Search

It has often been assumed rotational kinematics are improved with mobile-bearing TKA designs as the terms mobile-bearing and rotating platform imply. We tested this assumption by assessing the in vivo axial rotation magnitudes and patterns of 527 knees implanted with 12 different mobile-bearing TKA designs. Implants were grouped and compared by type--posterior stabilized (PS), posterior cruciate retaining (PCR), and posterior cruciate sacrificing (PCS)--and by specific design. We hypothesized all three mobile-bearing types (PS, PCR, and PCS) would achieve greater than 10 degrees average axial rotation and we would find no differences in axial rotation between types. Only 14% of PS knees, 3% of PCS knees, and 17% of PCR knees attained greater than 10 degrees axial rotation when measured from 0 degrees to 90 degrees . The percentage of PCS knees with greater than 10 degrees axial rotation was less compared with the other two groups. Axial rotation averaged 4.3 degrees , 2.5 degrees , and 3.8 degrees for the PS, PCS, and PCR knees, respectively. Incidences of reverse rotation were observed in 17% of PS knees, 32% of PCS knees, and 28% of PCR knees. Compared with the PCS group, the PS group achieved greater average axial rotation and had a lower percentage of knees displaying incidences of reverse rotation. The data refuted the hypotheses. [ABSTRACT FROM AUTHOR]

Case: Total hip arthroplasty (THA) is a commonly performed surgery with well-known complications. Unreported in the literature is a displaced meniscus tear in the acute postoperative period. We present the case of a displaced meniscus tear acutely after THA and discuss our management of this unique problem., Conclusions: Displaced meniscus tears after THA pose unique challenges and should be considered in patients with knee pain after THA. Arthroscopic intervention occurred 8 weeks after THA to minimize prosthetic joint dislocation and loosening during arthroscopy.

Background: Liposomal bupivacaine (Exparel) is a long-acting local anesthetic preparation with demonstrated efficacy over placebo in reducing postoperative pain and opioid requirement. Limited comparative efficacy and cost-effectiveness data exist for its use in total knee arthroplasty (TKA) when used in a multimodal, opioid-sparing analgesic and anesthetic approach. We hypothesized that liposomal bupivacaine offers no clinical advantage over our standard of care but carries significant economic impact., Methods: This is a prospective, randomized, single-blinded, controlled trial comparing liposomal bupivacaine periarticular injection (PAI) to our current approach including conventional bupivacaine PAI, in the setting of regional anesthesia. All adult unilateral TKA patients of the collaborating surgeon were eligible to participate in the study. Patients were randomized 1:1 to either the liposomal bupivacaine protocol or the standard-of-care protocol. All patients received regional anesthesia and standard postoperative analgesia protocols. Patients and all postoperative healthcare providers were blinded to study arm assignment., Results: A total of 59 patients were enrolled per our a priori power calculation after 1 exclusion for randomization error. No significant demographic differences between the study arms were found. There was no statistically significant difference in the primary outcome of number of physical therapy (PT) sessions required to achieve home-going discharge goals (3.0 ± 1.2 vs 3.6 ± 1.3, P = .137), nor in the clinical secondary outcomes. A significant difference in medication charges was found., Conclusion: Our study supports earlier literature suggesting no significant clinical benefit of using liposomal bupivacaine over standard of care in TKA and underscores cost-of-care concerns with this agent., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Much advancement has been made in the treatment of knee arthritis. A special area of interest has been the treatment of medial unicompartmental disease. However, patients with isolated lateral compartment arthritis represent a significant subset of the population. Lateral unicompartmental knee arthroplasty (UKA) is performed much less frequently than in the medial compartment and is known to be more technically demanding and less reproducible. Robotic-assisted arthroplasty provides a tool to improve component placement and reproducibility. The purpose of this study is to retrospectively review radiographic and clinical outcomes following robotic-assisted lateral UKA. We retrospectively reviewed 22 patients who underwent robotic-assisted lateral UKA by a single surgeon. Indications consisted of isolated lateral compartment arthritis with correctable valgus deformity and an intact anterior cruciate ligament. Eighteen patients met all inclusion criteria, resulting in 20 lateral UKA. Radiographic and clinical outcomes were evaluated and we found that robotic assistance during lateral UKA provided accurate and reproducible results. Native alignment of the tibia and femur were well maintained in the coronal and sagittal planes, and no overcorrection occurred. The standard deviation of tibial components was 1.8°, indicating strong accuracy and reproducibility. Operative times were increased, but this did not lead to intraoperative complications or slowed progression of postoperative rehabilitation. Robotic-assisted lateral UKA provides a tool for accurate and reproducible component placement with excellent short-term clinical outcomes.

