Lynne C. Jones

Nontraumatic osteonecrosis of the femoral head: ten years later.

The etiology of osteonecrosis of the hip may have a genetic basis. The interaction between certain risk factors and a genetic predisposition may determine whether this disease will develop in a particular individual. The rationale for use of joint-sparing procedures in the treatment of this disease is based on radiographic measurements and findings with other imaging modalities. Early diagnosis and intervention prior to collapse of the femoral head is key to a successful outcome of joint-preserving procedures. The results of joint-preserving procedures are less satisfactory than the results of total hip arthroplasty for femoral heads that have already collapsed. New pharmacological measures as well as the use of growth and differentiation factors for the prevention and treatment of this disease may eventually alter our treatment approach, but it is necessary to await results of clinical research with long-term follow-up of these patients.

Osteonecrosis : etiology, diagnosis, and treatment

Purpose of reviewThis review provides an update of the recent progress in etiology, pathogenesis, diagnosis, and treatment of osteonecrosis. Recent findingsConcerning pathogenesis, there is evidence that there is a genetic predilection for those who are exposed to the two leading etiologic associations for osteonecrosis: corticosteroids and alcohol. Studies concerning the treatment of osteonecrosis indicate that most preservative (ie, joint-sparing) procedures available today have better results in the precollapse stages of the disease and in smaller lesions. Therefore, researchers continue to develop and modify diagnostic techniques, particularly relating to MRI, for the identification and quantification of osteonecrotic lesions. Advances concerning bone grafting and arthroplasty procedures have resulted in improved clinical outcomes for this patient population. The future treatment of osteonecrosis may involve genetic or cell-based therapies. SummaryAlthough progress has been made, considerably more research is needed before we fully understand this disease. Hopefully, such research will lead to effective measures for saving the femoral head or, better yet, preventing osteonecrosis.

the Outcome of Total Knee Arthroplasty in Obese Patients

BACKGROUND Evidence linking increased body weight to osteoarthritis of the knee and the high prevalence of obesity underscore the importance of defining the outcome of total knee arthroplasty in obese patients. The purpose of this study was to compare the clinical and radiographic results of total knee arthroplasties performed in obese patients with those of total knee arthroplasties performed in nonobese patients. METHODS Clinical and radiographic data on seventy-eight total knee arthroplasties in sixty-eight obese patients were compared with data on a matched group of nonobese patients. The analysis was also performed after stratification of the obese group for the degree of obesity. All patients had the same prosthesis. The clinical data that were analyzed included the Knee Society objective and functional scores, patellofemoral symptoms, activity level, and complications. RESULTS The percentage of knees with a Knee Society score of > or =80 points at an average of eighty months was 88% in the obese group, which was significantly lower than the 99% rate in the nonobese group at the same time. The morbidly obese subgroup had a significantly higher revision rate than did the nonobese group (p = 0.02). CONCLUSIONS The results of the present study suggest that any degree of obesity, defined as a body mass index of > or =30, has a negative effect on the outcome of total knee replacement.

Variation of rotation moment arms with hip flexion.

Excessive flexion and internal rotation of the hip is a common gait abnormality among individuals with cerebral palsy. The purpose of this study was to examine the influence of hip flexion on the rotational moment arms of the hip muscles. We hypothesized that flexion of the hip would increase internal rotation moment arms and decrease external rotation moment arms of the primary hip rotators. To test this hypothesis we measured rotational moment arms of the gluteus maximus (six compartments), gluteus medius (four compartments), gluteus minimus (three compartments) iliopsoas, piriformis, quadratus femoris, obturator internus, and obturator externus. Moment arms were measured at hip flexion angles of 0, 20, 45, 60, and 90 degrees in four cadavers. A three-dimensional computer model of the hip muscles was developed and compared to the experimental measurements. The experimental results and the computer model showed that the internal rotation moment arms of some muscles increase with flexion; the external rotation moment arms of other muscles decrease, and some muscles switch from external rotation to internal rotation as the hip is flexed. This trend toward internal rotation with hip flexion was apparent in 15 of the 18 muscle compartments we examined, suggesting that excessive hip flexion may exacerbate internal rotation of the hip. The gluteus maximus was found to have a large capacity for external rotation. Enhancing the activation of the gluteus maximus, a muscle that is frequently underactive in persons with cerebral palsy, may help correct excessive flexion and internal rotation of the hip.

