Aims

We introduced a self-care pathway for minimally displaced distal radius fractures, which involved the patient being discharged from a Virtual Fracture Clinic (VFC) without a physical review and being provided with written instructions on how to remove their own cast or splint at home, plus advice on exercises and return to function.

Introduction:

Historically the incidence of Achilles re-ruptures has been described as around 5% after surgical repair and up to 21% after conservative management. In 2008 we commenced a dedicated Achilles tendon rupture clinic for both conservative and surgically managed patients using new standardised operating procedures (SOP). We have evaluated the impact of this new service, particularly with regard to re-rupture rate.

Statement of purpose

To demonstrate how contemplating reconstructive options among members of Orthoplastic team can prevent accidental damage during initial wound debridement in foot and ankle injuries

Complex defects of the foot and ankle often require input from plastic and orthopaedic surgeons. There are different reconstructive options but one excellent regional option for small defects is the Extensor Digitorum Brevis muscle (EDB) flap. The anatomy of the flap and surgical technique and utility are described and demonstrated through a case series.

We present a series of 4 consecutive cases of the use of the pedicled EDB flap for soft tissue coverage of difficult defects around the foot and ankle. This regional pedicled flap can be proximally based to cover defects around the ankle or distally based for distal foot coverage. When possible, it facilitates a reconstruction with minimal donor site morbidity, shorter operating times, and fewer complications than alternative options

The flap would usually be performed by the plastic surgical member of the orthoplastic team, but an understanding of it by foot and ankle and reconstructive orthopaedic surgeons is relevant as it's vascular supply via the lateral tarsal artery can be easily damaged, preventing its use in the management of wound complications or trauma.

Introduction

There is a high prevalence of obesity in the United States and the numbers are increasing. These patients comprise a significant portion of the shoulder arthroplasty patient population. There are several reports of outcomes in the literature on obese patients after total knee or hip replacement, however, this data is lacking in the shoulder arthroplasty patient population. The purpose of this study is to compare the functional outcomes and complications of obese patients undergoing shoulder arthroplasty with the non-obese population.

Aim

Case Report presentation of traumatic cartilage loss in a child.

Introduction

Chronic mid body Achilles tendinopathy is a common problem. There is no consensus on treatment. The aim of this review was to assess the effectiveness of physiotherapy interventions (non surgical and non pharmacological) for this condition.

Introduction

The Ponseti regime was introduced in Swansea in 2003 for the treatment of congenital talipes equinovarus (CTEV). The aim of this retrospective cohort study was to compare children treated with this regime with a historical group treated traditionally before then.

In cerebral palsy patients, while upper limb function is acknowledged as being important, it has traditionally taken a back seat to lower limb function. This is partly due to inexperience and partly due to difficulty deciding on the best way of improving upper limb function.

In Swansea since June 2008 we have been offering a multi-disciplinary service for the assessment and treatment of upper limb problems in cerebral palsy. The core team consists of a consultant orthopaedic surgeon, a consultant plastic surgeon with a special interest in CP upper limb problems, a consultant paediatric neurologist, a community paediatric physiotherapist and a community paediatric occupational therapist.

Upon referral, the physiotherapist and occupational therapist carry out initial functional assessment of the patient. This is followed by a joint assessment by the whole team in a special clinic held every 3 months. If required, the child is offered surgery, botox injections or both. Further follow-up is in the special clinic until the child is suitable for follow-up in a normal clinic.

We present our initial experience with this multi-disciplinary approach, the problems encountered in setting up the service and our plans for the future.

Primary hip and knee replacements can be associated with significant blood loss. Tranexamic acid is a fibrinolytic inhibitor that has been shown to significantly reduce blood loss and transfusion requirement in hip and knee replacement, however the cost-benefit has not been widely investigated.

Our study involved 100 patients, comprising a prospective cohort of 50 consecutive primary hip and knee replacements (treatment group) and a control group of the preceding 50 patients undergoing the same surgery. All knee replacements were computer navigated. The prospective cohort all had tranexamic acid 1g intravenously at the time of surgery, repeated at 8 and 16 hours. All patients had 28 days thromboprophylaxis with subcutaneous low-molecular-weight-heparin.

