Length changes of the hamstrings and adductors resulting from derotational osteotomies of the femur.

Derotational osteotomies of the femur are frequently performed to treat persons with cerebral palsy who walk with excessive internal rotation of the hip. However, whether these procedures stretch or slacken the surrounding muscles appreciably is unknown. Determination of how muscle lengths are altered by derotational osteotomies is difficult because the length changes depend not only on the osteotomy site and the degree of derotation, but also on the anteversion angle of the femur and the rotational position of the hip. We have developed a three-dimensional computer simulation of derotational osteotomies, tested by anatomical experiments, to examine how femoral anteversion, hip internal rotation, and derotation affect the lengths of the semitendinosus, semimembranosus, biceps femoris long head, adductor longus, adductor brevis, and gracilis muscles. Simulation of derotational osteotomies at the intertrochanteric, subtrochanteric, or supracondylar levels decreased the origin-to-insertion lengths of the hamstrings and gracilis in our model by less than 8 mm (1.8%). Hence, the lengths of the hamstrings and gracilis are not likely to be altered substantially by these procedures. The origin-to-insertion lengths of the adductor longus and adductor brevis decreased less than 4 mm (1.9%) with subtrochanteric correction in our model, but the length of adductor brevis increased 8 mm (6.3%) with 60 degrees of intertrochanteric derotation. These muscles are also unlikely to be affected by derotational osteotomies, unless a large degree of intertrochanteric derotation is performed.

Clubfoot analysis with three-dimensional foot models.

The purpose of this study was to develop a method of defining, in mathematical terms, the interpositional relationships of the bones of the hindfoot complex in the idiopathic clubfoot and the neurogenic clubfoot. The neurogenic clubfoot and contralateral normal-appearing foot of a stillborn infant with myelomeningocele, and the normal foot of a 10-year-old were sectioned with a cryomicrotome. Magnetic resonance images (MRIs) of the clubfoot and the normal foot of a 3-month-old boy were obtained. Using a computer program, three-dimensional foot models were generated from the digitized cryomicrotome sections and from the MRIs. The central principal axes were determined for the talus and calcaneus. The long central principal axes of the talus and calcaneus were neutrally rotated with reference to the bimalleolar axis in the idiopathic clubfoot while in the neurogenic clubfoot the long central principal axis of the talus was medially rotated 52 degrees and that of the calcaneus 10 degrees. The talocalcaneal angles defined by the long central principal axes in the superior and medial views were 0 degree and 10 degrees, respectively, in the idiopathic clubfoot, and 42 degrees and 56 degrees, respectively, in the neurogenic clubfoot.

Use of animal models in musculoskeletal research.

Understanding of the human musculoskeletal system and common clinical disorders of bones, joints and soft tissues has been enhanced by the use of experimental animal models. Articles reporting on the results of these biomedical experiments frequently include conclusions that are based on the assumption that the biology of the animal model is similar to that of a human being for the disease process under investigation. The purpose of this investigation was to study the criteria and the considerations for selection of an animal model in musculoskeletal research. Selected journals from the musculoskeletal literature published between January 1991 and November 1995 were scrutinized for the use of animal models, and several criteria used in the selection of the various animal models were investigated. The selection criteria analyzed in this study included the biologic characteristics of the model, budget issues, the reproducibility of a musculoskeletal disease, and animal handling factors. A computer-assisted search of the musculoskeletal literature published from 1965 to 1995 was also performed to screen for reports comparing mammals used as animal models in terms of these selection criteria. Our findings imply that the selection of animal models in research of the musculoskeletal system is based partly on non-standardized criteria that are not necessarily based on the biology of the disease process being studied. In addition, there are limited comparative data on the selection and use of different animals for musculoskeletal research. We believe the selection of models should be more standardized based on both biological and non-biological criteria. Researchers would then be able to put in a more meaningful perspective the results of research using animal models and their clinical implications.

Distraction osteogenesis in the hand.

Distraction osteogenesis was used to correct congenital hand deformities in 12 digits. The patients' ages at the time of distraction ranged between 2.5 and 7 years. A total of nine patients underwent lengthening of 12 bones. The average period of distraction was 31.1 +/- 17.6 days. The average length of distraction was 23.6 +/- 7.3 mm. Seventeen percent of the patients after lengthening had an angular deformity that required remodeling of the regenerate. No infections were noted. Distraction osteogenesis provides a useful tool for reliable and predictable correction of osseous defects with vascular bone in patients with congenital anomalies of the hand.

