Rib stress fracture in rowers

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Introduction

Stress fractures are a common injury in sports, especially in weight-bearing bone, however it is not uncommon to find them in non-weight bearing bones where load fatigue is seen. Elite rowers are one such group and experiencing a rib stress fracture (RSF) can have significant long-term significant consequences, as slow healing and recovery can prevent participation in training and competition. The condition is more common with certain other sports such as baseball, backpacking, dance, running, and windsurfing carry a risk of contributing to stress fractures. Stress fractures occur when a bone fails to withstand repetitive bouts of mechanical loading. This loading results in bone strain, which on its turn may cause micro-damage. With normal physiological loading, this micro-damage will be healed through the bone remodelling. With repetitive loading, however, an imbalance between the remodelling and micro-damage may occur, causing a stress fracture.

Rib-related injuries account for the most time lost from training and competition, which can have a negative impact on the affected rower, and on crew members and coaches. Furthermore, because injuries can require up to 6–8 weeks of rest, a rib stress fracture can be a season-ending injury at the elite level. This is especially worrisome because a stress fracture that occurs during training for a major championship could prevent the injured athlete from competing altogether

Epidemiology/Etiology

RSF is a frequently occurring pathology in the rower’s community, with an incidence of 6 to 12%. As RSF are not the result of impact forces the cause is thought to be due to mechanical mechanisms. There are thought to be 2 main causes that result in rib stress fractures:

• Altered movement and distribution of stress caused by muscle fatigue. This causes excessive force to be transmitted to focal areas in the bone.
• Rib cage compression or the prevention of compression caused by the strong force of muscle as it acts on bone resulting in an accumulation of damage.

Factors That Affect Rib Loading

3 characteristics are distinctive to the loading stimuli, which determine the formation of micro-damage :

• The magnitude of load applied
• The rate at which the load is applied
• The number of loading cycles

Micro-damage follows a threshold-principle: an increase in bone strain above a certain level leads to an increase in micro-damage. Bone strain which is induced over a shorter period results in a significant increase in the development of micro-damage(ref). It could be concluded that factors increasing the magnitude and rate of rib loading contribute to the formation of micro-damage, resulting in stress fractures. Whilst rowing, there is only a small impact on the ribs therefore micro-damage is the result of sources other than the forces associated with impact loading. Therefore, the mechanism of injury is thought to be multifactoral and more likely a combination of muscles, joints, rowing technique and rowing equipment.

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 end phase. Fatigue of the SA results in a decrease of force production, which leads to a decreased buffering of power applied by the abdominal muscles.

Joints

The costovertebral and costotransverse 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.

Technique and 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.

Factors That Affect the Response to Rib Loading

The ability to resist loads and in that way limit formation of micro-damage (skeletal factors):

1. The first skeletal factor which triggers the formation of rib stress fractures is 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.
2. 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 micro-damage (training and gender):

Training

Rapid changes in the training modalities can interrupt the relative homeostasis between micro-damage and the recovery of micro-damage. 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 micro-damage.

Gender

Women run an increased risk of 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 micro-damage. We see that physically active women have a higher prevalence in menstrual disturbances causing a decrease in bone turnover and formation.However in a study, collegiate female rowers had healthy bone mass, body composition, and superior radial vBMD (Bone Marrow Density) compared to controls.

Clinical Presentation

The symptoms can range from a generalised dull 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 coughing or breathing deeply, position change, after particularly vigorous training or use of the rowing ergometer; or with the causative activity, namely, the rowing stroke. The fractures are often located on the antero/posterolateral side of the ribs.

Patients may also present with stiffness or pain in the interscapular area of the thoracic spine, often at the costovertebral junction of the affected rib. There may be a tender area over oedema or a palpable callus, but tenderness may be experienced anywhere along the affected rib. Also, the patient may report pain with use of the serratus anterior muscle or trunk flexion.

Diagnostic Procedures

A bone scan or an MRI is the best way 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.

Physical Therapy Management

• The treatment consists of 4 up to 6 weeks of relative rest, where the rower is allowed to do everything within his pain threshold. According to the British guidelines, management typically aims to remove bending forces from the rib, usually by stopping all rowing mechanics, both on the water and during dry-land cross training.
• Exercises on stability are very important. Previously, a ‘train and treat’ approach was suggested for athletes who became injured in the weeks leading up to major competitions, and did not wish to take time off rowing for recovery.
• 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.
  

Technique

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:

1. Bent arms: this occurs when the rower starts the leg drive by pulling their arms rather than pushing with both legs resulting in an increase of lactic acid in the arms and reduce of the oxygen supply
2. 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
3. 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
4. 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.

Rowers need good basic aerobic condition, mobility and flexibility of the trunk, arms and legs, and physical strength, speed and endurance. In general, the training programme consists for 60 to 70% of aerobic training and 30 to 40% anaerobic training.

Exercises

1. Serratus Strengthening: before starting the exercise it is very important to ensure that the patient is able to maintain the scapula in the proper position. Secondly, we ask the patient to place his/her both hands, shoulder width, against the wall in an extended arm position. Then instruct the patient to pull the 2 medial borders of scapulae to each other and return to starting position. the intensity could be increased by either adding more repetitions or modifying the exercise into a weight-bearing positions by placing both hands on the ground in a kneeling position. In the following stage, we ask the patient to lie down on his/her back, holding 2 dumbbells in hands with extended arms and perform scapular protraction. Starting with a light weight/high repetitions then progressing to heavier weight/few repetitions.
2. Furthermore, pull down exercises could be used: patient holds the bar with two hands in extended arm position. Trunk and arms should form an angle of 100° in starting position with 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).
3. Dumbbells pullover: patient lies down with his upper back across a bench and his body perpendicular to the bench. Both arms are extended above chest holding a dumbbell with both hands. The patient should lower his/her arms above the 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.

References

Bibliography

• Essential information about equipment and techniques, Keith Maybery, 2002