Reducing blood loss during primary total knee arthroplasty (TKA) can improve outcomes by reducing transfusion requirements and wound complications. We examined the use of bovine thrombin to augment hemostasis during primary TKA. A double-blinded randomized trial was performed with 80 primary TKA patients. Half received intraarticular bovine thrombin at the time of wound closure, and half did not. Hemoglobin levels in the study group did decline less than the control group, but no statistically significant difference was found in rates of transfusion, drain outputs, length of stay, or Knee Society scores. This agent does appear to slightly reduce blood loss, but routine use is not cost effective. Thrombin may be considered for patients who would benefit more from greater blood conservation., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Significant controversy exists in the literature regarding the pitfalls and benefits of minimally invasive total knee arthroplasty (TKA). Regardless, most surgeons today use smaller exposures than in previous years. Although more difficult, rigid adherence to classical gap balancing techniques can allow a surgeon to achieve ideal ligament and flexion/extension gap balance in TKA through a minimally invasive approach. There are certain groups of patients (obesity/medical comorbidities/vascular insufficiency) in whom small incision approaches should not be attempted due to increased risks of wound complications. Additionally, achievement of gap balance requires sequential and safe removal of bone starting with the patellar cut, followed by the distal femoral cut, then by the tibial cut, and concluding with completion of the femoral component cuts. Use of special instruments such as protective metal patellar buttons, medial to lateral distal femoral cutting blocks, and low profile spacer blocks can facilitate the surgical process. Accurate femoral component rotation is more difficult in minimally invasive approaches and must be carefully checked. A tight extensor mechanism in flexion can mislead the surgeon to place the femoral component in an internally rotated position. Furthermore, with limited visualization, surgeons must avoid overaggressive ligament releases early in the procedure prior to completion of bone cuts. However, with appropriate patient selection and a systematic approach to minimally invasive total knee arthroplasty, surgeons can continue to achieve ideal ligament balance with a more soft tissue friendly operation., (Copyright 2010, SLACK Incorporated.)

This study's purpose was to analyze the complications that occurred during and after one surgeon's first 200 two-incision total hip arthroplasties. Complications included 4 intraoperative femur fractures, 4 postoperative femur fractures, 2 nondisplaced greater trochanter fractures greater than 2 cm, 14 asymptomatic greater trochanter fractures 2 cm or less, 1 malpositioned cup requiring revision, 1 loose stem, 7 cases of heterotopic ossification of grade 2 or higher, 4 dislocations, 1 superficial infection, 80 lateral femoral cutaneous nerve neuropraxias (78 resolved within 6 weeks), and 4 femoral nerve neuropraxias (3 resolved within 12 weeks). This study shows that the 2-incision technique can be performed with a low risk of major complications, and patients can expect reduced tissue trauma and faster rehabilitation. When carefully sought out, minor complications were not uncommon after 2-incision total hip arthroplasty., (2010 Elsevier Inc. All rights reserved.)

