How Accurate is the Use of Contralateral Implant Size as a Template in Bilateral Hemiarthroplasty?

PURPOSE

Accurately predicting implant size for hemiarthroplasties offers an important contribution to theatre efficiency and patients' intraoperative care. However, pre-operative sizing using templating of implants in hip fracture patients requiring a hemiarthroplasty is often difficult due to non-standard radiographs, absence of a calibration marker, poor marker placement, variable patient position, and in many institutions a lack of templating facilities. In patients who have previously undergone a hemiarthroplasty on the contralateral side, surgeons can use the contralateral implant size for pre-operative planning purposes. However, the accuracy of doing this has not previously been reported. The aim of this study was to investigate the reliability of using an in situ contralateral implant as a predictor of implant size on the contralateral side.

METHODS

A retrospective review of our local neck of femur fracture (NOF) database was undertaken to identify patients who had bilateral hip hemiarthroplasty. Operative records were reviewed to establish the size of prostheses used at operation. Correlation, agreement, and reliability analysis were performed using the least squares, Bland-Altman plot, and intra-class correlation coefficient (ICC) methods, respectively.

RESULTS

Operative records were identified for 45 patients who had bilateral hemiarthroplasties. There was a difference in implant size used in 58% of cases. Of these 77% required a larger implant on the right. Implant sizes were within 1 mm of the contralateral side in 78% and within 2 mm in 91% of patients. However, in 9% of patients, there was a discrepancy greater than 2 mm with some cases having up to 6 mm discrepancy. Correlation coefficient was 0.83 and the ICC 0.90.

CONCLUSIONS

The findings in this study indicated that using the size of a contralateral implant can be used as a reliable indicator of head size in cases of bilateral hemiarthroplasty. However, the surgeon should remain cautious as there is a one in ten chance of there being a 3 mm or more difference in implant size.

There is no 'weekend effect' in elective orthopaedic surgery

Introduction The 'weekend effect' is said to occur when patient outcomes are adversely affected by the day of the week on which they present to hospital or have surgery. However, it is uncertain whether such a phenomenon exists for elective orthopaedic surgery. We investigated whether there is a 'weekend effect' in elective orthopaedic patients. Methods Retrospectively collected data were obtained from our institution's electronic patient records. We collected demographic and International Statistical Classification of Diseases and Related Health Problems tenth revision coding data for all included patients. Multivariate analyses identified covariate-adjusted risk factors, associated with prolonged stays. Thirty-day mortality data were assessed according to the day on which surgery occurred. Results We analysed data for 892 patients over a one-year period. During the year, 457 patients had a total hip and 435 had a total knee replacement; 814 patients (91.3%) underwent surgery during the week, while 78 (8.7%) had surgery on a Saturday. There was no difference in average length of stay between the groups (5.0, 2.6 vs 5.0, 3.4, P = 0.95). Variables associated with prolonged hospitalisation included increasing age (covariate adjusted relative risk 1.02, 95% confidence interval 1.01-1.03, P < 0.001) and an American Society of Anesthesiologists score of 2, (relative risk 1.6, 95% confidence interval 1.15-2.20, P = 0.005). There was one death in a patient who underwent surgery on a Monday. Conclusions There is no 'weekend effect' for elective orthopaedic surgery.

P.F.C Sigma® cruciate retaining fixed-bearing versus mobile-bearing knee arthroplasty: a prospective comparative study with minimum 10-year follow-up

AIMS

To prospectively compare long-term clinical and radiological outcomes following a cruciate retaining fixed-bearing (FB) and a mobile-bearing (MB) primary total knee replacement (TKR).

METHODS

We prospectively reviewed 113 TKRs in 99 patients (14 bilateral) with a PFC sigma cruciate retaining rotating platform system, at an average follow-up of 11.1 years (range 10-12). Results were contrasted with those from 89 TKRs in 72 patients (17 bilateral) with a PFC sigma cruciate fixed-bearing prosthesis, at an average follow-up of 12.1 years (range 10-14.1). Outcomes collected included pre- and post-operative range of motion, Oxford Knee Scores, complications encountered, as well as radiographical assessments of polyethylene wear.

RESULTS

In the MB group, mean Oxford Knee Scores improved from 16 pre-operatively to 42 at final follow-up. The mean range of motion was 115° (75-130). In the FB group, mean Oxford Knee Scores improved from 16.2 pre-operatively to 42.5 at final follow-up. The mean range of motion was 111.2 (80-135) degrees at final follow-up.

