Third-Generation Minimally Invasive Chevron and Akin Osteotomies (MICA) in Hallux Valgus Surgery: Two-Year Follow-up of 292 Cases

A comparison of three techniques for the osteosynthesis after minimal invasive osteotomies for hallux valgus

PURPOSE

Third and fourth-generation minimal invasive osteotomies (MIO) for the treatment of hallux valgus (HV) have become popular procedures worldwide with promising results due to the improvement in the fixation method. The tricortical cannulated screw placement remains a complex procedure that is technically challenging and requires a long skill learning curve with high radiation exposure mainly in the form of intensifier shots (IS) required for the MIO fixation. This study aims to compare the number of X-ray IS required using three different techniques for the cannulated guide placement.

METHODS

A retrospective cross-sectional observational and comparative study was conducted to assess the number of X-rays IS required for correct cannulated screw guide placement using three different techniques: traditional perforator, the drill and joystick, and K-wire first techniques.

RESULTS

A total of 53 MIS procedures from thirty-one patients in two different hospitals were included. IS X-rays were 155.1 ± 29.7 in the traditional technique (n = 14), 143.0 ± 43.2 in the drill and joystick technique (n = 22), and 85 ± 18.7 in the K-wires first technique (n = 17), p =  < 0.001 using one-way ANOVA.

CONCLUSIONS

The K-wire first technique statistically significantly decreases X-ray IS numbers p ≤ 0.001. There were no statistically significant differences between the traditional (after osteotomy K-wire placement) and the drill and joystick techniques (p = 0.36).

Outcome comparison of minimally invasive proximal and distal chevron Akin osteotomies in patients with severe hallux valgus deformity: A randomized prospective study

PURPOSE

To date, the surgical treatment of severe hallux valgus deformity remains challenging despite the various methods presented. This study aimed to compare the effectiveness of minimally invasive distal chevron Akin osteotomies (d-MICA) and minimally invasive proximal chevron Akin osteotomies (p-MICA) in correcting severe hallux valgus deformities.

METHODS

This prospective follow-up study included patients randomly assigned to undergo p-MICA or d-MICA for hallux valgus deformities with a preoperative hallux valgus angle (HVA) ≥ 40° and/or a first to second intermetatarsal angle (IMA) ≥ 16°. After a minimum follow-up period of two years, we compared various clinico-radiographic parameters of patients whose HVA exceeded 15° at the final follow-up.

RESULTS

In the p-MICA and d-MICA groups, seven of 40 cases (17.5%) and 16 of 41 cases (39.0%), respectively, exhibited HVA > 15° at the final follow-up (P = 0.048). The preoperative parameters showed no significant differences. However, at the first weight-bearing assessment, the HVA, IMA, and relative second metatarsal length were significantly smaller, and the distal metatarsal articular angle (DMAA) was greater in the p-MICA group (all P < 0.05) compared with the d-MICA group. Postoperatively, both groups exhibited significant decreases in HVA and IMA at the final follow-up (P < 0.001 for all parameters). The p-MICA group showed no significant changes in DMAA and the relative length of the second metatarsal (P = 0.253 and 0.185, respectively). However, the d-MICA group showed a significant decrease in DMAA (P < 0.001) and an increase in the relative length of the second metatarsal at the final follow-up (P = 0.01).

CONCLUSIONS

p-MICA and d-MICA procedures demonstrated effective correction potential for severe hallux valgus deformities; however, the d-MICA procedure exhibited a notably higher incidence of unsatisfactory correction at the final follow-up than p-MICA. Therefore, d-MICA may be less predictable in achieving successful outcomes than p-MICA in treating severe hallux valgus deformities.

[Effectiveness of minimally invasive treatment of hallux valgus with small incision external articular osteotomy]

Objective

To compare the effectiveness of small incision external articular minimally invasive osteotomy and traditional Chevron osteotomy in the treatment of hallux valgus.

Methods

A retrospective analysis was conducted on the clinical data of 58 patients (58 feet) with hallux valgus who were admitted between April 2019 and June 2022 and met the selection criteria. Among them, 28 cases were treated with small incision external articular minimally invasive osteotomy (minimally invasive group), and 30 cases were treated with traditional Chevron osteotomy (traditional group). There was no significant difference in baseline data such as age, gender, disease duration, Mann classification, and preoperative inter metatarsal angle (IMA), hallux valgus angle (HVA), distal metatarsal articular angle (DMAA), forefoot width, tibial sesamoid position (TSP) score, American Orthopaedic Foot and Ankle Society (AOFAS) forefoot score, visual analogue scale (VAS) score, psychological score (SF-12 MCS score) and physiological score (SF-12 PCS score) of short-form 12 health survey scale, and range of motion (ROM) of metatarsophalangeal joint between the two groups ( P>0.05). The incision length, operation time, intraoperative blood loss, intraoperative fluoroscopy frequency, weight-bearing walking time, fracture healing time, and incidence of complications were recorded and compared between the two groups; as well as the changes of imaging indexes at last follow-up, and the clinical function score and ROM of metatarsophalangeal joint before operation, at 6 weeks after operation, and at last follow-up.

Results

All patients were followed up 11-31 months, with an average of 22 months. The incision length and intraoperative blood loss in the minimally invasive group were significantly less than those in the traditional group ( P<0.05), and the intraoperative fluoroscopy frequency and operation time in the minimally invasive group were significantly more than those in the traditional group ( P<0.05); but no significant difference was found in weight-bearing walking time and fracture healing time between the two groups ( P>0.05). There was 1 case of skin injury in the minimally invasive group and 3 cases of poor incision healing in the traditional group; all patients had good healing at the osteotomy site, and no complication such as infection, nerve injury, or metatarsal head necrosis occurred. At last follow-up, the imaging indexes of the two groups significantly improved when compared with those before operation ( P<0.05). The changes of DMAA and TSP score in the minimally invasive group were significantly better than those in the traditional group ( P<0.05), and there was no significant difference in the changes of IMA, HVA, and forefoot width between the two groups ( P>0.05). The clinical scores and ROM of metatarsophalangeal joint significantly improved in the two groups at 6 weeks after operation and at last follow-up when compared with preoperative ones ( P<0.05), and the indicators in the minimally invasive group were significantly better than those in the traditional group ( P<0.05).

Conclusion

Compared with traditional Chevron osteotomy, small incision external articular minimally invasive osteotomy can effectively improve HVA, IMA, and forefoot width, correct foot deformities, and has less trauma. It can better correct the first metatarsal pronation deformity and restore the anatomical position of the sesamoid bone, resulting in better effectiveness.

Minimally Invasive Chevron Akin (MICA) Osteotomy Corrects Radiographic Parameters but Not Central Metatarsal Loading in Moderate to Severe Hallux Valgus without Metatarsalgia

BACKGROUND

Central metatarsal pressure is increased in patients with hallux valgus, but the pedographic outcomes after hallux valgus (HV) correction are inconclusive. No known literature has reported the pedographic outcomes after HV correction with Minimally Invasive Chevron and Akin Osteotomy (MICA).

METHODS

A prospective cohort of 31 feet from 25 patients with moderate-to-severe symptomatic HV but without metatarsalgia underwent MICA and was evaluated using radiographic parameters and pedographic measurements (Footscan®, RSscan International, Olen, Belgium). Data were collected preoperatively and 3 months after surgery.

RESULTS

The radiographic parameters of the hallux valgus angle, intermetatarsal angle, distal metatarsal articular angle, first metatarsal head lateral shape, and lateral sesamoid grade significantly improved after MICA. The corrected first metatarsal length was significantly shortened by 2.3 mm, with consistent second metatarsal protrusion distance, lateral Meary's angle, and calcaneal pitch angle. Max force, max pressure, cumulative force, and cumulative pressure on the central metatarsals did not show significant changes between pre- and post-operative measurements, while these parameters significantly decreased in the hallux and first metatarsal area.

CONCLUSION

MICA effectively corrects radiographic parameters but does not reduce central metatarsal loading in patients with moderate-to-severe HV without metatarsalgia.

A Joy-Stick Assistant Three-Dimensional Modified Technique of Minimally Invasive Surgery for Mild or Moderate Hallux Valgus

BACKGROUND

Minimally invasive surgery (MIS) such as minimally invasive chevron osteotomy and Akin osteotomy (MICA) has become popular in the treatment of hallux valgus. However, how to correct three-dimensional deformities in hallux valgus effectively and simply in MICA is still difficult. Special equipment is required in MICA as has been reported before. It is meaningful and necessary to reduce the reliance on special equipment in MICA.

