Multiplanar reformation improves identification of the anterolateral ligament with MRI of the knee

The anterolateral ligament (ALL) is subject of the current debate concerning rotational stability in case of anterior cruciate ligament (ACL) injuries. Today, reliable anatomical and biomechanical evidence for its existence and course is available. Some radiologic studies claim to be able to identify the ALL on standard coronal plane MRI sections. In the experience of the authors, however, ALL identification on standard MRI sequences frequently fails and is prone to errors. The reason for this mainly lies in the fact, that the entire ALL often cannot be identified on a single MRI image. This study aimed to establish an MRI evaluation protocol improving the visualization of the ALL, using multiplanar reformation (MPR) with the goal to be able to evaluate the ALL on one MRI image. A total of 47 knee MRIs performed due to atraumatic knee pain between 2018 and 2019 without any pathology were analyzed. Identification of the ALL was performed twice by an orthopedic surgeon and a radiologist on standard coronal plane and after MPR. For the latter axial and coronal alignment was obtained with the femoral condyles as a reference. Then the coronal plane was adjusted to the course of the ALL with the lateral epicondyle as proximal reference. Visualization of the ALL was rated as “complete” (continuous ligamentous structure with a tibial and femoral insertion visible on one coronal image), “partial” (only parts of the ALL like the tibial insertion were visible) and “not visible”. The distances of its tibial insertion to the bony joint line, Gerdy’s tubercle and the tip of the fibular head were measured. On standard coronal images the ALL was fully visible in 17/47, partially visible in 27/47, and not visible in 3/47 cases. With MPR the ALL was fully visible in 44/47 and not visible in 3/47 cases. The median distance of its tibial insertion to the bony joint line, Gerdy’s tubercle and the tip of the fibular head were 9, 21 and 25 mm, respectively. The inter- (ICC: 0.612; 0.645; 0.757) and intraobserver (ICC: 0.632; 0.823; 0.857) reliability was good to excellent. Complete visualization of the ALL on a single MRI image is critical for its identification and evaluation. Applying multiplanar reformation achieved reliable full-length visualization of the ALL in 94% of cases. The described MPR technique can be applied easily and fast in clinical routine. It is a reliable tool to improve the assessment of the ALL.

Easy Surgical Approach of the Posterolateral Corner of the Knee

Background: The anatomy of the posterolateral corner (PLC) of the knee is complex. The approach of the PLC can be a challenging and stressful surgical time. Indications: The indications are posterolateral meniscal repair, open lateral meniscus allograft transplantation, posterolateral tibial plateau fracture, and PLC reconstruction for grade III sprains. Technique Description: The skin incision is straight, realized with the knee positioned at 90° of flexion, passing slightly posterior to the lateral epicondyle, anterior to the fibular head (FH), and ending on Gerdy’s tubercle. The subcutaneous tissues are dissected posteriorly so as to expose the FH and the biceps femoris (BF) tendon. The aponeurosis of the peroneus muscles is incised vertically opposite to the anterior side of the FH. The common fibular nerve is exposed at the neck of the fibula. Metzenbaum scissors are then inserted subaponeurotically, posteriorly, and parallel to the BF tendon, superficially to the nerve. An incision is made opposite the scissor’s blades, freeing the common fibular nerve. The BF tendon is spread forward and the lateral gastrocnemius is pulled posteriorly. Metzenbaum scissors are inserted in a closed position between the lateral gastrocnemius and the posterolateral joint capsule, and then spread to create a triangular door with a proximal base. The base consists of the BF tendon, the posterior side of the lateral gastrocnemius, and the anterior side of the posterolateral joint capsule. A counter-angled Hohmann retractor can now be applied against the posterior tibial plateau to retract the lateral gastrocnemius posteriorly and medially, exposing the PLC of the knee. Results: Noble structures are easily exposed and protected. The common fibular nerve is dissected and reclined posteriorly, and the popliteus vessels are reclined posteriorly and medially, protected by the lateral gastrocnemius. Passing under the BF tendon allows a better vision of the PLC along with less constraint than passing above, as the working window is further away from the femoral insertion of the lateral gastrocnemius. Discussion/Conclusion: The present surgical approach allows a simple, safe, and reproducible exposure of the PLC of the knee.

