Subjective vertical refers to an individual's perception of upright orientation.1 When a neurologically healthy individual stands upright, subjective vertical is accurately aligned with the physical vertical through an implicit representation of verticality.1 This internal representation of verticality is established and updated through an integration of inputs from visual, vestibular, and somatosensory sources.1,2 There are 3 components contributing to subjective vertical: visual-vertical, haptic or tactile vertical, and postural vertical.2 The visual-vertical component is dependent on visual and vestibular information.2 The haptic vertical is mediated by touch and pressure information from somatosensory receptors, and the postural vertical perception is derived from information about the direction of gravitational forces from gravireceptors.2
A decline in the accuracy of postural vertical perception in some adults as they age has been described by Barbieri and colleagues.3 The inaccuracy of postural vertical perception results in posterior postural tilt in standing and sitting, which increases in severity with advancing years and predisposes older adults to backward falls.3,4 The end result of this posterior bias in perception of postural vertical has been called backward disequilibrium (BD).4,5 Individuals with BD fail to shift their center of mass (COM) sufficiently forward when moving from sitting to standing6 and align their erect posture with a faulty intrinsic reference for vertical in the sagittal plane.4 Backward disequilibrium has been likened to the contraversive pushing behavior in the frontal plane that is observed in some individuals with hemiplegia.2,5,7,8 Both BD and contraversive pushing behavior are associated with deterioration in the representation of postural vertical,5,7 postural alignment with the COM outside the limits of the base of support (BOS), and resistance to correction.5,7,8
Backward disequilibrium is a component of the geriatric syndrome called psychomotor disadaptation syndrome (PDS).6,9,10 Psychomotor disadaptation syndrome is identified by the presence of (1) BD, (2) cautious gait with a wide BOS, short stride, and retropulsive behavior, (3) fear of falling identified by clutching and grabbing for support, and (4) fear when moving from sitting to standing.6,9,10 When standing, individuals with PDS demonstrate greater sway amplitude in all planes than healthy older adults.11 Psychomotor disadaptation syndrome has been frequently associated with white matter lesions on CT scan12 and may be similar to or the equivalent of frontal-subcortical clinical syndrome.13,14
The incidence and prevalence of both BD and PDS are not known5; however, clinical experience suggests that the prevalence is high among older adults receiving physical therapy in in-patient and home health settings. Backward disequilibrium may be differentiated from other postural disorders by using the Backward Disequilibrium Scale (BDS).4 The BDS consists of 5 items that are each scored on an ordinal scale ranging from 0 to 3, where 0 means no BD and 3 means severe BD. Total BDS scores 2 or less are considered normal, scores between 3 and 7 are associated with moderate BD, and scores greater than 7 are associated with severe BD.5 While PDS is identified on the basis of results of a clinical examination, the Mini Motor Test has been developed to measure the physical functioning of individuals with PDS.14 The Mini Motor Test consists of 20 items that are scored as yes, “1,” or no, “0.”10,14 Individuals with lower scores have more compromise in their function related to PDS than persons with higher scores.14
Published descriptions of appropriate interventions for individuals with either BD or PDS lack specificity.5,6,9,10,15 General recommendations have been suggested by a few authors and include (1) balance education and training to correct retropulsion and alignment of COM,6,9,10 (2) functional training beginning with rolling and progressing to gait training,5,6,9,10 and (3) training to rise from the floor.5,6 In one study of 28 subjects with PDS, physical and psychological interventions were provided weekly for 6 weeks.15 The 14 subjects who completed the interventions improved in their Mini Motor Test scores,14 dual task tests, ability to rise from the floor, fear of falling, and rate of falling.15 While the interventions described in this report are somewhat more detailed than other authors have provided, the detail given is insufficient for the intervention to be replicated.
The purposes of this case study are to describe BD and suggest a physical therapy management program for these individuals. The patient consented to our using her picture and information about her care for this case study. Her personal health information has been de-identified.
Patient History and Systems Review
The patient was an 83-year-old white woman who fell and sustained a displaced right femoral neck fracture with subsequent hemiarthroplasty. She received care in the acute hospital followed by physical and occupational therapy in a skilled nursing facility. She was discharged from the skilled nursing facility to her home in an assisted living facility with a plan for home health services. Home health services were initiated within a few days of her discharge from the assisted living facility. At this time, it was approximately 4 months after her initial injury.