METHODS

From January 2021 to July 2022, patients with mild or moderate hallux valgus were treated with a joy-stick assistant three-dimensional modified technique (Joy-stick 3D technique) of MIS. VAS, AOFAS Hallux MTP-IP scores, hallux valgus angle (HVA), intermetatarsal angle (IMA), and distal metatarsal articular angle (DMAA) were measured pre- and postoperatively at the last follow-up of at least 6 months. Scores and radiologic angles were compared using paired sample t-test.

RESULTS

A total of 36 cases were included. HVA, IMA, and DMAA were (22.3 ± 6.1)°, (14.0 ± 3.2)°, and (8.9 ± 3.2)° preoperatively, and decreased to (7.0 ± 1.8)°, (3.7 ± 1.0)°, and (3.3 ± 1.1)° postoperatively. VAS decreased from 4.3 ± 1.7 to 0.7 ± 0.7. AOFAS Hallux MTP-IP scores improved from 68.6 ± 7.6 to 92.9 ± 6.1. Comparing mild and moderate cases, though HVA, IMA, and DMAA were significantly different preoperatively, the angles became statistically similar after surgery.

CONCLUSIONS

A joy-stick assistant three-dimensional modified technique is proposed to control the three-dimensional position of the metatarsal head and to reduce dependence on special tools. Mild and moderate hallux valgus deformities are effectively corrected using Joy-stick 3D technique.

Changes in Foot Width in Minimally Invasive Bunionectomy

BACKGROUND

Minimally invasive bunionectomy (MISB) has emerged as a popular approach to treat symptomatic hallux valgus deformity. Although previous studies focused on distal foot width changes postsurgery, this research introduces a novel midshaft measurement to evaluate proximal transverse midfoot width, aiming for a comprehensive understanding of foot changes post-MISB.

METHODS

A retrospective review of 44 HV patients from an institutional registry was conducted. Demographic data, surgical details, radiographs, and foot width measurements were collected. Changes in hallux valgus angle (HVA) and intermetatarsal angle (IMA) were also measured.

RESULTS

Intraclass correlation coefficients (ICCs) demonstrated good to excellent interobserver reliability (all ICCs > 0.70) for all measurements. MISB resulted in a consistent reduction in distal foot width (P < .001). These reductions correlated with changes in HVA and IMA, suggesting that the extent of deformity correction influenced distal foot width: distal bone width decreased an average of 8 mm, P < .001). However, midshaft bony width increased an average of 4 mm, P < .001). Changes in midshaft foot width showed no correlation with HVA or IMA alterations.

CONCLUSION

We found in this cohort of 44 patients that MISB for HV leads to an expected decrease in distal bony foot width but, on average, an increase in midshaft foot width.

LEVEL OF EVIDENCE

Level III, retrospective comparison of prospectively collected data.

Radiographic Comparison of Open and Minimally Invasive Distal Chevron Metatarsal Osteotomy in Patients With Hallux Valgus

This study aimed to compare radiographic outcomes of open and minimally invasive surgery (MIS) in patients with hallux valgus. We reviewed data of patients with hallux valgus who underwent open or minimally invasive distal chevron osteotomy at our institution. Radiographic assessment was completed preoperatively, immediate postoperatively, and one year postoperatively using eight weight bearing parameters . The classic distal chevron osteotomy method was used for open surgery and a modified method that added percutaneous K-wire fixation to the minimal invasive Chevron-Akin (third-generation MIS) was used for correction of the distal metatarsal articular angle (DMAA). A total of 65 feet (33 open surgeries and 32 MIS) were included. The HVA, IMA, and DMAA improved significantly following surgery regardless of surgical method (p<0.001). Other radiographic indicators showed no statistically significant differences after surgery. DMAA improved by 71.0±14.2% after surgery, and the open surgery group showed less significant reduction in DMAA (49.7±25.7%, p<0.001). Other parameters showed no difference between the two groups regarding relative postoperative changes. The MIS group showed shorter operation time (p<0.001) and hospitalization period (p=0.034) than did the open surgery group. Therefore, the MIS group is expected to be cost-effective. Radiographic measurements revealed comparable outcomes of MIS compared with open surgery. Additionally, adding percutaneous K-wire fixation during MIS had an advantage in correcting DMAA compared with open surgery. Furthermore, the correction of DMAA could reduce recurrence of valgus deformity of the hallux.

Frontal Plane Correction of Hallux Valgus Deformity With a Minimally Invasive Third Generation Tecnique: Short-Term Radiographic Outcomes of a Prospective Case Series

A number of minimally invasive osteotomies have been described for the repair of hallux abducto valgus (HAV) deformities. However, there are no known published studies that evaluate the effects of minimally invasive surgery techniques on the reduction of frontal plane rotation in patients with HAV. The purpose of this study was to assess correction in the transverse and frontal planes in patients undergoing surgical repair of HAV deformity utilizing a modified percutaneous technique. One hundred and five feet in 105 patients with HAV deformity were treated with a third generation minimally invasive technique using a first metatarsal osteotomy that allowed for frontal plane correction in conjunction with an Akin osteotomy. The minimum follow-up time was 12 months. Preoperative and postoperative anteroposterior weightbearing x-ray images were assessed and four measurements were evaluated: hallux abductus angle (HAA), intermetatarsal angle (IMA), tibial sesamoid position and frontal plane rotation of the first metatarsal. There were statistically significant differences for each of the assessments between the preoperative and postoperative radiographs (p < .001). There was a mean reduction in the HAA of 23.5° ± 9.6°, in the IMA, 7.0° ± 3.5°, in the tibial sesamoid position, 2.6 ± 1.3, and an improvement in the assessment of first metatarsal pronation (1.4 ± 0.9). The overall complication rate was 18.1%, with 5.7% of the feet requiring reoperation. The minimally invasive procedure employed by the authors demonstrated suitable outcomes in reducing deformity in both the transverse and frontal planes.

Minimally invasive Chevron-Akin (MICA) osteotomies without Akin fixation in hallux valgus correction: a case series with 2-year follow-up

PURPOSE

The minimally invasive Chevron-Akin (MICA) is considered the third generation of minimally invasive hallux valgus (HV) surgery, and its original description included fixation of the Akin osteotomy with a screw. The aim of this study is to evaluate a series of patients undergoing HV correction using the MICA technique without screw fixation of the Akin osteotomy.

METHODS

We retrospectively evaluated 58 consecutive patients who underwent surgical correction for HV between August 2018 and March 2020. A total of 69 feet were evaluated with a minimum follow-up of 2 years. Clinical outcomes such as pain (VAS), function (AOFAS), range of movement, criteria personal satisfaction and complications were evaluated.

RESULTS

The AOFAS score (mean ± standard deviation) significantly improved from 57.0 ± 8.6 preoperatively to 93.9 ± 8.7 postoperatively (p < .001) with a minimum follow-up of 2 years. The VAS score improved from 6.0 ± 1.8 preoperatively to 0.6 ± 1.4 at 2-year follow-up (p < .001), and the hallux valgus angle reduced from 39.7 ± 6.9 to 8.9 ± 9.0 (p < .001). The majority of patients (95.6%) reported the result as excellent or good, and the most common complication was the need to remove the screw (7.2%).

CONCLUSIONS

The use of MICA without Akin osteotomy fixation resulted in successful correction of hallux valgus with improvements in clinical and radiographic parameters.

LEVEL OF EVIDENCE

IV, case series.

Fracturing the Lateral Hinge Improves Radiographic Alignment and Does Not Affect Clinical Outcomes of the Minimally Invasive Akin Osteotomy

BACKGROUND

Intraoperative fracture of the lateral cortex is common during Akin osteotomy. In a recent study, lateral cortex fracture did not impede healing or result in loss of correction in a combined cohort of open and percutaneous osteotomies stabilized by K-wire fixation. We hypothesize that undesired lateral cortex fracture will not affect radiographic correction and patient-reported outcomes in a percutaneous cohort stabilized by permanent, rigid screw fixation.

METHODS

Consecutive patients with hallux valgus who underwent first metatarsal osteotomy and percutaneous Akin osteotomy stabilized by permanent, rigid screw fixation between May 2020 and January 2022 were retrospectively reviewed. Patients were stratified based on fractured lateral cortex (FC) or its absence (nonfractured cortex [NFC]). Visual analog scale (VAS) and Foot Function Index (FFI) were used to assess pain and patient-reported outcomes at 1-year follow-up. Patients were polled for satisfaction at 1-year follow-up by yes/no survey.

