The Vascular Anatomy of the Scaphoid: New Discoveries Using Micro-Computed Tomography Imaging.

PURPOSE: The purpose of this study was to investigate the intraosseous vascular anatomy of the scaphoid using recent advances in micro-computed tomography (micro-CT) imaging and 3-dimensional reconstruction. We also studied the effect of scaphoid shape and screw position on the intraosseous vascular structure. METHODS: Thirteen upper extremities were injected with a contrast agent. The scaphoid bones were extracted and scanned using a micro-CT scanner. The vascular impact of screw insertion at various axes through the scaphoid was calculated and compared using the generated 3-dimensional models. The specimens were 3-dimensionally-printed and the morphology was assessed according to bone dimensions. A relationship between the internal vascular patterns and these morphological features was determined. RESULTS: All specimens received vascular inflow from the dorsal ridge forming a vascular network that supplied an average of 83% of the bone's volume. This network was supplemented in 4 specimens with volar vessels entering at the waist. Another network was identified, created by vessels entering volarly at the tubercle, which supplied the remainder of the scaphoid. One specimen did not receive any vessels at the tubercle. With regards to screw placement, screws placed in the central axis were the least disruptive to the internal vascularity, followed by the antegrade (dorsal) insertion axis. Two morphological bone types were identified: type I or full scaphoids and type II or slender scaphoids. Type I possessed a more robust internal vascular network than type II scaphoids. CONCLUSIONS: This study identifies 2 distinct types of scaphoid morphology with 1 of them having a less robust blood supply, which may prove to be related to development of nonunion, avascular necrosis, or Preiser disease. Central axis and antegrade (dorsal) screw fixation may be least disruptive to the internal blood supply. CLINICAL RELEVANCE: Safer fixation of the scaphoid bone may be achieved by knowledge of intraosseous vascular patterns.

A Three-Dimensional Micro-Computed Tomographic Study of the Intraosseous Lunate Vasculature: Implications for Surgical Intervention and the Development of Avascular Necrosis.

BACKGROUND: The purpose of this study was to use micro-computed tomography to demonstrate the intraosseous vascularity of the lunate within a three-dimensional orientation to identify areas of greatest perfusion and define vascular "safe zones" for surgical intervention. METHODS: Fourteen upper extremities were injected with a lead-based contrast agent. The lunates were harvested and scanned using a micro-computed tomography scanner. The intraosseous vascularity was incorporated into a three-dimensional image. Vessel number, diameter, distribution, and pattern were evaluated and analyzed. Vascularity of all specimens was projected onto one representative lunate to identity areas of higher and lower vascularity. RESULTS: Twelve specimens had nutrient vessels entering the bone from volar and dorsal; two specimens had no dorsal vessels. The intraosseous vascularity could be classified according to the Y, I, and X patterns described by Gelberman et al. Average number and diameter of vessels were 2.3 and 118.1 µm, respectively, for volar; and 1.4 and 135.8 µm, respectively, for dorsal. The long axis of the lunate showed the highest vascularity on both axial and lateral views. Lower vascularity was observed in the dorsoradial and volar-ulnar quadrants on the axial view, and in the proximal part on the lateral view. Lunate shape was not associated with an increase or decrease in nutrient vessels or vascular pattern. CONCLUSIONS: Vascular safe zones were identified, allowing for potentially safer surgical interventions to the lunate. Volar approaches to the lunate may result in localized ischemia in a subset of patients with absent dorsal nutrient vessels. This study may help to better define patients at risk for Kienböck disease.

The Distally Based Dorsal Metatarsal Artery Perforator Flap: Vascular Study and Clinical Implications.

Background Intrinsic flaps based on the dorsal metacarpal arteries are useful for coverage of dorsal hand, finger, and thumb defects. The purpose of this study was to explore the anatomy of the dorsal metatarsal arteries (DMtAs) in the foot to help define their clinical utility. We observed the size and numbers of distal perforators from the DMtAs and quantified the vascular perfusion pattern of the DMtA perforator across the skin. Methods Ten fresh cadaver feet were injected with latex and dissected to assess the size and number of distal perforators from the DMtAs. Five DMtA perforator flaps were injected with methylene blue to visualize and quantify the vascular territory of the skin flap to understand the clinical possibilities. In addition, a clinical case is described and shown. Results Ten fresh cadaver feet were dissected. The first DMtA was absent in two specimens and the second, third, or fourth DMtA was absent in one specimen each. The available DMtAs had between two and five cutaneous perforators supplying the skin (average, 3.7 perforators per DMtA). The largest perforators to the skin were always seen in the distal half of the DMtA and ranged from 0.4 to 0.8 mm (average, 0.5 mm). Methylene blue injections showed an average flap surface of 21.6 × 47.6 mm. Conclusion This cadaveric study demonstrates the usefulness of the DMtA perforator flap. The flap is a valuable addition to the arsenal of flaps to cover the dorsum of the toe, webspace, or defects exposing tendons on the distal dorsum of the foot.

Effects of trypsinization and mineralization on intrasynovial tendon allograft healing to bone.

The purpose of the current study was to develop a novel technology to enhance tendon-to-bone interface healing by trypsinizing and mineralizing (TM) an intrasynovial tendon allograft in a rabbit bone tunnel model. Eight rabbit flexor digitorum profundus (FDP) tendons were used to optimize the trypsinization process. An additional 24 FDP tendons were stratified into control and TM groups; in each group, 4 tendons were used for in vitro evaluation of TM and 8 were transplanted into proximal tibial bone tunnels in rabbits. The samples were evaluated histologically and with mechanical testing at postoperative week 8. Maximum failure strength and linear stiffness were not significantly different between the control and TM tendons. A thin fibrous band of scar tissue formed at the graft-to-bone interface in the control group. However, only the TM group showed obvious new bone formation inside the tendon graft and a visible fibrocartilage layer at the bone tunnel entrance. This study is the first to explore effects of TM on the intrasynovial allograft healing to a bone tunnel. TM showed beneficial effects on chondrogenesis, osteogenesis, and integration of the intrasynovial tendon graft, but mechanical strength was the same as the control tendons in this short-term in vivo study.

Combined composite osteofasciocutaneous fibular free flap and radial head arthroplasty for reconstruction of the elbow joint.

Reconstruction of the radial head can be complicated in cases of wide resection, particularly in those cases including the proximal radial shaft. In such cases, radial head replacement may not be possible because of lack of adequate bone stock. Here, we report the use of a radial head prosthesis incorporated with a vascularized fibula for immediate anatomic restoration of the forearm and elbow. We present a case of a pathologic fracture non-union in the proximal radius in a 57-year-old female with a history of multiple myeloma. Non-operative management of the fracture was unsuccessful after chemotherapy and radiation. The proximal radius and radial head were resected and reconstructed with vascularized fibula graft in conjunction with immediate radial head prosthesis. The osteotomy site healed at 6-weeks and follow-up at 1 year showed good functional outcome. We feel that the use of this construct has definite promise and may be considered for reconstruction following resection of the proximal radius.