Robot assisted surgery is becoming a widely popular technology and is now entering the total knee replacement. The development of total knee replacement and the operation system structure are introduced in this paper. The vision position technology and the related calibration technology, which are very important, are also analyzed. The experiments of error analysis in our WATO system demonstrate that the position and related calibration technologies have a high precision and can satisfy surgical requirement.
Arthroplasty, Replacement, Knee ; instrumentation ; methods ; Humans ; Pattern Recognition, Automated ; methods ; Robotics ; instrumentation ; Surgery, Computer-Assisted ; instrumentation ; methods

Finding the position of caput femoris center by exact and fast method is a key technique in total knee replacement navigation surgery. A method for finding the position of caput femoris center is described in this paper. The main idea is abstracting this problem to a geometrical model in which the center of a sphere can be easily worked out with a few known spherical points. Experiments show that the method is feasible and the precision satisfies the requirements of navigation surgery.
Algorithms ; Arthroplasty, Replacement, Knee ; instrumentation ; methods ; Biomechanical Phenomena ; Computer Simulation ; Humans ; Models, Biological ; Surgery, Computer-Assisted ; instrumentation ; methods

Artificial knee joint simulation test is an important form in the research and evaluation of prosthetic material and design. Natural knee joint could not be tested by conventional instruments because of complex motion and load in movement. Simulation test designed for artificial knee is needed. At present, two kinds of simulation, namely simplification method and complete simulation, are widely used. Complete simulation can be used for simultaneous evaluation of material and design of prosthesis, whereas simplification method is only useful in evaluating the material of prosthesis. In international standards, there are already two protocols for artificial knee joint experiment, namely load control and displacement control. This paper also reviews the evaluation criteria and measurement standards for artificial knee joint simulation test, and then envisages the researches in future.
Arthroplasty, Replacement, Knee ; instrumentation ; Computer Simulation ; Computer-Aided Design ; Equipment Failure Analysis ; methods ; Humans ; Knee Prosthesis ; Prosthesis Design ; methods

OBJECTIVETo compare clinical efficacy of individual osteotomy instrument and total knee arthrolplasty (TKA) in treating patients with knee osteoarthritis.

METHODSFrom June 2014 to December 2014, 40 patients with unilateral knee osteoarthritis were randomly divided into two groups and 20 cases were in each group. One group (individual group) were treated with TKA with individual osteotomy instrument,including 5 males and 15 females with an average age of (67.3 ± 6.5) years old; 8 cases on the left side and 12 cases on the right side. Another group (conventional group) were treated with conventional TKA , including 6 males and 14 females with an average age of (66.8 ± 7.3) years old; 9 cases on the left side and 11 cases on the right side. Operative time, blood loss, postoperative HSS score at 6 months, and changes of mechanical alignment before and after operation were analyzed.

RESULTSOperative time in individual group was (79.3 ± 4.7) min, and (83.5 ± 3.2) min in conventional group; blood loss in individual group was (287.1 ± 24.9) ml and (363.4 ± 47.2) ml in conventional group, there were statistical differences between two groups in these two items. There was no significant difference in postoperative HSS score at 6 months between individual group (84.8 ± 3.2) and conventional group (84.2 ± 2.5). Postoperative limb alignment in individual group was (2.8 ± 0.6)°, and (2.8 ± 0.6)° in conventional group, with no significant difference between two groups.

CONCLUSIONTKA with individual osteotomy instrument could reduce operative time and blood loss, but there was no differences in knee function, changes of mechanical alignment compared with TKA.

Adult ; Aged ; Arthroplasty, Replacement, Knee ; methods ; Case-Control Studies ; Female ; Humans ; Knee Joint ; surgery ; Male ; Operative Time ; Osteoarthritis, Knee ; surgery ; Osteotomy ; instrumentation ; methods ; Treatment Outcome

OBJECTIVETo summarize experience of using screws and cement to rebuild tibial bone defect in primary total knee arthroplasty (TKA) and to discuss the relationship between the number of required screws and the severity of tibial bone defects.

METHODSFrom July 2009 to May 2015, 34 patients (40 knees) with varus knees underwent TKA, and the screw and cement technique was used to rebuild medial tibia plateau during operation. There were 8 males (8 knees) and 26 females (32 knees), and the average age was (65.00 +/- 7.25) years old (ranged,55 to 82 years old). One to 6 screws were used in each case. Extension stems were used in 2 cases (4 and 5 screws was used respectively). The area percentages of the bone defects measured as defect area/tibia plateau area, depth of each defect, the number of screws needed in each case, were all used to determine the relationship between the number of screws and the area percentage in certain depth of bone defect by statistic methods, as well as the relationship between screw number and defect depth.

