Treatment of both simple and complex patella fractures is a challenging clinical problem. The aim of this study was to investigate the biomechanical performance of recently developed lateral rim variable angle locking plates versus tension band wiring used for fixation of simple and complex patella fractures.

Twelve pairs of human anatomical knees were used to simulate either two-part transverse simple AO/OTA 34C1 or five-part complex AO/OTA 34C3 patella fractures by means of osteotomies, with each fracture model created in six pairs. The complex fracture pattern was characterized by a medial and a lateral proximal fragment, together with an inferomedial, an inferolateral, and an inferior fragment mimicking comminution around the distal patellar pole. The specimens with simple fractures were pairwise assigned for fixation with either tension band wiring through two parallel cannulated screws, or a lateral rim variable angle locking plate. The knees with complex fractures were pairwise treated with either tension band wiring through two parallel cannulated screws plus circumferential cerclage wiring, or a lateral rim variable angle locking plate.

Each specimen was tested over 5000 cycles by pulling on the quadriceps tendon, simulating active knee extension and passive knee flexion within the range of 90° flexion to full knee extension. Interfragmentary movements were captured via motion tracking.

For both fracture types, the longitudinal and shear articular displacements measured between the proximal and distal fragments at the central patella aspect between 1000 and 5000 cycles, together with the relative rotations of these fragments around the mediolateral axis were all significantly smaller following the lateral rim variable angle locked plating compared with tension band wiring, p<0.01.

Lateral rim locked plating of both simple and complex patella fractures provides superior construct stability versus tension band wiring under dynamic loading.

Treatment of simple and complex patella fractures represents a challenging clinical problem. Controversy exists regarding the most appropriate fixation method. Tension band wiring, aiming to convert the pulling forces on the anterior aspect of the patella into compression forces across the fracture site, is the standard of care, however, it is associated with high complication rates. Recently, anterior variable-angle locking plates have been developed for treatment of simple and comminuted patella fractures. The aim of this study was to investigate the biomechanical performance of the novel anterior variable-angle locking plates versus tension band wiring used for fixation of simple and complex patella fractures.

Sixteen pairs of human cadaveric knees were used to simulate either two-part transverse simple AO/OTA 34-C1 or five-part complex AO/OTA 34-C3 patella fractures by means of osteotomies, with each fracture model created in eight pairs. The complex fracture pattern was characterized with a medial and a lateral proximal fragment, together with an inferomedial, an inferolateral and an inferior fragment mimicking comminution around the distal patellar pole. The specimens with simple fractures were pairwise assigned for fixation with either tension band wiring through two parallel cannulated screws, or an anterior variable-angle locking core plate. The knees with complex fractures were pairwise treated with either tension band wiring through two parallel cannulated screws plus circumferential cerclage wiring, or an anterior variable-angle locking three-hole plate. Each specimen was tested over 5000 cycles by pulling on the quadriceps tendon, simulating active knee extension and passive knee flexion within the range from 90° flexion to full knee extension. Interfragmentary movements were captured by motion tracking.

For both fracture types, the articular displacements, measured between the proximal and distal fragments at the central aspect of the patella between 1000 and 5000 cycles, together with the relative rotations of these fragments around the mediolateral axis were all significantly smaller following the anterior variable-angle locked plating compared with the tension band wiring, p < 0.01

From a biomechanical perspective, anterior locked plating of both simple and complex patella fractures provides superior construct stability versus tension band wiring.

Introduction and Objective

Intramedullary nails are frequently used for treatment of unstable distal tibia fractures. However, insufficient fixation of the distal fragment could result in delayed healing, malunion or nonunion. The quality of fixation may be adversely affected by the design of both the nail and locking screws, as well as by the fracture pattern and bone density. Recently, a novel concept for angular stable nailing has been developed that maintains the principle of relative stability and introduces improvements expected to reduce nail toggling, screw migration and secondary loss of reduction. It incorporates polyether ether ketone (PEEK) inlays integrated in the distal and proximal canal portions of the nail for angular stable screw locking. The nail can be used with new standard locking screws and low-profile retaining locking screws, both designed to enhance cortical fixation. The low-profile screws are with threaded head, anchoring in the bone and increasing the surface contact area due to the head's increased diameter.

