Fabricating patient-specific 3D printed drill guides to treat femoral head avascular necrosis.

BACKGROUND: Femoral head avascular necrosis (AVN), or death of femoral head tissue due to a lack of blood supply, is a leading cause of total hip replacement for non-geriatric patients. Core decompression (CD) is an effective treatment to re-establish blood flow for patients with AVN. Techniques aimed at improving its efficacy are an area of active research. We propose the use of 3D printed drill guides to accurately guide therapeutic devices for CD. METHODS: Using femur sawbones, image processing software, and 3D modeling software, we created a custom-built device with pre-determined drill trajectories and tested the feasibility of the 3D printed drill guides for CD. A fellowship trained orthopedic surgeon used the drill guide to position an 8 ga, 230 mm long decompression device in the three synthetic femurs. CT scans were taken of the sawbones with the drill guide and decompression device. CT scans were processed in the 3D modeling software. Descriptive statistics measuring the angular and needle-tip deviation were compared to the original virtually planned model. RESULTS: Compared to the original 3D model, the trials had a mean displacement of 1.440 ± 1.03 mm and a mean angle deviation of 1.093 ± 0.749º. CONCLUSIONS: The drill guides were demonstrated to accurately guide the decompression device along its predetermined drill trajectory. Accuracy was assessed by comparing values to literature-reported values and considered AVN lesion size. This study demonstrates the potential use of 3D printing technology to improve the efficacy of CD techniques.

The feasibility of a novel 3D-Printed patient specific cutting guide for extended trochanteric osteotomies.

BACKGROUND: The extended trochanteric osteotomy (ETO) is a surgical technique utilized to expose the intramedullary canal of the proximal femur, protect the soft tissues and promote reliable healing. However, imprecise execution of the osteotomy can lead to fracture, soft tissue injury, non-union, and unnecessary morbidity. We developed a technique to create patient specific, 3D-printed cutting guides to aid in accurate positioning of the ETO and improve osteotomy quality and outcomes. METHODS: Patient specific cutting guides were created based on CT scans using Synopysis Simpleware ScanIP and Solidworks. Custom 3D printed cutting guides were tested on synthetic femurs with foam cortical shells and on cadaveric femurs. To confirm accuracy of the osteotomies, dimensions of the performed osteotomies were compared to the virtually planned osteotomies. RESULTS: Use of the patient specific ETO cutting guides resulted in successful osteotomies, exposing the femoral canal and the femoral stem both in synthetic sawbone and cadaveric testing. In cadaveric testing, the guides allowed for osteotomies without fracture and cuts made using the guide were accurate within 6 percent error from the virtually planned osteotomy. CONCLUSION: The 3D-printed patient specific cutting guides used to aid in ETOs proved to be accurate. Through the iterative development of cutting guides, we found that a simple design was key to a reliable and accurate guide. While future clinical trials in human subjects are needed, we believe our custom 3D printed cutting guide design to be effective at aiding in performing ETOs for revision total hip arthroplasty surgeries.

Fabricating Patient-Specific 3D Printed Drill Guides to Treat Femoral Head Avascular Necrosis.

Background: Femoral head avascular necrosis (AVN), or death of femoral head tissue due to a lack of blood supply, is a leading cause of total hip replacement for non-geriatric patients. Core decompression (CD) is an effective treatment to re-establish blood flow for patients with AVN. Techniques aimed at improving its efficacy are an area of active research. We propose the use of 3D printed drill guides to accurately guide therapeutic devices for CD. Methods: Using femur sawbones, image processing software, and 3D modeling software, we created a custom-built device with pre-determined drill trajectories and tested the feasibility of the 3D printed drill guides for CD. A fellowship trained orthopedic surgeon used the drill guide to position an 8 ga, 230 mm long decompression device in the three synthetic femurs. CT scans were taken of the sawbones with the drill guide and decompression device. CT scans were processed in the 3D modeling software. Descriptive statistics measuring the angular and needle-tip deviation were compared to the original virtually planned model. Results: Compared to the original 3D model, the trials had a mean displacement of 1.440±1.03 mm and a mean angle deviation of 1.093±0.749°. Conclusions: The drill guides were demonstrated to accurately guide the decompression device along its predetermined drill trajectory. Accuracy was assessed by comparing values to literature-reported values and considered AVN lesion size. This study demonstrates the potential use of 3D printing technology to improve the efficacy of CD techniques.

An analytical model of lateral condylar plate working length.

