Proximal Screw Hole Research Articles

Anatomic Risks with Overpenetration of the Volar Locking Plates' Proximal Holes.

Background Volar locking plate fixation (VLP) is commonly used to treat distal radius fractures (DRF). Risk of dorsal compartment injury with distal screw hole fixation has been studied; however, the risk with proximal screw hole fixation is not well studied. Purpose The goal of this study was to investigate the risk of dorsal structure injury from the screw holes proximal to the two distal rows. Methods Nine cadaveric forearms were used. After volar distal radius exposure, a long VLP was applied. Kirschner wires were placed through the most proximal holes into the dorsal compartments. The extensor structures penetrated were noted and tagged with hemoclips. The distance from the dorsal cortex to the structures was measured. Results The abductor pollicis longus (APL) and extensor pollicis brevis (EPB) muscle bodies were only penetrated; no tendons were penetrated. Proportion of muscle penetration increased with the more proximal screw holes. EPB was more likely to be penetrated distally and APL proximally; both were injured at holes 2 and 3. The extensors were 2 mm from the dorsal cortex of the radius on average; this did not decrease with compression of the forearm. Conclusions This is the first study to examine the anatomic risk of extensor structure injury with VLP proximal screw hole penetration. No extensor tendons were penetrated by these proximal screw holes; first dorsal compartment muscle bellies may be irritated with overpenetration. Our findings suggest that proximal VLP screws do not need to be downsized if they are not over 2 mm prominent.

The risk of iatrogenic radial nerve and/or profunda brachii artery injury in anterolateral humeral plating using a 4.5 mm narrow DCP: A cadaveric study.

Fixation of humeral shaft fractures with a plate and screws can endanger the neurovascular structure if proper care is not taken. No studies to our knowledge have studied the risk of iatrogenic radial nerve and/or profunda brachii artery (RNPBA) injury from each screw hole of a 4.5 mm narrow dynamic compression plate (narrow DCP). The purpose of this study is to evaluate the risk of RNPBA injury in anterolateral humeral plating with a 4.5 mm narrow DCP. 18 humeri of 9 fresh-frozen cadavers in the supine position were exposed via the anterolateral approach with 45 degrees of arm abduction. A hypothetical fracture line was marked at the midpoint of each humerus. A precontoured ten-hole 4.5mm narrow DCP was applied to the anterolateral surface of the humerus using the fracture line to position the center of the plate. All screw holes were drilled and screws inserted. The cadaver was then turned over to the prone position with 45 degrees of arm abduction, and the RNPBA exposed. The holes through in which 100% of the screw had contact with or penetrated the RNPBA were identified as dangerous screw holes, while lesser percentages of contact were defined as risky. The relative distance ratios of the entire humeral length from the lateral epicondyle of the humerus to the 4th, 3rd, 2nd and 1st proximal holes were 0.64, 0.60, 0.56 and 0.52, respectively. The most dangerous screw hole was the 2nd proximal, in which all 18 screws had contacted or penetrated the nerve, followed by the risky 1st (12/18), 3rd (8/18) and 4th (2/18) holes. In humeral shaft plating with the 4.5mm narrow DCP using the anterolateral approach, the 2nd proximal screw hole carries the highest risk of iatrogenic radial nerve and/or profunda brachii artery injury.

Does the choice of syndesmotic screw versus suture button in ankle surgery has a silver lining? \u2013 a technical note

PurposeUnstable ankle fractures with associated syndesmotic injury are of considerable morbidity in the professional athlete population. The use of dynamic suture button versus static syndesmotic screws fixation, rehabilitation protocols and timing to return to play are still areas of debate. We report the use of novel algorithm of sequential static and dynamic syndesmotic fixation in an elite football player with Weber C ankle fracture.MethodsThe patient underwent open reduction and internal fixation for a weber C ankle fracture with associated syndesmotic and deltoid ligament injury. The osteosynthesis included lateral malleolus neutralizing plate, two syndesmotic screws and deltoid anchor repair. At 6 weeks post-operative both syndesmotic screws were removed and one suture button was implanted in the proximal screw hole. After the second operation the patient was allowed full weight bearing and range of motion in all direction with accelerated rehabilitation protocol.ResultsThe technique provided satisfactory results. At 4 month the player participated in a 90 min official football match. The fracture healed uneventfully with no recurrent syndesmotic diastasis.ConclusionThe presented technique of sequential dynamic and static fixation of associated syndesmotic injuries combined advantages of both syndesmotic screws and suture button implants. In an aim to allow earlier return to play in an elite football player. This opens the way for higher level of evidence clinical trials.

