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The effect of metallic radial head arthroplasty on radiocapitellar joint contact area.

OBJECTIVE: This study determined the effect of metallic radial head arthroplasty on radiocapitellar joint contact area. DESIGN: The contact area of eight intact radiocapitellar joints was assessed during simulated compressive loading. Subsequently, the same experiments were repeated after reconstruction with three different radial head implant sizes. BACKGROUND: There has been an increasing use of metal radial head implants relative to silicone implants. However, the contact characteristics with the metal reconstruction have not been determined. METHODS: A 100 N compressive load was applied to the radiocapitellar joint at three different flexion angles for the native joint and three different sizes of a metal head implant. An impression material was employed to quantify joint contact area. RESULTS: Following metallic radial head arthroplasty, the contact area decreased by approximately two-thirds relative to the native radiocapitellar joint (P<0.001). Smaller implant sizes resulted in slightly larger contact areas (P<0.05). In addition, contact area decreased as joint flexion angle increased (P<0.04). CONCLUSIONS: Selection of radial head implant size is likely not a significant factor with regard to contact area mechanics of the radiocapitellar articulation. RELEVANCE: The effect of radial head implant size on the contact area produced with the native capitellum is not known. This study shows that the design or selection of a metallic radial head implant from the viewpoint of size is likely not an important factor with regard to minimizing joint contact stresses.

Aged↗

Intrinsic stability of an unconstrained metacarpophalangeal joint implant.

OBJECTIVE: To compare the intrinsic stability of an unconstrained resurfacing metacarpophalangeal arthroplasty to that of a normal human cadaveric joint. DESIGN: Cadaveric joints and metacarpophalangeal prostheses were studied in a mechanical testing machine at different angles and axial loads to determine the stability ratio in eight directions of movement. BACKGROUND: An unconstrained resurfacing arthroplasty was designed to replicate the normal anatomy with the exception of the proximal component having a greater arc of curvature on its dorsal aspect. METHODS: Eight fresh-frozen cadaveric joints and five different sizes of the AVANTA metacarpophalangeal prosthesis were studied at 0 degrees, 45 degrees and 90 degrees angles of flexion and at eight different directions of motion with three different axial loads (0, 20, 40 N). A 6-component load cell measured the force needed to sublux the joint. The stability ratio was the measured outcome and is defined as ratio of the force of subluxation to the axial force. RESULTS AND CONCLUSIONS: The unconstrained resurfacing arthroplasty has more intrinsic stability than the cadaveric metacarpophalangeal joint in all eight directions tested. RELEVANCE: A major complication of metacarpophalangeal implants is ulnopalmar subluxation. The AVANTA implant is designed to decrease the risk of ulnopalmar subluxation by having a greater arc of curvature on the dorsal aspect of the proximal component. This study shows that the designed implant has greater stability due to the geometry of the implant compared to that of the anatomical joint.

Arthroplasty↗

Upper extremity injuries associated with strength training.

Most injuries sustained during strength training are mild strains that resolve with appropriate rest. More severe injuries include traumatic shoulder dislocations, tendon ruptures of the pectoralis major, biceps, and triceps; stress fractures of the distal clavicle, humerus, radius, and ulna; traumatic fractures of the distal radius and ulna in adolescent weightlifters; and compressive and stretch neuropathies. These more severe injuries are usually the result of improperly performing a strength training exercise. Educating athletes regarding proper strength-training techniques serves to reverse established injury patterns and to prevent these injuries in the first place. Recognizing the association of anabolic steroid use to several of the injury patterns further reinforces the need for medical specialists to counsel athletes against their use. With the increasing use of supplements such as creatine, the incidence and nature of strength-training injuries may change further. Greater emphasis on the competitive performance of younger athletes undoubtedly will generate enthusiasm for strength training at earlier ages in both sexes. The importance of proper supervision of these young athletes by knowledgeable persons will increase. As the popularity of strength training grows, there will be ample opportunity to continue to catalog the injury patterns associated with this activity.

Anabolic Agents↗

A comparison of joint stability between anterior cruciate intact and deficient knees: a new canine model of anterior cruciate ligament disruption.

