A matched cohort study between cementless TKA and cemented TKA shows a reduction in tourniquet time and manipulation rate

Abstract

Introduction

Cementless total knee arthroplasty (TKA) is now becoming more acceptable with the advent of newer ongrowth constructs and better initial fixation. It has been proposed that cementless TKA may save OR time and result in a lower incidence of manipulation. This study was designed to assess the difference between cemented and cementless TKA.

Methods

Our hospital statistician performed a matched cohort analysis between 127 cementless TKAs and 127 cemented TKRs performed by a single surgeon. Patients were matched on age and BMI. Mean tourniquet time between the cemented and cementless TKAs was assessed as well as the rate of manipulation between these groups. Of note, a tourniquet was routinely used in both the cementless and cemented cohorts to reduce confounding bias.

Results

A total of 127 cementless TKAs with a mean age of 60.8 years and mean BMI 32.2 were compared to 127 cemented TKAs with a mean age of 61.5 years and mean BMI of 32.2 at an average follow-up of 2.0 years. There was a statistically significant reduction in tourniquet time in the cementless TKA cohort at 45.7 min compared to the cemented TKA cohort at 54.8 min (p = 0.001). Estimated blood loss was similar in both the cementless (179.5 ml) and cemented (196 ml) cohorts (p = 0.3) and postoperative outcomes, including UCLA score.In addition, the cementless TKA cohort had a manipulation rate of 0% compared to 3.1% for the cemented TKA group (p = 0.044).

Discussion and conclusion

While cementless and cemented TKA have shown similar PROMs and survivorship, we demonstrated a significant reduction in tourniquet time with cementless TKRs, with similar estimated blood loss, and a lower incidence of manipulation with cementless TKRs in this matched cohort study. The increased cost of a cementless implant may be negated if one considers the cost savings of not using cement, the cost savings of not performing manipulations, and the shorter operative time.

1. Introduction

By 2040, the total annual total knee arthroplasty (TKA) surgeries performed in the United States is expected to increase by 401%.¹ TKA remains a reliable procedure by not only improving range of motion (ROM) and reducing joint pain, but also maintaining low morbidity and mortality rates. These efforts are aided by modifications in ligament preservation, surgical approach, and functionality of individual implant components.²

The discussion over ideal fixation of TKAs remains multifaceted. Cemented fixation offers: i) the addition of antibiotic material to reduce post-surgical infection and ii) fixation of prosthetic joint components to an osteoporotic bone. The drawbacks of cemented fixation are breakdown of bone/cement interface over time leading to osteolysis and revision surgery and cement debris causing inflammation and potential accelerated polyethylene wear.³ The advent of the cementless fixation provided perseveration of bone stock and potential for improved biologic long-term fixation.⁴

Several recent studies have compared cemented and cementless TKA and found favorable results in support of cementless TKA, including improved all-cause and aseptic survivorship,⁵ lower procedural implant cost,⁶ improved postoperative pain score in patients aged 60 years or younger,⁷ reduced operating room times,² and similar outcomes in terms of postoperative complications⁸ and functional outcomes.^5,9 The effect of cementation on manipulation rates has also been discussed inconclusively in the literature. Several studies have found that cementation was not a relevant risk factor for incidence of manipulation,^10,11 but both cemented TKA and cementless TKA maintained manipulation rates between 0 and 9%.¹²

We aimed to compare two matched cohorts of patients who underwent cemented TKA and cementless TKA by a single surgeon. We hypothesized that there would be: i) a reduction in tourniquet time in the cementless cohort compared to the cemented cohort, ii) reduced manipulation and revision rates, and iii) greater intraoperative blood loss in the cementless TKA cohort compared to the cemented TKA cohort.

2. Methods

A series of consecutive, primary TKA were performed by a single surgeon at one institution. The study was approved by our Institutional Review Board. Our statistician used the institution's database of prospectively collected data and matched the cohorts on the following criteria: 1:1 matching of cemented TKA and cemented TKA, exact sex, age ± 5 years, and body mass index (BMI) ±5 kg/m². The surgeon's overall workload can be observed to identify the relevant study cohorts (Fig. 1).

Fig. 1.

Study cohorts identified from overall surgeon workload.