Factors affecting stability after medial opening wedge high tibial osteotomy using locking plate: A cadaveric study

ObjectivesTo investigate the effect of screw length, lateral hinge fracture, and gap filling on stability after medial opening wedge high tibial osteotomy (MOW HTO) using a locking plate. MethodsForty tibiae from fresh-frozen cadavers were randomly allocated into five groups. Group A was bicortically fixated, while Group B and Group C were unicortically fixated: 90% and 55% of drilled tunnel length, respectively. Group D was fixated using 90% length screws with a fractured lateral hinge. Group E was fixated using 90% length screws with gap filling using a bone substitute. Operated tibiae were tested under axial compressive load using a material testing machine. The medial gap changes under the serial axial load of 100–600 N and ultimate failure load were measured. ResultsGroup D showed the biggest medial gap change and lowest failure load, while Group E presented the smallest gap change and highest failure load. The medial gap changes tended to increase with shorter screw length, but the difference was not significant between Groups A, B, and C. Group C and Group D showed greater medial gap change and lower failure load compared with Group E, while not differing from Group A and Group B. ConclusionsUnicortical fixation in proximal screw holes of a locking plate was not inferior to bicortical fixation regarding axial stability in MOW HTO, although proximal screws that are too short should be avoided. Lateral hinge fracture decreased, while gap filling with bone substitute increased axial stability.

Distal Normograde Intramedullary Pin and Locking Plate Placement in the Canine Humerus: A Cadaveric Study.

To identify a repeatable anatomic landmark for pin insertion and to describe the technique for placement of a distal normograde intramedullary (IM) pin of approximately 35% of the IM diameter using this approach combined with a locking compression plate (LCP) on the medial aspect of the canine humerus. Ex vivo anatomic study. Canine cadavers (n=10 Greyhounds). An anatomic landmark for pin insertion was identified based on three-dimensional reconstructions of previous elbow computed tomography studies and cadaveric dissection of the medial aspect of the humeral condyle. Bilateral distal normograde IM pin and LCP placement were performed and confirmed radiographically and by disarticulation and sagittal sectioning. The anatomic landmark for pin insertion was consistently identified in each specimen using the technique described. Distal normograde insertion of a 3.5 mm IM pin was possible in Greyhound cadaveric humeri at the described location in conjunction with a 3.5 mm LCP with fixed angle, locked screws. A monocortical locking screw was required to avoid interference with the IM pin in 28 of 60 of the 3 proximal screw holes. No pin interference was encountered in any of the distal screw holes. The anatomic landmark and technique described in our study enabled repeatable successful placement of a distal normograde IM pin of approximately 35% of the IM diameter combined with an LCP on the medial aspect of the canine humerus. This technique may be useful for locking plate-rod fixation of distal humeral diaphyseal fractures.

Construct Failure in an Atypical Femoral Fracture treated with Intramedullary Nailing: A Case Report.

The aim of this paper is to document a rare case of construct failure in a 68-year old Filipina who sustained an atypical femoral fracture (AFF) in her left subtrochanteric area. The patient previously had a 40-month history of alendronate 70mg + vitamin D 5600u therapy for osteoporosis and underwent closed intramedullary nailing for the AFF. Six months postoperatively, she began to experience progressive pain in her operated thigh. Radiographs revealed a broken nail at the proximal screw hole and non-union of the AFF. The patient was treated with exposure of the fracture site, removal of the broken device, exchange intramedullary nailing, and iliac bone grafting. She had radiographic and clinical union and was full weight bearing after three months.

