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Clinical Observations |
1 Department of Radiology, Royal National Orthopaedic Hospital NHS Trust,
Brockley Hill, Stanmore, Middlesex, HA7 4LP, United Kingdom.
2 Present address: Chelsea and Westminster Hospital, London, United
Kingdom.
3 Victoria House Medical Imaging, Melbourne, Australia.
4 Vimy House Private Hospital, Kew, Victoria, Australia.
5 Melbourne Orthopaedic Group, Melbourne, Australia.
Received June 20, 2005;
accepted after revision September 4, 2005.
Address correspondence to D. A. Connell (e-mail:
david.connell{at}rnoh.nhs.uk).
Abstract
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CONCLUSION. Stress injury to the distal humerus is a cause of chronic arm pain among elite tennis players and may be exacerbated during full competition. The degree of marrow edema on STIR MRI may be predictive of time to return to competition.
Keywords: bone • elbow • elite athletes • MRI • musculoskeletal imaging • sports medicine • stress fracture • stress reaction • stress response • tennis • upper limb
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Clinical symptoms of stress injury are nonspecific and include insidious onset of pain and tenderness. The diagnosis is often overlooked initially because the symptoms are nonspecific and are more commonly caused by soft-tissue overuse injury. Radiographs acquired early in the condition are likely to have normal findings [4]. Both MRI and bone scintigraphy are sensitive techniques for detecting stress injuries to bone [5]. It has been suggested that MRI is the preferred initial imaging technique because it is more specific and provides more information to the referring clinician than do other techniques [6].
We describe the MRI findings in the humerus in a group of elite tennis players who presented with symptoms at the 2002 and 2003 Australian Open tennis championships, at which a distinctive pattern of middle to distal humeral stress reaction was seen.
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Institutional review board approval for scanning control subjects and retrospective consent from the athletes were obtained. The control group consisted of 20 healthy volunteers and 10 elite tennis players without symptoms.
Each subject underwent MRI of the affected limb performed with a 1.5-T superconducting MRI system (Signa Horizon, GE Healthcare). MRI was performed on the dominant upper limb of the control subjects with the same sequences as for the patient group. An axial proton density sequence (TR/TE, 4,000/30-45; matrix size, 256 x 224; section thickness, 4 mm; no intersection gap) and coronal, sagittal, and axial STIR (5,000/45-60/120; matrix size, 256 x 256; section thickness, 3 mm; no intersection gap) sequences were used. The scans were evaluated for morphologic features and signal intensity of the humeral cortex, periosteum, and bone marrow. The extent of marrow edema was classified as mild (0-24%), moderate (25-74%), or severe (75-100%) according to the maximal cross-sectional area of abnormal marrow signal intensity on axial scans, as measured on the MRI workstation.
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One of the control elite tennis players had subclinical mild patchy increased STIR signal intensity in the distal part of the humerus. The STIR signal was normal in the other nine control tennis players and in all 20 control subjects who were not tennis players.
All 12 elite athletes with symptoms entered a rehabilitation program to prevent further stress injury. Clinical follow-up information was available for eight patients 1 year after presentation. One of the men had retired from the sport because of continued pain despite extended periods of rest. He had moderate bone marrow edema and posteromedial periostitis on STIR MR images. The other seven patients returned to the professional circuit within 6 months of presentation. The players with mild cases of edema returned to competitive tennis within 10 weeks, the two with moderate edema within 14 weeks, and the players with severe edema within 26 weeks of initial MRI diagnosis. None of the injuries progressed to frank humeral stress fracture.
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A stress fracture can be considered the end point of a continuum of bone response to overuse injury. The first step along this continuum may involve activation of the acute repair process in the periosteum, that is, periostitis. With persistent repetitive microtrauma, inflammatory change occurs within the cortical bone and marrow cavity, eventually leading to end-stage stress fracture [20]. These early inflammatory changes can be recognized on MRI as areas of increased STIR signal intensity.
The marrow changes seen in our patient group represent a debilitating stress reaction occurring in the middle to distal part of the humerus. The location within the bone is unusual and may relate to the action of the brachialis or pectoralis muscle or both on the humeral diaphysis. The repetitive excess muscle activity during active play, especially during the swing phase of the serve, results in marked torsion of the humeral shaft and subsequent stress reaction within the distal part of the humerus. It is possible that changes in racquet head size and weight and new ball types may have contributed to the cause of this condition.
All four women patients in the study had severe changes in the marrow, and two had associated periostitis. It may be that women are at higher risk of developing stress reactions as part of the female athlete triad. However, in a 15-year retrospective study [21] of stress injuries in collegiate athletes, including tennis players, there was no significant difference in injury patterns between the two sexes.
The differential diagnosis of lower humeral and elbow pain in the serving arm of an elite tennis player includes lateral humeral epicondylitis, brachialis or biceps brachii muscle and tendon abnormality, and osteochondral injury. The role of imaging in the management of stress injury is to establish the correct diagnosis and to identify early stress changes within bone. The principal aim in the management of stress reactions is to prevent progression toward full stress fracture. This goal should be attainable if conservative measures are instituted early in the rehabilitation period.
MR grading systems based on T1-weighted, T2-weighted, and STIR images have been described and used to predict patient outcome and to help plan treatment [22, 23]. In the system devised by Fredericson et al. [23], chronic stress injuries to the tibia in runners were graded 0 (completely normal) to 4 (fracture line) according to T1-weighted and STIR signal characteristics. Grade 1 was defined by periosteal reaction but normal marrow on T1-weighted and STIR images. Grade 2 was bone marrow edema on STIR but not T1-weighted images. Grade 3 was defined by abnormal T1-weighted and STIR marrow signal. Although we found periostitis in our cases, we used STIR marrow signal changes alone in our grading system. In this sense, the grading system we describe is an alternative classification of the Fredericson grade 2-3 stress response.
The absence of periostitis in the mild cases of edema in our study contradicts the grading system described by Fredericson et al. [23], in which periostitis is associated with lowergrade stress reactions. In our series, there appeared to be a trend in duration of symptoms, degree of marrow edema, and presence of periostitis. This difference may be explained by the different patient groups in the two studies. It may be that the anatomic features and stresses placed on the humerus in tennis players are not comparable with the stresses placed on the tibia in runners. We postulate that the stress injuries seen in our patient group were likely to be related to excess torsional and rotational forces applied to the humeral diaphysis from wielding the racquet rather than the distractional forces from muscle action applied to the tibia in runners. In addition, unlike the tibia, the humerus is not weight-bearing, and hence the biomechanical properties are different.
The main limitation of this study was the small population size. We describe an uncommon condition in a select patient group, and inevitably the numbers were small. We did not include T1-weighted imaging in our protocol and accept that some reviewers may see this as a limitation. However, we believe that our sequences were sufficient to exclude the presence of stress fracture. For the same reason, we did not perform CT on these patients. We also accept that there was potential for reporting bias because the radiologists were not blinded to the clinical information before each study, and reports were reached by consensus.
We conclude that the severity of marrow edema on STIR MRI as described with our criteria may be predictive of recovery time after distal humeral stress reaction in elite tennis players.
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  R. T. Silva, L. G. Hartmann, and C. F. de Souza Laurino Stress reaction of the humerus in tennis players Br. J. Sports Med., November 1, 2007; 41(11): 824 - 826. [Abstract] [Full Text] [PDF]
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