CONCLUSION

We failed to elicit an objectively demonstrable clinical difference between the MB- and FB-implanted knees. Similarly, radiological benefits of the MB implants with regard to polyethylene wear were not evident at a minimum 10-year follow-up.

Polyethylene in knee arthroplasty: A review

Polyethylene (PE) has been used extensively in knee arthroplasty since the mid 20th century. Progress in material manufacturing and processing has led to newer polyethylenes over last few decades with different material properties. It has been established that PE wear in knee arthroplasty causes particle induced osteolysis which is the main reason for late failure and requires revision surgery. Although there are various causes of wear, the properties of PE have long been a matter of investigation as a contributory factor. The advent of newer highly cross linked PE has been shown to improve wear rates in hip arthroplasty but the benefits have not been shown to be of the same degree in knee arthroplasty. The laboratory and clinical studies so far are limited and slightly conflicting in their conclusions. The risks of using highly cross linked PE in knee arthroplasty include tibial post fracture, disruption of locking mechanism, liner fracture which can lead to increased wear and osteolysis. The current evidence suggests that highly cross linked polyethylenes should be used with caution and only considered in younger active patients. The results of a recently completed randomized trial to compare the conventional with high molecular weight PE in knee arthroplasty are awaited.

Intramedullary fixation of a femoral shaft fracture with preservation of an existing hip resurfacing prosthesis

Femoral neck fractures have been reported as a cause for failure in patients with a hip resurfacing arthroplasty. However, the incidence and management of fractures of the femoral shaft with an ipsilateral hip resurfacing arthroplasty is relatively absent in current literature. Although, the gold standard for the fixation of a closed femoral shaft fracture is with the use of an intramedullary nail, this can be a challenge in the presence of a hip resurfacing arthroplasty. We describe the case of anterograde intramedullary nail fixation for a femoral shaft fracture in a patient with an ipsilateral hip resurfacing arthroplasty in situ.

Primary total knee arthroplasty using the P.F.C Sigma®-rotating platform cruciate retaining endoprosthesis--a 6 year follow up

BACKGROUND

Mobile-bearing Total Knee Replacement allows unconstrained axial rotation. Increased articular conformity minimizes polyethylene contact stresses, thereby reducing linear wear and fatigue failure.

METHODS

We prospectively reviewed a consecutive series of 161 patients with mobile bearing total knee replacements using the PFC Sigma Cruciate Retaining Rotating Platform System. (DePuy, Leeds, United Kingdom) with midterm follow up (minimum 6 and maximum 9 years, mean 7.2 years). One hundred forty-seven patients from February 2001 to March 2004 were followed up till date. Primary osteoarthritis 96%; was the main indication followed by rheumatoid arthritis 3% and one case of psoriatic arthritis. Fifty-seven percent were females with mean age of 69.5 years (Range 51-90 years). Oxford and American Knee Society scores were measured.

RESULTS

Mean Oxford score improved from 43 (Range 29-55) pre operatively to 21(Range 13-44) at last follow up and mean Knee Society score from 53 (Range 43-70) to 80 (Range 58-90). Range of movement improved from 91° (Range 70-110) to 113° (Range 75-130) at last follow up. One patient had dislocation of bearing needing manipulation. One patient had superficial infection treated with antibiotics. No patients had deep infection. There was one case reported of deep vein thrombosis and one of non-fatal pulmonary embolism.

CONCLUSION

The midterm results in our series with PFC Sigma mobile bearing knee replacement are excellent with good outcome scores. Cohort will be followed for long term results. Level of Evidence IV.

Expert practical operative skills teaching in Trauma and Orthopaedics at a nominal cost

BACKGROUND AND PURPOSE

The AO Foundation Operative Fracture Management course is the gold standard in training courses currently available for trainees at ST3 level. We have devised a low cost operative skills course comprising instructional lectures, demonstrations and practical dry bone workshops. To assess the quality of teaching, candidates' feedback was analysed in two cohorts for the running of the course over two consecutive years: 2008 and 2009.

METHODS

Trainees were given short instructional lectures by consultant surgeons followed by workshops, with a trainer to candidate ratio of 1:4. A trauma inventory was provided by Stryker Trauma UK, ensuring a nominal fee for each candidate (£50). Feedback was anonymously collected according to a Likert scale and analysed using non-parametric methods appropriate for ranked data.

