Introduction

Anterior tibial translation (ATT) is assessed in the acutely injured knee to investigate for ligamentous injury and rotational laxity. Specifically, there is a growing recognition of the significance of anterior medial rotary laxity (AMRI) as a crucial element in assessing knee stability. Anterior cruciate ligament (ACL) injuries are often accompanied with medial collateral ligament (MCL) damage. It has been suggested that Deep MCL (dMCL) fibres are a primary restraint in rotational displacement. This research aims to quantify the difference in rotational laxity of patients with ACL and MCL injuries to deem if the Feagin-Thomas test can robustly capture metrics of AMRI. 2.

Recruits undergoing arduous training at Commando Training Centre Royal Marines (CTCRM) carry a higher risk of femoral neck stress fractures than many other military populations. This injury has serious sequelae and requires urgent operative fixation if it is displaced. Existing literature advocates a low threshold for imaging patients where this injury is suspected, due to the prognostic advantage conferred by early intervention. CTCRM uses a locally produced scoring system based on history and clinical assessment, to guide the requirement for imaging. Since 2015 access to MRI has been possible through a fast track provider. Between 2012 and 2015, 3522 Royal Marine Recruits entered training. Over the period, 95 MRI scans of the hip were performed, of which 12 utilised private pathways. 13 stress fractures of the femoral neck were identified; 23% (n=3) were displaced and required fixation. The overall incidence rate for this injury is therefore 37 per 10,000, with a displaced incidence rate of 9 per 10,000. We compare these data with previous studies, discuss the use and efficacy of the scoring tool, and assess the benefit conferred by the local private MRI agreement.

Anterior Cruciate Ligament injuries are a common cause of downgrade in Service personnel. The Multidisciplinary Injury Assessment Clinic (MIAC) is a service which patients can be referred to for expert musculoskeletal injury management. MIAC has a Fast Track (FT) referral system in place for imaging, and can subsequently refer isolated ACL injuries to a private provider for reconstruction. We examined this pathway in the South West region which has an overall population at risk of 19775. Over 4 years 173 knee injuries were referred to MIAC, of which 32 were ACL injuries. Of the 29 patients referred for MRI, the median time to imaging was 8 days with FT (n=13, range 2–14) and

15 days via the NHS (n=16, range 5–64). The majority of injuries were found to involve multiple pathologies (n=19), excluding them from FT surgery. Time to NHS clinic from point of referral took a median time of 54 days, and onward delay to surgery was 47 days. None of the referrals to the private provider for reconstruction were accepted (n=3). We have identified aspects of current referral and treatment pathways that are inefficient and discuss a current solution utilising Military surgeons.

Fewer delays in starting a trauma list can reduce cancellations. A novel system has been previously described where a patient is identified the day before and optimised for theatre. The patient is listed first and designated “Golden Patient”. This project aimed to assess the impact of introducing a “Golden Patient” system on trauma list start times in a district general hospital.

Two months of first case sending and anaesthetic start times were recorded retrospectively (43 cases). The “Golden Patient” system was introduced with a multi-disciplinary implementation group. Target send time of 0830 hours (hrs) and anaesthetic start time of 0900hrs was agreed. First patients on trauma lists were noted in two cycles, two months apart (Cycle 1: 46, Cycle 2: 38).

Prior to implementation: Mean Send Time (MST) of 0855hrs, Mean Anaesthetic Start Time (AST) of 0921hrs.

Cycle 1: MST fell by 9 minutes (p = 0.03) and AST by 11 minutes (p = 0.023). Lists labelled with a “Golden Patient” (47.8%) were sent 14 minutes earlier (p = 0.004) and started 12 minutes earlier (p = 0.02) than those not labelled “Golden”.

Cycle 2: Implementation produced a 13-minute reduction in send times (p = o.oo3) and start times (p = 0.008) overall. “Golden Patient” cases (42.1%) showed an improved MST of 0836hrs and AST of 0902hrs, 10 minutes earlier than those not designated “Golden”.

