Changes in long-bone structural properties during the first 8 weeks of plate implantation.

The midplate structural rigidities of metal- and plastic-plated intact canine femora were experimentally determined after initial plate application and 8 weeks after in vivo implantation. Composite beam theory significantly overestimated the bending rigidities of the metal-plated bones. The rigidities of the plastic-plated bones were nearly identical to that of the isolated bone, as composite beam theory predicted. Plating with either plate increased the intracortical porosity and caused the deposition of periosteal new bone, which was greater with plastic than with metal plates. The increased rigidities provided by the attachment of the metal plates and, hence, the degree of bone strain shielding were variable. Platings for 8 weeks which provided little strain shielding with either metal or plastic plates caused an increase in bone flexural rigidity (measured after plate removal) with respect to the contralateral control. Platings that provided increasing amounts of strain shielding caused a decreasing midplate bone rigidity (measured after plate removal) and increasing bone deposition at the outer screws. These findings suggest that the surgical implantation of any plate (metal or plastic) will provide a net stimulus to bone formation and consequently increased bone structural rigidity, even though intracortical porosity is increased. If the plate significantly reduces the normal loads borne by the bone, however, there is a net stimulus to remove bone, resulting in a loss of midplate structural rigidity within 8 weeks of implantation.

Femoral component loosening using contemporary techniques of femoral cement fixation.

A radiographic study was done of 171 total hip replacements that had been followed for an average of 3.3 years (range, two to five years). The study was performed to assess the incidence of loosening of the femoral component in older adult patients (average age, sixty years) in whom the medullary canal had been plugged with methylmethacrylate (using the medullary plug syringe to introduce the plug) prior to introducing the cement (Simplex P) with a cement-gun. Most of the femoral components that were used were of the CAD or HD-2 design, and all were made of chromium-cobalt alloy. Three categories of loosening were defined: definite (requiring radiographic evidence of migration of the component or the cement), probable (requiring evidence of complete 100 per cent radiolucent zone around the cement mantle on one or more radiographs), and possible (requiring evidence of a radiolucent zone that occupied more than 50 but less than 100 per cent of the cement-bone interface on one or more radiographs). One hip required revision for a loose femoral component and another patient had asymptomatic subsidence of the femoral component. Thus, the total incidence of definitely loose femoral components was 1.1 per cent. No hip was classified as having probable loosening; seven hips (4 per cent) were rated as having possible loosening. Compared with the results of four other published reports of patients of similar age with similar follow-up, and using the same radiographic criterion for loosening, the current series demonstrated a statistically significant reduction in the incidence of definitely loose femoral components.

Hip disease in adults with Down syndrome.

The life expectancy of patients with Down syndrome has increased significantly in recent years. Hip abnormalities occur in children with this syndrome but little is known about their natural history in later life. In 65 adults with Down syndrome we found hip abnormalities in 28%, and this was statistically correlated with walking ability. A subgroup of 18 patients was followed by serial examination; this showed that hip instability occurred in adulthood and became worse with time. In some patients, hip instability started after skeletal maturity.

The role of hip arthroscopy in the diagnosis and treatment of hip disease.

Injuries to the hip are commonly encountered by orthopedic surgeons and will, for the most part, respond well to conservative therapy. When a patient's hip pain has not responded to the appropriate treatment and radiographic measurements have not shown any specific pathology, arthroscopy of the hip can be a valuable diagnostic and therapeutic procedure. We retrospectively reviewed 94 consecutive patients who experienced refractory hip pain that persisted longer than 6 months (average: 2.1 years) and who had an average follow up of 2.5 years. Statistical analysis was performed using Fisher's Exact Test (P value) and Pearson (r value) correlation coefficient to compare preoperative symptomatology and physical examination findings with intraoperative pathology. Statistically significant results were obtained when comparing preoperative symptoms of a painful hip click and mechanical symptoms of locking with acetabular labral injuries (P = .000, r = .896) and loose bodies (P = .000, r = .896), respectively. Radiologic studies were nondiagnostic in 76% of patients in this series. Hip arthroscopy can be a valuable and viable procedure in the diagnosis and treatment of protracted or progressive hip pain lasting more than 6 months.

Minimum four-year radiographic and clinical evaluation of results following femoral revision surgery with the S-ROM modular hip system.

