This study compares outcomes of fixation of subtrochanteric femoral fractures using a single lag screw (Gamma3 nail, GN) with a dual lag screw device (InterTAN nail, IN). The primary outcome was mechanical failure, defined as lag screw cut-out, back-out, nail breakage or peri-implant fracture. Technical factors associated with mechanical failure were also identified. All adult patients (>18yrs) with a subtrochanteric femoral fracture treated in a single centre were retrospectively identified using electronic records. Included patients underwent surgical fixation using either a long GN (2010–2017) or IN (2017–2022). Cox regression analysis was used to determine the risk of mechanical failure and technical predictors of failure. The study included 587 patients, 336 in the GN group (median age 82yrs, 73% female) and 251 in the IN group (median age 82yrs, 71% female). The IN group exhibited a higher prevalence of osteoporosis (p=0.002) and CKD□3 (p=0.007). There were no other baseline differences between groups. The risk of any mechanical failure was increased two-fold in the GN group (HR 2.51, p=0.020). Mechanical failure comprising screw cut-out (p=0.040), back-out (p=0.040) and nail breakage (p=0.51) was only observed in the GN group. The risk of peri-implant fracture was similar between the groups (HR 1.10, p=0.84). Technical predictors of mechanical included varus >5° for cut-out (HR 15.61, p=0.016), TAD>25mm for back-out (HR 9.41, p=0.020) and shortening >1cm for peri-implant fracture (HR 6.50, p=<0.001). Dual lag screw designs may reduce the risk of mechanical complications for patients with subtrochanteric femoral fractures

Introduction: Weber B fractures are one of the most common fractures of the ankle. Unstable fractures are treated with lateral plating and a lag screw. Another method of fixation is antiglide plating, this concept was first introduced by Brunner and Weber in 1982. Manoli and Schaeffer in 1987, showed that fixation by antiglide plate demonstrated superior static biomechanical properties compared to lateral plating. However there are some shortcomings in their study and hence we decided to perform our biomechanical study. The shortcomings of the Manoli study are. They did not use an interfragmentary lag screw for lateral plate fixation. It was a cadaveric study where the bone does not accurately represent the live bone. The quality of the bone ranging from normal to osteoporotic bone varies from cadaver to cadaver and hence there is no uniformity between the samples. Materials and Methods: We used 4th generation composite bone models validated to closely simulate human bone characteristics for fracture toughness, tensile strength, compressive strength, fatigue crack resistance and implant subsidence. 4th generation composite bone model provides uniformity of test samples which is not achievable in cadaveric studies. These bones were custom made for the experiment. We used two sets of bones, one representative of normal bone (Set A n=10) and the other of osteoporotic bone quality (Set B n=10). Each of the sets A & B will have two types of fixations for artificially created Weber B Fractures. Lateral plate with interfragmentary lag screw. Antiglide plate with interfragmentary lag screw. The strength of the fixation was measured by restressing the bone until the fixation failed using an Instron machine which simultaneously applied torque and compressive forces to the fibular construct. The resulting data was analysed on a computer and statistical analysis was performed. Results: When the two fixation constructs were stressed to failure, the lateral plate construct demonstrated less stiffness (3–5Nm/degree) and failed at lower energy levels (250Nm). Similar values obtained for the antiglide system were, stiffness of 12–16Nm/degree and energy absorbed to failure 350–450Nm. Antiglide plating was significantly more stable in the osteoporotic fibula. Conclusion: Antiglide plating with lag screw is much more stable than lateral plating. It is suitable for treatment without plaster cast post operatively. It results in a more stable fixation in osteoporotic bone

