Effect of limb malrotation on malalignment and osteoarthritis.

This article's goal is to review the causes of limb rotation and arthritis and establish the correlation between the two entities. Evidence cited in this article demonstrates that malrotation is coupled with axial malalignment and both are associated with arthrosis of the hip, knee, and ankle. The clinical significance of this observation is that the prognosis of arthrosis developing in a malrotated limb may be predicted. Furthermore, the durability of an osteotomy, arthroplasty, or other surgical intervention may be limited if the intrinsic rotational deformity is not addressed.

An in vitro study of proximal femoral allograft strains in revision hip arthroplasty.

Bone allografts are used frequently to replace bone stock subsequent to total hip arthroplasty. Revision of the failed hip replacement results in a complex structure of allograft bone, host bone and a metal femoral component. To evaluate the mechanics of the allograft-implant-host bone structure at the time of surgery, a strain gauge study was undertaken with six fresh/frozen human femora. Under defined loading conditions, cortical strain distributions were measured for five different cases: (1) normal bone, (2) bone with a femoral implant, (3) bone with the femoral component and an osteotomy at the mid-stem level of the implant (i.e. to stimulate the proximal allograft-host junction around the femoral stem), (4) bone with an osteotomy and an implant cemented into the 'allograft' (i.e. the proximal end of the femur), and (5) bone with an osteotomy and the implant cemented into both the proximal 'allograft' and the distal host bone. The results showed that, prior to making the osteotomy, proximal femoral strains were decreased with the insertion of a femoral stem. These strains were further decreased when an osteotomy had been made. This strain distribution did not change when the stem was cemented into the proximal 'allograft' bone, or cemented into the proximal 'allograft' and distal host bone. The decreases in strain for these test cases implied that the discontinuity between the bony segments caused an extended reduction in the tensile or compressive stresses transmitted through the cortices.(ABSTRACT TRUNCATED AT 250 WORDS)

Three-dimensional computed tomography reconstruction of tibial torsion.

The accuracy and reproducibility of computed tomography (CT) scanning techniques in assessing tibial version and torsion are measured in this study. A technique of three-dimensional CT reconstruction is introduced to assess the influence of selection and variation of landmarks on rotation measured in the tibia. The authors conclude that, within 2 cm of the articular surface, the level at which the proximal tibial axis is determined has no effect on the degree of torsion measured by CT scan. Furthermore, they conclude that the slope of the proximal tibial cut, with respect to the long tibial axis, has no effect on the measure of tibial torsion. Finally, they conclude that there is no significant difference in tibial torsion measured by reference to the posterior-condylar axis instead of the transtibial axis in cuts below the articular surface.

Mycobacterium chelonae infection following a total knee arthroplasty.

Infection following total knee arthroplasty is a major cause of implant failure, with an incidence of infections between 1 and 12%. Although there have been no previously reported cases of infection with Mycobacterium chelonae following total knee arthroplasty, this mycobacterium appears to be a potential pathogen in arthroplasty. When infection following total knee arthroplasty is evident but standard cultures come back negative, atypical mycobacterium infection should be considered. Mycobacterium chelonae does not grow in the normally allotted culture time, so false negative results are common. Once identified, M. chelonae is difficult to treat because of its resistance to standard drug therapies. Details of the first reported successful diagnosis and treatment of an infection with M. chelonae following a total knee arthroplasty are reported.

Lateral patellar burnishing in total knee arthroplasty following medialization of the patellar button.

This case report describes a total knee revision necessitated by painful contact between the exposed lateral facet of the patella and the femoral component. Pain was resolved following repositioning and enlarging the patellar component. The clinical significance of this report is that the contemporary practice of medializing the patellar component to improve patellar tracking should be performed in moderation to avoid overexposure of the lateral patella. In the setting of persistent anterior knee pain following total knee arthroplasty, the etiology of the pain may be identified as contact between the patellar and femoral component on the sunrise radiograph.

Femorotibial offset. A morphologic feature of the natural and arthritic knee.

Eccentric wear identified in retrieval studies of failed total knee arthroplasties may reflect unrecognized intrinsic morphologic characteristics of the knee. This study identifies a previously unreported morphologic offset between the center of the tibia and femur using computed tomography scans in 38 preoperative arthritic knees and 38 controls. There is a statistically significant offset between femur and tibia centers in patients and control subjects. There is no significant difference between patients and control subjects in either AP or mediolateral translation of centers. The clinical relevance of this observation is that it may prompt strategies to address morphologic offset, thereby reducing eccentric wear in total knee arthroplasty.

Malrotation associated with implant alignment technique in total knee arthroplasty.