Transection of the canine anterior cruciate ligament (ACL) is a well-established osteoarthritis (OA) model. This study evaluated a new method of canine ACL disruption as well as canine knee joint laxity and joint capsule (JC) contribution to joint stability at two time points (16 and 26 weeks) after ACL disruption (n=5/time interval). Ten crossbreed hounds were evaluated with force plate gait analysis and radiographs at intervals up to 34 weeks after monopolar radiofrequency energy (MRFE) treatment of one randomly selected ACL. Each contralateral ACL was sham treated. The MRFE treated ACLs ruptured approximately eight weeks (mean 52.5 days, SEM+/-1.0, range 48-56 days) after treatment. Gait analysis and radiographic changes were consistent with established canine ACL transection models of OA. Anterior-posterior (AP) translation and medial-lateral (ML) rotation were measured in each knee at 30 degrees, 60 degrees, and 90 degrees of flexion with and then without JC with loads of 40 N in AP translation and 4 Nm in ML rotation. A statistically significant interaction in AP translation included JC by cruciate (P=0.02), and there was a trend for a cruciate by time (P=0.07) interaction. Significant interactions in ML rotational testing included the presence of joint capsule (P=0.0001) and angle by cruciate (P=0.0012). This study describes a model in which canine ACLs predictably rupture approximately eight weeks after arthroscopic surgery and details the contribution of JC to canine knee stability in both ACL intact and deficient knees. The model presented here avoids the introduction of potential surgical variables at the time of ACL rupture and may contribute to studies of OA pathogenesis and inhibition. This model may also be useful for insight into the pathologic changes that occur in the knee as the ACL undergoes degeneration prior to rupture.

Animals↗

[Locking of the metacarpophalangeal joint of articular origin. Review of the literature and case report].

We report a case and review concerning literature of intrinsic locking of the metacarpophalangeal joint. These lockings are usually due commonly to degenerative arthritis of the joint, rarely to an abnormal shape of the head of metacarpal or intraarticular loose bodies. They should be differentiated from the extension lag of proximal interphalangeal joint usually encountered in "trigger finger" due to stenosing tenosynovitis. Conservative treatment must be careful and may fail or be complicated. Surgical treatment is effective, best done via an anatomical approach depending on the pathologic findings and the metacarpophalangeal joint locking etiology.

Adult↗

Removal and reinsertion of cemented femoral components during acetabular revision.

A retrospective review examined all patients who underwent removal and reinsertion of a cemented femoral component during isolated acetabular revision by one surgeon since 1981. All components were reinserted into the original, intact cement mantle. Forty-two hips with 2- to 10-year follow-up periods were reviewed. Average follow-up period since revision was 67 months. Average followup period since index procedure was 191 months. Average Harris hip score increased from 61 before surgery to 90 at follow-up examination. Two femurs are definitely loose by Harris criteria, but both are asymptomatic. One solidly fixed femoral component was revised because of joint instability. Two hips have postrevision cement fractures. One patient has mild thigh pain. In vitro testing of eight cadaver hips showed no increase in rotational micromotion following removal and reinsertion. It is concluded that this technique aids in isolated acetabular revision surgery by avoiding the complications of trochanteric osteotomy and femoral revision, improving acetabular exposure, and decreasing operative time with minimal risk of disrupting femoral component fixation.

Acetabulum↗

Prosthetic knee Candida parapsilosis infection.

We report a 77-year-old man who developed Candida parapsilosis infection following total knee arthroplasty. Knee joint effusion was noted 2 weeks after surgery, and repeated cultures of aspirated fluid established the diagnosis of Candida parapsilosis infection 4 weeks after surgery. Treatment consisted of debridement and lavage of the involved joint together with continuous irrigation with fluconazole for 4 weeks, followed by oral fluconazole for another 6 months. At 3 years follow-up, the patient was doing well and radiological examination of the affected knee showed a firm attachment of the prosthesis. We suggest that early identification of the causative organism followed by continuous irrigation and use of appropriate antifungal medication may prevent joint instability and spares the removal of the prosthesis.

Aged↗

Recognition and management of preoperative risk.

Internists are frequently asked to do preoperative consultations and to manage perioperative complications. Realistic goals are to identify patient factors that increase the risk of surgery, to quantify this risk in order to make decisions about the appropriateness of and timing of the surgery, to provide recommendations on how to minimize the risk, to identify and manage coexisting medical conditions and their associated medication requirements, to monitor the patient for perioperative problems, and to make recommendations to deal with these problems when they occur. With few exceptions, nonselective imaging and laboratory screening tests have repeatedly been shown to be of little value when the history and physical do not suggest a problem. The risk associated with the planned surgery can be estimated, with the most common serious complications being cardiac events. Updated versions of Goldman's risk indices are particularly helpful for this. Clinical variables are optimally combined with selective stress testing to discern which patients will benefit from preoperative revascularization. This has been studied best in the setting of vascular surgery. A critical guiding principle is that the value of revascularization must be judged in terms of long term gains rather than just immediate perioperative benefit. Other interventions include the selective use of beta blockers, adequate analgesia for all, control of hypertension, and appropriate volume management, especially in the settings of preexisting CHF or valvular disease. It must also be recognized that perioperative ischemia and CHF often present atypically. An approach that combines aspects of both the ACC/AHA and the ACP guidelines seems optimal. A variety of noncardiac issues must also be addressed. Postoperative pulmonary complications are common, especially with preexisting pulmonary disease, thoracic and upper abdominal surgery, and obesity. PFTs and ABGs are indicated in selected patients. Stopping smoking, incentive spirometry, and selective use of bronchodilators and antibiotics are helpful. Patients with rheumatologic diseases have specific concerns based on systemic manifestations of disease including anemia, thrombocytopenia, pulmonary fibrosis, pericarditis, and hypercoagulability; medication effects particularly from steroids and nonsteroidal anti-inflammatory drugs; and specific joint problems including contractures and atlantoaxial joint instability. Diabetes increases the risk of infection and cardiac complications. Prevention of ketoacidosis and glucose control are necessary and can be achieved through a variety of approaches, depending on whether the patient suffers from Type 1 or Type 2 diabetes. The threshold for transfusion has increased in recent years, as has the use of erythropoietin and autologous blood donation. There is no longer an absolute hemoglobin that requires transfusion, although most require transfusion for hemoglobins less than 8 mg/dL, especially in the setting of cardiac disease and bloody surgery. The elderly require surgery at an increased rate and often do not do as well as younger patients. The primary issues are, however, not their age but their increased frequency of underlying disease and diminished reserve. The latter makes them prone to postoperative delirium, sensitivity to medications, and cardiac and pulmonary problems. Despite the many diseases that patients often have and the stresses of surgery itself, modern anesthetic and surgical techniques allow almost all patients to undergo necessary procedures at acceptable risk. The internist plays a critical role in minimizing this risk even further.