Prior to her hip fracture, the patient received minimal verbal and occasional physical assistance from the facility staff with taking medication, bathing, and lower extremity dressing. Prior to the hip fracture, she used a walker or quad cane without assistance in her apartment but used a manual wheelchair for longer distances in the facility and community. She was independent with wheelchair propulsion indoor on level surfaces for approximately 1000 feet. The patient had a history of insulin-dependent diabetes mellitus, hypertension, coronary artery disease with a previous myocardial infarction, hyperlipidemia, congestive heart failure, cerebrovascular accident without residual deficits, and hearing loss.
At the beginning of the patient's home health episode of care, she was evaluated by a physical therapist and received 5 physical therapy sessions in her home with no significant progress reported. We do not have access to the detail of the clinical care the patient received while in the skilled nursing facility or in her first 5 home health visits. At the time of her return to the assisted living facility, she required assistance of 2 people for transfers and activities of daily living. The first author evaluated the patient on the sixth home care visit. At the time of this evaluation, the facility staff reported that the patient “did not know where her feet were,” and that she “kept falling backwards when sitting on the side of the bed.” The patient's stated goal was to stay in her current living situation and not to move to a nursing home. This case study focuses on the care provided by the first author starting with the patient's sixth home care visit, which was approximately 4 months after her right femoral neck fracture.
The first author performed an examination of the patient's movement system16 on the sixth home health visit. We have described this examination previously8 and in this report we have provided the instructions for completing the examination, interpretive guidelines, and a clinical reporting form (see Supplemental Digital Content 2, Movement System Diagnosis Examination, available at: https://links.lww.com/JNPT/A95).
Results of the patient's examination are provided in Table 1 with shading of those elements that contributed most to the identification of BD and PDS. In addition to the results in Table 1, the patient scored 17/30 on the Mini-Mental Status Examination,18 3/28 on the Performance Oriented Mobility Assessment,19,20 and 0/12 on the Short Physical Performance Battery,21,22 and had a gait speed of 0 meter per second.
On the basis of the patient's examination results, the examiner determined that the patient presented with Sensory Detection Deficit,8 both BD and PDS,4,5,6 and Force Production Deficit.8 The supporting evidence for each of these diagnoses is presented later.
Sensory Detection Deficit
The patient presented with absent joint position sense in both ankles. In addition, the patient demonstrated variable foot placement with stepping with crossing of midline with both feet. She reported difficulty knowing where her feet were in standing and with attempts at stepping. All of these findings were consistent with the diagnosis, Sensory Detection Deficit.8
BD and PDS
The patient exhibited retropulsive pushing behavior when moving from sitting to standing, during standing, and with attempts at ambulation. With efforts to assist her in bringing her COM forward over her BOS, she resisted correction. Her BDS score was 15, which indicates severe BD.4 She also demonstrated fear of falling consistent with PDS.6,9,10 While the patient's sensory detection deficit could contribute to the development of BD and PDS,1 Sensory detection deficit does not explain the patient's resistance to midline correction in the sagittal plane and fear of falling.
Force Production Deficit
The patient had significant weakness of the right lower extremity and muscle fatigue with repeated movements in both upper and lower extremities. She also demonstrated signs of weakness with task performance, most notably difficulty during the initiation phase of moving sitting to standing and inability to sustain right hip and knee extension during weight bearing. This collection of movement behaviors was consistent with the movement system diagnosis, force production deficit.8
After the first author's examination, the patient received 44 physical therapy visits over 15 weeks. There was one interruption in care during the seventh week when the patient was admitted to the hospital for 2 days due to pneumonia. The primary treatment of her Sensory Detection Deficit began on the first visit and consisted of the use of bilateral ankle foot orthoses fixed in a neutral position. With the use of the orthoses and visual guidance, the patient's foot placement with stepping was much improved. The orthoses stabilized the position of the leg relative to the foot and were intended to compensation for her loss of joint position sense. Subsequently, she was fitted for custom orthoses for ongoing use. Treatment for her force production deficit began in the third week of her episode of care and consisted of lower extremity strengthening exercises with an emphasis on the hip musculature. As the focus of this case study is on BD and since approximately 80% of the patient's interventions were targeted toward this movement system problem, only these interventions are described in detail. In addition to the narrative given later, the patient's response to and progression of each intervention provided for BD are described in Table 2 and illustrated in Table 3.
