Identifying Muscle Function-based Phenotypes Associated With Radiographic Progression of Secondary Hip Osteoarthritis.

OBJECTIVE: The purposes of our study were to (1) identify muscle function-based clinical phenotypes in patients with hip osteoarthritis (OA) and (2) determine the association between those phenotypes and radiographic progression of hip OA. DESIGN: Prospective cohort study. SETTING: Clinical biomechanics laboratory of a university. PARTICIPANTS: Fifty women patients with mild-to-moderate secondary hip OA (N=50) were recruited from the orthopedic department of a single institution. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Two-step cluster analyses were performed to classify the patients, using hip flexion, extension, abduction, and external/internal rotation muscle strength (cluster analysis 1); relative hip muscle strength to total hip strength (ie, hip muscle strength balance; cluster analysis 2); and both hip muscle strength and muscle strength balance (cluster analysis 3) as variables. The association between the phenotype and hip OA progression over 12 months (indicated by joint space width [JSW] >0.5 mm) was investigated by logistic regression analyses. Hip joint morphology, hip pain, gait speed, physical activity, Harris hip score, and SF-36 scores were compared between the phenotypes. RESULTS: Radiographic progression of hip OA was observed in 42% of the patients. The patients were classified into 2 phenotypes in each of the 3 cluster analyses. The solution in cluster analyses 1 and 3 was similar, and high-function and low-function phenotypes were identified; however, no association was found between the phenotypes and hip OA progression. The phenotype 2-1 (high-risk phenotype) extracted in cluster analysis 2, which had relative muscle weakness in hip flexion and internal rotation, was associated with subsequent hip OA progression, even after adjusting for age and minimum JSW at baseline (adjusted odds ratio [95% confidence interval], 3.60 [1.07-12.05]; P=.039). CONCLUSION: As preliminary findings, the phenotype based on hip muscle strength balance, rather than hip muscle strength, may be associated with hip OA progression.

The superior accuracy of a novel method in total hip wear calculations following radiographic measurement.

BACKGROUND: Polyethylene wear is one of the major concerns of orthopedic surgeons. However, there is no standardized calculation method for the wear rate following radiographic measurement. The purpose of this study was to propose a novel method of wear calculation and to compare its accuracy with a representative conventional method. METHODS: Relative position of the center of the femoral head to that of the cup progresses in one direction following arthroplasty surgery because of bedding-in and wear. We predetermined the amount of bedding-in, wear rate, and random error in measuring the head center position in a 2-dimensional plane. We calculated the wear rate using the head center coordinates over a certain number of measurement periods using a representative conventional method and our novel method. The conventional method consisted of transforming vector data into scalars and conducting a least-squares method. The least-squares method was directly applied to each component of the vector in the novel method. We evaluated the accuracy of these methods by comparing the expected value for the wear rate with their predetermined true values. RESULTS: If the error were limited to being random, the novel method could provide the predetermined wear rate as the calculation result. However, the conventional method could not. CONCLUSION: We recommend using the novel method for the wear calculation rather than the conventional method because of its mathematical accuracy.

Strategies for increasing gait speed in patients with hip osteoarthritis: their clinical significance and effects on hip loading.

