Intertarsal ligaments: high resolution MRI and anatomic correlation

The anterolateral ligament of the knee and the lateral meniscotibial ligament - Anatomical phantom versus constant structure within the anterolateral complex

BACKGROUND

Concerning the ongoing controversy about the existence and nature of the anterolateral ligament (ALL) of the knee joint, we reinvestigated the formation of the anterolateral part of its fibrous capsule in anatomic specimens. Furthermore, we wanted to clarify if the lateral meniscus has established a constant anchoring to the lateral tibial condyle via a lateral meniscotibial ligament (lmtl).

METHODS

Forty paired embalmed lower extremities taken from 20 human body donors (15 men and five women) underwent exact macroscopic dissection. For the detailed evaluation of the lmtl, additionally 12 specially dissected joint specimens were used. In two of these specimens, the lmtl underwent further histological examination.

RESULTS

In all specimens, the anterolateral part of the knee joint fibrous capsule was established by the iliotibial tract and the anterior arm of the aponeurosis of the biceps femoris muscle. According to their close connection and the fact that the anterolateral part of the fibrous capsule is exclusively assembled by these two aponeuroses, they do not leave any space for a distinct ALL connecting the lateral femoral epicondyle and the lateral tibial condyle. The constantly present lmtl was identified as a flat, rectangular bundle of collagen and also elastic fibers reinforcing the inner aspect of the fibrous capsule. Following an oblique direction, it connected the lateral face of the lateral meniscus with the superolateral margin of the lateral tibial condyle. The lmtl measured, on average, 17.1mm in longitudinal and 13mm in anteroposterior direction.

CONCLUSION

Our results show that there is no evidence for the existence of an ALL in human knee joints. It is represented either by the iliotibial tract or - most likely - by the anterior arm of the short head of the biceps femoris muscle. On the other hand, the lmtl was found to be a constantly present structure.

Ligaments of the Lisfranc joint in MRI: 3D-SPACE (sampling perfection with application optimized contrasts using different flip-angle evolution) sequence compared to three orthogonal proton-density fat-saturated (PD fs) sequences

PURPOSE

To compare the detection rate and visibility of the ligaments in the Lisfranc joint with a single 3D (-SPACE) MR sequence and three orthogonal PD fat-saturated sequences.

MATERIALS AND METHODS

Thirty-one asymptomatic feet and 15 patients with posttraumatic pain in the Lisfranc joint were evaluated with a 3D-SPACE-sequence (0.5 mm section thickness, acquisition time 10:22 min, secondary reformations) and three orthogonal PD fs sequences (2 mm section thickness, 9:20 min). The Lisfranc-ligament, the dorsal and plantar tarsometatarsal ligaments (TMT), the dorsal, interosseous, and plantar intermetatarsal ligaments (IMT) (24 ligaments for each foot) were assessed.

RESULTS

In asymptomatic feet, 692 ligaments were detected with the SPACE sequence, thereof 90.6 % exhibited normal signal, and most (96.9 %) were completely visible on one single image. A total of 659 ligaments were detected with the PD fs sequence, thereof 86.6 % yielded normal signal, and 28.5 % were completely visible on one single image. In patients, 327 ligaments were detected with SPACE, thereof 50.6 % appeared completely visible with high signal. On PD fs, 308 ligaments were detected, 42.2 % of the ligaments had high signals.

CONCLUSIONS

The ligaments of the Lisfranc joint are better detected with a single 3D-SPACE sequence and secondary reformations than with three orthogonal PD fs sequences.

Quantifying ligament cross-sectional area via molding and casting

Ligament cross-sectional areas are difficult to determine because ligaments are soft tissues, can be very short, and may be deep between bones. However, accurate measurements are required for determining the material properties from mechanical testing. Many techniques have been tried, but most suffer from one or more of the following: tissue deformation, tissue destruction, submersion of the tissue in saline, the need for a clear line of site, the inability to detect concavities, or poorly defined cross-sectional perimeters. Molding techniques have been used but have been limited by material issues such as large shrinkages, the inability to capture small detail, or the need to destroy the mold to remove the ligament. In this study, we developed a suitable molding and casting technique without systematic shrinkage that could accurately capture the odd shapes and concavities of foot and ankle ligaments with small clearances between bones. Metal rods of 1.62 mm, 2.90 mm, 3.18 mm, and 9.43 mm in diameter were molded using a liquid silicone rubber and cast with polyurethane. The effect of cutting the mold for specimen removal was investigated, and similar tests were done in the presence of saline. Image analysis software was used to determine the cross-sectional areas from photographs of cut castings. In addition, four different ligaments (each n=5) were dissected, molded, and cast. The cross-sectional area of each ligament was obtained. The maximum difference in area for all cases was 2.00%, with the majority being less than 1.00%; the overall root mean square error was 0.334 mm(2) or 0.97%. Neither cutting the mold for specimen removal nor the presence of saline affected the cross-sectional area of the castings. Various representative foot and ankle ligaments were also molded and cast to capture fine detail of the ligament midsubstance including concavities. We have developed a method of measuring ligament cross-sectional area that can overcome the limitations of other area measurement techniques, while accounting for the complicated anatomy of the bones of the foot. The method was validated using metal rods of known diameters, and a representative set foot ligaments (N=20) was analyzed.

Lisfranc joint ligamentous complex: MRI with anatomic correlation in cadavers

OBJECTIVE

The aim of our study was to clarify the ligamentous anatomy of the Lisfranc joint complex and show the diagnostic capability of MRI in the assessment of the Lisfranc joint complex with detailed anatomic correlation in cadavers.

MATERIALS AND METHODS

Ten fresh cadaveric feet were studied with high-spatial-resolution MRI before and after the intraarticular injection of a gadopentetate dimeglumine solution. MR images were evaluated by two readers in consensus, with emphasis on the visibility of the ligamentous structures and their appearance. Readers also measured the dimensions (length, width, and thickness) of the Lisfranc ligament and of the first plantar tarsometatarsal ligament, or plantar Lisfranc ligament. For anatomic analysis, nine cadaveric specimens were sectioned in 3-mm-thick slices in the same planes used during MRI. One additional foot specimen was used for dissection.

RESULTS

In all 10 cadaveric specimens we were able to identify and characterize with MRI the different ligamentous elements that contribute to the overall stability of the Lisfranc joint complex.

CONCLUSION

By clearly defining the normal ligaments that contribute to the stability of the Lisfranc joint, MRI allows a more precise and correct diagnosis of the origin of the Lisfranc joint instability, perhaps permitting a more specific surgical management. MRI also allows a better understanding of the normal imaging anatomy of the different ligamentous components of the Lisfranc joint, mainly of the Lisfranc and plantar Lisfranc ligaments.