Prediction of femoral head collapse in osteonecrosis.

The femoral head deteriorates in osteonecrosis. As a consequence of that, the cortical shell of the femoral head can buckle into the cancellous bone supporting it. In order to examine the buckling scenario we performed numerical analysis of a realistic femoral head model. The analysis included a solution of the hip contact problem, which provided the contact pressure distribution, and subsequent buckling simulation based on the given contact pressure. The contact problem was solved iteratively by approximating the cartilage by a discrete set of unilateral linear springs. The buckling calculations were based on a finite element mesh with brick elements for the cancellous bone and shell elements for the cortical shell. Results of 144 simulations for a variety of geometrical, material, and loading parameters strengthen the buckling scenario. They, particularly, show that the normal cancellous bone serves as a strong supporting foundation for the cortical shell and prevents it from buckling. However, under the development of osteonecrosis the deteriorating cancellous bone is unable to prevent the cortical shell from buckling and the critical pressure decreases with the decreasing Young modulus of the cancellous bone. The local buckling of the cortical shell seems to be the driving force of the progressive fracturing of the femoral head leading to its entire collapse. The buckling analysis provides an additional criterion of the femoral head collapse, the critical contact pressure. The buckling scenario also suggests a new argument in speculating on the femoral head reinforcement. If the entire collapse of the femoral head starts with the buckling of the cortical shell then it is reasonable to place the reinforcement as close to the cortical shell as possible.

Three-dimensional dynamic hip contact area and pressure distribution during activities of daily living.

Estimation of the hip joint contact area and pressure distribution during activities of daily living is important in predicting joint degeneration mechanism, prosthetic implant wear, providing biomechanical rationales for preoperative planning and postoperative rehabilitation. These biomechanical data were estimated utilizing a generic hip model, the Discrete Element Analysis technique, and the in vivo hip joint contact force data. The three-dimensional joint potential contact area was obtained from the anteroposterior radiograph of a subject and the actual joint contact area and pressure distribution in eight activities of daily living were calculated. During fast, normal, and slow walking, the peak pressure of moderate magnitude was located at the lateral roof of the acetabulum during mid-stance. In standing up and sitting down, and during knee bending, the peak pressures were located at the edge of the posterior horn and the magnitude of the peak pressure during sitting down was 2.8 times that of normal walking. The peak pressure was found at the lateral roof in climbing up stairs which was higher than that in going down stairs. These results can be used to rationalize rehabilitation protocols, functional restrictions after complex acetabular reconstructions, and prosthetic component wear and fatigue test set up. The same model and analysis can provide further insight to soft tissue loading and pathology such as labral injury. When the pressure distribution on the acetabulum is inverted onto the femoral head, prediction of subchondral bone collapse associated with avascular necrosis can be achieved with improved accuracy.

Prevention of thromboembolic disease after non-cemented hip arthroplasty. A multimodal approach.

Thromboembolism following total hip arthroplasty is a common complication that may result in significant morbidity and mortality. Despite this, optimal prophylactic regimen is controversial. We investigated the efficacy of a comprehensive approach encompassing the use of aspirin, intermittent compression devices ('foot pumps'), and early mobilization in a cohort of 200 consecutive patients after non-cemented total hip replacements. The surgical procedures were carried out under epidural anesthesia in most cases (91%). All patients were allowed full weight bearing and received ambulation training starting on the first post-operative day. Ankle-high pneumatic boots ('foot pumps') and aspirin (325 mg p.o./qd) were used immediately after surgery. The presence of deep vein thrombosis was determined with the routine use of venous duplex scans on post-operative day number 5 to 10 (mean 6.8). The duration of the follow-up was 3 months. No patients were lost to follow-up. Four distal DVT's (2%) were detected in three patients. None of the patients developed symptomatic pulmonary embolism during the follow-up period. There were no major wound complications. Venous thromboembolic disease after hip replacement surgery is largely associated with postoperative immobilization and venous stasis. It is the authors' opinion that a prevention strategy should include mechanical as well as pharmacological measures. The concomitant use of epidural anesthesia, "foot pumps", aspirin and early full weight bearing ambulation may be effective in further reducing the incidence of DVT after surgery.

Chondropathia patellae.

