Higher contact pressure of the lateral tibiofemoral joint in lateral extra-articular tenodesis with tensioned graft in external rotation than in neutral rotation: a biomechanical study

OBJECTIVE

To determine the mean contact pressure, peak contact pressure, and mean contact area of the lateral tibiofemoral joint in lateral extra-articular tenodesis (LET) with tension on the graft in tibial neutral and external rotation.

METHODS

A total of eight Thiel's embalmed cadaveric knees were prepared and divided into two groups (4 knees in each group): the LET-NR group (lateral extra-articular tenodesis tension in neutral rotation) and (2) the LET-ER group (lateral extra-articular tenodesis tension in external rotation). Each knee was prepared according to the corresponding technique. A hydraulic testing system (E10000, Instron) simulates an axial load of 735 N for 10 seconds in each group.

RESULTS

The LET-ER group exhibited a statistically significant higher peak contact pressure compared to the LET-NR group. The peak contact pressure values in the LET-NR and LET-ER groups were 702.3 ± 233.9 kPa and 1,235.5 ± 171.4 kPa, respectively (p = 0.010, 95% CI, -888.0--178.5). The mean contact pressure values in the LET-NR and LET-ER groups were 344.9 ± 69.0 kPa and 355.3 ± 34.9 kPa, respectively (p = 0.796, 95% CI, -105.1-84.2). The mean contact area values in the LET-NR and LET-ER groups were 36.8 ± 3.1 mm2 and 33.3 ± 6.4 mm2, respectively (p = 0.360, 95% CI, -5.2-12.2).

CONCLUSIONS

The peak contact pressure of the lateral tibiofemoral joint is greater in LET when the graft is tensioned in external rotation than in neutral rotation. However, no statistically significant difference in the mean contact pressure or the mean contact area was observed between the two groups.

LEVEL OF EVIDENCE

III.

The N-brace trial: Does arm position during immobilisation of proximal humerus fractures influence outcome - A preliminary study

Background

Traditional initial management of proximal humerus fractures (PHF) involves arm immobilisation in a simple sling (SS) in an internally rotated position. We believe this risks fracture displacement and imbalance of soft tissues, encouraging malunion and stiffness. A neutral-rotation brace (NRB) maintains an arm position which may prevent this, leading to quicker and superior recovery.

Methods

We randomised patients with two- to four-part PHF into 4 weeks of immobilisation with either a SS or NRB, independent of surgery. Range of motion (ROM), subjective shoulder value (SSV), DASH, Constant-Murley (CMS) and Oxford Shoulder (OSS) scores were assessed at 6-weeks, 3-months and 1-year post-injury.

Results

The SS group included 11 patients vs 9 in the NRB group. At final follow-up, the SS and NRB groups had mean DASH scores of 42 vs 35, OSS 42 vs 46, CMS 71 vs 86, SSV 84% vs 92%, respectively. ROM was superior with the NRB (elevation 159°, ER 47° and IR score 8 vs 140°, 37° and 7 with SS).

Conclusions

Despite being a small series, our results demonstrate a trend towards NRB providing better outcomes. This feasibility study supports the need for a larger multi-centre randomised controlled trial comparing these immobilisation methods for PHF.

Positioning of longest axis of the radial head in neutral forearm rotation

INTRODUCTION

The radial head has an ellipsoid shape so that a longest and a shortest axis can be defined. The aim of this study is to evaluate the position of the longest axis of the radial head (LARH) in relation to proximal radioulnar joint (PRUJ) and to the forearm in neutral position using 3D computed tomography (CT).

MATERIALS AND METHODS

3D CT reconstructions of the distal humerus, the radius and the ulna of 27 healthy volunteers (average age 27.65 ± 9.25; 24 males, 3 females) were created. First an evaluation of the elliptic form of the radial head and the location of its longest axis was performed. Next, three planes were defined: the PRUJ plane, the forearm plane and a neutral plane. Based on the angle between the forearm plane and the neutral plane, the rotation of the scanned forearm was measured. Taking this rotation into account, the position of the LARH compared to PRUJ plane and forearm plane in neutral position is recalculated.

RESULTS

The shape of the radial head is determined to be non-circular based on this study population (p < .001). In neutral position, the angle between the LARH and the forearm plane is 5.28° (SD: 15.09) and between the LARH and the PRUJ is 33.46° (SD: 13.91).

CONCLUSIONS

The position of the LARH is found to be approximately perpendicular to the forearm plane when the forearm is in neutral position and perpendicular to the PRUJ plane when the forearm is on average in 30° of pronation.

Immobilization in neutral rotation for a glenohumeral dislocation using a sling and splint

The purpose of this manuscript is to provide an expedient means of immobilizing a glenohumeral dislocation in neutral rotation. This technique for post-reduction immobilization of a glenohumeral dislocation is inexpensive and easy to fabricate. Anterior glenohumeral dislocations often involve an avulsion of the labrum from the glenoid rim. In contrast to immobilization in internal rotation, positioning the shoulder in 0-45° of external rotation approximates the labrum and glenoid rim. It is hypothesized that placing the shoulder in a more externally rotated position could allow for better healing and increased joint stability. This technique places the shoulder in neutral rotation, because 45° of external rotation is awkward and may interfere with certain activities of daily living. Structural aluminum malleable (SAM) splints are used as an alternative to a bolster sling. The SAM splints are lightweight, simply shaped, and easily stored.