Reed L. Bartz

The Effect of Femoral Component Head Size on Posterior Dislocation of the Artificial Hip Joint

Background: Posterior dislocation continues to be a relatively common complication following total hip arthroplasty. In addition to technical and patient-associated factors, prosthetic features have also been shown to influence stability of the artificial hip joint. In this study, a dynamic model of the artificial hip joint was used to examine the influence of the size of the head of the femoral component on the range of motion prior to impingement and posterior dislocation following total hip replacement. Methods: Six fresh cadaveric specimens were dissected, and an uncemented total hip prosthesis was implanted in each. Each specimen was mounted in a mechanical testing machine and loaded with use of a system of seven cables attached to the femur and pelvis that simulated the action of the major muscle groups crossing the hip joint. The hip was taken through a range of motion similar to that experienced when rising from a seated position. The three-dimensional position of the femur at the points of impingement and dislocation was recorded electronically. The range of joint motion was tested with prosthetic femoral heads of four different diameters (twenty-two, twenty-six, twenty-eight, and thirty-two millimeters). Results: Significant associations were noted between the femoral head size and the degree of flexion at dislocation in ten (p = 0.001), twenty (p < 0.001), and thirty (p = 0.003) degrees of adduction. Increasing the femoral head size from twenty-two to twenty-eight millimeters increased the range of flexion by an average of 5.6 degrees prior to impingement and by an average of 7.6 degrees prior to posterior dislocation; however, increasing the head size from twenty-eight to thirty-two millimeters did not lead to more significant improvement in the range of joint motion. The site of impingement prior to dislocation varied with the size of the femoral head. With a twenty-two-millimeter head, impingement occurred between the neck of the femoral prosthesis and the acetabular liner, whereas with a thirty-two-millimeter head, impingement most frequently occurred between the osseous femur and the pelvis. Conclusions: With the particular prosthesis that was tested, increasing the diameter of the femoral head component increased the range of motion prior to impingement and dislocation, decreased the prevalence of prosthetic impingement, and increased the prevalence of osseous impingement. Clinical Relevance: These results suggest that femoral heads with a twenty-eight-millimeter diameter increase the range of motion after total hip replacement. This may be beneficial when additional factors compromising joint stability are encountered.

Topographic Matching of Selected Donor and Recipient Sites for Osteochondral Autografting of the Articular Surface of the Femoral Condyles

The purpose of this study was to define the topography of the articular surface of the femoral condyles and to develop a method for computerized topographic matching of donor and recipient sites for osteochondral transplantation. The condyles of seven fresh cadaveric femurs were mounted on the rotating stage of a laser-based coordinate measuring machine. An anatomic coordinate system defining the articular surface of the condyles was created. Customized software was developed to allow selection and topographic matching of osteochondral graft donor and recipient sites from any location on the surface of the condyles. For cartilage defects within the weightbearing portions of the medial or lateral femoral condyles, grafts taken from sites from the most medial or lateral portions of the patellar groove provided a significantly better topographic match than did grafts taken from the central intercondylar notch.

The diagnosis of meniscus tears: the role of MRI and clinical examination.

Magnetic resonance imaging (MRI) and clinical examination are tools commonly used in the diagnosis of meniscus tears. It has been suggested routine MRI before therapeutic arthroscopy for clinically diagnosed meniscus tears will reduce the number and cost of unnecessary invasive procedures. We designed a systematic review of prospective cohort studies comparing MRI and clinical examination to arthroscopy to diagnosis meniscus tears. Thirty-two relevant studies were identified by a literature review. Careful evaluation by an experienced examiner identifies patients with surgically treatable meniscus lesions with equal or better reliability than MRI. MRI is superior when indications for arthroscopy are solely diagnostic. However, the methods by which such a clinician arrives at a conclusion have not been identified. To create an evidence-based algorithm for the diagnosis of a meniscus tear future investigations should prospectively assess the value of commonly used aspects of the patient history and meniscus tests. MRI is useful, but should be reserved for situations in which an experienced clinician requires further information before arriving at a diagnosis. Indications for arthroscopy should be therapeutic, not diagnostic in nature.Level of Evidence: Level II, systematic review. See Guidelines for Authors for a complete description of levels of evidence.

Arthroscopic treatment of osteoarthritis of the knee: are there any evidence-based indications?

Despite the lack of consensus guidelines and randomized control trials, the use of arthroscopy for the treatment of osteoarthritis of the knee has increased over the last decade. Techniques used for the arthroscopic treatment of osteoar-thritis of the knee include joint lavage, joint débridement, meniscectomy, abrasion arthroplasty, and microfracture. We performed a retrospective, evidence-based review of the current literature on the arthroscopic treatment of osteoar-thritis of the knee and provide insight into the study design flaws and difficulties associated with the current research on this controversial topic. Our literature search yielded 18 relevant studies. Of these, one was Level I evidence, five were Level II, six were Level III, and six were Level IV. We found limited evidence-based research to support the use of arthroscopy as a treatment method for osteoarthritis of the knee. Arthroscopic débridement of meniscus tears and knees with low-grade osteoarthritis may have some utility, but it should not be used as a routine treatment for all patients with knee osteoarthritis.Level of Evidence: Level IV, systematic review. See Guidelines for Authors for a complete description of levels of evidence.

