Search

PURPOSE OF THE STUDY The aim of this paper was to compare terminal extension in normal and anterior cruciate ligament (ACL) deficient knees, and therefore to determine the role of the ACL during this motion. MATERIAL AND METHODS Ten knees with ACL tears (7 knees with recent ACL tears, 3 knees with long-standing tears) and 10 normal contralateral knees have been examined using MRI in passive hyperextension, 20° flexion and 20° flexion with a 9 kg posteriorly directed load on the femur. Movements of the femoral condyles on the tibia were calculated using previously described methods. RESULTS 1. Under the load at 20° flexion, knees with ACL tear showed posterior femoral subluxation (equivalent to a Lachman test), chronic tears being more unstable. Contralateral normal knees were antero-posteriorly stable. In hyperextension, both femoral condyles subluxed posteriorly in ACL tears but not in normal knees. 2. In all knees with ACL tear, the lateral femoral condyle moved posteriorly from hyperextension to 20°, equating to femoral external rotation. 3. The longitudinal rotation axis during terminal extension in normal knees was medial but in ACL tears it was central causing the medial femoral condyle to move forward from hyperextension to 20°. In normal knees, the medial femoral condyle did not move antero-posteriorly from hyperextension to 20° flexion. DISCUSSION Internal rotation of the femur during terminal extension has been recognized for 150 years. The question remains: what causes the usual combination of longitudinal rotation and extension? In the current literature ACL is considered to be responsible for internal rotation of the femur during terminal extension of the knee. So far, as we are aware, the kinematics of terminal extension, including hyperextension, have not been reported after ACL tear in the living knee. CONCLUSIONS Results of this study imply that: 1. The ACL prevents anterior tibial subluxation in hyperextension. 2. The ACL does not cause rotation in terminal extension. 3. The ACL locates the axis of longitudinal rotation in terminal extension. We hope that by studying living knees with and without ACL tear we may not only clarify the nature and mechanism of rotation in terminal extension, and hence the role of the ACL, but do so in a context of direct clinical relevance. Key words: knee, terminal extension, ACL tear, axis of longitudinal rotation, antero-posterior instability, MRI.

Purpose of the Study: Treatment for tears of the anterior cruciate ligament (ACL) in paediatric patients has been a long-discussed issue because of complications associated with ligament reconstruction in the presence of growth plates. Various fixation materials and their efficiency as well as ACL techniques are still under investigation. The aim of our study was to find an optimal strategy of treating acute intra-articular ACL injury in childhood., Material and Methods: The paediatric patients treated for primary traumatic ACL injury between 2003 and 2013 were retrospectively evaluated. Only patients with a healthy contralateral knee (with no signs of instability or previous injury) and no record of previous ACL repair were included. A total of 78 patients were assessed; there were 39 girls and 39 boys with an average age of 15.4 years (11 - 16). The physical development of the patients was assessed on the Tanner scale, their satisfaction was recorded on the basis of the IKDC subjective knee evaluation form and the Tegner-Lysholm scoring system. The instrumented Lachman test using a rollimeter was performed to assess knee stability at 12 and 24 months of follow-up. In addition, the range of knee motion in comparison with the other side, complications and the re-rupture rate of reconstructed ACLs were recorded. Four patients with open growth plates were operated on using the transepiphyseal technique, the remaining 74 underwent reconstruction by the standard transphyseal method., Results: The average Tegner-Lysholm scores were 54 (41-62) pre-operatively and 86.1 (74-96) at 24 months post-operatively. The average IKDC score increased from 48 (42-56) points to 91 (73-97) points. The Lachman test was positive in all patients before ACL reconstruction and negative in 96% of them at 12 and 24 months after surgery. The full range of joint motion was restored after ACL surgery, with minimal motion restriction in flexion and extension, in 70 (89.7%) patients. Motion restriction by 15° or less in flexion and 5° or less in extension was recorded in seven (9%) patients and a significant restriction in extension exceeding 10° was found in one (1.3%) patient. No differences in results were found between the two scoring systems. Five patients (6.4 %) sustained a re-tear in the reconstructed ACL due to a trauma. Non-traumatic subjective instability after the primary repair was not recorded. Revision ACL surgery was carried out due to fixation materials protruding from the bone surface in two patients and because of a Cyclops lesion with extension deficit in one patient. No development of deformity or instability was observed at 24 months in the patients in whom the transepiphyseal technique was used. DISCUSSION In the current literature ACL reconstruction by the transphyseal technique has been described in patients older than 15 years of age but no optimal age has been suggested. Animal experiments have shown that tunnels taking up more that 7-9% of the growth plate surface can result in growth restriction or angular deformity. ACL reconstruction in patients with distinct bone immaturity carries a high risk. The effect of growth on the biomechanical properties of a graft and a long-term consequence of surgical intervention in the growth plate is not yet understood., Conslusions: Although indications for surgical ACL repair and its timing are bound to be different in each patient, we consider the age of over 15 years to be ideal for ACL reconstruction. In patients younger than 15 years, the necessity of surgical treatment is questionable and conservative therapy can give good outcomes. No adverse effect of an applied graft on the post-operative results was demonstrated. The features of an immature skeleton are specific and complicated therefore, in our view, the relevant health care for paediatric patients should be concentrated into specialised institutions.

PURPOSE OF THE STUDY Recent trends in the experimental surgical management of a partial anterior cruciate ligament (ACL) rupture in animals show repair of an ACL lesion using novel biomaterials both for biomechanical reinforcement of a partially unstable knee and as suitable scaffolds for bone marrow stem cell therapy in a partial ACL tear. The study deals with mechanical testing of the newly developed ultra-high-molecular-weight polyethylene (UHMWPE) biomaterial anchored to bone with Hexalon biodegradable ACL/PCL screws, as a new possibility of intra-articular reinforcement of a partial ACL tear. MATERIAL AND METHODS Two groups of ex vivo pig knee models were prepared and tested as follows: the model of an ACL tear stabilised with UHMWPE biomaterial using a Hexalon ACL/PCL screw (group 1; n = 10) and the model of an ACL tear stabilised with the traditional, and in veterinary medicine used, extracapsular technique involving a monofilament nylon fibre, a clamp and a Securos bone anchor (group 2; n = 11). The models were loaded at a standing angle of 100° and the maximum load (N) and shift (mm) values were recorded. RESULTS In group 1 the average maximal peak force was 167.6 ± 21.7 N and the shift was on average 19.0 ± 4.0 mm. In all 10 specimens, the maximum load made the UHMWPE implant break close to its fixation to the femur but the construct/fixation never failed at the site where the material was anchored to the bone. In group 2, the average maximal peak force was 207.3 ± 49.2 N and the shift was on average 24.1 ± 9.5 mm. The Securos stabilisation failed by pullout of the anchor from the femoral bone in nine out of 11 cases; the monofilament fibre ruptured in two cases. CONCLUSIONS It can be concluded that a UHMWPE substitute used in ex-vivo pig knee models has mechanical properties comparable with clinically used extracapsular Securos stabilisation and, because of its potential to carry stem cells and bioactive substances, it can meet the requirements for an implant appropriate to the unique technique of protecting a partial ACL tear. In addition, it has no critical point of ACL substitute failure at the site of its anchoring to the bone (compared to the previously used PET/PCL substitute). Key words: knee stabilisation, stifle surgery, ultra-high-molecular-weight polyethylene, UHMWPE, nylon monofilament thread, biodegradable screw, bone anchor.