Much attention has recently been paid to bioabsorbable polymeric materials, such as poly(L-lactic acid) (PLLA), in the field of orthopedics and oral surgery. For example, PLLA has extensively been used as resorbable bone fixation devices. Recently, hydroxyapatite (HA) micro-particles filled PLLA has also been developed to improve the bioactivity, elastic modulus and absorption rate of biomedical PLLA devices. Porous structures of PLLA and HA/PLLA composites have also been developed to improve osseous conduction so that these biomaterials can be used as scaffolds in tissue engineering for rejenerative medicine. Such porous materials may also be utilized as artificial bones in orthopedics. Thus, demand for porous PLLA and HA/PLLA is rapidly increasing, however, the relationships between their mechanical behavior and properties and their microstructure have not been well understood yet.

In the present study, porous structures of PLLA and HA/PLLA with continuous pores are developed by using a solid-liquid phase separation technique and a subsequent solvent sublimation process. Size of pores and porosity are varied by changing the concentration of the solutions. Compression and shear tests are performed to evaluate the elastic moduli and strengths. Field emission scanning electron microscopy (FE-SEM) of the deformation behavior at the critical transformation points from linear elastic to nonlinear deformation is conducted to characterize the mechanism of such microscopic deformation at the critical point. Microscopic deformation and failure behavior of such porous structures are then characterized on the basis of FE-SEM results, and then correlated with the macroscopic mechanical properties. Structural modification is also tried to improve the mechanical properties to extend the applicability of the porous biomaterials.

The authors did not receive grants or outside funding in support of their research or preparation of this manuscript. They did not receive any payments or make agreements to provide such benefit from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other non profit organization with which the authors are affiliated or associated.

Background: We observed early osteolysis and loosening of the rough surface-cement stem with a second generation metal-on-metal articulation. This study was to investigate the possible etiologic role of stem loosening and osteolysis by examination of the surface of the rough blast cement and related periprosthetic tissues that have been retrieved at revision.

Methods: We retrospectively analyzed 39 hips (37 patients) with use of metasul metal-on-metal total hip arthroplasty. Of the femoral stem, rough surface-cement stem used in 18 hips and cementless Ti-alloy stem in 21 hips. The mean duration of follow-up was 10.2 years. Of these eight rough blast cement stem were revised, seven in loosening and one in recurrent dislocation. By using energy disperse spectroscope and back scattered electron image, histologic studies were performed to the samples of periprosthetic tissues. Skin patch tests for metal hypersensitivity were done to select patients.

Results: All of cementless stems and cups showed excellent results at the last follow-up. However, eight cement hips were revised. Light microscopy showed polishing effect on retrieval femoral stem affected by the rotational force. EDS and BSE image revealed that there were abundant cement and related metal particles with size of 5-10μm. However there were few metal particles and had greater size (20–100μm) in periprosthetic tissues. Histologic finding shows perivascular infiltration of lymphocytes and accumulation of macrophages No relation was found between skin patch test and loosening.

Conclusion: These findings raise the possibility that early osteolysis and loosening in patients with metal-on-metal hip replacement were associated with rough blast surface cement stem. These mixed particles such as Fe and Zr maybe trigger lymphocytic reactivity suggestive delayed type hypersensitive reaction. This study suggests that cement stem which have rough blasted surface should be considered in metal-on-metal total hip arthroplasty.

Level of Evidence: Therapeutic level III-1(case-control study). See instructions to authors for a complete description of level of evidence.

To analyze the mechanism of failure and basic cause in cases of early failure which were required revision within 5 years index TKA. Between 1991 and 2006, 167 revisions TKA of aseptic failure were performed. Revision diagnosis or reason for failure were categorized as wear of tibial polyethylene insert, failure of tibial base plate, early imbalance between medial and lateral soft tension, tight or loose PCL and posterior capsule. The percentages of each failure category were calculated as a percentage of the overall number of revision TKA and a percentage of the early failures. A descriptive statistics were calculated for the time in situ for each failure category.

