Dislocation after bipolar hemiarthroplasty of the hip

Outcomes Following Hemiarthroplasty for Femoral Neck Fracture in Patients Who Have Hemiparesis

BACKGROUND

Hemiparesis increases the risk of femoral neck fracture (FNF) in the elderly, which frequently necessitates hemiarthroplasty. There are limited reports on the outcomes of hemiarthroplasty in patients who have hemiparesis. The purpose of this study was to evaluate hemiparesis as a potential risk factor for medical and surgical complications following hemiarthroplasty.

METHODS

Hemiparetic patients who have concomitant FNF and underwent hemiarthroplasty with at least 2 years of follow-up were identified using a national insurance database. A 10:1 matched control cohort of patients who did not have hemiparesis was created for comparison. There were 1,340 patients who have and 12,988 patients who did not have hemiparesis undergoing hemiarthroplasty for FNF. Multivariate logistic regression analyses were used to evaluate rates of medical and surgical complications between the 2 cohorts.

RESULTS

Aside from increased rates of medical complications including cerebrovascular accident (P < .001), urinary tract infection (P = .020), sepsis (P = .002), and myocardial infarction (P < .001), patients who have hemiparesis also experienced higher rates of dislocation within 1 and 2 years (Odds Ratio (OR) 1.54, P = .009; OR 1.52, P = .010). Hemiparesis was not associated with higher risk of wound complications, periprosthetic joint infection, aseptic loosening, and periprosthetic fracture, but was associated with higher incidence of 90-day ED-visits (OR 1.16, P = .031) and 90-day readmission (OR 1.32, P < .001).

CONCLUSION

While patients who have hemiparesis do not have increased risk of implant-related complications other than dislocation, they are at increased risk of developing medical complications following hemiarthroplasty for FNF.

Modern cemented Furlong hemiarthroplasty: Are dislocations rates better?

BACKGROUND

Dislocation following hip hemiarthroplasty is a major complication with increased mortality and morbidity. Data looking at dislocation following contemporary bipolar stems are lacking in literature.

METHODS

Retrospective review of our prospective national hip fracture database over a two-year period. Group 1 comprised of consecutive patients receiving bipolar Furlong prosthesis (N222) while Group 2 was made up of a historical cohort (uncemented; N254). Clinical and radiological records were reviewed to determine dislocation rates, causes and associative factors of dislocations. Data were analysed using SPSS.

RESULTS

Following 476 hemiarthroplasties performed during the study period, 12 (2.5%) dislocations were reported (eight in Group 1; four in Group 2). There was no significant difference in dislocation rates (3.6% vs 1.6%) between groups (p = 0.159). Subgroup analysis of Group 1 demonstrated a significant difference in dislocations with Furlong cemented (6%) as compared with Furlong uncemented (0%) hemiarthroplasties (p = 0.024). Following dislocation, death rates increased to 8.3% from 1.7% in both groups.

CONCLUSION

There is a statistically significant increase in dislocation rate following use of cemented Furlong prosthesis when compared to similar uncemented prosthesis at the same treatment period. However, when compared to traditional uncemented prosthesis, there is no difference in dislocation rates.

Factors associated with dislocation after bipolar hemiarthroplasty through an (antero-)lateral approach in elderly patients with a femoral neck fracture: a retrospective cohort study with a nested case-control subanalysis of radiographic parameters

Introduction

Dislocations of hip hemiarthroplasty (HHA) are serious complications. The aim of the study was to identify clinical aspects and radiographic parameters of the hip that put patients at risk for dislocation after HHA for femoral neck fractures.

Methods

This retrospective analysis included elderly patients with a femoral neck fracture treated with a HHA. A lateral (90.7%) and an anterolateral (9.3%) approach was applied. On pelvic radiographs, a nested-controlled analysis was performed. Two control patients were matched to one patient suffering a dislocation with respect to age, sex, and body-mass-index (BMI).

Results

In 527 HHA, 10 dislocations (1.9%) were identified. In the dislocation group (DG), all patients were female (100% vs. 73.5%, p = 0.071). No significant differences between the DG and the control group (CG) were found with respect to age, body-mass-index (BMI), ASA Score, routine laboratory parameters, and comorbidity. Radiographic analysis revealed a smaller center edge angle (CEA, 39.0, IQR 33.0–42.5 vs. 43.0, IQR 41.0–46.0, p = 0.013), a more varus neck-shaft angle (NSA, 130.0, IQR 125.8–133.5 vs. 135.0, IQR 134.0–137.0, p = 0.011) of the contralateral side and a higher femoral head extrusion index (FHEI) in the DG (FHEI, 11.5, IQR 9.8–16.3 vs. 2.0 IQR 0.0–9.0, p = 0.003). In addition, a greater trochanteric fracture was associated with an increased likelihood for HHA dislocations (30.0% vs 6.0%, p = 0.022).

Conclusion

A smaller radiographic center edge angle, a more varus neck-shaft angle of the contralateral side, a higher femoral head extrusion index and intraoperative fractures of the greater trochanter are associated with an increased risk of HHA dislocation.

Clinical results of short external rotators preserving posterolateral approach for hemiarthroplasty after femoral neck fractures in elderly patients

INTRODUCTION

Even though the dislocation rate is lower in the hemiarthroplasty (HA) than total hip arthroplasty, it has still developed as one of serious complications in elderly patients. We have used short external rotators (SER) preserving posterolateral approach to reduce dislocation after hip arthroplasty, especially in elderly patients. The present study was conducted to introduce SER preserving posterolateral approach and report the dislocation rate after HA via this approach in elderly patients with femoral neck fractures.

METHODS

Between January 2015 and July 2019, 307 consecutive elderly patients aged over 70 years who underwent cementless bipolar HA for femoral neck fractures and were followed up for at least one year, were enrolled in this study. All surgeries were performed using the SER preserving posterolateral approach. The demographic and perioperative data were examined and the complications including dislocation were investigated.

RESULTS

Mean operation time was 54.3 min, and mean estimated blood loss was 252.4 cc. The mean follow-up time was 22.1 months, HHS was 67.5 points at the final examination Dislocation following HA developed in only one patient (0.3%) with dementia during hospital stay, which was reduced closely with no subsequent recurrence. Periprosthetic femoral fracture occurred in two patients, which was treated with internal fixation in one patient and with stem revision in the other patient. There was no surgical site infection or periprosthetic infection as complications.

