Structural integrity of implanted WMT infinity hip and Osteonics Omnifit hip in fresh cadaveric femurs.

Five matched pairs of fresh human femurs were used to quantitatively assess the structural integrity of the implanted Wright Medical Technology modular Infinity hip and the Osteonics single-piece Omnifit hip. The results showed that neither bone implant system was able to recreate the femoral anteversion of the intact femur (p < 0.05). Although the micromotion at the bone-implant interface was well within the limits of achieving bone ingrowth, the axial micromotion was greater for the Infinity hip than for the Omnifit hip (p < 0.05), but the rotational micromotion did not show a significant difference between the two bone implant systems (p > 0.5). The anterior proximal femur deformation patterns were similar for both the two bone implant systems and intact femurs. However, the medial proximal femur deformation patterns showed that the Infinity hip-implanted femur was more similar to the intact femur than the Osteonics Omnifit hip-implanted femur.

Patellofemoral joint kinematics and contact pressures in total knee arthroplasty.

Patellofemoral joint kinematics, contact areas, and contact pressures were measured concomitantly before and after total knee arthroplasty in 10 fresh frozen human cadaver knees using an Instron machine, a custom patellofemoral joint testing jig, axial bone markers, a continuous video digitizing system, and Fuji pressure sensitive film. The implant used in this study was the Kirschner Performance Knee System with an all polyethylene, domed patellar component. For all tests, the patella was aligned in its anatomically neutral position. Patellofemoral joint contact areas decreased as much as 19-fold after total knee arthroplasty. Mean patellofemoral joint contact pressures increased as much as 32-fold, and peak patellofemoral joint contact pressures increased as much as 22-fold after total knee arthroplasty. No statistically significant differences between preoperative and postoperative specimens were observed with respect to the patellofemoral, patellotibial, or patellar tilt angles from 30 degrees to 120 degrees knee flexion. Thus, the elevated patellofemoral joint contact pressures observed after total knee arthroplasty in vitro are not a primary consequence of iatrogenically altered patellofemoral kinematics.

The influence of fixed rotational deformities of the femur on the patellofemoral contact pressures in human cadaver knees.

Patellofemoral contact pressures resulting from fixed rotational deformities of the femur were studied in human cadaver knees. The increase in the degree of fixed rotational deformities of the femur results in a nonlinear increase in patellofemoral contact pressures on the contralateral facets of the patella (i.e., external rotational deformity resulted in a contact pressure increase on the medial facet, and internal rotational deformity resulted in a contact pressure increase on the lateral facet of the patella). With the initial isometric tension of 200 N in the quadriceps tendon for 30 degrees, 60 degrees, 90 degrees, and 120 degrees knee flexion, the peak contact pressure showed no significant differences between the medial and lateral facets of the patella in its anatomic position. At 20 degrees of rotational deformity of the femur, only a slight increase was noted for the tension in the quadriceps tendon and the patellofemoral contact pressures on the contralateral facets of the patella. However, at 30 degrees rotational deformity of the femur, both the external and internal rotational deformity of the femur showed a significant increase in the tension of the quadriceps tendon and the patellofemoral contact pressures on contralateral facets of the patella. The greatest increase in patellofemoral contact pressures was observed at 30 degrees and 60 degrees knee flexion for both the external and internal rotational deformity of the femur. The external rotational deformity of the femur for all knee flexion angles showed significantly higher peak patellofemoral contact pressure increases on the medial facet of the patella as compared with the lateral patellofemoral contact pressure increase resulting from internal rotational deformity of the femur.

Revision arthroplasty facilitated by ultrasonic tool cement removal. Part II: Histologic analysis of endosteal bone after cement removal.

This conclusion of a two-part series examines the effects of ultrasonic cement removal from canine femurs on the underlying endosteal bone. The purpose of the investigation was twofold: to qualitatively assess the immediate in vivo effects on bone of direct coupling as a method of ultrasonic prosthesis removal, and to determine the immediate and delayed histologic responses of cortical bone to ultrasonic cement removal as well as compare the response after cement removal by high-speed burr instrumentation. This histologic study of an in vivo model demonstrated no significant cortical bone damage with the use of ultrasonically driven tools. The authors conclude that this method for the removal of bone cement and securely fixed prostheses is safe and efficacious.

