Comparison of Gap Balancing vs Measured Resection Technique in Patients Undergoing Simultaneous Bilateral Total Knee Arthroplasty: One Technique per Knee.

BACKGROUND: Total knee arthroplasty requires careful surgical technique to attain the goal of a well-aligned and symmetrically balanced knee. Soft tissue balance and correct femoral component rotation are paramount in achieving these goals. The two competing techniques to select femoral component rotation and soft tissue balance are the gap balance technique and the measured resection technique. METHODS: We performed a randomized, prospective study to compare the two techniques in patients undergoing simultaneous bilateral total knee arthroplasty, whereby one technique was performed in each knee. Fifty (50) subjects were enrolled into the study. The inclusion criteria were osteoarthritic varus knee deformities with similar deformities in both knees. Subjects were followed up for a minimum of two years. RESULTS: The knees balanced via the gap balance technique had significantly more posterior medial bone removed from the femur than those knees balanced via the measured resection technique (P < .001). Knees in the gap balance group tended to require more medial knee releases in extension and tended to have smaller sized femoral components as a result of cutting more bone from the femur in flexion. The modular tibial polyethylene bearing tended to be thicker in the gap balance group. Despite these differences, average knee flexion and functional revised Oxford Knee Scores at 2-year follow-up were not statistically different. CONCLUSION: At 2-year follow-up, there were no differences between the function and scores using the two techniques. Long-term follow-up will be necessary to evaluate any differences in long-term durability.

14-year median follow-up using the press-fit condylar sigma design for total knee arthroplasty.

Median 14-year follow-up (mean 11.8 years) of a cemented primary posterior cruciate-retaining total knee arthroplasty (TKA) utilizing the Press-Fit Condylar (PFC) Sigma design was evaluated in 77 patients (79 TKA). Follow-up assessment included implant survivorship, x-rays, Knee Society rating system, and clinical evaluation. Radiographic analysis demonstrated minor non-progressive osteolysis in 40% (10/25) knees. Two revisions, one for instability at 4 years and one for polyethylene wear at 10 years were performed. Survivorship of the PFC Sigma knee implant was 97% using revision for any reason and 100% using aseptic loosening as endpoints. The PFC Sigma had excellent survivorship at 14 years, the longest clinical follow-up reported.

Hydroxyapatite-coated femoral stem/porous-coated acetabulum survivorship at 15 years.

At 10 years, we reported survivorship of the Omnifit hydroxyapatite-coated femoral stem and the Omnifit-PSL porous-coated dual-radius acetabular shell (Stryker, Mahwah, NJ) with polyethylene liners sterilized by gamma radiation in air. Our 15-year follow-up examines survivorship and functional outcomes of this system. Ninety-two patients (98 hips) were identified from our database who had been involved with the prior study. The mean follow-up was 14.7 years (range, 11.8-17.0 years). Survival of the stem and cup was 98.8% and 69%, respectively. Osteolysis was seen in 56% of the proximal femur and 5% of the distal femur. This hydroxyapatite-coated stem continues to perform well at 15 years despite poor acetabular results. The performance of this acetabular component is consistent with previous literature.

Early follow-up for a hybrid total hip arthroplasty using a metal-backed acetabular component designed to reduce "backside" polyethylene wear.

Modular acetabular systems have several advantages; however, increased polyethylene wear has been recognized as a disadvantage. In our study, an acetabular shell design with a highly polished inner surface, a locking mechanism that minimizes micromotion, and a high polyethylene liner to shell conformity was evaluated. A prospective cohort of 50 consecutive hips was followed up for a mean of 3.6 years (range, 2-7 years). One patient required an early revision for recurrent instability. Mean linear head penetration rates were 0.242 mm/year (range, 0.048-0.655 mm/year). The true linear wear rate was calculated after subtracting the linear wear in the first follow-up year from the total wear at the end of the follow-up. The true linear wear rate was 0.173 mm/year (range, 0.03-0.423 mm/year). A positive correlation was found between wear rate and male gender. The low head penetration rates suggest that a polished liner with an improved locking mechanism and increased liner conformity can reduce polyethylene wear.