PubMed Health⌕ Search

Biomedical subjects

Merrill A Ritter

Publications and source records attributed to Merrill A Ritter.

At least 19 recordsLinked to original sources
PubMed2003

Excisional arthroplasty for patellar loosening in total knee arthroplasty.

Four thousand two hundred eighty-seven cases of Anatomic Graduated Components total knee replacements with a cemented, single-peg, all-polyethylene patellar component were performed at our institution over the past 15 years. One hundred eighty cases of patellar component loosening were found. Eleven knees (0.3%) in 11 patients required isolated patellar component reoperation. In all cases, the patellar component was excised and not reimplanted. The average follow-up for the 11 patients was 2.2 years. Five had a complete minimum follow-up of 2 years following reoperation. Pain and function were improved. Complications included infection in 3 knees and extensor lag in 1 knee. Because of the complication rate associated with isolated patellar component excision caused by a loose patellar component, we recommend surgical removal of the patellar component only in cases of severe pain and/or prominence of the component.

Arthroplasty, Replacement, Knee↗
PubMed2003

Acetabular options.

Cemented acetabular options have failed anywhere between 10% and 23% over the years and have not improved with increasing cement technology. Cementless technology, however, has basically stopped the problems of prosthesis loosening; however, wear has become a major concern. With present day cement techniques, no radiolucent lines, and a compression-molded polyethylene acetabular component, there is less than a 1% failure rate. The question is, however, whether cementing is technically feasible. Even for experienced surgeons, there is at least a 10% chance of a radiolucent line. Therefore, clinicians should work to develop better bearing surfaces so that cementless technology can be used extensively.

Acetabulum↗
PubMed2003

The AGC all-polyethylene tibial component: a ten-year clinical evaluation.

BACKGROUND: While high success rates have been achieved in association with other all-polyethylene tibial components, an alarming number of failures have occurred at our institution in association with the use of an all-polyethylene version of the AGC tibial component. The purpose of the present study was to describe the survival of the AGC all-polyethylene tibial component. METHODS: Five hundred and thirty-six AGC all-polyethylene tibial components were implanted in 405 patients and were followed over a ten-year period. The average age of the patients at the time of surgery was 70.3 years, the average weight was 78 kg, and the most common diagnosis was osteoarthritis (prevalence, 92.9%). A clinical and radiographic analysis was performed, Knee Society knee and function scores were determined, and Kaplan-Meier survivorship analysis was conducted. Failure was defined as aseptic loosening as evidenced by progressive radiolucent lines and/or revision due to aseptic loosening or collapse. RESULTS: A high rate of failure was noted in the early postoperative period, with a survival rate of 90.04% (95% confidence interval, 87.35% to 92.72%) after three years. At ten years, the survival rate was 68.11% (95% confidence interval, 57.57% to 78.65%). Fifty-eight (73.4%) of seventy-nine failures occurred in association with loosening or collapse of the bone beneath the medial tibial plateau. CONCLUSION: While some all-polyethylene tibial designs have been successful, the low success rate among knees treated with the AGC all-polyethylene tibial component suggests that the results associated with all-polyethylene tibial components are design-sensitive. 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.

Adult↗
PubMed2003

Predicting range of motion after total knee arthroplasty. Clustering, log-linear regression, and regression tree analysis.

BACKGROUND: Range of motion is a crucial measure of the outcome of total knee arthroplasty. The purpose of this study was to determine which factors are predictive of the postoperative range of motion. METHODS: We retrospectively studied 3066 patients (4727 knees) who had a primary total knee arthroplasty with the same type of implant at the same center between 1983 and 1998. Statistical clustering analysis paired with log-linear regression was used to determine groupings along continuous variables. Regression tree analysis was used to characterize the combinations of variables influencing the postoperative range of motion. The variables considered were preoperative and intraoperative flexion and extension, preoperative alignment, age, gender, and soft-tissue releases. RESULTS: Preoperative flexion was the strongest predictor of the postoperative flexion regardless of preoperative alignment. Other factors that were significantly related to reduced flexion were intraoperative flexion (p < 0.0001), gender (p < 0.0001), preoperative tibiofemoral alignment (p = 0.0005), age (p < 0.0001), and posterior capsular release (p < 0.0001). The removal of posterior osteophytes was related to the greatest increase in postoperative flexion in the group of patients with a varus tibiofemoral alignment preoperatively. CONCLUSIONS: The principal predictive factor of the postoperative range of motion was the preoperative range of motion. Removal of posterior osteophytes and release of the deep medial collateral ligament, the semimembranosus tendon, and the pes anserinus tendon in patients with large preoperative varus alignment and the attainment of a good intraoperative range of motion improved the likelihood that a good postoperative range of motion would be achieved.

