The geometry of slipped capital femoral epiphysis: implications for movement, impingement, and corrective osteotomy.

Metaphyseal impingement limits motion in high-grade slipped capital femoral epiphysis (SCFE). A three-dimensional volume/surface computer model was used to study the geometry of impingement, which may take the form of impaction, which causes levering or requires compensatory alteration in motion, or inclusion that occurs after remodeling and may lead to acetabular cartilage damage. The majority of deformities seen clinically can be reproduced with posterior epiphyseal displacement in the plane of the physis. By using the 3-D movements of normal walking, this model predicts little anterior metaphyseal impingement in the normal hip. As posterior slip angle increases to 25 degrees , minor impingement can be eliminated with as little as 20 degrees of external rotation. High-grade posterior slips (75 degrees ) require external rotation of 50-60 degrees during walking to minimize impaction. Sitting increases impingement for all slip geometries, requiring proportionately greater external rotation. As remodeling restores a more normal arc of motion, an increasing proportion of the femoral head is composed of the remodeled, included metaphyseal prominence. This study explores the potential role of contact between the acetabulum and the metaphysis in the production of abnormal range of motion after SCFE, and simulation estimates the correction needed by osteotomy to allow normal walking and sitting. The inclusion of significant metaphyseal surfaces in the remodeled hip may be one factor in subsequent degenerative changes associated with SCFE.

A comparison of surgeons' posture during laparoscopic and open surgical procedures.

BACKGROUND: There is increasing recognition of surgeons' physical fatigue in the new ergonomic environment of laparoscopic surgery. The purpose of this study was to determine what the differences are in the movement of the surgeon's axial skeleton between laparoscopic and open operations. METHODS: Surgeons' body positions were recorded on videotape during four laparoscopic (LAP) and six open (OP) operations. The percent of time the head and back were in a normal, bent, or twisted position as well as the number of changes in head and back position were tabulated using a computer program. A separate laboratory study was performed on four surgeons "walking" a 0.5-inch polyethylene tubing forward and backward using laparoscopic and open techniques. The movements of the surgeons' head, trunk, and pelvis were measured using a three-camera kinematic system (Kin). The center of pressure was recorded using a floor-mounted forceplate (Fp). RESULTS: In the operating room surgeons' head and back positions were more often straight in laparoscopic procedures and more often bent in open operations. The number of changes in back position per minute were significantly decreased when the laparoscopic-only part of surgery was analyzed. In the laboratory the subjects' head position was significantly (p = 0.02) more upright and the anteroposterior (AP) and rotational range of motion of the head was significantly reduced during laparoscopy. Subjects' CP was more anterior and there was a significant reduction in the AP range of motion of the CP during laparoscopy. CONCLUSIONS: Our study suggests that surgeons exhibit decreased mobility of the head and back and less anteroposterior weight shifting during laparoscopic manipulations despite a more upright posture. This more restricted posture during laparoscopic surgery may induce fatigue by limiting the natural changes in body posture that occur during open surgery.

Open fractures of the tibia and femur in children.

Forty-seven children with 32 open tibial fractures, 11 open femoral fractures, and six closed tibial fractures with compartment syndrome, which were surgically opened, were assessed for the time to union and incidence of nonunion and infection. Treatment varied with fracture severity and patient age. Tibial external fixators were supplemented by short-leg casts, and fixators were removed at an average of 7 weeks. No child required further surgery to achieve union. There was one (2%) delayed union and no nonunions. Three fractures (6%) developed infections. No pin-tract infections occurred in tibial fractures treated with external fixation with casting. The relation between age and time to union was statistically significant. In open fractures without segmental bone loss or soft-tissue loss requiring major reconstruction, bony healing can be expected within 6 months.

The use of caudal epidural anesthesia in clubfoot surgery.

We reviewed records of 31 children who had surgical release of 41 clubfeet under general anesthesia with supplemental caudal epidural anesthesia. Compared to an equivalent group of 27 children (39 feet), the caudal epidural group exhibited a statistically significant decrease in intraoperative narcotic requirement. One child had a bloody tap, and caudal epidural anesthesia was abandoned, but there were no other complications. Excellent postoperative pain relief persisted for > or = 8 h. Twenty-five of 31 caudal epidural patients were discharged safely on the same day as surgery without any surgical complications. Use of caudal epidural supplementation and outpatient surgery (where indicated) met with a high degree of parent satisfaction. Cost savings of outpatient clubfoot surgery, when compared to overnight stay, were disappointingly low.

Hamstrings in cerebral palsy crouch gait.

