Metallic or absorbable implants for ankle fractures: a comparative study of infections in 3,111 cases

Are Absorbable Plates More Resistant to Infection Than Titanium Implants? An Experimental Pre-Clinical Trial in Rabbits

Background: Infection of orthopaedic implants after internal fixation of bone fractures remains a major complication with occasionally devastating consequences. Recent studies have reported that the use of absorbable materials, instead of metallic ones, may lead to a lower incidence of postoperative infection. In this experimental pre-clinical animal study, we compared the infection rate between absorbable implants consisting of copolymers composed from trimethylene carbonate, L-polylactic acid, and D, L-polylactic acid monomers, and titanium implants after the inoculation of a pathogenic microorganism. Material and Methods: We used an experimental implant-related infection model in rabbits. Sixty animals were randomly and equally divided into two groups. In all animals, the right femur was exposed via a lateral approach and a 2.5 mm two-hole titanium plate with screws (Group A), or a two-hole absorbable plate and screws (Group B), were applied in the femoral shaft. Afterwards, the implant surface was inoculated with Pseudomonas Aeruginosa at a concentration of 2 × 108 CFU/mL. The primary outcome was the comparison of the incidence of developed infection between the two groups. The wound condition was monitored on a daily basis and radiographies were obtained at 12 weeks postoperatively. Infection-related laboratory markers (white blood cell count, erythrocyte sedimentation rate, and C-reactive protein values) were assessed at 3, 6, and 16 weeks postoperatively. Histologic analysis and cultures of tissue samples were also performed to evaluate the presence of infection. Results: Clinical and laboratory signs of infection were evident in 11 rabbits in Group A (36.7%), and 4 in Group B (13.3%). The difference between the groups was statistically significant (p = 0.04). Five animals in Group B (16.7%) had clinical and histologic signs of a foreign-body reaction with significantly elevated CRP and ESR values but no simultaneous presence of infection was identified (p = 0.04). Bone remodelling with thickening of the periosteum and surrounding sclerosis was demonstrated radiologically in animals developing infection or foreign-body reactions. Conclusions: Absorbable plates and screws show lower susceptibility to infection compared to titanium ones. However, their application is associated with foreign-body reaction and the potential need for a second surgical intervention.

Is routine removal of syndesmotic screw justified? A meta-analysis

BACKGROUND

Syndesmosis injuries are common with rotational ankle injuries, and placement of a positional syndesmotic screw to maintain its reduction is used as the ligaments heal. There is no clear consensus on routine removal or retention of syndesmotic screw. This study aimed to appraise the current evidence both on removal and retention of syndesmotic screw and to conduct a meta-analysis comparing outcomes and rate of complications of syndesmotic screw removal and retention.

METHODS

Following PROSPERO registration, a systematic search using was performed using keywords ('Syndesmosis' OR 'Syndesmotic' OR 'Transsyndesmotic' OR 'distal tibiofibular') AND ('Screw') AND ('Removal' OR 'Retention') AND 'Outcome' in various databases. No language restrictions were applied and the meta-analysis incorporated the PRISMA statement. VAS (Visual analogue scale for pain), AOFAS (American Orthopaedic Foot And Ankle Society) scores expressed as mean ± SD, and both groups' complication rates were compared. Comparisons with a random-effects model were performed, and heterogeneity between the studies was calculated using the I2 statistic. T-test for two independent sample means was used to compare pooled mean and Z-test for two proportions to assess the difference in the proportion of complications.

RESULTS

A total of 7 studies with 522 patients were included in this review for analysis. Pooled analysis showed non-significant difference in AOFAS score (MD = -1.84; 95% CI: -4.33 to 0.66; p = 0.150) as well as for VAS score (MD = -0.48; 95% CI: -1.56 to 0.60; p = 0.390) between the two groups. The value of z and p-value for complication rates was 0.6021 and 0.5485, respectively, which was not significant.

