Introduction: Metal-on-metal (MOM) hip resurfacing releases ions locally and into the systemic circulation, raising concern for potential long term complications of elevated trace metals. This study was designed to monitor serum cobalt (Co) and chromium (Cr) levels in patients after MOM resurfacing hip arthroplasty with the Cormet 2000 prosthesis and to compare detected levels with those previously reported for hip resurfacing prostheses.

Methods: We prospectively followed patients receiving the Cormet 2000 device. Serum samples were collected at 6 months, 1, 2, and 3 years following surgery. Pre-operative controls were obtained from subjects without implants. Serum Co/Cr levels were determined using high-resolution inductively coupled plasma mass spectrometry. ANOVA was used to compare ion levels in each group. Statistical significance was set at p< 0.05.

Results: 40 subjects (25 male) were followed. Average age was 51 years (33.7–66.1). Median preoperative Co/ Cr levels were 0.27 microg/L (0.087–0.601) and 0.19 (0.014–0.576), respectively. Co/Cr levels were significantly increased at all time points when compared to preoperative levels (p< 0.001). Peak Co and Cr levels were observed at 1 year (3.26 and 4.42, respectively). At three years, the median Co and Cr levels had dropped to 2.08 and 3.55, respectively, but this was not statistically significant.

Conclusion: Elevated serum Co/Cr levels were observed at all time points following implantation. Continued elevations at three years were observed; however, the levels appear to be trending down suggestive of a “wear-in” period. Long term elevations of Co/Cr levels are concerning and will require additional studies to assess long term health risks of these levels in this population.

Purpose: The purpose of this study was to monitor serum cobalt (Co) and chromium (Cr) levels in patients after metal-on-metal resurfacing hip arthroplasty with the Cormet 2000® prosthesis, and to evaluate the effect of patient characteristics, prosthesis characteristics, clinical and radiographic measures on metal levels.

Methods: Serum Co and Cr levels were determined in 32 patients with Cormet resurfacing prostheses at 0.5, 1 and 2 years postoperatively using ICP-MS and are reported as & #61549;g/L. Control levels were measured in 20 patients without implants.

Results: Medium Co and Cr were 0.21 and 0.16 in controls without implants. Medium Co at 6 months (2.65), 1 year (3.62) and 2 years (2.80), and Cr at 6 months (3.74), 1 year (4.73) and 2 years (4.68) were signifi-cantly increased in the Cormet group when compared to control levels (p < .0001). Metal levels did not correlate with cup inclination, component position, head size, age, weight, sex or Harris Hip scores. Markedly elevated Co (35, 63) and Cr (13, 70) levels were found in two patients with excessive cup abduction. In addition, one patient with a loose implant that required revision had markedly elevated Co (19) and Cr (44) levels.

Conclusions: Significantly increased levels of cobalt and chromium were released from Cormet 2000 articulations at all time points. Excessive cup abduction was associated with markedly elevated ion levels indicating that accurate cup placement is an important consideration in resurfacing arthroplasty. The significantly increased trace metal levels following resurfacing with the Cormet prosthesis is a concern and warrants further monitoring.

SEREX was used to identify candidate tumor antigens in the nonimmunogenic fibrosarcoma (NFSA) tumor model. One of the six clones identified was of particular interest. NFSA-5 was identified as the receptor for hylaronan-acid-mediated motility (RHAMM), which is involved in cell growth and metastasis. RHAMM is expressed in a variety of human tumors. RHAMM is differentially expressed, with significant levels not found in normal tissues other than testis, placenta, and thymus. Therefore, RHAMM may be an appealing target for human tumor vaccines. The identification of murine homologs to human tumor antigens may aid in the preclinical development of human tumor vaccines.

The goal of our studies was to use serological analysis of antigens by recombinant expression cloning (SEREX) to identify candidate tumor antigens in a nonimmunogenic murine fibrosarcoma model.

SEREX provides a rapid means of identifying candidate tumor antigens in murine cancer models.

The identification of murine homologs to human tumor antigens may aid in the preclinical development of human tumor vaccines.

The SEREX approach included construction of a cDNA expression library from NFSA tumors followed by immunoscreening of the library with sera from C3H mice growing NFSA tumors. The nucleotide sequence of insert cDNA was determined for positive clones. Sequence alignments were performed with BLAST software on GenBank database.

