An Anatomically Placed Tibial Tunnel does not Completely Surround a Simulated PCL Reconstruction Graft in the Proximal Tibia

Introduction It is hypothesized that anatomic tunnel placement will create tunnels with violation of the posterior cortex and subsequently an oblique aperture that is not circumferentially surrounded by bone. In this article, we aimed to characterize posterior cruciate ligament (PCL) tibial tunnel using a three-dimensional (3D) computed tomography (CT) model. Methods Ten normal knee CTs with the patella, femur, and fibula removed were used. Simulated 11 mm PCL tibial tunnels were created at 55, 50, 45, and 40 degrees. The morphology of the posterior proximal tibial exit was examined with 3D modeling software. The length of tunnel not circumferentially covered (cortex violation) was measured to where the tibial tunnel became circumferential. The surface area and volume of the cylinder both in contact with the tibial bone and that not in contact with the tibia were determined. The percentages of the stick-out length surface area and volume not in contact with bone were calculated. Results The mean stick-out length of uncovered graft at 55, 50, 45, and 40 degrees were 26.3, 20.5, 17.3, and 12.7 mm, respectively. The mean volume of exposed graft at 55, 50, 45, and 40 degrees were 840.8, 596.2, 425.6, and 302.9 mm3, respectively. The mean percent of volume of exposed graft at 55, 50, 45, and 40 degrees were 32, 29, 25, and 24%, respectively. The mean surface of exposed graft at 55, 50, 45, and 40 degrees were 372.2, 280.4, 208.8, and 153.3 mm2, respectively. The mean percent of surface area of exposed graft at 55, 50, 45, and 40 degrees were 40, 39, 34, and 34%, respectively. Conclusion Anatomic tibial tunnel creation using standard transtibial PCL reconstruction techniques consistently risks posterior tibial cortex violation and creation of an oblique aperture posteriorly. This risk is decreased with decreasing the angle of the tibial tunnel, though the posterior cortex is still compromised with angles as low as 40 degrees. With posterior cortex violation, a surgeon should be aware that a graft within the tunnel or socket posteriorly may not be fully in contact with bone. This is especially relevant with inlay and socket techniques.

Twelve Weeks of a Staged Balance and Strength Training Program Improves Muscle Strength, Proprioception, and Clinical Function in Patients with Isolated Posterior Cruciate Ligament Injuries

Ligament reconstruction is indicated in patients with an isolated posterior cruciate ligament (PCL) injury who fail conservative treatment. To eliminate the need for PCL reconstruction, an ideal rehabilitation program is important for patients with an isolated PCL injury. The purpose of this study was to investigate the improvement in functional outcome, proprioception, and muscle strength after a Both Sides Up (BOSU) ball was used in a balance combined with strength training program in patients with an isolated PCL injury. Ten patients with isolated PCL injuries were recruited to receive a 12 week training program as a study group. In the control group (post-PCL reconstruction group), ten subjects who had undergone isolated PCL reconstruction for more than 2 years were enrolled without current rehabilitation. The Lysholm score, IKDC score, proprioception (active and passive), and isokinetic muscle strength tests at 60°/s, 120°/s, and 240°/s, were used before and after training on the injured and normal knees in the study group, and in the post-PCL reconstruction group. The results were analyzed with a paired t-test to compare the change between pre-training, post-training, and the normal leg in the study group, and with an independent t-test for comparisons between the study and post-PCL reconstruction groups. Both the Lysholm and IKDC scores were significantly improved (p < 0.01) after training, and no difference was observed compared to the post-PCL reconstruction group. The active and passive proprioception was improved post-training compared to pre-training, with no difference to that in the post-PCL reconstruction group. Isokinetic knee quadriceps muscle strength was significantly greater post-training than pre-training in PCL injured knees at 60°/s, 120°/s, and 240°/s, and in hamstring muscle strength at 60°/s and 120°/s. Muscle strength in the post-training injured knee group showed no significant difference compared to that in the post-training normal leg and the post-PCL reconstruction group. The post-training improvement of muscle strength was higher in the PCL injured leg compared to the normal leg and there was no difference between the dominant and non-dominant injured leg in the study group. After 12 weeks of BOSU balance with strength training in patients with an isolated PCL injury, the functional outcome, proprioception, and isokinetic muscle strength were significantly improved, and comparable to the contralateral normal leg and the post-PCL reconstruction group. We suggest that programs combining BOSU balance and strength training should be introduced in patients with a PCL injury to promote positive clinical results.

