Keywords

Shoulder; dislocation; instability; skeletal immaturity; arthroscopic Bankart repair; outcomes

Flexible flat foot is considered one of the commonest normal variants in children's orthopaedic practice. The weightbearing foot is usually regarded as flexible on the basis of results from clinical and radiographic examination as well as measured foot-ground pressure pattern.

Our aim was to compare the pedobarographic and radiographic findings of normal arched and symptomatic flexible flat feet and investigate if there were sensitive markers that could be used in selecting patients for surgical correction.

We retrospectively collected data from eighteen patients (ten to sixteen year old). Our control group consisted of ten patients (twenty feet) with normal arched feet and the study group of eight patients (fifteen feet) with symptomatic flat feet who were awaiting surgical correction.

The mean and standard deviations of three radiographic markers (Calcaneal pitch, Naviculocuboid overlap and lateral Talo-1st metatarsal angle) in addition to foot pressures measured at the hindfoot, medial/lateral/total midfoot (MMF, LMF, TMF), forefoot and the percentage of weight going through the MMF over the TMF (medial midfoot ratio (MMFR) during the mid-stance gait phase are reported. In addition, the sensitivity, specificity, positive predictive value and negative predictive value of the pedobarographic parameters were estimated.

There was a significant difference in the Naviculocuboid overlap (P<0.001 T test) and Calcaneal pitch (P<0.05 T test) between both groups. The flat feet group had significantly higher MMF, LMF, TMF and MMFR (P < 0.001 Mann-Whitney). LMF had the highest sensitivity and negative predictive value (94%) whereas MMF, TMF and MMFR had the highest specificity and positive predictive value (100%).

Compared to our control group, patients with symptomatic flexible flat feet had significantly higher pressures distributed in the midfoot, in particular in the medial midfoot. Pedobarography appears to be a sensitive and specific tool that can be used, in conjunction with clinical and radiographic findings, in diagnosing flat feet.

Our study suggests that pedobarography could be used to measure the degree of deformity before and after surgical intervention.

Introduction

The purpose of this study was to comprehensively evaluate syndactyly correction. Patient selection, complexity, technique and aftercare are compared with scar quality, web-creep, hand function and patient satisfaction.

We evaluated the use of unreamed expanding nails in prophylactic stabilization of impending fractures in patients with multiple bone mets.

During 2004–2008 we treated 25 impending fractures due to metastasis (11 male, 14 female patients) with so-called expanding intramedullary nails. All they had multiple bone mets and signs of impending fracture due to extensive osteolysis. We stabilized 6 impending humeral fractures, 15 femoral and 1 tibial with antegrade nailing and 3 pertrochanteric with cephalomedullary nailing. Fluoroscopy was used to check the nail entry-point. No medullary reaming was performed. The nails were not interlocked at the mid-shaft but fixed rather firmly within the medullary cavity after introducing normal saline under pressure that expands its walls. The operation time ranged from 12min (humerus) to 25min (pertrochanteric). No blood transfusion was necessary. On follow-up (8–41 mos) all patients were reviewed. In all cases the risk of impending fracture was remarkably decreased. The patients with humeral fractures regained function quickly. The patiens with lower limb fractures were mobilized immediately post-op and were allowed to walk with TWB.

Surgery of impending fractures of long bones in patients with multiple bone mets is palliative. It aims in safer patient’s mobilization, fracture risk reduction, pain control and function restoration in order to render the patient capable to continue the treatment for the main disease. The expanding nailing is indicated in selected cases as it can be inroduced quickly and effectively with minimal blood loss and morbidity.

Background: Arthroscopic menisectomy is one of the most commonly performed procedures in the NHS, yet there is no recent review of contemporary knee arthroscopy for meniscal tears or comparisons of tear morphology and clinical findings. We aim to address this problem with a large, prospective longitudinal study.

Aims: The aims of this study were to examine the anatomical location and morphology of meniscal tears encountered at arthroscopy and to correlate this to the clinical findings.

Method: Data on 775 consecutive patients undergoing knee arthroscopy by a single surgeon between 1994 and 2004 was prospectively collected. Clinical data included age, sex, history of trauma, joint line tenderness and presence of an effusion. Meniscal tears were arthroscopically classified by site (medial/lateral, anterior/middle/posterior) and type (flap, horizontal cleavage, bucket-handle, radial, degenerative and other).

