调查了手术技术、内置假体存活率、功能结果、并发症以及解决手术后肢体长度差异 (LLD) 的方法。

患者和方法 本研究总共包括 15 名女孩和 16 名男孩，平均年龄分别为 9.1 岁（范围，4-12）和 8.9 岁（范围，5-13）。切除的股骨远端（15 例）和胫骨近端（16 例）的平均长度分别为 145.0 和 122.8 mm。总共使用了 19 个定制 SKMEP 和 12 个模块化单元来重建骨和关节缺损。

结果 平均随访时间为 82.8 个月（范围：4-225 个月）。五名患者因病死亡。平均 40.3 个月后，7 名 SKMEP 被修改为全膝关节内假体。19 名患者保留了原来的 SKMEP，平均 LLD 为 4.3 cm（范围，0-10 cm）。观察到 Henderson 1B 型、2A 型、2B 型和 5B 型故障各 1 例。两例发生膝关节半脱位。尽管体检时发现膝盖轻微松弛，但肌肉骨骼肿瘤协会 93 (MSTS93) 功能评分的平均为 84.5%（范围为 57-97%）。预计 5 年种植体存活率为 70.5%。

结论 这是报道 SKMEP 在骨肉瘤患者中应用的最大规模的回顾性研究。对于选定的骨骼未成熟骨肉瘤患者，SKMEP 是一种具有令人满意的功能结果和生存率的选择。然而，在通过进一步操作调整LLD之前，加高垫或鞋子来补偿LLD是必不可少的。