Anatomy of the Flexor Pollicis Longus Insertion
Devin W Collins, DO1; Dylon P Collins, BS2; David C Rehak, MD3; Mark C Snoddy, MD4
1Hughston Clinic, Columbus, GA; 2Nova Southeastern University College of Osteopathic Medicine, Fort Lauderdale, FL; 3The Hughston Clinic, Columbus, GA; 4Augusta University Department of Orthopaedic Surgery, Augusta, GA
Purpose The purpose of this study is to describe the distal insertional anatomy of the FPL tendon and aid surgeons in anatomical repair of the FPL insertion on the distal phalanx.
Methods Twenty fresh-frozen cadavers consisting of 11 right and 9 left hands were used. Each specimen was dyed with methylene blue. The FPL insertion was defined as the non-stained portion of the distal phalanx. The FPL insertion length, width and width at the midpoint of insertion and the distance from the joint to the most proximal point of the insertion were measured. Digital photographs were taken of each specimen and the 2-dimensional surface area of the distal phalanx and FPL insertion were then measured. The centroid of the FPL insertion, was calculated and marked using ImageJ software (https://imagej.nih.gov/ij). Statistical significance was defined as a P value less than 0.05.
Results The average FPL insertion distance from the proximal joint surface was 3.0 mm (1.9-3.9 mm). There was a statistically significant difference between males and females at 3.3 mm (2.9-3.9 mm) and 2.5 mm (1.9-3.0 mm), respectively (P<0.001). Average length of males was 9.5 mm (6.6-12.6 mm) and females was 7.3 mm (5.5-9.6 mm) (P<0.004). Average width for males was 10.5 mm (8.4-11.4 mm) and females was 9.4 mm (8.0-10.3 mm) (P<0.02). Between genders, there was a statistically significant difference between the FPL proximal insertional edge to the joint and from the centroid to the joint (P<0.001). The centroid to the joint line distance averaged 25.8% (21.0-31.2%) of the entire distal phalanx length.
Conclusion We demonstrated statistically significant differences between males and females regarding the FPL tendon insertional length, width and the distance of the centroid to the joint.
Clinical Relevance This study aids surgeons on understanding the insertional anatomy of the FPL at the distal phalanx.
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