The Protective Effect of Locking Screw Placement on Nonlocking Screw Extraction Torque in an Osteoporotic Supracondylar Femur Fracture Model

To examine the impact of number and position of locking screws in the diaphyseal portion of an osteoporotic distal femoral fracture model with hybrid fixation. Four groups containing 5 osteoporotic bone models were used with varying combinations of diaphyseal screw fixation: 4 nonlocking screws (control); 1 locking screw adjacent to the osteotomy and 3 nonlocking screws; 1 locking screw in the most proximal screw hole of the plate and 3 nonlocking screws; and 2 locking screws at opposite ends of the diaphyseal fixation with 2 nonlocking screws in between. Fixation in the distal articular segment was identical in all constructs. Testing was performed for 50,000 cycles at 2 Hz using simultaneous axial compression (700 N) and bidirectional torque (±5 Nm) applied along the long axis of the bone. All screws were inserted with 4 Nm of torque. The extraction torque for nonlocking screws in those specimens that had a locking screw nearest the osteotomy was significantly greater than those that did not (P = 0.037). In addition, the 10 constructs with a locking screw nearest the osteotomy had no failures compared with 5 of 10 failures in those without a locking screw in this position (P = 0.033). The placement of a locking screw adjacent to the osteotomy was more beneficial in protecting against failure and maintaining the extraction torque of neighboring proximal nonlocking screws. No benefit in adjacent screw extraction torque was seen with a locking screw proximal in the diaphysis. Two locking screws at opposite ends of the diaphyseal fixation were not superior to a single locking screw adjacent to the osteotomy in failure rates or screw extraction torque.

Stress fractures in the gapped area of a two implant construct: a case report

The concomitant occurrence of femoral shaft and hip fractures are not rare. The ideal management of ipsilateral intertrochanteric and femoral shaft fractures is still controversial and needs to be addressed. Cephalomedullary nail fixations of both the fractures have been described with excellent results. Similar results have been published with two implant constructs treating both of these injuries separately. We report the case of a stress fracture, in the gapped area above the proximal interlocking screw of a retrograde femoral nail placed for a segmental femur fracture and a trochanteric fracture treated with a sliding hip plate screw construct, 9 months after initial injury. The gapped area of a two implant construct is of concern and biomechanical studies have shown that the proximal end of the nail and the interlocking screws may act as a stress riser in the femur. A stress fracture in the gapped area of a two implant construct has not been described earlier, although a cadaveric study had shown that the area of the proximal screw hole of the retrograde nail is a common site for a fracture, on loading. Kissing or overlapping instrumentation increases the load to failure and creates a biomechanically stable construct.

In vitro biomechanical evaluation of antegrade femoral nailing at early and late postoperative stages

The present study addresses the question of evaluating, by combining both experimental and numerical methods, the stress/strain distribution within a standardized composite femur implanted with an anterograde intramedullary nail. A transverse diaphyseal fracture has been introduced in order to evaluate the implant response in the early postoperative clinical stage. By comparing these experimental data with those obtained in the fully healed stage, in which the bone continuity had been recovered, it was possible to get information on load sharing between the bone and the intramedullary nail, location of high strain concentrations, bone relative motion at the fracture site, and stiffness reduction caused by bone discontinuity. Experimental data were correlated with those predicted by a validated 3D finite element model of the complete implant/femur assembly to investigate the full field stress distribution either in the cortical bone, in the nail or in the locking screws. The obtained results suggest that full weight bearing in the immediate post-operating stage should not be allowed since high stress levels are generated in the outer shell of the cortical bone either around the proximal screw hole or the upper locking screw hole. Long-term implant reliability should be guaranteed instead, since after fracture consolidation equivalent von Mises stresses never exceed critical levels neither in the bone nor in the implant.

