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PURPOSE: Surgeons mainly consider the anterior anatomy of the distal femur in the treatment of patellar instability (PI) with trochlear dysplasia (TD). Through this research, the idea was to analyse the posterior femoral condyle length in TD. The research team posited the presence of morphological differences in the posterior part of the femoral epiphysis in TD compared to a control group. They also postulated that the posterior bicondylar angle (PCA), in the axial plane, was increased in TD. METHODS: This is a single-centre morphological study of 100 patients who had a computed tomography (CT) using the same protocol. 50 patients with PI (25 dysplasias A and 25 B-C-D according to the Dejour classification), and 50 controls were included. All patients presenting a clinical PI were considered for the study. None of these patients had undergone a surgical treatment prior to imaging. Demographic characteristics, BMI, and laterality were comparable in all patients. 20 pilot CT scans were used to establish the methodology. The following measurements were performed: anterior bicondylar angle, PCA, and condylar lengths with respect to the surgical transepicondylar axis. Ratios were calculated in relation to the femoral width. TD was classified according to the Dejour classification in grade A or grades B-C-D. An analysis of variance and a linear model were performed within some groups to investigate which parameters correlated with the classification's grade. RESULTS: This study showed a link between TD and the PCA: control group (1.4?±?0.2°), type A group (1.6?±?0.3°), and types B, C, D group (2.6?±?0.3°) (p?=?0.01). The difference between the control group and types B, C, D TD group was significant (p?=?0.002). In groups B, C, D, the PCA was more important, which proves that in these groups the posterior part of the lateral condyle was relatively shorter compared to the medial condyle. The greater the dysplasia, the longer the medial condyle was in the anterior posterior (p?=?0.02). CONCLUSIONS: This study shows not only an anterior but also a posterior anomaly in PI with TD. There is a correlation between the severity of the anterior deformation and the PCA: in other words, the knee is placed in valgus in flexure which promotes the external dislocation of the patella. This anatomical study could open a field of research on the development of surgical treatments based on the correction of posterior condylar femoral anomalies in PI. LEVEL OF EVIDENCE: III.

Previous research has demonstrated that women have a higher risk of anterior cruciate ligament (ACL) injury than men. Tibiofemoral articular geometry may play a role in the occurrence of ACL tears. The purpose of this study was to analyze the gender-specific geometric characteristics differences in tibiofemoral morphology in ACL-deficient patients. Medial tibial slope (MTS), lateral tibial slope (LTS), medial tibial plateau concavity, medial and lateral femoral condyle convexity, and lateral plateau convexity were analyzed in 276 patients with complete ACL injuries (138 females and 138 males). Two blinded observers measured the anatomical parameters of tibiofemoral geometry with use of multiplanar CT scans. Intra- and inter-rater reliabilities were assessed and comparisons between anatomic measures were made between male and female patients. The average ICC for all measurements was 0.90 (range 0.83–0.97) indicating good reliability. Male ACL injured patients demonstrated significantly greater LTS (10.5° ± 2.8) than female patients (9.6° ± 3.5°; p

Joint surface incongruence resulting from osteochondritis dissecans (OCD) alters the articular physiologic congruence, increasing the contact stress on adjacent joint surfaces and accelerating wear and the cascade of joint degeneration. Accordingly, the restoration of articular surface integrity is of major importance, especially in young adults where, in lesions left untreated or following simple fragment excision, early osteoarthritis can be anticipated. Therefore, the treatment algorithm in unstable knee OCD of the young adult foresees surgical options to restore the articular surface. Several procedures have been proposed, including refixation of the detached fragment bone marrow stimulation, osteochondral autograft implantation, fresh osteochondral allograft transplantation, and cell-based or cell-free regenerative techniques. The aim of this review was to summarize the evidence for these surgical strategies, reporting their results and limitations. The overall evidence documents positive results for each of the assorted surgical procedures applied to treat unstable OCD, thus indicating support for their selected use to treat osteochondral defects paying particular attention to their specific indications for the lesion characteristics. The fixation of a good quality fragment should be pursued as a first option, while unfixable small lesions may benefit from autografts. For large lesions, available cell-based or cell-free osteochondral scaffold are a feasible solution but with limitation in terms of regenerated tissue quality. In this light, fresh allografts may offer articular surface restoration with viable physiologic osteochondral tissue providing a predictably successful outcome, and therefore they may currently represent the most suitable option to treat unstable irreparable OCD lesion in young adults. LEVEL OF EVIDENCE: V.