Results: Data was complete for 724 patients (517 male and 207 female [m:f 2.5:1]). The mean age was 48 years (range 10 to 87 years). Mean duration of symptoms was 8 months.

54% of meniscal tears were medial, 12% lateral and 10% bilateral. Patients with a lateral tear were significantly younger (45 Vs 51 yrs, p< 0.001).

The most common type of medial tear was a flap tear (34%), followed by horizontal cleavage tears [HCT] (18%). The posterior 1/3 is the most common position. Laterally the tear morphology shows HCT comprising 25% and degenerative tears 17%, with the most common position a middle 1/3 tear. Lateral tears are more common in females (p< 0.05)

Patients with bucket handle tears were significantly younger (41 Vs 53yrs, p< 0.001) and more likely to have a history of trauma (p< 0.001). Medial joint line tenderness was the most sensitive test (79%) and had the highest positive predictive value (81%). McMurry’s test is the most specific for both medial and lateral tears (90%) but is not sensitive. Medial meniscal tears are more accurately diagnosed clinically than lateral (79% Vs 50%).

Conclusion: Meniscal tears are a common pathology, particularly on the medial side. Morphology and position of tears vary as to which side the tear is. Clinical details can help determine the type of tear found with clinical examination being more accurate for medial meniscal tears.

We examined rates of MRSA wound infection in patients admitted to the Leicester Royal Infirmary Trauma Unit between January 2004 and June 2006. The influence of MRSA status at the time of their admission, together with age, sex and diagnosis were examined using multivariant analysis.

3.2%(79/2473)) were MRSA carriers at time of admission and 96.8%(2394/2473) were MRSA negative. Those carrying MRSA at the time of admission were more likely to develop MRSA surgical site infections [8.8% (7/79)] as compared to non MRSA carrier at the time of admission [2.2% (54/2394), p< 0.001]. Further analysis revealed that hip fracture and increasing age (linear increase in relative risk of 1.8% per year) were also risk factors.

MRSA carriage at admission, age and pathology are all associated with an increased rate of developing MRSA wound infections. Identification of such risk factors at admission helps to target health care resources such as the use of glycopeptides at induction and increased vigilance for wound infection in the post operative phase

A consecutive group of 150 patients undergoing primary TKA performed by a single surgeon using single prosthesis were studied prospectively. The purpose of this study was to compare the clinical and radiographic results of TKA in obese and non-obese patients.

The patients were categorized into two groups: non-obese (body mass index (BMI < 30 kg/m2) and obese (BMI > 30 to 40 kg/m2). The Primary outcome measures: SF-12 and WOMAC scores were used as generic outcome measures, and the Knee Society scores were used to assess clinical outcome of TKA. The scores were done pre-operatively and at 1, 3 and 5 years post-operatively. Secondary outcome measures included patellar position, anterior knee pain, infections, revision rates, deep-vein thrombosis and pulmonary embolism, length of hospital stay and mortality.

Seventeen patients have died since and none were lost to follow-up. Obese patients had less benefit and overall KSS outcome scores at one year (p-value 0.05) but had similar scores at 3 and 5 years (p-values 0.3 and 0.5). Pre-operative WOMAC and SF-12 scores were significantly worst in obese patients (p-value 0.009 and 0.005) but had the similar outcome at 1, 3 and 5 years. Three patients in the series required revision surgery for infection. One patient had DVT and another had PE post-operatively.

Overall obese patients although had lower KSS scores at one year but had better outcome in SF-12 and WOMAC scores at one year. There was no difference at 3 and 5 years. We found that body weight did not influence adversely the outcome of TKA at medium term.

Background: Clostridium difficile (C diff) diarrhoea is a growing UK hospital problem. However, it is controversial whether patients die with C diff or of C diff. A series of infection control measures were introduced from August 2006 onwards to reduce the rate of C diff infection and to treat patients suffering from diarrhoea. These included a five-day antibiotic stop policy, a diarrhoea treatment policy, a hand washing campaign, increased investment in environmental cleaning and a change in policy for antimicrobial prophylaxis to coamoxiclav instead of cefuroxime. The aim of this study was to assess the impact of these measures on the incidence of C diff infection and to record the mortality associated with C diff. Fracture neck of femur patients were chosen as they are at particular risk.

