Purpose of Study/Background

To identify whether patients were satisfied with the overall educational component of the specialist nurse (CNS)/occupational therapist (OT) led pre-operative assessment clinic in order to identify areas which required improvement.

The pre-operative specialist nurse led clinic was set up in 2002. The aim was to provide high quality information to patients undergoing elective spinal surgery in order to manage expectations and optimise post-operative recovery. Initially the clinic was specialist nurse led however, in 2006 occupational therapy input was introduced in order to provide an increased depth of information in regard to function and activities of daily living post operatively. In addition this has allowed assistive equipment to be provided pre-operatively. The format of this clinic has enhanced the patient's journey by facilitating reduced length of stay and more timely discharge.

Background

The current ‘gold standard’ method for enabling weightbearing during non-invasive lower limb immobilisation is to use a Patella Tendon-Bearing (PTB) or Sarmiento cast. The Beagle Böhler Walker™ is a non-invasive frame that fits onto a standard below knee plaster cast. It is designed to achieve a reduction in force across the foot and ankle.

Our objective was to measure loading forces through the foot to examine how different types of casts affect load distribution. We aimed to determine whether the Beagle Böhler Walker™ is as effective or better, at reducing load distribution during full weightbearing.

Background

Osteomyelitis can be difficult to diagnose. Unlike septic arthritis no defined diagnostic criteria exist as a guide. Inflammatory markers are frequently utilized at initial presentation, (in addition to white cell count).

Background

Tibiotalocalcaneal arthrodesis is an important salvage method for patients with complex hindfoot problems including combined arthritis of the ankle and subtalar joints, complex hindfoot deformities and failed total ankle arthroplasty. The aim of this study was to report the elective results of combined subtalar and ankle arthrodesis using one design of dynamic retrograde intramedullary compression nail-the T2 Ankle Arthrodesis Nail(Stryker)

Purpose

Total disc replacement (TDR) devices have been restricted to designs with large, congruent articulations due to the limited wear properties of available materials. TDRs with more natural motion could be designed if materials were available which could resist the higher wear conditions. A novel TriLobe TDR design is self-centering and energetically stable, emulating the natural motion of the intact motion segment, but is not feasible using traditional materials due to small incongruent articulating surfaces. The objective of this study was to compare the wear properties of a medical grade polycrystalline diamond with wear properties of cobalt chrome (CoCr) and ultrahigh molecular weight polyethylene (UHMWPE) in aggressive high wear conditions.

Purpopse

Few Cervical Total Disc Replacement (TDR) devices are engineered to address both the Center of Balance (COB) and the Center of Rotation (COR) of the cervical motion segments. The COB is the axis in the intervertebral disc through which the axial compressive load is transmitted. TDRs placed posterior of this point tend to fall into kyphosis while devices placed anterior of this point tend to fall into lordosis. Thus from a “balancing” point of view the ideal placement would be at the COB. However, the COR position has been shown to be posterior and inferior to the disc space. It has also been shown that constrained devices tend to lose motion when there is a mismatch between device and anatomic centers. Mobile core devices may be placed at the COB since their unconstrained rotations and translations allow for the device COR to follow the anatomic COR, but they rely heavily on the facet joints and other anatomic features to resist the paradoxiacal motion.

The TriLobe cervical TDR (Figure 2) was engineered for both the COB and COR. The purpose of this study was to compare the 3D kinematic and biomechanical performance of the TriLobe to a ball and trough(BT) cervical TDR in an augmented pure moment cadaveric study to find the ideal AP implant placement.

Purpose

To assess the initial rise in inflammatory markers in paediatric patients presenting with long bone osteomyelitis and whether this is comparable with that in septic arthritis, and diagnostic.