The control group comprised 24 hip replacements and 26 knees versus 17 hips and 33 knees in the treatment group. Autologous transfusion drains were used in the control group knee replacements and the mean volume reinfused was 458ml. These drains were only used in the first 15 knee replacements in the treatment group as only one patient drained enough for reinfusion (100ml; p< 0.001). The mean fall in haemoglobin in the control group post surgery was 3.4g/dl versus 2.3g/dl in the treatment group (p< 0.001). Seven patients were transfused in the control group (14 units of red cells) versus two in the treatment group (5 units).

The potential cost saving per patient averaged across all joints in the treatment group is £102.51. This is a function of savings in transfusion, cessation of drains for re-infusion in knee replacement and the cost of tranexamic acid.

The only thromboembolic event was 1 deep vein thrombosis in the treatment group.

Our data shows the cost savings associated with the use of tranexamic acid in primary hip and knee surgery are considerable and supports its use to significantly reduce blood loss and transfusion requirement.

Suggestions for improved wear performance of total knee replacements have included replacement of standard CoCr femoral components with ceramic. Yttria-stabilized zirconia (y-TZP) was introduced as high-strength and high toughness ceramic as an alternative to alumina ceramic. Since the introduction of zirconia in 1985, the clinical outcomes and successes for hip joint have been controversial. Y-TZP ceramics have been studied both experimentally and clinically. Magnesia-stabilized zirconia (Mg-PSZ) also appears promising for total knee replacements (TKR).

Mg-ZrO2 and CoCr femoral condyles were compared in the VanguardTM knee configuration (Biomet Inc, IN). Molded tibial inserts (GUR1050) were gamma-irradiation sterilization to 3.2-Mrad under argon. Knee simulation was conducted on a 6 station simulator (Shore Western Manufacturing, Monrovia, CA). Motion included 20 degrees of flexion/extension, 5 degrees of internal/external rotation and 5 mm of AP-translation. All knee components were subjected to 6 million cycles of normal walking (2.9 kN max, freq 1.4 Hz). Lubricant was 50% alfa-calf serum diluted to 20 mg/ml protein and using EDTA additive. Test duration was 6 million cycles (6-Mc), and wear was measured by weight-loss techniques.

For wear trending of CoCr/PE and MGZ/PE, linear wear trends were apparent from 1 to 6 Mc test duration. The control implants (CoCr/PE) showed excellent linear trending (regression coeff r> 0.99) with wears rate averaging 6.3 mm3/Mc. These data showed good control of experimental variance (< 10%). The ZrO2/PE combination showed good linear trending (r > 0.86) with wear rate averaging only 0.8 mm3/Mc. This set also showed good control of experimental variance (< 15%. The MGZ/PE wear was 8-fold reduced from that of CoCr/PE.

The laboratory knee wear simulation appeared very supportive of femoral condyles of Mg-stabilized zirconia. Such implants may provide excellent performance for active patients who may risk high wear rates over many years of use.

Acetabular cup orientation in hip arthroplasty is critical to prevent edge loading and impingement. Aerial alignment guides position the cup at a specified angle to the orthogonal planes, but only if the pelvis is in strict lateral-decubitus. Computer navigation can also be used to position the acetabular cup, but there are limitations associated with defining the pelvic reference plane. It can also be postulated that a fixed angle of inclination and anteversion is not suitable for every patient and every cup design. This paper describes the development and testing of instrumentation that allows patient specific acetabular cup placement without knowing the exact pelvic orientation.

Stage 1 determines the cup position during a trial reduction. A Judd nail retractor is left in the pelvis during the trial reduction. A single-use laser pointer is attached to the top of this nail, is free to move and can be locked in position. The trial acetabular cup has a handle protruding at a fixed angle from the face of the cup. At the end of this handle is another single-use laser pointer that projects a laser beam parallel to the axis of the cup onto the wall/ceiling. Keeping the handle parallel to the medio-lateral axis to control inclination angle, the leg is moved through a range of motion (ROM). The anteversion of the trial cup is adjusted until a position is found where flexion extension ROM is possible without impingement and satisfactory abduction-adduction is achieved with stability. Once this position is found, the Judd nail laser (fixed to the pelvis) is adjusted until its projected point, on the wall/ceiling, coincides with that from the trial handle. The Judd nail laser is then fixed in position, the hip dislocated and trial components removed.

