Safety and efficacy of sequential simultaneous bilateral total knee arthroplasty: A single centre retrospective cohort study

Abstract

Background

Simultaneous bilateral total knee arthroplasty (TKA) is a promising option for patients with bilateral arthritis of the knee because of the requirement of a single hospitalization and anesthetic regimen, reduced overall hospital stay, lower overall costs, and quicker recovery compared to staged bilateral TKA. However, there are conflicting reports on the safety of the procedure, with little data available in the Indian setting. Herein, we compared the efficacy and safety of sequential simultaneous bilateral TKA (SSBTKA) with those of unilateral TKA (UTKA).

Methods

This retrospective analysis included cases of SSBTKA (n = 380, 760 knees) and UTKA (n = 754) performed by the same surgeon and followed up for a minimum duration of 1 year. The functional outcomes (postoperative changes in Oxford Knee Score [OKS] and Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC]), length of hospital stay (LOS), complications, and rates of revision and mortality were compared between the two groups.

Results

The mean follow-up durations were 40.59 and 36.69 months for the UTKA and SSBTKA groups, respectively. The LOS was significantly longer in the SSBTKA group than in the UTKA group (Median [Interquartile range]: 4[1] vs. 3[0], p < 0.001). The OKS and WOMAC scores increased with time in both groups. The improvements in each of these scores at 3, 6, and 12 months postoperatively were either statistically similar between the two groups or, if statistically different, the differences were too small to be clinically meaningful. Blood transfusions (4% [SSBTKA] vs.0.3% [UTKA], p < 0.001), cardiac complications (1.6% vs. 0.4%, p = 0.034), urine retention (3.7% vs. 1.2%, p = 0.005), and deep infection (0.8% vs. 0%, p = 0.015) were significantly more frequent in the SSBTKA group. None of the patients in the UTKA group had to undergo revision surgery, whereas in the SSBTKA group, 2 (0.6%) patients underwent revision TKA. The overall mortality rates were low in both groups (0.8% [SSBTKA] and 0.3% [UTKA]), with no significant between-group difference (p = 0.209).

Conclusion

The functional outcomes and mortality rates associated with SSBTKA are comparable to those associated with UTKA. The risk of complications and the need for revision, although higher with SSBTKA, the actual numbers are low enough to justify its use. Although the LOS in SSBTKA is longer than that in UTKA, it is likely to be shorter than the cumulative LOS for two UTKA procedures (i.e. a staged bilateral TKA). Thus, SSBTKA appears to be a safe and effective choice for appropriately selected patients.

1. Introduction

Total knee arthroplasty (TKA) is the mainstay of treatment for end-stage knee osteoarthritis.^1,2Approximately 20% of patients with osteoarthritis severe enough to necessitate TKA show bilateral involvement and need to undergo bilateral TKA (BTKA).³ BTKA can be performed either (a) as a single procedure in which both knees are operated upon simultaneously under a single anesthetic (simultaneous BTKA) or (b) as a staged procedure in which the two knees are operated upon separately under two different anesthetics, with a minimum of 3 months between the two procedures (staged BTKA). Simultaneous BTKA itself may be performed by a single surgeon (sequential simultaneous BTKA [SSBTKA]) or by two different surgeons (two-team simultaneous BTKA).^2,4

Simultaneous BTKA appears to be a better choice than staged BTKA in terms of patient convenience and satisfaction as it involves a single hospitalization and anesthetic regimen, less anesthesia time, lesser use of pain medication, shorter cumulative length of hospital stay (LOS, shorter by 4–6 days), reduced overall costs (by 18–36%), quicker postoperative recovery and rehabilitation, and less time in physical therapy.⁵⁻¹¹⁷,¹⁰In addition, its functional and radiographic outcomes as well as implant survivorship are comparable to those associated with unilateral TKA (UTKA).^5,8,9

However, there have been conflicting reports regarding the safety of simultaneous BTKA. Some studies, including meta-analyses and analyses of data from national registries, have reported higher rates of early mortality^{11, 12, 13} and postoperative complications, such as confusion,^14,15 cardiopulmonary complications(e.g., cardiac arrhythmia, myocardial infarction, pulmonary embolism),^{11,13, 14, 15, 16} and need for blood transfusion,¹⁵with simultaneous BTKA than with unilateral/staged procedures. As a result, many surgeons are hesitant to perform simultaneous BTKA. In contrast, some studies, including a systematic review, have shown that simultaneous BTKA is comparable to unilateral/staged procedures in terms of safety.^{17, 18, 19, 20}

The choice between simultaneous and staged BTKA is, thus, still a matter of debate in orthopedic practice. Particularly in India, few studies have been conducted to investigate this issue.²¹ Hence, we performed a comparative analysis of SSBTKA and UTKA in terms of safety and efficacy in Indian patients.

