Background

The indication of unicompartmental knee arthroplasty (UKA) for end-stage osteoarthritis (OA) remains controversial. This study aimed to investigate patient reported outcomes (PROs) of UKA in patients with severe varus deformity of the knee and compare the results with those of total knee arthroplasty (TKA) at mid-term follow up.

1.

Introduction

Metal-on-metal (MOM) hip joints have regained a favor in arthroplasty since they own excellent wear resistance. In this study, wear tests by using a hip joint simulator were conducted with MOM bearings of specified 40 mm femoral heads. The influence of clearance on the wear behavior was investigated. Furthermore, an optimized radial clearance was estimated by lubricant film thickness and contact pressure analysis.

Rapid manufacturing using laser beam and/or electron beam has been applied to fabrication of artificial hip and knee joints in quite recent years. In the electron beam melting (EBM) method, the high energy electron beam effectively melts the metal powder without creating flaws such as porosities or inclusions of oxide particles during building. Thus it is found that EBM technique for rapid manufacturing of artificial hip and knee joints processes a higher possibility as the next-generation methodology for fabrication of the medical devices such as hip and knee joints. In the present study, we focus on the EBM technique. The microstructures and mechanical properties of Co-29Cr-6Mo alloy with C and N additions, produced by using EBM method, were studied using X-ray diffraction, electron back scatter diffraction, transmission electron microscope (TEM), Vickers hardness tests, and tensile tests, focusing on the influences on the build direction and the various heat treatments after build. It is found that the microstructures for the as built specimens were changed from columnar (Fig. 1a) to eqiaxed grain structure (Fig. 1c) with average grain size of approximately 10–20 μm due to the heat treatment employing the reverse transformation from a lamellar (hcp + Cr₂N) phase to an fcc phase. Our results will contribute to the development of biomedical Ni-free Co–Cr–Mo–N-C alloys, produced by EBM method, with refined grain size and good mechanical properties, without requiring any hot workings.

Fig. 1 Inverse pole figure (IPF) maps of microstructure of samples produced by EBM method, taken by EBSD. (a) as-built, (b) after aging treatment, (c) after reverse transformation heat treatment (RT-HT).

Co-Cr-Mo alloys represent the most important category of metallic biomaterial for surgical implant applications. Recently, Chiba et al. developed a new type of bio- medical Co based alloy of Co-29Cr-6Mo-0.14N alloy. In this alloy design, the content of N is intended to be controlled to obtain the microstructure consisting of ? single phase. This developed alloy exhibits the lower stacking energy as compared to that of the practical bio-medical Co-Ni based alloy, thereby resulting in the deformation behavior accompanied by strain induced e martensitic transformation.

In this work, the damage process leading to fracture during tensile testing of a biomedical grade Co-29Cr-6Mo-0.14N alloy was analyzed on the basis of three-dimensional damage observation using X-ray tomography and electron backscattered diffraction of the fractured specimen. Initial cracking occurred at grain and annealing twin boundaries, where strain concentrates due to impingement of e-hcp plates formed through strain induced martensitic transformation (SIMT). Crack propagated along interface between ?-fcc matrix and SIMTed e-hcp on {111}, resulting in the occurrence of a quasi-cleavage fracture.

Co-Cr-Mo alloys are widely used for biomedical implant materials such as artificial hip and knee joints owing to their excellent corrosion and wear resistance as well as higher strengthening properties. However, the alloys exhibits sever brittle nature under an as-cast condition. It is generally recognized that refinement of the grain size of the metallic materials by means of hot-forging processes is an effective methodology to strengthen the alloy. Dynamic recrystallization (DRX) is an effective metallurgical process for grain refinement during hot deformation. However, there are few studies on the hot deformation behavior of Co-Cr-Mo alloy, especially grain refinement through DRX. In the present study, DRX and grain refinement during hot deformation of Co-29Cr-6Mo alloy has been investigated under various conditions such as deformation temperature and strain rate.

