Francis Van Glabbeek

Capitellar erosion caused by a metal radial head prosthesis. A case report.

The long-term results of resection of the radial head for the treatment of a simple radial head fracture have been generally satisfactory1-5. However, some late complications, such as proximal migration of the radius, can disable the patient and are difficult to treat. Proximal migration of the radius is usually asymptomatic3-5, although wrist pain develops in a minority of patients3-8. The options for treatment are limited, and clinical studies have shown poor and unreliable results9,10. Sowa et al. described a case in which a silicone radial head prosthesis was implanted for the treatment of wrist symptoms10. Proximal migration of the radius progressed, and it was concluded that a more rigid implant would be necessary. Sellman et al. reached a similar conclusion after performing a biomechanical study of this problem11. We report the case of a patient who had early progressive erosion of the capitellum after the insertion of a metal radial head prosthesis for the treatment of wrist pain following radial head resection after trauma. This complication has not been reported previously, to our knowledge. Our patient was informed that data concerning the case would be submitted for …

What Should the Surgeon Aim for When Performing Computer-Assisted Total Knee Arthroplasty?

S tability of the knee is a complex issue and involves ligaments that behave differently on the medial and lateral side. Correct positioning of the components and adequate soft-tissue balancing are critical steps in successful total knee arthroplasty1. A total knee prosthesis that is implanted “too tightly” may cause limited range of motion and compromise patient satisfaction. A total knee replacement that is implanted “too loosely” will be unstable2. Medial-lateral instability is the most common type of instability and may result from incompetent collateral ligaments, incomplete correction of a preoperative deformity, or incorrect bone cuts3. Separate studies have identified instability as a leading cause of early clinical failure of a primary total knee replacement, resulting in revision within three to five years4,5. It is generally accepted that the surgeon should aim for “some” medial-lateral laxity, but no numerical data are currently available at present to guide the surgeon. The purpose of this study was to quantify the ligament laxity in a normal nonarthritic knee before and after a standard total knee arthroplasty. A latest-generation fluoroscopy-based spatial navigation system was used to provide the numerical values of medial-lateral, anterior-posterior, and rotational laxity in cadaveric specimens. T welve fresh-frozen human cadaveric specimens of lower limbs with nonarthritic knees were used for the study. The age of the individuals at the time of death ranged from forty-seven to eighty-eight years (mean, sixty-eight years). Fig. 1 Preparation of the proximal part of the femur. Prior to the formal testing of the specimens, a pilot project was performed with use of another fresh-frozen human cadaveric lower limb to design the setup. Manual “clinical” testing was compared with instrumented testing with use of a digital dynamometer (Model CH 25 K 50; Kern, Balingen, Germany) with a maximum weighing …

The noncircular shape of the radial head

PURPOSE The purpose of this study was to define the shape of the radial head by identifying the relationship between precisely defined axes of the radial head. METHODS An anatomic study was done to define the shape of the radial head and specifically the relationship between the long and the short axis. Twenty-seven cadaveric upper extremities were used. The x and y axes of the radial head were defined in relationship to the radial notch of the ulna, with the forearm in neutral position. Outer diameters of the x and y axis were measured. These were compared with the actual maximum and minimum diameters of the radial head. X and y diameters of the articulating surface of the radial head also were measured. RESULTS Paired 1-tailed Students t-tests were used to compare the x and y diameters of the radial head. Regression analysis of x and y diameters of the radial head was done to identify a correlation between these parameters.Paired 1-tailed Students t-tests showed a significant difference between X and Y diameters of the radial head. Regression analysis of x and y diameters of the radial head showed a strong correlation between these 2 axes. CONCLUSIONS The radial head is not round. A strong correlation exists between the x and y diameters of the radial head. The orientation of the long axis is perpendicular to the radial notch with the forearm in neutral rotation. This finding will make it possible to approach the anatomy of the radial head more closely when designing radial head prostheses. The definition of the axes can be used as a guide when implanting the radial head prosthesis.

