Surgical Approach and Long-Term Recurrence After Ventral Hernia Repair.

Importance: The prevalence of robotic-assisted anterior abdominal wall (ventral) hernia repair has increased dramatically in recent years, despite conflicting evidence of patient benefit. Whether long-term hernia recurrence rates following robotic-assisted repairs are lower than rates following more established laparoscopic or open approaches remains unclear. Objective: To evaluate the association between robotic-assisted, laparoscopic, and open approaches to ventral hernia repair and long-term operative hernia recurrence. Design, Setting, and Participants: Secondary retrospective cohort analysis using Medicare claims data examining adults 18 years and older who underwent elective inpatient ventral, incisional, or umbilical hernia repair from January 1, 2010, to December 31, 2020. Data analysis was performed from January 2023 through March 2024. Exposure: Operative approach to ventral hernia repair, which included robotic-assisted, laparoscopic, and open approaches. Main Outcomes and Measures: The primary outcome was operative hernia recurrence for up to 10 years after initial hernia repair. To help account for potential bias from unmeasured patient factors (eg, hernia size), an instrumental variable analysis was performed using regional variation in the adoption of robotic-assisted hernia repair over time as the instrument. Cox proportional hazards modeling was used to estimate the risk-adjusted cumulative incidence of operative recurrence up to 10 years after the initial procedure, controlling for factors such as patient age, sex, race and ethnicity, comorbidities, and hernia subtype (ventral/incisional or umbilical). Results: A total of 161 415 patients were included in the study; mean (SD) patient age was 69 (10.8) years and 67 592 patients (41.9%) were male. From 2010 to 2020, the proportion of robotic-assisted procedures increased from 2.1% (415 of 20 184) to 21.9% (1737 of 7945), while the proportion of laparoscopic procedures decreased from 23.8% (4799 of 20 184) to 11.9% (946 of 7945) and of open procedures decreased from 74.2% (14 970 of 20 184) to 66.2% (5262 of 7945). Patients undergoing robotic-assisted hernia repair had a higher 10-year risk-adjusted cumulative incidence of operative recurrence (13.43%; 95% CI, 13.36%-13.50%) compared with both laparoscopic (12.33%; 95% CI, 12.30%-12.37%; HR, 0.78; 95% CI, 0.62-0.94) and open (12.74%; 95% CI, 12.71%-12.78%; HR, 0.81; 95% CI, 0.64-0.97) approaches. These trends were directionally consistent regardless of surgeon procedure volume. Conclusions and Relevance: This study found that the rate of long-term operative recurrence was higher for patients undergoing robotic-assisted ventral hernia repair compared with laparoscopic and open approaches. This suggests that narrowing clinical applications and evaluating the specific advantages and disadvantages of each approach may improve patient outcomes following ventral hernia repairs.

Use of statewide financial incentives to improve documentation of hernia and mesh characteristics in ventral hernia repair.

BACKGROUND: Documentation of intraoperative details is critical for understanding and advancing hernia care, but is inconsistent in practice. Therefore, to improve data capture on a statewide level, we implemented a financial incentive targeting documentation of hernia defect size and mesh use. METHODS: The Abdominal Hernia Care Pathway (AHCP), a voluntary pay for performance (P4P) initiative, was introduced in 2021 within the statewide Michigan Surgical Quality Collaborative (MSQC). This consisted of an organizational-level financial incentive for achieving 80% performance on eight specific process measures for ventral hernia surgery, including complete documentation of hernia defect size and location, as well as mesh characteristics and fixation technique. Comparisons were made between AHCP and non-AHCP sites in 2021. RESULTS: Of 69 eligible sites, 47 participated in the AHCP in 2021. There were N = 5362 operations (4169 at AHCP sites; 1193 at non-AHCP sites). At AHCP sites, 69.8% of operations had complete hernia documentation, compared to 50.5% at non-AHCP sites (p < 0.0001). At AHCP sites, 91.4% of operations had complete mesh documentation, compared to 86.5% at non-AHCP sites (p < 0.0001). The site-level hernia documentation goal of 80% was reached by 14 of 47 sites (range 14-100%). The mesh documentation goal was reached by 41 of 47 sites (range 4-100%). CONCLUSIONS: Addition of an organizational-level financial incentive produced marked gains in documentation of intra-operative details across a statewide surgical collaborative. The relatively large effect size-19.3% for hernia-is remarkable among P4P initiatives. This result may have been facilitated by surgeons' direct role in documenting hernia size and mesh use. These improvements in data capture will foster understanding of current hernia practices on a large scale and may serve as a model for improvement in collaboratives nationally.