Stage 2 aligns the definitive acetabular cup. The introducer has a laser pointer pointing parallel to its axis (away from the patient) and is attached to the definitive cup. The definitive cup is placed in the acetabulum and the introducer adjusted until its projected laser coincides with that from the Judd nail. The cup is then in the same orientation as determined during the trial reduction and can be impacted.

To demonstrate the accuracy of the laser alignment method, the position of the definitive cup was compared to that of the trial cup in polyurethane foam models. With the laser points projected onto an object > 2m away, the accuracy was ±2°.

To compare the laser guided instrumentation with the conventional aerial device, the ROM of the definitive cup was assessed in Sawbones resurfaced pelvis/femur models. The pelvis orientation was rotated by ±10° about the medio-lateral axis and the superio-inferior axis to investigate the effect of the pelvis being unknowingly out of lateral-decubitus. In the worst case of pelvis position, the aerial halved the required flexion and allowed double the required extension. The laser guided instrumentation maintained the physiological range of flexion/extension regardless of pelvis position and is therefore considered an improvement on current technology and a viable alternative to computer navigation.

Wear in polyethylene liners appears to be exacerbated by 3rd-body abrasion effects with the CoCr ball combinations used for total hip replacements. This has implications for various wear modes encountered in patients. Yet clinical and laboratory studies have offered weak and sometimes contradictory wear relationships with respect to crosslinking, ball diameter and roughness, and 3rd-body wear effects. Our hip simulator model investigated the effect of severe wear challenges by 3rd-body cement particles, using large diameter CoCr and alumina balls, with highly-crosslinked polyethylene liners (HXPE) irradiated to 75kGy compared to contemporary controls (CXPE 35kGy).

The polyethylene liners were gamma-irradiated to 35/75kGy under N2 (CXPE/HXPE). We used 32 and 44mm CoCr balls (ENCORE, Austin, TX) and 44mm alumina-ceramic (Biolox-forte, CeramTecAG) as ‘scratch-resistant’ standard of comparison. We compared 5 bearings pairs with different roughness characteristics using both new and pre-worn polyethylene liners. A 12-station orbital hip simulator with a physiological load profile (0.2kN–3kN load, frequency 1Hz) with cups mounted in “Inverted- position”. Diluted bovine serum (Hyclone Inc., Logan, UT) was used as lubricant (20mg/ml protein, 400ml volume). In phase I, all cups were run in standard (‘clean’) lubricant for 1.5 million cycles (1.5Mc). In phase II, the liners were run in a PMMA slurry of serum (5mg/ml) for 2Mc. In phase III, implants were run ‘clean’ for 1.5Mc. Wear-rate was measured each 0.25Mc event, and surface roughness measured by SEM (XL-30FEG) and white light interferometry (Newview600, Zygo) every 0.5Mc.

In phase I, Wear withnew CXPE and HXPE liners averaged 182mm3/Mc and 30mm3/Mc. Thus the HXPE liners averaged a 6.0-fold wear reduction compared to controls. Compared to new liners, the pre-worn CXPE and HXPE liners showed 10% and 25%, greater wear respectively. Here it was noted that CoCr balls maintained similar roughness (Sa:8–12nm). And alumina balls showed small, gradual increase (Sa: 2 to 2.5nm). The HXPE maintained a superior finish to CXPE controls. Roughness revealed a gradual decrease with time, pre-worn CXPE from 0.28 to 0.15um and pre-worn HXPE from 0.18 to 0.04um (Sa). In contrast, new HXPE showed a dramatic smoothing (0.8 to 0.1um) 92.8% decreased in first 0.5Mc. These effects have not been previously quantified. In phase II with abrasive mode, the liner wear-rates increased dramatically by 6 and 80-fold for CXPE and HXPE, respectively. These data confirmed that HXPE was sensitive to ‘severe’ wear against CoCr and alumina balls. In phase III, the polyethylene roughness dropped by > 90% and wear decreased to phase-I values. The wear-ratio was now 2:1 for CXPE:HXPE as predicted by the ‘diameter’ and ‘crosslinking’ algorithms.

It was clear that surface roughness was not a confounding factorfor either the CoCr or alumina balls. It was the polyethylene surface roughness that appeared to influence wear rates. Our analysis showed that there was a transient due to patches of abrasive cement transferring onto CoCr ball surfaces. Overall the actual roughness of the CoCr balls did not change and was therefore not a factor in increased polyethylene wear.

