Biomechanical Study Comparing Cut-out Resistance of the X-Bolt® and Dynamic Hip Screw at Various Tip-Apex Distances.

BACKGROUND: Bone quality in hip fractures is poor and there is a need to not only correctly position metalwork within the femoral head, but also for implants to resist cut-out. New implant designs may help to reduce metalwork cut-out, leading to fewer failures of fixation. This study compared the cut-out strength of a Dynamic Hip Screw (DHS) to that of an X-Bolt® (X-Bolt Orthopaedics, Dublin, Ireland) implant in an osteoporotic Sawbones® (Sawbones, Vashon Island, WA) model. METHODS: An unstable fracture model (AO 31-A2) was created using low-density 5 pound per cubic foot (pcf) Sawbones®. The DHS and X-Bolts® were inserted into the Sawbones® femoral head at Tip-Apex Distances (TAD) of 10mm, 15mm, 20mm, 25mm, 30mm and 40mm. A cyclic-loading Instron® machine (Instron Corp., Norwood, MA) pushed the bone at a compression rate of 5mm per minute at a 20-degree angle to the axis of the implant with an upper force limit of 4000N. Maximum force reached and load to failure, defined as movement of the implant by 5mm, were recorded. Four implants were used per group to give a total of 48 tests between the two groups. RESULTS: The X-Bolt® demonstrated a superior average maximum total load push-out force compared to the DHS group for all of the TAD configurations tested. The maximum force reached in the X-Bolt® group was significantly higher than that in the DHS group at a TAD of 10mm (X-Bolt® 3299.25N vs. DHS 2843.75N, P<0.029) and 30mm (X-Bolt® 2908.25N vs. DHS 2030N, P<0.029). The X-Bolt® also had a higher load to failure than the DHS group at all of the TAD values tested. CONCLUSIONS: The X-Bolt® implant gave superior performance compared to the standard DHS, as reflected by a greater push-out force in an osteoporotic Sawbones® model.

Conversion of unicompartmental knee arthroplasty to total knee arthroplasty: the challenges and need for augments.

The potential advantages of unicompartmental knee arthroplasty (UKA) include lower morbidity and mortality, quicker recovery, good range of motion, good medium and long-term survival results, potential bone conservation and perceived easier revision. Converting a UKA to a total knee arthroplasty (TKA) may be challenging due to issues of bone loss, need for augmentation, restoring joint line and rotation. We present the intraoperative findings of 201 cases of failed UKA's from the Trent Wales arthroplasty audit group (TWAAG) register. The objectives of the study were to determine the modes of failure, number of cases requiring augments and bone grafting, types of augments and implants used in revision surgery. This study does not include the clinical outcomes after revision knee surgery. The average age of the cohort at revision surgery was 67 years. There were 111 females and 90 males. The commonest modes of failure in young patients were unexplained pain/instability and aseptic loosening and in older patients they were aseptic loosening and progression of the disease. The survivorship of the implant was higher in the less than 55 years age group in comparison to the older patients. A total of 49 patients (25.9%) required bone grafting commonest in the 60 years and above age group (79.6%). Fifty patients (26.4%) required some form of augmentation, with the commonest site being tibia and commonest augment being tibial stem (35 cases). Only 8% of the cohort required revision knee implants whereas 78% of the cases received a cruciate retaining primary knee implant. To the author's knowledge, this is one of the largest studies in the literature which signifies the technical difficulties that might be experienced in revising the UKA's which will require appropriate pre-operative planning.

Must we appear to be all-knowing?: patients' and family physicians' perspectives on information seeking during consultations.

