A Quantifiable Risk Factor for ACL Injury: Applied Mathematics to Model the Posterolateral Tibial Plateau Surface Geometry

Background: The mechanism for traumatic ruptures of the native anterior cruciate ligament (ACL) is frequently a noncontact injury involving a valgus moment with internal rotation of the tibia. The abnormal rotation and translation of the lateral femoral condyle posteroinferiorly relative to the lateral tibial plateau is thought to be related to the geometry of the tibial plateau. Purpose/Hypothesis: The purpose of the study was to mathematically model the posterior tibial plateau geometry in patients with ACL injuries and compare it with that of matched controls. The hypothesis was that increased convexity and steepness of the posterior aspect of the lateral plateau would subject knees to higher forces, leading to a potentially higher risk of ACL injury. Study Design: Cross-sectional study; Level of evidence, 3. Methods: We mathematically modeled the posterior curvature of the lateral tibial plateau in 64 patients with ACL injuries and 68 matched controls. Using sagittal magnetic resonance imaging scans of the knee, points on the articular cartilage of the posterolateral tibial plateau were selected and curve-fitted to a power function ( y = a × xn). For coefficient a and coefficient n, both variables modulated the shape of the curve, where a larger magnitude represented an increase in slope steepness. Groups were compared using a Mann-Whitney test and α < .05. Results: There was a significant difference in surface geometry between the patients with ACL injuries and matched controls. The equation coefficients were significantly larger in the patients with ACL injuries: coefficient a (ACL injury, 0.9 vs control, 0.68; P < .0001) and coefficient n (ACL injury, 0.34 vs control, 0.30; P = .07). For coefficient a, there was a 78.9% sensitivity, 77.5% specificity, and odds ratio of 12.6 (95% CI, 5.5-29.0) for ACL injury using a cutoff coefficient a = .78. Conclusion: Patients with ACL injuries had a significantly greater posterolateral plateau slope. The steeper drop off may play a role in higher anterior translation forces, coupled with internal rotation torques on the knee in noncontact injury, which could increase ACL strain and predispose to ACL injury.

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The Effect Of Playing Surface On Anterior Cruciate Ligament Injury In NCAA Soccer

Orthopaedic Journal of Sports Medicine ◽

10.1177/2325967120s00125 ◽

2020 ◽

Vol 8 (3_suppl2) ◽

pp. 2325967120S0012

Author(s):

Mark Howard ◽

Hyunwoo Paco Kang ◽

Samantha Solaru ◽

Alexander E. Weber ◽

Mark F. Rick C

Keyword(s):

