Abstract
Introduction
Inadequate initial management of unstable pelvic injuries is usually associated with a fracture non-union and/or mal-union. Complete clinical and imaging evaluation is mandatory for a correct preoperative planning. Among other symptoms, sitting discomfort may arise from asymmetry of the ischial tuberosities or pressure from a prominent bony projection. Conventional radiographs are usually taken with the individual in a supine position and not in position where the symptoms are referred. We attempted to define a new radiological projection different than the regular pelvis views to study the position of pelvis of a normal person in sitting position. The second objective was to demonstrate its utility in the evaluation of a pelvic deformity.
Material and methods
Fifteen healthy individuals were evaluated with a radiological projection in a sitting position. One patient with a vertically migrated pelvis nonunion was also evaluated with the same radiological protocol.
Results
In each volunteer’s radiological study, a parallel line could be drawn between the sitting table and both distal aspects of the ischial tuberosities, sacral alas and superior aspect of the iliac wings. A plumb line perpendicular to the above mentioned ones could be drawn uniting the vertebras’ spinous processes. A 90⁰ line intersection confirms the absence of deformity. In the pathological case, a pseudo scoliosis of the thoracolumbar spine is detected trying to compensate the pelvis obliquity and maintain equilibrium.
Conclusions
We determined normal and pathological radiological features in the sitting imbalance of the pelvic in the anteroposterior plane of the pelvis. The study helps to understand the biomechanics and compensation of the pelvis to define surgical indications and predict post correction anatomy.
Keywords: pelvis, Malunion, Nonunion, Preoperative planning, Radiological test, Sitting posture
1. Introduction
An increased number (81%–90%) of injured patients with severe pelvic injuries survive due to enhanced understanding of the physiologic response to trauma and advances made in diagnostics, critical care medicine, and acute trauma management.1, 2, 3, 4, 5 Still, non-operative initial treatment, or inappropriate management such as the use of an external fixator as the definitive treatment of an unstable pelvic fracture will frequently lead to a nonunion and/or mal-union of the pelvic ring.6, 7, 8, 9, 10 In such cases, pain is by far the main recorded symptom in all the reviewed studies with an incidence of 97%.11, 12, 13, 14, 15, 16 It was recorded as anterior, posterior, or simultaneously at both areas,17 sitting discomfort,8,15,18,19 dyspareunia, and sexual problems of mechanical origin 20,21 to bed confinement for patients with continuous debilitating pain. As mentioned, difficulty in sitting is a common complaint after a pelvic fracture non-union and mal-union. This is secondary to sitting imbalance or pressure from a prominent bony projection. Sitting imbalance may arise from asymmetry of the ischial tuberosities. In series by Mears and Velyvis15 this asymmetry was due to vertical displacement and mal-rotation of hemi-pelvis in the sagittal plane. Prominent bony projections such as those resulting from posterior displacement of the hemi-pelvis or pelvic rotations may cause pressure symptoms while sitting or lying down. With cranial migration of the hemi-pelvis or bilateral pelvic wings the prominence of the sacrum or the coccyx may also be a cause of difficulty in sitting.15
Routinely, anteroposterior (AP), inlet, and outlet radiographs combined with a conventional pelvic and a three-dimensional CT scan was described for deformity analysis.18,22
For patients with a complaint of pelvic instability, a manual stress test under image-intensifier control can be undertaken with longitudinal traction and a rotational stress placed upon the pelvis. Single leg standing pelvis view have been also described23 to assess the deformity and the instability.
To our knowledge a specific imaging study to demonstrate and quantify sitting abnormalities related to a pelvis sequela has not been described.
Our purpose in this study is to define a study protocol for the pelvis in a sitting position which can be used to demonstrate a sitting imbalance situation in a patient with a pelvis nonunion/malunion and its comparison after correction.
2. Material and methods
Normal healthy adult individuals without history of pelvic trauma, neurological disease or spine pathology were recruited in this study after written consent to be analyzed.
A new radiological projection was developed to evaluate bilateral ischial weight transmisión in a sitting posture.
2.1. Description for radiological projection for evaluation of sitting imbalance
Anatomic region studied: Pelvis and lumbar spine.
Name of the test: Sitting Imbalance.
Xray Chassis position: Posterior.
Patient position: Sitting [Fig. 1].
Fig. 1.
A: “Sitting imbalance” patient’s position. B: Normal Radiological view. In a normal situation lines connecting the ischial tuberosities, upper aspect of sacral alas and upper aspect of the iliac wings are parallel. A plumb line perpendicular to the mentioned ones could be drawn joining the vertebrae spinous processes.
The evaluated subject sits on a radiolucent table with his/her back leaned over the Potter-Bucky. It is to be ensured that the trunk needs to be straight as to have the dorsal kyphosis and the sacrum-coccyx at the same vertical plane. The sagittal plane is perpendicular to the Potter-Bucky.
The lower limbs need to be positioned with the Hips in 45⁰ of abduction, knees bend 90⁰ and legs hanging downwards.
The upper limbs are placed on both the sides of the body as a pendulum.
Projection: Antero-Posterior.
Incidence: Perpendicular to the xray film.
Center point: Superior aspect of the pubic symphysis.
Chasis: 30 × 90 cm is the ideal size. The 35 × 43 can also be used as well.
Distance to the film: 1 m.
Special indications: Ask the patient for holding his breath, avoid upper or lower limb motion during the exposure.
Utility: Study the pelvis in a coronal plane while sitting in relation to the spine position in the same plane.
