Hip dislocations after 2,734 elective unilateral fast-track total hip arthroplasties: incidence, circumstances and predisposing factors

Body Mass Index Does Not Drive the Risk for Early Postoperative Instability After Total Hip Arthroplasty: A Matched Cohort Analysis

BACKGROUND

Instability remains the leading cause of revision following total hip arthroplasty (THA). The objective of the present investigation was to determine whether an elevated body mass index (BMI) is associated with an increased risk of instability after primary THA.

METHODS

An administrative claims database was queried for patients undergoing elective, primary THA for osteoarthritis between 2010 and 2022. Patients who underwent THA for a femoral neck fracture were excluded. Patients who had an elevated BMI were grouped into the following cohorts: 25 to 29.9 (n = 2,313), 30 to 34.9 (n = 2,230), 35 to 39.9 (n = 1,852), 40 to 44.9 (n = 1,450), 45 to 49.9 (n = 752), and 50 to 59.9 (n = 334). Patients were matched 1:1 based on age, sex, and Elixhauser Comorbidity Index, as well as a history of spinal fusion, neurodegenerative disorders, and alcohol abuse, to controls with a normal BMI (20 to 24.9). A multivariate logistic regression controlling for age, sex, Elixhauser Comorbidity Index, and additional risk factors for dislocation was used to evaluate dislocation rates at 30 days, 90 days, 6 months, 1 year, and 2 years. Rates of revision for instability were similarly compared at 1 year and 2 years postoperatively.

RESULTS

No significant differences in dislocation rate were observed between control patients and each of the evaluated BMI classes at all evaluated postoperative intervals (all P values > .05). Similarly, the risk of revision for instability was comparable between the normal weight cohort and each evaluated BMI class at 1 year and 2 years postoperatively (all P values > .05).

CONCLUSIONS

Controlling for comorbidities and known risk factors for instability, the present analysis demonstrated no difference in rates of dislocation or revision for instability between normal-weight patients and those in higher BMI classes.

Insufficient stem antetorsion and lower cup abduction is a combined risk factor for posterior hip dislocation in patients undergoing THA for femoral neck fractures: a retrospective analysis

BACKGROUND

The role of acetabular and femoral component positions with respect to the risk of post-operative instability and dislocation remains debated. In this study, we aimed to identify potential risk factors for early dislocation following primary total hip arthroplasty (THA) for displaced intracapsular femoral neck fractures (FNF) using radiological measurements.

METHODS

We retrospectively analyzed data for patients who underwent cementless primary THA for FNF using a posterolateral approach between January 2018 and December 2021. Follow-up duration, age, sex, affected side, and mean time from THA to dislocation were recorded. Leg-length inequality, abductor lever arm, vertical and horizontal femoral offsets, vertical and horizontal hip centers of rotation, abduction, anteversion of the acetabulum and femoral prosthesis, and combined anteversion were measured.

RESULTS

The study sample included 17 men and 34 women, with 21 and 30 patients undergoing left- and right-hip operations, respectively. The mean patient age was 70.18 ± 7.64 years, and the mean follow-up duration was 27.73 ± 13.52 months. The mean time between THA and dislocation was 1.58 ± 0.79 months. Seven patients (13.73%) sustained posterior dislocation of the hip. The abduction angle (36.05 ± 6.82° vs. 45.68 ± 8.78°) (p = 0.008) and anteversion of the femoral prosthesis (8.26 ± 4.47° vs. 19.47 ± 9.01°) (p = 0.002) were significantly lower in the dislocation group than in the control group. There were no significant differences in other parameters.

CONCLUSIONS

Insufficient stem antetorsion combined with lower abduction angle of the acetabular component were associated with a high risk of dislocation, especially in patients with deep flexion or internal rotation of the flexed hip joint and knees, or in patients with a stiff spine or anterior pelvic tilt, impingement may then occur in the neck of the prosthesis and cup component, ultimately resulting in posterior dislocation. These findings could remind surgeons to avoid simultaneous occurrence of both in THA surgery. These results provide new insight into risk factors for hip dislocation in patients undergoing primary THA for FNF and may aid in reducing the risk of instability and dislocation.

LEVEL OF EVIDENCE

Prospective comparative study Level II.

Risk Factors for Dislocation following Total Hip Arthroplasty in Developmental Dysplasia of the Hip: A Systematic Review and Meta-Analysis

PURPOSE

This systematic review and meta-analysis aimed to identify risk factors of dislocation after total hip arthroplasty (THA) in patients with developmental dysplasia of the hip (DDH).

METHODS

A systematic literature review was performed on 18th August 2022 using Medline, Embase, Scopus, Web of Science electronic databases, and a manual search. The study was conducted according to the PRISMA guidelines and registered with PROSPERO. Statistical analysis includes assessment of heterogeneity and data synthesis using RevMan 5.4.

RESULTS

Review of five studies including 2865 patients and 116 dislocated hips found that lower body mass index (BMI) (SMD = 0.22, p = 0.04, I2 = 0%), Crowe classification type IV versus I, II, and III (OR = 2.70, p = 0.004, I2 = 51%), higher cup inclination (SMD = 0.39 p = 0.0007, I2 = 0%), femoral head size < 28 mm (OR = 5.07, p = 0.003, I2 = 71%), lateral surgical approach (OR = 1.96, p = 0.02, I2 = 0%), and postoperative infection (OR = 6.26, p < 0.0001, I2 = 0%) were significant risk factors. However, age, gender, cup anteversion, femoral osteotomy, vertical (V-COR) centre of rotation, intraoperative fracture, preoperative and postoperative leg length discrepancy (LLD) and previous hip surgery were not found to be significant risk factors.

CONCLUSION

This study underscores importance of these risk factors in THA planning for DDH patients to reduce dislocation risk. Further research needed to understand mechanisms.

Fast Track Protocols and Early Rehabilitation after Surgery in Total Hip Arthroplasty: A Narrative Review

The Enhanced Recovery After Surgery (ERAS) or Fast Track is defined as a multi-disciplinary, peri- and post-operative approach finalized to reduce surgical stress and simplify post-operative recovery. It has been introduced more than 20 years ago by Khelet to improve outcomes in general surgery. Fast Track is adapted to the patient's condition and improves traditional rehabilitation methods using evidence-based practices. Fast Track programs have been introduced into total hip arthroplasty (THA) surgery, with a reduction in post-operative length of stay, shorter convalescence, and rapid functional recovery without increased morbidity and mortality. We have divided Fast Track into three cores: pre-, intra-, and post-operative. For the first, we analyzed the standards of patient selection, for the second the anesthesiologic and intraoperative protocols, for the third the possible complications and the appropriate postoperative management. This narrative review aims to present the current status of THA Fast Track surgery research, implementation, and perspectives for further improvements. By implementing the ERAS protocol in the THA setting, an increase in patient satisfaction can be obtained while retaining safety and improving clinical outcomes.