Anterior Cruciate Ligament ◽

Cruciate Ligament ◽

Acl Injury ◽

Soccer Players ◽

Injury Incidence ◽

Artificial Turf ◽

Acl Injuries ◽

Natural Grass ◽

Significant Difference ◽

Anterior Cruciate

Objectives: Previous orthopaedic literature has examined the effect of synthetic playing surfaces on the risk of anterior cruciate ligament (ACL) injury in athletes and produced varying and inconclusive results. The objective of this study was to examine the role of playing surface on the incidence and risk of ACL injury in collegiate soccer athletes. Methods: The NCAA Injury Surveillance Program (ISP) database was queried for ACL injuries for male and female soccer players from the 2004-05 through the 2013-14 seasons at all levels of competition. The number of athlete exposures (AEs), defined as 1 athlete participating in 1 practice or competition in which they were exposed to the possibility of athletic injury, were recorded for grass and synthetic playing surfaces. Both the reported injuries and exposures provided were weighted in order to represent the entire NCAA collegiate soccer population. Normalized ACL incidence rates were calculated as well as 95% confidence intervals (95%CI). Rate ratios comparing competition type amongst both competition and practice were calculated. Results: ACL injuries were more common on grass surfaces (1.16 per 10,000 AEs, 95%CI 1.12-1.20) than artificial turf (0.92 per 10,000 AEs, 95%CI 0.84-1.04). This difference was statistically significant (IRR 1.26, p<0.0001), and driven primarily by the difference in injury incidence during practice. The injury incidence during practice on natural grass (1.18 per 10,000 AEs, 95% CI 1.11-1.26) was significantly greater than the injury incidence rate during practice on artificial turf (0.067 per 10,000 AEs, 95%CI 0.043-0.096). Players were 17.7 times more likely (95%CI 10.6678-27.2187, p<0.0001) to sustain an ACL injury during practice on natural grass when compared to practice on artificial turf. However, there was no significant difference in injury incidence during matches (IRR 0.96, p=0.44), with matches on natural grass (3.35 per 10,000 AEs, 95% CI 3.21-3.51) equivalent to matches on artificial surfaces (3.49 per 10,000 AEs, 95%CI 3.18-3.81). When comparing exposure type, the injury rate was significantly greater during matches (3.38 per 10,000 AEs, 95% CI 3.25-3.52) compared to practices (0.82 per 10,000 AEs, 95%CI 0.77-0.88), with a 4.10-fold increase in ACL injury incidence during matches compared to practice (p<0.0001). Conclusion: Between 2004 and 2014, NCAA soccer players experienced a greater number of ACL injuries on natural grass playing surfaces compared with artificial turf playing surfaces. This difference is driven by injuries during practice, where athletes were nearly 18 times more likely to suffer an ACL injury on grass versus artificial turf. While ACL injuries were more likely during matches compared to practices, no difference in incidence was noted between playing surfaces. Additional study is warranted investigating potential causes for this observed increased risk with soccer practice on grass fields.

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Anterior Cruciate Ligament Injury

Orthopaedic Journal of Sports Medicine ◽

10.1177/2325967114s00250 ◽

2014 ◽

Vol 2 (12_suppl4) ◽

pp. 2325967114S0025

Author(s):

Tomas Vilaseca ◽

Jorge Chahla ◽

Gustavo Gomez Rodriguez ◽

Damián Arroquy ◽

Gonzalo Perez Herrera ◽

...

Keyword(s):

Anterior Cruciate Ligament ◽

Internal Rotation ◽

Cruciate Ligament ◽

Acl Injury ◽

T Test ◽

Control Group ◽

Recreational Athletes ◽

Significant Difference ◽

Anterior Cruciate ◽

Knee Pathology

Objectives: The objective of this study was to analyze whether it is more frequent the presence of a decreased range of motion in the hips of recreational athletes with primary injury of the anterior cruciate ligament (ACL) than in a control group of volunteers without knee pathology. Methods: We included prospectively recreational athletes between 18 and 40 years with an acute ACL injury between January 2011 and January 2013. They were compared with a control group of volunteers recreational athletes without lower limb pathology and in the same range of age. The internal and external rotations passively prior to the point at which the pelvis movement contributes were observed. The results were statistically analyzed using t test for related samples to the hips of patients with ACL injury and t test for independent variables for comparison with the control group. Results: 48 patients with ACL injury and 53 healthy volunteers were evaluated. The ACL group was composed of 32 males and 16 females with an average age of 29.3 years. In the control group 26 males and 27 females were studied with a mean age of 26.6 years. Internal (IR) and external (ER) rotation in the LCA group was 22,9º and 55,5º respectively in the ipsilateral hip and 27,9º and 57,7º in the contralateral. In the control group a 35,9º of IR and 55,2º of ER was observed. The analysis showed an association between ACL injury and hypomotility of the hip further expense of a decrease in internal rotation. The analysis showed an association between ACL injury and hypomotility of the hip at the expense to a greater decrease in internal rotation. Conclusion: We found a statistically significant difference in the mobility of the hips in patients with ACL injury predominantly due to internal rotation, pattern that allows us to interpret this injury not only as an intrinsic etiology of the knee but also of the adjacent joints. We consider very importance to incorporate prevention activities and screening of risk factors regarding to at least high performance athletes.