CONCLUSION

There doesn't appear to be a difference in functional outcome, pain scores, and complication rates between patients who had their syndesmotic screws removed and those where screw was retained. The fear of inferior outcomes with retained screws is thus unfounded, and routine removal adds to morbidity and financial burden. In conclusion, present data does not support the routine removal of the intact syndesmosis screw, and a change in practice is needed to abandon routine syndesmotic screw removal.

Weber C ankle fractures with tibiofibular diastasis: syndesmosis-only fixation

OBJECTIVES:

To evaluate syndesmosis-only fixation in Weber C ankle fractures with tibiofibular diastasis and to assess the need for additional fibular fixation.

METHODS:

Twenty-one patients with Weber C ankle fractures and tibiofibular diastasis were followed for at least 24 months after treatment. In treatment of the Weber C fractures, only a syndesmosis screw was used through a mini open lateral incision if the syndesmosis could be anatomically reduced and fibular length and rotation could be restored. At follow-up, anteroposterior tibiofibular distance, lateral fibular distance, medial mortise distance and fracture healing were compared and patients were clinically evaluated using the Olerud and Molander ankle scale scoring system.

RESULTS:

The average duration of follow-up was 49 months and the decreases in anteroposterior tibiofibular distance and lateral fibular distance were statistically significant. At the last follow-up the average clinical score was 86. Ankle mortise was reduced at follow-up in all cases except one, which resulted in a late diastasis.

CONCLUSIONS:

Syndesmosis-only fixation can be an effective method of treating Weber type-C lateral malleolar fractures with syndesmosis disruption in cases where intraoperative fibular length can be restored and anatomical syndesmosis reduction can be achieved. Level of Evidence IV, Case Series.

What are the patterns of prophylactic postoperative oral antibiotic use after foot and ankle surgery?

BACKGROUND

The CDC estimates 23% of healthcare-associated infections to be surgical site infections, with alarming prevalence of antibiotic-resistant organisms. While there is consensus regarding preoperative prophylaxis, orthopaedic surgeons' use of prophylactic postoperative oral antibiotics is less defined.

QUESTIONS/PURPOSES

We investigated surgeons' use of prophylactic postoperative oral antibiotics after elective outpatient foot or ankle procedures, identifying (1) frequency of use, (2) regimen preferences, (3) personal indications, and (4) associated experience and demographics.

METHODS

Using a cross-sectional survey design, a questionnaire was emailed to all active and candidate members of the American Orthopaedic Foot and Ankle Society. Supplementary questions captured demographic information. We invited 1136 members to participate; 22 addresses produced delivery failure messages, leaving 1114 members as potential participants. After nonresponses and exclusions, 312 (28%) responses were analyzed. Statistical analysis used Pearson's chi-square test, Fisher's exact test, and multivariate regression.

RESULTS

The majority (75%) of respondents reported use of prophylactic postoperative oral antibiotics. Most users (69%) prescribed to fewer than 25% of patients, although 16% prescribed for all elective cases. The most frequent regimen was cephalexin 500 mg four times a day (63%) and the most common duration was 5 to 7 days (50%). Surgeons' most common indications were previous infection (71%), medical comorbidities (65%), and previous wound-healing difficulties (56%). Those who do and do not prescribe prophylactic postoperative oral antibiotics showed no difference in surgical site infection rate or any demographic category.

CONCLUSIONS

Surgeons' reported use of prophylactic postoperative oral antibiotics after elective foot or ankle surgery was common, without demographic association. Commonalities were identified in antibiotic regimen and personal indications for this practice. Comparative clinical studies are warranted to elucidate the efficacy of prophylactic postoperative oral antibiotics and establish evidence-based guidelines for their use.

Efficacy of preparation solutions and cleansing techniques on contamination of the skin in foot and ankle surgery

We report a systematic review and meta-analysis of published randomised and quasi-randomised trials evaluating the efficacy of pre-operative skin antisepsis and cleansing techniques in reducing foot and ankle skin flora. The post-preparation culture number (Post-PCN) was the primary outcome. The data were evaluated using a modified version of the Cochrane Collaboration’s tool. We identified eight trials (560 participants, 716 feet) that met the inclusion criteria. There was a significant difference in the proportions of Post-PCN between hallux nailfold (HNF) and toe web spaces (TWS) sites: 0.47 vs 0.22, respectively (95% confidence interval (CI) 0.182937 to 0.304097; p < 0.0001).

