Abstract
Background:
Recalcitrant or persistent nonunions of the metatarsophalangeal (MTP) joint occur following failed MTP surgery for MTP fusion, failed MTP prosthesis, for hallux rigidus or due to infection and erosion. A deficient soft tissue envelope and compromised vascular supply of tissues in this region compound further attempts to salvage the great toe and preserve function. The medial femoral condyle (MFC) free flap provides vascularized corticocancellous bone and periosteum and has been successfully used for a variety of complex hindfoot and ankle pathologies. We present an additional indication with a small cohort study demonstrating its use in persistent nonunions of the first MTP joint.
Methods:
A retrospective review was completed of all MFC flaps used for revision of failed first MTP joint fusion from January 2019 to November 2022. Demographic information, comorbidities, as well as clinical and radiologic follow-up was obtained from the patient charts.
Results:
Three patients were included with MTP nonunion and an average of 7.5 (range, 5-11) failed prior surgeries. Mean age at index surgery was 50 (range, 46-57) years. An osseous union was achieved in all patients after 82 (range, 75-88) days. Hardware removal was possible after 81 (range, 55-98) days. Mean follow-up was 17 (range, 5-31) months. We note a 100% flap success rate without returns to the operating room. The lengths of the bone flaps were 2 to 4 cm, the volumes were 8 to 12 cm3. Fixation was performed with 1 intramedullary K-wire. The recipient vessel in all patients was the dorsalis pedis artery or a tributary thereof. All arterial anastomoses were performed under the operating microscope.
Conclusion:
The MFC free flap is a reasonable option for salvage of complex recalcitrant or persistent nonunions of the first MTP joint. More prospective long-term studies with functional outcomes are necessary to confirm these findings.
Level of Evidence:
Level IV, retrospective case series.
Keywords
Introduction
Osteoarthritis of the first metatarsophalangeal joint is a common painful forefoot condition interfering with normal ambulation. Clinically limited dorsiflexion of the first MTP joint as well as pain and swelling are often present. First MTP fusion is considered the gold standard for end-stage osteoarthritis. Other indications include failed joint-preserving osteotomies, severe deformity, or instability. The success rate is >90% with good long-term results if bony fusion is achieved.2,3 However, nonunion is a frequent complication with rates of approximately 5% to 15%.6,17,22 Risk factors for nonunion of arthrodesis of the foot are well studied and include systemic factors such as smoking, diabetes mellitus, osteoporosis, local factors like poor vascularity and infection, as well as surgical factors like fixation technique as well as experience.1,20
In general, re-fusion of symptomatic first MTP nonunion is often attempted; however, some authors offer their patients hardware removal with resultant pseudarthrosis. 10 Revision of nonunion is generally more challenging as the additional surgery exacerbates the problem by resulting in greater bone loss, soft tissue compromise, and possibly lower fusion rates. 7
Standard bone grafting techniques require a well-vascularized recipient bed to maintain osteocyte viability and allow for successful bony fusion. Compromised vascularity of the recipient site after multiple revision surgeries and comorbidities such as smoking and diabetes may negatively influence osseous healing.11,13 Relevant nonunion rates of 12% to 25% have been reported with the use different of auto- and allograft techniques.14 -16,21 When revision MTP fusion fails using conventional bone grafting procedures, vascularized bone grafting techniques should be evaluated in symptomatic patients as a salvage procedure.
Advantages of vascularized bone grafts include preservation of osteocyte viability within the transferred bone block. The medial femoral condyle (MFC) free flap, first described by Doi and Sakai, 4 enables transfer of vascularized periosteum with viable corticocancellous bone to promote osseous union in bone defects that are unlikely to achieve successful union with standard bone grafting technique, 4 a chimeric flap including skin or muscle can be harvested to achieve closure in cases of a skin defect or a deficient soft tissue envelope because of multiple prior revisions. MFC free flaps >5 cm in length are associated with a decreased torsional stability of the femur.5,9 In cases of greater bone defects, the free fibula remains the preferred vascularized bone grafting technique.
