Steven B. Haas

Magnetic Resonance Imaging of Articular Cartilage in the Knee. An Evaluation with Use of Fast-spin-echo Imaging*

The purpose of this study was to demonstrate that specialized magnetic resonance imaging provides an accurate assessment of lesions of the articular cartilage of the knee. Arthroscopy was used as the comparative standard.Eighty-eight patients who had an average age of thirty-eight years were evaluated with magnetic resonance imaging and subsequent arthroscopy because of a suspected meniscal or ligamentous injury. The magnetic resonance imaging was performed with a specialized sequence in the sagittal, coronal, and axial planes. Seven articular surfaces (the patellar facets, the trochlea, the femoral condyles, and the tibial plateaus) were graded prospectively on the magnetic resonance images by two independent readers with use of the 5-point classification system of Outerbridge, which was also used at arthroscopy.Six hundred and sixteen articular surfaces were assessed, and 248 lesions were identified at arthroscopy. Eighty-two surfaces had chondral softening; seventy-five, mild ulceration; fifty-three, deep ulceration, fibrillation, or a flap without exposure of subchondral bone; and thirty-eight, full-thickness wear. To simplify the statistical analysis, grades 0 and 1 were regarded as disease-negative status and grades 2, 3, and 4 were regarded as disease-positive status. When the grades that had been assigned by reader 1 were used for the analysis, magnetic resonance imaging had a sensitivity of 87 per cent (144 of 166), a specificity of 94 per cent (424 of 450), an accuracy of 92 per cent (568 of 616), a positive predictive value of 85 per cent (144 of 170), and a negative predictive value of 95 per cent (424 of 446) for the detection of a chondral lesion. Interobserver variability was minimum, as indicated by a weighted kappa statistic of 0.93 (almost perfect agreement).With use of this readily available modified magnetic resonance imaging sequence, it is possible to assess all articular surfaces of the knee accurately and thereby identify lesions that are amenable to arthroscopic treatment.

Minimally invasive total knee replacement through a mini midvastus approach: a comparative study.

Between September 2001 and September 2002, forty consecutive minimally invasive total knee replacements were done. A modified midvastus approach was used and the patella was subluxed, but not everted. We compared the results of this group with an age-matched and sex-matched cohort of total knee replacements done between June 2000 and September 2001 with a standard technique. A posterior-stabilized knee (Genesis II) was used in both groups. Patients achieved motion considerably faster in the minimally invasive total knee replacement group. Mean flexion for minimally invasive total knee replacement at 6 and 12 weeks was 114° (range, 90–132°) and 122° (range, 103–135°) respectively, compared with 95° (range, 65–125°) and 110° (range, 80–125°) for the control group. Improved range of motion was also seen at one year postoperatively. The average range of motion at one year postoperatively in the minimally invasive total knee replacement was 125° (range, 110–135°) compared with 116° (range, 95–130°) in the Control Group. Postoperative Knee Society scores were also higher in the minimally invasive total knee replacement group. There was no difference in xray alignment. There were no infections, extensor mechanism or neurovascular complications. The mini midvastus approach without patella eversion combined with a small incision was associated with a more rapid functional recovery and improved range of motion in total knee replacement without compromising implant positioning.

Revision total knee arthroplasty with use of modular components with stems inserted without cement.

We reviewed the results of seventy-six revision total knee replacements, performed between 1980 and 1988 on the Knee Service at The Hospital for Special Surgery, in seventy-four patients. Sixty-five patients (sixty-seven knees; 88 percent) had a complete clinical examination and radiographic evaluation, and nine patients (nine knees; 12 percent) were only interviewed by telephone. Survivorship analysis was performed for all patients. The average duration of follow-up was three years and six months (range, two to nine years). Only patients who had had revision of the femoral component or the tibial component, or both, because of aseptic failure were included. The tibial component of all prostheses that were used for revision had a metal backing. Cement was placed on the cut surfaces in the metaphyseal region of the femur and tibia. Fluted diaphyseal intramedullary rods were used in all patients and were not cemented. Metal wedges and augments were used to fill osseous defects when necessary. The average preoperative knee score, according to the rating scale of The Hospital for Special Surgery, was 49 points (range, 0 to 62 points). Postoperatively, the knee score improved to an average of 76 points (range, 0 to 97 points). Of the sixty-seven knees that had complete follow-up, fifty-six (84 percent) had an excellent or good result and five (7 percent) had a fair or poor result. In six (8 percent) of the seventy-six knees, the prosthesis failed, necessitating another revision. Failure was defined as removal or a recommendation for removal of the implant.(ABSTRACT TRUNCATED AT 250 WORDS)

