Traditional procedures for orthopedic total joint replacements have relied upon bone cement to achieve long-term implant fixation. This remains the gold standard in number of procedures including TKR and PKR. In many cases however, implants fixed with cement have proven susceptible to aseptic loosening and 3^rd body wear concerns. These issues have led to a shift away from cement fixation and towards devices that rely on the natural osteoconductive properties of bone and the ability of porous-coated implants to initiate on-growth and in-growth at the bone interface, leading to more reliable fixation.

To facilitate long-term fixation through osseointegration, several mechanical means have been utilized as supplemental mechanism to aid in stabilizing the prostheses. These methods have included integrated keels and bone screws. The intent of these components is to limit implant movement and provide a stable environment for bone ingrowth to occur. Both methods have demonstrated limitations on safety and performance including bone fracture due keel induced stresses, loosening due to inconsistent pressfit of the keel, screw-thread stripping in cancellous bone, head-stripping, screw fracture, screw loosening, and screw pullout. An alternative method of fixation utilizing blade-based anchoring has been developed to overcome these limitations.

The bladed-based fixation concept consists of a titanium alloy anchor with a “T-shaped” cross-section and sharped-leading end that can be impacted directly into bone. The profile is configured to have a bladed region on the horizontal crossbar of the “T” for engagement into bone and a solid rail at the other end to mates with a conforming slot on the primary body of the prosthesis. A biased chisel tip is added to the surface of the leading blade edge to draw the bone between the anchor's horizontal surface and surface of the implant, thus generating a compressive force at the bone-to-prothesis interface. The anchoring mechanism has been successfully been integrated into the tibial tray component of a partial knee replacement; an implant component that has a clinical history of revision due to loosening.

A detailed investigation into the pulloff strength, wear debris generation, compressive-force properties, and susceptibility to tibial bone fracture was carried out on the anchor technology when integrated in a standard tibial tray of a partial knee replacement. When tested in rigid polyurethane bone foam (Sawbones, Grade 15) the pulloff strength of the construct increased by 360% when utilizing the anchor. The tibial tray and anchor construct were cycled under compressive loading and demonstrated no evidence of interface corrosion or wear debris generation after 1 million cycles. In addition, the anchor mechanism was shown to generate 340N of compressive force at the tibial tray-to-bone interface when evaluated with pressure sensitive film (Fuji Prescale, Medium Grade). Finally, the ultimate compressive load to induce tibial fracture was shown to increase by 17% for the anchored tray as compared to a traditional keeled tray when tested in an anatomic tibial sawbones model; and by 19% when evaluated in human cadaveric tibias.

For any figures or tables, please contact authors directly.

Periprosthetic infection involving TKR has been projected to rise as the burden of implanted TKR continues to grow. A study by Kurtz et al. found a significant increase in the annual incidence of TKR infection, 2001 (2.05%) to 2.18% in 2009. Thus, deep prosthetic infection around a TKR remains a significant problem that has not been solved, even as technologies improve and the operation is more commonly performed.

The economic hospital cost of periprosthetic TKR infection is approximately $100,000 US for a two-stage removal and reimplantation; by the year 2020, it is estimated that 48,000 of these operations will be necessary. The total annual hospital cost for PJI treatment is expected to be over $1 billion by 2020, and does not include the doctor, pharmacologic, and physical therapy fees.

Many factors have been found to be associated with an increased risk of PJI. This lecture will focus upon the peri-, intra-, and post-operative factors that have been found historically to carry an increased or decreased risk of infection.

Preoperative factors that have been found to affect the risk of infection include: perioperative administration of intravenous antibiotics, patient nutrition, weight, and hemoglobin A1C in diabetic patients. Intraoperative factors include the duration of surgery, the use of antibiotic impregnated cement, and the use of dilute povidone/iodine solution irrigation. Postoperatively, wound care with antimicrobial agents, and a resistance to transfusing blood seem to lower the risk of infection.

