Aims: To investigate the effect of age and occupation on the outcome of carpal tunnel decompression.

Patients and Methods: A total of 271 patients undergoing primary carpal tunnel decompression by a single surgeon were studied. Patients with inflammatory joint disease, thyroid disease and diabetes mellitus were excluded. Outcome was assessed using the Levine-Katz carpal tunnel questionnaire at two weeks preoperatively and six months postoperatively. Cases were divided into six age groups (less than 40 years of age, 40 to 49, 50 to 59, 60 to 69, 70 to 79, and over 80 years of age) and 12 occupational groups according to the International Standard Classification of Occupations (ISCO-88). Statistical analysis was performed using one-way analysis of variance (ANOVA) and post ad-hoc analyses.

Results: Overall there was an improvement in total Levine scores in 269 (99.3%) patients (mean change 33.1, 95%CI: 31.5 to 34.7). This change was greatest in those over 80 years of age (mean 35.8, 95%CI: 29.0 to 42.6) and in those who were service or sales workers (mean 39.6, 95%CI: 34.9 to 44.2), and least in the 70–79 age group (mean 30.7, 95%CI 25.7 to 35.8) and craft and trade workers (mean 29.8, 95%CI: 21.8 to 37.9). Patients reported a greater improvement in symptoms (mean score change 21.4, 95%CI: 20.2 to 22.2), than function (mean 12, 95%CI: 11.1 to 12.7). We found no significant difference in the total, functional or symptomatic Levine score changes between the six age groups (p=0.05) and the 12 occupation groups (p=0.05) following carpal tunnel decompression.

Conclusion: Almost all patients improved after carpal tunnel decompression. However, we found no influence of age and occupation on the outcome of carpal tunnel decompression in our series of patients.

Introduction: Computer navigation systems allow real time evaluation of knee behaviour intraoperatively. Measurements made by navigation reflect soft tissue balance throughout surgery. We studied three different populations of patients undergoing total knee replacement (TKR) with a CT-free navigation system where the goal was to achieve normal alignment. We compared the initial pathological kinematics in each group with the resultant kinematics after correction.

Method: The Orthopilot® was used during TKR for three groups of patients A (n=71), B(n=60) and C(n=43) all with endstage osteoarthritis. Patients in groups A and B had TKR performed by surgeon 1, and group C by surgeon 2.

Results: Pre-operatively, the mean mechanical femoral axis and the mean mechanical femoro-tibial (MFT) angle were calculated. The mean mechanical femoral axis for group A was −0.5° varus (−6° to 9°), group B was −0.68° varus(−6° to 6°), and for group C was 2.67° valgus (−12° to 10°). P< 0.0001, using Kruskal-Wallis test. Pre-operatively, the mean MFT angle for group A was −3.75° varus(−15° to 17°), group B was −2.98° varus(−17° to 13°), and for group C was 0.16° valgus(−17° to 25°). P=0.003 using Kruskal-Wallis test. These results show that the initial preoperative kinematics are different for the three different populations.

Post-operatively we measured the mean MFT angle in groups A, B and C. In group A, the mean MFT angle was −0.38° varus (−4° to 2°), group B was −0.41° varus(−5° to 2°), and group C was −0.02° varus(−3° to 5°). P=0.7 using the Kruskal-Wallis test. These results show that the post-operative kinematics are similar between the three different populations.

Discussion: Populations A and B preoperatively exhibited a mean varus MFT angle (−0.5° and −0.68° respectively), compared with a mean valgus MFT angle for group C(2.67°), which were statistically significantly different. Although different surgeons operated on the 3 groups (surgeon 1 operated on groups A and B, and surgeon 2 operated on group C), post-operative kinematics were within a narrow range (−0.02° to −0.41°) and not statistically different (p=0.7).

Conclusion: The Orthopilot® results showed that these populations had different initial pathological kinematics. Despite this, and using different operators we obtained similar post-op results within a narrow range. Computer navigation produces reliable, reproducible results independent of population or operator variables.

Introduction: Accurate soft tissue balancing is an essential part of total knee replacement (TKR), but has been difficult to quantify using traditional instrumentation methods. Computer navigation systems allow us to accurately assess intra-operative kinematics, which are affected by soft tissue management. The aims of this study were to evaluate the role of varus and valgus stress measurements and subsequently devise an algorithm for soft tissue management during TKR.

Methods: We used the Orthopilot® CT-free navigation system during TKR for patients with primary end-stage arthritis. This was a prospective study with 71 patients collecting intra-operative kinematic data. 57 knees were varus, 13 valgus, and 1 well aligned.

Pre- and post-operatively, the surgeon applied a varus and valgus stress at maximum extension, recording the mechanical femorotibial (MFT) angle. There were no patellar resurfacings. We compared the kinematics of each varus knee. Based upon the kinematics and the surgeon’s experience the following medial releases were performed as usual and divided into three categories:

No release (limited medial approach).

Results: Pre-operatively, the mean MFT angle was −9.6° (−3° to −22°) with varus stress and −0.8° (4° to −11°) with valgus stress. Post-operatively, the mean MFT angle was −3.7° (−1° to −7°) with varus stress, and 1.1° (4° to −3°) with valgus stress. Using regressional analysis, there was a strong linear correlation between both varus (r=0.742, p< 0.0001) and valgus (r=0.771, p< 0.0001) stresses and the MFT angle.

With the following medial releases, these kinematics were found:

No release – MFT angle not less than −12° with varus stress, greater than 2° with valgus stress, and/or if extension deficit was not greater than 5°.

The results show that post-operatively, the mean MFT angle is maintained within a narrow range (−1° to −7° with varus stress, 4° to −3° with valgus stress). 5/57(9%) patients had a mean MFT angle of 6.4°(0° to 7°) with valgus stress, and were considered to have been over-corrected. There were no extension deficits.

Conclusions: Navigation allows us to quantify soft tissue balancing based upon the initial kinematics with varus and valgus stress testing. From these measurements, an algorithm was developed, which showed that an appropriate release was made in 52/57 (91%) patients, but this may require some adjustment to reduce the number of outlying results.

The purpose of the study was to evaluate if 2 week Levine score can provide an adequately responsive outcome measure in Carpal Tunnel Decompression by comparing it with 6 month score.

The treatment outcome of 300 patients with Carpal Tunnel Decompression was determined by using Levine score at 2 weeks and 6 months after surgery. The mean age of patients was 55 years and 6 months, 71.3% (214) were female with 55.33% (167) operations being performed on right hand. All patients were scored through Levine questionnaire pre operatively and at 2 weeks and 6 months from date of surgery. The correlation between the scores was evaluated.

Although statistical significance was found between the pre operative score and the scores at both 2 weeks and 6 months, no statistical difference was found between the scores at 2 weeks and 6 months post surgery. Multiple regression analysis with the 2 week–6 month score difference as the dependable variable shows a predictable outcome at 2 weeks.

We conclude that the Levine score at 2 weeks is a reliable, responsive and practical instrument for outcome measure in Carpal Tunnel Surgery. It coincides with suture removal and provides a convenient and predictive assessment of the medium term results in a high percentage of treated patients.

The accuracy of measurement in computer-assisted total knee arthroplasty is dependent on the quality of data acquisition at the start of the procedure; errors in landmark identification could lead to misalignment and therefore poorer longterm outcomes.

Some navigation systems require the surgeon to explicitly identify the femoral epicondyles in order to calculate the trans-epicondylar axis, whereas other systems are able to interpolate the epicondylar location based on a number of points acquired from the distal femoral surface. Significant inter-observer variability in landmark identification has been previously reported in dry bone studies. The purpose of this study was to test the accuracy of identification of the epicondyles during a simulated total knee replacement on a fresh cadaveric specimen.

An unfixed fresh cadaveric left lower limb was used to perform a navigated total knee replacement using the Orthopilot® (B|Braun-Aesculap, Tuttlingen, Germany) image-free navigation system.

Sixteen surgeons attending an advanced navigation training course were invited to take part. A single consultant surgeon performed initial dissection and pin placement, up to the point of landmark acquisition. Each subject was then asked to use a pointer tool to identify the medial and lateral epicondyles, as they would in an operative situation. Data were recorded by the Orthopilot® system, and exported as a 3D array for further analysis.

Initial visualisation with a 3D scatter plot showed that points were evenly distributed within a circular pattern around each epicondyle. The length of a vector between each point on each epicondyle was calculated in turn. The maximum distances between points were 15.6mm for the medial epicondyle, and 19.9mm for the lateral epicondyle.

We then calculated the length and angulation of the trans-epicondylar axis (TEA) for each observer, equivalent to the vector between each pair of points (medial and lateral epicondyle). An average TEA was calculated, and the range and standard deviation of angulation were determined. In the x axis the range was 16.3° (–8.3° to 7.9°, SD 5.1°), in the y axis the range was 18.7° (–8.7° to 10°, SD 5.2°) and in the z axis the range was 20.5° (–10.1° to 10.4°, SD 6.5°). Range of recorded TEA length was 64.5 to 74.9mm (mean 70.6mm, SD 3.3mm).

We conclude that in this simulated operative scenario, surgeons exhibited considerable variability when locating the epicondyles. Range of angulation of the TEA exceeded 16° (SD > 5.1°) in all 3 planes. We cannot recommend the use of a trans-epicondylar axis determined from 2 single points, as a reliable landmark in navigated total knee replacement.

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 was collected intra-operatively for 46 patients with primary end-stage osteoarthritis undergoing TKR surgery using a CT-free navigation system. All patients had preoperative varus knees and medial release was made using the surgeon’s experience. From this data an algorithm was developed to define the medial release based on the pre-operative mechanical femoral-tibial angle with valgus stress;

No release (tibial cut only) when valgus stress > −2/3°. Moderate release (medial aspect of tibia +/− semimembranosous tendon) when valgus stress > −5° and < −2°. Extensive release (proximal) when valgus stress < −5°. If there was a fixed flexion deformity > 5° then a posterior release was performed.

This algorithm was validated on a further set of 35 patients where it was used to determine the medial release based only on the kinematic data. The post-operative varus and valgus stress angles for the two groups were compared and showed good outcomes in terms of distribution and outliers.

The results showed that the algorithm was a suitable tool to indicate the type of release required 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.

Introduction: A departmental audit meeting identified a problem with mis-seating of the ceramic liner for the Trident Acetabular System.

Methods: We reviewed the initial postoperative radiographs of all patients who had undergone primary THR using the Trident Acetabulum. Independent review was performed by 3 experienced hip surgeons.

