Enhancing patient recovery following lower limb arthroplasty with a modern wound dressing: a prospective, comparative audit.

OBJECTIVE: To assess current wound care practice, implement a potentially improved regimen and re-evaluate practice. METHOD: Two prospective clinical audits were performed over a 6-month period, involving 100 patients undergoing hip or knee arthroplasty. Fifty consecutive patients with traditional dressings (Mepore; Mölnlycke) were evaluated prior to a change in practice to a modern dressing (Aquacel Surgical; ConvaTec). Fifty consecutive patients were then evaluated with the new dressing to complete the audit cycle. Clinical outcome measures were wear time, number of changes, blister rate and length of hospital stay. Statistical comparisons were performed using Mann Whitney or Fisher's exact test (statistical significance p < 0.05). RESULTS: Wear time for the traditional dressing (2 days) was significantly shorter than for the modern dressing (7 days; p < 0.001), and required more changes (0 vs 3; p < 0.001). Twenty per cent of patients developed blisters with the traditional dressing compared with 4% with the modern dressing (p=0.028). Median length of stay was the same for the modern dressing (4 days) compared with the traditional dressing (4 days). In the modern dressing group, 75% of patients were discharged by day 4, whereas in the traditional group this took until day 6. CONCLUSION: This audit highlights the problems associated with traditional dressings with frequent early dressing changes, blistering and delayed discharge. These adverse outcomes can be minimised with a modern dressing specifically designed for the demands of lower limb arthroplasty. Units planning to implement enhanced recovery regimens should consider adopting this dressing to avoid compromising patient discharge. DECLARATION OF INTEREST: There were no external sources of funding for this audit; however, one author (JC) received reimbursement of expenses to attend and present work at educational conferences from ConvaTec.

A prospective clinical audit of a new dressing design for lower limb arthroplasty wounds.

An audit of wound healing in patients undergoing total hip or knee arthroplasty in a Scottish hospital found that use of a barrier film made no difference to the effectiveness of a new Hydrofiber/hydrocolloid dressing combination.

A quantitative method of effective soft tissue management for varus knees in total knee replacement surgery using navigational techniques.

Total knee replacement (TKR) has become the standard procedure in management of degenerative joint disease with its success depending mainly on two factors: three-dimensional alignment and soft-tissue balancing. The aim of this work was to develop and validate an algorithm to indicate appropriate medial soft tissue release during TKR for varus knees using initial kinematics quantified via navigation techniques. Kinematic data were collected intraoperatively for 46 patients with primary end-stage osteoarthritis undergoing TKR surgery using a computer-tomography-free navigation system. All patients had preoperative varus knees and medial release was made using the surgeon's experience. Based on these data an algorithm was developed. This algorithm was validated on a further set of 35 patients where it was used to define the medial release based on the kinematic data. The post-operative valgus stress angles for the two groups were compared. These results showed that the algorithm was a suitable tool to indicate the type of medial release required in varus knees based on intra-operatively measured pre-implant valgus stress and extension deficit angles. It reduced the percentage of releases made and the results were more appropriate than the decisions made by an experienced surgeon.

The efficacy and safety of epidural filter catheters when used for post-operative intra-articular anaesthesia.

UNLABELLED: There are concerns about the risk of iatrogenic infection when employing local anaesthetic techniques with post-operative intra-articular infusions in total knee arthroplasty. This study aimed to determine the efficacy of intact epidural filters in preventing transit of bacteria and to develop a technique of administration which would prevent membrane rupture. Filter efficacy was assessed using a standardised test suspension of Pseudomonas aeruginosa. Twenty millilitres of suspension was injected through isolated epidural filters (n=10) or filters with 40cm of catheter tubing attached (n=30). For each filter, injections were carried out at 0, 8 and 24h. Filtrates were collected, incubated, sub-cultured onto Columbia horse blood agar and examined for bacterial growth. Three delivery techniques were tested: manually controlled syringe with 5ml of water at 20ml/min, forced administration syringe with 5ml of water at >240ml/min and an automated syringe driver delivering 40ml of water at 6.7ml/min. For the two techniques using syringes, three syringe sizes, 5ml, 10ml and 20ml, were tested. Each test condition was carried out on 10 filters (total n=70). Filters were examined for rupture. Intact epidural filters prevented bacterial transit in all cases. Manual controlled and automated syringe driver administration generated no filter ruptures. Manual forced administration generated 93% filter rupture. Ruptures occurred at peak pressures of approximately 620kPa. Epidural filters can be used to prevent bacterial transit. These results suggest automated devices remove the risk of filter rupture. This study is relevant to all specialties that utilise these filters during infiltration such as epidurals or other regional anaesthetic techniques. CLINICAL RELEVANCE: This study identified that filters are prone to rupture with high infusion rates and that manual techniques are particularly vulnerable. From these results, it is recommended that pumps are used to minimise risk of filter rupture.