Implementation of the “Golden Patient” produced a significant improvement in trauma list starts overall. Specifically, “Golden Patients” help to improve efficiency in sending and anaesthetic start times, by up to 19 minutes on average.

Proximal inter-phalangeal joint (PIPJ) arthrodesis is a commonly performed procedure as a part of hammer and claw-toe correction. Conventional K-wire stabilisation has the potential disadvantages of infection; violation of DIP joint; external protrusion or the wire and necessity of removal.

Newer intra-medullary stabilisation devices are also available, though tend to incur addition costs. We present our technique and results of using a single, buried 1.6 mm K-wire for proximal inter-phalangeal joint fusion

Our objectives were to assess union rates and patient satisfaction following intra-medullary K wires for PIP joint fusion. This involved reviewing 26 consecutive patients (34 toes) who had undergone hammer or claw toe correction. Case notes and radiographs were reviewed to establish results and complications and the need for revision surgery. Initial Radiographs taken at 6 weeks and a telephone survey was undertaken to assess patient satisfaction (16–44 weeks).

Our findings were that of the twenty-one women and five men underwent surgery, with a mean age of 59 years (24–77), stable union was achieved in 33 of 36 toes. No patients had superficial or deep infection and no patient required wire removal or a revision procedure.

In conclusion, PIPJ Arthrodesis with buried K Wires has excellent clinical outcome and high patient satisfaction.

Introduction

Occult hip fractures occur in 3% of cases. Delay in treatment results in significantly increased morbidity and mortality. NICE guidelines recommend cross-sectional imaging within 24 hours and surgery on the day of, or day after, admission. MRI was the standard imaging modality for suspected occult hip fractures in our institution, but since January 2013, we have switched to multi-detector CT (MDCT) scan.

Our aims were to investigate whether MDCT has improved the times to diagnosis and surgery; and whether it resulted in missed hip fractures.

Introduction:

The routine use of posterior hip dislocation precautions is typically utilized postoperatively following total hip arthroplasty via a posterior surgical approach. This has included use of an abduction pillow and limiting adduction, internal rotation and flexion more than 90 degrees for a minimum of 6 weeks postoperatively. This may slow the course of rehabilitation, increase the length of hospital stay and the total cost of the procedure, and add additional anxiety to the patient. We conducted this study to see if posterior hip precautions are necessary after total hip arthroplasty via a posterior approach when the hip meets certain intraoperative criteria for stability.

Introduction

The assessment of the accuracy of reduction of the ankle syndesmosis has traditionally been made using plain radiographic measurements. Recent studies have shown that computerized tomography (CT) scan is more sensitive than radiographs in detecting diastasis. The ethos has now therefore shifted towards CT scan assessment of the syndesmosis. There is however no validated method to scan the syndesmosis and measure it on the CT scans. This exposes the patient to significant radiation risk and also to anxiety from inappropriate interpretation from these scans.

The objectives of this research project are to investigate the current practice of CT scanning the syndesmosis at a University Hospital and to devise a new CT protocol to reduce radiation exposure to patients and to assist surgeons in interpreting the observations.

Roentgen stereophotogrammetric analysis (RSA) is the most accurate radiographic technique for the assessment of three-dimensional micromotion in joints. RSA has been used previously to study the kinematics of the anterior cruciate ligament (ACL)-deficient knee and to measure knee laxity after bone-tendon-bone (BTB) reconstructions. There is no published evidence on its use in assessing hamstring grafts in vivo, in comparing hamstring versus BTB reconstruction, or in-depth analyses of graft performance.

The aim of this project was to use RSA to measure laxity in both BTB and hamstring reconstructions, and to attempt a detailed analysis of graft behaviour in both reconstructions, with particular attention to graft stretching and slippage of the bony attachments.

