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.

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.

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.

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.

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 1.5x 10(6) 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.

Treatment of supracondylar femoral fracture above total knee replacement by custom made hinged prosthesis.

A supracondylar fracture above a total knee arthroplasty (TKA) is a devastating complication for both the patient and surgeon. Various methods of treatment are available. We have treated seven cases of displaced supracondylar fractures above a total knee replacement with custom made implants. This technique allows rapid post-operative recovery and gives a good functional outcome.

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.