Comparison of Staple, Anchor, and Tenodesis Screw for Posterior Tibialis Tendon Fixation: A Biomechanical Analysis

Various posterior tibialis tendon fixation techniques are described in literature. Suture anchor, staple and tenodesis screws are widely used for posterior tibialis tendon transfer, but their stiffness and the maximal ultimate failure load were not tested before. We aimed to compare the initial ultimate failure load and stiffnesses of suture anchor, staple and tenodesis screws on bovine tendon fixation to bovine metaphyseal bone. Thirty-five fresh bovine ankle joints and hooves were obtained from a local abattoir. Metatarsals bones with long extensor tendons were harvested. Staple group had 15, suture anchor group had 10, and tenodesis screw group had 10 samples. All fixations were tested with Instron® ElectroPuls® E10000 Test Instrument. Ultimate failure load and failure location were noted. Staple group's median ultimate failure load was 210.03 N (IQR: 133.43), suture anchor group's was 124.33 N (IQR: 63.67), and tenodesis screw group's was 394.46 N (IQR:115.09). Median stiffness of the staple group was 19.87 N/m (IQR: 15.29); the tenodesis screw group's was 20.28 N/m (IQR: 6.18), the anchor group's was 8.54 N/m (IQR: 4.35). Staples' failure occurred on tendon-staple interface, while suture anchors' occurred on anchor-suture interface and tenodesis screws' occurred on tendon-suture interface. Tenodesis screws' ultimate failure load was the highest (tenodesis vs anchor and staple p < .001 and p = .032, respectively). Staple fixation is less expensive than the other methods and can provide sufficient fixation strength but was weaker than the tenodesis screw fixation. Staples are still a good choice for tendon to bone fixation, whereas the suture anchors provide lower fixation strength at a higher cost.

Ionized and non-ionized radiation effects on coronary stent implantation

The purpose of this study is to examine the clinical radiation effects on patients with various stents. Several previous researches focused on the mechanical and physical features of the stents, but there have been few studies that focus on the interaction with radiological and clinical radiation. For stent material analysis, the ANSYS package program was employed. These materials and models are often built in three dimensions for three different types of stents made of three various materials. Estimates of blood pressure and thermal radiation were explored, as were the effects of non-ionizing radiation. Furthermore, the radiation attenuation characteristics of stent samples are investigated. The mass attenuation coefficient values are computed using MATLAB code over a large energy range of 0.015-15 MeV, and the findings are validated using theoretical WinXCom results. To determine the gamma-ray attenuation performances of the studied stent samples, variables such as the mass attenuation coefficient (MAC), half-value layer (HVL), tenth-value layer (TVL), mean free path (MFP), effective atomic number (Z_eff), exposure build-up factor (EBF), and energy absorption build-up factor (EABF) are computed. Effective removal cross-sections (Σ_R) of stent samples were acquired to determine the capacity of stent samples to stop fast neutrons. Finally, the ability of stent samples to stop charged alpha and proton particles was evaluated utilizing mass stopping power and projected range parameters. The discovery demonstrates that S3 has the best attenuation as well as the best proton, alpha, and gamma radiation attenuation capability.

Comparison of Monte Carlo simulations and theoretical calculations of nuclear shielding characteristics of various borate glasses including Bi, V, Fe, and Cd

The aim of this study is to evaluate both buildup factors and photon attenuation effectiveness of some borate glasses doped by Cd, Fe, V, and Bi. The mass attenuation coefficients (μ_m) of these glass systems have been calculated via MCNP6 and GEANT4 computer simulation codes over 0.02-10 MeV energy range and compared with the theoretical results of WinXCOM program. And then, half-value layer, (HVL), mean free path (MFP), and effective atomic number (Z_eff) for the different content based glasses have been determined. Through G-P fitting process, exposure buildup factors (EBF) have been found in the energy range of 0.015-15 MeV up to 40 mfp. It can be concluded that SrBiO20 glass is alternative material in terms of photon attenuation, respectively.

Bizarre Parosteal Osteochondromatous Proliferation (Nora's Lesion) in the Medial Sesamoid of the First Toe

Bizarre parosteal osteochondromatous proliferation, or Nora's lesion, is a unique bony lesion that generally originates from the small bones of the hands and feet in young adults. We report a case of a bizarre parosteal osteochondromatous proliferation originating from the medial sesamoid of the first toe that was managed surgically by en bloc excision. At 5-year follow-up, there was no evidence of recurrence.

