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Department of Orthopedic Surgery, Tokyo Women's Medical University, Tokyo, JapanInstitute of Rheumatology, Tokyo Women's Medical University Hospital, Tokyo, JapanDivision of Multidisciplinary Management of Rheumatic Diseases, Tokyo Women's Medical University, Tokyo, Japan
Optimal relative first metatarsal length is one of the keys to achieving sufficient results after osteotomy of the first metatarsal. An excessive shortening of the first metatarsal was associated with postoperative metatarsalgia, whereas a long first metatarsal has been implicated as a cause of hallux valgus. To adjust the relative first metatarsal length to the optimal range during surgery, a predictive tool would be beneficial for preoperative planning. However, there is no established tool for predicting relative first metatarsal length. Here, we report a simple method to predict postoperative relative first metatarsal length after proximal rotational closing-wedge osteotomy for rheumatoid forefoot deformities. Two board-certified orthopedic surgeons performed relative first metatarsal length prediction retrospectively on a computed radiography system in nine consecutive cases. Most of them underwent simultaneous modified shortening oblique osteotomy of the second metatarsal (7/9 cases). The interclass correlation coefficients of intraobserver and interobserver reliability for relative first metatarsal length prediction were 0.96 and 0.94, respectively. The mean absolute error on relative first metatarsal length prediction was 1.5 mm at 3-month postoperatively in the same case series. The average time required to perform the relative first metatarsal length prediction was 44.1 s (standard deviation 9.0). Predicting relative first metatarsal length preoperatively in a simple manner, which takes less than a minute to complete, has the potential to improve the surgical outcome of rheumatoid forefoot surgery.
There is increasing interest in joint-preserving surgery for forefoot deformities in patients with rheumatoid arthritis (RA). This article provides a technique tip for predicting postoperative relative first metatarsal (MT1) length (RML) after proximal rotational closing-wedge osteotomy (PRCO) for rheumatoid forefoot deformities.
Optimal RML is one of the keys to achieving sufficient results after osteotomy of the MT1. An excessive shortening of the MT1 was associated with postoperative metatarsalgia or painful plantar callosity formation after osteotomy of the MT1,
Therefore, most surgeons use intraoperative X-ray fluoroscopy to adjust the metatarsal length without accurate preoperative prediction. Nevertheless, there were some difficulties in adjusting the metatarsal length with an accuracy of millimeters with intraoperative X-ray fluoroscopy, occasionally resulting in unfavorable outcomes.
There are several possible reasons for the lack of a predictive tool for RML. One is that the amount of shortening is determined through three-dimensional geometric complexes, which makes it difficult to predict. Furthermore, a variety of osteotomy procedures are currently being used to correct hallux valgus (HV), which makes it difficult to make a generalized predictive tool; over 150 different procedures for correcting HV have been reported.
Here, we report a simple method to predict postoperative RML after PRCO.
Figure 1 shows the predictive method on a plain radiograph for postoperative RML after proximal rotational closing-wedge osteotomy of the MT1 with a planned correction IMA of 0°. Using a computed radiography (CR) system makes it easier to predict RML in a short time with a parallel line calculator to measure the distance between two parallel lines (Fig. 1C). When MT1 additional shortening and/or MT2 shortening osteotomy are planned to be performed simultaneously, the planned shortening length of MT1 and/or that of MT2 should be removed from/added to the calculation result.
To evaluate the usefulness of the method, two board-certified orthopedic surgeons (KI and KY) performed RML prediction retrospectively on a CR system in nine consecutive cases of primary PRCO performed by a single surgeon (KI) in patients with RA from August 2021 to November 2021. They were all women, and most of them underwent simultaneous modified shortening oblique osteotomy of the MT2 (7/9 cases). The sagittal saw blade with cut thickness of 0.6 mm was used for osteotomy. The MT1 osteotomy site was stabilized using a low-profile locking plate. When needed, the MT2 osteotomy site was temporarily fixed using a single 1.2 mm Kirschner wire for two weeks along with a suture ligation to gain better bone-on-bone contact. Data of MT1 additional shortening length and MT2 shortening length, if any, were retrieved from medical records.
