Introduction: The modified Lapidus-arthrodesis with standard AO screw-fixation is well known for the treatment of severe metatarsus primus varus deformity respectively a hypermobile or an arthrotic first tarso-metatarsal joint. High rates of non-union and malunion (range 3 to 12%) due to improper or poor fixation despite the postoperative course of nonweightbearing were reported in literature. The immediate postoperative weightbearing protocol varies from 2 to 6 weeks of cast immobilization. To our knowledge, this prospective investigation comprises the largest cohort of patients undergoing the Lapidus-arthrodesis, fixed with the Lapidus-Orthner locking plate.
Methods: 130 feet with an average patient’s age of 52 years (range 23 – 83 years), underwent the Lapidus fusion with the locking Orthner-plate. Indications were severe hallux valgus deformities respectively moderate hallux valgus deformities with a hypermobile first TMT 1- joint or an arthrotic first tarsometatarsal joint. The surgical technique was standardized, and the operations were performed by the inventor of the plate. All patients had a failed trial of nonoperative management (shoe-wear modification).
The 130 feet were divided into 2 groups. Group I was without TMT 1 – compression screw (n= 60) and group II with an additional compression-screw (n=70). Average age of group I was 54-years. The average age of group II was 50-years. The American-Orthopaedic-Foot and Ankle Society (AOFAS) Forefoot-Score, Visual-analog-pain-scale and foot radiographs were assessed preoperatively and after a mean of 23 months for group I and 39 months for group II. All 130 feet were treated immediately postoperative with a postoperative Darco orthowedge ® shoe.
Results: The average AOFAS score improved significantly from preoperative to follow up time-point in both groups. AOFAS pain-subscore significantly improved in both groups. The intermetatarsal-angle (IMA) of all 130 feet decreased significantly from 14° to 6° after surgery. At time of follow-up 9 % of non-unions were seen in group I whereas 0% were seen in group II with proximal compression screw, the difference is significant (p=0,024). The mean immobilisation with the Darco-Ortho® wedge shoe was 7,2 weeks (range 6 to 14 weeks) in group I and 6,3 weeks (range 5 to 12 weeks) in group II.
Conclusion: The prospective mid-term results from this study show that the locking Lapidus-Orthner plate is a very good and promising technique for the Lapidus-arthrodesis. The modified technique with compression screw has shown none non-union, despite of immediate weight-bearing in a post-op shoe after surgery. The procedure significantly reduced pain, the hallux valgus and intermetatarsal angle and increased the patient’s ambulatory capacity and patient satisfaction.
