Abstract
Operative Technique: The Use of a Flexor Retinacular Flap to Cover an Osteophytic Hook of Hamate Post repair of a Chronic Rupture of The Flexor Digitorum Profundus Tendon of The Little Finger Closed ruptures of the Flexor Digitorum Profundus (FDP) tendon associated with hook of hamate pathology are rare but have previously been described in the literature. It is mostly associated with fracture non-union of the Hook of Hamate resulting in roughened bone surfaces which over time can erode the flexor tendons. The preferred treatment for a spontaneous flexor tendon rupture in the hand is interposition tendon grafting. Most commonly a resection of the Hook of Hamate is performed however occasionally sharp, or roughened bone surfaces can persist. In our recent case of a closed FDP repair of the little finger we used a flexor retinacular flap to cover the roughened edge of the bone post resection of the Hook of Hamate to create a smooth surface for our tendon repair to glide. This flap should be considered as a beneficial technique in all cases requiring resection of arthritic bone within the carpal tunnel.
Keywords: Flexor Retinaculum, Tendon graft, Flap, Hook of Hamate
Introduction
Closed ruptures of the Flexor Digitorum Profundus (FDP) tendon associated with hook of hamate pathology are rare but have previously been described in the literature. It is mostly associated with fracture non-union of the Hook of Hamate resulting in roughened bone surfaces which over time can erode the flexor tendons.1 The hook of hamate forms the ulnar border of the carpal tunnel and acts as a lever to provide mechanical advantage to the flexor tendons of the little and ring finger as they traverse the palm from the carpal tunnel. The FDP tendons of these digits are therefor most at risk of attrition rupture.2 The preferred treatment for a spontaneous flexor tendon rupture in the hand is interposition tendon grafting. Tendon transfer using the Flexor Digitorum Superficialis (FDS) from the ring to the little finger is less favorable as it may compromise ring finger function. Tendon grafts from Palmaris Longus (PL) or a portion of the Flexor Carpi Radialis (FCR) Tendon are most commonly used.2 Prior to definitive repair the causative pathology must be treated. It is this aspect of the management which we have taken a special interest in Most commonly a resection of the Hook of Hamate is performed however occasionally sharp, or roughened bone surfaces can persist.2 The use of a flexor retinaculum flap to cover denuded bone within the carpal tunnel has been reported previously by Regan et al. in 1990 and shown to provide a smooth surface for repaired or partially damaged tendons to glide.3 Haussman has shown the benefit of this technique to cover the resulting defect post resection of bony spurs of the trapezium and scaphoid to provide a smooth surface for tendons to glide. They describe a radially based flexor retinacular flap 15 mm wide which is sutured below the flexor tendons to close the wrist capsule.4
Case
Our case is of a 70 year old right hand dominant male who presented 10 days post a closed rupture of the FDP tendon of the little finger. He reported that he was pull-starting the engine of a power washer when he experienced a sudden onset of pain in his hand and thereafter was unable to flex the tip of his right little finger. On exam, he had weak activation of the FDS and no activation of FDP in this finger. His X-ray showed no fractures and mild arthritic changes in the wrist. The patient reported that he had injured his wrist in a fall several years previously but had never sought any medical attention for it. The differential diagnosis included an FDP avulsion injury and a mid-substance FDP rupture. The decision was made to bring the patient to theatre for a formal exploration.
On exploration of the finger and the wrist the FDP tendon was found to be ruptured at the level of the carpal tunnel. The tendon ends were extremely frayed and encased in dense scar tissue indicating the chronic nature of the injury. A roughened osteophytic hook of hamate was discovered at the ulnar boarder of the carpal tunnel. On close examination of the other tendons within the carpal tunnel there was evidence of early damage to the FDP tendon to the ring finger, however its continuity was preserved.
Due to the jagged nature of the Hook of the Hamate a decision was made to resect the osteophyte and smoothen the surface of the remaining bone. An ulnarly based flap of flexor retinaculum approximately 20 × 30 mm in size (Figure 1) was brought beneath the flexor tendons and was sutured to the base of the carpal tunnel with a 3.0 PDS suture (Figure 2). Therefor allowing us to cover any remaining sharp bone edges and providing a smooth surface for the flexor tendon repair to glide. A primary tendon graft repair was performed with a piece of the FCR tendon using a Pulvertaft weave technique.
Figure 1.
Markings for ulnarly based flexor retinacular flap prior to raising the flap.
Figure 2.
Flexor retinacular flap sutured across osteophytic hook of hamate to provide smooth surface for the FDP repair. Flexor tendons retracted radially to expose the base of the carpal tunnel.
Post operatively the patient was referred to our Hand Therapy service and progressed very well with his rehab program. He was seen back at the 3-month time point with full active range of motion and no sign of injury to any other tendons.
Conclusion
Our case describes the use of a flexor retinaculum flap to cover over the resected hook of hamate which is a technique of which there are very few examples of in the literature. This flap has provided an excellent tissue bed for the FDP repair to glide over and has also aided in preventing any further trauma to the remaining flexor tendons. Our patient has had an excellent functional outcome. Treating the underlying cause in these cases is crucial to prevention of further injury. Hook of Hamate arthritis is a rare diagnosis and as stated previously is mostly caused by a fracture non-union. We feel this was likely the underlying cause in this case. This flap should be considered as a beneficial technique in all cases requiring resection of arthritic bone within the carpal tunnel.
Declaration of competing interest
None declared.
Acknowledgments
Funding
None.
Ethical approval
Not required.
Footnotes
Details of presentations: Poster Presentation at Irish Association of Plastic Surgery Meeting 2025 (IAPS).
References
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