The interclass correlation coefficients of intraobserver and interobserver reliability for RML prediction were 0.96 and 0.94, respectively. The mean absolute error on RML prediction was 1.5 mm at 3-month postoperatively in the same case series. The error in the RML prediction tended to be in the negative direction (8/9 cases). The average time required to perform the RML prediction was 44.1 s (standard deviation 9.0). This retrospective study was approved by our institutional review board (3314-R3).
To adjust the RML to the optimal range during surgery is one of the keys to achieving sufficient result after the osteotomy of MT1. The simple predictive tool for postoperative RML shown here would be beneficial for preoperative planning of proximal closing-wedge osteotomy.
Combined first and lesser metatarsal osteotomy is frequently required to correct foot deformities in patients with RA. When MT2 shortening osteotomy and/or MT1 additional shortening are planned to be performed simultaneously, add shortening length of MT2 to and/or remove shortening length of MT1 from the calculation result.
Although the method is theoretically correct for predicting RML, there may be a systematic error because the error in RML prediction tends to be in the negative direction. The possible reasons for this error in the negative direction are as follows: saw blade thickness, overcutting of MT1 and/or undercutting of MT2 at the planned osteotomy lines, and MT1 shortening and/or MT2 elongation at the osteotomy sites during and/or after the surgery. Among them, the saw blade thickness at the hinge point should always be considered for RML prediction, which might be a cause of the systematic error.
This RML prediction method is not only for PRCO, but it is applicable to certain limited situations to correct HV: closing-wedge osteotomy with osteotomy lines perpendicular to the bone axes of MT1 and MT2, and a planned correction IMA of 0°. Though it was not evaluated in this study, the method also can be applied in open-wedge osteotomy by drawing line D perpendicular to line B through the intersection of line C and the lateral, not medial, cortex of MT1, which would be the lateral hinge point (Fig. 1A). Predicting RML preoperatively in a simple manner, which takes less than a minute to complete, has the potential to improve the surgical outcome of rheumatoid forefoot surgery, and PRCO gains an advantage with an RML prediction method.
Declaration of Competing Interest
H.T. and K.O. declare no conflict of interest. K.I. has received lecture fees from Asahi Kasei Pharma Co., Astellas Pharma Inc., AbbVie Japan GK, Ayumi Pharmaceutical Corporation, Bristol Myers Squibb Co., Ltd., Chugai Pharmaceutical Co., Ltd., Eisai Co., Ltd., Eli Lilly Japan K.K., Janssen Pharmaceutical K.K., Kaken Pharmaceutical Co. Ltd., Mitsubishi Tanabe Pharma Co., Pfizer Japan Inc., Takeda Pharmaceutical Co. Ltd., Teijin Pharma Ltd, and UCB Japan Co. Ltd. K.I. has received consulting fees from Zimmer Biomet. K.Y. has received speakers bureau and consulting fees from Astellas Pharma Inc., AbbVie Japan GK, Ayumi Pharmaceutical Corporation, Bristol Myers Squibb Co., Ltd., Eisai Co., Ltd., Hisamitsu Pharmaceutical Co., Inc., Mochida Pharmaceutical Co., Ltd., and Takeda Pharmaceutical Co. Ltd. K.Y. has received consulting fees from Zimmer Biomet. Division of Multidisciplinary Management of Rheumatic Diseases is an endowment department, supported with an unrestricted grant from Ayumi Pharmaceutical Corporation, Chugai Pharmaceutical Co., Ltd., Mitsubishi Tanabe Pharma Co., Mochida Pharmaceutical Co., Ltd., Nippon Kayaku Co., Ltd., and Teijin Pharma Ltd. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.
We would like to thank Editage (www.editage.com) for English language editing.
Proximal rotational closing-wedge osteotomy of the first metatarsal in rheumatoid arthritis: clinical and radiographic evaluation of a continuous series of 35 cases.