Mortality and Severe Complications Among Newly Graduated Surgeons in the United States.

OBJECTIVE: To evaluate severe complications and mortality over years of independent practice among general surgeons. BACKGROUND: Despite concerns that newly graduated general surgeons may be unprepared for independent practice, it is unclear whether patient outcomes differ between early and later career surgeons. METHODS: We used Medicare claims for patients discharged between July 1, 2007 and December 31, 2019 to evaluate 30-day severe complications and mortality for 26 operations defined as core procedures by the American Board of Surgery. Generalized additive mixed models were used to assess the association between surgeon years in practice and 30-day outcomes while adjusting for differences in patient, hospital, and surgeon characteristics. RESULTS: The cohort included 1,329,358 operations performed by 14,399 surgeons. In generalized mixed models, the relative risk (RR) of mortality was higher among surgeons in their first year of practice compared with surgeons in their 15th year of practice [5.5% (95% CI: 4.1%-7.3%) vs 4.7% (95% CI: 3.5%-6.3%), RR: 1.17 (95% CI: 1.11-1.22)]. Similarly, the RR of severe complications was higher among surgeons in their first year of practice compared with surgeons in their 15th year of practice [7.5% (95% CI: 6.6%-8.5%) versus 6.9% (95% CI: 6.1%-7.9%), RR: 1.08 (95% CI: 1.03-1.14)]. When stratified by individual operation, 21 operations had a significantly higher RR of mortality and all 26 operations had a significantly higher RR of severe complications in the first compared with the 15th year of practice. CONCLUSIONS: Among general surgeons performing common operations, rates of mortality and severe complications were higher among newly graduated surgeons compared with later career surgeons.

Evaluating Educational Outcomes Using Patient Outcomes of New Surgeons Performing Partial Colectomy Compared to Cholecystectomy.

PURPOSE: Despite ongoing efforts to improve surgical education, surgical residents face gaps in their training. However, it is unknown if differences in the training of surgeons are reflected in the patient outcomes of those surgeons once they enter practice. This study aimed to compare the patient outcomes among new surgeons performing partial colectomy-a common procedure for which training is limited-and cholecystectomy-a common procedure for which training is robust. METHOD: The authors retrospectively analyzed all adult Medicare claims data for patients undergoing inpatient partial colectomy and inpatient cholecystectomy between 2007 and 2018. Generalized additive mixed models were used to investigate the associations between surgeon years in practice and risk-adjusted rates of 30-day serious complications and death for patients undergoing partial colectomy and cholecystectomy. RESULTS: A total of 14,449 surgeons at 4,011 hospitals performed 340,114 partial colectomy and 355,923 cholecystectomy inpatient operations during the study period. Patients undergoing a partial colectomy by a surgeon in their 1st vs 15th year of practice had higher rates of serious complications (5.22% [95% CI, 4.85%-5.60%] vs 4.37% [95% CI, 4.22%-4.52%]; P < .01) and death (3.05% [95% CI, 2.92%-3.17%] vs 2.83% [95% CI, 2.75%-2.91%]; P < .01). Patients undergoing a cholecystectomy by a surgeon in their 1st vs 15th year of practice had similar rates of 30-day serious complications (4.11% vs 3.89%; P = .11) and death (1.71% vs 1.70%; P = .93). CONCLUSIONS: Patients undergoing partial colectomy faced a higher risk of serious complications and death when the operation was performed by a new surgeon compared to an experienced surgeon. Conversely, patient outcomes following cholecystectomy were similar for new and experienced surgeons. More attention to partial colectomy during residency training may benefit patients.

