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Year of Publication
1.  Emerging Ideas: Instability-induced Periprosthetic Osteolysis Is Not Dependent on the Fibrous Tissue Interface 
Stable initial fixation of a total joint arthroplasty implant is critical to avoid the risk of aseptic loosening and premature clinical failure. With implant motion, a fibrous tissue layer forms at the bone-implant interface, leading to implant migration and periprosthetic osteolysis. At the time of implant revision surgery, proresorptive signaling cytokines are expressed in the periimplant fibrous membrane. However, the exact role of this fibrous tissue in causing periprosthetic osteolysis attributable to instability remains unknown.
We propose an alternative mechanism of periprosthetic osteolysis independent of the fibrous tissue layer, where pressurized fluid flow along the bone-implant interface activates mechanosensitive osteocytes in the periprosthetic bone, causing the release of proresorptive cytokines and subsequent osteoclast differentiation and osteolysis.
Method of Study
An animal model for instability-induced osteolysis that mimics the periprosthetic bone-implant interface will be used. In this model, a fibrous tissue membrane is allowed to form in the periprosthetic zone, and pressurized fluid flow transmitted through this membrane reliably creates osteolytic lesions in the periprosthetic bone. In this study, half of the rats will have the fibrous tissue present, while the other half will not. We will determine whether the fibrous tissue membrane is essential for the release of proosteoclastic cytokines, leading to osteoclast differentiation and periprosthetic bone loss, by measuring the volume of bone resorption and presence of proresorptive cytokines at the bone-implant interface.
We will determine whether the fibrous tissue membrane is crucial for osteoclastogenic signaling in the setting of periimplant osteolysis. In the future, this will allow us to test therapeutic interventions, such as specific cytokine inhibitors or alterations in implant design, which may translate into new, clinically relevant strategies to prevent osteolysis.
PMCID: PMC3706676  PMID: 23463289
2.  Hip Arthroscopy: The Use of Computer Assistance 
HSS Journal  2013;9(1):70-78.
Hip arthroscopy is rapidly becoming the mainstay of treatment for femoroacetabular impingement (FAI), but remains technically demanding and has its limitations. The failures of arthroscopic FAI surgery due to inaccurate and inadequate resection are reported to be increasing. Computer-assisted surgery (CAS) can theoretically improve the accuracy and precision of the osseous resections required to treat FAI. It does so by providing a preoperative assessment tool, an intraoperative tracking device, and a robotic-assisted cutting instrument.
The purpose of this review is to discuss the evolution of CAS to address the current limitations of arthroscopic FAI surgery and propose the features required of the ideal CAS solution for FAI.
A computerized keyword search of MEDLINE was performed for studies that investigated the use of computer assistance in FAI surgery. Data was collected on preoperative assessment tools, intraoperative navigation programs, and robotic-assisted execution of FAI surgery.
Sixty-one articles were identified after the keyword search. Nineteen studies met our inclusion criteria. Thirteen studies were selected to address our study questions: three studies were analyzed for preoperative planning, six for navigated osseous resection, and four for robotic-assisted execution.
Navigation and robotic-assisted surgery can preoperatively plan and execute osseous resection with greater accuracy compared to freehand techniques, although the clinical success and cost-effectiveness has yet to be demonstrated. The ideal CAS solution must be able to virtually plan a resection, guide the surgeon towards accurate execution of the plan, and facilitate post-resection assessment of the adequacy of resection.
PMCID: PMC3640715  PMID: 24426847
femoroacetabular impingement; computer-assisted surgery; non-arthritic hip pain; osteochondroplasty; osseous resection
3.  Ideal Femoral Head Size in Total Hip Arthroplasty Balances Stability and Volumetric Wear 
HSS Journal  2012;8(3):270-274.
Over the last several years, a trend towards increasing femoral head size in total hip arthroplasty to improve stability and impingement free range of motion has been observed.
The specific questions we sought to answer in our review were: (1) What are the potential advantages and disadvantages of metal-on-metal, ceramic-on-ceramic, and metal-on-polyethylene bearings? (2) What is effect that femoral head size has on joint kinematics? (3) What is the effect that large femoral heads have on bearing surface wear?
A PubMed search and a review of 2012 Orthopaedic Research Society abstracts was performed and articles were chosen that directly answered components of the specific aims and that reported outcomes with contemporary implant designs or materials.
A review of the literature suggests that increasing femoral head size decreases the risk of postoperative dislocation and improves impingement free range of motion; however, volumetric wear increases with large femoral heads on polyethylene and increases corrosion of the stem in large metal-on-metal modular total hip arthroplasty (THA); however, the risk of potentially developing osteolysis or adverse reactions to metal debris respectively is still unknown. Further, the effect of large femoral heads with ceramic-on-ceramic THA is unclear, due to limited availability and published data.
