Titrating the Amount of Bony Correction in Progressive Collapsing Foot Deformity

Passive Eversion Assessment for Progressive Collapsing Foot Deformity After Lateral Column Lengthening: A Cadaveric Biomechanical Study

BACKGROUND

Reduced hindfoot eversion motion has been proposed as a cause of increased lateral foot pressure following lateral column lengthening (LCL) for progressive collapsing foot deformity (PCFD). A subjective intraoperative assessment of passive eversion has been suggested to help evaluate correction; however, it is unclear how passive eversion correlates with objective measurements of foot stiffness. Our objectives were to quantify the relationship between the maximum passive eversion in hindfoot joints following LCL with plantar pressure during stance and to determine the influence of wedge size on these outcomes.

METHODS

Ten cadaveric specimens extending from the mid-tibia distally were tested on a 6-degrees-of-freedom robot to simulate the stance phase of level walking. Five conditions were tested: intact, simulated PCFD, and 3 LCL wedge conditions (4, 6, and 8 mm). Outcomes included the lateral-to-medial forefoot plantar pressure (LM) ratio during stance and the maximum passive eversion measured in the hindfoot joints. Simple linear regressions were performed to evaluate relationships between outcomes and wedge sizes.

RESULTS

A strong negative relationship was found between passive subtalar eversion and the LM ratio during stance (r[38] = -0.46; p = 0.0007), but not between passive talonavicular eversion and the LM ratio (r[38] = -0.02; p = 0.37). Wedge size was strongly related to subtalar eversion (r[38] = -0.77; p < 0.0001), talonavicular eversion (r[38] = -0.55; p = 0.0003), and the LM ratio (r[38] = 0.70; p < 0.0001). Increased wedge size resulted in average decreases in subtalar and talonavicular eversion of 1.0° (95% confidence interval [CI]: 0.8° to 1.3°) and 1.2° (95% CI: 0.6° to 1.6°), respectively. Increased wedge size also increased the LM ratio by 0.38 (95% CI: 0.25 to 0.50), indicating a lateral shift in plantar pressure.

CONCLUSIONS

Decreased hindfoot eversion following LCL was related to increased lateral plantar pressure during stance. Increasing wedge size correlated with decreasing passive hindfoot eversion and increasing lateral plantar pressure, suggesting that intraoperative preservation of eversion motion may be important for preventing excessive lateral loading.

CLINICAL RELEVANCE

To avoid overcorrection or undercorrection of the deformity, hindfoot eversion assessment in addition to radiographic evaluation may be important for optimizing the amount of lengthening to achieve successful LCL.

Biomechanical effects of Evans versus Hintermann osteotomy for treating adult acquired flatfoot deformity: a patient-specific finite element investigation

BACKGROUND

Evans and Hintermann lateral column lengthening (LCL) procedures are both widely used to correct adult acquired flatfoot deformity (AAFD), and have both shown good clinical results. The aim of this study was to compare these two procedures in terms of corrective ability and biomechanics influence on the Chopart and subtalar joints through finite element (FE) analysis.

METHODS

Twelve patient-specific FE models were established and validated. The Hintermann osteotomy was performed between the medial and posterior facets of the subtalar joint; while, the Evans osteotomy was performed on the anterior neck of the calcaneus around 10 mm from the calcaneocuboid joint surface. In each procedure, a triangular wedge of varying size was inserted at the lateral edge. The two procedures were then compared based on the measured strains of superomedial calcaneonavicular ligaments and planter facia, the talus-first metatarsal angle, and the contact characteristics of talonavicular, calcaneocuboid and subtalar joints.

RESULTS

The Hintermann procedure achieved a greater correction of the talus-first metatarsal angle than Evans when using grafts of the same size, indicating that Hintermann had stronger corrective ability. However, its distributions of von-Mises stress in the subtalar, talonavicular and calcaneocuboid joints were less homogeneous than those of Evans. In addition, the strains of superomedial calcaneonavicular ligaments and planter facia of Hintermann were also greater than those of Evans, but both generally within the safe range (less than 6%).