2. Methods

2.1. Study design

This retrospective analysis included cases of SSBTKA and UTKA performed at our tertiary care institute by the senior author from January 2011 to December 2016, following IRB approval. Preoperative patient data were collected from patient records in the Electronic Medical Record Department of our institute. Postoperative outcomes were recorded via telephonic follow-up and compared between the two groups.

2.2. Patient selection

Our study included patients with

• 1.Unilateral knee osteoarthritis who underwent UTKA,
• 2.Bilateral knee osteoarthritis who were deemed fit to undergo SSBTKA,
• 3.Complete medical records (including clinical details, operation notes),
• 4.Follow up of at least 12 months (except when death occurred within 12 months postoperatively).

Our exclusion criteria included

• 1Revision arthroplasty,
• 2.
  Staged BTKA, either voluntarily or because they were deemed unfit to undergo SSBTKA due to any of the following medical pathologies

  • a.
    Patients Active ischemic heart disease (positive stress test or a history of angina equivalents);
  • b.
    Decreased left ventricular function (left ventricular ejection fraction∖50%).
  • c.
    Patients with symptoms of dyspnoea on exertion, shortness of breath, or poor functional capacity
  • d.
    Pulmonary disease (moderate to severe pulmonary hypertension, oxygen-dependent pulmonary disease, oral steroid-dependent asthma, exercise-limiting chronic obstructive pulmonary disease)
  • e.
    Morbid obesity (body mass index[40 kg/m2)
  • f.
    Renal insufficiency (creatinine[1.6 mg/dL)
  • g.
    Chronic liver disease (functional impairment in liver function and/or ascites, Child’s Class B or greater)
  • h.
    Poorly controlled diabetes mellitus
  • i.
    Cerebrovascular disease with a history of a previous stroke; and
  • j.
    Major peripheral vascular disease involving the lower extremities with stents or vascular bypass.

2.3. Preoperative assessments

All patients underwent a preoperative assessment performed by the physician and anesthesiologist. Preoperative assessment by other specialists (cardiologist/endocrinologist and/or others, as needed) was performed as and when recommended by the physician and/or anesthesiologist. The following details were recorded for each patient: age, sex, indication for TKA (osteoarthritis/rheumatoid arthritis), ASA physical status, hemoglobin level, comorbidities (diabetes mellitus, cardiac comorbidity, hypertension, chronic obstructive pulmonary disease), and functional status (Oxford Knee Score [OKS] and Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC]).The OKS is a 12-item instrument that measures pain and physical disability after TKA with total scores ranging from 0 (worst outcome) to 48 (best outcome).²² The WOMAC is a similar scale ranging from 0 (worst outcome) to 100 (best outcome).²³

2.4. Operative procedure and follow-up

Before the operation, all patients were educated regarding the surgery using visual aids and information brochures. Prehabilitation procedures involved quadriceps strengthening exercises and hamstring stretching. Comorbidities such as diabetes, hypertension, asthma, and anemia were treated optimally. Most of the patients were given spinal anesthesia; general anesthesia was given to those who had a contraindication to spinal anesthesia or refused spinal anesthesia. After anesthesia induction, an ultrasound-guided adductor canal block was performed, followed by urinary catheterization.

A posterior stabilized/posterior cruciate substituting prosthesis was implanted using the midvastus approach. Patellaplasty was performed in all cases, using the technique described by Agarwala et al.²⁴After checking the trial implant, periarticular local infiltration analgesia was administered by injecting an anesthetic mixture in the posterior capsule, collateral attachments, synovium, Hoffa’s fat pad, tissue adjoining the arthrotomy incision, and subcutaneous tissue. The details of the analgesic drug mixture are provided in Table 1. The final implantation was performed with cement using both gap balancing and measure resection techniques and the wound was closed in layers over a closed negative pressure drain. The entire surgical procedure was carried out with a pneumatic tourniquet (>100 mmHg from baseline systolic blood pressure). The drain was clamped for 4 h after release of the tourniquet as we did not release the tourniquet prior to closure. Subsequently, the drain was removed 4 h after the clamps were opened (i.e., 8 h postoperatively), as described elsewhere.²⁵ The urinary catheter was removed 6 h postoperatively.

