Biomechanical Comparison of 2 Common Techniques of Minimally Invasive Hallux Valgus Correction

Biomechanical Consequences of Proximal Screw Placement in Minimally Invasive Surgery for Hallux Valgus Correction

Hallux valgus is one of the most common surgically corrected forefoot deformities. Studies evaluating clinical outcomes of minimally invasive chevron and akin (MICA) procedure have shown shorter operation time, faster recovery, and smaller scars compared to the open approach. Previous biomechanical cadaveric studies have largely focused on the open approach with minimal on MICA. To our knowledge, no studies have compared different proximal screw placements in MICA which can either be three-point fixation or intramedullary. This study aims to compare the biomechanical properties of fixation between these 2 techniques in MICA. Six matched pairs of human fresh frozen cadaveric feet were randomized to either 3-point fixation or intramedullary groups. Both procedures were performed by a single fellowship-trained orthopedic foot and ankle surgeon. Using a material testing machine, each specimen underwent 1000 cycles of plantar-to-dorsal uniaxial loads from 0 to 31 N in cantilever configuration while monitoring bending stiffness and distal fragment dorsal angulation. They were then subjected to load until failure at a compression rate of 10 mm/min. Specimens from both groups tolerated the walking fatigue test. Mean bending stiffness of 3-point fixation was 84% higher than intramedullary constructs (p = .002). Mean dorsal angulation of intramedullary was thrice that of 3-point fixation constructs (p = .008). Mean load to failure of 3-point fixation was 30% higher than intramedullary constructs (p = .001). Three-point fixation provide superior biomechanical stability compared to intramedullary proximal screw placement. The surgical technique using 3-point proximal screw fixation can offer robust fixation and lead to better clinical outcomes.

Biomechanical Evaluation of Fourth Generation Minimally Invasive Distal First Metatarsal Osteotomy-Akin Osteotomy Technique on First Ray Articular Contact Properties

BACKGROUND

Hallux valgus is a common deformity encountered but remains a complex clinical entity. Fourth-generation minimally invasive surgery (MIS) techniques consisting of a percutaneous distal metatarsal transverse osteotomy combined with an Akin osteotomy have been used to address mild to severe hallux valgus deformities. The benefits of an MIS approach include improved cosmesis, faster recovery, lower opiate requirement, immediate weightbearing, and favorable outcomes relative to a traditional, open procedure. An understudied area with respect to hallux valgus correction is the effect that osteotomies can have on the articular contact properties of the first ray following correction.

METHODS

Sixteen paired cadaveric specimens were dissected to include the first ray and tested in a customized apparatus. Specimens were randomized to receive a distal transverse osteotomy translated either 50% or 100% of the width of the first metatarsal shaft. The osteotomy was performed with either a 0° or 20° distal angulation of the burr relative to the shaft in the axial plane. Specimens were tested in the intact state and following the distal first metatarsal osteotomy for peak pressure, contact area, contact force and center of pressure at the first metatarsophalangeal (MTP) and first tarsometatarsal (TMT) joints. An Akin osteotomy was then performed on each specimen, and peak pressure, contact area, contact force, and center of pressure were recalculated.

RESULTS

There was a notable decrease in peak pressure, contact area, and contact force across the TMT joint with greater shifts of the capital fragment. However, at 100% translation of the capital fragment, distal angulation of the osteotomy by 20° appears to improve loading across the TMT joint. Addition of the Akin osteotomy at 100% translation also aids in increasing the contact force across the TMT joint. The MTP joint is less sensitive to changes in shifts and angulation of the capital fragment. The Akin osteotomy also leads to increased contact force across the MTP joint when the capital fragment is translated 100%.

CONCLUSION

While the clinical significance is unknown, larger shifts of the capital fragment lead to greater load alterations at the level of the TMT joint than the MTP joint. Distal angulation of the capital fragment and the addition of an Akin osteotomy can aid in reducing the size of those changes. The Akin can lead to increased contact forces at the MTP joint with 100% translation of the capital fragment.

