Femoral head collapse due to avascular necrosis (AVN) is a relatively rare occurrence following intertrochanteric fractures; however, with over thirty-thousand intertrochanteric fractures per year in England and Wales alone, and an incidence of up to 1.16%, it is still significant. Often patients are treated with a hip fixation device, such as a sliding hip screw or X-Bolt. This study aimed to investigate the influence of three factors on the likelihood of head collapse: (1) implant type; (2) the size of the femoral head; and (3) the size of the AVN lesion.

Finite element (FE) models of an intact femur, and femurs implanted with two common hip fixation designs, the Compression Hip Screw (Smith & Nephew) and the X-Bolt (X-Bolt Orthopaedics), were developed. Experimental validation of the FE models on 4^th generation Sawbones composite femurs (n=5) found the peak failure loads predicted by the implanted model was accurate to within 14%. Following validation on Sawbones, the material modulus (E) was updated to represent cancellous (E=500MPa) and cortical (E=1GPa) bone, and the influence of implant design, head size, and AVN was examined. Four head sizes were compared: mean male (48.4 mm) and female (42.2 mm) head sizes ± two standard deviations. A conical representation of an AVN lesion with a lower modulus (1MPa) was created, and four different radii were studied. The risk of head collapse was assessed from (1) the critical buckling pressure and (2) the peak failure stress.

The likelihood of head collapse was reduced by implantation of either fixation device. Smaller head sizes and greater AVN lesion size increased the risk of femoral head collapse. These results indicate the treatment of intertrochanteric fractures with a hip fixation device does not increase the risk of head collapse; however, patient factors such as small head size and AVN severity significantly increase the risk.

There is a lack of information about the association between patellofemoral osteoarthritis (PFOA) and both adolescent Anterior Knee Pain (AKP) and previous patellar dislocations.

This case-control study involved 222 participants from our knee arthroplasty database answering a questionnaire. 111 patients suffering PFOA were 1:1 matched with a unicompartmental tibiofemoral arthritis control group. Multivariate correlation and binary logistic regression analysis was performed, with odds ratios (ORs) and 95% confidence intervals (CIs) calculated. This analysis helps us assess the effect of both variables whilst adjusting for major confounders, such as previous surgery and patient-reported instability.

An individual is 7.5 times more likely to develop PFOA if they have suffered adolescent AKP (OR 7.5, 95% CIs 1.51–36.94). Additionally, experiencing a patellar dislocation increases the likelihood of development of PFOA, with an adjusted odds ratio of 3.2 (95% CIs 1.25–8.18). A 44-year difference in median age of first dislocation was also observed between the groups.

This should bring into question the traditional belief that adolescent anterior knee pain is a benign pathology. Patellar dislocation is also a significant risk factor. These patients merit investigation, we encourage clinical acknowledgement of the potential consequences when encountering patients suffering from anterior knee pain or patellar dislocation.

Introduction

The majority of primary total hip arthroplasty (THA) procedures performed throughout the world use modular junctions, such as the trunnion-head interface; however, the failure of these press-fit junctions is currently a key issue that may be exacerbated by the use of large diameter heads. Several factors are known to influence the strength of the initial connection, however, the influence of different head sizes has not previously been investigated. The aim of the study was to establish whether the choice of head size influences the initial strength of the trunnion-head connection.

Cement-induced thermal osteonecrosis is well documented, as is the potential for nerve injury from thermal energy. Cement is often used to augment fixation following excision of humeral metastases. Porcine femurs were used as a model. We sought to find out the maximum temperatures that would be reached in various parts of the bone during the cement setting process, to explore what negative effects this might have on neighbouring bone and nerve.

A 12mm by 12mm window was cut from 12 porcine femoral shafts, and Palacos R+D cement injected into the defect. As cement set, bone surface temperature was measured using infra-red thermal imaging and thermocouples used to measure temperatures at the bone-cement interface, 5mm from the cement bolus, 10mm from cement bolus and an area running around the shaft replicating radial nerve.

Bone surface temperature rose to a maximum of 34.0 C (on average), and 32.9 C in the ‘radial nerve’ thermocouple. Notably, in two bones there were fractures during specimen preparation, and maximum temperatures in these two areas exceeded 41 degrees C.

Average maximum temperatures were 58.1 C, 36.5 C and 30.1 C at the bone cement interface, 5mm and 10mm from the cement bolus respectively.

Triple-tapered cemented stems were developed in the hope that they would reduce aseptic loosening and prevent calcar bone loss.

Between March 2005 and April 2008, a consecutive series of 415 primary C-stem AMT hip arthroplasties in 386 patients were performed under the care of three surgeons at our institution. When all the patients had reached the 5-year anniversary of surgery, functional questionnaires were sent out by mail. In the event of non-response, reminders were sent by post before the patients were contacted by telephone. Postoperative radiographs were also reviewed.

Follow-up ranges from 60 to 99 months, with a mean of 76 months. 32 hips (8%) were lost to follow-up. The median OHS was 40, median SF-12 mental component score (MCS) was 50, and median SF-12 physical component score (PCS) was 39. Radiographic review showed that aseptic femoral component loosening has yet to be observed. At 99 months follow up, stem survivorship is 96.9% (95% confidence interval (CI) 82.5 to 99.5). Adverse events such as calcar fracture, greater trochanter fracture and dislocation were rare at <1%.

The C-stem AMT demonstrates excellent implant survivorship at 5–8 year follow-up, as well as good midterm functional outcome.