Table 1.

Drug regimen administered to the patients before, during, and after surgery.

Timing of intervention	Dose		Route	Number/frequency of doses	Details
Preoperative
Gabapentin	300 mg		Oral	3 doses	Given at night, starting on the night before surgery
Intraoperative
Subarachnoid block (0.5% bupivacaine heavy + buprenorphine) OR General anesthesia	Bupivacaine: 15 – 20 mg Buprenorphine: 1 μg/kg body weight		Intrathecal Intrathecal		In case of contraindication to or failure of subarachnoid block, standard general anesthesia was administered with endotracheal intubation.
Antibiotic: Cefuroxime	1.5 g		Intravenous	UTKA: 3 doses, SSBTKA: 4 doses	Given prior to surgery, prior to surgery of the second knee (in case of SSBTKA), 2 doses (12-hourly) thereafter
Adductor canal block: Ropivacaine 0.2%	12 mL		Adductor canal	1 dose	Ultrasound-guided, performed prior to surgery (on each side for SSBTKA)
Midazolam	0.02 mg/kg body weight		Intravenous	1 – 2 doses
Pantoprazole	40 mg		Intravenous/oral postop	1 dose	Continued 1 dose daily before breakfast
Paracetamol	1 g		Intravenous	1 dose
Tranexamic acid	500 – 1000 mg(10 mg/kg body weight)		Intravenous	1dose
Methylprednisolone	500 mg		Intravenous	1 dose
Ondansetron	4 – 8 mg		Intravenous	1 dose
Local infiltration analgesia	UTKA	SSBTKA	Intra-articular		The mixture was diluted to 100 mL. Infiltration was performed using 20-mL syringes and 18G needles.
		(Each knee)
Levobupivacaine 0.5%	30 mL	15 mL
Clonidine	75 μg	75 μg
Fentanyl	100 μg	100 μg
Adrenaline 1:1000	2drops	2 drops
Ketorolac	30 mg	30 mg
Tranexamic acid	1 g	500 mg
Postoperatively on the day of surgery					Drain kept clamped for 4 h, then released
Paracetamol	1 g		Intravenous	2 – 3doses
Ice application			Locally	4 times a day
Postoperative day 1
Ice application			Locally	4 times a day
Paracetamol	1 g		Oral	2 – 3 doses
Tramadol	50 mg		Intravenous		Rescue analgesic
Dalteparin sodium	5000U		Sc	1 dose	Given once daily till discharge
Buprenorphine patch	10 μg/h		Transdermal	Once
Nandrolone decanoate	100 mg		Intramuscular	1 dose
Vitamin C	2 g		Oral	1 dose	Given once daily for 5 days
Multivitamin with zinc			Oral	1 dose	Given once daily for 5 days

UTKA: Unilateral total knee arthroplasty; SSBTKA: Simultaneous sequential total knee arthroplasty.

After the operation, all patients were shifted to the recovery room in the theatre complex, which functioned as a post-anesthesia care unit (PACU). Adequate blood and fluid management was performed as described previously and the patients were kept under observation till recovery from anesthesia was complete. This ensured a smooth transition between the operation theatre and the patient ward. Visual analogue pain scores were monitored for the first 48 h postoperatively. Deep vein thrombosis (DVT) socks and intermittent compression devices were applied to the lower limbs and low molecular weight heparin was administered till the patient was discharged. All patients were encouraged to sit, stand, walk, and climb stairs on the day of surgery as well as on subsequent postoperative days. The details of the drugs administered to the patients before, during, and after the procedure are provided in Table 1.

Patients were followed up for at least 1 year postoperatively. At each follow-up, the patient’s functional status (OKS and WOMAC) and any adverse outcomes (complications, need for revision surgery, or death) were recorded. Those not following up were contacted telephonically.

2.5. Statistical analysis

Statistical analysis is done using software STATA/MP – 13.0. Stata Corp Lp, College Station, Texas, USA. for windows.

