Focal knee arthroplasty is an attractive alternative to knee arthroplasty for young patients because it allows preservation of a large amount of bone for potential revisions. However, the mechanical behaviour of cartilage has not yet been investigated because it is challenging to evaluate in vivo contact areas, pressure, and deformations from metal implants. Therefore, this study aimed to determine the contact pressure in the tibiofemoral joint with a focal knee arthroplasty using a finite element model. The mechanical behaviour of the cartilage surrounding a metal implant was evaluated using finite element analysis. We modelled focal knee arthroplasty with placement flush, 0.5 mm deep, or protruding 0.5 mm with regard to the level of the surrounding cartilage. We compared contact stress and pressure for bone, implant, and cartilage under static loading conditions.Aims
Methods
A functional anterior cruciate ligament (ACL) or posterior cruciate ligament (PCL) has been assumed to be required for patients undergoing unicompartmental knee arthroplasty (UKA). However, this assumption has not been thoroughly tested. Therefore, this study aimed to assess the biomechanical effects exerted by cruciate ligament-deficient knees with medial UKAs regarding different posterior tibial slopes. ACL- or PCL-deficient models with posterior tibial slopes of 1°, 3°, 5°, 7°, and 9° were developed and compared to intact models. The kinematics and contact stresses on the tibiofemoral joint were evaluated under gait cycle loading conditions.Aims
Methods
This study aimed to identify the effect of anatomical tibial component (ATC) design on load distribution in the periprosthetic tibial bone of Koreans using finite element analysis (FEA). 3D finite element models of 30 tibiae in Korean women were created. A symmetric tibial component (STC, NexGen LPS-Flex) and an ATC (Persona) were used in surgical simulation. We compared the FEA measurements (von Mises stress and principal strains) around the stem tip and in the medial half of the proximal tibial bone, as well as the distance from the distal stem tip to the shortest anteromedial cortical bone. Correlations between this distance and FEA measurements were then analyzed.Aims
Methods
Unicompartmental knee arthroplasty (UKA) has become a popular method of treating knee localized osteoarthritis (OA). Additionally, the posterior cruciate ligament (PCL) is essential to maintaining the physiological kinematics and functions of the knee joint. Considering these factors, the purpose of this study was to investigate the biomechanical effects on PCL-deficient knees in medial UKA. Computational simulations of five subject-specific models were performed for intact and PCL-deficient UKA with tibial slopes. Anteroposterior (AP) kinematics and contact stresses of the patellofemoral (PF) joint and the articular cartilage were evaluated under the deep-knee-bend condition.Aims
Methods
Mobile-bearing unicompartmental knee arthroplasty (UKA) with a flat tibial plateau has not performed well in the lateral compartment, leading to a high rate of dislocation. For this reason, the Domed Lateral UKA with a biconcave bearing was developed. However, medial and lateral tibial plateaus have asymmetric anatomical geometries, with a slightly dished medial and a convex lateral plateau. Therefore, the aim of this study was to evaluate the extent at which the normal knee kinematics were restored with different tibial insert designs using computational simulation. We developed three different tibial inserts having flat, conforming, and anatomy-mimetic superior surfaces, whereas the inferior surface in all was designed to be concave to prevent dislocation. Kinematics from four male subjects and one female subject were compared under deep knee bend activity.Aims
Methods
Commonly performed unicompartmental knee arthroplasty (UKA) is not designed for the lateral compartment. Additionally, the anatomical medial and lateral tibial plateaus have asymmetrical geometries, with a slightly dished medial plateau and a convex lateral plateau. Therefore, this study aims to investigate the native knee kinematics with respect to the tibial insert design corresponding to the lateral femoral component. Subject-specific finite element models were developed with tibiofemoral (TF) and patellofemoral joints for one female and four male subjects. Three different TF conformity designs were applied. Flat, convex, and conforming tibial insert designs were applied to the identical femoral component. A deep knee bend was considered as the loading condition, and the kinematic preservation in the native knee was investigated.Aims
Methods