Excellent PROM results after fast-track hip and knee arthroplasty with no postoperative restrictions: a cohort study validation of fast-track surgery without postoperative restrictions

Background

Fast-track hip and knee arthroplasty (HA and KA) has been increasingly common over the last decade. In the same time period, there was a strong trend toward less restrictive mobilization. However, few reports have been published on combining these novel programs while measuring the postoperative results by patient-reported outcome measures (PROMs). Descriptions of fast-track surgery programs and their results are warranted.

Methods

The aim of this retrospective cohort study was to examine if it is possible to achieve excellent PROM results for hip and knee arthroplasty patients in a fast-track pathway without postoperative restrictions. During 2014–2017, the stepwise introduction of a PROM program was implemented at Stavanger University Hospital for all scheduled HA and KA patients, with preoperative assessments and postoperative follow-ups at the outpatient clinic. Standardized information with a focus on early mobilization and no postoperative restrictions was also initiated for the same patients. The generic EuroQol questionnaire (EQ-5D) and either the Hip or Knee disability/injury and Osteoarthritis Outcome Score (HOOS or KOOS) were used.

Results

PROM response rates varied from 80 to 99%. The median (interquartile range) change from preoperative to one-year postoperative results were as follows for HA and KA patients, respectively: pain, 55 (43–68) and 47 (31–61); other symptoms, 50 (40–65) and 36 (19–50); function in daily living, 54 (41–65) and 44 (31–55); function in sports and recreation, 56 (38–75) and 40 (15–64); joint-related quality of life, 69 (50–81) and 56 (38–75). The length of stay (LOS) was reduced by 1.9 days (mean), corresponding to a 40% reduction for HA patients and a 37% reduction for KA patients.

Conclusions

We found excellent PROM results after fast-track HA and KA with no postoperative restrictions. We believe that a fast-track program focusing on mobilization without any postoperative restrictions is superior for most patients, but further comparative studies are warranted.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-022-05276-y.

Documented and Undocumented Psychiatric Conditions Affect the Length of Stay and Discharge Disposition Following Total Hip Arthroplasty

BACKGROUND

Despite increased efforts toward patient optimization, some patients have undocumented conditions that can affect costs and quality metrics for institutions and physicians. This study evaluates the effect of documented and undocumented psychiatric conditions on length of stay (LOS) and discharge disposition following total hip arthroplasty (THA).

METHODS

A retrospective review of all primary THAs from 2015 to 2020 at a high-volume academic orthopedic specialty hospital was conducted. Patients were separated into 3 cohorts: patients with a documented psychiatric diagnosis (+Dx), patients without a documented psychiatric diagnosis but with an actively prescribed psychiatric medication (-Dx), and patients without a psychiatric diagnosis or medication (control). Patient demographics, LOS, and discharge disposition were assessed.

RESULTS

A total of 5309 patients were included; 3048 patients had no recorded psychiatric medications (control); 2261 patients took at least 1 psychiatric medication, of which 1513 (65.9%) and 748 (34.1%) patients were put in the -Dx and +Dx cohorts, respectively. American Society of Anesthesiologists class differed between groups (P < .001). The -Dx and +Dx groups had increased LOS (3.15 ± 2.37 [75.6 ± 56.9] and 3.12 ± 2.27 [74.9 ± 54.5] vs 2.42 ± 1.70 [57.6 ± 40.8] days (hours), P < .001) and were more likely to be discharged to a secondary facility (23.0% and 21.7% vs 13.8%, P < .001) than the control group. Outcomes did not significantly differ between the -Dx and +Dx cohorts.

CONCLUSION

Most THA patients' psychiatric diagnoses were not documented. The presence of psychiatric medications was associated with longer LOS and a greater likelihood of discharge to secondary facilities. This has implications for both cost and quality metrics. Review of medications can help identify and optimize these patients before surgery.

LEVEL III EVIDENCE

Retrospective Cohort Study.

Dual Mobility Cup: Does It Improve Patient's Satisfaction After Total Hip Arthroplasty? A Prospective Comparative Randomized Study

INTRODUCTION

Despite the great success of total hip arthroplasty (THA), many patients were fairly dissatisfied after surgery. Therefore, patient-reported outcome measures have become of an utmost importance in assessing the results after joint replacement. This study was conducted to compare the postoperative patient-reported satisfactions after implantation of two commonly used THA designs.

METHODS

Of 180 patients, who initially fulfilled the study selection criteria and received cementless THA, 165 patients were finally eligible and enrolled in this prospective comparative randomized study. All surgeries were carried out between 2010 and 2018. Two groups of homogenous demographic and clinical data were present. Group A patients (n = 80) were treated by large head THA, whereas group B (n = 85) received dual mobility cup designs. The Western Ontario McMaster Universities Osteoarthritis Index and visual analog scale were used for clinical evaluation. The degree of improvement that the patient expected and hoped before undergoing their surgeries was estimated using the score of the new knee society. The self-administered patient satisfaction scale was used to record the levels of patient satisfaction after surgery, and their values were statistically analyzed in relation to preoperative expectation scores (ie, score of the new knee society) and different clinical and sociodemographic variables.

RESULTS

After a mean follow-up of 79 ± 4.13 months (range 24 to 96 months), both groups recorded a significant improvement (P < 0.05) in Western Ontario McMaster Universities Osteoarthritis Index and visual analogue scale scores. Patients of group B were significantly more satisfied (P < 0.05) than those of group A up to the first postoperative year. Certain studied variables were linked to superior satisfaction results among group B at the last follow-up.

CONCLUSIONS

Dual mobility THA provides better patient satisfaction than their standard large head alternatives specifically among elderly patients, socially unsupported individuals, farmers, heavy manual workers, and those with high levels of expectations.

CLINICAL TRIAL REGISTRATION

Clinical Trials.gov identifier: NCT04333316.