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Tendency of Driving to the Basket Is Associated With Increased Risk of Anterior Cruciate Ligament Tears in National Basketball Association Players: A Cohort Study

Orthopaedic Journal of Sports Medicine ◽

10.1177/23259671211052953 ◽

2021 ◽

Vol 9 (11) ◽

pp. 232596712110529

Author(s):

Blake J. Schultz ◽

Kevin A. Thomas ◽

Mark Cinque ◽

Joshua D. Harris ◽

William J. Maloney ◽

...

Keyword(s):

Anterior Cruciate Ligament ◽

Standard Deviation ◽

Cruciate Ligament ◽

Acl Injury ◽

National Basketball Association ◽

Acl Injuries ◽

Increased Risk ◽

Significant Difference ◽

Anterior Cruciate ◽

Level Performance

Background: Driving to the basket in basketball involves acceleration, deceleration, and lateral movements, which may expose players to increased anterior cruciate ligament (ACL) injury risk. It is unknown whether players who heavily rely on driving have decreased performance on returning to play after ACL reconstruction (ACLR). Hypothesis: Players with a greater tendency to drive to the basket would be more likely to tear their ACL versus noninjured controls and would experience decreased performance when returning to play after ACLR. Study Design: Case-control study; Level of evidence, 3. Methods: Season-level performance statistics and ACL injuries were aggregated for National Basketball Association (NBA) seasons between 1980 and 2017 from publicly available sources. Players’ tendency to drive was calculated using 49 common season-level performance metrics. Each ACL-injured player was matched with 2 noninjured control players by age, league experience, and style of play metrics. Points, playing minutes, driving, and 3-point shooting tendencies were compared between players with ACL injuries and matched controls. Independent-samples t test was utilized for comparisons. Results: Of 86 players with a total of 96 ACL tears identified in the NBA, 50 players were included in the final analysis. Players who experienced an ACL tear had a higher career-average drive tendency than controls ( P = .047). Players with career-average drive tendency ≥1 standard deviation above the mean were more likely to tear their ACL than players with drive tendency <1 standard deviation (5.2% vs 2.7%; P = .026). There was no significant difference in total postinjury career points ( P = .164) or career minutes ( P = .237) between cases and controls. There was also no significant change in drive tendency ( P = .152) or 3-point shooting tendency ( P = .508) after return to sport compared with controls. Conclusion: NBA players with increased drive tendency were more likely to tear their ACL. However, players who were able to return after ACLR did not underperform compared with controls and did not alter their style of play compared with the normal changes seen with age. This information can be used to target players with certain playing styles for ACL injury prevention programs.

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Tibial Plateau Slopes in Indian Patients with or without Anterior Cruciate Ligament Injury: A Magnetic Resonance Imaging Study

Journal of Orthopaedic Surgery ◽

10.1177/1602400303 ◽

2016 ◽

Vol 24 (3) ◽

pp. 289-293 ◽

Cited By ~ 1

Author(s):

Shyam Sundar ◽

Sarthak Patnaik ◽

Bobur Ubaydullaev ◽

Vinodh Kolandavelu ◽

David Rajan

Keyword(s):