CONCLUSION

The SER preserving technique in posterolateral approach effectively can be effective for reducing the dislocation after HA in elderly patients with femoral neck fracture. It can be encouraged in posterolateral approach for HA, especially in elderly patients under the risk of dislocation.

Cemented versus uncemented hemiarthroplasty for femoral neck fractures in patients with neuromuscular diseases: a minimum of 2 years' follow-up study

BACKGROUND

The aim of this study was to compare the outcomes of cemented and uncemented hemiarthroplasty for femoral neck fractures in patients with neuromuscular disease.

METHODS

We reviewed 156 patients with neuromuscular disease who underwent hemiarthroplasty between June 2015 and December 2019. Patients were divided into cemented group (n = 105) and uncemented group (n = 51), with a minimum follow-up of 2 years. Factors including preoperative features, duration of surgery, intraoperative blood loss, complications, pain, Harris hip scores (HHS), and quality of life were compared across groups, and Kaplan-Meier curves were used to estimate survival.

RESULTS

In the uncemented group, the mean duration of surgery was 16.0 min. shorter (p = 0.001) and the mean intraoperative blood loss was 71.1 mL less (p = 0.01). Visual analog scales (VAS), HHS, and European Quality of Life-5 Dimensions (EQ-5D) scores were not different between the groups. Despite a few potential trends, we did not observe a difference in complications such as periprosthetic fractures and dislocations. The rates of mortality were similar between groups (p=0.821).

CONCLUSIONS

Both arthroplasties may be used with good medium-term results in the treatment of femoral neck fractures in patients with neuromuscular diseases.

Cementless Hemiarthroplasty for Intracapsular Femoral Neck Fractures in the Octa- and Nonagenarians

Backgroud

Current evidence supports the use of cemented hemiarthroplasty for treatment of intracapsular femoral neck fractures since it is associated with a lower risk of implant-related complications. However, many medical centers employ the cementless technique for the frail elderly population because it is faster and has lower cardiovascular risks and perioperative mortality. This observational study reports the outcomes of cementless bipolar hemiarthroplasty for intracapsular femoral neck fractures in patients aged 80 years and older.

Methods

A total of 424 patients (female, 77.1%) with a mean age of 86.9 years were operated for intracapsular femoral neck fractures between January 2009 and December 2017. Of those, 66.7% had an American Society of Anaesthesiologists (ASA) score of 3 or more. All operations were performed with the posterolateral surgical approach and all patients received a cementless stem. Intraoperative and perioperative values and in-hospital outcomes were evaluated, and clinical and radiographical follow-up was done at 40 days, 90 days, and when possible between 5 months and 12 months postoperatively. Multivariate analysis was performed to evaluate if there were factors affecting mortality.

Results

The mean operative time was 50 minutes. There were no deaths intraoperatively. Intraoperative periprosthetic fractures occurred in 2.1% of the cases with 66.7% of them fixed through cerclage wires intraoperatively. The median length of hospitalization was 11 days (interquartile range, 8.75–15) and 2.4% of patients died while in hospital after surgery. Approximately 91.5% of patients presented with perioperative anemia. Only 1.9% of the complications were related to the implant, 62.5% of which were dislocations. More than 90% of patients were ambulatory either autonomously or with support at each follow-up assessment. Age, male sex, and higher ASA score were related to increased mortality.

Conclusions

Despite some limitations, this observational study underlines that a cementless femoral stem of modern design can give good clinical outcomes, thus being an appropriate solution especially for the frail elderly.

Thompson Hemiarthroplasty for Femoral Neck Fracture Is Associated With Increased Risk of Dislocation

BACKGROUND

This contemporaneous large multicenter retrospective study reflective of current practice, assesses the impact of patient factors, prosthesis selection, and implant features on the risk of dislocation after hip hemiarthroplasty for femoral neck fracture.

METHODS

Radiographic records for 4116 consecutive patients who underwent a hip hemiarthroplasty between January 1, 2009 and September 30, 2017 at 3 acute hospitals (including a regional major trauma center) for a neck of femur fracture were reviewed in conjunction with United Kingdom National Hip Fracture Database records.

RESULTS

In total, 4116 patients were eligible for inclusion in the study; 63 of 4116 (1.5%) dislocations were identified. Patient age, gender, preoperative abbreviated mental test score, postoperative abbreviated mental test score, and American Society of Anaesthesiologists grade were not found to be significant predictors of dislocation rates (P < .05). The Furlong prosthesis was the most commonly used implant (2280/4116, 55.4%) followed by the Exeter V40 + Unitrax head (1179/4116, 28.6%), other implants used during the study period were the monoblock Austin-Moore and Thompson implants. Hemiarthroplasty operations undertaken with the Thompson (24/273, 3.7%) were found to have significantly higher dislocation rates (P < .05). Cemented vs uncemented, variable vs fixed offset, and monoblock vs modular implant designs did not contribute to higher dislocation rates (P < .05). Surgeon seniority was also not a significant risk factor for subsequent dislocation (P < .05).

CONCLUSIONS

Thompson hip hemiarthroplasties are associated with higher dislocation rates when compared to a contemporaneous cohort of implant choices and considerations for their use should be made in conjunction with this major risk factor for the need for subsequent operations.

Factors affecting dislocation after bipolar hemiarthroplasty in patients with femoral neck fracture

PURPOSE

This study aimed to investigate the anatomic risk factors associated with dislocation following bipolar hemiarthroplasty for the treatment of femoral neck fracture.

MATERIALS AND METHODS

We retrospectively reviewed 208 consecutive patients (133 women, 75 men) with femoral neck fractures who were treated with bipolar hemiarthroplasty between 2015 and 2018. A comparative analysis was performed between dislocation (n = 18) and non-dislocation (n = 190) groups in terms of patient demographics, surgical and pelvic morphologic factors, and clinical outcomes, including postoperative Harris and modified Harris hip scores. Independent risk factors affecting dislocation were also evaluated.

