A computer simulation study for preserving the tibial posterior slope in open-wedge high tibial osteotomy.

OBJECTIVE: To measure the medial opening gap and examine a technique for preserving the tibial posterior slope (TPS) in open-wedge high tibial osteotomy (OWHTO) using computer-simulated three-dimensional (3D) surgery. MATERIALS AND METHODS: This study included 24 symptomatic knees from 20 patients (7 men and 13 women; mean age, 67.9 years; range 54-89 years). Digital imaging and communications from computed tomography examination were applied to a 3D picture software program, and several anatomical landmarks were registered. Then, computer simulation of OWHTO as a virtual surgery was performed: the correction angle was decided to make the femorotibial angle 170°, and the TPS did not differ between pre- and postplanification. The distance between the proximal and distal cortices of the medial tibia was measured at three points, which were the anterior (AD), posterior (PD), and longest (LD) distance sites in the sagittal plane, using the 3D view, and the ratios of AD/PD and AD/LD were measured. The anteromedial opening gap was compared to the posteromedial gap and the longest distance gap at the osteotomy site. Spearman's rank correlation coefficient test was used in statistical analysis. RESULTS: Mean AD/PD was 0.740 ± 0.051 (range 0.651-0.850), and mean AD/LD was 0.652 ± 0.040 (range 0.571-0.768). The correction angle was not associated with the values of both AD/PD and AD/LD. CONCLUSIONS: Difference in AD/PD and AD/LD between each patient was regarded as a significant variation. Therefore, preoperative planification with 3D computer simulation to measure AD/PD and AD/LD may be helpful to avoid a significant increase in TPS.

Should sagittal osteotomy line be parallel to tibial posterior slope in high tibial osteotomy?

BACKGROUND: The reason why the osteotomy line in the sagittal view should be parallel to the medial tibial posterior slope in open wedge high tibial osteotomy (OWHTO) remains unclear. In addition, previous study reported that a posterolateral hinge position led to an increase in tibial posterior slope (TPS) after OWHTO. Our aims were to examine the relationships between angles among the tibial plateau and osteotomy planes or the hinge point and the change in TPS, and the location of the hinge position after OWHTO using three-dimensional computed tomography (3DCT). We hypothesized that the sagittal angle between the tibial plateau and osteotomy planes with an anterior-widening proximal tibial fragment resulted in increased TPS, and the hinge position located posterolaterally. METHODS: Preoperative planning anticipated a weight-bearing line ratio of 62% on the radiograph. The anterior gap was 67% of the posterior gap in OWHTO. We identified the tibial plateau and upper and lower osteotomy planes on 3DCT of 82 patients with symptomatic medial osteoarthritic knee after OWHTO. The osteotomy plane angles between the tibial plateau and upper osteotomy planes, and opening gap angles between both osteotomy planes in the coronal and sagittal views were measured. The anteroposterior (AP) and lateral hinge position was displayed as a percentage on the upper osteotomy plane. We assessed the relationships among them. RESULTS: The TPS significantly increased after OWHTO (p = 0.002). There was no significant difference between the sagittal osteotomy plane angle and the change in TPS. The sagittal opening gap angle and the AP hinge position ratio were significantly correlated with the change in the TPS (r = 0.477 p < 0.001 and r = - 0.342, p = 0.002, respectively). The hinge position was located a mean of 16.0% from the lateral and 48.6% from the posterior tibial edge in the upper osteotomy plane. CONCLUSIONS: Contrary to our expectation, the osteotomy plane did not need to be parallel to the tibial plateau plane in the sagittal view. However, the osteotomy gap should be rectangular in the sagittal view. The hinge position located nearly in the center of the sagittal view.

Computer-assisted navigation decreases the change in the tibial posterior slope angle after closed-wedge high tibial osteotomy.

PURPOSE: The purpose of the present study was to compare the change in tibial posterior slope angle (PSA) between patients treated via computer-assisted and conventional closed-wedge high tibial osteotomy (CWHTO). It was hypothesized that a decrease in the PSA would be less in the computer-assisted group than in the conventional group. METHODS: Data on a total of 75 computer-assisted CWHTOs (60 patients) and 75 conventional CWHTOs (49 patients) were retrospectively compared using matched pair analysis. The pre- and postoperative mechanical axis (MA) and the PSA were radiographically evaluated. The parallel angle was defined as the angle between the joint line and the osteotomy surface. The data were compared between the two groups. RESULTS: The postoperative radiographic MA averaged 1.3° ± 2.6° valgus in the computer-assisted group and 0.3° ± 3.1° varus in the conventional group. The change in PSA averaged -0.8° ± 0.9° in the computer-assisted group and -4.0° ± 2.2° in the conventional group. The parallel angle averaged 0.2° ± 3.0° in the computer-assisted group and 6.2° ± 5.3° in the conventional group. CONCLUSION: Computer-assisted CWHTO using four guide pins could avoid inadvertent change in the PSA. The navigation can be used in anticipation of decreasing the risk of change in the PSA in CWHTO, especially in patients whose preoperative PSA is small. The special attention should be paid to locate the hinge axis acutely and to make the parallel proximal and distal osteotomy surfaces during CWHTO. LEVEL OF EVIDENCE: III.

