Stability with a Constrained Posterior Stabilized Primary Total Knee Arthroplasty Does Not Compromise Durability

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering

Background:

• Total knee arthroplasty (TKA) can be challenging in patients with complex knee deformities, such as ligamentous laxity or posttraumatic arthritis.
• Traditional prostheses may lack the necessary varus-valgus stability for these complex cases.
• Midlevel constraint (MLC) prostheses offer enhanced stability for such challenging TKA procedures.

Purpose of the Study:

• To evaluate the clinical and radiographic outcomes of primary total knee arthroplasty (TKA) utilizing a midlevel constraint (MLC) prosthesis.
• To assess the effectiveness of MLC implants in managing complex knee deformities.
• To determine the incidence of complications such as instability, loosening, or the need for revision surgery.

Main Methods:

• A retrospective review was conducted on 53 patients (62 knees) who underwent primary TKA with an MLC implant.
• Patients were followed for a mean of 31.6 months, with assessment of preoperative and postoperative range of motion (ROM).
• Radiographic review included alignment, radiolucent lines, component loosening, and osteolysis. Outcomes were compared between knees with and without short tibial stem extensions.

Main Results:

• Mean ROM significantly improved from 114.1 degrees preoperatively to 123.5 degrees postoperatively (p=0.001).
• Surgical correction of preoperative varus or valgus deformities resulted in a mean postoperative alignment of 4.3 degrees valgus (p<0.001).
• No radiographic evidence of radiolucent lines, component loosening, or osteolysis was observed. No patients required revision surgery. Arthrofibrosis requiring manipulation under anesthesia occurred in 9.7% of patients.

Conclusions:

• Total knee arthroplasty with a midlevel constraint (MLC) prosthesis yields satisfactory clinical and radiographic results in complex knee deformities.
• The MLC prosthesis demonstrates no evidence of component loosening, osteolysis, or instability at a minimum 2-year follow-up.
• The use of short tibial stem extensions did not significantly impact ROM, alignment, or the incidence of arthrofibrosis compared to non-stemmed implants.