Hip arthroplasty in patients with chronic renal failure

Patients with chronic renal failure who underwent total hip arthroplasty were retrospectively evaluated. Thirty hips in patients with renal transplants and 16 hips in patients on chronic renal dialysis were reviewed. The average follow-up period was 54 months. The renal transplant patients exhibited generally satisfactory results. Their postoperative course was comparable to that of patients with avascular necrosis undergoing hip reconstruction without underlying renal disease. However, patients undergoing hip arthroplasty while on chronic renal dialysis had poor results (81%), including a deep infection rate of 19%. It was concluded that total hip arthroplasty be reserved for patients who are expecting a renal transplant or preferably those who have already received a successful transplant.

The significance of calf thrombi after total knee arthroplasty

We reviewed the records of 1257 patients having 1625 total knee arthroplasties; all had pre-operative and postoperative perfusion lung scans and postoperative venograms which were classified as showing no thrombi, calf thrombi or proximal thrombi. Patients with calf thrombi were found to have a significantly greater risk for both symptomatic and asymptomatic pulmonary embolism compared with patients with no venographic thrombi. There were positive lung scans in 6.9% of patients with calf thrombi compared with 2.0% of patients with negative venograms (p < 0.001). Symptomatic pulmonary embolism occurred in 1.6% of patients with calf thrombi compared with 0.2% of patients with negative venograms (p = 0.034). The risk of pulmonary embolism was not significantly different between patients with treated proximal thrombi, and those with calf thrombi. Patients who develop deep-vein thrombosis despite prophylaxis are at increased risk for pulmonary embolism; these patients should receive treatment, or undergo follow-up studies to detect proximal propagation.

Resection Specimen Analysis of Proximal Tibial Anatomy Based on 100 Total Knee Arthroplasty Specimens

Although it is known that there is some asymmetry of the tibial plateau, most total knee arthroplasty designs currently have a symmetric tibial component. Using resection specimen analysis of the tibial plateau from 100 total knee arthroplasty specimens, the authors have examined the tibial plateau to further delineate, quantitatively, the medial and lateral tibial configuration. Unmagnified radiographs of each of the specimens were produced. A line was drawn along the mediolateral axis. The midpoint and points 10, 20, and 30% from the medial and lateral peripheries were then calculated. The average anteroposterior medial 10, 20, and 30% dimensions were 3.79, 4.74, and 5.06 cm, respectively. The average anteroposterior lateral 10, 20, and 30% dimensions were 3.48, 4.10, and 4.16 cm, respectively. The ratios of the lateral/medial anteroposterior distances at 10, 20, and 30% from the periphery were 92.10, 86.77, and 82.46%, respectively. A total knee arthroplasty system that recognizes the difference in the medial and lateral tibial plateaus and designs a prosthesis to account for the smaller, lateral tibial plateau may achieve the goal of maximizing tibial coverage as well as eliminate the problems associated with a symmetric design.

