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Study design A comparison between femoral ring and fibular strut allografts in anterior lumbar interbody arthrodesis, as assessed by biomechanical analysis. Objectives To assess the difference in stability and rigidity provided by the femoral ring allograft versus that provided by fibular strut allograft. Summary of background data Two commonly used techniques for spinal arthrodesis at L4-L5 include the femoral ring allograft and the fibular strut allograft. The postoperative stability has not been evaluated biomechanically. Methods An anterior lumbar interbody fusion on seven cadaveric specimens was performed using femoral ring and fibular strut allografts. Biplanar radiography was used to measure the 6 degrees of motion of L4 with respect to L5 during a range of loading maneuvers. Results When an extension moment was applied, the femoral ring allograft extended 4.2 degrees more than the intact specimen, compared with 1.6 degrees with the fibular strut allograft (P = 0.18). When the flexion moment was imposed, lateral bending increased by 2.2 degrees with the femoral ring, compared with 0.7 degree with the fibular strut allograft (P = 0.06). During lateral bending, increased lateral translation was observed to be 0.9 mm with the fibular strut allograft compared with 1.4 mm with the femoral ring allograft (P = 0.06). Conclusions Although not statistically significant, the fibular strut allograft creates a more rigid construct immediately after surgery during flexion-extension, lateral bending angulations, and lateral translation. One should consider using the fibular strut allograft over the femoral ring allograft, as it is more stable and rigid construct in the immediate postoperative period.

To find an accurate method to predict the position of the normal head center in severely deformed hips without a contralateral reference, we studied the relationships between the head center and dimensions of the normal proximal femur using cadaveric specimens. From a large anatomic collection, 32 cadaveric femora with neck-shaft angles ranging from 115° to 146° were selected. The two parameters with the greatest correlation with the height of the femoral head were the height of the neck isthmus ( r = .932) and the lowest point of neck saddle ( r = .790). Medial head offset was most strongly correlated with the offset of the neck isthmus ( r = .945) and the distance from the medullary axis to the outer borders of the medial cortex at the + 30% level ( r = .861). As a rule of thumb, the height of the head center can be predicted as the height of the midpoint of the neck isthmus plus 10 mm or as the height of the neck saddle with an accuracy of ±5.1 mm and ±8.3 mm. The offset of the head center can be predicted as the offset of the midpoint of the neck isthmus plus 15 mm or as the distance from the medullary axis to the medial cortex at the +30% level plus 15 mm with an accuracy of ±4.6 mm and ±6.3 mm.

Cementing technique has a profound influence on the incidence of aseptic loosening of total hip replacements. Two specific measures that seem to have the greatest impact on the longevity of cemented femoral stems are pressurization of cement and control of mantle thickness, typically through the use of modular centralizing devices attached to the tip of the prosthesis. Two laboratory studies are presented that examine the success of these measures in clinical practice. In the first study, the performance of five designs of intramedullary plugs in resisting migration during pressurization of cement was evaluated in human anatomic specimen femurs. Profound differences were observed between the performance of the different plug designs. In canals larger than 12 to 14 mm, most commercial devices failed to resist pressures greater than 30 to 40 pounds per square inch. Overall, it was estimated that between 6% to 76% of these devices would fail to resist cement pressures of 50 pounds per square inch in clinical practice. The second study examined the role of distal centralizers in the accumulation of air bubbles around the distal tip of the prosthesis during insertion of the stem into the femur. Acrylic replicas of a femoral stem were implanted in cavities simulating the femoral canal. Colored dyes, present within the cement, revealed the complex patterns of cement flow. It was shown that cement, dragged from the top of the femur, forms a thin layer that covers the entire surface of the prosthesis and the distal centralizer. Significant voids were present behind the trailing edges of the distal centralizer in 42% of the cases examined. These studies show that improvements in intramedullary plugs and stem centralizers are needed to increase the reproducibility of cement technique in total hip replacement.

Plantar fascia release has long been a mainstay in the surgical treatment of persistent heel pain, although its effects on the biomechanics of the foot are not well understood. With the use of cadaver specimens and digitized computer programs, the changes in the medial and lateral columns of the foot and in the transverse arch were evaluated after sequential sectioning of the plantar fascia. Complete release of the plantar fascia caused a severe drop in the medial and lateral columns of the foot, compared with release of only the medial third. Equinus rotation of the calcaneus and a drop in the cuboid indicate that strain of the plantar calcaneocuboid joint capsule and ligament is a likely cause of lateral midfoot pain after complete plantar fascia release.