Method: We assessed data on orthopaedic admissions in particular fracture neck of femur patients, C diff samples, and mortality up to one year. The incidence of C diff was compared between fracture neck of femur patients and other orthopaedic admissions and also before and since the introduction of the infection control policies. This was followed by a comparison of mortality between C diff positive patients and a control group matched by age, sex, ASA grade and place of residence. Mortality data was at 30days, 6 month and 1 year.

Results: Clostridium difficile was much more common in patients with fracture neck of femur (72 out of 1800, 4%) than in other orthopaedic admissions (51 out of 10000, 0.5%, p < 0.001). The incidence of C diff in patients with fracture neck of femur decreased from 49 of 548 (9%) in the 9 months pre-policy to 28 of 562 (5%, p=0.009) in the 9 months since policy Introduction: In those with C diff, mortality at 30 days and 6 months was 10/49 (20%) and 35/49 (71%) pre-policy and 9/28 (32%) and 20/28 (71%) since policy Introduction: Regardless of policy introduction, the overall mortality in 168 C diff positive patients at 30days, 6 months and 1 year was 31 (19%), 112 (67%) and 117 (70%) whilst that in the 168 matched controls was 19 (11%), 43 (26%) and 48 (29%).

Conclusion: The matched group data indicates that C diff increases mortality. It does not simply colonise the most frail. The percentage of deaths in C diff positive patients was no different after the diarrhoea treatment policy Introduction: The incidence of C diff was reduced by 43% using infection control measures. Our results indicate that the best way to reduce mortality due to C diff is to reduce the incidence, our current treatment policy was ineffective or in other words, ‘prevention was better than cure’. We recommend that similar measures could be introduced in other orthopaedic units in order to reduce the incidence and mortality in fracture neck of femur patients from Clostridium difficile.

Introduction: It has been shown that acrylic bone cement is weakened by its porosity, which enhances the formation of micro-cracks that contribute to major crack propagation. It has also been observed, that mixing procedures play a significant role in determining the quality of bone cement produced. A high degree of porosity is found to exist in cement that is inadequately mixed.

Currently mixing system allow for the preparation of the bone cement under the application of a vacuum in a closed, sealed chamber by means of a repeatable mixing action. These systems are perceived to be repeatable, reliable, and operator independent. The objective of this study is to evaluate the quality and consistency of acrylic bone cement prepared by scrub staff in an orthopaedic theatre using a commercially available third generation vacuum mixing syringe, in terms of the level of voids within the cement microsturcture.

Materials and Methods: The mixing devices were stored at 23°C ± 1°C for a minimum of 24 hours prior to mixing. The acrylic bone cement (Palacos R® with gentamicin, Biomet Merck, UK) was stored at 4°C ± 1°C for a minimum of 24 hours prior to mixing.

Bone cement was mixed using a commercially available third generation mixing device (vacuum = −550mmHg) at Musgrave Park Hospital, Belfast, Northern Ireland. The cement was mixed according to the device manufacturers’ instructions for use. Mixing was carried out during a joint replacement surgery by a number of experienced theatre scrub staff (n = 35). The cement remaining at the end of the procedure was allowed to cure within the delivery nozzle, made from linear low-density polyethylene (LLDPE) and having an internal diameter of 10mm. 205 nozzles were collected post-operatively and stored at 23°C ± 1°C prior to testing. The percentage porosities were determined by measuring the apparent densities based on Archimedes principle and, as a direct result; it was possible to calculate the mean percentage porosities.

Discussion: It can be observed that the majority of the theatre nurses, ie 46.8% prepared bone cement using the vacuum mixing system containing a porosity of between 2% to 4%. A cement porosity of this range would be the accepted optimum content for acrylic bone cement. However, 6.4% of the theatre nurses prepared cement demonstrating a porosity content ranging from 8–16%, which is highly unsatisfactory when you consider that the cement mixing system is perceived to be a consistent and reliable mixing device that is operator independent.