Effect of Tibial Posterior Slope on Knee Kinematics, Quadriceps Force, and Patellofemoral Contact Force After Posterior-Stabilized Total Knee Arthroplasty.

We used a musculoskeletal model validated with in vivo data to evaluate the effect of tibial posterior slope on knee kinematics, quadriceps force, and patellofemoral contact force after posterior-stabilized total knee arthroplasty. The maximum quadriceps force and patellofemoral contact force decreased with increasing posterior slope. Anterior sliding of the tibial component and anterior impingement of the anterior aspect of the tibial post were observed with tibial posterior slopes of at least 5° and 10°, respectively. Increased tibial posterior slope contributes to improved exercise efficiency during knee extension, however excessive tibial posterior slope should be avoided to prevent knee instability. Based on our computer simulation we recommend tibial posterior slopes of less than 5° in posterior-stabilized total knee arthroplasty.

Medial tibial plateau morphology and stress fracture location: A magnetic resonance imaging study.

AIM: To determine the location of medial tibial plateau stress fractures and its relationship with tibial plateau morphology using magnetic resonance imaging (MRI). METHODS: A retrospective review of patients with a diagnosis of stress fracture of the medial tibial plateau was performed for a 5-year period. Fourteen patients [three female and 11 male, with an average age of 36.4 years (range, 15-50 years)], who underwent knee MRI, were included. The appearance of the tibial plateau stress fracture and the geometry of the tibial plateau were reviewed and measured on MRI. RESULTS: Thirteen of 14 stress fractures were linear, and one of them stellated on MRI images. The location of fractures was classified into three types. Three fractures were located anteromedially (AM type), six posteromedially (PM type), and five posteriorly (P type) at the medial tibial plateau. In addition, tibial posterior slope at the medial tibial plateau tended to be larger when the fracture was located more posteriorly on MRI. CONCLUSION: We found that MRI showed three different localizations of medial tibial plateau stress fractures, which were associated with tibial posterior slope at the medial tibial plateau.

Changes in Femoral Posterior Condylar Offset, Tibial Posterior Slope Angle, and Joint Line Height after Cruciate-Retaining Total Knee Arthroplasty.

PURPOSE: Changes in the femoral posterior condylar offset (PCO), tibial posterior slope angle (PSA), and joint line height (JLH) after cruciate-retaining total knee arthroplasty (CR-TKA) were evaluated to determine their influence on the flexion angle. MATERIALS AND METHODS: A total of 125 CR-TKAs performed on 110 patients were retrospectively reviewed. Pre- and postoperative PCO, PSA, and JLH were compared using correlation analysis. Independent factors affecting the postoperative flexion angle of the knee were analyzed. RESULTS: The PCO was 28.2±2.0 mm (range, 24.5 to 33.1 mm) preoperatively and 26.7±1.8 mm (range, 22.2 to 31.2 mm) postoperatively (r=0.807, p<0.001). The PSA was 10.4°±4.9° (range, 1.6° to 21.2°) preoperatively and decreased to 4.9°±2.0° (2.2° to 10.7°) postoperatively (r=-0.023, p=0.800). The JLH was 16.2±3.0 mm (range, 10.2 to 27.5 mm) preoperatively and 16.1±2.6 mm (range, 11.1 to 24.8 mm) postoperatively (r=0.505, p<0.001). None of the independent factors affected the flexion angle (p>0.291). CONCLUSIONS: Although the PCO and JLH did not change significantly after CR-TKA, the PSA decreased by 5.5° with a small range of variation. Restoration of the PCO and JLH could promote optimization of knee flexion in spite of the decreased PSA after CR-TKA.

Changing Sagittal-Plane Landing Styles to Modulate Impact and Tibiofemoral Force Magnitude and Directions Relative to the Tibia.

