Aims. Accurate and precise acetabular reaming is a requirement for the press-fit stability of cementless acetabular hip replacement components. The accuracy of reaming depends on the reamer, the reaming technique and the bone quality. Conventional reamers wear with use resulting in inaccurate reaming diameters, whilst the theoretical beneficial effect of ‘whirlwind’ reaming over straight reaming has not previously been documented. Our aim was to compare the accuracy and precision of single use additively-manufactured reamers with new conventional reamers and to compare the effect of different acetabular reaming techniques. Materials and Methods. Forty composite bone models, half high-density and half low-density, were reamed with a new 61 mm conventional acetabular reamer using either straight or ‘whirlwind’ reaming techniques. This was repeated with a 61 mm single use additively-manufactured reamer. Reamed cavities were scanned using a 3D laser scanner with mean diameters of reamed cavities compared using the Mann-Whitney U test to determine any statistically significant differences between groups (p<0.05) [Fig. 1). Results. Reaming errors were significantly higher in low-density bone compared to high-density bone for both reamer types and reaming techniques tested (61.9 mm (SD 0.7) vs 61.4 mm (SD 0.4), respectively; p=0.0045). Whirlwind reaming was significantly more accurate and precise than straight reaming using both conventional (61.3 mm (SD 0.1) vs 62.3 mm (SD 0.4), respectively; p<0.0001) and single use reamers (61.1 mm (SD 0.3) vs 61.7 mm (SD 0.7), respectively; p=0.0058) [Fig. 2]. The novel single use reamer was significantly more accurate than the unused conventional reamer, using both the straight (61.7 mm (SD 0.7) vs 62.4 mm (SD 0.4), respectively; p=0.0011) and whirlwind techniques (61.2 mm (SD 0.3) vs 61.3 mm (SD 0.1), respectively; p=0.0002) [Fig. 3]. Conclusion. This is the first study to our knowledge that has assessed acetabular reaming technique in both low and high density saw bones. Improved reaming accuracy and precision was seen in both devices tested when using the ‘whirlwind’ technique in both high-density and low-density bone models when compared to a straight reaming technique. The single use device assessed reamed a cavity size closer to its stated size (61mm) compared to conventional reamers. Based on this study we suggest using a careful “whirlwind” technique when performing acetabular reaming, and for the surgeon to pay particular attention when performing joint replacement in patients with reduced bone quality as there is likely to be more variability in acetabular reaming accuracy in these patients

Introduction

Total hip arthroplasty (THA) is one of the most common orthopedic surgeries. The procedure is sophisticated and in addition to several factors affecting the outcomes such as patient's status, surgeon's expertise and implant type, using appropriate surgical tools is necessary. Acetabular component implantation necessitates the surgeon to ream the acetabular fossa which is time consuming and devastating. Utilizing currently-used reamers (figure 1), the size of the tool must be changed repeatedly for 5–20 times within a surgery. In every stage, the size of the reamer is increased up to 1–2 mm. This tiring process takes 15–30 minutes and is associated with some injuries to the soft tissue. Furthermore, the risk of mistakes is considerable.

Introduction

Primary stability is achieved by the press fit technique, where an oversized component is inserted into an undersized reamed cavity. The major geometric design of an acetabular shell is hemispherical type. On the other one, there are the hemielliptical type acetabular shells for enhanced peripheral contact.

In the case of developmental dysplasia of the hip (DDH), the aseptic loosening may be induced by instability due to decreased in the contact area between the acetabular shell and host bone.

The aim of this study was to assess the effect of reaming size on the primary stability of two different outer geometry shells in DDH models.

INTRODUCTION:

Recent trends in total hip arthroplasty (THA) have resulted in the use of larger acetabular components to achieve larger femoral head sizes to reduce dislocation, and improve range of motion and stability. Such practices can result in significant acetabular bone loss at the time of index THA, increasing risk of anterior/posterior wall compromise, reducing component coverage, component fixation, ingrowth surface and bone stock for future revision surgery. We report here on the effects of increasing acetabular reaming on component coverage and bone loss in a radiographic CT scan based computer model system.

Total Shoulder Resurfacing (TSR) provides a reliable solution for the treatment of glenohumeral arthritis. It confers a number of advantages over traditional joint replacement with stemmed humeral components, in terms of bone preservation and improved joint kinematics.

