Miami Hand and Upper Extremity Institute, Miami, FL.
Miami Hand and Upper Extremity Institute, Miami, FL.
J Hand Surg Am. 2021 Sep;46(9):816.e1-816.e7. doi: 10.1016/j.jhsa.2020.12.014. Epub 2021 Mar 13.
A complete ulnar head replacement may be indicated in cases of distal radial ulnar joint (DRUJ) dysfunction to address bony pathology in lieu of using a constrained total DRUJ prosthesis. Complete ulnar head implants are simple, but they may be unstable if soft tissue tension is not adequately restored. We hypothesized that incorporating an increased offset in the complete ulnar head replacement would lead to increased tension on the distal oblique interosseous ligament, increased contact force at the DRUJ, and improved joint stability.
Using a specially designed jig, we measured instability by comparing displacement under load (stiffness) of the DRUJ in 10 cadaveric specimens under 4 different conditions: (1) intact, (2) native head after excision of the triangular fibrocartilage complex, (3) replacement of the ulnar head with a standard offset ulnar head, and (4) replacement of the ulnar head with an increased offset ulnar head. No soft tissue repair was done. We measured anteroposterior displacement under load with maximum translation of 10 mm or maximum loads of 50 N. We tested all specimens with the forearm positioned in neutral, supination, and pronation.
Excising the triangular fibrocartilage complex decreased the average stiffness of the DRUJ to 46% of the intact state, creating a simulated state of DRUJ instability. Replacing the ulnar head with the standard offset head increased average stiffness to 54% of the intact state. Increasing the ulnar head offset with the simulated total ulnar head replacement increased average stiffness to 77% of the intact state.
An increased offset ulnar head replacement improves DRUJ stability compared with a standard anatomic offset ulnar head replacement.
Understanding DRUJ morphology and offset is important in the treatment of DRUJ arthritis and instability.
在桡尺远侧关节（DRUJ）功能障碍的情况下，完全切除尺骨头可能是一种治疗骨性病变的方法，而不是使用约束性 DRUJ 假体。完全切除尺骨头的植入物很简单，但如果不能充分恢复软组织张力，可能会不稳定。我们假设在完全切除尺骨头的植入物中增加偏心距会导致远端斜骨间韧带张力增加，DRUJ 的接触力增加，并改善关节稳定性。
使用专门设计的夹具，我们通过比较 10 个尸体标本在 4 种不同情况下（1）完整，（2）切除三角纤维软骨复合体后的原生头，（3）用标准偏心距尺骨头置换尺骨头，（4）用增加偏心距尺骨头置换尺骨头）在负载下（刚度）DRUJ 的不稳定性。未进行任何软组织修复。我们测量了在加载下的前后位移，最大平移 10mm 或最大负载 50N。我们将所有标本在前臂置于中立位、旋后位和旋前位进行测试。
切除三角纤维软骨复合体使 DRUJ 的平均刚度降低至完整状态的 46%，模拟 DRUJ 不稳定状态。用标准偏心距尺骨头置换尺骨头使平均刚度增加到完整状态的 54%。用模拟总尺骨头置换增加尺骨头偏心距使平均刚度增加到完整状态的 77%。
与标准解剖偏心距尺骨头置换相比，增加偏心距尺骨头置换可改善 DRUJ 稳定性。
了解 DRUJ 形态和偏心距对 DRUJ 关节炎和不稳定的治疗很重要。
