Radiographic and clinical data on patients treated for tall stature with two novel devices for epiphysiodesis in a single-centre institution between 2015 and 2019 were retrospectively reviewed. This study was approved by our Institutional Review Board (registration number 2020–319 f-S). The study findings are reported according to the Strengthening the Reporting of Observational Studies in Epidemiology guidelines [25].
The number of patients, predicted final height, proportion index, and underlying conditions were recorded, as well as the patient age at implantation (Table 1). The inclusion criteria were a projected height that was three standard deviations above the sex-specific mean height and open growth plates with a remaining growth potential of more than 5 cm. The exclusion criteria were preceding hormonal treatment, a LLD of more than 1 cm, and clinically significant coronal malalignment of the lower extremities.
Patients and legal guardians were informed about the underlying aetiology and that excessive height was a benign condition. Surgical treatment was generally discouraged. Adolescents nearing skeletal maturity in whom the predicted height reduction amounted to less than 5 cm were advised against surgery. However, if patients and families stated that the tall stature caused psychological strain and credibly assured that the estimated reduction of their final height was likely to improve the patient’s self-perceived body image and mental health, surgery was considered. Informed consent regarding potential benefits and risks was obtained from all patients.
In total, 34 patients (16 girls, 18 boys) with tall stature were included (Fig. 1). tED was performed in 11/34 patients (32%) and pED in 23/34 patients (68%). 14/34 patients (41%) showed familial tall stature, 11/34 patients (32%) presented with constitutional tall stature, and Marfan syndrome had been pre-diagnosed in 9/34 patients (27%). The mean follow-up was 2.9 years (range 0.5–6.0) in the entire cohort, 4.4 years (range 2.0–6.0) in patients treated with tED, and 1.4 years (range 0.5–2.0) in patients treated with pED.
Prediction of final height and assessment of body proportions
Body height at skeletal maturity was predicted using the multiplier method [26]. Anteroposterior radiographs of the left hand and wrist were obtained to assess bone age according to Greulich and Pyle [27].
Body proportions were evaluated according to Exner, documenting standing and sitting height to evaluate the proportion index [28]. A decreased sitting height/height ratio with a proportion index below 1.0 implies a disproportionally increased leg length of the individual.
Surgical technique and implants
All procedures were performed by two senior surgeons (RR, BV) who are also authors of this study. Duration of surgery (incision to suture) and fluoroscopy time were recorded.
Temporary epiphysiodesis
tED was conducted through the bilateral implantation of four RigidTacks™ around the knee (the lateral and medial distal femurs and the proximal tibia, respectively). This implant provides cannulated barbed prongs for guided insertion and sub-periosteal bone purchase and a reinforced crossbar for sustained compression across the physis during growth. The surgical technique was performed as previously described (Figs. 2, 3) [11].
Implants were retrieved in a subsequent surgery after skeletal maturation.
Permanent epiphysiodesis
pED was executed using a guided EpiStop™ bone trephine with a diameter of 11 mm. A bone cylinder containing the central part of the growth plate was extracted, and premature fusion of the growth plate was induced through the reimplantation of the cylinder with 90° rotation.
The procedure was conducted through a lateral incision of approximately 1–2 cm over the distal lateral femur and proximal lateral tibia. A K-wire was inserted through the growth plate, and the correct biplanar positioning in the centre of the growth plate was controlled under fluoroscopy. Subsequently, the trephine was bicortically inserted over the K-wire (Fig. 4a–d). After the retraction of the bone cylinder, complete extraction of the central part of the growth plate was controlled visually and radiologically (Fig. 4e,f,i). Ex situ, the extracted growth plate was rotated 90° under visual guidance before reinsertion. Correct vertical positioning of the reinserted physis was documented with fluoroscopy (Figs. 4, 5).
Postoperative treatment regimen
All patients were allowed pain-adapted full weight-bearing immediately postoperatively. Physiotherapy was commenced on the first postoperative day and executed daily during the hospital stay and twice per week within outpatient care until full range of motion of the knee joint was regained.
Clinical and radiological evaluation
Standardised clinical and radiological follow-up examinations at the outpatient department were conducted at 6-month intervals. Standing height and sitting height were recorded using a Harpenden stadiometer. Surgery-related complications were documented.
Radiographs of the left hand were obtained at initial presentation and at the estimated end of growth (approximately 2.5 years after the onset of puberty [29]) to document skeletal maturation. Pre- and postoperative long-standing anteroposterior radiological measurements were obtained. Changes in the mechanical axis (defined as the line between the femoral head and the centre of the tibial plafond) towards varus and valgus malalignment of the lower extremities were recorded. Every shift of the mechanical axis greater than 10 mm was considered clinically important [11]. Measurements of the calibrated radiographs were performed with the PACS® system (GE Healthcare, Chicago, IL, USA) and the post-processing software TraumaCad® (Brainlab, Munich, Germany). In tED, implant placement and bone purchase were reviewed to detect implant-associated complications.
Statistical analysis
Descriptive statistics were performed using the mean or median with the range. Mean values were compared using the paired t-test or the Mann–Whitney U test, and dichotomous variables were compared using the chi2 test. The level of significance was set at α < 0.05. Statistical tests were conducted using SPSS 27 (IBM, Armonk, USA).