Meta-analyses showed that alcoholic chlorhexidine had better efficacy than alcoholic povidone-iodine (PI) at HNF sites (risk difference 0.19 (95% CI 0.08 to 0.30); p = 0.0005); a two-step intervention using PI scrub and paint (S& P) followed by alcohol showed significantly better efficacy over PI (S& P) alone at TWS sites (risk difference 0.13 (95% CI 0.02 to 0.24); p = 0.0169); and a two-step intervention using chlorhexidine scrub followed by alcohol showed significantly better efficacy over PI (S& P) alone at the combined (HNF with TWS) sites (risk difference 0.27 (95% CI 0.13 to 0.40); p < 0.0001). No significant difference was found between cleansing techniques.

Cite this article: Bone Joint J 2013;95-B:498–503.

Absorbable implants versus metal implants for the treatment of ankle fractures: A meta-analysis

This meta-analysis was performed to evaluate the efficiency and the safety of absorbable implants. Five major electronic databases (PubMed, Embase, Cochrane Library, SinoMed and Wanfang Data) were systematically searched for randomized controlled trials (RCTs) from their establishment to November 2012. Studies on absorbable implants and metal implants for ankle fractures were selected. The meta-analysis was performed using RevMan 5.1. Ten studies with 762 patients were included and analyzed. Compared with metal implants, absorbable implants used for the internal fixation of ankle fractures produce similar radiographic and functional outcomes (P= 0.52). Normally, removal of the internal fixation is unnecessary (P<0.0001) and the incidence of palpable implants is lower (P=0.02) for absorbable implants. No statistically significant difference was observed between the two groups with regard to foreign body reactions (P=0.07), infection (P= 0.69), osteoarthritis (P= 0.39), pain (P= 0.06), refracture (P=0.67), skin necrosis (P=0.99), deep vein thrombosis (P=0.21) and nerve injury (P=0.94). Absorbable implants used in ankle fractures rarely require reoperation and result in similar functional outcomes and complications compared with metal implants. These characteristics make them efficient and reasonably safe for the treatment of ankle fractures.

Flexible stabilization of the distal tibiofibular syndesmosis: clinical and biomechanical considerations: a review of the literature

Syndesmotic rupture is present in 10 % of ankle fractures and must be recognized and treated to prevent late complications. The method of fixation is classically rigid fixation with one or two screws. Knowledge of the biomechanics of the syndesmosis has led to the development of new dynamic implants to restore physiologic motion during walking. One of these implants is the suture-button system. The purpose of this paper is to review the orthopaedic trauma literature, both biomechanical and clinical, to present the current state of knowledge on the suture-button fixation and to put emphasis on the advantages and disadvantages of this technique. Two investigators searched the databases of Pubmed/Medline, Cochrane Clinical Trial Register and Embase independently. The search interval was from January 1980 to March 2011. The search keys comprised terms to identify articles on biomechanical and clinical issues of flexible fixation of syndesmotic ruptures. Ninety-nine publications met the search criteria. After filtering using the exclusion criteria, 11 articles (five biomechanical and six clinical) were available for review. The biomechanical studies involved 90 cadaveric ankles. The suture-button demonstrated good resistance to axial and rotational loads (equivalent to screws) and resistance to failure. Physiologic motion of the syndesmosis was restored in all directions. The clinical studies (149 ankles) demonstrated good functional results using the AOFAS score, indicating faster rehabilitation with flexible fixation than with screws. There were few complications. Preliminary results from the current literature support the use of suture-button fixation for syndesmotic ruptures. This method seems secure and safe. As there is no strong evidence for its use, prospective randomized controlled trials to compare the suture-button to the screw fixation for ankle syndesmotic ruptures are required.

