The Prevention of Positioning Injuries During Gynecologic Surgery. Guideline of the DGGG, OEGGG and SGGG (S2k Level, AWMF Registry Number 015/077, October 2020)

Abstract

Purpose Positioning injuries are relatively common, forensically highly relevant complications of gynecologic surgery. The aim of this official AWMF S2k-guideline is to provide statements and recommendations on how to prevent positioning injuries using the currently available literature. The literature was evaluated by an interdisciplinary group of experts from professional medical societies. The consensus on recommendations and statements was achieved in a structured consensus process.

Method The current guideline is based on the expired S1-guideline, which was updated by a systematic search of the literature and a review of relevant publications issued between February 2014 and March 2019. Statements were compiled and voted on by a panel of experts.

Recommendations The guideline provides general and specific recommendations on the prevention, diagnosis and treatment of positioning injuries.

Key words

gynecologic surgery - positioning injuries - prevention

I  Guideline Information

Guidelines program of the DGGG, OEGGG and SGGG

For information on the guidelines program of the DGGG, OEGGG and SGGG, please refer to the end of the guideline.

Citation format

The Prevention of Positioning Injuries During Gynecologic Surgery. Guideline of the DGGG, OEGGG and SGGG (S2k Level, AWMF Registry Number 015/077, October 2020). Geburtsh Frauenheilk 2021; 81: 447 – 468

Guideline documents

The complete German-language long version and slide versions of both of these guidelines together with a list of the conflicts of interest of all of the authors are available on the homepage of the AWMF: http://www.awmf.org/leitlinien/detail/ll/015-077.html

Guideline authors

See [Tables 1] and [2].

Table 1 Lead author and/or coordinating guideline author.

Author	AWMF professional society
Prof. Dr. Markus Fleisch	DGGG

Table 2 Contributing guideline authors.

Author Mandate holder	DGGG working group/AWMF/non-AWMF professional society/ organization/association
Prof. Dr. Werner Bader	AGUB
Prof. Dr. Kai Baltzer	DGG
Prof. Dr. Carsten Boeing	AGO Vulva and Vagina
Prof. Dr. Dorothee Bremerich	DGAI
PD Dr. Verena Geissbühler	SGGG
Kristina Lippach, MHBA	DGP
Dr. Klaus Pietzner	NOGGO
Prof. Dr. Stefan Renner	EEL
Prof. Dr. Thomas Römer	AGE
Prof. Dr. Stephan Roth	DGU
Prof. Dr. Jalid Sehouli	AGO Ovary
Prof. Dr. Florian Schütz	AGO Breast
Prof. Dr. Wilhelm Schulte-Mattler	DGN
Prof. Dr. Karl Tamussino	OEGGG
Prof. Dr. Alexander Teichmann	Expert
Prof. Dr. Clemens Tempfer	AGO Uterus
Prof. Dr. Marc Thill	AWOGyn
Prof. Dr. Hans Tinneberg	SEF

This guideline was moderated by Dr. med. Monika Nothacker (AWMF-certified guideline moderator).

Dr. Martin Koch (UK Erlangen) provided methodological advice for the literature search.

Abbreviations

AORN: Association of periOperative Registered Nurses

ASA: American Society of Anesthesiologists

AST: Association of Surgical Technologists

BGH: Federal Court of Justice (of Germany)

BMI: body mass index

CS: compartment syndrome

CSp: cervical spine

DNQP: German Network for Quality Development in Nursing

DVT: deep vein thrombosis

EDC: epidural catheter

EMG: electromyography

EPUAP: European Pressure Ulcer Advisory Panel

HF: high frequency

HTA: health technology assessment

ICP: intracompartmental pressure

LSp: lumbar spine

MPBetreibV: German Medical Products Operator Ordinance

NPUAP: National Pressure Ulcer Advisory Panel

OLG: Higher Regional Court (of Germany)

PAD: peripheral artery disease
 

II  Guideline Application

Purpose and objectives

This guideline aims to provide statements and recommendations for the prevention, diagnosis and management of positioning injuries in gynecology, based on an interdisciplinary consensus which was achieved after reviewing the current literature.

Targeted areas of patient care

• Inpatient care

• Outpatient care

Target user groups/target audience

This guideline is aimed at the following groups of persons:

• hospital-based gynecologists

• gynecologists performing outpatient surgery

• anesthesiologists

• surgeons (general/visceral/vascular)

• nursing staff working in the operating room

• staff working in intensive care

• neurologists

Additional groups of persons (for the purpose of information):

• urologists

• medical lawyers

Adoption and period of validity

The validity of this guideline was confirmed by the executive boards/heads of the participating medical professional societies/working groups as well as by the boards of the DGGG, the DGGG guidelines commission, the SGGG and the OEGGG in September 2020 and thus approved in its entirety. This guideline is valid from 1st August 2020 through to 31st July 2025. Because of the contents of this guideline, this period of validity is only an estimate.

III  Methodology

Basic principles

The method used to prepare this guideline was determined by the class to which this guideline was assigned. The AWMF Guidance Manual (version 1.0) has set out the respective rules and requirements for different classes of guidelines. Guidelines are differentiated into lowest (S1), intermediate (S2), and highest (S3) class. The lowest class is defined as consisting of a set of recommendations for action compiled by a non-representative group of experts. In 2004, the S2 class was divided into two subclasses: a systematic evidence-based subclass (S2e) and a structural consensus-based subclass (S2k). The highest S3 class combines both approaches.

This guideline has been classified as: S2k.

Grading of recommendations

The grading of evidence based on the systematic search, selection, evaluation and synthesis of an evidence base which is then used to grade the recommendations is not envisaged for S2k guidelines. The different individual statements and recommendations are only differentiated linguistically, not by using symbols ([Table 3]):

Table 3 Grading of recommendations.

Level of obligation to comply with recommendation	Terminology
Strong recommendation, highly binding	must/must not
Recommendation, moderately binding	should/should not
Open recommendation, not binding	may/may not

Statements

Expositions or explanations of specific facts, circumstances or problems without any direct recommendations for action included in this guideline are referred to as “Statements”. It is not possible to provide any information about the grading of evidence for these statements.

Achieving consensus and level of consensus

At structured NIH-type consensus-based conferences (S2k/S3 level), authorized participants attending the session vote on draft statements and recommendations. The process is as follows. A recommendation is presented, its contents are discussed, proposed changes are put forward, and finally, all proposed changes are voted on. If a consensus is not achieved (> 75% of votes), there is another round of discussions, followed by a repeat vote. Finally, the extent of consensus is determined based on the number of participants ([Table 4]).