Results: One hundred and seventeen hips (113 patients) were identified. Nineteen had incomplete seating of the liner as judged by plain anteroposterior and lateral radiographs, (prevalence 16.3%). Pre-operative diagnosis was not a risk factor for mis-seating of the liner. One case of complete liner dissociation necessitating revision was identified; another mis-seated liner was also revised in the early postoperative period and two that were initially incompletely seated were noted on follow up radiograph to have spontaneously re-seated. Out of 15 surgeons who had used this system, 10 had at least one case where the liner was incompletely seated.

Discussion: There may be technical issues with regard to implanting this prosthesis of which surgeons should be aware. The Trident Ceramic Acetabular System has a unique design that features a titanium sleeve encapsulating the ceramic that is elevated at the periphery. This sleeve may prevent complete circumferential inspection of the liner when attempting to assess intra-operative seating. We also believe that the Trident shell can deform upon implantation, preventing complete seating of the liner. This theory is supported by the observation that two originally mis-seated liners were noted to have spontaneously re-seated on subsequent radiographs. This phenomenon can be explained by the viscoelasticity of bone and elastic recoil of the shell. The cases of persistent liner mis-seating may be explained if the hoop stresses upon implantation are large enough for plastic deformation to occur. Potential problems include metallosis, implant loosening and fatigue fracture of either the shell or liner as a result of fretting.

Introduction: Intra-articular injection of steroid to the hip prior to joint arthroplasty has been suggested in some studies to carry a risk of infection up to 30% and subsequent revision surgery required in up to 12.5%.

Methods: We undertook a review of all intra-articular hip injections performed at the Queen Alexandra Hospital, Portsmouth and the Royal Haslar Hospital, Ports-mouth between January 2000 and April 2006. Hospital notes including operation notes, anaesthetic preoperative assessments and clinic letters were used to collect the following data. Name, age, sex, and premorbid conditions in particular diabetes, medication, date of injection, substance injected, date of arthroplasty and post operative complications.

Results: 370 intra-articular hip injections were performed of which 55 subsequently had total hip arthroplasty. 1 required washout post operatively but components remained and to date have not required revision. 1 required excision arthroplasty to eradicate deep infection and is still awaiting revision arthroplasty. This shows an infection risk of 3.6% and revision rate of 1.8%.

Discussion: Our review does not show a high rate of infection following intra-articular injection. We conclude that the therapeutic and diagnostic benefits of intra-articular injection may be considered prior to total joint arthroplasty without the increased risk of subsequent infection

Performing Total Knee Replacement (TKR) surgery using computer assisted navigation systems results in more reproducibly accurate component alignment. Navigation allows real time evaluation of passive knee behaviour throughout flexion. These kinematic measurements reflect tibial rotation about the femoral condyles, patellar tracking and soft tissue balance throughout surgery. In this study, we aim to study dynamic knee function in navigated and standard instrumentation TKR patients performing a range of everyday activities using gait analysis.

A prospective randomised controlled trial evaluated the functional outcome using gait analysis with 20 patients in each of three groups – Standard, Navigated and Control. The same implant (Scorpio) and navigation system (Strykervision) was used for each patient. The control group were subjects with no history of knee pathology or gait abnormality. Using an 8-camera Vicon motion analysis system set at 120Hz (real-time motion), we assessed the following functional activies: walking, rising from/sitting in chair, ascending/descending stairs. One functional outcome measure we have analysed so far is the maximum flexion angle.

The maximum flexion angle was recorded for each activity in standard, navigated and control groups respectively. ANOVA was performed, with significance set at p< 0.05. Maximum flexion angle during gait was 65.6°, 72.6° (p=0.009) and 73.5° (p=0.74), chair rising/sitting was 82.5°, 92.8° (p=0.01), and 93.5° (p=0.64), stairs ascent/descent was 81.8°, 99° (p< 0.0001), and 113.4° (p< 0.0001).

In terms of dynamic functional outcome, we found that the average maximum flexion angle for the navigated group was greater than for the standard group; moreover, this was similar to the maximum flexion angle for the control group when performing a variety of normal daily activities.

Background & Objectives: Osteoporosis is one of the most prevalent bone diseases worldwide with fractures its major clinical consequence. Studies on the effect of osteoporosis on fracture repair are contradictory and although it might be expected for fracture repair to be delayed in osteoporotic individuals, a definitive answer still eludes us. Subsequently, the aim of this study was to attempt to clarify any such effect.

Methods: Osteoporosis was induced in 53 female Sprague-Dawley rats by ovariectomy (OVX) at 3 months. A femoral fracture was produced in these animals 12 weeks later {OVX+Fracture group (OVX+F)}. A control group received the fracture only group (F) at 6 months. The fracture consisted of an open osteotomy held with a unilateral external fixator. Outcome measures include histology, motion detector analysis, pQCT, biomechanical strength testing (BST) and digital radiography. Digital radiographs were taken at time of OVX, fracture (confirming satisfactory reduction) and sacrifice from which relative bone density (BMD) measurements were calculated.

Results: OVX+F animals were significantly heavier than F animals at fracture and sacrifice (p< 0.001 for both) and moved significantly less in days 1-4 (p=0.032) and 5-9 (p=0.020) post-fracture. Relative BMD measured in distal femur at fracture and sacrifice was significantly greater in F group (p< 0.001 for both). Furthermore, there was a significant decrease in relative BMD from fracture to sacrifice in OVX+F group (p< 0.001). pQCT showed a significantly greater total BMD {contralateral (p=0.021) and fractured femora (p< 0.001)} and trabecular BMD (p< 0.001 both limbs) in the distal femur of the F group. Histologically, no statistical differences were found, however, the F group generally displayed the most advanced repair. In the contralateral limb, the F group had significantly greater load to failure at 6 (p=0.026) and 8 (p=0.042) weeks and was significantly stiffer at 8 weeks (p=0.050). In the fractured leg, stiffness was significantly greater in the F group at 8 weeks (p=0.001).

Conclusion: OVX was linked to increased body weight, decreased motion, decreased BMD (with particular loss in trabecular BMD), and reduced mechanical properties. OVX did not have a significant effect on fracture healing and although there was no reduction in BMD at the fracture site, histology and reduced stiffness suggest it was delayed.

We prospectively studied 15 proximal tibial and 30 distal femoral fractures treated with the Less Invasive Stabilisation System for periarticular fractures about the knee.

Of these 45 fractures, one patient returned to Russia and was thus lost to follow up. The mean age of the remaining patients was 64.4 years (range 15–94 years). There were 26 females and 13 males. All fractures were classified according to the AO classification.

We found the use of temporary external fixation and mobile radiolucent wedge leg supports very helpful during surgery for these cases. We developed an increasingly aggressive postoperative mobilisation regime with increased experience of using this fixation technique.

Functional assessment was performed using the Schatzker and Lambert scores. The average time to union was 14.78 weeks (range 10– 28 weeks). 43 fractures have united with one fracture showing signs of delayed union. There were two implant failures, two deep vein thrombosis and two compartment syndromes. Five patients died of unrelated causes and without problems relating to their fracture.

We conclude that the Less Invasive Stabilisation System is a satisfactory method of treating these complex and difficult fractures about the knee with a high rate of union and good functional outcome.

Introduction: It is said that God gave us paired bilateral anatomical structures so that the trauma surgeon can compare the injured side with its uninjured counterpart. The axial rotational alignment of fingers, when disrupted by injury, may lead to scissoring. During examination, comparison is made between the rotational alignment of injured and uninjured fingers. This assumes that the rotational alignment of the fingers is symmetrical. A study was performed to ascertain normal rotational alignment, and establish whether this assumption is valid.

Materials and Methods: Standardised digital images were taken with fingers in extension. These were analysed using the angle-measuring tool on Adobe Photoshop software. The rotational angle used was that between a line joining the radial and ulnar borders of the nail plate, and the horizontal.

Results: Mean angles of rotation were 13° for the index finger, 10° for the middle, 5° for the ring and 12° for the little. Differences in the angle for ring and little fingers between the sides were not significant; these fingers are symmetrical. Index and middle fingers demonstrated statistically significant asymmetry of 2.6° (SD +/− 4.2°).

Discussion: Previous work has sought to quantify rotational alignment in cadavers or using wire markers and fluoroscopy. A new method, using digital photography and image analysis is described. We determined mean angles, showing symmetry of the ring and little but asymmetry of index and middle. Previous work has suggested that up to 10° of rotation can be tolerated. With only 2.6° of difference, clinical comparison of sides remains appropriate.

Introduction: Despite clinical history, examination and plain radiography it is occasionally difficult to locate the origin of hip pain. This is particularly relevant where the management will be a total hip arthroplasty. Local anaesthetic arthrogram of the hip may provide a simple, safe and reliable test to determine if the hip is the source of the patient’s symptoms. The aim of this study was to establish the use of this investigation in the management of hip pain.

Methods: All local anaesthetic hip arthrograms were reviewed from 1999 to 2005. All patients had completed a pain questionnaire following the arthrogram. Patients were classified into 3 groups; 1) Mild osteoarthritic changes on plain radiographs with possible referred pathology; 2) Minimal radiological changes but no obvious other pathology to refer pain; 3) Previous hip arthroplasty with unexplained pain. Those who subsequently had a primary or revision hip arthroplasty were assessed post-operatively by means of the Oxford hip score.

Results: Fifty-seven patients in total underwent a local anaesthetic hip arthrogram. From all the groups 34 patients obtained pain relief and 24 proceeded to primary or revision hip arthroplasty. Twenty three (96%) had a satisfactory post-operative outcome at an average follow-up of 2 years (average Oxford score 28). The remaining 10 patients with positive arthrograms are still waiting for surgery. All negative arthrogram patients were successfully discharged.

Discussion: A positive response to local anaesthetic hip arthrogram predicts a successful response to surgery. This permits accurate information of the results of hip surgery to be given to patients and aids in a management plan for a group of patients that can be otherwise challenging.

Background & Objectives: Statins have been shown to stimulate bone formation in vivo and in vitro in rodent models1 generating interest in the possibility that they may be useful therapeutic agents for osteoporosis. The major clinical consequence of osteoporosis are fractures that occur and although there is no firm evidence, there is a perceived associated delay in fracture repair. We examined the influence of atorvastatin on fracture repair in an ovariectomised rat fracture model.

Methods: 126 Sprague-Dawley rats had an ovariectomy (OVX) at three months and a femoral fracture (F) at six months. The fracture consisted of an open osteotomy held with an external fixator. All animals were randomly assigned into groups 1. OVX+F and early atorvastatin; 2. OVX+F and late atorvastatin; 3. OVX+F. Atorvas-tatin (5mg/kg) was given daily by oral gavage for three months in-group 1 between OVX and fracture and from time of fracture to sacrifice in-group 2. Outcome measures were histology, peripheral quantitative computed tomography (pQCT), biomechanical strength testing (BST) and digital radiography. Digital radiographs were taken at time of OVX, fracture (confirming satisfactory reduction) and sacrifice from which relative bone density (BMD) measurements were calculated.