This study analyzed three dimensional (3D) in vivo kinematic data from the squatting to standing position for 18 Japanese subjects (18 knees) implanted with either Legacy((R)) Posterior Stabilized (LPS) Flex Fixed Bearing TKA or LPS Flex Mobile Bearing TKA. Under weight-bearing conditions, for all patients, the average roll-forward motions for the medial and lateral condyles were 4.0+/-3.6 mm and 6.3+/-3.4 mm, and the average external axial rotation was 3.1 degrees +/-4.1 degrees . For both groups, the weight-bearing range-of-motion (ROM) (110.7 degrees +/-12.7 degrees ) was less than pre (127.2+/-15.5 degrees ) and post (135.6+/-5.4 degrees ) operative non-weight bearing ROM. As hypothesized, the incidence, average and maximum lift off for the squatting to standing activity were much less than those of deep knee bend (DKB), and condylar motions and kinematics were opposite that of the DKB. There was little statistical difference of their kinematic patterns during this activity between the LPS fixed and mobile TKA implants.

This retrospective study examined whether a coralline hydroxyapatite bone graft substitute adequately repaired bone defects during complex acetabular reconstructions. Seventeen patients who underwent acetabular revision using Pro Osteon 500 were assessed to determine whether any cups required re-revision, whether bone had incorporated into the coralline hydroxyapatite grafts, and whether the coralline hydroxyapatite grafts resorbed with time. At latest follow-up, no cups required re-revision, but 1 had failed. Radiographic evidence of bone incorporation was observed in every coralline hydroxyapatite graft. Graft resorption was not observed.

We aimed to determine whether preoperative angular deformity affects survivorship or postoperative alignment after cementless mobile bearing total knee arthroplasty. Nine hundred seventeen knees were grouped according to preoperative mechanical alignment: normal, 0-5 degrees ; abnormal, 6-10 degrees ; severely abnormal, >10 degrees. Ten-year survival estimates were 89.7% for the severely abnormal alignment group, 95.5% for the abnormal alignment group, and 94.9% for the normal alignment group. Postoperatively, normal alignment was restored in 95.6% of knees in the severely abnormal group and 94.5% of knees in the abnormal group. For the normal alignment group, 99.2% of knees remained normally aligned after TKA. These differences in postoperative alignment may explain the severely abnormal alignment group's inferior survivorship outcome. This study shows that cementless mobile bearing implants can be successfully used in a wide range of angulated deformed knees, although preoperatively deformed knees did not do as well as preoperatively undeformed knees.

In cementless acetabular arthroplasty, the interface between the metal backing and the ultra-high-molecular-weight polyethylene acetabular insert surface is a potential source of polyethylene debris. This study of 55 early-generation acetabular inserts found that severe wear of the convex insert surface correlates with osteolysis. Wear of the concave insert surface did not correlate strongly with osteolysis probably owing to prevalent micromotion and wear at the convex surface interface. Although concern over linear wear predominates with contemporary designs, if initial liner engagement is compromised or locking mechanism failure occurs with time, the convex insert surface again may become a significant source of debris contributing to osteolysis.

A quadrant system that defines the safe acetabular locations for screw placement exists for the anatomic hip center. We wanted to develop a similar system for the high hip center. The purposes of our study were to identify the anatomic structures at risk during placement of transacetabular screws in the high hip center, to identify maximum bone depth for screw purchase, and to determine if a high hip center quadrant system could be validated to guide placement of screws during acetabular arthroplasty. For this cadaver study of nine pelves, an acetabulum was reamed superiorly into the high hip center a distance equal to (1/2) of the native acetabular diameter. Screws exiting the acetabular bone by 15 mm were inserted before a computed tomography scan and a precise anatomic dissection were done. Structures at risk of penetration by screws include the external iliac vessels, the obturator nerve and vessels, the superior gluteal nerve and vessels, and the sciatic nerve. We found that a quadrant system at the high hip center can demarcate safe zones for screw placement. At the high hip center, only the peripheral (1/2) of the posterior quadrants are safe for screw placement.