Surgeons must balance the benefits of larger head size with the increased risk of volumetric wear when determining the appropriate head size for a given patient.
PMCID: PMC3470670  PMID: 24082871
femoral head size; total hip arthroplasty; volumetric wear; large femoral heads; dislocation
4.  Clinical Results and Failure Mechanisms of a Nonmodular Constrained Knee Without Stem Extensions 
HSS Journal  2012;8(2):96-102.
In the setting of persistent knee instability despite appropriate ligament balancing for primary total knee arthroplasty, most surgeons advocate the use of an implant with increased articular constraint. These implants are commonly supplemented with stem extensions to improve stress transfer and decrease the risk of aseptic loosening. However, disadvantages exist with the use of stem extensions, including increased cost, intramedullary invasion, and diaphyseal pain. The objectives of this study were to (1) compare the clinical results as assessed by the Knee Society, Hospital for Special Surgery, and SF-12 scores, (2) determine the incidence of failure as defined by the need for a revision procedure, and (3) to analyze the causes or modes of failure of a nonmodular constrained condylar knee without the use of stem extensions versus a conventional, posterior-stabilized design.
Materials and Methods
From 2002 to 2007, 190 TKAs were implanted using a primary, nonmodular constrained (NMC) prosthesis without stem extensions. During the same time period, clinical data were available for 140 TKAs implanted using a standard, posterior-stabilized (PS) design. Preoperative demographic data was reviewed, in addition to the rate and reason for revision in each cohort. Clinical data included HSS, Knee Society, and SF-12 scores at the latest follow-up, and the results of the NMC and PS cohorts were statistically compared using a Student’s two-tailed t test.
The mean age of patients in the NMC cohort was 72.3 ± 10.2 years, and the mean length of follow-up was 7.3 ± 2.1 years. The mean age of the PS cohort was 67.1 ± 8.7 years, with a mean follow-up of 6.1 ± 2.2 years. No statistically significant differences in the HSS, Knee Society, or SF-12 scores were appreciated between the two cohorts. The revision rate in the NMC cohort was 4.2 % compared to 4.3 % for the PS cohort. The most common cause of failure in the NMC cohort was femoral component loosening, all of which occurred when Palacos cement was used for fixation. NMC components (55.6 %) implanted with Palacos cement failed due to femoral component loosening. In contrast, all PS components requiring revision were revised for persistent instability.
At mid-term follow-up, NMC prostheses without stem extensions have excellent clinical results and are a viable option for patients with ligamentous instability. The use of Palacos cement in this scenario was associated with a high rate of femoral component loosening, possibly due to the decreased intrusion depth of Palacos when compared to Simplex cement.
PMCID: PMC3715634  PMID: 23874246
nonmodular; constrained total condylar knee; component loosening; Palacos cement
5.  Technique for Margin Convergence in Rotator Cuff Repair 
HSS Journal  2011;7(3):208-212.
The purpose of the present study is to describe the technique of margin convergence for U-shaped rotator cuff tears and report the clinical outcomes and ultrasonography with a minimum of 2 years follow-up. Three hundred eleven patients with a rotator cuff tear were prospectively enrolled in a registry at one institution. Inclusion criteria included any patient undergoing arthroscopic margin convergence for a rotator cuff tear. Exclusion criteria included open or mini-open rotator cuff repairs or suture anchor fixation to the cuff insertion without margin convergence. The outcome measurements included physical examination, manual muscle testing, the American Shoulder and Elbow Surgeons (ASES) score, and ultrasonography. Nineteen patients met the study criteria and 13 were available for 2-year follow-up (68.4%). The mean age of this cohort was 62.2 ± 7.5 years with a mean pre-operative rotator cuff tear size of 4.0 ± 1.6 cm. The ASES score increased significantly from 50.0 ± 17.7 before surgery to 83.3 ± 19.5 at 2 years (P = 0.01). The active forward elevation also improved from 156.2 ± 11.9° before surgery to 168.0 ± 12.1 at 2 years (P = 0.03). The active external rotation 54.4 ± 14.5 at baseline and improved to 57.1 ± 19.1 at 2 years (P = 0.04). The strength also increased significantly from 6.7 ± 6.4 to 10.6 ± 4.9 lb at 1 year (P = 0.048). The post-operative ultrasound demonstrated that 46.2% of rotator cuff tears were healed at 2 years. In conclusion, margin convergence is a useful technique for U-shaped tears that are difficult to mobilize.
PMCID: PMC3192885  PMID: 23024615
margin convergence; rotator cuff; shoulder arthroscopy
6.  Functional and Emotional Results Differ After Aseptic vs Septic Revision Hip Arthroplasty 
HSS Journal  2011;7(3):235-238.
It is widely believed that a deep implant infection leads to poor functional and emotional outcomes following total hip arthroplasty.
