Elbow coverage by the descending superficial radial artery flap: a clinical series and literature review.

PURPOSE: Soft tissue coverage of the posterior aspect of the elbow requires thin and flexible flaps to adapt to movements without constraining them. The authors report a clinical series of reconstruction by the descending superficial radial artery (DSRA) flap, a proximal forearm perforator flap which use is rarely reported in the literature. METHODS: Seven patients with a mean age of 50 years (range 24-88 years) were treated for a posterior elbow defect using the DSRA flap with an adipofascial pedicle. The flap was tunneled to the defect in the subcutaneous tissue or raised using the racket-like technique to avoid any pedicle compression. RESULTS: The mean follow-up was 3.3 months (range 1-12 months). A partial necrosis of the skin paddle occurred in an 88-year-old patient. In the other cases, the flap evolution was straightforward. At the last follow-up, the appearance of the flaps was satisfactory in terms of color, texture, and thickness. No complications were observed at the donor site. CONCLUSION: The DSRA flap with an adipofascial pedicle is a simple, reliable, and reproducible method for reconstruction of small to moderate-sized defect on the posterior aspect of the elbow. Its use is easier for defects on the posterolateral side, but it can reach the medial olecranon.

Surgical treatment of painful neuroma in amputated and non-amputated patients: does the level of neurotomy affect clinical outcomes?

PURPOSE: To compare the outcomes of distal neurotomy (DN) versus proximal neurotomy (PN) for the surgical management of painful neuromas in amputees and non-amputees, whether used in passive or active treatment. METHODS: A retrospective study was conducted on patients who underwent surgery for painful traumatic neuromas between 2019 and 2022. DN with neuroma excision was performed at the level of the injury or amputation. PN was performed using a separate proximal approach without neuroma excision. Outcomes included a Numerical Rating Scale (NRS) score and Patient-Reported Outcomes Measurement Information System (PROMIS) scores, as well as patients' subjective assessments. RESULTS: A total of 33 patients were included: 17 amputees and 16 non-amputees. They totalized 43 neuromas treated by DN in 21 cases and PN in 22 cases. At the median follow-up time of 13 months, there were significant decreases in all NRS and PROMIS scores in the whole series. The decrease in limb pain scores was not significantly different between groups, except for the decrease in pain interference and patient satisfaction which were higher in the DN group. Sub-group analyses found the same significant differences in amputees. Targeted muscle reinnervation (TMR) was associated with a higher decrease in PROMIS scores. CONCLUSION: DN seemed to give better results in amputees but there were confusing factors related to associated lesions. In other situations, the non-inferiority of PN was demonstrated. PN could be of interest for treating neuromas of superficial sensory nerves, for avoiding direct revision of a well-fitted stump and in conjunction with TMR.

Return to Sport and Duty in French Military Personnel after Medial Opening Wedge High Tibial Osteotomy.

INTRODUCTION: Medial opening wedge high tibial osteotomy (MOWHTO) is a surgical option for medial femorotibial osteoarthritis, which preserves articular cartilage by correcting the extra-articular deformities of the lower limbs that cause osteoarthritis. This is an increasingly popular treatment in a population with high functional demand, such as the French military population. The aim of this study was to evaluate the rate of return to work and military activities at 6 months postsurgery and at last follow-up in this military population following MOWHTO.The hypothesis of this study was that MOWHTO enabled a majority of service members to return to the same level of activity within 6 months of surgery. MATERIALS AND METHODS: This was a retrospective, multicenter study including all French military personnel operated on for MOWHTO alone for osteoarthritis of medial compartment between 2008 and 2018 in different Military Teaching Hospitals. We excluded civilian patients. For each patient, a questionnaire was used to collect epidemiological, professional, sports, and functional data. The primary endpoint was the rate of return to work at 6 months postsurgery. We also studied the recovery of sports activities and functional results at a 6.6-year follow-up by standardized questionnaires (Tegner activity scale, Lysholm, IKDC subjective (International Knee Documentation Commitee)). RESULTS: Twenty-four MOWHTOs were performed during this period in a cohort of 22 French military personnel. Return to work at 6 months was possible in 20/24 cases (83.3%). Of the four patients who did not return to work at 6 months, two changed their activities, while the other two returned to their jobs after 6 months. The rate of resumption of sporting activities at an equal or higher level was 50% (11/22). There was no difference between pre- and postoperative Tegner Activity Scale scores at the longest follow-up (P = .08). The mean postoperative Lysholm scores were 73.5 (standard deviation 17.8) and IKDC 59 (standard deviation 8.7). No intraoperative complications were found, and one case of postoperative infection was found. CONCLUSIONS: A total of 83% of the operated soldiers were able to return to their professional activities in less than 6 months. We observed a functional improvement at the last follow-up. Comparing these results with data from civilian populations, the rate of occupational recovery is comparable. However, the return to sport is much better in the series of nonmilitary patients with approximately 90% return to work and sport in the year following surgery. MOWHTO improves the functional results of the knee, enabling a return to work and sport in most cases in young, active populations such as the French military.