Unicompartmental knee arthroplasty (UKA) is an alternative to total knee arthroplasty with isolated medial or lateral compartment osteoarthritis. However, polyethylene wear can significantly reduce the lifespan of UKA. Different bearing designs and materials for UKA have been developed to change the rate of polyethylene wear. Therefore, the objective of this study is to investigate the effect of insert conformity and material on the predicted wear in mobile-bearing UKA using a previously developed computational wear method. Two different designs were tested with the same femoral component under identical kinematic input: anatomy mimetic design (AMD) and conforming design inserts with different conformity levels. The insert materials were standard or crosslinked ultra-high-molecular-weight polyethylene (UHMWPE). We evaluated the contact pressure, contact area, wear rate, wear depth, and volumetric wear under gait cycle loading conditions.Objectives
Methods
The aim of this study was to investigate the biomechanical effect of the anterolateral ligament (ALL), anterior cruciate ligament (ACL), or both ALL and ACL on kinematics under dynamic loading conditions using dynamic simulation subject-specific knee models. Five subject-specific musculoskeletal models were validated with computationally predicted muscle activation, electromyography data, and previous experimental data to analyze effects of the ALL and ACL on knee kinematics under gait and squat loading conditions.Objectives
Methods
Unicompartmental knee arthroplasty (UKA) is an alternative to total knee arthroplasty for patients who require treatment of single-compartment osteoarthritis, especially for young patients. To satisfy this requirement, new patient-specific prosthetic designs have been introduced. The patient-specific UKA is designed on the basis of data from preoperative medical images. In general, knee implant design with increased conformity has been developed to provide lower contact stress and reduced wear on the tibial insert compared with flat knee designs. The different tibiofemoral conformity may provide designers the opportunity to address both wear and kinematic design goals simultaneously. The aim of this study was to evaluate wear prediction with respect to tibiofemoral conformity design in patient-specific UKA under gait loading conditions by using a previously validated computational wear method. Three designs with different conformities were developed with the same femoral component: a flat design normally used in fixed-bearing UKA, a tibia plateau anatomy mimetic (AM) design, and an increased conforming design. We investigated the kinematics, contact stress, contact area, wear rate, and volumetric wear of the three different tibial insert designs.Objectives
Methods
Patient-specific (PS) implantation surgical technology has been introduced in recent years and a gradual increase in the associated number of surgical cases has been observed. PS technology uses a patient’s own geometry in designing a medical device to provide minimal bone resection with improvement in the prosthetic bone coverage. However, whether PS unicompartmental knee arthroplasty (UKA) provides a better biomechanical effect than standard off-the-shelf prostheses for UKA has not yet been determined, and still remains controversial in both biomechanical and clinical fields. Therefore, the aim of this study was to compare the biomechanical effect between PS and standard off-the-shelf prostheses for UKA. The contact stresses on the polyethylene (PE) insert, articular cartilage and lateral meniscus were evaluated in PS and standard off-the-shelf prostheses for UKA using a validated finite element model. Gait cycle loading was applied to evaluate the biomechanical effect in the PS and standard UKAs.Objectives
Methods
Posterior condylar offset (PCO) and posterior tibial slope (PTS) are critical factors in total knee arthroplasty (TKA). A computational simulation was performed to evaluate the biomechanical effect of PCO and PTS on cruciate retaining TKA. We generated a subject-specific computational model followed by the development of ± 1 mm, ± 2 mm and ± 3 mm PCO models in the posterior direction, and -3°, 0°, 3° and 6° PTS models with each of the PCO models. Using a validated finite element (FE) model, we investigated the influence of the changes in PCO and PTS on the contact stress in the patellar button and the forces on the posterior cruciate ligament (PCL), patellar tendon and quadriceps muscles under the deep knee-bend loading conditions.Objectives
Methods
Malalignment of the tibial component could influence the long-term survival of a total knee arthroplasty (TKA). The object of this study was to investigate the biomechanical effect of varus and valgus malalignment on the tibial component under stance-phase gait cycle loading conditions. Validated finite element models for varus and valgus malalignment by 3° and 5° were developed to evaluate the effect of malalignment on the tibial component in TKA. Maximum contact stress and contact area on a polyethylene insert, maximum contact stress on patellar button and the collateral ligament force were investigated.Objectives
