Preoperative Virtual Total Knee Arthroplasty Surgery Using a Computed Tomography-based 3-dimensional Model With Variation in Reference Points and Target Alignment to Predict Femoral Component Sizing

Background

The purpose of this study was to investigate the size differences of 19 different femoral component placements from the standard position in total knee arthroplasty using 3-dimensional virtual surgery.

Methods

Three-dimensional bone models were reconstructed from the computed tomography data of 101 varus osteoarthritic knees. The distal femoral bone was cut perpendicular to the femoral mechanical axis (MA) in the coronal plane. Twenty different component placements consisting of 5 cutting directions (perpendicular to MA, 3° and 5° extension relative to MA [3°E-MA and 5°E-MA, respectively], and 3° and 5° flexion relative to MA [3°F-MA and 5°F-MA, respectively]) in the sagittal plane, 2 rotational alignments (clinical epicondylar axis [CEA] and surgical epicondylar axis [SEA]), and 2 rotational types of anterior reference guide (central [CR] and medial [MR]) were simulated.

Results

The mean anteroposterior dimension of femur ranged from 54.3 mm (5°F-MA, SEA, CR) to 62.5 mm (5°E-MA, CEA, MR). The largest and smallest differences of anteroposterior dimension from the standard position (3°F-MA, SEA, and CR) were 7.1 ± 1.3 mm (5°E-MA, CEA, and MR) and −1.2 ± 0.2 mm (5°F-MA, SEA, and CR), respectively. Multiple regression analysis revealed that flexion cutting direction, SEA, and CR were associated with smaller component size.

Conclusions

The femoral component size can be affected easily by not only cutting direction but also the reference guide type and the target alignment. Our findings could provide surgeons with clinically useful information to fine-tune for unintended loose or tight joint gaps by adjusting the component size.

Anatomic Reconstruction of Lateral Ankle Ligaments and Both Peroneus Tendons After Open Fracture Dislocation of the Ankle: A Case Report

Extensive soft tissue defects of the ankle are an uncommon but challenging problem that require a combination of reconstructive options. We report the case of a complex injury involving the skin, lateral ankle ligaments, and peroneal tendons that were anatomically reconstructed. A 15-year-old girl was injured in an automobile accident resulting in extensive soft tissue defects and marked instability of her right ankle. The lower two-thirds of the anterior talofibular ligament (ATFL) had segmental defects, and calcaneofibular ligament (CFL) was completely torn, and both peroneal longus and brevis tendons were severely damaged. Initial debridement was performed on the day on injury. Two weeks after injury, the ATFL and CFL were reconstructed using a semitendinosus autograft and suture tape augmentation. Both peroneal tendons were reconstructed using a gracilis autograft. The skin defect (10 × 10 cm) was covered with an anterolateral thigh flap. After removing a short leg cast at 3 weeks postoperatively, the patient started range of motion exercises without using any brace. Weightbearing was allowed at 4 weeks. At the 24-month follow-up examination, she had returned to her preoperative level of work and sports activities.

[Bone and Joint Diseases in Present and Future]

With the increase of elderly population, orthopaedic surgeons need to deal with the diseases related to aging, such as joint disorders and fragility fractures. The number of total joint replacements, for example, is two times more than it was 10 years ago. With these backgrounds, the Japanese Orthopaedic Association (JOA) has proposed the concept of locomotive syndrome; conditions under which the elderly have been receiving care services due to problems of the locomotive organs. To prevent geriatric or disuse syndrome, JOA is currently providing the care‒prevention programs such as the loco-check and loco-training. Recent advances in the orthopaedic fields were cited in this review article, including the topics of new biomaterials, regenerative medicine of cartilage, spinal cord injury and computer assisted orthopaedic surgery. These new technologies and knowledge are changing or have potential to change the future orthopedic medical care.

Metatarsalgia After Hallux Valgus Correction is Associated with Relative First Metatarsal Length

Category:

Midfoot/Forefoot

Introduction/Purpose:

Metatarsalgia of the lesser metatarsal heads are frequently associated with hallux valgus. The aim of this study was to evaluate how the relative length and the position of the first metatarsal head influences the prognosis of metatarsalgia and plantar callosities beneath the lessor metatarsal heads.