Quantitative variables were presented as mean ± standard deviation or median (interquartile range [IQR]) and categorical variables as number (percentage). The Chi Square test was used to compare categorical variables between the two groups. For between-group comparison of quantitative variables, the independent t-test (for normally distributed variables) or Mann-Whitney test (for non-normally distributed variables) were used. Analysis of covariance was used to adjust for baseline values. Changes in each group over time were analyzed using the paired t-test. A p value < 0.05 was considered statistically significant.

3. Results

3.1. Baseline characteristics of the study population

A total of 1198 patients underwent TKA during the study period. After application of our inclusion and exclusion criteria, the records of 754 and 380 patients (754 and 760 knees, respectively) who underwent UTKA and SSBTKA, respectively, were available for analysis. The process of participant selection is presented in Fig. 1.

Fig. 1.

Flowchart illustrating the process of patient selection.

The mean follow-up durations were 40.59 (SD 19.54) and 36.69 (SD 17.73) months for the UTKA and SSBTKA groups, respectively. The baseline demographic characteristics of the two groups are summarized in Table 2. Both groups had a preponderance of female patients, with a much higher percentage in the SSBTKA group than in the UTKA group (78.7% vs. 62.1%, p < 0.001). The two groups did not show any significant difference with respect to underlying pathology (osteoarthritis vs. rheumatoid arthritis), mean age, age distribution (<65 years and ≥65 years), comorbidities, hemoglobin level, and ASA physical status (Table 2). The disease severity, as reflected by the OKS and WOMAC scores, was also comparable between the groups. The WOMAC scores did not show a significant between-group difference (44.19 ± 4.77 [UTKA] vs. 44.21 ± 4.85 [SSBTKA], p = 0.923). As regards OKS, although the two groups did show a statistically significant difference, the difference was too small to be clinically meaningful (15.16 ± 2.93 [UTKA] vs. 14.11 ± 2.98 [SSBTKA], p < 0.001).The implant types used in the two groups are given in Table 3.

Table 2.

Baseline demographic and clinical characteristics of the study population.

Variable		UTKA (n = 754)	SSBTKA (n = 380)	Total (n = 1134)	p value∗ (UTKA vs. SSBTKA)
Side†	Right	406(53.8)	380(50)	786(51.9)	0.134
	Left	348(46.2)	380(50)	728(48.1)
Sex	Male	286(37.9)	81(21.3)	367(32.4)	<0.001
	Female	468(62.1)	299(78.7)	767(67.6)
OA/RA	OA	701(93)	353(92.9)	1054(92.9)	0.962
	RA	53(7)	27(7.1)	80(7.1)
Age, years		62.91 ± 9.09	63.56 ± 8.62	63.13 ± 8.93	0.249
Age distribution	<65 years	441 (58.5)	201 (52.9)	640 (56.4)	0.079
	≥65 years	313 (41.6)	179 (47.1)	492 (43.6)
Comorbidities	Diabetes mellitus	169(22.4)	85 (22.4)	254 (22.4)	0.986
	Cardiac comorbidity	82 (10.9)	41 (10.8)	123 (10.8)	0.965
	Hypertension	172 (22.8)	88 (23.2)	260 (22.9)	0.896
	COPD	20 (2.7)	9 (2.4)	29 (2.6)	0.775
ASA physical status	Grade I	368 (48.8)	187 (49.2)	555 (48.9)	0.986
	Grade II	353 (46.8)	176 (46.3)	529 (46.7)
	Grade III	33 (4.4)	17 (4.5)	50 (4.4)
Hemoglobin level, g/dL		12.82 ± 1.21	12.82 ± 1.21	12.82 ± 1.21	0.942
OKS†		15.16 ± 2.93	14.11 ± 2.98	14.63 ± 3.0	<0.001
WOMAC†		44.19 ± 4.77	44.21 ± 4.85	44.20 ± 4.81	0.923

Data are presented as mean ± standard deviation for quantitative variables and number (percentage) for categorical variables. ∗p < 0.05 was considered statistically significant. The independent t-test was used for quantitative variables and the Chi Square test for categorical variables. ^†For this variable, the sample size was considered as 760 for the SSBTKA group (i.e. the total number of knees). UTKA: Unilateral total knee arthroplasty; SSBTKA: Simultaneous sequential bilateral total knee arthroplasty; OA: Osteoarthritis; RA: Rheumatoid arthritis; COPD: Chronic obstructive pulmonary disease; ASA: American Society of Anesthesiologists; OKS: Oxford Knee Score; WOMAC: Western Ontario and McMaster Universities Osteoarthritis Index.