Developing Trends and Core Knowledge in Posterior Cruciate Ligament Research: A Bibliometric and Visualized Analysis

Background: The Posterior Cruciate Ligament (PCL) has important research value and broad application prospects in sports medicine. This study provides information on the present status, worldwide trends, evolutionary path and frontier research hotspots in this field. Methods: Publications from 1971 to 2021 were obtained from the Web of Science database and analyzed using VOSviewer and CiteSpace software. Results: there is an increasing trend in the relative research interests and the number of publications per year globally. The research institution with the highest documents and citations was the University of Pittsburgh. The United States showed a dominant position in publication outputs, followed by China and South Korea. Leading researchers, their cooperative relationships, and their scientific masterpieces have been identified. Arthroscopy has published the most papers in this field, followed by Knee Surgery Sports Traumatology Arthroscopy and American Journal of Sports Medicine. The publications can be divided into eight clusters: “Total knee arthroplasty”, “PCL reconstruction”, “Injury and rehabilitation”, “Anatomy and diagnosis” and “Functional assessment and etiology”. A cluster of citation keywords showed that “tibial slope” is the new research focus in the field. Conclusions: The publications about PCL research would remain in a high level of relevance for the future, based on the current global trends. Double bundle PCL reconstruction is the preferred surgical method for most PCL complex injuries. Its surgical techniques and postoperative management are making continuous progress, with doctors paying more attention to rapid postoperative recovery and improvement of patient satisfaction. Bibliometrics analysis enables us to accurately identify scholars, institutions, and journals with great academic influence in the vast and miscellaneous literature. This helps us quickly understand the current development and future research trend of the field.

Risk Factors for Readmission following Anterior Cruciate Ligament Reconstruction

The purpose of this study is to identify risk factors for readmission after anterior cruciate ligament (ACL) reconstruction and to determine costs associated with readmission. Using a private insurance claims' database, we identified patients who underwent ACL reconstruction from 2010 to 2015 using the International Classification of Diseases, Version 9 (ICD-9) and Current Procedural Terminology (CPT) codes. Univariate analysis was performed on demographic data, surgical characteristics, and comorbidities. Variables with p < 0.10 were added to a multivariate logistic regression model which was created to identify independent risk factors for all-cause readmission within 90 days postoperatively. Significance was considered at p < 0.05. Overall, 90,263 patients were included (average age: 29 ± 13 years, 44% female), and 1,066 (1.2%) of patients had a hospital readmission within 90 days following surgery. Risk factors for hospital readmission included cerebrovascular disease (odds ratio [OR] = 3.4, 95% confidence interval [CI]: 1.9, 6.2), diabetes mellitus (OR = 2.6, 95% CI: 1.9, 3.5), concomitant medial collateral ligament (MCL) or lateral collateral ligament (LCL) reconstruction (OR = 2.5, 95% CI: 1.9, 3.3), concomitant posterior cruciate ligament (PCL) reconstruction (OR = 2.2, 95% CI: 1.4, 3.3), age between 44 and 65 years (OR = 2.1, 95% CI: 1.6, 2.9), and depression (OR = 1.88, 95% CI: 1.49, 2.38, p < 0.001). Female sex was associated with decreased odds of 90-day hospital readmission (OR = 0.8, 95% CI: 0.7, 0.9). Each hospital readmission accounted for an estimated $17,841 (95% CI: $17,173, 18,509) in gross health care payments, and patients with readmissions had substantially higher 1-year cumulative health care costs. Readmission after ACL reconstruction was 1.2%. The strongest risk factors for 90-day readmission include cerebrovascular disease, diabetes mellitus, concomitant MCL/LCL reconstruction, concomitant PCL reconstruction, and age between 44 and 65 years. Readmission was associated with substantial health care costs.

Gait Adaptations at 8 Years After Reconstruction of Unilateral Isolated and Combined Posterior Cruciate Ligament Injuries

Background: It remains unclear how posterior cruciate ligament (PCL) reconstruction influences long-term lower extremity joint biomechanics. Purpose: To determine whether patients who underwent PCL reconstruction exhibited long-term alterations in lower limb gait mechanics. Study Design: Controlled laboratory study. Methods: A total of 26 patients underwent gait analyses at 8.2 ± 2.6 years after primary unilateral PCL reconstruction. Sex- and age-matched healthy controls were analyzed for comparison. Gait data were collected using motion capture and force plates. Hip, knee, and ankle angles and moments were compared during initial contact, early stance, and late stance for the reconstructed and uninjured contralateral limbs of patients who underwent PCL reconstruction (PCL group) as well as the limbs of healthy control participants (CON group). Results: No side-to-side kinematic differences were noted between the reconstructed and contralateral limbs of the PCL group; some trivial differences were noted in knee and hip moments. However, major differences between the PCL and CON groups occurred at the knee. Reconstructed and contralateral limbs of the PCL group exhibited larger knee flexion angles during initial contact (Δ = 7.0° [ P < .001] and Δ = 6.9° [ P < .001], respectively), early stance (Δ = 5.8° [ P = .003] and Δ = 6.7° [ P < .001], respectively), and late stance (Δ = 7.9° [ P < .001] and Δ = 8.0° [ P < .001], respectively) compared with the CON group. During early stance, contralateral limbs of the PCL group displayed larger knee flexion moments (Δ = 0.20 N·m/kg; P = .014) compared with the CON group, and both reconstructed (Δ = 0.05 N·m/kg; P = .027) and contralateral (Δ = 0.07 N·m/kg; P = .001) limbs of the PCL group exhibited larger knee external rotation moments compared with the CON group. During late stance, reconstructed and contralateral limbs of the PCL group exhibited smaller knee extension moments (Δ = 0.24 N·m/kg [ P < .001] and Δ = 0.26 N·m/kg [ P < .001], respectively) and knee internal rotation moments (Δ = 0.06 N·m/kg [ P < .001] and Δ = 0.06 N·m/kg [ P < .001], respectively) compared with the CON group. No discrepancies were observed at the hip; minimal differences were noted in sagittal-plane ankle mechanics. Conclusion: Patients who underwent PCL reconstruction generally exhibited bilateral gait symmetry at 8 years after surgery. However, they exhibited important biomechanical deviations in both knees compared with healthy controls. These modifications likely reflect adaptive gait strategies to protect the PCL after reconstruction. Clinical Relevance: Long-term follow-up analyses of patients who underwent PCL reconstruction should not use the uninjured contralateral limb as a “healthy” reference, as it also exhibits mechanical differences compared with controls. Results could inform the development of neuromuscular and strength training programs targeting the restoration of knee biomechanics similar to healthy controls to prevent early-onset degeneration that is frequently associated with altered biomechanics.

