Anthropometric study of adult tibia bone for pre-operative determination of length of intramedullary nail

Abstract

Background: The tibia is the bone that is mostly fractured in the body. Surgical fixation of tibia fractures with intramedullary (IM) nail is a common procedure around the world.

Objective: This study discusses pre-operative determination of intramedullary nail length to be inserted for a fractured tibia based on  anthropometric measurements of dry tibia bones.

Design: This was a prospective descriptive study.

Methods: The study involved measurement of length and other parts of adult dry tibia bones. Data of patients that had tibia fracture fixation with intramedullary interlocking nails using SIgn ®nails were also retrieved. All measurements and data obtained were recorded and analyzed using STATA version 13 (StataCorp, Texas. USA).

Results: The Maximum Tibia Length (MTL) of 44 adult tibia bones ranged from 35.2cm to 43.6cm with an average of 39.9 ± 2.2cm. The Bicondylar Tibial Width (BTW) ranged from 68.9mm to 80.4mm with an average of 75.1 ± 3.4mm. Tibia length (cm) can be estimated using the equation “12.6 + 3.7*{Bicondylar Tibial width (cm)} ± 3cm”. The distance of the Tibial plateau to the tubercle (TTD) ranged from 2.66cm to 3.53cm with an average
of 3.03 ± 0. 23cm. The Medial Malleolus Height (MMH) ranged from 1.20cm to 1.86cm with an average of 1.51 ± 0. 17cm. Part of the tibia bone that is usually occupied by inserted nail is MTL – (TTD + MMH). Average TTD + MMH = 4.5 ± 0.4cm. Length of intramedullary nail = MTL – 4.5cm. The average length of intramedullary nail used in our centre was 34.7 ± 2.7cm. The difference between the average tibia length and IM nail inserted was 5cm, which is closed to the findings in this study (i.e length of intramedullary nail for a tibia = maximum length of the tibia – 4.5cm).

Conclusion: Pre-operative determination of intramedullary nail length for the tibia can be derived using: “Length of the tibia (from the knee joint to the tip of medial malleolus) minus 4.5cm” (for tibia tubercle as the entry point); “Length of the tibia (from the knee joint to the tip of medial malleolus) minus 1.5cm” (for entry point just below the tibia plateau; The diameter of the nail to be inserted can be estimated along with the
length of the IM nail using: Diameter of nail (mm) = {7.2 + 0.007* length of the nail (mm)} ± 1.5 mm. This study also showed that tibia length can be estimated from the equation “12.6 + {3.7*Bicondylar tibial width (cm)} ± 3cm”. This is useful in forensic medicine or when the contralateral limb is not available for use in a patient who is to undergo IM tibia nailing.

Key words: Tibia fracture, Pre-operative determination, Intramedullary nail, Tibia bone fixation, Africans, Anthropometry, Tibia, Interlocking nail