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Purpose: The main goal of this work was to evaluate the pivot shift test in awake and anesthetized patients by using two different quantitative methodologies and comparing the results with the standard clinical grading, taking advantage of a multicenter international study., Methods: Patients between 16 and 50 years of age undergoing primary unilateral single-bundle anterior cruciate ligament (ACL) reconstruction were considered eligible. The pivot shift test was performed pre-operatively, with the patient awake and again with the patient under general anaesthesia. The pivot shift test was clinically graded as defined by the International Knee Documentation Committee. The instrumented assessment was performed by using two non-invasive acquisition systems; specifically, a system exploiting an inertial sensor and a video-based application developed on a commercial tablet using skin markers. Lateral compartment translation and the tibial acceleration reached during joint reduction were used as quantitative parameters., Results: A total of 103 patients were enrolled in the study. Statistically significant difference was found between the distributions of clinical grade evaluated in awake patients and those under general anaesthesia (P < 0.01). Comparing awake patients to those under general anaesthesia, lower values were found both for tibial acceleration (3.7 ± 1.5 vs 6.0 ± 4.6 m/s 2 , P < 0.01) and lateral compartment translation of the involved limb (2.2 ± 1.7 vs 3.0 ± 2.2 mm, P < 0.01)., Conclusions: This study indicated that significant differences in the grading of the pivot shift test exist between awake and anesthetized patients, regardless of the use of quantitative instruments during the evaluation. Actual clinical assessment reported indeed its weakness, presenting subjective variability and dependence on tester's experience. However, several factors might influence the validity of awake examination such as experience level of examiner and cultural factors, as seen in this international multicenter study., Level of Evidence: Prospective comparative study, Level II.

Purpose: To quantify the influence of Single-Bundle with Lateral Plasty and Double-Bundle reconstruction on static and dynamic laxity in combined ACL- and ALL-deficient knees., Methods: The study included 10 fresh-frozen human knees. The joints were analyzed in the following conditions: ACL + ALL resection, Single-Bundle with Lateral Plasty (SBLP) reconstruction, Double-Bundle (DB) reconstruction. Testing parameters were: anterior displacement at 30° and 90° of flexion (AP30, AP90) applying a manual maximum load; internal rotation at 30° and 90° of flexion (INT30, INT90) applying a 5 Nm torque and acceleration and internal rotation Pivot-Shift (PS) test. Kinematics was acquired by a navigation system. Paired Student's t test was conducted to assess statistical difference (P < 0.05)., Results: At both 30° and 90° of knee flexion, both SBLP and DB surgical techniques showed a significant reduction (P < 0.01) of anterior-posterior tibial displacement compared to the resection of ACL + ALL. At 30° on knee flexion it is the SBLP that allows the greatest reduction of internal rotational laxity when compared to DB reconstruction. Concerning the PS test, only SBPL procedure had a significant laxity decrease considering the acceleration reached by the joint when compared with the ACL + ALL state (P < 0.01)., Conclusion: Clinical relevance of this study is that the internal rotation and PS test were more efficiently controlled by the SBLP technique than by the DB one at both 30° and 90° of flexion in case of ACL + ALL lesions.

Purpose: To quantify the influence of ALL lesions on static and dynamic laxity in ACL-deficient knee., Methods: The study was performed in 10 fresh-frozen knees. The joints were analysed in the following conditions: intact, ACL resection and ACL + ALL resection. Testing parameters were defined as: anterior displacement at 30° and 90° of flexion (AP30, AP90) applying a manual-maximum load; internal rotation at 30° and 90° of flexion (INT30, INT90) applying a 5 N m torque and internal rotation and acceleration during manual pivot-shift (PS) test. Kinematics was acquired by a navigation system; a testing rig and a torquemeter were used to control the limb position and the applied torque. Paired Student's t test was conducted to assess statistical difference, and significance was set at P < 0.05., Results: The ALL resection determined a significant increase in terms of internal rotation (INT30 P = 0.02, INT90 P = 0.03), while AP30 (P n.s) and AP90 (P n.s) were not affected. ALL resection produced a significant increase in terms of acceleration during PS test (P < 0.01), but no significant change in PS internal rotation was observed., Conclusion: The ALL plays a significant role in controlling static internal rotation and acceleration during PS test. On the other hand, ALL resection did not produce any significant change in terms of anterior displacement. A trend was seen for the internal rotation during the pivot-shift test to increase after ALL resection was higher when compared to the intact and isolated ACL lesion states; however, the differences were not significant. The results highlight the clinical relevance of this structure that should be assessed before an ACL reconstruction in order to avoid residual laxity.