Lag screw cut-out is a serious complication of dynamic hip screw fixation in trochanteric hip fractures. Lag screw position is recognised as a crucial factor influencing the occurrence of lag screw cut-out. We propose a modification of the Tip Apex Distance (TAD) and hypothesize that it could enhance the reliability of predicting lag screw cut-out in these injuries. A retrospective study of hip fracture cases was conducted from January 2018 to July 2022. A total of 109 patients were eligible for the final analysis. The modified TAD was measured in millimetres, based on the sum of the traditional TAD in the lateral view and the net value of two distances in the anteroposterior (AP) view. The first distance is from the lag screw tip to the opposite point on the femoral head along the lag screw axis, while the second distance is from that point to the femoral head apex. The first distance is a positive value, whereas the second distance is positive if the lag screw is superior and negative if it is inferior. Receiver operating characteristic (ROC) curve analysis was used to assess the reliability of various parameters for evaluating the lag screw position within the femoral head. Factors such as reduction quality, fracture pattern according to the AO/OTA classification, TAD, Calcar-Referenced TAD, Axis Blade Angle, Parker’s ratio in the AP view, Cleveland Zone 1, and modified TAD were statistically associated with lag screw cut-out. Among the tested parameters, the novel parameter exhibited 90.1% sensitivity and 90.9% specificity for predicting lag screw cut-out at a cut-off value of 25 mm, with a p-value < 0.001. The modified TAD demonstrated the highest reliability in predicting lag screw cut-out. A value of 25 mm may potentially reduce the risk of lag screw cut-out in trochanteric hip fractures

Introduction. The vast majority of intertrochanteric fractures treated with cephalomedullary nails (CMN) will heal. Occasionally even though bony union occurs excessive lag screw sliding can cause persistent pain and soft tissue irritation and return to surgery for hardware removal. The purpose of this study was to evaluate if fracture stability, lag screw tip-apex distance (TAD), and quality of reduction have any impact excessive lag screw sliding and potential cutout. Methods. As part of our level one trauma center's institutional hip fracture registry, a retrospective analysis identified 199 intertrochanteric fractures fixed with CMN between 2009 and 2015 with follow up to union or a minimum of three months. The mean follow-up was 22 months (3 to 94 months). Mean patient age was 75 years (50 to 97 years) and 72% were women. Postoperative radiographs were used to measure the TAD, quality of reduction, neck-shaft angle (NSA), and lateral lag screw prominence. Follow-up radiographs were reviewed to assess fracture union, translation, and progression of lateral lag screw prominence. Complications and reoperations were recorded. Results. The average lag screw sliding was 5±5 mm. Excessive lag screw sliding (defined as > 10 mm; one standard deviation above the mean) was present in 12% of patients. Lag screw sliding was more common in unstable fracture patterns (21% vs. 5%, p<0.01) and patients with calcar fracture gapping > 4 mm (26% vs. 4%, p<0.01). Lag screw sliding was not associated with age (p=0.9), sex (p=0.4), TAD (p=0.3), implant (p=0.8), distal interlocking screws (p=0.3), or NSA (p=0.2). There were seven (3%) patients with prominent lag screws that required removal. These patients experience more lag screw sliding than those that did not require removal (9 mm vs. 5 mm, p<0.01). The average TAD was 17±5 mm. 15 (7%) of patients had TAD of 25 mm or more. There were 2 cutouts (1%). The average TAD was larger in the cutout group (26 vs. 17 mm, p<0.01). Conclusion. In this series, the incidence of cutout was low and associated with a larger tip-apex distance. Excessive lag screw sliding was associated with unstable fracture patterns, calcar fracture gapping, and more reoperations for symptomatic hardware. Careful attention to calcar fracture reduction may minimize excessive lag screw sliding