CONCLUSION

This FE analysis study indicates that both Evans and Hintermann procedures have good corrective ability for AAFD. Compared to Evans, Hintermann procedure can provide a stronger corrective effect while causing greater disturbance to the biomechanics of Chopart joints, which may be an important mechanism of arthritis. Nevertheless, it yields a better protection to the subtalar joint than Evans osteotomy.

CLINICAL RELEVANCE

Both Evans and Hintermann LCL surgeries have a considerable impact on adjacent joints and ligament tissues. Such effects alongside the overcorrection problem should be cautiously considered when choosing the specific surgical method.

LEVEL OF EVIDENCE

Level III, case-control study.

Assessment of Flatfoot Deformity Using Digitally Reconstructed Radiographs: Reliability and Comparison to Conventional Radiographs

BACKGROUND

Digitally reconstructed radiographs (DRRs) generated from weightbearing computed tomography (WBCT) may potentially substitute for weightbearing plain radiographs (XRs) but have not been clinically validated. This study aims to test the reliability of 6 radiographic parameters of progressive collapsing foot deformity (PCFD) as measured on DRR, to investigate whether DRR represents comparably to XR through the same measurements, and to compare agreement of DRR and XR measurements of a standardized arch height parameter with reference measurements made on WBCT.

METHODS

DRR generated from preoperative WBCT of 71 patients (72 feet) treated surgically for PCFD were retrospectively compared with preoperative weight-bearing XR after exclusion criteria were applied. Six radiographic measurements were performed, including Meary angle, calcaneal pitch (CPA), medial cuneiform height (MCH), AP talar-first metatarsal angle (T-1MT), talonavicular coverage (TNCA), and talar incongruency (TIA). Arch height was measured on XR, DRR, and WBCT using a validated, standardized, navicular-based index. Intraclass correlation coefficients assessed DRR intraobserver and interobserver reliability. Paired samples t tests tested differences between XR and DRR. Bland-Altman limits of agreement analysis compared DRR and XR agreement with WBCT measurements.

RESULTS

Measurements were within standard PCFD ranges on XR and DRR. All measurements demonstrated excellent intrarater reliability and good to excellent interrater agreement, consistent with previous literature on XR. No differences were found for Meary, CPA, or TNCA. Minor differences were observed for MCH, T-1MT, and TIA. DRR measurements demonstrated greater agreement with WBCT than XR measurements.

CONCLUSION

DRR from WBCT may be a promising substitute for XR in the clinical evaluation of PCFD. Radiographic measurements made on DRR demonstrated good to excellent reliability. Although small differences were found between XR and DRR for certain measurements, DRR more accurately represented medial arch anatomy compared to gold standard WBCT data than XR. If validated as a clinical substitute, DRR could eventually obviate XR where WBCT is available.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

The painful lateral column of the foot: from back to front

The purpose of this article is to focus attention on the abnormalities which the radiologist may encounter in patients presenting with lateral ankle or foot pain outside of the context of acute trauma. These include anterolateral impingement, subfibular impingement, subtalar instability and tarsal sinus syndrome, tarsal coalition, sural neuromas, peroneal tendon abnormalities, calcaneocuboid instability and occult cuboid fractures, and painful accessory ossicles. The expected and unexpected findings on radiographs, CT, US, and MRI are discussed.

Managing Complications of Foot and Ankle Surgery: Reconstruction of the Progressive Collapsing Foot Deformity

Our understanding of the cause and principles of treatment of progressive collapsing foot deformity (PCFD) has significantly evolved in recent decades. The goals of treatment remain improvement in symptoms, correction of deformity, maintenance of joint motion, and return of function. Although notable advancements in understanding the deformity have been made, complications still occur and typically result from (1) poor decision making, (2) technical errors, and (3) patient-related conditions. In this article, we discuss common surgical modalities used in the treatment of PCFD and further highlight the common complications that occur and the techniques that can be used to prevent them.