Purpose: To quantitatively evaluate the biomechanical sealing function of an intact labrum and the effect of labral-chondral separation, cerclage suture labral repair, vertical mattress suture repair and partial labrectomy on distraction load and hip joint centre (HJC) displacement., Methods: Eight fresh-frozen cadaveric hips were tested using a navigation system for intra-operative kinematic analysis. A six-axis load cell was used to measure the manually applied force when performing the tests: hip pivoting movement and distraction. The HJC displacement that occurred during the distraction test has been evaluated in correspondence of seven different values of applied force. During the pivoting motion, the maximum value of HJC displacement was evaluated. Five different conditions were tested: labrum intact, labral-chondral separation, vertical mattress suture repair, cerclage suture repair, and partial labrectomy., Results: With regard to HJC displacement using at fixed value of force, the paired sample t test underscored the statistically significant differences (p < 0.05) for each of the five tested conditions among themselves. Only the comparison of intact versus labral-chondral separation was not significantly different. During pivoting motion, a statistically significantly greater displacement was identified after labrectomy when compared with the cerclage suture repair (p = 0.03) and vertical mattress repair (p < 0.01) in medial-lateral direction. Along proximal-distal direction, a significant lower displacement after labrectomy was identified when compared to the cerclage suture repair (p = 0.03). Performing the pivoting motion at the extreme ranges of motion demonstrated a higher value of displacement after labrectomy when compared with all the previously tested conditions., Conclusions: These results suggest that labral repair is important in the function of the hip and that the vertical mattress suture technique may be better than the cerclage suture repair.

Purpose: The hypothesis was that an alteration of different surgical variables of ACL reconstruction would produce significant changes in post-operative static laxity of knee joint., Methods: Joint laxity was acquired by a surgical navigation system for 17 patients just after graft fixation during single-bundle reconstruction with extra-articular lateral tenodesis. The analysed laxity parameters were: internal/external rotation at 30° (IE30) and 90° (IE90) of flexion, varus/valgus rotation at 0° (VV0) and 30° (VV30) of flexion and anterior/posterior displacement at 30° (AP30) and 90° (AP90) of flexion. As surgical variables, the angles between the tibial tunnel and the three planes were defined as well as the lengths of the tunnel and the relationship between native footprints and tunnels. The same analysis was performed for the femoral side. All surgical variables were combined in a multivariate analysis to assess for predictive factors between them and post-operative laxities values. To quantify the performance of each multivariate model, the correlation ratio (η 2 ) and the corresponding P value (*P < 0.050) have been evaluated., Results: Multivariate analysis underlined statistically significant models for the estimation of: AP30 (η 2  = 0.987; P = 0.014), IE30 (η 2  = 0.995; P = 0.005), IE90 (η 2  = 0.568; P = 0.010), VV0 (η 2  = 0.932; P = 0.003). The parameters that greatly affected the identified models were the orientation of the tibial tunnel with respect to the three anatomical planes. The estimation of AP30, IE30 and IE90 got lower value as the orientation of the tibial tunnel with respect to transverse plane decreases. Considering the orientation to sagittal ([Formula: see text]) and coronal ([Formula: see text]) plane, we found that their reduction provoked a decrease in the estimation of AP30, IE30 and IE90 (except [Formula: see text] that did not appear in the estimation of AP30). The estimation of VV0 got an increase of [Formula: see text], and [Formula: see text] which led to a laxity reduction., Conclusion: The main finding of the present in vivo study was the possibility to determine significant effects on post-operative static laxity level of different surgical variables of ACL reconstruction. In particular, the present study defined the conditions that minimize the different aspects of post-operative laxity at time-zero after surgery.

