Blumensaat's line is not always straight: morphological variations of the lateral wall of the femoral intercondylar notch

Femoral Tunnel Position in Anatomical Double-bundle ACL Reconstruction is not Affected by Blumensaat's Line Morphology

The aim of this study was to reveal the influence of the morphological variations of the Blumensaat's line on anteromedial (AM) and posterolateral (PL) femoral tunnel position in anatomical double-bundle anterior cruciate ligament (ACL) reconstruction.Fifty-three subjects undergoing anatomical double-bundle ACL reconstruction were included (29 female, 24 male; median age 27.4 years; range: 14-50 years). Using an inside-out transportal technique, the PL tunnel position was made on a line drawn vertically from the bottommost point of the lateral condyle at 90 degrees of knee flexion, spanning a distance of 5 to 8 mm, to the edge of the joint cartilage. AM tunnel position was made 2 mm distal to the PL tunnel position. Following Iriuchishima's classification, the morphology of the Blumensaat's line was classified into straight and hill (large and small) types. Femoral tunnel position was determined using the quadrant method. A Mann-Whitney U test was performed to compare straight and hill type knees according to AM and PL femoral tunnel position.There were 18 straight and 35 hill type knees (13 small and 22 large hill). AM and PL femoral tunnel position in straight type knees were 21.7 ± 7.0 and 33.6 ± 10.5% in the shallow-deep direction, and 42.1 ± 11.1 and 72.1 ± 8.5% in the high-low direction, respectively. In hill type knees, AM and PL femoral tunnel position were 21.3 ± 5.8 and 36.9 ± 7.1% in the shallow-deep direction, and 44.6 ± 10.7 and 72.1 ± 9.7% in the high-low direction, respectively. No significant difference in AM or PL femoral tunnel position was detected between straight and hill type knees.AM and PL femoral tunnel position in anatomical double-bundle ACL reconstruction was not affected by the morphological variations of the Blumensaat's line. Surgeons do not need to consider Blumensaat's line morphology if AM and PL femoral tunnel position is targeted at the bottommost point of the lateral condyle. This was a level of evidence III study.

Evaluation of the Angle Between the Long Axis of the Femoral Anterior Cruciate Ligament Footprint and Bony Morphology of the Knee: A Cadaveric Descriptive Study

Purpose

There have been numerous studies of the anterior cruciate ligament (ACL) anatomy, but few have focused on the long axis angle of the femoral ACL footprint. This study investigated the angle between the long axis of the femoral ACL footprint and the bony morphology of the knee.

Methods

This study is a cadaveric descriptive study. Thirty non-paired formalin-fixed knees of Japanese cadavers were used. Anteromedial (AM) and posterolateral (PL) bundles were identified according to the tension pattern differences during the complete range of motion of the knee. In the ACL femoral footprint, there is a fold between the mid-substance insertion site and fan-like extension fibers. After identifying AM and PL bundles of mid-substance fibers, the mid-substance and fan-like extension fibers were divided into those bundles and stained. We defined the line passing through the center of the AM and PL bundles as the long axis of the ACL. The center points of each of the four areas and the angle between the long axis of the ACL and the bony morphology of the knee were calculated using Image J software.

Results

The mean angle between the axis of the femoral shaft and the long axis of the ACL mid-substance insertion was 28.8 ± 12.2 degrees. The mean angle between the Blumensaat line and the long axis of the mid-substance was 54.2 ± 13.5 degrees.

Conclusion

The mean angle between the axis of the femoral shaft and the long axis of the femoral ACL footprint was approximately 29 degrees. There is a wide variation in the long axis of the femoral ACL footprint. To achieve better clinical results through a more anatomically accurate reconstruction, it can be beneficial to replicate the ACL femoral footprint along its native long axis.

Bilateral quadriceps tendon rupture: two injuries 6 years apart

We present a case of a fit man in his 50s, with simultaneous bilateral quadriceps tendon repair of injuries sustained 6 years apart. Spontaneous closed ruptures of the quadriceps tendon are uncommon. Clinical data of a single case of bilateral quadriceps tendon injury with simultaneous repair was gathered via the patient, notes and surgeon. Diagnosis was primarily based on history and clinical examination. Suggestive features on the plain radiographic imaging were also present. Confirmation was attempted using ultrasonography but yielded conflicting reports. The patient was screened for any associated predisposing conditions that would preclude surgical intervention or increase risk of recurrence. Repairs were accomplished by employing a combination of suture anchors and transpatellar cerclage reinforcement. Apposition of the tendon to the superior patellar pole was successful although with decreased passive flexion on the neglected side (approximately 30°) compared with the acute (approximately 90°). Follow-up continues with postoperative rehabilitation.

The apex of the deep cartilage is a stable landmark to evaluate the femoral tunnel position in ACL reconstruction

PURPOSE

To develop a simple and effective method for evaluating the femoral tunnel position using the apex of the deep cartilage (ADC) as the landmark.