Prescribed Opioid Dosages, Payer Type, and Self-Reported Outcomes After Surgical Procedures in Michigan, 2018-2020.

Importance: Collaborative quality improvement (CQI) models, often supported by private payers, create hospital networks to improve health care delivery. Recently, these systems have focused on opioid stewardship; however, it is unclear whether reduction in postoperative opioid prescribing occurs uniformly across health insurance payer types. Objective: To evaluate the association between insurance payer type, postoperative opioid prescription size, and patient-reported outcomes in a large statewide CQI model. Design, Setting, and Participants: This retrospective cohort study used data from 70 hospitals within the Michigan Surgical Quality Collaborative clinical registry for adult patients (age ≥18 years) undergoing general, colorectal, vascular, or gynecologic surgical procedures between January 1, 2018, and December 31, 2020. Exposure: Insurance type, classified as private, Medicare, or Medicaid. Main Outcomes and Measures: The primary outcome was postoperative opioid prescription size in milligrams of oral morphine equivalents (OME). Secondary outcomes were patient-reported opioid consumption, refill rate, satisfaction, pain, quality of life, and regret about undergoing surgery. Results: A total of 40 149 patients (22 921 [57.1%] female; mean [SD] age, 53 [17] years) underwent surgery during the study period. Within this cohort, 23 097 patients (57.5%) had private insurance, 10 667 (26.6%) had Medicare, and 6385 (15.9%) had Medicaid. Unadjusted opioid prescription size decreased for all 3 groups during the study period from 115 to 61 OME for private insurance patients, from 96 to 53 OME for Medicare patients, and from 132 to 65 OME for Medicaid patients. A total of 22 665 patients received a postoperative opioid prescription and had follow-up data for opioid consumption and refill. The rate of opioid consumption was highest among Medicaid patients throughout the study period (16.82 OME [95% CI, 12.57-21.07 OME] greater than among patients with private insurance) but increased the least over time. The odds of refill significantly decreased over time for patients with Medicaid compared with patients with private insurance (odds ratio, 0.93; 95% CI, 0.89-0.98). Adjusted refill rates for private insurance remained between 3.0% and 3.1% over the study period; adjusted refill rates among Medicare and Medicaid patients decreased from 4.7% to 3.1% and 6.5% to 3.4%, respectively, by the end of the study period. Conclusions and Relevance: In this retrospective cohort study of surgical patients in Michigan from 2018 to 2020, postoperative opioid prescription size decreased across all payer types, and differences between groups narrowed over time. Although funded by private payers, the CQI model appeared to have benefitted patients with Medicare and Medicaid as well.

Association Between Loneliness and Postoperative Mortality Among Medicare Beneficiaries.

This cohort study uses data from the Health and Retirement Study and Medicare claims to examine the association between loneliness and postoperative mortality after elective vs nonelective surgery among older adults.

Association of Postoperative Opioid Prescription Size and Patient Satisfaction.

OBJECTIVE: To evaluate the association between postoperative opioid prescription size and patient-reported satisfaction among surgical patients. SUMMARY BACKGROUND DATA: Opioids are overprescribed after surgery, which negatively impacts patient outcomes. The assumption that larger prescriptions increase patient satisfaction has been suggested as an important driver of excessive prescribing. METHODS: This prospective cohort study evaluated opioid-naive adult patients undergoing laparoscopic cholecystectomy, laparoscopic appendectomy, and minor hernia repair between January 1 and May 31, 2018. The primary outcome was patient satisfaction, collected via a 30-day postoperative survey. Satisfaction was measured on a scale of 0 to 10 and dichotomized into "highly satisfied" (9-10) and "not highly satisfied" (0-8). The explanatory variable of interest was size of opioid prescription at discharge from surgery, converted into milligrams of oral morphine equivalents (OME). Hierarchical logistic regression was performed to evaluate the association between prescription size and satisfaction while adjusting for clinical covariates. RESULTS: One thousand five hundred twenty patients met the inclusion criteria. Mean age was 53 years and 43% of patients were female. One thousand two hundred seventy-nine (84.1%) patients were highly satisfied and 241 (15.9%) were not highly satisfied. After multivariable adjustment, there was no significant association between opioid prescription size and satisfaction (OR 1.00, 95% CI 0.99-1.00). The predicted probability of being highly satisfied ranged from 83% for the smallest prescription (25 mg OME) to 85% for the largest prescription (750 mg OME). CONCLUSIONS: In a large cohort of patients undergoing common surgical procedures, there was no association between opioid prescription size at discharge after surgery and patient satisfaction. This implies that surgeons can provide significantly smaller opioid prescriptions after surgery without negatively affecting patient satisfaction.

