the most common causes for this condition found in literature are mass lesions or anomalous muscle belly in the carpal region . commonly , carpal tunnel release with excision of the lesion will achieve full relieve of the triggering symptoms . in this case report however , in different previous reports , the aetiology for this case is degenerative changes of the flexor tendon sheath , rather than occupying lesion . we report a case of a 50-year - old chinese female , right - hand dominant , manual labourer , who presented with multiple digit triggering . in september 2006 , she had undergone steroid injection to left middle , ring fingers , right index and middle fingers with initial symptom relief . subsequently , she had left middle , ring finger , right index , middle and ring finger trigger releases done during the period from may 2007 to october 2008 in four separate operations . she came back to our clinic seven years later in november 2015 with recurrent triggering of right middle and ring fingers . this was associated with numbness of the radial three and half digits of right hand . on examination , there was median nerve neuropathy with decreased radial three and half digits sensation . there was tendon triggering with palpable clicking over the mid - palm during finger flexion . there was no evident triggering at the level of a1 pulley in all digits of right hand . previous trigger release scars over the right middle and ring fingers were well healed with no underlying adhesions . there was no wrist tenderness and active range of motion in the wrist was full with no clicking . wrist ultrasound showed that the median nerve was swollen at the level of distal radius and was compressed at the level of the distal carpal tunnel . cross - sectional area ( csa ) at pisiform level was 11.6  mm ( upper limit 11 mm ) . flattening ratio ( fr ) and volar bulging ( vb ) of the flexor retinaculum were within normal ranges . there was no evidence of anomalous masses or migration of the lumbricals into the carpal tunnel during finger flexion . at about the level of the mid - palm , there were linear calcifications related to the middle and ring finger tendon sheath ( figure 1(a),(b ) ) . the affected flexor tendons appear to become distorted as they glide past the areas of calcification . these calcifications were not evident on plain x - ray ( figure 2 ) , which was normal with no significant degenerative changes seen in carpal joints . the nerve conduction study showed severe right carpal tunnel syndrome with significant impaired conduction velocity ( 26.9 m / s ) . laboratory tests including c - reactive protein , uric acid and rheumatoid factor were all normal . ultrasound study of the right hand and wrist . ( a ) linear calcifications of the middle finger tendon sheath of flexor digitorum superficialis and flexor digitorum profundus ( arrow ) . flexor tendons appear to be distorted ( red line ) when pass through the distal edge of transverse carpal ligament ( star mark ) . ( b ) linear calcifications of the ring finger tendon sheath of flexor digitorum superficialis and flexor digitorum profundus ( arrow ) . flexor tendons appear to be distorted ( red line ) when pass through the distal edge of transverse carpal ligament ( star mark ) . ( c ) flexor tendons of middle finger ( mf ) and ring finger ( rf ) are round and smooth at a1 pulley level ( transection view ) . plain x - ray of right wrist : anterior  posterior view and lateral view . intraoperative findings showed thickened transverse carpal ligament and tight carpal tunnel . no extra lumbricals or mass lesions were seen on visible tendons throughout their excursions within the carpal tunnel ( figure 3(a),(b ) ) . the previous palpated triggering at mid - palm immediately resolved and tendon excursion was normal after release of the carpal tunnel and no further exploration of the tendon sheaths was performed . on follow - up visit in our clinic , there was no more finger triggering or numbness . trigger finger at wrist is a rare condition which was first reported by eibel in 1961 . it is a triggering phenomenon of the fingers with the triggering point of the flexor tendons at the transverse carpal ligament . in literature however , this may be confused with clicking , snapping or crepitus of the wrist during wrist motion . we prefer the term  trigger finger at wrist for more accurate description of this condition . type a is due to tumour or nodular lesion occurring on the flexor tendon sheath which causes tendon triggering at the carpal tunnel . type b is due to anomalous muscle belly , including an abnormal lumbrical muscle or abnormal muscle belly of the flexor digitorum superficialis , within the carpal tunnel . type c is a combination of type a and type b. no malignant tumour was ever reported associated with trigger finger at wrist . by reviewing the existing reports , most cases fall into this classification . due to the low incidence of this diagnosis reported two cases of trigger finger at wrist secondary to partial laceration of the flexor digitorum superficialis tendon in 1986 and 1994 . reported another case caused by tendon adhesion between the flexor pollicis longus and flexor digitorum superficialis tendons after palmaris longus tendon harvest for elbow ligament reconstruction surgery . in our case , the triggering was contributed by both degenerative changes of the tendon and the thickened transverse carpal ligament , which has not previously been described as a cause of trigger finger at wrist . though the plaques are small , with combination of tight carpal tunnel , triggering of the flexor tendons might still occur . however , we are not able to explain why this phenomenon is so rare since carpal tunnel syndrome with tendon sheath degeneration should not be uncommon . one explanation might be that a lot of patients with carpal tunnel syndrome and trigger finger were treated concurrently which might have masked the true aetiology . on the other hand , preoperative ultrasound and intraoperative examination of the flexor tendon sheath are not common practice in clinical settings . the symptoms are similar to trigger finger at the a1 pulley , including finger triggering , snapping or catching . carpal tunnel syndrome is almost inevitably associated with this condition in most of the reported cases [ 28,11,13 ] . during physical examination , triggering at the a1 pulley might be palpable due to either coexistence of triggering at a1 pulley level or snapping conducted through the tendon from the carpal tunnel . a missed diagnosis of triggering at the wrist will result in a patient having unresolved symptoms after treatment or surgery for trigger release . ultrasound is able to provide dynamic pictures for the tendon triggering . as seen in our case , it demonstrated the thickened carpal tunnel , the calcification of the tendon sheath and tendon distortion during finger motion due to those calcified plaques . as a matter of fact , the ultrasound findings helped us to have a better understanding of the condition and eventually led us to proceed with surgical approach for the patient . mri and ct scans are also useful in cases with large tumours , for both evaluation and operation planning [ 48 ] . carpal tunnel release was done in all reported cases for associated carpal tunnel syndrome [ 28,11,13 ] . good results of trigger resolving have been shown in all the reports after surgical treatment [ 111,13 ] . for our case , trigger finger at wrist is rare , especially for aetiology described above . however , with combination of a tight carpal tunnel , lesions like calcification plaques can also cause triggering phenomenon . with help of imaging study , better understanding and outcome of the condition will be achieved .
abstracttrigger finger at wrist is a rare condition . 
 symptoms include finger triggering , snapping or catching at the wrist level . 
 carpal tunnel syndrome and median nerve compression neuropathy are almost always associated . 
 we reported one case which was caused by degenerative changes of the flexor tendon sheath and carpal tunnel syndrome .