The technique of delivery of peri-operative analgesia does not affect the rehabilitation or outcomes following total knee arthroplasty.

AIMS: This non-blinded randomised controlled trial compared the effect of patient-controlled epidural analgesia (PCEA) versus local infiltration analgesia (LIA) within an established enhanced recovery programme on the attainment of discharge criteria and recovery one year after total knee arthroplasty (TKA). The hypothesis was that LIA would increase the proportion of patients discharged from rehabilitation by the fourth post-operative day but would not affect outcomes at one year. PATIENTS AND METHODS: A total of 242 patients were randomised; 20 were excluded due to failure of spinal anaesthesia leaving 109 patients in the PCEA group and 113 in the LIA group. Patients were reviewed at six weeks and one year post-operatively. RESULTS: There was no difference in the proportion of patients discharged from rehabilitation by the fourth post-operative day, (77% in the PCEA group, 82% in the LIA group, p = 0.33), mean length of stay (four days in each group, p = 0.540), day of first mobilisation (p = 0.013) or pain (p = 0.278). There was no difference in mean Oxford Knee Scores (41 points in each group, p = 0.915) or the rate of complications in the two groups. CONCLUSION: Both techniques provided adequate pain relief, enabled early mobilisation and accelerated rehabilitation and good patient-reported outcomes up to one year post-operatively. PCEA and LIA are associated with similar clinical outcomes following TKA. Cite this article: Bone Joint J 2016;98-B1189-96.

Natural acetabular orientation in arthritic hips.

OBJECTIVES: Acetabular component orientation in total hip arthroplasty (THA) influences results. Intra-operatively, the natural arthritic acetabulum is often used as a reference to position the acetabular component. Detailed information regarding its orientation is therefore essential. The aim of this study was to identify the acetabular inclination and anteversion in arthritic hips. METHODS: Acetabular inclination and anteversion in 65 symptomatic arthritic hips requiring THA were measured using a computer navigation system. All patients were Caucasian with primary osteoarthritis (29 men, 36 women). The mean age was 68 years (SD 8). Mean inclination was 50.5° (SD 7.8) in men and 52.1° (SD 6.7) in women. Mean anteversion was 8.3° (SD 8.7) in men and 14.4° (SD 11.6) in women. RESULTS: The difference between men and women in terms of anteversion was significant (p = 0.022). In 75% of hips, the natural orientation was outside the safe zone described by Lewinnek et al (anteversion 15° ± 10°; inclination 40° ± 10°). CONCLUSION: When using the natural acetabular orientation to guide component placement, it is important to be aware of the differences between men and women, and that in up to 75% of hips natural orientation may be out of what many consider to be a safe zone. Cite this article: Bone Joint Res 2015;4:6-10.

Intra-operative deviation in limb alignment occurring at implantation in total knee arthroplasty.

BACKGROUND: Long-term survival of knee replacement depends on accurate alignment. Despite improvements in cut accuracy mal-alignment of 3° or more is still seen. All methods share common implantation techniques. This study examines the effect of implantation on overall limb alignment relating it to cut alignment and trial alignment. METHODS: A retrospective review of navigated primary knee replacements was undertaken (n=113). Overall coronal limb alignments for the aggregated cuts, trial and final implanted components were examined. RESULTS: All 113 knees had coronal aggregated cut alignment within 2° of neutral (range: 2° varus to 2° valgus). With trial components 99 knees (88%) had an overall coronal limb alignment within 2° of neutral (range: 3° varus to 4° valgus). After final implantation 106 knees (94%) were within 2° of neutral (range: 4° varus to 4° valgus). Forty eight knees (42%) showed no alignment deviation occurring between trial and the final implanted prostheses and 16 knees (14%) shoed a deviation of 2° or more. There was a correlation of both aggregated cut (r=0.284, p=0.002) and trial (r=0.794, p<0.001) with final alignment. There was no significant difference between the final alignment and the aggregated cut alignment(mean difference=-0.15°, p=0.254) or trial alignment (mean difference -0.13°, p=0.155). CONCLUSIONS: Even when the aggregated alignment produced by the bone cuts is accurate, inaccuracy in final alignment can result from the implantation process. It may be productive for surgeons to concentrate on the implantation process to improve alignment and reduce outliers.