Methods
Preservation of both anterior and posterior cruciate ligaments in total knee arthroplasty (TKA) can lead to near-normal post-operative joint mechanics and improved knee function. We hypothesised that a patient-specific bicruciate-retaining prosthesis preserves near-normal kinematics better than standard off-the-shelf posterior cruciate-retaining and bicruciate-retaining prostheses in TKA. We developed the validated models to evaluate the post-operative kinematics in patient-specific bicruciate-retaining, standard off-the-shelf bicruciate-retaining and posterior cruciate-retaining TKA under gait and deep knee bend loading conditions using numerical simulation.Objectives
Methods
Recently, the combination of press-fit acetabular cup with ceramic articulation is a widely used for implanting cementless acetabular components and has been shown to provide good initial stability. However, these methods may lead to elevating stresses, changing in the bearing geometries, and increasing wear due to deformation of the cup and insert. In addition, there is a potential for failure of ceramic inserts when a large ball head was used because it should be assembled with shallow thickness of the acetabular cup. For risk reduction of it, we applied direct metal tooling (DMT) based on 3D printing for porous coating on the cup. Due to its capability of mechanical strength, DMT coated cup could be feasible to provide better stability than conventional coating. Therefore, we constructed laboratory models for deformation test simulating an press-fit situation with large ceramic ball head to evaluate stability of the DMT coated cup compared with conventional coated cup. The deformation test was performed according to the test setup described by Z. M. Jin et al. The under reaming of the cavity in a two-point pinching cavity models of polyurethane (PU) foam block (SAWBONES, Pacific Research Laboratories, USA) with a grade 30 were constructed. Titanium plasma spray (TPS) and direct metal tooling (DMT) coated acetabular cups (BENCOX Mirabo and Z Mirabo Cup, Corentec Co. Ltd., KOREA) with a 52 mm size (n=3, respectively) were used for the test. These cups were implanted into the PU foam blocks, and followed by impaction of the inserts (BIOLOX delta, Ceramtec, GE) with a 36/44 size (n=6) into the acetabupar cups as shown in Fig. 1. Roundness and inner diameter of the acetabular cups and inserts were measured using a coordinate measuring machine (BHN 305, Mitutoyo Neuss, GE) in three levels; E2, E3, and E4 (3, 5, and 7 mm below the front face, respectively). Also, these parameters of the acetabular cup were measured in two level; E1 and E5 (5 and 11 mm below the front face) as shown in Fig. 2. Changes in roundness and inner diameter of the cup and insert were measured to evaluate deformation in relation to porous coating on the acetabular cups.Introduction
Materials and Methods
The Rotational alignment is an important factor for survival total knee Arthroplasty. Rotational malalignment causes knee pain, global instability, and wear of the polyethylene inlay. Also, the anterior cortex line was reported that more reliable and more easily identifiable landmark for correct tibial component alignment. The aims of the current study is to identify effect of inserting the tibial baseplate of using anterior cortex line landmark of TKA on stress/strain distributions within cortical bone and bone cement. Through the current study, final aim is to suggest an alternative position of tibia baseplate for reduction of TKA failures with surgical convenience. A three-dimensional tibia FE model with TKA was generated based on a traditional TKA surgical guideline. Here, a commercialized TKA (LOSPA, Corentc, Korea) was considered corresponded to a patient specific tibia morphology. Tibia baseplate was positioned at anterior cortex line. Alternative two positions were also considered based on tibia tuberosity 1/3 line and tibia tuberosity end line known as a gold standard Introduction
Materials and Method
The aim of the current study was to analyse the effects of posterior cruciate ligament (PCL) deficiency on forces of the posterolateral corner structure and on tibiofemoral (TF) and patellofemoral (PF) contact force under dynamic-loading conditions. A subject-specific knee model was validated using a passive flexion experiment, electromyography data, muscle activation, and previous experimental studies. The simulation was performed on the musculoskeletal models with and without PCL deficiency using a novel force-dependent kinematics method under gait- and squat-loading conditions, followed by probabilistic analysis for material uncertain to be considered.Objectives