Fluoroscopy has recently been used to analyze postoperative kinematics in total knee arthroplasty (TKA). These analyses have reported varying results even in patients with similar implant design. In addition, patterns of wear in retrieved tibial polyethylene inserts of similar design have been found to vary substantially. These findings suggest that surgical technique, especially soft tissue balancing, may play a role in postoperative kinematics and implant failure. Accurate soft-tissue balancing is hypothesized to result in similar pressures within the medial and lateral compartments of the knee. However, a method of easily measuring these pressures at TKA has not been developed. In the present study, 32 patients were implanted with a mobile-bearing LCS TKA utilizing the balanced gap technique. An electronic pressure sensor, developed specifically to record pressure magnitude and distribution in the medial and lateral compartments, was incorporated into the implant trials. The knee was then passively taken through a range of motion while pressure data was recorded via computer. Postoperatively, 16 patients underwent active fluoroscopic kinematic analysis to assess for condylar liftoff and femorotibial translation. We found that abnormal compartment pressures and distributions as recorded by the intraoperative pressure sensor were correlated with inappropriate or paradoxical postoperative kinematics. In addition, subjects having similar pressures in both compartments throughout a range of motion did not experience condylar liftoff values greater than 1.0 mm. These data suggest that surgical technique influences the magnitude and distribution of forces at the articulation, postoperative kinematics, and likely, implant longevity.

Fluoroscopic and retrieval analyses of knee implants show considerable variability even for the same implant design, and implicate the possible importance of surgical technique and compartment pressure balance in total knee arthroplasties. This study was done to correlate intraoperative computer-assessed compartment pressure measurements with postoperative kinematics to explain these variations. Thirty-eight patients had posterior cruciate-sacrificing low-contact stress total knee arthroplasties using a balanced gap technique. At trial reduction, an instrumented tibial insert designed to record the magnitude, location, and dynamic imprint of the pressures in the medial and lateral compartments was placed into the knee. Pressures were recorded electronically for a range of motion from 0 degrees - 120 degrees. Sixteen of the 38 patients agreed to do successive weightbearing deep knee bends under fluoroscopic surveillance. Only three of the 16 patients had condylar lift-off, but all experienced lift-off at a single flexion angle. In the three patients who had condylar lift-off, a compartment pressure imbalance, as measured by the intraoperative pressure sensor, occurred at the same flexion angle of lift-off. These data suggest that although a given implant design may have inherent kinematic tendencies, surgical technique and compartment pressure balance significantly impact kinematic performance.

Injury to intrapelvic structures during removal of screws in revision acetabular arthroplasty is an uncommon, yet potentially serious complication. Bicortical screws are at greatest risk for causing injury during removal, especially if directed toward intrapelvic vessels and nerves. Complications can be minimized with thorough evaluation of screw position before revision surgery. A study of seven cadaveric pelves was done to determine if plain radiographic views provide useful information regarding screw position. In each pelvis, bicortical transacetabular screws were fixed in all acetabular quadrants 15 mm longer than the measured depth. Afterward, anteroposterior, inlet, Judet, and cross-table lateral radiographic views were obtained and intrapelvic dissections were done. Radiographs and intrapelvic dissections were compared to determine screw position. We found that the obturator and iliac oblique (Judet) views were most useful in defining screw position. The iliac oblique view clearly revealed screws that violated the quadrilateral surface and therefore were directed toward the obturator vessels and nerve. The obturator oblique view revealed screws that violated the anterior column and therefore were directed toward the external iliac vessels. The lateral view additionally clarified such screws by determining general anterior or posterior direction.

Wear of the insert backside occurs ostensibly because of micromotion at the undersurface articulation that occurs with loading. When a cyclic axial load was applied to contemporary knee implants, all inserts tested moved 2 to 25 microm in the shear plane relative to the metal backing suggesting that undersurface motion may be inevitable. Variables that increase the forces between the insert and metal backing can worsen relative micromotion and backside wear. Forces at the undersurface articulation, created during physiologic loading, are influenced by insert type, articular design, and surgical technique. Increasing articular insert constraint can cause forces at the main articulation to be resisted and transferred to this and the other interfaces. Designs with a cam post mechanism that force rollback at a certain flexion angle create a significant force in this shear plane. Inserts with highly conforming articular geometries can have a similar affect if used to inhibit anteroposterior or mediolateral motion of the femur on the tibial insert. Component alignment and position, and ligament balance also may influence backside wear as suggested by the great variability of wear patterns seen on like insert retrievals and by kinematic differences observed in fluoroscopic studies of the same implant design. Only by understanding these potential causes of backside motion and subsequent wear, can backside wear be mitigated.

