الفهرس 
Chapter 2: BiomechanicsOnly 14 pages are availabe for public view
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Abstract
The first MPJ is an extremely complex joint, both in its function and with regards to the multiple structures that affect it. The normal function of the first MPJ requires plantar flexion of the first metatarsal to allow dorsiflexion of the hallux. The sesamoids must also be able to glide freely to promote first metatarsal plantar flexion or dorsiflexion..(1)
The pathophysiology of hallux rigidus is similar to that of degenerative arthritis in any joint. Overuse, injury, or abnormal joint mechanics lead to abnormal stresses on the articular cartilage. It is observed that the contact distribution shifted dorsally with increasing degrees of extension. These data are consistent with the observation that chondral erosions associated with hallux rigidus and degenerative arthritis initially affect the dorsal articular surface of the 1st metatarsal.(6)
Any amount of motion less than 65 degrees can indicate the presence of hallux limitus or hallux rigidus. It is important to load the 1st metatarsal by palpating the plantar surface of the head, and forcing it in a dorsal direction until no further range is available. Next, the other hand is used to dorsiflex the great toe. If the first 15- 20 degrees of motion are difficult to achieve, or no range of motion is available, then the presence of functional hallux limitus can be anticipated. (11) According to Hattrup and Johnson classification Grade1shows mild to moderate osteophytes formation but, joint space preservation.
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However, Grade 2 is found to have moderate osteophyte formation with joint space narrowing and subchondral sclerosis. Marked osteophyte formation and loss of the visible joint space, with or without subchondral cyst formation is the picture of grade 3. (19) The nonsurgical treatment for hallux limitus is directed to reducing pain, potentially slowing down the progression of further joint damage and allowing for improved function at the first MPJ when possible. In determining what conservative options may be appropriate, the grading of the hallux limitus, symptom level, and underlying etiology need to be taken into consideration. (25) Cheilectomies are the mainstay of joint-salvage procedures because they are the least invasive, have a minimal postoperative recovery, and allow for conversion to other procedures if needed. (37) In patients suffering from early stage hallux rigidus, osteotomies may be used as joint sparing procedures, with hopes to increase the amount of dorsiflexion of the first metatarsophalangeal joint. Proximal phalangeal osteotomy and 1st metatarsal osteotomy are performed to provide more dorsiflexion. (54) If arthrodesis is planned, the hallux should be fused 10° to 15° above the horizontal; this value should be added to the preoperatively measured metatarsal declination angle to allow for accurate positioning of the hallux on the metatarsal in the sagittal plane. (70)
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The ideal procedure would provide adequate pain-free motion of the first MPJ without shortening the hallux, is the arthroplasty, however, several complications of the implant materials have been discovered. (80)