This study aimed to determine if humeral reaming instruments produce a thermal insult to subchondral bone during TSR. This was tested in vivo on 13 patients (8 with rheumatoid arthritis and 5 with osteoarthritis) with a single reaming system and in vitro with three different humeral reaming systems on saw bone models. Real-time infrared thermal video imaging was used to assess the temperatures generated.

Synthes Epoca instruments generated average temperatures of 40.7°^C (SD 0.9°^C) in the rheumatoid group and 56.5°^C (SD 0.87°^C) in the osteoarthritis group (p = 0.001). Irrigation with room temperature saline cooled the humeral head to 30°^C (SD 1.2°^C). Saw bone analysis generated temperatures of 58.2°^C (SD 0.79°^C) in the Synthes (Epoca) 59.9°^C (SD 0.81°^C) in Biomet (Copeland) and 58.4°^C (SD 0.88°^C) in the Depuy (CAP) reamers (p=0.12).

Humeral reaming with power driven instruments generates considerable temperatures both in vivo and in vitro. This paper demonstrates that a significant thermal effect beyond the 47°^C threshold needed to induce osteonecrosis is observed with humeral reamers, with little variation seen between manufacturers. Irrigation with room temperature saline cools the reamed bone to physiological levels, and should be performed regularly during this step in TSR.

Retroversion, also referred to as posterior wear of the glenoid, can make resurfacing the glenoid challenging. However, careful pre-operative planning with three dimensional CT scanning can allow central placement of the glenoid component through removal of some of the anterior bone to allow contained placement and secure fixation within the glenoid vault.

Since the scapula is not a fixed skeletal structure and moves substantially on the chest wall, the actual degree of posterior wear (retroversion) frequently is the result of extraneous biomechanical forces and structures. For example, the degree of kyphosis and shape of the rib cage can have a substantial impact on the relative position of the glenoid surface as it articulates with the humerus. Attempts to totally equalise this through implant augmentation have not, to date, been shown to be effective, and in some cases can be destabilising. Restoration of enough alignment to place the implant centrally can be achieved without need for augmentation even in some very hypoplastic glenoids. The technique for this straight-forward approach will be presented, including pre-surgical planning, in some cases, patient specific instrumentation, with demonstration of functional outcomes.

Contracture of the anterior musculature causes posterior humeral head subluxation and results in a posterior load concentration on the glenoid. This reduced contact area causes glenoid wear, humeral medialisation and eventually posterior instability. After arthroplasty that does not correct for this, posterior wear stress increases in the implant, across the cement mantle and bone thus increasing the risk of aseptic loosening over time.

Correction of the posterior wear pattern at the time of arthroplasty of the shoulder is recommended. Asymmetric reaming of the glenoid has been recommended as a means to correct this deformity but leads to producing a smaller glenoid which is medialised. This shortening of the glenoid causes the stabilising muscle envelope to shorten and the glenoid vault to become much smaller in volume. These potential changes may have a destabilising effect on the implant leading to early loosening and secondary failure of the prosthetic implant.

Other options include using an implant to make the correction of the deformity such as augmented glenoid components. Early uses of these implants were not successful mainly due to the design flaws of the early implants. Newer implants have made design changes to overcome these early failures. CT scan evaluation is important to determine the degree of correction that is needed to balance the glenohumeral joint. Correcting the deformity and keeping the muscle envelope at the appropriate tension may lead to better long term outcomes. These implants are currently in use but long term outcome studies are not yet available to determine their ultimate values to the patients.

Introduction

Proper femoral reaming is a key factor for a successful outcome in cementless hip arthroplasty. Good quality reaming minimizes risks of intra-operative femoral fracture during reaming and prevents poor fitting of the implant which can lead to subsidance of the stem postoperativly. Determining the quality of reaming is largely a subjective skill and dependant on the surgeon's experience with no documented intraoprative method to assess it objectively.

Introduction

The goal of total hip arthroplasty (THA) should be to reconstruct the acetabulum by positioning the hip center as close as possible to the anatomical hip center. However, the true position of the anatomic hip center can be difficult to determine during surgery on an individual basis. In 2005, we designed, produced an acetabular reaming guide, and clinically used to enable cup placement in the ideal anatomical position. This study was examined the accuracy the reaming guide for THA in prospective study.