Although at strain of 5% hot deformed microstructure maintains the original grains, the grain size decreases with increasing the strain and exhibits the average grain size of approximately 2μm at strain of 60%. Ultra fine grained microstructure with the grain size of approximately 0.5 μm was obtained under deformation at a 1323 K at a strain rate of 0.1s^-1. The original grains are broken up into different grains due to the new boundary formation not only near the initial boundaries but also in the interior of the grains at large strain. This grain fragmentation without bulging in the course of hot deformation is associated with considerably low stacking fault energy (SFE) of the Co-29Cr-6Mo alloy even at the deformation temperatures.

Introduction

Although osteonecrosis of the femoral head has been observed in young adult patients with autoimmune diseases such as SLE and MCTD that are treated by corticosteroids, the pathogenesis of the osteonecrosis remains unclear. We established a rat model with osteonecrosis of the femoral head by injecting lipopolysaccharide (LPS) and corticosteroid, and assessed consequences of the histopathological alteration of the femoral head, the systemic immune response, and the lipid synthesis.

Purpose: Despite advances in surgical technique, neurological injury remains a potentially devastating complication of spinal deformity correction surgery. The purpose of the study is to describe surgical and patient factors associated with “electrophysiologic (EP) events” and neurogenic deficits.

Method: A retrospective chart review, looking at “EP events” during surgery, was conducted on 162 patients who received surgical treatment of their pediatric spine deformity from 1999 to 2004.

Results: Ninety three percent of cases (n=151) were successfully monitored by either somatosensory evoked potential (SEP) or motor evoked potential (MEP) monitoring. All three neurologic deficits that occurred in this study cases were successfully detected by EP monitoring (0.02%, p=.002). In those 151 cases that were successfully monitored, “EP events” were occured in twenty (13.2%) cases. The most common cause was systemic change (45%) and curve correction (40%). In those 20 cases, when corrective actions were made (n=15) “EP events” reversed to baseline values in all cases. When no corrective actions were taken (N=5) there was no reversals of “EP events” to baseline. Patients with kyphosis had a trend toward significantly higher rates of “EP events” (p=.174) and patients who had cardiopulmonary comorbidities had significantly higher rates of “EP events” (p=.007).

Conclusion: Consistent with existing literature, the EP monitoring was successful in the vast majority of deformity surgeries. “EP events” were able to be reversed with corrective action and to predict neurologic deficits. Our study found that patients with kyphosis and/or cardiopulmonary comorbidities have higher risk of significant “EP events” during the surgeries.

Purpose: To describe the clinical outcomes of adolescent patients, treated with hip distraction arthroplasty for avascular necrosis (AVN) of the femoral head. Outcomes were examined in order to better understand the usefulness and indications of performing hip arthrodia-stasis in this patient population.

Method: Retrospective review was performed on thirty-one hips with femoral head AVN treated with hip distraction arthroplasty. Mean age at treatment was 14.2 years. Preoperative and follow-up pain, and physical limitations, as well as follow-up range of motion (ROM) were assessed.

Results: Follow up assessment was obtained at 18.3 years of age. Time of follow up was 55.3 months after distraction. The etiologies of AVN were: 11 Slipped Capital Femoral Epyphysis (SCFE); 5 Idiopathic AVN; 3 with hip dysplasia; and 12 others. There was a significant difference in pain preoperatively and postoperatively (p< .001), the majority of patients (79.5%, n=23) had less pain after the treatment. Multivariate regression model demonstrated that patients with SCFE were likely to have less improvement in pain than patients with other etiologies (odds ratio: 24.8; p=.035). All patients had activity limitations before the treatment; at the postoperative assessment more than half of our patients (n=15) reported no limitations in their activities. Nine patients had minor complications with the fixator. At follow up, 5 (16.1 %) patients converted to total hip replacement or arthrodesis.

