Patrick F. Bergin

Chitosan: potential use as a bioactive coating for orthopaedic and craniofacial/dental implants

Chitosan is a biopolymer that exhibits osteoconductive, enhanced wound healing and antimicrobial properties which make it attractive for use as a bioactive coating to improve osseointegration of orthopaedic and craniofacial implant devices. Coatings made from 91.2% de-acetylated chitosan were chemically bonded to titanium coupons via silane-glutaraldehyde molecules. The bond strength of the coatings was evaluated in mechanical tensile tests, and their dissolution and cyto-compatibility were evaluated in vitro using cell-culture medium and UMR 106 osteoblastic cells, respectively. The results showed that the chitosan coatings were chemically bonded to the titanium substrate and that the bond strengths (1.5-1.8 MPa) were not affected by gas sterilization. However, the chitosan bond strengths were less than those reported for calcium-phosphate coatings. The gas-sterilized coatings exhibited little dissolution over 8 weeks in cell-culture solution, and the attachment and growth of the UMR 106 osteoblast cells was greater on the chitosan-coated samples than on the uncoated titanium. These results indicated that chitosan has the potential to be used as a biocompatible, bioactive coating for orthopaedic and craniofacial implant devices.

Comparison of Minimally Invasive Direct Anterior Versus Posterior Total Hip Arthroplasty Based on Inflammation and Muscle Damage Markers

BACKGROUND A number of surgical approaches are utilized in total hip arthroplasty. It has been hypothesized that the anterior approach results in less muscle damage than the posterior approach. We prospectively analyzed biochemical markers of muscle damage and inflammation in patients treated with minimally invasive total hip arthroplasty with an anterior or posterior approach to provide objective evidence of the local soft-tissue injury at the time of arthroplasty. METHODS Twenty-nine patients treated with minimally invasive total hip arthroplasty through a direct anterior approach and twenty-eight patients treated with the same procedure through a posterior approach were prospectively analyzed. Perioperative and radiographic data were collected to ensure cohorts with similar characteristics. Serum creatine kinase (CK), C-reactive protein (CRP), interleukin-6 (IL-6), interleukin-1 beta (IL-1ß), and tumor necrosis factor-alpha (TNF-a) levels were measured preoperatively, in the post-anesthesia-care unit (except for the CRP level), and on postoperative days 1 and 2. The Student t test and Fisher exact test were used to make comparisons between the two groups. Independent predictors of elevation in levels of markers of inflammation and muscle damage were determined with use of multivariate logistic regression analysis. RESULTS The levels of the markers of inflammation were slightly decreased in the direct-anterior-approach group as compared with those in the posterior-approach group. The rise in the CK level in the posterior-approach group was 5.5 times higher than that in the anterior-approach group in the post-anesthesia-care unit (mean difference, 150.3 units/L [95% CI, 70.4 to 230.2]; p < 0.05) and nearly twice as high cumulatively (mean difference, 305.0 units/L [95% CI, -46.7 to 656.8]; p < 0.05). CONCLUSIONS We believe that the anterior total hip arthroplasty approach used in this study caused significantly less muscle damage than did the posterior surgical approach, as indicated by serum CK levels. The clinical importance of the rise in the CK level needs to be delineated by additional clinical studies. The overall physiologic burden, as demonstrated by measurement of inflammation marker levels, appears to be similar between the anterior and posterior approaches. Objective measurement of muscle damage and inflammation markers provides an unbiased way of determining the immediate effects of surgical intervention in patients treated with total hip arthroplasty.