Introduction: Radiolucency in the DeLee and Charnley zone 1 of the acetabulum in the early post operative period is a strong predictor of long-term failure of the cemented acetabulum. There is a wide variety in the acetabular anatomy of patients presenting for total hip replacement. Zone 1 radiolucency is an indicator of the failure of penetration of cement into the relatively hard cortical bone encountered in zone 1. Cement penetration is achieved by adequate preparation, achieving containment and effective pressurisation.

Aim: To use pre operative radiological measurements to predict the risk of radiolucency around the cemented acetabular component post operation.

Hypotheses:

Dysplastic acetabuli are associated with a higher incidence of zone 1 radiolucency.

Materials and Methods: A cohort of 300 patients undergoing cemented THR in our institution was identified. Radiographs performed on the patients pre operatively, post operatively, at first follow up (6 weeks to 3months) and follow up at 1 year were analysed. The following measurements of the native acetabulum were performed: Tonnis grade of osteoarthritis, Crowe grade of dysplasia, acetabular index of depth to width, ACM angle, peak to edge distance, acetabular index of weight bearing zone, centre-edge angle of Widberg, acetabular angle of Sharp, cross over sign and posterior wall sign to assess retroversion, acetabular inclination and anteversion angle. Post operative films were then assessed for the presence of zone 1 keyholes, incidence and degree of radiolucency, cup inclination and anteversion.

Results: Patients with an acetabulum outside the normal range were more likely to have a post operative radiolucency. Radiolucency tended to progress with time. Zone 1 keyholes appeared to terminate this progression. Retroverted and steeply inclined acetabuli demonstrated a higher incidence of radiolucency. A large change in version from the native to prosthetic acetabulum was associated with an increased risk of radiolucency.

Conclusion: Thorough pre operative radiological assessment of the acetabular anatomy allows us to predict patients at high risk of post operative radiolucency. Patients with unsuitable anatomy may be more appropriate for an alternative method of fixation or require different techniques of acetabular preparation or augmentation in order to reduce their risk of loosening of the acetabular component in the long term.

Sixty four patients undergoing total hip replacement (THR) were randomized to receive a peri-articular intra-operative multi modal drug injection or to receive no injection. All patients received patient controlled analgesia (PCA) for 24 hours after surgery.

Patients receiving the peri-articular injection showed significantly less PCA consumption 6 hours postoperatively (P< 0.002). The 24 hour PCA requirement post surgery was also less (P< 0.009).

The VAS score for pain on activity in the post anaesthetic care unit (PACU) was significantly less for injected patients (P< 0.04). The VAS satisfaction score for injected patients in the PACU and 4 hours post-operatively showed no statistical difference.

Peri-articular intra-operative injection with multimodal drugs can significantly reduce post-operative patient controlled analgesia requirements and pain on activity in patients undergoing total hip replacement with no apparent increase in risk.

Background: The principal cause of late failure of the cemented acetabular component is aseptic loosening. The acetabulum is a horse shoe of cortico-cancellous bone surrounding a cortical fovea. The cancellous bone becomes denser and less porous peripherally, limiting cement penetration. A radiolucent line in the DeLee and Charnley zone 1 of the acetabulum increases the risk of loosening of the acetabular component by 38.8 times. We propose that the use of 0.5cm keyholes in zone 1 decreases the incidence of zone 1 radiolucency.

Materials and Methods: Two contemporous cohorts of 100 patients were analysed for the incidence of zone 1 radiolucency on the first post operative film. In one cohort, zone 1 keyholes were used and in the other they were not. The films were analysed independently by two blinded investigators. The incidence, length and thickness of any radiolucency were recorded.

Results: The cohort of patients in which zone 1 keyholes were used demonstrated a 9% incidence of any zone 1 radiolucency, 8% were of 1mm width or greater and 2% involved 50% or more of the zone. In the cohort of patients in which zone 1 keyholes were not used the incidence of zone 1 radiolucency was 40% with 29% demonstrating a width of 1mm or greater and 12% affecting 50% or more of the zone.

Conclusions: The use of peripheral keyholes aids penetration of cement into the denser peripheral acetabular bone as demonstrated by decreased rates of post operative zone 1 radiolucency. This decrease in the incidence of early radiolucency should result in lower rates of subsequent loosening of the acetabular component.

Introduction: Fresh autogenous cancellous bone graft is the material of choice in reconstruction and fusion procedures in foot and ankle surgery. There are many potential donor sites for graft harvest, all with recognised minor and major complications. The proximal tibia is one such potential site, and is particularly suited to foot and ankle surgery being within the operative field and under tourniquet control.

Purpose: To assess pain, morbidity and ability to weight bear in a large group of patients undergoing foot and ankle surgery utilising cancellous bone graft from the proximal tibia.

Method: A retrospective audit was undertaken of 148 procedures performed over a period of five years. Minimum follow-up was 3 months. Data were obtained from operation notes and patient interview.

Results: Most patients had no pain (78%) or very mild pain (20%) at the site of graft harvest immediately following surgery. At review, 96% had no pain; 4% had very mild pain with certain activities such as kneeling. There were no major complications. 4 patients (2.7%) had persisting areas of parasthaesia at review, but none were troubled by it. One patient had a superficial wound problem that resolved. The ability to bear weight was dictated by the primary procedure. Usually this was from 2–3 weeks. There were no complications related to early weight bearing in this series.

Conclusion: The proximal tibia is a suitable and safe site for bone graft harvest for foot and ankle surgery. There is no need for additional restriction in weight bearing following this procedure.