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Purpose of the Study: The purpose of the study was to develop a new non-invasive and quantitative method for evaluation of the anterior cruciate ligament function., Patients and Methods: The new method was tested in 24 asymptomatic subjects and in 58 patients (39 males and 19 females) with arthroscopically proven unilateral rupture of the anterior cruciate ligament. Anterior displacement of the tibia with the knee in 20 degrees flexion was achieved by using a redesigned device, constructed originally for stress-radiography, and detected by a 3-D optical motion analysis system., Results: In the normal group, the average difference (d) in anterior displacement of the tibia between the left and the right side under a displacement force of 250N was 0.56 mm (range 0.1 mm to 1.9 mm) or 17 p. 100 (range 2 p. 100 to 64 p. 100), while in patients the average difference (d) in anterior displacement of the tibia between the injured and uninjured side under a displacement force of 250N was 4.02 mm (range 0.6 mm to 9.4 mm) or 133.6 p; 100 (range 26 p. 100 to 451 p. 100). By the criteria for false negative results, i.e. the maximum value of the parameter d in normal subjects (1.9 mm and 64 p. 100), 10 p. 100 of the patients (6 patients) fell into the normal group. According to the criteria of false positive results, i.e. the minimum value of the parameter d in patients (0.6 mm and 26 p. 100), 17 p. 100 of the normal subjects (4 normal subjects) fell into the group of patients. The achieved level of differentiation is in the similar range as the most frequently used present methods., Discussion: The main advantage of the newly developed noninvasive optical measurement technique is that the direction of force and the amplitude and site of application are accurately defined and documented, and that dislocation movement of the tibia towards the femur during the application of a growing force is continuously monitored with the 3-D optical system and that it allows for several consecutive assessments based on statistical data.

Purpose of the Study: The goal of this study was to compare KT-1000 and Telos measurements after anterior cruciate ligament reconstruction (ACLR)., Material and Method: Forty eight patients with asymptomatic ACLR (4 failures with positive pivot shift and 12 knees with positive (+) Lachman test) were assessed (mean 2.5 years after surgery) by the same examiner by means of: 1) Lachman radiographic with Telos at 150 N, 2) MEDmetric KT-1000 at 69 N, 89 N and maxi-manuel (MM). The examiner tested more than 200 patients each year. Measurements were performed for KT-1000 according to the manufacturers' recommendations and for Telos according to Staübli. Only side to side differences in millimeters are reported. Reproducibility of KT-1000 measurements were also evaluated: interobserver reproducibility was assessed by 16 examiners on a healthy patient, and the experienced examiner tested 20 times a healthy patient., Results: An Interobserver error of 4 mm range (+/- 2 mm related to 0) was observed by 12 to 44 p. 100 of the examiners, respectively at 69 N to MM. An intraobserver error of 4 mm range (+/- 2 mm related to 0) was observed in 10 p. 100 at MM and in 20 p. 100 at 89 N. Mean side to side laxity with KT-1000 was 0.93 mm +/- 1.1 [-1 to 5] at 69 N, 1.3 mm +/- 1.6 [-2 to 6] at 89 N, and 1.41 +/- 1.8 [-2 to 6] at MM. With Telos the mean side to side laxity was 3.95 mm +/- 3.84 [0 to 15]. Significant differences (p = 0.0001) were found between measurements obtained by the two methods. No statistical correlation could be detected between values observed by Telos and KT-1000 (R < 0.1). If we consider a 3 mm side to side difference 23 knees (48 p. 100) had abnormal anterior laxity with Telos and with KT-1000 only 3 (6.2 p. 100) at 89 N and 6 (12.5 p. 100) at MM (1 (2 p. 100) at 69 N). With a 5 mm side to side difference, 12 knees (25 p. 100) had abnormal anterior laxity with Telos and with KT-1000 only 1 (2 p. 100) at 89 N and 1 (2 p. 100) at MM (0 at 69 N). Only Telos measurements were correlated to positive pivot shift (p = 0.007) and positive Lachman test (p = 0.01)., Conclusion: Interobserver reproducibility of KT-1000 measurements was low, but improved for intraobserver agreement. However, even for a unique KT-1000 experienced examiner, reliability of KT-1000 was poor when comparing Telos and KT-1000 predicitive value to diagnose ACLR failure. Telos results were much more pejorative but the only ones corelated with ACLR failures. We recommand Telos instead of KT-1000 to assess laxity after ACLR.