PURPOSE: The purpose of this study was to determine the test-retest reliability and the repeatability over multiple days of a robotic testing device when used to measure laxity of the lower leg during a simulated dial test. METHODS: Ten healthy subjects were evaluated using an instrumented robotic lower leg testing system over 4 days. Three testing cycles were performed each day. Each leg was rotated into external and then internal rotation by servomotors until a torque threshold of 5.65 N m was reached. Load-deformation curves were generated from torque and rotation data. Both average-measure and single-measure intraclass correlation coefficients (ICC) were compared across the curves. ICC scores were also compared for features of the curves including: maximum external rotation at -5.65 N m of torque, maximum internal rotation at 5.65 N m of torque, rotation at torque 0, compliance (slope of load-deformation curve) at torque 0, endpoint compliance in external rotation, endpoint compliance in internal rotation, and play at torque 0. Play at torque 0 was defined as the width of the hysteresis curve at torque 0. RESULTS: Average-measure ICC scores and test-retest scores were >0.95 along the entire load-deformation curve except around zero torque. ICC scores at maximum internal and external rotation ranged from 0.87 to 0.99 across the left and right knees. ICC scores for the other features of the curves ranged from 0.61 to 0.98. The standard error of the mean ranged from 0.0497 to 1.1712. CONCLUSIONS: The robotic testing device in this study proved to be reliable for testing a subject multiple times both within the same day and over multiple days. These findings suggest that the device can provide a level of reliability in rotational testing that allows for clinical use of test results. Objective laxity data can improve consistency and accuracy in diagnosing knee injuries and may enable more effective treatment.

PURPOSE: The purpose of this study is to review the indications for and outcomes of high tibial osteotomy in the treatment of patients with chronic knee laxity. METHODS: A comprehensive literature review was performed to identify surgical indications and results of high tibial osteotomy for the treatment of chronic knee laxity. RESULTS: Four distinct situations were identified in which a high tibial osteotomy may be advantageous: (1) anterior laxity with varus osteoarthritis, (2) chronic anterior laxity in the setting of varus with lateral ligamentous laxity, (3) chronic anterior laxity in the setting of a high tibial slope, and (4) chronic posterior laxity or posterolateral corner injury. A total of 24 studies were included in this report, including reports of the treatment of 410 knees as well as several review articles. The most frequently reported indication for that addition of HTO was anterior laxity in the setting of varus OA, which was noted to have good results, minimizing anterior knee laxity and allowing return to sports, while reducing the progression of osteoarthritis. More advanced cases in which lateral structures have also become stretched and incompetent are an excellent indication for HTO, with the need for subsequent lateral procedures dependent on the degree of varus laxity and especially hyperextension that is present. Excessive tibial slope has been identified as a cause of ACL reconstruction failure, and some authors have recommended addressing very high slope in revision cases. In knees with chronic posterior or posterolateral instability, correction of alignment first is generally recommended, with subsequent ligamentous procedures performed when instability persists. CONCLUSIONS: Knees with chronic instability pose a difficult treatment challenge. In all cases, the contribution of coronal plane alignment to varus-valgus knee stability must be carefully considered and addressed prior to ligament surgery. Sagittal plane alignment is also key and must not be overlooked. Such considerations drive the indication for osteotomy as well as the type of osteotomy that is chosen. Level of evidence IV.