RESULTS

Ninety-eight patients (89% female) were reviewed (98 feet; 43 NFC, 55 FC). Mean age was 48.3 years (range, 18-83 years). Mean preoperative VAS score was 7.5 and 7.7 in NFC and FC groups, which significantly decreased to 0.6 (P < .01) and 0.6 (P < .01), respectively. Mean total FFI was 53.9 and 54.2 and decreased to 17.9 (P < .01) and 17.2 (P < .01) in the NFC group and FC group, respectively. Overall, 97.8% of the NFC group and 96.4% of the FC group reported satisfaction.Mean HVA improved from 27.2 (16-42) degrees to 10.7 degrees (4-12) postoperatively in the NFC group. And in the FC group, HVA improved from 29.3 (19-39) degrees to 7.1 (4-12) degrees postoperatively. Postoperative HVA was significantly lower in the FC group (P < .05).

CONCLUSION

In an exclusively percutaneous surgical cohort with correction maintained by rigid screw fixation, fracture of the lateral cortex is associated with improved postoperative radiologic alignment without detriment to patient-reported outcomes.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Minimally Invasive Chevron Akin Osteotomy for Hallux Valgus Correction

Background

The minimally invasive chevron Akin osteotomy technique is indicated for the treatment of symptomatic mild to moderate hallux valgus deformities. The aim of the procedure is to restore alignment of the first ray while minimizing soft-tissue disruption.

Description

Prior to the procedure, radiographs are utilized to characterize the patient's hallux valgus deformity by determining the hallux valgus angle and intermetatarsal angle. The metatarsal rotation is also assessed via the lateral round sign and sesamoid view. To begin, a stab incision is made over the lateral aspect of the first metatarsophalangeal (MTP) joint and a lateral release is completed by percutaneous fenestration of the lateral capsule. Next, the chevron osteotomy of the first metatarsal is performed. To begin this step, a Kirschner wire is inserted in an anterograde fashion from the medial base of the first metatarsal to the lateral aspect of the metatarsal neck. The wire is then withdrawn just proximal to the osteotomy site. A stab incision is made at the medial aspect of the metatarsal neck, and periosteal elevation is utilized for soft-tissue dissection. A minimally invasive burr is utilized to complete the osteotomy cuts. With the osteotomy complete, the first metatarsal translator is utilized to lever the metatarsal head laterally. Once satisfactory alignment has been achieved, the Kirschner wire is advanced into the metatarsal head. A cannulated depth gauge is utilized to measure the length of the screw. The near cortex is drilled, and the screw is inserted over the Kirschner wire, which is then removed. The next step is the Akin osteotomy of the proximal phalanx. Again, a Kirschner wire is placed in an anterograde fashion from the medial base of the proximal phalanx to the lateral neck. The Kirschner wire is then withdrawn until the tip is just proximal to the osteotomy site. A stab incision is made over the medial aspect of the proximal phalangeal neck, and periosteal elevation is carried out. The burr is utilized to complete the osteotomy; however, care is taken not to cut the far cortex. The great toe is then rotated medially, collapsing on the osteotomy site and hinging on the intact far cortex. When satisfactory alignment has been achieved, the Kirschner wire is advanced across the osteotomy and far cortex. A cannulated depth gauge is utilized to measure the length of the screw, and the wire is then driven through the lateral skin and clamped. The near cortex is drilled, the cannulated screw is inserted, and the Kirschner wire is then removed. Final fluoroscopy is performed to assess adequate correction, alignment, and hardware placement. The stab incisions are closed with use of simple interrupted 3-0 nylon. A tongue-depressor bunion dressing is applied. The patient is discharged to home with this dressing, as well as with an offloading postoperative shoe.

Alternatives

Surgical alternatives include open distal chevron osteotomy, open Akin osteotomy, MTP joint arthrodesis, Lapidus fusion, and Scarf osteotomy7. Nonsurgical alternatives include the use of insoles, nonsteroidal anti-inflammatory drugs, wide-toed footwear, bunion shields and/or toe spacers, and physical therapy.

Rationale

The minimally invasive chevron Akin technique for hallux valgus correction provides alignment restoration of the first ray with less soft-tissue trauma than conventional open surgical procedures. This technique utilizes dorsal and medial stab incisions, instead of a more extensive open dorsal incision. These smaller incisions minimize the soft-tissue disruption, which has been reported to improve postoperative range of motion and to reduce loss of postoperative dorsiflexion related to scar tissue formation. Even while minimizing soft-tissue disruption, this technique still enables adequate correction and reliably stable fixation.

Expected Outcomes

The expected outcome of this procedure is a return to normal activities following the recovery period. Prior to correction, the patient is counseled regarding the risk of persistent or recurrent deformity postoperatively. The patient is also informed regarding potential postoperative stiffness. According to the literature, outcomes following minimally invasive chevron Akin hallux valgus correction have been shown to be equivalent to traditional open correction, with reported recurrence rates of <1% and excellent or good patient satisfaction in >90% of patients2-4. Function, as measured with use of the Manchester-Oxford Foot Questionnaire, has been shown to improve significantly from preoperatively (58.5 ± 15.9) to postoperatively (9.6 ± 9.2)2. Lastly, reported complication rates have varied according to the author's definition of complications, but typically range from 10% to 22%2-4.

Important Tips

If the chevron osteotomy cut accidentally turns into a transverse cut, then add a second screw to provide rotational stability.Obtain a perfect lateral view after placing the Kirschner wire in order to ensure satisfactory trajectory of the Kirschner wire in all planes.Drive the Akin Kirschner wire through the skin distally and clamp with a mosquito to prevent pullout after drilling.If the Akin Kirschner wire is too flimsy to get a good starting point and trajectory, exchange it for the chevron Kirschner wire and use the drill to exchange back just prior to screw insertion.Subtract approximately 4 mm from the measured screw length in order to ensure that the screw is not too long; otherwise, it may create a gap in the osteotomy site.

Acronyms and Abbreviations

NSAIDs = nonsteroidal anti-inflammatory drugsK-wire = Kirschner wireHVA = hallux valgus angleIMA = intermetatarsal angleMIS = minimally invasive surgeryAP = anteroposteriorOR = operating roomMTP = metatarsophalangealVAS = visual analog scaleMOXFQ = Manchester-Oxford Foot Questionnaire.

Impact of Sesamoid Coverage on Clinical Foot Function Following Fourth-Generation Percutaneous Hallux Valgus Surgery

Background

The impact of pronation and sesamoid coverage on clinical outcomes following percutaneous hallux valgus surgery are not currently known. The aim of this study was to investigate if sesamoid coverage was associated with worse clinical outcomes at 12-month follow-up following percutaneous hallux valgus surgery.

Methods

Retrospective comparative observational study of clinical and radiographic outcomes based on a previously published prospective dataset. Patients were stratified into 3 cohorts based on the degree of sesamoid coverage (normal, mild, or moderate) on 12-month weightbearing radiographs following fourth-generation percutaneous hallux valgus surgery. Primary outcome was a validated patient-reported outcome measure (PROM), the Manchester-Oxford Foot Questionnaire (MOXFQ). Secondary outcomes included Euroqol-5D, VAS Pain, and radiographic deformity correction.

Results

Forty-seven feet underwent primary fourth-generation HV surgery and were stratified into 3 cohorts. There were 19, 16, and 12 feet in the normal, mild, and moderate cohorts respectively. There was no significant difference in either pre- or postoperative foot function (all MOXFQ domains, P > .05) or health-related quality of life (EQ-5D Index or VAS, P > .05). The MOXFQ Index preoperatively was as follows: normal cohort, 56.1 ± 26.9; mild cohort, 54.1 ± 17.9; and severe cohort, 49.6 ± 23.8; and postoperatively was as follows: normal cohort, 15.6 ± 21.5; mild cohort, 11.4 ± 15.5; and severe cohort, 11.4 ± 13.6 (P = .737-.908). There was significantly worse hallux valgus angle (HVA) and intermetatarsal angle (IMA) between the cohorts (P < .01). Although HVA and IMA were corrected to normal parameters following surgery in all cohorts, there was a significantly worse postoperative HVA in the moderate sesamoid coverage (5.3 ± 3.9 vs 7.9 ± 5.3 vs 11.4 ± 3.7, P < .01); however, IMA was not significantly different (3.4 ± 2.2 vs 4.1 ± 2.7 vs 5.2 ± 2.9, P = .168).

Conclusion

This study found that cases where the sesamoids were not reduced had a poorer correction and had worse preoperative deformity. Clinical outcomes and foot function following fourth-generation percutaneous hallux valgus surgery were not affected by sesamoid coverage at the 12-month follow-up. The long-term implications in the difference in radiographic deformity between the 3 cohorts are not known, and further work should explore the relationship of first ray pronation and sesamoid position, particularly with regard to recurrence.

Level of evidence

Level III, retrospective comparative study of prospectively collected data.

