Simultaneous Post and Cone Fractures of a Polyethylene Insert in a Mobile-Bearing Posterior-Stabilized Total Knee Arthroplasty.

We report a novel case of the simultaneous post and cone fractures of a polyethylene (PE) insert in a mobile-bearing posterior-stabilized total knee arthroplasty. Twelve years after the primary total knee arthroplasty, the 72-year-old male patient presented with a recurring right knee instability and was diagnosed with the wear of the PE insert based on physical and radiological examinations. Revision surgery was performed. The post and cone of the PE insert had fractured simultaneously. Moreover, the femoral and tibial components were in direct contact with each other. One year post-revision, knee function had improved. To diagnose a PE breakage, such as a post or cone fracture, surgeons should consider the possibility of PE breakage even in the absence of pain since patients might complain of subjective instability only.

Improvement of rotational arc during deep flexion range of a novel designed polyethylene insert for posterior-stabilised total knee arthroplasty.

BACKGROUND: One of the remaining issues in total knee arthroplasty (TKA) is achieving sufficient rotational arc during deep flexion range of the knee for specific postures such as the 'seiza' or cross-legged sitting. This study aimed to evaluate whether there was a change in the actual in vivo rotational arc during deep flexion range before and after a design change of polyethylene (PE) inserts. METHODS: In 50 posterior-stabilised TKA cases, knee kinematics, including rotational movement, were measured intraoperatively using an image-free navigation system to compare a newly designed PE insert with reduced the posterior lip with a conventional PE insert. Femoral-tibial rotational angles at 30°, 45°, 60°, 90°, 120°, and 130° knee flexion were evaluated. Varus/valgus instability, knee range of motion, and femoral rollback were also measured. Obtained parameters were compared between new and conventional PE inserts. The independent factors associated with rotational arc during deep flexion range (120° and 130° knee flexion) were analysed using multivariate analysis. RESULTS: The newly designed PE insert demonstrated a significant increase in the rotational arc at 120° (22.9 ± 8.7° vs. 30.1 ± 11.9°, P < 0.001) and 130° (24.3 ± 9.5° vs. 32.5 ± 12.4°, P < 0.001) knee flexion compared with that with the conventionally designed posterior-stabilised insert. Multivariate analysis demonstrated that using the newly designed PE insert was an independent predictor of improved rotational arc during deep flexion range: regression coefficient was 11.2 (95% confidence interval 7.1-15.3, P < 0.001). CONCLUSION: The design change, which reduced the posterior lip of the PE insert, contributed to improved rotational arc in 120° and 130° deep flexion ranges.

Long-term clinical results of alumina ceramic medial pivot total knee arthroplasty: a 10-year follow-up study.

BACKGROUND: The newly-designed alumina ceramic medial pivot total knee prosthesis was introduced to reduce polyethylene wear and better fit the anatomical morphology of the Asian population. This study aimed to clarify the long-term clinical results of alumina medial pivot total knee arthroplasty over a minimum follow-up period of 10 years. METHODS: The data of 135 consecutive patients who underwent primary alumina medial pivot total knee arthroplasty were analyzed in this retrospective cohort study. Patients were examined over a minimum 10-year follow-up period. The knee range of motion, Knee Society Score (KSS) knee score, Knee Society Score function score, and radiological parameters were assessed. The survival rate was also evaluated by using reoperation and revision as endpoints. RESULTS: The mean follow-up period lasted 11.8 ± 1.4 years. Patients who were not followed accounted for 7.4% of the total cohort. Knee and function scores of KSS improved significantly following total knee arthroplasty (P < 0.001). In 27 individuals (28.1%), a radiolucent line was observed. Aseptic loosening occurred in three cases (3.1%). The survival rates for reoperation and revision were 94.8% and 95.8% 10 years after the operation, respectively. CONCLUSIONS: During a minimum 10-year follow-up period, the present model of alumina medial pivot total knee arthroplasty showed good clinical outcomes and survival rates.

Clinical usefulness and safety in the early phase after a newly designed rotating-platform total knee arthroplasty: A prospective multicentre cohort study with a 2-year follow up.