Bacterial skin contamination before and after surgical preparation of the foot, ankle, and lower leg in patients with diabetes and intact skin versus patients with diabetes and ulceration: a prospective controlled therapeutic study

Eradication of bacterial flora from the foot, especially the nailfolds and toe webspaces, through surgical preparation remains a challenge. All previous studies have involved healthy patients undergoing elective foot and ankle surgery or healthy volunteers. However, the patient with diabetes is considered an immunocompromised host with decreased ability to combat invasive bacterial infections. The use of an efficacious surgical preparation is therefore of paramount importance. The author conducted a prospective study involving patients with diabetes with and without ulceration who underwent the current "best evidence available" surgical preparation (i.e., chlorhexidine gluconate [4%] scrub followed by alcohol impregnated with iodine [1%] solution). Qualitative aerobic cultures before and after completion of this surgical preparation technique were obtained from the hallux nailfold; second, third, and fourth toe webspaces (as one culture); and distal anterior tibia. A total of 120 organisms were cultured before surgical preparation with 64 in the elective group and 56 in the ulcerated group. The most commonly isolated organism was methicillin-resistant Staphylococcus epidermidis, which was identified in 46 pre-preparation cultures (38.3%). This was followed by methicillin-sensitive S. epidermidis (16.7%) and "other" organisms (10.0%). There was a significant reduction for both numbers of organisms identified and positive cultures for the 3 most commonly isolated organisms after surgical preparation. Based on the results of this study, the surgical preparation used here appears to be an efficacious surgical preparation technique for eradicating aerobic bacterial pathogens from the foot in patients with diabetes both with and without ulceration. The high incidence of methicillin-sensitive and methicillin-resistant S. epidermidis found in this patient population is a cause for concern, especially when metallic fixation is intended to be implanted.

Functional outcomes after syndesmotic screw fixation and removal

OBJECTIVES

Ankle fractures with a syndesmotic injury have historically been treated with syndesmotic screw fixation. We compared range of motion and functional outcomes' scores to assess patient benefit from syndesmotic screw and plate removal.

DESIGN

Level IV--case series.

SETTING

Level I--trauma center.

PATIENTS/PARTICIPANTS

Twenty-five consecutive patients with unstable ankle fractures and syndesmotic injury confirmed on magnetic resonance imaging.

INTERVENTION

Locked syndesmotic screws and plates were removed; functional outcomes and range of motion were measured before and after screw removal.

MAIN OUTCOME MEASUREMENTS

Foot and Ankle Outcome Score, Olerud and Molander Ankle Score, and physical examination

RESULTS

There was a significant improvement in range of motion, Foot and Ankle Outcome, and Olerud and Molander Ankle scores at the immediate postoperative visit. This was not significantly changed at longer follow-up. There were no adverse events or complications in these patients. No patient had radiographic loss of syndesmotic reduction after screw removal.

CONCLUSIONS

Locked screw and plate removal improved function both subjectively and objectively. Transsyndesmotic implant removal seems to assist improvements in the speed of rehabilitation.

Biodegradable Polymers in Bone Tissue Engineering

The use of degradable polymers in medicine largely started around the mid 20^th century with their initial use as in vivo resorbing sutures. Thorough knowledge on this topic as been gained since then and the potential applications for these polymers were, and still are, rapidly expanding. After improving the properties of lactic acid-based polymers, these were no longer studied only from a scientific point of view, but also for their use in bone surgery in the 1990s. Unfortunately, after implanting these polymers, different foreign body reactions ranging from the presence of white blood cells to sterile sinuses with resorption of the original tissue were observed. This led to the misconception that degradable polymers would, in all cases, lead to inflammation and/or osteolysis at the implantation site. Nowadays, we have accumulated substantial knowledge on the issue of biocompatibility of biodegradable polymers and are able to tailor these polymers for specific applications and thereby strongly reduce the occurrence of adverse tissue reactions. However, the major issue of biofunctionality, when mechanical adaptation is taken into account, has hitherto been largely unrecognized. A thorough understanding of how to improve the biofunctionality, comprising biomechanical stability, but also visualization and sterilization of the material, together with the avoidance of fibrotic tissue formation and foreign body reactions, may greatly enhance the applicability and safety of degradable polymers in a wide area of tissue engineering applications. This review will address our current understanding of these biofunctionality factors, and will subsequently discuss the pitfalls remaining and potential solutions to solve these problems.