Femoral varus derotation osteotomy with or without acetabuloplasty for unstable hips in cerebral palsy.

We reviewed 39 children with cerebral palsy who had surgery for hip subluxation or dislocation. Of 55 treated hips, 31 had a varus derotation osteotomy alone, and 24 had a combination of varus derotation osteotomy and an acetabular procedure. There was no significant difference in the ages of the two groups. There was no difference in the preoperative acetabular indices of the two groups, but the average percentage of preoperative uncoverage of the femoral head was 56% in the group with varus derotation osteotomy and 63% in the group with combined varus derotation osteotomy with an acetabular procedure. The incidence of resubluxation or redislocation (24%) after varus derotation osteotomy alone was higher than that after varus derotation osteotomy with an acetabular procedure (13%). The incidence of postoperative hip instability was higher in the patients who had preoperative uncoverage of the femoral head ranging from 70 to 100%. This was in comparison with the patients who had preoperative uncoverage of the femoral head ranging from 30 to 70%. These results suggest that a combination of varus derotation osteotomy and an acetabular procedure decreases the incidence of resubluxation or redislocation, and that unstable hips with > 70% uncoverage of the femoral head should undergo the combined procedure.

Skeletal distraction of the hypoplastic mandible.

Six patients underwent percutaneous pin placement, 17 intraoral corticotomies, and application of an Orthofix lengthening device to facilitate complex multiplanar distraction as mandated by the patient's specific deformity. The patients underwent gradual bony and soft-tissue distraction at the rate of .25 mm four times a day. Average distraction was 18.3 +/- 5.5 mm (mean +/- SD). After distraction, a 2-day period of stabilization for each 1 mm of lengthening was used (36.4 +/- 10.7 days) (M +/- SD). All the patients had marked improvement in their occlusion postoperatively and significant amelioration of their preoperative respiratory and feeding difficulties. The patients all exhibited dramatic aesthetic improvement. Intraoral corticotomies performed in conjunction with gradual skeletal distraction appears to offer significant advantages over classical treatment for micrognathia in a very specific group of patients.

Preserving plantar flexion strength after surgical treatment for contracture of the triceps surae: a computer simulation study.

Contractures of the triceps surae commonly are treated by surgical lengthening of the gastrocnemius aponeurosis or the Achilles tendon. Although these procedures generally relieve contractures, patients sometimes are left with dramatically decreased plantar flexion strength (i.e., decreased capacity to generate plantar flexion moment). The purpose of this study was to examine the trade-off between restoring range of motion and maintaining plantar flexion strength after surgical treatment for contracture of the triceps surae. A computer model representing the normal moment-generating characteristics of the triceps surae was altered to represent two conditions: isolated contracture of the gastrocnemius and contracture of both the gastrocnemius and the soleus. The effects of lengthening the gastrocnemius aponeurosis and the Achilles tendon were simulated for each condition. The simulations showed that nearly normal moment-generating characteristics could be restored when isolated gastrocnemius contracture was treated with lengthening of the gastrocnemius aponeurosis. However, when isolated gastrocnemius contracture was treated with lengthening of the Achilles tendon, the moment-generating capacity of the plantar flexors decreased greatly. This suggests that lengthening of the Achilles tendon should be avoided in persons with isolated gastrocnemius contracture. Our simulations also suggest that neither lengthening of the gastrocnemius aponeurosis nor lengthening of the Achilles tendon by itself is an effective treatment for combined contracture of the gastrocnemius and soleus. Lengthening the gastrocnemius aponeurosis did not decrease the excessive passive moment developed by the contracted soleus. Lengthening the Achilles tendon restored the normal passive range of motion but substantially decreased the active force-generating capacity of the muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of residual clubfoot deformities using gait analysis.

Gait analysis was used to evaluate 15 patients who had previously undergone clubfoot surgery. Because six patients had had bilateral surgery, 21 feet had undergone previous clubfoot surgery. Three of the operated feet had no residual deformity. In the remaining 18 feet, the reason for referral was intoeing in 13, calcaneovalgus in three, hindfoot varus in one, and supination/adduction in one. Clinical assessment and information from the gait analysis were used to establish a treatment plan. Satisfactory treatment outcome was achieved in 13 patients, one result was unsatisfactory, and one result was undetermined.