PURPOSE: Static, one-dimensional testing cannot predict the behaviour of the anterior cruciate ligament (ACL)-deficient knee under realistic loading conditions. Currently, the most widely accepted method for assessing joint movement patterns is gait analysis. The purpose of the study was in vivo evaluation of the behaviour of the anterior cruciate ligament-deficient (ACLD) knees during walking, using 3D, real-time assessment tool. METHODS: Biomechanical data were collected prospectively on 30 patients with ACL rupture and 15 healthy subjects as a control group, with KneeKgTM System. Kinematic data were recorded in vivo during treadmill walking at self-selected speed. Flexion/extension, abduction/adduction, anterior/posterior tibial translation and external/internal tibial rotation were compared between groups. RESULTS: The ACLD patients showed a significant lower extension of the knee joint during stance phase (p < 0.05; 13.2° ± 2.1° and 7.3° ± 2.7°, for ACLD and control group, respectively). A significant difference in tibial rotation angle was found in ACLD knees compared to control knees (p < 0.05). The patients with ACLD rotated the tibia more internally (-1.4° ± 0.2°) during the mid-stance phase, than control group (0.2° ± 0.3°). There was no significant difference in anteroposterior translation and adduction-abduction angles. CONCLUSION: Significant alterations of joint kinematics in the ACLD knee were revealed in this study by manifesting a higher flexion gait strategy and excessive internal tibial rotation during walking that could result in a more rapid cartilage thinning throughout the knee. The preoperative data obtained in this study will be useful to understand the post-ACL reconstruction kinematic behaviour of the knee. CLINICAL RELEVANCE: The findings in this study indicate that ACLD knee may adapt functionally to prevent excessive anterior-posterior translation but they fail to avoid rotational instability.

The goal of this paper is to compare patient factors, intra-operative findings, and surgical techniques between patients followed in large cohorts in France, Norway, and North America.Data collected on 2,286 patients undergoing revision anterior cruciate ligament reconstruction (ACLR) were obtained. These data included 1,216 patients enrolled in the Multicenter ACL Revision Study (MARS) in North America, 793 patients undergoing revision ACLR and recorded in the Norwegian Knee Ligament Registry (NKLR), and 277 patients recorded in the revision ACL database of the Société Française d'Arthroscopie (SFA) in France. Data collected from each database included patient demographics (age, sex, height, and weight), graft choice and reason for failure of the primary ACLR, time from primary to revision ACLR, pre-revision patient-reported outcome scores (Knee Injury and Osteoarthritis Outcome Score, subjective International Knee Documentation Committee), associated intra-articular findings and treatments at revision, and graft choice for revision reconstruction.Patient demographics in the three databases were relatively similar. Graft choice for primary and revision ACLR varied significantly, with more allografts used in the MARS cohort. Hamstring autograft was favoured in the NKRL, while bone-patellar tendon-bone autograft was most common in the SFA cohort. Reasons for failure of the primary ACLR were comparable, with recurrent trauma noted in 46-56 % of patients in each of the three cohorts. Technical error was cited in 44-51 % of patients in the MARS and SFA cohorts, but was not clearly elucidated in the NKLR cohort. Biologic failure of the primary graft was more common in the MARS cohort. Differences in associated intra-articular findings were noted at the time of revision ACLR, with significantly more high-grade cartilage lesions noted in the MARS group.Significant differences exist between patient populations followed in revision ACL cohorts throughout the world that should be considered when applying findings from such cohorts to different patient populations.Retrospective comparative study, Level III.

PURPOSE: While there are numerous anatomic contributors to patellar instability, the role of patella alta has been traditionally under-appreciated. The goal of this systematic review is to identify the described techniques for treating patella alta in skeletally mature patients with episodic patellar dislocation (EPD) and review their published results. METHODS: A comprehensive literature review was performed to identify published surgical techniques and their results. Tibial tubercle distalization is the primary described treatment for patellar alta in patients with EPD, and five studies reporting results of this procedure were reviewed. RESULTS: Tibial tubercle distalization was generally successful in normalizing patellar height and preventing recurrent patellar dislocation. Physical examination tests for instability such as patellar apprehension remained positive in 15 to 33% of patients. Patient-reported outcomes were rarely reported and difficult to interpret given the lack of pre-operative values or comparison groups. CONCLUSION: Tibial tubercle distalization is an effective technique for correction of patellar height and preventing recurrent patellar dislocations. More comparative studies are required to evaluate patient-reported outcomes of this technique, the effect of an associated tubercle medialization, and the results of supplementing distalization with procedures such as MPFL reconstruction. LEVEL OF EVIDENCE: Systematic review of case series, Level IV.