Anterior Cruciate Ligament ◽

Magnetic Resonance ◽

Tibial Plateau ◽

Cruciate Ligament ◽

Acl Injury ◽

Magnetic Resonance Images ◽

Lateral Tibial Plateau ◽

Indian Patients ◽

Males And Females ◽

Anterior Cruciate

Purpose To compare anterior cruciate ligament (ACL)–injured and ACL-intact patients as well as males and females in terms of tibial plateau slopes to determine their association with ACL injury. Methods Magnetic resonance images (MRI) of the knee of 310 male and 179 female skeletally mature Indian patients (mean age, 40 years) with (n=170+29) or without (n=140+150) ACL injury were reviewed. Their medial and lateral tibial plateau slopes (MTPS and LTPS), medial tibial plateau depth (MTPD), and lateral tibial plateau height (LTPH) were measured using MRI. Results The ACL-injured and ACL-intact groups were comparable in terms of MTPS (6.72° vs. 6.73°, p=0.07), LTPS (5.68° vs. 5.70°, p=0.09), MTD (1.74 vs. 1.73 mm, p=0.356), and LTH (2.21 vs. 2.22 mm, p=0.393). Males and females were also comparable in terms of MTPS and LTPS in both ACL-injured and ACL-intact groups. Conclusion ACL-injured and ACL-intact patients as well as males and females were comparable in terms of the tibial plateau slope parameters.

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Lateral and medial tibial plateau angles in normal dogs

Veterinary and Comparative Orthopaedics and Traumatology ◽

10.3415/vcot-13-04-0043 ◽

2014 ◽

Vol 27 (02) ◽

pp. 135-140 ◽

Cited By ~ 12

Author(s):

M. K. Ocal ◽

S. S. Sabanci

Keyword(s):

Tibial Plateau ◽

Cruciate Ligament ◽

Axial Rotation ◽

T Test ◽

Medial Tibial Plateau ◽

Lateral Tibial Plateau ◽

Cranial Cruciate Ligament ◽

Significant Difference ◽

The Mean ◽

The Difference

SummaryTo measure lateral and medial tibial plateau angle values in isolated canine tibiae and to compare lateral and medial tibial plateau angle values between dogs based on sex and breed.Tibiae of 90 dogs from 24 different breeds were used. Photographs were taken of the medial and lateral aspects of the tibiae for measurement of the medial and lateral tibial plateau angles. Additionally, the medial tibial plateau angle was measured from radiographs of the tibiae. Two-way analysis of variance was used to test the effects of side, sex and breed on the medial and lateral tibial plateau angles as measured from photographs as well as the medial tibial plateal angles as measured from radiographs. The photographic and radiographic medial tibial plateau angles were compared by paired t-test, whereas the medial and lateral photographic tibial plateau angles were compared by t-test.When all dogs were included in the analysis, the difference between the mean medial tibial plateau angle (24.0 ± 3.19°) and the mean lateral tibial plateau angle (25.5 ± 3.84°) as measured from photographs was significant (p <0.05). The difference in the photographic medial tibial plateau angle between male and female dogs was significant (p <0.05), whereas the difference in the photographic lateral tibial plateau angle between sexes was not significant. There was a significant difference between the medial and lateral tibial plateau angles as measured from photographs in male dogs (p <0.05) but not in female dogs. Breed comparisons also showed significant differences for the photographic lateral tibial plateau angle (p <0.05).The axial rotation of the femoral condyles on the tibial plateau is probably affected by the discrepancy between the medial and lateral tibial plateau angles, and this difference in certain breeds might influence the prevalence of cranial cruciate ligament disease.

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Proximal tibial epiphysiodesis to reduce tibial plateau slope in young dogs with cranial cruciate ligament deficient stifle

Veterinary and Comparative Orthopaedics and Traumatology ◽

10.3415/vcot-07-05-0047 ◽

2008 ◽

Vol 21 (04) ◽

pp. 343-348 ◽

Cited By ~ 19

Author(s):

A. Bohorquez Vanelli ◽

M. Modenato ◽

J. Dziezyc ◽

T. Devine Slocum ◽

A. Vezzoni

Keyword(s):