The inclusion criteria included a primary TKA for a diagnosis of arthritis and the use of a tourniquet during surgery (Table 1). The exclusion criteria included a diagnosis other than arthritis, prior fracture of the knee, or bone defect observed on preoperative radiographs that precluded a normal surgical protocol. Indications for a cemented TKA include presence of osteoporosis, knee arthritis or insufficient bone stock quality. Indications for using a cementless TKA include good bone quality and adequate bone stock. The cemented implants were divided between Triathlon Titanium, n = 26, (Stryker Othopaedics, Mahwah, New Jersey, USA), Exactech Optetrak Logic, n = 89, (Exactech, Gainesville, Florida, USA) and Smith & Nephew Genesis II, n = 12, (Smith & Nephew, London, United Kingdom) systems, which create an interdigitated bone-interface using a uniform cement mixing process. The only cementless implant was the Triathlon Titanium, n = 127, (Stryker Othopaedics, Mahwah, New Jersey, USA), which incorporates a highly porous titanium coated, additively manufactured, baseplate with a delta keel and 4 peg system along with metal-backed patella components.¹⁴

Table 1.

Principle diagnosis between cohorts.

	Cemented TKA	Cementless TKA	P-value
Degenerative Arthritis	123 (96.9%)	126 (99.2%)	0.18
Inflammatory Arthritis	1 (0.8%)	0 (0%)	0.32
Juvenile Rheumatoid Arthritis	1 (0.8%)	0 (0%)	0.32
Post-Traumatic Arthritis	2 (1.6%)	1 (0.6%)	0.56

2.1. Tourniquet use and bleeding management

A tourniquet was used in every procedure. Tourniquet was used throughout the case for both cemented and cementless cohorts. Tourniquets were inflated to 250 mmHg routinely in both cohorts. We follow a strict blood management protocol, including the use of a 15 mg/kg intravenous dose of tranexamic acid (TXA).

2.2. Postoperative protocol

Patients were allowed full weight bearing after surgery. It was recommended to use cane for ambulation. It was also recommended to not engage in high impact activity and avoid impact loading. Follow-up clinical and radiology visits took place at 6 weeks, 3 months, 1 year, 2 years, and 5 years. At the follow-up clinical visit, the physician would assess function and range of motion (ROM) as well as record the patient's activity levels. The strict indication for manipulation under anesthesia was defined as range of motion <90° at 6 weeks postoperatively.

2.3. Statistical methods

A post-hoc power analysis was performed to determine the appropriate sample to achieve a power of 0.80 based on mean tourniquet time. Normally distributed continuous data was compared using the Students t-test. A p-value of <0.05 was determined to be statistically significant.

3. Results

The power analysis revealed a sample size of n = 125 in each cohort would achieve a power of 0.80. A single surgeon performed 917 consecutive primary TKA from 2009 to 2019 in a high-volume arthroplasty center, which was used to identify the study cohorts (Fig. 1). The average follow-up was 2.0 years in both cohorts. We found the principal diagnosis between the cemented TKA cohort and cementless TKA cohort was degenerative arthritis (123 vs. 126, p = 0.18), respectively (Table 1). The demographics of the matched cohorts reveal similar ages (61.5 vs. 60.8, p = 0.98), BMI (32.2 vs. 32.2, p = 0.34), male to female ratio (67:60 vs. 67:60, p = 0.99), and preoperative University of California at Los Angeles (UCLA) Activity scores (4.3 vs. 3.8, p = 0.60) (Table 2). In addtion, the principle deformity, namely varus, valgus, or neutral alignment, was categorized for each of the cohorts (Table 3).

Table 2.

Demographics between cohorts.

	Cemented TKA	Cementless TKA	P-value
Age (mean)	61.5 ± 6.3	60.8 ± 5.6	0.98
BMI (mean)	32.2 ± 5.2	32.2 ± 5.3	0.34
Males: females	67: 60	67: 60	0.99
UCLA Activity score	4.3	3.8	0.60
Follow-up (in years)	2.0 (range:1–5)	2.0 (range 1–3)	N/A

Table 3.

Principle deformity between cohorts.