A realistic quantum capacitance model for quantum Hall edge state based Fabry-Pérot interferometers

In this work, the classical and the quantum capacitances are calculated for a Fabry-Pérot interferometer operating in the integer quantized Hall regime. We first consider a rotationally symmetric electrostatic confinement potential and obtain the widths and the spatial distribution of the insulating (incompressible) circular strips using a charge density profile stemming from self-consistent calculations. Modelling the electrical circuit of capacitors composed of metallic gates and incompressible/compressible strips, we investigate the conditions to observe Aharonov-Bohm (quantum mechanical phase dependent) and Coulomb blockade (capacitive coupling dependent) effects reflected in conductance oscillations. In a last step, we solve the Schrödinger and the Poisson equations self-consistently in a numerical manner taking into account realistic experimental geometries. We find that, describing the conductance oscillations either by Aharanov-Bohm or Coulomb blockade strongly depends on sample properties also other than size, therefore, determining the origin of these oscillations requires further experimental and theoretical investigation.

The effect of screw thread length on initial stability of Schatzker type 1 tibial plateau fracture fixation: a biomechanical study

Background

This study compares the cyclic loading properties and failure loads of two screw combinations on a synthetic Schatzker type 1 tibia fracture model. Our hypothesis was that after adequate compression with first a partially threaded screw, addition of a fully threaded screw would provide more stability than an addition of a second partially threaded screw.

Methods

The Schatzker type 1 tibial plateau fracture model was created. Fixation was obtained in group A (n = 10) with two partially threaded screws and in group B (n = 10) with one fully threaded screw and one partially threaded screw. Load-displacement evaluation was made at each 1000-cycle interval up to 10,000 cycles. Failure load was identified as the load creating a 2-mm displacement. Two-factor (groups and periods) repeated measurement analysis of variance and independent sample t tests were used.

Results

According to the two-factor repeated analysis, there was no significant difference for periods (p = 0.29) and time-period interaction (p = 0.59) (Wilk’s Lambda F value, 1.507 and 0.871, respectively). In the test of between-subject effects, there was no significant difference between groups in terms of cyclic loadings (p = 0.06, F = 4.065). However, in the t test for each 1000-cycle interval, the value of mean displacement in group B was significantly lower than that in group A in the initial, 1000-, 2000-, and 3000-cycle intervals (p = 0.023, 0.031, 0.025, 0.043, respectively). The mean displacement and standard deviations increased with the number of cycles. The mean range of displacement initially was 0.66 mm for group A and 0.36 mm for group B. The mean range of displacement after 10,000 cycles was 0.79 mm for group A and 0.44 mm for group B. The mean failure load value was 682 ± 234 N for group A and 835 ± 245 N for group B. In independent sample t tests, there were no significant differences between the two groups in terms of failure load (p > 0.05).

Conclusions

Obtaining fixation with one partially and one fully threaded screw can minimize displacement at the fracture site at early cyclic loadings.

MMP-3 gene polymorphisms and Osteosarcoma

Osteosarcoma (OSA) is the most common adolescence cancer among all primary bone tumors next only to multiplemyeloma. It has a substantially worse prognosis and ability to metastasize to lung. MMPs (matrix metalloproteinases) are among the major proteases that take part in regulation of ECM (extracellular matrix). MMPs play an active role in the formation of the osteoid tissue, rich in collagens and other ECM proteoglycans. They also take part in pro-osteoclast, osteoclast, osteoblast, and osteoid formation. Many members of the MMP gene family have been linked to human cancers. It has been shown that MMPs particularly play a role in the tumor's acquisition of an invasive and metastatic character. In our study, the E45K and T102T polymorphisms of MMP-3 were studied using the PCR-RFLP method in 135 Turkish subjects (54 subjects with osteosarcoma and 81 healthy controls). We found that frequencies of E45K G allele (p:0,010, χ²:6,710, OR:1,429, 95% Cl: 1,019-1,858) and AG genotype (p:0,001, χ²:14,753, OR:2,32, 95% Cl: 1,491-3,626) were elevated in patients compared to controls. Besides, there was a significant difference in.E45K AA genotype between study groups (p:0,004, χ²:8,182, OR: 2,929, 95% Cl: 1,38-6,19). There were no significant differences between any genotypes or allele in the control and patient groups for MMP-3 T102T polymorphism. Our findings indicate that the G allele and AG genotype of MMP-3 E45K polymorphism is associated with increased risk of osteosarcoma in adolescent population of Turkey.

