Tristan Maerz

A Review of the Anterolateral Ligament of the Knee: Current Knowledge Regarding Its Incidence, Anatomy, Biomechanics, and Surgical Dissection

PURPOSE To systematically review current literature on the anterolateral ligament (ALL) of the knee. METHODS We searched the PubMed/Medline database for publications specifically addressing the ALL. We excluded studies not written in English, studies not using human cadavers or subjects, and studies not specifically addressing the ALL. Data extraction related to the incidence, anatomy, morphometry, biomechanics, and histology of the ALL and its relation to the Segond fracture was performed. RESULTS The incidence of the ALL ranged from 83% to 100%, and this range occurs because of small discrepancies in the definition of the ALLs bony insertions. The ALL originates anterior and distal to the femoral attachment of the lateral collateral ligament. It spans the joint in an oblique fashion and inserts between the fibular head and Gerdy tubercle on the tibia. Exact anatomic and morphometric descriptions vary in the literature, and there are discrepancies regarding the ALLs attachment to the capsule and lateral meniscus. The ALL is a contributor to tibial internal rotation stability, and histologically, it exhibits parallel, crimped fibers consistent with a ligamentous microstructure. The footprint of the ALL has been shown to be at the exact location of the Segond fracture. CONCLUSIONS The ALL is a distinct ligamentous structure at the anterolateral aspect of the knee, and it is likely involved in tibial internal rotation stability and the Segond fracture. LEVEL OF EVIDENCE Level IV, systematic review of anatomic and imaging studies.

Matrix Metalloproteinase Content and Activity in Low-Platelet, Low-Leukocyte and High-Platelet, High-Leukocyte Platelet Rich Plasma (PRP) and the Biologic Response to PRP by Human Ligament Fibroblasts

Background: Recent work has shown the presence of catabolic cytokines in platelet-rich plasma (PRP), but little is known about endogenous catabolic proteases such as matrix metalloproteinases (MMPs). Hypothesis/Purpose: To quantify MMP content in 2 commercially available PRP preparation systems: Arthrex Double Syringe System autologous conditioned plasma (ACP) and Biomet GPS (GPS). The hypothesis was that MMPs are actively secreted from PRP immediately after preparation. Study Design: Controlled laboratory study. Methods: PRP was prepared using either ACP (low platelet, low leukocyte) or GPS (high platelet, high leukocyte). MMP-2, MMP-3, and MMP-9 concentrations were measured using multiplex enzyme-linked immunosorbent assays for up to 6 days in 2 donors, and MMP activity was measured in 3 donors using kinetic activity kits able to detect the enzymatic cleavage of a fluorogenic peptide. Human ligament fibroblasts were cultured and exposed to both ACP and GPS from 1 donor each. MMP-2, -3, and -9 concentrations were assayed in culture media at 24 and 48 hours after exposure. Results: GPS exhibited higher total MMP-2, -3, and -9 concentrations for up to 144 hours of release, while ACP had higher platelet-normalized MMP-2 and MMP-3 concentrations. GPS had significantly higher total and endogenous MMP-2 activity (P = .004 and .014, respectively), MMP-3 activity (P = .020 and .015, respectively), and MMP-9 activity (P = .004 and .002, respectively) compared with ACP. Once normalized to platelet count, differences in MMP activity were not significant between ACP and GPS. Compared with controls, cells stimulated with interleukin-1 beta (IL-1β) and treated with ACP showed significantly higher fold changes of MMP-2 (P = .001) and MMP-3 (P = .003) concentrations at 24 hours than did cells treated with GPS. Total MMP-9 content was higher in the media of GPS-treated, IL-1β–stimulated cells compared with ACP-treated cells (P = .001). At 48 hours, IL-1β–stimulated cells treated with GPS exhibited higher fold changes of MMP-2 concentration (P = .002) compared with controls, but no difference in MMP-3 concentration was found. At 48 hours, there was a significantly higher concentration of MMP-9 in the cell culture media of ACP-treated cells compared with GPS-treated cells (P = .003). Conclusion: PRP prepared as both ACP and GPS contains MMP-2, -3, and -9, which is released over a period of at least 6 days. Furthermore, a large proportion of these MMPs are in their active form, and MMP activity is dependent on platelet count within the PRP preparation. Once exposed to ligament fibroblasts, both ACP and GPS cause the fibroblasts to release MMPs, most notably 24 hours after PRP exposure, and this release is dependent on prior IL-1β stimulation. Clinical Relevance: The results of this study demonstrate that PRP therapy delivers ng/mL-range concentrations of catabolic proteases, which could perpetuate inflammation and inhibit tissue healing.

