Functional tissue engineering of ligament healing

Ligaments and tendons are dense connective tissues that are important in transmitting forces and facilitate joint articulation in the musculoskeletal system. Their injury frequency is high especially for those that are functional important, like the anterior cruciate ligament (ACL) and medial collateral ligament (MCL) of the knee as well as the glenohumeral ligaments and the rotator cuff tendons of the shoulder. Because the healing responses are different in these ligaments and tendons after injury, the consequences and treatments are tissue- and site-specific. In this review, we will elaborate on the injuries of the knee ligaments as well as using functional tissue engineering (FTE) approaches to improve their healing. Specifically, the ACL of knee has limited capability to heal, and results of non-surgical management of its midsubstance rupture have been poor. Consequently, surgical reconstruction of the ACL is regularly performed to gain knee stability. However, the long-term results are not satisfactory besides the numerous complications accompanied with the surgeries. With the rapid development of FTE, there is a renewed interest in revisiting ACL healing. Approaches such as using growth factors, stem cells and scaffolds have been widely investigated. In this article, the biology of normal and healing ligaments is first reviewed, followed by a discussion on the issues related to the treatment of ACL injuries. Afterwards, current promising FTE methods are presented for the treatment of ligament injuries, including the use of growth factors, gene delivery, and cell therapy with a particular emphasis on the use of ECM bioscaffolds. The challenging areas are listed in the future direction that suggests where collection of energy could be placed in order to restore the injured ligaments and tendons structurally and functionally

Changes of meniscal interhorn distances: An in vivo magnetic resonance imaging study

The aim of this study was to evaluate the changes of the internal (IID) and external meniscal interhorn distance (EID) of the medial and the lateral meniscus under loading. Sagittal magnetic resonance images of 15 knees were studied. The medial and lateral meniscus were examined with the knee at 0 degrees and 30 degrees of flexion, under no load, with load equal to 50% of body weight and with load equal to 100% of body weight. Under no load, the mean IID was 19.9 mm for the medial meniscus and 12.3 mm for the lateral meniscus and the mean EID was 44.6 mm for the medial meniscus and 34.4 mm for the lateral meniscus. Under load equal to 50% and 100% of patient’s body weight, there was a significant increase in both distances (p < 0.05). Under constant loading, flexion of the knee from 0 degrees to 30 degrees, decreased the EID of both menisci. In conclusion, loading increases both IID and EID. Knee position affects only the EID. The quality of magnetic resonance images may affect the reliability of such measurements. (c) 2005 Elsevier B.V. All rights reserved

The effect of graft choice on functional outcome in anterior cruciate ligament reconstruction

A prospective, randomised, 5-year follow-up study was designed to compare the functional results between patellar tendon and hamstring tendon autografts after anterior cruciate ligament reconstruction. Primary reconstruction was performed in 32 patients using the central third of the patellar ligament and in 32 patients using double-looped semitendinosus and gracilis tendons. All reconstructions were performed by a single surgeon, with identical surgical technique and rehabilitation protocol. Of the total 64 patients in the study, 54 (85%) were available for the 5-year follow-up. No statistically significant differences were seen with respect to Lysholm score, International Knee Documentation Committee (IKDC) classification, clinical and KT-2000 arthrometer laxity testing, single-legged hop test and anterior knee pain. Graft rupture occurred in two patients (8%) in the patellar tendon group and in two patients (7%) in the hamstring tendon group; 23 patients (88%) in the patellar tendon group and 23 patients (82%) in the hamstring tendon group returned to their pre-injury activity level. Good subjective outcome and stability can be obtained by using either graft; no statistically significant differences were found in functional outcome between the grafts

Factors affecting the longevity and strength in an In Vitro model of the bone-ligament interface

The interfaces between musculoskeletal tissues with contrasting moduli are morphologically and biochemically adapted to allow the transmission of force with minimal injury. Current methods of tissue engineering ligaments and tendons do not include the interface and this may limit the future clinical success of engineered musculoskeletal tissues. This study aimed to use solid brushite cement anchors to engineer intact ligaments from bone-to-bone, creating a functional musculoskeletal interface in vitro. We show here that modifying anchor shape and cement composition can alter both the longevity and the strength of an in vitro model of the bone–ligament interface: with values reaching 23 days and 21.6 kPa, respectively. These results validate the use of brushite bone cement to engineer the bone–ligament interface in vitro and raise the potential for future use in ligament replacement surgery