Abstract
Background
Tourniquet use during total knee arthroplasty (TKA) reduces bleeding which optimises bone-cement interface for prosthesis stability and improves surgical field visualisation. However, prolonged usage can lead to complications and poorer outcomes. Some surgeons advocate for intermittent tourniquet application. Limited literature exists for patients with high body mass index (BMI). This study aims to compare the outcomes of intermittent tourniquet (IT) to throughout tourniquet (TT) use among obese patients undergoing primary TKA for knee osteoarthritis.
Methods
This was a retrospective cohort study. In the TT group, tourniquet was inflated from the beginning and released once the bone cement has hardened. In the IT group, tourniquet was inflated at the beginning, released after initial incision and haemostasis, then inflated again during cementation. Tourniquet was released once the bone cement had set. Categorical outcome measures were analysed using Chi-squared or Fisher's exact test. T-test or Kruskal-Wallis test were used for continuous data.
Results
When comparing IT to TT among patients with BMI≥30 (IT n = 48, TT n = 47), the mean duration of surgery was shorter in the TT group (p < 0.05). The difference in haemoglobin drop between the two groups was not statistically significant from post-operative day three onwards. There was no difference in transfusion rate (p > 0.05). ROM was greater in the IT group up to three weeks post-operatively (p < 0.05). When comparing patients with BMI <30 (n = 71) and BMI≥30 (n = 48) with IT use, there was no statistically significant difference in ROM and LOS.
Conclusion
Patients with BMI≥30 in the IT group had greater ROM in the initial post-operative period. Although operative time and blood loss were greater among the IT group, there was no difference in transfusion rate. Outcomes of TKA performed with IT were similar for patients with BMI≥30 and BMI <30. The authors recommend intermittent tourniquet use during TKA for patients with BMI≥30.
Level of evidence
3.
1. Introduction
Knee osteoarthritis is a prevalent chronic joint disease that leads to pain, disability and loss of function.1 A surgical option for patients is total knee arthroplasty (TKA), one of the most successful orthopaedic procedures that serves as a reliable solution for patients suffering from end-stage knee osteoarthritis. Patient-reported outcome measures have been reported to improve dramatically after TKA.2
During the procedure, the application of a tourniquet over the thigh is a common practice, with more than 90% of orthopaedic surgeons in the United States of America (USA) and United Kingdom (UK) reporting the use of a tourniquet during TKA.3, 4 The utility of the tourniquet is twofold. Firstly, it improves the bone-cement interface, contributing to a stable prosthesis.5 Secondly, The application of a tourniquet can reduce intra-operative bleeding, improve visualisation of the surgical field and consequently reduce operative time.6
The use of a tourniquet is not without its flaws. Studies have reported poorer post-operative knee range of movement (ROM), higher post-operative pain scores, tourniquet-related nerve injury and even venous thromboembolism (VTE) resulting in pulmonary embolism.3, 7, 8, 9 However, completely removing the use of a tourniquet may also compromise the cementation process during TKA, contributing to aseptic implant loosening.5 To maximise the benefits of tourniquet use while minimising the potential risks associated with it, some orthopaedic surgeons advocate for intermittent tourniquet use and have reported favourable outcomes.10, 11
While there have been previous studies comparing outcomes of intermittent tourniquet use and complete tourniquet use, there is limited literature focusing on patients with high body mass index (BMI). The prevalence of obesity worldwide is increasing, with an estimated 38% of the world's adult population being overweight by 2030.12 With obesity being a risk factor for knee osteoarthritis, the estimated number of obese patients undergoing TKA is expected to rise.13,14 Given the unique challenges in managing obese patients, studying the effects of intermittent tourniquet use in this group of patients is crucial.
This study aims to compare the outcomes of intermittent tourniquet (IT) to throughout tourniquet (TT) use among obese patients undergoing primary TKA for knee osteoarthritis.
2. Methods
This was a retrospective cohort study conducted in a tertiary hospital in Singapore with ethics approval obtained from a local institutional review board. Clinical records for all patients who had undergone primary TKA for osteoarthritis over eight years (January 1, 2013 to December 31, 2019) by the senior author were reviewed. All patients received pre-operative counselling by designated adult reconstruction case managers.