Table 4 Level of consensus based on extent of agreement.

Symbol	Level of consensus	Extent of agreement in percent
+++	Strong consensus	> 95% of participants agree
++	Consensus	> 75 – 95% of participants agree
+	Majority agreement	> 50 – 75% of participants agree
–	No consensus	< 51% of participants agree

Expert consensus

As the name already implies, this refers to consensus decisions taken specifically with regard to recommendations/statements made without a prior systematic search of the literature (S2k) or where evidence is lacking (S2e/S3). The term “expert consensus” (EC) used here is synonymous with terminology used in other guidelines such as “good clinical practice” (GCP) or “clinical consensus point” (CCP). The strength of the recommendation is graded as previously described in the chapter on the grading of recommendations; it is only expressed semantically (“must”/“must not” or “should”/“should not” or “may”/“may not”) without the use of symbols.

IV  Guideline

1  Introduction

Preoperative positioning and proper intraoperative positioning during gynecologic surgery is an interdisciplinary duty which requires the cooperation of medical staff across a range of different specialties. All persons involved have a legal obligation of due care. The goal must be to guarantee patient safety and prevent positioning injuries [1]. It is important to balance the surgeonʼs need for an optimal view of the operating site in every patient position and during any changes in positioning against the concerns of the anesthesiologist about maintaining the best and safest access to the patient. It is also important to ensure that the patientʼs dignity is protected throughout the procedure.

Incorrect positioning may result in adverse effects to the patientʼs health; the injury may be transient but it can also be permanent, leading to long-term functional impairments, secondary morbidity or even death.

Optimal positioning must prevent pressure damage (pressure ulcers), skin irritation, burns, nerve damage, circulatory problems, and hypothermia.

Positioning injuries may affect the skin and soft tissues, the joints, the ligaments and bones as well as the eyes, nerves and vessels.

There are patient-related and procedure-specific risk factors for positioning injuries ([Tables 5] and [6]).

Table 5 Reported patient-related risk factors for positioning injuries [2], [3], [4], [5], [6], [7].

Patient-related	Associated risk
BMI < 20 or > 30	Pressure ulcer, neuropathy
Restricted mobility (osteoarthrosis, arthritis, Bechterewʼs disease, knee and/or hip replacement, arthrodesis, etc.)	Neuropathy, pressure ulcer
Age > 70 years	Neuropathy, pressure ulcer
Malnutrition	Pressure ulcer
PAD	Neuropathy
Smoking and COPD	Neuropathy of the lower extremity, pressure ulcer
Anatomical anomalies (cervical rib, etc.)	Neuropathy
Preexisting neuropathies	Neuropathy, pressure ulcer

Table 6 Reported procedure-specific risk factors for positioning injuries [2], [3], [4], [5], [6], [7].

Operation-specific	Type of risk
“Lengthy” procedure (> 4 hours)	Pressure ulcer, neuropathy, compartment syndrome
Procedures carried out with the patient in the lithotomy position
Procedures carried out with the patient in a severe Trendelenburg position

2  Basic Forensic Aspects of Positioning

2.1  Division of tasks and responsibility

No.	Recommendation/Statement	Level of consensus	References
S.1	Positioning is an interdisciplinary task which requires the cooperation of professionals across a range of specialties.	+++
S.2	The individual responsibility for positioning depends on the stage of the operation: preoperative stage (anesthesiologist), intraoperative stage (surgeon), deliberate intraoperative change of positioning (surgeon), postoperative stage (anesthesiologist).	+++	[8]
E.1	When patient-specific risk factors are present or with certain types of positioning for surgery which are considered to have an inherent risk of positioning injury (primarily, lengthy procedures performed with patients in the lithotomy position), patients should be informed by their physician about potential specific positioning injuries (e.g., compartment syndrome).	+++
E.2	Documenting patient positions may be done with reference to the hospitalʼs mandatory positioning standards which should be on file. Deviations from these standards must be recorded.	+++
E.3	If there are no mandatory in-house standards, the surgical protocol or surgery report must include a detailed description of the patientʼs positions and any aids used (gel mats, etc.).	+++
S.3	Intraoperative checks by the surgeon whether the patients is still positioned correctly do not have to be recorded every time they are performed, but it is advisable to include a reference to routine checks in the surgical protocol or surgery report.	+++	[9]
S.4	The patientʼs position after an intraoperative change in position (e.g., repositioning the patient from a classic lithotomy position to a flat lithotomy position) is the responsibility of the surgeon. It must be controlled and the repositioning must be documented accordingly. The extent and type of control is not specified.	+++	[9]

3  General and Specific Aspects of Positioning

No.	Recommendation/Statement	Level of consensus	References
E.4	Surgical units must develop positioning standards, store them where they are easily accessible, communicate them to the different medical specialties, medical professionals and staff, and regularly revise them to ensure that they are still up-to-date.	+++
E.5	Positioning materials must be available in sufficient quantities and of a sufficient quality for all surgical procedures. The type and quantity of materials should depend on the patient population and the state of scientific knowledge. Particularly when positioning obese patients, it is important that the operating tables meet the required weight specifications.	+++
E.6	Co-morbidities and conditions relevant for the patientʼs positioning should be ascertained preoperatively and taken into account when the patient is positioned (ASA, AORN). This includes any endoprotheses or implanted devices, restricted joint mobility, and anatomical anomalies (if these are known preoperatively).	+++	[10], [11]
E.7	Positioning and repositioning, if done, must be carried out by a sufficient number of persons (AST, AORN) to ensure patient safety and the ergonomic safety of the staff.	+++	[10], [12]
E.8	When the patient is being repositioned on the operating table, the patient should not be slid but should be moved using suitable positioning aids (backboards, lifts) with as little friction as possible to avoid injuries to the skin from shear forces (AST).	+++	[12]
E.9	The pads on which the patient lies must be dry and crease-free.	+++
E.10	It is important that no parts of the body hang over the side of the operating table; the sacrum must not extend beyond the edge of the operating table (AST, AORN).	+++	[10], [12]
E.11	Padding must be placed under the head to ensure that the cervical spine (CSp) is in a neutral position and no pressure points develop at the back of the head.	++