Methods:

A retrospective analysis of the clinical data and radiographs of 102 cases was performed at a mean follow-up period of 16 months after biplane interlocking osteotomies. Clinical evaluation was made using the Japanese Society for Surgery of the Foot (JSSF) hallux scale. Radiological evaluation was made with standard weight-bearing AP radiographs, and the hallux valgus angle (HVA), inter-metatarsal 1-2 angle (IMA), distal metatarsal articular angulation (DMAA), and the sesamoid position were evaluated. Relative first metatarsal length (RML) was determined according to Nilsonne/Morton’s technique.

Results:

The mean preoperative HVA decreased from 37 to 3 degrees, and the mean IMA from 17 to 4 degrees. The mean JSSF- hallux score improved from 56 to 96 points. The mean preoperative area of plantar callosities decreased from 3.1 to 1.5 mm2. Sixty percent of metatarsalgia improved, and 85% of painless callosities disappeared postoperatively. Among radiological parameters, postoperative RML was most significantly associated with JSSF score (P < .0001) and the presence of postoperative metatarsalgia (P < .0001). ROC analysis revealed that the RML cut-off point was -3 mm for avoiding metatarsalgia, with an area under the curve of 0.884, a specificity of 88%, and a sensitivity of 85%.

Conclusion:

Preservation of RML during first metatarsal osteotomy is important to prevent postoperative metatarsalgia.

In vivo kinematics of healthy male knees during squat and golf swing using image-matching techniques

PURPOSE

Participation in specific activities requires complex ranges of knee movements and activity-dependent kinematics. The purpose of this study was to investigate dynamic knee kinematics during squat and golf swing using image-matching techniques.

METHODS

Five healthy males performed squats and golf swings under periodic X-ray images at 10 frames per second. We analyzed the in vivo three-dimensional kinematic parameters of subjects' knees, namely the tibiofemoral flexion angle, anteroposterior (AP) translation, and internal-external rotation, using serial X-ray images and computed tomography-derived, digitally reconstructed radiographs.

RESULTS

During squat from 0° to 140° of flexion, the femur moved about 25 mm posteriorly and rotated 19° externally relative to the tibia. Screw-home movement near extension, bicondylar rollback between 20° and 120° of flexion, and medial pivot motion at further flexion were observed. During golf swing, the leading and trailing knees (the left and right knees respectively in the right-handed golfer) showed approximately five millimeters and four millimeters of AP translation with 18° and 26° of axial rotation, respectively. A central pivot motion from set-up to top of the backswing, lateral pivot motion from top to ball impact, and medial pivot motion from impact to the end of follow-through were observed.

CONCLUSIONS

The medial pivot motion was not always recognized during both activities, but a large range of axial rotation with bilateral condylar AP translations occurs during golf swing. This finding has important implications regarding the amount of acceptable AP translation and axial rotation at low flexion in replaced knees.

LEVEL OF EVIDENCE

IV.

Accuracy of Proximal Tibial Bone Cut Using Anterior Border of Tibia as Bony Landmark in Total Knee Arthroplasty

The purpose of our study was to evaluate the accuracy of the tibial bone cut in total knee arthroplasty using the anterior tibial border as a guide compared to using bony and soft tissue landmarks of the ankle joint. The extramedullary alignment guide was set parallel to a line connecting the proximal and distal one-thirds of the anterior border of the tibia while the rotational direction of the distal end of the guide was adjusted to the anteroposterior axis of the proximal tibia. Significant differences were detected in the ideal coronal tibial component angles with improvements from 87.2% to 95.9%. The anterior tibial border was a reliable landmark in total knee arthroplasty in clinical practice, as shown by our previous computer simulation.

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.

Rotational alignment of the tibial component affects the kinematic rotation of a weight-bearing knee after total knee arthroplasty

PURPOSE

The purpose of this study is to elucidate how the rotational malalignment of prosthesis after total knee arthroplasty affects the rotational kinematics in a weight-bearing condition.

METHODS

In this study of 18 knees replaced with the posterior stabilizing fixed-bearing system, which has a relatively low-restricting design, rotational angles between the femoral and tibial components and between the femur and tibia during stair climbing were evaluated in vivo in three dimensions using radiologically based image-matching techniques. Rotational alignments of the components were assessed by postoperative CT. The correlations between the rotational alignments and the rotational angles during stair climbing were evaluated.

RESULTS

Rotational alignment of the tibial component significantly correlated with rotational angles between the components as well as between bones during stair climbing. Rotational malalignment of the tibial component toward internal rotation caused a rotational mismatch of the tibial component toward internal rotation relative to the femoral component in 0° extension and caused a rotational mismatch of the tibia (bone) toward external rotation relative to the femur (bone). The knee in which the tibial component was placed close to the AP axis of the tibia did not show any rotational mismatch between either components or bones.