After observing patients with increased anterior pelvic tilt following medial hamstring lengthening in cerebral palsy crouch gait, we became concerned that the hamstrings may be functionally important hip extensors. To evaluate this, we studied the three-dimensional motion of the hip and knee, calculated hamstring muscle length, and evaluated dynamic electromyography (EMG) of the medial hamstrings in 16 patients with diplegic cerebral palsy and crouch gait to determine if the hamstrings were extending the hip. Twelve of 16 patients exhibited marked prolongation of electrical activity in the medial hamstrings, and in eight of these 12, the hamstrings were contracting concentrically, thus aiding in hip extension during gait. Hamstrings may be important hip extensors in some cerebral palsy patients with crouch gait; however, other deformities contributing to crouch (such as hip flexion contracture) need to be considered before isolated hamstring lengthening is performed in these patients.

Magnetic resonance evaluation of "metaphyseal" changes in Legg-Calvé-Perthes disease.

Twenty involved hips in 16 patients with Legg-Calvé-Perthes disease (LCP) were studied with both plain radiographs and magnetic resonance imaging (MRI) scans to better evaluate the existence of "metaphyseal" changes. Thirty-four sets of radiographs and MRI scans were reviewed in a blinded fashion and compared for the presence and location of these changes. Of 23 hips with plain radiographic metaphyseal changes, 11 showed no such changes on MRI scans (48%). Twelve hips did show MRI changes located in the anterior metaphysis. One hip studied three times had a discrete cystic change located in the central metaphysis. Of 11 hips with no plain radiographic changes in the metaphysis, five showed metaphyseal changes on MRI. Metaphyseal changes in LCP remain poorly understood. Even with use of MRI, fine distinction between physis and metaphysis still proved difficult. It appears that most metaphyseal changes are physeal and epiphyseal irregularities. A few hips have truly metaphyseal lesions. The significance of these "cysts" is unclear.

Intramedullary nailing of femoral shaft fractures in adolescents.

Twenty-two femoral shaft fractures in 20 patients aged 10-14 years with open physes treated with closed reamed intramedullary nailing were studied retrospectively. Follow-up averaged 26.7 months in 18 of 20 patients. Eleven additional patients with 11 femoral shaft fractures treated with casting and traction were included for comparison of hospitalization time, cost, and time to mobilization. All of the fractures treated with an intramedullary nail healed without malunion or leg length inequality, and there was no evidence of growth plate arrest. The patients treated with an intramedullary nail had statistically significant shorter hospitalizations and shorter times to mobilization, and treatment had an estimated cost of less than half of traction treatment. Results of this study suggest that closed intramedullary nailing of femur fractures in adolescents is an effective treatment option.

"Metaphyseal" cysts in Legg-Calve-Perthes' disease.

Radiographic changes in the femoral metaphysis in Legg-Calve-Perthes' (LCP) remain poorly understood. Our hypothesis was that these "cysts" are not truly metaphyseal but are metaphyseal changes radiographically projected onto the metaphysis. Surface epiphyseal changes were made on a normal hip and a hip with LCP. These "lesions" appeared metaphyseal on radiograph, and in the specimen with LCP, projected deep within the metaphysis due to flattening and three-dimensional distortion. "Metaphyseal" cysts in LCP may be epiphyseal changes superimposed on the metaphysis. This would explain the correlation between the presence of a "metaphyseal" lucency and final result, since it is simply another indicator of the extent of epiphyseal involvement.

Flexible marker set for human gait analysis.

A redundant flexible set of 44 skin markers has been developed to study human gait. In practice, only subsets of the marker system are used for individual gait studies. Software structure allows extreme flexibility in specific marker selection sites. Analysis of identical kinematic studies with different marker sets demonstrates the inherent inaccuracies of rotational wands and skin marker sets that have been commonly used for motion analysis.

Oblique tibial osteotomy for Blount's disease (tibia vara).

Nine oblique proximal tibial osteotomies were performed on six children with genu varum, all but one of whom had Blount's disease. The osteotomy was a single-plane cut allowing simultaneous correction of varus and internal rotation and permitting postoperative cast wedging if necessary to improve position. All osteotomies healed within 10 weeks. The major complications were three episodes of weakness of the extensor hallucis longus, two of which resolved in 4 days and one of which resolved only partially. We were able to combine the osteotomy with other procedures, such as epiphyseal bar resection. All nine osteotomies achieved the desired correction of deformity.

Obesity and decreased femoral anteversion in adolescence.

The degree of femoral anteversion in a group of obese adolescent children and a group of adolescent children of normal weight was determined by either magnetic resonance imaging or computerized axial tomography. Compared with the children of normal weight, the obese children showed a significantly reduced angle of femoral anteversion. Increased biomechanical forces generated across the hip joint of obese children leads to increased remodeling of the femoral neck. This may account for the association of slipped capital femoral epiphysis, reduced femoral anteversion, and obesity in the adolescent population.

An instrumented brace for study of Legg-Calve-Perthes disease.