Primary stability of two uncementedacetabular components of different geometry: hemispherical or peripherallyenhanced?

OBJECTIVE: This study compared the primary stability of two commercially available acetabular components from the same manufacturer, which differ only in geometry; a hemispherical and a peripherally enhanced design (peripheral self-locking (PSL)). The objective was to determine whether altered geometry resulted in better primary stability. METHODS: Acetabular components were seated with 0.8 mm to 2 mm interference fits in reamed polyethylene bone substrate of two different densities (0.22 g/cm(3) and 0.45 g/cm(3)). The primary stability of each component design was investigated by measuring the peak failure load during uniaxial pull-out and tangential lever-out tests. RESULTS: There was no statistically significant difference in seating force (p = 0.104) or primary stability (pull-out p = 0.171, lever-out p = 0.087) of the two components in the low-density substrate. Similarly, in the high-density substrate, there was no statistically significant difference in the peak pull-out force (p = 0.154) or lever-out moment (p = 0.574) between the designs. However, the PSL component required a significantly higher seating force than the hemispherical cup in the high-density bone analogue (p = 0.006). CONCLUSIONS: Higher seating forces associated with the PSL design may result in inadequate seating and increased risk of component malpositioning or acetabular fracture in the intra-operative setting in high-density bone stock. Our results, if translated clinically, suggest that a purely hemispherical geometry may have an advantage over a peripherally enhanced geometry in high density bone stock. Cite this article: Bone Joint Res 2013;2:264-9.

Non-invasive, non-radiological quantificationof anteroposterior knee joint ligamentous laxity: A study in cadavers.

OBJECTIVES: We performed in vitro validation of a non-invasive skin-mounted system that could allow quantification of anteroposterior (AP) laxity in the outpatient setting. METHODS: A total of 12 cadaveric lower limbs were tested with a commercial image-free navigation system using trackers secured by bone screws. We then tested a non-invasive fabric-strap system. The lower limb was secured at 10° intervals from 0° to 60° of knee flexion and 100 N of force was applied perpendicular to the tibia. Acceptable coefficient of repeatability (CR) and limits of agreement (LOA) of 3 mm were set based on diagnostic criteria for anterior cruciate ligament (ACL) insufficiency. RESULTS: Reliability and precision within the individual invasive and non-invasive systems was acceptable throughout the range of flexion tested (intra-class correlation coefficient 0.88, CR 1.6 mm). Agreement between the two systems was acceptable measuring AP laxity between full extension and 40° knee flexion (LOA 2.9 mm). Beyond 40° of flexion, agreement between the systems was unacceptable (LOA > 3 mm). CONCLUSIONS: These results indicate that from full knee extension to 40° flexion, non-invasive navigation-based quantification of AP tibial translation is as accurate as the standard validated commercial system, particularly in the clinically and functionally important range of 20° to 30° knee flexion. This could be useful in diagnosis and post-operative evaluation of ACL pathology. Cite this article: Bone Joint Res 2013;2:233-7.

Computer-assisted measurements of coronal knee joint laxity in vitro are related to low-stress behavior rather than structural properties of the collateral ligaments.

The relationship between coronal knee laxity and the restraining properties of the collateral ligaments remains unknown. This study investigated correlations between the structural properties of the collateral ligaments and stress angles used in computer-assisted total knee arthroplasty (TKA), measured with an optically based navigation system. Ten fresh-frozen cadaveric knees (mean age: 81 ± 11 years) were dissected to leave the menisci, cruciate ligaments, posterior joint capsule and collateral ligaments. The resected femur and tibia were rigidly secured within a test system which permitted kinematic registration of the knee using a commercially available image-free navigation system. Frontal plane knee alignment and varus-valgus stress angles were acquired. The force applied during varus-valgus testing was quantified. Medial and lateral bone-collateral ligament-bone specimens were then prepared, mounted within a uni-axial materials testing machine, and extended to failure. Force and displacement data were used to calculate the principal structural properties of the ligaments. The mean varus laxity was 4 ± 1° and the mean valgus laxity was 4 ± 2°. The corresponding mean manual force applied was 10 ± 3 N and 11 ± 4 N, respectively. While measures of knee laxity were independent of the ultimate tensile strength and stiffness of the collateral ligaments, there was a significant correlation between the force applied during stress testing and the instantaneous stiffness of the medial (r = 0.91, p = 0.001) and lateral (r = 0.68, p = 0.04) collateral ligaments. These findings suggest that clinicians may perceive a rate of change of ligament stiffness as the end-point during assessment of collateral knee laxity.