Figure 2 illustrates a bar chart representing the bone cement porosity as a function of which orthopaedic theatre the cement was prepared. There was no significance difference when comparing the quality of the cement mixed in terms of porosity with the different theatres. The mean porosity values of the cement mixed ranged between 2.5% and 5.2% depending on which theatre was used.

Conclusions: Bone cement mixed using the commercially available third generation device in theatre by 35 scrub staff was found to have a high degree of variability. Thus demonstrating that even an alleged reproducible mixing system is independent on mixing technique when used in a clinical situation by a number of users. Thus illustrating the system is not wholly user independent.

As a consequence of this investigation it is recommended that the key to ensuring high quality bone cement, with a good mechanical strength, that can be consistently prepared in theatre by scrub staff are two fold.

The orthopaedic staff must be aware of the significance of cement mixing and how it is affected by a number of factors including the type of mixing system, vacuum level applied, and mixing technique.

Dislocation is a recognised complication following the posterior approach in total hip arthroplasty. The senior surgeons involved in this study had routinely repaired the short external rotators and capsule by directly suturing ‘tendon to tendon’ and ‘capsule to capsule’ using No 1 Vicryl®. Over a two-year period this had no impact on the incidence of dislocation as compared to “no soft tissue repair” that had been done historically. In order to assess the effectiveness of ‘soft tissue to soft tissue’ repair fifteen patients were assessed using radiographic markers inserted during surgery. In 14 of the 15 patients the repair was found to have failed by the time of the post-operative x-ray which was taken on day 3 to 5. Since then we have changed the repair so that the capsule and rotators are reattached to bone with No 5 Ethibond® using drill holes in the trochanteric region. This modification was evaluated using the same method. Of 15 patients in the second type of repair only 2 showed a failure of repair on the post operative X-ray. This appears to be a more secure form of repair. The impact of this on the incidence of dislocation is being evaluated.

We performed a prospective clinical study in order to assess the effectiveness of repair of the short hip rotators, divided in the course of total hip replacement by the posterior approach, by the use of radio-opaque markers.

Fifteen patients, each with a diagnosis of osteoarthritis of the hip, were selected consecutively from a single surgeon’s operating list. Uncemented Duraloc® acetabular components and custom made cemented femoral components were implanted via the posterior approach in all patients.

Following implantation, the capsule and the short rotator tendons were sutured on to tendinous soft tissue around the greater trochanter using No 1 Vicryl. One radio-opaque marker clip was attached to the short rotators and capsule and a second marker was attached to the greater trochanter.

Standard antero-posterior pelvic X-rays were taken at three to five days post-operatively, and at three months following surgery. Significant separation of the radio-opaque markers in fourteen of the fifteen patients was demonstrated on the day three to five X-ray, indicating failure of the repair.

We conclude that this soft tissue repair is unsatisfactory. It may be of value to develop a more effective repair technique, with the overall aim of reducing total hip replacement dislocation, and as such we are currently investigating a soft tissue to bone repair.

Work carried out by Bennett [1], identified a link between patient gait pattern and total hip prothesis wear rate. This study found that the shape of the patient gait pattern (as quantified by aspect ratio) and sliding distance of the movement loci were found to have an improved positive correlation with wear rate compared to the factors of activity and patient weight. The distribution of theoretical shear stresses at selected points on the acetabular cup suggests that orientation of the polymer chains may occur. Wang et al, 1997 [2] has shown that failure of the UHMWPE wear surfaces occurs in the form of transverse rupture between oriented molecules.

This work investigates the hypothesis that the gait pattern of pre-revision THR patients has an effect on the wear, surface characteristics and material properties of the artificial hip joint, in particular the degradation of chemical and mechanical properties of the UHMWPE acetabular socket. Gait analysis is performed on patients prior to revision of a primary THR, with the retrieved socket used for subsequent analysis.

