Primary Stability in Cementless Rotating Platform Total Knee Arthroplasty.

Highly porous ingrowth surfaces have been introduced into tibial tray fixation to improve long-term survivorship in cementless total knee arthroplasty. This study was designed to evaluate the effect of porous ingrowth surface on primary stability in the implanted cementless tibial component. Three tibial tray designs possessing sintered bead or roughened porous coating ingrowth surfaces were implanted into a foam tibia model with primary stability assessed via digital image correlation during stair descent and condylar liftoff loading. Follow-up testing was conducted by implanting matched-pair cadaveric tibias with otherwise identical trays with two iterations of ingrowth surface design. Trays were loaded and micromotion evaluated in a condylar liftoff model. The sintered bead tibial tray exhibited slightly lower micromotion than the roughened porous coating in stair descent loading. However, no significant difference in primary stability was observed in condylar liftoff loading in either foam or cadaveric specimens. Cementless tibial trays featuring two different iterations of porous ingrowth surfaces demonstrated both good stability in cadaveric specimens with less than 80 microns of micromotion and 1 mm of subsidence under cyclic loading. While improved ingrowth surfaces may lead to improved biological fixation and long-term osteointegration, this study was unable to identify a difference in primary stability associated with subsequent ingrown surface design iteration.

Progressive Tibial Bearing Sagittal Plane Conformity in Cruciate-Retaining Total Knee Arthroplasty.

BACKGROUND: We hypothesized that when the posterior cruciate ligament (PCL) is found deficient at total knee arthroplasty (TKA), using an anterior-stabilized (AS) tibial insert would provide similar function and survivorship when compared to using a more traditional cruciate-retaining (CR) bearing when the (PCL) is balanced. METHODS: A total of 1731 TKAs were performed using the same TKA design. Of them, 868 TKAs had a standard CR insert implanted (CR-S), 480 TKAs used a lipped CR insert (CR-L), and 383 TKAs used an AS insert. If the PCL was considered nonfunctional or absent, an AS bearing was placed. When the PCL was balanced, a CR-S or CR-L bearing was used. Follow-up was performed using the Knee Society scoring system. Kaplan-Meier survivorship was used with failure defined as aseptic loosening. RESULTS: At final follow-up, there were no significant differences in knee flexion, pain, function, or stair scores. Walking scores were significantly lower in the AS group. Posterior instability was higher in the CR-S group, whereas the manipulation rate was highest in the CR-L group (1.7%, 1.3%, and 0% for CR-L, CR-S, and AS groups, respectively). Kaplan-Meier survivorship at 5 years demonstrated no significant difference between the 3 groups (99% 100%, and 99% for CR-S, CR-L, and AS groups, respectively). CONCLUSION: Using an AS insert provided similar function and 5-year survivorship as compared to using a CR-S and CR-L tibial insert when the PCL was balanced. Using an ultracongruent AS dished tibial component appears to be a reasonable option when the PCL is completely released or found deficient at operation.

ACL Damage and Deficiency is Associated with More Severe Preoperative Deformity, Lower Range of Motion at the Time of TKA.

BACKGROUND: ACL status varies in the arthritic knee during TKA. QUESTIONS/PURPOSES: The purpose of this study was to examine clinical features and intraoperative findings associated with stages of ACL degeneration. METHODS: Coronal deformity, ROM, intra-articular degenerative patterns, and ligament releases were assessed for 1656 knees during TKA. Common patterns of deformity and severity of degenerative change were assessed as a function of the severity of ACL deficiency. RESULTS: Of the 1656 knees assessed, 27% had a normal ACL, 55% exhibited damage, and 18% exhibited complete absence of the ACL. Increased coronal deformity and lower preoperative ROM was associated with ACL deficiency. Increased chondral and meniscal damage and more extensive osteophyte formation were also found. More extensive ligament releases were required in ACL-deficient knees. CONCLUSIONS: The status of the ACL is predictive of the need for increased surgical deformity correction. A better understanding of ACL status is an important consideration during in choosing TKA as opposed to unicompartmental arthroplasty. The status of the ACL should be considered in planning for implant choice in TKA.

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.

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' institution's 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.].

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.

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.

Preoperative malalignment increases risk of failure after total knee arthroplasty.

BACKGROUND: Implant 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. METHODS: We 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. RESULTS: The 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). CONCLUSIONS: Patients 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 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.

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 patient's anatomy; however, the overall alignment is not as precise using the extramedullary system.

"Thicker" polyethylene bearings are associated with higher failure rates in primary total knee arthroplasty.

"Thin" modular polyethylene bearings have previously been associated with failure from wear. This study examined the influence of polyethylene thickness on survivorship in primary total knee arthroplasty (TKA). Do "thinner" or "thicker" bearings fail more? Six thousand seventy primary TKAs with a single implant design were reviewed. The failure rate in knees with bearings 14 mm or less was 0.7%, whereas the failure rate of knees with bearings 16 mm or greater was 2.3% (P < .0001; hazard ratio, 3.2). No knee was revised for polyethylene wear. Thicker bearings did not directly cause failure, but factors that lead to the insertion of a thicker bearing such as a deeper tibial resection and ligament imbalance may contribute to the observed increased failure. The significant influence of this often-unrecognized surgical variable has not been previously reported and must be carefully considered during TKA.

High preoperative range of motion is a significant risk factor for dislocation in primary total hip arthroplasty.

Dislocation after total hip arthroplasty (THA) is multifactorial and is dependent on surgical, implant, and patient factors. We hypothesized that high preoperative hip range of motion is an important variable contributing to instability after THA. We retrospectively reviewed 3379 THAs performed during a 21-year period. Average follow-up was 6.6 years. We examined the effect of surgical approach, femoral head size, and preoperative range of motion on dislocation rates. Patients with a posterior approach and 115 degrees or greater of combined preoperative flexion, adduction, and internal rotation dislocated at a significantly higher frequency than those with less than 115 degrees of combined motion (odds ratio, 1.9; P = .007). High preoperative motion in conjunction with a posterior approach and femoral head size less than 32 mm had the highest dislocation rate in our sample (5.9%). Preoperative range of motion is an important variable that should be taken into consideration during operative planning to help reduce the risk of dislocation.

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.

BACKGROUND: Ultraviolet 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. METHODS: From 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. RESULTS: Over 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. CONCLUSION: When 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.