The objective of this study was to investigate the biomechanical competence of the novel angular stable intramedullary nail concept for treatment of unstable distal tibia fractures, compared with four other nail designs in an artificial bone model under dynamic loading.

Femoral neck fractures account for half of all hip fractures and are recognized as a major public health problem associated with a high socioeconomic burden. Whilst internal fixation is preferred over arthroplasty for physiologically younger patients, no consensus exists about the optimal fixation device yet. The recently introduced implant Femoral Neck System (FNS) (DePuy Synthes, Zuchwil, Switzerland) was developed for dynamic fixation of femoral neck fractures and provides angular stability in combination with a minimally invasive surgical technique. Alternatively, the Hansson Pin System (HPS) (Swemac, Linköping, Sweden) exploits the advantages of internal buttressing. However, the obligate peripheral placement of the pins, adjacent to either the inferior or posterior cortex, renders the instrumentation more challenging. The aim of this study was to evaluate the biomechanical performance of FNS versus HPS in a Pauwels II femoral neck fracture model with simulated posterior comminution. Forty-degree Pauwels II femoral neck fractures AO 31-B2.1 with 15° posterior wedge were simulated in fourteen paired fresh-frozen human cadaveric femora, followed by instrumentation with either FNS or HPS in pair-matched fashion. Implant positioning was quantified by measuring the shortest distances between implant and inferior cortex (DI) as well as posterior cortex (DP) on anteroposterior and axial X-rays, respectively. Biomechanical testing was performed in 20° adduction and 10° flexion of the specimens in a novel setup with simulated iliopsoas muscle tension. Progressively increasing cyclic loading was applied until construct failure. Interfragmentary femoral head-to-shaft movements, namely varus deformation, dorsal tilting and rotation around the neck axis were measured by means of motion tracking and compared between the two implants. In addition, varus deformation and dorsal tilting were correlated with DI and DP. Cycles to 5/10° varus deformation were significantly higher for FNS (22490±5729/23007±5496) versus HPS (16351±4469/17289±4686), P=0.043. Cycles to 5/10° femoral head dorsal tilting (FNS: 10968±3052/12765±3425; HPS: 12244±5895/13357±6104) and cycles to 5/10° rotation around the femoral neck axis (FNS: 15727±7737/24453±5073; HPS: 15682±10414/20185±11065) were comparable between the implants, P≥0.314. For HPS, the outcomes for varus deformation and dorsal tilting correlated significantly with DI and DP, respectively (P=0.025), whereas these correlations were not significant for FNS (P≥0.148).

From a biomechanical perspective, by providing superior resistance against varus deformation and performing in a less sensitive way to variations in implant placement, the angular stable Femoral Neck System can be considered as a valid alternative to the Hansson Pin System for the treatment of Pauwels II femoral neck fractures.

Unstable distal tibia fractures are challenging injuries requiring surgical treatment. Intramedullary nails are frequently used; however, distal fragment fixation problems may arise, leading to delayed healing, malunion or nonunion. Recently, a novel angle-stable locking nail design has been developed that maintains the principle of relative construct stability, but introduces improvements expected to reduce nail toggling, screw migration and secondary loss of reduction, without the requirement for additional intraoperative procedures.

The aim of this study was to investigate the biomechanical competence of a novel angle-stable intramedullary nail concept for treatment of unstable distal tibia fractures, compared to a conventional nail in a human cadaveric model under dynamic loading.

Ten pairs of fresh-frozen human cadaveric tibiae with a simulated AO/OTA 42-A3.1 fracture were assigned to 2 groups for reamed intramedullary nailing using either a conventional (non-angle-stable) Expert Tibia Nail with 3 distal screws (Group 1) or the novel Tibia Nail Advanced system with 2 distal angle-stable locking low-profile screws (Group 2). The specimens were biomechanically tested under conditions including quasi-static and progressively increasing combined cyclic axial and torsional loading in internal rotation until failure of the bone-implant construct, with monitoring by means of motion tracking.