CONTEXT: Ground reaction force (GRF) and tibiofemoral force magnitudes and directions have been shown to affect anterior cruciate ligament loading during landing. However, the kinematic and kinetic factors modifying these 2 forces during landing are unknown. OBJECTIVE: To clarify the intersegmental kinematic and kinetic links underlying the alteration of the GRF and tibiofemoral force vectors secondary to changes in the sagittal-plane body position during single-legged landing. DESIGN: Crossover study. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: Twenty recreationally active participants (age = 23.4 ± 3.6 years, height = 171.0 ± 9.4 cm, mass = 73.3 ± 12.7 kg). INTERVENTION(S): Participants performed single-legged landings using 3 landing styles: self-selected landing (SSL), body leaning forward and landing on the toes (LFL), and body upright with flat-footed landing (URL). Three-dimensional kinetics and kinematics were recorded. MAIN OUTCOME MEASURE(S): Sagittal-plane tibial inclination and knee-flexion angles, GRF magnitude and inclination angles relative to the tibia, and proximal tibial forces at peak tibial axial forces. RESULTS: The URL resulted in less time to peak tibial axial forces, smaller knee-flexion angles, and greater magnitude and a more anteriorly inclined GRF vector relative to the tibia than did the SSL. These changes led to the greatest peak tibial axial and anterior shear forces in the URL among the 3 landing styles. Conversely, the LFL resulted in longer time to peak tibial axial forces, greater knee-flexion angles, and reduced magnitude and a more posteriorly inclined GRF vector relative to the tibia than the SSL. These changes in LFL resulted in the lowest peak tibial axial and largest posterior shear forces among the 3 landing styles. CONCLUSIONS: Sagittal-plane intersegmental kinematic and kinetic links strongly affected the magnitude and direction of GRF and tibiofemoral forces during the impact phase of single-legged landing. Therefore, improving sagittal-plane landing mechanics is important in reducing harmful magnitudes and directions of impact forces on the anterior cruciate ligament.

Quantification of the role of tibial posterior slope in knee joint mechanics and ACL force in simulated gait.

The anterior cruciate ligament (ACL) rupture is a common knee joint injury with higher prevalence in female athletes. In search of contributing mechanisms, clinical imaging studies of ACL-injured individuals versus controls have found greater medial-lateral posterior tibial slope (PTS) in injured population irrespective of the sex and in females compared to males, with stronger evidence on the lateral plateau slope. To quantify these effects, we use a lower extremity musculoskeletal model including a detailed finite element (FE) model of the knee joint to compute the role of changes in medial and/or lateral PTS by ±5° and ±10° on knee joint biomechanics, in general, and ACL force, in particular, throughout the stance phase of gait. The model is driven by reported kinematics/kinetics of gait in asymptomatic subjects. Our predictions showed, at all stance periods, a substantial increase in the anterior tibial translation (ATT) and ACL force as PTS increased with reverse trends as PTS decreased. At mid-stance, for example, ACL force increased from 181 N to 317 N and 460 N as PTS increased by 5° and 10°, respectively, while dropped to 102 N and 0 N as PTS changed by -5° and -10°, respectively. These effects are caused primarily by change in PTS at the tibial plateau that carries a larger portion of joint contact force. Steeper PTS is a major risk factor, especially under activities with large compression, in markedly increasing ACL force and its vulnerability to injury. Rehabilitation and ACL injury prevention programs could benefit from these findings.

Measurement and comparison of tibial posterior slope angle in different methods based on three-dimensional reconstruction.

BACKGROUND: The tibial posterior slope (PTS) is an important parameter for sagittal alignment which is associated with postoperative range of motion. However, the variations of different population subsets and different referential axes are still uncertain. METHODS: In this study, 80 healthy people from South China were recruited and measured on three-dimensional reconstruction of CT, with application of three referential axes, the proximal tibial long axis, the anterior and posterior cortices. RESULTS: The averages and standard deviations of medial PTS (MPTS) in the three methods were 8.43±3.06, 11.45±2.82 and 6.31±3.24, separately. The results of lateral PTS (LPTS) were 7.56±2.51, 10.17±2.42 and 5.22±2.59. There was no significant difference between the male and the female, and the two sides of one body. The results of the three axes varied but correlated with each other significantly. Through comparison it was found that, MPTS/LPTS of people from South China were different from the published data of other countries. CONCLUSIONS: Although PTS change markedly according to the reference axis, they show significant correlations with each other, and may be used safely. There are differences associated with races, but not gender nor the two sides of the body. CLINICAL RELEVANCE: The results of the study provided references for the reconstruction of the knee PTS, if the differences of reference axes, races and genders were considered.

The effect of tibial posterior slope on contact force and ligaments stresses in posterior-stabilized total knee arthroplasty-explicit finite element analysis.

PURPOSE: The purpose of this study is to evaluate the effect of change in tibial posterior slope on contact force and ligament stress using finite element analysis. MATERIALS AND METHODS: A 3-dimensional finite element model for total knee arthroplasty was developed by using a computed tomography scan. For validation, the tibial translations were compared with previous studies. The finite element analysis was conducted under the standard gait cycle, and contact force on ultra-high molecular weight polyethylene (UHMWPE) and stresses on lateral and medial collateral ligaments were evaluated. RESULTS: The tibial translations showed similarity with previous studies. As the tibial posterior slope angle increases, the contact stress area increased and was well distributed, and the contact force on UHMWPE decreased overall. However, the maximum contact force in the case for 10° case was greater than those for others. The stresses on ligaments were the greatest and smallest in 0° and 10° cases, respectively. CONCLUSIONS: The higher tibial posterior slope angle leads to the lower contact stress and more extensive stress distribution overall in posterior-stabilized total knee arthroscopy. However, it does not absolutely mean the smallest contact force. The stresses on ligaments increased with respect to the smaller tibial posterior slope angle.