A posterior stabilizing TKA (Legion, Smith & Nephew Inc, Memphis, TN, USA or PFC, Johnson & Johnson Depuy Synthes) was performed for every patient. The procedures were of routine difficulty.
Antibiotic prophylaxis with a stat dose of first-generation cephalosporin (cefazolin 2 g) was routinely used. The alternatives of erythromycin or clindamycin or vancomycin were considered accordingly when indicated, such as penicillin allergy. The type of anaesthesia administered (spinal or general) was decided at the discretion of the anaesthetist after discussion with the patient.
A medial parapatellar capsulotomy and mid-quadriceps incision were used. Synovectomy was performed. An intra-medullary femoral guide and an extra-medullary tibia guide were used. Electrocautery was used for haemostasis and the operative field was soaked in tranexamic acid (1 g in 60 mL of normal saline) for 3 min after the femoral and tibia components were implanted. After capsule repair, the wound closure was performed in layers with the knee at 90° flexion. Monocryl and Dermabond (Ethicon) were used for the skin. No drain was used.
From January 1, 2013, the tourniquet was inflated from the beginning and only released once bone cement had hardened. After June 1, 2017, tourniquet was inflated at the beginning, released after initial incision and haemostasis, then inflated again during cementation. Tourniquet was released once the bone cement had set.
All patients had mechanical deep vein thrombosis prophylaxis (calf pumps). Chemical prophylaxis was not routine. The pre-operative anticoagulant, if any, was restarted with cardiology consultation and based on clinical assessment. The pain control regime included regional analgesia such as femoral block administered on the day of surgery and oral analgesics. The oral analgesics included paracetamol, non-steroidal anti-inflammatory drugs (NSAIDs) and morphine. NSAIDs were used for patients less than 65 years of age if there were no contraindications. The ad hoc femoral block was administered before or after the surgery. An intra-operative 60 mL of local injection (adrenaline 400mcg, ketorolac 30 mg, morphine 5 mg and bupivacaine 100 mg) was routinely given into the operative site tissues unless contraindicated after the implant was cemented. The constituents of the injection were tailored according to the requirements of each patient.
A blood transfusion was ordered when the hemoglobin level was below 8 g/dL or when the patient was symptomatic if hemoglobin was above 8 g/dL. Physiotherapy was started on the first post-operative day and continued daily. The plan for a routine surgery was a 4-day inpatient stay. The duration of the inpatient stay was extended when there was a clinical indication.
The patients were classified into 2 groups: those who had throughout tourniquet (TT), and those who had intermittent tourniquet (IT). Biodata collected were age, gender, BMI and American Society of Anesthesiologists (ASA) score. Patients were defined as obese if their BMI was≥30.15 Outcome measures collected were operative duration, haemoglobin, haematocrit, knee ROM, Visual Analogue Scale (VAS), blood transfusion and length of stay (LOS).
Stata 17.0 (College Station, TX, USA) was used for statistical analysis. Descriptive statistics were conducted to compare the baseline characteristics between TT and IT groups. The categorical outcome measures were analysed using Chi-squared or Fisher's exact test and presented as proportions and percentages. T-test or Kruskal-Wallis test were used for continuous data and presented as means and standard deviations or median and interquartile range.
For primary analyses, we used a linear mixed model for repeated measures over time by groups to analyse the impact of the intermittent tourniquet intervention on the range of movement at baseline and follow-up with fixed effects of time, group, type of group, and the interactions between time and group. Linear mixed models can account for the correlations of response variables within the units by taking random variables for units’ levels including correlations between observations over time.16 We adjusted for the covariates (age, sex, duration of surgery, and transfusion) that could affect the outcome measures. For continuous secondary outcomes (Haemoglobin and Haematocrit), we used the same approach as the primary analysis, controlling for demographic and clinical variables.
No funding was required for this study.
3. Results
A total of 166 patients were identified. There were 95 patients with BMI≥30. Among this group, 48 had IT while 47 had TT. A separate group of interest were patients with BMI <30 and had IT. There were 71 patients in this group.
