A foot is often the first part of the body affected in patients with rheumatoid arthritis. Pain and deformity of the foot are early symptoms of the disease in many cases. Progression of the forefoot deformity usually progresses to medial cuneometatarsal joint instability.
The hypermobility of the first MTT is the subject of frequent discussion[16, 28–30]. In patients with rheumatoid arthritis, synovitis of the first MTP and CM joints together with a foot muscle imbalance leads to first MTT instability. The issue is whether the instability of the CM joint is the cause of the hallux valgus or its consequence.
Confirming the diagnosis of instability in clinical practice can be difficult, because the surgeon has to frequently rely on the physical examination and weight-bearing X-ray of the foot. Various hypermobility measurement aids and devices have been proposed, but they are difficult to use in clinical practice.
Klaue[13] demonstrated a relationship in which increased mobility of the first MTT increases the hallux valgus deformity. He designed a device to measure first MTT mobility as well. Physiological dorsal excursion of the first MTT is up to 8 mm and a greater range of motion is considered pathological and indicates hypermobility.
The important stabilizing element is the plantar fascia, which becomes loose as the valgus deformity of the great toe progresses. According to Sarrafian[31] the plantar aponeurosis is one of the stabilizers of the forefoot and the great toe position. This condition was also confirmed by Grebing[32] who studied the impact of the plantar aponeurosis on stability of the first MTT. Using a Klaue device, they compared a group of patients on which plantar fasciectomy had been performed due to plantar fibromatosis to a group of patients on which no such surgical procedure had been performed. Grebing found that the plantar aponeurosis plays an important role in ensuring the stability of the CM joint. Hypermobility of the first MTT was present more often in the case of patients who had undergone the surgery than those who had not.
When examining the instability of the first MTT, the position of the talus is important. Grebing[32] report in their work that hypermobility of the first MTT changes with the position of the talus during examination. Mobility of the first MTT is lower in dorsiflexion and it is greatest in plantar flexion. Their conclusions are important during the foot examination when the ankle has to be kept in a neutral position.
First MTT instability was diagnosed in 92 feet (64.3%) in our group of patients. Patients with rheumatoid arthritis can have progression of forefoot deformity and pain even without instability of the CM joint. Lapidus operation can be important for stability of the whole forefoot in these cases. During the procedure not only is the instability resolved, but the position of the MTT bone as well. The operation is based on arthodesis of the CM joint with bone resection of the joint surfaces and internal fixation, but it can be complicated to achieve correct postoperative orientation of the first MTT bone. Appropriate bone resection during the procedure is essential for a positive postoperative outcome of the surgery. We always remove wedged bone block from the proximal part of the first MTT during the surface resection. The wedge is orientated laterally to adjust the varus position of the metatarsal bone. The high of the block is directly proportional to valgosity of the great toe and inclination is directly proportional to varosity of the first metatarsal bone. Insufficient resection can lead to elevation of the first MTT in the sagittal plane. The removal of all osteophytes and in some cases even the medial part of the middle cuneiform bone is important for the reduction of the gap after resections. In some cases, resection of the lateral part of the first MTT base is also required. The first intermetatarsal angle has to be corrected unless the relapse of the hallux valgus is significant.
For the purpose of this study we used two Kirschner wires, two screws or two staples for the internal fixation, but standardly use only two memory staples introduced in the sagittal and horizontal planes. Each staple has to insert through both the cortical bones in the MTT and the CM bones. The fixation using two screws was sometimes problematic, particularly in the case of rheumatoid patients where osteoporosis is present. If the memory staples are inserted only through one cortical bone, the fixation is not firm enough. The staple cannot ensure firm fixation, which can be crucial in case of a patient with rheumatoid arthritis.
In general, various osteosynthetic materials are used for arthrodesis fixation (Kirschner wires, screws, various plates, staples) or external fixation is used[29, 33, 34]. Fixation using two memory staples has proven the most successful. The memory staple fixating is quick, simple and, according to our experience, it is also reliable.
Outcomes of the Lapidus procedure cannot be evaluated with real precision, especially in the case of patients with rheumatoid arthritis, due to comprehensive affliction to the foot. We did not find any significant statistical dependence between the decrease of intermetatarsal angle and postoperative AOFAS score in our study.
Shi et al.[35] assessed the outcomes of the procedure in 21 patients with rheumatoid arthritis. They report pain relief and the possibility to wear normal shoes. They also evaluated changes identified by the X-ray examination – the angle of valgus deformity of the great toe, the intermetatarsal angle between the first and second MTT (reduction from 13 to 8.3 degrees) and the angle between the first and fifth MTT bones (reduction from 32.2 to 21.1 degrees). They report that 17 patients reported significant pain relief and 16 patients are able to wear normal shoes.
Myerson and Badekas[36] discuss hypermobility of the first MTT as a predisposing factor for the emergence of hallux valgus, in particular in combination with affliction of the ligaments and muscle imbalance. Hypermobility frequently occurs in adolescents with hallux valgus, in particular when there is an increased intermetatarsal angle between the first and second metatarsals. The authors describe the clinical and X-ray indicators of the hypermobility and the use of Lapidus procedure to treat patients.
A discussed issue is the occurrence of nonunion after performing the Lapidus procedure – the occurance of nonunion ranged between 3.3% and 9%. Patel[37] reviewed a set of 227 surgical procedures where screws were used for arthrodesis fixation. In 12 cases (5.3 %) nonunion developed.
In our group of patients with rheumatoid arthritis we recorded nonunion in seven cases (4.9%) and persistent swelling of the dorsum of the foot occurred in 12 (8.4%) operated feet.