Abstract:

Metal-on-metal bearings are promoted as a low wear bearing alternative to traditional hip replacement bearings. While most in vitro studies support this, recent clinical reviews have found a significant number of early revisions in some designs of metal-on-metal bearings related to wear. Metal-on-metal bearings exhibit a bi-phasic wear pattern with high initial wear that generally settles down to low steady state wear. Previous publications from the authors have found that steady state wear occurs due to the formation of a critical conforming contact area. This contact area was found to be surprisingly constant regardless of bearing size, clearance, or even contact mode. The authors hypothesized that steady state wear may never be reached if formation of this critical conforming contact area is disrupted. Several hip simulator tests were performed to assess the wear performance of generic metal-on-metal samples at various angles of inclination. Three-dimensional modeling was performed on the generic bearing design as well as typical resurfacing and hemispherical bearing designs including various sizes and clearance ranges. Simulator results support the hypotheses, and wear rates were linear or accelerating when the critical contact area size could not be achieved due to its proximity to the rim of the bearing. Modeling studies show a correlation between bearing size and design and the maximum inclination angle allowed to reach steady state conditions. Smaller bearing size and shallower cup designs were found to reduce the maximum safe inclination angle and this corresponds to clinical observation of increased failure rates in these bearings. This simple method for assessing runaway wear risk can be utilized in the design of more robust and forgiving metal-on-metal bearings.

Authors:

Reginald K. Lee, MS, Jason Longaray, BS, Aaron Essner, MS, Aiguo Wang, PhD

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Abstract:

Modular total hip arthroplasty (THA) components have evolved significantly as the success of uncemented femoral fixation has been proven. Current trends in the United States include widespread use of cementless components (acetabular and femoral), usually with monoblock femoral stems with modular heads. Femoral offset has been proven to play a vital role in hip abductor strength, hip range of motion, and hip stability. Also critical to hip stability is the orientation of the acetabular and femoral components. Thus, offset and component positioning are fundamental to success in THA. Modularity of the femoral neck has been proposed to aid in further customizing the THA component fit. Neck-modular stems enable the adjustment of leg length, femoral anteversion, and femoral offset independently of stem size. Modularity of the neck allows the surgeon to precisely match the anatomic characteristics of each patient to yield improved range of motion, stability, abductor strength, and leg length equality. Disadvantages are related to cost and the addition of another interface. Neck-modular femoral stems are not a new concept; however, as tough component manufacturing has advanced, these stems have been reintroduced to the armamentarium of the hip surgeon.

Authors:

Nitin Goyal, MD, William J. Hozack, MD

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Abstract:

Reconstruction of the failed acetabular component in total hip arthroplasty (THA) can be challenging. Although there are multiple reconstructive options available, a cementless acetabular component inserted with screws has been shown to have good intermediate-term results and is the reconstructive method of choice for the majority of acetabular revisions This reconstruction is feasible provided at least 50% of the implant contacts host bone. When such contact is not possible, and there is adequate medial and peripheral bone, techniques using alternative uncemented implants can be used for acetabular reconstruction. An uncemented cup can be placed at a "high hip center." Alternatively, the acetabular cavity can be progressively reamed to accommodate extra-large cups. Oblong cups, which take advantage of the oval-shaped cavity resulting from many failed acetabular components, can also be used. The success of these cementless techniques depends on the degree and location of bone loss.

Authors:

Paolo Cherubino, MD, Fabio D'Angelo, MD, Michele Francesco Surace, MD, Luigi Murena, MD, Ettore Vulcano, MD

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Abstract:

Acetabular labral tears have been the focus of much attention in recent years. With the increased use of hip arthroscopy and magnetic resonance arthrography, the infrequent labral tear has proved to be more prevalent than previously thought. The majority of labral tears occur due to an underlying anatomic abnormality. Anatomic abnormalities that can lead to labral tears include femoracetabular impingement, acetabular retroversion, abnormal femoral head, Legg Calvé Perthes, slipped capital epiphysis, capsular laxity, and dysplasia of the hip. Tears in the labrum may lead to the advancement of osteoarthritis. Optimal management of a labral tear may involve addressing underlying anatomic abnormalities in addition to the labral tear itself.