The potentially dangerous zone of the dorsomedial cutaneous nerve in minimally invasive surgery for hallux valgus: a cadaveric study

BACKGROUND

This study aims to describe the distribution of the dorsomedial cutaneous nerve (DMCN) in the middle and proximal parts of the metatarsal from a lateral view. The purpose is to provide guidance to surgeons in protecting the nerve during the 3rd and 4th generation minimally invasive surgery (MIS) for hallux valgus (HV).

METHODS

A total of 20 cadaveric feet were dissected to expose the course of the DMCN and sentinel vein. Measurements of the distances between the nerve/vein and the upper border of the metatarsal, as well as the height of the metatarsal, were taken from a lateral view. The distribution area was then described in proportion.

RESULTS

At the base of the metatarsal, the DMCN was distributed in the upper 25.7% of the area. When it reached the middle of the metatarsal, the DMCN was distributed in the upper 13.2-47.2% of the area. As for the sentinel vein, it was distributed in the upper 23.5-71.9% and upper 4.1-52.7%, respectively, at these two positions.

CONCLUSIONS

The area, which is above the line connecting the upper 1/4 point at the base of the first metatarsal and the 1/2 point at the middle of the first metatarsal, is a dangerous zone for the DMCN. Avoiding the zone is recommended during MIS for HV.

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.

A modified minimally invasive osteotomy for hallux valgus enables reduction of malpositioned sesamoid bones

BACKGROUND

The current minimally invasive distal metatarsal osteotomy for hallux valgus (HV) is V-shaped, which prevents the correction of the rotational metatarsal head deformity and reduction of the sesamoid bones. We sought to determine the optimal method for sesamoid bone reduction during HV surgery.

METHODS

We reviewed the medical records of 53 patients who underwent HV surgery between 2017 and 2019 using one of three techniques: open chevron osteotomy (n = 19), minimally invasive V-shaped osteotomy (n = 18), and a modified straight minimally invasive osteotomy (n = 16). The sesamoid position was graded using the Hardy and Clapham method on weight-bearing radiographs.

RESULTS

When compared to open chevron and V-shaped osteotomies, the modified osteotomy resulted in significantly lower postoperative sesamoid position scores (3.74 ± 1.48, 4.61 ± 1.09, and 1.44 ± 0.81, respectively, P < 0.001). Furthermore, the mean change in postoperative sesamoid position score was greater (P < 0.001).

CONCLUSION

The modified minimally invasive osteotomy was superior to the other two techniques in correcting HV deformity in all planes, including sesamoid reduction.

Wide-Awake Local Anesthetic No Tourniquet Surgery of the Foot and Ankle

Wide awake local anesthetic no tourniquet (WALANT) surgery of the foot and ankle has the potential to offer safe and effective surgeon-based anesthesia for a significant number of surgeries about the foot and ankle. This has been documented with significant and growing body of literature. WALANT could offer significant advantages with respect to patient experience, per case cost of procedures as well as for improving access for patients to operative resources in a setting of scarcity or restricted access.

Preoperative degree of deformity and underlying disease affect the postoperative deformity of joint-preserving hallux valgus surgery

BACKGROUND

The combination of distal osteotomy with lateral dissection in joint-preserving surgery for severe hallux valgus deformity has recently begun to yield encouraging results. We examined the frequency of complications and risk factors of those for joint-preserving surgery in patients with and without rheumatoid arthritis (RA).

METHODS

A retrospective, observational study of 72 feet (27 patients with RA) was performed. The inclusion criteria were patients who underwent joint-preserving surgery for hallux valgus deformity at our hospital between January 2008 and March 2016 who could be followed up with for longer than 12 months.

RESULTS

The mean preoperative and immediate postoperative hallux valgus angles (HVA) were 41.8 and 4.4, respectively. The mean preoperative and immediate postoperative intermetatarsal angles between the first and second metatarsal bones (M1-M2A) were 14.6 and 5.8, respectively. At the final postoperative evaluation, the mean HVA was 8.8 and the mean M1-M2A was 6.4.Data were compared among the patients with complications (recurrent valgus deformity, varus deformity), and those without complications (normal HVA) at the final postoperative evaluation. The rate of RA in the varus deformity group was 71.4%, which tended to be higher than in other groups (p = .058). The mean preoperative HVA were 48.2 and 52.6 in the group of recurrent valgus deformity and varus deformity, which was higher than the normal HVA group (p = .001).

CONCLUSIONS

High preoperative HVA was a risk factor for the recurrence of valgus deformity. Most of the varus deformities were observed in the RA group with high preoperative HVA; therefore, caution should be exercised in operating on patients with severe deformity or those with RA.

LEVEL OF EVIDENCE

III.

Learning curve in relation to radiation exposure, procedure duration and complications rate for Minimally Invasive Chevron Akin (MICA) osteotomy

BACKGROUND

Minimally invasive chevron Akin osteotomy (MICA) has become increasingly common and is compatible with the traditional open approaches for hallux valgus correction. However, it is impeded by concerns regarding the steep learning curve, increased radiation exposure and some specific complications. No standardized method for identifying a learning curve exists. We used a reproducible mathematical model to accurately define the learning curve of MICA with a focus on fluoroscopy time, procedure duration and complications rate.

METHODS

We conducted a retrospective study of MICA procedure performed by a single surgeon during his initial experience with this procedure. The chronologic case number was plotted against variables of interest and learning was identified as the point at which instantaneous rate of change of a curve fit to the data set equalled the average rate of change of the data set.

RESULTS

One hundred cases have been analysed. Learning plateau in operation time was achieved after 29 cases, with the first 29 cases requiring a median of 60 min compared to 40 min for the latter 71 cases. Proficiency in fluoroscopy application occurred in case 30. The median fluoroscopy time for the first 30 cases was 86 seconds compared to 70 seconds in another 70 cases. The complication rate plateau was reached after 42 cases, with 15 of 22 complications occurring in the group operated first.

CONCLUSION

Results demonstrate surgeon's comfort with MICA to minimize operative time and radiation exposure after 30 cases. The plateau is achieved later for complications. Findings impose lag between surgeon feeling comfortable with procedure and a decrease in complications. Further research is reasonable to analyse several surgeons learning curve and to generate a potential reference learning curve that could serve as a normative.

TRIAL REGISTRATION

UKC-MB-KME-33/19, retrospectively registered.

Temporal Changes in Clinical Outcomes after Minimally Invasive Surgery for Hallux Valgus Correction in Women without Postoperative Complications

Minimally invasive surgery (MIS) is currently used to correct hallux valgus deformities. Most studies reporting on MIS techniques to correct hallux valgus deformities included patients with postoperative complications. These reported complications, with an average rate of 23%, had significant negative effects on the clinical outcomes in this patient population. In the present study, a cohort of 63 women who underwent MIS hallux valgus correction was assessed preoperatively and at a mean follow-up of 1.0, 4.7, and 6.5 years using the American Orthopaedic Foot and Ankle Society (AOFAS) scale and the Manchester Oxford Foot Questionnaire (MOXFQ). The main criterion for inclusion in this cohort was a lack of complications during the entire follow-up period. The results showed significant improvements in both AOFAS and MOXFQ scores between the preoperative and 1-year follow-up assessments. By contrast, clinically small and nonsignificant changes were observed among postoperative follow-up values. The number of enrolled patients needs to be increased in future studies, with different surgeons and techniques included. Nevertheless, our study findings will inform patients about the outcomes they can expect over the years if no complications occur.

Third-Generation Minimally Invasive Chevron Akin Osteotomy for Hallux Valgus: Three-Year Outcomes

Introduction

Numerous minimally invasive techniques have been developed for Hallux Valgus in recent years. Third-generation Minimally Invasive Chevron Akin (MICA) osteotomy has shown promising early results, but longer-term follow-up is required to assess whether patient clinical and radiological improvement is sustained. This cohort study presents three-year follow-up outcomes for patients of a single surgeon case series.

Methods

Thirty-three patients underwent third-generation MICA surgery between 2017 and 2018. Patient clinical-reported outcome measures included American Orthopaedic Foot & Ankle Society (AOFAS), Manchester-Oxford Foot Questionnaire (MOXFQ) scores, and Coughlin satisfaction. Radiographic outcomes were evaluated after a period of three years using hallux valgus angle (HVA) and inter-metatarsal angle (IMA), and compared to pre- and early post-operative outcomes.

Results

At 36 months, mean AOFAS scores improved from 48.2 to 95.6, mean MOXFQ scores improved from 57.6 to 6.7. Using the Coughlin scale, 81.8% of patients rated their outcome as 'Excellent' and 18.2% as 'Good'. Radiographic outcomes showed HVA and mean IMA decreased from 34.6 degrees to 16.0 degrees and from 13.1 to 6.1, respectively at 36 months.