Tibial Plateau ◽

Cruciate Ligament ◽

Tibial Slope ◽

Proximal Part ◽

Cranial Cruciate Ligament ◽

Acl Injuries ◽

Tibial Plateau Slope ◽

Intraoperative Fluoroscopy ◽

Significant Difference

SummaryThe purpose of this study was to evaluate the ability of proximal tibial epiphysiodesis to reduce the tibial plateau slope in young dogs with cranial cruciale ligament (CCL) deficient stifles. Of the 14 treated dogs, eight had a bilateral injury, for a total of 22 joints. After physical and radiographical examination and measurement of tibial plateau slope, all of the dogs underwent surgery. Insertion of the screw was placed in the most proximal part of the tibial plateau, in its medio-lateral centre, aiming to the tibial shaft and using a K wire predriven as a guide; correct position of the screw was confirmed with intraoperative fluoroscopy or radiography. In all of the dogs the tibial slope was decreased at the time of physis fusion and the degree of change depended on the age and the breed of the dog at the time of surgery. The minimum change was 4° and the maximum was 24°. There was a statistically significant difference between tibial slope measured before surgery compared to tibial slope measured at the last follow-up visit after surgery. This study shows that the partial proximal tibial fusion in dogs with ACL injuries was effective in reducing the tibial slope during the residual growing time to such an extent to stabilize the joint, provided that the surgery had been carried out when there was still residual growing potential. The technique appeared to be mini-invasive and malalignment complications could be avoided by correct and precise insertion of the screw.

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Distribution of Bone Contusion Patterns in Acute Noncontact Anterior Cruciate Ligament–Torn Knees

The American Journal of Sports Medicine ◽

10.1177/0363546520981569 ◽

2021 ◽

Vol 49 (2) ◽

pp. 404-409

Author(s):

Sophia Y. Kim-Wang ◽

Melissa B. Scribani ◽

Michael B. Whiteside ◽

Louis E. DeFrate ◽

Tally E. Lassiter ◽

...

Keyword(s):

Anterior Cruciate Ligament ◽

Tibial Plateau ◽

Femoral Condyle ◽

Cruciate Ligament ◽

Acl Injury ◽

Meniscal Tears ◽

Mri Scans ◽

Anterior Cruciate ◽

Operative Notes ◽

Bone Contusions

Background: Bone contusions are commonly observed on magnetic resonance imaging (MRI) in individuals who have sustained a noncontact anterior cruciate ligament (ACL) injury. Time from injury to image acquisition affects the ability to visualize these bone contusions, as contusions resolve with time. Purpose: To quantify the number of bone contusions and their locations (lateral tibial plateau [LTP], lateral femoral condyle [LFC], medial tibial plateau [MTP], and medial femoral condyle [MFC]) observed on MRI scans of noncontact ACL-injured knees acquired within 6 weeks of injury. Study Design: Cross-sectional study; Level of evidence, 3. Methods: We retrospectively reviewed clinic notes, operative notes, and imaging of 136 patients undergoing ACL reconstruction. The following exclusion criteria were applied: MRI scans acquired beyond 6 weeks after injury, contact ACL injury, and previous knee trauma. Fat-suppressed fast spin-echo T2-weighted MRI scans were reviewed by a blinded musculoskeletal radiologist. The number of contusions and their locations (LTP, LFC, MTP, and MFC) were recorded. Results: Contusions were observed in 135 of 136 patients. Eight patients (6%) had 1 contusion, 39 (29%) had 2, 41 (30%) had 3, and 47 (35%) had 4. The most common contusion patterns within each of these groups were 6 (75%) with LTP for 1 contusion, 29 (74%) with LTP/LFC for 2 contusions, 33 (80%) with LTP/LFC/MTP for 3 contusions, and 47 (100%) with LTP/LFC/MTP/MFC for 4 contusions. No sex differences were detected in contusion frequency in the 4 locations ( P > .05). Among the participants, 50 (37%) had medial meniscal tears and 52 (38%) had lateral meniscal tears. Conclusion: The most common contusion patterns observed were 4 locations (LTP/LFC/MTP/MFC) and 3 locations (LTP/LFC/MTP).

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ACL Injury Mechanism is Related to Articular Pressure Distribution: A Cadaveric and Finite Element Investigation

ASME 2012 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2012-80659 ◽

2012 ◽

Author(s):

Ata M. Kiapour ◽

Constantine K. Demetropoulos ◽

Ali Kiapour ◽

Carmen E. Quatman ◽

Jason W. Levine ◽

...

