To evaluate the rate of dislocation following dual mobility total hip arthroplasty (DM-THA) in patients with displaced femoral neck fractures, and to compare rates of dislocation, surgical-site infection, reoperation, and one-year mortality between DM-THA and bipolar hemiarthroplasty (BHA). Studies were selected based on the following criteria: 1) study design (retrospective cohort studies, prospective cohort studies, retrospective comparative studies, prospective comparative studies, and randomized controlled studies (RCTs)); 2) study population (patients with femoral neck fracture); 3) intervention (DM-THA or BHA); and 4) outcomes (complications during postoperative follow-up and clinical results). Pooled meta-analysis was carried out to evaluate the dislocation rate after DM-THA and to compare outcomes between DM-THA and BHA.Aims
Methods
As life expectancy increases, the number of octogenarians requiring primary and revision total knee arthroplasty (TKA) is increasing. Recently, primary TKA has become a common treatment option in octogenarians. However, surgeons are still hesitant about performing revision TKA on octogenarians because of concerning about risk- and cost-benefit. The purpose of this study was to investigate postoperative complications and mid-term survival in octogenarians following primary and revision total knee arthroplasty (TKA). We retrospectively reviewed 231 primary TKAs and 41 revision TKAs performed on octogenarians between 2000 and 2016. The mean age was 81.9 for primary TKA and 82.3 for revision TKA (p=0.310). The American Society of Anesthesiologists (ASA) score was not different, but the age-adjusted Charlson comorbidity index was higher in revision TKA (4.4 vs. 4.8, p=0.003). The mean follow-up period did not differ (3.8 vs. 3.5 years, p=0.451). The WOMAC scores and range of motion (ROM) were evaluated. The incidence of postoperative complication and survival rate (end point; death determined by telephone or mail communication with patient or family) were investigated.Background
Methods
The purpose of the present study was to evaluate the intercompartmental loads with a sensor placed on implants after conventional gap balancing during total knee arthroplasty (TKA) with a tensiometer. Fifty sensor-assisted TKA procedures were performed prospectively between August and September 2018 with a cruciate-retaining prosthesis. After applying a modified measured technique, conventional balancing between the resected surfaces was achieved. The equal and rectangular flexion–extension gaps were confirmed using a tensiometer. Then, the load distribution was evaluated with a sensor.Purpose
Methods
Long-term clinical and radiographic results and survival rates were compared between closed-wedge high tibial osteotomy (HTOs) and fixed-bearing unicompartmental knee arthroplasty (UKA) in patients with similar demographics. Sixty HTOs and 50 UKAs completed between 1992 and 1998 were retrospectively reviewed. There were no significant differences in preoperative demographics. The mean follow-up period was 10.7 ±5.7 years for HTO and 12.0 ±7.1 years for UKA (n.s.). The Knee Society knee and function scores, WOMAC, and range of motion (ROM) were investigated. The mechanical axis and femorotibial angle were evaluated. Kaplan–Meier survival analysis was performed (failure: revision to TKA), and the failure modes were investigated.Purpose
Methods
The purpose of this study was to compare intercompartmental loads and the proportion of knees with unbalanced loads after tensiometer-assisted balancing (TAB) between cruciate retaining (CR) and posterior stabilized (PS) total knee arthroplasty (TKA). Forty-five CR and 45 PS TKAs using a single prosthesis were prospectively evaluated. The intercompartmental loads in 10°, 45°, and 90° of knee flexion after TAB were evaluated; the proportions of load imbalance (medial load – lateral load >15 lbs) in each flexion angle after TAB were investigated. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of TAB were calculated, with the sensor-balanced loads considered the reference standard.Purpose
Materials and Methods
The purpose of the present study was to compare the clinical and radiographic results after TKA using a patellofemoral design modified prosthesis and its predecessor. The other purpose was to investigate whether the use of the recent prosthesis increase the risk of posterior tibial cortex injury or patellar fracture. The clinical and radiographic results of 300 knees which underwent TKA using the Attune®prosthesis (group A) were compared with those in a paired match-control group who underwent TKA using the P.F.C. Sigma® prosthesis (group B). The preoperative demographic data between the 2 groups did not differ significantly. The WOMAC, Feller and Kujala scores, and range of motion (ROM) were compared. The minimal distance between the tibial component stem to posterior tibial cortex, and the remnant patella thickness were compared.Objective