The Anatomy and Length Changes of the Lateral Patellofemoral Ligament and Lateral Patellotibial Ligament

Objectives: The lateral patellar restraints (lateral patellofemoral ligament [LPFL], lateral patellotibial ligament [LPTL] and lateral patellomeniscal ligament [LPML]) are relatively poorly understood entities, which are important in patellar stability. The purpose of this study is to perform a qualitative and quantitative anatomic evaluation of the LPFL, LPML, and LPTL attachment sites, with specific attention to their relationship to pertinent osseous and soft tissue landmarks. Methods: Six non-paired, fresh frozen human cadaveric knees (n = 6) were utilized for this study. Institutional review board approval was not required for this cadaveric study. Knees were dissected and a variety of anatomic locations and the LPFL, LPTL, and LPML attachment sites and attachment centers were marked with surgical marker. The knee was placed in a custom jig and the quadriceps tendon was loaded with a 1 kg weight. Ligament area was measured with a portable coordinate measuring device (Microscribe, Solution Technologies, Oella, MD) and ligament centers were identified at 0, 15, 30, 45, 60 and 90° of flexion. The 3D location via a ‘bird’s eye view’ was calculated in Rhinoceros 5.0 software (McNeel North America, Seattle, WA). Data analysis was performed in MATLAB (MathWorks, Natick, MA) and Microsoft Excel (Microsoft, Redmond, WA). Statistical analysis was conducted with one-way repeated measure ANOVAs and Spearman Rank Correlation, which was used for non-normally distributed data, in SPSS (v26, IBM, Armonk, NY). Results: The location of the LPFL on the femur was compared to local landmarks (Fig 1). In the sagittal plane, the center, anterior, and posterior aspect of the LPFL were a mean of 17.0±1.4, 11.8±2.0, and 8.0±1.9 mm from the lateral epicondyle, respectively. Distances to the anterior, central, and posterior cartilage from these locations were 14.3±1.8, 14.6±2.9, and 14.3±3.3mm, respectively. The area of the LPFL was a mean of 31.59±20.24mm2 in the vertical plane. The location of the LPFL on the patella was then analyzed. The superior aspect of the LPFL was 8.52±2.74 mm from the superior pole of the patella, while the distance from the inferior pole to the LPFL was 14.01±4.53mm. The average length of the patella was 4.10±0.34cm and the LPFL occupied 45.09% of its sagittal length. The distance from the LPML to the anterolateral root was 7.35±2.98mm. The center of the LPTL on the tibia was a mean distance of 5.88±3.00mm from Gerdy’s tubercle. LPFL length decreased in flexion with a mean length of 40.60±3.24mm at 0°, 36.27±6.29mm at 15°, 33.77±4.93mm at 30°, 31.41±4.72 mm at 45°, 30.05±4.10mm at 60°, and 26.05±3.02mm at 90°. Significant length changes through flexion were observed (p < 0.0005), pairwise comparison found significant differences between 0° and 45° (p=0.025), 0° and 60° (p=0.012), and 0° and 90° (p=0.005). However, a significant negative correlation between degree of flexion and length was observed (r=-0.734, p < 0.0005). Conclusions: To our knowledge, this is the first study to describe the anatomy of the components of the lateral stabilizers including the LPFL, LPTL, and LPML. Reproducible locations on the femur and patella were observed for the two LPFL attachments. In addition, the attachment sites were found to have consistent distances to anatomic landmarks. Our results demonstrate that the LPFL length significantly correlates with flexion and maintains isometry through flexion, in contrast to the medial patellofemoral ligament, which has the greatest length changes in the first 20° of flexion.