Atraumatic osteonecrosis of the knee

Background: The purposes of this study were to define the clinical, demographic, and radiographic patterns of atraumatic osteonecrosis of the distal part of the femur and the proximal part of the tibia at presentation and to report the outcome of treatment of this condition. Methods: Two hundred and forty-eight knees in 136 patients who were younger than the age of fifty-five years were treated at our institution between July 1, 1974, and September 15, 1998, for atraumatic osteonecrosis of the distal part of the femur or the proximal part of the tibia, or both. Demographic and radiographic features were characterized. The results of nonoperative treatment, core decompression, arthroscopic débridement, and total knee arthroplasty were evaluated. Results: There were 106 female patients and thirty male patients, and their mean age was thirty-six years (range, fifteen to fifty-four years) at the time of diagnosis. One hundred and one patients (74 percent) had involvement of other large joints, with eighteen (13 percent) presenting initially with knee symptoms. One hundred and one patients (74 percent) had a disease that affected the immune system; sixty-seven of them had systemic lupus erythematosus. One hundred and twenty-three patients (90 percent) had a history of corticosteroid use. Technetium-99m bone-scanning missed lesions in sixteen (29 percent) of fifty-six knees. Eight (20 percent) of forty-one initially symptomatic knees treated nonoperatively had a successful clinical outcome (a Knee Society score of at least 80 points and no additional surgery) at a mean of eight years. The knees that remained severely symptomatic for three months were treated with either core decompression (ninety-one knees) or total knee arthroplasty (seven knees). Seventy-two (79 percent) of the ninety-one knees treated with core decompression had a good or excellent clinical outcome at a mean of seven years. Efforts to avoid total knee arthroplasty with repeat core decompression or arthroscopic débridement led to a successful outcome in fifteen (60 percent) of twenty-five knees. Thirty-four (71 percent) of forty-eight knees treated with total knee arthroplasty had a successful clinical outcome at a mean of nine years. Conclusions: Atraumatic osteonecrosis of the knee predominantly affects women, and in our study it was associated with corticosteroid use in 90 percent of the patients. Evaluation should include standard radiographic and magnetic resonance imaging of all symptomatic joints. Prognosis was negatively related to large juxta-articular lesions. Nonoperative treatment should be reserved for asymptomatic knees only. Core decompression was successful (a Knee Society score of at least 80 points and no additional surgery) in 79 percent of the knees in which the disease was in an early stage. Total knee arthroplasty was successful in only 71 percent of the knees.

Osteonecrosis of the femoral head. Potential treatment with growth and differentiation factors.

Basic and clinical research have shown the efficacy of various cellular mediators (bone morphogenetic proteins, interleukins, angiogenic growth factors) in healing bone defects. The potential application of these growth and differentiation factors to other musculoskeletal conditions, including osteonecrosis of the femoral head, only recently has been explored. Osteonecrosis is a disease of unknown pathogenesis that usually progresses to hip joint destruction necessitating total hip arthroplasty. The pathology involves ischemic events followed by death of bone and marrow elements. A process of repair then is initiated, but unless the lesion is small (less than 15% of the femoral head involved), this repair process is usually ineffective. The net result is weakening of subchondral bone with subsequent collapse of the articular surface. Because the results of hip arthroplasty in patients with osteonecrosis are relatively poor, much focus has been on modalities aimed at femoral head preservation. The surgical alternatives may include core decompression, osteotomy, nonvascularized, and vascularized bone grafting, which might be enhanced with the use of growth and differentiation factors. At least three of these factors are potential candidates as therapeutic modalities: cytokines (such as interleukins, tumor necrosis factors, and signaling molecules such as fibroblast growth factors, platelet derived growth factors, insulinlike growth factors, and transforming growth factor betas), bone morphogenetic proteins, and angiogenic factors. Despite considerable effort, evaluation of these growth and differentiation factors has been hampered by the lack of an animal model that adequately simulates the pathology of osteonecrosis in humans. Therefore, investigators have attempted to model certain aspects of the disease process. Recently, several investigators have attempted to mimic osteonecrosis in the femoral head of large mammals by combinations of devascularization, freezing, osteotomy of the femoral neck, or creation of a head defect. Results from some of these studies have confirmed the potential for growth and differentiation factors to effect more rapid healing and filling of defects with biomechanically competent and viable bone. The application of this therapy shows promise, and clinical studies on efficacy and safety are ongoing.

Experimental determination of forces transmitted through the patello-femoral joint.

