The microbial profile of infected endoprosthetic reconstructions after wide excision for patients with musculoskeletal tumors: A call for pathogen-based practices.

BACKGROUND AND OBJECTIVES: Periprosthetic infection is a devastating complication following endoprosthetic reconstruction. This study utilized a large database of endoprostheses to describe the incidence, risk factors, and microbial profile of such infections to better catalogue and understand these catastrophic events. METHODS: A retrospective review of endoprosthetic reconstructions for an oncologic indication from January 1, 1981 to December 31, 2020 was performed. Demographic, oncologic, procedural and outcome data was analyzed. Multivariable logistic regression was used to identify potential risk factors for infection with significance defined as p < 0.05. RESULTS: Forty four out of 712 (6.2%) reconstructions resulted in infection at a mean time of 39.9 ± 44.5 months. Revision surgery (odds ratio [OR] 6.14, p < 0.001) or having a postoperative wound complication (OR 7.67, p < 0.001) were significantly associated with infection. Staphylococcus aureus and Staphylococcus epidermidis were the most commonly cultured organisms at a rate of 34.1% (15/44) and 22.7% (10/44), respectively. Ten infections resulted in amputation; five due to antimicrobial-resistant infections and three due to polymicrobial infections. CONCLUSION: Understanding the microbial profile of patients undergoing endoprosthetic reconstruction is paramount. This study demonstrates a relatively high rate of polymicrobial and antibiotic-resistant infections that portend worse outcomes, thus suggesting that pathogen-specific infectious practices may be warranted. LEVEL OF EVIDENCE: Retrospective cohort study, level III.

What are the indications and survivorship of tumor endoprosthetic reconstructions for patients with extremity metastatic bone disease?

BACKGROUND AND OBJECTIVES: Given advances in therapies, endoprosthetic reconstruction (EPR) in metastatic bone disease (MBD) may be increasingly indicated. The objectives were to review the indications, and implant and patient survivorship in patients undergoing EPR for MBD. METHODS: A review of patients undergoing EPR for extremity MBD between 1992 and 2022 at two centers was performed. Surgical data, implant survival, patient survival, and implant failure modes were examined. RESULTS: One hundred fifteen patients were included with a median follow-up of 14.9 months (95% confidence interval [CI]: 9.2-19.3) and survival of 19.4 months (95% CI: 13.6-26.1). The most common diagnosis was renal cell carcinoma (34/115, 29.6%) and the most common location was proximal femur (43/115, 37.4%). Indications included: actualized fracture (58/115, 50.4%), impending fracture (30/115, 26.1%), and failed fixation (27/115, 23.5%). Implant failure was uncommon (10/115, 8.7%). Patients undergoing EPR for failed fixation were more likely to have renal or lung cancer (p = 0.006). CONCLUSIONS: EPRs were performed most frequently for renal cell carcinoma and in patients with a relatively favorable survival. EPR was indicated for failed previous fixation in 23.5% of cases, emphasizing the importance of predictive survival modeling. EPR can be a reliable and durable surgical option for patients with MBD.

Proximal Femur Replacements for an Oncologic Indication Offer a Durable Endoprosthetic Reconstruction Option: A 40-year Experience.

BACKGROUND: Proximal femur replacements (PFRs) are an effective surgical option to treat primary and metastatic tumors causing large bony defects in the proximal femur. Given the relative rarity of these indications, current studies on PFR for oncologic indications are generally limited by patient volume or relatively short-term follow-up. Because recent advances in systemic therapy have improved the prognosis of patients who undergo limb salvage surgery for musculoskeletal tumors, data on the long-term durability of endoprosthetic reconstructions have become increasingly important. QUESTIONS/PURPOSES: (1) How does the long-term survival of cemented bipolar PFRs compare with patient survival in patients who underwent PFR for benign, aggressive, and metastatic tumors? (2) What are common reasons for revisions of primary PFRs? (3) Which factors are associated with survival of primary PFRs? (4) What is the survivorship free from conversion of bipolar PFRs to THA? METHODS: Between January 1, 1980, and December 31, 2020, we treated 812 patients with an endoprosthetic reconstruction for an oncologic indication. All patients who underwent a primary PFR for an oncologic indication were included in this study. The study cohort consisted of 122 patients receiving a primary PFR. Eighteen patients did not reach a censored endpoint such as death, revision, or amputation within 2 years. Thirty-three patients died within 2 years of their surgery. Of the 122 patients with primary PFRs, 39 did not reach a censored endpoint and have not been seen within the past 5 years. However, the mean follow-up time for these patients was longer than 10 years. The Social Security Death Index was queried to identify any patients who may have died but might not have been captured by our database To allow for adequate follow-up, endoprosthetic reconstructions performed after December 31, 2020 were excluded. The mean age at the time of the index surgery was 48 ± 22 years. The mean follow-up time of surviving patients was 7 ± 8 years. All PFRs were performed using a bipolar hemiarthroplasty with a cemented stem, and all implants were considered comparable. Demographic, oncologic, procedural, and outcome data including prosthesis survival, patient survival, complication rates, and rates of conversion to THA were analyzed. Patient, prosthesis, and limb salvage survival rates were generated, with implant revision as the endpoint and death as a competing risk. Statistical significance was defined as p < 0.05. RESULTS: Generally, patients with benign or low-grade (Stage I) disease outlived their implants (100% patient survival through 30 years; p = 0.02), whereas the opposite was true in patients with high-grade, localized Stage II disease (64% patient survival at 5 years [95% CI 49% to 76%]; p = 0.001) or widespread Stage III metastatic disease (6.2% patient survival at 5 years [95% CI 0.5% to 24%]; p < 0.001). Primary PFR implant survival at 5, 10, 20, and 30 years was 97% (95% CI 90% to 99%), 81% (95% CI 67% to 90%), 69% (95% CI 46% to 84%), and 51% (95% CI 24% to 73%), respectively. Eight percent (10 of 122) of primary PFRs were revised for any reason. The most common causes of revision were aseptic loosening (3% [four of 122]), infection (3% [three of 122]), breakage of the implant (2% [two of 122]), and tumor progression (1% [one of 122]). Follow-up time was the only factor that was associated with revision of primary PFRs. Neither segment length nor stem length were associated with revision of primary. Six percent (seven of 122) of PFRs were converted to THA at a mean 15 ± 8 years from the index procedure. Survivorship free from conversion to THA (accounting for death as a competing risk) was 94% (95% CI 85% to 99%), 86% (95% CI 68% to 94%). and 77% (95% CI 51% to 91%) at 10, 20, and 30 years, respectively. CONCLUSION: Cemented bipolar PFRs for an oncologic indication are a relatively durable reconstruction technique. Given the relative longevity and efficacy of PFRs demonstrated in our study, especially in patients with high-grade or metastatic disease where implant survival until all-cause revision was longer than patient survival, surgeons should continue to seriously consider PFRs in appropriate patients. The relative rarity of these reconstructions limits the number of patients in this study as well as in current research; thus, further multi-institutional collaborations are needed to provide the most accurate prognostic data for our patients. LEVEL OF EVIDENCE: Level III, therapeutic study.

