The Necessity Of Developing Double-bundle Posterior Cruciate Ligament Reconstruction

Background:The posterior cruciate ligament (PCL) is essential for the knee joint. Its anatomy position locates in the center of the knee, and it supports the knee to flex and pivot. Compare to anterior cruciate ligament, the PCL is deeper, and it is more susceptible to injury. The PCL injury is common in traffic incidents and usually combines with other ligament and tissue injury. The isolated PCL injury is common in the athletes of football, basketball, running and skating. The PCL injury or rupture will directly influences the kinematic and stability of knee joint. The conservative therapy is the main treatment at the day when the science is not advanced. With the development of the science, human’s request for lives quality and athlete’s competition level increase, the operation for PCL injury is necessary. Our topic contains three parts:we first proceed the anatomy observation and measuring of the PCL with the use of experiment animals, then we summarized the anatomy and biomechanics studies of PCL and therapy of PCL injury, last but not the least, we assembled the clinical studies comparing single-versus double-bundle PCL reconstruction to proceed a systematic review and meta analysis.The anatomy study of rabbit’s PCL:We proceed the rabbit PCL anatomy and biomechanics study to provide evidence for the clinical studies. We use the animals and tools for our experiments:(l) 6 New Zealand rabbits of 10 weeks old and weighted 10 KG provided by animals experiment center of Sun yet-san University. They were fed with normal diet in the animal experiment center.(2) Dissecting tool:dissecting scalpel, tissue scissors and nippers.(3) Measuring tools:compasses, protractor and rulers.(4) 3.6% chloral hydrate, injector, digital camera. First, we anesthetized the rabbit with the chloral hydrate entirely but not deadly and fastened it on the operation place. The left lower limb wassterilized with iodine and alcohol, its skin was cut off and its tissue was separated, the knee joint, femur and tibia were exposed. Then we used the nipple to shear the femur and tibia in the place where 4 cm long from the knee joint and dissected out the whole knee joint. The joint capsule was cut off by the tissue scissor, the anatomy of the knee was exposed, we separated the PCL and it AL and PM bundles carefully. Then we proceeded the Lachman’s test on the knee and observed the tightness of the PCL,AL and PM bundles. We draw the 0,30,60, and 90 degree angles on the paper and flexed the knee according to these angles and observed the anatomy of the PCL and its AL and PM bundles. We also measured the length of the total PCL and it AL and PM bundles under the knee flexion in the angles mentioned above. The data were recorded in means±SD form.Last, the rabbits were executed by injecting air into their ear vain.Through this experiment, we find that the anatomy of the rabbit’s PCL is similar to the human’s. The length of the PCL is longer in the 60°nd 90°flexion of knee than in 0° and 30°. The AL bundle is longer than the PM bundle when the knee is bent and is shorter when the knee is straight. So we concluded that the anatomy of rabbit’s PCL is similar to human’s and is suitable to substitute the human’s knee for anatomy and biomechanics researches. The AL and PM bundle of PCL have variable effect for kinetics of knee in different flexion degree of knee, double-bundle reconstruction for patients with total PCL rupture is necessary.The progress of the anatomy of PCL and PCL reconstruction:The cruciate ligament is very essential for the stability of knee joint. It is hinge-liked and connecting the tibia intercondylar and femur intercondylar fossa. This hinge could prevent the tibia to retrude excessively and fix the knee joint. The cruciate ligament includes anterior and posterior cruciate ligament. The anterior cruciate ligament starts at the inner face of the femor condylar and ends at the front of the tibia condylar and the meniscuc anterior horn. The PCL starts at the lateral surface of the medial femoral condyle and ends at the back of the tibial plateau. Its center is the narrowest part and it extends like the sector. The relationship of the anterior and posterior cruciate ligament is like that people’s middle finger which represents the ACL stacks on the forefinger which represents the PCL. According to incomplete statistics, there are about 8-10 million ACL reconstruction and only 10-20 thousand PCL reconstruction in our country. So the studies about ACL reconstruction is more than the PCL. With the increasement of the focus on the PCL therapy, the anatomy and biomechanics study about PCL becomes popular. The PCL could be diveded into two bundles(AL and PM bundles) for anatomy and biomechanics studies. The PCL reconstruction has been the golden standard of therapy for PCL rupture and now, the