Role of collateral ligaments in metatarsophalangeal stability: a cadaver study

Toes Deformities in Cavovarus: How to Approach Them

Sagittal lesser toe deformities (LTD) are the most common in cavus foot. They are mainly the result of muscular imbalance between intrinsic and extrinsic muscles. Surgery is the second-line treatment if medical treatment fails. The aim of the present study was to provide an update on classification and surgical management of LTD in cavus foot including percutaneous procedures with a special focus on sagittal deformities. Joint sparing procedures are preferred for reducible LTD, whereas lesser toe fusions are used for rigid one in association with tendon transfer or percutaneous procedures depending of surgeon's experience and patient's clinical examination.

Lesser-toe deformity

Lesser-toe deformity is frequent and varied, with severe functional impact. In elderly subjects, it leads to loss of autonomy and increases the risk of falls. The aim of the present study was to provide an update on management, addressing 5 questions. What are the normal anatomy and pathophysiology? These acquired deformities mainly result from imbalance between the intrinsic and extrinsic muscles of the foot or from capsule-ligament stabilizer failure. How to analyze the deformity? It is important to identify the cause, site, reducibility and metatarsophalangeal joint stability. What are the main deformities and how should they be classified? Classifications used to be based on confusing terminology as the deformities were poorly defined. The French Foot Surgery Association (AFCP) therefore validated a classification with standardized, exhaustive and reproducible morphologic descriptions. What treatments are there? Treatment needs to take account of the cause. Footwear adaptation, physiotherapy and podologic measures are in first line, with surgery in second line. Surgery concerns soft tissues (tendon lengthening, tendon transfer, arthrolysis, plantar plate repair), bone (metatarsal and phalangeal osteotomy) and joints (replacement and fusion), with percutaneous and open approaches. What are the treatment strategies? Surgery is performed sequentially, from proximal to distal, if necessary. Options are set out in the decision-trees included in this article. LEVEL OF EVIDENCE: V, expert opinion.

Presurgical Perspective and Postsurgical Evaluation of Plantar Plate and Turf Toe

Capsuloligamentous injury of the first metatarsophalangeal (MTP) joint (eponymously called "turf toe") mostly occurs in athletes and involves acute trauma, whereas tears of the lesser MTP joint plantar plate typically are an attritional-degenerative condition. This article reviews the anatomy, pathophysiology, mechanism and patterns of injury, grading and classification of injury, imaging appearances (pre- and postoperative), and management of first MTP joint capsuloligamentous injuries and lesser MTP joint plantar plate tears. These two distinct pathologies are discussed in separate sections.

Anatomy: Plantar Plate

The fibrocartilaginous component of the plantar plate offers stability at the metatarsophalangeal joint. In conjunction with the attachments of the deep transverse metatarsal ligaments and collateral ligaments, the plantar plate complex resists tensile forces anchored by the plantar fascia and compression forces under the metatarsal heads.

Plantar Plate Repair for Metatarsophalangeal Joint Instability of the Lesser Toes

The plantar plate is a known stabilizer of the lesser toe metatarsophalangeal (MTP) joint. MTP instability is a known common cause of metatarsalgia, most commonly in the second toe. In the last decade, clinical staging and anatomic grading mechanisms have been published to guide the surgeons on the treatment of MTP instability; this has also led to an understanding of how plantar plate tears relate to MTP joint instability. Direct surgical repair of the plantar plate has been described, short-term outcomes have been published, and the results are not perfect, but promising with respect to patient satisfaction and pain relief.

A versatile method for dorsal-approach plantar plate repair using standard operative instruments

Background

The plantar plate is an important static stabilizer of the lesser metatarsophalangeal joints, and disruptions of the plantar plate can lead to significant instability and lesser toe deformities. In recent years, direct plantar plate repair has been proposed. Although direct repair via a dorsal approach is attractive, a torn plantar plate is small and difficult to access using regular instruments in a restricted operative field.

Methods

In this report, a unique method for plantar plate repairs was used to repair various configurations of plantar plate tears with standard operative instruments that are available in most operating rooms.

