The scaphoid is unique in both its shape and its role within the carpus. The anatomy of each bone will be examined here, and then the basic anatomy of the STT joint will be described to help the reader understand the genesis of STT arthritis. The anatomy of the scaphoid, trapezium, and trapezoid and the articulations between these three carpal bones are unique and help explain why these three bones are often involved in arthritis of the wrist. The study did not, however, delineate the percentage of isolated scaphotrapezial or STT arthritis, leaving Ferris’ 9% incidence in the older than age 50 population as the best indicator of purely isolated, although not necessarily symptomatic, STT arthritis. In cadaveric studies of 68 wrists, North and Eaton identified thumb CMC arthritis in 68% and associated scaphotrapezial arthritis (pantrapezial) in 34%.
#Scaphoid pain series
In a series of 697 radiographic wrist examinations in patients older than age 50 years, Ferris and colleagues identified 63 wrists demonstrating isolated STT arthritis, for a 9% incidence. STT arthritis can exist as an isolated entity, but it can also be associated with dorsal intercalary segmental instability (DISI), calcium pyrophosphate deposition (CPPD) arthropathy, and thumb carpometacarpal (CMC) arthritis. Recognition of the specific patterns of instability, collapse, and arthritic change within the STT articulations is paramount in directing appropriate management, both nonoperative and surgical treatment. STT arthritis can only be fully appreciated by understanding that it represents one of many patterns of intercarpal arthritis, existing as a subset within the spectrum of carpal instabilities and carpal arthritic conditions. Since 1978 literally hundreds of articles, chapters, and presentations have focused on the pathology of carpal instability, arthritis, and its treatment options.
Linscheid and colleagues are credited with descriptions of carpal instability patterns in 1972 in their classic Journal of Bone and Joint Surgery article, “Traumatic Instability of the Wrist: Diagnosis, Classification and Pathomechanics.” Six years later, in 1978 Crosby, Linscheid, and Dobyns described scaphotrapezotrapezoidal (STT) arthritis and several treatment modalities. With increasing understanding of wrist kinematics and carpal instability patterns, our understanding of the relationships between individual carpal bones and patterned types of carpal instability and arthritis has also progressed. STT fusion provides reliable, reproducible pain relief and improved strength with minimal loss of preoperative wrist motion for isolated STT arthritis.ĭistal pole of the scaphoid excision has shown good early and mid-term results with fewer complications than STT fusion, although long-term outcomes are not available. STT arthritis can exist in isolation, or it may coexist with other carpal instabilities and arthritis patterns.Ĭareful exclusion of other coexisting arthritic conditions at the carpometacarpal (CMC) joint and radioscaphoid joint is critical because surgical treatment options are vastly different for each entity.ĭorsal intercalary segmental instability (DISI) pattern has been shown to be associated with STT arthritis.Ĭalcium pyrophosphate deposition arthropathy (pseudogout) should be considered in the differential when isolated STT arthritis is identified.Įither a volar or dorsal approach to the STT joint works for STT fusion, and surgeon’s comfort should dictate which approach is preferred.
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