Materials and Methods
Although total knee arthroplasty (TKA) in end-stage hemophilic arthropathy can reduce the severe joint pain and improve the functional disability, it is technically demanding. In addition, it has generally reported a high rate of complication including periprosthetic joint infection (PJI) and component loosening up to 20%. Although the Knee Society classification system of TKA complication was introduced, the complications of TKA in hemophilic arthropathy has not stratified using this classification system in previous articles to the best of our knowledge. The purpose of this study was to evaluate the mid-term outcomes and complications of TKA in hemophilic arthropathy. The study retrospectively reviewed 131 consecutive primary TKAs (102 patients) in single institute. The mean patient age was 41.0 years and mean follow-up time was 6.4 years. The clinical and radiographic results were evaluated. The complications were categorized according to the classification system of the Knee Society for TKA complications.Introduction
Methods
The knowledge about the common mode of failure and each period in primary and revision TKAs offers useful information to prevent those kinds of failure in each surgery. However, there has been limited report that simultaneously compared the mode of failure between primary and revision TKAs using single prosthesis. We compared the survival rate, mode of failure, and periods of each mode of failure between primary and revision TKAs. A consecutive cohort of 1606 knees (1174 patients) of primary TKA and 258 knees (224 patients) of revision TKA using P.F.C® prosthesis was retrospectively reviewed. The mean follow-up periods of primary and revision TKAs were 10.2 and 10.8 years, respectively. We compared the above variables between primary and revision TKAs.Background
Methods
The fourth generation ceramic, in which zirconia is incorporated into the alumina matrix, was developed to reduce the risk of ceramic fractures. The purpose of this study was to evaluate the survivorship, clinical and radiographic results, and bearing-related failures associated with total hip arthroplasty using zirconia-toughened alumina ceramic-on-ceramic bearings over a minimum follow-up of 5 years. We retrospectively analysed 135 patients (151 hips) who underwent cementless total hip arthroplasty using zirconia-toughened alumina ceramic-on-ceramic bearings. There were 58 men and 77 women with mean age of 55.9 years (range, 20 to 82 years) at index surgery. Acetabular and femoral components were cementless in all hips. A 36 mm head was used in 81 of 151 hips and a 32 mm head was used in 70 hips with smaller acetabular shells. The mean duration of follow-up was 6.1 years (range, 5 to 6.8 years).Purpose
Materials and methods
The use of tranexamic acid (TXA) in primary total hip arthroplasty (THA) is supported by many studies that confirm its efficacy for decreasing blood loss, but the comparison between topical intra-articular (IA) and intra-venous (IV) is unclear, especially combined with chemical prophylaxis. The purpose of this study is to verify non-inferior efficacy of topical IA TXA compared with IV TXA in primary THA. A single center, randomized, controlled clinical trial was performed to compare topical IA TXA (2 g of TXA in 100 cc of normal saline) with two IV doses of TXA (1 g dose before surgery and another 1 g dose 3 hours later) on blood loss. The primary outcome was total blood loss as calculated from the difference between the preoperative hemoglobin (Hb) and the lowest postoperative Hb. The secondary outcome included drained blood loss, transfusion volume, and thromboembolic events. The sample size of 112 patients was calculated to give a statistical power of 99% for demonstrating inferiority. Fifty-six patients each was assigned to receive topical IA TXA (IA group) and IV TXA (IV group). There were no significant differences in demographics and preoperative laboratory values between the two groups. Non-inferiority was estimated by comparing the confidence interval with a delta of 10%. All subjects took oral direct factor Xa inhibitor to prevent venous thromboembolism included during 2 weeks after surgery.Introduction
Methods & Methods
Wear and osteolysis are major contributors which limit the durability of total hip arthroplasty (THA) and ultimately cause it to fail. Efforts were made to decrease the wear by highly cross-linked polyethylene (HXLPE) and using ceramic bearings. The purpose of this study is to analyze the five year performance of large sized (32mm and 36mm) ceramic and metal heads on X3 HXLPE (Stryker, Mahwah, NJ). From Jan 2006 to June 2008, 81 consecutive patients with minimum 5 year radiographic and clinical followup were identified from out institutional prospective database. 51 non-cemented THA (45 patients) had ceramic on HXLPE (CoX3) group and 30 hips (29 patients) had metal on HXLPE (MoX3) group. Mean age was 36 ± 8 years (36–76) and 50 ± 9 years (51–86) in ceramic and metal group, respectively. Wear rates were measured on an anteroposterior weight-bearing pelvis radiographs using the computer-assisted Roman software.Introduction