What Is the Long-term Survivorship of Primary and Revision Cemented Distal Femoral Replacements for Limb Salvage of Patients With Sarcoma?

BACKGROUND: Cemented endoprosthetic reconstruction after resection of primary bone sarcomas has been in common use for decades. Although multiple studies have reported the survivorship of primary endoprostheses, implant survivorship after revision surgery is less well established. Given that earlier advances in systemic therapy improved survival of patients with sarcoma, the usage of revision endoprostheses can be expected to increase and, as such, understanding revision implant survivorship will help to inform patient and surgeon expectations. Additionally, as new implants are developed that allow alternative reconstruction options, a normative dataset establishing accurate expectations for revision cemented endoprostheses is a critical benchmark by which to measure progress. QUESTIONS/PURPOSES: (1) What is the implant survivorship free of all-cause revision for primary and revision cemented distal femoral replacements (DFRs) used in the treatment of malignant or benign tumors? (2) What are the most common indications for revision of primary and revision DFRs in an oncology population with mean follow-up of more than 10 years? (3) How does the indication for revision of a primary DFR affect the subsequent risk for and type of revision DFR complication? (4) What patient, tumor, or implant characteristics are associated with improved survivorship free of revision in cemented DFRs used in patients treated initially for primary malignant or benign tumors? METHODS: This was a retrospective, comparative study using our institution's longitudinally-maintained database of 806 cemented endoprostheses starting in 1980 and assessed through December 31, 2018. In all, 365 DFRs were inserted during this time, but 14% (51 of 365) were placed for nonprimary bone tumors and 1% (5 of 365) were cementless reconstructions, leaving 309 cemented DFRs. Seventy-one percent (218 of 309) were primary implants and 29 percent (91 of 309) were revision implants (used to revise a prior DFR in all patients). During this time period, our strong bias was to use cemented stems and, thus, nearly all of our patients had cemented stems. Six percent (13 of 218) of primary DFRs were implanted more than 2 years before the study end; however, they lacked 2 years of follow-up data and, thus, were considered lost to follow-up, leaving 205 implants in the primary DFR analysis group. Only the first revision after primary DFR revision surgery was included in the revision cohort analysis. Thirty-two percent (29 of 91) of revision DFRs were second or more revision patients and were excluded, leaving 62 implants in the revision analysis group. Most patients in both groups were men (57% [117 of 205] for primary and 71% [44 of 62] for revision) who had been diagnosed with osteosarcoma (75% [153 of 205] and 73% [45 of 62] for primary and revision, respectively). The primary cohort had mean age of 26 ± 16 years with a mean follow-up of 136 ± 122 months, and the revision cohort had mean age of 31 ± 13 years (p = 0.02) with 141 ± 101 months of follow-up. Study endpoints included all-cause implant revision and cause-specific revision for soft tissue complications, aseptic loosening, structural complications (defined as periprosthetic or implant fracture), infection, or tumor progression. Planned surgery for implant lengthening procedures was excluded. Implant survivorship free from all-cause revision was calculated using a competing risk (cumulative incidence) estimator with death as a competing risk. A log-rank test using chi-square analysis was used to evaluate the differences in implant survivorship between primary DFRs and first revisions. The cause-specific incidences of implant revision were tabulated for primary and revision DFRs. Cox regression analysis investigated the odds of subsequent all-cause revision surgery for revision cemented DFRs based on the primary implant complication. A binary logistic regression analysis using age, gender, indication for revision, tumor type, infection, perioperative chemotherapy, and radiation was performed to identify factors associated with a second DFR reoperation. Relative effect sizes are reported as ORs. RESULTS: The revision DFR cohort had a shorter mean survival to all-cause revision than the primary cohort (mean 10 years [95% CI 7 to 12] versus 18 years [95% CI 15 to 20]; p < 0.001). The most common complications necessitating revision for revision implants were periprosthetic or implant fracture in 37% (23 of 62) and aseptic loosening in 15% (9 of 62), and the type of primary implant complication was not associated with risk of subsequent all-cause revision surgery for revision implants. Stem diameter less than 15 mm was associated with repeat all-cause revision in cemented revision DFRs after controlling for resection length, stem length, implant fabrication (custom or modular), and presence of a porous collar (OR 4 [95% CI 1 to 17]; p = 0.03). No other parameters that we explored, including patient age, gender, chemoradiation history, or primary tumor diagnosis, were associated with repeat revision surgery. CONCLUSION: Understanding modifiable factors that can improve revision DFR survival is critical to achieving long-term limb salvage for patients with tumors around the knee. Our data suggest that utilizing implants with the largest possible stems-or at a minimum increasing the stem size over the primary implant-is important to revision cemented DFR survivorship and is an important part of our revision practice. Improving revision implants' resistance to aseptic loosening through designs that resist torsion (a common mode of cemented fixation failure)-such as with the use of custom cross-pin fabrication-may be one method to improve survivorship. Another will be improved implant metallurgy that is resistant to fatigue fracture. Next steps may include understanding the optimal ratio of femoral diaphyseal width to implant diameter in patients where anatomic constraints preclude the insertion of cemented stems 15 mm or more in diameter. LEVEL OF EVIDENCE: Level IV, therapeutic study.