Injuries to the tibiofibular syndesmosis

The management of injury to the distal tibiofibular syndesmosis remains controversial in the treatment of ankle fractures. Operative fixation usually involves the insertion of a metallic diastasis screw. There are a variety of options for the position and characterisation of the screw, the type of cortical fixation, and whether the screw should be removed prior to weight-bearing. This paper reviews the relevant anatomy, the clinical and radiological diagnosis and the mechanism of trauma and alternative methods of treatment for injuries to the syndesmosis.

Biodegradable polylactide membranes for bone defect coverage: biocompatibility testing, radiological and histological evaluation in a sheep model

Large bony defects often show a delayed healing and have an increasing risk of infection. Several materials are used for the coverage of large defects. These materials must be biocompatible, easy to use, and must have an appropriate stability to present a mechanical hindrance. Aim of this study was to investigate two different biodegradable membranes for defect coverage in a sheep model. Round cranial defects (1.5 cm diameter) were created in sheep. Six different treatments were investigated: defects without membrane, defects covered with a poly(D,L-lactide) or with a 70/30 poly(L/D,L-lactide) membrane and all defects with or without spongiosa filling. The sheep were sacrificed 12 or 24 weeks postoperatively. Bone formation in the defects was quantified by computer-assisted measurements of the area of the residual defect on CT radiographs. Histomorphometry and host-tissue response were evaluated by light microscopy. The biocompatibility was investigated by analyzing the amount of osteoclasts and foreign body cells. Both membranes served as a mechanical hindrance to prevent the prolapse of soft tissue into the defect. The biocompatibility test revealed no differences in the amount and distribution of osteoclasts at the two investigated time points and between the investigated groups. No negative effect on the tissue regeneration was detectable between the investigated groups related to the type of membrane, but a foreign body reaction around the two membrane types was observed. In the membrane-covered defects, the spongiosa showed a progressing remodeling to the native bony structure of the cranium. The groups without spongiosa partly revealed new bone formation, without complete bridging in any group or at any time point. Comparing the 12 and 24 weeks groups, an increased bone formation was detectable at the later time point. In conclusion, the results of the present in vivo study reveal a good biocompatibility and prevention of soft tissue prolapse of the two used membranes without differences between the membranes. An enhanced remodeling of the spongiosa into native bony structures under the membranes was detectable, but no osteopromoting effect was observed due to the membranes.

Les matériels d'ostéosynthèse résorbables

There is continued interest in the development of new biomaterials. The application of new implantable biomaterials requires intense research and thorough evaluation. Much time and effort has been required to overcome the risks and problems associated with the bioabsorbable devices. For surgical bone fixation, these materials were investigated since the 1960's. Different polymer properties were explored to ensure adequate strength and biocompatibility. High-molecular-weight bioabsorbable polymers were initially used, followed by addition of reinforcement materials. The most recent materials are self-reinforced, small yet strong devices. The newer generations contain bioactive substances such as antibiotics and growth factors. Bioabsorbable materials are constantly changing as we try to adopt the principles of tissue engineering. Surgeons are using new techniques to exploit these polymers and their bioabsorbable properties. It is hoped that this multidisciplinary approach of surgery and research will continue to help the further evolution of biomaterial science.

Hot compaction of poly(methyl methacrylate) composites based on fiber shrinkage results

Uniaxial self-reinforced composite poly(methyl methacrylate) (SRC-PMMA) is being investigated as a pre-coat material for the femoral component of total hip replacements. Hot compaction of self-reinforced composites is largely an empirical process which varies the processing parameters of time, temperature and pressure until the desired properties are obtained. Previous work has shown that PMMA fibers have unique thermal relaxation properties dependent upon the retained molecular orientation in them. This work processed composites at times and temperatures that span the relaxation process for a single fiber. It was found that molecular orientation, as measured by birefringence, was lost in composites processed at times greater than relaxation times for single fibers. Flexural properties were also found to vary with processing conditions, with the highest values of 165 +/- 15 MPa and 168 +/- 3 MPa found at high and low processing times, respectively. These are significantly stronger than unreinforced PMMA which has a flexural strength of 127 +/- 14 MPa. It is hypothesized that diffusion between fibers occurs much more quickly than the loss of molecular orientation and it was seen that SRC-PMMA processing conditions can be predicted from the relaxation times and temperatures from single fibers.