Methods
Malrotation of the femoral component can result in post-operative complications in total knee arthroplasty (TKA), including patellar maltracking. Therefore, we used computational simulation to investigate the influence of femoral malrotation on contact stresses on the polyethylene (PE) insert and on the patellar button as well as on the forces on the collateral ligaments. Validated finite element (FE) models, for internal and external malrotations from 0° to 10° with regard to the neutral position, were developed to evaluate the effect of malrotation on the femoral component in TKA. Femoral malrotation in TKA on the knee joint was simulated in walking stance-phase gait and squat loading conditions.Objectives
Materials and Methods
Revision total knee arthroplasy (TKA) has been often used with a metal block augmentation for patients with poor bone quality. However, bone resorption beneath metal block augmentation has been still reported and little information about the reasons of the occurrence of bone resorption is available. The aim of the current study is to identify a possibility of the potential occurrence of bone resorption beneath metal block augmentation, through evaluation of strain distribution beneath metal block augmentation in revision TKA with metal block augmentation, during high deep flexion. LOSPA, revision TKA with a metal block augmentation (Baseplate size #5, Spacer size #5, Stem size Φ9, L30, Augment #5 T5) was considered in this study. For the test, the tibia component of LOSPA was implanted to the tibia sawbone (left, #3401, Sawbones EuropeAB, Malmö, Sweden), which was corresponded to a traditional TKR surgical guideline. The femoral component of LOSPA was mounted to a customized jig attached to the Instron 8872 (Instron, Norwood, MA, USA), which was designed specially to represent the angles ranged from 0° to 140° with consideration of a rollback of knee joint (Figure. 1). Here, a compressive load of 1,600N (10N/s) was applied for each angle. Strain distribution was then measured from rossete strain gauge (Half Bridge type, CAS, Seoul, Korea) together (Figure 1).Introduction
Materials and Method
Unicompartmental knee arthroplasty (UKA) is often considered to be attractive alternate surgical technique to total knee arthroplasty (TKA) and high tibial osteotomy (HTO), in particular young patients. In addition, it is recently reported that preservation of joint line in UKA is crucial factor for positive long-term outcome, especially in revision case for UKA. However, the role of this joint line has neither been invested nor is it consciously bothered during surgical implantation. Validated finite element (FE) analysis was introduced in this study to investigate the effects of maximum contact stress on polyethylene (PE) insert and maximum compressive stress in opposite compartments for joint line in fixed-type UKA. As suggested by Weber et al., FE model for joint line was developed by means of determination of the angle between the pre-operative joint line and the reference line from lateral cortical is of the femur. Based on the method above, joint lines were modeled in −3, −2, −1, 0, +1, +2, and +3 mm cases and these seven FE models were compared and analyzed (Fig. 1). All implant components were modeled as linear elastic isotropic materials. However, the model was considered to have plastic characteristics of PE insert. FE analysis was performed using high kinematics displacement and rotation inputs, which were based on the kinematics of the natural knee. ISO standards were used for axial load and flexion (Fig. 2). The FE model was subjected to validation based on cadaveric experimental data available in the literature by Sohn et al. and from previous cadaveric tests conducted by current investigators. The maximum contact stress was found at around 43 % of the gait cycle in 0 mm case. There were no difference between ± 1 and 0 mm cases, but maximum contact stress on PE insert becomes greater in ± 3 mm cases. The maximum compressive stress of the lateral meniscus in 0 mm case occurred at 62 % of the gait cycle. There were no difference in positive joint line cases in maximum compressive stress, however maximum compressive stress of the lateral meniscus becomes greater in - 3 mm cases. This study emphasized the importance of joint line preservation after implantation of UKA. It would be critical to determine the joint line in UKA surgery in future based on the result showing that there has been no remarkable difference in stress but changed rapidly from the position beyond the joint line. In future study, it would be valuable study to compare between joint lines of fixed- and mobile-type UKA.