This study documents the malrotation between the femoral and tibial components associated with contemporary alignment techniques that position the tibial component relative to the tubercle, posterior tibial condyles, transtibial axis, and malleoli. The technique that allows the tibial component to float into alignment as the knee is passed through a range of motion and the technique of coupling the tibial component to the femoral component also were assessed. The average external rotation of the tibial component relative to the femoral component associated with each alignment technique is 19 degrees (tibial tubercle), 5 degrees (transtibial axis), 7 degrees (posttibial axis), 3 degrees (malleolar axis), and 14 degrees (range-of-motion technique). The coupled-component technique produced 2 degrees internal rotation. The observed tendency to externally rotate the tibial component relative to the femoral component with most alignment techniques may account for the high incidence of posteromedial polyethylene wear reported in retrieval studies.

Outcome studies of hip fractures. A functional viewpoint.

As the success rate for repair of hip fractures continues to increase, emphasis is shifting to outcomes beyond the simple fracture repair to include restoration of function. The orthopaedist's role is critical in understanding, assessing, and determining patient prognosis with respect to functional outcome. Multiple factors are predictive of outcome following hip fracture; these factors may facilitate the orthopaedist's decision making in providing care that will maximize restoration relative to a patient's premorbid ability to walk and live independently. This review of past research summarizes our current knowledge of hip-fracture outcomes and prognostic indicators.

Effect of age on bone formation around orthopaedic implants.

Bone and mineral metabolism are known to change with age, but studies of biologic fixation have traditionally ignored or poorly documented the effect of age on the quality and quantity of bone about implants. This study documents the effect of age on quality and quantity of biologic fixation about hydroxyapatite-coated and uncoated implants in young and old sheep. Mechanical and histologic tests demonstrate comparable fixation of implants in young and old sheep, indicating that age is not a dominant factor in the development or failure of implant osseointegration.

Femoral anteversion and arthritis of the knee.

Anteversion and arthritic changes were recorded in 110 well-preserved femora to identify a correlation between knee osteoarthritis and anteversion. Arthritis was recorded as no change (grade 0), osteophytes (grade 1), cysts or erosions (grade 2), and burnishing or eburnation (grade 3). Anteversion was identified by measure of the angle between the axis of the head-neck and the axis of the posterior condyles. There was no relation between anteversion and proximal femoral arthritis but increased arthritis of the distal femur with decreased anteversion (p < 0.04) was identified, establishing a correlation between femoral anteversion and arthritis of the knee.

Femoral morphometry and anterior knee pain.

By computed tomography scan, morphology of the femur in 20 adult patients with anterior knee pain was compared with that of ten volunteers without knee pain to identify femoral characteristics associated with the painful patella. Anteversion, measured as the difference between the axis of the head-neck and the axis of the posterior condyles, was significantly greater in symptomatic adults (p < 0.01). Configuration of the distal femur and position of the patella relative to the femur were similar in each group. Adult anterior knee pain was, therefore, associated with increased anteversion without compensatory change in trochlear morphology or patellar orientation to the femur.

Knee version associated with anterior knee pain.

Version of the knee in the presence and absence of anterior knee pain was evaluated by computed tomography in this study. Version of the knee is defined as the static rotation of the tibia with respect to the femur in full knee extension. Fourteen patients in whom conservative management for anterior knee pain failed were compared with 14 volunteers with no symptoms. Computed tomography images of the femoral condyles and tibial plateau were obtained with the knee extended. The angle between the bicondylar and posterior tibial axes was measured. This angle, representing external rotation of the tibia relative to the femur, was increased significantly in patients with symptoms (7 degrees) compared with volunteers with no symptoms (1 degree). This increased knee version identifies a unique morphologic characteristic of the knee with anterior pain.

Assessing rotational alignment in total knee arthroplasty.

The authors of this study demonstrate a new method for assessing relative rotational alignment of femoral and tibial components in total knee arthroplasty. This postoperative method requires only a lateral radiograph of the knee in full extension. This technique was demonstrated with repeated measurements by 2 independent observers to be accurate and reproducible in documenting the rotation of knee implants. This technique has clinical application in determining the accuracy of contemporary alignment techniques, assessing the reliability of anatomic landmarks referenced in implant alignment, and documenting the impact of malrotation on the function and longevity of components in total knee arthroplasty.

Location of the femoral sulcus in the osteoarthritic knee.

Morphology of the distal femur is characterized in patients with osteoarthritis to identify an etiology for the high incidence of patellar till, subluxation, and failure noted in total knee arthroplasty. This study demonstrates that the sulcus of the trochlear groove is not located in the midline as traditionally represented, but is lateral to the midline in both osteoarthritic and normal knees. The significance of this is that the patella will presumably track lateral to the midline unless surgically realigned, contributing to the prevalence of patellar tracking problems associated with symmetric femoral components with centralized sulci used in contemporary total knee arthroplasty.

Axial and rotational alignment of the leg.