METHODS

A total of 52 patients who underwent arthroscopic ACL reconstruction were recruited between June and September 2021. The femoral tunnel was placed on the central point of the anteromedial footprint with an accessory anteromedial and a high anterolateral portal. Then, the length from the ADC to the shallow cartilage margin (L₁) and to the center of the femoral tunnel (l₁), as well as the center to the low cartilage margin (H₁, intraoperative height), was measured under arthroscopy and on postoperative CT scans (L₂, l₂ and H₂). Moreover, intraoperative and postoperative cartilage ratios were equivalent to l₁/L₁ and l₂/L₂, respectively. Linear regression, Pearson correlation and Bland-Altman analysis were performed to evaluate the consistency between these two measurements of cartilage ratio (l/L) and height (H).

RESULTS

The mean age at the time of surgery was 28.7 years; 42 patients were male, and 17 patients were hurt in the left knee among 52 patients. The intraoperative cartilage ratio was 0.37 ± 0.04, and the height was 8.1 ± 1.1 mm with almost perfect inter-observer reproducibility. After the surgery, the cartilage ratio and height were measured as 0.39 ± 0.04 and 8.2 ± 1.3 mm on 3D-CT, respectively, with almost perfect intra- and inter-observer reproducibility. Significant positive correlations and linear regression were detected in the cartilage ratio (r = 0.844, p < 0.001), and height (r = 0.926, p < 0.001) intraoperatively and postoperatively. The Bland-Altman plot also showed excellent consistency between arthroscopy and 3D-CT.

CONCLUSIONS

The ADC is a good landmark in the assessment of femoral tunnel position, with excellent consistency between intraoperative arthroscopic measurements and postoperative 3D-CT.

CLINICALTRIALS

gov Identifier: NCT04937517.

LEVEL OF EVIDENCE

Level III.

Reconstruction of the Anterior Cruciate Ligament Using Ruler-Assisted Positioning of the Femoral Tunnel Relative to the Posterior Apex of the Deep Cartilage: A Single-Center Case Series

The techniques available to locate the femoral tunnel during anterior cruciate ligament (ACL) reconstruction have notable limitations. To evaluate whether the femoral tunnel center could be located intraoperatively with a ruler, using the posterior apex of the deep cartilage (ADC) as a landmark. This retrospective case series included consecutive patients with ACL rupture who underwent arthroscopic single-bundle ACL reconstruction at the Department of Orthopedics, Beijing Tongren Hospital between January 2014 and May 2018. During surgery, the ADC of the femoral lateral condyle was used as a landmark to locate the femoral tunnel center with a ruler. Three-dimensional computed tomography (CT) was performed within 3 days after surgery to measure the femoral tunnel position by the quadrant method. Arthroscopy was performed 1 year after surgery to evaluate the intra-articular conditions. Lysholm and International Knee Documentation Committee (IKDC) scores were determined before and 1 year after surgery. The final analysis included 82 knees of 82 patients (age = 31.7 ± 6.1 years; 70 males). The femoral tunnel center was 26 ± 1.5% in the deep-shallow (x-axis) direction and 31 ± 3.1% in the high-low (y-axis) direction, close to the "ideal" values of 27 and 34%. Lysholm score increased significantly from 38.5 (33.5-47) before surgery to 89 (86-92) at 1 year after surgery (p < 0.001). IKDC score increased significantly from 42.5 (37-47) before surgery to 87 (83.75-90) after surgery (p < 0.001). Using the ADC as a landmark, the femoral tunnel position can be accurately selected using a ruler.

Knees with straight Blumensaat's line have small volume of femoral intercondylar notch

PURPOSE

Smaller femoral intercondylar notch volume has been identified as a risk factor for anterior cruciate ligament injury. The present study aims to investigate differences in the intercondylar notch volume based on differences in the morphology of Blumensaat's line.

METHODS

Eighty-eight (88) subjects (42 male and 46 female: median age 27: range 15-49), were included in this study. Using 3-dimensional computed tomography (3D-CT), the volume of the intercondylar notch was calculated using a truncated-pyramid shape simulation with the formula: [Formula: see text]. Femoral condyle height (h) was measured in the sagittal plane of the knee in 3D-CT. The area of the intercondylar notch was measured in the axial slice containing the most proximal level (S1) and most distal level (S2) of Blumensaat's line. In the sagittal view of the knee, Blumensaat's line morphology was classified into either straight or hill type. Statistical analysis was performed to compare h, S1, S2, and notch volume between the straight and hill type groups.

RESULTS

Thirty-six subjects were classified as having straight type morphology and 52 subjects were classified as having hill type morphology. The measured h, S1, and S2, of the straight and hill types were 29 ± 4 and 31 ± 4 mm, 213 ± 72 and 205 ± 51 mm², 375 ± 114 and 430 ± 94 mm², respectively. The calculated femoral intercondylar notch volume of the straight and hill types was 8.1 ± 2 and 9.5 ± 2 cm³, respectively. Straight type knees showed significantly smaller S2 (p = 0.04), and notch volume (p = 0.01) when compared with hill type knees.