Heparin consumption and inflammatory response according to the coating of cardiopulmonary bypass circuits in cardiac surgery: A retrospective analysis.

INTRODUCTION: There are several types of surface treatments (coatings) aimed at improving the biocompatibility of cardiopulmonary bypass (CPB) circuit. Some coatings appear to require higher doses of heparin to maintain anticoagulation goals, and some of them might induce postoperative coagulopathy. In this study, we compared the amount of heparin required, postoperative bleeding, and inflammatory response according to three types of coatings. METHOD: We retrospectively included 300 consecutive adult patients who underwent cardiac surgery with CPB and received one of three coatings (Phisio®, Trillium®, and Xcoating™). Our primary objective was to compare, according to coating, the amount of heparin required to maintain an ACT > 400s during CPB. Our secondary objectives were to compare postoperative bleeding for 48 h and CRP rate. RESULTS: Baseline characteristics were comparable between groups except for age and preoperative CRP. We did not find a significant difference between the 3 coatings regarding the amount of heparin reinjected. However, we found less postoperative bleeding with the Xcoating™ circuit compared to the Phisio® circuit (-149 mL [-289; -26.5]; p = 0.02) and a lower elevation of CRP with the Phisio® circuit (2.8 times higher than preoperative CRP) compared to Trillium® (4.9 times higher) and Xcoating™ (6.4 times higher); p < 10-3. CONCLUSION: The choice of coating did not influence the amount of heparin required during CPB; however, the post-CPB inflammatory syndrome may be impacted by this choice.

Extremity injuries in the Sahelian conflict: lessons learned from a French Forward Surgical Team deployed in Gao, Mali.

PURPOSE: This study aimed to analyse extremity combat-related injuries (CRIs) and non-combat related injuries (NCRIs) treated in the French Forward Surgical Team deployed in Gao, Mali. PATIENTS AND METHODS: A retrospective study was conducted using the French surgical database OpEX (French Military Health Service) from January 2013 to August 2022. Patients operated on for an extremity injury less than one month old were included. RESULTS: During this period, 418 patients with a median age of 28 years [range 23-31 years] were included and totalized 525 extremity injuries. Among them, 190 (45.5%) sustained CRIs and 218 (54.5%) sustained NCRIs. Multiple upper extremity injuries and associated injuries were significantly more common in the CRIs group. The majority of NCRIs involved the hand. Debridement was the most common procedure in both groups. External fixation, primary amputation, debridement, delayed primary closure, vascular repair and fasciotomy were significantly predominant in the CRIs group. Internal fracture fixation and reduction under anaesthesia were statistically more frequent in the NCRIs group. The overall number of procedures and the overall number of surgical episodes were significantly higher in the CRIs group. CONCLUSION: CRIs were the most severe injuries and did not involve the upper and lower limbs separately. A sequential management was required with application of damage control orthopaedics followed by several procedures for reconstruction. NCRIs were predominant and mostly involved the hand among the French soldiers. This review supports the fact that any deployed orthopaedic surgeon should be trained in basic hand surgery and preferably have microsurgical skills. The management of local patients requires the execution of reconstructive surgery and therefore imposes the presence of adequate equipment.

Nerve transfer in the spastic equino varus foot: Anatomical feasibility study.