LEVEL OF EVIDENCE

Not applicable, Biomechanical study.

The Effect of First Metatarsal Shortening and Sagittal Displacement on Forefoot Pressure in Minimally Invasive Hallux Valgus Correction

BACKGROUND

Minimally invasive (MIS) treatment of hallux valgus (HV) deformity is increasing in popularity. A 2-mm diameter burr is used to create a distal first metatarsal osteotomy prior to capital fragment translation and fixation. The metatarsal will shorten by the burr's diameter (2 mm). Plantar or dorsal capital fragment displacement may also cause load transference and possibly transfer metatarsalgia. The purpose of this study is to examine the effect of MIS HV on forefoot loading mechanics with respect to metatarsal shortening and sagittal plane displacement.

METHODS

Four lower-limb cadaveric specimens were studied. A pedobarography pressure-sensing mat was used to record forefoot plantar pressure in a controlled weight-bearing stance position. Control and postosteotomy measurements were obtained with the capital fragment fixated in 3 possible positions: 0 mm, 5 mm dorsal, and 5 mm plantar displacement. Pedobarography data yielded pressure data within measurable graphical depictions. Raw mean contact pressure measurements were taken under the first and fourth metatarsal heads to establish medial and lateral forefoot loading pressure ratios. An a priori power analysis was performed based on previous peer-reviewed pedobarographic data, and our study was adequately powered.

RESULTS

Around 40 measurements were recorded, and ratios of medial-to-lateral forefoot loading were constructed. Medial forefoot pressure control versus 0 mm displacement, and control versus dorsal displacement were not found to be statistically significant (p = 0.525, p = 0.55, respectively). Medial pressure significantly increased when comparing control versus plantar displacement (P = .006). Lateral pressure significantly increased with dorsal displacement of the osteotomy (P = .013).

CONCLUSION

Our study found that MIS HV correction did not cause an increase in lateral forefoot pressure loading when sagittal plane displacements were controlled. Plantar displacement increased medial loading, and dorsal displacement increased lateral loading. It may be valuable for surgeons to consider metatarsal head position postosteotomy, as a decrease in medial loading and subsequent increase in lateral loading may lead to lateral forefoot pain and transfer metatarsalgia.

LEVELS OF EVIDENCE

IV.

Clinical guideline on the third generation minimally invasive surgery for hallux valgus

Minimally invasive surgery for hallux valgus correction, has been attracting great interests in the recent decades, due to the potential benefits of less pain, decreased recovery times, smaller scars with better cosmesis, and improved early post-operative range of motion. The most recent developments in minimally invasive surgery have evolved into the third generation with modifications of the chevron-type osteotomy. This evidence-based clinical guideline of the third generation minimally invasive surgery for hallux valgus is initiated and developed collectively by the Foot and Ankle Committee of Orthopedic Branch of Chinese Medical Doctor Association, Foot and Ankle Committee of Sports Medicine Branch of Chinese Medical Doctor Association, and Foot and Ankle Expert Committee of Orthopedic Branch of the Chinese Association of the Integrative Medicine. This clinical guideline provides recommendations for indications, contraindications, operative planning and techniques, post-operative management, management of complications, and prognosis of the third generation minimally invasive surgery for hallux valgus. The Translational Potential of this Article This comprehensive guideline aims to establish standardized recommendations for the indications, contraindications, operative techniques, and post-operative management of the third generation minimally invasive surgery for hallux valgus. By adhering to this guideline, the success rate of the procedure could be maximized. This comprehensive guideline serves as a valuable reference for practitioners interested in or preparing to perform minimally invasive surgery for hallux valgus.

Minimally Invasive Transverse Distal Metatarsal Osteotomy (MITO) for Hallux Valgus Correction: Early Outcomes of Mild to Moderate vs Severe Deformities

BACKGROUND

We compared the radiological and clinical outcomes of mild to moderate and severe hallux valgus (HV) treated with minimally invasive distal metatarsal transverse osteotomy (MITO) performed by a single surgeon.