4  Positioning of pregnant women

5  General Recommendations for the Lithotomy Position (“Good Practice Points”)

No.	Recommendation/Statement	Level of consensus	References
E.13	When the patient is positioned using medical stirrups, both stirrups must be padded and at the same height (AST, AORN).	+++	[10], [12]
E.14	Depending on the patientʼs constitution (obesity, joint mobility, etc.), the legs must be lifted into leg holders and lifted out again at the end of the procedure by a sufficient number of assistants to avoid lumbosacral injury and hyperflexion of the hips (AST, AORN).	+++	[10], [12]
E.15	The time the patient spends in the lithotomy position must be kept as short as required for the individual surgical procedure (AORN).	++	[10]
E.16	If the arms are placed alongside the body, it is important to look out for the position of the hand and particularly of the fingers to avoid crush injuries when moving the leg holders (AORN).	+++	[10]

6  Positioning-related Neuropathies

6.1  Positioning-related neuropathies

The overall incidence of postoperative nerve lesions (including lesions directly caused by the surgical procedure) is reported to be 0.6 – 1.2‰ [14]. Neuropathies are generally caused by a combination of stretching, ischemia and pressure [15].

6.1.1  Neuropathies of the upper extremities

Neuropathy of the brachial plexus

Injuries of the brachial plexus are rare but serious complications resulting from laparoscopic or robot-assisted procedures carried out with the patient in the Trendelenburg position [16], [17], [18]. With an estimated incidence of 0.16% for laparoscopic and robot-assisted interventions, they are reported to be the second most common nerve injury in anesthetized patients [18], [19], [20]. The plexus is at risk of injury because of its anatomical course, running from the neck, exiting the intervertebral foramina to reach the axilla, passing through the scalene triangle and between the clavicula and the first rib, with its proximal and distal attachments to the cervical vertebrae and its proximity to other moving bony structures which could potentially compress it [18], [21], [22]. Compression over the acromion or of soft tissues 4 – 6 cm medial to the acromion, for example by shoulder braces, and the resulting extension of the brachial plexus in the vicinity of the C5–T1 nerve roots is considered to be a major cause of positioning-related brachial plexus injuries [15], [16], [18], [23], [24], [25]. Another potential mechanism of injury is a dropping away of the shoulder girdle in an anesthetized, relaxed patient with subsequent entrapment of the brachial plexus between the clavicula and the first rib, as well as hyperextension combined with rotation at the cervical spine [26]. Symptoms for this type of plexus injury include various motor and sensory deficits in the shoulder, upper and lower arms and hands. Anatomical variants such as the presence of a cervical rib, an abnormal course of the plexus, or deformities caused by fractures are all predisposing patient-specific factors which increase the risk of brachial plexus injury [4], [27]. The prognosis for such injuries is generally good with a high probability that motor and sensory symptoms will resolve over time [28], although recovery may take several months. Nevertheless, cases with permanent functional impairments have also been reported in the literature [16].

In the steep Trendelenburg position, the patient is head-down in a supine position, with her feet on an incline up to 30° higher than her head. Shoulder braces are often used to prevent the patient from slipping on the operating table [16], [29]. The pressure exerted on the shoulders increases as the angle of the Trendelenburg position increases [29]. The combination of arm abduction with shoulder braces appears to particularly increase the risk of plexopathies [30]. Pressure on the peripheral part of the accessory nerve may additionally lead to paresis of the trapezius muscle. A study which prospectively compared three different systems to prevent intraoperative slipping of the patients and simultaneously measured the pressure exerted on the shoulders of non-anesthetized patients according to the angle of incline when the patient was in a head-down position showed that using a medical vacuum mattress system resulted in the least pressure on the shoulder area [29]. Whether the use of medical vacuum mattress systems reduces the incidence of brachial plexus injuries has not yet been confirmed, even though many authors advocate their use. One study comparing foam mattresses with gel mats with regard to patients sliding down intraoperatively found no differences between the two [31].

Ulnar nerve neuropathy

The ulnar nerve is at risk of pressure injury because of its largely unprotected course in the ulnar nerve sulcus [32]. A prospective study of 1502 patients reported the incidence of ulnar nerve injury to be 0.5% [33]. Analysis showed, however, that the risk population consisted primarily of men. This circumstance as well as the fact that clinical symptoms only occurred between two and seven days after surgery suggests that factors other than inadequate patient positioning may also play a role.

Clinical symptoms of injury include paresthesia of the fourth and fifth fingers and on the ulnar side of the hand. The full clinical picture with involvement of ulnar nerve motor fibers may result in an “ulnar claw” [21]. Pressure injures may occur as the result of direct pressure in the area of the elbow from incorrect positioning of the arm, non-physiological pressure on the arm caused by the surgeon leaning against the patient or pronation of the arm on the arm braces [21]. In cases with more severe injury (axonotmesis), the prognosis for spontaneous healing may not be good [34].

No.	Recommendation/Statement	Level of consensus	References
E.17	After weighing up the surgical aspects, the extent of tilt should be kept to a minimum and the duration of any procedure with the patient in the Trendelenburg position should be as short as possible.	+++
E.18	It is recommended that the head be positioned using appropriate devices; longer periods of hyperextension or lateral flexion/rotation should be avoided (AORN, ASA).	+++	[10], [11], [15]
E.19	Arm braces should be positioned in such a way as to prevent any dropping of the shoulder.	+++
E.20	Intraoperative sliding on the operating table must be prevented (AORN). A combination of shoulder braces with non-slip operating table pads is preferable to using only shoulder braces.	++	[10]
E.21	The shoulder braces must be padded, and the point of contact must be at the level of the acromioclavicular joints (AORN).	++
E.22	Any additional abduction of the arm should be avoided or minimized when using shoulder supports. Arm abduction must not exceed 90°.	++	[10]
E.23	If the arms are abducted, abduction up to approx. 60° should be done with the arms in a neutral position; arms which are abducted by more than 60° should be in a supination position. The arm must be slightly flexed at the elbow and the forearm must be supported by an arm brace (AST, AORN).	++	[10], [12]
E.24	If the arm is placed in an arm brace, the arm should be in a supination position (AORN, ASA).	++	[10], [12], [35]

6.1.2  Neuropathies of the lower extremity

According to the results of a retrospective analysis carried out at the Mayo Clinic (Rochester/USA), persistent (≥ 6 months) motor neuropathies of the lower extremity occur in around 1 of 3600 procedures performed with the patient in the lithotomy position [7]. In this study, every additional hour the patient spent in the lithotomy position increased the risk of developing a neuropathy by factor of 100. In 78% of cases, the peroneal nerve was affected; the sciatic nerve was affected in 15% of cases and the femoral nerve in 7%. Sensory neuropathies occurred in 15 of 1000 cases [7]. Complete regeneration within the space of one year occurred in less than half (43%) of all cases [7]. Multivariate analysis showed that risk factors included BMI ≤ 20, smoking within 30 days prior to surgery, and surgery with the patient in the lithotomy position for more than 4 hours ([Tables 5] and [6]).