An Experimental Model for Kinematic Analysis of the Knee

The description of the relative motion between rigid bodies is called kinematics. The knee joint is the largest joint of the human body and has an intricate anatomy, and thus its kinematics have intrigued researchers for a long time1. Apart from direct visual observation, the most popular tool for studying the joint has been radiography. Historically, the knee has been treated as if it were a planar mechanism 2. In other words, the movement of the knee was reduced to a two-dimensional projection of a three-dimensional reality. In recent years, the limitations of this methodology have become clear, with the major flaw being the inability to ascertain the location of the axes of rotation before performing kinematic analyses3. In 1983, Grood and Suntay presented a joint coordinate system that provided a geometric description of the three-dimensional rotational and translational motion between two rigid bodies, and they applied this system to the knee joint4. With use of this model, the described joint displacements became independent of the order in which the component rotations and translations occur. The new mathematical insights led to the concept of the helical axis and opened the door for a correct scientific description of the kinematics of the knee, thus allowing for six degrees of freedom5. However, as the mathematical accuracy improved, the complexity increased and the model appeared to be impractical and difficult to apply to the clinical setting (i.e., the clinicians failed to understand the engineers). Hollister et al., and later Churchill et al., tried to bridge the gap, reducing the descriptive model to essentially two degrees of freedom6,7. In the model of Hollister et al., knee motion was described as pure rotations occurring around two axes: the so-called flexion-extension axis and …

Accuracy of placement of the glenoid component in reversed shoulder arthroplasty with and without navigation

HYPOTHESIS Navigation can improve accuracy of placement of the glenoid component in reversed shoulder arthroplasty. MATERIAL AND METHODS A glenoid component of a reversed shoulder prosthesis was implanted in 14 paired scapulohumeral cadaver specimens. Seven procedures with standard instrumentation were compared with 7 procedures using navigation. The intraoperative goal was to place the component centrally in the glenoid in the axial plane and 10° inferiorly tilted in the frontal plane. Glenoid component version and tilt and screw placement were studied using CT scan and macroscopic dissection. RESULTS The mean version of the glenoid component in the standard instrumentation group was 8.7° of anteversion, compared with 3.1° of anteversion in the navigated group. The mean tilt of the glenoid component was 0.9° in the standard group and 5.4° of inferior tilt in the navigated group. Using navigation, the range of error for version was 8° (SD 3.3°) compared to 12° (SD 4.1°) in controls. For tilt, the range of error was 8° (SD 3.6°) in navigated specimens and 16° (SD 6.0°) for controls. In the control group, there were no perforations of the central peg, but 1 inferior screw and 4 superior screws were malpositioned. In the navigation group, no central peg perforated, all inferior screws were correctly positioned, and 2 superior screws were malpositioned. CONCLUSION Computer navigation was more accurate and more precise than standard instrumentation in its placement of the glenoid component in reversed shoulder arthroplasty.

Comparison of Two Percutaneous Volar Approaches for Screw Fixation of Scaphoid Waist Fractures Radiographic and Biomechanical Study of an Osteotomy-Simulated Model

BACKGROUND When a surgeon uses a percutaneous volar approach to treat scaphoid waist fractures, central screw placement is complicated by the shape of the scaphoid and by obstruction by the trapezium. In this study, we used radiographs and biomechanical tests to compare the standard volar percutaneous approach with the transtrapezial approach, with regard to central screw placement at the distal pole of the scaphoid. METHODS Fourteen matched pairs of cadaveric wrists were randomly assigned to two treatment groups. Under fluoroscopic control, a guidewire was drilled into the scaphoid, either through a transtrapezial approach or through a standard volar approach that avoided the trapezium. Guidewire position was measured in the coronal and sagittal planes. A transverse osteotomy was performed along the scaphoid waist, and this was followed by the insertion of the longest possible cannulated headless bone screw. Each specimen was placed into a fixture with a pneumatically driven plunger resting on the surface of the distal pole. Load was applied by using a load-controlled test protocol in a hydraulic testing machine. RESULTS All guidewires were inside the central one-third of the proximal pole. The guidewire positions at the distal pole differed significantly between the transtrapezial and standard volar approach groups (p < 0.001). The load to 2 mm of displacement and the load to failure averaged, respectively, 324.4 N (standard error of the mean [SEM] = 73.5 N) and 386.4 N (SEM = 65.6 N) for the transtrapezial approach group compared with 125.7 N (SEM = 22.6 N) (p = 0.002) and 191.4 N (SEM = 36.30 N) (p = 0.005) for the standard volar approach group. CONCLUSIONS The data suggest that, in a cadaveric osteotomy-simulated scaphoid waist fracture model, the transtrapezial approach reliably achieves central positioning of a screw in the proximal and distal poles. This position offers a biomechanical advantage compared with central placement in only the proximal pole.