Six positive clones were identified. Two clones coded for proteins with known expression in normal tissues. Two clones represented heat-shock proteins, known to be upregulated in human and murine tumors. Two of the clones were of particular interest. Clone NFSA-1 was the homolog to NY-REN-58, an antigen previously identified by SEREX analysis of renal cell carcinoma patients. NFSA-5 was identified as the receptor for the hylaronan-acid-mediated motility (RHAMM), which is involved in cell growth and metastasis. RHAMM was recently identified as a leukemia-associated antigen and is expressed in a variety of human solid tumors including renal cell carcinoma, breast carcinoma, and ovarian carcinoma. RHAMM is differentially expressed, with significant levels not found in normal tissues other than testis, placenta, and thymus. Therefore, RHAMM may be an appealing target for human tumor vaccines.

Funding: This study was supported by a grant received from the William E. McElroy Charitable Foundation.

To determine whether sacral chordoma is monoclonal or polyclonal in origin, a new assay to study the polymorphic human androgen receptor locus (HUMARA) was applied. The ratio of maternal inactive X-chromosone to the paternal inactive X (Lyon hypothesis) was determined via a methylation-specific polymerase chain reaction (PCR) technique. Seven of seven informative samples showed a polyclonal proliferation pattern. This study suggests that chordomas are more comparable to mesenchymal neoplasms than to monoclonal hematopoeitic neoplasms.

The purpose of this study was to determine whether sacral chordoma is monoclonal or polyclonal in origin via a new molecular genetic assay of the x-chromosome.

A polyclonal proliferation pattern was identified in all informative samples studied.

Characterization of the genetic tumorigenesis of this unpredictable neoplasm may lend insight into its biological behavior and offer novel therapeutic intervention.

Utilizing a new assay to study the polymorphic human androgen receptor locus (HUMARA), the ratio of maternal inactive X-chromosome to the paternal inactive X (Lyon hypothesis) is determined via a methylation-specific polymerase chain reaction (PCR) technique to detect X-chromosome polymorphisms. Eight female chordoma patients had their DNA harvested and their x-chromosome inactivation pattern and polymorphisms determined and compared to control. A polyclonal proliferation pattern was identified in seven of seven informative samples. The eighth sample showed a single x chromosome allele in normal and tumor tissue and was thus viewed as uninformative.

Introduction and Aims: The purpose of our study was to review our experience with the use of arthroscopy for the diagnosis and management of patients with problematic total knee replacements (TKRs).

Method: Forty-four patients were retrospectively reviewed to evaluate clinical and diagnostic efficacy of arthroscopy of TKR.

Results: Six patients with soft-tissue impingement had good-excellent outcome. Three patients had lateral retinacular release to correct patellar subluxation. Arthroscopic treatment of infection in two patients with significant comorbidities was able to control infection in one patient. Of the 13 patients with decreased range of motion due to intra-articular scarring, only four maintained increased motion. Of the 20 patients who had arthroscopy as a diagnostic procedure, 15 were successfully diagnosed and treated. Of the 10 patients with knee pain as the primary complaint, an intra-articular cause of the knee pain was identified in five patients and successfully treated in four, while no diagnosis was made in the remaining five patients.

Conclusion: The use of arthroscopy for the diagnosis and treatment of the problematic TKA is an effective and safe procedure when performed for specific indications. We found adhesiolysis of limited value for patients with decreased range of motion due to dense scar tissue.

Introduction: Atypical femoral geometry and bone stock loss may make fitting a press-fit, traditional one-piece stem difficult, if not impossible. Modularity that permits independent fitting of the diaphysis, metaphysis, length, offset, and version may greatly facilitate reconstruction and ultimate clinical performance.

Method: We prospectively evaluated the early clinical results of Exactech’s AcuMatch®^□ M-series prosthesis, a novel three-piece modular femoral stem. One hundred and twenty-seven were implanted in 114 patients. Ninety-one of these were primaries and 36 were revisions. The patients were followed prospectively and evaluated pre-operatively and at ≥2-year post-operatively.

Results: Harris hip score for primaries was 37 pre-operatively and 87 at last follow-up. Harris hip score for revision group was 35 pre-operatively and 84 at last follow-up. Four dislocations occurred and one prosthesis fractured in a 330-pound patient with deficient abductors. One prosthesis has been removed, due to sepsis in the primary group.

Conclusion: Through atraumatic milling of the bone and insertion of the implants, a minimal amount of intra-operative complications resulted. Ultimate restoration of hip biomechanics and soft tissue tension resulted in good clinical outcome with a very low dislocation rate.

Introduction and Aim: The bone preserving aspect of hip resurfacing combined with minimal wear metal-metal technology is a promising solution for the younger patient who requires a hip replacement. The purpose of this study is to evaluate the early outcomes of patients treated with the Cormet 2000 resurfacing hip prosthesis.

Method: All surgical procedures were performed by a single surgeon (DGA). Thirty-two patients, with a mean age of 52.7 years, were prospectively evaluated pre-operatively and at a minimum of one-year follow-up using standardised questionnaires, physical examinations, and radiographic evaluations.