Evaluation of Dislocation Risk Factors With Total Hip Arthroplasty in Developmental Hip Dysplasia Patients: A Multivariate Analysis

BACKGROUND

This study aimed to investigate the risk factors for dislocation in patients diagnosed with developmental dysplasia of the hip (DDH) who underwent total hip arthroplasty.

METHODS

We retrospectively reviewed 40 patients who developed dislocation and compared them with 400 patients in the control group without hip instability. Patients-, surgery-, and implant-related factors were investigated. Risk factors were evaluated using multivariate logistic regression.

RESULTS

The mean follow-up period was 32.3 months. The mean time to dislocation was 4.4 months. There were 7 men (17.5%) and 33 women (82.5%) in the dislocation group and 83 men (20.7%) and 317 women (79.3%) in the control group (P = .627). Diabetes mellitus (DM; P = .032) and history of previous hip surgery for DDH were associated with dislocation (P < .001). The subtrochanteric shortening osteotomy (P = .001), acetabular inclination (P = .037), acetabular anteversion (P < .001), femoral head size (P < .001), and postoperative infection (P = .003) were associated with dislocation. Major predictors of hip dislocation after total hip arthroplasty in patients with DDH were previous hip surgery (odds ratio [OR], 6.76; 95% confidence interval [CI], 1.86-24.6; P = .004), high hip center (OR, 2.90; 95% CI, 1.31-6.38; P = .008), DM (OR, 2.68; 95% CI, 1.06-6.80; P = .037), and acetabular inclination (OR, 2.62; 95% CI, 1.09-6.26; P = .03).

CONCLUSION

Patients with DM and previous hip surgery should be informed about increased dislocation rates. Using a larger head diameter and restoration of the true hip rotation center are essential to prevent hip dislocation in these patients. Furthermore, accurate positioning of the acetabular inclination and anteversion are also important.

Are hip movement precautions effective in preventing prosthesis dislocation post hip arthroplasty using a posterior surgical approach? A systematic review and meta-analysis

PURPOSE

To determine if hip movement precautions reduce hip prosthesis dislocation rates post hip arthroplasty using a posterior surgical approach compared to minimal or no movement restrictions.

MATERIALS AND METHODS

This review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and was registered prospectively. CINAHL, MEDLINE and Embase were searched from inception until September 2020 supplemented by citation tracking. Studies were included if patients had a hip arthroplasty using a posterior surgical approach with comparative data on hip movement precautions or minimal to no movement restrictions. Methodological quality was evaluated using the Downs and Black checklist.

RESULTS

From a yield of 8 studies, meta-analysis of 7 studies and 9599 total hip arthroplasties, there was low quality evidence of no increased risk of dislocation (RR = 0.98, 95%CI 0.58 to 1.67) for patients prescribed minimal or no hip movement restrictions compared with patients prescribed hip movement precautions. There were 121/5440 dislocations (2.2%) in the movement precaution group and 90/4159 dislocations in the minimally restricted group (2.2%).

CONCLUSIONS

Dislocation rates after total hip arthroplasty are low irrespective of movement precaution allocation. Resources allocated to implementing hip movement precautions may be better directed towards other clinical areas.IMPLICATIONS FOR REHABILITATIONThere was no difference in hip prosthesis dislocation rate between patients who received hip movement precautions compared to patients who received minimal or no restrictions after total hip arthroplasty using a posterior surgical approach.Health professionals involved in prescribing and monitoring adherence to hip movement precautions after total hip arthroplasty may be better allocating their resources to other areas of clinical care.Falls were associated with the greatest number of prosthesis dislocations, accounting for 24% of dislocations; resources may be better allocated towards evidence-based strategies to reduce falls.

Dual mobility acetabular construct with freedom constrained liner for treatment of recurrent dislocations after total hip arthroplasty: A case report and literature review

•

Dual-mobility bearings improve stability in total hip arthroplasty (THA) but may fail to prevent postoperative dislocation.

•

Dry revision with a compatible constrained liner system can provide an effective salvage option for instability after THA.

•

The unique G7 constrained liner system offers good short-term stability and range of motion.

Introduction

Recurrent dislocation after total hip arthroplasty (THA) using the dual mobility cup system can present challenges, while dual-mobility THA bearings can improve stability in both primary and revision total hip arthroplasties.

Presentation of case

A 72-year-old woman with a history of schizophrenia underwent a left primary THA using the G7 dual mobility system. Two postoperative posterior dislocations occurred within 2 months post-surgery. The patient underwent revision surgery in which the metal liner and dual mobility head were exchanged using the Freedom constrained liner system without revision of the cup and stem. As of this writing, 28 months after the revision surgery, no further dislocations have occurred. The implants are stable, and the patient has good range of motion.

Discussion

Dual-mobility bearings are utilized to improve stability in both primary and revision total hip arthroplasties, but even if the dual mobility system is chosen, it sometimes fails to prevent postoperative dislocation. Although a relatively high failure rate has been reported in THA using the constrained liner system, this patient’s clinical course suggests that the G7 Freedom constrained liner system can be an efficacious option for some patients with unstable hip joints who undergo THA using the dual mobility system.

Conclusion

A modern constrained liner system such as the G7 Freedom liner may provide an improved salvage solution for joint instability in dual mobility THA.

Review and synthesis of the experience of patients following total hip or knee arthroplasty in the era of rapidly decreasing hospital length of stay

AIM

The hospital length of stay for orthopedic surgery has been decreasing during the last couple of decades. Therefore, this study was performed to explore the postoperative experiences of adult/older patients (age ≥20 years) with osteoarthritis who underwent total hip or knee arthroplasty, focusing on the first 6 weeks following discharge.

METHODS

A systematic literature search on qualitative studies was conducted using six databases, such as Medline, CINAHL and Mednar. Verbatim interview data and themes or subthemes related to the patients' experience after discharge were extracted. Content analysis was used to code interview data. Codes similar in meaning were grouped, and subcategories were formed. These subcategories were then grouped into categories.

RESULTS

Sixteen qualitative studies with 253 participants were analyzed. In total, 136 codes were generated and formed 29 subcategories. Six categories were generated: (a) postoperative pain and medication; (b) difficulty in performing activities of daily living; (c) appreciation for support and difficulties associated with receiving support; (d) variability in recovery process and information-seeking; (e) lack of patient-centered care; and (f) transportation problems and social isolation.

