ACL-reconstructed Knees Research Articles

Tibial Rotation in Anterior Cruciate Ligament (ACL)-Deficient and ACL-Reconstructed Knees

Excessive tibial rotation has been documented in anterior cruciate ligament (ACL) deficiency during walking. ACL reconstruction has been unable to correct this abnormality in activities that are more demanding than walking and involve both anterior and rotational loading of the knee. These findings persist regardless of graft selection for the ACL reconstruction (bone-patellar tendon-bone or semitendinosus gracilis). Based on this research work, we propose a theoretical perspective for the development of osteoarthritis in both the ACL-deficient and the ACL-reconstructed knee. We propose that excessive tibial rotation will lead to abnormal loading of the cartilage areas that are not commonly loaded in the healthy knee. Over time, this abnormal loading will lead to osteoarthritis. We hypothesise that the development of new surgical procedures and grafts, such as a more horizontally oriented femoral tunnel or a double-bundle ACL reconstruction, could possibly restore tibial rotation to normal levels and prevent future knee pathology. However, in vivo gait analysis studies are needed to examine the effects of these surgical procedures on tibial rotation. Prospective in vivo and in vitro studies are also necessary to verify or refute our theoretical proposition for the development of osteoarthritis.

Dynamic Function of the ACL-reconstructed Knee during Running

Little is known about the three-dimensional behavior of the anterior cruciate ligament (ACL) reconstructed knee during dynamic, functional loading, or how dynamic knee function changes over time in the reconstructed knee. We hypothesized dynamic, in vivo function of the ACL-reconstructed knee is different from the contralateral, uninjured knee and changes over time. We measured knee kinematics for 16 subjects during downhill running 5 and 12 months after ACL reconstruction (bone-patellar tendon-bone or quadrupled hamstring tendon with interference screw fixation) using a 250 frame per second stereoradiographic system. We used repeated-measures ANOVA to ascertain whether there were differences between the uninjured and reconstructed limbs and over time. We found no differences in anterior tibial translation between limbs, but reconstructed knees were more externally rotated and in more adduction (varus) during the stance phase of running. Anterior tibial translation increased from 5 to 12 months after surgery in the reconstructed knees. Anterior cruciate ligament reconstruction failed to restore normal rotational knee kinematics during dynamic, functional loading and some degradation of graft function occurred over time. These abnormal motions may contribute to long-term joint degeneration associated with ACL injury and reconstruction.

The relationship between knee rating systems, isokinetic and isometric testing, and functional testing in the ACL-reconstructed and ACL deficient knee

Anterior cruciate ligament reconstruction has become a standard procedure with a documented good outcome of 70–90%. It is important to examine the relationship between commonly used knee rating systems and functional tests to assess whether there is a correlation between rating systems and functional performance. The purpose of this study was to determine if a correlation exists between four commonly used knee rating systems (Lysholm, Tegner, IKDC, Noyes) and commonly performed functional tests.

Decrease in anterior knee laxity by electrical stimulation of normal and reconstructed anterior cruciate ligaments

We have investigated the changes in anterior laxity of the knee in response to direct electrical stimulation of eight normal and 45 reconstructed anterior cruciate ligaments (ACLs). In the latter, the mean time from reconstruction was 26.7 months (24 to 32). The ACL was stimulated electrically using a bipolar electrode probe during arthroscopy. Anterior laxity was examined with the knee flexed at 20 degrees under a force of 134 N applied anteriorly to the tibia using the KT-2000 knee arthrometer before, during and after electrical stimulation. Anterior tibial translation in eight normal and 17 ACL-reconstructed knees was significantly decreased during stimulation, compared with that before stimulation. In 28 knees with reconstruction of the ACL, in 22 of which the grafts were found to have detectable somatosensory evoked potentials during stimulation, anterior tibial translation was not decreased. These findings suggest that the ACL-hamstring reflex arc in normal knees may contribute to the functional stability and that this may not be fully restored after some reconstructions of the ACL.

