Joint Replacement Institute, St Vincent Medical Center, 2200 West Third Street, Suite 400, Los Angeles, CA, 90057, USA.
Clin Orthop Relat Res. 2014 Feb;472(2):489-96. doi: 10.1007/s11999-013-3074-8.
Impingement of the femoral neck with the acetabular component after metal-on-metal hip resurfacing arthroplasty (HRA) is a possible cause of edge loading and accelerated bearing wear. No attempt has been made to correlate radiographic impingement signs and blood metal ion levels.
QUESTIONS/PURPOSES: We (1) compared serum cobalt (CoS) and chromium (CrS) concentrations between patients with and without radiographic impingement signs treated with unilateral HRA, (2) determined whether divot depth on the femoral neck correlated with CoS and CrS, and (3) assessed the predictive value of radiographic impingement signs for high levels of CoS and CrS.
A retrospective radiographic review of 141 patients with CoS and CrS analyses yielded 21 patients with and 120 without radiographic impingement signs (controls). Radiographic measurements included divot depth and orientation of the acetabular component to compute the contact patch to rim distance, a measure of functional head coverage. We defined a patient as having radiographic impingement signs if a remodeling of the femoral neck cortex showed a depression matching the predicted path of an impinging acetabular component. CoS and CrS were analyzed by inductively coupled plasma mass spectrometry and the radiographs were taken within 12 months of the last blood draw.
Median CoS and CrS were greater in the impingement group than in controls in patients with less than 10-mm contact patch to rim distances. Divot depth did not correlate with CoS or CrS. In predicting elevated ion levels (≥ 7 μg/L), the presence of a radiographic impingement sign showed a sensitivity of 50% for CoS and 33% for CrS and a specificity of 87% for both CoS and CrS.
Radiographic impingement signs influenced CoS and CrS only when the functional head coverage was insufficient due to poor socket positioning. Radiographic impingement signs alone were not a good predictor of elevated metal ion levels.
金属对金属髋关节表面置换术后股骨颈与髋臼组件的撞击是边缘负荷和加速轴承磨损的一个可能原因。尚未尝试将影像学撞击迹象与血液金属离子水平相关联。
问题/目的：我们（1）比较了单侧髋关节表面置换术后有和无影像学撞击迹象患者的血清钴（CoS）和铬（CrS）浓度，（2）确定了股骨颈上的凹陷深度与 CoS 和 CrS 的相关性，（3）评估了影像学撞击迹象对高 CoS 和 CrS 的预测价值。
对 141 例 CoS 和 CrS 分析患者的回顾性影像学检查，其中 21 例有影像学撞击迹象，120 例无影像学撞击迹象（对照组）。影像学测量包括凹陷深度和髋臼组件的方向，以计算接触斑到边缘的距离，这是功能头覆盖的一个衡量指标。如果股骨颈皮质的重塑显示出与撞击髋臼组件的预测路径相匹配的凹陷，则将患者定义为具有影像学撞击迹象。CoS 和 CrS 通过电感耦合等离子体质谱法进行分析，并且在最后一次采血后 12 个月内拍摄 X 光片。
在接触斑到边缘距离小于 10mm 的患者中，撞击组的 CoS 和 CrS 中位数均高于对照组。凹陷深度与 CoS 或 CrS 均无相关性。在预测离子水平升高（≥7μg/L）时，影像学撞击迹象对 CoS 的敏感性为 50%，对 CrS 的敏感性为 33%，CoS 和 CrS 的特异性均为 87%。
只有当由于髋臼位置不佳导致功能头覆盖不足时，影像学撞击迹象才会影响 CoS 和 CrS。单独的影像学撞击迹象不是金属离子水平升高的良好预测指标。
