Low Incidence of Postoperative Complications With Navigated Total Knee Arthroplasty.

BACKGROUND: A number of postoperative complications of navigated total knee arthroplasty (TKA) have been discussed in the literature, including tracker pin site infection and fracture. In this article, we discuss the low postoperative complication rate in a series of 3100 navigated TKAs and the overall complication rate in a systematic analysis of the literature. METHODS: Three thousand one hundred consecutive patients with navigated TKAs from 2001-2016 were retrospectively evaluated for complications specific to navigation. We discuss the 2 cases of postoperative fracture through tracker pin sites that we experienced and compare this systematically with the literature. RESULTS: Postoperatively, our 3100 patient cohort experienced a total of 2 fractures through pin sites for an incidence of 0.065%. One was a distal femoral fracture which was treated surgically, and the other was a proximal tibial fracture treated nonoperatively. Because of our incorporation of the tracker sites within our operative incision, there were no identifiable pin site infections, which others have noted at an incidence of 0.47%. Our 0.065% fracture rate compares favorably with the 0.16% rate of fracture published in the literature. CONCLUSION: There is an extremely low risk of perioperative complications because of the instrumentation used in navigated TKA when using the Stryker Navigation System and 4.0 mm anchoring pins placed within the surgical incision.

Short Term Outcomes of a Hydroxyapatite Coated Metal Backed Patella.

We retrospectively evaluated the records and radiographs of 101 knees with a hydroxyapatite coated metal backed patella (HAP) and 50 knees with a cemented polyethylene patella (CP) with minimum two year clinical follow up. There were no patellar revisions during the study period. Patients in both the HAP and CP groups had similar clinical outcomes at final follow-up. Forty-five percent of patients in the HAP group had 1-2mm areas of decreased trabecular bone density around the pegs, which were not observed in the CP group, and may represent stress shielding. This uncemented HAP component has satisfactory early clinical outcomes, but long-term follow up is necessary to determine the durability of this implant.

The Surgical Outcomes of Pedicle Subtraction Osteotomy per Different First Assistant: Retrospective Analysis of 312 Cases.

INTRODUCTION: Pedicle subtraction osteotomies (PSOs) are complex spinal deformity surgeries that are associated with high complication rates. They are typically done by an experienced spine surgeon with another attending, resident, or physician assistant serving as the first assistant. The purpose of this study was to determine whether selecting a surgical team for single-level PSO based on case difficulty and fusion length could equalize intraoperative and perioperative outcomes among three groups: dual-attending (DA), attending and orthopaedic resident (RS), and attending and physician assistant (PA). METHODS: This study was a retrospective cohort analysis of 312 patients undergoing single-level thoracic or lumbar PSO from January 2007 to December 2020 by a fellowship-trained orthopaedic spine surgeon. Demographic, intraoperative, and perioperative data within 30 days and 2 years of the index procedure were analyzed. RESULTS: Patient demographics did not markedly differ between surgical groups. The mean cohort age was 64.5 years with BMI 31.9 kg/m 2 . Patients with the DA approach had a significantly longer surgical time (DA = 412 min vs. resident = 372 min vs. physician assistant = 323 min; P < 0.001). Patients within the DA group experienced a significantly lower rate of infection (DA = 2.1% [3/140] vs. RS = 7.9% [9/114] vs. PA = 1.7% [1/58], P = 0.043), surgical complication rate (DA = 26% [37/140] vs. RS = 41% [47/114] vs. PA = 33% [19/58], P < 0 .001), and readmission rate (DA = 6.4% [9/140] vs. RS = 12.3% [14/114] vs. PA = 19% [11/58] P = 0.030) within 30 days of surgery. No notable differences were observed among groups in 2-year complication, infection, readmission, or revision surgery rates. CONCLUSIONS: These study results support the DA surgeon approach. Resident involvement, even in less complex cases, can still negatively affect perioperative outcomes. Additional selection criteria development is needed.

Superficial Femoral Artery Pseudoaneurysm After Intra-articular Adductor Canal Pain Catheter Placement for Total Knee Arthroplasty.

Vascular injury following total knee arthroplasty (TKA) is a rare complication. The authors present a case of superficial femoral artery aneurysm in a 60-year-old man following elective TKA in the setting of intra-articular On-Q* (Avanos Medical) pain catheter placement into the adductor canal for postoperative pain control. This is the second reported case of pseudoaneurysm secondary to adductor canal block. The patient presented on postoperative day 8 with thigh swelling, ecchymosis, and pain. The pseudoaneurysm was subsequently diagnosed and successfully stented after selective catheterization. The patient was discharged the next day. This case highlights the importance for a high index of suspicion in patients presenting with acute swelling in the postoperative period. If identified in a timely fashion, treatment with stenting or selective catheter embolization can successfully treat this issue and help avoid further complications. [Orthopedics. 2023;46(1):e58-e61.].

