Joint line restoration during revision total knee arthroplasty: an accurate and reliable method

Abstract

During revision total knee arthroplasty, the joint line is frequently malpositioned, due to the disappearance of the anatomical landmarks following previous interventions. This leads to decreased clinical outcome and increased risk of re-intervention. Many methods have been proposed to restore the joint line, but none of them has shown itself to be reliable. We describe an accurate and precise method to localize the exact position of the joint line which guarantees a better clinical knee score. The adductor tubercle (AT) is recognized to be the most reliable landmark used to localize the knee joint line (JL). The distance from the AT to the JL on antero-posterior radiographs (ATJL) and the femoral diameter (FD) on true lateral views were measured on 200 randomly selected normal knees. These measurements were tested for intra- and inter-observer differences. Then, the relationship between these two measurements was studied. A significant correlation and linear regression between FD and ATJL was found (p < 0.001), making the adductor tubercle a valid landmark to accurately position the prosthetic joint within 4 mm from the normal position. No significant difference was noted in the intra and inter-observer measurements (F test not significant). Sex was found to be an intervening variable (p ˂ 0.001). The correlation and regression between ATJL and FD had to be adjusted accordingly. Once the ATJL was determined preoperatively, the JL level is found during surgery by using a caliper that is held on the easily palpable AT. Knowing the femoral diameter, we can easily locate the joint line level surgically, using the adductor tubercle as a landmark. This method leads to better clinical outcomes and a reduced risk of re-intervention following revision total knee arthroplasty.

Keywords: Adductor tubercle; Arthroplasty; Joint line; Knee; Revision prosthesis.

Fig. 1

Graph showing the linear regression of ATJL in function of FD in female patients: ATJL = 0.657 FD + 27.211. The coefficient of determination R² is also mentioned

Fig. 2

Graph showing the linear regression of ATJL in function of FD in male patients: ATJL = 0.824 FD + 25.808. The coefficient of determination R² is also mentioned

Fig. 3

Per-operative ATJL determination: per-operative determination of the adductor tubercle during a revision total knee arthroplasty, and the measurement taken from this landmark to the distal femoral cut. The corresponding measurement will be subtracted from the calculated ATJL, in order to find the corresponding thickness of the prosthesis and augments to be inserted

Fig. 4

The two radiologic measurements: on the AP view, the distance ATJL from the adductor tubercle to the joint line was measured. On the lateral view, the femoral diameter FD was measured at the level of the flare of the posterior condyle