Materials and Method
Potential implant and technique related factors to improve patellofemoral (PF) kinematics in total knee arthroplasty (TKA) are design of trochlear geometry and patella, restoration of posterior offset, patellar tilt and avoid overstuffing. The primary aim of this prospective, matched pair study was to assess the radiographic features of PF kinematics with an anatomic patella. Between July 2012 and May 2013, 49 consecutive posterior stabilized cemented Attune TKAs (Depuy Synthes Warsaw Indiana) were matched to the 49 PFC Sigma (Depuy) based on age, gender, and body mass index (BMI). All surgeries were performed via medial parapatellar approach with patellar resurfacing. Radiographic analysis was performed prospectively with minimum 1-year follow-up and included overall limb alignment, anterior offset, posterior offset, joint line, patellar thickness, patellar tilt and patellar displacement by two independent observers.Introduction
Material and Methods
Total hip arthroplasty (THR) with non-cemented or hybrid fixation remains one of the most successful procedures performed today. The aim of this study was to assess the safety and efficacy of a hydroxyapatite (HA) coated, hemispherical cup. Between 2003 and 2007, 223 THAs (210 patients) with peripheral self-locking (PSL) cup and highly cross-linked polyethylene (Crossfire, Stryker, Mahwah, NJ) with minimum 5 years clinical and radiographic follow-up (5–9 years) were analyzed. The mean age was 62.5 years ± 10.8 (range, 32.7 – 86.3) at the time of surgery and the predominant preoperative diagnoses was osteoarthritis (97.8%). 72% were solid cups without screw augmentation and 28% were multi-hole with screw. Clinical analysis included Hospital for Special Surgery (HSS) hip scores at latest follow-up. Detail radiographic analysis was carried out on anteroposterior and false profile views for evidence of osseointegration in all Charnley's zones. Osseointegration was assessed based on presence of Stress Induced Reactive Cancellous Bone (SIRCaB) with trabecular bone hypertrophy 5–15mm extending from the cup, and absence of radiolucency or demarcation. EBRA software was used to assess cup positioning.Introduction
Material and Methods
Highly cross-linked polyethylene (HCLPE) was introduced to reduce wear and osteolysis in total hip arthroplasty (THA). There is no reported data regarding wear rates and clinical performance of Crossfire HCLPE (Stryker, Mahwah, New Jersey) in young and active patients. The purpose of this prospective study is to assess minimum 10-year wear rates and survivorship of Crossfire in young and active patients. Between January 2001 to December 2003, 52 consecutive THAs (43 patients; 26 males and 17 females), 55 years and younger, with an average University of California Los Angeles activity (UCLA) score of 7.3 ± 1.5 (5 – 10) at the time of surgery were prospectively followed. The mean age of patients was 47.4 ± 7.8 years old (range 24 to 55 years). Indication for surgery included osteoarthritis in all cases. All operations were performed by the senior surgeon via a posterolateral approach. All components were non-cemented SecurFit femoral stem, 28 mm Cobalt-Chromium (Co-Cr) femoral head, and Trident PSL cup with Crossfire HCLPE acetabular liner (Stryker, Mahwah, New Jersey). At minimum 10-years follow-up (mean 11.5 ± 0.94 years), wear rates were assessed using the Roman software. Hospital for Special Surgery (HSS) scores and survivorship data were analyzed.Background
Material and Methods
Unicompartmental knee arthroplasty (UKA) is a well established method for treatment of single compartment arthritis. However, a subset of patients still present with continued pain after their procedure in the setting of a normal radiographic examination. We propose the use of magnetic resonance imaging (MRI) as a useful modality in determining the etiology of symptoms in symptomatic unicompartmental knee arthroplasties. An IRB-approved retrospective analysis of 300 consecutive unicompartmental knee arthroplasties between 2008–2010 found 28 cases symptomatic for continued pain. Magnetic resonance imaging was performed with a 1.5 T Surface Coil unit after clinical and radiographic assessment. MRI evaluation included assessment for osteoarthritis, synovitis, osteolysis, and loosening. Validated questionnaires including PAQ, WOMAC and UCLA Activity Score were used for clinical assessmentIntroduction:
Materials & Methods:
We undertook this study to compare the flexion stabilities, the clinical outcomes, and complications in cases of TKA using either the robotic technique (ROB-TKA) or navigation-assisted technique (NA-TKA). Robot group (53 knees) and navigation group (56 knees) that underwent TKA for osteoarthritis were assessed for varus and valgus laxity at 90° of knee flexion after a minimum three-year follow-up. These evaluations included KS, WOMAC scores, and ROM. To evaluate flexion stability, varus and valgus laxities at 90° of knee flexion were measured using stress radiographs. KS and WOMAC scores were significantly improved at last follow-up. However, no significant difference was found between the ROB-TKA and NA-TKA groups for any clinical outcome parameter. No significant intergroup differences were found in mechanical axis or coronal alignments and the mean varus laxities. No significant difference was found for varus-valgus imbalance at 90° of knee flexion. Complications differed in the two groups but none of the cases were severe enough to warrant a revision. Both robotic and navigation assisted TKAs were found to restore good coronal leg and prosthesis alignments and good flexion stabilities. However, clinical knee scores and flexion stabilities were no better in short term for robot assisted TKA than for navigation assisted TKA.
The purpose of this study was to compare intraoperative varus-valgus laxities in total knee arthroplasty [TKA] using either a single-radius femoral design or multi-radius femoral design. 56 TKAs were performed by using a single radius femoral design (Scorpio NRG, SR group) and 59 TKAs were performed by using a multi-radius femoral design (Zimmer NexGen, MR group), both with a minimum of 1-year follow-up. We compared intra-operative varus-valgus laxities at 0°, 30°, 60°, 90° of flexion using the navigation system (Orthopilot, Aesculap, Tuttlingen, Germany). A series of clinical outcomes were evaluated at the time of the latest follow-up including HSS, WOMAC, VAS score during stair climbing. At 30°, 60° of flexion, the mean total varus-valgus laxities in SR group (6.2 ± 3.5° at 30° of flexion and 6.8 ± 1.5° at 60° of flexion) were significant less than those in MR group (9.2 ± 4.3° at 30° of flexion and 8.3 ± 3.8° at 60° of flexion) (p=0.027 and p=0.042, respectively). In the clinical results, there was not significant difference. The single-radius femoral designs for TKA showed evidently less intra-operative mid-flexion stability compared with the multi-radius femoral design. However clinical outcomes revealed no other significant dissimilarity on HSS, WOMAC and VAS scores during stair climbing.
The purpose of this study was to compare the laxity, radiological and clinical outcomes of TKA that performed using the navigation system and using the conventional technique at least 10-year follow-up. 47 navigational TKAs and 45 conventional TKAs were included for this study. Varus-valgus laxities were measured on the stress radiographs. The radiological measurements with regard to the mechanical axis, the inclination of the femoral and tibial components, femoral posterior condylar off-set difference and radiolucency were compared. The clinical evaluations were performed using ROM, WOMAC and KS score. There was no significant difference in the total laxity. However, more than 10° of total laxity was significantly reduced in the navigation group (1 knee in the navigation group and 6 knees in the conventional group). The mean of mechanical axis was not statistically different between two groups. But, the outlier numbers of mechanical axis in the two groups was significantly different. The difference in ROM was not observed between the two groups. HSS, WOMAC, KS scores were significantly better in the navigation group. The navigation system can provide good stability, improved alignment accuracy of the lower extremity and better clinical results compared with conventional technique.
We hypothesised that the excellent alignments achieved in UKA using a navigation system(NA-MIS UKA) would improve mid-term clinical results versus UKA without a navigation system(MIS-UKA). The clinical results and the component alignment accuracies of NA-MIS UKA and MIS UKA were compared after a minimum follow-up of five years. 56 UKAs in the navigation group and 42 UKAs in conventional group were included. The radiological measurements with regard to the mechanical axis, the inclination of the femoral and tibial components, and radiolucent line or loosening were evaluated and compared between two groups. The clinical evaluations were performed using ROM, WOMAC, HSS and pain score. A significant inter-group difference was found in terms of WOMAC or HSS, pain scores. In the sagittal inclination of the femoral and tibial components, radiolucent line, there were no statistical differences between two groups. However, the outlier numbers at mechanical axis, the mean of coronal inclination of the femoral and tibial component in the two groups was significantly different. The navigation system in UKA can provide improved alignment accuracy of the lower extremity, also there were significant differences in functional outcomes after 5 year-follow-up.