BACKGROUND: The locking plate is a common device to treat distal femur fractures. Healing is affected by construct stiffness, thus many surgeon-controlled variables such as working length have been examined for their effects on strain at the fracture. No convenient analytical model which aids surgeons in determining working length has yet been described. We propose an analytical model and compare it to finite element analysis and cadaveric biomechanical testing. METHODS: First, an analytical model based on a cantilever beam equation was derived. Next, a finite element model was developed based on a CT scan of a "fresh-frozen" cadaveric femur. Third, biomechanical testing in single-leg stance loading was performed on the cadaver. In all methods, strain at the fracture was recorded. An ANCOVA test was conducted to compare the strains. FINDINGS: In all models, as the working length increased so did strain. For strain at the fracture, the shortest working length (35 mm) had a strain of 8% in the analytical model, 9% in the finite element model, and 7% for the cadaver. The longest working length (140 mm) demonstrated strain of 15% in the analytical model, and the finite element and biomechanical tests both demonstrated strain of 14%. INTERPRETATION: The strain predicted by the analytical model was consistent with the strain observed in both the finite element and biomechanical models. As demonstrated in existing literature, increasing the working length increases strain at the fracture site. Additional work is required to refine and establish validity and reliability of the analytical model.

Simulating Prophylactic Fixation Methods for Osteoporotic Femoral Neck Fracture Prevention.

Introduction: Geriatric patients who suffer femoral neck fractures have high morbidity and mortality. Prophylactic fixation of the femoral neck is a potential avenue to reduce the incidence of femoral neck fractures. We studied 3 different implants traditionally used to stabilize the femoral neck: 6.5 mm cannulated screws (CANN), the femoral neck system (FNS) (Depuy Synthes), and the dynamic hip screw (DHS) (Depuy Synthes). Materials and Methods: Five osteoporotic Sawbone femurs were used for each model and a control group. Two scenarios were investigated: single leg stance to measure construct stiffness and lateral impact to measure construct stiffness, energy to fracture, and qualitative examination of fracture patterns. Stiffness for each femur and energy to fracture for the lateral impact scenario were calculated and compared between groups using one-way ANOVA. Results: DHS showed significantly higher stiffness than the other 2 implants and the control in single leg stance. In the lateral impact scenario, the DHS and CANN were significantly stiffer FNS and the control. Femurs implanted with CANN tended to fracture at the greater trochanter while FNS fractured in a transverse subtrochanteric pattern, and DHS fractured obliquely in the subtrochanteric region. Discussion: FNS and DHS experienced fracture patterns less amenable to surgical correction. CANN and DHS proved better able to resist external forces in the lateral fall scenario. CANN also proved better able to resist external forces in the single leg stance scenario and experienced a more amenable fracture pattern in the lateral fall scenario. Conclusions: FNS was less able to resist external forces compared with the other implants. This work informs the potential implications between the choice of implants that, although historically have not been used prophylactically, may be considered in the future for prophylactic stabilization of the femoral neck. Cadaveric study and clinical trials are recommended for further study.

Accuracy of guide wire placement for femoral neck stabilization using 3D printed drill guides.

BACKGROUND: The goal of stabilization of the femoral neck is to limit morbidity and mortality from fracture. Of three potential methods of fixation, (three percutaneous screws, the Synthes Femoral Neck System, and a dynamic hip screw), each requires guide wire positioning of the implant(s) in the femoral neck and head. Consistent and accurate positioning of these systems is paramount to reduce surgical times, stabilize fractures effectively, and reduce complications. To help expedite surgery and achieve ideal implant positioning in the geriatric population, we have developed and validated a surgical planning methodology using 3D modelling and printing technology. METHODS: Using image processing software, 3D surgical models were generated placing guide wires in a virtual model of an osteoporotic proximal femur sawbone. Three unique drill guides were created to achieve the optimal position for implant placement for each of the three different implant systems, and the guides were 3D printed. Subsequently, a trauma fellowship trained orthopedic surgeon used the 3D printed guides to position 2.8 mm diameter drill bit tipped guide wires into five osteoporotic sawbones for each of the three systems (fifteen sawbones total). Computed Tomography (CT) scans were then taken of each of the sawbones with the implants in place. 3D model renderings of the CT scans were created using image processing techniques and the displacement and angular deviations at guide wire entry to the optimal sawbone model were measured. RESULTS: Across all three percutaneous screw guide wires, the average displacement was 3.19 ± 0.12 mm and the average angular deviation was 4.10 ± 0.17o. The Femoral Neck System guide wires had an average displacement of 1.59 ± 0.18 mm and average angular deviation of 2.81 ± 0.64o. The Dynamic Hip Screw had an average displacement of 1.03 ± 0.19 mm and average angular deviation of 2.59 ± 0.39o. CONCLUSION: The use of custom 3D printed drill guides to assist with the positioning of guide wires proved to be accurate for each of the three types of surgical strategies. Guides which are used to place more than 1 guide wire may have lower positional accuracy, as the guide may shift during multiple wire insertions. We believe that personalized point of care drill guides provide an accurate intraoperative method for positioning implants into the femoral neck.

