The treatment of posterior malleolar fractures is developing. Mason and Molloy (Foot Ankle Int. 2017 Nov;38(11):1229-1235) identified only 49% of posterior malleolar rotational pilon type fractures had syndesmotic instabilities. This was against general thinking that fixation of such a fragment would stabilize the syndesmosis. We examined 10 cadaveric lower limbs that had been preserved for dissection at the Human Anatomy and Resource Centre at Liverpool University in a solution of formaldehyde. The lower limbs were carefully dissected to identify the ligamentous structures on the posterior aspect of the ankle. To compare the size to the rotational pilon posterior malleolar fracture (Mason and Molloy 2A and B) we gathered information from our posterior malleolar fracture database. 3D CT imaging was analysed using our department PACS system.Introduction
Methods
Shoulder motion results from a complex interaction between the interconnected segments of the shoulder girdle. Coordination is necessary for normal shoulder function and is achieved by synchronous and coordinated muscle activity. During rotational movements, the humeral head translates on the glenoid fossa in the anterior-posterior plane. Tension developed by the rotator cuff muscles compresses the humeral head into the glenoid fossa. This acts to limit the degree of humeral head translation and establishes a stable GH fulcrum about which the arm can be moved. Previous studies have been limited by the use of contrived movement protocols and muscular coordination has not been previously considered with regard to shoulder rotation movements. This study reports the activation profile and coordination of 13 muscles and 4 muscle groups during a dynamic rotational movement task based on activities of daily living. Eleven healthy male volunteers were included in the study. Electromyography (EMG) was recorded from 13 muscles (10 surface and 3 fine-wire intramuscular electrodes) using a wireless EMG system. EMG was recorded during a movement task in which the shoulder was consecutively rotated internally (phase 1) and externally (phase 2) with a weight in the hand. Muscle group data was calculated by ensemble averaging the activity of the individual component muscles. Mean signal amplitude and Pearson correlation coefficient (PCC) analysed muscle activation and coordination, respectively.Introduction
Methods
The study objective was to assess if the mechanical properties of Polylactic Acid (PLA) bio-absorbable suture anchors vary with temperature? Bio-absorbable suture anchors may offer advantages over metal anchors. However, their performance at body temperature has been questioned in recent literature (Meyer et al). In particular, constant tension at body temperature caused early failure at the anchor eyelet. Using a previously validated mechanical jig, 15 standard locked sliding arthroscopic knots (Duncan Loop + three alternate hitches) were tied by the senior author using PAN-ALOK anchors (DEPUY MITEK, Edinburgh, UK) and ETHIBOND sutures (ETHICON) and placed under a standard constant tensile load reproducing the action of the surgically repaired rotator cuff. All anchors were loaded for at least five days to match previous studies. Eight were incubated at a constant 37°C and six were kept at room temperature. The elongation of the suture knot/anchor construct was assessed by a rheostat within the mechanical jig. Sample unused, room temperature and body temperature anchors were blindly analysed using plane polarized light microscopy with a graticule to assess deformation, concentrating on the eyelet region. Mean elongation of body temperature anchors = 0.461mm (0.159 – 0.952) Mean elongation of room temperature anchors = 0.278mm (0.159 – 0.793) Unpaired t-test: p=0.24 Microscopic analysis of the anchor material showed no difference in structural deformation in the three anchors. Our model suggests no significant increase in elongation at body temperature for this commonly used arthroscopic suture anchor / knot construct. This counters previous work. It gives us confidence to continue to use such devices.
Little is known about how arthroscopic knots behave in terms of reverse slippage and creep during the first few hours following a Bankart repair. We aimed to assess differences between knot types tied with a variety of suture materials when exposed to loading which might be expected during the first 12 hours following a repair. This study uses an apparatus to model the tensioning of a slipknot, the closing of a Bankart lesion and any reverse slippage occurring on removal of the tensioning force. Eight examples each of the Duncan loop and SMC knots were tied by an experienced surgeon using 4 different suture materials (PDS, Ethibond, Panacryl, Fibrewire). An arthroscopic knotting technique was used utilising a knot pusher. Each knot was locked with 3 half-hitches alternating direction and post each time. Any reverse slippage occurring during the tying process was recorded. Each knot was then left in situ for 12 hours under loads equivalent to a repaired Bankart lesion and any subsequent reverse slippage was recorded at the end of this period. After initial passing of the Duncan loop the sutures were ranked inversely to size of suture loop (resistance to slippage) in order Panacryl (5.08±0.15mm); Fibrewire (5.7±1.03mm); Ethibond (7.22±3.47mm) and PDS (8.2±5.16mm). After passing of locking hitches, they ranked Ethibond (5.13±0.24mm); PDS (5.15±0.09mm); Panacryl (5.17±0.13mm) and Fibrewire (5.66±0.5mm – significant p<
0.05). After 12 hrs, some evidence of reverse slippage was noted, Ethibond (5.23±0.27mm); PDS (5.27±0.13mm); Panacryl (5.3±0.16mm) and Fibrewire (5.66±0.5mm – significant p<
0.05). The SMC knot showed similar results. If a slip-knot back slips it can be tightened with the first locking hitch. After this further hitches do not tighten the knot further. Some slippage was noted during the first 12 hrs. Using arthroscopic techniques, Fibrewire performs less well than other materials.
