Master of Science
Scaphoidectomy and four corner fusion (4CF), and proximal row carpectomy (PRC) are salvage procedures that may be offered in advanced wrist arthritis. The optimal clinical treatment remains unclear. Biomechanical studies comparing outcomes of these procedures often only report uniplanar motion, rather than multiplanar motion which is more representative of functional wrist motion. Further, the impact of altering the relationship of the proximal and distal carpal rows in the coronal plane during 4CF has not been well-studied.
The purpose of this in-vitro biomechanical study was to quantify changes in wrist kinematics during wrist flexion-extension, radial-ulnar deviation, and circumduction in “anatomic 4CF”, “radial 4CF”, and PRC conditions using an active motion simulator. Three important findings are reported: 1) Radial-aligned 4CF resulted in reduced wrist extension and total circumduction compared to the native state, 2) Anatomic 4CF was more restricted in wrist extension than PRC, while PRC was more restricted in radial deviation compared to 4CF, and 3) Total circumduction area was similar between anatomic 4CF and PRC.
These results suggest that 4CF and PRC have comparable motion outcomes. When patients are candidates for either operation, the advantages and disadvantages of each must be considered. If the decision to perform 4CF has been made, anatomic 4CF may provide a better motion profile, provided there is adequate bone stock between the capitate and lunate. In certain situations, adjusting the alignment of the proximal and distal carpal rows is required, making radial 4CF more appropriate. Further clinical investigation comparing these procedures is warranted.
Summary for Lay Audience
Wrist arthritis is a common condition. As arthritis progresses, it involves different areas of the wrist; consequently, treatment methods must be adjusted accordingly. Two commonly performed operations are “scaphoidectomy and four corner fusion”, where one wrist bone is removed and four others are connected together, and “proximal row carpectomy”, where three wrist bones are removed. There are specific indications for each, but some patients may be candidates for both operations. In this group of patients, there are no clinical or biomechanical studies demonstrating the superiority of either procedure, so the operative intervention is largely determined by surgeon experience rather than scientific evidence. Further, within four corner fusion, there is no consensus on the optimal position to connect the four bones.
A comprehensive overview of the current literature is reported in this thesis. The body of this work employs cadaveric wrists and an active motion simulator (whereby motors apply a force on tendons to control wrist motion) to evaluate how motion compares in a native wrist, two positions of four corner fusion, and proximal row carpectomy.
The primary objective of this work is to assist clinicians with decision-making by providing information as to which procedure best retains functional wrist motion in this patient population.
Fan, Stacy, "Comparing Motion Outcomes in Salvage Procedures for Wrist Arthritis" (2020). Electronic Thesis and Dissertation Repository. 7093.