Cementless arthroplasty has been widely used for younger patients with osteoarthritis and other joint pathology. Cementless arthroplasty will be required to porous surface which is to similar to the trabecular bone for bone ingrowth. Titanium Plasma Spray (TPS) has been worldwide used for the porous coating method on arthroplasty. However, TPS coating is limited that would not to establish optimal porosity for bone ingrowth due to arbitary position of melted powder by plasma gas on substrate. Therefore, it is reported coating detached from its substrate (i.e. arthroplasty) is induced implant loosening. Thus, a novel Laser-aided Direct Metal Tooling (DMT) based on Additive Manufacturing (AM) was developed to overcome these limitations. In this study, we were done to assess stereological analysis, static tensile, shear, abrasion test, and physical analysis for evaluation of the efficacy of DMT which was newly-developed coating technology. Then, mechanical characteristics of DMT coating were compared to commercial TPS coating's. First, porosity of the DMT coating was evaluated using Microphotography and Scanning Electron Microscopy (SEM), as described in Figure 1. Static tensile and shear test for assessment of mechanical characteristic in relation to the DMT and TPS coating specimens were conducted on the basis of ASTM F1147 and F1044 using universal testing machine (Endolab®, Servohydraulic Test Frame, DE). Maximum tensile strength and maximum shear strength were evaluated for each specimen (n=5). Abrasion test was performed based on ASTM F1978 using Taber® Rotary Platform Abraser Model 5135 (TABER®Industries, USA). Abrasion losses for each specimen (n=6) were measured at 2, 5, 10, and 100 cycles, respectively.Introduction
Materials and Methods
Revision total knee arthroplasty (TKA) has been often used with a metal block augmentation for patients with poor bone quality. However, bone defects are frequently detected in revision TKA used with metal block augmentation. This study focused on identification of a potential possibility of the bone defect occurrence through the evaluation of the strain distribution on the cortical bone of the tibia implanted revision TKA with metal block augmentation, during high deep flexion. Composite tibia finite element (FE) model was developed and revision TKA FE model with a metal block augmentation (Baseplate size #5 44AP/67ML, Spacer size #5 44AP/67ML, Stem size Φ9, L30, Augment #5 44AP/67ML thickness 5mm) was integrated with the composite tibia FE model. 0°, 30° 60°, 90°, 120° and 140° flexion positions were then considered with femoral rollback phenomenon [Introduction
Materials and Methods
This prospective study was undertaken to compare the clinical and radiological results and the in vivo stabilities of anteromedial (AM) and posterolateral (PL) bundle augmentation during anterior cruciate ligament (ACL) reconstruction. Forty-two ACL partial tears that underwent isolated bundle augmentation (22 AM and 20 PL bundles) were evaluated with a minimum follow-up of 1 year. For in vivo intraoperative stability testing, anteroposterior and external/internal rotation stabilities were measured at 0, 30, 60, and 90° of flexion using a navigation system. Ranges of motion, Lachman and pivot shift test results, Tegner activity scores, and Lysholm knee scores of the AM and PL bundle groups were compared. In addition, Telos arthrometer determined stabilities were compared. In-vivo intraoperative stability testing showed that mean preoperative anterior translation at 30° of flexion was greater in the AM group (8.7 vs. 6.5, p = 0.04), whereas mean rotational amount was larger in the PL group (by 2.9 at 0° and 3.6 at 30° of flexion). After ACL reconstruction, no significant differences were found between the two groups in terms of anterior and rotational stabilities at any flexion angle. Furthermore, clinical outcomes in the two groups were not significantly different. Lachman and pivot shift test results and instrumented laxity findings were similar for the two groups at final follow up. In this study, the authors carefully preserved the remnant injured ACL, and achieved excellent anterior stability recoveries and good rotatory stabilities. No significant intergroup difference was found in terms of intraoperative stability or clinical parameters after ACL reconstruction.
The purpose of this study were to evaluate early intra-operative experiences of a custom-fit total knee arthroplasty (TKA) system and to determine the precision of long leg alignment and component placement achieved using this system. Seventeen patients underwent sagittal MRI of an arthritic knee to determine component placement for TKA from October 2010 and March 2011. Cutting guides were machined to control all intra-operative cuts, and cutting guide placements were recorded by navigation system. Radiographic parameters regarding mechanical axis changes, and inclinations of the femoral and tibial components were measured. Outcome was defined as “excellent” when values of each parameters were within ± 2°, as “acceptable” when within ± 3°, and as “outliers” when >± 3° of optimum. The cutting guide placement was within ±2° of the target angle for inclinations of femoral and tibial components. The cutting heights were within 2mm for distal femoral and proximal tibia. Mechanical axis changed from a mean of 8.57° varus to 0.49° valgus, and mean coronal inclinations of femoral and tibial components were 89.52° and 90.12°, respectively, at last follow up visits. There were no outliers and all of them were classified as excellent. Mean sagittal inclinations of the femoral and tibial components were 1.06° and 84.56°, respectively. There were no intra-operative or acute post-operative complications. The custom-fit TKA system system provides an effective, safe means of achieving an accurate mechanical axis and of reducing prosthetic alignment outliers. However, further long term follow-up is needed.
