Oxidized Zirconium Versus Cobalt Chromium for Primary TKA: No Difference in Midterm Revision Rates From the American Joint Replacement Registry.

BACKGROUND: Cobalt chromium (CoCr) is the most commonly used material in TKA; however, the use of oxidized zirconium (OxZr) implants has increased. The advantages to this material demonstrated in basic science studies have not been borne out in clinical studies to date. QUESTION/PURPOSE: In the setting of the American Joint Replacement Registry (AJRR), how do revision rates differ between CoCr and OxZr after primary TKA? METHODS: The AJRR was accessed for all primary TKAs performed between 2012 and 2020 for osteoarthritis, resulting in 441,605 procedures (68,506 with OxZr and 373,099 with CoCr). The AJRR is the largest joint replacement registry worldwide and collects procedure-specific details, making it ideal for large-scale comparisons of implant materials in the United States. Competing risk survival analyses were used to evaluate the all-cause revision rates of primary TKAs, comparing CoCr and OxZr implants. Data from the Centers for Medicare and Medicaid Services claims from 2012 to 2017 were also cross-referenced to capture additional revisions from other institutions. Revision rates were tabulated and subclassified by indication. Multivariate Cox regression was used to account for confounding variables such as age, gender, region, and hospital size. RESULTS: After controlling for confounding variables, there were no differences between the OxZr and CoCr groups in terms of the rate of all-cause revision at a mean follow-up of 46 ± 23 months and 44 ± 24 months for CoCr and OxZr implants, respectively (hazard ratio 1.055 [95% confidence interval 0.979 to 1.137]; p = 0.16) The univariate analysis demonstrated increased rates of revisions for pain and instability in the OxZr group (p = 0.003 and p < 0.001, respectively). CONCLUSION: These findings suggest there is no difference in all-cause revision between OxZr and CoCr implants in the short-term to mid-term. However, further long-term in vivo studies are needed to monitor the safety and all-cause revision rate of OxZr implants compared with those of CoCr implants. OxZr implants may be favorable in patients who have sensitivity to metal. Despite similar short-term to mid-term all-cause revision rates to CoCr implants, because of the limitations of this study, definitive recommendations for or against the use of OxZr cannot be made. LEVEL OF EVIDENCE: Level III, therapeutic study.

Contributions of Pubic Rami Fracture Morphology and Fixation to Pelvic Ring Stability in Type 1 Lateral Compression Injuries: A Biomechanical Cadaveric Study.

BACKGROUND: Treatment of lateral compression type 1 (LC-1) injuries has historically been nonoperative with immediate weight-bearing. However, management of these injuries remains controversial, with reports of displacement at follow-up for nonoperatively managed LC-1 fractures. The goal of our study was to determine the effect of superior pubic ramus fracture morphology and fixation construct on pelvic stability. METHODS: Ten fresh-frozen cadaveric were transected into hemi-pelvises. Incomplete Denis type 1 sacral fractures were made. Hemi-pelvises were randomized to receive a transverse-type or oblique-type superior pubic ramus fracture with the contralateral hemi-pelvis receiving the opposing morphology. A lateral load to 135N was applied with an Instron materials testing machine and lateral displacement of the hemi-pelvis was recorded. Deflection and stiffness were calculated. Statistical analysis was conducted using a t test assuming unequal variances with an alpha = 0.05. RESULTS: Oblique-type superior pubic ramus fractures allowed more deflection compared with transverse-type fractures in the absence of fixation (P = 0.018). The posterior-only and combined anterior and posterior fixation configurations on average reduced deflection more than no fixation or anterior fixation only. In all fixation configuration cases, the average deflection for transverse-type fractures was less than that of the oblique-type fractures. CONCLUSIONS: Our findings suggest that displacement of LC-1 pelvic injuries may be related to pubic rami fracture morphology. When looking at initial injury imaging, oblique-type pubic rami fractures may suggest an increased potential for displacement over time. In such cases, we recommend an examination under anesthesia to evaluate for underlying instability and consideration for fixation. LEVEL OF EVIDENCE: Therapeutic Level V.

Superficial Siderosis Misdiagnosed As Parkinson's Disease in a 70-year-old Male Breast Cancer Survivor.

A 70-year-old African American male with a history of hypertension, congestive heart failure, breast cancer status-post six rounds of doxorubicin/cyclophosphamide, and Parkinson's disease managed with carbidopa/levodopa presented to the emergency department with bilateral hearing loss and ataxia. The patient was admitted and evaluated for possible traumatic, oncological, and pharmacological etiologies. Further investigation revealed hypointensities along the cerebellar folia and basal cisterns on MRI in addition to the two-year history of progressive bilateral hearing loss and gait ataxia. In view of these findings, the patient was diagnosed with superficial siderosis and Parkinson's medications were discontinued. Superficial siderosis should be considered as a diagnosis in cases of bilateral hearing loss and ataxia in patients with history of anticoagulation and risk factors for prior cerebrovascular accidents or head trauma.

Treatment of Zone 1 Fractures of the Proximal Fifth Metatarsal With CAM-Walker Boot vs Hard-Soled Shoes.

BACKGROUND: Zone 1 fractures of the proximal fifth metatarsal are usually treated nonsurgically using some type of immobilization. The aim of this study was to compare clinical and functional outcomes, time to return to prior activity levels, and rate of bone healing when using a hard-soled shoe (HSS) vs a controlled ankle motion (CAM)-walker boot (CWB). METHODS: Seventy-two consecutive patients with zone 1 fractures of the fifth metatarsal base were treated conservatively with either an HSS or CWB by 2 different providers. We included 57 women and 15 men, average age of 41.3 (range, 16-88) years. Radiographic findings, visual analog scale (VAS) for pain, and American Orthopaedic Ankle & Foot Society (AOFAS) midfoot score were assessed. Patients were followed at 4, 8, 10, 12, and 24 weeks or until asymptomatic and able to return to prior level of activities. Statistical analysis was performed using Mann-Whitney U, Fisher exact, and chi-square tests. P values <.05 were considered significant. RESULTS: Age and gender distributions were similar in both groups (P = .23 and P = .57). Patients had similar VAS and AOFAS scores after 8 (P = .34 and P = .83) and 12 (P = .87 and P = .79) weeks. Average time for bone healing was significantly faster using the CWB (7.2 weeks) when compared to the HSS (8.6 weeks) (P < .001). The average time to return to prior level of activities was similar in both groups (8.3 weeks for CWB and 9.7 weeks for HSS) (P = .11). Fracture displacement was equal in both groups, with a mean of 1.9 mm of displacement in patients using the HSS, and a mean of 1.6 mm in those using the CWB (P = .26). CONCLUSION: Zone 1 fractures of the proximal fifth metatarsal can be treated conservatively with either a hard-soled shoe or a CAM-walker boot. Even though patients treated in the CAM-walker boot demonstrated earlier signs of complete healing, similar clinical and functional results were achieved with both treatments. LEVEL OF EVIDENCE: Level III, retrospective comparative series.