Fixation of syndesmotic ruptures in 38 patients with a malleolar fracture: a randomized study comparing a metallic and a bioabsorbable screw

OBJECTIVES

To compare the performance of a metallic and a biodegradable screw in the fixation of tibia-fibula syndesmotic ruptures.

DESIGN

A randomized, prospective, and blinded study.

SETTING

Central hospital, Department of Surgery.

PATIENTS

Forty consecutive patients with a clinically verified syndesmotic rupture in association with a malleolar fracture, of whom 38 completed the study.

INTERVENTION

After syndesmosis rupture was diagnosed, implant selection was performed intraoperatively by a strict randomization with sealed envelopes. Eighteen patients were treated with a metallic screw, and 20 with a bioabsorbable polylevolactic acid screw. The metallic screws were removed in a second operation at 8 weeks postoperatively. All patients had a treatment-blinded clinical and radiographic control after a mean follow-up of 35 (range 17-51) months.

MAIN OUTCOME MEASURES

Return to previous physical activity level, evaluation of ankle stability, range of motion, circumference of the ankle, and a radiographic evaluation of both ankles including a measure of the talocrural, medial joint, and syndesmotic space widths.

RESULTS

More patients with a polylevolactic acid screw returned to their previous activity level, and there was less swelling in the ankles of these patients, but joint motion was similar between the groups. The mean values of syndesmotic and medial joint spaces were significantly higher in the radiographs of the operated ankles when compared to the uninjured ankle, but there was not a correlation to the type of screw used.

CONCLUSIONS

Polylevolactic acid screws worked as well, or slightly better than, metallic ones in syndesmosis fixation in patients with an ankle fracture.

Short term in vivo biocompatibility testing of biodegradable poly(D,L-lactide)—growth factor coating for orthopaedic implants

Fracture healing can be stimulated by exogenous application of growth factors. Using porcine and rat models the efficacy of locally delivered IGF-I and TGF-beta1 from an implant coating has been demonstrated. A thin and biomechanical stable biodegradable poly(D,L-lactide) was used to coat implants and serve as a drug carrier. Due to reports of possible foreign body reactions caused by polymer materials in orthopedic surgery, this study investigated the biocompatibility of the polylactide implant coating and the locally released growth factors during the time course of rat tibial fracture healing (days 5, 10, 15, and 28 after fracture). Monocytes/macrophages and osteoclast were detected using an monoclonal antibody against ED1 (comparable to CD68 in mice and human). The antibody ED1 stains monocytes, macrophages and osteoclast in the bone marrow and in the newly formed fracture callus. A moderate density of the monocytes/macrophages was seen in the proximal part of the medullary canal, but almost no cells were detectable in the region distal to the fracture. The amount of stained cells increased during the observation time with a maximum at days 10 and 15 followed by a decrease at day 28. No differences were detectable between the investigated groups from day 5 to 15 post fracture indicating, that the used poly(D,L-lactide) or the incorporated growth factors do not evoke an elevated immunological response compared to the uncoated titanium implant at the investigated time points. A significantly higher amount of ED1 positive cells was measured 28 days after fracture in the control group compared to the groups with the coated implants. In conclusion, no indication of a foreign body reaction due to the use of the polylactide or the growth factors was found indicating a good short-term biocompatibility of this bioactive coating.

Efficacy of surgical preparation solutions in foot and ankle surgery

BACKGROUND

Previous studies have demonstrated higher infection rates following orthopaedic procedures on the foot and ankle as compared with procedures involving other areas of the body. Previous studies also have documented the difficulty of eliminating bacteria from the forefoot prior to surgery. The purpose of the present study was to evaluate the efficacy of three different surgical skin-preparation solutions in eliminating potential bacterial pathogens from the foot.