Expansion of myeloid-derived suppressor cells contributes to metabolic osteoarthritis through subchondral bone remodeling.

BACKGROUND: Osteoarthritis (OA) subsequent to acute joint injury accounts for a significant proportion of all arthropathies. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of myeloid progenitor cells classically known for potent immune-suppressive activity; however, MDSCs can also differentiate into osteoclasts. In addition, this population is known to be expanded during metabolic disease. The objective of this study was to determine the role of MDSCs in the context of OA pathophysiology. METHODS: In this study, we examined the differentiation and functional capacity of MDSCs to become osteoclasts in vitro and in vivo using mouse models of OA and in MDSC quantitation in humans with OA pathology relative to obesity status. RESULTS: We observed that MDSCs are expanded in mice and humans during obesity. MDSCs were expanded in peripheral blood of OA subjects relative to body mass index and in mice fed a high-fat diet (HFD) compared to mice fed a low-fat diet (LFD). In mice, monocytic MDSC (M-MDSC) was expanded in diet-induced obesity (DIO) with a further expansion after destabilization of the medial meniscus (DMM) surgery to induce post-traumatic OA (PTOA) (compared to sham-operated controls). M-MDSCs from DIO mice had a greater capacity to form osteoclasts in culture with increased subchondral bone osteoclast number. In humans, we observed an expansion of M-MDSCs in peripheral blood and synovial fluid of obese subjects compared to lean subjects with OA. CONCLUSION: These data suggest that MDSCs are reprogrammed in metabolic disease, with the potential to contribute towards OA progression and severity.

Reliability of measuring long-standing lower extremity radiographs.

The mechanical axis of the lower extremity was measured using preoperative long-standing radiographs in 56 patients undergoing total knee arthroplasty with the Stryker Navigation System (Stryker, Kalamazoo, Mich). Each radiograph was measured by four physicians, three times, in random order, and at delayed intervals. Measurements from each physician produced intraclass correlation coefficients of 0.9872, 0.9973, 0.9958, and 0.9839. An intraclass correlation coefficient of 0.9844 was noted between each of the raters. Pre- and postoperative axial alignments were determined with Stryker Navigation. Preoperatively, each rater overestimated deformity approximately 1 degrees (P>.05); however, postoperatively each rater underestimated the degree of deformity by approximately 1 degrees (P>.05). Measuring long-standing lower extremity radiographs provides significant inter- and intrarater reliability in determining lower extremity alignment.

Effect of one- and two-pin reference anchoring systems on marker stability during total knee arthroplasty computer navigation.

OBJECTIVE: This study investigated different infrared marker reference base attachments in cadaveric bone and their effects on alignment outcome when different loads were applied. MATERIAL AND METHODS: Five cadaveric specimens were used to test four reference base attachments: a locking one-pin (4.0 mm and 5.0 mm pins) and a two-pin clamp (Hoffman fixator, 3.0 mm and 5.0 mm pins, Stryker Inc., NJ). Each was tested with metaphyseal and diaphyseal attachments. A navigation system (Stryker Navigation, MI) was used for testing with applied incremental loads and torques (65 N and 1.0 Nm) to the different reference base configurations. RESULTS: With 65 N the maximum change in distance to a verification point was 4.3 + 1.6 mm with the 4.0 mm locking pin in metaphyseal bone. No difference in verification point distances was found with any two-pin configuration. Alignment changes greater than 4 degrees resulted with the 65 N loads and a 4.0 mm pin. CONCLUSION: The results may prove beneficial in comparing the resulting error of different manufacturers and allow surgeons to realize the variability that may occur through incidental contact in the operating room.

Preoperative administration of epoetin alfa to total joint arthroplasty patients.

Epoetin alfa is indicated to reduce allogeneic transfusions in patients undergoing major operations. This study included 40 patients undergoing total joint arthroplasty who received 600 IU/kg doses of epoetin alfa 21, 14, and 7 days preoperatively. Statistically equal matches were obtained according to preoperative hemoglobin, operation, sex, and age. After controlling for autologous donation, the average hemoglobin level on postoperative day one in the treatment group (10.93 g/dL) was significantly higher than the matched patient group (9.86 g/dL). Likewise, treated patients were transfused with significantly less blood (0.68 units/patient) compared to the matched group (1.6 units/patient). In these patients, administration of epoetin alfa was associated with significantly higher perioperative hemoglobin levels and significantly fewer transfusions than matched counterparts. The use of epoetin alfa in this heterogeneous surgical population illustrates its success in a varied population.

