Risk factors for throwing elbow injuries during pitching analyzed by simulation using human musculoskeletal model in youth baseball pitchers.

BACKGROUND: Pitching mechanics are believed to be risk factors for throwing elbow injury. Thus, a prospective study of abnormal mechanics in youth baseball players is needed. This study aimed to analyze the ulnar collateral ligament during normal pitching using SIMM (Software for Interactive Musculoskeletal Modeling) for analysis and investigate the risk parameters of throwing elbow injuries in youth baseball players. We hypothesized that excessive ulnar collateral ligament force during pitching would be a risk factor for throwing elbow injuries in this population. METHODS: In this cohort study, youth baseball pitchers (aged 9-11 years) were instructed to throw a ball into a netted target. Using a SIMM musculoskeletal model, we analyzed the force of the anterior band of the anterior oblique ligament, posterior band of the anterior oblique ligament (AOL_PB), and elbow varus moment during pitching (foot contact to ball release). We calculated the integral of each force of the anterior band of the anterior oblique ligament and AOL_PB during pitching and summarized these data to establish an impulse at the medial epicondyle. Each participant was followed up for 12 months to assess the occurrence of throwing elbow injury. RESULTS: During the 12-month follow-up period, 18 pitchers (28.1%) reported throwing elbow injuries in the throwing arm. The results of this study showed that the maximum AOL_PB force and the impulse at the medial epicondyle were risk factors for throwing elbow injuries. The maximum AOL_PB force was significantly higher in the throwing elbow injury group than in the uninjured group (59.4 ± 17.8 N vs. 47.1 ± 17.5 N, P = .014). The impulse at the medial epicondyle was also significantly different (11.1 ± 4.0 N ï½¥ s in the throwing elbow injury group vs. 8.3 ± 4.4 N ï½¥ s in the uninjured group, P = .025). CONCLUSIONS: Increasing the AOL_PB force or the impulse at the medial epicondyle may increase the risk of throwing elbow injuries in youth baseball pitchers. It may be possible to reduce injury risk by focusing on ways to decrease AOL_PB load and cumulative stress on the medial epicondyle throughout the throwing motion while still maintaining high levels of ball velocity.

Patient-Reported Outcomes and Perioperative Complications of Total Hip Arthroplasty Following Joint Preservation Surgery for Hip Dysplasia.

BACKGROUND: There is growing recognition of the importance of patient-reported outcome measures and assessment of patient satisfaction in the evaluation of outcomes following surgical interventions. This study aimed to evaluate patient-reported outcomes and complication rates after total hip arthroplasty following joint preservation surgery for hip dysplasia. METHODS: Patient-reported outcomes and complication rates of 85 hips with previous joint preservation surgery (salvage group) were compared with those of 1279 hips without joint preservation surgery (primary arthroplasty group). As a patient-reported outcome measure, the Japanese Orthopedic Association Hip Disease Evaluation Questionnaire was used to evaluate the hip condition both preoperatively and 12 months postoperatively. Operative data and postoperative (within 12 months) complications were investigated. RESULTS: The salvage group had a longer operative time (56.8 vs 44.9 minutes, P < .001) and a higher total complication rate (5.9% vs 1.1%, P < .001). Additionally, the salvage group exhibited a lower degree of improvement in the visual analog scale value for satisfaction (75.1 vs 83.1 mm, P = .011), the pain and movement category scores, and the total score of the Japanese Orthopedic Association Hip Disease Evaluation Questionnaire (14.2 vs 16.2, P = .031; 13.7 vs 16.0, P = .005; and 42.3 vs 47.9, P = .007, respectively) compared with the primary arthroplasty group. CONCLUSION: This study demonstrated a lower rate of improvement in patient satisfaction and worse self-reported outcomes in the salvage group. Furthermore, these patients had a longer operative time and a higher risk of operative complications.

Cementless Tapered-Wedge Stem Length Affects the Risk of Periprosthetic Femoral Fractures in Direct Anterior Total Hip Arthroplasty.