Biomechanical Evaluation of the TightRope Versus Traditional Docking Ulnar Collateral Ligament Reconstruction Technique Kinematic and Failure Testing

Background: Numerous variations of ulnar collateral ligament (UCL) reconstruction have been described since the original technique by Jobe et al. Purpose/Hypothesis: To biomechanically compare the new TightRope technique and the traditional ulnar bone tunnels as used in the docking technique. The hypothesis was that the TightRope technique would exhibit improved kinematics and comparable failure properties. Study Design: Controlled laboratory study. Methods: Seven matched pairs of cadaveric arms (mean age, 44.71 years) were tested in both the native state and reconstructed state. Kinematics were assessed at 15° to 90° of flexion by applying a 1.5-N·m valgus torque and measuring the resultant angular displacement. Failure testing was performed by loading to failure at 4.5 deg/s in 70° of flexion. Sides of a matched pair were randomized to the TightRope (TR) and docking (DO) techniques after testing the native state. Results: There was no significant difference in kinematic results between the native state and reconstructed state in either the TR or DO group at 15° to 75° of flexion. At 90°, the TR group had significantly higher angular displacement (2.23° ± 1.0°) compared with the native state (1.31° ± 0.7°) (P = .020). The TR-reconstructed specimens had significantly lower initial stiffness (49.34 ± 19.3 N·m/rad vs 82.47 ± 36.0 N·m/rad, respectively; P = .007) and total stiffness (53.81 ± 27.8 N·m/rad vs 101.06 ± 34.4 N·m/rad, respectively; P < .001) than did the paired native specimens. In addition, the TR-reconstructed specimens had significantly lower torsional torque at 5° of valgus rotation (mean, 4.61 ± 2.2 N·m vs 7.62 ± 3.7 N·m, respectively; P = .010), at 15° of valgus rotation (12.24 ± 4.4 N·m vs 20.65 ± 6.8 N·m, respectively; P = .002), and at ultimate failure (19.18 ± 7.5 N·m vs 25.42 ± 7.1 N·m, respectively; P = .025) than did the paired native specimens. There was no significant difference in torsional torque between the TR and DO groups at 5° of valgus rotation (4.61 ± 2.2 N·m vs 4.09 ± 1.7 N·m, respectively; P = .644), at 15° of valgus rotation (12.24 ± 4.4 N·m vs 17.94 ± 7.23 N·m, respectively; P = .178), or at failure (19.18 ± 7.5 N·m vs 23.19 ± 10.6 N·m, respectively; P = .444). The DO group exhibited significantly higher angular displacement at failure than did the native state (28.12° ± 8.5° vs 18.04° ± 4.8°, respectively; P = .009), but there was no difference at 3 N·m of loading. There was no significant difference in angular displacement either at 3 N·m or at failure between the native state and reconstructed state in the TR group. Conclusion: Both the TR and DO techniques restored native joint kinematics from 15° to 75° of flexion under low loading conditions. While the TR technique exhibited inferior failure torque compared with the native state, the DO technique did not differ from the native state. No differences were found between the TR and DO groups when compared directly. The DO technique restored valgus stability under high loading to a greater extent than did the TR technique but also failed at higher angular displacement. Clinical Relevance: Strong postoperative UCL reconstruction fixation is important to restore ulnotrochlear joint stability. Our study demonstrates that the new TR technique has comparable kinematic and failure properties to the traditional DO technique.

The GraftLink Ulnar Collateral Ligament Reconstruction: Biomechanical Comparison With the Docking Technique in Both Kinematics and Failure Tests