MAIN FINDINGS

Twenty one of 22 (95%) candidates gave feedback in 2008 and 18 out of 18 candidates (100%) in 2009. The teaching provided was highly rated consistently for both years, apart from an informal session on theatre tips and tricks in 2008. This was not repeated in 2009 to allow more practical time. Only one session, an intramedullary nailing lecture, had a significant difference in scores between the 2 years (p = 0.044) because of improved scores in 2009.

CONCLUSIONS

Due to changes in training, trainees have reduced exposure in theatre and this has implications for the early stages of acquiring practical operative skills. As an adjunct to the AO course, practical skills teaching by consultants in the format of a low cost skills workshop outside of a theatre environment can be achieved with support from a trauma implant supplier.

Improvement in the assessment of wear of total knee replacements using coordinate-measuring machine techniques

Total joint replacement is one of the most common elective surgical procedures performed worldwide, with an estimate of 1.5×106 operations performed annually. Currently joint replacements are expected to function for 10–15 years; however, with an increase in life expectancy, and a greater call for knee replacement due to increased activity levels, there is a requirement to improve their function to offer longer-term improved quality of life for patients.

Wear analysis of total joint replacements has long been an important means in determining failure mechanisms and improving longevity of these devices. The effectiveness of the coordinate-measuring machine (CMM) technique for assessing volumetric material loss during simulated life testing of a replacement knee joint has been proved previously by the present authors. The purpose of the current work is to present an improvement to this method for situations where no pre-wear data are available.

To validate the method, simulator tests were run and gravimetric measurements taken throughout the test, such that the components measured had a known wear value. The implications of the results are then discussed in terms of assessment of joint functionality and development of standardized CMM-based product standards. The method was then expanded to allow assessment of clinically retrieved bearings so as to ascertain a measure of true clinical wear.

The fabella: a forgotten source of knee pain?

We present a case of chondromalacia of the fabella, describe a provocative diagnostic test and review the literature on this unusual cause of knee pain.

Experimental determination of stress distributions in articular cartilage before and after sustained loading

OBJECTIVE

To test the hypotheses that stress concentrations exist within articular cartilage, and are intensified by sustained 'creep' loading.

DESIGN

Matched-pair comparison of stress distributions in cartilage, in vitro, before and after creep.

BACKGROUND

The ability of cartilage to equalize contact stresses between articulating surfaces may be compromised by undulations in the subchondral bone, and by variations in chemical composition. Furthermore, any stress concentrations within cartilage may be affected by creep loading, which-reduces its water content.

METHODS

Sixteen specimens of apparently normal cartilage-on-bone, 12 mm x 15 mm, were removed from the femoral condyles and tibial plateaux of patients undergoing total knee replacement. The cartilage was subjected to a nominal compressive stress of 2 MPa by means of a 10 mm-diameter flat impermeable indentor. During the 20 s loading period, a miniature pressure transducer, side-mounted in a 0.9 mm-diameter needle, was pulled through the cartilage in a direction parallel to the surface, while transducer output and position were sampled at 25 Hz. 'Stress profiles' were obtained with the transducer pointing in the 12 o'clock and 3 o'clock directions, and were repeated after creep loading at 1.6 MPa for 2 h.

RESULTS

Validation tests indicated that transducer output was proportional to the average compressive stress, but overestimated it by 9-15%. Stresses were greatest under the centre of the indentor, and showed local variations ('concentrations') which were increased in number and size after creep loading.

CONCLUSIONS

Measured values of compressive stress incorporate small systematic errors. Nevertheless, the results presented clearly support both hypotheses.

Revision of unicompartmental arthroplasty of the knee. Clinical and technical considerations

In 73 unicompartmental arthroplasties of the knee that were revised, the major causes of failure were progression of arthritis and implant failure. The interval between the primary and revision averaged 56 months. Eighty-eight percent were revised to a variety of total condylar prostheses. Bone loss was classified by defect at the end of preparation. In 31 patients, there were none; in 17, the defect was in either the femur or the tibia; and in 25, there were defects in both the femur and the tibia. Forty-seven of these defects were small and contained, presenting little problem. Twenty defects were either large, contained, or peripheral, requiring reconstruction. Fifteen knees were lost as a result of death (but there had been satisfactory knee function); 2 were lost to follow-up evaluation, and 3 have required further revision. Seventy-nine percent of the surviving knees had excellent or good knee function at an average follow-up period of 56 months.