Peroneal nerve neuropathy

The common peroneal nerve is a branch of the sciatic nerve; it crosses the knee joint at the lateral aspect of the fibular neck [21] and divides into two branches. The superficial peroneal nerve provides sensory innervation but also innervates the peroneus longus and peroneus brevis muscles, which act as pronators of the foot. The deep peroneal nerve innervates the muscles required to lift the foot at the ankle joint and the arch of the foot and provides sensory innervation to the webbing between the hallux and the second digit. Because of the limited soft tissue cushioning at the fibular neck, there is a risk of direct pressure injury. This pressure is often caused by unpadded contact with the leg holder. Alternatively, a combination of hip flexion and knee extension can lead to non-physiological extension of the sciatic nerve and the peroneal nerves [36]. Postoperative symptoms of a common peroneal nerve neuropathy are sensory deficits in the lateral lower leg and at the arch of the foot. Motor deficits may include limited dorsiflexion of the foot, which may present clinically as foot drop (steppage gait). The differential diagnosis must include peroneal/sciatic injury and injury to a branch of the lumbosacral plexus which can occur in the lithotomy position [37]. A low BMI, smoking, and prolonged duration of surgical procedures increase the risk of injury ([Tables 5] and [6]).

Sciatic nerve neuropathy

Sciatic nerve neuropathies have been described after patients were positioned in the lithotomy position and after cesarean section [38], [39]. The lithotomy position may result in overextension of the peroneal branch of the sciatic nerve [36], [40], [41]. Perioperative sciatic nerve lesions usually result in weakness of the dorsiflexor muscles of the foot. Other muscles supplied by the sciatic nerve, especially the knee flexor muscles, are often only affected at a subclinical level [42]. This also applies to sensory deficits; hypesthesia of the lateral aspect of the calf and across the entire foot with the exception of the medial aspect only occurs in the context of severe injury.

Femoral nerve neuropathy

Several gynecologic case studies have described femoral nerve neuropathies following procedures performed with the patient in the lithotomy position, some of them caused by the placement of self-retaining surgical retractors [43]. In each case, hip abduction together with extreme hip flexion and external rotation were also cited as increasing the risk [44], [45], [46], [47], [48]. This type of positioning leads to mechanical bending of the femoral nerve which is pressed against the inguinal ligament. During a vaginal procedure with the patient in the lithotomy position this mechanism may even be intensified by the assistant leaning against the inner thigh [15]. Clinical symptoms of femoral nerve neuropathy include postoperative deficits in hip flexion and knee extension together with a diminished patellar reflex. Even the use of a split-leg table, i.e., with legs in a supine position and both hips abducted, is associated with femoral nerve neuropathy. The incidence of this complication after robot-assisted procedures with a hip abduction of 25° was reported to be 1.7% [49]. Common symptoms are numbness of the leg and a tendency to fall on mobilization. Most sensory deficits disappear within five days [2]. In one case study, 94% of patients with motor deficits had complete resolution within 10 weeks; the other subjects had complete remission within the space of four months [50].

Obturator nerve neuropathy

The obturator nerve is a branch of the lumbar plexus. There is only limited data on obturator nerve neuropathies following procedures performed with patients in the lithotomy position. Experiments have shown that even abduction of the thigh with an angle of between 30 – 45° in the hip joint leads to significant traction on the obturator nerve, which can be compensated for by hip flexion [51]. Injuries to the obturator nerve after vaginal delivery caused by pressure of the fetus against the internal pelvic wall have been described [52]. This phenomenon should be considered in the differential diagnosis of putative positioning-related obturator neuropathies after cesarean section.

No.	Recommendation/Statement	Level of consensus	References
E.25	The fibular neck must be positioned in such a way that no pressure is exerted on it.	++
E.26	When using leg supports with straps, the leg must not be in contact with the rods of the supports (AORN).	+++	[10]
E.27	Overextension of the ischiocrural muscles must be avoided; hip flexion must not exceed 90° if possible.	++	[11]
E.28	Hip flexion of > 90° in the lithotomy position should be avoided during longer vaginal procedures.	++
E.29	Extreme abduction and external rotation of the hip joint should be avoided.	+++
E.30	The surgical assistant must not lean against the patientʼs inner thigh (AORN).	+++
E.31	Abduction of the lower extremity by > 30° (lithotomy position or split-leg table) must be accompanied by flexion of the hip joint to prevent positioning-related obturator nerve neuropathy. The maximum angle of abduction should not exceed 45°.	+++

7  Injuries Caused by High-frequency Surgery

Technical or operator mistakes and procedure-related or patient-dependent factors (e.g., uncontrolled loss of bodily fluids, amniotic fluids, etc.) may potentially put both the patient and the user at risk. If the current density under the neutral electrode is too high at any point, this can lead to the unintentional release of high levels of thermal energy under the electrode [37], [53], which may then spread unnoticed from the neutral electrode. Burns generally develop when single-surface electrodes are used and it is not possible to monitor the quality of the contact between the electrode and the skin. In addition, a liquid bridge or a point of contact between the patientʼs body and a conductive material may result in leakage current. No HF generator is able to measure such leakage current and prevent it. Every user must be trained in the proper operation and associated risks of HF units, as stipulated in the German Medical Products Operator Ordinance (MPBetreibV).

Prior to every application, all materials used should be checked for defects or damage.

Suspicious skin lesions which are found postoperatively are not necessarily always associated with HF current, as they can also have been caused by heat, pressure, time, chemicals and/or moisture.

The patient must be placed on a dry and insulated support; wet sheets and underlays must be replaced by dry ones.

