Femoral radiographic landmarks for popliteus tendon reconstruction and repair: a new method of reference

Comparative Analysis of Sagittal-Plane Radiographic Landmarks Used to Identify the Femoral Attachments of Lateral Knee Structures

PURPOSE

To compare previously described radiographic parameters for the localization of the lateral knee (LK) structures, including the popliteal tendon (Pop), anterolateral ligament (ALL), and lateral collateral ligament (LCL), to determine which method best estimates the femoral attachment of each LK structure.

METHODS

Twenty-nine human cadaveric knee specimens were carefully dissected to identify the LCL, ALL, and Pop. The femoral attachment for each structure was labeled with a radiopaque bead. LK radiographic images were obtained using fluoroscopy. Two radiographic approaches were used to identify each LK structure (Pop-A, Pop-B, LCL-A, LCL-B, ALL-A, and ALL-B) via previously published methods based on radiographic landmarks including the posterior femoral cortex and the Blumensaat line. The identification of radiographic landmarks was performed at 2 different time points by 2 different surgeons to determine the Pearson correlation between values, as well as interobserver and intraobserver reliability and reproducibility. The paired t test was conducted to compare the distance between the actual attachment site (as determined by the bead location) and the 2 radiographically identified estimations of attachment locations.

RESULTS

For the LCL, the mean difference between the actual location and the estimated location via application of the LCL-B method (5.0 ± 2.4 mm) was significantly less than that estimated using the LCL-A method (8.2 ± 3.3 mm, P < .0001). Likewise, the Pop-B (5.7 ± 2.0 mm) and ALL-B (9.3 ± 4.5 mm) methods were shown to have smaller differences between the actual and estimated femoral attachment sites of the Pop insertion and ALL insertion, respectively (P < .0001). Methods for estimating the ALL femoral origin were the worst among the LK structures analyzed, with 90% of estimated values greater than 5 mm from the anatomic origin. Interobserver and intraobserver intraclass correlation coefficients were 0.785 or higher.

CONCLUSIONS

Previously described radiographic methods for localization of the femoral attachment sites of the LK structures resulted in estimated locations that were significantly different from the locations of the radiographic beads placed at the anatomic femoral attachment sites of these structures. Therefore, radiographic methods used to localize the femoral attachments of the LK structures may not be reliable.

CLINICAL RELEVANCE

This study shows the variability of the anatomy of the LK structures and the lack of reproducible radiographic criteria to identify these structures. As a result, there will be decreased reliance on radiographic landmarks to identify the placement of femoral grafts and fixation when reconstructing these structures.

Editorial Commentary: Fluoroscopy Is Seldom Required During Knee Posterolateral Reconstruction

Identifying the structures of the lateral knee is critical during knee posterolateral corner reconstruction. Several methods exist that can help estimate the femoral insertions of these structures on lateral radiographs. However, it is important to recognize the limitations of these methods and that anatomic visualization is often more practical and more accurate. Until percutaneous or more minimally invasive techniques become standardized, intraoperative fluoroscopy is seldom needed or used for posterolateral corner reconstruction, whereas radiographic analysis of lateral knee structures could be of benefit in cases of failed reconstruction to assess tunnel placement.

Anatomic, All-Arthroscopic Reconstruction of Posterolateral Corner of the Knee: A Cadaveric Biomechanical Study

PURPOSE

To assess the role of anatomic reconstruction of the posterolateral corner (PLC) of the knee arthroscopically in cadaveric knees with simulated isolated grade III posterolateral instability.

METHODS

A total of 12 nonpaired, fresh-frozen cadaveric knees were biomechanically subjected to a 10-Nm varus moment, 5-Nm external and internal rotation torques, and 134-N posterior tibial load at 0°, 15°, 30°, 60°, and 90° of knee flexion (0° for varus loading only). Testing was performed with an intact and sectioned PLC and after anatomic reconstruction of the PLC by an arthroscopic technique. Kinematics of each knee under various loading conditions was determined with a robotic universal force/moment sensor testing system.