Table 3.

Types of implants used in the two groups.

Implant type	UTKA (n = 754)	SSBTKA (n = 380)
Zimmer Nexgen®a	367 (48.7)	171 (45.0)
Zimmer Personna®a	25 (3.3)	16 (4.2)
Smith & Nephew Legion®b	312 (41.4)	160 (42.2)
Smith & Nephew Verilast®b	34 (4.5)	33 (8.7)

Values are presented as number (percentage). UTKA: Unilateral total knee arthroplasty; SSBTKA: Simultaneous sequential bilateral total knee arthroplasty.

^aZimmer Biomet, Warsaw, Indiana, USA.

^bSmith & Nephew, Memphis, USA.

3.2. Length of hospital stay and functional outcomes

The LOS was significantly longer in the SSBTKA group (median [IQR] {Q1- Q3}, 4 [1] {4–5} days) than in the UTKA group (median {IQR}, 3 days {3- 3}; p < 0.001 using the Mann-Whitney test). The same was observed for the tourniquet time (median [IQR] {Q1- Q3}, 100 [10] {96–106} min vs. median [IQR] {Q1- Q3}, 43 [5] {41–46} min; p < 0.001 using the Mann-Whitney test).

Both groups showed significant improvements in the OKS and WOMAC scores at 3, 6, and 12 months postoperatively compared to the preoperative values (Table 4). At all postoperative time points, both scores were significantly higher in the UTKA group than in the SSBTKA group, and the differences in OKS persisted even after adjustment for baseline OKS. However, all these differences were too small to be clinically meaningful (Table 4, Fig. 2).The improvement in each of the scores was also compared between the two groups at each time point. For both the WOMAC and OKS, the improvement at each postoperative time point was either statistically similar between the two groups or, if statistically different, the difference was too small to be clinically meaningful (Table 5).

Table 4.

WOMAC and OKS in the two study groups at different time points during the study.

Parameter	Time point	UTKA	p value∗ (vs. preoperative)	SSBTKA	p value∗ (vs. preoperative)	p value† (UTKA vs. SSBTKA)
OKS	Preoperative	15.16 ± 2.93	–	14.12 ± 2.98	–	<0.001
	3 months p.o.	37.01 ± 5.67	<0.001	36.34 ± 3.44	<0.001	0.006
	6 months p.o.	42.99 ± 1.75	<0.001	42.75 ± 2.31	<0.001	0.020
	12 months p.o.	46.78 ± 0.98	<0.001	46.42 ± 1.76	<0.001	<0.001
WOMAC	Preoperative	44.19 ± 4.77	–	44.21 ± 4.85	–	0.923
	3 months p.o.	80.66 ± 6.58	<0.001	78.53 ± 5.43	<0.001	<0.001
	6 months p.o.	92.07 ± 2.07	<0.001	91.44 ± 43.38	<0.001	<0.001
	12 months p.o.	97.57 ± 1.05	<0.001	96.88 ± 2.96	<0.001	<0.001

Values are presented as mean ± standard deviation. ∗Calculated using the paired t-test, with p values < 0.05 considered statistically significant. ^†Calculated using the independent t-test, with p values < 0.05 considered statistically significant. UTKA: Unilateral total knee arthroplasty; SSBTKA: Simultaneous sequential bilateral total knee arthroplasty; OKS: Oxford Knee Score; WOMAC: Western Ontario and McMaster Universities Osteoarthritis Index; p.o.: postoperative.

Fig. 2.

Functional status in the two groups at different time points during the study. (A) OKS (B) WOMAC.

Table 5.

Improvements in WOMAC and OKS in the two study groups at different time points.