No.	Recommendation/Statement	Level of consensus	References
E.32	With the exception of the ECG electrodes, the patient must not be in contact with electrically conductive surfaces.	++
E.33	The amount of disinfectant used must be sufficient to avoid puddles.	+++
E.34	The full-sized neutral electrode must be placed near the operating site preoperatively while maintaining its sterility.	+++
E.35	The entire surface of the neutral electrode must be in contact with the patientʼs skin; hairy areas must be shaved.	+
E.36	There must be no traces of liquids between the skin and the neutral electrode, and no additional gel should be used.	+++
E.37	Urine must be drained during lengthy surgical procedures (> 3 hours).	++
E.38	All jewelry must be removed preoperatively; if it cannot be removed, it must be covered with insulating tape. There must be no contact with or application of HF current in the vicinity of the area with the jewelry.	++

8  Positioning-related Pressure Ulcers

Pressure ulcers are undesirable complications of surgical procedures which could, in principle, be avoided. They involve additional suffering for the affected patients (pain), increase the time spent in hospital and result in additional treatment costs (materials and staff to treat the wound).

A clear understanding of the causes of the skin damage is an essential aspect of the definitive diagnosis (also to differentiate it from other types of skin damage).

Pressure ulcers often develop in underlying tissue (just above bone prominences in the musculature), while the overlying tissue layers may initially remain intact. The injury may only become visible several days after it occurred (during surgery).

8.1  Risk factors for developing pressure ulcers

In addition to the causes of pressure ulcers (pressure and shear), additional risk factors are also often discussed; however, their significance is not yet clear. Proposed causes during the perioperative period include: diabetes mellitus (OR = 2.15 [1.62 – 2.84]) [54], duration of anesthesia and total duration of hypotension (< 50 mmHg diastolic BP) [55], age > 71 years, dehydration, damp skin, malnutrition, sensory perception disorders, lung disease [56], central or peripheral nerve blockade (perioperative analgesia) [57], hypothermia [58], hypotension, vascular disease, smoking, COPD [3], patient position during surgery (a lateral position is associated with a higher risk than a supine position, OR = 8.1) and duration of the procedure (OR 3.7 for every doubling of the length of surgery) [5].

8.2  Perioperative prevention

8.2.1  Risk assessment

There are some situations in which every patient must be treated as a potentially high-risk patient. Risk factors include: duration of immobility prior to surgery, duration of the surgical procedure, increased number of episodes of hypotension during surgery, low core temperature during surgery, and limited mobility on the first postoperative day. In addition, anesthesia-related immobility and certain positions (sitting up, lateral position) increase pressure on exposed tissue. A compilation of risks should reveal the potential threat; this should then allow a preventive strategy to be planned and implemented which is tailored to the individual patient [59].

A Cochrane review of studies on the potential benefit of using pressure ulcer risk scales to reduce the incidence of pressure ulcers found no benefit from using such scales [60].

8.2.2  Pressure-relieving aids

A Cochrane review [61] analyzed studies on the efficacy of pressure-relieving aids (mattresses and overlays) and came to the conclusion that the use of pressure-relieving overlays on the operating table reduces the postoperative incidence of pressure ulcers, although two studies reported adverse skin reactions when foam overlays were used. The evidence was strengthened by a recent meta-analysis which also confirmed assumptions on the preventive effect of alternating pressure mattresses compared to standard foam mattresses [62].

A meta-analysis [63] confirmed the protective benefit of pressure-relief mattresses compared to standard mattresses, of foam mattresses compared to standard mattresses and of certain air-filled and foam overlays compared to standard mattresses with respect to the incidence of heel pressure sores. Finally, a high-quality HTA [64] and a high-quality systematic review [65] also confirmed the efficacy of using pressure-relieving overlays on operating tables.

The superiority of these aids compared to standard care is evident. Overweight and obese patients represent a separate patient cohort.

8.2.3  Positioning measures

The larger the area of the body being supported, the lower the pressure on tissue. For example, when offloading the heels, it is important to ensure that the heels are not elevated too high because this will increase pressure in the sacral area. The same applies if the head section of the table is too high. The hip abduction point of the operating table should be in a physiologically correct place. It is important to prevent the patient from “sliding down” (e.g., by placing a rolled-up towel under the ischial tuberosities), because sliding not only creates pressure but also may result in shearing.

No.	Recommendation/Statement	Level of consensus	References
E.39	Pressure-relieving overlays should be used on operating tables.	++	[61]
E.40	When using pressure-relieving aids, it is important to ensure that the weight of the leg is distributed over the entire calf area and no pressure is exerted on the Achilles heel. To reduce the risk of perioperative DVT, the knee must be slightly flexed.	++	[59]
E.41	The area of the body being supported must be as large as possible.	++
E.42	Hospitals/clinics should offer regular training on the prevention of perioperative pressure ulcers. The training should be adapted to the team and the organization and include the following aspects: etiology and risk factors, classification, differential diagnosis, risk assessment, skin assessment, documentation, prophylaxis and repositioning.	++	[62]
S.5	The use of standardized risk assessments is not recommended. All patients must be treated as though they are at risk.	+++
S.6	The prophylactic use of dressings (such as hydrocolloid dressings) to relieve pressures on healthy skin in specific sites (over bony prominences) is currently not recommended as investigated studies showed a too high risk of bias and interpretation of the results was limited.	+++	[62]

9  Compartment syndrome

Acute compartment syndrome (CS) of the lower extremity is a particularly serious if rare form of positioning injury, which has been described almost exclusively following lengthy surgical procedures with the patient in the lithotomy position [6], [66], [67]. Depending on the cohort, the incidence of CS in gynecologic surgical procedures performed with the patient in the lithotomy position has been reported to range between 0.028 and 0.28%, although the estimated number of unreported cases due to misdiagnoses and lack of attention appears to be even higher [68], [69], [70]. This complication is highly forensically relevant, as it is assumed to be a treatment error in more than 50% of cases (source: Advisory Body of the North-Rhine Medical Council).

The precise etiology of CS is not clear, but it appears that decreased perfusion pressure combined with increased pressure on tissue (caused by the calf resting on the support) leads to inadequate supply of the tissues. Numerous experiments have shown that perfusion pressure decreases significantly when the leg is elevated above the level of the right atrium or when the patient is placed in the Trendelenburg position [71]. Extreme lithotomy positions decrease the mean arterial blood pressure in the lower extremity down to values which correspond to those measured in manifest CS, and this effect is intensified if the patient is in the Trendelenburg position [69], [72]. These results suggest that minimizing the time during which the patient is either in a lithotomy or a Trendelenburg position could be the best means of preventing CS. CS has also been described after using a number of different leg support systems.