A method for open reduction and internal fixation of the unstable posterior sternoclavicular joint dislocation.

Posterior sternoclavicular joint (SCJ) dislocations are most often stable after reduction but may be associated with significant complications related to the location of the medial head of the clavicle within the mediastinum. In rare instances, a posterior SCJ dislocation is irreducible or redislocates after a closed reduction. Because of the potential hazards related to compression of vital structures within the superior mediastinum, open reduction and internal fixation is usually required. Although open reduction is widely accepted as the method of choice, the best method for achieving stable fixation remains unanswered. We present the case of an unstable SCJ stabilized, in anatomic position, with two large-bore cannulated screws in conjunction with open reduction. We believe that the risk of hardware migration reported with the use of pins and wires and its catastrophic complications are greatly minimized using our technique.

Experimental and computational simulation of total hip arthroplasty dislocation

Other than fatal pulmonary embolism and deep infection, dislocation following total hip replacement remains probably the most vexing complication to patient and surgeon. Subluxation and dislocation are complex, poorly understood phenomena. Many important questions in this area unfortunately do not lend themselves well to clinical or registry study. Appropriate realistic laboratory models have been lacking. This article synthesizes new work undertaken independently by two groups of biomechanical investigators using very different, but complimentary, methodologies to study the mechanisms of dislocation, and especially the influence of specific design and surgical variables.

A Biomechanical Comparison of Initial Fixation Strength of 3 Different Methods of Anterior Cruciate Ligament Soft Tissue Graft Tibial Fixation: Resistance to Monotonic and Cyclic Loading

Background Tibial fixation of soft tissue grafts continues to be problematic in the early postoperative period after anterior cruciate ligament reconstruction. Hypothesis No differences exist for resistance to slippage of soft tissue grafts fixed with CentraLoc, Intrafix, or 35-mm bioabsorbable interference screws. Study Design Controlled laboratory study. Methods Bovine tibia and hoof extensor tendons were divided into 3 matched groups with 12 tibia and 12 extensor tendons in each group. Within each group, 6 specimens underwent monotonic loading to failure (1 mm/s), and 6 underwent cyclic loading (10 000 cycles, 125-325 N, 1 Hz). Results No statistically significant differences were noted in mean load to failure or stiffness. The mean load to failure (and stiffness) for the 3 types of fixation were as follows: bioabsorbable interference screw, 631.6 ± 130.1 N (88.17 ± 6.79 N/mm); Intrafix, 644.3 ± 195.2 N (81.65 ± 16.5 N/mm); and CentraLoc, 791.1 ± 72.7 N (77.89 ± 7.07 N/mm). The slippage rates under cyclic loading for the 3 types of fixation were bioabsorbable interference screw, 0.336 ± 0.074 µm/cycle; Intrafix, 27.2 ± 31.6 µm/cycle; and CentraLoc, 0.0355 ± 0.0046 µm/cycle. In this model, CentraLoc proved statistically superior in resistance to cyclic loading compared with the bioabsorbable interference screw (P < .05) and Intrafix (P < .0001). The bioabsorbable interference screw proved statistically superior to Intrafix in resistance to cyclic loading (P < .05). Conclusions In this bovine model, CentraLoc and bioabsorbable interference screws provided superior resistance to cyclic loading compared with Intrafix. Clinical Relevance CentraLoc and bioabsorbable interference screws showed superior resistance to cyclic loading, which may indicate an increased resistance to clinical failure.

Tarsal navicular fractures in major league baseball players at bat.

Tarsal navicular fractures in athletes, although rare, can present both a diagnostic and therapeutic dilemma. Failure to recognize this injury and initiate treatment early can have devastating consequences. The physician must have a high index of suspicion for the injury in any patient with midfoot pain after a direct blow. Two case reports of tarsal navicular fractures sustained by baseball players at bat in which the diagnosis was not made early are presented.

Basic Biology and Response to Injury

This review of the basic biology of the meniscus and its biologic response to injury demonstrates that the menisci are an integral part of the complex biomechanics of the knee. Without the menisci, knee joint function is severely compromised. Lack of the menisci may lead to progressive degeneration of the chondral surfaces of the knees. Because the meniscus does not regenerate spontaneously and because injuries heal slowly or not at all, efforts must continue to find better methods and techniques to manage meniscus pathology. Improved therapy will help minimize the late instability of the joint, decrease pain associated with loss of the meniscus, minimize or prevent degenerative joint changes, and obviate the need for multiple surgical procedures. Specific targets should include improved methods of meniscectomy, new and better techniques of repair for meniscus tears, methods to enhance the cellular response for healing of meniscus tissue, and finally, new ways to regenerate or regrow lost or damaged meniscus tissue.

The Technique of Microfracture of Full-Thickness Chondral Lesions and Postoperative Rehabilitation

Various marrow stimulation techniques have been described for the treatment of full-thickness chondral injuries of the knee. This article describes the technique of microfracture for treatment of this condition. Indications and contraindications for the technique as well as the preoperative workup are also described. Strict adherence to the postoperative physical rehabilitation regimen described in this article is crucial for clinical success after the procedure.