METHODS

A prospective study was undertaken to evaluate 125 consecutive patients undergoing surgery of the foot and ankle. Each lower extremity was prepared with one of three randomly selected solutions: DuraPrep (0.7% iodine and 74% isopropyl alcohol), Techni-Care (3.0% chloroxylenol), or ChloraPrep (2% chlorhexidine gluconate and 70% isopropyl alcohol). After preparation, quantitative culture specimens were obtained from three locations: the hallux nailfold (the hallux site), the web spaces between the second and third and between the fourth and fifth digits (the toe site), and the anterior part of the tibia (the control site).

RESULTS

In the Techni-Care group, bacteria grew on culture of specimens obtained from 95% of the hallux sites, 98% of the toe sites, and 35% of the control sites. In the DuraPrep group, bacteria grew on culture of specimens obtained from 65% of the hallux sites, 45% of the toe sites, and 23% of the control sites. In the ChloraPrep group, bacteria grew on culture of specimens from 30% of the hallux sites, 23% of the toe sites, and 10% of the control sites. ChloraPrep was the most effective agent for eliminating bacteria from the halluces and the toes (p < 0.0001).

CONCLUSIONS

The use of effective preoperative preparation solution is an important step in limiting surgical wound contamination and preventing infection, particularly in foot and ankle surgery. Of the three solutions tested in the present study, the combination of chlorhexidine and alcohol (ChloraPrep) was most effective for eliminating bacteria from the forefoot prior to surgery.

Spotlight on naturally absorbable osteofixation devices

The practice of using implants is growing day by day, and more foreign materials are being inserted for various indications. The field of implantology thus deserves intensive research and careful evaluation of results. Solutions to overcome current problems and risks are necessary. It has taken a long time to arrive at where we are now. Bioabsorbable devices were explored in the 1960s for surgical bone fixation. Failures were followed by changes in ways of thinking and innovations. Improvements in the strength properties and biocompatibility were achieved. Bioabsorbable polymeric materials such as high-molecular-weight polymers were used and also reinforced with other material or, more recently, by self-reinforcement to produce small yet strong devices. New generations of implants include those that contain bioactive substances such as antibiotics and growth factors. Developments in bioabsorbable materials continue to accommodate the new way of thinking brought about by the emergence of the field of tissue engineering. Surgeons, conversely, are also inventing new surgical techniques and methods to exploit the plastic and bioabsorbability properties of these materials for the better future of our patients. Such a multidisciplinary approach that involves surgeons and materials scientists should help to find solutions to the current limitations of these devices.

Complications of open reduction and internal fixation of ankle fractures

This article discusses the complications after open reduction and internal fixation of ankle fractures. Complications are classified as perioperative (malreduction, inadequate fixation, and intra-articular penetration of hardware), early postoperative (wound edge dehiscence, necrosis, infection and compartment syndrome), and late (stiffness, distal tibiofibular synostosis, degenerative osteoarthritis, and hardware related complications). Emphasis is placed on preventive measures to avoid such complications.

Comparison of the biomechanics and histology of two soft-tissue fixators composed of bioabsorbable copolymers

The purpose of this study was to assess the dynamic in vitro and in vivo characteristics of two different bioabsorbable copolymer soft-tissue fixation devices and to determine their efficacy in reattaching soft tissue to bone. Suretac fixators (Smith & Nephew/Acufex MicroSurgical Inc., Northwood, MA), made of polyglyconate (2:1 glycolic acid:trimethylene carbonate), and Pop Rivets (Arthrotek, Warsaw, IN), made of LactoSorb (82% poly L-lactic acid, 18% polyglycolic acid), were anchored into synthetic bone, and their pull-out strengths were evaluated. The devices were also evaluated with the use of an in vivo goat model in which the medial collateral ligament (MCL) was elevated from the tibia and directly reattached. In the in vitro biomechanical study, the Suretac fixators had negligible strength remaining by four weeks, whereas the Pop Rivets retained 50% of their strength at 4 weeks, 20% at 8 weeks, and negligible strength at 12 weeks. The in vivo strength of MCL repairs affected by each implant was not statistically different at any of the time points. Histologically, both implants were absorbed by 52 weeks, and there was no appreciable adverse tissue response. In conclusion, both copolymer fixators were found to be biocompatible. The Pop Rivet fixators demonstrated in vivo performance comparable to the Suretac fixators, although the Pop Rivets retained strength longer in vitro. Our results suggest that both devices provide adequate strength of fixation before degrading to allow the healing soft tissues to reach or surpass their native strength.