Ceramic-on-ceramic bearings (ALX: pure alumina) have been used for human hip joints for almost 40 years. However an alumina matrix composite with zirconia (AMC) was introduced in year 2000 as a high-strength ceramic with almost double the fatigue resistance (AMC = 80.5%ALZ and 18vol% ZrO2). However we have not found any retrieval studies reported for this new ceramic bearing.

Wear maps were generated on three retrieved AMC femoral heads (28 and 36mm diameters) using x-ray diffraction, roughness and SEM imaging techniques. The wear study ran a physiologically appropriate, micro-separation test on 36mm ceramic balls and liners (AMC/ALZ). Wear rates were determined for the four combinations of balls and cups (ALX:AMC) with mapping of main-wear and stripe-wear zones, surface-roughness and analysis of debris morphology. In addition, the zirconia transformation to monoclinic phase was studied in AMC bearings

The retrieval study showed for the first time the wear phenomena occurring on three retrieved AMC femoral heads (at 1, 3, 6 years). Two had been paired with alumina liners and one with a polyethylene liner. Case-1 featured a 36mm ball in an UHMWPE socket, case-2 was an intact 28mm AMC ball and case-3 had a fractured ball from an IDE study. Laser interferometry and SEM were used to image ceramic wear and x-ray diffraction for analysis of transformation in the zirconia phase. Main-wear zones, stripe-wear zones, metal contamination and sites of implant impingement were also characterized. Surface roughness and in-vivo aging were quantified for both non-worn and worn areas. The SEM studies showed well-preserved articular surfaces, some with faint parallel scratches still evident. The latter likely represented the manufacturer’s original polishing marks. Multiple stripe-wear sites were identified with roughness 25–65nm (Sa) whereas polished main-wear zones averaged very low at 2–3nm. Metal impingements sites stained black with transfer of titanium increased roughness up to 140nm. Mildly worn areas of case-2 AMC ball averaged 10% transformation in the zirconia phase (tetragonal to monoclinic). In the stripe-wear zones, the monoclinic phase increased to 30%. The taper-bore and fracture surfaces in case-3 averaged 30% to 40% monoclinic, respectively. The stripe-wear zones and black metal contamination on these retrieved 28mm balls were correlated to multiple impingement sites on the rim of the alumina liners and titanium shells.

The laboratory model produced stripe wear on the ceramic balls and liners. The AlX/AlX controls produced the highest run-in and steady-state wear rates at 6.3 and 2mm3/Mc respectively). In contrast, the AMC/AMC combination produced the lowest wear rates at 0.5 and 0.1 mm3/Mc, respectively). With hybrid ball:cup combinations (AlX:AMC; AMC:AlX) the wear rates were similar and showed a 3-fold reduction compared to controls. In hybrid pairings, the AMC ceramic wore preferentially more than its AlX counterpart, regardless if present as a ball or cup implant. Thus the AMC ball contributed 66% to AMC/AlX total wear whereas the ALZ ball contributed only 33% of the total AlZ/AMC wear.

This study appears to be the first documentation of wear in retrieved AMC bearing surfaces. In general, the AMC surfaces worn in-vivo corresponded well to our in-vitro wear model. The stripe-wear zones in AMC femoral heads had rougher surfaces and higher monoclinic transformation than the main-wear zone. Overall the AMC ceramic appeared more resistant to stripe-wear effects created by the micro-separation and impingement phenomena.

Introduction: Up to 20% of Lisfranc injuries can go unrecognised with resultant long-term morbidity. Spontaneous relocation may mask the injury. Standard AP, lateral and oblique views of the foot are the primary radiological views. Weight bearing views may not be possible acutely and stress views may require anaesthesia. The standard AP view does not show the tarso-metatarsal joint clearly with alignment of the medial border of the second metatarsal to the medial border of the intermediate cuneiform all important.

Materials and methods: We used a tangential AP view of the tarso-metatarsal joint taken by tilting the x-ray beam cephalad. The degree of tilt was dictated by the declination angle of the first metatarsal seen on the lateral view of the foot (20–25 degrees for most people). Sixteen patients had standard AP, lateral and oblique views of their foot at the time of injury and were not diagnosed to have a Lisfranc injury. They remained symptomatic for an average period of 5 weeks (range, 2 to 15 weeks) before they had the tangential view of the Lisfranc joint.

