An evaluation of peri-operative clinical, serological and radiological parameters in hip arthroplasties -a prospective observational study of Indian cohorts

Abstract

Background

The scarcity of mortality data in our country led to systematic effort with aim of evaluating peri-operative parameters associated with mortality in hip arthroplasties to determine better fixation method and reducing avoidable variables.

Materials & methods

252 consecutive patients (133 males and 119 females; Mean age 58.68 years) operated for hip arthroplasties (cemented & uncemented THR and bipolar hemiarthroplasty) were observed prospectively for 2 years. Heart-rate, O₂ saturation and BP were recorded at specific surgical steps and post-operatively for 48 h. Post-operative Trop-T and 2D Echocardiography were done in all patients and D-Dimer and CTPA in indicated ones. All post-operative deaths were extensively studied.

Results

- Majority (63%) were operated for traumatic indications.48% belonged to ASA grade-1, 46% grade-2 and 4% grade-3. There was statistically significant association of diagnosis (traumatic aetiology), ASA grade 2, raised Troponin -T, raised D-dimer and pulmonary embolism with mortality. Mortality rate in our study at post-op 48 h was 5.5%, 30 day- 8% and 1-year mortality rate was 19%. With total of 14 deaths, 8 deaths (57.14%) occurred among 127 cemented arthroplasties and 6 deaths (42.86%) among 125 uncemented arthroplasties.

Conclusions

Selection of implant (cemented or uncemented) made no difference in eventual mortality. Collaborative effort of orthopaedic surgeon, anaesthetist and experts from respective fields in elderly high-risk patient with vigilant post-operative surveillance for minimum 48 h would help in lowering mortality associated with hip arthroplasties.

1. Introduction

As the prevalence of hip and knee osteoarthritis increases with age, orthopaedic surgery has become widely prevalent among elderly individuals. Most Total Hip Replacements [THRs] (>two-thirds) are performed in elderly patients (>65 years old) which happens to be a population with frequent comorbidities.¹ Newer techniques for THR have steadily improved functional outcomes and implant survivorship over the decades. Perpetual expansion of the indications for THR due to growing expectations for enhanced quality of life necessitates more attention towards identifying proficient approaches for preventing adverse outcomes, including death, following hip replacements. Mantilla CB² conducted a study to assess the complication rates associated with primary total hip or knee arthroplasty and reported the following complications: myocardial infarction (MI) (2.2%), pulmonary embolism (PE) (0.7%), deep venous thrombosis (DVT) (1.5%), and the devastating complication of death (0.5%). Total hip replacement causes a short-term increase in the risk of mortality. A study by Costain DJ³ et al. reported the 30 day and 1-year mortality to be 7% and 21% respectively in patients who underwent hemiarthroplasty. Among patients undergoing surgery for hip fractures, the reported all-cause 30-day mortality ranges from 2.5% to 8% and 1-year mortality is greater than 25%.⁴

An important cause of intra and post-operative morbidity and mortality in patients undergoing hip arthroplasty is the bone cement implantation syndrome (BCIS) which causes abrupt changes in hemodynamic and respiratory profile of the patient.^5,6 The incidence of BCIS remains unknown mainly due to the lack of a universally accepted definition.⁴ Most reports on BCIS focus on the mortalities and severe problems, and most mild BCIS cases go unreported. Contrary to expectations, cardiovascular complications appear to have overtaken fatal pulmonary emboli as the leading cause of death after hip replacement.⁷ It is important to quantify this and to identify modifiable risk factors so that the risk of post-operative mortality can be minimised.

There is a dearth in the availability of such data in our country. Mortality data is neither systematically collected nor published. This study was a systematic effort to clinically, radiologically and serologically assess intra-operative and post-operative mortalities in THR and bipolar hemiarthroplasty (cemented and uncemented) in a tertiary care centre. When available, the additional data that has been generated would aid surgeons in determining the best method of THR or hemiarthroplasty among different groups of patients. Also, a comprehensive evaluation of the mortalities would enable to improve the quality of post-operative care and mortalities can be significantly reduced.