CONCLUSION

Our review suggests that prospective patients and their caregivers need individually tailored presurgical education and advanced planning for postsurgical reduced mobility.

Introducing enhanced recovery after surgery in a high-volume orthopaedic hospital: a health technology assessment

BACKGROUND

The number of patients undergoing joint arthroplasty is increasing worldwide. An Enhanced Recovery After Surgery (ERAS) pathway for hip and knee arthroplasty was introduced in an Italian high-volume research hospital in March 2018.

METHODS

The aim of this mixed methods observational study is to perform a health technology assessment (HTA) of the ERAS pathway, considering 938 procedures performed after its implementation, by means of a hospital-based approach derived from the EUnetHTA (European Network for Health Technology Assessment) Core Model. The assessment process is based on dimensions of general relevance, safety, efficacy, effectiveness, economic and financial impact, equity, legal aspects, social and ethical impact, and organizational impact. A narrative review of the literature helped to identify general relevance, safety and efficacy factors, and a set of relevant sub-dimensions submitted to the evaluation of the professionals who use the technology through a 7-item Likert Scale. The economic and financial impact of the ERAS pathway on the hospital budget was supported by quantitative data collected from internal or national registries, employing economic modelling strategies to identify the amount of resources required to implement it.

RESULTS

The relevance of technology under assessment is recognized worldwide. A number of studies show accelerated pathways to dominate conventional approaches on pain reduction, functional recovery, prevention of complications, improvements in tolerability and quality of life, including fragile or vulnerable patients. Qualitative surveys on clinical and functional outcomes confirm most of these benefits. The ERAS pathway is associated with a reduced length of stay in comparison with the Italian hospitalization average for the same procedures, despite the poor spread of the pathway within the country may generate postcode inequalities. The economic analyses show how the resources invested in training activities are largely depreciated by benefits once the technology is permanently introduced, which may generate hospital cost savings of up to 2054,123.44 € per year.

CONCLUSIONS

Galeazzi Hospital's ERAS pathway for hip and knee arthroplasty results preferable to traditional approaches following most of the HTA dimensions, and offers room for further improvement. The more comparable practices are shared, the before this potential improvement can be identified and addressed.

Posterior approach, fracture diagnosis, and American Society of Anesthesiology class III-IV are associated with increased risk of revision for dislocation after total hip arthroplasty: An analysis of 33,337 operations from the Finnish Arthroplasty Register

Background and objective:

Dislocation is one of the most common reasons for revision surgery after primary total hip arthroplasty. Both patient related and surgical factors may influence the risk of dislocation. In this study, we evaluated risk factors for dislocation revision after total hip arthroplasty based on revised data contents of the Finnish Arthroplasty Register.

Methods:

We analyzed 33,337 primary total hip arthroplasties performed between May 2014 and January 2018 in Finland. Cox proportional hazards regression was used to estimate hazard ratios with 95% confidence intervals for first dislocation revision using 18 potential risk factors as covariates, such as age, sex, diagnosis, hospital volume, surgical approach, head size, body mass index, American Society of Anesthesiology class, and fixation method.

Results:

During the study period, there were 264 first-time revisions for dislocation after primary total hip arthroplasty. The hazard ratio for dislocation revision was 3.1 (confidence interval 1.7–5.5) for posterior compared to anterolateral approach, 3.0 (confidence interval 1.9–4.7) for total hip arthroplasties performed for femoral neck fracture compared to total hip arthroplasties performed for osteoarthritis, 2.0 (confidence interval 1.0–3.9) for American Society of Anesthesiology class III–IV compared to American Society of Anesthesiology class I, and 0.5 (0.4–0.7) for 36-mm femoral head size compared to 32-mm head size.

Conclusions:

Special attention should be paid to patients with fracture diagnoses and American Society of Anesthesiology class III–IV. Anterolateral approach and 36-mm femoral heads decrease dislocation revision risk and should be considered for high-risk patients.

It is safe to use minimal restrictions following posterior approach total hip arthroplasty: results from a large cohort study

BACKGROUND

To prevent early postoperative dislocation following a total hip arthroplasty (THA) procedure, patients must adhere to restrictions. Restrictive protocols are common if THA surgery is performed using the posterior approach, but scientific evidence form larger studies that supports these restrictions are scarce. In this large cohort study we compare the <90-days dislocation rate between patients receiving posterior approach THA managed with minimal versus extensive restrictions.

METHODS

Prospective cohort (n = 1049) of consecutive elective primary hip replacement surgery procedures (September 2014-July 2017) managed with minimal postoperative restrictions. Hospital charts were prospectively reviewed for patient demographics, risk factors and any hip dislocation. Control (n = 1102) consecutive primary elective THAs (January 2011-August 2014) managed with a traditional restrictive protocol. A posterior surgical approach was used in all procedures.

RESULTS

Minimal restrictions group: 17 dislocations <90 days (1.6%); Restricted group: 28 (2.5%), chi-square p = 0.1. Testing the hypothesis of inferiority by a minimum of 1% increase in ⩽90 days dislocation risk: p = 0.14 (test for difference) and p < 0.001 (non-inferiority test), allowing us to discard the null hypothesis (absolute increase in risk of ⩾1% with minimal restrictions). The proportion of surgeries performed with a femoral head size ⩾32 mm was higher in the minimal restrictions group.

CONCLUSIONS

Patients can be managed safely with minimal restrictions following posterior approach THA if combined with frequent use of larger femoral heads.

Dislocation of large-diameter head metal-on-metal total hip arthroplasty and hip resurfacing arthroplasty

INTRODUCTION

Dislocation of large-diameter head (LDH) metal-on-metal (MoM) total hip arthroplasty (THA) or hip resurfacing arthroplasty (HRA) is a rare complication. This study aimed to determine the incidence and risk factors for dislocation of LDH MoM THAs and HRAs.

METHODS

This retrospective analysis considered 4038 cementless LDH MoM THAs and HRAs, 3207 THAs in 2912 patients and 831 HRAs in 757 patients. The end of follow-up was revision due to dislocation. Incidence of dislocation was evaluated from this study population of 4038, and study groups were formed. The study was designed as a case-control study, and a threefold stratified randomised control group was formed. Demographic data were collected and radiological analyses were performed in the study groups.