The elevation of the joint line is considered a possible cause of mid-flexion instability in total knee arthroplasty (TKA). The authors evaluated the effects of joint line change on mid-flexion stability in cruciate retaining TKA. Seventy-nine knees treated by cruciate retaining TKA using a modified balanced gap technique were included in this prospective study. After prosthesis insertion, valgus and varus stabilities were measured under valgus and varus stress using a navigation system at 0, 30, 60 and 90° of knee flexion. Changes of joint lines were measured preoperatively and postoperatively and compared. The knees were allocated to a “No change group (≤4mm, 62 patients)” or to an “Elevation group (>4mm, 17 patients)”. Medio-lateral stabilities (defined as the sums of valgus and varus stabilities measured intra-operatively) were compared in the two groups. The mean joint line elevation was 4.6mm in the no change group and 1.7mm in the elevation group. Mean medio-lateral stability at 30° of knee flexion was 4.8±2.3 mm in the no change group and 6.3±2.7 mm in the elevation group, and these values were significantly different (p = 0.02). However, no significant differences in medio-lateral stability were observed at other flexion angles (p>0.05). Knees with a < 5mm joint line elevation provide better mid-flexion stability after TKA. The results of this study suggest that a < 5mm elevation in joint line laxity is acceptable for cruciate retaining TKA.
This study was performed to measure intra-operative varus-valgus laxities from 0° to 90° of flexion during cruciate retaining total knee arthroplasty (TKA) using the modified balanced gap technique. Forty nine patients awaiting unilateral TKA for osteoarthritis were enrolled into this prospective study. Flexion and extension gaps were measured at full extension and at 90° of flexion using a tensioning device before femoral bone cutting. After implantation and closing the medial parapatellar arthrotomy, varus-valgus laxities at 0, 30, 60 and 90° of flexion were also measured using a navigation system. Mean total varus-valgus laxities were significantly less at 0° of flexion (3.8±1.7°) than at the other selected flexion angles. Mean varus laxity was peaked at 3.1±2.2° at 60° of flexion and reached a nadir of 2.0±1.0° at 0° of flexion, which represented a significant difference. On increasing flexion from 0° to 60°, mean valgus laxity increased from 1.8±1.3° to 2.9±1.6°, which was significant, but no significant difference was found for other angles. The use of the balanced gap technique for cruciate retaining TKA using a navigation system, which allows accurate soft tissue balancing via real time gap size feedback, could be helpful for achieving good in vivo laxities throughout range of motion without significant mid flexion laxity.
Recently, axial radiography has received attention for the assessment of distal femur rotational alignment, and satisfactory results have been as compared with the CT method. The purpose of this study was to assess rotational alignment of the femoral component in knee flexion by axial radiography and to compare flexion stabilities achieved by navigational and robotic total knee arthroplasty (TKA). In addition, the authors also evaluated the effects of flexion stability on functional outcomes in these two groups. Sixty-four patients that underwent TKA for knee osteoarthritis with a minimum of follow-up of 1 year constituted the study cohort. Patients in the navigational group (N = 32) underwent TKA using the gap balancing technique and patients in the robotic group (N = 32) underwent TKA using the measured resection technique. To assess flexion stability using axial radiography a novel technique designed by the authors was used. Rotations of femoral components and mediolateral gaps in the neutral position on flexion radiographs was measured and compared. Valgus and varus stabilities under valgus-varus stress loading, and total flexion stabilities (defined as the sum of valgus and varus stability) were also compared, as were clinical outcomes at final follow up visits. A significant difference was found between the navigation and robotic groups for mean external rotation of the femoral component (2.1° and 0.4°, respectively; Both navigational and robotic techniques provide excellent clinical and flexion stability results. Furthermore, axial radiography was found to provide a useful, straightforward means of detecting rotational alignment, flexion gaps, and flexion stability.
