Biomedical subjects

Marius von Knoch

Publications and source records attributed to Marius von Knoch.

18 recordsLinked to original sources

PubMed2006

Misinterpretation of cup anteversion in total hip arthroplasty using planar radiography.

INTRODUCTION: Anteroposterior pelvic radiographs are routinely used to monitor cup orientation in total hip arthroplasty (THA). Analysis of planar radiographs leads to a certain degree of measurement error for the cup anteversion (AV). With the current study, we wanted to clarify whether planar radiography can be used for accurate evaluation of the THA position. MATERIALS AND METHODS: The postoperative orientation of pelvic implants in 42 patients was analyzed according to five documented mathematical algorithms using planar radiographs. Postoperative computed tomography (CT) pelvis scans were available for all patients. A CT-based navigation system was used to determine AV. RESULTS: The comparison showed that all five formulas presented substantial variations for the AV angle. Of these, Widmer's algorithm presented the smallest difference compared to the CT. Misinterpretation of postoperative planar radiographs is a common problem in THA. CONCLUSION: Planar radiographs are too imprecise for exact evaluation of the correct cup AV after THA. CT-based analysis may be necessary if exact values are required.

Arthroplasty, Replacement, Hip↗

PubMed2006

Over-expression of p53/BAK in aseptic loosening after total hip replacement.

Particle-induced osteolysis is a major cause of aseptic loosening after total joint replacement. The possible induction of apoptosis has not been addressed in great detail. Thus far, it has been shown that ceramic and polyethylene particles can induce apoptosis of macrophages in vitro. The purpose of this study was to test the hypothesis that wears debris generated from total hip arthroplasty could induce cellular damage and apoptosis in vivo. We therefore determined by immunohistochemical methods if increased expression of p53, an important transcription factor, and BAK and Bcl-2, two important regulators of apoptosis, can be found in interface membranes and capsules of hips with aseptically loose implants. Strongly positive immunohistochemical staining for p53 and BAK was found in peri-implant tissues from patients with aseptic hip implant loosening. Differentiation of various cell types showed that macrophages stained positive for p53 in all capsule and interface specimens. p53 was frequently detected in giant cells. Positive staining of BAK in macrophages and giant cells was seen in all specimens. Some positive reactions were observed in fibroblasts, only two of 19 cases stained for p53 and three cases for BAK within synovial cells. Positive macrophages and giant cells were localized around polyethylene particles. While T-lymphocytes showed a regular BAK-staining, the other leukocytes were negative. Statistical analyses showed significant positive correlations (p < 0.001) between the presence of polyethylene and metal debris and the expression of BAK and p53. Polyethylene particles were surrounded by more positive macrophages and giant cells than were metal particles, indicating that polyethylene debris may be a stronger inductor of cell cycle arrest and apoptosis than metal debris. In this study apoptosis of macrophages, giant cells and T-lymphocytes in capsules and interface membranes of patients with aseptic hip implant loosening has been demonstrated in vivo. It is possible that the apoptotic cascade could evolve as a novel therapeutic target to prevent particle-induced osteolysis.

Adult↗

PubMed2006

[Pressfit of equatorially roughened cementless acetabular components--a finite element analysis].

AIM: Does the pressfit anchorage of cementless acetabular cups depend on the roughness of the pole? To answer this question the primary pressfit of two cementless acetabular cups which differ only with regard to the roughness of their poles were compared by means of finite elements analysis. MATERIALS AND METHODS: It was assumed that the material properties of bone are homogeneous, isotropic and linearly elastic. Material-specific values of cancellous bone with three different bone densities were used. Assumption of isotropy represents an approximation. RESULTS: Comparison of the two prosthesis designs revealed that both designs/shapes cause similar patterns of bone deformation and tension. CONCLUSIONS: It can therefore be concluded that with regard to pressfit anchorage the prosthesis with milled polar surface is according to FEA mechanically equivalent to the prosthesis with non-milled polar surface.

Acetabulum↗

PubMed2006

Titanium serum levels may remain elevated despite hip revision surgery for wear-through of an acetabular component.

A 62-year-old female patient showed radiographic signs of severe linear wear of the acetabular component six years after cementless total hip arthroplasty. This suggested wear-through of the acetabular liner with secondary wear of the titanium shell. At revision surgery wear-through of both the inlay and the acetabular shell were confirmed. Despite meticulous debridement serum titanium levels remained elevated for more than 12 months. Wear-through of a polyethylene acetabular liner with secondary wear of the titanium shell can lead to increased titanium serum levels. Titanium serum levels can remain highly elevated despite revision surgery.