Purpose of the Study: The aim of this prospective study was to evaluate the objective postoperative laxity and functional results with a minimum follow-up of 10 years (mean 11.7 +/- 2 years) in chronic anterior knee instability treated by ACL reconstruction associated to a lateral extra-articular plasty., Material and Methods: 138 patients of a mean age of 27.8 +/- 8.5 years had been operated. Delay between injury and operation was 4 +/- 4.8 years. The surgical "Mac Injones" procedure used a free autologous patellar tendon graft with a bone-to-bone fixation, supplemented by a lateral extra-articular plasty using a strip of quadriceps tendon as a direct prolongation of the graft of the patellar tendon and patella itself. A rehabilitation program aimed to an early recovery of a complete range of motion. Anterior laxity had been measured before and after operation using two instrumented methods, KT-1000 and stress-radiography (at 20 degrees of flexion with a 9 kg load applied at the distal part of the thigh) with measurements of the displacement in medial and lateral compartments. Tunnel positioning was appreciated radiologically. Function was evaluated using the International Knee Documentation Committee score (I.K.D.C.)., Results: Elongation of the reconstructed ligament occurred mainly during the first 6 month, but was independent from early full range of motion recovery. Laxity was stabilized after one year. The final laxity gain of the medial compartment was 62 per cent and for the lateral compartment 77 per cent. The pivot shift test was negative in 66 per cent, grade 2 in 4 per cent, grade 1 in 30 per cent. Functional results were excellent and good (A and B) in 60.4 per cent and 76.7 per cent returned to sports activity. 12 reconstructed ligaments reruptured. Arthritis was the cause of poor results in other cases (13.8 per cent)., Discussion: Lateral extra-articular plasty is unable to better control translation of the medial compartment than isolated anterior cruciate ligament reconstruction, but laxity of the lateral compartment was minimized and the pivot shift test also. Incorrect position of the anterior cruciate ligament was correlated with poor results., Conclusion: This documented study on laxity of the two compartments confirms the interest of each type of reconstruction, in particular extra-articular plasty when made with quadriceps tendon and so doing, preserving the iliotibial-band for the control of varus stability.

Purpose of the Study: We determined retrospectively the influence of posterior tibial slope and anterior cruciate ligament (ACL) sparing on anterior tibial translation in 68 Cloutier total knee prosthesis. We also precised the influence of posterior tibial slope on knee functional score and appearance of tibial prosthetic interfaces., Material: 38 Cloutier total knee prosthesis (62 patients mean aged 62 +/- 10 years (36-76) at surgery) reviewed at systematic follow-up control, after a mean period of 5.5 +/- 3 years (2-15), were included in the study. The ACL was preserved in 38 knees and sacrified in 30 knees, the posterior cruciate ligament was preserved in all cases. The prosthetic design was the same whatever the number of cruciate ligament preserved. Osteoarthritis was the reason for surgery in 54 knees, and rheumatoid arthritis in 14 knees. Mean HSS knee score was 54 +/- 10 (29-80) before surgery and 89 +/- 10 (35-100) at follow-up. The mean range of motion was 103 +/- 24 degrees (30-130) before surgery and 110 +/- 14 degrees at follow-up (40-130)., Methods: Anterior tibial translation was determined on two profil x-rays (non weight bearing and weight bearing) at 20 degrees of flexion by comparing the position of tibial tray with regard to posterior edge of femoral prosthesis. Tibial slope was measured on lateral view with regard to peroneus axis. Appearance of tibial prosthetic interface was studied in 48 knees on AP and lateral x-rays orientated with an image intensifier in order to obtain the x-ray would be parallel to the tibial interface., Results: Posterior tibial slope (mean value 6.2 degrees +/- 4.2 degrees) was the main factor influencing the anterior tibial translation (mean value 3.9 +/- 4.6 mm) (p = 0.0007). A 10 degree increase of posterior tibial slope makes the anterior tibial translation rise by 5.6 mm in weight bearing situation. When ACL was preserved, the anterior tibial translation was lower but the decrease was not significant. Likewise, preservation of ACL or the degree of posterior tibial slope had no influence on: 1) HSS knee functional score, 2) range of motion. Radiolucent lines were observed in 18 out of 48 knees, but their occurrence was not influenced by the degree of posterior tibial slope or preservation of ACL., Discussion: Posterior tibial slope has a higher influence than ACL preservation on anterior tibial translation. The increase of posterior tibial slope in order to improve range of motion and to protect the bone-prosthetic tibial interface appeared unjustified with this non-constrained prosthesis. Moreover, implantation of tibial tray (whatever the preservation of ACL) with an important posterior inclination exposes to high anterior tibial translation in weight bearing situation. This last condition could reduce the survivorship of tibial polyethylene.