Medial portal reaming may allow for the creation of a more anatomically positioned femoral tunnel during Anterior Cruciate Ligament (ACL) reconstruction. However, this technique also results in a shorter tunnel which may make fixation difficult. The purpose of this study is to determine the average length of a femoral tunnel created using a medial portal technique and to correlate this with patient gender, height and Body Mass Index (BMI).

Fifty-four consecutive patients underwent ACL reconstruction with a femoral tunnel created using a medial portal technique. The tunnels were created using a spade tip guide pin (Arthrex, Naples, FL) with the goal of creating the tunnel in the 2-2:30 o'clock position (left knee) or 9:30-10 o'clock position (right knee). The total osseous length of the femur (TOL) was measured using a depth gauge. Descriptive statistics of the TOL were calculated and bivariate correlation coefficients (Pearson r) were calculated to determine the relationship between TOL and patient height and weight.

The mean TOL was found to be 33.77 ± 5.27 mm (24-50 mm). TOL was found to correlate with patient height (r=0.32, r²=0.10, p=0.04) and was not correlated to weight (r=0.24, r²=0.06, p=0.15) or BMI (r=0.06, r²=0.004, p=0.7). Men had a greater TOL (34.91 ± 5.4) than women (32.13 ± 4.80) but this difference was not found to be statistically significant (p=0.10).

ACL reconstruction using a medial portal yields a mean total osseous length of 33.77 mm. This length is significantly correlated with patient height.

ACL reconstruction using a medial portal approach to femoral reaming can lead to tunnels as short as 24 mm. Patient height may be a useful clinical tool to indicate the potential for a short femoral tunnel.

Mal-positioning of the acetabular component is associated with increased dislocation rate, increased wear and component impingement. Navigation provides real time feedback to the surgeon and allows the accurate position of implants. Compared to conventional techniques of total hip replacement; use of the imageless navigation system has shown to improve accuracy of implant positioning.

When impacting uncemented acetabular components under navigation, there is often a deviation from the planned abduction and anteversion measurement due to deflection of the implant in the reamed cavity. Although there exists the ability to navigate the reaming of the acetabular cavity; this is not widely performed. The ability to ream the acetabular cavity in the exact orientation of the planned acetabular component may provide some theoretical advantage on the final acetabular position. The purpose of this study was to compare the effect of navigated Vs free hand acetabulum reaming on achieving the planned orientation of acetabular component.

In a retrospective study we reviewed two groups of patients who underwent computer navigated placement of the acetabular component with reference to the anterior pelvic plane. We used an imageless computer navigation system for all cases (Brainlab, Munich). All procedures were performed by single surgeon (ETD) through a standard posterior approach. The patients were divided into two groups depending on the availability of the navigated reamer. In the first group (n = 57), acetabulum reaming was done under navigation and in the second group (n = 37) a non-navigated reamer was used. The acetabular cavity was reamed “line to line” or under reamed by 1 or 2mm. Intra-operative acetabular abduction and anteversion angles were planned using navigation at the discretion of the surgeon. Results of planned acetabular abduction and anteversion angles were compared with intra-operative verification using the navigation system.

In the navigated reamer group, the mean error from the planned to verified abduction angle was 1.7 degrees (SD 2.1 degrees) and in the non-navigated reamer group the mean error was 2 degrees (SD 2.6 degrees). In the navigated reamer group, the mean error from the planned to verified anteversion angle was 0.5 degrees (SD 2.8), and in the non-navigated reamer group the mean error was 0.1 degrees (SD 1.6). There was no statistically significant difference in the mean error between the navigated and non-navigated reaming groups for abduction angle (p = 0.54) or anteversion angle (p = 0.24). There was no statistical difference between the mean acetabular component size in the navigated (mean 53mm) and non-navigated (53mm) reamer groups (p = 0.8). There was no statistical difference in the mean difference in reamer size and the acetabular component size in the navigated (0.8mm) and non-navigated reamer groups (0.8mm, p = 0.52).

