Gao Yanchun, Lin Junqing, Hsu Peichun, Wang Yehui, Zhu Hongyi, Wei Haifeng
Department of Orthopedic Surgery, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai Jiao Tong University, Shanghai, PR China.
Clin Orthop Relat Res. 2025 May 14;483(11):2137-44. doi: 10.1097/CORR.0000000000003506.
Patellar fractures represent approximately 0.5% to 1.5% of all trauma-related fractures, and patella baja, or an abnormally low-lying patella, may be a result of treatment. This complication is underappreciated, and although patella baja may result in patient discomfort, stiffness, and later degenerative changes, the association between fracture type, operative treatment, and this complication is not well described.
QUESTIONS/PURPOSES: (1) What percentage of patients treated surgically for patellar fractures developed patella baja, and which fracture patterns were more likely to demonstrate postoperative patella baja? (2) What was the association between postoperative patella baja and functional outcomes as measured by ROM and Böstman score? (3) What complications were associated with the development of patella baja?
Between January 2018 and January 2021, we treated 3244 patients for patellar fractures at the National Center for Orthopaedics in Shanghai, PR China. The average age of the patients was 53.4 ± 12.0 years, and the male-to-female ratio was 1:1.34. After accounting for exclusion and inclusion criteria, 11% (259 of 2370) of patients were lost to follow-up before 2 years, leaving 2111 patients for review in this retrospective study at a mean of 32 ± 9 months after injury. During this time, we generally recommended surgery for patellar fractures when the fracture demonstrated an articular surface step-off exceeding 2 mm or there was loss of knee extension function. According to the AO/OTA (Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association) classification systems, the fractures were divided into eight subtypes: A1, B1, B2, C1.1, C1.2, C1.3, C2, and C3. All of these patients had CT scans and clinical data collected in our longitudinally maintained institutional database. Two independent observers classified the fractures based on the preoperative CT scan and recorded the Insall-Salvati index (ISI) on plain radiographs at the 2-year follow-up visit. An ISI of < 0.8 determined the presence of patella baja. Patient demographics, ROM, Böstman functional scores, complications, and implant removal rates were assessed. Binary logistic regression and linear regression models were employed to analyze risk factors for patella baja, associations, and treatment outcomes. Under the AO/OTA classification, the most common fracture patterns were C1.1 (30% [634 of 2111]) and C3 (25% [538 of 2111]).
Overall, 25% (527 of 2111) of patients had postoperative patella baja, and those with type A1 (OR 6.44 [95% confidence interval (CI) 4.57 to 9.10]), C1.3 (OR 4.96 [95% CI 3.68 to 7.10]), and C3 (OR 2.61 [95% CI 1.93 to 3.52]) fractures displayed a higher odds of developing patella baja. Patients with patella baja had poorer ROM in flexion than did patients without patella baja (116° ± 12° versus 125° ± 11° [95% CI 8.17° to 10.41°]; p < 0.01), and patients with patella baja did not have poorer Böstman scores at minimum 2-year follow-up (26.0 ± 3.2 versus 26.0 ± 3.2; p = 0.90). After controlling for potentially confounding variables such as sex, age, BMI, fracture classification, and complications, we found that fracture classification-specifically A1 (OR 6.7 [95% CI 4.8 to 9.5]), C1.3 (OR 5.0 [95% CI 3.6 to 6.9]), and C3 (OR 2.5 [95% CI 1.9 to 3.4])-deep infection (OR 10.5 [95% CI 4.2 to 26.5]; p < 0.001), and superficial infection (OR 2.4 [95% CI 1.4 to 4.4]; p = 0.003) were associated with the development of postoperative patella baja, whereas sex, BMI, and age were not. Postoperative infection was the only complication associated with patella baja.
The findings of this study underscore the importance for surgeons to be vigilant about the occurrence of patella baja after patellar fractures. In cases of the specific fracture types identified here, surgeons are encouraged to actively explore and adopt more suitable internal fixation techniques. By doing so, the incidence of postoperative patella baja may be effectively reduced, leading to better ROM and functional outcomes for patients.
Level III, therapeutic study.
髌骨骨折约占所有创伤相关骨折的0.5%至1.5%，低位髌骨或髌骨位置异常低下可能是治疗的结果。这种并发症未得到充分认识，尽管低位髌骨可能导致患者不适、僵硬及后期退行性改变，但骨折类型、手术治疗与该并发症之间的关联尚无详尽描述。
问题/目的：（1）接受髌骨骨折手术治疗的患者中，低位髌骨的发生率是多少？哪些骨折类型更易出现术后低位髌骨？（2）术后低位髌骨与通过活动度（ROM）和Böstman评分衡量的功能结果之间有何关联？（3）低位髌骨的发生会伴有哪些并发症？
2018年1月至2021年1月期间，我们在中国上海国家骨科中心治疗了3244例髌骨骨折患者。患者平均年龄为53.4±12.0岁，男女比例为1:1.34。在考虑纳入和排除标准后，11%（2370例中的259例）患者在2年之前失访，本回顾性研究中留下2111例患者进行分析，受伤后平均随访时间为32±9个月。在此期间，当骨折的关节面台阶超过2mm或存在膝关节伸直功能丧失时，我们通常建议对髌骨骨折进行手术治疗。根据AO/OTA（骨科学会/骨科创伤协会）分类系统，骨折分为八个亚型：A1、B1、B2、C1.1、C1.2、C1.3、C2和C3。所有这些患者的CT扫描和临床数据均收集于我们长期维护的机构数据库中。两名独立观察者根据术前CT扫描对骨折进行分类，并在2年随访时在X线平片上记录Insall-Salvati指数（ISI）。ISI<0.8确定为低位髌骨。评估患者的人口统计学特征、ROM、Böstman功能评分、并发症及内固定取出率。采用二元逻辑回归和线性回归模型分析低位髌骨的危险因素、关联及治疗结果。在AO/OTA分类下，最常见的骨折类型是C1.1（30%[2111例中的634例]）和C3（25%[2111例中的538例]）。
总体而言，25%（2111例中的527例）患者术后出现低位髌骨，A1型（比值比[OR]6.44[95%置信区间（CI）4.57至9.10]）、C1.3型（OR4.96[95%CI3.68至7.10]）和C3型（OR2.61[95%CI1.93至3.52]）骨折患者发生低位髌骨的几率更高。低位髌骨患者的屈曲活动度比无低位髌骨患者差（116°±12°对125°±11°[95%CI8.17°至10.41°]；p<0.01），在至少2年随访时，低位髌骨患者的Böstman评分并不更低（26.0±3.2对26.0±3.2；p = 0.90）。在控制了性别、年龄、体重指数、骨折分类和并发症等潜在混杂变量后，我们发现骨折分类——特别是A1型（OR6.7[95%CI4.8至9.5]）、C1.3型（OR5.0[95%CI3.6至6.9]）和C3型（OR2.5[95%CI1.9至3.4]）——深部感染（OR10.5[95%CI4.2至26.5]；p<0.001）和浅表感染（OR2.4[95%CI1.4至4.4]；p = 0.003）与术后低位髌骨的发生相关，而性别、体重指数和年龄则无关。术后感染是与低位髌骨相关的唯一并发症。
本研究结果强调了外科医生对髌骨骨折后低位髌骨发生情况保持警惕的重要性。对于此处确定的特定骨折类型，鼓励外科医生积极探索并采用更合适的内固定技术。这样做可以有效降低术后低位髌骨的发生率，为患者带来更好的活动度和功能结果。
三级，治疗性研究。