Radiologic evaluation: Both obturator foramens should be symmetrical and both ischial tuberosities should be resting on to the radiolucent table. A correct radiograph needs to show the table position to be in horizontal plane to lumbar one vertebrae when using the 35 × 45 chasis and the thoracic spine when using the 30 × 90 chasis.
Extra comments: It is essential to visualize the space between the table plane and the ischial tuberosities.
A pathological case was used as an example to demonstrate the utility of this study in the diagnosis, quantification and post-surgical correction control in patients with pelvis nonunion/mal-union associated with sitting imbalance. (Fig. 2). A written consent was signed by the patient for its evaluation.
Fig. 2.
Pelvis deformity evaluation. A: Conventional “sitting imbalance” evaluation. B: Left Ischial support to evaluate the correction needed. C: Radiological control after deformity correction.
3. Results
Fifteen volunteered individuals were subjected to the radiological test as per the method described. Seven males and 8 females with an average age of 32,4 years (Range 26–40 years). For 11 individuals the right side was the dominant one; in 4, the left side.
In each volunteer’s study a parallel line could be drawn between the table and both distal aspects of the ischial tuberosities, sacral alas and superior aspect of the iliac wings. A plumb line perpendicular to the mentioned ones could be drawn joining the vertebrae spinous processes. A 90⁰ line intersection confirms absence of deformity (Fig. 1).
Pathological case: To test the efficacy of this radiological test, sitting imbalance of the pelvis was tested in a case of malunion of pelvis. A pseudo scoliosis of the thoracolumbar spine was detected trying to compensate the pelvis obliquity and maintain equilibrium. An ischial enhancement placed under the affected side can define the amount of correction needed and the post-operative expected alignment.
In the post-operative study the planned correction can be confirmed. The pelvis alignment is restored. The ischial tuberosities height has been corrected and the pseudo scoliosis disappears [Fig. 2].
4. Discussion
Patients with a vertical migrated hemipelvis secondary to incorrect or insufficient initial surgical management can complain of sitting discomfort. This symptom can be described as pain, fatigue or difficulty to maintain a sitting situation for long periods of time.8,15,24, 25, 26, 27
The spine imbalance usually compensates for this imbalance by generating a pseudo scoliosis, seeking to maintain the head, eyes and ears close to the central axis and parallel to the floor to achieve equilibrium.6,9,27, 28, 29 To improve symptoms, many patients use a gluteal compensation cushion on the affected side.8
Similar clinical manifestations are referred in neuropathic patients, cerebral palsy, polio sequela, pelvis obliquity and after hemipelvectomy, among others15,24,25,28,30, 31, 32,34
Little information is available on long term outcomes in non-corrected pelvis deformities. In neuromuscular scoliosis the pelvic position has been evaluated both in the coronal and sagittal plane. The inadequate body weight transmission to ischial tuberosities in a oblique pelvis related to the scoliosis generates the well-known pressures sores.
Radiological evaluation of the pelvis during sitting has already been described. In a review article Lazennec et al. showed the modification of the lumbo-pelvic relations in normal individuals on sitting and standing radiographs in a sagittal projection. The lumbo-pelvic angulation changes and adapts to each position. They focused on the importance of this version evaluation before hip surgery and how spinal procedures can limit angle modification.35
This lumbo-pelvic information is not clear in the coronal projection, even more for abnormal situations. Conventional radiological studies are static and in dorsal decubitus.8,15,25, 26, 27,29 On the other hand, symptoms related to pelvic obliquity and the sitting imbalance are described in a different position. This fact generated the need to develop a new radiological projection to study the pelvis while sitting. This new projection allows to evaluate, understand and document normal and pathological situations. The name for this projection is “Sitting Imbalance evaluation”.
If the description of the study setting is followed, the radiological results are reproducible. We tested it in fifteen normal individuals. In patients with vertically migrated hemi-pelvis the study was able to highlight the deformity and it’s rendering over the lumbar spine. Even more, as a surgical plan a bottom support can be place under the injured side to compensate the deformity. We use 1 cm high wood blocks put one on to the other and as many as necessary to compensate the deformity. New sitting imbalance evaluation radiographs can be taken to define how the correction will impact the coronal aspect of the lumbar spine and check for pseudo-scoliosis correction. This study is designed to evaluate pelvic deformity for the delayed management of pelvic injuries. Although it can be a good option to document vertical instability, due to difficulty in pain management and hemodynamic control, it is not recommended in acute trauma. An isolated ischial fracture can generate sitting imbalance as well. This study is able to document it but the treatment type might be completely different. If the spine deformity is not corrected after the pelvis compensation pre-operative evaluation, a previous deformity needs to be considered. Further studies need to define how the pelvic correction may impact on the fixed deformity before the procedure.
Funding
No funding or grants were received or will be received from any commercial party relating to the subject of this article.
Declaration of competing interest
Dr Carlos F. Sancineto declares No conflict of interest to disclose.
Dr María V. Gimenez declares No conflict of interest to disclose.
Dr Danilo Taype declares No conflict of interest to disclose.
Dr Guido Carabelli declares No conflict of interest to disclose.
Dr Jorge Barla declares No conflict of interest to disclose.
Acknowledgements
None.
Contributor Information
Carlos F. Sancineto, Email: carlos.sancineto@hospitalitaliano.org.ar.
María V. Gimenez, Email: maria.gimenez@hospitalitaliano.org.ar.
Danilo Taype, Email: danilo.taype@hospitalitaliano.org.ar.
Guido Carabelli, Email: guido.carabelli@hospitalitaliano.org.ar.
Jorge Barla, Email: jorge.barla@hospitalitaliano.org.ar.
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