Rat Microvascular Model is Tolerant to Technical Errors.

BACKGROUND: Extensive studies have been conducted using the rat model to understand the potential technical errors that lead to anastomotic failure. However, current literature indicates that the rat model has excellent tolerance to diverse errors committed by microsurgeons. The error-investigating rat model is often created by one or two experienced surgeons, and only one isolated technical error is examined. These biases may potentially cause limitations of the results from previous studies. Meanwhile, venous anastomoses have rarely been investigated in previous literature. Therefore, it is important to elucidate this topic with a more comprehensive study design. METHODS: Ninety-four arterial and 94 venous anastomoses on Sprague-Dawley rat femoral vessels that were performed by 47 microsurgeons who participated in the microsurgery course at the Columbia University and the University of Thessaloniki were evaluated. In total, 10 technical errors were examined: (1) disruption of suture line, (2) back-wall stitch, (3) oblique stitch, (4) wide bite, (5) partial thickness bite, (6) unequal suture distance, (7) tear in vessel wall, (8) excessively tight suture, (9) suture threads in lumen, and (10) large edge overlap. The frequency of each error committed, and the 30-minute postoperative patency was also recorded. The underlying causal relationship between these errors, potential interaction, and the short-term anastomosis patency was analyzed statistically. RESULTS: Only the back-wall stitch was found to have a significant causal effect on arterial anastomosis failure (p < 0.001). Back-wall stitch, wide bite, and partial thickness bite significantly impact venous anastomosis patency (p < 0.001). No other statistically significant result was found. CONCLUSION: Overall, the rat model is highly resilient to various technical errors despite these mistakes being often considered clinically unacceptable. Therefore, researchers need to consider the resilience of the rat model when designing and analyzing future studies. In addition, microsurgery instructors should focus on individual stitch quality rather than the final patency.

Resorbable Nerve Wraps: Can They Be Overtightened?

BACKGROUND: Nerve wrapping has been advocated to minimize scarring and adhesion following neurorrhaphy or neurolysis. A wrap should provide an enclosure that is snug enough to protect and support the affected nerve without strangulating the nerve. The degree to which resorbable wraps should be ": tightened" around the nerve is largely subjective with scant literature on the subject. The purpose of this study was to evaluate the effects of tightly fitting resorbable nerve wraps around intact rat sciatic nerves. METHODS: Twenty-four Sprague-Dawley rats underwent exposure and circumferential measurement of the right sciatic nerve. Porcine-derived extracellular matrix (ECM) wraps were trimmed and sutured to enclose the nerve with a tight (same as that of the nerve, n = 8) or loose (2.5x that of the nerve, n = 8) circumference. Sham-surgery control animals (n = 8) had no wrap treatment. Functional outcome was recorded biweekly by sciatic functional index (SFI) with walking track analysis and electrical stimulation. Animals were sacrificed at 12 weeks for histologic analyses. RESULTS: No withdrawal response could be evoked in the tight-wrap group until week 9, while significant improvement in SFI first occurred between weeks 5 and 7. By week 12, the tight-wrap group required 60% more current compared with baseline stimulation to produce a withdrawal response. They recovered 81% of SFI baseline values but also demonstrated significantly greater intraneural collagen content (p < 0.001) and lower axon density (p < 0.05) than in the loose-wrap and sham groups. The loose-wrap group had comparable functional and histologic outcomes to the sham control group. CONCLUSION: Resorbable ECM nerve wraps applied tightly around intact rat sciatic nerves caused significant functional impairment and histological changes characteristic of acute nerve compression. Significant but incomplete functional recovery was achieved by the tight-wrap group after 12 weeks, but such recovery may not apply in humans.

Octogenarians Undergoing Medial Unicompartmental Knee Arthroplasty Have Similar Patient-Reported Outcomes as Their Younger Counterparts.