Parameter	Time point	UTKA	SSBTKA	p value∗ (UTKA vs. SSBTKA)
OKS improvement	3 months p.o.	21.85 ± 6.37	22.23 ± 4.68	0.190
	6 months p.o.	27.84 ± 3.41	28.63 ± 3.82	<0.001
	12 months p.o.	31.63 ± 3.07	32.28 ± 3.45	<0.001
WOMAC improvement	3 months p.o.	36.47 ± 8.25	34.32 ± 7.18	<0.001
	6 months p.o.	47.87 ± 5.24	47.23 ± 6.09	0.028
	12 months p.o.	53.37 ± 4.88	52.65 ± 5.95	0.011

Values are presented as mean ± standard deviation. ∗Calculated using the independent test, with p values < 0.05 considered statistically significant. UTKA: Unilateral total knee arthroplasty; SSBTKA: Simultaneous sequential bilateral total knee arthroplasty; OKS: Oxford Knee Score; WOMAC: Western Ontario and McMaster Universities Osteoarthritis Index; p.o.: postoperative.

The mean hemoglobin levels showed a drop in both the groups, with a greater decrease in the SSBTKA group than in the UTKA group (1.86 vs. 1.26 g/dL). Most of the patients were able to start walking on the day of the surgery itself in both the groups (85.0% [UTKA] vs. 77.6% [SSBTKA]), and by the second postoperative day, all the patients were able to walk (Table 6). All patients were able to climb stairs by the fourth postoperative day in the UTKA group and the seventh postoperative day in the SSBTKA group (Table 6).

Table 6.

Recovery of functional abilities (walking/climbing stairs) after surgery in the study groups.

Activity	Postoperative day	UTKA	SSBTKA
Walking	0	641(85.0)	295(77.6)
	1	111(14.7)	73(19.2)
	2	2(0.3)	12(3.2)
	Total	754(100)	380(100)
Climbing stairs	0	193 (25.6)	89(23.4)
	1	387 (51.3)	179(47.1)
	2	154 (20.4)	75(19.7)
	3	13 (1.7)	20(5.3)
	4	7 (0.9)	9(2.4)
	5	0 (0)	6(1.6)
	6	0 (0)	1(0.3)
	7	0 (0)	1(0.3)
	Total	754 (100)	380(100)

Values are presented as number (percentage). UTKA: Unilateral total knee arthroplasty; SSBTKA: Simultaneous sequential bilateral total knee arthroplasty.

3.3. Complications, revisions, and mortality

Blood transfusion (4% [SSBTKA] vs. 0.3% [UTKA], p < 0.001), cardiac complications (1.6% vs. 0.4%, p = 0.034), urine retention (3.7%vs. 1.2%, p = 0.005), and deep infection (0.8% vs. 0%, p = 0.015) were significantly more frequent in the SSBTKA group than in the UTKA group. Cardiac complications comprised 2 cases of arrhythmia and 1 of ST depression in the UTKA group, and 2 cases of arrhythmia, 3 of ST depression, and 1 of angina in the SSBTKA group. They were all managed successfully with appropriate medications. The incidence rates of the other complications were similar between the two groups (Table 7).

Table 7.

Postoperative complications.

Complication	UTKA (n = 754)	SSBTKA (n = 380)	p value∗
Blood transfusion	2(0.3)	15(4)	<0.001
Cardiac complications	3(0.4)	6(1.6)	0.034
Deep vein thrombosis	2(0.3)	4(1.1)	0.084
Electrolyte imbalance	10(1.3)	7(1.8)	0.500
Urine retention	9(1.2)	14(3.7)	0.005
Urinary tract infection	1(0.1)	2(0.6)	0.223
Superficial infection	2(0.3)	3(0.8)	0.208
Deep infection	0(0)	3(0.8)	0.015
Periprosthetic fracture	1(0.1)	1(0.2)	0.621

Values are presented as number (percentage). ∗Calculated using the Chi Square test, with p values < 0.05 considered statistically significant. UTKA: Unilateral total knee arthroplasty; SSBTKA: Simultaneous sequential bilateral total knee arthroplasty.

A significantly larger proportion of patients required postoperative observation in the intensive care unit (ICU) in the SSBTKA group (8.2% vs. 2%, p < 0.001; Table 8), with only one mortality in the SSBTKA group. The revision rates were also higher in the SSBTKA group (0.6% vs. 0%, p = 0.046), with 2 of the 3 patients with deep infection undergoing staged revision TKA (Table 8).

Table 8.

Postoperative ICU stay, mortality, and revision rates.

