Displaced Meniscus Tear in the Acute Postoperative Period After Total Hip Arthroplasty: A Case Report.

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.

Radiographic and Clinical Outcomes Following Robotic-Assisted Lateral Unicompartmental Knee Arthroplasty.

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.

Liposomal Bupivacaine Versus Standard Periarticular Injection in Total Knee Arthroplasty With Regional Anesthesia: A Prospective Randomized Controlled Trial.

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.

Use of bovine thrombin to reduce blood loss in primary total knee arthroplasty: a controlled randomized trial.

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.

Gap balancing through small incisions: competing goals.

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.

One surgeon's experience with the 2-incision technique for total hip arthroplasty.

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.

In vivo kinematic determination of total knee arthroplasty from squatting to standing.

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.

Lack of axial rotation in mobile-bearing knee designs.

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.

Coralline hydroxyapatite in complex acetabular reconstruction.

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.

The effect of varus and valgus deformity on results of cementless mobile bearing TKA.

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.

The acetabular insert-metal backing interface: an additional source of polyethylene wear debris.

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.

Acetabular anatomy and transacetabular screw fixation at the high hip center.

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.

Correlation of compartment pressure data from an intraoperative sensing device with postoperative fluoroscopic kinematic results in TKA patients.

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.

An intraoperative pressure-measuring device used in total knee arthroplasties and its kinematics correlations.

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.

Radiographic evaluation of screw position in revision total hip arthroplasty.

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.

The causes of insert backside wear in total knee arthroplasty.

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.