Abstract
Background:
Blood flow restriction (BFR) therapy has been proposed to help patients build strength with fewer repetitions than standard physical therapy (PT). We sought to determine if BFR would improve quadriceps and hamstring strength in patients with instability and perceived weakness >1 year after primary TKA.
Methods:
We retrospectively reviewed 48 patients with painful TKAs and flexion instability as well as quadriceps and hamstring weakness who performed a 6-week PT program and received isokinetic strength measurements (ISM). Thirty-six patients completed a standard PT program (non-BFR) and 12 patients completed a BFR regimen. ISMs were taken before and after PT to quantify quadriceps and hamstring power, torque, and work compared to the contralateral leg. Statistical analysis was conducted on pre- and post-PT ISM and decisions for revision surgery.
Results:
There were no differences in ISM after PT between the BFR and non-BFR groups. The non-BFR group showed statistically significant strength improvements in flexion but not extension (+28.7 - 32.8%, p=0.0145-0.0255). While no significant difference was found in the BFR group, they saw improvements in all extension strength metrics (19.4 - 23.4%, p=0.3315-0.3901) and flexion (25.7 - 29.9%, p=0.1994-0.2392). No difference was observed between the groups in the rates of subsequent revision TKA (8.3 vs 16.7%, p=0.3362).
Conclusion:
BFR did not improve quadriceps and hamstring strength compared to PT alone in patients with instability and weakness after TKA. Over 80% of total patients chose to avoid revision TKA after completion of focused PT with or without BFR.
Keywords: painful knee replacement, physical therapy, strengthening, blood flow restriction
Introduction:
Persistent quadriceps weakness has been linked to the development of flexion instability (FI) in patients after total knee arthroplasty (TKA) [1]. Prior work has demonstrated that a focused physical therapy (PT) program can improve quadriceps strength and may help patients avoid revision surgery [2]. Blood flow restriction (BFR) therapy was developed in the 1970s and is proposed to increase metabolic stress and mechanical tension to muscle by inflating a tourniquet during muscle work episodes. The increased stress leads to local tissue hypoxia, cellular swelling, and increased metabolites such as lactic acid and reactive oxygen species. This in turn leads to increased protein synthesis, increases in local and systemic anabolic hormones, and increased myogenic stem cells, with the result of increased muscle strength and hypertrophy [3]. The goal of BFR is to use low-load resistance training to increase strength for patients that are unable to tolerate high-load resistance training [4].
While BFR has been proposed as an adjuvant to focused PT in the sports medicine literature, there is no data on the use of BFR therapy for patients with painful TKA. The primary aim of this study is to ascertain whether the addition of BFR therapy to a defined PT program will improve quadriceps and hamstring strength versus PT alone in patients with painful TKA. Secondly, we sought to evaluate whether the completion of a BFR strengthening protocol may prevent the need for revision surgery. We hypothesize that the addition of BFR therapy to a focused PT program for TKA patients with instability will improve quadriceps and hamstring strength and those patients would choose to avoid revision surgery within the year of completing the program compared to a standard, non-BFR PT regimen.
Methods:
After Institutional Review Board (IRB) approval, we retrospectively reviewed internal referral claims for physical therapy between July 2016 and January 2019 by one of four fellowship-trained adult reconstruction surgeons in patients who had associated diagnoses for pain after TKA and/or instability of internal knee prosthesis (ICD codes T84.023 or T84.022).
All patients were initially evaluated in clinic by one of four fellowship-trained joint arthroplasty surgeons for FI after TKA and were sent for assessment and therapy. Patients were only included for this study if they had a primary TKA without prior revision surgery. All patients with global instability, prosthetic joint infection or implant loosening were excluded from this study. Patients were given the option to participate in BFR therapy or therapy alone and were included in the BFR if they had completed a minimum of 6 weeks of BFR therapy. Those patients that completed less than 6 weeks were excluded from the study. Individual patient charts were then reviewed to determine inclusion if a subject completed two or more isokinetic strength tests at least six weeks apart at our outpatient PT center.
Thirty-one patients had their primary TKA performed at our institution and 17 patients had their primary TKA performed at an outside facility. As commonplace with our practice, patients with clinically diagnosed FI more than 1-year after index TKA were sent for isokinetic strength measurement (ISM) testing at our institution’s PT center. We also noted subjects who completed BFR therapy based on PT documentation versus only a focused quadriceps and hamstring strengthen program alone. After these exclusions, we were left with a cohort of 48 patients with a diagnosis of FI after TKA who completed the ISM testing.