Tensions in the quadriceps tendon and infrapatellar ligament were measured as a function of flexion angle in eight cadaver knees using a load cell of a materials tester to determine the quadriceps force and a spring balance to quantify the patellar tendon force. The ratio between the tensions in the quadriceps tendon and the patellar tendon (FQ/FP) ranged from 1.55 at 70 degrees of flexion to 0.86 at 10 degrees of flexion. The patello-femoral joint reaction (PFJR) force for extension against resistance was maximal at 60 degrees. No change in the quadriceps force required to extend the knee occurred with changes of the Q-angle of +/- 5 degrees. This study demonstrates that FQ does not equal FP as several authors have reported (Bandi, 1972; Barry, 1979; Ficat and Hungerford, 1977; Hungerford and Barry, 1979; Reilly and Martens, 1972; Smidt, 1973). Furthermore, the difference in FQ and FP influences both the magnitude and direction of PFJR. Studies that assess the influence of surgical procedures which alter the patello-femoral joint or the extensor mechanism must take these differences into account.

Ligament-tendon fixation: analysis of a new stitch and comparison with standard techniques

A newly devised locking loop tendon-ligament suture was evaluated for its clinical application. The suture is relatively simple to use and is particularly suited to flat structures such as the medial collateral ligament, joint capsule, and patellar tendon. It affects tension and resistance to pull out without exerting major purse stringing or bunching. In a laboratory setting, this suture technique has been compared to fixation by individual sutures and several varieties of staple fixation. Simple suture fixation was quite weak, measuring 100 newtons (N). Staple fixation is not only weaker than the ligament suture, but is more highly dependent on bone quality and is generally more variable. When employed with strong suture material, a doubled ligament suture was found to be nearly twice as strong (392 N) as staple fixation into bone (208 N) and demonstrated a mean pullout strength close to the forces observed on human anterior cruciate ligaments. In combination with a well placed ligament staple into good quality bone, fixation was further enhanced (482 N) and statistically significantly improved (P greater than .05).

The Rationale of Cementless Revision of Cemented Arthroplasty Failures

Patients with failed cemented total hip replacements develop minor to massive bone loss. In nearly all cases, the quality of the endosteal surface has been converted to a sclerotic tube. Because of the bone loss and the change in character of the remaining bone stock with which to form an interface with polymethylmethacrylate (PMMA), the microinterlock necessary for long-term interface stability cannot be achieved. Moreover, the first failure leads to the production of cement particles that incite a histiocytic osteolytic response. The difficulty in achieving interfacial stability in the revision setting is borne out in the published clinical results of cemented revision total hip arthroplasties showing failure rates ranging from 17% to 60.3%. Porous-surfaced prostheses have been introduced to permit biologic fixation as an alternative to cement fixation of each implant component. The good midterm clinical results and the lack of catastrophic bone loss when failure does occur have given impetus to the application of this technology to the revision situation. The preliminary clinical experience with cementless revision arthroplasty has yielded favorable results. The authors have fully developed the rationale against the use of PMMA in revision total hip replacements and for the cementless approach with porous-surfaced metal prostheses and bone grafts. The latter appear as a viable approach to a growing clinical problem.

Systematic Analysis Of Classification Systems For Osteonecrosis Of The Femoral Head

BACKGROUND Multiple classification systems for osteonecrosis of the hip have been developed to assist physicians in the diagnosis and treatment of this potentially debilitating disorder. The purpose of this analysis was to delineate the classification systems utilized in reports published since 1985 and, through a comparison of the most commonly used systems, to identify consistent factors that would allow for cross-publication comparisons to be made. METHODS We performed a PubMed search for reports of outcome studies concerning treatment methods for osteonecrosis of the hip. All studies of reported outcomes with greater than ten patients were included in the analysis. Various classification systems were tabulated to determine usage frequencies. The four most commonly used systems were then analyzed to determine common factors used for classification. RESULTS One hundred and fifty-seven studies were available for analysis. Sixteen major classification systems that made use of more than one radiographic factor were identified, and nine of these systems had one to five modifications reported throughout the literature. Additionally, eleven other systems made use of single factors obtained from either magnetic resonance imaging or anatomic data. The review revealed that four classification systems accounted for greater than 85.4% of the reported studies. Parameters for these four systems were stratified to allow for uniformity of patient or study evaluation. CONCLUSIONS This analysis of the reported classification systems for osteonecrosis of the femoral head revealed several similarities between the most commonly used systems. An analysis of patients can be made with any of the four major systems if specific data are collected according to various magnetic resonance imaging and radiographic findings. This approach will allow for easier comparison of studies across different centers. LEVEL OF EVIDENCE Prognostic Level III. See Instructions to Authors on jbjs.org for a complete description of levels of evidence.