Detection of Periprosthetic Infections With Use of Ribosomal RNA-Based Polymerase Chain Reaction

BACKGROUND Previously described molecular biology techniques used to detect periprosthetic infections have been complicated by false-positive results. We have reported the development of a messenger RNA (mRNA)-based procedure to reduce these false-positive results. The limitations of this procedure are the lack of a universal target and reduced sensitivity due to a low concentration of bacterial mRNAs in test samples. The objective of the present study was to determine whether reverse transcription-quantitative polymerase chain reaction (RT-qPCR) using universal primers can be used to detect the more abundant bacterial ribosomal RNA (rRNA) as an indicator of periprosthetic infection. METHODS Serial dilutions of simulated synovial fluid infections were analyzed with rRNA RT-qPCR to determine the detection limit of this assay. Escherichia coli cultures treated with gentamicin were analyzed with RT-qPCR over a twenty-day time course to determine the degradation of rRNA as compared with the decrease in the viable cell count as determined by means of cell plating. As a proof of concept, group-specific polymerase chain reaction primers were developed for Streptococcus species and were tested against fifteen orthopaedically relevant organisms to show the potential for speciation with this assay. Sixty-four patients with a symptomatic effusion at the site of a total knee arthroplasty were enrolled, and complete patient information was documented in a prospective manner. Synovial fluid analysis with rRNA RT-qPCR was performed in a blind fashion. RESULTS The rRNA RT-qPCR assay was able to detect as few as 590 colony forming units/mL of Staphylococcus aureus and 2900 colony forming units/mL of Escherichia coli. The rRNA RT-qPCR signal closely followed cell death, pointing to its potential use as a viability marker. Three group-specific primer sets correctly identified their intended targets without amplifying closely related species. Clinically, the test correctly identified all six patients with a confirmed infection and all fifty patients who clearly did not have an infection. Eight patients had some laboratory or clinical signs of infection, but their status could not be confirmed. Infection was indicated by rRNA RT-qPCR in three of these patients who had elevated synovial fluid white blood-cell counts but negative results on culture. For statistical purposes, all patients who were categorized as indeterminate were considered to have an infection for the purpose of analysis, for a prevalence of 22% in this cohort. CONCLUSIONS With respect to current diagnostic tests, rRNA-based RT-qPCR demonstrated 100% specificity and positive predictive value with a sensitivity equivalent to that of intraoperative culture. The RT-qPCR signal followed bacterial culture trends but exhibited detectable level for seven days after sterilization, allowing for the detection of infection after the antibiotic administration. These findings indicate that rRNA RT-qPCR is a sensitive and reliable test that retains the universal detection and speciation of DNA-based methods while functioning as a viability indicator.

An S-2 alar iliac pelvic fixation. Technical note.

Multiple techniques of pelvic fixation exist. Distal fixation to the pelvis is crucial for spinal deformity surgery. Fixation techniques such as transiliac bars, iliac bolts, and iliosacral screws are commonly used, but these techniques may require separate incisions for placement, leading to potential wound complications and increased dissection. Additionally, the use of transverse connector bars is almost always necessary with these techniques, as their placement is not in line with the S-1 pedicle screw and cephalad instrumentation. The S-2 alar iliac pelvic fixation is a newer technique that has been developed to address some of these issues. It is an in-line technique that can be placed during an open procedure or percutaneously.

Functional outcomes for surgically treated 3- and 4-part proximal humerus fractures.

Surgical treatment of 3- and 4-part proximal humeral fractures remains challenging. This study retrospectively evaluated functional outcomes of locked plate fixation vs hemi-arthroplasty in 57 patients with 3- and 4-part proximal humerus fractures from 2003 to 2005 with a mean follow-up time of 35 months (range, 15.7-52.7 months). Mean patient age was 56.9 years (range, 29-81.7 years) for the open reduction and internal fixation group (n=42) and 66.4 years (range, 38.1-90 years) for hemiarthroplasty group (n=15). All 57 patients completed the American Shoulder and Elbow Surgeons score, the Simple Shoulder Test, the Euroqol EQ-5D, [corrected] and the visual analog pain scale. Range of motion, the Constant Score, and the UCLA Shoulder score were used to evaluate a subset of 33 patients. Forty-one patients in the open reduction and internal fixation group achieved union, and 1 had symptomatic avascular necrosis requiring subsequent hemiarthroplasty. Two patients had implant removal for impingement symptoms. In the hemiarthroplasty group, there was 1 revision for a loose prosthesis. The American Shoulder and Elbow Surgeons score (P=.023), Simple Shoulder Test (P=.012), patient satisfaction (P=.034), Constant Score (P=.008), Kelsh Adjusted Constant Score (P=.015), UCLA Shoulder score (P=.01), and range of motion (forward flexion, P=.002; abduction, P=.001) were significantly better in the open reduction and internal fixation group than the hemiarthroplasty group. No significant differences between the groups existed in terms of SF-12 (physical, P=.118; mental, P=.134), Euroqol EQ-5D [corrected] (P=.169), or visual analog pain scale scores (P=.135), but all trended toward better with open reduction and internal fixation.