Imaging of progressive collapsing foot deformity with emphasis on the role of weightbearing cone beam CT

The term progressive collapsing foot deformity (PCFD) is currently recommended as the replacement to adult-acquired flatfoot deformity and posterior tibial tendon dysfunction to better reflect its pathology, which consists of a complex three-dimensional deformity involving the foot and ankle. The new consensus has also provided a new classification that requires clinical and radiographic findings for patient stratification into each class. However, conventional radiographs are susceptible to errors resulting from the inadequate positioning of patients, incorrect angulation of the X-ray tube, and overlapping of bone structures. Weightbearing cone beam computed tomography (WBCBCT), which has greater diagnostic accuracy than conventional radiograph, is useful for evaluating progressive collapsing foot deformity to determine medial arch collapse, hindfoot alignment, peritalar subluxation, posterior subtalar joint valgus, intrinsic talus valgus, and lateral extra-articular bone impingement. The present review aimed to discuss the new recommendations for nomenclature, classification, and imaging evaluation of PCFD, with an illustrative and quantitative focus on the measurements used in conventional radiography and WBCBCT. The measurements presented here are important criteria for decision-making.

A Modified Extra-articular Lateral Column Lengthening Procedure for Adult Acquired Flatfoot Deformity

BACKGROUND

Lateral column lengthening (LCL), originally described by Evans, is an established procedure to correct stage II adult acquired flatfoot deformity (AAFD). However, the relative position between the facets is violated, and other problems may include nonunion, malunion, and calcaneocuboid (CC) joint subluxation. Herein, we report a modified extra-articular technique of LCL with hockey-stick osteotomy, which preserves the subtalar joint as a whole, increases bony apposition to enhance healing ability, and preserves the insertion of the calcaneofibular ligament to stabilize the posterior fragment to promote adduction of the forefoot.

METHODS

We retrospectively recruited 24 patients (26 feet) with stage II AAFD who underwent extra-articular LCL. The mean age was 55.7 ± 15.7 years, and the mean follow-up period was 33.4 ± 12.1 months. Associated procedures of spring ligament repair/reconstruction and posterior tibial tendon plication or flexor digitorum longus transfer were routinely performed and may also include a Cotton osteotomy, heel cord lengthening, or hallux valgus correction. Clinical and radiographic outcomes at the final follow-up were compared with the preoperative assessments.

RESULTS

All patients achieved calcaneus union within 3 months of operation. The VAS pain score improved from 5.3 ± 0.75 preoperatively to 1.2 ± 0.79 at the final follow-up (P < .001), and the AOFAS Ankle-Hindfoot Scale from 63.5 ± 8.5 to 85.8 ± 4.8 points (P < .001). The radiographic measurements significantly improved in terms of the preoperative vs final angles of 8.9 ± 5.3 vs 15.2 ± 3.6 degrees for calcaneal pitch (P < .001), 20.5 ± 9.2 vs 4.9 ± 4.8 degrees for Meary angle (P < .001), 46.5 ± 5.2 vs 41.9 ± 3.2 degrees for lateral talocalcaneal angle (P < .001), 23.9 ± 8.5 vs 3.9 ± 3.1 degrees for talonavicular coverage angle (P < .001), and 18.2 ± 9.2 vs 7.3 ± 5.0 degrees for talus-first metatarsal angle (P = .002). The CC joint subluxation percentage was 7.0% ± 5.4% preoperatively compared with 8.5% ± 2.4% at the final follow-up (P = .101). No case showed progression of CC joint arthritis or CC joint subluxation (>15% CC joint subluxation percentage). One case showed transient sural nerve territory paresthesia, and 1 had pin tract infection. Three cases had lateral foot pain, which could be relieved by custom insoles.

