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A simple method to predict postoperative relative first metatarsal length after proximal closing-wedge osteotomy

  • Author Footnotes
    These authors contributed equally to this work.
    Katsunori Ikari
    Correspondence
    Corresponding author.
    Footnotes
    † These authors contributed equally to this work.
    Affiliations
    Department of Orthopedic Surgery, Tokyo Women's Medical University, Tokyo, Japan

    Institute of Rheumatology, Tokyo Women's Medical University Hospital, Tokyo, Japan

    Division of Multidisciplinary Management of Rheumatic Diseases, Tokyo Women's Medical University, Tokyo, Japan
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  • Author Footnotes
    These authors contributed equally to this work.
    Haruki Tobimatsu
    Footnotes
    † These authors contributed equally to this work.
    Affiliations
    Department of Orthopedic Surgery, Tokyo Women's Medical University, Tokyo, Japan

    Institute of Rheumatology, Tokyo Women's Medical University Hospital, Tokyo, Japan
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  • Koichiro Yano
    Affiliations
    Department of Orthopedic Surgery, Tokyo Women's Medical University, Tokyo, Japan

    Institute of Rheumatology, Tokyo Women's Medical University Hospital, Tokyo, Japan
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  • Ken Okazaki
    Affiliations
    Department of Orthopedic Surgery, Tokyo Women's Medical University, Tokyo, Japan
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  • Author Footnotes
    These authors contributed equally to this work.
Open AccessPublished:August 28, 2022DOI:https://doi.org/10.1016/j.fastrc.2022.100240

      Abstract

      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.

      Keywords

      Introduction

      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.
      • Yano K.
      • Ikari K.
      • Iwamoto T.
      • et al.
      Proximal rotational closing-wedge osteotomy of the first metatarsal in rheumatoid arthritis: clinical and radiographic evaluation of a continuous series of 35 cases.
      ,
      • Yano K.
      • Ikari K.
      • Tobimatsu H.
      • Okazaki K.
      Patient-reported and radiographic outcomes of joint-preserving surgery for rheumatoid forefoot deformities: a retrospective case series with mean follow-up of 6 years.
      The advantages of PRCO are
      • Yano K.
      • Ikari K.
      • Iwamoto T.
      • et al.
      Proximal rotational closing-wedge osteotomy of the first metatarsal in rheumatoid arthritis: clinical and radiographic evaluation of a continuous series of 35 cases.
      larger correction of the intermetatarsal angle (IMA) due to proximal osteotomy compared to distal or shaft osteotomies,
      • Yano K.
      • Ikari K.
      • Tobimatsu H.
      • Okazaki K.
      Patient-reported and radiographic outcomes of joint-preserving surgery for rheumatoid forefoot deformities: a retrospective case series with mean follow-up of 6 years.
      correcting rotational deformity of MT1 simultaneously with a single osteotomy,
      • Nakagawa S.
      • Fukushi J.
      • Nakagawa T.
      • Mizu-Uchi H.
      • Iwamoto Y.
      Association of Metatarsalgia after hallux valgus correction with relative first metatarsal length.
      simple shortening of the MT1 according to the shortening of the lesser metatarsals, and
      • Tobimatsu H.
      • Ikari K.
      • Yano K.
      • Okazaki K.
      Radiographic factors associated with painful callosities after forefoot surgery in patients with rheumatoid arthritis.
      easy correction to the planned angle by contacting the osteotomy surfaces.
      • Yano K.
      • Ikari K.
      • Tobimatsu H.
      • Okazaki K.
      Patient-reported and radiographic outcomes of joint-preserving surgery for rheumatoid forefoot deformities: a retrospective case series with mean follow-up of 6 years.
      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,
      • Nakagawa S.
      • Fukushi J.
      • Nakagawa T.
      • Mizu-Uchi H.
      • Iwamoto Y.
      Association of Metatarsalgia after hallux valgus correction with relative first metatarsal length.
      ,
      • Tobimatsu H.
      • Ikari K.
      • Yano K.
      • Okazaki K.
      Radiographic factors associated with painful callosities after forefoot surgery in patients with rheumatoid arthritis.
      whereas a long MT1 has been implicated as a cause of hallux valgus (HV).
      • Mancuso J.E.
      • Abramow S.P.
      • Landsman M.J.
      • Waldman M.
      • Carioscia M.
      The zero-plus first metatarsal and its relationship to bunion deformity.
      Since the cut-off value of RML for the occurrence of painful callosities after PRCO was −3.4 mm,
      • Tobimatsu H.
      • Ikari K.
      • Yano K.
      • Okazaki K.
      Radiographic factors associated with painful callosities after forefoot surgery in patients with rheumatoid arthritis.
      the optimal range of RML for PRCO would be 0 to −3.4 mm.
      To adjust the RML to the optimal range during surgery, a predictive tool would be beneficial for preoperative planning. However, there is no established tool for predicting RML.
      • Wirth S.H.
      • Fuernstahl Furnstahl P.
      • Meyer D.C.
      • Viehoefer Viehofer A.F.
      Planning tool for first metatarsal length in hallux valgus surgery.
      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.
      • Helal B.
      Surgery for adolescent hallux valgus.
      Here, we report a simple method to predict postoperative RML after PRCO.

      Results

      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.
      Fig 1
      Fig. 1Predictive Method of Postoperative Relative First Metatarsal Length after Proximal Rotational Closing-wedge Osteotomy of the First Metatarsal.
      A. Preoperative planning. A weightbearing dorsoplantar foot radiograph is used. First, lines are drawn parallel to the bone axes of the MT1 and MT2 (dotted lines A and B). Second, a line is drawn perpendicular to line A through a point 15 mm distal from the first tarsometatarsal joint (line C, the distal osteotomy line of the MT1). Third, a line perpendicular to line B is drawn through the intersection of line C and the medial cortex of the MT1 (line D, the proximal osteotomy line of the MT1). The angle between lines C and D is equal to the preoperative IMA. The grayed area is the bony wedge to be removed. Fourth, lines perpendicular to the lines A and B are drawn through the metatarsal head apices of the MT1 and MT2 (lines E and F). Fifth, the distances between parallel lines C and E (dotted double arrow line α, MT1 length from the distal osteotomy line of MT1), and lines D and F (dotted double arrow line β, MT2 length from the proximal osteotomy line of MT1) is measured. After abducting and rotating the distal fragment of the MT1 until the nail of the great toe turned to the ceiling (bold arrows), osteotomy site will be stabilized using a low-profile locking plate.
      B. Predicted RML=α-β. When MT1 additional shortening and/or MT2 shortening osteotomy are planned to be performed simultaneously, remove shortening length of MT1 from and/or add shortening length of MT2 to the calculation result.
      C. Parallel line calculator on a computed radiography system to measure the distance between lines drawn perpendicular to the bone axes of MT1 and MT2 (lines C and E: α, and lines D and F: β).
      IMA, intermetatarsal angle; MT, metatarsal; RML, relative first metatarsal length.
      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).

      Discussion

      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.

      Financial disclosure

      None reported.

      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.

      Acknowledgement

      We would like to thank Editage (www.editage.com) for English language editing.

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