Revision arthroplasty facilitated by ultrasonic tool cement removal. Part I: In vitro evaluation.

Ultrasonically driven tools (UDTs) have been developed to facilitate removal of bone cement and securely fixed cemented components during revision arthroplasty. A two-part study was performed to evaluate the efficacy and safety to these tools. Heat generation at the endosteal surface during prosthesis and cement removal with a UDT was examined in an in vitro human femoral revision model. The histologic changes produced by the UDT at the endosteal surface were evaluated with an in vivo canine model. The heat generation studies demonstrated one-degree (C) temperature elevations at the endosteal surface during cement removal. We conclude that UDT use is safe and effective in the removal of cement and secure prostheses during revision total hip arthroplasty.

Fat embolism syndrome following the intramedullary alignment guide in total knee arthroplasty.

Fat embolism syndrome (FES) is a well-known complication of total hip arthroplasty (THA). FES occurs less frequently in total knee arthroplasty (TKA) than in THA. A 67-year-old woman developed FES after placement of the intramedullary femoral alignment guide during TKA. The diagnosis is based upon a subtle, but significant change in the oxygen saturation after placement of the guide. This potentially fatal complication may be avoided with a simple precautionary step of intramedullary canal marrow aspiration prior to placement of the alignment guide pin.

Potential application of photoplethysmography technique in evaluating microcirculatory status of STAMP patients: preliminary report.

Diabetes mellitus and peripheral vascular disease often lead to infections that result in lower extremity amputations. Transcutaneous oxygen pressure (TcPO2) has been shown by many investigators to be a highly reliable means of assessing cutaneous blood supply and, thus, predicting healing potential. However, TcPO2 measurements are time-consuming and subject to technical difficulties. For this reason, a potential application of photoplethysmography (PPG) as a method for assessing the level of cutaneous circulation was investigated by comparing PPG peak-to-peak voltages with corresponding TcPO2 measurements. The comparisons were made at 37 locations in 20 patients with an age range of from 20 to 81 years (mean = 64.4 years). Although the two methods are intrinsically different and measure two different physiological parameters, the peak-to-peak voltages from PPG were compared with TcPO2 measurements since TcPO2 was reported to be the best single adjunct in determining healing potential after amputation. Linear regression analysis correlating output peak-to-peak voltages from PPG with TcPO2 yielded a correlation coefficient of 0.60. The anatomic locations did not affect the PPG or the TcPO2 measurement. The results of this study encourage further investigation of this technique and instrumentation as a method of assessing the level of cutaneous circulation and ultimately aid in determination of optimal amputation levels.

Transfer of vascularized grafts of iliac bone to the extremities.

We treated sixteen patients, all of whom had a large segmental defect of bone in an extremity, with transfer of a vascularized graft of the iliac crest. Thirteen patients had an open defect that required an osteomuscular or osteocutaneous graft; the other three had a closed segmental osseous defect and the graft of the iliac crest was transferred without soft tissue. The average length of the osseous defect was seven centimeters. For the defects of the lower extremity, the average time to osseous union was 8.8 months. For the defects of the upper extremity, it was four months. Three patients had delayed union due to difficulty in positioning the graft on the tibia and maintaining circulation to the overlying skin; this led us to modify our method of transfer. In six patients, we used an osteomuscular graft and a separate skin graft instead of the osteocutaneous flap. When performing the transfers to the tibia, we tried to place the graft in the coronal plane against the fibula for better alignment and stability. For the transfers to the distal part of the forearm, we did a double microvascular anastomosis.

Microvascular reconstruction for close-range gunshot injuries to the distal forearm.

Three patients with compound defects in the distal forearm resulting from close-range gunshot injuries were treated with a free microvascular composite groin flap. The composite flap, which consisted of groin skin, the iliac crest, and abdominal muscles, was used to cover the exposed nerves, tendons, and vessels in one stage. The iliac crest replaced the segmental radial and ulnar defects, and the attached muscles were placed deep to the tendons to provide a gliding surface and to prevent adhesions to the bone. "Sandwiching" the damaged nerves and tendons between highly vascular soft tissue has the potential to improve tendon excursion, nerve regeneration, and ultimately the functional result in the hand. This microvascular reconstruction is presented as an alternative to conventional staged skin flap transfer and cancellous bone grafting.

