– Written by Mike Hayton, Kenneth Koo, and Guy Evans, UK
INTRODUCTION
Tennis is a popular racquet sport which involves a combination of high intensity of running, agility, hand eye coordination and the use of both hands and wrists. Injuries to the wrist are therefore common and can be either a single acute traumatic event or more chronic secondary to the repetitive impact of the racquet and ball1.
Ulnar sided wrist pain is common, where the high torque generated in the wrists of tennis players can lead to various injuries to the extensor carpi ulnaris (ECU) tendon such as a tendinopathy, instability of the tendon and ECU rupture2. It is thought that the repetitive forehand ground stroke with top spin is responsible for these different ECU pathologies however, such injuries have also been implicated by the double-handed backhand stroke where the ECU tendon is contracted eccentrically3,4. An understanding of the ulnar sided wrist anatomy can ensure a better understanding and management of ECU tendon injuries.
ECU ANATOMY
The ECU tendon is located along the dorso-ulnar aspect of the wrist and passes through the sixth extensor compartment of the wrist and inserts to the fifth metacarpal base. The extensor retinaculum acts as a pulley to guide the line of travel and prevent bowstringing of the ECU tendon. The extensor retinaculum inserts distally to the triquetrum and pisiform and not to the ulnar, to allow for pronosupination of the distal radioulnar joint (DRUJ)2.
Beneath the extensor retinaculum, the ECU tendon is enclosed within a fibroosseous tunnel lined by the ulnar head and the ECU subsheath which holds the ECU tendon within a groove to the ulnar head5,6. The ECU subsheath is composed of the deep antebrachial fascia that inserts on the groove to the ulnar head and is reinforced at its ulnar insertion by the linea jugata to prevent volar subluxation of the ECU2. The function of the ECU subsheath itself is to provide a mechanical advantage to the ECU tendon and act as a pulley6.
This subsheath is also a component of the triangular fibrocartilage complex (TFCC) which provides stability to the DRUJ. The ECU muscle is an important dynamic stabiliser to the DRUJ and contributes to wrist extension with wrist pronation, and flexion in wrist supination4. The relative stability of the ECU tendon in the ulnar groove also differs with wrist pronosupination whereby in full pronation the tendon is within its groove and in supination there is greater tension of the tendon against the subsheath, as demonstrated with clinical examination for ECU instability7,8.
In addition to the anatomy, an understanding of the biomechanics of the wrist provides a better understanding to wrist injuries in tennis players.
BIOMECHANICS
When hitting a ball with a tennis racquet, the wrist is subject to both internal and external forces. Internal forces include muscle contractions and torque at the wrist to move to racquet towards the ball. The internal forces are dependent on the type of grip on the racquet, the tightness of the grip and the type of spin that is imparted to the ball3,4,9,10. Eccentric contraction of the wrist extensors with a one or two handed backhand stroke has been implicated to be a key mechanism of injury in the upper limb of tennis players10.
External forces are resultant from the weight and size of the racquet, the position of the ball when it contacts the racquet and the tension of the strings of the racquet3,4,9-11. When there is an off-centre impact of the ball to the racquet, this causes the racquet to rotate which is compensated with an increase in grip strength to prevent an excessive rotation of the racquet10. The type of tennis ball and different playing conditions can also be considered as external forces affecting the tennis stroke, though these factors have not been reviewed previously.
Although present, it is not thought that the torque of the internal and external forces are great enough to cause injury from a single tennis groundstroke. Tennis players can perform more than 1100 ground strokes in one match, which suggests that wrist injuries are likely to be resultant of overuse9. This is in keeping with the chronic attritional findings of ECU tendinopathy, tears and subluxation, which can be found in tennis players who are asymptomatic12.
Mechanism of injury
The ECU tendon is most vulnerable to injury with wrist in supination, flexion and ulnar deviation which increases the tension to the ulnar side of the ECU subsheath. This wrist position is seen commonly with the hand closest to the racquet in the double handed backhand stroke2 (Figure 1). The same position of the wrist has been seen to cause ulnar sided wrist pains in other racquet and handle based sports such as golf. Interestingly, in professional tennis players, the hand furthest from the racquet tends to be more commonly affected with the double handed backhand in our experience.