Acetabulum↗

PubMed2005

Suppression of polyethylene particle-induced osteolysis by exogenous osteoprotegerin.

Alterations of the key regulators of osteoclastogenesis, receptor activator of NF-kappaB (RANK), RANK ligand (RANKL), and osteoprotegerin (OPG) have been implicated in wear particle-induced osteolysis, the most common cause for implant failure in total joint replacements. This study investigated the effect of exogenous OPG on ultra-high-molecular-weight polyethylene (UHMWPE) particle-induced osteolysis. The murine calvarial osteolysis model was utilized in 28 C57BL/6J mice randomized to four groups. Group I underwent sham surgery only, group II received UHMWPE particles, and group III and IV particles and subcutaneous OPG starting from day 0 (group III) or day 5 (group IV) until sacrifice. After 2 weeks, calvaria were prepared for histology and histomorphometry. Bone resorption was measured within the midline suture using Giemsa staining and osteoclast numbers were determined using TRAP staining. UHMWPE particle implantation resulted in grossly pronounced osteoclastogenesis and bone resorption. Both immediate and delayed treatment with OPG counteracted these particle-induced effects significantly, suppressing osteoclast formation and bone resorption (p < 0.001 and p < 0.001, respectively). In conclusion, exogenous OPG markedly suppressed UHMWPE particle-induced osteolysis in a murine calvarial model. This important finding underscores the crucial significance of the OPG-RANKL-RANK signaling in wear particle-induced osteolysis. Exogenous OPG may prove an effective treatment modality for wear debris-mediated periprosthetic osteolysis after total joint arthroplasty.

Animals↗

PubMed2005

The decrease of particle-induced osteolysis after a single dose of bisphosphonate.

The most common cause of implant failure in joint replacement is aseptic loosening due to particle-induced osteolysis. Bisphosphonates have been shown to be effective against particle-induced osteolysis when administered daily. We investigated the effect of a single subcutaneous dose of a more potent third generation bisphosphonate on particle-induced osteolysis. We utilized the murine calvaria osteolysis model in C57BL/J6 mice. Bone resorption was measured as resorption within the midline suture using Giemsa staining. Twenty-eight mice were used, seven per group. Seven animals were treated with a single dose of zoledronic acid (ZA) directly after surgery and seven animals were treated four days postoperatively. For statistical analysis one-way ANOVA and a Student's t-test were used. Bone resorption was 0.26+/-0.09 mm(2) in animals with particle implantation, 0.14+/-0.05 mm(2) in animals with particle implantation and ZA treatment directly after surgery (p = 0.0047), and 0.15+/-0.05 mm(2) in animals with particle implantation and ZA treatment on the fourth postoperative day (p = 0.006). In conclusion, particle-induced bone resorption was markedly decreased by a single s.c. dose of a third generation bisphosphonate. This important new finding holds great promise, because single dose treatment of particle-induced osteolysis may reduce side effects compared to repeated application of bisphosphonates.

Animals↗

PubMed2005

Stimulation of bone formation by zoledronic acid in particle-induced osteolysis.

We investigated the effect of a single subcutaneous dose of zoledronic acid on particle-induced osteolysis and observed excessive regional new bone formation. We utilized the murine calvarial osteolysis model and polyethylene particles in C57BL/J6 mice. Twenty-eight mice were used, seven per group. Specimens were stained with Giemsa dye. The osteoid tissue area was determined. Bone thickness was measured as an indicator of bone growth. Net bone growth was significantly increased in animals with zoledronic acid treatment: 0.02 mm(2)+/-0.03 mm(2) in animals with particle implantation only (group 2), 0.25 mm(2)+/-0.08 mm(2) with particle implantation and zoledronic acid treatment directly after surgery (group 3; p=0.0018), and 0.21 mm(2)+/-0.11 mm(2) with particle implantation and zoledronic acid treatment on the fourth postoperative day (group 4; p=0.0042). The mean bone thickness was 0.2 mm+/-0.04 mm (range 0.17 mm-0.31 mm) in group 1 (sham controls) and 0.16 mm+/-0.02 mm (range 0.14 mm-0.19 mm) in group 2, 0.31 mm+/-0.04 mm (range 0.28 mm-0.39 mm) in group 3, and 0.29 mm+/-0.02 mm (range 0.28 mm-0.34 mm) in group 4. Student's t-test revealed a statistically significant difference between groups 2 and 3 (p=0.00042), and groups 2 and 4 (p=0.0019). In conclusion, our observational study suggests that zoledronic acid may stimulate bone apposition locally in the process of particle-induced osteolysis.