Results: All patients rated their satisfaction with the procedure as good or excellent. Mean Harris hip scores increased from 51 pre-operatively to 92 at last follow-up. Level of pain and ability to perform activities of daily living were significantly improved compared to pre-operative scores. The mean leg length, offset and neck shaft angle were essentially restored to normal. There were no radiographic abnormalities and no significant clinical complications.

Conclusion: The short-term clinical outcome of the Cormet 2000 hip resurfacing prosthesis has been excellent.

Introduction: atypical femoral geometry and bone stock loss may make þtting a press þt traditional one-piece stem difþcult, if not impossible. modularity that permits independent þtting of the diaphysis, metaphysis, length, offset, and version may greatly facilitate reconstruction and ultimate clinical performance. Materials and methods: we prospectively evaluated the early clinical results of exactechñs acumatch? m-series prosthesis, a novel three-piece modular femoral stem. eighty-two were implanted in 80 patients. þfty-three of these were primaries and 29 were revisions. the patients were followed prospectively and evaluated with harris hip scores, range of motion, and complications pre-operatively and at ≥ 1-year post-operatively. Results: Harris hip score for primaries was 37 preoperatively and 84 at last follow-up. Harris hip score for revision group was 37 preopera-tively and 79 at last follow-up. Only one dislocation occurred in the 82 cases, in a patient who was revised for recurrent dislocation with deþcient abductors. There were three minor undisplaced calcar fractures in the primary group that did not alter the clinical outcome and in no case did the prosthesis penetrate the diaphysis. One prosthesis has been removed, and this was due to sepsis in the primary group. Conclusion: Through atraumatic milling of the bone and insertion of the implants, a minimal amount of intra-operative complications resulted. Ultimate restoration of hip biomechanics and soft tissue tension resulted in good clinical outcome with a very low dislocation rate.

Introduction: Whether to resurface or not resurface the patientñs patella at the time of TKA remains controversial. Our goal was to compare outcomes of 148 NexGen Legacy Posterior Stabilized TKAs in which the patella was resurfaced in 71 patients and left unresurfaced in 77 patients. Methods: Patients were followed prospectively and evaluated with Knee Society Scores, Hospital for Special Surgery scores, range of motion, SF12, and complications pre-operatively and at ≥ 2-year postoperatively. Results: There was no signiþcant difference in the Knee Society Function Subscore, range of motion, knee pain at rest, and SF12 scores at last follow-up. There was signiþcantly less knee pain while walking in patients who had their patella resurfaced, however there was no signiþcant difference in anterior knee pain. Hospital for Special Surgery and Knee Society Assessment Subscore were signiþcantly higher in the resurfaced group. One knee in the unresurfaced group was re-operated on with tibia tubercle osteotomy and medial reeþng for recurrent dislocation. This patient had a pre-operatively dislocated patellae. Another patient in the unresurfaced group had an undisplaced patellar fracture that was treated nonoperatively. This patient had extreme erosion of her patella pre-operatively. Conclusion: These results suggest that the innovative design of the NexGen Legacy Posterior Stabilized prosthesis may facilitate leaving the patella unresurfaced if indicated, however, pain scores may be superior with resurfacing.

Introduction: while modularity that permits independent fitting of the diaphysis, metaphysis, length, offset, and version may greatly facilitate reconstruction and ultimate clinical performance, potential generation of metallic wear debris due to fretting at the modular interface is a concern. Materials and methods: serum titanium was analyzed using inductively coupled plasma sector field mass spectrometry. titanium levels were analyzed preoperatively and at 1-year follow-up in patients treated with the acumatch^? m-series prosthesis, which has a three-piece modular femoral stem and preopera-tively, at 1-year and 2-year follow-up in patients treated with the versys nonmodular femoral stem. Results: Pre-operative mean serum titanium levels were not significantly different in patients receiving the modular Acumatch (0.25 ppb) or the nonmodular Versys (0.21 ppb) femoral stems. Titanium level in the Acumatch group was significantly higher at 1 year (2.56 ppb; range: 0.65–5.62) than those obtained for the Versys group at 1 year (1.86 ppb: range: 1.08–2.65) or 2 year (1.46 ppb: range: 1.12–2.02) post-operatively (P< 0.05). Titanium levels were significantly increased at each follow-up in both the Acumatch and Versys groups when compared to pre-operative levels (P< 0.001). Discussion/ Conclusion: Serum titanium levels were significantly increased in patients treated with the highly modular Acumatch hip prosthesis when compared to patients treated with the nonmodular Versys femoral stem. The clinical relevance of this finding is currently unknown.