The effect of anterior cruciate ligament recontruction on lower extremity relative phase dynamics during walking and running

The purpose of this investigation was to use relative phase dynamics to evaluate gait in individuals with a reconstructed anterior cruciate ligament (ACL) during walking and running. Relative phase dynamics can describe the coordination strategies between the interacting segments at the lower extremity. Ten subjects who had undergone ACL reconstruction using the central third of their patellar tendon and ten healthy controls walked and ran on a treadmill at a self-selected pace. Relative phase dynamics were calculated for the foot-shank and shank-thigh coordinative relationships. Statistical differences between the groups were noted for the foot-shank relationship (p < 0.05) during both walking and running and for the shank-thigh relationship (p < 0.05) during walking. Our results indicate that current ACL reconstructive techniques may result in altered relative phase dynamics. These changes in relative phase dynamics could be related to a loss of sensory information about joint position and velocity that is typically provided by the intact ACL. Additionally, relative phase adaptations could be a learned response from the early stages of postsurgical rehabilitation. Relative phase dynamics provide quantitative information about the dynamic status of the ACL-reconstructed knee that cannot be gained from the conventional time-series evaluation of gait analysis data. Relative phase dynamics measures should supplement the conventional gait analysis measures that are used today for the clinical evaluation of the functional dynamic stability of the reconstructed knee. The examination of relative phase dynamics could be clinically important for the quantification of new ACL surgical interventions and of patient performance at various stages of rehabilitation. Further research should incorporate relative phase dynamics to understand the influence of ACL reconstruction on coordination and functional patient outcomes.

Anterior cruciate ligament graft impingement against the posterior cruciate ligament: diagnosis using MRI plus three-dimensional reconstruction software

The purpose of this study was to evaluate anterior cruciate ligament (ACL) impingement against the posterior cruciate ligament (PCL) with the knee in an extended position, which arthroscopy cannot detect. Ten normal knees and 30 ACL-reconstructed knees were assessed using MR imaging. The three-dimensional reconstruction of the ACL, PCL, femur and tibia were carried out using commercially available three-dimensional reconstruction software. Anterior cruciate ligament impingement against the PCL was graded into three categories: Grade 1, some space between the ligaments; Grade 2, no space between the ligaments, and the reconstructed ACL ran straight; and Grade 3, the reconstructed ACL did not run straight. The angle of the reconstructed ACL against the tibial plateau was also measured. All normal knees were classified as Grade 1. The 30 reconstructed knees were classified as follows: Grade 1, 12 cases; Grade 2, 7 cases; and Grade 3, 11 cases. The mean angle of the Grade 3 reconstructed ACL knees was significantly more vertical against the tibia as compared with the Grade 1 knees (P<.05). The postoperative KT-2000 side-to-side difference of the Grade 3 knees (2.8+/-4.5 mm) was larger than that of the Grade 1 knees (0.2+/-1.7 mm) and Grade 2 knees (-0.6+/-2.2 mm), but no statistically significant difference could be detected between the three groups in the postoperative KT-2000 data. This method is useful to evaluate ACL impingement against PCL, which cannot be detected by conventional arthroscopy during the operation. The surgeon should pay careful attention to the coronal angle of the reconstructed ACL.

Tibiofemoral Kinematics following Successful Anterior Cruciate Ligament Reconstruction Using Dynamic Multiple Resonance Imaging

Background The aim of anterior cruciate ligament reconstruction is to reduce excess joint laxity, hoping to restore normal tibiofemoral kinematics and therefore improve joint stability. It remains unclear if successful ACL reconstruction restores normal tibiofemoral kinematics and whether it is this that is associated with a good result. Study Case series. Purpose To assess the kinematics of the anterior cruciate ligament-reconstructed knee using open-access MRI. Methods Tibiofemoral motion was assessed using open-access MRI, weightbearing through the arc of flexion from 0° to 90° in 10 patients with isolated reconstruction of the anterior cruciate ligament (hamstring autograft) in one knee and a normal contralateral knee. Midmedial and midlateral sagittal images were analyzed in all positions of flexion in both knees to assess the tibiofemoral relationship. Sagittal laxity was also assessed by performing the Lachman test while the knees were scanned dynamically using open-access MRI. Results The amount of excursion between the tibial and femoral joint surfaces was similar between the normal and reconstructed knees, but the relationship of tibia to femur was always different for each position of knee flexion assessed—the lateral tibia being about 5 mm more anterior in the anterior cruciate ligament-reconstructed knees. This anterior tibial position is statistically significantly different at 0° (P < .0006), 20° (P = .0004), 45° (P = .002), and 90° of flexion (P < .006). Anteroposterior laxity was similar between normal and anterior cruciate ligament-reconstructed knees. Conclusion Anterior cruciate ligament reconstruction reduces sagittal laxity to within normal limits but does not restore normal tibiofemoral kinematics despite a successful outcome.