Conclusion

Third-generation MICA demonstrates promising patient satisfaction scores post-operatively, and we have shown these improvements are sustained over a minimum three-year follow-up period.

Level of Evidence

Level IV, case series.

Early Outcomes of Third-Generation Minimally Invasive Chevron-Akin (MICA) Osteotomy for Symptomatic Hallux Valgus Deformity

Hallux valgus is a common progressive forefoot deformity. Although open techniques have shown good outcomes, no technique has been shown to be superior to other techniques. The current third generation of minimally invasive Chevron-Akin (MICA) technique features a percutaneous procedure with a stable internal fixation. The technique used in this study resulted in stable internal fixation; however, 1 screw was used in intramedullary fashion in the majority of cases. The purpose of this study is to review the early outcomes of MICA. Electronic Health Records (EHR) were queried for patients who underwent MICA to treat hallux valgus (HV) deformity, by a single surgeon. The primary clinical outcomes assessed were visual analog pain score (VAS), rate of revision surgery, and recurrence. Radiographic outcomes were assessed including pre and postoperative hallux valgus angle (HVA), intermetatarsal angle (IMA), and bony foot width. The secondary outcomes included postoperative complications. A total of 91 feet underwent MICA to correct symptomatic HV deformity. The mean age of this cohort was 53.63 ± 15.42 years, mean body mass index (BMI) of 26.81 ± 6.21 kg/m², mean follow-up of 6.33 ± 6.39 months and 87 feet belonged to female patients. Patients showed significant improvement in VAS and radiographic outcomes at final follow-up, with a mean improvement of 10.70° ± 6.42°, 2.39° ± 3.55°, and 5.30 mm ± 4.23 mm for the HVA, IMA, and bony foot width, respectively. Two patients (2.2%) required revision surgery for nonunion and removal of symptomatic hardware. One patient had a second metatarsal fracture treated nonoperatively. No feet had recurrence, hardware loosening, infection, or scar hypersensitivity. The current study reported on early outcomes for MICA. This technique appears to be effective and safe with no failure of fixation in our patients. We showed in our short-term follow-up, MICA led to significant improvement in pain and radiographic scores.Levels of Evidence: III, retrospective study.

Perspectives and trends for minimally invasive surgery for hallux valgus deformity in the Asia Pacific region

BACKGROUND

Evolving evidence and improved instrumentation have led to increasing importance of minimally invasive surgery (MIS) surgery in the treatment of hallux valgus deformity. This study aims to investigate the current trends of the practice of MIS hallux valgus surgery in the Asia Pacific region.

METHOD

A survey was sent via email to 30 fellowship-trained foot and ankle surgeons in 11 Asia Pacific countries, all registered with their respective national orthopaedic societies. The survey consisted of 8 questions and was designed to assess surgeon experience with MIS hallux valgus surgery, including common contraindications, satisfaction levels, learning curves and post-operative rehabilitation after MIS hallux valgus surgery.

RESULTS

The vast majority of surgeons (63%) performed MIS hallux valgus surgery. However, only 18% of surgeons performed MIS surgery in more than half of their hallux valgus cases. A severe deformity was the most common contraindication (81%), followed by the instability of the first tarsometatarsal joint (50%), and abnormal DMAA (Distal Metatarsal Articular Angle) (38%). There was no statistically significant difference between the satisfaction score of MIS versus open surgery (p-value 0.1). The median number of cases the surgeons needed to perform before they considered themselves comfortable performing the surgery was 10 cases (range 1-100). Most surgeons allowed full weight bearing at 4-6 weeks after surgery.

CONCLUSIONS

MIS hallux valgus surgery is gaining popularity in the Asia Pacific region, with the majority of surgeons adopting this practice. The fact that severe deformity is seen as the most frequent contraindication and that MIS surgery is still not the most popular alternative demonstrates that surgeons are still circumspect when it comes to MIS surgery. Surgeons can use the findings of this study to guide their adoption of MIS practices in hallux valgus surgery and gauge well they perform in comparison to their counterparts in the Asia Pacific region.

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.

Five-Year Follow-up of Third-Generation Percutaneous Chevron and Akin Osteotomies (PECA) for Hallux Valgus

BACKGROUND

Recent large studies of third-generation minimally invasive hallux valgus surgery (MIS) have demonstrated significant improvement in clinical and radiologic outcomes. It remains unknown whether these clinical and radiologic outcomes are maintained in the medium to long term. The aim of this study was to investigate the minimum 5-year clinical and radiologic outcomes following third-generation MIS hallux valgus surgery in the hands of a high-volume MIS surgeon.

METHODS

A retrospective observational single highly experienced MIS surgeon case series of consecutive patients undergoing primary isolated third-generation percutaneous chevron and Akin osteotomies (PECA) for hallux valgus with a minimum 60-month clinical and radiographic follow-up. Primary outcome was radiographic assessment of the hallux valgus angle (HVA) and intermetatarsal angle (IMA) preoperatively, 6 months, and ≥60 months following PECA. Secondary outcomes included the Manchester-Oxford Foot Questionnaire, patient satisfaction, EuroQol-5D visual analog scale and the visual analog scale for pain.

RESULTS

Between 2012 and 2014, 126 consecutive feet underwent isolated third-generation PECA, with complete data available for 78 (61.9%) feet. The median follow-up was 65.0 (IQR 64-69; range 60-88) months. There was a significant improvement in radiographic deformity correction; the median IMA improved from 12.0 degrees (interquartile range [IQR]: 10.8-14.2) to 6.0 degrees (IQR: 4.2-7.3) (P < .001), and the median HVA improved from 27.2 degrees (IQR: 20.6-34.4) to 7.2 degrees (IQR: 3.4-11.6). Median MOXFQ Index score at ≥60-month follow-up was 2.3 (IQR: 0.0-7.8). The radiographic recurrence rate (defined as HVA >15 degrees) was 7.7% at final follow-up. The complication rate was 4.8%.

CONCLUSION

Radiologic deformity correction for the 78 feet we were able to follow that had third-generation PECA performed by a single highly experienced MIS surgeon was found to be maintained at a mean follow-up of average 66.8 months, with a radiographic recurrence rate of 7.7%. Clinical PROMs and patient satisfaction levels were high and comparable to other third-generation studies with shorter duration of follow-up.

LEVEL OF EVIDENCE

Level IV, retrospective cohort study.

Radiographic Forefoot Width Following Minimally Invasive Chevron Akin Bunionectomy

Background

Hallux valgus (HV) is a common cause of pain and deformity of the forefoot. Minimally invasive chevron Akin (MICA) bunionectomy is a method for HV correction associated with less pain and swelling, with early return to weightbearing in a regular shoe. The purpose of this study was to determine how the MICA procedure affects forefoot width.

Methods

Twenty-eight patients (26 female, 2 male; 9 left, 19 right) at a single institution who underwent primary MICA for HV correction by 3 treating surgeons were retrospectively reviewed. Pre- and postoperative hallux valgus angle (HVA), intermetatarsal angle (IMA), distal metatarsal articular angle (DMAA), bony forefoot width, and soft tissue forefoot width were measured by 2 independent observers. Radiographic measurements were calibrated using fifth metatarsal length. Wilcoxon signed rank test compared changes in HVA, IMA, DMAA, and forefoot widths. Pearson correlation coefficient evaluated association between HVA, IMA, DMAA, and changes in forefoot width.

Results

At mean follow-up of 5.4 (range 3-13.7) months, bony forefoot width decreased significantly by 3.7 mm (4%, P < .001) and soft tissue forefoot width decreased by 2.5 mm (2%, P < .01). Decrease in HVA was moderately correlated with change in bony forefoot width (r = .38, P < .05) and change in soft tissue forefoot width (r = .45, P < .05). Decrease in IMA was moderately correlated with change in bony forefoot width (r = .45, P < .05) and change in soft tissue forefoot width (r = .44, P < .05).

Conclusion

The MICA procedure resulted in modest, yet significant, decrease in both bony and soft tissue forefoot width. Decrease in HVA and IMA demonstrated moderate correlation with changes in forefoot width. Patients can be counseled on these changes leading up to, and after, MICA bunionectomy surgery.

Level of Evidence

Level III, retrospective comparative series.

First metatarsal single-screw minimally invasive chevron-akin osteotomy: A cost effective and clinically reliable technique

Purpose

The common disease hallux valgus results in foot discomfort and dysfunction. Less soft tissue damage and faster wound healing have made minimally invasive surgery (MIS) more popular. However, little research has compared the fixation results of minimally invasive chevron-akin (MICA) osteotomy thus far. In this study, the clinical and radiographic results of MICA with first metatarsal single- or dual-screw fixation are being examined.

