Hindfoot alignment and TKR

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Persistent Hindfoot Valgus Causes Lateral Deviation of Weightbearing Axis after Total Knee Arthroplasty.

Mullaji AShetty GM.

Department of Orthopaedic Surgery, Breach Candy Hospital, Mumbai, India,

Abstract

BACKGROUND: The weightbearing axis of the limb goes from the pelvis to the ground and includes the hindfoot. However, the influence of hindfoot alignment on mechanical axis and overall limb alignment after TKA is unclear.

QUESTIONS/PURPOSES: We therefore addressed the following questions: (1) Does hindfoot alignment change after TKA for knee osteoarthritis? (2) What factors influence hindfoot alignment after TKA? (3) Does deviation of the mechanical axis from the center of the knee vary when the hindfoot is considered (ground mechanical axis) as compared with when it is not (conventional mechanical axis) after TKA?

PATIENTS AND METHODS: We prospectively reviewed the radiographs of 125 patients who underwent 165 TKAs. We evaluated the preoperative and postoperative hip-knee-ankle (HKA) angle, conventional mechanical axis deviation, ground mechanical axis (mechanical axis which included the hindfoot) deviation, and tibiocalcaneal angle.

RESULTS: The preoperative hindfoot valgus alignment decreased after TKA. Preoperative hindfoot alignment was the only factor that influenced hindfoot alignment after TKA. The conventional mechanical axis showed less deviation from the center of the knee when compared with ground mechanical axis which showed lateral deviation after TKA. Despite limb alignment being restored to within 3° of neutral of the conventional mechanical axis after TKA, 29% of limbs had a postoperative ground mechanical axis deviation of 10 mm or greater.

CONCLUSIONS: Accurate restoration of limb alignment after TKA may be associated with persistent hindfoot valgus alignment with the ground mechanical axis passing lateral to the center of the knee. This could have implications on long-term survival of the implant owing to possible excessive loading laterally and needs further investigation.

Clin Orthop Relat Res. 2010 Dec 1.

http://www.springerlink.com/content/b4603426230t8w43/

Comments

  1. gautam shetty says

    BY THE AUTHOR: This study finds that the weight bearing axis of the lower limb which includes the hindfoot falls lateral to the centre of the knee joint even if the mechanical axis of the limb (hip-knee-ankle angle) is restored to 180 degrees after TKA. This is due to the presence of hindfoot valgus seen in patients with knee osteoarthritis which persists even after TKA
    This needs further evaluation for implications on long term survival of the implant in patients where the weight bearing axis fall lateral to the knee centre after TKA. This also highlights the need to tailor your limb alignment during TKA based on the amount of hindfoot valgus inorder to bring the weight bearing axis as close to the knee centre as possible

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