Early failure within 5 years following index TKA occurred in 33 out of 167 TKA(20.0%). Average time in situ was 38.53 months(3.21 years). Wear of the tibial polyethylene insert occurred in 12 out of 33 cases(36.4%). All cases showed tight PCL. Loosening was the second leading cause occurring in 9 cases(27.2%). Pure instability with tight MCL occurred in 3 knees. Catastrophic early wear within one year after index surgery occurred in 18 knees. The cause of failure were flat surfaced poly in 11, fracture of metal tray 2, dislocation of the thick poly insert 1 and early poly wear due to unknown cause 4.

There were multiple factors of the early failure, which could be divided into design failure and surgical skill failure. However, they worked together in most of the cases.

Many reports show good results following procedures, such as intervertebral body fusion using cage or total disc replacement, that restore adequate disc height. However, there have been no references regarding the range of normal lumbar disc height in Korean adults which can be used as a standard for the implant size. The purpose of our study is to measure the lumbar disc height on radiographs in normal Korean. 132 subjects (age range 20 to 40 years) who had no previous history of low back pain and no significant finding on physical examination were enrolled. Plain lateral lumbar spine radiograph in supine position were taken. Intervertebral disc heights were measured at anterior, middle and posterior portion of each lumbar disc. The average magnification rate was 115%, and the disc heights were corrected by the magnification rate in each segment.

Lumbar disc height showed cranio-caudal pattern in both male and female groups. L4–5 disc heights were highest at anterior, middle and posterior portion in male. L4–5 disc heights were highest at middle and posterior portion in female. L5-S1 disc height was highest at anterior portion in female, but there was no statistically significant difference between L4–5 and L5-S1 disc height at anterior portion. There was no significant difference in disc height between male and female except anterior portion of L1–2 and L2–3 disc. Statistically significant decrease in disc height was not presented in overweight person at all measured site in male and female except posterior portion of L1–2 disc in male.

This research is meaningful in that it is an attempt to provide a reference value of lumbar disc height in Korean adults, and the measured values may also be useful in manufacturing Korean modeled artificial lumbar disc prosthesis or surgical instruments for lumbar interbody fusion.

Beta–tricalciumphosphate(β-TCP)coatinglayerisknown to be resorbed much faster than hydroxyapatite(HA), however, there has been few reports explaining the exact mechanism until now. Therefore, we investigated whether the resorption mechanisms of these two compounds are same, if not, what is the difference.

Eighty titanium discs with 12mm in diameter and 2mm in thickness were coated with HA(n=40) or β-TCP(n=40) by dip and spin coating method. In each group, the specimens were divided into 2 subgroups respectively; Dissolution (D, n=20) group and Osteoclast culture (C, n=20) group. The coated discs in D group were immersed in the cell culture media for 5 days, whereas, in C group, osteoclast-like cells (5×103 cells/500μ), which were isolated form human giant cell tumor, were seeded on the specimens and cultured for 5 days. Cultured cells were defined as osteoclast by the determination of osteoclast marker (tartrate-resistant acid phosphatase, TRAP). After immersion or osteoclast culture, the dissolution characteristics of coating surface were observed using light microscope (LM) and scanning electron microscope (SEM). And the area fraction of resorption lacunae formed by osteoclast was analyzed by image analysis to evaluate the activity of osteoclastic degradation.

After 5 days of dissolution, there were much more cracks and denuded areas in β-TCP coating compared to HA coating. In C group, the osteoclasts covering the coating layer were identified on LM and SEM images. Mean area fraction of resorption lacunae in HA-C group was 11.62%, which was significantly higher than that of 0.73% of β-TCP-C group (p=0.001).

We conclude that the resorption mechanism of HA and β-TCP coating layers was different each other in vitro study. The coated β-TCP was degraded mainly by dissolution and also tended to be separated from implant, on the other hand, the HA coating layer was resorbed by osteoclastic activity

Recently with the introduction of operations using various instrument of total ankle arthroplasty, we are showing quite satisfactory short term results on the treatment of resolved pain of ankle joint. However, there have been reports of high probability of complication from total ankle arthroplasty to other arthroplasty applied to other joints. Therefore in order to make the results of ankle arthroplasty superior, it is necessary to reduce these complications. We try to analyze complications that occur often and come up with the best results.