CONCLUSION

Intercondylar notch volume was significantly smaller in knees with straight type Blumensaat's line morphology. Considering that Blumensaat's line represents the roof of the femoral notch, morphological variations in Blumensaat's line are likely to reflect variation in notch volume. For clinical relevance, as a smaller notch volume is a risk factor for ACL injury, straight type Blumensaat's line may also be considered a potential risk factor for ACL injury.

LEVEL OF EVIDENCE

Level III.

The sagittal cutting plane affects evaluation of the femoral bone tunnel position on three-dimensional computed tomography after anterior cruciate ligament reconstruction

PURPOSE

To investigate how the femoral sagittal cutting plane affects evaluation of the bone tunnel position after anterior cruciate ligament (ACL) reconstruction using the quadrant method in three-dimensional computed tomography (CT) imaging.

METHODS

Thirty patients who underwent primary anatomic double-bundle ACL reconstruction and CT 2 weeks after surgery were enrolled. Three sagittal cutting planes with respect to the condylar axis were created using the CT images: at the top of the intercondylar notch (C-plane), 5% medial (M-plane), and 5% lateral (L-plane). The center of the bone tunnel position regarding depth and height of the anteromedial (AMB) and posterolateral bundle (PLB) were quantitatively evaluated using the quadrant method on the three different planes.

RESULTS

The mean depths of AMB and PLB were 27.4 ± 4.4% and 39.7 ± 5.1%, 27.0 ± 4.2% and 37.6 ± 4.9%, and 27.4 ± 4.5% and 38.5 ± 6.0%, at the M, C and L planes, respectively. The mean heights of AMB and PLB were 30.8 ± 6.3% and 56.2 ± 5.6%, 30.4 ± 6.2% and 56.6 ± 5.6%, and 25.4 ± 7.0% and 52.9 ± 6.9% at the M, C, and L planes, respectively. Both AMB and PLB bone tunnels were evaluated as higher positions in the L-plane than the C-plane (p < 0.01, p = 0.02, respectively) and M-plane (p < 0.01, p = 0.04, respectively), but there were no significant differences between the C-plane and M-plane (n.s.). There was no significant difference in the anteroposterior direction for all planes.

CONCLUSION

In evaluations of the bone tunnel position with the quadrant method using three-dimensional CT, the bone tunnel position depends on the femoral sagittal cutting plane. A consistent evaluation method should be used when evaluating the bone tunnel position after ACL reconstruction to enable correct evaluation clinically.

LEVEL OF EVIDENCE

Case-control study, Level III.

Posterior stability in posterior-stabilized vs medially congruent total knee replacement: A radiological comparison of two polyethylene designs in a single model

Objective:

The purpose of this radiological study was to assess the posterior laxity of a single model of a total knee arthroplasty design (TKA) having a medially constrained (MC) or a Posterior-Stabilized (PS) polyethylene insert using a well-documented stress x-ray. To the authors knowledge, this is the first report evaluating MC TKA outcomes according to the “kneeling view.”

Materials and Methods:

Sixty patients with non-traumatic primary knee osteoarthritis undergoing TKA were first matched by age, sex, BMI and diagnosis and then divided in two groups: group A (37 knees) received a MC TKA and group B (23 knees) a PS implant made by the same manufacturer. In all cases the posterior cruciate ligament (PCL) was resected. All patients underwent the same postoperative “kneeling view” and were also clinically evaluated according to the Knee Society Score (KSS) and Oxford Knee Score (OKS). Radiographic measurements were taken by tracing a line along the posterior cortex of the tibia and then measuring the perpendicular distance to a point marked at the posterior corner of Blumensaat’s line.

Results:

At 12 months minimum FU, no statistically significant differences were found between the two groups in all the clinical scores. There was a statistically significant difference on kneeling view values between the two groups (P = 0.0002): the mean value in the MC group was −1.97 ± 3.8 mm while was −5.6 ± 3.1 mm in the PS group. In both groups, the average position of the posterior cortex of the tibia was anterior to the posterior corner of Blumensaat’s line, showing absence of instability in flexion.

Conclusion:

This study highlighted that the PCL removal, accompanied by a precise surgical technique, did not increase the instability in flexion in two groups of patients having the same TKA design but polyethylene inserts characterized by different levels of constraint.

Morphology of the resident's ridge, and the cortical thickness in the lateral wall of the femoral intercondylar notch correlate with the morphological variations of the Blumensaat's line

PURPOSE

The purpose of this study was to reveal the morphological correlation between the lateral wall of femoral intercondylar notch and the Blumensaat's line.

METHODS

Forty-one non-paired human cadaveric knees were included in this study (23 female, 18 male: median age 83). Knees were resected, and 3 dimensional computed tomography (3D-CT) was performed. In the axial CT image, bony protrusion (resident's ridge) and cortical thickness in the lateral wall of the femoral intercondylar notch were detected. The length between the top of the ridge, or the most anterior, middle, and most posterior border of cortical thickness and posterior femoral condylar line was measured. Following Iriuchishima's classification, the morphology of the Blumensaat's line was classified into straight and hill types (small and large hill types). In the hill types, the length between the hilltop and the posterior border of the Blumensaat's line or the posterior border of the femoral condyle was evaluated. Statistical correlation was calculated between the top of the ridge location, cortical thickness location in the notch, and hilltop location.