Tibiotalocalcaneal arthrodesis is an important salvage method for patients with complex hindfoot problems including combined arthritis of the ankle and subtalar joints, complex hindfoot deformities and failed total ankle arthroplasty. The aim of this study was to report the elective results of combined subtalar and ankle arthrodesis using one design of dynamic retrograde intramedullary compression nail-the T2 Ankle Arthrodesis Nail(Stryker)

Retrospective review identified 53 consecutive patients who had 55 tibiotalocalcaneal arthrodesis procedures by two surgeons(ITS and NJT) using T2 Ankle nail fixation. 3 patients died of unrelated causes before follow up was complete which left 50 patients(52 nails); the largest consecutive series in the use of this device. Mean follow up was 23.5(3-72) months with the average age of patients being 61(range 22-89) years. An 84% response was achieved to a function and patient satisfaction questionnaire. Main indications for treatment were combined ankle and subtalar arthritis(63%-33/52) or complex hindfoot deformities(23%-12/52). Outcome was assessed by a combination of Clinical notes review, clinical examination, and telephone questionnaire.

46 patients(83.6%) achieved union at a mean time of 3.7 months. 8 patients required an allograft(femoral head) bone block procedure. 4 patients(10%) subjectively thought that the procedure was of no benefit or had a poor result whilst 35(83%) had a good or excellent result. The mean visual analog scale(VAS) score for preoperative functional pain was 7.1 compared to the mean post operative (VAS) score of 1.9(p<0.001). Complications consisted of 2 amputations, 2 deep infections and 5 removals of broken or painful screws. The use of preoperative functional aids and orthotics dropped from 32% to 18% and 22% to 18% respectively.

This device and technique is a safe and effective treatment of hindfoot arthrosis and deformity giving reliable compression and subsequent fusion with excellent results in terms of patient satisfaction and pain relief.

Statement of Purpose: Hard-on-hard bearing surfaces are finding increasing application in total hip replacements for wear reduction. Polycrystalline Diamond Compacts (PDCs) offer several potential advantages, including ultimate hardness, reduced metal ion release compared to metal-on-metal (MoM) articulations and increased strength/ toughness compared to ceramic-on-ceramic (CoC). This study investigates in-vitro wear and friction for a 28mm diamond-on-diamond (DoD) system under normal walking gait and also with distraction.

Methods: Six sets of 28mm PDC femoral heads and 28/41mm PDC acetabular liners (Dimicron, Utah) were tested on a hip simulator (AMTI, Boston). Radial clearances were 18–42 microns. Specimens were mounted anatomically with the cups superior and mounted at 45 degrees. All stations were lubricated with 37oC bovine serum diluted to 17g/l protein concentration. Components were subjected to a 3kN walking cycle (ISO14242-1) for 5 million cycles (MC). This was followed by 2MC of distraction testing with a reduced swing-phase load of 120N, an applied side force of 129N and with the abduction motion disabled. This produced approximately 0.5–0.7mm of horizontal displacement of the center of the head. The lubricant was changed and the components cleaned, dried and weighed at 0.5MC intervals.

Results: All heads and liners gained weight during each portion of the test. Potential mechanisms (still under investigation) include protein adsorption and hydration of metallic phases within the diamond compact. The weight gains were found to be somewhat reversible after drying in vacuum for extended periods (60–90 hours). However, the standard 1 hour drying cycle used for weight measurements during the test was found to be inadequate. Therefore, only the “dry weights” measured after 64–92 hours of vacuum drying at the beginning and end of each test portion were used to compute wear rates.

Overall wear rates for heads and liners for the 5MC of normal gait and the 2MC of distraction testing and for the whole 7MC. 95% confidence intervals are plotted for each set of six heads and liners. Weight changes were converted to volumetric wear using a density of 3,800kgm-3. Even after extended drying, the liners all showed small weight gains. The heads apparently wore slightly during the normal walking cycle but gained weight during the distraction cycle. Overall, the heads showed a small wear rate of 0.17±0.09mm3/MC and the liners showed a small ‘negative’ wear rate of −0.11±0.07mm3/MC. Due to the uncertainties involved in the drying procedure, it is concluded that DoD wear rates were unmeasurably low for this test. Distraction is known to increase wear rates for CoC systems [1] and might reasonably be expected to have a similar effect for DoD, due to the high elastic modulus of diamond.

However, the 2MC of distraction testing produced only small weight gains. The heads showed no evidence of ‘stripe wear’ as reported for CoC systems.

