Lateral Entry Point Research Articles

Reply to: Comments on Alentorn-Geli et al.: Anteromedial portal (AMP) versus transtibial (TT) drilling techniques in ACL reconstruction: a blinded cross-sectional study at two- to five-year follow-up

Dear Editor, We read with great interest the comments on our article entitled “Anteromedial portal (AMP) versus transtibial (TT) drilling techniques in ACL reconstruction: a blinded crosssectional study at twoto five-year follow-up” [1] by Sunil Gurpur Kini. In his first concern, Dr. Kini states that the TT group in our study may have more knee laxity because of a too vertical tibial starting point considering that we drilled at 20° in the coronal plane. Studies referenced by Dr. Kini to support his first concern reported a tibial tunnel orientation of 60–70° in the coronal plane, but these angles were considered from the horizontal line, whereas the 20° in our study was considered from the vertical line [4, 5, 7]. Other authors perform the tibial tunnel with a mean angulation of 60.6°, ranging up to 74.2° [9]. Thus, we can not assume our tibial tunnel significantly differs from the existing literature. Dr. Kini highlighted the excellent cadaveric study by Bedi et al. [3] comparing the AMP and TT drilling. The TT drilling was performed with oblique positioning of the tibial guide at 60° in the coronal plane, reaching a mean femoral angulation of 54.81° ± 7.17°, corresponding approximately to 10:45 in a clock position. The TT group in our study had the femoral tunnel in the 11 (or 13) o’clock position, which we believe is comparable with the interesting study by Bedi et al. Although both TT and AMP drilling may produce a femoral tunnel close to ACL footprints, the tibial starting point to achieve this position in the TT drilling must be more medial and could be too close to the tibial joint line. This may result in a short tibial tunnel and enlarged tibial tunnel aperture, which may in turn compromise the graft fixation and incorporation [6]. In addition, a too medialised tibial tunnel starting point during the TT technique may result in an increased risk of injury to the MCL, and may produce a more lateral and posterior tibial tunnel intraarticular entry point resulting in a less effective reconstruction from a biomechanical point of view [8]. In his other concern, Dr. Kini discusses the risk of a short femoral tunnel and the increased risk of posterior wall blow out with the AMP technique. In our experience with the AMP technique, the posterior wall blow out is extremely rare. Using the Acufex Endoscopic femoral drill guide (Smith and Nephew®), a security distance can be systematically left in the posterior wall of the femoral condyle, thus preventing its rupture. The posterior wall Eduard Alentorn-Geli and Gonzalo Samitier contributed equally to this work. E. Alentorn-Geli : P. Alvarez :R. Cugat Artroscopia Garcia-Cugat, Hospital Quiron, Barcelona, Spain

The role of lateral-entry Steinmann pins in the treatment of pediatric supracondylar humerus fractures

Loss of pin fixation in supracondylar fractures can occur with failure to achieve bicortical fixation. Bicortical fixation may be challenging for those pins that attempt to penetrate the diaphyseal cortex, where the bone is thick. Lateral-entry Steinmann pins may allow for better penetration through cortical bone because they are more rigid than typical Kirschner wires. A retrospective review of 16 children with type III supracondylar fractures treated by a single surgeon using Steinmann pins was undertaken. The average age at presentation was 6years. Following closed reduction, all fractures were maintained with three lateral-entry pins. At least one Steinmann pin was placed in the lateral column of the distal humerus in each pin construct. Follow-up radiographs indicated a mean Baumann's angle of 72.9° (range 64°-82°). There was no statistically significant change in the Baumann's angle or axial alignment at final follow-up. All but one fracture healed in an anatomic position on the lateral view. Steinmann pins placed through a lateral-entry point are effective in controlling the reduction of high-grade supracondylar fractures. The fixation is excellent and avoids potential ulnar nerve complications of medial entry.