PURPOSE: We want to evaluate the feasibility of transferring a motor branch of the anterior tibial muscle (ATM) to the extensor digitorum longus (EDL) to evaluate this procedure in patients with spastic equinovarus foot (EVF) following post-stroke hemiplegia. METHODS: Ten cadaveric dissections from five fresh frozen human cadavers were performed to establish the anatomic feasibility of transferring a motor branch of the deep peroneal nerve, usually destinated to the ATM, to the branch of the EDL to manage spastic EVF. RESULTS: Six cases (60%) presented three branches destinated to the ATM, one case (10%) presented give branches, and three cases (30%) had four branches. In all specimens, the coaptation between the motor branch to the ATM, referred as the "effector" branch, and the branch of the EDL "receiver" branch was feasible without tension and did not require any intraneural dissection. CONCLUSION: This anatomical study confirms the feasibility of transferring a motor branch from the ATM to the EDL to correct a spastic EVF.

Relevance of a Simulation Model to Microvascular Surgery for Military Surgical Residents.

Introduction: Microsurgical training is an asset for deployed military orthopaedic surgeons who frequently treat hand or nerve injuries in the field. The objective of this study was to evaluate a microvascular surgery simulation model intended to prepare residents prior to their enrolment in conventional microsurgery degree training. Methods: An experimental study was conducted to evaluate technical progress and satisfaction of military surgical residents using a model based on Japanese noodles with four tests of increasing difficulty. Objective endpoints included instruments handling, distribution, and quality of stitches, as well as anastomoses duration. Responses to the Structured Assessment of Microsurgery Skill self-assessment questionnaire were also analyzed. Results: Nine residents from different specialties participated in the study. Their anastomoses quality and average satisfaction significantly increased between the first and the last session (p < 0.05). Conversely, the average operating time decreased significantly over the sessions (p < 0.001). Conclusion: This simulation model seems to constitute a satisfactory initiation to microsurgery and could limit the use of animal models. It could also be included in the continuing education of military surgeons who have an occasional microsurgical practice during deployments.

Masquelet technique in military practice: specificities and future directions for combat-related bone defect reconstruction.

Because of its simplicity, reliability, and replicability, the Masquelet induced membrane technique (IMT) has become one of the preferred methods for critical bone defect reconstruction in extremities. Although it is now used worldwide, few studies have been published about IMT in military practice. Bone reconstruction is particularly challenging in this context of care due to extensive soft-tissue injury, early wound infection, and even delayed management in austere conditions. Based on our clinical expertise, recent research, and a literature analysis, this narrative review provides an overview of the IMT application to combat-related bone defects. It presents technical specificities and future developments aiming to optimize IMT outcomes, including for the management of massive multi-tissue defects or bone reconstruction performed in the field with limited resources.

Defects of the sciatic nerve and its divisions treated by direct suturing in 90 degrees knee flexion: report on the first clinical series.

OBJECTIVE: To evaluate functional results after treatment of large defects of the sciatic nerve and its divisions by direct nerve suturing in high knee flexion. METHODS: A retrospective review was conducted in patients treated for lower extremity nerve defects between 2011 and 2019. Inclusion criteria were a defect > 2 cm with a minimal follow-up period of 2 years for the sciatic nerve and 1 year for its divisions. Nerve defects were bridged by an end-to-end suture with the knee flexed at 90° for 6 weeks. Functional results were assessed based on the Medical Research Council's grading system. RESULTS: Seventeen patients with a mean age of 27.6 years were included. They presented with seven sciatic nerve defects and ten division defects, including eight missile injuries. The mean time to surgery was 12.3 weeks and the mean nerve defect length was 5 cm. Overall, 21 nerve sutures were performed, with eight in the tibial distribution and 13 in the fibular distribution. Post-operatively, there was no significant knee stiffness related to the immobilization. The mean follow-up time was 24.5 months. Meaningful motor and sensory recovery were observed after 7 of 8 sutures in the tibial distribution and 11 of 13 sutures in the fibular distribution. A functional sural triceps muscle with protective sensibility of the sole was restored in all patients. There were no differences according to the injury mechanisms. CONCLUSION: Temporary knee flexion at 90° allows for direct coaptation of sciatic nerve defects up to 8 cm, with promising results no matter the level or mechanism of injury.

