Gursoy Safa, Perry Allison K, Dandu Navya, Singh Harsh, Vadhera Amar S, Yanke Adam, LaPrade Robert F, Chahla Jorge
Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, Illinois, USA.
Twin Cities Orthopedics, Edina, Minnesota, USA.
Orthop J Sports Med. 2022 Jun 6;10(6):23259671221100216. doi: 10.1177/23259671221100216. eCollection 2022 Jun.
The contribution of anterior cruciate ligament (ACL) injury to lateral instability under varus stress, particularly compared with posterolateral structures, is not well known.
To investigate the effect of sectioning the ACL and posterolateral knee structures on lateral compartment gapping under varus stress.
Controlled laboratory study.
Fourteen nonpaired cadaveric knees were randomized to 1 of 2 groups: sequential sectioning of the ACL, fibular collateral ligament (FCL), popliteus tendon (PLT), and popliteofibular ligament (PFL) (ACL-first group) or sequential sectioning of the FCL, PLT, PFL, and ACL (FCL-first group). Knees were loaded onto a custom jig at a 20° flexion angle. A standardized 12-N·m varus moment was applied to each specimen in the intact state and after each randomized sequential-sectioning state. Lateral compartment opening was measured on radiographs to assess the contribution to the increase in the lateral gap caused by resecting the respective structure. The distance was measured by 3 observers on 15 images (5 testing states each imaged 3 times) per specimen, for a total of 210 radiographs. The articular cartilage surfaces were not included in the measurements.
The mean increase in lateral opening after sectioning all structures (ACL and posterolateral corner) was 4.6 ± 1.8 mm (range, 1.9-7.7 mm). The ACL and FCL sectioning contributed the most to lateral knee opening (1.3 ± 0.6 and 2.2 ± 1.3 mm, respectively). In both groups, lateral gapping >3 mm was achieved only after both the ACL and FCL were sectioned. All comparisons of increased mean gapping distances demonstrated a significant difference with subsequent sequential sectioning of structures, except comparisons between the FCL and PLT and the PLT and PFL. When considering the effect of the ACL on lateral opening, no significant difference was found between sectioning the ACL first or FCL first ( = .387).
ACL deficiency significantly increased lateral opening under varus stress, regardless of the sequence of injury. The effect of injury to the ACL in addition to the lateral structures should be considered when using varus stress radiographs to evaluate knee injuries.
With the current findings, understanding the effect of ACL and posterolateral corner injuries on lateral gapping under varus stress can aid in correctly diagnosing knee injuries and determining appropriate treatment plans.
前交叉韧带（ACL）损伤对内翻应力下外侧不稳定的影响，尤其是与后外侧结构相比，目前尚不清楚。
研究切断ACL和膝关节后外侧结构对内翻应力下外侧间隙增宽的影响。
对照实验室研究。
14个非配对尸体膝关节随机分为2组中的1组：依次切断ACL、腓侧副韧带（FCL）、腘肌腱（PLT）和腘腓韧带（PFL）（ACL先切断组）或依次切断FCL、PLT、PFL和ACL（FCL先切断组）。膝关节在20°屈曲角度加载到定制夹具上。在完整状态下以及每次随机顺序切断状态后，对每个标本施加标准化的12 N·m内翻力矩。在X线片上测量外侧间隙开口，以评估切除相应结构对外侧间隙增加的影响。由3名观察者在每个标本的15张图像（5种测试状态，每种状态成像3次）上测量距离，总共210张X线片。测量不包括关节软骨表面。
切断所有结构（ACL和后外侧角）后外侧开口的平均增加量为4.6±1.8 mm（范围1.9 - 7.7 mm）。ACL和FCL切断对膝关节外侧开口的贡献最大（分别为1.3±0.6和2.2±1.3 mm）。在两组中，仅在切断ACL和FCL后才实现外侧间隙增宽>3 mm。平均间隙增加距离的所有比较显示，与随后依次切断结构存在显著差异，但FCL与PLT以及PLT与PFL之间的比较除外。在考虑ACL对外侧开口的影响时，先切断ACL或先切断FCL之间未发现显著差异（P = 0.387）。
无论损伤顺序如何，ACL缺失均会显著增加内翻应力下的外侧开口。在使用内翻应力X线片评估膝关节损伤时，应考虑除外侧结构损伤外ACL损伤的影响。
基于当前研究结果，了解ACL和后外侧角损伤对内翻应力下外侧间隙增宽的影响有助于正确诊断膝关节损伤并确定合适的治疗方案。