BACKGROUND: Although the popularity of the direct anterior approach for total hip arthroplasty has increased, the femoral procedure in this approach is considered technically challenging, and one of the most frequent complications reported was periprosthetic femoral fractures. The present study aimed to identify factors for predicting the risk of periprosthetic femoral fractures after using stems with a cementless tapered-wedge design through the direct anterior approach. METHODS: We retrospectively assessed the medical records of 686 patients (851 hips) who underwent primary total hip arthroplasty using a single stem with a cementless tapered-wedge design having a short or standard length option. The direct anterior approach on a standard operating table was used for all hips. Multivariate logistic regression analysis was performed to identify the independent predictors of intraoperative and early postoperative periprosthetic fractures. RESULTS: Seventeen periprosthetic femoral fractures (2.0%) were observed, including 10 intraoperative (1.2%) and 7 postoperative (0.8%) fractures. The occurrence rate of fractures using short stems was significantly higher compared with that using standard stems. The multivariate logistic regression analysis revealed that only stem length was significantly associated with periprosthetic fractures. CONCLUSION: Our results indicate that the stem design affects the risk of periprosthetic femoral fractures.

Prospective analyses of female urinary incontinence symptoms following total hip arthroplasty.

INTRODUCTION AND HYPOTHESIS: Some patients with hip osteoarthritis report that urinary incontinence (UI) is improved following total hip arthroplasty (THA). However, the type and severity of UI remain unclear. In this study, we hypothesize that both stress urinary incontinence (SUI) and urge urinary incontinence (UUI) are improved after THA. We assess the characteristics of UI and discuss the anatomical factors related to UI and THA for improved treatment outcome. METHODS: Fifty patients with UI who underwent direct anterior-approach THA were evaluated. Type of UI was assessed using four questionnaires: Core Lower Urinary Tract Symptom Score (CLSS), Urogenital Distress Inventory Short Form (UDI-6), International Prostate Symptom Score (IPSS), and Overactive Bladder Symptom Score (OABSS). Uroflowmetry and postvoid residual urine were measured using ultrasound technology. Hip-joint function was evaluated using Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and range of motion (ROM). RESULTS: Of the 50 patients, 21 had SUI, 16 had mixed urinary incontinence (MUI), and eight had urgency urinary incontinence (UUI). In total, 36 patients were better than improved (72 %). The rate of cured and improved was 76 % for SUI, 100 % MUI, and 50 % UUI. The improvement of ROM was more significant in cured or improved patients than in stable or worse patients. CONCLUSIONS: Improvement in mild UI may be an added benefit for those undergoing THA for hip-joint disorders. These data suggest that for patients with hip-joint disorder, hip-joint treatment could prove to also be a useful treatment for UI.

Total Hip Arthroplasty after Previous Acetabular Osteotomy: Comparison of Three Types of Acetabular Osteotomy.

To compare surgical results of total hip arthroplasty (THA) following acetabular osteotomy, operative records of 13 hips following Chiari osteotomy (Chiari group), 22 hips following rotational periacetabular osteotomy (RAO; RAO group), 16 hips following shelf acetabuloplasty (Shelf group), and 2475 hips without previous osteotomy (Control group) were retrospectively reviewed. The operative time was significantly longer in the RAO group than in the Control group. Bulk bone augmentation was required more often in the Chiari and RAO groups than in the Control group. An early migration of the acetabular cup occurred in 2 hips in the RAO group. RAO made conversion to THA more complicated than did the Chiari osteotomy or the shelf acetabuloplasty.

Epidemiology of Dislocation Following Direct Anterior Total Hip Arthroplasty: A Minimum 5-Year Follow-Up Study.