Subtrochanteric femoral fractures are a subset of hip fractures generally treated with cephalomedullary nail fixation\[1\]. Single lag screw devices are most commonly-used, but integrated dual screw constructs have become increasingly popular\[2,3\]. The aim of this study was to compare outcomes of fixation of subtrochanteric femoral fractures using a single lag screw (Gamma3 nail, GN) with a dual screw device (InterTAN nail, IN). The primary outcome was mechanical failure, defined as lag screw cut-out, back-out, nail breakage or peri-implant fracture. Consecutive adult patients (18yrs) with subtrochanteric femoral fracture treated in a single centre were retrospectively identified using electronic records. Patients that underwent surgical fixation using either a long GN (2010–2017) or IN (2017–2022) were included. Medical records and radiographs were reviewed to identify complications of fixation. Cox regression analysis was used to determine the risk of mechanical failure and secondary outcomes by implant design. Multivariable regression models were used to identify predictors of mechanical failure. The study included 622 patients, 354 in the GN group (median age 82yrs, 72% female) and 268 in the IN group (median age 82yrs, 69% female). The risk of any mechanical failure was increased two-fold in the GN group (HR 2.44 \[95%CI 1.13 to 5.26\]; _p=0.024_). Mechanical failure comprising screw cut-out (_p=0.032_), back-out (_p=0.032_) and nail breakage (_p=0.26_) was only observed in the GN group. Technical predictors of failure included varus >5° for cut-out (OR 19.98 \[2.06 to 193.88\]; _p=0.01_), TAD;25mm for back-out (8.96 \[1.36 to 58.86\]; p=0.022) and shortening 1cm for peri-implant fracture (7.81 \[2.92 to 20.91\]; _p=<0.001_). Our results demonstrate that an intercalated screw construct is associated with a lower risk of mechanical failure compared with the a single lag screw device. Intercalated screw designs may reduce the risk of mechanical complications for patients with subtrochanteric femoral fractures

Introduction: Lag screw cut-out in gamma nailing is reported between 1,1% and 7.1% in the literature. Searching for predictive factors we performed a retrospective study, and we analyzed our cut-out cases. Material & Methods: We reviewed our first 1000 gamma nailings. A detailed analysis of the cut-out cases was performed. We focused on fracture type and the technical failures of the primary surgery. Fractures were classified according to AO. Timing of surgery, implant type and an estimated value of osteoporosis on x-ray was investigated. Distance of the tip of the lag screw from the cortical bone, from the ideal central line of the neck and head in AP and lateral view, and precision of reduction was measured and classified. We recorded the direction of cut-out and the occurrence of secondary varus displacement. Results: We had 29/1000 (2,9%) cut-outs. Average age was: 76 years. 14/29 (48%) AO A2.2 type and 8/29 (28%) A3.3 type fractures were found in the cut out group. Normal collo-diaphyseal angle was achieved in all cases primarily. In 21/29 (72%) the gap between main fragments was narrower than 5 mm, and in 8/29 (28%) it was bigger. The subjective evaluation of the reduction was 2/29 excellent, 9/29 good, 12/29 satisfactory and 6/29 bad. Primary position of the lag screw tip was caudal in 13/29, central in 10/29 and cranial in 6/29 cases. The distance of the lag screw from the central line in frontal/dorsal direction was 0–4 mm in 5/29, 5–9 mm in 12/29, 10–14 mm in 7/29 and 15–19 mm in 5/29 cases. The numbers of too short or too long lag screws were not high in this patient group. The cut out was cranial in 24/29 (83%) cases and central at 5/29 (17%) patients. We recorded 20/29 (68%) secondary varus displacement. We found 2/29 (7%) patients where none of the above mentioned technical problems could be justified. Conclusion: AO A2.2 and A3.3 fracture type is a predisposing factor. Cut-out appears relatively early. Correct positioning of the lag screw in both views is essential. Leaving the fracture in a significantly displaced position increases the risk of cut out, too. The lag screw migrates mainly cranial with a secondary varus dislocation. With adequate technique the majority of cut-outs can be avoided, but there is a little percentage of the cases when the primary mistake is not obvious. A possible explanation could be osteoporosis, but further investigation is necessary to clarify these unknown factors