2. Materials and methods

All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2008. Informed consent was obtained from all patients for being included in the study.

This was a prospective, observational study conducted at a tertiary care centre for a period of two years from September 2016 to August 2018. A total of 252 patients undergoing elective total hip arthroplasty (cemented or uncemented) and bipolar hemiarthroplasty (cemented or uncemented) at our centre were considered eligible for the study. The objective of our study is to characterize factors surrounding the outcome of perioperative mortality after primary hip arthroplasty-

• •The Clinical, Radiological and Serological Evaluation of Intra-Operative and Post-Operative Mortalities in cemented as well as uncemented hip arthroplasties
• •To calculate the incidence of perioperative mortalities in cemented as well as uncemented hip arthroplasties.

Furthermore, we pursued to identify risk factors for these outcomes and recognize the timing of fatal or near fatal events.

2.1. Inclusion criteria

Patients of any age or gender who were already planned for hip arthroplasty and were willing to give written informed consent were enrolled for the study.

2.2. Exclusion criteria

Patients with pre-existing thrombo-embolic disorder.

Patients with bony metastasis or pathological hip fractures (due to abnormal vascular channels causing erroneously more incidence of BCIS).

The Intra-operative parameters that were assessed included-

2.3. Clinical parameters

O₂ saturation.

Haemodynamics in the form of.

Heart rate.

Blood Pressure (systolic and diastolic) and.

Mean Arterial Pressure.

These parameters were monitored at the following steps in the surgical procedure-

• •Pre-operatively as baseline
• •Femoral Reaming
• •Acetabular cement Implantation
• •Femoral cement Implantation
• •Insertion of the Prosthesis
• •Joint Reduction

The post-operative parameters that were assessed included:

Continuous multi parameter clinical monitoring for 48 h which included:

• •Complaints of sudden onset chest pain in ward
• •Breathlessness in ward
• •Drop in O₂ saturation more than 5% of baseline
• •Sudden excessive hypotension >20% of baseline

2.4. Serological parameters

• •
  Trop-T screening was performed in all patients.

  • -
    Age adjusted cut-off value (≥14 pg/ml for patients aged less than 75 years and ≥45pg/ml for age more than 75 years) for post-operative Trop-T levels.⁸
• •
  D-dimer levels were documented and analysed in patients who showed following:

  • 1.
    Intra-operative drop in O₂ saturation more than 5% of baseline
  • 2.
    Intra-operative sudden excessive hypotension>20% of baseline

Radiological parameters:a) Post-operative 2D Echocardiographic evaluation was performed in all patients. b) Post op CT pulmonary angiography (CTPA) was performed when D-Dimer levels were positive (in order to assess the presence of any evidence of pulmonary emboli).

The age adjusted cut-off point for D-Dimer which was used is defined^9,10 as:

For patients ≥50 years → [age × 10].

For patients <50 years of age → 500 μg/L.

Any post-operative death occurring within 48 h of operation was evaluated in detail and the exact cause of death according to post mortem report was monitored. All patients were followed up for minimum two years post-surgery.

2.5. Statistical analysis

Descriptive statistics like mean, standard deviations and percentage proportions were used to describe baseline study participant parameters. Parametric tests were used to analyse parametric data if it passed the tests of normality; if it failed then non-parametric tests were used for analysis. Chi-square test was used to analyse categorical data. Pearson correlation test was used for parametric correlation analysis while Spearman correlation test was used to analyse non-parametric correlation. The data entry and analysis were performed using the MS Excel and GraphPad software.

3. Results

The analysis of the prospectively-collected data on 252 consecutive patients who had undergone hip replacement from September 2016 to August 2018 was done. Data was comprehensive and precise for peri-operative and 1 year mortality for all patients. In the present study, the mean age of our study patients was 58.68 ± 19.39 years. Of the 252 patients enrolled in our study, 58% were males, and 42% were females. In our study, most common indication for hip arthroplasty was trans-cervical neck femur fractures (49%), while the other causes were avascular necrosis (AVN) of the hip (25%), Intertrochanteric femur fracture (14%) and hip arthritis (11%).