Treatment of upper extremity nerve defects by direct suturing in high elbow or wrist flexion.

PURPOSE: To evaluate functional outcomes after direct suturing of upper extremity nerve defects in high elbow or wrist flexion. METHODS: A retrospective review was conducted in patients treated for median, ulnar, or radial nerve defects between 2011 and 2019. Inclusion criteria were a defect > 1 cm and a minimal follow-up period of 1 year. Nerve defects were bridged by an end-to-end suture in 90° elbow flexion or 70° wrist flexion for 6 weeks. RESULTS: Nine patients with a mean age of 30.2 years were included. The patients presented with two ulnar nerve defects, four median nerve defects, and three radial nerve defects at various levels. The mean time to surgery was 13.5 weeks for recent injuries. The mean defect length was 2.9 cm, and the mean follow-up time was 22.4 months. Two patients had joint stiffness that was more likely related to the associated injuries than the 6-week immobilization. Successful outcomes were achieved in eight of the nine patients. Meaningful motor recovery was observed in seven patients, and all recovered meaningful sensation. Excellent nerve recovery was noted in pediatric patients and in those with distal nerve defects. CONCLUSION: Temporary high joint flexion allows for direct coaptation of upper extremity nerve defects up to 4 cm located near the elbow or wrist. In this small and heterogenous cohort, functional outcomes seemed to be comparable to those obtained with short autografting.

Ballistic peripheral nerve injuries: basic concepts, controversies, and proposal for a management strategy.

Ballistic injuries to peripheral nerves are devastating injuries frequently encountered in modern conflicts and civilian trauma centers. Such injuries often produce lifelong morbidity, mainly in the form of function loss and chronic pain. However, their surgical management still poses significant challenges concerning indication, timing, and type of repair, particularly when they are part of high-energy multi-tissue injuries. To help trauma surgeons, this article first presents basic ballistic concepts explaining different types of missile nerve lesions, described using the Sunderland classification, as well as their usual associated injuries. Current controversies regarding their surgical management are then described, including nerve exploration timing and neurolysis's relevance as a treatment option. Finally, based on anecdotal evidence and a literature review, a standardized management strategy for ballistic nerve injuries is proposed. This article emphasizes the importance of early nerve exploration and provides a detailed method for making a diagnosis in both acute and sub-acute periods. Direct suturing with joint flexion is strongly recommended for sciatic nerve defects and any nerve defect of limited size. Conversely, large defects require conventional nerve grafting, and proximal injuries may require nerve transfers, especially at the brachial plexus level. Additionally, combined or early secondary tendon transfers are helpful in certain injuries. Finally, ideal timing for nerve repair is proposed, based on the defect length, associated injuries, and risk of infection, which correlate intimately to the projectile velocity.

Open Screw Fixation of Large Anterior Glenoid Rim Fractures Using a Deltopectoral Approach With Subscapularis Splitting.

Anterior glenoid rim fracture is a consequence of the humeral head impacting the glenoid fossa. The management of large glenoid fractures involving more than 20% of the articulating glenoid requires surgical treatment. The 2 main techniques are open reduction internal fixation (ORIF) by screws and arthroscopic treatment using suture anchors or transcutaneous screws. Next to the technical equipment, a surgeon requires extensive experience to achieve good results with the arthroscopic technique. The main disadvantage using the ORIF technique is the detachment of the subscapularis muscle, which is often criticized for causing functional deficits of the subscapularis. Our study demonstrates the feasibility of the ORIF technique through a deltopectoral approach and splitting of the subscapularis. To our knowledge, subscapularis splitting has never been described to treat glenoid fractures.

Application of the Masquelet technique in austere environments: experience from a French forward surgical unit deployed in Chad.

