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Hybrid fixation improves structural properties of a free tendon anterior cruciate ligament reconstruction.

PURPOSE: This study sought to characterize the structural properties of a combined bioabsorbable interference screw and closed loop and button fixation technique (Hybrid) for femoral fixation of a free tendon graft versus a bioabsorbable interference screw or closed loop and button suspension fixation method alone. METHODS: Eighteen porcine femora and quadrupled cadaveric flexor tendons were treated in 3 experimental fixation study groups: (1) closed loop and button suspension (CLBS), (2) bioabsorbable interference screw (BIF), and (3) closed loop and button suspension with supplemental biodegradable interference screw (Hybrid). An Instron testing machine (Instron, Canton, MA) was used to quantify each group's structural properties with cyclic loading and tensile load-to-failure. A video digitizing system measured graft deformation during load-to-failure. RESULTS: The Hybrid fixation group had significantly greater structural properties compared with the CLBS or BIF group. Ultimate loads (mean [SEM] in Newtons) were 1184 (88) N, 813 (83) N, and 561 (62) N for the Hybrid fixation group, CLBS group, and BIF group, respectively. Quasi-steady state cyclic stiffness (mean [SEM] in Newtons per millimeter) was also greatest for the Hybrid fixation group at 165 (11) N/mm, compared with CLBS (122 [8] N/mm), and BIF (95 [9] N/mm). CONCLUSIONS: Femoral free tendon hybrid fixation provides superior structural properties under tensile and cyclic displacement conditions while preserving the working length of the native anterior cruciate ligament. CLINICAL RELEVANCE: Hybrid femoral fixation may minimize postoperative laxity for free tendon anterior cruciate ligament reconstruction.

Absorbable Implants↗

Initial and 6 weeks postoperative structural properties of soft tissue anterior cruciate ligament reconstructions with cross-pin or interference screw fixation: an in vivo study in sheep.

PURPOSE: The purpose of this study was to evaluate the detrimental effects of interference screw fixation on soft tissue anterior cruciate ligament (ACL) reconstruction after 6 weeks and compare them with a cross-pin technique. METHODS: In an intra-articular model, ovine soft tissue grafts were fixed with two 3.3-mm biodegradable pins or with interference screws. Maximum load, yield load, and stiffness of the femur-graft-tibia complex were evaluated immediately after surgery and 6 weeks postoperatively. RESULTS: For knees with interference screw fixation, strength deteriorated by 81% and stiffness deteriorated by 67%. For knees with double cross-pin fixation, strength deteriorated by 48% and stiffness improved by 52%. These differences were statistically significant. At the time of surgery, all grafts failed by slippage of the graft past the screw or by cross-pin failure. At 6 weeks postoperatively, the grafts of both groups failed at the tibial or femoral tunnel entrance. CONCLUSIONS: After 6 weeks, the biomechanical characteristics of grafts that were fixed with cross-pins were superior to those of grafts after interference screw fixation. CLINICAL RELEVANCE: Because of significantly inferior biomechanical stability after interference screw fixation, a less aggressive program of rehabilitation might be recommended.

Achilles Tendon↗

An experimental in vivo analysis of the resorption to ultrasound activated pins (Sonic weld) and standard biodegradable screws (ResorbX) in sheep.

We compared the healing and reaction in the mandibles of 11 sheep of a conventional bioresorbable screw osteosynthesis with the newly developed ultrasound-activated pin osteosynthesis. The thermal stress caused by insertion of the ultrasound-aided pins leads to no cellular reaction around the pin. There is neither clinical nor histological evidence of any initial inflammation that could have been induced by the insertion. Adequate attachment of fibrous tissue to the pin head and the absence of any inflammation are important preconditions for the introduction of this new method of osteosynthesis into clinical practice. Further advantageous characteristics are easy intraoperative handling and a reduction in operating time, because cutting the thread is not required. There must be sufficient interlinkage of the polymer and the trabecular structures to ensure stability.

