"Baby Wrist" Tendonitis, The relationship between pregnancy and de Quervain's tenosynovitis in lactating mothers within the first 3 months of delivery has been reported . The cause is presumed to be endocrine in origin and similar to the carpal tunnel syndrome described during pregnancy and the lactating postpartum period. Endocrine causes and influence on fluid retention are thought to be primary , although the role of mechanical stress on the thumb from holding the baby may be contributory .
Overuse as a result of diaper wringing in the washing process was also proposed in the early 1960s, though patients presented during pregnancy, preceding infant care, and the condition continues despite modern washing appliances and disposable diapers. The postulated mechanism for the development of de Quervain's disease in our patients is an overuse of the abductor pollicis longus and extensor pollicis brevis tendons in the first extensor compartment. By forced, repetitive extension or flexion of the wrist with abduction of the thumb against resistance (holding of the baby's head), inflammation of the synovial sheaths of the tendons in the narrow fibroosseous tunnel can occur. In addition, normal variations of the first compartment may contribute to irritation and inflammation of the tendons within the narrow fibroosseous tunnel. This was presumed to be the case in two of our patients. Either one or both subdivisions of the first dorsal compartment may be stenotic. The various slips of the abductor pollicis longus may insert into the base of the first metacarpal, trapezium, volar carpal ligament, opponens pollicis, or abductor pollicis brevis ]. Wolfe reported a large variation of normal anatomy, with fewer than 20% having the so-called normal anatomic arrangement.
To our knowledge, no imaging study combined with clinical description of an overuse syndrome of the wrist and thumb associated with de Quervain's tenosynovitis around the eighth month postpartum has been conducted. In our series, overuse of the dominant wrist and thumb caused by prolonged periods of carrying heavy large babies who were over the 95th and 97th percentiles for weight and height was prevalent. All three mothers had a lack of local extended family who could have shared in carrying the baby. All mothers reported that their babies excessively leaned on their thumbs as if they were sofas. No mothers were lactating at the time of severe pain.
The MRI findings reported in our series are typical for those of de Quervain's tenosynovitis, with soft-tissue enlargement in the region of the first compartment of the wrist, thickening of the tendon sheath, and decreased signal intensity on both T1- and T2-weighting. Bone spurring at the site of attachment of the overlying extensor retinaculum is subtly evident in our series, as described in classic de Quervain's tenosynovitis .
Typically, classic de Quervain's tenosynovitis includes chronic inflammation scar formation with stenosis of the approximately 1-cm-long fibroosseous tunnel of the first dorsal compartment (the groove along the radial styloid process covered by the overlying extensor retinaculum through which the abductor pollicis longus and extensor pollicis brevis tendons run). Histologic examination of the disease, unrelated to pregnancy, reveals myxoid degeneration within the tendon sheath wall with ultrastructural studies supporting degeneration as the primary process rather than inflammation within the tendon sheath . The histologic appearances of de Quervain's disease occurring during pregnancy or related to lactation within 12 months of childbirth have findings the same as those described in patients with de Quervain's disease unrelated to pregnancy. Myxoid degeneration responsible for the thickening is observed in the sheath and intramural deposits of mucopolysaccharides predominantly within the subsynovial regions. This would account for the nonsharp margins of the tendon sheath and altered signal intensity within the adjacent subcutaneous fat on MRI.
The radiologic differential diagnoses for these MRI findings include atypical infections, scaphoid fracture or nonunions or radioscaphoid arthritis, and trapeziometacarpal joint arthritis. However, with careful review of the wrist joint compartment anatomy with findings centered in and around the first extensor compartment, especially in the axial plane, and with exclusion of other osseous disorders in the coronal plane images, other diagnoses should be excluded. Clinically, flexor carpi radialis tenosynovitis entrapment of the branches of the superficial radial nerve can mimic de Quervain's disease. Another rare differential diagnosis, both clinically and radiologically, is the intersection syndrome . Pain and swelling of the muscle bellies of abductor pollicis longus and extensor pollicis brevis 4 cm proximal to the wrist joint and the disorder location are probably caused by tenosynovitis of the second dorsal compartment of the wrist. Rheumatoid arthritis can be another cause of stenosing tenosynovitis of the wrist.
Awareness of the baby wrist overuse syndrome and MRI findings is important, because this entity is probably more common than recognized. Early diagnosis allows insight about the cause and potential altered behavior.
Current treatment for pregnancy- and early endocrine-related lactational postpartum de Quervain's tenosynovitis is conservative therapy with rest and immobilization and pain relief because the disease is largely self-limiting, usually resolving after cessation of breast feeding . If conservative measures fail after 4–6 months, surgery is recommended. Steroid injections have also been reported as being useful Nonpregnancy-related de Quervain's disease is currently best treated with surgery by unroofing or reconstruction of the fibroosseous tunnel after failed conservative treatment. At 1-year follow-up, all three patients in our study had pain relief with wrist splinting. With increasing age of the baby, increasing head control, development of crawling, and cessation of overuse of the wrist, the pain, swelling, and mass associated with the tenosynovitis resolved.
Unfortunately, our study included only three patients; however, increasing awareness of this syndrome may prompt further reviews, and the syndrome may prove more common than is currently known. Another limitation is the absence of histologic correlation; however, MRI confirmed the inflammatory component even without the use of contrast material. Although there was a normal variation (Figs. 3A, 3B, 3C and 4A, 4B, 4C) within the first dorsal compartment as described, which may be associated with more severe disease [1] necessitating surgical intervention after a failed trial of immobilization, surgical intervention was not required in any of the three patients.
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