Aims

Prior studies have identified that malseating of a modular dual mobility liner can occur, with previous reported incidences between 5.8% and 16.4%. The aim of this study was to determine the incidence of malseating in dual mobility implants at our institution, assess for risk factors for liner malseating, and investigate whether liner malseating has any impact on clinical outcomes after surgery.

Introduction

The use of irrigation solution during surgical procedures is a common and effective practice in reduction of bioburden and the risk of subsequent infection. The optimal irrigation solution to accomplish this feat remains unknown. Many surgeons commonly add topical antibiotics to irrigation solutions assuming this has topical effect and eliminates bacteria. The latter reasoning has never been proven. In fact a few prior studies suggest addition of antibiotics to irrigation solution confers no added benefit. Furthermore, this practice adds to cost, has the potential for anaphylactic reactions, and may also contribute to the emergence of antimicrobial resistance. We therefore sought to compare the antimicrobial efficacy and cytotoxicity of irrigation solution containing polymyxin-bacitracin versus other commonly used irrigation solutions.

The purpose of this randomized controlled trial is to evaluate the efficacy of using dilute betadine versus sterile saline lavage in aseptic revision total knee (TKA) and hip (THA) arthroplasty to prevent acute postoperative deep periprosthetic joint infection (PJI).

Of the 450 patients that were randomized, 5 did not have 90-day follow-up, 9 did not receive the correct treatment, and 4 were excluded for intraoperative findings consistent with PJI. 221 Patients (144 knees and 77 hips) received saline lavage only and 211 (136 knees and 75 hips) received a three-minute dilute betadine lavage (0.35%) prior to wound closure. Patients were observed for the incidence of acute postoperative deep PJI within 90 days of surgery. Statistical analysis was performed using t-tests or Fisher's exact test where appropriate. Power analysis determined that 285 patients per group are needed to detect a reduction in the rate of PJI from 5% to 1% (alpha=0.05, beta=0.20).

There were seven PJIs in the saline group and one in the betadine lavage group (3.2% vs. 0.5%, p=0.068). There were no significant differences in any baseline demographics between groups suggesting appropriate randomization.

Although we believe the observed difference between treatments is clinically relevant, it was not statistically significant with the sample size enrolled thus far and enrollment is ongoing. Nonetheless, we believe that these data suggests that dilute betadine lavage is a simple method to reduce the rate of acute postoperative PJI in patients undergoing aseptic revision procedures.

While advances in laboratory and imaging modalities facilitate the diagnosis of periprosthetic joint infection (PJI), clinical suspicion and a thorough history and physical remain the basis of evaluation. If clinical suspicion is high, the evaluation should be more vigorous, and vice versa.

The erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are inexpensive as well as ubiquitous, and should be obtained as a preliminary screening tool. These tests have been found to be cost-effective and highly sensitive. If both tests are negative, there is a low risk of periprosthetic joint infection (i.e., good negative predictive value). Positive results on both tests, in contrast, are not as specific but again raise suspicion.

When either the ESR or CRP is elevated, or if the clinical suspicion for infection is high, aspiration of the knee joint is suggested. Synovial fluid should be sent for a synovial fluid white blood cell count (WBC), differential and culture. Given the ability to get three data points from one intervention, arthrocentesis, is the best single maneuver the physician can perform to rule in or out PJI. The synovial fluid WBC count has demonstrated in multiple studies excellent specificity and sensitivity in the diagnosis of infection. Based on multiple recent studies, the proceedings of the International Consensus on PJI recommend cut-offs for the synovial fluid WBC count as >3000 cells/mL and > 80% neutrophils for the differential.

Synovial fluid biomarkers represent an expanding area of clinical interests based on the unique cascade of gene expression that occurs in white blood cells in response to pathogens. Deirmegian et al. described the unique gene expression and biomarker production by neutrophils in response to bacteria that are detectable in synovial fluid. Specifically, alpha-defensin is one such antimicrobial peptide. Along with synovial CRP, alpha-defensin can be measured in a currently commercially-available immunoassays.

The diagnosis of PJI can be difficult to make in spite of the variety of tests available. That being said, the diagnosis is easily made in our experience in 90% of patients by getting an ESR and CRP followed by selective aspiration of the joint if these values are elevated or if the clinical suspicion is high. Synovial fluid obtained should be sent for a synovial fluid WBC count, differential and cultures.

Dislocation remains among the most common complications of, and reasons for, revision of both primary and revision total hip arthroplasties in the United States. We have advocated identifying the primary cause of instability to plan appropriate treatment (Wera, Della Valle, et al., JOA 2012). Once implant position, leg length, and offset have been optimised and sources of impingement have been removed, the surgeon can opt for a large femoral head, a dual mobility articulation or a constrained liner. Given the limitations of constrained liners, we have looked to dual mobility articulations as an alternative, including its use in patients with abductor deficiency.