RESULTS

The mean follow-up period was 30.8 ± 2.0 (range, 12-48) months. The mean age was 79.2 ± 7.4 (range, 71-94) years. The dislocation rate was 8.6% (18/208), and the mean dislocation time after operation was 2.0 ± 1.1 (range, 1-4) months. Patient-related factors did not differ between the dislocated and non-dislocated groups. As regards dislocation, statistically significant difference was observed in surgical and pelvic morphologic factors, including femoral offset, residual femoral neck length, trochanter upper end and femoral head center distance, and height of the hip center of the operated side (p = 0.025, p = 0.013, p = 0.002, p = 0.008, respectively). Moreover, the femoral offset, height of the hip center, and femoral neck-shaft angle of the non-operated side are significantly different between the groups (p = 0.007, p = 0.001, p = 0.027, respectively). Decrease in the center edge (CE) angle, offset of prosthesis, and increase in femoral head extrusion index (FHEI) of the operated side and decrease in the height of the hip center of the non-operated side increased the risk of dislocation (p = 0.030, OR: 1,306; p = 0.041, OR: 8.15; p = 0.020, OR: 1.038; p = 0.010, OR: 2.02, respectively).

CONCLUSIONS

Pelvic morphologic features and surgical factors were found to affect dislocation. Patients with smaller OP, CE angle of the operated side, and higher FHEI and smaller height of the hip center of the non-operated side should be carefully monitored to decrease postoperative dislocation.

Morphological risk factors associated with dislocation after bipolar hemiarthroplasty of the hip in patients with femoral neck fractures-a nested case-control study

Background

The relationship between preoperative hip measurements and dislocation after bipolar hemiarthroplasty is presently unclear. In the current study, we investigated the morphological risk factors associated with dislocation after bipolar hemiarthroplasty of the hip in patients with femoral neck fractures.

Methods

Between January 2011 and June 2017, a nested case-control design study was used to analyze the risk factors for dislocation in 348 patients who had undergone bipolar hemiarthroplasty because of femoral neck fractures. Twelve patients underwent at least one dislocation postoperatively. Sixty patients without dislocation were selected as controls matched in terms of time of surgery, age, and sex, at a ratio of 1:5. Patient acetabular measurements were compared between the dislocation group and the control group, including the center-edge angle, abduction angle, acetabular width and depth, depth-to-width ratio, femoral neck offset, leg length discrepancy, and femoral head coverage ratio. A multivariate logistic regression model was used to evaluate the morphological risk factors of dislocation.

Results

Postoperatively, the incidence of dislocation was 3.4%. A smaller center-edge angle was found to be a risk factor associated with dislocation after bipolar hemiarthroplasty of the hip. Patients with small acetabular depth and a small acetabular depth–width ratio were prone to dislocation. Patients with a center-edge angle of ≤ 45.4° or an acetabular depth of ≤ 19.12 mm were more likely to suffer dislocation.

Conclusions

Careful preoperative measurements before bipolar hemiarthroplasty of the hip are important. Surgical intervention for femoral neck fracture patients with a shallow acetabulum should be carefully planned and total hip arthroplasty should be considered when necessary.

Management and outcome of the dislocated hip hemiarthroplasty

AIMS

This study describes and compares the operative management and outcomes in a consecutive case series of patients with dislocated hemiarthroplasties of the hip, and compares outcomes with those of patients not sustaining a dislocation.

PATIENTS AND METHODS

Of 3326 consecutive patients treated with hemiarthroplasty for fractured neck of femur, 46 (1.4%) sustained dislocations. Of the 46 dislocations, there were 37 female patients (80.4%) and nine male patients (19.6%) with a mean age of 83.8 years (66 to 100). Operative intervention for each, and subsequent dislocations, were recorded. The following outcome measures were recorded: dislocation; mortality up to one-year post-injury; additional surgery; residential status; mobility; and pain score at one year.

RESULTS

Of 43 dislocations, 30 (70%) occurred within one month and 42 (98%) occurred within three months of hip fracture surgery. Seven (16%) of these patients were treated with a single closed reduction and sustained no further dislocations. Four (9%) were treated with open reduction and experienced no further dislocations. Three (7%) hips were left dislocated and the remaining 32 (74%) patients required additional surgery of further closed reduction, revision, or excision arthroplasty. The one-year mortality rates for patients treated with two or fewer reductions (open or closed), successful revision arthroplasty, and excision arthroplasty were 3/14 (21%), 1/7 (14%), and 8/14 (57%) respectively. The only statistically significant difference in mortality was the difference between patients who did not sustain a dislocation and those who did and were treated by excision arthroplasty (p = 0.03). Patients treated by excision arthroplasty had the greatest reduction in mobility scores and highest pain scores. The excision arthroplasty group also included the greatest proportion of patients not able to mobilize and the smallest proportion of patients remaining in their own home.

CONCLUSION

Most dislocations of hemiarthroplasties of the hip occur within one month of surgery. Closed reduction is generally unsuccessful. For those patients with unsuccessful closed reduction, revision arthroplasty should be considered when possible, as this results in a better functional outcome with a lower mortality than excision arthroplasty.

The Dislocated Hip Hemiarthroplasty: Current Concepts of Etiological factors and Management

Background:

Hip hemiarthroplasty (HA) following an intracapsular neck of femur fracture is an increasingly common procedure as a result of an ageing population. Patients are often frail and so morbidity and mortality figures are significant. As a result the National Institute for Health and Clinical Excellence (NICE) has formulated guidelines and a Best Practice Tariff (BPT) in an attempt to improve the care of such patients. Dislocation following HA is a potentially devastating complication with a reported incidence ranging from 1 to 15%. Multiple causative factors have been cited and studied in an effort to reduce the incidence of this complication which has a high rate of recurrence following the first episode and is associated with a high mortality rate and significant financial burden on the health economy. This paper reviews the available literature in an effort to identify the most pertinent factors affecting dislocation rates and thus reduce the incidence of this serious complication.

Methods:

A comprehensive review of the literature was performed using the search engine PubMed with the keywords ‘hip’, ‘hemiarthroplasty’ and ‘dislocation’. Two hundred and forty three articles were identified and assessed by the 3 authors independently. Data from fifty-two articles pertinent to the review on hemiarthroplasty dislocation epidemiology, risk factors and management were extracted in a standardised fashion.

Results:

Following review of the papers multiple causative factors relating to HA dislocation were identified and grouped into 4 broad categories for analysis. The factors with the strongest correlation with dislocation included patient cognition, previous failed surgery, delay to surgery, surgical approach and femoral offset.

Conclusion:

Hip hemiarthroplasty remains the gold standard for elderly patients with intracapsular neck of femur fractures. In each individual case the factors most strongly associated with postoperative dislocation should be recognised. Delays to surgery should be minimised and the posterior approach avoided. In addition to good surgical technique, particular attention should be paid to restoring the patient’s native femoral offset and post operatively those with cognitive impairment should be closely monitored.