Chemical and mechanical analysis of a large number of retrieved UHMWPE acetabular sockets has shown clear structural changes, which are dependent on the length on time in-vivo. Increasing the length of time in-vivo between 2 and 20 years results in an increase in the percentage crystallinity of the UHMWPE of 12.7 %. A positive linear correlation (R2 = 0.765) between percentage crystallinity and number of years in-vivo is shown. This suggests recrystallisation of the polymer at a constant rate over time. This partial recrystallisation of the amorphous region correlates with degradation in the mechanical properties of the material. This pilot study aims to assess the effect of patient gait pattern on the chemical and mechanical degradation of UHMWPE, which will ultimately affect the clinical performance of the prothesis.

Introduction: The Spotorno cementless femoral stem relies on proximal press-fit at time of surgery and subsequent osseointegration for long-term fixation. The aim of the study is to assess the long-term survivorship and clinical outcome of the Spotorno stem used in primary hip replacement surgery in younger patients.

Materials and Methods: 74 patients were identified who had undergone 90 THRs using the Spotorno CLS stem between January 1987 and May 1992. There was variation in the acetabular components used. 5 patients (6 hips) were lost to follow-up, leaving a study group of 84 hips. The patients were assessed using the Harris Hip Score and the Oxford Hip Score.

Results: Mean age at operation was 40.1years (range 23–65years). Commonest diagnoses were primary osteoarthritis, developmental dysplasia of the hip and rheumatoid arthritis. Mean duration of follow-up was 12.25 years (range 8½ – 15yrs 3months). At most recent follow-up, the mean Oxford Hip Score was 23.8 and mean Harris Hip Score was 81. Taking revision for any cause as an end point, 19 hips from the initial group of 84 had undergone some form of revision surgery at most recent review. 15 of the 19 hips that failed had aseptic loosening of the acetabular component, which was the Mecring component, and underwent revision of acetabulum only. Four stems were revised, 2 for loosening and 2 for infection. 80 out of 84 of stems originally implanted remained intact at most recent review, which represents a stem survivorship of 95.2% at mean 12.25yrs follow-up when used in young patients.

Conclusion: Our findings indicate excellent long-term survival of this titanium alloy stem when used in patients under 65years. We attribute this to stem design and the principle of proximal press-fit fixation. Careful consideration must be given to acetabular component selection in cementless total hip arthroplasty.

In Britain 8 million people consult their general practitioner annually with musculoskeletal conditions leading to referral of 1.5 million patients to Orthopaedics/ Rheumatology. Northern Ireland has the highest waiting lists for outpatients in Britain. The demand on orthopaedics continues to rise despite past attempts to reduce waiting lists. Trauma and orthopaedics accounted for 14% of the excess waiters for outpatients at June 2002. (DHSSPS Sept 2002) Roland et al 1991, etc. demonstrated that 43% of all orthopaedic referrals were inappropriate. In Belfast, G.P.s and Physiotherapists in partnership with the Regional Orthopaedic Service decided to pilot a Primary Care Orthopaedic Triage Service. The vast majority of orthopaedic referrals relate to three main body parts: lumbar spine 28%, knees 34% and hips 25% and these were chosen to be triaged for the pilot. Approval was sought and granted from Queen’s University Belfast Ethics Committee.

Phase 1 involved the training of 2 GPs and 2 physiotherapists at the Musgrave Park and Royal Victoria Hospital with the full cooperation of the orthopaedic surgeons.

Phase 2 tested independently the diagnostic capability of the trained professionals and assessed the appropriateness and management of orthopaedic referrals against the consultants decision as ‘gold standard’.

95 patients participated in the study.

55.8% of referrals were deemed appropriate by the consultants, compared to 44.6% by the GP/physio team. The Kappa statistical score was 0.79 reflecting a good level of agreement and is comparable to other clinical specialties (Sackett 1991). The sensitivity of the trained professionals on orthopaedic referrals was 83% and the specificity was 97%. Kappa value for management of inappropriate referrals was 0.83.

Orthopaedic referral can be acceptably triaged by primary care professionals reducing the number of onward referrals to outpatients by 40% and increasing the appropriate referrals from 56% to 97%.

Currently, all details regarding implants are entered into a real time application on the Musgrave Park Hospital site using the Belfast Orthopaedic Information System (BOIS). This is a visual basic client application with data being stored in an SQL server database. This data collection system operates throughout every location within the hospital including the theatre block.