Abnormal Rotational Knee Motion during Running after Anterior Cruciate Ligament Reconstruction

Background The effectiveness of anterior cruciate ligament reconstruction for restoring normal knee kinematics is largely unknown, particularly during sports movements generating large, rapidly applied forces. Hypothesis Under dynamic in vivo loading, significant differences in 3-dimensional kinematics exist between anterior cruciate ligament-reconstructed knees and the contralateral, uninjured knees. Study Design Prospective, in vivo laboratory study. Methods Kinematics of anterior cruciate ligament-reconstructed and contralateral (uninjured) knees were evaluated for 6 subjects during downhill running 4 to 12 months after anterior cruciate ligament reconstruction, using a 250 frame/s stereoradiographic system. Anatomical reference axes were determined from computed tomography scans. Kinematic differences between the uninjured and reconstructed limbs were evaluated with a repeated-measures analysis of variance. Results Anterior tibial translation was similar for the reconstructed and uninjured limbs. However, reconstructed knees were more externally rotated on average by 3.8 ± 2.3° across all subjects and time points (P = .0011). Reconstructed knees were also more adducted, by an average of 2.8 ± 1.6° (P = .0091). Although differences were small, they were consistent in all subjects. Conclusions Anterior cruciate ligament reconstruction failed to restore normal rotational knee kinematics during dynamic loading. Clinical Relevance Although further study is required, these abnormal motions may contribute to long-term joint degeneration associated with anterior cruciate ligament injury/reconstruction.

Bilateral Comparison of Motor Unit Activation in Unilateral ACLReconstructed Individuals

2005 Knee strength deficits after anterior cruciate ligament reconstruction (ACLR) are common even after post-op rehabilitation has been completed. A loss of full muscle activation has been suggested as a contributing factor of weakness of the quadriceps in ACLR knees. PURPOSE: To bilaterally compare knee extension strength, thigh circumference, and motor unit activation of individuals who have unilateral ACLR. METHODS: Eight females (age 20 ± 1.6 yrs, height 163.5 ± 6.6 cm, weight 603.7 ± 50.4 N) and 6 males (20.8 ± 3.3 yrs, 180.3 ± 7.4 cm, 828.6 ± 152.8 N) with unilateral ACLR (2.3 ± 1.7 yrs post-op; 10 patellar tendon autograft, 1 hamstring autograft, 3 allograft) participated in this study. Knee extension torques were assessed using a KinCom AP125 isokinetic dynamometer at speeds of 60 and 180 °/s. The circumference at mid-thigh of each extremity was measured using a flexible measuring tape. Motor unit activation of the quadriceps was evaluated by delivering interpolated supramaximal tetanus twitches to the quadriceps while the subject performed an isometric knee extension at 90° knee flexion with maximum effort. The central activation ratio (peak force preceding stimulation divided by peak force after the stimulation) was used to determine the efficiency of the subject in recruiting available motor units. RESULTS: T-tests revealed lower peak isokinetic knee extension torques in the ACLR knee compared to the uninjured knee when tested at 60 °/s (141 vs. 155 Nm, respectively, p = .002) and 180 °/s (105 vs. 119 Nm, respectively, p = .054). Thigh circumference of the ACLR leg was found to be significantly smaller than the same measure for the uninjured leg (50.6 vs. 51.6 cm, respectively, p = .002). No significant differences were found between mean central activation ratios in ACLR knees and uninjured knees (93 vs. 94%, respectively, p = .917). CONCLUSION: Assuming that there is no change in the effective moment arm of the quadriceps muscle due to ACLR, our results suggest that a decrease in knee extension strength in ACLR knees is primarily due to muscle atrophy and not a deficit in motor unit activation or quality of the quadriceps muscle. Supported in part by the University of Florida Opportunity Fund.