	Cemented TKA	Cementless TKA	P-value
Neutral	5 (3.9%)	2 (1.6%)	0.25
Valgus	15 (11.8%)	10 (7.9%)	0.29
Varus	107 (84.3%)	116 (91.3%)	0.13

There was no significant difference in terms of principle deforimity between the cohorts. The cemented TKA cohort had 107 varus knees, 15 valgus knees, and 5 neutral knees compared to 116 varus knees (p=0.13), 10 valgus knees (p=0.29), and 2 neutral knees (p=0.25) in the cementless TKA cohort, respectively (Table 3). In terms of postoperative Patient Reported Outcome Measurements (PROMs) and complications, we found similar ROM (117.0 vs. 117.2, p = 0.27), UCLA Activity scores (4.8 vs. 4.5, p = 0.85), and revision rates (1.6% vs. 0.8%, p = 0.56) between the cemented and cementless cohorts, respectively. We did find significantly different manipulation rates (3.1% for cemented vs. 0% for cementless, p = 0.04), tourniquet times (54.8 min for cemented vs. 60.8 min cementless, p = 0.001). However, estimated intraoperative blood loss (179.5 ml for cemented vs. 196.0 ml for cementless, p = 0.3) was similar between the cohorts. (Table 4).

Table 4.

Postoperative Patient Reported Outcome Measurements and Complications between cohorts.

	Cemented TKA	Cementless TKA	P-value
Range of Motion	117.0°	117.2°	0.27
UCLA Activity score	4.8	4.5	0.85
Manipulation rate	3.1%	0%	.04
Revision rate	1.6%	0.8%	0.56
Intraoperative blood loss (ml)	179.5	196.0	0.3
Tourniquet time (in minutes)	54.8 ± 25.7 (range: 26.0–250.0)	45.7 ± 12.6 (range: 25.0–95.0)	0.001

4. Discussion

Our major findings supported our hypotheses by showing reduced tourniquet time for the cementless TKA cohort (54.8 min vs. 60.8 min, p = 0.001), lower manipulation rates (3.1% vs. 0%, p = 0.04), and similar estimated blood loss (179.5 ml vs. 196.0 ml, p = 0.3) compared to the cemented TKA cohort. However, we did not find a difference in revision rates between the cohorts (1.6% vs. 0.8%, p = 0.56) and PROMs, including UCLA Activity score. The literature supports the findings of reduced tourniquet time in cementless TKA^15,16 and similar blood loss.^17,18 To our knowledge, this is the first study to show lower manipulation rates in a cementless TKA cohort compared to cemented TKA in a matched analysis of similar BMI, age, and gender patients.

Tourniquet duration during surgery in the cementless TKA group was significantly shorter than the cemented TKA group by 9 min (55 min vs. 46 min). Our study benefitted from the use of a post-hoc power analysis to reveal a power of 0.80 was achieved at n = 120 in each cohort using the mean tourniquet times in each cohort. The literature discusses the use of a tourniquet during cementation only for its reduction in knee pain and postoperative complications, including stiffness and wound complications.¹⁹ One study found every additional 10 min of tourniquet time was associated with a 20% increased risk of complications.²⁰ Another study found nerve injuries were greatly increased for each 30 min of tourniquet time²¹ Additionally, if the duration of tourniquet application was within 150 min, the risk of complications may be reduced.²² Reduced tourniquet duration was not associated with improved postoperative function and range of motion in our study as it has been reported in some studies.^23,24 We attribute this difference to the performance of a single surgeon as well as a consistent postoperative protocol. Overall, it is hard to attribute the shorter tourniquet time in the cementless TKA cohort to improved postoperative outcomes, but may explain the reduced manipulation rate in the cementless TKA cohort when controlling for BMI, age, and gender in our study.