BACKGROUND: As a procedure with lower surgical morbidity, unicompartmental knee arthroplasty (UKA) may present a practical solution for elderly patients with unicompartmental arthritis. However, few studies have analyzed the results of UKA in the extreme elderly. This study compared the functional and perioperative outcomes between octogenarians and age-appropriate controls undergoing UKA. METHODS: Prospectively collected data of 44 patients aged ≥80 years who underwent unilateral UKA were analyzed. Each octogenarian was matched 1:3 with 132 patients aged 65-74 years using propensity scores adjusting for gender, body mass index, Charlson comorbidity index, and preoperative scores. Knee Injury and Osteoarthritis Outcome Score for Joint Replacement and Short Form-12 were collected preoperatively and 2 years postoperatively. Complications, reoperations, readmissions, and unplanned visits were recorded up to 1 year postoperatively. RESULTS: The mean age was 70.0 ± 2.7 years in the control group and 83.0 ± 3.0 years in the octogenarian group (P < .001). The percentage of outpatient procedures was comparable (control 50.0%; octogenarian 45.5%; P = .601). With the exception of poorer Short Form-12 physical scores in octogenarians at 2 years (39.4 ± 14.1 vs 44.9 ± 9.2, P = .028), there was no difference in final postoperative scores or improvement in scores between the groups. The rate of complications, reoperations, readmissions, and emergency room visits was also similar. The five-year survivorship was 97% in the control group and 93% in the octogenarian group (P = .148). CONCLUSION: Octogenarians undergoing UKA can experience clinical outcomes that are similar to those of their younger counterparts. The clinical trajectory outlined may help clinicians provide valuable prognostic information to elderly patients and guide preoperative counseling.

Creation of a Rat Lower Limb Lymphedema Model.

BACKGROUND: Lymphedema is a frequent complication after surgical treatments of cancer involving lymph node resection. However, research of lymphedema treatments, such as vascularized lymph node transfer, is limited by the absence of an adequate lymphedema animal model. The purpose of this study was to determine if we could create sustainable lower limb lymphedema in the rat with a combination of inguinal lymphadenectomy, circumferential skin and subcutaneous tissue excision, and radiotherapy. METHODS: Inguinal lymphadenectomies were completed in 15 Sprague-Dawley rats. In cohort A, 5 rats received a 0.5- to 1.0-cm wide excision of proximal thigh skin and subcutaneous tissue. This step was omitted for the 10 rats in cohort B. Cohort A then received a single radiation dose of 22.7 Gy, whereas cohort B received a cumulative dose of 40.5 Gy. Bioimpedance measurements were obtained monthly to assess lymphedema progression, and lymphatic drainage at 6 months postradiation was visualized via indocyanine green (ICG) lymphangiography. RESULTS: Two rats in cohort A developed visually appreciable lymphedema in the lower limb, with bioimpedance ratios of 0.684 and 0.542 and ankle circumference ratios of 1.294 and 1.061, respectively, consistent with lymphedema. Furthermore, ICG lymphangiography in these cohort A rats revealed impaired lower limb lymphatic drainage. In cohort B, however, bioimpedance and circumference ratios, and ICG lymphangiography, did not reveal abnormal lymphatic drainage. CONCLUSIONS: The combination of inguinal lymphadenectomy, circumferential skin and subcutaneous tissue excision, and radiotherapy can successfully create lower limb lymphedema in the rat. When soft tissue excision is omitted, lymphedema does not develop.

Torsion is Tolerated in Arterial End to Venous Side Anastomoses in the Rat Model.

BACKGROUND: End-to-side (ETS) anastomoses are necessary for many procedures in microvascular surgery, such as free flap transfers. In training courses that use the rat model, the arterial end to venous side (AEVS) anastomosis is a common training exercise for ETS anastomoses. Surgeons-in-training often inadvertently twist the artery when completing the AEVS anastomosis; however, in the clinical setting, torsion is a reported risk factor for ETS anastomosis failure. The purpose of this study was to determine if torsion in an AEVS anastomosis would have a negative effect on patency in the rat model, accurately simulating the clinical scenario. METHODS: All AEVS anastomoses were completed in 15 Sprague-Dawley rats divided into three torsion cohorts: 0, 90, and 180 degrees. Torsion was created in the AEVS anastomosis by mismatching the first two sutures placed between the free femoral artery end and the venotomy. Patency was verified at 0, 2, and 4 hours postoperation via the oxygenated-deoxygenated test and transit-time ultrasound blood flow measurements. RESULTS: All AEVS anastomoses were patent 0, 2, and 4 hours postoperation according to both the oxygenated-deoxygenated test and transit-time ultrasound blood flow measurements. For the average blood flow measurements at 4 hours postoperation, the proximal measurements for 0, 90, and 180 degrees were -34.3, -18.7, and -13.8 mL/min respectively, and the distal measurements were 4.48, 3.46, and 2.90 mL/min, respectively. CONCLUSION: Torsion of 180 degrees does not affect early AEVS anastomosis patency in the rat model. This contrasts with the clinical setting, where torsion is reported to cause ETS anastomosis failure. Since AEVS anastomosis torsion is often difficult to appreciate visually, we suggested that microvascular surgery training instructors include a method to both detect and prevent AEVS anastomosis torsion, such as by marking the free femoral artery end with a marking pen or suture before beginning the anastomosis.