Is High-dose Radiation Therapy Associated With Early Revision Due to Aseptic Loosening in Patients With a Sarcoma of the Lower Extremities Reconstructed With a Cemented Endoprosthesis?

BACKGROUND: The durability of endoprostheses after limb salvage surgery is influenced by surgical factors (resection length, implant location, and residual bone quality), implant design (modular versus custom design, rotating versus fixed hinge, coating, collars, and the use of cross pins), and host factors (patient's immune status, activity levels, and age). In general, radiation therapy increases the risk of fractures, infection, delayed wound healing, and impaired osseointegration. Several studies have shown exposure to radiation to be associated with higher endoprosthesis revision rates and higher periprosthetic infection rates, but results are inconsistent. Although radiation therapy is not routinely used in the treatment of many bone sarcomas in current practice, it is still used in high doses after resection and prosthetic reconstruction in patients who have Ewing sarcoma with close or positive margins and in patients with soft tissue sarcoma. It is also used in varying doses after prosthetic reconstruction in patients with myeloma or bone metastasis after resection of periarticular destructive tumors. These patients may be at an increased risk of complications due to their radiation exposure, but this is a difficult question to study given the rarity of these diagnoses and poor overall survival of these patients. We therefore leveraged a large, longitudinally collected, 40-year endoprosthesis database that included patients who received radiation to the extremity for many bone and soft tissue sarcomas to investigate the association between preoperative or postoperative radiation therapy and endoprosthesis survival. QUESTIONS/PURPOSES: (1) Is receiving preoperative or postoperative radiation therapy in low or high doses for the treatment of bone or soft tissue malignancy of the lower extremities associated with decreased implant survivorship free from amputation or revision due to any cause? (2) Is receiving preoperative or postoperative radiation therapy in low or high doses for the treatment of bone or soft tissue malignancy of the lower extremities associated with decreased implant survivorship free from revision specifically due to aseptic loosening? (3) Is receiving preoperative or postoperative radiation therapy for the treatment of Ewing sarcoma of the femur specifically associated with decreased implant survivorship free from revision specifically due to aseptic loosening? METHODS: This was a retrospective, comparative study using our institution's database of 822 endoprostheses. Between 1980 and 2019, we treated 541 patients with primary cemented endoprostheses of the extremities. Of those patients, 8% (45 of 541) were excluded due to unknown radiation status, 3% (17 of 541) because of prior failed allograft, 15% (83 of 541) due to metastatic disease from a carcinoma, 1% (6 of 541) due to a nononcologic diagnosis, 4% (20 of 541) due to benign tumor diagnosis, 16% (87 of 541) due to upper extremity tumor location, 9% (49 of 541) due to not receiving chemotherapy, and 3% (14 of 541) due to expandable prostheses. Of the remaining 220 patients, 6% (13) were considered missing because they did not have 2 years of follow-up and did not reach a study endpoint. No patients had surgery within the last 2 years of the study end date. In all, 207 patients met inclusion criteria and were eligible for analysis. Patients who had received radiation to the lower extremities at any point in their treatment course were included in the radiation group and were compared with patients who did not receive radiation. For patients where radiation dose was available, the radiation group was subdivided into a low-dose (≤ 3000 cGy) and high-dose (> 3000 cGy) group. Revision surgery was defined as any surgery necessitating removal or replacement of the tibial or femoral stem. The complications necessitating revision or amputation were poor wound healing, aseptic loosening, implant breakage, deep infection, and tumor progression. The primary outcome of interest was implant survival free from revision or amputation due to any cause. The secondary outcome of interest was implant survival free from revision or amputation specifically due to aseptic loosening. The Kaplan-Meier survivorship curves were generated with implant survival free from revision or amputation as the endpoint and patient death as a competing risk. A log-rank test was used to identify differences in survivorship between the patients who received radiation and those who did not. Multivariate regression was used to identify factors associated with decreased implant survival. An odds ratio was used to determine relative effect size among the factors associated with decreased implant survival. RESULTS: The mean implant survival time for patients who did not receive radiation was 18.3 years (95% confidence interval [CI] 15.4 to 21.3) whereas the mean implant survival time for patients who received low- and high-dose radiation were 19.1 years (95% CI 14.5 to 23.7; p = 0.59) and 13.8 years (95% CI 8.2 to 19.5; p = 0.65), respectively. The mean implant survival free from revision for aseptic loosening for patients who did not receive radiation was 27.1 years (95% CI 24.1 to 30.1) whereas the mean implant survival for patients who received low- and high-dose radiation were 24.1 years (95% CI 19.1 to 29.1; p = 0.34) and 16.4 years (95% CI 10.6 to 22.2; p = 0.01), respectively. Patients who received high-dose radiation had decreased 5-year implant survivorship free from amputation or revision due to aseptic loosening (73% [95% CI 44% to 89%]) compared with patients who did not receive radiation (95% [95% CI 90% to 99%]; p = 0.01). For patients treated for Ewing sarcoma of the femur, the 5-year implant survival free from amputation or revision due to aseptic loosening for patients who did not receive radiation (100% [95% CI 100% to 100%]) was no different compared with patients who received radiation (71% [95% CI 35% to 90%]; p = 0.56). CONCLUSION: The results of this study may apply to scenarios where radiation is used, such as Ewing sarcoma with positive margins or local recurrence and after prosthetic reconstruction in patients with myeloma or bone metastasis after resection of periarticular destructive tumors. Surgeons may consider closer monitoring for early clinical and radiographic signs of aseptic loosening in patients who received high-dose radiation. These patients may also benefit from constructs that have increased resistance to aseptic loosening such as cross-pin or side plate fixation. The association between radiation and aseptic loosening should be further studied with larger studies with homogeneity in tumor diagnosis and prosthesis. The dose-dependent relationship between radiation and bone-related complications may also benefit from controlled, laboratory-based biomechanical studies. LEVEL OF EVIDENCE: Level III, therapeutic study.

