Constraint in Primary Total Knee Arthroplasty

Surgical Technique: Computer-assisted Sliding Medial Condylar Osteotomy to Achieve Gap Balance in Varus Knees During TKA

“…For surgeons balancing the flexion gap by placing the AP cutting block parallel to the tibial cut, it would require internal rotation of the femoral component to balance the flexion gap medially, with possible adverse consequences for patellar tracking [8]. Lastly, constrained implants in such complex varus deformities have been reported to give good short-and intermediate-term functional outcomes and survival rates after primary TKA [3,9,11,13,14]. However, in view of the prohibitive cost involved and complexity of revision surgery if required, we reserve constraint implants only for arthritic knees with complex deformities associated with substantial instability, especially in elderly, sedentary patients [9,14].…”

“…Lastly, constrained implants in such complex varus deformities have been reported to give good short-and intermediate-term functional outcomes and survival rates after primary TKA [3,9,11,13,14]. However, in view of the prohibitive cost involved and complexity of revision surgery if required, we reserve constraint implants only for arthritic knees with complex deformities associated with substantial instability, especially in elderly, sedentary patients [9,14]. These risks are mitigated by osteotomizing the medial condyle as the superficial MCL maintains its integrity.…”

“…This carries the risk of mediolateral instability (if there is overrelease or inadvertent total detachment of the superficial MCL) and results in the flexion gap exceeding the extension gap, both of which increase the potential need for a constrained prosthesis [14]. On the other hand, leaving the knee with mediolateral imbalance due to inadequate medial release may lead to long-term instability, polyethylene wear, and potential loosening of tibial component from persistent adductor thrust [22].…”

Constraints in total knee arthroplasty: current status and review of literature

“…The trade-off of constrained prostheses is that at the expense of increased stability, it substantially increase stresses across implant-cement-bone interface, which might lead to early loosening and failure. 16,36 Also increase stresses on constraint mechanism, i.e. hinge of RHK, cam and post of CCK, is of concern for their early mechanical failure.…”

“…RHK is considered for grossly unstable knee due to complete absence of medial and lateral collateral ligaments, poor soft tissue envelope, severe bone loss, and severe varus-valgus and flexion contracture. [13][14][15][16] It is also considered utilitarian for extensor mechanism incompetency, distal femoral or proximal tibial defect resulting from a tumour lesion or mechanical problem, or a comminuted fracture or malunion of the distal femur in the elderly subjects. 17,18 Neuropathic joints, elderly people with poor soft tissue envelope are relative indications for their use.…”