Optimal Trajectory for the Atlantooccipital Transarticular Screw

Radiologic evaluation of computed tomography (CT) scans using screw insertion simulation software. To investigate the optimal entry point and trajectory of atlantooccipital transarticular screws. To our knowledge, no large series focusing on the placement of atlantooccipital transarticular screws have been published. We used 1.0-mm sliced CT scans and 3-dimensional screw trajectory software to simulate 4.0-mm screw placement. Four entry points were evaluated. Screw placement success rate, safe range of medial angulation, and screw length using each entry point were determined. CT scans of 126 patients were evaluated, for a total of 252 screws for each entry point. On simulation, the 2 lateral entry points showed significantly higher success rates and safe range of medial angulation than the 2 middle points. The 2 lateral entry points had similar success rates (98.0% for anteriolateral (AL) point and 97.6% for posteriolateral (PL) point). Although the safe range of medial angulation was significantly wider for the AL point (26.1 degrees) than for the PL point (23.7 degrees), the screw lengths were significantly longer for the PL point (32.6 mm) than for the AL point (29.4 mm). For both points, 30 degrees of medial angulation led to highest rate of successful screw placement, but the rate was only 79.4% and 80.2%, respectively. Although there was no significant difference in success rates between AL and PL points, PL is likely the best entry point. Although 30 degrees medial and approximately 5 degrees upward angulation led to the highest rate of successful screw placement, the rate was only around 80%. Given the wide individual variation, we recommend that a preoperative 3-dimensional CT scan be obtained when attempting atlantooccipital transarticular screw fixation.

Lateral Insertion Points in Antegrade Femoral Nailing and Their Influence on Femoral Bone Strains

Insertion of rigid uniplane bent femoral nails through the piriform fossa has been reported to cause neurovascular complications. New nails were designed for more lateral entry points. However, these may be associated with a higher risk of iatrogenic fractures. This study investigated if two differently bent nails with more lateral entry points induce higher cortical bone strains than a uniplane bent nail introduced through the piriform fossa. Three groups of 8 cadaveric femurs were instrumented using the following nail systems and entry points: Cannulated Femoral Nail, piriform fossa; Antegrade Femoral Nail, trochanteric tip; and helical nail, lateral of the trochanteric tip. During insertion, the maximum principal bone strains were recorded at 9 locations at the proximal femur and the diaphysis. The occurrence of iatrogenic fractures or fissures was documented. The highest strains recorded were between 2000 and 4500 mum/m and mainly located at the posterior aspect of the greater trochanter and at the medial side of the entry point. In most of these cases fissures or fractures occurred, the number of which was higher for the trochanteric tip group as compared with the other groups. This was thought to be due to the thin cortical walls as a result of the larger reamer diameter in this group. Low strains (below 2000 microm/m) occurred at the medial cortex where the laterally inserted nails were expected to impinge. Bone strains at the medial impingement location were low for all nails. Entry portals with thin cortical walls due to, for example, larger reamer diameters and a small greater trochanter seem to be more susceptible to insertion accuracy, which may influence strain and fissure or fracture occurrence. Furthermore, we do not recommend determination of the entry point of laterally inserted nails based solely on anatomic landmarks of the greater trochanter because this may influence insertion accuracy. This implies that biplanar imaging is important for accurate and safe insertion of laterally started nails.

A Simplified Approach to Vertical Infraclavicular Brachial Plexus Blockade Using Hand-Held Doppler

In this observational study, we used Doppler ultrasound during the performance of vertical infraclavicular brachial plexus blockade. The success rate at inserting the needle at the point where the sound of the subclavian artery via Doppler reached its maximum audibility was compared with that of the classical insertion point. In 89 of the 100 patients, the medial or posterior cord was found at first needle pass. Using the Doppler point for insertion resulted in a significantly more lateral entry point compared with the classical point (P < 0.001) and was associated with a high success rate of infraclavicular block.