Results: Non-statin treated animals moved significantly more in 4 days post-fracture (p=0.015), had signifi-cantly more relative (p=0.037) and total BMD (distal femur) than statin treated (p=0.040, early and p=0.036, late treatment). Total BMD at the fracture site was also significantly greater in the OVX+F than the late statin group (p=0.047) while in the adjacent site of the con-tralateral limb, the early statin group had significantly more (p=0.018) than the late statin group. However no differences were found between the early statin and OVX+F groups. Histologically, the rate of repair increased significantly in early statin (p=0.013) and OVX+F (p=0.011) groups. BST data showed no signifi-cant difference in stiffness at six or eight weeks.

Conclusion: Fractures healed in all three groups. Statins did not prevent OVX induced bone loss. Initial evidence suggests that early statin treatment may have a positive effect on early fracture, as shown by x-ray analysis and histology, however this effect was lost by week 8. Overall the evidence suggests that atorvastatin may have impaired fracture repair, particularly with late administration (relative BMD and pQCT results).

Elevated serum cobalt and chromium ion levels associated with carcinogenesis and chromosomal damage in animals have raised concerns that metal-on-metal (MOM) total hip replacement (THR) in humans may produce the same effects over time. Considering that the risks may be related to the level of these ions in the body, this study compared the serum cobalt and chromium ion levels in patients with unilateral versus bilateral 28 mm diameter MOM THR.

All patients having THR at our institution were prospectively registered on a computerised database. From our database, we identified 108 patients with Ultima (Johnson and Johnson, Leeds) MOM THR with 28 mm bearing made of cobalt-chromium alloy. After patient review in clinic and before blood results were known, patient matching was performed by date after surgery at blood sampling, activity level and body mass. Using these stringent criteria, 11 unilateral THR could be adequately matched with 11 bilateral THR. Blood serum was taken with full anti-contamination protocols and serum analysed via inductively coupled plasma mass spectrometry.

The serum cobalt ion level after unilateral MOM THR was 4.4 times normal (median 22 nmol/L, range 15 to 37 nmol/L) compared to 8.4 times normal (median 42 nmol/L, range 19 to 221 nmol/L) for bilateral MOM THR (p=0.001). The serum chromium ion level after unilateral MOM THR was 3.8 times normal (median 19 nmol/L, range 2 to 35 nmol/L) compared to 10.4 times normal (median 52 nmol/L, range 19 to 287 nmol/ L) for bilateral MOM THR (p=0.04).

This study has shown that the serum cobalt and chromium ion levels in patients with bilateral MOM THR are significantly higher than those in patients with unilateral MOM THR. With levels of up to 50 times the upper limit of normal, this finding may be of relevance for the potential development of long-term side effects.

The majority of diaphyseal forearm fractures in children are treated by closed reduction and plaster immobilisation. There is a small subset of patients where operative treatment is indicated. Recent reports indicate that elastic intramedullary nailing (EIN) is gaining popularity over plate fixation. We report the results of EIN for diaphyseal fractures of the forearm in 44 children aged between 5 and 15 years during a three-year period. The indications were instability (26), redisplacement (14), and open fractures (4). Closed reduction and nailing was carried out in 18 cases. A single bone had to be opened in 16 cases and in 10 cases both bones were opened for achieving reduction. Out of the 39 both bone forearm fractures, 35 patients had stabilisation of both radius and ulna and in 4 cases only a single bone was nailed (Radius 3, Ulna 1).

Union was achieved in all the 44 cases at an average time of 7 weeks with one delayed union. All patients regained full flexion and extension of the elbow and wrist. Pronation was restricted by an average of 20° in 30% patients.

Complications were seen in 10 patients (20%). 4 patients had prominent metal work which required early removal. There was refracture in one case, which was treated by nail removal and re-fixation. Two patients developed post operative compartment syndrome requiring fasciotomy. EIN of the radius alone in a patient with fractures of both the bones of forearm, led to secondary displacement of the ulna. This resulted in ulnar malunion and a symptomatic distal radio-ulnar joint subluxation. This was successfully treated by ulnar osteotomy.

Compared to forearm plating EIN involves minimal scarring, easier removal and less risk of nerve damage. We therefore recommend EIN for the treatment of unstable middle and proximal third forearm fractures.

The experimental determination of residual stress fields on the surface of retrieved femoral heads represents a fundamental step in understanding their wear degradation behavior and the tribological mechanisms, which are operative on the femoral joint during its working life time. In this work, the surface of retrieved alumina and zirconia (Al2O3 and ZrO2) femoral heads were investigated by piezo-spectroscopic tecniques based both on photoluminescence and Raman effects. The high spatial resolution of the laser, impinging on the investigated surface (typically about 1 micron of lateral resolution), enabled us estimating patterns and magnitude of residual stress in extremely narrow zones, comparable with the grain size of the material.

Four retrieved ceramic femoral heads were analyzed. Two balls were made of alumina with a typical grain size of from 4 to 10 microns. Both alumina balls were retrieved after only few years from implantation, due to septic and aspetic loosening. The remaining two femoral heads were made of zirconia with a typical grain size of 1 micron. These latter balls were retrieved after 2 and 13 years, respectively (both for loosening problems). With a systematic collection of a large number of data on a microscopic level it was possible to assess the retrieved femoral heads in to to, thus extending the microscopic analysis to the entire joint.

In allumina balls retrieved after short time implantation, a macroscopic stress field was found, which arose from manufacturing, loading history, and the displacements acting on the femoral head during its lifetime. This stress field was completely overcome by a microscopic residual stress field due to local contacts (e.g., local shocks owing to microseparation, impinging and wear contacts). On the other hand, in zirconia femural heads, the major amount of surface deterioration after long-term exposure arose from tetragonal-to-monoclinic transformation in biological environment. These data allowed us to draw interesting considerations about the role of the material microstructure and the peculiar kinematic mechanisms involved with the use of femoral heads made of different materials.

Spectroscopic techniques, which are complementary to in vitro testing procedures and stress analyses based on finite-element methods, can be very useful for improving the design of the femoral head and for optimizing the microstructural characteristics of the ceramic materials employed. Based on this and previous fluorescence and Raman spectroscopic studies, we also propose that a systematic screening of the ceramic implants before implantation can strongly reduce the probability of failure of the implant.

Alumina ceramic has been used in total hip arthoplasty since the 70’s and, in the last 30 years, a considerable evolution has occurred in designing the microstructural features of this material, taking advantage of improved processing techniques, as the hot isostatic pressing. As a result, a high degree of densification (> 99.5) has been achieved in materials with a high degree of purity and, especially, with a fine grain size ( 2 microns). The surface stress field acting on a femoral head inoperation is not only due to working conditions, but also to unexpected factors, as local impacts on the surface as a result of partial dislocations, formation of debris, etc. These additional factors greatly contribute to activate degradation mechanisms which, unfortunately, may lead to failure of the implant.

In this study, five alumina femoral heads were investigated, which were retrieved from patients after different periods of time. Among those investigated femoral heads, two belonged to a first-generation type of alumina material with a relatively coarse grainsize (average value 8 microns) and were retrieved due to surface degradation after long periods of implantation (19 and 17 years, respectively); the remaining three implants analyzed were instead recently manufactured implants with a fine grain size; they were retrieved after relatively short periods because of different causes as, for example, cup or stem loosening.

Surface stress analysis using the luminescence of Cr3+impurity in alumina was performed on the retrieved femoral heads and a statistical comparison was attempted among implants with different microstructural characteristics. The investigation led to estimate average residual stress and statistical stress distributions as a function of the location on the femoral head.

The analysis was performed both on the very surface and in the sub-surface of the head, using the confocal and the through-focus configurations of the optical spectrometer, respectively. Different statistical distributions of residual stress were observed in alumina femoral heads with different grain sizes and models were created to understand their dependence on processing and surface loading.

Metal-on-metal (MOM) bearings after total hip arthroplasty are known to elevate the serum concentrations of metal ions, raising concerns about the long-term effects. One potential modifier of ion release is the bearing diameter used. Resurfacing MOM bearings have a large surface area available for corrosion compared to the typical bearing size of 28 mm in total hip replacement (THR) but may benefit from improved lubrication and reduced production of corrodible wear debris. The net effect of these two variables on metal ion release is unknown. In this study, we compared the level of ion release in patients after large bearing MOM hip resurfacing arthroplasty with patient after small bearing MOM THR.

We measured the serum cobalt and chromium levels from 22 patients with large bearing diameter MOM hip resurfacing arthroplasty (Cormet 2000 and Birmingham Hip Resurfacing) and compared them to the serum cobalt and chromium levels of 22 patients with small bearing diameter (28 mm) MOM THR (Ultima). Patients were prospectively matched for activity level, body mass and date after surgery at blood sampling. All were at least 6 months after surgery.

We found the median cobalt and chromium levels after hip resurfacing arthroplasty to be 7.6 times normal (median 38 nmol/L, range 14 to 144 nmol/L) and 10.5 times normal (median 53 nmol/L, range 25 to 165 nmol/ L) respectively. This is compared to 4.4 times normal (median 22 nmol/L, range 15 to 87 nmol/L) for cobalt and 3.8 times normal (median 19 nmol/L, range 2 to 58 nmol/L) for chromium after 28 mm MOM THR (p=0.0021 and p< 0.0001).

Conclusion: Large diameter MOM bearings result in greater release of cobalt and chromium ions than do small diameter MOM bearings. This may be of relevance when the potential effects of long-term exposure to elevated these metal ions is considered.

Prior studies have compared the bacterial load observed in laminar flow operating theatres (LFOTs) and standard operating theatres (STOTs) by wound culture and air sampling during surgery. However many organisms responsible for low grade infection after THR are not readily identified on routine culture and may be detectable only by more sensitive techniques such as the poly-merase chain reaction (PCR). This study assessed the wound contamination rate during THRs and compared the results in STOT with that in LFOTs using PCR.

We recruited patients undergoing primary THR for osteoarthritis. Surgery was performed in either STOTs or LFOTs, using identical skin preparation solutions, surgical drapes and operating attire. Specimens of the deep tissue, taken at the beginning and end of surgery, were each immediately separated into two sterile containers, one sent for culture (aerobic, anaerobic and enriched meat broth) and the other frozen at minus 80 degrees Celsius for PCR at a later date.

In each theatre type, 40 specimens from 20 THRs were analysed by both PCR and culture. Using PCR, bacterial DNA was identified on 12 of 40 specimens (30%) from STOTs, of which 3 were taken at the start of surgery and 9 at the end of the surgery, giving a 45% wound contamination rate (9 of 20). Two specimens (5%), both taken at the end of surgery, were positive on enriched culture. In LFOTs, bacterial DNA was identified by PCR on 8 of 40 specimens (20%), of which 2 were taken at the start of surgery and 6 at the end of surgery, giving a 30% wound contamination rate (6 of 20). No specimens were positive on enriched culture.