The aim of our study was to evaluate knee rotational laxity and proprioceptive function 2 years after partial anterior cruciate ligament (ACL) reconstruction. According to our hypothesis, partial ACL reconstruction could restore knee laxity and function to the intact level. Methods : We conducted a study in fifteen consecutive patients undergoing partial ACL reconstruction. Fifteen anteromedial bundle tears were identified intra-operatively. Partial ACL reconstructions were performed by the same senior surgeon using a single-incision technique. A bone- patellar tendon-bone graft was used in 13 cases and a double-stranded semitendinosus graft in 2 cases of chronic patellar tendonitis. The mean age at surgery was 29 years. The time between ACL tear and surgery averaged 7.8 months (range 2.5-29.5 months). We developed an original device designed to assess knee proprioception (passive and active) and measure weight bearing rotational laxity in full extension and at 30 , 60 and 90 of knee flexion. All measurements were taken on both the reconstructed and healthy knee. The mean follow-up of the study was 3.4 years (range 2.6-4.4). No statistically significant difference in rotational laxity, active or passive proprioception could be observed between the reconstructed and healthy knee. External rotation was significantly greater than internal rotation in full extension and at 30 of flexion in the reconstructed and the healthy knee (P\\0.05). For each knee, active proprioception was found to be significantly different (higher) than passive proprioception (P\\0.05). Our study did not detect any difference in rotational laxity and proprioception between the reconstructed and the healthy knee. Therefore, partial ACL reconstruction appears to restore satisfactory knee laxity and function in case of partial ACL tear. Level of evidence IV. Anterior cruciate ligament - Partial rupture - Rotational laxity - Proprioception

Purpose Accurately quantifying knee joint motion is not simple. Skin movement over the medial and lateral femoral condyles is the greatest obstacle to obtaining accurate movement data non-invasively. The KneeKGTM system was developed with the objective of providing high reliability movement analysis. The goal of this manuscript is to review the technical details, clinical evidence, and potential applications of this system for evaluation of rotational knee laxity. Methods A comprehensive review of the MEDLINE database was carried out to identify all clinical and biomechanical studies related to KneeKGTM system. Results The KneeKGTM system non-invasively quantifies knee abduction/adduction, axial rotation, and relative translation of the tibia and femur. The accuracy and reproducibility of the system have been assessed. The average accuracy of the acquisition is 0.4_ for abduction/ adduction, 2.3_ for axial rotation, 2.4 mm for anteroposterior translation, and 1.1 mm for axial translation. This clinical tool enables an accurate and objective assessment of the tri-planar function of the knee joint. The measured biomechanical parameters are sensitive to changes in gait due to knee osteoarthritis and ACL deficiency. Conclusion The KneeKGTM system provides reliable movement analysis. This system has the potential to improve understanding the biomechanical consequences of trauma or degenerative changes of the knee as well as more accurately quantify rotational laxity as detected by a positive pivot-shift test. Knee - Movement analysis - KneeKG - Rotational laxity

The influence of the medial patellar ligamentous structures on patellar tracking has rarely been studied. Thus the main purpose of this cadaveric biomechanical study was to determine the influence of the medial patellofemoral (MPFL), medial patellomeniscal (MPML) and medial patellotibial (MPTL) ligaments on the three-dimensional patellar tracking during knee flexion. This study was conducted using a validated cadaveric optoelectronic protocol for analysis of patellar kinematics. Methods For each cadaveric knee study, four successive acquisitions were performed; first was studied patellar tracking in healthy knees, then the junction between MPFL and vastus medialis obliquus (VMO) was sectioned, the MPFL was released at its patellar attachment and finally was released the insertion of the MPML and MPTL. Results In this study, the MPFL accounts for 50-60% of the medial stabilization forces of the lateral patellar shift during patellar engagement in the femoral trochlea. This work confirm and clarify the role of the MPFL as the primary stabilizer of the patella during the initial 30° of knee flexion. Moreover, this study shows no significant results regarding the stabilizing action of the VMO on the patella during knee flexion. Conclusion This in vitro study, conducted with an experimental protocol previously validated in the literature, helps quantify the actions of the MPFL, the VMO, and the MPML/MPTL respectively, and identify areas of joint motion where these structures have the most significant influence. This confirms the importance of reconstruction in the treatment of chronic patellar instability. During its reconstruction, care should be taken to adjust the MPFL balance during the initial 20°-30° of flexion.