It is believed by some authors that ulnar sided wrist pain in tennis players is due to poor technique with groundstrokes4,13, although this is controversial in the proven elite athlete. Hand grip positions can affect both load transmission from the ball to racket to wrist as well as stroke biomechanics with single handed ‘western or semi-western forehand grips’ being attributed to ECU injuries 4,13 (Figure 2). This is thought to be due to the increased load through the ulnar side of the wrist during wrist extension, supination and ulnar deviation9,13. The clinician should always be mindful to a recent change in load (i.e. hitting time or intensity), change of grip, technique, equipment including the racquet, strings, balls and playing surface1,4.
DIAGNOSIS AND IMAGING
Dorsoulnar wrist pain presents a diagnostic challenge due to the close proximity of a number of anatomical structures. The history provides an important clue to the diagnosis and injury sustained. This can either be an acute onset of pain, where the player recalls a pain following a single groundstroke or where there is an insidious onset of pain persisting for weeks when playing a certain shot. In both instances, the pain is localised to the dorsoulnar aspect of the wrist with associated swelling, reduction in grip strength and possibly, a snapping or flicking sensation over the dorsoulnar wrist with rotation at the wrist14. It is also important to identify those who have ECU subluxation secondary to tendon hypermobility which can be associated with connective tissue disorders and are more difficult to treat15.
The examination occurs through the “look, feel, move” mantra with swelling and tenderness along the ECU tendon may be suggestive of a tenosynovitic picture. The range of motion at the wrist must be noted with particular attention to wrist extension, supination and ulnar deviation16. Provocative tests include the ECU synergy test which involves the patient resting their arm with the elbow flexed at 90o and forearm in full supination. On resisted radial abduction of the thumb, the ECU tendon synergistically contracts and can be palpated17. Bowstringing or pain palpated along the length of the ECU tendon can then be thought to be due to pathological extraarticular lesion to ECU or its subsheath17 (Figure 3).
For ECU tendon instability, one of the authors (MJH) has described a novel clinical test which simulates the action of ‘scooping ice cream’ with the hand7. The patient’s wrist is initially positioned in full pronation, ulnar deviation and extension. The ulnar deviation is maintained and the wrist is supinated against resistance with palpation of the ECU tendon (Figure 4). Snapping of the tendon results in a positive test.
Subluxation of ECU on active supination with the wrist in resisted flexion and ulnar deviation is also indicative of instability, described as the Cobra test5. The ECU tendon is seen to reduce with active pronation of the wrist.
Imaging used for diagnosis include radiographs of the wrist, MRI scan and an ultrasound scan. A T1 weighted MRI scan with Gadolinium enhancement is thought to be most accurate in identifying ECU subsheath pathology18. Dynamic instabilities of the tendon relative to the ulnar groove can be identified with an ultrasound scan19. Each modality adds a further diagnostic layer to the presenting symptoms. The important questions to be answered on advanced imaging are:
- The depth of the ECU groove on the ulna
- ECU tendinosis with delamination
- ECU tendinopathy
- Subsheath pathology including tears or rupture
- 6th extensor compartment attenuation
- Ulna variance
ECU PATHOLOGY
ECU tendon pathology can range from chronic tendinopathies to more acute tendon ruptures and instability. The management of each condition differs but the pathophysiology all relates to the ECU tendon relationship with the ulnar head and the fibro-osseous subsheath.
Tendinopathy
ECU tendinopathy presents with a chronic history of pain following repetitive motion. The excessive friction between the tendon and its subsheath can cause degenerative changes to the ECU tendon. ECU tendinopathies have been classified as constrained and unconstrained tendinopathies with the integrity of the subsheath being the differentiating factor6. Constrained tendinopathies can further be subdivided to the common ECU tendinosis and a stenosing tendovaginitis.
ECU tendinosis is associated with an overuse pathology where repeatedly applied stress to the ECU tendon can cause the tendon to thicken, have disorganised matrix of collagen and are prone to areas of deterioration which histologically is referred to an angiofibrobalstic hyperplasia6. If left untreated, an advanced tendinosis can eventually lead to a complete rupture of the tendon6. A chronic systemic inflammatory condition (i.e. inflammatory arthropathy, gout) can also lead to the same histological findings with tendons however with less repeated stresses.