PURPOSE: We sought to evaluate the results of the Masquelet-induced membrane technique (IMT) for long bone defect reconstruction within the limited-resource setting of a French forward surgical unit deployed in Chad. METHODS: A prospective and observational study was conducted in all patients with a traumatic segmental bone defect in any anatomical location treated by IMT from November 2015 to December 2019. Although IMT was applied by various orthopedic surgeons with variable expertise, all followed the same surgical protocol. Endpoint assessment was performed 12 months after IMT application. RESULTS: Sixteen patients with a mean age of 32.7 years were included in the study. Bone defects were located on the tibia (n = 8), the femur (n = 6) or the radius (n = 2). Thirteen bone defects were infected. After debridement, the mean bone defect length was 4.3 cm. External fixation of the tibia and femur was predominant in both stages. Bone union was achieved in only 8 of the 16 cases at a mean time of 7.6 months. All failures were related to persistent infection or insufficient fixation stability in the second stage. CONCLUSIONS: This series is the first to report IMT use in a forward surgical unit. Despite frequent complications, local patients can benefit from this procedure, which is the only available method for bone reconstruction in areas with limited medical resources. A rigorous technical completion at both stages is crucial to limit septic or mechanical failures.

Single versus double tendon transfer for foot drop due to post-traumatic common fibular nerve palsy.

PURPOSE: To compare functional outcomes of single versus double tendon transfer for foot drop correction and toe drop prevention in posttraumatic common fibular nerve palsy. METHODS: A retrospective study was conducted on data from patients with posttraumatic common fibular nerve palsy treated by tendon transfer between 2001 and 2018. In cases of single tendon transfer (STT) the tibialis posterior (TP) tendon was transferred anteriorly through the interosseous membrane to a new insertion on the lateral cuneiform. In cases of double tendon transfer (DTT), the same TP tendon transfer was combined with a transfer of the flexor digitorum longus to the extensor digitorum longus and extensor hallucis longus tendons. Functional assessment was based on the Carayon score to evaluate foot drop correction and on the Yeganeh score to evaluate toe drop prevention. RESULTS: A total of 27 patients were included: 13 in the STT group and 14 in the DTT group. Functional results were comparable between groups in terms of reduction of foot drop, active range of ankle motion and Carayon score. Prevention of toe drop, active toe extension and Yeganeh score were significantly greater in the DTT group, however, active toe extension of was only restored in only 8 cases in the DTT group. CONCLUSIONS: Double transfer of TP and FDL tendons is a reliable method to restore balanced ankle dorsiflexion and prevent toe drop. However, recovery of active toe extension was inconsistent and Carayon scores were not superior to those obtained with a single TP tendon transfer.

Military Orthopedic Surgeons Are Not Just Traumatologists.

INTRODUCTION: Each French military orthopedic surgeon is both an orthopedic surgeon and a trauma surgeon. Their mission is to support the armed forces in France and on deployment. The aim of this study was to describe the type of orthopedic surgery performed for the armed forces in France. Our hypothesis was that scheduled surgery was more common than trauma surgery. METHODS: We conducted a retrospective descriptive analysis of the surgical activity for military patients in the orthopedic surgery departments of the four French military platform hospitals. All surgical procedures performed during 2020 were collected. We divided the procedures into the following categories: heavy and light trauma, posttraumatic reconstruction surgery, sports surgery, degenerative surgery, and specialized surgery. Our primary endpoint was the number of procedures performed per category. RESULTS: A total of 827 individuals underwent surgery, 91 of whom (11%) were medical returnees from deployment. The surgeries performed for the remaining 736 soldiers present in metropolitan France (89%) consisted of 181 (24.6%) trauma procedures (of which 86.7% were light trauma) and 555 (75.4%) scheduled surgery procedures (of which 60.8% were sports surgery). Among the medical returnees, there were 71 traumatology procedures (78%, of which 87.3% were light traumatology) and 20 procedures corresponding to surgery usually carried out on a scheduled basis (22%, of which 95% were sports surgery). CONCLUSION: Military orthopedic surgeons are not just traumatologists; their activity for the armed forces is varied and mainly consists of so-called programmed interventions.

Retired French Military Orthopedic Surgeons' Opinions on Their Careers.