Background: Ulnar collateral ligament (UCL) reconstruction aims to restore valgus stability, and numerous techniques have been described in the literature. Hypothesis/Purpose: To biomechanically compare the GraftLink (GL) technique with traditional bone tunnels used in the docking (DO) technique. It is hypothesized that the GL method will offer a stiffer, less lax construct compared with the DO. Study Design: Controlled laboratory study. Methods: Native and reconstructed states were tested in 7 matched pairs of cadaveric arms. To test kinematics, a 1.5-N·m valgus torque was applied and the resultant displacement at 15° to 90° of flexion was measured. Dissipated energy and the torque at the peak of the 10th cycle of preconditioning were analyzed during kinematic tests. Failure testing was performed by internal rotation of the humerus at 4.5 deg/s in 70° of flexion. Ulnotrochlear joint (UTJ) gapping was quantified during failure tests by use of video tracking. Results: Kinematics testing revealed no differences between the native state and the reconstructed state in either the DO or the GL group at any flexion angle. Stiffness was lower in the reconstructed specimens in both the DO (39.92 N·m/rad) and GL (50.74 N·m/rad) groups compared with their matched native states (DO Native, 71.41 N·m/rad, P = .005; GL Native, 86.36 N·m/rad, P = .002). There was no difference in stiffness between DO and GL. Reconstructed specimens in the GL group had lower torque at failure compared with native specimens (17.404 N·m vs 24.63 N·m, P = .038), but there was no difference in the DO group at failure. There was no difference in torque at failure between DO and GL. The DO exhibited higher angular displacement at failure compared with the native state (34.21° vs 21.79°, P = .010) and compared with the GL when normalized (1.58-fold vs 1.19-fold, P = .039). Compared with their native states, both DO and GL had significantly higher UTJ gapping at 3 N·m and at failure. The DO had significantly higher normalized UTJ gapping than the GL at 3 N·m (P = .037) and at failure (P = .043). Conclusion: The DO and GL both restored joint kinematics under low loading conditions. Although less stiff, the GL exhibited lower joint gapping and laxity than did the DO. Clinical Relevance: Understanding the biomechanics of UCL reconstruction has significant implications for postoperative management as it relates to early rehabilitation. Biomechanically inferior constructs could risk graft failure or early loosening during rehabilitation, and comparing the biomechanics of new techniques to established, widely used procedures such as the docking technique can provide important information about the immediate postoperative performance.

Arthroscopic suture bridge rotator cuff repair: functional outcome, repair integrity, and preoperative factors related to postoperative outcome

ABSTRACT Objectives: To assess the retear rate, retear size and location, the clinical impact of a retear, and preoperative patient factors related to postoperative outcome after arthroscopic suture bridge rotator cuff repair. Methods: Fifty six patients with an isolated, full-thickness supraspinatus tendon tear who underwent arthroscopic suture bridge rotator cuff repair were retrospectively identified. Patients were evaluated and rotator cuff integrity was assessed using ultrasonography. Visual analog score (VAS), the American Shoulder and Elbow Surgeon (ASES) score, shoulder range of motion and strength were used for clinical evaluation. Retears were assessed for size and location on ultrasonography. Results: Forty two patients (75%) aged a mean 59.7 ± 8.6 years (range 41–79 years) were available for follow-up at a mean 13.5 months. Postoperative evaluation indicated significant improvements in ASES score (49.76 ± 18.2 to 86.57 ± 13.4, P < 0.001), VAS pain score (4.69 ± 2.17 to 0.63 ± 1.29, P < 0.001), forward elevation range of motion (144.1° ± 29.9 to 159.69 ° ± 13.9, P = 0.002), and internal rotation ROM (44.13° ± 12.0 to 52.09° ± 12.0, P = 0.003). The retear rate was 14.28% (6/42). Patients with retears were not older (P = 0.526) but had a larger preoperative tear size (3.25 cm ± 0.5 vs 2.05 cm ± 0.48, P < 0.001). Preoperative tear size was significantly associated with a postoperative retear (P < 0.001). The duration of preoperative symptoms was significantly associated with pain (P = 0.029), pain improvement (P = 0.013), internal rotation ROM (P = 0.002), and internal rotation strength (P = 0.004). Conclusions: Arthroscopic suture bridge repair provides good clinical results with a low retear rate. The duration of preoperative symptoms was associated with postoperative outcome, indicating that delaying surgery may result in inferior outcomes. Level of Evidence: IV, Case Series

Intra– and Interdisciplinary Agreement in the Rating of Acromioclavicular Joint Dislocations

