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

• Published in: Clinical orthopaedics and related research Vol. 469; no. 4; pp. 1154 - 1160
• Main Authors: Mullaji, Arun, Shetty, Gautam M.
• Format: Journal Article
• Language: English
• Published: New York Springer-Verlag 01-04-2011; Springer; Lippincott Williams & Wilkins Ovid Technologies
• Subjects: Aged; Aged, 80 and over; Ankle Joint - diagnostic imaging; Ankle Joint - physiopathology; Arthroplasty, Replacement, Hip - adverse effects; Biological and medical sciences; Biomechanical Phenomena; Clinical Research; Conservative Orthopedics; Diseases of the osteoarticular system; Female; Hip Joint - diagnostic imaging; Hip Joint - physiopathology; Humans; India; Knee; Knee Joint - diagnostic imaging; Knee Joint - physiopathology; Knee Joint - surgery; Male; Medical sciences; Medicine; Medicine & Public Health; Middle Aged; Orthopedic surgery; Orthopedics; Prospective Studies; Radiography; Range of Motion, Articular; Sports Medicine; Surgery; Surgery (general aspects). Transplantations, organ and tissue grafts. Graft diseases; Surgical Orthopedics; Treatment Outcome; Weight-Bearing; Limb Alignment; Varus Deformity; Valgus Knee; Mechanical Axis Deviation; Mechanical Axis; Total knee arthroplasty; Orthopedic surgery; Treatment; Lateral; Orthopedics
• ISSN: 0009-921X; 1528-1132
• DOI: 10.1007/s11999-010-1703-z

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.