Transfer of the rectus femoris: effects of transfer site on moment arms about the knee and hip.

Decreased range of knee motion during gait is often treated by surgically releasing the rectus femoris from the patella and transferring it to one of four sites: semitendinosus, gracilis, sartorius, or the iliotibial tract. This study was conducted to determine if there are differences between these four tendon transfer sites in terms of post-surgical moment arms about the knee and hip. A graphics-based model of the lower extremity was used to simulate the origin-to-insertion path of the rectus femoris after transfer. Anatomical studies were conducted to evaluate the accuracy of the simulated tendon transfers by comparing knee flexion moment arms calculated with the computer model to moment arms measured in two anatomical specimens. The computer simulations and anatomical studies revealed substantial differences in the knee moment arms between the four sites. We found that the rectus femoris has the largest peak knee flexion moment arm (4-5 cm) after transfer to the semitendinosus. In contrast, after transfer to the iliotibial tract the rectus femoris has a slight (0-5 mm) knee extension moment arm. None of the transfers to muscle-tendon complexes on the medial side of the knee (semitendinosus, gracilis, sartorius) substantially affect the hip rotation moment arm of the rectus femoris. Transferring to the iliotibial tract increases hip internal rotation moment arm of the rectus femoris, but only when the hip is externally rotated.

Longitudinal tendon splitting: a simple technique.

Orthopaedic surgeons are frequently confronted with the problem of joint contractures and the need for tendon lengthening. We describe a simple reproducible technique for longitudinal splitting of a tendon. We use this method for Z-lengthenings and split tendon transfers and recommend its use to other surgeons.

Limb salvage tumor surgery in children.

Limb salvage tumor surgery in children is quite popular. Low local recurrence rates and patient survival statistics prove it is a viable option for many patients. We review the major changes in medicine and paramedical fields that have allowed limb salvage to develop. We then discuss patient selection, limb salvage goals, review the surgical staging system, and examine common errors in evaluating a tumor patient. A discussion (with case examples) of various surgical options and a brief look at some current trends is then presented.

Analysis of the components of residual deformity in clubfeet presenting for reoperation.

We reviewed the records and radiographs of 125 children with 159 clubfeet reoperated for residual deformity after operative repair (210 reoperations). We concluded that residual forefoot adduction and supination were the most common persistent deformities (present in 95% of the feet) and that these deformities resulted from undercorrection at the time of primary operation. Although not then apparent, the persistent deformities became more evident with growth, and additional treatment became necessary. Undercorrection resulted from not releasing the calcaneocuboid joint and plantar fascia and failure to recognize residual forefoot adduction on the interoperative radiographs at primary operation.

Ultrasound screening of high-risk infants. A method to increase early detection of congenital dysplasia of the hip.

Congenital dysplasia of the hip (CDH) continues to be missed by routine physical screening examinations in the early months when treatment is most effective. Real-time ultrasonography (US) is valuable in the detection of CDH in the young infant. We performed a prospective study to evaluate one US screening strategy that targets a select "high-risk newborn" population at risk for CDH aiming to increase the early diagnosis of this condition. From 1772 consecutive births at one hospital, we identified 97 (5.5%) newborns with risk factors for CDH: breech delivery, 73 babies; family history, 26 babies; postural abnormalities, five babies; and oligohydramnios, four babies. Eleven newborns had two risk factors. We studied 69 of these newborns with US. There were four cases of CDH in this group. Three of these babies had completely normal pediatric physical examination results at the time of the US study (at 14, 75, and 100 days, respectively) despite dysplasia diagnosed by US. All were successfully treated with a harness as outpatients. We conclude that a screening program entailing identification and subsequent US of the hip of newborns with specific physical and historical risk factors for CDH increases early diagnosis. Further analysis suggests this approach is cost-effective.

Femoral shaft fractures in children treated with early spica cast.

We retrospectively reviewed 51 patients aged 3-11 years with femoral shaft fractures selected for treatment with early spica cast immobilization. Shortening greater than 20 mm was the most common complication, occurring in 22 (43%) of the 51 patients. Factors associated with unacceptable shortening were shortening at the time of spica cast application greater than 10 mm, shortening greater than 20 mm at initial examination, and increasing age. Achieving less than 1 cm shortening at the time of cast application and close follow-up during the first 2 weeks after cast application are advised in order to achieve an acceptable final outcome.