Anatomic Landmarks for Basal Joint Injections

Abstract

Objective:
Basal joint arthritis is a common cause of pain and disability, particularly in elderly women. Corticosteroid injection with splinting provides a reliable long-term relief for patients with mild arthritis. Proper location of the basal joint with anatomic landmarks can facilitate diagnosis and treatment of basal joint arthritis while avoiding inadvertent injury to local structures. The purpose of this study is to identify bony anatomic landmarks for basal joint injections and aid clinicians in avoiding inadvertent injury to surrounding structures on the radial side of the wrist.

Methods:
Twenty fresh cadaveric wrists were dissected with the aid of loupe magnification. The distal edge of the radial styloid and the palpable dorsal aspect of the thumb metacarpophalangeal joint were used as bony anatomic landmarks for the identification of the basal joint along a longitudinal vector. Measurements of the distance from our anatomic landmarks to the basal joint space were recorded. The locations of the radial artery and the superficial branch of the radial nerve were noted in relation to the borders of the anatomic snuffbox at the basal joint level.

Results:
The basal joint of the thumb is located 2.44 ± 0.34 cm distal to the distal edge of the radial styloid, and 4.47 ± 0.29 cm proximal to the metacarpophalangeal joint. At the level of the basal joint, the radial artery is found 0.76 ± 0.12 cm dorsal to the extensor pollicis brevis tendon. The first branch of the superficial branch of the radial nerve is volar to the abductor pollicis longus tendon in 84% of the specimens and courses over the abductor pollicis longus tendon in 16%.

Conclusion:
The basal joint of the thumb is approximately 2.4 cm distal to the radial styloid and 4.5 cm proximal to the metacarpophalangeal joint. Placement of a needle in the basal joint space immediately dorsal to extensor pollicis brevis tendon while applying longitudinal traction on the thumb is more likely to avoid damage to the radial artery and the superficial branch of the radial nerve.