Yang et al. found that diabetes mellitus carried a 1.6x greater risk of TKR infection, in a meta-analysis of 11 cohort studies. In a registry study of over 32,000 TKA, increasing BMI from 25 kg/m2 to 35 kg/m2 was found to be associated with a greater risk of wound infection in TKR patients, increasing from 3 to 4.1%. Preoperative colonization with MRSA has been found by several investigators to be a risk for surgical site infection, despite attempts at eradication.

Operatively, a wash of the surgical site for 3 minutes with a dilute solution of betadine has been found by Brown et al. to have decreased the incidence of periprosthetic joint infection from 0.97% to 0.15%.

Postoperatively, the type of dressing placed over the incision may play a role; Grosso et al. found a significantly reduced rate of PJI (0.33% vs. 1.58%) when a silver impregnated, antimicrobial, dressing was used as compared to standard xeroform gauze. Finally, patients who received an allogeneic blood transfusion were found to have a higher risk of PJI (1.67%) than those who did not (0.72%).

Acetabular implant position is important for the stability, function, and long-term wear properties of a total hip arthroplasty (THA). Prior studies of acetabular implant positioning have demonstrated a high percentage of outliers, even in experienced hip surgeons, when conventional instruments are used.

Computer navigation is an attractive tool for use in (THA, as it has been shown to improve the precision of acetabular component placement and reduce the incidence of outliers. However, computer navigation with imageless, large-console systems is costly and often interrupts the surgeon's workflow, and thus, has not been widely adopted.

Another method to improve acetabular component positioning during THA is the use of fluoroscopy with the direct anterior approach. Studies have demonstrated that the supine position of the patient during surgery facilitates the use of fluoroscopic guidance, thus improving acetabular component position.

A handheld, accelerometer based navigation unit for use in total hip replacement has recently become available to assist the surgeon in positioning the acetabular component during anterior approach THA, potentially reducing the need for intraoperative fluoroscopic studies. We sought to compare the radiographic results of direct anterior THA performed with conventional instrumentation vs. handheld navigation to determine the accuracy of the navigation unit, and to see whether or not there was a reduction in the fluoroscopic time used during surgery. Furthermore, we timed the use of the navigation unit to see whether or not it required a substantial addition to surgical time.

Our results demonstrate that a handheld navigation unit used during anterior approach THA had no difference with regard to acetabular cup positioning when compared to fluoroscopically assisted THA, but led to a reduction in the use of intraoperative fluoroscopy time.

Orthopaedic joint replacement surgery requires surgical assistants holding retractors in order to adequately visualise the operative field. Typically, total hip and knee replacement operations require at least one surgical assistant and preferably two. As such, tremendous resources are consumed in order to perform elective TJA.

A mechanised pulley system, called the Gripper (Medenvision, Belgium), has been devised to assist with this need for extra “hands” to hold retractors. The Gripper is a table mounted, disposable device used to hold retractors, and is infinitely adjustable with regard to position in space. As such, it can be used in a variety of situations to provide an additional retractor holder, without the need for extra manpower. It is sterile, in the operative field, and can fit retractors with a flat handle. With positioning of the table mounts before prepping and draping, the Gripper can be used during the operation to hold retractors that would otherwise require a surgical assistant. The Gripper can be moved around during different portions of the operation in order to make the most of it use.

In our experience, the Gripper has been most useful in direct anterior approach THA, holding a curved anterior retractor to facilitate acetabular exposure. It is also useful in holding a retractor placed over the tip of the greater trochanter during femoral preparation. In our estimation, it is able to replace a human surgical assistant at a fraction of the cost. Furthermore, the Gripper does not fatigue during the operation and does not compromise the surgical field by needing to adjust its handhold. Because of this, even in an academic center with residents, fellows, and visiting medical students, the Gripper is preferable to human hands holding retractors.

We estimate that a surgical assistant with a starting level salary would have to scrub in on over 300 cases per year in order to make him/herself more cost effective than the Gripper.