Absorbable Implants↗

Septic arthritis of the major joints of the lower limb after periarticular external fixation application: are conventional safe corridors enough to prevent it?

Septic arthritis as a result of pin track infection, following application of external fixators in periarticular fractures of the lower limb, is a rare, but serious complication. Several studies, combining cadaver dissection and MRI scans or conventional X-ray measurements, have tried to define the exact anatomy of the capsular reflection in the major joints of the lower limb (hip, knee and ankle), in order to provide specific safe corridors for extra-capsular wire and pin placement. These studies are reviewed, their methods and results are presented, and their conclusions are evaluated as suggested guidelines for safe extra-capsular wire and pin insertion.

Arthritis, Infectious↗

A randomised study in all cervical hip fractures osteosynthesis with Hansson hook-pins versus AO-screws in 199 consecutive patients followed for two years.

A consecutive series of patients with all types of cervical hip fracture (both undisplaced and displaced) were randomised to osteosynthesis with Hansson hook-pins (n = 98) or AO-screws (n = 101). Background parameters, fracture type and reduction of the fracture did not differ significantly between the groups. Fifty-seven percent of the patients were operated on within 6 h of admission to hospital, 74% within 12 h and 92% within 24 h. The mean (median) time for operation was 36 (30) min for the hook-pins and 40 (35) min for the AO-screws. The devices were significantly better positioned in the hook-pin group (81% of cases good) compared to the AO-screws (66% good) (p = 0.04). In all, 72% of the patients had no deficiency either in reduction of the fracture, positioning of the implants or had drill penetration of the femoral head. Direct unrestricted weight bearing was encouraged in 92% of the hook-pin and 90% of the AO-screws group. The mean (median) hospital time was 13 (10) days with no significant difference between the groups. Following treatment, 5% walked without aids, 76% of the patients walked with some aids, and 16% could not walk. The walking ability was not known for 4%. At four months, 59% of the patients were living in their own home (64% before fracture), 18% (25% before) in a nursing home, 5% (11% before) in other accommodation and 18% were dead. After two years, 77% of the hook-pin patients had not needed any re-operation compared to 73% in the AO-screw group. In total a secondary hemi-arthroplasty had been performed in 7% and total hip arthroplasty in 12% of the patients. Extraction only of osteosynthesis material had been performed in 5%. The difference in the reoperation rates between the two methods was not significant. In the undisplaced fractures, 84% of the patients had not needed any reoperation after two years compared to 70% among the displaced fractures. Major reoperation had been performed in 10% (1% hemi and 9% total hip arthroplasty) in the patients with undisplaced fractures compared to 26% in those with displaced fractures (10% hemi, 16% total hip arthroplasty and 1% Girdlestone operation). The remaining patients had only undergone removal of metalwork. Osteosynthesis thus proved to be a successful operation in many of the patients with displaced fractures. A preoperative, prognostic-based selection between osteosynthesis and arthroplasty is the future goal for optimised femoral neck fracture treatment.

Adult↗

Surgical aspects of infection involving osteosynthesis implants: implant design and resistance to local infection.

Infection is still a major complication associated with surgery in orthopedics and traumatology. The implant design, the implant material, and the implantation technique may play essential roles in preventing infection. The goal of this paper is to discuss a series of experiments evaluating different aspects of both surgical procedures and implants. For this purpose, standardized local application of the human pathogen Staphylococcus aureus was performed in an animal model. Although these experimental results may be clinically relevant, direct extrapolation to clinical infection rates should be avoided.

Animals↗

Physical and technical aspects of intramedullary reaming.

Intramedullary pressure during reaming is influenced by various factors, including those of the patient, such as bone morphology and location and type of fracture, and those related to reaming technique and instruments. Through intensive research, technical developments and the use of modern materials, intramedullary pressure caused by modern reaming systems can be reduced to a minimum and, perhaps, completely avoided through use of the reaming-irrigation-aspiration system.

Bone Nails↗

Dynamic traction and minimal internal fixation for thumb and digital pilon fractures.