The axial and rotational alignments of the lower extremity are commonly referenced independently, with minimal research on whether coexistent axial and rotational malalignment cause pathologies. The present study analyzed whether a correlation exists between the axial and rotational alignments of the leg. The methodology to measure both alignments was adapted for computer tomography. Fifty patients were analyzed at five reference images to determine axial and rotational alignment. The reference images included the femoral head, the femoral shaft (at the level of the lesser trochanter), the distal femur, the proximal tibia, and the ankle joint. Axial alignment was calculated by using horizontal and vertical measurements of the location of the femoral head, the distal femur, and the ankle joint. Rotational alignments of femur, knee, and tibia were calculated using four angles: proximal femoral, distal femoral, proximal tibial, and ankle joint angles defined relative to a fixed reference. Pearson correlation analysis between axial alignment and the three mentioned rotational alignments were calculated. The correlation coefficient values ranged between -0.15-0.07 when comparing axial to rotational alignment, indicating that a week correlation exists between the two alignments. Though these results were derived using highly reproducible methods, the hypothesis of an existing correlation between the axial and rotational alignments of the leg was rejected. These findings allow for an improved understanding of lower extremity mechanics, which merit importance when considering pathologies of the leg and the surgical techniques that could ultimately benefit patients suffering from these pathologies.

The Ranawat Award. Sulcus morphology of the distal femur.

Traditional images of the distal femur place the intercondylar groove midway between the condyles. The location of the sulcus of the intercondylar groove in a large Sudanese skeletal population was verified using a custom stereotactic device. The results of this study show that the femoral sulcus is lateral to the midplane between the 2 femoral condyles. This study also shows that the configuration of the sulcus is linear and is oriented between the traditional anatomic and mechanical axes of the femur.

Version of the osteoarthritic knee.

Version of normal and osteoarthritic knees is evaluated by computed tomography in this study. Version of the knee is defined as the static rotation of the tibia with respect to the femur in full knee extension. It is measured as the difference between the transverse axes of the femoral condyles and tibia. The average knee version, or external rotation of the tibia with respect to the femur across the normal knee, was 0 degree. Version of the osteoarthritic knee was 5 degrees. Rotation of the tibia with respect to the femur across the extended osteoarthritic knee is a relationship that will affect the placement of components in total knee arthroplasty. This relationship should be addressed in alignment instrumentation and technique to avoid component malalignment in total knee arthroplasty.

Outcomes and costs after hip fracture and stroke. A comparison of rehabilitation settings.

OBJECTIVE: To assess whether outcomes and costs differ for elderly patients admitted to rehabilitation hospitals, subacute nursing homes, and traditional nursing homes. DESIGN: Inception cohort stratified by provider type and followed prospectively for 6 months. SETTING: A total of 92 hospital-based units and freestanding facilities from 17 states. PATIENTS: A total of 518 randomly selected patients with hip fracture and 485 stroke patients admitted from November 1991 to February 1994. MAIN OUTCOME MEASURES: At 6 months comparing community residence, recovery to premorbid levels in 5 activities of daily living (ADLs), Medicare costs, and the number of therapy and physician visits. Outcomes were adjusted for premorbid residence and function, caregiver availability, comorbid illness, admission function, cognition, depression, sensory deficits, and mobility impairments. RESULTS: On admission, rehabilitation hospital patients were more likely (P<.001) to have caregivers and better cognitive and physical function. Hip fracture patients admitted to rehabilitation hospitals did not differ from patients admitted to nursing homes in returning to the community (adjusted odds ratio [OR], 1.3; 95% confidence interval [CI], 0.6-2.6) or in the number of ADLs recovered to premorbid level (difference, 0.09 ADL; 95% CI, -0.27-0.44), but stroke patients admitted to rehabilitation hospitals were more likely to return to the community (adjusted OR, 3.3; 95% CI, 1.5-7.2) and recover ADLs (difference, 0.63 ADL; 95% CI, 0.20-1.07). Subacute nursing home patients with stroke were more likely than traditional nursing home patients to return to the community (adjusted OR, 6.8; 95% CI, 2.2-21.4), there was no difference in return to the community for patients with hip fracture (adjusted OR, 1.6; 95% CI, 0.7-3.6), and there were no differences in recovery of ADLs for either condition. Medicare costs were greater (P<.001) for rehabilitation hospital patients than for subacute nursing home patients, and the costs for subacute nursing home patients were greater (P=.03 for stroke and .009 for hip fracture) than for traditional nursing home patients. CONCLUSIONS: Study findings are consistent with enhanced outcomes for elderly patients with stroke treated in rehabilitation hospitals but not for patients with hip fracture. Subacute nursing homes were more effective than traditional nursing homes in returning patients with stroke to the community, despite comparable functional outcomes.