Growth arrest is a major concern after ACL reconstruction in children. It usually occurs in patients near to closure of the growth plates. Growth disturbances without growth arrest are also possible and more vicious; the authors analyse the mechanism of two patients with growth disturbance due to overgrowth following ACL reconstruction. One was a symmetrical overgrowth process with 15 mm limb length discrepancy treated with percutaneous epiphysiodesis. Full correction at the time of skeletal maturity was achieved. The second patient developed an asymmetrical overgrowth with progressive tibial valgus deformity. This mechanism was similar to a posttraumatic tibial valgus deformity. After nonoperative treatment, a spontaneous correction of the deformity was noticed. Both children were young (7 and 10 years old) at the time of ACL reconstruction with an autologous iliotibial band graft. The clinical relevance of overgrowth disturbance is usually limited when compared to growth arrest but could require a second surgical procedure as reported in this study. Parents must be informed that even in experienced hands, and despite the use of a physeal sparing technique, this specific risk of growth disturbance is still present.

The anterior cruciate ligament (ACL) is one of the most frequently studied structures of the musculoskeletal system and continues to stimulate debate and challenges among researchers and surgeons. The ultimate goal of anatomic reconstruction surgery is to restore the native anatomy as much as possible. However, this requires thorough knowledge of its anatomy. The aim of this article is to review the current knowledge of the anatomy of ACL along with its macrostructural and ultrastructural properties.

We present an algorithmic release approach to the varus knee, including a novel pie crust release technique of the superficial MCL, in 359 total knee arthroplasty patients and report the clinical and radiological outcome. Medio-lateral stability was evaluated as normal in 97% of group 0 (deep MCL), 95% of group 1 (pie crust superficial MCL) and 83% of group 2 (distal superficial MCL). The mean preoperative hip-knee angle was 174.0, 172.1, and 169.5 and was corrected postoperatively to 179.1, 179.2, and 177.6 for groups 0, 1, and 2, respectively. A satisfactory correction in the coronal plane was achieved in 82.9% of all-comers falling within the 180 degrees +/- 3 degrees interval. An algorithmic release approach can be beneficial for soft tissue balancing. In all patients, the deep medial collateral ligament should be released and otseophytes removed. The novel pie crust technique of the superficial MCL is safe, efficient and reliable, provided a medial release of 6-8 mm or less is required. The release of the superficial MCL on the distal tibia is advocated in severe varus knees. Preoperative coronal alignment is an important predictor for the release technique, but should be combined with other parameters such as reducibility of the deformity and the obtained gap asymmetry.

The purpose of this study was to evaluate cases of early aseptic failures presented during the first 5-year follow-up in a group of 981 primary total knee arthroplasty (primary TKA). Predisposing factors as well causes of failures and postoperative complications in different groups of aseptic failures were re-assessed and compared to a control group. A retrospective and cohort study compared one group of 944 primary TKA without surgical revision (890 patients) (Group A) with 22 primary TKA (22 patients) (Group B) that had revision TKA secondary to aseptic failure during the first five years follow-up. The cases of isolated patellar button replacement (n = 8) and infection (n = 7) were not considered in this study. All patients underwent a systematic assessment that included clinical and radiographic examinations, and IKS scores. Aseptic failure was more prevalent at the first 2-year follow-up (63%). TKA loosening (n = 11) and undiagnosed pain (n = 7) were considered the most frequent modes of failures, and laxity (n = 1) was a very rare early cause of failure. The aseptic failure group was characterized as average 5 years younger with a greater number of previous knee surgeries, lower IKS scores improvement, and more postoperative pain compared to control group, despite the fact that the aseptic failure group showed a prevalence of cases during the first 2-year follow-up. Inside this group, the undiagnosed pain group had lower improvement of IKS scores, a remarkable prevalence in prior surgical procedure (71%) and a minor mean interval between primary and revision TKA (11.6 months).