Cardiovascular Diseases↗

[Screening of congenital dislocation of the hip in the newborn. A systematic and rigorous clinical examination. A restricted use of imaging].

(1) Clinical examination of the hips should be systematically performed in the newborn, in order to detect a possible congenital dislocation. This translates into hip joint instability, which can be evidenced by both Ortolani's and Barlow's signs, the latter being more sensitive. Special attention should be paid for abduction range, as limited abduction is a warning sign. (2) Use of imaging, especially sonography will be restricted to specific cases only. It's prescription, technical realization as well as interpretation have to be carefully done, so that it is actually relevant to uncertain or "at risk" situations. (3) Treatment if needed, should be ideally managed by a paediatric orthopaedic surgeon.

Diagnosis, Differential↗

[Partial wrist prosthesis: concept and preliminary results in 13 cases].

The author introduces a novel concept, namely the partial wrist prosthesis. This new technique combines a proximal row carpectomy with resurfacing of the lunate fossa of the radius and the head of the capitate. Results of the first 13 cases are reported with a mean follow-up of 32.7 months (13-72 m). This prosthesis can be used in degenative arthritis of the wrist instead of total fusion.

Arthroplasty, Replacement↗

[Conservative treatment of shoulder disorders].

The extreme complexity of the shoulder joint results from the coordinated activity of five different articulations and the supporting soft-tissue girdle. Any perturbation of this system has deleterious biomechanical consequences to the shoulder muscular girdle integrity and will eventually lead to pain and functional limitations. A functional diagnosis of the lesion will always be a prerequisite for a targeted conservative therapy. Treating pain is often the basis of the treatment, but it should rapidly be implemented with a broad range of physiotherapeutic techniques and manual therapy as well when appropriate. The guidelines for therapy include an active stabilisation program in case of joint instability and passive mobilisation whenever functional limitations are present. This paper deals with the different problem-oriented interdisciplinary therapeutic modalities used in frequent shoulder problems.

Acute Disease↗

Altered mechanics of cartilage with osteoarthritis: human osteoarthritis and an experimental model of joint degeneration.

OBJECTIVE: Studies of cartilage mechanics seek to determine the fundamental relationships between mechanical behavior and the composition and structure of healthy cartilage and to determine mechanisms for changes associated with degeneration. METHOD: The mechanics of normal and osteoarthritic (OA) human articular cartilage are reviewed. Studies of the initiation and pathogenesis of cartilage degeneration in the anterior cruciate ligament transection (ACLT) model of joint instability are also presented. RESULTS: In human cartilage with OA, tensile, compressive and shear behaviors are dramatically altered. These changes present as decreases in the modulus or stiffness of OA cartilage in tension, compression and shear loading, and increases in the propensity to swell as compared to healthy cartilage. In the ACL transection model of OA, similar changes in the mechanics of cartilage have been observed. In addition, changes in structure, composition, and as metabolism consistent with human OA have been found. Deterioration of the collagen-proteoglycan solid network, which appears to be focused at the articular surface, has been the earliest cartilage changes in the model. It remains to be determined if the initial disruption of the cartilage surface is a direct result of mechanical forces or a product of altered chondrocyte activity. CONCLUSIONS: These data and continued research using experimental models of OA provide a basis for our understanding of the pathogenesis and the time course of events in OA and will lead to the development of better procedures for disease intervention and treatment.

Animals↗

[Total shoulder arthroplasty vs. hemiarthroplasty].