The variability in alignment of the natural patellar groove was determined about various anatomic axes of the femur, using 3 plane radiographs and electronic digitization. After the patellar groove was identified and marked on 15 anatomic specimen femurs, radiographs were taken in the coronal, sagittal, and transverse planes so that principal anatomic axes could be outlined. Through electronic digitization, a 3-dimensional representation of the patellar groove was constructed about the distal anatomic axis, mechanical axis, transepicondylar axes, and transcondylar axes. Regarding these 4 principal anatomic axes, the variability in orientation of the patellar groove was profound in both coronal and transverse planes, typically involving a range of 11 degrees to 16 degrees about the mean. The average orientation most closely approximated the perpendicular to the transepicondylar axis in the coronal plane; however, the range varied extensively. None of the anatomic axes tested proved reliable as a reference axis for proper position of the patellar groove, and this study shows that the orientation of the natural patellar groove is more variable than previously suspected. The failure of femoral components to accommodate this variability may explain many complications associated with the patellar component in total knee arthroplasty.

We measured changes in anterior translation of the tibia with sequential sectioning of the bundles of the anterior cruciate ligament and correlated these changes with the clinical examination. Six fresh cadav eric lower extremities were examined by three experi enced knee surgeons in a masked fashion with the anterior cruciate ligament intact and after sectioning of the posterolateral bundle, the posterolateral bundle and 50% of the anteromedial bundle, and the entire ligament. Lachman, anterior drawer, and lateral pivot shift tests were performed. Both KT-1000 arthrometer testing (30 pounds) and biplanar radiography demon strated progressive increases in anterior translation with incremental sectioning of the anterior cruciate lig ament. However, significant ( P < 0.05) increases in translation were found only after sectioning both the posterolateral bundle and half of the anteromedial bun dle and after complete sectioning of the anterior cruci ate ligament. The examiners were accurate in their interpretation of the status of the anterior cruciate lig ament in 89% of the intact specimens and 80% of completely sectioned ligaments. Only 11 % of the ex aminations correctly diagnosed the anterior cruciate ligament as partially cut when the posterolateral bundle was sectioned. A soft end point to the Lachman exam ination was noted only after cutting at least 75% of the ligament, but was not always present. Clinical evalua tion is accurate in defining intact and completely sec tioned anterior cruciate ligaments. However, it is un able to differentiate a sectioned posterolateral bundle from an intact anterior cruciate ligament, or a 75% sectioned ligament from a completely sectioned liga ment. The clinical diagnosis of a partial tear of the anterior cruciate ligament is more likely to represent a complete or "functionally complete" tear.

The design of cementless femoral prostheses is based on the assumption that age and gender do not affect the shape of the proximal femur. To test this hypothesis, standard anteroposterior and lateral radiographs were prepared of 4 sets of 20 femora, obtained from young (range, 40-60 years) and elderly (range, 60-90 years) donors of both genders. The intracortical and extracortical borders of each femur were digitized electronically, and key parameters were measured to define the shape and dimensions of the medullary canal and the position of the femoral head. Systematic differences were observed between the size and shape of male and female femora. Extracortical dimensions were larger in the male femora by 14% to 19%, and endosteal dimensions by 11% to 24%. However, there were no significant differences between the canal shape of young male and young female femora in the coronal, sagittal, or transverse planes. The male femora displayed no significant differences in canal shape or endosteal width as a function of age. Profound differences were observed in the endosteal shape and diaphyseal dimensions of the young and old female femora. The older female femora had wider canals at the level of the isthmus, with a significant reduction in the canal flare index (the ratio between the canal width proximal to the lesser trochanter and at the isthmus). This study demonstrates that cementless femoral prostheses of 1 standard shape cannot provide a close fit to the endosteal contours of young and elderly women.

UNLABELLED The dial osteotomy, an acetabular reorientation procedure based on radiographs, was developed by R. H. Eppright for treatment of hip dysplasia; however, long-term results are not recorded. The aim of this study was to evaluate retrospectively the results of the dial osteotomy as done in 37 patients (44 hips) at an average followup of 12.6 years. Articular pressures with the application of a time and pressure algorithm were calculated from radiographs to correlate calculated intraarticular pressures with progression of degenerative disease. Clinical results at followup were 32 (73%) satisfactory and 12 (27%) unsatisfactory hips. Six (13%) hips failed between 10-20 years (average 14.7 years). A satisfactory result correlated with the preoperative functional score. Radiographically, the anterior center-edge angle increased from an average of 6.7 degrees to 37.9 degrees. At followup, radiographic indices of degeneration indicated that eight (18%) hips had improved, 18 (41%) had stabilized, and 18 (41%) had deteriorated. Severin indices improved in 21 (48%) hips. Joint space width at followup provided the only correlation between radiographic parameters and clinical result. Contact pressures were reduced from 4.45 MPa to 1.12 MPa. The cumulative exposure to articular pressures averaged 61.6 MPa-years, and did not correlate with radiographic parameters or clinical success. LEVEL OF EVIDENCE Therapeutic study, Level IV (case series--no, or historical control group). See the Guidelines for Authors for a complete description of levels of evidence.