Results

Using this method, 10 patients underwent plantar plate repairs, and the mean follow-up period was 24 (range, 14–38) months. The mean visual analog scale score for pain preoperatively was 4.1 (range, 0–6) and decreased to 0.6 (range, 0–3) at last follow-up. Postoperatively, the mean visual analog scale score for satisfaction was 9.6 (range, 8–10) and the mean American Orthopedic Foot and Ankle Society forefoot score was 88.8 (range, 75–100).

Conclusions

Our study proposes an inexpensive and versatile method for plantar plate repair via a dorsal approach that uses standard operative instruments.

Trial registration

ClinicalTrials.gov, NCT04949685. July 2, 2021 - Retrospectively registered,

Level of clinical evidence

4

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04951-w.

One-Year Outcome Study of Anatomic Reconstruction of Lesser Metatarsophalangeal Joints

Background: Lesser metatarsophalangeal joint (MTPJ) and plantar plate pathologies are commonly seen forefoot conditions. Traditional rebalancing techniques are commonly used but can have concerning adverse effects. The purpose of this study was to analyze the 1-year outcomes of a new technique consisting of anatomic repair of the plantar plate and collateral ligaments involving lesser MTPJs. Methodology: A retrospective cohort study of 50 consecutive patients treated with anatomic plantar plate and collateral ligament reconstruction were evaluated for lesser MTPJ imbalances between 2013 and 2016. The primary outcome was postoperative digital stability defined as a normal dorsal drawer test and normal paper pull-out test. Secondary outcomes included pre- and postoperative visual analogue scale pain measurements, MTPJ radiographic alignment, and ACFAS Forefoot module scores. Results: All patients had digital instability prior to the surgical intervention. Final follow-up revealed that 92% of patients showed improved digital stability, P = .0005. Multivariate regression found statistically significant improvement in pain reduction via the visual analogue scale of 51.2 mm (P < .0001) and ACFAS Forefoot module scores improved to 92 (P < .0001). The 45 joints with preoperative abnormal transverse plane deformity, had either complete (n = 29) or partial (n = 16) radiographic MTPJ correction. Conclusion: These results suggest that anatomic repair of lesser MTPJ improved digital stability, pain, function and radiographic alignment with greater than one year of follow-up.Levels of Evidence: Level IV: Retrospective cohort study.

State of the Art in Lesser Metatarsophalangeal Instability

Advancements in lesser metatarsophalangeal (MTP) instability have involved the use of minimally invasive surgery techniques, synthetic augmentation of existing transfers, and use of arthroscopy for both diagnosing and addressing MTP disorder. Advances in imaging modalities, particularly MRI, have aided in diagnosing subtle instability. Clinical outcomes seem to be similar to traditional approaches as the indications and applicability continue to evolve.

Plantar Plate Injury and Angular Toe Deformity

Lesser toe plantar plate injuries at the metatarsophalangeal (MTP) joint are a common source of metatarsalgia. The second MTP joint is the most commonly affected digit. The fibrocartilaginous plantar plate is the most important static stabilizer of the MTP joint; high loading with weight bearing can lead to attritional plantar plate injuries. Chronic pain with weight bearing is the common presentation of lesser toe instability. Untreated plantar plate instability can lead to hammer toe and mallet toe deformities. Combined Weil osteotomy and plantar plate repair yields favorable pain relief and angular deformity correction for patients who fail conservative treatment.

Anatomic Reconstruction Versus Traditional Rebalancing in Lesser Metatarsophalangeal Joint Reconstruction

Traditional rebalancing techniques, such as capsulotomies and capsulorrhaphies, are commonly performed during complex hammertoe and lesser metatarsal osteotomy procedures involving metatarsophalangeal joint (MTPJ) contractures; however, floating toes, digital instability, and malalignment are concerns. We critically analyzed the outcomes after anatomic reconstruction of the plantar plate and collateral ligaments compared with those after traditional rebalancing techniques. A case-control study was conducted of 54 patients who had undergone surgical correction of lesser MTPJ imbalances due to complex hammertoe deformities (power 80%, type I error = 0.05). Cases were defined as consecutive patients treated with anatomic plantar plate and collateral ligament reconstruction. Controls had undergone traditional lesser MTPJ rebalancing and were matched to cases by age, gender, follow-up duration (minimum 12 months), and concomitant procedures of the same lesser ray. Multivariate logistic regression demonstrated that patients treated with anatomic reconstruction had greater digital stability (negative dorsal drawer and negative paper pull-out test findings) at final follow-up examination compared with the controls. American College of Foot and Ankle Surgeons (ACFAS) forefoot module scores were greater in the anatomic group in all domains (p ≤ .05). Controls had greater postoperative radiographic MTPJ angles than the cases, with no differences detected between the 2 groups in visual analog scale scores or proximal interphalangeal joint angles. The importance of restoration of the plantar plate and collateral ligament integrity as a digital stabilizer is generally accepted but has not been well studied. We found that anatomic reconstruction yielded greater digital stability, greater ACFAS Forefoot module scores, and better radiographic MTPJ alignment than controls. Additional studies are warranted to assess the long-term viability of anatomic lesser MTPJ reconstruction.