Management of Distal Radius Fractures in Adolescent Patients.

BACKGROUND: While management recommendations for distal radius fractures in both young and skeletally mature patients have been generally well-established, controversy still exists regarding optimal management in adolescent patients approaching skeletal maturity. Thus, the goal of this review is to analyze relevant literature and provide expert recommendations regarding the management of distal radius fractures in this patient population. METHODS: A PubMed search was performed to identify literature pertaining to distal radius fractures in adolescent patients, defined as 11 to 14 years in girls and 13 to 15 years in boys. Relevant articles were selected and summarized. RESULTS: Distal radius fractures demonstrate significant potential for remodeling of angular deformity and bayonet apposition, even in patients older than 12 years of age. Rotational forearm range of motion and functional outcomes are acceptable with up to 15 degrees of residual angulation. Closed reduction and percutaneous pinning reduces fracture redisplacement but has a high associated complication rate. There is no literature comparing plate versus pin fixation of distal radius fractures in the pediatric population, but in adults plate fixation is associated with higher cost with no improvement in long-term functional outcomes. CONCLUSIONS: Remodeling can still be expected to occur in adolescent patients, and even with residual deformity functional outcomes after distal radius fractures are excellent. Up to 15 degrees of residual angulation can be accepted before considering operative management. Smooth pins should be considered over plates as first-line operative management for unstable fractures that fail nonoperative treatment.

When Should Instrumentation to the Pelvis be Considered in Minimally Ambulatory Adolescents With Neuromuscular Scoliosis?

INTRODUCTION: The goal of neuromuscular scoliosis (NMS) surgery is to improve sitting balance, facilitate daily care, and alleviate pain. In nonambulatory patients, where sitting balance is key, fusion to the pelvis is usually required. However, in minimally ambulatory patients, fusion to the pelvis remains controversial, and there is considerable practice variability in this patient population. The purpose of this study is to evaluate and summarize the available evidence regarding fusion constructs in minimally ambulatory patients with NMS and to provide expert opinion regarding when fusion to the pelvis should be considered. METHODS: A search of the English literature was performed using PubMed to identify papers pertaining to patients with NMS treated with instrumented posterior spinal fusion. Papers published before 2000, case reports, and level V evidence were excluded. RESULTS: The authors identified 8 studies for review. The majority included both nonambulatory and minimally ambulatory patients. Structured review of the literature demonstrated fusion to the pelvis may allow for greater curve and pelvic obliquity correction, but it is also associated with increased blood loss and operative time. There is no evidence that fusing to the pelvis decreases ambulatory status in minimally ambulatory patients. CONCLUSIONS: In minimally ambulatory patients with NMS, fusion short of the pelvis may be considered in patients with adequate head control without the presence of hip subluxation or dislocation and when pelvic obliquity is <15 degrees. Fusion to the pelvis is recommended in patients who do not meet these criteria.

Metaphyseal Stem Tip Location is a Risk Factor for Aseptic Loosening of Cemented Distal Femoral Replacements.

BACKGROUND: The objective of this study was to describe the incidence of aseptic loosening (AL) of cemented stem distal femoral replacements (DFR) and to identify modifiable risk factors for its development. METHODS: A retrospective review was performed of 245 consecutive primary, cemented stem DFRs implanted at a single institution over a 40-year period. The primary outcome was revision surgery for AL. A multivariate analysis was performed to identify risk factors for AL. Radiographs were reviewed to identify stem tip location, which was defined as diaphyseal or metaphyseal. Implant survival to AL was compared using Kaplan-Meier analysis. RESULTS: AL and structural failure were the most common causes of implant failure (incidence 11.8%, 29/245). Younger age (P = .002), male sex (P = .01), longer resection length (P = .04), and nonmodular implants (P = .002) were all significantly associated with AL. After 1:1 matching, stem tip location in metaphyseal bone was independently associated with AL (P = .04). 36% (9/25) of implants that loosened had a stem tip located in the metaphysis vs only 8% (2/25) of implants that did not fail. 30-year survival to AL was lower for implants with a metaphyseal stem tip than implants with a diaphyseal stem tip (22.7% vs 47.6%; P = .11). CONCLUSION: A stem tip location in metaphyseal bone is associated with diminished survival to AL. When templating before DFR, stem tip location can assist in identifying high-risk reconstructions that may benefit from alternative or supplemental fixation techniques to prevent the development of AL.