3D mapping and classification of tibial plateau fractures

Aims Tibial plateau fractures (TPFs) are complex injuries around the knee caused by high- or low-energy trauma. In the present study, we aimed to define the distribution and frequency of TPF lines using a 3D mapping technique and analyze the rationalization of divisions employed by frequently used classifications. Methods In total, 759 adult patients with 766 affected knees were retrospectively reviewed. The TPF fragments on CT were multiplanar reconstructed, and virtually reduced to match a 3D model of the proximal tibia. 3D heat mapping was subsequently created by graphically superimposing all fracture lines onto a tibia template. Results The cohort included 405 (53.4%) cases with left knee injuries, 347 (45.7%) cases with right knee injuries, and seven (0.9%) cases with bilateral injuries. On mapping, the hot zones of the fracture lines were mainly concentrated around the anterior cruciate ligament insertion, posterior cruciate ligament insertion, and the inner part of the lateral condyle that extended to the junctional zone between Gerdy’s tubercle and the tibial tubercle. Moreover, the cold zones were scattered in the posteromedial fragment, superior tibiofibular syndesmosis, Gerdy’s tubercle, and tibial tubercle. TPFs with different Orthopaedic Trauma Association/AO Foundation (OTA/AO) subtypes showed peculiar characteristics. Conclusion TPFs occurred more frequently in the lateral and intermedial column than in the medial column. Fracture lines of tibial plateau occur frequently in the transition zone with marked changes in cortical thickness. According to 3D mapping, the four-column and nine-segment classification had a high degree of matching as compared to the frequently used classifications. Cite this article: Bone Joint Res 2020;9(6):258–267.

Anatomical study of Gerdy’s tubercle, its shape, texture and clinical application.

Objectives: The objective of this study is to lay emphasis on Gerdy’s tubercle, its morphology and clinical significance of Gerdy’s safe area in upper lateral part of tibia for any surgical intervention to avoid injury to neighboring common peroneal nerve. Study Design: Comparative anatomical study. Setting: Anatomy Department Faisalabad Medical University Faisalabad. Period: From 1st September 2018 to 20th Feb 2019. Material & Methods: Total 72 dried Pakistani tibia irrespective of sex (38 right and 34 left) were taken from the bone bank of Anatomy Department FMU. The upper end of tibia was studied with respect to the shape and texture of Gerdy’s tubercle. The shape is divided in to Group A having triangular, Group B oval, Group C irregular and group D unidentified in both right and left bones and their % age was calculated. Similarly the texture Of GT was divided in to Group A facet (smooth), Group B tubercle (rough) and Group C unidentified in both right and left tibia and then % age was calculated. Results: Total 72 dried human tibia were examined out of which 38 were of right side and rest 34 were of left side all showed presence of Gerdry’s tubercle. Regarding shape of GT Right tibia showed 12(31.5%) triangular (group A), Oval shape was 20 (52.6%) (Group B), number of irregular was 6 (15.9%) (Group C) and none unidentified (0%) (Group D). Regarding texture GT Right Tibia showed facet type Group A 16(42%), Group B 57% were of tubercle type (22) and non unidentified (Group D) Zero %. Total 34 left tibia Shape of GT was examined and found triangular (group A) in 18 tibia (52%) and oval shaped 6(17.6%) in group B. Whereas in group C 10 (29.4%). were irregular. The texture of left tibia 41.1% (14) were of facet Type Group A and 58.82% (20) were of tubercle type (group B). Total Number of Tibia (N=72) GT showed 41.6% triangular, 36.1% oval and 22.2% irregular. While 41.6% were facet and 58.3% tubercle in texture. Conclusion: This study concluded that the morphological study of Gerdy’s tubercle is mandatory to approach the lateral compartment of the knee joint for any surgical intervention. The calculation of safe area is so important to avoid injury to common peroneal nerve.

