Comparison of the ACL and ACL graft forces before and after ACL reconstruction an in-vitro robotic investigation

Background?Long-term follow-up studies have indi-cated that there is an increased incidence of arthrosis following anterior cruciate ligament (ACL) reconstruc-tion, suggesting that the reconstruction may not repro-duce intact ACL biomechanics. We studied not only the magnitude but also the orientation of the ACL and ACL graft forces

Methods?10 knee specimens were tested on a robotic testing system with the ACL intact, deficient, and recon-structed (using a bone-patella tendon-bone graft). The magnitude and orientation of the ACL and ACL graft forces were determined under an anterior tibial load of 130?N at full extension, and 15, 30, 60, and 90° of flexion. Orientation was described using elevation angle (the angle formed with the tibial plateau in the sagit-tal plane) and deviation angle (the angle formed with respect to the anteroposterior direction in the transverse plane)

Results?ACL reconstruction restored anterior tibial translation to within 2.6?mm of that of the intact knee under the 130-N anterior load. Average internal tibial rotation was reduced after ACL reconstruction at all flexion angles. The force vector of the ACL graft was significantly different from the ACL force vector. The average values of the elevation and deviation angles of the ACL graft forces were higher than that of the intact ACL at all flexion angles

Interpretation?Contemporary single bundle ACL reconstruction restores anterior tibial translation under anterior tibial load with different forces (both magni-tude and orientation) in the graft compared to the intact ACL. Such graft function might alter knee kinematics in other degrees of freedom and could overly constrain the tibial rotation. An anatomic ACL reconstruction should reproduce the magnitude and orientation of the intact ACL force vector, so that the 6-degrees-of-freedom knee kinematics and joint reaction forces can be restored.     

Twist and its effect on ACL graft forces.

Graft tension is a controversial topic in anterior cruciate ligament (ACL) surgery. Evidence suggests a narrow range of graft tensions, which allow the graft to remodel to a stable and mature neoligament. In previous cadaver experiments, we showed that twisting the graft could modulate the graft forces. In this study we hypothesized that the same phenomena would be found in patients, and that twisting the graft intraoperatively can reduce peak forces in the graft. The effects of twist on graft forces in bone-patellar tendon-bone grafts were measured during anterior cruciate ligament surgery on 15 consecutive patients using a custom-made tension-measurement device. Variations in surgical procedure that could potentially affect the graft force patterns were quantified. Graft force as a function of knee-flexion angle was measured with the graft in the neutral, untwisted position and repeated with the tibial bone block rotated externally or internally by 180 degrees. In eight of the 15 knees, external twisting of the graft reduced the maximal graft force to 50%. However, in five knees the forces in extension increased by twisting to a maximum of 300%. Of the surgical variables, only the femoral tunnel position appeared to have a consistent effect on the graft force pattern. Due to the unpredictable effect of graft twisting, a general recommendation on whether the graft should be twisted, and if so, in which direction, cannot be given. Intraoperatively, graft twisting may however be considered in every individual knee to modulate the graft force as a function of flexion angle.     

ACL reconstruction using an abnormally thick autogenous patellar tendon graft.

This prospective study measured the patellar tendon thickness of 543 patients who underwent anterior cruciate ligament (ACL) reconstruction with an autogenous bone-patellar tendon-bone graft to document the normal range of patellar tendon thickness and to determine if using thicker than normal patellar tendons as an ACL graft source affected postoperative outcome. The postoperative results of 55 patients who underwent ACL reconstruction with a patellar tendon > or =7 mm thick (thick tendon group) were compared with those of 488 patients who underwent ACL reconstruction with a patellar tendon < or =6 mm thick (normal tendon group). 5 mm (4.5 mm in women and 5.3 mm in men) with a range of 3-11 mm (3-7 mm in women and 3-11 mm in men). There was no statistically significant difference in the postoperative KT-1000 arthrometer mean manual maximum difference (2.0 mm for grafts < or =6 mm thick and 1.9 mm for grafts > or =7 mm thick), postoperative quadriceps muscle strength scores, modified Noyes questionnaire subjective scores (mean of 91 points for grafts < or =6 mm thick and 92 points for grafts > or =7 mm thick), or postoperative stability and pain scores. These results indicate that an abnormally thick patellar tendon should not preclude the use of this involved tendon as a graft source for ACL reconstruction.     