Good lag screw holding power in trabecular bone of the femoral head is a requisite to achieve stability in the management of proximal femoral fractures. It has been demonstrated that insertion torque and pullout strength of lag screw are linearly correlated. Therefore, insertion torque measurement could be a method to estimate the achieved screw purchase. Manual perception is not reliable [1], but the use of an instrumented screwdriver would make the procedure feasible. The aim of this study was to assess the accuracy achievable using the insertion torque as predictor of lag screw purchase. Four different screw designs (two cannulated and two solid-core screws) were investigated in this study. Each screw was inserted into a block of trabecular bone tissue following a standardised procedure designed to maximise the experimental repeatability. The blocks of trabecular tissue were extracted from human as well as bovine femora to increase the range of bone mineral density. The prediction accuracy was evaluated by plotting pullout strength versus insertion torque, performing a linear regression analysis and calculating the difference (as percentage) between predicted and measured values. Insertion torque showed a strong linear correlation (coefficient of determination R. 2. : 0.95–0.99) with the pullout strength of lag screw. However the prediction error in pullout strength estimation was greater than 40% for small values of insertion torque, decreasing down to 15% when the lag screw was driven into good quality bone tissue. Measuring insertion torque can supply quantitative information about the achieved lag screw purchase. Since screw design and insertion procedure have been shown to affect both the insertion torque and the pullout strength [2], the prediction model must be screw-specific and determined, closely simulating the clinical procedure defined by the screw manufacturer. However, the surgeon must be aware that, even under highly repeatable experimental conditions, the prediction error was found to be high when small insertion torque was measured, i.e. when the screw was driven in low quality bone tissue. Therefore, insertion torque is not reliable in evaluating lag screw purchase in the management of proximal femur fracture of osteoporotic patients

Purpose: A variety of second generation femoral interlocking intramedullary nails, in which the proximal lag screw is engaged in the femoral head, are now available for the treatment of complex comminuted pertrochanteric femoral fractures. Jamming of the lag screw results in a rigid device which is more likely to cut-out of the femoral head. The aim of this study was to determine the sliding characteristics and jamming potential of the lag screws of five different devices used to treat these fractures. Method: The devices examined include; the single lag screw devices: the DHS, the Gamma nail and the Intramedullary hip screw (IMHS), and the double lag screw devices: the Russell-Taylor Reconstruction nail (RTN) and the Austofix Hip nail. The devices were mounted in a servo-hydraulic testing apparatus and examined by two different techniques. The first set-up looked at lag screw motion with respect to loads applied which were representative of the single limb stance phase of gait (SLSPOG). The second set-up which, was first described by Kyle in 1980, looked at the forces required to initiate sliding. Results: For the first set up (SLSPOG), all single lag screw devices demonstrated sliding across the normal physiological range of applied load. The Russell Taylor Reconstruction nails demonstrated conflicting results with the lag screws of two nails sliding and one nail jamming. All the Austofix nails jammed at the higher angles of the normal physiological range (1590, 1640). Using the Kyle set-up, the forces required to initiate sliding were found to be lowest with the Synthes DHS (42.33±5.77N), Zimmer CHS (52.67±26.56N), and the IMHS (45.33±10.97N). These were closely followed by the Gamma nail (79.33±8.39N) and the Richards Classic hip screw (82.00±16.37N). The highest forces were for the RTN (98.00±18.52N) and the Austofix hip nail (283.00±70.62N). These results were significantly different. (p< 0.001, ANOVA). Conclusion: The results demonstrate that double lag screw implants require greater loads to initiate sliding and have a greater potential for jamming. Whilst all single lag screw nails slide, barrel length does alter the forces required to initiate sliding. Further testing using a lubricant is currently being undertaken

Lag screw fixation with plate osteosynthesis is the usual recommendation for oblique non-comminuted lateral malleolus fractures. Lag screw fixation may sometimes pose varying difficulties depending on the orientation of the fracture and in osteoporotic bones where the process may cause disintegration of the bone. The purpose of this study was to evaluate whether additional lag screw fixation with plate osteosynthesis offered any advantage over plate only fixation in non-comminuted oblique fractures of the lateral malleolus. A simple method of fixation was employed where the fracture was reduced and held temporarily with a K wire. After fixation with plate the K wire was removed. A total of 20 patients who had non-comminuted unstable oblique fractures of their lateral malleolus that had been surgically fixed plate only fixation were retrospectively evaluated. The patients were aged between 17 and 70 yrs. Evaluation of the success of fixation, complications, resultant mobility and patient satisfaction was based on information gathered from X-ray findings and clinic notes. These results were compared to an agematched group of 20 consecutive patients treated with lag screw fixation and plate osteosynthesis. There was no significant difference in the rate of or functional outcomes in either groups. Lag screw fixation offers no additional advantage when combined with plate synthesis of non-comminuted oblique lateral malleolus fractures

