Aims

Spontaneous osteonecrosis of the knee (SONK) mainly affects the medial femoral condyle, would be a good indication for UKA. The primary aim of this study was to assess the clinical, functional and radiographic outcomes at middle to long-term follow-up, of a consecutive series of fifty UKA used for the treatment of SONK. The secondary aim was to assess the volume of necrotic bone and determine if this influenced the outcome.

[Purpose]

There have been only a few reports about the efficacy of postoperative cryotherapy following total hip arthroplasty (THA), and past studies have described that local cooling is efficacy for pain relief. The purpose of this study is whether the continuous local cooling following THA is effective for pain relief and the reduction of blood loss, swelling, and the duration of hospital stay.

[Introduction]

Surgical-site-infections (SSI) prolong hospital stay, and they are leading nosocomial cause of morbidity and a source of excess cost. Recently, a waterless hand-rubbing protocol containing aqueous 1% chlorhexidine gluconate was developed before surgery, but there is no literature in orthopaedic surgery. The aim was to compare the SSI rates between waterless hand-rubbing and traditional hand-scrubbing protocol.

Introduction

The purpose of this study was to examine if Sugioka's transtrochanteric rotational osteotomy (TRO) of the femoral head could be a valid option in treating idiopathic osteonecrosis of the femoral head.

Introduction

Osteonecrosis of the femoral head (ONFH) is one of the most serious complications associated with corticosteroid therapy. In patients with ONFH, collapse of the femoral head often occurs and causes severe hip pain and impaired hip joint function. Despite the widely spread use of corticosteroids for treating various diseases and a known association between prevalence of ONFH and daily dose of corticosteroids, the pathomechanism for the development of ONFH has not been identified. Since hepatic cytochrome P4503A (CYP3A) is a predominant enzyme responsible for metabolizing corticosteroids and its activities varies more than 10-fold, low hepatic CYP3A activity leads to a remarkable increase of corticosteroid levels and its effect. We have previously reported that hepatic CYP3A levels are significantly lower in patients with corticosteroid-induced ONFH than that in control patients and patients with alcohol-related ONFH and that hepatic CYP3A activity inversely correlated with the incidence of osteonecrosis and extent of the necrotic area caused by the same dose of corticosteroids in a rabbit model, suggesting possible prevention of the corticosteroid-induced osteonecrosis by adjusting corticosteroid dose based on the level of individual hepatic CYP3A activity prior to corticosteroid therapy. To examine hepatic CYP3A activity, measuring clearance of administrated midazolam (MDZ) is a reliable method, as shown by the significant correlations between the clearance of midazolam and hepatic CYP3A levels measured by biopsy and the clearance of other CYP3A-specific substrates. However, the method is invasive and time consuming for measuring clearance of administrated MDZ, needing multiple blood samplings over half a day for each subject. The aim of this study was to develop the simple, safe and noninvasive methods for measuring the level of hepatic CYP3A activity, which is applicable to prevent the occurrence of corticosteroid-induced osteonecrosis prior to corticosteroid therapy.

The introduction of porous tantalum metal (Trabecular Metal; Zimmer, Warsaw, IN) for acetabular component fixation in total hip arthroplasty has shown optimum fixation qualities and “gap filling” effect. Recently, trabecular metal was introduced in tibial component for total knee prosthesis, however its effect on the bone mineral density (BMD) was not reported. The purpose of this study was to compare the BMD of proximal part of the tibia between trabecular metal and another cemented tibial component.

31 knees receiving trabecular metal tibial component and 33 knees receiving cemented tibial component (PFC Sigma RP, Depuy, Warsaw, IN) had dual energy x-ray absorptiometry (DEXA) scans at preoperatively and 3 weeks, 3, 6, 12, 18, 24 months post-operatively. To assess peri-prosthetic BMD, three regions of interest (ROI) were measured for each case. They were medial aspect (ROI 1), center aspect (ROI 2) and lateral aspect (ROI 3) of tibia. Average follow up period was 1.8 (range: 1.5 to 2) years. In both groups, BMD in tibia decrease postoperatively. Comparing postoperative decrease of BMD in lateral aspect of tibia (ROI 3) between both groups, it was significantly less in trabecular metal component (−0.09 g/cm2 +/−0.27) than cemented tibial component (−0.31 g/cm2 +/− 0.21) (p=0.0007).

