Research
Exercise
November 4, 2024
Trunk Stabilizing Exercises Post-Sternotomy
Introduction
Although heart valve surgery is necessary for increasing life expectancy in those affected by valvular heart disease, about 1 in 4 may need hospital readmission within 30 days. One frequent cause of hospital readmission is sternal instability and non-union of the, by the median sternotomy procedure, bisected sternum. The delayed or non-healing of the wound also raises the risk of infection. During the first 2 postoperative weeks, it is normal for the bisected sternum to show non-physiological movements. However, this should be followed by healing in which the sternum becomes a stable unit again. The current paper wanted to explore the effectiveness of recruiting muscles that help stabilize the divided sternum to minimize excessive motion of the two halves and to find if trunk stabilizing exercises post-sternotomy could improve sternal stability
Methods
The current paper used a randomized controlled trial design to study the effectiveness of trunk stabilizing exercises post-sternotomy. Women aged 40-50 who underwent heart valve surgery via median sternotomy were recruited one week postoperatively. Exclusion criteria included a history of previous thoracic surgery, significant medical conditions like diabetes or uncontrolled hypertension, and conditions that could affect physiotherapy.
They were assigned either to the experimental group, which received trunk stabilizing exercises in addition to standard cardiac rehabilitation, or the control group, which only participated in cardiac rehabilitation.
- Control Group: This group participated in the cardiac rehabilitation program without additional trunk stabilization exercises. This involved progressive mobilization, education on disease management, and moderate-intensity exercises like treadmill and arm/leg ergometer workouts. The exercise intensity was at 75-80% of the maximum heart rate, which was calculated by the formula 220-age. In case the participants took bèta-blockers, the target heart rate was 20 bpm above the resting heart rate.
- Experimental Group: Along with the standard cardiac rehabilitation program as described above, participants performed trunk stabilizing exercises targeting the abdominal and anterior chest wall muscles. These exercises were designed to minimize unwanted motion of the bisected sternum. The exercises were performed three times per week for four weeks. Each exercise was repeated 5 to 10 times per exercise session. The exercises aimed to stabilize the sternum during trunk movements in both the sagittal and horizontal planes. See the exercise prescription below.
The primary outcome was sternal separation measured using ultrasound. The distance between the two halves of the sternum was quantified and the point of greatest separation was marked. As a secondary outcome, the Sternal Instability Scale was used which evaluates sternal integrity from grade 0 (clinically stable sternum) to grade 3 (substantial movement or separation). The measurements were obtained at baseline (7th day postoperative) and week 4.
Results
Thirty-six women who had acute sternal instability confirmed by ultrasound were included. The baseline characteristics showed two comparable groups. They had a baseline sternal separation of 0.23cm
The primary outcome of sternal separation at week 4 was 0.13cm in the experimental group and 0.22 in the control group. This produced a between-group difference of -0.09cm (95% CI 0.07 to 0.11) in favor of the intervention group performing trunk stabilizing exercises post-sternotomy.
The secondary outcomes showed that the experimental group was twice as likely to improve by at least one grade on the Sternal Instability Scale (RR 2.00, 95% CI 1.07 to 3.75). The experimental group was almost three times as likely to achieve a clinically stable sternum (grade 0) by four weeks (RR 2.75, 95% CI 1.07 to 7.04).
Questions and thoughts
Sternal stability can last up to two weeks postoperatively and healing of the sternum is reported to take 2-3 months. Yet in this study, the participants were already recruited on day 7 after surgery. This is an excellent time period since we can expect that people in both groups can be compared on an equal basis of sternal separation.
Which muscles do we have to recruit to get a bracing action on the sternum?
The muscles that have a bracing action in the transverse direction: M. Transversus Abdominis, M. Transversus Thoracis, M. Obliquus Internus Abdominis. The contraction of the abdominal muscles can be felt and controlled. The contraction of the M. Transversus Thoracis muscle can not, but is active during forced expiration. Therefore, the inclusion of respiratory exercises, for pulmonary drainage, sternal bracing, and recovery of the opened rib cage may seem appropriate but was not studied in the current RCT.
