Palpable Anatomical Landmarks Research Articles

Bony Landmarks for Determining the Mechanical Axis of the Femur in the Sagittal Plane during Total Knee Arthroplasty

BackgroundThere is no accepted landmark for the mechanical axis of the femoral axis in sagittal plane in conventional total knee arthroplasty.MethodsAs palpable anatomic landmarks of the femur, lateral epicondyle, and anterior margin of the greater trochanter were identified. The line connecting these two landmarks was defined as the "palpable sagittal axis". The mechanical axis of the femur was compared with the palpable sagittal axis and the distal femoral anterior cortex axis. These axes were also compared with sagittal bowing of the femur.ResultsThe distal femoral anterior cortex axis and the palpable sagittal axis were flexed by 4.1° and 2.4° more than the sagittal mechanical axes, respectively (p < 0.05). However, the palpable sagittal axis was not correlated with sagittal bowing of the femur (Spearman's rs, 0.17; p = 0.14).ConclusionsThe palpable sagittal axis showed a consistent relationship with the sagittal mechanical femoral axes regardless of the severity of the sagittal bowing of the femur.

Joint kinematics estimate using wearable inertial and magnetic sensing modules

Background and aims In many applications, it is essential that the evaluation of a given motor task is not affected by the restrictions of the laboratory environment. To accomplish this requirement, miniature triaxial inertial and magnetic sensors can be used. This paper describes an anatomical calibration technique for wearable inertial and magnetic sensing modules based on the direct measure of the direction of anatomical axes using palpable anatomical landmarks. An anatomical frame definition for the estimate of joint angular kinematics of the lower limb is also proposed. Methods The performance of the methodology was evaluated in an upright posture and a walking trial of a single able-bodied subject. The repeatability was assessed with six examiners performing the anatomical calibration, while its consistency was evaluated by comparing the results with those obtained using stereophotogrammetry. Results Results relative to the up-right posture trial revealed an intra- and inter-examiner variability which is minimal in correspondence to the flex-extension angles (0.2–2.9°) and maximal to the internal–external rotation (1.6–7.3°). For the level walking, the root mean squared error between the kinematics estimated with the two measurement techniques varied from 2.5% to 4.8% of the range of motion for the flex-extension, whereas it ranged from 13.1% to 41.8% in correspondence of the internal–external rotation. Conclusion The proposed methodology allowed for the estimate of lower limb joint angular kinematics in a repeatable and consistent manner, enabling inertial and magnetic sensing based systems to be used especially for outdoor human movement analysis applications.

Discrepancies in Knee Joint Moments Using Common Anatomical Frames Defined by Different Palpable Landmarks

The aim was to investigate the effects of three anatomical frames using palpable anatomical landmarks of the knee on the net knee joint moments. The femoral epicondyles, femoral condyles, and tibial ridges were used to define the different anatomical frames and the segment end points of the distal femur and proximal tibia, which represent the origin of the tibial coordinate system. Gait data were then collected using the calibrated anatomical system technique (CAST), and the external net knee joint moments in the sagittal, coronal, and transverse planes were calculated based upon the three anatomical frames. Peak knee moments were found to be significantly different in the sagittal plane by approximately 25% (p <or= 0.05), but no significant differences were seen in the coronal or transverse planes. Based on these findings it is important to consider the definition of anatomical frames and be aware that the use of numerous anatomical landmarks around the knee can have significant effects on knee joint moments.

Complications of Cervical Selective Nerve Root Blocks Performed with Fluoroscopic Guidance

2Department of Neurosurgery, Allegheny General Hospital, Pittsburgh, PA. ervical nerve root blocks have been performed since the late 19th century [1], and the use of the procedure has been increasing over the past decade [2]. Cervical nerve root blocks are used to manage or treat spinal pain, radiculopathy, and complex regional pain syndromes. Many such blocks are performed in outpatient clinics with and without imaging guidance such as fluoroscopy or CT. If imaging guidance is not used, palpable anatomic landmarks are generally used to direct needle placement. Various complications associated with the nerve block procedure have previously been described [3–7]. The most serious reported complications include death, stroke, arrhythmias, sensory or motor loss, meningitis, bleeding, and seizures. To our knowledge, arterial dissection has not previously been reported after a cervical selective nerve root block (SNRB). Our purpose is to present two cases that show potentially devastating outcomes when a cervical SNRB is performed using fluoroscopic guidance and to evaluate possible alternative methods currently available.