This study appears to show that performing reaming of the acetabular cavity under navigation does not improve the final orientation of the acetabular component when compared to using conventional non-navigated reamers. However, this study only considered the abduction and anteversion orientation of the component. The move to a range of movement or kinematic orientation of the acetabular component in hip arthroplasty requires control over the off-set of the acetabular component which may be more easily achieved when the reaming is performed under navigation. This study used a conventional posterior approach rather than a minimal incision technique, where the use of navigated reaming may also provide some theoretical advantage when visibility is limited. Further study is required in these two areas.

There appears to be a slightly higher standard deviation for the anteversion measurement in the navigated reamer group when compared to the non navigated reamer group, although this is not significant. It is difficult to account for this as it appears to be opposite of what one would predict. One explanation for this may come in the difference in the angled geometry of the navigated reamer when compared to the straight non navigated reamer. The angled reamer can be more difficult to control forming a cavity in the correct orientation but with the possibility for the cavity to not been perfectly hemispherical.

When using navigation to insert the acetabular component in a planned abduction and anteversion position during hip arthroplasty through a standard incision, navigating the reaming of the acetabular component does not appear to provide any advantage over the use of conventional non-navigated reamers in the final acetabular orientation.

Introduction. Reaming of the canal is an important step in the debridement phase of treating intramedullary infections. Numerous techniques of radical canal debridement have been successfully reported. The use of the Reamer-Irrigation-Aspiration system (RIA-Synthes) is currently expanding to include this clinical scenario. Materials and methods. Prospective collection of data related to infected cases treated with the use of the RIA in a tertiary referral centre referring to a 3 year period. Peri-operative details, microbiology results, and follow-up outcome over a minimum period of 12 months post-surgery are reported. Results. Twenty patients (13 men), with average age 44.8 years (18–75), suffering from 7 tibial and 13 femoral infections represent the study cohort. There were 19 surgical-site-infections, and 1 spontaneous haematogenous infection in non-previously operated extremity. The canal was stabilised using an antibiotic-loaded-cement-nail in 18 cases. The antibiotic nail was subsequently removed after 6–8 weeks. The most commonly isolated organism was staphylococcus aureus. There were followed-up regularly (2,6, 12 weeks, and then at 6 months and 12, 24, 36 months). At 6 months follow up (range 12–43 months) no recurrence was observed. Two patients died during the course of the study. One patient at the day after surgery due to septic shock, and another one at 2 years due to irrelevant causation. Another patient had a below knee amputation after debriding of the canal for pan-medullary osteomyelitis. However, there was no recurrence in the stump at the latest follow up after 1 year. Conclusion. The usage of this new device shows promising results in the treatment of intramedullary osteomyelitis. Reaming under simultaneous irrigation and suction appears to be an effective and safe alternative for debridement of the intra medullary infections of femur and tibia. Long term follow up is essential, as post traumatic osteomyelitis can occur at any time after surgical treatment although the majority of recurrences are seen within 2 years

Introduction:. Acetabular revision Jumbo cups are used in revision hip surgeries to allow for large bone to implant contact and stability. However, jumbo cups may also result in hip center elevation and instability. They may also protrude through anterior wall leading to ilopsoas tendinitis. Methods:. The study was conducted using two methods:. Computer simulation study. 265 pelvic CT scans consisting of 158 males and 107 females were converted to virtual 3-dimensional bones. The average native acetabular diameter was 52.0 mm, SD = 4.0 mm (males in 52.4 mm, SD = 2.8 mm and 46.4 mm, SD = 2.6 mm in females). Images were analyzed by custom CT analytical software (SOMA™ V.3.2). 1. and over-sized reaming was simulated. Four distinct points, located in and around the acetabular margins, were used to determine the reamer sphere. Points 1, 2, 3 were located at the inferior and inferior-medial acetabular margins, and Point 4 was located superiorly and posteriorly in the acetabulum to simulate a bony defect in this location, Point 4 was placed at 10%, 20%, 30%, 40%, 50% and 60% of the distance from the superior – posterior margin of the acetabular rim to the sciatic notch to simulate bony defects of increasing size. (Figure 1). Radiographical study. Retrospective chart review of patient records for all cementless acetabular revisions utilizing jumbo cups between January 1, 1998 and March 30, 2012 at UCFS (98 patients with 57 men, 41 women). Jumbo cups: ≥66 mm in males; <62 mm in females. Reaming was directed inferiorly to the level of the obturator foramen to place the inferior edge of the jumbo cup at the inferior acetabulum. To determine the vertical position of the hip center, a circle was first made around both the jumbo and the contralateral acetabular surfaces using Phillips iSite PACS software. The center of this circle was assumed to correspond to the “hip center”. The height of the hip center was estimated by measuring the height of a perpendicular line arising from the interteardrop line (TL) and ending at the hip center. Results:. The computer simulation and radiographic analysis deomonstrated similar results. The computer simulation predicted that the hip center shifted superiorly and anteriorly as the reamer size increased. The hip center shifted 0.27 mm superiorly and 0.02 mm anteriorly for every millimeter in diameter increased for the reaming. (Figure 2) Anterior column bone removal was increased 0.86 mm for every 1 mm of reamer size increase. (Figure 3). Results of radiographical study is shown in Table bellow:. Discussion:. Use of a jumbo cup in revision THA results in elevation of the hip center. Therefore a longer femoral head may be needed to compensate for hip center elevation when a jumbo cup is used. Reaming for a jumbo cup can also result in loss of anterior bone stock and protrusion of the cup anteriorly which may cause iliopsoas tendonitis