Treatment of Pediatric Supracondylar Humerus Fractures in the Community Hospital

Supracondylar fractures of the humerus are among the most common elbow injuries in the pediatric population. Because of the significant morbidity associated with treating displaced pediatric supracondylar humerus fractures, most community-based orthopedic surgeons prefer to transfer these injuries to specialty children's hospitals. Our intention in writing this article was to document and evaluate the results we obtained using the lateral diverging pin technique to treat patients at our community hospital. In doing so, we set out to determine if our results were comparable to those of specialty hospitals, allowing us in the future to eliminate the inconvenience placed on patients and their families when being transferred to a specialty facility. We retrospectively reviewed the patients treated surgically at our institution for a closed Gartland type II or type III supracondylar distal humerus fracture during the months of September and October of 2005. The medical records and radiographs of all children who had been treated for a displaced extension-type supracondylar humerus fractures were evaluated. The data recorded from the chart review included the age and sex of the patients, preoperative and postoperative neurovascular status, operative techniques (2 vs 3 lateral entry point Kirschner wires), and the operative time (start to close). The radiographs were reviewed to determine the Gartland type of fracture and the Baumann angle on the anteroposterior film immediately postoperative and at the time of fracture union. Four Gartland type II and 3 Gartland type III fractures were identified during the study period. There were 3 boys and 4 girls with a mean age of 6.29 years (range, 3.92-8.58 years). The mean immediate postoperative Baumann angle was 18.29 degrees (range, 10-25 degrees). At the time of fracture union, the mean Baumann angle was 19.0 degrees (range, 14-22 degrees). The mean range-of-motion loss as compared with the extension loss (range, 10-2 degrees) and 4.57 degrees of flexion loss (range, 10-2 degrees). The mean operative time was 20.43 minutes (range, 7-37 minutes). Our results show the change in Baumann angle and loss of range of motion compare favorably with results of studies done at specialty hospitals. We believe that the divergent lateral pinning technique, in combination with postoperative splinting and a sling can provide excellent results while eliminating the risk of injury to the ulnar nerve. With this knowledge, we feel that the advantage to treating these fractures at a community hospital is the elimination of the anxiety, stress, and time spent waiting in the emergency department of multiple hospitals.

Graded Activity of Transcription Factor Runx3 Specifies the Laminar Termination Pattern of Sensory Axons in the Developing Spinal Cord

Different functional classes of dorsal root ganglion sensory neurons project their axons to distinct target zones within the developing spinal cord. To explore the mechanisms that link sensory neuron subtype identity and axonal projection pattern, we analyzed the roles of Runx and ETS transcription factors in the laminar targeting of sensory afferents. Gain- and loss-of-function studies in chick embryos reveal that the status of Runx3 expression is a major determinant of the dorso-ventral position of termination of proprioceptive and cutaneous sensory axons. In addition, the level of expression and/or activity of Runx3 in individual proprioceptive sensory neurons appears to specify whether their axons terminate in intermediate or ventral regions. Our findings suggest that the selectivity of Runx3 expression, and its level of activity, control sensory afferent targeting in the developing spinal cord.

The innervation of patella: anatomical and clinical study

As much interest has been focused on afferent innervation of knee than that of patella, there are few articles about patellar innervation. But in clinical practice anterior knee pain due to patellar disorders is a quite frequent problem. Our aim was to review the innervation pattern of patella and to give the topographic anatomy of the nerves. We dissected 30 knees of 15 formaldehyde-fixed cadavers. Two nerves from vastus medialis and lateralis were found to reach patellar edge. Apart from these, we were unable to find any other neural structures around patellae. Mean distances between the tuberosity of the tibia and medial and lateral nerve entry points were 90.1(range 74-102) and 96.3 mm (range 76-109), respectively. The angles between lines which join the entry points of nerves and vertical line to the center point of patella were measured in frontal plane. It was approximately 60 degrees medially and 40 degrees laterally. To confirm that these nerves are patellar pain afferents, we performed a local anesthesia test in 32 knees of 20 patients with patellofemoral pain. Clinically, there was a significant difference between the visual analogue scale (VAS) scores before and after local anesthetic injections (p<0.01). Previous studies have emphasized especially the medial innervation. We found that both superomedial and superolateral nerves were important for patellar innervation. We described precisely the entry points of these nerves to patella for selective denervation.