An anatomic study of local infiltration analgesia in total knee arthroplasty.

BACKGROUND: Local infiltration analgesia (LIA) is a relatively novel technique developed for effective pain control following total knee arthroplasty (TKA), reducing requirements for epidural or parenteral postoperative analgesia. This study investigated the anatomical spread of an LIA used in TKA to identify the nerve structures reached by the injected fluid. METHODS: Six fresh-frozen cadaveric lower limbs were injected according to a standardised LIA technique with a solution of latex and India ink to enable visualisation. Wounds were closed and limbs placed flat in a freezer at -20°C for two weeks. Limbs were then either sliced or dissected to identify solution locations. RESULTS: Solution was found from the proximal thigh to the middle of the lower leg. The main areas of concentration were the popliteal fossa, the anterior aspect of the femur and the subcutaneous tissue of the anterior aspect of the knee. There was less solution in the lower popliteal fossa. The solution was found to reach the majority of nerves, with good infiltration of nerves supplying the knee. CONCLUSIONS: These results support the positive clinical outcomes with this LIA technique. However, the lack of infiltration into the lower popliteal fossa suggests more fluid or a different injection point could be used. The solution reaching the extensor muscles of the lower leg is likely to have no beneficial analgesic effect for a TKA patient. The LIA technique is already used in clinical practice following total knee arthroplasty. Results from this study show there may be scope to optimise the injection sites in LIA technique.

Is patient self-assessment of flexion after TKR able to identify risk of manipulation under anaesthesia?

BACKGROUND: Patient self-assessment of postoperative knee flexion following knee replacement was introduced at our institution. This protocol had a dual objective: improve follow-up and act as an early indicator to identify patients at risk of requiring a manipulation under anaesthesia. The aim of our study was to audit the use of this patient self-assessment tool and evaluate whether these outcomes were being achieved. MATERIALS AND METHODS: A prospective audit of patients admitted for total knee replacements under the care of one orthopaedic consultant between April and October 2009. Participants were asked to measure and record daily maximum knee flexion whilst sitting, from discharge through to six-week follow-up. Patients were advised to contact the arthroplasty team if flexion reduced by 10° or more for three consecutive days. Patient's documented knee flexion was compared to that measured on discharge and at six weeks postoperatively by clinicians. RESULTS: Seventy-nine participants (82 knees) were included with 61 participants (64 knees) returning data for analysis (78% compliance rate). Comparison of patient and clinician measurements showed a mean difference of +2° with limits of agreements from -12° to +15°. At a mean follow-up of six weeks maximum flexion (measured by clinician) was 99° (95%CI 97°, 102°) and 92% had a 90°flexion or greater. During the audit period, six patients met the criteria to contact the arthroplasty team, however none of them followed this instruction. DISCUSSION: Patient self-assessment of knee flexion at home with a simple goniometer was accurate enough to be useful and 92% of patients reached 90° maximum flexion at six weeks. However this self-assessment method was not successful as an early indicator to identify patients at risk of requiring a manipulation under anaesthesia. Future studies into alternative identifiers are required. LEVEL OF EVIDENCE: Level III. Investigating a diagnostic test.

An enhanced recovery programme for primary total knee arthroplasty in the United Kingdom--follow up at one year.

The concepts of Enhanced Recovery Programmes (ERP) are to reduce peri-operative morbidity whilst accelerating patient's rehabilitation resulting in a shortened hospital stay following primary joint arthroplasty. These programmes should include all patients undergoing surgery and should not be selective. We report a consecutive series of 1081 primary total knee arthroplasties undergoing an enhanced recovery programme with a one year follow up period. A comparative cohort of 735 patients from immediately prior to the enhanced recovery programme implementation was also reviewed. The median day of discharge home was reduced from post-operative day six to day four (p<0.001) for the ERP group. Post-operative urinary catheterisation (35% vs. 6.9%) and blood transfusion (3.7% vs. 0.6%) rates were significantly reduced (p<0.001). Within the ERP group median pain scores (0 = no pain, 10 = maximal pain) on mobilisation were three throughout hospital stay with 95% of patients ambulating within 24h. No statistical difference was found in post-operative thrombolytic events (p=0.35 and 0.5), infection (p=0.86), mortality rates (p=0.8) and Oxford Knee Scores (p=0.99) at follow up. This multidisciplinary approach provided satisfactory post-operative analgesia allowing early safe ambulation and expedited discharge to home with no detriment to continuing rehabilitation, infection or complication rates at one year.