We retrospectively compared a consecutive series of revision THA that were at high risk for instability and treated with either a constrained liner or a dual mobility articulation. At a minimum of two years, there were ten dislocations in the constrained group (10/43 or 23.3%) compared to three in the dual-mobility group (3/36 or 8.3%; p = 0.06). With repeat revision for instability as an endpoint, the failure rate was 23% for the constrained group and 5.5% for the dual mobility group (p = 0.03).

We have also performed a systematic review of the published literature on the use of dual mobility in revision THA. Of the 3,088 hips reviewed, the dislocation rate was 2.2%, the risk of intraprosthetic dislocation was 0.3% and overall survivorship was 96.6% at 5 years.

Dual mobility articulations offer anatomic sized femoral heads that greatly increase jump distance, without many of the negatives of a constrained liner. While dual mobility is associated with its own concerns and problems (including intraprosthetic dislocation and wear) our initial results suggest that they are a viable alternative to a constrained liner, even in the most challenging situations.

Accurate placement of the acetabular component is essential in Total Hip Arthroplasty (THA). The purpose of this study is to determine if an analog spirit level can improve the surgeon's ability to achieve acetabular inclination within the “safe-zone” of 30 to 50 degrees.

We reviewed 167 primary THAs performed by a single surgeon over 14 months. Procedures were performed at two facilities, an inpatient hospital where a spirit level was utilized and an ambulatory facility where it was not. We excluded 47 patients with a BMI>40, age>68 or a surgical indication other than osteoarthritis who were not candidates for the ambulatory center. Cup inclination angles were measured from de-identified plain radiographs by two blinded investigators not involved in the index procedures. The effect of level usage on inclination angle was determined using multivariate regression analysis.

The mean inclination angle for the 68 hips performed with the level was 42.9 degrees (95% CI: 41.7–44.0) compared to 46.5 degrees (95% CI: 45.2–47.7) for the 52 hips without it (p<.001). Regression analysis demonstrated a 9.1% difference in cup inclination due to the level (p<.001), and THAs performed without the level were 3 times more likely to result in inclinations > 50 degrees (OR 2.8, p=.036). The two investigators' measurements demonstrated a correlation of 0.95 (95% CI: 0.93–0.97).

Use of a simple spirit level resulted in a significant reduction in the number of outliers compared to the freehand technique. The spirit level may be a simple and inexpensive tool to improve acetabular component abduction angles.

Among the most critical factors to reducing the risk of infection include the use of pre-incisional antibiotics, appropriate skin preparation with clippers (as opposed to a razor for hair removal) and the use of an alcohol-based skin preparation. Host factors are also likewise critically important including obesity, diabetes, inflammatory arthritis, renal insufficiency, skin disorders and patients who are otherwise immune-compromised. If modifiable risk factors are identified, it would seem reasonable to delay elective surgery until these can be optimised.

One other factor to consider is the nutritional status of the patient. In a study of 501 consecutive revisions, we found that serological markers suggestive of malnutrition (albumin, transferrin or total lymphocyte count) were extremely common. Specifically, 53% of patients who presented for treatment of a chronic infection had at least one marker for malnutrition, compared to 33% in the group of patients undergoing revision for an aseptic reason. Malnutrition was found to be an independent risk factor for septic failure (p < 0.001 and OR 2.1). Interestingly, malnutrition was most common among patients of normal weight but was also common among obese patients (so-called “paradoxical” malnutrition). What was more disturbing, however, was that of those patients undergoing an aseptic revision, serum markers of malnutrition were associated with a 6× risk of acute post-operative infection complicating the patient's aseptic revision. We have confirmed this association using the NSQIP database where hypoalbuminemia was associated with a higher risk of infection, pneumonia and readmission.

At our center, we also have studied the use of dilute betadine at the end of the case, prior to wound closure, in an attempt to decrease the load of bacteria in the wound. In a retrospective review the prevalence of acute post-operative infection was reduced from just under 1% (18/1862) to 0.15% (1 of 688; p = 0.04). It is critical that the betadine utilised be STERILE and the dilution we use is 0.35% made by diluting 17.5cc of 10% povidone-iodine paint in 500cc of normal saline.

Recurrent dislocation following total hip arthroplasty (THA) is a complex, multifactorial problem that has been shown to be the most common indication for revision THA. At our center, we have tried to approach the unstable hip by identifying the primary cause of instability and correcting that at the time of revision surgery.

Type 1:

Malposition of the acetabular component treated with revision of the acetabular component and upsizing the femoral head.

The most common etiologies of instability in our experience include cup malposition (Type 1) and abductor deficiency (Type 3).

We reviewed 75 hips revised for instability and at a mean 35.3 months 11 re-dislocations occurred (14.6%). Acetabular revisions were protective against re-dislocation (p<0.02). The number of previous operations (p=0.04) and previously failed constrained liners (p<0.02) were risk factors for failure. The highest risk of failure was in patients with abductor insufficiency with revisions for other etiologies having a success rate of 90%.