Tissue responses to molecularly reinforced polylactide-co-glycolide implants

Plates for internal fixation fabricated from biodegradable polymers degrade via an autocatalytic route. When they are used in bone implants of significant size and thickness, hollowing of the implant may occur while the overall dimensions appear unchanged. We hypothesized that incorporation of a cross-linked polypropylene fumarate matrix into polylactide-co-glycolide bone plates may provide an internal molecular network which prevents implant collapse. Cross-linking reagents of varying hydrophilicity including N-vinylpyrrolidone (VP), hydroxyethylmethacrylate (HEMA), and ethyleneglycol dimethacrylate (EGDMA) were employed. With the objective of determining the most biocompatible and structurally sound composition for molecular reinforcement, we investigated tissue responses in both subcutaneous and orthotopic rodent implantation models in relation to maintenance of implant integrity by histologic, histomorphometric, and stereomicroscopic analysis. Results showed that tissue responses were correlated with dimensional stability of the implants. The most favorable results were seen with the hydrophobic cross-linker EGDMA; this may have been related to the initial reduction of the water uptake by the implant. Cross-linking of polypropylene fumarate with EGDMA within a polylactide-co-glycolide bone plate may offer a means to maintain excellent biocompatibility while improving dimensional stability of biodegradable bone plates.

Absorbable screws through the greater trochanter do not disturb physeal growth: rabbit experiments

We studied the effect of implantation of self-reinforced polyglycolic acid (SR-PGA) screws through the greater trochanter in rabbits. 15 rabbits aged 10 weeks had an SR-PGA screw inserted through the left trochanter physis. A similar drilling was made through the right greater trochanter without screw implantation. The animals were assigned to 3 groups of 5, and were killed after 1, 2 or 3 months. Radiographs of both femurs were obtained monthly and the articulo-trochanteric distance and the neck-shaft angle were measured. After killing the animals, a histological study was performed. The drilling on the right trochanter generated a bony bridge in all the animals. The SR-PGA screws did not give rise to an epiphysiodesis. The progressive peripheral degradation of the implants gave rise to the formation of only modest bridges, which were smaller in size than those observed in the control trochanter. Our findings suggest that absorbable PGA screws implanted through a growth plate cause only minor bone formation and no epiphyseodesis.

In vivo measurements show tensile axial strain in the proximal lateral aspect of the human femur

Two conflicting theories exist concerning the stress pattern for the proximal lateral aspect of the human femur. According to the classic theory of Pauwels, a bending moment on the femur leads to compression medially and to tension laterally. The alternative theory is that muscle forces contribute to a moment-free loading of the femur, with both the medial and lateral cortices subjected to compression. To examine these theories, we measured the strain at the external surface of the proximal lateral aspect of the femur of two female patients undergoing surgery for "snapping hip syndrome." During the surgical procedure, a strain-gauge rosette was bonded to the lateral aspect of the femur and the cortical strains were monitored while the patient performed a series of activities. In both patients, principle tensile strain increased significantly during one-legged stance, walking, and stair climbing as compared with that during two-legged stance. During each loading situation, the principal tensile strain was aligned within 22 degrees to the longitudinal femoral axis. Dynamic strain measurements consistently revealed tensile axial strain at the lateral aspect of the femur during each activity. The present study supports the classic bending theory of Pauwels and demonstrates that the proximal lateral aspect of the femur is subjected to tension during the stance phase of gait.