Large and Uneven Bites in End-to-End Anastomosis of the Rat Femoral Artery.

BACKGROUND: Successful microvascular anastomosis depends on sutures that adequately oppose both cut vessel edges. Trainees tend to take oversized or uneven bite. To improve early microsurgical skill acquisition using the rat, this study tests the belief that such bites compromise early patency by applying exaggerated bites to end-to-end arterial anastomoses. METHODS: Twelve Sprague-Dawley rats were randomly assigned to one of the four bite techniques to be applied to both femoral arteries (mean diameter, 0.8 mm). Large (L) and standard (S) bites measured 1.0 and 0.2 mm from the edge, respectively. Eight simple interrupted anastomoses were performed per bite technique, each labeled according to every proximal end bite size, followed by every distal end bite size: LL, LS, SL, and SS. Anastomosis time and blood flow rates were recorded and analyzed statistically. After sacrifice 5 days postoperation, anastomosis sections of each technique were examined histologically. RESULTS: All 24 anastomoses (100%) maintained patency for 5 days. There was no statistical difference between all postoperative blood flow measurements at any given time. Anastomosis times using LL, LS, SL, and SS bite techniques were 41.6, 33.2, 34.8, and 25.5 minutes, respectively. Anastomosis time for the traditional bite technique (SS) was significantly shorter than all other bite techniques (p < 0.05). Histological examination of the harvested segments from each group revealed similar pathophysiological features. CONCLUSION: Oversized bites (1 mm), placed symmetrically and asymmetrically across the anastomosis, do not affect early patency in the rat femoral artery. A reduced reliance on conventional guidelines for suture bites appears acceptable during microarterial anastomoses if the goal is vessel patency. However, we believe clinical competence involves the ability to place small, even bites consistently and uniformly. During microsurgical training, the occasional large bite need not be replaced; however, the trainee should be encouraged to take standard bites.

Acetabular Screws With Cement Augment for Tibial Plateau Defects in Dynamic Spacer Implantation: A Case of Recalcitrant Native Knee Septic Arthritis.

Treating tibial bone defects in the setting of recalcitrant native knee arthritis presents a challenging biomechanical problem for orthopaedic surgeons. A dynamic antibiotic spacer offers an effective solution to preserve patient function and manage infection. However, severe bone loss may compromise the fixation of the dynamic spacer. We describe the application of acetabular screws as rebar in a case of an Anderson Orthopaedic Research Institute type 3 defect of the medial tibial plateau. Additionally, we outline a facile method for fabricating the tibial stem component to ensure optimal fit within the intramedullary canal. Short-term follow-up (8 months) indicates successful fixation of the tibial component, absence of knee pain, and a knee range of motion up to 100 degrees.

The Statistical Fragility of Marrow Stimulation for Cartilage Defects of the Knee: A Systematic Review of Randomized Controlled Trials.

OBJECTIVE: Marrow stimulation is used to address knee cartilage defects. In this study, we used the fragility index (FI), reverse fragility index (rFI), and fragility quotient (FQ) to evaluate statistical fragility of outcomes reported in randomized controlled trials (RCTs) evaluating marrow stimulation. DESIGN: PubMed, Embase, and MEDLINE were queried for recent RCTs (January 1, 2010-September 5, 2023) assessing marrow stimulation for cartilage defects of the knee. The FI and rFI were calculated as the number of outcome event reversals required to alter statistical significance for significant and nonsignificant outcomes, respectively. The FQ was determined by dividing the FI by the study sample size. RESULTS: Across 155 total outcomes from 21 RCTs, the median FI was 3 (interquartile range [IQR], 2-5), with an associated median FQ of 0.067 (IQR, 0.033-0.010). Thirty-two outcomes were statistically significant, with a median FI of 2 (IQR, 1-3.25) and FQ of 0.050 (IQR, 0.025-0.069). Ten of the 32 (31.3%) outcomes reported as statistically significant had an FI of 1. In total, 123 outcomes were nonsignificant, with a median rFI of 3 (IQR, 2-5). Studies assessing stem cell augments were the most fragile, with a median FI of 2. In 55.5% of outcomes, the number of patients lost to follow-up was greater than or equal to the FI. CONCLUSION: Statistical findings in RCTs evaluating marrow stimulation for cartilage defects of the knee are statistically fragile. We recommend combined reporting of P-values with FI and FQ metrics to aid in the interpretation of clinical findings in comparative trials assessing cartilage restoration.