Simulated graft recession in endoscopic ACL reconstruction: influence on graft strain

Eight fresh cadaveric knee specimens underwent arthroscopic-assisted ACL reconstruction to examine the influence of femoral graft recession on graft strain pattern. Length changes between tibial origin and femoral insertion (simulating graft strain or isometry pattern) were measured throughout knee motion (0 degrees-90 degrees) with a simulated ACL construct. Measurements were taken at the "endo" position (replicating the normal endoscopic position) and in progressive 1.5-mm increments proximally within the femoral tunnel (mimicking femoral graft recession). After recession up to a maximum of 15 mm, a block was placed anterior to the "recessed" graft construct (simulating placement of bone graft anterior to the recessed graft) and strain patterns were remeasured. Graft strain patterns were altered with as little as 1.5 mm recession in two of eight specimens. Compared to the "endo" position, all specimens showed a statistically significant decrease in strain by 3 mm of graft recession (P<.001 for 7 of 8, and P=.0138 for 1 of 8). A direct relationship exists between graft placement and ACL strain patterns, with more proximal graft "recession" adversely influencing normal graft strain. Bone graft placement anterior to the recessed graft restores strain patterns to those seen at the normal "endoscopic" position.     

Cryotherapy after ACL reconstruction: a meta-analysis

Cryotherapy is a common treatment modality after orthopedic surgery procedures. Single institutional randomized clinical trials have evaluated the efficacy of cryotherapy after arthroscopically-assisted anterior cruciate ligament (ACL) reconstruction. Most of these studies were, however, underpowered to detect clinically relevant outcomes differences. This meta-analysis assessed the combined scientific evidence of studies evaluating the effectiveness of cryotherapy after arthroscopically-assisted ACL reconstruction. Electronic databases and bibliographic references of relevant articles were used to identify all relevant randomized clinical trials comparing cryotherapy to a placebo group after ACL reconstruction. Outcomes under investigation were postoperative drainage, range of motion, and pain. Random-effects models were used to combine the findings of the randomized controlled trials. Seven randomized clinical trials were included in the meta-analysis. Postoperative drainage (P=.23) and range of motion (P=.25) were not significantly different between cryotherapy and control group. However, cryotherapy was associated with significantly lower postoperative pain (P=.02). This meta-analysis showed that cryotherapy has a statistically significant benefit in postoperative pain control, while no improvement in postoperative range of motion or drainage was found. As the cryotherapy apparatus is fairly inexpensive, easy to use, has a high level of patient satisfaction, and is rarely associated with adverse events, we believe that cryotherapy is justified in the postoperative management of knee surgery.     

Osteoarthritis of the knee after ACL reconstruction

Summary One hundred and fourteen knees with deficiency of the anterior cruciate ligament (ACL) which had undergone reconstruction of the ligament using semitendinosus and gracilis were reviewed at a mean of 61 months after operation. Radiological and clinical evaluation was undertaken. A significant correlation was found between the number of meniscectomies performed in acute cases and those undertaken on the chronic knee. There was also significant correlation between meniscectomy and the Fairbank grading of degenerative changes seen on the radiographs. There was no correlation between the clinical results, residual laxity and the development of osteoarthritis. In ACL deficient knees with irreparable meniscal tears, or in which meniscectomy had been undertaken, the development of osteoarthritis seemed independent of the degree of stability, but in such knees with no meniscal tear or meniscal repair, reconstruction appeared to save the menisci and preserve the joint.