Although instability can be multifactorial, by identifying the primary cause of instability, a rational approach to treatment can be formulated. In general the poorest results were seen in patients with abductor deficiency. Given the high rate of failure of constrained liners (9 of the 11 failures were constrained), we currently are exploring alternatives such as dual mobility articulations. Our early experience with dual mobility suggests improved results when compared to constrained liners.

Malnutrition is a potentially modifiable risk factor that may contribute to complications following geriatric hip fracture surgery. The purpose of this study was to investigate the association between preoperative hypoalbuminemia, a marker for malnutrition, and complications during the thirty days following surgery for geriatric hip fracture.

The American College of Surgeons National Surgical Quality Improvement Program was used to conduct a retrospective cohort study of geriatric patients (>65 years) undergoing surgery for hip fracture. Patients without preoperative serum albumin concentration were excluded. Outcomes were compared between patients with and without hypoalbuminemia (defined as serum albumin concentration <3.5g/dL). All comparisons were adjusted for baseline differences between populations.

17,651 Patients were identified. Of these, 8,272 (46.9%) underwent hemiarthroplasty, 759 (4.3%) total joint arthroplasty, 324 (1.9%) percutaneous fixation, 2,445 (13.9%) plate/screw fixation, and 5,833 (33.1%) intramedullary fixation. The prevalence of hypoalbuminemia was 45.9% (Figure 1). The risk for death was strongly associated with serum albumin concentration, with a linear increase in risk observed as albumin fell below 3.5 g/dL (p<0.001; Figure 2). Following adjustment for all demographic, comorbidity, and procedural characteristics, patients with hypoalbuminemia had higher rates of death (9.94% versus 5.53%, adjusted relative risk [RR]=1.54, p<0.001), pneumonia (5.30% versus 3.77%, adjusted RR=1.20, p=0.012), sepsis (1.19% versus 0.53%, adjusted RR=1.90, p<0.001), and hospital readmission (10.91% versus 9.03%, adjusted RR=1.11, p<0.036; Table 1).

The present study suggests that hypoalbuminemia is a powerful independent risk factor for death following surgery for geriatric hip fracture. This association persists over-and-above any associations of death with age, sex, body mass index, and comorbidities. Based on these data, we propose that the nutritional status of hip fracture patients should receive greater attention, and that randomized trials testing for efficacy of aggressive postoperative nutritional interventions may be warranted.

For any figures or tables, please contact the authors directly by clicking on ‘Info & Metrics’ above to access author contact details.

Patients with a painful or failed total joint arthroplasties should be evaluated for periprosthetic joint infection (PJI). The purpose of this study was to determine if patients referred to a tertiary care centre had been evaluated for PJI according to the American Academy of Orthopaedic Surgeons (AAOS) clinical practice guidelines.

113 Patients with painful hip (43) or knee (70) arthroplasties were referred to a single provider by orthopaedic surgeons outside our practice between 2012 and 2014. We retrospectively evaluated the workup by referring physicians, including measurement of serum erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), performance of a joint aspiration if these values were abnormal, and obtainment of synovial fluid white blood cell (WBC) count, differential, and cultures.

Sixty-two of the 113 patients (55%) did not have a workup that followed AAOS guidelines. Serum ESR and CRP were ordered for 64 of the 113 patients (57%). Of 25 patients with elevated inflammatory markers warranting aspiration, 15 (60%) had an aspiration attempted, with synovial fluid WBC, differential, and cultures obtained in 9 of 12 (75%) aspirations that yielded fluid. Of the 62 patients with an incomplete infection workup, 11 (18%) had a bone scan, 6 (10%) a CT scan, and 3 (5%) an MRI. Twelve of the 113 patients (11%) were ultimately diagnosed with PJI, with 5 undiagnosed prior to referral.

The AAOS guidelines to evaluate for PJI are frequently not being followed. Improving awareness of these guidelines may avoid unnecessary and costly evaluations and delay in the diagnosis of PJI.

Recently, corrosion at the head-neck junction in metal-on-polyethylene bearing total hip arthroplasty (THA) has been recognized as a cause of adverse local tissue reactions (ALTR). Serum metal levels have been advocated as a tool for the diagnosis of ALTR, however no prior studies have specifically examined their utility. The purpose of this study was to determine the optimal cut-off values for serum cobalt and chromium in diagnosing ALTR after metal-on-polyethylene bearing THA.

We reviewed 447 consecutive patients with serum metal levels tested at our institution and identified 62 with a metal-on-polyethylene bearing who had axial imaging or underwent reoperation to confirm the presence or absence of ALTR. Receiver operating characteristic curves were produced to identify cut-off thresholds to optimize sensitivity and diagnostic test performance was characterized.