We found low revision rates and manipulation rates in both cohorts. However, there was a significant difference favoring the cementless TKA cohort, in terms of lower manipulation rates postoperatively. Napier et al. also found a 0% manipulation rate in their cohort of cementless TKA at a follow-up of 10 years.¹² Prudhon et al. found manipulation rates of 9% for their cemented TKA cohort and 6% for their cementless TKA cohort at a minimum follow-up of 11 years. However, they did not report or tourniquet time or blood loss in their study, focusing on long-term survivorship. Since the study design was akin to ours, it would be beneficial to compare patient selection for use of cemented or cementless TKA, but they did not include this information in their study. The comparison of revision rates remains unclear in the literature as another study found a lower revision rate at 10 years (4.15% vs. 3.39%), favoring the cemented TKA cohort.²¹ A recent study found similar aseptic revision rates and time to failure (p = 0.26 and p = 0.09, respectively) were similar between the groups in a short-term matched analysis of 3849 patients.²⁶

Tourniquet use has been associated with higher incidence of DVT and pulmonary embolism postoperatively, but also it has been associated with decreased intraoperative blood loss.^27,28 We found a similar estimated intraoperative blood loss in each cohort (cemented 179.5 ml vs. cementless 196.0 ml). During cemented TKA, a tourniquet during cementation only has been shown to improve pain and Knee Society Scores.²⁹ Hood et al. found greater blood loss for the cementless TKA cohort even with the use of tranexamic acid (28.5 ml vs. 12.7 ml, p < 0.001).³⁰ This can be associated with the cut surfaces of the bone that are not sealed by cement leading to continue bone bleeding after the knee is closed. Other studies, even with similar designs and outcomes (low revision rates), similarly found no significant difference in blood loss, including blood transfusions between cohorts.^14,31 The significance of intraoperative blood remains unclear in the literature in the decision to use a cemented implant or cementless implant. We found only a minimal difference in estimated intraoperative blood loss in our cohorts which was quite low in both groups of patients. We suspect that the routine use of intravenous tranexamic acid (TXA) in our study minimized blood, which has support in the literature.³²

Recent studies have supported the use of cementless TKA, albeit without regards to manipulation rate as was done in the current analysis. Long-term survivorship was not examined in the study, but cementless TKA has showed improved long-term survivorship of 99.1% for cementless TKA compared to 88.2 for cemented TKA at 8 years (p = 0.02) in the morbidly obese.³³ The all-cause survivorship was 98.6% in a cohort of 134 patients older than 75 years at a mean follow-up of 4 years.³⁴ Also, Kim et al. found similar long-term survivorship in patients less than 50 years who received bilateral, sequential TKAs.³⁵ One recent analysis found an all-cause survivorship of 98% of 114 consecutive cementless TKA at a mean of 8 years.³⁶ In addition, the overall procedural cost difference and operating room time cost of implanting a cementless TKA appear similar to a cemented TKA, especially considering the mean cemented TKA was 11.6 min longer for cemented TKA compared to cementless TKA. The total time cost was $418 higher for cementing TKA ($3373 vs. $2956) compared to cementless TKA.³⁷ The finding suggests that cementless TKA decreases tourniquet time could play a role in the lower operating room time cost.

There are limitations in the current study. While the study design was retrospective, we performed a matched cohort analysis with large sample sizes from the power analysis, which help to support our findings. In addition, we only evaluated estimated intraoperative blood loss and not postoperative blood loss, total blood loss, or transfusion requirements which has been evaluated in previous studies.^14,31 It would be beneficial to report findings from medium-term follow-up since the average follow-up of our cohorts was only 2.0 years. Short term follow-up, however, does play a role in gauging perioperative issues such as early PROMs, manipulation rates and estimated blood loss as was evaluated in this study. Also, we did not include cost information of the systems we used in the study so we had to rely on the differences from the literature. We still validate the findings from based on the rigorous selection process, strict inclusion criteria, and consistent preoperative baseline levels between cohorts.

5. Conclusion

In a matched cohort analysis, cementless TKA utilized less tourniquet time and a lower rate of manipulation than cemented TKA, with similar estimated intraoperative blood loss. Postoperatively, activity scores, range of motion, and revision rates were similar in both cohorts. This supports the literature that decreased tourniquet time may lead to lower postoperative complications, but added novel information with significantly reduced manipulation rates between cohorts. A longer follow-up is necessary, but this study is significant in supporting the use of cementless TKA in the first matched cohort analysis of this size.

Funding

There is no funding source.

Ethical approval

This article does not contain any studies with human participants or animals performed by any of the authors.

Informed consent

Informed consent was obtained from all individual participants included in the study.

Declaration of competing interest

The following COI are reported: Exactech (royalties, paid consultant, research support), Styker (paid consultant, research support), DJO (paid consultant, research support), Eastern Orthopedic Association (board member).