Wound contamination of primary THR occurs frequently in both STOTs and LFOTs. Although STOTs showed evidence of more frequent wound contamination than LFOTs, with the numbers available, no significant difference was detected. These data remind us the importance of aseptic surgical technique as significant wound contamination can occur despite the use of ultra clean air operating theatres.

Distal tibial fractures may be satisfactorily held in reduction by fine-wire external fixation techniques, avoiding the need for open reduction and internal fixation. However, as the use of external fixation is associated with pin-site infection, extra-articular placement of the wires is recommended. This study assesses the proximal extension of the capsule of the ankle joint in order to provide information on the safety of wire placement for distal tibia fractures.

We recruited 7 patients who were electively scheduled for an MRI ankle investigation with the suspicion of osteochondral defect and/or meniscoid lesion. Patients with a history of ankle fracture or ankle surgery were excluded from the study. Just prior to MRI, the ankle joint was injected with 5 to 15 ml of contrast solution (1 mM dimeglumine gadopentetate). Selected fat-saturated T1-weighted MRI scans with sagittal, coronal and axial views were obtained. The site and proximal extent of the capsular reflection with reference to the anterior joint line were measured.

All contrast-enhanced MRIs of the ankle joint space were well defined and unambiguous. Proximal capsular extensions above the plane of the anterior joint line were noted at the antero-medial and antero-lateral aspect of the joint (mean 8.9 mm, range 4.9 to 13.4 mm) and at the tibia-fibular recess (mean 18.7 mm, range 13.3 to 23.6 mm), areas that are frequently traversed by wire insertion.

Conclusion: This in vivo contrast-enhanced MRI ankle study demonstrates an appreciable capsular extension above the joint line of the ankle. The proximal capsular extensions at the antero-medial and antero-lateral aspect of the joint and at the tibio-fibular recess run the risk of being traversed during fine-wire placement for distal tibia fractures. Surgeons using these techniques should be aware of this anatomy.

Zirconia (ZrO2) on Polyethylene (PE) has been used for18 years. However, a majority of clinical results expressed caution, citing surprisingly high wear and osteolysis. The most recent clinical study (Walters 2004) reports 20% higher wear with ZrO2/PE compared to CoCr/PE The PE wear may be the result of increased surface roughness of the ball, due to zirconia transformation from tetragonal to monoclinic phase. Impingement of metal cup backing on zirconia may result in high stress that drives the transformation. Our objective was to simulate the conditions most likely to transform the zirconia ball surface.

In phase one, the rim of a titanium cup was loaded against a zirconia ball with a static load range of 0.01kN to 10kN to simulate impingement-dislocation stress. The ball was cleaned with acid, ultrasonic cleaning, and then observed under SEM. Ball sections were made for XRD study. In phase two, the zirconia balls were pressure stressed in a hip simulator (static load range of 1kN to 4kN) for 600 cycles. Wear studies follow.

In phase one, the rim of a titanium cup was loaded against a zirconia ball with a static load range of 0.01kN to 10kN to simulate impingement-dislocation stress. The ball was cleaned with acid, ultrasonic cleaning, and then observed under SEM. Ball sections were made for XRD study. In phase two, the zirconia balls were pressure stressed in a hip simulator (static load range of 1kN to 4kN) for 600 cycles. Wear studies follow.

Pressure alone does not appear to transform zirconia in the articular surface. The phase two simulator studies include combinations of mechanical stress, environmental aging (autoclave) and lubricants (air, water, serum). The role of the heavy metal transfer may actually protect the zirconia surface from transformation phenomena.

Idiopathic osteoarthritis (OA) is a complex, late-onset disease whose causes are still unknown. In spite of tremendous efforts, the search for the genes pre-disposing towards osteoarthritis has so far met with little success. We hypothesize that epigenetic changes play a major role in the pathology of OA. Epigenetics refers to stable, heritable, but potentially reversible modifications of gene expression that do not involve mutations in the DNA sequence, for example DNA methylation or histone modification. Epigenetic changes are gene and cell-type specific, may arise sporadically with increasing age or be provoked by environmental factors. To investigate whether epigenetic changes are significant factors in OA, we examined the DNA methylation status of the promoter regions of three genes that are expressed by OA, but not by normal, articular chondrocytes, namely MMP-3 (stromelysin-1), MMP-9 (gelatinase B) and MMP-13 (collagenase3). We hypothesized that these genes are silenced in normal chondrocytes by methylation of the cytosines of CpG dinucleotides in the respective promoter regions, but that abnormal expression is associated with a de-methylation, leading to eunsilencing f of gene expression. Cartilage was obtained from the femoral heads of 16 OA and 10 femoral neck fracture (#NOF) patients, which served as controls due to the inverse relationship between osteoporosis and OA. The cartilage was milled in a freezer mill with liquid nitrogen, DNA was extracted with a Qiagen kit, digested with methylation sensitive restriction enzymes, followed by PCR amplification. These enzymes will cut at their specific cleavage sites only if the CpGs is not methylated and thus allow us to determine methylation status of specific CpG sites.

Results. Less than 5% of the chondrocytes in superficial layer from #NOF cartilage expressed degradative enzymes, whereas all cloned chondrocytes from advanced-stage OA cartilage were immunopositive. The overall % of CpG demethylation in the promoters of control patients (whose chondrocytes did not express the enzymes) was 20.1%, whereas 48.6% of CpG sites were demethylated in degradative chondrocytes of OA patients (p< 0.001). For MMP-13, the increase in demethylation between control and OA was from 4 ^..20%; for MMP-9 from 47 ^..81% and for MMP-3 from 30 ^..57%. However, not all available CpG sites were equally demethylated. Some sites were uniformly methylated in both OA and controls, others were demethylated even in controls. However, there was at least one crucial site for each degradative enzyme, where the differences in the degree of methylation were greatest and statistically different. These sites were at −110 for MMP-13; −36 for MMP-9; −635 for MMP-3. There was no relation between the % demethylation and the patient fs age and no apparent difference between males and females.

Conclusions: We have demonstrated an association between abnormal gene expression of MMP-3, MMP-9 and MMP-13 and promoter DNA demethylation. This epigenetic dysregulation of genes appeared to be clonally inherited by daughter cells and may be typical for osteoarthritis and other complex, late-onset diseases.

In osteoarthritis (OA) there is a loss of matrix components, especially aggrecan, which is a major structural component important for the integrity and function of articular cartilage. The breakdown of aggrecan is mediated by enzymes from the ADAM-TS (a disintegrin and metalloproteinase with thrombospondin motifs) family and recent studies have suggested that, in humans, ADAM-TS4 (aggrecanase-1) plays a major role. Articular chondrocytes do not express ADAM-TS4 in contrast to clonal OA chondrocytes. Since in any somatic cell non-expressed genes are thought to be silenced by DNA methylation in the promoter region, the aims of the project were twofold:

to localize enzyme expression for ADAM-TS4 by immunocytochemistry and

Using immunocytochemistry, we confirmed that there is an increased expression of ADAM-TS4 in OA chondrocytes, which initially occurs in chondrocytes of the superficial zone. As the Mankin score increases, ADAM-TS4 positive chondrocytes were found in duplets, then quadruplets until, at Mankin score > 10, all the cells in a typical OA clone were immunopositive for ADAM-TS4, suggesting that abnormal enzyme expression was inherited by daughter cells. DNA was extracted from femoral head cartilage of 24 patients, who had undergone hip replacement surgery for either symptomatic OA or following a fracture of neck of femur (#NOF). The latter was used as control due to the inverse relationship between OA and osteoporosis. For OA samples, it was important to sample only those regions for which immunocytochemistry had shown the presence of ADAM-TS4 synthesizing cells, i.e. the superficial zones near the weight-bearing region. DNA methylation only occurs at cytosines of the sequence 5′...CG...3′, the so-called CpG sites. To determine methylation status of specific CpG sites, methylation sensitive restriction enzymes were used, which will only cut DNA in the absence of methylation. By designing PCR primers that bracketed these sites, presence or absence of PCR bands could distinguish between methylated and non-methylated CpGs respectively. The ADAM-TS4 promoter contains a total of 13 CpG sites. Using restriction enzyme/primers combinations, it was possible to analyze 7 of these sites for methylation status. In the control group, all 7 CpG sites were methylated, while there was an overall 49% decrease of methylation in the OA group (p=< 0.0001). Some of the CpG sites were more consistently demethylated then others, one site at −753bp upstream from the transcription start site, showed a 86% decrease in methylation in OA compared to the control group (p=0.0005), while at other sites the decrease in methylation ranged from 36–50%. Conclusions. This study confirmed by immunocytochemistry that ADAM-TS4 is produced by OA chondrocytes, contributing to the degradation of their matrix. This abnormal enzyme expression is associated with DNA methylation. If a causal relationship could be proven in the future, then DNA de-methylation might play an important role in the pathogenesis of osteoarthritis and future therapies might be directed at influencing the methylation status.

Introduction: There is some debate about the pros and cons of selective screening of DDH in neonates as opposed to general screening. General screening puts a lot of stress on the resources available, especially in the modern day NHS, but the advocates state that this minimises the cost incurred in treating a missed DDH (by selective screening) with surgery later on.

Aim: The aim of this retrospective study was to find out the effectiveness of the Southampton selective screening of babies with risk factors for DDH by finding out the number of patients presenting late with an established DDH.

Materials And Methods: 6116 babies out of 26,932 live births (22.7%) in Southampton were screened between 1998 and 2003. The details of the individual outcomes and the reasons for the late presentation were obtained from the patient notes and the records of the screening program which are maintained in the clinics and by the senior author.

Results: 248 new patients had Pavlik’s harness fitted for the treatment of DDH which presents a treatment rate of 0.92%. 8 patients (0.03%) presented late because they did not undergo ultrasound scanning as they did not have the risk factors as required by this selective program. 10 (0.036%) failed Pavlik’s and needed late surgery to have their DDH treated. The total operation rate was 0.066%.

Discussion: The late presentation of patients in this screening program is very low and comparable to the other papers from this department and from around the world. The cost implications of treating these 8 late presenting patients was found to be a lot cheaper than carrying out a general screening program which would mean, in this case 4 times more than the cost of the present screening program.