The diagnosis of CS is based on clinical examination. If the patient has an inlying epidural catheter (EDC), symptoms should not be exclusively ascribed to the EDC; instead, the possibility of incipient CS should be considered. A review found no delay occurred in making the diagnosis despite postoperative analgesia if the patient was adequately monitored [73]. To verify or exclude sensory deficits and paresthesia caused by analgesia administered in the vicinity of the spinal cord (e.g., an EDC), the anesthesiologist must be informed and called in immediately. To obtain a differential diagnosis, it is useful to interrupt administration of the local analgesic through the catheter to verify whether this is then followed by a decrease in sensory and/or motor deficits.

Invasive measurement of the intracompartmental pressure (ICP) provides additional information in cases where the constellation of symptoms is unclear, although the routine use of invasive measurement techniques is not indicated. The ICP threshold which would indicate the presence of manifest CS is still controversially discussed in the literature [74]. The use of pulse oximeters to monitor the extremities offers no benefits as arterial perfusion and oxygen saturation only drop at a very late stage [75].

To date, there are no evidence-based recommendations on the prevention of CS, as none of the measures proposed in the literature have been validated yet in prospective studies. A prospective observational study of a patient population at high risk for CS, which consisted of patients undergoing extensive endometriosis surgery, reported a decrease in the incidence of CS from 0.8% to 0% after implementing a combination of different measures [76]. They included minimizing the number of surgical procedures carried out with the patient in the lithotomy procedure in favor of a modified supine position with the legs abducted, intermittent mobilization of the legs during the procedure, and the use of vacuum mattresses to prevent the patient from slipping. The routine use of intermittent compression devices (mainly used in in Anglo-American countries) has also been recommended; however, other studies have reported an increased risk of complications when these compression stockings are used.

The treatment of manifest CS consists of fasciotomy of all affected muscle compartments.

No.	Recommendation/Statement	Level of consensus	References
E.43	The amount of time a patient spends in the lithotomy position should be limited to a minimum (AST, AORN), particularly if the surgical procedure does not require access to the perineum or the vagina. Potential alternatives such as placing the legs flat with an abduction of 45° together with slight flexion of the hip must be considered.	++	[10, 12]
E.44	Where possible, the legs should be positioned at the level of or below the right atrium.	++
E.45	The time the patient spends in the Trendelenburg position should also be kept to a minimum.	++
E.46	Sliding of the patient in a cranial direction must be prevented using suitable positioning aids.	++
E.47	The use of typical knee and lower leg supports (Goepel) should be avoided. When such leg holders are used, additional padding with gel mats is necessary.	++
E.48	All persons involved in the treatment and care of the patient should be aware of the possibility of CS and be familiar with the clinical signs of postoperative CS after lengthy surgical procedures carried out with the patient in the lithotomy position.	++
S.7	Routine intraoperative measurement of compartmental pressure is not necessary.	++
E.49	Routine intraoperative repositioning of the legs, e.g. every three hours, to reduce intracompartmental pressure should not be carried out.	++
S.8	If the patient receives analgesia perioperatively administered in the vicinity of the spinal cord and sensory or motor deficits occur after surgery, an anesthesiologist must be consulted. The anesthesiologist must make the differential diagnosis and identify or exclude compartment syndrome.	++

10  Avoiding Perioperative Hypothermia

Confict of Interest/Interessenkonflikt

The conflicts of interest of all of the authors are listed in the long version of the guideline./Die Interessenkonflikte der Autoren sind in der Langfassung der Leitlinie aufgelistet.