Initial axial construct stiffness, although being higher in Group 2, did not significantly differ between the 2 nail systems, p=0.29. In contrast, initial torsional construct stiffness was significantly higher in Group 2 compared to Group 1, p=0.04. Initial nail toggling of the distal tibia fragment in varus and flexion was lower in Group 2 compared to Group 1, being significant in flexion, p=0.91 and p=0.03, respectively. After 5000 cycles, interfragmentary movements in terms of varus, flexion, internal rotation, axial displacement and shear displacement at the fracture site were all lower in Group 2 compared to Group 1, with flexion and shear displacement being significant, p=0.14, p=0.04, p=0.25, p=0.11 and p=0.04, respectively. Cycles to failure until both interfragmentary 5° varus and 5° flexion were significantly higher in Group 2 compared to Group 1, p=0.04.

From a biomechanical perspective, the novel angle-stable intramedullary nail concept has the potential of achieving a higher initial axial and torsional relative stability and maintaining it with a better resistance towards loss of reduction under dynamic loading, while reducing the number of distal locking screws, compared to conventional locking in intramedullary nailed unstable distal tibia fractures.

Introduction

The incidence of distal femoral fractures in the geriatric population is growing and represents the second most common insufficiency fracture of the femur following fractures around the hip joint. Fixation of fractures in patients with poor bone stock and early mobilisation in feeble and polymorbide patients is challenging. Development of a fixation approach for augmentation of conventional LISS (less invasive stabilization system) plating may result in superior long-term clinical outcomes and enhance safe weight bearing.

Three Cannulated Screws (3CS), Dynamic Hip Screw (DHS) with antirotation screw (DHS–Screw) or with a Blade (DHS–Blade) are the gold standards for fixation of unstable femoral neck fractures. Compared to 3CS, both DHS systems require larger skin incision with more extensive soft tissue dissection while providing the benefit of superior stability. The newly designed Femoral Neck System (FNS) for dynamic fixation combines the advantages of angular stability with a less invasive surgical technique. The aim of this study is to evaluate the biomechanical performance of FNS in comparison to established methods for fixation of the femoral neck in a human cadaveric model.

Twenty pairs of fresh–frozen human cadaveric femora were instrumented with either DHS–Screw, DHS–Blade, 3CS or FNS. A reduced unstable femoral neck fracture 70° Pauwels III, AO/OTA31–B2.3 was simulated with 30° distal and 15° posterior wedges. Cyclic axial loading was applied in 16° adduction, starting at 500N and with progressive peak force increase of 0.1N/cycle until construct failure. Relative interfragmentary movements were evaluated with motion tracking.

Highest axial stiffness was observed for FNS (748.9 ± 66.8 N/mm), followed by DHS–Screw (688.8 ± 44.2 N/mm), DHS–Blade (629.1 ± 31.4 N/mm) and 3CS (584.1 ± 47.2 N/mm) with no statistical significances between the implant constructs. Cycles until 15 mm leg shortening were comparable for DHS–Screw (20542 ± 2488), DHS–Blade (19161 ± 1264) and FNS (17372 ± 947), and significantly higher than 3CS (7293 ± 850), p<0.001. Similarly, cycles until 15 mm femoral neck shortening were comparable between DHS–Screw (20846 ± 2446), DHS–Blade (18974 ± 1344) and FNS (18171 ± 818), and significantly higher than 3CS (8039 ± 838), p<0.001.

From a biomechanical point of view, the Femoral Neck System is a valid alternative to treat unstable femoral neck fractures, representing the advantages of a minimal invasive angle–stable implant for dynamic fixation with comparable stability to the two DHS systems with blade or screw, and superior to Three Cannulated Screws.

Introduction

Periprosthetic femur fractures are a serious complication after hip replacement surgery. In an aging population these fractures are becoming more and more common. Open reduction and plate osteosynthesis is one of the available treatment options.

Periprosthetic femur fractures are severe complications after hip arthroplasty. There is a high re-operation rate due to malunion, refracture and stem loosening. Fixation is more rigid when screws are used for proximal fixation of the plate instead of cables. Screws penetrating the cement mantle may damage it and induce loosening of the prosthesis stem.