There were 45 cases of 42 patients of HINTEGRA^® (Newdeal SA, Lyon, France) model from November 2004 to August 2006. Follow up averaged 33.5 months, the average age of patients was 61.1 years, with 14 males and 28 females. We evaluated the complications and analyzed the causes of failures. There was a total 15 cases of complications; 5 cases of medical impingement syndrome, 3 cases of varus malposition, 2 cases of delayed healing of wound, 1 case of peroneal nerve problem, medial malleolar fracture, postoperative deep infection and gouty arthritis pain and Achilles tendinitis.

Our conclusion is that total ankle arthroplasty had more complication rate than other joint arthroplasty, so we need a more meticulous preoperative and perioperative care.

Introduction: Alendronate is a well known inhibitor of osteoclastic activity and is used for the treatment of various metabolic bone diseases. Recent studies indicate that alendronate may have additional effect on osteoblastic activity. In this study, we evaluated the effect of alendronate on the osteogenic differentiation of mouse mesenchymal stem cells.

Materials and Methods: D1 cells, known as multipotent mouse mesenchymal stem cells, were cultured in the presence of osteogenic differentiation medium (ODM) for 7 days, then treated with alendronates, and 2 days later the cells were used for testing. The cell proliferation was analyzed using an MTT assay. Alizarin red staining was done for mineralization. Alkaline phosphatase activity was measured using a commercial ELISA kit. Calcification was analyzed using energy dispersive X-ray spectrophometric analysis (EDX). Osteogenic gene expression was analyzed using RT-PCR. The change of CD 44 expression was observed using confocal microscopy and FACS analysis.

Results: The D1 cells, in the presence of ODM, differentiated into osteoblasts. The evidence of osteogenic differentiation was confirmed by the positive stain by Alizarin red S, the increased activity of ALP, the increased mRNA expression of osteocalcin, a calcium peak in the EDX analysis, and by the positive immunofluorescence staining against CD 44 (an antigen detected on osteoblasts). With the addition of alendronate in the ODM medium, the osteogenic differentiation was enhanced. The enhancing effect was confirmed by the increased intensity of the Alizarin red S staining, higher activity of ALP, the higher mRNA expression of osteocalcin, a higher calcium peak in the EDX analysis, and by the increased immunofluorescence staining against CD 44 in the FACS analysis.

Conclusion: We have demonstrated that alendronate enhances osteogenic differentiation when given to mouse mesenchymal stem cells in association with the ODM. Alendronate may increase the bone density not only by inhibiting the osteoclastic activity but also by increasing the osteogenic differentiation of the mesenchymal stem cells.

Introduction: A hypothesis that combined necrotic angle measurement using MRI scans predicts the subsequent risk of collapse of femoral head osteonecrosis was tested.

Materials and Methods: Thirty-seven hips with early-stage osteonecrosis in 33 consecutive patients were investigated. The arc of the necrosis was measured by the method of Kerboul et al. using mid-coronal and mid-sagittal MRI scans of the femoral head instead of anteroposterior and lateral radiographs, and the two angles were added. Hips were classified into four categories based on the magnitude of the added angle; grade 1 (< 200), grade 2 (200–249), grade 3 (250–299), and grade 4 (≥300). After the initial evaluations, the hips were randomly assigned to a core-decompression group or a non-operatively-treated group. Patients underwent regular follow-up until femoral head collapse or for a minimum of five years.

Results: Seven hips in grade 4 and 16 hips in grade 3 developed femoral head collapse in 36 months; six out of nine hips in grade 2, and none of five hips in grade 1 developed collapse (log rank test, p< 0.01). In a retrospective analysis, none of four hips with combined necrotic angle < 190 (low risk group) collapsed, and all 25 hips with combined necrotic angle > 240 (high risk group) collapsed, and four (50%) of eight hips with combined necrotic angle between 190 and 240 (moderate risk group) collapsed during the study.