INTRODUCTION. Reaming of the acetabular cavity prior to cementless cup implantation aims to create a defined press-fit between implant and bone. The goal is to achieve full implant seating with the desired press-fit to reduce the risk of early cup loosening and the risk of excessive cup deformation. Current research concentrated on the spherical deviations of the reamed cavity compared to the reamer size, but the direct relationship between nominal press-fit, reamer geometry, cavity shape and bone-implant contact has not yet been investigated. The aim of this study was to determine the influence of the reaming process, the surface coating, and the implantation force on the achieved press-fit situation. METHODS. Fresh-frozen porcine acetabulae (n = 20) were prepared and embedded. Hemispherical reamers were used and the last reaming step was performed using a vertical drilling machine to ensure a proper alignment of the cavity axis. A hand-guided 3D laser scanner was used (HandySCAN 700, Creaform) to determine the reamer geometry and the cavity shape. Press-fit cups with two different surface coatings (Ø44 mm, Porocoat/Gription, DePuy Synthes) were implanted using a drop tower. The Porocoat cup was implanted with impacts from lower drop heights (low implantation force) and press-fits of 1 mm and 2 mm. The Gription cup, exhibiting a rougher surface, was implanted with low and high implantation forces and a press-fit of 1 mm. Bone-implant contact was analysed by the registration of the cup and cavity surface models, scanned prior to implantation, to the scan of the implanted cup. The cup surface was divided in areas with and without contact to the surrounding cavity. Overhang indicates that there was no adjacent cavity surface surrounding the implanted cup. The transition between contact and a gap at the cup dome was defined as contact depth and used as indicator for the cup seating. RESULTS. The peripheral cavity diameter was on average 0.94 ± 0.29 mm smaller than the reamer diameter due to the sub-hemispherical distribution of the cutting blades. This led to an increased effective press-fit in the peripheral area of the cavity. The contact area between cup and bone increased with the implantation force (p = 0.008) and ranged from 13.1 % to 27.8 %. The contact depth was larger for the smoother Porocoat coating (p = 0.008), a press-fit of 2 mm (p = 0.008) and a higher implantation force (p = 0.008). DISCUSSION. This study shows that, assuming similar implantation forces, an increased surface roughness of the cup coating increases the risk of an insufficient cup seating. For a given press-fit, higher implantation forces would be necessary to fully seat the cup in order to enhance the bone-implant contact. Implantation of a cup without a defined nominal press-fit could increase the contact area; however a high reaming accuracy and an increased friction coefficient of the cup coating are required to compensate for a reduction in initial fixation strength caused by reduced radial compressive forces. For any figures or tables, please contact authors directly