The Effect of Locked Distal Screws in Retrograde Nailing of Osteoporotic Distal Femur Fractures

To examine the effects of locked distal screws in retrograde nails used in unstable osteopenic distal femur fractures. Biomechanical testing of paired human cadaveric femurs. Seven matched pairs of embalmed, moderately osteopenic cadaver femurs were instrumented with 12-mm intramedullary nails in a statically locked, retrograde fashion. One femur of each pair had locked distal screws and the other femur had unlocked distal screws. A 2.5-cm gap of bone was cut nine centimeters from the distal condyles to simulate an unstable fracture. The locked distal screw nails were compared to unlocked distal screw nails for collapse of the fracture gap, medial-lateral and anterior-posterior translation of the nail within the fracture site, and fracture angulation. The femurs were axially loaded, cycled, and then loaded to failure. Motion at the fracture site with axial cyclic loading and site of failure when loaded to failure. After cycling, both locked distal screw and unlocked distal screw nails demonstrated several millimeters medial and anterior translation within the fracture site and approximately 1 mm collapse of the fracture gap. Although no statistically significant differences were found, the locked distal screw nails had less anterior and medial translation, angulation, and collapse of the fracture gap after cycling. Loads to failure were similar for both locked distal screw and unlocked distal screw nails. It was noted that proximal femur failure occurred at the level of the proximal screw hole in the nail at the subtrochanteric level in 7 (4 locked distal screws and 3 unlocked distal screw groups) of the 14 samples. Four other samples failed through the intertrochanteric region (2 locked distal screw and 2 unlocked distal screw groups) and the remainder within the distal fragment by fracture of the femur along the medial cortex. Although most differences in fixation stability were not significant, the locked distal screw nails exhibited less fracture collapse and anterior and medial translation of the nail at the fracture site than the unlocked distal screw nails. The degree of varus angulation after cyclic loading was also less for the locked distal screw nails. The length of the nail chosen should avoid having proximal locking screws distal to the lesser trochanter, thus averting proximal femur stress risers and fractures.

Tibiotalocalcaneal Arthrodesis With a Retrograde Intramedullary Nail: A Biomechanical Analysis of the Effect of Nail Length

Fatigue fractures of the tibia have been observed at the level of the proximal end of the nail after successful tibiocalcaneal arthrodesis with a retrograde intramedullary device. To study the effect of nail length, five matched pairs of cadaver tibiae were instrumented with strain gauges and potted in methylmethacrylate from a level 3 cm proximal to the distal medial malleolus to simulate a successful tibiocalcaneal arthrodesis. A standard length (15 cm) ankle arthrodesis nail and an identical longer device terminating in the proximal tibial metaphysis were inserted in each paired tibia using appropriate technique. The strain of the posterior cortex of the tibia was recorded under bending moments of up to 50 Nm for each intact specimen after nail insertion and after proximal locking of the nail. The nails were then exchanged between the specimens of the same pairs and the experiment was repeated to insure uniformity. The standard length locked nail increased the principal strain of the posterior cortex of the tibia at the level of the proximal screw holes 5.3 times more than the locked long nail (353 and 67 microstrains), respectively. This stress concentration was not observed when the proximal extent of the nail terminated within the proximal tibial metaphysis. A successful tibiocalcaneal arthrodesis with a standard length locked intramedullary nail creates stress concentration around the proximal screw holes that may be responsible for the fractures observed clinically. This study supports the use of a "long" retrograde locked intramedullary nail for tibiocalcaneal arthrodesis in patients with systemic or localized osteopenia.

Mechanical comparison of fixation techniques for the offset V osteotomy: a saw bone study

Four different techniques for the fixation of an offset V bunionectomy were tested on solid-foam saw-bone models for the purpose of determining the strongest form of fixation for the osteotomy. Twenty identical models were placed into 4 different groups. Groups varied as to the placement and caliber of fixation. Models were loaded with a servo-hydraulic testing machine until failure of fixation occurred. Video analysis was used to record the pattern of failure of the fixation. Failure occurred either distal to the first screw, through the first screw hole, between the 2 screws, through the second screw hole, or proximal to the second screw. The mean force to failure of the groups was group 1, 58.1 N; group 2, 59.3 N; group 3, 64.0 N; and group 4, 105.66 N. There was a statistical significant difference between group 4 and the other 3 groups (F 1 = 55.45, P < 0.05). There was no statistical difference between groups 1 to 3. In groups 1 to 3, 87% of the failures were through the distal screw hole, whereas the remaining 13% were through the proximal screw hole. In group 4, 60% of the failures were through the proximal screw hole and 40% were through the distal screw hole. It was concluded that, in this model, the strongest form of fixation for an offset V osteotomy was the 2.7-mm cortical screw placed distally with the proximal point of fixation being a threaded 0.062-inch Kirschner wire.