A review of delayed unions of open tibia fractures treated with external fixation and pulsing electromagnetic fields.

Seventeen cases of open tibia fractures complicated by delayed union were reviewed. Only severe injuries requiring external fixation for tissue management and multiple surgical procedures were included in this study. All were ultimately treated with pulsing electromagnetic fields. Our purpose was to evaluate the efficacy of electrical stimulation in these cases and any synergism with combined surgical procedures. Fifteen of 17 cases (88.2%) united within an average of 5.65 months after electrical stimulation was implemented. The average time interval from injury to application of electrical stimulatin was 13.75 months. Pin tract infections occurred in an alarmingly high number of patients; however, all responded to treatment. A notable synergistic relationship with bone grafting was found when stimulation was applied postoperatively.

Compression arthrodesis of the ankle following failed ankle arthroplasty using hoffmann® external fixation.

Nine patients with failed Irvine Total Ankle Arthroplasties have been treated by compression arthrodesis with Hoffmann external fixators. Six were men and three were women; ages ranged from 33 to 70 years. An anterior approach was used with application of a Hoffmann external fixator. Three pins were placed in the distal tibia, and three pins in the talus. After six to eight weeks, the fixator was removed. The patients were placed in a short leg walking cast until fusion was complete. All nine ankles fused primarily, in an average of 16.9 weeks (range: ten to 23 weeks). There were two complications of delayed wound closures. There were no problems with pin tract infections or osteomyelitis.

Use of the Hoffmann external fixator in the treatment of femoral fractures.

The Hoffmann external fixator has proved to be an effective means of stabilizing complex femoral fractures in patients in whom prolonged traction or internal fixation is not advisable. It provides for the prompt mobilization of multiple-trauma victims and assists in the evaluation of the "floating knee." Pin tract infections and lack of stability or adaptability of the frame are not major problems. Increased risks of delayed union or nonunion are often attributed to this mode of therapy. Within the limits of the present study these difficulties could not be directly related to the use of the fixator. In four patients nonunions were not unexpected and could have occurred with any form of therapy. Improved results may be achieved by earlier recognition of situations in which healing potential is compromised so that bone grafts may be applied at an early stage for prevention of nonunion.

Evaluation of the pritchard total elbow arthroplasty.

Total elbow arthroplasty is a valuable therapeutic modality in incapacitating degenerative joint disease from rheumatoid arthritis. This study is a retrospective analysis of 17 elbow arthroplasties in 13 patients with rheumatoid arthritis using the Pritchard elbow prosthesis. The Pritchard elbow prosthesis has several distinctive design features. This is a semiconstrained prosthesis that has abduction, adduction and rotational capabilities. The prosthesis requires minimal bone resection, providing significant inherent stability. Patient selection for this study has been limited to incapacitating degenerative joint disease from rheumatoid arthritis. The grading system of Pritchard has been adopted to evaluate the results of this study. Greater than 94% of the patients obtained excellent and good results. All of the patients were satisfied with their results. Complications included transient ulnar neuropathy, humerus fracture, and Mark I humeral component fracture. There were no infections and no loosening. The complications reflected technical problems and design limitations of the Mark I prosthesis only. Careful patient selection is the key factor in total elbow arthroplasty.

Use of the Hoffmann apparatus in myocutaneous pedicle flap.

The use of the Hoffmann apparatus has been extended to include primary cross-leg myocutaneous flaps. Three patients are presented with severe soft-tissue loss to the lower extremities. The Hoffmann apparatus was used for stabilization and proved to be very beneficial for neurovascular monitoring, graft and wound care, and patient comfort.

Results of patellar realignment in patients older than thirty.

A retrospective study of patellar realignment procedures was performed on patients over the age of 30 years, with a mean follow-up of 32 months on 16 operated-on-knees in 14 patients. The best results were achieved in patients with preoperative apprehension and compression signs, as well as a typical history for patellar subluxation. when these signs were absent after operation, the result was better than seen in patients whose clinical signs persisted. There was no correlation of results with the grade of chondromalacia noted at surgery. Good or excellent results were achieved in about 75% of the patients. An accurate preoperative diagnosis in the selection of operative candidates is imperative.