Segmental defects of the acetabulum are often encountered in revision surgery. Many times these can be handled with hemispherical cups. However when larger defects are encountered particularly involving the dome and/or posterior wall structural support for the cup is often needed. In the past structural allograft was used but for the last 12 years at our institution trabecular metal augments have been used in the place of structural allograft in all cases. This talk will focus on technique and mid-term results using augments in association with an uncemented revision shell. The technique can be broken down into 6 steps outlined below: 1. Exposure, 2. Reaming, 3. Trialing, 4. Augment Inserted, 5. Cup Insertion/Stabilization, 6. Trial Reduction/Liner Cementation. A recent study was undertaken to assess the mid-term results of this technique. We prospectively followed the first 56 patients in whom these augments were utilised in combination with a trabecular metal acetabular component in our unit. Details of this study will be presented. The median follow up of the surviving patients was 110 months (range 88–128 months). Survivorship of the augments at 10 years was 92.2% (95% CI: 97.0–80.5%). In one case the augment was revised for infection and in 3 for loosening. In 1 of the revised cases there was a pre-operative pelvic discontinuity, the other 2 discontinuities in the series were not revised and remain asymptomatic. Conclusions. The results of the acetabular trabecular metal augments continue to be encouraging in the medium to long term with low rates of revision or loosening in this complex group of patients

Revision hip surgery is about simplification. As such, a single revision stem makes sense. The most important advantage of Tapered Conical Revision (TCR) stem is versatility - managing ALL levels of femoral bone loss (present before revision or created during revision). The surgeon and team quickly gain familiarity with the techniques and instruments for preparation and implantation and subsequently master its use for a variety of situations. This ability to use the stem in a variety of bone loss situations eliminates intraoperative shuffle (changes in the surgical plan resulting in more instruments being opened), as bone loss can be significantly underestimated preoperatively or may change intraoperatively. Furthermore, distal fixation can be obtained simply and reliably. Paprosky 1 femoral defects can be treated with a primary-type stem for the most part. All other femoral defects can be treated with a TCR stem. Fully porous coated stems also work for many revisions but why have two different revision stem choices available when the TCR stems work for ALL defects?. TCR stems can be modular or monolithic but there are common keys to success. First and foremost, proper exposure is essential to assess bone defects and to safely prepare the femur. An extended osteotomy is often useful. Reaming distally to prepare a cone for fixation of the conical stem is a critical requirement to prevent subsidence (true for all revision stems). Restoration of hip mechanics (offset, leg length and stability) is fundamental to the clinical result. TCR stems have instrumentation and techniques that ensure this happens, since all this occurs AFTER distal stability is achieved. Modular TCR versions have some advantages. The proximal body size and length can be adjusted AFTER stem insertion if the stem goes deeper than the trial. Any proximal/distal bone size mismatch can be accommodated. If the surgeon believes that proximal bone ingrowth is important to facilitate proximal bone remodeling, modular TCR stems can more easily accomplish this. Further, proximal bone contact and osseointegration will protect the modular junction from stress and possible risk of fracture. Monolithic TCR versions also have some advantages. Modular junction mechanical integrity cannot accommodate smaller bone sizes. Shorter stem lengths are not available in modular versions, and shorter TCR stems are an option in many revision cases. The possibility of modular junction corrosion is eliminated and fracture of the stem at that junction, of course, is not possible. The monolithic stem option is less expensive as well. Consider Modular TCR stems in your learning curve, if you feel proximal bone osseointegration is important and if proximal/distal size mismatch is present. Consider Monolithic TCR stems after your learning curve to reduce cost, when a short stem works, and if a small stem is needed. Both Modular and Monolithic stems can be used for ALL cases with equal quality of result

