Thomas I. Sherman, Paul W. Ackermann.
Response/Recommendation: Non-weight-bearing restrictions of the lower extremity are an independent risk factor for venous thromboembolic (VTE) events. This risk is mitigated by load-bearing of the operative limb greater than 50%. No additional conclusions can be made regarding the selection of VTE prophylaxis as it relates to non-weight-bearing based on the available literature.
Strength of Recommendation: Limited.
Rationale: A period of non-weight-bearing restrictions after foot and ankle (F&A) surgery is often required to protect the surgical limb and optimize outcomes. Weight-bearing restrictions after F&A surgery commonly coincide with immobilization of the operative limb (e.g., in a plaster cast or orthosis). These postoperative restrictions, though seemingly innocuous, are not without risks. To this end, immobilization of the lower extremity has been identified as a strong contributor to VTE complications1,2. The pathomechanism of immobilization and VTE events is related to the diminished venous return conferred by immobility and static positioning of the limb3,4. The impact, if any, that non-weight-bearing restrictions have on the development of VTE complications is not as clearly understood, and the relevance that non-weight-bearing restrictions should have on post-surgical VTE prophylaxis selection is debated.
There is a relative dearth of literature reporting on the association of VTE complications and non-weight-bearing restrictions. The literature by and large has focused on immobilization specifically and non-weight-bearing as an independent factor in VTE complications. However, weight-bearing has been shown to increase venous emptying of the lower extremity and may be of clinical relevance in the development of VTE events5.
A level I prospective study evaluated 150 patients that underwent open achilles tendon repair6. Patients were randomized to a protocol consisting of either early full weight-bearing in an orthosis or a conventional postoperative protocol consisting of two weeks of non-weight-bearing in a cast followed by 4 weeks of weight-bearing in an orthosis. No patients were prescribed VTE prophylaxis, and all patients were screened for VTE with bilateral doppler ultrasounds two and six weeks after surgery. The authors identified that loading of the limb less than or equal to 50% of the body weight in the first week following surgery was an independent risk factor for developing VTE and conferred 4.3 times higher odds of developing a VTE in the first two weeks after surgery. Notably, there was no association of VTE, and the number of steps taken per day, which indicates that loading of the operative limb is independently relevant to developing VTE complications.
A separate study by Barg et al., investigated risk factors for VTE in a series of 665 patients undergoing total ankle replacement over a 9 year period7. Patients were instructed to weight-bear while immobilized in a cast or orthosis starting three to four days after surgery unless they had concomitant osteotomies. All patients were prescribed prophylaxis with low-molecular-weight heparin (LMWH) 5000 IU. Three-point nine percent of patients developed a symptomatic deep venous thrombosis (DVT). Multiple regression analysis identified the absence of full post-operative weight-bearing as an independent risk factor for symptomatic VTE, with an odds ratio of 4.53.
A prospective multi-center study by Mizel et al., included 2,733 over the course of a year. Patient demographics, administered medication, orthopaedic procedure and postoperative ordinations including anticoagulation and weight-bearing status was reported by the treating orthopaedic surgeon. Postoperative follow-up averaged 91 days and symptomatic DVT were confirmed by venogram or ultrasonography. Of the six patients that developed DVT, all had been non-weight-bearing corresponding to a relative risk of 1.0 (95% confidence interval [CI] 1.0009 to 1.008, p = 0.014). Two of these 6 patients had received anticoagulation. Furthermore, 4 of the 6 patients with DVT developed non-fatal pulmonary emboli (PE), though whether these received anticoagulation was not specified8.
A retrospective analysis of a series of patients over a one-year period at a single hospital was conducted by Thomas and Van Kampen on a series of patients to evaluate risk factors for symptomatic VTE9. The authors reported that 7 of the 381 (1.84%) patients included in their analysis developed DVT, 4 of which developed a PE. Chart review revealed that all patients that had a PE were instructed to be non-weight-bearing for injuries consisting of ankle fractures (2), distal tibia and fibula fracture (1), and achilles rupture (1). None of the patients underwent surgery and no prophylaxis was prescribed. The study was not powered to determine the statistical significance of weight-bearing restrictions on VTE events, but these findings are notable nonetheless.