Motor Points for the Neuromuscular Blockade of the Subscapularis Muscle

Harrison TP, Sadnicka A, Eastwood DM. Motor points for the neuromuscular blockade of the subscapularis muscle. Objective To locate the motor points of the subscapularis muscle in relation to palpable anatomic landmarks and hence suggest a technique for botulinum toxin injection into subscapularis applicable to patients of all ages. Design Anatomic dissection of the innervation of 20 subscapular muscles. Setting University dissecting room. Cadavers Ten formalin-preserved cadavers. Interventions Not applicable. Main Outcome Measure The location of motor points in relation to anatomic landmarks. Results The median number of motor points for the subscapularis was 5 (range, 3−6). All motor point measurements were related to surface points and converted into proportional values along reference lines. Motor points from the 20 dissections showed clustering in a band. A line of best fit was calculated ( y=1.48 x–0.743). Conclusions We describe an injection technique that would deliver botulinum toxin close to the motor points of the subscapularis, a surrogate marker of the motor endplate zones. By using proportional distances, this technique is applicable to an adult and pediatric population. This should lead to an increased efficacy and decreased side-effect profile in clinical practice, although clinical trials will need to confirm this.

How does soft tissue distribution affect anteversion accuracy of the palpation procedure in image-free acetabular cup navigation? An ultrasonographic assessment

Navigation of the acetabular cup in total hip replacement (THR) is used to improve the reproducibility of acetabular component positioning. When the palpation of anatomic landmarks, which is necessary to determine the pelvic coordinate system, is performed epicutaneously, the question as to how uneven soft tissue distribution can influence navigation accuracy arises.To obtain data, the questionable soft tissue thickness was measured in 72 patients scheduled for THR. In addition, distances between the landmarks were recorded. On the basis of this information, we were able to calculate the expected misinterpretation of the anteversion given by a navigation system for each patient.The calculations suggest that a navigation system would have underestimated the anteversion on average by 2.8° ± 1.8°. The median of anteversion misinterpretation was 2.4° and its 95% confidence interval was calculated to be 2.2°–3.0°. No correlation with substantial significance between anteversion misinterpretation and the patients' biometrical data could be found.According to the current knowledge, acetabular cups in THR should be positioned within a range of 30°–50° of inclination and 10°–30° of anteversion. In comparison with these permitted ± 10° windows, the amount of misinterpretation that was found due to uneven soft tissue distribution seems to be acceptable.

How does soft tissue distribution affect anteversion accuracy of the palpation procedure in image-free acetabular cup navigation? An ultrasonographic assessment

Navigation of the acetabular cup in total hip replacement (THR) is used to improve the reproducibility of acetabular component positioning. When the palpation of anatomic landmarks, which is necessary to determine the pelvic coordinate system, is performed epicutaneously, the question as to how uneven soft tissue distribution can influence navigation accuracy arises.To obtain data, the questionable soft tissue thickness was measured in 72 patients scheduled for THR. In addition, distances between the landmarks were recorded. On the basis of this information, we were able to calculate the expected misinterpretation of the anteversion given by a navigation system for each patient.The calculations suggest that a navigation system would have underestimated the anteversion on average by 2.8° ± 1.8°. The median of anteversion misinterpretation was 2.4° and its 95% confidence interval was calculated to be 2.2°–3.0°. No correlation with substantial significance between anteversion misinterpretation and the patients' biometrical data could be found.According to the current knowledge, acetabular cups in THR should be positioned within a range of 30°–50° of inclination and 10°–30° of anteversion. In comparison with these permitted ± 10° windows, the amount of misinterpretation that was found due to uneven soft tissue distribution seems to be acceptable.