Scapulothoracic arthrodesis in facioscapulohumeral dystrophy with multifilament cable

Patients with facioscapulohumeral dystrophy (FSHD) are affected mostly by impaired shoulder function. Scapulothoracic arthrodesis was introduced to improve shoulder function. We evaluated the outcomes of scapulothoracic arthrodesis using multifilament cables, performed on 13 patients with FSHD (18 shoulders). There were eight males and five females (mean age, 29 years; range, 20-50 years). Outcome criteria were active shoulder forward flexion and abduction, the Disabilities of the Arm, Shoulder, and Hand (DASH) score, respiratory function tests, and a new shoulder function score. Patients were followed for a minimum of 24 months (average, 35.5 months; range, 24-87 months). Solid fusion was obtained in all shoulders (two after revision); active abduction range increased from 47.2 degrees +/- 11.6 degrees to 102.2 degrees +/- 10.0 degrees (mean +/- standard deviation) and anterior flexion range from 55.6 degrees +/- 16.1 degrees to 126.1 degrees +/- 20.9 degrees . The DASH score decreased from 33.6 +/- 8.9 points preoperatively to 11.6 +/- 8.0 points postoperatively. Shoulder function score increased from 15.9 +/- 2.4 points to 22.2 +/- 1.3 points. Scapulothoracic arthrodesis provides satisfactory function in patients with FSHD. Our data suggest use of multifilament cables for fixation is a reasonable option with an acceptable complication rate.

LEVEL OF EVIDENCE

Level IV, case series. See the Guidelines for Authors for a complete description of levels of evidence.

Effect of antibiotic loading on the shear strength at the stem-cement interface (Shear strength of antibiotic loaded cement)

The purpose of this study was to investigate the effects of addition of antibiotics into cement powder on the shear properties of the cement-metal interface. The approach involved adding 800 mg of teicoplanin to 40 g bone cement powder in the t-800 group, 1,600 mg teicoplanin in the t-1,600 group, and no antibiotic in the control group. Industrially prepared bone cement containing 500 mg of gentamicin was used as group g-500. Each group consisted of ten samples. Cement-metal interfaces were produced using metal discs with porous surfaces (1 microm) and templates at the third minute. Shear stability of specimens was measured in a material testing machine. The ANOVA test was used for comparison between the mean shear results of each group. Results showed that mean shear stress to failure values were 12.28+/-3.35 MPa for the control group, 11.72+/-3.09 MPa for the t-800 group, 13.25+/-2.36 MPa for the t-1,600 group and 13.09+/-2.58 MPa for the g-500 group. No statistically significant differences were found between results of the groups. Results of the study have proven that addition of 1,600 mg of teicoplanin or 500 mg gentamycin in 40 g of bone cement does not decrease the shear strength at the cement-metal interface significantly on the day of application.

Methylenetetrahydrofolate reductase C677T gene polymorphism in osteosarcoma and chondrosarcoma patients

This study was designed to investigate the association of MTHFR C677T polymorphism and the risk of two common musculoskeletal sarcomas, osteosarcoma and chondrosarcoma. MTHFR genotypes were determined in 56 patients (44 osteosarcoma, 12 chondrosarcoma) and 44 controls using the PCR-RFLP technique. In the gender subgroup analysis, wild-type A allele frequency was higher in male osteosarcoma patients than in male control subjects (P = 0.064). Mutant V allele and mutant VV genotype were similar in the control group compared to the sarcoma groups (P > 0.05). No correlation could be proved between patient tumour site, presence of metastasis, and local tumour relapse and MTHFR polymorphism. The MTHFR C677T polymorphism may not be important in an individual's susceptibility to osteosarcoma and chondrosarcoma in Turkey and may not be a useful marker for identifying patients at high risk of developing sarcomas.

The genotoxic effects in lymphocyte cultures of children treated with radiosynovectomy by using yttrium-90 citrate colloid

The aim of this study was to investigate the genotoxic effect on the peripheral blood lymphocytes potentially induced by yttrium-90 citrate colloid (Y-90) in children who were undergoing radiosynovectomy for hemophilic synovitis, using chromosomal aberration analysis (CA) and the micronuclei (MN) assay for detecting chromosomal aberrations, as well as the sister chromatid exchanges (SCE) technique for assessed DNA damage.