PEDIATRIC REFERENCE ANATOMY FOR ANTEROLATERAL LIGAMENT RECONSTRUCTION– A CADAVERIC STUDY

Background: The anatomy of the anterolateral ligament (ALL) has been controversial, with modern studies varying in their description of the precise origin and insertion, as well as relation to surrounding structures on the lateral femur and anterolateral tibia Regardless of such controversy, principles of reconstruction, even non-anatomic, require a clear understanding of the referenced anatomy and surrounding structures. Due to high rates of primary and recurrent ACL tears in pediatric/adolescent patients, the use of ALL reconstruction is increasing in these groups. No pediatric cadaveric study to date has clearly identified the locations of the known surrounding structures of the anterolateral ligamentous complex. Purpose: The purpose of this study was to quantitatively assess the anatomy of the pediatric lateral collateral ligament (LCL) origin, the popliteus origin, and in the tibial insertion of the iliotibioband (ITB). Methods: Nine pediatric cadaveric knee specimens were dissected to identify the ligamentous femoral origin of the LCL, popliteus, and tibial insertion of the ITB.. Marking pins were used to localize the central footprint of these structures, followed by CT Scans. Results: LCL & Popliteus: On the femur, the popliteus was consistently found deep to the LCL and inserted both distally and anteriorly to the LCL a mean distance of 4.6 mm (range 1.9 to 7.6 mm; std dev 2.0). The LCL measured a mean of 12.5 mm to the joint line while the popliteus measured a mean of 8.2 mm from the joint line. Both the LCL and popliteus were consistently distal to the physis. The LCL was a mean distance of 4.4 mm (range 1.0 - 9.5 ) and the popliteus was a mean distance of 8.2 (range 1.7 – 12.5), respectively. ITB insertion: The ITB insertion at Gerdy’s tubercle had an average footprint measuring 28.2 mm2 (range 10.3-58.4), and the ITB center was found proximal to the physis in 6 specimens and distal in 3 specimens. Mean distance from the footprint center to the physis was 1.6 mm proximal (range 7.1 mm proximal to 2.2 mm distal). Conclusion: This study provides quantitative anatomy to structures on the lateral femur and anterolateral tibia, commonly referenced in descriptions of the ALL and lateral extraarticular reconstruction techniques. Knowledge of these structures will define the anterolateral complex and guide extra-articular procedures that provide extraarticular anterolateral rotatory stabilization in the pediatric patients. [Figure: see text][Figure: see text]

Lateral Extra-Articular Tenodesis Does Not Affect Rotatory Knee Instability in Anatomic ACL Reconstruction

Objectives: Single-bundle, anatomic anterior cruciate ligament reconstruction (ACLR) may not fully restore rotatory knee stability, and the addition of a lateral extra-articular tenodesis (LET) has been proposed as means for reducing residual rotatory knee instability. However, the magnitude of the in vivo, time zero effects of these procedures on rotatory knee instability remain poorly defined. The pivot shift test is used to assess for rotatory knee instability; however, it is a subjective grading system with limited generalizability and ability to predict clinical outcomes. Consequently, a quantified pivot shift (QPS) test software application, PIVOT iPad, has been developed and validated to measure the magnitude of rotatory knee laxity. The objective of this study was use intraoperative QPS (iQPS) to assess for differences in residual rotatory knee instability after ACLR versus ACLR augmented with lateral extra-articular tenodesis (ACLR + LET.) Methods: During examination under anesthesia (EUA), QPS was performed on both the operative and non-operative knees prior to ACLR (Figure 1A) Three, yellow ¾ inch markers were attached to skin overlying bony landmarks: lateral epicondyle, Gerdy’s tubercle and 3 cm posterior to Gerdy’s tubercle. The PIVOT software application was used to measure lateral compartment translation (Figure 1B) ACLR were randomly augmented with a LET if the lateral compartment translation measured during QPS was greater than or equal to double the amount of lateral compartment translation measured for the unaffected knee. iQPS measurements were subsequently performed after either ACLR or ACLR + LET with sterile markers (Figure 1C) iQPS data were recorded and compared to both the preoperative QPS measurements of the affected and unaffected knees. Based upon normative QPS data established from a database of >150 previously performed ACLR at our institution, it was determined that 8 patients in each group would be required to achieve 80% power with an effect size of 1.2 mm and an alpha level of 0.05. Post-procedure iQPS data were compared to preoperative QPS measurements with paired samples t-tests. Results: iQPS measurements were performed in 20 ACLR (10 ACLR and 10 ACLR + LET). The mean age in the cohort was 17.3 years old (range: 17-24 years old.). Both ACLR and ACLR + LET resulted in significant decreases in rotatory knee instability when compared to preoperative QPS measurements (pre-ACLR: 4.7 ± 1.9 v. post-ACLR: 1.3 ± 0.70, P < 0.001; pre-ACLR +LET: 3.6 ± 1.8 v. post-ACLR + LET: 0.9 ± 0.5, P < 0.001.) When comparing isolated ACLR to ACLR + LET, no significant differences were observed in the magnitude of change in iQPS between the pre and post-intervention states (ACLR: - 3.5 ± 1.6 mm v. ACLR + LET: -1.5 ± 3.1 mm, P = N.S.) Furthermore, there were no significant differences in lateral compartment translation between the operative knees and non-operative knees (ACLR: -0.1 ± 0.9 mm v. ACLR + LET: -0.5 ± 1.0 mm, P = N.S.), suggesting that neither ACLR nor ACLR + LET led to over-constrained kinematics. Conclusion: In this randomized control study, both ACLR and ACLR + LET resulted in significant decreases in rotatory knee instability. However, there were no significant differences in time-zero, rotatory knee instability detected between isolated ACLR versus ACLR combined with LET in patients. The utility of combining a LET with ACLR remains unclear, and future research is necessary to refine the indications for LET in patients with high-grade rotatory knee instability.

