Robert A. Malinzak

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

BACKGROUNDnThe 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.nnnMETHODSnWe 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.nnnRESULTSnFailure 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.nnnCONCLUSIONSnAttaining 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 patients size, as determined by the BMI, is also a major factor in total knee replacement failure.

Morbidly Obese, Diabetic, Younger, and Unilateral Joint Arthroplasty Patients Have Elevated Total Joint Arthroplasty Infection Rates

The study aims to delineate the deep infection rates and infection risk factors for primary total knee and total hip arthroplasty patients. A retrospective review was conducted on 6108 patients from 1991 to 2004. The deep infection cases were compared to the noninfected cohort whereby infection risk factors were identified. Of the 8494 joint arthroplasties, 43 (0.51%) developed a deep infection (30 total knee arthroplasties, 13 total hip arthroplasties). Patients with a body mass index greater than 50 had an increased odds ratio of infection of 21.3 (P < .0001). Diabetic patients were 3 times as likely to become infected compared to nondiabetic patients (P = .0027). Simultaneous bilateral total joint arthroplasties were found to have developed infection 3 times less frequently than those performed as unilateral procedures (P = .0024). The average age in our infection cohort was 64.3 and 68.4 in the noninfected cohort. In this retrospective review study, obesity, diabetes, and younger age were found to be risk factors for joint arthroplasty infection.

Ultraviolet Lighting During Orthopaedic Surgery and the Rate of Infection

BACKGROUNDnUltraviolet lighting is an alternative to laminar airflow in the operating room that may be as effective for lowering the number of environmental bacteria and possibly lowering infection rates by killing the bacteria rather than simply reducing the number at the operative site. The purpose of the present study was to compare the infection rates following joint replacement procedures performed by one orthopaedic surgeon with and without the use of ultraviolet lighting.nnnMETHODSnFrom July 1986 to July 2005, one surgeon performed 5980 total joint replacements at one facility. In September 1991, ultraviolet lighting was installed in the operating rooms. All procedures that were performed before the installation of the ultraviolet lighting utilized horizontal laminar airflow, whereas all procedures that were performed after that date utilized ultraviolet lighting without laminar airflow. Factors associated with the rate of infection were analyzed.nnnRESULTSnOver a nineteen-year period, forty-seven infections occurred following 5980 joint replacements. The infection rate without ultraviolet lighting (and with laminar airflow) was 1.77%, and the infection rate with ultraviolet lighting was 0.57% (p < 0.0001). The odds of infection were 3.1 times greater for procedures performed without ultraviolet lighting (and with laminar airflow) as compared with those performed with only ultraviolet lighting (p < 0.0001). The infection rate associated with total hip replacement decreased from 1.03% to 0.72% (p = 0.5407), and the infection rate associated with total knee replacement decreased from 2.20% to 0.50% (p < 0.0001). Revision surgery, previous infection, age, total body mass index, use of cement, disease, and diagnosis were not associated with an elevated infection rate.nnnCONCLUSIONnWhen appropriate safety precautions are taken, ultraviolet lighting appears to be an effective way to lower the risk of infection in the operating room during total joint replacement surgery.

Preoperative Malalignment Increases Risk of Failure After Total Knee Arthroplasty

