Lower limb alignment and soft tissue balance are important factors affecting patient satisfaction, clinical functional outcome, and prosthetic long-term survival rate after total knee arthroplasty (TKA). Robot-assisted TKA (rTKA) has the advantages of achieving precise osteotomy and soft tissue balance. However, rTKA under the guidance of classic mechanical alignment principles does not significantly improve the functional outcome after operation. The new TKA alignment principles, such as kinematic alignment (KA) and functional alignment (FA), can better consider the patient’s own knee joint morphology and kinematic characteristics, which may help improve the clinical results of TKA. With the help of more objective and accurate soft tissue balance assessment tool such as pressure sensors, KA and FA have been proven to better achieve soft tissue balance. rTKA can achieve non-neutral alignment goals such as KA or FA more accurately and reproducibly. The use of these lower limb alignment and soft tissue balancing strategies will be expected to further increase the patients’ satisfaction rate after rTKA.
ObjectiveTo investigate the effectiveness of soft tissue balance technique by flexor pollicis longus (FPL) tendon transfer for Wassel Ⅳ-D thumb duplication in children. Methods A clinical data of 14 children with Wassel Ⅳ-D thumb duplication met the selection criteria between January 2017 and January 2021 was retrospectively analyzed. There were 5 boys and 9 girls with an average age of 21.6 months (range, 18-35 months). Ten cases were left hand deformity and 4 cases were right hand deformity. During operation, the radial thumb was excised, and the FPL tendon of the radial thumb was used to reconstruct the soft tissue balance of the ulnar thumb. Postoperative evaluation included the range of motion (ROM) of passive flexion and extension of the interphalangeal joint (IP) and metacarpophalangeal joint (MCP), the alignments of the IP and MCP, the percentage of the width of the nail plate and the circumference of the thumb at the level of the IP to contralateral thumb. Results All operations were completed successfully, and all incisions healed by first intention. The children were followed up 12-36 months (mean, 21.7 months). At last follow-up, the ROM of passive flexion and the deviation of the IP, and the deviation of the MCP significantly improved when compared with those before operation (P<0.05); the ROM of passive extension of the IP and the ROM of passive flexion of the MCP did not significantly improve when compared with those before operation (P>0.05). The ROMs of passive extension of the MCP were 0° before and after operation. The width of the nail plate was 76.6%±4.1% of the unaffected side, and the circumference of the thumb at the level of the IP was 92.0%±9.1% of the unaffected side. ConclusionThe soft tissue balance technique by FPL tendon trasfer can effectively correct the alignment of the Wassel Ⅳ-D thumb duplication in children, and maintain the correction effect effectively, but further follow-up and comprehensive evaluation are needed to investigate the long-term effectiveness.