3.1. IT compared to TT among patients with BMI≥30
In the IT group, there were 26 females (54.2%) and 22 males (45.8%), with an average age of 61.9 years (SD 6.8). The average BMI was 35.0 kg/ (SD 4.1). The mean ASA score was 2.5 (SD 0.7), and the mean pre-operative haemoglobin level was 13.5 g/dL (SD 0.7). In the TT group, there were 32 females (68.1%) and 15 males (31.9%), with an average age of 62.8 years (SD 7.3). The average BMI was 33.8 kg/ (SD 4.0). The mean ASA score was 2.6 (SD 0.50), and the mean pre-operative haemoglobin level was 13.4 g/dL (SD 1.2). There were no significant differences in demographics, ASA scores, and pre-operative haemoglobin levels between the two groups. The pre-operative ROM in the IT group was lower than that of the TT group (94.4° vs. 102.2°, p < 0.05). For additional information, refer to Table 1.
Table 1.
Demographics for BMI≥30.
| Intermittent Tourniquet (IT) n = 48, 58% | Throughout Tourniquet (TT) n = 47, 42% | p-value | |
|---|---|---|---|
| Sex | |||
| Female | 26 (54.2%) | 32 (68.1%) | 0.208 |
| Male | 22 (45.8%) | 15 (31.9%) | |
| Age | |||
| Mean (SD) | 61.9 (6.8) | 62.8 (7.3) | 0.549 |
| Age Groups | |||
| <60 | 18 (37.4%) | 16 (34.0%) | 0.762 |
| 60–69 | 21 (43.8%) | 24 (51.1%) | |
| 70–79 | 9 (18.8%) | 7 (14.9%) | |
| BMI | |||
| mean (SD) | 35.0 (4.1) | 33.8 (4.0) | 0.135 |
| BMI Categories | |||
| Obese (30 - <40) | 43 (89.6%) | 44 (93.6%) | 0.714 |
| Morbidly Obese (≥40) | 5 (10.4%) | 3 (6.4%) | |
| ASA | |||
| Mean (SD) | 2.5 (0.70) | 2.6 (0.50) | 0.327 |
| Pre-Op Hb | |||
| Mean (SD) | 13.5 (1.4) | 13.4 (1.2) | 0.765 |
| Pre-op ROM | |||
| Mean (SD) | 94.4 (10.2) | 102.2 (15.1) | 0.004 |
The mean duration of surgery was 159.3 min (SD 25.9) in the IT group and 135 min (SD 20.6) in the TT group (p < 0.05). As depicted in Fig. 1, both groups experienced a drop in post-operative haemoglobin levels. The difference in haemoglobin drop between the two groups was not statistically significant from post-operative day three onwards (Refer to supplementary material for more details). The proportion of patients who received transfusions was 18.8% in the IT group and 14.9% in the TT group (p > 0.05). On post-operative day one, the median visual analogue scale (VAS) score was 1.5 (0, 2) in the IT group and 2 (0, 4) in the TT group (p < 0.05).
Fig. 1.
Mean (SD) haemoglobin level in g/dL from post-operative day 0 to post-operative day 5.
In the immediate post-operative period, the ROM was greater in the IT group on post-operative day one (p < 0.05), day two (p < 0.05), days three to five (p < 0.05) and days 14–21 (p < 0.05). The TT group exhibited a slower improvement in ROM compared to the IT group. The difference in ROM reduction remained significant until 3 weeks post-operatively. However, starting from six weeks post-operatively, there was no significant difference in the mean ROM between the two groups (Refer to Fig. 2).
Fig. 2.
Mean (SD) ROM in degrees from pre-operatively to post-operative day 180.
The average length of stay for the IT group was 5.8 days (SD 3.6), compared to 7.2 days (SD 4.8) for the TT group (p > 0.05). For more details, please refer to Table 2.
Table 2.