Postoperative Opioid Prescription and Use After Outpatient Vascular Access Surgery.

BACKGROUND: Larger opioid prescriptions are associated with increased consumption without improvements in pain, and the majority of opioids prescribed go unused. We examined postoperative opioid prescription and use in patients undergoing vascular access surgery, where preoperative opioid exposure is common. METHODS: A retrospective analysis was conducted in adult CKD patients who underwent outpatient vascular access surgery. Patients were surveyed by telephone >2 weeks after surgery to assess pain level and opioid and non-opioid medication use. RESULTS: Of 117 patients contacted, 76 responded (65% response rate), with a median (interquartile range) age of 56 (42-69) years. Sixty-three patients (83%) were prescribed an opioid postoperatively. Respondents were prescribed 60 (38-75) oral morphine equivalents (OMEs) and consumed 0 (0-15) OMEs over 1 day with a pain score of 5 out of 10. Thirty-nine patients (>50%) used no opioids. There were no differences in postoperative opioid prescribing or use in patients with recent opioid exposure compared to patients without. Patients who underwent arteriovenous fistula (AVF) creation (short surgical incision procedure) were prescribed 60 (38-75) OMEs, compared with 75 (56-111) OMEs for patients who underwent AVF superficialization, AVG, or BVT (long surgical incision procedure; P < 0.01) and consumed 0 (0-15) OMEs compared with 10 (0-43) OMEs, respectively (P = 0.07). CONCLUSION: Regardless of preoperative opioid exposure, CKD patients undergoing vascular access surgery consumed fewer opioids than prescribed, with a median of <10% of opioids used. Therefore, we've reduced our institutional prescribing recommendations to 4 and 6 oxycodone 5mg pills for short and long surgical incision procedures, respectively.

Assessment of a quality improvement intervention to decrease opioid prescribing in a regional health system.

BACKGROUND: Opioids are prescribed in excess after surgery. We leveraged our continuous quality improvement infrastructure to implement opioid prescribing guidelines and subsequently evaluate changes in postoperative opioid prescribing, consumption and patient satisfaction/pain in a statewide regional health system. METHODS: We collected data regarding postoperative prescription size, opioid consumption and patient-reported outcomes from February 2017 to May 2019, from a 70-hospital surgical collaborative. Three iterations of prescribing guidelines were released. An interrupted time series analysis before and after each guideline release was performed. Linear regression was used to identify trends in consumption and patient-reported outcomes over time. RESULTS: We included 36 022 patients from 69 hospitals who underwent one of nine procedures in the guidelines, of which 15 174 (37.3%) had complete patient-reported outcomes data following surgery. Before the intervention, prescription size was decreasing over time (slope: -0.7 tablets of 5 mg oxycodone/month, 95% CI -1.0 to -0.5 tablets, p<0.001). After the first guideline release, prescription size declined by -1.4 tablets/month (95% CI -1.8 to -1.0 tablets, p<0.001). The difference between these slopes was significant (p=0.006). The second guideline release resulted in a relative increase in slope (-0.3 tablets/month, 95% CI -0.1 to -0.6, p<0.001). The third guideline release resulted in no change (p=0.563 for the intervention). Overall, mean (SD) prescription size decreased from 25 (17) tablets of 5 mg oxycodone to 12 (8) tablets. Opioid consumption also decreased from 11 (16) to 5 (7) tablets (p<0.001), while satisfaction and postoperative pain remained unchanged. CONCLUSIONS: The use of procedure-specific prescribing guidelines reduced statewide postoperative opioid prescribing by 50% while providing satisfactory pain care. These results demonstrate meaningful impact on opioid prescribing using evidence-based best practices and serve as an example of successful utilisation of a regional health collaborative for quality improvement.