A more uncommon cause of ECU tendinopathy involves the thickening of the ECU subsheath which restricts the gliding of the ECU tendon through its tunnel, causing pain and inflammation. The pathophysiology of a stenosis tendovaginitis is not completely known but it appears similar to that seen with trigger fingers and De Quervains Tenosynovitis6,20.
ECU instability
Instability of the ECU tendon within its subsheath is an example of an unconstrained tendinopathy of ECU. Subsheath rupture is sustained with a sudden forceful contraction of the ECU with the wrist in ulnar deviation, supination and flexion6,21,22. The rupture will then allow for the volar subluxation or dislocation of the ECU tendon from its ulnar groove. Inoue and Tamara had described three different types of ECU dislocation, all with differing management strategies (Figure 5).
In tennis players, an isolated ECU instability is seldom found where most have an associated TFCC tears6,23.
ECU tendon rupture
Complete tendon rupture is a very rare ECU pathology amongst tennis players but can be considered a career ending injury if not diagnosed promptly2. Tendon rupture can result from a chronic tendinopathy that leads to degenerative changes of the tendon2,5,6. Incomplete rehabilitation following an injury to the wrist can also rarely lead to a complete tendon rupture. A case report of an ice hockey player who had injured his wrist on hitting a goal post, but had continued to play the remainder of the season without rest24. Eight months after the injury it was noted that he had sustained a complete ECU tendon rupture24.
Repeated corticosteroid injections into the subsheath can also cause a weakening of the ECU tendon and eventual rupture. Incidentally this treatment was also performed in the above case report and may have contributed to the tendon rupture24.
MANAGEMENT
Initial treatment in an elite athlete involves relief of pain and to prevent further degeneration of the ECU tendon. As such, the treatment regime needs to be tailored to each individual athlete from a shared decision-making process. Although rare, cases of ECU ruptures have presented in athletes with persistent ulnar sided wrist pains and alternating period of rest and play2,24. A realistic timeline of recovery should be shared with the athlete throughout the rehabilitation. An initial course of conservative management is usually recommended when treating ECU injuries.
Non operative management
Conservative management of ECU tendinopathies tend to be effective in the first instance with patient understanding of the condition being paramount to the rehabilitation process. Anti-inflammatory medication is effective to relieve pain and swelling, with some clinicians recommending short term splinting of the wrist in pronation, slight extension and radial deviation6,25. The key to successful treatment is early diagnosis which limits the degeneration of the tendon. If symptoms persist, then an ultrasound guided injection of corticosteroid within the ECU sheath may be beneficial but with the added risk of causing tendon weakness and rupture. A platelet rich plasma (PRP) injection is an alternative without the risk of tendon weakness26. The authors prefer PRP injections over coticosteroid injections around such an important tendon, that if ruptured, would be potentially career ending.
Different ECU tendon treatment protocols have been devised for treating the elite tennis players which are individualised for each patient. The Lawn Tennis Association (LTA) divides the protocol into preservation of tendon health, regain strength around the wrist, regain athleticism whilst reloading the wrist, increasing on-court tennis training and a return to full training and match practice. This is similar to a protocol devised by Graham, who divides the rehabilitation into an immobilisation, motion recovery, strength recovery and a sport-specific preparation phase 25. The immobilisation phase involves splinting of the wrist to preserve tendon health and persists until the wrist is comfortable without the use of a brace followed by a gradual increase in intensity of range of motion exercises to the wrist with the ECU taped25. If the pain does not settle then an ultrasound guided PRP or corticosteroid injection to the sheath can be performed followed by splint immobilisation before resuming the motion recovery phase of rehabilitation. The strength recovery phase then follows with the ECU tendon taped both proximal and distal to the ulnar head to allow for free flexion and extension of the wrist and full ECU tendon excursion 25. The strength recovery phase is continued until 75% of strength is regained in comparison to the contralateral wrist, before proceeding to the sport-specific preparation phase. This phase is conducted under the guidance of the tennis coaching team, which usually involves free swinging of a racquet before a gradual progression of groundstrokes with a tennis ball25.