Long term outcomes of total humeral replacement for oncological reconstructions: A single institution experience.

BACKGROUND: There is a paucity of data on long-term survivorship and outcomes for total humerus replacements (THR) with only two series reporting 10-year survival. PATIENTS AND METHODS: A review of 769 consecutive, prospectively collected endoprosthetic reconstructions for oncological diagnoses at a single-center between 1980 and 2019 was performed. Patients with THRs were isolated and analyzed for outcomes, complications, and modes of failure. RESULTS: Eighteen patients with 20 THR implants were identified. The median follow-up for surviving patients was 148 months (interquartile range [IQR] = 74-194) and 60 months (IQR = 17-155 months) for all patients. Two prostheses required revision for failure, both for symptomatic shoulder dislocation. There were three local recurrences. Revision-free survival at 5, 10, and 15 years was 100%, 86% and 86%, respectively. There were no cases of ulnar component failure, radial nerve palsy, or periprosthetic infection. CONCLUSIONS: THR prosthesis survivorship is comparable to the previous series, with a longer follow-up than has previously been reported. Symptomatic shoulder instability was common (25%), and was the only cause of revision. Reverse total shoulder could be an important way to address this in the future. Local recurrence rates were high, as has been reported elsewhere for THR.

Defining a Safe Zone for All-Inside Lateral Meniscal Repairs in Pediatric Patients: A Magnetic Resonance Imaging Study.

PURPOSE: To establish a safe zone for all-inside meniscal fixation in pediatric patients by use of magnetic resonance imaging (MRI) measurements between the popliteal tendon (PT) and popliteal neurovascular bundle (PNVB). METHODS: Patients aged 5 to 16 years with normal or nearly normal knee MRI scans were included. They were grouped by age: group I, 5 to 7 years (n = 61); group II, 8 to 10 years (n = 59); group III, 11 to 13 years (n = 60); and group IV, 14 to 16 years (n = 70). At the level of the lateral meniscus, 2 lines starting at the lateral patellar tendon border and ending at the medial edge of the PT (D1) and the lateral edge of the PNVB (D2) were made on an axial knee MRI scan. A third line (D3) connected D1 to D2 at the meniscocapsular junction of the posterior horn of the lateral meniscus (PHLM). A fourth line (D4), derived geometrically, was parallel and 8 mm anterior to D3, simulating the anterior edge of the PHLM. RESULTS: Axial MRI scans of 250 pediatric patients (aged 5-16 years) were retrospectively reviewed. Analysis showed significant correlation between age and sex for D3 (P < .0001). For D3, there were significant differences among all age groups, except between groups III and IV. The average D3 by age group was 14.1 mm (standard deviation [SD], 3.1 mm) for group I, 15.8 mm (SD, 2.5 mm) for group II, 17.0 mm (SD, 3.3 mm) for group III, and 17.2 mm (SD, 3.1 mm) for group IV. The average D4 was 11.39 mm (SD, 2.6 mm), 13.24 mm (SD, 2.24 mm), 14.59 mm (SD, 2.89 mm), and 14.80 mm (SD, 2.79 mm), respectively. There were significant differences in D3 and D4 in male versus female patients (17.6 mm vs 15.7 mm, P < .001, and 14.9 mm vs 13.2 mm, P < .001, respectively), particularly in groups III and IV (17.0 mm vs 13.8 mm and 16.8 mm vs 13.9 mm, respectively). CONCLUSIONS: This study provides normative data of the distance between the PNVB and PT at the meniscocapsular junction (D3) and anterior edge of the PHLM (D4) with the knee in full extension. Combined with previous studies showing that the addition of knee flexion increases the distance between the meniscus and the neurovascular bundle, these data can be used by surgeons to improve the safety of PHLM repair in pediatric patients. LEVEL OF EVIDENCE: Level III, diagnostic study of nonconsecutive patients.

Multicenter Analysis of the Epidemiology of Injury Patterns and Return to Sport in Collegiate Gymnasts.

Background: Gymnastics requires intense year-round upper and lower extremity strength training typically starting from an early age. As such, the injury patterns observed in these athletes may be unique. Purpose: To characterize the types of injuries and provide return-to-sport data in male and female collegiate gymnasts. Study Design: Descriptive epidemiology study. Methods: A conference-specific injury database was utilized to perform a retrospective review of injuries for male and female National Collegiate Athletic Association (NCAA) Division I gymnasts within the Pacific Coast Conference between 2017 and 2020 (N = 673 gymnasts). Injuries were stratified by anatomic location, sex, time missed, and injury diagnoses. Relative risk (RR) was used to compare results between sexes. Results: Of the 673 gymnasts, 183 (27.2%) experienced 1093 injuries during the study period. Injuries were sustained in 35 of 145 male athletes (24.1%) as compared with 148 of 528 female athletes (28.0%; RR, 0.86 [95% CI, 0.63-1.19]; P = .390). Approximately 66.1% (723/1093) of injuries occurred in a practice setting, compared with 84 of 1093 injuries (7.7%) occurring during competition. Overall, 417 of 1093 injuries (38.2%) resulted in no missed time. Shoulder injuries and elbow/arm injuries were significantly more common in male versus female athletes (RR, 1.99 [95% CI, 1.32-3.01], P = .001; and RR, 2.08 [95% CI, 1.05-4.13], P = .036, respectively). In total, 23 concussions affected 21 of 673 athletes (3.1%); 6 concussions (26.1%) resulted in the inability to return to sport during the same season. Conclusion: For the majority of musculoskeletal injuries, the gymnasts were able to return to sport during the same season. Male athletes were more likely to experience shoulder and elbow/arm injuries, likely because of sex-specific events. Concussions occurred in 3.1% of the gymnasts, highlighting the need for vigilant monitoring. This analysis of the incidence and outcomes of injuries observed in NCAA Division I gymnasts may guide injury prevention protocols as well as provide important prognostic information.