Because the diagnosis of FI is subjective, our surgeons followed the criteria proposed by Abdel et al [4] for diagnosis in all patients in our study, which relies on a combination of patient complaints of knee buckling, difficulty with stair descent, or recurrent effusions, and the required physical exam finding of >10mm of anterior translation of the tibia when gravity is eliminated and the knee is flexed to 90° [1]. It is our practice to offer patients with FI after TKA initial conservative options such as bracing, activity modification and focused PT, as previous work has demonstrated that such patients exhibit notable quadriceps and hamstring weakness [1]. The use of BFR in PT was decided upon by the surgeon and therapist as a supplement to offer in those without significant vascular occlusive or cardiac disease. All patients returned to clinic 4-8 weeks after completing a minimum of 12 PT sessions (with or without BFR) and were asked if they had subjective improvements in their pain and function in the affected limb. At this visit, patients decided whether to undergo revision TKA based on their residual knee symptoms. For those patients who did not pursue revision surgery, they were followed clinically for an average of 18 months.
Like our previous study protocol, we collected three distinct measurements of strength during an initial ISM testing and the same three measurements after a minimum of 12 sessions (12-15 sessions) of focused PT with and without a BFR component over a period of 6-10 weeks [2]. The measurements were recorded as averages including power per repetition (Watts), peak torque (foot-pounds), and work per rep (foot-pounds) for both the affected and contralateral leg. The HUMAC NORM dynamometer (Computer Sports Medicine, Inc., Stoughton, MA, USA) was used to perform all isokinetic strength tests [1,6].
For subjects approved for BFR, a licensed physical therapist certified in BFR training directly supervised all therapy sessions. Patients were first familiarized with the BFR cuff and given an overview of the exercise protocol. Partial vascular occlusion was attained utilizing a Delphi PTS Personalized Tourniquet System (Delphi Medical, Vancouver, BC, Canada). An Easy-Fit Tourniquet Cuff (Delphi Medical, Vancouver, VC, Canada) was placed around the most proximal aspect of the patient’s thigh. Cuff width of 10cm was used for all patients. The length of the cuff varied based on the circumference of the patient’s thigh. The subject was asked to lie supine, in a relaxed position, prior to beginning calibration process. Total limb occlusion pressure (LOP) was attained utilizing the Delphi PTS system. Partial vascular occlusion was achieved by setting the tourniquet to 80% of the LOP. A lower percentage, down to 50% LOP, was utilized based on patient tolerance [7,8]. These patients performed opened and closed chain lower extremity strengthening exercises under partial vascular occlusion including short and long arc quadriceps sets, straight leg raises, leg press, hamstring curls, step up/downs and sit-to-stand repetitions. Exercises were performed at an estimated 20-30% of 1 repetition maximum (RM). Subjects performed 4 sets of each exercise with a 30/15/15/15 repetition protocol. A 30-second rest period was utilized between sets. Tourniquet inflation was maintained throughout the individual exercises, including rest periods, with a minimum 1-minute rest period between individual exercises and a maximum inflation period of 8 minutes.
Patient demographics were recorded from the medical record and are listed in Table 1. Radiographs and PT notes were reviewed to determine whether the contralateral limb had been previously replaced. Twelve subjects (8 female and 4 male) completed the BFR therapy protocol and were compared to 36 patients (20 female and 16 male) who completed a focused PT regimen alone. All patients completed pre and post therapy ISM testing as previously described [1]. A minimum of 12-therapy sessions were completed by all subjects and no patients dropped out after starting the BFR therapy arm with an average clinical follow-up of 18 months (9 months – 31 months). Pain during therapy was not routinely recorded at the time.
Table 1.
Descriptive patient demographics
| Demographics | BFR Pre & Post-PT ISO Testing | Non BFR Pre & Post-PT ISO Testing |
|---|---|---|
| Participants | 12 | 36 |
| Female | 8 | 20 |
| Male | 4 | 16 |
| Avg BMI (kg/m2) | 30.38 | 32.81 (p=0.13) |
| Avg Age (years) | 66.92 | 69.89 (p=0.08) |
BFR = blood flow restriction; BMI = body mass index; FI = flexion instability
Patient demographic characteristic are reported using mean and interquartile ranges (IQR) for continuous variables and frequencies (percent) for categorical variables. Pre- and post-therapy (with and without BFR) strength tests for the affected versus contralateral limb were all compared using a two-tailed t-test (GraphPad Prism 6.04, La Jolla, CA). Likewise, we evaluated for any differences in strength improvement between those who went on to revision TKA versus those who avoided revision. Clinical significance was set at p<0.05.