METHODS

Eighty-four patients who underwent MITO between May 2018 and March 2020 were recruited and followed for at least 24 months. The severe group was defined as having a preoperative hallux valgus angle (HVA) >40 degrees or preoperative first-to-second intermetatarsal angle (1-2 IMA) >16 degrees; the mild to moderate group was defined as having an HVA <40 degrees and a 1-2 IMA <16 degrees. Pre- and postoperative measurements of the HVA, 1-2 IMA, distal metatarsal articular angle, and tibial sesamoid position were obtained. The visual analog scale for pain, the Foot and Ankle Outcome Score, and the Medical Outcomes Study Short Form Health Survey-36 physical component summary were used to assess clinical outcomes.

RESULTS

A total of 116 feet were included in this study and median follow-up period of 29.0 months (range, 24-52 months). Both groups showed significant improvements in all radiologic parameters postoperatively, with the degrees of correction greater in the severe group than in the mild to moderate group. All clinical scores improved significantly from the preoperative to the last follow-up visit. Final clinical outcomes and degrees of improvement were comparable in both groups.

CONCLUSION

This study showed that short-term radiographic results for patients with either mild to moderate or severe HV treated with MITO were favorable. Overall clinical outcomes were comparable to those of conventional treatments. In this series, we found MITO with screw fixation to be a satisfactory surgical option for patients with mild to severe HV deformities.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Fourth-Generation Minimally Invasive Hallux Valgus Surgery With Metaphyseal Extra-Articular Transverse and Akin Osteotomy (META): 12 Month Clinical and Radiologic Results

BACKGROUND

Fourth-generation minimally invasive surgery (MIS) includes the multiplanar rotational deformity correction achieved through manipulation of an extra-articular distal first metatarsal osteotomy that is held with rigid fixation using 2 fully threaded screws, of which one must be bicortical to provide rotational and biomechanical stability. The aim of this study is to report the clinical and radiologic outcomes of an evolved fourth-generation MIS hallux valgus technique.

METHODS

A prospective single-surgeon series of consecutive patients undergoing fourth-generation MIS was performed using a distal transverse osteotomy with a minimum 12-month follow-up. The primary outcome was the Manchester-Oxford Foot Questionnaire (MOXFQ), a validated clinical patient-reported outcome measure (PROM). Secondary outcomes included radiographic deformity correction, clinical assessment, and EuroQol-5D-5L PROMs.

RESULTS

Between September 2019 and June 2021, 50 feet underwent fourth-generation MIS. The mean age was 55.8±15.3 years with a mean follow-up of 1.4 years. Preoperative and minimum 12-month primary outcome data were available for 100% of feet. There was a significant improvement in all MOXFQ domain scores, with the index domain improving from 53.4 to 13.1 (P < .001). There was a significant improvement (P < .001) in hallux valgus angle (32.7 to 7.9 degrees), intermetatarsal angle (14.0 to 4.2 degrees) and distal metatarsal articular angle (18.5 to 5.6 degrees). There was a significant improvement in general health-related quality of life EQ-5D-5L index and EQ-VAS scores (P < .05).

CONCLUSION

The fourth-generation MIS technique is a safe and effective approach to hallux valgus deformity correction with significant improvement in clinical and radiographic outcomes.

LEVEL OF EVIDENCE

Level IV, prospective case series.

Minimally Invasive Foot and Ankle Surgery: A Primer for Orthopaedic Surgeons

There is rapidly growing interest in minimally invasive surgery (MIS) of the foot and ankle. Technological advances, specifically with the advent of low-speed high-torque burrs, have enabled the expansion of MIS techniques. Accordingly, there is growing literature reporting excellent outcomes of MIS surgery to address many different pathologies of the foot and ankle. MIS techniques are particularly useful for conducting percutaneous osteotomies and bony débridement. These can be used to address bunion deformity, hammertoes, metatarsalgia, bunionette deformity, bone spurs, and hindfoot deformity. A detailed understanding of the technology, equipment, and techniques is crucial to safely conduct MIS of the foot and ankle. When done safely, MIS provides favorable outcomes with an expedited recovery and limited complications.