Results: In all 16 patients the first and second tarso-metatarsal joint and the first inter-metatarsal space were more clearly visible. Thirteen patients had abnormal findings to confirm the diagnosis of Lisfranc injury and for 2 surgical treatment would have been appropriate if identified earlier than 14 and 15 weeks respectively.

Discussion and conclusion: This view confirmed the diagnosis in 13 patients who would have otherwise been discharged as a minor soft tissue injury.

We have also used this view successfully for injecting local anaesthetic in the tarso-metatarsal joints to elucidate the exact source of pain.

We recommend this simple view should be routinely used in addition to the standard AP, lateral and oblique views of the foot for mid foot injuries.

Introduction: Several patients with fracture neck of femur were noted to have alarmingly low postoperative haemoglobin unexplained by the intra-operative and postoperative blood loss. We conducted this study to determine the magnitude of preoperative fall in haemoglobin in patients with hip fractures.

Methods: Full blood count was repeated after a minimum of 12 hours of fluid resuscitation in 50 consecutive patients admitted with fracture neck of femur. Patients requiring blood transfusion prior to collection of second specimen were excluded. Patients were grouped according to the type of fracture (intracapsular, inter-trochanteric and sub-tro-chanteric).

Results: The average drop in haemoglobin of 0.8 (range,0–2.1), 0.8 (range,0–2.8) and 2.5 (range,0.6–4.9) gm/dl in intracapsular, inter-trochanteric and sub-trochanteric fractures respectively were statistically significant in all three groups (student-t-test, p-value < 0.05) but appears to be clinically significant in only sub-trochanteric group. By close analysis of data it is noted that although average drop in first two groups is low but at least 15 % of patients in both groups dropped their haemoglobin by 2 gm/dl or more. This can be compounded by the drop in haemoglobin following surgery, the average of which was 2.5 gm/dl (range,0–6.4)

Discussion and Conclusion: During this study at least 5 patients were saved from going to theatre with dangerously low haemoglobin with no cross-matched blood. There is clinically significant drop in haemoglobin prior to surgery in patients admitted with fracture neck of femur. On admission haemoglobin can be falsely reassuring. We recommend all patients with sub-trochanteric fracture and all patients with intra-capsular and inter-trochanteric fractures with haemoglobin of 12 gm/dl or less to have a repeat haemoglobin check prior to their surgery. This practice may reduce the morbidity and mortality associated with very low haemoglobin in this group of patients with high pre-existent co-morbidities.

Purpose: In the modern political climate our practice is increasingly being compared with that of our peers. Outcome measures will form the basis of this. Good outcome measures have two essential requirements; they should be valid and reliable. Outcome measures are not easy to construct. Traditionally subjective walking distances have formed a portion of the assessment. This has never been validated.

Method: Null hypothesis - patients can accurately estimate their actual walking distance.

After gaining COREC approval we compared the objective to subjective walking distance of patients who had sustained a fractured Os Calcis over the past two years and were allowed to full weight bear. Patients were assessed by a senior physiotherapist and Doctor. Both the American Orthopaedic Foot and Ankle Score and Maryland Score were performed. Patients were asked to estimate their maximum walking distance prior to objective treadmill assessment.

Results: 20 patients, 6 female and 14 male were assessed. Average age was 67yrs (range 46–83yrs). One patient was excluded as they were breathless at rest. Good correlation was found between the subjective walking assessments of the two scores. All patients’ uniformly over estimated their walking ability. This was a highly significant difference, p-value 0.002. Therefore the null hypothesis has been disproved; patients’ subjective walking distance is inaccurate.

Significance: Walking distance assessment is used is as a measure in many fields of orthopaedics namely foot and ankle outcome measures and lower limb arthroplasty. This study has shown it to be an inaccurate method. It also highlights the need to validate all outcome measures.

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

Objective: To evaluate the effects of a new potent bisphosphonate on the formation, mineralisation, density, and mechanical properties of bone in distraction osteogenesis.

