Clinical and Radiographic Outcomes of Nitinol Compression Staples for Midfoot and Chopart Arthrodesis

Category: Midfoot/Forefoot; Hindfoot Introduction/Purpose: Continuous compression implant (nitinol staples) use in orthopaedic surgery has increased in recent years. There are several advantages of nitinol staples, including a lower profile when compared to traditional fixation methods. They are easy to apply and take up a smaller footprint than most plating techniques, thus decreasing surgical time and dissection. Additionally, continuous compression across the fusion site is maintained during the resorptive phase of bone healing. Biomechanical studies provide useful data supporting the use of nitinol staples in the foot and ankle; however, clinical data is limited. This study’s purpose is to determine the efficacy of nitinol staples to achieve stable, bony healing in midfoot and Chopart joint arthrodesis, and examine their clinical outcomes, complications, and pain scores. Methods: A retrospective chart review was performed on 127 midfoot/Chopart joints (71 patients) that underwent arthrodesis using nitinol staples in isolation over a five-year period (January 2017 – February 2022). The primary outcome variable was radiographic evidence of healing. Radiographs were blinded, randomized, and independently reviewed by three board certified foot and ankle surgeons. Each investigator reviewed digital radiographs independently and recorded their radiographic finding responses. Fusions were deemed healed if greater than 50% of the arthrodesis site contained bridging bone. A partially healed arthrodesis was defined as some bridging bone, but less than 50% of the overall arthrodesis site, and a nonunion was defined as no healing seen radiographically or loss of reduction. There were no cases of complete inter-surgeon radiographic disagreement in this study. Pain scores and clinical outcomes were also collected. Smokers and diabetics represented 27% (n = 19) and 13% (n=9) of the patient population, respectively. Results: Complete/partial union was seen in 89% of all joints (113/127) and 93% of midfoot joints (98/106). Chopart joints had a significantly lower healing rate (15/21; 71%) compared to midfoot joints (p = 0.013) and TMT joints in isolation (86/91; 95%) (p = 0.006). Neuropathy and smoking had no effect on healing but diabetes did (p = 0.004). Joints requiring bone grafting had a worse healing rate (38/49; 76%) (p = 0.002). For all joints, post-operative VAS scores were significantly lower than pre-operative (p < 0.00001). Midfoot and Chopart pre-operative pain scores did not differ (p= 0.30), but differed post-operatively (p = 0.003). Midfoot joints had significantly lower pain scores post-operatively than pre-operatively (p < 0.00001). No such significance existed in Chopart joints (p = 0.070). Conclusion: Isolated nitinol staples are a viable option for midfoot arthrodesis, especially TMT joints, and offer significant pain improvement. Staples are lower profile, decreasing hardware irritation and potential secondary surgeries, and ease of use makes insertion efficient and reproducible. They offer the benefit of continuous compression of the fusion site, and are rigid enough to maintain reduction. Chopart joints, however, may require a more rigid fixation than nitinol staples can provide, given the lower healing rate. Caution should be exercised in diabetics and joints that may require bone grafting

Outcomes after Bipolar Osteochondral Allograft Transplantation in the Ankle

Category: Ankle Arthritis; Ankle Introduction/Purpose: Surgical treatment options for symptomatic, full-thickness articular cartilage loss in the ankle are not consistently effective in restoring ankle function. Osteochondral allograft transplantation provides a standard-of-care alternative for patients, however, outcomes reported to date have been only fair, with a high incidence of reoperation and revision. However, recent cartilage storage and preservation techniques have significantly improved the percent viable chondrocytes at the time of implantation in OCAs. These high-chondrocyte-viability allografts should lead to improved survivability of OCAs and improved outcome measures. This study aimed to document the initial outcomes for patients undergoing bipolar OCA transplantation in the ankle after advances in tissue preservation, transplantation techniques, and patient management strategies. Methods: Patients with symptomatic tibiotalar arthritis were prospectively enrolled into a registry designed to follow outcomes after OCA surgeries in the ankle. All patients underwent complete OCA replacement of their tibial plafond and talar dome, with most undergoing fibular articular resurfacing. All OCA were size and side matched and preserved in Missouri Osteochondral Allograft Preservation System (MOPS). Patients followed a standardized, procedure-specific rehabilitation protocol after surgery, including remaining non-weight bearing for 8 weeks, weekly therapy visits, limited step count during recovery, and avoidance of high impact activities until 1 year after surgery. Patients followed-up with their physician at regular post-operative timepoints. Radiographs and patient reported outcome measures (VAS, AAOS Foot and Ankle, PROMIS PF, PROMIS Mobility) were obtained at each follow-up visit. Demographic and operative data were collected from the electronic medical record. All reported complications, reoperations, revisions, and failures were recorded in the EMR. Results: 14 patients were included for analyses with 12 undergoing primary OCA transplantation, and 2 undergoing revision OCA transplantation. Mean age and follow up was 36 and 44.1 months, respectively. All patients underwent tibia and talus OCA transplantation, with 10/14 including a fibula OCA transplantation. Initial success was 92.9% with one documented failure (tibial OCA collapse). Radiographic assessments indicated OCA integration and maintenance of joint space in 12 patients (85.7%). AAOS and VAS pain scores improved significantly from preoperative measures at each timepoint (p=.002, p=.03), while postoperative improvements in PROMIS Mobility and PROMIS Physical Function scores did not reach significance (p>0.15) (Table 1). Patients that were non-adherent to postoperative restriction and rehabilitation protocols, all 1-year postoperative PROs were significantly lower than for patients who were adherent. Conclusion: Ankle osteoarthritis in young patients continues to present a challenging dilemma. Previous attempts at large bipolar OCAs in the ankle have yielded fair, to poor, results. However, recent advances in bulk osteochondral allograft preservation has improved chondrocyte viability. Based on the results of our study, the use of high-chondrocyte-viability allografts for OCA transplantation is a viable option for the treatment of symptomatic bipolar osteochondral defects in the ankle joint. However, post operative rehab protocols are equally important in determining outcomes, and patient selection and education is key to ensuring successful outcomes. Longer term follow up is ongoing