Clonal chondrocytes of osteoarthritic (OA) cartilage express an aberrant set of genes. We hypothesize that this aberrant gene expression may be due to clonally inherited epigenetic changes, defined as altered gene expression without changes in genetic sequence. The major epigenetic changes are due to altered DNA methylations in crucial parts of the promoter region. If the cytosines of CpG dinucleotides are methylated, the gene will be silenced, even if the right transcription factors are present. Similarly, de-methylations may activate previously silenced genes. Our aims were to provide ‘proof-of-concept’ data by examining the methylation status of genes in OA vs non-OA chondrocytes. Articular cartilage was obtained a) from the cartilage of fracture-neck-of-femur (#NOF) patients and b) from or around the eroded regions of OA samples. The former was full thickness cartilage, the latter was partially degraded cartilage, which contained mostly clonal chondrocytes as confirmed by histology. The cartilage samples were ground in a freezer mill (Glen Creston, UK) and DNA was extracted with a Qiagen DNeasy maxi kit. To assess DNA methylation status, the genomic DNA was treated overnight with methylation-sensitive restriction enzymes. Cleavage of selected sites was detected by PCR amplifications with primer pairs designed to bracket selected promoter regions. Loss of the PCR band after digestion with the enzymes indicated absence of methylations, whereas presence of the band indicated methylated cytosine. We selected MMP-9 as one of genes that is activated in OA. Transcription of mmp-9 is regulated by a 670 bp sequence at the 5′-end flanking region, which contains 6 CpGs and a further 21 CpGs within the 1.5 kb region further upstream. A PCR primer pair was designed to bracket a 350bp sequence upstream from the transcription start site of mmp-9, which contained four of the six potential methylation sites, cleaved by the methylation-sensitive enzymes AciI and HhaI. DNA from 9 OA patients, 5 #NOF patients and 1 rheumatoid arthritic (RA) patient were digested with HhaI or AciI and examined for the presence or absence of PCR bands. In all patients, digestion with HhaI abolished the PCR band, indicating that the HhaI site was never methylated in either #NOF or OA patients. However, a remarkable difference was found after digestion with AciI: in 8/9 OA patients, the PCR band was no longer detectable, while in 4/5 #NOF patients the PCR band was still present. This suggested that all three AciI cleavage sites were methylated in the majority of chondrocytes from #NOF patients, while at least one of the three AciI cleavage sites was unmethylated in OA patients. Interestingly, the PCR band was present in the RA patient, suggesting methylation of the AciI cleavage sites. The present study provides the first ‘proof-of-concept’ data that suggest epigenetic changes may play a role in the etiology of osteoarthritis. Clearly further work is required to establish the generality of the present findings and whether de-methylations are also found in the promoter regions of other genes that are aberrantly expressed in OA.

Introduction Surgeons request cross-match based on habit not evidence. The spinal unit requested 686 units of blood during 2002–2003 and transfused only 42 for elective lumbar spine surgery. This wastes money, time and blood.

Aim Optimise the transfusion requests in elective lumbar spinal surgery by creating evidence based guidelines.

Methods The data on elective operations performed on the lumbar spine during the period June 2002 to June 2003 was collected from the spinal unit database and cross-referenced with the records of blood transfusion. Cross-match: Transfusion ratios (C:T Ratio) and Transfusion Index (TI) for common procedures were calculated. Based on these results, a Maximum Surgical Blood Ordering Schedule (MSBOS) was created and prospectively audited for six months.

Conclusion Eighty units were cross-matched during the prospective audit. Therefore, in one year one hundred and sixty units would be requested. This represents a reduction of over five hundred units.

Introduction: Chondro-epiphyseal cartilage is generally resistant to vascular invasion. At the time of formation of the secondary ossification center in skeletal ‘long’ bones, the anti-angiogenic nature of cartilage is altered in favor of angiogenesis and vascular invasion takes place. We studied the control of this angiogenic ‘switch’ by experimentally investigating two factors which might influence vascular invasion. MMP 9 is a 92Kda gelatinase which degrades collagen types IV, V and X and gelatin (denatured collagen). It has been implicated in the control of endochondral ossification at the growth plate and has been shown to modulate endothelial cell morphogenesis. Basic Fibro-blast Growth Factor (b-FGF) is a cytokine with well established angiogenic capability and has also been implicated in the development of the growth plate. We investigated whether MMP-9 caused an effect on the development of the vasculature of the chondro-epiphysis of neo-natal rabbits and compared this to the effects of b-FGF.

Materials and Methods: The CAM Culture consists of placing a small tissue explant onto the the chorioallantoic membrane of 10 day-old chick embryos and continuing culture for a further 10 days. CAM derived vessels will invade the tissue, unless anti-angiogenic factors are present. Hence, CAM culture is used as an assay system for angiogenesis and factors that will influence it. We utilized the CAM culture model to investigate vascular in-growth into explants of femoral and humeral heads from 4 day old postnatal rabbits to test the influence of MMP-9 and b-FGF. A small nylon membrane, pre-soaked in a solution containing the factor, was placed on to a tangential cut across the perichondrium. The explant was then cultured on the CAM for 3–10 days.

Results: In control epiphyses, the in-growth of CAM derived blood vessels was rare and invasion of cartilage canals through the perichondrium seldom occurred, thus confirming the anti-angiogenic nature of epiphyseal cartilage. The initial presence of MMP 9 caused a tremendous increase in the de novo vascular invasion. MMP 9 treated epiphyses contained numerous large cartilage canals. In b-FGF treated epiphyses, a greater level of vascular in-growth was seen compared with controls, but this was not as marked as with MMP 9.

Our findings indicate that b-FGF and perhaps, more interestingly, MMP-9 are implicated in the activation of the angiogenic ‘switch’ at the chondroepiphysis leading to vascular invasion. The fact that MMP-9 can act as a stimulator to angiogenesis is a novel finding. The mechanism of action remains unclear although it is possible that it is involved in the deactivation of inhibitors of vasculogenesis or the activation of angiogenic factors, or both.

Study Design: Prospective cohort study

Summary of Background data: A definite link between Modic end plate changes and discogenic low back pain has yet to be established. However, current prospective data indicates that Modic changes strongly correlate with the pain provocation of lumbar discography and improved clinical outcome following instrumented posterolateral fusion. Consequently, there is recent heightened awareness using this radiological entity in the selection of patients for interbody fusion or total disc replacement.

Objective: To prospectively evaluate whether Modic changes can predict improved clinical outcome following antero-posterior lumbar interbody fusion using femoral ring allograft.

Methods: A cohort of chronic low back pain patients were investigated with MRI and lumbar discography. Twenty-six patients with disco-graphically-proven concordant pain reproduction were prospectively entered into the study. Clinical results were collected using the Oswestry Disability Index (ODI), Visual Analogue Scale (VAS) and Short Form 36 Health Questionnaire (SF-36) at the pre-operative and two-year follow up. The minimal clinically important difference (MCID) was taken as 10 points for ODI, 2 points for VPAS, and 7 points for the physical function and bodily pain subset of the SF-36 questionnaire.

Results: MRI scans evaluated for the level fused revealed 13 patients with no end-plate changes (Type 0), whilst 2 patients had Modic Type I and 11 had Modic Type II changes. MCID in ODI were achieved in Type 0, Type 1 and Type 2, but improvement in VAS only was achieved in the Type 0 and Type 1. For SF-36, the MCID of 7 points was reached in most domains for all types of Modic change. There was no statistical difference in clinical outcome between those patients with Modic Type 0 and those with Modic type I or II.

Conclusion: This prospective study shows that Modic changes do not predict improved clinical outcome following antero-posterior interbody fusion using the femoral ring allograft.

Introduction: In the 1970’s, ‘viscosupplementation’ with hyaluronan was proposed as a potential treatment for OA with the idea that it would improve joint lubrication. However, despite studies showing its ability to reduce pain, the fact that the resident time within a joint (48 hours) is much less than its clinical effect (several months) along with pharmacological effects on chondroctyes and synoviocytes has confirmed that injected hyaluronan acts as a pharmaceutical rather than as a lubricant as originally thought. In this regard, the effects of inert synthetic lubricants on arthritic joints have not previously been adequately investigated.

This study examines the effect of injecting an inert synthetic lubricant, perfluoroalkylether (PFAE16350), as a mechanical joint lubricant to prevent the development of osteoarthritis in a surgically induced model of osteoarthritis in the adult guinea pig.

Materials & Methods: Osteoarthritic changes were initiated in the hind knee joint of 12 adult male Dunkin-Hartley guinea-pigs by excision of the medial meniscus and anterior cruciate ligament.

After wound closure, the animals were randomly assigned to 1 of 2 groups: (1) Single intra-articular injection of 1ml synthetic, sterile lubricant (PFAE16350) or (2) Control group with single intra-articular injection of 1ml 0.9% sterile saline.

At 9 weeks after surgery, after sacrifice, knee arthrotomy was performed, the presence of synthetic lubricant noted and the articular cartilages examined for macroscopic evidence of osteoarthritis. These cartilages were then fixed, embedded, sectioned, stained and graded histologically for osteoarthritis according to a modified Mankin scoring system.

Immunohistochemical studies were performed to assess for any inflammatory or cytotoxic effect by the lubricant.

Results: All guinea-pigs remained healthy and mobile throughout the study.

Subjective macroscopic assessment of the medial tibial plateau osteophyte was noted to be larger and the articular surface more roughened in the control cases compared to the lubricated cases. Synthetic lubricant was noted at arthrotomy in all cases where it was injected.

Guinea-pig joints treated with the synthetic lubricant showed a mean modified Mankin score of 3.0 points compared with the guinea-pig joints treated with saline where the median modified Mankin score was 8.5 points (p< 0.001). There was no evidence of an inflammatory or cytotoxic response by immunohistochemical studies.

Discussion: This study has confirmed that inert synthetic perfluoroalkylether lubricants can remain in the articular space for prolonged periods and inhibit the development of osteoarthritis without initiating an inflammatory response. Synthetic lubricants such as PFAE16350 warrant further investigation for potential use in osteoarthritis.

A 12 year old girl presented with a history of intermittent pain in her left knee since she started walking. She was seen in the vascular clinic due to engorged veins in her left leg and was diagnosis of Klippel-Trenaunay syndrome was made. Her knee pain worsened and an orthopaedic opinion was obtained. A history of repeated knee effusion and swelling was noted.

Examination revealed partial gigantism of the left leg and reduced range of motion of the knee. There was soft tissue swelling of the knee with no effusion. Blood investigations were normal. X-rays showed an arthritic joint. MRI scans revealed synovial thickening and a vascular malformation suggesting a synovial haemangioma. She underwent Radical Open Synovectomy and excision of the haemangioma. Blood loss was minimal. Extensive haemosiderin deposition was noted along with Grade IV arthritic changes. Postoperative recovery was uneventful. Surgeons have been reluctant to excise synovial hemangiomas due to the risk of haemorrhage.