A prospective study was undertaken on 14 patients who underwent ACL reconstruction. Seven had BTB reconstruction, and seven had four-stranded semitendinosus/gracilis (STG). Tantalum markers were inserted at the time of surgery, into distal femur and proximal tibia, and also directly into the graft itself. Stress radiographs (90N anterior and 90N posterior force) were taken early post-operatively, and then at 6 weeks, and 3, 6 and 12 months.

In addition to measuring total anteroposterior knee laxity, a detailed analysis of the graft itself was possible. The BTB grafts had stretched by an average of 1.54%, and the bone plugs had migrated by 0.50 mm at the femoral end and by 0.61mm at the tibial end. The hamstring grafts had stretched on average 3.94%, and the intraosseous ends had migrated by 3.96mm at the femoral end and by 7.10mm at the tibial end. This is believed to be the most detailed application of RSA in analysing the performance of the two commonly used grafts in ACL reconstruction. Details such as graft stretching and fixation slippage have not been available previously; the data obtained in this study may have implications for clinical practice.

Purpose of the study: Insufficient patellar bone can raise problems for revision total knee arthroplasty and for certain cases of lateral patellofemoral degeneration. Several options are proposed: non-resurfacing, resurfacing on an asymmetrical bone cut, patellar thinning possibly leading to fracture, or patellar bone graft to obtain a regular thick bone.

Material and methods: We report a series of 26 patellar reconstructions among 19 primary osteoarthritis cases with lateral patellofemoral degeneration and five revisions. The patellar reconstruction involved the entire patellar surface in five cases and the lateral facet in 19. For only two cases, a bank graft was used. For the others, the graft was shaped from the tibial resection. Stabilisation used screw fixation in only one case. For the others, two cemented patellar anchor buttons were used to stabilise the graft. All patients were reviewed clinically and radiographically at minimum 12 months. Mean follow-up was 54 months (12–95).

Results: Patellar thickness measured during surgery was improved from 18.1 mm (10–25) to 24.5 mm (21–31). The DMS and function scores improved respectively: 45.5 and 40.7 preoperatively and 89.1 and 72.8 at last follow-up. Seven patients were noted C in the Charnley classification at last follow-up and five used one or two crutches for walking. Twelve patients used the hand rail when climbing stairs and seven needed to use their hands to get up from a chair. All grafts except the allograft fused and all patellar buttons remained stable. There was one lucency at last follow-up. Among the 13 patella exhibited a shift preoperatively, only one remained at last follow-up. There were no subluxations at last follow-up (15 preoperatively).

Discussion: This work shows the pertinence of patellar bone grafts to restore bone stock and avoid complications related to resurfacing asymmetry: pain and patellar shift. Fixation by osteosynthesis does not appear to be necessary. Autographs can be used without risk. Allografts still have to prove their efficacy in this indication.

Background: Acute traumatic rupture of the Tendo-Achilles is a common problem. Review of the published literature shows a conflict between surgical and non-surgical management. Primarily, surgical treatment has repeatedly been shown to have a lower re-rupture rate compared with conservative treatment. However, it is associated with a higher rate of other complications, principally infective soft tissue complications. Debate concerning the method and duration of conservative treatment regimens also remains.

Methods: We aimed to assess the effect of knee position on the gap in acute tendo-Achilles ruptures. Our null hypothesis was there is no difference in tendon gap with variation of knee position. Patients with a history and examination consistent with an acute rupture were collected prospectively. They were imaged by the same consultant musculoskeletal consultant radiologist using ultrasound. Tendon gap was measured with the foot in neutral and full tolerable equinus with the knee both flexed to 90° and fully extended. A pilot study of 10 patients was used to provide data for a power calculation and consequently a total of 25 patients were recruited.

Results: All patients had their clinical diagnosis confirmed and tendon gap measured in each of the 4 positions. A paired t-test was used to compare mean differences between each position. This confirmed there was no significant difference in the tendon gap with the knee flexed or extended providing the foot is in full equinus. This may have considerable implications on the rationale behind conservative treatment and splinting of acute tendo-Achilles ruptures.

