3D-printed hallux and lesser metatarsophalangeal joint replacement





Definition




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    Custom/patient-specific 3D-printed metallic porous hemiarthroplasty for the treatment of hallux and lesser toe metatarsophalangeal joint (MTPJ) arthritis to improve pain while maintaining range of motion (ROM).



Anatomy/pathogenesis




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    The first metatarsal head is unique as its dorsoplantar diameter is smaller than the transverse plane diameter.


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    The first MTPJ articular surface is functionally divided into superior and inferior fields. The superior metatarsal field is convex and is larger than the superior phalangeal concavity, but the inferior metatarsal is larger than the superior metatarsal field, with articulations for the sesamoids as demonstrated in Fig. 20.1 .




    • Fig. 20.1


    Image showing the larger superior first metatarsal joint surface relative to the superior phalanx joint surface. This includes dorsal osteophytes, as evident in hallux rigidus. This image also demonstrates the larger inferior metatarsal articular surface relative to the superior metatarsal articular surface with articulation for the sesamoids.

    (CAD images reprinted with permission from restor3d, Inc, Durham, NC.)


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    The plantar plate is part of the capsuloligamentous complex that provides stability to the first MTPJ.


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    The normal ROM for the first MTPJ ranges from 65 to 110 degrees of dorsiflexion and 23 to 45 degrees of plantarflexion. Passive non–weight-bearing ROM correlates to active, dynamic ROM while walking.


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    Hallux rigidus is a restriction of the first MTPJ ROM with progressive osteoarthritic changes resulting in pain and functional limitations during weight bearing.


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    Various etiologies have been proposed for hallux rigidus, including most commonly trauma, followed by osteochondritis dissecans, metatarsus primus elevatus, and family history. ,


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    Dorsal osteophytes act as a mechanical block and can severely limit ROM of the hallux MTPJ, especially with dorsiflexion.


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    The 2nd metatarsal acts as a keystone in the arch of the foot and is often the longest of the metatarsals.


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    During the toe-off phase of gait, the 2nd metatarsal is driven down into the ground and the base of the proximal phalanx rides dorsally over the metatarsal, creating compressive and shear forces that damage the cartilage of the metatarsal head.


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    Second MTPJ pain can be caused by many conditions including osteoarthritis, synovitis, Freiberg’s infraction, osteochondral lesions, and MTPJ instability. Other conditions such as plantar plate tears and trauma can contribute, especially in the setting of osteoarthritis.



History and physical exam findings




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    Localized pain to the MTPJ of concern.


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    Adjacent metatarsal pain (transfer metatarsalgia).


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    Restricted ROM, pain through the midarc of motion, as well as terminal dorsiflexion with hallux rigidus.


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    Hallux valgus deformity with a palpable, tender dorsal osteophyte, and medial eminence.


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    A history of radiating, burning pain due to stretch of the dorsomedial cutaneous nerve.


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    Pain with weight bearing as well as palpation of the joint.


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    Pain through passive ROM of the 2nd MTPJ as well as instability with drawer of the joint.


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    Weak propulsion during gait.



Imaging and other diagnostic testing




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    Radiographic:



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      Hallux rigidus radiographic findings are consistent with a classic osteoarthritis appearance in other joints such joint space narrowing, osteophyte formation, subchondral sclerosis, and subchondral cysts. Dorsal osteophytes are often the most pronounced findings.


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      A second toe MTPJ radiographic appearance can differ based on the etiology of the pain. Osteoarthritis has a similar appearance as described for above for hallux rigidus. Freiberg’s infarction manifests as widening of the joint space and collapse of the metatarsal head with sclerosis. 2nd MTPJ instability appearance will show dorsal subluxation/dislocation of the proximal phalanx relative to the metatarsal head in the sagittal plane with plantar plate tear or extensor/flexor tendon imbalance, or collateral ligament injury in the coronal plane ( Fig. 20.2 ).




      • Fig. 20.2


      An anteroposterior radiograph and sagittal CT scan demonstrating a large central osseous defect status post failed Cartiva

      (Stryker 325 Corporate Drive Mahwah, NJ 07430) implant for hallux rigidus.





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    Advanced imaging (CT/MRI):



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      Both CT/MRI can be useful in understanding the etiology of the MTPJ pain and deformity.


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      CT is typically best utilized for the analysis of bony anatomy including staging avascular necrosis (AVN) or subchondral collapse, as seen in Figs. 20.3 and 20.4 . CT is more helpful in surgical planning with 3D printing technology.




      • Fig. 20.3


      CT images showing 2nd metatarsal head avascular necrosis with collapse more focal on the superior aspect of the joint.



      • Fig. 20.4


      Intraoperative findings correlating with 2nd metatarsal head avascular necrosis and collapse seen in Fig. 20.3 with delamination of the cartilage.


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      MRI is better utilized for soft tissue anatomy, including the visualization of cartilage damage in OCDs, ligaments in plantar plate/collateral ligament tears, or diagnosing AVN when it is not obvious on plain radiographs. MRI provides information on the extraarticular soft tissues as well, which enhances its diagnostic value.



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    Other testing:



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      Noninvasive vascular testing should be considered if there is concern for vascular pathology.


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      Infectious and bone metabolism workup should be obtained if there is concern for infection or bone quality that may compromise a joint implant, including: white blood cells (WBCs), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), vitamin D, parathyroid hormone (PTH), and thyroid-stimulating hormone (TSH).


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      Electromyography (EMG)/nerve conduction study (NCS) can be considered for patients presenting with neuropathic symptoms.




Nonoperative treatment




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    Hallux and lesser toe MTPJ pathology is usually treated with shoe modification; orthotics; immobilization; rest, ice, compression, elevation (RICE) therapy; nonsteroidal antiinflammatory drugs (NSAIDs); and steroid injections. Morton’s extension can be considered with hallux rigidus. Orthotics with metatarsal pads can be useful for lesser toe MTPJ, especially metatarsalgia



Traditional surgical management




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    Dorsal cheilectomy: early osteoarthritic changes of the hallux MTPJ are typically treated with cheilectomy to remove the dorsal osteophytes, which removes impingement pain and increases ROM.


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    Interposition arthroplasty: can be useful as a salvage technique for hallux or lesser toe MTPJ but it has variable results.


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    Hallux metatarsophalangeal fusion: the “gold standard” for more severe arthritis but it completely eliminates ROM of the joint, so may not be ideal for all patients.


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    Hemiarthroplasty: can provide significant pain relief and maintains some ROM, even more so than total MTPJ arthroplasty.


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    Total MTPJ arthroplasty: provides some pain relief but is associated with higher complication rates than other surgery, less pain relief, and less ROM than hemiarthroplasty. ,


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    Metatarsal head shortening osteotomy: Weil osteotomy can be used to shorten the metatarsal decompression joint and improve metatarsalgia. However, it is often associated with transfer metatarsalgia and can be less useful in MTPJ instability and AVN with collapse.


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    Resection arthroplasty: can be useful as salvage in low-demand patients.



3D-printed implant and/or instrumentation considerations



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Jul 15, 2023 | Posted by in ORTHOPEDIC | Comments Off on 3D-printed hallux and lesser metatarsophalangeal joint replacement

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