These complex reconstructions combining orthopedic and microvascular expertise remain routinely performed with a coordinated orthoplastic approach. In a continuous effort to improve limb salvage rate and minimize great toe amputation rates, we present a small cohort including the first 3 patients who have been successfully salvaged and have achieved bony union of the metatarsophalangeal joint after multiple failed prior surgical attempts at our institution.
Methods
A retrospective medical chart review of MFC free flaps was performed for first metatarsophalangeal fusion by the senior author between January 2019 and November 2022. Three patients were identified to be included in this cohort study. IRB approval was obtained (University of Pennsylvania IRB 853101) and all patients agreed to participate in the study and signed the consent form. All patients were initially reviewed by different foot and ankle surgeons and then referred to the senior author (L.S.L.) for evaluation if the clinical situation warranted vascularized bone graft transfer to obtain bony fusion after multiple prior surgeries had failed to achieve union. Factors that were considered indications for performing MFC reconstruction included (1) symptomatic pathology with significant functional impairment warranting surgical intervention; (2) failure of multiple prior surgical interventions without the use of vascularized bone transfers but with the use of nonvascularized bone transfers; (3) anticipated osseous defect of a maximum of 4 cm; (4) poor surrounding soft tissue; (5) presence of suitable recipient vessels for microvascular anastomosis as assessed by a strong Doppler signal prior to indication. Contraindications to the surgery include general contraindication for prolonged anesthesia and contraindications to free flap surgery (severe peripheral artery disease, heavy smoker, relative contraindication: single vessel run-off). Patient demographics, operative details, and postoperative outcomes were obtained for analysis, and comorbidities were evaluated. Over the study period, 3 MFC free flap reconstructions for persistent nonunions of the first metatarsophalangeal joint were performed. Mean age was 50 (range, 46-57) years, body mass index was 29 (range, 23-37), risk factors for nonunion included s/p status post bacterial infection (2 of 3), and former smoker (2 of 3).
Osseous union was confirmed using serial radiographs and computed tomography, with complete union defined as the date of the imaging study when complete union was noted based on the radiology report.
Orthoplastic Approach and Surgical Technique
A 2-team orthoplastic approach was used in all cases to ensure that all flaps were harvested to the reconstructive requirements of the metatarsophalangeal defect of the first ray (Figure 1). In a first step, the orthopaedic portion of the procedure was performed, including the approach to the bone, hardware removal, debridement of necrotic bone tissue, and scarred soft tissue. Adequate bone debridement was defined as resection to the level of bleeding bone. In a second step, the recipient vessels were prepared. The anterior tibial artery and vein were used in all cases. On completion, the MFC flap was harvested under tourniquet control as previously described. 8
(A) Intraoperative image depicting the surgical approach for the removal of the pseudarthrosis and necrotic bone. (B) The medial femoral condyle (MFC) harvest from the ipsilateral knee depicting the descending geniculate artery. (C) The chimeric MFC graft consisting of a corticocancellous bone block with its periosteum nurtured by the descending geniculate artery and a small piece of vastus lateralis muscle on a single perforator. Pulsatile bleeding from the cancellous bone and pulsatile flow in the artery is confirmed by the light reflex and doppler sonography prior to sectioning of the pedicle. (D) Picture depicting the impacted corticocancellous MFC flap fixed with a K-wire, which is no longer visible as it is under the skin. The artery and vein have been successfully anastomosed. Postoperative image depicting the soft tissue coverage of the well vascularized periosteum with split thickness skin graft. (Note that there is no extra bulk potentially limiting normal shoe wear.) (E) Postoperative image 8 weeks after surgery with a 100% take-up of the split-thickness skin graft on the periosteum. (Note the tip of the K-wire protruding the skin facilitating removal after the bone is fused) (F).
The osseous flap was fixed with a 0.62-mm Kirschner wire along the first ray. The pedicle was oriented proximally laterally. Anastomosis to the dorsalis pedis vessels was performed under the operating microscope in an end-to-end fashion in all cases. In one of the 3 patients, a chimeric flap was harvested with muscle tissue attached on a perforator (m. vastus medialis). If a primary skin closure was not possible because of excessive pressure on the flap pedicle, a split-thickness skin graft was applied directly onto the periosteum.