42 Of the 62 patients (66%) were positive for an ALTR. The best test for the diagnosis of ALTR was the serum cobalt level (area under the curve [AUC]=99%). A threshold cut-off of ≥ 1.0 ng/ml had a sensitivity of 100%, specificity of 90%, positive predictive value (PPV) of 96%, and negative predictive value (NPV) of 100%. Serum chromium levels were also diagnostic (AUC=87%). A threshold cut-off of ≥ 0.15 ng/ml had a sensitivity of 100%, specificity of 50%, PPV of 81%, and NPV of 100%. Finally, serum cobalt to chromium ratio was also helpful for diagnosis (AUC=90%). A threshold cut-off of 1.4 for the cobalt to chromium ratio offered a sensitivity of 93%, specificity of 70%, PPV of 87%, and NPV of 82%.

Measurement of serum cobalt with a threshold value of 1.0 ng/ml in our experience is the best test for identifying the presence of ALTR in patients with a metal-on-polyethylene THA. Measurement of chromium and the ratio of cobalt to chromium are also of value.

Introduction

Preservation of the anterior cruciate ligament (ACL), along with the posterior cruciate ligament, is believed to improve functional outcomes in total knee replacement (TKR). The purpose of this study was to examine gait differences and muscle activation levels between ACL sacrificing (ACL-S) and bicruciate retaining (BCR) TKR subjects during level walking, downhill walking, and stair climbing.

INTRODUCTION

As the demographic of the patient population requiring revision total knee arthroplasty (rTKA) continues to expand, varying preoperative conditions and activity levels need to be taken into consideration when analyzing postoperative outcomes. Factoring in preoperative activity levels can help manage the expectations of patients. The purpose of this study was to analyze the outcomes of low and high activity patients receiving a contemporary rTKA.

Introduction

The benefits of femoral head-neck modularity in hip surgery have been recognized for decades. However, reports of head/neck taper fretting & corrosion has led to research being conducted, yet the clinical effect of these processes remains unclear. Whilst femoral head size, material and the characteristics of the taper have been a focus of research, potential contributing variables such as in vivo head-neck assembly technique on the performance of these connections is not clear. We performed an observational study to investigate variation in femoral head-neck taper assembly during surgery, with the initial focus being the number of head impactions.

Introduction

The first highly crosslinked and melted polyethylene acetabular component for use in total hip arthroplasty was implanted in 1998 and femoral heads larger than 32mm in diameter introduced 2004.

The purpose of this study was to re-assemble a previous multi-center patient cohort in order to evaluate the radiographic and wear analysis of patients receiving this form of highly crosslinked polyethylene articulating against large diameter femoral heads at a minimum of 10 years follow-up.

Introduction

The first highly crosslinked and melted polyethylene acetabular component for use in total hip arthroplasty was implanted in 1998. Numerous publications have reported reduced wear rates and a reduction in particle induced peri-prosthetic osteolysis at short to mid-term follow-up.

The purpose of this study was to re-assemble a previous multi-center patient cohort in order to evaluate the radiographic and wear analysis of patients receiving this form of highly crosslinked polyethylene articulating against 32mm femoral heads or less at a minimum of 13 years follow-up.

Minimizing the risk of periprosthetic joint infection (PJI) is of interest to all surgeons performing hip and knee arthroplasty. Among the most critical factors to reducing the risk of infection include the use of pre-incisional antibiotics, appropriate skin preparation with clippers (as opposed to a razor for hair removal) and the use of an alcohol-based skin preparation. Host factors are also likewise critically important including obesity, diabetes, inflammatory arthritis, renal insufficiency, skin disorders and patients who are otherwise immune-compromised. If modifiable risk factors are identified, it would seem reasonable to delay elective surgery until these can be optimised.

One other factor to consider is the nutritional status of the patient. In a study of 501 consecutive revisions, we found that serological markers suggestive of malnutrition (albumin, transferrin or total lymphocyte count) were extremely common in the revision population. Specifically, among patients who presented for treatment of a chronic infection, 53% (67 of 126) had at least one marker for malnutrition. The prevalence of serological markers of malnutrition was lower (33%) in the group of patients undergoing revision for an aseptic reason suggesting that malnutrition was a risk factor for septic failure (p < 0.001 and OR 2.1). Interestingly, malnutrition was most common among patients of normal weight but was also common among obese patients (so-called “paradoxical” malnutrition). What was more disturbing, however, that of those patients undergoing an aseptic revision, serum markers of malnutrition were associated with a 6x risk of acute postoperative infection complicating the patient's aseptic revision.

At our center, we also have studied the use of dilute betadine at the end of the case, prior to wound closure, in an attempt to decrease the load of bacteria in the wound. In a retrospective review the prevalence of acute postoperative infection was reduced from just under 1% (18/1862) to 0.15% (1 of 688; p = 0.04). It is critical that the betadine utilised be STERILE and the dilution we use is 0.35% made by diluting 17.5cc of 10% povidone-iodine paint in 500cc of normal saline. Although this is a retrospective review, it does suggest a benefit and we have not seen any problems associated with its use.

