Blackthorn (Prunus spinosus), a member of Rosacea family is well known for causing infections and tissue reactions of synovial structures. Three interesting cases of cystic blackthorn granuloma, blackthorn synovitis with digital nerve entrapment, and multiple blackthorn syndrome are presented. Removal of foreign body fragments and surrounding reactive tissues resulted in an uneventful recovery with full return of joint and tendon functions.
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CASE 1: CYSTIC LUMP CAUSED BY A BLACKTHORN GRANULOMA
A 47 year old man presented with a 2×1 cm size mobile, tender, cystic lump over the dorsum of the left hand. He had a minor injury two weeks previously while pruning. The lump was explored and removed in total as he showed no improvement to a prolonged course of anti-staphylococcal antibiotic therapy. Histopathological examination showed a small organised abscess, granulation tissue, chronic inflammatory infiltrates with a piece of blackthorn. His postoperative period was uneventful.
CASE 2: BLACKTHORN SYNOVITIS WITH DIGITAL NERVE ENTRAPMENT
A 53 year old woman presented with a swollen, tender right index finger at the level of proximal interphalangeal (PIP) joint. She gave a history of cutting hedges a week ago. A small piece of blackthorn with reactive synovium was removed on exploration. She remained asymptomatic for few months period before re-attending the clinic because of the appearance of an exquisitely tender lump at the site of scar with some numbness over the radial aspect of the index finger. Her PIP joint was re-explored and the swelling was excised together with releasing the digital nerve. The lump showed the presence of a 1.2 cm size blackthorn with inflamed hypertrophic synovial tissues. Her digital nerve symptoms recovered fully.
CASE 3: MULTIPLE BLACKTHORN SYNDROME
A 52 year old farmer attended the emergency department three days after a history of hedge cutting. He sustained a deep penetrating injury with a history of vigorous attempts for self extraction of the thorn. He presented with red, hot, swollen dorsum of the little finger and a tender fifth metacarpophalangeal (MCP) joint. On exploration, a large piece of blackthorn was found in the subcutaneous tissue plane. On further dissection, two blackthorn pieces were found, embedded in extensor tendons of the little finger. The decision was taken intraoperatively to explore the MCP joint. This revealed four small pieces of blackthorn lodged in the joint, with inflammatory synovitis. All the blackthorn pieces and reactive synovial tissues were removed. He had an uneventful recovery.
Blackthorn injury can give rise to a wide variety of manifestations ranging from mechanical dermatitis, cellulitis, abscess, foreign body granuloma, peritendinitis, tendinitis, pericapsulitis, synovitis to acute septic arthritis.1,2 Human synovial tissue is very prone to react to organic substances like blackthorns.3 Removal of the blackthorn fragments causes prompt resolution of the inflammation.1–5
Granulomatous reaction is a well known manifestation caused by blackthorn.4 Expectant treatment by conservative medical therapy did not improve the thorn granuloma as showed in the first case.
Foreign body synovitis attributable to joint penetration by a blackthorn may be a cause of monoarticular arthritis, which may easily be overlooked because of its uncommon nature and difficulty in diagnosing it.5 Thorough exploration should be performed. Arthrotomy (opening up the joint), if considered necessary on table, should be performed by a consultant, or at least under consultant supervision, to avoid any recurrent problems as shown in the second case.
You should be aware of the migration of blackthorns in the coronal, sagittal, and deeper tissue planes on exploration as highlighted in the third case.
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