Results:
Before PT intervention there were no baseline differences in quadriceps or hamstring strength measures between the two groups (Table 2). The 36 patients in the non-BFR PT group showed weaker pre-intervention quadriceps strength that was statistically significant when compared to their post-intervention strength (p=0.0071 power/rep; p=0.0082 peak torque; p= 0.0076 work/rep) and hamstring strength that trended towards but did not reach statistical significance (p=0.0994 power/rep; p=0.2211 peak torque; p= 0.1217 work/rep) (Table 3).
Table 2 –
Blood Flow Restriction Isokinetic Group
| BFR ISO Group (n=12) |
Ext Avg Power/Rep |
Ext Peak Torque |
Ext Work/Rep |
Flex Avg Power/Rep |
Flex Peak Torque |
Flex Avg Work/Rep |
|---|---|---|---|---|---|---|
| Pre-Therapy | 32.25 (20.25) | 37.25 (23.25) | 37.75 (26.00) | 25.75 (9.50) | 28.58 (8.75) | 30.08 (11.00) |
| Post-Therapy | 40.67 (32.50 | 45.25 (33.50) | 47.75 (35.75) | 34.83 (22.00) | 37.00 (23.50) | 40.08 (16.75) |
| AFF % difference pre vs post | 23.09% | 19.39% | 23.39% | 29.98% | 25.68% | 28.51% |
| AFF Pre vs Post | 0.3464 | 0.3901 | 0.3315 | 0.1994 | 0.2392 | 0.2162 |
| CL Pre-Therapy | 44.58 (23.75) | 52.50 (26.50) | 53.83 (33.00) | 34.58 (13.25) | 35.83 (13.25) | 41.17 (17.75) |
| CL Post-Therapy | 52.50 (30.75) | 59.33 (29.00) | 63.17 (41.25) | 38.83 (22.00) | 40.33 (19.75) | 45.08 (22.00) |
| CL % difference pre vs post | 16.32% | 12.22% | 15.97% | 11.58% | 11.82% | 9.07% |
| CL Pre vs Post | 0.3168 | 0.3957 | 0.3406 | 0.4526 | 0.4088 | 0.5683 |
| % difference AFF vs CL pre | 32.09% | 33.98% | 35.12% | 29.27% | 22.51% | 31.13% |
| AFF vs CL Pre | 0.0996 | 0.0701 | 0.0821 | 0.1630 | 0.2491 | 0.1527 |
| % difference AFF vs CL post | 25.39% | 26.93% | 27.80% | 10.86% | 8.61% | 11.74% |
| AFF vs CL Post | 0.0682 | 0.0200 | 0.0328 | 0.4278 | 0.5940 | 0.2949 |
Interquartile range(IQR) in parenthesis; ISO - Isokinetic; Avg - Average; AFF - Affected leg; CL - Contralateral leg; Ext - Extension; Flex - Flexion; Rep - Repetition. Units: Power (Watts); Torque (Foot-Pounds); Work (Foot-Pounds)
Table 3 –
Non-Blood Flow Restriction Isokinetic Group
| Non-BFR ISO Group (n=36) |
Ext Avg Power/Rep |
Ext Peak Torque |
Ext Work/Re P |
Flex Avg Power/Re P |
Flex Peak Torque |
Flex Avg Work/Rep |
|---|---|---|---|---|---|---|
| Pre-Therapy | 36.33 (38.50) | 43.28 (39.50) | 43.67 (45.50) | 28.75 (22.00) | 31.58 (24.25) | 33.58 (26.00) |
| Post-Therapy | 47.83 (38.50) | 54.69 (43.00) | 58.56 (49.25) | 38.78 (23.75) | 42.19 (28.50) | 46.78 (29.75) |
| AFF % difference pre vs post | 27.33% | 23.29% | 34.17% | 29.13% | 28.77% | 32.85% |
| AFF Pre vs Post | 0.0619 | 0.0995 | 0.0544 | 0.0204 | 0.0255 | 0.0145 |
| CL Pre-Therapy | 52.81 (34.25) | 61.67 (42.00) | 65.08 (49.00) | 35.81 (22.00) | 37.36 (19.75) | 42.06 (20.50) |
| CL Post-Therapy | 55.08 (36.75) | 64.33 (46.50) | 69.31 (53.75) | 41.22 (25.50) | 43.64 (29.75) | 51.28 (41.25) |
| CL % difference pre vs post | 4.21% | 4.22% | 6.30% | 14.05% | 15.51% | 19.76% |
| CL Pre vs Post | 0.344000 | 0.356000 | 0.249000 | 0.103000 | 0.092400 | 0.045500 |
| % difference AFF vs CL pre | 36.98% | 35.05% | 39.37% | 21.87% | 16.77% | 22.42% |
| AFF vs CL Pre | 0.0071 | 0.0082 | 0.0076 | 0.0994 | 0.2211 | 0.1217 |