Shoulder arthroplasty remains problematic despite the dramatic development of the new implant systems, due to the anatomical characteristics of the shoulder joint. The development of the modern third and fourth generation of shoulder prostheses enables the surgeon by its the three dimensional modularity to adjust the inclination and dorsomedial offset and to reconstruct the anatomic center of rotation. The fixation of the glenoid component is one of the most complicated aspects in the total shoulder arthroplasty. The main criteria regarding hemi- or total arthroplasty are based on morphological changes in the glenoid, the condition of the rotator cuff muscles, disorder etiology, age and activity level of the patient. The cup arthroplasty has proven itself as an alternative to standard humeral shaft arthroplasty. The main advantages of this new system are the elimination of the obligatory humeral head resection and the possibility of converting to the classical humeral shaft prosthesis method. First experiences with the cup system have been evaluated in the department of accident and reconstructive surgery of the UKBF in Berlin as part of a clinical trial. Between March 1998 and June 1999 15 shoulder prostheses in 14 patients were implanted in this hospital. The implants were inserted 8 times in a rheumatic shoulder, 4 times in posttraumatic arthrosis and in 3 humeral head necroses. 13 patients with 14 prostheses were available for follow up. An improvement from 23 to 55 average score points (Constant-Score) was attained by implantation of the cup system within a mean postoperative observation period of 6.1 months.

Arthritis, Rheumatoid↗

[Indication, biomechanics and early results of artificial disk replacement].

AIM: Judgment of factors concerning the indication for the implantation of an artificial disc endoprosthesis, the rating of this operation and biomechanical considerations. METHOD: Presentation of the indication and the value of a new operative concept in comparison to a so-called dynamic stabilization procedure (Dynesys' method). Indications for the operation are: unsuccessful, orthopedic conservative treatment for > 6 months, segmental pain, age < 45 years, evidence of an MRI demonstrable mono- or bisegmental disc degeneration with or without disc prolabation, exclusion of psychogenic disease and positive preoperative, diagnostic measures such as facet joint infiltration and discography. RESULTS: In an earlier investigation the efficacy of the Link method was demonstrated as shown by the reduction of the analgesic use, the angle of the lumbar lordosis (L1-S1) increased from 35.6 degrees to 42.6 degrees (20.2 %), the segmental angle from 19 degrees to 30 degrees (57.5 %). The new investigation using the Aesculap endoprosthesis resulted in a change of the angle of lumbar lordosis from 35.4 degrees to 45.4 degrees (25.4 %) and a change of the segmental angle from 17.3 degrees to 29.1 degrees (57.6 %). This method is a real endoprosthetic instrumentation in the field of spinal surgery. CONCLUSION: In younger patients with mono- or bisegmental disc degeneration there is an indication for the implantation of a disc endoprosthesis. A facet joint arthrosis and an age over 45 years are contraindications for the operation. The indication in patients with a classic failed back surgery syndrome is still unclear, the improvement of the instrumentation and a further adaptation of the systems to the known biomechanics of the lumbar spine are mandatory as is an intensive discussion of the operative procedure in the case of revision operations. The Dynesys method, with the inherent danger of segmental kyphozitation, a published, significant revision quota combined with a reduction of motility, does not fulfill this criterion.

Adult↗

[Sagittal alignment and segmental range of motion after total disc replacement of the lumbar spine].

AIM: To evaluate changes in static and dynamic values, X-rays of patients who underwent total disc replacement for degenerative disc disease were analyzed. METHOD: An analysis of pre- and postoperative lateral X-rays in 22 patients with 24 total disc replacements (Prodics, Spine Solutions) was performed. The total lumbar lordosis, the segmental lordosis angle, the disc height and the range of motion in the operated level were measured. RESULTS: Postoperatively a significant increase was observed for the following parameters: the anterior (pre: 9.0 +/- 3.4 mm; post: 16.7 +/- 2.4 mm; p < 0.001) and posterior (pre: 4.4 +/- 1.3 mm; post: 8.8 +/- 1.3 mm; p < 0.001) disc height and the segmental lordosis angle (pre: 20 degrees +/- 7.2 degrees; post: 27.7 degrees +/- 7.4 degrees; p < 0.001). Statistically no significant changes could be observed postoperatively for the total lumbar lordosis (pre: 56.2 degrees +/- 10.7 degrees; post: 58.6 degrees +/- 9.3 degrees; p = 0.196) and the range of motion (pre: 5.0 degrees +/- 4.0 degrees; post: 5.9 degrees +/- 3.5 degrees; p = 0.293). CONCLUSION: Total disc replacement for degenerative disc disease of the lumbar spine with the current concept does not alter the range of motion but significantly increases the disc height. The significant increase in segmental lordosis without a change in the total lumbar lordosis accounts for a change in lordosis in adjacent segments.

Adult↗