A quantitative analysis of valgus torque on the ACL: a human cadaveric study

The loads needed to elicit a positive pivot shift test in a knee with an anterior cruciate ligament (ACL) rupture have not been quantified. The coupled anterior tibial translation (ATT), coupled internal tibial rotation (ITR), and the in situ force in the ACL in response to a valgus torque, an inherent component of the pivot shift test, were measured in 10 human cadaveric knee specimens. Using a robotic/universal force–moment sensor testing system, valgus torques ranging from 0.0 to 10.0 N m were applied in nine increments on the intact and ACL-deficient knee in flexion ranging from 0° to 90°. At 15° of knee flexion, the coupled ATT and ITR were significantly increased in the ACL-deficient knee when compared to the intact knee. Coupled ATT increased a maximum of 291% (6.7 mm, p<0.05), while coupled ITR increased a maximum of 85% (5.1°, p<0.05). At 30°, the increases in coupled ATT and ITR were significant at valgus loads of 3.3 N m and greater with a maximum increase in coupled ATT of 137% (6.3 mm, p<0.05) and a maximum increase in coupled ITR of 38% (3.6°, p<0.05). At 45°, coupled ATT increased significantly (maximum of 69%, 4.4 mm, p<0.05), but only at torques ⩾6.7 N m. The in situ force in the ACL was less than 20 N for all flexion angles when a torque between 3.3 and 5.0 N m was applied. Low valgus torque elicited tibial subluxation in the ACL-deficient knee with low in situ ACL forces, similar to a positive pivot shift test. Thus, application of a valgus torque may be suitable to evaluate ACL-deficient and ACL-reconstructed knees, since subluxation can be achieved with minimal harm to the ACL graft. This work is important in understanding one load component needed for the pivot shift examination; further studies quantifying other load components are essential for better comprehension of the in vivo pivot shift examination.

전방십자인대 수술이 시행되어진 슬관절과 정상 슬관절의 유효 모멘트암 (effective moment arm) 비교 분석

The purpose of this study is (a) to estimate effective moment arms of quadriceps forces and (b) to compare the <TEX>$d_e$</TEX> between the ACL-reconstructed and uninjured knees from the same individual. One female (20 yrs old, 2 yrs post-op, hamstring tendon autograft) and two males (22 yrs old, 2 yrs post-op; 28 yrs old, 4 yrs post-op; Patellar tendon autografts for both). Sagittal view radiographs were obtained for 6-7 different angles <TEX>$(range\;5^{\circ}-110^{\circ})$</TEX> from each knee. The do was determined by the method of Chow et al. (1999a). The results showed that the maximum de values ranged from 4.61 to 5.59cm and 4.59 to 4.89cm for the ACL-reconstructed and uninjured knees, respectively. The maximum <TEX>$d_e$</TEX> occurred between <TEX>$35^{\circ}\;and\;50^{\circ}\;and\;20^{\circ}\;and\;50^{\circ}$</TEX> for the ACL-reconstructed and uninjured knees, respectively. The minimum do values ranged from 4.12 to 4.35 cm and 3.12 to 3.63cm for the ACL-reconstructed and uninjured knees, respectively. The effective moment arm of the knee extensor affects the loads on knee ligaments during knee-extension exercises. Because apparent differences in the moment arm of the quadriceps in different participants, it is very important to use personalized knee joint geometry for the computation of knee joint force. In the present study, no noticeable bilateral difference was found in the male subjects. However, apparent bilateral differences in de were observed in the female subject. This suggests that the effects of ACL reconstruction surgery on patellar mechanism deserve further investigation.

Effect of harvesting the hamstrings tendon for anterior cruciate ligament reconstruction on the morphology and movement of the hamstrings muscle: a novel MRI technique.