We conclude that trabecular metal tibial component showed a favorable effect on BMD of proximal part of the tibia after total knee arthroplsaty.

Cup orientation of total hip arthroplasty (THA) is critical for dislocation, range of motion, polyethylene wear, pelvic osteolysis, and component migration. But, substantial error under manual technique has been reported. Therefore, various navigation systems were introduced to reduce outliers. CT based navigation (CTN) was reported to reduce outliers in cup orientation. Recently, a noble technique, fluoroscopy-CT-based navigation (FCTN), has recently been developed using 2D-3D matching technique. Because of much less registration points, FCTN might be friendly to MIS THA and cases with sever bone deformity. Between October 2006 and April 2008, 33 THAs were performed through MIS approach with navigations.

We prospectively randomized those into two groups, CTN and FCTN groups. We implanted cementless hemispherical cups in 18 hips using CTN (VectorVision CT Hip 3.1) and in 15 hips using FCTN (VectorVision CT Hip 3.5). For all the patients, volumetric post-operative CT scan was performed to measure 3D cup orientation. using 3D image-processing software (JMM, Japan). The difference from target angles of anteversion was 2.7 ± 2.4 degrees in FCTN group, and 12.1 ± 5.7 degrees in CTN group (p < 0.001). The absolute value of difference from target angles of inclination was 2.7 ± 2.4 degrees in FCTN group, and 6.5 ± 4.5 degrees in CTN group (p = 0.006). FCTN does not need surface registration around acetabulum, which is great advantage to MIS THA. Our study clearly showed that FCTN significantly improved a cup orientation to CTN.

Highly closslinked polyethylene has been developed to reduce polyethylene wear and to expect the longevity of THA. In daily activity of patients, total hip prostheses repeatedly suffer impact loading. However, the mechanical properties, especially impact load transmission, are not well investigated and the viscoelasticity might influence the loosening of cemented all-polyethylene cup. In this study, the impact load transmission through the complex of polyethylene cup, ceramic ball and metallic femoral stem was investigated.

Impact compressive tests on the complex were performed using Hopkinson pressure bar apparatus. Conventional and highly crosslinked polyethylene cups of three different sizes (40mm, 50mm, 56mm)were compared. The impact load was applied either from the cup or from the stem. The impact load transmission ratio (ILTR) i.e. the ratio of the magnitude of transmitted load to that of incident one was investigated. The loading pulse profiles were theoretically calculated based on the one dimensional elastic wave propagation theory and were compared with experimental results.

The ILTR was independent of the cup size in all experimental conditions. When the impact load was applied from the cup, the ILTR was not different between two types of polyethylene. On the other hand, when the impact load was applied from the stem, the ratio was greater than the previous loading condition, while the ratio of crosslinked polyethylene was significantly lower than that of conventional one (p < 0.05). The theoretically predicted stress pulse profiles were well correlated to the experimental ones.

The lower ILTR in highly crosslinked polyethylene is considered to be due to lower stiffness. These mechanical properties increase the deformity of the cup and may cause the loosening of the cup. These results indicated that the ILTR was not different among cup sizes, while the ratio was significantly affected by the loading conditions and the type of polyethylene.

Highly crosslinked polyethylene has been developed to reduce polyethylene wear and to expect the longevity of THA. In daily activity of patients, total hip prostheses repeatedly suffer impact loading. However, the mechanical properties, especially impact load transmission, are not well investigated and the viscoelasticity might influence the loosening of cemented all-polyethylene cup. In this study, the impact load transmission through the complex of polyethylene cup, ceramic ball and metallic femoral stem was investigated.

