Caron M, Kron E, Saltrick K R
American College of Foot and Ankle Surgeons, Weston, Florida, USA.
Clin Podiatr Med Surg. 1999 Apr;16(2):337-61.
The technical aspects of fusion of the rheumatoid ankle do not deviate from those in the post-traumatic or osteoarthritic ankle. Screw fixation can usually be achieved, and rarely is fixation failure a problem in rheumatoid ankle arthrodesis. If fixation is difficult because of deformity or bone quality, external fixation or locking intramedullary nails should be used. The placement of cannulated screws and adequacy of screw fixation has not been a problem (Fig. 13). Screw fixation provides compression and prevents rotation. The surgeon, however, needs to be assured that no screws invade the subtalar joint and that all threads are beyond the arthrodesis site. A washer may be necessary for further stability if this screw is not inserted at too great an angle. The authors have found that troughing out of the cortical surface of the tibia with a power bur aids in screw insertion. Not only does the trough act as a countersink, but it also provides a path for screw insertion and prevents palpable screw irritation. Malalignment is unforgiving. The foot must be placed neutral to dorsiflexion and plantarflexion. Equinus positioning places added stress on the tibia and a back-knee gait occurs. Approximately 5 degrees of valgus is recommended, and varus positioning is unforgiving. Internal and external rotation is determined by the position of the contralateral extremity. Nonunion does not seem to be a problem with rigid internal fixation to any greater degree in patients with RA. Despite this, patients may continue to have pain despite solid fusion, which can be caused by incomplete correction of deformity, painful internal fixation, or adjacent joint pathology. Additionally, patients may experience supramalleolar pain above the fusion site consistent with tibial stress fracture, which is more common if the subtalar or midtarsal joint is rigid or if the patient is obese. A rocker sole shoe with impact-absorbing soles used after brief periods of guarded mobilization in a removable walking cast alleviates this stress on the tibia. Neurovascular insult can be avoided with careful dissection direct to bone, incisions placed in nerve-free zones, and avoidance of plunging deep posteriorly-medially and anteriorly when dissecting and resecting surfaces. Arthrodesis of the tibiotalar joint in the patient with RA should be performed to relieve severe pain caused by advanced arthrosis. Achieving a solid arthrodesis does not seem to be a problem and provides the patient with pain relief; however, marked improvement in patient function and level of activity remains limited by the nature of RA and adjacent joint involvement.
类风湿性踝关节融合的技术方面与创伤后或骨关节炎性踝关节并无差异。通常能够实现螺钉固定，在类风湿性踝关节融合术中，固定失败很少成为问题。如果因畸形或骨质问题导致固定困难，应使用外固定或锁定髓内钉。空心螺钉的置入及螺钉固定的充分性并非问题（图13）。螺钉固定可提供加压并防止旋转。然而，外科医生需确保没有螺钉侵入距下关节，且所有螺纹均超出融合部位。如果螺钉置入角度不是过大，为获得进一步稳定性可能需要垫圈。作者发现，使用动力磨钻在胫骨皮质表面开槽有助于螺钉置入。该槽不仅可作为埋头孔，还能为螺钉置入提供路径并防止可触及的螺钉刺激。对线不良是不可原谅的。足部必须置于背屈和跖屈中立位。马蹄足位会给胫骨增加额外压力，并出现屈膝步态。建议有大约5度的外翻，内翻位是不可接受的。内外旋由对侧肢体的位置决定。在类风湿性关节炎患者中，坚固的内固定似乎在很大程度上不会导致骨不连问题。尽管如此，即使融合牢固，患者仍可能持续疼痛，这可能是由于畸形矫正不完全、内固定疼痛或相邻关节病变所致。此外，患者可能会在融合部位上方出现内踝上疼痛，与胫骨应力性骨折相符，如果距下或中跗关节僵硬或患者肥胖，这种情况更常见。在可拆除行走石膏中进行短期保护性活动后，使用带有减震鞋底的摇摆底鞋可减轻胫骨上的这种压力。通过直接仔细解剖至骨、在无神经区域放置切口以及在解剖和切除表面时避免向深部后内侧和前侧深入，可以避免神经血管损伤。类风湿性关节炎患者的胫距关节融合术应旨在缓解晚期关节病引起的严重疼痛。实现牢固的融合似乎不是问题，可为患者缓解疼痛；然而，患者功能和活动水平的显著改善仍受类风湿性关节炎的性质和相邻关节受累情况的限制。