Methods

A total of 107 feet of 103 patients with mild to moderate symptomatic hallux valgus treated MICA from January 2018 to June 2020 were retrospective evaluated, with at least 12-months follow-up. 51 patients underwent single-screw fixation procedures and 52 patients received dual-screw fixation procedures. Patients were assessed preoperatively and at the final follow-up with radiographic measurements [hallux valgus angle (HVA), intermetatarsal angle (IMA) and distal metatarsal articular angle (DMAA)] and clinical scores (american orthopaedic foot and ankle society (AOFAS) forefoot score, visual analog scale (VAS) and Manchester-Oxford Foot Questionnaire (MOxFQ) scores). The coughlin satisfaction scores were also obtained.

Results

Both groups showed significantly improved HVA, IMA and DMAA at the final follow-up (P < 0.001). Regarding clinical outcomes, the AOFAS, VAS and MOxFQ in two categories also significantly improved postoperatively (P < 0.001). There was no obvious difference in the clinical and radiographic outcomes between the two groups (HVA, P = 0.833; IMA, P = 0.073; DMAA, P = 0.35; AOFAS, P = 0.48; VAS, P = 0.86; MOxFQ, P = 0.87). However, the single-screw fixation group showed significantly lower operation time and less number of intraoperative fluoroscopy (P < 0.001). No serious complications were observed in either group. The single-screw fixation technique saves at least $1,086 compared with the dual-screw group.

Conclusion

At the final follow-up, both the single- and dual-screw fixation groups had comparable good to excellent clinical and radiographic outcomes, as well as a similar incidence of complications. Additionally, the single-screw fixation group reduces overall surgical costs, number of intraoperative fluoroscopy and operational time.

[Minimally invasive forefoot surgery: concept and techniques]

Minimally invasive surgery (MIS) has advanced to an established approach in the correction of all deformities of the forefoot. For the first ray the minimally invasive chevron and Akin osteotomy (MICA) shows very good clinical results and provides a broad spectrum of indications in comparison to the classical chevron osteotomy. The minimally invasive treatment of hallux rigidus also seems to achieve comparable results to the open techniques, although the surgical indications must be thoroughly evaluated. Lesser toe deformities are often easier to treat with minimally invasive osteotomy, capsule release and tendon lengthening than with complex open procedures and usually do not require any internal fixation material. Compared to the classical Weil osteotomy, distal metatarsal osteotomy shows a reduced rate of cock-up deformities and does not require internal fixation. In relation to open procedures, minimally invasive approaches should be accepted as a valuable addition and alternative to the classical open techniques due to the reduced rate of wound healing disorders and postoperative pain.

The Learning Curve of Third-Generation Percutaneous Chevron and Akin Osteotomy (PECA) for Hallux Valgus

The learning curve to reach technical proficiency for third-generation percutaneous or minimally invasive chevron and Akin osteotomies (PECA/MICA) is recognized to be steep however it is poorly defined in the literature. This study is a retrospective review of the first 58 consecutive PECA cases of a single surgeon. The primary outcome was the number of cases required to reach technical proficiency as defined by the operation time. Secondary outcomes included radiation exposure, radiographic deformity correction, and complication rates. Between November 2017 and March 2019, 61 consecutive PECA cases were performed with outcome data available for 58 of these (95%). Technical proficiency was reached after 38 cases. Operation time and radiation exposure significantly decreased after this transition point (p < .05). There was no difference in complication rate or radiographic deformity correction regardless of position along the learning curve (p > .05). In conclusion, the mean number of cases required to reach technical proficiency in third-generation PECA is 38 cases. The complication rate does not correlate to the number of cases performed, therefore surgeons interested in learning minimally invasive surgery can be reassured that there is unlikely to be an additional risk of harm to a patient during the learning curve.

Clinical and Radiographic Outcomes of Percutaneous Third-Generation Double First Metatarsal Osteotomy Combined With Closing-Wedge Proximal Phalangeal Osteotomy for Moderate and Severe Hallux Valgus

BACKGROUND

The treatment for severe hallux valgus deformity presents a challenge with high risk of complications. Third generation MIS techniques have increased their publications in recent years. The aim was to compare clinical and radiologic outcomes in moderate and severe cases and report minor and major complications.

METHODS

Retrospective series of cases with prospective data collection of 156 consecutive feet that underwent percutaneous double first metatarsal osteotomy (PEDO) and first phalanx osteotomy between 2008 and 2019 for moderate (hallux valgus angle [HVA] between ≥20 and <40 degrees and/or intermetatarsal angle [IMA] <16 degrees) and severe (HVA ≥40 degrees and/or IMA ≥16 degrees) hallux valgus deformities. Primary outcomes included radiographic and clinical parameters. Secondary outcomes included minor and major complications.

RESULTS

A total of 156 procedures were performed in 128 patients. Mean age was 54.3 years (SD 14.3) (range, 19-82 years), median follow-up was 22.6 months (range, 12-96 months). Radiographic changes pre- to postoperation were as follows: HVA changed from 38.2 (SD 10.1) degrees to 11.2 (SD 8.3) degrees (P < .001), IMA from 14.7 (SD 3.2) degrees to 7.9 (SD 3.7) degrees (P < .001), and distal articular metatarsal angle from 19.7 (SD 6.3) degrees to 8.8 (SD 5.7) degrees (P < .001) after PEDO technique. Clinical changes pre- to postoperation were as follows: American Orthopaedic Foot & Ankle Society ankle-hindfoot scale scores improved from 47.3 (SD 16.5) to 87 (SD 11.6) (P < .001) and visual analog scale scores from 5 (2.7) to 0.9 (1.3) (P < .001). The satisfaction rate was 97% in the total sample. Recurrence rate (HVA ≥20 degrees) was 7.7%. Hallux varus (HVA <0 degrees) occurred in 5.8%, acute osteomyelitis in 1.3%, partial avascular necrosis in 0.6%, screw removal in 0.6%, and reoperation in 1.9%. No nonunion was observed.

CONCLUSION

Clinical and radiographic parameters improved significantly, with a minimum of 12 months of follow-up in moderate and severe hallux valgus. Long experience in percutaneous surgery and specific instruments are needed for this technique. Recurrence was linked to preoperative HVA ≥40 degrees and postoperative tibial sesamoid position; Hallux varus was linked to lateral soft tissue release.

LEVEL OF EVIDENCE

Level IV, case series.

Time to maximum clinical improvement following minimally invasive chevron and Akin osteotomies (MICA) in hallux valgus surgery

BACKGROUND

There is increasing evidence of positive improvement in clinical and radiological outcomes following minimally invasive hallux valgus deformity correction surgery (MIS). This study investigated the rate of improvement in clinical patient reported outcome measures (PROMs) following MIS as this is not well understood.

METHODS

Between July 2014 and July 2019, data was prospectively collected from consecutive patients pre-operatively and at 6, 12, and 24 months following third-generation minimally invasive chevron and Akin osteotomies (MICA). Radiographic deformity and correction was assessed using weight-bearing radiographs pre-operatively and 6 weeks post-operatively. The primary outcome measure was the change in Manchester Oxford Foot Questionnaire (MOXFQ) score at each time point. Secondary outcomes include radiographic deformity correction, health-related quality of life PROMs and exploration of cases where PROMs did not improve.

RESULTS

There were 202 feet with complete PROM data for every time point. There was a statistically significant improvement in MOXFQ Index score at each time point (p < 0.05) following MICA surgery. The majority of the improvement occurred within the first 6 months. A subgroup of 17 feet (8.4%) were identified which had worse MOXFQ Index scores 6 months following MICA. For 14 feet in this subgroup (82.4%), the MOXFQ Index score subsequently improved over time such that by two years, their score had significantly improved compared to their pre-operative score.

CONCLUSION

The majority of PROM improvement with MICA is gained by 6 months post-operatively but further significant improvement can be seen up to 2 years. Those patients who have not improved at 6 months, are likely to do so with time.

LEVEL OF EVIDENCE

IV.

Minimally Invasive Chevron-Akin for Correction of Moderate and Severe Hallux Valgus Deformities: Clinical and Radiologic Outcomes With a Minimum 2-Year Follow-up

BACKGROUND

The minimally invasive chevron-Akin (MICA) technique has already demonstrated efficacy compared with other known surgical treatments for mild to moderate hallux valgus (HV). MICA combines percutaneous osteotomies with the benefits of modern, rigid internal fixation. The aim of study was to evaluate the radiographic parameters, clinical improvement, and potential complications in moderate to severe HV cases, operated using the MICA technique.