Minimally invasive total knee arthroplasty-The mini-midvastus approach

Minimally invasive knee surgery offers the potential for earlier return of motion. To ascertain whether this potential is realized we retrospectively reviewed 335 consecutive patients (391 knees) who underwent minimally invasive total knee arthroplasties from September 2001 to September 2004 using the mini midvastus approach. There were 248 women and 87 men, with an average preoperative range of motion (ROM) of 109°. Sixty-three percent of patients had a body mass index of less than 30% and 33% had a body mass index from 30 to 39. Patients received epidural anesthesia and a posterior-stabilized knee. We obtained Knee Society scores and determined ROM. The mean ROM at 6 weeks postoperatively was 111°, 121° at 3 months, and 125° at 1 year and 2 years postoperatively. Knee Society scores were 95 or over at all followup periods. Postoperative ROM was related to preoperative ROM, although patients with less preoperative motion had the greatest improvements at 6 weeks and 3 months postoperatively. We observed no increased complication rate with this approach. Minimally invasive total knee arthroplasty with a mini midvastus approach was associated with rapid functional recovery and substantial improvements in ROM. This procedure can be performed safely and provides high Knee Society scores short term. Level of Evidence: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Total Knee Arthroplasty After Varus Osteotomy of the Distal Part of the Femur

Background: There is little information in the literature regarding the outcome of total knee arthroplasty following distal femoral varus osteotomy. The purpose of the present study was to evaluate the intermediate-term results of total knee arthroplasty following distal femoral varus osteotomy.Methods: The study group consisted of nine consecutive patients (eleven knees) who had had a total knee arthroplasty following varus osteotomy of the distal part of the femur. The average age of the patients was forty-four years (range, fifteen to seventy years) at the time of the arthroplasty. The results were evaluated with use of the Knee Society score preoperatively and after a mean duration of follow-up of 5.1 years. Radiographs made preoperatively and at the time of follow-up were evaluated for alignment in the coronal plane.Results: The mean Knee Society knee score was 35 points before the arthroplasty and 84 points after the arthroplasty. The mean Knee Society function score was 49 points before the arthroplasty and 68 points after the arthroplasty. The mean interval between the femoral osteotomy and the total knee replacement was fourteen years (range, two to thirty-two years). A constrained prosthesis was required in five of the eleven knees. Two knees had an excellent result, five had a good result, and four had a fair result. The mean arc of motion improved from 81.8° to 105.9°. The mean radiographic alignment was 3.6° of valgus (range, 7° of varus to 18° of valgus) before the arthroplasty and 3.3° of valgus (range, 1° of valgus to 6° of valgus) at the time of the latest follow-up. There were no infections or wound complications.Conclusion: Total knee arthroplasty following distal femoral varus osteotomy decreases pain and improves knee function, but the procedure is technically demanding and is associated with inferior results when compared with those of primary arthroplasty performed in a patient without a prior femoral osteotomy. In the present series, the use of an intramedullary femoral alignment guide increased the tendency to place the femoral component in relative varus angulation (that is, in <5° of valgus). We recommend checking the alignment of the femoral component with an extramedullary guide in knees that have had a previous distal femoral varus osteotomy.Level of Evidence: Therapeutic study, Level IV (case series [no, or historical, control group]). See Instructions to Authors for a complete description of levels of evidence.

Inlay autogeneic bone grafting of tibial defects in primary total knee arthroplasty.

Reinforcement of the proximal tibia with autogeneic bone grafts preserves an area of subchondral bone essential for optimal thickness of cement and fixation of the implants. Bone grafts reduce the need for custom implants and may prevent fragmentation of large amounts of eccentrically placed methylmethacrylate and implant failure.

Minimally invasive knee arthroplasty

Interest in minimal-incision surgery among physicians and patients has led to the investigation of whether minimal-incision concepts have a role in knee arthroplasty. Successful outcomes in knee arthroplasty have been traditionally measured by long-term implant performance and low revision rates, with less emphasis on the size of the incision or the length of time to complete recovery. There are two evolving lines of development in minimal-incision knee arthroplasty: the small-incision approach and the new technology approach. The small incision approach seeks to minimize the length of the incision required to implant standard total knee components by altering the approach and instrumentation. The new technology approach seeks to develop lower profile implants and computer-assisted techniques to fundamentally change the way knee arthroplasty is done. The burden of proof as to whether these new approaches will stand the test of time remains with the investigators.