CONCLUSIONS

Rotational alignment of the tibial component affects the kinematic rotation of the replaced knee during a weight-bearing condition even though using a low-restricting designed surface, and the AP axis can be a reliable reference in determining rotational alignment for the tibial component.

Patient-specific computer model of dynamic squatting after total knee arthroplasty

Knee forces are highly relevant to performance after total knee arthroplasty especially during high flexion activities such as squatting. We constructed subject-specific models of two patients implanted with instrumented knee prostheses that measured knee forces in vivo. In vivo peak forces ranged from 2.2 to 2.3 times bodyweight but peaked at different flexion angles based on the type of squatting activity. Our model predicted tibiofemoral contact force with reasonable accuracy in both subjects. This model can be a very useful tool to predict the effect of surgical techniques and component alignment on contact forces. In addition, this model could be used for implant design development, to enhance knee function, to predict forces generated during other activities, and for predicting clinical outcomes.

Influence of the posterior tibial slope on the flexion gap in total knee arthroplasty

BACKGROUND

Adjusting the joint gap length to be equal in both extension and flexion is an important issue in total knee arthroplasty (TKA). It is generally acknowledged that posterior tibial slope affects the flexion gap; however, the extent to which changes in the tibial slope angle directly affect the flexion gap remains unclear. This study aimed to clarify the influence of tibial slope changes on the flexion gap in cruciate-retaining (CR) or posterior-stabilizing (PS) TKA.

METHODS

The flexion gap was measured using a tensor device with the femoral trial component in 20 cases each of CR- and PS-TKA. A wedge plate with a 5° inclination was placed on the tibial cut surface by switching its front-back direction to increase or decrease the tibial slope by 5°. The flexion gap after changing the tibial slope was compared to that of the neutral slope measured with a flat plate that had the same thickness as that of the wedge plate center.

RESULTS

When the tibial slope decreased or increased by 5°, the flexion gap decreased or increased by 1.9 ± 0.6mm or 1.8 ± 0.4mm, respectively, with CR-TKA and 1.2 ± 0.4mm or 1.1 ± 0.3mm, respectively, with PS-TKA.

CONCLUSIONS

The influence of changing the tibial slope by 5° on the flexion gap was approximately 2mm with CR-TKA and 1mm with PS-TKA.

CLINICAL RELEVANCE

This information is useful when considering the effect of manipulating the tibial slope on the flexion gap when performing CR- or PS-TKA.

Changes in patellar alignment after total knee arthroplasty

Although the results of total knee arthroplasty continue to improve, problems related to the patellofemoral joint remain significant. This study examined the factors affecting patellar alignment after total knee arthroplasty and subsequent changes in 56 knees during a postoperative period of 5.3 years. None of the knees examined displayed any clinical complications of the patellofemoral joint; no revision surgeries were necessary, with acceptable patellar alignment on average. The patellar resection angle had a strong influence on patellar alignment. Thinning of the patellar remnant on the medial side can increase postoperative lateral tilt, which leads to a need for lateral retinacular release. Although the changes in patellar alignment were minimal, the tendency that postoperative varus alignment resulted in patellar lateral tilt was observed. As postoperative femorotibial misalignment can lead to patellofemoral problems after total knee arthroplasty, surgeons need to pay scrupulous attention to femorotibial alignment and proper patellar preparation to decrease patellofemoral complications.

The evaluation of post-operative alignment in total knee replacement using a CT-based navigation system