BACKGROUNDnImplant survival after total knee arthroplasty has historically been dependent on postoperative knee alignment, although failure may occur when alignment is correct. Preoperative knee alignment has not been thoroughly evaluated as a possible risk factor for implant failure after arthroplasty. The purpose of this study was to analyze the effect of preoperative knee alignment on implant survival after total knee arthroplasty.nnnMETHODSnWe performed a retrospective review of 5342 total knee arthroplasties performed with use of cemented Anatomic Graduated Component implants from 1983 to 2006. Each knee was independently measured preoperatively and postoperatively for overall coronal alignment. Neutral ranges for preoperative and postoperative alignment were defined by means of Cox proportional hazards regression.nnnRESULTSnThe overall failure rate was 1.0% (fifty-four of 5342 prostheses); failure was defined as aseptic loosening of the femoral and/or tibial component. The average preoperative anatomical alignment (and standard deviation) was 0.1° ± 7.7° of varus (range, 25° of varus to 35° of valgus), and the average postoperative anatomical alignment (and standard deviation) was 4.7° ± 2.5° of valgus (range, 12° of varus to 20° of valgus). The failure rate in knees in >8° of varus preoperatively (2.2%; p = 0.0005) or >11° of valgus preoperatively (2.4%; p = 0.0081) was elevated when compared with knees in neutral preoperatively (0.71%). Knees with preoperative deformities corrected to postoperative neutral alignment (2.5° through 7.4°) had a lower failure rate (1.9%) than undercorrected or overcorrected knees (3.0%) (p = 0.0103). Knees with postoperative neutral alignment, regardless of preoperative alignment, had a lower failure rate (0.74%) than knees with postoperative alignment of <2.5° or >7.4° of anatomic valgus (1.7%) (p < 0.0001).nnnCONCLUSIONSnPatients with excessive preoperative alignment (>8° of varus or >11° of valgus) have a greater risk of failure (2.3%). Neutral postoperative alignment (2.5° through 7.4° of valgus) improves (1.9% for preoperatively deformed knees) but does not completely eliminate the risk of failure (0.5% for knees that were neutral both preoperatively and postoperatively). Careful attention should be paid to knee alignment during total knee arthroplasty, especially for patients with severe preoperative deformities.

The Planovalgus Foot: A Harbinger Of Failure Of Posterior Cruciate-retaining Total Knee Replacement

T he etiology of posterior tibial tendon insufficiency is multifactorial; the disorder may be due to chronic attrition, rheumatoid arthritis (in 13% to 64% of cases1), chronic overpronation, degenerative joint disease, or Charcot neuropathy. More than half of the affected patients report no history of trauma. Rather, an insidious and progressive flatfoot may develop with or without medial or lateral pain in the hindfoot2. Patients with posterior tibial tendon insufficiency and a planovalgus foot demonstrate abnormal kinematics during the gait cycle, including lateral shift of the tibiotalar contact area3 (Fig. 1), functional malalignment3, increased valgus stress at the knee4,5, and relative internal rotation of the tibia and talus (external rotation of the foot)6. The offset of the mechanical axis of the lower extremity increases with the severity of the hindfoot deformity3. Consequently, these changes raise concern about potential problems with an ipsilateral total knee arthroplasty. The purpose of this study was to evaluate the relationship between failed total knee arthroplasties and ipsilateral posterior tibial tendon insufficiency.nnnnFig. 1 nStanding anteroposterior radiographs of the right and left ankles of a patient with posterior tibial tendon insufficiency on the left side. The arrows depict the point of tibiotalar contact used to measure the mechanical axis of the extremity.nnnnB etween July 1983 and April 2002, a total of 9475 primary posterior cruciate-retaining AGC (Anatomic Graduated Component) total knee …

Intramedullary vs extramedullary femoral alignment guides: a 15-year follow-up of survivorship.

The influence of intramedullary (IM) and extramedullary (EM) femoral cutting guides on survivorship of total knee arthroplasty was studied in 6726 total knee arthroplasty guided by either an IM (4993 knees) or EM (1733 knees) system. Fifteen-year survivorship of the 2 cohorts showed no statistically significant difference (EM 97.9% vs IM 98.5%; P = .2500, log rank). Medial bone collapse comprised the highest proportion of all failure modes for both groups (0.35% vs 0.40%, respectively, P = .6731, Cox regression). Mean tibiofemoral (overall) anatomical alignment was statistically more accurate in the IM group (IM 4.6° [± 2.2°] valgus vs EM 5.1° [± 3.1°] valgus; P < .0001). The mean tibial alignment was 90.5° (± 3.0) and 90.3° (± 2.2) (P = .0077). The EM group had a significantly larger tibial component alignment variance (SD(2)) than the IM group. No statistical difference in postoperative Knee Society scores, pain, or stair-climbing abilities was found. The choice of either alignment system should be determined by the patients anatomy; however, the overall alignment is not as precise using the extramedullary system.

The Effect of Rotating Platform TKA on Strain Distribution and Torque Transmission on the Proximal Tibia

Limited experimental data exist comparing the mechanical response of the tibial cortex between fixed and rotating platform (RP) total knee arthroplasty (TKA), particularly in the revision setting. We asked if RP-TKA significantly affects tibiofemoral torque and cortical stain response in both the primary and revision settings. Fixed and RP tibial trays were implanted into analogue tibias and biomechanically tested under axial and torsional loading. Torque and strain response were analyzed using digital image correlation. Fixed bearing designs exhibited 13.8 times greater torque (P<0.01), and 69% (P<0.01) higher cortical strain than RP designs. Strain response was similar in the primary and revision cohorts. The decrease in torque transfer could act as a safeguard to reduce stress, micromotion and torsional fatigue in scenario of poor bone stock.

