Background 

Osteosarcoma and Ewing sarcoma are more common diagnoses in preadolescent and adolescent children compared with the adult population. A greater percentage of patients are treated with limb salvage and reconstruction using modular tumor endoprostheses. Implant-to-bone fixation can be cemented or cementless. Cementless tumor endoprostheses rely on biologic osteointegration for implant stability, and chemotherapy during childhood and adolescence can disturb the bone turnover rate and reduce bone mineral density, which in turn may predispose patients with uncemented endoprostheses to a high rate of revision surgeries.

Questions/purposes 

(1) What is the cumulative incidence of revision operations for any cause (wound dehiscence, periprosthetic fracture, hinge breakage, aseptic loosening, infection, local recurrence, implant removal, and amputation) of cementless tumor endoprostheses around the knee? (2) What is the cumulative incidence of aseptic loosening, periprosthetic fracture, hinge breakage, and infection, and what proportion of patients had other complications? (3) What was the mean limb length discrepancy (LLD) at the time of skeletal maturity? (4) What was the median Musculoskeletal Tumor Society (MSTS) score at most recent follow-up or just before implant removal/amputation if implant removal/amputation were performed?

Methods 

Between 2008 and 2019, we treated 328 patients younger than 18 years for a primary bone sarcoma around the knee at our institution. Of those, 138 were treated with resection and reconstruction using two different types of modular tumor endoprostheses. During this period, our general indications for an endoprosthesis were patients who were candidates for an intraarticular resection of the distal femur or proximal tibia and who were at least 10 years of age. Uncemented fixation was always preferred. Cemented fixation was only done when intraoperative press-fitting of a cementless stem was not possible. Among uncemented implants, 26 patients died before completing 2 years of follow-up with intact implants and without further surgery, three were lost to follow-up before 2 years, and four patients received implants as a secondary salvage surgery after a failed primary biologic reconstruction with a vascularized fibular bone graft, leaving 94 patients for evaluation in this retrospective study. The mean age was 15 ± 2 years and the median (interquartile range) follow-up duration was 51 months (39 to 74). We did a competing risks analysis to tally cumulative incidence of all-cause revision procedures and cumulative incidence of aseptic loosening, periprosthetic fracture, hinge breakage, and infection. Other complications, including wound dehiscence, local recurrence, and stem breakage, were characterized descriptively and ascertained by review of electronic records of a longitudinally maintained institutional database by the treating surgeons. LLD was measured by serial clinical assessments and CT scans, starting since primary salvage surgery and until the latest follow-up of every patient. For the analysis of remaining LLD, we included only patients who were skeletally immature at time of primary resection and who had reached skeletal maturity by their latest follow-up (73% [69 of 94]). Functional outcome was assessed using MSTS scores obtained from a review of electronic records of a longitudinally maintained institutional database.

Results 

The 8-year cumulative incidence of revision surgery for any cause was 32% (95% confidence interval 23% to 42%). The 8-year cumulative incidence of aseptic loosening was 5% (95% CI 2% to 11%), periprosthetic fracture was 9% (95% CI 4% to 15%), hinge breakage was 19% (95% CI 12% to 28%), and infection was 7% (95% CI 3% to 14%). Other complications included wound dehiscence in 2% (2 of 94), stem breakage in 2% (2 of 94), and local recurrence in 2% (2 of 94) of patients. Stress shielding of the cortical bone around implanted stems was observed in 26% (24 of 94). The mean LLD for those who were skeletally immature at the time of primary resection and who reached skeletal maturity was 3.5 ± 2.6 cm. At latest follow-up, the median (IQR) MSTS score for all patients, excluding those who had complete implant removal or amputation, was 26 (24 to 27) of a maximum score of 30.

Conclusion 

We observed a high rate of early revision and relatively frequent complications associated with the use of cementless fixation, and although this was not a comparative study, the findings were not superior to those reported by others who have studied cemented fixation for this indication. Furthermore, there may be some disadvantages with cementless fixation, such as stress shielding. Comparative studies about fixation methods are needed. The prevalence of bushing breakage in the current study highlights the importance of future modifications in the hinge design of both types of prostheses used in this study. Patients who were skeletally immature at the time of primary surgery had a LLD no more than 5 cm at skeletal maturity; consequently, nonexpandable endoprostheses may be appropriate for some adolescent patients who have limited remaining growth, although which patients are best suited for this approach would require specific study.

Level of Evidence 

Level IV, therapeutic study.