Opioid prescribing exceeds consumption following common surgical oncology procedures.

BACKGROUND AND OBJECTIVES: Surgical oncology patients are vulnerable to persistent opioid use. As such, we aim to compare opioid prescribing to opioid consumption for common surgical oncology procedures. METHODS: We prospectively identified patients undergoing common surgical oncology procedures at a single academic institution (August 2017-March 2018). Patients were contacted by telephone within 6 months of surgery and asked to report their opioid consumption and describe their discharge instructions and opioid handling practices. RESULTS: Of the 439 patients who were approached via telephone, 270 completed at least one survey portion. The median quantity of opioid prescribed was significantly larger than consumed following breast biopsy (5 vs. 2 tablets of 5 mg oxycodone, p < .001), lumpectomy (10 vs. 2 tablets of 5 mg oxycodone, p < .001), and mastectomy or wide local excision (20 tablets vs. 2 tablets of 5 mg oxycodone, p < .001). The majority of patients reported receiving education on taking opioids, but only 27% received instructions on proper disposal; 82% of prescriptions filled resulted in unused opioids, and only 11% of these patients safely disposed of them. CONCLUSIONS: This study demonstrates that opioid prescribing exceeds consumption following common surgical oncology procedures, indicating the potential for reductions in prescribing.

Spillover Effect of Opioid Reduction Interventions From Adult to Pediatric Surgery.

BACKGROUND: Procedure-specific prescribing guidelines and trainee education have reduced opioid overprescribing in adult surgical patients, but tailored interventions do not yet exist for children. It is unknown what effect these adult interventions have had on postoperative opioid prescribing in children at the same institution, where trainees rotate across both adult and pediatric services. MATERIALS AND METHODS: This retrospective study of patients (<18 y) undergoing pediatric surgery (PS), pediatric otolaryngology (ENT), or pediatric urology (URO) procedures at a single tertiary academic center assessed opioid doses per patient before (January 01, 2015 to September 30, 2016) and after (January 01, 2017 to March 31, 2018) opioid prescribing guidelines and trainee education were instituted for adult laparoscopic cholecystectomy. Patient demographics, postoperative opioid prescribing, opioid refills, and emergency department (ED) visits <21 d after surgery were compared using chi-squared analyses and t-tests. Interrupted time-series analyses (ITSA) assessed changes in the rate of opioid prescribing pre- and postintervention for each subspecialty. RESULTS: There were 3371 patients preintervention and 2439 patients postintervention. After the intervention, fewer patients were prescribed opioids (ENT: 97% versus 93%, P < 0.001; URO: 98% versus 94%, P < 0.001; PS: 61% versus 25%, P < 0.001) and fewer opioid doses were prescribed in each prescription (ENT: 63.8 ± 26.1 versus 50.8 ± 22.0 doses, P < 0.001; URO: 33.5 ± 23.4 versus 22.1 ± 11.3, P < 0.001; PS: 20.4 ± 12.8 versus 13.8 ± 11.4 doses, P < 0.001). There were no changes in opioid refill or ED visit rates postintervention. A decreasing rate in ENT prescribing was seen preintervention, with no significant change postintervention (-2.3 ± 1.1 versus -3.3 ± 0.7; P = 0.24). Whereas, the rate of decrease in PS and URO prescribing significantly slowed postintervention (PS: -2.0 ± 0.1 versus -0.9 ± 0.1, P < 0.001; URO: -4.2 ± 0.2 versus -2.3 ± 0.5, P = 0.005). CONCLUSIONS: Opioid prescribing rates are decreasing, but adult interventions did not achieve reductions in pediatric opioid prescribing at the same institution. There was no concomitant rise in postoperative ED visits or opioid refills as prescribing declined, indicating that the risks of reducing opioid prescriptions may be minimal. Development of evidence-based, procedure-specific prescribing guidelines that specifically address pediatric patients are needed to effectively minimize opioid overprescribing in this population.