RESULTS

There were 7 straight type knees and 34 hill type knees (9 small hill type knees and 25 large hill type knees). Only the hill types of knees were evaluated. The top of the ridge, anterior margin, middle, and posterior border of cortical thickness in the lateral wall of the femoral intercondylar notch existed at 61.8 ± 4.6%, 58.3 ± 12.3%, 42.1 ± 7.9%, and 25.5 ± 5.4% from the posterior condylar line, respectively. The hilltop existed at 24.9 ± 5.9% and 30.7 ± 5.0%, from the posterior border of the Blumensaat's line and from the posterior border of the femoral condyle, respectively. Significant correlation was observed between resident's ridge top, cortical thickness location and hilltop location.

CONCLUSION

In all cadaveric knees, cortical thickness was detected in the lateral wall of the femoral intercondylar notch. The resident's ridge and cortical thickness location had significant correlation with the hill location in the Blumensaat's line, indicating a continuation of the cortical bone from the posterior cortex of the femoral shaft via the hilltop of the Blumensaat's line to the cortical thickness in the lateral wall of the femoral intercondylar notch. For clinical relevance, hilltop location in the Blumensaat's line is a new bony landmark in anterior cruciate ligament surgery.

The location of the femoral ACL footprint center is different depending on the Blumensaat's line morphology

PURPOSE

The purpose of this study was to evaluate the difference in the center point of the femoral ACL footprint according to the morphological variations of the Blumensaat's line.

METHODS

Fifty-nine non-paired human cadaver knees were used. The ACL was cut in the middle, and the femoral bone was cut at the most proximal point of the femoral notch. Digital images were evaluated using the Image J software. The periphery of the femoral ACL footprint was outlined and the center point was measured automatically. Following Iriuchishima's classification, the morphology of the Blumensaat's line was classified into straight and hill types (small and large hill types). The center of the femoral ACL footprint and hilltop placement were evaluated using the quadrant method. A quadrant grid was placed uniformly, irregardless of hill existence, and not including the articular cartilage. A correlation analysis was performed between the center point of the femoral ACL footprint and hilltop placement.

RESULTS

The straight type consisted of 19 knees, and the hill type 40 knees (small hill type 13 knees and large hill type 27 knees). The center of the femoral ACL footprint (shallow-deep/high-low) in the straight and hill type knees was 33.7/47.6%, and 37.2/50.3%, respectively. In the hill type, the ACL footprint center was significantly more shallow when compared to the straight type. Significant correlation was observed between the center point of the femoral ACL footprint and hilltop placement of the Blumensaat's line.

CONCLUSION

The center point of the femoral ACL footprint was significantly more shallow in the hill type knees when compared to the straight type. For clinical relevance, considering that the location of the femoral ACL footprint center is different depending on the Blumensaat's line morphology, to perform accurate ACL reconstruction, femoral ACL tunnel placement should be made based on Blumensaat's line morphological variations.

Inclination of Blumensaat's line influences on the accuracy of the quadrant method in evaluation for anterior cruciate ligament reconstruction

PURPOSE

The quadrant method is used to evaluate the bone tunnel position with the grid based on the Blumensaat's line in anterior cruciate ligament (ACL) reconstruction. This study aimed to clarify the influence of variation in the Blumensaat's line on the accuracy of the quadrant method measurements.

METHODS

A retrospective review of the radiological records of patients aged 18-30 years who underwent computed tomography (CT) scanning of the knee joint was conducted. The Blumensaat's line inclination angle (BIA), along with the most posterior point of the posterior condyle (point P) position using the quadrant method and morphology of the Blumensaat's line were measured on true lateral transparent three-dimensional CT images of the distal femoral condyle in 147 patients. Statistical analysis was conducted to determine associations among these measurements.

RESULTS

BIA was 37.5° (standard deviation 4.2°; range 27°-48°). The point P position was significantly correlated with BIA in the high/low (R² = 0.590, P < 0.0001) and deep/shallow (R² = 0.461, P < 0.0001) directions. The morphology of the Blumensaat's line was straight in 35 knees (23.8%); whereas, the remaining 112 knees (76.2%) were not straight but had some hill on the Blumensaat's line. No significant difference among the morphological variation of the Blumensaat's line was observed in BIA and the point P position.

CONCLUSION

There was a strong correlation between BIA and the point P measured using the quadrant method, suggesting the influence of the Blumensaat's line on the accuracy of the quadrant method measurements in ACL reconstruction. As for the clinical relevance, surgeons should be careful in application of the quadrant method for ACL reconstruction, because the variation of the Blumensaat's line inclination influences the accuracy of this method.

