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Tarsometatarsal (TMT) arthrodesis is a commonly performed procedure in the management of midfoot arthritis, trauma, or deformity with patients often experiencing substantial improvement in pain and function following successful fusion . A variety of fixation devices and techniques have been utilized in TMT fusion including Kirschner wires, lag screws, staples, compression plates, and external fixators. Midfoot osteoarthritis often presents as a disabling condition affecting patients’ quality of life . The most common causes of midfoot arthritis are post-traumatic arthritis followed by primary osteoarthritis . Fracture or dislocation of the TMT joints is uncommon, however, the initial injury is often missed or misdiagnosed . Additionally, even with anatomic reduction and appropriate initial treatment, both bony and ligamentous Lisfranc injuries have been shown to lead to symptomatic post-traumatic arthritic changes in up to 58 % of patients ^, . Consequently, arthrodesis of the TMT joints has been advocated for select acute injuries as well as symptomatic TMT arthritis that has failed non-operative measures ^,,, . TMT fusion utilizing standard techniques has been shown to have high fusion rates, with many studies reporting an arthrodesis rate of around 90 % ^,,,,,, . There are several concerns regarding open TMT arthrodesis using larger incisions including infection and wound healing complications, with the latter reported as high as 15 % ^, . Percutaneous fusion techniques benefit from smaller incision and less soft tissue dissection which can lead to decreased wound complications. However, percutaneous TMT fusion is uncommonly performed and outcome data in the literature is limited. This study aims to report outcomes utilizing a percutaneous minimally invasive TMT fusion technique using bone autograft, fully threaded non-compression screws, and immediate postoperative weightbearing.

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The study was conducted with IRB approval (n. ORT 34252). The inclusion criteria for this study were patients over the age of 18 with history of midfoot osteoarthritis that failed 3 months of nonoperative treatment or patients with acute Lisfranc fracture-dislocations with intra-articular involvement. Nonoperative management included activity modification, shoe modification, and corticosteroid injections. All patients had at least 1 year follow-up from surgery. All patients had preoperative anteroposterior (AP), oblique, and lateral weightbearing x-rays as well as a CT scan. The exclusion criteria included previous nonunion following TMT fusion, Lapidus fusions for hallux valgus correction, patients with a hemoglobin A1c over 8.5, and patients undergoing concomitant procedures in addition to TMT fusion.

Thirty-eight consecutive patients (with a total of 86 TMT joints) of a single fellowship-trained orthopedic foot and ankle surgeon were retrospectively identified between February 2018 and June 2021. Joints were selected for fusion based on the presence of symptoms, clinical examination, and radiographic evidence of arthritis or acute intra-articular injury. For all patients, demographic information, preoperative and postoperative Visual Analogue Scale (VAS), and preoperative and postoperative Foot Function Index (FFI) including the Pain, Disability and Activity Restriction sub-scales were recorded. At each postoperative visit, patients obtained weightbearing 3-view x-rays of the foot, as well as a CT scan at 3 months. Data analysis was performed using Stata/MP 16.1 (College Station, TX). Descriptive statistical analysis was performed on all variables, yielding frequency and percentages for categorical variables, and mean, SD, and ranges for continuous variables. Fisher exact test was used to determine association between categorical variables. A P value ≤.05 was considered to be statistically significant.

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The patient is positioned supine on a radiolucent table with the foot at the end of the bed for easy access of the mini C-arm. A tourniquet must never be used to prevent thermal injury to the tissues. The TMT joints are identified fluoroscopically. For the 1st TMT, a straight medial approach is used, whereas for the 2nd and 3rd TMTs a straight dorsal approach is used ( Fig. 1 ) . A 2 mm incision is then made at the affected TMT joint. A straight mosquito clamp is used to dissect the deep tissues and allow insertion of a 2x12mm cutting burr into the joint. An example of the approach and angle the burr is held for the 1st, 2nd, and 3rd TMT joint can be seen in Figs. 2–4 . The burr is activated and the joint debrided of cartilage. Irrigation of the burr should be performed by an assistant or via one of the automated handpieces for minimally invasive surgery. Upon completion of the debridement the joint can be palpated with a small (arthroscopic) curette to feel for any remaining cartilage. After irrigation of the wound with an 18-gauge needle, the joint is prepped with a 2 mm k-wire to perforate the subchondral bone. This is done through the same small incisions used for joint preparation with repeated puncturing of the distal and proximal joint line. While the incision for the 1st TMT joint preparation is more medial, joint preparation can still be performed through this incision as the k-wire is malleable and thin. Autologous calcaneus bone graft is then inserted into the joints using a straight mosquito clamp. Next, the joints are pinned with two crossed k-wires (dorsal to plantar) at the 1st TMT joint ( Fig. 5 ) or with one k-wire (dorso-distal to plantar-proximal) across the 2nd and 3rd TMTs ( Fig. 5 ). If the indication for surgery is an acute traumatic Lisfranc injury, a screw is also placed from the medial cuneiform to the 2nd metatarsal for further stabilization. Upon fluoroscopic confirmation of adequate k-wire trajectory, the wires are over-drilled to accommodate for fully threaded headless screws ( Fig. 5 ). The authors prefer to use fully threaded cannulated screws instead of compression screws for increased biomechanical stability.