Recurrent dislocation following total hip arthroplasty (THA) is a complex, multifactorial problem that has been shown to be the most common indication for revision THA. At our center, we have tried to approach the unstable hip by identifying the primary cause of instability and correcting that at the time of revision surgery.

Type 1: Malposition of the acetabular component treated with revision of the acetabular component and upsizing the femoral head.

Type 2: Malposition of the femoral component treated with revision of the femur and upsizing the femoral head.

Type 3: Abductor deficiency treated with a constrained liner or dual mobility bearing.

Type 4: Soft tissue or bony impingement treated with removal of impingement sources and upsizing the femoral head.

Type 5: Late wear of the bearing treated with bearing surface exchange and upsizing the femoral head.

Type 6: Unclear etiology treated with a constrained liner or dual mobility articulation.

The most common etiologies of instability in our experience include cup malposition (Type 1) and abductor deficiency (Type 3).

We reviewed 75 hips revised for instability and at a mean 35.3 months 11 re-dislocations occurred (14.6%). Acetabular revisions were protective against re-dislocation (p<0.015). The number of previous operations (p=0.0379) and previously failed constrained liners (p<0.02) were risk factors for failure. The highest risk of failure was in patients with abductor insufficiency with revisions for other etiologies having a success rate of 90%.

Although instability can be multifactorial, by identifying the primary cause of instability, a rational approach to treatment can be formulated. In general the poorest results were seen in patients with abductor deficiency. Given the high rate of failure of constrained liners (9 of the 11 failures were constrained), we currently are exploring alternatives such as dual mobility articulations.

Wound closure is typically not the surgeon's favorite part of the case. It is critical, however, for preventing infection, avoiding early re-operation and is the portion of the procedure that is most directly visible to the patient. The purpose of this study was to investigate the use of bidirectional, barbed suture for wound closure in primary total hip (THA) and knee arthroplasty (TKA) to determine whether its use is safe, cosmetic and associated with time savings when compared with traditional suture.

We carried out a blinded, randomised controlled trial comparing bidirectional, barbed suture (Quill™ SRS; Angiotech Pharmaceuticals) and a traditional absorbable layered closure following primary THA and TKA. We randomised 20 THAs (10 Quill; 10 traditional) and 31 TKAs (16 Quill; 15 traditional). Power analysis determined that a minimum of 23 patients per arm of the study were required to show a significant difference in closure times using an alpha of 0.05 and a beta of 0.80.

Wound closure in the Quill group was significantly faster than traditional suture by a mean of 4.1 minutes (9.2 vs. 13.2 minutes; p = 0.0005). Traditional closure required a mean 5.6 sutures, compared to a mean 2.7 sutures (p < 0.0001). The unit cost of the barbed suture was 5–12 times that of conventional suture. One patient who had undergone Quill closure developed a superficial reaction that was managed non-operatively.

Our results have been confirmed by a similar recently published randomised study by Gilland et al, who showed a mean reduction in closure time of 4.7 minutes. However, these authors concluded that overall costs were lower with a barbed suture based on a reduction in operative times. This method of closure has also been shown to provide a stronger and more water-tight closure than traditional interrupted sutures.

Minimizing the risk of periprosthetic joint infection (PJI) is of interest to all surgeons performing hip and knee arthroplasty. Among the most critical factors to reducing the risk of infection include the use of pre-incisional antibiotics, appropriate skin preparation with clippers (as opposed to a razor for hair removal) and the use of an alcohol-based skin preparation. Host factors are also likewise critically important including obesity, diabetes, inflammatory arthritis, renal insufficiency, skin disorders and patients who are otherwise immune-compromised. If modifiable risk factors are identified, it would seem reasonable to delay elective surgery until these can be optimised.

One other factor to consider is the nutritional status of the patient. In a study of 501 consecutive revisions, we found that serological markers suggestive of malnutrition (albumin, transferrin or total lymphocyte count) were extremely common in the revision population. Specifically, among patients who presented for treatment of a chronic infection, 53% (67 of 126) had at least one marker for malnutrition. The prevalence of serological markers of malnutrition was lower (33%) in the group of patients undergoing revision for an aseptic reason suggesting that malnutrition was a risk factor for septic failure (p < 0.001 and OR 2.1). Interestingly, malnutrition was most common among patients of normal weight but was also common among obese patients (so-called “paradoxical” malnutrition). What was more disturbing, however, that of those patients undergoing an aseptic revision, serum markers of malnutrition were associated with a 6× risk of acute post-operative infection complicating the patient's aseptic revision.