BACKGROUND: The cumulative mid- to long-term risk of dislocation following total hip arthroplasty is considerably greater than has been reported in short-term studies. We retrospectively investigated the epidemiology of first-time dislocation following total hip arthroplasty using 28-mm heads through the direct anterior approach in patients with hip dysplasia who were followed up for more than 5 years. METHODS: The operative records of 871 hips in 790 consecutive patients were reviewed to determine the incidence of postoperative first-time dislocation. RESULTS: The mean follow-up duration was 7.8 (range, 5.6-11.7) years. The direct anterior approach was used for all hips. Postoperative dislocation was observed in 8 hips (0.92%) in 8 patients. First-time dislocation occurred during the first 3 weeks in 6 hips (75%). The cumulative risk of postoperative dislocation was 0.69% at 1 month, 0.80% at 1 year, and 0.93% at 5 years. One patient underwent revision surgery for recurrent dislocation within the first month due to malalignment of the cup. CONCLUSION: Our findings demonstrated that the direct anterior approach limits the time of dislocation to the very early postoperative period; that is, the risk of a first-time dislocation after the first month is considerably low. Preserving muscular structures may contribute to continuous dynamic stability of the hip, which could explain the slight increase in the cumulative risk of first-time dislocation.

Comparison of patient satisfaction after unilateral or simultaneous bilateral total hip arthroplasty through a direct anterior approach: Evaluation using the Japanese Orthopaedic Association Hip Disease Evaluation Questionnaire.

BACKGROUND: The aim of this study was to compare patients' perception of treatment outcome after unilateral or simultaneous total hip arthroplasty (THA) using the newly developed Japanese Orthopaedic Association Hip Disease Evaluation Questionnaire (JHEQ). METHODS: This study included 429 patients treated with primary THA using a direct anterior approach, namely 304 cases of in the unilateral THA (58 males and 246 females; mean age, 62.3 years) and 125 cases of in the simultaneous bilateral THA (24 males and 101 females; mean age, 58.3 years). Items for evaluation included clinical outcomes and all four aspects of the JHEQ score, namely visual analog scale (VAS), pain, movement, and mental status. RESULTS: The mean operative time per hip was 51.3 ± 19.4 min (range, 22-180 min) in unilateral group and 46.2 ± 15.1 min (range, 26-106 min) in simultaneous bilateral group. The mean operative blood loss per hip was 421.2 ml ± 232.1 ml (range, 70-1300 ml) in unilateral group and 200.8 ± 149.8 ml (range, 30-1040 ml) in simultaneous bilateral group. The total JHEQ score (pain/motion/mental status) improved from 26.5 ± 13.6 (preoperative, 10.1/6.8/9.6) to 69.4 ± 14.8 (1 year postoperatively, 25.1/20.5/23.8) in unilateral group and from 21.0 ± 8.2 (preoperative, 11.9/2.3/6.9) to 74.9 ± 9.5 (1 year postoperatively, 27.2/22.6/25.0) in simultaneous bilateral group. These results demonstrated a significant improvement before and after surgery for patients in both groups. There were not major complications such as dislocation, bone fracture, nerve palsy or symptomatic pulmonary embolism were observed. CONCLUSION: In this study, we observed greater improvement in JHEQ in patients treated with bilateral simultaneous THA than in those treated with unilateral THA. These findings demonstrated that bilateral simultaneous THA was related to high patient satisfaction as well as high safety.

Perioperative complication rate of one-stage bilateral total hip arthroplasty using the direct anterior approach.

BACKGROUND: To date, details of the surgical and clinical outcomes of one-stage bilateral total hip arthroplasty using the direct anterior approach have not been widely available. The purpose of this study was to report the perioperative blood management and investigate the perioperative complication rate of one-stage bilateral total hip arthroplasty using the direct anterior approach. METHODS: We retrospectively assessed 325 consecutive patients (650 hips) who underwent one-stage bilateral total hip arthroplasty through the direct anterior approach. RESULTS: The mean intraoperative blood loss and operating time were 412 g and 87.2 min, respectively. One patient (0.3%) required postoperative transfusions of allogeneic blood. Post-operative local major complications occurred in 6 hips (0.9%) in 6 patients, including 2 (0.3%) dislocations, 2 (0.3%) early cup migrations, and 2 (0.3%) peri-prosthetic femoral fractures. No systemic major complication was detected. CONCLUSION: We conclude that the low rate of systemic complications in this study was due to supine positioning and the minimally invasive aspect of the direct anterior approach, and that the approach is therefore a reasonable choice for one-stage bilateral THA.