Background: The bunionette is a lateral prominence of the fifth metatarsal head. It is usually caused by a wide intermetatarsal angle (IMA) between the 4th and 5th metatarsals with associated varus of the metatarsophalangeal (MTP) joint. Increased pressure placed on the head of the 5th metatarsal results in pain and plantar callus formation. Failure of conservative treatment warrants bony corrective surgery. Various distal, shaft and basal osteotomies have been described in the literature.

Methods: We have used a ‘reverse’ scarf osteotomy in 12 cases (10F: 2M) with a mean follow-up of 12 months (range 5–22 months). All patients filled up a Foot Function Index (FFI) questionnaire pre-operatively and a repeat questionnaire at the latest follow-up. All angles were measured on a weight bearing AP radiograph of the foot. Post-operatively we mobilised the patients immediately using a heel bearing shoe. All osteotomies healed sufficiently at 6 weeks to allow unprotected weight bearing. Full weight bearing was allowed after clinical and radiological union was achieved.

Results: Pre-op mean IMA was 13.1 degrees (range: 10.4–18 degrees) and mean 5th MTP angle was 19.9 degrees (range 12.7–25.5 degrees). Pre-op mean FFI was 34.2 (range 14–71.3). Post operatively, mean IMA was 7.27 degrees (range: 2.0–11.5 degrees); mean 5th MTP angle was 6.36 degrees (range: 2.8–9.0 degrees) and post-operative mean FFI was 5 (range 0–16.7). All except one patient were pleased with the cosmetic correction obtained. One patient did not like the scar but her foot was asymptomatic and her FFI improved from 27 to 0. All patients would undergo the same procedure on the other foot if required and would recommend the same to a friend.

Conclusion: ‘Reverse’ Scarf osteotomy in the correction of bunionette deformity offers promising results in the short term. Further longterm follow-up would help to establish the benefits of this procedure.

We audited all patients who underwent Foot and Ankle surgery at the University Hospital of Wales over one financial year (April 2007 – March 2008).

Patients were identified from the hospital OPCS-4 coding system and all scheduled and unscheduled visits to hospital investigated. Both trauma and elective patients were included. Patients were followed up for a mean period of 9 months (Range 1–14 months) following surgery.

The records for 1052 patients were evaluated. Of these, 77% were elective cases and 23% were trauma related. Overall about 10 % of our foot and ankle patients (100/1052) either attended the A& E Department or had an unplanned clinic visit at some stage of their follow up. Three quarters of these patients were admitted to hospital (median stay 1 day, range 1–51 days).

Twenty five patients (24 A& E; 1 medical) simply re-attended, but were not admitted. The majority of these (58%) had plaster-related problems (8\24) or superficial wound infections (6/24). The remaining patients presented with pain around the operated area, and were discharged after investigation. One patient presented to the physicians 44 days after excision of a Morton’s neuroma with a DVT.

Seventy five patients (7%) were re-admitted to hospital. Two were admitted under the physicians: one with a pulmonary embolus (30 days post ORIF ankle) and one following a cardiac arrest (20 days post ORIF ankle). Out of the remainder 34 patients had planned removal of metalwork, 9 patients had metalwork removed because of infection and 21 patients had soft-tissue infection requiring antibiotics or debridement. Overall, 9 patients underwent revision surgery (0.85%).

The overall infection and thromboembolic rate was 3.42 %(6 A& E + 30 T& O/1052) and 0.28% (1A& E + 2 medical/1052) respectively.

Anatomical variation of Lisfranc mortise has been implicated in the susceptibility of Lisfranc fracture-dislocation. We investigated whether the variations in the dimensions of second metatarsal base makes the joint vulnerable to fracture dislocation.