Animals↗

PubMed2005

The effect of simvastatin on polyethylene particle-induced osteolysis.

This study aimed to investigate the effects of the HMG-CoA reductase inhibitor simvastatin on ultra-high molecular weight polyethylene (UHMWPE) particle-induced osteolysis. The murine calvarial osteolysis model was used in 21 C57BL/J6 mice randomized to three groups. Group I underwent sham surgery only, group II received UHMWPE particles, and group III, particles and simvastatin treatment. After two weeks, calvaria were processed for histomorphometry. Bone resorption was measured as resorption within the midline suture using Giemsa staining. Osteoclast numbers were determined per high-power field using TRAP-staining. Statistical analysis was performed using one-way ANOVA and Student's t-test. Bone resorption in midline suture was 0.094+/-0.007 mm(2) in sham controls (group I), 0.25+/-0.025 mm(2) after particle implantation without further intervention (group II), and 0.131+/-0.02 mm(2) with particle implantation and additional simvastatin treatment (group III) (p=0.00003). Osteoclast numbers were 15.3+/-3.6 in group I, 48.7+/-7.1 in group II and 6.2+/-3.1 in group III (p=0.00002). In conclusion, simvastatin treatment markedly decreased UHMWPE particle-induced osteolysis in a murine calvarial model. This finding suggests that simvastatin may have a role for noninvasive prevention and treatment of wear debris-mediated periprosthetic osteolysis after total joint arthroplasty.

Animals↗

PubMed2005

Promotion of bone formation by simvastatin in polyethylene particle-induced osteolysis.

The effects of statins on bone formation in periprosthetic osteolysis have not been determined to date. We investigated the effect of the HMG-CoA reductase inhibitor simvastatin on osteoblastic bone formation under conditions of ultra-high molecular weight polyethylene (UHMWPE) particle-induced osteolysis. The murine calvarial osteolysis model was utilized in 21 C57BL/J6 mice randomized to three groups. Group I underwent sham surgery only, group II received UHMWPE particles, and group III, particles and simvastatin treatment. After 2 weeks, calvaria were processed for histomorphometry and stained with Giemsa dye. New bone formation was measured as osteoid tissue area within the midline suture. Bone thickness was quantified as indicator of net bone growth. Statistical analysis was performed using one-way ANOVA and a Student's t-test. New bone formation and bone thickness were significantly enhanced following simvastatin treatment. New bone formation was 0.008+/-0.008 mm2 in sham controls (group I), 0.015+/-0.012 mm2 after particle implantation without further intervention (group II), compared to 0.083+/-0.021 mm2 with particle implantation and simvastatin treatment (group III) (p=0.003). The bone thickness was 0.213+/-0.007 mm in group I, 0.183+/-0.005 mm in group II, and 0.238+/-0.009 mm in group III (p=0.00008). In conclusion, simvastatin treatment markedly promoted bone formation and net bone growth in UHMWPE particle-induced osteolysis in a murine calvarial model. These new findings indicate that simvastatin may have favorable osteoanabolic effects on wear debris-mediated osteolysis after total joint arthroplasty, involving local stimulation of osteoblastic bone formation.

Animals↗

PubMed2005

Comparison of subtraction arthrography, radionuclide arthrography and conventional plain radiography to assess loosening of total knee arthroplasty.

The value of plain radiographs, digital subtraction arthrography and radionuclide arthrography was analysed in 23 cases of failed total knee arthroplasty. The preoperative diagnosis was compared with the intraoperative assessment. Sensitivity, specificity and the positive and negative predictive value for assessing a loose component were determined separately for the femoral and tibial components. At revision we found 13 loose femoral and 12 loose tibial implants. In eight cases both components were unstable. Plain radiography had a sensitivity of 77% for loosening of the femoral and 83% for the tibial component; digital subtraction arthrography 77% for the femoral and 8% for the tibial component and radionuclide arthrography 31% and 8%. The specificity for plain radiography was 90% for the femoral and 72% for the tibial implant. For subtraction arthrography it was 50% and 82% and for subtraction arthrography 70% and 82%. Radiography had the highest positive and negative predictive values for both components compared with the other two techniques. As a diagnostic tool to detect implant loosening, plain radiography is the most effective in this study. Subtraction arthrography and radionuclide arthrography are not suitable for use as routine methods for detection of total knee arthroplasty loosening.