Hip dysfunction-related urinary incontinence: a prospective analysis of 189 female patients undergoing total hip arthroplasty.

Patients reporting that their symptoms of urinary incontinence have decreased after total hip arthroplasty can be encountered in orthopedic practice. In this questionnaire-based study, we prospectively evaluated the symptoms of urinary incontinence before and after total hip arthroplasty. The International Consultation on Incontinence Questionnaire-Short Form was used to prospectively evaluate these symptoms in 189 consecutive female patients undergoing total hip arthroplasty. The patients were asked to fill in a questionnaire before and 3 months after surgery. A decrease in the International Consultation on Incontinence Questionnaire-Short Form score of ≥1 point was defined as an improvement, whereas an increase of ≥1 point was defined as worsening. A total of 81 (43%) patients reported urinary incontinence before total hip arthroplasty. At 3 months after surgery, symptoms of urinary incontinence were improved in 64% of these patients, remained unchanged in 32% and worsened in 4%. Mean International Consultation on Incontinence Questionnaire-Short Form score in patients with urinary incontinence before surgery significantly improved from 6.0 to 3.5 (P = 0.0002). These findings suggest a relationship between hip joint function and pelvic floor function, and consequently a hip dysfunction-related urinary incontinence.

An anatomic study of the impressions on the greater trochanter: bony geometry indicates the alignment of the short external rotator muscles.

In this study, 44 hip regions from 25 embalmed cadavers were dissected to identify the bony landmarks on the greater trochanter, which indicate the individual short external rotator muscle insertions. Micro-computed tomography (micro-CT) images were obtained to identify the bony impressions on the greater trochanter. Then, the soft tissues were removed and their insertions were identified to assess correlation with micro-CT images. Bony landmarks indicating the insertions and the running course of the piriformis muscle, the obturator internus muscle, and the obturator externus muscle were identified on the greater trochanter in all specimens. These findings could be helpful for preserving muscles during capsular release in the anterior approach because the alignment of the short external rotator muscles can be estimated preoperatively using CT images.

Total hip arthroplasty with subtrochanteric shortening osteotomy for Crowe grade 4 dysplasia using the direct anterior approach.

Between September 2006 and June 2011, 1521 primary total hip arthroplasties were performed using the direct anterior approach on a standard surgical table. In 12 hips, subtrochanteric shortening osteotomy was required. Full weight bearing was allowed 1 week after surgery. The mean follow-up period was 3.7 years. All patients limped preoperatively, but no patient had a positive Trendelenburg or Duchenne limp at the last follow-up. On the basis of our findings, we believe that the direct anterior approach is a safe and reproducible technique for total hip arthroplasty with subtrochanteric shortening osteotomy in the case of Crowe grade 4 dysplasia. It allows the steady recovery of the abductor muscles, a shorter period to postoperative partial weight bearing, and elimination of limping.

Association Between Anterior Hip Capsule Thickening and Sagittal Pelvic Alignment Among Patients With Developmental Dysplasia of the Hip.