The distal metatarsal screw is not always necessary in third-generation MICA: a case-control study

INTRODUCTION

To evaluate the clinical and radiological results after fixation of the first metatarsal head (MTH) with one or two screws as part of the third-generation minimally invasive Chevron-Akin osteotomy (MICA) for hallux valgus deformities.

MATERIALS AND METHODS

Between August 2020 and November 2021, 55 MICA procedures (50 patients, male:female = 7:43), 22 with two (MICA2), 33 with one screw (MICA1) were performed for mild to severe hallux valgus deformities. Exclusion criteria were a concomitant pes adductus (Sgarlato angle > 20°) or hindfoot/midfoot deformities requiring treatment. In 27 cases, additional procedures on the forefoot (small toe corrections or metatarsal osteotomies II-V) were necessary. Pre- and post-operatively, hallux valgus angle (HVA) and intermetatarsal I/II angle (IMA) were measured. Clinically, subjective satisfaction, range of motion (ROM) of the first metatarsophalangeal joint (MTPJ), and pain level (NRS score) were evaluated. The minimum follow-up was 12 months.

RESULTS

Displacement of MTH was 70-90% on average, all osteotomies showed full consolidation at latest follow-up. In one case of either group, a slight subsidence of MTH was documented. The radiological and clinical parameters showed no differences between the groups. The pain level improved by an average of three points. The mobility of the MTPJ showed a slight reduction in nine cases after three months (4 MICA2, 5 MICA1) which persisted in three cases. Fifty-two of 55 patients (95%) would opt again for the operation.

CONCLUSIONS

Fixation of the first MTH with a single bicortical screw in MICA with moderate lateralization of MTH shows stable anchoring and good clinical results. The routine use of a second metatarsal screw can be omitted.

3rd generation MICA with the "K-wires-first technique" - a step-by-step instruction and preliminary results

BACKGROUND

Minimally-invasive techniques for hallux valgus correction are becoming increasingly popular. In the last decades, multiple techniques for minimally-invasive hallux valgus correction have been described. MICA (Minimally-invasive Chevron & Akin), representing the 3rd generation of minimally-invasive hallux valgus correction, combines the advantages of an extraarticular osteotomy, stable internal fixation, and high potential for correction. This report aims to provide a step-by-step instruction of the surgical technique with the "K-wires-first" MICA modification, illustrated by detailed imaging of both intraoperative fluoroscopy and clinical imaging as well as corresponding sawbone models for each step. Preliminary results including radiological outcome and complications of the first 50 cases will be discussed.

METHODS

Between May 2018 and May 2021, 50 consecutive MICAs in 47 patients were performed with the K-wires-first technique. There were 40 women and 7 men with an average of 57.4y (range 25-78). The mean preoperative IMA was 16.2° (range 11.0-21.5), the HVA 30.6° (range 21.8-42.1).

RESULTS

There was one intraoperative conversion to an open surgical bunion correction corresponding to a 2% conversion rate respectively (1/50). On 3 feet (2 patients), removal of the Chevron screws was performed after 7, 9, and 12 months due to prominent and disturbing screw heads at the level of the medial cortex, accounting for a revision rate of 6% (3/50). There were no other secondary revision surgeries. The IMA decreased after MICA by a mean of 10.8° from 16.2° to 5.4° and the HVA by a mean of 22.1° from 30.6° to 8.5°, demonstrating MICA's high potential for correction.

CONCLUSIONS

Compared to other MICA techniques, the K-wires-first modification helps to reduce hardware malpositioning and the risk of conversion to open surgery. Furthermore, our preliminary results demonstrate a high potential for correction even for severe hallux deformities.

TRIAL REGISTRATION

Retrospectively registered, swissethics BASEC-ID 2021-01537, July 16th, 2021 ( www.raps.swissethics.ch ).