Frequency of Visits
As noted previously, several authors have suggested general guidelines for treating the deficits exhibited by patients with BD.3,5,8,23–25 All of these guidelines include increasing the individual's awareness of his or her postural control deficit and resetting the internal model of verticality. Because of the need to reset the internal model of verticality, the interventions for this patient were dosed at a higher frequency than is typical in the home care setting. The patient was treated 4 to 5 times per week for 4 weeks. The initial plan was to treat at this frequency for 2 weeks, measure response to treatment by assessing the patient's performance on initial attempts at coming to standing, standing, and attempted stepping, and extend the visits at this frequency if the patient was improving but deficits persisted. After 4 weeks of intervention, the patient was demonstrating enough consistency in improved vertical alignment that the frequency of care was reduced to 3 times per week for the remainder of her episode of care.
Standards of Care for BD
The interventions for BD consisted of 5 primary components that we consider standards of care for this movement system problem: (1) standing with the back against the wall with heels touching the wall, (2) practicing moving from sitting to standing, (3) practicing moving from standing to sitting, (4) walking with continuous stepping, and (5) stepping backward.
Standing with the back against the wall heels touching the wall
In this component of BD intervention, the individual is aligning his or her standing position with the physical vertical. The objective is for the individual to relax in and sustain this position in an effort to reset the internal reference for verticality. Having our patient stand with her back against the wall with her heels touching the wall was initiated on the second visit and continued as a part of her treatment plan. There were 2 time points at which her performance improved significantly, the first at the end of week 1 and the second at the end of week 3 (see Table 3). The following are the general guidelines used in implementing and progressing this intervention:
- Stand with the heels against the wall and not resist being in the position; use an assistive device if needed for weight-bearing support or confidence.
- Progressively decrease upper extremity support (if being used) but maintain the patient's foot position. Increase the amount of time the patient is standing without showing signs of resisting the position.
- Produce active sway forward so that the COM moves toward the forward limits of stability. Forward sway may be induced by sliding a rigid or semirigid object such as a clip board or file folder between the patient and the wall with the verbal cue, “Let me slide this behind you.” The patient does not need to be proficient with the previous 2 steps to attempt the active sway forward.
- Perform upper extremity movements without moving the feet forward or demonstrating other signs of resisting the position.
- Practice walking and/or sit to stand after a bout of standing against the wall.
Sitting to standing
In practicing moving from sitting to standing, primary emphasis was placed on preventing posterior displacement of the tibia relative to the foot and promoting anterior translation of the tibia during the execution phase of the activity. Schultz and colleagues26 have demonstrated that the anterior translation of the tibia relative to the foot accounts for more than 50% of the necessary forward movement of the COM over the BOS when coming to standing. The following are the general guidelines used when implementing this intervention for this diagnosis:
- Practice without upper extremity support if possible; raise the height of the sitting surface initially to accommodate for weakness during the initiation phase.
- If not possible to practice without upper extremity support, instruct the patient to use the upper extremities only during initiation and then have the patient let go and bring the arms across the chest.
- Provide a manual block to posterior translation of the tibia relative to the foot during execution by placing a hand at the posterior aspect of the proximal tibia and preventing posterior movement.
- Provide assistance with anterior translation of the tibia relative to the foot by providing manual cues or assistance at the posterior aspect of the proximal tibia during execution.
- Provide encouragement and support related to fear of falling.
This component was a part of the patient's plan from the first week throughout her episode of care. There were 3 time points at which her performance improved significantly (see Table 3).
Standing to sitting
In practicing moving from standing to sitting, the primary emphasis was placed on maintaining the COM over rather than posterior to the BOS during the execution phase. The concern was that if the patient sat down repeatedly by shifting her COM behind her BOS, it may have contributed to a faulty representation of postural vertical.27 The general guidelines for providing this intervention include the following:
- Practice initiating sitting by flexing the knees keeping, the COM over the BOS during the first half of execution.
- Avoid teaching the patient to initiate sitting down by reaching back for the chair.
- Avoid teaching the patient to step back until the back of the knees touch the chair.*
- If the patient has insufficient strength to control the descent into the chair, practice using the upper extremities to compensate only during the last half of the execution phase.