Adolescent↗
PubMed2003

Simultaneous bilateral, staged bilateral, and unilateral total knee arthroplasty. A survival analysis.

BACKGROUND: The rates of perioperative morbidity and mortality are areas of concern associated with simultaneous bilateral total knee replacement. The purpose of this paper was to compare the rates of morbidity and mortality and the clinical outcome in large groups of consecutive patients undergoing simultaneous bilateral total knee replacement, unilateral total knee replacement, or staged bilateral total knee replacement. METHODS: A total of 6200 total knee replacements, performed in 3998 patients between 1983 and 2000, consisted of 2050 simultaneous bilateral, 1796 unilateral, and 152 staged bilateral total knee replacements. A review of each group was conducted to compare the rates of morbidity and mortality, the survival of the prosthesis, and the clinical outcome. Kaplan-Meier survival analyses were performed with failure defined as revision because of aseptic loosening and as patient death. Complications and Knee Society scores were compared throughout the fifteen-year follow-up period (average, 4.3 years of follow-up). RESULTS: The unilateral group had significantly lower Knee Society scores than the simultaneous bilateral group (p < 0.0001 up to twelve years, and p = 0.0067 at fifteen years) across all postoperative time-intervals. The percentage of patients who had thrombophlebitis was significantly higher in the simultaneous bilateral group (0.9%) than in the unilateral group (0.3%) (p = 0.0326). No significant differences were found with regard to prosthetic failure, cardiac complications, and the rates of death in the three groups. Ten years postoperatively, the simultaneous bilateral group had a significantly higher rate of patient survival than did the unilateral group (78.6% compared with 72.0%) (p = 0.0062). CONCLUSIONS: The significantly higher rate of thrombophlebitis in the simultaneous bilateral group compared with that in the unilateral group may represent a greater risk to those patients. However, we believe that when there are adequate indications for bilateral total knee replacement, simultaneous bilateral arthroplasty is beneficial to patients, with a minimal increase in the risk of death or other complications compared with that associated with unilateral and staged procedures.

Aged↗
PubMed2003

A malpractice episode: a sequence of events.

A malpractice suit is an event that no orthopaedic surgeon wants to go through; however, reality says you will. The authors outlined a step by step approach to your needs during such a suit and offer possible helpful actions by recommending collecting and securing all of the written documentation, being able to familiarize yourself with the entire events without notes, constant appraisal and discussion of the events with your attorney, considerations for settling, and finally emotional events surrounding the trial. The initial shock and insult eventually will subside, your patients will not note the difference, but you never will forget the event.

Humans↗
PubMed2003

The spectrum of prosthesis design for primary total knee arthroplasty.

Many types of prostheses are currently used for total knee arthroplasty. Controversy exists, however, regarding which prostheses are the most appropriate for use by individual surgeons and specific patient groups. Six types of prostheses are currently being used in the United States for primary total knee arthroplasty: posterior cruciate ligament-retaining prostheses; posterior cruciate ligament-substituting prostheses; prostheses with ceramic components; mobile-bearing prostheses; nonmodular, compression-molded polyethylene prostheses; and medial-pivot prostheses. The historical and current result of using these different types of prostheses are discussed, and the indications, contraindications, and recommendations for each type are delineated.

Anterior Cruciate Ligament↗
PubMed2002

The in vitro elution characteristics of vancomycin combined with imipenem-cilastatin in acrylic bone-cements: a pharmacokinetic study.

The aim of this in vitro study was to compare the elution characteristics of vancomycin alone and in combination with imipenem-cilastatin from 3 acrylic bone-cements (CMW1 [DePuy International, Blackpool, UK], Palacos R [Schering-Plough, Wehrheim, Germany], and Simplex P [Howmedica International, London, UK]). Six groups of 3 antibiotic-loaded cement disks were prepared, incorporating 2 g of vancomycin (3 groups) and 2 g of vancomycin plus 2 g of imipenem-cilastatin (3 groups). The disks were placed in saline baths for 5 weeks, with the baths being sampled periodically and the elution rates calculated. The total amount of vancomycin released by the cements treated with vancomycin alone was 7.98 mg for CMW1, 7.74 mg for Palacos R, and 6.76 mg for Simplex P; with the addition of imipenem-cilastatin, the total amount of vancomycin released by the 3 cements increased by 30.58%, 50.52%, and 50.15%. CMW1 had better elution characteristics than the other cements when treated with vancomycin alone; the elution of Palacos R and Simplex P was better than that of CMW1 when vancomycin was combined with imipenem-cilastatin.