PURPOSE: This study evaluates the use of limited internal fixation and dynamic traction for the treatment of severely displaced digital and thumb pilon fractures. METHODS: Six patients were evaluated both clinically and radiographically at an average of 29 months after surgery (range, 18-36 months) for pain, range of motion, and radiographic signs of joint space narrowing and congruence. Surgery involved the placement of a pin for dynamic traction and an assessment of the adequacy of the articular alignment. A limited incision and supplemental K-wires were often used to improve the position of severely displaced fragments or for the repair of the central tendon. RESULTS: Three patients were pain free, 2 patients experienced pain with prolonged activity, and 1 patient had pain associated with activities of daily living. Average digital arc of motion of the proximal interphalangeal joint was 94 degrees (range, 90 degrees-100 degrees) and thumb interphalangeal motion was 62.5 degrees (range, 60 degrees-65 degrees). The average duration of digital traction was 3.5 weeks. Four patients had greater than 1 mm incongruity of the articular surface immediately after surgery. At final evaluation, all patients had good joint congruency and 2 patients had joint space narrowing but were asymptomatic. There was 1 minor pin tract infection. CONCLUSIONS: Dynamic traction combined with limited internal fixation can be an effective treatment for displaced intra-articular pilon fractures. This technique may allow for earlier removal of traction and simultaneous repair of soft tissue injuries.

Activities of Daily Living↗

Management of the failed biaxial wrist replacement.

Nine cases of failed biaxial wrist replacement underwent revision surgery and subsequent clinical and radiographic assessment at a mean follow-up of 28 months. Clinical assessment included the hospital for special surgery (HSS) and activities of daily living scoring systems. Five patients had a revision biaxial wrist replacement, three had wrist fusions and two underwent an excision arthroplasty. The mean HSS score was 73 for the revision biaxial replacements, 63 for the wrist fusions and 92 for the excision arthroplasties. The mean activities for daily living score was 16 for the revision biaxial replacements, 14 for the wrist fusion and 20 for the excision arthroplasties. Despite the experience of implant failure, six patients would still choose a primary wrist replacement again. All patients in this small series appear to have had good clinical outcomes. Revision to another wrist replacement appears no worse than a wrist fusion in the short term and patients value the preservation of movement that an implant offers.

Activities of Daily Living↗

Pin arthrodesis of the wrist--a modified technique.

An intramedullary pin is commonly used for wrist arthrodesis in patients with rheumatoid arthritis. However, pin migration is a recognized complication of this technique. We report the results of wrist fusion in 15 patients using a modified technique with a transverse blocking screw inserted into the metacarpal distal to the intramedullary pin to prevent distal migration and backing out of the intramedullary pin. The procedure is simple to perform, does not add significantly to the operating time and has not been associated with any complications.

Adult↗

Replacement of an extruded segment of radius after autoclaving and sterilising with gentamicin.

A 10 year-old boy had a traumatic extrusion of 10 cm of the distal radius. The segment of bone was replaced after washing it with providine iodine solution and normal saline, autoclaving and dipping in gentamicin solution for 2 hour. At four and half year's follow-up, there was complete incorporation of the segment with almost full functional recovery. We report this case for its rarity and discuss the treatment.

Bone Nails↗

Repeat pelvic osteotomy in patients with failed closure of bladder exstrophy: applications and outcomes.

BACKGROUND/PURPOSE: In patients with failed primary or secondary closure of bladder exstrophy, repeat osteotomy is useful in facilitating reconstruction. The clinical consequences of repeated surgical disruption of the pelvic ring have not been carefully described, however. METHODS: We reviewed our experience with exstrophy patients who had undergone repeat pelvic osteotomy (RPO) and analyzed patient history, complications, and orthopedic outcomes. RESULTS: Fifty-six patients who underwent RPO were identified. All had previously failed at least one attempted bladder closure. The patients underwent RPO at a mean age of 23.2 months. The mean time from initial osteotomy to RPO was 20.5 months. Anterior innominate or combined iliac/innominate approaches comprised 80% of RPO procedures. Of the patients, 95% had a normal gait after RPO; all 3 patients with an abnormal gait had osteotomy site nonunion, which was treated with bone grafting. Five patients had local fixator pin site infections, which were managed with local care and oral antibiotics, and 1 patient had late osteomyelitis requiring incision and drainage. No patient had femoral or sciatic nerve palsy after RPO at our institution. CONCLUSIONS: Orthopedic complications after RPO are uncommon, and most patients have a normal gait postoperatively. Repeat pelvic osteotomy is useful in the complex reconstruction of failed exstrophy closures, and few cases fail reclosure when the reconstruction is combined with RPO.