Femoral Tunnel Placement Analysis in ACL Reconstruction Through Use of a Novel 3-Dimensional Reference With Biplanar Stereoradiographic Imaging

Background:

The femoral-sided anatomic footprint of the anterior cruciate ligament (ACL) has been widely studied during the past decades. Nonanatomic placement is an important cause of ACL reconstruction (ACLR) failure.

Purpose:

To describe femoral tunnel placement in ACLR through use of a comprehensive 3-dimensional (3D) cylindrical coordinate system combining both the traditional clockface technique and the quadrant method. Our objective was to validate this technique and evaluate its reproducibility.

Study Design:

Descriptive laboratory study.

Methods:

The EOS Imaging System was used to make 3D models of the knee for 37 patients who had undergone ACLR. We designed an automated cylindrical reference software program individualized to the distal femoral morphology of each patient. Cylinder parameters were collected from 2 observers’ series of 3D models. Each independent observer also manually measured the corresponding parameters using a lateral view of the 3D contours and a 2-dimensional stereoradiographic image for the corresponding patient.

Results:

The average cylinder produced from the first observer’s EOS 3D models had a 30.0° orientation (95% CI, 28.4°-31.5°), 40.4 mm length (95% CI, 39.3-41.4 mm), and 19.3 mm diameter (95% CI, 18.6-20.0 mm). For the second observer, these measurements were 29.7° (95% CI, 28.1°-31.3°), 40.7 mm (95% CI, 39.7-41.8 mm), and 19.7 mm (95% CI, 18.8-20.6 mm), respectively. Our method showed moderate intertest intraclass correlation among all 3 measuring techniques for both length (r = 0.68) and diameter (r = 0.63) but poor correlation for orientation (r = 0.44). In terms of interobserver reproducibility of the automated EOS 3D method, similar results were obtained: moderate to excellent correlations for length (r = 0.95; P < .001) and diameter (r = 0.66; P < .001) but poor correlation for orientation (r = 0.29; P < .08). With this reference system, we were able to describe the placement of each individual femoral tunnel aperture, averaging a difference of less than 10 mm from the historical anatomic description by Bernard et al.

Conclusion:

This novel 3D cylindrical coordinate system using biplanar, stereoradiographic, low-irradiation imaging showed a precision comparable with standard manual measurements for ACLR femoral tunnel placement. Our results also suggest that automated cylinders issued from EOS 3D models show adequate accuracy and reproducibility.

Clinical Relevance:

This technique will open multiple possibilities in ACLR femoral tunnel placement in terms of preoperative planning, postoperative feedback, and even intraoperative guidance with augmented reality.

The Blumensaat's line morphology influences to the femoral tunnel position in anatomical ACL reconstruction

PURPOSE

The purpose of this study was to reveal the influence of the morphological variations of the Blumensaat's line on femoral tunnel position in anatomical anterior cruciate ligament (ACL) reconstruction.

METHODS

Thirty-eight subjects undergoing anatomical single-bundle ACL reconstruction were included in this study (22 female, 16 male: median age 45: 15-63). Using a trans-portal technique, the femoral tunnel was targeted to reproduce the center of antero-medial bundle. Following Iriuchishima's classification, the morphology of the Blumensaat's line was classified into straight and hill types (small and large hill types). Femoral ACL tunnel position was evaluated using the quadrant method. When the quadrant method grid was applied, the baseline of the grid was matched to the anterior part of the Blumensaat's line, without considering the existence of a hill. Using pre-operative 3D-CT data, the axial and sagittal morphology of the knee was also compared, establlishing straight and hill types.

RESULTS

There were 12 straight type knees and 26 hill type knees (7 small hill type knees and 19 large hill type knees). The femoral tunnel position in straight type knees was 23.6 ± 3.7% in the shallow-deep direction, and 41.3 ± 8.2% in the high-low direction. In hill type knees, the tunnel position was 27 ± 4.7% in the shallow-deep direction, and 51 ± 10.1% in the high-low direction. The femoral tunnel was placed significantly more shallow and lower in hill type knees when compared with straight type knees.

CONCLUSION

Femoral ACL tunnel placement was significantly influenced by the morphological variations of the Blumensaat's line. As detecting morphological variation in arthroscopic surgery is difficult, surgeons should confirm such variations pre-operatively using radiograph or CT so as to avoid making extremely shallow and low tunnels in hill type knees.

LEVEL OF EVIDENCE

Case-controlled study, III.

Anatomical rectangular tunnels identified with the arthroscopic landmarks result in excellent outcomes in ACL reconstruction with a BTB graft

PURPOSE

To elucidate tunnel locations and clinical outcomes after anatomic rectangular tunnel (ART) anterior cruciate ligament reconstruction (ACLR) using a bone-patellar tendon-bone (BTB) graft.

METHODS

Sixty-one patients with a primary unilateral ACL injury were included. Tunnels were created inside the ACL attachment areas after carefully removing the ACL remnant and clearly identifying the bony landmarks. Using 3-dimensional computed tomography (3-D CT) images, the proportion of the tunnel apertures to the anatomical attachment areas was evaluated at 3 weeks. The clinical outcomes were evaluated at 2 years postoperatively.