Full text

Anatomic Landmarks for Basal Joint Injections
Ron Hazani, MD, Nitin J. Engineer, MD, Josh Elston, BS, and Bradon J. Wilhelmi, MD
University of Louisville School of Medicine, Division of Plastic surgery, Louisville, KY
Correspondence: ronmdsurg@hotmail.com
Published January 18, 2012
Objective: Basal joint arthritis is a common cause of pain and disability, particularly
in elderly women. Corticosteroid injection with splinting provides a reliable l ong-term
relief for patients with mild arthritis. Proper location of the basal joint with anatomic
landmarks can facilitate diagnosis and treatment of basal joint arthritis while avoiding
inadvertent injury to local structures. The purpose of this study is to identify bony
anatomic landmarks for basal joint injections and aid clinicians in avoiding inadvertent
injury to surrounding structures on the radial side of the wrist. Methods: Twenty fresh
cadaveric wrists were dissected with the aid of loupe magnification. The distal edge of
the radial styloid and the palpable dorsal aspect of the thumb metacarpophalangeal joint
were used as bony anatomic landmarks for the identification of the basal joint along a
longitudinal vector. Measurements of t he distance from our anatomic landmarks to the
basal joint space were recorded. The locations of the radial artery and the superficial
branch of the radial nerve were noted in relation to the borders of the anatomic snuffbox
at the basal joint level. Results: The basal joint of the thumb is located 2.44 ± 0.34 cm
distal to the distal edge of the radial styloid, and 4.47 ± 0.29 cm proximal to the
metacarpophalangeal joint. At the level of the basal joint, the radial artery is found
0.76 ± 0.12 cm dorsal to the extensor pollicis brevis tendon. The first branch of the
superficial branch of the radial nerve is volar to the abductor pollicis longus tendon in
84% of the specimens and courses over the abductor pollicis longus tendon in 16%.
Conclusion: The basal joint of the thumb is approximately 2.4 cm distal to the radial
styloid and 4.5 cm proximal to the metacarpophalangeal joint. Placement of a needle in
the basal joint space immediately dorsal to extensor pollicis brevis tendon while applying
longitudinal traction on the thumb is more likely to avoid damage to the radial artery
and the superficial branch of the radial nerve.
The basal joint allows for the greatest freedom of motion in the hand. It is responsible
for placing the thumb in innumerable positions and its stability allows for a fine and strong
pinch.
1
The basal joint is the second most commonly involved site of osteoarthritis after
the distal interphalangeal joint.
2
Nonetheless, its involvement causes far more significant
functional disability secondary to pain and weakness.
2
During the early stages of basal joint arthritis, steroid injections with splinting can
provide a reliable long-ter m relief.
3
Accuracy of needle placement has generated much
controversy in the literature regarding the need for image-guided location of the joint, and
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HAZANI ET AL
may depend on the experience of the practicing clinician.
4-7
In most cases, the palpable
radial and proximal edge of the base of the first metacarpal can be used as a reliable
landmark. Occasionally, a patient may present with a “thicker” wrist, which can be a
challenge to the inexperienced examining clinician. Finding the basal joint in these cases is
particularly difficult as the joint is nestled at the base of the anatomic snuffbox. Superficial
bony anatomic landmarks for the basal joint can facilitate a safer and more reliable approach
to the percutaneous treatment of this disease. In our online PubMed literature search, no
previous anatomic landmark studies for the basal joint were found. The purpose of this
study is to identify bony anatomic landmarks for basal joint injections and aid clinicians in
avoiding inadvertent injury to the surrounding structures of the radial wrist.
METHODS
The basal joint is nestled within the anatomic snuffbox at the radial aspect of the wrist. The
boundaries of the three-sided snuffbox are easily palpable by placing the thumb in a fully
abducted position. It is bounded on the palmar side by the tendons of the abductor pollicis
longus (APL) and extensor pollicis brevis (EPB), and dorsally by the tendon of the extensor
pollicis longus (EPL). The distal edge of the radial styloid forms the proximal border. The
apex of the schematic snuffbox isosceles triangle forms the distal border (Fig 1).
8
Figure 1. The basal joint within the anatomic snuffbox is bounded volarly by the tendons
of the abductor pollicis longus (APL) and extensor pollicis brevis (EPB), and dorsally by
the tendon of the extensor pollicis longus (EPL).
Twenty fresh cadaveric wrists were dissected with the aid of loupe magnification.
The distal edge of the radial styloid (RS) and the palpable dorsal aspect of the thumb
metacarpophalangeal (MCP) joint were used as bony anatomic landmarks for predicting
the location of the basal joint along a longitudinal vector. For consistent measurements from
the basal joint to its anatomic landmarks, the wrist and thumb were placed in the following
position. The wrist was at 30
◦
of extension with no radial or ulnar deviation. The thumb was
at a rest position situated in a plane at about a 60
◦
angle to that of the palm and its palmar
surface was facing ulnarly. The metacarpophalangeal (MCP) joint was at 30
◦
of flexion
and the interphalangeal (IP) joint was at 45
◦
of flexion. All structures were then aligned
along the longitudinal axis of radial wrist. A longitudinal incision was created, extending
from the radial aspect of the distal forearm to the midline of the thumb dorsal aspect of
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the IP joint. Skin and subcutaneous dissection facilitated exposure of the snuffbox borders,
the basal joint, the superficial branch of the radial nerve (SBRN), and the radial artery
