The Effect of Taper Angle and Spline Geometry on the Initial Stability of Tapered, Splined Modular Titanium Stems.

Design parameters affecting initial mechanical stability of tapered, splined modular titanium stems (TSMTSs) are not well understood. Furthermore, there is considerable variability in contemporary designs. We asked if spline geometry and stem taper angle could be optimized in TSMTS to improve mechanical stability to resist axial subsidence and increase torsional stability. Initial stability was quantified with stems of varied taper angle and spline geometry implanted in a foam model replicating 2cm diaphyseal engagement. Increased taper angle and a broad spline geometry exhibited significantly greater axial stability (+21%-269%) than other design combinations. Neither taper angle nor spline geometry significantly altered initial torsional stability.

The effect of stuffing the patellofemoral compartment on the outcome of total knee arthroplasty.

BACKGROUND: The effect of so-called stuffing of the patellofemoral compartment at the time of total knee arthroplasty (that is, increasing the anterior patellar displacement, the anteroposterior femoral size, or the combined anteroposterior patellofemoral size) has not been well studied. The purpose of the present study was to evaluate the effect of stuffing the patellofemoral compartment on the outcome of primary total knee arthroplasty. METHODS: A retrospective review of 1100 primary total knee arthroplasties that had been performed in 1997 and 1998 was conducted. Eight hundred and thirty arthroplasties (75.5%) met the diagnostic and minimum two-year follow-up criteria for inclusion in this report. Radiographic measurements were made to determine preoperative and postoperative anterior patellar displacement, anteroposterior femoral size, combined anteroposterior patellofemoral size, anterior femoral offset, and posterior femoral offset. Regression analysis was performed to determine the effects of changes in these variables on the range of motion, the Knee Society Knee Score, the Knee Society Function Score, the Knee Society Pain Score, and the rate of lateral retinacular release. RESULTS: Preoperative to postoperative changes in anterior patellar displacement, anteroposterior femoral size, combined anteroposterior patellofemoral size, anterior femoral offset, and posterior femoral offset had no clinically meaningful effect on the range of motion of the knee or on any of the Knee Society scores. Increases in anterior patellar displacement were associated with a lower probability of the need for a lateral retinacular release. Increases in measured anteroposterior femoral size were associated with a higher probability of the need for lateral release. Even when combined, however, these relationships explained only 10.1% of the observed variance in the need for lateral retinacular release. Moreover, analyses indicated that patient gender, large as opposed to medium patellar size, and absolute femoral component size influenced the likelihood of lateral release more than did anterior patellar displacement and measured anteroposterior femoral size. CONCLUSIONS: Our findings do not support the widely held belief that stuffing of the patellofemoral joint results in adverse outcomes after total knee arthroplasty. Furthermore, the need for lateral release appears to be multifactorial and likely involves a more complex set of factors. Thus, without evidence of other identifiable causes of failure, we do not recommend revision for the treatment of pain of an overstuffed knee joint.

The effect of femoral notching during total knee arthroplasty on the prevalence of postoperative femoral fractures and on clinical outcome.

BACKGROUND: The treatment of a supracondylar femoral fracture following total knee arthroplasty is complicated by the presence of the prosthetic components. Anterior femoral notching during arthroplasty has been implicated as a contributing risk factor for femoral fracture. We retrospectively reviewed the effect of anterior femoral notching on the subsequent occurrence of a periprosthetic supracondylar fracture of the distal aspect of the femur and the outcomes of primary total knee arthroplasty in such patients. METHODS: The prevalence and depth of femoral notching were determined on a review of the lateral radiographs by observers blinded to the clinical results of 1089 consecutive total knee replacements performed in 1997 and 1998. Linear and logistic regression modeling was used to analyze the relationship between femoral notching and the prevalence of supracondylar femoral fracture, postoperative range of motion, the Knee Society score, and the Knee Society functional and pain scores. RESULTS: Femoral notching was performed in 325 (29.8%) of the 1089 knees in our series. During an average follow-up period of 5.1 years, only two supracondylar femoral fractures occurred, both in femora treated without notching. Femoral notching was not associated with an increased rate of fracture (p = 1.000) or with significant differences in the measures of outcome (range of motion [p = 0.117], knee score [p = 0.967], functional score [p = 0.861], need for a lateral release [p = 0.234], or postoperative pain [p = 0.948]). CONCLUSIONS: This study demonstrated no difference in knees managed with or without notching of the anterior distal aspect of the femur with respect to the occurrence of a supracondylar fracture, range of motion, Knee Society score, Knee Society function, or pain.