BACKGROUND: This study aimed to assess the clinical results and safety of a newly designed rotating-platform posterior-stabilised total knee arthroplasty (TKA) in the early postoperative phase, within 2 years of follow up. METHODS: This prospective, multicentre cohort study included 100 consecutive patients who underwent rotating-platform posterior-stabilised (PS) TKA (Vanguard PSRP). After excluding dropouts, 93 patients were analysed. The objective Knee Society Score (KSS)-2011, subjective KSS-2011, knee range of motion, EuroQol 5 Dimension index, complications, and survival rates were assessed before TKA and at 6 months, 1 year, and 2 years postoperatively. The scores at each time-point were compared, and the survival rate was assessed with revision as the endpoint. To demonstrate non-inferiority, the clinical outcomes of patients who underwent rotating-platform PS TKA were compared with those collected retrospectively from 50 patients who underwent fixed-PS TKA (Vanguard PS), defined as the control group. RESULTS: All clinical outcomes at the final follow up significantly improved compared with their preoperative values (P < 0.001). The objective KSS-2011 was 90.0 ± 8.2 points, subjective KSS-2011 satisfaction was 30.7 ± 8.6 points, expectation was 10.4 ± 2.1 points, and functional activity was 74.0 ± 18.5 points at 2 years postoperatively. Complications included knee dislocation in one patient and surgical site infection in one patient. The survival rate was 99% at 2 years postoperatively. Clinical outcomes, complications, and survival rates of newly designed TKA were not statistically different compared with the control group. CONCLUSION: The newly designed rotating-platform PS TKA showed good clinical results and suitable safety during the early postoperative phase in this prospective multicentre cohort study.

Age-related differences in morphology and kinematics of the native hip.

Our objectives were to clarify morphology of the hip as well as infinitesimal femoral head movement in specific positions in young and elderly volunteers without joint degeneration. Both hips of 20 young and 20 elderly healthy volunteers were examined. Magnetic resonance imaging was performed at four different positions for each hip: neutral, 45° flexion, 15° extension, and the Patrick position. Femoral and pelvic bone images were separately extracted when in the neutral position and superimposed over the images of each different position by using voxel-based registration. The distance between the acetabular center and the femoral head center (FHC) at the neutral position was defined as 3D-migration. The distance between FHCs at neutral position and that at each different position was defined as 3D-translation. The x-, y-, and z-axes pointed in the anterior, cranial, and lateral directions, respectively. 3D-migration-y in the elderly was more caudal than that in the young (P < .001). 3D-translation of 45° flexion in the elderly was larger than that in the young with statistical significance (P = .001), while 3D-translation of the Patrick position in the elderly was smaller than that in the young (P = .012). Age was significantly correlated with 3D-translation in 45° flexion (r = .431; P < .001) and that in Patrick (r = -.296; P = .008). These results can be used as a basis for the natural course with aging of morphometry and kinematics of the hip, as well as for potential disease progression in osteoarthritis of the hip.

An easy and safe training method for trunk function improves mobility in total knee arthroplasty patients: A quasi-randomized controlled trial.

OBJECTIVE: Total knee arthroplasty (TKA) is aimed mainly at reducing pain and restoring mobility. However, mobility deficits can persist even longer than 1 year. The trunk function and movement velocity of any region have been recently recognized to be critical for determining mobility in older people. Therefore, the main goal of this quasi-randomized trial is to clarify the effectiveness of a novel training method, the seated side tapping (SST) training, for improving mobility by focusing on movement velocity of trunk function in the short term after TKA. METHODS: SST training consists of side trunk movements repeated as quickly as possible in a seated position. All participants after TKA were randomly assigned to the SST training group (n = 37) or control training group (n = 38). The participants in the SST group performed SST training plus the standard rehabilitation program 5 days per week for 3 weeks after TKA, while the control group performed only the standard rehabilitation programs. The primary outcome was the effect of SST training on mobility, indicated by gait speed and the timed up and go test (TUG) time. Measurements were performed before and 1, 2, and 3 weeks after surgery. RESULTS: At all-time points, the patients in the SST group showed significantly better mobility, despite that knee function, represented by muscle strength, range of motion, and degree of pain at the knee joint, was similar in both groups. The difference in gait speed between the groups was >0.1 m/s at all time points, which is clinically significant. CONCLUSION: SST training significantly improved patients' mobility within 3 weeks after TKA, despite that no additional benefit was observed in knee function. The findings in this study indicate that SST training may be considered as a part of the rehabilitation program after TKA, although further evaluation of its long-term effectiveness is needed. TRIAL REGISTRATION: University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR; UMIN000027909).

Exercise Therapy Interventions in Patients With Hip Osteoarthritis: Comparison of the Effects of DVD and Website-Based Interventions.

