The advantage of navigation for knee with lateral femoral bowing in total knee arthroplasty

Abstract

Purpose: We have analyzed the surgical outcomes of primary total knee arthroplasty (TKA) using computer-assisted (CA) navigation in terms of postoperative coronal alignment depending on preoperative lateral femoral bowing. Methods: We conducted a retrospective study of patients who have undergone navigated primary TKA from January 2016 through January 2020. Two hundred and ninety-nine cases with lateral femoral bowing of 3° or less were assigned to group 1, 95 cases of lateral femoral bowing between 3° and 5° were assigned to group 2, and 89 cases with lateral femoral bowing of more than 5° were assigned to group 3. The postoperative mechanical hip–knee–ankle (mHKA) angle was measured from scanograms, which were taken 3 months after surgery. The appropriate range of coronal alignment was set as 0 ± 3°. Results: The number of outliers of mHKA occurred was 31 cases (10.4%) in group 1, 17 cases (17.9%) in group 2, and 17 cases (19.1%) in group 3. There was a significant correlation between the degree of lateral femoral bowing and the occurrence rate of mHKA outliers. Multiple variables logistic regression analysis showed occurrence rate of outliers in group 3 to be 2.04 times higher than group 1. After adjusting the patient’s age, sex, body mass index, and preoperative HKA deformity, the occurrence rate of outliers in group 3 was still 1.96 times higher than group 1. Conclusion: The benefit of CA navigation during TKA in obtaining coronal alignment within 0 ± 3° may be lessened when the preoperative lateral femoral bowing is severely advanced.

Navigation makes more accurate femur resection compared to conventional total knee arthroplasty in lateral femoral bowing greater than 5º

“…Theoretically, in navigation-assisted TKA, since the femoral axis is calculated based on 2 points after the registration of the patient femoral head and distal femoral anatomy, it is not affected by the bowing that occurs in the femoral shaft. [ 7 ] Also, since the insertion of the IM rod is not necessary, no error occurs during insertion. For this reason, we think that constant distal femoral cutting is possible regardless of the degree of lateral femoral bending in navigation TKA.…”

“…The allowable ranges of these values were set as 0° ± 3° and 90° ± 3°, respectively. [7,16] 7. Statistical analysis SPSS version 18.0 (SPSS Inc., Chicago, IL, USA) was used for all statistical analyses.…”

“…[ 5 , 6 ] Another option is utilizing navigation for greater accuracy. [ 7 ] Navigation has been developed and used to obtain a coronal axis within 0° ± 3°. In many studies, it is known that it is more helpful in obtaining an appropriate axis than conventional total knee arthroplasty (TKA).…”

“…In many studies, it is known that it is more helpful in obtaining an appropriate axis than conventional total knee arthroplasty (TKA). [ 2 , 7 , 8 ] If the navigation-assisted technique is used, the femoral axis is determined using the femoral head and distal femoral anatomy; so, it is not affected by the lateral femoral bowing of the diaphysis. Therefore, even without using an IM rod, it is possible to have a constant femoral resection.…”

“…Therefore, even without using an IM rod, it is possible to have a constant femoral resection. [ 7 ] However, navigation has the disadvantage that errors may occur during registration. [ 9 ] Therefore, there are many disagreements about the merits of navigation in TKA.…”