BACKGROUND: Changes in gait speed are required in various situations and can be achieved by changing stride length, cadence, or both. Differences in strategies for increasing gait speed may have different effects on hip joint and physical function. The purpose of this study was to determine the effects of strategies for increasing gait speed on hip pain, physical function, and changes in hip loading during gait in patients with hip osteoarthritis (OA). We hypothesized that patients who increase gait speed mainly by increasing cadence would have lesser hip pain, a higher physical function, and a lower rate of increase in hip moments with increasing gait speed. METHODS: Forty-seven patients with secondary hip OA (age, 48.3 ± 11.0 years) were included. Gait speed, stride length, cadence, and peak and impulse of the hip moments were measured during gait at self-selected normal and fast gait speeds. The patients were classified as types S (with mainly increasing stride length, n = 11 [23.4%]), C (with mainly increasing cadence, n = 23 [48.9%]), and SC (with increasing stride length and cadence, n = 13 [27.7%]) according to whether they used changes in stride length and/or cadence to transition from normal to fast gait. Hip pain, physical function, and hip moment changes during gait were compared between types. RESULTS: The physical function was higher in types C (38.0 ± 8.8, P = 0.018) and SC (40.6 ± 8.5, P = 0.015) than in type S (28.2 ± 7.8), even after adjustment for age and minimum joint space width. Hip pain was not significantly different between types. The robustness of these results was confirmed with sensitivity analysis. The rates of increases in peak external hip adduction (P = 0.003) and internal rotation moments (P = 0.009) were lower in type C than in type SC. CONCLUSIONS: Type C tended to suppress the increase in hip moments during fast gait. Types C and SC, which included increased cadence, maintained higher physical function levels than type S. Encouraging the use of cadence-increasing strategy may be useful for reducing hip loading and maintaining physical function in patients with hip OA.

Clinical phenotypes based on clinical prognostic factors in patients with secondary hip osteoarthritis: preliminary findings from a prospective cohort study.

OBJECTIVES: Recently, several clinical prognostic factors for hip osteoarthritis (OA) progression such as spinal malalignment, reduced spinal mobility, and excessive daily cumulative hip loading have been identified. This study aimed to identify clinical phenotypes based on clinical prognostic factors in patients with secondary hip OA using data from prospective cohort studies and to define the clinical features of each phenotype. METHODS: Fifty patients participated. Two-step cluster analysis was performed to identify the phenotypes using the following potential prognostic factors for hip OA progression: spinal inclination in standing, thoracolumbar spine mobility, daily cumulative hip moment, and minimum joint space width (JSW) at baseline. Comprehensive basic and clinical features (age, body mass index, hip pain, Harris hip score, JSW, radiographic hip morphology, hip impairments, spinal alignment and mobility, and gait-related variables) and ratio of progressors in 12 months were compared among the phenotypes using bootstrap method (unadjusted and adjusted for age). RESULTS: Three phenotypes were identified and each phenotype was characterized as follows (P < 0.05): phenotype 1 (30%)-relatively young age and higher daily cumulative hip loading; phenotype 2 (42.0%)-relatively older age, reduced JSW, and less spinal mobility; and phenotype 3 (28.0%)-changed thoracic spine alignment and less spinal (especially in the thoracic spine) mobility. The ratio of progressors among the phenotypes was not statistically significantly different. These characteristics remained after adjustment for age. CONCLUSION: Three phenotypes with similar progression risk were identified. This finding will help in designing treatment tailored to each phenotype for hip OA progression prevention.Key Points• Three phenotypes with similar progression risk were identified based on clinical prognostic factors.• Phenotype 1 was characterized by young age and higher daily cumulative hip loading.• Phenotype 2 was relatively old age and had reduced JSW and less spinal mobility.• Phenotype 3 had changed thoracic spine alignment and less thoracic spine mobility.

Gait kinematics of the hip, pelvis, and trunk associated with external hip adduction moment in patients with secondary hip osteoarthritis: toward determination of the key point in gait modification.