INTRODUCTION: The pathogenesis and pathology of secondary osteoarthritis (OA) of the hip, which is mainly due to developmental dysplasia of the hip (DDH), in Japan are obscure. There are some reports on the thickening of the hip capsule, but the relationship between the thickness of the hip capsule and the pelvic alignment due to hip deformity is not well known. This research investigated whether the capsular thickness of female DDH patients was related to pelvic alignment. METHODS: This single-center cross-sectional study included female patients aged 50-79 years (n=13) who had undergone primary total hip arthroplasty (THA) due to secondary hip OA with a background of DDH. The part of the hip capsule including the iliofemoral ligament was resected and measured directly with a digital caliper. The Sharp angle, center-edge (CE) angle, sacral slope (SS), pelvic tilt (PT), pelvic incidence (PI), and lumbar lordosis angle (LLA) were measured with an X-ray image to investigate the relationship between the capsular thickness and the pelvic posture. RESULTS: Pearson's correlation coefficient showed a negative correlation between hip capsular thickness and Sharp angle (r=-0.57, p>0.05). No significant correlation was found between the thickness of the hip capsule and the sagittal X-ray parameters including SS, PT, PI, LLA, and CE angle in the coronal plane. CONCLUSION: The thickness of the hip capsule is moderately associated with the Sharp angle on the coronal plane. The results of this study suggest that the thickness of the joint capsule does not necessarily relate to the degenerative process among patients with DDH and the process can be complex to apply two-dimensional postural indices for the explanation.

Completion of the full-length genome sequence of human parainfluenza virus types 4A and 4B: sequence analysis of the large protein genes and gene start, intergenic and end sequences.

We have already reported the nucleotide sequences of the NP, P/V, M, F and HN genes of human parainfluenza virus type 4A (hPIV-4A) and type 4B (hPIV-4B). Here, we have determined the sequences of the L protein genes as well as the gene start, intergenic and end sequences, thereby completing the full-length genome sequence of hPIV-4A and 4B. hPIV-4A and 4B have 17,052 and 17,304 nucleotides, respectively. The end sequence of hPIV-4, especially 4B, was extraordinarily long. In a comparison with members of the genus Rubulavirus, the hPIV-4 L proteins were closely related to those of mumps virus (MUV) and hPIV-2, less closely related to those of Menangle virus and Tioman virus, and more distantly related to those of Mapuera virus and porcine rubulavirus.

A Case of Cementless Impaction Bone Graft in a Revision Total Hip Arthroplasty Requiring Calcar Reconstruction.

INTRODUCTION: In cases of bone deficiency or osteoporosis, and especially in revision cases, there were only two options for treatment until the impaction bone graft procedure was proposed. These were cemented or cementless femoral prosthesis. In the early 1990s, the use of impaction bone graft with a cemented mantle had gained popularity and had proven to be clinically effective. In Germany, a cementless impaction bone graft procedure using Corail® (DePuy Synthes) stems was devised, and functional scores were similar to conventional cemented Impaction bone grafts. Case presentation. A 48-year-old man presented with femur loosening of a reamed bipolar arthroplasty performed in 1990. The patient was treated with a cementless impaction bone graft using a Corail® (DePuy Synthes) stem in the femur in revision THA surgery, and the calcar was reconstructed by allograft. RESULTS: At five years, the calcar allograft united with the host bone, and the femoral component showed no subsidence. CONCLUSION: Calcar reconstruction with a strut allograft, aimed at preventing sinking of the stem was key in this operation. Surgical indication for femoral cementless impaction bone graft should be for loosened femoral prosthesis in a type II Paprosky classification, where only the cortical bone of the isthmus is partially affected, cortical thinning does not exist, and it is mechanically strong enough for the allograft tip impaction. The procedure was safely feasible through the direct anterior approach.

Radiographic factors to predict operation time of direct anterior total hip arthroplasty for dysplastic hips.