A systematic review and meta-analysis of the direct anterior approach for hemiarthroplasty for femoral neck fracture

BACKGROUND

We performed a systematic review and meta-analysis to assess whether the direct anterior approach (DAA) is associated with improved functional and clinical outcomes compared to other surgical approaches for hemiarthroplasty for displaced femoral neck fractures.

MATERIALS AND METHODS

Randomized trials and cohort studies of hemiarthroplasty performed via DAA versus another surgical approach (anterolateral, lateral, posterolateral, posterior) were included. Our primary outcome was postoperative functional mobility. Secondary outcomes included overall complication rate, dislocation rate, perioperative fracture, infection rate, re-operation rate, overall mortality, operative time, pain, intra-operative blood loss, and length of stay.

RESULTS

Nine studies met inclusion criteria, comprising a total of 698 hips (330 direct anterior, 57 anterolateral, 89 lateral, 114 posterolateral, 108 posterior approach). With regard to functional mobility, DAA was favored in 4 studies, and no study favored another approach over DAA. DAA had a significantly lower dislocation rate compared to posterior capsular approaches. Analysis of other secondary outcomes did not identify statistically significant differences.

CONCLUSION

This is the first systematic review and meta-analysis of the DAA for hemiarthroplasty. Available evidence suggests superior early functional mobility with the DAA. The DAA is associated with a significantly lower dislocation rate compared to posterior capsular approaches for hemiarthroplasty.

What Are the Risk Factors for Dislocation of Hip Bipolar Hemiarthroplasty Through the Anterolateral Approach? A Nested Case-control Study

BACKGROUND

Hip dislocation after treatment of a femoral neck fracture with a hemiarthroplasty remains an important problem in the treatment of hip fractures, but the associations between patient factors and surgical factors, and how these factors contribute to dislocation in patients who have undergone bipolar hemiarthroplasty through an anterolateral approach for femoral neck fracture currently are only poorly characterized.

QUESTIONS/PURPOSES

We evaluated patients with bipolar hemiarthroplasty dislocation after surgery for femoral neck fracture treated through an anterolateral approach and asked: (1) What are the frequency, characteristics, and risk factors of bipolar hemiarthroplasty dislocations? (2) What are the frequency, characteristics, and risk factors of bipolar hemiarthroplasty dissociations?

METHODS

A review of hospital records for patients who underwent bipolar hip hemiarthroplasty for femoral neck fracture at one hospital between July 2004 and August 2014 was conducted. During that time, 1428 patients were admitted with a diagnosis of femoral neck fracture; 508 of these patients underwent bipolar hip hemiarthroplasty, of whom 61 died and 23 were lost to followup during the first year, leaving 424 (83%) available for analysis. The remainder of the patients during that time were treated with internal fixation (512), unipoloar hip arthroplasty (17), or THA (391). For each patient with dislocation, we selected five control patients from the cohort according to sex, age (± 3 years), and year of entry in the study to eliminate some confounding factors. We recorded patient characteristics regarding demographics, medical comorbidities, Katz score, American Society of Anesthesiologists score, Mini-Mental State Examination (MMSE) score, and anesthesia type. Medical comorbidities included diabetes, chronic pulmonary disease, heart disease, neuromuscular diseases, and dementia. Univariate analyses were used to search for possible risk factors. Conditional logistic regression analyses on dislocation or dissociation were performed to estimate hazard rates (HRs) and corresponding 95% CIs with covariates of a probability less than 0.1 in univariate analysis.

RESULTS

In this cohort, there were 26 dislocations including four that were also dissociations. The proportion of patients experiencing a dislocation was 6% (26 of 424). The mean interval from surgery to dislocation was 56 weeks (range, 0-433 weeks), and 18 dislocations (69%) occurred within 3 months after surgery. Three variables were independently associated with an increased risk of hip dislocation: dementia (HR, 3.51; 95% CI, 1.19-10.38; p = 0.02), discrepancy of offset (HR, 1.72; 95% CI, 1.15-2.58; p = 0.008), and lower MMSE score (HR, 0.93; 95% CI, 0.88-0.98; p = 0.007). The proportion of patients experiencing a dissociation was 0.9% (four of 424). The result of conditional logistic regression for dissociation showed that cup size smaller than 43 mm was the risk factor (HR = 513.05). However, there was no statistical difference with the probability equaling 0.47.

CONCLUSIONS

After the anterolateral approach for treatment of femoral neck fracture using bipolar hemiarthroplasty, 6% of hips dislocated and 0.9% experienced dissociation. Cognitive dysfunction and discrepancy of offset were independent risk factors associated with an increased risk of prosthetic dislocation. The small cup without a safety ring may be the risk factor of dissociation. Discrepancy of offset should be avoided during the operation by performing an accurate femoral osteotomy and choosing an adequate femoral stem neck length. For patients with cognitive dysfunction and a small cup, suturing the joint capsule during the operation and reinforcing protective measures after surgery might reduce the occurrence of dislocation and dissociation, however a study addressing this is necessary to confirm this.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Risk Factors Associated with Dislocation after Bipolar Hemiarthroplasty in Elderly Patients with Femoral Neck Fracture

Purpose

We investigated the incidence and time of dislocation and other factors associated with dislocation of bipolar hemiarthroplasty related to the treatment of femoral neck fracture in old age patients.

Materials and Methods

Between January 2002 and April 2014, 498 femoral neck fractures (467 patients) were treated with bipolar hemiarthroplasty and included in this study. All surgeries were performed using the postero-lateral approach. The incidence of dislocation was investigated. A comparative analysis between a control group and dislocation group was performed with respect to patient factors including age, gender, body mass index, comorbidities, the ASA (American Society of Anesthesiologists) score, mental status and center-edge angle, and surgical factors including type of femoral stem, leg length discrepancy, femoral offset and method of short external rotator (SER) reconstruction.

Results

The incidence of dislocation was 3.8%, and the dislocation occurred on average 2.2 months (range, 0.6-6.5 months) after operation. No difference in patient-related factors was observed between the two groups. However, a smaller center edge (CE) angle was observed in the dislocation group (42.1°±3.2° vs. 46.9°±5.4°, P<0.001), and significantly lower incidence of dislocation was observed in tendon to bone repair group (0.7% vs 7.8%, P<0.001).