Surface coatings have been introduced to total joint orthopaedics over the past decades to enhance osseointegration between metal implants and bone. However, complications such as aseptic loosening and infection persist. Inadequate osseointegration remains a complication associated with implants that rely on osseointegration for proper function. This is particularly challenging with implants having relatively flat and small surface areas that have high shear loading, such as noncemented uni and total condylar knee tibial trays. Faster osseointegration can enhance recovery as a result of improved load distribution and a more stable bone-implant interface. Traditionally noncemented porous bone ingrowth coatings on knee, hip and shoulder implants are typically texturised by thermal plasma spray coating, sintered metal bead coatings, or 3-D additive manufactured structures that provide porous surface features having the rough texture with pore sizes on the order of 150 to 300 micrometers. These surfaces are often further chemically enhanced with hydroxyapatite (HA) deposition. This provides macro-mechanical (millimeter scale) and micro-mechanical (micrometer scale) bone remodeling into the implant surface. However, at the nanoscale and cellular level, these surfaces appear relatively smooth. More recent studies are showing the importance of controlling the macro, micro, and the nano (nanometer scale) surface topographies to enhance cell interaction. In vitro and in vivo research shows surfaces with nanoscale features in the metal substrate result in enhanced osseointegration, greater bone-implant contact area and pullout force, and potentially bactericidal.

One surface modification treatment technique of particular promise is nano-texturing via electrochemical anodization to bio-mimicking TiO2 nanotube arrays that are superimposed onto existing porous surface microstructures to further enhance the already known bone ingrowth properties of these porous structures by superimposing onto the existing microstructure arrays of nanotubes approximately 100 nanometers in outside diameter and 300–500 nanometers in height.

In an ovine model, 3-D printed Direct Metal Laser Deposition (DMLS) additive manufactured porous Ti-6Al-4V implant with and without TiO2 nanotube array nano-texturing were compared to similar sized implants with commercially available sintered beads with HA coating and additive manufactured cobalt chrome implants. The average bond strength was significantly higher (42%) when the implants were nano-texturised and similarly stronger (53%) compared to HA coated sintered bead implants. Histology confirms over 420% more direct bonded growth of new bone from 0.5mm to 1.0mm deep into the porosity on the implants when the same implants are nano-texturised. Nano-texturing also changes the surface of the implant to repel methicillin-resistant staphylococcus aureus (MRSA) in an in vivo rabbit model limiting biofilm formation on the porous surface compared with non-treated porous surfaces.

Since nano-texturizing only modifies the nano-morphology of the surface and does not add antibiotics or other materials to the implant, these animal studies shows great promise that nano-texturizing the TiO2 coating may not only enhance osseointegration, but also repels bacteria from porous implant surfaces. As such, we believe nano-texturing of porous implants will be the next advancement in surface coating technology.

Acetabular implant position is important for the stability, function, and long-term wear properties of a total hip arthroplasty (THA). Prior studies of acetabular implant positioning have demonstrated a high percentage of outliers, even in experienced hip surgeons, when conventional instruments are used.

Computer navigation is an attractive tool for use in THA, as it has been shown to improve the precision of acetabular component placement and reduce the incidence of outliers. However, computer navigation with imageless, large-console systems is costly and often interrupts the surgeon's workflow, and thus, has not been widely adopted.

Another method to improve acetabular component positioning during THA is the use of fluoroscopy with the direct anterior approach. Studies have demonstrated that the supine position of the patient during surgery facilitates the use of fluoroscopic guidance, thus improving acetabular component position.

A handheld, accelerometer-based navigation unit for use in total hip replacement has recently become available to assist the surgeon in positioning the acetabular component during anterior approach THA, potentially reducing the need for intra-operative fluoroscopic studies. We sought to compare the radiographic results of direct anterior THA performed with conventional instrumentation vs. handheld navigation to determine the accuracy of the navigation unit, and to see whether or not there was a reduction in the fluoroscopic time used during surgery. Furthermore, we timed the use of the navigation unit to see whether or not it required a substantial addition to surgical time.

Our results demonstrate that a handheld navigation unit used during anterior approach THA had no difference with regard to acetabular cup positioning when compared to fluoroscopically assisted THA, but led to a reduction in the use of intra-operative fluoroscopy time.