RESULTS

Geographically, the 3-D CT evaluation showed the entire femoral tunnel aperture; at least 75% of the entire tibial tunnel aperture area was consistently located inside the anatomical attachment areas surrounded by the bony landmarks. In the International Knee Documentation Committee (IKDC) subjective assessment, all patients were classified as 'normal' or 'nearly normal'. The Lachman test and pivot-shift test were negative in 98.4% and 95.1% of patients, respectively. The mean side-to-side difference of the anterior laxity at the maximum manual force with a KT- 1000 Knee Arthrometer was 0.2 ± 0.9 mm, with 95.1% of patients ranging from - 1 to + 2 mm.

CONCLUSION

By identifying arthroscopic landmarks, the entire femoral tunnel aperture and at least 75% of the entire tibial tunnel aperture area were consistently located inside the anatomical attachment areas. With properly created tunnels inside the anatomical attachment areas, the ART ACLR using a BTB graft could provide satisfactory outcomes both subjectively and objectively in more than 95% of patients.

LEVEL OF EVIDENCE

Case series, Level IV.

Femoral tunnel length in anatomical single-bundle ACL reconstruction is correlated with height, weight, and knee bony morphology

PURPOSE

The purpose of this study was to reveal the correlation between femoral tunnel length in anatomical single-bundle anterior cruciate ligament (ACL) reconstruction and body size and/or knee morphology.

METHODS

Thirty-one subjects undergoing anatomical single-bundle ACL reconstruction were included in this study (20 female, 11 male; median age 46, 15-63). Pre-operative height, body weight, and body mass index (BMI) were measured. In pre-operative magnetic resonance imaging, the thickness of the quadriceps tendon and the whole anterior-posterior (AP) length of the knee were measured using the sagittal slice. Using post-operative three-dimensional computed tomography, accurate axial and lateral views of the femoral condyle were evaluated. The correlation of femoral tunnel length, which was measured intra-operatively, with the height, weight, BMI, quadriceps tendon thickness, AP length of the knee, trans-epicondylar length, the notch area (axial), length of Blumensaat's line, and the height and area of the lateral wall of the femoral intercondylar notch were statistically analyzed. Tunnel placement was also evaluated using a Quadrant method.

RESULTS

The average femoral tunnel length was 35.6 ± 4.4 mm. The average height, body weight, and BMI were 162.7 ± 7.2 cm, 61.9 ± 10 kg, and 23.4 ± 3.5, respectively. Femoral tunnel length was significantly correlated with height, body weight and the height and area of lateral wall of the femoral intercondylar notch, and the length of the Blumensaat's line.

CONCLUSION

For clinical relevance, the risk of creating a femoral tunnel of insufficient length in anatomical single-bundle ACL reconstruction exists in subjects with small body size. Surgeons should pay careful attention to prevent this from occurring.

LEVEL OF EVIDENCE

Case-controlled study, Level III.

The lateral femoral notch sign: a reliable diagnostic measurement in acute anterior cruciate ligament injury

PURPOSE

To describe the validity and inter- and intra-observer reliability of the lateral femoral notch sign (LFNS) as measured on conventional radiographs for diagnosing acute anterior cruciate ligament (ACL) injury.

METHODS

Patients (≤ 45 years) with a traumatic knee injury who underwent knee arthroscopy and had preoperative radiographs were retrospectively screened for this case-control study. Included patients were assigned to the ACL injury group (n = 65) or the control group (n = 53) based on the arthroscopic findings. All radiographs were evaluated for the presence, depth and location of the LFNS by four physicians who were blind to the conditions. To calculate intra-observer reliability, each observer re-assessed 25% of the radiographs at a 4-week interval.

RESULTS

The depth of the LFNS was significantly greater in ACL-injured patients than in controls [median 0.8 mm (0-3.1 mm) versus 0.0 mm (0-1.4 mm), respectively; p = 0.008]. The inter- and intra-observer reliabilities of the LFNS depth were 0.93 and 0.96, respectively. Secondary knee pathology (i.e., lateral meniscal injury) in ACL-injured patients was correlated with a deeper LFNS [median 1.1 mm (0-2.6 mm) versus 0.6 mm (0-3.1 mm), p = 0.012]. Using a cut-off value of 1 mm for the LFNS depth, a positive predictive value of 96% was found.

CONCLUSION

This was the first study to investigate the inter- and intra-observer agreement of the depth and location of the LFNS. The depth of the LFNS had a very high predictive value for ACL-injured patients and could be used in the emergency department without any additional cost. A depth of > 1.0 mm was a good predictor for ACL injury. Measuring the depth of the LFNS is a simple and clinically relevant tool for diagnosing ACL injury in the acute setting and should be used by clinicians in patients with acute knee trauma.

LEVEL OF EVIDENCE

Diagnostic study, level II.

The quadrant method measuring four points is as a reliable and accurate as the quadrant method in the evaluation after anatomical double-bundle ACL reconstruction

PURPOSE

The quadrant method was described by Bernard et al. and it has been widely used for postoperative evaluation of anterior cruciate ligament (ACL) reconstruction. The purpose of this research is to further develop the quadrant method measuring four points, which we named four-point quadrant method, and to compare with the quadrant method.