Characterizing Health Events and Return to Sport in Collegiate Swimmers.

Background: There is limited literature characterizing the incidence, variety, and effects of injuries and illnesses observed in elite swimmers. Purpose: To describe the epidemiology of injuries and illnesses affecting elite intercollegiate competitive swimmers. Study Design: Descriptive epidemiology study. Methods: This retrospective study utilized a deidentified injury and illness database of National Collegiate Athletic Association Division I swimmers in the Pacific Coast Conference from the academic years 2016 to 2017 and 2019 to 2020. A health event was defined as an illness or musculoskeletal injury that was identified by an athletic trainer or team physician. Musculoskeletal injuries and nonmusculoskeletal injuries and illnesses were stratified by body location. Injuries were further characterized as career-ending, season-ending, missed time but the athlete returned to sport in the same season, or those that did not cause missed time. Relative risk (RR) was used to compare the percentage of athletes affected between women and men, with statistical significance being defined by a 95% CI not including 1. Results: Included were 641 collegiate swimmers (301 male, 340 female). There were 1030 health events among 277 women and 173 men, with 635 (61.7%) occurring in women and 395 (38.3%) in men. There were 540 musculoskeletal injuries reported, most of which involved the shoulder (n = 126; 23.3%), spine (n = 95; 17.6%), foot/ankle/lower leg (n = 81; 15.0%), knee/thigh (n = 67; 12.4%), and hand/wrist/forearm (n = 52; 9.6%). A total of 490 nonmusculoskeletal health events were reported and included events such as respiratory tract infections (n = 119; 24.3%), unspecified medical illness (n = 93; 19.0%), concussions (n = 58; 11.8%), ear infections (n = 25; 5.1%), and gastrointestinal illnesses (n = 24; 4.9%). Compared with male swimmers, female swimmers were at a higher risk of sustaining both musculoskeletal injury (RR, 1.5; 95% CI, 1.22-1.83) and nonmusculoskeletal injury/illness (RR, 1.32; 95% CI, 1.04-1.68). There were 58 documented concussions, with 8 (13.8%) being season-ending, but not career-ending and 14 (24.1%) being career-ending. Women had a higher rate of concussion (9.1% vs 4.3% for men; RR, 2.11; 95% CI, 1.13-3.96). Conclusion: This retrospective study identified the most common injuries and illnesses observed among elite collegiate swimmers. Awareness of the incidence and outcome of injuries and illnesses that affect competitive swimmers may allow for more targeted analyses and injury prevention strategies.

The Utility of Virtual Reality in Orthopedic Surgical Training.

OBJECTIVE: To examine the efficacy of virtual reality (VR) to prepare surgical trainees for a pediatric orthopedic surgery procedure: pinning of a slipped capital femoral epiphysis (SCFE). DESIGN: Participants were randomly assigned to a standard, study guide (SG) group or to a VR training group. All participants were provided a technique video and SG; the VR group additionally trained via an Osso VR surgical trainer (ossovr.com) with real-time feedback and coaching from an attending pediatric orthopedic surgeon. Following training, participants performed a SCFE guidewire placement on a SawBones model embedded in a soft-tissue envelope (SawBones model 1161). Participants were asked to achieve "ideal placement" based on the training provided. Participants were evaluated on time, number of pin "in-and outs," penetration of the articular surface, angle between the pin and the physis, distance from pin tip to subchondral bone and distance from the center-center point of the epiphysis. SETTING: Orthopedic Institute for Children, Los Angeles, CA. PARTICIPANTS: Twenty fourth-year medical students, first- and second-year orthopedic residents without experience with the SCFE procedure. RESULTS: Twenty participants were randomized to SG (n = 10) or VR (n = 10). Average time to final pin placement was 19% shorter in VR group (706 vs 573 seconds, p = 0.26). When compared to SG, the VR group had, on average, 70% less pin in-and-outs (1.7 vs 0.5, p = 0.28), 50% less articular surface penetrations (0.4 vs 0.2, p = 0.36), and 18% smaller distance from pin tip to subchondral bone on lateral view (7.1 vs 5.8 mm, p = 0.42). Moreover, the VR group had a lower average angle deviation between pin and line perpendicular to the physis on coronal view (4.9° vs 2.5°, p < 0.05). CONCLUSIONS: VR training is potentially more effective than traditional preparatory methods. This pilot study suggests that VR training may be a viable surgical training tool, which may alleviate constraints of time, money, and safety concerns with resultant broad applicability for surgical education.

Thoracic Outlet Syndrome in Major League Baseball Pitchers: Return to Sport and Performance Metrics After Rib Resection.