Conclusion

SERs should be repaired using the tendon-to-bone repair method to reduce dislocation rate in elderly patients who undergo bipolar hemiarthroplasty using the postero-lateral approach due to femoral neck fracture. In addition, patients with smaller CE angle should be carefully monitored due to high incidence of dislocation.

Low femoral antetorsion as a risk factor for bony impingement after bipolar hemiarthroplasty

Introduction

Reports of dislocation after bipolar hemiarthroplasty (BHA) abound in literature, and several studies have mentioned the factors that are associated with an increased risk of dislocation. However, there is no report detailing the pattern of impingement in BHA and how femoral antetorsion can affect the range of motion (ROM) after BHA.

Purpose

The purpose of this study was to evaluate the pattern of impingement in BHA and whether femoral antetorsion affects the ROM after BHA using three-dimensional (3D) dynamic motion analysis.

Methods

Using the computed tomography (CT) data of 60 patients (60 hips), including 31 men and 29 women who underwent BHA for the treatment of idiopathic osteonecrosis (ION) of the femoral head, we calculated the antetorsion of the femoral neck, ROM of flexion (Flex), internal rotation (Int-R), and external rotation (Ext-R) using a CT-based 3D simulation software. We evaluated the pattern of impingement and the relationship between femoral antetorsion and ROM in BHA. As for the implant position in the 3D simulation software, the anteversion of the femoral implant was set to be the same as the natural antetorsion of the femoral neck and neck length was set to be the standard neck in all cases.

Results

This study revealed the mechanism of impingement in BHA: (1) bone to bone impingement and (2) implant to bone impingement. We found a significant decrease in the ROM of Flex and Int-R inversely proportional to the femoral antetorsion. In patients with lower femoral antetorsion, the ROM of Flex and Int-R decreased due to bony impingement (the anterior great trochanteric region of the femur impinges on the anteroinferior edge of the anteroinferior iliac spine). Whereas, high anteversion of the femoral implant may decrease the ROM of Ext-R; however, our results also showed that even the lowest ROM of Ext-R with 10° hip extension was over 40°.

Conclusions

We demonstrated that lower femoral antetorsion substantially affects the ROM of Flex and Int-R due to bony impingement. For these patients, there should be consideration given to retaining femoral “anterior offset” in BHA.

Dislocation of bipolar hip hemiarthroplasty through a postero-lateral approach for femoral neck fractures: A cohort study

PURPOSE

To analyze postoperative global femoral offset (FO), leg length discrepancy (LLD) and Wiberg angle as risk factors for prosthetic dislocation after treatment with bipolar hemiarthoplasty (HA) through a postero-lateral approach for femoral neck fracture (FNF).

METHODS

Three hundred and seventy three patients treated with a cemented bipolar HA through a postero-lateral approach between January 2006 and December 2013 were included in a cohort study with a follow-up time ranging from 6 months to 7 years. Radiographs and all surgical records were reviewed regarding Global FO, LLD and Wiberg angle. We compared stable hips without dislocation to those with either a single dislocation and those with recurrent instability.

RESULTS

Three hundred and twenty eight hips fulfilled the inclusion criteria and were analyzed in the study. The incidence of prosthetic dislocation was 10.7% (36/373). The mean time from surgery to first dislocation was 3.9 months (0-47) and 62.5% had recurrent dislocations. Patients with dislocation had a statistically significantly decreased postoperative global FO (-6.4 mm vs. -2.8 mm, p = 0.04), LLD (-2 vs. 1.5 mm, p = 0.03) and smaller Wiberg angle (40° vs. 46°, p = 0.01) on the operated side compared with the rest of cohort. In comparison to age and sex-matched control groups from the cohort, the difference in the radiographic parameters were significant in patients with recurrent dislocations but not in patients with a single dislocation.

CONCLUSION

Patients with recurrent dislocations had a decreased postoperative global FO, shorter leg and shallower acetabulum on the operated side compared with their controls. These factors might decrease the soft-tissue tension around the operated hip and predispose to dislocation.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Treatment of femoral neck fractures with bipolar hemiarthroplasty using a modified minimally invasive posterior approach in patients with neurological disorders

Bipolar hemiarthroplasty is a useful treatment for displaced femoral neck fractures in elderly patients. Although uncommon, dislocation is problematic, particularly in older patients, and those with neurologic disorders are at an increased risk for this complication. Recently, a modified posterior approach to the hip intended to enhance hip joint stability by preserving the short external rotators was described. Therefore, the dislocation rate was compared after bipolar hemiarthroplasty using the modified or standard minimally invasive posterior approach.A retrospective analysis was performed of 67 patients older than 65 years with displaced femoral neck fractures and neurological disorders who underwent bipolar hemiarthroplasty using the modified and standard approaches in 28 and 39 hips, respectively. Follow-up averaged 19.3 months. Dislocation rates for the treatment and control groups were 0% and 7.7%, respectively (P<.01). No significant difference existed in postoperative bleeding, operative time, or length of hospital stay between groups. These data suggest a lower dislocation rate after bipolar hemiarthroplasty via the modified, short external rotator-sparing approach for treating displaced femoral neck fractures in elderly patients with neurological disorders.

Is the dislocation rate higher after bipolar hemiarthroplasty in patients with neuromuscular diseases?

BACKGROUND

Patients with neuromuscular disease reportedly have a higher incidence of postoperative dislocation after bipolar hemiarthroplasty. Although the literature has focused on a high prevalence of preoperative neurologic conditions in patients who had dislocations after bipolar hemiarthroplasties, the relative incidence of dislocation in patients with neuromuscular disease and without is unclear.

QUESTIONS/PURPOSES

We therefore (1) asked whether the incidence of postoperative dislocation after bipolar hemiarthroplasty was greater in patients with neuromuscular disease than for those without, and (2) whether function differed between the two groups, and (3) explored potential risk factors for dislocation in two groups.

METHODS

We retrospectively reviewed 190 patients who underwent bipolar hemiarthroplasties for fracture of the femoral neck between 1996 and 2008. Of the 190 patients, 42 had various neuromuscular diseases and 148 had no history of neuromuscular disease. Intraoperative stability was tested and posterior soft tissue repair was performed in all patients. We determined the incidence of dislocation, postoperative leg length discrepancy, and femoral offset in patients with or without neuromuscular disease.