Functional outcomes of simultaneous bilateral versus unilateral total knee arthroplasty.

Many patients in need of total knee arthroplasty (TKA) have bilateral symptoms and require surgery to both extremities. Performance of a bilateral procedure under a single anesthetic provides a reduced hospitalization time, an isolated anesthesia risk, a single rehabilitation, and substantial cost savings. While most current research examines postoperative complication rates, the primary purpose of TKA is the alleviation of pain and improved quality of life. The purpose of this study was to assess pain and functional outcomes associated with simultaneous bilateral TKA. The authors believe that patients with advanced destructive arthritis to numerous joints cannot achieve complete restoration of their functional status until comprehensive treatment of their disease process occurs. A retrospective review of 697 TKAs in 511 consecutive patients with bilateral knee arthritis was performed. Patients underwent either simultaneous bilateral TKA (n=186), performed sequentially under the same anesthetic, or unilateral TKA (n=325). The same intra- and postoperative protocols were followed in each group. There was no statistically significant difference in postoperative pain, represented by Knee Society Score (P=.161). However, there was a significantly higher postoperative functional outcomes-including increased total range of motion (P=.001), flexion (P=.003), and function score (P<.001)-associated with bilateral TKA. Simultaneous bilateral TKA is an effective treatment option and may be worth possible added risk in appropriate patients because it produces a better functional outcome.

A blood-conservation algorithm to reduce blood transfusions after total hip and knee arthroplasty.

BACKGROUND: Donation of autologous blood before total joint arthroplasty is inconvenient and costly, causes a phlebotomy-induced anemia, and may be wasteful and unnecessary for the nonanemic patient. We developed a blood-conservation algorithm that does not require predonation of autologous blood, employs selective use of epoetin alfa, and uses evidence-based transfusion criteria. Our hypothesis was that use of this algorithm would reduce the rate of transfusion after unilateral total hip and knee arthroplasty as compared with the rates described in previous reports. METHODS: We retrospectively reviewed the records of 500 consecutive patients in whom unilateral primary total hip or knee arthroplasty had been performed by a single surgeon. The same blood-conservation algorithm was recommended to all patients. Two groups of patients were identified: the first group consisted of 433 patients in whom the algorithm was followed, and the second group consisted of sixty-seven patients in whom the algorithm was not followed. RESULTS: In the group in which the algorithm was followed, the rates of allogeneic transfusion after total knee and total hip arthroplasty were 1.4% (three of 220) and 2.8% (six of 213), respectively. The overall rate of transfusion in this group was only 2.1% (nine of 433). The prevalence of transfusion in the group in which the algorithm was not followed was 16.4% (eleven of sixty-seven). This difference was significant (p = 0.0001). CONCLUSIONS: The use of this blood-conservation algorithm resulted in a significant reduction in the need for allogeneic blood transfusions after unilateral total hip and knee arthroplasty, and the results compare favorably with the rates of transfusion described in previous reports.

The effect of alignment and BMI on failure of total knee replacement.