Patients and Methods: 31 normal (group A) and 23 injured (group B) foot x-rays were compared. The average age of patients was 33(range 16–64) years. Routine AP and 45 degree oblique foot x-rays were used to measure second metatarsal parameters such as L (length of second metatarsal) were measured on x-rays in both groups. Additionally D (height of base of second metatarsal in sagittal plane of foot) was measured in CT scans. Statistical analysis was performed to test the viability of the null hypothesis that states that the relationship of second metatarsal length and height at the base does not correlate with increased susceptibility of Lisfranc injury. Similar analyses of the relevant parameters at the second metatarsal mortice were also calculated.

Results: Mean values of D, L and D/L were obtained in both groups. Statistically the value of D/L was found to be significantly different between injured group and normal group, with a P value of 0.03, while the values of length of second metatarsal itself was not significantly different between two groups (P=0.15). However, no significant correlation was noticed using other parameters of the second metatarsal mortice.

Conclusion: Previously shallowness of the second metatarsal mortice was shown to be significantly correlated with increased risk of Lisfranc injury. However, this study suggests that dimensions of second metatarsal such as, depth/length of the second metatarsal significantly increase the risk of Lisfranc injury. In other words more slender metatarsal dimensions at its base carry increased risk to Lisfranc injury. Thus, anatomical variation at the base of the second metatarsal makes the Lisfranc joint susceptible to injury.

Ankle injuries in cricket fast bowlers are of topical interest with a number of elite pace bowlers recently sustaining injuries. Previous biomechanical research has concentrated on the injury risk to the fast bowler’s lumbar spine with no research focused on the leading leg and specifically the ankle biomechanics of the fast bowler and its predisposition to injury.

We investigate the leading leg biomechanics in maximal and submaximal fast bowling. Ten fast-medium paced bowlers of elite level had their leading leg biomechanics assessed during their bowling action. Using a nine camera infra-red ViconTM 612 motion analysis system linked to a KistlerTM 9281CA force platform the moments of the subjects leading leg during their delivery stride was analysed. Each subject performed ten trials at a maximal ball release speed (> 97km/hr) and ten trials at a submaximal ball release speed (< 97km/hr) with the speed of the ball tracked by a SR3600 radar gun.

All three large joints of the leg were observed and joint moments examined in both directions of all three orthogonal planes giving a total of eighteen joint moments investigated. Of these results only the difference in the ankle plantar flexion was found to be significant. The average ankle plantar flexion peak moment in the maximal and submaximal ball release speed groups were found to be 2.008Nm/kg and 1.790Nm/kg respectively. This difference was statistically significant (p< 0.02)

The increased ankle plantar moment reflects the important role the ankle plays in the generation of extra ball release speed in the fast bowler. However this role does place increased stress on the ankle which may predispose it to injury. This study suggests that the ankle plays a significant role in the fast bowler’s delivery action and post injury rehabilitation needs to take this into consideration.

Introduction: Ankle injuries in cricketers are of topical interest with a number of elite fast bowlers sustaining injuries. Previous research has concentrated on the injury risk to the bowler’s vertebrae with no research focused on the ankle of the fast bowler and exploring the biomechanical basis for its predisposition to injury.

Materials and methods: Ten elite level cricket fast bowlers had their ankle biomechanics assessed during their bowling action. Using a nine-camera infra-red ViconTM 612 motion analysis system linked to a KistlerTM 9281CA force platform the moments of the subjects leading leg ankle during their delivery stride was calculated and analysed. Each subject performed ten trials at their maximum ball release speed (> 97km/hr) and ten trials at less than their maximum ball release speed (< 97km/hr) with the velocity of the ball tracked by a SR3600 radar gun.

Results: All six joint moments of the ankle were examined in both directions of all three orthogonal planes. Of these results only the difference in the ankle plantar flexion was found to be pertinent. The average ankle plantar flexion peak moment in the maximal ball release speed group was 2.008Nm/kg and in the sub-maximal ball release speed group 1.790Nm/kg. This difference was analysed using the paired Student t-test and was statistically significant (p< 0.02).