The Impact of Education and Prescribing Guidelines on Opioid Prescribing for Breast and Melanoma Procedures.

BACKGROUND: Excessive opioid prescribing is common in surgical oncology, with 72% of prescribed opioids going unused after curative-intent surgery. In this study, we sought to reduce opioid prescribing after breast and melanoma procedures by designing and implementing an intervention focused on education and prescribing guidelines, and then evaluating the impact of this intervention. METHODS: In this single-institution study, we designed and implemented an intervention targeting key factors identified in qualitative interviews. This included mandatory education for prescribers, evidence-based prescribing guidelines, and standardized patient instructions. After the intervention, interrupted time-series analysis was used to compare the mean quantity of opioid prescribed before and after the intervention (July 2016-September 2017). We also evaluated the frequency of opioid prescription refills. RESULTS: During the study, 847 patients underwent breast or melanoma procedures and received an opioid prescription. For mastectomy or wide local excision for melanoma, the mean quantity of opioid prescribed immediately decreased by 37% after the intervention (p = 0.03), equivalent to 13 tablets of oxycodone 5 mg. For lumpectomy or breast biopsy, the mean quantity of opioid prescribed decreased by 42%, or 12 tablets of oxycodone 5 mg (p = 0.07). Furthermore, opioid prescription refills did not significantly change for mastectomy/wide local excision (13% vs. 14%, p = 0.8), or lumpectomy/breast biopsy (4% vs. 5%, p = 0.7). CONCLUSION: Education and prescribing guidelines reduced opioid prescribing for breast and melanoma procedures without increasing the need for refills. This suggests further reductions in opioid prescribing may be possible, and provides rationale for implementing similar interventions for other procedures and practice settings.

Transitions of Care for Postoperative Opioid Prescribing in Previously Opioid-Naïve Patients in the USA: a Retrospective Review.

BACKGROUND: New persistent opioid use is a common postoperative complication, with 6% of previously opioid-naïve patients continuing to fill opioid prescriptions 3-6 months after surgery. Despite these risks, it is unknown which specialties prescribe opioids to these vulnerable patients. OBJECTIVE: To identify specialties prescribing opioids to surgical patients who develop new persistent opioid use. DESIGN, SETTING, AND PARTICIPANTS: Using a national dataset of insurance claims, we identified opioid-naïve patients aged 18-64 years undergoing surgical procedures (2008-2014) who continued filling opioid prescriptions 3 to 6 months after surgery. We then examined opioid prescriptions claims during the 12 months after surgery, and identified prescribing physician specialty using National Provider Identifier codes. MAIN MEASURES: Percentage of opioid prescriptions provided by each specialty evaluated at 90-day intervals during the 12 months after surgery. KEY RESULTS: We identified 5276 opioid-naïve patients who developed new persistent opioid use. During the first 3 months after surgery, surgeons accounted for 69% of opioid prescriptions, primary care physicians accounted for 13%, Emergency Medicine accounted for 2%, Physical Medicine & Rehabilitation (PM&R)/Pain Medicine accounted for 1%, and all other specialties accounted for 15%. In contrast, 9 to 12 months after surgery, surgeons accounted for only 11% of opioid prescriptions, primary care physicians accounted for 53%, Emergency Medicine accounted for 5%, PM&R/Pain Medicine accounted for 6%, and all other specialties provided 25%. CONCLUSIONS: Among surgical patients who developed new persistent opioid use, surgeons provide the majority of opioid prescriptions during the first 3 months after surgery. By 9 to 12 months after surgery, however, the majority of opioid prescriptions were provided by primary care physicians. Enhanced care coordination between surgeons and primary care physicians could allow earlier identification of patients at risk for new persistent opioid use to prevent misuse and dependence.

Large Animal Model of Pumpless Arteriovenous Extracorporeal CO2 Removal Using Room Air via Subclavian Vessels.