Are Anatomic Landmarks Reliable in Determination of Fusion Level in Posterolateral Lumbar Fusion?

Determination of the fusion level by direct observation and palpation of anatomic landmarks is compared with the finding obtained from a lateral intraoperative radiograph. To assess the reliability of the use of intraoperative anatomic landmarks in determination of the fusion level. Accurate determination of the level to be fused in noninstrumented posterolateral fusion is crucial. No studies are available in which the value of direct observation and palpation of the anatomic landmarks in determination of the fusion level has been assessed. Eighty patients who underwent posterolateral fusion without instrumentation in the lumbosacral spine were included in this study. During surgery, first, the cephalad transverse process at the desired level to be fused was determined by direct observation and palpation of the anatomic landmarks; second, a metal mark was placed beneath the cephalad transverse process at the level determined by anatomic landmarks. This was followed by a lateral radiograph. The consistency and discrepancy between the use of the anatomic landmarks and lateral radiography in determining the desired fusion level were recorded. The fusion level determined by direct observation and palpation of the anatomic landmarks was accurate in 76 (95%) cases. In the remaining four cases, intraoperative x-rays determined that the selection of the cephalad transverse process for fusion was one level too high in three cases and one level too low in the other case. All errors in determination of the level to be fused occurred in patients who had extensive laminectomy at L4-S1. Determination of fusion level by direct observation and palpation of the anatomic landmarks is not reliable in patients who have had or require decompressive procedures. A lateral radiograph should be routinely obtained for accurate identification of the level to be fused.

Sonographic guidance when using the right internal jugular vein for central vein access.

The intent of this study was to substantiate the advantages of the use of sonographic guidance for central venous access via the right internal jugular vein. Eighty sequential patients requiring central vein access were examined with a hand-held sonography transducer to determine the size, patency, and location of the right internal jugular vein before puncture. Access to the right internal jugular vein was subsequently performed, under sterile conditions, using sonographic guidance. Periprocedural complications were prospectively recorded. Subsequently, we compared our findings with published reports of complications when visible and palpable anatomic landmarks were used for guidance during cannulation of the internal jugular vein. Among these 80 patients, the anatomy of the right internal jugular vein was typical in only 57 (71%). In another 13 patients (16%), sonography showed a medial position of the right internal jugular vein, anterior to the common carotid artery. In three other patients (4%), the right internal jugular vein was positioned laterally by more than 1 cm. In the remaining seven patients (9%), the vein was thrombosed. Its diameter, measured without use of the Valsalva maneuver, also varied, measuring 0.5-2.0 cm. Cannulation was achieved in all 73 patients with a patent right internal jugular vein. One puncture was required in 68 patients (93%); two punctures in three other patients (4%); and three punctures in the remaining two patients (3%). In no case was the common carotid artery inadvertently punctured. Only one periprocedural complication occurred, and it was unrelated to the use of sonographic guidance. Sonographic guidance for central vein access via the right internal jugular vein is safer and more efficient than the traditional landmark approach.

External fixation of the calcaneus and talus: an anatomical study for safe pin insertion.