main controversy is about whether the double-bundle reconstruction is superior than the single-bundle recontruction.The systematic review and meta-analysis of single-versus double-bundle PCL recontruction:Comparing to the single-bundle reconstruction, the double-bundle reconstruction has many advantages, for example:1, double-bundle reconstruction has higher stability than single-bundle reconstruction.2, double-bundle reconstruction has more advantages in biomechanics than single-bundle reconstruction. In theory, double-bundle reconstruction is better than single-bundle reconstruction, but whether it has better clinical outcome is still unclear. Thus, we assemble the clinical studies comparing the single-versus double-bundle PCL reconstruction to perform a systematic review and meta-analysis.This systematic review was conducted according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines with a PRISMA checklis24(Fig.1). Two reviewers independently conducted the online search using the PubMed, Embase, and the Cochrane Library databases. The electronic search keywords were as follows:"posterior cruciate ligament reconstruction"; "PCL reconstruction"; "single-bundle" and "double-bundle". Language limited to the English. There was no restriction on the study of published year. If the abstract indicated a possibility that the study had a comparative study design,involved human subjects, and demonstrated any clinically relevant outcome, then the article was retrieved for more detailed evaluation.To be included, a study must be a clinical research with a prospective or retrospective comparative design (level of evidence Ⅰ, Ⅱ, or III).Furthermore,each study had to meet six inclusion criteria related to (1) the population that was considered to be acceptable for study (patients of any age), (2) it was a study of posterior cruciate ligament reconstruction, with use of arthroscopically assisted transtibial surgical technique in all group, comparing single-bundle with double-bundle, (4) the outcomes included any clinically relevant outcome, tunnel-enlargement, or complication,(5) the minimum duration of follow-up (two years), (6)the minimum study size (twelve patients in each group). Any study that failed to meet all of the inclusion criteria was excluded. Specifically, the case series (Level of Evidence IV) and biomachanic researches were excluded.Two authors independently extracted relevant data from each included study. The specific data that were extracted included the published year, country where the research was conducted, research design, level of envidance, sample size, number of patients, follow-up,femoral and tibial fixation, and implanted graft. Simultaneously, outcome measures included functional assessment scores such as the International Knee Documentation Committee (IKDC) scores, the Lysholm scores, and Tegner activity scores; stability assessments such as Lachman testing and mean side-to-side difference(SSD); imaging including radiography and computed tomography (CT) for femoral tunnel widening and the postoperactive complication.The methodologic quality of included studies was assessed by two authors using the Cochrane Collaboration’s risk-of-bias tool.This tool contains assessment of randomization(sequence generation and allocation concealment),blinding (participants, personnel, and outcome assessors), completeness of outcomes data, selection of outcomes reported, and other sources of bias. The risk of bias was categorized as low, unclear, or high for each of the included research.Only the RCT were pooled into the meta-analysis. Statistical analysis of the data was performed using RevMan 5.2 software.Dichotomous data were reported as odds ratio (OR) and 95% confidence intervals (CI).When possible, the outcomes were dichotomized into good and poor results. Continuous data were as mean difference(MD) and 95% confidence intervals (CI). Heterogeneity was assessed using I2 for each meta-analysis.Six clinical studies included 278 patients (single-bundle group:141, double-bundle group:137) were included into our systematic review, mean age: 23.5-37 years old, mean follow-up:18-51.2 months. The results of meta-analysis reveals that, comparing to the single-bundle reconstruction, double-bundle reconstruction had higher IKDC (P=0.04), Lysholm (P=0.02) and Tegner (P =0.02) scores, I2 test reveals no significant heterogenity between 2 groups, but there was not enough evidence to prove the difference of tunnel-widden and complication between the 2 groups.Conclusion:1. The AL and PM bundle of PCL have variable effect for kinetics of knee in different flexion degree of knee, double-bundle reconstruction for patients with total PCL rupture is necessary.2. The double-bundle PCL reconstruction could more effective restore the function of knee than single-bundle reconstruction, more clinical studies to develop double-bundle PCL reconstruction are necessary.