Background: Thoracic outlet syndrome (TOS) is a rare injury that affects Major League Baseball (MLB) pitchers and is often corrected with surgical resection of the first rib. There are limited return-to-play (RTP) data for this surgery in MLB pitchers. Hypothesis: It was hypothesized that MLB pitchers who undergo first rib resection for TOS will show (1) a high rate of RTP, (2) no difference in postoperative career length compared with controls, (3) no difference in pre- and postoperative performance, and (4) no difference in postoperative performance compared with controls. Study Design: Cohort study; Level of evidence, 3. Methods: This retrospective cohort study evaluated MLB pitchers with neurogenic or vascular TOS who underwent rib resection surgery between January 1, 2001, and December 31, 2019. Players were identified through public injury reports from press releases, the MLB website, MLB team injury reports, and blogs. A demographics- and performance-matched control group was generated for comparison. Each player in the control group was given an index year that corresponded to the surgery year of the case group. Performance data included innings pitched (IP), games played (GP), earned run average (ERA), complete GP, shutouts, saves, hits, runs, home runs (HR), walks, strikeouts (K), walks plus hits per IP (WHIP), and earned runs (ER). Results: We identified 26 MLB pitchers who underwent rib resection for neurogenic or vascular TOS; 21 players (81%) had a successful RTP. Pitchers were 30 ± 3.6 years old at the time of surgery and had played 6.2 ± 3.5 seasons before undergoing surgery. Average postoperative career length was 3.1 ± 2.0 seasons, with an average time from surgery to RTP being 10 ± 4.7 months. Pitchers who RTP showed no significant differences in performance metrics compared with controls. Players pitch 0.94 (P < .05) more IP/GP in the season directly following RTP compared with the season before surgical intervention. Conclusion: MLB pitchers undergoing rib resection for TOS demonstrated (1) high RTP rates following rib resection, (2) no difference in postoperative career length compared with controls, (3) improvement in postoperative performance, and (4) no difference in postoperative performance compared with controls.

Intermittent and Transient Hypotension-related Anterior Cord Syndrome following Elective Cervical Spine Surgery: A Case Report.

INTRODUCTION: Anterior cord syndrome (ACS) is a type of incomplete spinal cord injury caused by either direct compression of the anterior spinal cord, or by ischemia of the anterior spinal artery. This phenomenon has neither been described transiently nor intraoperatively. CASE REPORT: We describe the case of a 61-year-old male who developed intermittent and transient anterior spinal cord syndrome secondary to hypotension related hypoperfusion of the anterior spinal artery after elective cervical spine surgery. Through close blood pressure monitoring and intensive care unit support, the patient regained full neurological recovery. CONCLUSION: Anterior spinal cord syndrome is a rare condition affecting the anterior 2/3 of the spinal cord, resulting in incomplete paralysis. Blood flow can be disrupted through the anterior spinal artery, either through thrombosis or hypotension. We describe our rare case so that surgeons may recognize this potentially devastating condition.

Incidence and Risk Factors for the Development of Acute Colonic Pseudo-Obstruction (Ogilvie Syndrome) in Total Joint Arthroplasty Patients.

BACKGROUND: Acute colonic pseudo-obstruction (Ogilvie syndrome [OS]) is a rare but devastating condition that can develop in orthopaedic patients postoperatively. The objective of this study was to identify the risk factors for developing OS after total hip arthroplasty (THA) or total knee arthroplasty (TKA) and to compare the outcomes between patients who did and did not develop OS postoperatively. METHODS: This was a retrospective review using the National Inpatient Sample, a national database incorporating inpatient hospitalization information. ICD-9 codes were used to identify patients who underwent primary and revision THA or TKA. Patients were separated based on the diagnosis of OS. Primary outcomes assessed included patient mortality, postoperative complications, length of stay, and cost during index hospitalization. RESULTS: From 2001 to 2014, a total of 12,541,169 patients underwent primary and revision THA or TKA. Of those, 3,182 patients (0.03%) developed OS postoperatively. There was an increased incidence of OS in revision THA and TKA compared with primary THA and TKA. Fluid and electrolyte disorders were associated with the largest increased adjusted risk of OS. Patients with OS had an increased adjusted risk of overall postoperative complications and being discharged to skilled nursing facility. Patients with OS had an increased average length of stay and hospitalization cost compared with patients without OS. DISCUSSION: Given our findings, the risk factors for the development of OS, including revision surgery, should be identified and minimized during the perioperative period to prevent the development of this morbid and potentially life-threatening complication. LEVEL OF EVIDENCE: III (Retrospective cohort study).

Platelet Deficiency Represents a Modifiable Risk Factor for Periprosthetic Joint Infection in a Preclinical Mouse Model.

BACKGROUND: Well known for their hemostatic function, platelets are increasingly becoming recognized as important immunomodulators. The purpose of the present study was to assess the impact of platelet depletion on antimicrobial host defense in a mouse model of periprosthetic joint infection (PJI). METHODS: Thrombocytopenia (TCP) was induced in C57BL/6 mice with use of a selective antibody against platelet CD41 (anti-CD41). Whole blood from pre-treated mice was incubated with Staphylococcus aureus to assess antimicrobial efficacy with use of bioluminescent imaging, quantitative histological staining, and colony forming unit (CFU) quantification. In parallel, untreated heterologous platelets were added to TCP blood to assess potential rescue of antimicrobial efficacy. In vivo, TCP and control mice underwent placement of a titanium implant in the femur inoculated with bioluminescent Xen36 S. aureus. Longitudinal bioluminescent imaging was performed postoperatively to quantify the evolution of bacterial burden, which was confirmed via assessment of S. aureus CFUs on the implant and in peri-implant tissue on postoperative day (POD) 28. RESULTS: Anti-CD41 treatment resulted in significant dose-dependent reductions in platelet count. Ex vivo, platelet-depleted whole blood demonstrated significantly less bacterial reduction than control blood. These outcomes were reversed with the addition of untreated rescue platelets. In vivo, infection burden was significantly higher in TCP mice and was inversely correlated with preoperative platelet count (r2 = 0.63, p = 0.037). Likewise, CFU quantification on POD28 was associated with increased bacterial proliferation and severity of periprosthetic infection in TCP mice compared with controls. CONCLUSIONS: Thrombocytopenia resulted in an increased bacterial burden both ex vivo and in vivo in a mouse model of PJI. CLINICAL RELEVANCE: In orthopaedic patients, deficiencies in platelet quantity or function represent an easily modifiable risk factor for PJI.

