Hyponatraemia is a potentially preventable post-operative complication following hip arthroplasty. There is a paucity of literature reporting its incidence and guidelines for prevention - unlike AKI which has been prioritised to great success. Hyponatraemia is now rife in elective orthopaedics causing multiple symptoms that delay ambulation and increase the length of hospital stay. We aim to assess the incidence of hyponatraemia and AKI as a benchmark following elective primary total hip arthroplasty (THA), as well as identify patients most at risk in a high volume arthroplasty centre.

Between April 2018 and September 2018 all primary THA surgeries performed in one hospital were retrospectively reviewed. Pre-operative and 1 day post operative bloods were analysed. Patients included had normal pre-operative sodium.

A total of 221 patients underwent THA. The mean age was 73.6 and ASA 2.1. No patients had a recorded AKI, however 42% of patients had a new post operative hyponatraemia. Of the hyponatraemia cases, 75% were mild, 18% were moderate, and 7% were severe. There was correlation between increased age and increased severity of hyponatraemia. The mean age of patients with mild hyponatraemia was 72.1, moderate was 77.7, and severe was 78.8. An association between ASA and severity of hyponatraemia was noted. In patients who had an ASA of 4 and hyponatraemia, 66% were moderate or severe, ASA 3 was 25%, ASA 2 was 24% and ASA 1 was 0%. The patients who had severe hyponatraemia received on average 3.5L fluid input perioperatively.

Rates of post op hyponatraemia are significantly higher than AKI in primary THA. Severity of hyponatraemia increases with age and ASA. Due to its negative outcomes on recovery the high levels of hyponatraemia are worrying. We have identified which patient cohorts are more at risk and recommend more care should be taken in their perioperative fluid balance. It may be beneficial to consider successful AKI prevention and management campaigns and apply them to the prevention of hyponatraemia following hip arthroplasty.

Aims

Day-case arthroplasty is gaining popularity in Europe. We report outcomes from the first 12 months following implementation of a day-case pathway for unicompartmental knee arthroplasty (UKA) and total hip arthroplasty (THA) in an NHS hospital.

NICE technology appraisal guidance 157 suggests that the oral anticoagulation medication Dabigatran etexilate (Pradaxa®, Boehringer Ingelheim) can be used for the primary prevention of venous thromboembolic events (VTE's) in adult patients who have undergone elective total hip (THR) or knee replacement (TKR) surgery.

The NICE guidance and the Pradaxa® Summary of Product characteristics (SPC) report that 13.8% of patients receiving recommended doses of Dabigatran experience adverse bleeding events. In the manufacturer's pivotal clinical trials, wound secretion accounted for 4.9% of patients treated with Dabigatran as compared to 3.0% treated with Enoxaparin.

The aim of this audit was to assess the impact of Dabigatran on wound complications at a UK district general hospital and to quantify the effect on the postoperative discharge home support services provided by the award-winning South Warwickshire Accelerated Transfer Team (SWATT).

We report our experience of Dabigatran use at Warwick Hospital from March 2009 to March 2010.

Of the 788 lower limb arthroplasties performed, 681 patients (81.0%) were accepted for SWATT follow-up. Fifty-five (8.6%) of patients accepted by SWATT showed increased wound secretion for greater than 5 days. This included 12.7% of THR and 5.5% of TKR patients. Increased wound secretion resulted in 226 extra home visits by SWATT, at an extra cost of £23,104 (7.5% increase in SWATT budget).

Twenty-six of the 55 patients had positive microbial growth when wound secretions were swabbed. Five patients were admitted for management of wound infections. Incidentally, there were 2 reported cases of DVT and PE. These were not in the increased wound secretion patients.

In summary, Dabigatran at Warwick Hospital was associated with a higher than predicted incidence of surgical site morbidity, increased resource output and increased postoperative discharge costs. As a consequence, Dabigatran use has been reduced and other oral anticoagulants are being trialled.

NICE technology appraisal guidance 157 suggests that the oral anticoagulation medication Dabigatran etexilate can be used for the primary prevention of venous thromboembolic events (VTE's) in adult patients who have undergone elective total hip or knee replacement surgery.

The NICE guidance reports that 13.8% of patients receiving recommended doses of Dabigatran experienced adverse bleeding events. In the pivotal hip and knee VTE trial, wound secretion only accounted for 4.9% of patients treated with Dabigatran (cf 3.0% of patients treated with Enoxaparin).

We report our wound secretion experience after Dabigatran use at Warwick Hospital from March 2009 to March 2010. Of the 788 lower-limb arthroplasties performed, 55 patients (6.9%) had oozing wounds after discharge (Mean=8 days, Range=1-39 days). This resulted in 226 extra home-visits by discharge nurses, 26 positive microbiology cultures and 5 confirmed wound infections needing antibiotic treatment and/or surgical intervention. Incidentally, there were also 2 known cases each of deep vein thrombosis and pulmonary embolus in this cohort. The number of complications was markedly increased from previous years when LMWH was the VTE prophylaxis used.