RESULTS

The incidence of dislocation was 2.6% in all patients. We observed similar rates of dislocation in the two groups: 4.8% (two of 42 hips) in patients with neuromuscular disease and 2.0% (three of 148 hips) in patients without neuromuscular disease.

CONCLUSIONS

In femoral neck fractures in patients with neuromuscular disease, careful preoperative management and operative technique such as a posterior soft tissue repair might decrease the risk of postoperative dislocation; therefore, we consider the bipolar hemiarthroplasty a reasonable treatment option.

LEVEL OF EVIDENCE

Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Dislocation of hip hemiarthroplasty following posterolateral surgical approach: a nested case-control study

PURPOSE

Hip hemiarthroplasty dislocation is a serious complication in treatment of displaced intracapsular hip fractures. We investigated factors associated with an increased risk of dislocation after cemented hip hemiarthroplasty following the posterolateral approach.

METHODS

Between January 2002 and December 2008, 602 hip fractures were treated with cemented unipolar hip hemiarthroplasty. A registry-based analysis was carried out to determine the total number of hemiarthroplasty dislocations in these patients. A control group of 96 patients without dislocation was randomly selected. Logistic regression analysis was performed to evaluate clinical and operative factors associated with dislocation.

RESULTS

Thirty-four patients (5.6%) experienced at least one dislocation. Most were the result of a fall and occurred within two months after surgery. There was a trend for increased dislocation in patients who had been operated on more than 48 hours after admission and in patients who had a longer operative time. Smaller centre-edge angle and hip offset were observed in patients with dislocation. Recurrent dislocation was a significant problem, as 18 patients (62%) experienced multiple dislocations.

CONCLUSIONS

The risk of hemiarthroplasty dislocation following the posterolateral surgical approach may be reduced by prompt surgical treatment and fall prevention in the early postoperative period. Patients with smaller acetabular coverage seem more predisposed to dislocation after the posterolateral approach and may be more suitable for other surgical approaches.

Hip precautions after hemiarthroplasty: what is happening in the UK and at what cost?

INTRODUCTION

The aim of this study was to observe current practice of the use of hip precautions following hemiarthroplasty for hip fractures in England and to audit the cost of hip precautions in this patient group.

METHODS

A telephone review was undertaken of all units identified by the National Hip Fracture Database as receiving centres for hip fractures across England to ascertain current practice in the use of hip precautions. A prospective audit of occupational therapy (OT) practice including the cost of equipment provision and OT time was carried out locally.

RESULTS

All 174 units in England were successfully contacted. Practice varied between centres but hip precautions were in use at 78% of centres. Prior to stopping hip precautions at the local hospital, we audited the costs associated with their use. Mean equipment costs per patient decreased by £12 (from £49 to £37, range: £0–£83) and mean OT time per patient decreased by 1.5 hours (from 8 hours to 6.5 hours, range: 1–22 hours) following removal of hip precaution guidelines. A mean of 0.25 days' discharge delay (range: 0–4 days) due to equipment provision was identified prior to removing hip precautions with no discharge delay following.

CONCLUSIONS

This study has highlighted the variation in practice across the country and inconsistency with the advice published by the British Orthopaedic Association and British Geriatrics Society in the ‘Blue Book’ (The Care of Patients with Fragility Fracture). Hip precautions are unnecessary after hemiarthroplasty, cost money both in therapist time and equipment provision and increase the length of hospital stay. Nevertheless, they continue to be used by three-quarters of trauma hospitals in England.

Treatment of femoral neck fractures in elderly patients over 60 years of age - which is the ideal modality of primary joint replacement?

BACKGROUND

Femoral neck fractures in the elderly are frequent, represent a great health care problem, and have a significant impact on health insurance costs. Reconstruction options using hip arthroplasty include unipolar or bipolar hemiarthroplasty (HA), and total hip arthroplasty (THA). The purpose of this review is to discuss the indications, limitations, and pitfalls of each of these techniques.

METHODS

The Pubmed database was searched for all articles on femoral neck fracture and for the reconstruction options presented in this review using the search terms "femoral neck fracture", "unipolar hemiarthroplasty", "bipolar hemiarthroplasty", and "total hip arthroplasty". In addition, cross-referencing was used to cover articles eventually undetected by the respective search strategies. The resulting articles were then reviewed with regard to the different techniques, outcome and complications of the distinct reconstruction options.

RESULTS

THA yields the best functional results in patients with displaced femoral neck fractures with complication rates comparable to HA. THA is beneficially implanted using an anterior approach exploiting the internervous plane between the tensor fasciae latae and the sartorius muscles allowing for immediate full weight-bearing. Based on our findings, bipolar hemiarthroplasty, similar to unipolar hemiarthroplasty, cannot restorate neither anatomical nor biomechanical features of the hip joint. Therefore, it can only be recommended as a second line of defense-procedure for patients with low functional demands and limited live expectancy.

CONCLUSIONS

THA is the treatment of choice for femoral neck fractures in patients older than 60 years. HA should only be implanted in patients with limited life expectancy.

Failure of closed reduction after dislocation of Austin Moore hemiarthroplasty: an analysis of risk factors a 6-year follow-up study

The aim of this study was to determine the factors associated with failure of closed reduction of dislocated Austin Moore hemiarthroplasty for subcapital neck of femur fracture. There were 44 (1.8%) cases of dislocation for a 6-year period. There were 28 females and 12 males, and mean age was 85.6 years. Thirty-two patients (80%) had redislocations, and 13 patients (40%) required 2 or more closed reductions. Twenty-eight patients subsequently had a Girdlestone arthroplasty. Dementia and a previous failed closed reduction were associated with a higher failure rate (P = .03 and .04, respectively). Failed close reduction patients also had a higher 6-month mortality rate (P = .04). Closed reduction after Austin Moore hip dislocation has a higher failure rate significantly in patients with dementia and are associated with a higher mortality rate. We believe closed reduction should be avoided in these groups of patients, and Girdlestone procedure was considered after initial first dislocation.