At our center, we also have studied the use of dilute betadine at the end of the case, prior to wound closure, in an attempt to decrease the load of bacteria in the wound. In a retrospective review the prevalence of acute post-operative infection was reduced from just under 1% (18/1862) to 0.15% (1 of 688; p = 0.04). It is critical that the betadine utilised be STERILE and the dilution we use is 0.35% made by diluting 17.5 cc of 10% povidone-iodine paint in 500 cc of normal saline. Although this is a retrospective review, it does suggest a benefit and we have not seen any problems associated with its use.

This session will present a series of challenging and complex primary and revision cases to a panel of knee arthroplasty experts. A variety of cases representing the spectrum of not uncommonly presenting pathologies will be discussed in terms of appropriate work-up, clinical management, surgical approach, and aftercare. This will be an interactive case-based session that at its conclusion should leave the attendee with a more thorough approach to these challenging issues.

Constrained liners are a tantalizing solution to both prevent and treat instability, as they markedly increase the force needed for a dislocation to occur. They have, however, several important negatives that the surgeon must consider before entertaining their use including: Increased stresses at the implant bone interface which can increase the risk of loosening or cause catastrophic failure in the early post-operative period; Decreased range of motion with a greater risk of impingement; and Usually require an open reduction if they dislocate or otherwise fail.

Given the limitations of constrained liners, we have looked to dual mobility articulations as an alternative to constrained liners in the past five years in our practice, including patients with abductor deficiency.

We retrospectively compared a consecutive series of revision THA that were at high risk for instability and treated with either a constrained liner or a dual mobility articulation. Indications for both groups included abductor insufficiency, revision for instability, or inadequate intra-operative stability when trialing. Forty-three hips were reviewed in the constrained group (mean follow-up 3.4 years) and thirty-six in the dual-mobility group (mean follow-up 2.4 years). The rate of failure was compared using a Fisher's exact test with a p-value of < 0.05 considered significant.

At a minimum of two years, there were 10 dislocations in the constrained group (10/43 or 23.3%) compared to 3 in the dual-mobility group (3/36 or 8.3%; p = 0.06). There were 15 repeat revisions in the constrained group (10 for instability, 4 for infection, and 1 broken locking mechanism) compared to 4 in the dual mobility group (2 mechanical failures of cemented dual mobility liners with dislocation and 2 for infection); 34.9% vs. 11.1% (p = 0.01). With repeat revision for instability as an endpoint, the failure rate was 23% for the constrained group and 5.5% for the dual mobility group (p = 0.03). Mean Harris Hip Score (HHS) improved from 45 to 76 points in the constrained liner group, and from 46 to 89 points in the dual-mobility group.

Dual mobility articulations offer anatomic sized femoral heads that greatly increase jump distance, without many of the negatives of a constrained liner. While dual mobility is associated with its own concerns and problems (including intra-prosthetic dislocation and wear) our initial results suggest that they are a viable alternative to a constrained liner, even in the most challenging situations.

Obtaining adequate exposure is key to optimising outcomes in revision total knee arthroplasty. Goals of the exposure include protecting the extensor mechanism, safe removal of the components that are in place and implantation of the revision components. Challenges to these goals include prior skin incisions, arthrofibrosis, and patella baja.

Choosing a skin incision is the first important step. The blood supply to the skin is predominantly derived MEDIALLY and thus the most LATERAL skin incision that works for obtaining exposure is selected. If skin flaps are required, they MUST be full thickness as the blood supply to the skin runs deep just over the fascial layer and partial thickness flaps risk skin necrosis. Avoid acute angles between old skin incisions of <60 degrees and kin bridges, if necessary must be at least 6cm in width.

The work-horse of revision TKA is the medial parapatellar approach. It includes a generous medial release that allows the surgeon to externally rotate and deliver the tibia by pivoting on the extensor mechanism. An anterior synovectomy is then performed to re-establish the medial and lateral gutters followed by re-establishment of the space behind the patellar tendon to free it from the proximal tibia and finally subluxation of the patella (preferable to formal eversion). A lateral release (or peel of the soft tissue off of the lateral side of the patella) is a final step to mobilise the extensor mechanism (if required). After the components are removed, a posterior capsular release and re-establishment of the flexion space behind the femur further enhances tibial exposure for both bony preparation and revision component implantation.

If the above maneuvers are performed, and exposure is still inadequate, the easiest way to improve exposure is by performing a quadriceps snip. This is an oblique, apical extension of the arthrotomy ACROSS THE PATELLAR TENDON (NOT in the muscle; it is hard to repair if performed in the muscle). It is repaired side to side with no need to alter postoperative physical therapy and heals reliably.

A V-Y Quadricepsplasty is a proximal release of the extensor mechanism; essentially perform by connecting the apical extension of the medial parapatellar arthrotomy with a lateral release across the quadriceps tendon. It is classically indicated for patients with extensor mechanism contracture where the surgeon wishes to attempt lengthening the extensor mechanism. Usually results in increased flexion at the expense of an extensor lag and is used rarely in contemporary practice.