MATERIALS AND METHODS

Cytogenetic analyses were undertaken in 18 boys (mean age, 14.5 +/- 2.1 years) with hemophilic synovitis who underwent radiosynovectomy with Y-90. CA, MN, and SCE were evaluated just prior to, then at 2 and 90 days following radiosynovectomy from the peripheral lymphocytes of the children. An activity of 185 MBq of Y-90 was injected into the 18 knee joints under aseptic conditions. To check the possibility of leakage from the joint and its migration within the body, the patients underwent scanning under a dual-headed gamma camera at the hours 2 and 48 following the procedure.

RESULTS

The procedure was well tolerated in all the children, and there was no extra-articular activity owing to extra-articular leakage of radioactive material in whole-body imaging. The mean frequency of CA in lymphocytes determined prior to the onset of therapy (0.31 +/- 0.48/900 cells) was not significantly increased, in comparison to the control values obtained 2 (0.30 +/- 0.48/900 cells) and 90 days (0.15 +/- 0.37/900 cells) after radiosynovectomy (p = 1.0 and 0.625, respectively). We observed that MN frequency was mildly increased in lymphocytes 2 days after therapy (8.30 +/- 1.89 MN/1000 binucleated cells vs. 9.23 +/- 1.79 MN/1000 binucleated cells; p = 0.013). But there was no significant difference between the baseline and the day 90 control levels of MN (p = 0.196). In the analysis of SCE frequency, there were no significant differences between the baseline (8.11 +/- 0.77) and the control analysis performed 2 and 90 days following radiosynovectomy (8.18 +/- 0.77 and 8.07 +/- 0.74; p = 0.710 and 0.662, respectively).

CONCLUSIONS

The results of this study indicated that high radiation doses are not obtained by peripheral lymphocytes of children who undergo Y-90 radiosynovectomy and, therefore, they contradict a high cancer risk.

Monitoring the genotoxic effects of radiosynovectomy with Re-186 in paediatric age group undergoing therapy for haemophilic synovitis

PURPOSE

The aim of this study was to investigate the genotoxic effect on the peripheral blood lymphocytes potentially induced by Re-186 in paediatric age group undergoing radiosynovectomy for haemophilic synovitis, by using chromosomal aberration analysis (CA) and the micronuclei (MN) assay for detecting chromosomal aberrations, as well as the sister chromatid exchanges (SCE) technique for assessing DNA damage.

METHODS

Cytogenetic analyses were evaluated in 20 boys (mean age: 13.8 +/- 2.7 years) before, and 2 and 90 days after radiosynovectomy from the peripheral lymphocytes of the patients. Joint retention and extra-articular spread of the radionuclides were evaluated by using quantitative gamma camera imaging.

RESULTS

Imaging after radiosynovectomy revealed local lymph node visualization in 8 (40%) patients and hepatosplenic visualization in 3 (15%) patients due to extra-articular leakage of radioactive material. The mean frequency of chromosome aberrations (0.2 +/- 0.4/1000 cells) determined prior to the onset of therapy was not significantly increased in comparison with control values obtained 2 days (0.4 +/- 0.5/1000 cells) and 90 days (0.2 +/- 0.4/1000 cells) after therapy (P = 0.754 and P = 1.0). In the analysis of MN and SCE, when we compare the baseline levels, the mean MN and SCE frequencies were slightly higher in the control analyses performed 2 and 90 days after radiosynovectomy but there were no significant differences between baseline and control levels (chi(2) = 2.621, P = 0.270 and F = 0.573, P = 0.569, respectively).

CONCLUSION

The major finding of this study with relatively small sample is that, radiosynovectomy with Re-186 does not seem to induce early genotoxic effects on the peripheral blood lymphocytes in paediatric age group.

Posterior bone block for footdrop: a report of two cases

A posterior bone-block operation is one of the few treatment options in cases of paralytic footdrop. A case with a flail ankle and no bony deformity is ideal for this approach. Two cases of acquired flail ankle with equinus deformity were treated using a new modification of the bone-block technique that does not interfere with subtalar joint motion. A bone block harvested from the iliac crest was fixed at the posterior talus after partial resection of the posterior tubercle. The graft was in contact with the posterior malleolus of the tibia. Satisfactory correction was achieved, and both patients could walk without the use of external splints.

