Surgical Science, 2011, 2, 353-355
doi:10.4236/ss.2011.26076 Published Online August 2011 (http://www.SciRP.org/journal/ss)
Case Report: Osteochondral Fragment—A Rare Cause of
Locked Metacarpophalangeal Joint
Kelvin Ramsey, S. Overstall, A. Fleming
St. George’s Ho sp ital, London, UK
Received April 1, 2011; revised May 2, 2011; accepted Ju ly 14, 2011
Abstract
We describe the presentation of a patient with sudden, sharp pain associated with a snapping sensation,
swelling and pain over the metacarpophalangeal joint (MCPJ) with no history of direct trauma. The finger
was held in 30 degrees of flexion and significantly deviated to the ulnar side with loss of extension. A diag-
nosis of traumatic rupture of the radial sagittal band of the extensor mechanism was made but the cause at
exploration was found to be impingement of an osteochondral fracture fragment. This is a rare cause of irre-
ducible loose body “locking” of the metacarpophalangeal joint.
Keywords: Metacarpophalangeal Joint, Locking, Osteochondral, Fragment
1. Introduction
A 72 year old, right-handed female rheumatoid arthritis
patient was referred to our department with an acutely
painful, swollen left middle finger. One week prior to
arrival she had picked up a kettle and noticed a sudden,
sharp pain associated with a snapping sensation. The
finger immediately became swollen and painful over the
dorsum of her third metacarpophalangeal joint (MCPJ)
and she noticed that she was unable to fully straighten
the digit. There had been no history of direct trauma to
the affected hand.
On examination the left middle finger was held in 30
degrees of flexion and significantly deviated to the ulnar
side, lying underneath the ring finger (Figure 1). The
MCPJ was swollen and tender. Active extension was not
possible and passive extension was painful. Flexor digi-
torum superficialis and profunda function were intact
with full passive interphalangeal joint range of motion.
There were no palpable nodules on the volar aspect nor
any other abnormal findings. On close inspection of the
radiograph, a small abnormality was visible on the volar
aspect of the joint, of uncertain significance given the
clinical picture (Figure 2).
The diagnosis of traumatic rupture of the radial sagit-
tal band of the extensor mechanism was made, and the
patient was listed for semi-urgent repair.
Under regional anaesthesia the finger was still held in
30 degrees of flexion and passive extension was not pos-
sible. The extensor mechanism was explored using a
curvilinear incision over the dorsum of the MCPJ. The
extensor tendon was found to lie perfectly in th e midline
and the sagittal bands were intact.
The volar aspect of the finger (o v er the A1 pu lley) was
exposed to exclude an impacted trigger finger. A small
incidental flexor sheath ganglion was found and excised
but the flexor tendons were running freely prior to this.
The MCP joint capsule was then opened and explored.
Lying within the joint on the dorsal aspect of the meta-
Figure 1. Left middle finger held in 30 degrees of flexion
and significantly deviated to the ulnar side.

K. RAMSEY ET AL. 354
Figure 2. Pre-operative radiograph showing a small ab-
normality on the volar aspect of the joint but nothing seen
dorsally.
carpal head was a small osteochondral fragment, which
was impinging at the point of articulation with the base of
the proximal phalanx and preventing extension of the joint.
This fragment had fractured from the ulnar aspect of the
head of the metacarpal on the palmar side and migrated
within the joint capsule (Figures 3 and 4). This was re-
moved and the joint irrigated (Figure 5). The passive
range of movement of the joint returned to normal. The
wound was closed and the hand placed in a resting splint.
The patient was referred to hand therapy for immedi-
ate mobilization and made a full recovery.
2. Discussion
We suggest that this represents a rare cause of irreducible
loose body “locking” of the metacarpophalangeal joint,
resulting in ulnar deviation and masquerading as a sagit-
tal band rupture. The pre-operative radiograph, with the
benefit of retrospect, showed small fragments at the site
of fracture but did not explain the cause of the locking
nor was the main fragment, which was causing im-
pingement within the joint, visible.
There have been numerous reports of isolated “locked
fingers” in the literature. This is commonly confused
Figure 3. Site of fracture of osteochondral fragment from
ulnar aspect of metacarpal head on volar aspect.
Figure 4. Small osteochondral fragment found lying within
the joint on the dorsal aspect of the metacarpal head.
Figure 5. Osteochondral fragment after removal.

K. RAMSEY ET AL. 355
with triggering of the flexor tendon under the A1 pulley
[1]. True locking can occur when the volar plate or col-
lateral ligament catches on an osteophyte [2] or abnor-
mally shaped metacarpal head. Other causes include:
entrapment of a sesamoid bone behind an exostosis of
the metacarpal head, subluxation of the dorsal interosse-
ous tendon over a dorsal exostosis [3], foreign bodies
within the flexor sheath [4], volar plate interposition,
volar plate haemangioma [5] or gouty degeneration of
the MCP joint. The successful treatment of a locked fin-
ger with gentle manipulation under regional anaesthesia
has also been described [6,7] but this was not possible in
our case. Forced manipulation of a locked finger has also
been described as a cause of intra-articular fractures [8].
Spontaneous rupture of the sagittal bands with subse-
quent subluxation of the extensor tendon is a common
finding in patients with rheumatoid arthritis. It may also
follow forced flexio n of the finger in the non-rh eumatoid
patient. It more commonly affects the middle finger, and
the radial sagittal band ruptures more commonly than the
ulnar band, resulting in ulnar deviation and extensor lag.
The presentation of this condition is identical to that
described in our case, and justifies our initial diagnosis.
However, this rare cause of joint locking due to fracture
fragment (despite minimal injury) illustrates the impor-
tance of considering alternative diagnoses even in the
most clear-cut clinical presentation.
3. References
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doi:10.1016/0266-7681(88)90100-3
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[8] G. Inoue, R. Nakamura and T. Miura, “Intra-Articular
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