Tibial Tubercle Osteotomy is a distal release of the extensor mechanism that is most useful for accessing the canal to remove long-stemmed cemented tibial components. It is a coronal osteotomy made from the medial side of the tubercle that is usually made 5–8cm in length, tapering from approximately 1cm thick proximally to 5mm distally.

Revision of the failed femoral component of a total hip arthroplasty can be challenging. Multiple reconstructive options are available and the operation itself can be particularly difficult and thus meticulous preoperative planning is required to pick the right “tool” for the case at hand. The Paprosky Femoral Classification is useful as it helps the surgeon determine what bone stock is available for fixation and hence, which type of femoral reconstruction is most appropriate.

Monoblock, fully porous coated diaphyseal engaging femoral components are the “work-horse” of femoral revision. This type of a stem is used in my practice for Type 1–3a femoral defects. These stems are not used, however, in the following situations: The canal diameter is greater than 18mm; There is less than 4cm available for distal fixation in the isthmus; There is proximal femoral remodeling into retroversion.

While many surgeons often believe that revision femoral components need to be “long”, they really only need to be long enough to engage 4cm of intact femoral isthmus, which is oftentimes the shortest, “primary length” fully porous coated stem. Advantages of using a shorter revision stem include: Easier surgical technique as you avoid the femoral bow, with a lower risk of fracture and under-sizing; Preserves bone stock for future revisions if required; Easier to remove if required.

A “two-stage exchange” remains the gold standard for treatment of the infected TKA in North America. Although there is interest in “one-stage exchange” this technique is not as familiar to many US surgeons and it is unclear if the reported results of Europe can be translated to North American practice. Specific concerns include the “radicalness” of the debridement required (which oftentimes includes the collateral ligaments, hence the popularity of hinged implants where this approach is common) and the use of fully cemented stems, which are extremely difficulty to remove if infection recurs. Thus while the idea of a one stage exchange is attractive to many North American surgeons, careful study will be required to determine if success can be achieved with a more “conservative” debridement and the use of cementless stems which are preferred by some surgeons.

The basic principles of a two-stage exchange include: Thorough debridement of all infected appearing foreign material and all cement; Placement of an interval antibiotic loaded spacer (note that the addition of antibiotics to bone cement is NOT FDA approved) – 4–6g of antibiotics per pkg of cement; typically vancomycin + tobramycin; Higher viscosity cement may be associated with higher elution; The combination of antibiotics also leads to higher elution.

Antibiotic spacers can be “articulating” or “static”. Potential advantages of an articulating spacer include greater patient comfort and an easier approach at the second stage exchange as soft tissue tension and range of motion is maintained. However, these spacers are oftentimes more costly and can break or dislocate.

The first stage is followed by approximately 6 weeks of organism specific IV antibiotics. An interdisciplinary approach with an infectious disease specialist, internal medicine and a nutritionist optimises outcomes.

Our protocol then includes weekly ESR and CRP to monitor their trend. These labs are re-checked two weeks after cessation of antibiotics to ensure the trend has not changed. The knee is routinely aspirated at this time point and the fluid obtained sent for a synovial fluid WBC count with differential and cultures (although the value of such cultures is controversial). We have found that while the ESR and CRP are significantly lower than prior to removal of the infected implant, they often times DO NOT normalise and there is no specific cut-off value that predicts persistent infection.

Obtaining adequate exposure is key to optimising outcomes in revision total knee arthroplasty. Goals of the exposure include protecting the extensor mechanism, safe removal of the components that are in place and implantation of the revision components. Challenges to these goals include prior skin incisions, arthrofibrosis, and patella baja.

Choosing a skin incision is the first important step. The blood supply to the skin is predominantly derived MEDIALLY and thus the most LATERAL skin incision that works for obtaining exposure is selected. If skin flaps are required, they MUST be full thickness as the blood supply to the skin runs deep just over the fascial layer and partial thickness flaps risk skin necrosis. Avoid acute angles between old skin incisions of <60 degrees and skin bridges, if necessary, must be at least 6cm in width.

The work-horse of revision TKA is the medial parapatellar approach. It includes a generous medial release that allows the surgeon to externally rotate and deliver the tibia by pivoting on the extensor mechanism. An anterior synovectomy is then performed to re-establish the medial and lateral gutters followed by re-establishment of the space behind the patellar tendon to free it from the proximal tibia and finally subluxation of the patella (preferable to formal eversion). A lateral release (or peel of the soft tissue off of the lateral side of the patella) is a final step to mobilise the extensor mechanism (if required). After the components are removed, a posterior capsulectomy is performed followed by re-establishment of the flexion space behind the femur further enhances tibial exposure for both bony preparation and revision component implantation.