Biomechanical Evaluation of Suture Configurations in Lesser Toe Plantar Plate Repairs

BACKGROUND

Lesser toe metatarsal-phalangeal (MTP) joint instability can be a major source of pain and dysfunction. Instability occurs when there is incompetence of the plantar plate and/or collateral ligaments. Newer operative treatments focus on performing anatomic repairs of the plantar plate. The goal of this study was to compare the biomechanical properties of 3 suture configurations that may be used for plantar plate repairs.

METHODS

Biomechanical analysis of 27 lesser toe plantar plates from fresh frozen human cadavers was completed. The plantar plate was detached from the proximal phalanx, and suture was placed in the distal plantar plate in a horizontal mattress, luggage-tag, or Mason-Allen suture configuration. Cyclic loading followed by load-to-failure testing was performed.

RESULTS

There was a significant difference in peak load-to-failure force between constructs (mattress: 115.53 ± 15.95 N; luggage-tag 102.42 ± 19.33 N; Mason-Allen: 89.96 ± 15.78 N; P = .015). Post hoc analysis demonstrated that the mattress configuration had significantly higher load-to-failure force compared with the Mason-Allen configuration ( P = .004). There were no significant differences between the mattress and the luggage-tag configurations or the luggage-tag and the Mason-Allen configurations. There were no differences in construct stiffness, axial displacement at the time of failure, or number of cycles required to produce 2 mm of displacement.

CONCLUSION

The mattress configuration demonstrated better peak load-to-failure force compared with the Mason-Allen configuration but was not statistically different from the luggage-tag configuration. Although not significant, the mattress configuration trended toward higher load-to-failure force compared with the luggage-tag.

CLINICAL RELEVANCE

The horizontal mattress stitch may be the biomechanically superior configuration in plantar plate repairs.

Lesser Metatarsophalangeal Joint Instability: Treatment with Tendon Transfers

Complex digital deformities and metatarsophalangeal joint instability encompass a wide range of pathology, and we must identify the different degrees of ligamentous disruption. It is important to address a combination of procedures to treat gross deformities of the lesser toes. Surgical treatment should be individualized and requires a sequential process for adequate reduction and deformity correction. There is no gold standard procedure for every deformity. Although residual stiffness can result from tendon transfer, overall patient satisfaction levels remain high when it is performed under the proper indications and concomitantly with other procedures to gain full correction of these challenging deformities.

Lesser Metatarsophalangeal Joint Instability: Advancements in Plantar Plate Reconstruction

The plantar plate and associated collateral ligaments are the main stabilizers of each of the lesser metatarsophalangeal joints. Although clinical examination and plain radiographs are usually sufficient to establish the diagnosis of a plantar plate tear, MRI or fluoroscopic arthrograms may help in specific cases. Recent results with a dorsal approach to plantar plate repair are promising with respect to pain relief and patient satisfaction.

Anatomy and Physiology of the Lesser Metatarsophalangeal Joints

Knowledge and command of anatomy is paramount to effectively treating disorders of the lesser metatarsophalangeal (MTP) joints. The osseous structures consist of the proximal phalanx of the toe and the metatarsal head. The soft tissues on the dorsum of the MTP joint include the joint capsule and the tendons of extensor digitorum longus and extensor digitorum brevis. The proper and accessory collateral ligaments form the medial and lateral walls and contribute to stability in the coronal and sagittal planes. The plantar plate forms the plantar border of the MTP joint and stabilizes the MTP joint against hyperextension and dorsal translation.