Active rheumatoid arthritis in a mouse model is not an independent risk factor for periprosthetic joint infection.

INTRODUCTION: Periprosthetic joint infection (PJI) represents a devastating complication of total joint arthroplasty associated with significant morbidity and mortality. Literature suggests a possible higher incidence of periprosthetic joint infection (PJI) in patients with rheumatoid arthritis (RA). There is, however, no consensus on this purported risk nor a well-defined mechanism. This study investigates how collagen-induced arthritis (CIA), a validated animal model of RA, impacts infectious burden in a well-established model of PJI. METHODS: Control mice were compared against CIA mice. Whole blood samples were collected to quantify systemic IgG levels via ELISA. Ex vivo respiratory burst function was measured via dihydrorhodamine assay. Ex vivo Staphylococcus aureus Xen36 burden was measured directly via colony forming unit (CFU) counts and crystal violet assay to assess biofilm formation. In vivo, surgical placement of a titanium implant through the knee joint and inoculation with S. aureus Xen36 was performed. Bacterial burden was then quantified by longitudinal bioluminescent imaging. RESULTS: Mice with CIA demonstrated significantly higher levels of systemic IgG compared with control mice (p = 0.003). Ex vivo, there was no significant difference in respiratory burst function (p = 0.89) or S. aureus bacterial burden as measured by CFU counts (p = 0.91) and crystal violet assay (p = 0.96). In vivo, no significant difference in bacterial bioluminescence between groups was found at all postoperative time points. CFU counts of both the implant and the peri-implant tissue were not significantly different between groups (p = 0.82 and 0.80, respectively). CONCLUSION: This study demonstrated no significant difference in S. aureus infectious burden between mice with CIA and control mice. These results suggest that untreated, active RA may not represent a significant intrinsic risk factor for PJI, however further mechanistic translational and clinical studies are warranted.

Outcomes of Total Hip Arthroplasty in Patients With Acetabular Protrusio.

BACKGROUND: Acetabular protrusio (AP) is associated with distorted anatomic landmarks and insufficient bone stock that increases complexity of total hip arthroplasty (THA). This study used a large national database to compare outcomes after THA in patients with and without AP. METHODS: The Nationwide Readmissions Database was used to identify patients with and without AP who underwent THA from 2010 to 2014. Primary outcomes analyzed included complications during index hospitalization and within 90 days of THA. RESULTS: Propensity score matching generated 4,395 patients without AP and 4,603 patients with AP. Patients with AP were older (68.1 versus 65.2 years, P < 0.0001), more predominantly women (82.1% versus 55.9%), and had more medical comorbidities as measured by the Elixhauser Comorbidity Index (2.29 versus 1.89, P < 0.0001). Patients with AP had an increased risk of requiring bone graft (odds ratio [OR] = 47.97, 95% confidence interval [CI]: 14.27 to 161.22), receiving a blood transfusion (OR = 1.90, 95% CI: 1.57 to 2.29), and suffering a periprosthetic fracture (OR = 2.56, 95% CI: 1.10 to 5.97) within 90 days of THA. Length and cost of index hospitalization were greater for patients with AP (5.0 versus 4.3 days, P = 0.002; $19,211.88 versus $27,736.30, P < 0.0001). CONCLUSION: Given the current emphasis on hospital cost optimization, it is important to ensure that patients with AP are managed appropriately. Attention should be placed on comprehensive preoperative planning and postoperative monitoring in this population.

Current Trends in Orthopaedic Surgery Residency Applications and Match Rates.

BACKGROUND: The current U.S. orthopaedic residency application process is becoming increasingly impersonal in the wake of an increasing number of applications. Through an analysis of orthopaedic surgery residency application statistics, we have highlighted the effect that the number of orthopaedic applications has on match rate, and we have suggested methods for a more personalized application process. METHODS: Data from the Association of American Medical Colleges (AAMC) and the National Resident Matching Program (NRMP) for United States orthopaedic residency applicants from 2008 to 2018 were collected. These data included the average number of applications submitted per applicant, the average number of applications received per program, the total number of residency positions offered in the U.S., the total number of U.S. applicants, and the total number of U.S. applicants who matched to a U.S. orthopaedic surgery residency program. U.S. applicant match rates and the average number of applications received per residency position offered were calculated. Linear regression models were used to determine the rate at which these variables changed over time. RESULTS: The average number of applications submitted by an applicant increased from 46.5 in 2008 to 74.9 in 2018. The average number of applications received per residency position offered increased from 54.1 in 2008 to 85.7 in 2018. The number of U.S. applicants was 740 in 2008 and 849 in 2018. The number of U.S. orthopaedic residency programs only slightly increased from 160 in 2008 to 171 in 2018. The match rate for U.S. medical school applicants has remained stable from 2008 to 2018 at a mean of 76.9% and a standard deviation of 2.3%. CONCLUSIONS: The match rate has remained stable from 2008 to 2018 despite an increase in the number of applications per position. This discrepancy suggests that increasing the number of submitted applications may not correlate with applicant success. We address this discrepancy and suggest methods that can potentially allow for a more targeted orthopaedic application experience.