Purpose: Recently, the functional flexion axis has been considered to provide a proper rotational alignment of the femoral component in total knee arthroplasty. Several factors could influence the identification of the functional flexion axis. The purpose of this study was to analyse the estimation of the functional flexion axis by separately focusing on passive flexion and extension movements and specifically assessing its orientation compared to the transepicondylar axis, in both the axial plane and the frontal plane., Methods: Anatomical and kinematic acquisitions were performed using a commercial navigation system on 79 patients undergoing total knee arthroplasty with cruciate substituting prosthesis design. The functional flexion axis was estimated from passive movements, between 0° and 120° of flexion and back. Intra-observer agreement and reliability, internal-external rotation and the angle with the surgical transepicondylar axis, in axial and frontal planes, were separately analysed for flexion and extension, in pre- and post-implant conditions., Results: The analysis of reliability and agreement showed good results. The identification of the functional flexion axis showed statistically significant differences both in relation to flexion and extension and to pre- and post-implant conditions, both in frontal plane and in axial plane. The analysis of internal-external rotation confirmed these differences in kinematics (p < 0.05, between 25° and 35° of flexion)., Conclusions: The identification of the functional flexion axis changed in relation to passive flexion and extension movements, above all in frontal plane, while it resulted more stable and reliable in axial plane. These findings supported the possible clinical application of the functional flexion axis in the surgical practice by implementing navigated procedures. However, further analyses are required to better understand the factors affecting the identification of the functional flexion axis., Level of Evidence: IV.

Recent publications have generated renewed interest in the anatomy of the anterolateral capsule. Knowledge of the biomechanical function of the anterolateral components is lacking. Further research is required to evaluate the influence of the anterolateral capsule on rotatory laxity of the knee. The role of surgical procedures, such as an extra-articular tenodesis or lateral plasty, has to be defined based on quantification of the injury. This article seeks to summarize the current literature and discusses the role of the anterolateral capsule and reconstructive techniques in combined ligamentous knee trauma. Level of evidence V.

Purpose: Posterolateral corner structures functionally interact with the ACL. The aim of this study was to investigate the capability of an isolated ACL reconstruction control laxity parameters in a knee with combined ACL and PLC and the increase in terms of laxity produced by the resection of the PC in an ACL-deficient knee., Method: An in vitro cadaveric study was performed on seven knees. The joints were analysed in the following conditions: intact, after ACL resection, after popliteus complex resection, after ACL reconstruction and after LCL. Testing laxity parameters were recorded with an intra-operative navigation system and defined as: AP displacement at 30° and 90° of flexion (AP30 and AP90) applying a 130 N load and IE at 30° and 90° of knee flexion with a 5 N load., Results: Sectioning the ACL significantly increased the AP30 at 30° and 90° of knee flexion (p < 0.05). At 90° of knee flexion, the resection of the LCL determined a significant increase in terms of AP laxity (p < 0.05). At 90° has been found a significant difference for the IE laxity (p < 0.05) after PC resection. Sectioning the LCL produced a significant increase in IE laxity at 30° and 90° of knee flexion (p < 0.05)., Conclusion: Isolated ACL reconstruction is able to control the AP laxity with a combined complete lesion of the PLC at 30° of knee flexion, but not at higher angle of knee flexion. Considering the IE rotations, the reconstruction was not sufficient not even to control a partial lesion of the PLC. These findings suggest that additional surgical procedures should be considerate even when facing combined PLC lesion.

Purpose: Providing correct rotational alignment of femoral component in total knee arthroplasty (TKA) is mandatory to achieve correct kinematics, good ligament balance and patellar tracking. The purpose of this study was to evaluate potential clinical applications of functional flexion axis (FFA) by analysing the differences between pre- and post-implant placement. This evaluation was supported by the analysis of repeatability, assessing the robustness of the proposed method., Methods: Anatomical acquisitions and passive kinematics were acquired on 87 patients undergoing TKA using a commercial navigation system. Knee FFA was estimated, before and after implant positioning, from three flexion-extension movements between 0 and 120°. The angle between FFA and transepicondylar axis was analysed in frontal and axial planes. Repeatability coefficient and intraclass correlation coefficient (ICC) were used to analyse the reliability and the agreement in identifying the axis., Results: The analysed angle presented differences between pre- and post-operative conditions only in the frontal plane (from -8.3 ± 5.5° to -2.8 ± 5.3°) (p < 0.0001). There was good intraobserver reliability and agreement. Repeatability coefficient ranged between 4.4° (3.7-4.9°) and 3.4° (2.9-3.8°), the ICC between 0.87 (0.83-0.91) and 0.93 (0.90-0.95) and the standard deviation ranged between 1.3 and 1.0°., Conclusions: The present study demonstrated that TKA affected the estimation of FFA only in the frontal plane. This method reported good repeatability, demonstrating its usefulness for clinical purposes particularly to evaluate rotational positioning of the femoral component in the axial plane., Level of Evidence: Case series, Level IV.