Conclusion: Hip distraction arthroplasty in adolescent patients with symptomatic AVN reduces the amount of pain and limitation in daily activities, at a follow up of 4.6 years. Arthrodiastasis is not the final solution to AVN, with longer follow up patient’s symptomatology increases. Patients with AVN secondary to SCFE do not beneficiate of this procedure as much as other patients do. Hip distraction is a safe and appropriate procedure to perform in these patients. The procedure might be able to delay definitive surgical procedures at an early age, restoring function and improving the patient s quality of life.

Purpose: The current literature lacks a truly comprehensive examination of the use of a valgus osteotomy to treat osteonecrosis of the femoral head and Perthes disease in the pediatric and adolescent population. Owing to the severity of the pathology, a retrospective examination of the success of valgus osteotomies in treating avascular necrosis and Perthes disease in children and adolescents is warranted.

Method: Twenty-four patients with diagnosis of osteo-necrosis of the femoral head or Perthes disease treated between 1995 and 2007 with a proximal femoral valgus osteotomy were identified. The causes of avascular necrosis were Perthes (N=14, 60.9%), slipped capital femoral epiphyses, (N=4, 17.4%), femoral neck fracture (N=2, 8.7%), hip septic arthritis (N=2, 8.7%) and developmental delays and idiopathic osteonecrosis (N=1, 4.3%). The average age of receiving a femoral valgus osteotomy was 10± 3.6 years. The average age at follow-up was 12.2± 4 years, mean time of follow-up from the initial valgus osteotomy to last assessment was 23± 15.3 months.

Results: Postoperative pain improved significantly compared to preoperative pain (p=.002). Seventy five percent of patients (n=9) who had limitations in their daily activities preoperatively reported that they no longer experienced them after the treatment. External rotation (p=.005) and abduction (p=.003) improved significantly at follow up. Postoperative Ficat & Arlet classification was significantly better when compared to the classification before valgus osteotomy (p=0.007). Univariate analysis showed that sixty percent of patients (n=6) who had Perthes had improved in their Ficat & Arlet stage whereas one (14.3%) patient with a different diagnosis improved (p=.082). Complications from the surgery were reported in 5 of the 23 (21.7%) cases.

Conclusion: The results of this study suggest that proximal femoral valgus osteotomy is a safe and effective treatment method for osteonecrosis of the femoral head in the pediatric population. Perthes patients improved their femoral head shape more than all other etiologies; there was a trend toward statistical significance in this change. Proximal femoral valgus osteotomy may improve pain and activity limitations in children with osteonecrosis of the femoral head. It is also effective at improving range of motion and femoral head x-ray appearance of the femoral head for these children.

The purpose of this study was to investigate the effect of knee flexion contracture on trunk kinematics.

Ten healthy old women, averaged sixty-two years, participated in this study. Subjects were tested at our laboratory with use of gait analysis system which consisted of eight retro-reflective markers (placed at bilateral acromion, anterior and posterior superior iliac spine, and iliaccrest), and five cameras. Unilateral (only right side) knee flexion contractures of zero, fifteen, and thirty degrees were simulated with a hard brace. All subjects performed walking trials at their preferred speed with or without simulation. First, level walking was measured without simulation, and then, with simulation at zero, fifteen and thirty degrees of flexion in order. Walking trials without brace was used as control. We evaluated walking velocity (m/s) and trunk kinematics (degrees). In the coronal plane, shoulder-pelvis bending angle was defined as the angle between shoulder girdle line and pelvic line. In the sagittal plane, anterior inclination of the trunk was defined by the slope linked right acromion and iliac crest, and anterior inclination of the pelvis was defined by the slope linked right superior anterior iliac spine and right superior posterior iliac spine. Shoulder-pelvis rotation angle was defined as the angle between shoulder girdle line and pelvic line in the axial plane. Maximum values were calculated.