The purpose of this retrospective comparative review was to determine if patients who undergo two-stage, septic revision hip arthroplasty will have decreased emotional and general health scores, in addition to decreased function, compared to the aseptic revision group.
Patients and Methods
One hundred forty-five of 195 patients who underwent aseptic total hip revision for aseptic loosening (mean follow-up = 61 months) and 45 of 73 patients who underwent two-stage, septic revision hip arthroplasty (mean follow-up = 48 months) met the inclusion criteria and had a technically successful outcome. All patients were retrospectively evaluated using Harris Hip Scores (HHS), ad hoc questions, and the SF-36 Health Survey.
The average HHS were 73.2 ± 20.5 (aseptic) and 57.4 ± 20.6 (septic). Significant differences in the SF-36 Health Survey were found between the two groups in: physical functioning (p = 0.026) and role limitations due to physical health (p = 0.004). No significant difference in SF-36 scores was seen in: Energy/Fatigue, General Health Perception, Personal or Emotional Problems, Role Limitations due to Emotional Well Being, Social Functioning, and Bodily Pain.
Two-stage, septic revision produces a poor functional outcome compared to aseptic revision; however, the overall impact of a septic revision emotionally and socially was not significantly different than patients undergoing aseptic revision.
PMCID: PMC3192895  PMID: 23024619
septic; aseptic; revision; outcomes; hip arthroplasty
7.  Defining the Origins of the Iliofemoral, Ischiofemoral, and Pubofemoral Ligaments of the Hip Capsuloligamentous Complex Utilizing Computer Navigation 
HSS Journal  2011;7(3):239-243.
To use computer navigation software to investigate the specific origins of the hip capsuloligamentous complex.
Six fresh frozen cadaver hips were anatomically landmarked utilizing a three-dimensional computer navigation system. The acetabular origins of the iliofemoral, pubofemoral, and ischiofemoral ligaments were statically digitized. Computer software was used to create a 180° (6:00) meridian line positioned over the midpoint of the acetabular notch, and to present the results in a clocklike manner in hours and minutes (00:00) and also degrees relative to the 12 o’clock position.
The iliofemoral ligament origin starts at 17° (±31°) from the 12 o’clock position, or 12:35 (±1:02) in hours and minutes, and ends at 69° (±13°) or 2:18 (±0:25), spanning a mean distance of 52° (±19°). The ischiofemoral ligament has the broadest origin, starting at 262° (±12°) or 8:44 (±0:24), and ending at 353° (±17°) or 11:45 (±0:14), spanning a mean distance of 90° (±6°). The pubofemoral ligament origin is the smallest, starting at 121° (±5°) or 4:02 (±0:11), and ending at 163° (±9°) or 5:27 (±0:18), spanning a mean distance of 42° (±5°). The iliofemoral ligament origin demonstrates the greatest anatomic variability with regards to its location and its size (p = 0.002).
This study demonstrates that there is significant variability in the size and location of the iliofemoral ligament origin versus the pubofemoral and ischiofemoral ligaments.
Level of Evidence
Level IV anatomic cadaveric study. See the guidelines online for a complete description of level of evidence.
PMCID: PMC3192898  PMID: 23024620
hip ligaments; computer navigation; hip capsule; hip arthroscopy
8.  Traumatic Osteochondral Injury of the Femoral Head Treated by Mosaicplasty: A Report of Two Cases 
HSS Journal  2010;6(2):228-234.
The increased risk of symptomatic progression towards osteoarthritis after chondral damage has led to the development of multiple treatment options for cartilage repair. These procedures have evolved from arthroscopic lavage and debridement, to marrow stimulation techniques, and more recently, to osteochondral autograft and allograft transplants, and autogenous chondrocyte implantation. The success of mosaicplasty procedures in the knee has led to its application to other surfaces, including the talus, tibial plateau, patella, and humeral capitellum. In this report, we present two cases of a chondral defect to the femoral head after a traumatic hip dislocation, treated with an osteochondral autograft (OATS) from the ipsilateral knee, and the inferior femoral head, respectively, combined with a surgical dislocation of the hip. At greater than 1 year and greater than 5 years of follow-up, MRI studies have demonstrated good autograft incorporation with maintenance of articular surface conformity, and both patients clinically continue to have no pain and full active range of motion of their respective hips. In our opinion, treatment of osteochondral defects in the femoral head surface using a surgical dislocation combined with an OATS procedure is a promising approach, as full exposure of the femoral head can be obtained while preserving its vasculature, thus enabling adequate restoration of the articular cartilage surface.
PMCID: PMC2926357  PMID: 21886541
hip dislocation; osteochondral autograft transplant; femoral head; osteochondral defect; osteochondral injury; mosaicplasty

Results 1-8 (8)