– Clinical photo showing the incisions for the 1st, 2nd, and 3rd TMT fusion. The most proximal incisions in this photograph are those used for TMT fusion. The 1st TMT is accessed from a straight medial approach. The 2nd and 3rd TMT joints are access through a straight dorsal approach.

– Fluoroscopy image of 1st TMT joint preparation with the MIS burr. The burr is held medially to the joint to visualize the joint while preparing it.

Fluoroscopy image of 2nd TMT joint preparation with the MIS burr. The burr is held dorso-medially to the joint to visualize the joint while preparing it.

– Fluoroscopy image of 3rd TMT joint preparation with the MIS burr. The burr is held dorso-laterally to view the joint as it is being prepared.

– Fluoroscopy image of the 1st through 3rd TMT joints showing the completed screw insertion at the 2nd and 3rd TMT joints. The 1st TMT joint demonstrates the crossed k-wire configuration prior to over drilling and screw insertion.

Post-operatively, the patient is allowed full weightbearing in a forefoot off-loading surgical sandal for six weeks, followed by a sneaker thereafter regardless of the number joints included in the fusion.

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Thirty-eight patients with a total of 86 TMT joints were included in this study. Table 1 lists the total number of joints fused by TMT joint. A single patient had an isolated 2nd TMT fusion. The average joints fused per patient were 2.3. The mean age was 60.8 years (range, 46–89 years). Sixty-seven patients were female (78 %) and 19 were male (22 %). Six (15.8 %) patients had type 2 diabetes, 2 (5.2 %) had peripheral vasculopathy, and 2 (5.2 %) had rheumatoid arthritis. Mean follow-up was 26.2 months (range, 21–39 months). Mean VAS scores improved from 7.5 (range, 6–10) pre-operatively to 0.2 (range, 0–3) post-operatively (p < 0.0001). Mean pre-operative Foot Function Index (FFI) in pain, disability, activity restriction, and total score were 21.1 (range, 15–26), 16.5 (range, 12–24), 18.3 (range, 13–22) and 56.2 (range, 48–61), respectively. Mean post-operative FFI in pain, disability, activity restriction, and total score was 4.3 (range, 2–9), 4.7 (range, 3–7), 6.5 (range, 3–12) and 15.7 (range, 10–27), respectively. All pre- and post-operative differences in FFI were statistically significant (p < 0.0001). Fusion was achieved in 78/86 TMT joints (90.1 %) at 3 months. All patients that did not achieve fusion at 3 months were observed further. Fusion was achieved in 81/86 TMT joints (94.1 %) at 8 months. Only patients that became symptomatic in the setting of a non-union underwent revision surgery performed with open fixation and bone grafting. Five TMT joints (5.8 %) in 3 patients (7.9 %) developed a symptomatic nonunion requiring revision surgery ( Table 2 ). Non-unions occurred in the 2nd and 3rd TMT joints only. The patients with non-unions all had varied fusion constructs. The first patient received a 1st-3rd TMT fusion and had a non-union at the 2nd and 3rd TMT. The second patient received a 2nd-3rd TMT fusion and had a non-union at the 2nd and 3rd TMT. The third patient was an isolated 2nd TMT fusion and had a non-union at that joint. The number of non-unions was too small for any correlation to be observed. One patient (2.6 %) with symptomatic hardware underwent removal of hardware. Zero patients developed wound complications, surgical site infections or neurovascular deficits. The overall complication rate was 7.9 % based on the number of joints treated, and 10.5 % based on the number of patients treated.

Table 1

Number of joints fused by tarsometatarsal (TMT) Joint.

Joint	Number of Joints Fused (Total)
1st TMT Joint	27
2nd TMT Joint	38
3rd TMT Joint	21
Average Joints Per Patient	2.3

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