Comparing IT to TT among patients with BMI≥30.
| IT n = 48, 50.5% | TT n = 47, 49.5% | p-value | |
|---|---|---|---|
| Length of stay (days) | |||
| Mean (SD) | 5.8 (3.6) | 7.2 (4.8) | 0.111 |
| Transfusion | |||
| No | 39 (81.2%) | 40 (85.1%) | 0.785 |
| Yes | 9 (18.8%) | 7 (14.9%) | |
| Surgery Duration (mins) | |||
| Mean (SD) | 159.3 (25.9) | 135.0 (20.6) | <0.0001 |
| VAS POD1 | |||
| Median (IQR) | 1.5 (0, 2) | 2 (0, 4) | 0.042 |
3.2. IT use among patients with BMI≥30 compared to patients BMI <30
In the BMI <30 group, there were 46 females (64.8%) and 25 males (35.2%), with an average age of 68.0 years (SD 7.6). The mean ASA score was 2.3 (SD 0.52), and the mean pre-operative haemoglobin level was 12.9 g/dL (SD 1.5). The pre-operative ROM was 104.6° (SD 13.3). There was no significant difference in the gender distribution and mean ASA score between patients with BMI <30 and BMI≥30. However, patients with BMI≥30 were younger (p < 0.05), had a higher pre-operative haemoglobin level (p > 0.05), and lesser pre-operative ROM (p < 0.05). The details are presented in Table 3.
Table 3.
Demographics for all intermittent tourniquet.
| BMI <30 (n = 71, 59.7%) | BMI≥30 (n = 48, 40.3%) | p-value | |
|---|---|---|---|
| Sex | |||
| Female | 46 (64.8%) | 26 (55.4%) | 0.258 |
| Male | 25 (35.2%) | 22 (44.6%) | |
| Age | |||
| Mean (SD) | 68.0 (7.6) | 61.9 (6.8) | <0.0001 |
| Age Groups | |||
| <60 | 8 (11.3%) | 18 (37.5%) | 0.002 |
| 60–69 | 35 (49.3%) | 21 (43.8%) | |
| 70–79 | 23 (32.4%) | 9 (18.8%) | |
| ≥80 | 5 (7%) | 0 | |
| ASA | |||
| Mean (SD) | 2.3 (0.52) | 2.5 (0.7) | 0.108 |
| Pre-Op Hb | |||
| Mean (SD) | 12.9 (1.5) | 13.5 (1.4) | 0.073 |
| Pre-Op ROM | |||
| Mean (SD) | 104.6 (13.3) | 94.4 (10.2) | <0.0001 |
The mean duration of surgery was 159.3 min (SD 25.9) in the BMI≥30 group and 151.8 min (SD 24.5) in the BMI <30 group (p > 0.05). As depicted in Fig. 3, both groups experienced a drop in post-operative haemoglobin levels. However, the difference in haemoglobin drop between the two groups was not statistically significant except at post-operative day five. The proportion of patients who received transfusions was 38.1% in the BMI <30 group and 18.8% in the BMI≥30 group (p < 0.05). On post-operative day one, the median VAS score was 1.5 (0, 2) in the BMI >= 30 group and 2 (0, 2) in the BMI < 30 group (p > 0.05).
Fig. 3.
Linear mixed effect model (mean with 95% CI) comparing difference in the change in haemoglobin levels in g/dL from post-operative day 0 to post-operative day 5 between patients with BMI <30 and BMI≥30 who underwent TKA with IT.
There was no significant difference in ROM between the two groups at 6 months (Refer to Fig. 4).
Fig. 4.
Linear mixed effect model (mean with 95% CI) comparing difference in the change in ROM in degrees from pre-operatively to post-operative day 180 between patients with BMI <30 and BMI≥30 who underwent TKA with IT.
The average length of stay for patients with BMI <30 and BMI≥30 were 5.6 days (SD 3.4) and 5.8 days (SD 3.6) respectively (p > 0.05). Additional information can be found in Table 4.
Table 4.
Comparing BMI <30 to BMI≥30 for IT.