中文翻译：

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对于 18 岁或以下的膝部原发性骨肉瘤患者，修复手术的累积发生率是多少？与带柄非骨水泥不可伸展内置假体相关的并发症有哪些

背景 

与成年人相比，骨肉瘤和尤文肉瘤在青春期前和青少年儿童中更常见。更大比例的患者接受使用模块化肿瘤内置假体进行保肢和重建治疗。种植体与骨的固定可以是骨水泥固定或非骨水泥固定。无骨水泥肿瘤内置假体依靠生物骨整合来保持种植体稳定性，而儿童和青少年时期的化疗会扰乱骨转换率并降低骨矿物质密度，这反过来可能使非骨水泥内置假体患者易于进行翻修手术。

问题/目的 

(1) 膝关节周围非骨水泥肿瘤内置假体因任何原因（伤口裂开、假体周围骨折、铰链断裂、无菌性松动、感染、局部复发、植入物移除和截肢）而进行翻修手术的累积发生率是多少？(2) 无菌性松动、假体周围骨折、铰链断裂和感染的累积发生率是多少？出现其他并发症的患者比例是多少？(3) 骨骼成熟时的平均肢体长度差异（LLD）是多少？(4) 最近一次随访时或植入物移除/截肢前（如果进行了植入物移除/截肢）的中位肌肉骨骼肿瘤协会 (MSTS) 评分是多少？

方法 

2008 年至 2019 年间，我们机构治疗了 328 名 18 岁以下的膝部原发性骨肉瘤患者。其中，138 例接受了使用两种不同类型的模块化肿瘤内置假体进行切除和重建的治疗。在此期间，我们使用内置假体的一般适应症是适合进行股骨远端或胫骨近端关节内切除术且年龄至少 10 岁的患者。非骨水泥固定始终是首选。仅当术中无法压装无骨水泥柄时才进行骨水泥固定。在非骨水泥种植体中，26 名患者在使用完整种植体完成 2 年随访且未进行进一步手术之前死亡，3 名患者在 2 年前失访，4 名患者在初次生物重建失败后接受了种植体作为二次抢救手术带有血管的腓骨骨移植物，在这项回顾性研究中留下了 94 名患者进行评估。平均年龄为 15 ± 2 岁，中位（四分位距）随访时间为 51 个月（39 至 74）。我们进行了竞争风险分析，以统计全因翻修手术的累积发生率以及无菌性松动、假体周围骨折、铰链断裂和感染的累积发生率。其他并发症，包括伤口裂开、局部复发和茎断裂，通过治疗外科医生对纵向维护的机构数据库的电子记录进行描述性表征和确定。LLD 通过连续临床评估和 CT 扫描进行测量，从初次挽救手术开始直至每位患者的最新随访。为了分析剩余的 LLD，我们仅纳入了初次切除时骨骼尚未成熟且在最近一次随访时已达到骨骼成熟的患者（73% [94 人中的 69 人]）。使用从纵向维护的机构数据库的电子记录审查中获得的 MSTS 分数来评估功能结果。

结果 

因任何原因进行翻修手术的 8 年累计发生率为 32%（95% 置信区间为 23% 至 42%）。无菌性松动的 8 年累积发生率为 5%（95% CI 2% 至 11%），假体周围骨折为 9%（95% CI 4% 至 15%），铰链断裂为 19%（95% CI 12%）至 28%），感染率为 7%（95% CI 3% 至 14%）。其他并发症包括 2% 的患者（94 名患者中的 2 名）出现伤口裂开、2% 的患者（94 名患者中的 2 名）出现茎断裂，以及 2% 的患者（94 名患者中的 2 名）出现局部复发。26% 的患者（94 例中的 24 例）观察到植入茎周围皮质骨的应力屏蔽。对于初次切除时骨骼未成熟和达到骨骼成熟的患者，平均 LLD 为 3.5 ± 2.6 cm。在最近一次随访中，除植入物完全移除或截肢的患者外，所有患者的中位 (IQR) MSTS 评分为 26 分（24 至 27 分），最高分为 30 分。

结论 

我们观察到与使用无骨水泥固定相关的早期翻修率很高，并发症也相对频繁，尽管这不是一项比较研究，但研究结果并不优于其他研究该适应症的骨水泥固定的人所报告的结果。此外，无骨水泥固定可能存在一些缺点，例如应力屏蔽。需要对固定方法进行比较研究。当前研究中衬套断裂的普遍性凸显了未来对本研究中使用的两种类型假体的铰链设计进行修改的重要性。初次手术时骨骼尚未成熟的患者，骨骼成熟时的 LLD 不超过 5 厘米；因此，不可扩张的内置假体可能适合一些剩余生长有限的青少年患者，尽管哪些患者最适合这种方法还需要具体研究。

证据水平 

IV级，治疗研究。