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Résumé Les auteurs ont revu, avec un recul de 61 mois, 114 genoux opérés pour reconstruction du ligament croisé antérieur (LCA) au moyen du demitendineux et du droit interne. Une évaluation clinique et radiologique a été effectuée. L'analyse des radiographies en charge a montré une corrélation significative entre l'existence de signes de dégradation articulaire et les méniscectomies effectuées dans le même temps que la reconstruction ligamentaire. Une bonne corrélation a été également retrouvée entre le niveau sportif post-opératoire et la présence de ces signes. Aucune corrélation n'a été trouvée entre l'évolution de l'arthrose et le résultat clinique, en ce qui concerne la stabilité. En conclusion, dans les cas comportant une lésion irréparable des ménisques et une méniscectomie, la reconstruction du LCA ne semble pas capable de prévenir le développement de l'arthrose post-traumatique.

     

Influence of anthropometric features on graft diameter in ACL reconstruction

Background

There is a paucity of literature regarding the influence of anthropometric features on the hamstring graft obtained in ACL reconstruction. This study was undertaken to assess the influence of anthropometric measurements on the graft diameter obtained at ACL reconstruction surgery within the European population. We hypothesise that anthropometric features do influence graft thickness in ACL reconstruction.

Materials and methods

Data from 121 consecutive patients who had undergone ACL reconstruction by the same surgeon using quadruple hamstring grafts were analysed. The body mass index (BMI), height and weight of these patients were correlated with the graft diameter obtained during surgery. Regression analysis was undertaken to assess the influence of individual anthropometric variables on the graft diameter.

Results

There were 121 patients with mean age of 32 years (14–55). There was a statistically significant positive correlation individually between the height and graft diameter (r = 0.38, p < 0.01) as well as between the body weight and graft diameter (r = 0.29, p < 0.01). However, when the body mass index was calculated, the correlation was not statistically significant (r = 0.08, p > 0.1). Regression analysis confirmed that BMI was not statistically significant as a predictor of hamstring graft diameter whereas height was statistically the most important predictor (F = 20.1; p < 0.01).This yielded the predictive equation, graft diameter = 4.5 + 0.02 x Ht (in cm).

Conclusion

Although body mass index did not significantly correlate, body height may be a predictive variable in predicting the graft diameter in ACL reconstruction and provide useful pre operative information.     

Rotatory instability of the knee after ACL tear and reconstruction

Although ACL reconstructions provide satisfactory clinical results nowadays, regardless of the type of graft or the surgical technique used (out-in vs in-out or single- vs double-bundle), the residual rotatory instability which is often detected at clinical follow-ups is still a matter of concern among surgeons. In this paper we try to analyze all the aspects which might contribute to this phenomenon by summarizing the biomechanical functions of the two bundles of the ACL, and by evaluating all the other factors strictly related to the rotatory instability of a reconstructed knee, such as the anatomical positioning of the single- or double-bundle new ACL, or the importance of a valid lateral compartment (LCL, ALTFL). Clinical, biomechanical and cadaver studies are discussed in order to contribute to better understanding of the origin of post-operative residual rotatory instability.     

Electromechanical delay after ACL reconstruction: an innovative method for investigating central and peripheral contributions