Conclusions: DoD wear rates were found to be unmeasurably low for an anatomical hip simulator test with and without distraction. Friction factors for DoD were slightly lower than for metal-on-UHMWPE.

A critical objective of cervical total disc replacement (TDR) is to restore predictable reproducible range-of-motion (ROM) with correct kinematics, while maintaining stability of the segment. Current articulating cervical TDR devices feature fixed centers of rotation, sometimes coupled with unconstrained translation in one or more vectors. The difficulty they have in restoring reproducible, kinematically correct motion has manifest as subsequent facet degeneration as well as other problems. A Tri-Lobe articulating cervical TDR has been developed to recreate predictable, kinematically correct motion, as well as to address other common TDR problems including placement sensitivity, excess wear, instability, and imaging compatibility. The Tri-Lobe TDR design features three incongruent, self-centering, hard-on-hard articulations arranged in a tripod configuration -three hemispherical lobes oriented in a tripod configuration on the superior component articulating against mating non-congruent hemispherical pockets on the inferior component. The diameter and spacing of these articulations determines a specific -kinematic -envelope, and has been designed to match the 6-D anatomic motion data from available published sources. It has diamond-on-diamond articulations to sustain the elevated Hertzian stresses of its incongruent bearing geometry, and is engineered to couple motions in a physiologic manner. This study was designed to compare the variability and reproducibility of a Tri-Lobe cervical TDR as compared to the intact spine, and compared to a ball & trough control TDR design.

Seven human cervical spines (C2-C7) were studied (two pilot and five test specimens) utilizing a 7-Axis spinal testing system. A hybrid load/position control protocol was used to test the specimens. The intact spine was tested first in flexion/extension, lateral bending, and axial rotation to 1.5Nm. Then the C4-C5 segment was implanted with the test and control TDRs utilizing an implant placement fixture that provided accurate reproducible placement of the device in the spine. The order of test and control device placement was randomly varied. Data collected included applied moments, forces, and rotations at C2 and C7, and 3D vertebral movements via an optical tracking system (Optotrak). Statistical analysis of kinematic data was performed with paired-ANOVA followed by a Tukey-Kramer HSD post hoc test.

The ROM for flexion/extension (FE), lateral bending (LB), and axial rotation (AR) are as follows: Intact cervical motion segment FE ROM averaged 4.6±1.0 degrees (max 7.5, min 2.6, range 5.0), LB ROM averaged 1.6±0.6 degrees (max 2.5, min 1.3, range 1.2), and AR ROM averaged 9.3±0.8 degrees (max 11.7, min 6.8, range 4.8). For the Tri-Lobe TDR FE ROM averaged 4.7±0.7 degrees (max 6.5, min 2.5, range 4.0), LB ROM averaged 1.9±0.3 degrees (max 2.5, min 1.2, range 1.3), and AR ROM averaged 10.7±0.3 degrees (max 11.9, min 8.4, range 3.5). For the Ball & Trough TDR FE ROM averaged 4.9±1.6 degrees (max 9.3, min 1.5, range 7.8), LB ROM averaged 2.1±0.5 degrees (max 3.1, min 0.7, range 2.4), and AR ROM averaged 11.0±1.3 degrees (max 13.6, min 8.3, range 5.3). While there was not a statistically significant difference between the Average ROM for the intact, Tri-Lobe, or ball & trough design (p=.96), this is misleading. The variance for motion in all three categories for the ball & trough was significantly greater than for both the intact and Tri-Lobe case. Further, for the minima and maxima, the ball and trough had values that were significantly outside the intact values, while, the Tri-Lobe had values close to that of the intact. The ball & trough design exhibited 1.95, 1.84, and 1.51 times the Range of the ROM compared to the Tri-Lobe in FE, LB, and AR respectively.

