No effect of obesity on limb and component alignment after computer-assisted total knee arthroplasty

• Limb and component alignment accuracy was checked after navigated TKA in the obese
• Limb and component alignment were measured on hip-to-ankle radiographs
• These were compared between obese and non-obese groups
• No significant difference in postoperative alignment was found between the groups
• Navigation will help achieve consistently accurate alignment in the obese

PurposeThis retrospective study aimed to determine if computer navigation provides consistent accuracy for limb and component alignment during TKA irrespective of body mass index (BMI) by comparing limb and component alignment and the outlier rates in obese versus non-obese individuals undergoing computer-assisted TKA.MethodsSix hundred and thirty-five computer assisted total knee arthroplasties (TKAs) performed in non-obese individuals (BMI < 30 kg/m2) were compared with 520 computer-assisted TKAs in obese individuals (BMI ≥ 30 kg/m2) for postoperative limb and component alignment using full length standing hip-to-ankle radiographs.ResultsNo significant difference in postoperative limb alignment (179.7° ± 1.7° vs 179.6° ± 1.8°), coronal femoral (90.2° ± 1.6° vs 89.8° ± 1.9°) and tibial component (90.2° ± 1.6° vs 90.3° ± 1.7°) alignment and outlier rates (6.2% vs 7.5%) was found between non-obese and obese individuals. Similarly, alignment and the outlier rates were similar when non-obese individuals and a subgroup of morbidly obese individuals (BMI > 40 kg/m2) were compared.ConclusionsComputer navigation can achieve excellent limb and component alignment irrespective of a patient's BMI. Although obesity may not be an indication per se for using computer navigation during TKA, it will help achieve consistently accurate limb and component alignment in obese patients.Level of EvidenceLevel II