BACKGROUND: A larger daily cumulative hip loading, which is the product of the external hip adduction moment (HAM) impulse during gait and the number of steps per day has been identified as a factor associated with the progression of secondary hip osteoarthritis (OA). The cause of the increased HAM impulse in patients with hip OA has not been identified. The purpose of this study was to identify the gait parameters associated with HAM impulse during gait in patients with secondary hip OA. METHODS: Fifty-five patients (age 22-65 years) with mild-to-moderate secondary hip OA participated in this cross-sectional study. The HAM impulse during gait was measured using a three-dimensional gait analysis system. To identify the gait parameters associated with HAM impulse, hierarchical multiple regression analysis was performed. The first model (basic model) included body weight and stance phase duration. The second models included gait parameters (gait speed; ground reaction force [GRF] in frontal plane; and hip, pelvic, and trunk angle in frontal plane) and hip pain in addition to the basic model. RESULTS: Body weight and stance phase duration explained 61% of the variance in HAM impulse. In the second model, which took into account body weight and stance phase duration, hip adduction angle (9.4%), pelvic tilt (6.5%), and trunk lean (3.2%) in addition to GRF explained the variance in the HAM impulse. Whereas larger hip adduction angle and pelvic tilt toward the swing limb were associated with a larger HAM impulse, larger trunk lean toward the stance limb was associated with smaller HAM impulse. CONCLUSION: In patients with excessive hip adduction and pelvic tilt toward the swing limb during gait, gait modification may contribute to the reduction of hip joint loading.

Gait- and Posture-Related Factors Associated With Changes in Hip Pain and Physical Function in Patients With Secondary Hip Osteoarthritis: A Prospective Cohort Study.

OBJECTIVE: To identify gait- and posture-related factors associated with changes in hip pain and physical function in patients with hip osteoarthritis (OA). DESIGN: Prospective cohort study. SETTING: Clinical biomechanics laboratory of a university. PARTICIPANTS: Consecutive sampling of female patients with mild-to-moderate secondary hip OA (N=30). MAIN OUTCOME MEASURES: Hip pain (visual analog scale) and physical function (physical component summary of the Medical Outcomes Study 36-Item Short-Form Health Survey) were measured at baseline and 12 months later. With changes in hip pain and physical function as dependent variables, linear regression analyses were performed with gait- and posture-related factors as independent variables with and without adjustment for age, joint space width, and hip pain or physical function at baseline. Posture-related factors included angles of thoracic kyphosis, lumbar lordosis, sacral inclination, spinal inclination, and spinal mobility. Gait-related factors were walking speed, steps per day, joint angles, external hip joint moment impulses, and daily cumulative hip moments. RESULTS: Multiple linear regression analyses showed that limited hip extension (adjusted standardized B coefficient [95% confidence interval]: -0.52 [-0.88 to -0.17]) and limited external rotation angles (-0.51 [-0.85 to -0.18]) during walking were associated with the worsening of hip pain. An increased thoracic kyphosis (-0.54 [-0.99 to -0.09]), less sacral anterior tilt (0.40 [0.01-0.79]), reduced thoracic spine mobility (0.59 [0.23-0.94]), less steps per day (0.53 [0.13-0.92]), and a slower walking speed (0.45 [0.04-0.86]) were associated with deterioration in physical function. CONCLUSIONS: Gait- and posture-related factors should be considered when assessing risk and designing preventive interventions for the clinical progression of secondary hip OA.

Patient- and Surgery-Related Factors that Affect Patient-Reported Outcomes after Total Hip Arthroplasty.

Patient-reported outcome measures (PROMs) are used to assess satisfaction after total hip arthroplasty (THA); however, the factors that determine these PROMs remain unclear. This study aimed to identify the patient- and surgery-related factors that affect patient satisfaction after THA as indicated by the Oxford Hip Score (OHS). One-hundred-and-twenty patients who underwent primary THA were included. Various patient-related factors, including clinical scores, and surgery-related factors were examined for potential correlations with the OHS at 3, 6, and 12 months post-THA. Univariate regression analysis showed that higher preoperative University of California Los Angeles (UCLA) activity score (p = 0.027) and better preoperative OHS (p = 0.0037) were correlated with better OHS at 3 months post-THA. At 6 months post-THA, the factors associated with better OHS were higher preoperative UCLA activity score (p = 0.039), better preoperative OHS (p = 0.0006), and use of a cemented stem (p = 0.0071). At 12 months post-THA, the factors associated with better OHS were higher preoperative UCLA activity score (p = 0.0075) and better preoperative OHS (p < 0.0001). Multivariate regression analysis showed that the factors significantly correlated with better OHS were female sex (p = 0.011 at 3 months post-THA), osteoarthritis (p = 0.043 at 6 months), higher preoperative OHS (p < 0.001 at 3 and 12 months, p = 0.018 at 6 months), higher preoperative Harris Hip Score (p = 0.001 at 3 months), higher preoperative UCLA activity score (p = 0.0075 at 3 months), and the use of a cemented femoral component (p = 0.012 at 6 months). Patient- and surgery-related factors affecting post-THA PROMs were identified, although the effect of these factors decreased over time.