INTRODUCTION

Traditionally, acetabular component insertion in direct anterior approach (DAA) total hip arthroplasty (THA) has been performed using fluoroscopic guidance. Handheld navigation systems can be used to address issues of alignment, cup placement and accuracy of measurements. Previous navigation systems have been used successfully in total knee arthroplasty (TKA) and has now been introduced in THA. We investigated the use of a new accelerometer-based, handheld navigation system during DAA THA to compare it to traditional means. This study aims to determine accuracy of acetabular cup placement as well as fluoroscopy times between two groups of patients.

INTRODUCTION

Childhood diseases involving the proximal femoral epiphysis often cause abnormalities that can lead to end-stage arthritis at a relatively young age and the need for total hip arthroplasty (THA). The young age of these patients makes hip resurfacing arthroplasty (HRA) an alternative and favorable option due to the ability to preserve femoral bone.

Patients presenting with end-stage hip arthritis as sequelae of childhood diseases such as Legg-Calves-Perthes (LCP) and slipped capital femoral epiphysis (SCFE) pose altered femoral anatomy, making HRA more technically complicated. LCP patients can result in coxa magna, coxa plana and coxa breva causing altered femoral head-to-neck ratio. There can also be acetabular dysplasia along with the proximal femoral abnormalities. SCFE patients have altered femoral head alignment. In particular, the femoral head is rotated medially and posteriorly, reducing the anterior and lateral offset. Additionally, many of these patients have retained hardware, making resurfacing more complicated.

We report findings of a cohort of patients, with history of either LCP or SCPE who underwent HRA to treat end-stage arthritis.

Acetabular implant position is important for the stability, function, and long-term wear properties of a total hip arthroplasty (THA). Prior studies of acetabular implant positioning have demonstrated a high percentage of outliers, even for experienced hip surgeons, when conventional instruments are used.

Computer navigation is an attractive tool for use in THA, as it has been shown to improve the precision of acetabular component placement and reduce the incidence of outliers. However, computer navigation with imageless, large-console systems is costly and often interrupts the surgeon's workflow, and thus has not been widely adopted.

Another method to improve acetabular component positioning during THA is the use of fluoroscopy with the direct anterior approach. Studies have demonstrated that the supine position of the patient during surgery facilitates the use of fluoroscopic guidance, thus improving acetabular component position.

A handheld, accelerometer based navigation unit for use in total hip replacement has recently become available to assist the surgeon in positioning the acetabular component during anterior approach THA, potentially reducing the need for intra-operative fluoroscopic studies. We sought to compare the radiographic results of direct anterior THA performed with conventional instrumentation vs. handheld navigation to determine the accuracy of the navigation unit, and to see whether or not there was a reduction in the fluoroscopic time used during surgery. Furthermore, we timed the use of the navigation unit to see whether or not it required a substantial addition to surgical time.

Our results demonstrate that a handheld navigation unit used during anterior approach THA had no difference with regard to acetabular cup positioning when compared to fluoroscopically assisted THA, but led to a reduction in the use of intra-operative fluoroscopy time.

A total knee replacement (TKR) with instability is one in which the supporting soft tissues have failed or are unable to function due to component size and/or position. Instability following TKR can lead to the need for surgery in 10–22% of revision cases. Patients may complain of symptoms of giving way, difficulty climbing stairs, and the sensation that their knee may buckle under stress. Physical findings may include soft-tissue tenderness in the peripatellar and pes anserine regions, recurrent joint effusions, and joint laxity. The cause of instability after TKR should be determined pre-operatively so the problem may be corrected at the time of revision.

Instability after TKR may be due to component loosening, ligament rupture/incompetence, component malposition, mismatched flexion/extension gaps, or failure to correct ligament imbalance at the time of the index procedure. A common scenario after a cruciate-retaining TKR is that of PCL rupture, thus leading to instability in flexion and excessive posterior translation of the tibia. Other scenarios leading to TKR instability are pre-operative valgus alignment with MCL stretching, resulting in the post-operative recurrence of medial instability; or excessive resection of the posterior femoral condyles from undersizing of the femoral component, leading to laxity in flexion.