RESULTS

There were 26/3207 (0.8%) early dislocations in the THA group, and 6/831 (0.7%) in the HRA group ( p = 0.9). Most LDH THA dislocations occurred in a group with head size ⩽ 38 mm (18/26) ( p < 0.001). In dislocated hips, there were more dysplastic acetabula and post-traumatic hips than in the control group ( p = 0.036). In the dislocation group, the mean acetabulum component anteversion angle was 19.6° (standard deviation [SD] 13.4°) and in the control group it was 23.2° (SD 10.4°) ( p = 0.006); 7/32 (21.8%) of dislocated THAs needed revision surgery, and mean time to revision from the index surgery was 1.2 (SD 2.6) years.

DISCUSSION

Dislocations occurred more often in THAs of head size ⩽ 38 mm and with a smaller anteversion angle of the acetabulum component. Hip dysplasia and post-traumatic osteoarthritis were more common in patients with dislocation.

Varying but reduced use of postoperative mobilization restrictions after primary total hip arthroplasty in Nordic countries: a questionnaire-based study

Background and purpose - Mobilization has traditionally been restricted following total hip arthroplasty (THA) in an attempt to reduce the risk of dislocation and muscle detachment. However, recent studies have questioned the effect and rationale underlying such restrictions. We investigated the use of postoperative restrictions and possible differences in mobilization protocols following primary THA in Denmark (DK), Finland (FIN), Norway (NO), and Sweden (SWE). Patients and methods - All hospitals performing primary THA in the participating countries were identified from the latest national THA registry report. A questionnaire containing questions regarding standard surgical procedure, use of restrictions, and postoperative mobilization protocol was distributed to all hospitals through national representatives for each arthroplasty registry. Results - 83% to 94% (n = 167) of the 199 hospitals performing THA in DK, FIN, NO, and SWE returned correctly filled out questionnaires. A posterolateral approach was used by 77% of the hospitals. 92% of the hospitals had a standardized mobilization protocol. 50%, 41%, 19%, and 38% of the hospitals in DK, FIN, NO, and SWE, respectively, did not have any postoperative restrictions. If utilized, restrictions were applied for a median of 6 weeks. Two-thirds of all hospitals have changed their mobilization protocol within the last 5 years-all but 2 to a less restrictive protocol. Interpretation - Use of postoperative restrictions following primary THA differs between the Nordic countries, with 19% to 50% allowing mobilization without any restrictions. There has been a strong tendency towards less restrictive mobilization over the last 5 years.

No increase in readmissions or adverse events after implementation of fast-track program in total hip and knee replacement at 8 Swedish hospitals: An observational before-and-after study of 14,148 total joint replacements 2011-2015

Background and purpose - Fast-track care programs in elective total hip and knee replacement (THR/TKR) have been introduced in several countries during the last decade resulting in a significant reduction of hospital stay without any rise in readmissions or early adverse events (AE). We evaluated the risk of readmissions and AE within 30 and 90 days after surgery when a fast-track program was introduced in routine care of joint replacement at 8 Swedish hospitals. Patients and methods - Fast-track care programs were introduced at 8 public hospitals in Västra Götaland region from 2012 to 2014. We obtained data from the Swedish Hip and Knee Arthroplasty Registers for patients operated with THR and TKR in 2011-2015. All readmissions and new contacts with the health care system within 3 months with a possible connection to the surgical intervention were requested from the regional patient register. We compared patients operated before and after the introduction of the fast-track program. Results - Implementation of the fast-track program resulted in a decrease in median hospital length of stay (LOS) from 5 to 3 days in both THR and TKR. The total readmission rate <90 days for THR was 7.2% with fast-track compared with 6.7% in the previous program, and for TKR 8.4% in both groups. Almost half of the readmissions occurred without any AE identified. There was no statistically significant difference concerning readmissions or AE when comparing the programs. Interpretation - Implementation of a fast-track care program in routine care of elective hip and knee replacement is effective in reducing hospital stay without increasing the risk of readmissions or adverse events within 90 days after surgery.

Cost and determinants of acute kidney injury after elective primary total joint arthroplasty

Background

Acute kidney injury (AKI) is a serious complication after major surgery, which may lead to increased morbidity and mortality. The aim of this study was to identify cost and determinants of AKI after total joint arthroplasty.

Methods

A retrospective case-controlled study was conducted with 1719 primary elective total hip or knee replacements performed from January 2004 through September 2015 at an urban teaching hospital. Patients who developed AKI were matched in a 1:3 ratio with those in a control group who did not develop AKI based on age, sex, race, operated joint, and comorbidities including hypertension and diabetes. Increased postoperative serum creatinine was considered indicative of AKI.

Results

Fifty-four patients (3.1%) had AKI that was significantly associated with increased length of hospital stay (8.07 days) compared with that of the control group (4.50 days, P < .0001) and incurred significantly higher hospital charges ($224,533) than those of the control group ($142,753, P < .0001). We identified high body mass index, undergoing bilateral surgery in one session, high estimated blood loss, and longer duration of surgery as significant risk factors for AKI in univariate analysis. Elevated preoperative creatinine, large postoperative drop in hemoglobin, and high American Society of Anesthesiologists physical status scores were significant independent predictors of AKI in multivariate analysis.

Conclusions

Health-care providers and patients should work together to manage risk factors and to lower the risk of morbidity and mortality, longer in-hospital stay, and high associated costs of AKI.

Nationwide multicenter follow-up cohort study of hip arthroplasties performed for osteonecrosis of the femoral head

PURPOSE

To identify modifiable factors related to post-operative dislocation and reoperation in patients with osteonecrosis of the femoral head (ONFH) in a large cohort.

METHODS

We studied 4995 hip arthroplasties: total hip arthroplasty (THA) was performed in 79% of patients; bipolar hemiarthroplasty (BP), 17%; total resurfacing arthroplasty (tRS), 3%; and hemi-resurfacing arthroplasty (hRS), 1%. A new type of BP (accounting for 49% of BPs) comprised a femoral component with a polished or smooth, small-diameter (approximately 10 mm) neck with a round or oval axial cut surface and no sharp corners.

RESULTS

The infection rate was relatively low (0.56%) even though 58% of cases of ONFH were associated with systemic steroid use, a known risk factor for infection. Post-operative dislocation occurred in 4.3% of cases, with re-operation needed in 3.9%. The dislocation rate was related to surgery type: 5.2% in THA, 0.9% in BP, and 0% in tRS and hRS. Among total arthroplasties with six month or longer follow-up (3670 THAs and 159 tRSs), the risk factors for post-operative dislocation were younger (≤ 40 years) or older (≥ 62 years) age, higher body weight, posterolateral approach, and smaller prosthetic head diameter. Regarding the need for re-operation, higher body weight and surgery type were identified as risk factors.