A Case-Control Study of Hip Fracture Surgery Timing and Mortality at an Academic Hospital: Day Surgery May Be Safer than Night Surgery.

Time from hospital admission to operative intervention has been consistently demonstrated to have a significant impact on mortality. Nonetheless, the relationship between operative start time (day versus night) and associated mortality has not been thoroughly investigated. Methods: All patients who underwent hip fracture surgery at a single academic institution were retrospectively analyzed. Operative start times were dichotomized: (1) day operation-7 a.m. to 4 p.m.; (2) night operation-4 p.m. to 7 a.m. Outcomes between the two groups were evaluated. Results: Overall, 170 patients were included in this study. The average admission to operating room (OR) time was 26.0 ± 18.0 h, and 71.2% of cases were performed as a day operation. The overall 90-day mortality rate was 7.1% and was significantly higher for night operations (18.4% vs. 2.5%; p = 0.001). Following multivariable logistic regression analysis, only night operations were independently associated with 90-day mortality (aOR 8.91, 95% confidence interval 2.19-33.22; p = 0.002). Moreover, these patients were significantly more likely to return to the hospital within 50 days (34.7% vs. 19.0%; p = 0.029) and experience mortality prior to discharge (8.2% vs. 0.8%; p = 0.025). Notably, admission to OR time was not associated with in-hospital mortality (29.22 vs. 25.90 h; p = 0.685). Hip fracture surgery during daytime operative hours may minimize mortalities.

Crossing the Cervicothoracic Junction in Cervical Arthrodesis Results in Lower Rates of Adjacent Segment Disease Without Affecting Operative Risks or Patient-Reported Outcomes.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: To evaluate the risks and benefits of crossing the cervicothoracic junction (CTJ) in cervical arthrodesis. SUMMARY OF BACKGROUND DATA: Whether the CTJ should be crossed in cervical arthrodesis remains up for debate. Keeping C7 as the distal end of the fusion risks adjacent segment disease (ASD) and can result in myelopathy or radiculopathy. Longer fusions are thought to increase operative risk and complexity but result in lower rates of ASD. MATERIALS AND METHODS: Patients undergoing cervical spine fusion surgery ending at C7 or T1 with ≥1-year follow-up were included. To evaluate operative risk, estimated blood loss (EBL), operative time, and length of hospital stay were collected. To evaluate patient-reported outcomes (PROs), Neck Disability Index (NDI) and SF-12 questionnaires (PCS12 and MCS12) were obtained at follow-up. Revision surgery data were also obtained. RESULTS: A total of 168 patients were included and divided into a C7 end-of-fusion cohort (NC7=59) and a T1 end-of-fusion cohort (NT1=109). Multivariate regression analysis adjusting for age, sex, race, surgical approach, and number of levels fused showed that EBL (P=0.12), operative time (P=0.07), and length of hospital stay (P=0.06) are not significantly different in the C7 and T1 end-of-fusion cohorts. Multivariate regression of PROs showed no significant difference in NDI (P=0.70), PCS12 (P=0.23), or MCS12 (P=0.15) between cohorts. Fisher analysis showed significantly higher revision rates in the C7 end-of-fusion cohort (7/59 for C7 vs. 2/109 for T1; odds ratio, 6.4; 95% confidence interval, 1.2-65.1; P=0.01). CONCLUSIONS: Crossing the CTJ in cervical arthrodesis does not increase operative risk as measured by blood loss, operative time, and length of hospital stay. However, it leads to lower revision rates, likely because of the avoidance of ASD, and comparable PROs. Thus, crossing the CTJ may help prevent ASD without negatively affecting operative risk or long-term PROs.

Cannulated Lag Screw Fixation of Displaced Lateral Humeral Condyle Fractures Is Associated With Lower Rates of Open Reduction and Infection Than Pin Fixation.