OBJECTIVES: The purpose of this study was to investigate the electromechanical properties of atrophied muscle in patients with anterior cruciate ligament (ACL) reconstruction and to examine the relationship of changes in these properties for a voluntarily elicited maximal isometric contraction and peripherally stimulated twitch contraction. BACKGROUND: It is not known if, following ACL reconstruction, a prolonged reaction time to a sudden stimulus is due to impaired proprioception in the knee joint, a prolonged processing interval in the central nervous system, or a greater elasticity in the series elastic component of the quadriceps femoris. METHODS: Seventeen patients were recruited 2 to 3 months following a unilateral ACL reconstruction. Both the involved leg (ACL-invo group) and the uninvolved leg (ACL-uninvo group) were studied. Twenty-two athletes (training group) and 18 control subjects (control group) were also tested. These subjects performed voluntary maximal isometric contraction (MVC) of the quadriceps femoris. Maximal twitch response was also elicited by a supramaximal electrical stimulation to the femoral nerve, and surface electromyograms were recorded from the vastus lateralis in all four groups. RESULTS: Total reaction time for MVC in the ACL-invo group (250.47 ms) was prolonged compared to that of the control and training groups. Twitch response in the ACL-invo group (25.26 ms) was prolonged compared to that of the other three groups. Premotor time during both MVC and twitch response did not differ among the four groups. Electromechanical delay during MVC (53.62 ms) and the evoked electromechanical delay in twitch response (20.04 ms) were prolonged in the ACL-invo group as compared to the other three groups. CONCLUSIONS: Prolonged electromechanical delay in twitch response may be due to peripheral physiological disruptions (eg, stiffness of the series elastic component, changes of peripheral muscle fiber-type composition, or a decrease in function of the excitation-contraction coupling process). A prolonged electromechanical delay in twitch response can also explain the prolonged electromechanical delay observed for MVC. These findings suggest that prolonged total reaction time in MVC, when secondary to a visual stimulus in atrophied human quadriceps femoris muscle after ACL reconstruction, may be principally due to prolongation of electromechanical delay produced by peripheral physiological alterations. However, the contribution of premotor time to prolonged total reaction time was not revealed. Our results do not completely eliminate the possibility that central nervous system processing time and other neural factors are involved in the prolongation of reaction time.     

ACL reconstruction by bone-patellar tendon-bone graft: mechanical evaluation of the elastic modulus and failure modes

The aim of this study was to apply an engineering approach to study the biomechanical behaviour of both native and reconstructed anterior cruciate ligaments (ACL) under tensile test, simulating the primary stability of the reconstructed ACL in the immediate postoperative period, when the bone callus has not formed yet. We used the bovine bone-patellar tendon-bone grafts to reconstruct ACL in bovine knees. The grafts were fixed by means of titanium interference screws and titanium transverse compressive screws. We tested 18 native and 18 reconstructed ligaments (7 with interference screws and 11 with transverse compressive screws). We applied mechanical tension at a 500 mm/min strain rate, and observed the mode of failure. The data analysis confirmed the different behaviour recorded in load elongation curves, a difference enhanced in stress-strain curves for both fixation methods. The stress-strain patterns for the interference screw and for the native ligament were quite similar.     

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 ACL-deficient 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°. Received: October 17, 2001 / Accepted: December 26, 2001     

Comparison of outside-in and inside-out technique for tibial fixation of a soft-tissue graft in ACL reconstruction using the Shim technique

Introduction

The aim of this study was to compare the biomechanical properties of tibial fixation of a free tendon graft in ACL reconstruction using the Shim, a new wedge-shaped implant, in an outside-in technique to fixation by the Shim used in an inside-out technique and fixation by interference screw in a porcine model.

Materials and methods

Porcine tibia and flexor tendons were used. In Group 1, the Shim was applied outside-in. In Group 2, the Shim was inserted inside-out. In the Group 3, an 8-mm interference screw was used. Ten specimens were tested in each group. Load-to-failure, elongation, stiffness and failure mode were recorded. Cyclic loading was performed between 5 and 250 N for 1,000 cycles, followed by a load to failure testing.

Results

Mean maximum load-to-failure was 629.53 N in Group 1,648.54 N in Group 2 and 749.53 N in Group 3. There was no significant difference between the groups. Stiffness varied between 127.34 N/mm in Group 1, 151.27 N/mm in Group 2 and 182.25 N/mm in Group 3. No significant differences were found between outside-in Shim and interference screw fixation. No significant difference was found for elongation among the three groups. The main failure mode was a rupture of the tendon in the IFS group and a slippage of either the implant or the tendon in both groups using the Shim.

Conclusions

As no statistically significant difference could be seen concerning load to failure, stiffness and elongation between the inside-out and the outside-in techniques, the Shim can be used for tibial fixation in an outside-in or inside-out technique depending on the preference of the surgeon. To prevent slippage of the graft a hybrid fixation should be considered.     