The articular surface of the patella and the contiguous articular surfaces of the femoral condyles are sometimes affected by disintegrational changes of the articular cartilage, which remain localized there for a longer period of time. In consideration of the pronounced functional impairment arising at marked changes of these articular surfaces, resection of the patellar surface, metallic resurfacing of the patella, periosteal resurfacing of the patella, or patellectomy have been described as treatment by various authors. Most of these modalities were followed by shortcomings of the results, as indicated in pertinent follow-up examinations and reports. Thus, a more physiological modality of treatment, organic resurfacing of the patella with synovial tissue, was applied in 7 patients and led to satisfactory results as ascertained by long-term follow-up examinations.

Contracture of the shoulder joint.

The movements of the shoulder joint may sometimes be markedley limited due to posttraumatic or inflammatory changes in the shoulder joint or in adjacent organs, a condition designated as contracture of the shoulder joint or frozen shoulder. The routine treatment consists of positioning the arm as often as possible in abduction, and of diligent active and passive mobilization exercises. In those patients who started the treatment after a long delay so that the articular as well as the periarticular tissues were very shrunken, manipulation of the shoulder joint was carried out under general anesthesia this led to the return of full motion of the joint in the great majority of these patients. However, in those patients who did not benefit by manipulation, surgical revision of the joint and of periarticular structures was carried out for excision of all scarified tissues. The result was restoration of the mobility of the joint to an adequate although not total range.

Reexamination of hip biomechanics during unilateral stance.

The Koch model, as initially proposed, is an incomplete representation of hip biomechanics during the unilateral support phase of midstance. The model proposed by this study includes the iliotibial band as a tension band lateral to the femoral shaft. During the unilateral support phase of gait, the iliotibial band creates compression loading laterally and medially throughout the femur distal to the greater trochanteric apophysis. Bench testing of cadaveric femora with and without protheses demonstrated the necessity of a total hip replacement femoral component to engage the proximal lateral femoral cortex as an additional area of support against subsidence. This model, byproviding a more complete and accurate depiction of hip biomechanics, creates a more valid basis for analysis of hip function.

A missing link in the evolution of THR: "discovery" of the lateral femur.

Using cadaveric studies and mathematical models that include consideration of the iliotibial band (ITB) as a "tension band," the authors have demonstrated that compression loading occurs throughout the entire lateral femoral cortex from the apophyseal line of the greater trochanter to the lateral femoral epicondyle at the knee. This model suggests that the magnitude of this load on the medial and lateral cortices is proportional to the medial displacement of these cortices from the ITB. The authors have further demonstrated that the "tension band" model is more consistent with actual bone morphology and function than existing models and is a strong argument for the incorporation of design concepts such as lateral extensions into total hip arthroplasty femoral components. Such extensions would permit use of lateral femoral cortical bone as an additional base of prosthesis support, distributing loads over a greater area of the proximal femur. This model, therefore, would theoretically reduce the areas of stress concentration in diaphyseal bone and stress shielding of the proximal femur, both of which appear to be deficiencies of present femoral stem designs.

The anterior cruciate ligament-deficient knee: a diagnostic and therapeutic algorithm.

The anterior cruciate ligament (ACL) of the knee is a common site of sports-related injury. The natural history of chronic instability, reinjury, and further intra-articular damage is well documented. Appropriate management of ACL insufficiency must be based upon a knowledge of the available diagnostic and therapeutic options, their indications, and their effectiveness. At the same time, the treatment plan must be tailored to the demands and expectations of the individual patient.

Functional outcome of hip fusion in the young patient. Follow-up study of 10 patients.

In the young patient, an osteoarthritic or osteonecrotic hip presents a challenging therapeutic problem. Until the long-term results of noncemented total hip arthroplasty are known, hip fusion provides an option to cemented total hip arthroplasty in the young patient with hip disease. The authors describe the outcome of hip fusion in 10 patients with an average follow-up period of 8.5 years. Seventy percent of the patients had a good or very good result with pain relief, and 90% or more had a good or excellent functional result with support aids, ambulation, and climbing stairs. All 10 patients were subjectively satisfied with their hip fusion. A lower incidence of pain in the contralateral hip, ipsilateral knee, and lower back was noted at 8.5 years than that reported at long-term follow-up evaluation and was associated with a satisfactory anatomic position of hip arthrodesis.

Malignant fibrous histiocytoma of the distal fibula: a case report.

A 25-year-old female with primary malignant fibrous histiocytoma of the distal fibula is presented. Malignant fibrous histiocytoma of bone is a rare primary bone tumor in this anatomic location. Careful preoperative staging studies and neoadjunct chemotherapy permitted an unusual resection to be performed resulting in successful limb salvage for the patient.