BACKGROUND: This study aimed to identify radiographic factors that could predict surgical difficulty in direct anterior total hip arthroplasty (THA) for dysplastic hips. PATIENTS AND METHODS: The clinical records of 160 patients (204 hips) who underwent primary THA for the treatment of developmental dysplasia of the hip were retrospectively investigated. All THAs were performed through a direct anterior approach by a single surgeon. A multiple regression analysis was developed to identify the independent predictor of operation time, including variables such as age, sex, height, body mass index (BMI), the use of bone cement, previous hip surgery, and radiographic references, including the pelvic horizontal to vertical ratio, the extent of proximal and horizontal migration of the femoral head, flatness of the femoral head, and the vertical distance between the tips of the greater trochanter and the femoral head. RESULTS: A multiple regression analysis revealed that as radiographic factors, proximal migration of the femoral head, and lower position of the femoral head related to the greater trochanter were significantly associated with longer operation time. In addition, our results revealed that younger age, male sex, height, high BMI, cement use, and previous hip surgery were also significantly associated with longer operation time. CONCLUSIONS: Our findings indicate that proximal migration of the femoral head and high-riding greater trochanter are isolated radiographic predictors of the longer operation time of direct anterior THA for dysplastic hips.

Usefulness of an Accelerometer-Based Portable Navigation System for Total Knee Arthroplasty: A Multicenter Prospective Randomized Controlled Trial.

BACKGROUND: An accelerometer-based portable navigation system was recently introduced to improve prosthetic alignment during total knee arthroplasty (TKA). The purpose of this multicenter prospective randomized controlled trial (RCT) was to evaluate the effects of this accelerometer-based portable navigation system for achieving more accurate alignment during TKA in the clinical setting. METHODS: One hundred patients with primary varus osteoarthritis of the knee were enrolled in this prospective RCT conducted in 5 hospitals. A navigation system was utilized in 50 patients (navigation group), and a conventional intramedullary femoral guide and an extramedullary tibial guide were utilized in 50 patients (conventional group). At 6 months postoperatively, weight-bearing radiographs were obtained of the whole operative leg. An experienced surgeon who was blinded to the treatment assignments then measured the alignment to 1 decimal place with use of computer software. Power analysis showed that 41 knees were required in each group. RESULTS: There were no complications as a result of the use of the accelerometer-based portable navigation system. Postoperative radiographs were obtained in 45 patients from each group. There were no significant differences in sex, age, height, body weight, body mass index, preoperative femorotibial angle, and operative time between groups. The absolute differences of the femoral prosthesis (p = 0.01), tibial prosthesis (p < 0.01), and hip-knee-ankle angle (p < 0.01) from a neutral mechanical axis were less in the navigation group compared with those in the conventional group. Alignment outliers (>2° away from the neutral mechanical axis) of the tibial prosthesis and hip-knee-ankle angle were less in the navigation group (9% and 27%, respectively) compared with those in the conventional group (31% and 49%; p = 0.01 and p = 0.04, respectively). CONCLUSIONS: To our knowledge, this is the first multicenter prospective RCT to evaluate an accelerometer-based portable navigation system. An accelerometer-based portable navigation system provides more accurate prosthetic and limb alignment in the coronal plane than conventional techniques, without extended operative time or an increased rate of complications. The results of this study may help orthopaedic surgeons decide whether or not to use an accelerometer-based portable navigation system. LEVEL OF EVIDENCE: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Improvement of the Gap Adjustment in Total Knee Arthroplasty Using the Posterior Condylar Pre-cut Technique.

To provide adequate gaps for knee extension and flexion during total knee arthroplasty, a femoral component placement decreases the extension gap because the posterior capsule tension increases against the protrusion of the posterior part of the femoral component. We thought that the influence of this component on the extension gap depends on the amount of posterior femoral bone resection and the thickness of the posterior femoral components. We hypothesized that less bone resection and a thinner posterior part of the femoral component might avoid these problems. To verify our hypothesis, a 4-mm posterior condylar pre-cut technique and temporary femoral components that were 8 and 4 mm thick in the distal and posterior parts, respectively, were made using the FINE Total Knee System (Teijin-Nakashima Medical Co., Okayama, Japan). After bone resection, the pre-cut trial component was set to the femur, and the bone and component setting gaps were estimated. Seventy-one patients (98 knees) were investigated. The average bone gaps were 17.2/15.0 mm (extension/flexion, after pre-cut), 18.3/16.3 mm (after soft tissue release), and 8.7/12.2 mm (after pre-cut trial setting). After pre-cut trial setting, the extension gap decreased significantly; the amount was 1.6 mm (0-4 mm) on average (p < 0.0001), whereas a change of 3 mm or more occurred in 15 knees (15.3%), which could be problematic. The degree of these changes after component setting could be reduced by using the posterior femoral condylar pre-cut technique. However, the problem of component setting on the extension gap was not completely resolved. To precisely project the intraoperative gap to the ultimate postoperative gap, a posterior small protrusion device such as a pre-cut trial with the pre-cut technique would be necessary.