• References

• 1 Bommert M, Wagner JK, Sehouli J. et al. Perioperative management of positioning in gynecological cancersurgery: a national NOGGO-AGO intergroup survey. Int J Gynecol Cancer 2020; 30: 1589-1594
• 2 Warner MA. Perioperative neuropathies. Mayo Clin Proc 1998; 73: 567-574
• 3 Loorham-Battersby C. Heel Damage And Epidural Analgesia. Are the two linked?. Saarbrücken: LAP LAMBERT Academic Publishing; 2012
• 4 Peterson T, Wissing H. Lagerungsschäden beim Patienten mit unbekanntem „thoracic outlet syndrome“. Anästhesiol Intensivmed Notfallmed Schmerzther 1995; 30: 516-518
• 5 Stevens J, Nichelson E, Linehan WM. et al. Risk factors for skin breakdown after renal and adrenal surgery. Urology 2004; 64: 246-249
• 6 Bauer ECA, Koch N, Janni W. et al. Compartment syndrome after gynecologic operations: evidence from case reports and reviews. Eur J Obstet Gynecol Reprod Biol 2014; 173: 7-12
• 7 Warner MA, Warner DO, Harper CM. et al. Lower extremity neuropathies associated with lithotomy positions. Anesthesiology 2000; 93: 938-942
• 8 Vereinbarung über die Zusammenarbeit in der operativen Gynäkologie und in der Geburtshilfe der Deutschen Gesellschaft für Anästhesiologie und Intensivmedizin und des Berufsverbands Deutscher Anästhesisten mit der Deutschen Gesellschaft für Gynäkologie und Geburtshilfe und dem Berufsverband der Frauenärzte. 1996 Accessed March 30, 2020 at: https://www.bda.de/docman/alle-dokumente-fuer-suchindex/oeffentlich/empfehlungen/536-eev-2011-s-19-24/file.html
• 9 Weissauer W. Abgrenzung der Verantwortung für die operative Lagerung des Patienten und Haftung für Lagerungsschäden. Unfallchirurg 2002; 105: 404-412
• 10 Association of Perioperative Registered Nurses. Recommended practices for positioning the patient in the perioperative practice setting. AORN J 2001; 73: 231-235 237–238. Erratum in: AORN J 2001; 74: 201 Erratum in: AORN J 2001; 74: 201
• 11 Practice advisory for the prevention of perioperative peripheral neuropathies: a report by the American Society of Anesthesiologists Task Force on Prevention of Perioperative Peripheral Neuropathies. Anesthesiology 2000; 92: 1168-1182
• 12 (AST) Association of surgical technologists (AST). AST recommended Standards of Practice for Surgical Positioning, 2011. Accessed March 27, 2020 at: https://www.ast.org/uploadedFiles/Main_Site/Content/About_Us/Standard Surgical Positioning.pdf
• 13 Cluver C, Novikova N, Hofmeyr GJ. et al. Maternal position during caesarean section for preventing maternal and neonatal complications. Cochrane Database Syst Rev 2013; (03) CD007623
• 14 Cohen MM, Duncan PG, Pope WD. et al. A survey of 112,000 anaesthetics at one teaching hospital (1975–83). Can Anaesth Soc J 1986; 33: 22-31
• 15 Winfree CJ, Kline DG. Intraoperative positioning nerve injuries. Surg Neurol 2005; 63: 5-18 discussion 18
• 16 Shveiky D, Aseff JN, Iglesia CB. Brachial plexus injury after laparoscopic and robotic surgery. J Minim Invasive Gynecol 2010; 17: 414-420
• 17 Reich H. Laparoscopic treatment of extensive pelvic adhesions, including hydrosalpinx. J Reprod Med 1987; 32: 736-742
• 18 Romanowski L, Reich H, McGlynn F. et al. Brachial plexus neuropathies after advanced laparoscopic surgery. Fertil Steril 1993; 60: 729-732
• 19 Cheney FW, Domino KB, Caplan RA. et al. Nerve injury associated with anesthesia: a closed claims analysis. Anesthesiology 1999; 90: 1062-1069
• 20 Kretschmer T, Heinen CW, Antoniadis G. et al. Iatrogenic nerve injuries. Neurosurg Clin N Am 2009; 20: 73-90 vii
• 21 Bradshaw AD, Advincula AP. Optimizing patient positioning and understanding radiofrequency energy in gynecologic surgery. Clin Obstet Gynecol 2010; 53: 511-520
• 22 Zhang J, Moore AE, Stringer MD. Iatrogenic upper limb nerve injuries: a systematic review. ANZ J Surg 2011; 81: 227-236
• 23 Eteuati J, Hiscock R, Hastie I. et al. Brachial plexopathy in laparoscopic-assisted rectal surgery: a case series. Tech Coloproctol 2013; 17: 293-297
• 24 Advincula AP, Song A. The role of robotic surgery in gynecology. Curr Opin Obstet Gynecol 2007; 19: 331-336
• 25 JACKSON L, KEATS AS. MECHANISM OF BRACHIAL PLEXUS PALSY FOLLOWING ANESTHESIA. Anesthesiology 1965; 26: 190-194
• 26 Britt BA, Gordon RA. PERIPHERAL NERVE INJURIES ASSOCIATED WITH ANAESTHESIA. Can Anaesth Soc J 1964; 11: 514-536
• 27 Cooper DE, Jenkins RS, Bready L. et al. The prevention of injuries of the brachial plexus secondary to malposition of the patient during surgery. Clin Orthop Relat Res 1988; (228) 33-41
• 28 Ben-David B, Stahl S. Prognosis of intraoperative brachial plexus injury: a review of 22 cases. Br J Anaesth 1997; 79: 440-445
• 29 Suozzi BA, Brazell HD, OʼSullivan DM. et al. A comparison of shoulder pressure among different patient stabilization techniques. Am J Obstet Gynecol 2013; 209: 478.e1-478.e5
• 30 Coppieters MW. Shoulder restraints as a potential cause for stretch neuropathies: biomechanical support for the impact of shoulder girdle depression and arm abduction on nerve strain. Anesthesiology 2006; 104: 1351-1352
• 31 Klauschie J, Wechter ME, Jacob K. et al. Use of anti-skid material and patient-positioning to prevent patient shifting during robotic-assisted gynecologic procedures. J Minim Invasive Gynecol 2010; 17: 504-507
• 32 Haupt WF. Intraoperative Lagerungsschäden des Nervus ulnaris bei anatomischen Varianten. Dtsch Med Wochenschr 1989; 114: 1789-1792
• 33 Warner MA, Warner DO, Matsumoto JY. et al. Ulnar neuropathy in surgical patients. Anesthesiology 1999; 90: 54-59
• 34 Padua L, Aprile I, Caliandro P. et al. Natural history of ulnar entrapment at elbow. Clin Neurophysiol 2002; 113: 1980-1984
• 35 Stoelting RK. Postoperative ulnar nerve palsy–is it a preventable complication?. Anesth Analg 1993; 76: 7-9
• 36 Burkhart FL, Daly JW. Sciatic and peroneal nerve injury: a complication of vaginal operations. Obstet Gynecol 1966; 28: 99-102
• 37 Aschemann D. Hrsg. OP-Lagerungen für Fachpersonal. Heidelberg: Springer; 2009
• 38 Roy S, Levine AB, Herbison GJ. et al. Intraoperative positioning during cesarean as a cause of sciatic neuropathy. Obstet Gynecol 2002; 99: 652-653
• 39 Umo-Etuk J, Yentis SM. Sciatic nerve injury and caesarean section. Anaesthesia 1997; 52: 605-606
• 40 Batres F, Barclay DL. Sciatic nerve injury during gynecologic procedures using the lithotomy position. Obstet Gynecol 1983; 62 (3 Suppl.): 92s-94s
