The anatomy of the mortise of the Lisfranc joint between the medial and lateral cuneiforms was studied in detail, with particular reference to features which may predispose to injury. In 33 consecutive patients with Lisfranc injuries we measured, from conventional radiographs, the medial depth of the mortise (A), the lateral depth (B) and the length of the second metatarsal (C). MRI was used to confirm the diagnosis. We calculated the mean depth of the mortise (A+B)/2, and the variables of the lever arm as follows: C/A, C/B and C/mean depth. The data were compared with those obtained in 84 cadaver feet with no previous injury of the Lisfranc joint complex. Statistical analysis used Student’s two-sample The mean medial depth of the mortise was found to be significantly less in patients with Lisfranc injuries than in the control group. Stepwise logistic regression identified only this depth as a significant risk factor for Lisfranc injuries. The odds of being in the injury group is 0.52 (approximately half) that of being a control if the medial depth of the mortise is increased by 1 mm, after adjusting for the other variables in the model. Our findings show that the mortise in patients with injuries to the Lisfranc joint is shallower than in the control group and the shallower it is the greater is the risk of injury.
In a series of 1160 arthroscopies we found 16 meniscal cysts; 12 involved the lateral joint line and two the medial, and two were intra-articular. In all but two cases, arthroscopy showed meniscal tears. We recommend arthroscopy of all cases to correct the meniscal lesion, and to evacuate the cyst into the joint by opening the joint capsule. This was successful in 12 cases, with no recurrence after an average follow-up of 18 months. Only two patients with no meniscal lesion on arthroscopy required an additional external incision for cyst removal.