(Fig 2). Measurements of the distance from the basal joint to our anatomic landmarks
(mean ± standard deviation), the course of the SBRN and location radial artery within the
snuffbox were recorded.
Figure 2. A photo demonstrating one cadaveric specimen f ollowing dissection of the radial
wrist, depicting the boundaries of the anatomic snuffbox, the basal joint, and its bony
anatomic landmarks.
∗
indicates basal joint space; APL, Abductor pollicis longus; EPB,
extensor pollicis brevis; EPL, extensor pollicis longus; MCPJ, metacarpophalangeal joint;
RA, radial artery; RS, wire placed at the distal edge of the radial styloid; SBRN, superficial
branch of the radial nerve.
RESULTS
The basal joint of the thumb is located 2.44 ± 0.34 cm distal to the distal edge of the RS,
and 4.47 ± 0.29 cm proximal to the MCP joint (Fig 3). At the level of the basal joint space,
the radial artery is found 0.76 ± 0.12 cm dorsal to the EPB tendon. The first branch of the
SBRN is volar to the APL tendon in 84% of the specimens and coursing over the APL
tendon in 16%. In all of the specimens, the second branch of the SBRN and its smaller
contributions, course over the distal aspect of the snuffbox—away from the basal joint
space.
DISCUSSION
Intra-articular corticosteroid injections have been used since the 1950s to alleviate pain and
swelling in arthritic joints.
9
In a prospective study of 30 patients, Day et al
3
demonstrated
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HAZANI ET AL
that steroid injection with splinting provided reliable long-term relief in thumbs with Eaton
stage 1 disease. All of the injections were administered by the senior hand surgeons and
without the aid of fluoroscopy. It is important to recognize that the method of injection can
vary significantly and may depend on the clinician’s level of training. Some authors advocate
the use of fluoroscopy or ultrasound as a guide for proper intra-articular needle placement.
Pollard et al
6
reported a 100% rate of intra-articular accuracy with fluoroscopy-guided
injections as compared with 82% in the traditional “blind” group. In an ultrasound-guided
cadaveric study, injections to the trapeziometacarpal joint were successful in 94% of the
specimens.
5
Figure 3. The distal edge of the radial styloid and the palpable dorsal metacarpopha-
langeal (MCP) joint as bony anatomic landmarks for predicting the location of the basal
joint along a longitudinal vector. The basal joint is approximately 2.4 cm distal to the
radial styloid and 4.5 cm proximal to the MCP joint.
Advocates of the t raditional “blind” injection technique (one that does not rely on
ultrasound or fluoroscopy) claim that the use of anatomic landmarks is a reliable method
and probably obviates the need for radiologic guidance.
7
No specific landmarks were
discussed in their study. In this clinical study of 32 symptomatic patients, ultrasound
evidence of intra-articular injection was demonstrated in all patients.
7
Mandl et al
7
suggest
that contrasting findings with regard to the practice of “blind” injections in the office may
require an experienced clinician.
As an adjunct to clinical experience, we suggest the use of the RS and the MCP joint
of the thumb as reliable superficial anatomic landmarks for the basal joint. Soft tissue
landmarks can be difficult to identify in “thicker” wrists and possibly change with motion.
Therefore, the use of easily palpable bony landmarks such as the RS and MCP joint is likely
to be superior to other structures when palpating the radial wrist structures.
In addition to locating the basal joint at the radial wrist, predicting the course of
neurovascular structures traversing the anatomical snuffbox is imperative. Although there
are no reports of injured SBRN and radial artery for basal joint injections, it is necessary to
recognize the location of such structures at the level of the basal joint. Inadvertent injury to
the SBRN can cause pain, numbness, and dysesthesias. Injury to the radial artery may result
in bleeding or a false aneurysm.
10
This jeopardy is hypothetical in view of the fact that
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ePlasty VOLUME 12
there have been no previously reported cases. We relate to the results of Steinberg et al
10
regarding a safe zone within the proximal anatomic snuffbox and propose an additional
window of safety at the level of the basal joint.
Using our longitudinal measurements from the radial styloid and the dorsal aspect of
the thumb MCP joint, a needle can safely be inser ted immediately dorsal to the EPB tendon.
In this location, it is less likely to injure the radial artery as it courses approximately 7 mm
dorsal to the EPB tendon. In addition, the first branch of the SBRN is safely located volar
to the EPB tendon. While needle placement immediately dorsal to the APL tendon is safe,
the EPB tendon is the most dorsal structure of the two tendons, which is easier to identify
within the boundaries of the snuffbox (Fig 2). Longitudinal traction on the thumb will widen
the basal joint space distal to the radial artery and avoid puncture of the traversing artery.
We recommend caution with any needle advancement causing sharp pain, numbness, or
tingling—indicating injury to the first branch due to an anomalous location or to cutaneous
nerves branching off of the second branch of the SBRN. Although not encountered in our
dissections, the lateral cutaneous nerve of the forearm may also innervate the radial aspect
of the thumb in an anomalous distribution.
11
In conclusion, anatomic landmarks for the basal joint can facilitate a safe and reliable
approach to the percutaneous treatment of basal joint arthritis. The basal joint is approxi-
mately 2.4 cm distal to t he RS and 4.5 cm proximal to the MCP joint. Placement of a needle
immediately dorsal to the EPB tendon while applying longitudinal traction on the thumb
is less likely to cause damage to the radial artery and the superficial branch of the radial
nerve.
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