In our study 63% people were operated for traumatic indications and the remaining 37% for non-traumatic indications. While it is difficult to establish causal relationships from our data, it is reasonable that traumatic cases do present with less time for optimization of medical problems.

Among our 252 patients, 48% were identified with (American society of Anaesthesiologists) ASA grade 1, 46% with ASA grade 2 and 4% with ASA grade 3. In our study, majority, i.e. 96% patients did not have a significant history of any major cardiac/respiratory disease, as compared to remaining 4% that reported a significant history.

In our study, 10% patients underwent cemented THA, 35% patients underwent uncemented THA, 40% patients underwent cemented bipolar hemiarthroplasty and 15% patients underwent uncemented bipolar hemiarthroplasty.

We recorded the following intraoperative haemodynamic parameters: Drop in saturation level >20% was seen in 2 out of 252 patients while there was no drop in BP >20% in any of our patients. Postoperative troponin T levels were raised in 15% patients while it was within normal limits in 85% patients. Postoperative 2D echo was performed and within normal limits in 90% patients whereas it could not be done in 10% patients.

Postoperatively, chest pain and breathlessness were observed in 4% patients while it was absent in the rest 96% patients. Postoperative D-Dimer levels were raised in 1% patients while it was not applicable to be done in 99% patients. In the present study, postoperative CTPA revealed pulmonary embolus in 1 patient while it was not applicable to be done in the rest 251 patients.

During our study there were death of 14 patients post operatively. All the deaths were studied in detail and the following observations were made (Table 1, Table 2, Table 3).

Table 1.

Association between mortality and various factors.

Factors	% (n = 14)	R	p-value
Diagnosis
Hip arthritis (1/14)	07.14	−0.117	0.24636
IT Femur fracture(1/14)	07.14
TC Neck femur fracture(12/14)	85.71
ASA grade
1(4/14)	28.57	0.31106	0.00163
2(8/14)	57.14
3(2/14)	14.28
Surgery
Cemented bipolar(7/14)	50	−0.17622	0.07947
Uncemented bipolar(5/14)	35.72
Uncemented THA(1/14)	7.14
Cemented THA(1/14)	7.14
Intraoperative drop
Saturation	0	–	–
BP	0
Trop-T
Raised(8/14)	57.78	0.55291	0
WNL(6/14)	42.22
2D Echo
Could not be done(12/14)	85.78	–	–
WNL(2/14)	14.22
Postoperative assessment
Chest pain & breathlessness(8/14)	77.78	0.87238	0
D-dimer (raised) (1/14)	11.11	0.20466	0.04109
CTPA (PE) (1/14)	11.11	0.31958	0.00119

Calculated using Spearman's correlation coefficient (r).

Where r = 1 means a perfect positive correlation and.

r = −1 means a perfect negative correlation.

P-value <0.05 considered statistically significant.

Table 2.

Association between Mortality and various parameters.

Significant	Non-significant
•Traumatic	•Cemented or Uncemented
•ASA grade ≥2
•↑Trop-T
•↑ D-dimer

Table 3.

Schematic representation of various peri-operative parameters and its association with mortality (Total 14 post-operative deaths).