A long-term comparative study between two different designs of cemented stems: Distal-cylindrical versus distal-taper.

INTRODUCTION: The aim of this study was to calculate the wear rate of highly cross-linked polyethylene (HXLPE) and investigate long-term clinical and radiographic outcomes related to two femoral stem designs, the distal-cylindrical (DC) and distal-taper (DT) stems. MATERIALS AND METHODS: Outcomes for the DC and DT stems were evaluated in 110 patients, who underwent total hip arthroplasty using an HXLPE socket, over a 5-year follow-up period. There were 56 hips (53 patients) in the DC group and 60 hips (57 patients) in the DT group. Clinical outcomes were measured using the Japanese Orthopaedic Association (JOA) score and radiographic changes. Polyethylene wear rate was calculated using a computer software. RESULTS: The mean follow-up period was 135.7 and 124.0 months for the DC and DT groups, respectively. Both stem designs improved hip function. On radiographic assessment, osteolysis around the tip of the stem was more frequent in the DC than in the DT group. Three cases of aseptic loosening of the stem were identified in the DC group, and no cases were identified in the DT group. The 10-year stem survival, using aseptic loosening as the primary endpoint, was 94.1% and 100% for the DC and DT groups, respectively (p = 0.06). The polyethylene wear rate was comparable for both stem groups. CONCLUSION: Better clinical outcomes were obtained with the DT stem than with the DC stem regardless of the equivalent polyethylene wear rate for the two designs. The DC shape of the stem may increase the risk of aseptic loosening.

Polyethylene and highly cross-linked polyethylene for cemented total hip arthroplasty: A comparison of over ten-year clinical and radiographic results.

INTRODUCTION: We investigated the long-term tribological outcomes of conventional polyethylene (CPE) and highly cross-linked polyethylene (HXLPE). METHODS: Ninety-four consecutive primary cemented THAs were performed using either HXLPE or CPE at our hospital. CPE sockets were used in 26 hips, and HXLPE sockets were implanted in 68 hips. RESULTS: A 10-year follow-up was completed for 69 cases. Linear wear rates of 0.138 ± 0.074 mm/year for CPE and 0.011 ± 0.020 mm/year for HXLPE were calculated. Osteolysis was identified in 10 cases (CPE group, 7; HXLPE group, 3). CONCLUSION: HXLPE had significantly less wear than CPE, and polyethylene wear was associated with osteolysis.

The Relationship Between Subluxation Percentage of the Femoroacetabular Joint and Acetabular Width in Asian Women with Developmental Dysplasia of the Hip.