Torsion deformity and joint loading for medial knee osteoarthritis.

PURPOSE: The consequences of lower limb torsion deformity on knee loading in knee osteoarthritis are poorly understood. The purpose of this study was to quantify the associations between the mechanical axis, tibial torsion and knee loading in subjects with medial knee OA and in controls. METHODS: Twenty-four subjects: end-staged medial knee osteoarthritis (OA) with apparent torsion deformity (TKO, n=6) and without torsion deformity (KOA, n=8) and controls (CON, n=10) were imaged using long standing lower extremity (LSLE) radiographs and computed tomography (CT). Medial knee loading was assessed using the internal knee varus moment determined by gait analysis. The LSLE mechanical axis, CT tibial torsion and the foot progression angle were used to predict medial knee loading. RESULTS: The TKOs had significantly greater mechanical axis varus and knee varus moment compared to KOAs and CONs. The regression model predicting medial knee loading using the mechanical axis (ß=0.898), tibial torsion (ß=0.264) and foot progression angle (ß=-0.369) showed a goodness of fit of 0.774. CONCLUSIONS: Medial knee loading was predicted by the mechanical axis and the foot progression angle. Future longitudinal studies are needed to assess the role of tibial intorsion during disease progression and following total knee replacement surgery.

Passive knee kinematics before and after total knee arthroplasty: are we correcting pathologic motion?

The change in coronal plane deformity throughout a range of flexion before and after total knee arthroplasty (TKA) has not been reported. Unlike most alignment assessments traditionally reporting coronal plane alignment in a standing position under static conditions, this study reports deformity throughout the flexion arc before and after deformity correction. One hundred fifty-two TKA patients using the anteroposterior axis for femoral component rotation and computer navigation techniques were included in the study. Deformity before TKA ranged from 17.5 degrees varus (deformity apex away from the midline) to 20.5 degrees valgus (deformity apex toward the midline) in full extension. Before TKA, deformity was not constant through an arc of motion and significantly decreased with flexion of 60 degrees and more (P < .01). The deformity after performing a TKA was not different (P = .478) throughout the flexion arc. The data determined that deformity is not constant throughout flexion in osteoarthritic knees preoperatively and that deformity throughout flexion can be corrected with the use of conventional alignment techniques during TKA.

Enhancing femoral cement fixation in total knee arthroplasty.

Several factors have been shown to be associated with early development of radiolucent lines at the bone-cement interface in total knee arthroplasty (TKA). The posterior condylar surfaces, in particular, seem subject to poor cement technique, which could lead to early loosening. This study compares two cementation techniques in TKA, with respect to depth of cement penetration and radiolucency in the posterior condyles. All penetration depths were greater in group I (injected) versus group II (noninjected). Sixty-seven percent of group I showed penetration depths >1.5 mm compared with 23% of group II. No specimen in group I had gaps in the cement mantle on visual inspection or radiolucency on radiographic evaluation. No statistical differences, however, could be demonstrated between the two groups.

Reliability and validity of a new caliper for measuring patellar thickness.

The process of patellar resurfacing during total knee arthroplasty involves measuring patellar thickness. The optimal residual patellar bone thickness has been questioned. The surgeon's ability to measure patellar thickness currently rests on a standard caliper. Standard methods involve use of a smooth-mouthed caliper, which can overestimate patellar thickness because of soft tissue interposition. This brief communication introduces a new spiked caliper design that can be used to measure patellar bone thickness more accurately. Improved accuracy in measuring patellar bone thickness allows the operating surgeon to assess more correctly a patient's patellar bony status. This knowledge may result in fewer postoperative fracture complications resulting from deficiencies of bone owing to excessive resection.

A radiographic study of the detection limits of bone-cement remnants in total joint arthroplasty.

Management of an infected hip prosthesis typically requires that all associated cement be removed. In the absence of gross mantle loosening, the surgeon frequently resorts to intraoperative radiographs to assess the completeness of removal. For this reason, we undertook a study to determine limits of detection of retained cement by routine radiography. Polymethyl methacrylate bone-cement beads (Simplex-P; Stryker-Howmedica-Osteonics, Allendale, NJ) were fashioned into graduated sizes and placed within cadaver medullary canals using 2 different methods. Standard radiographic images were obtained. Individually and independently, we viewed these images and proposed the limit of resolution to be 2.4 to 3.2 mm. It is difficult to remove all cement based on radiographs alone. These results suggest a need to use techniques that permit visualization of the canal to ensure adequate cement removal.