Bladder Exstrophy↗

Scapulothoracic fusion for painful winging of the scapula in nondystrophic patients.

A modified technique of scapulothoracic fusion was used in 6 patients who did not have muscular dystrophy and who were later evaluated clinically. The cause of the painful winging of the scapula was traumatic disruption of the trapezius and the accessory nerve in 3 patients, injury to the brachial plexus in 2, and Sprengel's deformity in 1. To obtain fusion, double wires were passed around each of 4 ribs. A Rush pin was then contoured to fit the curvature of the scapula, and the wires were passed through the scapula and tied over the Rush pin with bone graft. The mean age of the patients was 30 years (range, 22-39 years), with a mean follow-up of 49 months. The mean increase in elevation was 18 degrees with significant pain relief. The medium-term results showed that this operation was successful in achieving stability of the scapula while improving pain and function in patients without facioscapulohumeral dystrophy.

Adult↗

A structural fingertip model for simulating of the biomechanics of tactile sensation.

Tactile performance of human fingertips is associated with activity of the nerve endings and sensitivity of the soft tissue within the fingertip to the static and dynamic skin indentation. The nerve endings in the fingertips sense the stress/strain states developed within the soft tissue, which are affected by the material properties of the tissues. The vibrotactile sensation and tactile performance are thus believed to be strongly influenced by the nonlinear and time-dependent properties of the soft tissues. The purpose of the present research is to simulate the biomechanics of tactile sensation. A two-dimensional model, which incorporates the essential anatomical structures of a finger (i.e. skin, subcutaneous tissue, bone, and nail), has been used for the analysis. The skin tissue is assumed to be hyperelastic and viscoelastic. The subcutaneous tissue is considered to be a nonlinear, biphasic material composed of a hyperelastic solid and an inviscid fluid phase. The nail and bone are considered to be linearly elastic. The advantages of the proposed fingertip model over the previous "waterbed" and "continuum" fingertip models include its ability to predict the deflection profile of the fingertip surface, the stress and strain distributions within the soft tissue, and most importantly, the dynamic response of the fingertip to mechanical stimuli. The proposed model is applied to simulate the mechanical responses of a fingertip under a line load, and in one-point (1PT) and two-point (2PT) tactile discrimination tests. The model's predictions of the deflection profiles of a fingertip surface under a line load agree well with the reported experimental data. Assuming that the mechanoreceptors in the dermis sense the stimuli associated with normal strains (the vertical and horizontal strains) and strain energy density, our numerical results suggest that the threshold of 2PT discrimination may lie between 2.0 and 3.0 mm, which is consistent with the published experimental data. The present study represents an effort to develop a structural model of the fingertip that incorporates its anatomical structure, and the nonlinear and time-dependent properties of the soft tissues.

Animals↗

Subtrochanteric femur fractures.

Subtrochanteric femur fractures have demanded special consideration in orthopaedic traumatology, given the high rate of complications associated with their management. The intense concentration of compression, tensile, and torsional stresses and decreased vascularity of the region has challenged orthopaedists with problems of malunion, delayed union, and nonunion resulting from loss of fixation, implant failure, and iatrogenic devascularization of the operative exposure. Only recently has a better understanding of fracture biology, reduction techniques, and biomechanically improved implants allowed for subtrochanteric fractures to be addressed with consistent success.

Adult↗