BACKGROUND: Implantation of the acetabular cup insert in the "true" location of the acetabulum is a fundamental principle of total hip arthroplasty for the treatment of secondary osteoarthritis due to developmental dysplasia of the hip (DDH). As knowledge of the morphology of the acetabulum is required for accurate placement, we investigated the relationship between acetabular width and the Crowe classification of subluxation percentage of the hip. We also analyzed factors associated with the acetabular width ratio (AWR), defined as the acetabular width of the dysplastic hip divided by that of the unaffected, contralateral hip. METHODS: We completed a retrospective review of the preoperative standard anteroposterior radiographs and computed tomography (CT) scans of 207 female patients who underwent primary total hip arthroplasty for unilateral DDH. The "true" acetabular plane was defined on each CT reconstruction as a plane perpendicular to the anterior pelvic plane, parallel to the teardrop line, and passing through the center of the femoral head on the unaffected, contralateral side. The acetabular width was measured for both the affected hip and the contralateral, reference hip on the true acetabular plane, with the acetabular width defined as the distance between the edges of the anterior and posterior walls of the acetabulum. All hips were classified according to the Crowe groupings on the basis of the subluxation percentage of the dysplastic hip; the subluxation percentage increased from groups I to IV, with group IVb showing joint dislocation. RESULTS: The acetabular width decreased from Crowe groups I to IVb, with a negative correlation found between the AWR and the subluxation percentage (Spearman correlation coefficient, ρ = -0.404; p < 0.001). Multivariate regression analysis identified subluxation percentage and femoral neck-shaft angle as independent factors associated with the AWR. CONCLUSIONS: Characterization of factors associated with the AWR, namely subluxation percentage and femoral neck-shaft angle, will guide surgeons in correctly implanting the acetabular cup insert during total hip arthroplasty in patients with DDH.

Effects of High- and Low-Velocity Resistance Training on Gait Kinematics and Kinetics in Individuals with Hip Osteoarthritis: A Randomized Controlled Trial.

OBJECTIVE: The aim of this study was to investigate the effects of high-velocity (HV) and low-velocity (LV) resistance training on gait kinematics and kinetics in patients with hip osteoarthritis. DESIGN: This was a single-blind, randomized controlled trial. Forty-six women with hip osteoarthritis were randomly allocated to the HV (n = 23) or LV (n = 23) training group. The participants underwent an 8-week home-based the HV or LV resistance-training program, involving the hip and knee muscles. Outcome measures included gait kinematics and kinetics using 3-dimensional analyses, muscle strength and power, the Harris Hip Score, and hip pain using the visual analog scale. RESULTS: There was no significant difference in changes for any of the outcome measures between groups. After the training session, muscle power, walking speed, and cadence significantly increased only in the HV group, whereas stride length and the peak hip extension angle during gait significantly increased, and pain on the visual analog scale and the peak ankle dorsiflexion moment during gait significantly decreased only in the LV group. Muscle strength and Harris Hip Score significantly increased in both groups. CONCLUSIONS: The results of this study may indicate that the potential effect of resistance training on abnormal gait pattern depends on movement velocities during training.

Mid- and long-term results of femoral component revision using the cement-in-cement technique: Average 10.8-year follow-up study.

BACKGROUND: Few reports are available on the long-term outcomes of femoral component revision by using the cement-in-cement technique. We report the mid- and long-term results of femoral component revision in total hip arthroplasty using the cement-in-cement technique. METHODS: Between April 1996 and June 2009, 62 consecutive total hip arthroplasties with femoral component revision were performed in 57 patients by using the cement-in-cement technique. We retrospectively reviewed the cases with a follow-up period of at least five years. Three patients died, and two were lost to follow-up. Thus, 52 patients (57 hips), comprising 51 women and one man, were followed for average 10.8 years. RESULTS: The mean Japanese Orthopaedic Association hip score improved from 57.6 points (range, 28-95 points) preoperatively to 79.8 points (range, 52-98 points) at one year postoperatively and to 77.4 points (range, 59-96 points) at the final follow up. Three revisions of the femoral component were necessary. One of the causes for the revision was a periprosthetic infection that occurred 20 months postoperatively. Another was aseptic loosening that occurred 99 months postoperatively and required revision of the acetabular component. The well-fixed femoral component was revised using the cement-in-cement technique at time of the acetabular revision. The third case was aseptic loosening of the femoral component that occurred 84 months postoperatively. The five-, 10-, and 15-year survival rates for the femoral re-revision due to any reason were 98.4%, 94.0%, and 94.0%, respectively. CONCLUSION: Use of the cement-in-cement technique for revision total hip arthroplasty resulted in good mid- and long-term radiological and clinical outcomes.