The treatment of instability after TKR generally requires component revision and balancing of the flexion and extension gaps. Isolated ligament reconstruction is not successful in the setting of a prosthetic joint due to the lack of inherent joint stability. At the time of revision, the surgeon must carefully assess the flexion gap; often posterior femoral augments must be used to upsize the femoral component and tighten the flexion space relative to the extension space; for this reason, isolated polyethylene exchange is not successful for flexion instability. For instability in the varus/valgus plane, rebalancing the knee by performing ligament releases and using a more stabilizing polyethylene insert may by sufficient.

The results of revision TKR for instability has been successful in the majority of cases, decreasing the symptoms of giving way and difficulty stairclimbing. A careful assessment of the varus/valgus stability of the prosthetic knee and the flexion/extension spaces at the time of revision TKR, along with the use of augments and more stabilised articulations, is mandatory in order to achieve good results.

Stiffness after TKR is a frustrating complication that has many possible causes. Though the definition of stiffness has changed over the years, most would agree that flexion > 75 degrees and a 15-degree lack of extension constitutes stiffness. This presentation will focus upon the potential causes of a stiff TKR, intra-operative tips, the post-operative evaluation and management, and the results of revision for a stiff TKR.

The management of this potentially unsatisfying situation begins pre-operatively with guidance of the patient's expectations; it is well-known that pre-operative stiffness is strongly correlated with post-operative lack of motion. At the time of surgery, osteophytes must be removed and the components properly sised and aligned and rotated. Soft-tissue balancing must be attained in both the flexion/extension and varus/valgus planes. One must avoid overstuffing the tibio-femoral and/or patello-femoral compartments with an inadequate bone resection.

Despite these surgical measures and adequate pain control and rehabilitation, certain patients will continue to frustrate our best efforts. These patients likely have a biological predisposition for formation of scar tissue. Other potential causes for the stiff TKR include complex regional pain syndrome or joint infection.

Close followup of a patient's progress is crucial for the success in return of ROM. Should motion plateau early in the recovery phase, the patient should be evaluated for manipulation under anesthesia. At our institution, most manipulations are performed within 3 months post-operative under an epidural anesthetic; patients will stay overnight for continuous epidural pain relief and immediate aggressive PT.

The results of re-operations for a stiff TKR are variable due to the multiple etiologies. A clear cause of stiffness such as component malposition, malrotation or overstuffing of the joint has a greater chance of regaining motion than arthrofibrosis without a clear cause. Although surgical treatment with open arthrolysis, isolated component or complete revision can be used to improve TKR motion, results have been variable and additional procedures are often necessary.

Titanium (Ti) alloy is the material of choice for the porous bone ingrowth materials for non-cemented total Joint arthroplasty. Recent studies have shown the importance of controlling the macro, micro, and nano surface topographies on the bone apposition surfaces of these implants. Historically, much attention has been given to the designs of macro fixation features (millimeter scale), and the design of micro fixation porosity (micrometer scale). More recently, the importance of the nano-surface texture (nanometer scale) is being recognised as an integral component of the design. Nano-textures are being enhanced during implant processes to optimise the bond between implant and bone.

The ultra-hydrophilic nano-texture of an implant interacts with the corresponding nano-texture of the outer cell membranes to increase cell adhesion and differentiation. This speeds the osseointegration rate between Ti alloys, and the surrounding osteoblast tissues. Living cells sense and respond to surface texturing on the nanoscale which in turn direct stem cell and osteoblast differentiation. This has been recognised to improve the speed at which the implant interface bonds to bone with the end goal of ultimately allowing patients to weight bear on non-cemented arthroplasty implants sooner.

One surface modification treatment technique of particular promise is nano-texturing via. electrochemical anodization to form arrays of vertically aligned, laterally spaced titanium dioxide (TiO2) nanotubes on titanium implant surfaces in areas where enhanced implant-to-bone fixation is desired. Bio-mimicking TiO2 nanotube arrays are superimposed onto existing porous surface micro-structures to further enhance the already known bone ingrowth properties of these porous structures. These nanotube arrays show an accelerated osseointegration. Foundational work has demonstrated that the TiO2 nanotube surface architecture significantly accelerates osteoblast cell growth, improves bone-forming functionality, and even directs mesenchymal stem cell fate. Current generation nano-surface modification technologies show improved osseointegration response between implant materials and surrounding tissue and also provide surfaces that resist microbial adhesion.