Thirty-four patients were reviewed following revision modular cementless reconstruction for proximal femoral deficiency. One patient underwent a Girdlestone conversion for sepsis at 3 years postoperatively, leaving 33 patients with an average follow-up of 51 months (range 48 to 62 months). The average age at surgery was 60 years, and there were 17 right and 16 left hips. Patients were assessed clinically using the Merle d'Aubigné and Postel hip rating system. Radiographic assessment was performed on preoperative and postoperative films. Femoral assessment was performed using the Engh fixation stability score, Gruen zonal system for radiolucencies and observing for the presence or absence of osteolysis. The average pain score was 5.4/6 with 88% having slight or no pain. Only one patient (3%) had thigh pain. Radiographically, the average fixation stability score was 21.7 with features of bony ingrowth present in 97%, and one case with features of stable fibrous ingrowth. There was no evidence of osteolysis.

Endoscopic lateral retinacular release: a preliminary report.

Thirty-nine knees with lateral subluxation syndrome of the patellofemoral joint were analyzed after 18 months of follow-up examinations. Based on subjective criteria, the results of lateral release by endoscopic technique compared favorably with other methods of treatment of patellofemoral malalignment. Excellent ratings based on the complete absence of symptoms and return to full activity were obtained in 19 knees (48.7%). Thirteen knees (33.3%) were improved with a subjective rating of 6.8 on a scale of ten; seven knees (18.0%) were rated poor with no improvement in symptoms or levels of physical activity.

Correlated changes in feeding behavior on selection for large and small body size in mice.

An automated method was used to record the temporal pattern of feeding of lines of mice selected over 15 generations for high and low body weight (L-mice and S-mice, respectively). Both L-mice and S-mice eat in meals concentrated during the night, and meal frequency is similar in the two lines, but L-mice consume much larger meals, each made up of many more separate feeding bouts. The outbred strain from which the selected lines were derived has a similar basic pattern of feeding in meals, which becomes like that of L-mice when the animal's thermogenic metabolic rate is high, and like that of S-mice when it is low, suggesting that the differences between the feeding patterns of the two selected lines are a secondary consequence of alterations in whole body metabolic rate.

The effects of selection for different combinations of weights at two ages on the growth curve of mice.

The weights of mice in lines selected for different combinations of high and low body weights at 5 and at 10 weeks of age were recorded from 3 to 21 weeks of age. The average growth curve for each line was computed using the Gompertz function. The growth curves of lines selected for high or low weight at a single age (ST lines) showed large differences in estimates of mature size and small differences in estimates of maturing rate, i.e. of the relative rate of growth to maturity. The growth curves of lines selected by independent culling for divergent combinations of deviations of opposite sign in 5- and 10-week weights (ICL lines) showed little difference in estimates of mature size and a large difference in estimates of maturing rate. The growth curves of lines selected by index for divergence in 5-week weight with no change in 10-week-weight or for divergence in 10-week-weight with no change in 5-week weight showed large differences in estimates of mature size and large differences in estimates of the maturing rate. The relationship between mature size and maturing rate was affected in different ways by the three types of selection.

The role of hip arthroscopy in the diagnosis and treatment of hip disease.

OBJECTIVE: To report the results of arthroscopy performed on adults with hip disease who did not respond to extended conservative treatment and to evaluate the relationship between clinical findings, radiologic tests and surgical abnormalities. DESIGN: A case study. SETTING: New England Baptist Hospital, Boston, Mass. PATIENTS: Fifty-nine patients (32 women, 27 men) with refractory hip pain, between the ages of 17 and 69 years, who were seen between January 1989 and January 1992. INTERVENTION: Hip arthroscopy. MAIN OUTCOME MEASURES: Cause of hip pain, results of physical examination and operative findings. RESULTS: In 26 patients the cause of hip pain was traumatic; in 21 the cause was idiopathic. On physical had pain on straight leg examination, 56% of patients reported painful clicking of the hip joint, 37% had pain on straight leg raising, 9% had decreased extension and 34% had had episodes of locking of the joint. Five percent had pain predominantly in the thigh, 41% reported at least one episode of "giving way" of the hip and 7% had snapping of the iliotibial band. At arthroscopy, 69% of patients had synovitis in the hip joint, 59% had a tear of the acetabular labrum, 39% had loose bodies, 32% had degenerative arthritis and 27% had a chondral defect. On statistical analysis, significant (p < 0.05) relationships were found between acetabular labral tears and preoperative complaints of clicking or giving way, between loose bodies and preoperative locking and between degeneration of the hip joint and thigh pain. CONCLUSION: Arthroscopy of the hip is a valuable diagnostic and therapeutic procedure for patients with hip pain refractory to conservative therapy.

Frequency Stabilization of a Ho:Tm:YLF Laser to Absorption Lines of Carbon Dioxide.