If the above maneuvers are performed, and exposure is still inadequate, the easiest way to improve exposure is by performing a quadriceps snip. This is an oblique, apical extension of the arthrotomy ACROSS THE PATELLAR TENDON (NOT in the muscle; it is hard to repair if performed in the muscle). It is repaired side to side with no need to alter post-operative physical therapy and heals reliably.

The V-Y Quadricepsplasty is a proximal release of the extensor mechanism; essentially perform by connecting the apical extension of the medial parapatellar arthrotomy with a lateral release across the quadriceps tendon. It is classically indicated for patients with extensor mechanism contracture where the surgeon wishes to lengthen it. It usually results in increased flexion at the expense of an extensor lag and is used rarely in contemporary practice.

Tibial Tubercle Osteotomy is a distal release of the extensor mechanism that is most useful for accessing the canal to remove long-stemmed cemented tibial components. It is a coronal osteotomy made from the medial side of the tubercle that is usually made 5–8 cm in length, tapering from approximately 1cm thick proximally to 5mm distally.

Dislocation remains among the most common complications of, and reasons for, revision of both primary and revision total hip arthroplasties in the United States. Hence, there is great interest in maximising stability to prevent this complication.

Highly crosslinked polyethylene has allowed us to increase femoral head size, without a clinically important increase in wear. As femoral head size increases, stability is augmented, secondary to a decrease in component-to-component impingement, which is theoretically eliminated at head sizes greater than 36mm in diameter (however osseous impingement can still occur). Larger heads sizes also greatly increase the “jump distance” required for the head to dislocate (in an appropriately positioned cup) and eliminate the need for skirts. Hence, large heads have become the mainstay for preventing and treating instability in contemporary practice. Large heads, however, have been shown to have poor performance in patients with abductor insufficiency.

Constrained liners are a tantalising solution to both prevent and treat instability, as they markedly increase the force needed for a dislocation to occur. They have, however, several important negatives that the surgeon must consider before entertaining their use including: –

Increased stresses at the implant bone interface which can increase the risk of loosening or cause catastrophic failure in the early post-operative period

Given the limitations of constrained liners, we have moved to dual mobility articulations in most situations where we would have used a constrained liner in the past, including patients with abductor deficiency. These articulations offer anatomic sized femoral heads that greatly increase the jump distance, without many of the negatives of a constrained liner. While dual mobility is associated with its own concerns and problems (including intraprosthetic dislocation and wear) our initial results suggest that they are a viable alternative to a constrained liner, even in the most challenging situations.

The aim of the work is to develop innovative antibacterial surface modification treatments for titanium capable to limit the bacterial adhesion and proliferation as weel as the biofilm formation while maintaining an high osteointegrative potential. The goal is to contrast the infections which represent a serius complication related to the use of implantable devices.

Periprosthetic fractures present several unique challenges including gaining fixation around implants, poor bone quality and deciding on an appropriate treatment strategy.

A “two-stage exchange” remains the gold standard for treatment of the infected THA in North America. Although there is interest in “one-stage exchange” this technique is predicated on the use of fixation of the revision implants with antibiotic loaded cement, which is not as popular in North America.

Diagnosis is critical and in general consists of a screening serum ESR and CRP followed by selective aspiration if the above are abnormal and/or if the clinical history is suspicious. The aspirated fluid is sent for a synovial fluid WBC (cut-off approximately 3,000 WBC/μL), differential (cut-off 80% PMN) and culture.

The basic tenets of treatment include:

Thorough debridement of all infected appearing cement and all foreign material

Antibiotic spacers can be “articulating” or “static”. Potential advantages of an articulating spacer include greater patient comfort and an easier approach at the second stage exchange as leg length and soft tissue tension is maintained. However, these spacers are oftentimes more costly and can dislocate. May not be appropriate in cases where there is severe bone loss that cannot support partial weight bearing or if the abductors are compromised (higher risk of dislocation).

The first stage is followed by approximately 6 weeks of organism specific IV antibiotics. An interdisciplinary approach with an infectious disease specialist, internal medicine and a nutritionist optimises outcomes.

Our protocol then includes weekly ESR and CRP to monitor their trend. These labs are re-checked two weeks after cessation of antibiotics to ensure the trend has not changed. We have found that while the ESR and CRP are significantly lower than prior to the 1st stage, they often times DO NOT normalise and there is no specific cut-off value that predicts persistent infection. An intra-operative aspiration for synovial fluid WBC count and differential is obtained intra-operatively (cut-off values of approximately 3,000 WBC/μl and 80% PMN) and are the best tests to identify persistent infection.

Introduction

Total hip replacements using highly cross-linked polyethylene show excellent clinical outcomes, low wear, and minimal lysis at 5 years follow-up. A recent RSA study reports a significant increase in femoral head penetration between 5 and 7 years. This study is a multi-center radiographic analysis to determine whether the RSA observation is present in a large patient cohort.