RESULTSAll the patients were followed up and the average duration was 24 months (ranged, 1 to 72 months). The average preoperative HSS score was 43.33 +/- 6.11 (ranged, 32 to 51 scores). Whereas the average postoperative HSS score was 92.15 +/- 4.64 (ranged,83 to 96 scores). The preoperative individual scores including pain, function, activity, nuscle strength, flexion deformity and stability were all improved compared with preoperation,and the differences were statistically significant. All the patients received normal alignment postoperatively, femoraltibial angle was improved from (167.00 +/- 6.39) degrees preoperatively to (175.00 +/- 2.69) degrees postoperatively, the tibial angle was improved from (78.09 +/- 4.51) degrees preoperatively to (88.75 +/- 1.24) degrees postoperatively. Both area percentage and depth of bone defect in a fitting Ologistic model had a significant statistical relationship with the screw number, and a rectangular coordinate system could be formed according to the relationship.

CONCLUSIONScrews and cement technique is a simple, safe and convenient method to rebuild tibial bone defects in primary TKA and its short-term and midterm effect are both reliable. During opera- tion, according to the rectangular coordinate system, the screw number needed in the operation can be inferred form th area and depth of tibia defect, which could have a guiding function in surgery.

Aged ; Aged, 80 and over ; Arthroplasty, Replacement, Knee ; instrumentation ; methods ; Bone Screws ; utilization ; Female ; Fracture Fixation, Internal ; Humans ; Knee Injuries ; surgery ; Knee Joint ; surgery ; Male ; Middle Aged ; Tibia ; surgery

BACKGROUND: Despite the importance of soft tissue balancing during total knee arthroplasty (TKA), all estimating techniques are dependent on a surgeon's manual distraction force or subjective feeling based on experience. We developed a new device for dynamic gap balancing, which can offer constant load to the gap between the femur and tibia, using pneumatic pressure during range of motion. METHODS: To determine the amount of distraction force for the new device, 3 experienced surgeons' manual distraction force was measured using a conventional spreader. A new device called the consistent load pneumatic tensor was developed on the basis of the biomechanical tests. Reliability testing for the new device was performed using 5 cadaveric knees by the same surgeons. Intraclass correlation coefficients (ICCs) were calculated. RESULTS: The distraction force applied to the new pneumatic tensioning device was determined to be 150 N. The interobserver reliability was very good for the newly tested spreader device with ICCs between 0.828 and 0.881. CONCLUSIONS: The new pneumatic tensioning device can enable us to properly evaluate the soft tissue balance throughout the range of motion during TKA with acceptable reproducibility.
Arthroplasty, Replacement, Knee/*instrumentation/methods ; Biomechanics ; Equipment Design ; Femur/surgery ; Humans ; Knee Joint/physiology/*surgery ; Mechanical Processes ; Range of Motion, Articular ; Reproducibility of Results ; Tibia/surgery

Determination of femoral anatomic axis plays an important role in robot-assisted surgery of total knee replacement. In traditional total knee replacement surgery, the axis is obtained by inserting a rod into femoral lumen. However, in the robot-assisted total knee replacement based on CT model. the femoral anatomic axis must be determined preoperatively. Because the lengths in femurs are quite different in different patients, besides noises, the upper segment and lower segment of the femur influence the design of the axis greatly. Traditionally, the femoral anatomic axis is obtained by using the least-squares method directly. However, this method is easily disturbed by noise. To avoid the noise disturbance of CT data, the least median of squares method is used to fit the femoral anatomic axis for its characteristic of robust regression. The least median squares method eliminates the disadvantage brought by the method of least squares. In finding the best-fit line, genetic algorithms are used in the paper. In our experiment, we use the proposed method to fit the femoral anatomic axis and obtain an excellent result.
Algorithms ; Arthroplasty, Replacement, Knee ; methods ; Femur ; anatomy & histology ; diagnostic imaging ; surgery ; Humans ; Robotics ; Surgery, Computer-Assisted ; instrumentation ; methods ; Tomography, X-Ray Computed