Keyword(s):

Finite Element ◽

Pressure Distribution ◽

Tibial Plateau ◽

Cruciate Ligament ◽

Acl Injury ◽

High Rate ◽

Bone Bruise ◽

Acl Injuries ◽

Injury Mechanisms ◽

Anterior Cruciate

Acute anterior cruciate ligament (ACL) injury can be devastating, and often results in clinical sequelae that include meniscal tears, chondral lesions and osteoarthritis. Various bone bruise patterns of the femur or tibia, and bone contusions of the lateral tibial plateau have been associated in more than 80% of partial or complete ACL ruptures [1]. As quantification of articular cartilage pressure distribution under high-rate loading conditions remains challenging, validated finite element (FE) models of the knee can be used to characterize the effects of different loading parameters on tibiofemoral (TF) joint pressure distribution. This study combines high-rate cadaveric experiments with FE analysis to simulate ACL injuries and associated bone bruise patterns following landing from a jump. We hypothesized that a potential relationship exists between ACL injury mechanisms and resultant tibial plateau bone bruise patterns. This relationship may enhance our understanding of ACL injury mechanisms, which may provide insight to improve current prevention strategies that aim to decrease the risk of ACL injury and damage to secondary anatomical structures. All of this may in turn minimize associated posttraumatic knee osteoarthritis.

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MEDIAL AND LATERAL POSTERIOR TIBIAL SLOPE IN THE SKELETALLY IMMATURE: A HUMAN CADAVERIC STUDY

Orthopaedic Journal of Sports Medicine ◽

10.1177/2325967119s00130 ◽

2019 ◽

Vol 7 (3_suppl) ◽

pp. 2325967119S0013

Author(s):

Nicolas G. Anchustegui ◽

Audrey Rustad ◽

Cooper Shea ◽

Stockton Troyer ◽

Aleksei Dingel ◽

...

Keyword(s):

Tibial Plateau ◽

Femoral Condyle ◽

Slope Angle ◽

Acl Injury ◽

Tibial Slope ◽

Posterior Tibial Slope ◽

Skeletally Immature ◽

Lateral Tibial Plateau ◽

Posterior Tibial ◽

Text Figure

Background: Recent research has identified posterior tibial slope as a risk factor for anterior cruciate ligament (ACL) injury, due to increased forces on the ACL with this tibial anatomy. Biomechanical studies suggest that altering a patient’s posterior tibial slope may lower the risk of ACL injury. Due to the presence of an open physis, guided growth may be used to reduce the posterior tibia slope in this high risk skeletally immature population. The primary purpose of this study was to quantify and measure the posterior tibial slope in pediatric knees. Methods: Forty-four pediatric knee CT scans were analyzed using OsiriX, an imaging software. Specimens analyzed were between the ages of 2 and 12 years of age. The proximal tibial slope for each specimen was measured on CT scan sagittal slices at 2 locations: 1) At the medial tibial plateau at the mid region of the medial femoral condyle, as determined on a coronal slice through the femoral condyle; 2) At the lateral tibial plateau at the mid region of the lateral femoral condyle, as determined on the coronal slice through the femoral condyle. The measurement of the posterior tibial slope was determined by placing two lines parallel to the diaphysis of the tibia, one located in the middle of the diaphysis and one located at the most posterior aspect of the diaphysis. The most proximal aspect of both the medial and lateral tibial plateau were then identified and angle measurements were taken in reference to the parallel lines. The angle measurements were plotted graphically by age in order to account for variability in development within age groups. The anterior medial and lateral tibia plateau widths were measured by identifying the mid region of the respective plateaus. From this point, the distance between the top of the tibial plate and the physis was measured. Results: The average posterior tibial slope angle for the medial and lateral tibial plateau were (5.53° ± 4.17°) and (5.95° ± 3.96°) respectively. Independent samples t-test and ANOVA indicate the difference between the posterior tibial slope angle of the medial and lateral tibial plateau were not statistically significant (p < 0.05). When plotted graphically by age, a slight negative trend between age and posterior tibial slope was identified. As age increases, the medial and lateral posterior tibial slope decreases. The mean anterior medial tibial plateau width and lateral tibial plateau width were .99 cm and 1.19 cm respectively. Discussion/Conclusion: ACL primary and secondary injury occur at very high rates in the skeletally immature, especially in females at age 11 and older, and in males at age 13 and older. This data set offers some preliminary values for posterior tibial slope in patients without a history of ACL injury, allowing for comparisons to patients with ACL Injury. Increased tibial slope is a risk factor for ACL injury. In the skeletally immature, one option to alter the tibial slope is the use of guided growth with implants to slow the anterior growth of the proximal tibia, reducing the posterior slope of the tibia, and possibly lower the risk of ACL injury in this high-risk population. [Figure: see text][Figure: see text][Figure: see text][Figure: see text][Figure: see text][Table: see text][Table: see text]

