Berber Reshid, Khoo Michael, Cook Erica, Guppy Andrew, Hua Jia, Miles Jonathan, Carrington Richard, Skinner John, Hart Alister
Royal National Orthopaedic Hospital, Brockley Hill , Stanmore, Middlesex.
Acta Orthop. 2015 Jun;86(3):351-7. doi: 10.3109/17453674.2015.1006981. Epub 2015 Jan 14.
Muscle atrophy is seen in patients with metal-on-metal (MOM) hip implants, probably because of inflammatory destruction of the musculo-tendon junction. However, like pseudotumors, it is unclear when atrophy occurs and whether it progresses with time. Our objective was to determine whether muscle atrophy associated with MOM hip implants progresses with time.
We retrospectively reviewed 74 hips in 56 patients (32 of them women) using serial MRI. Median age was 59 (23-83) years. The median time post-implantation was 83 (35-142) months, and the median interval between scans was 11 months. Hip muscles were scored using the Pfirrmann system. The mean scores for muscle atrophy were compared between the first and second MRI scans. Blood cobalt and chromium concentrations were determined.
The median blood cobalt was 6.84 (0.24-90) ppb and median chromium level was 4.42 (0.20-45) ppb. The median Oxford hip score was 34 (5-48). The change in the gluteus minimus mean atrophy score between first and second MRI was 0.12 (p = 0.002). Mean change in the gluteus medius posterior portion (unaffected by surgical approach) was 0.08 (p = 0.01) and mean change in the inferior portion was 0.10 (p = 0.05). Mean pseudotumor grade increased by 0.18 (p = 0.02).
Worsening muscle atrophy and worsening pseudotumor grade occur over a 1-year period in a substantial proportion of patients with MOM hip implants. Serial MRI helps to identify those patients who are at risk of developing worsening soft-tissue pathology. These patients should be considered for revision surgery before irreversible muscle destruction occurs.
金属对金属（MOM）髋关节置换患者中可见肌肉萎缩，可能是由于肌腱结合处的炎性破坏所致。然而，与假肿瘤一样，目前尚不清楚萎缩何时发生以及是否会随时间进展。我们的目的是确定与MOM髋关节置换相关的肌肉萎缩是否会随时间进展。
我们对56例患者（其中32例为女性）的74个髋关节进行了回顾性研究，采用系列磁共振成像（MRI）。中位年龄为59（23 - 83）岁。植入后的中位时间为83（35 - 142）个月，扫描之间的中位间隔为11个月。采用Pfirrmann系统对髋部肌肉进行评分。比较首次和第二次MRI扫描时肌肉萎缩的平均评分。测定血液中钴和铬的浓度。
血液中钴的中位浓度为6.84（0.24 - 90）ppb，铬的中位水平为4.42（0.20 - 45）ppb。牛津髋关节评分的中位数为34（5 - 48）。首次和第二次MRI之间臀小肌平均萎缩评分的变化为0.12（p = 0.002）。臀中肌后部（不受手术入路影响）的平均变化为0.08（p = 0.01），下部的平均变化为0.10（p = 0.05）。假肿瘤平均分级增加0.18（p = 0.02）。
在相当一部分MOM髋关节置换患者中，肌肉萎缩和假肿瘤分级在1年时间内会恶化。系列MRI有助于识别那些软组织病变可能恶化的患者。在不可逆的肌肉破坏发生之前，应考虑对这些患者进行翻修手术。