Abstract. Background. Multiple devices can stabilise the MTP joint for arthrodesis. The ideal implant should be easy to use, provide reproducible and high quality results, and ideally enable early rehabilitation to enable faster return to function, whilst lessening soft tissue irritation. We prospectively evaluated the combination of the IO-Fix (Extremity Medical, NJ, USA) device which consists of an intra-osseous post and lag screw that offers these features with full bearing of weight after surgery. Methods. 67 feet in 65 patients were treated over 31 months. After excluding patients lost to follow-up, undergoing revision arthrodesis, or concomitant first ray procedures, there were 54 feet in 52 patients available with a minimum 12 month follow-up with clinical and radiographic outcomes. All patients were treated using a similar operative technique with immediate bearing of weight in a rigid soled shoe. Results. The mean MOXFQ score improved from 46.4 (range 18 – 64) before surgery to 30.2 (range 0 – 54) at 6 months after surgery (p=0.02), and 18.4 (range 0 – 36) (p< 0.001) at latest follow-up. Arthrodesis across the MTP joint was achieved in 52 feet (96%), at a mean of 61 days (range 39–201). Non-union was observed in two feet; superficial wound infections in two feet; and metalwork impingement in three feet. Conclusions. In the largest reported series to date, the IO-Fix device achieved a union rate of 96% across the MTP joint when coupled with immediate bearing of weight. Significant improvements were seen in patient reported outcomes with low complication rates

Minimizing tip-apex distance has been shown to reduce clinical failure of sliding hip screws used to fix peritro-chanteric fractures. The purpose of this study was to determine if such a relationship exists for the position of the lag screw in the femoral head using a cephalomedullary device. Methods: Thirty intact synthetic femur specimens (Model #3406, Pacific Research Laboratories, Vashon, WA) were potted into cement blocks distally for testing on an Instron 8874 (Instron, Canton, MA). A long cephalomedullary nail (Long Gamma 3 Nail, Stryker, Mahwah, NJ) was inserted into each of the femurs. An unstable four-part fracture was created, anatomically reduced, and repaired using one of 5 lag screw placements in the femoral head:. Superior (N=6),. Inferior (N=6),. Anterior (N=6),. Posterior (N=6),. Central (N=6). Mechanical tests were repeated for axial, lateral and torsional stiffness. All specimens were radiographed in the anterioposterior and lateral planes and tip-apex (TAD) distance was calculated. A calcar referenced tip-apex distance (CalTAD) was also calculated. ANOVA was used to compare means of the five treatment groups. Linear regression analysis was used to compare axial, lateral and torsional stiffness (dependant variables) to both TAD and CalTAD (independent variables). Results: ANOVA testing proved that the mean axial (p< 0.01) and torsional stiffness (p< 0.01) between the 5 groups was significantly different, but lateral stiffness was not statistically different (p=0.494). Post hoc analysis showed that the inferior lag screw position provided significantly higher mean axial stiffness (568.14±66.9N/ mm) than superior (428.0±45.6N/mm; p< 0.01), anterior (443.2±45.4N/mm; p=0.02) and posterior (456.7±69.3N/ mm; p=0.04) lag screw positions. There was no significant difference in mean axial stiffness between inferior (568.14±66.9N/mm) and central (525.4±81.7N/mm) lag screw positions (p=0.77). Post hoc analysis revealed significantly less mean torsional stiffness for the superior lag screw position compared to other lag screw positions (p< 0.01 all 4 pairings). There were no significant correlations between TAD and axial (r=−0.33, p=0.08), lateral (r=−0.22, p=0.24) or torsional (r=0.08, p=0.69) stiffness. There were significant correlations between CalTAD and axial (r=−0.66, p< 0.01), lateral (r=−0.38, p=0.04) and torsional (r=−0.38, p=0.04) stiffness. Discussion: Our results suggest that placement of the lag screw inferiorly in the femoral head when using a cephalomedullary nail to treat an unstable peritrochanteric fracture results in the stiffest construct in axial and torsional biomechanical testing. A simple radiographic measurement, CalTAD, provides an intraoperative method of determining optimal cephalomedullary nail lag screw position to achieve greatest construct stiffness