Impact compressive tests on the complex were performed using Hopkinson pressure bar apparatus. Conventional and highly crosslinked polyethylene cups of three different sizes (40mm, 50mm, 56mm) were compared. The impact load was applied either from the cup or from the stem. The impact load transmission ratio (ILTR) i.e. the ratio of the magnitude of transmitted load to that of incident one was investigated. The loading pulse profiles were theoretically calculated based on the one dimensional elastic wave propagation theory and were compared with experimental results.

The ILTR was independent of the cup size in all experimental conditions. When the impact load was applied from the cup, the ILTR was not different between two types of polyethylene. On the other hand, when the impact load was applied from the stem, the ratio was greater than the previous loading condition, while the ratio of crosslinked polyethylene was significantly lower than that of conventional one (p < 0.05). The theoretically predicted stress pulse profiles were well correlated to the experimental ones.

The lower ILTR in highly cross linked polyethylene is considered to be due to lower stiffness. These mechanical properties increase the deformity of the cup and may cause the loosening of the cup. These results indicated that the ILTR was not different among cup sizes, while the ratio was significantly affected by the loading conditions and the type of polyethylene.

Acetabular revision in patients with bone deficiency is often difficult because of the poor quality and quantity of the acetabular bone stock. The purpose of this study was to evaluate the midterm clinical and radiographic outcomes of acetabular revision with use of an impaction bone-grafting technique and a cemented polyethylene cup.

Results: thirty consecutive acetabular revisions were performed with impaction bone-grafting and use of a cemented cup in twenty-eight patients with bone deficiency. The average age at the revision was sixty-eight years. The minimum duration of follow-up of all reconstructions that were still functioning or that were followed until the time of death was three years (mean, 8.1 years; range, three to fifteen years). The acetabular bone defects were classified as cavitary in fifteen hips and as combined segmental-cavitary in fifteen hips according to AAOS classification.

One hip had a repeat revision. Radiographic analysis that had not been revised showed loosening in four hips. All these four hips were treated by bulk bone graft covering more than 50% of cups. Kaplan-Meier analysis demonstrated a prosthetic survival rate, with aseptic loosening as the end point, of 72% at fourteen years and, with revision as the endpoint, of 100% at ten years and 83% at fourteen years.

Impaction bone-grafting was an excellent option to manage acetabular revision surgery. However, excessive bulk bonegraft should not be used.

Introduction: Osteonecrosis of the femoral head (ONFH) has a close association with corticosteroid therapy. As corticosteroids are accepted to be metabolized mainly by CYP3A4 in the liver, low constitutive levels of the enzyme might lead to an excessive response to corticosteroids and lead to adverse events including bone necrosis. This clinical study was designed to elucidate this hypothesis and to present potential modalities to avoid corticosteroid-associated ONFH by tailoring the steroid dose according to individual metabolic capacities of corticosteroid.

Materials and Methods: Twenty-two steroid-associated ONFH patients, 27 alcohol-related ONFH patients, and 65 general population controls were enrolled in this study. To estimate functional level of hepatic CYP3A4 level, a midazolam (MDZ) clearance test was carried out in respective subjects. The results from the tests were compared between those groups.

Results: The distribution profile of the MDZ clearance in steroid-associated ONFH patients were shifted to the left, indicating lower hepatic CYP3A4 activity in those patients when compared with the general population. By using an unconditional logistic regression model, patients with low (< 9.7) MDZ clearance due to low hepatic CYP3A4 activity were at 9.5 times greater risk for corticosteroid-induced ONFH compared with those with high (9.7+) MDZ clearance (OR 9.5 [95% CI 2.79–32.2], p< 0.001). The hepatic CYP3A4 activity was not associated with prevalence of alcohol-associated ONFH.

Discussion: A significantly low constitutive hepatic CYP3A4 function in corticosteroid-associated ONFH patients was found. The corticosteroid-associated ONFH might result from excessive responsiveness to corticosteroids in those patients due to prolonged exposure of bone to high levels of corticosteroids because of low functional level of the steroid metabolizing enzymes. The steroid-associated ONFH might be avoided by tailoring the corticosteroid dose in accordance with the functional level of hepatic CYP3A4.