Adult↗

PubMed2005

Effect of femoral head diameter and operative approach on risk of dislocation after primary total hip arthroplasty.

BACKGROUND: It has been postulated that use of a larger femoral head could reduce the risk of dislocation after total hip arthroplasty, but only limited clinical data have been presented as proof of this hypothesis. METHODS: From 1969 to 1999, 21,047 primary total hip arthroplasties with varying femoral head sizes were performed at one institution. Patients routinely were followed at defined intervals and were specifically queried about dislocation. The operative approach was anterolateral in 9155 arthroplasties, posterolateral in 3646, and transtrochanteric in 8246. The femoral head diameter was 22 mm in 8691 of the procedures, 28 mm in 8797, and 32 mm in 3559. RESULTS: One or more dislocations occurred in 868 of the 21,047 hips. The cumulative risk of first-time dislocation was 2.2% at one year, 3.0% at five years, 3.8% at ten years, and 6.0% at twenty years. The cumulative ten-year rate of dislocation was 3.1% following anterolateral approaches, 3.4% following transtrochanteric approaches, and 6.9% following posterolateral approaches. The cumulative ten-year rate of dislocation was 3.8% for 22-mm-diameter femoral heads, 3.0% for 28-mm heads, and 2.4% for 32-mm heads in hips treated with an anterolateral approach; 3.5% for 22-mm heads, 3.5% for 28-mm heads, and 2.8% for 32-mm heads in hips treated with a transtrochanteric approach; and 12.1% for 22-mm heads, 6.9% for 28-mm heads, and 3.8% for 32-mm heads in hips treated with a posterolateral approach. Multivariate analysis showed the relative risk of dislocation to be 1.7 for 22-mm compared with 32-mm heads and 1.3 for 28-mm compared with 32-mm heads. CONCLUSIONS: In total hip arthroplasty, a larger femoral head diameter was associated with a lower long-term cumulative risk of dislocation. The femoral head diameter had an effect in association with all operative approaches, but the effect was greatest in association with the posterolateral approach.

Aged↗

PubMed2004

Chylous leakage after thoracolumbar fracture may cause paraplegia.

STUDY DESIGN: Retrospective case report. PURPOSE: This case demonstrates that paraplegia can develop due to chylous leakage into the spinal canal without obvious retroperitoneal or intrathoracic involvement. BACKGROUND INFORMATION: This clinical presentation of chylous leakage has not been reported previously. RESULTS A 61-year-old female with osteoporosis suffered a pathologic fracture of the vertebral bodies T12 and L1 and developed partial paraplegia two weeks later. Imaging showed expansive pooling of intraspinal fluid without intrathoracic or retroperitoneal involvement. A blood-tinged fluid was aspirated from dorsal. Repeated surgery by a posterior approach with drainage of the fluid did not improve the patient's condition, so she was finally transferred to our hospital. Under the suspected diagnosis of lymphatic leakage a scintiscan with 123I-iodinephenylpentadekanacid-marked cream verified the presumption of a lymph fistula at the level of T12/L1, originating from the thoracic duct. By permanent draining of the posterior fistula without suction and strict intravenous alimentation the fluid production decreased continuously and finally ceased completely. Simultaneously, the neurologic state improved gradually without returning to normal completely. CONCLUSIONS: This case demonstrates that paraplegia can develop due to chylous leakage into the spinal canal without obvious retroperitoneal or intrathoracic involvement. This differential diagnosis should be kept in mind when treating patients with abundant fluid drainage into or from the spinal canal.

Chyle↗

PubMed2004

The effectiveness of polyethylene versus titanium particles in inducing osteolysis in vivo.