Discussion: This study shows the ankle plays a significant part in the fast bowler’s delivery action and suggests a biomechanical reason for ankle injuries in these individuals. It is recommended that in fast bowlers with ankle injuries a graduated return to maximal speed bowling is utilised in rehabilitation to prevent further injury and long term morbidity.

Conclusion: The increased ankle plantar moment reflects the important role the ankle plays in the generation of extra ball release speed in the cricket fast bowler.

A recurrence of objectively measured knee laxity after anterior cruciate ligament (ACL) reconstruction has previously been reported in various papers; the purpose of this study was to accurately measure in vivo knee laxity after both bone-tendon-bone (BTB) and hamstring reconstruction using radiostereometric analysis (RSA), and to differentiate between graft fixation slippage and graft stretching and their relative contributions to any increase in laxity.

Twenty patients were studied prospectively after ACL reconstruction. Ten had been operated on using BTB grafts, and ten using hamstring (four-stranded semitendinosus/gracilis) grafts. Tantalum markers were inserted in the distal femur, proximal tibia and into the graft itself. (RSA) was used to measure sagittal laxity, graft stretching and fixation slippage early post-operatively, and then at intervals up to 1 year.

A steady increase in total anteroposterior laxity was found in both groups over the year. For the BTB group, total mean slippage of the bone plugs increased to 1.28 mm at 1 year. For the hamstring group, the tunnel attachments had slipped by a total of 6.82 mm. More stretching was found for the hamstrings grafts than for the BTB grafts and the amount of stretching increased significantly with time post-surgery. The hamstring grafts stretched by a mean of 4.18%, the BTB grafts by 1.18%.

This is believed to be the most detailed application of RSA in analysing the performance of the two commonly used grafts in ACL reconstruction. Details such as graft stretching and fixation slippage have not been available previously; the data obtained in this study may have implications for clinical practice.

Aims: Evaluate the outcome of orthopaedic intervention in children who sustained peripheral ischaemia resulting from meningococcal septicaemia and to assess the benefit of fasciotomies within this group.

Introduction: There have been only two published series on the orthopaedic management of meningococcal septicaemia in children. We carried out a retrospective review of all patients who had undergone this intervention in RHSC.

Methods: Between 1994 and 2004 there were 190 admissions to paediatric intensive care unit (PICU) with meningococcal septicaemia. 12 had significant Orthopaedic/Plastic Surgical input. Case notes were examined to establish admission patterns, limb progress, subsequent operative intervention and eventual outcomes.

All presented with vague viral symptoms and developed rapidly spreading purpuric rashes within 24hours. 8 children were admitted from A& E and 4 were transferred from other hospitals. All received antibiotics, fluid resuscitation, ventilation and inotropic support. One child died within 14 hours of PICU admission. Haemofiltration was used in 11 children (mean 14.8 days, range 2–60 days).

We were able to follow up 8 of the survivors clinically.

Results: All children had some form of surgical treatment. 9 children had one or more amputations. Two children did not require amputations. Seven of the 12 children had fasciotomies performed (mean 34 hours after admission, range 2–96 hours). The child who died from overwhelming sepsis had multiple fasciotomies at 9 hours post admission. The remaining children had varying amputations. The other five children did not have fasciotomies. Of these one child did not require any amputations, three children had partial amputation of a single limb and one child had partial amputations of two limbs. All five within this group required additional split-skin grafts.

8 children were followed clinically. 7 were mobile with walking aids with a mean of 1.3 prosthetic lower limbs (range 0–2).

Conclusion: There is no evidence from our study that early fasciotomies are detrimental to survival, limb function or subsequent wound healing after definitive amputation. In other published series fasciotomy has been advocated within 24hours.