We compared the alignment of 39 total knee replacements implanted using the conventional alignment guide system with 37 implanted using a CT-based navigation system, performed by a single surgeon. The knees were evaluated using full-length weight-bearing anteroposterior radiographs, lateral radiographs and CT scans. The mean hip-knee-ankle angle, coronal femoral component angle and coronal tibial component angle were 181.8 degrees (174.2 degrees to 188.3 degrees), 88.5 degrees (84.0 degrees to 91.8 degrees) and 89.7 degrees (86.3 degrees to 95.1 degrees), respectively for the conventional group and 180.8 degrees (178.2 degrees to 185.1 degrees), 89.3 degrees (85.8 degrees to 92.0 degrees) and 89.9 degrees (88.0 degrees to 93.0 degrees), respectively for the navigated group. The mean sagittal femoral component angle was 85.5 degrees (80.6 degrees to 92.8 degrees) for the conventional group and 89.6 degrees (85.5 degrees to 94.0 degrees) for the navigated group. The mean rotational femoral and tibial component angles were -0.7 degrees (-8.8 degrees to 9.8 degrees) and -3.3 degrees (-16.8 degrees to 5.8 degrees) for the conventional group and -0.6 degrees (-3.5 degrees to 3.0 degrees) and 0.3 degrees (-5.3 degrees to 7.7 degrees) for the navigated group. The ideal angles of all alignments in the navigated group were obtained at significantly higher rates than in the conventional group. Our results demonstrated significant improvements in component positioning with a CT-based navigation system, especially with respect to rotational alignment.

Computed tomography-based navigation to determine the socket location in total hip arthroplasty of an osteoarthritis hip with a large leg length discrepancy due to severe acetabular dysplasia

For osteoarthritis hips due to severe acetabular dysplasia such as Crowe type 3 or 4, placement of the socket is a difficult procedure in total hip arthroplasty. Because the acetabular bone stock is poor, suitable location for the socket is very limited with respect to achieving good coverage with the host bone. A 51-year-old woman who had an osteoarthritis hip with a large leg length discrepancy due to severe acetabular dysplasia required total hip arthroplasty. The purpose of the total hip arthroplasty was to improve the hip disorder as well as to reduce the leg length discrepancy to achieve good gait function. We present technical solutions to aid the surgeons in placing the acetabular socket at the proper location by using computed tomography-based navigation system.

The effect of ankle rotation on cutting of the tibia in total knee arthroplasty

BACKGROUND

Extramedullary alignment guides are commonly used to prepare the tibia during total knee arthroplasty. One disadvantage is that the guide is easily affected by the position of the ankle joint. The tibia may have a rotational mismatch between its proximal and distal ends. We hypothesized that a rotational mismatch might cause incorrect positioning of an extramedullary alignment guide and evaluated such a mismatch on the predicted postoperative coronal alignment of the tibia.

METHODS

Fifty-three osteoarthritic knees with varus deformity in fifty-one patients were evaluated with use of computerized tomography scans before total knee arthroplasty. We defined one anteroposterior axis of the ankle joint and five different anteroposterior axes of the proximal aspect of the tibia using three-dimensional bone models from the computerized tomography data. We measured the rotational angle between the anteroposterior axis of the ankle joint and the proximal part of the tibia. The distal end of the extramedullary guide was placed in front of the center of the ankle joint (on the line of the extended anteroposterior axis of the ankle joint), and the proximal end was placed on the line of the extended anteroposterior axis of the proximal part of the tibia. We established spatial coordinates to evaluate the effect of the rotational angle on the predicted postoperative coronal alignment of the tibia and calculated the presumed tibial coronal alignment.

RESULTS

The rotational angle was positive (3.6 degrees to 19.7 degrees) for all of the anteroposterior axes of the proximal aspect of the tibia, indicating that the ankle joint was externally rotated relative to the proximal part of the tibia. The predicted tibial coronal alignment was varus (0.5 degrees to 5.1 degrees) for all of the anteroposterior axes of the proximal part of the tibia.

CONCLUSIONS

When an extramedullary alignment guide is used to prepare the tibia in total knee arthroplasty, varus alignment of the tibial component can occur because of a rotational mismatch between the proximal part of the tibia and the ankle joint.

Tibial shaft axis does not always serve as a correct coronal landmark in total knee arthroplasty for varus knees

Predicted postoperative knee alignment was calculated when total knee arthroplasty was performed after 1 of 3 different methods of tibia preparation in 30 osteoarthritic knees with varus deformity. In Method 1, the tibia was cut perpendicular to the tibial shaft. In Method 2, the tibia was cut perpendicular to a line connecting the center of the tibial plateau and the center of the talar dome. In method 3, tibial resection was determined with an original template so that tibial resection would be perpendicular to a line connecting the center of the resected tibial plateau and the center of the talar dome. Methods 1 and 2 caused significantly more valgus alignment than Method 3 (P<.0001). The postoperative weight-bearing ratio was in Method 1, 57.7%, in Method 2, 53.6% and 50.0% in Method 3. These results suggest that cutting the tibia perpendicular to the tibial shaft can cause valgus alignment in total knee arthroplasty for varus knees.