gms | German Medical Science

Objectives: Different procedures in guided growth treatment of the lower limb such as temporary or permanent epiphysiodesis require standardized radiographic references of the knee joint. Whereas physiological mechanical und anatomical orientation angels of the knee joint have been defined previously (Paley D., Principles of Deformity Correction, Springer, 2002, New York) there is lack of a standard reference defining the physiological position of the fibular head in relation to the proximal tibia.

Methods: As a new coronal radiographic reference, we measured the distance between the tip of the fibular head and a horizontal line drawn through the centre of the proximal tibial growth plate (Figure 1a [Fig. 1]).

In order to establish a standardized nomenclature, we will refer to this value as the „distance between the proximal tibial physis and the fibular head“ (dPTFH).

The dPTFH was measured on healthy legs in 428 calibrated long standing radiographs of children and adolescents aged from 8 to 16 years. So far 175 female and 253 male patients have been included. The x-ray examinations were performed for various unilateral conditions of the opposite leg. Patients who underwent systemic treatment i.e. chemotherapy, growth hormone therapy as well as congenital growth disorders i.e. achondroplasia, osteogenesis imperfecta where excluded.

Results and conclusion: In the 428 examined healthy legs of patients from 8-16 years, the overall mean value of the dPTFH was -2.55mm (f = -2.2mm, m= -2.9mm), meaning that in general the tip of the fibular head is located 2.55mm more distal than the centre of the proximal tibial growth plate (Figure 1a [Fig. 1]). First standard deviation (1SD): 3.28mm (f); 3.05mm (m); 3.16mm (f, m).

For the ease of clinical practicability, the questionable relevance of a 0,5-1mm difference in the fibular height and taking measuring inaccuracy into consideration, the values for the dPTFH and the first SD were rounded to -3mm and 3mm, respectively.

We suggest that a dPTFH of -3mm should be regarded as a standard reference value for the proximal fibular height in relation to the proximal tibial growth plate. Measurements within the 1.SD of +/- 3mm (dPTFH < = 0mm to -6mm) should be considered as „normal". dPTFH of -6mm to -9mm, or 0mm to +3mm should be considered as a mild (grade1) deviation.

We propose to consider differences greater than the 2.SD as relevant (grade 2) overgrowth or shortening (dPTFH > +6mm or dPTFH < -9mm) (Figure 1b [Fig. 1]).