Rib stress fracture in rowers

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Rib stress fractures in rowers

Table of content
1. Search Strategy
2. Definition/Description
3. Clinically Relevant Anatomy
4. Epidemiology /Etiology
5. Characteristics/Clinical Presentation
6. Differential Diagnosis
7. Diagnostic Procedures
8. Outcome Measures
9. Examination
10. Medical Management
11. Physical Therapy Management
12. Key Evidence
13. Resources
14. Clinical Bottom Line
15. Recent Related Research (from Pubmed)
16. References

1. Search strategy
To get some more information about this topic I used following databases: Pubmed, Medline and Pedro. I entered following keywords: stress fractures rib, ribloading, rowing. I went to the library as well and used the book of Keith Maybery (level of evidence D) as one of my sources.

2. Definition/description
A stress fracture occurs when a bone fails to withstand repetitive bouts of mechanical loading. This loading results in bone strain, which on its turn may cause microdamage. With normal physiological loading this microdamages will be healed through the bone remodeling. With repetitive loading however an imbalance between the remodeling and microdamage may occur, causing a stress fracture.

3. Clinically relevant anatomy
4. Epidemiology/etiology

A rib stress fracture is a frequently occurring pathology in the rower’s community, with an incidence of 6 to 12%. There are 2 sorts of causes which can lead to rib stress fractures:
On the one hand there are factors which influence the rib loading, on the other hand there are the factors which influence the reaction to the rib loading.

Factors that affect rib loading:

3 characteristics are distinctive to the loading stimuli, which determine the formation of microdamages :
• The magnitude of load applied
• The rate at which the load is applied
• The number of loadingcycles
Microdamages follow a threshold-principle: an increase in bone strain above a certain level leads to an increase in microdamages . Bone strains which are induced over a shorter period result in a significant increase in the development of microdamages. We can conclude that factors increasing the magnitude and rate of rib loading contribute to the formation of microdamages, resulting in stress fractures. While rowing, there is only a small impact on the ribs therefore we can conclude that microdamages are the result of other sources than the forces associated with impact loading. Following sources will be discussed below: muscles, joints, rowing technique and rowing equipment.
o Muscles:
• Abdominal muscles
Pressure applied by the abdominal muscles on the sternum and lower ribs result in a loading of the entire ribcage.
Radiological evidence shows a large amount of ribcage compression in the final stage of rowing, caused by the abdominal muscles .
• Serratus Anterior
SA protects the ribs by resisting the abdominal rib loading at the endfase. Fatigue of the SA results in a decrease of force production, which leads to a decreased buffering of power applied by the abdominal muscles.
o Joints
The costovertebral and costotransversal joints are the most important joints in the ribcage and form a mechanical connection between ribs and thoracic vertebrae. This mechanical connection enables the ribcage to provide protection to the thoracic region by redistributing the transmitted forces to the thoracic spine.
o Rowing technique
o Rowing equipment
• Oar: since the 90’s, smaller and shorter oars made out of carbon are used. These oars are easier to use, but result in a larger loading since a greater force is generated at the handle when applying the same load. This exposes the ribs to a greater level of strain.
• Boat: larger boats increase the development of stress fractures. The larger the boat, the larger the water resistance and the bigger the oars needed to provide the necessary resistance due to leveraging.
• Positioning: bow rowers have a smaller chance at rib stress fractures because they have to apply a smaller force, at a lower rate.

Factors that affect the response to rib loading:

• The ability to resist loads and in that way limit formation of microdamages (skeletal factors):
o The first skeletal factor which triggers the formation of rib stress fractures is the bone geometry. A narrower bone leads to a smaller cross-sectional area moment of inertia, which is an important factor in the ability of a bone to resist bending .
o Second important skeletal factors are the properties of the bone material. A low bone density causes a decreased resistance against fatigue, resulting in the development of stress fractures .
• The ability of the skeleton to recover from microdamages (training and gender)
o Training: rapid changes in the training modalities can interrupt the relative homeostasis between microdamages and the recovery of microdamages. This causes an increase in the amount of active remodelling units, which will result in a decrease of bone elasticity. This will result in an increased strain, causing an increase in microdamages.
o Gender: women run an increased risk at stress fractures at any location of the body . This can be explained by gender-specific endocrine factors which alter the recovery response of the body to microdamages. We see that physically active women have a higher prevalence in menstrual disturbances causing a decrease in bone turnover and formation.

5. Characteristics/clinical presentation

The symptoms can range from a generalised pain in the rib area, persisting with activity and gradually becoming more specific, to a palpable bony callus with increased pain when pressure is applied. In the worst case the rower experiences pain when breathing deep or rolling over in bed. The fractures are often located on the antero- or posterolateral side of the ribs.

6. Differential diagnosis
7. Diagnostic procedures

A bone scan or an MRI are the best ways to detect a stress fracture, although it may take a few months before there is real evidence of callus formation. A sonography or an RX can also be used to diagnose.

8. Outcome measures

Bone scan: black spots
MRI: white spots

9. Examination
10. Medical management
11. Physical therapy management

The treatment consist of 4 up to 6 weeks of relative rest, where the rower is allowed to do everything within his pain treshold. Exercises on stability are very important. Strengthening exercises for the serratus anterior are recommended. Normally they should lead to increased power and additional loading on the rib cage. In the case of costovertebral and costostransverse joint stiffness, passive mobilisation of the thoracic spine and costovertebral joints is advised as treatment. Rowing is not advised, since it is often painful and since it is the cause of the fracture. When working on an ergometer, one must see at it carefully that the old flaws in technique are handled. Application of ice will diminish the pain, but does not heal the stress fracture.