BACKGROUND: The purpose of this study was to determine the effect of tibiofemoral alignment, femoral and tibial component alignment, and body-mass index (BMI) on implant survival following total knee replacement. METHODS: We retrospectively reviewed 6070 knees in 3992 patients with a minimum of two years of follow-up. Each knee was classified on the basis of postoperative alignment (overall tibiofemoral alignment and alignment of the tibial and the femoral component in the coronal plane). Failures (defined as revision for any reason other than infection) were analyzed with use of Cox regression; patient covariates included overall alignment, component alignments, and preoperative BMI. RESULTS: Failure was most likely to occur if the orientation of the tibial component was <90° relative to the tibial axis and the orientation of the femoral component was ≥8° of valgus (failure rate, 8.7%; p < 0.0001). In contrast, failure was least likely to occur if both the tibial and the femoral component were in a neutral orientation (≥90° and <8° of valgus, respectively) (failure rate, 0.2% [nine of 4633]; p < 0.0001). "Correction" of varus or valgus malalignment of the first implanted component by placement of the second component to attain neutral tibiofemoral alignment was associated with a failure rate of 3.2% (p = 0.4922) for varus tibial malalignment and 7.8% (p = 0.0082) for valgus femoral malalignment. A higher BMI was associated with an increased failure rate. Compared with patients with a BMI of 23 to 26 kg/m2, the failure rate in patients with a BMI of ≥41 kg/m2 increased from 0.7% to 2.6% (p = 0.0046) in well-aligned knees, from 1.6% to 2.9% (p = 0.0180) in varus knees, and from 1.0% to 7.1% (p = 0.0260) in valgus knees. CONCLUSIONS: Attaining neutrality in all three alignments is important in maximizing total knee implant survival. Substantial "correction" of the alignment of one component in order to compensate for malalignment of the other component and thus produce a neutrally aligned total knee replacement can increase the risk of failure (p = 0.0082). The use of conventional guides to align a total knee replacement provides acceptable alignment; however, the surgeon should be aware that the patient's size, as determined by the BMI, is also a major factor in total knee replacement failure.

Is there a functional benefit to obtaining high flexion after total knee arthroplasty?

Clinical evidence is lacking to support the functional benefit of high flexion after total knee arthroplasty (TKA). A retrospective review of 511 TKAs in 370 patients was performed. The mean follow-up was 3.7 years (range, 2-8 years). Regression analysis determined the effect of obtaining high flexion (>125 degrees ) on Knee Society, stair, function, and pain scores. Of 511 TKAs, 340 (66.5%) obtained range of motion greater than 115 degrees , and 63 (12.3%) TKAs obtained high flexion greater than 125 degrees . There was no difference between the patients who obtained flexion greater than 115 degrees and those who obtained high flexion greater than 125 degrees in Knee Society scores (P = .34) and function scores (P = .57). Patients with greater than 125 degrees of flexion are 1.56 times more likely to demonstrate optimal stair function (P = .02). Obtaining flexion greater than 125 degrees after TKA does not offer a benefit in overall knee function. However, obtaining a high degree of flexion appears to optimize stair climbing.

The effect of retropatellar fat pad excision on patellar tendon contracture and functional outcomes after total knee arthroplasty.

Excision of the fat pad is common in total knee arthroplasty to enhance surgical exposure. However, the effect of this has not been clearly established. A retrospective review of 1055 primary total knee arthroplasties was preformed in 720 patients from 1997 to 1998. Regression analysis was performed to determine the effect of excising the fat pad on patellar tendon contracture, range of motion, Knee Society Score, function, and pain scores. Fat pad excision had no significant effect on patellar tendon contracture (P = .4599), range of motion (P = .7361), Knee Society Score (P = .7247), or function scores (P = .6786). Patients whose fat pad had been removed were nearly twice as likely to experience postoperative pain (P = .0005).

The role of flexion contracture on outcomes in primary total knee arthroplasty.

This study examined the role that flexion contracture plays in postoperative outcomes after total knee arthroplasty using a retrospective database review. The relationships between preoperative and postoperative knee extension, walking ability, stair climbing ability, Knee Society scores, pain scores, and knee function scores were studied in 5,622 knees. A preoperative flexion contracture was associated with an increased incidence of a persistent postoperative flexion deformity. A postoperative flexion contracture was associated with poorer postoperative results. Furthermore, a postoperative hyperextension deformity of greater than 10 degrees was associated with an increased risk of suboptimal pain and Knee Society scores. Knee extension deformities play a substantial detrimental role in the functional outcome of primary total knee arthroplasty.

Failure mechanisms of total hip resurfacing: implications for the present.