Bearing surface wear and periprosthetic osteolysis due to wear particles are among the most common reasons for joint replacement failure. A murine calvarial model of wear particle-induced osteolysis has been used to identify different biologic factors associated with this problem and to test nonsurgical methods of modulating the host response to particulate debris. This model has utilized titanium particles, however, in clinical practice the most common source of particulate debris is polyethylene particles from bearing surface wear. We now report a calvarial model of wear particle-induced osteolysis based on commercially available polyethylene particles. We found that compared to sham surgery osteoclast recruitment and bone resorption can be induced by introduction of the titanium particles or polyethylene particles. However, bone resorption was significantly higher with polyethylene particles compared to titanium particles (p=0.02). We consider the polyethylene based murine calvarial model of wear particle-induced osteolysis a reliable and clinically relevant tool to understand the host factors and potential pharmacologic interventions that can influence wear debris generated osteolysis. This model might serve as an extension of the well-established titanium based bone resorption model.

Animals↗

PubMed2004

The diagnostic value of digital subtraction arthrography and radionuclide arthrography in revision total hip arthroplasty.

An analysis of plain radiographs, digital subtraction arthrography, and radionuclide arthrography was performed in 25 revision hip arthroplasties to evaluate the efficacy and usefulness of these methods in the diagnosis of loosening. The findings by each method were compared with intraoperative assessment of the status of components and expressed in terms of sensitivity, specificity, and predictive accuracy. Overall accuracy for the acetabular component by plain radiographs was 80%; by digital subtraction arthrography, 88%; by radionuclide arthrography, 68%. Overall accuracy for the femoral component by plain radiographs was 92%; by digital subtraction arthrography, 84%; radionuclide arthrography, 76%. We consider subtraction arthrography and radionuclide arthrography to be adjuvant diagnostic tools which may be indicated in individual cases of suspected implant loosening of total hip arthroplasty. The routine use of these two methods is not warranted when compared to plain radiographs.

Arthrography↗

PubMed2004

The cumulative long-term risk of dislocation after primary Charnley total hip arthroplasty.

BACKGROUND: A widely variable prevalence of dislocation after total hip arthroplasty has been reported, partly because of varying durations of follow-up for this specific end-point. The effect of demographic factors on the long-term risk of dislocation as a function of time after total hip arthroplasty is not well understood. The purpose of the present study was to determine the risk of dislocation as a function of time after Charnley total hip arthroplasty and to investigate the demographic factors that influence the cumulative risk of dislocation. METHODS: Six thousand six hundred and twenty-three consecutive primary Charnley total hip arthroplasties were performed in 5459 patients at one institution between 1969 and 1984. The patients included 2869 female patients and 2590 male patients with a mean age of sixty-three years. All procedures were performed with a 22-mm femoral head, and all femoral and acetabular components were fixed with cement. The patients were followed at routine intervals and were specifically queried about dislocation. The cumulative risk of dislocation was calculated with use of the Kaplan-Meier method. RESULTS: Three hundred and twenty hips (4.8%) dislocated. The cumulative risk of a first-time dislocation was 1% at one month and 1.9% at one year and then rose at a constant rate of approximately 1% every five years to 7% at twenty-five years for patients who were alive and had not had a revision by that time. Multivariate analysis revealed that the relative risk of dislocation for female patients (as compared with male patients) was 2.1 and that the relative risk for patients who were seventy years old or more (as compared with those who were less than seventy years old) was 1.3. Three underlying diagnoses-osteonecrosis of the femoral head, acute fracture or nonunion of the proximal part of the femur, and inflammatory arthritis-were associated with a significantly greater risk of dislocation than osteoarthritis was. CONCLUSIONS: The cumulative long-term risk of dislocation after total hip arthroplasty is considerably greater than has been reported in short-term studies. The incidence of dislocation is highest in the first year after arthroplasty and then continues at a relatively constant rate for the life of the arthroplasty. Patients at highest risk are female patients and those with a diagnosis of osteonecrosis of the femoral head or an acute fracture or nonunion of the proximal part of the femur. LEVEL OF EVIDENCE: Prognostic study, Level II-1 (retrospective study). See Instructions to Authors for a complete description of levels of evidence.

Adolescent↗

PubMed2004

Patient survival after hip arthroplasty for metastatic disease of the hip.