Purpose: Healing may be problematic after lag screw osteosynthesis of pertrochanteric fractures in osteoporotic bone due to the greater risk of defective fixation. Acrylic cement has been proposed to reinforce the fixation of the lag screw in these patients, principally to avoid the risk of cutout, but the acrylic cement’s thermal toxicity, its poor biocompatibility, and the difficult manipulation are important drawbacks. Cortoss® is a new composite biomaterial composed of bisphenol-aglycidly (bis-GMA) which could be an attractive alternative to classical cements. Cortoss is an injectable material with mechanical properties similar to human cortical bone. The purpose of this clinical study was to describe the new method for injection the material and to assess the anchoring force and safety of Cortoss in osteoporotic patients undergoing surgical fixation of pertrochanteric fractures. Material and methods: This prospective study was approved by the local ethics committee. Twenty consecutive patients aged 70 years or more with pertro-chanteric fracture were included. The lag screw was inserted under fluoroscopic guidance, and the maximum insertion torque was measured. The screw was then unscrewed seven turns (length of the threaded head), and 2.5 cm Cortoss was injected via a polyimide catheter measuring 2.5 mm in diameter. The screw was then rescrewed in place to a troque 30% above that measured without Cortoss. Results: Eighteen women and two men, age 70 – 96 years, gave their informed consent to participate in the study. Mean maximal insertion torque without Cortoss was 1.23 Nm (min 0, max 4.8 Nm), which was increased 30% with Cortoss. Posto-operative x-rays showed that the screw head was embedded in an envelope of Cortoss and that the Cortoss had diffused into the adjacent bone. There were no adverse effects. Discussion and conclusion: Cortoss provided effective reinforcement of the fixation as demonstrated by the higher insertion torque. Cortoss can also increase the mechanical resistance of the screw-cancellous bone interface, limit fixation default, and reduce secondary displacement of the lag screw in patients with osteoporotic bone. Improved stability can also reduce immobilisation time and facilitate bone healing without increasing the risk of secondary displacement and subsequent morbidity. Due to its safety, easy use, and efficacy, Cortoss provides a better alternative than acrylic cement for reinforcement of lag screw fixation of porotic bone

Purpose: Minimizing tip-apex distance (TAD) has been shown to reduce clinical failure of extramedullary sliding hip screws used to fix peritrochanteric fractures. There is debate regarding the optimal position of the lag screw in the femoral head when a cephalomedullary nail is used to treat a peritrochanteric fracture. Some authors suggest the TAD should be minimized as with an extramedullary sliding hip screw, while others suggest the lag screw should be placed inferior within the femoral head. The primary goal of this study was to determine which of 5 possible lag screw positions in the femoral head provides greatest mechanical stiffness and/or load-to-failure for an unstable peritrochanteric fracture treated with a cepha-clomedullary nail. The secondary goal was to determine if there is a linear correlation between implant-femur mechanical stiffness and/or load to failure (dependent variables) with a series of five radiographic measurements (independent variables) of distance from the lag screw tip to the femoral head apex. Method: Long Gamma 3 Nails (Stryker, Mahwah, NJ) were inserted into 30 left synthetic femurs (Pacific Research Laboratories, Vashon, WA). An unstable four-part fracture was created, anatomically reduced, and repaired using one of 5 lag screw placements in the femoral head:. superior (n=6),. inferior (n=6),. anterior (n=6),. posterior (n=6),. central (n=6). All specimens were radiographed in the anterioposterior and lateral planes, and radiographic measurements including TAD and a calcar referenced tip-apex distance (CalTAD) were calculated. All specimens were tested for axial, lateral, and torsional stiffness, and then loaded-to-failure in the axial position using an Instron 8874 (Canton, MA). ANOVA was used to compare means of the five treatment groups. Linear regression analysis was used to compare stiffness and load-to-failure (dependant variables) with radiographic measurements (independent variables). A post hoc power analysis was performed. Results: The inferior lag screw position had significantly greater mean axial stiffness than superior (p< 0.01), anterior (p=0.02) and posterior (p=0.04) positions. Analysis revealed significantly less mean torsional stiffness for the superior lag screw position compared to other lag screw positions (p< 0.01 all 4 pairings). No statistical differences were noted for lateral stiffness. Superior and central lag screw positions had significantly greater mean load-to-failure than anterior (p< 0.01 and p=0.02) and posterior (p< 0.01 and p=0.05) positions. There were significant negative linear correlations between stiffness tests with CalTAD, and load-to-failure with TAD. Power was greater than 95% for axial stiffness, torsional stiffness and load-to-failure tests. Conclusion: Position of the lag screw in the femoral head affects the biomechanical properties of the implant-femur construct. Central placement of the lag screw with minimization of TAD may provide the best combination of stiffness and load-to-failure

