Hypermobility of the First Ray: the Cinderella of the measurements conventionally assessed for correction of Hallux Valgus

Abstract

Background and aim of the work: hypermobility of the first ray (FRH) began to be considered as a pathological entity from Morton's studies and was associated as a primary cause of hallux valgus (HV ). Currently, this relationship is in discussion, and various authors consider FRH as a consequence of the deformity. The purpose of this narrative review is to summarise the most influential publications relating to First Ray Mobility (FRM) to increase knowledge and promote its conventional assessment during clinical practice.

Methods: papers of the last century were selected to obtain a homogeneous and up-to-date overview of I-MTCJ mobility and HV, as well as their relationship and management.

Results: in recent years, FRH was studied from a biomechanical and pathophysiologic point of view. There is still not enough data regarding the aetiology of FRM. The higher rate of instability found in HV lacks an explanation of which is the cause and which is the effect. However, the Lapidus arthrodesis is still a valid method in cases of FRH and HV, even if is not rigorously indicated to treat both. When approaching FRH, radiographic or clinical findings are mandatory for the right diagnosis.

Conclusions: FRM is an important factor that must be considered in routine clinical practice and prior and post HV surgery, as much as the conventional parameters assessed. Surgeons should consider performing I-MTCJ arthrodesis only if strictly necessary, also paying attention to soft tissue balancing. Improving the measurement of FRH could be useful to determine if it is a cause or effect of the HV deformity.

Figure 1.

A and B: Manual examination to clinically assess FRM according to Morton. A dorsally directed forced is applied to the first ray with one hand, while other hand stabilises second to fifth metatarsals.

Figure 2.

A and B: Manual examination to clinically assess FRM by displacing the first metatarsal head at an angle of 45 degrees to the transverse plane.

Figure 3.

Correct position of foot for the measurement of FRM using the Klaue device: A) the foot is placed in the ankle orthosis with the ankle in neutral position and calf, ankle and midfoot are immobilised; B) the micrometre overlies the first metatarsal head in order to measure the mobility first in the sagittal plane.

Figure 4.

With one hand, the examiner immobilises second to fifth metatarsal bones, and with the other hand, exerts a force on the plantar side of the first metatarsal head, first A) in a purely dorsal direction; and then B) at a dorsomedial angle of 45 degrees to the transverse plane. Displacements were measured with the patient sitting in a non-weightbearing position, according to the method established by Klaue.

Figure 5.

Manual examination to clinically assess FRM using handheld rulers.