Critical surgical objectives in cervical TDR include restoring predictable inematicallycorrect motion to the segment while maintaining stability. Both incorrect and excess motion can lead to instability or facet degeneration. Too little motion fails to relieve adjacent segments of the increased stresses occurring with fusion, and can lead to auto-fusion as well. With conventional articulating cervical TDR, issues such as TDR placement within the disc space as well as variations in normal anatomy can adversely affect reconstructed kinematics. The Trilobe cervical TDR studied in this experiment was able to accommodate variations in anatomy and placement providing a highly predictable and reproducible ROM matching very closely the kinematic envelope for the intact spinal motion segment. Its incongruent bearings are the key to its tolerance of variation in anatomy and placement. Its tripod design contributes to its intrinsic stability and self-centering. It may be more forgiving to surgical variability. This is not only desirable in providing the surgeon with flexibility in selecting implantation position to address deformity and bone defects, but also in providing tolerance to unpredictable variations in facet anatomy permitting acceptable motion with stability for a broad range of conditions.

Previous studies have suggested that bone ongrowth occurs following revision hip arthroplasty to a tapered long stem distal fit modular prosthesis. This may affect outcome. We sought to quantify proximal bone ongrowth to one such prosthesis and correlate this with functional outcome.

A series of eight patients undergoing revision total hip arthroplasty with the a long taper, distal fit, grit blasted modular prosthesis (ZMR) had a CT performed within three months and then greater than one year following surgery. Changes in periprosthetic bone stock were measured. Functional scores at a minimum of five years were analysed.

Proximal bone ongrowth was generally poor and did not correlate with functional outcome score.

When more sensitive imaging is used to analyse bone ongrowth in this long stem distal fit prosthesis, proximal ongrowth is poor and not the key determinate of functional outcome.

In relation to the conduct of this study, no funding has been received from any source to support the costs of this study

Thirty-four patients were studied through the whole of the Perthes’ disease in Alder Hey Children’s Hospital, Liverpool. The acetabular changes included osteopaenia of the roof, irregularity of its contour, and decrease in the depth. These changes were proportional to the femoral head involvement. The purpose of the study was to know the effect of the morphological changes of the femoral head on the acetabulum and its outcome.

Radioisotope scans of the hip were examined in fourteen children with unilateral Perthes’ disease and comparison was made with the contralateral hip. These scans showed increased uptake on the lateral part of the acetabulum and no uptake over the avascular part of the femoral head. Average follow-up was ten years and on an average children were followed up from six years to fifteen years of age. Six readings of the measurements of various dimensions of the acetabulum and the femoral head were done. CT scan also showed irregularity in the acetabulum. Statistical tests lead to the conclusion that the decrease in the depth of the acetabulum was secondary to the femoral head involvement and the extent of its dimensional changes affected the final congruity between the femoral head and the acetabulum. Also the remodelling potential of acetabulum decreases as the child grows older. Therefore containment procedures could be done by femoral osteotomy in younger children and acetabular osteotomy may benefit older children.

This paper presents the experience of a tertiary referral centre for pelvic and acetabular trauma.

From August 1999 a tertiary referral centre was established in Christchurch to provide management for pelvic and acetabular trauma for the South Island. The experience of unit was reviewed.

One hundred and twenty four unstable pelvic and acetabular fractures were treated between August 1999 and March 2005. Ninety two percent of fractures were treated by one or both of two fellowship trained trauma surgeons. While the rate of complications was low, there were 6 significant infections, 3 nerve injuries, and 2 non-unions. The experience of the unit is presented.

A tertiary referral centre for pelvic and acetabular trauma has been able to provide a successful service to the South Island with satisfactory results.

Introduction: Using Automated Implant Design and Analysis (AIDATM ) a library of femoral CT scans was analyzed. Design goals of fit and offset allowed generation of nine sizes each of right and left implants for off-the-shelf use. The five to nine year follow-up of 96 (12 bilateral) consecutive primary total hip arthroplasties using this titanium alloy hydroxylapatite (HA) one-third coated femoral stem is reported. The purpose of this study is to determine if the incorporated engineering design goals produced results equal to or superior to other published mid-term follow-up studies.

Methods: Seventy-five femoral CT scans from patients undergoing cementless primary total hip arthroplasty were used as the anatomic database. The stem was conceived as a metaphyseal filling implant with flat posterior and lateral sides. Prior micro-motion cadaver research of other stems by the authors has shown that stems with the best fit on the Medial and Anterior quadrants as well as the Medial-Anterior corner (“MAMA” fit) are the most stable. Therefore the medial and anterior surfaces were contoured and were given priority fit. Distally the stem was cylindrical, and allowed for diaphyseal contact over a distance of two outer canal diameters. Five modular femoral heads were assumed with the design goal to be within 5 mm of the existing head center in 95% of cases.