CONCLUSIONS

The relatively high dislocation rate of 5.2% in THA is a cause for concern. The identified risk factors for dislocation should be considered when selecting THA for treatment. Prosthesis survivorship in hRSs was inferior to that in BPs or THAs. Body weight also affected the survivorship of hip arthroplasties.

Prevention of Dislocation After Total Hip Arthroplasty

BACKGROUND

Prevention of dislocation after primary total hip arthroplasty (THA) begins with patient preoperative assessment and planning.

METHODS

We performed a literature search to assess historical perspectives and current strategies to prevent dislocation after primary THA. The search yielded 3458 articles, and 154 articles are presented.

RESULTS

Extremes of age, body mass index >30 kg/m², lumbosacral pathology, surgeon experience, and femoral head size influence dislocation rates after THA. There is mixed evidence regarding the effect of neuromuscular disease, sequelae of pediatric hip conditions, and surgical approach on THA instability. Sex, simultaneous bilateral THA, and restrictive postoperative precautions do not influence the dislocation rates of THA. Navigation, robotics, lipped liners, and dual-mobility acetabular components may improve dislocation rates.

CONCLUSIONS

Risks for dislocation should be identified, and measures should be taken to mitigate the risk. Reliance on safe zones of acetabular component positioning is historical. We are in an era of bespoke THA surgery.

Reduced length of uninterrupted institutional stay after implementing a fast-track protocol for primary total hip replacement

Background and purpose - Fast-track protocols have been successfully implemented in many hospitals as they have been shown to result in shorter length of stay (LOS) without compromising results. We evaluated the effect of fast-track implementation on the use of institutional care and results after total hip replacement (THR). Patients and methods - 3,193 THRs performed in 4 hospitals between 2009-2010 and 2012-2013 were identified from the Finnish Hospital Discharge Register and the Finnish Arthroplasty Register. Hospitals were classified as fast-track (Hospital A) and non-fast-track (Hospitals B, C, and D). We analyzed LOS, length of uninterrupted institutional care (LUIC, including LOS), discharge destination, readmission, revision rate, and mortality in each hospital. We compared these outcomes for THRs performed in Hospital A before and after fast-track implementation and we also compared outcomes, excluding readmission rates, with the corresponding outcomes for the other hospitals. Results - After fast-track implementation, median LOS in Hospital A diminished from 5 to 2 days (p < 0.001) and (median) LUIC from 6 to 3 (p = 0.001) days. No statistically significant changes occurred in discharge destination. However, the reduction in LOS was combined with an increase in the 42-day readmission rate (3.1% to 8.3%) (p < 0.001). A higher proportion of patients were at home 1 week after THR (p < 0.001) in Hospital A after fast-tracking than before. Interpretation - The fast-track protocol reduces LUIC but needs careful implementation to maintain good quality of care throughout the treatment process.

Can Surgeons Reduce the Risk for Dislocation After Primary Total Hip Arthroplasty Performed Using the Posterolateral Approach?

BACKGROUND

Hip dislocation is one of the most common postoperative complications after total hip arthroplasty (THA). Potential contributors include patient- and surgical-related factors. We performed a retrospective cohort study to identify risk factors for postoperative dislocation in patients receiving THA via the posterolateral approach.

METHODS

We assessed 1326 consecutive primary THAs performed between 2010 and 2015. Patient information was documented, and plain radiographic films were used to evaluate cup positioning, hip offset, and hip length change. A multiple logistic regression was used to identify risk factors for dislocation. Follow-up was coordinated by the Danish National Patient Registry.

RESULTS

Age and American Society of Anesthesiologists scores were higher in dislocating THA compared with those in the nondislocating THA. Cup anteversion was less in dislocating THA compared with that in nondislocating THA. Independent risk factors for cup dislocation were increased age, body mass index <25 and >30 kg/m², and leg shortening of >5 mm.

CONCLUSION

Surgeons should aim for a shortening of leg length <5 mm to reduce the risk of postoperative dislocation in primary THA. Although anteversion was reduced for dislocating THA, there is likely no universal safe zone for cup positioning. Hip stability is multifactorial, and optimal cup positioning may vary from patient to patient.

Quantifying Pelvic Motion During Total Hip Arthroplasty Using a New Surgical Navigation Device

BACKGROUND

Accurate cup positioning is one of the most challenging aspects of total hip arthroplasty (THA). Undetected movement of the patient during THA surgery can lead to inaccuracies in cup anteversion and inclination, increasing the potential for dislocation and revision surgery. Investigations into the magnitude of patient motion during THA are not well represented in the literature.

METHODS

We analyzed intraoperative pelvic motion using a novel navigation device used to assist surgeons with cup position, leg length, and offset during THA. This device uses an integrated accelerometer to measure motion in 2 orthogonal degrees of freedom. We reviewed the data from 99 cases completed between February and September 2016.

RESULTS

The mean amount of pitch recorded per patient was 2.7° (standard deviation, 2.2; range, 0.1°-9.9°), whereas mean roll per patient was 7.3° (standard deviation, 5.5; range, 0.3°-31.3°). Twenty-one percent (21 of 99) of patients demonstrated pitch of >4°. Sixty-nine percent (68 of 99) of patients demonstrated >4° of roll, and 25% (25 of 99) of patients demonstrated roll of ≥10°.

CONCLUSION

Our findings indicate that while the majority of intraoperative motion is <4°, many patients experience significant roll, with a large proportion rolling >10°. This degree of movement has implications for acetabular cup position, as failure to compensate for this motion can result in placement of the cup outside the planned safe zone, thus, increasing the potential for dislocation. Further study is warranted to determine the effect of this motion on cup position, leg length, and offset.