Time-dependent changes in failure loads of 3 biceps tenodesis techniques: in vivo study in a sheep model

BACKGROUND

Failure load of the tendon-fixation material-bone unit has a crucial importance for the rehabilitation protocol after tenodesis procedures.

PURPOSE

To investigate and compare the time-dependent changes in fixation strengths of 3 proximal biceps tenodesis techniques.

STUDY DESIGN

Controlled laboratory study.

METHODS

Two intraosseous techniques (suture sling and tenodesis screw) and 1 extraosseous technique (2 suture anchors) were investigated. Biceps tenodesis was performed on 45 shoulders of 26 sheep, 15 shoulders for each technique. Twelve similar cadaveric sheep shoulders (4 for each technique) provided the day 0 results. Sheep were sacrificed at 3, 6, and 9 weeks, and specimens were tested for the failure load of the tenodeses.

RESULTS

All 3 tenodesis techniques were found to have similar failure loads at all time intervals tested. All 3 curves remained below the failure load of the intact tendon (862 +/- 96 N) and above their day 0 results for the study period; similarly, at each time interval, results tended to be better compared to the previous test. The tenodesis screw group exhibited significantly higher failure loads at week 3 (419 +/- 53 N) compared to day 0 values (164 +/- 45 N) (P = .009). The same level of significance was observed at week 6 in the remaining 2 groups.

CONCLUSION

Tenodesis of the biceps tendon on the proximal humerus at an extra-articular site does not weaken after surgery. The tenodesis screw group had a significantly higher increase in the fixation strength within the first 3 weeks.

CLINICAL RELEVANCE

No significant differences could be found between the failure loads of all 3 investigated tenodeses for the first 9 weeks.

Tensile strength of ligaments after thermal shrinkage depending on time and immobilization: in vivo study in the rabbit

The effects of immobilization on healing collagenous tissue treated with thermal shrinkage are investigated in an in vivo rabbit model. Thermal shrinkage was performed on 45 of 50 medial collateral ligaments in 25 mature New Zealand rabbit knees. In half of the knees, the joints were immobilized. Animals were killed at 0, 3, 6, and 9 weeks postoperatively. Failure loads of ligaments were determined, and morphologic changes were evaluated by electron microscopy. The failure load of shrunken ligaments was significantly lower than that of the intact ligaments on the day of operation (P<.05). Shrunken ligaments reached their highest failure loads in the third week within the first 9 weeks. The immobilized ligaments remained weaker than the mobile group, but this difference was statistically significant only in the ninth week (P<.05). Immobilization seems to have negative effects on the healing ligament. Ideal timing for remobilization is still controversial, and abandoning immobilization protocols for longer than 3 weeks should be considered.

Complications encountered during lengthening over an intramedullary nail

BACKGROUND

In limb-lengthening, the quest for increased patient comfort and a reduced period of external fixation has led to techniques such as lengthening over an intramedullary nail. The goals of this study were to investigate the rate and types of complications encountered during lengthening over an intramedullary nail and to identify solutions to these complications.

METHODS

Forty-two segments (thirty-five femora and seven tibiae) in thirty-five patients were lengthened. The mean age of the patients was 26.6 years, the mean amount lengthened was 6.3 cm (range, 2.5 to 11.5 cm), the mean external fixation index was 18.7 days/cm, and the mean lengthening index was 31.2 days/cm. The patients were followed for a mean period of forty-four months postoperatively.

RESULTS

Eighteen complications occurred in sixteen (38%) of the forty-two segments for a rate of 0.43 complication per segment. Complications were classified, according to the system of Paley et al., as two problems, thirteen obstacles, and three sequelae. Sixteen of them required additional surgical interventions. A preoperative score of >6.5 on the system of Paley et al., a lengthening of >6 cm, and a lengthening percentage of >21.5% of the original bone length were indicators of a higher probability of the occurrence of complications.

CONCLUSIONS

Lengthening over an intramedullary nail provides increased patient comfort and reduces the external fixation period. If the problems encountered are treated aggressively, the result of the treatment can be quite satisfactory.

