Background/Purpose:
The calcaneonavicular or spring ligament (SL) is a group of 3 stout non-elastic fibrocartilaginous bands in the medial mid-foot that is important in maintaining the long arch of the foot & is an integral component of the articular socket for the head of the talus. In its entirety this socket is referred to as the “acetabulum pedis” of the talocalcaneonavicular(TCN) joint & is analogous to the acetabulum of the hip allowing a wide range of motion: gliding, rotation, inversion & eversion. There is also a synovial gliding layer externally where it effaces the overlying posterior tibialis tendon (PTT) sheath. The SL provides a “window” (SLW) to assess synovial disease with direct visualization of articulating surfaces & a prominent tendon sheath. High frequency musculoskeletal ultrasound (MSUS) visualization of the SL has been described in both normal subjects & patients with non-rheumatic mid-foot disorders. This study aims to evaluate the joint-ligament complex in cadaveric specimens & to utilize MSUS to view the TCN joint & measure the ligament in controls & rheumatoid arthritis (RA) patients.
Methods:
MSUS (GE P6 machine, 5-16MHz transducer) was performed on 4 fresh cadaveric feet. The SLW was obtained in long-axis over the articulating cartilaginous surface of the medial aspect of the head of the talus by fixing the distal end of the vertically oriented probe over the sustentaculum tali & rotating the proximal end of the probe counterclockwise from vertical until the medial aspect of the talar head was visualized. The transverse diameter of the SL at the midpoint of the interface of the talar cartilage & the articulating portion of the ligament was measured. This axis of the probe was marked on the cadaver foot surface & the refrozen specimen was cut with a band saw along this axis. Specimens were examined & measured with calipers, by two physicians blinded to each other’s findings.
Healthy controls & RA patients underwent MSUS while supine with the ankle in a neutral position. The SLW was visualized as described above. Thus, the view obtained included the sustentaculum tali, the PTT, the sharp bony acoustic medial border of the talus with its distinct anechoic cartilage surface & the overlying hyperechoic fibrillar ligament. The spring ligament diameter was measured.
Results: The medial aspect of the TCN joint was easily identified with MSUS in cadaver, healthy & rheumatoid feet through the SLW using the technique described above & offered a unique view into the interior joint. The mean transverse diameter of the cadaveric ligament was 0.55cm (Range = 0.475 – 0.625cm) by MSUS & 0.58cm (Range = 0.47 – 0.7cm) by caliper anatomic measurement (n = 4). There was no significant difference between MSUS & anatomic measurement (p = 0.767). In RA patients (n = 28) mean transverse diameter by MSUS was 0.384cm (Range = 0.21 – 0.6cm) & in healthy controls (n = 10) it was 0.39cm (Range = 0.35 – 0.47cm), with no significant difference between groups (p = 0.392).
Conclusion: The SLW should be considered as part of the routine MSUS examination in rheumatic diseases affecting the foot & offers a unique intra-articular perspective.
Disclosure:
J. Kitchen,
None;
I. Moller,
None;
M. Miguel-Perez,
None;
D. A. Bong,
None.
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-spring-ligament-window-a-unique-sonoanatomic-view-into-a-complex-rheumatoid-joint/