The Anatomy of the Clavicle: A Three-dimensional Cadaveric Study

The clavicle has a complex osteologic structure that makes morphological analysis extremely difficult. A three‐dimensional study was conducted to examine the anatomical variations and characteristics of the bone. Sixty‐eight human cadaver clavicles were dissected, CAT‐scanned, and reconstructed. An automated parameterization and correspondence shape analysis system was developed. A new length, designated as centerline (CL) length, was defined and measured. This length represents the true length of the clavicle. The endpoint length was measured as the distance between two endpoints. The width and curvature were measured in the axial (AX) and frontal (FR) plane and defined along the CL. Next gender and side characteristics and variations were examined. The mean CL length was 159.0 ± 11.0 mm. The mean endpoint length was 149.4 ± 10.3 mm, which was statistically significantly shorter than the CL. The male clavicle was significantly longer (166.8 ± 7.3 mm vs. 151.0 ± 8.2 mm), wider (14.6 ± 1.5 mm vs. 12.7 ± 1.3 mm lateral FR plane, 25.9 ± 4.1 mm vs. 23.5 ± 3.0 mm lateral AX plane and 24.7 ± 2.8 mm vs. 22.8 ± 2.8 mm medial AX plane), and more curved (10.8 ± 2.8 mm vs. 8.6 ± 2.3 mm medial and 10.5 ± 3.3 mm vs. 9.1 ± 2.5 mm lateral) than the female one. Left clavicles were significant longer (159.8 ± 10.9 mm vs. 158.0 ± 11.2 mm) than right clavicles. A novel three‐dimensional system was developed, used and tested in order to explore the anatomical variations and characteristics of the human clavicle. This information, together with the automated system, can be applied to future clavicle populations and to the design of fixation plates for clavicle fractures. Clin. Anat. 27:712–723, 2014.

Relationship of the Scarf Valgus-Inducing Osteotomy of the Calcaneus to the Medial Neurovascular Structures

Background: The Scarf valgus inducing osteotomy of the calcaneus is an operative technique to correct varus deformity of the hindfoot. It is versatile with significant corrective power; however, the neurovascular structures are in close proximity on the medial side and thus may be harmed during the osteotomy. Moreover, because this type of osteotomy can cause a great lateral translation, traction of the medial neurovascular structures is possible. We performed an anatomic study to evaluate the medial soft tissues after a lateralizing Scarf-type calcaneal osteotomy. Materials and Methods: The osteotomies were carried out on ten fresh-frozen cadaver specimens. We performed the osteotomy and induced valgus. Then we performed a medial dissection to identify the important medial structures: the medial and lateral plantar nerve (MPN, LPN) and the posterior tibial artery (PTA). We noted their relation to the osteotomy and their integrity. Results: In several cases, one or more of the structures were sectioned. In five cases, all the structures crossed the osteotomy, four of which even a transection of one or both of the plantar nerves occurred. Although the PTA crossed the osteotomy in eight specimens, there was no transection of this structure. Conclusion: Scarf osteotomy of the calcaneus is a highly corrective osteotomy. However, caution must be exercised when performing as the medial neurovascular structures cross the osteotomy lines and transection can occur. Clinical Relevance: When performing the osteotomy one should keep in mind that vigorous sawing and large displacement can cause damage to the medial neurovascular structures.

Bilateral ulnar nerve entrapment by the M. anconeus epitrochlearis. A case report and literature review

Ulnar neuropathy at the elbow is the second most common entrapment neuropathy. Ulnar nerve entrapment has several causes. A case report is presented with the presence of the M. anconeus epitrochlearis at both sides. The patient contacted our department with chronic, diffuse bilateral elbow pain irradiating into both forearms. She experienced typical nocturnal paresthesias involving digit IV and V of both hands. Tinel’s sign was present just proximal to the medial epicondyle. A bilateral ulnar nerve entrapment was clinically suspected. An electromyographic (EMG) investigation revealed slowing of the motor conduction velocity in the ulnar nerve across the elbow. An ultrasound and MRI investigation demonstrated the presence of an anomalous muscle, called the M. anconeus epitrochlearis, at both sides. Treatment consisted of bilateral surgical excision of the muscle and retinacular release, followed by physical therapy. The outcome was favourable.

The Anterolateral Ligament of the Knee: What the Radiologist Needs to Know

The anterolateral ligament (ALL) was recently identified as a distinct component of the anterolateral capsule of the human knee joint with consistent origin and insertion sites. Biomechanical studies revealed that the current association between the pivot shift and an injured anterior cruciate ligament (ACL) should be loosened and that the rotational component of the pivot shift is significantly affected by the ALL. This may change the clinical approach toward ACL-injured patients presenting with anterolateral rotatory instability (ALRI), the most common instability pattern after ACL rupture. Radiologists should be aware of the importance of the ALL to ACL injuries. They should not overlook pathology of the anterolateral knee structures, including the ALL, when reviewing MR images of the ACL-deficient knee. In this article, the current knowledge regarding the anatomy, biomechanical function, and imaging appearance of the ALL of the knee is discussed with emphasis on the clinical implications of these findings.