Increased risk of intraoperative and early postoperative periprosthetic femoral fracture with uncemented stems

Background and purpose - The use of uncemented fixation in total hip arthroplasty (THA) is increasing. Registry studies have indicated an increased risk of revision of uncemented implants due to early periprosthetic femoral fracture. In this paper, we describe the incidence and predisposing factors for intraoperative and early postoperative (≤ 90 days) periprosthetic femoral fractures after cemented and uncemented THA. Patients and methods - This was a prospective observational study in 8 Danish high-volume centers from February 2010 to November 2013. We used the 90-day follow-up from the Danish National Patient Registry and patient records. We obtained intraoperative information from the Danish Hip Arthroplasty Registry and from surgical notes. Results - Of 7,169 primary consecutive THAs, 5,482 (77%) were performed using uncemented femoral components. The total incidence of periprosthetic femoral fractures ≤ 90 days postoperatively was 2.1% (n = 150). 70 fractures were detected intraoperatively (46 required osteosynthesis). 51 postoperatively detected fractures occurred without trauma (42 of which were reoperated) and 29 were postoperative fall-related fractures (27 of which were reoperated). 134 fractures (2.4%) were found in uncemented femoral components and 16 (0.9%) were found in cemented femoral components (p < 0.001). Uncemented femoral stem (relative risk (RR) = 4.1, 95% CI: 2.3-7.2), medically treated osteoporosis (RR =2.8, CI: 1.6-4.8), female sex (RR =1.6, CI: 1.1-2.2), and age (RR =1.4 per 10 years, CI: 1.2-1.6) were associated with increased risk of periprosthetic femoral fracture when analyzed using multivariable regression analysis. Interpretation - Uncemented femoral components were associated with an increased risk of early periprosthetic femoral fractures, especially in elderly, female, and osteoporotic patients.

Fast track in hip arthroplasty

‘Fast-track’ surgery was introduced more than 20 years ago and may be defined as a co-ordinated peri-operative approach aimed at reducing surgical stress and facilitating post-operative recovery.

The fast-track programmes have now been introduced into total hip arthroplasty (THA) surgery with reduction in post-operative length of stay, shorter convalescence and rapid functional recovery without increased morbidity and mortality. This has been achieved by focusing on a multidisciplinary collaboration and establishing ‘fast-track’ units, with a well-defined organisational set-up tailored to deliver an accelerated peri-operative course of fast-track surgical THA procedures.

Fast-track THA surgery now works extremely well in the standard THA patient. However, all patients are different and fine-tuning of the multiple areas in fast-track pathways to get patients with special needs or high co-morbidity burden through a safe and effective fast-track THA pathway is important.

In this narrative review, the principles of fast-track THA surgery are presented together with the present status of implementation and perspectives for further improvements.

Cite this article: EFORT Open Rev 2017;2. DOI: 10.1302/2058-5241.2.160060. Originally published online at www.efortopenreviews.org

Acetabular cup position and risk of dislocation in primary total hip arthroplasty

Background and purpose - Hip dislocation is one of the most common complications following total hip arthroplasty (THA). Several factors that affect dislocation have been identified, including acetabular cup positioning. Optimal values for cup inclination and anteversion are debatable. We performed a systematic review to describe the different methods for measuring cup placement, target zones for cup positioning, and the association between cup positioning and dislocation following primary THA. Methods - A systematic search of literature in the PubMed database was performed (January and February 2016) to identify articles that compared acetabular cup positioning and the risk of dislocation. Surgical approach and methods for measurement of cup angles were also considered. Results - 28 articles were determined to be relevant to our research question. Some articles demonstrated that cup positioning influenced postoperative dislocation whereas others did not. The majority of articles could not identify a statistically significant difference between dislocating and non-dislocating THA with regard to mean angles of cup anteversion and inclination. Most of the articles that assessed cup placement within the Lewinnek safe zone did not show a statistically significant reduction in dislocation rate. Alternative target ranges have been proposed by several authors. Interpretation - The Lewinnek safe zone could not be justified. It is difficult to draw broad conclusions regarding a definitive target zone for cup positioning in THA, due to variability between studies and the likely multifactorial nature of THA dislocation. Future studies comparing cup positioning and dislocation rate should investigate surgical approach separately. Standardized tools for measurement of cup positioning should be implemented to allow comparison between studies.

Does BMI influence hospital stay and morbidity after fast-track hip and knee arthroplasty?

Background and purpose - Body mass index (BMI) outside the normal range possibly affects the perioperative morbidity and mortality following total hip arthroplasty (THA) and total knee arthroplasty (TKA) in traditional care programs. We determined perioperative morbidity and mortality in such patients who were operated with the fast-track methodology and compared the levels with those in patients with normal BMI. Patients and methods - This was a prospective observational study involving 13,730 procedures (7,194 THA and 6,536 TKA operations) performed in a standardized fast-track setting. Complete 90-day follow-up was achieved using national registries and review of medical records. Patients were grouped according to BMI as being underweight, of normal weight, overweight, obese, very obese, and morbidly obese. Results - Median length of stay (LOS) was 2 (IQR: 2-3) days in all BMI groups. 30-day re-admission rates were around 6% for both THA (6.1%) and TKA (5.9%), without any statistically significant differences between BMI groups in univariate analysis (p > 0.4), but there was a trend of a protective effect of overweight for both THA (p = 0.1) and TKA (p = 0.06). 90-day re-admission rates increased to 8.6% for THA and 8.3% for TKA, which was similar among BMI groups, but there was a trend of lower rates in overweight and obese TKA patients (p = 0.08 and p = 0.06, respectively). When we adjusted for preoperative comorbidity, high BMI in THA patients (very obese and morbidly obese patients only) was associated with a LOS of >4 days (p = 0.001), but not with re-admission. No such relationship existed for TKA. Interpretation - A fast-track setting resulted in similar length of hospital stay and re-admission rates regardless of BMI, except for very obese and morbidly obese THA patients.

Should We Think Twice About Psychiatric Disease in Total Hip Arthroplasty?

BACKGROUND

Psychiatric disease (PD) is common, and the effect on complications in total hip arthroplasty (THA) is poorly understood. The purpose of this study was to evaluate the medical and surgical postoperative complication profile in patients with PD, and we hypothesize that they will be significantly increased compared with control group.

METHODS

A search of the entire Medicare database from 2005 to 2011 was performed using International Classification of Disease version 9 codes to identify 86,976 patients who underwent primary THA with PD including bipolar (5626), depression (82,557), and schizophrenia (3776). A cohort of 590,689 served as a control with minimum 2-year follow-up. Medical and surgical complications at 30-day, 90-day, and overall time points were compared between the 2 cohorts.

