Hand and Wrist Injuries Associated With Application of Physical Restraints: A Systematic Review

Abstract

While handcuffs and zip ties are common methods of physical restraint used by law enforcement, they have been noted to damage soft tissue and bony structures of the hand and wrist. This paper seeks to characterize the safety of physical restraints by summarizing its effects on hand and wrist function and disability. Relevant studies were gathered through an independent double selection and extraction process using 3 electronic databases (EMBASE, MEDLINE, and CINAHL) from database inception to June 19, 2020. A total of 16 studies involving 807 participants were included. Lesion to the superficial branch of the radial nerve was the most commonly reported injury noted in 82% (42/55) of hands examined. A total of 6% (5/77) of examined hands had bony injury, including 3 radial styloid fractures and 2 scaphoid fractures. Both studies on zip ties noted presence of handcuff neuropathy, with 1 case report documenting severe rapidly progressing ischemic monomelic neuropathy. Overall, the use of handcuffs and zip ties is associated with entrapment neuropathies and bony injury to the hand and wrist. Further studies of higher quality evidence are necessary to understand the effects of physical restraint on hand function and disability.

Introduction

Since the original invention of the modern-day handcuff in 1912, there have been revisions to the design and technique in which physical restraints have been applied. A common mechanism of handcuffs involves the use of a ratchet that only allows for further tightening of the cuffs. This mechanism prevents the individual being restrained from loosening the handcuffs upon application. However, tightening often requires little force and when the handcuffs are tightened until resistance is met, structures in the wrist and hand can experience substantial compression.^1-3

In addition to the design of the handcuffs itself, there has been a change in the technique in which handcuffs are used. In particular, while hands were initially restrained in front of the individual, it has become commonplace for hands to be restrained behind the back—preventing individuals from picking the lock, but also from bracing themselves from potential falls. ¹

Furthermore, in recent protests and demonstrations, it was observed that many peaceful protesters were firmly restrained en masse with the use of zip ties. ⁴ Often methods of physical restraint can serve a necessary role in ensuring the safety and wellbeing of the broader community, law enforcement, and the individual themselves. However, despite handcuffs and zip ties being common methods of physical restraint, there is currently no clear evidence regarding its safety to the hand or wrist. ⁵

Previous case reports have documented compression of nerves in the wrist, in what has been termed “handcuff neuropathy.”^6,7 Furthermore, excessive tightening of physical restraints may result in bony injury, including fractures to the wrist and carpal bones. As a result, this systematic review seeks to characterize the literature regarding injuries to the hand and wrist from the application of physical restraints by law enforcement.

Methods

Search Strategy

The authors systematically searched 3 databases, including MEDLINE, EMBASE, and CINAHL from database inception to June 19, 2020. A complete search strategy is provided in the Appendix (Appendix table 1).

Study Screening

This review was conducted according to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines. Systematic article screening was performed through an independent screening and extraction process, from titles to full text review in duplicate. Throughout the title and abstract screening stages, any article with discordance between reviewers was included to ensure that no relevant articles were prematurely excluded. The reviewers discussed any disagreements at the full text stage and study eligibility was resolved through a third reviewer. The reference lists of all included studies were additionally hand searched for relevant articles (see Figure 1).

Figure 1.

PRISMA flow chart.

Assessment of Study Eligibility

The search included all original case reports, observational studies, and randomized control trials in English investigating the effects of physical restraint on hand and wrist outcomes. The primary outcomes included documented frequencies of nerve entrapment and soft tissue and bony injury, and patient-reported pain and disability scores. Studies on physical restraints outside the context of law enforcement, or the use of physical restraints of other extremities were excluded. Studies on animal and cadaveric models were excluded.

Data Extraction

Data extraction occurred in duplicate. The year of publication, author, location of study, and study design were recorded. Outcome data were analyzed quantitatively when possible, and outcomes reported across multiple included studies were pooled and reported as a frequency-weighted mean.