Purpose: Retinacular restraints have a critical role in patellar tracking, limiting the movement of the patella in the trochlear groove. The medial patellofemoral ligament (MPFL) is probably the main stabilizer against lateral displacement; few studies are focused on MPFL role on patellofemoral kinematics and patellar stability. The main goal of this in vitro study was to analyse the influence of the MPFL on the kinematics of the patellofemoral joint and patellar stability., Methods: Using a non-image-based navigation system, kinematics and anatomical data of six fresh-frozen specimens were collected. A passive flexion-extension from 0° to 90° and static acquisitions at 0°, 30°, 60° and 90°, with and without 25 N of lateral load, were performed with intact and resected MPFL with a 60 N axial force applied to the isolated quadriceps tendon. Patellar tilt and shift were analysed., Results: The MPFL intact state showed a shift in medial direction during the first degrees of knee flexion-that disappeared in MPFL resected condition-followed by a lateral shift, similar to that of MPFL resected condition. Tilt analysis showed that patella rotated laterally until 85° of knee flexion for intact MPFL condition and until 70° for resected MPFL condition and after rotated medially. Static tests showed that patellar stability was significantly affected by MPFL resected condition in particular at 30° and 60°., Conclusions: The MPFL has an aponeurotic nature. It works as a restraint during motion, with an active role under high stress on lateral side, but with a small contribution during neutral knee flexion. Its biomechanical behaviour under loading conditions should be kept into account when performing surgical reconstruction of this ligamentous structure.

Purpose: Aim of the study is to assess the contribution of peri-articular soft tissues to hip joint kinematics and their influence on hip stability., Methods: Four hemi-corpse specimens (3 males, average age 72 years) were studied using a custom navigation system. Hip kinematics (femoral head motion relative to the acetabulum and joint range of motion) were evaluated with the hip manually positioned in 36 different positions with (I) soft tissues intact, (II) after removal of the skin and muscles and (III) after partial capsulectomy. Each position was repeated 3 times in each state., Results: Excellent interclass correlation for each test was determined (ICC range, 0.84-0.96). Femoral head anatomical centre displacement relative to the acetabulum occurred in all 3 planes, even with all the soft tissue intact (average, 3.3 ± 2.8 mm lateral translation; 1.4 ± 1.8 mm posterior translation and 0.3 ± 1.5 mm distally). These translations increased as more soft tissue was removed, except medial-lateral displacement, with an average 4.6 ± 2.9 mm lateral translation, 0.7 ± 1.3 mm posterior translation and 1.5 ± 1.9 mm distal translation when partial capsulectomy was performed. Range of motion increased in all 3 planes with increasing removal of the soft tissues., Conclusions: This study showed that femoral head anatomical centre displacement within the acetabulum occurs and increases with increasing removal of peri-articular soft tissues, confirming their influence on hip stability. Hip kinematics was also influenced by peri-articular soft tissues; specifically range of motion increases with increasing removal of those tissues. From clinicians' point of view, they have therefore to consider the influence of their surgeries on peri-articular soft tissues, since excessive translations may promote hip arthritis.

Purpose: This study aims to identify and summarize the evidence on the biomechanical parameters and the corresponding technologies which have been used to quantify the pivot shift test during the clinical and functional assessment of anterior cruciate ligament (ACL) injury and surgical reconstruction., Methods: Search strategy Internet search of indexed scientific articles on the PubMed database, Web of Science and references on published manuscripts. No year restriction was used. Selection criteria Articles included were written only in English and related to search terms: "pivot shift" AND (OR "ACL"). The reviewers independently selected only those studies that included at least one quantitative parameter for the analysis of the pivot shift test, including both in vitro and in vivo analyses performed on human joint. Those studies that analysed only clinical grading were excluded from the analysis. Analysis After evaluating the methodological quality of the articles, the parameters found were summarized., Results: Six hundred and eight studies met the inclusion criteria, and finally, 68 unique studies were available for the systematic review. Quantitative results were heterogeneous. The pivot shift test has been quantified by means of 25 parameters, but most of the studies focused on anterior-posterior translations, internal-external rotation and acceleration in anterior-posterior direction., Conclusion: Several methodologies have been identified and developed to quantify pivot shift test. However, clinical professionals are still lacking a 'gold standard' method for the quantification of knee joint dynamic laxity. A widespread adoption of a standardized pivot shift manoeuvre and measurement method to allow objective comparison of the results of ACL reconstructions is therefore desirable. Further development of measurement methods is indeed required to achieve this goal in a routine clinical scenario.