Tendon graft fixation in ACL reconstruction: in vitro evaluation of bioabsorbable tenodesis screw

BACKGROUND: Conventional ACL reconstruction requires sufficient tibial bone quality for secure graft fixation. We evaluated the mechanical characteristics of a supplemental tenodesis screw in cadaveric specimens. MATERIAL AND METHODS: One group of 7 specimens from 7-paired tibiae was randomly assigned to undergo tibialis anterior tendon graft-bone tunnel fixation with a bioabsorbable interference screw, using conventional ACL reconstruction techniques. The other group of 7 specimens underwent the same procedure supplemented with a bioabsorbable tenodesis screw. All specimens were subjected to pullout testing on a servo hydraulic device. RESULTS: Specimens in the supplemental fixation group had double the load to failure (tenodesis = 467 (SD 184) N, control group = 223 (SD 66) N, p = 0.02) and were also one-third stiffer (tenodesis = 31 (SD 13) N/mm, control group = 21 (SD 6) N/mm, p = 0.03) than the specimens in the conventional fixation group. INTERPRETATION: Supplemental bioabsorbable tenodesis screw fixation may be advantageous for primary reconstruction in patients with low tibial bone mineral density or during revision procedures. By providing secure soft tissue graft-tibia fixation during the early phase after ACL reconstruction, supplemental tenodesis fixation may enable patients to participate safely in more intense, early rehabilitation.     

Quadrupled bone-semitendinosus ACL reconstruction: a prospective clinical investigation in 100 patients

Abstract The hypothesis of our study was that a quadrupled bonesemitendinosus tendon graft could combine the advantage of bone-tobone healing with the high cross-sectional area of a quadrupled hamstring graft in ACL reconstruction. ACL reconstruction with a semitendinosus tendon graft was performed on 100 patients with isolated ACL injury from January 1996 to December 1999: femoral fixation was obtained with Endobutton and tibial fixation with Fastlok. Patients were evaluated for standard knee scores and functional strength tests, postoperative pain rating, knee radiographs taken after surgery and at final follow-up, magnetic resonance images at 3 and 6 months, isokinetic flexion-extension and internal-external rotation tests at 3, 6, and 12 months. Computerized laxity analysis was performed at final evaluation. Average surgical time was 85 minutes, including 13 minutes for graft preparation; 90% of the patients were discharged within 24 h. Subjective knee rating was 80%; kneeling test was positive in 7% and Werner score was 44 (range, 30–48). Lachman test was negative in 90% at final evaluation (mean follow-up, 38 months). Sensory changes at the anterior part of the proximal tibia were present in 30% at 3 months and 10% had definite hyposthesia. MRI showed graft incorporation at 3 months. Computerized laxity analysis revealed 90% with less than 3-mm side-to-side differences. Isokinetic testing showed normal hamstring and quadriceps peak torques at 12 months. The functional strength tests were normal by 6 months. Average Noyes score was 87.9, Lysholm score 93, and Tegner activity rating 6.0 (pre-injury, 6.1). IKDC score showed 90 normal or nearly normal knees, 9 abnormal, and one severely abnormal knee. Quadrupled bone-semitendinosus is a viable graft for ACL reconstruction and should be considered, especially in patients with pre-existing extensor mechanism problems.     

Arthroscopic treatment of flexion deformity after ACL reconstruction

After anterior cruciate ligament (ACL) reconstruction, one frequent complication is the restriction of the range of motion and loss of extension. In addition to the presence of adhesions in the suprapatellar pouch, it is possible to detect two different pathological findings in the intercondylar notch: a misplacement of graft causing an intercondylar impingement, or the presence of hypertrophic tissue originating from the graft that blocks the last degrees of extension, causing an "anterior impingement." We reviewed 18 consecutive cases treated by arthroscopic release. All patients had knee range-of-motion restriction after an ACL procedure. The follow-up at 1 and at 6 months shows that good results have been obtained in cases of anterior impingement, whereas in cases of intercondylar impingement a restricted range of motion, especially of flexion, did remain. In all cases, after arthroscopic treatment the postoperative extension was between 5 and 10 degrees, but this deficit regressed after 6 months in 12 patients, whereas a dropout case was necessary in the remaining 6 patients.