Femoral stem displacement during closed reduction of a dislocated bipolar hemiarthroplasty of the hip

This article describes a case of femoral stem displacement during closed reduction of a redislocated bipolar hemiarthroplasty of the hip in a 72-year-old woman who had undergone bipolar hemiarthroplasty using a polished, tapered cemented femoral stem. The polished, tapered cemented femoral stem is vulnerable to displacement when exposed to traction forces. Six days after bipolar hemiarthroplasty, the patient experienced her first dislocation, and immediate reduction of the dislocated hip was easily achieved. However, on the ninth postoperative day, redislocation occurred, and this time, reduction was not achieved. Subsequent radiographs revealed an unreduced state with posterosuperior dislocation of the hip and dissociation of the femoral stem at the cement-stem interface with proximal migration. Open reduction was then performed, and it was noted that the bipolar prosthesis had dislocated posterosuperiorly, the neck of the femoral stem was incarcerated between the short external rotators, and the femoral stem had migrated proximally by approximately 8 cm. The femoral stem was repositioned by freeing it from the short external rotators and gently tapping it into the cement mantle. Our surgical solution is questionable, because the stability of the stem is likely to be inadequate. According to the established study, no difference in stuffiness was observed before extraction and after reinsertion, which supports the surgical solution we chose. Pre-reduction analysis should be conducted to determine the cause and status of a dislocation, and open reduction should be performed if closed reduction fails when treating dislocated bipolar hemiarthroplasty patients.

Disassembly and dislocation of a bipolar hip prosthesis

Dislocation of a hip prosthesis is a common complication. In usual cases of hip prosthesis dislocation, the prosthetic femoral head comes out from either the natural acetabular cavity in a bipolar hemiarthroplasty or the prosthetic acetabulum in a total hip arthroplasty. Only a few cases of bipolar hip prosthesis dislocation due to dissociation between the polyethylene and inner head of the prosthesis have been reported. We describe a rare case of disassembly of the inner head from the bipolar outer prosthesis in an osteoarthritic acetabulum. A 72-year-old woman had undergone bipolar hemiarthroplasty due to fracture of the left femoral neck about 10 years previously. Recently, she sustained an injury after falling from a chair, and examinations revealed an unusual disassembly-dislocation of the bipolar hip prosthesis. We classified this failure in our patient as a type II failure, representing extreme varus position of the outer head in the acetabulum, dislocation of the inner head from the outer head, and a detached locking ring around the stem neck. This mechanism of failure as shown in our patient rarely occurs in the bipolar prosthesis of the self-centering system. Osteoarthritic change of the acetabulum would place the outer head in the varus position, increasing wear on the beveled rim by impinging the femoral stem neck and causing dislodgment of the inner locking ring and consequent disassembly-dislocation of the inner head.

Dislocation rate after conversion from hip hemiarthroplasty to total hip arthroplasty

BACKGROUND

Revision hip arthroplasty is associated with a dislocation rate that is three to five times greater than the rate following primary hip replacement. Conversion of a hip hemiarthroplasty to a total hip replacement is a revision arthroplasty, but it differs from revisions of total hip arthroplasties because a native acetabulum is replaced and the subsequent prosthetic femoral head is smaller. It was our purpose to determine whether the risk of dislocation following conversion surgery is the same as or greater than that following revision total hip replacement.

METHODS

From 1994 to 2005, eighty-nine hemiarthroplasties were converted to a total hip arthroplasty in seventy-seven patients, and the results were compared with those of 115 first-time revision total hip replacements following a primary total hip replacement in 111 patients. A retrospective chart review was performed, and radiographic measurements were obtained. The patient demographics were similar between the two groups. The percentages of patients who had undergone revision of only the acetabular component as compared with both components as well as the percentages of those who had received a modular femoral stem as compared with a nonmodular stem were also similar between the two groups.

RESULTS

Postoperatively, the femoral head size and the positioning of the acetabular component were similar between the two groups. The acetabular components were significantly larger (p < 0.001) in the group in which a total hip arthroplasty had been revised because they required additional acetabular reaming for placement of a new component. There were significantly more dislocations after the conversion procedures (22%) than after the revisions of the total hip arthroplasties (10%) (p < 0.018). Within both groups, the size of the acetabular component, the intraoperative range of motion, and the positioning of the acetabular component were similar between the hips that dislocated and those that did not. However, smaller femoral head components were at greater risk for dislocation after conversion surgery than after revision of a total hip arthroplasty.

CONCLUSIONS

A substantial reduction of the size of the prosthetic femoral head is unique to conversion arthroplasty and appears to play a role in instability after the revision surgery. While the smallest heads dislocated in the conversion group, a larger femoral head did not ensure stability. The increased dislocation risk with conversion surgery requires emphasis on soft-tissue balance and avoidance of excessive downsizing of the femoral head in an attempt to maximize hip stability.

Unconstrained tripolar implants for primary total hip arthroplasty in patients at risk for dislocation

We performed a retrospective study on 167 primary total hip arthroplasty (THA) procedures in 163 patients at high risk for instability to assess the reliability of unconstrained tripolar implants (press-fit outer metal shell articulating a bipolar polyethylene component) in preventing dislocations. Eighty-four percent of the patients had at least 2 risk factors for dislocation. The mean follow-up length was 40.2 months. No dislocation was observed. Harris hip scores improved significantly. Six hips were revised, and no aseptic loosening of the cup was observed. The tripolar implant was extremely successful in achieving stability. However, because of the current lack of data documenting polyethylene wear at additional bearing, the routine use of tripolar implants in primary THA is discouraged and should be considered at the present time only for selected patients at high risk for dislocation and with limited activities.

Dislocation of primary total hip arthroplasty with 36 and 40-mm femoral heads

Some authors suggest the use of larger (36 and 40 mm) femoral heads against highly cross-linked polyethylene acetabular liners will reduce the prevalence of early dislocation after primary total hip arthroplasty (THA). We prospectively followed 61 consecutive patients at high risk for dislocation to determine the prevalence of early dislocation after primary THA with 36 and 40 mm femoral heads. We established specific indications for the use of these larger heads in primary arthroplasty. There were 65 hips in 61 patients with a minimum followup of 1 year (mean 2 years, range 1-4 years). There were 55 36 mm heads and 10 40 mm heads. All arthroplasties were performed by the posterior approach with capsular repair. The prevalence of early dislocation was 4.6% (3 of 65). There was one patient with an anterior dislocation and two with posterior dislocation. No patient underwent reoperation for dislocation. There was no dislocation in the 10 hips that had a 40 mm head. We identified no complications related to the larger femoral heads. The use of larger femoral heads did not notably reduce the prevalence of early dislocation after primary THA in high risk patients compared to historical controls.