Purpose: Different approaches have been proposed to diagnose femoroacetabular impingement (FAI) condition and hip instability. It is still debatable which test is the most effective to make a correct diagnosis. The true mechanics of the hip during particular physical examination manoeuvres is unknown., Methods: Eight fresh frozen hips were passively taken through 3 different commonly used positions for FAI diagnosis and hip instability: 90° Flexion-Adduction-Internal Rotation, Hyperextension-Adduction-External Rotation and Hyperextension-Neutral-External Rotation. Kinematics and anatomical data were acquired by an optoelectronic system. The contact areas between acetabulum and femoral head were analysed to determine whether these tests are able to localize regions of the hip that may give patients pain., Results: In the hip positions where the femur was in Hyperextension-External Rotation, the contact area was mainly concentrated in the posterosuperior area of the acetabulum, while during 90° Flexion-Adduction-Internal Rotation position, there was a wider distribution of contact, not specific to the anterolateral acetabulum., Conclusions: The results confirm the ability of the Hyperextension-External Rotation tests to particularly analyse the posterior region of the acetabulum. Placing the hip in 90° of Flexion-Adduction-Internal Rotation allows for testing a wider zone of the acetabulum and is not specific to abutment of the femoral head-neck region against the anterolateral acetabulum.

Purpose: The pivot-shift phenomenon has been identified to be one of the essential signs of functional anterior cruciate ligament (ACL) insufficiency. However, the pivot-shift test remains a surgeon-subjective examination, lacking a general recognized quantitative measurement. The goal of the present study was to validate the use of an inertial sensor for quantifying the pivot-shift test, using a commercial navigation system., Methods: An expert surgeon intra-operatively performed the pivot-shift test on 15 consecutive patients before ACL reconstruction. A single accelerometer and a commercial navigation system simultaneously acquired limb kinematics. An additional optical tracker mounted on the accelerometer allowed following sensor movements. Anteroposterior (a-p) tibial acceleration obtained with the navigation system was compared with three-dimensional (3D) acceleration acquired by the accelerometer. The effect of skin artifacts and test-retest positioning were estimated. Repeatability of the acceleration parameter and waveform was analyzed. Correlation between the two measurements was also assessed., Results: Average root mean square (RMS) error in test-retest positioning reported a good value of 5.5 ± 2.9 mm. Mean RMS displacement due to soft tissue artifacts was 4.9 ± 2.6 mm. The analysis of acceleration range repetitions reported a good intra-tester repeatability (Cronbach's alpha = 0.86). Inter-patients similarity analysis showed a mean acceleration waveform correlation of 0.88 ± 0.14. The acceleration ranges demonstrated a good positive correlation between the two measurements (rs = 0.72, P < 0.05)., Conclusion: This study showed good reliability of the new device and good correlation with the navigation system results. Therefore, the accelerometer is a valid method to assess dynamic joint laxity., Level of Evidence: II.

Purpose: To assess the ability of anatomic double-bundle anterior cruciate ligament reconstruction in eliminating the pivot-shift phenomenon when identified by a quantitative measuring system (computer navigation or magnetic resonance imaging)., Methods: Literature review. Medline, Google Scholar and Cochrane Reviews computerized databases research using the keywords "pivot-shift," "anterior cruciate ligament reconstruction" and "double bundle." Twelve (7 in vitro and 5 in vivo) studies met the inclusion criteria., Results: There was a wide variation in the absolute value of translation and rotation measured after anatomic double-bundle anterior cruciate ligament reconstruction. There were also differences in fixation methods, pivot-shift execution conditions, applied stresses during the pivot-shift, calculation methods and reference systems utilized by measurement systems., Conclusions: The double-bundle reconstruction was shown to over-constrain the knee with respect to the intact value, especially closer to knee extension. This review demonstrated that anatomic double-bundle anterior cruciate ligament reconstruction is able to eliminate pathological translations and rotations during the pivot-shift phenomenon, as identified by quantitative measurement systems., Level of Evidence: Review of Level III studies, Level III.