Changes in Femoral Posterior Condylar Offset, Tibial Posterior Slope Angle, and Joint Line Height after Cruciate-Retaining Total Knee Arthroplasty

PURPOSE: Changes in the femoral posterior condylar offset (PCO), tibial posterior slope angle (PSA), and joint line height (JLH) after cruciate-retaining total knee arthroplasty (CR-TKA) were evaluated to determine their influence on the flexion angle. MATERIALS AND METHODS: A total of 125 CR-TKAs performed on 110 patients were retrospectively reviewed. Pre- and postoperative PCO, PSA, and JLH were compared using correlation analysis. Independent factors affecting the postoperative flexion angle of the knee were analyzed. RESULTS: The PCO was 28.2+/-2.0 mm (range, 24.5 to 33.1 mm) preoperatively and 26.7+/-1.8 mm (range, 22.2 to 31.2 mm) postoperatively (r=0.807, p0.291). CONCLUSIONS: Although the PCO and JLH did not change significantly after CR-TKA, the PSA decreased by 5.5degrees with a small range of variation. Restoration of the PCO and JLH could promote optimization of knee flexion in spite of the decreased PSA after CR-TKA.

The Effect of Tibial Posterior Slope on Contact Force and Ligaments Stresses in Posterior-Stabilized Total Knee Arthroplasty-Explicit Finite Element Analysis

PURPOSE: The purpose of this study is to evaluate the effect of change in tibial posterior slope on contact force and ligament stress using finite element analysis. MATERIALS AND METHODS: A 3-dimensional finite element model for total knee arthroplasty was developed by using a computed tomography scan. For validation, the tibial translations were compared with previous studies. The finite element analysis was conducted under the standard gait cycle, and contact force on ultra-high molecular weight polyethylene (UHMWPE) and stresses on lateral and medial collateral ligaments were evaluated. RESULTS: The tibial translations showed similarity with previous studies. As the tibial posterior slope angle increases, the contact stress area increased and was well distributed, and the contact force on UHMWPE decreased overall. However, the maximum contact force in the case for 10degrees case was greater than those for others. The stresses on ligaments were the greatest and smallest in 0degrees and 10degrees cases, respectively. CONCLUSIONS: The higher tibial posterior slope angle leads to the lower contact stress and more extensive stress distribution overall in posterior-stabilized total knee arthroscopy. However, it does not absolutely mean the smallest contact force. The stresses on ligaments increased with respect to the smaller tibial posterior slope angle.

Relationship Between ground Surface and Tibial Posterior Slope at Erect Posture in Total Knee Arthroplasty

PURPOSE: To evaluate the perioperative changes of the relationship between tibial posterior slope and ground surface and the factors which influence the perioperative changes of the relationship between tibial posterior slope and ground surface following total knee arthroplasty. MATERIALS AND METHODS: Between Sept. 2005 and Feb. 2006, 94 consecutive primary total knee arthroplasty with posterior cruciate ligament-retaining type performed in 50 patients by one surgeon. Posterior slope of the proximal tibia resection in extramedullary guide was fixed at 5degrees. All the retrieved patients wore a 90degrees ankle brace and stood on the ground during radiographic examination. We prospectively analyzed the measurement of tibial posterior slope angle, the angle between tibial posterior slope and ground surface and the angle between a midline from 1st metatarsal shaft to talus and ground surface on preoperative and postoperative 2-weeks radiographs. RESULTS: On preoperative radiograph, average of tibial posterior slope angle is 11.3degrees and 11.5degrees in right and left knee, respectively. Angle between tibial posterior slope and ground surface is an average of 8.8degrees and 9.5degrees in right and left knee, respectively. On postoperative 2-weeks radiograph, tibial posterior slope angle is an average of 9.3degrees and 9.1degrees in right and left knee, respectively. Angle between tibial posterior slope and ground surface is an average of 6.2degrees and 6.4degrees in right and left knee. There are significant differences between tibial posterior slope angle and the angle between tibial posterior slope and ground surface on preoperative and postoperative 2-weeks radiograph (p<0.05). CONCLUSION: According to ankle lateral angle, it is possible that tibial posterior slope associated with the ground surface may decrease at erect posture in total knee arthroplasty. This may lead to overly decrease tibial posterior slope associated with the ground surface at comfortable erect posture in total knee arthroplasty.