Purpose: Evaluation of the inter- and intra-observer reliability of a new developed knee laxity measurement device for tibiofemoral rotation.

Methods: 30 healthy subjects (15m, 15w, mean age of 24 years) were examined with the Rotameter knee laxitiy measurement device. The Beigthon score was reported to test the general laxitiy of the subjects.

After fixation of the device on the lower extremity and positioning of the patient in the starting position the device was first externally and then internally rotated at an applied torque of 5,10 and 15 Nm. To decrease the measurement error the procedure was repeated 5 times. Afterwards 5 measurements were performed by a second examiner in the same way to measure the inter-observer reliability. All 30 patients were measured again after a mean of 31 ± 43 days by the same examiners to test the intra-observer reliability. Statistical analysis was performed using the intra class correlation coefficient (ICC). Pearson correlation coefficient were used to compare the measurements of the left and the right knee.

Results: The Beigthon Score showed a mean of 0.8 ± 1.1 (0–4). At an applied torque of 5 Nm the ICC for the intra-observer reliability of was 0.81 for the external rotation and 0.67 for the internal rotation, the ICC for the inter-observer reliability was 0.94 for the external and 0.94 for the internal rotation. At 10 Nm of rotation torque an ICC for the intra-observer reliability of 0.79 was reached for internal and 0.88 for external rotation, the ICC for the inter-observer reliability was 0.97 for internal and 0.95 for external rotation. At the highest applied torque of 15 Nm an ICC for the intra-observer reliability of 0.93 was observed for the external rotation and 0.83 was found for internal rotation. For the inter-tester reliability the ICC was 0.95 for external and 0.98 for internal rotation.

The comparison of the measurements of the left and the right knee showed high Pearson correlation (.90) at all applied torques.

Conclusion: The Rotameter testing device for the measurement of tibiofemoral rotation showed a high inter-observer and intra-observer reliability. It is easy to perform and might be used in a wide field to examine the rotational stability of the knee.

Purpose: The objective of this investigation was to evaluate the precision of tibial tunnel drilling for anatomic anchoring of meniscus transplants at the tibial insertion area, using previously obtained percentage references.

Methods: In 20 cadaveric tibial heads, anterior and posterior horn insertions of both the lateral and the medial meniscus were dissected and their circumferences outlined. Standardized photographs of the tibial plateau were obtained. Applying previously obtained percentage values for radiographic determination of the meniscus insertion midpoints, tibial tunnels were drilled with the use of a standard ACL-guide. The positioning of the drilling guide was performed by solely using the midpoints as determined on standard ap and lateral radiographs; during the procedure, no position correction related to the anatomic insertions was made. After tibial tunnel drilling, a second set of standardized photographs of the tibial plateau was obtained. Adobe Photo Shop permitted the superposition of pre- and postoperative images. Coincidence between the anatomic insertion areas and the footprint of the tibial tunnel exit was determined, as well as the distance between the borders of the insertion areas and the tunnel footprint.

Results: For the lateral meniscus, the mean coincidence of insertion area and tunnel footprint was 60.5 ± 34.6 % for the anterior horn insertion and 62.4 ± 32.0 % for the posterior horn insertion. The mean distance between the borders of insertion area and tunnel footprint was 1.7 ± 1.5 mm for the anterior horn insertion and 2.3 ± 1.7 mm for the posterior horn insertion.

For the medial meniscus, the mean coincidence of insertion area and tunnel footprint was 88.4 ± 15.5 % for the anterior horn insertion and 60.3 ± 31.6 % for the posterior horn insertion. The mean distance between the borders of insertion area and tunnel footprint was 0.8 ± 0.8 mm for the anterior horn insertion and 2.1 ± 1.4 mm for the posterior horn insertion.

Conclusions: The use of percentage references for tibial meniscus insertion midpoint determination in combination with a radiographic positioned standard ACL-guide permits a precise drilling of tibial tunnels at the anatomic location of the meniscus insertions.

Clinical relevance: Enhancement of the surgical technique for bone plug fixation of lateral and medial meniscus transplants.

Introduction: The purpose of our investigation was to determine if tibial lateral meniscus insertions (anterior and posterior horn) can precisely and reproducibly be determined on preoperative radiographs. Bony landmarks and their topographic relations to the meniscus insertions were described, measured and statistically evaluated. We concentrated on the lateral meniscus because there are many reasons to restrict the indications for meniscus replacement on the lateral compartment.

Methods: We prepared the lateral meniscus insertions in 22 tibial plateaus from 11 body donors. Insertion site outline was performed on anterior and posterior horns with radio opaque 1.6 mm steal balls. Anteroposterior and lateral radiographs were performed. On these radiographs, different landmarks of the tibial head were defined and their distances measured (width, depth, distance from lateral tibia border to meniscus midpoint, distance from lateral tibia border to lateral tibial spine). These measures were statistically evaluated and percent values for meniscus insertion midpoint position were determined.

Results: On anteroposterior radiographs, from lateral to medial, the anterior meniscus midpoint was located on 45.1 % ± 1.3 % of the tibial width, the posterior meniscus midpoint on 49.8 % ± 1.9 % of the tibial width. On lateral radiographs, from anterior to posterior, the anterior meniscus midpoint was located on 41.9 % ± 3.2 % of the tibial depth, the posterior meniscus midpoint on 72.1 % ± 2.3 % of the tibial depth. With linear regression analysis, we could show that the lateral meniscus insertions have constant relations, as well to the dimensions of the tibia plateau as to the lateral tibial spine.

Conclusions: We think that it is possible to determine precisely and reproducibly on preoperative anteroposterior and lateral radiographs the insertions of the lateral meniscus. Our results and the method to determine preoperatively meniscus insertions might bring decisive advantages considering the optimal fixation of meniscus transplants, enhancing biomechanical conditions and possibly improving postoperative results.