The accepted clinical method for treating children with Legg-Calve-Perthes disease is by means of abduction bracing. To evaluate the effectiveness of this method, one major necessary step is solving the three-dimensional inverse dynamics problem for the intersegmental loads at the hip joint. In order to provide part of the external loading data on the lower limb required to solve this problem, an instrumented abduction brace has been designed. The instrumented brace duplicates the mechanical behavior of the Scottish Rite Atlanta treatment brace, currently a clinically popular device. Instrumentation of the actual Atlanta brace was not considered, since its complicated mechanism couples forces applied by the brace to the thighs, resulting in moments difficult to measure. The new design eliminates all moments and simply applies one single force to the center of the femur. This single force is measured by a strain gage dynamometer. To assess the utility of the instrumented brace, the brace was fitted to three test subjects and the brace force was recorded while children walked through multiple trials. Testing of the brace demonstrates that it can be considered a dependable tool in studying the mechanical interactions between the brace and patient.

Mapping of surface area 'containment' of the femoral head during walking.

This note describes a mathematical method for the calculation of surface area of the femoral head covered ('contained') by the acetabulum as a time-dependent function. It uses displacement vectors from the center of rotation of the hip joint to the femoral joint surface, and rotates these vectors in small increments to simulate the desired motion. At each interval, the vectors are tested to determine whether they lie within the coverage area of the acetabulum. The result is a containment density plot which displays coverage area as a function of time. The general method is used in a variety of clinically important situations, and an example of its use in the study of abduction bracing is described.

An improved method for pinning of chronic slipped capital femoral epiphysis.

A simple method is described for pinning of slipped capital femoral epiphysis with a stationary x-ray machine and the limb draped free. The leg is "frogged" for a lateral view, and positioned under radiographic control to avoid pin penetration into the joint.

A technique for determining femoral head containment during gait.

Kinematic gait analysis was carried out on 42 hips, including normal joints and joints affected with Legg-Calvé-Perthes disease. Data were analyzed by a computer algorithm that calculated three-dimensional femoral head contact with the acetabulum (containment). Patients were studied in and out of various abduction orthoses. The three-dimensional containment of the hip is reproducibly altered by various devices; specifically, the Atlanta brace increases posterior coverage and slightly increases lateral coverage, and Petrie casts improve lateral and anterior coverage at the expense of posterior containment. This analysis allows modeling of osteotomies and enhances clinical assessment of actual changes in containment with bracing.

Determination of femoral head containment during gait.

Using three-dimensional gait data, a mathematical model of the proximal femur was developed that will predict the loading conditions in the child's hip joint during walking. The model is based on knowledge of rim coordinates of the acetabulum, and consists of rotating unit vectors emanating from the center of the epiphysis. The results will be used in a variety of three-dimensional stress analyses of the femoral head in Legg-Perthes disease (a disorder of femoral head collapse).

Three-dimensional finite element analysis of Legg-Calve-Perthes disease.

We studied the theoretical stress distribution in the proximal femoral epiphysis by means of a three-dimensional finite element model that allowed simulation of the central epiphyseal necrosis found in Legg-Calve-Perthes disease. The model was altered to study effects of age, extent of necrosis, portion of gait cycle, and effects of osteotomy on containment. It was found that small infarcts were less likely to exhibit collapse because of stress shielding, which decreased when the infarct was extensive or the area was not contained. There was little difference in stresses regardless of age or portion of the gait cycle. Femoral and pelvic osteotomies did little to modify mechanical stresses, and specifically failed to stimulate stress shielding in the case of extensive necrosis. This study suggests that basic mechanical behavior of the femoral epiphysis is similar in younger and older children, and good results in the former may be due to remodelling and low body weight. Although containment may have a place in less extensive lesions, there is no obvious mechanical support for the practice of performing osteotomies in the face of extensive epiphyseal necrosis.

Bilateral total hip arthroplasty in a Jehovah's Witness with chronic anemia.

A 15-year-old girl demonstrated the ability of a youthful person with systemic disease and chronic anemia to withstand major reconstructive surgery, despite religious beliefs prohibiting blood transfusion. With careful preoperative planning and meticulous hemostasis, as well as hypotensive anesthesia, such patients need not be denied the benefits of various reconstructive procedures, provided they and their families understand and appreciate the risks involved.

Containment of the hip: a theoretical comparison of osteotomies.

Using a computerized model derived from anatomic specimens, coverage of the femoral head by the acetabulum during the gain cycle was studied and compared for normal hips, varus-derotation osteotomy, and innominate osteotomy (Salter). Theoretical estimates of joint reaction force were also studied during the gain cycle for the three conditions. The entire proximal femoral epiphysis was never covered by the acetabulum with any of these procedures. Innominate osteotomy gave better anterior coverage (with resultant poorer posterior coverage) than the femoral procedure. Varus-derotation osteotomy increased medial shear force at the epiphyseal plate to twice body weight, but in all cases the major component of force was normal to the epiphyseal plate (compression) rather than parallel to it (shear).