Methods: Thirty immature New Zealand White rabbits had a 10.5 millimetre lengthening of their tibia performed over 2 weeks using an Orthofix M-100 fixator. Ten control rabbits received saline only; 10 received the new bisphosphonate at the time of surgery, and 10 received a second dose at the end of distraction. Bone mineral content (BMC) and density (BMD) measurements were made at two, four and six weeks. Quantitative CT analysis of regenerate, proximal and distal bone, and corresponding segments in the non-operated limb was performed after culling. Mechanical testing was by 4-point bending.

Results: Bone mineral accrual was significantly faster in both treatment groups (ANOVA p< 0.01). BMD increased in all treated animals (ANOVA p< 0.01). Cross sectional area of regenerate at six weeks was increased by 49% in the single dosed group versus controls and by 59% in the re-dosed group. (ANOVA p< 0.01). BMC of the regenerate was increased by 92% in the single dose group and by 111% in the re-dosed group (ANOVA p< 0.01). Moment of inertia of the regenerate was significantly increased in both treated groups (ANOVA p< 0.05). The difference between single dose and controls was significant (p< 0.05), the difference between re-dosed and single dosed was not (p=0.5).

Conclusion: Bisphosphonate therapy significantly increased new bone formation, bone mineralisation and mechanical properties. Osteoporotic effects were reversed. This effect could have wide ranging implications for many orthopaedic practices

The objective of this study was to compare the wear mode of 100 Mrad PE cups run in a hip simulator to retrieved 100 Mrad PE cups, and to evaluate the efficacy of the PE wear model.

15 In-vitro PE cups: 3 each 0,2.5.50,100 and 150 Mrad (9 channel hip simulator, 6.2 million cycle duration, physiological load profile by Paul, 2000N maximum load at 1Hz using 30% bovine serum). 5 Retrieved PE cups: three SOM cups (Mizuho Medical Instrument Co., COP alloy 28 mm head)-0 Mrad after 8 years of clinical use, two 100 Mrad cups after 15 years of clinical use, two T28 PE 2.5 Mrad cups (Zimmer): 18 years and 13 years of clinical use. The cups were examined using a SEM (Philip XL30 FEG) for wear scar locations and PE wear-topography.

Original machine marks were observed in the weight-bearing areas of the highly cross-linked in-vitro PE. No machine marks were observed for the 0 and 2.5 Mrad in-vitro cups and none were seen in any of the retrieved cups. The formation of more nodules and fibrils in the 0Mrad cups compared to the extensivley cross-linked cups (in-vitro and retrieved) was striking. The frequency of occurrence and length of the fibrils and nodules was dependent on the dose of gamma irradiation. More ripples were formed in the 2.5 Mrad and higher cups compared to the non-irradiated cups (in-vitro and retrieved). The in-vitro cups formed more ripples than the retrieved cups. In general, the SEM features for in-vitro Mrad cups appeared similar to those of the retrieved Mrad cups.

The in-vitro Mrad cups accurately reflected the conditions of the artificial joint in living body. Therefore, comparisons of retrieved PE cups with simulator PE cups appeared to be a very powerful research tool.

(2) SEM observation demonstrated far less wear damage in the extensively cross-linked cups than in the non-extensively cross-linked PE. Thus the extensive cross-linked PE cups appeared to be a significant improvement over conventional PE cups in terms of wear resistance.

The bisphosphonate, pamidronate, has been used successfully in our hospital for the management of osteogenesis imperfecta with an excellent safety profile in growing children. We have performed several research studies on distraction osteogenesis in New Zealand white rabbits showing significant increases in new bone formation and the abolition of stress shielding osteopaenia using both pamidronate and zoledronic acid. Recent studies have shown that bisphosphonates positively effect osteoblasts as well as inhibiting osteoclastic bone resorption.

We present a series of early cases where this research has been used in humans. Two cases of pamidronate assisted distraction osteogenesis are presented, one of which also had congenital pseudarthrosis of the tibia, which united after pamidronate administration.

Two cases of post-traumatic avascular necrosis have been successfully treated such that osteolysis and collapse of the necrotic femoral head did not occur. Bisphosphonates may act to slow bone resorption while simultaneously increasing new bone formation, such that the mechanical integrity of the necrotic segment can be maintained during revascularisation.

A randomised controlled trial of bisphosphonates in distraction osteogenesis at our hospital has now received ethical approval. Newer bisphosphonates have proven their clinical value in osteogenesis imperfecta and adult osteoporosis, but other potential roles are emerging for these compounds, which have extremely potent effects on bone.