AN INVESTIGATION OF THE SURGICAL ANATOMY OF THE PEDIATRIC ILIOTIBIAL BAND

Background: Previous work on adult specimens have demonstrated some differential thickness of the iliotibial band (ITB) tissue in different areas. The purpose of this study was twofold: 1) to quantitatively and qualitatively describe the relevant surgical anatomy of the ITB, at the level of the knee, in pediatric cadaveric specimens in which either an iliotibial band tenodesis or extraphyseal reconstruction would be considered, and 2) to provide recommendations that allow the surgeon to obtain the ideal graft in terms of tissue width and location on the larger ITB structure. Methods: Pediatric cadaveric specimens (n=24) were dissected by a group of fellowship trained pediatric orthopaedic surgeons. Digital photography of each specimen was obtained prior to collecting quantitative data of the ITB and its three main divisions using digital calipers and a coordinated measurement device (Hexagon Romer Absolute V3 CMM). Measurements included thickness, surface area, length, and width of each branch; surface area and length of each insertion; and distance of insertion in relation to other pertinent anatomical landmarks. Specimens were grouped into four age groups (Group 1: 2 year olds, Group 2: 3 and 4 year olds, Group 3: 5-7 year olds, and Group 4: 9-11 year olds). The four age groups were compared utilizing ANOVA and nonparametric Kruskal-Wallis tests with post-hoc analysis using the Tukey method. In order to correlate measurements and age, a Spearman’s correlation was used. Results: All specimens (mean age 4.7 years; range 2-11) contained a visible ITB with a direct primary arm to Gerdy’s tubercle. Sixteen specimens (66.6%) had a visible trifurcation point, in which the aggregate of ITB fibers diverge into three distinct branches: a direct arm, the iliopatellar branch, and the iliotendinous branch (Figure 1). Fibers from the central third of the iliotibial band, as described as the primary site for harvest, do not terminate on Gerdy’s tubercle, but diverge to the patella, patellar tendon and a portion of Gerdy’s tubercle. The length from the trifurcation point to the insertion of the direct arm at Gerdy’s tubercle increased with each age group (21.3 mm, 29.9 mm, 31.5 mm, and 41.8 mm, respectively) with a significant difference seen between Group 1 and 4 (p<0.01) and Group 2 and 4 (p=0.03), indicating migration of this point with longitudinal growth. The mean thicknesses of the direct arm (0.55 mm), the iliopatellar branch (0.74 mm), and iliotendinous branch (0.42 mm) were not statistically different between age groups. Length, width, and surface area were also not statistically different between age groups. Conclusion: The ITB is a consistent, well-defined structure in pediatric specimens. While some longitudinal changes in the ITB and its insertions were seen with increasing age, the thickness and width of the direct arm of the ITB, typically harvested for extra-physeal ACL reconstruction, does not appear to differ between age groups and does not represent the thickest distal branch of the ITB. The location of ITB harvest may influence the impact that the extra-articular “capsular tightening” has on joint mechanics, including altering the compression across the joint, and/or the impact on the Pivot-Shift/rational laxity of the knee undergoing ITB reconstructions. Further study of the graft location/harvest and its impact on knee biomechanics is warranted. [Figure: see text]