Tibial Tubercle-Trochlear Groove Distance Influences Patellar Tilt After Total Knee Arthroplasty

BACKGROUND

Tibial tubercle-trochlear groove (TT-TG) distance is associated with a greater risk of recurrent patellar dislocation in young, active patients. However, the effect of TT-TG distance after total knee arthroplasty (TKA) has not been investigated. The purpose is to analyze the effect of TT-TG distance and component rotation on patellar tilt and patellar shift after TKA.

METHODS

After TKA, axial computed tomography scans and axial radiograph were taken in 115 consecutive knees. TT-TG distance was measured between the most anterior point of the tibial tuberosity and the deepest point of the femoral component relative to a line connecting the anterior condyles. Femoral and tibial component rotation was measured relative to the femoral and tibial rotational axis, respectively. Pearson correlation coefficients were calculated.

RESULTS

TT-TG distance had a significant correlation with patellar tilt in extension (R = 0.220, P = .018), patellar tilt in flexion (R = 0.438, P < .001), and patellar shift (R = 0.330, P < .001). Tibial component rotation had a significant correlation with patellar tilt in flexion (R = -0.251, P = .007) and patellar shift (R = -0.360, P < .001). Femoral component rotation had no significant correlations. Tibial component rotation had a significant correlation with TT-TG distance (R = -0.573, P < .001), whereas femoral component rotation had no correlation (P = .192).

CONCLUSION

TT-TG distance had a significant correlation with patellar tilt and patellar shift. Surgeons need to understand the factors affecting TT-TG distance and to pay attention to avoiding excessive TT-TG distance after TKA.

Preoperative Radiological Parameters Predicting the Need for Lateral Retinacular Release in Total Knee Arthroplasty

BACKGROUND

Proper patellar tracking is essential for well-functioning total knee arthroplasty (TKA). Besides implanting components in the correct position and rotation, balancing parapatellar soft tissues is also important in aiding normal patellar tracking. Patellar maltracking during TKA can be improved by lateral retinacular release (LRR).

METHODS

We studied the incidence of LRR in consecutive primary TKA with nonresurfaced patella and posterior-stabilized implant design. We analyzed data from 250 consecutive primary TKAs (212 patients) from January 2016 to May 2016. We evaluated the preoperative radiological parameters like patellar tilt, patellar shift, patellar morphology, Insall-Salvati ratio, femoro-tibial angle, distal femoral valgus angle, and proximal tibia varus angle which predict the need for LRR during TKA. We used multivariate regression analysis to find the association of individual radiological parameters and the LRR.

RESULTS

The need for LRR is significantly associated with preoperative radiological parameters like patellar shift and patellar tilt (P < .001). Compared to the nonreleased group, the adjusted odds of LRR were greater for morphological parameters like Wiberg type 3 patella (odds ratio [OR] 17.45, 95% confidence interval [CI] 7.21-42.20), lateral facet thinning (OR 4.38, 95% CI 2.37-8.07), lateral patellofemoral arthritis (OR 14.36, 95% CI 6.82-30.23), and coronal valgus deformity (OR 4.95, 95% CI 1.60-10.68).

CONCLUSION

Preoperative assessment of these radiological parameters in the axial view implies a high chance of tight lateral retinacular structures. This helps in identifying patients who have a higher likelihood for patellar maltracking during TKA. Appropriate LRR helps to provide better patellar tracking post TKA.

Effect of Patellar Resurfacing on Patellofemoral Crepitus in Posterior-Stabilized Total Knee Arthroplasty

BACKGROUND

Patellofemoral crepitus (PC) is a complication of total knee arthroplasty (TKA). Although patellar resurfacing (PR) directly influences the kinematics of the patellofemoral joint, the influence of PR on PC is unclear. The purpose of this study was to investigate the influence of PR on the incidence of PC.

METHODS

This study included 84 knees from 69 patients who underwent TKA using the Vanguard Complete Total Knee System, with or without PR (n = 42 each). Clinical evaluation of the incidence of PC; Knee Society Score; and radiographic measurements of patellar tilt, patellar distance, patellar shift, Insall-Salvati ratio, patellar flexion, femorotibial angle; and rotation of the femoral component was performed. Parameters were evaluated preoperatively and at postoperative months 2, 6, 12, and 24. Logistic regression analysis was conducted to investigate the effect of PR on the risk of PC.

RESULTS

The incidence of PC was significantly higher in the non-PR group than the PR group (33.3% vs 4.8%). The knees of the PR group displayed a significantly increased patellar tilt, medially shifted patella, and decreased patella flexion angle compared with those of the non-PR group. There were no significant differences in the other radiographic parameters or Knee Society Score. The absence of PR was associated with a much higher risk of PC (odds ratio, 10.37; 95% confidence interval, 2.18-10.37).

CONCLUSION

PR may decrease the incidence of PC by increasing the patellar tilt and medial shift and positioning the patella more closely parallel to the femur. PR is recommended during TKA with this prosthesis.