Modularity in femoral revision evolved to address the specific weaknesses in the execution and results of the early Wagner SL stem, namely dislocations and subsidence. With modularity, distal canal fit can be achieved independently, and the proximal geometry can be created to re-establish the leg length and offset. The benefits of modularity relate specifically to being able to modify a plan intra-operatively based on the conditions that are encountered in mid battle. Inherent in this concept is the principle of predictability. The extent to which the conditions of operation may change requires alternatives to manage those changes. More importantly we need to be able to predict how an implant will sit in the bone. At the inception and with subsequent manifestations of modular fluted stems, our ability to predict where the final implant will seat based on the trial options that existed was poor. For this reason, some modular stem designs offered no trial. This was part of the imperative for modularity, so that if the implant set too high it could be easily removed with reaming a little deeper and put back in. If the stem sat more deeply than had been anticipated, the change could be compensated by an alteration in the proximal modular segment. Reproducible mid- to long-term results have been published with this type of stem. Potential negatives of the modular junction include stem breakage, fretting and corrosion, cost, and the need to accommodate a large sized proximal segment within the proximal femur. The most important feature in modern non-modular implants will be predictability. We need to be able to predict that the final reamer will sit at a particular level in the femoral bone, and the trial will reproduce this level, and the final implant will reproduce this level. More importantly, we need to be able to predict that implants will remain where they are put, and not subside. Subsidence has been causally associated with implant under-sizing, which is an error in surgical execution. As such, design features that optimise the ability to achieve intimate and broad endosteal contact between the implant and the bone can help reduce subsidence. These include precise, sharp reamers, implants in 1 mm increments, and trials that reproduce the position of the final implant. A larger implant is less likely to break, and we recommend preparation for the largest implant that the diaphysis can accommodate, often evident in the tactile feedback from the reamer, and the quality of the reamed bone being removed. Reaming is performed eccentrically in the proximal femur, so as to engage the diaphysis optimally. The need for a kink in the stem is important for modular stems, which have bulky proximal segments that can create conflict with the peritrochanteric bone in smaller patients. Non-modular stems can have a smaller proximal diameter, such that a straight stem can be accommodated in most revision cases. Early follow-up of a modern non-modular stem has shown excellent clinical improvement and reproducible ingrowth. Subsidence of > 10 mm occurred in 6 hips (6%), which is a notable improvement in historical values for this stem type, but remain short of some reports with modular stems. Improvements in goals and techniques of reaming and implantation are surely part of the improvements that have been documented, as well as those yet to be realised. Predictability will lead to simplicity and intuitiveness

Introduction. Good outcomes in reverse shoulder arthroplasty (RSA) rely in part on stability of the humeral component. Traditionally humeral components have been cemented, however there has been recent interest in press-fit fixation of humeral components in RSA. Lateralization of the head center in RSA can impart larger moments on the humeral component than for anatomic reconstructions, increasing the importance of distal humeral canal preparation for implant stability. To date, the primary stability of any type of press-fit humeral prosthesis has been largely unexplored. The goal of this study is to evaluate the effect of over-reaming the distal humeral canal in a press-fit humeral component in RSA. Methods. Computed tomography (CT) data of the shoulder were obtained from 55 shoulders. Images were segmented to produce digital models of the humerus. Humeral components for RSA (2mm diameter size increments) were sized and placed per the surgical technique, including preparation of the humerus with the appropriate reamers (1mm increments). Finite element models for each specimen were created with heterogeneous bone properties derived from the CT scan. Pressfit between the bone and stem was resolved to quantify the initial contact pressure on the stem; each stem was then loaded at 566N oriented 20° lateral and 45° anterior. Overall motion of the stem was measured, as well as interfacial micromotion in the porous coating region (Fig. 1). The effect of line-to-line (L2L) reaming and over-reaming by 1 mm was evaluated using an unpaired Student's t-test, with significance defined at p<0.05. Results. Across all specimens, stem sizes 8 (n=3), 10 (n=25), 12 (n=20), 14 (n=2), and 16 (n=1) were used. Stem motion ranged from approximately 250–750μm; micromotion remained under 300μm (Fig. 2). Stem motion was significantly less for L2L reaming as compared to over-reaming for both size 10 (p=.008) and size 12 (p=.002) stems; micromotion was significantly less for size 12 (p=.002) stems. L2L reaming to a larger diameter stem resulted in significantly reduced stem motion (average 390μm versus 530μm, p<.001) and micromotion (average 53μm versus 135μm, p=.001) than over-reaming and using a smaller diameter stem. Stem rotation following L2L reaming was generally below 0.5°, and exceeded 0.75° when over-reaming. Discussion and Conclusion. Reaming of the humeral canal directly impacts the stability of humeral stems in RSA. Even with satisfactory proximal press-fit, over-reaming enables increased rotation of the stem under functional loading prior to cortical engagement, and results in increased micromotion. In cases in which the reamer and stem offerings result in over-reaming, L2L reaming to the next larger stem significantly reduces stem motion and micromotion. However, reaming up also removes distal cortical bone, and thus the strength of the prepared humerus must be considered. In conclusion, line-to-line reaming significantly reduces the micromotion of humeral stems as compared to over-reaming