In our study 2 of our 7 patients who underwent fasciotomy the demarcation level receded distally post decompression leading to more distal amputation levels.

Purpose: To correlate arthroscopic appearances of the anterior and posterior meniscofemoral ligaments (aMFL and pMFL respectively) with their appearances on magnetic resonance imaging.

Methods: 50 patients underwent MRI scanning of their knees for a variety of suspected pathologies. The radiological presence or absence of the MFLs was assessed by examination of sequential coronal and sagittal T2 weighted MRI scans. Arthroscopic examination of the knees was subsequently performed, during which the MFLs were identified using several anatomical cues. These included their femoral and meniscal attachments, their obliquity relative to the PCL, and the meniscal “tug test”. Identification was classed as “easy” or “hard” by the operating surgeon.

Results: From 50 knees 44 (88%) aMFLs and 30 (60%) pMFLs were identified on MRI scanning, whilst 47 (94%) aMFLs and 5 (10%) pMFLs were identified arthroscopically. Identification of the presence or absence of the aMFL was classed as easy in 47 (94%), whilst the pMFL was easy to identify in only 5 (10%) of knees, of which 3 (6%) had a ruptured PCL. Using arthroscopy of the aMFL as the gold standard, the sensitivity and specificity of MRI in detecting the aMFL were 94% and 75% respectively. Equivalent values for the pMFL were not calculated due to the difficulty of identifying the pMFL arthroscopically. Thus, with the exception of PCL-deficient knees, it was felt that many pMFLs were missed due to difficulties in identification through anterior portals.

Conclusions: This is the first study correlating the MRI appearances of the MFLs with arthroscopic findings. MRI is relatively sensitive in identifying the aMFL, but its accuracy in identifying the pMFL remains undetermined. Accurate identification of the MFLs at MRI is of value when assessing the status of the PCL, as these ligaments may contribute to stabilising the PCL-deficient knee.

Due to their superior wear characteristics, oxidized Zr-2.5Nb heads are used with hip stems made of conventional orthopaedic alloys. Galvanic interactions between Zr-2.5Nb (Zr) and Ti-6Al-4V (Ti), cobalt-chromium (CoCr), and 316L stainless steel (SS) alloys were evaluated.

Galvanic current density was measured for Zr/Ti,Zr/CoCr, Zr/SS, CoCr/Ti, and CoCr/SS couples under static conditions in aneutral Ringer’s solution and in an acidic (1.7 pH) solution. To simulate fretting, one or both coupled alloys in the neutral solution subsequently were abraded by a bone cement pin (82 MPa Hertzian stress). An extended(7-day) static test in the acidic solution was performed for Zr/SS and CoCr/Ti to simulate crevice conditions. The dissolved metal ion concentration was determined using direct coupled plasma emission spectrometry.

Mean initial current densities of the Zr/SS, SS/CoCr,Zr/CoCr, CoCr/Ti, and Zr/Ti couples were 3.0, 0.36, 0.16, 0.05, and 0.04μA/cm2, respectively, in the neutral solution, and 0.57, −0.29, 0.04, 0.02, and 0.03 μA/cm2, respectively, in the acidic solution (positive when first alloy was anode). Within 30 minutes, all values decreased below 0.02μA/cm2. The current densities increased by orders of magnitude under fretting conditions. When both alloys were abraded, the highest values were minus;677 and 464 μA/cm2 for CoCr/Ti and Zr/SS, respectively. In the extended static test of Zr/SS, the mean total metal ion concentration decreased from 8.15 mg/L when the alloys were uncoupled to 4.50 mg/L(p=0.007) when they were coupled. For CoCr/Ti, the change from 1.28 to 1.72mg/L when the alloys were coupled was not statistically significant(p=0.22).

With its strong tendency to passivate, the Zr alloy produced galvanic interactions within the range observed with conventional alloy couples. Its anodic characteristic helped protect SS in a galvanic couple.