Discussion: The Kerboul combined necrotic angle ascertained by MRI scans instead of radiographs is a major predictor of future femoral head collapse.

The purpose this prospective, randomized clinical trial was to determine if unilateral or bilateral simultaneous total hip arthroplasty procedures resulted in a differing incidence of fat embolization, degree of hemodynamic compromise, levels of hypoxemia or mental status changes. Also, the incidence of fat embolization was compared between the cemented and cementless total hip arthroplasty in the patients with a unilateral- and bilateral simultaneous total hip arthroplasty.

One hundred and fifty-six consecutive patients undergoing primary total hip arthroplasty were enrolled prospectively in the study after giving informed consent. The group consisted of fifty patients undergoing bilateral simultaneous total hip arthroplasty and 106 patients undergoing unilateral total hip arthroplasty. One hundred and three hips were cemented and 103 hips were cementless. To determine the hemodynamic changes and to detect the fat and bone marrow embolization, arterial and right atrial blood samples were obtained before implantation (baseline) and at one, three, five and ten minutes after implantation of the acetabular component. Also, arterial and right atrial blood samples were obtained at one, three, five and ten minutes after implantation of the femoral component. And then blood samples were obtained at twenty-four and forty-eight hours after the operation. Arterial blood pressure, right atrial pressure, arterial oxygen tension and carbon-dioxide tension were monitored at corresponding times. The presence of lipid was determined with oil red O fat stain and the presence of cellular contents of bone marrow was determined with Wright-Giemsa stain.

The incidence of fat embolism was not statistically different (P=1.000) between the patients with a bilateral total hip arthroplasty (twenty seven patients or 54 per cent) and the patients with a unilateral total hip arthroplasty (fifty-two patients or 49 per cent). In the semiquantitative analysis of fat globules in both groups, there was no tendency to have a higher number of fat globules in the bilateral group than in the unilateral group. Also, the incidence of bone marrow embolization was not statistically different (P=0.800) between the patients with a bilateral total hip arthroplasty (eight patients or 16 per cent) and the patients with a unilateral total hip arthroplasty (fourteen patients or 13 per cent). There was no statistical difference (P=0.800) in the incidence of the presence of fat globule between the cemented total hip (thirty-four patients or 34 per cent) and the cementless total hip arthroplasty (forty-seven patients or 44 per cent). Also, there was no statistical difference (P=0.627) in the incidence of the presence of bone marrow cells between the cemented total hip arthroplasty (thirteen patients or 13 per cent) and the cement-less total hip arthroplasty (twelve patients or 11 per cent). Four patients with positive bone marrow cells had neurological manifestation. All of these four patients developed diffuse encephalopathy with confusion and agitation for about twenty-four hours.

The present study confirmed that the incidence of fat and bone marrow embolization is similar in the patients with a bilateral simultaneous-and unilateral total hip arthroplasty as well as in the patients with cemented and cementless total hip arthroplasty. The patients with bone marrow cell emboli had a significantly lower arterial oxygen tension (p=0.022) and oxygen saturation (p=0.017) than the patients without bone marrow cell emboli. On the contrary, the number of fat globules did not affect the perioperative hemodynamic changes. Encephalopathy is related to the biochemical and/or mechanical changes by bone marrow cells.

Introduction: A potential cause of premature loosening of the total hip prosthesis in patients with osteonecrosis is abnormal cancellous bone in the acetabulum and proximal femur. The purpose of this prospective study was to investigate the hypothesis that osteonecrosis is not confined to the femoral head but may extend proximally into acetabulum and distally into the proximal femoral bone. Also, the clinical and radiographic results of total hip arthroplasty with so-called third-generation cementless total hip prostheses were evaluated in sixty-three consecutive patients with osteonecrosis of the femoral head.