At the conclusion of the surgery, the patients were placed in a posterior splint with leg elevation and strict nonweightbearing for 8 weeks, followed by a progressive weightbearing regimen over the next 6 weeks in a hard-soled shoe. Dangling started 14 days postoperatively according to the institutions’ protocol.
Statistical Analysis
Because of the low number of cases, a statistical analysis was not performed. All variables are displayed as means and range. This is a purely descriptive study.
Results
Demographic results are summarized in Table 1. All 3 patients had a history of multiple failed surgical attempts to achieve a fusion, including nonvascularized bone grafting. An average of 7.5 (range, 5-11) surgeries were performed before indication of a vascularized MFC free flap, and a medical history of up to 6 years of persistent failed nonunion was noted (Table 2). The ipsilateral knee was used as the MFC donor in all cases. A Kirschner wire fixation (1.6mm) was used in all 3 cases. In 2 cases, an additional Kirschner wire of 0.032 in. was necessary for additional stability of the corticocancellous bone block.
Demographics and results.
Abbreviations: BMI, body mass index; LOS, Length of stay; s/p, status post; STSG, split-thickness skin graft.
Prior Surgeries.
Abbreviations: MTP, metatarsophalangeal; ORIF, Open reduction internal fixation.
The mean osseous volume was 9.3 cm3 (range 8-12 cm3), and the length of the corticocancellous bone block ranged from 2 to 4 cm. The periosteal sleeve was approximately twice the size of the bone block. In 2 cases, the periosteal sleeve was directly covered with a split-thickness skin graft to ensure a tension-free skin closure. The dorsalis pedis artery was used as the recipient vessel in all cases. The venous outflow was coupled with a venous coupling device (Synovis Micro Companies Alliance, Birmingham, AL) (n = 2) or hand-sewn (n = 1). Average postoperative length of stay was 6 (range, 4-7) days.
Postoperatively, the patients were seen regularly in clinic and remained nonweightbearing for 3 months in a controlled ankle motion boot shoe. Dangling was prohibited for the first 14 days after the surgery and progressively increased thereafter to 60 minutes every 6 hours on postoperative day 21.
Osseous union as documented radiologically was seen 75, 88, and 83 days after MFC flap surgery.
Removal of the K-wire was performed 91, 98, and 55 days after index surgery. Full weightbearing was allowed at the time of radiologically documented osseous union.
No flap complications occurred, and no takeback was required. Apart from the removal of the K-wire, which was performed in the outpatient clinic, no further surgeries were required. There was no significant donor site morbidity apart from mild pain around the knee for less than 8 weeks in all patients. Mean follow-up is 17 (range, 5-31) months. All patients are subjectively doing well, ambulate without assistance in normal shoe wear, and do not need painkillers.
Case examples
Case 1
A 57-year-old female patient presented with a history of hallux valgus deformity, which was addressed surgically but unfortunately resulted in a symptomatic hallux varus deformity. Additional surgeries included first-MTP silicone implant, which failed, and consequently a metal implant for the first MTP joint. A periprosthetic fracture was treated with allograft interposition in 2015 that failed to heal. A revision nonvascularized bone graft procedure was performed in 2017. The hardware had to be removed because of deep infection, necessitating multiple debridements. In August 2020, after clearance of the infection a dorsal approach to the MTP joint was performed. The extensor tendon was identified and sectioned and lengthened by Z-plasty. The fibrous tissue was removed, and the bone was resected until healthy bleeding bone was seen. An MFC flap of 2 × 2 × 2 cm was harvested from the ipsilateral knee and tailored to fit the defect. It was then impacted into place. Fixation was achieved with 2 K-wires. An end-to-end anastomosis to the dorsal metatarsal artery was performed with interrupted 10-0 microsuture. The veins were anastomosed with a 3-0-mm venous coupling device. The patient’s radiographs depicting the procedure are seen in Figure 2.
Series of dorsoplantar forefoot x-rays from case 1 depicting the nonunion preoperative (A), the immediate postoperative image (B) a postoperative follow- up after 40 days (C) as well as complete fusion 2 years after surgery (D). The k-wire was removed 98 days after surgery after confirmation of fusion 88 days after index surgery on the depicted sagittal CT slices (E, F).