Assessment of Agreement

Unweighted kappa (κ) and 95% confidence intervals (CIs) were calculated for the title, abstract, and full-text screening stages. The interpretation of kappa values was decided a priori where a κ > 0.60 indicated substantial agreement, 0.20 ≤ κ ≤ 0.60 indicated moderate agreement, and κ < 0.20 indicated slight agreement.

Risk of Bias

The Risk of Bias Assessment Tool for Nonrandomized Studies (RoBANS) tool was used to assess methodological quality of included studies. Studies were appraised independently by 2 independent reviewers (S.K. and A.C.) (see Figure 2).

Figure 2.

Overall risk of bias assessment.

Results

Systematic Screening

There were 929 studies identified through MEDLINE, EMBASE, and CINAHL, with 909 records after duplicate removal. Following title and abstract screening, 19 records were identified. A total of 13 studies were included after full text review (see Figure 1). An additional 3 studies were identified upon hand searching the reference letters of included studies, resulting in a total of 16 studies.^2-4,^6-18 There was substantial agreement between the 2 independent reviewers as indicated by a kappa > 0.60 during title and abstract screening, and full-text review.

Characteristics of Studies and Included Participants

The majority of studies were from the United States (n = 7) and the United Kingdom (n = 5), with the remainder of studies from Canada, France, Turkey, and Pakistan. There was 1 prospective cohort study, 4 retrospective cohort studies, 5 case series, and 6 case reports (Appendix table 2). Most studies examined injuries associated with handcuffs (n = 15), with 2 studies reporting injuries associated with zip tie use.

Studies included a total of 807 participants with 629 with restraint associated injury. Of the studies that reported the sex of patients with injuries, 86.6% (123/142) were men. The average age of included participants was 35 (range: 17-69). A total of 41% (31/76) of patients injured by physical restraints were reported to be under the influence of alcohol or substance use (Appendix table 3).

Distribution of Nerve Injuries and Fractures

Lesion to the superficial branch of the radial nerve was the most commonly reported injury noted in 82% (42/55) hands examined for nerve injury (Appendix table 3). Lesion to both the ulnar nerve, namely the dorsal branch, was reported in 39% (18/46) of hand injuries. Comparably, lesion to the median nerve was also observed in 39% (19/49) of hand injuries. Only one study by Wali ⁴ reported injury to the musculocutaneous nerve with an overall frequency of 1% (1/77). Specifically, it was noted that application of a zip tie resulted in low motor amplitudes of bilateral musculocutaneous, median, radial, and ulnar nerves with nonrecordable sensory nerves. A total of 6% (5/77) of examined hands showed bony injury, including 3 radial styloid fractures and 2 scaphoid fractures (Appendix table 4).

Effects of Zip Ties

Only 2 studies investigated the effects of plastic zip ties on hand function. Wali ⁴ described a case report showing that zip ties can produce rapid and severe ischemic monomelic neuropathy, leading to devastating axonal loss within hours. Meanwhile, Kantarci et al ¹⁷ specifically compared the effects of plastic and metal handcuffs and found a statistically significant difference between the injury rate between plastic zip ties and metal handcuff use. In particular, the rate of damage to the epidermis was 46.2% with zip ties and 4.8% with metal handcuffs. Furthermore, handcuff neuropathy was seen in 15% (6/40) plastic handcuff cases and 8.1% (5/62) of metal handcuff cases.

Prevalence of Nerve Injury

The individual nerve injuries reported are summarized below (Appendix table 4). Three studies assessed the prevalence of nerve injury in a population of individuals who were physically restrained. Rogers et al ¹³ reported a prevalence of 42.7% noting, “Although 96 of these detained persons had been handcuffed, only 41 complained of, or were coincidentally noted to have injuries resulting from the use of the handcuffs.” Meanwhile, Cook ¹¹ specifically assessed the prevalence of radial nerve injury and found a prevalence of 19% noting, “Four of 21 (19%) U.S. prisoners of war from Operation Desert Storm Reported numbness or paresthesia in a distribution consistent with injury of the superficial branch of the radial nerve.” Similarly, Chariot et al ¹⁶ : “Twelve of 190 (6.3%) consecutive subjects kept in police custody presented distal neurological symptoms possibly related to handcuff application.”