Loss of continuity occurs however when joint replacement takes place in Musgrave Park Hospital and then revision surgery or other procedures are carried out at other locations. The goal therefore of the Northern Ire-land Implant Register is to collect information on all implants performed and their revisions regardless of their location.

The dataset collected is based on the work of the National Joint Replacement Registry. Our system is designed to support and extend that dataset to provide a more comprehensive joint replacement registry database. This means that reports can be provided to individual sites and data entered into the National registry if required at a later stage.

At present every hospital in Northern Ireland is connected to the HPSS network (similar to the HPSSNet in the UK). What has been developed is a web browser based front end, which requires no complex software installation on any client machine. From this web based tool, staff at other locations can access information held at Musgrave Park Hospital, they can select an implant, or record a new implant and then link any revisions or other procedures carried out.

As all of the information is entered directly into the BOIS database, there is no delay in the information being available to all who access the system. This reduces the need for case notes to be transferred to other sites and the need to contact the other site directly regarding the case. The interface also provides a comprehensive reporting capability so that commonly requested standard reports are available for authorized staff to run from their web browser.

We present an overview of how the web interface works in practice and how data is entered into the system.

To maximise the long-term survivorship of any hip prosthesis it is important to recreate joint centre. Normal joint centre is determined by horizontal offset and vertical height of the acetabular and femoral components. In this study joint centre and horizontal offset were analysed in 200 consecutive patients operated on from October 1998 in whom the opposite hip was normal. Joint centre was defined relative to the acetabulum and femur both pre- and post-operatively. On the acetabular side a horizontal line was drawn across the pelvis immediately below each teardrop. A vertical line was drawn at right angles through the middle of each teardrop. Acetabular offset was defined as the horizontal distance from the vertical trans teardrop line to head centre. For femoral offset a screened x-ray was taken to show maximum offset. The anatomical axis was drawn and the offset was defined as the distance from the anatomical axis to head centre.

Our results show on the acetabular side there was an overall tendency to leave the joint centre medial and so decrease acetabular offset. However, we found that 90% of our sockets were placed within 6 mm of normal joint centre. We attribute this accuracy to the principle of visualising the transverse acetabular ligament intra-operatively and using this landmark to control depth of socket insertion. Conversely, on the femoral side there was a slight tendency to increase the offset. Nevertheless, 98% of the custom stems were within 10mm of normal joint centre. When we looked at total horizontal offset i.e. the combination of femoral and acetabular offset we found that joint centre had been restored to within 10mm in 93% of cases.

This study confirms the effectiveness of the custom femoral stem and Duraloc socket in restoring joint centre.

Recurrent posterior dislocation is a recognised complication following primary total hip arthroplasty. Incidences of between 0.11% and 4.5% have been reported in the literature.

Component revision is regarded as standard management of recurrent posterior dislocation. However, revision surgery is a major surgical procedure and is often unsuitable for elderly, frail patients.

A congruent, ultra-high molecular weight polyethylene acetabular augment with a stainless steel backing plate has been developed. This can be inserted providing there is no malalignment, wear or loosening of the primary components.

In this study we compared twenty patients who underwent conventional revision surgery to twenty patients who had a PLAD inserted for recurrent posterior dislocation following primary Charnley total hip arthroplasty. Both groups were age and sex-matched and the average number of dislocations prior to surgery was three for each group.

For the PLAD group, the mean operative time, the mean intraoperative blood loss, the time spent in HDU, the transfusion requirements and the duration of hospital stay was significantly less than that for the revision group. Furthermore, there was no significant difference in the Oxford Hip Score recorded preoperatively and at 6 weeks, 6 months, one year and two years following surgery. None of the patients had sustained a further dislocation at latest review.

We conclude that the Posterior Lip Augmentation Device is a safe and effective option in the management of patients with recurrent posterior hip dislocation when there is no evidence of component failure or gross malposition.

