Background

Successful use of bioabsorbable anchors for capsulolabral and rotator cuff repair is well documented. The bioknotless anchor (DePuy mitek) has demonstrated reliable fixation of these pathologies. However, this poly (L-lactide) polymer has recently demonstrated some similar complications to those documented for the earlier polyglycolic acid implants; namely synovitis and chondral damage with osteolysis. We report three cases with osteolysis and chondral damage associated with bioknotless anchors.

Patients overestimate pain following hip and knee replacement.

Ninety two patients awaiting hip or knee replacement were asked at their pre-operative assessment to estimate the level of pain they expected following their surgery on a 10cm visual analogue scale. Note was made of their age, gender, previous surgeries, Amsterdam anxiety score as regards the anaesthetic and surgery and an information score relating to their anaesthetic and surgery. Seventy nine patients had pain scores collected on a daily basis post surgery.

Mean (std dev) age of the group was 68 (11) years and with a female to male ratio of 1.57. Females were significantly more anxious about the surgery than males (t-test, p< 0.007). Patients were more anxious about the anaesthetic and the surgery with hip replacement compared to knee replacement although this did not reach significance (t-test p=0.07). The mean (std dev) pain score pre-operatively was 7.5 (1.6). The mean (std dev) pain score expected was 7.0 (2.2) on the first post operative day and 4.3 (2.2) on the sixth post operative day. Forty four per cent of patients expected to have pain greater than their arthritis pain on the day following surgery.

The level of pain experienced post-operatively was significantly lower than expected. Mean (std dev) pain score was 5.1 (2.7) on day 1 post op and 3.3 (2.4) on day 6 (t-test, p< 0.05 for both). There was no correlation between age, gender, number of previous surgeries, anxiety or information scores and the expected level of pain.

The majority of patients, whatever their age, gender or level of anxiety over estimate their level of post-operative pain after joint replacement. Studies are needed to assess whether educating patients about pain post surgery will be of benefit, particularly in their early rehabilitation.

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.