What exercises were performed?
- Supine Abdominal Contraction: The patient lies on their back with a rolled towel under the scapulae to minimize pain and improve comfort. They contract the abdominal muscles (focusing on the transverse abdominis), hold for 6-10 seconds, then relax. This is repeated 5-10 times.
- Sitting Abdominal Contraction: The same abdominal contraction as in the supine position, but performed while seated.
- Standing Abdominal Contraction: This exercise is the same as above, but done while standing.
- Sitting with Upper Limb Resistance (0.5 kg weights): While sitting, the patient contracts the abdominal muscles and raises both arms, each holding 0.5 kg, to shoulder level, then lowers them back down.
- Standing with Upper Limb Resistance: The same as the above, but done while standing.
- Sitting Bilateral Arm Elevation: The patient raises both arms without added weights to shoulder level while maintaining core contraction, then relaxes.
- Standing Bilateral Arm Elevation: The same as the above, but performed while standing.
- Sitting Unilateral Arm Elevation: The patient raises the right arm to shoulder level, then relaxes and repeats with the left arm. This is done while contracting the abdominal muscles.
- Standing Unilateral Arm Elevation: The same as the previous exercise, but performed while standing.
- Sitting Unilateral Arm Elevation with Resistance: The patient raises the right arm, weighted with 0.5 kg, to shoulder level, then repeats the exercise with the left arm.
- Standing Unilateral Arm Elevation with Resistance: This exercise is the same as above but performed while standing
This link shows a video of a median sternotomy procedure. Warning: not for sensitive viewers.
Talk nerdy to me
Only women were included in this study, which limits the generalizability of the study findings. No clear rationale for this decision was provided by the authors.
To calculate the number of required participants, the authors used pilot data. Furthermore, information from other studies was integrated into the design. For example, a study by El-Ansary et al. (2007) found that the degree of sternal separation was not associated with the type of upper limb movements performed. On the other hand, more sternal pain was found with the performance of unilateral limb movements, both unloaded and loaded. The current study therefore minimized unilateral movements in the exercise prescription
The trunk stabilizing exercises post-sternotomy from the intervention group were better in terms of improving sternal separation. This difference in sternal separation was statistically significant but also the confidence interval was very narrow and thus precise. The improvement was however very small: 1 millimeter. Yet since only 2.3 millimeters of separation were found at baseline, this 1-millimeter improvement stands for an approximately 43% improvement, compared to only a 0.1-millimeter improvement in the control group (5% improvement).
However the improvements were small, the clinical relevance of optimizing sternal healing is important. El-Ansary et al. (2007) found that people who underwent heart surgery and had chronic sternal instability still had greater degrees of complicated sternal motion and separation when measured months to years after they underwent heart surgery.
The secondary outcomes supported the primary analysis, but had a much wider confidence interval. Therefore, much more uncertainty was found in the outcome of the Sternal Instability Scale. Some participants had improved significantly, while others had improved very little. However, the Sternal Instability Scale is a subjective measure because it is assessed during physical examination in which the degree of movement of the sternum is evaluated. However, this requires expertise and the very small movements to be assessed are highly subject to error and researcher bias. This may partly explain why these findings had a much wider confidence interval. El-Ansary et al (2000) reported perfect inter-rater (99%) and intra-rater reliability (98%) after a training and standardized examination procedure. Nevertheless, the subjective nature of this study and the palpation of such small movements may require further validation.
Take home messages
Trunk stabilizing exercises post-sternotomy can be safely introduced into physiotherapy rehabilitation programs after heart valve surgery. The exercises are simple, require minimal equipment, and can be incorporated into standard care to enhance patient recovery and prevent complications such as prolonged sternal separation.
Reference
Learn more
Cardiac rehabilitation: Rehabilitation in Acute Coronary Syndrome
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