This study evaluated intramuscular movement of hamstrings muscle after reconstruction of the ACL with a hamstrings tendon graft. The movement of the muscles during knee flexion was measured using a novel MRI technique called the "tagging snapshot" technique, which labels multiple tagging bands within the musculature. Eleven patients who underwent ACL reconstruction using autogenous semitendinosus and gracilis tendons were studied. The difference in the maximum active knee flexion angle between the ACL-reconstructed and the intact knee was calculated as knee flexion lag. Knee flexion strength was measured in 8 of the 11 patients. The semitendinosus muscle of the ACL-reconstructed knee exhibited three different morphological patterns; group I, similar shape to the intact knee with distal tendonlike structures; group II, smaller proximally than the intact knee with distal tendonlike structures; and group III, considerably smaller proximally than the intact knee without distal tendonlike structures. Each group was associated with a different knee flexion lag and different knee flexion strength. Our results indicated that the effect of hamstrings tendon harvest on knee function is not uniform.

Restoration of anterior cruciate ligament-hamstring reflex arc after anterior cruciate ligament reconstruction.

It has recently been emphasized that restoration of neuromuscular function contributes to dynamic stability of the anterior cruciate ligament (ACL) reconstructed knee. The existence of an ACL-hamstring reflex arc, one of the protective ligament-muscular pathways, has been revealed in normal human knees. Although reinnervation to the reconstructed ACL has been observed histologically, it remains unclear whether the ACL-hamstring reflex arc is reestablished. This study examined the existence of the ACL-hamstring reflex arc in ACL-reconstructed knees by analyzing the changes in the hamstring EMG elicited by electrical stimulation to the reconstructed ACL. The patellar tendon grafts transplanted as an ACL substitute in three patients were electrically stimulated via a bipolar wire electrode inserted arthroscopically. The surface EMG was monitored from the ipsilateral biceps femoris and semitendinosus. In two of the three patients the significantly increased EMG value of the biceps femoris was detected between 120 and 140 ms after the onset of electrical ACL stimulation. The increased EMG activity detected in the biceps femoris after the stimulation to the patellar tendon graft indicated reestablishment of the ACL-hamstring reflex arc in the ACL-reconstructed knee.

Three-Dimensional Tibiofemoral Kinematics of the Anterior Cruciate Ligament-Deficient and Reconstructed Knee during Walking

It is possible that gait abnormalities may play a role in the pathogenesis of meniscal or chondral injury as well as osteoarthritis of the knee in patients with anterior cruciate ligament deficiency. The three-dimensional kinematics of anterior cruciate ligament-deficient knees are changed even during low-stress activities, such as walking, but can be restored by reconstruction. Case control study. Using a three-dimensional optoelectronic gait analysis system, we examined 13 patients with anterior cruciate ligament-deficient knees, 21 patients with anterior cruciate ligament-reconstructed knees, and 10 control subjects with uninjured knees during walking. Normal patterns of knee flexion-extension, abduction-adduction, and internal-external rotation during the gait cycle were maintained by all subjects. A significant difference in tibial rotation angle during the initial swing phase was found in anterior cruciate ligament-deficient knees compared with reconstructed and control knees. The patients with anterior cruciate ligament-deficient knees rotated the tibia internally during the initial swing phase, whereas the others rotated externally. Patients with anterior cruciate ligament-deficient knees experienced repeated episodes of rotational instability during walking, whereas patients with reconstruction experienced tibial rotation that is closer to normal. Repeated episodes of knee rotational instability may play a role in the development of pathologic knee conditions.

The effect of soft-tissue graft fixation in anterior cruciate ligament reconstruction on graft-tunnel motion under anterior tibial loading