Authors:

Raviinder Parmar, BS, Javad Parvizi, MD, FRCS

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Abstract:

In the case of extensively damaged meta-diaphyseal femoral bone with cortices thinning and widened femoral canal, tapered stems allow a good primary fixation and early weight-bearing. A retrospective review was conducted to evaluate long-term results of modular revision taper stems implanted from March 1999 to December 2002. Sixty-five consecutive hip revision surgeries were performed, mostly for aseptic loosening (75% of the cases). Femoral bone stock defects were classified according to AAOS's criteria and consisted mainly in type II (cavitary defects, 44.6%) and type III (combined defects, 33.9%). A trochanteric osteotomy was performed in 25 cases (38%) to remove primary implants that were cemented in 35 cases (54%). The mean postoperative follow-up was 109 months (range, 76 to 131 months). Clinical assessment at follow-up showed a significantly improved mean Harris Hip Score from 42 points preoperatively to 81 points postoperatively, while the x-ray examination did show a satisfactory distal integration of the stem in all cases and satisfactory reconstitution of the femoral bone stock in 47% of cases. The average subsidence of the stem at follow-up was less than one millimeter. According to data analysis, a leg-length discrepancy exceeding 15 millimeters caused significantly worse functional outcome and pain.

Authors:

Paolo Cherubino, MD, Alessandro Fagetti, MD, Fabio D'Angelo, MD, Michele Francesco Surace, MD

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Abstract:

Emerging minimally invasive surgery (MIS) techniques in hip arthroplasty heralded an increase in intraoperative femoral periprosthetic fractures, likely due to diminished visibility, auditory, and tactile feedback. This study attempts to identify a method to supplement the surgeon's tactile and auditory senses by analyzing vibration characteristics during femoral component impaction. A cementless femoral component was instrumented with accelerometers and a piezoelectric (PZT) patch. Data was obtained during implant impaction into replicate femurs. Acceleration measurements were obtained and signal processing techniques were applied. Metrics were analyzed from PZT excitation data. The two most correlative indices are the frequency of the anti-resonance in the 10.5 to 12 kHz band and the peak magnitude in the 9 to 11 kHz band. Both demonstrate good convergence as the prosthesis is inserted. Impact test data revealed the sum of the acceleration divided by the sum of the impact force demonstrates good convergence with implant insertion. This pattern of convergence indicates these two indices may demonstrate the ability to accurately predict optimal implant seating. This methodology is promising and has the potential to enable intraoperative determination of maximal femoral component seating and provide the surgeon valuable information to potentially prevent intraoperative fractures.

Authors:

R. Michael Meneghini, MD, Mike Guthrie, BS, Hunter D. Moore, BS, Deena Abou-Trabi, BS, Phillip Cornwell, PhD, Aaron G. Rosenberg, MD

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Abstract:

Concerns about blood loss and the safety of allogenic blood transfusion have led to the development of many transfusion options for lower extremity joint arthroplasty. Techniques for dealing with such blood loss include allogenic blood transfusion, autologous donation and transfusion, hemodilution, perioperative blood salvage, intraoperative cell savers, bipolar sealers, and pharmacological agents. A blood management strategy must consider both the patient and the surgical procedure, assess the transfusion risks, and formulate a plan to address them appropriately. This article is an overview of the blood management techniques for lower extremity joint arthroplasty. The purpose of this review is to report our opinion regarding the use of alternative blood management strategies and to discuss the possible advantages and disadvantages of each technique. The results of this review indicate that a patient-focused algorithm using one or more strategies such as preoperative administration of erythropoietin, preoperative autologous blood donation, use of a bipolar sealer, intraoperative blood collection and reinfusion, as well as postoperative reinfusion drains may reduce the need for allogenic blood transfusions in patients undergoing primary and revision lower-extremity joint arthroplasties. The authors believe that a patient-specific algorithm utilizing the aforementioned techniques can lead to a substantial decrease in morbidity and mortality and an overall cost saving for both patients and medical institutions.

Authors:

Slif D. Ulrich, MD, Brad Kyle, BS, Aaron J. Johnson, MD, Mike G. Zywiel, MD, Michael A. Mont, MD

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Abstract:

Recently, studies have begun to assess the use of custom-fit arthroplasty sytsems that use magnetic resonance imaging to determine component placement. The purpose of this study was to assess how commonly this new technique is being used by surgeons and whether they perceive any benefits to their patients and/or to their practices. Fifty orthopaedic surgeons responded to a 19-question survey regarding custom-fit positioning total knee arthroplasty as part of a regional orthopaedic meeting. Overall, 10 of the 50 surgeons surveyed reported using custom-fit positioning technology. Of the remaining questionnaire participants, 29 of 40 indicated that they were interested in trying the new technique. The two reasons that were most frequently cited by the surgeons who were not interested in adopting the technique were costs and not enough clinical outcomes reports. The results of the present study suggest that if additional clinical studies at longer-term follow-up support these findings, then more surgeons may adopt this technique. Although cost was a perceived barrier to using this technique, the results of this survey suggest that some surgeons who use this technique may have reduced procedure time.