Implant surfaces treated with and without TiO2 nanotubes were compared to grit blasted Ti controls in-vitro and in-vivo. The samples we evaluated after exposure to human mesenchymal stem cell (hMSC). Additionally, implants have been evaluated in multiple animal models with and without TiO2 nanotubes. The bones with implants were retrieved for mechanical testing and histology analysis. The average bond strength was significantly higher (150% to 600%, depending on the in-vivo animal model) for TiO2 nanotube implants compared to the non-treated Ti control implants. The histology confirms direct bonded growth of new bone onto the nanotubes with a significantly less trapped amorphous tissue at the implant-bone interface compared to the controls. Both in-vitro and in-vivo analysis indicates that TiO2 nano-texturing enhances the speed and proliferation of osseointegration. This surface treatment technique can be applied to non-porous or porous surfaces on TJA implants where improved bone fixation is desired.

In recent years, cementless stems have dominated the North American market. There are several categories of cementless stems, but in the past 20 years, the two most popular designs in the United States have been the extensively coated cylindrical cobalt-chrome (CoCr) stem and the proximally coated tapered titanium stem, which in recent years has become the most common. The 10-year survival for both stem types has been over 95% with a distinction made on factors other than stem survival, including thigh pain, stress shielding, complications of insertion, and ease of revision. Conventional wisdom holds that proximally coated titanium stems have less stress shielding, less thigh pain, and a higher quality clinical result. Recent studies, however, including randomised clinical trials have found that the incidence of thigh pain and clinical result is essentially equivalent between the stem types, however, there is a modest advantage in terms of stress shielding for a tapered titanium stem over an extensively coated CoCr stem. One study utilizing pain drawings did establish that if a CoCr cylindrical stem was utilised, superior clinical results in terms of pain score and pain drawings were obtained with a fully coated versus a proximally coated stem. In spite of the lack of a clinically proven advantage in randomised trials, tapered titanium stems have been favored because of the occasional occurrence of substantial stress shielding, the increased clinical observation of thigh pain severe enough to warrant surgical intervention, ease of use of shorter tapered stems that involve removal of less trochanteric bone and less risk of fracture both at the trochanter and the diaphysis due to the shorter, and greater ease of insertion through more limited approaches, especially anterior approaches. When tapered stems are utilised, there may be an advantage to a more rectangular stem cross-section in patients with type C bone. In spite of the numerous clinical advantages of tapered titanium stems, there still remains a role for more extensively coated cylindrical stems in patients that have had prior surgery of the proximal femur, particularly for a hip fracture, which makes proximal fixation, ingrowth, and immediate mechanical stability difficult to assure consistently. Cement fixation should also be considered in these cases. While the marketplace and the clinical evidence strongly support routine use of tapered titanium proximally coated relatively short stems with angled rather than straight proximal lateral geometry in the vast majority of cases, there still remains a role for more extensively coated cylindrical and for specific indications.

Background

Coronal malalignment has been proposed as a risk factor for mechanical failure after total knee arthroplasty (TKA). In response to these concerns, technologies that provide intraoperative feedback to the surgeon about component positioning have been developed with the goal of reducing rates of coronal plane malalignment and improving TKA longevity. Imageless hand-held portable accelerometer technology has been developed to address some the limitations associated with other computer assisted navigation devices including line-of-sight problems, preoperative imaging requirements, extra pin sites, up-font capital expenditures, and learning curve. The purpose of this study was to compare the accuracy and precision of a hand-held portable navigation system versus conventional instrumentation for tibial and femoral resections in TKA.

Perioperative blood conservation remains an important topic today in order to reduce complications, improve function, and facilitate recovery after a total knee replacement (TKR). Studies have shown that the degree of postoperative anemia is related to an increase in complications. A greater blood loss and need for transfusion is associated with a higher risk of infection, a slower recovery process, increased morbidity to patients, as well as an increased cost to the health care system.