Parameter		UTKA (n = 754)	SSBTKA (n = 380)	pvalue∗
Postoperative ICU stay		15 (2)	31 (8.2)	<0.001
Revision		0 (0)	2 (0.6)	0.046
Mortality	1-month	0 (0)	1 (0.2)	0.159
	3 month	0 (0)	1 (0.2)	0.159
	1 year	2 (0.3)	3 (0.8)	0.209
	Overall	2 (0.3)	3 (0.8)	0.209

Values are presented as number (percentage). ∗Calculated using the Chi Square test, with p values < 0.05 considered statistically significant. UTKA: Unilateral total knee arthroplasty; SSBTKA: Simultaneous sequential bilateral total knee arthroplasty; ICU: Intensive care unit.

The overall mortality rates were low in both groups (0.8% [SSBTKA] vs. 0.3% [UTKA]), with no significant between-group difference (p = 0.209).The 1-month, 3-month, and 1-year mortality rates were also similar between groups (Table 8).

4. Discussion

The present study compared the safety and outcomes of UTKA and SSBTKA. We found that the two procedures were comparable in terms of functional outcomes and mortality rates. However, SSBTKA was associated with a longer LOS, a higher revision rate, and higher rates of cardiac complications, urine retention, deep infection, and blood transfusion. The reason for comparing UTKA (as opposed to staged BTKA) with SSBTKA is that in routine practice, staged BTKA is generally performed on high-risk patients (i.e., older age or with comorbidities) and hence, a retrospective analysis of SSBTKA vs. staged BTKA is likely to have an inherent selection bias that would affect the results.

Our results with respect to functional outcomes (OKS and WOMAC scores) associated with the two procedures corroborate those of previous studies in non-Indian populations.^{17,26, 27, 28} Huang et al. evaluated functional outcomes at 6 months after simultaneous BTKA and the first stage of a staged BTKA, and observed no significant differences. However, this study was limited by its small sample size (144 participants) and short follow-up duration.^{17, 26, 27, 28} We have obtained similar results using a much larger sample size and a longer (12-month) follow-up. A more recent study by Putnis et al. also used changes in OKS as a measure of functional improvement at a minimum of 1 year after SSBTKA or UTKA, and demonstrated no significant difference between the two groups. Our patients had much worse preoperative knee function than those in Putnis et al.’s study, as reflected by the much lower mean preoperative OKS in our study. The final scores were somewhat similar in both studies and the overall improvement in each group was, thus, much greater in our study, indicating the efficacy of both procedures even in patients with poor baseline knee function.¹⁷

We also observed no significant difference in mortality rates between groups, once again in line with a majority of previous findings.^{17,18,29, 30, 31} One previous study by Odum et al. that analyzed the 2004 –2007 Nationwide Inpatient Sample data did show higher mortality rates for simultaneous BTKA compared with UTKA, but the rates reported were in-hospital mortality rates.^{17, 18, 29, 30, 31} Although the mortality rates in our study were very low (<1% for both procedures), they were slightly higher than previously reported values, which may be attributed to the longer follow-up in our study (the 30-day mortality rates in our study were similar to those reported previously).^{17,18,29,31,32} All patients (2 from UTKA and 3 from SSBTKA) died secondary to cardiac complications. A large study by Vaishya et al., has clearly shown the safety of SSBTKA in an elderly population.³³

Simultaneous BTKA has previously been shown to be an independent risk factor for increased LOS, with a number of studies demonstrating a longer LOS in case of simultaneous BTKA compared to UTKA.^{1,17,18,29,31,34} We obtained similar results in our study (median LOS: 4 [SSBTKA] vs. 3 [UTKA] days). However, considering a staged BTKA to be equivalent to 2 UTKA procedures, the median LOS would be 2 days shorter for SSBTKA than for staged BTKA, which would ultimately result in substantially reduced hospital costs.

Previous studies on the relative risk of complications after UTKA and SSBTKA have reported conflicting results, with some demonstrating a higher rate of complications after SSBTKA^{1,6,29, 30, 31,34} and others reporting no difference between the two.^{17, 18, 19} However, most of these studies were fraught with methodological limitations such as a small sample size,^1,18,19 short observation period (either in-hospital or 30-day complications),^{6,18,29, 30, 31} dependence on the accuracy of medical claims data (in case of database studies),³⁴ and procedure-related heterogeneity within the study groups (e.g., inclusion of both truly simultaneous and sequential simultaneous BTKAs in the BTKA group or inclusion of stage 1of staged BTKA in the UTKA group).^29,30 With a fairly large sample size, a minimum follow-up of 1 year, inclusion of only sequential simultaneous procedures, and exclusion of staged BTKAs, our study attempts to overcome the abovementioned limitations and provide a more accurate picture of complications after UTKA and SSBTKA.