A recent paper from Switzerland suggested excision was possible with minimal blood loss. Haemosiderin deposition due to recurrent haemarthrosis may predispose to articular damage. We recommend early excision of synovial haemangiomas to minimise articular damage.

Introduction: The National Bone Bank of Ireland was established in June 1996 at Cappagh National Orthopaedic Hospital, Dublin in response to the increased demand of allogenic bone grafts in Ireland. We reviewed the Bone Bank performance since it started with special emphasis on Microbiological monitoring of bone allograft as infection is the main complication of bone allograft (Chapman and Villar 1992).

Material and Methods: The femoral head allograft is harvested from living volunteer donors who are undergoing primary total hip replacement at Cappagh Hospital and have been assessed by the Bone Bank Co-Ordinator.

Harvesting: The bone is retrieved and harvested at the time of total hip replacement according to a strict protocol.

Storage: The bone is stored in the “Quarantine” freezer at −80 degrees C for a minimum period of 180 days. Each specimen is subjected to a full technical review by the Bone Bank Co-Ordinator and Medical Director and only when results of screening confirmed negative, the bone designated suitable for “Issue Stock” freezer.

Issue of Allografts: Bone is supplied for use, only after receiving full details of recipient to allow tracking. The results of the culture swab taken at the time of implantation and details of any post operative infection in recipients are forwarded to the bone bank.

Results: From June 1996 to December 2003, 5089 Primary Total Hip Replacements done at Cappagh Hospital and 1921 (38%) femoral heads were harvested. 109 (5.7%) of grafts had initial positive swabs/chips and 22 of these were discarded because of second positive chips. 1457 femoral head grafts supplied to 876 recipients and were used in Revision Total Hip Replacement (60%), Spine Surgeries (15%), Revision Total Knee (12%), Fractures, Tumours, Foot and Ankle (12%). 6 swabs at the time of grafting in recipients grew Staphylococcus Epidermidis but no clinical infection reported in our follow-up system. To double check, we posted a questioner to all consultants with list and details of their recipient patients and only 2 cases of suspected grafts related infection reported.

Discussion and Conclusion: Microbiological surveillance of bone grafts protect recipients from infection and is useful as a quality control of the process of bone banking (Farrington et al 1998). Our study showed contamination rate of 5.7%. Minimum infection rate post Revision Hip Replacement has been reported by Tomford in 1990, but after massive femoral allograft, infection has been reported 4% – 5% (Tomford 1990) and over 11% by Lord et al in 1988. Our experience showed only 2 cases in spite of strict follow-up protocol. We follow the policy of discarding the heavily contaminated grafts (Chapman 1992).

The quality performance of a Bone Bank depend on a full time bone bank co-ordinator, identification of donors, retrieval and harvesting of grafts, blood and microbiological assessment, medical supervision for decisions about contaminated grafts, a strict follow-up protocol and a regular audit of bone bank (Ivory and Thomas 1993). We also suggest that regular correspondence to the consultant using the bone grafts will improve the accuracy of follow-up.

Study Design: Retrospective chart review.

Objective: To assess the clinical and radiological outcome of surgery for both dystrophic and non-dystrophic curves resulting from neurofibromatosis Type I.:

Subjects: 10 patients (7 females, 3 males) underwent surgical correction for neurofibromatous kypho-scoliosis between 1997–2003. The mean age at surgery was 16 years (range 8–37 years). Average follow-up 20 months (range 9 months – 4.5 years). Seven patients had MRI proven dystrophic curves (group I). These underwent 2–3 level apical vertebrectomy, followed by 2–3 weeks in Halo traction, followed by instrumented posterior spinal fusion and anterior rib strut grafting. Three patients had non-dystrophic curves (group II). Two underwent posterior instrumented fusion and one (aged 8 years) underwent convex epiphyseodesis with posterior Luque trolley.

Outcome Measures: Cobb angle, thoracic kyphosis, lumbar lordosis, global apical vertebral translation (AVT), regional AVT, coronal and sagittal balance, complications and Modified SRS Outcomes Instrument completed at final follow.

Results: For the dystrophic curves the Cobb angle improved from a mean of 81.5 degrees (mean bending film to 76 degrees) to 26.6 degrees post-operatively (68% correction) and 35.8 degrees at final follow-up (56% correction) and the global AVT improved from 61.5 mm to 29 mm at final follow-up. The average score for the modified SRS outcome instrument was 91.6 (Good). For the non-dystrophic curves the Cobb angle improved from a mean of 57.5 degrees (mean bending film to 47 degrees) to 23.5 degrees post-operatively ( 60% correction) and 24.6 degrees at final follow-up (57% correction) and the global AVT improved from 56.8 mm to 27.8 mm at final follow-up. The average score for the modified SRS outcome instrument was 98.5 (Good). All complications occurred in the dystrophic group including superficial infection in 2, dural leaks in 3, temporary brachial plexus injury in 1, worsening of lower limb neurological deficit in 1 and one death (upper GI haemorrhage). There was no failure of metalwork or evidence of pseudarthrosis identified. Seven of eight patients stated that they would have the surgery done again.

Conclusions: Non-dystrophic curves maybe treated by posterior fusion alone achieving 60% Cobb correction and 55% AVT correction. Close observation should be maintained for the appearance of dystrophic features and deterioration of correction. Dystrophic curves should be treated early and aggressively by two/three stage apical vertebrectomy, grafting and posterior spinal fusion. In this series 68% coronal Cobb and 63% AVT correction was achieved post-operatively. Complications can be expected with scoliosis associated with more than 50 degrees of kyphosis.

The use of designer scaffolds to deliver biologically active osteogenic growth factors such as recombinant human bone morphogenetic protein-2 (rhBMP-2) to the sites of tissue regeneration in for example orthopaedics, has tremendous therapeutic implications. The aims of this study were to generate biomimetic biodegradable porous osteogenic scaffolds using a supercritical fluid process to encapsulate rhBMP-2, and to examine the ability of the scaffolds to promote human osteoprogenitor differentiation and bone formation in vitro and in vivo.

The rhBMP-2 encapsulated in Poly(-lactic acid) (PLA) scaffolds (100ng/mg PLA) were generated using an innovative supercritical fluid mixing method. The bioactivity of rhBMP-2 encapsulated PLA scaffolds were confirmed by induction of the C2C12 promyoblast cell line into the osteogenic lineage as detected by alkaline phosphatase expression. No induction of alkaline phosphatase-positive cells was observed using blank scaffolds. BMP-2 released from encapsulated constructs promoted adhesion, migration, expansion and differentiation of human osteoprogenitor cells on 3-D scaffolds. Enhanced matrix synthesis and cell differentiation on growth factor encapsulated scaffolds was observed following culture of human osteoprogenitors on explants of chick femoral bone wedge defects in an ex vivo model of bone formation developed using the chick chorioallantoic membrane model. In vivo studies using diffusion chamber implantation and subcutaneous implantation of human osteoprogenitors on rhBMP-2 encapsulated scaffolds showed morphologic evidence of new bone matrix and cartilage formation in athymic mice as assessed by x-ray analysis, immunocytochemistry and birefringence. These studies provide evidence of controlled release of BMP-2 from biodegradable polymer scaffolds initiating new bone formation in vivo.

The generation of 3-D biomimetic structures incorporating osteoinductive factors such as BMP-2 indicates their potential for de novo bone formation that exploits cell-matrix interactions and, significantly, realistic delivery protocols for growth factors in musculo-skeletal tissue engineering.

Introduction: Although there is evidence that laminar flow operating theatres (LFOTs) can reduce the incidence of wound infection over standard operating theatres (STOTs) when no routine peri-operative antibiotics were used, the evidence for the use with concurrent parenteral antibiotics is less compelling. A number of prior studies have compared the bacterial load observed in LFOTs and STOTs by wound culture and air sampling during surgery. However many organisms responsible for low grade infection after THR are not readily identified on routine culture and may be detectable only by more sensitive techniques such as the polymerase chain reaction (PCR), a molecular biology test for the presence of bacterial DNA. The purpose of this study was to compare the wound contamination rate during THRs performed in STOT with that in LFOTs using PCR.

Method: Patients undergoing primary THR for osteoarthritis without a history of joint infection were recruited for the study. Surgery was performed in either STOTs or LFOTs, using identical skin preparation solutions, surgical drapes and operating attire. Specimens of the deep tissue, taken at the beginning and end of surgery, were each immediately separated into two sterile containers, one sent for culture (aerobic, anaerobic and enriched meat broth) and the other frozen at minus 80 degrees Celsius for PCR at a later date.

Results: In each theatre type, 40 specimens from 20 THRs were analysed by both PCR and culture (80 specimens and 40 THRs in total).

Using PCR, bacterial DNA was identified on 12 of 40 specimens (30%) from STOTs. Of these 12, three were taken at the start of surgery and nine at the end of the surgery, equivalent to a 45% wound contamination rate (9 of 20). Only two specimens (5%), both taken at the end of surgery, were positive on enriched culture.

In LFOTs, bacterial DNA was identified by PCR on eight of 40 specimens (20%). Of these eight, two were taken at the start of surgery and six at the end of surgery, equivalent to a 30% wound contamination rate (6 of 20). None of the specimens were positive on enriched culture.

Discussions: We concluded that wound contamination of primary THR occurs frequently in both STOTs and LFOTs. Although STOTs showed evidence of more frequent wound contamination than LFOTs, with the numbers available, no significant difference was detected. These data are important in that they confirm that continued vigilance to technique continue to be important as significant wound contamination can occur despite the use of ultra clean air operating theatres.

Introduction: Metal-on-metal (MOM) bearings after total hip arthroplasty are known to elevate the serum concentrations of metal ions, raising concerns about the long term effects. One potential modifier of ion release is the bearing diameter used. Resurfacing MOM bearings have a large surface area available for corrosion compared to the typical bearing size of 28 mm in total hip replacement (THR) but may benefit from improved lubrication and reduced production of corrodible wear debris. The net effect of these two variables on metal ion release is unknown. In this study, we compared the level of ion release in patients after large bearing MOM hip resurfacing arthroplasty with patient after small bearing MOM THR.

Methods: We measured the serum cobalt and chromium levels from 22 patients with large bearing diameter MOM hip resurfacing arthroplasty (Cormet 2000 and Birmingham Hip Resurfacing) and compared them to the serum cobalt and chromium levels of 22 patients with small bearing diameter (28 mm) MOM THR (Ultima). Patients were prospectively matched for activity level, body mass and date after surgery at blood sampling. All were at least 6 months after surgery.