Typical blood loss estimates range from 800cc to over 1700cc, when accounting not only for intraoperative but postoperative blood loss. Several strategies have been developed to help mitigate the risk of perioperative blood loss and need for subsequent transfusion.

Firstly, preoperative measures such as vitamin and mineral supplementation can ensure the starting hemoglobin and red cell count are maximised. Additionally, erythropoietin can be helpful in refractory cases of preoperative anemia. Preoperative autologous blood donation was used extensively in the past, but has fallen out of favor due to its inefficiency and cost.

Intraoperatively, measures such as the use of a tourniquet, meticulous technique, and expeditious surgery can help reduce blood loss. The most effective method, however, has been the use of tranexamic acid (TXA). TXA, an antifibrinolytic compound, has been extremely effective at reducing perioperative blood loss without increasing the risk of thromboembolic events. TXA can be used topically or intravenously. Other methods that can reduce intraoperative blood loss include the use of fibrin sealants, applied to the soft tissues and bony surfaces around the knee.

Postoperatively, the avoidance of wound drains is associated with a higher blood count and reduced transfusion risk. Alternatively, drainage reinfusion systems can be used to raise the postoperative blood count, particularly in cases of bilateral TKR.

Nerve palsy occurring after elective primary total hip arthroplasty (THA) is a devastating complication because of its effect on motor strength, walking ability, potential for pain, and unexpected nature. In general, the nerve distribution involved is the peroneal branch of the sciatic nerve, and the level of involvement is usually mixed motor and sensory.

Prior publications have associated limb lengthening, dysplasia and use of the posterior approach to be associated with a higher incidence of nerve palsy. In the literature, the incidence of sciatic nerve palsy is estimated to be 0.2 to 1.9%.

We examined the rate of sciatic nerve palsy after THA performed by the joint replacement service at Hospital for Special Surgery between the years 1998–2013. Each case was matched with 2 controls that underwent THA and did not develop postoperative neuropathy. Controls were matched by surgical date having been within 7 days of their matched case's surgery date. Patient and surgical variables were reviewed using data from patient charts and the institution's total joint replacement registry. A multivariable logistic regression model was created to identify potential risk factors for neuropathy following THA while adjusting for potential confounders.

We found that, of 39,056 primary THA cases, there were 81 cases of sciatic nerve palsy, giving an incidence of 0.21%. The factors with the greatest odds ratios for nerve palsy were: history of smoking (OR=3.45); history of spinal stenosis (OR=4.45), and time of day of 1PM or later (OR=3.98). We did not find limb lengthening, dysplasia, or type of fixation to be associated with nerve palsy.

In conclusion, post-surgical neuropathy has a low incidence after primary THA, but at our institution, was associated with several factors. Spine-related comorbidities, such as spinal stenosis and lumbar spine disease, and smoking history should be closely monitored to inform the patient and surgeon for the potential increased risk of postoperative neuropathy following THA.

Femoral neck fractures continue to be one of the most common orthopaedic injuries treated today. Owing to the increased longevity of patients, enduring activity of older patients, and widespread osteoporosis in the population, there are more femoral neck fractures treated nowadays than ever before. Over 1 million femoral neck fractures were treated in the >65-year-old population, in the United States, between the years 1991–2008.

The treatment of femoral neck fractures is unique because some fractures are amenable to internal fixation, while others require endoprosthetic replacement, either with a hemiarthroplasty or total hip replacement. Traditionally, less displaced fractures are treated with internal fixation; however, in younger patients, an attempt to fix the displaced fractures may be performed, in order to avoid a joint replacement in this population. The age at which an attempt at internal fixation is performed is still controversial, and treatment must be individualised to each patient. In general, patients younger than 60 would likely have internal fixation of the femoral neck fracture, rather than joint replacement.

The paradigm for the treatment of femoral neck fractures has been changing in the last 10 years, due to advances in implant technology, surgical technique, and scientific papers that have compared the results of all three treatment options. Larger diameter femoral heads in combination with highly crosslinked polyethylene, or dual mobility head options, provide greater joint stability today than was possible in the past, thus making THA a more appealing option. Furthermore, greater use of the direct anterior approach to THA may also reduce the postoperative dislocation rate, due to preservation of the posterior capsule and short external rotators.