INTRODUCTION: Owing to their professional and personal experiences, retired military orthopedic surgeons' views of their careers are a unique source of inspiration. Reflecting on their experiences allows them to grasp the positive points and those that need to be improved for future generations. The purpose of this study is to gather the opinions of retired surgeons on the career of military orthopedic surgeons. METHODS: We addressed a questionnaire to all retired French military orthopedic surgeons in the database of the Chair of Applied Surgery for the Armed Forces as of December 2020, retrained in the civilian sector. A questionnaire sent by email made it possible to collect demographic, professional, and personal data about their careers. Subjective data were evaluated using a visual analog scale from 0 to 10 or a subjective qualification scale. The main assessment criterion was the average score (out of 10) of the retired surgeons' opinions on their careers. RESULTS: Fifty-two percent of retired surgeons replied (32 out of 61), with the respondents having an average age of 63 years. They had been in military retirement for an average of 14 years and had practiced for approximately 13.5 years. The majority (28 out of 32) had had a civilian activity after leaving the army. The three main reasons for leaving were the unsatisfactory working environment, the high number of deployments, and insufficient pay. Nevertheless, the respondents were satisfied with their activity, their job, and their training. The average score given for the overall opinion on their careers was 8.14/10. The three main disadvantages of the career that were noted were the quality of family life, the conditions of employment, and the financial aspects. The majority were very satisfied with the second half of their civil career. CONCLUSION: Overall, the opinion of retired French military orthopedic surgeons on their careers is very good. Their point of view provides interesting elements for reflection from both a professional point of view and a personal point of view. They were very satisfied with the quality of their training, their job, and their activity. However, the quality of their personal/family life, working conditions, and the financial aspects of the career reduced this satisfaction. The results also have potential application in improving the preparation of young military orthopedic surgeons.

Management of musculoskeletal tumours of the extremity in low-resource settings.

BACKGROUND: Management of extremity tumor is particularly challenging in low-resource settings where patients are often referred with late presentations. First, diagnostic means are limited, with CT scan, MRI, and pathology usually not being available. Limitations are also related to therapeutic means, as the absence of adjuvant therapy (chemotherapy and radiotherapy) may preclude any improvement in overall survival despite a curative surgical treatment. OBJECTIVE: The authors suggest a kind of "toolbox" combining a diagnostic guide, based on clinical examination and X-rays, and therapeutic advice adapted to this context of care. The objective is to help the surgeon to better categorize the tumor to decide whether or not to operate or act in a relevant way. CONCLUSION: The authors do not aim to provide recommendations but rather an inventory of what the isolated surgeon should know to decide on the best treatment strategy which, however, can only be symptomatic.

Prolonged tactical tourniquet application for extremity combat injuries during war against terrorism in the Sahelian strip.

PURPOSE: This study reports on complications following extended tourniquet application in patients with combat extremity injuries treated by the French Military Health Service in the Sahelian strip. METHODS: A retrospective review was performed in a French forward medical treatment facility deployed in Gao, Mali, between 2015 and 2020. All patients treated for an extremity injury with the application of at least one tourniquet for a minimum of 3 h were included. Prehospital data were injury pattern, associated shock, tourniquet location, and duration. Subsequent complications and surgical procedures performed were analyzed. RESULTS: Eleven patients with a mean age of 27.4 years (range 21-35 years) were included. They represented 39% of all patients in whom a tourniquet was applied. They had gunshot wounds (n = 7) or multiple blast injuries (n = 4) and totaled 14 extremity injuries requiring tourniquet application. The median ISS was 13 (interquartile range: 13). Tourniquets were mostly applied proximally on the limb for a mean duration of 268 min (range 180-360 min). Rhabdomyolysis was present in all cases. The damage control surgeries included debridement, external fixation, vascular repair, and primary amputation. Ten injuries were complicated by compartment syndrome requiring leg or thigh fasciotomy in the field or after repatriation. Two severely injured patients died of their wounds, but the others had a favorable outcome even though secondary amputation was sometimes required. CONCLUSIONS: Extended and proximal tourniquet applications led to significant morbidity related to compartment syndrome and rhabdomyolysis. Hemorrhagic shock, mass casualty incident, and tactical constraints often precluded revising the temporary tourniquet applied under fire.