Case 2
A 46-year-old patient presented with a recalcitrant first MTP nonunion. Initial MTP 1 fusion was attempted in 2015. Multiple prior surgeries including allografts as well as corticocancellous non-vascularized bone grafts from the pelvis were attempted. A total of eleven surgeries were performed prior to presentation to the senior author’s clinic in 2021. An MFC free flap was obtained from the ipsilateral knee to fit the defect following debridement of all non-compromised bone and soft tissue. Anastomosis of the descending geniculate artery to the dorsalis pedis artery was performed with 9-0 microsutures. The veins were anastomosed with a 3-0 mm venous coupling device. This patient’s x-rays are depicted in Figure 3.
Series of nonweightbearing dorsoplantar foot radiographs from case 2: (A) preoperative image depicting persistent nonunion; (B) immediately postoperatively; (C) 75 days postoperatively depicting excellent bony fusion of the medial femoral condyle flap linking the metatarsal bone and the proximal phalanx; and (D) after hardware removal 91 days postoperatively.
Discussion
Recalcitrant and persistent nonunions of the MTP joint can present as challenging problems for the foot and ankle surgeon. After failure of nonvascularized bone grafting procedures, the vascularized MFC flap should be considered as a reliable treatment option for this condition. In our study, we have achieved a 100% bony union rate after an average of 82 (range, 75-88) days.
In primary MTP fusion, nonunion rates of 10% to 15% have been reported independent of surgical technique.6,17,22 In cases of multiple failed surgeries resulting in scarring and diminished blood supply, any additional surgery further devascularizes the tissue and further decreases the likelihood of bony fusion. Because of failed primary surgery, subsequent procedures additionally increase the size of the bone defect, making the likelihood of nonvascularized bone grafts less reliable as a means to achieve fusion. The vascularized MFC flap offers a great limb salvage option as it carries its own blood supply and can support structural reconstructions up to 4 cm in length.12,18
We have previously reported on the successful use of the vascularized MFC graft for reconstruction of the hindfoot, for the treatment of talar AVN and nonunions of the talus, calcaneus, and distal tibia.8,19 The use of the MFC flap as a salvage procedure for persistent metatarsophalangeal nonunion has never been described to our knowledge. Based on the success of these preliminary results, we have included the symptomatic persistent nonunion of the MTP joint as an indication for a vascularized MFC after conventional methods of revision including nonvascularized bone grafting have failed.
There are numerous limitations to this study. The main limitation is certainly the number of patients included in this study. However, luckily the incidence of persistent MTP nonunion is low and the majority can be treated without a vascularized bone graft. The retrospective nature of the study and the lack of a control group again due to the small number of patients are additional limitations. A direct comparison in a prospective manner, however, would be challenging as each case is unique in terms of their surgical history. An objective validated functional outcome measure could not be calculated because of the retrospective nature of the study.
Nonetheless, this is the first study demonstrating the successful utilization of the MFC flap for salvage of persistent nonunion of the MTP joint.
Conclusion
The MFC free flap is a reasonable option for salvage of complex recalcitrant or persistent nonunions of the first MTP joint. More prospective long-term studies with functional outcomes are necessary to confirm these findings.
Supplemental Material
sj-pdf-1-fao-10.1177_24730114231191135 – Supplemental material for Medial Femoral Condyle Free Flap for Persistent Osseous Nonunion of the First Metatarsophalangeal Joint: A Preliminary Report of a New Surgical Indication for the Medial Femoral Condyle Free Flap
Supplemental material, sj-pdf-1-fao-10.1177_24730114231191135 for Medial Femoral Condyle Free Flap for Persistent Osseous Nonunion of the First Metatarsophalangeal Joint: A Preliminary Report of a New Surgical Indication for the Medial Femoral Condyle Free Flap by Dominik Kaiser and L. Scott Levin in Foot & Ankle Orthopaedics
Footnotes
Ethical Approval
IRB approval obtained from the University of Pennsylvania IRB (no. 853101).
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. ICMJE forms for all authors are available online.
Funding
The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: Dominik Kaiser, MD, was supported by a financial contribution from the stipend funds of Swiss Orthopaedics.
References
Supplementary Material
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