Materials and Methods: Twenty-five patients who had simultaneous bilateral total hip arthroplasty, and thirty-eight patients who had a unilateral total hip arthroplasty were included in the study. A cementless acetabular and femoral component were used in all hips. There were fifty-five men and eight women. The mean age at the time of the arthroplasty was 47 years (range, twenty-five to sixty-four years). We performed histological examination of the femoral heads and cancellous bone biopsies from five regions of the hip in patients undergoing total hip arthroplasty. Clinical and radiographic evaluations were performed preoperatively; at six weeks; at three, six, and twelve months; and yearly thereafter. The average duration of follow-up was 4.9 years.

Results: The majority of patients with idiopathic or alcohol induced osteonecrosis had normal bone in the acetabulum and proximal femur. The average Harris hip scores in the group treated with unilateral arthroplasty (96 points) and the group treated with bilateral arthroplasty (94 points) were similar at the time of final follow-up. No component had aseptic loosening. In one hip (1%), an acetabular component and a femoral component were revised because of infection. No hip had detectable wear or osteolysis in the acetabulum or in the proximal femur.

Conclusions: Normal or nearly normal cancellous bone in the acetabulum and proximal femur and advancements in surgical technique and better designs have greatly improved the intermediate-term survival of cementless total hip implants in young patients with osteonecrosis of the femoral head. An absence of osteolysis in these high-risk young patients is partly related to use of ceramic-on-ceramic bearing; solid fixation of the component; and short-term follow-up.

Introduction: Hyperlipidemia is related to hypercoagulability and hypofibrinolysis, which may cause a tendency to intravascular thrombosis and result in osteonecrosis (ON). Recently PPARs were confirmed to induce adipocyte differentiation, and fatty acids were identified as the transcriptional effectors for PPARs, which may cause the hyperlipidemia and fatty marrow. The aim of this study was to identify whether the adipocytic differentiation was increased in the bone marrow obtained from the femoral head in patients with osteonecrosis.

Materials and Methods: A lipid profile (cholesterol, triglyceride, LDL, and free fatty acid) was performed for patients with osteonecrosis of the femoral head. The PPARγ2 expression was checked as to whether the mesenchymal stem cells differentiate toward adipocytes rather than osteogenic cells. RT-PCRs were completed using the bone marrow stroma cells obtained during THA from 11 patients with osteonecrosis and 9 control patients. As not all of alcoholics and steroid users develop osteonecrosis, genetic differences may relate to susceptibility to the osteonecrosis. Therefore, we determined the polymorphism of the PPARγ2 gene for 34 osteonecrosis patients and 76 controls.

Results: Among 89 cases of osteonecrosis, increased free fatty acid (above 580mg%) was the most frequent finding (40.8%), and triglyceride was the next (29.6%). Cholesterol was increased in only 9.0%. Seven of the osteonecrosis cases (63.6%) and 4 of the control cases (44.4%) expressed PPARγ2. Pro/Ala (C/G) polymorphism was found in seven (20.6%) ON cases and four control cases (5.3%), and Ala/Ala (G/G) polymorphism was found in only 1 case in the control group. The numbers of patients with elevated triglyceride among osteonecrosis were much higher (71.4%) in polymorphism (C/G) than osteonecrosis (21.5%) without polymorphism.

Discussion: In conclusion, hyperlipidemia and higher expression of the PPARγ2 were found in ON, and Pro/Ala PPARγ2 polymorphism was more common in ON.

Introduction: It is desirable to delay or avoid total joint replacement in young patients who have osteonecrosis of femoral head. There are some head preserving surgical procedures that attempt this including osteotomy, core decompression, and bone grafting. The vascularized fibular graft has been reported to be a reliable procedure, but unfortunately it has donor site morbidity and is considered technically demanding. Therefore, materials have been developed to substitute for structural fibular graft. New trabecular metal has been developed to be used for osteonecrosis of femoral head. The purpose of this study was to review the clinical outcomes of trabecular metal as a treatment intervention method for osteonecrosis of the femoral head.

Materials and Methods: Seven patients (8 hips) with osteonecrosis of femoral head received core decompression and a trabecular metal implant, beginning in March 2003. The stage of osteonecrosis was I or II according to Ficat and Arlet except for one case (stage III). The procedure consists of a core decompression and insertion of trabecular metal rod (porous tantalum, Zimmer Inc./ Implex Incorporation). A Harris Hip Score was obtained pre-operatively, and at three and at three and six months. Radiographic data was collected at the same time of clinical follow-up.