Acetabular revision using a Kerboull-type reinforcement device through direct anterior approach.

BACKGROUND: The direct anterior approach has gained popularity in total hip arthroplasty (THA) over the past decade. However, there are few reports that describe the use of this approach for cases of complex revision. The purpose of this study was to report the surgical procedure and early clinical results of acetabular revision in the presence of bone defects using a Kerboull-type reinforcement device through the direct anterior approach. METHODS: Eleven patients who had undergone acetabular reconstruction using a Kerboull-type reinforcement device for aseptic or septic loosening bone defects were enrolled. All procedures were performed using the direct anterior approach on a standard operating table. The mean age was 71.8 years, the mean period from initial surgery to revision THA was 14.5 years, and the mean follow-up period was 19.8 months. RESULTS: The Kerboull-type acetabular reinforcement device with cemented cup combined with allogenic femoral head bone grafts was used in all hips. The mean operative time and intraoperative blood loss were 148 min and 743 g, respectively. None of the patients required allogeneic blood transfusion. One patient required revision surgery 11 months postoperatively because of device displacement. No other major or minor orthopedic complications were observed. CONCLUSION: The direct anterior approach allows for less invasive acetabular reconstruction using a Kerboull-type reinforcement device.

Natural Remission of Major Periprosthetic Osteolysis following Total Hip Arthroplasty with Metal-on-Metal Bearings.

The natural course of adverse events following the use of metal-on-metal (MoM) bearings in total hip arthroplasty (THA) is not well known. In this article, we report the case of a patient with asymptomatic major acetabular osteolysis following MoM THA that diminished gradually without any surgical intervention. A 58-year-old male underwent one-stage bilateral MoM THA for bilateral osteoarthritis. Four years after THA, major acetabular osteolysis developed in his right hip without any local or systemic symptoms. The patient underwent a careful radiographic and clinical observation without any surgical intervention because he did not want to undergo revision surgery. The lesion gradually diminished after 7 years, and most of the osteolytic area was replaced by newly formed bone at 10 years. He continues to be followed with no evidence of cup loosening or migration. Our observation suggests that a periprosthetic osteolytic change related to the use of MoM bearings has the potential for natural remission.

Total hip arthroplasty through a direct anterior approach for fused hips.

INTRODUCTION: Conversion to total hip arthroplasty (THA) from a fused hip is a challenging procedure because of the technical difficulties involved. Here we report the surgical procedure and the early clinical outcome of conversion THA from a fused hip through a direct anterior approach. METHODS: 9 consecutive THAs following hip fusion were performed in 9 patients. Of these, 6 patients had undergone surgical hip fusion and 3 patients had nonsurgical fusion. RESULTS: The mean time interval between fusion and THA was 29.7 years. The mean follow-up period was 5.2 years. All THAs were performed using a direct anterior approach on a standard surgical table. The mean operative time was 68.7 minutes. The mean intraoperative blood loss was 377 g. All acetabular components were placed within Lewinnek's safe zone. The mean Japanese Orthopaedic Hip Score significantly improved from 54.0 to 73.2. One early anterior dislocation occurred and was treated conservatively. No revision surgery was required. CONCLUSIONS: The direct anterior approach allows for an accurate and less invasive implantation of the total hip components.