A comparison of radiological and computer navigation measurements of lower limb coronal alignment before and after total knee replacement.

We compared lower limb coronal alignment measurements obtained pre- and post-operatively with long-leg radiographs and computer navigation in patients undergoing primary total knee replacement (TKR). A series of 185 patients had their pre- and post-implant radiological and computer-navigation system measurements of coronal alignment compared using the Bland-Altman method. The study included 81 men and 104 women with a mean age of 68.5 years (32 to 87) and a mean body mass index of 31.7 kg/m(2) (19 to 49). Pre-implant Bland-Altman limits of agreement were -9.4° to 8.6° with a repeatability coefficient of 9.0°. The Bland-Altman plot showed a tendency for the radiological measurement to indicate a higher level of pre-operative deformity than the corresponding navigation measurement. Post-implant limits of agreement were -5.0° to 5.4° with a repeatability coefficient of 5.2°. The tendency for valgus knees to have greater deformity on the radiograph was still seen, but was weaker for varus knees. The alignment seen or measured intra-operatively during TKR is not necessarily the same as the deformity seen on a standing long-leg radiograph either pre- or post-operatively. Further investigation into the effect of weight-bearing and surgical exposure of the joint on the mechanical femorotibial angle is required to enable the most appropriate intra-operative alignment to be selected.

Profile of the distal femur anterior cortex--a computer-assisted cadaveric study.

INTRODUCTION: Accurate positioning and sizing of the femoral component in total knee arthroplasty is important for stability and functional outcome. The purpose of the study was to evaluate the bony profiles of the distal anterior femoral cortex (AFC). MATERIALS AND METHODS: Anatomical bony landmarks on 50 adult cadaveric femora were collected. Critical points were used to identify the distal AFC surface. RESULTS: There were four anterior cortex profiles: (1) lateral side highest and medial side lowest (56%); (2) lowest height in median area (26%); (3) highest height in median area (14%); (4) medial side highest and lateral side lowest (4%). DISCUSSION: Anterior referencing in TKA needs to represent the anterior shape of the distal femoral cortex to prevent notching, femoro-patellar overstuffing or flexion gap mismanagement. Due to the variability of the AFC, surgeons have to carefully select the AFC landmark to be sure of avoiding complications.

Measuring the positional accuracy of computer assisted surgical tracking systems.

Computer Assisted Orthopaedic Surgery (CAOS) technology is constantly evolving with support from a growing number of clinical trials. In contrast, reports of technical accuracy are scarce, with there being no recognized guidelines for independent measurement of the basic static performance of computer assisted systems. To address this problem, a group of surgeons, academics and manufacturers involved in the field of CAOS collaborated with the American Society for Testing and Materials (ASTM) International and drafted a set of standards for measuring and reporting the technical performance of such systems. The aims of this study were to use these proposed guidelines in assessing the positional accuracy of both a commercially available and a novel tracking system. A standardized measurement object model based on the ASTM guidelines was designed and manufactured to provide an array of points in space. Both the Polaris camera with associated active infrared trackers and a novel system that used a small visible-light camera (MicronTracker) were evaluated by measuring distances and single point repeatability. For single point registration the measurements were obtained both manually and with the pointer rigidly clamped to eliminate human movement artifact. The novel system produced unacceptably large distance errors and was not evaluated beyond this stage. The commercial system was precise and its accuracy was well within the expected range. However, when the pointer was held manually, particularly by a novice user, the results were significantly less precise by a factor of almost ten. The ASTM guidelines offer a simple, standardized method for measuring positional accuracy and could be used to enable independent testing of tracking systems. The novel system demonstrated a high level of inaccuracy that made it inappropriate for clinical testing. The commercially available tracking system performed well within expected limits under optimal conditions, but revealed a surprising loss of accuracy when movement artifacts were introduced. Technical validation of systems may give the user community more confidence in CAOS systems as well as highlighting potential sources of point registration error.