Plantar Plate Repair for Lesser Metatarsophalangeal Joint Instability

BACKGROUND

Lesser metatarsophalangeal (MTP) joint instability is a common cause of forefoot pain. Advances in operative technique and instrumentation have made it possible to anatomically treat plantar plate tears through a dorsal approach. Our goal was to evaluate the subjective, functional, and radiographic outcomes of plantar plate repair (PPR) from a dorsal approach.

METHODS

A prospective case series was performed evaluating the results of PPR in 97 feet with 138 plantar plate tears. Patients underwent PPR from a dorsal approach with a Weil osteotomy. We followed patients at regular intervals for 12 months and collected data preoperatively and postoperatively with respect to visual analog scale (VAS) scores, MTP range of motion (ROM), paper pull-out test, American Orthopaedic Foot & Ankle Society (AOFAS) scores, satisfaction, and radiographic measures.

RESULTS

Eighty percent of patients scored "good" to "excellent" satisfaction scores at 12 months. The mean VAS pain score preoperatively was 5.4/10, and postoperatively was 1.5/10. The mean AOFAS scores increased from 49 to 81 points following surgery. The mean MTP ROM preoperatively was 43 degrees and postoperatively 31 degrees. Forty-two percent of toes passed the paper pull out test prior to surgery and 54% at 12 months. Mean metatarsal shortening was 2.4/3.1/1.2 mm for the second, third, and fourth metatarsals, respectively. The mean MTP joint angles preoperatively were 2/4.9/-1.3 degrees and postoperatively were 7.4/9.6/0.2 degrees, respectively, for the second, third, and fourth MTP joints.

CONCLUSION

We found that the plantar plate could be repaired through a dorsal approach with reliable outcomes. PPR was a viable option to anatomically restore the ligamentous support in the unstable lesser MTP joint.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Surgical reduction and ligament reconstruction for chronic dorsal dislocation of the lesser metatarsophalangeal joint associated with hallux valgus

BACKGROUND

Hallux valgus (HV) is occasionally associated with chronic dislocation of the lesser metatarsophalangeal (MTP) joints. We have developed a novel surgical procedure to treat dislocation of the lesser MTP joints. This study aimed to describe our procedure and investigate the outcomes of surgical intervention in the treatment of HV with dislocation of the lesser MTP joints.

METHODS

Twenty-three patients (27 feet, average age: 63.6 years, average follow-up: 49.5 months; a minimum follow-up of 24 months) underwent surgical intervention for HV and dislocation of the lesser MTP joints. Twenty-three feet had dislocation (10 feet) or subluxation (13 feet) of the second MTP joint, whereas 4 feet had dislocation of the second and third MTP joints. The surgical procedure included a distal soft-tissue procedure combined with proximal osteotomy for correction of the HV, and reconstruction of the collateral ligaments (CL) following open reduction with complete release of the capsule and the CL at the metatarsal head for dislocation of the lesser MTP joints. Outcomes were assessed using the Japanese Society for Surgery of the Foot (JSSF) scale and radiological examinations.

RESULTS

The JSSF score improved significantly from an average of 49.7 points preoperatively to 93.1 points postoperatively. The average HV angle and intermetatarsal angle decreased significantly from 44.6° and 18.1° preoperatively to 7.9° and 6.0° postoperatively, respectively. The average extension and flexion of the second MTP joint was 53.1° and 13.8° at the most recent follow-up, respectively. Postoperatively, no feet had dislocation of the second or third MTP joint, three had subluxation of the second MTP joint, and one had subluxation of the third MTP joint. Osteoarthritis of the lesser MTP joint had developed in two feet (7.4 %) at the time of the most recent follow-up.

CONCLUSION

Our surgical procedure achieved significant correction of HV, a low rate of postoperative re-dislocation of the lesser MTP joints, and significant improvement of pain and function for symptomatic moderate-to-severe HV with dislocation of the lesser MTP joints.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Deep transverse metatarsal ligament and static stability of lesser metatarsophalangeal joints: a cadaveric study

BACKGROUND

The static support that guides motion around the lesser metatarsophalangeal joints (MTPJs) is complex. Biomechanical studies revealed important roles of both the plantar plane and collateral ligaments. Since part of the plantar plate is attached to the deep transverse metatarsal ligament (DTML), we hypothesized that the transection of the DTML in the intermetatarsal space may substantially reduce the MTPJ stability.