Purpose: No study, up to now, has examined the effect of arthritis on pathologic subjects using functional flexion axis (FFA). The purpose of this study is to understand whether arthritis affects somehow the FFA evaluation and to assess whether the FFA could be considered a usable reference for implant positioning for osteoarthritic knees., Methods: Using a navigation system, FFA orientation was evaluated intraoperatively (computed with the mean helical axis method) in three different ranges of motion (0°-120°; 35°-80°; 35°-120°) and in two different planes (coronal and axial), for 111 osteoarthritis patients undergoing total knee arthroplasty. The results were compared with a control group of 60 patients that underwent ACL reconstruction. The angle between the transepicondylar axis (TEA) and FFA was computed., Results: Results showed in arthritic knees on frontal plane, an average difference between TEA and FFA of -2.8° ± 5.0° while on axial plane it was 0.6° ± 4.7°. No statistical difference was found between the three ranges in axial view, whereas some difference was found in frontal view (P < 0.0001). The TEA-FFA angle was not correlated with limb alignment on axial plane, while it was, even if poor, in frontal plane. In the control group, in frontal and in axial view, no statistical difference was found for the angle between TEA and FFA., Conclusions: FFA can be used as reference for implant positioning in axial plane also in pathologic knees, while for the frontal plane further investigations are required.

Purpose: Combinations of intra- and extra-articular procedures have been proposed for anterior cruciate ligament reconstruction with the aim of achieving an optimal control of translational and rotational knee laxities. Recently, the need for better reproducing the structural and functional behavior of the native anterior cruciate ligament led to the definition of anatomic double-bundle surgical approach. This study aimed to quantitatively verify whether the in vivo static and dynamic behavior obtained using over-the-top single-bundle with extra-articular tenodesis reconstruction was comparable to the results achieved by anatomic double-bundle approach., Methods: Thirty-five consecutive patients, with an isolated anterior cruciate ligament injury, were included in the study. Standard clinical laxities and pivot-shift test were quantified before and after anterior cruciate ligament reconstruction by means of a surgical navigation system dedicated to kinematic assessment; displacements of medial and lateral compartment during stress tests were also analyzed., Results: Single-bundle with extra-articular tenodesis approach presented statistically better laxity reduction in varus/valgus stress test at full extension and in internal/external rotation at 90° of flexion; lateral plasty controlled better the lateral compartment during drawer test and varus/valgus stress test both at 0° and 30° of flexion and both the compartments during internal/external rotation at 90° of flexion. On the other hand, pivot-shift phenomenon was better controlled by anatomic double-bundle reconstruction., Conclusions: Both the reconstructions worked similarly for static knee laxity. The extra-articular procedure played an important role in better constraining the displacement of lateral tibial compartment, whereas the anatomic double-bundle reconstruction better restored the dynamic behavior of knee joint highlighted under pivot-shift stress test., Study Design: Case series.

Purpose: The purpose of this study was to compare subjective, objective and radiographic outcome of the lateralized single-bundle bone-patellar tendon-bone autograft with a non-anatomical double-bundle hamstring tendons autograft anterior cruciate ligament (ACL) reconstruction technique at long-term follow-up., Methods: Seventy-nine non-consecutive randomized patients (42 men; 37 women) with unilateral ACL insufficiency were prospectively evaluated, before and after ACL reconstruction by means of the above-mentioned techniques, with a minimum follow-up of 8 years (range 8-10 years; mean 8.6 years). In the double-bundle hamstrings technique, we used one tibial and one femoral tunnel combined with one "over-the-top" passage, cortical staple's fixation and we left intact hamstrings' tibial insertion. Patients were evaluated subjectively and objectively, using IKDC score, Tegner level, manual maximum displacement test with KT-2000™ arthrometer. Radiographic evaluation was performed according to IKDC grading system, and re-intervention rate for meniscal lesions was also recorded., Results: The subjective and objective IKDC were similar in both groups while double-bundle hamstrings group showed significantly higher Tegner level (P = 0.0007), higher passive range of motion recovery (P = 0.0014), faster sport resumption (P = 0.0052), lower glide pivot-shift phenomenon (P = 0.0302) and lower re-intervention rate (P = 0.0116) compared with patellar tendon group. Radiographic evaluation showed significant lower objective degenerative changes in double-bundle hamstrings group at final follow-up (P = 0.0056)., Conclusion: Although both techniques provide satisfactory results, double-bundle ACL reconstruction shows better functional results, with a faster return to sport activity, a lower re-operation rate and lower degenerative knee changes.