Biomechanical Comparison of Nitinol Compression Staples vs Fully Threaded Lag Screws for Talonavicular Arthrodesis

Category: Hindfoot; Other Introduction/Purpose: The talonavicular joint is a crucial component of the hindfoot complex. Talonavicular arthrodesis has significant effects on foot biomechanics and motion. Current techniques for talonavicular arthrodesis vary and include a variety of constructs. Despite favorable clinical results, there is a lack of data regarding the biomechanical performance of second-generation nitinol compression staples compared to screw fixation for talonavicular arthrodesis. The objective of this study was to compare nitinol compression staples with fully threaded lag screws in talonavicular fusion with respect to their clinically relevant biomechanical properties during functional testing. Methods: A single orthopaedic surgeon used either two nitinol compression staples (Arthrex, Naples, FL) or two fully threaded lag screws (Arthrex, Naples, FL) on cadaveric feet (n=12; 6 matched pairs) to perform surgical arthrodesis of the talonavicular joint; each pair undergoing each procedure in random order and alternating between left and right feet. Optical tracking markers were attached to the talus and navicular bone to track displacements. Specimens were loaded at 89N/sec from 30N to 445N for 1 minute. A continuous compressive load of 445N was applied while cycling from 30° plantarflexion to 15° dorsiflexion for 10 cycles. Translation data were recorded along the X, Y, Z planes. Rotation data were recorded for roll, pitch, and yaw. Significant (p < 0.05) differences were determined using paired t-Tests, comparing staple fixation versus screw fixation for each measured variable. Results: There were no statistically significant differences between staples and screws between translation in the X, Y, and Z planes. When comparing rotation (roll, pitch, and yaw), there were no statistically significant differences with the exception of increased roll rotation for staple fixation versus lag screw fixation during static compression testing only (p=0.009). Conclusion: Based on clinically relevant biomechanical properties measured during functional robotic testing of the hindfoot, nitinol compression staples are a viable option for use in talonavicular arthrodesis

Obesity and Ankle Fractures: Are Outcomes and Complications Really Worse?

Category: Ankle; Trauma Introduction/Purpose: Existing literature has established that obese patients have nearly double the risk of sustaining an ankle fracture when compared to a non-obese population. However, few studies have investigated obesity’s effect on fracture complications and patient reported outcomes (PROs) when patients are stratified by fracture type. Furthermore, as the average body mass index (BMI) of our population steadily rises, it becomes prudent to investigate variations in complications rates and patient reported outcomes in various stages of obesity. The aim of this study is to identify trends in complication rates and patient reported outcome scores among patients of different BMI before and after dividing by fracture complexity. Methods: We retrospectively assessed clinical and surgical data from 595 patients who underwent ankle fracture surgery at a single institution between 2017 and 2021 for surgical related complications. All patients had a minimum of 18 months follow up (mean-42.2 [18.2-71.4] months). PROMIS Physical Health and Visual Analog Scale pain scores surveys were available only for patients receiving surgery after November 2019. We aggregated survey data for timepoints between three months and two years post-operatively to assess only patients with meaningful clinical data in regard to their recovery. Patients were divided based on BMI and fracture type. BMI subgroups were classified as: Non-obese (18.5-24.9 kg/m 2 , n=88), Overweight/Obese I (25-34.9 kg/m 2 , n=314), Obese II/III (≥35 kg/m 2 , n=192). Fracture subgroups were divided into two groups: Simple (Unimalleolar types) and complex (Bimalleolar and Trimalleolar variants). Data analysis was performed using Chi-Square and T-Tests with statistical significance set at an alpha (α) of ≤ 0.05. Results: We observed a whole cohort complication rate of (15.3%, n=91/594). Complication rates when stratified by BMI were: Non-obese (12.3%, n=9), Overweight/Obese class I (19.4%, n=61), Obese class II/III (10.3%, n=20). Complication rates for Overweight/Obese I patients were significantly higher when compared to Non-obese patients (p=0.044, OR=2.11). However, there was no significant difference when comparing Non-obese to Class II/III (p=0.972). We observed no significant differences in complications when performing a sub analysis on specific fracture types, regardless of BMI group. Pain scores were significantly higher in both Overweight/Obese I and Obese II/III groups when compared to Non-Obese patients (p= < 0.001, p=0.015). Physical health scores were significantly lower only in the Obese II/III group when compared to Non-Obese patients (p=0.011). Conclusion: Our results indicate that patients who are Overweight/Obese I have a significantly higher risk of complication when compared to patients of normal BMI. Surprisingly, our cohort demonstrated nearly equivalent risk between Obese II/III and Non- obese patient groups. Patient reported outcome data shows different trends with worse pain scores and lower physical health outcomes in the Obese II/III group. These findings add to the growing debate surrounding obesity’s effect on ankle fracture complication rates as well as patient reported outcomes and suggest that increased BMI cannot be viewed purely as a one-to-one relationship with negative outcomes