Background: Prophylactic taping is commonly used to prevent ankle injuries during sports. However unnatural constraint of the ankle joint may increase the risk of injury to proximal joints such as the knee. Any association between the use of ankle tape and knee joint loading has not previously been investigated. Purpose: To determine changes in ankle and knee kinetics and kinematics associated with use of ankle taping during athletic activities. Thereby, both the prophylactic benefits and the potential of taping to be an isolated mechanism for a ligamentous injury of the knee will be examined.

Methods: A kinematic and inverse dynamics model was used to determine ankle and knee joint motion and loading in 22 healthy male participants undertaking running and sidestepping tasks. Both tasks were randomized to planned and unplanned conditions, and undertaken with and without the use of ankle tape.

Results: Taping reduced the range of motion at the ankle in all three planes (p< 0.05), as well as peak inversion (p=0.017) and average eversion moments (p=0.013). At the knee, internal rotation moments (p=0.049), internal rotation impulse (0.034), varus moment (p=0.015) and varus impulse (p=0.050) were reduced with the use of ankle tape. There was a trend toward increased valgus impulse for sidestepping trials undertaken with ankle tape (p=0.056).

Conclusion: By limiting motion at the ankle, taping increased the mechanical stability of this joint. Ankle taping also provided protective benefits to the knee via reduced internal rotation moments and varus impulses, although the effects were task-specific. Medial collateral and anterior cruciate ligament injuries may, however, occur through increased valgus impulse during sidestepping undertaken with ankle tape.

Introduction: Primary operative stabilisation of Grade III injuries of the acromio-clavicular (AC) joint remains controversial, with recent literature providing support for conservative management. The aim of this research was to compare the clinical and radiological outcome of operative and non-operative treatment of this injury.

Materials and Methods: 56 patients (51 men, 5 women, aged 18 – 78 years) with an acromio-clavicular dislocation Tossy III were recruited into the study. 28 were managed surgically with a hook plate, and 28 were treated non-operatively with a sling until they were pain-free after a few days. The mean follow-up time was 23 months (8 – 31 months). At follow-up the patients were either examined clinically and radiologically or they were surveyed by phone. Clinical results were expressed in the Constant score and the subjective satisfaction of each patient was recorded.

Results: Eleven patients were lost to follow-up. Five patients were operated at their home hospital after initial treatment at our clinic, and four non-surgical patients were later treated with a modified Weaver-Dunn procedure.

Of the remaining 36 patients, 25 were examined clinically and radiologically and 11 were surveyed by telephone. The clinical outcome showed a mean Constant score of 87 in the operative group and 96 in the non-operative group. 30 of 36 patients were highly satisfied or satisfied (19 in the operative group, 11 in the non-operative group), 5 were mostly satisfied (operative group), 1 was unsatisfied (operative group). Radiologically, all of the operated patients showed changes of the AC-joint including widening of the joint, redislocation of the distal clavicle, and degenerative changes. In the non-operative group, three patients showed a decreasing clavicular elevation.

Conclusion: Clinical outcomes were comparable between operative and non-operative treatment of AC-dislocations grade III. Some conservatively treated patients did, however, require a secondary stabilisation. The hook plate was observed to cause additional local injury to the AC-joint, and must be removed after recovery to prevent rotator cuff damage. This procedure incurs high risk of loss of reduction. In our opinion, it is disputable to operate twice on the AC-joint to achieve similar results as those obtained with conservative treatment. We prefer a secondary anatomical reconstruction in cases of failed conservative treatment.

Introduction: Since the introduction of locked implants new possibilities in the treatment of proximal humeral fractures have evolved. Despite the success using locked plates recent publications report the cutting of screws through the humeral head in up to 30% of the cases. The distribution of the bone strength in the humeral head is not linear. Can polyaxial screw positioning in areas with higher bone strength reduce the “cutout” rate? Which effect has an inferomedial screw if the medial hinge is not restored?