Polyethylene wear is the most important risk factor affecting the durability of total knee arthroplasty. We developed a new method of measuring wear of the tibial polyethylene insert in total knee arthroplasty (TKA) on standard standing radiographs.

Methods: We developed a new method of measuring the shortest distance between the femoral component and the tibial metal tray taking its 3-D position into consideration. The accuracy of the method was examined in 3 conditions. An in vitro examintion measured the thickness of the polyethylene on radiographs of a new PFC prosthesis set on a table. The radiographs were taken from various directions. An in vivo examination measured the polyethylene thickness on patient discharge radiographs of 78 knees. These measurements were compared with known thicknesses of the used inserts. In the third study, wear of the tibial polyethylene insert was measured retrospectively in a series of 84 PFC TKAs with follow-up of 2 to 10 years (6.6 years on average).

Results: The average measurement error was 0.05 mm (SD 0.09 mm) in the in vitro study and 0.14 mm (SD 0.17 mm) in the in vivo study using discharge radiographs. In the series of 84 PFC TKAs, impending failure occurred in 7 knees, 4 of which were revised. Radiographically measured wear of the tibial insert was significantly greater in these failed TKAs than in the other TKAs. The radiographic measurements were well correlated with 3-D measurements of 4 retrieved inserts.

Discussion: Although the radiographic measurement of the tibial insert in TKA was less accurate than that of the socket in THA, it is useful enough to identify TKAs at risk of failure. When the radiographic wear exceeded 1mm, there was a significantly increased probability of impending failure or need for revision.

By 1998, 10 patients had undergone 12 revision total knee arthroplasties at our institute. One patient died three weeks after surgery due to cerebral infarction, leaving 11 knees of nine patients for evaluation. Average follow-up was 4.8 years (1 to 9 years). All components were subjected to revision surgery in five knees, the tibial tray and insert in four knees, and only the insert in two knees. Patients were evaluated with clinical examinations, radiographs, and the Knee Society Clinical Rating System.

After revision surgery, the Knee Scores and ROMs were restored to almost the same level as just after the first TKA. Re-revision was performed on two patients, one 103 months and the other 82 months after revision TKA. In those two patients, huge bone loss of the proximal tibial canal was filled with cement without bone graft. The other patients, however whose tibial trays were fixed with cement on adequate grafted bone obtained good results.

The femoral components that were not treated with revision surgery despite small flaws or scratches due to wear and tear of the tibial insert did not cause marked wear of the new tibial insert.

Conclusion: Bone loss of the proximal tibial canal should be filled with bone graft, not with cement only. Femoral components with small flaws or scratches, and without other ploblems, need not to be treated with revision surgery.

Aim: In alumina-on-alumina (Al/Al) THA, microsepa-ration is reported to accelerate wear and to be a risk factor of alumina cup fracture. While microseparation after THA is detected during walking, microseparation also occurs in relation to the hip position. Using Al/Al THA with cemented polyethylene-back alumina cup, the microseparation is clearly visible on plain roentgen-ograms. The aim of this study is to investigate the factors that affect hip position related microseparation. Materials and Methods: We performed 65 primary Al/Al THA. An average age at operation was 61.1 years and an average follow-up period was 29.5 months. Roentgenograms were taken in hip neutral position, abduction, adduction, external rotation and internal rotation. Results: Microseparation was observed in 15 hips (23.1%); 10 hips with hip external rotation and 5 hips with hip abduction. An average abduction angle of the cup was 33.5±9.8 degrees with microseparation and 36.6±7.3 degrees without microseparation. An average anteversion of the cup was 9.7±6.7 degrees and 7.8±5.8 degrees, respectively. The factors that brought about microseparation were postoperative muscle weakness in 3 hips, impingement in 9, cup malposition (abduction angle: 19, 23 degrees) in 2, and short off-set stem in one. Discussion and Conclusions: It should be noted that microseparation is not a rare phenomenon and it occurs in hip particular position even if it can not be detected on routine roentgenograms.