Fifteen fresh-frozen adult cadaver feet were dissected to investigate areas in the hindfoot where external fixation pins could be safely inserted with the least risk to underlying nerves, vessels, and tendons. Using palpable anatomic landmarks, four relative "safe zones" on the calcaneus and talus were delineated. These included an area on the medial calcaneus, the medial talus, the lateral calcaneus, and the lateral talus. The medial calcaneal safe zone was a large, easily definable rectangular area on the posterior aspect of the tuberosity, posterior to the neurovascular bundle and extrinsic tendons. The medial talar safe zone was located on the medial talar neck, anterior and superior to the tibialis posterior tendon. The lateral calcaneal safe zone consisted of a large area of the lateral calcaneal tuberosity, located posterior to the peroneal tendons and sural nerve trunk. The lateral talar safe zone included only a narrow, vaguely palpable, quadrangular area on the lateral neck of the talus. The medial safe zones could be easily delineated by palpation and appeared safe for routine unilateral external fixation across the medial hindfoot and ankle. The lateral safe zones appeared safe and useful if both medial and lateral frames were required. The structures most at risk for injury during pin insertion in the zones described were the medial and lateral calcaneal nerve branches, which inconsistently crossed the medial and lateral calcaneal safe zones, respectively. In these areas overlying the tuberosity, however, the subcutaneous tissues were thin, and iatrogenic nerve injury during pin insertion appeared avoidable if blunt dissection was used to reach the calcaneal cortex. The data presented here provide information to assist selection of pin sites that minimize risk to underlying soft tissues during external fixation of the talus and calcaneus.

Puncturing the Pulseless Femoral Artery: A Simple Technique That Uses Palpation of Anatomic Landmarks

The authors report a simple technique in which palpation of anatomic landmarks is used to localize the pulseless common femoral artery. A finger is placed immediately lateral to the pubic tubercle and inferior to the inguinal ligament to palpate the point allowing the most posterior depression. Anatomically, this depression lies between the iliopsoas muscle laterally and the pectineus muscle medially. The femoral vein lies in the floor of this depression, and 1.5 cm lateral to the depression lies the femoral artery. This anatomic relationship and its usefulness for locating the common femoral artery were verified by puncture and dissection of nine cadaveric groins and successful puncture of 19 pulseless arteries of 17 patients. The described technique was found to be quick, simple, and reliable and is now the authors' method of choice for puncturing the pulseless femoral artery.

The anatomical variations of the distal course of the superficial peroneal nerve: recommendations to avoid injury during surgical procedures

Entrapment of the distal superficial peroneal nerve has been reported. Direct injury is uncommon. The recent introduction of circular external fixator frames such as the Ilizarov necessitates the placement of multiple pins in established precise locations to avoid the larger posterior and anterior neurovascular bundles. The distal branch of the superficial peroneal nerve is at risk of injury. This study illustrates one such case. The superficial peroneal nerves of 20 cadaver limbs were dissected and the course, variations and dimensions of the nerve described. A ‘danger area’ was identified in relation to palpable anatomical landmarks. Avoidance of pin insertion within this area should reduce the risk of nerve injury and significant morbidity.

Humeroscapular positions in a shoulder range-of-motion-examination

Positions of the arm are traditionally described in relation to the thorax. Yet shoulder pathology most often lies in and about the glenohumeral joint, which then becomes the focus of treatment. Little is known about the relative motion between the humerus and the scapula primarily because there is no clinically accepted method for assessing and describing these positions. This paper proposes a clinical method for describing and measuring humeroscapular positions based on an anatomic definition of the plane of the scapula. Humeroscapular positions achieved by 75 normal subiects during a conventional (humerothoracic) shoulder range-of-motion examination are presented. Identification of the plane of the scapula is based on four palpable anatomic landmarks: (7) the inferior pole of the scapula, (2) the medial border of the scapula at the level of the scapular spine, (3) the posterolateral corner of the acromion, and (4) the tip of the coracoid. The plane of the scapula is defined by the line connecting the first two of these points and a point midway between the last two. Humeroscapular positions are specified by the plane of elevation and the angle of elevation in relation to this mobile scapular plane. Measurement of these positions was done with a goniometer facilitated by a "scapula-locating device" designed for this study. Maximal humerothoracic elevation of the arm was achieved with the humerus lust behind the scapular plane at 90° of humeroscapular elevation. Cross-body adduction positioned the humerus in a plane 51° anterior to the plane of the scapula, with most of the cross-body motion occurring between the scapula and thorax. External rotation at 90° of elevation in the coronal plane of the body (the apprehension position) positioned the humerus in a plane 17° posterior to the scapular plane. Humerothoracic extension and reaching up the back took place at very low angles of humeroscapular elevation.