PMC5650637_01
Radiographs of the right hind foot acquired on the day of admission. Dorsal is to the left on lateromedial images and lateral to the left on dorsoproximal images. (A,B) Lateromedial and dorsal60proximal-plantarodistal oblique views of the right hind foot with a metal probe in place in the discharging tract. The probe can be seen passing just lateral to the midline in a plantaroproximal direction to the level of the proximal third of the middle phalanx. No osseous abnormalities are seen. (C) Standing lateromedial view with a needle in place within the navicular bursa (NB), contacting the plantar compact bone of the navicular bone. There is a second needle further proximally, at the plantar extent of the deep digital flexor tendon (DDFT), which is the needle subsequently inserted into the proximal recess of the NB. (D) Positive contrast bursogram showing that the NB is intact. Both needles described in (C) remain in place. A small volume of contrast is extravasated plantar to the DDFT and lymphatic drainage of contrast is seen proximally.
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F1
Despite the needle being placed in the correct position (Figure 1C) fluid could not be aspirated. A second needle was placed in the proximal recess, resulting in two needle advancements through the DDFT (Figures 1C,D).
MRI images of the right hind foot. Lateral is to the left of the images. (A,B) Slice matched T1-weighted gradient echo (GRE) images of the right hind foot at the level of the proximal third of the navicular bone. (A) was acquired at the time of admission and (B) at the time of representation. In panel (A), the medial lobe of the deep digital flexor tendon (DDFT) is normal in appearance. In panel (B) a well-defined hyperintense line is seen traversing the axial portion of the medial lobe from plantar to dorsal, consistent with a parasagittal split in the tendon (white arrow). (C,D) Slice matched T2-weighted fast spin echo images within the proximal recess of the navicular bursa (NB), acquired at initial presentation (C) and the time of repeat presentation (D). In image (D), the previously described hyperintense linear lesion in the medial lobe is seen (arrowhead). There is well defined linear material extending dorsally from the medial portion of the DDFT to the collateral sesamoidean ligament (arrows), which is markedly increased when compared to that seen in (C). The NB remains effused. (E,F) Transverse slice matched T1GRE images within the proximal recess of the NB acquired at initial presentation (E) and repeat presentation (F). The hyperintense linear lesion within the medial lobe is clearly seen in panel (F) (arrow head). There is a region of mildly hyperintense material dorsal to the tendon in panel (F) (arrow), which is consistent with the presence of adhesions as seen in image (D). (G,H) Slice matched transverse T2*WGRE image at the distal horizontal border of the navicular bone. The previously described lesion in the medial lobe of the DDFT remains visible in panel (H) at this level (arrow) demonstrating continuation of the lesion distal to the navicular bone.
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F3
There was a discrete core lesion within the tendon at the mid point of the proximal phalanx, which widened into a parasagittal split at the level of the proximal recess of the NB and extended distally to involve the insertion (Figure 3). The parasagittal split was located at the axial aspect of the medial lobe of the DDFT, adjacent to the midline septum (Figures 3A-F). T1W and T2*W GRE sequences as it traversed the navicular bone, with focal regions of signal hyperintensity on T2W FSE sequences. There was a marked irregularity of the dorsal border of the DDFT within the proximal recess of the NB, with soft tissue material extending between the dorsal border of the DDFT and the plantar border of the collateral sesamoidean ligament, suggestive of intrabursal adhesion formation (Figures 3C,D).
(A) Deep digital flexor tendon neovascularisation and fibrosis (4x magnification) with scattered haemosiderophages (inset at 40x magnification). H&E stain. (B) Areas of fibrocartilaginous metaplasia at 10x magnification. (C) Collagenolysis on H&E section of tendon at 20x magnification with inset highlighting degenerate collagen (stained red on Masson's Trichome).
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F4
Histologically in all sections, there was neovascularisation with tunica media hypertrophy, multifocal to coalescing fibrosis (Figure 4A), fibrocartilaginous metaplasia (Figure 4B) and collagenolysis (Figure 4C).