Failure strength of bioabsorbable interference screws: effects of in vivo degradation for 12 weeks

We investigated the effect of in vivo degradation for 6-12 weeks on the fixation strength of polylactide bioabsorbable interference screws. Ten bioabsorbable interference screws were used to fix the patellar tendon autograft in ten live sheep knees, which were equally divided into two groups and killed in the 6th or 12th week. The control group consisted of four cadaveric knees. Following the killing of the animals the screws were retrieved and reused to fix patellar tendon grafts in cadaveric sheep knees. Tendon pull-out tests were performed for the partially degraded screws, for the control group, and for the reused screws of the control group. Macroscopic and microscopic examinations of the 6- and 12-week specimens were performed. Tendons pulled-out with an average force of 357+/-30 N in the cadaveric control group on the first use and with 465+/-118 N on the second use. The partially degraded screws failed with a mean load of 399+/-119 N in the 6-week group, and 12-week screws at 447+/-72 N. No macroscopic sign of degradation was observed on the retrieved screws. Histological examination of the 6 week specimens showed necrotic changes in the tendon around screw contact areas. Healing with granulation tissue was present in the same area in the 12th week. Foreign body reaction or an excessive inflammatory reaction was not observed. In vivo degradation of poly- l-lactide interference screws for 12 weeks thus causes neither a loss in the fixation strength of the screws nor an obvious inflammatory reaction.

Primary fixation strength of rotator cuff repair techniques: a comparative study

PURPOSE

The goal of the study was to compare the primary fixation strength of transosseous suture, suture anchor, and hybrid repair techniques for rotator cuff repair.

TYPE OF STUDY

Animal model experiment.

METHODS

Thirty-two sheep shoulders were divided into 4 homogeneous groups, according to bone density and tendon dimensions. Infraspinatus tendons were transected from their insertions and reattached using 4 different techniques. Group 1 was repaired with a single Mason-Allen stitch and 2 transosseous tunnels for each end of the suture, knotted on the lateral cortex of proximal humerus; group 2 was repaired with double Mason-Allen stitches and 2 transosseous tunnels; group 3 was repaired with 2 Corkscrews (Arthrex, Germany); and group 4 was repaired with 2 Corkscrews combined with a single Mason-Allen transosseous suture. All specimens were tested for their fixation strengths with a material testing system.

RESULTS

The mode of failure in group 1 was mainly suture breakage. In groups 3 and 4, the tendons pulled out from the sutures. In group 2, sutures broke the bony bridge between the 2 tunnels. The mean load to failure value was 160.31 +/- 34.59 N in group 1, 199.36 +/- 11.73 N in group 2, 108.32 +/- 15.98 N in group 3, and 214.24 +/- 28.52 N in group 4. Anchor fixation was significantly weaker compared with other groups (P <.001). Combination of a transosseous suture and anchor fixation (group 4) was significantly stronger than the single transosseous suture (group 1) and double anchor techniques (group 3) (P <.001).

CONCLUSIONS

Hybrid technique was the strongest among the tested rotator cuff repair techniques. With the addition of one transosseous suture to two anchors, the strength of the repair could be doubled.

S1 pediculoiliac screw fixation in instabilities of the sacroiliac complex: biomechanical study and report of two cases

OBJECTIVE

A new technique for posterior sacroiliac fixation is described and compared with conventional techniques.

PATIENTS/MATERIAL AND METHODS

A patient with sacral alar fracture (zone 1) and another one with sacroiliac joint instability due to tuberculous infection underwent fixation using screws placed in the S1 pedicle and the iliac bone. Vertical stability of the new technique also was investigated using polyurethane pelvic bone analogs and compared with anterior double plating (group P) and iliosacral screw fixation (group ISS) techniques.

RESULTS

Healing was obtained and reduction was maintained in both patients on the final follow-up examination at 2 years postoperatively. Vertical loading tests revealed that failure loads within the first 10 mm of displacement of the new pediculoiliac screw fixation technique (group PIS) was higher than plating (P = 0.03) and lower than ISS techniques (P = 0.002). Ultimate failure load of the PIS technique was slightly higher than plating (P = 0.277) and lower than ISS techniques (P = 0.003). With the addition of an iliosacral screw to the pediculoiliac screw construction (PIS+ISS), the PIS technique became more stable in early (P = 0.110) and ultimate failure loads (P = 0.003).

CONCLUSIONS

Pediculoiliac screw fixation for sacroiliac joint disruptions and zone I sacrum fractures using iliac and S1 pedicle screws is a new and effective alternative for obtaining and maintaining anatomic reduction.