A Time-Zero Biomechanical Study of the Effective Length of the Graft in Posterior Cruciate Ligament Reconstruction

Background The effect of effective length on the biomechanical properties of the graft is regarded as an essential variable influencing the posterior cruciate ligament reconstruction. However, the effect has not been fully studied. The purpose was to compare the effects of different effective graft lengths (35 mm, 55 mm, 65 mm) on the time-zero biomechanical properties of the graft in posterior cruciate ligament (PCL) reconstruction.Methods Bovine digital flexor tendons and porcine tibias were used to establish in-vitro PCL reconstruction models. Tensile strength testing was performed at 3 different effective lengths of the graft: short (35 mm, n = 10, group 1), medium (55 mm, n = 10, group 2), and long (65 mm, n = 10, group 3). A computer software (Trapezium X; Shimadzu) was used to record the load-elongation curve, ultimate load (N), the elongation of the graft during the test (mm), tensile stiffness (N/mm), and energy absorption (J). The failure pattern was evaluated by visual observation.Results All the samples failed because the grafts slipped out from the bones, except two grafts ruptured in group 1. The tensile stiffness and ultimate load in group 1 were significantly higher than those in group 2 and group 3 (tensile stiffness, 50.49 ± 11.43 N/mm in group 1 vs 31.20 ± 10.44 N/mm in group 2[P < 0.001] and 19.18 ± 6.18 N/mm in group 3 [P < 0.001]; ultimate load, 452.40 ± 54.52 N in group 1 vs 338.50 ± 26.79 N in group 2 [P < 0.001]and 268.70 ± 28.30 N in group 3 [P < 0.001]). There were significant differences between group 1 and group 3 in energy absorption(9.61 ± 3.25 J vs 5.22 ± 2.43 J, P = 0.002). At 50 N and 100 N of applied load, no statistically significant differences were detected on the elongation of the grafts (P > 0.05). The elongation of the short grafts under 150 N and 200 N of applied load was significantly less than that of the long grafts (150 N, 1.77 ± 0.83 mm in group 1 vs 4.14 ± 1.75 mm in group 3, P = 0.047; 200 N, 2.62 ± 1.10 mm in group 1 vs 7.06 ± 3.20 mm in group 3, P = 0.006).Conclusions This study demonstrated the time-zero biomechanical properties of the graft with short effective length were superior to those of the graft with medium and long effective lengths in PCL reconstruction.

The Posterior Cruciate Ligament: Anatomy, Biomechanics, and Double-Bundle Reconstruction

The posterior cruciate ligament (PCL) is the largest intra-articular ligament in the knee and is the primary stabilizer to posterior tibial translation. Historically, the PCL’s functional dynamics and appropriate management after injury have been controversial. However, recent biomechanical and anatomic studies have elucidated a better understanding of PCL function, which has led to development of more anatomic reconstruction techniques. The larger anterolateral bundle and the smaller posteromedial bundle of the PCL exhibit a codominant relationship and have a wide femoral attachment footprint. For these reasons, the native kinematics of the knee is better restored with a double-bundle PCL reconstruction (DB-PCLR) technique than with a single-bundle PCL reconstruction (SB-PCLR). Likewise, clinical studies have demonstrated excellent outcomes for DB-PCLR compared to SB-PCLR, with decreased posterior knee laxity on stress radiography and improved International Knee Documentation Committee scores. This review will provide a detailed overview of the clinically relevant anatomy, biomechanics, injury evaluation, and treatment options, with an emphasis on arthroscopic DB-PCLR.

Transtibial Posterior Cruciate Ligament Reconstruction

The keys to successful posterior cruciate ligament (PCL) reconstruction are to identify and treat all pathology, utilize strong graft material, accurately place tunnels in anatomic insertion sites, minimize graft bending, mechanical graft tensioning, secure graft fixation, and the appropriate postoperative rehabilitation program. Adherence to these technical principles results in successful single- and double-bundle arthroscopic transtibial tunnel PCL reconstruction based upon stress radiography, arthrometer, knee ligament rating scales, and patient satisfaction measurements. The purpose of this manuscript is to describe the arthroscopic transtibial tunnel posterior cruciate ligament reconstruction surgical technique.