• 41 McQuarrie HG, Harris JW, Ellsworth HS. et al. Sciatic neuropathy complicating vaginal hysterectomy. Am J Obstet Gynecol 1972; 113: 223-232
• 42 Cherian RP, Li Y. Clinical and Electrodiagnostic Features Of Nontraumatic Sciatic Neuropathy. Muscle Nerve 2019; 59: 309-314
• 43 Chan JK, Manetta A. Prevention of femoral nerve injuries in gynecologic surgery. Am J Obstet Gynecol 2002; 186: 1-7
• 44 Hopper CL, Baker JB. Bilateral femoral neuropathy complicating vaginal hysterectomy. Analysis of contributing factors in 3 patients. Obstet Gynecol 1968; 32: 543-547
• 45 Räber G, Schneider HP. Femoralisparese nach vaginaler Hysterektomie und ihre forensische Bedeutung. Zentralbl Gynakol 1993; 115: 273-278
• 46 al Hakim M, Katirji B. Femoral mononeuropathy induced by the lithotomy position: a report of 5 cases with a review of literature. Muscle Nerve 1993; 16: 891-895
• 47 Roblee MA. Femoral neuropathy from the lithotomy position: case report and new leg holder for prevention. Am J Obstet Gynecol 1967; 97: 871-872
• 48 Sinclair RH, Pratt JH. Femoral neuropathy after pelvic operation. Am J Obstet Gynecol 1972; 112: 404-407
• 49 Koç G, Tazeh NN, Joudi FN. et al. Lower extremity neuropathies after robot-assisted laparoscopic prostatectomy on a split-leg table. J Endourol 2012; 26: 1026-1029
• 50 Goldman JA, Feldberg D, Dicker D. et al. Femoral neuropathy subsequent to abdominal hysterectomy. A comparative study. Eur J Obstet Gynecol Reprod Biol 1985; 20: 385-392
• 51 Litwiller JP, Wells RE, Halliwill JR. et al. Effect of lithotomy positions on strain of the obturator and lateral femoral cutaneous nerves. Clin Anat 2004; 17: 45-49
• 52 Lindner A, Schulte-Mattler W, Zierz S. Postpartales Nervus obturatorius-Syndrom: Fallbericht und Ubersicht über die Nervenkompressionssyndrome während Schwangerschaft und Geburt. Zentralbl Gynakol 1997; 119: 93-99
• 53 Fleisch MC. Risiken der Anwendung von Koagulationsgeräten im kleinen Becken. Gynäkologe 2016; 49: 888-890 doi:10.1007/s00129-016-3953-7
• 54 Liu P, He W, Chen H-L. Diabetes mellitus as a risk factor for surgery-related pressure ulcers: a meta-analysis. J Wound Ostomy Continence Nurs 2012; 39: 495-499
• 55 Connor T, Sledge JA, Bryant-Wiersema L. et al. Identification of pre-operative and intra-operative variables predictive of pressure ulcer development in patients undergoing urologic surgical procedures. Urol Nurs 2010; 30: 289-295 305
• 56 Lindholm C, Sterner E, Romanelli M. et al. Hip fracture and pressure ulcers – the Pan-European Pressure Ulcer Study – intrinsic and extrinsic risk factors. Int Wound J 2008; 5: 315-328
• 57 Edwards JL, Pandit H, Popat MT. Perioperative analgesia: a factor in the development of heel pressure ulcers?. Br J Nurs 2006; 15: S20-S25
• 58 Scott EM, Leaper DJ, Clark M. et al. Effects of warming therapy on pressure ulcers–a randomized trial. AORN J 2001; 73: 921-927 929–933, 936–938
• 59 EPUAP/NPUAP. Prävention und Behandlung von Dekubitus: Kurzfassung der Leitlinie, 2014. Accessed March 27, 2020 at: https://www.epuap.org/wp-content/uploads/2016/10/german_quick-reference-guide.pdf
• 60 Moore ZE, Patton D. Risk assessment tools for the prevention of pressure ulcers. Cochrane Database Syst Rev 2019; (01) CD006471
• 61 McInnes E. The use of pressure-relieving devices (beds, mattresses and overlays) for the prevention of pressure ulcers in primary and secondary care. J Tissue Viability 2004; 14: 4-6 8, 10 passim
• 62 Deutsches Netzwerk für Qualitätsentwicklung in der Pflege (DNQP). Expertenstandard Dekubitusprophylaxe in der Pflege. 2. Aktualisierung, 2017. Accessed March 22, 2021 at: https://www.dnqp.de/fileadmin/HSOS/Homepages/DNQP/Dateien/Expertenstandards/Dekubitusprophylaxe_in_der_Pflege/Dekubitus_2Akt_Auszug.pdf
• 63 Nicosia G, Gliatta AE, Woodbury MG. et al. The effect of pressure-relieving surfaces on the prevention of heel ulcers in a variety of settings: a meta-analysis. Int Wound J 2007; 4: 197-207
• 64 Cullum N, Nelson EA, Flemming K. et al. Systematic reviews of wound care management: (5) beds; (6) compression; (7) laser therapy, therapeutic ultrasound, electrotherapy and electromagnetic therapy. Health Technol Assess 2001; 5: 1-221
• 65 Reddy M, Gill SS, Rochon PA. Preventing pressure ulcers: a systematic review. JAMA 2006; 296: 974-984
• 66 Adler LM, Loughlin JS, Morin CJ. et al. Bilateral compartment syndrome after a long gynecologic operation in the lithotomy position. Am J Obstet Gynecol 1990; 162: 1271-1272
• 67 Lawrenz B, Kraemer B, Wallwiener D. et al. Lower extremity compartment syndrome after laparoscopic radical hysterectomy: brief report of an unusual complication of laparoscopic positioning requirements. J Minim Invasive Gynecol 2011; 18: 531-533
• 68 Schofield PF, Grace RH. Acute compartment syndrome of the legs after colorectal surgery. Colorectal Dis 2004; 6: 285-287
• 69 Halliwill JR, Hewitt SA, Joyner MJ. et al. Effect of various lithotomy positions on lower-extremity blood pressure. Anesthesiology 1998; 89: 1373-1376
• 70 Bauer ECA, Koch N, Erichsen CJ. et al. Survey of compartment syndrome of the lower extremity after gynecological operations. Langenbecks Arch Surg 2014; 399: 343-348
• 71 Martin JT. Compartment syndromes: concepts and perspectives for the anesthesiologist. Anesth Analg 1992; 75: 275-283
• 72 Svendsen LB, Flink P, Wøjdemann M. et al. Muscle oxygen saturation during surgery in the lithotomy position. Clin Physiol 1997; 17: 433-438
• 73 Mar GJ, Barrington MJ, McGuirk BR. Acute compartment syndrome of the lower limb and the effect of postoperative analgesia on diagnosis. Br J Anaesth 2009; 102: 3-11
• 74 Pfeffer SD, Halliwill JR, Warner MA. Effects of lithotomy position and external compression on lower leg muscle compartment pressure. Anesthesiology 2001; 95: 632-636
• 75 Mars M, Hadley GP. Failure of pulse oximetry in the assessment of raised limb intracompartmental pressure. Injury 1994; 25: 379-381
• 76 Wey JM, Guinn GA. Ulnar nerve injury with open-heart surgery. Ann Thorac Surg 1985; 39: 358-360
• 77 AWMF. S3 Leitlinie „Vermeidung perioperativer Hypothermie“. Aktualisierung 2019. Accessed March 30, 2020 at: https://www.awmf.org/uploads/tx_szleitlinien/001-018l_S3_Vermeidung_perioperativer_Hypothermie_2019-08.pdf

Publication History

Received: 26 January 2021
Received: 02 December 2020

Accepted: 29 January 2021

Article published online:
14 April 2021