Mortality rates in our study at 48 h post-op was 5.5%, 30-day mortality was 8% and 1-year mortality rate was 19%. No intra operative deaths were noted in our study. With regard to deaths, we obtained a follow-up of 100% at 1 year. Out of 14 deaths – 10 were of traumatic aetiology and 4 were non-traumatic in aetiology. Further among traumatic cases, 9 were transcervical neck of femur fracture and 1 was inter trochanteric femur fracture. 4 non-traumatic deaths included 3 avascular necrosis and 1 hip arthritis due to Rheumatoid arthritis. There were 8 deaths (out of 14 deaths-57.14%) in cemented hip arthroplasties out of 127 total cemented hips (6.29%) and 6 deaths (out of 14 deaths-42.86%) among 125 uncemented hip arthroplasties (4.80%). The Spearman's correlation coefficient (r) was used to assess the association between mortality and various parameters. There was a statistically significant association of diagnosis (p = 0.00241) especially traumatic aetiology with mortality. There was no statistically significant association (0.07947) of the type of surgery (whether cemented or uncemented) with mortality. The chi-square test was used to compare the association between the type of surgery and death and revealed no statistically significant difference (p = 0.24941). The debate regarding superiority of cemented versus uncemented techniques remains unresolved since their introduction. Scientific evaluation published in the world literature conclude no difference. Systematic reviews and meta-analysis by pioneers in arthroplasty like Morshed, Abdul Karim, Olsen F, Costain DJ, Ning GZ, reveal selection of implant whether cemented or uncemented did not make a difference in the eventual mortality of patients.^11,12

A statistically significant association (p = 0.00163) was observed between ASA grade 2 and mortality. None of the patients that did not survive experience an intraoperative drop in saturation or BP. There was a statistically significant association (p = 0) between raised troponin-T levels and mortality. We observed a statistically significant associations between mortality and chest pain and breathlessness (p = 0), raised d-dimer levels (p = 0.04109) and pulmonary embolism (0.00119).

4. Discussion

A few meta-analyses have reported no difference in mortality rates between cemented and uncemented techniques. A meta-analysis of 12 studies by Ning GZ et al., found no significant difference in mortality, hospital stay, blood loss, operation time, residual pain, and complication rate between those treated with cemented and uncemented hemiarthroplasty.¹¹ Another systematic review and meta-analysis of RCTs comparing cemented and uncemented THRs, reported no significant difference in the Harris hip functional score, radiological osteolysis, mortality and complications.¹² While a retrospective analysis of patients who underwent cemented or uncemented hemiarthroplasty for hip fractures found a higher mortality rate during initial hospital treatment in those treated with cemented hemiarthroplasty (4.1%) compared to uncemented (1%), though it was not significant. No significant difference was found in the rate of dislocations, deep infections and peri-prosthetic fractures during follow up between the two groups.¹³ In yet another study by Kim YH et al., comparing patients younger than 50 years of age who underwent hybrid and cementless THR, found no significant difference in post-operative HHS, WOMAC scores and UCLA activity scores. They also reported that the rate of survival and revision of the acetabular and femoral component to be comparable between the two fixation methods.¹⁴ Mäkelä KT et al., conducted a study using data from the Nordic Arthroplasty Register Association database and found the 10-year survival rate of cemented implants to be 93.8% in patients aged 65–74 years and 95.9% in those 75 years or older; compared to 92.9% and 93.0% in uncemented implants, 91.6% and 93.9% in hybrid implants and 90.7% and 93.2% in reverse hybrid implants. Among patients aged 55–64 years no significant difference was found between cemented (92.2%) and uncemented (91.8%) implants.¹⁵ Olsen F et al. ⁽³⁾, in a retrospective study of patients who underwent cemented hemiarthroplasty reported the incidence of BCIS grade 1, 2, and 3 to be 21%, 5.1%, and 1.7% respectively. The mortality rate was 9% at 30 days and 29% after 1 year. Of those who died within the first 48 h, 95% were grade 2 or 3. The reported predictors for severe BCIS were ASA grade III—IV, chronic obstructive pulmonary disease, and use of diuretics or warfarin.⁴ A study from Norway found the incidence of intraoperative cardiovascular collapse or death in grade 3 BCIS patients to be 0.5%.¹⁶ It has been revealed that overall death rate (5.5%) in our study at 48 h is low and compares favourably with 1 year mortality rates cited in the world literature (7%–9%). Also 1-year mortality rate (19%) is lower as compared to world literature (25–30%).

We took the following measures to mitigate the surgical and anaesthetic risk which may have contributed to the lower mortality rates.