METHODS

Retrospective study including 70 feet with HV operated using the MICA technique. The AOFAS hallux MTP-IP score and radiographics for HV evaluation were applied preoperatively, and after 6 months, 1 year, and 2 years of follow-up. The following radiographic parameters were measured: metatarsophalangeal hallux valgus angle (HVA), distal metatarsal articular angle (DMAA), interphalangeal angle (IPA), and intermetatarsal angle (IMA).

RESULTS

The average preoperative VAS pain score was 8.2 ± 1.5, which improved to 1.2 ± 2.2 at 24 months. The mean preoperative IMA was 14.8 ± 3.6 degrees compared with a mean of 7.5 ± 2.1 degrees (P < .01) at 24 months. The preoperative HVA value averaged 30.4 ± 9.8 degrees and at 6 months postoperatively 11.1 ± 6.8 degrees (P < .01), which remained stable until measured at 24 months. The mean preoperative DMAA was 16.3 ± 8.6 degrees and at the 6-month follow-up was 7.8 ± 5.4 degrees (P < .01). The mean preoperative IPA was 7.63 ± 4.4 degrees compared with a mean of 6.28 ± 3.5 degrees (P > .05) at 24 months. Complications included painful hardware (14.28%), neuropathic pain (2.85%), and loss of correction (4.28%).

CONCLUSION

In this retrospective review from a single center, we found the MICA technique to be an effective procedure for correcting moderate to severe HV, with a low rate of recurrence and an acceptable rate of complications. Patients undergoing the surgical procedure in our series showed a significant reduction in radiographic parameters and a significant improvement in clinical scores, maintaining these results over time.

LEVEL OF EVIDENCE

Level IV, retrospective study.

Valgus Second Toe Deformity Treated With a Percutaneous Extracapsular Closing-Wedge Osteotomy of the Proximal Phalanx

BACKGROUND

Coronal and sagittal plane deformities of the lesser toes are common yet challenging to treat. Traditional open releases and translational Weil osteotomies can be unpredictable and lead to postoperative stiffness. We present the results of a percutaneous closing wedge extracapsular osteotomy of the proximal phalanx to treat valgus deformity of the second toe.

METHODS

Thirty-one patients underwent 40 percutaneous osteotomies at a median age of 58.6±9.4 years. Using a small dorsomedial incision, a percutaneous proximal metaphyseal medial closing-wedge extracapsular osteotomy of the second toe is performed, leaving the dorsolateral cortex intact. An irrigated low-speed, high-torque 2- × 8-mm burr is used under image guidance. The osteotomy is then closed to correct deformity and taped for 2 weeks. Patient-reported outcomes and weightbearing radiographs were obtained.

RESULTS

Questionnaire data was available for 89.7% (n=35) of cases. Most cases (91.4%) were either satisfied or extremely satisfied with the procedure. Radiographs were available for 90.0% of osteotomies, with a median length from surgery to radiographic follow-up of 1.6 years (range 0.5-6.3; SD ±1.5). Median second-toe valgus angle (STVA) decreased from 16.2±10.7 degrees to 5.0±7.0 degrees (P < .001) at final follow-up. All osteotomies united with no delayed union. There were no wound complications or infections. We found 2 cases of radiographic recurrence.

CONCLUSION

Percutaneous proximal phalanx base metaphyseal closing wedge extracapsular osteotomies of lesser toes to correct coronal plane deformity is useful adjunct to first-ray corrective surgery and is associated with high levels of patient satisfaction.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Midterm Outcomes of Sliding Distal Metatarsal Minimally Invasive Osteotomy to Treat Bunionette Deformity

BACKGROUND

Bunionette deformity is described as a painful bony prominence on the lateral aspect of the fifth metatarsal head. The present study prospectively assessed the clinical, functional, and radiographic outcomes of sliding distal metatarsal minimally invasive osteotomy (S-DMMO) used in a large series of patients with a midterm follow-up period.

METHODS

From December 2015 to December 2018, we evaluated 74 feet (57 patients). Radiologic (4-to-5 intermetatarsal angle, fifth metatarsophalangeal angle, the fifth metatarsal head width, lateral deviation angle, fifth metatarsal length, medial displacement, and elevation), clinician-reported scores (AOFAS score, visual analog scale [VAS]) and patient-reported outcomes measure (Foot and Ankle Ability Measure [FAAM] activities of daily living [ADL], FAAM sports, Manchester-Oxford Foot Questionnaire [MOXFQ], and patient satisfaction survey) were included in the analysis. The time to bone union was also assessed.

RESULTS

The average 4-to-5 intermetatarsal angle improved from 11.1 degrees preoperatively to 4.5 degrees postoperatively (P < .001), whereas the average fifth metatarsophalangeal angle improved from 15.7 degrees preoperatively to 4.8 degrees postoperatively (P < .001). The lateral deviation angle was found to be 2.2 degrees. The fifth metatarsal length decreased from 66.6 to 64.3 mm postoperatively. The average initial medial displacement was 4.67 mm preoperatively and 4.54 mm at final follow-up. The elevation of the fifth metatarsal head was 1.08 mm. The American Orthopaedic Foot & Ankle Society score improved from 54.3 ± 20.86 points preoperatively to 93.4 ± 17.3 (P < .001). VAS score decreased from 7.9 to 0.7 (P < .001). Also, FAAM ALD, FAAM Sport, and MOXFQ showed statistically significant differences (P < .001) between preoperative and postoperative periods. Patients found the procedure excellent in 89.1% of cases, very good in 5.4%, and good in 5.4%. Bone union was obtained at 8.1 weeks.

CONCLUSION

The most important finding of the present study is that S-DMMO showed improvement in function and pain associated with a high satisfaction rate. Also, we found substantial capacity to correct deformities and a low incidence of complications.

LEVEL OF EVIDENCE

Level IV, case series.

Early Radiographic Outcomes of Minimally Invasive Chevron Bunionectomy Compared to the Modified Lapidus Procedure

Background

Minimally invasive (MIS) bunion surgery has become increasingly popular. Although early reports on outcomes have been encouraging, no study to date has compared outcomes from the MIS chevron and Akin procedures to the modified Lapidus procedure. Our primary aim was to compare early radiographic outcomes of the MIS chevron and Akin osteotomies to those of the modified Lapidus procedure in patients with comparable deformities, and secondarily to compare clinical outcomes.

Methods

Patients were retrospectively reviewed for inclusion from a prospectively collected foot and ankle registry. Patients were eligible if they underwent either the MIS bunionectomy or modified Lapidus procedure and had preoperative and minimum 5-month postoperative weightbearing radiographs. Forty-one patients who underwent MIS bunionectomy were matched to 41 patients who underwent Lapidus bunionectomy based on radiographic parameters. Demographics, radiographic parameters, complications, reoperations, and PROMIS scores were compared between groups.

Results

Both groups achieved similar radiographic correction. There was no significant difference in pre- or postoperative PROMIS scores between groups. Procedure duration was significantly faster in the MIS group (P < .001). Bunion recurrence (hallux valgus angle ≥20 degrees) occurred in 1 MIS patient and 2 Lapidus patients, with all patients asymptomatic. The most common reason for reoperation was removal of hardware (4 patients in the MIS group, 2 patients in the Lapidus group).

Conclusion

This is the first study to our knowledge to compare early radiographic outcomes between MIS bunionectomy and the modified Lapidus procedure in patients matched for bunion severity. We found that patients with similar preoperative deformities experience similar radiographic correction following MIS chevron and Akin osteotomies vs modified Lapidus bunionectomy. Further research is needed to investigate satisfaction differences between the procedures, longer-term outcomes, and which deformities are best suited to each procedure.

Level of Evidence

Level III, Retrospective case control study.

Pre- and Post-Operative Relationship between Radiological Measures and Clinical Outcomes in Women with Hallux Valgus

The surgical correction of a hallux valgus (HV) deformity improves radiological parameters and clinical outcomes. However, it is not known how these improvements are related between themselves. In this retrospective study, 73 women were assessed preoperatively and 60 months after HV surgical correction. Several radiological parameters were measured: the hallux valgus angle (HVA), I−II intermetatarsal angle (IMA) and sesamoid position. The functional outcomes were assessed using the American Orthopaedic Foot and Ankle Society (AOFAS) Hallux Metatarsophalangeal-Interphalangeal (HMI) scale, and patient-reported outcomes (PROMs) were recorded with the Manchester−Oxford Foot Questionnaire (MOXFQ). A pre−post-surgery comparison of radiological and clinical values was performed, the correlation among them was studied and the differences pre−post-surgery in the radiological measurements compared with those for the clinical outcomes were studied. The results show that all the radiological parameters, functional outcomes and PROMs improved significantly from their pre-operative values to the follow-up values. Multivariate regression analysis showed a significant relationship (p < 0.001) between the differential pre−post-surgery AOFAS scoring only with two sesamoid position differential pre−post-surgery measures: position of medial sesamoid (PMS) and translation of the first metatarsal head (TMH). However, no significant association was observed between the pre−post-surgery radiological differences and the pre−post-surgery MOXFQ scoring.