End-stage lung disease (ESLD) causes progressive hypercapnia and dyspnea and impacts quality of life. Many extracorporeal support (ECS) configurations for CO2 removal resolve symptoms but limit ambulation. An ovine model of pumpless ECS using subclavian vessels was developed to allow for ambulatory support. Vascular grafts were anastomosed to the left subclavian vessels in four healthy sheep. A low-resistance membrane oxygenator was attached in an arteriovenous (AV) configuration. Device function was evaluated in each animal while awake and spontaneously breathing and while mechanically ventilated with hypercapnia induced. Sweep gas (FiO2 = 0.21) to the device was increased from 0 to 15 L/min, and arterial and postdevice blood gases, as well as postdevice air, were sampled. Hemodynamics remained stable with average AV shunt flows of 1.34 ± 0.14 L/min. In awake animals, CO2 removal was 3.4 ± 1.0 ml/kg/min at maximum sweep gas flow. Respiratory rate decreased from 60 ± 25 at baseline to 30 ± 11 breaths per minute. In animals with induced hypercapnia, PaCO2 increased to 73.9 ± 15.1. At maximum sweep gas flow, CO2 removal was 3.4 ± 0.4 ml/kg/min and PaCO2 decreased to 49.1 ± 6.7 mm Hg. Subclavian AV access is effective in lowering PaCO2 and respiratory rate and is potentially an effective ambulatory destination therapy for ESLD patients.

Reproduction of in vivo motion using a parallel robot.

Although alterations in knee joint loading resulting from injury have been shown to influence the development of osteoarthritis, actual in vivo loading conditions of the joint remain unknown. A method for determining in vivo ligament loads by reproducing joint specific in vivo kinematics using a robotic testing apparatus is described. The in vivo kinematics of the ovine stifle joint during walking were measured with 3D optical motion analysis using markers rigidly affixed to the tibia and femur. An additional independent single degree of freedom measuring device was also used to record a measure of motion. Following sacrifice, the joint was mounted in a robotic/universal force sensor test apparatus and referenced using a coordinate measuring machine. A parallel robot configuration was chosen over the conventional serial manipulator because of its greater accuracy and stiffness. Median normal gait kinematics were applied to the joint and the resulting accuracy compared. The mean error in reproduction as determined by the motion analysis system varied between 0.06 mm and 0.67 mm and 0.07 deg and 0.74 deg for the two individual tests. The mean error measured by the independent device was found to be 0.07 mm and 0.83 mm for the two experiments, respectively. This study demonstrates the ability of this system to reproduce in vivo kinematics of the ovine stifle joint in vitro. The importance of system stiffness is discussed to ensure accurate reproduction of joint motion.

A potential animal model for creating a controlled and reversible anterior cruciate ligament insufficiency.

We developed and tested a device to manipulate the axial position of the tibial anterior cruciate ligament (ACL) insertion in vitro to create a potential animal model that could simulate both ACL insufficiency and 'optimal' ACL reconstruction. This model is based on the concept that controlled incremental proximal displacement of the tibial ACL insertion simulates ACL insufficiency. Replacing the insertion at the joint level and then adjusting its position until the forces recorded equaled those in the ACL-intact knee can simulate 'optimal' ACL reconstruction. Anterior tibial translation (ATT) was quantified in vitro in 24 sheep cadaver knees with the ACL intact and after the ACL was cut or detached (ACL insufficiency). In 8 knees, a bone plug including the tibial ACL insertion was detached, mounted in a specially designed device, and adjusted to reproduce ATT of the ACL-intact knee. ATT was then measured after proximal displacement of the tibial ACL insertion in calibrated 1 mm increments. The results revealed that detaching the ACL increased ATT by 132-700%. Controlled 3 mm proximal displacement of the insertion using this device increased ATT by more than 100%. Comparing the increase in ATT due to controlled displacement of the ACL insertion to that due to detaching the ACL, in only one case was the same magnitude of ACL insufficiency reproduced. Despite the variability between knees, the device was able to reproduce ATT of the ACL-intact knee and to substantially increase ATT with controlled proximal displacement of the tibial ACL insertion. Use of this device, if successful in an in vivo ACL reconstruction model, could help define any quantitative association between altered joint kinematics and degenerative changes in the joint.