Similar ECU treatment protocols have also been used with acute subluxation/dislocations of the ECU tendon but with a longer immobilisation period and full return to play after 5 to 6 months2,6,18. When there is a persistence of pain and discomfort which impairs competitive level activity, operative treatment can be considered.
Operative management
The aim of surgery is to restore or reinforce the ECU subsheath and preventing the development of ECU instability and tendinopathy.
It has been suggested that chronic ECU subluxation/dislocations are not feasible for direct repair with high failure rates, especially when retraction and atrophy of the edges of the sheath are present however, a direct anatomic reconstruction can be considered6. Open reduction of the tendon and reconstruction of the sheath is recommended through a dorsoulnar approach to the wrist. Various techniques have been described, each with its own advantages and disadvantages. The use of the extensor retinaculum as a sling around the ECU tendon has shown success with return to previous sporting activities6,14,22,23. This technique has further been modified by many surgeons who favour a radially-based sling around the ECU tendon to ensure that the tendon is retained within the groove in full pronation of the wrist with a return to grip strength 9 months post-surgery3,6,22. The ulnar groove can also be inspected, where those with a shallow ulnar groove can be deepened with a burr although the authors have some concerns regarding this technique unless absolutely necessary27. Other techniques of reconstruction with the extensor retinaculum have also been described but all eventually lead to a limitation in pronosupination thought to be from adhesions6,14,22. A capsulotomy has been described for this complication, that describes lifting and ulnarly based capsuloperiosteal flap from the ulnar groove and relocation of the ECU tendon subperiosteally within the groove6. The radial edge of the capsuloperiosteal flap is then repaired to the radial side of the ulnar groove with suture anchors6.
Inoue and Tamura had described different operations based on the type of ECU subluxation/dislocation from their classification with type A and B injuries being repaired anatomically with a strip of fascia or direct repair respectively6 (Figure 6). Type C injuries were repaired by reattaching the periosteum to the ulnar to reform the ECU subsheath6. All described techniques had anatomically restored the ECU subsheath with full pronosupination described with all patients6,14.
The preferred method of type C injuries by the authors is to place a row of 1mm soft anchors along the ulna ridge of the ECU groove to close the “dead space” and prevent subluxation (Figure 7).
For all forms of surgical repair, a prolonged period of immobilisation from rotation is required for healing to occur, followed by rehabilitation due to the deconditioning of the wrist.
RETURN TO PLAY AND PREVENTATIVE MEASURES
For an athlete to return to previous levels of tennis, a comprehensive rehabilitation period is likely to be required with both operative and non-operative management.
Preventative measures include the appropriate technique and grips as the ECU are prone to injury with wrist position and certain groundstrokes as described earlier2,4,9,13. It is also thought that participation in tennis at an early age can also contribute to an increasing number of wrist injuries whereby the physically immature body cannot resist the increased repetitive load of competitive sport9. These factors would need to be considered by tennis coaching teams to ensure training loads are appropriate for age and stage in order to optimised performance and prevent injuries.
CONCLUSION
The ECU tendon is an important dynamic stabiliser of both the radiocarpal and midcarpal joint which is intimately attached to the other structures of the ulnar side of the wrist. The ECU and its subsheath can be injured in both an acute and chronic manner associated with an ulnar deviated, flexion and supination at the wrist which is a common movement for tennis players. Early diagnosis and treatment is paramount in order for successful treatment of these injuries and requires a high index of suspicion in order to prevent a potential career threatening consequence.
Mike Hayton MBChB, F.R.C.S. (Tr&Orth), B.Sc. (Hons), F.F.S.E.M.
Upper Limb Unit, Wrightington Hospital
Wrightington, Wigan, UK
Kenneth Kin Hoo Koo MBChB, F.R.C.S. (Tr&Orth), M.Sc. (Hons), B.Sc. (Hons)
Upper Limb Unit, Wrightington Hospital
Wrightington, Wigan, UK
Guy Evans MBChB, MRCGP, F.F.S.E.M., M.Sc. (Hons)
Chief Medical Officer, Lawn Tennis Association
London, UK
Contact: kenneth.koo@doctors.org.uk
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Header image by Marianne Bevis (Cropped)