METHODS

Three-dimensional computed tomography (3D-CT) analyses were performed in 25 patients who underwent double-bundle ACL reconstruction using the outside-in technique. The four points in this study's quadrant method were defined as point1-highest, point2-deepest, point3-lowest, and point4-shallowest, in femoral tunnel position. Value of depth and height in each point was measured. Antero-medial (AM) tunnel is (depth1, height2) and postero-lateral (PL) tunnel is (depth3, height4) in this four-point quadrant method. The 3D-CT images were evaluated independently by 2 orthopaedic surgeons. A second measurement was performed by both observers after a 4-week interval. Intra- and inter-observer reliability was calculated by means of intra-class correlation coefficient (ICC). Also, the accuracy of the method was evaluated against the quadrant method.

RESULTS

Intra-observer reliability was almost perfect for both AM and PL tunnel (ICC > 0.81). Inter-observer reliability of AM tunnel was substantial (ICC > 0.61) and that of PL tunnel was almost perfect (ICC > 0.81). The AM tunnel position was 0.13% deep, 0.58% high and PL tunnel position was 0.01% shallow, 0.13% low compared to quadrant method.

CONCLUSIONS

The four-point quadrant method was found to have high intra- and inter-observer reliability and accuracy. This method can evaluate the tunnel position regardless of the shape and morphology of the bone tunnel aperture for use of comparison and can provide measurement that can be compared with various reconstruction methods. The four-point quadrant method of this study is considered to have clinical relevance in that it is a detailed and accurate tool for evaluating femoral tunnel position after ACL reconstruction.

LEVEL OF EVIDENCE

Case series, Level IV.

Sagittal femoral condyle morphology correlates with femoral tunnel length in anatomical single bundle ACL reconstruction

PURPOSE

The purpose of this study was to reveal the correlation between femoral tunnel length and the morphology of the femoral intercondylar notch in anatomical single bundle anterior cruciate ligament (ACL) reconstruction using three-dimensional computed tomography (3D-CT).

METHODS

Thirty subjects undergoing anatomical single bundle ACL reconstruction were included in this study (23 female, 7 male: average age 45.5 ± 16.7). In the anatomical single bundle ACL reconstruction, the femoral and tibial tunnels were created close to the antero-medial bundle insertion site with trans-portal technique. Using post-operative three-dimensional computed tomography (3D-CT), accurate axial and lateral views of the femoral condyle were evaluated. The correlation of femoral tunnel length, which was measured intra-operatively, with the transepicondylar length (TEL), notch width index, notch outlet length, the notch area (axial), length of Blumensaat's line, and the height and area of the lateral wall of the femoral intercondylar notch was statistically analyzed. Tunnel placement was also evaluated using a Quadrant method.

RESULTS

The average femoral tunnel length was 35.4 ± 4.4 mm. The average TEL, NWI, notch outlet length, and the axial notch area, were 76.9 ± 5.1 mm, 29.1 ± 3.8%, 19.5 ± 3.9 mm, and 257.4 ± 77.4 mm², respectively. The length of Blumensaat's line and the height and area of the lateral wall of the femoral intercondylar notch were 33.8 ± 3.2 mm, 22.8 ± 2.3 mm, and 738.7 ± 129 mm², respectively. The length of Blumensaat's line, the height, and the area of the lateral wall of the femoral intercondylar notch were significantly correlated with femoral tunnel length. Femoral tunnel placement was 23.4 ± 4.5% in a shallow-deep direction and 35.4 ± 8.8% in a high-low direction.

CONCLUSION

The length of Blumensaat's line, height, and area of the lateral wall of the femoral intercondylar notch are correlated with femoral tunnel length in anatomical single bundle ACL reconstruction. For clinical relevance, these parameters are useful in predicting the length of the femoral tunnel in anatomical single bundle ACL reconstruction for the prevention of extremely short femoral tunnel creation.

LEVEL OF EVIDENCE

Case controlled study, Level III.

The importance of Blumensaat's line morphology for accurate femoral ACL footprint evaluation using the quadrant method

PURPOSE

The purpose of this study was to evaluate the difference in the center position of the ACL footprint based on grid placement using the quadrant method according to the morphological variations of the Blumensaat's line.

METHODS

Fifty-nine non-paired human cadaver knees were used. The ACL was cut in the middle, and the femoral bone was cut at the most proximal point of the femoral notch, and the digital images were evaluated using Image J software. The femoral ACL footprint was periphery outlined and the center position was automatically measured. Following Iriuchishima's classification, the morphology of the Blumensaat's line was classified into straight, small hill, and large hill types. From the images, grid quadrants were placed as: Grid (1) without consideration of hill existence and not including the chondral lesion. Grid (2) without consideration of hill existence and including the chondral lesion. Grid (3) with consideration of hill existence and not including the chondral lesion. Grid (4) with consideration of hill existence and including the chondral lesion.