Therefore, the author will propose the use of arthroplasty for displaced femoral neck fractures in patients younger than 60 years of age, owing to the reliability and reproducibility of THA over ORIF. Furthermore, the advances in arthroplasty materials and surgical techniques can restore function in this group of younger patients, with greater longevity of the implant than in the past.

Metal-on-metal (MOM) hip arthroplasty has been associated with a variety of new failure modes that may be unfamiliar to surgeons who traditionally perform metal-on-polyethylene THR. These failure modes include adverse local tissue reaction to metal debris, hypersensitivity to metal debris, accelerated wear/metallosis, pseudotumours, and corrosion. A significant number of patients with metal-on-metal hip arthroplasty may present to surgeons for routine followup, concern over their implant, or frank clinical problems.

A common issue with MOM hip arthroplasty that can lead to accelerated wear and failure is implant malposition. Malposition of a hard-on-hard bearing can lead to edge loading and accelerated wear at the articular surfaces, which will lead to elevation in blood metal ion levels and metallosis. Distinct from this failure mode is the possibility of metal hypersensitivity, which is believed to be an immunologically mediated reaction to normal amounts of metal debris. Because a modular MOM THR has multiple junctions and tapers that come into contact with one another, there also is the possibility of non-articular metal debris production and corrosion. This type of corrosion reaction can lead to soft tissue destruction not commonly seen with hip resurfacing.

Therefore, it is important for orthopaedic surgeons to be aware of the intricacies of following a metal-on-metal hip arthroplasty and to be able to interpret test results such as metal ion levels and cross-sectional imaging. Furthermore, there is a difference in the incidence of problems depending upon the type of implant: hip resurfacing, small-diameter head metal-on-metal total hip replacement, and large diameter head MOM THR. This presentation will discuss the importance of routine monitoring and followup for patients with MOM THR, as well as the utility of measuring blood metal ion levels. The published risk stratification algorithm from the Hip Society will be reviewed.

Surface replacement of the hip was established in the 1970's as a bone preserving alternative to total hip replacement. However, problems with femoral neck fracture, osteolysis, and component loosening led to early failures and an abandonment of the procedure.

The modern generation of hip resurfacing, however, has improved upon past results with new implant designs and materials. Better surgical guides and a short femoral stem allow for more accurate placement of the implants. A metal-on-metal articulation creates a larger diameter bearing and avoids polyethylene wear debris. Also paramount in the recent successes of surface replacement are refinements in surgical techniques, leading to more accurate component positioning, avoidance of neck notching, and an appreciation of the femoral head blood supply. It has been well-established that surgeons with higher volumes of hip resurfacing operations have a lower complication rate. The mid-term results of these newer hip resurfacing devices, coupled with appropriate patient selection and good surgical technique, have been encouraging.

Although, more recently, surface replacement has come under fire because of the metal-on-metal articulation, the Australian National Joint Registry finds that a certain group of patients has greater survivorship with resurfacing than with total hip replacement. Additionally, the benefits of surface replacement include the preservation of bone, a lower dislocation rate, and potentially a higher activity level. Therefore, the presenter feels that surface replacement arthroplasty is still a viable option, for the right patient and surgeon.

Introduction

Hip Resurfacing Arthroplasty (HRA) has been performed in the United States for over 10 years and is an alternative to standard Total Hip Arthropastly (THA). It is appealing to younger patients with end stage osteoarthritis who seek to maintain active lifestyles. Benefits of HRA versus THR include a larger femoral ball size, potential to return to impact activities, decreased dislocation rates, and restoration of normal hip biomechanics. Patients ≤50 years old are a particularly challenging patient group to treat with THA because of their young age and high activity level, and as such, are well-suited for HRA. However, there are limited reports in the literature about clinical, radiographic and functional outcomes for this patient cohort. We present results of a clinical investigation at our institution for this patient cohort with minimum 5-year follow up, including long term survivorship and outcome scores.