In our study, the rates of blood transfusion, cardiac complications, urine retention, and deep infection were higher after SSBTKA. Postoperative blood transfusion is a cause of concern because of its reported association with increased hospitalization costs³⁴ and the risk of transfusion-related diseasetransmission.^{29, 30} Preoperative hemoglobin level and SSBTKA have previously been shown to be independent predictors of the need for postoperative blood transfusion.^{29, 30} Although preoperative hemoglobin levels were similar between the two groups in our study, the greater transfusion requirements after SSBTKA could be attributed to a greater drop in hemoglobin in this group. Even so, the rate still remained low (4%) and did not translate into a high mortality rate in the SSBTKA group. Similar low rates of complications were also described by Vaishya et al. in their long term follow-up.³³

Appropriate measures such as preoperative optimization, intravenous and local tranexamic acid and clamping of drains were used to minimize blood loss and drop in hemoglobin; with only 15 transfusions needed in the SSBTKA group. This did not impact the milestones or clinical outcome. Drop in hemoglobin though directly associated with increased cardiovascular complications, did not result in increased mortality in our study; with overall number of cardiac complications being minimal. Our results are in line with those of a previous study on Indian patients by Shetty et al.,²¹ who observed a higher rate of blood transfusion after SSBTKA than after UTKA (18% vs. 6%), although the overall rate of other complications was similar (10% vs. 8%, p > 0.05). However, this study was limited by its small sample size (n = 50 for each group) and the significantly lower mean age in the SSBTKA group. In our study, we have validated Shetty et al.’s results while addressing both these limitations.

The cardiac complications observed in our study were not life-threatening and were managed with medications as advised by the cardiologist in both the groups. The incidence of deep infections, although higher in the SSBTKA group, was still very low (0.8%), in line with previous reports.^{1,17,29, 30, 31,35} Moreover, longer operative duration and LOS have been shown to be independent predictors of periprosthetic joint infection after total joint arthroplasty.^36,37 Since SSBTKA reduces the cumulative operative duration and LOS compared to staged BTKA, we believe that it would also be associated with lower cumulative infection rates. However, conclusive results regarding this can be obtained only by directly comparing simultaneous and staged BTKA procedures. The two revision surgeries required in the SSBTKA group were also because of deep infections.

The cause of the higher incidence of urine retention in the SSBTKA group is difficult to speculate; however, it is noteworthy that this higher rate did not translate into a higher rate of urinary tract infection in this group. As per our operative protocol, all patients were catheterized and the catheter was removed on the same day. Patients who experienced urine retention were recatheterized if they were unable to void voluntarily after encouragement, mobilization, and application of cold compresses. Regarding postoperative ICU care, all patients with cardiac complications, DVT, or hypertension as well as those who were high-risk to begin with (i.e. ASA grades 2 and 3) were monitored in the ICU postoperatively. Though the requirement for ICU care was higher in the SSBTKA group, the overall numbers were low and all except one were managed successfully with appropriate medication.

There are a few limitations to our study. First, it has an inherent bias because of its nonrandomized, retrospective design. Second, the assumption that a staged BTKA is equivalent to two consecutive UTKA procedures is rather simplistic and hence, a comparison of UTKA with SSBTKA is not truly representative of the relative risks of staged BTKA vis-à-vis SSBTKA. A randomized comparative study between patients undergoing staged BTKA and those undergoing SSBTKA would provide a more accurate solution to this dilemma. Lastly, our sample size, though fairly large for a single-center study, is still small when compared with registry data analyses. This might have resulted in the low complication rates observed by us.

In conclusion, SSBTKA is associated with good functional outcomes and low revision and mortality rates. Although the risk of certain postoperative complications may be increased compared to a staged procedure, they are mostly easily managed and the absolute risk is still quite low. All aspects considered, the risks associated with SSBTKA are more than offset by the benefits offered by it in terms of patient convenience and reduced expenditure. Hence, it appears to be a safe and effective procedure for appropriately selected patients. Further randomized studies with a larger sample size comparing SSBTKA directly with staged BTKA are warranted to corroborate our findings.

Funding

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Declaration of competing interest

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