Acrylic Resins↗
PubMed2002

Transfusion options in total joint arthroplasty.

Concern about the safety of allogeneic blood transfusion, including the risk of viral infection and immunosuppression, has led to the development of transfusion options in total joint arthroplasty, including intraoperative and postoperative blood salvage, autologous donation, hemodilution, and the use of epoetin alfa. Intraoperative or postoperative blood salvage has been shown not to be cost-effective at our institution except in revision hip arthroplasties because not enough blood is collected. Autologous donation is not helpful. One third of patients undergoing joint arthroplasty have hemoglobin values between 10 and 13 g/dL preoperatively. The most efficient way to decrease allogeneic risk in these patients is epoetin alfa. Epoetin alfa decreases allogeneic risk to 12.9%, which is acceptable. Patients with preoperative hemoglobin >14 g/dL undergoing single total knee or total hip arthroplasty do not need anything because their allogeneic risk is minimal.

Arthroplasty, Replacement, Hip↗
PubMed2002

One-staged contralateral or ipsilateral total hip and total knee arthroplasty.

One-staged ipsilateral and contralateral total hip and total knee arthroplasties were compared. A total of 103 patients underwent a 1-staged total knee arthroplasty and total hip arthroplasty between January 1975 and July 1997 (67 contralateral and 36 ipsilateral patients). No prostheses were found to be loose or revised. The contralateral group had a 10.5% hip dislocation rate, and the ipsilateral group had an 8.3% hip dislocation rate. Most of the patients were discharged home (contralateral, 66%; ipsilateral, 56%). There was no significant difference in survival between the contralateral and ipsilateral groups. There was only 1 death within 3 months of the operation. The severity of these patients' deformity may necessitate these procedures be done at 1 operation with consideration of mortality and morbidity risks.

Adult↗
PubMed2002

A method for improving acetabular preparation during cemented all-polyethylene acetabular component insertion during total hip arthroplasty.

Long-term outcome from cemented acetabular components has been correlated with the presence of radiolucency on early postoperative radiographs. We describe a means for enhancing acetabular bed preparation to decrease blood at the bone-cement interface and to obtain better pressurization of the cement into the cancellous bone of the acetabulum during cemented acetabular component insertion.

Acetabulum↗
PubMed2002

Fat embolism in revision total hip arthroplasty.

Two patients developed fat embolism syndrome after revision of loose total hip arthroplasties (THAs). During both procedures, the prosthesis became rigidly fixed 1 to 1.5 cm before the expected level of fixation. After uncomplicated operative courses, Patient A remained obtunded and febrile for 2.5 days, and Patient B died 1 day postoperatively. In Patient A, a presumptive diagnosis of fat embolism syndrome was based on the postoperative course and a radiograph of the lungs. In Patient B, the diagnosis was confirmed by evidence of cerebral edema on a computed tomography scan of the head. Fat embolism syndrome is unexpected after revision THA because the fatty tissue is removed from the femoral canal during primary THA. In these 2 cases, the rigid fixation and multiple attempts to impact and subsequently to remove the prosthesis may have caused fat embolism syndrome.

Arthroplasty, Replacement, Hip↗
PubMed2002

Long-term followup of nonmodular total knee replacements.

The purpose of the current study was to evaluate and determine the mechanism and etiology of failure of components that failed in long-term followup of Anatomic Graduated Component total knee replacements. The authors previously reported the survivorship of 4583 Anatomic Graduated Component total knee arthroplasties done during a 17-year period. The current study was done to evaluate the etiology and cause of failure of the components that failed. There were six (0.18%) failures of the femoral component. There were 21 tibia components that failed (0.46%). Twelve tibial components failed because of an osteonecrotic lesion in the medial tibia plateau. The clinical survival rate with revision or loosening of one or more components was 98.9% at 15 years. No component was revised for polyethylene wear or osteolysis. This total knee replacement has proved to have minimal wear and excellent longevity with time with no revisions between 10 and 15 years despite having nearly flat-on-flat geometry and retaining the posterior cruciate ligament. The most common cause for revision (12 tibial components) was because of an osteonecrotic lesion in the medial tibia plateau, which developed after surgery and led to loosening.

Adult↗