BACKGROUND: The hip joint is a common location for metastatic disease. Actual as well as impending fractures at this site are frequently due to mechanical instability after tumor invasion and are usually treated surgically with hip arthroplasty. The objective of this study was to analyze survival and influences on survival after hip arthroplasty for metastatic hip disease. METHODS: Two hundred and ninety-nine patients who had undergone a total of 306 hemiarthroplasty or total hip arthroplasty procedures for treatment of a pathologic or an impending pathologic hip fracture between 1969 and 1996 at our institution were included in this study. Data that had been acquired prospectively within the total joint registry of our institution were reviewed retrospectively. RESULTS: The median duration of survival after the arthroplasty was 8.6 months. The duration of survival was significantly associated with the site of the fracture, location of the primary tumor, and time from the diagnosis of the primary tumor to the surgery for the fracture (p < or = 0.05). The time from the diagnosis to the arthroplasty was a significant independent predictor of survival. CONCLUSIONS: Patients undergoing hip arthroplasty for metastatic disease have a limited life expectancy, with only 40% (120) of the 299 patients in our series still alive at one year after the surgery. By identifying prognostic factors regarding life expectancy, this study provides surgeons and oncologists with information with which to weigh risks and benefits of hip arthroplasty for individual patients preoperatively.

Adult↗

PubMed2003

Absence of surface roughness changes after insertion of one type of matte cemented femoral component during 2 to 15 years.

Theoretically, micromotion might occur even in stable cement-implant interface conditions. It was hypothesized that smoothing of the matte surfaces of femoral components because of abrasion or corrosion phenomena is a possible consequence of micromotion. Two new and 11 femoral components that were retrieved after 2 to 15 years of stable cement-implant interface conditions were inspected, investigated with light microscopy, and evaluated with surface roughness measurement by a profilometer. No surface changes were observed such as abrasion or corrosion phenomena except at the tip and the collar of the femoral components. The surface roughness was Ra = 1.0 and 1.1 micro m in the new femoral components and Ra (mean) = 0.96 micro m (range; 0.8-1.5 micro m) in the retrieved components. There was no correlation between time in situ and surface roughness as confirmed by regression analysis. These data suggest that significant micromotion was not present at the studied interface.

Aged↗

PubMed2002

Late dislocation after total hip arthroplasty.

BACKGROUND: Some patients have a dislocation for the first time many years after a total hip arthroplasty, but little is known about the risk factors and outcomes associated with late dislocation. The purposes of this study were (1) to determine the prevalence of late dislocation after total hip arthroplasty, (2) to characterize demographic and other factors associated with such late dislocations, and (3) to report the outcomes of such late dislocations. METHODS: Between 1969 and 1995, 19,680 primary total hip arthroplasties were performed in 15,964 patients at our institution. According to a prospective surveillance protocol, the patients were followed routinely at regular intervals and were specifically queried at each time-point about whether (and, if so, when) the hip had dislocated. First dislocations that occurred five years or more after the operation were defined as late dislocations. RESULTS: Five hundred and thirteen (2.6%) of the 19,680 hips dislocated. Of the 513 hips, 165 (0.8% of the entire cohort; 32% of the dislocated hips) first dislocated five or more years after the primary arthroplasty. The median time until the occurrence of these late dislocations was 11.3 years (range, five to 24.9 years) after the operation. Late dislocation was more frequent than early dislocation in women (p = 0.03), and late dislocation was associated with a younger age at the time of the primary total hip arthroplasty (median, sixty-three years) than was early dislocation (median, sixty-seven years) (p = 0.02). Clinical factors associated with late dislocation included previous subluxations without dislocation in twenty patients, a substantial episode of trauma in eleven patients, and onset of marked cognitive or motor neurologic impairment in eleven patients. Radiographically, the late dislocation occurred in association with polyethylene wear of >2 mm in eighteen hips, with implant loosening with migration or a change in position in eight, and with initial malposition of the acetabular implant (anteversion of <0 degrees or >30 degrees or abduction of >55 degrees) in thirty. Late dislocation recurred in ninety (55%) of the 165 hips and was treated with a reoperation in fifty-five hips (33% of the hips with late dislocation; 61% of the hips with recurrent dislocation). CONCLUSIONS: Late dislocation is more common than was previously thought. Several separate processes, some distinct from those associated with early dislocation, can lead to late dislocation. Late dislocation can occur in association with a long-standing problem with the prosthesis that manifests late (such as malposition of the implant or recurrent subluxation), it can occur in association with a new problem (such as neurologic decline, an episode of trauma, or polyethylene wear), or it can occur in association with any combination of these factors. The likelihood of the first late dislocation recurring is high.

Adolescent↗