METHODS

The second, third, and fourth MTPJ stabilities of 6 fresh-frozen human cadaveric foot specimens were measured under load control. Both dorsiflexion and dorsal subluxation conditions were tested. After the intact condition was assessed, the DTML was sequentially transected such that each MTPJ had a unilateral and then a bilateral DTML transection. Stiffness data were calculated using the loading range in each test condition. Paired Student t tests were performed to test for statistical significance (P value less than .05).

RESULTS

In intact specimens, the mean stiffness with dorsiflexion of the second, third, and fourth toes was 0.52 ± 0.15 N/deg. When the DTML was operatively transected on one side, the dorsiflexion stiffness significantly decreased 17.3% to an average of 0.43 ± 1.00 N/deg (P < .001). Subsequent transection of the DTML on the other side of each joint resulted in a further significant decrease of 5.8% to an average of 0.40 ± 0.08 N/deg (P < .001). The mean stiffness with dorsal subluxation of the intact second, third, and fourth toes was 3.55 ± 0.66 N/mm. When the DTML was operatively transected on one side, the dorsal subluxation stiffness significantly decreased 16.1% to an average of 2.98 ± 0.64 N/mm (P < .001). Subsequent transection of the DTML on the other side of each joint resulted in a further significance decrease of 7.6% to an average of 2.71 ± 0.48 N/mm (P = .016).

CONCLUSION

The DTML has a significant role in maintaining lesser MTPJ ligament stability. Both unilateral and bilateral DTML transections caused substantial instability of the lesser MTPJ.

CLINICAL RELEVANCE

The DTML is part of the natural static restraint to dorsiflexion or dorsal subluxation of the lesser MTPJ. Operative transection, injury, or degeneration of this ligament may predispose the adjacent MTPJ to instability.

Etiology and management of lesser toe metatarsophalangeal joint instability

The terms crossover toe and lesser metatarsophalangeal joint instability both describe a deterioration of the soft tissue structures that give stability to the lesser MTP joints. Initial treatment regimens focused on indirect repair of the instability without addressing the primary pathology. A staging system of the clinical examination and a grading system of the surgical findings are now available to help surgeons classify and treat the plantar plate insufficiency. Improved imaging techniques and direct surgical repair techniques through a dorsal approach have changed the treatment and possibly the results of this difficult condition.

Metatarsophalangeal joint instability of the lesser toes and plantar plate deficiency

Our understanding of lesser toe metatarsophalangeal joint instability has increased substantially over the past few decades. Some recent articles on the subject have provided detailed anatomic descriptions that help to characterize the primary stabilizing structures of the joint. Some surgeons now advocate the incorporation of a primary repair of the plantar plate into the surgical plan for correction of metatarsophalangeal joint deviation in the sagittal and transverse planes. New surgical techniques have been developed to expose, inspect, and reliably repair the plantar plate, if necessary. Dorsal and plantar approaches have both been used successfully to repair the plantar plate. Tears of the plantar plate can be repaired primarily or advanced on the base of the proximal phalanx through bone tunnels. Outcomes of these procedures are promising, with improvements in pain and function reported along with sustained deformity correction.

Metatarsophalangeal joint instability of the lesser toes

Metatarsophalangeal joint instability of the lesser toes is a common finding and a common cause of metatarsalgia. The clinical presentation can include swelling without digital deformity; however, often, this can progress to the development of coronal and transverse plane malalignment. In some cases, frank metatarsophalangeal joint dislocation can develop. The treatment regimen has historically focused on indirect surgical realignment using soft tissue release, soft tissue reefing, tendon transfers, and periarticular osteotomies. An improved understanding of the plantar plate has recently led to the development of a clinical staging system and surgical grading system of plantar plate attenuation. A dorsal surgical approach, using a Weil osteotomy, allows the surgeon to directly access and repair or advance the plantar plate to the base of the proximal phalanx. The addition of direct plantar plate repair could be a significant advancement in the reconstruction and realignment of metatarsophalangeal joint instability.