Ｒｅｔｒｏｇｒａｄｅ Ｉｎｔｒａｍｅｄｕｌｌａｒｙ Ｎａｉｌ（チタン製）の折損した１例

A case of the failure of the ACE Retrograde Trauma (ART) Femoral Nail System (9mm, Titanium alloy) is presented. A 55-year-old female was injured in a traffic accident, and X-ray films showed right femoral supracondylar and shaft fracture. She was treated using an ACE Retrograde Trauma (ART) Femoral Nail System (9mm, Titanium alloy) at our hospital. Partial weight-bearing gait was started 4 weeks after operation, and full weight-bearing 6 weeks. The patient complained of right femoral pain 11 weeks after operation. The nail was broken at the proximal screw hole and femoral shaft fracture was displaced again. The patient was reoperated on using the Osteo IC-Nail System (11mm). The surface of the broken nail was analyzed by Scanning Electron Microscopy (SEM). It was shown that the cause of nail breakage was fatigue destruction. In conclusion, we should use larger nails in this case.

Influences of some design parameters on the biomechanics of the unreamed tibial intramedullary nail.

Several questions relating to the biomechanics of the AO unreamed tibial nail were addressed in this study. These included the effects of the location of the nail bend on the reduction of a high proximal fracture, and the relation of proximal locking screw hole orientation and fracture component cortical contact to the mechanical stiffness of the construct. To measure fracture site malalignment with nail insertion, a motion transducer mounted on the distal tibial shaft was used to track the position of the proximal component during and after insertion of the nail. For studying the effect of screw hole orientation, the intramedullary (IM) nail was modified by drilling a second set of proximal screw holes with oblique instead of parallel alignment. The axial, torsional, and varus-valgus stiffnesses of the constructs with parallel or oblique screws and with or without fracture site contact were determined. In an experimental model with an osteotomy located proximal to the position of the bend in the nail when fully inserted, anterior displacement of the proximal fracture component (or posterior displacement of the distal component) of up to 1 cm was measured. Oblique proximal locking screws significantly decreased both varus/valgus angulation and medial/lateral translation under load, compared with the parallel screws. Constructs were 117% and 55% as rigid as the intact tibia in axial loading with and without cortical contact, and 6.5% and 3.1% as stiff in torsion.(ABSTRACT TRUNCATED AT 250 WORDS)

Forearm fracture plates: To remove or not to remove

Eighty dynamic compression plates used to fix fractures of the radius and/or ulna were removed from 51 of 98 adult patients. Thirty-seven patients had plates removed electively. Fourteen patients had plates removed for clinical reasons. The average time from insertion to removal was 13.6 months, with a range from 4.4 to 36 months. Only one refracture occurred through the unhealed both bone forearm fracture site in a patient whose plate was taken out 6 months after surgery. One refracture also occurred through the proximal screw hole of a still implanted ulna plate that had been inserted 3 years earlier. Leaving a plate in for the remaining life of a young patient cannot be considered a benign decision considering the persisting chance for refracture and the potential complications from prolonged exposure to metal corroion complexes and metal ions.

Biomechanical considerations in intramedullary nailing of femoral shaft fractures

Recent laboratory investigations have led to clinically useful information about intramedullary nailing. These studies have identified several mechanical variables that are important during nail insertion. In particular, a high degree of bending stiffness of the nail combined with an anterior position of the starting hole can cause the femur to burst. Other studies of nail-bone constructs have demonstrated that a femur with a subtrochanteric fracture fixed with a slotted interlocking nail is about 2% as stiff as an intact femur in torsion and about 80% as stiff in bending. Using a closed-section, unslotted nail increases the torsional stiffness to 50% of the stiffness of an intact femur in torsion. Locking rods have been found to support 300% to 400% of a typical person's body weight in axial loading and to fail under load by bending, cracking along the axis of the proximal screw hole, or protruding with the screw through the greater trochanter.