Swan Neck Deformity: An Unusual Complication Following Trigger Finger Release.

Introduction: Swan neck deformity (SND) is a common pathologic finding often observed in patients with severe rheumatoid arthritis. However, it has also been seen in injuries such as mallet finger, flexor digitorum superficialis laceration, and intrinsic contracture. Open surgical release of a trigger finger most commonly involves the release of the A1 pulley to relieve a mechanical impingement. Bowstringing is a rare trigger finger release complication caused by excessive pulley resection, usually due to resection of the A2 pulley. As a result of this complication, the flexor tendons move away from their center of rotation, gaining an increased mechanical advantage over the extensors and can ultimately result in a SND. Case Report: We present a case report of a 61-year-old patient that presented to our clinic with a SND of the 4th digit following a trigger finger release. Conclusion: Our case demonstrated that a previous trigger finger release with disruption of the A2 pulley can cause a cascade of events that can result in SND.

Outcomes and Complications Following Chronic Patellar Tendon Repair: A Systematic Review.

The purpose of this systematic review is to report outcomes and complications following the reconstruction of chronic patellar tendon ruptures. Four databases (Cochrane Database of Systematic Reviews, PubMed, Embase, MEDLINE) were searched from inception to July 2021. Inclusion criteria included articles that (1) analyzed outcomes and complications following chronic patellar tendon reconstruction (>4 weeks from injury to repair), (2) were written in English, (3) greater than five patients, and (4) a minimum 2-year follow-up. Exclusion criteria included (1) non-original research and (2) patellar tendon repair/reconstruction with prior total knee arthroplasty. Data on outcome metrics and complications were extracted from the included studies and reported in a qualitative manner. Nine studies (number of patients = 96) were included after screening. Seven studies analyzed autograft reconstruction, and three of those seven studies analyzed reconstructions with additional augmentation. The remaining two studies evaluated reconstruction utilizing a bone-tendon-bone (BTB) allograft. Four of the autograft studies (n=40 patients) showed a range of post-operative mean Lysholm scores of 74-94. Additionally, four studies reported a post-operative extensor lag of 0-3°. Post-operative protocol for autograft studies included delayed motion and was either contained to a bivalved cast or a hinged knee brace for six weeks. The two allograft studies reported a range of mean Lysholm scores from 62 to 67, and each immobilized the leg in full extension until six weeks. While chronic patellar tendon ruptures are a rare injury of the extensor mechanism, there are viable options for reconstruction. Overall, chronic patellar tendon ruptures reconstructed with both autograft and allograft will provide fair to good outcomes with low complication rates. Following surgery, immobilization for at least six weeks should be emphasized to protect the graft and optimize patient outcomes.

Smoothing the steep microsurgery learning curve: considering alternative suture sizes for early-stage microsurgery training with in vivo rat models.

BACKGROUND: Laboratory microsurgery training using invivo rat models is essential for clinical operation. However, challenges existin a structured training course when students transition from a non-livingmodel exercise to a living one. In the present article, we first demonstratethis steep learning curve in early-stage microsurgery training. We then proposethe potential solution of using various sizes of sutures for different trainingpurposes. METHODS: Twoseparate preliminary studies were included. First, we reviewed the records of25 students enrolled in our basic microsurgery training course. Each studentcompleted exercises in a non-living model before graduating to a live animalmodel where their performance on end-to-end arterial and venous anastomoses wasevaluated. Second, we examined the feasibility of different suture sizes in amillimeter microvascular anastomosis. Four groups of identical procedures inrat femoral artery were completed using sutures from 8-0 to 11-0. Patency rateand mean blood flow at 60 min post-op were measured and compared. RESULTS: Thirty-minute patency rates for firstarterial and venous anastomoses were 18/25 and 14/25. Those students who hadnon-patent anastomoses spent significantly longer time than those who hadpatent ones (p<.05). For varioussuture sizes, all groups achieved a 100% patency rate. No significantdifferences were found between the mean blood flow volume at 60 min post-op (p>.05). CONCLUSIONS: Steep learning curve existed in the early-stagemicrosurgery training when transitioning from non-living to living exercisemodels. The feasibility of using various suture sizes in millimeter anastomosismay be a potential solution for instructors to ease this steep learning curve.Level of Evidence: Not gradable.