One hundred six patients treated consecutively with total knee arthroplasty were evaluated to determine whether preoperative comorbidity (as measured by patient class, knee score, short form, anesthesia severity assessment, and number of medical comorbidities) correlated with perioperative and postoperative outcomes, including length of stay, total (and specific) hospital charges, and validated outcome scores. The length of stay for total knee arthroplasty was longer in patients who had lower preoperative knee scores and for patients with greater medical and musculoskeletal morbidity. Greater total hospital costs were associated with Class C patients and patients with poor anesthesia morbidity ratings. Patients who were debilitated medically and had four or more risk factors had decreased postoperative outcome scores. Preoperative medical and musculoskeletal morbidity influence the results of total knee arthroplasty. These findings may be useful to surgeons for optimizing resource utilization and outcomes in patients undergoing total knee arthroplasty. These data must be accounted for when contrasting total knee arthroplasty results between different surgeons and institutions.

Sixty-seven ultrahigh molecular weight polyethylene tibial inserts from cementless total knee arthroplasties were retrieved at autopsy and revision surgery and analyzed for evidence of articular and nonarticular surface wear after a mean implantation time of 62.8 months (range, 4-131 months). Polyethylene cold flow and abrasive wear on the nonarticular insert surface (undersurface) were assigned a wear severity score (Grade 0-4). The severity of articular wear was assessed quantitatively and graded. Corresponding prerevision radiographs were evaluated for evidence of tibial metaphyseal osteolysis and osteolysis around tibial fixation screws. Exact nonparametric conditional inference methods were used to establish correlations between different variables and the occurrence of tibial metaphyseal osteolysis. Severe Grade 4 wear of the tibial insert undersurface was associated with tibial metaphyseal osteolysis or osteolysis around fixation screws. Time in situ statistically was related to Grade 4 undersurface wear and tibial metaphyseal osteolysis. The occurrence of tibial osteolysis was not related statistically to articular wear severity, insert thickness, or implant type. The main articulation between the femoral implant and ultrahigh molecular weight polyethylene insert has been assumed to be the primary source of polyethylene debris contributing to osteolysis and total knee arthroplasty implant failure. The undersurface of the insert is an additional source of polyethylene debris contributing to tibial metaphyseal osteolysis. To lessen polyethylene debris produced at this modular interface, the tibial implant locking mechanism should fix the insert firmly to the metal backing to decrease relative micromotion. Because motion between the insert and metal backing may be inevitable, the wear characteristics of the inner tray surface should be optimized to minimize wear debris production at this other articulation.

Seventy-six consecutive infected total knee arthroplasties in 74 patients were treated between December 1981 and March 1990. The average follow-up period was 57 months (range, 24-121 months). No patients were lost to follow-up evaluation and 12 patients died from unrelated causes. Patients were classified, based on the duration of their symptoms prior to treatment, as acutely infected (< 2 weeks) or chronically infected (> 2 weeks). All knees were evaluated following surgical treatment with radiographs and Knee Society knee score assessment. Successful eradication of infection was defined as a knee without clinical evidence of infection for a minimum of 2 years. The initial treatment modality was successful in eliminating the infection in 69 of 76 patients (90%). Infection was eventually eradicated in 72 of 76 (94%) patients. The individual clinical result was found to be more dependent on a patient's medical and musculoskeletal status (patient class A, B, C) than on knee score or radiographic assessment. Careful treatment selection based on patient class and duration of infection can result in a predictable and successful result.

The initial migration and micromotion of the revision femoral stem stabilized with morselized impacted cancellous allograft and bone-cement and the influence of cement pressurization on fixation of the cement/allograft composite to the host were examined with human cadaver femurs. The stability of the allograft/cemented reconstruction was found to be intermediate between those of conventional cemented and cementless stems. In most cases, the stability of the reconstruction was closer to that of cemented than to that of cementless stems. This may account for histologic findings of graft incorporation in experimental and retrieved specimens reported by other authors. Although increased cement pressurization led to greater penetration of cement into the graft bed, greater cement penetration did not increase fixation strength of the cement/allograft composite to the host.