Results: The median Harris score is 91% (max 100) with 77% good or excellent. The mean pain score is 39.5 (max. 44) with 80% having none or slight pain. Ten hips (11%) have slight to mild thigh pain. One stem was revised for late loosening due to osteolysis. All others remain well-fixed (Engh grade I). Six hips were re-operated: two head & liner changes for recurrent dislocations and four for wear and acetabular osteolysis. Radiographic analysis showed all stems became well bonded over the HA coating with no RLZ’s and accretion of bone in the lower half of Zones 1 & 7 at the end of the HA coating. There was no subsidence. Stress shielding was limited to the upper half of Zones 1 & 7. Osteolysis was common above the HA coating around the shoulders of the implant, but extended distally in only one stem (revised).

Discussion & Conclusion: These results at Five-year minimum follow-up compare favorably with other published series of cementless stems at the same follow-up. The 100% incidence of ingrowth combined with the absence of stress-shielding below the upper half of Zones 1 & 7, serves to validate the design concepts and methodology used to create this implant.

Introduction: Patient specific cementless femoral components for THR were developed as a means of addressing the anatomic variations of the proximal femur and hip joint in an effort to achieve long term implant survival and optimum patient function. Design rules were developed with goals of achieving rigid initial stability, maximal endosteal contact for bone integration, and the precise restoration of hip kinematics.

Methods: Beginning in 1989, this series of cementless titanium implants included proximal circumferential HA coating over a macrotextured surface for biologic fixation. All patients who were candidates for cementless arthroplasty (age < 65, active, or overweight) received a custom femoral component. Forty-nine consecutive primary THR in 39 patients were performed during the study period. No patients died and one patient was lost prior to 10 years; all had well fixed stems at latest follow up. The remaining 38 patients (48 hips), 16 females and 22 males, with average age 54 (28-70) and weight 181 (98-270) at surgery, were evaluated at minimum 10 years (range 10-11).

Results: Average modified Harris Hip Scores were 49 (27-87) pre- and 89 (24-100) postoperatively, with pain scores of 17 (0-40) and 42 (10-44) respectively. All femoral components remain well-fixed (Engh Class 1) at final follow-up. No areas of osteolysis were seen distal to the proximal HA-bone interface. Small, focal areas of probable osteolysis were seen at the implant shoulder (4 cases), at the calcar corner (2 cases), and at both sites (1 case). Complications included four proximal margin femoral fissures recognised at surgery, two patients with dislocation, and one non-fatal PE. Reoperations included six head and liner exchanges; two for recurrent dislocation, and four for excessive wear with associated osteolysis (3 pelvic, 1 femoral); and one for fixation and grafting of a trochanteric nonunion.

Discussion: The use of cementless femoral implants based on individual patient characteristics and a set of strict design rules has resulted in excellent clinical and radiographic results at 10-year follow-up. Recent data with some OTS systems have shown comparable excellent results and have diminished the need for the routine use of custom implants in uncomplicated primary situations. However, this series validates the design concepts of this system, supports its use in more complex situations, and suggests applicability on a routine basis where other available implants may be less than optimal.

Introduction: Conventional approaches to cementless revision THR include cemented and cementless stems, which are graft dependent for initial stability (Type 3 reconstructions), distally fixed extensively porous coated implants and modular implants. CT and radiographic visualization, preoperative planning, and patient specific implant fabrication enable the surgeon to achieve the following objectives simultaneously and without compromise: bypass or fill specific bony defects, implement precisely the surgeon’s individual implant design goals, optimise proximal, distal, or regional fit objectives, achieve supplemental fixation via collars, fluted stems, and targeted ingrowth zones/ treatments, and establish head center, neck length, lateral offset, anteversion angle, and leg length.

