Intraoperative morphometric measurement of distal femur dimensions and correlation with implant sizing in female total knee arthroplasty patients

• Main Author: Radhakrishnan, Sanjeevan
• Format: Thesis
• Language: English
• Published: 2018
• Subjects: RD Surgery
• Online Access: http://eprints.usm.my/57607/1/Sanjeevan%20AL%20Radhakrishnan%20-%20e.pdf; http://eprints.usm.my/57607/

Accurate implant sizing is one of the major determinants in defining the success of total knee arthroplasty. TKA implants currently in used are based on Caucasian knee morphometry which is well documented to be larger than Asian knees. The significant clinical implication of implant mismatch has led researches to greatly delve into this field of study worldwide. With regards to sizing, implant mismatch tends to be more evident in the female population. This study was designed to evaluate the distal femur dimensions of female patients who underwent TKA in our institution and to compare them with the current prosthetic system in use. Total of 101 female patients (105 knees) who underwent TKA were recruited in this study. Intraoperatively, the AP dimensions (medial and lateral condyles) and mediolateral (ML) width were measured. Known dimension of the femoral component of the prosthetic knee system currently in use were compared with the morphological data. The average femoral component overhang was 2.11mm (SD 3.94mm). There was significant difference between the mean ML width of the resected femur and the femoral component (p<0.01). Analysis also revealed a significant positive and weak relationship between both, AP (medial and lateral) and ML dimension. The aspect ratio for the morphological data showed a larger ratio for smaller knees and inversely a smaller ratio for larger knees. Although the aspect ratio of the morphological data were generally smaller than the implant aspect ratio, the trend of change in the aspect ratios of the initial five sizes of implant were seen to follow the morphological data. However, the larger implant sizes showed little change in its aspect ratio. In other words, the implant ML overhang is expected to be more pronounced in the larger knees. Implants should be designed based on the morphological data of the local population. Implant manufactures should tailor them to accommodate a smaller change in ML width for an increment in the AP length and provide several ML widths for one AP length to obtain a better fitting prosthesis hence curbing the problem of ML overhang.