The anatomic suitability of the C2 vertebra for intralaminar and pedicular fixation: a computed tomography study

BACKGROUND CONTEXT Several methods have been used to stabilize the atlantoaxial joint, including the use of C2 pedicle and laminar screws. No report has used computed tomography (CT) angiograms to compare the risk to the vertebral artery or assess the suitability for each fixation technique. PURPOSE To compare the suitability of C2 pedicle versus laminar screws using CT angiograms. STUDY DESIGN We retrospectively evaluated the anatomic dimensions of the C2 lamina and pedicle in 50 patients using CT angiograms. METHODS We retrospectively reviewed the last 50 patients admitted who underwent CT angiograms of the head and neck. Data recorded included the pedicle length and width and the laminar length and width. Vertebral artery anatomy was also assessed to determine if an aberrant location would preclude pedicle fixation. RESULTS Mean pedicle length and width were 15.5±3.5 and 4.7±1.7 mm, respectively, with 24% of patients having anatomy that would preclude 3.5-mm pedicle screw fixation. The mean lamina length and width were 25.2±3.6 and 5.5±1.4 mm, and more than 90% of patients could tolerate a 3.5-mm C2 laminar screw. CONCLUSION Preoperative CT angiography or noncontrast CT is an excellent method to delineate the anatomy at C2 to determine the suitability for pedicle or intralaminar fixation. In cases where vertebral artery anatomy precludes C2 pedicle fixation, more than 90% of patients may be a candidate for C2 intralaminar fixation.

The use of spinal osteotomy in the treatment of spinal deformity.

As a result of reading this article, physicians should be able to: 1. Discuss the normal sagittal plane curves in the nonpathological spine in terms of lordosis and kyphosis. 2. Explain the impact of spinal sagittal balance and the potential impact on quality of life in patients with this issue. 3. List the types of spinal osteotomy and the indications that are most appropriate for each osteotomy and the corresponding deformity. 4. Describe the various strategies and develop an implementation strategy to avoid complications in spinal osteotomy surgery.

Modes of failure of custom expandable repiphysis prostheses: a report of three cases.

Limb preservation surgery for patients with sarcomas of the extremity is recognized as a valid, safe, and effective means of treating local disease1. However, one of the major dilemmas in lower limb preservation in skeletally immature children is the ability to maintain leg-length equality as the child ages and grows. Many prosthetic designs that allow expansion of the internal prosthesis and consequent limb-lengthening, either noninvasively or through a minor surgical procedure, have evolved2,3. One of the latest of the noninvasive expandable implants is the Repiphysis expandable limb salvage system (Wright Medical Technology, Arlington, Tennessee), originally called the Phenix prosthesis (Phenix Medical, Paris, France)4,5. Although used in Europe since the early 1990s, the first Phenix prosthesis was implanted in the United States in 1998, and in 2002, the device became approved by the Food and Drug Administration. While this system offers many advantages over earlier expandable limb salvage implants, we observed three failures among sixteen Repiphysis prostheses implanted (in fourteen patients) between 2003 and 2010 by the senior author (R.M.H.). The patients and their parents were informed that the data concerning these cases would be submitted for publication, and they consented. Case 1. An eight-year-old girl was diagnosed as having stage-IIB osteosarcoma, according to the Musculoskeletal Tumor Society (MSTS) system developed by Enneking et al.6, in the distal end of the left femur. A wide local resection was done at another institution with limb reconstruction with use of a Lewis Expandable Adjustable Prosthesis (LEAP, Wright Medical Technology) with an expansion capacity of 2.5 cm. Two years later, she presented to us with a fixed knee flexion deformity of 80° and an inability to bear weight on that leg because of the deformity and limb-length discrepancy. Following serial casting to …

Radiographic Evaluation of Intermetatarsal Angle Correction Following First MTP Joint Arthrodesis for Severe Hallux Valgus.