CONCLUSION

Modified extra-articular LCL as part of AAFD correction is a feasible alternative technique without subtalar joint invasion and may be associated with less CC joint subluxation compared with the Evans osteotomy.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Biomechanical Effects of Graft Shape for the Evans Lateral Column Lengthening Procedure: A Patient-Specific Finite Element Investigation

BACKGROUND

The Evans calcaneal lengthening osteotomy procedure is widely used for correcting progressive collapsing foot deformity. However, it can result in overcorrection and degenerations of the calcaneocuboid joint. Different shapes of graft have been used in the Evans calcaneal osteotomy, but potential differences in their biomechanical effects is still unclear. The present study was designed to explore the biomechanical effects of graft shape and improve the Evans procedure to avoid or minimize detrimental effects.

METHODS

Twelve patient-specific finite element models were established and validated. A triangular or rectangular wedge of varying size was inserted at the lateral edge of calcaneus, and the degree of correction was quantified. The stress in spring ligaments and plantar fascia and the contact characteristics of the talonavicular and calcaneocuboid joints were calculated and compared accordingly.

RESULTS

The rectangular graft provided a much higher degree of correction than triangular grafts did. However, the contact characteristics of the calcaneocuboid joint and talonavicular joint were abnormal, with clear sensitivity to increased graft size, and the modeled strain of the spring ligament increased.

CONCLUSION

The finite element analysis predicts that the rectangular grafts provide a higher degree of correction, but risks overcorrection compared with triangular grafts. The triangular graft may have a lower degree of disturbance to the biomechanical behaviors of the midtarsal joint.

CLINICAL RELEVANCE

The model shows that both the shape and size of an Evans osteotomy bone wedge can have effects on the contiguous joints and ligamentous structures. Those effects should be considered when selecting a bone wedge for an Evans calcaneal osteotomy.

LEVEL OF EVIDENCE

Level III, case-control study.

Association Between Hindfoot Alignment and First Metatarsal Rotation

BACKGROUND

The association between forefoot and hindfoot position for planus and cavus feet is fundamental to the treatment of these deformities. However, no studies have evaluated the association between hindfoot alignment and first metatarsal (M1) axial rotation. Understanding this possible relationship may help to understand the deformity and improve patient care. The purpose of this study is to determine a correlation between hindfoot alignment and metatarsal rotation as assessed by weightbearing computed tomography (WBCT).

METHODS

Patients who underwent weightbearing plain radiography (WBPR) and WBCT between 2015 and 2018 were evaluated. Hindfoot alignment was measured with the calcaneal moment arm (CMA). M1 rotation was measured using the Kim and Saltzman angles. Patient subgroups were created according to the severity of valgus/varus hindfoot alignment. Statistical analyses were performed to evaluate for association between variables.

RESULTS

Among the 196 patient feet included in the study, the average CMA was 6.0 ± 16.2 mm. The average Kim and Saltzman angles were 7.7 ± 12.9 degrees and 2.8 ± 13.1 degrees, respectively. The average Meary angle was 182.0 ± 11.9 degrees. A moderately strong association was found between the CMA and the Saltzman (r = 0.641, P < .01) and Kim angles (r = 0.615, P < .01). Hindfoot valgus was associated with M1 pronation and hindfoot varus with M1 supination. Additionally, inverse relationships between the Meary angle and the Saltzman (r = -0.600, P < .01) and Kim angles (r = -0.529, P < .01) were identified.

CONCLUSION

In this well-defined cohort, we found substantial correlation between hindfoot alignment and M1 rotation. Hindfoot valgus was associated with M1 pronation, and hindfoot varus was associated with M1 supination. Surgeons correcting cavovarus/planovalgus deformities should be aware of this association and evaluate the need for first-ray derotation.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Progressive Collapsing Foot Deformity: Should We Be Staging It Differently?

This article cursorily reviews the history of classification systems for pathologic flatfoot deformity in the adult and also critically reviews the recent introduction of a classification system intended to improve on the deficiencies of prior systems. The article concludes by offering suggestions for further work in evolving even more utilitarian systems for the staging and treatment of adult flatfoot disorder.

Calcaneal Osteotomies in the Treatment of Progressive Collapsing Foot Deformity. What are the Restrictions for the Holy Grail?