Results: We found the median cobalt and chromium levels after hip resurfacing arthroplasty to be 7.6 times normal (median 38 nmol/L, range 14 to 144 nmol/L) and 10.5 times normal (median 53 nmol/L, range 25 to 165 nmol/L) respectively. This is compared to 4.4 times normal (median 22 nmol/L, range 15 to 87 nmol/L) for cobalt and 3.8 times normal (median 19 nmol/L, range 2 to 58 nmol/L) for chromium after 28 mm MOM THR (p=0.0021 and p< 0.0001).

Discussion: We concluded that large diameter MOM bearings result in greater release of cobalt and chromium ions than do small diameter MOM bearings. This may be of relevance when the potential side-effects of long-term exposure to elevated these metal ions is considered. It is not known to what extent this difference is due to corrosion of the component surfaces or of the wear particles produced.

Aims: Elevated serum cobalt and chromium ion levels associated with carcinogenesis and chromosomal damage in animals has raised concerns that metal-on-metal (MOM) total hip replacement (THR) in humans may produce the same effects over time. Considering that the risks may be related to the level of these ions in the body, this study compared the serum cobalt and chromium ion levels in patients with unilateral versus bilateral 28 mm diameter MOM THR.

Methods: All patients having THR at our institution were prospectively registered on a computerised database. From our database, we identified 108 patients with Ultima (Johnson and Johnson, Leeds) MOM THR with 28 mm bearing made of cobalt-chromium alloy. After patient review in clinic and before blood results were known, patient matching was performed by date after surgery at blood sampling, activity level and body mass. Using these stringent criteria, 11 unilateral THR could be adequately matched with 11 bilateral THR. Blood serum was taken with full anti-contamination protocols and serum analysed via inductively coupled plasma mass spectrometry.

Statistical analysis used the Mann-Whitney U test.

Results: The serum cobalt ion level after unilateral MOM THR was 4.4 times normal (median 22 nmol/L, range 15 to 37 nmol/L) compared to 8.4 times normal (median 42 nmol/L, range 19 to 221 nmol/L) for bilateral MOM THR (p=0.001). The serum chromium ion level after unilateral MOM THR was 3.8 times normal (median 19 nmol/L, range 2 to 35 nmol/L) compared to 10.4 times normal (median 52 nmol/L, range 19 to 287 nmol/L) for bilateral MOM THR (p=0.04).

Conclusions: This study has shown that the serum cobalt and chromium ion levels in patients with bilateral MOM THR are significantly higher than those in patients with unilateral MOM THR. With levels of up to 50 times the upper limit of normal, this finding may be of relevance for the potential development of long-term side effects.

Study Design. A reliability study of the Modic classification.

Objective. To determine the reliability and reproducibility of the Modic classification for lumbar vertebral marrow changes.

Summary of Background data. In 1988, Modic with colleagues described two degenerative stages of vertebral marrow and endplate morphology. These were Type I (inflammatory phase) and Type II (fatty phase). Later in 1988, he added a third variety; Type III where there was marked sclerosis adjacent to the endplates. No formal reliability or reproducibility studies had been performed on the Modic classification.

Methods. This study involved five independent observers of differing spinal experience using the Modic classification to grade fifty sagittal T1 and T2 weighted MRI scans. The observers repeated the assessment at three weeks. Intra- and inter-observer reliabilities were assessed using kappa statistics.

Results. There were 7 type I, 40 type II, 1 type III and 2 normal levels. The individual intra-observer agreement was substantial or excellent with kappa values ranging from 0.71 to 1.00. The overall inter-observer agreement was excellent with a kappa value of 0.85. There was complete agreement in 78% of the levels, a difference of one type in 14% and a difference of two or more in 8% of levels. The level of experience of the observer did not correlate with a better score.

Conclusions. We have shown that the Modic classification is both reliable and reproducible. It is simple and easy to apply for observers of varying clinical experience. We therefore recommend its use in clinical research and practice.

Introduction: To review the medium term outcome of staged surgery for treating recalcitrant idiopathic talipes equinovarus.

Methods: Between 1988 and 1995, we studied 91 club feet from a series of 120 recalcitrant feet in 86 patients requiring surgical treatment. The initial results have been reported previously and this cohort has been subsequently followed up for between 7 and 15years. The mean age at initial operation was 8.9 months. Surgery consisted of an initial plantar medial release followed two weeks later by a posterolateral release. This strategy was used specifically to address the problems of wound healing associated with single-stage surgery and to ascertain the rate of relapse after a two-stage procedure. The feet were classified preoperatively and prospectively into four grades according to the system suggested by Dimeglio et al. Reported relapse at last review was 0.0% in grade 2, 20.4% in grade 3 and 65.4% in grade 4 feet. The rate of overall relapse was 30.8%. At 7 to 15 year review an additional 9.1% in grade 2, 7.4% in grade 3, 11.5% in grade 4 had relapsed. Overall a further 8.8% had relapsed and were treated with further surgery. Functional outcome of the group remains good with 95.6% overall finding no restrictions to activities.

Conclusion: This review confirms that the strategy of staged surgery is supported in the medium term when considering rates of relapse and functional outcome.

Introduction: It has been proposed that the presence of the capital femoral ossific nucleus confers protection against ischaemic injury or avascular necrosis (at the time of reduction of a congenitally dislocated hip). The current literature is contradictory.

Materials & Methods: A prospective study was undertaken of the clinical and radiological outcomes following closed or open reduction. 50 hips were included in the study. These cases had either presented late or had failed conservative treatment. In 28 hips treatment was intentionally delayed until the appearance of the ossific nucleus (but not beyond 13 months) and in 22 the ossific nucleus was present at clinical presentation. 6 hips reached the age of 13 months without an ossific nucleus appearing and progressed to treatment. The significant avascular necrosis rate (> grade 1) was 7% for closed reduction and 14% for open. However, the amended rate if hips were excluded that had failed Pavlik harness treatment was 0.0% and 9% respectively (4% overall). Further surgical procedures were necessary in 57% of hips undergoing closed reduction and 41% after open, which compares favourably with other series.

Discussion: It is concluded that the presence of the ossific nucleus is an important factor in the prevention of AVN, particularly after late closed reduction. Intentional delay in the timing of surgery does not condemn a hip to open surgery but there is a comparable rate of secondary procedures becoming necessary particularly after closed reduction. The delayed strategy to await the appearance of the ossific nucleus for previously untreated dislocation allows a simple treatment algorithm to be employed which produces good clinical and radiological outcomes. The use of the Pavlik harness has been abandoned in cases of irreducible dislocation of the hip.

Alumina has been the dominant ceramic used in orthopaedics since 1970. It is near diamond hardness is superior to all other biomaterials and its wettability has been a great benefit for tribological reasons. Over the past 30 years, this ceramic has gradually been optimized with superior processing, higher purity, greater density, and somewhat higher strength. Also serial numbers have been added to uniquely identify implant components and proof-testing now ensures that every implant is pre-clinically tested, compared to prior methods of sampling only 2–3% for destructive tests. The clinical downside remaining has been the small but troublesome fracture incidence of alumina implants. Historically, this has averaged 0.015% (15 per 100,000 cases) overall but varied from 0.08% up to 13% in those clinical series experiencing fractures (Heros, Sem. Arthrop-98). As well as creating patient hardships, fracture of any implant in the USA frequently leads to major lawsuits. Thus ceramic implants must be treated w While there has as yet been no FDA-approval given to market ceramic cups in the USA, there are a number of ceramic candidates being developed for both THR and TKR. These include zir-conia-alumina composites as well as new zironia/zirconia or zirconia/alumina combinations for THR. In addition, there are new combinations of toughened aluminas and also other choices such as silicone nitrides proposed for use with either metal CoCr heads or CoCr cups. Finally an alternate approach has been to provide a metal zirconium knee joint with a ceramic zirconia coating for improved bearing performance. Thus, the state of the art of alumina implants will be reviewed and put into perspective with the “new and improved” ceramics currently on the horizon. This survey will put into perspective the physical and mechanical attributes as well as the clinical performance of ceramic implants.

Major long-term complication of total hips is osteolysis in the more active patients. Osteolysis is a result of the biological response to the wear debris particles. This has resulted in the search for improved bearings such as metal and ceramic on polyethylene, all ceramic, and all metal total hips. Wear ranking of metal-polyethylene, ceramic-polyethylene, metal-metal, and ceramic-ceramic total hips has become clear at ratios of 1,000:500:10:1. However, wear debris from polyethylene, ceramic, and metal wear tests average about 0.6, 0.3, and 0.02 microns, respectively. From this information we can now deduce the number of particles librated is millions for ceramics, billions for polyethylene, and trillions for metal.

In recent years, studies have revealed new information on the biological response to various types of wear debris. Factors such as number of particles, particle morphology (size and shape), and surface to volume ratio are becoming keys to a partial comprehension of this biological response and osteolysis. Recent studies have demonstrated that smaller particles (< 0.1 microns) may be more toxic to cells than larger particles (> 0.1 microns). Studies have shown that crosslinking of polyethylene reduces the size of the wear debris particles and that for gamma irradiated polyethylene this reduction in size is proportional to the radiation dose. It has also been shown that crosslinking results in a significant reduction in fibril particles. Therefore, large reductions in wear rate do not necessarily mean that the total joint will be more successful. Thus, two factors, which interact, are the volume rate of wear and the morphology of the wear debris particles. Some investigators have developed a biological ind

Ceramic on ceramic hip-joint replacements (THR) are known for their excellent wear resistance. Such rigid-rigid bearings generally exhibit a biphasic wear-performance, i.e. a rapid run-in phase decreasing into a steady-state phase. However, due to the ultra-low wear of ceramics, few studies have adequately characterized these wear phases. Since this behavior was not well defined for modern alumina-on-alumina hips, we studied this phenomenon using hip simulator techniques. We also compared all-ceramic THR to UHMWPE wear-rates for exact comparison. Run-in wear was measured at 200,000 cycle intervals to 1 million cycles (1 Mc) followed by 500,000 cycle intervals to 14 Mc.

Alumina heads started off with high wear but then demonstrated a curvilinear run-in phase that smoothly transited into steady-state wear. The alumina liners had linear run-in to 0.6 Mc and then abruptly transited into steady-state by 0.8 Mc. During run-in, the liner wear was 40% greater than for the mating heads. Steady-state liner wear varied from 0.002 to 0.007 mm3/Mc. It was also clear that at least 10 million cycles were required to define the steady-state wear for alumina implants due to their ultra-low wear magnitudes. Combined head and cup run-in wear averaged 0.33 mm3/Mc and was completed within 0.8 Mc while steady-state wear was < 0.01 mm3/Mc up to 20 Mc. This was a remarkable 30-fold reduction from run-in.