We performed arthrodesis with a cobra head compression plate in 18 young adults with severely degenerative arthritis of the hip. The aetiology was trauma in 4 patients, sepsis in 3, slipped upper femoral epiphysis in 3, Perthes disease in one, acute lymphblastic lymphoma in one, alcohol related avascular necrosis in 2, epiphyseal dysplasia in one, multiple osteochondromatosis in one, (bilateral) idiopathic chondrolysis in one and in the remaining case there was no apparent cause. At a mean follow up of 4 years 14 patients were complaining of back pain compared to 4 patients preoperatively. Preoperatively 4 patients had ipsilateral knee pain compared to 5 patients postoperatively. Four patients complained of pain at rest or night. Eleven of the 18 patients have returned to work. The average score of satisfaction on a scale of zero to ten was 7.2, with only 3 patients giving a mark of 4 and below.

The management of osteoarthritis of the hip in the young adult is challenging and arthrodesis of the hip is a reasonable option for the very painful arthritic hip.

Introduction: Since 1992 over 3000 custom-made cemented titanium femoral components have been implanted during total hip replacement in our centre.

Stems are machined using CAD-CAM. Measurements are made from screened AP and lateral x-rays of known magnification. Normal joint centre is recreated by controlling offset and vertical height of the femoral component.

Method: Joint centre and limb length were analysed radiologically in consecutive 100 patients following total hip replacement for unilateral arthritis. Joint centre was defined relative to the pelvis and femur.

The anatomical axis and offset of the femur were defined using a screened x-ray of known magnification taken to show maximum offset. Femoral centre height was defined relative to the greater trochanter.

Results: In general, acetabular joint centre was placed medial and high, tending to reduce limb length slightly. Conversely, on the femoral side the tendency was to leave the component proud, producing an increase in limb length. Most patients had limb length restored to within 6mm of normal.

This study confirms the effectiveness of the Belfast Custom Stem in restoring joint centre and limb length.

In Musgrave Park Hospital, Belfast, younger patients requiring THR were treated by custom-made titanium alloy femoral prosthesis. The identifit hips, which were used initially, were intraoperatively customised by preparing a silicon mould of the endosteal cavity and immediate computer assisted fabrication. The Xpress hips used measurements from preoperative marker x-rays allowing creation of templates and subsequent computer analysis to mill a stem prior to surgery.

7 identifit and 51 Xpress primary uncemented custom THRs were inserted in 50 patients between May 92 and June 96. The average age for the indentifit cases was 47 years (range 24–72) and the Xpress cases 39 years (range 23–51). The Xpress cases were followed up to an average of 47 months (range 12–74 months) and identifit cases to an average of 59 months (range 14–77 months). The indications for arthroplasty were osteoarthrosis in 15 hips, CDH in 14, dysplasia in 11, AVN in 4, rheumatoid arthritis in 3 and other diagnosis in 11. Clinical assessments were made using the Oxford score and the Modified Harris Hip score. The postoperative radiographs were evaluated for subsidence of the prosthesis; and adaptive osseous changes like osteolysis, hypertrophic cortical remodelling, sclerotic radiolucent line formation around the prosthesis and formation of a bone pedestal below the tip of the prosthesis.

The average post-op Oxford hip score for those patients not revised was 32.5 /60 (range 12–51).

16 of the 51 Xpress hips underwent revision and 2 were awaiting revision, which is a failure rate of 35.3%. Of the identifit hips 1 out of the 7 was revised (14.3%). Overall 32.8% was the rate of failure. The average duration from primary operation to revision was 47 months for Xpress hips and 90 months for the identifit hips. Of the Xpress hips, revision was done for acetabular component in 1, femoral component in 4, both components in 1, acetabular liner + femoral head in 1 and acetabular liner + femoral component in 9. The 1 revision in the identifit hip was for recurrent dislocation.

The reasons for revision in the Xpress hips were dislocation in 2 cases, loose femoral component in 13 cases and infection in 1.

Average subsidence of the femoral component was 6mm (range 0–25.9) and this did not have significant correlation with predicting outcome. Pedestal formation (intramedullary formation of bone beneath the tip of the femoral stem) was seen in 87%, sclerotic rediolucent lines were seen in 64%, osteolysis was found in 31% and hypertrophic cortical remodelling was seen in 31%. These also did not reach significance in predicting outcome.

Thus even though the idea of an uncemented custom THR is attractive, especially in the younger age group, the failure rate was found to be unacceptably high. On the basis of these data we have discontinued the use of this custom made non-porous uncemented femoral prosthesis.