BACKGROUND: The single radius total knee prosthesis was introduced with the advantage of reduced patellar symptoms; however, there is no long-term follow-up study of the same. The purpose of this study was to determine the survival rate of single radius posterior-stabilized total knee arthroplasty and patellofemoral complication rates in a consecutive series. METHODS: Seventy-one patients (103 knees) who underwent arthroplasty without patellar resurfacing using a single radius posterior-stabilized total knee prosthesis were followed up for a minimum 10 years. Clinical evaluation using Knee Society knee and function scores and radiologic evaluation were performed at regular intervals. Anterior knee pain as well as patellofemoral complications were evaluated with a simple questionnaire. The Kaplan-Meier product-limit method was used to estimate survival. RESULTS: Seventeen patients (23 knees) were excluded due to death (12 knees) or lost to follow-up (11 knees). Of the 80 knees enrolled, all femoral components and 78 tibial components were well fixed without loosening at final follow-up. Two revisions were performed because of tibial component loosening and periprosthetic joint infection. One patient with tibial component loosening refused to have revision surgery. No obvious tibial insert polyethylene wear was observed. The survivorships at 132 months were 96.7% using revision or pending revision as end points. Anterior knee pain was present in 6 patients (6 knees, 7.5%) at the latest follow-up. No patellofemoral complication requiring revision was encountered. CONCLUSIONS: The single radius posterior-stabilized total knee prosthesis demonstrated an excellent minimum 10-year survivorship. The low rates of implant loosening and 7.5% of anterior knee pain as a patellofemoral complication are comparable with those reported for other modern total knee prosthesis.
Aged ; Arthralgia/*surgery ; Arthroplasty, Replacement, Knee/*instrumentation/*methods ; Cementation ; Female ; Follow-Up Studies ; Humans ; Knee Joint/*surgery ; Knee Prosthesis ; Male ; Middle Aged ; Patella/surgery ; Prosthesis Failure ; Retrospective Studies ; Treatment Outcome

BACKGROUND: The purpose of this study was to determine the degree of infection control and postoperative function for new articulating metal-on-cement spacer. METHODS: A retrospective study of 19 patients (20 cases), who underwent a two-stage revision arthroplasty using mobile cement prosthesis, were followed for a minimum of 2 years. This series consisted of 16 women and 3 men, having an overall mean age of 71 years. During the first stage of revision, the femoral implant and all the adherent cement was removed, after which it was autoclaved before replacement. The tibial component was removed and a doughy state, antibiotic-impregnated cement was inserted on the tibial side. To achieve joint congruency, intraoperative molding was performed by flexing and extending the knee joint. Each patient was evaluated clinically and radiologically. The clinical assessments included range of motion, and the patients were scored as per the Hospital for Special Surgery (HSS) and Knee Society (KS) criteria. RESULTS: The mean range of knee joint motion was 70degrees prior to the first stage operation and 72degrees prior to the second stage revision arthroplasty; following revision arthroplasty, it was 113degrees at the final follow-up. The mean HSS score and KS knee and function scores were 86, 82, and 54, respectively, at the final follow-up. The success rate in terms of infection eradication was 95% (19/20 knees). No patient experienced soft tissue contracture requiring a quadriceps snip. CONCLUSIONS: This novel technique provides excellent radiological and clinical outcomes. It offers a high surface area of antibiotic-impregnated cement, a good range of motion between first and second stage revision surgery for the treatment of chronic infection after total knee arthroplasty, and is of a reasonable cost.
Aged ; Anti-Bacterial Agents/*administration & dosage/*therapeutic use ; Arthroplasty, Replacement, Knee/*adverse effects/*instrumentation/methods ; Bone Cements/*therapeutic use ; Female ; Humans ; Male ; Middle Aged ; Prosthesis-Related Infections/*surgery ; Range of Motion, Articular/physiology ; Reoperation/*instrumentation/methods ; Retrospective Studies ; Treatment Outcome

BACKGROUND: A two-stage revision remains as the "gold standard" treatment for chronically infected total knee arthroplasties. METHODS: Forty-five septic knee prostheses were revised with a minimum follow-up of 5 years. Static antibiotic-impregnated cement spacers were used in all cases. Intravenous antibiotics according to sensitivity test of the culture were applied during patients' hospital stay. Oral antibiotics were given for another 5 weeks. Second-stage surgery was undertaken after control of infection with normal erythrocyte sedimentation rate and C-reactive protein values. Extensile techniques were used if needed and metallic augments were employed for bone loss in 32 femoral and 29 tibial revisions. RESULTS: The average interval between the first-stage resection and reimplantation was 4.4 months. Significant improvement was obtained with respect to visual analog scale pain and clinical and functional scores, and infection was eradicated in 95.6% of cases following a two-stage revision total knee arthroplasty. Radiographic evaluation showed suitable alignment without signs of mechanical loosening. CONCLUSIONS: This technique is a reasonable procedure to eradicate chronic infection in knee arthroplasty and provides proper functional and clinical results. However, it sometimes requires extensile surgical approaches that could imply arduous surgeries. Metallic augments with cementless stems available in most of the knee revision systems are a suitable alternative to handle bone deficiencies, avoiding the use of bone allografts with its complications.
Aged ; Aged, 80 and over ; Anti-Bacterial Agents/*administration & dosage ; Arthroplasty, Replacement, Knee/*adverse effects ; Female ; Humans ; Knee Joint/physiology/radiography/surgery ; *Knee Prosthesis ; Male ; Middle Aged ; Prosthesis Design ; Prosthesis-Related Infections/*therapy ; Range of Motion, Articular ; Replantation/adverse effects/instrumentation/*methods ; Retrospective Studies ; Treatment Outcome