BACKGROUND: Prevalence of developmental hip dysplasia is high in Japan. Exercise therapy has been proven effective to treat certain aspects of hip osteoarthritis. Moreover, therapy provided via digital video discs (DVDs) and websites allows patients to exercise in the comfort of their own homes. However, no studies have evaluated the effectiveness of visual instructions in patients with hip disorders. OBJECTIVE: This study aimed to compare the effectiveness of exercise therapy administered via DVD and that administered via a website. METHODS: We developed a six-step progressive exercise therapy program for patients with hip osteoarthritis, which included three kinds each of open kinetic chain and closed kinetic chain exercises. Once the program was developed, exercise DVDs were produced. In addition to the six-step exercise program, our website was enabled to count the number of exercises performed by each patient and was accessible via the Internet at any time. Patients with hip osteoarthritis for whom surgery was not advised were enrolled by one university hospital in the Kansai area in Japan. Clinical symptoms and hip function were quantified using the Japanese Orthopedic Association Hip Disease Evaluation Questionnaire (JHEQ) and the Oxford Hip Score (OHS). Quality of life was measured using the SF-8 Health Survey, and self-efficacy for continued exercise was measured using the General Self-Efficacy Scale (GSES). Questionnaires were completed preintervention and after 6 months. RESULTS: At 6-month follow-up, 10 DVD users (1 male, 9 female; mean age 51.3, SD 16.1 years) and 18 website users (2 male, 16 female; mean age 52.4, SD 10.4 years) were reachable. The change in each parameter could not be confirmed a significant improvement. However, most items tended to reflect overall improvement during the 6 months of intervention (P=.05-.94; paired t test). Regarding effect size, we considered a small effect to be greater than 0.2. Little effect was observed for JHEQ pain, SF-8 physical component summary (PCS), and SF-8 mental component summary in the DVD group, as well as OHS, SF-8 (PCS), and GSES in the website group. CONCLUSIONS: When comparing the effectiveness of exercise therapy between our DVD and website, we found that although both groups tended to improve in physical function, only the website group showed tendency of enhanced self-efficacy.

A forty millimetre head significantly improves range of motion compared with a twenty eight millimetre head in total hip arthroplasty using a computed tomography-based navigation system.

PURPOSE: Larger-diameter (≥40 mm) femoral heads decrease the incidence of post-operative dislocation in total hip arthroplasty (THA). This study was conducted to discover whether larger-diameter femoral heads result in greater range of motion of the hip with the use of a computed tomography (CT)-based navigation system. METHODS: Thirty-nine primary THAs were performed via a posterolateral approach using a CT-based navigation system. The stem was inserted in the femur in line with the original femoral neck anteversion. Considering the range of motion during various daily activities which could occur without impingement, the cup anteversion was decided at 10 ° increments according to the stem anteversion. While the cup inclination was set at 40 ° in order to avoid a high inclination angle to prevent the edge roading between the HXLPE liner and ceramic head. After implantation, trial liners and femoral heads were used with either 28 or 40 mm diameter. Maximal hip flexion, extension, abduction, external rotation in extension at 0° and internal rotation angles in flexion at 90 ° were measured. The differences between the ranges of motion with the 40-mm and 28-mm heads were tested. The results were assessed with paired Student t-tests. RESULTS: The ranges of motion in flexion, extension, abduction and internal rotation angles improved significantly with the 40-mm heads compared with the 28-mm heads. The ranges of motion of cases where maximal flexion angle was 90° or less were excluded, improved significantly with the 40 mm heads. CONCLUSIONS: We concluded that the larger-diameter 40-mm femoral prosthetic heads result in greater ranges of motion in flexion, extension, abduction and internal rotation.

Morphological analysis of the acetabular cartilage surface in elderly subjects.

PURPOSE: The geometry of acetabular cartilage surface plays an important role in hip joint biomechanics. The aim of this study was to analyze the morphology of acetabular articular cartilage surface in elderly donated bodies to science using a 3D-digitizer. METHODS: Twenty hemipelves from 12 subjects (mean ages 85 years) were scanned with 3D-digitizer. Each acetabular surface model was divided into four regions: anterosuperior (AS), anteroinferior (AI), posterosuperior (PS), and posteroinferior (PI). In the global acetabulum and each region, the acetabular sphere radius and the standard deviation (SD) of the distance from the acetabular sphere center to the acetabular cartilage surface were calculated. In the global acetabulum, the distance between the acetabular surface model and the maximum sphere which did not penetrate over the acetabular surface model was calculated as the inferred femoral head, and then the distribution was mapped at intervals of 0.5 mm. RESULTS: The SD in AS was significantly larger than that in AI (p = 0.006) and PI (p = 0.001). The SD in PS was significantly larger than that in PI (p = 0.005). The closest region (0-0.5 mm) tended to be distributed at anterior or posterosuperior acetabular edge. CONCLUSIONS: The contact between the femoral head and acetabulum might start at the periphery of the lunate surface, especially in the anterior or posterosuperior region. From viewpoint of acetabular morphology, the acetabular articular cartilage in the anterior or posterosuperior edge could be more vulnerable due to direct contact mechanism.