Team physician #6. Surgical treatment of Achilles tendon rupture.

The ideal treatment of Achilles tendon ruptures has always been controversial. Nonoperative treatment has been criticized for its high rerupture rate and surgical treatment has been criticized for its high complication rate. This paper describes a surgical method of repair that can be used for acute or late ruptures, and has been associated with a low complication and rerupture rate.

Low-intensity pulsed galvanic current and the healing of tenotomized rat achilles tendons: preliminary report using load-to-breaking measurements.

The possible beneficial effects of low-intensity, pulsed galvanic currents on the healing of tenotomized Achilles tendons was investigated in three groups (20 animals each) of male Sprague-Dawley rats. Treatments via implanted electrodes were given once daily for 15 minutes over a two-week period. Although a portable high-voltage galvanic stimulator was used, stimulus intensity was only 75 microA at a frequency of 10/sec. Tendons were tested after two weeks for the load required to rebreak them at the original tenotomy site. The group treated with anodal current withstood significantly greater loads (p less than 0.001) than did either the group which healed normally (ie, without stimulation) or the group treated with cathodal current.

Heterotopic ossification. Incidence and relation to trochanteric osteotomy in 100 total hip arthroplasties.

Heterotopic ossification can impair the functional results of total hip arthroplasty. The causative role of trochanteric osteotomy in heterotopic ossification is uncertain. Postoperative radiographs of 100 total hip arthroplasties were analyzed for incidence of heterotopic ossification. Forty procedures were performed with trochanteric osteotomy and 60 without. There was a 17% overall incidence of clinically significant heterotopic ossification, 22% with osteotomy and 13% without. High- and low-risk categories revealed clinically significant heterotopic ossification in 25% of the high-risk group and in 8% of the low-risk group. In the high-risk group there was a 32% incidence with trochanteric osteotomy and 22% without osteotomy. In the low-risk group there was a 16% incidence without trochanteric osteotomy and a 3% incidence with trochanteric osteotomy. The increase in clinically significant heterotopic ossification in the high-risk group over that of the low-risk group was statistically significant. The present study showed that trochanteric osteotomy tended to increase the incidence and severity of clinically significant heterotopic ossification. These data suggest that trochanteric osteotomy should be avoided, if possible, during total hip arthroplasty to decrease the risk of heterotopic ossification.

Pathology, clinic, and treatment of osgood-schlatter disease.

Osgood-Schlatter disease is a disorder of enchondral ossification, and should be differentiated from heterotopic ossification in the patellar ligament. The symptoms and functional impairment arising in the former condition require treatment. Whereas many orthopedic surgeons feel that Osgood-Schlatter disease can be treated by conservative methods, others point out that surgical treatment is needed in some cases, and therefore have recommended rather extensive operative procedures. A survey of 142 patients, all initially treated by various conservative modalities, was carried out. Whereas 116 patients became thus symptom-free and regained normal function, 26 patients retained essential impairment in the use of the leg and needed surgical treatment. This operation consisted of excision of a portion of the surface of the tibial tuberosity, and multiple perforation by a thin drill point. Complete ossification of the tibial tuberosity and fusion with the tibial metaphysis was the outcome, followed by return of normal function of the leg. On the other hand, nine of the 116 conservatively treated patients returned several years later complaining of a protruding knob below the knee cap, persistent swelling in this area, and frequent soreness on kneeling or forceful use of the knee joint.

The natural history and diagnosis of anterior cruciate ligament insufficiency.

In 233 knees with anterior cruciate ligament insufficiency the characteristic diagnostic signs and symptoms were: a specific mechanism of injury; an audible "pop" at the time of injury; a positive anterior drawer sign' "giving away"; functional disability; periarticular degenerative changes. Unresolved anterior cruciate ligament insufficiency follows a predictable natural history typified by a course of progressive knee dysfunction and deterioration. The progress of deterioration can be significantly modified or arrested by repair or reconstruction of the injured ligament.

Injury to the anterior cruciate ligament producing the pivot-shift sign.

The clinical entity termed the pivot shift was studied in cadaver specimens and its significance was evaluated. It was found to be highly correlated with a tear of the anterior cruciate ligament, and it corresponded to a sudden anterior-internal rotation subluxation-dislocation of the tibia and posterior horn of the lateral meniscus beneath the lateral femoral condyle.