Results: All 7 patients are doing well. Radiographic review shows no evidence of further femoral head collapse.

Discussion: Even though this is short term follow-up, the authors propose that the use of trabecular metal in osteonecrosis patients is simple, safe, and effective for the salvage of the hip.

Introduction: The rate of failure of primary total hip arthroplasty in patients with osteonecrosis of the femoral head is higher than in patients with osteoarthritis. The purpose of this prospective study was to document the clinical and radiographic results of arthroplasty with so-called third generation cementing and the results of second generation cementless total hip arthroplasty in ninety-eight consecutive patients with osteonecrosis of the femoral head.

Materials and Methods: Fifty patients who had simultaneous bilateral total hip arthroplasties with a cemented stem in one hip and a cementless stem in the other and forty-eight patients who had unilateral total hip arthroplasties with a cementless stem were included in the study. A cementless acetabular component was used in all hips. The presumed cause of the osteonecrosis was ethanol abuse in fifty-seven patients, unknown in twenty-seven, fracture of the femoral neck in nine, and steroid use in five. There were eighty men and eighteen women. The mean age the time of the arthroplasty was 47 years (range, twenty-six to fifty-eight years). Clinical and radiographic evaluations were performed preoperatively, at six weeks, at three, six, and twelve months; yearly thereafter. The average duration of follow-up was 9.3 years.

Results: The average Harris hip scores in the group treated with unilateral arthroplasty (97 points) and the group treated with bilateral arthroplasty (94 points) were similar at the time of final follow-up. They were also similar between the group treated with cement (mean, 96 points) and that treated without cement (95 points). No component had aseptic loosening in either group. In one hip, a cemented femoral stem (2 %) and a cementless cup were revised because of infection. Two cementless stems (2%) were revised because of fracture of the proximal part of the femur with loosening of the stem. Annual wear of the polyethylene liner averaged 0.22 mm in the group treated with cement (a zirconia head) and 0.14 mm in the group treated without cement (a cobalt-chrome head). The prevalence of osteolysis in zones 1 and 7 of femur was 16 % in the femur was 16% in the group treated with cement and 24% in the group treated without cement.

Discussion: Advances in surgical technique and better designs have greatly improved the long-term survival of cemented and cementless implants in young patients with osteonecrosis of femoral head. Although there was no aseptic loosening of the components, the high rate of linear wear of the polyethylene liner and high rate of osteolysis in these high risk young patients remain challenging problems.

To evaluate the results critically of cemented total hip arthroplasty using a fourth generation cement technique and polished femoral stem, a prospective study was performed in patients under 50 years of age who underwent primary total hip arthroplasty. 55 patients (64 hips) were enrolled in the study (43 were male and 12 were female). Average age of patients was 43.4 years (21–50 years). Elite plus stems (DePuy, Leeds, UK) were cemented and cementless Duraloc cups (DePuy, Warsaw, IN.) were implanted in all hips. 22 mm zirconia femoral head (DePuy, Leeds UK) was used in all hips. All surgeries were performed by one surgeon (YHK). The diagnosis was osteonecrosis (43 hips or 67%), osteoarthritis (5 hips or 4%), O.A. 2° to childhood T.B. or pyogenic arthritis (4 hips or 6%), R.A, (3 hips or 5%), DDH (2 hips or 3%) and others (7 hips or 11%). The average F.U. was 7.2 years (6–8 years). The 4th generation cement technique was utilized including: medullary plug, pulsatile lavage, vaccum mixing of Simplex P cement; cement gun, distal centralizer and proximal rubber seal to pressurize cement. Thigh pain was evaluated using a visual analog scale (10 points). Clinical (Harris hip score) and x-ray follow-up was performed at 6 weeks, 3 months, 6 months, 1 year and then annually. Cementing technique was graded. Abductor moment arm, femoral offset, neck and limb length, center of rotation of hips, cup angle and anteversion were measured in all hips. Linear and volumetric wear were measured by software program. Osteolysis was identified. There was no aseptic loosening or subsidence of components. One hip was revised due to late infection. Incidence of thigh pain was 11% (7 hips). All thigh pain disappeared at 1 year postoperatively. Preoperative Harris hip score was 47.2 (7–67) points and 92.2 (81–100) points at the final F.U. Femoral cementing was classified as grade A in 50 hips (78%), grade B in 6 hips (9%), and grade C1 in 8 hips (13%). There was no cases in grades C2 and D. All bones had type A femoral bone. The average linear wear and annual rate were 1.25 and 0.21 mm, respectively. The average volumetric wear was 473.48 mm3. There was statistically significant relationship between the liner wear, age (under 40), male patient, and the cup angle. Yet there was no statistical relationship between the wear and Dx., wt., hip score, R-O-M, anteversion, anbductor moment arm, femoral offset, neck and limb length and center of rotation of hip. Osteolysis was identified in zone 7A in 6 hips (9%). No hip had distal osteolysis. Advanced cementing technique, polished improved stem design, strong trabecular bone, and utilizing a smaller head and thick polys greatly improved the mid-term survival of the implants in these young patients. Good cementing technique eliminated distal osteolysis and markedly reduced the proximal osteolysis. Yet high linear and volumetric wear of polyethylene liner remains to be a challenging problem.