A computer navigation system was used to collect kinematic data of 18 subjects undergoing ACL reconstruction. Surgical procedure was an anatomical four-tunnel hamstring double-bundle reconstruction. Static laxity and dynamic laxity were analyzed before and after graft passage and fixation. Correlations between static and dynamic laxities as well as with the preoperative IKDC score were determined. Static and dynamic laxities were significantly reduced after anatomic double-bundle ACL reconstruction (P < 0.05). There were no significant correlations between static and dynamic laxities (r < 0.4, P > 0.05). The preoperative IKDC score was only related to preoperative dynamic laxity (P < 0.01). The dynamic evaluation of pivot shift is able to better describe knee laxity, in particular rotational laxities and has no correlation with static laxity.

Interest in the kinematics of reconstructed knees has increased since it was shown that the alteration of knee motion could lead to abnormal wear and damage to soft tissues. We performed intraoperative kinematic measurements using a navigation system to study knee kinematics before and after posterior substituting rotating platform total knee arthroplasty (TKA). We verified intraoperatively (1) if varus/valgus (VV) laxity and anterior/posterior (AP) laxity were restored after TKA; (2) if TKA induced abnormal femoral rollback; and (3) how tibial axial rotation was influenced by TKA throughout the range of flexion. We found that TKA improved alignment in preoperative osteoarthritic varus knees which became neutral after surgery and maintained a neutral alignment in neutral knees. The VV stability at 0 degrees was restored while AP laxity at 90 degrees significantly increased after TKA. Following TKA, the femur had an abnormal anterior translation up to 60 degrees of flexion, followed by a small rollback of 12 +/- 5 mm. TKA influenced the tibia rotation pattern during flexion, but not the total amount of internal/external rotation throughout whole range of flexion, which was preserved after TKA (6 degrees +/- 5 degrees ). This study showed that the protocol proposed might be useful to adjust knee stability at time zero and that knee kinematic outcome during total knee replacement can be monitored by a navigation system.

The objective of this study was to quantify, in vivo, the reduction of knee laxity obtained by an extra-articular procedure, added to hamstring single-bundle (SB) anterior cruciate ligament (ACL) reconstruction in controlling coupled tibial translation during the Lachman and drawer tests. Twenty-eight patients were evaluated with a computer-assisted kinematic evaluation protocol; patients with associated ligament tears or meniscal damages were not included in the study. All patients underwent an hamstring ACL with an additional extra-articular procedure. During the intervention, tibia was tracked during the Lachman and drawer tests with ACL-deficient knee, after SB fixation and after extra-articular plasty fixation, performed with the remnant part of the hamstring tendons, from end of lateral condyle to Gerdy's tubercle. Statistical analysis was performed to see whether there was a difference in knee laxity after the tests in the three steps. At 30 degrees , the SB graft reduces AP translation of about 5 mm (P < 0.05) while the extra-articular procedure controls lateral tibial compartment, reducing translation by 1.6 mm (P < 0.05). At 90 degrees the SB graft reduces AP translation more in the lateral compartment (P < 0.05), while the extra-articular procedure contributes in controlling tibial translation reducing laxity by 1 mm (P < 0.05) in both compartments. Result shows that, in vivo, the addition of an extra-articular procedure to single-bundle ACL reconstruction may be effective in controlling coupled tibial translation during the Lachman test and reduces AP laxity at 90 degrees of flexion.

A real improvement in anterior cruciate ligament (ACL) surgery would be achieved if a global kinematic evaluation of graft performance could be made during surgery. A quantitative evaluation of all residual instabilities would be helpful in the evaluation of graft performances. This paper describes a new protocol for an accurate and extensive computer-assisted in vivo evaluation of joint laxities during ACL reconstruction. Fifteen in vivo kinematic evaluations during ACL reconstruction were performed using an optical localizer and custom software. The capability of the protocol was studied by analyzing the accuracy and repeatability of the results, the ergonomics of the setup, time taken, interactions with the surgical steps, and efficacy of the acquisitions. Repeatability of the tests, at maximum force, remained under 1 mm/2 degrees . Repeatability in tibia position and orientation was lower than 1 mm/4 degrees . Secondary laxities during stress tests remained under 2 mm/3 degrees . Added time to surgery was about 11 min. ACL graft increased joint stability up to 52% with respect to the preoperative level. The simplicity and morbidity of the test procedure and system was minimally invasive and allowed a quantitative evaluation of knee laxities at time zero. The repeatability of the tests opens the way for future research on in vivo evaluation of different ACL reconstruction techniques, which may lead to a better understanding of associated lesions and their role to the global knee stability.