Prognostic factors in prosthetic replacement for acute proximal humerus fractures

OBJECTIVES

To investigate the effect of some epidemiological and radiologic factors on the outcome of prosthetic replacement in acute proximal humerus fractures.

DESIGN

Retrospective clinical study.

PATIENTS

Thirty-two patients [mean age 58 (range 37-83 years)] with a mean follow-up period of 35 months (range 8-80 months). Fifteen cases had Neer type IV, 2 had type III, and 15 patients had fracture-dislocations.

MAIN OUTCOME MEASUREMENTS

Neer's criteria, Constant score, and elevation degree were used. Radiological parameters were union and position of the tuberosities, bone stock, and position of the prosthesis.

RESULTS

Excellent or good results according to Neer's criteria were obtained in 24 of the 32 cases (75%), and unsatisfactory results in 8 cases (25%). Mean Constant score was 68 (range 19-98) and mean elevation degree 113 (range 30-180). Thirty-one cases (97%) had no or mild pain. Cases operated within 14 days following injury had a better general outcome (p = 0.005). The humeral offset was directly correlated to the elevation degree (p = 0.011) and Constant score (p = 0.002), whereas the head height was inversely correlated to the same parameters (p = 0.001 for both). The cutoff point for the humeral offset-general outcome correlation was calculated as 23 mm using ROC curve analysis. The most common complications were problems concerning the tuberosities (50%), and they adversely affected the clinical outcome (p = 0.002).

CONCLUSIONS

Preoperative delay, problems of tuberosity fixation, and position of the tuberosities were parameters influencing the clinical outcome. Lateralization of the tuberosities results in better scores, whereas their distal transfer can be related to a poorer outcome.

Muscular buttonholing: An unusual cause of irreducible knee dislocation

In cases of irreducible knee dislocation, all the medial joint structures have been reported to be the obstructing tissue. The case presented, the first in the English-language literature, is buttonholing of the femoral condyle through the vastus medialis muscle. Entrapment of the muscle bundle was diagnosed preoperatively using magnetic resonance imaging scans. The joint could be reduced easily, following sectioning of the muscle bundle.

Modification of Bankart reconstruction with lateral capsulotomy and selective anatomic repair using suture anchors

Twenty consecutive patients (17 male, 3 female) with a diagnosis of traumatic recurrent anterior instability of the shoulder were treated by a modified Bankart procedure using suture anchors. The technique consists of vertical incision of the capsule, just medial to the lateral insertion on the humerus and anatomic repair of the Bankart lesion. Humeral-based capsular shifting was performed in patients with anterior-inferior instability. The average age was 24 years (range: 14 to 39 years), and average follow-up period 68 months (range: 2 to 8 years). The average Bankart rating score was 92.5 (range: 70 to 100); with 16 (80%) excellent (score 90 to 100), 2 (10%) good (score 75 to 89), and 2 (10%) fair results. Failure in terms of recurrent dislocation was not reported. Eleven patients (55%) had a loss of 5 degrees to 10 degrees of external rotation either with the extremity at the side or at 90 degrees of abduction. Nine (45%) patients had external rotation equal to the contralateral side. We believe selective anatomic Bankart reconstruction by lateral capsulotomy and humeral-based capsular shifting in cases with marked inferior laxity is a more anatomic and physiologic technique.

Time-dependent reduction in load to failure of wedge-type polyglyconate suture anchors

SUMMARY

Thirty-two absorbable (polyglyconate) and 24 nonabsorbable (polyacetal) wedge-type suture anchors (TAG; Acufex, Mansfield, MA) were implanted into sheep tibiae. Load to failure tests were performed on the day of insertion and at weeks 3, 6, and 12, followed by macroscopic examination. Failure type was suture breakage for nonabsorbable anchors in all groups, with average forces of 142.5 +/- 4.8 N on the first day, 138.0 +/- 6.6 N in week 6, and 135.6 +/- 2.9 N in week 12. In the absorbable group, suture breakage occurred on the first day with a mean force of 133.5 +/- 4. 2 N. In weeks 3, 6, and 12, suture cutout occurred with average forces of 33.75 +/- 5.0 N, 23.25 +/- 2.2 N, and 23.25 +/- 5.9 N, respectively. For absorbable anchors, results at weeks 3, 6, and 12 were significantly lower compared with initial results (P <.001). These results show that wedge-type polyglyconate anchors lose 75% of their initial pullout strength within the first 3 weeks and 84% in 6 weeks.