Patellar Impingement on Tibial Polyethylene after Primary Total Knee Arthroplasty without Patellar Resurfacing.

Patellar impingement on tibial polyethylene (PIP) is one potential complication of total knee arthroplasty (TKA). When PIP occurs, it is often related to inaccurate restoration of the joint line or due to soft-tissue contracture. We investigated the prevalence and etiology of PIP in Asian patients with deeply flexed knees following posterior stabilized (PS)-TKA. We retrospectively reviewed 54 patients (65 knees) with PIP after primary PS-TKAs without patellar resurfacing performed between 2008 and 2011. These patients were compared with a group of 124 patients (130 knees) without PIP matched for age, sex, and body mass index (BMI). The minimum follow-up was 5 years (range, 5-8.1 years). Patients were evaluated by blinded, independent observers using the Oxford knee score, the Waters score, and radiographic parameters. Impingement between the patella and the tibial polyethylene had a mean onset of 13.5 months after PS-TKA. The development of PIP was significantly associated with change in patellar tendon length (odds ratio [OR] = 11.4, 95% confidence interval [CI]: 11.2-11.6%), shorter postoperative patellar tendon length (OR = 2.1, 95% CI: 1.8-2.5%), change in the Insall-Salvati ratio (OR = 0.9, 95% CI: 0.8-1.0%), and joint line elevation (OR = 5.3, 95% CI: 4.8-5.8%) on multiple logistic regression analysis. Our findings reinforce the importance of accurate joint line restoration and the avoidance of iatrogenic injury to the patellar tendon, which can lead to shortening of the patellar tendon. This is a retrospective comparative study and its level of evidence is III.

Fractured polyethylene tibial post in a posterior-stabilized knee prosthesis presenting as a floating palpable mass.

Complications associated with posterior-stabilized total knee arthroplasty (TKA) include patellar clunk syndrome, posterior subluxation of the tibial component, tibial post wear, and tibial post failure. Recently, an increasing number of reports have been issued on polyethylene tibial post failure in posterior-stabilized TKA. In most of these cases, tibial post failure in a well-functioning posterior-stabilized TKA was suspected based on clinical symptoms, such as a sudden onset of pain, effusion, patellar clunking, knee instability, and prosthesis dislocation. However, a floating, palpable, hard, mass-like symptom in the knee joint has not been previously reported. The authors report a case of a fractured polyethylene tibial post in a posterior-stabilized TKA that manifested as a palpable mass in the suprapatellar pouch.

Lateral meniscus and lateral femoral condyle cartilage injury by retained cement after medial unicondylar knee arthroplasty.

The authors experienced an unusual case of a patient with a complex tear of the lateral meniscus and adjacent lateral femoral condyle cartilage injury in the contralateral compartment by retained cement, possibly located at the posteromedial side of the medial tibial component after unicondylar knee arthroplasty. Arthroscopic partial meniscectomy and cartilage microfracture were successfully performed. Two small cement fragments were removed from the posterolateral compartment. A sharp pain in the lateral side disappeared postoperatively and posterior knee pain was much reduced.

Treatment of persistent extraarticular infection using a temporary cement spacer on the tibia after ACL reconstruction.

Postoperative infection after anterior cruciate ligament (ACL) reconstruction is an uncommon but serious complication. Although several treatments for intraarticular infection have been reported, no report has been recorded on the treatment of persistent extraarticular infections. The authors experienced reconstructed graft removal due to a refractory extraarticular infection on tibia. Early ACL reimplantation was performed using a temporary cement spacer containing antibiotics and a irradiated bone patellar tendon bone allograft.