| BMI <30 n = 71, 59.7% | BMI≥30 n = 48, 40.3% | p-value | |
|---|---|---|---|
| Length of stay (days) | |||
| Mean (SD) | 5.6 (3.4) | 5.8 (3.6) | 0.801 |
| Transfusion | |||
| No | 44 (61.9%) | 39 (81.2%) | 0.0270 |
| Yes | 27 (38.1%) | 9 (18.8%) | |
| Surgery Duration | |||
| Mean (SD) | 151.8 (24.5) | 159.3 (25.9) | 0.112 |
| VAS POD1 | |||
| Median (IQR) | (0, 2) | 2 (0, 2) | 0.650 |
4. Discussion
The majority of orthopaedic surgeons use a tourniquet during TKA.6,11 However, the stages during the surgery when it is inflated differs. Traditionally, the tourniquet is inflated from the beginning of the surgery and only released after the joint capsule is closed or at the end of the surgery.17,18 Although the benefits of using a tourniquet are clear, the associated risks of VTE, nerve injury, as well as higher post-operative pain scores and reduced ROM prompts surgeons to consider limiting the total duration of the tourniquet being inflated.3, 7, 8, 9 This had led to the practice of intermittent tourniquet use with studies reporting favourable results.10, 11 However, it is not known if these effects apply to patients with high BMI as well. This is an important consideration as minimising tourniquet related risks would help reduce the overall surgical risk of this patient group.14
4.1. Duration of surgery and blood loss
Among patients with BMI≥30, the surgery duration was longer for IT compared to TT. This is not unexpected due to the increased difficulty in visualising the surgical field due to comparatively more bleeding and time needed to achieve haemostasis. One benefit of having a shorter duration of surgery is potentially reducing risk of prosthetic joint infection (PJI).19 However, it has also been shown that multiple factors can contribute to the development of PJI and there is no significant effect of operative time on rates of infection.20 With a longer operative time among the IT group, there was also an expected greater post-operative haemoglobin level reduction compared to the TT group. However, this discrepancy was no longer present from post-operative day three. There was also no difference in transfusion rate between the two groups. This is concordant with previous studies.11 The above results signify that although there was greater blood loss in the IT group, it has minimal clinical significance with no difference in requirement for transfusion.
When comparing patients with BMI <30 and≥30 who underwent TKA with IT use, there was no significant difference in the duration of surgery. There was also no significant difference in haemoglobin level reduction between the two groups. Of interest, the transfusion rates were higher among patients with BMI <30. One possible explanation was that patients with BMI≥30 were younger (p < 0.05) compared to their counterparts. This was likely due to the accelerated development of end-stage knee OA among patients with higher BMI.21 Among this younger group of patients, the pre-operative haemoglobin levels were higher than the group with BMI <30. Although the average haemoglobin level reduction was similar between the two groups, more patients in the BMI <30 group required a blood transfusion due to their lower starting haemoglobin levels.
4.2. Range of motion and pain
Among patients with BMI≥30, post-operative day one VAS was lesser in the IT group in comparison to the TT group. This was likely due to the reduced duration of total tourniquet time. Thigh pain is a well documented detriment of tourniquet use.22 The reduction in pain with IT use may have contributed to a greater ROM in the IT group compared to the TT group in the initial post-operative period. However, there was no significant difference in ROM after three weeks. A previous study reported a similar finding of increase in post-operative ROM until day five and no significant difference thereafter.10 This greater ROM in the early post-operative period plays a significant role in the patient's rehabilitation as it enables patients to participate in more rehabilitation earlier on in their recovery. This has been shown to be crucial in the outcome after TKA23 as patients can perform certain activities more comfortably and potentially result in a shorter hospital stay. It is worthwhile to note that in the current study, there was no significant difference in post-operative ROM between patients with BMI≥30 and those with BMI <30 with IT use.
4.3. Length of stay
For patients with BMI≥30, the hospital LOS was almost two days shorter for the IT group compared to the TT group. Although the results did not achieve statistical significance, it is still worthwhile noting the difference as a resultant reduction in hospital stay can reduce the risks of nosocomial infections and other hospital admission associated complications.24 There was no significant difference in hospital LOS between patients with BMI <30 and BMI≥30 who had IT.
4.4. Strengths and limitations
This study possess several notable strengths. It comprises a consecutive series conducted by a single surgeon within a single tertiary hospital, and with a standardised post-operative recovery protocol. This eliminates potential variations that could compromise the validity of the results, enhancing the reliability and comparability of the outcomes. The potential confounding factors and the variable accuracy of data collection via a registry method were not present. Also, using linear mixed models, this study was able to account for the occurrence of missing data and perform analysis of unbalanced designs.25
The limitations include the improvement in the surgeon's skill and technique when operating on patients in the IT group as that was later on in the surgeon's career. This may have contributed to the better outcomes among the IT group. Finally, this was a retrospective cohort study and potential factors that can influence the outcomes of interest were not fully within control.