RESULTS

Patients with PD were more likely to be younger (age < 65 years; odds ratio [OR] = 4.51, P < .001), female (OR = 2.02, P < .001) and more medically complex (significant increase in 28/28 Elixhauser medical comorbidities, P < .001). There was a significant increase (P < .001) in 13/14 (92.8%) recorded postoperative medical complications rates at the 90-day time point. In addition, there was a statistically significant increase in periprosthetic infection (OR = 2.26, P < .001), periprosthetic fracture (OR = 2.09, P < .001), dislocation (OR = 2.30, P < .001), and THA revision (OR = 1.93, P < .001) at overall follow-up.

CONCLUSION

Patients with PD who undergo elective primary THA have significantly increased medical and surgical complication rates in the global period and short-term follow-up, and these patients need to be counseled accordingly.

Patient-reported importance of assistive devices in hip and knee replacement Enhanced Recovery after Surgery (ERAS) pathways

Introduction

This study examines patients’ perceptions of the usefulness of occupational therapy and assistive devices provided, in achieving discharge criteria and assisting with activities of daily living once home, following an Enhanced Recovery After Surgery protocol for total hip and total knee replacement patients.

Methods

Two weeks following discharge, 197 patients who had undergone total hip replacement or total knee replacement were telephoned to ask how useful they found occupational therapy education and advice and the assistive devices provided.

Results

114 patients (58%) answered the call. Over 96% of patients found occupational therapy education and advice useful. Ninety-seven percent of posterior total hip replacement patients were still using the assistive devices 2 weeks following discharge, compared to 90% of anterior total hip replacement patients and 87% of total knee replacement patients. Over 95% of all patients found that assistive devices enhanced their ability to undertake activities of daily living, and were extremely or partly useful in achieving early discharge.

Conclusion

Over 85% of patients who responded perceived the occupational therapist’s advice and education, and assistive devices provided, to be useful in achieving discharge criteria, and in enhancing their ability to undertake activities of daily living once back in a home environment.

The rate of dislocation is not increased when minimal precautions are used after total hip arthroplasty using the posterolateral approach

Aims

In order to prevent dislocation of the hip after total hip arthroplasty (THA), patients have to adhere to precautions in the early post-operative period. The hypothesis of this study was that a protocol with minimal precautions after primary THA using the posterolateral approach would not increase the short-term (less than three months) risk of dislocation.

Patients and Methods

We prospectively monitored a group of unselected patients undergoing primary THA managed with standard precautions (n = 109, median age 68.9 years; interquartile range (IQR) 61.2 to 77.3) and a group who were managed with fewer precautions (n = 108, median age 67.2 years; IQR 59.8 to 73.2). There were no significant differences between the groups in relation to predisposing risk factors. The diameter of the femoral head ranged from 28 mm to 36 mm; meticulous soft-tissue repair was undertaken in all patients. The medical records were reviewed and all patients were contacted three months post-operatively to confirm whether they had experienced a dislocation.

Results

There were no dislocations in the less restricted group and one in the more restricted group (p = 0.32).

Conclusion

For experienced surgeons using the posterolateral approach at THA and femoral heads of diameter ≥ 28 mm, it appears safe to manage patients in the immediate post-operative period with minimal precautions to protect against dislocation. Larger studies with adequate statistical power are needed to verify this conclusion. Take home message: Experienced orthopaedic surgeons using the posterolateral approach for THA should not fear an increased dislocation rate if they manage their patients with a minimal precautions protocol. Cite this article: Bone Joint J 2016;98-B:589–94.

Can computer-assisted surgery help restore leg length and offset during THA? A continuous series of 321 cases

INTRODUCTION

Total hip arthroplasty (THA) can bring about complications - particularly leg length differences - that are becoming increasingly litigious. Computer-assisted orthopedic surgery (CAOS) can help optimize the procedure, but its ability to effectively restore leg length is controversial. As a consequence, we carried out a study to determine: (1) its contribution to meeting leg length and offset objectives, (2) its reliability, by evaluating the correlation between radiological and navigation data, (3) its safety, by evaluating navigation-specific and non-specific complications.

HYPOTHESIS

CAOS will help to restore leg length within ± 5 mm in more than 80% of cases.

MATERIAL AND METHODS

A series of 321 continuous cases of cementless THA implanted through the posterolateral approach using CAOS was analyzed retrospectively. With a minimum 1 year follow-up, we evaluated whether the leg length and offset goals were achieved, how well the navigation and radiology data were correlated and whether navigation-specific and non-specific complications occurred. Based on our hypothesis that 80% of patients would have less than 5 mm leg length difference and the null hypothesis (PA = P0) with an alpha of 0.05, 200 observations were required to achieve a power of 90%.

RESULTS

The leg length and offset objectives were achieved in 83.3% and 88% of cases, respectively. Twenty-two patients required a heel wedge to compensate for leg length differences. The correlation between the radiology and surgical navigation data was satisfactory - the Pearson coefficient was 0.79 for length and 0.74 for offset. Intraoperative and postoperative complications or adverse events were found in 14.6% of cases; these were specific to CAOS in 12.1% of cases and non-specific in 2.5% of cases.

CONCLUSION

This study shows the relevance of CAOS for achieving preoperative leg length objectives, with good correlation between navigation and radiology data, and without major complications.

LEVEL OF EVIDENCE

IV - retrospective study.

Risk factors for renal dysfunction after total hip joint replacement; a retrospective cohort study

Background and purpose of the study

Renal injury and dysfunction are serious complications after major surgery, which may lead to increased morbidity and mortality. The objective of our study was to identify the possible risk factors for renal dysfunction after total hip joint replacement surgery.

Methods

A retrospective study was conducted among 599 consecutive primary hip joint replacements performed between January 2011 and December 2013. According to the RIFLE criteria, increased postoperative serum creatinine was considered indicative of postoperative renal injury. The Welch two-sample test, chi-square test, and Fisher exact test were used for statistical analysis.

Results

Eighty-one patients (13.8 %) had significant moderate or severe postoperative renal dysfunction in which 10 patients (1.7 %) acquired severe and permanent renal impairment.

Conclusion

We identified advanced age, hypertension, general anesthesia, high ASA scores, low intra-operative systolic BP, and prophylactic dicloxacillin as significant risk factors. Low baseline systolic BP, low baseline diastolic blood pressure, and hip fracture diagnosis were independent risk factors for postoperative increase in serum creatinine. Smoking, diabetes mellitus, high BMI, gender, and duration of surgery were not identified as significant risk factors.