Purpose: To compare the motion of an anterior cruciate ligament (ACL) replacement graft within the femoral bone tunnel (graft-tunnel motion) when a soft-tissue graft is secured either by a titanium button and polyester tape (EndoButton fixation; Acufex, Smith & Nephew, Mansfield, MA) or by a biodegradable interference screw (Biointerference fixation; Endo-fix; Acufex, Smith & Nephew) An additional purpose was to evaluate the effect of the graft-tunnel motion on the kinematics of ACL-reconstructed knees and in situ force of the ACL replacement graft. Type of Study: Biomechanical experiment using an in vitro animal model. Methods: ACL reconstruction with a flexor tendon autograft was performed in 8 cadaveric knees of skeletally mature goats. The knee kinematics and the in situ force in the ACL replacement graft in response to anterior tibial loads were evaluated using the robotic/universal force-moment sensor testing system. The longitudinal and transverse graft-tunnel motion during anterior tibial loading was determined based on radiographic measurements parallel and perpendicular to the femoral bone tunnel, respectively. Results: In response to an anterior tibial load of 100 N, the longitudinal graft-tunnel motion for EndoButton fixation and Biointerference fixation was 0.8 ± 0.4 mm and 0.2 ± 0.1 mm, respectively (P < .05), whereas the transverse graft-tunnel motion was 0.5 ± 0.2 mm and 0.1 ± 0.1 mm, respectively (P < .05). Furthermore, the anterior tibial translation for EndoButton fixation (5.3 ± 1.2 mm) was also significantly larger than that for Biointerference fixation (4.2 ± 0.9 mm) (P < .05). With both fixations, however, no significant difference between the in situ forces in the ACL replacement graft and that in the intact ACL could be detected. Conclusions: EndoButton fixation of a soft-tissue graft via an elastic material resulted in significantly larger graft-tunnel motion, and consequently, greater anterior knee laxity compared with more rigid fixation using an interference screw closer to the intra-articular entrance of the bone tunnel. In terms of force distribution, the ACL replacement graft in both fixations still functioned as a primary restraint to an anterior tibial load close to the intact ACL.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 18, No 9 (November- December), 2002: pp 960–967

Characteristics of anterior tibial translation with active and isokinetic knee extension exercise before and after ACL reconstruction

The aim of this study was to investigate the biomechanical characteristics of anterior tibial translation (ATT) in anterior cruciate ligament (ACL)-deficient or -reconstructed knees with active and isokinetic knee extension exercise. Forty-nine patients with unilateral isolated ACL-deficient knees were enrolled. Follow-up examinations were carried out at a mean of 24 months postoperatively. An electrogoniometer system was applied to compare the amount of ATT in ACL-deficient and -reconstructed knees. For both active and isokinetic knee extension, the mean ATT of ACLdeficient knees was considerably greater than that for the normal side, within a range of flexion 0°–70° and 0°–60°, respectively. In contrast, no mean ATT differences were seen during both active and isokinetic exercise from 90° to 0° at follow-up. Within a range of flexion between 50° and 70°, the side-to-side difference in ATT with active knee extension was significantly greater than that with isokinetic extension in ACL-reconstructed knees. These results suggest that the amount of ATT is significantly improved with both active and isokinetic exercise, postoperatively. However, postoperative ATT with isokinetic extension is smaller than that with active knee extension from 50° to 70°.

Anterior cruciate ligament reconstruction with a reharvested bone-patellar tendon-bone graft.

We sought to determine the results in patients who underwent revision anterior cruciate ligament reconstruction with a reharvested bone-patellar tendon-bone graft. Preoperative magnetic resonance imaging of the patellar tendon was used to determine the width of the tendon and the quality of the tissue. The section of the tendon harvested included 7 to 8 mm of the regenerated tendon and 2 to 3 mm of previously untouched tendon either medial or lateral to the healed tissue. The mean time from primary graft harvest to reharvest was 71.0 +/- 44 months (range, 32 to 180). An accelerated rehabilitation program was used postoperatively. Objective follow-up of more than 2 years after surgery was available for 8 patients at a mean of 49.0 +/- 15.4 months. The average range of motion in the anterior cruciate ligament-reconstructed knee was 6/0/133 at 1 month postoperatively and 6/0/145 at long-term follow-up. The mean manual maximum KT-1000 arthrometer difference between knees was 1.6 +/- 1.2 mm. The mean isokinetic quadriceps muscle strength of the reharvested graft donor knee was 103% +/- 7% of that of the opposite knee. Subjective scores were obtained from 11 patients (12 knees) at a mean of 51.5 +/- 35.7 months (range, 24 to 150) after surgery; the mean score was 89.3 +/- 6.9 points. We conclude that with appropriate preoperative planning, a reharvested patellar tendon can be used for revision anterior cruciate ligament reconstruction to obtain reliable stability and strength postoperatively.

