Article
The effect of surgery for base of thumb osteoarthritis on range of dart thrower’s motion at the wrist in cadavers
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Authors
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Mohamed Elajnaf
- Anatomy, Edinburgh Medical School: Biomedical Sciences, University of Edinburgh, Edinburgh, United Kingdom
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Philippa Rust
- Hand Surgery Unit, St John's Hospital, Livingston, United Kingdom
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Robert Wallace
- Department of Biomechanical Engineering, University of Edinburgh, Edinburgh, United Kingdom
| Published: | February 6, 2020 |
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Outline
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Objectives/Interrogation: Dart thrower's motion (DTM) is considered the functional plane of motion at the wrist used in most activities of daily living. DTM is the plane of oblique motion from radial extension to ulnar flexion (Moritomo et al., 2007). It occurs at the midcarpal joint, specifically at the scaphotrapeziotrapezoid (STT) joint, guided by an oblique ridge on the distal scaphoid (Moritomo et al., 2000). The articular surfaces of the scaphoid, trapezium and trapezoid bones allow the wrist the characteristic DTM plane of oblique motion (Slutsky, 2010). Surgical treatment of thumb osteoarthritis is commonly performed, but their effect on DTM is not documented in the literature. It is therefore important to assess how this plane of motion is affected by surgery, to provide patient information for better outcome. The aim of this study is to identify the range of DTM and compare it with the effects of simulated basal thumb osteoarthritis surgeries (STT joint fusion, distal pole of scaphoid excision and trapeziectomy).
Methods: Thirteen fresh-frozen cadaveric specimens were dissected and placed in a specially designed jig to measure the range of DTM (Figure 1 [Fig. 1]). Simulated STT fusion was performed on all specimens and DTM measured. Post STT fusion measurements were recorded afterwards to ensure fusion did not alter control range. Distal pole of scaphoid excision was then performed on left side specimens and trapeziectomy on right side specimens. Measurements taken for each and all results were compared using t-tests.
Results and Conclusions: Arc of dart thrower's motion averaged 117° in intact wrists. Simulated STT fusion reduced the range of DTM significantly to an average of 104° (87% of control, P=.00004). Neither distal pole of scaphoid excision (average 117°) nor trapeziectomy (average 121°) significantly altered the range of DTM.
Theories on DTM suggest that free movement occurs between the scaphoid trapezium trapezoid through range. Our results of STT joint fusion are consistent with this theory. However, DTM is not be affected by distal pole of scaphoid excision or trapeziectomy, providing better pre-operative decisions.