| % difference AFF vs CL post | 14.09% | 16.19% | 16.81% | 6.10% | 3.38% | 9.18% |
| AFF vs CL Post | 0.2680 | 0.1965 | 0.2003 | 0.5809 | 0.7624 | 0.4407 |
Interquartile range(IQR) in parenthesis; ISO - Isokinetic; Avg - Average; AFF – Affected leg; CL - Contralateral leg; Ext - Extension; Flex - Flexion; Rep - Repetition. Units: Power (Watts); Torque (Foot-Pounds); Work (Foot-Pounds)
As a group, the 12 FI patients who received BFR therapy did not obtain significant improvements in any quadriceps or hamstring strength measurements (p=0.1994-0.3901). However, this group did achieve net improvements in strength from 19.39%-29.98% (Table 2). Exclusion of the single BFR patient who went on to revision TKA did not alter the calculations for strength improvements.
The 36 patients from the non-BFR group saw significant improvements in all extension isokinetic strength measurements (p=0.0071-0.0082) but not in the flexion strength measurements (p=0.0994-0.2211) after completing their PT sessions. The 30 patients who avoided revision TKA saw no significant improvements in quadriceps power per repetition (p=0.2411), peak torque (p=0.1908), or work per repetition (p=0.1850), or in hamstring power per repetition (p=0.7283), peak torque (p=0.8810), or work per repetition (p=0.5557) (Table 4). The 6 patients who went on to revision did not achieve significant gains in any of the quadriceps or hamstring strength metrics (p=0.5063-0.9335) (Table 5). There were no significant differences in any of the strength measures when comparing the BFR to the non-BFR group (p=0.3249-0.9098) (Table 6). One of the 12 BFR patients and 6 of the 36 standard PT subjects elected to undergo revision TKA based on their continued instability symptoms and knee pain (p=0.3362).
Table 4 –
Non-Blood Flow Restriction Isokinetic Group who Avoided Revision Total Knee Arthroplasty
| Non-BFR ISO Group (n=30) |
Ext Avg Power/Rep |
Ext Peak Torque |
Ext Work/Rep |
Flex Avg Power/Rep |
Flex Peak Torque |
Flex Avg Work/Rep |
|---|---|---|---|---|---|---|
| Pre-Therapy | 36.53 (43.75) | 43.53 (45.75) | 44.30 (50.25) | 29.30 (24.00) | 32.20 (26.00) | 34.23 (29.75) |
| Post-Therapy | 47.07 (39.50) | 54.17 (42.75) | 57.77 (49.00) | 39.03 (25.25) | 42.47 (29.50) | 46.93 (33.25) |
| AFF % difference pre vs post | 28.83% | 24.42% | 30.40% | 33.22% | 31.88% | 37.10% |
| AFF Pre vs Post (p value) | 0.1233 | 0.1744 | 0.125 | 0.0516 | 0.0618 | 0.0406 |
| CL Pre-Therapy | 52.97 (30.25) | 62.43 (39.00) | 66.27 (47.75) | 35.07 (17.75) | 37.73 (17.25) | 42.50 (19.25) |
| CL Post-Therapy | 55.47 (42.25) | 64.97 (43.25) | 70.33 (51.00) | 40.80 (26.50) | 43.30 (31.25) | 50.90 (41.75) |
| CL % difference pre vs post | 4.72% | 4.06% | 6.14% | 16.35% | 14.75% | 19.76% |
| CL Pre vs Post (p value) | 0.7195 | 0.7528 | 0.6753 | 0.2523 | 0.3177 | 0.2254 |
| % difference AFF vs CL pre | 31.03% | 30.27% | 33.15% | 16.44% | 14.66% | 19.45% |
| AFF vs CL Pre | 0.0511 | 0.0154 | 0.0173 | 0.2337 | 0.3073 | 0.1905 |
| % difference AFF vs CL post | 15.14% | 16.62% | 17.87% | 4.33% | 1.92% | 7.79% |
| AFF vs CL Post | 0.2411 | 0.1908 | 0.1850 | 0.7283 | 0.8810 | 0.5557 |
