Four-dimensional computed tomography (4DCT: three dimensional + time) allows to measure individual bone position over a period of time usually during motion. This method has been found useful in studying the joints around the wrist as dynamic instabilities are difficult to detect during static CT scans while they can be diagnosed using a 4DCT scan [1]–[3]. For the foot, the PedCAT system (Curvebeam, Warrington, USA) has been developed to study the foot bones under full weight bearing, however its use is limited to static images. On the contrary, dynamic measurements of the foot kinematics using skin markers can only describe motion of foot segments and not of individual bones. However, the ability to measure individual bone kinematics during gait is of paramount importance as such detailed information could be used to detect instabilities, to evaluate the effect of joint degeneration, to help in pre-operative planning as well as in post-operative evaluation.

The overall gait kinematics of two healthy volunteers were measured in a gait analysis lab (Movement Analysis Lab Leuven, Belgium) using a detailed foot-model (Oxford foot model, [4]). The measured plantar-dorsiflexion and in-eversion were used to manipulate their foot during a 4D CT acquisition. The manipulation was performed through a custom made foot manipulator that controls the position and orientation of the foot bed according to input kinematics. The manipulator was compatible with the 4D CT Scanner (Aquilion One, Toshiba, JP), and a sequence of CT scans (37 CT scans over 10 seconds with 320 slices for each scan and a slice thickness of 0.5 mm) was generated over the duration of the simulation. The position of the individual bones was determined using an automatic segmentation routine after which the kinematics of individual foot bones were calculated. To do so, three landmarks were tracked on each bone over time allowing to construct bone-specific coordinate frames. The motion of the foot bed was compared against the calculated kinematics of the tibia-calcaneus as the angles between these two bones are captured with skin markers.

There is high repeatability between the imposed plantar/dorsiflexion and inversion/eversion and the calculated. Although the internal/external rotation was not imposed, the calculated kinematics follow the same pattern as the measured in the gait-analysis lab. Based on the validation of the tibia-calcaneus, the kinematics were also calculated between four other joints: tibia-talar, talar-calcaneus, calcaneus-cuboid and talar-navicular. Repeatable measurements of individual foot bone motion were obtained for both volunteers.

The use of 4D CT-scanning in combination with a foot manipulator can provide more detailed information than skin marker-based gait-analysis e.g. for the study of the the tibia-talar joint. In the future, the foot manipulator will be tested for its sensitivity for specific pathologies (e.g. metatarsal coalition) and will be further developed to better resemble a real-life stance phase of gait (i.e. to include isolated heel contact and toe off).

Introduction: In spite of the common occurrence of hallux valgus deformity and the multiple corrective procedures that have been proposed, only few studies have been published about the anatomy of this joint. None of these studies mention the existence of a meniscal structure in the first MTP joint. The fact that this structure is often seen during bunion surgery evoked this study.

Material and methods: A hunderd and two human cadaveric feet were dissected primarly to study the anatomy of the first metatarsophalangeal (MTP) joint. The anatomical findings on the specimens were correlated with clinical findings on 100 consecutive hallux valgus procedures. Particular attention was paid to the localization and histology of this meniscal structure. Based on this study, possible associations between the presence of this structure and the pathophysiology of the hallux valgus deformity and chondral lesions are proposed.

Results: A meniscal structure was present in 19 percent of the cadavers. A striking negative correlation is found between the presence of a meniscus and the extent of chondral lesions (P < 0.05). The presence of the meniscus was higher in cadavers with hallux valgus deformity (33%), however no significant correlation is found between the occurrence of hallux valgus deformity and the presence of this meniscus (P = 0.2). In our clinical study this meniscus was seen in 40% and was particularly high in younger patients with mild -painful-bunions.

Conclusions: The presence of this meniscal structure seems to stabilize the MTP joint, preventing hallux valgus (or rotational ) deformities. Once the rotational deformity increases the meniscus tears becomes painful and slips into the joint. In the more advanced hallux valgus deformity this meniscus plays little function and seems to disappear, leading to arthrosis.

Objective: to investigate the long-term clinical and radiological outcome of talar avascular necrosis after treatment by a patellar-tendon bearing brace (PTB), and if parameters predictive for a positive or negative outcome could be identified.

Patients and methods: 21 patients were reviewed retrospectively, 10 had a non-traumatic origin and 11 a traumatic one (groups comparable to gender and age). Mean follow-up was 5,5 and 6,3 years, respectively; mean use of the PTB was 17,2 and 14,8 months. Clinical outcome was assessed by the Mazur scale and the Kitaoka score for function, and a VAS for pain and subjective satisfaction; radiological outcome by the Ficat & Arlet classification and by the Kellgren scale. Clinical parameters were analysed for their positive or negative predictive value on outcome.

Results: A very early pain control was achieved in both groups (2.1 versus 1.9 weeks). On both the Mazur scale and the Kitaoka score the non-traumatic group scored lower as the posttraumatic group (66,3 versus 77,6 and 76.1 versus 78.1). Both VAS were similar in both groups: 3,1 and 3,6 for pain and 6,8 and 7,1 for satisfaction. The need for analgesic medication was slightly higher in the non-traumatic group: 4 versus 3 patients. Radiologically both groups showed a similar outcome with both evaluation systems. Older age, delay in treatment, corticosteroids, alcohol, hyperlipidaemia and female gender were identified as negative predictive parameters.

Conclusions: A PTB is an efficient treatment for talar avascular necrosis of both non-traumatic and traumatic origin. Clinical outcome is better in the posttraumatic group, although radiological outcome is comparable. Only negative predictive parameters could be identified.

Aims: The aim of this study was to clinically and radiologically assess the outcome of the HINTEGRA total ankle prosthesis. The HINTEGRA implant is an uncemented (hydroxyapatite-coated) prosthesis of anatomical, multiaxial, congruent and unconstrained design. Methods: All of the consecutive 19 patients who got a HINTEGRA total ankle replacement between June 2000 and June 2001 were assessed. Pre- and postoperative functional and clinical assessment was carried out using a questionnaire, range of motion and Kofoed score which assigns 50 points for pain, 30 for function and 20 for range of motion, giving a maximum of 100. Results: 19 patients (6 female, 13 male), mean age 55,3 years (21–82 years), mean followup 14,3 months (10–21 months). The general satisfaction at subjective evaluation was 27,3/100 preoperatively and 80/100 postoperatively. The mean Kofoed score was 26,3 preoperatively and 78,4 postoperatively. The mean range of motion from maximum extension to maximum ßexion was 16,4¡ preoperatively and 29,1¡ postoperatively. None of the replacements showed any progressive radiolucency, although in 3 patients there was a small area (< 2mm) of radiolucency between the tibial component and bone. Conclusions: Our results with the uncemented HINTEGRA, anatomical shaped threecomponent total ankle replacement, are satisfactory and encouraging. Total ankle replacement is a useful alternative to ankle arthrodesis with pain relief and preservation of joint motion and stability.