Introduction. Total hip arthroplasty has seen a transition from cemented acetabular components to press-fit porous coated components. Plasma sprayed titanium implants are often press-fit with 1mm under-reaming of the acetabulum; however, as porous coating technologies evolve, the amount of under-reaming required for initial stability may be reduced. This reduction may improve implant seating due to lowered insertion loads, and reduce the risk of intraoperative fracture. The purpose of this study was to investigate the initial fixation provided by a high porosity coating (P2, DJO Surgical), and a plasma sprayed titanium coating under rim loading with line-to-line and 1mm press-fit surgical preparation. Methods. Five, 52mm high porosity acetabular cups (60% average porosity) and five 52mm plasma sprayed titanium coated cups were inserted into low density (0.24g/cc) biomechanical test foam (Pacific Research Laboratories). Foam test material was cut into uniform 90×90×40mm blocks. Reaming was performed using standard instrumentation mounted on a vertical mill. Cups were first inserted into foam blocks prepared with line-to-line (52mm) reaming. Following mechanical testing, cups were removed from the foam, cleaned, and inserted into foam blocks prepared with 1mm under reaming (51mm). In total 4 test conditions were evaluated:. Group A: P2 + line-to-line. Group B: Plasma sprayed + line-to-line,. Group C: P2 + 1mm under-reaming. Group D: Plasma sprayed + 1mm-under reaming. Acetabular cup impaction was carried out using a single axis servohydraulic test machine (Instron 8500). Cups were inserted at 1mm/s to a load of 5kN. Insertion load was calculated as a 0.1mm offset from the linear portion of the force/displacement curve; insertion energy was the area under the curve. Tangential rim loading was applied at 0.0254mm/s by a conical indenter to the implant rim. Load data were recorded at 1kHz. Cup displacement was recorded by a 3D, marker-based tracking system at 15Hz (DMAS, Spicatek). Six markers were attached to a disk secured in the acetabular cup (Figure 1). Yield failure was defined as 0.331o of angular displacement (150µm of relative displacement). Angular displacement was derived by calculating the normal vector of a best-fit plane based on marker centroids. Results. Under-reamed groups (C,D) showed statistically higher insertion loads and insertion energies than line-to-line groups (A,B), with group C requiring the highest insertion load. Despite greater ease of insertion, groups A and B attained comparable yield loads with group A statistically outperforming D. Group C attained the highest ultimate failure loads, outperforming A and D (Figure 2). Discussion. Implants with high porosity coating and line-to-line preparation required less effort for full seating and maintained yield and ultimate performance which exceeded, or was comparable to, plasma sprayed titanium coated implants in either under-reamed or line-to-line preparation. Limitations of this study include the use of a mill for foam block preparation and automated implant insertion. Initial results in three matched cadaveric acetabular pairs with line-to-line preparation indicate that the advantages of high porosity coating may be preserved in human tissue with average yield failure and ultimate failure load improvements of 108% and 73% respectively (Figure 3). Study is ongoing

Purpose. The aim of this study was to investigate whether growth factors essential for fracture healing are released in the immediate aftermath following fracture and whether reaming of IM cavity causes increased liberation of these autocoids. Methods. Consecutive adult patients with femoral shaft fractures forming two groups (a group who received unreamed nail (n=10) and a second group who received reamed nail (n=10) were recruited for this study. Peripheral blood samples and samples from the femoral canal before and after reaming and before and after the solid nail insertion were collected. Serum was extracted and using Elisa colorimetric assays the concentration of Platelet Derived Growth Factor (PDGF), Vascular Endothelial Growth Factor (VEGF), Insulin-like Growth Factor I (IGF-I) Transforming Growth Factor beta 1 (TGF-. 2. 1) and BMP-2 levels was measured. Results. In total 20 patients were studied. The mean age was 38 years (range 20-63). Reaming substantially increased all studied growth factors locally in the femoral canal. VEGF and PDGF were increased after reaming by 111.2% and 115.6% respectively. IGF-1 was increased by 31.5% and TGF-b1 was increased by 54.2%. In the unreamed group the levels of PDGF-BB, VEGF and TGF-. 2. 1 were not changed while the levels of IGF-I were decreased by 10%. The levels of these factors in peripheral circulation were not altered despite the technique used. BMP-2 levels during all time points were below the detection limit of the immunoassay. Conclusion and significance. This study indicates that reaming of IM Canal is associated with increased liberation of growth factors. The osteogenic effect of reaming could be secondary not only to grafting debris but also to the increased liberation of these molecules