Aims

The first metatarsal pronation deformity of hallux valgus feet is widely recognized. However, its assessment relies mostly on 3D standing CT scans. Two radiological signs, the first metatarsal round head (RH) and inferior tuberosity position (ITP), have been described, but are seldom used to aid in diagnosis. This study was undertaken to determine the reliability and validity of these two signs for a more convenient and affordable preoperative assessment and postoperative comparison.

Congenital hallux varus had been a well-described condition for many years before acquired hallux varus as a condition arising from bunion correction was not described until 1935. In that year, McBride discussed this potential problem when describing this as a potential problem from his described technique, identifying possible mechanisms to prevent the disorder from occurring. Authors such as Joplin and Kelikian echoed the concept in the early 1960's, spawning a series of corrective procedures. Miller brought this to common practice in 1975, describing the tendon imbalance seen across the precarious 1. st. MTP joint. The first metatarsophalangeal joint moves in the sagittal plane, dorsiflexion and plantarflexion only. Four intrinsic muscles stabilize the digit, with the abductor and adductor hallucis taking the lion share of this function. The abductor tendon actually functions primarily as a plantarflexor of the first metatarsophalangeal joint 83% of the time (Thompson) due to its primary plantar location. This fact, in combination with the pronation generally seen in severe bunion deformities, contributes to acquired hallux varus following bunion correction. Besides the obvious cause of over-correction of the metatarsal osteotomy creating hallux varus, imbalance of the tendon complex post-operatively can create an equally catastrophic circumstance. Hawkins demonstrated that severing the adductor tendon complex (the conjoined tendon) will not product hallux varus when the hallux is not rotated. However, in more severe hallux valgus, pronation of the hallux may be proportional to the deformity of the hallux itself. This rotational deformity places the insertions of the abductor (and medial insertion of the flexor brevis) more plantarward and lateral, increasing the valgus deformity. If the entire conjoined tendon is sectioned and the internal rotation deformity corrected the insertion of the contracted abductor moves medially, pulling the toe into varus. If the center of the base of the proximal phalanx is brought beyond the mid-point of the first metatarsal head, the extensor hallucis longus will bowstring, pulling the great toe into varus while creating a hallux flexus deformity. Finally, if the lesser toes are in varus and not corrected, this deforming force will create hallux varus following bunion correction with a lateral release. The message is clear: not all patients require a lateral release, and, if done, should be done with caution. Once present, correction can be difficult. Tendon transfers utilizing the extensor hallucis longus (Johnson) or extensor hallucis brevis (Myerson) only have beneficial effects in non-arthritic, mobile first metatarsophalangeal joints. In addition, if metatarsal deformity is not corrected, the deformity will recur. Thus, in many circumstances, arthrodesis of the first metatarsophalangeal joint becomes the treatment of choice, and is commensurate with a disappointed patient who underwent a primary bunion correction and was left with a fused great toe. This lecture will explore the above mechanism and salvage situations, in hopes of eliminating this unwelcomed outcome from your practice

Proximal Metatarsal osteotomies are used for larger deformities, generally those with an intermetatarsal angle greater than 15°. These osteotomies usually are combined with a Distal Soft Tissue Release, which is necessary to correct metatarsophalangeal (MTP) sub-luxation with a Hallux Valgus Angle greater than 35°. Many types of osteotomies have been described. These include a medial opening wedge, a lateral closing wedge, proximal chevron, and a crescentic. Additional osteotomies include the Scarf, Ludloff, and Mao osteotomies. Presently, the proximal chevon and crescentic osteotomies are widely used. In our study we used the proximal chevon osteotomy combined with Distal Soft Tissue Release and approximation of the 1. st. and 2. nd. metatarsus using a string to further decrease the intermetatarsal angle. From January 2000 to June 2005 the basal chevon osteotomy was selected in 44 patients (37 female and seven male patients, ages 14 to 80, mean: 54.97 years) total of 49 feet with moderate metatarsus primus varus (IMA 13 to 20 degrees) and hallux valgus deformities (less than 50 degrees). The AOFAS Hallux Metatarsopha-langeal-Interphalangeal Scale and patient satisfaction were monitored prior to surgery, and postoperatively. Changes in the IMA and HV angle were measured in the conventional method and documented. All patients were treated in a Darco Post operative splint. Results: Multiple complications were encountered. The most common is transfer metatarsalgia. This occurred in 10 patients (20%). Other complications include delayed union (4%), increase in the height of the first metatarsus (10%), floating toe (6%), superficial infection (15%), local parenthesis and early recurrence of deformity in 3%. 38 patients were available for follow-up. The hallux valgus angle improved significantly more than 20 degrees on average postoperatively. The intermeta-tarsal angle also improved significantly (more than 10 degrees on average) postoperatively. The position of the sesamoids was realigned to beneath the first metatarsal head and the metatarsal length remained essentially unchanged. The AOFAS score preoperatively was a mean of 75.64 with respect to pain, deformity, motion, disability, and cosmetic. The AOFAS score postoperatively was a mean of 94.55. The mean improvement was 18.91. About 95.45 percent (42/44) were satisfied and would recommend the surgery to a friend. Conclusions: The basal chevron osteotomy combined with Distal Soft Tissue Release and realignment using a string is a technically demanding procedure and has multiple potential complications but provdes a reliable method with respect to stability, technical ease and satisfactory surgical outcome for correction of moderate and severe bunion deformity, both as a primary and revision procedure