Methods: This series of cementless titanium implants achieved initial press-fit fixation on host bone with bony attachment via proximally HA coated macrotextured surface. The extramedullary portion of the implant is designed to restore leg length and normal joint mechanics. The initial 44 consecutive revision hips using this rationale were reviewed for inclusion. At surgery, all femoral reconstructions were completed without resorting to Type 3 structural grafts. Six patients died prior to 10 years f/u, and three (4 hips) were lost. Two stems were removed prior to minimum follow up: one at five weeks post-op for deep sepsis, and one for aseptic loosening presumed secondary to metabolic derangements from poorly controlled end-stage renal disease. The remaining 31 patients (34 hips), 18 females and 13 males with a mean age of 61 (range 31-75) and average weight of 168 (85-240) pounds, were evaluated at minimum 10 years (range 10 to 11 years).

Results: All 34 components remain well-fixed (Engh Class 1) at last follow up (97% implant survival). Stress shielding was uncommon outside the calcar region. Average modified Harris Hip Scores were 49 (10-88) pre-operative and 81 (48-100) at final follow-up, with pain scores of 18 (0-44) and 41 (30-44) respectively. Complications included fracture (intraop: 4 fissures, 2 stable type II, 1 unstable type III, and 1 late periprosthetic fractures distally), and three dislocations.

Discussion: The concept of a metaphysical loading, proximally ingrown, collared patient specific revision implant gave results comparable to Engh’s series of extensively coated revision stems, while avoiding the high failure rate associated with structural allograft, the worrisome proximal bone loss associated with fully porous coated stems, the high cost of modular implants.

Introduction Peri-acetabular osteolysis is a serious complication of total hip arthroplasty (THA). The aim of this study was to determine, using quantitative computed tomography (CT), the location, volume and rate of progression of peri-acetabular osteolytic lesions, and to determine the validity of this CT technique with intra-operative measurements.

Methods High-resolution spiral multislice CT scan (Somatom Volume Zoom, Siemens, Munich, Germany), with metal-artefact suppression protocol, was used to measure the volume of osteolytic lesions around 47 cementless THAs in 36 patients (median age 73 years, duration 14 years, range five to 24 years). In vitro validation was undertaken. CT scans were taken from the top of sacroiliac joint down to two centimetres below the end of the prosthesis. Reconstruction images were analysed by two different observers and progression of osteolysis with time was determined. In some patients, subsequently revised, in-vivo CT measurements were compared to intra-operative measurements. The rate of progression of osteolytic lesions was calculated. The technique was optimised and validated by extensive in-vitro studies, using bovine and human pelves.

Results The incidence of lesions located in each site was: the ilium, 65%; around fixation screws, 20%; in the anterior column, nine percent; and in the medial wall, six percent. Some lesions were shown to be relatively quiescent, while others were aggressively osteolytic. Intra and inter-observer error for the CT measurement technique was four percent and 2.8%, respectively. In vitro volumetric measurements of simulated bone defects adjacent to the acetabular component and fixation screw were accurate to within 96% and precise to 98%. In addition, preliminary data obtained intra-operatively indicate the accuracy of CT in identifying the sites of osteolysis.

Conclusions CT is thus a valid and reliable technique for investigating the natural history of osteolysis and the factors that may influence its progression. It will also enable assessment of non-surgical treatments of osteolysis.

In relation to the conduct of this study, one or more of the authors is in receipt of a research grant from a non-commercial source.

Limitations in the material properties of arthroplasty bearings have been a major impediment to increasing the longevity and durability of total joint replacement. These limitations most often manifest as wear debris related osteolysis and bearing failure. While these problems cause serious complications in THR and TKR, as arthroplasty is applied to the spine, such problems could become catastrophic. An ideal bearing material and design would be biocompatible, provide for restoration of normal range of motion, and be durable enough to sustain long term unrestricted high demand activities without mechanical failure, significant wear, or contribution to particulate related osteolysis. A new material, Polycrystalline Diamond Compact (PDC), appears to closely approximate the ideal bearing material for applications from large joints to intervertebral discs.