The purpose of this study was to compare posterior tibial slope preoperatively and postoperatively in patients undergoing navigational opening-wedge High tibial osteotomy (HTO) and to compare posterior slope changes for 2 and 3-dimentional (D) navigation versions. Between May 2009 and September 2010, 35 patients with unicompartmental osteoarthritis and varus deformity were treated by navigation-assisted open-wedge HTO. Patients were randomly divided into two groups according to the version of the Orthopilot (Aesculap) navigation system used; 2D group (18 patients, 2-D version) and 3D group (17 patients, 3-D version). Radiologic evaluations were conducted using pre- and postoperative leg axes. Posterior slope of proximal tibiae were measured using the proximal tibial anatomic axis method. Postoperatively the mechanical axis was corrected adequately to a mean valgus of 2.81° in 2D group and of 3.15° in 3D group. Mean posterior slopes were well maintained, and measured 7.9° and 10.3° preoperatively and 8.99° and 9.14° postoperatively in 2D and 3D groups, respectively. No significant difference was found between the two navigation versions with respect to posterior tibial slope; mean tibial slope changes were 1.09° and −0.2° in 2D and 3D groups ( Navigation-assisted opening-wedge HTO greatly improves the accuracy of the desired postoperative mechanical femorotibial axis and posterior tibial slope, and the use of 3D navigation results in significantly less change in posterior tibial slope. The authors recommend the use of the 3D navigation because they provide real time intraoperative information about coronal, sagittal, and transverse axis, which are important for the maintenance of a normal posterior tibial slope.
The preoperative prediction of gap balance after robotic total knee arthroplasty (TKA) is difficult. The purpose of this study was to evaluate the effectiveness of a new method of achieving balanced flexion-extension gaps during robotic TKA. Fifty one osteoarthritic patients undergoing cruciate retaining TKA using robotic system were included in this prospective study. Preoperative planning was based on the amount of lateral laxity in extension and flexion using varus stress radiograph. After complete milling by the robot and soft tissue balancing, intra-operative extension and flexion gaps were measured using a tensioning device. Knees were subdivided into three groups based on lateral laxities in 0° and 90° of flexion, as follows; the tight extension group (≥ 2mm smaller in extension than flexion laxity), the tight flexion group (≥ 2mm smaller in flexion than extension laxity), and the balanced group (< 2mm difference between laxities). In addition, intra-operative gap balance results were classified as acceptable (0–3mm larger in flexion than in extension), tight (larger in extension than in flexion) or loose (> 3mm larger in flexion than in extension) based on differences between extension and flexion gaps. During preoperative planning, 34 cases were allocated to the balanced group, 16 to the tight extension group and 1 case was allocated to the tight flexion group. Intra-operative gap balance was acceptable in 46 cases, 4 cases had a tight result, and one case had a loose flexion gap. We concluded that preoperative planning based on the amount of lateral laxity determined using varus stress radiographs may be useful for predicting intraoperative gap balance and help to achieve precise gap balance during robotic TKA.
We examined the differences in post-operative
functional disability and patient satisfaction between 56 patients who
underwent a lumbar fusion at three or more levels for degenerative
disease (group I) and 69 patients, matched by age and gender, who
had undergone a one or two level fusion (group II). Their mean age
was 66 years (49 to 84) and the mean follow-up was 43 months (24
to 65). The mean pre-operative Oswestry Disability Index (ODI) and visual
analogue scale (VAS) for back and leg pain, and the mean post-operative
VAS were similar in both groups (p >
0.05), but post-operatively
the improvement in ODI was significantly less in group I (40.6%)
than in group II (49.5%) (p <
0.001). Of the ten ODI items, patients
in group I showed significant problems with lifting, sitting, standing,
and travelling (p <
0.05). The most significant differences in
the post-operative ODI were observed between patients who had undergone
fusion at four or more levels and those who had undergone fusion
at less than four levels (p = 0.005). The proportion of patients
who were satisfied with their operations was similar in groups I
and II (72.7% and 77.0%, respectively) (p = 0.668). The mean number
of fused levels was associated with the post-operative ODI (r =
0.266, p = 0.003), but not with the post-operative VAS or satisfaction
grade (p >
0.05). Post-operative functional disability was more
severe in those with a long-level lumbar fusion, particularly at
four or more levels, but patient satisfaction remained similar for
those with both long- and short-level fusions.
The purpose of this study was to determine the annual incidence of Perthes’ disease in Korea and compare this with other populations. A survey identified all newly diagnosed children with Perthes’ disease aged 14 years or younger in South Honam, Korea, between January 1999 and December 2001. A total of 84 children were included: 29 in 1999, 28 in 2000 and 27 in 2001. The mean annual incidence was 3.8 per 100 000. This is similar to that reported in other Asian countries, but higher than in black populations and lower than in Caucasians.