Radiographic and clinical factors associated with one-leg standing and gait in patients with mild-to-moderate secondary hip osteoarthritis.

A decline in physical function associated with secondary hip osteoarthritis (OA) may be caused by both radiographic and clinical factors; however, the underlying mechanism remains unclear. The purpose of this study was to determine how joint degeneration, hip morphology, pain, hip range of motion (ROM), and hip muscle strength relate to one-leg standing (OLS) and gait in patients with mild-to-moderate secondary hip osteoarthritis. Fifty-five female patients (ages 22-65 years) with mild-to-moderate hip OA secondary to hip dysplasia were consecutively enrolled. Balance during OLS and three-dimensional hip angle changes while maintaining the OLS and at foot-off of the raised leg were measured. Gait speed and peak three-dimensional hip joint angles during gait were also measured. The associations between dependent variables (balance, gait speed, and hip kinematic changes) and independent variables (age, body mass index, pain, joint degeneration, hip morphologic abnormality, passive hip ROM, and hip muscle strength) were determined. While lower hip muscle strength was associated with hip kinematic changes such as flexion and internal rotation while maintaining OLS, decreased acetabular head index (AHI) and increased pain were associated with hip extension and abduction at foot-off in OLS. Decreased passive hip ROM was associated with decreased peak hip angles (extension, adduction, and external and internal rotation) during gait, although increased pain and decreased hip extension muscle strength were associated with slower gait speed. In this study of patients with secondary hip OA, AHI, pain, and hip impairments were associated with OLS and gait independently from age and radiographic degeneration.

Extremely early stage osteonecrosis of the femoral head in a patient with hip pain secondary systemic steroid pulse therapy for Vogt-Koyanagi-Harada syndrome: A case report.

INTRODUCTION: Osteonecrosis of the femoral head (ONFH) is a corticosteroid-associated disease that mostly cause femoral head collapse and gait disturbance. At the final stage of ONFH, the most reliable treatment is total hip arthroplasty even in young patients. Although magnetic resonance imaging (MRI) is useful for early diagnosis, initial stages are asymptomatic, with pain intensifying after femoral head collapse. PRESENTATION OF CASE: A 34-year-old female patient with rapid bilateral loss of vision was diagnosed Vogt-Koyanagi-Harada syndrome. She immediately received corticosteroid pulse therapy. While undergoing therapy, she complained of groin pain. The initial MRI of the hip did not show abnormal findings. As the right proximal thigh pain progressed, an MRI of the lumbar spine was performed. No compression of the spinal cord was observed, and right ONFH was suspected on the basis of a characteristic band image. The patient was diagnosed with Stage 1 ONFH 7 weeks after the initial symptoms. She was successfully treated by joint-preserving regenerative therapy using growth factor. After surgery, the patient completely recovered from pain. DISCUSSION: The occurrence of hip pain while receiving corticosteroid therapy was very rare. The present case was considered a result of reduction of the blood supply to the femoral head induced by hip pain that progressed to ONFH for unknown reasons. CONCLUSION: It is difficult to identify cases of corticosteroid-associated ONFH even in patients with potential risk. In this case, we could identify the patient extremely early based on the ONFH image and could provide joint-preserving regenerative therapy.

Associations of radiographic degeneration and pain with daily cumulative hip loading in patients with secondary hip osteoarthritis.