The progressive collapsing foot deformity is a complex three-dimensional deformity, including valgus malalignment of the heel. The medial displacement calcaneal osteotomy is an established surgical procedure reliably resulting in an efficient correction of the inframalleolar alignment. However, complications are common, including undercorrection of underlying deformity, progression of hindfoot osteoarthritis and/or deformity, and/or symptomatic hardware.

Is Arthrodesis Sufficient in the Setting of Complex, Severe and Rigid Progressive Collapsing Foot Deformities?

Arthrodesis of the hindfoot is typically used for the correction of severe and arthritic progressive collapsing foot deformity. Concomitant bony or soft tissue procedures may be helpful in patients with congenital abnormalities including the ball-and-socket ankle or congenital vertical talus. Dysplasia of the hindfoot bones may be more common than previously recognized, and corrective procedures or alterations in technique may need to be performed during hindfoot arthrodesis to account for bony deformity. Intraarticular osteotomies, extraarticular osteotomies, tendon lengthening, and tendon transfer procedures may be used in specific instances to aid in deformity correction and improve overall function.

Spare the Talonavicular Joint! The Role of Isolated Subtalar Joint Fusion in the Treatment of Progressive Collapsing Foot Deformity

Surgical management of progressive collapsing foot deformity continues to evolve. Previous studies have demonstrated that fusion of the talonavicular joint results in limited hindfoot motion and, therefore, may accelerate adjacent-joint arthrosis. Recent literature has supported using alternative arthrodesis constructs that spare the talonavicular joint, such as naviculocuneiform or isolated subtalar fusions, which may maintain some hindfoot motion through the talonavicular joint yet adequately address a patient's deformity. Concomitant reconstructive procedures may be used in addition to subtalar fusion to address severe deformities. Isolated subtalar fusions may be considered in cases of sinus tarsi or subfibular impingement deformities.

Distal Tibiofibular Syndesmotic Widening in Progressive Collapsing Foot Deformity

BACKGROUND

Lateral overload in progressive collapsing foot deformity (PCFD) takes place as hindfoot valgus, peritalar subluxation, and valgus instability of the ankle increase. Fibular strain due to chronic lateral impingement may lead to distraction forces over the distal tibiofibular syndesmosis (DTFS). This study aimed to assess and correlate the severity of the foot and ankle offset (FAO) as a marker of progressive PCFD with the amount of DTFS widening and to compare it to controls.

METHODS

In this case-control study, 62 symptomatic patients with PCFD and 29 controls who underwent standing weightbearing computed tomography (WBCT) examination were included. Two fellowship-trained blinded orthopedic foot and ankle surgeons performed FAO (%) and DTFS area measurements (mm²). DTFS was assessed semiautomatically on axial-plane WBCT images, 1 cm proximal to the apex of the tibial plafond. Values were compared between patients with PCFD and controls, and Spearman correlation between FAO and DTFS area measurements was assessed. P values of less than .05 were considered significant.

RESULTS

Patients with PCFD demonstrated significantly increased FAO and DTFS measurements in comparison to controls. A mean difference of 6.9% (P < .001) in FAO and 10.4 mm² (P = .026) in DTFS was observed. A significant but weak correlation was identified between the variables, with a Þ of 0.22 (P = .03). A partition predictive model demonstrated that DTFS area measurements were highest when FAO values were between 7% and 9.3%, with mean (SD) values of 92.7 (22.4) mm².

CONCLUSION

To our knowledge, this was the first study to assess syndesmotic widening in patients with PCFD. We found patients with PCFD to demonstrate increased DTFS area measurements compared to controls, with a mean difference of approximately 10 mm². A significantly weak positive correlation was found between FAO and DTFS area measurements, with the highest syndesmotic widening occurring when FAO values were between 7% and 9.3%. Our study findings suggest that chronic lateral impingement in patients with PCFD can result in a negative biomechanical impact on syndesmotic alignment, with increased DTFS stress and subsequent widening.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.