In the past decade, there has been a renewed interest in hip resurfacing due to recent design improvements. It is unclear whether the recent improvements have accounted for all of the previous failure mechanisms. We determined the long-term performance of hip resurfacing, while paying special attention to the mechanisms of failure. We retrospectively reviewed 62 patients (65 hips) who had Indiana conservative hip prostheses implanted between 1977 and 1981. Forty-one of 62 joints had failed, representing a failure rate of 66%. The time to failure averaged 9.7 years with a range of 6 months to 21.5 years. There were 23 femoral failures (37%). Eleven were caused by femoral fracture, and 12 were caused by femoral loosening. All late femoral failures (greater than 10 years postoperatively) showed narrowing of the femoral neck secondary to stress shielding. There were 18 acetabular failures (29%) with 10 failing secondary to polyethylene wear and eight failing secondary to acetabular loosening. Failure of the Indiana conservative hip prosthesis continues over time related to femoral and acetabular failure mechanisms. These data should be considered in the context of growing enthusiasm for resurfacing with new bearing surfaces and cementless fixation.

The effect of the Insall-Salvati ratio on outcome after total knee arthroplasty.

The effect of total knee arthroplasty (TKA) on the Insall-Salvati ratio (ISR) and the effect of the ISR on the outcome of TKA have not been clearly established. A retrospective review of 1055 primary TKAs performed in 1997 to 1998 was performed. Radiographic measurements were made preoperatively and postoperatively, and the ISR was calculated. Regression analysis was performed to determine the effects of these variables on range of motion (ROM), Knee Society Score, and stair, function, and pain scores. Total knee arthroplasty resulted in a decrease in the patella tendon length, as measured by the ISR in 50% of cases. Patella infera (ISR less than 0.8) developed postoperatively in 9.8% of TKAs and was twice as likely to occur in women as men. A decrease in the ISR was associated with diminished stair and function scores (P = .0004 and 0.0081, respectively). There was no effect of the ISR upon ROM, Knee Society Score, or pain scores. Optimal outcomes occurred in patients where the ISR was not decreased after TKA, with superior stair and function scores.

Lateral patellar contact after total knee arthroplasty: an analysis of the effects on postoperative pain and outcome.

Although medialization of the patellar component during primary total knee arthroplasty (TKA) has been advocated for biomechanical reasons, this can lead to lateral patellar contact with the femoral component. Using blinded radiographic evaluations, we evaluated 980 consecutive primary TKAs performed from 1997 to 1998. The prevalence of lateral patellar contact in this series was found to be 46.1%. Lateral patellar contact was not correlated with significant differences in our measures of outcome (knee score [P = .1066], functional score [P = .2457], or range of motion [P = .2514]). The average pain score in knees with lateral patellar contact was higher (48.1) (less pain) when compared with knees without (46.7). Total knee arthroplasties without lateral patellar contact had a 1.61 times odds of experiencing postoperative pain compared with those TKAs with lateral patellar contact (P = .0025).

Brake response time after total knee arthroplasty: when is it safe for patients to drive?

Total knee arthroplasty (TKA) dramatically decreases pain and improves mobility and quality of life. However, little has been reported on its effect on driving ability in the early postoperative period. This prospective study was conducted to compare preoperative and postoperative brake response times (BRTs) in patients undergoing TKA for osteoarthritis. The results showed that patients returned to preoperative BRT as early as 3 weeks after surgery, and at 9 weeks after surgery, BRTs were significantly improved over baseline. Based on BRT analysis patients undergoing TKA may be allowed to return to driving 6 weeks after surgery.

Total joint arthroplasty in the extremely elderly: hip and knee arthroplasty after entering the 89th year of life.

The goal of this study was to evaluate the complications and efficacy of total joint arthroplasty in the extremely elderly and compare the survival with the normal age-matched population. One hundred one joint arthroplasties (45 total knee arthroplasties [TKAs], 56 total hip arthroplasties [THAs]) were performed in 83 patients 89 years old and older. Over an average follow-up period of 2.5 years, 26 (31%) of the patients died. Three patients (3.6%) died within the first 2 months' postoperatively. The perioperative medical complication rate (excluding deaths) was 14%. Significant improvements were noted in pain scores, Harris Hip Scores, and Knee Society Scores. The survival of patients in their nineties who undergo total joint arthroplasty is at least equal to the survival of an age-matched population for 2.5 years following surgery. With careful patient selection and patient care to minimize medical complications, total joint arthroplasty can be an excellent option for patients who are age 89 and older.