PDC is a diamond structure formed at ultra high pressure and temperature and bonded to a metal substrate. Bond strength to substrate approximates substrate tensile strength. PDC has unprecedented impact toughness and hardness, and has the lowest unlubricated coefficient of friction of any manmade contact bearing. A screening study was used to evaluate wear properties with ceramic and CoCr controls. Full prototypes were tested in a PMED hip simulator for 10 million cycles and on a spinal disc simulator for 30 million cycles.

In the screening study, PDC specimens demonstrated a significant advantage in wear over controls, whose wear rates were consistent with earlier studies. In simulator studies, the PDC specimens experienced extremely low wear at 10 million cycles (~1.0 mg per bearing surface) under austere conditions of no lubrication. In the spinal disc simulator, wear was approximately 0.3 mg at 20 million cycles under similar austere condition.

PDC’s unique material properties lend themselves to designs with thin (5 mm) acetabular bearings that provide for improved ROM and decreased dislocation risk, as well as to spinal applications where space is at a premium. Its properties of extraordinary impact toughness and high wear resistance lend themselves to arthroplasty applications which may require no undue activity restrictions, and may make prostheses available in which bearing wear and mechanical failure are no longer a factor affecting longevity.

A common finding in acetabular revisions is loss of medial bone stock. Using a standard cementless hemispherical component, alternatives for reconstruction include medialisation of the cup, medial particulate allograft with rim fixation on host bone, or use of a “mega-cup”. A cementless shell that has 6 mm of lateral augmentation is useful in restoring the joint centre while at the same time achieving implant stability and increasing host bone contact without loss of additional bone.

From 1991 to 2000, a total of 142 acetabular revisions were performed with the Arthropor TM DP+6 implant (Joint Medical Products/J& J/DePuy). These patients have been prospectively followed bi-annually with Harris Hip Scores and monitoring of complications and radiographic findings. Average follow-up is 5 years (range 2 to 11 years).

Implant survivorship is 100%. There have been seven re-operations: one for infection (debrided), two for femoral revision and four head/liner changes for recurrent dislocations. Dislocation incidence is 7.8%. The average Total Harris Score at 5 years is 74.3, with an average Harris Pain Score of 34.9 (out of a maximum of 44). Radiographic analysis showed frequent zone 3 radiolucent zones. Initial migration of > 2 mm with subsequent stabilisation occurred in 18%. The joint centre was restored to within 5 mm of the contralateral hip in 85% of cases.

We have found this type of implant to be efficacious in the more common acetabular revisions where the loss of bone stock is mainly medial/cavitary, with an intact posterior column and small medial segmental defects.

Obesity is increasing among patients requesting total hip replacement. Obesity is often considered though, a relative contraindication to arthroplasty surgery due to difficult access, greater blood loss, oozy wounds, poor mobilisation and delayed discharge. We have attempted to demonstrate the evidence for this.

Patients were evaluated preoperatively with regards to their height and weight to allow a body mass index (BMI) to be calculated. The length of inpatient stay was then monitored and early postoperative complications recorded. This data was used to assess if obesity or age could be used to predict a prolonged hospital stay caused by poor rehabilitation and early post operative complications.

The results of 70 consecutive patients between 1999–2001 are reported. The average age was 69.3 with a range of 46.5–85.4 years. The sex distribution was approximately 2:1 female to male (N=48:22 respectively). Two patients were identified as being under their recommended weight, 24 as healthy, 26 as over weight and 18 as obese. Urinary tract infection was confirmed by microbiological culture in 6 patients, superficial wound swab grew organisms in 5 patients while 2 developed culture positive chest infections. No thromboembolic events were recorded (Stroke, Deep Vein Thrombosis, Pulmonary Embolism) however one patient died of ischemic heart disease (BMI 35 obese). Data was examined by an Excel statistical package and an ANOVA plot produced.

No statistical relationship was found between obesity and infective postoperative problems. No delay in discharge was found when BMI was considered, R2 value of 0.0015,

F-significance 0.75. When age alone was considered R2 value of 0.003 and F-significance of 0.65 was recorded. When age and obesity were considered together R2 was 0.005 and

F-significance 0.57. We find no evidence of increased rates of early postoperative complications or delayed hospital discharge in obese patients with a BMI less than 40.