Interquartile range(IQR) in parenthesis; ISO - Isokinetic; Avg - Average; AFF - Affected leg; CL - Contralateral leg; Ext - Extension; Flex - Flexion; Rep - Repetition. Units: Power (Watts); Torque (Foot-Pounds); Work (Foot-Pounds)
Table 5 –
Non-Blood Flow Restriction Isokinetic Group who went on to Revision Total Knee Arthroplasty
| Non-BFR ISO on to Revision Group (n=6) |
Ext Avg Power/Rep |
Ext Peak Torque |
Ext Work/Rep |
Flex Avg Power/Rep |
Flex Peak Torque |
Flex Avg Work/Rep |
|---|---|---|---|---|---|---|
| Pre-Therapy | 35.33 (19.75) | 42.00 (20.75) | 40.50 (18.25) | 26.00 (15.75) | 28.50 (17.50) | 30.33 (20.50) |
| Post-Therapy | 51.67 (23.50) | 57.33 (33.25) | 62.50 (37.75) | 37.50 (13.75) | 40.83 (11.50) | 46.00 (8.50) |
| AFF % difference pre vs post | 37.56% | 30.87% | 42.72% | 36.22% | 35.57% | 41.06% |
| AFF Pre vs Post | 0.2995 | 0.3332 | 0.1984 | 0.1416 | 0.1482 | 0.1380 |
| CL Pre-Therapy | 52.00 (47.50) | 57.83 (48.25) | 59.17 (43.50) | 39.50 (21.50) | 35.50 (20.75) | 39.83 (17.50) |
| CL Post-Therapy | 53.17 (29.00) | 61.17 (39.25) | 64.17 (49.00) | 43.33 (20.25) | 45.33 (15.25) | 53.17 (26.75) |
| CL % difference pre vs post | 2.22% | 5.61% | 8.11% | 9.25% | 24.32% | 28.69% |
| CL Pre vs Post | 0.9490 | 0.8682 | 0.7803 | 0.1137 | 0.4345 | 0.5522 |
| % difference AFF vs CL pre | 38.18% | 31.71% | 37.46% | 41.22% | 21.88% | 27.08% |
| AFF vs CL Pre | 0.2992 | 0.3406 | 0.2272 | 0.1589 | 0.4508 | 0.3526 |
| % difference AFF vs CL post | 2.86% | 6.48% | 2.64% | 14.43% | 10.45% | 14.46% |
| AFF vs CL Post | 0.9335 | 0.8440 | 0.9307 | 0.5063 | 0.5746 | 0.7040 |
Interquartile range(IQR) in parenthesis; ISO - Isokinetic; Avg - Average; AFF - Affected leg; CL - Contralateral leg; Ext - Extension; Flex - Flexion; Rep - Repetition. Units: Power (Watts); Torque (Foot-Pounds); Work (Foot-Pounds)
Table 6 –
Comparison of Blood Flow Restriction Group to Non-Blood Flow Restriction Group
| BFR ISO vs Non- BFR ISO |
Ext Avg Power/Rep |
Ext Peak Torque |
Ext Work/Rep |
Flex Avg Power/Rep |
Flex Peak Torque |
Flex Avg Work/Rep |
|---|---|---|---|---|---|---|
| BFR vs Non-BFR Pre AFF | 0.5702 | 0.4745 | 0.5167 | 0.5840 | 0.6134 | 0.6079 |
| BFR vs Non-BF Post AFF | 0.4415 | 0.3474 | 0.3419 | 0.5347 | 0.4495 | 0.3841 |
| BFR vs Non-BFR Pre CL | 0.3401 | 0.3375 | 0.3249 | 0.8409 | 0.8185 | 0.9098 |
| BFR vs Non-BFR Post CL | 0.7642 | 0.6097 | 0.5834 | 0.6962 | 0.6016 | 0.4487 |
Interquartile range(IQR) in parenthesis; ISO - Isokinetic; Avg - Average; AFF - Affected leg; CL - Contralateral leg; Ext - Extension; Flex - Flexion; Rep - Repetition. Units: Power (Watts); Torque (Foot-Pounds); Work (Foot-Pounds)
Discussion:
In this study, we determined that the addition of BFR to a focused PT regimen for quadriceps and hamstring strengthening did not provide benefits when compared to PT alone in patients with FI after TKA. Deficits of quadriceps activation are expected in the early post-operative period after TKA and often persist in patients with FI [9,10]. While the strength of the knee extensors can be improved with PT, the addition of BFR did not improve results or lead to additional patients who avoided revision surgery. This is important as revision surgery for patients with FI after TKA has been proven to be less successful than revision surgery for other diagnoses such as loosening [11].