4.1. Surgical risk reduction

In order to avoid BCIS development surgery was delayed in non-emergency cases till the cardiorespiratory reserves and other serological parameters were brought to satisfactory levels.⁵ A thorough medullary lavage was given every time the canal was instrumented. We ensured good haemostasis before canal preparation in both cemented and uncemented surgeries. The safest ways to reduce BCIS incidence is Cement gun and retrograde insertion was employed. Cement guns cause more even pressure distribution in medullary cavity and less fall in oxygen saturation. A vent was placed distally above the plug to reduce pressure at the cement/marrow vessel interface during insertion of the cement.

4.2. Anaesthetic risk reduction

Due to the lack of clinical trials comparing BCIS management approaches, the current recommendations are based on empiric evidence, from case reports¹⁷ and on basic physiological principles.¹ Consensus meet by group of expert anaesthetist from United Kingdom gave an attempt to formulate safety guidelines with the goal of preventing complications associated with cemenetd hemi-arthroplasty.¹⁸ Despite the fact that there is no strong evidence regarding the influence of anaesthetic procedure on BCIS, the broad-spectrum doctrines of management comprised of preoperative recognition of high-risk patients, enhancement of their cardiovascular reserve prior to surgery and intraoperative maintenance of high inspired oxygen concentrations and normovolemia.

Since the syndrome is a revocable time-limited phenomenon, supportive treatment and hostile resuscitation are indispensable to diminish associated morbidity as well as mortality.¹⁹ Invasive anaesthetic monitoring was carried out in high-risk patients undergoing cemented arthroplasty.¹ The first sign of BCIS in an anaesthetized patient in the form of a fall in the end tidal carbon dioxide concentration was paid attention to. In patients given regional anaesthesia, dyspnoea and altered sensorium are the first signs indicative of BCIS.²⁰ Hence, the anaesthetic technique was chosen based on the individual patient and the type of prosthesis involved.

However, the limitations of the study must be recognised. Our study included relatively small numbers of patients, and we feel that this area is worthy of further study. Since mortality after total hip replacement surgeries is low large number of patients are needed to obtain statistically significant effects. Treatment allocation was not randomised and may have introduced a bias which we have been unable to measure. A prospective randomised study would be an ideal way to compare the efficacy of management modalities of BCIS. However, instituting such a study, may not be ethical. Post-operative deaths remain an enigma and result in innumerable sleepless nights for the surgeons and patients alike. The alarmingly high mortality rates post hip arthroplasty strongly indicate that the prevention and treatment of thromboembolic events should play a central role when targeting to reduce or eliminate avoidable deaths following hip replacements.

Age remains an independent risk factor for mortality even after adjustments for comorbidity burden and other variables have been made. Appropriate attention to the care of elderly and comorbid patients would help to achieve a larger drop in mortality. This study provides good baseline estimates on mortality for future studies. Our data can be utilised to evaluate the risk for perioperative mortality and to create targeted intervention to decrease the risk. Our data can be used in order to inform surgeons and their patients of the risk of mortality surrounding these surgical procedures and integrated in the consent process. In patients with numerous risk factors for mortality a discussion of risks and benefits seems sensible. It is unrealistic to expect to completely eliminate post-operative mortality associated with hip arthroplasties, specifically in elderly high-risk patients, but as healthcare providers we can strive for minimization of avoidable risk factors.

5. Conclusion

The findings from the present study highlight the importance of considering following factors to curb complications following hip arthroplasties. In order to reduce these complications, there is a need for:

• •Identification, scrutinization and optimization of high-risk patients (particularly those with cardiovascular and respiratory co-morbidities).
• •Selection of implant whether cemented or uncemented did not make a difference in the eventual mortality of patients.
• •For a post-operative period of 48 h intensive monitoring of patients in an adequate setup should be done especially for the high-risk ones. Orthopedicians and anaesthetists must assess and evaluate the risk for each patient on an individual basis and a decision should be made with the best interests of the patient being paramount.