Methods: 4 groups were formed from 31 fresh frozen proximal humeral cadavers. A polyaxial proximal humeral locking plate was used to perform the tests. A standardised unstable intraarticular fracture was created. Main Outcome measure was the load and cycle where at least one screw was cutting through the cartilage.

Results: Polyaxial screw placement in areas of incresead bone strength compared to random screw placement had no effect on the cutout behaviour (p=0.7). Increased screw number (3 vs. 5) significantly increases the resistance against cutout (p< 0.04). An inferomedial screw significantly increases the resistance to develop a cutout compared to the control groups(p=0.03 and p< 0.05).

Discussion: The placement of an inferomedial screw significantly increases the resistence to develop a cutout in proximal humeral fractures without a medial hinge independently of the total screw number. In addition we could also show that the number of screws in the humeral head has a significant effect on cutout resistance in a human cadaver setup.

Background: A radiological audit of the local use of the Dynamic Hip Screw in extracapsular proximal femur fractures. Study aim: to identify cases of mechanical failure and revision, to determine predictors of fixation failure.

Methods: A retrospective radiological review of 567 consecutive cases at Western Australian tertiary hospitals over a 3 year period (2002 – 2004) using the Picture Archive Computer System (PACS).

Results: Female: male ratio was 2.79: 1. Evan’s classification: 418 fractures stable (73.7%), 149 unstable (26.3%). Failure of fixation occurred in 14 cases (2.5%); ten due to hip screw cut out (1.8%) and four due to plate pull off (0.8%). All cases of cut out had a significantly higher mean tip apex distance (TAD) (31 vs 20mm, P < 0.001) and an unstable fracture configuration; 8 of 10 had a poor reduction. Bivariate logistical regression revealed TAD of 25mm or more to be most predictive of cut out; followed by mean TAD, superior anterior and inferior posterior screw placement, unstable fracture configuration and poor reduction. Unassociated factors included gender, age, American Society of Anesthesiologists’ score, plate angle and length, operation time and surgeon level. A three-variable model found TAD of 25mm or more and unstable fracture configuration to be predictive, but not poor reduction. Cases with a TAD of 25mm or more with unstable fracture configuration and a poor reduction had a 21.6% chance of cut out (8 of 29).

Conclusions: This is the first multifactorial multivariate analysis of a single implant sliding hip screw series. Compared with the literature, the rate of failure is low. Possible reasons include appropriate choice of implant for fracture type, improved performance with use of a single model of implant, and low exclusion rates due to the use of PACS.

Fracture healing results in increased markers of bone turnover and callus formation. The exact patterns of these changes after different type and locations of fractures as well as weight bearing are unknown.

Bone markers and the callus index were measured prospectively for 6 month following osteosynthesis of different fractures of the lower limb. Serum and urin samples were collected at day 0, 1, 3, 7 and after 2, 6, 12 and 24 weeks. X-rays were taken direct postoperatively and after 6 and 24 weeks. Labarotory parameters for bone formation were: bone-specific alkaline phosphatase (BnAP), Osteocalcin (OC), procollagen type I N- and type III C-terminal propeptide (PINP, PIIICP); markers for bone resorption were: free and peptid-bound forms of urinary pyridinium crosslinks (Dpd, Pyr,), N – terminal propeptides of type I collagen (NTx). All fractures healed within 6 month without complications.

Results: We present preliminary data obtained from 12 adults (10 male, 2 female, mean age 45±15 years). a great variability of bone formation and resorption markers was observed during the first two weeks, probably due to the type trauma and amount of soft tissue injury. Accelerated bone resorption, and a decrease of bone formation was observed during the first week. Thereafter, an increase in OC and BnAP was noted despite persistently elevated bone resorption markers. With increasing weigth bearing, a decrease of bone resorption markers with unchanged or slightly increasing levels of bone formation markers occured.

Conclusions: No fracture specific trends for changes in bone remodelling markers were observed. Accelerated bone resorption is followed by increased bone formation; the longer and steeper the increase on bone resorption, the later and more pronounced the increase in bone formation. For further evaluation of the relationship between changes in bone remodeling markers and fracture healing, more patients will be included into the ongoing study.