Risk of Bias Assessment

The overall risk of bias of included summaries was moderate. A summary of the results is outlined in Figure 2.

Discussion

This systematic review, including 16 studies and 807 patients, describes the outcomes of physical restraints on hand and wrist functioning. The majority of studies found lesions to peripheral nerves, largely involving the superficial branch of the radial nerve and the dorsal branch of the ulnar nerve, as common injuries associated with handcuff use. Injury to these nerves likely occur more frequently as they lie superficial and adjacent to bony structures, making them susceptible to external compression. There is further documentation of radial styloid and scaphoid fractures associated with handcuff use. In the absence of long-term data and variation in severity of initial insult and duration of physical restraint application, it remains unclear of the full extent of physical restraint injuries on hand and wrist function.

Furthermore, only 2 studies examined the safety of zip ties. One case report showed the large capacity for harm, documenting rapid and severe ischemic monomelic neuropathy, leading to axonal loss within hours. ⁴ Kantarci et al ¹⁷ specifically compared the safety of plastic zip ties to metal ones and found a statistically significantly higher rate of damage to the epidermis with zip ties. There was further a trend toward higher peripheral nerve damage with zip tie use.

However, despite unclear safety data, the use of handcuffs, and increasingly the use of zip ties, are being used as methods of physical restraint. For instance, following the aftermath of mass demonstrations for the 2020 death of George Floyd in Minneapolis, one report documented testimonies of protestors who described being kept restrained with zip ties on their wrists, even after being placed in cells. The testimony describes injury to circulation and peripheral nerves. ⁵ The report states,

The [Office of the Attorney General] received a significant number of complaints about troubling arrest-related practices, including, among others, using extremely tight zip ties to restrict hands, transporting protesters long distances to arrest processing centers, holding protesters for a significant amount of time after arrest, misgendering detainees, and holding protesters in cramped cells under unsafe conditions in light of the ongoing COVID-19 pandemic. ⁵

Ultimately, detainees are a vulnerable population and often have difficulty accessing care, with limited capacity to follow-up with their routine health-care providers. Given the capacity for substantial soft tissue and bony injury, there is a role for the hand surgeon community to study and advocate for safer methods of physical restraint on anatomical structures. ¹⁹ This may include restrictions on the use of zip ties as a physical restraint method. While low-cost, zip ties only allow for progressive tightening once the cable tie is past the ratchet. Given their thinness, zip ties apply external compression over a smaller surface area, potentially increasing risk of nerve injury in comparison to conventional handcuffs. The use of restraints that provide feedback to the amount of force that has been applied may prove to be a safer alternative.

While some may view handcuffs as a necessary means of apprehending violent offenders, physical restraints have been applied for several nonviolent offenders. Studies have documented commonplace application of handcuffs for individuals being transferred to mental health units and those exercising their lawful right to collectively bargain.^20,21 Furthermore, the tightening of handcuffs is often assumed to have been performed safely in the absence of any vocal outcry, however, individuals under the influence of alcohol or those in other disinhibited states may not have the foresight or consciousness to request relief from overtightening.^7,8

To the authors’ knowledge, this systematic review is the first to summarize the literature regarding the safety of physical restraints, including zip tie use. It identifies a high degree of precaution needed to ensure safe application of physical restraints in the context of multiple studies showing its capacity to injure peripheral nerves and cause bony injury, with unclear long-term recovery. This study is limited in the lack of prospective and randomized controlled trials studying the safety of handcuffs and zip ties. As such, further evidence is needed to characterize the short-term and long-term harms of handcuffs and zip ties on the hand and wrist, and inform future practice regarding safer methods of physical restraint.

Conclusion

The use of handcuffs and zip ties are associated with entrapment neuropathies and bony injury to the hand and wrist. Further studies of higher quality evidence are necessary to understand the effects of physical restraint on hand function and disability.