Dissociation of bipolar hemiarthroplasty of the hip after dislocation. A report of five different cases and review of literature

Little information is available about the rare but serious disadvantage of dissociation of modular components during dislocation or after close reduction in the bipolar hemiarthroplasty of the hip. In most cases, simple dislocation after primary bipolar hemiarthroplasty can safely be reduced by close methods. Dissociation leads almost always to reoperation and possible revision of the prosthesis. To avoid this complication, strict adherence to the surgical technique during the initial procedure and extra precaution during close reduction are recommended, in order to provide enhanced security over component disassembly. In the five cases presented in this study, dissociation is reported at different circumstances, along with the different methods of treatment required in each patient.

Dislocation of bipolar hemiarthroplasty: rate, contributing factors, and outcome

Dislocation of bipolar hemiarthroplasty of the hip is a rare complication. The objectives of our study were to assess the incidence, contributing factors, and outcomes of bipolar prosthesis dislocation. From 1974 to 2001, 1812 primary bipolar hemiarthroplasties were done at our institution. Seventy-four percent were done in patients with fractures of the femoral neck. An anterolateral surgical approach was used in 79% of hips, a posterolateral approach was used in 14% of hips, and a transtrochanteric approach was used in 7% of hips. Thirty-two hips dislocated. The cumulative probabilities of dislocation at 1 year, 5 years, 10 years, and 20 years were 1.1% (95% CI range, 0.6%-1.6%), 1.5% (95% CI range, 0.9%-2.1%), 2.1% (95% CI range, 1.2%-3.1%), and 5% (95% CI range, 1.9%-9.6%), respectively. There was no significant association of dislocation with the surgical approach or with the primary operative diagnosis. More than (1/2) of the dislocations occurred within 6 months postoperative. Late dislocations occurred most commonly in patients with Bateman prostheses and osteonecrosis and were associated with inner bearing dissociation. Closed reduction was successful in preventing additional surgery in only 30% of patients. The surgeon must be aware that closed reduction may be unsuccessful, and open reduction with replacement of components may be necessary.

LEVEL OF EVIDENCE

Therapeutic study, Level IV (case series). See the Guidelines for Authors for a complete description of levels of evidence.

Failed closed reduction of hip arthroplasty secondary to prosthetic incarceration in the pelvis

This report describes a patient with dislocation of a unipolar hemiarthroplasty that could not be reduced by closed reduction methods because of perforation of the prosthesis through the ileum.

Dislocation after revision of hemiarthroplasty to total hip replacement

Over a 3-year period, nine hemiarthroplasties were revised to total hip arthroplasty. The hemiarthroplasties were all performed for an original diagnosis of subcapital fracture, and the revisions were for a variety of indications including instability, loosening and acetabular erosion. Four of the revised prostheses subsequently dislocated, and one has recurrent subluxation. This dislocation rate of 50% is higher than previously reported. Factors contributing to this are discussed. These include: previous strokes, advanced age, difficulty complying with instructions, and a hip capsule not contracted by osteoarthritis. Preventative factors are discussed. It is imperative to treat this group of patients differently from those having other hip arthroplasties, and to consider prophylactic bracing post-operatively. The capsule or pseudo-capsule should be preserved wherever possible.

Stability of total hip arthroplasty in patients 75 years or older

Increasing patient age (> 75 years) is a known risk factor for dislocation of total hip arthroplasty. This is a study of total hip arthroplasties by one surgeon in patients 75 years or older to determine the prevalence of dislocation and a review of the surgical options for prevention and treatment of instability in this population. Of 140 primary total hip arthroplasties done in patients 75 years or older who were followed up for at least 1 year, the preoperative diagnosis was osteoarthritis in 82% and the mean followup time was 4 years. The acetabular component was cementless: modular in 121 arthroplasties and cemented in 19 arthroplasties. There were five dislocations (3.5%), but only two were recurrent and the patients were treated successfully by modular component exchange. Bipolar arthroplasty has a lower rate of dislocation, but there are problems with residual pain and high rates of reoperation, wear, and osteolysis. Constrained components may be indicated in older patients with dementia, abductor insufficiency, or failure of modular exchange. Large femoral heads, to increase the range of motion before dislocation occurs, may be used with highly cross-linked acetabular liners. Modular cementless acetabular components are preferable in patients who are 75 years or older. A 28-mm or 32-mm femoral head is recommended, but larger femoral heads should be considered in patients with fractures and for the treatment of recurrent dislocation.

Femoral head sizes larger than 32 mm against highly cross-linked polyethylene

The advent of highly cross-linked ultrahigh molecular weight polyethylene, which shows extremely low wear independent of head size in vitro, allows for the reevaluation of the use of femoral heads larger than 32 mm. The current authors discuss information that supports this hypothesis. The supporting information includes in vitro wear testing and in vitro anatomic studies, and prior clinical studies in which large femoral heads were used.

Long-term survivorship of cemented bipolar hemiarthroplasty for fracture of the femoral neck

Cemented bipolar hemiarthroplasty commonly is used to treat displaced fractures of the femoral neck in elderly patients. The purpose of the current study was to review the results and survivorship of 212 bipolar hemiarthroplasties done in 205 patients for acute femoral neck fracture between 1976 and 1985. The mean age of the patients at the time of surgery was 79 years (range, 61-100 years). The mean followup for the patients who were alive was 11.7 years (range, 5.3-16.8 years) and 5.8 years (range, 51 days-19.4 years) for the entire group. Ten hips (4.7%) were revised or removed: five for aseptic femoral component loosening, one for acetabular erosion, one for chronic dislocation, and three for infection. In living patients with surviving implants, 96.2% had no or slight pain. Ten-year survivorship free of reoperation for any reason was 93.6%, free of revision surgery for aseptic femoral loosening or acetabular cartilage wear was 95.9%, free of revision surgery for aseptic femoral loosening was 96.5%, and free of revision surgery for acetabular cartilage wear was 99.4%. Cemented bipolar hemiarthroplasty for acute femoral neck fracture is associated with excellent component survivorship in elderly patients. The rate of complications was low, and the arthroplasty provided satisfactory pain relief for the lifetime of the majority of elderly patients.

Epidemiology of instability after total hip replacement

This article reviews the epidemiology of dislocation after total hip arthroplasty. The overall prevalence, prevalence as a function of time after arthroplasty, and prevalence of recurrent dislocation are reviewed. Risk factors for dislocation are reviewed according to patient characteristics, implant design characteristics, and factors related to surgical technique.