The rigidity of a sliding compression screw and three cannulated lag screws in the treatment of subcapital fractures was compared in five pairs of female cadaver femora. There were no significant differences between the compressive strength, bone density, cortical thickness or Singh index of the bones in each pair. A subcapital fracture was standardised using a perpendicular saw cut across the femoral neck. A uniaxial 'load test system' with force and length measurement facilities was used to mimic cyclical stressing applied in vivo at a frequency of 0.5 Hz from 0 to 3 times body-weight. There was no significant difference between the fixation afforded by the sliding compression screw and three lag screws. Bone quality was the single most important factor in the stability of the bone implant unit

Hypothesis. The proximal geometry and design of trochanteric nails affects initial construct stiffness, fatigue survival, and preservation of biomechanical stability over time. Materials & Methods. Eight pairs of human cadaveric femora were implanted with two different short intramedullary nails with (Intertan, (S&N)) and without (Gamma 3, (Stryker)) interlocking lag screws. Femoral osteotomies were performed to generate a pertrochanteric multifragmentary unstable fracture (OTA 31-A 2.2). The bones were tested in a cyclic testing protocol with increasing loads of 100 N every 20.000 cycles (start point 50/500 N) simulating one leg stance. The position of the femur was 10° adduction and 10° extension. Stiffness, failure load, and cycles to failure were measured. Results. Initially, stiffness of the interlocking lag screw nail was 40 % higher (p < 0,05) than for the non-interlocking nail. During the test, the difference in stiffness gradually decreased. Load to failure (9 %, p < 0,05) and cycles to failure (13 %, p < 0,05) were also higher for the interlocking nail construct. Discussion & Conclusion. The interlocking screw design of intramedullary nail constructs improves the mechanical performance in unstable trochanteric fractures. This may result in improved clinical performance

Purpose: Cephalomedullary nails rely on a large lag screw that provides fixation into the femoral head. There is an option to statically lock the lag screw (static mode) or to allow the lag screw to move within the nail to compress the intertrochanteric fracture (dynamic mode). The purpose of this study was to compare the biomechanical stiffness of static and dynamic modes for a cephalomedullary nail used to fix an unstable peritrochanteric fracture. Method: Thirty intact synthetic femur specimens (Model #3406, Pacific Research Laboratories, Vashon, WA) were potted into cement blocks distally for testing on an Instron 8874 (Instron, Canton, MA). A long cephalomedullary nail (Long Gamma 3 Nail, Stryker, Mahwah, NJ) was then inserted into each of the femurs. An unstable four-part fracture was created, anatomically reduced, and the cephallomedullary nail was reinserted. Mechanical tests were conducted for axial, lateral, and torsional stiffness with the lag screws in:. static and. dynamic modes. A paired student’s t test was used to compare the 2 modes. Results: The axial stiffness of the cephalomedullary nail was significantly greater (p< 0.01) in the static mode (484.3±80.2N/mm) than in the dynamic mode (424.1±78.0N/mm) (Fig.2A). Similarly, the lateral bending stiffness of the nail was significantly greater (p< 0.01) in the static mode (113.9±8.4N/mm) than in the dynamic mode (109.5±8.8N/mm). The torsional stiffness of the nail was significantly greater (p=0.02) in the dynamic mode (114.5±28.2N/mm) than in the static mode (111.7±27.0N/mm). A post hoc power analysis with & #945;=0.05 and & #946;=0.20 revealed that the paired t test on 30 samples was sufficiently powered to determine a difference in mean axial stiffness of 33.0N/mm (6.8% of static stiffness), a difference in mean lateral bending stiffness of 3.6N/mm (3.2% of static stiffness) and a difference in mean torsional stiffness of 3.4N/mm (3.0% of static stiffness). Conclusion: Our results show that there is a 60N/mm reduction in axial stiffness of the cephalomedullary nail when the lag screw is changed from static to dynamic mode. This represents a 12.4% reduction in axial stiffness with a change from axial to dynamic modes which may be clinically significant. The differences in lateral (4.4N/mm, 3.9%) and torsional (2.8N/mm, 2.4%) are small enough that they are likely not clinically significant. We felt that a difference of greater than 10% in axial stiffness and a difference of greater than 5% in lateral or torsional stiffness would be clinically significant. Our study was adequately powered to detect these differences. Given the significant reduction in axial stiffness with dynamization of the cephalomedullary nail construct, we recommend use of the static mode when treating unstable peritrochanteric fractures with a cephalomedullary nail