A prospective descriptive study was performed on a group of 216 patients who underwent various F&A surgeries10. Short leg cast immobilization and non-weight-bearing for at least 4 weeks was required in 130 patients, while 88 patients underwent hallux surgery that did not require immobilization or weight-bearing restrictions. No patients received VTE prophylaxis. Screening by ultrasound at 2 and 6 weeks after surgery revealed an overall incidence of DVT of 5.09% with no clots being identified in the hallux valgus subgroup who were permitted to weight-bear immediately, and 8.46% incidence in the group immobilized in a cast with non-weight-bearing restrictions. These results are descriptive, as the study was not sufficiently powered to determine individual risk factors; however, these findings do coincide with previous reports that have identified an association between non-weight-bearing restrictions and VTE events.
These findings in summation do suggest that non-weight-bearing restrictions are an independent risk factor for VTE events and merit the attention of the surgeon. The literature supporting this conclusion, however, is limited, with the work of Aufwerber et al., representing the only Level I evidence identifying this association. The pathomechanism of non-weight-bearing restrictions on VTE is likely related to the resultant restricted venous return, which does conversely increase with weight-bearing. Clinicians should consider non-weight-bearing restrictions when determining patients’ risks for VTE events following F&A surgery. This risk may be mitigated by permitting at least partial loading of the limb even when immobilized6. No recommendation regarding the use of additional VTE prophylaxis medications or interventions for patients requiring non-weight-bearing after surgery can be made. Determining the need for chemoprophylaxis based on non-weight-bearing restrictions following surgery has not been independently investigated. It is notable, however, that a recent Cochrane review did investigate LMWH VTE prophylaxis specifically in patients with lower limb immobilization but did not specifically analyze non-weight-bearing restrictions2. From the authors’ analysis of 3,680 participants from 8 randomized controlled trials, it was concluded that LMWH prophylaxis did significantly lower the incidence of DVT in patients requiring lower extremity immobilization. These results were based on moderate-quality evidence. Investigation regarding the use of VTE prophylaxis in patients undergoing F&A surgery requiring postoperative weight-bearing restrictions is needed.
1. Bertoletti L, Righini M, Bounameaux H, et al. Acute venous thromboembolism after non-major orthopaedic surgery or post-traumatic limb immobilisation. Findings from the RIETE registry. Thromb Haemost. 2011;105(4):739-741. doi:10.1160/TH10-11-0751
2. Zee AA, van Lieshout K, van der Heide M, Janssen L, Janzing HM. Low molecular weight heparin for prevention of venous thromboembolism in patients with lower-limb immobilization. Cochrane Database Syst Rev. 2017;8:CD006681. doi:10.1002/14651858.CD006681.pub4
3. Stein PD, Yaekoub AY, Ahsan ST, et al. Ankle exercise and venous blood velocity. Thromb Haemost. 2009;101(6):1100-1103.
4. Craik JD, Clark A, Hendry J, Sott AH, Hamilton PD. The effect of ankle joint immobilization on lower limb venous flow. Foot Ankle Int. 2015;36(1):18-23. doi:10.1177/1071100714552823
5. Broderick BJ, Corley GJ, Quondamatteo F, Breen PP, Serrador J, Ólaighin G. Venous emptying from the foot: influences of weight bearing, toe curls, electrical stimulation, passive compression, and posture. J Appl Physiol (1985). 2010;109(4):1045-1052. doi:10.1152/japplphysiol.00231.2010
6. Aufwerber S, Heijne A, Edman G, Grävare Silbernagel K, Ackermann PW. Early mobilization does not reduce the risk of deep venous thrombosis after Achilles tendon rupture: a randomized controlled trial. Knee Surg Sports Traumatol Arthrosc. 2020;28(1):312-319. doi:10.1007/s00167-019-05767-x
7. Barg A, Henninger HB, Hintermann B. Risk factors for symptomatic deep-vein thrombosis in patients after total ankle replacement who received routine chemical thromboprophylaxis. J Bone Joint Surg Br. 2011;93(7):921-927. doi:10.1302/0301-620X.93B7.26257
8. Mizel MS, Temple HT, Michelson JD, et al. Thromboembolism after foot and ankle surgery. A multicenter study. Clin Orthop Relat Res. 1998;(348):180-185.
9. Thomas S, Van Kampen M. Should orthopedic outpatients with lower limb casts be given deep vein thrombosis prophylaxis? Clin Appl Thromb Hemost. 2011;17(4):405-407. doi:10.1177/1076029610371472
10. Saragas NP, Ferrao PNF, Saragas E, Jacobson BF. The impact of risk assessment on the implementation of venous thromboembolism prophylaxis in foot and ankle surgery. Foot Ankle Surg. 2014;20(2):85-89. doi:10.1016/j.fas.2013.11.002