For this patient, being able to move from standing to sitting improved very slowly and to a limited degree. Her ongoing difficulty with this activity may reflect the limit of correction we were able to make in her internal reference for vertical and vulnerability for ongoing postural control deficits.27
Whenever the patient practiced ambulation, the goal was to practice continuous stepping, without stopping and starting, maintaining a forward progression of the COM. This was accomplished by the therapist pulling the wheeled walker forward and assisting the patient with weight shift and limb advancement as needed. The intervention was progressed very slowly over the 15 weeks due to the patient's significant right proximal lower extremity weakness. There were 4 time points at which her performance improved significantly (see Table 3).
Moving backward without falling backward seems to be a significant challenge for patients with BD. Backward stepping was attempted on several occasions over several sessions before it was integrated into the patient's treatment plan. As shown in Table 2, she progressed with the activity, but it continued to be difficult for her. There were 3 time points at which her performance improved somewhat (see Table 3).
The patient's outcomes, as measured by objective measures and standardized tests, are presented in Table 4. Only those measures that changed significantly are included in the table. During the episode of care described, the patient (1) progressed from requiring assistance of 2 caregivers to requiring standby to minimal assistance of 1 caregiver for activities of daily living and mobility, (2) achieved a minimal clinically important improvement in gait speed29 and on the Short Physical Performance Battery,22 (3) surpassed the minimal detectable change30 on the Performance-Oriented Mobility Assessment,19,20 and (4) achieved her primary goal of being able to stay in her own apartment at an assisted living facility rather than move to a nursing home. She had no falls, and as of 1 year after the episode of care had continued to live in her apartment.
We have described the literature on a clinical condition known as BD. We have presented the clinical examination of a patient with this movement system problem and have outlined a specific physical therapy management program for this condition. Increased awareness of the characteristics of BD facilitates clinical decision making and diagnostic accuracy. A growing knowledge base combined with competency in performing an informative clinical examination may allow for the recognition of patterns that are the building blocks of diagnoses.31 Backward disequilibrium is an example of a clinical pattern present in older adults. Knowledge of this pattern coupled with a thorough clinical examination may assist physical therapists in identifying this clinical condition and employing the specific intervention we have proposed.
For clinicians engaged in clinical reasoning, how knowledge is structured appears to have an impact on how rapidly it is retrieved.32 We have long been proponents of describing the patterns of movement system problems observed in clinical practice as a means to disseminate knowledge gained from practice.8,33,34 Labeling common movement system conditions, such as BD, provides a mechanism for organizing knowledge so that it is clinically useful.8,32,35,36 As noted previously, both BD and contraversive pushing behavior are associated with deterioration in the representation of postural vertical,5,7 postural alignment with the COM outside the limits of the BOS, and resistance to correction.5,7,8 For these reasons and to be consistent with our previously described movement system diagnoses, we have grouped patients with BD with patients with contraversive pushing behavior in a category labeled, Postural Vertical Deficit. An updated description of this movement system diagnosis is found in Supplemental Digital Content 3, Movement System Diagnosis Descriptions, available at: https://links.lww.com/JNPT/A96.
The patient with BD who is the subject of this case study made functional gains and achieved her goal of staying in her home with only a small improvement in her BDS score and ongoing classification of severe BD. There are no published data on the minimal clinically important difference for the BDS. For this patient, her 4-point change was associated with meaningful functional outcomes. We do not know for how long this patient had signs of BD or whether her BD contributed to her fall and subsequent hip fracture. The literature describes BD as a condition that worsens over time and increases fall risk.3–6 Perhaps early detection of BD and implementation of the standards of care we have described in this case study would reduce fall risk and functional decline in this group of patients.
In this case study, we have illustrated the use of a systematic informative clinical examination and the identification and labeling of a condition known as BD. Because we understood BD as a distinct movement system condition, we developed and implemented a treatment program specific to the nature of this condition. We believe that the ability to recognize and appropriately manage our patient's condition enabled the development of functional skills that allowed her to remain in her home, when her condition might otherwise have led to nursing home placement.
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* When a patient with backward disequilibrium sits down by first stepping back until the chair touches the back of the knees, he/she initiates sitting with a posterior sway. Initiating any movement with a posterior sway reinforces the postural control problem for these patients. The patient steps back in approaching a chair and begins descent from stand to sit when his/her legs are 2-3″ from the chair. The patient is still close enough to the chair to prevent them from missing the chair. The intervention described is a skilled intervention provided by a licensed physical therapist or physical therapist assistant. The timing of when this element is incorporated into the patient's performance in the absence of the licensed clinician is a clinical judgment made based on the specific patient circumstances.