2.1

This is a retrospective case series with prospectively collected outcome data in pediatric patients within a research ethics board (REB)-approved foot and ankle registry (REB# 1000079019). All patients and/or their substitute decision maker consented to surgery and enrollment in the registry. Patients were treated by a single surgeon at a tertiary care pediatric hospital and underwent a PDCO as part of a foot deformity reconstruction. Patients who underwent O-PDCO were compared to those who had MI-PDCO, including clinical, and radiographic details, and PROMs. Inclusion criteria were age ≤ 18 years at time of PDCO, surgery between January 1, 2019, and September 15, 2021, at least 3 months follow up, and complete medical records, pre, intra- and postoperative radiographs.

Patient demographic information, past medical history, physical exams and treatment/surgical details were recorded. Intra- and postoperative radiographs were assessed to measure the amount of calcaneal displacement ( Fig. 1 ) and determine osteotomy union. Postoperative clinical outcomes recorded included neurologic and vascular injuries, wound healing disturbances and local infections.

Axial view demonstrating measurement of calcaneal displacement.

2.2

All surgeries were performed by a single pediatric and foot and ankle fellowship-trained surgeon (MB). PDCOs were performed concurrently with other soft tissue and bony procedures. For flatfoot reconstructions, a PDCO was performed with a calcaneal lengthening osteotomy (CLO) if the patient presented with a rigid flatfoot deformity, excessive hindfoot valgus, or if inadequate hindfoot correction was achieved intraoperatively with CLO alone. Ancillary procedures in flatfoot included gastrocnemius or Achilles lengthening, peroneus brevis lengthening, plication of the tibialis posterior and talonavicular joint, and medial cuneiform osteotomy to correct the residual forefoot supination, adduction or abduction ^, . For cavovarus feet or residual clubfeet, the PDCO was required to correct stiff hindfoot varus deformities or any residual varus after correction of the forefoot cavus. An approach for operative planning of pes cavus has been described by the senior author elsewhere as well as other sources ^,, .

The author initially performed calcaneal osteotomies using an open technique but changed their operative technique to the more modern, minimally invasive later on their practice. Therefore, the MI-PDCO cases in this paper were performed at the beginning of the treating surgeon’s learning curve.

In all cases, the patients were supine with a bump under the ipsilateral hip and a non-sterile thigh tourniquet. Tourniquet was always let down prior to performing the MI-PDCO to minimize heat production during the osteotomy but remained inflated for the open procedures. Depending on availability, either a large or mini C-arm fluoroscopy was used intraoperatively.

The O-PDCO was performed through an oblique 3–4 cm incision over the lateral calcaneus with an oscillating saw and completed with an osteotome in the plane of the metatarsal head cascade, as described by Mosca .

The percutaneous osteotomy for the MI-PDCO was done through a 5 mm incision with the start point, as well as the plane of the osteotomy, marked using fluoroscopy. ( Fig. 2 a-b ) A 15 blade was used to incise skin, followed by a snap to bluntly dissect to bone, and special rasps (Wright Medical Inc.) to elevate all soft tissues circumferentially around the calcaneal tuberosity. Using a narrow, low-speed, high torque, cortical self-irrigating burr (2x20mm Shannon burr, PROSTEP™ Wright Medical) under intermittent fluoroscopic guidance to ensure the burr remained in the correct plane ( Fig. 2 c ). The tuberosity was cut first going through the lateral cortex of the calcaneus both dorsal and plantar then carefully advanced to the far medial cortex dorsally and plantarly, as described by Mourkus et al. . As the surgeon’s learning curve improved, fluoroscopy was only used to mark the start point and plane prior to use of the burr, and to confirm the amount of translation and screw position after osteotomy completion ( Fig. 2 a-e ). Bony fixation was achieved with K-wires if the patient had a minimally ossified calcaneal apophysis (typically age <10 years) or 1–2 fully or partial threaded 4.5 cannulated screws ( Fig. 2 d-e and Fig. 3 ). Postoperatively, patients were immobilized in a well-padded below knee non-weight bearing cast for 6 weeks. If inserted, K-wires were removed in the outpatient clinic at 6 weeks.

a-e: Intra-operative fluoroscopy demonstrating surgical technique of a minimally invasive posterior calcaneal displacement osteotomy in an immature patient with residual varus clubfoot deformity. A. Demonstrates the start point for the burr at the tip of the snap. B. Demonstrates a K wires in the plane of the desired calcaneal osteotomy. C. Demonstrates the burr as it exits plantarly in the calcaneal tuberosity in the desired planned plane from image B. D. Demonstrates a lateral slide of the tuberosity with assistance of a Williger elevator. E. PDCO with screw fixation.

Intraoperative axial view immediately following MI-PDCO and screw placement.

2.3

Univariate statistics were used to summarize the features of the dataset, including mean, standard deviation (±SD), and frequency (%). Continuous variables were described with mean±SD, while categorical variables were presented as counts (n) and frequencies (%). Student’s t test was used to compare continuous variables, while Chi-square and Fisher exact tests was used for categorical variables. Missing data was excluded from the analyses. Statistical analyses were performed with SAS Version 9.04 (Cary, North Carolina) and the level of significance was set at p < 0.05.