Arthroscopic meniscus repair with bioabsorbable arrows

Purpose: The clinical results of a single surgeon’s experience with Meniscus Arrows (Bionx, Blue Bell, PA) for meniscal repair are reviewed and reported to determine the safety and efficacy of this device. Type of Study: Consecutive sample. Methods: Over a 3-year period, the senior author has used only Meniscus Arrows for all meniscal repairs. All patients who underwent meniscal repair with at least 12 months of follow-up were evaluated for this study. Thirty patients had a meniscal repair, and 29 were available for follow-up. The average age at surgery was 29 years (range, 15 to 45 years) and there were 24 male and 5 female patients; 25 patients had an anterior cruciate ligament (ACL) reconstruction with the meniscal repair, 2 repairs were performed in ACL-deficient knees, and 2 repairs were performed in ACL stable knees. The average follow-up was 24 months (range, 12 to 42 months). Results: The average Lysholm knee scores for ACL reconstruction, ACL-intact, and ACL-deficient knees improved from 47, 6, and 35, respectively, to 91, 96, and 81 postoperatively. Tegner activity scores improved from 2.7, 0, and 1.5, respectively, to 7.4, 6.5, and 4.5 after surgery. There were no surgical complications, no infections, and no neurovascular injuries. Five patients had mild subcutaneous irritation caused by the Arrow tips, but in each case this resolved within 3 to 7 months. There were 2 failures (7%) that required later arthroscopy and partial meniscectomy. One failure was in an ACL-deficient knee, and the other was in an ACL-reconstructed knee. Conclusions: Although the data presented in this report are based on short-term clinical follow-up, the preliminary results of the Meniscal Arrow repair are encouraging.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 18, No 3 (March), 2002: pp 246–253

The position of the tibia during graft fixation affects knee kinematics and graft forces for anterior cruciate ligament reconstruction.

Ten cadaveric knees (donor ages, 36 to 66 years) were tested at full extension, 15 degrees, 30 degrees, and 90 degrees of flexion under a 134-N anterior tibial load. In each knee, the kinematics as well as in situ force in the graft were compared when the graft was fixed with the tibia in four different positions: full knee extension while the surgeon applied a posterior tibial load (Position 1), 30 degrees of flexion with the tibia at the neutral position of the intact knee (Position 2), 30 degrees of flexion with a 67-N posterior tibial load (Position 3), and 30 degrees of flexion with a 134-N posterior tibial load (Position 4). For Positions 1 and 2, the anterior tibial translation and the in situ forces were up to 60% greater and 36% smaller, respectively, than that of the intact knee. For Position 3, knee kinematics and in situ forces were closest to those observed in the intact knee. For Position 4, anterior tibial translation was significantly decreased by up to 2 mm and the in situ force increased up to 31 N. These results suggest that the position of the tibia during graft fixation is an important consideration for the biomechanical performance of an anterior cruciate ligament-reconstructed knee.

Interaction between the ACL graft and MCL in a combined ACL+MCL knee injury using a goat model.

The optimal treatment for the MCL in the combined ACL and MCL-injured knee is still controversial. Therefore, we designed this study to examine the mechanical interaction between the ACL graft and the MCL in a goat model using a robotic/universal force-moment sensor testing system. The kinematics of intact, ACL-deficient, ACL-reconstructed, and ACL-reconstructed/ MCL-deficient knees, as well as the in situ forces in the ACL, ACL graft, and MCL were determined in response to two external loading conditions: 1) anterior tibial load of 67 N and 2) valgus moment of 5 N-m. With an anterior tibial load, anterior tibial translation in the ACL-deficient knee significantly increased from 2.0 and 2.2 mm to 15.7 and 18.1 mm at 30 degrees and 60 degrees of knee flexion, respectively. The in situ forces in the MCL also increased from 8 to 27 N at 60 degrees of knee flexion. ACL reconstruction reduced the anterior tibial translation to within 2 mm of the intact knee and significantly reduced the in situ force in the MCL to 17 N. However, in response to a valgus moment, the in situ forces in the ACL graft increased significantly by 34 N after transecting the MCL. These findings show that ACL deficiency can increase the in situ forces in the MCL while ACL reconstruction can reduce the in situ forces in the MCL in response to an anterior tibial load. On the other hand, the ACL graft is subjected to significantly higher in situ forces with MCL deficiency during an applied valgus moment. Therefore, the ACL-reconstructed knee with a combined ACL and MCL injury should be protected from high valgus moments during early healing to avoid excessive loading on the graft.