Fifty-five unconstrained polyethylene tibial inserts were retrieved at revision total knee arthroplasty and examined for evidence of wear after a mean implantation time of 34.2 months (2.5-80 months). Twenty inserts were ultra-high molecular weight polyethylene (UHMWPE) and 35 were carbon-reinforced polyethylene. Topographic maps of the articular and metal-backed surfaces of each component were constructed to characterize the extent and location of polyethylene degradation, identified visually by mode. In 32 of the retrieved inserts, pre- and postarthroplasty or prerevision radiographs were analyzed for component positioning, sizing, and extremity alignment. These factors then were compared with the patterns and severity of polyethylene wear on the inserts to establish correlations. Severe generalized articular wear was seen in inserts with third body wear from patellar metal-backed failure and cement debris. Severe localized delamination wear was seen in inserts with rotational-subluxation patterns of wear (p = 0.05). The external rotation subluxation wear pattern was strongly associated with knees that had lateral subluxation of the patella (p = 0.0002). Articular wear and cold flow into screw holes tended to be greater in the tightest prearthroplasty compartment (medial in the varus knee [p = 0.0157]; lateral in the valgus knees [p = 0.0226]). Fourteen of 16 knees with a preoperative varus deformities--even when corrected to a normal postarthroplasty anatomic axis--still had greater medial compartment articular wear (p = 0.001). Twelve of these knees did not have a medial release at the time of initial arthroplasty. Preoperative varus also was found to be related to the occurrence of posteromedial cold flow of polyethylene into tibial tray screw holes (p = 0.007). Increasing tibial insert posterior slope was associated with increasingly posterior articular wear track location (p = 0.03). This study indicates that unconstrained tibial component wear patterns and severity may be associated with clinical and mechanical factors under the surgeon's control, including component size and position, and knee alignment and ligament balance.

Complete awareness of the anatomy of the pelvis and proximal femur is required if neurologic and vascular complications are to be avoided following total hip arthroplasty. Avoidance of the anterior quadrants for acetabular screw fixation is critical. Cementing techniques are important, and all acetabular and femoral defects should be bone grafted to avoid inadvertent cement migration. Knowledge of the location of pertinent neural and vascular structures should guide retractor placement. Planned lengthening of an extremity during total hip arthroplasty poses a significant risk to neurologic structures, and SSEP monitoring should be considered. In difficult revision procedures and complex primary total hip arthroplasty, preoperative neural and vascular assessment and SSEP monitoring should be done. With the occurrence of a postoperative nerve palsy, careful review of the procedure should be performed to determine the cause of the injury. In this manner the surgeon can best offer appropriate counseling to the patient as to the likelihood of neurologic recovery.

An anatomical and radiographic study was undertaken to determine the safest zones in the acetabulum for the transacetabular placement of screws during uncemented acetabular arthroplasty. To avoid injury to intrapelvic structures, which are not visible to the surgeon during placement of the screws, cadavera were studied to define the location of these structures with respect to fixed points of reference within the acetabulum. Four clinically useful acetabular quadrants were delineated. The quadrants are formed by drawing a line from the anterior superior iliac spine through the center of the acetabulum to the posterior fovea, forming acetabular halves. A second line is then drawn perpendicular to the first at the mid-point of the acetabulum, forming four quadrants. The posterior superior and posterior inferior acetabular quadrants contain the best available bone stock and are relatively safe for the transacetabular placement of screws. The anterior superior and anterior inferior quandrants should be avoided whenever possible, because screws placed improperly in these quadrants may endanger the external iliac artery and vein, as well as the obturator nerve, artery, and vein. The acetabular-quadrant system provides the surgeon with a simple intraoperative guide to the safe transacetabular placement of screws during primary and revision acetabular arthroplasty.