We report our experience in 42 patients, using corticocancellous bone grafts and lag screw fixation for un-united scaphoid fractures. Using a grading system, we analysed the suitability of the method for three types of nonunion. We recommend the operation for the treatment of scaphoid nonunion, except where there is avascular necrosis of the proximal pole

The compression produced by and the resistance to pullout of the 6.5 mm cannulated Herbert screw were compared with those of ASIF headed screws. The latter were tested with and without washers and in the following sizes: 4.5 mm cortical, 6.5 mm cancellous with a 16 mm threaded segment, and 6.5 mm cancellous with a 32 mm threaded segment. Polyurethane foam was used as a substitute for cancellous bone and ASIF artificial bone for corticocancellous bone. The compression produced by a cancellous lag screw with a washer was significantly greater than that produced by a Herbert screw of equivalent size (p < 0.05). When the screws were tested using the corticocancellous composite the ASIF cancellous screw without a washer produced significantly greater compression (p < 0.05); when used with a washer the difference was highly significant (p < 0.001). The dual pitch Herbert screw is not appropriate for the management of fractures in which compression is of greater importance than the need to avoid prominence of the screw head

Over the past four decades, internal fixation has continued to gain popularity as a method for treating fractures because of significant improvements in both implant design and materials. This biomechanical study compares the compressive forces generated by a conventional 4.5 AO/ASIF cortical screw lag screw with a differential pitch cortical compression screw in a simulated fracture model using whole bone composite femur. The differential pitch screw investigated in this study generates 82% of the compression generated by a conventional 4.5mm AO/ASIF cortical screw. Proving compression in diaphyseal fractures is achievable using a differential pitch screw. Sufficient compression is generated to allow osteosynthesis using a plate to be preformed independent of the lag screw positioning. It is thus advantageous over the traditional compromise that arises when exposure to the fracture site is limited, of either incorporating the lag screw into the plate of choosing a non-optimal plate or screw position. It is proposed as an adjunct to the internal fixation of long bone fractures and not a single fixation device

Objectives: To compare the biomechanical properties of lag screw insertion in a laboratory model. Two blades, the Synthes Dynamic Helical Hip Screw (DHHS) and Proximal Femoral Nail Antirotation (PFNA), and two screws, the Synthes Dynamic Hip Screw (DHS) and Stryker Gamma 3 lag screw, were compared. Setting: Orthopaedic biomechanics laboratory. Design: Insertion testing was carried out in high and low density polyurethane foam mounted and attached to a Zwick Roell Amsler Hydrowin. Outcome Measures: The axial load and torque during insertion of the implants was measured. Results: The force required to insert the DHHS and PFNA blades was greater than the DHS and Gamma 3 screws into both low and high density foam. The force required to insert the DHHS and PFNA blades into high density foam was greater than low density foam. The torque required to insert the DHHS and PFNA blades into high density foam was less than that to insert the DHS and Gamma 3 screws. The torque required to insert the DHS and Gamma 3 screws into low density foam was less than the DHHS and PFNA blades. The torque during insertion of the DHHS and PFNA blades seemed to be independent of foam density. Conclusions: The insertional properties of blades are significantly different to screws and this may have clinical importance