5. Conclusion
In this study, the patients with BMI≥30 in the IT group had a reduced pain score and greater ROM in the initial post-operative period and this correlated with a shorter LOS. Although the operative time and blood loss was greater among the IT group, there was no difference in transfusion rate. The outcomes were similar for patients with BMI≥30 and BMI <30 with TKA performed with IT. The authors recommend intermittent tourniquet use during TKA for patients with BMI≥30.
Patient's consent
De-identified data was used for analysis and individual patient's consent was not required.
Funding statement
No funding was received for the project.
CRediT authorship contribution statement
Yong Yao Tan: Project administration, Writing – original draft, Writing – review & editing. Ke Xin Magneline Ang: Data curation. Mon Hnin Tun: Formal analysis. Sir Young James Loh: Conceptualization, Methodology, Supervision.
Acknowledgement
Not applicable.
References
- 1.Hunter DJ, Bierma-Zeinstra S. Osteoarthritis. Lancet. 2019;393(10182):1745–1759. doi: 10.1016/S0140-6736(19)30417-9. [DOI] [PubMed] [Google Scholar]
- 2.Trieu J, Gould DJ, Schilling C, Spelman T, Dowsey MM, Choong PF. Patient-reported outcomes following total knee replacement in patients <65 years of age-A systematic review and meta-analysis. J Clin Med. 2020;9(10) doi: 10.3390/jcm9103150. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Zhang W, Li N, Chen S, Tan Y, Al-Aidaros M, Chen L. The effects of a tourniquet used in total knee arthroplasty: a meta-analysis. J Orthop Surg Res. 2014;9(1):13. doi: 10.1186/1749-799X-9-13. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Berry DJ, Bozic KJ. Current practice patterns in primary hip and knee arthroplasty among members of the American Association of Hip and Knee Surgeons. J Arthroplasty. 2010;25(6 Suppl):2–4. doi: 10.1016/j.arth.2010.04.033. [DOI] [PubMed] [Google Scholar]
- 5.Lu C, Song M, Chen J, Li C, Lin W, Ye G, et al. Does tourniquet use affect the periprosthetic bone cement penetration in total knee arthroplasty? A meta-analysis. J Orthop Surg Res. 2020;15(1):602. doi: 10.1186/s13018-020-02106-6. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.Ahmed I, Chawla A, Underwood M, Price AJ, Metcalfe A, Hutchinson C, et al. Tourniquet use for knee replacement surgery. Cochrane Database Syst Rev. 2020;12(12) doi: 10.1002/14651858.CD012874.pub2. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7.Horlocker TT, Hebl JR, Gali B, Jankowski CJ, Burkle CM, Berry DJ, et al. Anesthetic, patient, and surgical risk factors for neurologic complications after prolonged total tourniquet time during total knee arthroplasty. Anesth Analg. 2006;102(3):950–955. doi: 10.1213/01.ane.0000194875.05587.7e. [DOI] [PubMed] [Google Scholar]
- 8.Li B, Wen Y, Wu H, Qian Q, Lin X, Zhao H. The effect of tourniquet use on hidden blood loss in total knee arthroplasty. Int Orthop. 2009;33(5):1263–1268. doi: 10.1007/s00264-008-0647-3. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 9.Sukur E, Ozturkmen Y, Akman YE, Senel A, Azboy I. The effect of tourniquet and knee position during wound closure after total knee arthroplasty on early recovery of range of motion: a prospective, randomized study. Arch Orthop Trauma Surg. 2016;136(12):1773–1780. doi: 10.1007/s00402-016-2582-x. [DOI] [PubMed] [Google Scholar]
- 10.Fan Y, Jin J, Sun Z, Li W, Lin J, Weng X, et al. The limited use of a tourniquet during total knee arthroplasty: a randomized controlled trial. Knee. 2014;21(6):1263–1268. doi: 10.1016/j.knee.2014.08.002. [DOI] [PubMed] [Google Scholar]