Minimally invasive surgery for severe hallux valgus in 106 feet

BACKGROUND

There is widespread variation in the optimal procedure for correction of severe hallux valgus deformity defined as hallux valgus angle (HVA) (≥40°) and/or 1-2 intermetatarsal angle (IMA) (≥20°). There is limited evidence investigating the clinical or radiological outcomes following treatment of severe hallux valgus deformity with third-generation minimally invasive chevron and Akin osteotomies (MICA).

METHODS

This was a prospective observational single surgeon series of consecutive patients who underwent primary third-generation MICA with screw fixation for severe hallux valgus. The primary outcome was a validated patient reported outcome measure (PROM), the Manchester-Oxford Foot Questionnaire (MOXFQ), assessed minimum 2 years following MICA. Secondary outcomes were radiographic deformity correction (assessed 6 weeks post-operatively), complication rates and other quality of life PROMs (EQ-5D and Visual Analogue Pain Scale).

RESULTS

Between September 2014 and November 2018, 106 consecutive feet (n = 78 patients; 73 female, 5 male) met the inclusion criteria. Prospectively collected pre-operative and 2 year PROM MOXFQ data was available for 86 feet (81.1%). At two years following surgery, the MOXFQ score significantly improved for the Pain, Walking and Standing and Social Interaction domains from 39.2 to 7.5, 38.2 to 5.9 and 48.6 to 5.5, respectively (p < 0.001). Pre- and 6 week post-operative radiographic data was available for all 106 feet. Mean IMA improved from 18.2° to 6.3° (p < 0.001) whilst mean HVA improved from 45.3° to 10.9° (p < 0.001). The complication rate was 18.8% and the screw removal rate was 5.6%.

CONCLUSION

This study has demonstrated third-generation MICA for the treatment of severe hallux valgus deformity enables substantial deformity correction and is associated with significant improvements in clinical PROMs 2 years following surgery.

Technique Tip: Medial prominence bone spur resection in the third-generation percutaneous Chevron-Akin Osteotomy Technique (PECA) for hallux valgus correction

The third-generation percutaneous chevron and Akin osteotomy (PECA) technique for surgical management of hallux valgus has shown improvement in clinical and radiographic outcomes. During this procedure, lateral translation and fixation of the first metatarsal head results in the formation of a bony prominence on the medial side of the distal aspect of the first metatarsal which can cause pain and discomfort to the patient. We describe two techniques to address this bony prominence; either i) excision osteotomy and removal of the fragment or ii) a dorsal closing wedge osteotomy retaining the bony fragment. LEVEL OF EVIDENCE: Level V, expert opinion.

Radiographic and clinical outcomes of minimally invasive surgery versus open osteotomies for the correction of hallux valgus

PURPOSE

Hallux valgus is a common disease which causes pain and dysfunction of the foot. Although numerous methods of procedures have been introduced, a single procedure cannot correct all deformities of hallux valgus. The study aims to evaluate the radiographic and clinical effectiveness of a new minimally invasive surgery (MIS) versus open Chevron-Akin procedures.

METHODS

This was a retrospective comparative study. Data were collected from May 2018 to January 2020. A total of 27 patients (31 feet) undergoing MIS for hallux valgus were included in this study. The average age of patients underwent MIS was 59.9 years. The mean follow-up was 25.1 months. Open osteotomies were performed in 30 patients (31 feet) during the same period. The mean age of these patients at the time of surgery was 59.1 years. The mean follow-up was 26.1 months. Pre-operative and post-operative radiographic outcome measures included HVA, IMA, DMAA, the Sgarlato's angle and the length of the first metatarsal, and distance between the dorsal cortex of first and second metatarsal necks. The AOFAS and VAS were used to assess foot function.

RESULTS

The preoperative HVA in MIS group and open group were 34.8° and 33.1° respectively. The post-operative HVA were 20.4° and 13.7°. The pre-operative IMA in MIS group and open group were 13.0° and 12.1°. The post-operative IMA were 11.4° and 5.5° respectively. The pre-operative DMAA were 14.8° and 15.1° respectively. The post-operative DMAA were 6.3° and 8.7°. The AOFAS increased from 44.0 to 90.2 in MIS group and from 47.6 to 89.5 in open group. The VAS decreased from 7.3 to 1.3 in MIS group and from 7.1 to 1.2 in open group.

CONCLUSION

Although open osteotomies were superior than MIS in HVA and IMA, MIS showed advantages in correcting DMAA. MIS provided equivalent functional outcomes compared to open surgery.

Third-Generation Minimally Invasive Chevron-Akin Osteotomy for Hallux Valgus Produces Similar Clinical and Radiological Outcomes as Scarf-Akin Osteotomy at 2 Years: A Matched Cohort Study

BACKGROUND

The minimally invasive chevron-Akin (MICA) osteotomy is an increasingly popular technique for the correction of hallux valgus. However, there is a paucity of literature comparing it with traditional open techniques. The purpose of this study was to compare the clinical and radiological outcomes of the MICA osteotomy using a new-generation MICA screw and scarf-Akin osteotomy for hallux valgus correction.

METHODS

Thirty cases of MICA osteotomy were propensity score matched 1:1 with a control group of 30 scarf-Akin osteotomy cases. The groups were matched for age, sex, body mass index, preoperative visual analog scale (VAS) score, American Orthopaedic Foot & Ankle Society (AOFAS) metatarsophalangeal-interphalangeal (MTP-IP) score, 36-Item Short-Form Health Survey (SF-36) physical component score (PCS) and mental component score (MCS), preoperative hallux valgus angle (HVA) and intermetatarsal angle (IMA), and concomitant procedures. Outcomes were compared at 6 and 24 months postoperatively. Early postoperative VAS scores were also compared.

RESULTS

Both groups demonstrated significant improvements in VAS score, AOFAS score, and SF-36 PCS and MCS at 6 and 24 months postoperatively. For the MICA group, HVA improved from 23.5 to 7.7 degrees, and IMA improved from 13.5 to 7.5 degrees. For the scarf-Akin osteotomy group, HVA improved from 23.7 to 9.3 degrees, and IMA improved from 13.6 to 7.8 degrees. The first 24-hour postoperative VAS score was significantly lower in the MICA group compared with the scarf-Akin group (2.0 ± 2.0 vs 3.4 ± 2.6, P = .029). However, there was no significant difference in clinical or radiological outcomes between the groups at 6 and 24 months.

CONCLUSION

The MICA procedure with the new-generation MICA screw is an attractive option for the correction of hallux valgus, yielding similar midterm radiological and clinical outcomes compared with the well-established scarf-Akin osteotomy. The first 24-hour postoperative VAS score in the MICA group was also statistically lower, although its clinical significance remains to be determined.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

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 ).

Percutaneous, intra-articular, chevron osteotomy (PeICO) for the treatment of mild-to-moderate hallux valgus: a case series

PURPOSE

Treatment for hallux valgus (HV) remains challenging. Third-generation percutaneous procedures try to reproduce chevron-type osteotomies to replicate their benefits, such as intrinsic stability and reproducibility. We report the first results using a percutaneous, intra-articular, chevron osteotomy (PeICO) technique that mimics the classic intra-articular open chevron procedure, associated with a percutaneous adductor tendon release (PATR) for the treatment of mild-to-moderate HV.

METHODS

From May 2015 to October 2018, a total of consecutive 114 feet (74 patients) were included. Primary outcome measures included radiographic (hallux valgus and intermetatarsal angles) and clinical parameters such as visual analog scale (VAS), FAAM Activities of Daily Living (ADL), and FAAM Sport, AOFAS Score, and MOXFQ, preoperatively and at final follow-up (Minimum 18 months). A patient satisfaction survey was also performed. Pronation and length of the first metatarsal were also assessed. Secondary outcomes included fluoroscopic time, length of surgery, complications, recurrence, and re-operation rates.

RESULTS

At 24.09 months on average, the AOFAS score improved from 52.1 points preoperatively to 91.1 (p < 0.001) at the latest follow-up. VAS decreased from 6.3 to 1. Also, FAAM ALD, FAAM Sport, and MOXFQ showed statistically significant differences (p < 0.001) when comparing pre-operative and post-operative periods. Patients found the procedure to be excellent in 82% and very good in 13.5% of cases. Our global complication and re-operation rates were 5.26% and 3.5% (screw removal), respectively.

CONCLUSION

PeICO combined with PATR proved to be a safe, reliable, and effective technique for the correction of mild-to-moderate HV deformity.