In vivo hip joint contact distribution and bony impingement in normal and dysplastic human hips.

Our objectives were to clarify the 3D articular contact areas of the in vivo normal hip joint and acetabular dysplasia during specific positions using magnetic resonance imaging (MRI), voxel-based registration, and proximity mapping. Forty-two normal and 24 dysplastic hips were examined. MRI was performed at four positions: neutral; 45° flexion; 15° extension; and the Patrick position. Femur and pelvis bone models were reconstructed at the neutral position and superimposed over the images of each different position using voxel-based registration. The inferred cartilage contact and bony impingement were investigated using proximity mapping. The femoral head translated in the anterior or posteroinferior, anterosuperior, and posteroinferior direction from neutral to 45° flexion, 15° extension, and the Patrick position, respectively. Multiple regression analyses showed age, femoral head sphericity, and acetabular sphericity to be associated with higher hip instability. The present technique using subject-specific models revealed the in vivo hip joint contact area in a population of healthy individuals and dysplastic patients without radioactive exposure. These results can be used for analyzing disease progression in the dysplastic hip and pathogenesis of acetabular labral tear.

In vivo kinematic analysis of squatting after total hip arthroplasty.

BACKGROUND: The in vivo kinematics of squatting after total hip arthroplasty is unclear. The purpose of the present study was to determine the range of motion of the hip joint during squatting after total hip arthroplasty. METHODS: Using fluoroscopy, we investigated 15 primary cementless total hip arthroplasties performed using a computed tomography-based navigation system. An acetabular component with concavities around the rim and a femoral component with reduced neck geometry were used. The motion of the acetabular and femoral components based on the neutral standing position was analyzed using a two-dimensional to three-dimensional registration technique. FINDINGS: No prosthetic impingement occurred in any hips. The mean maximum hip flexion range of motion was 86.2° (range, 55.1°-117.4°) and was not always consistent with maximum squatting. The mean maximum pelvic posterior tilting angle was 25.7° (range, 5.5°-43.5°). The pelvis began to tilt posteriorly at 50°-70° of the hip flexion range of motion. At maximum squatting, the mean ratio of the pelvic posterior tilting angle to the femoral flexion angle was 23.2% (range, 3.8%-45.7%). The mean minimum angle up to the theoretical prosthetic impingement was 26.2° (range, 11.8°-39.8°). INTERPRETATION: Although this is a preliminary study, three-dimensional assessment of dynamic squatting motion after total hip arthroplasty using the two-dimensional to three-dimensional registration technique appears to enable elucidation of the range of motion of the hip joint, the contribution of pelvic posterior tilting, and the minimum angle up to theoretical prosthetic impingement during squatting.

Characteristics of fracture and related factors in patients with rheumatoid arthritis.

To examine the clinical features of vertebral and non-vertebral fractures in patients with rheumatoid arthritis (RA), including insufficiency fractures, and to assess the risk factors for fracture, we prospectively studied 209 outpatients with rheumatoid arthritis for 1 year. The age, gender, Steinbrocker's functional class, glucocorticoid use, history of lower limb surgery, serum C-reactive protein (CRP), and use of bisphosphonates were evaluated. Examination for fractures was performed by radiography, computed tomography (CT), magnetic resonance imaging (MRI), and bone scanning. Thirty-three fractures occurred in 24 patients over the 1-year study period, and the incidence was 15.8 fractures per 100 patient-years. Fractures occurred at various sites. The majority (70%) was insufficiency fracture, and more than 50% caused ambulatory dysfunction. Radiographic findings were absent in 39% of the fractures at the onset of pain. The functional class and glucocorticoid dose were significantly associated with fracture development. This prospective study showed that the incidence of fractures, especially insufficiency fractures, was very high in patients with rheumatoid arthritis and that most of their fractures caused gait disturbance. Early intervention to prevent secondary osteoporosis is recommended to maintain the quality of life in patients with rheumatoid arthritis, especially those with functional impairment or undergoing glucocorticoid therapy.