Unicompartmental knee arthroplasty: all-poly versus metal-backed tibial component-a long-term follow-up study.

INTRODUCTION: While considered a satisfactory solution, unicompartmental knee arthroplasty (UKA) still raises concerns in regard to its durability. These concerns particularly focus on the tibial component. This study aims to compare two different cemented tibial components belonging to the same UKA design: all polyethylene (AP) versus metal backed (MB), at a long-term follow-up. MATERIALS AND METHODS: We retrospectively reviewed 143 successive patients, 83 of which underwent surgery with AP tibial component UKA (37 males, 46 females), and 67 with MB ones (17 males, 50 females). All implants had the same prosthetic design (Accuris UKA, Smith e Nephew) with identical femoral oxinium component but different tibial component, AP or MB. The KSS and KOOS were assessed at a mean of 11.5-year follow-up and compared to pre-operative, post-operative, and one year evaluation. Statistical analysis was performed with SPSS for Mac (version 17.0). To assess potential statistically significant differences, t test was used and significance was set at P < 0.05. RESULTS: Final KSS at a mean of 11.5-year follow-up was 94.27 for the AP group and 96.12 for the MB ones. The final KOOS was 87 for AP components and 89.67 for the MB group. These results demonstrated, in all cases, statistically significant better results for MB tibial components compared to AP regarding KSS (P = 0.048), KOOS (P = 0.000), and pain (P = 0.014) at the 11.5-year follow-up. Survivorship for AP tibial component implants was 97.6%, while it was 89.5% for MB ones. CONCLUSION: While the survivorship rate has been found to be greater for AP implants compared to MB tibial components, this study reveals statistically better functional results according to KSS and KOOS, and pain, at a long-term follow-up for MB implants.

A comparison of dynamic rotational knee instability between anatomic single-bundle and over-the-top anterior cruciate ligament reconstruction using triaxial accelerometry.

PURPOSE: Recently, single-bundle (SB) anterior cruciate ligament (ACL) reconstruction has been advanced by the anatomic concept, but the biomechanical outcome of the anatomic method has not been fully investigated, especially for rotational instability. Anatomic SB and the single over-the-top procedures are the treatment of choice for primary cases and revision or skeletally immature cases, respectively. The purpose of this study was to investigate the dynamic rotational instability of anatomic SB and over-the-top reconstruction during a pivot shift test using triaxial accelerometry. METHODS: Eight fresh frozen human cadaveric knees were used in this study. Rotational instability measurement was conducted during a pivot shift test by the use of a triaxial accelerometer attached to the tibia. The tests were performed in the ACL-intact, ACL-deficient and ACL-reconstructed knees with two different procedures (anatomic SB and over-the-top). The acceleration in three directions and the magnitude of acceleration were measured to evaluate rotational instability and compare between four different knee states. RESULTS: The overall magnitude of acceleration was significantly different (P < 0.01) between the ACL-intact knees and the ACL-deficient knees. Both anatomic SB and over-the-top ACL reconstruction significantly reduced the overall magnitude of acceleration compared to the ACL-deficient knees, but still had larger accelerations compared to the ACL-intact knees. There was no significant difference for the overall magnitude of acceleration between anatomic SB and over-the-top reconstruction procedure. CONCLUSION: Over-the-top reconstruction provides comparable result to anatomic SB reconstruction in terms of controlling the dynamic rotational stability. Over-the-top reconstruction might be one of the options for revision cases and in skeletally immature patients.

Use of transtibial aimer via the accessory anteromedial portal to identify the center of the ACL footprint.

PURPOSE: To assess the ability of a transtibial aimer with a 7-mm off-set in a standardized position to reach the center of the ACL footprint on the femur through the AM portal. METHODS: Nineteen cadaveric knees were dissected, and the perimeter of the femoral ACL footprint was marked. The aimer was placed just superior to the medial joint line close to the medial condyle through the AM portal. The guide was rested upon the posterior cortex and placed in three different positions: (A) at zero degrees in frontal plane and 60° in axial plane, (B) at 45° in frontal and 45° in axial, and (C) at the center of the ACL insertion site under direct visualization. A digital camera was used to take pictures on the axial plane, and Image J software was used for angle measurement. Aluminum beads were used to mark the three positions indicated by the aimer, and CT scans were performed. The distances from the true center of the ACL to each point were determined. RESULTS: Position A resulted in femoral tunnel placement furthest from the center of the ACL footprint (8.6 mm). Position B was at a distance of 3.2 mm, and position C was the most accurate, with an average distance of 2.0 mm. The angles required by Position C varied with an average of 54° ± 11° in the frontal plane and an average of 44° ± 6° in the axial plane. CONCLUSION: The 7-mm transtibial aimer was unable to reach the center of ACL footprint at a fixed orientation.

Femoral intercondylar notch shape and dimensions in ACL-injured patients.

The femoral intercondylar notch has been an anatomic site of interest as it houses the anterior cruciate ligament (ACL). The objective of this study was to arthroscopically evaluate the femoral notch in patients with known ACL injury. This evaluation included establishing a classification for notch shapes, identifying the shape frequency, measuring notch dimensions, and determining correlation between notch shape, notch dimensions, and demographic patient data. In this clinical cohort study, 102 consecutive patients underwent diagnostic arthroscopic evaluation of the notch. Several intra-operative photos, videos, and measurements were taken of the notch. Demographic data for each patient were recorded including age, gender, height, weight, and BMI. Three categories of notch shape were established: 1. A-shaped; 2. U-shaped; and 3. W-shaped. Two blinded independent orthopedic surgeons were asked to categorize the recorded notches. Notch shape, dimensions, and demographic factors were correlated. Of the 102 notches evaluated, 55 notches were found to be "A-shaped," 42 "U-shaped," and 5 "W-shaped." "A-shaped" notches were narrower in all width dimensions than "U-shaped" notches. Only patient height was found to influence notch shape with a positive association between taller patients and "U-shaped" and "W-shaped" notches (P = 0.011). Women had a smaller notch width at the base and middle of the notch. With this data, surgeons who enter the knee and appreciate an "A-shaped" notch should consider placing the arthroscope in the anteromedial portal and drill the femoral tunnel through an accessory medial portal to improve visualization and accuracy in anatomic femoral tunnel creation.