Soft tissue injury related to choice of entry point in antegrade femoral nailing: piriform fossa or greater trochanter tip

Intramedullary nailing through the piriform fossa results in some cases in loss of abduction strength and persistent pain. Nail insertion at the tip of the greater trochanter may be favourable. The aim of this study was to assess (possible) iatrogenic injury to the abductor and external rotator musculature, branches of the superior gluteal nerve and branches of the MFCA in relation to the two different entry points. In 10 fresh human cadaver femurs, five unreamed femoral nails (UFN) were inserted through the piriform fossa and five AO prototype nails (AFN) through the trochanteric tip. The iatrogenic injury at each nailing procedure was assessed. Various muscles and tendons, branches of the MFCA along with the hip joint capsule were injured or largely at risk during nail insertion through the piriform fossa. Most of these structures were not exposed during insertion through the trochanteric tip. The reported clinical morbidity after nailing through the piriform fossa may find its origin in direct soft tissue injury and may be reduced by choosing a lateral nail entry point.

Anatomical considerations for percutaneous proximal humeral fracture fixation

Purpose: To investigate the hypothesis that percutaneous wire fixation of proximal humeral fractures is prone to regional neurovascular injury. Materials and Methods: 40 cadaveric shoulders had percutaneous wires inserted from anterior and lateral humeral shaft entry points into the humeral head. The shoulders were then dissected to identify the neurovascular structures in this area. Results: The axillary nerve trunk and posterior circumflex humeral artery were found to be within the field of dissection. The axillary nerve was damaged on three occasions by the lateral wires, two of which were direct nerve penetrations. The anterior wires caused a single perineural injury of a terminal branch. The main neurovascular leash was 57 mm (range 35–70 mm) from the acromion tip laterally and 51 mm (range 35–85 mm) anteriorly, with a width of 6 mm (range 4–13 mm) laterally, and 12 mm (range 7–15 mm) anteriorly. Conclusions: Percutaneous wire stabilisation is an attractive fixation option but this study highlights the close proximity of the important neurovasculature. Such fixation should be performed utilising a limited open approach, with dissection to bone under direct vision, with the subsequent use of a drill-sleeve for soft-tissue protection.

A new technique for positioning tangential fields

Purpose : A technique that eliminates the use of a mechanical “breast-bridge” for positioning tangential fields for treatment of the intact breast or chest wall has been developed. Methods and Materials : Treatment set-up parameters are determined using measuring capabilities (gantry angles and source-skin distances) available on a standard simulator unit. A programmable scientific calculator is used to determine field geometry from polar coordinates for various points on the patient's skin. The calculator program determines the field size, a depth and lateral shift from a skin reference point to the isocenter for the tangential fields, and the gantry angles. The program provides additional information which facilitates the simulation process: First, the coordinates of the isocenter for the tangential fields are expressed relative to couch coordinates for an initial arbitrary isocenter so that the “auto go to” capability available on some simulators can be used. Second, the coordinates of the medial and lateral entry points can be edited when the first set of tangents are not accepted. This part of the program allows quick and efficient adjustment of the fields to obtain adequate treatment volume coverage and a minimum of irradiated lung or heart. Results : Simulation of more than 300 patients has shown the technique to be a practical and efficient method for positioning tangential fields for breast or chest wall irradiation. Conclusion : The technique described here takes full advantage of the capabilities of the new generation of computer controlled simulators, and offers an alternative to previous methods employing a mechanical “breast-bridge.”