RESULTS

The straight type consisted of 19 knees, the small hill type 13 knees, and the large hill type 27 knees. Depending on the quadrant grid placement, significant center position difference was observed both in the shallow-deep, and high-low direction. When hill existence was considered, the center position of the ACL was significantly changed to a high position.

CONCLUSION

The center position of the ACL footprint exhibited significant differences according to Blumensaat's line morphology. For clinical relevance, when ACL surgery is performed in knees with small or large hill type variations, surgeons should pay close attention to femoral tunnel evaluation and placement, especially when using the quadrant method.

The intercondylar notch ceiling: an accurate reference for distal femoral resection in total knee arthroplasty for severely degenerated varus knees

PURPOSE

To measure the distance from the intercondylar ceiling to the lowest point of the medial and lateral femoral condyles in a healthy population so to obtain a clearly discernible and accurate landmark for proper distal femoral resection during total knee arthroplasty (TKA).

METHODS

Three-dimensional models of the lower extremities of 100 healthy Chinese subjects were constructed using computed tomography scans. The distance between the distal surface of the medial femoral condyle and the intercondylar notch ceiling, in the direction of the femoral mechanical axis, was measured.

RESULTS

The mean distance from the distal surface of the medial femoral condyle to the intercondylar notch ceiling was 9.1 ± 1.4 and 8.2 ± 1.4 mm in male and female subjects, respectively. Interestingly, this distance did not differ significantly with varying sizes of the distal femur.

CONCLUSIONS

The intercondylar notch ceiling could be used as an accurate landmark to determine the proper distal femoral resection level during TKA. For the clinical relevance, the distal femoral bone cut should be at the level of the intercondylar notch ceiling when using the most of the current TKA prosthesis systems.

The correlation of femoral tunnel length with the height and area of the lateral wall of the femoral intercondylar notch in anatomical single-bundle ACL reconstruction

PURPOSE

The purpose of this study was to reveal the correlation between femoral tunnel length and the height and area of the lateral wall of the femoral intercondylar notch in anatomical single-bundle anterior cruciate ligament (ACL) reconstruction .

METHODS

Twenty-four subjects undergoing anatomical single-bundle ACL reconstruction were included in this study (19 females and 5 males; average age 45.5 ± 16.7). In the anatomical single-bundle ACL reconstruction, the femoral and tibial tunnels were created close to the anteromedial bundle insertion site. Using post-operative three-dimensional computed tomography (3D-CT), an accurate lateral view of the femoral condyle was evaluated. The correlation of femoral tunnel length, which was measured intra-operatively, with the length of Blumensaat's line, and the height and area of the lateral wall of the femoral intercondylar notch was statistically analysed. Tunnel placement was also evaluated using 3D-CT (Quadrant method).

RESULTS

The average femoral tunnel length was 35.3 ± 4.9 mm. The length of Blumensaat's line, and the height and area of the lateral wall of the femoral intercondylar notch were 33.6 ± 3.4, 22.8 ± 2.4, and 734.6 ± 136 mm², respectively. Both the height and the area of the lateral wall of the femoral intercondylar notch were significantly correlated with femoral tunnel length. Femoral tunnel placement was 24.1 ± 3.9 % in a shallow-deep direction, and 33.5 ± 7.7 % in a high-low direction.

CONCLUSION

The height and area of the lateral wall of the femoral intercondylar notch are correlated with femoral tunnel length in anatomical single-bundle ACL reconstruction. For clinical relevance, surgeons should be careful not to make the femoral tunnel too short in knees in which the femoral intercondylar notch is low in height or small in size.

LEVEL OF EVIDENCE

Case-controlled study, Level III.

Is the femoral lateral condyle's bone morphology the trochlea of the ACL?

PURPOSE

The purpose of this study was to investigate the association of different osteoarticular femoral and tibial morphology and morphometric parameters with the risk of anterior cruciate ligament (ACL) rupture.

METHODS

Thirty-six patients (29 male and 7 female) with an ACL rupture (<6 months) and 36 age and sex-matched controls were included. The anatomomorphological parameters and morphometrics of the distal epiphysis of the femur and proximal epiphysis of the tibia were measured through conventional lateral radiography of the knee.

RESULTS

It was found statistically significant smaller heights of femur's lateral condyle, AP distances of the tibial plateaus and smaller XY and WX distances, as well as, higher XY/AB and B/AB ratios (p < 0.05). In turn, women had smaller AP distances of the femur's lateral condyle, AP distances of the femur's diaphysis, AP distances of the tibial plateaus and heights of femur's lateral condyle, as well as, higher values of XY/AB (Porto ratio) and B/AB ratios (p < 0.05).

CONCLUSIONS

Several femoral and tibial bone morphological parameters were identified as potential risk factors for sustaining an ACL injury. These parameters are clinically relevant to identify individuals with higher risk of ACL injury, decide between conservative or surgical treatment and identify individuals who may benefit from preventive neuromuscular programs.

LEVEL OF EVIDENCE

Case-control study, Level III.