OBJECTIVE: To compare patients' opinions about family physicians looking up medical information during consultations with family physicians' expectations of how patients would respond to their using sources to find answers to medical questions. DESIGN: Survey. SETTING: North York, Ont. PARTICIPANTS: One hundred fifty-three family practice patients, 54 family physicians, and 21 family practice residents. MAIN OUTCOME MEASURES: Patients' self-reported confidence in their family physicians and their perceptions of the quality of care after seeing physicians look up medical information, both without specifying the physician's source of information and with reference to several specific information media. Family physicians' predictions for how patients would respond to their using resources to answer medical questions. RESULTS: When the information source used by physicians was not specified, 9% and 7% of patients reported decreased confidence and perceived lower quality of care, respectively. When the information source used by physicians was specified, the proportions of negative responses for patients' confidence and their perceptions of quality of care were 39% and 31%, respectively, for Internet search engines (ISEs); 8% and 7% for online resources designed for physicians (ORDP); 27% and 27% for personal digital assistants (PDAs); and 10% and 9% for hard-copy medical textbooks (HMTs). When the information source was not specified, 32% and 12% of physicians expected patients to report negative responses for confidence and perceptions of quality of care, respectively. When the information source was specified, 51% and 33% of physicians expected patients to report negative responses for confidence and perceptions of quality of care, respectively, for their use of ISEs; 16% and 8% for ORDP; 20% and 12% for PDAs; and 36% and 21% for HMTs. Younger patients were more likely to respond negatively to physicians' use of resources, especially if the source was an ISE (P<.001). Physicians earlier in their careers were more likely to expect negative patient responses (P<.05). CONCLUSION: Family physicians overestimated the decrease in patients' confidence caused by seeing them look up medical questions. While most patients responded positively, a substantial proportion of younger patients reported decreased confidence. Patients believed the best sources of information were ORDP and HMTs.

Bilateral Proximal Tibial Sleeve Fractures in a Child: A Case Report.

INTRODUCTION: A sleeve fracture classically describes an avulsion of cartilage or periosteum with or without osseous fragments and usually occurs at the inferior margin of the patella. Tibial tubercle sleeve fractures in the skeletally immature are extremely rare. CASE PRESENTATION: In this report the authors describe a 12-year-old boy with no systemic disease and no steroid use who sustained bilateral proximal tibial sleeve fractures whilst playing football. Both ruptures were associated with rupture of the medial patellofemoral ligament and tear of the medial retinaculum. Treatment was performed with primary end-to-end repair, reinforcement with bone anchors and cerclage wires with an excellent outcome. CONCLUSIONS: We feel this rare, currently unclassified variant of a tibial tubercle avulsion fracture should be recognised and consideration taken to adding it to existing classification systems.

Accuracy of the surgeon's eye: use of the tip-apex distance in clinical practice.

Tip-apex distance is a well described method for assessment of screw placement in dynamic hip screw fixation of proximal femoral fracture. A distance of <25mm is associated with a significantly lower rate of cut out of the fixation device. Measurement is frequently performed retrospectively, although there has been no demonstration as to what accuracy the surgeon has of estimating tip-apex distance from image intensifier images, whilst scrubbed in theatre. Thirty-one clinicians working within orthopaedic departments were tested in their ability to identify adequacy of tip-apex distance on a series of image intensifier images. Level of seniority, awareness of the concept of tip-apex distance and use of the concept in clinical practice were each assessed. The accuracy in identifying the correct TAD was 82.5% in consultants, 83.8% in registrars and 71.1% in Senior house officers (SHO). The method was used in clinical practice by 50% of consultants, 89% of registrars and none of the SHOs.

Outcomes of infected revision knee arthroplasty managed by two-stage revision in a tertiary referral centre.

BACKGROUND: A two-stage revision remains the gold standard to eradicate deep infection in total knee arthroplasty. Higher failure rates are associated with a number of factors including poly-microbial infections, multiresistant organisms and previous operations. The aims are to investigate [1] the overall success rate of a two-stage revision for infections in TKA, [2] the outcome of repeat two-stage revisions in recurrent infections and [3] the factors affecting the outcomes of such cases. METHODS: We present the outcomes of a consecutive, retrospective case series of 51 periprosthetic joint infections managed with a two-stage revision knee arthroplasty over a three year period. RESULTS: Forty-six (90%) of 51 were referred from other hospitals. Infection was successfully eradicated in 24 (65%) of 37 patients undergoing an initial two-stage procedure. Following a failed two-stage revision, a repeat two-stage revision was performed in 19 patients eradicating infection in 8 (42%). A third two-stage was performed in five of these patients eradicating infection in three with an average follow-up of 43 months. Multidrug resistance was present in 69%, and 47% of the patients were infected with multiple organisms. All unsuccessful outcomes involved at least one multidrug-resistant organism compared to 43% in the successful cohort (P=0.0002). Serological markers prior to a second-stage procedure were not significantly different between successful and unsuccessful outcome groups. CONCLUSION: Single or multiple two-stage revisions can eradicate infection despite previous failed attempts. In this series, failure is associated with multidrug resistance, previous failed attempts to eradicate infection and a less favourable host response.