The purpose of this study was to investigate the associations of radiographic and clinical variables of hip osteoarthritis (OA) with alterations in gait and joint loading in patients with secondary hip OA. Fifty females with secondary hip OA were participated. The minimum joint space width (mJSW) of the hip as a degenerative sign and Sharp and center edge (CE) angles as morphological variables were measured radiographically. Hip joint pain was assessed using a visual analog scale. As gait variables, walking speed, range of hip motion, hip moment peak, and hip moment impulse were calculated. Daily cumulative hip loading was calculated as the hip moment impulse multiplied by the mean number of steps per day. After bivariate correlation analyses between dependent (mJSW and pain) and independent variables (age, body mass index, sharp/CE angles, steps per day, and gait variables), separate forward-backward stepwise multiple regression analyses were performed for each dependent variable. Daily cumulative hip loading in the sagittal plane (ß = 0.30, p = 0.021) and age (ß = -0.36, p = 0.007) were significantly associated with the mJSW. Walking speed (ß = -0.36, p = 0.008) and age (ß = 0.29, p = 0.031) were significantly associated with hip joint pain. Decrease in daily cumulative hip loading in the sagittal plane was associated with mJSW independently of age. Although the causal relationship was not clear, patients with hip OA reduced total exposure to hip joint loading adaptively rather than lowering the hip moment peak concerning worsening of hip degeneration. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1977-1983, 2016.

Clinical and radiographic evaluation of cemented socket fixation concomitant to acetabular bone grafting fixed with absorbable hydroxyapatite-poly-l-lactide composite screws.

BACKGROUND: The durability of uncalcined and unsintered hydroxyapatite-poly-l-lactide composite screws is unclear when used for the fixation of acetabular bone graft in total hip arthroplasty under full-weight conditions. We have used this type of screw for the fixation of acetabular bone graft in cemented or reverse-hybrid total hip arthroplasty since 2003. Hence, we conducted a follow-up study to assess the safety and efficacy of these screws when used for cemented socket fixation. METHODS: In this study, 98 patients (106 cases) who underwent fixation of acetabular bone graft in cemented or reverse-hybrid total hip arthroplasty using hydroxyapatite-poly-l-lactide composite screws were followed up for over 5 years and evaluated clinically and radiographically. The patient population comprised 10 men and 88 women with a mean age of 60.3 years (range, 41-81 years) at the time of surgery. The original diagnosis for primary total hip arthroplasty was secondary osteoarthritis in 97 cases and high hip dislocation in nine cases. RESULTS: The mean follow-up period was 7.6 years (range, 5-11 years). No patient in this series required revision surgery, and no radiographical loosening occurred during the follow-up period. The mean Japanese Orthopaedic Association score improved from 48 (range, 7-73) preoperatively to 87 (range, 50-100) at the final follow-up. Radiographically bone graft consolidation was confirmed in all cases, and no apparent osteolysis around the cemented socket or composite screws was detected. Kaplan-Meier survival analyses with socket revision surgery for any reason, socket loosening, and appearance of a radiolucent line >1 mm in any zone as the endpoints yielded survival rates of 100%, 100%, and 86.8% at 5 years, and 100%, 100%, and 81.0% at 10 years, respectively. CONCLUSION: This absorbable screw seems to have no negative effects on the mid-term clinical results of cemented socket fixation.

Hip external rotator exercise contributes to improving physical functions in the early stage after total hip arthroplasty using an anterolateral approach: a randomized controlled trial.

PURPOSE: The purpose of this study was to investigate the effects of an exercise program focusing on hip external rotator muscle on physical recovery in the early post-operative period of total hip arthroplasty (THA). METHODS: Patients who underwent THA were randomized to an exercise group (n = 14) or a control group (n = 14). In exercise group, the hip external rotator exercise program was performed 5 times per week for four weeks. Outcome measures were hip pain, hip range of motion, muscle strength of lower extremity and Timed Up and Go (TUG) test. RESULTS: Both the hip abductor strength (effect size = 0.60) and TUG test (effect size= -0.53) in the exercise group improved significantly after the intervention. CONCLUSIONS: The results of the present study demonstrated that exercise program focusing on hip external rotator muscle was an effective intervention, especially in improving both hip abductor strength and walking ability in the acute post-THA stage. Implication for Rehabilitation After THA, in order to safely progress patients back to their desired activity level, there is a need to develop rehabilitation strategies to expedite and promote the recovery during the acute postoperative period. Exercise program focusing on hip external rotator muscle may lead to significant improvement of hip abductor muscle strength and gait ability in the acute post-THA stage.