RESULTS

After sectioning, significant increases were found in varus rotation at 0°, 15°, 30°, 60°, and 90° of knee flexion; in external rotation at 15°, 30°, 60°, and 90° of knee flexion; in internal rotation at 60° of knee flexion only; and in posterior translation at 15° and 30° of knee flexion. After reconstruction, full recovery of knee stability was observed in varus rotation, external rotation, internal rotation, and posterior translation at all selected flexion angles without any overconstraint of knee kinematics.

CONCLUSIONS

Anatomic reconstruction of the PLC can be performed arthroscopically with isolated grade III posterolateral instability of the knee, and nearly normal stability of the knee can be restored.

CLINICAL RELEVANCE

PLC reconstruction by an anatomic, all-arthroscopic technique achieves optimal stability control and kinematics of the knee.

Femoral footprint of the popliteus tendon may be at the risk of damage during total knee arthroplasty

PURPOSE

The present study focused on the prevalence of incidental excision of the femoral footprint of the popliteus tendon during total knee arthroplasty and its associated risk factors.

METHODS

A total of 275 knee arthroplasties were performed for 226 patients with varus knee osteoarthritis. The status of the femoral footprint of the popliteus tendon was intraoperatively evaluated and classified into three groups (preserved, partially excised, and completely excised), and the prevalence of the excision was identified. Femoral component size, the thickness of the resected distal femoral condyle, and preoperative patient demographic data were compared for the three groups. Ordinal logistic regression analysis was performed to reveal risk factors associated with the excision.

RESULTS

The femoral footprint of the popliteus tendon was preserved in 132 knees (48.0 %), partially excised in 94 knees (34.2 %) and completely excised in 49 knees (17.8 %). The ordinal logistic regression analysis revealed thicker resection of the distal femoral condyle (p < 0.0001) and shorter body height (p = 0.0266) to be the independent risk factors for the excision.

CONCLUSIONS

The incidental partial or complete excision of the femoral footprint of the popliteus tendon was identified in approximately half of the evaluated knees. Thicker resection of the distal femoral condyle and shorter body height were the most significant risk factors for the excision.

LEVEL OF EVIDENCE

Case-control study, Level III.

Radiographic identification of the anterior and posterior root attachments of the medial and lateral menisci

BACKGROUND

Anatomic root placement is necessary to restore native meniscal function during meniscal root repair. Radiographic guidelines for anatomic root placement are essential to improve the accuracy and consistency of anatomic root repair and to optimize outcomes after surgery.

PURPOSE

To define quantitative radiographic guidelines for identification of the anterior and posterior root attachments of the medial and lateral menisci on anteroposterior (AP) and lateral radiographic views.

STUDY DESIGN

Descriptive laboratory study.

METHODS

The anterior and posterior roots of the medial and lateral menisci were identified in 12 human cadaveric specimens (average age, 51.3 years; age range, 39-65 years) and labeled using 2-mm radiopaque spheres. True AP and lateral radiographs were obtained, and 2 raters independently measured blinded radiographs in relation to pertinent landmarks and radiographic reference lines.

RESULTS

On AP radiographs, the anteromedial and posteromedial roots were, on average, 31.9 ± 5.0 mm and 36.3 ± 3.5 mm lateral to the edge of the medial tibial plateau, respectively. The anterolateral and posterolateral roots were, on average, 37.9 ± 5.2 mm and 39.3 ± 3.8 mm medial to the edge of the lateral tibial plateau, respectively. On lateral radiographs, the anteromedial and anterolateral roots were, on average, 4.8 ± 3.7 mm and 20.5 ± 4.3 mm posterior to the anterior margin of the tibial plateau, respectively. The posteromedial and posterolateral roots were, on average, 18.0 ± 2.8 mm and 19.8 ± 3.5 mm anterior to the posterior margin of the tibial plateau, respectively. The intrarater and interrater intraclass correlation coefficients (ICCs) were >0.958, demonstrating excellent reliability.

CONCLUSION

The meniscal root attachment sites were quantitatively and reproducibly defined with respect to anatomic landmarks and superimposed radiographic reference lines. The high ICCs indicate that the measured radiographic relationships are a consistent means for evaluating meniscal root positions.

CLINICAL RELEVANCE

This study demonstrated consistent and reproducible radiographic guidelines for the location of the meniscal roots. These measurements may be used to assess root positions on intraoperative fluoroscopy and postoperative radiographs.