Introduction: Sock application is a daily task that can pose a dislocation risk to implanted hips. The aim of this study was to measure hip flexion and rotation using three seated techniques of sock application. Namely:- 1. The leg crossed in a “figure of four” technique, 2. The lean forward technique, and 3. using a specialised sock applicator (Foxy Sock Aid).

Methods: The movement of 32 hips in 16 healthy male volunteers, aged 20–43, were assessed as socks were applied using the 3 techniques listed above. Hip flexion and axial rotation were measured with a “Polhemus Fastrak” magnetic tracking system. Data was recorded from magnetic sensors attached around the subjects femur and Iliac Spine. The sensors measurement accuracy was 0.15 degrees.

Results: All measurements started with the subjects sitting with their hips in approximately 90 degrees of flexion. The mean (SD) additional flexion required for each of the 3 techniques were:- Cross leg = 57.2⁰ (13.7), Lean forward = 51.3⁰ (17.7), and Sock applicator = 11.2⁰ (7.2). Hence the sock applicator required 40.1 degrees less flexion (P< < 0.001) than the lean forward technique. The lean forward technique required 5.9 degrees less flexion (P=0.007) than the cross legged technique.

The mean (SD) peak rotations for each of the 3 techniques were:- Cross leg = 35.1⁰ (9.8) external, Lean forward = 0.1⁰ (3.8) internal, and Sock applicator = 0.8⁰ (4.0) internal.

Discussion: The sock applicator, when used correctly, requires very little hip flexion. When patients stop using the sock applicator, they should be encourage to use the lean forward technique, as this requires little axial rotation.

Introduction

Osteochondritis dissecans (OCD) is a localised disorder of subchondral bone and the overlying articular cartilage. The most commonly used classification systems involve arthroscopy and MRI.

Aim

To investigate the correlation between arthroscopic and MR findings in patients with OCD of the talus.

Methods

16 ankles in 14 patients with radiographically proven OCD were reviewed. Nine were male and five female. Mean age was 35yrs (range 18–64yrs). The lesions were staged independently using the Guhl1 arthroscopic and Dipaola2 MR classification systems.

Results

Arthroscopically there were eight stable and eight unstable lesions. Of the eight stable lesions, MRI staged five as stable and three as unstable. Of the eight unstable lesions, MRI staged six as unstable and two as stable. This gives a sensitivity of diagnosing unstable lesions as 0.75, with a specificity of 0.63.

Conclusions

This small study demonstrates that MR scans may have some limitations in classifying OCD lesions of the talus. Possible explanations are discussed. We propose that MRI findings, of OCD of the talus, should not be taken in isolation, but correlated with the patients symptoms and signs to avoid unnecessary arthroscopy.

Purpose: Femoral roll causes the sagittal plane axis of the knee to move posteriorly and anteriorly with flexion and extension. The aim of this study was to measure this movement with a surface marker imaging system and assess the effect of Anterior Cruciate Ligament (ACL) deficiency on the Sagittal Axis Pathway (SAP) of the knee.

Method: Twelve normal and fourteen unilateral ACL deficient subjects were video recorded as they flexed and extended their knees in the sagittal plane. Video stills were captured at 150 intervals from 90o flexion to full extension. An imaging system was then used to extract the co-ordinates of leg markers from each still. These co-ordinates were then processed to derive the SAP for each knee throughout its range of movement.

Results: Pooling all the normal results together (24 bilateral + 14 unilateral = 38 knees), it was found that a 90° knee extension caused the sagittal axis to displace anteriorly with a mean value of 20.0mm (SD=7.8). In comparison the 14 ACL deficient knees were found to have a mean anterior displacement of 9.2 mm (SD=8.0). A bilateral comparison of the 12 pairs of normal knees showed no significant difference between left and right sides (paired-t, p=0.99). However, a bilateral comparison of the 14 unilateral ACL deficient patients showed a significant difference between normal and injured sides (paired-t, p=0.00025). In this group, the normal knees axis at full extension had a mean location 28.9mm (SD=8.8) posterior to the front of the tibial plateau. In comparison the injured knees axis has a mean location 37.8 mm (SD=8.5) posterior to the front of the tibial plateau. Again, this was highly significant (paired-t, p=0.0001).

Conclusion: These results indicate that normal knees have a mean forward roll of 20 mm for a 90° knee extension. In comparison ACL deficient knees have a reduced roll of 9.2 mm which occurs at the rear of the joint. This reduction in roll is consistent with the abnormal ligament biomechanics.