A pilot study of regenerative therapy using controlled release of recombinant human fibroblast growth factor for patients with pre-collapse osteonecrosis of the femoral head.

PURPOSE: We evaluated the safety and clinical outcomes of a single local administration of gelatin hydrogel impregnated with recombinant human fibroblast growth factor (rhFGF)-2 for the treatment of the precollapse stage of osteonecrosis of the femoral head (ONFH). METHODS: Patients with ONFH (precollapse stage ≤2) received a single local administration of 800 µg of rhFGF-2-impregnated gelatin hydrogel and were followed up for one year. The surgery was performed using a minimally invasive technique involving a 1-cm skin incision, and walking was allowed from day one postoperatively. The primary outcomes included occurrence of adverse events and complications. The secondary outcomes included changes in the Harris hip scores, visual analog scale for pain scores, University of California, Los Angeles (UCLA) activity scores, and radiological images. RESULTS: We included ten patients, of which five experienced 14 adverse events, including one complication from spinal anesthesia. However, patients completely recovered from all adverse events. The mean clinical scores significantly improved by one year postoperatively compared with the pre-operative scores (before vs. after: visual analog score for pain, 21.2 vs. 5.3 mm; UCLA activity score, 5.5 vs. 6.6; Harris hip score, 81.0 vs. 96.9 points). There was only one case of femoral head collapse; however, this occurred in a hip with extensive necrosis. Stage progression and collapse did not occur in the other nine cases. Computed tomography confirmed bone regeneration in the femoral heads. CONCLUSIONS: Clinical application of rhFGF-2-impregnated gelatin hydrogel for patients with precollapse ONFH was feasible and safe.

Factors associated with restricted hip extension during gait in women after total hip arthroplasty.

PURPOSE: A decreased peak hip extension angle in the late stance phase is a major gait abnormality in patients with THA. The purpose of this study was to determine the relationship between peak hip extension angle during gait and functional impairments such as muscle weakness and the limitation in joint range of motion and to identify the clinical factors influencing peak hip extension angle during gait. METHODS: 67 female volunteers with THA were examined. Biomechanical gait analysis was performed to measure peak hip extension angle during gait. Maximal isometric strength of the hip and knee, passive hip extension range of motion, leg length discrepancy, and hip pain were assessed. RESULTS: Peak hip extension angle during gait significantly correlated with passive hip extension range of motion (r = 0.259), hip pain (r = -0.264), isometric strengths of the hip musculature (r = 0.278-0.491), and knee extensor (r = 0.386). Stepwise multiple regression analysis revealed that hip abductor torque (ß = 0.355, P = 0.001), hip pain (ß = -0.353, P = 0.001), and passive hip extension range of motion (ß = 0.258, P = 0.011) were significant contributors to peak hip extension angle during gait (R2 = 0.408). CONCLUSIONS: Our findings suggest that THA rehabilitation aimed at improving gait ability should focus on strengthening the hip abductors, controlling hip pain and increasing range of motion of hip extension.

Minimum 10-Year Wear Analysis of Highly Cross-Linked Polyethylene in Cementless Total Hip Arthroplasty.

Fifty-four patients (64 hips) underwent cementless total hip arthroplasty between 2000 and 2003 with a 22-mm zirconia ceramic bearing on highly cross-linked polyethylene, and were evaluated with a mean 11.9-year postoperative follow-up (range, 10-14 years). Linear wear was measured on the anteroposterior radiograph of the hip. No evidence of osteolysis and loosening was found on the final radiograph in any of the cases, and the steady-state linear wear rate was 0.017±0.018 mm/year. No significant correlation was found between the linear wear rate and age, body weight, cup inclination angle, or polyethylene thickness. Highly cross-linked polyethylene showed excellent wear resistance for >10 years when used in combination with 22-mm zirconia heads.