The purpose of this study was to compare the
results of proximal and distal chevron osteotomy in patients with moderate
hallux valgus. We retrospectively reviewed 34 proximal chevron osteotomies without
lateral release (PCO group) and 33 distal chevron osteotomies (DCO
group) performed sequentially by a single surgeon. There were no
differences between the groups with regard to age, length of follow-up,
demographic or radiological parameters. The clinical results were
assessed using the American Orthopaedic Foot and Ankle Society (AOFAS)
scoring system and the radiological results were compared between
the groups. At a mean follow-up of 14.6 months (14 to 32) there were no significant
differences in the mean AOFAS scores between the DCO and PCO groups
(93.9 (82 to 100) and 91.8 (77 to 100), respectively; p = 0.176).
The mean hallux valgus angle, intermetatarsal angle and sesamoid
position were the same in both groups. The metatarsal declination
angle decreased significantly in the PCO group (p = 0.005) and the
mean shortening of the first metatarsal was significantly greater
in the DCO group (p <
0.001). We conclude that the clinical and radiological outcome after
a DCO is comparable with that after a PCO; longer follow-up would
be needed to assess the risk of avascular necrosis. Cite this article:
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.
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.
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.
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.
Ultra-high molecular weight polyethylene (UHMWPE) has been used for the bearing liner or inlay components in total joint replacements such as total hip, knee, and artificial disk since 1960’s. UHMWPE components generate wear debris during articulation, which play a key role in osteolysis, subsequent aseptic loosening, and eventually revision surgery. Efforts to solve the wear problem in UHMWPE and to quantify the amount of wear have driven many studies. But in vivo radiographic penetration depth measurement is the result of both wear and viscoelastic creep. Previous study reported that over 70% of the dimensional changes in UHMWPE acetabular cups were due to creep. Creep deformation was quantified under the static and dynamic compressive pressures (2, 4, 8Mpa) that are clinically relevant for the hip joint loads in normal motions. However, according to the finite element stress analyses in UHMWPE components under the active motions in hip, knee, and artificial disk replacements, very high level of contact pressures locally ranged from under 10MPa up to over 60Mpa. In this study, we quantified the creep of UHMWPE under the several high levels of dynamic compressive pressures and compared the results from the previous results. For creep tests, UHMWPE rectangular blocks (10mm long, 10mm wide, 8mm thick) were manufactured from molded unirradiated Chirulen® 1020 sheet (MediTECH, Deutchland). MTS 858 hydraulic test machine was used for conducting the dynamic compressive creep tests under the four different sinusoidal (1Hz) maximum pressures of 10, 20, 40, and 60MPa and minimum pressures of 1, 2, 4, and 6MPa, respectively. All tests were conducted for a total duration of 4×103 minutes at ambient conditions. During the test the displacements of crosshead were stored and the changes in thickness of block specimen devided by the initial thickness were calculated to get the creep strain. The mean dynamic compressive creep strain increased as the loading time increased and had a linear relationship (R2=0.96) with the logarithmic scale of time for all maximun pressures. Over 90% of total creep strain occurred within the first 103 minutes. The rates of creep strain (slopes of curve fitting in logarithmic scale of time) for each maximum pressure were listed in Table 1 with the rates of creep strain for low maximum pressures from the previous study [3]. The rates of creep strain increased linearly as the maximum pressure increased for both current study (R2=0.96) and previous study (R2=0.99). The slope of linearity for the current study with high levels of contact pressures was a little larger than that for the previous study with low levels of contact pressures. This difference in the slope of linearity between current and previous studies lies in the creep recovery during measurement of specimen thickness by micrometer in the previous study. Neglecting this difference, the results of current study can be extrapolated to anticipate the creep strain of UHMWPE under the dynamic compression for the low levels of contact pressures.
