Foot & Ankle

First metatarsophalangeal joint arthroplasties: perhaps some more work to do

The treatment of arthritis of the first metatarsophalangeal joint (MTPJ) continues to evolve, and in the last few years replacement arthroplasty has largely been the focus in attempts to improve outcomes. There is now a wide variety of hemi and total joint arthroplasty implants available commercially, however, there is less in the way of evidence to support their use. The data recently published from the Cartiva Motion Study Group concern the early results of their viscoelastic hemiarthroplasty for the first metatarsal head. The literature reflecting the mid-term results of these implants is conflicting, but some series have reported revision rates of 24% at 33 months, leading to abandonment of the procedure.¹ The recurrent difficulty appears to be failure of osseointegration of the metatarsal implant. In response to this, efforts to find range of movement-preserving solutions to end-stage MTPJ arthritis are ongoing. The study team designed their own prospective, randomised non-inferiority study involving patients from 12 centres in the USA, Canada and the UK. A total of 202 patients were enrolled in the study and randomised to receive either the implant or arthrodesis.² This non-inferiority study reveals no difference in pain relief or patient satisfaction at two-year follow-up, but a quicker recovery and return to function in the early post-op phase for the implant group. The conversion rate to arthrodesis at two years was 9.2%, all of which were undertaken for persistent pain of unknown cause. This would appear to compare favourably with a secondary surgery rate of 14% in the arthrodesis group (7 of 50), however, these were usually small operations, mostly metalwork removal. Five-year follow-up data are awaited, but with a failure rate of nearly 10% at two years, patients should be counselled carefully prior to receiving this novel implant.

The neuropathic foot: understanding the muscle drivers

Acquired deformity and abnormal weight distribution, combined with the loss of protective sensibility, are the major factors in the development of ulceration in the diabetic neuropathic foot. The well recognised changes of metatarsophalangeal joint (MTPJ) hyperextension leading to abnormal forefoot weight distribution is probably the most common acquired deformity seen in neuropaths. This forefoot abnormality is commonly seen in conjunction with subtle contractures of the tendoachilles complex, which manifest as ankle stiffness and contribute to the plantar forefoot overload which is causative in diabetic foot ulceration. The initial driver for this whole process is largely unknown but is ascribed to a general imbalance between the long extensor and short flexors of the foot. An interesting paper from St Louis, Missouri (USA) sheds some light on the potential underlying causes. The authors aim to categorise intrinsic muscle fatty infiltration, peripheral neuropathy and the presence of accumulated advanced products of glycosylation with the degree of deformity measured at the MTPJs of diabetic patients, in an attempt to understand the pathological process.³ Their study reports data from 34 patients, all with diabetic neuropathy. Cross-sectional CT and MRI imaging of the foot was undertaken, allowing the deformity and muscle changes to be measured. In addition, glycosylation was measured with skill fluorescence and kinematic studies to establish range of motion in the hind- and forefoot. The authors established that the lean muscle volume correlated well to the MTPJ deformity, as did hindfoot deformity, and were able to account for 35% of the variation in forefoot deformity. Whilst neuropathy did have a predictive effect on forefoot deterioration, the level of skin fluorescence did not. The paper also usefully describes a novel algorithm which can be applied to MRI scans of the forefoot to accurately measure total lean muscle volumes within the flexor compartment. Previous studies have used single slice acquisition techniques and applied atrophy criteria as determined by a clinician. This is interesting in itself as a possible screening tool to identify feet at risk of ulceration, with a view to initiating preventative measures. (total contact innersoles, stretching programmes, etc.). Given the enormous cost burden of diabetic feet, any measure which prevents complications arising in this population is likely to be beneficial.

Primary fusion and Lisfranc injuries

Radiographic severity important in predicting outcomes in total ankle arthroplasty

It is widely known and accepted that in total knee arthroplasty, the best predictor of post-operative outcome is pre-operative function. However, this is not a concept that has ported across to the world of ankle arthroplasty. Reasoning that patient selection for total ankle arthroplasty is key to achieving the best outcomes, researchers in Newcastle upon Tyne (UK) set out to investigate the impact that the pre-operative radiographic arthritis grade may have on post-operative functional results in total ankle arthroplasty (TAA).⁷ The research team focused on a large series of 178 ankle replacements in 170 patients. They undertook a retrospective review of their pre-operative radiographs and prospectively collated clinical outcome data (Foot and Ankle Outcome Score [FAOS; pain, function, and stiffness], MOS 36-item and Short-Form Health Survey [SF-36] scores). The patients were subdivided by the pre-operative Kellgren-Lawrence scores assessed on pre-operative weight-bearing films. There were few differences in patient demographic data; perhaps most interestingly, pre-operative FAOS scores were similar across all three groups with no statistically significant differences observed. However, the improvements in both domain-specific and general outcome scores differed dramatically between the groups. As perhaps might be expected, those patients with severe or end-stage arthritis had the greatest post-operative satisfaction rates (achieving > 90% at two years in severe arthritis), whereas in the mild to moderate group rates were as low as 50%. This paper informs decision making in an area where technologies continue to evolve and the relative indications for arthroplasty are not yet clear.

Osteolysis around the ankle: a ballooning problem?

Posterior fixation of the ankle?

Resection versus fusion in the lesser toes

This is a simple paper that does exactly what it says on the tin. The authors have designed a neat randomised controlled trial to evaluate the benefits or otherwise of proximal interphalangeal joint fusion (PIPJ) over a simple resection of the joint in patients undergoing a hammertoe correction. The clinical trial based in Breda (The Netherlands) reports the outcomes of 55 patients randomised to either resection (26 patients, 39 toes) or fusion (29 patients, 50 toes),¹⁰ sadly leaving somewhat uneven groups. The PIPJ procedure was combined as necessary with metatarsophalangeal releases to correct the toes’ attitude. Outcomes were assessed at one year following surgery using the American Orthopaedic Foot & Ankle Society scale, the Foot Function Index, and visual analogue scale pain outcome scores. In addition to clinical scores, the alignment of the toes was evaluated at final follow-up. Essentially there were no differences in functional outcome scores between the two groups, however, the fusion group had a superior alignment in the sagittal plane at final follow-up. It is reasonable to presume that late recurrence will also be less common in the fusion group, although longer follow-up is clearly required to establish this. This study really does leave the choice of surgery to the patient and surgeon. However, although there are no differences in the clinical outcomes selected by the study design team, given that the aim of the surgery is to correct toe malalignment and there was a significant difference in favour of the fusion group with regard to sagittal malalignment, we can’t help thinking that perhaps the authors have not quite been definite enough with their conclusions. A fusion, we would conclude, is more reliable and has the same functional outcomes.

Minimally invasive ankle fixations?