A good rower needs following ingredients:
• Technique
Needs to be continuously fine tuned. Often, small flaws in technique can be a cause or related to the of stress fractures. Some examples of most occurring technique faults:
o Bent arms: this occurs when the rower starts the leg drive with pulling theirs arms rather than pushing with both legs resulting in an increase of lactic acid in the arms and reduce of the oxygen supply
o High pull: this occurs when the rower pulls the oar too high during the pull phase which results in their back leaning too far back and a higher energy consumption
o Bending backwards too early: this occurs when the rower starts to lean back too early in the drive phase instead of driving back with his legs resulting in a weaker movement
o Over-reaching: this occurs when the rower comes back in and stretches too far forwards pushing their shins passed the vertical position. This results in a weak starting position for the following drive phase, increasing the injury risk.
• Good basic aerobic condition, mobility and flexibility of the trunk, arms and legs
• Physical strength, speed and endurance
In general, the training programme consists for 60 to 70% of aerobic training and 30 to 40% anaerobic training.

12. Key research

The main focus of this literature search was the involvement of the m. Serratus Anterior in the development of stress fractures. Assumptions were found concerning the SA :
• Most rib stress fractures are situated at the anterolateral side of the costal origin of the SA .
• Contraction of the SA causes rib stress
• The usage of an ergometer caused an avulsion injury of the costal origin of the SA, suggesting a strong contraction of the SA .

One needs to look at these assumptions critically. For example, an equal amount of stress fractures has been found at the posterolateral side in the study of Holden et al and Warden et al (level of evidence 2A). There is little evidence linking the SA with stress fractures. Various factors cause researchers to suspect that the SA does not generate sufficient rib loading to contribute to the formation of a stress fracture, as its principal activity occurs during the recovery when the resistance is low. However, a study of Vinther et al (level of evidence 2C) concluded that increased thoracic muscle co-contraction between the serratus anterior and trapezius muscles altered movement patterns. The results of their study uncovered a peak SA co-contraction of relatively high intensity in the initial recovery phase. Because of this, we cannot rule out a potential injury mechanism involving the SA co-contraction. In conclusion; further research is required.

13. Resources

14. Clinical bottom line

This clinical bottom line is related to some straitening exercises for the m. serratus anterior.
• Before we start exercising it is really important that the patient is able to set his scapula in the right position. Therefor we start by doing some scapula settings.
• Secondly we ask the patient to put his both hands, shoulder width, against the wall in an extended arm position. We then instruct the patient to bring his 2 margo medialis scapulae to each other and return to starting position. To increase the intensity we increase the number of repetitions or make the exercise weight baring by putting both hands on the ground in a kneeled position
• In the following stage we ask to the patient to lie down on his back, holding 2 dumbbells in his hands with extended arms. We now ask the patient to perform a protraction of the shoulder. In the beginning we use small weight and a high number of repetitions. Afterwards we narrow down the repetitions and increase the weight.
• Furthermore there is an exercise at the pully where the patient holds the bar with his two hands in extended arm position. His trunk and arms should form an angle of 100° in starting position with his legs in 15° flexion. We ask the patient to pull the bar in the direction of his thighs and back up. The back up phase should take a little longer (3 seconds) than the pulling phase (2 seconds).
• At least there is the dumbbells pullover where the patient lies down with his upper back across a bench and his body perpendicular to the bench. His both arms are extended above his chest holding a dumbbell with both hands. The patient should lower his arms above his head and reverse the movement on the way back up. Using a medicine ball instead of a bench or raising the weight may increase the difficulty of this exercise.

15. Recent related research
16. References/ used sources
a. Vinther A, Kanstrup IL, Christiansen E, Ekdahl C, Aagaard P, Exercise-induced rib stress fractures: potential risk factors related to thoracic muscle co-contraction and movement pattern; Scand J Med Sci 2006; 15:188-196 -> level of evidence: 2C: outcomes research
b. Essential information about equipment and techniques, Keith Maybery, 2002 -> level of evidence : D
c. Rumball JS, Lebrun CM, Di Ciacca SR, Orlando K, Rowing injuries; Sports Med 2005; 35 (6): 537-555 -> level of evidence: 2A: systematic review cohort studies
d. Warden SJ, Gutschlag FR, Wajswelner H, et al. Aetiology of rib stress fractures in rowers. Sports Med 2002; 32 (13): 819-36 -> level of evidence: 2A: systematic review cohort studies
e. Partin NB, Stone JA, Ryan EJ, Lueken JS, Timm KE, Upper extremity proprioceptive training; J Athl Train. 1994 Mar;29(1):15-8 -> level of evidence: 5C expert opinion
f. Smoljanovic T, Bojanic I, Hannafin JA, Hren D, Delimar D, Pecina M, Traumatic and overuse injuries among international elite junior rowers; Am J Sports Med. 2009 Jun;37(6):1193-9 -> level of evidence: 4B: case series
g. Dragoni S, Giombini A, Di Cesare A, Ripani M, Magliani G, Stress fractures of the ribs in elite competitive rowers: a report of nine cases; Skeletal Radiol. 2007 Oct;36(10):951-4 -> level of evidence: 4B: case series