A single-frequency Ho:Tm:YLF laser, operating at an eye-safe wavelength of 2 mum, has been developed with tuning characteristics optimized for spectroscopy of absorption features. The laser frequency was stabilized to three different absorption lines of carbon dioxide by a wavelength modulation technique. Long-term frequency drift has been eliminated from the laser, and shorter-term jitter has been reduced to within 13.5 MHz of the absorption line center. This stabilized laser is an ideal injection seed source for a differential absorption lidar system for measurement of atmospheric gases.

Custom and modular components in primary total hip replacement.

Cementless custom implants attempted to enhance fit and fill of variable hip geometry. Fabrication of custom implants in referenced from a computed tomography scan, thus allowing three dimensional specifications of femoral anatomy. However, the aggregate charge of manufacturing the implant and obtaining the computed tomography scan is prohibitive in today's healthcare climate. Clinical studies have not shown that customized implants incrementally improve clinical success or implant longevity. Modular prostheses allow the surgeon intraoperative versatility, allowing adjustment of leg length, offset, neck length, anteversion, and fixation. This is particularly helpful in developmental dysplasia of the hip and posttraumatic arthritis. Other advantages of modularity include decreased implant inventory and the ability to remove the femoral head at revision surgery to improve exposure or change head size without component removal. Subsequent clinical experience has witnessed significant drawbacks associated with modularity. These include corrosion, especially with mixed metals, fretting, dissociation, implant fracture below the head and neck taper joint, and reduced range of motion. In addition, thin acetabular polyethylene contributes to higher were rates, earlier failure, local or distal debris particles, and osteolysis. Finally, the cost of modular implants is generally higher than a comparable monolithic prosthesis. In primary hip arthroplasty, use of custom or modular implants should be judicious. Modularity beyond the head and neck junction should be reserved for those cases where a comparable monolithic implant would not suffice.

Accuracy enhancement of in-vivo bone strain measurements and analysis.

A numerical technique is presented to evaluate and correct the zero-strain reference points determined experimentally for certain in-vivo strain rosette applications on long bones. The method is used to determine whether significant transverse stresses are present at the gage site during in-vivo activities. If transverse stresses are shown to be negligible, the experimentally determined zeroes can be appropriately adjusted to provide an increased accuracy of the strain measurements. In addition, the transverse Poisson's ratio is calculated and can be incorporated in subsequent in-vivo stress calculations.

Loosening of the femoral component of total hip replacement after plugging the femoral canal.

A roentgen follow-up study was done of 171 total hip replacements at an average of 3.3 years (range 2 to 5 years) after insertion to assess the loosening rate in older adult patients (average age 60 years) in whom the medullary canal was plugged. The cement (Simplex P) was introduced using a cement gun. The femoral components used were CAD and HD-2 in design, made of chrome cobalt alloy. Evaluation was made according to three categories of loosening: definite (requiring evidence of migration of the component or the cement), probable (requiring a continuous radiolucent zone around the cement mantle in one or more radiographic views), or possible (requiring a radiolucent zone that occupied 50% or more of the cement-bone interface in one or more views but was not continuous). One hip was revised for a loose femoral component. Another patient has asymptomatic subsidence of the femoral component. Thus the total incidence of definitely loose femoral components was 1.1%. No hip was classified as probably loose. Seven hips (4%) were rated as possibly loose. Compared to four other reported series of similar groups of patients followed for like duration, this incidence of definitely loose components is statistically significantly less than in nonplugged canals. The other differences among the series compared, such as stem design, type of cement introduction, modulus of elasticity of the metal used, presence or absence of a collar, and dates during which the surgery was done, are also discussed. Plugging the femoral canal; introducing the cement with a cement gun; using a femoral stem that largely fills the medullary canal, has a collar, and has a rounded rectangular cross section with no medial stress risers made of a superalloy with a modulus of elasticity of about 200 GPa--all these factors were associated with a low (1.1%) incidence of femoral component loosening at 3 years.

The Otto E. Aufranc Award: The role of labral lesions to development of early degenerative hip disease.

The current authors examined the hypothesis that labral lesions contribute to early degenerative hip disease. Between 1993 and 1999, 436 consecutive hip arthroscopies were done by the senior author. In addition, 54 acetabula were harvested from human adult cadavers. Two hundred forty-one of the 436 (55.3%) patients who had arthroscopies had a 261 labral tears, all located at the articular, not capsular margin of the labrum. Stereomicroscopic examination of the 54 acetabula from cadavers revealed 52 labral lesions. Overall, there was no significant difference between the arthroscopic and cadaveric populations in terms of the incidence of labral tears. (Overall, 73% of patients with fraying or a tear of the labrum had chondral change. Arthroscopic and anatomic observations support the concept that labral disruption and degenerative joint disease are frequently part of a continuum of joint disease.