BFR has been previously described for use in rehabilitation following anterior cruciate ligament (ACL) reconstruction. A systematic review showed that patients observed muscle hypertrophy, increases in knee extension strength, and subjective outcomes as compared to traditional rehabilitation therapy [12]. While the benefits shown in this review are promising, the patients were a mean age of 24.2 years. These patients may be able to better tolerate strength training and recover more quickly with BFR than TKA subjects in our cohort, where the mean age is 68.5 years. Recent studies have also shown no benefit to BFR after ACL reconstruction when combined with heavy load resistance training [13,14].
No adverse effects were observed in our study using BFR on patients with TKA instability. There are concerns with the safety of BFR including thrombus formation, peripheral nerve compression and rhabdomyolysis. We did not observe any of these adverse effects in our study population, and all 12 participants were able to complete the prescribed twelve minimum sessions. In studies of nearly 13,000 individuals undergoing BFR therapy, the incidence of deep vein thrombosis (DVT) was 0.06% and BFR was not felt to directly cause DVT [15,16]. The incidence of peripheral nerve compression is reported less than 2% and is likely due to inappropriately placed tourniquets or high tourniquet pressures [15]. Controversy exists as to whether BFR can lead to muscle injury. Rhabdomyolysis has occurred at a rate of 0.07% in published series [17]. Case reports of rhabdomyolyses after BFR have been reported [18,19]. One study had shown an increase in creatinine kinase, but these laboratory changes did not correlate with adverse effects such as clinical rhabdomyolysis [20]. BFR is currently the subject of a prospective study examining strength improvement in subjects with knee osteoarthritis before knee replacement [21]. A case report exists describing BFR in the immediate rehabilitation after knee replacement [22]. In our study, however, all patients were at least one year out from their index TKA and peri-surgical inflammation likely does not play a role in the possible development of rhabdomyolysis given the time discrepancy. We do not know the effects of BFR if applied closer to the time of surgery.
The patients treated with BFR in our study had a mean age of almost 69 years, which represents a distinctly older patient group than investigated in previous studies. While BFR has been shown to be effective in younger individuals, it is also believed to be effective in older subjects [23]. BFR has been shown to increase muscle strength and lead to muscle hypertrophy in older patients [3]. It has been hypothesized that BFR would allow older individuals to accomplish the same amount of work in less time than with traditional therapy and improve general muscle mass and physical function to combat sarcopenia [24-26]. Our study did not show any differences in outcomes between BFR and traditional therapy approaches, but we do not have detailed information to determine the actual amount of time spent with either approach. Furthermore, we do not know if the 12-sessions over a minimum of six weeks provides the necessary time to develop differing strength gains compared to standard therapy regimens.
Our study is not without limitations. First, this is a retrospective study and the patients completing BFR with their PT protocol may have potentially been more motivated to complete their therapy and avoid revision surgery than those who did not do BFR. Unfortunately, given the infrequency of FI presentation and the subjective, individual nature surrounding decisions to undergo revision surgery, we are underpowered to report the possible efficacy of adding BFR specifically to avoid further surgery. Additionally, patients were not randomized to use of either method of rehabilitation, which adds an element of selection bias. It is also possible that patients went to outside institutions to undergo revision TKA, but we cross-referenced these patients with our state’s shared electronic health record (Care Everywhere, EPIC Systems Corporation, Madison, WI) to capture all ipsilateral knee procedures. A final limitation is that we were not regularly collecting patient reported outcome scores at the time of this study and instead relied on “yes or no” patient statements to differentiate improvements in symptoms and decisions regarding choosing whether to undergo revision TKA.
In conclusion, the addition of BFR to a focused PT protocol for quadriceps and hamstring strengthening in patients with weakness and instability after TKA did not improve patients’ isokinetic strength measurements. Over 83% of FI TKA subjects were able to avoid revision surgery at an average follow-up of 18 months with a focused PT program regardless of additional BFR. Future prospective randomized studies are needed to ascertain whether blood flow restriction may have a role for enhanced rehabilitation after primary TKA.
Supplementary Material
Footnotes
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