Abstract Background: Acromioclavicular (AC) joint dislocation is a common injury observed and treated by physicians from several disciplines; proper classification and communication of the diagnosis between physicians is essential to manage injuries properly. This study assessed inter- and intradepartmental agreement in the rating of AC joint dislocations and compared departments of orthopedic surgery, musculoskeletal (MSK) radiology, and emergency medicine (EM). Methods: Fifty radiographs indicating a random distribution of AC dislocations (Rockwood types I, II, III, and V) were sent to 25 resident, fellow, and attending physicians; the study group consisted of orthopedic surgeons (n = 9), MSK radiologists (n = 7), and EM physicians (n = 9). Dislocations were rated by physicians using the Rockwood classification (excluding type IV) and rating agreement was derived using the multirater κ statistic. Results: Moderate rating agreement was found among orthopedic surgeons (κ = 0.5147), which was higher than among radiologists (κ = 0.3628) or EM physicians (κ = 0.1894). Interdisciplinary rating agreement was highest between orthopedic surgeons and MSK radiologists and lowest between MSK radiologists and EM physicians. Attending orthopedic surgeons showed the highest rating agreement (κ = 0.5167) compared with attending MSK radiologists (κ = 0.3585) and attending EM physicians (κ = 0.2612). In-training orthopedic surgeons had higher rating agreement (κ = 0.4918) than in-training MSK radiologists (κ = 0.4218) and in-training EM physicians (κ = 0.1410). Discussion: Orthopedic surgeons exhibited the highest intradepartmental rating agreement in assessing AC joint injuries, but interdepartmental rating agreement was low. It is unclear if low interdepartmental rating agreement reflects classification or training weaknesses; recognition of these differences may help develop a more standardized education for physicians to improve the management of AC joint injuries. Conclusions: Interdisciplinary rating agreement of AC joint injuries is low. Further study may help improve education and communication about AC joint injuries among physicians.

Cartilage Thickness and Surface Roughness Patterns in Healthy and Osteoarthritis Knees: Novel 3D Analysis of Subjects from the Osteoarthritis Initiative

Objectives: Three-dimensional (3D) magnetic resonance imaging (MRI) enables characterization of articular cartilage (AC) morphology. AC is traditionally analyzed using mean cartilage thickness (MCT), but OA can occur without drastic changes in MCT due to regions of both thickening and thinning, as shown in recent studies. Our group recently developed a method to assess 3D AC morphology in terms of both MCT and surface roughness (Sa) using mesh parameterization, an image processing technique that projects 3D data onto a 2D domain. The objective of this study was to apply this technique to characterize changes in MCT and Sa in subjects from the Osteoarthritis Initiative (OAI) with varying degrees of OA. Methods: Under institutional approval, image data was obtained from OAI. Inclusion criteria were availability of a baseline 3D double-echo steady state (DESS) MRI of the right knee and Kellgren-Lawrence (KL) score. Exclusion criteria were history of systemic testosterone, estrogen, GNRH, PTH, or bisphosphonate use, prior fracture, knee replacement, hyaluronic acid or steroid injections, and evidence of unreported knee injury or other anomaly on x-ray review. From the resulting pool, 10 subjects (5 men and 5 women) were randomly selected from each KL grade (0 - 4). Using our parameterization method, AC regions of interest were isolated from the MRI stacks and converted to 2D height maps (Figure 1). MCT and normalized surface roughness (Sa) were calculated for the whole femur, whole tibia and individual compartments. Femurs and tibias of KL0, KL2 and KL4 subjects have been analyzed. Analysis of patellae and remaining KL grades is ongoing. Results were compared between groups using t-tests with α = 0.05. Results: Representative KL0 and KL4 AC thickness maps are shown in Fig1A, B. Compared to KL0, KL4 exhibits thinning with adjacent thickening on the medial femoral condyle (MFC). There were no significant differences in MCT between KL grades in any femoral compartment. On the tibia, KL0 exhibits congruent AC with natively-thicker AC at the weight-bearing aspect. KL4 tibiae exhibit global thinning with a zone of severe thinning on the medial plateau (MP). Whole-tibia MCT of KL4 was significantly lower compared to KL2 and KL0 (Fig. 1D). In contrast to MCT, Sa was highly sensitive to compartment-dependent degeneration. In the whole femur, Sa was significantly higher in KL4 compared to both KL2 and KL0. On the MFC, Sa increased steadily with increasing KL grade (Fig1E), and the lateral condyle of KL4 exhibited higher Sa compared to KL0. No differences in Sa were observed on the trochlea. On the tibia, Sa was significantly elevated in KL4 compared to both KL0 and KL2 in all compartments (Fig1F). Conclusion: The presented technique enabled repeatable visualization, compartmental segmentation, and quantification of MCT and Sa of the whole joint. No differences in femoral MCT were found, which can be attributed to adjacent thickening and thinning. Femoral and tibial OA changes were detected more sensitively using Sa, with significant increases observed in the whole femur and both condyles and plateaux. Significant differences in Sa between KL0 and KL2 femurs indicate sensitivity of this technique to subtle changes in early OA. More sensitive characterization of compartmental and sub-compartmental morphologic changes associated with OA can increase our understanding of its progression and facilitate more sensitive early diagnosis.