Purpose of the Study: The aim of this prospective study was to measure the stiffness of the ACL in normal knees, ACL deficient knees and after ACL reconstructions or meniscectomies. Stiffness is a physical quantity which expresses objectively the mechanical efficiency of the ACL., Material and Methods: 1502 tests were performed on: 480 normal control knees, 191 acute tears and 171 chronic instabilities pre and post-operatively, 60 extra-articular plasties, 30 meniscectomies and 64 arthritic knees before and after a cruciate sparing arthroplasty. The force displacement measurements were made on radiograms of the medial and lateral compartment of each knee at 20 degrees flexion by applying a postero anterior force from 0 to 300 N with increments of 50 N. The stiffness is the slope of the F/dl curve., Results: In the normal knee the medial compartment is fixed. Its stiffness is 13.8 x 10(4) N/m and does not depend on age and sex. The diagnosis of ACL rupture is made when the right/left difference on the medial compartment is at least 4 mm at 250 N. The lowest level for an accurate diagnostic is 180 N. The positive predictive value is 99 per cent. In acute tears the stiffness is 2.5 x 10(4) N/m. It is 3.4 x 10(4) N/m in chronic instability (p = 0.0001). When a meniscectomy was performed in chronic instability the stiffness decreases significantly (M+: 3.7 x 10(4) N/m; M-: 2.1 x 10(4) N/m) (p = 0.03). After a bone-patellar tendon-bone plasty (BPTB) the stiffness was 6.0 x 10(4) N/m and did not decrease with the passage of time but after the extra-articular plasty (EAP) the stiffness was 4.7 x 10(4) N/m after 24 months and 3.0 x 10(4) N/m after 60 months. Meniscectomy decreases the stiffness in both procedures, however it remains stable after BPTB, but decreases with the passage of time after EAP., Discussion: Stiffness is a biomechanical parameter of knee ligaments. It is highly correlated with the clinical symptoms of instability (p = 0.0001). It is more accurate than laxity which is a numerical value without mechanical significance., Conclusion: This method gives functional information on the ACL deficient knee. It is the more precise method for the diagnostic of ACL rupture with an efficiency of 98.5 per cent. It has a high prognostic value after ACL surgery and can be considered as the mechanical survival of the plasty.

Purpose of the Study: Passive hyperextension is a rare mechanism of injury of knee ligaments in clinical practice. The lesions are often complex and no consensus exists about their sequence. Our purpose was to study the mechanical behavior and the anatomical lesions of the knee following passive hyperextension until rupture., Material and Methods: 12 pairs of fresh human cadaveric knees were tested after resection of soft tissue except for the ligaments and the Popliteus muscle. Some of them had specific ligaments sections (PCL or posterior capsule). We used a "four point bending" model at a constant rate (V = 3 10E-4 m/s) and measured failure torque and bending stiffness of the knee. Results were expressed as percent of the response of the normal contra lateral knee., Results: A wide range of absolute data was noted and correlated to the age and bone quality. Bony avulsion was constant. The posterior capsule was the first structure injured at an average of 23 degrees of recurvatum, followed by the posterolateral ligament. The PCL was the ultimate structure to fail at its femoral attachment, preceding complete dislocation of the knee. No ruptures of the ACL and medial collateral ligament were noted. After section of the posterior capsule, the stiffness of the knee decreased 40 to 80 percent compared to the normal opposite knee, whereas the isolated section of the PCL had no significant effect., Discussion: The method used in this study appears reliable. "The four point bending" is a reproducible model and the use of paired specimens allows a quantitative approach. The use of elderly specimens at a low strain rate in this experiment remains a questionable point. Passive hyperextension is characterized by automatic external rotation resulting in asymmetrical posterior lesions and tears of the PCL at its femoral attachment. On the contrary, active hyperextension of the knee can produce ACL injury by anterior translation of the tibia under the femur consecutive to Quadriceps femoris contraction., Conclusion: Our experimental model is an effective and reproducible method to create passive hyperextension of the knee. The first structure to fail is the posterior capsule followed by the posterolateral ligament. The PCL is the ultimate structure to fail and no ACL rupture has been noted before dislocation., Clinical Relevance: if passive hyperextension mechanism is suspected, isolated posterior capsule lesion may occur and should be repaired. On the contrary, PCL tear should never be isolated and always associated with peripheral ligament injuries.