- 11.Wang C, Zhou C, Qu H, Yan S, Pan Z. Comparison of tourniquet application only during cementation and long-duration tourniquet application in total knee arthroplasty: a meta-analysis. J Orthop Surg Res. 2018;13(1):216. doi: 10.1186/s13018-018-0927-6. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 12.Smith KB, Smith MS. Obesity statistics. Prim Care. 2016;43(1):121–135. doi: 10.1016/j.pop.2015.10.001. ix. [DOI] [PubMed] [Google Scholar]
- 13.Singer SP, Dammerer D, Krismer M, Liebensteiner MC. Maximum lifetime body mass index is the appropriate predictor of knee and hip osteoarthritis. Arch Orthop Trauma Surg. 2018;138(1):99–103. doi: 10.1007/s00402-017-2825-5. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.Boyce L, Prasad A, Barrett M, Dawson-Bowling S, Millington S, Hanna SA, et al. The outcomes of total knee arthroplasty in morbidly obese patients: a systematic review of the literature. Arch Orthop Trauma Surg. 2019;139(4):553–560. doi: 10.1007/s00402-019-03127-5. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 15.Weir CB, Jan A. BMI Classification Percentile And Cut Off Points. StatPearls; 2023. Treasure Island (FL) ineligible companies. Disclosure: Arif Jan declares no relevant financial relationships with ineligible companies. [PubMed] [Google Scholar]
- 16.Verbeke Geert, Molenberghs Geert. Vol. 1. Chapman and Hall/CRC; 2008. (Longitudinal Data Analysis). [Google Scholar]
- 17.Tai TW, Chang CW, Lai KA, Lin CJ, Yang CY. Effects of tourniquet use on blood loss and soft-tissue damage in total knee arthroplasty: a randomized controlled trial. J Bone Joint Surg Am. 2012;94(24):2209–2215. doi: 10.2106/JBJS.K.00813. [DOI] [PubMed] [Google Scholar]
- 18.Ledin H, Aspenberg P, Good L. Tourniquet use in total knee replacement does not improve fixation, but appears to reduce final range of motion. Acta Orthop. 2012;83(5):499–503. doi: 10.3109/17453674.2012.727078. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19.Ravi B, Jenkinson R, O’Heireamhoin S, Austin PC, Aktar S, Leroux TS, et al. Surgical duration is associated with an increased risk of periprosthetic infection following total knee arthroplasty: A population-based retrospective cohort study. EClinicalMedicine. 2019;16:74–80. doi: 10.1016/j.eclinm.2019.09.015. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 20.Naranje S, Lendway L, Mehle S, Gioe TJ. Does operative time affect infection rate in primary total knee arthroplasty? Clin Orthop Relat Res. 2015;473(1):64–69. doi: 10.1007/s11999-014-3628-4. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 21.Martinez-Cano JP, Zamudio-Castilla L, Chica J, Martinez-Arboleda JJ, Sanchez-Vergel A, Martinez-Rondanelli A. Body mass index and knee arthroplasty. J Clin Orthop Trauma. 2020;11(Suppl 5):S711–S716. doi: 10.1016/j.jcot.2020.06.015. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 22.Wang K, Ni S, Li Z, Zhong Q, Li R, Li H, et al. The effects of tourniquet use in total knee arthroplasty: a randomized, controlled trial. Knee Surg Sports Traumatol Arthrosc. 2017;25(9):2849–2857. doi: 10.1007/s00167-015-3964-2. [DOI] [PubMed] [Google Scholar]
- 23.Khan F, Ng L, Gonzalez S, Hale T, Turner-Stokes L. Multidisciplinary rehabilitation programmes following joint replacement at the hip and knee in chronic arthropathy. Cochrane Database Syst Rev. 2008;2008(2) doi: 10.1002/14651858.CD004957.pub3. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 24.Lagoe RJ, Johnson PE, Murphy MP. Inpatient hospital complications and lengths of stay: a short report. BMC Res Notes. 2011;4:135. doi: 10.1186/1756-0500-4-135. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 25.Jos W.R., Twisk V. Applied Longitudinal Data Analysis for Epidemiology: A Practical Guide. Cambridge University Press; Cambridge, United Kingdom: 2003. [Google Scholar]