This data suggests that the use of Dabigatran in Warwick Hospital may significantly increase surgical site morbidity and resource output after lower limb arthroplasty.

The Oxford mobile bearing unicompartmental knee replacement (UKR) is a validated, highly successful implant with an excellent ten-year survivorship. From November 2001 to September 2006 three hundred and eighty two patients who had a medial cemented Oxford Unicompartmental knee replacement (Biomet, Bridgend, UK) via a minimally invasive approach were prospectively entered into a database and followed up as per departmental policy in the specialist joint assessment clinic. We have noted a minority of patients have persistent postoperative pain and/or mechanical symptoms resistant to the standard postoperative therapies. We report the outcome of 22 patients who had an arthroscopy for persistent pain and/or mechanical symptoms a median of 15 months (range 4 months – 31 months) following medial unicompartmental knee replacement. The median follow up time following arthroplasty was 38 months (range 16 months – 63 months). Post arthroscopy we divided our study patients into two groups; those who had an improvement in symptoms and those who had none. These groups were then compared, with particular reference to demographics, check radiographs and arthroscopic findings. The results showed that patients with anterior or anteromedial symptoms in whom a medial rim of scar tissue was identified and debrided sixty seven percent had a significantly increased probability of symptomatic improvement (p<0.005). In addition men appeared to significantly improve more that women (p<0.043). When performed this therapeutic intervention many prevent or at least defer the need for early revision to total knee replacement in some cases and we have no complications as a result of the arthroscopic intervention. This observational study provides evidence for a role for arthroscopy in selected patients with pain following unicompartmental knee replacement.

Introduction: Numerous studies in the orthopaedic literature have reported changes in knee kinematics following rupture of the Anterior Cruciate Ligament (ACL). Gait analysis is currently the preferred method for studying these in vivo kinematics. The accuracy of this method of analysis remains limited due to errors related to skin movement artefact. Most studies have therefore been limited to analysing subjects performing simple tasks such as straight-line walking, since results become increasingly inaccurate as the subject moves faster. Standard skin marker formats allow measurements of knee flexion angle and varus/valgus angles to be recorded relatively accurately during such tasks. Accurate measurements of rotations and translations at the knee joint, however, are not possible with these set-ups.

Aim: To produce a new method for interpretation of kinematic data from gait analysis, to allow accurate measurement of 3-D displacements at the knee joint during dynamic activity.

Method: We employed two different sets of skin markers in an attempt to increase the accuracy of our data, by diminishing the effects of skin movement. The Kabada¹ marker set was used with retroreflective spheres of 14.5mm diameter. This marker set was used to establish 3-D femoral and tibial co-ordinate systems. We then established a femoral and tibial co-ordinate centre within the distal femur and proximal tibia respectively. A second set of markers was used similar to the “point-cluster” method described by Andriacchi et al². This involved groups of eight smaller spheres (9.5mm diameter) placed in a non-uniform distribution on each of the thigh and shank segments. The positions of all these remaining markers, relative to the co-ordinate centres were then established. 15 subjects were then recorded while performing a series of running and cutting tasks. For each trial that was then analysed, we used all visible markers to optimize the recorded position of the tibial and femoral co-ordinate centres, using a method similar to that described by Soderkvist³. The displacements of these co-ordinate centres were then used to calculate the 3-D tibio-femoral kinematics. Reliability and repeatability tests suggest that this method produces results accurate to 3–4mm.

Conclusion: We believe we have developed a practical and accurate method to analyse 3-D joint kinematics from gait laboratory data.

Introduction and Aims: Since existing data relating to the kinematics of ACL-deficient knee joints relates mainly to walking, the kinematics during more dynamic activities remains unknown; therefore, the aim of this unique study was to describe in vivo ACL-deficient knee kinematics and muscle activity during running and cutting.

Method: Fifteen subjects with proven unilateral ACL rupture were measured performing running and cutting tasks prior to surgical reconstruction. Gait analysis was used to determine inter-limb differences in displacements at the knee joint during stance phase. Simultaneous EMG analysis was performed to give temporal measures of lower limb muscle activity.

Results: No significant inter-limb difference was seen for tibio-femoral translation in the sagittal or coronal planes during any part of stance phase. The ACLD limb showed a significantly reduced maximum knee flexion angle (40.4 vs. 44.0 degrees) compared to the ACL-intact (ACLI) limb (p=0.04). Internal tibial rotation was significantly greater (7.3 vs. 0.7 degrees) in the ACLD limb at toe-off (p=0.03). The quadriceps muscle group was found to be active for a significantly greater percentage of stance phase in the ACLD limb compared to the ACLI limb (p=0.001).

Conclusion: The ACL-deficient gait involves consistently greater knee extensor activity than ACL-intact gait during running, and as a consequence maximum knee flexion angle is reduced. These findings contrast with the description of ‘quadriceps-avoidance’ gait often described for ACL-deficient subjects. ACL-deficient gait also demonstrates increased rotational instability during terminal stance phase.