Introduction: Based on epidemiological results, steroid (glucocorticoid) hormone is accepted as a major causative agent of osteonecrosis, though its pathomechanism is not elucidated. However, not all patients who receive high doses of steroid develop osteonecrosis. This fact suggests risk factor(s) for steroid-induced osteonecrosis. In order to identify such risk factors, the association of CYP3A6 (a major enzyme metabolizing glucocorticoid in rabbit) level with the incidence and extent of osteonecrosis in a rabbit model was determined.

Materials and Methods: In this rabbit model, the CYP3A6 level was modulated by an inhibitory (Itraconazole, 150mg p.o. twice a day for 3 weeks) or inducing agent (rifampicin, 100mg/kg i.p. in first 3 days). Three weeks after modulation of CYP3A6, steroid-induced osteonecrosis was generated by i.m. injection of methyl-prednisolone (20mg/kg BW). Three weeks later, the animals were sacrificed and bilateral femurs were excised and examined histologically for bone and marrow necrosis.

Results: In control animals without modulation of CYP3A6, focal and/or extensive necrosis was noted in 5 of 7 animals. In Itraconazole-treated animals, all of 5 animals revealed extensive necrosis in femoral bone marrow. In rifampicin- treated animals, incidence of necrosis was similar to that of controls but necrotic foci were significantly smaller than those in controls.

Discussion: These experimental results indicated that low level of steroid-metabolizing enzyme CYP3A6 (CYP3A4 in humans) at the time of steroid treatment might be a risk factor for extension of steroid-induced bone necrosis, and that induction of CYP3A6 might prevent steroid-induced bone necrosis.

The benefit of mobile-bearing mechanism in total knee arthroplasty (TKA) has been controversial. The aim of this paper is to analyse the rotation of polyethylene (PE) and its effect on the range of motion (ROM) in mobile-bearing, posterior stabilised TKA (LPS-Flex™, Zimmer Co. Ltd.).

Thirty-four consecutive PS-Flex™ TKAs (28 patients) were analysed. Three tantalum markers were inserted in the PE and the tibia (one for medial side and two for lateral side; total six markers). The rotation of the PE and the tibia was analysed in fluoroscopically-controlled radiograph taken at one years in full extension, 90 degrees flexion and passive maximum flexion. The markers in the tibia were identifiable in 19 knees and the analysis was based on these knees.

The tibia rotated internally relative to the femur by 7.1± 5.2 degrees (mean ± SD, range −1 to 20 degrees). The amount of tibial rotation has no correlation to ROM. The rotation of the PE relative to the femur was unpredictable showing three knees with external rotation and four knees without rotation (Average; 4.0 ± 4.5 degrees internal rotation). The rotation of the PE on the tibia was 4.2± 5.2 degrees and seven knees (37 %) showed no rotation and 12 knees (63 %) showed less than 5 degrees rotation. There was a positive correlation between the amount of PE rotation on the tibia and ROM, which approached to statistical significance (p = 0.0684).

This study has demonstrated that the rotation of the PE on the tibial tray is generally small (< 5 degrees). Because not tibial internal rotation but PE movement on the tibia correlated to ROM, the essential benefit of the mobile-bearing mechanism could be to compensate the rotational mismatch between the components rather than to reproduce normal knee kinematics.

The new 3-Dimensional (3D) polyethylene wear measurement software GAWDI (Genetic Algorithm for Wear Detect Instrument) was developed to evaluate in vivo movement of the femoral head into the polyethylene liner. It enabled to detect 3D position of femoral head against polyethylene socket from two radiographs. Inter observer error of this system was 0.09 mm, intra observer error was 0.08 mm. Fifteen patients after THA was taken anterior-posterior (AP) and semi-lateral radiographs in both standing and supine position one year post operation. The difference of the 3D position of the femoral head was not observed between standing and supine position. However 8.1 degrees (mean) and 0.2 to 16.5 degrees (range) pelvic tilt was observed between these positions. 0.8 mm (mean) difference was observed by 2-Dimensional measurement system although no difference was observed by 3D system. Small separation between head and socket was observed in a few patients. However the influence of pelvic tilt was main origin of the difference between 2D and 3D measurement methods.