Clinical predictors for possible failure after total hip arthroplasty.

Introduction With the rising number of total hip arthroplasties (THAs) each year, it is increasingly important for surgeons to have evidence-based information on which to determine how often patients should be examined postoperatively. The purpose of this research was to determine whether it is possible to identify – based on Harris Hip Score (HHS) – early signs or predictors of THA failure so that methods of postoperative follow-up can be scheduled in advance of the time frame indicated by those predictors of failure. Methods The HHS of 9,949 primary THAs performed from 1973 to 2012 was reviewed retrospectively to identify the clinical predictors of failure. 1,131 hips were completely lost to follow-up, leaving 8,331 primary THAs in 6,979 patients. Time to failure was recorded with Kaplan-Meier analysis performed with aseptic loosening or revision of any component as the endpoint. Results Regression analysis revealed that a pain score of 30 or less at any time of follow-up (p<0.0001) was a significant risk and strongly indicative of later failing. A low distance walked score of 5 or less at 6 months (p = 0.0087) and 1 year (p = 0.0167) served as an early predictor of future failure. A lower stairs score of 2 or less was also an early predictor at 1 year (p = 0.0343) and at 3 years (p = 0.0245). A lower limp score of 8 or less was a mid-term predictor at 3 (p = 0.0001), 5 (p = 0.0002), 7 (p = 0.0191) and 10 (0.0028) years postoperative follow-up. Conclusions Pain, walk, stairs and limp scores are predictive of THA failure. Surgeons with patients who present with these indicators should optimise postoperative follow-ups to alert their patients.

Use of Screws and Cement in Revision TKA With Primary or Revision Specific Prosthesis With Up to 17 Years Followup

The purpose of this study was to investigate the use for screws and cement, and primary and revision specific prosthesis for revision TKA. Between July 1989 and February 2010, 839 consecutive revision TKAs were performed, with 609 knees meeting inclusion criteria. At 17 years followup, Kaplan-Meier survivorship was 0.9859 for revision specific prosthesis with screws and cement, 0.9848 for revision prosthesis with no screws, 0.9118 for primary prosthesis with screws, and 0.9424 for primary prosthesis with no screws. Revision TKAs using screws had greater defects (P<.0001). Use of revision prosthesis along with screws and cement to correct largely defective revision TKAs is highly recommended.

Midterm Results of the Vanguard SSK Revision Total Knee Arthroplasty System

Revision total knee arthroplasty (TKA) is becoming increasingly common as the population ages and the number of existing primary TKAs continues to increase. Revision TKA systems use a greater range of component modularity than primary TKA systems, including stems, augments, and varying levels of constraint. The purpose of this study was to retrospectively review the authors institutions use of one specific revision knee implant system and its midterm results. The Vanguard SSK Revision Knee System (Biomet, Warsaw, Indiana) was implanted 297 times in 272 patients between 2005 and 2013. Average patient age was 67.2 years, average body mass index was 33 kg/m(2), and average follow-up was 4.8 years. The most common diagnoses leading to use of this system were failed previous TKA (45.5%) and periprosthetic infection (23.2%). The SSK system was used in 78 (26.3%) complex primary TKAs at the discretion of the operating surgeon. There were 22 failures: 12 septic and 10 aseptic. Of the 12 infections, 6 occurred after 2-staged treatment of periprosthetic joint infection, with all 6 of these reinfections having a different causative organism. Aseptic failures included aseptic loosening (n=3), periprosthetic fracture (n=2), patellar maltracking (n=2), instability (n=1), arthrofibrosis (n=1), and extensor mechanism disruption (n=1). Aseptic implant survivorship was 97.2%, 95.6%, 93.1%, and 93.1% at 1, 3, 5, and 7 years postoperatively, respectively. The Vanguard SSK demonstrates excellent performance at medium-range follow-up with respect to complications, clinical scores, and prosthesis survivorship. [Orthopedics.2016; 39(5):e833-e837.].