To determine the results critically of cementless third generation prosthesis (proximal fit, porous coated, and tapered distal stem), a prospective study was performed only in Charnley class A patients under 50 years of age who underwent primary total hip arthroplasty. 50 patients (50 hips) were included in study (37 were male and 13 were female). Average age of patients was 45.4 years (26–50 years). IPS(Immediate Postoperative Stability) stems (DePuy, Leeds, UK) were implanted in all hips. Cementless Duraloc cups (DePuy, warsaw, IN.) were used in all hips. 22 mm zirconia femoral head was used in all hips. All surgeries were performed by one surgeon (YHK). The redominant Dx. was osteonecrosis (30 hips or 60%), O.A. 2° to childhood T.B. or pyogenic arthritis (8 hips or 16%) and others (12 hips or 24%). The average F.U. was 6.3 years (5–7 years). Thigh pain was evaluated using a visual analog scale (10 points). Clinical (Harris hip score) and x-ray follow-up was performed at 6 weeks, 3 months, 6 months, 1 year and then annually. Linear and volumetric wear were measured by software program. Abductor moment arm, femoral offset, neck and limb length, center of rotation of hips, cup angle and anteversion were measured and the results were compared between normal and operated hips. All hips had satisfactory fit in A-P and lateral planes. There was no aseptic loosening or subsidence of components. Incidence of thigh pain was 14% (7 of 50 hips). All thigh pain disappeared at 3 years postoperatively. Preoperative Harris hip score was 52.3 (7–64) points and 92.9 (80–100) points at the final F.U. The values of abductor moment arm, femoral offset, neck and limb length, center of rotation of hips, cup angle and anteversion of operated hips were comparable to normal unoperated hips. The average linear wear and annual wear rate were 1.25 and 0.21 mm, respectively. The average volumetric wear was 473.48 mm3. There was statistically significant relationship between the liner wear, age (under 40), male patient, and the cup angle. Yet there was no statistical relationship between the wear and Dx., wt., hip score, R-O-M, anteversion, abductor moment arm, femoral offset, neck and limb length and center of rotation of hip. Osteolysis was identified in zones 1A and 7A in 4 hips (8%). No hip had distal osteolysis. Close fit cementless stem in coronal and saggital planes without having distal stem fixation were proved to have an excellent mechanical fixation and provided favorable mechanical loading. Close fit in the proximal canal with a circumferential porous coating reduced the incidence of osteolysis. Factors contributing to good results in this young patient group are improved design of the prosthesis, improved surgical technique, strong trabecular bone and the use of smaller femoral head and thick polys. Although there was no aseptic loosening of the hip, high incidence of linear and volumetric wear of polyethylene liner in these young patients remains to be a challenging problem.