We report a prospective series of 33 unicompartmental knee arthroplasties (UKAs) operated for a spontaneous osteonecrosis of the knee (SPONK) compared with 35 UKAs operated for osteoarthritis (OA). The mean follow-up was 5 years. Preoperative functional score in the SPONK group was significantly lower than that in the OA group. The results were comparable in terms of pain, knee score and function. At the last follow-up, the survival rate was 92.8% for the SPONK group and 95.4% for the OA group. We found a higher rate of radiolucencies in the SPONK group, however, without any clinical symptoms. The UKA is a good option in the treatment of SPONK.

The purpose of this study was to compare the biomechanical characteristics and patient outcomes after either isolated intraarticular ACL reconstruction or intraarticular reconstruction with lateral extra-articular tenodesis. In addition, we aimed to evaluate biomechanical parameters of the entire uninjured, contralateral knee as a baseline during the analysis. METHODS: Eighteen patients were evaluated at an average of 9.3 years after ACL reconstruction. Twelve patients had an intraarticular reconstruction (BTB), and six had an additional lateral extraarticular procedure (BTB/EAR). Patients were selected for the additional procedure by the operating surgeon based on clinical and radiological criteria. At the time of review, each patient was assessed using subjective patient questionnaires, manual laxity testing, and instrumented laxity testing. Each knee was also evaluated using a robotic lower leg axial rotation testing system. This system measured maximum internal and external rotations at 5.65 Nm of applied torque and generated load deformation curves and compliance data. Pointwise statistical comparisons within each group and between groups were performed using the appropriate paired or unpaired t test. Features were extracted from each load deformation curve for comparative analysis. RESULTS: There were no significant differences between the two groups with respect to the patient satisfaction scores or to laxity testing (manual or instrumented). Robotic testing results for within-group comparisons demonstrated a significant reduction in maximum external rotation (8.77°) in the reconstructed leg when compared to the healthy leg (p < 0.05) in the BTB/EAR group, with a non-significant change in internal rotation. The slope of the curve at maximum internal rotation was also significantly greater in the reconstructed legs for the BTB/EAR group (p < 0.05), indicating reduced endpoint compliance or a harder endpoint. Finally, the leg that received the extra-articular tenodesis had a trend towards a reduced total leg axial rotation. Conversely, patients in the BTB group demonstrated no significant differences between their legs. For between-group comparisons, there was a significant increase in maximum internal rotation in the healthy legs in the BTB/EAR group compared with the healthy legs in the BTB group (p < 0.05). If the injured/reconstructed legs were compared, the significant difference at maximum internal rotation disappeared (p < 0.10). Similarly, the healthy legs in patients in the BTB/EAR group had a significantly more compliant or softer endpoint in internal rotation, greater maximum internal rotation, and more internal rotation at torque 0 in their healthy legs compared with the healthy legs in the BTB group (p < 0.05). These same differences were not noted in the reconstructed knees. The only identifiable significant difference between the injured/reconstructed legs was rotation at 0 torque (p < 0.05). CONCLUSIONS: In this group of patients who were at an average of 9 years from surgery, the addition of a lateral extra-articular reconstruction to a standard bone-tendon-bone intraarticular ACL reconstruction does reduces internal rotation of the tibia with respect to the femur when compared to intraarticular reconstruction alone. It appears that the selection process for inclusion into the BTB/EAR group included an increase in total axial rotation of the healthy knee during the examination along with a decrease in endpoint stiffness at maximum internal rotation. LEVEL OF EVIDENCE: II.