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Theoretical estimates of cruciate ligament forces: Effects of tibial surface geometry and ligament orientations

Proceedings of the Institution of Mechanical Engineers Part H Journal of Engineering in Medicine ◽

10.1243/0954411981534556 ◽

1997 ◽

Vol 211 (6) ◽

pp. 425-439 ◽

Cited By ~ 27

Author(s):

A Imran ◽

J J O'Connor

Keyword(s):

Tibial Plateau ◽

Sagittal Plane ◽

Femoral Condyle ◽

Cruciate Ligament ◽

Mechanical Analysis ◽

Concave Surface ◽

Surface Geometry ◽

Flat Surfaces ◽

Posterior Tilt ◽

Anterior Cruciate

A mathematical model of the knee in the sagittal plane was used to analyse the effect of tibial surface geometry and ligament orientations on the estimates of cruciate ligament forces. An elementary mechanical analysis was used to calculate the ligament forces L during a simulated antero-posterior (A-P) laxity test (passive test), and during isometric quadriceps contraction (IQE). Three sets of anatomical parameters (sites of bony attachments and lengths of the ligaments) were used from the literature. Flat, concave and convex shapes were considered for the tibial plateau articulating with a compatible convex femoral condyle. Also, the effects of position and posterior tilt of the tibial plateau were analysed for the concave and flat surfaces. The analysis showed that the ligament forces rose steeply as they approached collinearity with the contact force, C. For a flat tibia, the direction of C remained independent of flexion angle or position of the tibial plateau. For the concave tibia, the direction of C varied with flexion as well as with position of the centre of curvature, O, of the tibial plateau. C had an anterior component synergistic with the posterior cruciate ligament (PCL) when the point of contact, F, was anterior to O. On the other hand, C had a posterior component synergistic with the anterior cruciate ligament (ACL) when F was posterior to O. Also, posterior tilt of the flat or concave surfaces resulted in an increase in the anterior component of C. The effects of the convex tibial surface were opposite to those of the concave surface. During the A-P laxity test, the ligament forces arising from the concave tibia were very sensitive to the A-P position of O and to the posterior tilt of the plateau which allowed C and L to approach collinearity. Proximo-distal movement of O had a relatively insignificant effect on the ligament force. Similarly, compared to the concave surface, the posterior tilt of the flat tibia had a lesser effect on the ligament forces. Compared to the passive test, use of the muscle forces during IQE resulted in larger ligament forces, though the trends in force behaviour over the flexion range remained the same. The analysis emphasizes the importance of correct graft placement during ligament reconstruction, and the need to avoid steep inclination (more than 70° to tibial plateau). Increasing the inclination from 70 to 80° doubles the ligament force. Further, the analysis suggests that, in bicompartmental knee replacement, the efficacy of concave surfaces in replacing cruciate ligament function depends critically on the horizontal placement of the tibial component and its orientation about the mediolateral axis.

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