Walking velocity was significantly decreased at thirty degrees contracture (1.19 at controls, 0.98 at thirty degrees contracture). In the coronal plane, trunk significantly tilted leftward rather (4.5) than rightward (1.8) at thirty degrees contracture. In the sagittal plane, trunk anterior inclination significantly increased at thirty degrees contracture (0.1 at controls, 3.1 at thirty degrees contracture). However, pelvic anterior inclination was similar. In the axial plane, trunk significantly rotated rightward (6.7) rather than leftward (4.3) at thirty degrees contracture.

Knee flexion contracture significantly influences physiological trunk kinematics in each plane. In particular, lateral bending to the contracture side was restricted, and this fact indicated that the lumbar spine may bend convexly to knee contracture side. These facts may result in Knee-Spine Syndrome.

Purpose: The purpose of this study was to investigate the relationship between knee flexion contracture and spinal alignment.

Methods: Ten healthy women (mean age 62) participated in this study. Subjects were examined with posture analysis system, using twelve retro-reflective markers (placed at bilateral acromion, bilateral anterior and posterior superior iliac spine, iliaccrest, greater trochanter, lateral knee joint, lateral malleolus, lateral calcaneus, and fifth metatarsal head), five cameras and a force plate. Unilateral (only right side) knee flexion contractures were simulated by using a hard brace at 0, 15 and 30 degrees. First, relaxed standing was measured without simulation, and then the same measurement was performed with each simulation. The posture without brace was used as control. The shoulder tilting angle was defined by the height difference in right and left acromions. The pelvic tilting angle was defined by the height difference in right and left superior posterior iliac spines. The anterior-bent of the trunk was defined by the slope linked right acromion and right iliac crest. The posterior-bent of the pelvis was defined by the slope linked right superior anterior iliac spine and right superior posterior iliac spine. Knee resultant force (% body weight) was calculated by using inverse dynamics technique.

Results: When contracture angle increased, the trunk was significantly tilted leftward (1.4 degrees at 30 degrees contracture), and the pelvis was significantly tilted rightward (1.8 degrees at 30 degrees contracture). In anterior-bent of the trunk, no significant difference was detected. The posterior-bent of the pelvis was significantly increased (1.5 degrees at 30 degrees contracture). The severer the right knee contracture, the smaller the right knee resultant force (41.5 at controls, 28.7 at 30 degrees contracture) and the larger the left knee resultant force (40.2 at controls, 59.9 at 30 degrees contracture).

Conclusions: This study showed the influence of knee flexion contracture not only in the sagittal plane, as the previous study reported, but also in the coronal plane. Severe unilateral knee flexion contracture can cause the lumbar spine bent convexly to the contracture side. This may result in Knee-Spine Syndrome.

The outcomes of various operative methods for osteochondritis dissecans of the femoral condyles were reviewed, and choice of these operative methods were discussed.

Twenty-four cases (19 males and 5 females) which underwent operative treatments were reviewed. The operative methods included drilling, repositioning and fixation of the osteochodral fragment, and bone graft or osteochondral graft. The minimum follow-up period was two years. The medial femoral condyle was involved in 17 cases, and the lateral, in seven. Lateral discoid meniscus or meniscal injury was combined in all the 7 cases in the lateral. The operative methods were decided from the condition of the cartilage. Drilling was performed in cases with no or minimal cartilage damages (10 cases). Repositioning (if required) and fixation of the fragment using absorbable pins was carried out in cases with a partial or total fragmentation (7 cases). Bone graft or osteochondral graft was performed when the original site was already degenerated (7 cases). Partial meniscectomy was added when the meniscal injury was combined.

In patients who received drilling, the lesion healed radiographically in all the cases and they complained of no or minimal symptoms. In patients who received the fragment fixation, re-union of the fragment was observed in 71% and the clinical outcomes were satisfactory in most of the cases. In patients who received bone graft or osteochondral graft, although union of the graft was observed in all the cases radiographically, 71% of the patients complained of residual pain.

From the results, drilling is sufficient if the cartilage surface is not damaged. When the fragmentation occurred already, the fragment should be repositioned and fixed to the original site before degenerated, as its clinical symptoms were much better than those with bone graft or osteochondral graft.