Authors:

Michael A. Mont, MD, Aaron J. Johnson, MD, Michael G. Zywiel, MD, Peter M. Bonutti, MD

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Abstract:

Previous studies have demonstrated that using a bipolar sealer device for hemostasis in hip and knee arthroplasty results in a decreased blood loss and transfusion requirement. The anterior supine intermuscular total hip arthroplasty is a minimally invasive approach with a faster initial recovery compared with more traditional hip replacement surgery. A retrospective consecutive series of 100 anterior supine total hip arthroplasties performed by one surgeon was reviewed. In the first 50 cases, traditional electrocautery was used. In the second 50 cases, a bipolar sealer device was used. No significant differences with operative times, intraoperative blood loss, postoperative hemoglobin levels, and length of hospitalization were demonstrated between the two groups. There was a lower rate of intraoperative and postoperative transfusions in the bipolar sealer group.

Authors:

Michael J. Morris, MD, Keith R. Berend, MD, Adolph V. Lombardi, Jr., MD, FACS

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Abstract:

This prospective, randomized study compares functional outcomes between a novel support device (Secure Tracks™) and a standard walker following unilateral total knee replacement. Thirty patients were randomized for the study; 15 walker patients (70.7 +/- 6.4 yrs) and 15 Secure Track patients (68.2 +/- 6.7 yrs) (p=0.31). Total distance walked during all therapy sessions was nearly two times greater in the Secure Track (2,332 ft) than with the walker (1,241 ft)(p=.053). This trend began on the day of surgery (275 ft vs. 176 ft, p<.069) and was statistically significant by the following morning (287 ft vs. 151 ft, p=.019). Patients in the Secure Track spent a greater amount of time up and ambulating with the therapists in all sessions (.006< p >.30). At the first clinical follow-up, patients that had walked in the Secure Track completed the timed up and go test (TUG), a predictor of fall risk, 3 seconds faster than the standard rehabilitation group (9.6 vs. 12.9 seconds, p<.091). The novel therapy patients demonstrated significantly greater pain relief following the TUG test (p=.005). This study demonstrates that the choice of support device can increase patient ambulation following surgery, which will in turn improve functional outcomes and pain relief.

Authors:

David J. Jacofsky, MD, Sarah Kocisky, PA-C, Donald Dixon, PT, Marc C. Jacofsky, PhD

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Abstract:

Symptomatic degenerated spinal discs and spinal stenosis are common problems that can often be treated conservatively, but some require decompressive spinal surgery for relief. Traditional open spinal discectomy is associated with significant tissue trauma, higher morbidity and complication rates, a longer convalescence, and even destabilization of the spine. The trend of spinal surgery is rapidly moving toward less traumatic minimally invasive spine surgery (MISS).1,2 The problem that faces the surgeon performing endoscopic MISS is that it is done with limited surgical exposure and visualization of the surgical field. The surgical field can only be viewed through an endoscope to correlate the lesion/pathology in relationship to imaging studies aided by C-arm fluoroscopy. In response, a logical and simple Grid Positioning System (GPS) was developed to provide a precise surgical trajectory/approach for the disc lesion to undergo decompression. GPS involves 3D geometric triangulation of 3 different planes guided by fluoroscopy for introduction of surgical instruments along a geometric line toward the lesion without compromising healthy anatomical structures. This system facilitates MISS, especially in the morbidly obese. In this chapter, we will describe the GPS system and its application to aid in facilitating minimally invasive decompressive spine surgery for alleviating symptoms of degenerative spinal disease, herniated disc, and spinal stenosis, while avoiding the complications and risks of conventional more traumatic spinal surgery and fusion.

Authors:

John C. Chiu, MD, DSC, FRCS, Ali M. Maziad, MD

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Abstract:

Cervical discectomy is commonly required for spinal cord and nerve compression disorders. Currently, anterior cervical discectomy and fusion is the standard procedure for the treatment of cervical disc herniations and cervical degenerative disorders, whereas endoscopic cervical discectomy is considered an important alternative. Despite the advancement in surgical technology, endoscopically removing hard pathological tissues remains challenging. Inspired by lumbar epidurogram-guided decompression, we have developed an epidurogram-guided endoscopic cervical decompression technique. The technique uses contrast dye through cervical discography to generate an epidurogram. Under fluoroscopic view, the spinal cord is posterior to the contrast line. The endoscopic instruments can safely reach the epidural space, if it's necessary, as long as they stay anterior to the contrast line. We have used this technique to treat both soft and hard cervical disc herniations, and we have found it makes the surgical procedures safer when more aggressive decompression is required.

Authors:

Kai-Xuan Liu, MD, PhD, Bryan Massoud, MD

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