Background: Arthrodesis is a standard operative treatment for symptomatic arthritis of the first metatarsophalangeal (MTP) joint. Patients with degenerative joint disease (DJD), severe hallux valgus, and metatarsus primus varus may also require fusion of the first MTP joint. An important question in the latter group of patients is whether a proximal first metatarsal osteotomy is required, in addition to the first MTP joint fusion. Our hypothesis was that patients with severe hallux valgus and metatarsus primus varus, treated with first MTP joint arthrodesis alone, would have correction of the first-to-second intermetatarsal angle (1-2 IMA) and hallux valgus angle (HVA) to near population norms, without the addition of a proximal first metatarsal osteotomy. Methods: Preoperative and postoperative radiographs of 19 feet, in 17 patients, with preoperative IMA greater than 15 were analyzed. Weight-bearing radiographs were divided into pre- and postoperative cohorts. Three independent reviewers measured these radiographs and mean 1-2 IMA and HVA were calculated. Mean follow-up was 10 months. Results: The mean preoperative 1-2 IMA was 19.2 degrees (15.6-24.3). The mean preoperative HVA was 48.5 (36-56.6). The mean postoperative values for 1-2 IMA and HVA were 10.8 and 12.3 degrees, respectively. The mean change in IMA was 8.3 degrees and in the hallux valgus angle was 36.4 degrees. The differences between pre- and postoperative measurement for both angles were statistically significant (P < .001). Seven of 19 (37%) feet were corrected to an IMA of less than 9 degrees (normal), whereas in 15/19 feet the postoperative IMA was 12.3 degrees or less. The postoperative HVA was less than 15 degrees in 15/19 (79%) feet. Conclusion: This pre- and postoperative radiographic analysis of patients with severe bunion deformity demonstrated that HVA and 1-2 IMA were acceptably corrected without the addition of a proximal first metatarsal osteotomy. Level of Evidence: Level III, retrospective comparative series.

Inpatient soft tissue protocol and wound complications in calcaneus fractures.

Background: Operative treatment of calcaneus fractures is associated with the risk of early wound complications. Though accepted practice dictates surgery should be delayed until soft tissues recover from the initial traumatic insult, optimal timing of surgery has not been delineated. Methods: A retrospective chart and radiographic review at a level I trauma center was performed to determine if an aggressive inpatient soft tissue management protocol designed to decrease the time delay from injury to surgery is effective at reducing complications. Ninety-seven patients (17 female, 80 male; mean age, 39.7 ± 14.0 years) with 102 calcaneus fractures treated between October 1995 and January 2005 were identified. Differences in complication rates and quality of reduction between the inpatient and outpatient treatment groups were analyzed. Quality of reduction was determined by measuring postoperative Bohlers angle and posterior facet articular step-off. Results: Mean time from injury to surgery was 6.2 days for the inpatient group and 10.8 days for the outpatient group (p < 0.0001). The overall complication rate was over twice as high in the outpatient group (27 versus 12%, p = 0.04) and the serious complication rate was 6.5 times higher when patients were managed as outpatients (9% versus 1%, p = 0.09). With the numbers available, there were no significant differences in the quality of reduction obtained at surgery. Conclusion: This study suggests that this inpatient soft tissue management protocol of calcaneal fractures is a feasible treatment option when a patient is kept in the hospital that offers a reduction in postoperative wound complications while enabling surgery 4 days earlier on average. Level of Evidence: III, Retrospective Comparative Study