The run-in phase would probably be completed by the first year of follow-up. Compared to UHMWPE cups, the alumina implants demonstrated a 9,000-fold wear-reduction over 20 million cycles in the simulator. This may correspond to 20 years in the typical patient. In addition, the alumina/UHMWPE combination has been favored historically because using CoCr/ UHMWPE bearings resulted in a doubling of the wear-rates in comparative clinical studies. Clearly the all-ceramic THR offers a much superior alternative with its massive reduction in wear-debris volume.

Aims: Identifying low-grade infection in failed total hip replacements (THR) is an important but often difficult task. Recently, there has been interest in the use of molecular biology techniques as potential sensitive tests for low-grade infection by identifying fragments of bacterial DNA within human tissue. Methods: We investigated the ability of a molecular biology technique known as the polymerase chain reaction (PCR) to identify low-grade infection during revision of THR considered to have failed from aseptic causes. We analysed 113 specimens of tissue and synovial fluid from 31 THR revised for aseptic loosening and compared them to 105 control specimens taken during 28 primary THR. All cases were performed in laminar flow theatres. No primary or revision specimen had positive microbiological cultures. No revision specimen had histological evidence suggestive of infection. Results: Using PCR, we identified bacterial DNA in 39 of 85 revision THR tissue specimens (46%) compared to 18 of 84 primary THR specimens (21.4%, p=0.001). Bacterial DNA was identified within the synovial fluid in three specimens taken from 28 revision THR (10.7%) and in two specimens taken from 21 primary THR (9.5%, p=0.36). As multiple specimens were sent per case, 16 of 31 revision THR (52%) and eight of 28 primary THR (29%) were considered to be infected (p=0.072). Conclusions: Our results suggest that many aseptically loose revision THR actually contain bacterial DNA within the peri-prosthetic tissue, but infrequently within the synovial fluid. With an overall specimen contamination rate of 19%, however, PCR has poor specificity for routine diagnostic use in revision THR.

Aims: Cobalt (Co) and chromium (Cr) ion associated carcinogenesis and chromosomal damage in animals has raised concerns that metal-on-metal (MOM) total hip replacement (THR) in humans may produce the same effects over time. Considering that the risks may be related to the level of these ions in the body, this study compared the serum Co and Cr levels in patients with unilateral versus bilateral 28 mm diameter MOM THR. Methods: All patients having THR at our institution were prospectively registered on a computerised database. From our database, 108 Ultima MOM THR with 28 mm CoCrMo bearing were identiþed. After patient review in clinic and before blood results were known, patient matching was performed by date after surgery, activity level and weight. Using these stringent criteria, 11 unilateral THR could be adequately matched with 11 bilateral THR. Blood serum was taken with full anti-contamination protocols and serum analysed via atomic absorption spectrometry. Statistical analysis used the Mann-Whitney U test. Results: The median serum Co level after unilateral MOM THR was 22 nmol (range 15 to 37 nmol) compared to 42 nmol (range 19 to 221 nmol) for bilateral MOM THR (p=0.001). The median serum Cr level after unilateral MOM THR was 19 nmol (range 2 to 35 nmol) compared to 52 nmol (range 19 to 287 nmol) for bilateral MOM THR (p=0.04). Conclusions: This study has shown that the serum Co and Cr levels in patients with bilateral MOM THR are signiþcantly higher than those with unilateral MOM THR. With levels of up to 50 times the upper limit of normal, this þnding may be of relevance for the potential development of long-term side effects.

Aims: There are no large published studies examining the complication rates associated with use of Kirschner wires in þxation of a wide variety of paediatric fractures. The aim of this study is to analyse the outcomes of fracture þxation using K-wire in upper limb fractures in children and to critically assess the incidence and type of complications. Methods: This study is a retrospective review of a consecutive series of 107 fractures in 105 paediatric trauma cases treated with K-wire in between 01.09.99 to 10.09.01. Results: The fractures were fractures around Wrist (47%) and around elbow (45%). 66 (61.68%) were performed by closed percutaneous technique, 27 (25.23%) by open method and in 14 (13.08%) combined approach was used. Around there were 13 cases with over-granulation at wound site, 6 cases of Soft tissue infection, 2 cases with tendinitis, 1 case of Osteo-myelitis and 1 case with hyper-sensitive scar. 3 cases found to have postoperative neurapraxia and 1 case with axonotmesis. Metal migration was detected in 4 cases and 14 cases found to have shown wire loosening. 10 fractures have lost position in postoperative period out of which 2 cases were reoperated for Re K-wire, 1 had undergone Re-MUA and 7 left for remodelling. Conclusions: K-wires are versatile but are not inherently benign. We conclude that best results could be achieved if total life of K-wire can be restricted to 3–4 weeks. We recommend one should explain all these risks and complications during consenting for K-wiring procedures.

Aim: Unicameral bone cysts are difficult to treat as partial cyst healing may reverse and it may be difficult to assess between active and latent types.

Materials and Methods: 19 patients with unicameral bone cysts were reviewed with a mean age of 8.5 years (16 males and 3 females). These 19 patients were reviewed over a period of fifteen years and all except one, had an active cyst abutting the growth plate. 18 cases were treated with curettage and burring using a dental burr and six cases were treated with elastic nailing. 12 cases were treated with bone marrow injection either alone or in combination with the above procedures. 2 cases were treated with steroid injections. No cases were bone grafted.

Results: The best results were obtained with curettage and burring of the lining of the cysts. Bone marrow injection alone did not produce resolution of any of the cysts. Migration of the cysts away from the growth plate in response to treatment (conversion from active to latent status) was predictive of successful treatment with no symptoms and no further fractures, irrespective of the age of the patient.

Conclusion: Successful treatment of unicameral bone cysts can be predicted by the appearance of normal bone formation by the physis and subsequent migration of the cyst away from the growth plate. The association of successful treatment and conversion to latency of the cyst has not previously been reported.

Lubricated metal-on-metal (MOM) bearing surfaces are not easily separated, unlike ceramic- or metal-on-UHMWPE (COP, MOP), due to interfacial forces and low diametric clearance that provides a ‘suction-fit’. In vivo videofluoroscopic studies have shown that patients with MOP/COP THRs exhibit separation of bearing surfaces by up to 3.1 mm during normal gait and 5.4 mm during active abduction while patients with MOM bearings do not. In this regard, MOM bearings may have similarities to constrained bearings with the potential to lower dislocation rates.

All patients under 70 years old undergoing primary THRs for primary osteoarthritis were prospectively registered on a computer database. From 1993–8, patients were offered a 28 mm COP bearing. After 1998, as part of a clinical trial, a 28 mm MOM bearing was inserted instead. For all cases, we used a metal-backed, uncemented acetabulum allowing a modular 10-degrees posteriorly augmented insert (Duraloc/PFC/Ultima, J& J) and the same cemented femoral stem (Ultima, J& J). The same experienced surgeon performed all operations using the posterior approach. Interfacial forces between bearing surfaces were assessed in vitro with a variable-speed-motor winch (APT) and a load-cell (E375/RDP) by recording peak-retaining-forces of bearing couples during separation with variable impact-distraction velocities. Statistical analysis used the Chi-square and student’s t-test.

We identified 140 COP THRs in 129 patients and 109 MOM THRs in 100 patients. Nine of 140 (6.4%) COP bearings dislocated within 3 months of surgery compared to 1 of 109 (0.9%) in the MOM group (p=0.024). No significant differences were identified between groups when comparing patient and prosthesis factors. In vitro assessment demonstrated that MOM bearing possessed interfacial retaining forces up to 30N more than COP bearing (p< 0.001).

This study demonstrates a significantly lower dislocation rate in THR with MOM bearing compared with COP. A potential explanation is the differential ease of separation that the two lubricated bearing couples possess due to interfacial retaining forces (viscous tension and ionic adhesive forces) exerted by the lubricating fluid.

Aims: Cobalt (Co) and chromium (Cr) ion associated carcinogenesis and chromosomal damage in animals have raised concerns that metal-on-metal (MOM) total hip replacement (THR) in humans may produce the same effects over time. Considering that the risks may be related to the level of these ions in the body, this study compared the serum Co and Cr levels in patients with unilateral versus bilateral 28 mm diameter MOM THR.

Methods: All patients having THR at our institution were prospectively registered on a computerised database. From our database, 108 Ultima MOM THR with 28 mm CoCrMo bearing were identified. After patient review in clinic and before blood results were known, patient matching was performed by date after surgery, activity level and weight. Using these stringent criteria, 11 unilateral THR could be adequately matched with 11 bilateral THR. Blood serum was taken with full anti-contamination protocols and serum analysed via inductively coupled plasma mass spectrometry (ICP-MS) Statistical analysis used the Mann-Whitney U test.

Results: The median serum Co level after unilateral MOM THR was 22 nmol (range 15 to 37 nmol) compared to 42 nmol (range 19 to 221 nmol) for bilateral MOM THR (p=0.001). The median serum Cr level after unilateral MOM THR was 19 nmol (range 2 to 35 nmol) compared to 52 nmol (range 19 to 287 nmol) for bilateral MOM THR (p=0.04).

Conclusions: This study has shown that the serum Co and Cr levels in patients with bilateral MOM THR are significantly higher than those with unilateral MOM THR. With levels of up to 50 times the upper of limit of normal, this finding may be of relevance for the development of potential long-term side effects.

According to the knee simulator test results in 1970s, the total decrease in thickness of UHMWPE tibial tray in combination with ceramic femoral component [F-Comp] was less than one tenth as that of the combination with metal [1]. These advantages led to development of total knee prosthesis [TKP] with alumina ceramics. In this study, we report the wear surface observation, the clinical wear and the oxidation of the retrieved TKP used clinically for 23 years, comparing with a metal TKP.

The retrieved TKP was implanted in 1979, and retrieved on January 9th in 2002. This TKP consisted of an alumina ceramic F-Comp and a UHMWPE tray combined with a alumina ceramic tibial component. Observations of the surface of alumina F-Comp and UHMWPE tray were carried out using SEM. Shape of UHMWPE tray was determined three-dimensionally. Comparing the result with original shape based on the product’s plan, liner wear and volumetric wear were calculated. Oxidation index was determined by Fourier transform infrared spectrophotometry.

Alumina F-Comp did not have any scratch on the surface by seeing with naked eye. UHMWPE tray had deformation and scratches obviously. The liner wear rate was 37 micrometer/year and volumetric wear rate was 18.8 mm3/year. The oxidation indexes were 0.6 in the unworn area, 1.2 in the worn area and 0.2 in the inner area.

SEM observations of the F-Comp demonstrated no scratch or pit. In contrast, many scratches were clearly observed on the UHMWPE tray. However, higher magnification observations did not demonstrate severe wear, which was shown on the wear analysis of a metallic F-Comp. Oxidation degradation is a problem to solve. However, the low wear rate and mild wear pattern demonstrate that ceramic F-Comp reduced UHMWPE wear.