BACKGROUND: Open reduction/internal fixation remains the most common way to surgically stabilize displaced pediatric lateral humeral condyle fractures, but closed reduction and internal fixation is being increasingly used. Our goal was to compare the clinical and functional results of treating displaced pediatric lateral humeral condylar fractures with traditional smooth or threaded pin fixation versus single cannulated screw fixation. METHODS: From 1998 through 2012, the lateral humeral condyle fractures of 48 patients were treated with pin fixation (22 patients, until 2006) or cannulated, partially threaded screw fixation (26 patients, from 2006 onward). In each, closed reduction with percutaneous fixation was attempted first, followed by open reduction if anatomic reduction was not achieved. For the pin and screw groups, preoperative maximum radiographic displacement averaged 8.4 mm (range, 3.8 to 18.4 mm) and 6.3 mm (range, 2.2 to 15.5 mm), respectively; follow-up averaged 4.3 months (range, 1.5 to 20 mo) and 10.3 months (range, 2 to 30 mo), respectively. We reviewed preoperative and postoperative images and all follow-up clinical examination findings; serially assessed initial displacement, Baumann and carrying angles, range of motion limitations, and clinical alignment; evaluated functional results via the system of Hardacre and colleagues; and investigated all complications. RESULTS: Open reduction was required in 73% (16/22) and 15% (4/26) of the pin and screw groups, respectively (P<0.001). All fractures were reduced to <1 mm postoperative displacement. Postoperative immobilization averaged 5.9 weeks (range, 4 to 11 wk) and 4.5 weeks (range, 3 to 8 wk) for the pin and screw groups, respectively. The only significant difference in complications was the infection rate: 5 (1 deep) in the pin group and none in the screw group (P<0.05). CONCLUSIONS: Closed reduction and percutaneous 4.5-mm lag screw fixation of displaced pediatric lateral humeral condyle fractures is safe and reliable, enabling a higher rate of closed reduction, significantly lower infection rate, and earlier mobilization than traditional pin fixation. LEVEL OF EVIDENCE: Level III-Therapeutic.

Low Prevalence of Anterior and Posterior Cruciate Ligament Injuries in Patients With Achondroplasia.

BACKGROUND: Anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) injuries and their subsequent reconstructions are common in the general population, but there has been no research regarding ACL or PCL injuries in patients with achondroplasia, the most common skeletal dysplasia. Our goals were to (1) evaluate the prevalence of ACL and PCL injuries in adolescents and adults with achondroplasia, (2) compare this prevalence with that reported for the general population, (3) determine how many patients with ACL or PCL injuries underwent ligament reconstruction as treatment, and (4) determine patient activity levels as they relate to the rate of ACL/PCL injuries and reconstructions. METHODS: We reviewed medical records of 430 patients with achondroplasia seen in the senior author's clinic from 2002 through 2014. Demographic data were reviewed, as well as any documentation of ACL or PCL injury or reconstruction. We called all 430 patients by telephone, and 148 agreed to participate in our survey, whereas 1 declined. We asked these patients about their history of ACL or PCL injury or reconstruction, as well as current and past physical activity levels. RESULTS: No ACL or PCL injuries were found on chart review. One patient reached by telephone reported an ACL injury that did not require reconstruction. This yielded a theoretical prevalence of 3/430 (0.7%). Of the 148 patients surveyed, 43 (29%) reported low physical activity, 75 (51%) reported moderate physical activity, and 26 (17%) reported high physical activity. There was no significant difference in the rate of ACL injury when stratified by physical activity level (P=0.102). CONCLUSIONS: ACL and PCL injuries and reconstructions are extremely rare in patients with achondroplasia, which cannot be completely ascribed to a low level of physical activity. One possible explanation is that patients with achondroplasia, on an average, have a more anterior tibial slope compared with those without achondroplasia, which decreases the force generated within the ACL and may protect against ACL injury. Further research is needed to explore possible causes. LEVEL OF EVIDENCE: Level IV-retrospective review.

Effect of a "pill mill" law on opioid prescribing and utilization: The case of Texas.

BACKGROUND: States have attempted to reduce prescription opioid abuse through strengthening the regulation of pain management clinics; however, the effect of such measures remains unclear. We quantified the impact of Texas's September 2010 "pill mill" law on opioid prescribing and utilization. METHODS: We used the IMS Health LRx LifeLink database to examine anonymized, patient-level pharmacy claims for a closed cohort of individuals filling prescription opioids in Texas between September 2009 and August 2011. Our primary outcomes were derived at a monthly level and included: (1) average morphine equivalent dose (MED) per transaction; (2) aggregate opioid volume; (3) number of opioid prescriptions; and (4) quantity of opioid pills dispensed. We compared observed values with the counterfactual, which we estimated from pre-intervention levels and trends. RESULTS: Texas's pill mill law was associated with declines in average MED per transaction (-0.57 mg/month, 95% confidence interval [CI] -1.09, -0.057), monthly opioid volume (-9.99 kg/month, CI -12.86, -7.11), monthly number of opioid prescriptions (-12,200 prescriptions/month, CI -15,300, -9,150) and monthly quantity of opioid pills dispensed (-714,000 pills/month, CI -877,000, -550,000). These reductions reflected decreases of 8.1-24.3% across the outcomes at one year compared with the counterfactual, and they were concentrated among prescribers and patients with the highest opioid prescribing and utilization at baseline. CONCLUSIONS: Following the implementation of Texas's 2010 pill mill law, there were clinically significant reductions in opioid dose, volume, prescriptions and pills dispensed within the state, which were limited to individuals with higher levels of baseline opioid prescribing and utilization.