The Masquelet Technique: Can Disposable Polypropylene Syringes be an Alternative to Standard PMMA Spacers? A Rat Bone Defect Model.

BACKGROUND: Usually, the two-stage Masquelet induced-membrane technique for extremity reconstruction begins with a polymethylmethacrylate (PMMA) cement spacer-driven membrane, followed by an autologous cancellous bone graft implanted into the membrane cavity to promote healing of large bone defects. In exceptional cases, spacers made of polypropylene disposable syringes were successfully used instead of the usual PMMA spacers because of a PMMA cement shortage caused by a lack of resources. However, this approach lacks clinical evidence and requires experimental validation before being recommended as an alternative to the conventional technique. QUESTIONS/PURPOSES: To (1) develop and (2) validate a critical-sized femoral defect model in rats for two stages of the Masquelet technique and to (3) compare the biological and bone healing properties of polypropylene-induced membranes and PMMA-induced membranes in this model. METHODS: Fifty male Sprague Dawley rats aged 8 weeks old received a 6-mm femur defect, which was stabilized with an external fixator that was converted into an internal device. In the development phase, the defect was filled with PMMA in 16 rats to determine the most favorable timing for bone grafting. Two rats were excluded since they died of anesthetic complications. The other 14 were successively euthanized after 2 weeks (n = 3), 4 weeks (n = 4), 6 weeks (n = 4), and 8 weeks (n = 3) for induced membrane analyses. In the validation phase, 12 rats underwent both stages of the procedure using a PMMA spacer and were randomly assigned to two groups, whether the induced membrane was preserved or removed before grafting. To address our final objective, we implanted either polypropylene or PMMA spacers into the defect (Masquelet technique Stage 1; n = 11 rats per group) for the period established by the development phase. In each group, 6 of 11 rats were euthanized to compare the biological properties of polypropylene-induced membranes and PMMA-induced membranes using histological qualitative analysis, semiquantitative assessment of the bone morphogenic protein-2 content by immunostaining, and qualitative assessment of the mesenchymal stromal cell (MSC; CD31-, CD45-, CD90+, and CD73+ phenotypes) content by flow cytometry. Quantitative measurements from serum bone turnover markers were also performed. The five remaining rats of each group were used for Masquelet technique Stage 2, in which rat bone allografts were implanted in the induced membrane cavity after the polypropylene or PMMA spacers were removed. These rats recovered for 10 weeks before being euthanized for microCT quantitative measurements and bone histology qualitative assessment to evaluate and compare the extent of bone regeneration between groups. RESULTS: Induced membrane analyses together with serum bone turnover measurements indicated that a 4-week interval time between stages was the most favorable. Removal of the induced membrane before grafting led to almost constant early implant failures with poor bone formation. Four-week-old rats with polypropylene-triggered induced membranes displayed similar histologic organization as rats with PMMA-driven induced membranes, without any difference in the cell density of the extracellular matrix (4933 ± 916 cells per mm2 for polypropylene versus 4923 ± 1284 cells per mm2 for PMMA; p = 0.98). Induced membrane-derived MSCs were found in both groups with no difference (4 of 5 with polypropylene versus 3 of 3 with PMMA; p > 0.99). Induced membrane bone morphogenic protein-2 immunolabeling and serum bone turnover marker levels were comparable between the polypropylene and PMMA groups. MicroCT analysis found that bone regeneration in the polypropylene group seemed comparable with that in the PMMA group (29 ± 26 mm3 for polypropylene versus 24 ± 18 mm3 for PMMA; p > 0.99). Finally, qualitative histological assessment revealed a satisfactory endochondral ossification maturation in both groups. CONCLUSION: Using a critical-sized femoral defect model in rats, we demonstrated that polypropylene spacers could induce membrane encapsulation with histologic characteristics and bone regenerative capacities that seem like those of PMMA spacers. CLINICAL RELEVANCE: In a same bone site, polymers with close physical properties seem to lead to similar foreign body reactions and induce encapsulating membranes with comparable bone healing properties. Polypropylene spacers made from disposable syringes could be a valuable alternative to PMMA. These results support the possibility of a cementless Masquelet technique in cases of PMMA shortage caused by a lack of resources.