This study evaluates the three-dimensional anatomy of the femur with congenital dysplasia of the hip (CDH) in comparison with healthy controls. Computed tomographic scans were obtained from 207 women (154 with dysplasia; 54 healthy controls) with an average age of 51.6 years (range, 18-82 years). Most of the dysplastic joints were classified as Crowe I (43%), or Crowe II or III (48%), with 9% Crowe IV. Individualized three-dimensional computer models of the femur were generated by reconstruction of the CT scans. Dimensional and morphometric parameters were derived by computer analysis of each of the femoral reconstructions. The dysplastic femurs had shorter necks and smaller, straighter canals than the controls. The shape of the canal became more abnormal with increasing subluxation. Detailed analysis showed that the primary deformity of the dysplastic femur is rotational, with an increase in anteversion of 5 degrees to 16 degrees, depending on the degree of subluxation of the hip. The rotational deformity of the dysplastic femur arises within the diaphysis between the lesser trochanter and the isthmus and is not attributable to a torsional deformity of the metaphysis. This study shows that there is a significant difference in the geometry of the normal femurs and those with CDH, even in mild cases. In CDH cases, we recommend the use of modular or specially-designed components to accommodate the shape of the dysplastic canal.

The purpose of this study was to define the topography of the articular surface of the femoral condyles and to develop a method for computerized topographic matching of donor and recipient sites for osteochondral transplantation. The condyles of seven fresh cadaveric femurs were mounted on the rotating stage of a laser-based coordinate measuring machine. An anatomic coordinate system defining the articular surface of the condyles was created. Customized software was developed to allow selection and topographic matching of osteochondral graft donor and recipient sites from any location on the surface of the condyles. For cartilage defects within the weightbearing portions of the medial or lateral femoral condyles, grafts taken from sites from the most medial or lateral portions of the patellar groove provided a significantly better topographic match than did grafts taken from the central intercondylar notch.

PURPOSE Although CT scans are widely believed to provide the most accurate measurements of femoral anteversion, any estimate of the anteversion of the femur depends on the accuracy of the calculated axis of the femoral neck. We devised a method to measure the anteversion of the femur precisely using a 3D femoral computer model reconstructed from digitized femoral contours. Using this method, we compared the accuracy of three popular methods of anteversion measurement based on CT scans. METHOD The three popular CT methods were as follows: (a) the classic method of Weiner et al., based on a single CT image; (b) the method of Reikeras et al., in which the neck axis is defined by two superimposed images of the femoral head and neck; and (c) the method of Murphy et al., utilizing centroids of the head and the medullary canal. The accuracy of the single slice method was also examined using slices taken at four different neck slice levels within the proximal femur. CT scans of 30 femora were obtained using a helical CT scanner and reconstructed using custom software. RESULTS Based on the 3D model, the true anteversion of the femora averaged 19.8 +/- 9.3 degrees (SD). Using the method of Weiner et al., the anteversion of the femora was underestimated by an average of 6.4 degrees (predicted value 13.4 +/- 10.4 degrees). Conversely, Murphy et al.'s method overestimated anteversion by an average of 6.3 degrees with an average value of 26.0 +/- 9.1 degrees. The difference between the true anteversion and the values predicted by both of these methods was statistically significant (p < 0.001). The average anteversion measured according to the method of Reikeras et al. was 17.8 +/- 8.9 degrees, 2.0 degrees less than the true anteversion of the sample (p < 0.005). Anteversion angles predicted from a slice just below the inferior edge of the head averaged 18.3 +/- 9.5 degrees, only 1.5-3.1 degrees less than the true anteversion of the femur (p = 0.14). CONCLUSION The single slice CT method has sufficient accuracy for use, provided the slice is taken just below the femoral head. In cases with a femoral head deformity or a valgus neck or where difficulty is encountered in positioning the patient, 3D reconstruction appears essential for accurate measurement of anteversion.

Eight cadaveric lower extremities were examined by three experienced knee surgeons in blinded fashion. The knees were examined with intact anterior cruciate ligaments, sectioned anteromedial bundles, and completely sec tioned anterior cruciate ligaments to evaluate detectable laxity changes. Lachman, anterior drawer, lateral pivot shift, and KT-1000 arthrometer testing were performed. Optimized biplanar radiography using a defined spatial co ordinate reference system was performed with a 30- pound anterior force at 30° of flexion to confirm clinical findings. Physical examination and arthrometertesting de tected no difference between intact and partially sectioned anterior cruciate ligaments; these ligaments were signifi cantly different than completely sectioned ligaments, with the Lachman test being the most sensitive. Despite consistent clinical detection of complete sec tioning of the anterior cruciate ligament by both physical examination and arthrometer testing, neither method proved accurate in the diagnosis of isolated tears of the anteromedial bundle, but both did show that partially sectioned anterior cruciate ligament closely resembled intact ligament and differed significantly from com pletely sectioned ligament, as confirmed by radiologic data. Clinically diagnosed "partial tear" is likely to be complete rupture of the anterior cruciate ligament. His torically, clinically diagnosed partial tears of the anterior cruciate ligament have tended to "progress" to symp tomatic instability. Our data imply these patients may have had functionally incompetent ligaments from time of injury and, in fact, were demonstrating the expected natu ral history of an anterior cruciate ligament-deficient knee.