Arthritis of the midfoot (midtarsal and tarsometatarsal joints) has emerged as a challenging problem because of its potential for resulting in chronic pain and functional disability.
The incidence of patients presenting with symptomatic midfoot arthritis is increasing, however, there is no appropriate guidance for clinical decision making in the literature.
Causes of midfoot arthritis include primary (idiopathic), inflammatory and post-traumatic (after Lisfranc injuries, most common type). Lisfranc injuries are particularly concerning because as many as 20% may be missed or misdiagnosed.
Midfoot stability during the mid-stance phase of gait is critical because it facilitates forward progression of the body weight on a stable foot. Loss of this stability may lead to a failure to position the foot effectively for push-off. This not only gets reflected in symptoms during level walking but also manifests as difficulty in going up and down the stairs and activities that require heel raise.
These changes correspond to flattening of the medial arch and may lead to increased tensile stresses on the supporting plantar ligaments on loading of the foot resulting in pain. This alteration of the gait pattern may lead to higher demands of the muscles and ligaments leading to further stress around the midfoot region. Individually or combined, foot posture, motion, and plantar loading may be linked to abnormal articular loads and subsequent damage at the tarsometatarsal joints.
Patients with degenerative arthritis and post-traumatic arthritis present with similar symptoms that include pain, progressive deformity, severe restriction in the ability to walk and to perform activities of daily living, problems with foot posture and wearing shoes.
The primary aim of treatment is to provide pain relief by restoring midfoot stability and modifying loads sustained at the affected joints.
Conservative treatment is always the first line of management. NSAIDs have long been considered the first line of treatment; however, their adverse effects make extended usage undesirable.
Shoewear modifications and foot orthoses are currently the mainstay of treatment in these patients to provide adequate support and pain relief. The options include medial arch support insoles, stiff soles, rocker bottom soles and AFOs.
The custom-moulded three-quarter length rigid shoe inserts are often recommended in these patients, however, some recent clinical experience has shown that patients may continue to report foot pain during walking, suggesting that this orthosis does not provide adequate control of midfoot stability and may load the foot in regions that do not tolerate excess loading.
Another available option is the full-length carbon foot plate (CFP). A recent retrospective review and other preliminary studies indicate that the pain and dysfunction may improve with these shoe inserts. Findings from one study report that symptomatic improvement associated with the use of the CFP were accompanied by a 35% reduction in average pressure and a 21% reduction in contact time at the medial midfoot, compared with the three-quarter insoles.
Another study found a 22% improvement in Foot Function Index after 4 weeks of intervention with the CFP shoe inserts. These positive outcomes support the use of the full-length CFP as a viable alternative in the conservative management of patients with midfoot arthritis.
Injections are frequently used for pain management of midfoot arthritis, both for diagnostic and therapeutic purpose. Although, steroid and hyaluronic acid injections have had extensive study in other joints, there have been no published studies on the effectiveness of these injections in the midfoot joints.
Assessment and Decision-Making for Surgery
Weight-bearing radiographs of the foot and ankle are obtained to assess the tarsometatarsal and naviculo-cuneiform joints prior to surgery (joint space narrowing, osteophyte formation, sclerosis, and cyst formation) and alignment of the foot and ankle in the frontal and sagittal planes.
The decision making can be difficult as to which joints to address surgically. Targeted local anaesthetic injections under fluoroscopic guidance may provide some help to localise the most affected joints.
A recent study on injections found that there could be leakage of the anaesthetic from the second TMT joint laterally in more than 20% of the cases, raising some questions on the diagnostic value of these injections.
It is rare to fuse a single midfoot joint in isolation. Therefore, the recommended choice is a combination of the first, second, and potentially third TMT joints and, if symptomatic, the corresponding naviculo-cuneiform joint is included as well. This requires a details clinical and radiographic assessment (additional CT and/or MRI scans) and discussion with the patient.
Indications for Surgery
Mann et al. described the indications for surgery as severe loss of function due to pain, with or without deformity that had failed to respond to conservative treatment (for at least a 6 month period). They defined severe loss of function as the inability to return to usual occupation or to perform activities of daily living.
Compression/lag screw fixation of these joints is necessary to achieve a successful fusion and resolution of symptoms. Care is taken to obtain a tight apposition of the second metatarsal base with the medial cuneiform as well as the first metatarsal base to re-establish Lisfranc joint alignment.
The choice of screws include partially-threaded cancellous screws or variable-pitch fully-threaded cannulated screws, the latter providing ease of positioning with an initial K-wire placement. Variable compression fully-threaded screws provide a higher fatigue resistance to fracture.
Alternative options include a compressive plating fixation. Various types of plates are available but no studies provide any comparison and the choice depends on the treating surgeon and availability in the local centre.
Local bone graft or substitutes may be used to augment the union process depending on surgeons’ preference and consideration; however no published studies are available to assess the effectiveness of these agents in midfoot fusion.
Anatomical reduction is considered the most important predictor of good outcome. Studies have shown that the age and the mechanism of injury are not significant predictors of outcomes after midfoot arthrodesis.
Sangeorzan et al. reported good to excellent results in 69% (11/16) of patients who had arthrodesis of the midfoot following a failed conservative treatment for Lisfranc fracture dislocations.
Myerson et al., in their study, reported 49% good to excellent result, and 51% fair to good result at 4.2 years of follow-up after midfoot arthrodesis. Although midfoot arthrodesis surgery leads to an improvement in pain, the available studies have shown a modest improvement in function.
Complications after surgery of the midfoot include wound-related problems, infections (3%), nerve injuries (9%), neuroma formation (7%), non-union (3%-7%), implant-related problems and screw irritation (9%), metatarsalgia (6%), stiffness, secondary arthritis in adjacent joints and CRPS. Foot rigidity occurring subsequent to arthrodesis is well-tolerated by the patients.
Smita Rao, Deborah A. Nawoczenski, Judith F. Baumhauer, Midfoot Arthritis: Nonoperative Options and Decision Making for Fusion, Techniques in Foot & Ankle Surgery 7(3):188–195, 2008.
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